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Sample records for energy detection threshold

  1. Detection threshold energy of high energy cascade showers using thermoluminescence PTFE-sheet and hot-gas reader

    NASA Technical Reports Server (NTRS)

    Kino, S.; Nakanishi, A.; Miono, S.; Kitajima, T.; Yanagita, T.; Nakatsuka, T.; Ohmori, N.; Hazama, M.

    1985-01-01

    A new thermoluminescence (TL) sheet was developed as a detector for high energy components in air showers. For the investigation of detection threshold energy for a cascade showeer, TL sheets were exposed at Mt. Fuji with X ray films in emulsion chambers and were scanned by a hot-gas reader. It is concluded that if a gamma ray whose energy is more than 6 TeV enters vertically into lead chambers, the resulting cascade shower is readily detectable at maximum development.

  2. Taste Detection Thresholds of Resveratrol.

    PubMed

    Koga, Clarissa C; Becraft, Alexandra R; Lee, Youngsoo; Lee, Soo-Yeun

    2015-09-01

    Resveratrol is a polyphenol that is associated with numerous health benefits related to heart disease, cancer, diabetes, and neurological function. The addition of this compound to food products would help to deliver these health benefits to the consumer. However, bitterness associated with resveratrol may impart negative sensory qualities on the food products into which resveratrol is added; thus, decreasing consumer acceptability. This concern may be resolved by encapsulating resveratrol through spray drying, an innovative processing technique. The objectives of this research were to (1) compare taste detection thresholds of unencapsulated resveratrol and encapsulated resveratrol and (2) determine if the inclusion of anhydrous milk fat in the formulation of the encapsulation wall material affects the taste detection threshold of resveratrol within the microcapsules. Resveratrol microcapsules were produced by encapsulating resveratrol in a protein matrix through spray drying. R-index measure by the rating method was used to determine the average taste detection threshold and the pooled group taste detection threshold. The average and pooled group taste detection thresholds of unencapsulated resveratrol, sodium-caseinate-based resveratrol microcapsule without fat (SC), and sodium-caseinate-based resveratrol microcapsule with fat (SCAMF) were 90 and 47 mg resveratrol/L (unencapsulated), 313 and 103 mg resveratrol/L (SC), 334 and 108 mg resveratrol/L (SCAMF), respectively. The findings demonstrate that the encapsulation of resveratrol decreased the detection of the compound and provided a means to incorporate resveratrol into food products without imparting negative sensory properties.

  3. On computational Gestalt detection thresholds.

    PubMed

    Grompone von Gioi, Rafael; Jakubowicz, Jérémie

    2009-01-01

    The aim of this paper is to show some recent developments of computational Gestalt theory, as pioneered by Desolneux, Moisan and Morel. The new results allow to predict much more accurately the detection thresholds. This step is unavoidable if one wants to analyze visual detection thresholds in the light of computational Gestalt theory. The paper first recalls the main elements of computational Gestalt theory. It points out a precision issue in this theory, essentially due to the use of discrete probability distributions. It then proposes to overcome this issue by using continuous probability distributions and illustrates it on the meaningful alignment detector of Desolneux et al.

  4. Detection thresholds of macaque otolith afferents.

    PubMed

    Yu, Xiong-Jie; Dickman, J David; Angelaki, Dora E

    2012-06-13

    The vestibular system is our sixth sense and is important for spatial perception functions, yet the sensory detection and discrimination properties of vestibular neurons remain relatively unexplored. Here we have used signal detection theory to measure detection thresholds of otolith afferents using 1 Hz linear accelerations delivered along three cardinal axes. Direction detection thresholds were measured by comparing mean firing rates centered on response peak and trough (full-cycle thresholds) or by comparing peak/trough firing rates with spontaneous activity (half-cycle thresholds). Thresholds were similar for utricular and saccular afferents, as well as for lateral, fore/aft, and vertical motion directions. When computed along the preferred direction, full-cycle direction detection thresholds were 7.54 and 3.01 cm/s(2) for regular and irregular firing otolith afferents, respectively. Half-cycle thresholds were approximately double, with excitatory thresholds being half as large as inhibitory thresholds. The variability in threshold among afferents was directly related to neuronal gain and did not depend on spike count variance. The exact threshold values depended on both the time window used for spike count analysis and the filtering method used to calculate mean firing rate, although differences between regular and irregular afferent thresholds were independent of analysis parameters. The fact that minimum thresholds measured in macaque otolith afferents are of the same order of magnitude as human behavioral thresholds suggests that the vestibular periphery might determine the limit on our ability to detect or discriminate small differences in head movement, with little noise added during downstream processing.

  5. Improvement of the Mutation-Discrimination Threshold for Rare Point Mutations by a Separation-Free Ligase Detection Reaction Assay Based on Fluorescence Resonance Energy Transfer.

    PubMed

    Hagihara, Kenta; Tsukagoshi, Kazuhiko; Nakajima, Chinami; Esaki, Shinsuke; Hashimoto, Masahiko

    2016-01-01

    We previously developed a separation-free ligase detection reaction assay based on fluorescence resonance energy transfer from a donor quantum dot to an acceptor fluorescent dye. This assay could successfully detect one cancer mutation among 10 wild-type templates. In the current study, the mutation-discrimination threshold was improved by one order of magnitude by replacing the original acceptor dye (Alexa Fluor 647) with another fluorescent dye (Cyanine 5) that was spectrally similar but more fluorescent. PMID:26960620

  6. Detection thresholds for small haptic effects

    NASA Astrophysics Data System (ADS)

    Dosher, Jesse A.; Hannaford, Blake

    2002-02-01

    We are interested in finding out whether or not haptic interfaces will be useful in portable and hand held devices. Such systems will have severe constraints on force output. Our first step is to investigate the lower limits at which haptic effects can be perceived. In this paper we report on experiments studying the effects of varying the amplitude, size, shape, and pulse-duration of a haptic feature. Using a specific haptic device we measure the smallest detectable haptics effects, with active exploration of saw-tooth shaped icons sized 3, 4 and 5 mm, a sine-shaped icon 5 mm wide, and static pulses 50, 100, and 150 ms in width. Smooth shaped icons resulted in a detection threshold of approximately 55 mN, almost twice that of saw-tooth shaped icons which had a threshold of 31 mN.

  7. Sputtering Threshold Energies of Heavy Ions

    NASA Technical Reports Server (NTRS)

    Mantenieks, Maris A.

    1999-01-01

    Sputter erosion in ion thrusters has been measured in lifetests at discharge voltages as low as 25 V. Thruster operation at this discharge voltage results in component erosion rates sufficiently low to satisfy most mission requirements. It has been recognized that most of the internal sputtering in ion thrusters is done by doubly charged ions. Knowledge of the sputtering threshold voltage of a xenon molybdenum system would be beneficial in understanding the sputtering process as well as making more accurate calculations of the sputtering rates of ion thruster components. Sputtering threshold energies calculated from various formulations found in the literature results in values ranging from 28 to 200 eV. It is evident that some of these formulations cannot be relied upon to provide sputtering thresholds with any degree of accuracy. This paper re-examines the threshold energies measurements made in the early sixties by Askerov and Sena, and Stuart and Wehner. The threshold voltages as derived by Askerov and au have been reevaluated by using a different extrapolation method of sputter yields at low ion energies. The resulting threshold energies are in general similar to those measured by Stuart and Wehner. An empirical relationship is derived,for mercury and xenon ions for the ratio of the sputtering threshold energy to the sublimation energy as a function of the ratio of target to ion atomic mass.

  8. Experimental and environmental factors affect spurious detection of ecological thresholds

    USGS Publications Warehouse

    Daily, Jonathan P.; Hitt, Nathaniel P.; Smith, David; Snyder, Craig D.

    2012-01-01

    Threshold detection methods are increasingly popular for assessing nonlinear responses to environmental change, but their statistical performance remains poorly understood. We simulated linear change in stream benthic macroinvertebrate communities and evaluated the performance of commonly used threshold detection methods based on model fitting (piecewise quantile regression [PQR]), data partitioning (nonparametric change point analysis [NCPA]), and a hybrid approach (significant zero crossings [SiZer]). We demonstrated that false detection of ecological thresholds (type I errors) and inferences on threshold locations are influenced by sample size, rate of linear change, and frequency of observations across the environmental gradient (i.e., sample-environment distribution, SED). However, the relative importance of these factors varied among statistical methods and between inference types. False detection rates were influenced primarily by user-selected parameters for PQR (τ) and SiZer (bandwidth) and secondarily by sample size (for PQR) and SED (for SiZer). In contrast, the location of reported thresholds was influenced primarily by SED. Bootstrapped confidence intervals for NCPA threshold locations revealed strong correspondence to SED. We conclude that the choice of statistical methods for threshold detection should be matched to experimental and environmental constraints to minimize false detection rates and avoid spurious inferences regarding threshold location.

  9. Milagro: A low energy threshold extensive air shower array

    SciTech Connect

    Sinnis, G.

    1992-01-01

    Milagro is a proposed extensive air shower (EAS) array with a large water Cerenkov detector at its center. It will have a low energy threshold, {approximately} 500 GeV, and good angular resolution, {approximately} 0.4{degrees}. With the large aperture and duty factor of an EAS array, and the energy threshold of an atmospheric Cerenkov telescope, it will be ideally poised to discover new, steady sources of very high energy gamma radiation similar to the Crab nebula, and transient phenomena analogous to the gamma ray bursts seen at lower energies. Here we describe the Milagro detector and give results of tests performed at the CYGNUS array that demonstrate the capabilities of the water Cerenkov technique in detecting and reconstructing extensive air showers.

  10. Milagro: A low energy threshold extensive air shower array

    SciTech Connect

    Sinnis, G.; CYGNUS and MILAGRO Collaborations

    1992-10-01

    Milagro is a proposed extensive air shower (EAS) array with a large water Cerenkov detector at its center. It will have a low energy threshold, {approximately} 500 GeV, and good angular resolution, {approximately} 0.4{degrees}. With the large aperture and duty factor of an EAS array, and the energy threshold of an atmospheric Cerenkov telescope, it will be ideally poised to discover new, steady sources of very high energy gamma radiation similar to the Crab nebula, and transient phenomena analogous to the gamma ray bursts seen at lower energies. Here we describe the Milagro detector and give results of tests performed at the CYGNUS array that demonstrate the capabilities of the water Cerenkov technique in detecting and reconstructing extensive air showers.

  11. Threshold power and energy confinement for ITER

    SciTech Connect

    Takizuka, T.

    1996-12-31

    In order to predict the threshold power for L-H transition and the energy confinement performance in ITER, assembling of database and analyses of them have been progressed. The ITER Threshold Database includes data from 10 divertor tokamaks. Investigation of the database gives a scaling of the threshold power of the form P{sub thr} {proportional_to} B{sub t} n{sub e}{sup 0.75} R{sup 2} {times} (n{sub e} R{sup 2}){sup +-0.25}, which predicts P{sub thr} = 100 {times} 2{sup 0{+-}1} MW for ITER at n{sub e} = 5 {times} 10{sup 19} m{sup {minus}3}. The ITER L-mode Confinement Database has also been expanded by data from 14 tokamaks. A scaling of the thermal energy confinement time in L-mode and ohmic phases is obtained; {tau}{sub th} {approximately} I{sub p} R{sup 1.8} n{sub e}{sup 0.4{sub P{sup {minus}0.73}}}. At the ITER parameter, it becomes about 2.2 sec. For the ignition in ITER, more than 2.5 times of improvement will be required from the L-mode. The ITER H-mode Confinement Database is expanded from data of 6 tokamaks to data of 11 tokamaks. A {tau}{sub th} scaling for ELMy H-mode obtained by a standard regression analysis predicts the ITER confinement time of {tau}{sub th} = 6 {times} (1 {+-} 0.3) sec. The degradation of {tau}{sub th} with increasing n{sub e} R{sup 2} (or decreasing {rho}{sub *}) is not found for ELMy H-mode. An offset linear law scaling with a dimensionally correct form also predicts nearly the same {tau}{sub th} value.

  12. Threshold detection in generalized non-additive signals and noise

    SciTech Connect

    Middleton, D., LLNL

    1997-12-22

    The classical theory of optimum (binary-on-off) threshold detection for additive signals and generalized (i.e. nongaussian) noise is extended to the canonical nonadditive threshold situation. In the important (and usual) applications where the noise is sampled independently, a canonical threshold optimum theory is outlined here, which is found formally to parallel the earlier additive theory, including the critical properties of locally optimum Bayes detection algorithms, which are asymptotically normal and optimum as well. The important Class A clutter model provides an explicit example of optimal threshold envelope detection, for the non-additive cases of signal and noise. Various extensions are noted in the concluding section, as are selected references.

  13. Color-detection thresholds in rhesus macaque monkeys and humans.

    PubMed

    Gagin, Galina; Bohon, Kaitlin S; Butensky, Adam; Gates, Monica A; Hu, Jiun-Yiing; Lafer-Sousa, Rosa; Pulumo, Reitumetse L; Qu, Jane; Stoughton, Cleo M; Swanbeck, Sonja N; Conway, Bevil R

    2014-07-15

    Macaque monkeys are a model of human color vision. To facilitate linking physiology in monkeys with psychophysics in humans, we directly compared color-detection thresholds in humans and rhesus monkeys. Colors were defined by an equiluminant plane of cone-opponent color space. All subjects were tested on an identical apparatus with a four-alternative forced-choice task. Targets were 2° square, centered 2° from fixation, embedded in luminance noise. Across all subjects, the change in detection thresholds from initial testing to plateau performance (“learning”) was similar for +L − M (red) colors and +M − L (bluish-green) colors. But the extent of learning was higher for +S (lavender) than for −S (yellow-lime); moreover, at plateau performance, the cone contrast at the detection threshold was higher for +S than for −S. These asymmetries may reflect differences in retinal circuitry for S-ON and S-OFF. At plateau performance, the two species also had similar detection thresholds for all colors, although monkeys had shorter reaction times than humans and slightly lower thresholds for colors that modulated L/M cones. We discuss whether these observations, together with previous work showing that monkeys have lower spatial acuity than humans, could be accounted for by selective pressures driving higher chromatic sensitivity at the cost of spatial acuity amongst monkeys, specifically for the more recently evolved L − M mechanism.

  14. Color-detection thresholds in rhesus macaque monkeys and humans

    PubMed Central

    Gagin, Galina; Bohon, Kaitlin S.; Butensky, Adam; Gates, Monica A.; Hu, Jiun-Yiing; Lafer-Sousa, Rosa; Pulumo, Reitumetse L.; Qu, Jane; Stoughton, Cleo M.; Swanbeck, Sonja N.; Conway, Bevil R.

    2014-01-01

    Macaque monkeys are a model of human color vision. To facilitate linking physiology in monkeys with psychophysics in humans, we directly compared color-detection thresholds in humans and rhesus monkeys. Colors were defined by an equiluminant plane of cone-opponent color space. All subjects were tested on an identical apparatus with a four-alternative forced-choice task. Targets were 2° square, centered 2° from fixation, embedded in luminance noise. Across all subjects, the change in detection thresholds from initial testing to plateau performance (“learning”) was similar for +L − M (red) colors and +M − L (bluish-green) colors. But the extent of learning was higher for +S (lavender) than for −S (yellow-lime); moreover, at plateau performance, the cone contrast at the detection threshold was higher for +S than for −S. These asymmetries may reflect differences in retinal circuitry for S-ON and S-OFF. At plateau performance, the two species also had similar detection thresholds for all colors, although monkeys had shorter reaction times than humans and slightly lower thresholds for colors that modulated L/M cones. We discuss whether these observations, together with previous work showing that monkeys have lower spatial acuity than humans, could be accounted for by selective pressures driving higher chromatic sensitivity at the cost of spatial acuity amongst monkeys, specifically for the more recently evolved L − M mechanism. PMID:25027164

  15. Modeling threshold detection and search for point and extended sources

    NASA Astrophysics Data System (ADS)

    Friedman, Melvin

    2016-05-01

    This paper deals with three separate topics. 1)The Berek extended object threshold detection model is described, calibrated against a portion of Blackwell's 1946 naked eye threshold detection data for extended objects against an unstructured background, and then the remainder of Blackwell's data is used to verify and validate the model. A range equation is derived from Berek's model which allows threshold detection range to be predicted for extended to point objects against an un-cluttered background as a function of target size and adapting luminance levels. The range equation is then used to model threshold detection of stationary reflective and self-luminous targets against an uncluttered background. 2) There is uncertainty whether Travnikova's search data for point source detection against an un-cluttered background is described by Rayleigh or exponential distributions. A model which explains the Rayleigh distribution for barely perceptible objects and the exponential distribution for brighter objects is given. 3) A technique is presented which allows a specific observer's target acquisition capability to be characterized. Then a model is presented which describes how individual target acquisition probability grows when a specific observer or combination of specific observers search for targets. Applications for the three topics are discussed.

  16. Mammographic calcification cluster detection and threshold gold thickness measurements

    NASA Astrophysics Data System (ADS)

    Warren, L. M.; Mackenzie, A.; Cooke, J.; Given-Wilson, R.; Wallis, M. G.; Chakraborty, D. P.; Dance, D. R.; Young, K. C.

    2012-03-01

    European Guidelines for quality control in digital mammography specify acceptable and achievable standards of image quality (IQ) in terms of threshold gold thickness using the CDMAM test object. However, there is little evidence relating such measurements to cancer detection. This work investigated the relationship between calcification detection and threshold gold thickness. An observer study was performed using a set of 162 amorphous selenium direct digital (DR) detector images (81 no cancer and 81 with 1-3 inserted calcification clusters). From these images four additional IQs were simulated: different digital detectors (computed radiography (CR) and DR) and dose levels. Seven observers marked and rated the locations of suspicious regions. DBM analysis of variances was performed on the JAFROC figure of merit (FoM) yielding 95% confidence intervals for IQ pairs. Automated threshold gold thickness (Tg) analysis was performed for the 0.25mm gold disc diameter on CDMAM images at the same IQs (16 images per IQ). Tg was plotted against FoM and a power law fitted to the data. There was a significant reduction in FoM for calcification detection for CR images compared with DR; FoM decreased from 0.83 to 0.63 (p<=0.0001). Detection was also sensitive to dose. There was a good correlation between FoM and Tg (R2=0.80, p<0.05), consequently threshold gold thickness was a good predictor of calcification detection at the same IQ. Since the majority of threshold gold thicknesses for the various IQs were above the acceptable standard despite large variations in calcification detection by radiologists, current EU guidelines may need revising.

  17. A novel method for determining target detection thresholds

    NASA Astrophysics Data System (ADS)

    Grossman, S.

    2015-05-01

    Target detection is the act of isolating objects of interest from the surrounding clutter, generally using some form of test to include objects in the found class. However, the method of determining the threshold is overlooked relying on manual determination either through empirical observation or guesswork. The question remains: how does an analyst identify the detection threshold that will produce the optimum results? This work proposes the concept of a target detection sweet spot where the missed detection probability curve crosses the false detection curve; this represents the point at which missed detects are traded for false detects in order to effect positive or negative changes in the detection probability. ROC curves are used to characterize detection probabilities and false alarm rates based on empirically derived data. It identifies the relationship between the empirically derived results and the first moment statistic of the histogram of the pixel target value data and then proposes a new method of applying the histogram results in an automated fashion to predict the target detection sweet spot at which to begin automated target detection.

  18. Carbon monoxide exposure and human visual detection thresholds

    SciTech Connect

    Hudnell, H.K.; Benignus, V.A.

    1989-01-01

    In order to test for low level CO exposure effects on vision, a battery of visual tests was administered to male college students. All subjects completed the battery of tests both before and during an exposure period in a double-blind study. Experimental subjects received CO during the exposure period, whereas control subjects received only room air. The battery of visual tests was designed for the assessment of scotopic (dark adapted, rod mediated) vision, photopic (light adapted, cone mediated) vision, the pattern detection process and the motion detection process. Contrast thresholds for the detection of stimulus pattern and for the detection of stimulus motion were measured under both photopic and scotopic viewing conditions, and sensitivity was monitored throughout the course of dark adaptation by measuring luminance thresholds. The results indicated that visual function in healthy, young adult males was not affected by a COHb level of about 17% which was maintained for over 2 hours.

  19. Variable threshold method for ECG R-peak detection.

    PubMed

    Kew, Hsein-Ping; Jeong, Do-Un

    2011-10-01

    In this paper, a wearable belt-type ECG electrode worn around the chest by measuring the real-time ECG is produced in order to minimize the inconvenient in wearing. ECG signal is detected using a potential instrument system. The measured ECG signal is transmits via an ultra low power consumption wireless data communications unit to personal computer using Zigbee-compatible wireless sensor node. ECG signals carry a lot of clinical information for a cardiologist especially the R-peak detection in ECG. R-peak detection generally uses the threshold value which is fixed. There will be errors in peak detection when the baseline changes due to motion artifacts and signal size changes. Preprocessing process which includes differentiation process and Hilbert transform is used as signal preprocessing algorithm. Thereafter, variable threshold method is used to detect the R-peak which is more accurate and efficient than fixed threshold value method. R-peak detection using MIT-BIH databases and Long Term Real-Time ECG is performed in this research in order to evaluate the performance analysis.

  20. Detection thresholds for 60 Hz electric fields by nonhuman primates

    SciTech Connect

    Orr, J.L.; Rogers, W.R.; Smith, H.D.

    1995-12-31

    Because responses of animals to detection of the presence of an electric field (EF) are a possible mechanism for production of biological effects, it is important to know what EF intensities are detectable. Operant methods were used to train six baboons (Papio cynocephalus) to perform a psychophysical task involving detection of EF presence. During the response phase of a trial, a subject responded on one push button to report the presence of the EF and on a different push button to report the absence of the EF. Correct reports of EF presence or absence produced delivery of food rewards. The subjects became proficient at performing this psychophysical detection task; during 35 days of testing, false alarm rates averaged 9%. The average EF detection threshold was 12 kV/m; the range of means among subjects was 5--15 kV/m. Two special test procedures confirmed that the subjects were responding directly to EF presence or absence and not to artifacts that might be associated with EF generation. The EF detection threshold of nonhuman primates is similar to thresholds reported for rats and humans.

  1. Pregnancy does not affect human olfactory detection thresholds.

    PubMed

    Cameron, E Leslie

    2014-02-01

    Hyperosmia is suspected in pregnancy; however, no empirical study using validated measures of olfactory function has clearly confirmed the anecdotal reports of this phenomenon. The goal of the current study is to compare the olfactory sensitivity of pregnant women to that of nonpregnant women and men. All participants rated their sense of smell and pregnant women listed the odors to which they were most sensitive. Detection thresholds were measured using a well-validated protocol. A group of pregnant and nonpregnant women was studied longitudinally using a signal detection procedure designed to detect small differences in sensitivity. Pregnant women, particularly in the 1st trimester, rated their sense of smell to be higher than nonpregnant women and men and indicated many (primarily unpleasant) odors to which they were more sensitive. Women rated their sense of smell higher than men. However, there was no sex difference in thresholds and neither thresholds nor signal detection measures of sensitivity were significantly affected by either sex or pregnancy status. The implications of the lack of relationship between self-report and measures of olfactory sensitivity, particularly in pregnancy, are discussed.

  2. Orion MPCV Touchdown Detection Threshold Development and Testing

    NASA Technical Reports Server (NTRS)

    Daum, Jared; Gay, Robert

    2013-01-01

    A robust method of detecting Orion Multi-Purpose Crew Vehicle (MPCV) splashdown is necessary to ensure crew and hardware safety during descent and after touchdown. The proposed method uses a triple redundant system to inhibit Reaction Control System (RCS) thruster firings, detach parachute risers from the vehicle, and transition to the post-landing segment of the Flight Software (FSW). An in-depth trade study was completed to determine optimal characteristics of the touchdown detection method resulting in an algorithm monitoring filtered, lever-arm corrected, 200 Hz Inertial Measurement Unit (IMU) vehicle acceleration magnitude data against a tunable threshold using persistence counter logic. Following the design of the algorithm, high fidelity environment and vehicle simulations, coupled with the actual vehicle FSW, were used to tune the acceleration threshold and persistence counter value to result in adequate performance in detecting touchdown and sufficient safety margin against early detection while descending under parachutes. An analytical approach including Kriging and adaptive sampling allowed for a sufficient number of finite element analysis (FEA) impact simulations to be completed using minimal computation time. The combination of a persistence counter of 10 and an acceleration threshold of approximately 57.3 ft/s2 resulted in an impact performance factor of safety (FOS) of 1.0 and a safety FOS of approximately 2.6 for touchdown declaration. An RCS termination acceleration threshold of approximately 53.1 ft/s(exp)2 with a persistence counter of 10 resulted in an increased impact performance FOS of 1.2 at the expense of a lowered under-parachutes safety factor of 2.2. The resulting tuned algorithm was then tested on data from eight Capsule Parachute Assembly System (CPAS) flight tests, showing an experimental minimum safety FOS of 6.1. The formulated touchdown detection algorithm will be flown on the Orion MPCV FSW during the Exploration Flight Test 1

  3. Tactile and thermal detection thresholds of the scalp skin.

    PubMed

    Mehrabyan, Anahit; Guest, Steve; Essick, Greg; McGlone, Francis

    2011-01-01

    The tactile and thermal sensitivity of diverse regions of the human body have been documented extensively, with one exception being the scalp. Additionally, sensory changes may accompany the hair loss from the scalp in androgen-related alopecia (ARA), but formal quantitative sensory testing (QST) has not been reported in respect of this. Therefore, light touch detection thresholds were obtained at nine scalp sites and one forehead site, using Semmes-Weinstein filaments (Von Frey hairs), and for warming and cooling from skin baseline temperature, using 28 and 256 mm(2) thermodes. Affective, thermal, and nociceptive sensations experienced at thermal detection threshold were quantified. Thirty-two male participants were recruited, 10 of whom had normal hair coverage, 12 of whom had shaved scalp but with potentially normal hair coverage, and 10 of whom exhibited ARA to some extent. The scalp was relatively insensitive to tactile and thermal stimulation at all tested sites, especially so along the midline and near the apex of the skull. Threshold level warm stimuli were rated less pleasant, the less sensitive the test site. After correction for age-related changes in sensitivity, bald scalp sites were found more sensitive to cooling than the same sites when shaved, consistent with prior informal reports of increased sensitivity for some scalp sensations in ARA. QST on hair-covered sites was subject to methodological issues that render such testing non-ideal, such as bias in measurement of resting skin temperatures, and the near impossibility of delivering filament stimuli to the scalp skin without disturbing neighboring hairs.

  4. Orion MPCV Touchdown Detection Threshold Development and Testing

    NASA Technical Reports Server (NTRS)

    Daum, Jared; Gay, Robert

    2013-01-01

    A robust method of detecting Orion Multi ]Purpose Crew Vehicle (MPCV) splashdown is necessary to ensure crew and hardware safety during descent and after touchdown. The proposed method uses a triple redundant system to inhibit Reaction Control System (RCS) thruster firings, detach parachute risers from the vehicle, and transition to the post ]landing segment of the Flight Software (FSW). The vehicle crew is the prime input for touchdown detection, followed by an autonomous FSW algorithm, and finally a strictly time based backup timer. RCS thrusters must be inhibited before submersion in water to protect against possible damage due to firing these jets under water. In addition, neglecting to declare touchdown will not allow the vehicle to transition to post ]landing activities such as activating the Crew Module Up ]righting System (CMUS), resulting in possible loss of communication and difficult recovery. A previous AIAA paper gAssessment of an Automated Touchdown Detection Algorithm for the Orion Crew Module h concluded that a strictly Inertial Measurement Unit (IMU) based detection method using an acceleration spike algorithm had the highest safety margins and shortest detection times of other methods considered. That study utilized finite element simulations of vehicle splashdown, generated by LS ]DYNA, which were expanded to a larger set of results using a Kriging surface fit. The study also used the Decelerator Systems Simulation (DSS) to generate flight dynamics during vehicle descent under parachutes. Proto ]type IMU and FSW MATLAB models provided the basis for initial algorithm development and testing. This paper documents an in ]depth trade study, using the same dynamics data and MATLAB simulations as the earlier work, to further develop the acceleration detection method. By studying the combined effects of data rate, filtering on the rotational acceleration correction, data persistence limits and values of acceleration thresholds, an optimal configuration

  5. Spin-system dynamics and fault detection in threshold networks

    SciTech Connect

    Kirkland, Steve; Severini, Simone

    2011-01-15

    We consider an agent on a fixed but arbitrary node of a known threshold network, with the task of detecting an unknown missing link. We obtain analytic formulas for the probability of success when the agent's tool is the free evolution of a single excitation on an XX spin system paired with the network. We completely characterize the parameters, which allows us to obtain an advantageous solution. From the results emerges an optimal (deterministic) algorithm for quantum search, from which a quadratic speedup with respect to the optimal classical analog and in line with well-known results in quantum computation is gained. When attempting to detect a faulty node, the chosen setting appears to be very fragile and the probability of success too small to be of any direct use.

  6. Ultrasonic flaw detection using threshold modified S-transform.

    PubMed

    Benammar, Abdessalem; Drai, Redouane; Guessoum, Abderrezak

    2014-02-01

    Interference noising originating from the ultrasonic testing defect signal seriously influences the accuracy of the signal extraction and defect location. Time-frequency analysis methods are mainly used to improve the defects detection resolution. In fact, the S-transform, a hybrid of the Short time Fourier transform (STFT) and wavelet transform (WT), has a time frequency resolution which is far from ideal. In this paper, a new modified S-transform based on thresholding technique, which offers a better time frequency resolution compared to the original S-transform is proposed. The improvement is achieved by the introduction of a new scaling rule for the Gaussian window used in S-transform. Simulation results are presented and show correct time frequency information of multiple Gaussian echoes under low signal-to-noise ratio (SNR) environment. In addition, experimental results demonstrate better and reliable detection of close echoes drowned in the noise.

  7. Detection Thresholds of Falling Snow from Satellite-Borne Active and Passive Sensors

    NASA Technical Reports Server (NTRS)

    Jackson, Gail

    2012-01-01

    Precipitation, including rain and snow, is a critical part of the Earth's energy and hydrology cycles. In order to collect information on the complete global precipitation cycle and to understand the energy budget in terms of precipitation, uniform global estimates of both liquid and frozen precipitation must be collected. Active observations of falling snow are somewhat easier to estimate since the radar will detect the precipitation particles and one only needs to know surface temperature to determine if it is liquid rain or snow. The challenges of estimating falling snow from passive spaceborne observations still exist though progress is being made. While these challenges are still being addressed, knowledge of their impact on expected retrieval results is an important key for understanding falling snow retrieval estimations. Important information to assess falling snow retrievals includes knowing thresholds of detection for active and passive sensors, various sensor channel configurations, snow event system characteristics, snowflake particle assumptions, and surface types. For example, can a lake effect snow system with low (2.5 km) cloud tops having an ice water content (Iwe) at the surface of 0.25 g m-3 and dendrite snowflakes be detected? If this information is known, we can focus retrieval efforts on detectable storms and concentrate advances on achievable results. Here, the focus is to determine thresholds of detection for falling snow for various snow conditions over land and lake surfaces. The analysis relies on simulated Weather Research Forecasting (WRF) simulations of falling snow cases since simulations provide all the information to determine the measurements from space and the ground truth. Results are presented for active radar at Ku, Ka, and W-band and for passive radiometer channels from 10 to 183 GHz (Skofronick-Jackson, et al. submitted to IEEE TGRS, April 2012). The notable results show: (1) the W-Band radar has detection thresholds more

  8. Enhancement of visual motion detection thresholds in early deaf people.

    PubMed

    Shiell, Martha M; Champoux, François; Zatorre, Robert J

    2014-01-01

    In deaf people, the auditory cortex can reorganize to support visual motion processing. Although this cross-modal reorganization has long been thought to subserve enhanced visual abilities, previous research has been unsuccessful at identifying behavioural enhancements specific to motion processing. Recently, research with congenitally deaf cats has uncovered an enhancement for visual motion detection. Our goal was to test for a similar difference between deaf and hearing people. We tested 16 early and profoundly deaf participants and 20 hearing controls. Participants completed a visual motion detection task, in which they were asked to determine which of two sinusoidal gratings was moving. The speed of the moving grating varied according to an adaptive staircase procedure, allowing us to determine the lowest speed necessary for participants to detect motion. Consistent with previous research in deaf cats, the deaf group had lower motion detection thresholds than the hearing. This finding supports the proposal that cross-modal reorganization after sensory deprivation will occur for supramodal sensory features and preserve the output functions.

  9. Enhancement of Visual Motion Detection Thresholds in Early Deaf People

    PubMed Central

    Shiell, Martha M.; Champoux, François; Zatorre, Robert J.

    2014-01-01

    In deaf people, the auditory cortex can reorganize to support visual motion processing. Although this cross-modal reorganization has long been thought to subserve enhanced visual abilities, previous research has been unsuccessful at identifying behavioural enhancements specific to motion processing. Recently, research with congenitally deaf cats has uncovered an enhancement for visual motion detection. Our goal was to test for a similar difference between deaf and hearing people. We tested 16 early and profoundly deaf participants and 20 hearing controls. Participants completed a visual motion detection task, in which they were asked to determine which of two sinusoidal gratings was moving. The speed of the moving grating varied according to an adaptive staircase procedure, allowing us to determine the lowest speed necessary for participants to detect motion. Consistent with previous research in deaf cats, the deaf group had lower motion detection thresholds than the hearing. This finding supports the proposal that cross-modal reorganization after sensory deprivation will occur for supramodal sensory features and preserve the output functions. PMID:24587381

  10. Signal Detection Theory Applied to Helicopter Transmission Diagnostic Thresholds

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Keller, Jonathan A.; Wade, Daniel R.

    2009-01-01

    Helicopter Health Usage Monitoring Systems (HUMS) have potential for providing data to support increasing the service life of a dynamic mechanical component in the transmission of a helicopter. Data collected can demonstrate the HUMS condition indicator responds to a specific component fault with appropriate alert limits and minimal false alarms. Defining thresholds for specific faults requires a tradeoff between the sensitivity of the condition indicator (CI) limit to indicate damage and the number of false alarms. A method using Receiver Operating Characteristic (ROC) curves to assess CI performance was demonstrated using CI data collected from accelerometers installed on several UH60 Black Hawk and AH64 Apache helicopters and an AH64 helicopter component test stand. Results of the analysis indicate ROC curves can be used to reliably assess the performance of commercial HUMS condition indicators to detect damaged gears and bearings in a helicopter transmission.

  11. Signal Detection Theory Applied to Helicopter Transmission Diagnostic Thresholds

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Keller, Jonathan A.; Wade, Daniel R.

    2008-01-01

    Helicopter Health Usage Monitoring Systems (HUMS) have potential for providing data to support increasing the service life of a dynamic mechanical component in the transmission of a helicopter. Data collected can demonstrate the HUMS condition indicator responds to a specific component fault with appropriate alert limits and minimal false alarms. Defining thresholds for specific faults requires a tradeoff between the sensitivity of the condition indicator (CI) limit to indicate damage and the number of false alarms. A method using Receiver Operating Characteristic (ROC) curves to assess CI performance was demonstrated using CI data collected from accelerometers installed on several UH60 Black Hawk and AH64 Apache helicopters and an AH64 helicopter component test stand. Results of the analysis indicate ROC curves can be used to reliably assess the performance of commercial HUMS condition indicators to detect damaged gears and bearings in a helicopter transmission.

  12. Research of adaptive threshold edge detection algorithm based on statistics canny operator

    NASA Astrophysics Data System (ADS)

    Xu, Jian; Wang, Huaisuo; Huang, Hua

    2015-12-01

    The traditional Canny operator cannot get the optimal threshold in different scene, on this foundation, an improved Canny edge detection algorithm based on adaptive threshold is proposed. The result of the experiment pictures indicate that the improved algorithm can get responsible threshold, and has the better accuracy and precision in the edge detection.

  13. Threshold detection in an on-off binary communications channel with atmospheric scintillation

    NASA Technical Reports Server (NTRS)

    Webb, W. E.

    1975-01-01

    The optimum detection threshold in an on-off binary optical communications system operating in the presence of atmospheric turbulence was investigated assuming a poisson detection process and log normal scintillation. The dependence of the probability of bit error on log amplitude variance and received signal strength was analyzed and semi-empirical relationships to predict the optimum detection threshold derived. On the basis of this analysis a piecewise linear model for an adaptive threshold detection system is presented. The bit error probabilities for nonoptimum threshold detection systems were also investigated.

  14. Colour detection thresholds in faces and colour patches.

    PubMed

    Tan, Kok Wei; Stephen, Ian D

    2013-01-01

    Human facial skin colour reflects individuals' underlying health (Stephen et al 2011 Evolution & Human Behavior 32 216-227); and enhanced facial skin CIELab b* (yellowness), a* (redness), and L* (lightness) are perceived as healthy (also Stephen et al 2009a International Journal of Primatology 30 845-857). Here, we examine Malaysian Chinese participants' detection thresholds for CIELab L* (lightness), a* (redness), and b* (yellowness) colour changes in Asian, African, and Caucasian faces and skin coloured patches. Twelve face photos and three skin coloured patches were transformed to produce four pairs of images of each individual face and colour patch with different amounts of red, yellow, or lightness, from very subtle (deltaE = 1.2) to quite large differences (deltaE = 9.6). Participants were asked to decide which of sequentially displayed, paired same-face images or colour patches were lighter, redder, or yellower. Changes in facial redness, followed by changes in yellowness, were more easily discriminated than changes in luminance. However, visual sensitivity was not greater for redness and yellowness in nonface stimuli, suggesting red facial skin colour special salience. Participants were also significantly better at recognizing colour differences in own-race (Asian) and Caucasian faces than in African faces, suggesting the existence of cross-race effect in discriminating facial colours. Humans' colour vision may have been selected for skin colour signalling (Changizi et al 2006 Biology Letters 2 217-221), enabling individuals to perceive subtle changes in skin colour, reflecting health and emotional status.

  15. A new EC-PC threshold estimation method for in vivo neural spike detection

    NASA Astrophysics Data System (ADS)

    Yang, Zhi; Liu, Wentai; Keshtkaran, Mohammad Reza; Zhou, Yin; Xu, Jian; Pikov, Victor; Guan, Cuntai; Lian, Yong

    2012-08-01

    This paper models in vivo neural signals and noise for extracellular spike detection. Although the recorded data approximately follow Gaussian distribution, they clearly deviate from white Gaussian noise due to neuronal synchronization and sparse distribution of spike energy. Our study predicts the coexistence of two components embedded in neural data dynamics, one in the exponential form (noise) and the other in the power form (neural spikes). The prediction of the two components has been confirmed in experiments of in vivo sequences recorded from the hippocampus, cortex surface, and spinal cord; both acute and long-term recordings; and sleep and awake states. These two components are further used as references for threshold estimation. Different from the conventional wisdom of setting a threshold at 3×RMS, the estimated threshold exhibits a significant variation. When our algorithm was tested on synthesized sequences with a different signal to noise ratio and on/off firing dynamics, inferred threshold statistics track the benchmarks well. We envision that this work may be applied to a wide range of experiments as a front-end data analysis tool.

  16. Pressure Systems Stored-Energy Threshold Risk Analysis

    SciTech Connect

    Paulsen, Samuel S.

    2009-08-25

    Federal Regulation 10 CFR 851, which became effective February 2007, brought to light potential weaknesses regarding the Pressure Safety Program at the Pacific Northwest National Laboratory (PNNL). The definition of a pressure system in 10 CFR 851 does not contain a limit based upon pressure or any other criteria. Therefore, the need for a method to determine an appropriate risk-based hazard level for pressure safety was identified. The Laboratory has historically used a stored energy of 1000 lbf-ft to define a pressure hazard; however, an analytical basis for this value had not been documented. This document establishes the technical basis by evaluating the use of stored energy as an appropriate criterion to establish a pressure hazard, exploring a suitable risk threshold for pressure hazards, and reviewing the methods used to determine stored energy. The literature review and technical analysis concludes the use of stored energy as a method for determining a potential risk, the 1000 lbf-ft threshold, and the methods used by PNNL to calculate stored energy are all appropriate. Recommendations for further program improvements are also discussed

  17. Detection and Modeling of High-Dimensional Thresholds for Fault Detection and Diagnosis

    NASA Technical Reports Server (NTRS)

    He, Yuning

    2015-01-01

    Many Fault Detection and Diagnosis (FDD) systems use discrete models for detection and reasoning. To obtain categorical values like oil pressure too high, analog sensor values need to be discretized using a suitablethreshold. Time series of analog and discrete sensor readings are processed and discretized as they come in. This task isusually performed by the wrapper code'' of the FDD system, together with signal preprocessing and filtering. In practice,selecting the right threshold is very difficult, because it heavily influences the quality of diagnosis. If a threshold causesthe alarm trigger even in nominal situations, false alarms will be the consequence. On the other hand, if threshold settingdoes not trigger in case of an off-nominal condition, important alarms might be missed, potentially causing hazardoussituations. In this paper, we will in detail describe the underlying statistical modeling techniques and algorithm as well as the Bayesian method for selecting the most likely shape and its parameters. Our approach will be illustrated by several examples from the Aerospace domain.

  18. Comparison of the orthonasal and retronasal detection thresholds for carbon dioxide in humans.

    PubMed

    Melzner, Johannes; Bitter, Thomas; Guntinas-Lichius, Orlando; Gottschall, Reiner; Walther, Mario; Gudziol, Hilmar

    2011-06-01

    Several studies have investigated the orthonasal detection threshold for carbon dioxide (CO(2)) in humans. The aim of current study was to investigate whether 24 healthy young subjects exhibited differences of CO(2) detection thresholds during orthonasal or retronasal stimulation. As nasal mucosa is believed to desensitize to CO(2) concentrations at or below 4% (v/v) during expiration, the second aim of the study was to explore the influence during nasal versus oral breathing on the detection thresholds. CO(2) stimuli of varying concentrations and a duration of 1000 ms were applied with an air-dilution olfactometer in either the anterior nasal cavity or the nasopharynx during nasal respectively oral breathing. In these 4 conditions, the mean CO(2) detection thresholds using the staircase forced-choice procedure were between 3.9% and 5.3% (v/v). Statistical analysis revealed a significant difference between orthonasal and retronasal stimulation. The CO(2) detection threshold was lower in retronasal stimulation. The nasopharyngeal mucosa is more sensitive to perithreshold CO(2) stimuli than the nasal mucosa. The breathing route had no influence on the detection thresholds. The results of this study indicate that the natural contact of the nasal mucosa with approximately 4% (v/v) CO(2) during nasal expiration does not influence CO(2) detection thresholds.

  19. Low energy threshold corrections to neutrino masses and mixing angles

    NASA Astrophysics Data System (ADS)

    Chankowski, P. H.; Wąsowicz, P.

    2002-03-01

    We compute the low energy threshold corrections to neutrino masses and mixing in the standard model (SM) and its minimal supersymmetric version, using the effective theory technique. We demonstrate that they stabilize the results for neutrino masses and mixing with respect to the choice of the scale to which the renormalization group (RG) equation is integrated. (This confirms the correctness of the recent re-derivation of the RGE for the SM in hep-ph/0108005.) Since, as is known, those corrections are potentially very important for phenomenology we derive for them the explicit formulae that can be applied to specific models of neutrino masses and mixing.

  20. Detection Thresholds of Falling Snow from Satellite-Borne Active and Passive Sensors

    NASA Technical Reports Server (NTRS)

    Skofronick-Jackson, Gail; Johnson, Benjamin T.; Munchak, S. Joseph

    2012-01-01

    Precipitation, including rain and snow, is a critical part of the Earth's energy and hydrology cycles. Precipitation impacts latent heating profiles locally while global circulation patterns distribute precipitation and energy from the equator to the poles. For the hydrological cycle, falling snow is a primary contributor in northern latitudes during the winter seasons. Falling snow is the source of snow pack accumulations that provide fresh water resources for many communities in the world. Furthermore, falling snow impacts society by causing transportation disruptions during severe snow events. In order to collect information on the complete global precipitation cycle, both liquid and frozen precipitation must be collected. The challenges of estimating falling snow from space still exist though progress is being made. These challenges include weak falling snow signatures with respect to background (surface, water vapor) signatures for passive sensors over land surfaces, unknowns about the spherical and non-spherical shapes of the snowflakes, their particle size distributions (PSDs) and how the assumptions about the unknowns impact observed brightness temperatures or radar reflectivities, differences in near surface snowfall and total column snow amounts, and limited ground truth to validate against. While these challenges remain, knowledge of their impact on expected retrieval results is an important key for understanding falling snow retrieval estimations. Since falling snow from space is the next precipitation measurement challenge from space, information must be determined in order to guide retrieval algorithm development for these current and future missions. This information includes thresholds of detection for various sensor channel configurations, snow event system characteristics, snowflake particle assumptions, and surface types. For example, can a lake effect snow system with low (approx 2.5 km) cloud tops having an ice water content (IWC) at the

  1. A Bispectral Composite Threshold Approach for Automatic Cloud Detection in VIIRS Imagery

    NASA Technical Reports Server (NTRS)

    LaFontaine Frank J.; Jedlovec, Gary J.

    2015-01-01

    The detection of clouds in satellite imagery has a number of important applications in weather and climate studies. The presence of clouds can alter the energy budget of the Earth-atmosphere system through scattering and absorption of shortwave radiation and the absorption and re-emission of infrared radiation at longer wavelengths. The scattering and absorption characteristics of clouds vary with the microphysical properties of clouds, hence the cloud type. Thus, detecting the presence of clouds over a region in satellite imagery is important in order to derive atmospheric or surface parameters that give insight into weather and climate processes. For many applications however, clouds are a contaminant whose presence interferes with retrieving atmosphere or surface information. In these cases, is important to isolate cloud-free pixels, used to retrieve atmospheric thermodynamic information or surface geophysical parameters, from cloudy ones. This abstract describes an application of a two-channel bispectral composite threshold (BCT) approach applied to VIIRS imagery. The simplified BCT approach uses only the 10.76 and 3.75 micrometer spectral channels from VIIRS in two spectral tests; a straight-forward infrared threshold test with the longwave channel and a shortwave - longwave channel difference test. The key to the success of this approach as demonstrated in past applications to GOES and MODIS data is the generation of temporally and spatially dependent thresholds used in the tests from a previous number of days at similar observations to the current data. The paper and subsequent presentation will present an overview of the approach and intercomparison results with other satellites, methods, and against verification data.

  2. Low energy response of the NICER detectors and "threshold efficiency" effect

    NASA Astrophysics Data System (ADS)

    Prigozhin, Gregory; Doty, John; LaMarr, Beverly; Malonis, Andrew; Remillard, Ronald A.; Scholze, Frank; Laubis, Christian; Krumrey, Michael

    2016-04-01

    The Neutron Star Interior Composition ExploreR (NICER) is an instrument that is planned to be installed on the International Space Station in 2016 to study time-resolved spectra of the rapidly changing celestial ojects. The focal plane of the instrument consists of 56 Silicon Drift Detectors (SDDs). Signal from each SDD is fed to shaping amplifiers and triggering circuits that determine both amplitude and time of arrival for each "event".Zero crossing timing circuit is used in order to suppress energy dependent "time walk". That is done with a chain producing a derivative of the shaped signal, and the same chain detects threshold crossings marking the arrival of an X-ray photon. Higher noise of the differentiated signal leads to a somewhat extended band of signal amplitudes close to the threshold value, for which detection efficiency is less than 100%. Detection efficiency in this area affects the low energy portion of the detector response, and is very well described by an error function. We will present accurate measurements of this effect, show the consequences for the instrument quantum efficiency and the shape of the response function and will describe the calibration procedures that would allow selection of optimal threshold values for each observation.

  3. Dependence of Nociceptive Detection Thresholds on Physiological Parameters and Capsaicin-Induced Neuroplasticity: A Computational Study

    PubMed Central

    Yang, Huan; Meijer, Hil G. E.; Doll, Robert J.; Buitenweg, Jan R.; van Gils, Stephan A.

    2016-01-01

    Physiological properties of peripheral and central nociceptive subsystems can be altered over time due to medical interventions. The effective change for the whole nociceptive system can be reflected in changes of psychophysical characteristics, e.g., detection thresholds. However, it is challenging to separate contributions of distinct altered mechanisms with measurements of thresholds only. Here, we aim to understand how these alterations affect Aδ-fiber-mediated nociceptive detection of electrocutaneous stimuli. First, with a neurophysiology-based model, we study the effects of single-model parameters on detection thresholds. Second, we derive an expression of model parameters determining the functional relationship between detection thresholds and the interpulse interval for double-pulse stimuli. Third, in a case study with topical capsaicin treatment, we translate neuroplasticity into plausible changes of model parameters. Model simulations qualitatively agree with changes in experimental detection thresholds. The simulations with individual forms of neuroplasticity confirm that nerve degeneration is the dominant mechanism for capsaicin-induced increases in detection thresholds. In addition, our study suggests that capsaicin-induced central plasticity may last at least 1 month. PMID:27252644

  4. Detection thresholds of potassium salts are related to the molar conductivity of the anion.

    PubMed

    Schiffman, S S; Manning, M P; Warwick, Z S; Crumbliss, A L

    1995-01-01

    In a previous study, we found that human taste detection thresholds for Na+ salts were linearly correlated with molar conductivity values at infinite dilution of their anions. In the present study, detection threshold concentrations for potassium salts were also found to be linearly correlated (r = -0.92) with the molar conductivity of the anion of the salt. Detection thresholds were determined here for nine potassium salts with the same anions as the sodium salts previously tested. The mean detection thresholds for these potassium salts were found to be: K Acetate (0.00311 M), K Carbonate (0.00286 M), K Chloride (0.00242 M), K Citrate (0.000300 M), K Phosphate (0.00196 M), K Sulfate (0.00090 M), K Tartrate (0.00164 M), K Glutamate (0.00153 M), and K Ascorbate (0.00375 M). The rank order correlation between the detection threshold values for sodium and potassium salts was 0.88. This finding suggests that detection thresholds for both Na+ and K+ salts are determined by the charge mobility of the anion.

  5. Quantification and threshold detection in real-time hyperspectral imaging

    NASA Astrophysics Data System (ADS)

    Driver, Richard D.

    2009-05-01

    The technical challenges of applying hyperspectral imaging techniques to on-line real-time food monitoring is discussed. System optimization must be applied to the design of the hyperspectral imaging spectrograph, the choice and operation of the imaging detector, the design of the illumination system and finally the development of software algorithms to correctly quantify the hyperspectral images. The signal to noise limitation of hyperspectral detection is discussed with particular emphasis on the detection of moving objects at high measurement bandwidths. An example is given of the development of a simple but accurate algorithm for the detection and discrimination of rust particles on leaves.

  6. High-energy above-threshold detachment from negative ions

    SciTech Connect

    Gazibegovic-Busuladzic, A.; Milosevic, D.B.; Becker, W.

    2004-11-01

    Above-threshold detachment of electrons from negative ions by an elliptically polarized laser field is analyzed within the strong-field approximation. The low-energy part of the spectrum, that is, its structure and its apparent cutoff, strongly depends on the orbital quantum number l of the initial ground state. The high-energy part is characterized by the usual extended plateau caused by rescattering, which is essentially independent of the ground state. The potential that the returning electron experiences during rescattering is modeled by the sum of a polarization potential and a static potential. This rescattering potential does not have much effect on the shape of the plateau, but it does on its height. For H{sup -} (l=0), the yield of rescattered electrons is five orders of magnitude below the direct electrons, while for I{sup -} (l=1) the yields only differ by a factor of 40. We also analyze the dependence of the angle-resolved energy spectrum on the ellipticity of the laser field and confirm general symmetry properties. An angle-integrated elliptic dichroism parameter is introduced and analyzed.

  7. Ambient noise levels and detection threshold in Norway

    NASA Astrophysics Data System (ADS)

    Demuth, Andrea; Ottemöller, Lars; Keers, Henk

    2016-07-01

    Ambient seismic noise is caused by a number of sources in specific frequency bands. The quantification of ambient noise makes it possible to evaluate station and network performance. We evaluate noise levels in Norway from the 2013 data set of the Norwegian National Seismic Network as well as two temporary deployments. Apart from the station performance, we studied the geographical and temporal variations, and developed a local noise model for Norway. The microseism peaks related to the ocean are significant in Norway. We, therefore, investigated the relationship between oceanic weather conditions and noise levels. We find a correlation of low-frequency noise (0.125-0.25 Hz) with wave heights up to 900 km offshore. High (2-10 Hz) and intermediate (0.5-5 Hz) frequency noise correlates only up to 450 km offshore with wave heights. From a geographic perspective, stations in southern Norway show lower noise levels for low frequencies due to a larger distance to the dominant noise sources in the North Atlantic. Finally, we studied the influence of high-frequency noise levels on earthquake detectability and found that a noise level increase of 10 dB decreases the detectability by 0.5 magnitude units. This method provides a practical way to consider noise variations in detection maps.

  8. Wavelet-based acoustic emission detection method with adaptive thresholding

    NASA Astrophysics Data System (ADS)

    Menon, Sunil; Schoess, Jeffrey N.; Hamza, Rida; Busch, Darryl

    2000-06-01

    Reductions in Navy maintenance budgets and available personnel have dictated the need to transition from time-based to 'condition-based' maintenance. Achieving this will require new enabling diagnostic technologies. One such technology, the use of acoustic emission for the early detection of helicopter rotor head dynamic component faults, has been investigated by Honeywell Technology Center for its rotor acoustic monitoring system (RAMS). This ambitious, 38-month, proof-of-concept effort, which was a part of the Naval Surface Warfare Center Air Vehicle Diagnostics System program, culminated in a successful three-week flight test of the RAMS system at Patuxent River Flight Test Center in September 1997. The flight test results demonstrated that stress-wave acoustic emission technology can detect signals equivalent to small fatigue cracks in rotor head components and can do so across the rotating articulated rotor head joints and in the presence of other background acoustic noise generated during flight operation. This paper presents the results of stress wave data analysis of the flight-test dataset using wavelet-based techniques to assess background operational noise vs. machinery failure detection results.

  9. Reliability of a Simple Method for Determining Salt Taste Detection and Recognition Thresholds.

    PubMed

    Giguère, Jean-François; Piovesana, Paula de Moura; Proulx-Belhumeur, Alexandra; Doré, Michel; Sampaio, Karina de Lemos; Gallani, Maria-Cecilia

    2016-03-01

    The aim of this study was to assess the reliability of a rapid analytical method to determine salt taste detection and recognition thresholds based on the ASTM E679 method. Reliability was evaluated according to criterion of temporal stability with a 1-week interval test-retest, with 29 participants. Thresholds were assessed by using the 3-AFC technique with 15 ascending concentrations of salt solution (1-292 mM, 1.5-fold steps) and estimated by 2 approaches: individual (geometric means) and group (graphical) thresholds. The proportion of agreement between the test and retest results was estimated using intraclass coefficient correlations. The detection and recognition thresholds calculated by the geometric mean were 2.8 and 18.6mM at session 1 and 2.3 and 14.5mM at session 2 and according to the graphical approach, 2.7 and 18.6mM at session 1 and 1.7 and 16.3mM at session 2. The proportion of agreement between test and retest for the detection and recognition thresholds was 0.430 (95% CI: 0.080-0.680) and 0.660 (95% CI: 0.400-0.830). This fast and simple method to assess salt taste detection and recognition thresholds demonstrated satisfactory evidence of reliability and it could be useful for large population studies. PMID:26733539

  10. Detection thresholds for 2-isopropyl-3-methoxypyrazine in Concord and Niagara grape juice.

    PubMed

    Pickering, G J; Karthik, A; Inglis, D; Sears, M; Ker, K

    2008-08-01

    2-isopropyl-3-methoxypyrazine (IPMP) is the compound responsible for the off-flavor known as ladybug taint, which occurs when Harmnonia axyridis beetles become incorporated with the grapes during juice processing. It is also an important grape-derived component of juice flavor in some varieties. The main objective of this study was to determine the orthonasal (ON) and retronasal (RN) detection thresholds for IPMP in juice. The ASTM E679 ascending forced choice method of limits was used to determine detection thresholds for 26 individuals in Concord and Niagara juices. Group best estimate thresholds (BETs) averaged 0.93 ng/L and were 50% and 21% higher in Concord than in Niagara juices for ON and RN evaluation, respectively. Group BETs for IPMP (ng/L) for Concord were ON: 1.11; RN: 1.02 and for Niagara were ON: 0.74; RN: 0.84. Variation in individual detection thresholds was observed, although familiarity with ladybug taint was not associated with individual threshold values. We conclude that humans are very sensitive to IPMP in juice, and that detection thresholds are more strongly influenced by grape variety than evaluation mode. These results may assist juice producers in establishing tolerance levels for IPMP in juice affected by ladybug taint or derived from grapes of suboptimal ripeness. PMID:19241569

  11. Neuronal detection thresholds during vestibular compensation: contributions of response variability and sensory substitution

    PubMed Central

    Jamali, Mohsen; Mitchell, Diana E; Dale, Alexis; Carriot, Jerome; Sadeghi, Soroush G; Cullen, Kathleen E

    2014-01-01

    The vestibular system is responsible for processing self-motion, allowing normal subjects to discriminate the direction of rotational movements as slow as 1–2 deg s−1. After unilateral vestibular injury patients’ direction–discrimination thresholds worsen to ∼20 deg s−1, and despite some improvement thresholds remain substantially elevated following compensation. To date, however, the underlying neural mechanisms of this recovery have not been addressed. Here, we recorded from first-order central neurons in the macaque monkey that provide vestibular information to higher brain areas for self-motion perception. Immediately following unilateral labyrinthectomy, neuronal detection thresholds increased by more than two-fold (from 14 to 30 deg s−1). While thresholds showed slight improvement by week 3 (25 deg s−1), they never recovered to control values – a trend mirroring the time course of perceptual thresholds in patients. We further discovered that changes in neuronal response variability paralleled changes in sensitivity for vestibular stimulation during compensation, thereby causing detection thresholds to remain elevated over time. However, we found that in a subset of neurons, the emergence of neck proprioceptive responses combined with residual vestibular modulation during head-on-body motion led to better neuronal detection thresholds. Taken together, our results emphasize that increases in response variability to vestibular inputs ultimately constrain neural thresholds and provide evidence that sensory substitution with extravestibular (i.e. proprioceptive) inputs at the first central stage of vestibular processing is a neural substrate for improvements in self-motion perception following vestibular loss. Thus, our results provide a neural correlate for the patient benefits provided by rehabilitative strategies that take advantage of the convergence of these multisensory cues. PMID:24366259

  12. Neurometric amplitude-modulation detection threshold in the guinea-pig ventral cochlear nucleus.

    PubMed

    Sayles, Mark; Füllgrabe, Christian; Winter, Ian M

    2013-07-01

    Amplitude modulation (AM) is a pervasive feature of natural sounds. Neural detection and processing of modulation cues is behaviourally important across species. Although most ecologically relevant sounds are not fully modulated, physiological studies have usually concentrated on fully modulated (100% modulation depth) signals. Psychoacoustic experiments mainly operate at low modulation depths, around detection threshold (∼5% AM). We presented sinusoidal amplitude-modulated tones, systematically varying modulation depth between zero and 100%, at a range of modulation frequencies, to anaesthetised guinea-pigs while recording spikes from neurons in the ventral cochlear nucleus (VCN). The cochlear nucleus is the site of the first synapse in the central auditory system. At this locus significant signal processing occurs with respect to representation of AM signals. Spike trains were analysed in terms of the vector strength of spike synchrony to the amplitude envelope. Neurons showed either low-pass or band-pass temporal modulation transfer functions, with the proportion of band-pass responses increasing with increasing sound level. The proportion of units showing a band-pass response varies with unit type: sustained chopper (CS) > transient chopper (CT) > primary-like (PL). Spike synchrony increased with increasing modulation depth. At the lowest modulation depth (6%), significant spike synchrony was only observed near to the unit's best modulation frequency for all unit types tested. Modulation tuning therefore became sharper with decreasing modulation depth. AM detection threshold was calculated for each individual unit as a function of modulation frequency. Chopper units have significantly better AM detection thresholds than do primary-like units. AM detection threshold is significantly worse at 40 dB vs. 10 dB above pure-tone spike rate threshold. Mean modulation detection thresholds for sounds 10 dB above pure-tone spike rate threshold at best modulation

  13. An Optional Threshold with Svm Cloud Detection Algorithm and Dsp Implementation

    NASA Astrophysics Data System (ADS)

    Zhou, Guoqing; Zhou, Xiang; Yue, Tao; Liu, Yilong

    2016-06-01

    This paper presents a method which combines the traditional threshold method and SVM method, to detect the cloud of Landsat-8 images. The proposed method is implemented using DSP for real-time cloud detection. The DSP platform connects with emulator and personal computer. The threshold method is firstly utilized to obtain a coarse cloud detection result, and then the SVM classifier is used to obtain high accuracy of cloud detection. More than 200 cloudy images from Lansat-8 were experimented to test the proposed method. Comparing the proposed method with SVM method, it is demonstrated that the cloud detection accuracy of each image using the proposed algorithm is higher than those of SVM algorithm. The results of the experiment demonstrate that the implementation of the proposed method on DSP can effectively realize the real-time cloud detection accurately.

  14. Thresholding for biological material detection in real-time multispectral imaging

    NASA Astrophysics Data System (ADS)

    Yoon, Seung Chul; Park, Bosoon; Lawrence, Kurt C.; Windham, William R.

    2005-09-01

    Recently, hyperspectral image analysis has proved successful for a target detection problem encountered in remote sensing as well as near sensing utilizing in situ instrumentation. The conventional global bi-level thresholding for target detection, such as the clustering-based Otsu's method, has been inadequate for the detection of biologically harmful material on foods that has a large degree of variability in size, location, color, shape, texture, and occurrence time. This paper presents multistep-like thresholding based on kernel density estimation for the real-time detection of harmful contaminants on a food product presented in multispectral images. We are particularly concerned with the detection of fecal contaminants on poultry carcasses in real-time. In the past, we identified 2 optimal wavelength bands and developed a real-time multispectral imaging system using a common aperture camera and a globally optimized thresholding method from a ratio of the optimal bands. This work extends our previous study by introducing a new decision rule to detect fecal contaminants on a single bird level. The underlying idea is to search for statistical separability along the two directions defined by the global optimal threshold vector and its orthogonal vector. Experimental results with real birds and fecal samples in different amounts are provided.

  15. Comparisons between detection threshold and loudness perception for individual cochlear implant channels

    PubMed Central

    Bierer, Julie Arenberg; Nye, Amberly D

    2014-01-01

    Objective The objective of the present study, performed in cochlear implant listeners, was to examine how the level of current required to detect single-channel electrical pulse trains relates to loudness perception on the same channel. The working hypothesis was that channels with relatively high thresholds, when measured with a focused current pattern, interface poorly to the auditory nerve. For such channels a smaller dynamic range between perceptual threshold and the most comfortable loudness would result, in part, from a greater sensitivity to changes in electrical field spread compared to low-threshold channels. The narrower range of comfortable listening levels may have important implications for speech perception. Design Data were collected from eight, adult cochlear implant listeners implanted with the HiRes90k cochlear implant (Advanced Bionics Corp.). The partial tripolar (pTP) electrode configuration, consisting of one intracochlear active electrode, two flanking electrodes carrying a fraction (σ) of the return current, and an extracochlear ground, was used for stimulation. Single-channel detection thresholds and most comfortable listening levels were acquired using the most focused pTP configuration possible (σ ≥ 0.8) to identify three channels for further testing – those with the highest, median, and lowest thresholds – for each subject. Threshold, equal-loudness contours (at 50% of the monopolar dynamic range), and loudness growth functions were measured for each of these three test channels using various partial tripolar fractions. Results For all test channels, thresholds increased as the electrode configuration became more focused. The rate of increase with the focusing parameter σ was greatest for the high-threshold channel compared to the median- and low-threshold channels. The 50% equal-loudness contours exhibited similar rates of increase in level across test channels and subjects. Additionally, test channels with the highest

  16. Stress lowers the detection threshold for foul-smelling 2-mercaptoethanol.

    PubMed

    Pacharra, Marlene; Schäper, Michael; Kleinbeck, Stefan; Blaszkewicz, Meinolf; Wolf, Oliver T; van Thriel, Christoph

    2016-01-01

    Previous studies have reported enhanced vigilance for threat-related information in response to acute stress. While it is known that acute stress modulates sensory systems in humans, its impact on olfaction and the olfactory detection of potential threats is less clear. Two psychophysical experiments examined, if acute stress lowers the detection threshold for foul-smelling 2-mercaptoethanol. Participants in Experiment 1 (N = 30) and Experiment 2 (N = 32) were randomly allocated to a control group or a stress group. Participants in the stress group underwent a purely psychosocial stressor (public mental arithmetic) in Experiment 1 and a stressor that combined a physically demanding task with social-evaluative threat in Experiment 2 (socially evaluated cold-pressor test). In both experiments, olfactory detection thresholds were repeatedly assessed by means of dynamic dilution olfactometry. Each threshold measurement consisted of three trials conducted using an ascending method of limits. Participants in the stress groups showed the expected changes in heart rate, salivary cortisol, and mood measures in response to stress. About 20 min after the stressor, participants in the stress groups could detect 2-mercaptoethanol at a lower concentration than participants in the corresponding control groups. Our results show that acute stress lowers the detection threshold for a malodor.

  17. Cooperative Spectrum Sensing with Multiple Antennas Using Adaptive Double-Threshold Based Energy Detector in Cognitive Radio Networks

    NASA Astrophysics Data System (ADS)

    Bagwari, A.; Tomar, G. S.

    2014-04-01

    In Cognitive radio networks, spectrum sensing is used to sense the unused spectrum in an opportunistic manner. In this paper, multiple antennas based energy detector utilizing adaptive double-threshold for spectrum sensing is proposed, which enhances detection performance and overcomes sensing failure problem as well. The detection threshold is made adaptive to the fluctuation of the received signal power in each local detector of cognitive radio (CR) user. Numerical results show that by using multiple antennas at the CRs, it is possible to significantly improve detection performance at very low signal-to-noise ratio (SNR). Further, the scheme was analyzed in conjunction with cooperative spectrum sensing (CSS), where CRs utilize selection combining of the decision statistics obtained by an adaptive double-threshold energy detector for making a binary decision of the presence or absence of a primary user. The decision of each CR is forwarded over error free orthogonal channels to the fusion centre, which takes the final decision of a spectrum hole. It is further found that CSS with multiple antenna-based energy detector with adaptive double-threshold improves detection performance around 26.8 % as compared to hierarchical with quantization method at -12 dB SNR, under the condition that a small number of sensing nodes are used in spectrum sensing.

  18. The effects of age on sensory thresholds and temporal gap detection in hearing, vision, and touch

    PubMed Central

    Humes, Larry E.; Busey, Thomas A.; Craig, James C.; Kewley-Port, Diane

    2010-01-01

    Differences in sensory function between young (n = 42, 18–31 years old) and older (n = 137, 60–88 years old) adults were examined for auditory, visual, and tactile measures of threshold sensitivity and temporal acuity (gap-detection threshold). For all but one of the psychophysical measures (visual gap detection), multiple measures were obtained at different stimulus frequencies for each modality and task. This resulted in a total of 14 dependent measures, each based on four to six adaptive psychophysical estimates of 75% correct performance. In addition, all participants completed the Wechsler Adult Intelligence Scale (Wechsler, 1997). Mean data confirmed previously observed differences in performance between young and older adults for 13 of the 14 dependent measures (all but visual threshold at a flicker frequency of 4 Hz). Correlational and principal-components factor analyses performed on the data from the 137 older adults were generally consistent with task and modality independence of the psychophysical measures. PMID:19429964

  19. A threshold-based approach for muscle contraction detection from surface EMG signals

    NASA Astrophysics Data System (ADS)

    Morantes, Gaudi; Fernández, Gerardo; Altuve, Miguel

    2013-11-01

    Surface electromyographic (SEMG) signals are commonly used as control signals in prosthetic and orthotic devices. Super cial electrodes are placed on the skin of the subject to acquire its muscular activity through this signal. The muscle contraction episode is then in charge of activating and deactivating these devices. Nevertheless, there is no gold standard" to detect muscle contraction, leading to delayed responses and false and missed detections. This fact motivated us to propose a new approach that compares a smoothed version of the SEMG signal with a xed threshold, in order to detect muscle contraction episodes. After preprocessing the SEMG signal, the smoothed version is obtained using a moving average lter, where three di erent window lengths has been evaluated. The detector was tuned by maximizing sensitivity and speci city and evaluated using SEMG signals obtained from the anterior tibial and gastrocnemius muscles, taken during the walking of ve subjects. Compared with traditional detection methods, we obtain a reduction of 3 ms in the detection delay, an increase of 8% in sensitivity but a decrease of 15% in speci city. Future work is directed to the inclusion of a temporal threshold (a double-threshold approach) to minimize false detections and reduce detection delays.

  20. Olfactory Detection Thresholds and Adaptation in Adults with Autism Spectrum Condition

    ERIC Educational Resources Information Center

    Tavassoli, T.; Baron-Cohen, S.

    2012-01-01

    Sensory issues have been widely reported in Autism Spectrum Conditions (ASC). Since olfaction is one of the least investigated senses in ASC, the current studies explore olfactory detection thresholds and adaptation to olfactory stimuli in adults with ASC. 80 participants took part, 38 (18 females, 20 males) with ASC and 42 control participants…

  1. [A cloud detection algorithm for MODIS images combining Kmeans clustering and multi-spectral threshold method].

    PubMed

    Wang, Wei; Song, Wei-Guo; Liu, Shi-Xing; Zhang, Yong-Ming; Zheng, Hong-Yang; Tian, Wei

    2011-04-01

    An improved method for detecting cloud combining Kmeans clustering and the multi-spectral threshold approach is described. On the basis of landmark spectrum analysis, MODIS data is categorized into two major types initially by Kmeans method. The first class includes clouds, smoke and snow, and the second class includes vegetation, water and land. Then a multi-spectral threshold detection is applied to eliminate interference such as smoke and snow for the first class. The method is tested with MODIS data at different time under different underlying surface conditions. By visual method to test the performance of the algorithm, it was found that the algorithm can effectively detect smaller area of cloud pixels and exclude the interference of underlying surface, which provides a good foundation for the next fire detection approach.

  2. Thermal nociceptive threshold testing detects altered sensory processing in broiler chickens with spontaneous lameness.

    PubMed

    Hothersall, Becky; Caplen, Gina; Parker, Richard M A; Nicol, Christine J; Waterman-Pearson, Avril E; Weeks, Claire A; Murrell, Joanna C

    2014-01-01

    Lameness is common in commercially reared broiler chickens but relationships between lameness and pain (and thus bird welfare) have proved complex, partly because lameness is often partially confounded with factors such as bodyweight, sex and pathology. Thermal nociceptive threshold (TNT) testing explores the neural processing of noxious stimuli, and so can contribute to our understanding of pain. Using an acute model of experimentally induced articular pain, we recently demonstrated that TNT was reduced in lame broiler chickens, and was subsequently attenuated by administration of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs). This study extended these findings to a large sample of commercial broilers. It examined factors affecting thermal threshold (Part 1) and the effect of an NSAID drug (meloxicam, 5 mg/kg) and of an opioid (butorphanol; 4 mg/kg) (Part 2). Spontaneously lame and matched non-lame birds (n=167) from commercial farms were exposed to ramped thermal stimulations via a probe attached to the lateral aspect of the tarsometatarsus. Baseline skin temperature and temperature at which a behavioural avoidance response occurred (threshold) were recorded. In Part 1 bird characteristics influencing threshold were modelled; In Part 2 the effect of subcutaneous administration of meloxicam or butorphanol was investigated. Unexpectedly, after accounting for other influences, lameness increased threshold significantly (Part 1). In Part 2, meloxicam affected threshold differentially: it increased further in lame birds and decreased in non-lame birds. No effect of butorphanol was detected. Baseline skin temperature was also consistently a significant predictor of threshold. Overall, lameness significantly influenced threshold after other bird characteristics were taken into account. This, and a differential effect of meloxicam on lame birds, suggests that nociceptive processing may be altered in lame birds, though mechanisms for this require further investigation

  3. Detection thresholds for amplitude modulations of tones in budgerigar, rabbit, and human.

    PubMed

    Carney, Laurel H; Ketterer, Angela D; Abrams, Kristina S; Schwarz, Douglas M; Idrobo, Fabio

    2013-01-01

    Envelope fluctuations of complex sounds carry information that is -essential for many types of discrimination and for detection in noise. To study the neural representation of envelope information and mechanisms for processing of this temporal aspect of sounds, it is useful to identify an animal model that can -sensitively detect amplitude modulations (AM). Low modulation frequencies, which dominate speech sounds, are of particular interest. Yet, most animal -models studied previously are relatively insensitive to AM at low modulation -frequencies. Rabbits have high thresholds for low-frequency modulations, -especially for tone carriers. Rhesus macaques are less sensitive than humans to low-frequency -modulations of wideband noise (O'Conner et al. Hear Res 277, 37-43, 2011). Rats and -chinchilla also have higher thresholds than humans for amplitude -modulations of noise (Kelly et al. J Comp Psychol 120, 98-105, 2006; Henderson et al. J Acoust Soc Am 75, -1177-1183, 1984). In contrast, the budgerigar has thresholds for AM detection of wideband noise similar to those of human listeners at low -modulation frequencies (Dooling and Searcy. Percept Psychophys 46, 65-71, 1981). A -one-interval, two-alternative operant conditioning procedure was used to estimate AM -detection thresholds for 4-kHz tone carriers at low modulation -frequencies (4-256 Hz). Budgerigar thresholds are comparable to those of human subjects in a comparable task. Implications of these comparative results for temporal coding of complex sounds are discussed. Comparative results for masked AM detection are also presented. PMID:23716245

  4. Detectability Thresholds and Optimal Algorithms for Community Structure in Dynamic Networks

    NASA Astrophysics Data System (ADS)

    Ghasemian, Amir; Zhang, Pan; Clauset, Aaron; Moore, Cristopher; Peel, Leto

    2016-07-01

    The detection of communities within a dynamic network is a common means for obtaining a coarse-grained view of a complex system and for investigating its underlying processes. While a number of methods have been proposed in the machine learning and physics literature, we lack a theoretical analysis of their strengths and weaknesses, or of the ultimate limits on when communities can be detected. Here, we study the fundamental limits of detecting community structure in dynamic networks. Specifically, we analyze the limits of detectability for a dynamic stochastic block model where nodes change their community memberships over time, but where edges are generated independently at each time step. Using the cavity method, we derive a precise detectability threshold as a function of the rate of change and the strength of the communities. Below this sharp threshold, we claim that no efficient algorithm can identify the communities better than chance. We then give two algorithms that are optimal in the sense that they succeed all the way down to this threshold. The first uses belief propagation, which gives asymptotically optimal accuracy, and the second is a fast spectral clustering algorithm, based on linearizing the belief propagation equations. These results extend our understanding of the limits of community detection in an important direction, and introduce new mathematical tools for similar extensions to networks with other types of auxiliary information.

  5. Measurement of Vibration Detection Threshold and Tactile Spatial Acuity in Human Subjects.

    PubMed

    Moshourab, Rabih; Frenzel, Henning; Lechner, Stefan; Haseleu, Julia; Bégay, Valérie; Omerbašić, Damir; Lewin, Gary R

    2016-01-01

    Tests that allow the precise determination of psychophysical thresholds for vibration and grating orientation provide valuable information about mechanosensory function that are relevant for clinical diagnosis as well as for basic research. Here, we describe two psychophysical tests designed to determine the vibration detection threshold (automated system) and tactile spatial acuity (handheld device). Both procedures implement a two-interval forced-choice and a transformed-rule up and down experimental paradigm. These tests have been used to obtain mechanosensory profiles for individuals from distinct human cohorts such as twins or people with sensorineural deafness. PMID:27684317

  6. Fusion of threshold rules for target detection in wireless sensor networks

    SciTech Connect

    Zhu, Mengxia; Ding, Shi-You; Brooks, Richard R; Wu, Qishi; Rao, Nageswara S

    2010-03-01

    We propose a binary decision fusion rule that reaches a global decision on the presence of a target by integrating local decisions made by multiple sensors. Without requiring a priori probability of target presence, the fusion threshold bounds derived using Chebyshev's inequality ensure a higher hit rate and lower false alarm rate compared to the weighted averages of individual sensors. The Monte Carlo-based simulation results show that the proposed approach significantly improves target detection performance, and can also be used to guide the actual threshold selection in practical sensor network implementation under certain error rate constraints.

  7. Determination of ortho- and retronasal detection thresholds for 2-isopropyl-3-methoxypyrazine in wine.

    PubMed

    Pickering, G J; Karthik, A; Inglis, D; Sears, M; Ker, K

    2007-09-01

    2-Isopropyl-3-methoxypyrazine (IPMP) is a grape-derived component of wine flavor in some wine varieties as well as the causal compound of the off-flavor known as ladybug taint (LBT), which occurs when Harmonia axyridis beetles are incorporated with the grapes during juice and wine processing. The main objective of this study was to obtain robust estimates of the orthonasal (ON) and retronasal (RN) detection thresholds (DTs) for IPMP in wines of differing styles. The ASTM E679 ascending forced choice method of limits was used to determine DTs for 47 individuals in 3 different wines--Chardonnay, Gewürztraminer, and a red wine blend of Baco Noir and Marechel Foch. The group best estimate thresholds (BETs) obtained for IPMP (ng/L) were Chardonnay, ON: 0.32; Gewürztraminer, ON: 1.56, RN: 1.15, and red wine blend, ON: 1.03, RN: 2.29. A large variation in individual DTs was observed. Familiarity with LBT was inversely correlated with DTs for Gewürztraminer, and no difference in thresholds was observed between winemakers and nonwinemakers. We conclude that the human DT for IPMP is extremely low and influenced significantly by wine style and evaluation mode. We recommend against the reporting of single-threshold values for wine flavor compounds, and encourage the determination of consumer rejection thresholds for IPMP in wine. PMID:17995659

  8. Simulated performance of an order statistic threshold strategy for detection of narrowband signals

    NASA Technical Reports Server (NTRS)

    Satorius, E.; Brady, R.; Deich, W.; Gulkis, S.; Olsen, E.

    1988-01-01

    The application of order statistics to signal detection is becoming an increasingly active area of research. This is due to the inherent robustness of rank estimators in the presence of large outliers that would significantly degrade more conventional mean-level-based detection systems. A detection strategy is presented in which the threshold estimate is obtained using order statistics. The performance of this algorithm in the presence of simulated interference and broadband noise is evaluated. In this way, the robustness of the proposed strategy in the presence of the interference can be fully assessed as a function of the interference, noise, and detector parameters.

  9. Fisher's linear discriminant ratio based threshold for moving human detection in thermal video

    NASA Astrophysics Data System (ADS)

    Sharma, Lavanya; Yadav, Dileep Kumar; Singh, Annapurna

    2016-09-01

    In video surveillance, the moving human detection in thermal video is a critical phase that filters out redundant information to extract relevant information. The moving object detection is applied on thermal video because it penetrate challenging problems such as dynamic issues of background and illumination variation. In this work, we have proposed a new background subtraction method using Fisher's linear discriminant ratio based threshold. This threshold is investigated automatically during run-time for each pixel of every sequential frame. Automatically means to avoid the involvement of external source such as programmer or user for threshold selection. This threshold provides better pixel classification at run-time. This method handles problems generated due to multiple behavior of background more accurately using Fisher's ratio. It maximizes the separation between object pixel and the background pixel. To check the efficacy, the performance of this work is observed in terms of various parameters depicted in analysis. The experimental results and their analysis demonstrated better performance of proposed method against considered peer methods.

  10. Input-output relation and energy efficiency in the neuron with different spike threshold dynamics

    PubMed Central

    Yi, Guo-Sheng; Wang, Jiang; Tsang, Kai-Ming; Wei, Xi-Le; Deng, Bin

    2015-01-01

    Neuron encodes and transmits information through generating sequences of output spikes, which is a high energy-consuming process. The spike is initiated when membrane depolarization reaches a threshold voltage. In many neurons, threshold is dynamic and depends on the rate of membrane depolarization (dV/dt) preceding a spike. Identifying the metabolic energy involved in neural coding and their relationship to threshold dynamic is critical to understanding neuronal function and evolution. Here, we use a modified Morris-Lecar model to investigate neuronal input-output property and energy efficiency associated with different spike threshold dynamics. We find that the neurons with dynamic threshold sensitive to dV/dt generate discontinuous frequency-current curve and type II phase response curve (PRC) through Hopf bifurcation, and weak noise could prohibit spiking when bifurcation just occurs. The threshold that is insensitive to dV/dt, instead, results in a continuous frequency-current curve, a type I PRC and a saddle-node on invariant circle bifurcation, and simultaneously weak noise cannot inhibit spiking. It is also shown that the bifurcation, frequency-current curve and PRC type associated with different threshold dynamics arise from the distinct subthreshold interactions of membrane currents. Further, we observe that the energy consumption of the neuron is related to its firing characteristics. The depolarization of spike threshold improves neuronal energy efficiency by reducing the overlap of Na+ and K+ currents during an action potential. The high energy efficiency is achieved at more depolarized spike threshold and high stimulus current. These results provide a fundamental biophysical connection that links spike threshold dynamics, input-output relation, energetics and spike initiation, which could contribute to uncover neural encoding mechanism. PMID:26074810

  11. Input-output relation and energy efficiency in the neuron with different spike threshold dynamics.

    PubMed

    Yi, Guo-Sheng; Wang, Jiang; Tsang, Kai-Ming; Wei, Xi-Le; Deng, Bin

    2015-01-01

    Neuron encodes and transmits information through generating sequences of output spikes, which is a high energy-consuming process. The spike is initiated when membrane depolarization reaches a threshold voltage. In many neurons, threshold is dynamic and depends on the rate of membrane depolarization (dV/dt) preceding a spike. Identifying the metabolic energy involved in neural coding and their relationship to threshold dynamic is critical to understanding neuronal function and evolution. Here, we use a modified Morris-Lecar model to investigate neuronal input-output property and energy efficiency associated with different spike threshold dynamics. We find that the neurons with dynamic threshold sensitive to dV/dt generate discontinuous frequency-current curve and type II phase response curve (PRC) through Hopf bifurcation, and weak noise could prohibit spiking when bifurcation just occurs. The threshold that is insensitive to dV/dt, instead, results in a continuous frequency-current curve, a type I PRC and a saddle-node on invariant circle bifurcation, and simultaneously weak noise cannot inhibit spiking. It is also shown that the bifurcation, frequency-current curve and PRC type associated with different threshold dynamics arise from the distinct subthreshold interactions of membrane currents. Further, we observe that the energy consumption of the neuron is related to its firing characteristics. The depolarization of spike threshold improves neuronal energy efficiency by reducing the overlap of Na(+) and K(+) currents during an action potential. The high energy efficiency is achieved at more depolarized spike threshold and high stimulus current. These results provide a fundamental biophysical connection that links spike threshold dynamics, input-output relation, energetics and spike initiation, which could contribute to uncover neural encoding mechanism.

  12. Ischemia detection using Isoelectric Energy Function.

    PubMed

    Kumar, Amit; Singh, Mandeep

    2016-01-01

    A novel method has been proposed for the detection of ischemia using an isoelectric energy function (IEEF) resulting from ST segment deviations in ECG signals. The method consists of five stages: pre-processing, delineation, measurement of isoelectric energy, a beat characterization algorithm and detection of ischemia. The isoelectric energy threshold is used to differentiate ischemic beats from normal beats for ischemic episode detection. Then, ischemic episodes are classified as transmural or subendocardial. The method is validated for recordings of the annotated European ST-T database (EDB). The results show 98.12% average sensitivity (SE) and 98.16% average specificity (SP). These results are significantly better than those of existing methods cited in the literature. The advantage of the proposed method includes simplicity, ruggedness and automatic discarding of noisy beats. PMID:26623944

  13. Ischemia detection using Isoelectric Energy Function.

    PubMed

    Kumar, Amit; Singh, Mandeep

    2016-01-01

    A novel method has been proposed for the detection of ischemia using an isoelectric energy function (IEEF) resulting from ST segment deviations in ECG signals. The method consists of five stages: pre-processing, delineation, measurement of isoelectric energy, a beat characterization algorithm and detection of ischemia. The isoelectric energy threshold is used to differentiate ischemic beats from normal beats for ischemic episode detection. Then, ischemic episodes are classified as transmural or subendocardial. The method is validated for recordings of the annotated European ST-T database (EDB). The results show 98.12% average sensitivity (SE) and 98.16% average specificity (SP). These results are significantly better than those of existing methods cited in the literature. The advantage of the proposed method includes simplicity, ruggedness and automatic discarding of noisy beats.

  14. Fast microcalcification detection in ultrasound images using image enhancement and threshold adjacency statistics

    NASA Astrophysics Data System (ADS)

    Cho, Baek Hwan; Chang, Chuho; Lee, Jong-Ha; Ko, Eun Young; Seong, Yeong Kyeong; Woo, Kyoung-Gu

    2013-02-01

    The existence of microcalcifications (MCs) is an important marker of malignancy in breast cancer. In spite of the benefits in mass detection for dense breasts, ultrasonography is believed that it might not reliably detect MCs. For computer aided diagnosis systems, however, accurate detection of MCs has the possibility of improving the performance in both Breast Imaging-Reporting and Data System (BI-RADS) lexicon description for calcifications and malignancy classification. We propose a new efficient and effective method for MC detection using image enhancement and threshold adjacency statistics (TAS). The main idea of TAS is to threshold an image and to count the number of white pixels with a given number of adjacent white pixels. Our contribution is to adopt TAS features and apply image enhancement to facilitate MC detection in ultrasound images. We employed fuzzy logic, tophat filter, and texture filter to enhance images for MCs. Using a total of 591 images, the classification accuracy of the proposed method in MC detection showed 82.75%, which is comparable to that of Haralick texture features (81.38%). When combined, the performance was as high as 85.11%. In addition, our method also showed the ability in mass classification when combined with existing features. In conclusion, the proposed method exploiting image enhancement and TAS features has the potential to deal with MC detection in ultrasound images efficiently and extend to the real-time localization and visualization of MCs.

  15. A Universal Dynamic Threshold Cloud Detection Algorithm (UDTCDA) supported by a prior surface reflectance database

    NASA Astrophysics Data System (ADS)

    Sun, Lin; Wei, Jing; Wang, Jian; Mi, Xueting; Guo, Yamin; Lv, Yang; Yang, Yikun; Gan, Ping; Zhou, Xueying; Jia, Chen; Tian, Xinpeng

    2016-06-01

    Conventional cloud detection methods are easily affected by mixed pixels, complex surface structures, and atmospheric factors, resulting in poor cloud detection results. To minimize these problems, a new Universal Dynamic Threshold Cloud Detection Algorithm (UDTCDA) supported by a priori surface reflectance database is proposed in this paper. A monthly surface reflectance database is constructed using long-time-sequenced MODerate resolution Imaging Spectroradiometer surface reflectance product (MOD09A1) to provide the surface reflectance of the underlying surfaces. The relationships between the apparent reflectance changes and the surface reflectance are simulated under different observation and atmospheric conditions with the 6S (Second Simulation of the Satellite Signal in the Solar Spectrum) model, and the dynamic threshold cloud detection models are developed. Two typical remote sensing data with important application significance and different sensor parameters, MODIS and Landsat 8, are selected for cloud detection experiments. The results were validated against the visual interpretation of clouds and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation cloud measurements. The results showed that the UDTCDA can obtain a high precision in cloud detection, correctly identifying cloudy pixels and clear-sky pixels at rates greater than 80% with error rate and missing rate of less than 20%. The UDTCDA cloud product overall shows less estimation uncertainty than the current MODIS cloud mask products. Moreover, the UDTCDA can effectively reduce the effects of atmospheric factors and mixed pixels and can be applied to different satellite sensors to realize long-term, large-scale cloud detection operations.

  16. Adaptive Thresholds

    SciTech Connect

    Bremer, P. -T.

    2014-08-26

    ADAPT is a topological analysis code that allow to compute local threshold, in particular relevance based thresholds for features defined in scalar fields. The initial target application is vortex detection but the software is more generally applicable to all threshold based feature definitions.

  17. Reduced visual surround suppression in schizophrenia shown by measuring contrast detection thresholds

    PubMed Central

    Serrano-Pedraza, Ignacio; Romero-Ferreiro, Verónica; Read, Jenny C. A.; Diéguez-Risco, Teresa; Bagney, Alexandra; Caballero-González, Montserrat; Rodríguez-Torresano, Javier; Rodriguez-Jimenez, Roberto

    2014-01-01

    Visual perception in schizophrenia is attracting a broad interest given the deep knowledge that we have about the visual system in healthy populations. One example is the class of effects known collectively as visual surround suppression. For example, the visibility of a grating located in the visual periphery is impaired by the presence of a surrounding grating of the same spatial frequency and orientation. Previous studies have suggested abnormal visual surround suppression in patients with schizophrenia. Given that schizophrenia patients have cortical alterations including hypofunction of NMDA receptors and reduced concentration of GABA neurotransmitter, which affect lateral inhibitory connections, then they should be relatively better than controls at detecting visual stimuli that are usually suppressed. We tested this hypothesis by measuring contrast detection thresholds using a new stimulus configuration. We tested two groups: 21 schizophrenia patients and 24 healthy subjects. Thresholds were obtained using Bayesian staircases in a four-alternative forced-choice detection task where the target was a grating within a 3∘ Butterworth window that appeared in one of four possible positions at 5∘ eccentricity. We compared three conditions, (a) target with no-surround, (b) target embedded within a surrounding grating of 20∘ diameter and 25% contrast with same spatial frequency and orthogonal orientation, and (c) target embedded within a surrounding grating with parallel (same) orientation. Previous results with healthy populations have shown that contrast thresholds are lower for orthogonal and no-surround (NS) conditions than for parallel surround (PS). The log-ratios between parallel and NS thresholds are used as an index quantifying visual surround suppression. Patients performed poorly compared to controls in the NS and orthogonal-surround conditions. However, they performed as well as controls when the surround was parallel, resulting in significantly

  18. Shape anomaly detection under strong measurement noise: An analytical approach to adaptive thresholding

    NASA Astrophysics Data System (ADS)

    Krasichkov, Alexander S.; Grigoriev, Eugene B.; Bogachev, Mikhail I.; Nifontov, Eugene M.

    2015-10-01

    We suggest an analytical approach to the adaptive thresholding in a shape anomaly detection problem. We find an analytical expression for the distribution of the cosine similarity score between a reference shape and an observational shape hindered by strong measurement noise that depends solely on the noise level and is independent of the particular shape analyzed. The analytical treatment is also confirmed by computer simulations and shows nearly perfect agreement. Using this analytical solution, we suggest an improved shape anomaly detection approach based on adaptive thresholding. We validate the noise robustness of our approach using typical shapes of normal and pathological electrocardiogram cycles hindered by additive white noise. We show explicitly that under high noise levels our approach considerably outperforms the conventional tactic that does not take into account variations in the noise level.

  19. Electron-nuclear energy sharing in above-threshold multiphoton dissociative ionization of H2.

    PubMed

    Wu, J; Kunitski, M; Pitzer, M; Trinter, F; Schmidt, L Ph H; Jahnke, T; Magrakvelidze, M; Madsen, C B; Madsen, L B; Thumm, U; Dörner, R

    2013-07-12

    We report experimental observation of the energy sharing between electron and nuclei in above-threshold multiphoton dissociative ionization of H2 by strong laser fields. The absorbed photon energy is shared between the ejected electron and nuclei in a correlated fashion, resulting in multiple diagonal lines in their joint energy spectrum governed by the energy conservation of all fragment particles.

  20. Innovative qPCR using interfacial effects to enable low threshold cycle detection and inhibition relief

    PubMed Central

    Harshman, Dustin K.; Rao, Brianna M.; McLain, Jean E.; Watts, George S.; Yoon, Jeong-Yeol

    2015-01-01

    Molecular diagnostics offers quick access to information but fails to operate at a speed required for clinical decision-making. Our novel methodology, droplet-on-thermocouple silhouette real-time polymerase chain reaction (DOTS qPCR), uses interfacial effects for droplet actuation, inhibition relief, and amplification sensing. DOTS qPCR has sample-to-answer times as short as 3 min 30 s. In infective endocarditis diagnosis, DOTS qPCR demonstrates reproducibility, differentiation of antibiotic susceptibility, subpicogram limit of detection, and thermocycling speeds of up to 28 s/cycle in the presence of tissue contaminants. Langmuir and Gibbs adsorption isotherms are used to describe the decreasing interfacial tension upon amplification. Moreover, a log-linear relationship with low threshold cycles is presented for real-time quantification by imaging the droplet-on-thermocouple silhouette with a smartphone. DOTS qPCR resolves several limitations of commercially available real-time PCR systems, which rely on fluorescence detection, have substantially higher threshold cycles, and require expensive optical components and extensive sample preparation. Due to the advantages of low threshold cycle detection, we anticipate extending this technology to biological research applications such as single cell, single nucleus, and single DNA molecule analyses. Our work is the first demonstrated use of interfacial effects for sensing reaction progress, and it will enable point-of-care molecular diagnosis of infections. PMID:26601245

  1. Automated microcalcification detection in mammograms using statistical variable-box-threshold filter method

    NASA Astrophysics Data System (ADS)

    Wilson, Mark; Mitra, Sunanda; Roberson, Glenn H.; Shieh, Yao-Yang

    1997-10-01

    Currently early detection of breast cancer is primarily accomplished by mammography and suspicious findings may lead to a decision for performing a biopsy. Digital enhancement and pattern recognition techniques may aid in early detection of some patterns such as microcalcification clusters indicating onset of DCIS (ductal carcinoma in situ) that accounts for 20% of all mammographically detected breast cancers and could be treated when detected early. These individual calcifications are hard to detect due to size and shape variability and inhomogeneous background texture. Our study addresses only early detection of microcalcifications that allows the radiologist to interpret the x-ray findings in computer-aided enhanced form easier than evaluating the x-ray film directly. We present an algorithm which locates microcalcifications based on local grayscale variability and of tissue structures and image statistics. Threshold filters with lower and upper bounds computed from the image statistics of the entire image and selected subimages were designed to enhance the entire image. This enhanced image was used as the initial image for identifying the micro-calcifications based on the variable box threshold filters at different resolutions. The test images came from the Texas Tech University Health Sciences Center and the MIAS mammographic database, which are classified into various categories including microcalcifications. Classification of other types of abnormalities in mammograms based on their characteristic features is addressed in later studies.

  2. A comparison of signal detection theory to the objective threshold/strategic model of unconscious perception.

    PubMed

    Haase, Steven J; Fisk, Gary D

    2011-08-01

    A key problem in unconscious perception research is ruling out the possibility that weak conscious awareness of stimuli might explain the results. In the present study, signal detection theory was compared with the objective threshold/strategic model as explanations of results for detection and identification sensitivity in a commonly used unconscious perception task. In the task, 64 undergraduate participants detected and identified one of four briefly displayed, visually masked letters. Identification was significantly above baseline (i.e., proportion correct > .25) at the highest detection confidence rating. This result is most consistent with signal detection theory's continuum of sensory states and serves as a possible index of conscious perception. However, there was limited support for the other model in the form of a predicted "looker's inhibition" effect, which produced identification performance that was significantly below baseline. One additional result, an interaction between the target stimulus and type of mask, raised concerns for the generality of unconscious perception effects.

  3. Sodium chloride detection threshold in the rat determined using a simple operant taste discrimination task.

    PubMed

    Slotnick, B M

    1982-04-01

    A method for training rats to lick at high rates for a water reinforcer after presentation of one tastant and to inhibit or decrease response rate to avoid a time-out, punisher after presentation of another tastant is described and evaluated. The method produced rapid acquisition of simple discrimination and detection tasks, The absolute mean detection threshold for sodium chloride in three rats was 0.0038% (0.0031%-0.0043%. The operant conditioning technique is simple, efficient, and should prove useful for psychophysical and physiological studies of gustation. PMID:7079384

  4. Verification of threshold activation detection (TAD) technique in prompt fission neutron detection using scintillators containing 19F

    NASA Astrophysics Data System (ADS)

    Sibczynski, P.; Kownacki, J.; Moszyński, M.; Iwanowska-Hanke, J.; Syntfeld-Każuch, A.; Gójska, A.; Gierlik, M.; Kaźmierczak, Ł.; Jakubowska, E.; Kędzierski, G.; Kujawiński, Ł.; Wojnarowicz, J.; Carrel, F.; Ledieu, M.; Lainé, F.

    2015-09-01

    In the present study ⌀ 5''× 3'' and ⌀ 2''× 2'' EJ-313 liquid fluorocarbon as well as ⌀ 2'' × 3'' BaF2 scintillators were exposed to neutrons from a 252Cf neutron source and a Sodern Genie 16GT deuterium-tritium (D+T) neutron generator. The scintillators responses to β- particles with maximum endpoint energy of 10.4 MeV from the n+19F reactions were studied. Response of a ⌀ 5'' × 3'' BC-408 plastic scintillator was also studied as a reference. The β- particles are the products of interaction of fast neutrons with 19F which is a component of the EJ-313 and BaF2 scintillators. The method of fast neutron detection via fluorine activation is already known as Threshold Activation Detection (TAD) and was proposed for photofission prompt neutron detection from fissionable and Special Nuclear Materials (SNM) in the field of Homeland Security and Border Monitoring. Measurements of the number of counts between 6.0 and 10.5 MeV with a 252Cf source showed that the relative neutron detection efficiency ratio, defined as epsilonBaF2 / epsilonEJ-313-5'', is 32.0% ± 2.3% and 44.6% ± 3.4% for front-on and side-on orientation of the BaF2, respectively. Moreover, the ⌀ 5'' EJ-313 and side-on oriented BaF2 were also exposed to neutrons from the D+T neutron generator, and the relative efficiency epsilonBaF2 / epsilonEJ-313-5'' was estimated to be 39.3%. Measurements of prompt photofission neutrons with the BaF2 detector by means of data acquisition after irradiation (out-of-beam) of nuclear material and between the beam pulses (beam-off) techniques were also conducted on the 9 MeV LINAC of the SAPHIR facility.

  5. Sonar gain control and echo detection thresholds in the echolocating bat, Eptesicus fuscus.

    PubMed

    Simmons, J A; Moffat, A J; Masters, W M

    1992-02-01

    The echolocating bat, Eptesicus fuscus, detects sonar echoes with a sensitivity that changes according to the time elapsed between broadcasting of each sonar signal and reception of echoes. When tested in an electronic target simulator on a two-choice echo-detection task, the bat's threshold improved by 11.5 dB as echo delay changed from 2.3 to 4.6 ms (target ranges of 40 and 80 cm). Earlier experiments measured the change in detection threshold for delays from 1 to 6.4 ms (target ranges from about 17 to 110 cm) and obtained about 11 dB of improvement per doubling of delay. The new experiments used electronic delay lines to simulate echo delay, thus avoiding movement of loudspeakers to different distances and the possible creation of delay-dependent backward masking between stimulus echoes and cluttering echoes from the loudspeaker surfaces. The slope of the threshold shift defines an echo gain control that keeps echoes from point targets at a fixed sensation level--reducing sensitivity by 11 to 12 dB as echo amplitude increases by 12 dB per halving of range during the bat's approach to the target. A recent experiment using loudness discrimination of echoes at 70 to 80 dB SPL (roughly 50 dB above threshold) found a slope of about 6 dB per halving of range, so the gain-control effect may be level dependent. The observed effect is operationally equivalent to forward masking of echoes by the transmission, but any events correlated with vocalization which impair hearing sensitivity for a short interval following transmissions could cause a decline in sensitivity to echoes. Contractions of the bat's middle-ear muscles synchronized to transmissions may account for the observed threshold shift, at least for a span of echo delays associated with the most critical portion of the approach stage of pursuit. Forward masking by the sonar transmissions may contribute to the threshold shift, too, but middle-ear muscle contractions do occur and must be a significant part of the

  6. Thermal detection and pain thresholds but not pressure pain thresholds are correlated with psychological factors in women with chronic whiplash-associated pain.

    PubMed

    Wallin, Mia; Liedberg, Gunilla; Börsbo, Björn; Gerdle, Björn

    2012-01-01

    Whiplash-associated disorders (WAD) have been associated with sensory disturbances such as hypersensitivity or hypoesthesia. Different psychological factors seem to be important for prognosis and symptom presentation in WAD. Multivariate correlations between pain thresholds for pressure (PPT), cold and heat (CPT, HPT), detection thresholds for cold and warmth, pain intensity variables, and psychological aspects in women with chronic WAD (n=28) and in healthy pain-free controls (n=29) were investigated. Quantitative Sensory Testing (QST) for thermal thresholds and algometry for PPT at various sites in the body were used. Psychological aspects, including catastrophizing, anxiety, and depression were registered using a questionnaire. WAD showed generalized decreased PPT and CPT, altered HPT and cold detection thresholds in the upper part of the body, and a worse psychological situation. Multivariate correlations were found between QST and PPT variables, habitual pain, and psychological factors in WAD. Different psychological variables were generally stronger predictors of CPT and HPT than pain intensity in WAD. Pain intensity aspects were generally the strongest predictors of PPT in WAD. In contrast, no correlations existed between QST and PPT variables and psychological variables in controls. These results indicate the need to consider that a blend of factors influences the pain thresholds in chronic WAD and emphasize the need for a biopsychosocial model when interpreting QST and PPT variables. PMID:21750459

  7. Thermal detection and pain thresholds but not pressure pain thresholds are correlated with psychological factors in women with chronic whiplash-associated pain.

    PubMed

    Wallin, Mia; Liedberg, Gunilla; Börsbo, Björn; Gerdle, Björn

    2012-01-01

    Whiplash-associated disorders (WAD) have been associated with sensory disturbances such as hypersensitivity or hypoesthesia. Different psychological factors seem to be important for prognosis and symptom presentation in WAD. Multivariate correlations between pain thresholds for pressure (PPT), cold and heat (CPT, HPT), detection thresholds for cold and warmth, pain intensity variables, and psychological aspects in women with chronic WAD (n=28) and in healthy pain-free controls (n=29) were investigated. Quantitative Sensory Testing (QST) for thermal thresholds and algometry for PPT at various sites in the body were used. Psychological aspects, including catastrophizing, anxiety, and depression were registered using a questionnaire. WAD showed generalized decreased PPT and CPT, altered HPT and cold detection thresholds in the upper part of the body, and a worse psychological situation. Multivariate correlations were found between QST and PPT variables, habitual pain, and psychological factors in WAD. Different psychological variables were generally stronger predictors of CPT and HPT than pain intensity in WAD. Pain intensity aspects were generally the strongest predictors of PPT in WAD. In contrast, no correlations existed between QST and PPT variables and psychological variables in controls. These results indicate the need to consider that a blend of factors influences the pain thresholds in chronic WAD and emphasize the need for a biopsychosocial model when interpreting QST and PPT variables.

  8. Seismicity and detection/location threshold in the southern Great Basin seismic network

    USGS Publications Warehouse

    Gomberg, J.

    1991-01-01

    A spatially varying model of the detection/location capabilities of the Southern Great Basin seismic network (SGBSN) has been derived that is based on simple empirical relations and statistics. This permits use of almost all the catalog data gathered; instead of ignoring data that are below the threshold of completeness, a spatially varying threshold model is developed so that subregions having lower completeness levels than the network as a whole can be outlined and the completeness level of each sub-region determined. The predominantly aseismic regions located include the area west of the Death Valley/Furnace Creek fault system and an almost complete absence of events at Yucca Mountain. -from Author

  9. Milagro: A low energy threshold extensive air shower array

    SciTech Connect

    Sinnis, C.

    1994-12-31

    Observations of high-energy gamma rays from astronomical sources have revolutionized our view of the cosmos. Gamma rays with energies up to {approximately}10 GeV can be observed directly with space-based instruments. Above 100 GeV the low flux of gamma rays requires one to utilize ground-based instruments. Milagro is a new type of gamma-ray detector based on water Cerenkov technology. This new design will enable to continuously observe the entire overhead sky, and be sensitive to cosmic rays with energies above {approximately}250 GeV. These attributes make Milagro an ideal detector for the study of high-energy transient phenomenon.

  10. Detection of Near-Threshold Sounds is Independent of EEG Phase in Common Frequency Bands

    PubMed Central

    Zoefel, Benedikt; Heil, Peter

    2013-01-01

    Low-frequency oscillations in the electroencephalogram (EEG) are thought to reflect periodic excitability changes of large neural networks. Consistent with this notion, detection probability of near-threshold somatosensory, visual, and auditory targets has been reported to co-vary with the phase of oscillations in the EEG. In audition, entrainment of δ-oscillations to the periodic occurrence of sounds has been suggested to function as a mechanism of attentional selection. Here, we examine in humans whether the detection of brief near-threshold sounds in quiet depends on the phase of EEG oscillations. When stimuli were presented at irregular intervals, we did not find a systematic relationship between detection probability and phase. When stimuli were presented at regular intervals (2-s), reaction times were significantly shorter and we observed phase entrainment of EEG oscillations corresponding to the frequency of stimulus presentation (0.5 Hz), revealing an adjustment of the system to the regular stimulation. The amplitude of the entrained oscillation was higher for hits than for misses, suggesting a link between entrainment and stimulus detection. However, detection was independent of phase at frequencies ≥1 Hz. Furthermore, we show that when the data are analyzed using acausal, though common, algorithms, an apparent “entrainment” of the δ-phase to presented stimuli emerges and detection probability appears to depend on δ-phase, similar to reports in the literature. We show that these effects are artifacts from phase distortion at stimulus onset by contamination with the event-related potential, which differs markedly for hits and misses. This highlights the need to carefully deal with this common problem, since otherwise it might bias and mislead this exciting field of research. PMID:23717293

  11. Detection of fiducial points in ECG waves using iteration based adaptive thresholds.

    PubMed

    Wonjune Kang; Kyunguen Byun; Hong-Goo Kang

    2015-08-01

    This paper presents an algorithm for the detection of fiducial points in electrocardiogram (ECG) waves using iteration based adaptive thresholds. By setting the search range of the processing frame to the interval between two consecutive R peaks, the peaks of T and P waves are used as reference salient points (RSPs) to detect the fiducial points. The RSPs are selected from candidates whose slope variation factors are larger than iteratively defined adaptive thresholds. Considering the fact that the number of RSPs varies depending on whether the ECG wave is normal or not, the proposed algorithm proceeds with a different methodology for determining fiducial points based on the number of detected RSPs. Testing was performed using twelve records from the MIT-BIH Arrhythmia Database that were manually marked for comparison with the estimated locations of the fiducial points. The means of absolute distances between the true locations and the points estimated by the algorithm are 12.2 ms and 7.9 ms for the starting points of P and Q waves, and 9.3 ms and 13.9 ms for the ending points of S and T waves. Since the computational complexity of the proposed algorithm is very low, it is feasible for use in mobile devices. PMID:26736854

  12. Perceptual thresholds for detecting modifications applied to the acoustical properties of a violin.

    PubMed

    Fritz, Claudia; Cross, Ian; Moore, Brian C J; Woodhouse, Jim

    2007-12-01

    This study is the first step in the psychoacoustic exploration of perceptual differences between the sounds of different violins. A method was used which enabled the same performance to be replayed on different "virtual violins," so that the relationships between acoustical characteristics of violins and perceived qualities could be explored. Recordings of real performances were made using a bridge-mounted force transducer, giving an accurate representation of the signal from the violin string. These were then played through filters corresponding to the admittance curves of different violins. Initially, limits of listener performance in detecting changes in acoustical characteristics were characterized. These consisted of shifts in frequency or increases in amplitude of single modes or frequency bands that have been proposed previously to be significant in the perception of violin sound quality. Thresholds were significantly lower for musically trained than for nontrained subjects but were not significantly affected by the violin used as a baseline. Thresholds for the musicians typically ranged from 3 to 6 dB for amplitude changes and 1.5%-20% for frequency changes. Interpretation of the results using excitation patterns showed that thresholds for the best subjects were quite well predicted by a multichannel model based on optimal processing. PMID:18247771

  13. Perceptual thresholds for detecting modifications applied to the acoustical properties of a violin.

    PubMed

    Fritz, Claudia; Cross, Ian; Moore, Brian C J; Woodhouse, Jim

    2007-12-01

    This study is the first step in the psychoacoustic exploration of perceptual differences between the sounds of different violins. A method was used which enabled the same performance to be replayed on different "virtual violins," so that the relationships between acoustical characteristics of violins and perceived qualities could be explored. Recordings of real performances were made using a bridge-mounted force transducer, giving an accurate representation of the signal from the violin string. These were then played through filters corresponding to the admittance curves of different violins. Initially, limits of listener performance in detecting changes in acoustical characteristics were characterized. These consisted of shifts in frequency or increases in amplitude of single modes or frequency bands that have been proposed previously to be significant in the perception of violin sound quality. Thresholds were significantly lower for musically trained than for nontrained subjects but were not significantly affected by the violin used as a baseline. Thresholds for the musicians typically ranged from 3 to 6 dB for amplitude changes and 1.5%-20% for frequency changes. Interpretation of the results using excitation patterns showed that thresholds for the best subjects were quite well predicted by a multichannel model based on optimal processing.

  14. Critical review and hydrologic application of threshold detection methods for the generalized Pareto (GP) distribution

    NASA Astrophysics Data System (ADS)

    Mamalakis, Antonios; Langousis, Andreas; Deidda, Roberto

    2016-04-01

    Estimation of extreme rainfall from data constitutes one of the most important issues in statistical hydrology, as it is associated with the design of hydraulic structures and flood water management. To that extent, based on asymptotic arguments from Extreme Excess (EE) theory, several studies have focused on developing new, or improving existing methods to fit a generalized Pareto (GP) distribution model to rainfall excesses above a properly selected threshold u. The latter is generally determined using various approaches, such as non-parametric methods that are intended to locate the changing point between extreme and non-extreme regions of the data, graphical methods where one studies the dependence of GP distribution parameters (or related metrics) on the threshold level u, and Goodness of Fit (GoF) metrics that, for a certain level of significance, locate the lowest threshold u that a GP distribution model is applicable. In this work, we review representative methods for GP threshold detection, discuss fundamental differences in their theoretical bases, and apply them to 1714 daily rainfall records from the NOAA-NCDC open-access database, with more than 110 years of data. We find that non-parametric methods that are intended to locate the changing point between extreme and non-extreme regions of the data are generally not reliable, while methods that are based on asymptotic properties of the upper distribution tail lead to unrealistically high threshold and shape parameter estimates. The latter is justified by theoretical arguments, and it is especially the case in rainfall applications, where the shape parameter of the GP distribution is low; i.e. on the order of 0.1 ÷ 0.2. Better performance is demonstrated by graphical methods and GoF metrics that rely on pre-asymptotic properties of the GP distribution. For daily rainfall, we find that GP threshold estimates range between 2÷12 mm/d with a mean value of 6.5 mm/d, while the existence of quantization in the

  15. Development of CDMS-II Surface Event Rejection Techniques and Their Extensions to Lower Energy Thresholds

    NASA Astrophysics Data System (ADS)

    Hofer, Thomas James

    2014-10-01

    The CDMS-II phase of the Cryogenic Dark Matter Search, a dark matter direct-detection experiment, was operated at the Soudan Underground Laboratory from 2003 to 2008. The full payload consisted of 30 ZIP detectors, totaling approximately 1.1 kg of Si and 4.8 kg of Ge, operated at temperatures of 50 mK. The ZIP detectors read out both ionization and phonon pulses from scatters within the crystals; channel segmentation and analysis of pulse timing parameters allowed effective fiducialization of the crystal volumes and background rejection sufficient to set world-leading limits at the times of their publications. A full re-analysis of the CDMS-II data was motivated by an improvement in the event reconstruction algorithms which improved the resolution of ionization energy and timing information. The Ge data were re-analyzed using three distinct background-rejection techniques; the Si data from runs 125--128 were analyzed for the first time using the most successful of the techniques from the Ge re-analysis. The results of these analyses prompted a novel "mid-threshold" analysis, wherein energy thresholds were lowered but background rejection using phonon timing information was still maintained. This technique proved to have significant discrimination power, maintaining adequate signal acceptance and minimizing background leakage. The primary background for CDMS-II analyses comes from surface events, whose poor ionization collection make them difficult to distinguish from true nuclear recoil events. The novel detector technology of SuperCDMS, the successor to CDMS-II, uses interleaved electrodes to achieve full ionization collection for events occurring at the top and bottom detector surfaces. This, along with dual-sided ionization and phonon instrumentation, allows for excellent fiducialization and relegates the surface-event rejection techniques of CDMS-II to a secondary level of background discrimination. Current and future SuperCDMS results hold great promise for

  16. Direct measurement of the energy thresholds to conformational isomerization in tryptamine: experiment and theory.

    PubMed

    Clarkson, Jasper R; Dian, Brian C; Moriggi, Loïck; DeFusco, Albert; McCarthy, Valerie; Jordan, Kenneth D; Zwier, Timothy S

    2005-06-01

    The methods of stimulated emission pumping-hole filling spectroscopy (SEP-HFS) and stimulated emission pumping population transfer spectroscopy (SEP-PTS) were applied to the conformation-specific study of conformational isomerization in tryptamine [TRA, 3-(2-aminoethyl)indole]. These experimental methods employ stimulated emission pumping to selectively excite a fraction of the population of a single conformation of TRA to well-defined ground-state vibrational levels. This produces single conformations with well-defined internal energy, tunable over a range of energies from near the zero-point level to well above the lowest barriers to conformational isomerization. When the SEP step overcomes a barrier to isomerization, a fraction of the excited population isomerizes to form that product. By carrying out SEP excitation early in a supersonic expansion, these product molecules are subsequently cooled to their zero-point vibrational levels, where they can be detected downstream with a third tunable laser that probes the ground-state population of a particular product conformer via a unique ultraviolet transition using laser-induced fluorescence. The population transfer spectra (recorded by tuning the SEP dump laser while holding the pump and probe lasers fixed) exhibit sharp onsets that directly determine the energy thresholds for conformational isomerization in a given reactant-product conformer pair. In the absence of tunneling effects, the first observed transition in a given X-Y PTS constitutes an upper bound to the energy barrier to conformational isomerization, while the last transition not observed constitutes a lower bound. The bounds for isomerizing conformer A of tryptamine to B(688-748 cm(-1)), C(1)(860-1000 cm(-1)), C(2)(1219-1316 cm(-1)), D(1219-1282 cm(-1)), E(1219-1316 cm(-1)), and F(688-748 cm(-1)) are determined. In addition, thresholds for isomerizing from B to A(<1562 cm(-1)), B to F(562-688 cm(-1)), and out of C(2) to B(<747 cm(-1)) are also

  17. Direct measurement of the energy thresholds to conformational isomerization in Tryptamine: Experiment and theory

    NASA Astrophysics Data System (ADS)

    Clarkson, Jasper R.; Dian, Brian C.; Moriggi, Loïck; DeFusco, Albert; McCarthy, Valerie; Jordan, Kenneth D.; Zwier, Timothy S.

    2005-06-01

    The methods of stimulated emission pumping-hole filling spectroscopy (SEP-HFS) and stimulated emission pumping population transfer spectroscopy (SEP-PTS) were applied to the conformation-specific study of conformational isomerization in tryptamine [TRA, 3-(2-aminoethyl)indole]. These experimental methods employ stimulated emission pumping to selectively excite a fraction of the population of a single conformation of TRA to well-defined ground-state vibrational levels. This produces single conformations with well-defined internal energy, tunable over a range of energies from near the zero-point level to well above the lowest barriers to conformational isomerization. When the SEP step overcomes a barrier to isomerization, a fraction of the excited population isomerizes to form that product. By carrying out SEP excitation early in a supersonic expansion, these product molecules are subsequently cooled to their zero-point vibrational levels, where they can be detected downstream with a third tunable laser that probes the ground-state population of a particular product conformer via a unique ultraviolet transition using laser-induced fluorescence. The population transfer spectra (recorded by tuning the SEP dump laser while holding the pump and probe lasers fixed) exhibit sharp onsets that directly determine the energy thresholds for conformational isomerization in a given reactant-product conformer pair. In the absence of tunneling effects, the first observed transition in a given X -Y PTS constitutes an upper bound to the energy barrier to conformational isomerization, while the last transition not observed constitutes a lower bound. The bounds for isomerizing conformer A of tryptamine to B(688-748cm-1), C(1)(860-1000cm-1), C(2)(1219-1316cm-1), D(1219-1282cm-1), E(1219-1316cm-1), and F(688-748cm-1) are determined. In addition, thresholds for isomerizing from B to A(<1562cm-1), B to F(562-688cm-1), and out of C(2) to B(<747cm-1) are also determined. The A →B and B

  18. Simulation studies of MACE-I: Trigger rates and energy thresholds

    NASA Astrophysics Data System (ADS)

    Borwankar, Chinmay; Bhatt, Nilay; Bhattacharyya, Subir; Rannot, R. C.; Tickoo, A. K.; Koul, R.; Thoudam, Satyendra

    2016-11-01

    The MACE (Major Atmospheric Cherenkov Experiment) is an upcoming Very High Energy (VHE) γ-ray telescope, based on imaging atmospheric Cherenkov technique, being installed at Hanle, a high altitude astronomical site in Ladakh, India. Here we present Monte Carlo simulation studies of trigger rates and threshold energies of MACE in the zenith angle range of 0°-60° for on-axis γ-ray coming from point source and various cosmic ray species. We have simulated the telescope's response to γ-rays, proton, electron and alpha initiated atmospheric Extensive Air Showers (EAS) in the broad energy range of 5 GeV to 20 TeV. For γ-rays we consider power law and log parabolic spectra while other particles are simulated with their respective cosmic ray spectrum. Trigger rates and threshold energies are estimated for the trigger configuration of 4 Close Cluster Nearest Neighbour(CCNN) pixels as implemented in MACE hardware, in combination with single channel discriminator threshold ranging from 6-10 photo electrons (pe). We find that MACE can achieve the γ-ray trigger energy threshold of ∼ 17 GeV (4 CCNN, 9 pe) at 0° zenith angle for power law spectrum. The total trigger rate at 0° zenith is expected to be ∼650 Hz, with protons contributing ∼ 80% to it. For the zenith range of 0°-40° we find that the telescope can achieve γ-ray trigger threshold energies of ∼22 GeV at 20° zenith angle and ∼40 GeV at 40° zenith angle. Integral rates are also almost constant for this zenith angle range. At zenith angle of 60°, trigger energy threshold increases to ∼173 GeV and total integral rate falls down to ∼305 Hz.

  19. Above-threshold ionization for very low electron energy

    NASA Astrophysics Data System (ADS)

    Becker, W.; Milošević, D. B.

    2015-08-01

    The rescattering term of the ionization amplitude in the strong-field approximation is analyzed for very low electron energy and emission in arbitrary direction, first in terms of the classical simple-man model and then in the quantum-mechanical quantum-orbit expansion of the strong-field-approximation amplitude. Particular orbits can be associated with particular patterns in the velocity map. The different roles of forward and backscattering are investigated. In addition to known features such as the LES and the fork, a characteristic and pronounced V structure in the velocity map is identified, which has been observed in recent experiments (2014 Phys. Rev. A 90 063424).

  20. The relationship between intelligence and creativity: New support for the threshold hypothesis by means of empirical breakpoint detection

    PubMed Central

    Jauk, Emanuel; Benedek, Mathias; Dunst, Beate; Neubauer, Aljoscha C.

    2013-01-01

    The relationship between intelligence and creativity has been subject to empirical research for decades. Nevertheless, there is yet no consensus on how these constructs are related. One of the most prominent notions concerning the interplay between intelligence and creativity is the threshold hypothesis, which assumes that above-average intelligence represents a necessary condition for high-level creativity. While earlier research mostly supported the threshold hypothesis, it has come under fire in recent investigations. The threshold hypothesis is commonly investigated by splitting a sample at a given threshold (e.g., at 120 IQ points) and estimating separate correlations for lower and upper IQ ranges. However, there is no compelling reason why the threshold should be fixed at an IQ of 120, and to date, no attempts have been made to detect the threshold empirically. Therefore, this study examined the relationship between intelligence and different indicators of creative potential and of creative achievement by means of segmented regression analysis in a sample of 297 participants. Segmented regression allows for the detection of a threshold in continuous data by means of iterative computational algorithms. We found thresholds only for measures of creative potential but not for creative achievement. For the former the thresholds varied as a function of criteria: When investigating a liberal criterion of ideational originality (i.e., two original ideas), a threshold was detected at around 100 IQ points. In contrast, a threshold of 120 IQ points emerged when the criterion was more demanding (i.e., many original ideas). Moreover, an IQ of around 85 IQ points was found to form the threshold for a purely quantitative measure of creative potential (i.e., ideational fluency). These results confirm the threshold hypothesis for qualitative indicators of creative potential and may explain some of the observed discrepancies in previous research. In addition, we obtained

  1. Photoproduction of Λ(1115) on a deuteron at threshold energies

    NASA Astrophysics Data System (ADS)

    Beckford, Brian; NKS2 Collaboration

    2013-10-01

    The electromagnetic production of strange mesons and baryons continues to be a growing topic in more recent years due in part to the continual increase of beam energies at accelerator facilities. It is well known that production of strangeness on nucleons provides details about hadronic structures including form factors. We present results on cross sections for Λ in the γd --> Λ X reaction measured at the Research Center for Electron Photon Science (ELPH), at tagged photon energies between 0.8-1.08 GeV. The experiment was successfully performed using the upgraded Neutral Kaon Spectrometer (NKS2 +) where the produced Λ was measured by the pπ- decay channel. Momentum and angular distributions were measured in addition to the integrated cross section for forward Λ scattering angles. From integrated measurements of Λ from γd --> Λ X, total cross sections of γd -->K0 Λ p were estimated. The results of the Saclay-Lyon A (SLA) and Regge-Plus-Resonance (RPR-2007) model calculations compared favorably to the data. This work was supported by the JSPS KAKENHI grant, 16GS0201 and 21002.

  2. Flood Extent Mapping for Namibia Using Change Detection and Thresholding with SAR

    NASA Technical Reports Server (NTRS)

    Long, Stephanie; Fatoyinbo, Temilola E.; Policelli, Frederick

    2014-01-01

    A new method for flood detection change detection and thresholding (CDAT) was used with synthetic aperture radar (SAR) imagery to delineate the extent of flooding for the Chobe floodplain in the Caprivi region of Namibia. This region experiences annual seasonal flooding and has seen a recent renewal of severe flooding after a long dry period in the 1990s. Flooding in this area has caused loss of life and livelihoods for the surrounding communities and has caught the attention of disaster relief agencies. There is a need for flood extent mapping techniques that can be used to process images quickly, providing near real-time flooding information to relief agencies. ENVISAT/ASAR and Radarsat-2 images were acquired for several flooding seasons from February 2008 to March 2013. The CDAT method was used to determine flooding from these images and includes the use of image subtraction, decision based classification with threshold values, and segmentation of SAR images. The total extent of flooding determined for 2009, 2011 and 2012 was about 542 km2, 720 km2, and 673 km2 respectively. Pixels determined to be flooded in vegetation were typically <0.5 % of the entire scene, with the exception of 2009 where the detection of flooding in vegetation was much greater (almost one third of the total flooded area). The time to maximum flooding for the 2013 flood season was determined to be about 27 days. Landsat water classification was used to compare the results from the new CDAT with SAR method; the results show good spatial agreement with Landsat scenes.

  3. Spatial and Temporal Varying Thresholds for Cloud Detection in Satellite Imagery

    NASA Technical Reports Server (NTRS)

    Jedlovec, Gary; Haines, Stephanie

    2007-01-01

    A new cloud detection technique has been developed and applied to both geostationary and polar orbiting satellite imagery having channels in the thermal infrared and short wave infrared spectral regions. The bispectral composite threshold (BCT) technique uses only the 11 micron and 3.9 micron channels, and composite imagery generated from these channels, in a four-step cloud detection procedure to produce a binary cloud mask at single pixel resolution. A unique aspect of this algorithm is the use of 20-day composites of the 11 micron and the 11 - 3.9 micron channel difference imagery to represent spatially and temporally varying clear-sky thresholds for the bispectral cloud tests. The BCT cloud detection algorithm has been applied to GOES and MODIS data over the continental United States over the last three years with good success. The resulting products have been validated against "truth" datasets (generated by the manual determination of the sky conditions from available satellite imagery) for various seasons from the 2003-2005 periods. The day and night algorithm has been shown to determine the correct sky conditions 80-90% of the time (on average) over land and ocean areas. Only a small variation in algorithm performance occurs between day-night, land-ocean, and between seasons. The algorithm performs least well. during he winter season with only 80% of the sky conditions determined correctly. The algorithm was found to under-determine clouds at night and during times of low sun angle (in geostationary satellite data) and tends to over-determine the presence of clouds during the day, particularly in the summertime. Since the spectral tests use only the short- and long-wave channels common to most multispectral scanners; the application of the BCT technique to a variety of satellite sensors including SEVERI should be straightforward and produce similar performance results.

  4. Study of vegetation index selection and changing detection thresholds in land cover change detection assessment using change vector analysis

    NASA Astrophysics Data System (ADS)

    Nguyen, Duy; Tran, Giang

    2012-07-01

    In recent years, Vietnamese rapidly developing economy has led to speedy changes in land cover. The study of changing detection of land cover plays an important role in making the strategy of the managers. There are two main approaches in changing detection research by using remote sensing and GIS: post- classification change detection analysis approach and pre-classification changing spectral determination approach. Each has their own different advantages and disadvantages. The second one is further divided into: Image Differencing, Multi-date Principal Component Analysis (MPCA); Change Vector Analysis (CVA). In this study, researchers introduce CVA method. This method is based on two important index to show the primary feature of land cover, such as: vegetation index (NDVI-) and barren land index (-BI). Ability to apply methods of CVA has been mentioned in the studies [1, 2, 3, and 4]. However, in these studies did not mention the NDVI index selection and changing detection threshold in changing detection assessment? This paper proposes application to solve these two problems.

  5. Semi-empirical AGN detection threshold in spectral synthesis studies of Lyman-continuum-leaking early-type galaxies

    NASA Astrophysics Data System (ADS)

    Cardoso, Leandro S. M.; Gomes, Jean-Michel; Papaderos, Polychronis

    2016-10-01

    Various lines of evidence suggest that the cores of a large portion of early-type galaxies (ETGs) are virtually evacuated of warm ionised gas. This implies that the Lyman-continuum (LyC) radiation produced by an assumed active galactic nucleus (AGN) can escape from the nuclei of these systems without being locally reprocessed into nebular emission, which would prevent their reliable spectroscopic classification as Seyfert galaxies with standard diagnostic emission-line ratios. The spectral energy distribution (SED) of these ETGs would then lack nebular emission and be essentially composed of an old stellar component and the featureless power-law (PL) continuum from the AGN. A question that arises in this context is whether the AGN component can be detected with current spectral population synthesis in the optical, specifically, whether these techniques effectively place an AGN detection threshold in LyC-leaking galaxies. To quantitatively address this question, we took a combined approach that involves spectral fitting with Starlight of synthetic SEDs composed of stellar emission that characterises a 10 Gyr old ETG and an AGN power-law component that contributes a fraction 0 ≤ xAGN < 1 of the monochromatic luminosity at λ0 = 4020 Å. In addition to a set of fits for PL distributions Fν ∝ ν- α with the canonical α = 1.5, we used a base of multiple PLs with 0.5 ≤ α ≤ 2 for a grid of synthetic SEDs with a signal-to-noise ratio of 5-103. Our analysis indicates an effective AGN detection threshold at xAGN ≃ 0.26, which suggests that a considerable fraction of ETGs hosting significant accretion-powered nuclear activity may be missing in the AGN demographics.

  6. Neural Variability, Detection Thresholds, and Information Transmission in the Vestibular System

    PubMed Central

    Sadeghi, Soroush G.; Chacron, Maurice J.; Taylor, Michael C.; Cullen, Kathleen E.

    2016-01-01

    A fundamental issue in neural coding is the role of spike timing variation in information transmission of sensory stimuli. Vestibular afferents are particularly well suited to study this issue because they are classified as either regular or irregular based on resting discharge variability as well as morphology. Here, we compared the responses of each afferent class to sinusoidal and random head rotations using both information theoretic and gain measures. Information theoretic measures demonstrated that regular afferents transmitted, on average, two times more information than irregular afferents, despite having significantly lower gains. Moreover, consistent with information theoretic measures, regular afferents had angular velocity detection thresholds that were 50% lower than those of irregular afferents (~4 vs 8°/s). Finally, to quantify the information carried by spike times, we added spike-timing jitter to the spike trains of both regular and irregular afferents. Our results showed that this significantly reduced information transmitted by regular afferents whereas it had little effect on irregular afferents. Thus, information is carried in the spike times of regular but not irregular afferents. Using a simple leaky integrate and fire model with a dynamic threshold, we show that differential levels of intrinsic noise can explain differences in the resting discharge, the responses to sensory stimuli, as well as the information carried by action potential timings of each afferent class. Our experimental and modeling results provide new insights as to how neural variability influences the strategy used by two different classes of sensory neurons to encode behaviorally relevant stimuli. PMID:17251416

  7. An adaptive threshold based image processing technique for improved glaucoma detection and classification.

    PubMed

    Issac, Ashish; Partha Sarathi, M; Dutta, Malay Kishore

    2015-11-01

    Glaucoma is an optic neuropathy which is one of the main causes of permanent blindness worldwide. This paper presents an automatic image processing based method for detection of glaucoma from the digital fundus images. In this proposed work, the discriminatory parameters of glaucoma infection, such as cup to disc ratio (CDR), neuro retinal rim (NRR) area and blood vessels in different regions of the optic disc has been used as features and fed as inputs to learning algorithms for glaucoma diagnosis. These features which have discriminatory changes with the occurrence of glaucoma are strategically used for training the classifiers to improve the accuracy of identification. The segmentation of optic disc and cup based on adaptive threshold of the pixel intensities lying in the optic nerve head region. Unlike existing methods the proposed algorithm is based on an adaptive threshold that uses local features from the fundus image for segmentation of optic cup and optic disc making it invariant to the quality of the image and noise content which may find wider acceptability. The experimental results indicate that such features are more significant in comparison to the statistical or textural features as considered in existing works. The proposed work achieves an accuracy of 94.11% with a sensitivity of 100%. A comparison of the proposed work with the existing methods indicates that the proposed approach has improved accuracy of classification glaucoma from a digital fundus which may be considered clinically significant.

  8. Validation of efficiency tracing and zero detection threshold techniques using liquid scintillation analyser TriCarb.

    PubMed

    Reddy, P J; Bhade, S P D; Babu, D A R; Sharma, D N

    2011-11-01

    Efficiency tracing with unquenched 14C and zero detection threshold with unquenched 3H as tracers are practical and simple techniques which have been implemented to quantify the activity of various beta emitters using liquid scintillation analyser. These techniques are used to study the influence of quench level on activity quantification and the activity levels up to which these techniques are applicable. The results indicate that, for an activity level of 166.67 Bq, both the techniques are in good agreement with the reference activity with a relative discrepancy of ≤4.6 %. The relative discrepancy of ~10 % is observed for extreme quench values of ~111. For all the radionuclides with the activity level of 1.67 Bq, the uncertainty in activity quantification raises to ~8 % and for the activity level from 8.33 to 100 Bq, the uncertainty reduces to 1 %. PMID:21196460

  9. Threshold-based system for noise detection in multilead ECG recordings.

    PubMed

    Jekova, Irena; Krasteva, Vessela; Christov, Ivaylo; Abächerli, Roger

    2012-09-01

    This paper presents a system for detection of the most common noise types seen on the electrocardiogram (ECG) in order to evaluate whether an episode from 12-lead ECG is reliable for diagnosis. It implements criteria for estimation of the noise corruption level in specific frequency bands, aiming to identify the main sources of ECG quality disruption, such as missing signal or limited dynamics of the QRS components above 4 Hz; presence of high amplitude and steep artifacts seen above 1 Hz; baseline drift estimated at frequencies below 1 Hz; power-line interference in a band ±2 Hz around its central frequency; high-frequency and electromyographic noises above 20 Hz. All noise tests are designed to process the ECG series in the time domain, including 13 adjustable thresholds for amplitude and slope criteria which are evaluated in adjustable time intervals, as well as number of leads. The system allows flexible extension toward application-specific requirements for the noise levels in acceptable quality ECGs. Training of different thresholds' settings to determine different positive noise detection rates is performed with the annotated set of 1000 ECGs from the PhysioNet database created for the Computing in Cardiology Challenge 2011. Two implementations are highlighted on the receiver operating characteristic (area 0.968) to fit to different applications. The implementation with high sensitivity (Se = 98.7%, Sp = 80.9%) appears as a reliable alarm when there are any incidental problems with the ECG acquisition, while the implementation with high specificity (Sp = 97.8%, Se = 81.8%) is less susceptible to transient problems but rather validates noisy ECGs with acceptable quality during a small portion of the recording.

  10. Evaluation of a change detection methodology by means of binary thresholding algorithms and informational fusion processes.

    PubMed

    Molina, Iñigo; Martinez, Estibaliz; Arquero, Agueda; Pajares, Gonzalo; Sanchez, Javier

    2012-01-01

    Landcover is subject to continuous changes on a wide variety of temporal and spatial scales. Those changes produce significant effects in human and natural activities. Maintaining an updated spatial database with the occurred changes allows a better monitoring of the Earth's resources and management of the environment. Change detection (CD) techniques using images from different sensors, such as satellite imagery, aerial photographs, etc., have proven to be suitable and secure data sources from which updated information can be extracted efficiently, so that changes can also be inventoried and monitored. In this paper, a multisource CD methodology for multiresolution datasets is applied. First, different change indices are processed, then different thresholding algorithms for change/no_change are applied to these indices in order to better estimate the statistical parameters of these categories, finally the indices are integrated into a change detection multisource fusion process, which allows generating a single CD result from several combination of indices. This methodology has been applied to datasets with different spectral and spatial resolution properties. Then, the obtained results are evaluated by means of a quality control analysis, as well as with complementary graphical representations. The suggested methodology has also been proved efficiently for identifying the change detection index with the higher contribution.

  11. Brain tumour classification and abnormality detection using neuro-fuzzy technique and Otsu thresholding.

    PubMed

    Renjith, Arokia; Manjula, P; Mohan Kumar, P

    2015-01-01

    Brain tumour is one of the main causes for an increase in transience among children and adults. This paper proposes an improved method based on Magnetic Resonance Imaging (MRI) brain image classification and image segmentation approach. Automated classification is encouraged by the need of high accuracy when dealing with a human life. The detection of the brain tumour is a challenging problem, due to high diversity in tumour appearance and ambiguous tumour boundaries. MRI images are chosen for detection of brain tumours, as they are used in soft tissue determinations. First of all, image pre-processing is used to enhance the image quality. Second, dual-tree complex wavelet transform multi-scale decomposition is used to analyse texture of an image. Feature extraction extracts features from an image using gray-level co-occurrence matrix (GLCM). Then, the Neuro-Fuzzy technique is used to classify the stages of brain tumour as benign, malignant or normal based on texture features. Finally, tumour location is detected using Otsu thresholding. The classifier performance is evaluated based on classification accuracies. The simulated results show that the proposed classifier provides better accuracy than previous method.

  12. [Automatic detection of exudates in retinal images based on threshold moving average models].

    PubMed

    Wisaeng, K; Hiransakolwong, N; Pothiruk, E

    2015-01-01

    Since exudate diagnostic procedures require the attention of an expert ophthalmologist as well as regular monitoring of the disease, the workload of expert ophthalmologists will eventually exceed the current screening capabilities. Retinal imaging technology is a current practice screening capability providing a great potential solution. In this paper, a fast and robust automatic detection of exudates based on moving average histogram models of the fuzzy image was applied, and then the better histogram was derived. After segmentation of the exudate candidates, the true exudates were pruned based on Sobel edge detector and automatic Otsu's thresholding algorithm that resulted in the accurate location of the exudates in digital retinal images. To compare the performance of exudate detection methods we have constructed a large database of digital retinal images. The method was trained on a set of 200 retinal images, and tested on a completely independent set of 1220 retinal images. Results show that the exudate detection method performs overall best sensitivity, specificity, and accuracy of 90.42%, 94.60%, and 93.69%, respectively. PMID:26016034

  13. CAMS verification of single-linked high-threshold D-criterion detected meteor showers

    NASA Astrophysics Data System (ADS)

    Jenniskens, Peter; Nénon, Quentin

    2016-03-01

    From preliminary 2010-2011 results of the Cameras for Allsky Meteor Surveillance (CAMS) meteoroid orbit survey, which were combined with published 2007-2009 SonotaCo video meteor network data, 55 new meteor showers (##448-502) were identified and added to the IAU Working List on Meteor Showers in 2012. These showers were identified based on an automated single-linked DSH-criterion analysis of a combined 105,000 orbits with high-threshold (a low DSH < 0.05), but low acceptable sample size (⩾6 members). Three more years of CAMS and four more years of SonotaCo observations have now increased the meteoroid orbit database four fold. The earlier detections are verified by searching for number density enhancements in drift-corrected radiant and orbital element maps. Twenty showers are detected in both surveys and are now certain to exist. Median orbital elements are presented. Not detected in this manner were 19% of the fast Vg > 40 km/s showers, 54% of the Vg = 18-40 km/s showers, and 90% of the slow Vg < 18 km/s showers.

  14. Evaluation of a Change Detection Methodology by Means of Binary Thresholding Algorithms and Informational Fusion Processes

    PubMed Central

    Molina, Iñigo; Martinez, Estibaliz; Arquero, Agueda; Pajares, Gonzalo; Sanchez, Javier

    2012-01-01

    Landcover is subject to continuous changes on a wide variety of temporal and spatial scales. Those changes produce significant effects in human and natural activities. Maintaining an updated spatial database with the occurred changes allows a better monitoring of the Earth’s resources and management of the environment. Change detection (CD) techniques using images from different sensors, such as satellite imagery, aerial photographs, etc., have proven to be suitable and secure data sources from which updated information can be extracted efficiently, so that changes can also be inventoried and monitored. In this paper, a multisource CD methodology for multiresolution datasets is applied. First, different change indices are processed, then different thresholding algorithms for change/no_change are applied to these indices in order to better estimate the statistical parameters of these categories, finally the indices are integrated into a change detection multisource fusion process, which allows generating a single CD result from several combination of indices. This methodology has been applied to datasets with different spectral and spatial resolution properties. Then, the obtained results are evaluated by means of a quality control analysis, as well as with complementary graphical representations. The suggested methodology has also been proved efficiently for identifying the change detection index with the higher contribution. PMID:22737023

  15. Development of CDMS-II Surface Event Rejection Techniques and Their Extensions to Lower Energy Thresholds

    SciTech Connect

    Hofer, Thomas James

    2014-12-01

    The CDMS-II phase of the Cryogenic Dark Matter Search, a dark matter direct-detection experiment, was operated at the Soudan Underground Laboratory from 2003 to 2008. The full payload consisted of 30 ZIP detectors, totaling approximately 1.1 kg of Si and 4.8 kg of Ge, operated at temperatures of 50 mK. The ZIP detectors read out both ionization and phonon pulses from scatters within the crystals; channel segmentation and analysis of pulse timing parameters allowed e ective ducialization of the crystal volumes and background rejection su cient to set world-leading limits at the times of their publications. A full re-analysis of the CDMS-II data was motivated by an improvement in the event reconstruction algorithms which improved the resolution of ionization energy and timing information. The Ge data were re-analyzed using three distinct background-rejection techniques; the Si data from runs 125 - 128 were analyzed for the rst time using the most successful of the techniques from the Ge re-analysis. The results of these analyses prompted a novel \\mid-threshold" analysis, wherein energy thresholds were lowered but background rejection using phonon timing information was still maintained. This technique proved to have signi cant discrimination power, maintaining adequate signal acceptance and minimizing background leakage. The primary background for CDMS-II analyses comes from surface events, whose poor ionization collection make them di cult to distinguish from true nuclear recoil events. The novel detector technology of SuperCDMS, the successor to CDMS-II, uses interleaved electrodes to achieve full ionization collection for events occurring at the top and bottom detector surfaces. This, along with dual-sided ionization and phonon instrumentation, allows for excellent ducialization and relegates the surface-event rejection techniques of CDMS-II to a secondary level of background discrimination. Current and future SuperCDMS results hold great promise for mid- to low

  16. Location Performance and Detection Threshold of the Spanish National Seismic Network

    NASA Astrophysics Data System (ADS)

    D'Alessandro, Antonino; Badal, José; D'Anna, Giuseppe; Papanastassiou, Dimitris; Baskoutas, Ioannis; Özel, Nurcan M.

    2013-11-01

    Spain is a low-to-moderate seismicity area with relatively low seismic hazard. However, several strong shallow earthquakes have shaken the country causing casualties and extensive damage. Regional seismicity is monitored and surveyed by means of the Spanish National Seismic Network, maintenance and control of which are entrusted to the Instituto Geográfico Nacional. This array currently comprises 120 seismic stations distributed throughout Spanish territory (mainland and islands). Basically, we are interested in checking the noise conditions, reliability, and seismic detection capability of the Spanish network by analyzing the background noise level affecting the array stations, errors in hypocentral location, and detection threshold, which provides knowledge about network performance. It also enables testing of the suitability of the velocity model used in the routine process of earthquake location. To perform this study we use a method that relies on P and S wave travel times, which are computed by simulation of seismic rays from virtual seismic sources placed at the nodes of a regular grid covering the study area. Given the characteristics of the seismicity of Spain, we drew maps for M L magnitudes 2.0, 2.5, and 3.0, at a focal depth of 10 km and a confidence level 95 %. The results relate to the number of stations involved in the hypocentral location process, how these stations are distributed spatially, and the uncertainties of focal data (errors in origin time, longitude, latitude, and depth). To assess the extent to which principal seismogenic areas are well monitored by the network, we estimated the average error in the location of a seismic source from the semiaxes of the ellipsoid of confidence by calculating the radius of the equivalent sphere. Finally, the detection threshold was determined as the magnitude of the smallest seismic event detected at least by four stations. The northwest of the peninsula, the Pyrenees, especially the westernmost segment

  17. Vibrationally resolved electron-nuclear energy sharing in above-threshold multiphoton dissociation of CO

    NASA Astrophysics Data System (ADS)

    Sun, Xufei; Li, Min; Shao, Yun; Liu, Ming-Ming; Xie, Xiguo; Deng, Yongkai; Wu, Chengyin; Gong, Qihuang; Liu, Yunquan

    2016-07-01

    We study the photon energy sharing between the photoelectron and the nuclei in the process of above-threshold multiphoton dissociative ionization of CO molecules by measuring the joint energy spectra. The experimental observation shows that the electron-nuclear energy sharing strongly depends on the vibrational state. The experimental observation shows that both the energy deposited to the nuclei of C O+ and the emitted photoelectron decrease with increasing the vibrational level. Through studying the vibrationally resolved nuclear kinetic energy release and photoelectron energy spectra at different laser intensities, for each vibrational level of C O+ , the nuclei always tend to take the same amount of energy in every vibrational level regardless of the laser intensity, while the energy deposited to the photoelectron varies with respect to the laser intensity because of the ponderomotive shifted energy and the distinct dissociative ionization mechanisms.

  18. The energy distribution cross section in threshold electron-atom impact ionization

    NASA Technical Reports Server (NTRS)

    Temkin, A.

    1974-01-01

    The flatness of the energy differential cross section in impact ionization is derived analytically in the Wannier theory. However it is shown that the Wannier zone is confined to a region of the order E/5 is less than or equal to epsilon is less than or equal to 4E/5, where E is the available energy and epsilon is the energy of the electrons. By contrasting the known results of photoionization and photodetachment, one can cogently argue that in the complementary region where electrons share their energy very unequally the cross section rises to a value independent of E, and that this region determines the form of the threshold law.

  19. Low-energy backscattering quantum orbits in above-threshold ionization

    NASA Astrophysics Data System (ADS)

    Milošević, D. B.

    2016-09-01

    Using the quantum–orbit formalism we consider the influence of the backward-scattering quantum orbits on the low-energy above-threshold ionization spectra. It is shown that the corresponding ionization rate exhibits sharp peaks for electron energies ≲ 0.1 {U}{{P}} ({U}{{P}} is the electron ponderomotive energy) at the same places where the forward-scattering-induced low-energy structures appear. The corresponding incident rescattering electron velocities are very small. Semiclassical expressions for the positions of these peaks as functions of {U}{{P}} and the ionization potential are derived.

  20. Sputtering of cobalt and chromium by argon and xenon ions near the threshold energy region

    NASA Technical Reports Server (NTRS)

    Handoo, A. K.; Ray, P. K.

    1993-01-01

    Sputtering yields of cobalt and chromium by argon and xenon ions with energies below 50 eV are reported. The targets were electroplated on copper substrates. Measurable sputtering yields were obtained from cobalt with ion energies as low as 10 eV. The ion beams were produced by an ion gun. A radioactive tracer technique was used for the quantitative measurement of the sputtering yield. Co-57 and Cr-51 were used as tracers. The yield-energy curves are observed to be concave, which brings into question the practice of finding threshold energies by linear extrapolation.

  1. Evaluation of pre-processing, thresholding and post-processing steps for very small target detection in infrared images

    NASA Astrophysics Data System (ADS)

    Yardımcı, Ozan; Ulusoy, Ä.°lkay

    2016-05-01

    Pre-processing, thresholding and post-processing stages are very important especially for very small target detection from infrared images. The effects of these stages to the final detection performance are measured in this study. Various methods for each stage are compared based on the final detection performance, which is defined by precision and recall values. Among various methods, the best method for each stage is selected and proved. For the pre-processing stage, local block based methods perform the best, nearly for all thresholding methods. The best thresholding method is chosen as the one, which does not need any user defined parameter. Finally, the post processing method, which is suitable for the best performing pre-processing and thesholding methods is selected.

  2. Sensory detection thresholds are modulated across the cardiac cycle: evidence that cutaneous sensibility is greatest for systolic stimulation.

    PubMed

    Edwards, L; Ring, C; McIntyre, D; Winer, J B; Martin, U

    2009-03-01

    The visceral afferent feedback hypothesis proposes that sensorimotor function is impaired by cortical inhibition associated with increased baroreceptor activation. This study is the first to examine the effects of naturally occurring variations in baroreceptor activity across the cardiac cycle on cutaneous sensory detection thresholds. In each trial, an electrocutaneous stimulus was delivered to the index finger at one of three intervals (0, 300, 600 ms) after the R-wave of the electrocardiogram. Separate interleaving up-down staircases were used to determine the 50% detection threshold for each R-wave to stimulation interval. Cutaneous sensory detection thresholds were lower for stimuli presented at R+300 ms than R+0 ms or R+600 ms. The finding that cutaneous sensibility was greater when stimulated during systole than diastole may be accounted for by a modified afferent feedback hypothesis.

  3. Image overlay solution based on threshold detection for a compact near infrared fluorescence goggle system

    PubMed Central

    Gao, Shengkui; Mondal, Suman B.; Zhu, Nan; Liang, RongGuang; Achilefu, Samuel; Gruev, Viktor

    2015-01-01

    Abstract. Near infrared (NIR) fluorescence imaging has shown great potential for various clinical procedures, including intraoperative image guidance. However, existing NIR fluorescence imaging systems either have a large footprint or are handheld, which limits their usage in intraoperative applications. We present a compact NIR fluorescence imaging system (NFIS) with an image overlay solution based on threshold detection, which can be easily integrated with a goggle display system for intraoperative guidance. The proposed NFIS achieves compactness, light weight, hands-free operation, high-precision superimposition, and a real-time frame rate. In addition, the miniature and ultra-lightweight light-emitting diode tracking pod is easy to incorporate with NIR fluorescence imaging. Based on experimental evaluation, the proposed NFIS solution has a lower detection limit of 25 nM of indocyanine green at 27 fps and realizes a highly precise image overlay of NIR and visible images of mice in vivo. The overlay error is limited within a 2-mm scale at a 65-cm working distance, which is highly reliable for clinical study and surgical use. PMID:25607724

  4. Image overlay solution based on threshold detection for a compact near infrared fluorescence goggle system.

    PubMed

    Gao, Shengkui; Mondal, Suman B; Zhu, Nan; Liang, RongGuang; Achilefu, Samuel; Gruev, Viktor

    2015-01-01

    Near infrared (NIR) fluorescence imaging has shown great potential for various clinical procedures, including intraoperative image guidance. However, existing NIR fluorescence imaging systems either have a large footprint or are handheld, which limits their usage in intraoperative applications. We present a compact NIR fluorescence imaging system (NFIS) with an image overlay solution based on threshold detection, which can be easily integrated with a goggle display system for intraoperative guidance. The proposed NFIS achieves compactness, light weight, hands-free operation, high-precision superimposition, and a real-time frame rate. In addition, the miniature and ultra-lightweight light-emitting diode tracking pod is easy to incorporate with NIR fluorescence imaging. Based on experimental evaluation, the proposed NFIS solution has a lower detection limit of 25 nM of indocyanine green at 27 fps and realizes a highly precise image overlay of NIR and visible images of mice in vivo. The overlay error is limited within a 2-mm scale at a 65-cm working distance, which is highly reliable for clinical study and surgical use.

  5. Quantitative prediction of perceptual decisions during near-threshold fear detection

    NASA Astrophysics Data System (ADS)

    Pessoa, Luiz; Padmala, Srikanth

    2005-04-01

    A fundamental goal of cognitive neuroscience is to explain how mental decisions originate from basic neural mechanisms. The goal of the present study was to investigate the neural correlates of perceptual decisions in the context of emotional perception. To probe this question, we investigated how fluctuations in functional MRI (fMRI) signals were correlated with behavioral choice during a near-threshold fear detection task. fMRI signals predicted behavioral choice independently of stimulus properties and task accuracy in a network of brain regions linked to emotional processing: posterior cingulate cortex, medial prefrontal cortex, right inferior frontal gyrus, and left insula. We quantified the link between fMRI signals and behavioral choice in a whole-brain analysis by determining choice probabilities by means of signal-detection theory methods. Our results demonstrate that voxel-wise fMRI signals can reliably predict behavioral choice in a quantitative fashion (choice probabilities ranged from 0.63 to 0.78) at levels comparable to neuronal data. We suggest that the conscious decision that a fearful face has been seen is represented across a network of interconnected brain regions that prepare the organism to appropriately handle emotionally challenging stimuli and that regulate the associated emotional response. decision making | emotion | functional MRI

  6. Different thresholds for detection and discrimination of odors in the honey bee (Apis mellifera).

    PubMed

    Wright, Geraldine A; Smith, Brian H

    2004-02-01

    Naturally occurring odors used by animals for mate recognition, food identification and other purposes must be detected at concentrations that vary across several orders of magnitude. Olfactory systems must therefore have the capacity to represent odors over a large range of concentrations regardless of dramatic changes in the salience, or perceived intensity, of a stimulus. The stability of the representation of an odor relative to other odors across concentration has not been extensively evaluated. We tested the ability of honey bees to discriminate pure odorants across a range of concentrations at and above their detection threshold. Our study showed that pure odorant compounds became progressively easier for honey bees to discriminate with increasing concentration. Discrimination is, therefore, a function of odorant concentration. We hypothesize that the recruitment of sensory cell populations across a range of concentrations may be important for odor coding, perhaps by changing its perceptual qualities or by increasing its salience against background stimuli, and that this mechanism is a general property of olfactory systems.

  7. Image overlay solution based on threshold detection for a compact near infrared fluorescence goggle system

    NASA Astrophysics Data System (ADS)

    Gao, Shengkui; Mondal, Suman B.; Zhu, Nan; Liang, RongGuang; Achilefu, Samuel; Gruev, Viktor

    2015-01-01

    Near infrared (NIR) fluorescence imaging has shown great potential for various clinical procedures, including intraoperative image guidance. However, existing NIR fluorescence imaging systems either have a large footprint or are handheld, which limits their usage in intraoperative applications. We present a compact NIR fluorescence imaging system (NFIS) with an image overlay solution based on threshold detection, which can be easily integrated with a goggle display system for intraoperative guidance. The proposed NFIS achieves compactness, light weight, hands-free operation, high-precision superimposition, and a real-time frame rate. In addition, the miniature and ultra-lightweight light-emitting diode tracking pod is easy to incorporate with NIR fluorescence imaging. Based on experimental evaluation, the proposed NFIS solution has a lower detection limit of 25 nM of indocyanine green at 27 fps and realizes a highly precise image overlay of NIR and visible images of mice in vivo. The overlay error is limited within a 2-mm scale at a 65-cm working distance, which is highly reliable for clinical study and surgical use.

  8. Different thresholds for detection and discrimination of odors in the honey bee (Apis mellifera).

    PubMed

    Wright, Geraldine A; Smith, Brian H

    2004-02-01

    Naturally occurring odors used by animals for mate recognition, food identification and other purposes must be detected at concentrations that vary across several orders of magnitude. Olfactory systems must therefore have the capacity to represent odors over a large range of concentrations regardless of dramatic changes in the salience, or perceived intensity, of a stimulus. The stability of the representation of an odor relative to other odors across concentration has not been extensively evaluated. We tested the ability of honey bees to discriminate pure odorants across a range of concentrations at and above their detection threshold. Our study showed that pure odorant compounds became progressively easier for honey bees to discriminate with increasing concentration. Discrimination is, therefore, a function of odorant concentration. We hypothesize that the recruitment of sensory cell populations across a range of concentrations may be important for odor coding, perhaps by changing its perceptual qualities or by increasing its salience against background stimuli, and that this mechanism is a general property of olfactory systems. PMID:14977809

  9. Effect of strain and temperature on the threshold displacement energy in body-centered cubic iron

    NASA Astrophysics Data System (ADS)

    Beeler, Benjamin; Asta, Mark; Hosemann, Peter; Grønbech-Jensen, Niels

    2016-06-01

    The threshold displacement energy (TDE) is the minimum amount of kinetic energy required to displace an atom from its lattice site. The magnitude of the TDE displays significant variance as a function of the crystallographic direction, system temperature and applied strain, among a variety of other factors. It is critically important to determine an accurate value of the TDE in order to calculate the total number of displacements due to a given irradiation condition, and thus to understand the materials response to irradiation. In this study, molecular dynamics simulations have been performed to calculate the threshold displacement energy in body-centered cubic iron as a function of strain and temperature. With applied strain, a decrease of the TDE of up to approximately 14 eV was observed. A temperature increase from 300 K to 500 K can result in an increase of the TDE of up to approximately 9 eV.

  10. Collisional energy deposition threshold for extended damage depths in ion-implanted silicates

    SciTech Connect

    Arnold, G.W.; Battaglin, G.; Boscolo-Boscoletto, A.; Caccavalle, F.; De Marchi, G.; Mazzoldi, P.; Miotello, A.

    1991-12-31

    Many properties of implanted fused silica (e.g., surface stress, hardness) exhibit maximum implantation-induced changes for collisional energy deposition values of {approximately}10{sup 20} keV/cm{sup 3}. We have observed a second critical energy deposition threshold value of about 10{sup 22} keV/cm{sup 3} in stress and hardness measurements as well as in many other experiments on silicate glasses (leaching, alkali depletion, etching rate, gaseous implant redistribution). The latter show evidence for damage depths exceeding TRIM ranges by about a factor of 2. For crystalline quartz, a similar threshold value has been found for extended damage depths (greater than TRIM) for 250 kev ions (H-Au) as measured by RBS and interference fringes. This phenomenon at high damage deposition energy may involve the large stress gradients between damaged and undamaged regions and the much increased diffusion coefficient for defect transport. 13 refs., 6 figs.

  11. Collisional energy deposition threshold for extended damage depths in ion-implanted silicates

    SciTech Connect

    Arnold, G.W. ); Battaglin, G. ); Boscolo-Boscoletto, A. ); Caccavalle, F.; De Marchi, G.; Mazzoldi, P. ); Miotello, A. (Consorzio INFM, Dipartiment

    1991-01-01

    Many properties of implanted fused silica (e.g., surface stress, hardness) exhibit maximum implantation-induced changes for collisional energy deposition values of {approximately}10{sup 20} keV/cm{sup 3}. We have observed a second critical energy deposition threshold value of about 10{sup 22} keV/cm{sup 3} in stress and hardness measurements as well as in many other experiments on silicate glasses (leaching, alkali depletion, etching rate, gaseous implant redistribution). The latter show evidence for damage depths exceeding TRIM ranges by about a factor of 2. For crystalline quartz, a similar threshold value has been found for extended damage depths (greater than TRIM) for 250 kev ions (H-Au) as measured by RBS and interference fringes. This phenomenon at high damage deposition energy may involve the large stress gradients between damaged and undamaged regions and the much increased diffusion coefficient for defect transport. 13 refs., 6 figs.

  12. Whole body motion-detection tasks can yield much lower thresholds than direction-recognition tasks: implications for the role of vibration.

    PubMed

    Chaudhuri, Shomesh E; Karmali, Faisal; Merfeld, Daniel M

    2013-12-01

    Earlier spatial orientation studies used both motion-detection (e.g., did I move?) and direction-recognition (e.g., did I move left/right?) paradigms. The purpose of our study was to compare thresholds measured with motion-detection and direction-recognition tasks on a standard Moog motion platform to see whether a substantial fraction of the reported threshold variation might be explained by the use of different discrimination tasks in the presence of vibrations that vary with motion. Thresholds for the perception of yaw rotation about an earth-vertical axis and for interaural translation in an earth-horizontal plane were determined for four healthy subjects with standard detection and recognition paradigms. For yaw rotation two-interval detection thresholds were, on average, 56 times smaller than two-interval recognition thresholds, and for interaural translation two-interval detection thresholds were, on average, 31 times smaller than two-interval recognition thresholds. This substantive difference between recognition thresholds and detection thresholds is one of our primary findings. For motions near our measured detection threshold, we measured vibrations that matched previously established vibration thresholds. This suggests that vibrations contribute to whole body motion detection. We also recorded yaw rotation thresholds on a second motion device with lower vibration and found direction-recognition and motion-detection thresholds that were not significantly different from one another or from the direction-recognition thresholds recorded on our Moog platform. Taken together, these various findings show that yaw rotation recognition thresholds are relatively unaffected by vibration when moderate (up to ≈ 0.08 m/s(2)) vibration cues are present.

  13. Electrodynamic model of the field effect transistor application for THz/subTHz radiation detection: Subthreshold and above threshold operation

    SciTech Connect

    Dobrovolsky, V.

    2014-10-21

    Developed in this work is an electrodynamic model of field effect transistor (FET) application for THz/subTHz radiation detection. It is based on solution of the Maxwell equations in the gate dielectric, expression for current in the channel, which takes into account both the drift and diffusion current components, and the equation of current continuity. For the regimes under and above threshold at the strong inversion the response voltage, responsivity, wave impedance, power of ohmic loss in the gate and channel have been found, and the electrical noise equivalent power (ENEP) has been estimated. The responsivity is orders of magnitude higher and ENEP under threshold is orders of magnitude less than these values above threshold. Under the threshold, the electromagnetic field in the gate oxide is identical to field of the plane waves in free-space. At the same time, for strong inversion the charging of the gate capacitance through the resistance of channel determines the electric field in oxide.

  14. Detection threshold for percutaneous electrical stimuli: asymmetry with respect to handedness.

    PubMed Central

    Friedli, W G; Fuhr, P; Wiget, W

    1987-01-01

    Sensory strength-duration curves were obtained using percutaneous true square-wave pulses ranging from 0.1 to 20.0 ms produced by an isolated constant current stimulator. In 119 healthy volunteers sensory thresholds were measured bilaterally by stimulating the distal phalange of the little finger. In order to examine the relationship of sensory threshold and handedness the latter was assessed by means of the Edinburgh Inventory. An asymmetry of sensory threshold was found for all the subjects and this was more pronounced with shorter stimuli. Of right-handers tested 73.5% had a lower threshold on the left side while 70.8% of left-handers had a lower threshold on the right side. Although threshold asymmetry is associated with handedness this is not necessarily due to cerebral lateralization. PMID:3625210

  15. Energy conservation using face detection

    NASA Astrophysics Data System (ADS)

    Deotale, Nilesh T.; Kalbande, Dhananjay R.; Mishra, Akassh A.

    2011-10-01

    Computerized Face Detection, is concerned with the difficult task of converting a video signal of a person to written text. It has several applications like face recognition, simultaneous multiple face processing, biometrics, security, video surveillance, human computer interface, image database management, digital cameras use face detection for autofocus, selecting regions of interest in photo slideshows that use a pan-and-scale and The Present Paper deals with energy conservation using face detection. Automating the process to a computer requires the use of various image processing techniques. There are various methods that can be used for Face Detection such as Contour tracking methods, Template matching, Controlled background, Model based, Motion based and color based. Basically, the video of the subject are converted into images are further selected manually for processing. However, several factors like poor illumination, movement of face, viewpoint-dependent Physical appearance, Acquisition geometry, Imaging conditions, Compression artifacts makes Face detection difficult. This paper reports an algorithm for conservation of energy using face detection for various devices. The present paper suggests Energy Conservation can be done by Detecting the Face and reducing the brightness of complete image and then adjusting the brightness of the particular area of an image where the face is located using histogram equalization.

  16. Ab initio molecular dynamics simulations of threshold displacement energies in SrTiO3

    SciTech Connect

    Liu, Bin; Xiao, Haiyan; Zhang, Yanwen; Aidhy, Dilpuneet S; Weber, William J

    2013-01-01

    Ab initio molecular dynamics simulations have been carried out to study low-energy recoil events in SrTiO3. The threshold displacement energies are shown to be strongly dependent on both the orientation and the corresponding atomic arrangement. The minimum threshold displacement energies are 13 eV for an O recoil along the <100> O-O chain, 25 eV for a Sr recoil along the <100> Sr-Sr chain and 38 eV for a Ti recoil along the <110> Ti-Ti chain. The weighted average threshold displacement energies along the primary crystallographic directions are 35.7, 53.5 and > 64.9 eV for O, Sr and Ti, respectively. The interstitial configurations produced by the recoil events are <100> and <111> split-interstitials for O and Sr, respectively, together with a Ti interstitial occupying a distorted bridge position between two Sr sites. It is found that the recoil events in SrTiO3 are partial- charge transfer assisted processes, and the partial- charge transfer plays an important role in these recoil events.

  17. The photodetachment cross-section and threshold energy of negative ions in carbon dioxide

    NASA Technical Reports Server (NTRS)

    Helmy, E. M.; Woo, S. B.

    1974-01-01

    Threshold energy and sunlight photodetachment measurements on negative carbon dioxide ions, using a 2.5 kw light pressure xenon lamp, show that: (1) Electron affinity of CO3(+) is larger than 2.7 e.V. and that an isomeric form of CO3(+) is likely an error; (2) The photodetachment cross section of CO3(-) will roughly be like a step function across the range of 4250 to 2500A, having its threshold energy at 4250A; (3) Sunlight photodetachment rate for CO3(-) is probably much smaller than elsewhere reported; and (4) The probability of having photodetached electrons re-attach to form negative ions is less than 1%. Mass identifying drift tube tests confirm that the slower ion is CO3(-), formed through the O(-) + 2CO2 yields CO3(-) + CO2 reaction.

  18. Enhanced detection threshold for in vivo cortical stimulation produced by Hebbian conditioning

    NASA Astrophysics Data System (ADS)

    Rebesco, James M.; Miller, Lee E.

    2011-02-01

    Normal brain function requires constant adaptation, as an organism learns to associate important sensory stimuli with the appropriate motor actions. Neurological disorders may disrupt these learned associations and require the nervous system to reorganize itself. As a consequence, neural plasticity is a crucial component of normal brain function and a critical mechanism for recovery from injury. Associative, or Hebbian, pairing of pre- and post-synaptic activity has been shown to alter stimulus-evoked responses in vivo; however, to date, such protocols have not been shown to affect the animal's subsequent behavior. We paired stimulus trains separated by a brief time delay to two electrodes in rat sensorimotor cortex, which changed the statistical pattern of spikes during subsequent behavior. These changes were consistent with strengthened functional connections from the leading electrode to the lagging electrode. We then trained rats to respond to a microstimulation cue, and repeated the paradigm using the cue electrode as the leading electrode. This pairing lowered the rat's ICMS-detection threshold, with the same dependence on intra-electrode time lag that we found for the functional connectivity changes. The timecourse of the behavioral effects was very similar to that of the connectivity changes. We propose that the behavioral changes were a consequence of strengthened functional connections from the cue electrode to other regions of sensorimotor cortex. Such paradigms might be used to augment recovery from a stroke, or to promote adaptation in a bidirectional brain-machine interface.

  19. Design of a New Somatosensory Stimulus Delivery Device for Measuring Laryngeal Mechanosensory Detection Thresholds in Humans

    PubMed Central

    2009-01-01

    Laryngeal control is essential for airway protection, breathing, deglutition, speech, and voice. Unfortunately, integration of laryngeal sensory assessment in research and clinical practice is limited by technical and practical limitations of commercially available technology. A commercial device is available, but reported limitations include procedural complexity requiring two or three individuals to operate, limited stimulus dynamic range, device generated noise, and questionable stimulus reproducibility. The objective of this study was to design a new laryngeal somatosensory stimulus delivery device that provides direct, reliable control over the timing, duration, and dynamic range of stimulus presentation, and test the device in individuals who may manifest a laryngeal sensory deficit. The new device operates silently and has more than four times greater stimulus dynamic range than the commercial device. Testing with the new device revealed laryngeal mechanosensory detection thresholds in an individual with Parkinson’s disease that were seven times higher than those of healthy controls. These data would have otherwise gone undetected due to limited stimulus dynamic range in the commercial device. The new design resulted in a new assessment instrument that is simple to use for routine clinical assessment, yet sufficiently versatile for integration within rigorous clinical research protocols. PMID:19272888

  20. A Novel Thresholding Based Algorithm for Detection of Vertical Root Fracture in Nonendodontically Treated Premolar Teeth

    PubMed Central

    Johari, Masume; Esmaeili, Farzad; Andalib, Alireza; Garjani, Shabnam; Saberkari, Hamidreza

    2016-01-01

    In this paper, an efficient algorithm is proposed for detection of vertical root fractures (VRFs) in periapical (PA), and cone-beam computed tomography (CBCT) radiographs of nonendodontically treated premolar teeth. PA and CBCT images are divided into some sub-categories based on the fracture space between the two fragments as small, medium, and large for PAs and large for CBCTs. These graphics are first denoised using the combination of block matching 3-D filtering, and principle component analysis model. Then, we proposed an adaptive thresholding algorithm based on the modified Wellner model to segment the fracture and canal. Finally, VRFs are identified with a high accuracy through applying continuous wavelet transform on the segmented radiographs and choosing the most optimal value for sub-images based on the lowest interclass variance. Performance of the proposed algorithm is evaluated utilizing the different tested criteria. Results illustrate that the range of specificity deviations for PA and CBCT radiographs are 99.69 ± 0.22 and 99.02 ± 0.77, respectively. Furthermore, the sensitivity changes from 61.90 to 77.39 in the case of PA and from 79.54 to 100 in the case of CBCT. Based on our statistical evaluation, the CBCT imaging has the better performance in comparison with PA ones, so this technique could be a useful tool for clinical applications in determining the VRFs. PMID:27186535

  1. New approaches for detecting thresholds of human nephrotoxicity using cadmium as an example.

    PubMed Central

    Mueller, P W; Price, R G; Finn, W F

    1998-01-01

    Damage to the kidneys is one of the primary toxic actions of metals. Nephrotoxic substances not only cause renal disease directly, but they can also destroy renal reserve capacity, potentially placing those people with additional risk factors, such as diabetes, hypertension, cardiovascular disease, and genetic predispositions, at greater risk. To detect nephrotoxicity in people at a stage where intervention can be effective, sensitive methods are needed. One of the major advantages of using sensitive biomarkers of renal damage is that people who may be particularly susceptible to renal damage can be identified early, at a reversible stage of damage, and the progression to end-stage renal disease may be halted or delayed. Various categories of tests can be used to detect effects of nephrotoxic substances on the kidney. Through the use of biomarkers of damage to various parts of the nephron, U.S. and European studies have both shown a similar pattern of damage among men occupationally exposed to cadmium. These studies indicate various thresholds of renal effects, which researchers suggest represent a cascade of progressively severe damage to the kidney. Research into new biomarkers of damage caused by exposure to nephrotoxic substances centers around mechanisms of cell death, including necrosis and apoptosis; mechanisms of cell growth, regeneration, and proliferation, including factors that control cell cycle, influence gene expression, and modulate nucleic acid synthesis; and genetic factors that increase susceptibility to renal disease. Examples of types of candidate biomarkers include cytokines, lipid mediators, growth factors, transcription factors and protooncogenes, extracellular matrix components (collagen, glycoproteins, and proteoglycans), and cell adhesion molecules. Research into new categories of biomarkers may provide additional insights into the mechanisms of damage caused by nephrotoxins. PMID:9647892

  2. Modeling of damage generation mechanisms in silicon at energies below the displacement threshold

    SciTech Connect

    Santos, Ivan; Marques, Luis A.; Pelaz, Lourdes

    2006-11-01

    We have used molecular dynamics simulation techniques to study the generation of damage in Si within the low-energy deposition regime. We have demonstrated that energy transfers below the displacement threshold can produce a significant amount of damage, usually neglected in traditional radiation damage calculations. The formation of amorphous pockets agrees with the thermal spike concept of local melting. However, we have found that the order-disorder transition is not instantaneous, but it requires some time to reach the appropriate kinetic-potential energy redistribution for melting. The competition between the rate of this energy redistribution and the energy diffusion to the surrounding atoms determines the amount of damage generated by a given deposited energy. Our findings explain the diverse damage morphology produced by ions of different masses.

  3. Individual differences in sour and salt sensitivity: detection and quality recognition thresholds for citric acid and sodium chloride.

    PubMed

    Wise, Paul M; Breslin, Paul A S

    2013-05-01

    Taste sensitivity is assessed with various techniques, including absolute detection and quality recognition. For any stimulus, one might expect individual differences in sensitivity to be reflected in all measures, but they are often surprisingly independent. Here, we focus on sensitivity to sour and salty taste, in part because processing of these qualities is poorly understood relative to other tastes. In Study 1, we measured retest reliability for detection (modified, forced-choice staircase method) and recognition (modified Harris-Kalmus procedure) for both citric acid (CA) and sodium chloride (NaCl). Despite good retest reliability, individual differences in detection and recognition were weakly correlated, suggesting that detection and recognition of sour and salty stimuli may reflect different physiological processes. In Study 2, a subset of subjects returned to contribute full detection (psychometric) functions for CA and NaCl. Thresholds estimated from full detection functions correlated with both staircase and recognition thresholds, suggesting that both tasks may reflect absolute sensitivity to some extent. However, the ranges of individual differences were systematically compressed for staircase thresholds relative to those from full detection functions. Thus, individual differences in sensitivity appear to interact with different test methodologies in lawful ways. More work will be required to understand how different taste phenotypes relate to one another.

  4. Threshold conditions, energy spectrum and bands generated by locally periodic Dirac comb potentials

    NASA Astrophysics Data System (ADS)

    Dharani, M.; Shastry, C. S.

    2016-01-01

    We derive expressions for polynomials governing the threshold conditions for different types of locally periodic Dirac comb potentials comprising of attractive and combination of attractive and repulsive delta potential terms confined symmetrically inside a one dimensional box of fixed length. The roots of these polynomials specify the conditions on the potential parameters in order to generate threshold energy bound states. The mathematical and numerical methods used by us were first formulated in our earlier works and it is also very briefly summarized in this paper. We report a number of mathematical results pertaining to the threshold conditions and these are useful in controlling the number of negative energy states as desired. We further demonstrate the correlation between the distribution of roots of these polynomials and negative energy eigenvalues. Using these results as basis, we investigate the energy bands in the positive energy spectrum for the above specified Dirac comb potentials and also for the corresponding repulsive case. In the case of attractive Dirac comb the base energy of the each band excluding the first band coincides with specific eigenvalue of the confining box whereas in the repulsive case it coincides with the band top. We deduce systematic correlation between band gaps, band spreads and box eigenvalues and explain the physical reason for the vanishing of band pattern at higher energies. In the case of Dirac comb comprising of orderly arranged attractive and repulsive delta potentials, specific box eigenvalues occur in the middle of each band excluding the first band. From our study we find that by controlling the number and strength parameters of delta terms in the Dirac comb and the size of confining box it is possible to generate desired types of band formations. We believe the results from our systematic analysis are useful and relevant in the study of various one dimensional systems of physical interest in areas like nanoscience.

  5. Detection threshold for sound distortion resulting from noise reduction in normal-hearing and hearing-impaired listeners.

    PubMed

    Brons, Inge; Dreschler, Wouter A; Houben, Rolph

    2014-09-01

    Hearing-aid noise reduction should reduce background noise, but not disturb the target speech. This objective is difficult because noise reduction suffers from a trade-off between the amount of noise removed and signal distortion. It is unknown if this important trade-off differs between normal-hearing (NH) and hearing-impaired (HI) listeners. This study separated the negative effect of noise reduction (distortion) from the positive effect (reduction of noise) to allow the measurement of the detection threshold for noise-reduction (NR) distortion. Twelve NH subjects and 12 subjects with mild to moderate sensorineural hearing loss participated in this study. The detection thresholds for distortion were determined using an adaptive procedure with a three-interval, two-alternative forced-choice paradigm. Different levels of distortion were obtained by changing the maximum amount of noise reduction. Participants were also asked to indicate their preferred NR strength. The detection threshold for overall distortion was higher for HI subjects than for NH subjects, suggesting that stronger noise reduction can be applied for HI listeners without affecting the perceived sound quality. However, the preferred NR strength of HI listeners was closer to their individual detection threshold for distortion than in NH listeners. This implies that HI listeners tolerate fewer audible distortions than NH listeners.

  6. 30 CFR 62.174 - Follow-up corrective measures when a standard threshold shift is detected.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Follow-up corrective measures when a standard threshold shift is detected. 62.174 Section 62.174 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR UNIFORM MINE HEALTH REGULATIONS OCCUPATIONAL NOISE EXPOSURE § 62.174 Follow-up...

  7. 30 CFR 62.174 - Follow-up corrective measures when a standard threshold shift is detected.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Follow-up corrective measures when a standard threshold shift is detected. 62.174 Section 62.174 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR UNIFORM MINE HEALTH REGULATIONS OCCUPATIONAL NOISE EXPOSURE § 62.174 Follow-up...

  8. 30 CFR 62.174 - Follow-up corrective measures when a standard threshold shift is detected.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Follow-up corrective measures when a standard threshold shift is detected. 62.174 Section 62.174 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR UNIFORM MINE HEALTH REGULATIONS OCCUPATIONAL NOISE EXPOSURE § 62.174 Follow-up...

  9. Regular threshold-energy increase with charge for neutral-particle emission in collisions of electrons with oligonucleotide anions.

    PubMed

    Tanabe, T; Noda, K; Saito, M; Starikov, E B; Tateno, M

    2004-07-23

    Electron-DNA anion collisions were studied using an electrostatic storage ring with a merging electron-beam technique. The rate of neutral particles emitted in collisions started to increase from definite threshold energies, which increased regularly with ion charges in steps of about 10 eV. These threshold energies were almost independent of the length and sequence of DNA, but depended strongly on the ion charges. Neutral particles came from breaks of DNAs, rather than electron detachment. The step of the threshold energy increase approximately agreed with the plasmon excitation energy. It is deduced that plasmon excitation is closely related to the reaction mechanism.

  10. The fluorescence and photofragmentation of liquid saturated hydrocarbons at energies above the photoionization threshold

    NASA Astrophysics Data System (ADS)

    Schwarz, Frederick P.; Smith, Diane; Lias, Sharon G.; Ausloos, P.

    1981-10-01

    Fluroescence quantum yields (φF) are reported for saturated hydrocarbons excited by photon absorption in the liquid phase at energies below and above the photoionization threshold. The quantum yields of fluorescence obtained in the subionization region are in excellent agreement with those reported by Lipsky and colleagues. In the phtotionization region, emission occurs as a result of both charge recombination processes and deactivation of the superexcited molecule to the vibrationally relaxed first excited singlet state. The presence of these two populations of fluorescing species above the ionization threshold is manifested in differences in the slopes of plots of φF as a function of energy above and below the ionization onset. Since, for saturated hydrocarbons, photofragmentation is the only nonradiative channel, the variations in the relative importances of the major modes of fragmentation have been examined as a function of energy for selected molecules. It is observed that the two main dissociative processes, H and H2 elimination, show a continuous variation with photon energy. While at the absorption threshold H2 elimination predominates, at the highest energy used in this study (11.6 eV) H atom detachment from the excited molecules (both those formed by direct photon absorption and those formed by charge recombination) is of comparable importance. Liquid phase radiolysis experiments show a ratio of H atom elimination to H2 formation which is substantially higher than that measured at the highest photon energy. The role of equilibrated excited singlet state (S1)0 in saturated hydrocarbons is examined in the context of the wavelength-dependent fluorescence and photochemical data. The results indicate that, at energies above the ionizatin thresholds for the various molecules, ion pair recombination has a probability below unity of leading to the formation of vibrationally relaxed (S1)0 emitting states. In the radiolysis of liquid C6-C10 alkanes, it is

  11. Congenital hypothyroidism with neurological and respiratory alterations: a case detected using a variable diagnostic threshold for TSH.

    PubMed

    Barreiro, Jesús; Alonso-Fernández, Jóse Ramón; Castro-Feijoo, Lidia; Colón, Cristóbal; Cabanas, Paloma; Heredia, Claudia; Castaño, Luis Antonio; Gómez-Lado, Carmen; Couce, M Luz; Pombo, Manuel

    2011-01-01

    We report a case of congenital hypothyroidism (CH) with neurological and respiratory alterations due to a heterozygotic c.374-1G > A mutation of TITF1/NKX2-1. The hypothyroidism was detected using a neonatal screening protocol in which the thyroid stimulating hormone (TSH) threshold is re-set each day on the basis of within-day variability and between-day variation. In this case, the threshold on the day of the initial analysis was 8.2 mIU/L, and the measured TSH level in heel-prick blood was 8.3 mIU/L.

  12. Congenital hypothyroidism with neurological and respiratory alterations: a case detected using a variable diagnostic threshold for TSH.

    PubMed

    Barreiro, Jesús; Alonso-Fernández, Jóse Ramón; Castro-Feijoo, Lidia; Colón, Cristóbal; Cabanas, Paloma; Heredia, Claudia; Castaño, Luis Antonio; Gómez-Lado, Carmen; Couce, M Luz; Pombo, Manuel

    2011-01-01

    We report a case of congenital hypothyroidism (CH) with neurological and respiratory alterations due to a heterozygotic c.374-1G > A mutation of TITF1/NKX2-1. The hypothyroidism was detected using a neonatal screening protocol in which the thyroid stimulating hormone (TSH) threshold is re-set each day on the basis of within-day variability and between-day variation. In this case, the threshold on the day of the initial analysis was 8.2 mIU/L, and the measured TSH level in heel-prick blood was 8.3 mIU/L. PMID:22155464

  13. Congenital Hypothyroidism with Neurological and Respiratory Alterations: A Case Detected Using a Variable Diagnostic Threshold for TSH

    PubMed Central

    Barreiro, Jesús; Castro-Feijoo, Lidia; Colón, Cristóbal; Cabanas, Paloma; Heredia, Claudia; Castaño, Luis Antonio; Gómez-Lado, Carmen; Couce, M.Luz; Pombo, Manuel

    2011-01-01

    We report a case of congenital hypothyroidism (CH) with neurological and respiratory alterations due to a heterozygotic c.374-1G > A mutation of TITF1/NKX2-1. The hypothyroidism was detected using a neonatal screening protocol in which the thyroid stimulating hormone (TSH) threshold is re-set each day on the basis of within-day variability and between-day variation. In this case, the threshold on the day of the initial analysis was 8.2 mIU/L, and the measured TSH level in heel-prick blood was 8.3 mIU/L. Conflict of interest:None declared. PMID:22155464

  14. Finite-time Lyapunov exponents and metabolic control coefficients for threshold detection of stimulus-response curves.

    PubMed

    Duc, Luu Hoang; Chávez, Joseph Páez; Son, Doan Thai; Siegmund, Stefan

    2016-01-01

    In biochemical networks transient dynamics plays a fundamental role, since the activation of signalling pathways is determined by thresholds encountered during the transition from an initial state (e.g. an initial concentration of a certain protein) to a steady-state. These thresholds can be defined in terms of the inflection points of the stimulus-response curves associated to the activation processes in the biochemical network. In the present work, we present a rigorous discussion as to the suitability of finite-time Lyapunov exponents and metabolic control coefficients for the detection of inflection points of stimulus-response curves with sigmoidal shape. PMID:27416142

  15. The transfer function of a target limits the jitter detection threshold with signals of echolocating FM-bats.

    PubMed

    Beedholm, Kristian

    2006-05-01

    The delay jitter discrimination threshold in bats is a disputed subject. Some investigators have obtained results indicating that bats are able to discriminate alternations in delay down to 10 ns, which appears incredible for purely physical reasons. Using actual bat echolocation sequences recorded during an easy detection task to measure simulated delay jitter, it is shown here that jitter detection thresholds in the order of some tens of nanoseconds are actually physically realizable. However, if the transfer function of the target simulating apparatus is not perfect, the lowest thresholds are in the order of hundreds of nanoseconds and variable between individual bats. This phenomenon is shown to arise as a consequence of the variation in signal parameters from call to call. When the transfer function from a real jitter experiment was artificially applied to the echoes, the jitter detection thresholds again were several hundred nanoseconds. This is the first study to point out a limiting role of the transfer function of a system faced with variations in echolocation signal parameters, something that should be considered in evaluating all sonar systems with variable signal structure.

  16. Ground truth and detection threshold from WWII naval clean-up in Denmark

    NASA Astrophysics Data System (ADS)

    Larsen, Tine B.; Dahl-Jensen, Trine; Voss, Peter

    2013-04-01

    The sea bed below the Danish territorial waters is still littered with unexploded mines and other ammunition from World War II. The mines were air dropped by the RAF and the positions of the mines are unknown. As the mines still pose a potential threat to fishery and other marine activities, the Admiral Danish Fleet under the Danish Navy searches for the mines and destroy them by detonation, where they are found. The largest mines destroyed in this manner in 2012 are equivalent to 800 kg TNT each. The Seismological Service at the National Geological Survey of Denmark and Greenland is notified by the navy when ammunition in excess of 100 kg TNT is detonated. The notifications include information about position, detonation time and the estimated amount of explosives. The larger explosions are clearly registered not only on the Danish seismographs, but also on seismographs in the neighbouring countries. This includes the large seismograph arrays in Norway, Sweden, and Finland. Until recently the information from the Danish navy was only utilized to rid the Danish earthquake catalogue of explosions. But the high quality information provided by the navy enables us to use these ground truth events to assess the quality of our earthquake catalogue. The mines are scattered though out the Danish territorial waters, thus we can use the explosions to test the accuracy of the determined epicentres in all parts of the country. E.g. a detonation of 135 kg in Begstrup Vig in the central part of Denmark was located using Danish, Norwegian and Swedish stations with an accuracy of less than 2 km from ground truth. A systematic study of the explosions will sharpen our understanding of the seismicity in Denmark, and result in a more detailed understanding of the detection threshold. Furthermore the study will shed light on the sensitivity of the network to various seismograph outages.

  17. Detection thresholds for intensity increments in a single harmonic of synthetic Japanese macaque (Macaca fuscata) monkey coo calls.

    PubMed

    Le Prell, Colleen G; Moody, David B

    2002-09-01

    There is evidence that Japanese macaques (Macaca fuscata) are extremely sensitive to dynamic changes in the relative amplitudes of coo call harmonics during discrimination tests. To verify this evidence using more controlled stimulus configurations, the authors examined threshold sensitivity of macaque monkeys to amplitude increments added to the standard level of coo call harmonics. Psychophysical threshold determination methods paralleled those used previously to determine macaque sensitivity to amplitude increments added to vowel-like stimuli. Variation was detectable although thresholds were elevated relative to those obtained with vowel-like stimuli in another investigation (C. G. Le Prell, A. J. Niemiec, & D. B. Moody, 2001). This elevation was probably a function of natural amplitude modulation in the standard stimuli.

  18. Probability-based particle detection that enables threshold-free and robust in vivo single-molecule tracking.

    PubMed

    Smith, Carlas S; Stallinga, Sjoerd; Lidke, Keith A; Rieger, Bernd; Grunwald, David

    2015-11-01

    Single-molecule detection in fluorescence nanoscopy has become a powerful tool in cell biology but can present vexing issues in image analysis, such as limited signal, unspecific background, empirically set thresholds, image filtering, and false-positive detection limiting overall detection efficiency. Here we present a framework in which expert knowledge and parameter tweaking are replaced with a probability-based hypothesis test. Our method delivers robust and threshold-free signal detection with a defined error estimate and improved detection of weaker signals. The probability value has consequences for downstream data analysis, such as weighing a series of detections and corresponding probabilities, Bayesian propagation of probability, or defining metrics in tracking applications. We show that the method outperforms all current approaches, yielding a detection efficiency of >70% and a false-positive detection rate of <5% under conditions down to 17 photons/pixel background and 180 photons/molecule signal, which is beneficial for any kind of photon-limited application. Examples include limited brightness and photostability, phototoxicity in live-cell single-molecule imaging, and use of new labels for nanoscopy. We present simulations, experimental data, and tracking of low-signal mRNAs in yeast cells.

  19. Probability-based particle detection that enables threshold-free and robust in vivo single-molecule tracking

    PubMed Central

    Smith, Carlas S.; Stallinga, Sjoerd; Lidke, Keith A.; Rieger, Bernd; Grunwald, David

    2015-01-01

    Single-molecule detection in fluorescence nanoscopy has become a powerful tool in cell biology but can present vexing issues in image analysis, such as limited signal, unspecific background, empirically set thresholds, image filtering, and false-positive detection limiting overall detection efficiency. Here we present a framework in which expert knowledge and parameter tweaking are replaced with a probability-based hypothesis test. Our method delivers robust and threshold-free signal detection with a defined error estimate and improved detection of weaker signals. The probability value has consequences for downstream data analysis, such as weighing a series of detections and corresponding probabilities, Bayesian propagation of probability, or defining metrics in tracking applications. We show that the method outperforms all current approaches, yielding a detection efficiency of >70% and a false-positive detection rate of <5% under conditions down to 17 photons/pixel background and 180 photons/molecule signal, which is beneficial for any kind of photon-limited application. Examples include limited brightness and photostability, phototoxicity in live-cell single-molecule imaging, and use of new labels for nanoscopy. We present simulations, experimental data, and tracking of low-signal mRNAs in yeast cells. PMID:26424801

  20. A prior-knowledge-based threshold segmentation method of forward-looking sonar images for underwater linear object detection

    NASA Astrophysics Data System (ADS)

    Liu, Lixin; Bian, Hongyu; Yagi, Shin-ichi; Yang, Xiaodong

    2016-07-01

    Raw sonar images may not be used for underwater detection or recognition directly because disturbances such as the grating-lobe and multi-path disturbance affect the gray-level distribution of sonar images and cause phantom echoes. To search for a more robust segmentation method with a reasonable computational cost, a prior-knowledge-based threshold segmentation method of underwater linear object detection is discussed. The possibility of guiding the segmentation threshold evolution of forward-looking sonar images using prior knowledge is verified by experiment. During the threshold evolution, the collinear relation of two lines that correspond to double peaks in the voting space of the edged image is used as the criterion of termination. The interaction is reflected in the sense that the Hough transform contributes to the basis of the collinear relation of lines, while the binary image generated from the current threshold provides the resource of the Hough transform. The experimental results show that the proposed method could maintain a good tradeoff between the segmentation quality and the computational time in comparison with conventional segmentation methods. The proposed method redounds to a further process for unsupervised underwater visual understanding.

  1. Photo-Double Ionization: Threshold Law and Low-Energy Behavior

    NASA Technical Reports Server (NTRS)

    Bhatia, Anand

    2008-01-01

    The threshold law for photoejection of two electrons from atoms (PDI) is derived from a modification of the Coulomb-dipole (C-D) theory. The C-D theory applies to two-electron ejection from negative ions (photo-double detachment:PDD). The modification consists of correctly accounting for the fact that in PDI that the two escaping electrons see a Coulomb field, asymptotically no matter what their relative distances from the residual ion are. We find in the contralinear spherically symmetric model that the analytic threshold law Q(E),i. e. the yield of residual ions, to be Qf(E)approaches E + CwE(sup gamma(w)) + CE(sup 5/4)sin[1/2 ln(E + theta)]/ln(E). The first and third terms are beyond the Wannier law. Our threshold law can only be rigorously justified for residual energies less than or equal to 10(exp -3) eV. Nevertheless in the present experimental range (0.1 - 4 eV), the form, even without the second term, can be fitted to experimental results of PDI for He, Li, and Be, in contrast to the Wannier law which has a larger deviation from the data for Li and Be, for both of which the data show signs of modulation.

  2. Photo-Double Ionization: Threshold Law and Low-Energy Behavior

    NASA Technical Reports Server (NTRS)

    Bhatia, A. K.; Temkin, A.

    2007-01-01

    The threshold law for photoejection of two electrons from atoms (PDI) is derived from a modification of the Coulomb-dipole (C-D) theory. The C-D theory applies to two-electron ejection from negative ions (photo-double detachment:PDD). The modification consists of correctly accounting for the fact that in PDI that the two escaping electrons see a Coulomb field, asymptotically no matter what their relative distances from the residual ion are. We find in the contralinear spherically symmetric model that the analytic threshold law Q(E), i.e. the yield of residual ions, to be Q Integral of (E) varies as E + (C(sub w) E(sup gamma W)) +CE(sup 5/4) sin [1/2 ln E + phi]/ln(E). The first and third terms are beyond the Wannier law. Our threshold law can only be rigorously justified for residual energies <= 10(exp -3) eV. Nevertheless in the present experimental range (0.1 - 4 eV), the form, even without the second term, can be fitted to experimental results of PDI for He, Li, and Be, in contrast to the Wannier law which has a larger deviation from the data for Li and Be.

  3. Direct Measurement of the Bubble Nucleation Energy Threshold in a CF3I Bubble Chamber

    SciTech Connect

    Behnke, E.; Benjamin, T.; Brice, S. J.; Broemmelsiek, D.; Collar, J. I.; Cooper, P. S.; Crisler, M.; Dahl, C. E.; Fustin, D.; Hall, Jeter C.; Harnish, C.; Levine, I.; Lippincott, W. H.; Moan, T.; Nania, T.; Neilson, R.; Ramberg, E.; Robinson, A. E.; Ruschman, M.; Sonnenschein, Andrew; Vazquez-Jauregui, E.; RIvera, R. A.; Uplegger, L.

    2013-07-30

    Here, we measured the energy threshold and efficiency for bubble nucleation from iodine recoils in a CF3I bubble chamber in the energy range of interest for a dark matter search. These interactions cannot be probed by standard neutron calibration methods, so we develop a new technique by observing the elastic scattering of 12 GeV/c negative pions. The pions are tracked with a silicon pixel telescope and the reconstructed scattering angle provides a measure of the nuclear recoil kinetic energy. The bubble chamber was operated with a nominal threshold of (13.6±0.6) keV. Interpretation of the results depends on the response to fluorine and carbon recoils, but in general we find agreement with the predictions of the classical bubble-nucleation theory. Moreover, this measurement confirms the applicability of CF3I as a target for spin-independent dark matter interactions and represents a novel technique for calibration of superheated fluid detectors.

  4. The threshold photoelectron spectrum of cyanovinylacetylene leads to an upward revision of the ionization energy

    NASA Astrophysics Data System (ADS)

    Holzmeier, Fabian; Lang, Melanie; Fischer, Ingo; Hemberger, Patrick

    2015-10-01

    Cyanovinylacetylene C5H3N was investigated by threshold photoelectron spectroscopy. The ionization energy (IE) was determined to be 10.04 eV. This value constitutes an upward revision of the earlier value of 9.33 eV. For both stereoisomers (trans and cis) computations predict very similar IEs and spectra. At 11.08 eV and 11.17 eV excited cationic states are observed. For the precursor 3-bromopyridine an IE of 9.34 eV was obtained. The appearance energy AE0K (3-bromopyridine, 3-pyridyl+) was determined to be 11.71 eV and a bond dissociation energy of the Csbnd Br bond in the 3-bromopyridine cation of 229 kJ mol-1 was derived.

  5. Dynamic spike threshold and nonlinear dendritic computation for coincidence detection in neuromorphic circuits.

    PubMed

    Hsu, Chih-Chieh; Parker, Alice C

    2014-01-01

    We present an electronic cortical neuron incorporating dynamic spike threshold and active dendritic properties. The circuit is simulated using a carbon nanotube field-effect transistor SPICE model. We demonstrate that our neuron has lower spike threshold for coincident synaptic inputs; however when the synaptic inputs are not in synchrony, it requires larger depolarization to evoke the neuron to fire. We also demonstrate that a dendritic spike is key to precisely-timed input-output transformation, produces reliable firing and results in more resilience to input jitter within an individual neuron.

  6. Threshold detection for the generalized Pareto distribution: Review of representative methods and application to the NOAA NCDC daily rainfall database

    NASA Astrophysics Data System (ADS)

    Langousis, Andreas; Mamalakis, Antonios; Puliga, Michelangelo; Deidda, Roberto

    2016-04-01

    In extreme excess modeling, one fits a generalized Pareto (GP) distribution to rainfall excesses above a properly selected threshold u. The latter is generally determined using various approaches, such as nonparametric methods that are intended to locate the changing point between extreme and nonextreme regions of the data, graphical methods where one studies the dependence of GP-related metrics on the threshold level u, and Goodness-of-Fit (GoF) metrics that, for a certain level of significance, locate the lowest threshold u that a GP distribution model is applicable. Here we review representative methods for GP threshold detection, discuss fundamental differences in their theoretical bases, and apply them to 1714 overcentennial daily rainfall records from the NOAA-NCDC database. We find that nonparametric methods are generally not reliable, while methods that are based on GP asymptotic properties lead to unrealistically high threshold and shape parameter estimates. The latter is justified by theoretical arguments, and it is especially the case in rainfall applications, where the shape parameter of the GP distribution is low; i.e., on the order of 0.1-0.2. Better performance is demonstrated by graphical methods and GoF metrics that rely on preasymptotic properties of the GP distribution. For daily rainfall, we find that GP threshold estimates range between 2 and 12 mm/d with a mean value of 6.5 mm/d, while the existence of quantization in the empirical records, as well as variations in their size, constitute the two most important factors that may significantly affect the accuracy of the obtained results.

  7. A comparison of acoustic cavitation detection thresholds measured with piezo-electric and fiber-optic hydrophone sensors.

    PubMed

    Bull, Victoria; Civale, John; Rivens, Ian; Ter Haar, Gail

    2013-12-01

    A Fabry-Perot interferometer fiber-optic hydrophone (FOH) was investigated for use as an acoustic cavitation detector and compared with a piezo-ceramic passive cavitation detector (PCD). Both detectors were used to measure negative pressure thresholds for broadband emissions in 3% agar and ex vivo bovine liver simultaneously. FOH-detected half- and fourth-harmonic emissions were also studied. Three thresholds were defined and investigated: (i) onset of cavitation; (ii) 100% probability of cavitation; and (iii) a time-integrated threshold where broadband signals integrated over a 3-s exposure duration, averaged over 5-10 repeat exposures, become statistically significantly greater than noise. The statistical sensitiviy of FOH broadband detection was low compared with that of the PCD (0.43/0.31 in agar/liver). FOH-detected fourth-harmonic data agreed best with PCD broadband (sensitivity: 0.95/0.94, specificity: 0.89/0.76 in agar/liver). The FOH has potential as a cavitation detector, particularly in applications where space is limited or during magnetic resonance-guided studies.

  8. Threshold level laser photoablation of crystalline silver: Ejected ion translational energy distributions

    NASA Astrophysics Data System (ADS)

    Helvajian, H.; Welle, R.

    1989-08-01

    We have conducted an experiment which measures, for a single laser shot, the ejected mass and nascent velocity distributions of ionic species ablated at laser fluences near the threshold for ion production. Our results show that for a crystalline silver target, the laser-ablated ion products are ejected with fixed kinetic energy equal to 9±1 eV (3 eV FWHM). The kinetic energy of the ejecta (Ag+,Ag+2, adsorbed Fe+) do not vary with wavelength (351 and 248 nm), nor with the ion product mass, and within limits are independent of the incident laser intensity. We do see a wavelength dependence in the threshold for ion production and in the dimer/monomer (Ag+/Ag+2) ion ratio. A number of possible mechanisms are presented to explain the data, although none is without some objection. Among these, the process whereby desorption is induced by electronic transitions (DIET processes) has some merit in explaining our data.

  9. Theoretical detection threshold of the proton-acoustic range verification technique

    PubMed Central

    Ahmad, Moiz; Xiang, Liangzhong; Yousefi, Siavash; Xing, Lei

    2015-01-01

    Purpose: Range verification in proton therapy using the proton-acoustic signal induced in the Bragg peak was investigated for typical clinical scenarios. The signal generation and detection processes were simulated in order to determine the signal-to-noise limits. Methods: An analytical model was used to calculate the dose distribution and local pressure rise (per proton) for beams of different energy (100 and 160 MeV) and spot widths (1, 5, and 10 mm) in a water phantom. In this method, the acoustic waves propagating from the Bragg peak were generated by the general 3D pressure wave equation implemented using a finite element method. Various beam pulse widths (0.1–10 μs) were simulated by convolving the acoustic waves with Gaussian kernels. A realistic PZT ultrasound transducer (5 cm diameter) was simulated with a Butterworth bandpass filter with consideration of random noise based on a model of thermal noise in the transducer. The signal-to-noise ratio on a per-proton basis was calculated, determining the minimum number of protons required to generate a detectable pulse. The maximum spatial resolution of the proton-acoustic imaging modality was also estimated from the signal spectrum. Results: The calculated noise in the transducer was 12–28 mPa, depending on the transducer central frequency (70–380 kHz). The minimum number of protons detectable by the technique was on the order of 3–30 × 106 per pulse, with 30–800 mGy dose per pulse at the Bragg peak. Wider pulses produced signal with lower acoustic frequencies, with 10 μs pulses producing signals with frequency less than 100 kHz. Conclusions: The proton-acoustic process was simulated using a realistic model and the minimal detection limit was established for proton-acoustic range validation. These limits correspond to a best case scenario with a single large detector with no losses and detector thermal noise as the sensitivity limiting factor. Our study indicated practical proton-acoustic range

  10. Theoretical detection threshold of the proton-acoustic range verification technique

    SciTech Connect

    Ahmad, Moiz; Yousefi, Siavash; Xing, Lei; Xiang, Liangzhong

    2015-10-15

    Purpose: Range verification in proton therapy using the proton-acoustic signal induced in the Bragg peak was investigated for typical clinical scenarios. The signal generation and detection processes were simulated in order to determine the signal-to-noise limits. Methods: An analytical model was used to calculate the dose distribution and local pressure rise (per proton) for beams of different energy (100 and 160 MeV) and spot widths (1, 5, and 10 mm) in a water phantom. In this method, the acoustic waves propagating from the Bragg peak were generated by the general 3D pressure wave equation implemented using a finite element method. Various beam pulse widths (0.1–10 μs) were simulated by convolving the acoustic waves with Gaussian kernels. A realistic PZT ultrasound transducer (5 cm diameter) was simulated with a Butterworth bandpass filter with consideration of random noise based on a model of thermal noise in the transducer. The signal-to-noise ratio on a per-proton basis was calculated, determining the minimum number of protons required to generate a detectable pulse. The maximum spatial resolution of the proton-acoustic imaging modality was also estimated from the signal spectrum. Results: The calculated noise in the transducer was 12–28 mPa, depending on the transducer central frequency (70–380 kHz). The minimum number of protons detectable by the technique was on the order of 3–30 × 10{sup 6} per pulse, with 30–800 mGy dose per pulse at the Bragg peak. Wider pulses produced signal with lower acoustic frequencies, with 10 μs pulses producing signals with frequency less than 100 kHz. Conclusions: The proton-acoustic process was simulated using a realistic model and the minimal detection limit was established for proton-acoustic range validation. These limits correspond to a best case scenario with a single large detector with no losses and detector thermal noise as the sensitivity limiting factor. Our study indicated practical proton

  11. Spectroscopic investigation of laser water interaction beyond the breakdown threshold energy

    NASA Astrophysics Data System (ADS)

    De Giacomo, A.; Dell'Aglio, M.; De Pascale, O.; Capitelli, M.

    2007-02-01

    The interaction between ns-laser pulse at 532 nm and water, or heavy water (deuterium dioxide), has been studied by Stimulated Raman Scattering (SRS) and optical emission spectroscopy. Both the photolysis and breakdown processes have been considered. When the photolysis is the main process, structural change in water occurs as a consequence of electron and proton hydration. The rearrangement of the water structure and the subsequent photon absorption by free electrons raising the breakdown threshold occur. Moreover, charge separation in bulk water, under laser induced electromagnetic field, leads to a notable enhancement of the SRS signal. On the other hand, for a high laser pulse energy density, electrons gain energy enough to escape from the hydrating water structure, generating electron impact dominated plasma.

  12. Dynamics of strangeness production in heavy-ion collisions near threshold energies

    SciTech Connect

    Feng Zhaoqing; Jin Genming

    2010-11-15

    Within the framework of the improved isospin-dependent quantum molecular dynamics (ImIQMD) model, the dynamics of strangeness (K{sup 0,+}, {Lambda}, and {Sigma}{sup -,0,+}) production in heavy-ion collisions near threshold energies is investigated systematically, with the strange particles considered to be produced mainly by inelastic collisions of baryon-baryon and pion-baryon. Collisions in the region of suprasaturation densities of the dense baryonic matter formed in heavy-ion collisions dominate the yields of strangeness production. Total multiplicities as functions of incident energies and collision centralities are calculated with the Skyrme parameter SLy6. The excitation function of strangeness production is analyzed and also compared with the KaoS data for K{sup +} production in the reactions {sup 12}C+{sup 12}C and {sup 197}Au+{sup 197}Au.

  13. {phi}-Meson Photoproduction with Linearly Polarized Photons at Threshold Energies

    SciTech Connect

    Salamanca, Julian; Cole, Philip L.

    2007-10-26

    The observables provided by linearly-polarized photons are of interest in delineating the contributions of the various hadronic processes giving rise to vector meson photoproduction. In particular, we describe how {phi}-meson production affords an incisive tool for exploring the nature of the parity exchange at threshold energies, the strangeness content of proton, as well as extracting signatures for the violation of Okubo-Zweig-Iizuka observation (OZI rule). Our goal is to study the {gamma}-vectorp{yields}{phi}p reaction, with {phi}{yields}K{sup +}K{sup -}, in the photon energy range of 1.7 to 2.1 GeV by using the Coherent Linear Bremsstrahlung Facility in Hall B of Jefferson Laboratory, Newport News, VA. The data were collected during the g8b run in the summer of 2005.

  14. Φ-Meson Photoproduction with Linearly Polarized Photons at Threshold Energies

    SciTech Connect

    Salamanca, Julian; Cole, Philip L

    2007-10-01

    The observables provided by linearly-polarized photons are of interest in delineating the contributions of the various hadronic processes giving rise to vector meson photoproduction. In particular, we describe how Φ-meson production affords an incisive tool for exploring the nature of the parity exchange at threshold energies, the strangeness content of proton, as well as extracting signatures for the violation of Okubo-Zweig-Iizuka observation (OZI rule). Our goal is to study the γp → Φp reaction, with Φ → K+K-, in the photon energy range of 1.7 to 2.1 GeV by using the Coherent Linear Bremsstrahlung Facility in Hall B of Jefferson Laboratory, Newport News, VA. The data were collected during the g8b run in the summer of 2005.

  15. Toward perpetual wireless networks: Opportunistic large arrays with transmission thresholds and energy harvesting

    NASA Astrophysics Data System (ADS)

    Kailas, Aravind

    Solving the key issue of sustainability of battery-powered sensors continues to attract significant research attention. The prevailing theme of this research is to address this concern using energy-efficient protocols based on a form of simple cooperative transmission (CT) called the opportunistic large arrays (OLAs), and intelligent exploitation of energy harvesting and hybrid energy storage systems (HESSs). The two key contributions of this research, namely, OLA with transmission threshold (OLA-T) and alternating OLA-T (A-OLA-T), offer an signal-to-noise ratio (SNR) advantage (i.e., benefits of diversity and array (power) gains) in a multi-path fading environment, thereby reducing transmit powers or extending range. Because these protocols do not address nodes individually, the network overhead remains constant for high density networks or nodes with mobility. During broadcasting across energy-constrained networks, while OLA-T saves energy by limiting node participation within a single broadcast, A-OLA-T optimizes over multiple broadcasts and drains the nodes in an equitable fashion. A major bottleneck for network sustainability is the ability of a rechargeable battery (RB) to store energy, which is limited by the number of charge-discharge cycles. Energy harvesting using a HESS that comprises a RB and a supercapacitor (SC) will minimize the RB usage, thereby preserving the charge-discharge cycles. Studying the HESS is important, rather than the SC-alone because while an SC with harvested energy may be sufficient for routine monitoring, if there is an alert, the RB could be used as necessary to support the heavier reporting requirements. Therefore, another key contribution of this research is the design and analysis of a novel routing metric called communications using HESS (CHESS), which extends the RB-life by relaying exclusively with SC energy.

  16. Precipitation thresholds and debris flow warning: comparing gauge versus weather radar detection

    NASA Astrophysics Data System (ADS)

    Marra, Francesco; Borga, Marco; Creutin, Jean-Dominique

    2013-04-01

    Methods relying on rainfall thresholds for debris-flow warning have a long tradition in geomorphology. Usually, the precipitation thresholds are developed based on rain gauge and debris flows data. However, it is well known that extreme rainfall sampling errors over rugged topography may lead to biased precipitation thresholds. At least two reasons contribute to such sampling errors: i) the regions of complex topography have low rain gauge densities; ii) orography may enhance intense precipitation at very localized places. We studied six storm events that triggered several debris flows each over the Trentino-Alto Adige Region, in the central Italian Alps, between 2005 and 2010. The region is monitored by i) a rain gauge network with an average density of 1/100 km2 and ii) a C-band radar instrument. Radar data have been accurately corrected for errors due to ground clutter contamination, beam blockages, vertical profile of reflectivity, attenuation and wet radome in order to obtain a high quality set of radar-based rainfall fields. We characterized the variability of each rainfall event using space (horizontal) and time variograms and we investigated the altitude (vertical) distribution of rainfall using hypsometric rainfall moments. We also defined the local severity of the rainfall accumulations over the debris flow areas for different time accumulations. We used the radar precipitation fields to represent space-time rainfall variability and we simulated gauge sampling with a stochastic model accounting for sub-grid variability of precipitation and for gauge measurement errors. We show that rain gauges systematically underestimate the local severity over the proven debris flow triggering locations. This leads to biased precipitation thresholds. In this respect gauge spatial sampling appears inappropriate both in the horizontal and in the vertical dimensions while the usual gauge time sampling looks appropriate. Moreover, this shows the potential of rainfall

  17. Olfaction and Environment: Tsimane’ of Bolivian Rainforest Have Lower Threshold of Odor Detection Than Industrialized German People

    PubMed Central

    Sorokowska, Agnieszka; Sorokowski, Piotr; Hummel, Thomas; Huanca, Tomas

    2013-01-01

    Olfactory sensitivity varies between individuals. However, data regarding cross-cultural and inter-group differences are scarce. We compared the thresholds of odor detection of the traditional society of Tsimane’ (native Amazonians of the Bolivian rainforest; n = 151) and people living in Dresden (Germany; n = 286) using “Sniffin’ Sticks” threshold subtest. Tsimane’ detected n-butanol at significantly lower concentrations than the German subjects. The distribution of thresholds of the Tsimane’ was very specific, with 25% of Tsimane’ obtaining better results in the olfactory test than any member of the German group. These data suggest that differences in olfactory sensitivity seem to be especially salient between industrialized and non-industrialized populations inhabiting different environmental conditions. We hypothesize that the possible sources of such differences are: (i) the impact of pollution which impairs the olfactory abilities of people from industrialized countries; (ii) better training of olfaction because of the higher importance of smell in traditional populations; (iii) environmental pressures shaping olfactory abilities in these populations. PMID:23922693

  18. ML-PMHT track detection threshold determination for K-distributed clutter

    NASA Astrophysics Data System (ADS)

    Schoenecker, Steven; Willett, Peter; Bar-Shalom, Yaakov

    2014-06-01

    Recentwork developed a novelmethod for determining tracking thresholds for theMaximumLikelihood ProbabilisticMulti- Hypothesis Tracker (ML-PMHT). Under certain "ideal" conditions, probability density functions (PDFs) for the peak points in the ML-PMHT log-likelihood ratio (LLR) due to just clutter measurements could be calculated. Analysis of these clutter-induced peak PDFs allowed for the calculation of tracking thresholds, which previously had to be donewith time-consumingMonte Carlo simulations. However, this work was done for a very specific case: the amplitudes of both target and cluttermeasurements followed Rayleigh distributions. The Rayleigh distribution is a very light-tailed distribution, and it can be overly optimistic in predicting that high-SNR measurements are target-originated. This work examines the case where the clutter amplitudes do not follow a Rayleigh distribution at all, but instead follow a K-distribution, which more accurately describes active acoustic clutter. This will provide a framework for determining accurate tracking thresholds for the ML-PMHT algorithm.

  19. Detecting Fragmentation Extinction Thresholds for Forest Understory Plant Species in Peninsular Spain

    PubMed Central

    Rueda, Marta; Moreno Saiz, Juan Carlos; Morales-Castilla, Ignacio; Albuquerque, Fabio S.; Ferrero, Mila; Rodríguez, Miguel Á.

    2015-01-01

    Ecological theory predicts that fragmentation aggravates the effects of habitat loss, yet empirical results show mixed evidences, which fail to support the theory instead reinforcing the primary importance of habitat loss. Fragmentation hypotheses have received much attention due to their potential implications for biodiversity conservation, however, animal studies have traditionally been their main focus. Here we assess variation in species sensitivity to forest amount and fragmentation and evaluate if fragmentation is related to extinction thresholds in forest understory herbs and ferns. Our expectation was that forest herbs would be more sensitive to fragmentation than ferns due to their lower dispersal capabilities. Using forest cover percentage and the proportion of this percentage occurring in the largest patch within UTM cells of 10-km resolution covering Peninsular Spain, we partitioned the effects of forest amount versus fragmentation and applied logistic regression to model occurrences of 16 species. For nine models showing robustness according to a set of quality criteria we subsequently defined two empirical fragmentation scenarios, minimum and maximum, and quantified species’ sensitivity to forest contraction with no fragmentation, and to fragmentation under constant forest cover. We finally assessed how the extinction threshold of each species (the habitat amount below which it cannot persist) varies under no and maximum fragmentation. Consistent with their preference for forest habitats probability occurrences of all species decreased as forest cover contracted. On average, herbs did not show significant sensitivity to fragmentation whereas ferns were favored. In line with theory, fragmentation yielded higher extinction thresholds for two species. For the remaining species, fragmentation had either positive or non-significant effects. We interpret these differences as reflecting species-specific traits and conclude that although forest amount is of

  20. Detecting fragmentation extinction thresholds for forest understory plant species in peninsular Spain.

    PubMed

    Rueda, Marta; Moreno Saiz, Juan Carlos; Morales-Castilla, Ignacio; Albuquerque, Fabio S; Ferrero, Mila; Rodríguez, Miguel Á

    2015-01-01

    Ecological theory predicts that fragmentation aggravates the effects of habitat loss, yet empirical results show mixed evidences, which fail to support the theory instead reinforcing the primary importance of habitat loss. Fragmentation hypotheses have received much attention due to their potential implications for biodiversity conservation, however, animal studies have traditionally been their main focus. Here we assess variation in species sensitivity to forest amount and fragmentation and evaluate if fragmentation is related to extinction thresholds in forest understory herbs and ferns. Our expectation was that forest herbs would be more sensitive to fragmentation than ferns due to their lower dispersal capabilities. Using forest cover percentage and the proportion of this percentage occurring in the largest patch within UTM cells of 10-km resolution covering Peninsular Spain, we partitioned the effects of forest amount versus fragmentation and applied logistic regression to model occurrences of 16 species. For nine models showing robustness according to a set of quality criteria we subsequently defined two empirical fragmentation scenarios, minimum and maximum, and quantified species' sensitivity to forest contraction with no fragmentation, and to fragmentation under constant forest cover. We finally assessed how the extinction threshold of each species (the habitat amount below which it cannot persist) varies under no and maximum fragmentation. Consistent with their preference for forest habitats probability occurrences of all species decreased as forest cover contracted. On average, herbs did not show significant sensitivity to fragmentation whereas ferns were favored. In line with theory, fragmentation yielded higher extinction thresholds for two species. For the remaining species, fragmentation had either positive or non-significant effects. We interpret these differences as reflecting species-specific traits and conclude that although forest amount is of

  1. NHANES III: influence of race on GFR thresholds and detection of metabolic abnormalities.

    PubMed

    Foley, Robert N; Wang, Changchun; Ishani, Areef; Collins, Allan J

    2007-09-01

    Whether the creatinine-based glomerular filtration rate (GFR) thresholds used to define chronic kidney disease (CKD) identify metabolic abnormalities similarly in minority and nonminority populations is unknown. We addressed this question among adult participants in the Third National Health and Nutrition Examination Survey (NHANES III) (n = 15,837). GFR was estimated from serum creatinine values and metabolic abnormalities were defined by 5th or 95th percentile values. After adjustment for age, demographic characteristics, and GFR, black participants were significantly more likely than white participants to have abnormal levels of systolic and diastolic blood pressure, hemoglobin, phosphorus, and uric acid. Hispanic subjects were significantly more likely to have abnormal levels of systolic blood pressure, hemoglobin, bicarbonate, and phosphorus. Among participants with GFR < 60 mL/min per 1.73 m(2), black participants were significantly more likely to have abnormal levels of systolic and diastolic blood pressure, hemoglobin, and uric acid; Hispanic subjects were significantly more likely to have abnormal systolic blood pressure levels. Metabolic abnormalities were more common in minority populations, and low GFR appeared to have a multiplicative effect. Defining CKD using a single GFR threshold may be disadvantageous for minority populations because metabolic abnormalities are present at higher levels of GFR.

  2. Perimetry of contrast detection thresholds of moving spatial sine wave patterns. IV. The influence of the mean retinal illuminance.

    PubMed

    Koenderink, J J; Bouman, M A; Bueno de Mesquita, A E; Slappendel, S

    1978-06-01

    Contrast detection thresholds for moving sine wave gratings were obtained at the fovea and at eccentricities of 6 degrees, 21 degrees, and 50 degrees on the nasal horizontal meridian. The targets subtended from 30 X 30 minutes of arc up to 16 degrees X 16 degrees. Mean retinal illuminance was varied between 10 and 0.01 trolands. The transition from the de Vries-Rose to the Weber region occurs in the far peripheral visual field at a 2-3 decades lower illuminance level than at the fovea. The spatio-temporal contrast detection thresholds become comparable over the whole visual field if the mean distance between retinal ganglion cells is taken as a yardstick, and field width, spatial frequency, and quantum density are scaled accordingly. This means that at scotopic illuminance levels coarse or medium gratings are preferentially detected at other than foveal locations. (The fine gratings cannot be resolved at all at such levels.) It is argued that both electrophysiological and psychophysical evidence indicates that Weber behavior starts whenever some small fixed number of quantum absorptions occur within an area of 1 mean interganglion cell distance across. Or, equivalently, if a fixed small number of "neural quanta" enters a 100 X 100 micron2 area of the visual cortex.

  3. Comparison of Threshold Detection Methods for the Generalized Pareto Distribution (GPD): Application to the NOAA-NCDC Daily Rainfall Dataset

    NASA Astrophysics Data System (ADS)

    Deidda, Roberto; Mamalakis, Antonis; Langousis, Andreas

    2015-04-01

    One of the most crucial issues in statistical hydrology is the estimation of extreme rainfall from data. To that extent, based on asymptotic arguments from Extreme Excess (EE) theory, several studies have focused on developing new, or improving existing methods to fit a Generalized Pareto Distribution (GPD) model to rainfall excesses above a properly selected threshold u. The latter is generally determined using various approaches that can be grouped into three basic classes: a) non-parametric methods that locate the changing point between extreme and non-extreme regions of the data, b) graphical methods where one studies the dependence of the GPD parameters (or related metrics) to the threshold level u, and c) Goodness of Fit (GoF) metrics that, for a certain level of significance, locate the lowest threshold u that a GPD model is applicable. In this work, we review representative methods for GPD threshold detection, discuss fundamental differences in their theoretical bases, and apply them to daily rainfall records from the NOAA-NCDC open-access database (http://www.ncdc.noaa.gov/oa/climate/ghcn-daily/). We find that non-parametric methods that locate the changing point between extreme and non-extreme regions of the data are generally not reliable, while graphical methods and GoF metrics that rely on limiting arguments for the upper distribution tail lead to unrealistically high thresholds u. The latter is expected, since one checks the validity of the limiting arguments rather than the applicability of a GPD distribution model. Better performance is demonstrated by graphical methods and GoF metrics that rely on GPD properties. Finally, we discuss the effects of data quantization (common in hydrologic applications) on the estimated thresholds. Acknowledgments: The research project is implemented within the framework of the Action «Supporting Postdoctoral Researchers» of the Operational Program "Education and Lifelong Learning" (Action's Beneficiary: General

  4. A chromogenic limulus test for detection of microbes that decreases the laser damage threshold of potassium dihydrogen phosphate crystals

    NASA Astrophysics Data System (ADS)

    Yokotani, A.; Nishida, Y.; Fujioka, K.; Sasaki, T.; Yamanaka, T.; Yamanaka, C.

    1987-05-01

    The chromogenic limulus test has been applied for the first time to detect an organic impurity contained in potassium dihydrogen phosphate (KDP) crystals. Impurities arise from microbes present during crystal growth, and are responsible for a reduced laser damage threshold. A sensitivity of 10 pg/g KDP (10-5 ppm) was achieved, provided that the KDP solution was neutralized to ˜pH 7. Endotoxin content in the prismatic region of KDP crystals grown in a microbe-rich solution was approximately 100 pg/g KDP. The presence of an organic material in seemingly perfect KDP crystals could be experimentally confirmed.

  5. Fall detection algorithm in energy efficient multistate sensor system.

    PubMed

    Korats, Gundars; Hofmanis, Janis; Skorodumovs, Aleksejs; Avots, Egils

    2015-01-01

    Health issues for elderly people may lead to different injuries obtained during simple activities of daily living (ADL). Potentially the most dangerous are unintentional falls that may be critical or even lethal to some patients due to the heavy injury risk. Many fall detection systems are proposed but only recently such health care systems became available. Nevertheless sensor design, accuracy as well as energy consumption efficiency can be improved. In this paper we present a single 3-axial accelerometer energy-efficient sensor system. Power saving is achieved by selective event processing triggered by fall detection procedure. The results in our simulations show 100% accuracy when the threshold parameters are chosen correctly. Estimated energy consumption seems to extend battery life significantly. PMID:26737408

  6. Measuring single electron charging energy in self-assembled single nanoparticle devices: Coulomb blockade threshold vs. Arrhenius energy

    NASA Astrophysics Data System (ADS)

    Dhirani, Al-Amin; Zabet-Khosousi, Amir

    2009-03-01

    Single-nanoparticle (NP) devices formed by self-assembling NPs onto alkanedithiol-functionalized break junctions exhibit Coulomb blockade (CB) conductance suppressions at low temperatures. We have studied temperature dependence of conductance inside the CB region and find multiple activation energies (Ea): A small Ea at low temperatures, and a larger Ea at high temperatures. The small Ea is independent of NP size and is attributed to an energy state located at the metal--molecule contact. The larger Ea scales with NP size and is attributed to single electron charging energy of the NPs. Importantly, we observe a significant (˜5--100 fold) discrepancy between values of charging energies obtained from CB voltage thresholds and Ea. To account for the discrepancy, we propose a model in which electrons are temporarily localized at the energy states near the metal--molecule interface and lose energy. The proposed model is supported by ultraviolet photoelectron spectroscopy of alkanedithiol monolayers on gold which indicates a presence of energy states close to the Fermi level of gold likely arising from gold--thiolate bonds. A suitably modified Orthodox theory successfully describes our measurements.

  7. Lowering IceCube's Energy Threshold for Point Source Searches in the Southern Sky

    NASA Astrophysics Data System (ADS)

    Aartsen, M. G.; Abraham, K.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Altmann, D.; Andeen, K.; Anderson, T.; Ansseau, I.; Anton, G.; Archinger, M.; Arguelles, C.; Arlen, T. C.; Auffenberg, J.; Bai, X.; Barwick, S. W.; Baum, V.; Bay, R.; Beatty, J. J.; Becker Tjus, J.; Becker, K.-H.; BenZvi, S.; Berghaus, P.; Berley, D.; Bernardini, E.; Bernhard, A.; Besson, D. Z.; Binder, G.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blot, S.; Boersma, D. J.; Bohm, C.; Börner, M.; Bos, F.; Bose, D.; Böser, S.; Botner, O.; Braun, J.; Brayeur, L.; Bretz, H.-P.; Burgman, A.; Buzinsky, N.; Casey, J.; Casier, M.; Cheung, E.; Chirkin, D.; Christov, A.; Clark, K.; Classen, L.; Coenders, S.; Collin, G. H.; Conrad, J. M.; Cowen, D. F.; Cruz Silva, A. H.; Daughhetee, J.; Davis, J. C.; Day, M.; de André, J. P. A. M.; De Clercq, C.; del Pino Rosendo, E.; Dembinski, H.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de Wasseige, G.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; di Lorenzo, V.; Dujmovic, H.; Dumm, J. P.; Dunkman, M.; Eberhardt, B.; Ehrhardt, T.; Eichmann, B.; Euler, S.; Evenson, P. A.; Fahey, S.; Fazely, A. R.; Feintzeig, J.; Felde, J.; Filimonov, K.; Finley, C.; Flis, S.; Fösig, C.-C.; Fuchs, T.; Gaisser, T. K.; Gaior, R.; Gallagher, J.; Gerhardt, L.; Ghorbani, K.; Gladstone, L.; Glagla, M.; Glüsenkamp, T.; Goldschmidt, A.; Golup, G.; Gonzalez, J. G.; Góra, D.; Grant, D.; Griffith, Z.; Ha, C.; Haack, C.; Haj Ismail, A.; Hallgren, A.; Halzen, F.; Hansen, E.; Hansmann, B.; Hansmann, T.; Hanson, K.; Hebecker, D.; Heereman, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hignight, J.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Holzapfel, K.; Homeier, A.; Hoshina, K.; Huang, F.; Huber, M.; Huelsnitz, W.; Hultqvist, K.; In, S.; Ishihara, A.; Jacobi, E.; Japaridze, G. S.; Jeong, M.; Jero, K.; Jones, B. J. P.; Jurkovic, M.; Kappes, A.; Karg, T.; Karle, A.; Katz, U.; Kauer, M.; Keivani, A.; Kelley, J. L.; Kemp, J.; Kheirandish, A.; Kim, M.; Kintscher, T.; Kiryluk, J.; Klein, S. R.; Kohnen, G.; Koirala, R.; Kolanoski, H.; Konietz, R.; Köpke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Krings, K.; Kroll, M.; Krückl, G.; Krüger, C.; Kunnen, J.; Kunwar, S.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Lanfranchi, J. L.; Larson, M. J.; Lennarz, D.; Lesiak-Bzdak, M.; Leuermann, M.; Leuner, J.; Lu, L.; Lünemann, J.; Madsen, J.; Maggi, G.; Mahn, K. B. M.; Mancina, S.; Mandelartz, M.; Maruyama, R.; Mase, K.; Matis, H. S.; Maunu, R.; McNally, F.; Meagher, K.; Medici, M.; Meier, M.; Meli, A.; Menne, T.; Merino, G.; Meures, T.; Miarecki, S.; Middell, E.; Mohrmann, L.; Montaruli, T.; Nahnhauer, R.; Naumann, U.; Neer, G.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke Pollmann, A.; Olivas, A.; Omairat, A.; O'Murchadha, A.; Palczewski, T.; Pandya, H.; Pankova, D. V.; Penek, Ö.; Pepper, J. A.; Pérez de los Heros, C.; Pfendner, C.; Pieloth, D.; Pinat, E.; Posselt, J.; Price, P. B.; Przybylski, G. T.; Quinnan, M.; Raab, C.; Rädel, L.; Rameez, M.; Rawlins, K.; Reimann, R.; Relich, M.; Resconi, E.; Rhode, W.; Richman, M.; Riedel, B.; Robertson, S.; Rongen, M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Sabbatini, L.; Sandrock, A.; Sandroos, J.; Sarkar, S.; Satalecka, K.; Schimp, M.; Schlunder, P.; Schmidt, T.; Schoenen, S.; Schöneberg, S.; Schönwald, A.; Schumacher, L.; Seckel, D.; Seunarine, S.; Soldin, D.; Song, M.; Spiczak, G. M.; Spiering, C.; Stahlberg, M.; Stamatikos, M.; Stanev, T.; Stasik, A.; Steuer, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Ström, R.; Strotjohann, N. L.; Sullivan, G. W.; Sutherland, M.; Taavola, H.; Taboada, I.; Tatar, J.; Ter-Antonyan, S.; Terliuk, A.; Tešić, G.; Tilav, S.; Toale, P. A.; Tobin, M. N.; Toscano, S.; Tosi, D.; Tselengidou, M.; Turcati, A.; Unger, E.; Usner, M.; Vallecorsa, S.; Vandenbroucke, J.; van Eijndhoven, N.; Vanheule, S.; van Rossem, M.; van Santen, J.; Veenkamp, J.; Vehring, M.; Voge, M.; Vraeghe, M.; Walck, C.; Wallace, A.; Wallraff, M.; Wandkowsky, N.; Weaver, Ch.; Wendt, C.; Westerhoff, S.; Whelan, B. J.; Whitehorn, N.; Wickmann, S.; Wiebe, K.; Wiebusch, C. H.; Wille, L.; Williams, D. R.; Wills, L.; Wissing, H.; Wolf, M.; Wood, T. R.; Woschnagg, K.; Xu, D. L.; Xu, X. W.; Xu, Y.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zoll, M.; IceCube Collaboration

    2016-06-01

    Observation of a point source of astrophysical neutrinos would be a “smoking gun” signature of a cosmic-ray accelerator. While IceCube has recently discovered a diffuse flux of astrophysical neutrinos, no localized point source has been observed. Previous IceCube searches for point sources in the southern sky were restricted by either an energy threshold above a few hundred TeV or poor neutrino angular resolution. Here we present a search for southern sky point sources with greatly improved sensitivities to neutrinos with energies below 100 TeV. By selecting charged-current ν μ interacting inside the detector, we reduce the atmospheric background while retaining efficiency for astrophysical neutrino-induced events reconstructed with sub-degree angular resolution. The new event sample covers three years of detector data and leads to a factor of 10 improvement in sensitivity to point sources emitting below 100 TeV in the southern sky. No statistically significant evidence of point sources was found, and upper limits are set on neutrino emission from individual sources. A posteriori analysis of the highest-energy (˜100 TeV) starting event in the sample found that this event alone represents a 2.8σ deviation from the hypothesis that the data consists only of atmospheric background.

  8. Inclusive neutrino scattering off deuteron from threshold to GeV energies

    SciTech Connect

    Gang Shen, Laura E. Marcucci, Joseph Carlson, Stefano Gandolfi, Rocco Schiavilla

    2012-09-01

    Cross sections for inclusive neutrino scattering off deuteron induced by neutral and charge-changing weak currents are calculated from threshold up to GeV energies, using the Argonne v{sub 18} potential and consistent nuclear electroweak currents with one- and two-body terms. Two-body contributions are found to be small, and increase the cross sections obtained with one-body currents by less than 10% over the whole range of energies. Total cross sections obtained by describing the final two-nucleon states with plane waves differ negligibly, for neutrino energies {approx}> 500 MeV, from those in which interaction effects in these states are fully accounted for. The sensitivity of the calculated cross sections to different models for the two-nucleon potential and/or two-body terms in the weak current is found to be weak. In order to illustrate nuclear structure effects, the cross sections are compared to those obtained in a naive model in which the deuteron is taken to consist of a free proton and neutron at rest.

  9. Proton and Electron Threshold Energy Measurements for Extravehicular Activity Space Suits. Chapter 2

    NASA Technical Reports Server (NTRS)

    Moyers, M. F.; Nelson, G. D.; Saganti, P. B.

    2003-01-01

    Construction of ISS will require more than 1000 hours of EVA. Outside of ISS during EVA, astronauts and cosmonauts are likely to be exposed to a large fluence of electrons and protons. Development of radiation protection guidelines requires the determination of the minimum energy of electrons and protons that penetrate the suits at various locations. Measurements of the water-equivalent thickness of both US. and Russian EVA suits were obtained by performing CT scans. Specific regions of interest of the suits were further evaluated using a differential range shift technique. This technique involved measuring thickness ionization curves for 6-MeV electron and 155-MeV proton beams with ionization chambers using a constant source-to-detector distance. The thicknesses were obtained by stacking polystyrene slabs immediately upstream of the detector. The thicknesses of the 50% ionizations relative to the maximum ionizations were determined. The detectors were then placed within the suit and the stack thickness adjusted until the 50% ionization was reestablished. The difference in thickness between the 50% thicknesses was then used with standard range-energy tables to determine the threshold energy for penetration. This report provides a detailed description of the experimental arrangement and results.

  10. Displacement Threshold Energy and Recovery in an Al-Ti Nanolayered System with Intrinsic Point Defect Partitioning

    SciTech Connect

    Gerboth, Matthew D.; Setyawan, Wahyu; Henager, Charles H.

    2014-01-07

    A method is established and validated using molecular dynamics (MD) to determine the displacement threshold energies as Ed in nanolayered, multilayered systems of dissimilar metals. The method is applied to specifically oriented nanolayered films of Al-Ti where the crystal structure and interface orientations are varied in atomic models and Ed is calculated. Methods for defect detection are developed and discussed based on prior research in the literature and based on specific crystallographic directions available in the nanolayered systems. These are compared and contrasted to similar calculations in corresponding bulk materials, including fcc Al, fcc Ti, hcp Al, and hcp Ti. In all cases, the calculated Ed in the multilayers are intermediate to the corresponding bulk values but exhibit some important directionality. In the nanolayer, defect detection demonstrated systematic differences in the behavior of Ed in each layer. Importantly, collision cascade damage exhibits significant defect partitioning within the Al and Ti layers that is hypothesized to be an intrinsic property of dissimilar nanolayered systems. This type of partitioning could be partly responsible for observed asymmetric radiation damage responses in many multilayered systems. In addition, a pseudo-random direction was introduced to approximate the average Ed without performing numerous simulations with random directions.

  11. Threshold quantum cryptography

    SciTech Connect

    Tokunaga, Yuuki; Okamoto, Tatsuaki; Imoto, Nobuyuki

    2005-01-01

    We present the concept of threshold collaborative unitary transformation or threshold quantum cryptography, which is a kind of quantum version of threshold cryptography. Threshold quantum cryptography states that classical shared secrets are distributed to several parties and a subset of them, whose number is greater than a threshold, collaborates to compute a quantum cryptographic function, while keeping each share secretly inside each party. The shared secrets are reusable if no cheating is detected. As a concrete example of this concept, we show a distributed protocol (with threshold) of conjugate coding.

  12. Temporal variation in spectral detection thresholds of substrate and vegetation in AVIRIS images

    NASA Technical Reports Server (NTRS)

    Sabol, Donald E., Jr.; Roberts, Dar A.; Smith, Milton O.; Adams, John B.

    1992-01-01

    The ability to map changes over large surface areas over time is one of the advantages in using remote sensing as a monitoring tool. Temporal changes in the surface may be gradual, making them difficult to detect in the short-term, and because they commonly occur at the subpixel scale, they may be difficult to detect in the long-term as well. Also, subtle changes may be real or merely an artifact of image noise. It is, therefore, necessary to understand the factors that limit the detection of surface materials in evaluating temporal data. The spectral detectability of vegetation and soil in the 1990 July and October Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data of Jasper Ridge, CA was evaluated and compared.

  13. Development and utility of an internal threshold control (ITC) real-time PCR assay for exogenous DNA detection.

    PubMed

    Ni, Weiyi; Le Guiner, Caroline; Moullier, Philippe; Snyder, Richard O

    2012-01-01

    Sensitive and specific tests for detecting exogenous DNA molecules are useful for infectious disease diagnosis, gene therapy clinical trial safety, and gene doping surveillance. Taqman real-time PCR using specific sequence probes provides an effective approach to accurately and quantitatively detect exogenous DNA. However, one of the major challenges in these analyses is to eliminate false positive signals caused by either non-targeted exogenous or endogenous DNA sequences, or false negative signals caused by impurities that inhibit PCR. Although multiplex Taqman PCR assays have been applied to address these problems by adding extra primer-probe sets targeted to endogenous DNA sequences, the differences between targets can lead to different detection efficiencies. To avoid these complications, a Taqman PCR-based approach that incorporates an internal threshold control (ITC) has been developed. In this single reaction format, the target sequence and ITC template are co-amplified by the same primers, but are detected by different probes each with a unique fluorescent dye. Sample DNA, a prescribed number of ITC template molecules set near the limit of sensitivity, a single pair of primers, target probe and ITC probe are added to one reaction. Fluorescence emission signals are obtained simultaneously to determine the cycle thresholds (Ct) for amplification of the target and ITC sequences. The comparison of the target Ct with the ITC Ct indicates if a sample is a true positive for the target (i.e. Ct less than or equal to the ITC Ct) or negative (i.e. Ct greater than the ITC Ct). The utility of this approach was demonstrated in a nonhuman primate model of rAAV vector mediated gene doping in vivo and in human genomic DNA spiked with plasmid DNA.

  14. A multichannel integrated circuit for neural spike detection based on EC-PC threshold estimation.

    PubMed

    Wu, Tong; Yang, Zhi

    2013-01-01

    In extracellular neural recording experiments, spike detection is an important step for information decoding of neuronal activities. An ASIC implementation of detection algorithms can provide substantial data-rate reduction and facilitate wireless operations. In this paper, we present a 16-channel neural spike detection ASIC. The chip takes raw data as inputs, and outputs three data streams simultaneously: field potentials down sampled at 1.25 KHz, band-pass filtered neural data, and spiking probability maps sampled at 40 KHz. The functionality and the performance of the chip have been verified in both in-vivo and benchtop experiments. Fabricated in a 0.13 µm CMOS process, the chip has a peak power dissipation of 85 µW per channel and achieves a data-rate reduction of 98.44%.

  15. Acetic Acid Detection Threshold in Synthetic Wine Samples of a Portable Electronic Nose

    PubMed Central

    Macías, Miguel Macías; Manso, Antonio García; Orellana, Carlos Javier García; Velasco, Horacio Manuel González; Caballero, Ramón Gallardo; Chamizo, Juan Carlos Peguero

    2013-01-01

    Wine quality is related to its intrinsic visual, taste, or aroma characteristics and is reflected in the price paid for that wine. One of the most important wine faults is the excessive concentration of acetic acid which can cause a wine to take on vinegar aromas and reduce its varietal character. Thereby it is very important for the wine industry to have methods, like electronic noses, for real-time monitoring the excessive concentration of acetic acid in wines. However, aroma characterization of alcoholic beverages with sensor array electronic noses is a difficult challenge due to the masking effect of ethanol. In this work, in order to detect the presence of acetic acid in synthetic wine samples (aqueous ethanol solution at 10% v/v) we use a detection unit which consists of a commercial electronic nose and a HSS32 auto sampler, in combination with a neural network classifier (MLP). To find the characteristic vector representative of the sample that we want to classify, first we select the sensors, and the section of the sensors response curves, where the probability of detecting the presence of acetic acid will be higher, and then we apply Principal Component Analysis (PCA) such that each sensor response curve is represented by the coefficients of its first principal components. Results show that the PEN3 electronic nose is able to detect and discriminate wine samples doped with acetic acid in concentrations equal or greater than 2 g/L. PMID:23262483

  16. Acetic acid detection threshold in synthetic wine samples of a portable electronic nose.

    PubMed

    Macías, Miguel Macías; Manso, Antonio García; Orellana, Carlos Javier García; Velasco, Horacio Manuel González; Caballero, Ramón Gallardo; Chamizo, Juan Carlos Peguero

    2012-12-24

    Wine quality is related to its intrinsic visual, taste, or aroma characteristics and is reflected in the price paid for that wine. One of the most important wine faults is the excessive concentration of acetic acid which can cause a wine to take on vinegar aromas and reduce its varietal character. Thereby it is very important for the wine industry to have methods, like electronic noses, for real-time monitoring the excessive concentration of acetic acid in wines. However, aroma characterization of alcoholic beverages with sensor array electronic noses is a difficult challenge due to the masking effect of ethanol. In this work, in order to detect the presence of acetic acid in synthetic wine samples (aqueous ethanol solution at 10% v/v) we use a detection unit which consists of a commercial electronic nose and a HSS32 auto sampler, in combination with a neural network classifier (MLP). To find the characteristic vector representative of the sample that we want to classify, first we select the sensors, and the section of the sensors response curves, where the probability of detecting the presence of acetic acid will be higher, and then we apply Principal Component Analysis (PCA) such that each sensor response curve is represented by the coefficients of its first principal components. Results show that the PEN3 electronic nose is able to detect and discriminate wine samples doped with acetic acid in concentrations equal or greater than 2 g/L.

  17. Maximizing allele detection: Effects of analytical threshold and DNA levels on rates of allele and locus drop-out.

    PubMed

    Rakay, Christine A; Bregu, Joli; Grgicak, Catherine M

    2012-12-01

    Interpretation of DNA evidence depends upon the ability of the analyst to accurately compare the DNA profile obtained from an item of evidence and the DNA profile of a standard. This interpretation becomes progressively more difficult as the number of 'drop-out' and 'drop-in' events increase. Analytical thresholds (AT) are typically selected to ensure the false detection of noise is minimized. However, there exists a tradeoff between the erroneous labeling of noise as alleles and the false non-detection of alleles (i.e. drop-out). In this study, the effect ATs had on both types of error was characterized. Various ATs were tested, where three relied upon the analysis of baseline signals obtained from 31 negative samples. The fourth AT was determined by utilizing the relationship between RFU signal and DNA input. The other ATs were the commonly employed 50, 150 and 200 RFU thresholds. Receiver Operating Characteristic (ROC) plots showed that although high ATs completely negated the false labeling of noise, DNA analyzed with ATs derived using analysis of the baseline signal exhibited the lowest rates of drop-out and the lowest total error rates. In another experiment, the effect small changes in ATs had on drop-out was examined. This study showed that as the AT increased from ∼10 to 60 RFU, the number of heterozygous loci exhibiting the loss of one allele increased. Between ATs of 60 and 150 RFU, the frequency of allelic drop-out remained constant at 0.27 (±0.02) and began to decrease when ATs of 150 RFU or greater were utilized. In contrast, the frequency of heterozygous loci exhibiting the loss of both alleles consistently increased with AT. In summary, for samples amplified with less than 0.5ng of DNA, ATs derived from baseline analysis of negatives were shown to decrease the frequency of drop-out by a factor of 100 without significantly increasing rates of erroneous noise detection.

  18. Rational Manual and Automated Scoring Thresholds for the Immunohistochemical Detection of TP53 Missense Mutations in Human Breast Carcinomas.

    PubMed

    Taylor, Nicholas J; Nikolaishvili-Feinberg, Nana; Midkiff, Bentley R; Conway, Kathleen; Millikan, Robert C; Geradts, Joseph

    2016-07-01

    Missense mutations in TP53 are common in human breast cancer, have been associated with worse prognosis, and may predict therapy effect. TP53 missense mutations are associated with aberrant accumulation of p53 protein in tumor cell nuclei. Previous studies have used relatively arbitrary cutoffs to characterize breast tumors as positive for p53 staining by immunohistochemical assays. This study aimed to objectively determine optimal thresholds for p53 positivity by manual and automated scoring methods using whole tissue sections from the Carolina Breast Cancer Study. p53-immunostained slides were available for 564 breast tumors previously assayed for TP53 mutations. Average nuclear p53 staining intensity was manually scored as negative, borderline, weak, moderate, or strong and percentage of positive tumor cells was estimated. Automated p53 signal intensity was measured using the Aperio nuclear v9 algorithm combined with the Genie histology pattern recognition tool and tuned to achieve optimal nuclear segmentation. Receiver operating characteristic curve analysis was performed to determine optimal cutoffs for average staining intensity and percent cells positive to distinguish between tumors with and without a missense mutation. Receiver operating characteristic curve analysis demonstrated a threshold of moderate average nuclear staining intensity as a good surrogate for TP53 missense mutations in both manual (area under the curve=0.87) and automated (area under the curve=0.84) scoring systems. Both manual and automated immunohistochemical scoring methods predicted missense mutations in breast carcinomas with high accuracy. Validation of the automated intensity scoring threshold suggests a role for such algorithms in detecting TP53 missense mutations in high throughput studies.

  19. Threshold displacement energies in graphene and single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Merrill, Andrew; Cress, Cory D.; Rossi, Jamie E.; Cox, Nathanael D.; Landi, Brian J.

    2015-08-01

    The threshold displacement energy Ed has been determined for graphene and 216 different (n , m ) single-walled carbon nanotube chiralities, with 5 ≤n ≤20 and 0 ≤m ≤n , under several model conditions using classical molecular dynamics. The model conditions vary by particle (electron or carbon ion), empirical potential (two parametrizations of Tersoff [J. Tersoff, Phys. Rev. B 39, 5566 (1989), 10.1103/PhysRevB.39.5566; L. Lindsay and D. A. Broido, Phys. Rev. B 81, 205441 (2010), 10.1103/PhysRevB.81.205441] and one of Brenner et al. [D. W. Brenner, O. A. Shenderova, J. A. Harrison, S. J. Stuart, B. Ni, and S. B. Sinnott, J. Phys.: Condens. Matter 14, 783 (2002), 10.1088/0953-8984/14/4/312]), and momentum transfer direction (towards or away from the nanotube axis). For electron irradiation simulations, Ed exhibits a smoothly varying chirality dependence and a characteristic curvature influenced by the momentum transfer direction. Changing the empirical potential shifts the magnitude of Ed, but the trend is preserved for electron simulations. However, the perturbation in the knock-on dynamics introduced by the carbon ion leads to Ed trends that diverge from the equivalent electron simulation. Thus, the ion interaction has a non-negligible effect on the dynamics of the collision and leads to Ed values that can distinctly vary depending on the selected carbon nanostructure.

  20. Abort Trigger False Positive and False Negative Analysis Methodology for Threshold-Based Abort Detection

    NASA Technical Reports Server (NTRS)

    Melcher, Kevin J.; Cruz, Jose A.; Johnson Stephen B.; Lo, Yunnhon

    2015-01-01

    This paper describes a quantitative methodology for bounding the false positive (FP) and false negative (FN) probabilities associated with a human-rated launch vehicle abort trigger (AT) that includes sensor data qualification (SDQ). In this context, an AT is a hardware and software mechanism designed to detect the existence of a specific abort condition. Also, SDQ is an algorithmic approach used to identify sensor data suspected of being corrupt so that suspect data does not adversely affect an AT's detection capability. The FP and FN methodologies presented here were developed to support estimation of the probabilities of loss of crew and loss of mission for the Space Launch System (SLS) which is being developed by the National Aeronautics and Space Administration (NASA). The paper provides a brief overview of system health management as being an extension of control theory; and describes how ATs and the calculation of FP and FN probabilities relate to this theory. The discussion leads to a detailed presentation of the FP and FN methodology and an example showing how the FP and FN calculations are performed. This detailed presentation includes a methodology for calculating the change in FP and FN probabilities that result from including SDQ in the AT architecture. To avoid proprietary and sensitive data issues, the example incorporates a mixture of open literature and fictitious reliability data. Results presented in the paper demonstrate the effectiveness of the approach in providing quantitative estimates that bound the probability of a FP or FN abort determination.

  1. Energy Detection Based on Undecimated Discrete Wavelet Transform and Its Application in Magnetic Anomaly Detection

    PubMed Central

    Nie, Xinhua; Pan, Zhongming; Zhang, Dasha; Zhou, Han; Chen, Min; Zhang, Wenna

    2014-01-01

    Magnetic anomaly detection (MAD) is a passive approach for detection of a ferromagnetic target, and its performance is often limited by external noises. In consideration of one major noise source is the fractal noise (or called 1/f noise) with a power spectral density of 1/fa (0energy detection method based on undecimated discrete wavelet transform (UDWT) is proposed in this paper. Firstly, the foundations of magnetic anomaly detection and UDWT are introduced in brief, while a possible detection system based on giant magneto-impedance (GMI) magnetic sensor is also given out. Then our proposed energy detection based on UDWT is described in detail, and the probabilities of false alarm and detection for given the detection threshold in theory are presented. It is noticeable that no a priori assumptions regarding the ferromagnetic target or the magnetic noise probability are necessary for our method, and different from the discrete wavelet transform (DWT), the UDWT is shift invariant. Finally, some simulations are performed and the results show that the detection performance of our proposed detector is better than that of the conventional energy detector even utilized in the Gaussian white noise, especially when the spectral parameter α is less than 1.0. In addition, a real-world experiment was done to demonstrate the advantages of the proposed method. PMID:25343484

  2. Visible Contrast Energy Metrics for Detection and Discrimination

    NASA Technical Reports Server (NTRS)

    Ahumada, Albert; Watson, Andrew

    2013-01-01

    Contrast energy was proposed by Watson, Robson, & Barlow as a useful metric for representing luminance contrast target stimuli because it represents the detectability of the stimulus in photon noise for an ideal observer. Like the eye, the ear is a complex transducer system, but relatively simple sound level meters are used to characterize sounds. These meters provide a range of frequency sensitivity functions and integration times depending on the intended use. We propose here the use of a range of contrast energy measures with different spatial frequency contrast sensitivity weightings, eccentricity sensitivity weightings, and temporal integration times. When detection threshold are plotting using such measures, the results show what the eye sees best when these variables are taken into account in a standard way. The suggested weighting functions revise the Standard Spatial Observer for luminance contrast detection and extend it into the near periphery. Under the assumption that the detection is limited only by internal noise, discrimination performance can be predicted by metrics based on the visible energy of the difference images

  3. Tunnel effect wave energy detection

    NASA Technical Reports Server (NTRS)

    Kaiser, William J. (Inventor); Waltman, Steven B. (Inventor); Kenny, Thomas W. (Inventor)

    1995-01-01

    Methods and apparatus for measuring gravitational and inertial forces, magnetic fields, or wave or radiant energy acting on an object or fluid in space provide an electric tunneling current through a gap between an electrode and that object or fluid in space and vary that gap with any selected one of such forces, magnetic fields, or wave or radiant energy acting on that object or fluid. These methods and apparatus sense a corresponding variation in an electric property of that gap and determine the latter force, magnetic fields, or wave or radiant energy in response to that corresponding variation, and thereby sense or measure such parameters as acceleration, position, particle mass, velocity, magnetic field strength, presence or direction, or wave or radiant energy intensity, presence or direction.

  4. Energy Detection Based Estimation of Channel Occupancy Rate with Adaptive Noise Estimation

    NASA Astrophysics Data System (ADS)

    Lehtomäki, Janne J.; Vuohtoniemi, Risto; Umebayashi, Kenta; Mäkelä, Juha-Pekka

    Recently, there has been growing interest in opportunistically utilizing the 2.4GHz ISM-band. Numerous spectrum occupancy measurements covering the ISM-band have been performed to analyze the spectrum usage. However, in these campaigns the verification of the correctness of the obtained occupancy values for the highly dynamic ISM-band has not been presented. In this paper, we propose and verify channel occupancy rate (COR) estimation utilizing energy detection mechanism with a novel adaptive energy detection threshold setting method. The results are compared with the true reference COR values. Several different types of verification measurements showed that our setup can estimate the COR values of 802.11 traffic well, with negligible overestimation. The results from real-time real-life measurements also confirm that the proposed adaptive threshold setting method enables accurate thresholds even in the situations where multiple interferers are present in the received signal.

  5. An ultra low energy biomedical signal processing system operating at near-threshold.

    PubMed

    Hulzink, J; Konijnenburg, M; Ashouei, M; Breeschoten, A; Berset, T; Huisken, J; Stuyt, J; de Groot, H; Barat, F; David, J; Van Ginderdeuren, J

    2011-12-01

    This paper presents a voltage-scalable digital signal processing system designed for the use in a wireless sensor node (WSN) for ambulatory monitoring of biomedical signals. To fulfill the requirements of ambulatory monitoring, power consumption, which directly translates to the WSN battery lifetime and size, must be kept as low as possible. The proposed processing platform is an event-driven system with resources to run applications with different degrees of complexity in an energy-aware way. The architecture uses effective system partitioning to enable duty cycling, single instruction multiple data (SIMD) instructions, power gating, voltage scaling, multiple clock domains, multiple voltage domains, and extensive clock gating. It provides an alternative processing platform where the power and performance can be scaled to adapt to the application need. A case study on a continuous wavelet transform (CWT)-based heart-beat detection shows that the platform not only preserves the sensitivity and positive predictivity of the algorithm but also achieves the lowest energy/sample for ElectroCardioGram (ECG) heart-beat detection publicly reported today.

  6. Non-human primate skull effects on the cavitation detection threshold of FUS-induced blood-brain barrier opening

    NASA Astrophysics Data System (ADS)

    Wu, Shih-Ying; Tung, Yao-Sheng; Marquet, Fabrice; Chen, Cherry C.; Konofagou, Elisa E.

    2012-11-01

    Microbubble (MB)-assisted focused ultrasound is a promising technique for delivering drugs to the brain by noninvasively and transiently opening the blood-brain barrier (BBB), and monitoring BBB opening using passive cavitation detection (PCD) is critical in detecting its occurrence, extent as well as assessing its mechanism. One of the main obstacles in achieving those objectives in large animals is the transcranial attenuation. To study the effects, the cavitation response through the in-vitro non-human primate (NHP) skull was investigated. In-house manufactured lipid-shelled MB (medium diameter: 4-5 um) were injected into a 4-mm channel of a phantom below a degassed monkey skull. A hydrophone confocally aligned with the FUS transducer served as PCD during sonication (frequency: 0.50 MHz, peak rarefactional pressures: 0.05-0.60 MPa, pulse length: 100 cycles, PRF: 10 Hz, duration: 2 s) for four cases: water without skull, water with skull, MB without skull and MB with skull. A 5.1-MHz linear-array transducer was also used to monitor the MB disruption. The frequency spectra, spectrograms, stable cavitation dose (SCD) and inertial cavitation dose (ICD) were quantified. Results showed that the onset of stable cavitation and inertial cavitation in the experiments occurred at 50 kPa, and was detectable throught the NHP skull since the both the detection thresholds for stable cavitation and inertial cavitation remained unchanged compared to the non-skull case, and the SCD and ICD acquired transcranially may not adequately represent the true extent of stable and inertial cavitation due to the skull attenuation.

  7. Quantitative measurement of odor detection thresholds using an air dilution olfactometer, and association with genetic variants in a sample of diverse ancestry

    PubMed Central

    Cook, Gillian R.; Krithika, S; Edwards, Melissa; Kavanagh, Paula

    2014-01-01

    Genetic association studies require a quantitative and reliable method for odor threshold assessment in order to examine the contribution of genetic variants to complex olfactory phenotypes. Our main goal was to assess the feasibility of a portable Scentroid air dilution olfactometer for use in such studies. Using the Scentroid SM110C and the SK5 n-butanol Sensitivity Kit (IDES Canada Inc.), n-butanol odor thresholds were determined for 182 individuals of diverse ancestry (mean age: 20.4 ± 2.5 years; n = 128 female; n = 54 male). Threshold scores from repeat participants were used to calculate a test–retest reliability coefficient, which was statistically significant (r = 0.754, p < 0.001, n = 29), indicating that the Scentroid provides reliable estimates of odor thresholds. In addition, we performed a preliminary genetic analysis evaluating the potential association of n-butanol odor thresholds to six single-nucleotide polymorphisms (SNPs) putatively involved in general olfactory sensitivity (GOS). The results of multiple linear regression analysis revealed no significant association between the SNPs tested and threshold scores. However, our sample size was relatively small, and our study was only powered to identify genetic markers with strong effects on olfactory sensitivity. Overall, we find that the Scentroid provides reliable quantitative measures of odor detection threshold and is well suited for genetic studies of olfactory sensitivity. PMID:25392755

  8. Internal energy distribution of the NCO fragment from near-threshold photolysis of isocyanic acid, HNCO

    SciTech Connect

    Brown, S.S.; Berghout, H.L.; Crim, F.F.

    1996-05-09

    We report the first measurement of the vibrational- and rotational-state distributions in the NCO fragment resulting from photolysis of HNCO. Recent studies have drawn conclusions about the photochemistry of HNCO and the vibrational distribution in the NCO fragment from observations of kinetic energy distribution of the H atom produced in this photolysis; however, there has been no direct observation of the NCO fragment itself. We use laser-induced fluorescence to detect the nascent NCO photoproducts and spectral simulations to extract vibrational-state populations. The rotational distributions, where we can measure them, show little excitation, and the vibrational energy preferentially appears in the bending mode. The vibrational-state distribution results directly from the excited-state geometry of the HNCO parent, in which the NCO group is bent. The dissociation proceeds from this bent NCO group to a linear NCO fragment, strongly exciting the bending mode. We find about 65% of the total energy in relative translation of the fragments, while 30% goes into vibration and 5% into rotation of NCO. 49 refs., 7 figs., 2 tabs.

  9. Cross-matching: a modified cross-correlation underlying threshold energy model and match-based depth perception

    PubMed Central

    Doi, Takahiro; Fujita, Ichiro

    2014-01-01

    Three-dimensional visual perception requires correct matching of images projected to the left and right eyes. The matching process is faced with an ambiguity: part of one eye's image can be matched to multiple parts of the other eye's image. This stereo correspondence problem is complicated for random-dot stereograms (RDSs), because dots with an identical appearance produce numerous potential matches. Despite such complexity, human subjects can perceive a coherent depth structure. A coherent solution to the correspondence problem does not exist for anticorrelated RDSs (aRDSs), in which luminance contrast is reversed in one eye. Neurons in the visual cortex reduce disparity selectivity for aRDSs progressively along the visual processing hierarchy. A disparity-energy model followed by threshold nonlinearity (threshold energy model) can account for this reduction, providing a possible mechanism for the neural matching process. However, the essential computation underlying the threshold energy model is not clear. Here, we propose that a nonlinear modification of cross-correlation, which we term “cross-matching,” represents the essence of the threshold energy model. We placed half-wave rectification within the cross-correlation of the left-eye and right-eye images. The disparity tuning derived from cross-matching was attenuated for aRDSs. We simulated a psychometric curve as a function of graded anticorrelation (graded mixture of aRDS and normal RDS); this simulated curve reproduced the match-based psychometric function observed in human near/far discrimination. The dot density was 25% for both simulation and observation. We predicted that as the dot density increased, the performance for aRDSs should decrease below chance (i.e., reversed depth), and the level of anticorrelation that nullifies depth perception should also decrease. We suggest that cross-matching serves as a simple computation underlying the match-based disparity signals in stereoscopic depth

  10. Cross-matching: a modified cross-correlation underlying threshold energy model and match-based depth perception.

    PubMed

    Doi, Takahiro; Fujita, Ichiro

    2014-01-01

    Three-dimensional visual perception requires correct matching of images projected to the left and right eyes. The matching process is faced with an ambiguity: part of one eye's image can be matched to multiple parts of the other eye's image. This stereo correspondence problem is complicated for random-dot stereograms (RDSs), because dots with an identical appearance produce numerous potential matches. Despite such complexity, human subjects can perceive a coherent depth structure. A coherent solution to the correspondence problem does not exist for anticorrelated RDSs (aRDSs), in which luminance contrast is reversed in one eye. Neurons in the visual cortex reduce disparity selectivity for aRDSs progressively along the visual processing hierarchy. A disparity-energy model followed by threshold nonlinearity (threshold energy model) can account for this reduction, providing a possible mechanism for the neural matching process. However, the essential computation underlying the threshold energy model is not clear. Here, we propose that a nonlinear modification of cross-correlation, which we term "cross-matching," represents the essence of the threshold energy model. We placed half-wave rectification within the cross-correlation of the left-eye and right-eye images. The disparity tuning derived from cross-matching was attenuated for aRDSs. We simulated a psychometric curve as a function of graded anticorrelation (graded mixture of aRDS and normal RDS); this simulated curve reproduced the match-based psychometric function observed in human near/far discrimination. The dot density was 25% for both simulation and observation. We predicted that as the dot density increased, the performance for aRDSs should decrease below chance (i.e., reversed depth), and the level of anticorrelation that nullifies depth perception should also decrease. We suggest that cross-matching serves as a simple computation underlying the match-based disparity signals in stereoscopic depth perception.

  11. Amplitude-modulation detection by recreational-noise-exposed humans with near-normal hearing thresholds and its medium-term progression

    PubMed Central

    Stone, Michael A.; Moore, Brian C.J.

    2014-01-01

    Noise exposure can affect the functioning of cochlear inner and outer hair cells (IHC/OHC), leading to multiple perceptual changes. This work explored possible changes in detection of amplitude modulation (AM) at three Sensation Levels (SL) for carrier frequencies of 3, 4 and 6 kHz. There were two groups of participants, aged 19 to 24 (Young) and 26 to 35 (Older) years. All had near-normal audiometric thresholds. Participants self-assessed exposure to high-level noise in recreational settings. Each group was sub-grouped into low-noise (LN) or high-noise (HN) exposure. AM detection thresholds were worse for the HN than for the LN sub-group at the lowest SL, for the males only of the Young group and for both genders for the Older group, despite no significant difference in absolute threshold at 3 and 4 kHz between sub-groups. AM detection at the lowest SL, at both 3 and 4 kHz, generally improved with increasing age and increasing absolute threshold, consistent with a recruitment-like process. However, poorer AM detection was correlated with increasing exposure at 3 kHz in the Older group. It is suggested that high-level noise exposure produces both IHC- and OHC-related damage, the balance between the two varying across frequency. However, the use of AM detection offers poor sensitivity as a measure of the effects. PMID:25260433

  12. Resonances and threshold effects in low-energy electron collisions with methyl halides

    SciTech Connect

    Gallup, Gordon A.; Fabrikant, Ilya I.

    2007-03-15

    Cross sections for elastic and inelastic electron collisions with CH{sub 3}X (X=Cl,Br,I) molecules are calculated. For the lowest partial wave, the resonance R-matrix theory, and for the higher partial waves, the theory of scattering by dipolar plus polarization potential, are used. It is shown that the rotationally elastic scattering amplitude for a polar molecule in the fixed-nuclei approximation is logarithmically divergent for the forward direction, and a closure formula is derived to speed up the convergence at small angles. In treating the nuclear motion, only C-X stretch vibrations are taken into account. The dipole moment as a function of the C-X distance is modeled by a function incorporating the experimental value of the molecular dipole moments at the equilibrium distance and the derivatives of the dipole moments extracted from the experimental data on infrared intensities. This is supplemented by ab initio calculations of the dipole moment function for CH{sub 3}Br using the multiconfigurational valence bond method. The results for scattering cross sections show pronounced features caused by vibrational Feshbach resonances and threshold cusps. The features are most noticeable at the v=6, 7, and 8 thresholds in CH{sub 3}Cl, at the v=3 and 4 thresholds in CH{sub 3}Br, and at the v=1 threshold in CH{sub 3}I.

  13. The stopping of heavy ions in the low-to-intermediate energy range: The apparent velocity threshold

    NASA Astrophysics Data System (ADS)

    Lifschitz, A. F.; Arista, N. R.

    2013-12-01

    We present a non-linear study of the energy loss of heavy ions in solids, which is based on the transport cross section (TCS) and the extension of the Friedel sum rule (EFSR) for moving ions. We apply this approach to study the velocity dependence of the energy loss of heavy ions in the energy region below the stopping power maximum. With this formulation we are able to explain some striking effects in the energy loss of heavy ions which have been experimentally observed long time ago (Brown and Moak (1972) [14]), but have not been explained so far by the existing theoretical models: the deviations from the proportionality with ion velocity (predicted by alternative models in the low energy range), and the "apparent velocity threshold".

  14. Cooperativity and interaction energy threshold effects in recognition of the -10 promoter element by bacterial RNA polymerase.

    PubMed

    Mekler, Vladimir; Severinov, Konstantin

    2013-08-01

    RNA polymerase (RNAP) melts promoter DNA to form transcription-competent open promoter complex (RPo). Interaction of the RNAP σ subunit with non-template strand bases of a conserved -10 element (consensus sequence T-12A-11T-10A-9A-8T-7) is an important source of energy-driving localized promoter melting. Here, we used an RNAP molecular beacon assay to investigate interdependencies of RNAP interactions with -10 element nucleotides. The results reveal a strong cooperation between RNAP interactions with individual -10 element non-template strand nucleotides and indicate that recognition of the -10 element bases occurs only when free energy of the overall RNAP -10 element binding reaches a certain threshold level. The threshold-like mode of the -10 element recognition may be related to the energetic cost of attaining a conformation of the -10 element that is recognizable by RNAP. The RNAP interaction with T/A-12 base pair was found to be strongly stimulated by RNAP interactions with other -10 element bases and with promoter spacer between the -10 and -35 promoter elements. The data also indicate that unmelted -10 promoter element can impair RNAP interactions with promoter DNA upstream of the -11 position. We suggest that cooperativity and threshold effects are important factors guiding the dynamics and selectivity of RPo formation.

  15. Critical study of photodetachment of H- at energies up to the n=4 threshold

    NASA Astrophysics Data System (ADS)

    Tang, Jian-Zhi; Wakabayashi, Yoshihiro; Matsuzawa, Michio; Watanabe, Shinichi; Shimamura, Isao

    1994-02-01

    We apply the close-coupling method in terms of the hyperspherical coordinates to the two-electron system H-. A two-dimensional matching procedure is used to connect the close-coupling wave function to an independent-electron wave function in the asymptotic region. The latter is described as the wave function of a detached electron moving in a dipole potential field of the neutral hydrogen atom. The total phbotodetachment cross sections and the partial cross sections for the production of the H atoms in different states n are calculated up to the n=4 hydrogenic threshold. The results obtained in the length and acceleration forms agree within about three significant figures. The magnitude and shape of the 1Po shape resonance just above the n=2 threshold are found to depend sensitively on the initial-state wave function. This appears to be one of the reasons for a disparity among the cross sections in the literature. The present result improves greatly on the existing computational results. The relative magnitudes of the partial cross sections for the production of H (n=1,2,3) atoms below the n=4 threshold are substantially different from the only previous results of the eigenchannel R-matrix calculations [H. R. Sadeghpour, C. H. Greene, and M. Cavagnero, Phys. Rev. A 45, 1587 (1992)]. The present results on both partial and total cross sections are in excellent agreement with experiments.

  16. Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experiments.

    PubMed

    Herrmann, H W; Kim, Y H; Young, C S; Fatherley, V E; Lopez, F E; Oertel, J A; Malone, R M; Rubery, M S; Horsfield, C J; Stoeffl, W; Zylstra, A B; Shmayda, W T; Batha, S H

    2014-11-01

    A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ≤400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C2F6, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ∼400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds. PMID:25430303

  17. Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experiments

    SciTech Connect

    Herrmann, H. W. Kim, Y. H.; Young, C. S.; Fatherley, V. E.; Lopez, F. E.; Oertel, J. A.; Batha, S. H.; Malone, R. M.; Rubery, M. S.; Horsfield, C. J.; Stoeffl, W.; Zylstra, A. B.; Shmayda, W. T.

    2014-11-15

    A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ≤400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C{sub 2}F{sub 6}, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ∼400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds.

  18. Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experiments.

    PubMed

    Herrmann, H W; Kim, Y H; Young, C S; Fatherley, V E; Lopez, F E; Oertel, J A; Malone, R M; Rubery, M S; Horsfield, C J; Stoeffl, W; Zylstra, A B; Shmayda, W T; Batha, S H

    2014-11-01

    A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ≤400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C2F6, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ∼400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds.

  19. Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experimentsa)

    NASA Astrophysics Data System (ADS)

    Herrmann, H. W.; Kim, Y. H.; Young, C. S.; Fatherley, V. E.; Lopez, F. E.; Oertel, J. A.; Malone, R. M.; Rubery, M. S.; Horsfield, C. J.; Stoeffl, W.; Zylstra, A. B.; Shmayda, W. T.; Batha, S. H.

    2014-11-01

    A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ≤400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C2F6, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ˜400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds.

  20. HIGH ENERGY POLARIZATION OF BLAZARS: DETECTION PROSPECTS

    SciTech Connect

    Chakraborty, N.; Pavlidou, V.; Fields, B. D.

    2015-01-01

    Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (with X-Calibur offering the most promising prospects), space-based missions should detect the brightest blazars for polarization fractions down to a few percent. Typical flaring activity of blazars could boost the overall number of polarimetric detections by nearly a factor of five to six purely accounting for flux increase of the brightest of the comprehensive, all-sky, Fermi-LAT blazar distribution. The instantaneous increase in the number of detections is approximately a factor of two, assuming a duty cycle of 20% for every source. The detectability of particular blazars may be reduced if variations in the flux and polarization fraction are anticorrelated. Simultaneous use of variability and polarization trends could guide the selection of blazars for high-energy polarimetric observations.

  1. Influence of Microbubble Size on Postexcitation Collapse Thresholds for Single Ultrasound Contrast Agents Using Double Passive Cavitation Detection

    PubMed Central

    Gauthier, Marianne; King, Daniel A.; O'Brien, William D.

    2014-01-01

    For the first time, and using an acoustical method, it has been shown experimentally that the inertial cavitation threshold pressure of an albumin-shelled microbubble is significantly correlated with its initial size. PMID:23661121

  2. Spin-spin correlations in proton-proton collisions at high energy and threshold enhancements

    SciTech Connect

    de Teramond, G.F.

    1988-05-01

    The striking effects in the spin structure observed in elastic proton collisions and the Nuclear Transparency phenomenon recently discovered at BNL are described in terms of heavy quark threshold enhancements. The deviations from scaling laws and the broadening of the angular distributions at resonance are also consistent with the introduction of new degrees of freedom in the pp system. This implies new s-channel physics. Predictions are given for the spin effects in pp collisions near 18.5 GeV/c at large p/sub T//sup 2/ where new measurements are planned. 9 refs., 4 figs.

  3. Laser-induced electron emission from a tungsten nanotip: identifying above threshold photoemission using energy-resolved laser power dependencies

    NASA Astrophysics Data System (ADS)

    Bionta, M. R.; Chalopin, B.; Champeaux, J. P.; Faure, S.; Masseboeuf, A.; Moretto-Capelle, P.; Chatel, B.

    2014-06-01

    We present an experiment studying the interaction of a strongly focused 25 fs laser pulse with a tungsten nanotip, investigating the different regimes of laser-induced electron emission. We study the dependence of the electron yield with respect to the static electric field applied to the tip. Photoelectron spectra are recorded using a retarding field spectrometer and peaks separated by the photon energy are observed with a 45% contrast. They are a clear signature of above threshold photoemission (ATP), and are confirmed by extensive spectrally resolved studies of the laser power dependence. Understanding these mechanisms opens the route to control experiment in the strong-field regime on nanoscale objects.

  4. Within-herd prevalence thresholds for the detection of Mycobacterium avium subspecies paratuberculosis-positive dairy herds using boot swabs and liquid manure samples.

    PubMed

    Donat, K; Hahn, N; Eisenberg, T; Schlez, K; Köhler, H; Wolter, W; Rohde, M; Pützschel, R; Rösler, U; Failing, K; Zschöck, P M

    2016-01-01

    The control of Johne's disease requires the identification of Mycobacterium avium ssp. paratuberculosis (MAP)-positive herds. Boot swabs and liquid manure samples have been suggested as an easy-to-use alternative to sampling individual animals in order to diagnose subclinical Johne's disease at the herd level, but there is a need to evaluate performance of this approach in the field. Using a logistic regression model, this study aimed to calculate the threshold level of the apparent within-herd prevalence as determined by individual faecal culture, thus allowing the detection of whether a herd is MAP positive. A total of 77 boot swabs and 75 liquid manure samples were taken from 19 certified negative and 58 positive dairy herds. Faecal culture, three different polymerase chain reaction (PCR) methods and the combination of faecal culture with PCR were applied in order to detect MAP. For 50% probability of detection, a within-herd prevalence threshold of 1·5% was calculated for testing both matrices simultaneously by faecal culture and PCR, with the threshold increased to 4·0% for 90% probability of detection. The results encourage the use of boot swabs or liquid manure samples, or a combination both, for identifying MAP-positive herds and, to a certain extent, for monitoring certified Johne's disease-negative cattle herds.

  5. The effect of signal onset/offset envelope on underwater detection thresholds of a harbor seal (Phoca vitulina).

    PubMed

    Turnbull, S D; Terhune, J M

    1995-07-01

    The effects of signal onset/offset envelope on the underwater hearing thresholds of a harbor seal (Phoca vitulina) were measured. Pure-tone, 540-ms pulses at 2, 4, 8, and 16 kHz were presented as test signals. An ANOVA revealed that there were no significant differences between repeated threshold measures for abrupt onset/offset signal envelopes versus slow onset/offset signal envelopes [F = 4.380, d.f. = (1,18), p > 0.05]. Seal vocalizations which have an abrupt onset/offset may be serving a short-range communicative function by helping the listener determine the direction of a nearby sender.

  6. Low-energy X-ray detection with an in-vacuum PILATUS detector

    NASA Astrophysics Data System (ADS)

    Marchal, Julien; Luethi, Benjamin; Ursachi, Catalin; Mykhaylyk, Vitaliy; Wagner, Armin

    2011-11-01

    The feasibility of using PILATUS single-X-ray-photon counting detectors for long-wavelength macromolecular crystallography was investigated by carrying out a series of experiments at Diamond Light Source. A water-cooled PILATUS 100k detector was tested in vacuum with monochromatic 3 keV X-rays on the Diamond test beamline B16. Effects of detector cooling on noise performance, energy calibration and threshold trimming were investigated. When detecting 3 keV X-rays, the electronic noise of the analogue output of pixel preamplifiers forces the threshold to be set at a higher level than the 50% energy level recommended to minimize charge-sharing effects. The influence of threshold settings at low X-ray energy was studied by characterizing the detector response to a collimated beam of 3 keV X-rays scanned across several pixels. The relationship between maximum count rate and minimum energy threshold was investigated separately for various detector gain settings.

  7. Teager energy operator for multi-modulation extraction and its application for gearbox fault detection

    NASA Astrophysics Data System (ADS)

    Soltani Bozchalooi, I.; Liang, Ming

    2010-07-01

    This paper presents a parameter-free and broadband approach to detecting gear faults based on vibration signals. The technique is implemented using the Teager energy operator (TEO). It is shown that this operator can extract amplitude, phase and frequency modulations that are associated with various gear faults. Spectral analysis of the TEO-transformed signal provides the necessary information for fault detection. To improve the effectiveness of the proposed technique, we also devised a wavelet de-noising step based on online threshold estimation. In the de-noising step, the threshold estimation is performed through a frequency domain median absolute deviation (FMAD) scheme. The proposed fault detection technique is tested on simulated as well as experimental data acquired from a single-stage bevel gearbox and a two-stage parallel gearbox. US patent pending (serial number: 12/631,528).

  8. Effect of Strain Field on Threshold Displacement Energy of Tungsten Studied by Molecular Dynamics Simulation

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Gao, Ning; Setyawan, W.; Kurtz, R. J.; Wang, Zhi-Guang; Gao, Xing; He, Wen-Hao; Pang, Li-Long

    2016-09-01

    Not Available Supported by the National Natural Science Foundation of China under Grant Nos 11375242, 91026002, 91426301 and 11405231, the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No XDA03010301. WS and RJK acknowledge the support of the Office of Fusion Energy Sciences, U.S. Department of Energy under Contract DE-AC05-76RL01830.

  9. Dynamical thresholds and quantum undulations in the energy dependence of rotationally inelastic integral cross sections

    SciTech Connect

    Schinke, R.

    1981-12-01

    We report the observation of distinct structures in the energy dependence of rotationally inelastic integral cross sections for the systems He--Na/sub 2/ and Ne--Na/sub 2/. The calculations are performed within the infinite-order-sudden and the coupled states approximation using accurate ab initio potential energy surfaces. The integral cross section for a 0..-->..j' transition typically rises steeply at low energies, reaches a maximum, and declines slowly to the high energy region showing more or less pronounced quantum undulations. The onset of the cross section is determined by dynamical constraints rather than energy conservation. All structures in the integral cross sections are explained in terms of the energy dependence of rotational rainbow features in the corresponding differential cross sections. In particular, the undulations at higher energies stem from the supernumerary rotational rainbows. In this sense they are interpreted as analogous to the glory maxima in the elastic integral cross section for scattering from isotropic potentials. The observed structures are sensitive to the anisotropy of the repulsive branch of the potential energy surface.

  10. 30 CFR 62.174 - Follow-up corrective measures when a standard threshold shift is detected.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., DEPARTMENT OF LABOR UNIFORM MINE HEALTH REGULATIONS OCCUPATIONAL NOISE EXPOSURE § 62.174 Follow-up corrective... determines the standard threshold shift is neither work-related nor aggravated by occupational noise exposure... controls to identify and correct any deficiencies....

  11. Estimation of signal coherence threshold and concealed spectral lines applied to detection of turbofan engine combustion noise.

    PubMed

    Miles, Jeffrey Hilton

    2011-05-01

    Combustion noise from turbofan engines has become important, as the noise from sources like the fan and jet are reduced. An aligned and un-aligned coherence technique has been developed to determine a threshold level for the coherence and thereby help to separate the coherent combustion noise source from other noise sources measured with far-field microphones. This method is compared with a statistics based coherence threshold estimation method. In addition, the un-aligned coherence procedure at the same time also reveals periodicities, spectral lines, and undamped sinusoids hidden by broadband turbofan engine noise. In calculating the coherence threshold using a statistical method, one may use either the number of independent records or a larger number corresponding to the number of overlapped records used to create the average. Using data from a turbofan engine and a simulation this paper shows that applying the Fisher z-transform to the un-aligned coherence can aid in making the proper selection of samples and produce a reasonable statistics based coherence threshold. Examples are presented showing that the underlying tonal and coherent broad band structure which is buried under random broadband noise and jet noise can be determined. The method also shows the possible presence of indirect combustion noise. PMID:21568410

  12. Estimation of Signal Coherence Threshold and Concealed Spectral Lines Applied to Detection of Turbofan Engine Combustion Noise

    NASA Technical Reports Server (NTRS)

    Miles, Jeffrey Hilton

    2010-01-01

    Combustion noise from turbofan engines has become important, as the noise from sources like the fan and jet are reduced. An aligned and un-aligned coherence technique has been developed to determine a threshold level for the coherence and thereby help to separate the coherent combustion noise source from other noise sources measured with far-field microphones. This method is compared with a statistics based coherence threshold estimation method. In addition, the un-aligned coherence procedure at the same time also reveals periodicities, spectral lines, and undamped sinusoids hidden by broadband turbofan engine noise. In calculating the coherence threshold using a statistical method, one may use either the number of independent records or a larger number corresponding to the number of overlapped records used to create the average. Using data from a turbofan engine and a simulation this paper shows that applying the Fisher z-transform to the un-aligned coherence can aid in making the proper selection of samples and produce a reasonable statistics based coherence threshold. Examples are presented showing that the underlying tonal and coherent broad band structure which is buried under random broadband noise and jet noise can be determined. The method also shows the possible presence of indirect combustion noise. Copyright 2011 Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.

  13. Detection of low energy antimatter with emulsions

    NASA Astrophysics Data System (ADS)

    Aghion, S.; Ariga, A.; Ariga, T.; Bollani, M.; Dei Cas, E.; Ereditato, A.; Evans, C.; Ferragut, R.; Giammarchi, M.; Pistillo, C.; Romé, M.; Sala, S.; Scampoli, P.

    2016-06-01

    Emulsion detectors feature a very high position resolution and consequently represent an ideal device when particle detection is required at the micrometric scale. This is the case of quantum interferometry studies with antimatter, where micrometric fringes have to be measured. In this framework, we designed and realized a new emulsion based detector characterized by a gel enriched in terms of silver bromide crystal contents poured on a glass plate. We tested the sensitivity of such a detector to low energy positrons in the range 10–20 keV . The obtained results prove that nuclear emulsions are highly efficient at detecting positrons at these energies. This achievement paves the way to perform matter-wave interferometry with positrons using this technology.

  14. Lowered threshold energy for femtosecond laser induced optical breakdown in a water based eye model by aberration correction with adaptive optics.

    PubMed

    Hansen, Anja; Géneaux, Romain; Günther, Axel; Krüger, Alexander; Ripken, Tammo

    2013-06-01

    In femtosecond laser ophthalmic surgery tissue dissection is achieved by photodisruption based on laser induced optical breakdown. In order to minimize collateral damage to the eye laser surgery systems should be optimized towards the lowest possible energy threshold for photodisruption. However, optical aberrations of the eye and the laser system distort the irradiance distribution from an ideal profile which causes a rise in breakdown threshold energy even if great care is taken to minimize the aberrations of the system during design and alignment. In this study we used a water chamber with an achromatic focusing lens and a scattering sample as eye model and determined breakdown threshold in single pulse plasma transmission loss measurements. Due to aberrations, the precise lower limit for breakdown threshold irradiance in water is still unknown. Here we show that the threshold energy can be substantially reduced when using adaptive optics to improve the irradiance distribution by spatial beam shaping. We found that for initial aberrations with a root-mean-square wave front error of only one third of the wavelength the threshold energy can still be reduced by a factor of three if the aberrations are corrected to the diffraction limit by adaptive optics. The transmitted pulse energy is reduced by 17% at twice the threshold. Furthermore, the gas bubble motions after breakdown for pulse trains at 5 kilohertz repetition rate show a more transverse direction in the corrected case compared to the more spherical distribution without correction. Our results demonstrate how both applied and transmitted pulse energy could be reduced during ophthalmic surgery when correcting for aberrations. As a consequence, the risk of retinal damage by transmitted energy and the extent of collateral damage to the focal volume could be minimized accordingly when using adaptive optics in fs-laser surgery.

  15. Lowered threshold energy for femtosecond laser induced optical breakdown in a water based eye model by aberration correction with adaptive optics.

    PubMed

    Hansen, Anja; Géneaux, Romain; Günther, Axel; Krüger, Alexander; Ripken, Tammo

    2013-06-01

    In femtosecond laser ophthalmic surgery tissue dissection is achieved by photodisruption based on laser induced optical breakdown. In order to minimize collateral damage to the eye laser surgery systems should be optimized towards the lowest possible energy threshold for photodisruption. However, optical aberrations of the eye and the laser system distort the irradiance distribution from an ideal profile which causes a rise in breakdown threshold energy even if great care is taken to minimize the aberrations of the system during design and alignment. In this study we used a water chamber with an achromatic focusing lens and a scattering sample as eye model and determined breakdown threshold in single pulse plasma transmission loss measurements. Due to aberrations, the precise lower limit for breakdown threshold irradiance in water is still unknown. Here we show that the threshold energy can be substantially reduced when using adaptive optics to improve the irradiance distribution by spatial beam shaping. We found that for initial aberrations with a root-mean-square wave front error of only one third of the wavelength the threshold energy can still be reduced by a factor of three if the aberrations are corrected to the diffraction limit by adaptive optics. The transmitted pulse energy is reduced by 17% at twice the threshold. Furthermore, the gas bubble motions after breakdown for pulse trains at 5 kilohertz repetition rate show a more transverse direction in the corrected case compared to the more spherical distribution without correction. Our results demonstrate how both applied and transmitted pulse energy could be reduced during ophthalmic surgery when correcting for aberrations. As a consequence, the risk of retinal damage by transmitted energy and the extent of collateral damage to the focal volume could be minimized accordingly when using adaptive optics in fs-laser surgery. PMID:23761849

  16. Lowered threshold energy for femtosecond laser induced optical breakdown in a water based eye model by aberration correction with adaptive optics

    PubMed Central

    Hansen, Anja; Géneaux, Romain; Günther, Axel; Krüger, Alexander; Ripken, Tammo

    2013-01-01

    In femtosecond laser ophthalmic surgery tissue dissection is achieved by photodisruption based on laser induced optical breakdown. In order to minimize collateral damage to the eye laser surgery systems should be optimized towards the lowest possible energy threshold for photodisruption. However, optical aberrations of the eye and the laser system distort the irradiance distribution from an ideal profile which causes a rise in breakdown threshold energy even if great care is taken to minimize the aberrations of the system during design and alignment. In this study we used a water chamber with an achromatic focusing lens and a scattering sample as eye model and determined breakdown threshold in single pulse plasma transmission loss measurements. Due to aberrations, the precise lower limit for breakdown threshold irradiance in water is still unknown. Here we show that the threshold energy can be substantially reduced when using adaptive optics to improve the irradiance distribution by spatial beam shaping. We found that for initial aberrations with a root-mean-square wave front error of only one third of the wavelength the threshold energy can still be reduced by a factor of three if the aberrations are corrected to the diffraction limit by adaptive optics. The transmitted pulse energy is reduced by 17% at twice the threshold. Furthermore, the gas bubble motions after breakdown for pulse trains at 5 kilohertz repetition rate show a more transverse direction in the corrected case compared to the more spherical distribution without correction. Our results demonstrate how both applied and transmitted pulse energy could be reduced during ophthalmic surgery when correcting for aberrations. As a consequence, the risk of retinal damage by transmitted energy and the extent of collateral damage to the focal volume could be minimized accordingly when using adaptive optics in fs-laser surgery. PMID:23761849

  17. Multiple ionization of helium and krypton by electron impact close to threshold: appearance energies and Wannier exponents

    NASA Astrophysics Data System (ADS)

    Denifl, S.; Gstir, B.; Hanel, G.; Feketeova, L.; Matejcik, S.; Becker, K.; Stamatovic, A.; Scheier, P.; Märk, T. D.

    2002-11-01

    We determined appearance energy (AE) values AE(Xn+/X) for the formation of singly (He+) and doubly charged (He2+) He ions and multiply charged Kr ions Krn+ up to n = 6 following electron impact on He and Kr atoms using a high-resolution electron impact ionization mass spectrometer. The data analysis employs an iterative, non-linear least-squares fitting routine, the Marquart-Levenberg algorithm, in conjunction with either a 2-function or a 3-function fit based on a power threshold law. This allows us to extract the relevant AEs and also the corresponding exponents for a Wannier-type power law from the measured near-threshold data. The values of the AEs determined in this work are compared with other available experimental and with spectroscopic AE values and the extracted exponents p are compared with other available experimental data and with the predictions of the various Wannier-type power law models. One observation is particularly noteworthy, namely the fact that none of the available experimental data seem to support the large values of 'p' predicted by the Wannier-Geltman and the generalized Wannier law for n > 3.

  18. Electron impact multiple ionization of neon, argon and xenon atoms close to threshold: appearance energies and Wannier exponents

    NASA Astrophysics Data System (ADS)

    Gstir, B.; Denifl, S.; Hanel, G.; Rümmele, M.; Fiegele, T.; Cicman, P.; Stano, M.; Matejcik, S.; Scheier, P.; Becker, K.; Stamatovic, A.; Märk, T. D.

    2002-07-01

    We report the results of the experimental determination of the appearance energy values AE(Xn + /X) for the formation of multiply charged Ne, Ar and Xe ions up to n = 4 (Ne), n = 6 (Ar) and n = 8 (Xe) following electron impact on Ne, Ar and Xe atoms using a dedicated high-resolution electron impact ionization mass spectrometer. The data analysis uses the Marquart-Levenberg algorithm, which is an iterative, nonlinear least-squares-fitting routine, in conjunction with either a two-function or a three-function fit based on a power threshold law. This allows us to extract the relevant AEs and corresponding exponents for a Wannier-type power law from the measured near-threshold data. The values of the AEs determined in this work are compared with other available experimental and spectroscopic values of the AEs and the extracted exponents are compared with other available experimental data and with the predictions of the various Wannier-type power law models.

  19. Energy Thresholds of DNA Damage Induced by UV Radiation: An XPS Study.

    PubMed

    Gomes, P J; Ferraria, A M; Botelho do Rego, A M; Hoffmann, S V; Ribeiro, P A; Raposo, M

    2015-04-30

    This work stresses on damage at the molecular level caused by ultraviolet radiation (UV) in the range from 3.5 to 8 eV, deoxyribonucleic acid (DNA) films observed by X-ray photoelectron spectroscopy (XPS). Detailed quantitative XPS analysis, in which all the amounts are relative to sodium-assumed not to be released from the samples, of the carbon, oxygen, and particularly, nitrogen components, reveals that irradiation leads to sugar degradation with CO-based compounds release for energies above 6.9 eV and decrease of nitrogen groups which are not involved in hydrogen bonding at energies above 4.2 eV. Also the phosphate groups are seen to decrease to energies above 4.2 eV. Analysis of XPS spectra allowed to conclude that the damage on bases peripheral nitrogen atoms are following the damage on phosphates. It suggests that very low kinetic energy photoelectrons are ejected from the DNA bases, as a result of UV light induced breaking of the phosphate ester groups which forms a transient anion with resonance formation and whereby most of the nitrogen DNA peripheral groups are removed. The degree of ionization of DNA was observed to increase with radiation energy, indicating that the ionized phosphate groups are kept unchanged. This result was interpreted by the shielding of phosphate groups caused by water molecules hydration near sodium atoms. PMID:25844940

  20. Maintenance energy requirements of odor detection, explosive detection and human detection working dogs.

    PubMed

    Mullis, Rebecca A; Witzel, Angela L; Price, Joshua

    2015-01-01

    Despite their important role in security, little is known about the energy requirements of working dogs such as odor, explosive and human detection dogs. Previous researchers have evaluated the energy requirements of individual canine breeds as well as dogs in exercise roles such as sprint racing. This study is the first to evaluate the energy requirements of working dogs trained in odor, explosive and human detection. This retrospective study evaluated twenty adult dogs who maintained consistent body weights over a six month period. During this time, the average energy consumption was [Formula: see text] or two times the calculated resting energy requirement ([Formula: see text]). No statistical differences were found between breeds, age or sex, but a statistically significant association (p = 0.0033, R-square = 0.0854) was seen between the number of searches a dog performs and their energy requirement. Based on this study's population, it appears that working dogs have maintenance energy requirements similar to the 1974 National Research Council's (NRC) maintenance energy requirement of [Formula: see text] (National Research Council (NRC), 1974) and the [Formula: see text] reported for young laboratory beagles (Rainbird & Kienzle, 1990). Additional research is needed to determine if these data can be applied to all odor, explosive and human detection dogs and to determine if other types of working dogs (tracking, search and rescue etc.) have similar energy requirements.

  1. Detecting Energy Modulation in a Dielectric Laser Accelerator

    SciTech Connect

    Lukaczyk, Louis

    2015-08-21

    The Dielectric Laser Acceleration group at SLAC uses micro-fabricated dielectric grating structures and conventional infrared lasers to accelerator electrons. These structures have been estimated to produce an accelerating gradient up to 2 orders of magnitude greater than that produced by conventional RF accelerators. The success of the experiment depends on both the laser damage threshold of the structure and the timing overlap of femtosecond duration laser pulses with the electron bunch. In recent dielectric laser acceleration experiments, the laser pulse was shorter both temporally and spatially than the electron bunch. As a result, the laser is theorized to have interacted with only a small portion of the electron bunch. The detection of this phenomenon, referred to as partial population modulation, required a new approach to the data analysis of the electron energy spectra. A fitting function was designed to separate the accelerated electron population from the un-accelerated electron population. The approach was unsuccessful in detecting acceleration in the partial population modulation data. However, the fitting functions provide an excellent figure of merit for previous data known to contain signatures of acceleration.

  2. Difluorocarbene studied with threshold photoelectron spectroscopy (TPES): measurement of the first adiabatic ionization energy (AIE) of CF(2).

    PubMed

    Innocenti, Fabrizio; Eypper, Marie; Lee, Edmond P F; Stranges, Stefano; Mok, Daniel K W; Chau, Foo-tim; King, George C; Dyke, John M

    2008-01-01

    The first photoelectron band of difluorocarbene CF(2), has been studied by threshold photoelectron (TPE) spectroscopy. CF(2) was prepared by microwave discharge of a flowing mixture of hexafluoropropene, C(3)F(6), and argon. A vibrationally resolved band was observed in which at least twenty-two components were observed. In the first PE band of CF(2), the adiabatic ionization energy differs significantly from the vertical ionization energy because, for the ionization CF(2) (+) (X(2)A(1))+e(-) <-- CF(2) (X(1)A(1)), there is an increase in the FCF bond angle (by approximately 20 degrees ) and a decrease in the C--F bond length (by approximately 0.7 A). The adiabatic component was not observed in the experimental TPE spectrum. However, on comparing this spectrum with an ab initio/Franck-Condon simulation of this band, using results from high-level ab initio calculations, the structure associated with the vibrational components could be assigned. This led to alignment of the experimental TPE spectrum and the computed Franck-Condon envelope, and a determination of the first adiabatic ionization energy of CF(2) as (11.362+/-0.005) eV. From the assignment of the vibrational structure, values were obtained for the harmonic and fundamental frequencies of the symmetric stretching mode (nu(1)') and symmetric bending mode (nu(2)') in CF(2) (+) (X(2)A(1)). PMID:19006171

  3. The perils of thresholding

    NASA Astrophysics Data System (ADS)

    Font-Clos, Francesc; Pruessner, Gunnar; Moloney, Nicholas R.; Deluca, Anna

    2015-04-01

    The thresholding of time series of activity or intensity is frequently used to define and differentiate events. This is either implicit, for example due to resolution limits, or explicit, in order to filter certain small scale physics from the supposed true asymptotic events. Thresholding the birth-death process, however, introduces a scaling region into the event size distribution, which is characterized by an exponent that is unrelated to the actual asymptote and is rather an artefact of thresholding. As a result, numerical fits of simulation data produce a range of exponents, with the true asymptote visible only in the tail of the distribution. This tail is increasingly difficult to sample as the threshold is increased. In the present case, the exponents and the spurious nature of the scaling region can be determined analytically, thus demonstrating the way in which thresholding conceals the true asymptote. The analysis also suggests a procedure for detecting the influence of the threshold by means of a data collapse involving the threshold-imposed scale.

  4. Dark rearing alters the normal development of spatiotemporal response properties but not of contrast detection threshold in mouse retinal ganglion cells.

    PubMed

    Akimov, Nikolay P; Rentería, René C

    2014-07-01

    The mouse visual system is immature when the eyes open two weeks after birth. As in other mammals, some of the maturation that occurs in the subsequent weeks is known to depend on visual experience. Development of the retina, which as the first stage of vision provides the visual information to the brain, also depends on light-driven activity for proper development but has been less well studied than visual cortical development. The critical properties for retinal encoding of images include detection of contrast and responsiveness to the broad range of temporal stimulus frequencies present in natural stimuli. Here we show that contrast detection threshold and temporal frequency response characteristics of ON and OFF retinal ganglion cells (RGCs), which are poor at eye opening, subsequently undergo maturation, improving RGC performance. Further, we find that depriving mice of visual experience from before birth by rearing them in the dark causes ON and OFF RGCs to have smaller receptive field centers but does not affect their contrast detection threshold development. The modest developmental increase in temporal frequency responsiveness of RGCs in mice reared on a normal light cycle was inhibited by dark rearing only in ON but not OFF RGCs. Thus, these RGC response characteristics are in many ways unaffected by the experience-dependent changes to synaptic and spontaneous activity known to occur in the mouse retina in the two weeks after eye opening, but specific differences are apparent in the ON vs. OFF RGC populations.

  5. Low energy threshold analysis of the phase I and phase II data sets of the Sudbury neutrino observatory

    SciTech Connect

    Seibert, S R; Hime, A; Elliott, S R; Rielage, K

    2009-01-01

    Results are reported from a joint analysis of Phase I and Phase II data from the Sudbury Neutrino Observatory. The effective electron kinetic energy threshold used is T{sub eff} = 3.5 MeV, the lowest analysis threshold yet achieved with water Cherenkov detector data. In units of 10{sup 6} cm{sup -2} s{sup =1}, the total flux of active-flavor neutrinos from {sup 8}B decay in the Sun measured using the neutral current (NC) reaction of neutrinos on deuterons, with no constraint on the {sup 8}B neutrino energy spectrum, is found to be {Phi}{sub NC} = 5.140{sub -0.158}{sup +0.160}(stat){sub -0.117}{sup +0.132}(syst). These uncertainties are more than a factor of two smaller than previously published results. Also presented are the spectra of recoil electrons from the charged current reaction of neutrinos on deuterons and the elastic scattering of electrons. A fit to the SNO data in which the free parameters directly describe the total {sup 8}B neutrino flux and the energy-dependent Ve survival probability provides a measure of the total {sup 8}B neutrino flux {Phi}{sub 8{sub B}} = 5.046{sub -0.152}{sup +0.159}(stat){sub -0.123}{sup +0.107}(syst). Combining these new results with results of all other solar experiments and the KamLAND reactor experiment yields best-fit values of the mixing parameters of {theta}{sub 12} = 34.06{sub -0.84}{sup +1.16} degrees and {Delta}m{sub 21}{sup 2} = 7.59{sub -0.21}{sup +0.20} x 10{sup -5} eV{sup 2}. The global value of {Phi}{sub 8{sub B}} is extracted to a precision of {sub -2.95}{sup +2.38}%. In a three-flavor analysis the best fit value of sin{sup 2} {theta}{sub 13} is 2.00{sub -1.63}{sup +2.09} x 10{sup -2}. Interpreting this as a limit implies an upper bound of sin{sup 2} {theta}{sub 13} < 0.057 (95% C. L.).

  6. [Conditioned feedback and inhibitory reorganization of the receptive fields of the cortical neurons as a basis for the subconscious change in the thresholds of visual recognition and detection].

    PubMed

    Shevelev, I A

    1990-01-01

    In the paper three groups of facts are compared: significant adaptative and adaptational modification of receptive fields of cat's visual cortex neurones, conditioned selective subsensory change of the threshold of perception (detection and recognition) of a letter by man in relation to two control ones and the role of spatially specialized cortical inhibition in formation and adaptative modifications of receptive fields and detector properties of the visual cortex neurones. Interconnection is discussed of the phenomena described as well as community of their mechanisms. PMID:1964326

  7. Competitive threshold collision-induced dissociation: Gas-phase acidities and bond dissociation energies for a series of alcohols

    SciTech Connect

    DeTuri, V.F.; Ervin, K.M.

    1999-09-02

    Energy-resolved competitive collision-induced dissociation methods are used to measure the gas-phase acidities of a series of alcohols (methanol, ethanol, 2-propanol, and 2-methyl-2-propanol). The competitive dissociation reactions of fluoride-alcohol, [F{sup {minus}}{center{underscore}dot}HOR], alkoxide-water, [RO{sup {minus}}{center{underscore}dot}HOH], and alkoxide-methanol [RO{+-}{center{underscore}dot}HOCH{sub 3}] proton-bound complexes are studied using a guided ion beam tandem mass spectrometer. The reaction cross sections and product branching fractions to the two proton transfer channels are measured as a function of collision energy. The enthalpy difference between the two product channels is found by modeling the reaction cross sections near threshold using RRKM theory to account for the energy-dependent product branching ratio and kinetic shift. From the enthalpy difference, the alcohol gas-phase acidities are determined relative to the well-known values of HF and H{sub 2}O. The measured gas-phase acidities are {Delta}{sub acid}H{sub 298}(CH{sub 3}OH) = 1599 {+-} 3 kJ/mol, {Delta}{sub acid}H{sub 298}(CH{sub 3}CH{sub 2}OH) = 1586 {+-} 5 kJ/mol, {Delta}{sub acid}H{sub 298}((CH{sub 3}){sub 2}CHOH) = 1576 {+-} 4 kJ/mol, and {Delta}{sub acid}H{sub 298}((CH{sub 3}){sub 3}COH) = 1573 {+-} 3 kJ/mol.

  8. Dissociation of internal energy-selected methyl bromide ion revealed from threshold photoelectron-photoion coincidence velocity imaging

    NASA Astrophysics Data System (ADS)

    Tang, Xiaofeng; Zhou, Xiaoguo; Sun, Zhongfa; Liu, Shilin; Liu, Fuyi; Sheng, Liusi; Yan, Bing

    2014-01-01

    Dissociative photoionization of methyl bromide (CH3Br) in an excitation energy range of 10.45-16.90 eV has been investigated by using threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging. The coincident time-of-flight mass spectra indicate that the ground state X2E of CH3Br+ is stable, and both A2A1 and B2E ionic excited states are fully dissociative to produce the unique fragment ion of CH3+. From TPEPICO 3D time-sliced velocity images of CH3+ dissociated from specific state-selected CH3Br+ ion, kinetic energy release distribution (KERD) and angular distribution of CH3+ fragment ion are directly obtained. Both spin-orbit states of Br(2P) atom can be clearly observed in fast dissociation of CH3Br+(A2A1) ion along C-Br rupture, while a KERD of Maxwell-Boltzmann profile is obtained in dissociation of CH3Br+(B2E) ion. With the aid of the re-calculated potential energy curves of CH3Br+ including spin-orbit coupling, dissociation mechanisms of CH3Br+ ion in A2A1 and B2E states along C-Br rupture are revealed. For CH3Br+(A2A1) ion, the CH3+ + Br(2P1/2) channel is occurred via an adiabatic dissociation by vibration, while the Br(2P3/2) formation is through vibronic coupling to the high vibrational level of X2E state followed by rapid dissociation. C-Br bond breaking of CH3Br+(B2E) ion can occur via slow internal conversion to the excited vibrational level of the lower electronic states and then dissociation.

  9. Assimilation of Chinese Fengyun-3B Microwave Temperature Sounder radiances into the Global GRAPES system with an improved cloud detection threshold

    NASA Astrophysics Data System (ADS)

    Li, Juan; Liu, Guiqing

    2016-03-01

    Fengyun-3B (FY-3B) is the second polar-orbiting satellite in the new Fengyun-three series. This paper describes the assimilation of the FY-3B Microwave Temperature Sounder (MWTS) radiances in the Chinese Numerical Weather prediction system — the Global and Regional Assimilation and PrEdiction System (GRAPES). A quality control procedure for the assimilation of the FY-3B MWTS radiance was proposed. Extensive monitoring before assimilation shows that the observations of channel 4 are notably contaminated. Channels 2 and 3 are used in this research. A cloud detection algorithm with an improved cloud-detection threshold is determined and incorporated into the impact experiments. The clear field-of-view (FOV) percentage increased from 42% to 57% with the new threshold. In addition, the newly added FOVs are located in the clear region, as demonstrated by the cloud liquid water path data from NOAA-18. The impact of the MWTS radiances on the prediction of GRAPES was researched. The observation biases of FY-3B MWTS O-B (differences between satellite observations and model simulations) significantly decreased after an empirical bias correction procedure. After assimilation, the residual biases are small. The assimilation of the FY-3B MWTS radiances shows a positive impact in the Northern Hemisphere and a neutral impact in the Southern Hemisphere.

  10. One-photon mass-analyzed threshold ionization (MATI) spectroscopy of pyridine: determination of accurate ionization energy and cationic structure.

    PubMed

    Lee, Yu Ran; Kang, Do Won; Kim, Hong Lae; Kwon, Chan Ho

    2014-11-01

    Ionization energies and cationic structures of pyridine were intensively investigated utilizing one-photon mass-analyzed threshold ionization (MATI) spectroscopy with vacuum ultraviolet radiation generated by four-wave difference frequency mixing in Kr. The present one-photon high-resolution MATI spectrum of pyridine demonstrated a much finer and richer vibrational structure than that of the previously reported two-photon MATI spectrum. From the MATI spectrum and photoionization efficiency curve, the accurate ionization energy of the ionic ground state of pyridine was confidently determined to be 73,570 ± 6 cm(-1) (9.1215 ± 0.0007 eV). The observed spectrum was almost completely assigned by utilizing Franck-Condon factors and vibrational frequencies calculated through adjustments of the geometrical parameters of cationic pyridine at the B3LYP/cc-pVTZ level. A unique feature unveiled through rigorous analysis was the prominent progression of the 10 vibrational mode, which corresponds to in-plane ring bending, and the combination of other totally symmetric fundamentals with the ring bending overtones, which contribute to the geometrical change upon ionization. Notably, the remaining peaks originate from the upper electronic state ((2)A2), as predicted by high-resolution photoelectron spectroscopy studies and symmetry-adapted cluster configuration interaction calculations. Based on the quantitatively good agreement between the experimental and calculated results, it was concluded that upon ionization the pyridine cation in the ground electronic state should have a planar structure of C(2v) symmetry through the C-N axis.

  11. One-photon mass-analyzed threshold ionization (MATI) spectroscopy of pyridine: Determination of accurate ionization energy and cationic structure

    SciTech Connect

    Lee, Yu Ran; Kang, Do Won; Kim, Hong Lae E-mail: hlkim@kangwon.ac.kr; Kwon, Chan Ho E-mail: hlkim@kangwon.ac.kr

    2014-11-07

    Ionization energies and cationic structures of pyridine were intensively investigated utilizing one-photon mass-analyzed threshold ionization (MATI) spectroscopy with vacuum ultraviolet radiation generated by four-wave difference frequency mixing in Kr. The present one-photon high-resolution MATI spectrum of pyridine demonstrated a much finer and richer vibrational structure than that of the previously reported two-photon MATI spectrum. From the MATI spectrum and photoionization efficiency curve, the accurate ionization energy of the ionic ground state of pyridine was confidently determined to be 73 570 ± 6 cm{sup −1} (9.1215 ± 0.0007 eV). The observed spectrum was almost completely assigned by utilizing Franck-Condon factors and vibrational frequencies calculated through adjustments of the geometrical parameters of cationic pyridine at the B3LYP/cc-pVTZ level. A unique feature unveiled through rigorous analysis was the prominent progression of the 10 vibrational mode, which corresponds to in-plane ring bending, and the combination of other totally symmetric fundamentals with the ring bending overtones, which contribute to the geometrical change upon ionization. Notably, the remaining peaks originate from the upper electronic state ({sup 2}A{sub 2}), as predicted by high-resolution photoelectron spectroscopy studies and symmetry-adapted cluster configuration interaction calculations. Based on the quantitatively good agreement between the experimental and calculated results, it was concluded that upon ionization the pyridine cation in the ground electronic state should have a planar structure of C{sub 2v} symmetry through the C-N axis.

  12. SU-C-BRE-07: Sensitivity Analysis of the Threshold Energy for the Creation of Strand Breaks and of Single and Double Strand Break Clustering Conditions

    SciTech Connect

    Pater, P

    2014-06-15

    Purpose: To analyse the sensitivity of the creation of strand breaks (SB) to the threshold energy (Eth) and thresholding method and to quantify the impact of clustering conditions on single strand break (SSB) and double strand break (DSB) yields. Methods: Monte Carlo simulations using Geant4-DNA were conducted for electron tracks of 280 eV to 220 keV in a geometrical DNA model composed of nucleosomes of 396 phospho-diester groups (PDGs) each. A strand break was created inside a PDG when the sum of all energy deposits (method 1) or energy transfers (method 2) was higher than Eth or when at least one interaction deposited (method 3) or transferred (method 4) an energy higher than Eth. SBs were then clustered into SSBs and DSBs using clustering scoring criteria from the literature and compared to our own. Results: The total number of SBs decreases as Eth is increased. In addition, thresholding on the energy transfers (methods 2 and 4) produces a higher SB count than when thresholding on energy deposits (methods 1 and 3). Method 2 produces a step-like function and should be avoided when attempting to optimize Eth. When SBs are grouped into damage patterns, clustering conditions can underestimated SSBs by up to 18 % and DSBs can be overestimated by up to 12 % compared to our own implementation. Conclusion: We show that two often underreported simulation parameters have a non-negligible effect on overall DNA damage yields. First more SBs are counted when using energy transfers to the PDG rather than energy deposits. Also, SBs grouped according to different clustering conditions can influence reported SSB and DSB by as much as 20%. Careful handling of these parameters is required when trying to compare DNA damage yields from different authors. Research funding from the governments of Canada and Quebec. PP acknowledges partial support by the CREATE Medical Physics Research Training Network grant of the Natural Sciences and Engineering Research Council (Grant number: 432290)

  13. Thermal detection thresholds of Aδ- and C-fibre afferents activated by brief CO2 laser pulses applied onto the human hairy skin.

    PubMed

    Churyukanov, Maxim; Plaghki, Léon; Legrain, Valéry; Mouraux, André

    2012-01-01

    Brief high-power laser pulses applied onto the hairy skin of the distal end of a limb generate a double sensation related to the activation of Aδ- and C-fibres, referred to as first and second pain. However, neurophysiological and behavioural responses related to the activation of C-fibres can be studied reliably only if the concomitant activation of Aδ-fibres is avoided. Here, using a novel CO(2) laser stimulator able to deliver constant-temperature heat pulses through a feedback regulation of laser power by an online measurement of skin temperature at target site, combined with an adaptive staircase algorithm using reaction-time to distinguish between responses triggered by Aδ- and C-fibre input, we show that it is possible to estimate robustly and independently the thermal detection thresholds of Aδ-fibres (46.9±1.7°C) and C-fibres (39.8±1.7°C). Furthermore, we show that both thresholds are dependent on the skin temperature preceding and/or surrounding the test stimulus, indicating that the Aδ- and C-fibre afferents triggering the behavioural responses to brief laser pulses behave, at least partially, as detectors of a change in skin temperature rather than as pure level detectors. Most importantly, our results show that the difference in threshold between Aδ- and C-fibre afferents activated by brief laser pulses can be exploited to activate C-fibres selectively and reliably, provided that the rise in skin temperature generated by the laser stimulator is well-controlled. Our approach could constitute a tool to explore, in humans, the physiological and pathophysiological mechanisms involved in processing C- and Aδ-fibre input, respectively.

  14. The Nature of Psychological Thresholds

    ERIC Educational Resources Information Center

    Rouder, Jeffrey N.; Morey, Richard D.

    2009-01-01

    Following G. T. Fechner (1966), thresholds have been conceptualized as the amount of intensity needed to transition between mental states, such as between a states of unconsciousness and consciousness. With the advent of the theory of signal detection, however, discrete-state theory and the corresponding notion of threshold have been discounted.…

  15. Dissociation of internal energy-selected methyl bromide ion revealed from threshold photoelectron-photoion coincidence velocity imaging

    SciTech Connect

    Tang, Xiaofeng; Zhou, Xiaoguo E-mail: yanbing@jlu.edu.cn; Liu, Shilin; Sun, Zhongfa; Liu, Fuyi; Sheng, Liusi; Yan, Bing E-mail: yanbing@jlu.edu.cn

    2014-01-28

    Dissociative photoionization of methyl bromide (CH{sub 3}Br) in an excitation energy range of 10.45–16.90 eV has been investigated by using threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging. The coincident time-of-flight mass spectra indicate that the ground state X{sup 2}E of CH{sub 3}Br{sup +} is stable, and both A{sup 2}A{sub 1} and B{sup 2}E ionic excited states are fully dissociative to produce the unique fragment ion of CH{sub 3}{sup +}. From TPEPICO 3D time-sliced velocity images of CH{sub 3}{sup +} dissociated from specific state-selected CH{sub 3}Br{sup +} ion, kinetic energy release distribution (KERD) and angular distribution of CH{sub 3}{sup +} fragment ion are directly obtained. Both spin-orbit states of Br({sup 2}P) atom can be clearly observed in fast dissociation of CH{sub 3}Br{sup +}(A{sup 2}A{sub 1}) ion along C–Br rupture, while a KERD of Maxwell-Boltzmann profile is obtained in dissociation of CH{sub 3}Br{sup +}(B{sup 2}E) ion. With the aid of the re-calculated potential energy curves of CH{sub 3}Br{sup +} including spin-orbit coupling, dissociation mechanisms of CH{sub 3}Br{sup +} ion in A{sup 2}A{sub 1} and B{sup 2}E states along C–Br rupture are revealed. For CH{sub 3}Br{sup +}(A{sup 2}A{sub 1}) ion, the CH{sub 3}{sup +} + Br({sup 2}P{sub 1/2}) channel is occurred via an adiabatic dissociation by vibration, while the Br({sup 2}P{sub 3/2}) formation is through vibronic coupling to the high vibrational level of X{sup 2}E state followed by rapid dissociation. C–Br bond breaking of CH{sub 3}Br{sup +}(B{sup 2}E) ion can occur via slow internal conversion to the excited vibrational level of the lower electronic states and then dissociation.

  16. Prospects of hydroacoustic detection of ultra-high and extremely high energy cosmic neutrinos

    NASA Astrophysics Data System (ADS)

    Dedenko, L. G.; Karlik, Ya. S.; Learned, J. G.; Svet, V. D.; Zheleznykh, I. M.

    2001-07-01

    The prospects of construction of deep underwater neutrino telescopes in the world's oceans for the goals of ultra-high and super-high energy neutrino astrophysics (astronomy) using acoustic technologies are reviewed. The effective detection volume of the acoustic neutrino telescopes can be far greater than a cubic kilometer for extreme energies. In recent years, it was proposed that an existing hydroacoustic array of 2400 hydrophones in the Pacific Ocean near Kamchatka Peninsula could be used as a test base for an acoustic neutrino telescope SADCO (Sea-based Acoustic Detector of Cosmic Objects) which should be capable of detecting acoustic signals produced in water by the cosmic neutrinos with energies 1019-21 eV (e.g., topological defect neutrinos). We report on simulations of super-high energy electron-hadron and electron-photon cascades with the Landau-Pomeranchuk-Migdal effect taken into account. Acoustic signals emitted by neutrino-induced cascades with energies 1020-21 eV were calculated. The possibilities of using a converted hydroacoustic station MG-10 (MG-10M) of 132 hydrophones as a basic module for a deep water acoustic neutrino detector with the threshold detection energy 1015 eV in the Mediterranean Sea are analyzed (with the aim of searching for neutrinos with energies 1015-16 eV from Active Galactic Nuclei). .

  17. TPD-based evaluation of near threshold mono-energetic proton energies for the (7)Li(p,n)(7)Be production of neutrons for BNCT.

    PubMed

    Bengua, Gerard; Kobayashi, Tooru; Tanaka, Kenichi; Nakagawa, Yoshinobu; Unesaki, Hironobu

    2006-08-21

    An evaluation of mono-energetic proton energies ranging from 1.885 MeV to 1.920 MeV was carried out to determine the viability of these near threshold energies in producing neutrons for BNCT via the (7)Li(p,n)(7)Be reaction. Neutron fields generated at these proton energies were assessed using the treatable protocol depth (TPD) and the maximum TPD (TPD(max)) as evaluation indices. The heavy charged particle (HCP) dose rate to tumour was likewise applied as a figure of merit in order to account for irradiation time and required proton current. Incident proton energies closer to the reaction threshold generated deeper TPDs compared to higher energy protons when no boron dose enhancers (BDE) were placed in the irradiation field. Introducing a BDE resulted in improved TPDs for high proton energies but their achievable TPD(max) were comparatively lower than that obtained for lower proton energies. In terms of the HCP dose rate to tumour, higher proton energies generated neutron fields that yielded higher dose rates both at TPD(max) and at fixed depths of comparison. This infers that higher currents are required to deliver the prescribed treatment dose to tumours for proton beams with energies closer to the (7)Li(p,n)(7)Be reaction threshold and more achievable proton currents of around 10 mA or less for proton energies from 1.900 MeV and above. The dependence on incident proton energy of the TPD, TPD(max) and the HCP dose rate to tumour with respect to the (10)B concentration in tumour and healthy tissues were also clarified in this study. Increasing the (10)B concentration in tumour while maintaining a constant T/N ratio resulted in deeper TPD(max) where a greater change in TPD(max) was obtained for proton energies closer to the (7)Li(p,n)(7)Be reaction threshold. The HCP dose rates to tumour for all proton energies also went up, with the higher proton energies benefiting more from the increased (10)B concentration.

  18. Calibration of a solid state nuclear track detector (SSNTD) with high detection threshold to search for rare events in cosmic rays

    NASA Astrophysics Data System (ADS)

    Dey, S.; Gupta, D.; Maulik, A.; Raha, Sibaji; Saha, Swapan K.; Syam, D.; Pakarinen, J.; Voulot, D.; Wenander, F.

    2011-06-01

    We have investigated a commercially available polymer for its suitability as a solid state nuclear track detector (SSNTD). We identified that polymer to be polyethylene terephthalate (PET) and found that it has a higher detection threshold compared to many other widely used SSNTDs which makes this detector particularly suitable for rare event search in cosmic rays as it eliminates the dominant low Z background. Systematic studies were carried out to determine its charge response which is essential before any new material can be used as an SSNTD. In this paper we describe the charge response of PET to 129Xe, 78Kr and 49Ti ions from the REX-ISOLDE facility at CERN, present the calibration curve for PET and characterize it as a nuclear track detector.

  19. Photodissociation spectroscopy of stored CH+ ions: Detection, assignment, and close-coupled modeling of near-threshold Feshbach resonances

    NASA Astrophysics Data System (ADS)

    Hechtfischer, Ulrich; Williams, Carl J.; Lange, Michael; Linkemann, Joachim; Schwalm, Dirk; Wester, Roland; Wolf, Andreas; Zajfman, Daniel

    2002-11-01

    We have measured and theoretically analyzed a photodissociation spectrum of the CH+ molecular ion in which most observed energy levels lie within the fine-structure splitting of the C+ fragment and predissociate, and where the observed irregular line shapes and dipole-forbidden transitions indicate that nonadiabatic interactions lead to multichannel dynamics. The molecules were prepared in low rotational levels J''=0-9 of the vibrational ground state X 1Sigma+ (v'')=0 by storing a CH+ beam at 7.1 MeV in the heavy-ion storage ring TSR for up to 30 s, which was sufficient for the ions to rovibrationally thermalize to room temperature by spontaneous infrared emission. The internally cold molecules were irradiated with a dye laser at photon energies between 31 600-33 400 cm-1, and the resulting C+ fragments were counted with a particle detector. The photodissociation cross section displays the numerous Feshbach resonances between the two C+ fine-structure states predicted by theory for low rotation. The data are analyzed in two steps. First, from the overall structure of the spectrum, by identifying branches, and by a Le Roy-Bernstein analysis of level spacings we determine the dissociation energy D0=(32 946.7plus-or-minus1.1) cm-1 (with respect to the lower fine-structure limit) and assign the strongest features to the vibrational levels v'=11-14 of the dipole-allowed A 1Pi state. The majority of the 66 observed resonances cannot be assigned in this way. Therefore, in a second step, the complete spectrum is simulated with a close-coupling model, starting from recent ab initio Born-Oppenheimer potentials. For the long-range induction, dispersion and exchange energies, we propose an analytical expression and derive the C6 coefficients. After a systematic variation of just the vibrational defects of the four Born-Oppenheimer potentials involved, the close-coupling model yields a quantitative fit to the measured cross section in all detail, and is used to assign most of

  20. Identification of Threshold Prostate Specific Antigen Levels to Optimize the Detection of Clinically Significant Prostate Cancer by Magnetic Resonance Imaging/Ultrasound Fusion Guided Biopsy

    PubMed Central

    Shakir, Nabeel A.; George, Arvin K.; Siddiqui, M. Minhaj; Rothwax, Jason T.; Rais-Bahrami, Soroush; Stamatakis, Lambros; Su, Daniel; Okoro, Chinonyerem; Raskolnikov, Dima; Walton-Diaz, Annerleim; Simon, Richard; Turkbey, Baris; Choyke, Peter L.; Merino, Maria J.; Wood, Bradford J.; Pinto, Peter A.

    2015-01-01

    Purpose Prostate specific antigen sensitivity increases with lower threshold values but with a corresponding decrease in specificity. Magnetic resonance imaging/ultrasound targeted biopsy detects prostate cancer more efficiently and of higher grade than standard 12-core transrectal ultrasound biopsy but the optimal population for its use is not well defined. We evaluated the performance of magnetic resonance imaging/ultrasound targeted biopsy vs 12-core biopsy across a prostate specific antigen continuum. Materials and Methods We reviewed the records of all patients enrolled in a prospective trial who underwent 12-core transrectal ultrasound and magnetic resonance imaging/ultrasound targeted biopsies from August 2007 through February 2014. Patients were stratified by each of 4 prostate specific antigen cutoffs. The greatest Gleason score using either biopsy method was compared in and across groups as well as across the population prostate specific antigen range. Clinically significant prostate cancer was defined as Gleason 7 (4 + 3) or greater. Univariate and multivariate analyses were performed. Results A total of 1,003 targeted and 12-core transrectal ultrasound biopsies were performed, of which 564 diagnosed prostate cancer for a 56.2% detection rate. Targeted biopsy led to significantly more upgrading to clinically significant disease compared to 12-core biopsy. This trend increased more with increasing prostate specific antigen, specifically in patients with prostate specific antigen 4 to 10 and greater than 10 ng/ml. Prostate specific antigen 5.2 ng/ml or greater captured 90% of upgrading by targeted biopsy, corresponding to 64% of patients who underwent multiparametric magnetic resonance imaging and subsequent fusion biopsy. Conversely a greater proportion of clinically insignificant disease was detected by 12-core vs targeted biopsy overall. These differences persisted when controlling for potential confounders on multivariate analysis. Conclusions Prostate

  1. A thermalization energy analysis of the threshold voltage shift in amorphous indium gallium zinc oxide thin film transistors under positive gate bias stress

    NASA Astrophysics Data System (ADS)

    Niang, K. M.; Barquinha, P. M. C.; Martins, R. F. P.; Cobb, B.; Powell, M. J.; Flewitt, A. J.

    2016-02-01

    Thin film transistors (TFTs) employing an amorphous indium gallium zinc oxide (a-IGZO) channel layer exhibit a positive shift in the threshold voltage under the application of positive gate bias stress (PBS). The time and temperature dependence of the threshold voltage shift was measured and analysed using the thermalization energy concept. The peak energy barrier to defect conversion is extracted to be 0.75 eV and the attempt-to-escape frequency is extracted to be 107 s-1. These values are in remarkable agreement with measurements in a-IGZO TFTs under negative gate bias illumination stress (NBIS) reported recently (Flewitt and Powell, J. Appl. Phys. 115, 134501 (2014)). This suggests that the same physical process is responsible for both PBS and NBIS, and supports the oxygen vacancy defect migration model that the authors have previously proposed.

  2. Use of threshold-specific energy model for the prediction of effects of smoking and radon exposure on the risk of lung cancer.

    PubMed

    Böhm, R; Sedlák, A; Bulko, M; Holý, K

    2014-07-01

    Lung cancer is the leading cause of cancer death in both men and women. Smoking causes 80-90% of cases of lung cancer. In this study, an attempt was made to assess the impact of cigarette smoking on the risk of lung cancer by the so-called threshold-specific energy model. This model allows to analyse the biological effects of radon daughter products on the lung tissue, and is based on the assumption that the biological effect (i.e. cell inactivation) will manifest itself after the threshold-specific energy z0 deposited in the sensitive volume of the cell is exceeded. Cigarette smoking causes, among others, an increase in the synthesis of the survivin protein that protects cells from apoptosis and thereby reduces their radiosensitivity. Based on these facts, an attempt was made to estimate the shape of the curves describing the increase in the oncological effect of radiation as a function of daily cigarette consumption.

  3. Use of threshold-specific energy model for the prediction of effects of smoking and radon exposure on the risk of lung cancer.

    PubMed

    Böhm, R; Sedlák, A; Bulko, M; Holý, K

    2014-07-01

    Lung cancer is the leading cause of cancer death in both men and women. Smoking causes 80-90% of cases of lung cancer. In this study, an attempt was made to assess the impact of cigarette smoking on the risk of lung cancer by the so-called threshold-specific energy model. This model allows to analyse the biological effects of radon daughter products on the lung tissue, and is based on the assumption that the biological effect (i.e. cell inactivation) will manifest itself after the threshold-specific energy z0 deposited in the sensitive volume of the cell is exceeded. Cigarette smoking causes, among others, an increase in the synthesis of the survivin protein that protects cells from apoptosis and thereby reduces their radiosensitivity. Based on these facts, an attempt was made to estimate the shape of the curves describing the increase in the oncological effect of radiation as a function of daily cigarette consumption. PMID:24711526

  4. Multiple-laser-energy detection system

    NASA Technical Reports Server (NTRS)

    Jarrett, O., Jr.; Northam, G. B.

    1977-01-01

    Technique monitors energy output of each of four sequentially-pulsed dye lasers for the Airborne LIDAR Oceanographic Probing Experiment system. Fiber optics attached to output mirrors transmit optical signal proportional to output energy.

  5. Molecular host-guest energy-transfer system with an ultralow amplified spontaneous emission threshold employing an ambipolar semiconducting host matrix.

    PubMed

    Toffanin, Stefano; Capelli, Raffaella; Hwu, Tsyr-Yuan; Wong, Ken-Tsung; Plötzing, Tobias; Först, Michael; Muccini, Michele

    2010-01-14

    We report on the characteristics of a host-guest lasing system obtained by coevaporation of an oligo(9,9-diarylfluorene) derivative named T3 with the red-emitter 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran dye (DCM). We demonstrate that the ambipolar semiconductor T3 can be implemented as an active matrix in the realization of a host-guest system in which an efficient energy transfer takes place from the T3 matrix to the lasing DCM molecules. We performed a detailed spectroscopic study on the system by systematically varying the DCM concentration in the T3 matrix. Measurements of steady-state photoluminescence (PL), PL quantum yield (PLQY), time-resolved picosecond PL, and amplified spontaneous emission (ASE) threshold are used to optimize the acceptor concentration at which the ASE from DCM molecules takes place with the lowest threshold. The sample with a DCM relative deposition ratio of 2% shows an ASE threshold as low as 0.6 kW/cm(2) and a net optical gain measured by femtosecond time-resolved pump-and-probe spectroscopy as high as 77 cm(-1). The reference model system Alq(3):DCM sample measured in exactly the same experimental conditions presents an one-order-of-magnitude higher ASE threshold. The ASE threshold of T3:DCM is the lowest reported to date for a molecular host-guest energy-transfer system, which makes the investigated blend an appealing system for use as an active layer in lasing devices. In particular, the ambipolar charge transport properties of the T3 matrix and its field-effect characteristics make the host-guest system presented here an ideal candidate for the realization of electrically pumped organic lasers.

  6. Detecting dark energy with wavelets on the sphere

    NASA Astrophysics Data System (ADS)

    McEwen, Jason D.

    2007-09-01

    Dark energy dominates the energy density of our Universe, yet we know very little about its nature and origin. Although strong evidence in support of dark energy is provided by the cosmic microwave background, the relic radiation of the Big Bang, in conjunction with either observations of supernovae or of the large scale structure of the Universe, the verification of dark energy by independent physical phenomena is of considerable interest. We review works that, through a wavelet analysis on the sphere, independently verify the existence of dark energy by detecting the integrated Sachs-Wolfe effect. The effectiveness of a wavelet analysis on the sphere is demonstrated by the highly statistically significant detections of dark energy that are made. Moreover, the detection is used to constrain properties of dark energy. A coherent picture of dark energy is obtained, adding further support to the now well established cosmological concordance model that describes our Universe.

  7. CERES Detects Earth's Heat and Energy

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Clouds and the Earth's Radiant Energy System, CERES, monitors solar energy reflected from the Earth and heat energy emitted from the Earth. In this image, heat energy radiated from the earth is shown in varying shades of yellow, red, blue and white. The brightest yellow areas, such as the Sahara Desert and Arabian Peninsula, are emitting the most energy out to space, while the dark blue polar regions and bright white clouds are the coldest areas on Earth, and are emitting the least energy. The animation (1.5MB) (high-res (4MB)) shows roughly a week of CERES data. For more information: CERES images through Visible Earth. CERES web site Image courtesy of the CERES instrument team

  8. Radio detection of ultra-high energy cosmic neutrinos

    SciTech Connect

    Vieregg, Abigail G.

    2015-07-15

    Ultra-high energy (UHE) neutrino astronomy constitutes a new window of observation onto the UHE universe. The detection and characterization of astrophysical neutrinos at the highest energies (E> 10{sup 18} eV) would reveal the sources of high-energy cosmic rays, the highest energy particles ever seen, and would constrain the evolution of such sources over time. UHE neutrino astrophysics also allows us to probe weak interaction couplings at energies much greater than those available at particle colliders. One promising way of detecting the highest energy neutrinos is through the radio emission created when they interact in a large volume of dielectric, such as ice. Here I discuss current results and future efforts to instrument large volumes of detector material with radio antennas to detect, point back, and characterize the energy of UHE astrophysical neutrinos.

  9. Evaluating energy sorghum harvest thresholds and tillage cropping systems to offset negative environmental impacts and harvesting equipment-induced soil compaction

    NASA Astrophysics Data System (ADS)

    Meki, M. N.; Snider, J. L.; Kiniry, J. R.; Raper, R. L.; Rocateli, A. C.

    2011-12-01

    Energy sorghum (Sorghum bicolor L. Moench) could be the ideal feedstock for the cellulosic ethanol industry because of its robust establishment, broader adaptability and drought tolerance, water and nutrient use efficiency, and the relatively high annual biomass yields. Of concern, however, is the limited research data on harvest thresholds, subsequent environmental impacts and the potential cumulative effects of harvesting equipment-induced soil compaction. Indiscriminate harvests of the high volume wet energy sorghum biomass, coupled with repeated field passes, could cause irreparable damage to the soil due to compaction. Furthermore, biomass harvests result in lower soil organic matter returns to the soil, making the soil even more susceptible to soil compaction. Compacted soils result in poor root zone aeration and drainage, more losses of nitrogen from denitrification, and restricted root growth, which reduces yields. Given the many positive attributes of conservation tillage and crop residue retention, our research and extension expectations are that sustainable energy sorghum cropping systems ought to include some form of conservation tillage. The challenge is to select cropping and harvesting systems that optimize feedstock production while ensuring adequate residue biomass to sustainably maintain soil structure and productivity. Producers may have to periodically subsoil-till or plow-back their lands to alleviate problems of soil compaction and drainage, weeds, insects and disease infestations. Little, however, is known about the potential impact of these tillage changes on soil productivity, environmental integrity, and sustainability of bioenergy agro-ecosystems. Furthermore, 'safe' energy sorghum feedstock removal thresholds have yet to be established. We will apply the ALMANAC biophysical model to evaluate permissible energy sorghum feedstock harvest thresholds and the effects of subsoil tillage and periodically plowing no-tilled (NT) energy sorghum

  10. A new real-time method for detecting the effect of fentanyl using the preoperative pressure pain threshold and Narcotrend index: a randomized study in female surgery patients.

    PubMed

    Duan, Guangyou; Guo, Shanna; Zhan, Huiming; Qi, Dongmei; Zhang, Yuhao; Zhang, Xianwei

    2015-01-01

    Individual variability in the effects of opioid analgesics such as fentanyl remains a major challenge for tailored pharmacological treatment including postoperative analgesia. This study aimed to establish a new real-time method for detecting the effects of fentanyl and their individual differences in the preoperative period, using the pressure pain threshold (PPT) and Narcotrend index (NTI) test.Eighty women undergoing elective surgery under general anesthesia were enrolled in this randomized, double-blinded, placebo-controlled study to receive either intravenous fentanyl (Group F) or saline (Group S). Before (T1) and 5 (T2) and 10 min (T3) after intravenous injection, the PPT, NTI, respiratory rate, heart rate, blood pressure, and pulse oxygen saturation were measured. The initial time at which the Narcotrend index showed a decline was also recorded.In total, 40 patients in Group S and 38 patients in Group F were included in the final analysis. At 5 min and 10 min after intravenous fentanyl administration, the analgesic effect was determined by measuring the PPT, which was significantly increased (P < 0.001), and the sedative effect was detected using the NTI, which was significantly decreased (P < 0.001). The distribution of percentage changes of the PPT and NTI showed individual differences. At T2 and T3, the absolute changes in NTI and PPT were positively correlated (r = 0.444 at T2, P = 0.005; r = 0.332 at T3, P = 0.042).Through the PPT and NTI, it was feasible to easily detect the effects of fentanyl and their individual differences in real time before induction of anesthesia in the operation room. This method could potentially be applied to preoperatively determine patients' sensitivity to fentanyl.

  11. Development of the detection threshold concept from a close look at sorption occurrence inside a glass vial based on the in-vial vaporization of semivolatile fatty acids.

    PubMed

    Kim, Yong-Hyun; Kim, Ki-Hyun; Szulejko, Jan E; Parker, David

    2014-07-01

    Headspace (HS) analysis has been recommended as one of the most optimal methods for extracting and analyzing volatile organic compounds from samples in diverse media such as soil and water. Short-chain volatile fatty acids (VFA, C3-C7) with strong adsorptivity were selected as the target compounds to assess the basic characteristics of the HS analysis through simulation of HS conditions by in-vial vaporization of liquid-phase standards (VL) in 25 mL glass vials. The reliability of the VL approach was assessed by apportioning the in-vial VFA mass into three classes: (1) vaporized fraction, (2) dynamic adsorption on the vial walls (intermediate stage between vaporization and irreversible absorption), and (3) irreversible absorptive loss (on the vial wall). The dynamic adsorption partitioning inside the vial increased with n-VFA carbon number, e.g., 43% (C2: acetic acid, extrapolated value), 65% (C3: propanoic acid), and 98% (C7: heptanoic acid). The maximum irreversible losses for the studied n-VFAs exhibited a quadratic relationship with carbon number. If the detection threshold limit (DTL: the onset of mass detection after attaining the maximum irreversible loss) is estimated, the DTL values for target VFAs were in the range of 101 ng for i-valeric acid to 616 ng for propionic acid, which are larger than the method detection limit by about 3 orders of magnitude. Consequently, quantitation of VFAs using the VL approach should be critically assessed by simultaneously considering the DTL criterion and the initial VFA masses loaded into the vial.

  12. High Energy Electron Detection with ATIC

    NASA Technical Reports Server (NTRS)

    Chang, J.; Schmidt, W. K. H.; Adams, James H., Jr.; Ahn, H.; Ampe, J.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    The ATIC (Advanced Thin Ionization Calorimeter) balloon-borne ionization calorimeter is well suited to record and identify high energy cosmic ray electrons. The instrument was exposed to high-energy beams at CERN H2 bean-dine in September of 1999. We have simulated the performance of the instrument, and compare the simulations with actual high energy electron exposures at the CERN accelerator. Simulations and measurements do not compare exactly, in detail, but overall the simulations have predicted actual measured behavior quite well.

  13. Can the Existence of Dark Energy be Directly Detected?

    SciTech Connect

    Perl, Martin L.; /SLAC /KIPAC, Menlo Park

    2011-11-23

    The majority of astronomers and physicists accept the reality of dark energy and also believe that it can only be studied indirectly through observation of the motions of stars and galaxies. In this paper I open the experimental question of whether it is possible to directly detect dark energy through the presence of dark energy density. Two thirds of this paper outlines the major aspects of dark energy density as now comprehended by the astronomical and physics community. The final third summarizes various proposals for direct detection of dark energy density or its possible effects. At this time I do not have a fruitful answer to the question: Can the Existence of Dark Energy Be Directly Detected?

  14. Metal specificity of cyanobacterial nickel-responsive repressor InrS: cells maintain zinc and copper below the detection threshold for InrS

    PubMed Central

    Foster, Andrew W; Pernil, Rafael; Patterson, Carl J; Robinson, Nigel J

    2014-01-01

    InrS is a Ni(II)-responsive, CsoR/RcnR-like, DNA-binding transcriptional repressor of the nrsD gene, but the Ni(II) co-ordination sphere of InrS is unlike Ni(II)-RcnR. We show that copper and Zn(II) also bind tightly to InrS and in vitro these ions also impair InrS binding to the nrsD operator-promoter. InrS does not respond to Zn(II) (or copper) in vivo after 48 h, when Zn(II) sensor ZiaR responds, but InrS transiently responds (1 h) to both metals. InrS conserves only one (of two) second co-ordination shell residues of CsoR (Glu98 in InrS). The allosteric mechanism of InrS is distinct from Cu(I)-CsoR and conservation of deduced second shell residues better predicts metal specificity than do the metal ligands. The allosteric mechanism of InrS permits greater promiscuity in vitro than CsoR. The factors dictating metal-selectivity in vivo are that KNi(II) and ΔGCNi(II)-InrS·DNA are sufficiently high, relative to other metal sensors, for InrS to detect Ni(II), while the equivalent parameters for copper may be insufficient for copper-sensing in S ynechocystis (at 48 h). InrS KZn(II) (5.6 × 10−13 M) is comparable to the sensory sites of ZiaR (and Zur), but ΔGCZn(II)-InrS·DNA is less than ΔGCZn(II)-ZiaR·DNA implying that relative to other sensors, ΔGCZn(II)-Sensor·DNA rather than KZn(II) determines the final detection threshold for Zn(II). PMID:24666373

  15. A prospective multicenter study on the safety of a pacemaker with automatic energy control: influence of the electrical factor on chronic stimulation threshold. PEACE Investigators.

    PubMed

    Madrid, A H; Olagüe, J; Cercas, A; del Ojo, J L; Muñoz, F; Moro, C; Sanz, O

    2000-09-01

    The effectiveness and safety of a pacemaker with automatic control of capture was evaluated in 162 patients followed at 27 Spanish centers. The aim of our prospective, multicenter, and randomized trial was to determine the relationship between the voltage output of the pulse generator and the stimulation threshold. We randomized 162 patients (107 men, mean age 75 +/- 12 years). We implanted a ventricular pacemaker model Regency SR+ or SC+ with Pacesetter's low polarization bipolar leads Membrane E 1450. The patients were randomized to receive Autocapture or not; group I (81 patients) Autocapture On, pulse output automatically adjusted and group II (81 patients) Autocapture Off, fixed output parameters (3.9 V, 0.37 ms). We performed a 6-month follow-up measuring stimulation threshold by means of the VARIO test and Autocapture test, evoked response signal, and R wave signal. The mean R wave was 15.77 +/- 3.5 mV at the end of the follow-up for group I, and 14.91 +/- 6.8 mV for group II (P = NS). The measured evoked response at the end of the follow-up was 9.25 mV in Group I and 8.48 mV in Group II (P = NS). The stimulation threshold was not different between groups. The current density created with the voltage and pulse width used in this study (< or = 3.9 V and 0.37 ms) at the tip of this electrode during the maturation process had no influence on the development of the chronic detection and stimulation thresholds. PMID:11025891

  16. State-selected chemical reaction dynamics at the S matrix level - Final-state specificities of near-threshold processes at low and high energies

    NASA Technical Reports Server (NTRS)

    Chatfield, David C.; Truhlar, Donald G.; Schwenke, David W.

    1992-01-01

    State-to-state reaction probabilities are found to be highly final-state specific at state-selected threshold energies for the reactions O + H2 yield OH + H and H + H2 yield H2 + H. The study includes initial rotational states with quantum numbers 0-15, and the specificity is especially dramatic for the more highly rotationally excited reactants. The analysis is based on accurate quantum mechanical reactive scattering calculations. Final-state specificity is shown in general to increase with the rotational quantum number of the reactant diatom, and the trends are confirmed for both zero and nonzero values of the total angular momentum.

  17. High resolution multiple electron impact ionisation of He, Ne, Ar, Kr and Xe atoms close to threshold: Appearance energies and Wannier exponents

    NASA Astrophysics Data System (ADS)

    Gstir, B.; Denifl, S.; Hanel, G.; Rümmele, M.; Fiegele, T.; Stano, M.; Feketeova, L.; Matejcik, S.; Becker, K.; Scheier, P.; Märk, T. D.

    2003-05-01

    We have determined appearance energies AE(X n+ /X) for the formation of multiply charged He, Ne, Ar, Kr and Xe ions up to charge state n=2 (He), n=4 (Ne), n=6 (Ar), n=6 (Kr) and n=8 (Xe) using a recently commissioned high-resolution electron impact ionization mass spectrometer. The data analysis is based on the Marquart-Levenberg algorithm, involving an iterative, non-linear least-squares fitting of the threshold data assuming a 2-function or a 3-function fit based on a Wannier-type power law. This allows us to extract the relevant AEs and corresponding Wannier exponents.

  18. Detection of chemical agents using a novel energy cell

    NASA Astrophysics Data System (ADS)

    Shewchun, John

    2007-04-01

    The detection, classification and tracking of chemical agents (explosives) being surreptitiously smuggled into public areas, such as airports, for destructive purposes is difficult to solve by unobtrusive means. We propose the use of a novel energy cell with gas/vapor sniffing capability. Variants of such devices are routinely used by police to detect alcohol emanating from the breath of suspected impaired vehicle drivers. We have advanced this technology with the development of a Pethanol Alkaline Energy Cell which is capable of reading gaseous emissions ultimately in the parts per billion range. Our work is described in terms of detecting TATAP (acetone peroxide).

  19. A thermalization energy analysis of the threshold voltage shift in amorphous indium gallium zinc oxide thin film transistors under simultaneous negative gate bias and illumination

    SciTech Connect

    Flewitt, A. J.; Powell, M. J.

    2014-04-07

    It has been previously observed that thin film transistors (TFTs) utilizing an amorphous indium gallium zinc oxide (a-IGZO) semiconducting channel suffer from a threshold voltage shift when subjected to a negative gate bias and light illumination simultaneously. In this work, a thermalization energy analysis has been applied to previously published data on negative bias under illumination stress (NBIS) in a-IGZO TFTs. A barrier to defect conversion of 0.65–0.75 eV is extracted, which is consistent with reported energies of oxygen vacancy migration. The attempt-to-escape frequency is extracted to be 10{sup 6}−10{sup 7} s{sup −1}, which suggests a weak localization of carriers in band tail states over a 20–40 nm distance. Models for the NBIS mechanism based on charge trapping are reviewed and a defect pool model is proposed in which two distinct distributions of defect states exist in the a-IGZO band gap: these are associated with states that are formed as neutrally charged and 2+ charged oxygen vacancies at the time of film formation. In this model, threshold voltage shift is not due to a defect creation process, but to a change in the energy distribution of states in the band gap upon defect migration as this allows a state formed as a neutrally charged vacancy to be converted into one formed as a 2+ charged vacancy and vice versa. Carrier localization close to the defect migration site is necessary for the conversion process to take place, and such defect migration sites are associated with conduction and valence band tail states. Under negative gate bias stressing, the conduction band tail is depleted of carriers, but the bias is insufficient to accumulate holes in the valence band tail states, and so no threshold voltage shift results. It is only under illumination that the quasi Fermi level for holes is sufficiently lowered to allow occupation of valence band tail states. The resulting charge localization then allows a negative threshold voltage

  20. Optic nerve sheath diameter threshold by ocular ultrasonography for detection of increased intracranial pressure in Korean adult patients with brain lesions

    PubMed Central

    Lee, Si Un; Jeon, Jin Pyeong; Lee, Hannah; Han, Jung Ho; Seo, Mingu; Byoun, Hyoung Soo; Cho, Won-Sang; Ryu, Ho Geol; Kang, Hyun-Seung; Kim, Jeong Eun; Kim, Heung Cheol; Jang, Kyung-Sool

    2016-01-01

    Abstract Optic nerve sheath diameter (ONSD) seen on ocular US has been associated with increased intracranial pressure (IICP). However, most studies have analyzed normal range of ONSD and its optimal cut-off point for IICP in Caucasian populations. Considering ONSD differences according to ethnicity, previous results may not accurately reflect the association between IICP and ONSD in Koreans. Therefore, we conducted this study to investigate normal range of ONSD and its optimal threshold for detecting IICP in Korean patients. This prospective multicenter study was performed for patients with suspected IICP. ONSD was measured 3 mm behind the globe using a 13-MHz US probe. IICP was defined as significant brain edema, midline shift, compression of ventricle or basal cistern, effacement of sulci, insufficient gray/white differentiation, and transfalcine herniation by radiologic tests. The results of the ONSD are described as the median (25th–75th percentile). The differences of ONSD according to disease entity were analyzed. A receiver operator characteristic (ROC) curve was generated to determine the optimal cut-off point for identifying IICP. A total of 134 patients were enrolled. The patients were divided into 3 groups as follows: patients with IICP, n = 81 (60.5%); patients without IICP, n = 27 (20.1%); and control group, n = 26 (19.4%). ONSD in patients with IICP (5.9 mm [5.8–6.2]) is significantly higher than those without IICP (5.2 mm [4.8–5.4]) (P < 0.01) and normal control group (4.9 mm [4.6–5.2]) (P < 0.001). Between patients without IICP and normal control group, the difference of ONSD did not reach statistical significance (P = 0.31). ONSD >5.5 mm yielded a sensitivity of 98.77% (95% CI: 93.3%–100%) and a specificity of 85.19% (95% CI: 66.3%–95.8%). In conclusion, the optimal cut-off point of ONSD for identifying IICP was 5.5 mm. ONSD seen on ocular US can be a feasible method for detection and serial monitoring of ICP in

  1. A study of threshold effects in the energy loss of slow protons in semiconductors and insulators using dielectric and non-linear approaches

    NASA Astrophysics Data System (ADS)

    Archubi, Claudio Darío; Arista, Nestor R.

    2016-03-01

    The energy loss of slow protons in nonconducting materials, including semiconductors and insulators, is studied using different theoretical methods. First we apply two dielectric models proposed by Brandt and Reinheimer on one side, and by Levine and Louie on the other, and describe in detail the properties of individual and collective contributions according to each model. In addition, we perform an alternative calculation using a non-linear approach based on transport-cross-section methods. These different approaches are compared with experimental results for two semiconductors (Si and Ge) and two insulators (LiF and AlF3), obtaining an approximate description of threshold effects at very low energies. Some interesting similarities and discrepancies are found, which show the current limitations of the theoretical descriptions provided by these methods.

  2. CARA Risk Assessment Thresholds

    NASA Technical Reports Server (NTRS)

    Hejduk, M. D.

    2016-01-01

    Warning remediation threshold (Red threshold): Pc level at which warnings are issued, and active remediation considered and usually executed. Analysis threshold (Green to Yellow threshold): Pc level at which analysis of event is indicated, including seeking additional information if warranted. Post-remediation threshold: Pc level to which remediation maneuvers are sized in order to achieve event remediation and obviate any need for immediate follow-up maneuvers. Maneuver screening threshold: Pc compliance level for routine maneuver screenings (more demanding than regular Red threshold due to additional maneuver uncertainty).

  3. Near Threshold Coincident Electrofission of Uranium -238.

    NASA Astrophysics Data System (ADS)

    Dowell, David Harry

    Using the 100% duty cycle electron beam from the University of Illinois MUSL-2 accelerator, inelastic electron scattering form factors have been measured in coincidence with the fission decay of ('238)U. Data was taken at effective elastic momentum transfers of .36, .41 .45 and .59 fm(' -1) and electron-fission fragment angular correlations were measured perpendicular to and along the momentum transfer axis. The beam energies used were 67.11, 56.91 and 46.49 MeV, with the outgoing electron detected at 60(DEGREES) and 80(DEGREES), relative to the beam direction. The electron energy resolution was .1% and the form factors were measured for excitation energies from 2 to 12 MeV. Thin films of scintillator plastic (.5 mg/cm('2)) were used to detect the fission fragments from a 1 mg/cm('2) UF(,4) target evaporated onto a .240 mg/cm('2) aluminum backing. A prominent, anisotropic threshold peak is seen in the coincident form factors. An analysis of the q-dependence of the data and of the angular correlation indicates the observed strength is E2. Fission threshold for this E2 strength is about 5.7 MeV as compared with 6 MeV for E1 decays. The peak itself is due to the onset of neutron competition at 6.15 MeV. The threshold region, when analyzed using a Gaussian K-distribution to describe the statistical density of K -states near the fission barrier, exhibits a step-like change in the value of K(,0)('2) at .7 MeV above threshold. This indicates a possible energy gap in the E2 transition states. The decay is isotropic above 7.5 MeV excitation energy. From 7 to 11.7 MeV, the distribution of E2/EO strength is relatively flat with the total strength in this region exhausting approximately 10% of an energy weighted sum rule. A comparison with hadron scattering experiments suggests that some of the strength near 11.5 MeV is due to the fission decay of the giant monopole resonance with a fission probability similar to that of E2 transitions.

  4. Robust Fault Detection of Wind Energy Conversion Systems Based on Dynamic Neural Networks

    PubMed Central

    Talebi, Nasser; Sadrnia, Mohammad Ali; Darabi, Ahmad

    2014-01-01

    Occurrence of faults in wind energy conversion systems (WECSs) is inevitable. In order to detect the occurred faults at the appropriate time, avoid heavy economic losses, ensure safe system operation, prevent damage to adjacent relevant systems, and facilitate timely repair of failed components; a fault detection system (FDS) is required. Recurrent neural networks (RNNs) have gained a noticeable position in FDSs and they have been widely used for modeling of complex dynamical systems. One method for designing an FDS is to prepare a dynamic neural model emulating the normal system behavior. By comparing the outputs of the real system and neural model, incidence of the faults can be identified. In this paper, by utilizing a comprehensive dynamic model which contains both mechanical and electrical components of the WECS, an FDS is suggested using dynamic RNNs. The presented FDS detects faults of the generator's angular velocity sensor, pitch angle sensors, and pitch actuators. Robustness of the FDS is achieved by employing an adaptive threshold. Simulation results show that the proposed scheme is capable to detect the faults shortly and it has very low false and missed alarms rate. PMID:24744774

  5. Robust fault detection of wind energy conversion systems based on dynamic neural networks.

    PubMed

    Talebi, Nasser; Sadrnia, Mohammad Ali; Darabi, Ahmad

    2014-01-01

    Occurrence of faults in wind energy conversion systems (WECSs) is inevitable. In order to detect the occurred faults at the appropriate time, avoid heavy economic losses, ensure safe system operation, prevent damage to adjacent relevant systems, and facilitate timely repair of failed components; a fault detection system (FDS) is required. Recurrent neural networks (RNNs) have gained a noticeable position in FDSs and they have been widely used for modeling of complex dynamical systems. One method for designing an FDS is to prepare a dynamic neural model emulating the normal system behavior. By comparing the outputs of the real system and neural model, incidence of the faults can be identified. In this paper, by utilizing a comprehensive dynamic model which contains both mechanical and electrical components of the WECS, an FDS is suggested using dynamic RNNs. The presented FDS detects faults of the generator's angular velocity sensor, pitch angle sensors, and pitch actuators. Robustness of the FDS is achieved by employing an adaptive threshold. Simulation results show that the proposed scheme is capable to detect the faults shortly and it has very low false and missed alarms rate.

  6. Robust fault detection of wind energy conversion systems based on dynamic neural networks.

    PubMed

    Talebi, Nasser; Sadrnia, Mohammad Ali; Darabi, Ahmad

    2014-01-01

    Occurrence of faults in wind energy conversion systems (WECSs) is inevitable. In order to detect the occurred faults at the appropriate time, avoid heavy economic losses, ensure safe system operation, prevent damage to adjacent relevant systems, and facilitate timely repair of failed components; a fault detection system (FDS) is required. Recurrent neural networks (RNNs) have gained a noticeable position in FDSs and they have been widely used for modeling of complex dynamical systems. One method for designing an FDS is to prepare a dynamic neural model emulating the normal system behavior. By comparing the outputs of the real system and neural model, incidence of the faults can be identified. In this paper, by utilizing a comprehensive dynamic model which contains both mechanical and electrical components of the WECS, an FDS is suggested using dynamic RNNs. The presented FDS detects faults of the generator's angular velocity sensor, pitch angle sensors, and pitch actuators. Robustness of the FDS is achieved by employing an adaptive threshold. Simulation results show that the proposed scheme is capable to detect the faults shortly and it has very low false and missed alarms rate. PMID:24744774

  7. LAT Perspectives in Detection of High Energy Cosmic Ray Electrons

    NASA Technical Reports Server (NTRS)

    Moiseev, Alexander; Ormes, J. F.; Funk, Stefan

    2007-01-01

    The GLAST Large Area Telescope (LAT) science objectives and capabilities in the detection of high energy electrons in the energy range from 20 GeV to approx. 1 TeV are presented. LAT simulations are used to establish the event selections. It is found that maintaining the efficiency of electron detection at the level of 30% the residual hadron contamination does not exceed 2-3% of the electron flux. LAT should collect approx. ten million of electrons with the energy above 20 GeV for each year of observation. Precise spectral reconstruction with high statistics presents us with a unique opportunity to investigate several important problems such as studying galactic models of IC radiation, revealing the signatures of nearby sources such as high energy cutoff in the electron spectrum, testing the propagation model, and searching for KKDM particles decay through their contribution to the electron spectrum.

  8. Randomness fault detection system

    NASA Technical Reports Server (NTRS)

    Russell, B. Don (Inventor); Aucoin, B. Michael (Inventor); Benner, Carl L. (Inventor)

    1996-01-01

    A method and apparatus are provided for detecting a fault on a power line carrying a line parameter such as a load current. The apparatus monitors and analyzes the load current to obtain an energy value. The energy value is compared to a threshold value stored in a buffer. If the energy value is greater than the threshold value a counter is incremented. If the energy value is greater than a high value threshold or less than a low value threshold then a second counter is incremented. If the difference between two subsequent energy values is greater than a constant then a third counter is incremented. A fault signal is issued if the counter is greater than a counter limit value and either the second counter is greater than a second limit value or the third counter is greater than a third limit value.

  9. Biradical thermochemistry from collision-induced dissociation threshold energy measurements. Absolute heats of formation of ortho-, meta-, and para-benzyne

    SciTech Connect

    Wenthold, P.G.; Squires, R.R. )

    1994-07-13

    The absolute heats of formation of 1,2-, 1,3-, and 1,4-dehydrobenzene (ortho, meta-, and para-benzyne) have been determined from measurements of the threshold energies for collision-induced dissociation (CID) of ortho, meta-, and para-chlorophenyl anions in a flowing afterglow-triple quadrupole apparatus. The 298 K heats of formation for ortho-, meta-, and para-benzyne derived in this manner are 106.6 [+-] 3.0, 122.0 [+-] 3.1, and 137.3 [+-] 3.3 kcal/mol, respectively. The values for meta- and para-benzyne are higher than those reported previously but are in excellent agreement with recently reported MCSCF and CI calculations. Several control experiments are described which demonstrate that the earlier results for meta- and para-benzyne suffered from an acid-catalyzed isomerization of the reactant chlorophenyl anions in the flowing afterglow prior to CID threshold analysis. 70 refs., 5 figs., 4 tabs.

  10. High Energy Telescope With Neutron Detection Capabilities (HETn)

    NASA Astrophysics Data System (ADS)

    Posner, A.; Wimmer-Schweingruber, R. F.; Böhm, E.; Böttcher, s.; Connell, J. J.; Dröge, W.; Hassler, D. M.; Heber, B.; Lopate, C.; McKibben, R. B.; Steigies, C. T.

    2007-01-01

    The High-Energy Telescope with neutron detection capabilities (HETn) for the Solar Orbiter will measure and resolve energetic charged particles, in particular electrons, proton, and heavy ions up to Fe including selected isotopes up to energies equivalen to the penetration depth of 100 MeV protons. The full active anti-coincidence encloses detectors sensitive to 1-30 MeV neutrons and 0.5-5 MeV X-/gamma-rays. The sensor consists of the angle-detecting inclined sensors (ADIS) solid-state detector detector telescope utilizing a shared calorimeter for total energy and X-/gamma-ray measurement. A separate plastic detector provides sensitivity to neutrons via the recoil process. HETn will open a new window on solar eruptive events with its neutron detection capability and allows determination of high-energy close to the Sun. Timing and spectral information on neutral particles (neutrons and X-/gamma rays ), on relativistic electrons and high-energy heavy ions will provide new insights into the processes which accelerate particles to high energies at the sun and into transport processes between the source and the spacecraft in the near-Sun environment.

  11. Luminescence imaging of water during irradiation of X-ray photons lower energy than Cerenkov- light threshold

    NASA Astrophysics Data System (ADS)

    Yamamoto, Seiichi; Koyama, Shuji; Komori, Masataka; Toshito, Toshiyuki

    2016-10-01

    Luminescence imaging of water using X-ray photon irradiation at energy lower than maximum energy of ~200 keV is thought to be impossible because the secondary electrons produced in this energy range do not emit Cerenkov- light. Contrary to this consensus assumption, we show that the luminescence imaging of water can be achieved by X-ray irradiation at energy lower than 120 keV. We placed water phantoms on a table with a conventional X-ray imaging system, and luminescence images of these phantoms were measured with a high-sensitivity, cooled charge coupled device (CCD) camera during X-ray photon irradiation at energy below 120 keV. We also carried out such imaging of an acrylic block and plastic scintillator. The luminescence images of water phantoms taken during X-ray photon irradiation clearly showed X-ray photon distribution. The intensity of the X-ray photon images of the phantom increased almost proportionally to the number of X-ray irradiations. Lower-energy X-ray photon irradiation showed lower-intensity luminescence at the deeper parts of the phantom due to the higher X-ray absorption in the water phantom. Furthermore, lower-intensity luminescence also appeared at the deeper parts of the acrylic phantom due to its higher density than water. The intensity of the luminescence for water was 0.005% of that for plastic scintillator. Luminescence imaging of water during X-ray photon irradiation at energy lower than 120 keV was possible. This luminescence imaging method is promising for dose estimation in X-ray imaging systems.

  12. Variations in lithium target thickness and proton energy stability for the near-threshold 7Li(p,n)7Be accelerator-based BNCT.

    PubMed

    Kobayashi, Tooru; Bengua, Gerard; Tanaka, Kenichi; Nakagawa, Yoshinobu

    2007-02-01

    The usable range of thickness for the solid lithium target in the accelerator-based neutron production for BNCT via the near-threshold (7)Li(p,n)(7)Be reaction was investigated. While the feasibility of using a (7)Li-target with thickness equal to that which is required to slow down a mono-energetic 1.900 MeV incident proton to the 1.881 MeV threshold of the (7)Li(p,n)(7)Be reaction (i.e., t(min) = 2.33 microm) has already been demonstrated, dosimetric properties of neutron fields from targets greater than t(min) were assessed as thicker targets would last longer and offer more stable neutron production. Additionally, the characteristics of neutron fields generated by (7)Li(p,n)(7)Be for Gaussian incident protons with mean energy of 1.900 MeV were evaluated at a (7)Li-target thickness t(min). The main evaluation index applied in this study was the treatable protocol depth (TPD) which corresponds to the depth in an irradiated medium that satisfies the requirements of the adapted dose protocol. A maximum TPD (TPD(max)) was obtained for each irradiation condition from the relationship between the TPD and the thickness of boron dose enhancer (BDE) used. For a mono-energetic 1.900 MeV proton beam, the deepest TPD(max) of 3.88 cm was attained at the (7)Li-target thickness of t(min) and a polyethylene BDE of 1.10 cm. When the intended TPD for a BNCT clinical treatment is shallower than the deepest TPD(max), the usable (7)Li-target thickness would be between t(min) and an upper limit t(upper) whose value depends on the BDE thickness used. In terms of the effect of stability of the incident proton energy, Gaussian incident proton energies stable to within +/-10 keV of 1.900 MeV were found to be feasible for the neutron production via the near-threshold (7)Li(p,n)(7)Be reaction for BNCT provided that a suitable BDE is used.

  13. The fluorescence action spectra of some saturated hydrocarbon liquids for excitation energies above and below their ionization thresholds

    SciTech Connect

    Ostafin, A.E.; Lipsky, S. )

    1993-04-01

    Fluorescence action spectra have been obtained for the neat liquids, [ital cis]-decalin, [ital trans]-decalin, bicyclohexyl, cyclohexane, methylcyclohexane, isobutylcyclohexane, 2,3,4-trimethylpentane, 2,3-dimethylbutane, 3-methylhexane, 3-methylpentane, [ital n]-decane, [ital n]-dodecane, and [ital n]-pentadecane at excitation energies, [epsilon], ranging from their absorption onsets (at ca. 7 eV) to 10.3 eV. For all compounds, with the exception of [ital cis]-decalin, the fluorescence quantum yield is observed to monotonically decline with increasing [epsilon], reaching a minimum value at an energy, [epsilon][sub [ital m

  14. Near-threshold (7)Li(p,n)(7)Be neutrons on the practical conditions using thick Li-target and Gaussian proton energies for BNCT.

    PubMed

    Kobayashi, Tooru; Hayashizaki, Noriyosu; Katabuchi, Tatsuya; Tanaka, Kenichi; Bengua, Gerard; Nakao, Noriaki; Kosako, Kazuaki

    2014-06-01

    The near threshold (7)Li(p,n)(7)Be neutrons generated by incident proton energy having Gaussian distribution with mean energies from 1.85 to 1.95MeV, were studied as a practical neutron source for BNCT wherein an RFQ accelerator and a thick Li-target are used. Gaussian energy distributions with the standard deviation of 0, 10, 20 and 40keV for mean proton energies from 1.85 to 1.95MeV were surveyed in 0.01MeV increments. A thick liquid Li-target whose dimensions were established in our previous experiments (i.e., 1mm-thick with 50mm width and 50mm length) was considered in this study. The suitable incident proton energy and physical dimensions of Pb layer which serves as a gamma absorber and a Polyethylene layer which is used as a BDE were surveyed by means of the concepts of TPD. Dose distribution were calculated by using MCNP5. A proton beam with mean energy of 1.92MeV and a Gaussian energy distribution with a standard deviation of 20keV at a current of 10mA was selected from the viewpoint of irradiation time and practically achievable proton current. The suitable thicknesses of Pb gamma absorber was estimated to be about 3cm. The estimated thickness of the polyethylene BDE was about 24mm for an ideal proton current of 13mA, and was 18mm for a practical proton current of 10mA.

  15. Extreme-Ultraviolet-Initated High-Order Harmonic Generation: Driving Inner-Valence Electrons Using Below-Threshold-Energy Extreme-Ultraviolet Light.

    PubMed

    Brown, A C; van der Hart, H W

    2016-08-26

    We propose a novel scheme for resolving the contribution of inner- and outer-valence electrons in extreme-ultraviolet (XUV)-initiated high-harmonic generation in neon. By probing the atom with a low-energy (below the 2s ionization threshold) ultrashort XUV pulse, the 2p electron is steered away from the core, while the 2s electron is enabled to describe recollision trajectories. By selectively suppressing the 2p recollision trajectories, we can resolve the contribution of the 2s electron to the high-harmonic spectrum. We apply the classical trajectory model to account for the contribution of the 2s electron, which allows for an intuitive understanding of the process.

  16. Momentum-Transfer-Resolved Electron Energy Loss Spectroscopy of BaBiO3: Anisotropic Dispersion of Threshold Excitation and Optically Forbidden Transition

    NASA Astrophysics Data System (ADS)

    Wang, Y. Y.; Dravid, V. P.; Bulut, N.; Han, P. D.; Klein, M. V.; Schnatterly, S. E.; Zhang, F. C.

    1995-09-01

    Momentum-transfer-resolved electron energy loss spectroscopy of the valence band transitions in BaBiO3 has revealed for the first time that dispersion of the excitation at the optical gap \\(~2 eV\\) and an optically forbidden transition at 4.5 eV are all anisotropic along [100] and [110]. The anisotropic dispersion of the threshold excitation cannot be described by a simple charge density wave picture but can be explained by a small exciton model proposed in this paper. The optically forbidden transition is found to agree well with a proposed molecular orbital model, where the transition is assigned as the excitation from the O 2pσ nonbonding states to the empty Bi 6s state.

  17. Extreme-Ultraviolet-Initated High-Order Harmonic Generation: Driving Inner-Valence Electrons Using Below-Threshold-Energy Extreme-Ultraviolet Light.

    PubMed

    Brown, A C; van der Hart, H W

    2016-08-26

    We propose a novel scheme for resolving the contribution of inner- and outer-valence electrons in extreme-ultraviolet (XUV)-initiated high-harmonic generation in neon. By probing the atom with a low-energy (below the 2s ionization threshold) ultrashort XUV pulse, the 2p electron is steered away from the core, while the 2s electron is enabled to describe recollision trajectories. By selectively suppressing the 2p recollision trajectories, we can resolve the contribution of the 2s electron to the high-harmonic spectrum. We apply the classical trajectory model to account for the contribution of the 2s electron, which allows for an intuitive understanding of the process. PMID:27610852

  18. Extreme-Ultraviolet-Initated High-Order Harmonic Generation: Driving Inner-Valence Electrons Using Below-Threshold-Energy Extreme-Ultraviolet Light

    NASA Astrophysics Data System (ADS)

    Brown, A. C.; van der Hart, H. W.

    2016-08-01

    We propose a novel scheme for resolving the contribution of inner- and outer-valence electrons in extreme-ultraviolet (XUV)-initiated high-harmonic generation in neon. By probing the atom with a low-energy (below the 2 s ionization threshold) ultrashort XUV pulse, the 2 p electron is steered away from the core, while the 2 s electron is enabled to describe recollision trajectories. By selectively suppressing the 2 p recollision trajectories, we can resolve the contribution of the 2 s electron to the high-harmonic spectrum. We apply the classical trajectory model to account for the contribution of the 2 s electron, which allows for an intuitive understanding of the process.

  19. Teager–Kaiser energy operator signal conditioning improves EMG onset detection

    PubMed Central

    Rider, Patrick; Steinweg, Ken; DeVita, Paul; Hortobágyi, Tibor

    2010-01-01

    Accurate identification of the onset of muscle activity is an important element in the biomechanical analysis of human movement. The purpose of this study was to determine if inclusion of the Teager–Kaiser energy operator (TKEO) in signal conditioning would increase the accuracy of popular electromyography (EMG) onset detection methods. Three methods, visual determination, threshold-based method, and approximated generalized likelihood ratio were used to estimate the onset of EMG burst with and without TKEO conditioning. Reference signals, with known onset times, were constructed from EMG signals collected during isometric contraction of the vastus lateralis (n = 17). Additionally, vastus lateralis EMG signals (n = 255) recorded during gait were used to evaluate a clinical application of the TKEO conditioning. Inclusion of TKEO in signal conditioning significantly reduced mean detection error of all three methods compared with signal conditioning without TKEO, using artificially generated reference data (13 vs. 98 ms, p < 0.001) and also compared with experimental data collected during gait (55 vs. 124 ms, p < 0.001). In conclusion, addition of TKEO as a step in conditioning surface EMG signals increases the detection accuracy of EMG burst boundaries. PMID:20526612

  20. Near-threshold photoproduction of Φ mesons from deuterium

    DOE PAGES

    Qian, X.; Chen, W.; Gao, H.; Hicks, K.; Kramer, K.; Laget, J. M.; Mibe, T.; Qiang, Y.; Stepanyan, S.; Tedeschi, D. J.; et al

    2011-01-05

    In this report, we measure the differential cross section onmore » $$\\phi$$-meson photoproduction from deuterium near the production threshold for a proton using the CLAS detector and a tagged-photon beam in Hall B at Jefferson Lab. The measurement was carried out by a triple coincidence detection of a proton, $K^+$ and $K^-$ near the theoretical production threshold of 1.57 GeV. Moreover, the extracted differential cross sections $$\\frac{d\\sigma}{dt}$$ for the initial photon energy from 1.65-1.75 GeV are consistent with predictions based on a quasifree mechanism. Ultimately, this experiment establishes a baseline for a future experimental search for an exotic $$\\phi$$-N bound state from heavier nuclear targets utilizing subthreshold/near-threshold production of $$\\phi$$ mesons.« less

  1. Near-threshold photoproduction of Φ mesons from deuterium

    SciTech Connect

    Qian, X.; Chen, W.; Gao, H.; Hicks, K.; Kramer, K.; Laget, J. M.; Mibe, T.; Qiang, Y.; Stepanyan, S.; Tedeschi, D. J.; Xu, W.; Adhikari, K. P.; Amaryan, M.; Anghinolfi, M.; Ball, J.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Bellis, M.; Biselli, A. S.; Bookwalter, C.; Branford, D.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Careccia, S. L.; Carman, D. S.; Cole, P. L.; Collins, P.; Crede, V.; D'Angelo, A.; Daniel, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Dey, B.; Dhamija, S.; Djalali, C.; Doughty, D.; Dupre, R.; Egiyan, H.; El Alaoui, A.; Eugenio, P.; Fegan, S.; Gabrielyan, M. Y.; Gevorgyan, N.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Gothe, R. W.; Graham, L.; Griffioen, K. A.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Hassall, N.; Holtrop, M.; Ilieva, Y.; Ireland, D. G.; Jawalkar, S. S.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Khetarpal, P.; Kim, A.; Kim, W.; Klein, A.; Klein, F. J.; Konczykowski, P.; Kubarovsky, V.; Kuleshov, S. V.; Kuznetsov, V.; Livingston, K.; Martinez, D.; Mayer, M.; McAndrew, J.; McCracken, M. E.; McKinnon, B.; Meyer, C. A.; Mikhailov, K.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Moreno, B.; Moriya, K.; Morrison, B.; Moutarde, H.; Munevar, E.; Nadel-Turonski, P.; Ni, A.; Niccolai, S.; Niculescu, I.; Niroula, M. R.; Osipenko, M.; Ostrovidov, A. I.; Paremuzyan, R.; Park, K.; Park, S.; Pereira, S. Anefalos; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Protopopescu, D.; Ricco, G.; Ripani, M.; Ritchie, B. G.; Rosner, G.; Rossi, P.; Sabatié, F.; Saini, M. S.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Seraydaryan, H.; Sharabian, Y. G.; Smith, E. S.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Stepanyan, S. S.; Stoler, P.; Strakovsky, I. I.; Strauch, S.; Taiuti, M.; Taylor, C. E.; Tkachenko, S.; Ungaro, M.; Vernarsky, B.; Vineyard, M. F.; Voutier, E.; Weinstein, L. B.; Weygand, D. P.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, B.; Zhao, Z. W.

    2011-01-05

    In this report, we measure the differential cross section on $\\phi$-meson photoproduction from deuterium near the production threshold for a proton using the CLAS detector and a tagged-photon beam in Hall B at Jefferson Lab. The measurement was carried out by a triple coincidence detection of a proton, $K^+$ and $K^-$ near the theoretical production threshold of 1.57 GeV. Moreover, the extracted differential cross sections $\\frac{d\\sigma}{dt}$ for the initial photon energy from 1.65-1.75 GeV are consistent with predictions based on a quasifree mechanism. Ultimately, this experiment establishes a baseline for a future experimental search for an exotic $\\phi$-N bound state from heavier nuclear targets utilizing subthreshold/near-threshold production of $\\phi$ mesons.

  2. New states above charm threshold

    SciTech Connect

    Eichten, Estia J.; Lane, Kenneth; Quigg, Chris; /Fermilab

    2005-11-01

    We revise and extend expectations for the properties of charmonium states that lie above charm threshold, in light of new experimental information. We refine the Cornell coupled-channel model for the coupling of c{bar c} levels to two-meson states, defining resonance masses and widths by pole positions in the complex energy plane, and suggest new targets for experiment.

  3. Resonant energy transfer based biosensor for detection of multivalent proteins.

    SciTech Connect

    Song, X.; Swanson, Basil I.

    2001-01-01

    We have developed a new fluorescence-based biosensor for sensitive detection of species involved in a multivslent interaction. The biosensor system utilizes specific interactions between proteins and cell surface receptors, which trigger a receptor aggregation process. Distance-dependent fluorescence self-quenching and resonant energy transfer mechanisms were coupled with a multivalent interaction to probe the receptor aggregation process, providing a sensitive and specific signal transduction method for such a binding event. The fluorescence change induced by the aggregation process can be monitored by different instrument platforms, e.g. fluorimetry and flow cytometry. In this article, a sensitive detection of pentavalent cholera toxin which recognizes ganglioside GM1 has been demonstrated through the resonant energy transfer scheme, which can achieve a double color change simultaneously. A detection sensitivity as high as 10 pM has been achieved within a few minutes (c.a. 5 minutes). The simultaneous double color change (an increase of acceptor fluorescence and a decrease of donor fluorescence intensity) of two similar fluorescent probes provides particularly high detection reliability owing to the fact that they act as each other's internal reference. Any external perturbation such as environmental temperature change causes no significant change in signal generation. Besides the application for biological sensing, the method also provides a useful tool for investigation of kinetics and thermodynamics of a multivalent interaction. Keywords: Biosensor, Fluorescence resonant energy transfer, Multivalent interaction, Cholera Toxin, Ganglioside GM1, Signal Transduction

  4. Threshold Concepts in Biochemistry

    ERIC Educational Resources Information Center

    Loertscher, Jennifer

    2011-01-01

    Threshold concepts can be identified for any discipline and provide a framework for linking student learning to curricular design. Threshold concepts represent a transformed understanding of a discipline, without which the learner cannot progress and are therefore pivotal in learning in a discipline. Although threshold concepts have been…

  5. Frequency and load ratio effects on critical strain energy release rate Gc thresholds of graphite/epoxy composites

    NASA Technical Reports Server (NTRS)

    Adams, Donald F.; Zimmerman, richard S.; Odom, Edwin M.

    1987-01-01

    Graphite/epoxy composite laminates of T300/BP907 and AS6/HST-7 were axial-tension fatigue tested. Tests were conducted at 5 and 10 Hz, and at loading ratios of R = 0.1 and R = 0.5. Edge delamination was monitored as a function of number of fatigue cycles by monitoring stiffness reduction during fatigue testing. Delamination was confirmed and documented using dye-enhanced X-ray and optical photography. Critical strain energy release rates were then calculated. The composites delaminated readily, with loading ratio having a significant influence. Frequency effects were negligible.

  6. Detection of artifacts from high energy bursts in neonatal EEG.

    PubMed

    Bhattacharyya, Sourya; Biswas, Arunava; Mukherjee, Jayanta; Majumdar, Arun Kumar; Majumdar, Bandana; Mukherjee, Suchandra; Singh, Arun Kumar

    2013-11-01

    Detection of non-cerebral activities or artifacts, intermixed within the background EEG, is essential to discard them from subsequent pattern analysis. The problem is much harder in neonatal EEG, where the background EEG contains spikes, waves, and rapid fluctuations in amplitude and frequency. Existing artifact detection methods are mostly limited to detect only a subset of artifacts such as ocular, muscle or power line artifacts. Few methods integrate different modules, each for detection of one specific category of artifact. Furthermore, most of the reference approaches are implemented and tested on adult EEG recordings. Direct application of those methods on neonatal EEG causes performance deterioration, due to greater pattern variation and inherent complexity. A method for detection of a wide range of artifact categories in neonatal EEG is thus required. At the same time, the method should be specific enough to preserve the background EEG information. The current study describes a feature based classification approach to detect both repetitive (generated from ECG, EMG, pulse, respiration, etc.) and transient (generated from eye blinking, eye movement, patient movement, etc.) artifacts. It focuses on artifact detection within high energy burst patterns, instead of detecting artifacts within the complete background EEG with wide pattern variation. The objective is to find true burst patterns, which can later be used to identify the Burst-Suppression (BS) pattern, which is commonly observed during newborn seizure. Such selective artifact detection is proven to be more sensitive to artifacts and specific to bursts, compared to the existing artifact detection approaches applied on the complete background EEG. Several time domain, frequency domain, statistical features, and features generated by wavelet decomposition are analyzed to model the proposed bi-classification between burst and artifact segments. A feature selection method is also applied to select the

  7. PVAL breast phantom for dual energy calcification detection

    NASA Astrophysics Data System (ADS)

    Koukou, V.; Martini, N.; Velissarakos, K.; Gkremos, D.; Fountzoula, C.; Bakas, A.; Michail, C.; Kandarakis, I.; Fountos, G.

    2015-09-01

    Microcalcifications are the main indicator for breast cancer. Dual energy imaging can enhance the detectability of calcifications by suppressing the tissue background. Two digital images are obtained using two different spectra, for the low- and high-energy respectively, and a weighted subtracted image is produced. In this study, a dual energy method for the detection of the minimum breast microcalcification thickness was developed. The used integrated prototype system consisted of a modified tungsten anode X-ray tube combined with a high resolution CMOS sensor. The breast equivalent phantom used was an elastically compressible gel of polyvinyl alcohol (PVAL). Hydroxyapatite was used to simulate microcalcifications with thicknesses ranging from 50 to 500 μm. The custom made phantom was irradiated with 40kVp and 70kVp. Tungsten (W) anode spectra filtered with 100μm Cadmium and 1000pm Copper, for the low- and high-energy, respectively. Microcalcifications with thicknesses 300μm or higher can be detected with mean glandular dose (MGD) of 1.62mGy.

  8. Observation of a helium ion energy threshold for retention in tungsten exposed to hydrogen/helium mixture plasma

    NASA Astrophysics Data System (ADS)

    Thompson, M.; Deslandes, A.; Morgan, T. W.; Elliman, R. G.; De Temmerman, G.; Kluth, P.; Riley, D.; Corr, C. S.

    2016-10-01

    Helium retention is measured in tungsten samples exposed to mixed H/He plasma in the Magnum-PSI linear plasma device. It is observed that there is very little He retention below helium ion impact energies of 9.0+/- 1.4 eV, indicating the existence of a potential barrier which must be overcome for implantation to occur. The helium retention in samples exposed to plasma at temperatures  >1000 K is strongly correlated with nano-bubble formation measured using grazing incidence small-angle x-ray scattering. The diameters of nano-bubbles were not found to increase with increasing helium concentration, indicating that additional helium must be accommodated by increasing the bubble concentration or an increase in bubble pressure. For some samples pre-irradiation with heavy ions of 2.0 MeV energy is investigated to simulate the effects of neutron damage. It is observed that nano-bubble sizes are comparable between samples pre-irradiated with heavy-ions, and those without heavy-ion pre-irradiation.

  9. A hydrophone prototype for ultra high energy neutrino acoustic detection

    NASA Astrophysics Data System (ADS)

    Cotrufo, A.; Plotnikov, A.; Yershova, O.; Anghinolfi, M.; Piombo, D.

    2009-06-01

    The design of an air-backed fiber-optic hydrophone is presented. With respect to the previous models this prototype is optimized to provide a bandwidth sufficiently large to detect acoustic signals produced by high energy hadronic showers in water. In addiction to the geometrical configuration and to the choice of the materials, the preliminary results of the measured performances in air are presented.

  10. Detection and Analysis of Threats to the Energy Sector: DATES

    SciTech Connect

    Alfonso Valdes

    2010-03-31

    This report summarizes Detection and Analysis of Threats to the Energy Sector (DATES), a project sponsored by the United States Department of Energy and performed by a team led by SRI International, with collaboration from Sandia National Laboratories, ArcSight, Inc., and Invensys Process Systems. DATES sought to advance the state of the practice in intrusion detection and situational awareness with respect to cyber attacks in energy systems. This was achieved through adaptation of detection algorithms for process systems as well as development of novel anomaly detection techniques suited for such systems into a detection suite. These detection components, together with third-party commercial security systems, were interfaced with the commercial Security Information Event Management (SIEM) solution from ArcSight. The efficacy of the integrated solution was demonstrated on two testbeds, one based on a Distributed Control System (DCS) from Invensys, and the other based on the Virtual Control System Environment (VCSE) from Sandia. These achievements advance the DOE Cybersecurity Roadmap [DOE2006] goals in the area of security monitoring. The project ran from October 2007 until March 2010, with the final six months focused on experimentation. In the validation phase, team members from SRI and Sandia coupled the two test environments and carried out a number of distributed and cross-site attacks against various points in one or both testbeds. Alert messages from the distributed, heterogeneous detection components were correlated using the ArcSight SIEM platform, providing within-site and cross-site views of the attacks. In particular, the team demonstrated detection and visualization of network zone traversal and denial-of-service attacks. These capabilities were presented to the DistribuTech Conference and Exhibition in March 2010. The project was hampered by interruption of funding due to continuing resolution issues and agreement on cost share for four months in 2008

  11. Dual energy detection of weapons of mass destruction

    NASA Astrophysics Data System (ADS)

    Budner, Gregory J.

    2006-03-01

    There is continuing plans and actions from terrorists to use "violence to inculcate fear with intent to coerce or try to intimidate governments or societies in the pursuit of goals that are generally political, religious or ideological." (Joint Pub 3-07.2) One can characterize the types of attacks and plan to interdict terrorist actions before they become crises. This paper focuses on Radiological (RDD) and Nuclear (WMD) threats. The X-ray inspection process and the use of dual-energy imaging will interdict materials for WMDs. Listed herewith is "several major characteristics that one can exploit for the detection. First, both WMDs and RDDs are radioactive. Therefore, one can hope to detect radiation coming from the containers to identify the threat. However since uranium and plutonium are largely self-shielding and since lead can be used to shield and hide these substances, passive detection of emitted radiation can be easily defeated. An important second characteristic is that WMDs and shielded dirty bombs contain materials with very high atomic numbers. Since normal commerce rarely contains materials with atomic numbers higher than that of iron, dual-energy imaging technology can detect such materials automatically, for the successful interdiction of WMDs and dirty bombs". (Bjorkolm 2005)

  12. Detecting Partial Energy Modulation in a Dielectric Laser Accelerator - Oral Presentation

    SciTech Connect

    Lukaczyk, Louis

    2015-08-24

    The Dielectric Laser Acceleration group at SLAC uses micro-fabricated dielectric grating structures and conventional infrared lasers to accelerator electrons. These structures have been estimated to produce an accelerating gradient up to 2 orders of magnitude greater than that produced by conventional RF accelerators. The success of the experiment depends on both the laser damage threshold of the structure and the timing overlap of femtosecond duration laser pulses with the electron bunch. In recent dielectric laser acceleration experiments, the laser pulse was shorter both temporally and spatially than the electron bunch. As a result, the laser is theorized to have interacted with only a small portion of the electron bunch. The detection of this phenomenon, referred to as partial population modulation, required a new approach to the data analysis of the electron energy spectra. A fitting function was designed to separate the accelerated electron population from the unaccelerated electron population. The approach was unsuccessful in detecting acceleration in the partial population modulation data. However, the fitting functions provide an excellent figure of merit for previous data known to contain signatures of acceleration.

  13. Whole-body vibration perception thresholds

    NASA Astrophysics Data System (ADS)

    Parsons, K. C.; Griffin, M. J.

    1988-03-01

    This paper presents the results of a series of laboratory experiments concerned with perception thresholds for whole-body vibration. The nature of absolute perception thresholds is discussed and a method of determining vibration thresholds, based upon signal detection theory, is proposed. Thresholds of subjects exposed to x-, y- and z-axis sinusoidal vibration were determined for sitting and standing subjects (from 2 to 100 Hz). Perception thresholds have also been determined for supine subjects exposed to vertical ( x-axis) sinusoidal vibration (10-63 Hz). In additional experiments the effects of complex (e.g., random) vibration and the effects of duration on the perception thresholds were investigated. The relation between perception thresholds and vibration levels, said by subjects to be unacceptable if they occurred in their own homes, was investigated as well as the effects of subjects' personality and the visual and acoustic conditions in the laboratory. For the vertical vibration of seated subjects no significant differences were found between the responses of male and female subjects. Significant differences were found between perception thresholds for sitting and standing postures. The median threshold was approximately 0·01 m/s 2 r.m.s. between 2 and 100 Hz. Perception thresholds for x-axis and y-axis vibration were not significantly different in either sitting or standing subjects but significant differences in thresholds were found between sitting and standing positions for both x-axis and y-axis vibration. Subjects tended to be more sensitive to vibration when lying than when sitting or standing. The results suggested that the perception of random vibrations can be predicted from a knowledge of the perception of its component vibrations. The number of cycles of vibration did not affect perception thresholds for vibration durations of more than about 0·25 s. Some assessments suggested that vibration at more than twice the perception threshold may not

  14. Threshold energies for the reactions Oh- + Ch3X yields Ch30H + X- (X = Cl, Br) measured by tandem mass spectrometry: Deprotonation energies (acidities) of Ch3Cl and Ch3Br. (Reannouncement with new availability information)

    SciTech Connect

    Hierl, P.M.; Henchman, M.J.; Paulson, J.F.

    1992-12-31

    In a tandem mass spectrometer, a beam of OH{sup {minus}} ions was reacted with methyl chloride and methyl bromide at collision energies in the range 0.2 < ET < 5 eV. For both of the methyl halides, excitation functions, sigma (ET), were measured for the two competing channels, endoergic proton transfer and exoergic nucleophilic displacement: OH{sup {minus}} + CH3X yields H20 + CH2X yields CH3OH + X{sup {minus}}. The threshold energies estimated for the proton transfer reactions are used to derive energies of deprotonation for CH3Cl and CH3Br of 1672 + or - 10 and 1660 + or - lO kJmol{sup {minus}1} respectively.

  15. Exploring the relationship between SDNR and detectability in dual-energy breast x-ray imaging

    NASA Astrophysics Data System (ADS)

    Karunamuni, Roshan; Kanamaluru, Swathiu; Lau, Kristen; Gavenonis, Sara; Bakic, Predrag R.; Maidment, Andrew D. A.

    2013-03-01

    Contrast-enhanced (CE) digital breast tomosynthesis (DBT) provides a technique to increase the contrast of radiographic imaging agents by suppressing soft-tissue signal variation. By reducing the effect of the soft-tissue anatomical noise, it is then possible to quantify the signal from an iodinated contrast agent. The combination of dual-energy and tomographic acquisitions allows for both the accurate quantification and localization of an iodinated lesion. Here, we present our findings demonstrating the relationship that exists between the signal difference to noise ratio (SDNR) and reader detectability of iodinated lesions in a physical anthropomorphic phantom. The observer study was conducted using the ViewDEX software platform with a total of nine readers. The readers were asked to score each of the iodinated lesions on a scale from 1 (entire boundary and area are visible) to 5 (not visible). Both SDNR and lesion detectability were found to improve as the concentration of the iodine increases, and the thickness of the phantom decreases. Lesion detectability was better in the tomographic slice that best matches the focal plane of the imaged object. However, SDNR does not significantly change with focal plane. Our results demonstrated that observer lesion detectability correlated well with SDNR. Lesions whose SDNR fell below 1 were difficult to distinguish from the background and were in general not visible. Lesions that were rated entirely visible corresponded to those with SDNR values above 3. Lesions with intermediate SDNR values were visualized but not confidently from the surrounding background. These threshold SDNR values can be used to optimize the imaging parameters in CE-DBT.

  16. A new dual threshold time-over-threshold circuit for fast timing in PET.

    PubMed

    Grant, Alexander M; Levin, Craig S

    2014-07-01

    Time-over-threshold (ToT) is attractive as a method of combined timing and energy encoding in positron emission tomography (PET) due to its simplicity in implementation and readout. However, conventional single threshold ToT has a nonlinear response and generally suffers from a tradeoff between timing and energy resolution. The resulting poor performance is not fit for applications requiring fast timing, such as time-of-flight (ToF) PET. In this work it is shown experimentally that by replacing single threshold ToT with a dual threshold method in a new compact circuit, excellent time resolution can be achieved (154 ps FWHM for 3 × 3 × 5 mm(3) LYSO crystals), suitable for ToF. Dual threshold ToT timing results have been compared to a similar single threshold design, demonstrating that dual threshold ToT performance is far superior to that of single threshold ToT (154 ps versus 418 ps coincidence time resolution for the dual and single threshold cases, respectively). A method of correcting for nonlinearity in dual threshold ToT energy spectra is also demonstrated.

  17. Photoproduction of the phi (1020) near threshold in CLAS

    SciTech Connect

    Tedeschi, D J

    2002-06-01

    The differential cross section for the photoproduction of the phi(1020) near threshold (E_{gamma} - 1.57GeV ) is predicted to be sensitive to production mechanisms other than diffraction. However, the existing low energy data is of limited statistics and kinematical coverage. Complete measurements of phi meson production on the proton have been performed at the Thomas Jefferson National Accelerator Facility using a liquid hydrogen target and the CEBAF Large Acceptance Spectrometer (CLAS). The phi was identified by missing mass using a proton and positive kaon detected by CLAS in coincidence with an electron in the photon tagger. The energy of the tagged, bremsstrahlung photons ranged from phi-threshold to 2.4 GeV. A description of the data set and the differential cross section far (E_{gamma} = 2.0 GeV ) will be presented and compared with present theoretical calculations.

  18. Echo thresholds for reflections from acoustically diffusive architectural surfaces.

    PubMed

    Robinson, Philip W; Walther, Andreas; Faller, Christof; Braasch, Jonas

    2013-10-01

    When sound reflects from an irregular architectural surface, it spreads spatially and temporally. Extensive research has been devoted to prediction and measurement of diffusion, but less has focused on its perceptual effects. This paper examines the effect of temporal diffusion on echo threshold. There are several notable differences between the waveform of a reflection identical to the direct sound and one from an architectural surface. The onset and offset are damped and the energy is spread in time; hence, the reflection response has a lower peak amplitude, and is decorrelated from the direct sound. The perceptual consequences of these differences are previously undocumented. Echo threshold tests are conducted with speech and music signals, using direct sound and a simulated reflection that is either identical to the direct sound or has various degrees of diffusion. Results indicate that for a speech signal, diffuse reflections are less easily detectable as a separate auditory event than specular reflections of the same total energy. For a music signal, no differences are observed between the echo thresholds for reflections with and without temporal diffusion. Additionally, echo thresholds are found to be shorter for speech than for music, and shorter for spatialized than for diotic presentation of signals.

  19. Unimolecular isomerization of CH2FCD2Cl via the interchange of Cl and F atoms: assignment of the threshold energy to the 1,2-dyotropic rearrangement.

    PubMed

    Tucker, Mary K; Rossabi, Samuel M; McClintock, Corey E; Heard, George L; Setser, D W; Holmes, Bert E

    2013-08-01

    The room-temperature gas-phase recombination of CH2F and CD2Cl radicals was used to prepare CH2FCD2Cl molecules with 91 kcal mol(-1) of vibrational energy. Three unimolecular processes are in competition with collisional deactivation of CH2FCD2Cl; HCl and DF elimination to give CHF═CD2 and CH2═CDCl plus isomerization to give CH2ClCD2F by the interchange of F and Cl atoms. The Cl/F interchange reaction was observed, and the rate constant was assigned from measurement of CHCl═CD2 as a product, which is formed by HF elimination from CH2ClCD2F. These experiments plus previously published results from chemically activated CH2ClCH2F and electronic structure and RRKM calculations for the kinetic-isotope effects permit assignment of the three rate constants for CH2FCD2Cl (and for CH2ClCD2F). The product branching ratio for the interchange reaction versus elimination is 0.24 ± 0.04. Comparison of the experimental rate constant with the RRKM calculated rate constant permitted the assignment of a threshold energy of 62 ± 3 kcal mol(-1) for this type-1 dyotropic rearrangement. On the basis of electronic structure calculations, the nature of the transition state for the rearrangement reaction is discussed. The radical recombination reactions in the chemical system also generate vibrationally excited CD2ClCD2Cl and CH2FCH2F molecules, and the rate constants for DCl and HF elimination were measured in order to confirm that the photolysis of CD2ClI and (CH2F)2CO mixtures was giving reliable data for CH2FCD2Cl. PMID:23837645

  20. Energy Transfer Based Nanocomposite Scintillator for Radiation Detection

    NASA Astrophysics Data System (ADS)

    Aslam, Soha; Sahi, Sunil; Chen, Wei; Ma, Lun; Kenarangui, Rasool

    2014-09-01

    Scintillators are the materials that emit light upon irradiation with high energy radiation like X-ray or gamma-ray. Inorganic single crystal and organic (plastic and liquid) are the two most used scintillator types. Both of these scintillator kinds have advantages and disadvantages. Inorganic single crystals are expensive and difficult to grow in desire shape and size. Also, single crystal scintillator such as NaI and CsI are very hygroscopic. On the other hand, organic scintillators have low density which limits their applications in gamma spectroscopy. Due to high quantum yield and size dependent emission, nanoparticles have attracted interested in various field of research. Here, we have studies the nanoparticles for radiation detection. We have synthesized nanoparticles of Cerium fluoride (CeF3), Zinc Oxide (ZnO), Cadmium Telluride (CdTe), Copper complex and Zinc sulfide (ZnS). We have used Fluorescence Resonance Energy Transfer (FRET) principle to enhance the luminescence properties of nanocomposite scintillator. Nanocomposites scintillators are structurally characterized with X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). Optical properties are studied using Photoluminescence, UV-Visible and X-ray. Enhancements in the luminescence are observed under UV and X-ray excitation. Preliminary studies shows nanocomposite scintillators are promising for radiation detection. Scintillators are the materials that emit light upon irradiation with high energy radiation like X-ray or gamma-ray. Inorganic single crystal and organic (plastic and liquid) are the two most used scintillator types. Both of these scintillator kinds have advantages and disadvantages. Inorganic single crystals are expensive and difficult to grow in desire shape and size. Also, single crystal scintillator such as NaI and CsI are very hygroscopic. On the other hand, organic scintillators have low density which limits their applications in gamma spectroscopy. Due to high quantum

  1. Selective chemical detection by energy modulation of sensors

    DOEpatents

    Stetter, J.R.; Otagawa, T.

    1985-05-20

    A portable instrument for use in the field in detecting, identifying, and quantifying a component of a sampled fluid includes a sensor which chemically reacts with the component of interest or a derivative thereof, an electrical heating filament for heating the sample before it is applied to the sensor, and modulating means for continuously varying the temperature of the filament (and hence the reaction rate) between two values sufficient to produce the chemical reaction. In response to this thermal modulation, the sensor produces a modulated output signal, the modulation of which is a function of the activation energy of the chemical reaction, which activation energy is specific to the particular component of interest and its concentration. Microprocessor means compares the modulated output signal with standard responses for a plurality of components to identify and quantify the particular component of interest. 4 figs.

  2. Bayesian Threshold Estimation

    ERIC Educational Resources Information Center

    Gustafson, S. C.; Costello, C. S.; Like, E. C.; Pierce, S. J.; Shenoy, K. N.

    2009-01-01

    Bayesian estimation of a threshold time (hereafter simply threshold) for the receipt of impulse signals is accomplished given the following: 1) data, consisting of the number of impulses received in a time interval from zero to one and the time of the largest time impulse; 2) a model, consisting of a uniform probability density of impulse time…

  3. Pausing at the Threshold

    ERIC Educational Resources Information Center

    Morgan, Patrick K.

    2015-01-01

    Since about 2003, the notion of threshold concepts--the central ideas in any field that change how learners think about other ideas--have become difficult to escape at library conferences and in general information literacy discourse. Their visibility will likely only increase because threshold concepts figure prominently in the Framework for…

  4. Threshold Concepts in Economics

    ERIC Educational Resources Information Center

    Shanahan, Martin

    2016-01-01

    Purpose: The purpose of this paper is to examine threshold concepts in the context of teaching and learning first-year university economics. It outlines some of the arguments for using threshold concepts and provides examples using opportunity cost as an exemplar in economics. Design/ Methodology/Approach: The paper provides an overview of the…

  5. Evidence for an anaerobic syntrophic benzoate degradation threshold and isolation of the syntrophic benzoate degrader

    SciTech Connect

    Hopkins, B.T.; McInerney, M.J.; Warikoo, V.

    1995-02-01

    An anaerobic, motile, gram-negative, rod-shaped, syntrophic. benzoate-degrading bacterium, strain SB. was isolated in pure culture with crotonate as the energy source. Benzoate was degraded only in association with an H{sub 2}-using bacterium. The kinetics of benzoate degradation by cell suspensions of strain SB in coculture with Desulfovibrio strain G-11 was studied by using progress curve analysis. The coculture degraded benzoate to a threshold concentration of 214 nM to 6.5 {mu}M, with no further benzoate degradation observed even after extended incubation times. The value of the threshold depended on the amount of benzoate added and, consequently, the amount of acetate produced. The addition of sodium acetate. but not that of sodium chloride, affected the threshold value; higher acetate concentrations resulted in higher threshold values for benzoate. When a cell suspension that had reached a threshold benzoate concentration was reamended with benzoate, benzoate was used without a lag. The hydrogen partial pressure was very low and formate was not detected in cell suspensions that had degraded benzoate to a threshold value. The Gibbs free energy change calculations showed that the degradation of benzoate was favorable when the threshold was reached. These studies showed that the threshold for benzoate degradation was not caused by nutritional limitations. the loss of metabolic activity, or inhibition by hydrogen or formate. The data are consistent with a thermodynamic explanation for the existence of a threshold, but a kinetic explanation based on acetate inhibition may also account for the existence of a threshold.

  6. A curved detection-slit to improve ERD (Elastic Recoil Detection) energy/depth resolution

    SciTech Connect

    Brice, D.K.; Doyle, B.L.

    1989-01-01

    Recoil atoms detected in Elastic Recoil Detection (ERD) experiments emerge from an initial collision area along cones of constant energy due to the cylindrical symmetry of the elastic scattering cross section. The constant energy cones therefore intercept planar slit plates placed before the detectors in conic sections. For ease of fabrication slits are typically configured as long narrow rectangles, and as a result energy resolution is adversely affected. It has been shown that the kinematic broadening caused by using rectangular slits is minimized when L = 2 (W z tan/Theta//sub recoil/)/sup 1/2/ where W is the slit width, L is the slit length, z is the slit-target distance and /Theta//sub recoil/ is the lab-frame recoil angle. The improved energy resolution which results when rectangular slits are replaced by appropriate curved slits is examined here. Formulas are given for the conic sections associated with the curved slits as a function of experimental geometry. When slit dimensions are small compared with the full extent of the conic section slit geometry can be accurately approximated as the arc of a circle with radius R/sub c/ = z tan/Theta//sub recoil/. Energy loss effects on the resolution are also accounted for in our treatment. The use of curved slits with L = 4 (W z tan/Theta//sub recoil/)/sup 1/2/ is shown to improve kinematic broadening by /approximately/50% as compared to optimized rectangular slits of the same area. 2 refs., 5 figs.

  7. Synthesis of new structures on the surface of Pd rod and HHPC elements and their chemical composition in nuclear reactions induced by bremstrahlung γ quanta with threshold energy of 10 MeV in molecular hydrogen at a pressure of 0.5 kbar

    NASA Astrophysics Data System (ADS)

    Didyk, A. Yu.; Wiśhnewski, R.

    2015-07-01

    A high-pressure chamber filled with molecular hydrogen (HHPC) at a pressure of 0.5 kbar with Pd rod inside has been irradiated for 14 h with γ rays having a threshold energy of 10 MeV produced by an electron beam current of 20-21 μA. Postirradiation studies of the changes in the structure and elemental composition of Pd rod and irregularities of all internal surfaces of the HHPC elements, as well as the large synthetic structures detected, reveal the presence of light elements from carbon to calcium. Multiple small particles of lead have also been found and studied. The detected synthesized particles have complex shapes and compositions. Also, thin-walled microtubes are detected on the inner surfaces inside HHPC. Based on fission reactions of intermediate mass nuclei (descending reactions), as well as the reactions of synthesis from hydrogen and heavy nuclei (ascending reactions), an attempt to explain the anomalies that were observed is made.

  8. Automated detection and delineation of lung tumors in PET-CT volumes using a lung atlas and iterative mean-SUV threshold

    NASA Astrophysics Data System (ADS)

    Ballangan, Cherry; Wang, Xiuying; Eberl, Stefan; Fulham, Michael; Feng, Dagan

    2009-02-01

    Automated segmentation for the delineation of lung tumors with PET-CT is a challenging task. In PET images, primary lung tumors can have varying degrees of tracer uptake, which sometimes does not differ markedly from normal adjacent structures such as the mediastinum, heart and liver. In addition, separation of tumor from adjacent soft tissues and bone in the chest wall is problematic due to limited resolution. For CT, the tumor soft tissue density can be similar to that in the blood vessels and the chest wall; and although CT provides better boundary definition, exact tumor delineation is also difficult when the tumor density is similar to adjacent structures. We propose an innovative automated adaptive method to delineate lung tumors in PET-CT images in conjunction with a lung atlas in which an iterative mean-SUV (Standardized Uptake Value) threshold is used to gradually define the tumor region in PET. Tumor delineation in the CT data is performed using region growing and seeds obtained autonomously from the PET tumor regions. We evaluated our approach in 13 patients with non-small cell lung cancer (NSCLC) and found it could delineate tumors of different size, shape and location, even when when the NSCLC involved the chest wall.

  9. Setting the Triggering Thresholds on Swift

    SciTech Connect

    McLean, Kassandra M.; Fenimore, E.E.; Palmer, David; Barthelmy, S.; Gehrels, N.; Krimm, H.; Markwardt, C.; Parsons, A.

    2004-09-28

    The Burst Alert Telescope (BAT) on Swift has two main types of 'rate' triggers: short and long. Short trigger time scales range from 4ms to 64ms, while long triggers are 64ms to {approx_equal} 16 seconds. While both short and long trigger have criteria with one background sample (traditional 'one-sided' triggers), the long triggers can also have criteria with two background samples ('bracketed' triggers) which remove trends in the background. Both long and short triggers can select energy ranges of 15-25, 15-50, 25-100 and 50-350 KeV. There are more than 180 short triggering criteria and approximately 500 long triggering criteria used to detect gamma ray bursts. To fully utilize these criteria, the thresholds must be set correctly. The optimum thresholds are determined by a tradeoff between avoiding false triggers and capturing as many bursts as possible. We use realistic simulated orbital variations, which are the prime cause of false triggers.

  10. High-field quench behavior and dependence of hot spot temperature on quench detection voltage threshold in a Bi2Sr2CaCu2Ox coil

    NASA Astrophysics Data System (ADS)

    Shen, Tengming; Ye, Liyang; Turrioni, Daniele; Li, Pei

    2015-07-01

    Small insert solenoids have been built using a multifilamentary Ag/Bi2Sr2CaCu2Ox round wire insulated with a mullite sleeve (˜100 μm in thickness) and characterized in background fields to explore the quench behaviors and limits of Bi2Sr2CaCu2Ox superconducting magnets, with an emphasis on assessing the impact of slow normal zone propagation on quench detection. Using heaters of various lengths to initiate a small normal zone, a coil was quenched safely more than 70 times without degradation, with the maximum coil temperature reaching 280 K. Coils withstood a resistive voltage of tens of mV for seconds without quenching, showing the high stability of these coils and suggesting that the quench detection voltage should be greater than 50 mV in order not to falsely trigger protection. The hot spot temperature for the resistive voltage of the normal zone to reach 100 mV increased from ˜40-˜80 K while increasing the operating wire current density Jo from 89 A mm-2 to 354 A mm-2, whereas for the voltage to reach 1 V, it increased from ˜60-˜140 K. This shows the increasing negative impact of slow normal zone propagation on quench detection with increasing Jo and the need to limit the quench detection voltage to <1 V. These measurements, coupled with an analytical quench model, were used to assess the impact of the maximum allowable detection voltage and temperature upon quench detection on the quench protection, assuming a limit of the hot spot temperature to <300 K.

  11. Double Photoionization Near Threshold

    NASA Technical Reports Server (NTRS)

    Wehlitz, Ralf

    2007-01-01

    The threshold region of the double-photoionization cross section is of particular interest because both ejected electrons move slowly in the Coulomb field of the residual ion. Near threshold both electrons have time to interact with each other and with the residual ion. Also, different theoretical models compete to describe the double-photoionization cross section in the threshold region. We have investigated that cross section for lithium and beryllium and have analyzed our data with respect to the latest results in the Coulomb-dipole theory. We find that our data support the idea of a Coulomb-dipole interaction.

  12. Selective chemical detection by energy modulation of sensors

    DOEpatents

    Stetter, J.R.; Otagawa, T.

    1991-09-10

    A portable instrument for use in the field in detecting, identifying, and quantifying a component of a sampled fluid includes a sensor which chemically reacts with the component of interest or a derivative thereof, an electrical heating filament for heating the sample before it is applied to the sensor, and modulator for continuously varying the temperature of the filament (and hence the reaction rate) between two values sufficient to produce the chemical reaction. In response to this thermal modulation, the sensor produces a modulated output signal, the modulation of which is a function of the activation energy of the chemical reaction, which activation energy is specific to the particular component of interest and its concentration. Microprocessor which compares the modulated output signal with standard responses for a plurality of components to identify and quantify the particular component of interest. In particular, the concentration of the component of interest is proportional to the amplitude of the modulated output signal, while the identifying activation output energy of the chemical interaction indicative of that component is proportional to a normalized parameter equal to the peak-to-peak amplitude divided by the height of the upper peaks above a base line signal level. 5 figures.

  13. Selective chemical detection by energy modulation of sensors

    DOEpatents

    Stetter, Joseph R.; Otagawa, Takaaki

    1991-01-01

    A portable instrument for use in the field in detecting, identifying, and quantifying a component of a sampled fluid includes a sensor which chemically reacts with the component of interest or a derivative thereof, an electrical heating filament for heating the sample before it is applied to the sensor, and modulator for continuously varying the temperature of the filament (and hence the reaction rate) between two values sufficient to produce the chemical reaction. In response to this thermal modulation, the sensor produces a modulated output signal, the modulation of which is a function of the activation energy of the chemical reaction, which activation energy is specific to the particular component of interest and its concentration. Microprocessor which compares the modulated output signal with standard responses for a plurality of components to identify and quantify the particular component of interest. In particular, the concentration of the component of interest is proportional to the amplitude of the modulated output signal, while the identifying activation output energy of the chemical interaction indicative of that component is proportional to a normalized parameter equal to the peak-to-peak amplitude divided by the height of the upper peaks above a base line signal level.

  14. Threshold bubble chamber for measurement of knock-on DT neutron tails from magnetic and inertial confinement experiments

    SciTech Connect

    Fisher, R.K.; Zaveryaev, V.S.; Trusillo, S.V.

    1997-01-01

    We propose a new {open_quotes}threshold{close_quotes} bubble chamber detector for measurement of knock-on neutron tails. These energetic neutrons result from fusion reactions involving energetic fuel ions created by alpha knock-on collisions in tokamak and other magnetic confinement experiments, and by both alpha and neutron knock-on collisions in inertial confinement fusion (ICF) experiments. The energy spectrum of these neutrons will yield information on the alpha population and energy distribution in tokamaks, and on alpha target physics and {rho}R measurements in ICF experiments. The bubble chamber should only detect neutrons with energies above a selectable threshold energy controlled by the bubble chamber pressure. The bubble chamber threshold mechanism, detection efficiency, and proposed applications to the International Thermonuclear Experimental Reactor and National Ignition Facility experiments will be discussed. {copyright} {ital 1997 American Institute of Physics.}

  15. Threshold bubble chamber for measurement of knock-on DT neutron tails from magnetic and inertial confinement experiments

    SciTech Connect

    Fisher, R.K.; Zaveryaev, V.S.; Trusillo, S.V.

    1996-07-01

    We propose a new {open_quotes}threshold{close_quotes} bubble chamber detector for measurement of knock-on neutron tails. These energetic neutrons result from fusion reactions involving energetic fuel ions created by alpha knock-on collisions in tokamak and other magnetic confinement experiments, and by both alpha and neutron knock-on collisions in inertial confinement fusion (ICF) experiments. The energy spectrum of these neutrons will yield information on the alpha population and energy distribution in tokamaks, and on alpha target physics and {rho}R measurements in ICF experiments. The bubble chamber should only detect neutrons with energies above a selectable threshold energy controlled by the bubble chamber pressure. The bubble chamber threshold mechanism, detection efficiency, and proposed applications to the International Thermonuclear Experimental Reactor (ITER) and National Ignition Facility (NIF) experiments will be discussed.

  16. Improved estimates of boreal Fire Radiative Energy using high temporal resolution data and a modified active fire detection algorithm

    NASA Astrophysics Data System (ADS)

    Barrett, Kirsten

    2016-04-01

    Reliable estimates of biomass combusted during wildfires can be obtained from satellite observations of fire radiative power (FRP). Total fire radiative energy (FRE) is typically estimated by integrating instantaneous measurements of fire radiative power (FRP) at the time of orbital satellite overpass or geostationary observation. Remotely-sensed FRP products from orbital satellites are usually global in extent, requiring several thresholding and filtering operations to reduce the number of false fire detections. Some filters required for a global product may not be appropriate to fire detection in the boreal forest resulting in errors of omission and increased data processing times. We evaluate the effect of a boreal-specific active fire detection algorithm and estimates of FRP/FRE. Boreal fires are more likely to escape detection due to lower intensity smouldering combustion and sub canopy fires, therefore improvements in boreal fire detection could substantially reduce the uncertainty of emissions from biomass combustion in the region. High temporal resolution data from geostationary satellites have led to improvements in FRE estimation in tropical and temperate forests, but such a perspective is not possible for high latitude ecosystems given the equatorial orbit of geostationary observation. The increased density of overpasses in high latitudes from polar-orbiting satellites, however, may provide adequate temporal sampling for estimating FRE.

  17. Prediction-based threshold for medication alert.

    PubMed

    Kawazoe, Yoshimasa; Miyo, Kengo; Kurahashi, Issei; Sakurai, Ryota; Ohe, Kazuhiko

    2013-01-01

    This study presents a prediction-based approach to determine thresholds for a medication alert in a computerized physician order entry. Traditional static thresholds can sometimes lead to physician's alert fatigue or overlook potentially excessive medication even if the doses are belowthe configured threshold. To address this problem, we applied a random forest algorithm to develop a prediction model for medication doses, and applied a boxplot to determine the thresholds based on the prediction results. An evaluation of the eight drugs most frequently causing alerts in our hospital showed that the performances of the prediction were high, except for two drugs. It was also found that using the thresholds based on the predictions would reduce the alerts to a half of those when using the static thresholds. Notably, some cases were detected only by the prediction thresholds. The significance of the thresholds should be discussed in terms of the trade-offs between gains and losses; however, our approach, which relies on physicians' collective experiences, has practical advantages. PMID:23920550

  18. A threshold for dissipative fission

    SciTech Connect

    Thoennessen, M.; Bertsch, G.F.

    1993-09-21

    The empirical domain of validity of statistical theory is examined as applied to fission data on pre-fission data on pre-fission neutron, charged particle, and {gamma}-ray multiplicities. Systematics are found of the threshold excitation energy for the appearance of nonstatistical fission. From the data on systems with not too high fissility, the relevant phenomenological parameter is the ratio of the threshold temperature T{sub thresh} to the (temperature-dependent) fission barrier height E{sub Bar}(T). The statistical model reproduces the data for T{sub thresh}/E{sub Bar}(T) < 0.26 {plus_minus} 0.05, but underpredicts the multiplicities at higher T{sub thresh}/E{sub Bar}(T) independent of mass and fissility of the systems.

  19. Towards a Low Threshold SuperCDMS Experiment

    NASA Astrophysics Data System (ADS)

    Welliver, Bradford

    2013-04-01

    Astrophysical evidence points to the existence of particle dark matter that comprises the majority of the mass of the universe. A natural candidate for these particles are Weakly Interacting Massive Particles, or WIMPs. Lately there has been much interest in dark matter search experiments for low mass WIMPs. Detection of WIMP dark matter with mass below 20 GeV/c^2 requires a low-energy trigger threshold. However, lowering the trigger threshold also makes us sensitive to triggering on random noise which can hamper livetime. In order to minimize triggering on this random noise the original trigger filters for SuperCDMS were replaced with improved filters that reduce the amplitude of random noise substantially compared to an event-generated signal, thus allowing us to lower the trigger thresholds without the livetime penalty we would otherwise accrue. An overview of how this was accomplished as well as post-triggering methods of noise discrimination will be discussed. Predictions for the improved low thresholds will be compared to data, and the impact on a low mass WIMP search will be described.

  20. MOS Circuitry Would Detect Low-Energy Charged Particles

    NASA Technical Reports Server (NTRS)

    Sinha, Mahadeva; Wadsworth, Mark

    2003-01-01

    Metal oxide semiconductor (MOS) circuits for measuring spatially varying intensities of beams of low-energy charged particles have been developed. These circuits are intended especially for use in measuring fluxes of ions with spatial resolution along the focal planes of mass spectrometers. Unlike prior mass spectrometer focal-plane detectors, these MOS circuits would not be based on ion-induced generation of electrons, and photons; instead, they would be based on direct detection of the electric charges of the ions. Hence, there would be no need for microchannel plates (for ion-to-electron conversion), phosphors (for electron-to-photon conversion), and photodetectors (for final detection) -- components that degrade spatial resolution and contribute to complexity and size. The developmental circuits are based on linear arrays of charge-coupled devices (CCDs) with associated readout circuitry (see figure). They resemble linear CCD photodetector arrays, except that instead of a photodetector, each pixel contains a capacitive charge sensor. The capacitor in each sensor comprises two electrodes (typically made of aluminum) separated by a layer of insulating material. The exposed electrode captures ions and accumulates their electric charges during signal-integration periods.

  1. Detecting special nuclear materials in containers using high-energy gamma rays emitted by fission products

    DOEpatents

    Norman, Eric B.; Prussin, Stanley G.

    2007-10-02

    A method and a system for detecting the presence of special nuclear materials in a container. The system and its method include irradiating the container with an energetic beam, so as to induce a fission in the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

  2. Cross Psi(B)-energy operator-based signal detection.

    PubMed

    Boudraa, Abdel-Ouahab; Cexus, Jean-Christophe; Abed-Meraim, Karim

    2008-06-01

    In this paper, two methods for signal detection and time-delay estimation based on the cross Psi(B)-energy operator are proposed. These methods are well suited for mono-component AM-FM signals. The Psi(B) energy operator measures how much one signal is present in another one. The peak of the Psi(B) operator corresponds to the maximum of interaction between the two signals. Compared to the cross-correlation function, the Psi(B) operator includes temporal information and relative changes of the signal which are reflected in its first and second derivatives. The discrete version of the continuous-time form of the Psi(B) operator, which is used in its implementation, is presented. The methods are illustrated on synthetic and real signals and the results compared to those of the matched filter and the cross correlation. The real signals correspond to impulse responses of buried objects obtained by active sonar in iso-speed single path environments. PMID:18537379

  3. Cross Psi(B)-energy operator-based signal detection.

    PubMed

    Boudraa, Abdel-Ouahab; Cexus, Jean-Christophe; Abed-Meraim, Karim

    2008-06-01

    In this paper, two methods for signal detection and time-delay estimation based on the cross Psi(B)-energy operator are proposed. These methods are well suited for mono-component AM-FM signals. The Psi(B) energy operator measures how much one signal is present in another one. The peak of the Psi(B) operator corresponds to the maximum of interaction between the two signals. Compared to the cross-correlation function, the Psi(B) operator includes temporal information and relative changes of the signal which are reflected in its first and second derivatives. The discrete version of the continuous-time form of the Psi(B) operator, which is used in its implementation, is presented. The methods are illustrated on synthetic and real signals and the results compared to those of the matched filter and the cross correlation. The real signals correspond to impulse responses of buried objects obtained by active sonar in iso-speed single path environments.

  4. High-resolution threshold photoelectron-photoion coincidence experiments performed on beamline 9.0.2.2: Kinetic energy release study of the process SF{sub 6} + hv {yields} SF{sub 5}{sup +} F + e{sup -}

    SciTech Connect

    Evans, M.; Ng, C.Y.; Hsu, C.W.; Heimann, P.

    1997-04-01

    Vacuum ultraviolet (VUV) photoionization mass spectrometry has been used extensively to determine the energetics of neutral radicals and radical cations, as well as to study the dynamics of the dissociative photoionization process. Very often these measurements are concerned with determining the appearance energy (AE) for a dissociative ionization process, as well as determining the heats of formation of the species involved. One such photoionization mass spectrometric technique employed on End Station 2 of the Chemical Dynamics Beamline (9.0.2.2) at the Advanced Light Source is the threshold photoelectron-photoion coincidence (TPEPICO) method. TPEPICO involves measuring the time-of-flight (TOF) mass spectrum of a given cation in coincidence with threshold photoelectrons at a known photoionization energy.

  5. Computational gestalts and perception thresholds.

    PubMed

    Desolneux, Agnès; Moisan, Lionel; Morel, Jean-Michel

    2003-01-01

    In 1923, Max Wertheimer proposed a research programme and method in visual perception. He conjectured the existence of a small set of geometric grouping laws governing the perceptual synthesis of phenomenal objects, or "gestalt" from the atomic retina input. In this paper, we review this set of geometric grouping laws, using the works of Metzger, Kanizsa and their schools. In continuation, we explain why the Gestalt theory research programme can be translated into a Computer Vision programme. This translation is not straightforward, since Gestalt theory never addressed two fundamental matters: image sampling and image information measurements. Using these advances, we shall show that gestalt grouping laws can be translated into quantitative laws allowing the automatic computation of gestalts in digital images. From the psychophysical viewpoint, a main issue is raised: the computer vision gestalt detection methods deliver predictable perception thresholds. Thus, we are set in a position where we can build artificial images and check whether some kind of agreement can be found between the computationally predicted thresholds and the psychophysical ones. We describe and discuss two preliminary sets of experiments, where we compared the gestalt detection performance of several subjects with the predictable detection curve. In our opinion, the results of this experimental comparison support the idea of a much more systematic interaction between computational predictions in Computer Vision and psychophysical experiments. PMID:14766147

  6. Computational gestalts and perception thresholds.

    PubMed

    Desolneux, Agnès; Moisan, Lionel; Morel, Jean-Michel

    2003-01-01

    In 1923, Max Wertheimer proposed a research programme and method in visual perception. He conjectured the existence of a small set of geometric grouping laws governing the perceptual synthesis of phenomenal objects, or "gestalt" from the atomic retina input. In this paper, we review this set of geometric grouping laws, using the works of Metzger, Kanizsa and their schools. In continuation, we explain why the Gestalt theory research programme can be translated into a Computer Vision programme. This translation is not straightforward, since Gestalt theory never addressed two fundamental matters: image sampling and image information measurements. Using these advances, we shall show that gestalt grouping laws can be translated into quantitative laws allowing the automatic computation of gestalts in digital images. From the psychophysical viewpoint, a main issue is raised: the computer vision gestalt detection methods deliver predictable perception thresholds. Thus, we are set in a position where we can build artificial images and check whether some kind of agreement can be found between the computationally predicted thresholds and the psychophysical ones. We describe and discuss two preliminary sets of experiments, where we compared the gestalt detection performance of several subjects with the predictable detection curve. In our opinion, the results of this experimental comparison support the idea of a much more systematic interaction between computational predictions in Computer Vision and psychophysical experiments.

  7. Hydrodynamics of sediment threshold

    NASA Astrophysics Data System (ADS)

    Ali, Sk Zeeshan; Dey, Subhasish

    2016-07-01

    A novel hydrodynamic model for the threshold of cohesionless sediment particle motion under a steady unidirectional streamflow is presented. The hydrodynamic forces (drag and lift) acting on a solitary sediment particle resting over a closely packed bed formed by the identical sediment particles are the primary motivating forces. The drag force comprises of the form drag and form induced drag. The lift force includes the Saffman lift, Magnus lift, centrifugal lift, and turbulent lift. The points of action of the force system are appropriately obtained, for the first time, from the basics of micro-mechanics. The sediment threshold is envisioned as the rolling mode, which is the plausible mode to initiate a particle motion on the bed. The moment balance of the force system on the solitary particle about the pivoting point of rolling yields the governing equation. The conditions of sediment threshold under the hydraulically smooth, transitional, and rough flow regimes are examined. The effects of velocity fluctuations are addressed by applying the statistical theory of turbulence. This study shows that for a hindrance coefficient of 0.3, the threshold curve (threshold Shields parameter versus shear Reynolds number) has an excellent agreement with the experimental data of uniform sediments. However, most of the experimental data are bounded by the upper and lower limiting threshold curves, corresponding to the hindrance coefficients of 0.2 and 0.4, respectively. The threshold curve of this study is compared with those of previous researchers. The present model also agrees satisfactorily with the experimental data of nonuniform sediments.

  8. Cadmium zinc telluride (CZT) nanowire sensors for detection of low energy gamma-ray detection

    NASA Astrophysics Data System (ADS)

    Gandhi, T.; Raja, K. S.; Misra, M.

    2008-04-01

    Bulk single crystals of CdZnTe compound semiconductor is used for room temperature radiation detection in commercial radiation sensors. A large volume of detector material with low defect density is required for increasing the detection efficiency. Manufacture of such a bulky detector-quality material with low defect density is expensive. In this communication, synthesis of nanowires arrays of CdZnTe that can be used for detecting low energy radiation is reported for the first time. CdZnTe ternary compound semiconductor, referred as CZT, was electrodeposited in the form of nanowires onto a TiO II nanotubular template in non-aqueous electrolytes using a pulse-reverse process at 130 °C. Very high electrical resistivity of the CZT nanowires (in the order of 10 10 Ω-cm) was obtained. Such a high resistivity was attributed to the presence of deep defect states such as cadmium vacancies created by the anodic cycle of the pulse-reverse electrodeposition process. Stacks of series connected CZT nanowire arrays were impressed with different bias potentials. The leakage current was in the order of tens of PicoAmperes. When exposed to a radiation source (Am -241, 60 keV), the current flow in the circuit increased. The preliminary results indicate that the CZT nanowire arrays can be used as radiation detector materials at room temperature with a much low bias potential (0.7 - 2.3 V) as against 300 - 500 V applied to the bulk detector materials.

  9. Threshold concepts: implications for the management of natural resources

    USGS Publications Warehouse

    Guntenspergen, Glenn R.; Gross, John

    2014-01-01

    Threshold concepts can have broad relevance in natural resource management. However, the concept of ecological thresholds has not been widely incorporated or adopted in management goals. This largely stems from the uncertainty revolving around threshold levels and the post hoc analyses that have generally been used to identify them. Natural resource managers have a need for new tools and approaches that will help them assess the existence and detection of conditions that demand management actions. Recognition of additional threshold concepts include: utility thresholds (which are based on human values about ecological systems) and decision thresholds (which reflect management objectives and values and include ecological knowledge about a system) as well as ecological thresholds. All of these concepts provide a framework for considering the use of threshold concepts in natural resource decision making.

  10. A Temporal Model of Level-Invariant, Tone-in-Noise Detection

    ERIC Educational Resources Information Center

    Berg, Bruce G.

    2004-01-01

    Level-invariant detection refers to findings that thresholds in tone-in-noise detection are unaffected by roving-level procedures that degrade energy cues. Such data are inconsistent with ideas that detection is based on the energy passed by an auditory filter. A hypothesis that detection is based on a level-invariant temporal cue is advanced.…

  11. Intra-individual variation of GH-dependent markers in athletes: comparison of population based and individual thresholds for detection of GH abuse in sports.

    PubMed

    Kniess, Astrid; Ziegler, Eckart; Thieme, Detlef; Müller, R Klaus

    2013-10-01

    The GH-2000 discriminant functions, using insulin-like growth factor I (IGF-I) and the N-terminal propeptide of type III procollagen (PIIINP), enabled the detection of growth hormone (GH) doping despite the broad inter-individual normal range of both peptides. The sensitivity of the discriminant function-based methodology may perhaps be further increased in future by applying individual athlete profiles. The purpose of the present study was to evaluate the intra-individual variability of IGF-I, PIIINP and the GH-2000 scores in athletes. For this purpose a total of eight blood samples were taken from each of fifty male and female elite athletes over a period of up to 18 months. The IGF-I and PIIINP levels, we found, lay predominantly within the reference range for elite athletes. The intra-individual variability for IGF-I ranged between 6 and 26%, while that for PIIINP ranged between 6 and 33%. The intra-individual variations of both parameters were higher in female than in male subjects and were found to be mostly moderate. We found that the intra-individual variations of the GH-2000 test scores, expressed as CV, ranged from 4 to 36% and were in most of the subjects markedly smaller than the inter-individual variation. Individual cut-offs for the GH-2000 scores would be lower than population based ones in most of the cases.

  12. Methods for threshold determination in multiplexed assays

    SciTech Connect

    Tammero, Lance F. Bentley; Dzenitis, John M; Hindson, Benjamin J

    2014-06-24

    Methods for determination of threshold values of signatures comprised in an assay are described. Each signature enables detection of a target. The methods determine a probability density function of negative samples and a corresponding false positive rate curve. A false positive criterion is established and a threshold for that signature is determined as a point at which the false positive rate curve intersects the false positive criterion. A method for quantitative analysis and interpretation of assay results together with a method for determination of a desired limit of detection of a signature in an assay are also described.

  13. Hyperon and Charged Kaon Pair Production Close to Threshold

    SciTech Connect

    Wolke, M.; Adam, H.H.; Balewski, J.T.; Budzanowski, A.; Goodman, C.; Grzonka, D. Jarczyk, L.; Jochmann, M.; Khoukaz, A.; Kilian, K.; Koehler, M.; Kowina, P.; Lister, T.; Moskal, P.; Lang, N.; Oelert, W.; Quentmeier, C.; Santo, R.; Schepers, G.; Seddik, U.; Sefzick, T.; Sewerin, S.; Siemaszko, M.; Smyrski, J.; Strzalkowski, A.; Wuestner, P.; Zipper, W.

    2000-12-31

    Close-to-threshold data on the elementary kaon and antikaon production channels in the proton{endash}proton interaction have been taken using the COSY-11 installation at the cooler synchrotron COSY Juelich. The experimental technique applied at the internal COSY-11 facility{emdash}designed for meson production studies at small excess energy{emdash}is outlined. The threshold excitation functions for the kaon{endash}hyperon production via the reactions pp {yields} pK{sup +}{Lambda} and pp {yields} pK{sup +}{Sigma}{sup 0} are presented. The magnitude of the production amplitudes is compared at equal excess energies, and physical implications of the observed {Sigma}{sup 0} suppression in the threshold region are discussed. In addition, within a Dalitz plot analysis the spin-averaged S-wave scattering parameters could be extracted for the {Lambda}{endash}p channel. With the possibility of detecting all final state particles the elementary antikaon production in the reaction pp {yields} ppK{sup +}k{sup {minus}} has been investigated. Results on the exclusive total cross section fix the scale of the strangeness dissociation into two kaons.

  14. Radio Detection of High-Energy Cosmic Rays: LOPES

    NASA Astrophysics Data System (ADS)

    Haungs, A.; Apel, W. D.; Badea, F.; Bekk, K.; Blümer, J.; Bozdog, H.; Daumiller, K.; Doll, P.; Engel, R.; Heck, D.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Nehls, S.; Obenland, R.; Oehlschläger, J.; Ostapchenko, S.; Plewnia, S.; Rebel, H.; Schieler, H.; Ulrich, H.; van Buren, J.; Weindl, A.; Wochele, J.; Bähren, L.; Butcher, H.; de Bruyn, G.; de Vos, C. M.; Falcke, H.; Kant, G. W.; Koopman, Y.; Pepping, H. J.; Schoonderbeek, G.; van Capellen, W.; Wijnholds, S.; Bercuci, A.; Brancus, I. M.; Mitrica, B.; Petcu, M.; Sima, O.; Toma, G.; Bertaina, M.; Chiavassa, A.; di Pierro, F.; Navarra, G.; Valchierotti, S.; Biermann, P. L.; Horneffer, A.; Huege, T.; Zensus, J. A.; Brüggemann, M.; Buchholz, P.; Kolotaev, Y.; Over, S.; Walkowiak, W.; Zimmermann, D.; Buitink, S.; Kuijpers, J.; Lafebre, S.; Nigl, A.; Petrovic, J.; Gemmeke, H.; Krömer, O.; Ghia, P. L.; Morello, C.; Trinchero, G. C.; Glasstetter, R.; Kampert, K.-H.; Hörandel, J. R.; Roth, M.; Stümpert, M.; Klein, U.; Risse, A.; Zabierowski, J.

    The detection of radio pulses emitted in the atmosphere during the air shower development of high-energy primary cosmic rays is the task of the LOPES (LOFAR Prototype Station) project. LOFAR (Low Frequency Array) is a new digital radio interferometer under development using high bandwidth ADCs and fast data processing to filter out most of the interference. By storing the whole waveform information in digital form transient events like air showers can be analyzed even after they have been recorded. To test this technology and to demonstrate its ability to measure air showers a LOPES is set up to operate in conjunction with an existing air shower experiment (KASCADE-Grande). The LOPES antennas are operating in the frequency range of 40-80 MHz. For several air-shower events a coincident and coherent signal has been found and a preliminary analysis has already been performed. The main goal of further investigations is to calibrate the radio signal with help of the observables of the individual air-showers given by KASCADE-Grande.

  15. Seeking to Improve Low Energy Neutral Atom Detection in Space

    NASA Technical Reports Server (NTRS)

    Shappirio, M.; Coplan, M.; Chornay, D.; Collier, M.; Herrero, F.; Ogilvie, K.; Williams, E.

    2007-01-01

    The detection of energetic neutral atoms allows for the remote examination of the interactions between plasmas and neutral populations in space. Before these neutral atoms can be measured, they must first be converted to ions. For the low energy end of this spectrum, interaction with a conversion surface is often the most efficient method to convert neutrals into ions. It is generally thought that the most efficient surfaces are low work functions materials. However, by their very nature, these surfaces are highly reactive and unstable, and therefore are not suitable for space missions where conditions cannot be controlled as they are in a laboratory. We therefore are looking to optimize a stable surface for conversion efficiency. Conversion efficiency can be increased either by changing the incident angle of the neutral particles to be grazing incidence and using stable surfaces with high conversion efficiencies. We have examined how to increase the angle of incidence from -80 degrees to -89 degrees, while maintaining or improving the total active conversion surface area without increasing the overall volume of the instrument. We are developing a method to micro-machine silicon, which will reduce the volume to surface area ratio by a factor of 60. We have also examined the material properties that affect the conversion efficiency of the surface for stable surfaces. Some of the parameters we have examined are work function, smoothness, and bond structure. We find that for stable surfaces, the most important property is the smoothness of the surface.

  16. Crossing the Writing Threshold.

    ERIC Educational Resources Information Center

    Clark, Carol Lea

    What pushes a writer over the edge of thought into text production--over what may be called "the writing threshold?" This is the moment when the thoughts in a writer's mind, the writing situation, and personal motivations create a momentum that results in a pattern of written words. There is evidence that not everyone crosses the writing threshold…

  17. Elaborating on Threshold Concepts

    ERIC Educational Resources Information Center

    Rountree, Janet; Robins, Anthony; Rountree, Nathan

    2013-01-01

    We propose an expanded definition of Threshold Concepts (TCs) that requires the successful acquisition and internalisation not only of knowledge, but also its practical elaboration in the domains of applied strategies and mental models. This richer definition allows us to clarify the relationship between TCs and Fundamental Ideas, and to account…

  18. ''Magic'' Energies for Detecting Light Elements with Resonant Alpha Particle Backscattering

    SciTech Connect

    Wetteland, C.J.; Maggiore, C.J.; Tesmer, J.R.; He, X-M.; Lee, D-H.

    1998-11-04

    Resonant backscattering is widely used to improve the detection limit of the light elements such as B, C, N and O. One disadvantage, however, is that several incident energies are normally needed if the sample contains a number of the light elements. There are ''magic'' energies at which several light elements can be detected simultaneously with suitable sensitivities. When these energies are used along with the elastic recoil detection of hydrogen, multiple elements can be detected without changing the beam energy, and the analysis time is greatly reduced. These reactions along with examples will be discussed.

  19. Detection of Medium-Sized Polycyclic Aromatic Hydrocarbons via Fluorescence Energy Transfer

    PubMed Central

    Serio, Nicole; Prignano, Lindsey; Peters, Sean; Levine, Mindy

    2015-01-01

    Reported herein is the use of proximity-induced non-covalent energy transfer for the detection of medium-sized polycyclic aromatic hydrocarbons (PAHs). This energy transfer occurs within the cavity of γ-cyclodextrin in various aqueous environments, including human plasma and coconut water. Highly efficient energy transfer was observed, and the efficiency of the energy transfer is independent of the concentration of γ-cyclodextrin used, demonstrating the importance of hydrophobic binding in facilitating such energy transfer. Low limits of detection were also observed for many of the PAHs investigated, which is promising for the development of fluorescence-based detection schemes. PMID:25821390

  20. Detection, Diagnosis and Prognosis: Contribution to the energy challenge: Proceedings of the Meeting of the Mechanical Failures Prevention Group

    NASA Technical Reports Server (NTRS)

    Shives, T. R. (Editor); Willard, W. A. (Editor)

    1981-01-01

    The contribution of failure detection, diagnosis and prognosis to the energy challenge is discussed. Areas of special emphasis included energy management, techniques for failure detection in energy related systems, improved prognostic techniques for energy related systems and opportunities for detection, diagnosis and prognosis in the energy field.

  1. Threshold photoelectron source for the study of low-energy electron scattering: Total cross section for electron scattering from krypton in the energy range from 14 meV to 20 eV

    SciTech Connect

    Kurokawa, M.; Kitajima, M.; Toyoshima, K.; Odagiri, T.; Kato, H.; Kawahara, H.; Hoshino, M.; Tanaka, H.; Ito, K.

    2010-12-15

    An experimental technique for the measurement of the total cross section for electron scattering from atoms and molecules at high resolution is described. The total cross sections for electron scattering from Kr in the energy range from 14 meV to 20 eV obtained with the technique are also reported. The present technique employs a combination of the penetrating field technique and the threshold photoionization of rare-gas atoms using synchrotron radiation as an electron source in order to produce a high-resolution electron beam at very low energy. The characteristics of the electron sources were determined by measuring the ionizing photon energy dependence of photoelectron yield. Absolute total cross sections for electron scattering are obtained by the attenuation method. The measured absolute values of the total cross sections for electron scattering from Kr agree with those obtained by other groups down to 175 meV, above which several experimental works have been reported. Below 175 meV, the present results generally agree with theoretical cross sections down to 14 meV. The resonant structures in the total cross sections due to Kr{sup -} (4p{sup 5}5s{sup 2} {sup 2}P{sub 3/2}) and the Kr{sup -} (4p{sup 5}5s{sup 2} {sup 2}P{sub 1/2}) Feshbach resonances are also reported. The resolution of the present setup has been estimated from a fit of the measured profile of the Kr{sup -} (4p{sup 5}5s{sup 2} {sup 2}P{sub 3/2}) resonance by the theoretical curve obtained from the resonant scattering theory.

  2. Threshold behaviour in hydrological systems as (human) geo-ecosystems: manifestations, controls, implications

    NASA Astrophysics Data System (ADS)

    Zehe, E.; Sivapalan, M.

    2009-07-01

    In this paper we review threshold behaviour in environmental systems, which are often associated with the onset of floods, contamination and erosion events, and other degenerative processes. Key objectives of this review are to a) suggest indicators for detecting threshold behavior, b) discuss their implications for predictability, c) distinguish different forms of threshold behavior and their underlying controls, and d) hypothesise on possible reasons for why threshold behaviour might occur. Threshold behaviour involves a fast qualitative change of either a single process or the response of a system. For elementary phenomena this switch occurs when boundary conditions (e.g., energy inputs) or system states as expressed by dimensionless quantities (e.g. the Reynolds number) exceed threshold values. Mixing, water movement or depletion of thermodynamic gradients becomes much more efficient as a result. Intermittency is a very good indicator for detecting event scale threshold behavior in hydrological systems. Predictability of intermittent processes/system responses is inherently low for combinations of systems states and/or boundary conditions that push the system close to a threshold. Post hoc identification of "cause-effect relations" to explain when the system became critical is inherently difficult because of our limited ability to perform observations under controlled identical experimental conditions. In this review, we distinguish three forms of threshold behavior. The first one is threshold behavior at the process level that is controlled by the interplay of local soil characteristics and states, vegetation and the rainfall forcing. Overland flow formation, particle detachment and preferential flow are examples of this. The second form of threshold behaviour is the response of systems of intermediate complexity - e.g., catchment runoff response and sediment yield - governed by the redistribution of water and sediments in space and time. These are controlled

  3. Network problem threshold

    NASA Technical Reports Server (NTRS)

    Gejji, Raghvendra, R.

    1992-01-01

    Network transmission errors such as collisions, CRC errors, misalignment, etc. are statistical in nature. Although errors can vary randomly, a high level of errors does indicate specific network problems, e.g. equipment failure. In this project, we have studied the random nature of collisions theoretically as well as by gathering statistics, and established a numerical threshold above which a network problem is indicated with high probability.

  4. Two-Source Double-Slit Interference in Angle-Resolved High-Energy Above-Threshold Ionization Spectra of Diatoms

    SciTech Connect

    Okunishi, M.; Itaya, R.; Shimada, K.; Pruemper, G.; Ueda, K.; Busuladzic, M.; Gazibegovic-Busuladzic, A.; Milosevic, D. B.; Becker, W.

    2009-07-24

    When an electron from a diatomic molecule undergoes tunneling-rescattering ionization, a novel form of destructive interference can be realized that involves all four geometric orbits that are available to the electron when it is freed, because both ionization and rescattering may take place at the same or at different centers. We find experimentally and confirm theoretically that in orientation-averaged angle-resolved high-order above-threshold ionization spectra the corresponding destructive interference is visible for O{sub 2} but not for N{sub 2}. This effect is different from the suppression of ionization that is well known to occur for O{sub 2}.

  5. Islanding detection technique using wavelet energy in grid-connected PV system

    NASA Astrophysics Data System (ADS)

    Kim, Il Song

    2016-08-01

    This paper proposes a new islanding detection method using wavelet energy in a grid-connected photovoltaic system. The method detects spectral changes in the higher-frequency components of the point of common coupling voltage and obtains wavelet coefficients by multilevel wavelet analysis. The autocorrelation of the wavelet coefficients can clearly identify islanding detection, even in the variations of the grid voltage harmonics during normal operating conditions. The advantage of the proposed method is that it can detect islanding condition the conventional under voltage/over voltage/under frequency/over frequency methods fail to detect. The theoretical method to obtain wavelet energies is evolved and verified by the experimental result.

  6. Effect of nitrogen addition on the band gap, core level shift, surface energy, and the threshold field of electron emission of the SrTiO3 thin films

    NASA Astrophysics Data System (ADS)

    Bian, H. J.; Chen, X. F.; Pan, J. S.; Zhu, W.; Sun, Chang Q.

    2007-12-01

    The effect of nitrogen (N) doping on the behavior of field emission, surface energy and the band structure of strontium titanate (SrTiO3) thin films coated on silicon tip arrays has been examined in detail. Measurements using x-ray photoelectron spectroscopy, ellipsometry, water contact angle and field emission testing revealed that the optimal 50%-nitrogen partial pressure (PN) could improve substantially the threshold field of electron emission of the SrTiO3 films accompanied with narrowed band gap, lowered surface energy and work function and a negative energy shift of the N 1s level from 404 to 396 eV. Results evidence consistently the presence of the nonbonding lone pairs and the lone pair induced antibonding dipoles upon tetrahedron formation which is responsible for the observations. At PN below and above the optimal value physisorption and hydrogen bond likes formation like to occur.

  7. Photoproduction of the phi (1020) near threshold

    SciTech Connect

    D.J. Tedeschi; M. Huertas

    2000-05-12

    Photoproduction of phi mesons at photon energies below 2 GeV were measured at the CLAS detector in Hall B of Thomas Jefferson National Accelerator Facility. Preliminary differential cross sections are reported from the proton near threshold. The measurement are extended to the region in the variable t where production mechanisms beyond that of diffraction are expected to become significant.

  8. Sulfur K{beta} x-ray emission from carbonyl sulfide: Variations with polarization and excitation energy at the S K threshold

    SciTech Connect

    Miyano, K.E.; Arp, U.; Southworth, S.H.; Meehan, T.E.; Walsh, T.R.; Larkins, F.P.

    1998-04-01

    Sulfur K{beta} x-ray-emission spectra from carbonyl sulfide have been measured with resonant excitation at the sulfur K absorption threshold and compared with results of self-consistent field and singles-doubles configuration-interaction calculations. For excitation to the strong 4{pi} absorption resonance, a splitting of the main emission peak is interpreted in terms of influence of the 4{pi} electron on the final valence-hole states. The polarization selectivity of the emission spectrometer was used to distinguish emission polarized parallel versus perpendicular with respect to the polarization of the excitation radiation. The observed polarization dependence is consistent with the molecular symmetries of the calculated intermediate and final states. {copyright} {ital 1998} {ital The American Physical Society}

  9. Threshold Monitoring Maps for Under-Water Explosions

    NASA Astrophysics Data System (ADS)

    Arora, N. S.

    2014-12-01

    Hydro-acoustic energy in the 1-100 Hz range from under-water explosions can easily spread for thousands of miles due to the unique properties of the deep sound channel. This channel, aka SOFAR channel, exists almost everywhere in the earth's oceans where the water has at least 1500m depth. Once the energy is trapped in this channel it spreads out cylindrically, and hence experiences very little loss, as long as there is an unblocked path from source to receiver. Other losses such as absorption due to chemicals in the ocean (mainly boric acid and magnesium sulphate) are also quite minimal at these low frequencies. It is not surprising then that the International Monitoring System (IMS) maintains a global network of hydrophone stations listening on this particular frequency range. The overall objective of our work is to build a probabilistic model to detect and locate under-water explosions using the IMS network. A number of critical pieces for this model, such as travel time predictions, are already well known. We are extending the existing knowledge-base by building the remaining pieces, most crucially the models for transmission losses and detection probabilities. With a complete model for detecting under-water explosions we are able to combine it with our existing model for seismic events, NET-VISA. In the conference we will present threshold monitoring maps for explosions in the earth's oceans. Our premise is that explosive sources release an unknown fraction of their total energy into the SOFAR channel, and this trapped energy determines their detection probability at each of the IMS hydrophone stations. Our threshold monitoring maps compute the minimum amount of energy at each location that must be released into the deep sound channel such that there is a ninety percent probability that at least two of the IMS stations detect the event. We will also present results of our effort to detect and locate hydro-acoustic events. In particular, we will show results

  10. Coloring geographical threshold graphs

    SciTech Connect

    Bradonjic, Milan; Percus, Allon; Muller, Tobias

    2008-01-01

    We propose a coloring algorithm for sparse random graphs generated by the geographical threshold graph (GTG) model, a generalization of random geometric graphs (RGG). In a GTG, nodes are distributed in a Euclidean space, and edges are assigned according to a threshold function involving the distance between nodes as well as randomly chosen node weights. The motivation for analyzing this model is that many real networks (e.g., wireless networks, the Internet, etc.) need to be studied by using a 'richer' stochastic model (which in this case includes both a distance between nodes and weights on the nodes). Here, we analyze the GTG coloring algorithm together with the graph's clique number, showing formally that in spite of the differences in structure between GTG and RGG, the asymptotic behavior of the chromatic number is identical: {chi}1n 1n n / 1n n (1 + {omicron}(1)). Finally, we consider the leading corrections to this expression, again using the coloring algorithm and clique number to provide bounds on the chromatic number. We show that the gap between the lower and upper bound is within C 1n n / (1n 1n n){sup 2}, and specify the constant C.

  11. Laser threshold magnetometry

    NASA Astrophysics Data System (ADS)

    Jeske, Jan; Cole, Jared H.; Greentree, Andrew D.

    2016-01-01

    We propose a new type of sensor, which uses diamond containing the optically active nitrogen-vacancy (NV-) centres as a laser medium. The magnetometer can be operated at room-temperature and generates light that can be readily fibre coupled, thereby permitting use in industrial applications and remote sensing. By combining laser pumping with a radio-frequency Rabi-drive field, an external magnetic field changes the fluorescence of the NV- centres. We use this change in fluorescence level to push the laser above threshold, turning it on with an intensity controlled by the external magnetic field, which provides a coherent amplification of the readout signal with very high contrast. This mechanism is qualitatively different from conventional NV--based magnetometers which use fluorescence measurements, based on incoherent photon emission. We term our approach laser threshold magnetometer (LTM). We predict that an NV--based LTM with a volume of 1 mm3 can achieve shot-noise limited dc sensitivity of 1.86 fT /\\sqrt{{{Hz}}} and ac sensitivity of 3.97 fT /\\sqrt{{{Hz}}}.

  12. High Energy Electron and Gamma - Ray Detection with ATIC

    NASA Technical Reports Server (NTRS)

    Chang, J.; Schmidt, W. K. H.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    The Advanced Thin Ionization Calorimeter (ATIC) balloon borne ionization calorimeter is well suited to record and identify high energy cosmic ray electrons, and at very high energies gamma-ray photons as well. We have simulated the performance of the instrument, and compare the simulations with actual high energy electron exposures at the CERN accelerator. Simulations and measurements do not compare exactly, in detail, but overall the simulations have predicted actual measured behavior quite well. ATIC has had its first 16 day balloon flight at the turn of the year over Antarctica, and first results obtained using the analysis methods derived from simulations and calibrations will be reported.

  13. The use of Schottky CdTe detectors for high-energy astronomy: application to the detection plane of the instrument SVOM/ECLAIRs

    NASA Astrophysics Data System (ADS)

    Nasser, G.; Godet, O.; Atteia, J.-L.; Amoros, C.; Barret, D.; Bordon, S.; Cordier, B.; Gevin, O.; Gonzalez, F.; Houret, B.; Lacombe, K.; Mandrou, P.; Marty, W.; Mercier, K.; Pons, R.; Rambaud, D.; Ramon, P.; Rouaix, G.; Waegebaert, V.

    2014-07-01

    Ohmic CdZnTe and CdTe detectors have been successfully used in high-energy missions such as IBIS on-board INTEGRAL and the Swift-BAT in the past two decades. Such detectors provide very good quantum efficiency in the hard X-ray band. For the future generation of hard X-ray coded mask detectors, a higher sensitivity will be required. A way to achieve this is to increase the effective area of the pixilated detection plane, to change the mask pattern and/or the properties of the semi-conductors paving the detection plane. For the future Chinese-French Gamma-ray burst mission SVOM, the GRB trigger camera ECLAIRs will make use of a new type of high-energy detectors, the Schottky CdTe detectors. Such detectors, when reversely biased, are known to present very low leakage current, resulting in lower values of the low-energy threshold (down to 4 keV or less) than for previous missions (i.e. > 10 keV for the Swift-BAT and INTEGRAL/IBIS). Such low values will enable ECLAIRs with a moderate geometrical area of 1024 cm2 and a low-energy threshold of 4 keV to be more sensitive to high-redshift GRBs (emitting mainly in X-rays) than the Swift-BAT with a higher effective area and low-energy threshold. However, the spectral performance of such detectors are known to degrade over time, once polarized, due to the polarization effect that strongly depends on the temperature and the bias voltage applied to the detectors. In this paper, we present an intensive study of the properties of Schottky CdTe detectors as used on SVOM/ECLAIRs such as I-V characteristics, polarization effect, activation energy and low temperature annealing effects. We discuss the implications of these measurements on the use of this type of detectors in future high-energy instruments.

  14. Detection of explosives, nerve agents, and illicit substances by zero-energy electron attachment

    NASA Technical Reports Server (NTRS)

    Chutjian, A.; Darrach, M. R.

    2000-01-01

    The Reversal Electron Attachment Detection (READ) method, developed at JPL/Caltech, has been used to detect a variety of substances which have electron-attachment resonances at low and intermediate electron energies. In the case of zero-energy resonances, the cross section (hence attachment probability and instrument sensitivity) is mediated by the so-called s-wave phenomenon, in which the cross sections vary as the inverse of the electron velocity. Hence this is, in the limit of zero electron energy or velocity, one of the rare cases in atomic and molecular physics where one carries out detection via infinite cross sections.

  15. Threshold of the precedence effect in noise

    PubMed Central

    Freyman, Richard L.; Griffin, Amanda M.; Zurek, Patrick M.

    2014-01-01

    Three effects that show a temporal asymmetry in the influence of interaural cues were studied through the addition of masking noise: (1) The transient precedence effect—the perceptual dominance of a leading transient over a similar lagging transient; (2) the ongoing precedence effect—lead dominance with lead and lag components that extend in time; and (3) the onset capture effect—determination by an onset transient of the lateral position of an otherwise ambiguous extended trailing sound. These three effects were evoked with noise-burst stimuli and were compared in the presence of masking noise. Using a diotic noise masker, detection thresholds for stimuli with lead/lag interaural delays of 0/500 μs were compared to those with 500/0 μs delays. None of the three effects showed a masking difference between those conditions, suggesting that none of the effects is operative at masked threshold. A task requiring the discrimination between stimuli with 500/0 and 0/500 μs interaural delays was used to determine the threshold for each effect in noise. The results showed similar thresholds in noise (10–13 dB SL) for the transient and ongoing precedence effects, but a much higher threshold (33 dB SL) for onset capture of an ambiguous trailing sound. PMID:24815272

  16. Radar detection of ultra high energy cosmic rays

    NASA Astrophysics Data System (ADS)

    Myers, Isaac J.

    TARA (Telescope Array Radar) is a cosmic ray radar detection experiment co-located with Telescope Array, the conventional surface scintillation detector (SD) and fluorescence telescope detector (FD) near Delta, UT. The TARA detector combines a 40 kW transmitter and high gain transmitting antenna which broadcasts the radar carrier over the SD array and in the FD field of view to a 250 MS/s DAQ receiver. Data collection began in August, 2013. TARA stands apart from other cosmic ray radar experiments in that radar data is directly compared with conventional cosmic ray detector events. The transmitter is also directly controlled by TARA researchers. Waveforms from the FD-triggered data stream are time-matched with TA events and searched for signal using a novel signal search technique in which the expected (simulated) radar echo of a particular air shower is used as a matched filter template and compared to radio waveforms. This technique is used to calculate the radar cross-section (RCS) upper-limit on all triggers that correspond to well-reconstructed TA FD monocular events. Our lowest cosmic ray RCS upper-limit is 42 cm2 for an 11 EeV event. An introduction to cosmic rays is presented with the evolution of detection and the necessity of new detection techniques, of which radar detection is a candidate. The software simulation of radar scattering from cosmic rays follows. The TARA detector, including transmitter and receiver systems, are discussed in detail. Our search algorithm and methodology for calculating RCS is presented for the purpose of being repeatable. Search results are explained in context of the usefulness and future of cosmic ray radar detection.

  17. The variations in visual threshold measurement.

    PubMed

    Hallett, P E

    1969-06-01

    1. This paper presents a statistical analysis of the thresholds of test flashes viewed against zero, steady or transient backgrounds by peripheral vision. The method of threshold measurement is that of the Medical Research Council Report (Pirenne, Marriott & O'Doherty, 1957; Hartline & McDonald, 1943). The data are from the previous paper (Hallett, 1969b) and consist of k days' samples of n threshold measurements on an intensity scale of interval 0.087 log. The collection of a sample required 5-6 min and the samples were spread over a 3-month period.2. The analysis suggests that the nature of biological variations is that the ;instantaneous' frequency-of-seeing curve can occupy a variety of positions, or levels, scattered about its typical position on the log. energy axis. Change of the position of the curve for a given threshold task is most obvious when one compares threshold measurements obtained on different days, but this is not true day-to-day variation; the same sorts of change occur on the same day if the viewing conditions (independent variables) are changed and are perhaps due to shifts in the observer's signal/noise criterion K.3. Two important consequences of the analysis are (i) the errors of visual threshold functions are worse than one method of calculating error suggests and (ii) it is possible to eliminate part of the biological variations from a particular sort of frequency-of-seeing curve and thus obtain a better estimate of the instantaneous curve which is the physiological function of prime interest.4. Some possible causes of the biological variations are considered. The design of experiments is discussed. The method of the M.R.C. Report is to be recommended since it can be applied without prior assumptions about the value of the mean threshold or the nature of the errors. PMID:5784294

  18. Analysis of experimental data on doublet neutron-deuteron scattering at energies below the deuteron-breakup threshold on the basis of the pole approximation of the effective-range function

    SciTech Connect

    Babenko, V. A.; Petrov, N. M.

    2008-01-15

    On the basis of the Bargmann representation of the S matrix, the pole approximation is obtained for the effective-range function k cot {delta}. This approximation is optimal for describing the neutron-deuteron system in the doublet spin state. The values of r{sub 0} = 412.469 fm and v{sub 2} = -35 495.62 fm{sup 3} for the doublet low-energy parameters of neutron-deuteron scattering and the value of D = 172.678 fm{sup 2} for the respective pole parameter are deduced by using experimental results for the triton binding energy E{sub T}, the doublet neutron-deuteron scattering length a{sub 2}, and van Oers-Seagrave phase shifts at energies below the deuteron-breakup threshold. With these parameters, the pole approximation of the effective-range function provides a highly precise description (the relative error does not exceed 1%) of the doublet phase shift for neutron-deuteron scattering at energies below the deuteron-breakup threshold. Physical properties of the triton in the ground (T) and virtual (v) states are calculated. The results are B{sub v} = 0.608 MeV for the virtuallevel position and C{sub T}{sup 2} = 2.866 and C{sub v}{sup 2} = 0.0586 for the dimensionless asymptotic normalization constants. It is shown that, in the Whiting-Fuda approximation, the values of physical quantities characterizing the triton virtual state are determined to a high precision by one parameter, the doublet neutron-deuteron scattering length a{sub 2}. The effective triton radii in the ground ({rho}{sub T} = 1.711 fm) and virtual ({rho}{sub v} = 74.184 fm) states are calculated for the first time.

  19. Development of a Cerenkov radiation sensor to detect low-energy beta-particles.

    PubMed

    Yoo, Wook Jae; Han, Ki-Tek; Shin, Sang Hun; Seo, Jeong Ki; Jeon, Dayeong; Lee, Bongsoo

    2013-11-01

    We fabricated a novel fiber-optic Cerenkov radiation sensor using a Cerenkov radiator for measuring beta-particles. Instead of employing a scintillator, transparent liquids having various refractive indices were used as a Cerenkov radiator to serve as a sensing material. The experimental results showed that the amount of Cerenkov radiation due to the interaction with beta-particles increased as the refractive index of the Cerenkov radiator was increased as a results of a decrease of the Cerenkov threshold energy for electrons.

  20. High-energy neutron detection and spectrometry with superheated emulsions

    NASA Astrophysics Data System (ADS)

    d'Errico, Francesco; Prokofiev, Alexander; Sannikov, Alexander; Schuhmacher, Helmut

    2003-06-01

    The response of some superheated emulsions was investigated using quasi-monoenergetic neutron beams in the 46-134 MeV energy range at the Université Catholique de Louvain, Louvain la Neuve, Belgium and at The Svedberg Laboratory, Uppsala, Sweden. In order to determine the detector response to the high-energy beams, the spectra of incident neutrons were folded over functions modeled after the cross-sections for the neutron-induced production of heavy ions from the detector elements. The cross-sections for fluorine and chlorine were produced in this work by means of the Monte Carlo high-energy transport code HADRON based on the cascade-exciton model of nuclear interactions.

  1. Particle and Photon Detection: Counting and Energy Measurement.

    PubMed

    Janesick, James; Tower, John

    2016-05-12

    Fundamental limits for photon counting and photon energy measurement are reviewed for CCD and CMOS imagers. The challenges to extend photon counting into the visible/nIR wavelengths and achieve energy measurement in the UV with specific read noise requirements are discussed. Pixel flicker and random telegraph noise sources are highlighted along with various methods used in reducing their contribution on the sensor's read noise floor. Practical requirements for quantum efficiency, charge collection efficiency, and charge transfer efficiency that interfere with photon counting performance are discussed. Lastly we will review current efforts in reducing flicker noise head-on, in hopes to drive read noise substantially below 1 carrier rms.

  2. Techniques and methods for the low-energy neutrino detection

    NASA Astrophysics Data System (ADS)

    Ranucci, Gioacchino

    2016-04-01

    Low-energy neutrino physics and astrophysics has been one of the most active field of particle physics research over the past two decades, achieving important and sometimes unexpected results, which have paved the way for a bright future of further exciting studies. The methods, the techniques and the technologies employed for the construction of the many experiments which acted as important players in this area of investigation have been crucial elements to reach the many accumulated physics successes. The topic covered in this review is, thus, the description of the main features of the set of methodologies at the basis of the design, construction and operation of low-energy neutrino detectors.

  3. Wind shear detection using measurement of aircraft total energy change

    NASA Technical Reports Server (NTRS)

    Joppa, R. G.

    1976-01-01

    Encounters with wind shears are of concern and have caused major accidents, particularly during landing approaches. Changes in the longitudinal component of the wind affect the aircraft by changing its kinetic energy with respect to the air. It is shown that an instrument which will measure and display the rate of change of total energy of the aircraft with respect to the air will give a leading indication of wind shear problems. The concept is outlined and some instrumentation and display considerations are discussed.

  4. Particle and Photon Detection: Counting and Energy Measurement.

    PubMed

    Janesick, James; Tower, John

    2016-01-01

    Fundamental limits for photon counting and photon energy measurement are reviewed for CCD and CMOS imagers. The challenges to extend photon counting into the visible/nIR wavelengths and achieve energy measurement in the UV with specific read noise requirements are discussed. Pixel flicker and random telegraph noise sources are highlighted along with various methods used in reducing their contribution on the sensor's read noise floor. Practical requirements for quantum efficiency, charge collection efficiency, and charge transfer efficiency that interfere with photon counting performance are discussed. Lastly we will review current efforts in reducing flicker noise head-on, in hopes to drive read noise substantially below 1 carrier rms. PMID:27187398

  5. Thresholded Power law Size Distributions of Instabilities in Astrophysics

    NASA Astrophysics Data System (ADS)

    Aschwanden, Markus J.

    2015-11-01

    Power-law-like size distributions are ubiquitous in astrophysical instabilities. There are at least four natural effects that cause deviations from ideal power law size distributions, which we model here in a generalized way: (1) a physical threshold of an instability; (2) incomplete sampling of the smallest events below a threshold x0; (3) contamination by an event-unrelated background xb; and (4) truncation effects at the largest events due to a finite system size. These effects can be modeled in the simplest terms with a “thresholded power law” distribution function (also called generalized Pareto [type II] or Lomax distribution), N(x){dx}\\propto {(x+{x}0)}-a{dx}, where x0 > 0 is positive for a threshold effect, while x0 < 0 is negative for background contamination. We analytically derive the functional shape of this thresholded power law distribution function from an exponential growth evolution model, which produces avalanches only when a disturbance exceeds a critical threshold x0. We apply the thresholded power law distribution function to terrestrial, solar (HXRBS, BATSE, RHESSI), and stellar flare (Kepler) data sets. We find that the thresholded power law model provides an adequate fit to most of the observed data. Major advantages of this model are the automated choice of the power law fitting range, diagnostics of background contamination, physical instability thresholds, instrumental detection thresholds, and finite system size limits. When testing self-organized criticality models that predict ideal power laws, we suggest including these natural truncation effects.

  6. Probabilistic monitoring in intrusion detection module for energy efficiency in mobile ad hoc networks

    NASA Astrophysics Data System (ADS)

    De Rango, Floriano; Lupia, Andrea

    2016-05-01

    MANETs allow mobile nodes communicating to each other using the wireless medium. A key aspect of these kind of networks is the security, because their setup is done without an infrastructure, so external nodes could interfere in the communication. Mobile nodes could be compromised, misbehaving during the multi-hop transmission of data, or they could have a selfish behavior to save energy, which is another important constraint in MANETs. The detection of these behaviors need a framework that takes into account the latest interactions among nodes, so malicious or selfish nodes could be detected also if their behavior is changed over time. The monitoring activity increases the energy consumption, so our proposal takes into account this issue reducing the energy required by the monitoring system, keeping the effectiveness of the intrusion detection system. The results show an improvement in the saved energy, improving the detection performance too.

  7. Threshold collision-induced dissociation of Sr(2+)(H(2)O)(x) complexes (x=1-6): An experimental and theoretical investigation of the complete inner shell hydration energies of Sr(2+).

    PubMed

    Carl, D R; Chatterjee, B K; Armentrout, P B

    2010-01-28

    The sequential bond energies of Sr(2+)(H(2)O)(x) complexes, where x=1-6, are determined by threshold collision-induced dissociation using a guided ion beam tandem mass spectrometer equipped with an electrospray ionization source. The electrospray source produces an initial distribution of Sr(2+)(H(2)O)(x) complexes, where x=6-9. Smaller Sr(2+)(H(2)O)(x) complexes, where x=1-5, are accessed using a recently developed in-source fragmentation technique that takes place in the high pressure region of a rf-only hexapole ion guide. This work constitutes the first experimental study for the complete inner shell of any multiply charged ion. The kinetic energy dependent cross sections are determined over a wide energy range to monitor all possible dissociation products and are modeled to obtain 0 and 298 K binding energies for loss of a single water molecule. These binding energies decrease monotonically for the Sr(2+)(H(2)O) complex to Sr(2+)(H(2)O)(6). Our experimental results agree well with previous literature results obtained by equilibrium and kinetic studies for x=5 and 6. Because there has been limited theory for the hydration of Sr(2+), we also present an in-depth theoretical study on the energetics of the Sr(2+)(H(2)O)(x) systems by employing several levels of theory with multiple effective core potentials for Sr and different basis sets for the water molecules.

  8. Anomalous threshold laws in quantum sticking.

    PubMed

    Clougherty, Dennis P

    2003-11-28

    It has been stated that for a short-ranged surface interaction, the probability of a low-energy particle sticking to a surface always vanishes as s approximately k with k-->0 where k=sqrt[E]. Deviations from this so-called universal threshold law are derived using a linear model of particle-surface scattering. The Fredholm theory of integral equations is used to find the global conditions necessary for a convergent solution. The exceptional case of a zero-energy resonance is considered in detail. Anomalous threshold laws, where s approximately k(1+alpha),alpha>0 as k-->0, are shown to arise from a soft gap in the weighted density of states of excitations; alpha is determined by the behavior of the weighted density of states near the binding energy. PMID:14683254

  9. Anomalous Threshold Laws in Quantum Sticking

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis P.

    2003-11-01

    It has been stated that for a short-ranged surface interaction, the probability of a low-energy particle sticking to a surface always vanishes as s˜k with k→0 where k=√(E). Deviations from this so-called universal threshold law are derived using a linear model of particle-surface scattering. The Fredholm theory of integral equations is used to find the global conditions necessary for a convergent solution. The exceptional case of a zero-energy resonance is considered in detail. Anomalous threshold laws, where s˜k1+α,α>0 as k→0, are shown to arise from a soft gap in the weighted density of states of excitations; α is determined by the behavior of the weighted density of states near the binding energy.

  10. Anomalous Threshold Laws in Quantum Sticking

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis

    2004-03-01

    It has been stated that for a short-ranged surface interaction, the probability of a low-energy particle sticking to a surface always vanishes as s ˜ k with k→ 0 where k=√E. Deviations from this so-called universal threshold law are derived using a linear model of particle-surface scattering. The Fredholm theory of integral equations is used to find the global conditions necessary for a convergent solution. The exceptional case of a zero-energy resonance is considered in detail. Anomalous threshold laws, where s ˜ k^1+α, α > 0 as k→ 0, are shown to arise from a soft gap in the weighted density of states of excitations; α is determined by the behavior of the weighted density of states near the binding energy.

  11. Particle and Photon Detection: Counting and Energy Measurement

    PubMed Central

    Janesick, James; Tower, John

    2016-01-01

    Fundamental limits for photon counting and photon energy measurement are reviewed for CCD and CMOS imagers. The challenges to extend photon counting into the visible/nIR wavelengths and achieve energy measurement in the UV with specific read noise requirements are discussed. Pixel flicker and random telegraph noise sources are highlighted along with various methods used in reducing their contribution on the sensor’s read noise floor. Practical requirements for quantum efficiency, charge collection efficiency, and charge transfer efficiency that interfere with photon counting performance are discussed. Lastly we will review current efforts in reducing flicker noise head-on, in hopes to drive read noise substantially below 1 carrier rms. PMID:27187398

  12. Detection of high-energy gamma rays from winter thunderclouds.

    PubMed

    Tsuchiya, H; Enoto, T; Yamada, S; Yuasa, T; Kawaharada, M; Kitaguchi, T; Kokubun, M; Kato, H; Okano, M; Nakamura, S; Makishima, K

    2007-10-19

    A report is made on a comprehensive observation of a burstlike gamma-ray emission from thunderclouds on the Sea of Japan, during strong thunderstorms on 6 January 2007. The detected emission, lasting for approximately 40 sec, preceded cloud-to-ground lightning discharges. The burst spectrum, extending to 10 MeV, can be interpreted as consisting of bremsstrahlung photons originating from relativistic electrons. This ground-based observation provides the first clear evidence that strong electric fields in thunderclouds can continuously accelerate electrons beyond 10 MeV prior to lightning discharges. PMID:17995261

  13. Detection of programmed cell death using fluorescence energy transfer.

    PubMed Central

    Xu, X; Gerard, A L; Huang, B C; Anderson, D C; Payan, D G; Luo, Y

    1998-01-01

    Fluorescence energy transfer (FRET) can be generated when green fluorescent protein (GFP) and blue fluorescent protein (BFP) are covalently linked together by a short peptide. Cleavage of this linkage by protease completely eliminates FRET effect. Caspase-3 (CPP32) is an important cellular protease activated during programmed cell death. An 18 amino acid peptide containing CPP32 recognition sequence, DEVD, was used to link GFP and BFP together. CPP32 activation can be monitored by FRET assay during the apoptosis process. PMID:9518501

  14. Detecting Plasmon Resonance Energy Transfer with Differential Interference Contrast Microscopy

    SciTech Connect

    Augspurger, Ashley E.; Stender, Anthony S.; Han, Rui; Fang, Ning

    2013-12-30

    Gold nanoparticles are ideal probes for studying intracellular environments and energy transfer mechanisms due to their plasmonic properties. Plasmon resonance energy transfer (PRET) relies on a plasmonic nanoparticle to donate energy to a nearby resonant acceptor molecule, a process which can be observed due to the plasmonic quenching of the donor nanoparticle. In this study, a gold nanosphere was used as the plasmonic donor, while the metalloprotein cytochrome c was used as the acceptor molecule. Differential interference contrast (DIC) microscopy allows for simultaneous monitoring of complex environments and noble metal nanoparticles in real time. Using DIC and specially designed microfluidic channels, we were able to monitor PRET at the single gold particle level and observe the reversibility of PRET upon the introduction of phosphate-buffered saline to the channel. In an additional experiment, single gold particles were internalized by HeLa cells and were subsequently observed undergoing PRET as the cell hosts underwent morphological changes brought about by ethanol-induced apoptosis.

  15. NOSTOS: a spherical TPC to detect low energy neutrinos

    SciTech Connect

    Aune, S.; Colas, P.; Ribas, E. Ferrer; Giomataris, Y.; Irastorza, I. G.; Dolbeau, J.; Gorodetzky, P.; Patzak, T.; Salin, P.; Fanourakis, G.; Geralis, T.; Kousouris, K.; Gounaris, G. J.; Savvidis, I.; Lepeltier, V.; Paschos, E.A.; Vergados, J.D.

    2005-09-08

    A novel low-energy ({approx}few keV) neutrino-oscillation experiment NOSTOS, combining a strong tritium source and a high pressure spherical Time Projection Chamber (TPC) detector 10 m in radius has been recently proposed. The oscillation of neutrinos of such energies occurs within the size of the detector itself, potentially allowing for a very precise (and rather systematics-free) measure of the oscillation parameters, in particular, of the smaller mixing angle {theta}13, which value could be determined for the first time. This detector could also be sensitive to the neutrino magnetic moment and be capable of accurately measure the Weinberg angle at low energy. The same apparatus, filled with high pressure Xenon, exhibits a high sensitivity as a Super Nova neutrino detector with extra galactic sensitivity. The outstanding benefits of the new concept of the spherical TPC will be presented, as well as the issues to be demonstrated in the near future by an ongoing R and D. The very first results of small prototype in operation in Saclay are shown.

  16. Probabilistic Threshold Criterion

    SciTech Connect

    Gresshoff, M; Hrousis, C A

    2010-03-09

    The Probabilistic Shock Threshold Criterion (PSTC) Project at LLNL develops phenomenological criteria for estimating safety or performance margin on high explosive (HE) initiation in the shock initiation regime, creating tools for safety assessment and design of initiation systems and HE trains in general. Until recently, there has been little foundation for probabilistic assessment of HE initiation scenarios. This work attempts to use probabilistic information that is available from both historic and ongoing tests to develop a basis for such assessment. Current PSTC approaches start with the functional form of the James Initiation Criterion as a backbone, and generalize to include varying areas of initiation and provide a probabilistic response based on test data for 1.8 g/cc (Ultrafine) 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) and LX-17 (92.5% TATB, 7.5% Kel-F 800 binder). Application of the PSTC methodology is presented investigating the safety and performance of a flying plate detonator and the margin of an Ultrafine TATB booster initiating LX-17.

  17. Threshold fatigue and information transfer

    PubMed Central

    Lindner, Benjamin; Longtin, André

    2016-01-01

    Neurons in vivo must process sensory information in the presence of significant noise. It is thus plausible to assume that neural systems have developed mechanisms to reduce this noise. Theoretical studies have shown that threshold fatigue (i.e. cumulative increases in the threshold during repetitive firing) could lead to noise reduction at certain frequencies bands and thus improved signal transmission as well as noise increases and decreased signal transmission at other frequencies: a phenomenon called noise shaping. There is, however, no experimental evidence that threshold fatigue actually occurs and, if so, that it will actually lead to noise shaping. We analyzed action potential threshold variability in intracellular recordings in vivo from pyramidal neurons in weakly electric fish and found experimental evidence for threshold fatigue: an increase in instantaneous firing rate was on average accompanied by an increase in action potential threshold. We show that, with a minor modification, the standard Hodgkin–Huxley model can reproduce this phenomenon. We next compared the performance of models with and without threshold fatigue. Our results show that threshold fatigue will lead to a more regular spike train as well as robustness to intrinsic noise via noise shaping. We finally show that the increased/reduced noise levels due to threshold fatigue correspond to decreased/increased information transmission at different frequencies. PMID:17436067

  18. Learning foraging thresholds for lizards

    SciTech Connect

    Goldberg, L.A.; Hart, W.E.; Wilson, D.B.

    1996-01-12

    This work gives a proof of convergence for a randomized learning algorithm that describes how anoles (lizards found in the Carribean) learn a foraging threshold distance. This model assumes that an anole will pursue a prey if and only if it is within this threshold of the anole`s perch. This learning algorithm was proposed by the biologist Roughgarden and his colleagues. They experimentally confirmed that this algorithm quickly converges to the foraging threshold that is predicted by optimal foraging theory our analysis provides an analytic confirmation that the learning algorithm converses to this optimal foraging threshold with high probability.

  19. Hardware Design of the Energy Efficient Fall Detection Device

    NASA Astrophysics Data System (ADS)

    Skorodumovs, A.; Avots, E.; Hofmanis, J.; Korāts, G.

    2016-04-01

    Health issues for elderly people may lead to different injuries obtained during simple activities of daily living. Potentially the most dangerous are unintentional falls that may be critical or even lethal to some patients due to the heavy injury risk. In the project "Wireless Sensor Systems in Telecare Application for Elderly People", we have developed a robust fall detection algorithm for a wearable wireless sensor. To optimise the algorithm for hardware performance and test it in field, we have designed an accelerometer based wireless fall detector. Our main considerations were: a) functionality - so that the algorithm can be applied to the chosen hardware, and b) power efficiency - so that it can run for a very long time. We have picked and tested the parts, built a prototype, optimised the firmware for lowest consumption, tested the performance and measured the consumption parameters. In this paper, we discuss our design choices and present the results of our work.

  20. Searches for Anisotropies in the Arrival Directions of the Highest Energy Cosmic Rays Detected by the Pierre Auger Observatory

    NASA Astrophysics Data System (ADS)

    Aab, A.; Abreu, P.; Aglietta, M.; Ahn, E. J.; Samarai, I. Al; Albuquerque, I. F. M.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Alves Batista, R.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Aramo, C.; Aranda, V. M.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Awal, N.; Badescu, A. M.; Barber, K. B.; Bäuml, J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blaess, S. G.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brancus, I.; Bridgeman, A.; Brogueira, P.; Brown, W. C.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, B.; Caccianiga, L.; Candusso, M.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Cester, R.; Chavez, A. G.; Chiavassa, A.; Chinellato, J. A.; Chudoba, J.; Cilmo, M.; Clay, R. W.; Cocciolo, G.; Colalillo, R.; Coleman, A.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Cordier, A.; Coutu, S.; Covault, C. E.; Cronin, J.; Curutiu, A.; Dallier, R.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; de Jong, S. J.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; del Peral, L.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Di Matteo, A.; Diaz, J. C.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dorofeev, A.; Dorosti Hasankiadeh, Q.; Dova, M. T.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Fang, K.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Fernandes, M.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fox, B. D.; Fratu, O.; Freire, M. M.; Fröhlich, U.; Fuchs, B.; Fujii, T.; Gaior, R.; García, B.; Garcia-Gamez, D.; Garcia-Pinto, D.; Garilli, G.; Gascon Bravo, A.; Gate, F.; Gemmeke, H.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Glaser, C.; Glass, H.; Gómez Berisso, M.; Gómez Vitale, P. F.; Gonçalves, P.; Gonzalez, J. G.; González, N.; Gookin, B.; Gordon, J.; Gorgi, A.; Gorham, P.; Gouffon, P.; Grebe, S.; Griffith, N.; Grillo, A. F.; Grubb, T. D.; Guarino, F.; Guedes, G. P.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Hartmann, S.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Hollon, N.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huber, D.; Huege, T.; Insolia, A.; Isar, P. G.; Jandt, I.; Jansen, S.; Jarne, C.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Kasper, P.; Katkov, I.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuempel, D.; Kunka, N.; LaHurd, D.; Latronico, L.; Lauer, R.; Lauscher, M.; Lautridou, P.; Le Coz, S.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Malacari, M.; Maldera, S.; Mallamaci, M.; Maller, J.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, V.; Mariş, I. C.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Martraire, D.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurel, D.; Maurizio, D.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Meissner, R.; Melissas, M.; Melo, D.; Menshikov, A.; Messina, S.; Meyhandan, R.; Mićanović, S.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morello, C.; Mostafá, M.; Moura, C. A.; Muller, M. A.; Müller, G.; Müller, S.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Nguyen, P. H.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, L.; Ochilo, L.; Oikonomou, F.; Olinto, A.; Oliveira, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.; Pech, M.; Pȩkala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Petermann, E.; Peters, C.; Petrera, S.; Petrov, Y.; Phuntsok, J.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porcelli, A.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Purrello, V.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rizi, V.; Rodrigues de Carvalho, W.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Rogozin, D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Roulet, E.; Rovero, A. C.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Saleh, A.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarmento, R.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Schmidt, D.; Scholten, O.; Schoorlemmer, H.; Schovánek, P.; Schröder, F. G.; Schulz, A.; Schulz, J.; Schumacher, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Squartini, R.; Srivastava, Y. N.; Stanič, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Taborda, O. A.; Tapia, A.; Tepe, A.; Theodoro, V. M.; Timmermans, C.; Todero Peixoto, C. J.; Toma, G.; Tomankova, L.; Tomé, B.; Tonachini, A.; Torralba Elipe, G.; Torres Machado, D.; Travnicek, P.; Trovato, E.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van Bodegom, P.; van den Berg, A. M.; van Velzen, S.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villase ñor, L.; Vlcek, B.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Werner, F.; Widom, A.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Williams, C.; Winchen, T.; Wittkowski, D.; Wundheiler, B.; Wykes, S.; Yamamoto, T.; Yapici, T.; Yuan, G.; Yushkov, A.; Zamorano, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zepeda, A.; Zhou, J.; Zhu, Y.; Zimbres Silva, M.; Ziolkowski, M.; Zuccarello, F.; Pierre Auger Collaboration

    2015-05-01

    We analyze the distribution of arrival directions of ultra-high-energy cosmic rays recorded at the Pierre Auger Observatory in 10 years of operation. The data set, about three times larger than that used in earlier studies, includes arrival directions with zenith angles up to 80°, thus covering from -90{}^\\circ to +45{}^\\circ in declination. After updating the fraction of events correlating with the active galactic nuclei (AGNs) in the Véron-Cetty and Véron catalog, we subject the arrival directions of the data with energies in excess of 40 EeV to different tests for anisotropy. We search for localized excess fluxes, self-clustering of event directions at angular scales up to 30°, and different threshold energies between 40 and 80 EeV. We then look for correlations of cosmic rays with celestial structures both in the Galaxy (the Galactic Center and Galactic Plane) and in the local universe (the Super-Galactic Plane). We also examine their correlation with different populations of nearby extragalactic objects: galaxies in the 2MRS catalog, AGNs detected by Swift-BAT, radio galaxies with jets, and the Centaurus A (Cen A) galaxy. None of the tests show statistically significant evidence of anisotropy. The strongest departures from isotropy (post-trial probability ˜ 1.4%) are obtained for cosmic rays with E\\gt 58 EeV in rather large windows around Swift AGNs closer than 130 Mpc and brighter than 1044 erg s-1 (18° radius), and around the direction of Cen A (15° radius).

  1. Searches for anisotropies in the arrival directions of the highest energy cosmic rays detected by the Pierre Auger Observatory

    DOE PAGES

    Aab, Alexander

    2015-05-01

    We analyze the distribution of arrival directions of ultra-high-energy cosmic rays recorded at the Pierre Auger Observatory in 10 years of operation. The data set, about three times larger than that used in earlier studies, includes arrival directions with zenith angles up to 80°, thus covering from -90° to +45° in declination. After updating the fraction of events correlating with the active galactic nuclei (AGNs) in the Véron-Cetty and Véron catalog, we subject the arrival directions of the data with energies in excess of 40 EeV to different tests for anisotropy. We search for localized excess fluxes, self-clustering of event directions at angular scales up to 30°, and different threshold energies between 40 and 80 EeV. We then look for correlations of cosmic rays with celestial structures both in the Galaxy (the Galactic Center and Galactic Plane) and in the local universe (the Super-Galactic Plane). We also examine their correlation with different populations of nearby extragalactic objects: galaxies in the 2MRS catalog, AGNs detected by Swift-BAT, radio galaxies with jets, and the Centaurus A (Cen A) galaxy. None of the tests show statistically significant evidence of anisotropy. As a result, the strongest departures from isotropy (post-trial probabilitymore » $$\\sim 1.4$$%) are obtained for cosmic rays with $$E\\gt 58$$ EeV in rather large windows around Swift AGNs closer than 130 Mpc and brighter than 1044 erg s-1 (18° radius), and around the direction of Cen A (15° radius).« less

  2. Searches for anisotropies in the arrival directions of the highest energy cosmic rays detected by the Pierre Auger Observatory

    SciTech Connect

    Aab, Alexander

    2015-05-01

    We analyze the distribution of arrival directions of ultra-high-energy cosmic rays recorded at the Pierre Auger Observatory in 10 years of operation. The data set, about three times larger than that used in earlier studies, includes arrival directions with zenith angles up to 80°, thus covering from -90° to +45° in declination. After updating the fraction of events correlating with the active galactic nuclei (AGNs) in the Véron-Cetty and Véron catalog, we subject the arrival directions of the data with energies in excess of 40 EeV to different tests for anisotropy. We search for localized excess fluxes, self-clustering of event directions at angular scales up to 30°, and different threshold energies between 40 and 80 EeV. We then look for correlations of cosmic rays with celestial structures both in the Galaxy (the Galactic Center and Galactic Plane) and in the local universe (the Super-Galactic Plane). We also examine their correlation with different populations of nearby extragalactic objects: galaxies in the 2MRS catalog, AGNs detected by Swift-BAT, radio galaxies with jets, and the Centaurus A (Cen A) galaxy. None of the tests show statistically significant evidence of anisotropy. As a result, the strongest departures from isotropy (post-trial probability $\\sim 1.4$%) are obtained for cosmic rays with $E\\gt 58$ EeV in rather large windows around Swift AGNs closer than 130 Mpc and brighter than 1044 erg s-1 (18° radius), and around the direction of Cen A (15° radius).

  3. INFLUENCE OF MASS ON DISPLACEMENT THRESHOLD

    SciTech Connect

    Setyawan, Wahyu; Selby, A.; Nandipati, Giridhar; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.

    2014-12-30

    Molecular dynamics simulations are performed to investigate the effect of mass on displacement threshold energy in Cr, Mo, Fe and W. For each interatomic potential, the mass of the atoms is varied among those metals for a total of 16 combinations. The average threshold energy over all crystal directions is calculated within the irreducible crystal directions using appropriate weighting factors. The weighting factors account for the different number of equivalent directions among the grid points and the different solid angle coverage of each grid point. The grid points are constructed with a Miller index increment of 1/24 for a total of 325 points. For each direction, 10 simulations each with a different primary-knock-on atom are performed. The results show that for each interatomic potential, the average threshold energy is insensitive to the mass; i.e., the values are the same within the standard error. In the future, the effect of mass on high-energy cascades for a given interatomic potential will be investigated.

  4. In-situ fault detection apparatus and method for an encased energy storing device

    DOEpatents

    Hagen, Ronald A.; Comte, Christophe; Knudson, Orlin B.; Rosenthal, Brian; Rouillard, Jean

    2000-01-01

    An apparatus and method for detecting a breach in an electrically insulating surface of an electrically conductive power system enclosure within which a number of series connected energy storing devices are disposed. The energy storing devices disposed in the enclosure are connected to a series power connection. A detector is coupled to the series connection and detects a change of state in a test signal derived from the series connected energy storing devices. The detector detects a breach in the insulating layer of the enclosure by detecting a state change in the test signal from a nominal state to a non-nominal state. A voltage detector detects a state change of the test signals from a nominal state, represented by a voltage of a selected end energy storing device, to a non-nominal state, represented by a voltage that substantially exceeds the voltage of the selected opposing end energy storing device. Alternatively, the detector may comprise a signal generator that produces the test signal as a time-varying or modulated test signal and injects the test signal into the series connection. The detector detects the state change of the time-varying or modulated test signal from a nominal state, represented by a signal substantially equivalent to the test signal, to a non-nominal state, representative by an absence of the test signal.

  5. An Energy efficient application specific integrated circuit for electrocardiogram feature detection and its potential for ambulatory cardiovascular disease detection.

    PubMed

    Jain, Sanjeev Kumar; Bhaumik, Basabi

    2016-03-01

    A novel algorithm based on forward search is developed for real-time electrocardiogram (ECG) signal processing and implemented in application specific integrated circuit (ASIC) for QRS complex related cardiovascular disease diagnosis. The authors have evaluated their algorithm using MIT-BIH database and achieve sensitivity of 99.86% and specificity of 99.93% for QRS complex peak detection. In this Letter, Physionet PTB diagnostic ECG database is used for QRS complex related disease detection. An ASIC for cardiovascular disease detection is fabricated using 130-nm CMOS high-speed process technology. The area of the ASIC is 0.5 mm(2). The power dissipation is 1.73 μW at the operating frequency of 1 kHz with a supply voltage of 0.6 V. The output from the ASIC is fed to their Android application that generates diagnostic report and can be sent to a cardiologist through email. Their ASIC result shows average failed detection rate of 0.16% for six leads data of 290 patients in PTB diagnostic ECG database. They also have implemented a low-leakage version of their ASIC. The ASIC dissipates only 45 pJ with a supply voltage of 0.9 V. Their proposed ASIC is most suitable for energy efficient telemetry cardiovascular disease detection system. PMID:27284458

  6. An Energy efficient application specific integrated circuit for electrocardiogram feature detection and its potential for ambulatory cardiovascular disease detection.

    PubMed

    Jain, Sanjeev Kumar; Bhaumik, Basabi

    2016-03-01

    A novel algorithm based on forward search is developed for real-time electrocardiogram (ECG) signal processing and implemented in application specific integrated circuit (ASIC) for QRS complex related cardiovascular disease diagnosis. The authors have evaluated their algorithm using MIT-BIH database and achieve sensitivity of 99.86% and specificity of 99.93% for QRS complex peak detection. In this Letter, Physionet PTB diagnostic ECG database is used for QRS complex related disease detection. An ASIC for cardiovascular disease detection is fabricated using 130-nm CMOS high-speed process technology. The area of the ASIC is 0.5 mm(2). The power dissipation is 1.73 μW at the operating frequency of 1 kHz with a supply voltage of 0.6 V. The output from the ASIC is fed to their Android application that generates diagnostic report and can be sent to a cardiologist through email. Their ASIC result shows average failed detection rate of 0.16% for six leads data of 290 patients in PTB diagnostic ECG database. They also have implemented a low-leakage version of their ASIC. The ASIC dissipates only 45 pJ with a supply voltage of 0.9 V. Their proposed ASIC is most suitable for energy efficient telemetry cardiovascular disease detection system.

  7. An Energy efficient application specific integrated circuit for electrocardiogram feature detection and its potential for ambulatory cardiovascular disease detection

    PubMed Central

    Bhaumik, Basabi

    2016-01-01

    A novel algorithm based on forward search is developed for real-time electrocardiogram (ECG) signal processing and implemented in application specific integrated circuit (ASIC) for QRS complex related cardiovascular disease diagnosis. The authors have evaluated their algorithm using MIT-BIH database and achieve sensitivity of 99.86% and specificity of 99.93% for QRS complex peak detection. In this Letter, Physionet PTB diagnostic ECG database is used for QRS complex related disease detection. An ASIC for cardiovascular disease detection is fabricated using 130-nm CMOS high-speed process technology. The area of the ASIC is 0.5 mm2. The power dissipation is 1.73 μW at the operating frequency of 1 kHz with a supply voltage of 0.6 V. The output from the ASIC is fed to their Android application that generates diagnostic report and can be sent to a cardiologist through email. Their ASIC result shows average failed detection rate of 0.16% for six leads data of 290 patients in PTB diagnostic ECG database. They also have implemented a low-leakage version of their ASIC. The ASIC dissipates only 45 pJ with a supply voltage of 0.9 V. Their proposed ASIC is most suitable for energy efficient telemetry cardiovascular disease detection system. PMID:27284458

  8. Energy-shunting external hip protector attenuates the peak femoral impact force below the theoretical fracture threshold: an in vitro biomechanical study under falling conditions of the elderly.

    PubMed

    Parkkari, J; Kannus, P; Heikkilä, J; Poutala, J; Sievänen, H; Vuori, I

    1995-10-01

    The first objective of this study was to design a hip protector that would effectively attenuate and shunt away from the greater trochanter the impact energies created in typical falls of the elderly. As the shock absorption material, the protector included the 12 mm-thick Plastazote, which was found to be the most efficient energy-absorbing material in our previous in vitro biomechanical tests. With an anatomically designed semiflexible outer shield of the protector (high density polyethylene), the impact surface was increased and the impact energy shunted away from the greater trochanter. In the second phase of the study, we determined the force attenuation capacity of this device in realistic (in vitro) falling conditions of the elderly. With the impact force of 6940 N used (a typical hip impact force measured in in vitro falling tests), the trochanteric soft tissue (25 mm-thick polyethylene foam) attenuated the peak femoral impact force to 5590 N and the tested protector to 1040 N. In the second series of this experiment, the peak femoral impact force was set to be so high (13,130 N) that the protector, if effective, should prevent the hip fracture in almost all cases. The trochanteric soft tissue attenuated this peak impact force to 10,400 N and the tested protector to 1810 N. Thus, the force received by the proximal femur still remained clearly below 4170 N, the average force required to fracture in vitro the proximal femur of the elderly in a fall loading configuration. In conclusion, our test results suggest that an anatomically designed energy-shunting and energy-absorbing hip protector can provide an effective impact force attenuation in typical falling conditions of the elderly. However, the efficacy of the protector in the prevention of hip fractures can only be evaluated in randomized clinical trials.

  9. Stochastic undersampling steepens auditory threshold/duration functions: implications for understanding auditory deafferentation and aging

    PubMed Central

    Marmel, Frédéric; Rodríguez-Mendoza, Medardo A.; Lopez-Poveda, Enrique A.

    2015-01-01

    It has long been known that some listeners experience hearing difficulties out of proportion with their audiometric losses. Notably, some older adults as well as auditory neuropathy patients have temporal-processing and speech-in-noise intelligibility deficits not accountable for by elevated audiometric thresholds. The study of these hearing deficits has been revitalized by recent studies that show that auditory deafferentation comes with aging and can occur even in the absence of an audiometric loss. The present study builds on the stochastic undersampling principle proposed by Lopez-Poveda and Barrios (2013) to account for the perceptual effects of auditory deafferentation. Auditory threshold/duration functions were measured for broadband noises that were stochastically undersampled to various different degrees. Stimuli with and without undersampling were equated for overall energy in order to focus on the changes that undersampling elicited on the stimulus waveforms, and not on its effects on the overall stimulus energy. Stochastic undersampling impaired the detection of short sounds (<20 ms). The detection of long sounds (>50 ms) did not change or improved, depending on the degree of undersampling. The results for short sounds show that stochastic undersampling, and hence presumably deafferentation, can account for the steeper threshold/duration functions observed in auditory neuropathy patients and older adults with (near) normal audiometry. This suggests that deafferentation might be diagnosed using pure-tone audiometry with short tones. It further suggests that the auditory system of audiometrically normal older listeners might not be “slower than normal”, as is commonly thought, but simply less well afferented. Finally, the results for both short and long sounds support the probabilistic theories of detectability that challenge the idea that auditory threshold occurs by integration of sound energy over time. PMID:26029098

  10. High energy neutrino detection with KM3NeT

    NASA Astrophysics Data System (ADS)

    Migliozzi, Pasquale; KM3NeT Collaboration

    2016-05-01

    The KM3NeT Collaboration has started the construction of a next generation high-energy neutrino telescope in the Mediterranean Sea: the largest and most sensitive neutrino research infrastructure. The full KM3NeT detector will be a several cubic kilometres distributed, networked infrastructure. In Italy, off the coast of Capo Passero, and in France, off the coast of Toulon. Thanks to its location in the Northern hemisphere and to its large instrumented volume, KM3NeT will be the optimal instrument to search for neutrinos from the Southern sky and in particular from the Galactic plane, thus making it complementary to IceCube. In this work the technologically innovative component of the detector, the status of construction and the first results from prototypes of the KM3NeT detector will be described as well as its capability to discover neutrino sources are reported.

  11. Near Threshold K0Λ Photoproduciton on the Neutron Studied with an Electromagnetic Calorimeter FOREST

    NASA Astrophysics Data System (ADS)

    Tsuchikawa, Y.; Fujimura, H.; Fukasawa, H.; Hashimoto, R.; He, Q.; Honda, Y.; Ishikawa, T.; Iwata, T.; Kaida, S.; Kasagi, J.; Kawano, A.; Kuwasaki, S.; Maeda, K.; Masumoto, S.; Miyabe, M.; Miyahara, F.; Mochizuki, K.; Muramatsu, N.; Nakamura, A.; Nawa, K.; Ogushi, S.; Okada, Y.; Onodera, Y.; Ozawa, K.; Sakamoto, Y.; Sato, M.; Shimizu, H.; Sugai, H.; Suzuki, K.; Tajima, Y.; Takahashi, S.; Taniguchi, Y.; Yamazaki, H.; Yamazaki, R.; Yoshida, H. Y.

    The K0Λ photoproduction has been measured for the incident photon energy ranging from the threshold to 1.15 GeV by using a 4π electromagnetic calorimeter complex FOREST. The large acceptance of FOREST enables us to detect all the final state particles generated by the KS0 to π 0π 0 to 4γ and Λ → pπ- decay chains. The KS0 produced events are clearly observed in the π0π0 invariant mass distributions. The K0 angular distribution for the γn → K0Λ reaction shows flat shape near the threshold, and becomes backward peaking in the high energy region.

  12. Detection methods for cereal grains treated with low and high energy electrons

    NASA Astrophysics Data System (ADS)

    Cutrubinis, Mihalis; Delincée, Henry; Stahl, Mario; Röder, Olaf; Schaller, Hans Jürgen

    2005-04-01

    Cereal grains can be treated with low energy (<300keV) or high energy (1-10MeV) electrons for decontamination of phytopathogenic and spoilage organisms. In this preliminary study, wheat and barley samples were treated with low energy electrons of 145keV or high energy electrons of 10MeV. To identify the electron treatment, different detection methods have been investigated: (1) photostimulated luminescence (PSL), (2) thermoluminescence (TL), (3) electron spin resonance (ESR) and (4) DNA Comet Assay. These four methods are already standardised at a European level and are now adopted as general Codex methods for detection of irradiated foodstuffs. The results suggest that the most suitable detection methods for electron-treated grains are the PSL and TL methods. The results from the other two methods (ESR and Comet Assay) are not so promising because they seem only to be applicable in special cases.

  13. Life below the threshold.

    PubMed

    Castro, C

    1991-01-01

    This article explains that malnutrition, poor health, and limited educational opportunities plague Philippine children -- especially female children -- from families living below the poverty threshold. Nearly 70% of households in the Philippines do not meet the required daily level of nutritional intake. Because it is often -- and incorrectly -- assumed that women's nutritional requirements are lower than men's, women suffer higher rates of malnutrition and poor health. A 1987 study revealed that 11.7% of all elementary students were underweight and 13.9% had stunted growths. Among elementary-school girls, 17% were malnourished and 40% suffered from anemia (among lactating mothers, more than 1/2 are anemic). A 1988 Program for Decentralized Educational Development study showed that grade VI students learn only about 1/2 of what they are supposed to learn. 30% of the children enrolled in grade school drop out before they reach their senior year. The Department of Education, Culture and Sports estimates that some 2.56 million students dropped out of school in l989. That same year, some 3.7 million children were counted as part of the labor force. In Manila alone, some 60,000 children work the streets, whether doing odd jobs or begging, or turning to crime or prostitution. the article tells the story of a 12 year-old girl named Ging, a 4th grader at a public school and the oldest child in a poor family of 6 children. The undernourished Ging dreams of a good future for her family and sees education as a way out of poverty; unfortunately, her time after school is spend working in the streets or looking after her family. She considers herself luckier than many of the other children working in the streets, since she at least has a family.

  14. Efficient threshold for volumetric segmentation

    NASA Astrophysics Data System (ADS)

    Burdescu, Dumitru D.; Brezovan, Marius; Stanescu, Liana; Stoica Spahiu, Cosmin; Ebanca, Daniel

    2015-07-01

    Image segmentation plays a crucial role in effective understanding of digital images. However, the research on the existence of general purpose segmentation algorithm that suits for variety of applications is still very much active. Among the many approaches in performing image segmentation, graph based approach is gaining popularity primarily due to its ability in reflecting global image properties. Volumetric image segmentation can simply result an image partition composed by relevant regions, but the most fundamental challenge in segmentation algorithm is to precisely define the volumetric extent of some object, which may be represented by the union of multiple regions. The aim in this paper is to present a new method to detect visual objects from color volumetric images and efficient threshold. We present a unified framework for volumetric image segmentation and contour extraction that uses a virtual tree-hexagonal structure defined on the set of the image voxels. The advantage of using a virtual tree-hexagonal network superposed over the initial image voxels is that it reduces the execution time and the memory space used, without losing the initial resolution of the image.

  15. Anaerobic threshold in total artificial heart animals.

    PubMed

    Chiang, B Y; Pantalos, G; Burns, G L; Long, J W; Khanwilkar, P S; Everett, S D; Mohammad, S F; Olsen, D B

    1994-01-01

    The anaerobic threshold represents an objective measure of functional capacity and is useful in assessment of pulmonary and cardiovascular dysfunction. This study determined the anaerobic threshold in total artificial heart animals and evaluated the performance of the total artificial heart system. Five animals with total artificial hearts were put under incremental exercise testing after exercise training. The intensity of exercise ranged from 2.0 to 4.5 km/hr, with an increment of 0.5 km/hr every 3 min. The anaerobic threshold was 6.72 +/- 0.84 ml/kg/min as detected by the lactate method, and 6.48 +/- 0.79 by the CO2 method. The value of the anaerobic threshold in total artificial heart animals implies that the performance capacity of a total artificial heart is not sufficient to meet the oxygen requirements of vigorously exercising skeletal muscle. The protocol does not allow for driving parameter changes during exercise, and this situation, combined with the manual mode of the control system used, was inadequate to allow the total artificial heart animals to exercise more vigorously. Using an automatic control mode might be helpful, as well as considering the relationship between indices of oxygen metabolism, such as oxygen delivery, oxygen consumption, and oxygen extraction rate, in the control algorithms in total artificial heart control systems.

  16. Two-photon above-threshold ionization of hydrogen over the photon energy range from 15 eV to 50 keV

    SciTech Connect

    Florescu, Viorica; Budriga, Olimpia; Bachau, Henri

    2011-09-15

    We investigate the absorption of two identical photons from the ground state of hydrogen-like atoms over an energy range that extends beyond that explored up to now. Our approach is based on a hybrid formula, valid in second-order perturbation theory, in which the A{sup 2} contribution from the nonrelativistic Hamiltonian is treated exactly, while the A{center_dot}P contribution is calculated in dipole approximation. We find that, at least up to 50 keV, the nonrelativistic dipole approximation, based only on the A{center_dot}P contribution, determines the values of the total cross section. Our numerical results, covering photon energies from 90 nm (13.7 eV) to 0.0248 nm (50 keV) are in very good agreement with most previous theoretical works. Differences with recent results are discussed.

  17. Experimental investigation of the complete inner shell hydration energies of Ca2+: threshold collision-induced dissociation of Ca(2+)(H2O)x Complexes (x = 2-8).

    PubMed

    Carl, Damon R; Armentrout, P B

    2012-04-19

    The sequential bond energies of Ca(2+)(H(2)O)(x) complexes, where x = 1-8, are measured by threshold collision-induced dissociation (TCID) in a guided ion beam tandem mass spectrometer. From an electrospray ionization source that produces an initial distribution of Ca(2+)(H(2)O)(x) complexes where x = 6-8, complexes down to x = 2 are formed using an in-source fragmentation technique. Ca(2+)(H(2)O) cannot be formed in this source because charge separation into CaOH(+) and H(3)O(+) is a lower energy pathway than simple water loss from Ca(2+)(H(2)O)(2). The kinetic energy dependent cross sections for dissociation of Ca(2+)(H(2)O)(x) complexes, where x = 2-9, are examined over a wide energy range to monitor all dissociation products and are modeled to obtain 0 and 298 K binding energies. Analysis of both primary and secondary water molecule losses from each sized complex provides thermochemistry for the sequential hydration energies of Ca(2+) for x = 1-8 and the first experimental values for x = 1-4. Additionally, the thermodynamic onsets leading to the charge separation products from Ca(2+)(H(2)O)(2) and Ca(2+)(H(2)O)(3) are determined for the first time. Our experimental results for x = 1-6 agree well with previously calculated binding enthalpies as well as quantum chemical calculations performed here. Agreement for x = 1 is improved when the basis set on calcium includes core correlation.

  18. Threshold collision-induced dissociation of hydrated magnesium: experimental and theoretical investigation of the binding energies for Mg(2+)(H2O)x complexes (x=2-10).

    PubMed

    Carl, Damon R; Armentrout, Peter B

    2013-03-18

    The sequential bond energies of Mg(2+)(H2O)x complexes, in which x=2-10, are measured by threshold collision-induced dissociation in a guided ion beam tandem mass spectrometer. From an electrospray ionization source that produces an initial distribution of Mg(2+)(H2O)x complexes in which x=7-10, complexes down to x=3 are formed by using an in-source fragmentation technique. Complexes smaller than Mg(2+)(H2O)3 cannot be formed in this source because charge separation into MgOH(+)(H2O) and H3O(+) is a lower-energy pathway than simple water loss from Mg(2+)(H2O)3. The kinetic energy dependent cross sections for dissociation of Mg(2+)(H2O)x complexes, in which x=3-10, are examined over a wide energy range to monitor all dissociation products and are modeled to obtain 0 and 298 K binding energies. Analysis of both primary and secondary water molecule losses from each sized complex provides thermochemistry for the sequential hydration energies of Mg(2+) for x=2-10 and the first experimental values for x=2-4. Additionally, the thermodynamic onsets leading to the charge-separation products from Mg(2+)(H2O)3 and Mg(2+)(H2O)4 are determined for the first time. Our experimental results for x=3-7 agree well with quantum chemical calculations performed here and previously calculated binding enthalpies, as well as previous measurements for x=6. The present values for x=7-10 are slightly lower than previous experimental results and theory, but within experimental uncertainties.

  19. Threshold Concepts and Information Literacy

    ERIC Educational Resources Information Center

    Townsend, Lori; Brunetti, Korey; Hofer, Amy R.

    2011-01-01

    What do we teach when we teach information literacy in higher education? This paper describes a pedagogical approach to information literacy that helps instructors focus content around transformative learning thresholds. The threshold concept framework holds promise for librarians because it grounds the instructor in the big ideas and underlying…

  20. Threshold Hypothesis: Fact or Artifact?

    ERIC Educational Resources Information Center

    Karwowski, Maciej; Gralewski, Jacek

    2013-01-01

    The threshold hypothesis (TH) assumes the existence of complex relations between creative abilities and intelligence: linear associations below 120 points of IQ and weaker or lack of associations above the threshold. However, diverse results have been obtained over the last six decades--some confirmed the hypothesis and some rejected it. In this…

  1. Near threshold studies of photoelectron satellites

    SciTech Connect

    Heimann, P.A.

    1986-11-01

    Photoelectron spectroscopy and synchrotron radiation have been used to study correlation effects in the rare gases: He, Ne, Ar, Kr, and Xe. Two kinds of time-of-flight electron analyzers were employed to examine photoionization very close to threshold and at higher kinetic energies. Partial cross sections and angular distributions have been measured for a number of photoelectron satellites. The shake-off probability has been determined at some inner-shell resonances. 121 refs., 28 figs., 13 tabs.

  2. Power threshold for neutral beam current drive

    SciTech Connect

    Politzer, P.A. ); Porter, G.D. )

    1989-10-02

    For fully noninductive current drive in tokamaks using neutral beams, there is a power and density threshold condition, setting a minimum value for P{sup 3/2}/n{sup 2}. If this condition is not met, stationary state cannot occur, and a tokamak discharge will collapse. This is a consequence of the coupling between current and electron temperature, or between current drive efficiency and energy confinement time. 4 figs.

  3. Thresholds in conservation effectiveness under climate change

    NASA Astrophysics Data System (ADS)

    Hansen, A.; Phillips, L.

    2007-12-01

    We describe a new approach to conservation that derives from the effect of energy on ecosystem properties and then evaluate potential threshold responses of conservation effectiveness under climate change. Many tests of species energy theory provide evidence that species richness varies with measures of energy such as net primary productivity (NPP). Across continents, this relationship is most often unimodal, with species richness peaking in intermediate energy places and decreasing at higher NPP levels. NPP also influences ecosystem response to habitat fragmentation, recovery after disturbance, and trophic relationships. We have developed a topology for conservation whereby conservation priorities and management effectiveness differ among low, intermediate, and high energy ecosystems. We evaluated the projected change in NPP and conservation topology of ecoregions under future climate change scenarios. We found that projected NPP under climate change caused a subset of ecoregions to shift across the peak of the unimodal species energy curve, suggesting dramatic changes in conservation effectiveness are possible.

  4. Brain MRI Tumor Detection using Active Contour Model and Local Image Fitting Energy

    NASA Astrophysics Data System (ADS)

    Nabizadeh, Nooshin; John, Nigel

    2014-03-01

    Automatic abnormality detection in Magnetic Resonance Imaging (MRI) is an important issue in many diagnostic and therapeutic applications. Here an automatic brain tumor detection method is introduced that uses T1-weighted images and K. Zhang et. al.'s active contour model driven by local image fitting (LIF) energy. Local image fitting energy obtains the local image information, which enables the algorithm to segment images with intensity inhomogeneities. Advantage of this method is that the LIF energy functional has less computational complexity than the local binary fitting (LBF) energy functional; moreover, it maintains the sub-pixel accuracy and boundary regularization properties. In Zhang's algorithm, a new level set method based on Gaussian filtering is used to implement the variational formulation, which is not only vigorous to prevent the energy functional from being trapped into local minimum, but also effective in keeping the level set function regular. Experiments show that the proposed method achieves high accuracy brain tumor segmentation results.

  5. Benefits of texture analysis of dual energy CT for Computer-Aided pulmonary embolism detection.

    PubMed

    Foncubierta-Rodríguez, Antonio; Jiménez del Toro, Óscar Alfonso; Platon, Alexandra; Poletti, Pierre-Alexandre; Müller, Henning; Depeursinge, Adrien

    2013-01-01

    Pulmonary embolism is an avoidable cause of death if treated immediately but delays in diagnosis and treatment lead to an increased risk. Computer-assisted image analysis of both unenhanced and contrast-enhanced computed tomography (CT) have proven useful for diagnosis of pulmonary embolism. Dual energy CT provides additional information over the standard single energy scan by generating four-dimensional (4D) data, in our case with 11 energy levels in 3D. In this paper a 4D texture analysis method capable of detecting pulmonary embolism in dual energy CT is presented. The method uses wavelet-based visual words together with an automatic geodesic-based region of interest detection algorithm to characterize the texture properties of each lung lobe. Results show an increase in performance with respect to the single energy CT analysis, as well as an accuracy gain compared to preliminary work on a small dataset.

  6. Benefits of texture analysis of dual energy CT for Computer-Aided pulmonary embolism detection.

    PubMed

    Foncubierta-Rodríguez, Antonio; Jiménez del Toro, Óscar Alfonso; Platon, Alexandra; Poletti, Pierre-Alexandre; Müller, Henning; Depeursinge, Adrien

    2013-01-01

    Pulmonary embolism is an avoidable cause of death if treated immediately but delays in diagnosis and treatment lead to an increased risk. Computer-assisted image analysis of both unenhanced and contrast-enhanced computed tomography (CT) have proven useful for diagnosis of pulmonary embolism. Dual energy CT provides additional information over the standard single energy scan by generating four-dimensional (4D) data, in our case with 11 energy levels in 3D. In this paper a 4D texture analysis method capable of detecting pulmonary embolism in dual energy CT is presented. The method uses wavelet-based visual words together with an automatic geodesic-based region of interest detection algorithm to characterize the texture properties of each lung lobe. Results show an increase in performance with respect to the single energy CT analysis, as well as an accuracy gain compared to preliminary work on a small dataset. PMID:24110602

  7. Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products

    DOEpatents

    Norman, Eric B [Oakland, CA; Prussin, Stanley G [Kensington, CA

    2009-05-05

    A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

  8. Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products

    DOEpatents

    Norman, Eric B.; Prussin, Stanley G.

    2009-01-27

    A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

  9. Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products

    DOEpatents

    Norman, Eric B.; Prussin, Stanley G.

    2009-01-06

    A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

  10. Calculations of atomic sputtering and displacement cross-sections in solid elements by electrons with energies from threshold to 1. 5 MV

    SciTech Connect

    Bradley, C.R.

    1988-12-01

    The kinetics of knock-on collisions of relativistic electrons with nuclei and details of the numerical evaluation of differential, recoil, and total Mott cross-sections are reviewed and discussed. The effects of electron beam induced displacement and sputtering, in the transmission electron microscope (TEM) environment, on microanalysis are analyzed with particular emphasis placed on the removal of material by knock-on sputtering. The mass loss predicted due to transmission knock-on sputtering is significant for many elements under conditions frequently encountered in microanalysis. Total Mott cross-sections are tabulated for all naturally occurring solid elements up to Z = 92 at displacement energies of one, two, four, and five times the sublimation energy and for accelerating voltages accessible in the transmission electron microscope. Fortran source code listings for the calculation of the differential Mott cross-section as a function of electron scattering angle (dMottCS), as a function of nuclear recoil angle (RECOIL), and the total Mott cross-section (TOTCS) are included. 48 refs., 21 figs., 12 tabs.

  11. Absence of a {open_quote}{open_quote}Threshold Effect{close_quote}{close_quote} in the Energy Loss of Slow Protons Traversing Large-Band-Gap Insulators

    SciTech Connect

    Eder, K.; Semrad, D.; Bauer, P.; Golser, R.; Maier-Komor, P.; Aumayr, F.; Penalba, M.; Arnau, A.; Ugalde, J.M.; Echenique, P.M.

    1997-11-01

    The electronic stopping cross section {var_epsilon} of slow hydrogen projectiles in large-band-gap insulators has been measured at energies of a few keV. Even at velocities as low as v{sub 0}/3 (v{sub 0}=c/137) , we find no influence of the band gap on the velocity dependence of {var_epsilon} , contrary to the case of gaseous targets with similar minimum excitation energy. The magnitude of {var_epsilon} and its essentially linear velocity dependence allow us to arrive at the following conclusion: Electron promotion processes contribute substantially to stopping due to formation of molecular orbitals. This points towards the existence of a bound electron state at a proton that moves slowly in an insulator. A simple model based on the calculation of molecular orbital correlation diagrams for the H/LiF collision system supports the idea of local reduction of the band gap of an insulating target. {copyright} {ital 1997} {ital The American Physical Society}

  12. Bayesian analysis of energy and count rate data for detection of low count rate radioactive sources.

    PubMed

    Klumpp, John; Brandl, Alexander

    2015-03-01

    A particle counting and detection system is proposed that searches for elevated count rates in multiple energy regions simultaneously. The system analyzes time-interval data (e.g., time between counts), as this was shown to be a more sensitive technique for detecting low count rate sources compared to analyzing counts per unit interval (Luo et al. 2013). Two distinct versions of the detection system are developed. The first is intended for situations in which the sample is fixed and can be measured for an unlimited amount of time. The second version is intended to detect sources that are physically moving relative to the detector, such as a truck moving past a fixed roadside detector or a waste storage facility under an airplane. In both cases, the detection system is expected to be active indefinitely; i.e., it is an online detection system. Both versions of the multi-energy detection systems are compared to their respective gross count rate detection systems in terms of Type I and Type II error rates and sensitivity.

  13. Bayesian analysis of energy and count rate data for detection of low count rate radioactive sources.

    PubMed

    Klumpp, John; Brandl, Alexander

    2015-03-01

    A particle counting and detection system is proposed that searches for elevated count rates in multiple energy regions simultaneously. The system analyzes time-interval data (e.g., time between counts), as this was shown to be a more sensitive technique for detecting low count rate sources compared to analyzing counts per unit interval (Luo et al. 2013). Two distinct versions of the detection system are developed. The first is intended for situations in which the sample is fixed and can be measured for an unlimited amount of time. The second version is intended to detect sources that are physically moving relative to the detector, such as a truck moving past a fixed roadside detector or a waste storage facility under an airplane. In both cases, the detection system is expected to be active indefinitely; i.e., it is an online detection system. Both versions of the multi-energy detection systems are compared to their respective gross count rate detection systems in terms of Type I and Type II error rates and sensitivity. PMID:25627949

  14. Threshold magnitude for Ionospheric TEC response to earthquakes

    NASA Astrophysics Data System (ADS)

    Perevalova, N. P.; Sankov, V. A.; Astafyeva, E. I.; Zhupityaeva, A. S.

    2014-02-01

    We have analyzed ionospheric response to earthquakes with magnitudes of 4.1-8.8 which occurred under quiet geomagnetic conditions in different regions of the world (the Baikal region, Kuril Islands, Japan, Greece, Indonesia, China, New Zealand, Salvador, and Chile). This investigation relied on measurements of total electron content (TEC) variations made by ground-based dual-frequency GPS receivers. To perform the analysis, we selected earthquakes with permanent GPS stations installed close by. Data processing has revealed that after 4.1-6.3-magnitude earthquakes wave disturbances in TEC variations are undetectable. We have thoroughly analyzed publications over the period of 1965-2013 which reported on registration of wave TIDs after earthquakes. This analysis demonstrated that the magnitude of the earthquakes having a wave response in the ionosphere was no less than 6.5. Based on our results and on the data from other researchers, we can conclude that there is a threshold magnitude (near 6.5) below which there are no pronounced earthquake-induced wave TEC disturbances. The probability of detection of post-earthquake TIDs with a magnitude close to the threshold depends strongly on geophysical conditions. In addition, reliable identification of the source of such TIDs generally requires many GPS stations in an earthquake zone. At low magnitudes, seismic energy is likely to be insufficient to generate waves in the neutral atmosphere which are able to induce TEC disturbances observable at the level of background fluctuations.

  15. Adaptive Harmonic Detection Control of Grid Interfaced Solar Photovoltaic Energy System with Power Quality Improvement

    NASA Astrophysics Data System (ADS)

    Singh, B.; Goel, S.

    2015-03-01

    This paper presents a grid interfaced solar photovoltaic (SPV) energy system with a novel adaptive harmonic detection control for power quality improvement at ac mains under balanced as well as unbalanced and distorted supply conditions. The SPV energy system is capable of compensation of linear and nonlinear loads with the objectives of load balancing, harmonics elimination, power factor correction and terminal voltage regulation. The proposed control increases the utilization of PV infrastructure and brings down its effective cost due to its other benefits. The adaptive harmonic detection control algorithm is used to detect the fundamental active power component of load currents which are subsequently used for reference source currents estimation. An instantaneous symmetrical component theory is used to obtain instantaneous positive sequence point of common coupling (PCC) voltages which are used to derive inphase and quadrature phase voltage templates. The proposed grid interfaced PV energy system is modelled and simulated in MATLAB Simulink and its performance is verified under various operating conditions.

  16. Bayesian estimation of dose thresholds

    NASA Technical Reports Server (NTRS)

    Groer, P. G.; Carnes, B. A.

    2003-01-01

    An example is described of Bayesian estimation of radiation absorbed dose thresholds (subsequently simply referred to as dose thresholds) using a specific parametric model applied to a data set on mice exposed to 60Co gamma rays and fission neutrons. A Weibull based relative risk model with a dose threshold parameter was used to analyse, as an example, lung cancer mortality and determine the posterior density for the threshold dose after single exposures to 60Co gamma rays or fission neutrons from the JANUS reactor at Argonne National Laboratory. The data consisted of survival, censoring times and cause of death information for male B6CF1 unexposed and exposed mice. The 60Co gamma whole-body doses for the two exposed groups were 0.86 and 1.37 Gy. The neutron whole-body doses were 0.19 and 0.38 Gy. Marginal posterior densities for the dose thresholds for neutron and gamma radiation were calculated with numerical integration and found to have quite different shapes. The density of the threshold for 60Co is unimodal with a mode at about 0.50 Gy. The threshold density for fission neutrons declines monotonically from a maximum value at zero with increasing doses. The posterior densities for all other parameters were similar for the two radiation types.

  17. Differential equation models for sharp threshold dynamics.

    PubMed

    Schramm, Harrison C; Dimitrov, Nedialko B

    2014-01-01

    We develop an extension to differential equation models of dynamical systems to allow us to analyze probabilistic threshold dynamics that fundamentally and globally change system behavior. We apply our novel modeling approach to two cases of interest: a model of infectious disease modified for malware where a detection event drastically changes dynamics by introducing a new class in competition with the original infection; and the Lanchester model of armed conflict, where the loss of a key capability drastically changes the effectiveness of one of the sides. We derive and demonstrate a step-by-step, repeatable method for applying our novel modeling approach to an arbitrary system, and we compare the resulting differential equations to simulations of the system's random progression. Our work leads to a simple and easily implemented method for analyzing probabilistic threshold dynamics using differential equations. PMID:24184349

  18. Ku-band radar threshold analysis

    NASA Technical Reports Server (NTRS)

    Weber, C. L.; Polydoros, A.

    1979-01-01

    The statistics of the CFAR threshold for the Ku-band radar was determined. Exact analytical results were developed for both the mean and standard deviations in the designated search mode. The mean value is compared to the results of a previously reported simulation. The analytical results are more optimistic than the simulation results, for which no explanation is offered. The normalized standard deviation is shown to be very sensitive to signal-to-noise ratio and very insensitive to the noise correlation present in the range gates of the designated search mode. The substantial variation in the CFAR threshold is dominant at large values of SNR where the normalized standard deviation is greater than 0.3. Whether or not this significantly affects the resulting probability of detection is a matter which deserves additional attention.

  19. Differential equation models for sharp threshold dynamics.

    PubMed

    Schramm, Harrison C; Dimitrov, Nedialko B

    2014-01-01

    We develop an extension to differential equation models of dynamical systems to allow us to analyze probabilistic threshold dynamics that fundamentally and globally change system behavior. We apply our novel modeling approach to two cases of interest: a model of infectious disease modified for malware where a detection event drastically changes dynamics by introducing a new class in competition with the original infection; and the Lanchester model of armed conflict, where the loss of a key capability drastically changes the effectiveness of one of the sides. We derive and demonstrate a step-by-step, repeatable method for applying our novel modeling approach to an arbitrary system, and we compare the resulting differential equations to simulations of the system's random progression. Our work leads to a simple and easily implemented method for analyzing probabilistic threshold dynamics using differential equations.

  20. Automatic detection of bone fragments in poultry using multi-energy x-rays

    DOEpatents

    Gleason, Shaun S [Knoxville, TN; Paulus, Michael J [Knoxville, TN; Mullens, James A [Knoxville, TN

    2002-04-09

    At least two linear arrays of x-ray detectors are placed below a conveyor belt in a poultry processing plant. Multiple-energy x-ray sources illuminate the poultry and are detected by the detectors. Laser profilometry is used to measure the poultry thickness as the x-ray data is acquired. The detector readout is processed in real time to detect the presence of small highly attenuating fragments in the poultry, i.e., bone, metal, and cartilage.

  1. Simulations of threshold displacement in beryllium

    NASA Astrophysics Data System (ADS)

    Jackson, Matthew L.; Fossati, Paul C. M.; Grimes, Robin W.

    2016-07-01

    Atomic scale molecular dynamics simulations of radiation damage have been performed on beryllium. Direct threshold displacement simulations along a geodesic projection of directions were used to investigate the directional dependence with a high spatial resolution. It was found that the directionally averaged probability of displacement increases from 0 at 35 eV, with the energy at which there is a 50% chance of a displacement occurring is 70 eV and asymptotically approaching 1 for higher energies. This is, however, strongly directionally dependent with a 50% probability of displacement varying from 35 to 120 eV, with low energy directions corresponding to the nearest neighbour directions. A new kinetic energy dependent expression for the average maximum displacement of an atom as a function of energy is derived which closely matches the simulated data.

  2. Linear fitting of multi-threshold counting data with a pixel-array detector for spectral X-ray imaging

    PubMed Central

    Muir, Ryan D.; Pogranichney, Nicholas R.; Muir, J. Lewis; Sullivan, Shane Z.; Battaile, Kevin P.; Mulichak, Anne M.; Toth, Scott J.; Keefe, Lisa J.; Simpson, Garth J.

    2014-01-01

    Experiments and modeling are described to perform spectral fitting of multi-threshold counting measurements on a pixel-array detector. An analytical model was developed for describing the probability density function of detected voltage in X-ray photon-counting arrays, utilizing fractional photon counting to account for edge/corner effects from voltage plumes that spread across multiple pixels. Each pixel was mathematically calibrated by fitting the detected voltage distributions to the model at both 13.5 keV and 15.0 keV X-ray energies. The model and established pixel responses were then exploited to statistically recover images of X-ray intensity as a function of X-ray energy in a simulated multi-wavelength and multi-counting threshold experiment. PMID:25178010

  3. Jost function description of near threshold resonances

    NASA Astrophysics Data System (ADS)

    Simbotin, I.; Shu, D.; Côté, R.

    2015-05-01

    The low energy behavior of cross sections for any scattering problem can be drastically affected by the presence of a resonance near the threshold. In this work, we show that any such strong dependence on energy can be accounted for in terms of the much simpler behavior of the Jost function. Although this is an old idea, see, and despite its advantages, it has not been employed widely. However, this method provides not only a theoretical tool for scattering problems in general, but also a convenient numerical approach in practice. Partially supported by AFOSR (IS), NSF (DS), and ARO (RC).

  4. Particle Detection in Superfluid Helium: R&D for Low Energy Solar Neutrinos

    SciTech Connect

    Lanou, Robert E., Jr.

    2006-03-31

    This report presents a summary of the results from R&D conducted as a feasibility study in the Department of Physics of Brown University for detection of low energy solar neutrinos utilizing a superfluid helium target. The report outlines the results in several areas: 1) development of experimental facilities, 2) energy deposition by electrons and alphas in superfluid helium, 3) development of wafer and metallic magnetic calorimeters, 4) background studies, 5) coded apertures and conceptual design, 6) Detection of single electrons and 7) a simulation of expected performance of a full scale device. Recommendations for possible future work are also presented. A bibliography of published papers and unpublished doctoral theses is included.

  5. X-ray reflectivity measurements of surface roughness using energy dispersive detection

    SciTech Connect

    Chason, E.; Warwick, D.T.

    1990-01-01

    We describe a new technique for measuring x-ray reflectivity using energy dispersive x-ray detection. The benefits of this method are the use of a fixed scattering angle and parallel detection of all energies simultaneously. These advantages make the technique more readily useable with laboratory x-ray sources and more compatible with growth chambers. We find excellent agreement between the calculated Fresnel reflectivity and the reflectivity obtained from a smooth Ge (001) surface. Reflectivities obtained during 500 eV Xe ion bombardment of Ge surfaces demonstrate the sensitivity of the technique to be better than 1 {angstrom}. 9 refs., 4 figs.

  6. Energy Detectives! Introduce Students to a Promising Career in Energy Auditing

    ERIC Educational Resources Information Center

    Helmholdt, Nick

    2012-01-01

    The growing field of energy assessment for buildings presents opportunities for teachers to engage students in topics related to current issues, science, technology, and communication skills. Students who find satisfaction in energy auditing can expand their interests into careers as the demand to stop wasteful practices in homes and businesses…

  7. Optimum threshold selection method of centroid computation for Gaussian spot

    NASA Astrophysics Data System (ADS)

    Li, Xuxu; Li, Xinyang; Wang, Caixia

    2015-10-01

    Centroid computation of Gaussian spot is often conducted to get the exact position of a target or to measure wave-front slopes in the fields of target tracking and wave-front sensing. Center of Gravity (CoG) is the most traditional method of centroid computation, known as its low algorithmic complexity. However both electronic noise from the detector and photonic noise from the environment reduces its accuracy. In order to improve the accuracy, thresholding is unavoidable before centroid computation, and optimum threshold need to be selected. In this paper, the model of Gaussian spot is established to analyze the performance of optimum threshold under different Signal-to-Noise Ratio (SNR) conditions. Besides, two optimum threshold selection methods are introduced: TmCoG (using m % of the maximum intensity of spot as threshold), and TkCoG ( usingμn +κσ n as the threshold), μn and σn are the mean value and deviation of back noise. Firstly, their impact on the detection error under various SNR conditions is simulated respectively to find the way to decide the value of k or m. Then, a comparison between them is made. According to the simulation result, TmCoG is superior over TkCoG for the accuracy of selected threshold, and detection error is also lower.

  8. Extracellular voltage threshold settings can be tuned for optimal encoding of movement and stimulus parameters

    NASA Astrophysics Data System (ADS)

    Oby, Emily R.; Perel, Sagi; Sadtler, Patrick T.; Ruff, Douglas A.; Mischel, Jessica L.; Montez, David F.; Cohen, Marlene R.; Batista, Aaron P.; Chase, Steven M.

    2016-06-01

    Objective. A traditional goal of neural recording with extracellular electrodes is to isolate action potential waveforms of an individual neuron. Recently, in brain–computer interfaces (BCIs), it has been recognized that threshold crossing events of the voltage waveform also convey rich information. To date, the threshold for detecting threshold crossings has been selected to preserve single-neuron isolation. However, the optimal threshold for single-neuron identification is not necessarily the optimal threshold for information extraction. Here we introduce a procedure to determine the best threshold for extracting information from extracellular recordings. We apply this procedure in two distinct contexts: the encoding of kinematic parameters from neural activity in primary motor cortex (M1), and visual stimulus parameters from neural activity in primary visual cortex (V1). Approach. We record extracellularly from multi-electrode arrays implanted in M1 or V1 in monkeys. Then, we systematically sweep the voltage detection threshold and quantify the information conveyed by the corresponding threshold crossings. Main Results. The optimal threshold depends on the desired information. In M1, velocity is optimally encoded at higher thresholds than speed; in both cases the optimal thresholds are lower than are typically used in BCI applications. In V1, information about the orientation of a visual stimulus is optimally encoded at higher thresholds than is visual contrast. A conceptual model explains these results as a consequence of cortical topography. Significance. How neural signals are processed impacts the information that can be extracted from them. Both the type and quality of information contained in threshold crossings depend on the threshold setting. There is more information available in these signals than is typically extracted. Adjusting the detection threshold to the parameter of interest in a BCI context should improve our ability to decode motor intent

  9. Extracellular voltage threshold settings can be tuned for optimal encoding of movement and stimulus parameters

    NASA Astrophysics Data System (ADS)

    Oby, Emily R.; Perel, Sagi; Sadtler, Patrick T.; Ruff, Douglas A.; Mischel, Jessica L.; Montez, David F.; Cohen, Marlene R.; Batista, Aaron P.; Chase, Steven M.

    2016-06-01

    Objective. A traditional goal of neural recording with extracellular electrodes is to isolate action potential waveforms of an individual neuron. Recently, in brain-computer interfaces (BCIs), it has been recognized that threshold crossing events of the voltage waveform also convey rich information. To date, the threshold for detecting threshold crossings has been selected to preserve single-neuron isolation. However, the optimal threshold for single-neuron identification is not necessarily the optimal threshold for information extraction. Here we introduce a procedure to determine the best threshold for extracting information from extracellular recordings. We apply this procedure in two distinct contexts: the encoding of kinematic parameters from neural activity in primary motor cortex (M1), and visual stimulus parameters from neural activity in primary visual cortex (V1). Approach. We record extracellularly from multi-electrode arrays implanted in M1 or V1 in monkeys. Then, we systematically sweep the voltage detection threshold and quantify the information conveyed by the corresponding threshold crossings. Main Results. The optimal threshold depends on the desired information. In M1, velocity is optimally encoded at higher thresholds than speed; in both cases the optimal thresholds are lower than are typically used in BCI applications. In V1, information about the orientation of a visual stimulus is optimally encoded at higher thresholds than is visual contrast. A conceptual model explains these results as a consequence of cortical topography. Significance. How neural signals are processed impacts the information that can be extracted from them. Both the type and quality of information contained in threshold crossings depend on the threshold setting. There is more information available in these signals than is typically extracted. Adjusting the detection threshold to the parameter of interest in a BCI context should improve our ability to decode motor intent

  10. Detection of high energy X-rays from the galactic center region

    NASA Technical Reports Server (NTRS)

    Dennis, B. R.; Beall, J. H.; Cutler, E. P.; Crannell, C. J.; Dolan, J. G.; Frost, K. J.; Orwig, L. E.

    1979-01-01

    Observations of the galactic center region made with the high energy X-ray detector on OSO-8 are discussed. A strong hard X-ray which was detected during these observations from the vicinity of the galactic center are examined. The counting rate spectrum and the photon number spectrum of the flux are determined. Comparisons with the high energy X-ray fluxes observed from sources in the region by others are discussed.

  11. Prospects for Lunar Satellite Detection of Radio Pulses from Ultrahigh Energy Neutrinos Interacting with the Moon

    SciTech Connect

    Staal, O.; Bergman, J. E. S.; Thide, B.; Daldorff, L. K. S.; Ingelman, G.

    2007-02-16

    The Moon provides a huge effective detector volume for ultrahigh energy cosmic neutrinos, which generate coherent radio pulses in the lunar surface layer due to the Askaryan effect. In light of presently considered lunar missions, we propose radio measurements from a Moon-orbiting satellite. First systematic Monte Carlo simulations demonstrate the detectability of Askaryan pulses from neutrinos with energies above 10{sup 20} eV at the very low fluxes predicted in different scenarios.

  12. Methods of sequencing and detection using energy transfer labels with cyanine dyes as donor chromophores

    DOEpatents

    Glazer, Alexander N.; Mathies, Richard A.; Hung, Su-Chun; Ju, Jingyue

    2000-01-01

    Cyanine dyes are used as the donor fluorophore in energy transfer labels in which light energy is absorbed by a donor fluorophore and transferred to an acceptor fluorophore which responds to the transfer by emitting fluorescent light for detection. The cyanine dyes impart an unusually high sensitivity to the labels thereby improving their usefulness in a wide variety of biochemical procedures, particularly nucleic acid sequencing, nucleic acid fragment sizing, and related procedures.

  13. Fluorescent resonance energy transfer based detection of biological contaminants through hybrid quantum dot-quencher interactions.

    PubMed

    Ramadurai, D; Norton, E; Hale, J; Garland, J W; Stephenson, L D; Stroscio, M A; Sivananthan, S; Kumar, A

    2008-06-01

    A nanoscale sensor employing fluorescent resonance energy transfer interactions between fluorescent quantum dots (QDs) and organic quencher molecules can be used for the multiplexed detection of biological antigens in solution. Detection occurs when the antigens to be detected displace quencher-labelled inactivated (or dead) antigens of the same type attached to QD-antibody complexes through equilibrium reactions. This unquenches the QDs, allowing detection to take place through the observation of photoluminescence in solution or through the fluorescence imaging of unquenched QD complexes trapped on filter surfaces. Multiplexing can be accomplished by using several different sizes of QDs, with each size QD labelled with an antibody for a different antigen, providing the ability to detect several types of antigens or biological contaminants simultaneously in near real-time with high specificity and sensitivity.

  14. Parton distributions with threshold resummation

    NASA Astrophysics Data System (ADS)

    Bonvini, Marco; Marzani, Simone; Rojo, Juan; Rottoli, Luca; Ubiali, Maria; Ball, Richard D.; Bertone, Valerio; Carrazza, Stefano; Hartland, Nathan P.

    2015-09-01

    We construct a set of parton distribution functions (PDFs) in which fixed-order NLO and NNLO calculations are supplemented with soft-gluon (threshold) resummation up to NLL and NNLL accuracy respectively, suitable for use in conjunction with any QCD calculation in which threshold resummation is included at the level of partonic cross sections. These resummed PDF sets, based on the NNPDF3.0 analysis, are extracted from deep-inelastic scattering, Drell-Yan, and top quark pair production data, for which resummed calculations can be consistently used. We find that, close to threshold, the inclusion of resummed PDFs can partially compensate the enhancement in resummed matrix elements, leading to resummed hadronic cross-sections closer to the fixed-order calculations. On the other hand, far from threshold, resummed PDFs reduce to their fixed-order counterparts. Our results demonstrate the need for a consistent use of resummed PDFs in resummed calculations.

  15. Thresholds for cavitation produced in water by pulsed ultrasound.

    PubMed

    Atchley, A A; Frizzell, L A; Apfel, R E; Holland, C K; Madanshetty, S; Roy, R A

    1988-09-01

    The threshold for transient cavitation produced in water by pulsed ultrasound was measured as a function of pulse duration and pulse repetition frequency at both 0.98 and 2.30 MHz. The cavitation events were detected with a passive acoustic technique which relies upon the scattering of the irradiation field by the bubble clouds associated with the events. The results indicate that the threshold is independent of pulse duration and acoustic frequency for pulses longer than approximately 10 acoustic cycles. The threshold increases for shorter pulses. The cavitation events are likely to be associated with bubble clouds rather than single bubbles.

  16. An edge-on charge-transfer design for energy-resolved x-ray detection.

    PubMed

    Shi, Zaifeng; Yang, Haoyu; Cong, Wenxiang; Wang, Ge

    2016-06-01

    As an x-ray beam goes through the human body, it will collect important information via interaction with tissues. Since this interaction is energy-sensitive, the state-of-the-art spectral CT technologies provide higher quality images of biological tissues with x-ray energy information (or spectral information). With existing energy-integrating technologies, a large fraction of energy information is ignored in the x-ray detection process. Although the recently proposed photon-counting technology promises to achieve higher image quality at a lower radiation dose, it suffers from limitations in counting rate, performance uniformity, and fabrication cost. In this paper, we focus on an alternative approach to resolve the energy distribution of transmitted x-ray photons. First, we analyze the x-ray attenuation in a silicon substrate and describe a linear approximation model for x-ray detection. Then, we design an edge-on architecture based on the proposed energy-resolving model. In our design, the x-ray-photon-induced charges are transferred sequentially resembling the working process of a CCD camera. Finally, we numerically evaluate the linear approximation of x-ray attenuation and derive the energy distribution of x-ray photons. Our simulation results show that the proposed energy-sensing approach is feasible and has the potential to complement the photon-counting technology.

  17. An edge-on charge-transfer design for energy-resolved x-ray detection.

    PubMed

    Shi, Zaifeng; Yang, Haoyu; Cong, Wenxiang; Wang, Ge

    2016-06-01

    As an x-ray beam goes through the human body, it will collect important information via interaction with tissues. Since this interaction is energy-sensitive, the state-of-the-art spectral CT technologies provide higher quality images of biological tissues with x-ray energy information (or spectral information). With existing energy-integrating technologies, a large fraction of energy information is ignored in the x-ray detection process. Although the recently proposed photon-counting technology promises to achieve higher image quality at a lower radiation dose, it suffers from limitations in counting rate, performance uniformity, and fabrication cost. In this paper, we focus on an alternative approach to resolve the energy distribution of transmitted x-ray photons. First, we analyze the x-ray attenuation in a silicon substrate and describe a linear approximation model for x-ray detection. Then, we design an edge-on architecture based on the proposed energy-resolving model. In our design, the x-ray-photon-induced charges are transferred sequentially resembling the working process of a CCD camera. Finally, we numerically evaluate the linear approximation of x-ray attenuation and derive the energy distribution of x-ray photons. Our simulation results show that the proposed energy-sensing approach is feasible and has the potential to complement the photon-counting technology. PMID:27192190

  18. An edge-on charge-transfer design for energy-resolved x-ray detection

    NASA Astrophysics Data System (ADS)

    Shi, Zaifeng; Yang, Haoyu; Cong, Wenxiang; Wang, Ge

    2016-06-01

    As an x-ray beam goes through the human body, it will collect important information via interaction with tissues. Since this interaction is energy-sensitive, the state-of-the-art spectral CT technologies provide higher quality images of biological tissues with x-ray energy information (or spectral information). With existing energy-integrating technologies, a large fraction of energy information is ignored in the x-ray detection process. Although the recently proposed photon-counting technology promises to achieve higher image quality at a lower radiation dose, it suffers from limitations in counting rate, performance uniformity, and fabrication cost. In this paper, we focus on an alternative approach to resolve the energy distribution of transmitted x-ray photons. First, we analyze the x-ray attenuation in a silicon substrate and describe a linear approximation model for x-ray detection. Then, we design an edge-on architecture based on the proposed energy-resolving model. In our design, the x-ray-photon-induced charges are transferred sequentially resembling the working process of a CCD camera. Finally, we numerically evaluate the linear approximation of x-ray attenuation and derive the energy distribution of x-ray photons. Our simulation results show that the proposed energy-sensing approach is feasible and has the potential to complement the photon-counting technology.

  19. Semiclassical approaches to below-threshold harmonics

    SciTech Connect

    Hostetter, James A.; Tate, Jennifer L.; Schafer, Kenneth J.; Gaarde, Mette B.

    2010-08-15

    We study the generation of below-threshold harmonics in a model atom by extending the three-step semiclassical model of harmonic generation to include effects of the atomic potential. We explore the generalization of semiclassical trajectories of the electron in the presence of the combined laser-atom potential and calculate the intensity-dependent dipole phase associated with these trajectories. Our results are in good agreement with fully quantum mechanical calculations, as well as with recent experimental observations. We show that the so-called long trajectory readily generalizes to below-threshold harmonic generation and is relatively insensitive to the choice of initial conditions. We also find that the short trajectory can only lead to low-energy harmonics for electrons that have been released close to the ion core in a process that is closer to multiphoton than to tunnel ionization.

  20. Threshold models in radiation carcinogenesis

    SciTech Connect

    Hoel, D.G.; Li, P.

    1998-09-01

    Cancer incidence and mortality data from the atomic bomb survivors cohort has been analyzed to allow for the possibility of a threshold dose response. The same dose-response models as used in the original papers were fit to the data. The estimated cancer incidence from the fitted models over-predicted the observed cancer incidence in the lowest exposure group. This is consistent with a threshold or nonlinear dose-response at low-doses. Thresholds were added to the dose-response models and the range of possible thresholds is shown for both solid tumor cancers as well as the different leukemia types. This analysis suggests that the A-bomb cancer incidence data agree more with a threshold or nonlinear dose-response model than a purely linear model although the linear model is statistically equivalent. This observation is not found with the mortality data. For both the incidence data and the mortality data the addition of a threshold term significantly improves the fit to the linear or linear-quadratic dose response for both total leukemias and also for the leukemia subtypes of ALL, AML, and CML.

  1. Face verification with balanced thresholds.

    PubMed

    Yan, Shuicheng; Xu, Dong; Tang, Xiaoou

    2007-01-01

    The process of face verification is guided by a pre-learned global threshold, which, however, is often inconsistent with class-specific optimal thresholds. It is, hence, beneficial to pursue a balance of the class-specific thresholds in the model-learning stage. In this paper, we present a new dimensionality reduction algorithm tailored to the verification task that ensures threshold balance. This is achieved by the following aspects. First, feasibility is guaranteed by employing an affine transformation matrix, instead of the conventional projection matrix, for dimensionality reduction, and, hence, we call the proposed algorithm threshold balanced transformation (TBT). Then, the affine transformation matrix, constrained as the product of an orthogonal matrix and a diagonal matrix, is optimized to improve the threshold balance and classification capability in an iterative manner. Unlike most algorithms for face verification which are directly transplanted from face identification literature, TBT is specifically designed for face verification and clarifies the intrinsic distinction between these two tasks. Experiments on three benchmark face databases demonstrate that TBT significantly outperforms the state-of-the-art subspace techniques for face verification.

  2. Magnetic calorimeter with a SQUID for detecting weak radiations and recording the ultralow energy release

    SciTech Connect

    Golovashkin, Aleksander I; Zherikhina, L N; Kuleshova, G V; Tskhovrebov, A M; Izmailov, G N

    2006-12-31

    The scheme of a magnetic calorimeter for recording extremely low energy releases is developed. The calorimeter is activated by the method of adiabatic demagnetisation and its response to the energy release is measured with a superconducting quantum interference device (SQUID). The estimate of the ultimate sensitivity of the calorimeter with the SQUID demonstrates the possibilities of its application for detecting ultralow radiation intensity, recording single X-ray quanta in the proportional regime and other events with ultralow energy releases. The scheme of the calorimeter with the SQUID on matter waves in superfluid {sup 4}He is proposed. (radiation detectors)

  3. Nuclear recoil energy scale in liquid xenon with application to the direct detection of dark matter

    NASA Astrophysics Data System (ADS)

    Sorensen, Peter; Dahl, Carl Eric

    2011-03-01

    We show for the first time that the quenching of electronic excitation from nuclear recoils in liquid xenon is well-described by Lindhard theory, if the nuclear recoil energy is reconstructed using the combined (scintillation and ionization) energy scale proposed by Shutt et al. We argue for the adoption of this perspective in favor of the existing preference for reconstructing nuclear recoil energy solely from primary scintillation. We show that signal partitioning into scintillation and ionization is well described by the Thomas-Imel box model. We discuss the implications for liquid xenon detectors aimed at the direct detection of dark matter.

  4. Nuclear recoil energy scale in liquid xenon with application to the direct detection of dark matter

    SciTech Connect

    Sorensen, P; Dahl, C E

    2011-02-14

    We show for the first time that the quenching of electronic excitation from nuclear recoils in liquid xenon is well-described by Lindhard theory, if the nuclear recoil energy is reconstructed using the combined (scintillation and ionization) energy scale proposed by Shutt et al.. We argue for the adoption of this perspective in favor of the existing preference for reconstructing nuclear recoil energy solely from primary scintillation. We show that signal partitioning into scintillation and ionization is well-described by the Thomas-Imel box model. We discuss the implications for liquid xenon detectors aimed at the direct detection of dark matter.

  5. Muon detection studied by pulse-height energy analysis: Novel converter arrangements.

    PubMed

    Holmlid, Leif; Olafsson, Sveinn

    2015-08-01

    Muons are conventionally measured by a plastic scintillator-photomultiplier detector. Muons from processes in ultra-dense hydrogen H(0) are detected here by a novel type of converter in front of a photomultiplier. The muon detection yield can be increased relative to that observed with a plastic scintillator by at least a factor of 100, using a converter of metal, semiconductor (Ge), or glass for interaction with the muons penetrating through the metal housing of the detector. This detection process is due to transient formation of excited nuclei by the well-known process of muon capture, giving beta decay. The main experimental results shown here are in the form of beta electron energy spectra detected directly by the photomultiplier. Events which give a high-energy tail in the energy spectra are probably due to gamma photons from the muons. Sharp and intense x-ray peaks from a muonic aluminium converter or housing material are observed. The detection conversion in glass and Ge converters has a time constant of the order of many minutes to reach the final conversion level, while the process in metal converters is stabilized faster. The time constants are not due to lifetimes of the excited nuclei or neutrons but are due to internal charging in the insulating converter material. Interaction of this charging with the high voltage in the photomultiplier is observed. PMID:26329180

  6. Ratio-metric sensor to detect riboflavin via fluorescence resonance energy transfer with ultrahigh sensitivity

    NASA Astrophysics Data System (ADS)

    Wang, Jilong; Su, Siheng; Wei, Junhua; Bahgi, Roya; Hope-Weeks, Louisa; Qiu, Jingjing; Wang, Shiren

    2015-08-01

    In this paper, a novel fluorescence resonance energy transfer (FRET) ration-metric fluorescent probe based on heteroatom N, S doped carbon dots (N, S-CDs) was developed to determine riboflavin in aqueous solutions. The ratio of two emission intensities at different wavelengths is applied to determine the concentration of riboflavin (RF). This method is more effective in reducing the background interference and fluctuation of diverse conditions. Therefore, this probe obtains high sensitivity with a low limit of detection (LOD) of 1.9 nM (0.7 ng/ml) which is in the highest level of all riboflavin detection approaches and higher than single wavelength intensity detection (1.9 μM). In addition, this sensor has a high selectivity of detecting riboflavin in deionized water (pH=7) with other biochemical like amino acids. Moreover, riboflavin in aqueous solution is very sensitive to sunlight and can be degraded to lumiflavin, which is toxic. Because the N, S doped carbon dots cannot serve as an energy donor for N, S doped carbon dots and lumiflavin system, this system makes it easy to determine whether the riboflavin is degraded or not, which is first to be reported. This platform may provide possibilities to build a new and facile fluorescence resonance energy transfer based sensor to detect analytes and metamorphous analytes in aqueous solution.

  7. Muon detection studied by pulse-height energy analysis: Novel converter arrangements.

    PubMed

    Holmlid, Leif; Olafsson, Sveinn

    2015-08-01

    Muons are conventionally measured by a plastic scintillator-photomultiplier detector. Muons from processes in ultra-dense hydrogen H(0) are detected here by a novel type of converter in front of a photomultiplier. The muon detection yield can be increased relative to that observed with a plastic scintillator by at least a factor of 100, using a converter of metal, semiconductor (Ge), or glass for interaction with the muons penetrating through the metal housing of the detector. This detection process is due to transient formation of excited nuclei by the well-known process of muon capture, giving beta decay. The main experimental results shown here are in the form of beta electron energy spectra detected directly by the photomultiplier. Events which give a high-energy tail in the energy spectra are probably due to gamma photons from the muons. Sharp and intense x-ray peaks from a muonic aluminium converter or housing material are observed. The detection conversion in glass and Ge converters has a time constant of the order of many minutes to reach the final conversion level, while the process in metal converters is stabilized faster. The time constants are not due to lifetimes of the excited nuclei or neutrons but are due to internal charging in the insulating converter material. Interaction of this charging with the high voltage in the photomultiplier is observed.

  8. Muon detection studied by pulse-height energy analysis: Novel converter arrangements

    SciTech Connect

    Holmlid, Leif; Olafsson, Sveinn

    2015-08-15

    Muons are conventionally measured by a plastic scintillator–photomultiplier detector. Muons from processes in ultra-dense hydrogen H(0) are detected here by a novel type of converter in front of a photomultiplier. The muon detection yield can be increased relative to that observed with a plastic scintillator by at least a factor of 100, using a converter of metal, semiconductor (Ge), or glass for interaction with the muons penetrating through the metal housing of the detector. This detection process is due to transient formation of excited nuclei by the well-known process of muon capture, giving beta decay. The main experimental results shown here are in the form of beta electron energy spectra detected directly by the photomultiplier. Events which give a high-energy tail in the energy spectra are probably due to gamma photons from the muons. Sharp and intense x-ray peaks from a muonic aluminium converter or housing material are observed. The detection conversion in glass and Ge converters has a time constant of the order of many minutes to reach the final conversion level, while the process in metal converters is stabilized faster. The time constants are not due to lifetimes of the excited nuclei or neutrons but are due to internal charging in the insulating converter material. Interaction of this charging with the high voltage in the photomultiplier is observed.

  9. DEVELOPMENT OF A REAL-TIME FLUORESCENCE RESONANCE ENERGY TRANSFER (FRET) PCR TO DETECT ARCOBACTER SPECIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A real-time PCR targeting the gyrase A subunit gene outside the quinolone resistance-determining region has been developed to detect Arcobacter species. The species identification was made by probe hybridization and melting curve analysis, using the Fluorescence Resonance Energy Transfer technology...

  10. DEVELOPMENT OF A REAL-TIME FLUORESCENCE RESONANCE ENERGY TRANSFER PCR TO DETECT ARCOBACTER SPECIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A real-time PCR targeting the gyrase A subunit gene outside the quinolone resistance-determining region has been developed to detect Arcobacter species. The species identification was made by probe hybridization and melting curve analysis, using Fluorescence Resonance Energy Transfer technology. D...

  11. Array-Based Detection of Persistent Organic Pollutants via Cyclodextrin Promoted Energy Transfer

    PubMed Central

    Serio, Nicole; Moyano, Daniel F.; Rotello, Vincent M.; Levine, Mindy

    2015-01-01

    We report herein the selective array-based detection of 30 persistent organic pollutants via cyclodextrin-promoted energy transfer. The use of three fluorophores enabled the development of an array that classified 30 analytes with 100% accuracy and identified unknown analytes with 96% accuracy, as well as identifying 92% of analytes in urine. PMID:26096542

  12. Mass calibration of the energy axis in ToF-E elastic recoil detection analysis

    NASA Astrophysics Data System (ADS)

    Meersschaut, J.; Laricchiuta, G.; Sajavaara, T.; Vandervorst, W.

    2016-03-01

    We report on procedures that we have developed to mass-calibrate the energy axis of ToF-E histograms in elastic recoil detection analysis. The obtained calibration parameters allow one to transform the ToF-E histogram into a calibrated ToF-M histogram.

  13. Guidelines for Auditory Threshold Measurement for Significant Threshold Shift.

    PubMed

    Campbell, Kathleen; Hammill, Tanisha; Hoffer, Michael; Kil, Jonathan; Le Prell, Colleen

    2016-09-01

    The purpose of this article is to provide guidelines for determining a Significant Noise-Induced Threshold Shift in clinical trials involving human populations. The article reviews recommendations for the standards to be referenced for human subjects, equipment, test environment, and personnel. Additional guidelines for military populations are provided. Guidelines for the calibration of audiometers, sound booth noise levels, and immitance equipment are provided. In addition the guidance provides specific suggestions for the subjects history before study onset, and otoscopy.Test frequencies for threshold determination and methods of threshold determination are reviewed for both air conduction and bone conduction for both baseline testing and later determination of either a temporary (TTS) or permanent threshold shift (PTS). Once a Significant Noise-Induced Threshold Shift has been determined, subjects should be retested, conductive component should be ruled out or addressed, and the subject should be counseled or referred for additional medical evaluation. Guidance for reporting procedures and the computerized study database are described. Finally, experimental designs suggested for noise-induced otoprotection clinical trials are described.

  14. Guidelines for Auditory Threshold Measurement for Significant Threshold Shift.

    PubMed

    Campbell, Kathleen; Hammill, Tanisha; Hoffer, Michael; Kil, Jonathan; Le Prell, Colleen

    2016-09-01

    The purpose of this article is to provide guidelines for determining a Significant Noise-Induced Threshold Shift in clinical trials involving human populations. The article reviews recommendations for the standards to be referenced for human subjects, equipment, test environment, and personnel. Additional guidelines for military populations are provided. Guidelines for the calibration of audiometers, sound booth noise levels, and immitance equipment are provided. In addition the guidance provides specific suggestions for the subjects history before study onset, and otoscopy.Test frequencies for threshold determination and methods of threshold determination are reviewed for both air conduction and bone conduction for both baseline testing and later determination of either a temporary (TTS) or permanent threshold shift (PTS). Once a Significant Noise-Induced Threshold Shift has been determined, subjects should be retested, conductive component should be ruled out or addressed, and the subject should be counseled or referred for additional medical evaluation. Guidance for reporting procedures and the computerized study database are described. Finally, experimental designs suggested for noise-induced otoprotection clinical trials are described. PMID:27518134

  15. An estimation method for echo signal energy of pipe inner surface longitudinal crack detection by 2-D energy coefficients integration

    SciTech Connect

    Zhou, Shiyuan Sun, Haoyu Xu, Chunguang Cao, Xiandong Cui, Liming Xiao, Dingguo

    2015-03-31

    The echo signal energy is directly affected by the incident sound beam eccentricity or angle for thick-walled pipes inner longitudinal cracks detection. A method for analyzing the relationship between echo signal energy between the values of incident eccentricity is brought forward, which can be used to estimate echo signal energy when testing inside wall longitudinal crack of pipe, using mode-transformed compression wave adaptation of shear wave with water-immersion method, by making a two-dimension integration of “energy coefficient” in both circumferential and axial directions. The calculation model is founded for cylinder sound beam case, in which the refraction and reflection energy coefficients of different rays in the whole sound beam are considered different. The echo signal energy is calculated for a particular cylinder sound beam testing different pipes: a beam with a diameter of 0.5 inch (12.7mm) testing a φ279.4mm pipe and a φ79.4mm one. As a comparison, both the results of two-dimension integration and one-dimension (circumferential direction) integration are listed, and only the former agrees well with experimental results. The estimation method proves to be valid and shows that the usual method of simplifying the sound beam as a single ray for estimating echo signal energy and choosing optimal incident eccentricity is not so appropriate.

  16. {sup 16}O resonances near 4α threshold through {sup 12}C({sup 6}Li,d) reaction

    SciTech Connect

    Rodrigues, M. R. D.; Borello-Lewin, T.; Miyake, H.; Horodynski-Matsushigue, L. B.; Duarte, J. L. M.; Rodrigues, C. L.; Faria, P. Neto de; Cunsolo, A.; Cappuzzello, F.; Foti, A.; Agodi, C.; Cavallaro, M.; Napoli, M. di; Ukita, G. M.

    2014-11-11

    Several narrow alpha resonant {sup 16}O states were detected through the {sup 12}C({sup 6}Li,d) reaction, in the range of 13.5 to 17.5 MeV of excitation energy. The reaction was measured at a bombarding energy of 25.5 MeV employing the São Paulo Pelletron-Enge-Spectrograph facility and the nuclear emulsion technique. Experimental angular distributions associated with natural parity quasi-bound states around the 4α threshold are presented and compared to DWBA predictions. The upper limit for the resonance widths obtained is near the energy resolution (15 keV)

  17. Automatic Classification of Kepler Threshold Crossing Events

    NASA Astrophysics Data System (ADS)

    McCauliff, Sean; Catanzarite, Joseph; Jenkins, Jon Michael

    2014-06-01

    Over the course of its 4-year primary mission the Kepler mission has discovered numerous planets. Part of the process of planet discovery has involved generating threshold crossing events (TCEs); a light curve with a repeating exoplanet transit-like feature. The large number of diagnostics 100) makes it difficult to examine all the information available for each TCE. The effort required for vetting all threshold-crossing events (TCEs) takes several months by many individuals associated with the Kepler Threshold Crossing Event Review Team (TCERT). The total number of objects with transit-like features identified in the light curves has increased to as many as 18,000, just examining the first three years of data. In order to accelerate the process by which new planet candidates are classified, we propose a machine learning approach to establish a preliminary list of planetary candidates ranked from most credible to least credible. The classifier must distinguish between three classes of detections: non-transiting phenomena, astrophysical false positives, and planet candidates. We use random forests, a supervised classification algorithm to this end. We report on the performance of the classifier and identify diagnostics that are important for discriminating between these classes of TCEs.Funding for this mission is provided by NASA’s Science Mission Directorate.

  18. The Cryogenic Dark Matter Search low ionization-threshold experiment

    SciTech Connect

    Basu Thakur, Ritoban

    2014-01-01

    Over 80 years ago we discovered the presence of Dark Matter in our universe. Endeavors in astronomy and cosmology are in consensus with ever improving precision that Dark Matter constitutes an essential 27% of our universe. The Standard Model of Particle Physics does not provide any answers to the Dark Matter problem. It is imperative that we understand Dark Matter and discover its fundamental nature. This is because, alongside other important factors, Dark Matter is responsible for formation of structure in our universe. The very construct in which we sit is defined by its abundance. The Milky Way galaxy, hence life, wouldn't have formed if small over densities of Dark Matter had not caused sufficient accretion of stellar material. Marvelous experiments have been designed based on basic notions to directly and in-directly study Dark Matter, and the Cryogenic Dark Matter Search (CDMS) experiment has been a pioneer and forerunner in the direct detection field. Generations of the CDMS experiment were designed with advanced scientific upgrades to detect Dark Matter particles of mass O(100) GeV/c2. This mass-scale was set primarily by predictions from Super Symmetry. Around 2013 the canonical SUSY predictions were losing some ground and several observations (rather hints of signals) from various experiments indicated to the possibility of lighter Dark Matter of mass O(10) GeV/c2. While the SuperCDMS experiment was probing the regular parameter space, the CDMSlite experiment was conceived to dedicatedly search for light Dark Matter using a novel technology. "CDMSlite" stands for CDMS - low ionization threshold experiment. Here we utilize a unique electron phonon coupling mechanism to measure ionization generated by scattering of light particles. Typically signals from such low energy recoils would be washed under instrumental noise. In CDMSlite via generation of Luke-Neganov phonons we can detect the small ionization energies, amplified in phonon

  19. Using a CCD for the direct detection of electrons in a low energy space plasma spectrometer

    NASA Astrophysics Data System (ADS)

    Bedington, R.; Kataria, D.; Walton, D.

    2012-01-01

    An E2V CCD64 back-illuminated, ion-implanted CCD (charge-coupled device) has been used as a direct electron imaging detector with CATS (Conceptual And Tiny Spectrometer), a highly miniaturised prototype plasma analyser head. This is in place of an MCP (microchannel plate) with a position sensing anode which would more conventionally be used as a detector in traditional low energy space plasma analyser instruments. The small size of CATS however makes it well matched to the size of the CCD, and the ion implants reduce the depth of the CCD backside electron potential well making it more sensitive to lower energy electrons than standard untreated silicon. Despite ionisation damage from prolonged exposure to excessively energetic electrons, the CCD has been able to detect electrons with energies above 500eV, at temperatures around room temperature. Using both a long integration 'current measuring' mode and a short integration `electron counting' mode it has been used to image the low energy electrons exiting the analyser, enhancing our understanding of the CATS electrostatic optics. The CCD has been selected as the detector for use with CATS for an instrument on a low-altitude student sounding rocket flight. Although it cannot detect the lowest energy electrons that an MCP can detect, and it is more sensitive to stray light, the low voltages required, the lack of vacuum requirements and its novelty and availability made it the most attractive candidate detector.

  20. A detection system for very low-energy protons from {beta}-delayed proton decay

    SciTech Connect

    Spiridon, A.; Pollacco, E.; Trache, L.; Simmons, E.; McCleskey, M.; Roeder, B. T.; Tribble, R. E.; Pascovici, G.; Riallot, M.; Mols, J. P.; Kebbiri, M.

    2012-11-20

    We have recently developed a gas based detection system called AstroBox, motivated by nuclear astrophysics studies. The goal was to detect very low-energy protons from {beta}-delayed p-decay with reduced beta background and improved energy resolution. The detector was tested using the {beta}-delayed proton-emitter 23Al previously studied with a set-up based on thin double-sided Si strip detectors. The proton spectrum obtained with AstroBox showed no beta background down to {approx}80 keV. The low energy (206 keV, 267 keV) proton peaks were positively identified, well separated, and the resolution was improved.

  1. Further studies on the detection of chemical agents using an alkaline energy cell

    NASA Astrophysics Data System (ADS)

    Shewchun, John

    2008-04-01

    The detection, classification and tracking of chemical agents (explosives) being surreptitiously smuggled into public areas, such as airports, for destructive purposes is difficult to solve by unobtrusive means. We propose the use of a novel Alkaline Energy Cell (AEC) with gas/vapor sniffing capability as a potential solution. Variants of such devices are routinely used by police to detect alcohol emanating from the breath of suspected impaired vehicle drivers. We reported previously at the SPIE Symposium in 2007 the details of our technology and results. We have continued to advanced this capability with the development of an AEC which is capable of detecting gaseous emissions ultimately in the parts per billion range. Our work is described in terms of detecting TATP (acetone peroxide). Other explosive materials have also been investigated and will be reported on.

  2. Properties of carbon-based structures synthesized in nuclear reactions induced by bremsstrahlung γ quanta with threshold energy of 10 MeV at helium pressure of 1.1 kbar

    NASA Astrophysics Data System (ADS)

    Didyk, A. Yu.; Wiśniewski, R.

    2016-07-01

    Helium gas with an initial pressure of about 1.1 kbar inside a high-pressure chamber (HeHPC) has been irradiated by bremsstrahlung γ quanta with a threshold energy of 10 MeV for 1.0 × 105 s produced by an electron-beam current of 22-24 μA. After opening the HeHPC, the residual pressure of helium is equal to 430 bar. Synthesized black foils with a variety of other objects are found inside the HeHPC. They are located on the inner surfaces of the reaction chamber made of high-purity copper (99.99%), the entrance the window of γ quanta made of beryllium bronze and a copper container of nuclear and chemical reaction products. Elemental analysis with the use of scanning electron microscopy and X-ray microprobe analysis has revealed that the foils contain predominantly carbon and small quantities of other elements from carbon to iron. The results are in good agreement with the cycle of investigations of the authors devoted to the γ-quanta irradiation of dense hydrogen and helium gases in the presence (absence) of metals in a reaction chamber.

  3. The carbon-based structures synthesized through nuclear reactions in helium at 1.1 kbar pressure under irradiation with braking γ-rays of 10 MeV threshold energy

    NASA Astrophysics Data System (ADS)

    Didyk, A. Yu.; Wisniewski, R.; Wilczynska-Kitowska, T.

    2015-01-01

    A helium high-pressure chamber (HeHPC), made from beryllium bronze, filled with gaseous helium at an initial pressure of about 1.1 kbar was irradiated by braking γ-rays of 10 MeV threshold energy during 1.0×105 \\text{s} at an electron beam current 22\\text-24 μ \\text{A} . Before opening of the chamber, the residual pressure inside was equal to 430 bar. Synthesized foils of black colour and other multiple objects were found inside the HeHPC at the inner surfaces of the reaction chamber made of high-purity copper, at the entrance window for γ-rays of beryllium bronze, and at the copper collector of nuclear and chemical reaction products. The element analysis using scanning electron microscopy (SEM) and microprobe roentgen analysis (MPRA) allowed us to establish that the foils were predominantly made of carbon and smaller quantities of other elements from carbon to iron. The developed approach agrees well with a series of studies carried out by the authors where dense hydrogen and deuterium gases are acted on by γ-rays in the presence or absence of metals in the reaction chamber.

  4. Adaptive local thresholding for robust nucleus segmentation utilizing shape priors

    NASA Astrophysics Data System (ADS)

    Wang, Xiuzhong; Srinivas, Chukka

    2016-03-01

    This paper describes a novel local thresholding method for foreground detection. First, a Canny edge detection method is used for initial edge detection. Then, tensor voting is applied on the initial edge pixels, using a nonsymmetric tensor field tailored to encode prior information about nucleus size, shape, and intensity spatial distribution. Tensor analysis is then performed to generate the saliency image and, based on that, the refined edge. Next, the image domain is divided into blocks. In each block, at least one foreground and one background pixel are sampled for each refined edge pixel. The saliency weighted foreground histogram and background histogram are then created. These two histograms are used to calculate a threshold by minimizing the background and foreground pixel classification error. The block-wise thresholds are then used to generate the threshold for each pixel via interpolation. Finally, the foreground is obtained by comparing the original image with the threshold image. The effective use of prior information, combined with robust techniques, results in far more reliable foreground detection, which leads to robust nucleus segmentation.

  5. Threshold photodetachment spectroscopy of negative ions

    SciTech Connect

    Kitsopoulos, T.N.

    1991-12-01

    This thesis is concerned with the development and application of high resolution threshold photodetachment spectroscopy of negative ions. Chapter I deals with the principles of our photodetachment technique, and in chapter II a detailed description of the apparatus is presented. The threshold photodetachment spectra of I{sup {minus}}, and SH{sup {minus}}, presented in the last sections of chapter II, indicated that a resolution of 3 cm{sup {minus}1} can be achieved using our technique. In chapter III the threshold photodetachment spectroscopy study of the transition state region of I + HI and I + Di reactions is discussed. Our technique probes the transition state region directly, and the results of our study are the first unambiguous observations of reactive resonances in a chemical reaction. Chapters IV, V and VI are concerned with the spectroscopy of small silicon and carbon clusters. From our spectra we were able to assign electronic state energies and vibrational frequencies for the low lying electronics states of Si{sub n} (n=2,3,4), C{sub 5} and their corresponding anions.

  6. ELENA MCP detector: absolute detection efficiency for low-energy neutral atoms

    NASA Astrophysics Data System (ADS)

    Rispoli, R.; De Angelis, E.; Colasanti, L.; Vertolli, N.; Orsini, S.; Scheer, J. A.; Mura, A.; Milillo, A.; Wurz, P.; Selci, S.; Di Lellis, A. M.; Leoni, R.; D'Alessandro, M.; Mattioli, F.; Cibella, S.

    2012-09-01

    Microchannel Plates (MCP) detectors are frequently used in space instrumentation for detecting a wide range of radiation and particles. In particular, the capability to detect non-thermal low energy neutral species is crucial for the sensor ELENA (Emitted Low-Energy Neutral Atoms), part of the package SERENA (Search for Exospheric Refilling and Emitted Natural Abundances) on board the BepiColombo mission of ESA to Mercury to be launched in 2015. ELENA is a Time of Flight (TOF) sensor, based on a novel concept using an ultra-sonic oscillating shutter (Start section), which is operated at frequencies up to 50 kHz; a MCP detector is used as a Stop detector. The scientific objective of ELENA is to detect energetic neutral atoms in the range 10 eV - 5 keV, within 76° FOV, perpendicular to the S/C orbital plane. ELENA will monitor the emission of neutral atoms from the whole surface of Mercury thanks to the spacecraft motion. The major scientific objectives are the interaction between the plasma environment and the planet’s surface, the global particle loss-rate and the remote sensing of the surface properties. In particular, surface release processes are investigated by identifying particles released from the surface, via solar wind-induced ion sputtering (< 1eV - < 100 eV) as well as Hydrogen back-scattered at hundreds eV. MCP absolute detection efficiency for very low energy neutral atoms (E < 30 eV) is a crucial point for this investigation. At the MEFISTO facility of the Physical Institute of the University of Bern (CH), measurements on three different types of MCP (with and without coating) have been performed providing the detection efficiencies in the energy range 10eV - 1keV. Outcomes from such measurements are discussed here.

  7. Lower and upper estimates on the excitation threshold for breathers in discrete nonlinear Schroedinger lattices

    SciTech Connect

    Cuevas, J.; Palmero, F.

    2009-11-15

    We propose analytical lower and upper estimates on the excitation threshold for breathers (in the form of spatially localized and time periodic solutions) in discrete nonlinear Schroedinger (DNLS) lattices with power nonlinearity. The estimation, depending explicitly on the lattice parameters, is derived by a combination of a comparison argument on appropriate lower bounds depending on the frequency of each solution with a simple and justified heuristic argument. The numerical studies verify that the analytical estimates can be of particular usefulness, as a simple analytical detection of the activation energy for breathers in DNLS lattices.

  8. Thresholds in chemical respiratory sensitisation.

    PubMed

    Cochrane, Stella A; Arts, Josje H E; Ehnes, Colin; Hindle, Stuart; Hollnagel, Heli M; Poole, Alan; Suto, Hidenori; Kimber, Ian

    2015-07-01

    There is a continuing interest in determining whether it is possible to identify thresholds for chemical allergy. Here allergic sensitisation of the respiratory tract by chemicals is considered in this context. This is an important occupational health problem, being associated with rhinitis and asthma, and in addition provides toxicologists and risk assessors with a number of challenges. In common with all forms of allergic disease chemical respiratory allergy develops in two phases. In the first (induction) phase exposure to a chemical allergen (by an appropriate route of exposure) causes immunological priming and sensitisation of the respiratory tract. The second (elicitation) phase is triggered if a sensitised subject is exposed subsequently to the same chemical allergen via inhalation. A secondary immune response will be provoked in the respiratory tract resulting in inflammation and the signs and symptoms of a respiratory hypersensitivity reaction. In this article attention has focused on the identification of threshold values during the acquisition of sensitisation. Current mechanistic understanding of allergy is such that it can be assumed that the development of sensitisation (and also the elicitation of an allergic reaction) is a threshold phenomenon; there will be levels of exposure below which sensitisation will not be acquired. That is, all immune responses, including allergic sensitisation, have threshold requirement for the availability of antigen/allergen, below which a response will fail to develop. The issue addressed here is whether there are methods available or clinical/epidemiological data that permit the identification of such thresholds. This document reviews briefly relevant human studies of occupational asthma, and experimental models that have been developed (or are being developed) for the identification and characterisation of chemical respiratory allergens. The main conclusion drawn is that although there is evidence that the

  9. Technology Thresholds for Microgravity: Status and Prospects

    NASA Technical Reports Server (NTRS)

    Noever, D. A.

    1996-01-01

    The technological and economic thresholds for microgravity space research are estimated in materials science and biotechnology. In the 1990s, the improvement of materials processing has been identified as a national scientific priority, particularly for stimulating entrepreneurship. The substantial US investment at stake in these critical technologies includes six broad categories: aerospace, transportation, health care, information, energy, and the environment. Microgravity space research addresses key technologies in each area. The viability of selected space-related industries is critically evaluated and a market share philosophy is developed, namely that incremental improvements in a large markets efficiency is a tangible reward from space-based research.

  10. ICEMAN - Microwave detection of ultra-high energy neutrinos in ice

    NASA Astrophysics Data System (ADS)

    Ralston, John P.; McKay, Douglas W.

    1990-01-01

    A muon from an ultra-high energy neutrino interaction produces an electromagnetic shower of considerable length. Coherent Cerenkov emission at microwave frequencies from the electric-charge imbalance developing in such a shower serves as an efficient signal of the event. The detection of upward-going UHE neutrinos is discussed in the Antarctic ice by detecting this microwave signal with comparatively cheap and simple antennas located on the ice surface. A pilot experiment to measure UHE neutrinos from point sources such as Cygnus X-3 is feasible.

  11. Method, apparatus and system for low-energy beta particle detection

    DOEpatents

    Akers, Douglas W.; Drigert, Mark W.

    2012-09-25

    An apparatus, method, and system relating to radiation detection of low-energy beta particles are disclosed. An embodiment includes a radiation detector with a first scintillator and a second scintillator operably coupled to each other. The first scintillator and the second scintillator are each structured to generate a light pulse responsive to interaction with beta particles. The first scintillator is structured to experience full energy deposition of low-energy beta particles, and permit a higher-energy beta particle to pass therethrough and interact with the second scintillator. The radiation detector further includes a light-to-electrical converter operably coupled to the second scintillator and configured to convert light pulses generated by the first scintillator and the second scintillator into electrical signals. The first scintillator and the second scintillator have at least one mutually different characteristic to enable an electronic system to determine whether a given light pulse is generated in the first scintillator or the second scintillator.

  12. Influence of auditory fatigue on masked pure-tone thresholds

    NASA Technical Reports Server (NTRS)

    Parker, D. E.; Tubbs, R. L.; Johnston, P. A.; Johnston, L. S.

    1976-01-01

    A description is presented of four related experiments involving conditions of 3-kHz low-intensity masking, a replication of experiment I with slight variations, 3-kHz high-intensity masking, and 6-kHz low-intensity masking. The frequencies of the tones which the observers detected were 3 and 6 kHz. The observed change in masked-tone threshold as a function of fatigue is discussed. It is found that masked-tone-detection thresholds remain essentially unchanged following fatigue if the masking-noise intensity is sufficiently great.

  13. Taste preference thresholds for Polycose, maltose, and sucrose in rats.

    PubMed

    Sclafani, A; Nissenbaum, J W

    1987-01-01

    The taste preference thresholds of adult female rats for polysaccharide (Polycose), maltose, and sucrose were compared. The nondeprived animals were given 24-hr two-bottle preference tests (saccharide solution vs. water) and, starting at 0.008%, the saccharide concentration was increased daily. The rats first preferred the Polycose solution to water at 0.01% (0.0001 M), the maltose solution to water at 0.09% (0.0025 M), and the sucrose solution to water at 0.09% (0.0026 M). Thus, on a molar basis the rats' Polycose threshold was 25 to 26 times lower than their maltose and sucrose threshold. It was postulated that the low taste threshold for polysaccharides allows the rat to detect starch which, unlike sugar, is very low in solubility.

  14. Energy requirements for methods improving gas detection by modulating physical properties of resistive gas sensors

    NASA Astrophysics Data System (ADS)

    Trawka, M.; Kotarski, M.

    2016-01-01

    One of the most important disadvantage of resistive gas sensors is their limited gas selectivity. Therefore, various methods modulating their physical properties are used to improve gas detection. These methods are usually limited to temperature modulation or UV light irradiation for the layers exhibiting photocatalytic effect. These methods cause increased energy consumption. In our study we consider how much energy has to be supplied to utilize such methods and what kind of additional information can be gathered. We present experimental results of selected resistive gas sensors, including commercial and prototype constructions, and practical solutions of modulating their physical properties.

  15. Gridless retarding potential analyzer for use in very-low-energy charged particle detection

    NASA Technical Reports Server (NTRS)

    Shyn, T. W.; Sharp, W. E.; Hays, P. B.

    1976-01-01

    The theory of the hyperbolic retarding potential analyzer in the electrostatic mode is developed in detail and verified in the laboratory. A monoenergetic electron beam is used for the laboratory investigation. The analyzer (acronym HARP) has advantages over other conventional electrostatic analyzers; among them are less contact potential influence and high throughput because of the symmetry shape of the analyzer. The most useful application of the HARP is in detecting low-energy charged particles. A sample of low-energy particle data obtained in the earth's ionosphere is given.

  16. Upconversion Nanoparticle-Based Förster Resonance Energy Transfer for Detecting DNA Methylation.

    PubMed

    Kim, Seockjune; Hwang, Sang-Hyun; Im, Su-Gyeong; Lee, Min-Ki; Lee, Chang-Hun; Son, Sang Jun; Oh, Heung-Bum

    2016-01-01

    Aberrant methylation of a crucial CpG island is the main mechanism for the inactivation of CDKN2A in the early stages of carcinogenesis. Therefore, the detection of DNA methylation with high sensitivity and specificity is important, and various detection methods have been developed. Recently, upconversion nanoparticles (UCNPs) have been found to display a high signal-to-noise ratio and no photobleaching, making them useful for diagnostic applications. In this pilot study, we applied UCNPs to the detection of CDKN2A methylation and evaluated the feasibility of this system for use in molecular diagnostics. DNA PCR was performed using biotinylated primers, and the PCR amplicon was then intercalated with SYTOX Orange dye, followed by incubation with streptavidin-conjugated UCNPs. Fluorescence detection of the Förster resonance energy transfer (FRET) of the UCNPs (MS-UC-FRET) was then performed, and the results were compared to those from real-time PCR (RQ-PCR) and pyrosequencing. Detection by MS-UC-FRET was more sensitive than that by either RQ-PCR or pyrosequencing. Our results confirmed the success of our MS-UC-FRET system for detecting DNA methylation and demonstrated the potential application of this system in molecular diagnostics. PMID:27517925

  17. Upconversion Nanoparticle-Based Förster Resonance Energy Transfer for Detecting DNA Methylation

    PubMed Central

    Kim, Seockjune; Hwang, Sang-Hyun; Im, Su-Gyeong; Lee, Min-Ki; Lee, Chang-Hun; Son, Sang Jun; Oh, Heung-Bum

    2016-01-01

    Aberrant methylation of a crucial CpG island is the main mechanism for the inactivation of CDKN2A in the early stages of carcinogenesis. Therefore, the detection of DNA methylation with high sensitivity and specificity is important, and various detection methods have been developed. Recently, upconversion nanoparticles (UCNPs) have been found to display a high signal-to-noise ratio and no photobleaching, making them useful for diagnostic applications. In this pilot study, we applied UCNPs to the detection of CDKN2A methylation and evaluated the feasibility of this system for use in molecular diagnostics. DNA PCR was performed using biotinylated primers, and the PCR amplicon was then intercalated with SYTOX Orange dye, followed by incubation with streptavidin-conjugated UCNPs. Fluorescence detection of the Förster resonance energy transfer (FRET) of the UCNPs (MS-UC-FRET) was then performed, and the results were compared to those from real-time PCR (RQ-PCR) and pyrosequencing. Detection by MS-UC-FRET was more sensitive than that by either RQ-PCR or pyrosequencing. Our results confirmed the success of our MS-UC-FRET system for detecting DNA methylation and demonstrated the potential application of this system in molecular diagnostics. PMID:27517925

  18. An improved modal strain energy method for damage detection in offshore platform structures

    NASA Astrophysics Data System (ADS)

    Li, Yingchao; Wang, Shuqing; Zhang, Min; Zheng, Chunmei

    2016-06-01

    The development of robust damage detection methods for offshore structures is crucial to prevent catastrophes caused by structural failures. In this research, we developed an Improved Modal Strain Energy (IMSE) method for detecting damage in offshore platform structures based on a traditional modal strain energy method (the Stubbs index method). The most significant difference from the Stubbs index method was the application of modal frequencies. The goal was to improve the robustness of the traditional method. To demonstrate the effectiveness and practicality of the proposed IMSE method, both numerical and experimental studies were conducted for different damage scenarios using a jacket platform structure. The results demonstrated the effectiveness of the IMSE method in damage location when only limited, spatially incomplete, and noise-polluted modal data is available. Comparative studies showed that the IMSE index outperformed the Stubbs index and exhibited stronger robustness, confirming the superiority of the proposed approach.

  19. Dual-energy computed tomography for detection of coronary artery disease

    PubMed Central

    Danad, Ibrahim; Ó Hartaigh, Bríain; Min, James K.

    2016-01-01

    Recent technological advances in computed tomography (CT) technology have fulfilled the prerequisites for the cardiac application of dual-energy CT (DECT) imaging. By exploiting the unique characteristics of materials when exposed to two different x-ray energies, DECT holds great promise for the diagnosis and management of coronary artery disease. It allows for the assessment of myocardial perfusion to discern the hemodynamic significance of coronary disease and possesses high accuracy for the detection and characterization of coronary plaques, while facilitating reductions in radiation dose. As such, DECT enabled cardiac CT to advance beyond the mere detection of coronary stenosis expanding its role in the evaluation and management of coronary atherosclerosis. PMID:26549789

  20. Comparasion of Energy Detection in Cognitive Radio over different fading channels

    NASA Astrophysics Data System (ADS)

    Buttar, Simar

    2012-07-01

    With the advance of wireless communications, the problem of bandwidth scarcity has become more prominent. Cognitive radio technology has come out as a way to solve this problem by allowing the unlicensed users to use the licensed bands opportunistically. To sense the existence of licensed users, many spectrum sensing techniques have been devised. In this paper, energy detection and cyclic prefix is used for spectrum sensing.The comparison of ROC curves has been done for various wireless fading channels using squaring and cubingoperation,the improvement has gone as high as up to 0.6 times for AWGN channel and 0.4 times for Rayleigh channel as we go from squaring to cubing operation in an energy detector. Closed form expressions for Probability of detection for AWGN and Rayleigh channels are described.Nakagami fading channel shows worst results .