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1

Threshold detection in pulsed laser ranging  

Microsoft Academic Search

Suzaki and Tachibana (1972, 1973) have developed a method for detecting the arrival time of the return pulse in pulsed laser ranging based on the identification of the time at which the preset threshold level is exceeded by the output of the optical detector. The received optical pulse is considered to be made up of cells of width equal to

R. S. Iyer

1976-01-01

2

Breast Cancer Detection Using Multilevel Thresholding  

E-print Network

This paper presents an algorithm which aims to assist the radiologist in identifying breast cancer at its earlier stages. It combines several image processing techniques like image negative, thresholding and segmentation techniques for detection of tumor in mammograms. The algorithm is verified by using mammograms from Mammographic Image Analysis Society. The results obtained by applying these techniques are described.

Rejani, Y Ireaneus Anna

2009-01-01

3

Threshold detection in pulsed laser ranging  

NASA Technical Reports Server (NTRS)

Suzaki and Tachibana (1972, 1973) have developed a method for detecting the arrival time of the return pulse in pulsed laser ranging based on the identification of the time at which the preset threshold level is exceeded by the output of the optical detector. The received optical pulse is considered to be made up of cells of width equal to the resolution time of the receiver and an equation is derived for P sub j, the probability that the threshold is first exceeded in the j-th cell. Using the density P sub j, expressions are obtained for the mean position of the cell at which threshold occurs and for the standard deviation (rms error) in the detection cell. The present paper maintains that, since the number j is purely an artifice for identifying the cells, its mean and standard deviation are inadequate for characterizing the detection cell and detection errors. It is proposed that if the detection cell is defined as the cell at which P sub j attains a maximum, then the above-cited ambiguity would be eliminated.

Iyer, R. S.

1976-01-01

4

Breast Cancer Detection Using Multilevel Thresholding  

Microsoft Academic Search

This paper presents an algorithm which aims to assist the radiologist in\\u000aidentifying breast cancer at its earlier stages. It combines several image\\u000aprocessing techniques like image negative, thresholding and segmentation\\u000atechniques for detection of tumor in mammograms. The algorithm is verified by\\u000ausing mammograms from Mammographic Image Analysis Society. The results obtained\\u000aby applying these techniques are described.

Y. Ireaneus Anna Rejani; S. Thamarai Selvi

2009-01-01

5

Cryostat for Ultra-low-energy Threshold Germanium Spectrometers  

E-print Network

This paper presents progress on the development of a cryostat intended to improve upon the low-energy threshold (below 0.5 keV) of p-type point contact germanium gamma-ray spectrometers. Ultra-low energy thresholds are important in the detection of low-energy nuclear recoils, an event class relevant to both dark matter direct detection and measurement of coherent neutrino-nucleus scattering. The cryostat design, including a thermal and electrical-field model, is given. A prototype cryostat has been assembled and data acquired to evaluate its vacuum and thermal performance.

Craig E. Aalseth; Ricco M. Bonicalzi; James E. Fast; Todd W. Hossbach; John L. Orrell; Cory T. Overman; Brent A. Vandevender

2012-10-08

6

Cryostat for Ultra-low-energy Threshold Germanium Spectrometers  

SciTech Connect

Abstract: This paper presents progress on the development of a cryostat intended to improve upon the low-energy threshold (below 0.5 keV) of p-type point contact germanium gamma-ray spectrometers. Ultra-low energy thresholds are important in the detection of low-energy nuclear recoils, an event class relevant to both dark matter direct detection and measurement of coherent neutrino-nucleus scattering. The cryostat design, including a thermal and electrical-field model, is presented. A prototype cryostat has been assembled and data acquired to evaluate its vacuum and thermal performance.

Aalseth, Craig E.; Bonicalzi, Ricco; Fast, James E.; Hossbach, Todd W.; Orrell, John L.; Overman, Cory T.; VanDevender, Brent A.

2013-04-01

7

Sputtering Threshold Energies of Heavy Ions  

NASA Technical Reports Server (NTRS)

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.

Mantenieks, Maris A.

1999-01-01

8

Energy Switching Threshold for Climatic Benefits  

NASA Astrophysics Data System (ADS)

Climate change is one of the great challenges facing humanity currently and in the future. Its most severe impacts may still be avoided if efforts are made to transform current energy systems (1). A transition from the global system of high Greenhouse Gas (GHG) emission electricity generation to low GHG emission energy technologies is required to mitigate climate change (2). Natural gas is increasingly seen as a choice for transitions to renewable sources. However, recent researches in energy and climate puzzled about the climate implications of relying more energy on natural gas. On one hand, a shift to natural gas is promoted as climate mitigation because it has lower carbon per unit energy than coal (3). On the other hand, the effect of switching to natural gas on nuclear-power and other renewable energies development may offset benefits from fuel-switching (4). Cheap natural gas is causing both coal plants and nuclear plants to close in the US. The objective of this study is to measure and evaluate the threshold of energy switching for climatic benefits. We hypothesized that the threshold ratio of energy switching for climatic benefits is related to GHGs emission factors of energy technologies, but the relation is not linear. A model was developed to study the fuel switching threshold for greenhouse gas emission reduction, and transition from coal and nuclear electricity generation to natural gas electricity generation was analyzed as a case study. The results showed that: (i) the threshold ratio of multi-energy switching for climatic benefits changes with GHGs emission factors of energy technologies. (ii)The mathematical relation between the threshold ratio of energy switching and GHGs emission factors of energies is a curved surface function. (iii) The analysis of energy switching threshold for climatic benefits can be used for energy and climate policy decision support.

Zhang, X.; Cao, L.; Caldeira, K.

2013-12-01

9

Experimental and environmental factors affect spurious detection of ecological thresholds  

USGS Publications Warehouse

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 (?) 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.

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

2012-01-01

10

Retronasal smell and detection thresholds of iron and copper salts  

Microsoft Academic Search

Iron and copper salts, when placed in the mouth, may give rise to odorous compounds which complicate their functioning as chemical stimuli. The contribution of retronasal smell to perception of these metal salts at threshold has not been determined. Detection thresholds of the sulfate and chloride salts of ferrous iron and copper, and sodium chloride (as a control) were determined

Effie M. Epke; Harry T. Lawless

2007-01-01

11

THRESHOLD ENERGY DETERMINATION IN THICK SEMICONDUCTOR SAMPLES (*)  

E-print Network

des électrons d'énergies variées en utilisant des mesures de capacité-tension sur des diodes Schottky displacement 03C3 by energetic electrons, versus penetration depth x, is given. Curves of 03C3(x) computed for various values of the threshold energy for displacement are given in the case of silicon. The profiles

Paris-Sud XI, Université de

12

IMAGE THRESHOLDING FOR LANDSLIDE DETECTION BY GENETIC PROGRAMMING  

E-print Network

IMAGE THRESHOLDING FOR LANDSLIDE DETECTION BY GENETIC PROGRAMMING Paul L. Rosin Department of landslides and their active sectors in change detected multitem- poral aerial images. 1 Introduction Detecting landslides and monitoring their activity is of great relevance for natural hazard assessment

Martin, Ralph R.

13

Threshold detection in generalized non-additive signals and noise  

SciTech Connect

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.

Middleton, D., LLNL

1997-12-22

14

Approximate thresholds of interval mapping tests for QTL detection.  

PubMed

A general method is proposed for calculating approximate thresholds of interval mapping tests for quantitative trait loci (QTL) detection. Simulation results show that this method, when applied to backcross and F2 populations, gives good approximations and is useful for any situation. Programs which calculate these thresholds for backcross, recombinant inbreds and F2 for any given level and any chromosome with any given distribution of codominant markers were written in Fortran 77 and are available under request. The approach presented here could be used to obtain, after suitable calculations, thresholds for most segregating populations used in QTL mapping experiments. PMID:8001790

Reba, A; Goffinet, B; Mangin, B

1994-09-01

15

Color-detection thresholds in rhesus macaque monkeys and humans.  

PubMed

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

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

16

Neutron threshold activation detectors (TAD) for the detection of fissions  

NASA Astrophysics Data System (ADS)

Prompt fission neutrons are one of the strongest signatures of the fission process. Depending on the fission inducing radiation, their average number ranges from 2.5 to 4 neutrons per fission. They are more energetic and abundant, by about 2 orders of magnitude, than the delayed neutrons (?3 vs. ?0.01) that are commonly used as indicators for the presence of fissionable materials. The detection of fission prompt neutrons, however, has to be done in the presence of extremely intense probing radiation that stimulated them. During irradiation, the fission stimulation radiation, X-rays or neutrons, overwhelms the neutron detectors and temporarily incapacitate them. Consequently, by the time the detectors recover from the source radiation, fission prompt neutrons are no longer emitted. In order to measure the prompt fission signatures under these circumstances, special measures are usually taken with the detectors such as heavy shielding with collimation, use of inefficient geometries, high pulse height bias and gamma-neutron separation via pulse-shape discrimination with an appropriate organic scintillator. These attempts to shield the detector from the flash of radiation result in a major loss of sensitivity. It can lead to a complete inability to detect the fission prompt neutrons. In order to overcome the blinding induced background from the source radiation, the detection of prompt fission neutrons needs to occur long after the fission event and after the detector has fully recovered from the source overload. A new approach to achieve this is to detect the delayed activation induced by the fission neutrons. The approach demonstrates a good sensitivity in adverse overload situations (gamma and neutron "flash") where fission prompt neutrons could normally not be detected. The new approach achieves the required temporal separation between the detection of prompt neutrons and the detector overload by the neutron activation of the detector material. The technique, called Threshold Activation Detection (TAD), is to utilize appropriate substances that can be selectively activated by the fission neutrons and not by the source radiation and then measure the radioactively decaying activation products (typically beta and gamma rays) well after the source pulse. The activation material should possess certain properties: a suitable half-life of the order of seconds; an energy threshold below which the numerous source neutrons will not activate it (e.g., 3 MeV); easily detectable activation products (typically >1 MeV beta and gamma rays) and have a usable cross-section for the selected reaction. Ideally the substance would be a part of the scintillator. There are several good material candidates for the TAD, including fluorine, which is a major constituent of available scintillators such as BaF 2, CaF 2 and hydrogen free liquid fluorocarbon. Thus the fluorine activation products, in particular the beta particles, can be measured with a very high efficiency in the detector. The principles, applications and experimental results obtained with the fluorine based TAD are discussed.

Gozani, Tsahi; Stevenson, John; King, Michael J.

2011-10-01

17

Detection thresholds for 60 Hz electric fields by nonhuman primates  

SciTech Connect

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.

Orr, J.L.; Rogers, W.R.; Smith, H.D. [Southwest Research Inst., San Antonio, TX (United States). Dept. of Biosciences and Bioengineering

1995-12-31

18

Orion MPCV Touchdown Detection Threshold Development and Testing  

NASA Technical Reports Server (NTRS)

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 (EFT-1) mission in the second half of 2014.

Daum, Jared; Gay, Robert

2013-01-01

19

Modelling detection thresholds for sounds repeated at different delays.  

PubMed

Detection thresholds for pairs or multiple copies of sounds are better than those for a single sound, an observation commonly interpreted as indicating temporal integration by the auditory system. Detection thresholds for pairs of brief tones depend on the delay between the tones (if short) and on frequency, suggesting frequency-dependent temporal overlap of auditory-filter responses elicited by the two successive stimuli (Krumbholz and Wiegrebe, 1998). The model presented by Krumbholz and Wiegrebe did not account for all aspects of their data, despite its complexity. This study shows that a simple probabilistic model based on Neubauer and Heil (2008) predicts the increase in threshold for short temporal delays as well as the asymptotic behaviour towards longer delays. The model entails (i) a 4th-order gammatone filter with a brief impulse response and thus broad bandwidth (shorter and broader than those of a filter normally assumed), (ii) the formation of stochastic 'spikes' or 'events' whose probability of occurrence is proportional to the filter output (half-wave rectified fine-structure or amplitude envelope), raised to a power of 3, and (iii) probability summation. The same model with the same front-end filter also predicts thresholds for pairs of clicks presented in band-reject noise, measured by Hall and Lummis (1973). The model accurately predicts the magnitudes and the decay of the alternating increase and decrease of thresholds as the delay between the click varies, the small effects of click polarity, and the dependence of thresholds for pairs of clicks with unequal intensities on their temporal order. Finally, we show that this model also correctly predicts the decrease in threshold with increasing number of temporally separated brief sounds, reported in several studies. While the latter data do not constrain the characteristics of the front-end filter, they do confirm the exponent of 3 in the model. Our paper stresses the viability of the model and raises the possibility that the bandwidths of filters estimated with psychophysical techniques may depend more strongly on the experimental paradigms and stimuli than hitherto thought. PMID:23268356

Heil, Peter; Verhey, Jesko L; Zoefel, Benedikt

2013-02-01

20

Accuracy threshold for concatenated error detection in one dimension  

E-print Network

Estimates of the quantum accuracy threshold often tacitly assume that it is possible to interact arbitrary pairs of qubits in a quantum computer with a failure rate that is independent of the distance between them. None of the many physical systems that are candidates for quantum computing possess this property. Here we study the performance of a concatenated error-detection code in a system that permits only nearest-neighbor interactions in one dimension. We make use of a new message-passing scheme that maximizes the number of errors that can be reliably corrected by the code. Our numerical results indicate that arbitrarily accurate universal quantum computation is possible if the probability of failure of each elementary physical operation is below approximately 10^{-5}. This threshold is three orders of magnitude lower than the highest known.

A. M. Stephens; Z. W. E. Evans

2009-07-29

21

Threshold energy effect on avalanche breakdown voltage in semiconductor junctions  

Microsoft Academic Search

The band bending for avalanche breakdown in semiconductor junctions and its temperature dependence are predicted taking account of threshold energy effects on the ionization process in semiconductors. Where experimental results exist, the theoretical predictions and experimental results are in excellent agreement. In the high electric field region inclusion of both bulk and boundary threshold energy effects is essential. The predictions

Y. Okuto; C. R. Crowell

1975-01-01

22

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

NASA Technical Reports Server (NTRS)

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 than an order of magnitude lower than the future GPM sensors, (2) the cloud structure macrophysics influences the thresholds of detection for passive channels, (3) the snowflake microphysics plays a large role in the detection threshold for active and passive instruments, (4) with reasonable assumptions, the passive 166 GHz channel has detection threshold values comparable to the GPM DPR Ku and Ka band radars with 0.05 g m-3 detected at the surface, or an 0.5-1 mm hr-l melted snow rate (equivalent to 0.5-2 cm hr-l solid fluffy snowflake rate).

Jackson, Gail

2012-01-01

23

Orion MPCV Touchdown Detection Threshold Development and Testing  

NASA Technical Reports Server (NTRS)

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 was determined. The lever arm calculation, which removes the centripetal acceleration caused by vehicle rotation, requires that the vehicle angular acceleration be derived from vehicle body rates, necessitating the addition of a 2nd order filter to smooth the data. It was determined that using 200 Hz data directly from the vehicle IMU outperforms the 40 Hz FSW data rate. Data persistence counter values and acceleration thresholds were balanced in order to meet desired safety and performance. The algorithm proved to exhibit ample safety margin against early detection while under parachutes, and adequate performance upon vehicle splashdown. Fall times from algorithm initiation were also studied, and a backup timer length was chosen to provide a large safety margin, yet still trigger detection before CMUS inflation. This timer serves as a backup to the primary acceleration detection method. Additionally, these parameters were tested for safety on actual flight test data, demonstrating expected safety margins.

Daum, Jared; Gay, Robert

2013-01-01

24

Ultrasonic flaw detection using threshold modified S-transform.  

PubMed

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. PMID:24120270

Benammar, Abdessalem; Drai, Redouane; Guessoum, Abderrezak

2014-02-01

25

Spin-system dynamics and fault detection in threshold networks  

SciTech Connect

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.

Kirkland, Steve; Severini, Simone [Hamilton Institute, National University of Ireland, Maynooth County Kildare (Ireland); Department of Physics and Astronomy, University College London, WC1E 6BT London (United Kingdom)

2011-01-15

26

Sub-Threshold Design: The Challenges of Minimizing Circuit Energy  

E-print Network

, especially for circuits with parallel leakage paths [11]. A 0.18µm CMOS FFT processor uses circuitsSub-Threshold Design: The Challenges of Minimizing Circuit Energy B. H. Calhoun1 , A. Wang2 , N identify the key challenges that oppose sub- threshold circuit design and describe fabricated chips

Calhoun, Benton H.

27

Dynamic multiple thresholding breast boundary detection algorithm for mammograms  

SciTech Connect

Purpose: Automated detection of breast boundary is one of the fundamental steps for computer-aided analysis of mammograms. In this study, the authors developed a new dynamic multiple thresholding based breast boundary (MTBB) detection method for digitized mammograms. Methods: A large data set of 716 screen-film mammograms (442 CC view and 274 MLO view) obtained from consecutive cases of an Institutional Review Board approved project were used. An experienced breast radiologist manually traced the breast boundary on each digitized image using a graphical interface to provide a reference standard. The initial breast boundary (MTBB-Initial) was obtained by dynamically adapting the threshold to the gray level range in local regions of the breast periphery. The initial breast boundary was then refined by using gradient information from horizontal and vertical Sobel filtering to obtain the final breast boundary (MTBB-Final). The accuracy of the breast boundary detection algorithm was evaluated by comparison with the reference standard using three performance metrics: The Hausdorff distance (HDist), the average minimum Euclidean distance (AMinDist), and the area overlap measure (AOM). Results: In comparison with the authors' previously developed gradient-based breast boundary (GBB) algorithm, it was found that 68%, 85%, and 94% of images had HDist errors less than 6 pixels (4.8 mm) for GBB, MTBB-Initial, and MTBB-Final, respectively. 89%, 90%, and 96% of images had AMinDist errors less than 1.5 pixels (1.2 mm) for GBB, MTBB-Initial, and MTBB-Final, respectively. 96%, 98%, and 99% of images had AOM values larger than 0.9 for GBB, MTBB-Initial, and MTBB-Final, respectively. The improvement by the MTBB-Final method was statistically significant for all the evaluation measures by the Wilcoxon signed rank test (p<0.0001). Conclusions: The MTBB approach that combined dynamic multiple thresholding and gradient information provided better performance than the breast boundary detection algorithm that mainly used gradient information.

Wu, Yi-Ta; Zhou Chuan; Chan, Heang-Ping; Paramagul, Chintana; Hadjiiski, Lubomir M.; Daly, Caroline Plowden; Douglas, Julie A.; Zhang Yiheng; Sahiner, Berkman; Shi Jiazheng; Wei Jun [Department of Radiology, University of Michigan, Ann Arbor, Michigan 48109 (United States); Department of Human Genetics, University of Michigan, Ann Arbor, Michigan 48109 (United States); Department of Radiology, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2010-01-15

28

Sparse representation based multi-threshold segmentation for hyperspectral target detection  

NASA Astrophysics Data System (ADS)

A sparse representation based multi-threshold segmentation (SRMTS) algorithm for target detection in hyperspectral images is proposed. Benefiting from the sparse representation, the high-dimensional spectral data can be characterized into a series of sparse feature vectors which has only a few nonzero coefficients. Through setting an appropriate threshold, the noise removed sparse spectral vectors are divided into two subspaces in the sparse domain consistent with the sample spectrum to separate the target from the background. Then a correlation and a vector 1-norm are calculated respectively in the subspaces. The sparse characteristic of the target is used to ext ract the target with a multi -threshold method. Unlike the conventional hyperspectral dimensionality reduction methods used in target detection algorithms, like Principal Components Analysis (PCA) and Maximum Noise Fraction (MNF), this algorithm maintains the spectral characteristics while removing the noise due to the sparse representation. In the experiments, an orthogonal wavelet sparse base is used to sparse the spectral information and a best contraction threshold to remove the hyperspectral image noise according to the noise estimation of the test images. Compared with co mmon algorithms, such as Adaptive Cosine Estimator (ACE), Constrained Energy Minimizat ion (CEM) and the noise removed MNF-CEM algorithm, the proposed algorithm demonstrates higher detection rates and robustness via the ROC curves.

Feng, Wei-yi; Chen, Qian; Miao, Zhuang; He, Wei-ji; Gu, Guo-hua; Zhuang, Jia-yan

2013-08-01

29

Signal Detection Theory Applied to Helicopter Transmission Diagnostic Thresholds  

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

30

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

NASA Technical Reports Server (NTRS)

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.

Webb, W. E.

1975-01-01

31

The detection threshold, noise and stochastic resonance in the Fitzhugh-Nagumo neuron model  

Microsoft Academic Search

In a class of experiments in sensory biology sub- or slightly supra-threshold stimuli are applied at the periphery while making action potential recordings at a higher level in the nervous system. In many cases the records are largely noise but with a small coherence with the stimulus. The detection threshold for increasing stimulus intensity is frequently measured, and this threshold

Xing Pei; Ken Bachmann; Frank Moss

1995-01-01

32

An Algorithm for 353 Odor Detection Thresholds in Humans  

PubMed Central

One hundred and ninety three odor detection thresholds, ODTs, obtained by Nagata using the Japanese triangular bag method can be correlated as log (1/ODT) by a linear equation with R2 = 0.748 and a standard deviation, SD, of 0.830 log units; the latter may be compared with our estimate of 0.66 log units for the self-consistency of Nagata's data. Aldehydes, acids, unsaturated esters, and mercaptans were included in the equation through indicator variables that took into account the higher potency of these compounds. The ODTs obtained by Cometto-Muiz and Cain, by Cometto-Muiz and Abraham, and by Hellman and Small could be put on the same scale as those of Nagata to yield a linear equation for 353 ODTs with R2 = 0.759 and SD = 0.819 log units. The compound descriptors are available for several thousand compounds, and can be calculated from structure, so that further ODT values on the Nagata scale can be predicted for a host of volatile or semivolatile compounds. PMID:21976369

Snchez-Moreno, Ricardo; Cometto-Muiz, J. Enrique; Cain, William S.

2012-01-01

33

Pooling optimal combinations of energy thresholds in spectroscopic CT  

NASA Astrophysics Data System (ADS)

Photon counting detectors used in spectroscopic CT are often based on small pixels and therefore offer only limited space to include energy discriminators and their associated counters in each pixel cell. For this reason, it is important to make efficient use of the available energy discriminators in order to achieve an optimized material contrast at a radiation dose as low as possible. Unfortunately, the complexity of evaluating every possible combination of energy thresholds, given a fixed number of counters, rapidly increases with the resolution at which this search is performed, and makes brute-force approaches to this problem infeasible. In this work, we introduce methods from machine learning, in particular sparse regression, to perform a feature selection to determine optimal combinations of energy thresholds. We will demonstrate how methods enforcing row-sparsity on a linear regression's coefficient matrix can be applied to the multiple response problem in spectroscopic CT, i.e. the case in which a single set of energy thresholds is sought to simultaneously retrieve concentrations pertaining to a multitude of materials in an optimal way. These methods are applied to CT images experimentally obtained with a Medipix3RX detector operated in charge summing mode and with a CdTe sensor at a pixel pitch of 110?m. We show that the least absolute shrinkage and selection operator (lasso), generalized to the multiple response case, chooses four out of 20 possible threshold positions that allow discriminating PMMA, iodine and gadolinium in a contrast agent phantom at a higher accuracy than with equally spaced thresholds. Finally, we illustrate why it might be unwise to use a higher number of energy thresholds than absolutely necessary.

Koenig, Thomas; Zuber, Marcus; Hamann, Elias; Runz, Armin; Fiederle, Michael; Baumbach, Tilo

2014-03-01

34

Thresholds for detection and awareness of masked facial stimuli.  

PubMed

It has been suggested that perception without awareness can be demonstrated by a dissociation between performance in objective (forced-choice) and subjective (yes-no) tasks, and such dissociations have been reported both for simple stimuli and more complex ones including faces. However, signal detection theory (SDT) indicates that the subjective measures used to assess awareness in such studies can be affected by response bias, which could account for the observed dissociation, and this was confirmed by Balsdon and Azzopardi (2015) using simple visual targets. However, this finding may not apply to all types of stimulus, as the detectability of complex targets such as faces is known to be affected by their configuration as well as by their stimulus energy. We tested this with a comparison of forced-choice and yes-no detection of facial stimuli depicting happy or angry or fearful expressions using a backward masking paradigm, and using SDT methods including correcting for unequal variances in the underlying signal distributions, to measure sensitivity independently of response criterion in 12 normal observers. In 47 out 48 comparisons there was no significant difference between sensitivity (da) in the two tasks: hence, across the range of expressions tested it appears that the configuration of complex stimuli does not enhance detectability independently of awareness. The results imply that, on the basis of psychophysical experiments in normal observers, there is no reason to postulate that performance and awareness are mediated by separate processes. PMID:25307748

Heeks, Frances; Azzopardi, Paul

2015-03-01

35

Displacement threshold and Frenkel pair formation energy in ionic systems  

NASA Astrophysics Data System (ADS)

Displacement threshold energies (Ed) and Frenkel pair formation energies (EFp) are investigated in detail by molecular dynamics computer simulation for three different ionic systems with the same crystal structure, MgO, SrO and NaCl in order to see if there is a functional relationship between them. It is found that there are wide variations in the values of Ed depending on the direction in which energy is imparted to a static atom in the lattice. Large values of Ed are found along the major crystallographic directions and lower values elsewhere. Typically these thresholds are between 5 and 9 times bigger than the Frenkel pair formation energies EFp with no observable dependence on mass or ion charge. The differences in the interaction potentials also means that for any given direction, there is only limited correlation between values of Ed in the different systems studied and no quantifiable relationship with EFp.

Kittiratanawasin, L.; Smith, Roger; Uberuaga, B. P.; Sickafus, Kurt

2010-10-01

36

Size and Energy of Threshold Circuits Computing Mod Functions  

NASA Astrophysics Data System (ADS)

Let C be a threshold logic circuit computing a Boolean function MOD_m: \\{ 0, 1\\}^n rightarrow \\{0, 1\\}, where n ? 1 and m ? 2. Then C outputs 0 if the number of 1s in an input x ? {0, 1} n to C is a multiple of m and, otherwise, C outputs 1. The function MOD2 is the so-called PARITY function, and MOD n + 1 is the OR function. Let s be the size of the circuit C, that is, C consists of s threshold gates, and let e be the energy complexity of C, that is, at most e gates in C output 1 for any input x ? { 0, 1} n . In the paper, we prove that a very simple inequality n/(m - 1) ? s e holds for every circuit C computing MOD m . The inequality implies that there is a tradeoff between the size s and energy complexity e of threshold circuits computing MOD m , and yields a lower bound e = ?((logn - logm)/loglogn) on e if s = O(polylog(n)). We actually obtain a general result on the so-called generalized mod function, from which the result on the ordinary mod function MOD m immediately follows. Our results on threshold circuits can be extended to a more general class of circuits, called unate circuits.

Uchizawa, Kei; Nishizeki, Takao; Takimoto, Eiji

37

Age-related changes in neural gap detection thresholds in the rat auditory cortex.  

PubMed

The ability of the auditory system to resolve sound temporal information is crucial for the understanding of human speech and other species-specific communications. Gap detection threshold, i.e. the ability to detect the shortest duration of a silent interval in a sound, is commonly used to study the auditory temporal resolution. Behavioral studies in humans and rats have shown that normal developing infants have higher gap detection thresholds than adults; however, the underlying neural mechanism is not fully understood. In the present study, we determined and compared the neural gap detection thresholds in the primary auditory cortex of three age groups of rats: the juvenile group (postnatal day 20-30), adult group I (8-10weeks), and adult group II (28-30weeks). We found age-related changes in auditory temporal acuity in the auditory cortex, i.e. the proportion of cortical units with short neural gap detection thresholds (<5ms) was much lower in juvenile groups compared with that in both adult groups at a constant sound level, and no significant differences in neural gap detection thresholds were found between the two adult groups. In addition, units in the auditory cortex of each group generally showed better gap detection thresholds at higher sound levels than at lower sound levels, exhibiting a level-dependent temporal acuity. These results provided evidence for neural correlates of age-related changes in behavioral gap detection ability during postnatal hearing development. PMID:25388865

Zhao, Yin; Xu, Xiaoxiao; He, Juan; Xu, Jinghong; Zhang, Jiping

2014-11-12

38

Setting objective thresholds for rare event detection in flow cytometry.  

PubMed

The accurate identification of rare antigen-specific cytokine positive cells from peripheral blood mononuclear cells (PBMC) after antigenic stimulation in an intracellular staining (ICS) flow cytometry assay is challenging, as cytokine positive events may be fairly diffusely distributed and lack an obvious separation from the negative population. Traditionally, the approach by flow operators has been to manually set a positivity threshold to partition events into cytokine-positive and cytokine-negative. This approach suffers from subjectivity and inconsistency across different flow operators. The use of statistical clustering methods does not remove the need to find an objective threshold between between positive and negative events since consistent identification of rare event subsets is highly challenging for automated algorithms, especially when there is distributional overlap between the positive and negative events ("smear"). We present a new approach, based on the F? measure, that is similar to manual thresholding in providing a hard cutoff, but has the advantage of being determined objectively. The performance of this algorithm is compared with results obtained by expert visual gating. Several ICS data sets from the External Quality Assurance Program Oversight Laboratory (EQAPOL) proficiency program were used to make the comparisons. We first show that visually determined thresholds are difficult to reproduce and pose a problem when comparing results across operators or laboratories, as well as problems that occur with the use of commonly employed clustering algorithms. In contrast, a single parameterization for the F? method performs consistently across different centers, samples, and instruments because it optimizes the precision/recall tradeoff by using both negative and positive controls. PMID:24727143

Richards, Adam J; Staats, Janet; Enzor, Jennifer; McKinnon, Katherine; Frelinger, Jacob; Denny, Thomas N; Weinhold, Kent J; Chan, Cliburn

2014-07-01

39

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

NASA Technical Reports Server (NTRS)

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 surface of 0.25 g / cubic m 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 results rely 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. Sensitivity analyses were performed to better ascertain the relationships between multifrequency microwave and millimeter-wave sensor observations and the falling snow/underlying field of view. In addition, thresholds of detection for various sensor channel configurations, snow event system characteristics, snowflake particle assumptions, and surface types were studied. Results will be presented for active radar at Ku, Ka, and W-band and for passive radiometer channels from 10 to 183 GHz.

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

2012-01-01

40

Determining the detection thresholds for harbor porpoise clicks of autonomous data loggers, the Timing Porpoise Detectors.  

PubMed

Timing Porpoise Detectors (T-PODs, Chelonia Ltd.) are autonomous passive acoustic devices for monitoring odontocetes. They register the time of occurrence and duration of high frequency pulsed sounds as possible odontocetes echolocation clicks. Because of evolution, five T-POD versions exist. Although the manufacturer replaced those by a digital successor, the C-POD, T-PODs are still used, and data from many field studies exist. Characterizing the acoustic properties of T-PODs enables the interpretation of data obtained with different devices. Here, the detection thresholds of different T-POD versions for harbor porpoise clicks were determined. While thresholds among devices were quite variable in the first T-POD generations, they became more standardized in newer versions. Furthermore, the influence of user-controlled settings on the threshold was investigated. From version 3 on, the detection threshold was found to be easily adjustable with version-dependent setting options "minimum intensity" and "sensitivity," enabling the presetting of standard thresholds. In version 4, the setting "click bandwidth" had a strong influence on the detection threshold, while "selectivity" in version 3 and "noise adaptation = ON" or "OFF" in version 4 hardly influenced thresholds obtained in the tank tests. Nevertheless, the latter setting may influence thresholds in a complex acoustic environment like the sea. PMID:23968043

Verfu, Ursula K; Dhne, Michael; Gallus, Anja; Jabbusch, Martin; Benke, Harald

2013-09-01

41

Mass analyzed threshold ionization detected infrared spectroscopy: isomerization activity of the phenol-Ar cluster near the ionization threshold.  

PubMed

The structure of the phenol-argon cluster (PhOH-Ar) in high-n Rydberg states is investigated by the newly developed technique of mass analyzed threshold ionization detected infrared (MATI-IR) spectroscopy. This method selectively measures IR spectra of molecular clusters in very high-n Rydberg states (n > 100) utilized in zero kinetic energy (ZEKE) photoelectron and MATI spectroscopy, whose ionic cores are essentially the same as the corresponding bare cation. The MATI-IR spectrum exhibits only the free OH stretching vibration (?) when the ?-bound cluster of the neutral ground electronic state (S0) is resonantly excited via the S1 origin to Rydberg states converging to its adiabatic ionization energy level, IE0(?). When Rydberg states converging to vibrationally excited levels of the local ?-bound minimum are prepared, in addition to ? also the hydrogen-bonded OH stretching vibration (?) of the H-bonded global minimum is observed in the MATI-IR spectra, even for vibrational excitation of only 14 cm(-1) above IE0(?). These results show that the ?? H site switching reaction of the Ar ligand from the aromatic ring to the OH group proceeds only from vibrationally excited states in the ?-bound cation core with a small barrier of less than 14 cm(-1) from IE0(?). On the other hand, directly photoionized PhOH(+)-Ar shows both ? and ? in the IR spectra, even when it is just ionized to IE0(?). This result implies that the ionization-induced ?? H site switching occurs without excess energy in the H-bound or ?-bound cations, in contrast to very high-n Rydberg states converging to levels of the ?-bound cation. The different efficiencies of the site switching for the Rydberg ion core and the bare ion and the mechanism for the ?? H site switching are interpreted by direct ionization from the ?-bound to the H-bound structures in addition to the conventional vertical ionization and transitions to high-n Rydberg states. PMID:25491162

Miyazaki, Mitsuhiko; Yoshikawa, Shunpei; Michels, Franois; Misawa, Kentaro; Ishiuchi, Shun-Ichi; Sakai, Makoto; Dopfer, Otto; Mller-Dethlefs, Klaus; Fujii, Masaaki

2015-01-28

42

Non-Threshold based Event Detection for 3D Environment Monitoring in Sensor Networks  

E-print Network

are monitored in a three dimensional (3D) space of underground tunnels in the mine. Several event-detection- 1 - Non-Threshold based Event Detection for 3D Environment Monitoring in Sensor Networks Mo Li and Technology {limo, liu, leichen}@cs.ust.hk ABSTRACT Event detection is a crucial task for wireless sensor net

Liu, Yunhao

43

Detecting modulated signals in modulated noise: (II) neural thresholds in the songbird forebrain  

Microsoft Academic Search

Sounds in the real world fluctuate in amplitude. The vertebrate auditory system exploits patterns of amplitude fluctuations to improve signal detection in noise. One experimental paradigm demonstrating these general effects has been used in psychophysical studies of 'comodulation detection difference' (CDD). The CDD effect refers to the fact that thresholds for detecting a modulated, narrowband noise signal are lower when

Mark A. Bee; Michael Buschermhle; Georg M. Klump

2007-01-01

44

Behaviorally measured audiograms and gap detection thresholds in CBA\\/CaJ mice  

Microsoft Academic Search

Tone detection and temporal gap detection thresholds were determined in CBA\\/CaJ mice using a Go\\/No-go procedure and the psychophysical\\u000a method of constant stimuli. In the first experiment, audiograms were constructed for five CBA\\/CaJ mice. Thresholds were obtained\\u000a for eight pure tones ranging in frequency from 1 to 42kHz. Audiograms showed peak sensitivity between 8 and 24kHz, with\\u000a higher thresholds at

Kelly E. Radziwon; Kristie M. June; Daniel J. Stolzberg; Matthew A. Xu-Friedman; Richard J. Salvi; Micheal L. Dent

2009-01-01

45

Effect of four different step detection thresholds on nonmotorized treadmill sprint measurement.  

PubMed

The purpose of this study was to investigate the effect of 4 different step detection thresholds (10, 15, 20, and 30% body mass [BM]) on the kinetics and kinematics of a youth population sprinting on a Woodway nonmotorized treadmill (NMT). A total of 16 male youth athletes sprinted 30 m from a split start position. Of the 15 variables measured, significant differences (p ? 0.05) were found in the measurement of 5 kinematic (step length, vertical displacement, contact time, eccentric, and concentric time) and 2 kinetic (vertical and leg stiffness) variables between the 10 vs. 20 and 30% BM step detection thresholds. Contact time was also significantly different (12%) between 15 vs. 30% BM step detection thresholds. In terms of reliability, the 15 and 30% BM step detection thresholds were found the most stable across all variables (average coefficient of variation ?6.0%). Given this information, a step detection threshold of 15% BM is recommended for quantifying kinematic and kinetic variables on a NMT, as this threshold seems to account for signal variability appropriately without compromising reliability. PMID:25250860

Cronin, John B; Rumpf, Michael C

2014-10-01

46

The effect of four different step detection thresholds on non-motorized treadmill sprint measurement.  

PubMed

The purpose of this study was to investigate the effect of four different step detection thresholds (10, 15, 20, and 30% body mass - BM) on the kinetics and kinematics of a youth population sprinting on a Woodway non-motorized treadmill (NMT). A total of 16 male youth athletes sprinted 30 meters from a split start position. Of the 15 variables measured, significant differences (p < 0.05) were found in the measurement of five kinematic (step length, vertical displacement, contact time, eccentric and concentric time) and two kinetic (vertical and leg stiffness) variables between the 10 versus 20 and/or 30% BM step detection thresholds. Contact time was also significantly different (12%) between 15 vs. 30% BM step detection thresholds. In terms of reliability, the 15 and 30 % BM step detection thresholds were found the most stable across all variables (average coefficient of variation ?6.0 %). Given this information, a step detection threshold of 15% BM is recommended for quantifying kinematic and kinetic variables on a NMT, as this threshold seems to account for signal variability appropriately without compromising reliability. PMID:24796983

Cronin, John B; Rumpf, Michael

2014-05-01

47

Pressure Systems Stored-Energy Threshold Risk Analysis  

SciTech Connect

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

Paulsen, Samuel S.

2009-08-25

48

Dynamo threshold detection in the von Krmn sodium experiment  

NASA Astrophysics Data System (ADS)

Predicting dynamo self-generation in liquid metal experiments has been an ongoing question for many years. In contrast to simple dynamical systems for which reliable techniques have been developed, the ability to predict the dynamo capacity of a flow and the estimate of the corresponding critical value of the magnetic Reynolds number (the control parameter of the instability) has been elusive, partly due to the high level of turbulent fluctuations of flows in such experiments (with kinetic Reynolds numbers in excess of 106). We address these issues here, using the von Krmn sodium experiment and studying its response to an externally applied magnetic field. We first show that a dynamo threshold can be estimated from analysis related to critical slowing down and susceptibility divergence, in configurations for which dynamo action is indeed observed. These approaches are then applied to flow configurations that have failed to self-generate magnetic fields within operational limits, and we quantify the dynamo capacity of these configurations.

Miralles, Sophie; Bonnefoy, Nicolas; Bourgoin, Mickael; Odier, Philippe; Pinton, Jean-Franois; Plihon, Nicolas; Verhille, Gautier; Boisson, Jean; Daviaud, Franois; Dubrulle, Brengre

2013-07-01

49

Long-term deficits in motion detection thresholds and spike count variability after unilateral vestibular lesion.  

PubMed

The vestibular system operates in a push-pull fashion using signals from both labyrinths and an intricate bilateral organization. Unilateral vestibular lesions cause well-characterized motor deficits that are partially compensated over time and whose neural correlates have been traced in the mean response modulation of vestibular nuclei cells. Here we compare both response gains and neural detection thresholds of vestibular nuclei and semicircular canal afferent neurons in intact vs. unilateral-lesioned macaques using three-dimensional rotation and translation stimuli. We found increased stimulus-driven spike count variability and detection thresholds in semicircular canal afferents, although mean responses were unchanged, after contralateral labyrinth lesion. Analysis of trial-by-trial spike count correlations of a limited number of simultaneously recorded pairs of canal afferents suggests increased noise correlations after lesion. In addition, we also found persistent, chronic deficits in rotation detection thresholds of vestibular nuclei neurons, which were larger in the ipsilesional than the contralesional brain stem. These deficits, which persisted several months after lesion, were due to lower rotational response gains, whereas spike count variability was similar in intact and lesioned animals. In contrast to persistent deficits in rotation threshold, translation detection thresholds were not different from those in intact animals. These findings suggest that, after compensation, a single labyrinth is sufficient to recover motion sensitivity and normal thresholds for the otolith, but not the semicircular canal, system. PMID:24848470

Yu, Xiong-Jie; Thomassen, Jakob S; Dickman, J David; Newlands, Shawn D; Angelaki, Dora E

2014-08-15

50

A preliminary evaluation of a speed threshold incident detection algorithm  

E-print Network

detection algorithm. San Antonio's new traffic management center, TransGuide, uses a new speed based algorithm, The TXDOT (Texas Department of Transportation) Speed algorithm. This research compares the TXDOT Speed algorithm with California algorithm #8...

Kolb, Stephanie Lang

1996-01-01

51

Thresholds for human detection of patient setup errors in digitally reconstructed portal images of prostate fields  

Microsoft Academic Search

Purpose: Computer-assisted methods to analyze electronic portal images for the presence of treatment setup errors should be studied in controlled experiments before use in the clinical setting. Validation experiments using images that contain known errors usually report the smallest errors that can be detected by the image analysis algorithm. This paper offers human error-detection thresholds as one benchmark for evaluating

Brooke L Phillips; Michael R Jiroutek; Gregg Tracton; Michelle Elfervig; Keith E Muller; Edward L Chaney

2002-01-01

52

Dynamo threshold detection in the von Krmn sodium experiment.  

PubMed

Predicting dynamo self-generation in liquid metal experiments has been an ongoing question for many years. In contrast to simple dynamical systems for which reliable techniques have been developed, the ability to predict the dynamo capacity of a flow and the estimate of the corresponding critical value of the magnetic Reynolds number (the control parameter of the instability) has been elusive, partly due to the high level of turbulent fluctuations of flows in such experiments (with kinetic Reynolds numbers in excess of 10(6)). We address these issues here, using the von Krmn sodium experiment and studying its response to an externally applied magnetic field. We first show that a dynamo threshold can be estimated from analysis related to critical slowing down and susceptibility divergence, in configurations for which dynamo action is indeed observed. These approaches are then applied to flow configurations that have failed to self-generate magnetic fields within operational limits, and we quantify the dynamo capacity of these configurations. PMID:23944544

Miralles, Sophie; Bonnefoy, Nicolas; Bourgoin, Mickael; Odier, Philippe; Pinton, Jean-Franois; Plihon, Nicolas; Verhille, Gautier; Boisson, Jean; Daviaud, Franois; Dubrulle, Brengre

2013-07-01

53

Threshold effects and Planck scale Lorentz violation: Combined constraints from high energy astrophysics  

NASA Astrophysics Data System (ADS)

Recent work has shown that dispersion relations with Planck scale Lorentz violation can produce observable effects at energies many orders of magnitude below the Planck energy M. This opens a window on physics that may reveal quantum gravity phenomena. It has already constrained the possibility of Planck scale Lorentz violation, which is suggested by some approaches to quantum gravity. In this work we carry out a systematic analysis of reaction thresholds, allowing unequal deformation parameters for different particle dispersion relations. The thresholds are found to have some unusual properties compared with standard ones, such as asymmetric momenta for pair creation and upper thresholds. The results are used together with high energy observational data to determine combined constraints. We focus on the case of photons and electrons, using vacuum ?erenkov, photon decay, and photon annihilation processes to determine order unity constraints on the parameters controlling O(E/M) Lorentz violation. Interesting constraints for protons (with photons or pions) are obtained even at O((E/M)2), using the absence of vacuum ?erenkov and the observed GZK cutoff for ultrahigh energy cosmic rays. A strong ?erenkov limit using atmospheric PeV neutrinos is possible for O(E/M) deformations provided the rate is high enough. If detected, ultrahigh energy cosmological neutrinos might yield limits at or even beyond O((E/M)2).

Jacobson, T.; Liberati, S.; Mattingly, D.

2003-06-01

54

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

PubMed Central

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 frequency are (95% CI) 11.6% (10.013.1) for PL units, 9.8% (8.211.5) for CT units, and 10.8% (8.413.2) for CS units. The most sensitive guinea-pig VCN single unit AM detection thresholds are similar to human psychophysical performance (?3% AM), while the mean neurometric thresholds approach whole animal behavioural performance (?10% AM). PMID:23629508

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

2013-01-01

55

Orientation tuning in human colour vision at detection threshold  

PubMed Central

We measure the orientation tuning of red-green colour and luminance vision at low (0.375?c/deg) and mid (1.5?c/deg) spatial frequencies using the low-contrast psychophysical method of subthreshold summation. Orientation bandwidths of the underlying neural detectors are found using a model involving Minkowski summation of the rectified outputs of a bank of oriented filters. At 1.5?c/deg, we find orientation-tuned detectors with similar bandwidths for chromatic and achromatic contrast. At 0.375?c/deg, orientation tuning is preserved with no change in bandwidth for achromatic stimuli, however, for chromatic stimuli orientation tuning becomes extremely broad, compatible with detection by non-oriented colour detectors. A non-oriented colour detector, previously reported in single cells in primate V1 but not psychophysically in humans, can transmit crucial information about the color of larger areas or surfaces whereas orientation-tuned detectors are required to detect the colour or luminance edges that delineate an object's shape. PMID:24594749

Gheiratmand, Mina; Mullen, Kathy T.

2014-01-01

56

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

NASA Astrophysics Data System (ADS)

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.

Morantes, Gaudi; Fernndez, Gerardo; Altuve, Miguel

2013-11-01

57

Detection Threshold and Mechanical Impedance of the Hand in a Pen-Hold Posture  

Microsoft Academic Search

We report position and force detection thresholds for sinusoidal waveforms in the frequency range 10-500 Hz delivered through a stylus. The participants were required to hold the stylus in a way similar to that of holding the stylus of a force-feedback device. A minishaker moved the stylus along its length so that the majority of vibrations were presented tangentially to

Ali Israr; Seungmoon Choi; Hong Z. Tan

2006-01-01

58

Olfactory Detection Thresholds and Adaptation in Adults with Autism Spectrum Condition  

ERIC Educational Resources Information Center

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

Tavassoli, T.; Baron-Cohen, S.

2012-01-01

59

Study on low-energy sputtering near the threshold energy by molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

Using molecular dynamics simulation, we have studied the low-energy sputtering at the energies near the sputtering threshold. Different projectile-target combinations of noble metal atoms (Cu, Ag, Au, Ni, Pd, and Pt) are simulated in the range of incident energy from 0.1 to 200 eV. It is found that the threshold energies for sputtering are different for the cases of M1 < M2 and M1 ? M2, where M1 and M2 are atomic mass of projectile and target atoms, respectively. The sputtering yields are found to have a linear dependence on the reduced incident energy, but the dependence behaviors are different for the both cases. The two new formulas are suggested to describe the energy dependences of the both cases by fitting the simulation results with the determined threshold energies. With the study on the energy dependences of sticking probabilities and traces of the projectiles and recoils, we propose two different mechanisms to describe the sputtering behavior of low-energy atoms near the threshold energy for the cases of M1 < M2 and M1 ? M2, respectively.

Yan, C.; Zhang, Q. Y.

2012-09-01

60

The Training Level of Experts Influences their Detection Thresholds for Key Wine Compounds  

Microsoft Academic Search

Wine experts usually rely on chemical tracers of qualities or defects to judge wines. While part of their expertise is determined\\u000a by their sensory ability to detect these key compounds, their level of sensitivity is generally unknown. The olfactory detection\\u000a thresholds for 10 key odorant compounds in wine were, therefore, measured in a large sample of professionals (100 n <

Sophie Tempere; Elonore Cuzange; Jinane Malak; Jean Claude Bougeant; Gilles de Revel; Gilles Sicard

61

Thermal Nociceptive Threshold Testing Detects Altered Sensory Processing in Broiler Chickens with Spontaneous Lameness  

PubMed Central

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. PMID:24847799

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

2014-01-01

62

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

NASA Astrophysics Data System (ADS)

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.

Bagwari, A.; Tomar, G. S.

2014-04-01

63

Fusion of threshold rules for target detection in wireless sensor networks  

SciTech Connect

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.

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

2010-03-01

64

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

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

65

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

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

66

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

PubMed Central

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 lower suppression indices in patients. To examine whether the difference in suppression was driven by the lower NS thresholds for controls, we examined a matched subgroup of controls and patients, selected to have similar thresholds in the NS condition. Patients performed significantly better in the PS condition than controls. This analysis therefore indicates that a PS raised contrast thresholds less in patients than in controls. Our results support the hypothesis that inhibitory connections in early visual cortex are impaired in schizophrenia patients. PMID:25540631

Serrano-Pedraza, Ignacio; Romero-Ferreiro, Vernica; Read, Jenny C. A.; Diguez-Risco, Teresa; Bagney, Alexandra; Caballero-Gonzlez, Montserrat; Rodrguez-Torresano, Javier; Rodriguez-Jimenez, Roberto

2014-01-01

67

A threshold-based fall-detection algorithm using a bi-axial gyroscope sensor  

Microsoft Academic Search

A threshold-based algorithm, to distinguish between Activities of Daily Living (ADL) and falls is described. A gyroscope based fall-detection sensor array is used. Using simulated-falls performed by young volunteers under supervised conditions onto crash mats and ADL performed by elderly subjects, the ability to discriminate between falls and ADL was achieved using a bi-axial gyroscope sensor mounted on the trunk,

A. K. Bourke; G. M. Lyons

2008-01-01

68

Detecting Departure From Additivity Along a Fixed-Ratio Mixture Ray With a Piecewise Model for Dose and Interaction Thresholds  

PubMed Central

For mixtures of many chemicals, a ray design based on a relevant, fixed mixing ratio is useful for detecting departure from additivity. Methods for detecting departure involve modeling the response as a function of total dose along the ray. For mixtures with many components, the interaction may be dose dependent. Therefore, we have developed the use of a three-segment model containing both a dose threshold and an interaction threshold. Prior to the dose threshold, the response is that of background; between the dose threshold and the interaction threshold, an additive relationship exists; the model allows for departure from additivity beyond the interaction threshold. With such a model, we can conduct a hypothesis test of additivity, as well as a test for a region of additivity. The methods are illustrated with cytotoxicity data that arise when Chinese hamster ovary cells are exposed to a mixture of nine haloacetic acids. PMID:21359103

Gennings, Chris; Wagner, Elizabeth D.; Simmons, Jane Ellen; Plewa, Michael J.

2010-01-01

69

A contrast stretching bilateral closing top-hat Otsu threshold technique for crack detection in images.  

PubMed

Detection of cracks from stainless steel pipe images is done using contrast stretching technique. The technique is based on an image filter technique through mathematical morphology that can expose the cracks. The cracks are highlighted and noise removal is done efficiently while still retaining the edges. An automated crack detection system with a camera platform has been successfully implemented. We compare crack extraction in terms of quality measures with those of Otsu's threshold technique and the another technique (Iyer and Sinha, 2005). The algorithm shown is able to achieve good results and perform better than these other techniques. PMID:22777599

Sim, K S; Kho, Y Y; Tso, C P; Nia, M E; Ting, H Y

2013-01-01

70

Design and Synthesis of Ultralow Energy Spin-Memristor Threshold Logic  

NASA Astrophysics Data System (ADS)

A threshold logic gate (TLG) performs weighted sum of multiple inputs and compares the sum with a threshold. We propose Spin-Memeristor Threshold Logic (SMTL) gates, which employ memristive cross-bar array (MCA) to perform current-mode summation of binary inputs, whereas, the low-voltage fast-switching spintronic threshold devices (STD) carry out the threshold operation in an energy efficient manner. Field programmable SMTL gate arrays can operate at a small terminal voltage of ~50mV, resulting in ultra-low power consumption in gates as well as programmable interconnect networks. We evaluate the performance of SMTL using threshold logic synthesis. Results for common benchmarks show that SMTL based programmable logic hardware can be more than 100x energy efficient than state of the art CMOS FPGA.

Fan, Deliang; Sharad, Mrigank; Roy, Kaushik

2014-05-01

71

Fine-Grained Emotion Detection in Suicide Notes: A Thresholding Approach to Multi-Label Classification  

PubMed Central

We present a system to automatically identify emotion-carrying sentences in suicide notes and to detect the specific fine-grained emotion conveyed. With this system, we competed in Track 2 of the 2011 Medical NLP Challenge,14 where the task was to distinguish between fifteen emotion labels, from guilt, sorrow, and hopelessness to hopefulness and happiness. Since a sentence can be annotated with multiple emotions, we designed a thresholding approach that enables assigning multiple labels to a single instance. We rely on the probability estimates returned by an SVM classifier and experimentally set thresholds on these probabilities. Emotion labels are assigned only if their probability exceeds a certain threshold and if the probability of the sentence being emotion-free is low enough. We show the advantages of this thresholding approach by comparing it to a nave system that assigns only the most probable label to each test sentence, and to a system trained on emotion-carrying sentences only. PMID:22879761

Luyckx, Kim; Vaassen, Frederik; Peersman, Claudia; Daelemans, Walter

2012-01-01

72

Voice-Related Modulation of Mechanosensory Detection Thresholds in the Human Larynx  

PubMed Central

Rapidly adapting mechanoreceptors within the laryngeal mucosa provide the central nervous system with perceptual and proprioceptive afference for a variety of essential yet diverse human functions including voice sound production and airway protection. It is unknown why mechanosensory information that yields a defensive response when an individual breathes may go largely unnoticed when the individual voices. Therefore, a central question is whether there is voice-related modulation of laryngeal mechanosensory detection. Such modulation would be consistent with current models of afferent laryngeal control, and may be important to maintain fluent voice in the presence of potentially distracting sensory input. Therefore, we employed endoscopic assessment of laryngeal mechanosensory detection thresholds in ten healthy adults during tidal breathing and a voice task. We tested the hypothesis that laryngeal mechanosensory detection thresholds would be higher during the voice task. We found that thresholds were significantly higher for all participants during the voice task, and that these changes were significantly more modest in women. Our findings suggest that the laryngeal sensorium may modulate mechanosensory afference to attenuate the potentially distracting influence of sensory input during voice. The finding that women maintain a greater sensitivity during the voice task than men (lower thresholds) may have important implications for the higher prevalence of sensorimotor voice disturbances in women. Our results are consistent with the presence of mechanosensory modulation in other motor systems and with observed sensory differences between women and men. Such modulation has important implications for understanding the underlying neural mechanisms of laryngeal control and how these mechanisms may operate in individuals with laryngeal disturbances. PMID:24217976

Hammer, Michael J.; Krueger, Mallory A.

2014-01-01

73

A dynamic thresholds scheme for contaminant event detection in water distribution systems.  

PubMed

In this study, a dynamic thresholds scheme is developed and demonstrated for contamination event detection in water distribution systems. The developed methodology is based on a recently published article of the authors (Perelman et al., 2012). Event detection in water supply systems is aimed at disclosing abnormal hydraulic or water quality events by exploring the time series behavior of routine hydraulic (e.g., flow, pressure) and water quality measurements (e.g., residual chlorine, pH, turbidity). While event detection raises alerts to the possibility of an event occurrence, it does not relate to origins, thus an event may be hydraulically-driven, as a consequence of problems like sudden leakages or pump/pipe malfunctions. Most events, however, are related to deliberate, accidental, or natural contamination intrusions. The developed methodology herein is based on off-line and on-line stages. During the off-line stage, a genetic algorithm (GA) is utilized for tuning five decision variables: positive and negative filters, positive and negative dynamic thresholds, and window size. During the on-line stage, a recursively Bayes' rule is invoked, employing the five decision variables, for real time on-line event detection. Using the same database, the proposed methodology is compared to Perelman et al. (2012), showing considerably improved detection ability. Metadata and the computer code are provided as Supplementary material. PMID:23384516

Arad, Jonathan; Housh, Mashor; Perelman, Lina; Ostfeld, Avi

2013-04-01

74

Behaviorally gated reduction of spontaneous discharge can improve detection thresholds in auditory cortex.  

PubMed

Animals often listen selectively for particular sounds, a strategy that could alter neural encoding mechanisms to maximize the ability to detect the target. Here, we recorded auditory cortex neuron responses in well trained, freely moving gerbils as they performed a tone detection task. Each trial was initiated by the animal, providing a predictable time window during which to listen. No sound was presented on nogo trials, permitting us to assess spontaneous activity on trials in which a signal could have been expected, but was not delivered. Immediately after animals initiated a trial, auditory cortex neurons displayed a 26% reduction in spontaneous activity. Moreover, when stimulus-driven discharge rate was referenced to this reduced baseline, a larger fraction of auditory cortex neurons displayed a detection threshold within 10 dB of the behavioral threshold. These findings suggest that auditory cortex spontaneous discharge rate can be modulated transiently during task performance, thereby increasing the signal-to-noise ratio and enhancing signal detection. PMID:24623785

Buran, Bradley N; von Trapp, Gardiner; Sanes, Dan H

2014-03-12

75

Behaviorally Gated Reduction of Spontaneous Discharge Can Improve Detection Thresholds in Auditory Cortex  

PubMed Central

Animals often listen selectively for particular sounds, a strategy that could alter neural encoding mechanisms to maximize the ability to detect the target. Here, we recorded auditory cortex neuron responses in well trained, freely moving gerbils as they performed a tone detection task. Each trial was initiated by the animal, providing a predictable time window during which to listen. No sound was presented on nogo trials, permitting us to assess spontaneous activity on trials in which a signal could have been expected, but was not delivered. Immediately after animals initiated a trial, auditory cortex neurons displayed a 26% reduction in spontaneous activity. Moreover, when stimulus-driven discharge rate was referenced to this reduced baseline, a larger fraction of auditory cortex neurons displayed a detection threshold within 10 dB of the behavioral threshold. These findings suggest that auditory cortex spontaneous discharge rate can be modulated transiently during task performance, thereby increasing the signal-to-noise ratio and enhancing signal detection. PMID:24623785

Buran, Bradley N.; von Trapp, Gardiner

2014-01-01

76

Saltation threshold detection in a wind tunnel by the measurement of the net electrostatic charge  

NASA Technical Reports Server (NTRS)

The Mars surface wind tunnel (MARSWIT) is an open circuit wind tunnel used for aeolian studies and is located inside a large vacuum chamber allowing testing at Martian surface atmospheric pressure. Since direct access is not available to the tunnel during operation at low pressure, a remote method of saltation detection is needed. The bed is observed by means of closed circuit video, but it is often difficult to determine the initiation of threshold. The measurement by means of an electrometer of the net electric charge produced by the saltating particles has provided a reliable means of saltation threshold detection. Saltating particles become charged several ways, both in wind tunnels and in a natural environment. The most significant of these methods are tribo-charging and contact charging, which always occur. Fracture charging may also occur under the high velocities associated with particle transport on Mars or under simulated Martian conditions. Detection in MARSWIT is achieved by allowing the saltating particles to impinge on a planar conducting surface normal to the flow that is connected to ground through a Keithly electrometer. The signal from the electrometer is connected to a strip chart recorder along with the analog signal from the pitot tube transducer that is used to determine the wind velocity in the tunnel. Thus, a record of wind velocity and the initiation of particle saltation is conveniently displayed together. While both positive and negative charges are produced during saltation, this method measures only the net charge; thus the charge may be either positive or negative depending upon the particles being tested, the size and size distribution of the test material, and the wind velocity. This has proven to be a very trustworthy and sensitive method of saltation threshold detection, being especially useful with the smaller sized particles which are the most difficult to observe visually.

Leach, Rodman N.

1991-01-01

77

Direction detection thresholds of passive self-motion in artistic gymnasts.  

PubMed

In this study, we compared direction detection thresholds of passive self-motion in the dark between artistic gymnasts and controls. Twenty-four professional female artistic gymnasts (ranging from 7 to 20 years) and age-matched controls were seated on a motion platform and asked to discriminate the direction of angular (yaw, pitch, roll) and linear (leftward-rightward) motion. Gymnasts showed lower thresholds for the linear leftward-rightward motion. Interestingly, there was no difference for the angular motions. These results show that the outstanding self-motion abilities in artistic gymnasts are not related to an overall higher sensitivity in self-motion perception. With respect to vestibular processing, our results suggest that gymnastic expertise is exclusively linked to superior interpretation of otolith signals when no change in canal signals is present. In addition, thresholds were overall lower for the older (14-20 years) than for the younger (7-13 years) participants, indicating the maturation of vestibular sensitivity from childhood to adolescence. PMID:24463426

Hartmann, Matthias; Haller, Katia; Moser, Ivan; Hossner, Ernst-Joachim; Mast, Fred W

2014-04-01

78

Influence of the mean luminance on the detection threshold for red-green chromatic gratings  

NASA Astrophysics Data System (ADS)

The objective of the study was to examine the influence of the mean luminance level on the detection thresholds for red-green chromatic gratings of three different spatial frequencies. Data for chromatic sinusoidal gratings with higher mean luminance levels (within the photopic level) than those ones used in previous works were reported. The study analyzed the transition luminance between the DeVries- Rose law and the Weber law regions, and considered the validity of the constant-flux hypothesis for the three spatial frequencies tested. The results suggest that the 'flux' would not be a critical factor in the processing of chromatic gratings in the low spatial frequency range.

Nieves Gomez, Juan L.; Valero, E.; Hernandez-Andres, Javier; Garcia, Jose A.; Romero, Javier

2002-06-01

79

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

PubMed

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. PMID:23889391

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

2013-07-12

80

Electron-Nuclear Energy Sharing in Above-Threshold Multiphoton Dissociative Ionization of H2  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

81

MOA-2010-BLG-311: A PLANETARY CANDIDATE BELOW THE THRESHOLD OF RELIABLE DETECTION  

SciTech Connect

We analyze MOA-2010-BLG-311, a high magnification (A{sub max} > 600) microlensing event with complete data coverage over the peak, making it very sensitive to planetary signals. We fit this event with both a point lens and a two-body lens model and find that the two-body lens model is a better fit but with only {Delta}{chi}{sup 2} {approx} 80. The preferred mass ratio between the lens star and its companion is q = 10{sup -3.7{+-}0.1}, placing the candidate companion in the planetary regime. Despite the formal significance of the planet, we show that because of systematics in the data the evidence for a planetary companion to the lens is too tenuous to claim a secure detection. When combined with analyses of other high-magnification events, this event helps empirically define the threshold for reliable planet detection in high-magnification events, which remains an open question.

Yee, J. C.; Hung, L.-W.; Gould, A.; Gaudi, B. S. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Bond, I. A. [Institute for Information and Mathematical Sciences, Massey University, Private Bag 102-904, Auckland 1330 (New Zealand); Allen, W. [Vintage Lane Observatory, Blenheim (New Zealand); Monard, L. A. G. [Bronberg Observatory, Centre for Backyard Astrophysics, Pretoria (South Africa); Albrow, M. D. [Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8020 (New Zealand); Fouque, P. [IRAP, CNRS, Universite de Toulouse, 14 avenue Edouard Belin, F-31400 Toulouse (France); Dominik, M. [SUPA, University of St. Andrews, School of Physics and Astronomy, North Haugh, St. Andrews, KY16 9SS (United Kingdom); Tsapras, Y. [Las Cumbres Observatory Global Telescope Network, 6740B Cortona Drive, Goleta, CA 93117 (United States); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Zellem, R. [Department of Planetary Sciences/LPL, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721 (United States); Bos, M. [Molehill Astronomical Observatory, North Shore City, Auckland (New Zealand); Christie, G. W. [Auckland Observatory, P.O. Box 24-180, Auckland (New Zealand); DePoy, D. L. [Department of Physics, Texas A and M University, 4242 TAMU, College Station, TX 77843-4242 (United States); Dong, Subo [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Drummond, J. [Possum Observatory, Patutahi (New Zealand); Gorbikov, E. [School of Physics and Astronomy, Raymond and Beverley Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel Aviv 69978 (Israel); Han, C., E-mail: liweih@astro.ucla.edu, E-mail: rzellem@lpl.arizona.edu, E-mail: tim.natusch@aut.ac.nz [Department of Physics, Chungbuk National University, 410 Seongbong-Rho, Hungduk-Gu, Chongju 371-763 (Korea, Republic of); Collaboration: muFUN Collaboration; MOA Collaboration; OGLE Collaboration; PLANET Collaboration; RoboNet Collaboration; MiNDSTEp Consortium; and others

2013-05-20

82

Energy Detectives at Work  

NSDL National Science Digital Library

Students search for clues of energy around them. They use what they find to create their own definition of energy. They also relate their energy clues to the engineering products they encounter every day.

Integrated Teaching And Learning Program

83

Adaptive optics for reduced threshold energy in femtosecond laser induced optical breakdown in water based eye model  

NASA Astrophysics Data System (ADS)

In ophthalmic microsurgery tissue dissection is achieved using femtosecond laser pulses to create an optical breakdown. For vitreo-retinal applications the irradiance distribution in the focal volume is distorted by the anterior components of the eye causing a raised threshold energy for breakdown. In this work, an adaptive optics system enables spatial beam shaping for compensation of aberrations and investigation of wave front influence on optical breakdown. An eye model was designed to allow for aberration correction as well as detection of optical breakdown. The eye model consists of an achromatic lens for modeling the eye's refractive power, a water chamber for modeling the tissue properties, and a PTFE sample for modeling the retina's scattering properties. Aberration correction was performed using a deformable mirror in combination with a Hartmann-Shack-sensor. The influence of an adaptive optics aberration correction on the pulse energy required for photodisruption was investigated using transmission measurements for determination of the breakdown threshold and video imaging of the focal region for study of the gas bubble dynamics. The threshold energy is considerably reduced when correcting for the aberrations of the system and the model eye. Also, a raise in irradiance at constant pulse energy was shown for the aberration corrected case. The reduced pulse energy lowers the potential risk of collateral damage which is especially important for retinal safety. This offers new possibilities for vitreo-retinal surgery using femtosecond laser pulses.

Hansen, Anja; Krueger, Alexander; Ripken, Tammo

2013-03-01

84

Electron-Nuclear Energy Sharing in Above-Threshold Multiphoton Dissociative Ionization of H2  

E-print Network

Electron-Nuclear Energy Sharing in Above-Threshold Multiphoton Dissociative Ionization of H2 J. Wu­4], where the photon energy is shared by the freed electrons and the nuclear fragments. For the molecular ionization [10­15], and the imaging of inter- nuclear distance using nuclear kinetic energy release spec- tra

Thumm, Uwe

85

State-selective x-ray studies of radiative recombination into bare and H-like uranium at threshold energies  

NASA Astrophysics Data System (ADS)

A state-selective investigation of radiative recombination (RR) at threshold energies has been performed by x-ray detection at the electron cooler of the experimental storage ring (ESR) at Gesellschaft fr Schwerionenforschung (GSI) for decelerated bare and hydrogenlike uranium ions. The application of the deceleration mode enabled us to observe state-selective RR into the K and L shells of bare and H-like uranium. The observed relative RR intensities into these low-lying bound states exhibit a good agreement with rigorous relativistic predictions, whereas the nonrelativistic approach fails to reproduce the data. Furthermore, the scaled relativistic one-electron treatment seems to be insufficient for the state-selective description of RR into H-like species at extremely low energies, suggesting the importance of electron-electron interactions for the RR process at the threshold.

Reuschl, R.; Gumberidze, A.; Kozhuharov, C.; Spillmann, U.; Tashenov, S.; Sthlker, Th.; Eichler, J.

2008-03-01

86

Research on detectable threshold of double MCP ultraviolet image intensifier tube  

NASA Astrophysics Data System (ADS)

In order to research the influence of the quantity of the Micro-Channel Plates (MCP) on the detectable threshold of the ultraviolet image intensifier tube, the wide spectrum image intensifier gain tester produced by Nanjing University of Science and Technology is employed to test the relation curves between self-made one single MCP ultraviolet image intensifier tube, two double MCP ultraviolet image intensifier tubes, and photocathode incidence radiation illumination respectively. With reference to the 3rd-generation low-light image intensifier failure theory, if the radiation gain of the ultraviolet image intensifier tube is defined as 1,000cd/m2, the tube will lose the effect of image intensification, when the corresponding photocathode incidence radiation illumination will be the minimum detectable threshold. Viewed from the test results, the minimum detectable threshold of the single MCP ultraviolet image intensifier tube is 3.010-6 W/m2, with the radiance gain linear interval between 3.010-6 W/m2 ?4.610-5 W/m2; and that of the double MCP ultraviolet image intensifier tubes is 410-7 W/m2, with the radiance gain linear interval between 4.010-7 W/m2 ?2.010-5 W/m2. The test results were analyzed on the basis of the MCP self-saturation effect, concluding that the saturation current density of the single-unit MCP is a fixed , but there may be certain difference among the saturation current density of different MCPs due to different materials and manufacturing processes. The test results show that the maximum of the radiation gain linear interval of the three ultraviolet image intensifier tubes are at the magnitude of 10-5 W/m2, and the non-significant differences also verified the theory. In the double MCP ultraviolet image intensifier tubes, the photocathode-produced photocurrent is multiplied in passing the first MCP and then reaches the second MCP, so the second MCP will reach the state of current saturation earlier than the first MCP, making the minimum detectable threshold of the double MCP ultraviolet image intensifier tubes is lower than that of the single ultraviolet image intensifier tube by one order of magnitude, with the linear gain interval increasing by one magnitude, and the absolute of the corresponding radiation gain of the same radiation illumination within the linear gain interval increasing by 10 times, verifying that the double MCPs can detect much lower and weaker ultraviolet radiation and realize the high gain theory. The research results has certain guiding effect towards the promotion and application of the double ultraviolet image intensifier tubes, and has great significance on enhancing the high ultraviolet radiation detection and imaging technology.

Cheng, Hong-chang; Duanmu, Qing-duo; Shi, Feng; Shi, Hong-li; Liu, Hui; Feng, Liu; He, Ying-ping; Hou, Zhi-peng; Yan, Lei; Ren, Ling

2013-08-01

87

Low-energy-threshold analysis of the Phase I and Phase II data sets of the Sudbury Neutrino Observatory  

E-print Network

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 Teff=3.5 MeV, the lowest analysis threshold yet achieved ...

Monroe, Jocelyn

88

Thresholds of Detection For Falling Snow From Satellite-Borne Active and Passive Sensors  

NASA Astrophysics Data System (ADS)

Estimates of falling snow must be captured to obtain the true global precipitation water cycle and snowfall accumulations are required for hydrological studies. While satellite-based remote sensing provides global coverage of falling snow events and the science is relatively new, retrievals are still undergoing development with challenges remaining. The Global Precipitation Measurement (GPM) mission scheduled for launch in 2013 is specifically designed to measure both liquid rain and frozen snow precipitation. CloudSat is already collecting reflectivities of falling snow events. This work seeks to determine what snow events can be detected from passive and active spaceborne sensors using a theoretical analysis. These challenges of estimating falling snow 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 snow flakes and their impact on 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. Information must be determined in order to guide retrieval algorithm development for the current and future missions. This information includes thresholds of detection for various sensor channel configurations, snow event system characteristics, and surface types. For example, can a lake effect snow system with low cloud tops having an ice water content (IWC) at the surface of 1.0 g m-3 be detected? If this information is known, we can focus retrieval efforts on detectable storms and concentrate advances on achievable results. The results rely 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. In this work, the focus is to determine thresholds of detection for falling snow for various snow conditions over land and lake surfaces. The simulations are used to compute brightness temperatures (TBs) for channels from 10 to 183 GHz over the great lakes and snow-covered and snow-free surfaces. The models are also used to compute radar reflectivities (Z) at Ku, Ka, and W-bands. Both the Z and TB use the same cloud hydrometeors that allow for non-spherical snow and graupel particles. This work shows that under relatively perfect situations, that ice water paths (IWP) of ~4.0, 1.0, and 0.5 kg m-2 can be detected at 37, 89, and 166 GHz respectively. For active sensors such as those being designed for GPM and the current CloudSat radar, the minimum detectable signal by the sensor drives the thresholds of detection of falling snow near the surface range gates and is usually capable of detecting snow rates lower than that of passive sensors. This presentation will describe the procedure and results in detail.

Skofronick Jackson, G.; Johnson, B. T.; Munchak, S. J.

2011-12-01

89

Comparison of odor detection thresholds and odor discriminablities of a conducting polymer composite electronic nose versus mammalian olfaction  

Microsoft Academic Search

Response data from an array of conducting polymer composite vapor detectors that form an electronic nose were collected for the purpose of comparing selected, quantitatively measurable, phenomena in odor detection and classification to the olfactory characteristics of monkeys and humans. Odor detection thresholds and discriminability between structurally similar pairs of odorants were the two primary quantities evaluated for this comparison.

Brett J. Doleman; Nathan S. Lewis

2001-01-01

90

Methods for detecting and estimating population threshold concentrations for air pollution-related mortality with exposure measurement error  

SciTech Connect

The association between daily fluctuations in ambient particulate matter and daily variations in nonaccidental mortality have been extensively investigated. Although it is now widely recognized that such an association exists, the form of the concentration-response model is still in question. Linear, no threshold and linear threshold models have been most commonly examined. In this paper the authors considered methods to detect and estimate threshold concentrations using time series data of daily mortality rates and air pollution concentrations. Because exposure is measured with error, they also considered the influence of measurement error in distinguishing between these two completing model specifications. The methods were illustrated on a 15-year daily time series of nonaccidental mortality and particulate air pollution data in Toronto, Canada. Nonparametric smoothed representations of the association between mortality and air pollution were adequate to graphically distinguish between these two forms. Weighted nonlinear regression methods for relative risk models were adequate to give nearly unbiased estimates of threshold concentrations even under conditions of extreme exposure measurement error. The uncertainty in the threshold estimates increased with the degree of exposure error. Regression models incorporating threshold concentrations could be clearly distinguished from linear relative risk models in the presence of exposure measurement error. The assumption of a linear model given that a threshold model was the correct form usually resulted in overestimates in the number of averted premature deaths, except for low threshold concentrations and large measurement error.

Cakmak, S.; Burnett, R.T.; Krewski, D. [Health Canada, Ottawa, Ontario (Canada)] [Health Canada, Ottawa, Ontario (Canada)

1999-06-01

91

Bayesian decision threshold, detection limit and confidence limits in ionising-radiation measurement.  

PubMed

Based on Bayesian statistics and the Bayesian theory of measurement uncertainty, characteristic limits such as the decision threshold, detection limit and limits of a confidence interval can be calculated taking into account all sources of uncertainty. This approach consists of the complete evaluation of a measurement according to the ISO Guide to the Expression of Uncertainty in Measurement (GUM) and the successive determination of the characteristic limits by using the standard uncertainty obtained from the evaluation. This procedure is elaborated here for several particular models of evaluation. It is, however, so general that it allows for a large variety of applications to similar measurements. It is proposed for the revision of those parts of DIN 25482 and ISO 11929 that are still based on conventional statistics and, therefore, do not allow to take completely into account all the components of measurement uncertainty in the calculation of the characteristic limits. PMID:16868015

Weise, K; Hbel, K; Rose, E; Schlger, M; Schrammel, D; Tschner, M; Michel, R

2006-01-01

92

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

PubMed Central

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/s2) vibration cues are present. PMID:24068754

Chaudhuri, Shomesh E.; Karmali, Faisal

2013-01-01

93

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

PubMed

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. PMID:22902891

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

2012-09-01

94

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

PubMed Central

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 Earths 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

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

2012-01-01

95

Milagro: A low energy threshold extensive air shower array  

SciTech Connect

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.

Sinnis, C.

1994-12-31

96

Variation-driven device sizing for minimum energy sub-threshold circuits  

Microsoft Academic Search

Sub-threshold operation is a compelling approach for energy- constrained applications, but increased sensitivity to varia- tion must be mitigated. We explore variability metrics and the variation sensitivity of stacked device topologies. We show that upsizing is necessary to achieve robustness at re- duced voltages and propose a design methodology to meet yield constraints. The need for upsizing imposes an energy

Joyce Kwong; Anantha P. Chandrakasan

2006-01-01

97

Development Of An Electronic Nose For Environmental Monitoring: Detection Of Specific Environmentally Important Gases At Their Odor Detection Threshold Concentration  

NASA Astrophysics Data System (ADS)

The use of a sensor array is demonstrated to be an effective approach to evaluate hazardous odor (or gas) emissions from industrial sites1. Therefore the possibility to use electronic noses for the prolonged survey of odor emissions from industrial sites is of particular interest for environmental monitoring purposes2. At the Olfactometric Laboratory of the Politecnico di Milano, in collaboration with Sacmi Group, Imola, an innovative electronic nose for the continuous monitoring of environmental odors is being developed. The aim of this work is to show the laboratory tests conducted to evaluate the capability of the electronic nose to recognize some specific environmentally important gases at their odor detection threshold concentration. The laboratory studies up to now focused on ammonia and butyric acid, those being compounds that can typically be found in the emissions from waste treatment plants, that may cause health effects when they exceed a given concentration level. The laboratory tests proved the sensors to be sensitive towards the considered compounds and the system to be capable of discriminating between odorous or non-odorous air, with a detection limit comparable with the detection limit of human nose.

Dentoni, Licinia; Capelli, Laura; Sironi, Selena; Del Rosso, Renato; Centola, Paolo; Della Torre, Matteo; Dematt, Fabrizio

2011-09-01

98

Location Performance and Detection Threshold of the Spanish National Seismic Network  

NASA Astrophysics Data System (ADS)

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 Geogrfico 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, the Betic Cordillera, and Tenerife Island are the best-monitored zones. Origin time and focal depth are data that are far from being constrained by regional events. The two Iberian areas with moderate seismicity and the highest seismic hazard, the Pyrenees and Betic Cordillera, and the northwestern quadrant of the peninsula, are the areas wherein the focus of an earthquake is determined with an approximate error of 3 km. For M L 2.5 and M L 3.0 this error is common for almost the whole peninsula and the Canary Islands. In general, errors in epicenter latitude and longitude are small for near-surface earthquakes, increasing gradually as the depth increases, but remaining close to 5 km even at a depth of 60 km. The hypocentral depth seems to be well constrained to a depth of 40 km beneath the zones with the highest density of stations, with an error of less than 5 km. The M L magnitude detection threshold of the network is approximately 2.0 for most of Spain and still less, almost 1.0, for the western sector of the Pyrenean region and the Canary Islands.

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

2013-11-01

99

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

SciTech Connect

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.

Dobrovolsky, V., E-mail: vdobrovolsky@voliacable.com [Institute of Semiconductor Physics, Nauki Av., 41, Kiev 03028 (Ukraine)

2014-10-21

100

Automatic Detection of Masses in Mammograms Using Quality Threshold Clustering, Correlogram Function, and SVM.  

PubMed

Breast cancer is the second most common type of cancer in the world. Several computer-aided detection and diagnosis systems have been used to assist health experts and to indicate suspect areas that would be difficult to perceive by the human eye; this approach has aided in the detection and diagnosis of cancer. The present work proposes a method for the automatic detection of masses in digital mammograms by using quality threshold (QT), a correlogram function, and the support vector machine (SVM). This methodology comprises the following steps: The first step is to perform preprocessing with a low-pass filter, which increases the scale of the contrast, and the next step is to use an enhancement to the wavelet transform with a linear function. After the preprocessing is segmentation using QT; then, we perform post-processing, which involves the selection of the best mass candidates. This step is performed by analyzing the shape descriptors through the SVM. For the stage that involves the extraction of texture features, we used Haralick descriptors and a correlogram function. In the classification stage, the SVM was again used for training, validation, and final test. The results were as follows: sensitivity 92.31 %, specificity 82.2 %, accuracy 83.53 %, mean rate of false positives per image 1.12, and area under the receiver operating characteristic (ROC) curve 0.8033. Breast cancer is notable for presenting the highest mortality rate in addition to one of the smallest survival rates after diagnosis. An early diagnosis means a considerable increase in the survival chance of the patients. The methodology proposed herein contributes to the early diagnosis and survival rate and, thus, proves to be a useful tool for specialists who attempt to anticipate the detection of masses. PMID:25277539

de Nazar Silva, Joberth; de Carvalho Filho, Antonio Oseas; Corra Silva, Aristfanes; Cardoso de Paiva, Anselmo; Gattass, Marcelo

2014-10-01

101

Location Performance and Detection Magnitude Threshold of the Romanian National Seismic Network  

NASA Astrophysics Data System (ADS)

Romania is an earthquake prone area with a few destructive earthquakes per century. The National Institute for Earth Physics carries out the seismic survey of Romania through the Romanian National Seismic Network (RNSN) consisting of 65 real-time seismic stations. Daily reports and monthly bulletins are delivered after routinely analyzing and processing the recorded data. In the present paper we applied the Seismic Network Evaluation through Simulation method for the RNSN configuration as it was in August 2011 to estimate the background noise level, assess the appropriateness of the velocity model adopted in routine location procedure, evaluate the hypocenter location uncertainty and determine the detection magnitude threshold. Areas of greater (southern Romania) and lower (Carpathians and Apuseni Mountains) background noise within the RNSN are identified by mapping the average power of noise in 1-12 Hz frequency range. The statistical study of the P and S phases residual times allow us to assess the appropriateness of the velocity model used in routine location. Both P- and S-wave velocity models can be optimized to improve the quality of the hypocenter location. As shown by our analysis, the RNSN is able to detect and locate earthquakes with M L magnitude above 2.5 anywhere on the Romanian territory, except the border areas, such as the Crisana-Maramures seismic source zone. Merging data from both sides of the border significantly improves the quality of hypocenter location in these areas.

D'Alessandro, Antonino; D?ne?, Anton; Grecu, Bogdan

2012-12-01

102

The vibrational energies of ozone up to the dissociation threshold: Dynamics calculations on an accurate potential energy surface  

E-print Network

The vibrational energies of ozone up to the dissociation threshold: Dynamics calculations present an ab initio potential energy surface for the ground electronic state of ozone. It is global, i. All bound states of nonrotating ozone up to more than 99% of the dissociation energy are calculated

Farantos, Stavros C.

103

Individual Differences in Sour and Salt Sensitivity: Detection and Quality Recognition Thresholds for Citric Acid and Sodium Chloride  

PubMed Central

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 HarrisKalmus 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. PMID:23413310

2013-01-01

104

Energy conservation using face detection  

NASA Astrophysics Data System (ADS)

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.

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

2011-10-01

105

Robust model-based detection of the lung field boundaries in portable chest radiographs supported by selective thresholding  

E-print Network

Robust model-based detection of the lung field boundaries in portable chest radiographs supported of the lung field boundaries in portable chest radiographs supported by selective thresholding D K Iakovidis1, Technological Educational Institute of Lamia, GR-35100 Lamia, Greece 2 1st Department of Thoracic Surgery, Chest

Athens, University of

106

Thresholds for the detection of the direction of whole-body, linear movement in the horizontal plane.  

PubMed

Thresholds for the detection (at p = 0.67 correct) of the direction of discrete linear movements in the horizontal plane, having a cosine bell velocity trajectory and duration of 3 s, were determined in 24 subjects. Thresholds in the Z body axis (mean 0.154 m X s-2) were significantly higher than thresholds for movement in the X (mean 0.063 m X s-2) and Y (mean 0.057 m X s-2) body axes. In 8 subjects, X axis acceleration threshold was found to increase as a monotonic function of stimulus duration over the range 0.98 to 6.96 s and exhibited similar frequency-dependent characteristics to thresholds for the detection of continuous oscillatory stimuli. This finding implies that the sensory system mediating the transduction and perception of liminal, whole-body linear movement is sensitive to a combination of the acceleration and rate change of acceleration (jerk) of the motion stimulus, and has similar dynamics to the "irregular" sensory receptors of the otolith organs. PMID:3790028

Benson, A J; Spencer, M B; Stott, J R

1986-11-01

107

Modifying the high-energy part of the above-threshold-ionization spectrum  

SciTech Connect

We show that the high-energy part of the above-threshold-ionization spectrum can be modified considerably if a driving laser pulse composed of several harmonic frequencies is used. To find such a pulse we rely on classical calculation. We present results of the quantum-mechanical calculation confirming classical results.

Ivanov, I. A. [Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2010-09-15

108

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

PubMed Central

Normal brain function requires constant adaptation, as an organism learns to associate important sensory stimuli with 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 postsynaptic activity has been shown to alter stimulus-evoked responses in vivo, however, to date, such protocols have not been shown to affect the animals 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 rats 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 stroke, or to promote adaptation in a bidirectional brain machine interface. PMID:21252415

Rebesco, James M.; Miller, Lee E.

2011-01-01

109

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

NASA Astrophysics Data System (ADS)

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.

Rebesco, James M.; Miller, Lee E.

2011-02-01

110

CanalOtolith Interactions and Detection Thresholds of Linear and Angular Components During Curved-Path Self-Motion  

PubMed Central

Gravitational signals arising from the otolith organs and vertical plane rotational signals arising from the semicircular canals interact extensively for accurate estimation of tilt and inertial acceleration. Here we used a classical signal detection paradigm to examine perceptual interactions between otolith and horizontal semicircular canal signals during simultaneous rotation and translation on a curved path. In a rotation detection experiment, blindfolded subjects were asked to detect the presence of angular motion in blocks where half of the trials were pure nasooccipital translation and half were simultaneous translation and yaw rotation (curved-path motion). In separate, translation detection experiments, subjects were also asked to detect either the presence or the absence of nasooccipital linear motion in blocks, in which half of the trials were pure yaw rotation and half were curved path. Rotation thresholds increased slightly, but not significantly, with concurrent linear velocity magnitude. Yaw rotation detection threshold, averaged across all conditions, was 1.45 0.81/s (3.49 1.95/s2). Translation thresholds, on the other hand, increased significantly with increasing magnitude of concurrent angular velocity. Absolute nasooccipital translation detection threshold, averaged across all conditions, was 2.93 2.10 cm/s (7.07 5.05 cm/s2). These findings suggest that conscious perception might not have independent access to separate estimates of linear and angular movement parameters during curved-path motion. Estimates of linear (and perhaps angular) components might instead rely on integrated information from canals and otoliths. Such interaction may underlie previously reported perceptual errors during curved-path motion and may originate from mechanisms that are specialized for tilt-translation processing during vertical plane rotation. PMID:20554843

MacNeilage, Paul R.; Turner, Amanda H.

2010-01-01

111

Laser-induced breakdown spectroscopy in water: Improvement of the detection threshold by signal processing  

NASA Astrophysics Data System (ADS)

Laser-induced breakdown spectroscopy (LIBS) has been performed on immersed solid samples with different grades of surface roughness and material homogeneity and on bulk water solutions. The underwater plasma was produced by applying double-pulse excitation at 1064 nm, with different sets of laser pulse energies. LIBS spectra were recorded separately for each couple of laser pulses in order to monitor shot-to-shot plasma behavior and to apply signal post processing. The latter was aimed at improving the detection limits for elemental analyses. Except in the case of flat homogeneous solid samples at high laser pulse energies, the measurements were affected by strong shot-to-shot signal oscillations. Automatic elimination of low intensity spectra reduced the detection limit up to a factor of seven. The optimum level for spectral filtering depends strongly on sample properties. For bulk water, a poor correlation was observed between the peak line intensities and the plasma continuum emission, making the peak-to-background ratio unsuitable for internal standardization purposes. The analytical performance of LIBS for bulk liquid was also affected by the spatial fluctuations of the breakdown location, a phenomenon known as "moving breakdown" in the literature, which was responsible for the signal depletion in the detection region. In preliminary measurements on water solutions, the detection limit of 0.2 mg/l for magnesium has been obtained after applying data post processing.

Lazic, V.; Colao, F.; Fantoni, R.; Spizzicchino, V.

2005-08-01

112

Ultra-high energy cosmic rays threshold in Randers-Finsler space  

E-print Network

Kinematics in Finsler space is used to study the propagation of ultra high energy cosmic rays particles through the cosmic microwave background radiation. We find that the GZK threshold is lifted dramatically in Randers-Finsler space. A tiny deformation of spacetime from Minkowskian to Finslerian allows more ultra-high energy cosmic rays particles arrive at the earth. It is suggested that the lower bound of particle mass is related with the negative second invariant speed in Randers-Finsler space.

Zhe Chang; Xin Li

2008-09-27

113

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

114

Direct measurement of the bubble-nucleation energy threshold in a CF3I bubble chamber  

NASA Astrophysics Data System (ADS)

We have directly 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 12GeV/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 (13.60.6)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. 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.

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

2013-07-01

115

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

116

Determination of navigation FDI thresholds using a Markov model. [Failure Detection and Identification in triplex inertial platform systems for Shuttle entry  

NASA Technical Reports Server (NTRS)

A method for determining time-varying Failure Detection and Identification (FDI) thresholds for single sample decision functions is described in the context of a triplex system of inertial platforms. A cost function consisting of the probability of vehicle loss due to FDI decision errors is minimized. A discrete Markov model is constructed from which this cost can be determined as a function of the decision thresholds employed to detect and identify the first and second failures. Optimal thresholds are determined through the use of parameter optimization techniques. The application of this approach to threshold determination is illustrated for the Space Shuttle's inertial measurement instruments.

Walker, B. K.; Gai, E.

1978-01-01

117

Limiting absorption principle for some long range perturbations of Dirac systems at threshold energies  

E-print Network

We establish a limiting absorption principle for some long range perturbations of the Dirac systems at threshold energies. We cover multi-center interactions with small coupling constants. The analysis is reduced to study a family of non-self-adjoint operators. The technique is based on a positive commutator theory for non self-adjoint operators, which we develop in appendix. We also discuss some applications to the dispersive Helmholzt model in the quantum regime.

Nabile Boussaid; Sylvain Golnia

2009-06-08

118

Quantitative prediction of perceptual decisions during near-threshold fear detection  

Microsoft Academic Search

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

Luiz Pessoa; Srikanth Padmala

2005-01-01

119

Threshold anomaly for the 7Be +58Ni system at near-Coulomb-barrier energies  

NASA Astrophysics Data System (ADS)

By using recent fusion cross section measurements for the weakly bound system 7Be+58Ni around the Coulomb barrier, a simultaneous ?2 analysis of elastic scattering and fusion cross section data is performed. The analysis is carried out with optical polarization potentials for the fusion and direct reaction processes. That is, the nuclear polarization potential UN is split into a volume part UF which accounts for fusion reactions and a surface part UD R that is responsible for direct reactions. The parameters of fusion and direct reaction Woods-Saxon polarization potentials are determined by the analysis of the data. The presence of the threshold anomaly is investigated from the energy dependence of these polarization potentials. It is found that, contrary to other weakly bound systems, the 7Be+58Ni reaction presents the usual threshold anomaly.

Gmez Camacho, A.; Aguilera, E. F.

2014-12-01

120

Detection of low energy solar neutrinos with HPGermanium  

E-print Network

The potential of the GENIUS proposal to measure the spectrum of low energy solar neutrinos in real time is studied. The detection reaction is elastic neutrino-electron scattering. The energy resolution for detecting the recoil electrons is about 0.3 %, the energy threshold is a few keV. The expected number of events for a target of one ton of natural germanium is 3.6 events/day for pp-neutrinos and 1.3 events/day for 7Be-neutrinos, calculated in the standard solar model (BP98). It should be feasible to achieve a background low enough to measure the low energy solar neutrino spectrum.

L. Baudis; H. V. Klapdor-Kleingrothaus

1999-06-30

121

Threshold choices of Huber regularization using global- and local-edge-detecting operators for X-ray computed tomographic reconstruction.  

PubMed

Statistical iterative reconstruction (SIR) approaches have shown great potential in x-ray computed tomographic (CT) reconstruction in the case of low-dose protocol. For yielding high quality image, an edge-preserving regularization should be incorporated into the objective function of SIR approaches. A typical example is the Huber regularization with an edge-preserving non-quadratic potential function which increases less rapidly than the quadratic potential function for sufficiently large arguments. However, a major drawback of the Huber regularization is the determining the threshold, which precludes its extensive applications. In this paper, we investigate both global- and local- edge-detecting operators for threshold choices of Huber regularization and apply them to SIR CT image reconstruction with low-dose scan protocol. Experiments were performed on XCAT phantom by using a CT simulator to obtain the low-dose projection data. PMID:24110197

Zhang, Hua; Zhang, Shanli; Hu, Debin; Zeng, Dong; Bian, Zhaoying; Lu, Lijun; Ma, Jianhua; Huang, Jing

2013-01-01

122

Odor detection thresholds and enantiomeric distributions of several 4-alkyl substituted gamma-lactones in Australian red wine.  

PubMed

The individual enantiomers of gamma-octalactone (1), gamma-nonalactone (2), gamma-decalactone (3) and gamma-dodecalactone (4) have been synthesized. The (R) series of enantiomers was prepared from L-glutamic acid by a strategy involving deamination and reduction to (S)-5-oxo-2-tetrahydrofurancarboxaldehyde (S)-7. The different length side chains were introduced by a series of Wittig reactions, varying in the choice of phosphorane used. Hydrogenation then gave the final gamma-lactones 1-4. The (S) series of enantiomers was prepared in an analogous fashion beginning with d-glutamic acid. Aroma detection thresholds for all eight enantiomers were determined in a "bag in a box" dry red wine by the application of ASTM method E 679, employing a panel of 25 members. The lowest threshold determined was 8 microg/L for (R)-dodecalactone (4) while the highest threshold was 285 microg/L for (R)-nonalactone (2). With the exception of gamma-decalactone (3) there were statistically significant differences (at the 5% level) in aroma detection thresholds between the two enantiomers of the same lactone. A stable isotope method developed for quantification of the lactones 1-4 has been extended for use with chiral phase GC (Rt-betaDEXcst capillary column) allowing quantification of the individual enantiomers. The enantiomeric distribution of gamma-octalactone (1) and gamma-nonalactone (2) in seven botrytized wines and of 2 in a total of 34 red wines were thus determined; with few exceptions, the (R) enantiomer of gamma-nonalactone (2) was found to be more prevalent than its (S) counterpart in the dry red and botrytized white wines analyzed. The same was true for gamma-octalactone (1) in the botrytized white wines. PMID:19228057

Cooke Ne Brown, Rachel C; van Leeuwen, Katryna A; Capone, Dimitra L; Gawel, Richard; Elsey, Gordon M; Sefton, Mark A

2009-03-25

123

Calculating Differential Cross Sections for Electron-Impact Ionization at Energies Near Threshold  

NASA Astrophysics Data System (ADS)

Previously^1, we showed that the method of Exterior Complex Scaling can produce accurate wave functions describing all aspects, including ionization, of electron-hydrogen collisions above the ionization threshold. The correctness of these wave functions was demonstrated by extrapolating the quantum-mechanical flux to produce differential cross sections for ionization. However, that procedure has no rigorous error-bounds and is unable to describe ionization when one electron carries most of the total available energy. The "two-potential" formalism, developed by McCurdy and Rescigno^2, has recently been shown, within the context of two-dimensional model problems, to be highly effective at analyzing the double continuum. The differential cross sections produced this way are valid over the full range of energy sharing and are more accurate than those derived from flux-extrapolation. By applying this new approach of extracting detailed ionization information to the complete problem of electron-hydrogen scattering we can probe the delicate dynamics of near-threshold ionization and observe behaviors such as the qualitative change in energy sharing as the excess energy approaches zero. The "two-potential" formalism enables us, at least in principle, to calculate any differential cross section imaginable. Its applicability should extend to more complicated systems and to other methods for generating scattering wave functions. ^1 M. Baertschy ph et al., Phys. Rev. A, 63, 022712 (2000). ^2 C. W. McCurdy ph et al., Phys. Rev A, 63, 022711 (2000).

Baertschy, Mark

2001-05-01

124

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

NASA Technical Reports Server (NTRS)

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.

Bhatia, A. K.; Temkin, A.

2007-01-01

125

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

NASA Technical Reports Server (NTRS)

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.

Bhatia, Anand

2008-01-01

126

Influence of near threshold visual distractors on perceptual detection and reaching movements.  

PubMed

Providing evidence against a dissociation between conscious vision for perception and unconscious vision for action, recent studies have suggested that perceptual and motor decisions are based on a unique signal but distinct decisional thresholds. The aim of the present study was to provide a direct test of this assumption in a perceptual-motor dual task involving arm movements. In 300 trials, 10 participants performed speeded pointing movements toward a highly visible target located at 10 from the fixation point and 45 from the body midline. The target was preceded by one or two close to threshold distractor(s) (80 ms stimulus onset asynchrony) presented 30 according to the target location. After each pointing movement, participants judged whether the distractor was present or not on either side of the target. Results showed a robust reaction time facilitation effect and a deviation toward the distractor when the distractor was both present and consciously perceived (Hit). A small reaction time facilitation was also observed when two distractors were physically present but undetected (double-miss)--this facilitation being highly correlated with the physical contrast of the distractors. These results are compatible with the theory proposing that perceptual and motor decisions are based on a common signal but emerge from a contrast dependent fixed threshold for motor responses and a variable context dependent criterion for perceptual responses. This paper thus extends to arm movement control previous findings related to oculomotor control. PMID:20702742

Deplancke, A; Madelain, L; Chauvin, A; Cardoso-Leite, P; Gorea, A; Coello, Y

2010-10-01

127

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

128

On using Extreme Values to detect global stability thresholds in multi-stable systems: The case of transitional plane Couette flow  

E-print Network

Extreme Value Theory (EVT) is exploited to determine the global stability threshold $R_g$ of plane Couette flow --the flow of a viscous fluid in the space between two parallel plates-- whose laminar or turbulent behavior depends on the Reynolds number R. Even if the existence of a global stability threshold has been detected in simulations and experiments, its numerical value has not been unequivocally defined. $R_g$ is the value such that for $R > R_g$ turbulence is sustained, whereas for $R positive and negative extremes are bounded. As the critical Reynolds number is approached from above, the probability of observing a very low minimum increases causing asymmetries in the distributions of maxima and minima. On the other hand, the maxima distribution is unaffected as the fluctuations towards higher values of the perturbation energy remain bounded. This tipping point can be detected by fitting the data to the Generalized Extreme Value (GEV) distribution and by identifying $R_g$ as the value of $R$ such that the shape parameter of the GEV for the minima changes sign from negative to positive. The results are supported by the analysis of theoretical models which feature a bistable behavior.

Davide Faranda; Valerio Lucarini; Paul Manneville; Jeroen Wouters

2014-03-21

129

Off-axis low-energy structures in above-threshold ionization  

NASA Astrophysics Data System (ADS)

The velocity map of the above-threshold ionization electron spectrum at long laser wavelength exhibits a characteristic structure normal to the laser polarization, which has the appearance of a trident or a three-pronged fork. The forklike structure vanishes for few-cycle laser pulses. It is explained in terms of the classical-electron-trajectories model of strong-field ionization augmented so as to allow for rescattering. The analysis reveals its relation to the so-called low-energy structure, which was recently observed for very small transverse momenta.

Mller, M.; Meyer, F.; Sayler, A. M.; Paulus, G. G.; Kling, M. F.; Schmidt, B. E.; Becker, W.; Miloevi?, D. B.

2014-08-01

130

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

NASA Astrophysics Data System (ADS)

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 91 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.

Helvajian, H.; Welle, R.

1989-08-01

131

R peak detection in electrocardiogram signal based on an optimal combination of wavelet transform, hilbert transform, and adaptive thresholding.  

PubMed

Electrocardiogram (ECG) is one of the most common biological signals which play a significant role in the diagnosis of heart diseases. One of the most important parts of ECG signal processing is interpretation of QRS complex and obtaining its characteristics. R wave is one of the most important sections of this complex, which has an essential role in diagnosis of heart rhythm irregularities and also in determining heart rate variability (HRV). This paper employs Hilbert and wavelet transforms as well as adaptive thresholding method to investigate an optimal combination of these signal processing techniques for the detection of R peak. In the experimental sections of this paper, the proposed algorithms are evaluated using both ECG signals from MIT-BIH database and synthetic data simulated in MATLAB environment with different arrhythmias, artifacts, and noise levels. Finally, by using wavelet and Hilbert transforms as well as by employing adaptive thresholding technique, an optimal combinational method for R peak detection namely WHAT is obtained that outperforms other techniques quantitatively and qualitatively. PMID:22606663

Rabbani, Hossein; Mahjoob, M Parsa; Farahabadi, E; Farahabadi, A

2011-05-01

132

Threshold quantum cryptography  

SciTech Connect

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.

Tokunaga, Yuuki [NTT Information Sharing Platform Laboratories, NTT Corporation, 1-1 Hikari-no-oka, Yokosuka, Kanagawa 239-0847 (Japan); Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Okamoto, Tatsuaki [NTT Information Sharing Platform Laboratories, NTT Corporation, 1-1 Hikari-no-oka, Yokosuka, Kanagawa 239-0847 (Japan); Imoto, Nobuyuki [Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan)

2005-01-01

133

Why longer song elements are easier to detect: threshold level-duration functions in the Great Tit and comparison with human data.  

PubMed

Our study estimates detection thresholds for tones of different durations and frequencies in Great Tits (Parus major) with operant procedures. We employ signals covering the duration and frequency range of communication signals of this species (40-1,010 ms; 2, 4, 6.3 kHz), and we measure threshold level-duration (TLD) function (relating threshold level to signal duration) in silence as well as under behaviorally relevant environmental noise conditions (urban noise, woodland noise). Detection thresholds decreased with increasing signal duration. Thresholds at any given duration were a function of signal frequency and were elevated in background noise, but the shape of Great Tit TLD functions was independent of signal frequency and background condition. To enable comparisons of our Great Tit data to those from other species, TLD functions were first fitted with a traditional leaky-integrator model. We then applied a probabilistic model to interpret the trade-off between signal amplitude and duration at threshold. Great Tit TLD functions exhibit features that are similar across species. The current results, however, cannot explain why Great Tits in noisy urban environments produce shorter song elements or faster songs than those in quieter woodland environments, as detection thresholds are lower for longer elements also under noisy conditions. PMID:23338560

Pohl, Nina U; Slabbekoorn, Hans; Neubauer, Heinrich; Heil, Peter; Klump, Georg M; Langemann, Ulrike

2013-03-01

134

Spectroscopic investigation of laser water interaction beyond the breakdown threshold energy  

NASA Astrophysics Data System (ADS)

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.

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

2007-02-01

135

Development and Utility of an Internal Threshold Control (ITC) Real-Time PCR Assay for Exogenous DNA Detection  

PubMed Central

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. PMID:22570718

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

2012-01-01

136

DYNAMIC THRESHOLDING METHOD FOR IMPROVING CONTAMINANT DETECTION ACCURACY WITH HYPERSPECTRAL IMAGES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Detection of fecal contamination in the visceral cavity of broiler carcasses is important for food safety to protect consumers from food pathogens. The simple ratio of reflectance values of 565-nm image to 517-nm image was effective for fecal detection in the visceral cavity. Since the accuracy of...

137

Low-energy-threshold analysis of the Phase I and Phase II data sets of the Sudbury Neutrino Observatory  

Microsoft Academic Search

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 Teff=3.5 MeV, the lowest analysis threshold yet achieved with water Cherenkov detector data. In units of 106 cm-2 s-1, the total flux of active-flavor neutrinos from B8 decay in the Sun measured using

B. Aharmim; S. N. Ahmed; A. E. Anthony; N. Barros; E. W. Beier; A. Bellerive; B. Beltran; M. Bergevin; S. D. Biller; K. Boudjemline; M. G. Boulay; T. H. Burritt; B. Cai; Y. D. Chan; D. Chauhan; M. Chen; B. T. Cleveland; G. A. Cox; X. Dai; H. Deng; J. Detwiler; M. Dimarco; P. J. Doe; G. Doucas; P.-L. Drouin; C. A. Duba; F. A. Duncan; M. Dunford; E. D. Earle; S. R. Elliott; H. C. Evans; G. T. Ewan; J. Farine; H. Fergani; F. Fleurot; R. J. Ford; J. A. Formaggio; N. Gagnon; J. Tm. Goon; K. Graham; E. Guillian; S. Habib; R. L. Hahn; A. L. Hallin; E. D. Hallman; P. J. Harvey; R. Hazama; W. J. Heintzelman; J. Heise; R. L. Helmer; A. Hime; C. Howard; M. A. Howe; M. Huang; B. Jamieson; N. A. Jelley; K. J. Keeter; J. R. Klein; L. L. Kormos; M. Kos; C. Kraus; C. B. Krauss; T. Kutter; C. C. M. Kyba; J. R. Leslie; I. T. Lawson; K. T. Lesko; I. Levine; J. C. Loach; R. MacLellan; S. Majerus; H. B. Mak; J. Maneira; R. Martin; N. McCauley; A. B. McDonald; S. McGee; M. L. Miller; B. Monreal; J. Monroe; B. Morissette; B. G. Nickel; A. J. Noble; H. M. O'Keeffe; N. S. Oblath; G. D. Orebi Gann; S. M. Oser; R. A. Ott; S. J. M. Peeters; A. W. P. Poon; G. Prior; S. D. Reitzner; K. Rielage; B. C. Robertson; R. G. H. Robertson; M. H. Schwendener; J. A. Secrest; S. R. Seibert; O. Simard; D. Sinclair; P. Skensved; T. J. Sonley; L. C. Stonehill; G. Tesic; N. Tolich; T. Tsui; C. D. Tunnell; R. van Berg; B. A. Vandevender; C. J. Virtue; B. L. Wall; D. Waller; H. Wan Chan Tseung; D. L. Wark; J. F. Wilkerson; J. R. Wilson; J. M. Wouters; A. Wright; M. Yeh; F. Zhang; K. Zuber

2010-01-01

138

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

139

A new approach for rapid detection of nearby thresholds in ecosystem time series  

E-print Network

to address an impending significant event. During the Cold War, scientists developed a family of methods been used for early detection of cyber attacks (Tartakovsky et al. 2006). In ecology, a growing

Pace, Michael L.

140

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

NASA Astrophysics Data System (ADS)

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.

Kailas, Aravind

141

Effects of pion potential and nuclear symmetry energy on the $?^{-}/?^{+}$ ratio in heavy-ion collisions at beam energies around the pion production threshold  

E-print Network

Within the framework of an isospin-dependent Boltzmann-Uehling-Uhlenbeck(IBUU) transport model, we studied the effects of the pion potential and the symmetry energy on the pion production in the central $^{197}Au+^{197}Au$ collisions around the pion production threshold. It is found that the pion potential affects the value of $\\pi^-/\\pi^+$ ratio around the Coulomb peak and also in the high energy region of pion mesons. The effect of the pion potential on the $\\pi^-/\\pi^+$ ratio becomes large in heavy-ion collisions at beam energies below the pion production threshold. And at beam energies below the pion production threshold, with the pion potential, the effect of the symmetry energy on the $\\pi^-/\\pi^+$ ratio becomes quite small compared with that above the pion production threshold.

Wen-Mei Guo; Gao-Chan Yong; Hang Liu; Wei Zuo

2014-10-18

142

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

SciTech Connect

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.

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

2014-01-07

143

A method for measurements of neutral fragments kinetic energies released to a specific dissociation threshold: optical translational spectroscopy  

Microsoft Academic Search

The optical translational spectroscopy technique, based on the principles of fast ion beam laser spectroscopy (FIBLAS) and translational spectroscopy, allows the kinetic energies study of neutral fragments released through free dissociation of a neutral molecule. This method presents interesting features such as near-threshold energy measurements and selection of a specific dissociation limit. The fragments resulting from free dissociation (not induced)

A. Roney; C. Frigon; M. Larzillire

1999-01-01

144

Particle identification with Polyethylene Terephthalate (PET) detector with high detection threshold  

NASA Astrophysics Data System (ADS)

In the present work we describe the results of studies, using accelerator data, to determine the accuracy with which particles can be identified and their energies determined with a commercially available polymer (PET) used as a Nuclear Track Detector (NTD). The achieved charge resolution was 1. The initial energy of stopping particle in PET was determined with an accuracy of 10% for ion energies above the Bragg peak.

Dey, S.; Maulik, A.; Raha, Sibaji; Saha, Swapan K.; Syam, D.

2014-10-01

145

Energy detection based on undecimated discrete wavelet transform and its application in magnetic anomaly detection.  

PubMed

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 ? is less than 1.0. In addition, a real-world experiment was done to demonstrate the advantages of the proposed method. PMID:25343484

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

2014-01-01

146

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

PubMed Central

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 ? is less than 1.0. In addition, a real-world experiment was done to demonstrate the advantages of the proposed method. PMID:25343484

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

2014-01-01

147

Feasibility and Threshold of Tree Mortality Detection across Different Biomes Using MODIS Data  

NASA Astrophysics Data System (ADS)

The critical urgency of forecasting climate impacts and feedbacks makes understanding, quantifying, and predicting terrestrial carbon balance and subsequent climate impacts one of the greatest science challenges currently facing the world. The real-time monitoring systems for dominant types of disturbances will provide a key foundation for our understanding of global carbon balance. Detection of drought/insect-caused tree mortality generally relies on high-resolution remote sensing images; however, their feasibility of global mortality detection is generally infeasible due to the high image cost and computation requirement. A key step for this system is to determine whether we are able to rapidly detect tree mortality from remote sensing data of MODIS, a mature product freely available from NASA and is a common remote sensing tool for monitoring earth system processes globally. In this study, we used a MODIS-based tree mortality quantification system developed at LANL to identify the critical amount of tree mortality that is detectable from MODIS. This system is based on the fusion of different sources of information including real-time mortality signal from MODIS, vegetation change information simulated from a vegetation dynamics model (ED), radiative transfer and reflectance information from a forest reflectance model (FRT), and different sources of background information from forest inventory and remote sensing products. Our test sites include the US southwest, Amazon and boreal forests. Our analyses will provide a key foundation on global tree mortality quantification using MODIS.

Xu, C.; Muss, J.; McDowell, N. G.

2013-12-01

148

Establishing the detection threshold for Bacillus subtilis in a complex matrix using an inorganic fingerprint approach.  

PubMed

Methods for the detection and characterization of airborne biological warfare agents, such as bacteria, using their DNA or organic composition are fairly well developed. This approach is useful for identifying the type of bacterial strain once the organism has been isolated from the matrix sampled (e.g., dust particles) and can identify genetically related organisms, which might be helpful during a forensic investigation. However, this genetic signature will not reveal information related to the methods used to grow and weaponize the organism. Bacteria will take on an inorganic signature that is related to their growth and processing history. Therefore, the ability to characterize the inorganic fingerprint of a biological particle has the potential to detect the presence of a bio-agent and expand the forensic tools available to those investigating the origin of biological weapons. This investigation builds on previous work documenting the usefulness of the inorganic fingerprint and evaluates the limits of detection in the presence of background dust. Based on ICP-MS measurements and mixing models of digested mixtures of laboratory cultured Bacillus subtilis (anthrax stimulant) and NIST Standard Reference Material 2709 (dust stimulant), the inorganic fingerprint method is capable of detecting toxicologically relevant levels of a bio-warfare agent in the presence of a complex background matrix. PMID:21872011

Lev, S M; Gasparich, G; Choi, F; King, L; Moore, J; Zimmerman, S

2011-09-30

149

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

PubMed Central

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

Macas, Miguel Macas; Manso, Antonio Garca; Orellana, Carlos Javier Garca; Velasco, Horacio Manuel Gonzlez; Caballero, Ramn Gallardo; Chamizo, Juan Carlos Peguero

2013-01-01

150

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

PubMed

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

Macas, Miguel Macas; Manso, Antonio Garca; Orellana, Carlos Javier Garca; Velasco, Horacio Manuel Gonzlez; Caballero, Ramn Gallardo; Chamizo, Juan Carlos Peguero

2013-01-01

151

Robust model-based detection of the lung field boundaries in portable chest radiographs supported by selective thresholding  

NASA Astrophysics Data System (ADS)

Portable chest radiography is a valuable tool for screening patients hospitalized in intensive care, providing visual cues for diagnosis and physiological measurements. However, its practicality comes at the cost of quality, which is mainly affected by misaligned body positioning, thus increasing x-ray misinterpretation rates. This paper presents a novel methodology for the detection of the lung field boundaries in portable chest radiographs of patients with bacterial pulmonary infections. Such infections are radiographically manifested as foci of consolidations which can lead to vague or invisible lung field boundaries, difficult to distinguish even by experienced physicians. Conventional and state-of-the-art approaches address mainly stationary radiographs, whereas only a few of them cope with pulmonary infections. The proposed methodology is based on an active shape model incorporating shape prior information about the lung fields. The model is initialized by a novel technique utilizing a set of salient points detected on the peripheral anatomic structures of the lungs. A selective thresholding algorithm based on a spinal cord sampling process supports both the initialization and the evolution of the model for the detection of the lung field boundaries. The experiments show that the proposed methodology outperforms state-of-the-art approaches.

Iakovidis, D. K.; Savelonas, M. A.; Papamichalis, G.

2009-10-01

152

Threshold energies for filamentation and spectral characteristics of supercontinuum generation in THEOS-based nanocomposite organosilicon media  

NASA Astrophysics Data System (ADS)

We have experimentally determined the threshold energy for filamentation in THEOS-based hybrid silicate nanocomposite materials containing polysaccharides and hyperbranched polyglycidols and the conversion efficiency from the 800-nm femtosecond Ti : sapphire laser output to a supercontinuum in the range 420 700 nm. The addition of sodium hyaluronate (polysaccharide) and low concentrations of Au nanoparticles or CdS quantum dots with an average diameter of 3 5 nm has been shown to considerably reduce the threshold energy for filamentation and improve the laser output to supercontinuum conversion efficiency.

Kul'chin, Yu N.; Mayor, A. Yu; Proschenko, D. Yu; Chekhlenok, A. A.; Postnova, I. V.; Golik, S. S.; Bukin, O. A.; Shchipunov, Yu A.

2014-08-01

153

CISN ShakeAlert: Faster Warning Information Through Multiple Threshold Event Detection in the Virtual Seismologist (VS) Early Warning Algorithm  

NASA Astrophysics Data System (ADS)

The Virtual Seismologist (VS) earthquake early warning (EEW) algorithm is one of 3 EEW approaches being incorporated into the California Integrated Seismic Network (CISN) ShakeAlert system, a prototype EEW system that could potentially be implemented in California. The VS algorithm, implemented by the Swiss Seismological Service at ETH Zurich, is a Bayesian approach to EEW, wherein the most probable source estimate at any given time is a combination of contributions from a likehihood function that evolves in response to incoming data from the on-going earthquake, and selected prior information, which can include factors such as network topology, the Gutenberg-Richter relationship or previously observed seismicity. The VS codes have been running in real-time at the Southern California Seismic Network since July 2008, and at the Northern California Seismic Network since February 2009. We discuss recent enhancements to the VS EEW algorithm that are being integrated into CISN ShakeAlert. We developed and continue to test a multiple-threshold event detection scheme, which uses different association / location approaches depending on the peak amplitudes associated with an incoming P pick. With this scheme, an event with sufficiently high initial amplitudes can be declared on the basis of a single station, maximizing warning times for damaging events for which EEW is most relevant. Smaller, non-damaging events, which will have lower initial amplitudes, will require more picks to initiate an event declaration, with the goal of reducing false alarms. This transforms the VS codes from a regional EEW approach reliant on traditional location estimation (and the requirement of at least 4 picks as implemented by the Binder Earthworm phase associator) into an on-site/regional approach capable of providing a continuously evolving stream of EEW information starting from the first P-detection. Real-time and offline analysis on Swiss and California waveform datasets indicate that the multiple-threshold approach is faster and more reliable for larger events than the earlier version of the VS codes. In addition, we provide evolutionary estimates of the probability of false alarms (PFA), which is an envisioned output stream of the CISN ShakeAlert system. The real-time decision-making approach envisioned for CISN ShakeAlert users, where users specify a threshhold PFA in addition to thresholds on peak ground motion estimates, has the potential to increase the available warning time for users with high tolerance to false alarms without compromising the needs of users with lower tolerances to false alarms.

Cua, G. B.; Fischer, M.; Caprio, M.; Heaton, T. H.; Cisn Earthquake Early Warning Project Team

2010-12-01

154

Visible Contrast Energy Metrics for Detection and Discrimination  

NASA Technical Reports Server (NTRS)

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

Ahumada, Albert; Watson, Andrew

2013-01-01

155

Energy dependence of electron damage and displacement threshold energy in 6H silicon carbide  

Microsoft Academic Search

The frequency response of silicon carbide (SiC) light-emitting diodes has been used to measure the energy dependence of displacement damage produced in 6H SiC by energetic electrons. The minimum electron energy required to produce displacement damage was determined to be 1087 keV, corresponding to an atomic displacement of silicon atoms. For electrons of energies greater than 0.5 MeV, the damage

A. L. Barry; B. Lehmann; D. Fritsch; D. Braeunig

1991-01-01

156

Modifications of the pion-production threshold in the nuclear medium in heavy ion collisions and the nuclear symmetry energy  

NASA Astrophysics Data System (ADS)

Using the relativistic Vlasov-Uehling-Uhlenbeck (RVUU) equation based on mean fields from the nonlinear relativistic NL? and NL? ? models, which have same nuclear equation of state and symmetry energy but different symmetry energy slope parameters, we study the effect of medium modification of the pion-production threshold on the total pion yield and the ?-/?+ ratio in Au+Au collisions. We find that the in-medium threshold effect enhances both the total pion yield and the ?-/?+ ratio, compared to those without this effect. Furthermore, including the medium modification of the pion-production threshold leads to a larger ?-/?+ ratio for the NL? ? model with a larger symmetry energy parameter than the NL? model with a smaller symmetry energy parameter, opposite to that found without the in-medium threshold effect. To reproduce the total pion yield measured by the FOPI Collaboration, we introduce a density-dependent cross section for ? baryon production from nucleon-nucleon collisions, which suppresses the total pion yield but hardly changes the ?-/?+ ratio. Because of the small difference in the stiffness of their symmetry energies, the ?-/?+ ratios obtained from both the NL? and NL? ? models are consistent with the FOPI data within the experimental errors.

Song, Taesoo; Ko, Che Ming

2015-01-01

157

1. DARK ENERGY DETECTION: AN EXPERIMENTAL PROBLEM  

E-print Network

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

Martin L. Perl

158

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

NASA Astrophysics Data System (ADS)

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.

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

2012-11-01

159

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

PubMed Central

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 6kHz. 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 4kHz between sub-groups. AM detection at the lowest SL, at both 3 and 4kHz, 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 3kHz 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

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

2014-01-01

160

Experimental design of pulsed CO2 laser damage threshold testing at the high-energy laser systems test facility  

Microsoft Academic Search

Experimental laser damage threshold tests were designed and successfully carried out at the High Energy Laser Systems Test Facility utilizing the Pulsed Laser Vulnerability Test System against optical components from a tactical weapon system in a simulated battlefield environment. The objectives of the experimental tests were to measure laser fluence levels corresponding to minimum damage, maximum functional degradation, and catastrophic

Chris T. Beairsto; Stephen M. Squires; Kevin J. Suter

1994-01-01

161

Keplerian periodogram for Doppler exoplanet detection: optimized computation and analytic significance thresholds  

NASA Astrophysics Data System (ADS)

We consider the so-called Keplerian periodogram, in which the putative detectable signal is modelled by a highly non-linear Keplerian radial velocity function, appearing in Doppler exoplanetary surveys. We demonstrate that for planets on high-eccentricity orbits the Keplerian periodogram is far more efficient than the classic Lomb-Scargle periodogram and even the multiharmonic periodograms, in which the periodic signal is approximated by a truncated Fourier series. We provide a new numerical algorithm for computation of the Keplerian periodogram. This algorithm adaptively increases the parametric resolution where necessary, in order to uniformly cover all local optima of the Keplerian fit. Thanks to this improvement, the algorithm provides more smooth and reliable results with minimized computing demands. We also derive a fast analytic approximation to the false alarm probability levels of the Keplerian periodogram. This approximation has the form (Pz3/2 + Qz)Wexp ( - z), where z is the observed periodogram maximum, W is proportional to the settled frequency range, and the coefficients P and Q depend on the maximum eccentricity to scan.

Baluev, Roman V.

2015-01-01

162

Measurements of the pair production cross section close to the threshold energy  

NASA Astrophysics Data System (ADS)

We have measured the total cross section for production of e+e- pairs by photons in the Coulomb field of Ge nuclei. Up to 1016 ? quanta per second were produced by thermal-neutron capture reactions of a natural gadolinium target, placed inside the high-flux reactor of the ILL Grenoble. Out of this stream of ? rays various strong discrete ? lines were extracted using the GAMS5 Bragg spectrometer of the ILL. A well-collimated beam of reflected ? rays irradiated a germanium detector placed inside an anti-Compton shield, consisting of eight bismuth germanate crystals, assembled as a pair spectrometer. Using this new technique we have measured, for the first time, the pair production cross section at only 18.2 keV above the 1022-keV threshold. Our measurements indicate that the pair production cross section, expressed in units of Bethe-Heitler, grows monotonously toward low energies and does not support the claim of other works of a maximum at 65 keV.

Jentschel, M.; Urban, W.; Mutti, P.; Courtois, P.; Simpson, G. S.; Frahm, R.

2011-11-01

163

Towards operational near real-time flood detection using a split-based automatic thresholding procedure on high resolution TerraSAR-X data  

Microsoft Academic Search

In this paper, an automatic near-real time (NRT) flood detection approach is presented, which combines histogram thresholding and segmentation based classification, specifically oriented to the analysis of single-polarized very high resolution Synthetic Aperture Radar (SAR) satellite data. The challenge of SAR-based flood detection is addressed in a completely unsupervised way, which assumes no training data and therefore no prior information

S. Martinis; A. Twele; S. Voigt

2009-01-01

164

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

NASA Astrophysics Data System (ADS)

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.

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

165

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

SciTech Connect

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.

Herrmann, H. W., E-mail: herrmann@lanl.gov; Kim, Y. H.; Young, C. S.; Fatherley, V. E.; Lopez, F. E.; Oertel, J. A.; Batha, S. H. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Malone, R. M. [National Security Technologies, LLC, Los Alamos, New Mexico 87544 (United States); Rubery, M. S.; Horsfield, C. J. [Atomic Weapons Establishment, Aldermaston, Berkshire RG7 4PR (United Kingdom); Stoeffl, W. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Zylstra, A. B. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Shmayda, W. T. [Laboratory for Laser Energetics, Rochester, New York 14623 (United States)

2014-11-15

166

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

PubMed

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

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

167

Experimental Evidence of Threshold Effects in the Energy Loss of Protons in Carbon and Aluminum due to Inner Shell Ionization  

NASA Astrophysics Data System (ADS)

We explore the contributions of inner shell ionization to the energy loss of 7 to 270 keV protons in C and Al foils under experimental conditions such that the product of the observation angle and the projectile energy is kept constant. By normalizing these energy loss measurements to the energy loss in the forward direction we observe a pronounced rising behavior with increasing energy. This effect appears in the same range of energies where the respective K- and L-shell ionization cross sections of these elements show a similar threshold behavior. Based also on various theoretical considerations we interpret these results as clear evidence of the inner shell ionization contribution to the energy loss.

Fam, M.; Eckardt, J. C.; Lantschner, G. H.; Arista, N. R.

2000-11-01

168

Low-frequency approximation for above-threshold ionization by a laser pulse: Low-energy forward rescattering  

NASA Astrophysics Data System (ADS)

In the context of the development of new sources of strong laser pulses in the mid-infrared region new nonperturbative methods for analysis of strong-laser-field induced or assisted atomic and molecular processes are welcome. We formulate such a theory of above-threshold ionization by a strong low-frequency laser pulse. We call this theory the low-frequency approximation (LFA). A detailed derivation of the LFA, both for short and long laser pulses, is given. As an example the LFA is applied to the analysis of recently discovered low-energy structures in the above-threshold ionization spectra of atoms ionized by long-wavelength laser pulses. It was found that these low-energy structures are caused by the forward soft recollision of the ionized electrons with the parent ion which is enhanced by the Coulomb effect.

Miloevi?, D. B.

2014-12-01

169

High Energy Polarization of Blazars: Detection Prospects  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

170

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

Code of Federal Regulations, 2010 CFR

... Follow-up corrective measures when a standard threshold...Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR UNIFORM MINE HEALTH REGULATIONS OCCUPATIONAL... Follow-up corrective measures when a standard...

2010-07-01

171

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

PubMed Central

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

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

2014-01-01

172

Acetate Threshold Concentrations Suggest Varying Energy Requirements during Anaerobic Respiration by Anaeromyxobacter dehalogenans  

Microsoft Academic Search

Acetate threshold concentrations were determined under chlororespiring and Fe(III)-reducing conditions for Anaeromyxobacter dehalogenans strain 2CP-C. The acetate threshold concentrations measured were 69 4, 19 8, and <1 nM for chlororespiration, amorphous Fe(III) reduction, and Fe(III) citrate reduction, respectively. Residual G values of 75.4 kJ\\/mol of electrons for chlororespiration and 41.5 kJ\\/mol of electrons for amorphous Fe(III) reduction were calculated at

Qiang He; Robert A. Sanford

2004-01-01

173

Zero Kinetic Energy Photofragment Spectroscopy: The Threshold Dissociation of NO2 J. A. Mueller, S. A. Rogers, and Paul L. Houston*  

E-print Network

to the fragment recoil velocity.4-9 Values of the anisotropy parameter in the range from 0.6 to 1.8 were obtainedZero Kinetic Energy Photofragment Spectroscopy: The Threshold Dissociation of NO2 J. A. Mueller, S be useful in the accurate identification of the dissociation threshold. The technique is demonstrated

Houston, Paul L.

174

Alternative Detection Methods for Highest Energy Neutrinos  

E-print Network

Several experimental techniques are currently under development, to measure the expected tiny fluxes of highest energy neutrinos above 10**18 eV. Projects in different stages of realisation are discussed here, which are based on optical and radio as well as acoustic detectors. For the detection of neutrino events in this energy range a combination of different detector concepts in one experiment seems to be most promising.

Rolf Nahnhauer

2004-11-26

175

Energy detection of unknown deterministic signals  

Microsoft Academic Search

By using Shannon's sampling formula, the problem of the detection of a deterministic signal in white Gaussian noise, by means of an energy-measuring device, reduces to the consideration of the sum of the squares of statistically independent Gaussian variates. When the signal is absent, the decision statistic has a central chi-square distribution with the number of degrees of freedom equal

H. Urkowitz

1967-01-01

176

Track detector of CR39-DAP-copolymer with variable threshold to detect trans-iron nuclei in galactic cosmic rays  

Microsoft Academic Search

Observation of trans-iron nuclei in galactic cosmic rays (Z?30) requires a high performance cosmic ray detector telescope with a large exposure area because of their extremely low fluxes. A solid-state track detector such as CR-39 has the advantage of easy extension of exposure area, but it is necessary to raise the Z\\/? detection threshold in order to suppress background tracks

S. Kodaira; M. Aasaeda; T. Doke; M. Hareyama; N. Hasebe; K. Ogura; N. Yasuda; T. Tsuruta; Y. Kori

2008-01-01

177

Tethered balloons for radio detection of ultra high energy cosmic neutrinos in Antarctica  

NASA Astrophysics Data System (ADS)

We present a brief overview of experimental efforts in Antarctica to search for radio pulses from electron-hadron cascades produced by cosmic ultrahigh-energy neutrinos in Antarctic ice. Thus far, the essential features (energy thresholds, effective recording volumes, etc.) of Antarctic neutrino radio experiments can be classified according to the deployment scheme employed: either (1) on the surface of the glacierRAMAND-type, (2) in holes in the ice at depths of several hundred metersRICE-type or (3) on board of a stratospheric balloon at an altitude of 40 kmANITA-type. We herein propose an alternative possibility, namely to use tethered balloons for placing the radio antennas at modest (compared to ANITA) altitudes above the ice surface (1-2 km). This configuration of antennas will reduce (as compared to ANITA) the energy threshold for detection of neutrinos and increase the observation time.

Besson, D.; Dagkesamanskii, R.; Kravchenko, E.; Kravchenko, I.; Zheleznykh, I.

2012-01-01

178

High Energy Polarization of Blazars : Detection Prospects  

E-print Network

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 (wit...

Chakraborty, Nachiketa; Fields, Brian

2015-01-01

179

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

NASA Technical Reports Server (NTRS)

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.

Miles, Jeffrey Hilton

2010-01-01

180

Resonance {eta} Prime -meson photoproduction on protons at photon energies from the reaction threshold to 3700 MeV  

SciTech Connect

The parameters of six resonances of the isobar model for {eta} Prime -meson photoproduction were fitted to experimental differential cross sections for the reaction {gamma}{pi} {yields} {eta} Prime p that weremeasured by the CLAS-2009 and CBELSA/TAPS Collaborations (Mainz, Germany). It was shown that, in the photon energy region from the reaction threshold to 3700MeV, a good description of the experimental cross sections was attained by taking into account the contributions of high-angular-momenta heavy resonances alone.

Tryasuchev, V. A., E-mail: tva@tpu.ru [National Research Tomsk Polytechnical University (Russian Federation)

2013-06-15

181

Lowering the background level and the energy threshold of Micromegas x-ray detectors for axion searches  

E-print Network

Axion helioscopes search for solar axions by their conversion in x-rays in the presence of high magnetic fields. The use of low background x-ray detectors is an essential component contributing to the sensitivity of these searches. In this work, we review the recent advances on Micromegas detectors used in the CERN Axion Solar Telescope (CAST) and proposed for the future International Axion Observatory (IAXO). The actual setup in CAST has achieved background levels below 10$^{-6}$ keV$^{-1}$ cm$^{-2}$ s$^{-1}$, a factor 100 lower than the first generation of Micromegas detectors. This reduction is based on active and passive shielding techniques, the selection of radiopure materials, offline discrimination techniques and the high granularity of the readout. We describe in detail the background model of the detector, based on its operation at CAST site and at the Canfranc Underground Laboratory (LSC), as well as on Geant4 simulations. The best levels currently achieved at LSC are low than 10$^{-7}$ keV$^{-1}$ cm$^{-2}$ s$^{-1}$ and show good prospects for the application of this technology in IAXO. Finally, we present some ideas and results for reducing the energy threshold of these detectors below 1 keV, using high-transparent windows, autotrigger electronics and studying the cluster shape at different energies. As a high flux of axion-like-particles is expected in this energy range, a sub-keV threshold detector could enlarge the physics case of axion helioscopes.

F. J. Iguaz; S. Aune; F. Aznar; J. F. Castel; T. Dafni; M. Davenport; E. Ferrer-Ribas; J. Galan; J. A. Garcia; J. G. Garza; I. Giomataris; I. G. Irastorza; T. Papaevangelou; A. Rodriguez; A. Tomas; T. Vafeiadis; S. C. Yildiz

2015-01-07

182

Essays on price dynamics, discovery, and dynamic threshold effects among energy spot markets in North America  

NASA Astrophysics Data System (ADS)

Given the role electricity and natural gas sectors play in the North American economy, an understanding of how markets for these commodities interact is important. This dissertation independently characterizes the price dynamics of major electricity and natural gas spot markets in North America by combining directed acyclic graphs with time series analyses. Furthermore, the dissertation explores a generalization of price difference bands associated with the law of one price. Interdependencies among 11 major electricity spot markets are examined in Chapter II using a vector autoregression model. Results suggest that the relationships between the markets vary by time. Western markets are separated from the eastern markets and the Electricity Reliability Council of Texas. At longer time horizons these separations disappear. Palo Verde is the important spot market in the west for price discovery. Southwest Power Pool is the dominant market in Eastern Interconnected System for price discovery. Interdependencies among eight major natural gas spot markets are investigated using a vector error correction model and the Greedy Equivalence Search Algorithm in Chapter III. Findings suggest that the eight price series are tied together through six long-run cointegration relationships, supporting the argument that the natural gas market has developed into a single integrated market in North America since deregulation. Results indicate that price discovery tends to occur in the excess consuming regions and move to the excess producing regions. Across North America, the U.S. Midwest region, represented by the Chicago spot market, is the most important for price discovery. The Ellisburg-Leidy Hub in Pennsylvania and Malin Hub in Oregon are important for eastern and western markets. In Chapter IV, a threshold vector error correction model is applied to the natural gas markets to examine nonlinearities in adjustments to the law of one price. Results show that there are nonlinear adjustments to the law of one price in seven pair-wise markets. Four alternative cases for the law of one price are presented as a theoretical background. A methodology is developed for finding a threshold cointegration model that accounts for seasonality in the threshold levels. Results indicate that dynamic threshold effects vary depending on geographical location and whether the markets are excess producing or excess consuming markets.

Park, Haesun

2005-12-01

183

Luteinizing Hormone Pulsatility Is Disrupted at a Threshold of Energy Availability in Regularly Menstruating Women  

Microsoft Academic Search

To investigate the dependence of LH pulsatility on energy availability (dietary energy intake minus exercise energy ex- penditure), we measured LH pulsatility after manipulating the energy availability of 29 regularly menstruating, habitu- ally sedentary, young women of normal body composition for 5 d in the early follicular phase. Subjects expended 15 kcal\\/kg of lean body mass (LBM) per day in

ANNE B. LOUCKS; JEAN R. THUMA

2010-01-01

184

Progressive constrained energy minimization for subpixel detection  

NASA Astrophysics Data System (ADS)

Constrained energy minimization (CEM) has been widely used for subpixel detection. It makes use of the sample correlation matrix R by suppressing the background thus enhancing detection of targets of interest. In many real world problems, implementing target detection on a timely basis is crucial, specifically moving targets. However, since the calculation of the sample correlation matrix R needs the complete data set prior to its use in detection, CEM is prevented from being implemented as a real time processing algorithm. In order to resolve this dilemma, the sample correlation matrix R must be replaced with a causal sample correlation matrix formed by only those data samples that have been visited and the currently being processed data sample. This causality is a pre-requisite to real time processing. By virtue of such causality, designing and developing a real time processing version of CEM becomes feasible. This paper presents a progressive CEM (PCEM) where the causal sample correlation matrix can be updated sample by sample. Accordingly, PCEM allows the CEM to be implemented as a causal CEM (C-CEM) as well as real time (RT) CEM via a recursive update equation in real time.

Wang, Yulei; Schultz, Robert; Chen, Shih-Yu; Liu, Chunhong; Chang, Chein-I.

2013-05-01

185

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

PubMed Central

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

Hansen, Anja; Gneaux, Romain; Gnther, Axel; Krger, Alexander; Ripken, Tammo

2013-01-01

186

Backward conditioned connection and inhibitory reorganization of the receptive fields of cortical neurons as the basis of subconscious change in the thresholds of visual recognition and detection.  

PubMed

Three groups of facts are compared in this study: the significant adaptive and adaptational modification of the receptive fields of neurons of the visual cortex of the cat, the conditioned, selective, subsensory change in the threshold of perception (detection and recognition) by an individual of a letter in relation to two control letters, and the role of spatially-specialized cortical inhibition in the formation and adaptive modifications of the receptive fields and detector properties of neurons of the visual cortex. The relationship of the described phenomena and the commonality of their mechanisms is discussed. PMID:1803270

Shevelev, I A

1991-01-01

187

[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

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

Shevelev, I A

1990-01-01

188

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

Microsoft Academic Search

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

Aravind Kailas

2010-01-01

189

Double-threshold based narrowband signal extraction  

Microsoft Academic Search

A localization algorithm based on double-thresholding (LAD) is a computationally simple method for localizing narrowband signals in the frequency domain. The method does not need any a priori information about the narrowband signal. The localization is based on two thresholds. The lower threshold is used to compose adjacent signal samples into clusters whereas the upper threshold is used to detect

J. Vartiainen; J. J. Lehtomaki; H. Saarnisaari

2005-01-01

190

S-wave threshold in electron attachment - observations and cross sections in CCl4 and SF6 at ultralow electron energies  

SciTech Connect

The threshold photoionization method was used to study low-energy electron attachment phenomena in and cross sections of CCl4 and SF6 compounds, which have applications in the design of gaseous dielectrics and diffuse discharge opening switches. Measurements were made at electron energies from below threshold to 140 meV at resolutions of 6 and 8 meV. A narrow resolution-limited structure was observed in electron attachment to CCl4 and SF6 at electron energies below 10 meV, which is attributed to the divergence of the attachment cross section in the limit epsilon, l approaches zero. The results are compared with experimental collisional-ionization results, electron-swarm unfolded cross sections, and earlier threshold photoionization data. 34 refs.

Chutjian, A.; Alajajian, S.H.

1985-05-01

191

s-wave threshold in electron attachment - Observations and cross sections in CCl4 and SF6 at ultralow electron energies  

NASA Technical Reports Server (NTRS)

The threshold photoionization method was used to study low-energy electron attachment phenomena in and cross sections of CCl4 and SF6 compounds, which have applications in the design of gaseous dielectrics and diffuse discharge opening switches. Measurements were made at electron energies from below threshold to 140 meV at resolutions of 6 and 8 meV. A narrow resolution-limited structure was observed in electron attachment to CCl4 and SF6 at electron energies below 10 meV, which is attributed to the divergence of the attachment cross section in the limit epsilon, l approaches zero. The results are compared with experimental collisional-ionization results, electron-swarm unfolded cross sections, and earlier threshold photoionization data.

Chutjian, A.; Alajajian, S. H.

1985-01-01

192

Effects of nuclear symmetry energy and in-medium NN cross section in heavy-ion collisions at beam energies below the pion production threshold  

E-print Network

Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck(IBUU04) transport model, we explored effects of in-medium $NN$ elastic scattering cross section and nuclear symmetry energy on the sub-threshold pion production in $^{132}Sn+^{124}Sn$ reaction. We find that with decrease of incident beam energy, effects of in-medium $NN$ elastic scattering cross section on the $\\pi^{-}/\\pi^{+}$ ratio are larger than that of the symmetry energy although the latter may be also larger. While keeping the effect of symmetry energy, the double ratio of $\\pi^{-}/\\pi^{+}$ from neutron-rich and neutron-poor reaction systems (with the same mass number of system) $^{132}Sn+^{124}Sn$ and $^{128}Pm+^{128}Pm$ almost fully cancels out the effects of in-medium $NN$ elastic scattering cross section.

Wen-Mei Guo; Gao-Chan Yong; Wei Zuo

2014-09-24

193

Radio Detection of Ultra High Energy Neutrinos  

NASA Astrophysics Data System (ADS)

Ultra high energy cosmic rays interact with the cosmic microwave background radiation, resulting in the production of energetic pions. These interactions result in energy loss by the incident cosmic ray leading to the Greisen-Zatsepin-Kuzmin (GZK) feature in the cosmic ray spectrum at about 410^19 eV, and the decay of the charged pions produced in these interactions results in neutrinos known as Berezinskii-Zatsepin (BZ) neutrinos. These neutrinos interact only via the weak interaction, with negligible absorption over cosmic distances but interaction lengths in the Earth of a few hundred kilometers. When these neutrinos interact in a dense medium, the electromagnetic component of the resulting shower develops a negative charge excess due to Compton scattering of the electrons from the medium and depletion of positrons by in-flight annihilation. This macroscopic charge excess moves at nearly the speed of light, and its passage through a dielectric medium results in coherent Cherenkov radiation at radio wavelengths longer than the size of the radiating region. This process is known as the Askaryan mechanism, and has been observed in accelerator experiments. The radio pulse is impulsive, and can be detected over large volumes in materials with long radio attenuation lengths, most notably the cold ice in the Antarctic ice sheet. Upper limits on the neutrino flux obtained by the balloon-borne instrument ANITA are now approaching the expected flux, and prototype in-ice antenna arrays are now being deployed. Prospects for large detectors capable of detecting hundreds of these neutrinos will be discussed. This work is supported by NASA under grants NNX08AC17G and NNX11AC45G, by the NSF under grant PHY-0758082, and by the Ohio State Center for Cosmology and Particle Astrophysics (CCAPP).

Beatty, James J.

2011-05-01

194

ECG Compression for Remote Healthcare Systems using Selective Thresholding based on Energy  

E-print Network

-off between the compression ratio (CR) and the fidelity of the reconstructed signal, to preserve an average compression ratio of 16.5:1, an average percent root mean square difference of 0.75 and an average methodology is based on the Discrete Wavelet Transform (DWT). The energy packing efficiency of the DWT

195

On the feasibility of RADAR detection of high-energy neutrino-induced showers in ice  

NASA Astrophysics Data System (ADS)

In this article we try to answer the question whether the radar detection technique can be used for the detection of high-energy-neutrino induced particle cascades in ice. A high-energy neutrino interacting in ice will induce a particle cascade, also referred to as a particle shower, moving at approximately the speed of light. Passing through, the cascade will ionize the medium, leaving behind a plasma tube. The different properties of the plasma-tube, such as its lifetime, size and the charge-density will be used to obtain an estimate if it is possible to detect this tube by means of the radar detection technique. Next to the ionization electrons a second plasma due to mobile protons induced by the particle cascade is discussed. An energy threshold for the cascade inducing particle of 4 PeV for the electron plasma, and 20 PeV for the proton plasma is obtained. This allows the radar detection technique, if successful, to cover the energy-gap between several PeV and a few EeV in the currently operating neutrino detectors, where on the low side IceCube runs out of events, and on the high side the Askaryan radio detectors begin to have large effective volumes.

de Vries, Krijn D.; Hanson, Kael; Meures, Thomas

2015-01-01

196

The Nature of Psychological Thresholds  

ERIC Educational Resources Information Center

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.

Rouder, Jeffrey N.; Morey, Richard D.

2009-01-01

197

Energy distribution and quantum yield for photoemission from air-contaminated gold surfaces under ultraviolet illumination close to the threshold  

NASA Astrophysics Data System (ADS)

The kinetic energy distributions of photo-electrons emitted from gold surfaces under illumination by UV-light close to the threshold (photon energy in the order of the material work function) are measured and analyzed. Samples are prepared as chemically clean through Ar-ion sputtering and then exposed to atmosphere for variable durations before quantum yield measurements are performed after evacuation. During measurements, the bias voltage applied to the sample is varied and the resulting emission current measured. Taking the derivative of the current-voltage curve yields the energy distribution which is found to closely resemble the distribution of total energies derived by DuBridge for emission from a free electron gas. We investigate the dependence of distribution shape and width on electrode geometry and contaminant substances adsorbed from the atmosphere, in particular, to water and hydro-carbons. Emission efficiency increases initially during air exposure before diminishing to zero on a timescale of several hours, whilst subsequent annealing of the sample restores emissivity. A model fit function, in good quantitative agreement with the measured data, is introduced which accounts for the experiment-specific electrode geometry and an energy dependent transmission coefficient. The impact of large patch potential fields from contact potential drops between sample and sample holder is investigated. The total quantum yield is split into bulk and surface contributions which are tested for their sensitivity to light incidence angle and polarization. Our results are directly applicable to model parameters for the contact-free discharge system onboard the Laser Interferometer Space Antenna (LISA) Pathfinder spacecraft.

Hechenblaikner, Gerald; Ziegler, Tobias; Biswas, Indro; Seibel, Christoph; Schulze, Mathias; Brandt, Nico; Schll, Achim; Bergner, Patrick; Reinert, Friedrich T.

2012-06-01

198

Point-defect and threshold displacement energies in Ni3Al I. Point-defect properties  

Microsoft Academic Search

The energy and volume change associated with the creation of point defects in Ni3Al have been calculated by computer simulation using a modified version of the many-body potentials of Vitek, Ackland and Cserti. The potentials have been adjusted to provide a better description of the interaction between atoms at separations inside the normal nearest-neighbour spacing. This region is important for

F. Gao; D. J. Bacon; G. J. Ackland

1993-01-01

199

Low Energy Threshold Analysis of the Phase I and Phase II Data Sets of the Sudbury Neutrino Observatory  

E-print Network

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_eff=3.5 MeV, the lowest analysis threshold yet achieved with water Cherenkov detector data. In units of 10^6 cm^{-2} s^{-1}, the total flux of active-flavor neutrinos from 8B decay in the Sun measured using the neutral current (NC) reaction of neutrinos on deuterons, with no constraint on the 8B neutrino energy spectrum, is found to be Phi_NC = 5.140 ^{+0.160}_{-0.158} (stat) ^{+0.132}_{-0.117} (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 8B neutrino flux and the energy-dependent nu_e survival probability provides a measure of the total 8B neutrino flux Phi_8B = 5.046 ^{+0.159}_{-0.152} (stat) ^{+0.107}_{-0.123} (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_{12}=34.06 ^{+1.16}_{-0.84} degrees and Delta m^2_{21}=7.59 ^{+0.20}_{-0.21} x 10^{-5} eV^2. The global value of Phi_8B is extracted to a precision of ^{+2.38}_{-2.95} %. In a three-flavor analysis the best fit value of sin^2\\theta_{13} is 2.00 ^{+2.09}_{-1.63} x 10^{-2}. Interpreting this as a limit implies an upper bound of sin^2\\theta_{13} < 0.057 (95% C. L.).

The SNO Collaboration

2010-06-09

200

Conditional global regularity of Schrdinger maps: sub-threshold dispersed energy  

E-print Network

We consider the Schr\\"odinger map initial value problem into the sphere in 2+1 dimensions with smooth, decaying, subthreshold initial data. Assuming an a priori $L^4$ boundedness condition on the solution, we prove that the Schr\\"odinger map system admits a unique global smooth solution provided that the initial data is sufficiently energy-dispersed. Also shown are global-in-time bounds on certain Sobolev norms of the solution. Toward these ends we establish improved local smoothing and bilinear Strichartz estimates, adapting the Planchon-Vega approach to such estimates to the nonlinear setting of Schr\\"odinger maps.

Paul Smith

2013-01-28

201

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

E-print Network

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.

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

2011-03-23

202

Near-threshold sputtering of MoSi2  

NASA Astrophysics Data System (ADS)

This paper presents a comprehensive experimental, theoretical and computer simulation study of very low-energy (3-35 eV) argon ion sputtering of ?-MoSi2 (0 0 0 1) . Modification of MoSi2 surface composition under low-energy ion bombardment was studied by Auger electron spectroscopy (AES) and X-ray photoelectronic spectroscopy (XPS). The detected changes of surface composition were attributed to preferential sputtering combined with threshold effects. To verify the interpretation, an analytical theory of near-threshold sputtering of compounds is developed which provides a general relation between the sputter threshold energy of target atoms on one side and their atomic masses, surface-binding energies as well with the ion atomic mass on the other side. Elementary mechanisms of near-threshold sputtering are found from the theory and molecular dynamics simulation for MoSi2. Threshold energies for various mechanisms of Mo and Si sputtering are calculated and used to explain the experimental evidence. From results of the work it is concluded that the experimental study of surface composition changes after near-threshold sputtering provides a radically new approach to investigate surface binding in compounds.

Soshnikov, I. P.; Stepanova, M. G.; Matin, E. N.; Shakhmin, A. L.; Khodorkovsky, M. A.; Bert, N. A.

203

Cognitive load and detection thresholds in car following situations: safety implications for using mobile (cellular) telephones while driving  

Microsoft Academic Search

This study was aimed at investigating drivers ability to detect a car ahead decelerating, while doing mobile phone related tasks. Nineteen participants aged between 20 and 29 years, (2000125?000 km driving experience) drove at 80 km\\/h, 50 m behind a lead car, on a 30 km section of motorway in normal traffic. During each trial the lead car started to

Dave Lamble; Tatu Kauranen; Matti Laakso; Heikki Summala

1999-01-01

204

The absolute threshold of cone vision.  

PubMed

We report measurements of the absolute threshold of cone vision, which has been previously underestimated due to suboptimal conditions or overly strict subjective response criteria. We avoided these limitations by using optimized stimuli and experimental conditions while having subjects respond within a rating scale framework. Small (1' fwhm), brief (34 ms), monochromatic (550 nm) stimuli were foveally presented at multiple intensities in dark-adapted retina for 5 subjects. For comparison, 4 subjects underwent similar testing with rod-optimized stimuli. Cone absolute threshold, that is, the minimum light energy for which subjects were just able to detect a visual stimulus with any response criterion, was 203 38 photons at the cornea, ~0.47 log unit lower than previously reported. Two-alternative forced-choice measurements in a subset of subjects yielded consistent results. Cone thresholds were less responsive to criterion changes than rod thresholds, suggesting a limit to the stimulus information recoverable from the cone mosaic in addition to the limit imposed by Poisson noise. Results were consistent with expectations for detection in the face of stimulus uncertainty. We discuss implications of these findings for modeling the first stages of human cone vision and interpreting psychophysical data acquired with adaptive optics at the spatial scale of the receptor mosaic. PMID:21270115

Koenig, Darren; Hofer, Heidi

2011-01-01

205

Formation of very-low-energy states crossing the ionization threshold of argon atoms in strong mid-infrared fields  

NASA Astrophysics Data System (ADS)

Atomic ionization by intense mid-infrared (mid-IR) pulses produces low-electron-energy features that the strong-field approximation, which is expected to be valid in the tunneling ionization regime characterized by small Keldysh parameters (? ?1 ), cannot describe. These features include the low-energy structure (LES), the very-low-energy structure (VLES), and the more recently found zero-energy structure (ZES). They result from the interplay between the laser electric field and the atomic Coulomb field which controls the low-energy spectrum also for small ? . In the present joint experimental and theoretical study we investigate the vectorial momentum spectrum of photoelectrons emitted from an Ar gas target at very low energies. Using a reaction microscope optimized for the detection of very-low-energy electrons, we have performed a thorough study of the three-dimensional momentum spectrum well below 1 eV. Our measurements are complemented by quantum and classical simulations, which allow for an interpretation of the LES and VLES and of the ZES in terms of two-dimensional Coulomb focusing and recapture into Rydberg states, respectively.

Wolter, Benjamin; Lemell, Christoph; Baudisch, Matthias; Pullen, Michael G.; Tong, Xiao-Min; Hemmer, Michal; Senftleben, Arne; Schrter, Claus Dieter; Ullrich, Joachim; Moshammer, Robert; Biegert, Jens; Burgdrfer, Joachim

2014-12-01

206

On the Energy Detection of Unknown Signals Over Fading Channels  

Microsoft Academic Search

This letter addresses the problem of energy detection of an unknown signal over a multipath channel. It starts with the no-diversity case, and presents some alternative closed-form expressions for the probability of detection to those recently reported in the literature. Detection capability is boosted by implementing both square-law combining and square-law selection diversity schemes

Fadel F. Digham; Mohamed-slim Alouini; Marvin K. Simon

2007-01-01

207

Adaptive thresholding with inverted triangular area for real-time detection of the heart rate from photoplethysmogram traces on a smartphone.  

PubMed

Photoplethysmogram (PPG) signals acquired by smartphone cameras are weaker than those acquired by dedicated pulse oximeters. Furthermore, the signals have lower sampling rates, have notches in the waveform and are more severely affected by baseline drift, leading to specific morphological characteristics. This paper introduces a new feature, the inverted triangular area, to address these specific characteristics. The new feature enables real-time adaptive waveform detection using an algorithm of linear time complexity. It can also recognize notches in the waveform and it is inherently robust to baseline drift. An implementation of the algorithm on Android is available for free download. We collected data from 24 volunteers and compared our algorithm in peak detection with two competing algorithms designed for PPG signals, Incremental-Merge Segmentation (IMS) and Adaptive Thresholding (ADT). A sensitivity of 98.0 % and a positive predictive value of 98.8 % were obtained, which were 7.7 % higher than the IMS algorithm in sensitivity, and 8.3 % higher than the ADT algorithm in positive predictive value. The experimental results confirmed the applicability of the proposed method. PMID:25570674

Jiang, Wen Jun; Wittek, Peter; Li Zhao; Shi Chao Gao

2014-08-01

208

Electrophysiological Correlates of the Threshold to Detection of Passive Motion: An Investigation in Professional Volleyball Athletes with and without Atrophy of the Infraspinatus Muscle  

PubMed Central

The goal of the present study is to compare the electrophysiological correlates of the threshold to detection of passive motion (TTDPM) among three groups: healthy individuals (control group), professional volleyball athletes with atrophy of the infraspinatus muscle on the dominant side, and athletes with no shoulder pathologies. More specifically, the study aims at assessing the effects of infraspinatus muscle atrophy on the cortical representation of the TTDPM. A proprioception testing device (PTD) was used to measure the TTDPM. The device passively moved the shoulder and participants were instructed to respond as soon as movement was detected (TTDPM) by pressing a button switch. Response latency was established as the delay between the stimulus (movement) and the response (button press). Electroencephalographic (EEG) and electromyographic (EMG) activities were recorded simultaneously. An analysis of variance (ANOVA) and subsequent post hoc tests indicated a significant difference in latency between the group of athletes without the atrophy when compared both to the group of athletes with the atrophy and to the control group. Furthermore, distinct patterns of cortical activity were observed in the three experimental groups. The results suggest that systematically trained motor abilities, as well as the atrophy of the infraspinatus muscle, change the cortical representation of the different stages of proprioceptive information processing and, ultimately, the cortical representation of the TTDPM. PMID:23484136

Salles, Jos Incio; Cossich, Victor Rodrigues Amaral; Amaral, Marcus Vinicius; Monteiro, Martim T.; Cagy, Maurcio; Motta, Geraldo; Velasques, Bruna; Piedade, Roberto; Ribeiro, Pedro

2013-01-01

209

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

NASA Astrophysics Data System (ADS)

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 the remaining features to the dipole-forbidden a 3Pi state (v')=17-20, and some to the weakly bound c 3Sigma+ state (v')=0-2. The model potentials, which reproduce the spectrum and compactly represent the spectroscopic data, should help to predict more accurately C++H scattering in the interstellar medium.

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

2002-11-01

210

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

NASA Astrophysics Data System (ADS)

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 (2A2), 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 C2v symmetry through the C-N axis.

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

2014-11-01

211

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

PubMed

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. PMID:25381510

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

2014-11-01

212

Detecting dark energy with wavelets on the sphere  

E-print Network

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.

J. D. McEwen

2007-08-29

213

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

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?detected using the NTI, which was significantly decreased (P?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. PMID:25569647

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

2015-01-01

214

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

SciTech Connect

Dissociative photoionization of methyl bromide (CH{sub 3}Br) in an excitation energy range of 10.4516.90 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 CBr 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 CBr 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. CBr 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.

Tang, Xiaofeng [Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China) [Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Zhou, Xiaoguo, E-mail: xzhou@ustc.edu.cn, E-mail: yanbing@jlu.edu.cn; Liu, Shilin [Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China) [Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Sun, Zhongfa [Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China)] [Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); Liu, Fuyi; Sheng, Liusi [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China)] [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Yan, Bing, E-mail: xzhou@ustc.edu.cn, E-mail: yanbing@jlu.edu.cn [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China)] [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China)

2014-01-28

215

Photon counting threshold optimization in mammography  

NASA Astrophysics Data System (ADS)

The influence of detection threshold on the performance of ideal photon counting sensors is investigated in mammography for several X-ray tube anode/filter combinations and various breast thicknesses. Based on linear X-ray system theory, a method is proposed to take into consideration detector contrast modulation in the domain of X-ray energy as well as effects related to scattered radiation. Breast screening procedures are modelled as radiographic tasks in which low-contrast objects (tumours or microcalcifications) have to be detected in a noisy image background. For ideal photon counting detectors, results at zero spatial frequency show that higher detection thresholds must be implemented when imaging a thick compressed breast, compared to a thin compressed breast. In practice, the photon counting threshold also affects the image noise and the spatial resolution of hybrid pixel detectors, by tuning the amount of charge-shared events. To be generalized to more realistic imaging situations, this analysis must be performed over the full range of spatial frequencies and include additional detector noise parameters.

Marchal, Julien; Hussein, Khalid; John, Lester R.; Vaughan, Christopher L.

2006-07-01

216

How Real Detector Thresholds Create False Standard Candles  

SciTech Connect

GRB satellites are relatively inefficient detectors of dim hard bursts. For example, given two bursts of identical peak luminosity near the detection threshold, a dim soft burst will be preferentially detected over a dim hard burst. This means that a high E{sub peak} burst will need a higher peak luminosity to be detected than a low E{sub peak} GRB. This purely detector-created attribute will appear as a correlation between E{sub peak} and luminosity, and should not be interpreted as a real standard candle effect. This result derives from Monte Carlo simulations utilizing a wide range of initial GRB spectra, and retriggering to create a final ''detected'' sample. In sum, E{sub peak} is not a good standard candle, and its appearance as such in seeming correlations such as the Amati and other L{sub iso} vs. E{sub peak} relations is likely a ghost of real energy-related detection thresholds.

Shahmoradi, Amir; Nemiroff, Robert [Department of Physics, Michigan Technological University (United States)

2009-05-25

217

CERES Detects Earth's Heat and Energy  

NASA Technical Reports Server (NTRS)

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

2002-01-01

218

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

Microsoft Academic Search

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 [+-

Paul G. Wenthold; Robert R. Squires

1994-01-01

219

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

PubMed Central

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 ?GCNi(II)-InrSDNA 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 ?GCZn(II)-InrSDNA is less than ?GCZn(II)-ZiaRDNA implying that relative to other sensors, ?GCZn(II)-SensorDNA rather than KZn(II) determines the final detection threshold for Zn(II). PMID:24666373

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

2014-01-01

220

Can the Existence of Dark Energy Be Directly Detected?  

E-print Network

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?

Martin L. Perl

2008-10-06

221

Spallation Neutron Energy Spectrum Determination with Yttrium as a Threshold Detector on U/Pb-assembly ``Energy plus Transmutation''  

NASA Astrophysics Data System (ADS)

Results of two experiments with Yttrium-89 samples on U/Pb-assembly Energy plus Transmutation [1] are presented. The assembly is a lead cylindrical target (8.4 cm diameter, 45.6 cm length) with natural uranium blanket (206.4 kg). The lead target was irradiated with JINR Dubna NUCLOTRON with 1.60 and 2.52 GeV deuteron beam. The final purpose of the experiments was to measure neutron field inside the assembly. Yttrium-89 activation detectors were located throughout the entire U/Pb-assembly. Irradiated sample gamma activity was measured with HPGe spectrometer. The gamma spectra were analyzed and the net peak areas were calculated using the DEIMOS program [2]. After short presentation of the activation results neutron spectrum determination method is proposed and its results presented. Assuming reaction model through compound nucleus and using some mathematical tricks Yttrium isotope k production rate discrete formula I_k = Nintlimits_{E_{thr,k} }^infty {? left( E right)? _k left( {E,E_{thr} } right)} dE was transformed into Volterra's integral equation of the first kind and then solved. The method and its applicability still to be discussed. The results as the preliminary ones are for illustrative purpose only.

Kilim, S.; Bielewicz, M.; Strugalska-Gola, E.; Szuta, M.; Wojciechowski, A.; Krivopustov, M. I.; Kovalenko, A. D.; Adam, I.; Krasa, A.; Majerle, M.; Wagner, V.

222

Spallation Neutron Energy Spectrum Determination with Yttrium as a Threshold Detector on U/Pb-assembly "Energy plus Transmutation"  

NASA Astrophysics Data System (ADS)

Results of two experiments with Yttrium-89 samples on U/Pb-assembly "Energy plus Transmutation" [1] are presented. The assembly is a lead cylindrical target (8.4 cm diameter, 45.6 cm length) with natural uranium blanket (206.4 kg). The lead target was irradiated with JINR Dubna NUCLOTRON with 1.60 and 2.52 GeV deuteron beam. The final purpose of the experiments was to measure neutron field inside the assembly. Yttrium-89 activation detectors were located throughout the entire U/Pb-assembly. Irradiated sample gamma activity was measured with HPGe spectrometer. The gamma spectra were analyzed and the net peak areas were calculated using the DEIMOS program [2]. After short presentation of the activation results neutron spectrum determination method is proposed and its results presented. Assuming reaction model through compound nucleus and using some mathematical tricks Yttrium isotope "k " production rate discrete formula I_k = Nintlimits_{E_{thr,k} }^infty {? left( E right)? _k left( {E,E_{thr} } right)} dE was transformed into Volterra's integral equation of the first kind and then solved. The method and its applicability still to be discussed. The results as the preliminary ones are for illustrative purpose only.

Kilim, S.; Bielewicz, M.; Strugalska-Gola, E.; Szuta, M.; Wojciechowski, A.; Krivopustov, M. I.; Kovalenko, A. D.; Adam, I.; Krasa, A.; Majerle, M.; Wagner, V.

223

Online Fault Detection and Tolerance for Photovoltaic Energy Harvesting Systems  

E-print Network

Online Fault Detection and Tolerance for Photovoltaic Energy Harvesting Systems Xue Lin 1 , Yanzhi (PV systems) are subject to PV cell faults, which decrease the efficiency of PV systems and even shorten the PV system lifespan. Manual PV cell fault detection and elimination are expensive and nearly

Pedram, Massoud

224

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)

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 fields. The presentation will provide long-term insights into the sustainability of the proposed interventions with regards to 'safe' harvest thresholds, feedstock yields, SOC storage and rate of change, and sediment and nutrient (N&P) losses. Model calibration and validation datasets have already been compiled from rainfed and irrigated energy sorghum field studies conducted in Arkansas and Alabama during the years: 2008 to 2010. We compiled energy sorghum crop parameters based on data extracted from the literature, expert judgment and field experiments. Simulations will be made for combinations of biomass harvest rates, tillage systems, weather, soil type, and dryland production over a 51-year time series (1960-2010).

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

2011-12-01

225

Resonant Raman scattering contribution to attenuation of x rays at energies in lower vicinity of the K-shell ionization threshold of some elements  

NASA Astrophysics Data System (ADS)

Attenuation of the x rays and ? rays in the T22i, N41b, T69m, Y70b, and L71u elements have been measured with special emphasis for the x ray energies (Ein) in lower vicinity of the K shell ionization threshold (BK) of the element. The incident photon beam is obtained from decay of the F55e, A241m, and C57o radioisotopes, and fluorescence of the V23, Y70b, L71u, W74, O76s, and T90h targets excited by the x rays and ? rays from the radioisotopes. The measurements were performed using energy dispersive setups involving Ge detectors. The measured attenuation coefficients agree with the available theoretical values except at the photon energies with (BK-Ein) less than or nearly equal to the K-shell width (?K), where significant positive deviations as large as factor of 2 have been observed. In view of reliability of the available theoretical cross sections for the photoionization and the photon scattering processes, the magnitude of positive alteration at the photon energy in lower vicinity of the ionization threshold is attributed to the K shell resonant Raman scattering (RRS) process and the corresponding cross sections have been deduced. Possible matrix effects in the energy dispersive x ray spectrometry due to RRS are also discussed.

Kumar, Sanjeev; Sharma, Veena; Kumar, Sunil; Alrakabi, Muhanad; Mehta, D.; Singh, Nirmal

2009-05-01

226

Energy thresholds that determine membrane integrity and injury in a renal epithelial cell line (LLC-PK1). Relationships to phospholipid degradation and unesterified fatty acid accumulation.  

PubMed Central

This study related ATP levels with membrane damage, lipid abnormalities, and cell death in energy-depleted LLC-PK1 cells. Oxidative phosphorylation was inhibited by antimycin A, and glycolysis was regulated by graded glucose deprivation to achieve stepwise ATP depletion. Over a range of ATP levels down to approximately equal to 5% of normal, over 5 h, cells were altered only minimally, or injured reversibly. Such cells maintained mitochondrial potential, and retained more K+ than cells without an energy source. Over the same duration, cells without an energy source were lethally injured. Treatment with antimycin induced increments of triglycerides and decreases of phospholipids. With severe ATP depletion (approximately equal to 5-10% of normal after 5 h), decrease of phospholipids was marked. Cells in which ATP was not measurable (or was less than 5% of normal) showed comparable phospholipid declines but, in addition, showed massive and progressive increase of unesterified fatty acids. The results identified a low threshold of ATP, at best 5-10% of normal, which preserved viability in LLC-PK1 cells despite major loss of membrane phospholipids. This threshold also determined the ability of cells to maintain their normally low levels of unesterified fatty acids. Failure of energy-dependent mechanisms that normally metabolize unesterified fatty acids may be a correlate of the extent of energy depletion that determines lethal injury. Images PMID:3125228

Venkatachalam, M A; Patel, Y J; Kreisberg, J I; Weinberg, J M

1988-01-01

227

Near threshold absolute TDCS: first results  

NASA Astrophysics Data System (ADS)

A new method, and first results for an impact energy 2 eV above the threshold of ionisation of helium, are presented for the measurement of absolute triple differential cross sections (TDCS) in a crossed beam experiment. The method is based upon measurement of beam/target overlap densities using known absolute total ionisation cross sections and of detection efficiencies using known absolute double differential cross sections (DDCS). For the present work the necessary absolute DDCS for 1 eV electrons had also to be measured. Results are presented for several different coplanar kinematics and are compared with recent DWBA calculations.

Rsel, T.; Schlemmer, P.; Rder, J.; Frost, L.; Jung, K.; Ehrhardt, H.

1992-12-01

228

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

PubMed Central

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

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

2014-01-01

229

Pulse-energy dynamics of passively mode-locked solid-state lasers above the Q-switching threshold  

Microsoft Academic Search

We have investigated the dynamical behavior of various passively mode-locked solid-state lasers by measuring how a modulation of the pump power affects the output power. We show theoretically and experimentally how the damping of the relaxation oscillations is reduced and finally becomes zero when the pump power is reduced so that the threshold for Q-switched mode locking is approached. For

Adrian Schlatter; S. C. Zeller; R. Grange; R. Paschotta; U. Keller

2004-01-01

230

The Acoustic Detection of Ultra High Energy Neutrinos  

E-print Network

Attempts have been made to parameterise the thermoacoustic emission of particle cascades induced by EeV neutrinos interacting in the sea. Understanding the characteristic radiation from such an event allows us to predict the pressure pulse observed by underwater acoustic sensors distributed in kilometre scale arrays. We find that detectors encompassing thousands of cubic kilometres are required, with a minimum of 100 hydrophones per kilometre cubed, in order to observe the flux of neutrinos predicted by the attenuation of ultra high energy cosmic rays on cosmic microwave background photons. The pressure threshold of such an array must be in the range 5-10 mPa and the said detector will have to operate for five years or more. Additionally a qualitative analysis of the first acoustic data recorded by the Rona hydrophone array off the north-west coast of Scotland is reported.

J. Perkin

2008-01-07

231

LAT Perspectives in Detection of High Energy Cosmic Ray Electrons  

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

232

Seebeck Nanoantennas for Infrared Detection and Energy Harvesting Applications  

E-print Network

In this letter we introduce a new type of infrared sensor, based on thermocouple nanoantennas, which enables the energy detection and gathering in the mid-infrared region. The proposed detector combines the Seebeck effect, as a transduction mechanism, with the functionalities of the optical antennas for optical sensing. By using finite-element numerical simulations we evaluate the performance and optical-to-electrical conversion efficiency of the proposed device, unveiling its potential for optical sensing and energy harvesting applications.

Briones, Edgar; Martinez-Anton, J C; Cuadrado, Alexander; McMurtry, Stefan; Hehn, Michel; Montaigne, Franois; Alda, Javier; Gonzlez, Javier

2014-01-01

233

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

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 0.650.75?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 2040?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 shift, but only under conditions of simultaneous negative gate bias and illumination, as observed experimentally as the NBIS effect.

Flewitt, A. J., E-mail: ajf@eng.cam.ac.uk [Electrical Engineering Division, Cambridge University, J J Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Powell, M. J. [252, Valley Drive, Kendal LA9 7SL (United Kingdom)

2014-04-07

234

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  

NASA Astrophysics Data System (ADS)

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 106-107 s-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 shift, but only under conditions of simultaneous negative gate bias and illumination, as observed experimentally as the NBIS effect.

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

2014-04-01

235

High Energy Telescope With Neutron Detection Capabilities (HETn)  

NASA Astrophysics Data System (ADS)

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.

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

2007-01-01

236

Directed energy active illumination for near-Earth object detection  

NASA Astrophysics Data System (ADS)

On 15 February 2013, a previously unknown ~20 m asteroid struck Earth near Chelyabinsk, Russia, releasing kinetic energy equivalent to ~570 kt TNT. Detecting objects like the Chelyabinsk impactor that are orbiting near Earth is a difficult task, in part because such objects spend much of their own orbits in the direction of the Sun when viewed from Earth. Efforts aimed at protecting Earth from future impacts will rely heavily on continued discovery. Ground-based optical observatory networks and Earth-orbiting spacecraft with infrared sensors have dramatically increased the pace of discovery. Still, less than 5% of near-Earth objects (NEOs) >=100 m/~100 Mt TNT have been identified, and the proportion of known objects decreases rapidly for smaller sizes. Low emissivity of some objects also makes detection by passive sensors difficult. A proposed orbiting laser phased array directed energy system could be used for active illumination of NEOs, enhancing discovery particularly for smaller and lower emissivity objects. Laser fiber amplifiers emit very narrow-band energy, simplifying detection. Results of simulated illumination scenarios are presented based on an orbiting emitter array with specified characteristics. Simulations indicate that return signals from small and low emissivity objects is strong enough to detect. The possibility for both directed and full sky blind surveys is discussed, and the resulting diameter and mass limits for objects in different observational scenarios. The ability to determine both position and speed of detected objects is also discussed.

Riley, Jordan; Lubin, Philip; Hughes, Gary B.; O'Neill, Hugh; Meinhold, Peter; Suen, Jonathan; Bible, Johanna; Johansson, Isabella E.; Griswold, Janelle; Cook, Brianna

2014-09-01

237

Accuracy threshold for postselected quantum computation  

E-print Network

We prove an accuracy threshold theorem for fault-tolerant quantum computation based on error detection and postselection. Our proof provides a rigorous foundation for the scheme suggested by Knill, in which preparation circuits for ancilla states are protected by a concatenated error-detecting code and the preparation is aborted if an error is detected. The proof applies to independent stochastic noise but (in contrast to proofs of the quantum accuracy threshold theorem based on concatenated error-correcting codes) not to strongly-correlated adversarial noise. Our rigorously established lower bound on the accuracy threshold, 1.04 \\times 10^{-3}, is well below Knill's numerical estimates.

Panos Aliferis; Daniel Gottesman; John Preskill

2007-09-17

238

Detection and analysis of three highly excited vibrational bands of 16O3 by CW-CRDS near the dissociation threshold  

NASA Astrophysics Data System (ADS)

The present contribution is devoted to the analysis of three extremely weak A-type bands of 16O3 recorded near 7686, 7739 and 7860 cm-1i.e. only a few % below the dissociation limit, D0, at about 8560 cm-1. They correspond to the most excited vibration-rotation states of ozone observed so far via high-resolution absorption spectroscopy. They were detected by high sensitivity CW-cavity ring down spectroscopy with a typical noise equivalent absorption, ?min, on the order of 210-10 cm-1 and modelled using the effective operator approach. The derived band centres and rotational constants show a very good agreement with recent theoretical predictions based on a new ab initio potential energy surface.

Campargue, A.; Kassi, S.; Mondelain, D.; Barbe, A.; Starikova, E.; De Backer, M.-R.; Tyuterev, Vl. G.

2015-02-01

239

Detection of artifacts from high energy bursts in neonatal EEG.  

PubMed

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 feature subset producing highest classification accuracy. The suggested feature based classification method is executed using our recorded neonatal EEG dataset, consisting of burst and artifact segments. We obtain 78% sensitivity and 72% specificity as the accuracy measures. The accuracy obtained using the proposed method is found to be about 20% higher than that of the reference approaches. Joint use of the proposed method with our previous work on burst detection outperforms reference methods on simultaneous burst and artifact detection. As the proposed method supports detection of a wide range of artifact patterns, it can be improved to incorporate the detection of artifacts within other seizure patterns and background EEG information as well. PMID:24209926

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

2013-11-01

240

Experimental double-differential cross sections and derived kerma factors for oxygen at incident neutron energies from reaction thresholds to 65 MeV  

NASA Astrophysics Data System (ADS)

The double-differential cross sections (energy spectra) for the (n, px), (n, dx), (n, tx) and (n, x) reactions on oxygen have been measured for nine incident neutron energies in the range 25 to 65 MeV at lab angles between and in steps of . From these measurements, the energy differential cross sections have been determined and consequently the partial and total kerma factors. Based on the obtained experimental partial kerma factors in the incident neutron energy range 25-65 MeV, a procedure is proposed for the extrapolation of these values to the reaction threshold energy of each measured reaction channel. Results of the experimental double-differential, energy differential and total cross sections are presented. The deduced partial and total kerma factors of the present work are compared with results of previous measurements and theoretical predictions.

Benck, S.; Slypen, I.; Meulders, J. P.; Corcalciuc, V.

1998-12-01

241

Resonant energy transfer based biosensor for detection of multivalent proteins.  

SciTech Connect

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

Song, X. (Xuedong); Swanson, Basil I.

2001-01-01

242

Measurement of Low Energy Detection Efficiency of a Plastic Scintillator: Implications on the Lower Energy Limit and Sensitivity of a Hard X-Ray Focal Plane Compton Polarimeter  

NASA Astrophysics Data System (ADS)

The polarization measurements in X-rays offer a unique opportunity for the study of physical processes under the extreme conditions prevalent at compact X-ray sources, including gravitation, magnetic field, and temperature. Unfortunately, there has been no real progress in observational X-ray polarimetry thus far. Although photoelectron tracking-based X-ray polarimeters provide realistic prospects of polarimetric observations, they are effective in the soft X-rays only. With the advent of hard X-ray optics, it has become possible to design sensitive X-ray polarimeters in hard X-rays based on Compton scattering. An important point that should be carefully considered for the Compton polarimeters is the lower energy threshold of the active scatterer, which typically consists of a plastic scintillator due to its lowest effective atomic number. Therefore, an accurate understanding of the plastic scintillators energy threshold is essential to make a realistic estimate of the energy range and sensitivity of any Compton polarimeter. In this context, we set up an experiment to investigate the plastic scintillators behavior for very low energy deposition events. The experiment involves the detection of Compton scattered photons from a long, thin, plastic scintillator (a similar configuration as the eventual Compton polarimeter) by a high resolution CdTe detector at different scattering angles. We find that it is possible to detect energy deposition well below 1 keV, though with decreasing efficiency. We present detailed semianalytical modeling of our experimental setup and discuss the results in the context of the energy range and sensitivity of the Compton polarimeter involving plastic scintillators.

Chattopadhyay, T.; Vadawale, S. V.; Shanmugam, M.; Goyal, S. K.

2014-05-01

243

High-energy threshold reaction rates on 0.8 GeV proton-irradiated thick Pb-target  

E-print Network

This works presents results of activation-aided determination of threshold reaction rates in 92 209Bi, natPb, 197Au, 181Ta, 169Tm, natIn, 93Nb, 64Zn, 65Cu, 63Cu, 59Co, 19F, and 12C samples and in 121 27Al samples. All the samples were aligned with the proton beam axis inside and outside the demountable 92-cm thick Pb target of 15-cm diameter assembled of 23 4-cm thick discs. The samples were placed on 12 target disks to reproduce the long axis distribution of protons and neutrons. In June 2006, the target was exposed for 18 hours to a 800-MeV proton beam extracted from the ITEP U-10 accelerator. The proton fluence and the proton beam shape were determined using the 27Al(p,x)7Be monitor reaction. The reaction rates were determined by the direct gamma-spectrometry techniques. In total, 1196 gamma-spectra have been measured, and about 1500 reaction rates determined. The measured reaction rates were simulated by the MCNPX code using the following databases: ENDF/B6 for neutrons below 20 MeV, MENDL2 for 20-100 MeV neutrons, and MENDL2P for proton cross sections up to 200 MeV. An acceptable agreement of simulations with experimental data has been found.

Yu. E. Titarenko; V. F. Batyaev; A. Yu. Titarenko; M. A. Butko; K. V. Pavlov; R. S. Tikhonov; S. N. Florya; S. G. Mashnik; W. Gudowski

2007-05-08

244

Use of the Teager-Kaiser Energy Operator for Muscle Activity Detection in Children  

PubMed Central

The purpose of this study was to demonstrate the usefulness of the Teager-Kaiser Energy (TKE) operator to assess surface electromyographic (sEMG) activity from the hip and trunk muscles during pediatric gait in children with and without cerebral palsy (CP). Muscle activity was recorded from the trapezius, erector spinae, rectus abdominus, external oblique, gluteus maximus and medius, rectus femoris, and semitendinosus bilaterally in ten children with typical development (TD) and five children with CP ages 44.4 18.6 months. Duration of muscle activity was calculated as a percentage of the gait cycle, and compared to two common onset detection methods, a standard deviation (SD) amplitude threshold method, and the visual inspection from two raters (R1, R2). Relative and absolute agreement was determined using intraclass correlation coefficients (ICCs) and Bland-Altman plots. Of the two automated methods, the TKE method demonstrated better agreement with visual inspection (0.450.89) than the SD (0.110.76) method. The Bland-Altman plots indicated a smaller bias and 95% confidence interval for the TKE method in comparison to the raters (TKE to R1: ?5, 113%; TKE to R2: 4, 95%; SD to R1: ?24, 170%; SD to R2: ?15, 151%). The use of the TKE operator may better detect sEMG activity in children than the standard amplitude method. PMID:19484385

Lauer, Richard T.; Prosser, Laura A.

2009-01-01

245

Threshold effect in the energy loss of hydrogen and helium ions transmitted in channeling conditions in gold single crystal  

Microsoft Academic Search

The energy loss of hydrogen and helium ions in the low energy range (10keV\\/u) in single crystal gold targets is investigated experimentally. We found that the stopping power for helium ions shows a deviation from the proportionality with ion velocity predicted theoretically. This behavior has been also observed for protons in previous experiments. Additionally, we found that for a small

C. Celedn; N. R. Arista; J. E. Valds; P. Vargas

2008-01-01

246

Detection and Analysis of Threats to the Energy Sector: DATES  

SciTech Connect

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. This resulted in delays in finalizing agreements with commercial partners, and in particular the Invensys testbed was not installed until December 2008 (as opposed to the March 2008 plan). The project resulted in a number of conference presentations and publications, and was well received when presented at industry forums. In spite of some interest on the part of the utility sector, we were unfortunately not able to engage a utility for a full-scale pilot deployment.

Alfonso Valdes

2010-03-31

247

Is the dynamics of scaling dark energy detectable?  

SciTech Connect

We highlight the unexpected impact of nucleosynthesis and other early universe constraints on the detectability of scaling quintessence dynamics at late times, showing that such dynamics may well be invisible until the unveiling of the Stage-IV dark energy experiments (DUNE, JDEM, LSST, SKA). Nucleosynthesis strongly limits potential deviations from {Lambda}CDM. Surprisingly, the standard Chevallier-Polarski-Linder parametrization, w(z) = w{sub 0}+w{sub a}z/(1+z), cannot match the nucleosynthesis bound for minimally coupled scaling fields. Given that such models are arguably the best-motivated alternatives to a cosmological constant these results may significantly impact future cosmological survey design and imply that dark energy may well be dynamical even if we do not detect any dynamics in the next decade.

Bassett, Bruce A; Hlozek, Renee [South African Astronomical Observatory, Observatory, Cape Town (South Africa)] [South African Astronomical Observatory, Observatory, Cape Town (South Africa); Brownstone, Mike; Fantaye, Yabebal; Kotze, Jacques; Okouma, Patrice [Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch, 7700, Cape Town (South Africa)] [Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch, 7700, Cape Town (South Africa); Cardoso, Antonio [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 2EG (United Kingdom)] [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 2EG (United Kingdom); Cortes, Marina, E-mail: bruce@saao.ac.za, E-mail: mikeb@nassp.uct.ac.za, E-mail: antonio.cardoso@port.ac.uk, E-mail: M.V.Cortes@sussex.ac.uk, E-mail: yabebal@nassp.uct.ac.za, E-mail: reneeh@nassp.uct.ac.za, E-mail: jacques@maths.uct.ac.za, E-mail: okouma@nassp.uct.ac.za [Astronomy Centre, University of Sussex, Brighton BN1 9QH (United Kingdom)] [Astronomy Centre, University of Sussex, Brighton BN1 9QH (United Kingdom)

2008-07-15

248

Accuracy threshold for postselected quantum computation  

Microsoft Academic Search

We prove an accuracy threshold theorem for fault-tolerant quantum computation based on error detection and postselection. Our proof provides a rigorous foundation for the scheme suggested by Knill, in which preparation circuits for ancilla states are protected by a concatenated error-detecting code and the preparation is aborted if an error is detected. The proof applies to independent stochastic noise but

Panos Aliferis; Daniel Gottesman; John Preskill

2007-01-01

249

Dual energy detection of weapons of mass destruction  

NASA Astrophysics Data System (ADS)

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)

Budner, Gregory J.

2006-03-01

250

A hydrophone prototype for ultra high energy neutrino acoustic detection  

NASA Astrophysics Data System (ADS)

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.

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

2009-06-01

251

Observation of threshold energy and hysteresis in high current ion beam guiding and transmission through a micro-glass-capillary  

NASA Astrophysics Data System (ADS)

The energy dependent guiding of high current density (0.1-3 A/m2) argon ion beams through a micro-glass-capillary is studied. It is observed that ion transmission through the capillary takes place only if its energy is greater than the retarding potential barrier, which depends upon the amount of charge deposited on the capillary inner wall. Foremost evidence of the observation that the transmitted current exhibits hysteresis with ion energy is presented. Particle in cell simulations carried out by solving Poisson's and Newton's force equation self-consistently, agree reasonably well with the experimental results.

Paul, Samit; Jayakiran, A.; Bhattacharjee, Sudeep

2012-11-01

252

Observation of threshold energy and hysteresis in high current ion beam guiding and transmission through a micro-glass-capillary  

SciTech Connect

The energy dependent guiding of high current density (0.1-3 A/m{sup 2}) argon ion beams through a micro-glass-capillary is studied. It is observed that ion transmission through the capillary takes place only if its energy is greater than the retarding potential barrier, which depends upon the amount of charge deposited on the capillary inner wall. Foremost evidence of the observation that the transmitted current exhibits hysteresis with ion energy is presented. Particle in cell simulations carried out by solving Poisson's and Newton's force equation self-consistently, agree reasonably well with the experimental results.

Paul, Samit; Jayakiran, A.; Bhattacharjee, Sudeep [Department of Physics, Indian Institute of Technology, Kanpur, Uttar Pradesh 208016 (India)

2012-11-26

253

Vacuum ultraviolet mass-analyzed threshold ionization spectroscopy of p-, m-, and o-difluorobenzenes. Ionization energies  

E-print Network

-difluorobenzenes. Ionization energies and vibrational frequencies and structures of the cations Chan Ho Kwon, Hong Lae Kim,a) and Myung Soo Kimb) National Creative Research Initiative Center for Control of Reaction Dynamics and School

Kim, Myung Soo

254

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

PubMed

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. PMID:24491682

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

2014-06-01

255

Research on energy transmission calculation problem on laser detecting submarine  

NASA Astrophysics Data System (ADS)

The laser detection and identification is based on the method of using laser as the source of signal to scan the surface of ocean. If the laser detection equipment finds out the target, it will immediately reflect the returning signal, and then through receiving and disposing the returning signal by the receiving system, to realize the function of detection and identification. Two mediums channels should be though in the process of laser detection transmission, which are the atmosphere and the seawater. The energy loss in the process of water transport, mainly considering the surface reflection and scattering attenuation and internal attenuation factors such as seawater. The energy consumption though atmospheric transmission, mainly considering the absorption of atmospheric and the attenuation causing by scattering, the energy consumption though seawater transmission, mainly considering the element such as surface reflection, the attenuation of scattering and internal attenuation of seawater. On the basis of the analysis and research, through the mode of establishment of atmospheric scattering, the model of sea surface reflection and the model of internal attenuation of seawater, determine the power dissipation of emitting lasers system, calculates the signal strength that reaches the receiver. Under certain conditions, the total attenuation of -98.92 dB by calculation, and put forward the related experiment scheme by the use of Atmospheric analog channel, seawater analog channel. In the experiment of the theory, we use the simulation pool of the atmosphere and the sea to replace the real environment where the laser detection system works in this kind of situation. To start with, we need to put the target in the simulating seawater pool of 10 meters large and then control the depth of the target in the sea level. We, putting the laser detection system in position where it is 2 kilometers far from one side, secondly use the equipment to aim at the target in some distance. Lastly, by launching and detecting the signal of returning wave, identify the effect of the image produced by the system.

Fu, Qiang; Li, Yingchao; Zhang, Lizhong; Wang, Chao; An, Yan

2014-12-01

256

Nuclear threshold effects and neutron strength functions  

NASA Astrophysics Data System (ADS)

The present work is devoted to study of spectroscopic aspects, in terms of neutron strength function, for the threshold effects with non-light nuclei. Relations to the neutron strength functions of the anomal effects observed at threshold of neutron analogue channel, in deuteron stripping reactions on A ? 90 mass target nuclei and in nucleon mirror reactions with A ? 30 nuclei, are established. It is proved that these threshold effects follow the mass dependance of the neutron strength functions. The connection between threshold effects and neutron strength functions, proves that the threshold effects are related to spectroscopy of ancestral zero-energy neutron particle resonance. One can conclude the threshold effects depend not only on penetration factors of opening neutron channel, as in Cusp Theory, but also on Multichannel Reaction Dynamics as well as on Spectroscopy of neutron threshold state. The present study is based on Reduced Scattering Matrix, describing the effect of invisible threshold channel on open observed ones. The determining role of Nuclear Reaction Dynamics, Quasiresonant Scattering and Spectroscopy of Neutron Threshold State, on threshold effects is evinced.

Comisel, H.; Hategan, C.; Wolter, H. H.

2010-07-01

257

Energy resolution of superconducting tunnel diodes in low-energy radiation detection  

Microsoft Academic Search

In this paper, we obtain an expression for the energy resolution of superconducting tunnel diodes for detection of low-energy\\u000a x-rays. We show that the major contribution to the energy resolution comes from the relative variance of the probability that\\u000a a quasielectron tunnels from one layer to another, which is due to the spatial dependence of the probability of interaction\\u000a between

V. V. Samedov

1998-01-01

258

Echo thresholds for reflections from acoustically diffusive architectural surfaces.  

PubMed

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. PMID:24116414

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

2013-10-01

259

A Temporal Model of Level-Invariant, Tone-in-Noise Detection  

ERIC Educational Resources Information Center

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.

Berg, Bruce G.

2004-01-01

260

5@5 - a 5 GeV energy threshold array of imaging atmospheric Cherenkov telescopes at 5 km altitude  

E-print Network

We discuss the concept and the performance of a powerful future ground-based astronomical instrument - a stereoscopic array of several large imaging atmospheric Cherenkov telescopes installed at a very high mountain elevation of about 5 km a.s.l. or more - for the study of the gamma-ray sky at energies from several GeV to 100 GeV.

F. A. Aharonian; A. K. Konopelko; H. J. Voelk; H. Quintana

2000-06-12

261

New detection technologies for ultra-high energy cosmic rays and neutrinos  

NASA Astrophysics Data System (ADS)

Even with an accumulated data set from an integrated six years of lifetime from the Auger experiment, no point sources of charged cosmic rays have be identified at the highest energies. Significantly increased apertures such as promised by the JEMEUSO mission will be required to identify these sources from the cosmic ray signatures themselves. However, in employing water-cherenkov surface detectors as well as fluorescence telescopes, Auger has demonstrated the power provided by the hybrid technology approach. New detection technologies thus provide a valuable tool, in particular for the study of systematic effects. Over the past decade, in particular radio detection of cosmic ray air-showers has become a viable future detection technology to enhance and complement existing air-shower experiments. Following the proof-of-principle provided by the Lopes experiment, this technology is now being pursued in all major air-shower detectors. In the MHz regime, the radio signal is dominated by geomagnetic emission from the electrons deflected in the earth magnetic field, with secondary contributions from a global charge excess. As the majority of the energy in the shower is carried by these electron and the radio signal traverses the atmosphere basically unattenuated, this approach not only promises superior energy resolution but may also provide an independent handle on the longitudinal shower development and hence the primary composition. Theoretical signal predictions provided by detailed Monte-Carlo simulations as well as analytic shower parametrizations are in good agreement with measurements provided by the AERA and Codalema experiments. Recent efforts also include studies of the radio emission in the GHz regime, where the ambient noise is significantly reduced, yet the emission mechanism in this regime has not been firmly established yet. As neutrinos are not deflected in the intergalactic magnetic fields, the detection of neutrino-induced cascades in dense media provides another promising approachfor the identification of the sources of cosmic rays. The low event rates and large required target volumes limit the experimental methods to far-ranging signatures .from the cascade, such as acoustic emission from the quasi-instantaneous energy deposit or Cherenkov emission from the charged particles in the cascade. Searching for optical Cherenkov photons in a cubic-kilometer of Antarctic ice, the IceCube experiment has recently found an excess of high-energy neutrinos in the TeV-PeV range.Yet its effective volume is too small to detect the GZK flux predicted from interaction of the highest-energy cosmic rays with the ambient cosmic microwave background. Seeking to increase the observed target volume, radio observations of the rim of the moon have energy thresholds well beyond the EeV scale and thus are more likely to find interactions of charged cosmic rays than GZK neutrinos. The currently best sensitivity to this flux is provided from searches for GHz radio emission of neutrino-induced cascades in the antarctic ice from the ANITA ballon experiment. While no high-energy neutrinos have been found, a geomagnetic emission component from air-showers

Bser, Sebastian

2013-06-01

262

QRS detection using S-Transform and Shannon energy.  

PubMed

This paper presents a novel method for QRS detection in electrocardiograms (ECG). It is based on the S-Transform, a new time frequency representation (TFR). The S-Transform provides frequency-dependent resolution while maintaining a direct relationship with the Fourier spectrum. We exploit the advantages of the S-Transform to isolate the QRS complexes in the time-frequency domain. Shannon energy of each obtained local spectrum is then computed in order to localize the R waves in the time domain. Significant performance enhancement is confirmed when the proposed approach is tested with the MIT-BIH arrhythmia database (MITDB). The obtained results show a sensitivity of 99.84%, a positive predictivity of 99.91% and an error rate of 0.25%. Furthermore, to be more convincing, the authors illustrated the detection parameters in the case of certain ECG segments with complicated patterns. PMID:24856322

Zidelmal, Z; Amirou, A; Ould-Abdeslam, D; Moukadem, A; Dieterlen, A

2014-08-01

263

Chemiluminescence resonance energy transfer-based detection for microchip electrophoresis.  

PubMed

Since the channels in micro- and nanofluidic devices are extremely small, a sensitive detection is required following microchip electrophoresis (MCE). This work describes a highly sensitive and yet universal detection scheme based on chemiluminescence resonance energy transfer (CRET) for MCE. It was found that an efficient CRET occurred between a luminol donor and a CdTe quantum dot (QD) acceptor in the luminol-NaBrO-QD system and that it was sensitively suppressed by the presence of certain organic compounds of biological interest including biogenic amines and thiols, amino acids, organic acids, and steroids. These findings allowed developing sensitive MCE-CL assays for the tested compounds. The proposed MCE-CL methods showed desired analytical figures of merit such as a wide concentration range of linear response. Detection limits obtained were approximately 10(-9) M for biogenic amines including dopamine and epinephrine and approximately 10(-8) M for biogenic thiols (e.g., glutathione and acetylcysteine), organic acids (i.e., ascorbic acid and uric acid), estrogens, and native amino acids. These were 10-1000 times more sensitive than those of previously reported MCE-based methods with chemiluminescence, electrochemical, or laser-induced fluorescence detection for quantifying corresponding compounds. To evaluate the applicability of the present MCE-CL method for analyzing real biological samples, it was used to determine amino acids in individual human red blood cells. Nine amino acids, including Lys, Ser, Ala, Glu, Trp, etc., were detected. The contents ranged from 3 to 31 amol/cell. The assay proved to be simple, quick, reproducible, and very sensitive. PMID:20121202

Zhao, Shulin; Huang, Yong; Shi, Ming; Liu, Rongjun; Liu, Yi-Ming

2010-03-01

264

Chemiluminescence Resonance Energy Transfer-based Detection for Microchip Electrophoresis  

PubMed Central

Since the channels in micro- and nanofluidic devices are extremely small, a sensitive detection is required following microchip electrophoresis (MCE). This work describes a highly sensitive and yet universal detection scheme based on chemiluminescence resonance energy transfer (CRET) for MCE. It was found that an efficient CRET occurred between a luminol donor and a CdTe quantum dot (QD) acceptor in the luminol-NaBrO-QD system, and that it was sensitively suppressed by the presence of certain organic compounds of biological interest including biogenic amines and thiols, amino acids, organic acids, and steroids. These findings allowed developing sensitive MCE-CL assays for the tested compounds. The proposed MCE-CL methods showed desired analytical figures of merit such as a wide concentration range of linear response. Detection limits obtained were ~10?9 M for biogenic amines including dopamine and epinephrine, and ~ 10?8 M for biogenic thiols (e.g. glutathione and acetylcysteine), organic acids (i.e. ascorbic acid and uric acid), estrogens, and native amino acids. These were 10 to 1000 times more sensitive than those of previously reported MCE-based methods with chemiluminescence, electrochemical, or laser induced fluorescence detection for quantifying corresponding compounds. To evaluate the applicability of the present MCE-CL method for analyzing real biological samples, it was used to determine amino acids in individual human red blood cells. Nine amino acids including Lys, Ser, Ala, Glu, Trp, etc. were detected. The contents ranged from 3 to 31 amol /cell. The assay proved to be simple, quick, reproducible, and very sensitive. PMID:20121202

Huang, Yong; Shi, Ming; Liu, Rongjun

2010-01-01

265

Detecting special nuclear materials in containers using high-energy gamma rays emitted by fission products  

DOEpatents

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.

Norman, Eric B. (Oakland, CA); Prussin, Stanley G. (Kensington, CA)

2007-10-02

266

Bayesian Threshold Estimation  

ERIC Educational Resources Information Center

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

Gustafson, S. C.; Costello, C. S.; Like, E. C.; Pierce, S. J.; Shenoy, K. N.

2009-01-01

267

Ecological thresholds: a survey  

Microsoft Academic Search

The existence of ecological discontinuities and thresholds has been recognised by ecological economics as a key feature to take into account in the study of environmenteconomy interactions. This paper reviews some theoretical developments and empirical studies dealing with ecological phenomena involving non-linear dynamics. The literature about this issue reveals that there is abundant evidence of discontinuities and threshold effects as

Roldan Muradian

2001-01-01

268

Selective chemical detection by energy modulation of sensors  

DOEpatents

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.

Stetter, J.R.; Otagawa, T.

1991-09-10

269

Selective chemical detection by energy modulation of sensors  

DOEpatents

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.

Stetter, Joseph R. (Naperville, IL); Otagawa, Takaaki (Solon, OH)

1991-01-01

270

Detecting single-nucleotide polymorphism by single-nucleotide polymorphism interactions in rheumatoid arthritis using a two-step approach with machine learning and a Bayesian threshold least absolute shrinkage and selection operator (LASSO) model.  

PubMed

The objective of this study was to detect interactions between relevant single-nucleotide polymorphisms (SNPs) associated with rheumatoid arthritis (RA). Data from Problem 1 of the Genetic Analysis Workshop 16 were used. These data consisted of 868 cases and 1,194 controls genotyped with the 500 k Illumina chip. First, machine learning methods were applied for preselecting SNPs. One hundred SNPs outside the HLA region and 1,500 SNPs in the HLA region were preselected using information-gain theory. The software weka was used to reduce colinearity and redundancy in the HLA region, resulting in a subset of 6 SNPs out of 1,500. In a second step, a parametric approach to account for interactions between SNPs in the HLA region, as well as HLA-nonHLA interactions was conducted using a Bayesian threshold least absolute shrinkage and selection operator (LASSO) model incorporating 2,560 covariates. This approach detected some main and interaction effects for SNPs in genes that have previously been associated with RA (e.g., rs2395175, rs660895, rs10484560, and rs2476601). Further, some other SNPs detected in this study may be considered in candidate gene studies. PMID:20018057

Gonzlez-Recio, Oscar; de Maturana, Evangelina Lpez; Vega, Andrs T; Engelman, Corinne D; Broman, Karl W

2009-01-01

271

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  

E-print Network

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...

Flewitt, Andrew J.; Powell, M.J.

2014-01-01

272

Direct Detection Rates of Dark Matter Coupled to Dark Energy  

E-print Network

We investigate the effect of a coupling between dark matter and dark energy on the rates for the direct detection of dark matter. The magnitude of the effect depends on the strength $\\kappa$ of this new interaction relative to gravity. The resulting isothermal velocity distribution for dark matter in galaxy halos is still Maxwell-Boltzmann (M-B), but the characteristic velocity and the escape velocity are increased by $\\sqrt{1+\\kappa^2}$. We adopt a phenomenological approach and consider values of $\\kappa$ near unity. For such values we find that: (i) The (time averaged) event rate increases for light WIMPs, while it is somewhat reduced for WIMP masses larger than 100 GeV. (ii) The time dependence of the rate arising from the modulation amplitude is decreased compared to the standard M-B velocity distribution. (iii) The average and maximum WIMP energy increase proportionally to $1+\\kappa^2$, which, for sufficiently massive WIMPs, allows the possibility of designing experiments measuring $\\gamma$ rays following nuclear de-excitation.

N. Tetradis; J. D. Vergados; Amand Faessler

2006-09-07

273

A novel threshold Cherenkov detector  

NASA Astrophysics Data System (ADS)

We are studying a novel threshold Cherenkov detector system for the discrimination between charged pions and kaons in an experiment on CP breaking at LEAR, CERN. Cherenkov UV-light is produced in an FC72 radiator and detected in a row of 2 cm diameter quartz tubes filled with TMAE vapour at 45C. Inside a tube a wire is stretched along the axis as anode and a nichrome spiral functions as cathode. Computer simulations have shown that good pion/kaon discrimination can be obtained. First results obtained with a small quartz-tube light detector are presented.

Okx, W. J. C.; van Eijk, C. W. E.; Looman, M.; Tanner, N. W.

1988-12-01

274

Methods for threshold determination in multiplexed assays  

DOEpatents

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.

Tammero, Lance F. Bentley; Dzenitis, John M; Hindson, Benjamin J

2014-06-24

275

Effects of nuclear symmetry energy and in-medium NN cross section in heavy-ion collisions at beam energies below the pion production threshold  

NASA Astrophysics Data System (ADS)

Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU04) transport model, we explored effects of in-medium NN elastic scattering cross section and nuclear symmetry energy on the subthreshold pion production in the Sn132+Sn124 reaction. We find that, with the decrease of the incident beam energy, the effects of the in-medium NN elastic scattering cross section on the ?-/?+ ratio are larger than that of the symmetry energy, although the latter may be also larger. While keeping the effect of symmetry energy, the double ratio of ?-/?+ from neutron-rich and neutron-poor reaction systems (with the same mass number of system) Sn132+Sn124 and Pm128+Pm128 almost fully cancels out the effects of the in-medium NN elastic scattering cross section.

Guo, Wen-Mei; Yong, Gao-Chan; Zuo, Wei

2014-10-01

276

New low threshold detectors for measuring electron and gamma ray fluxes from thunderclouds  

NASA Astrophysics Data System (ADS)

Strong electric fields inside thunderclouds give rise to enhanced fluxes of high-energy electrons and, consequently, gamma rays and neutrons. During thunderstorms at mountain Aragats, hundreds of Thunderstorm Ground Enhancements (TGEs) comprising millions of energetic electrons and gamma rays, as well as neutrons, were detected at Aragats Space Environmental Center (ASEC) on 3200 m altitude. The energy spectra of the electrons have an exponential shape and extend in energy range 2- 30 MeV. Recovered energy spectra of the gamma rays is also exponential in energy range 2-10 MeV, then turns to power law and is extending up to 100 MeV. It is of upmost importance to research energy spectra of TGE electrons and gamma rays from the lowest possible energies to clarify the shape of energy spectra and huge multiplication of the avalanche particles. The particle detectors operated at ASEC was designed for the registration of solar modulation effects and the lowering energy threshold was not of first importance. Thus, particle detectors have energy threshold of 7-10 MeV. The new generation of ASEC detectors comprises from 1 and 3 cm thick molded plastic scintillators arranged in stacks (3cm and 1cm STAND detectors) and in cubical structures surrounded thick scintillators and NaI crystals for purification of detected neutral flux (Cube 1 cm and Cube 3 cm detectors). In presented paper we describe new detectors and analyze their operational characteristics, as well as provide examples of TGE detection with new techniques.

Arakelyan, Karen; Avakyan, Karen; Chilingarian, Ashot; Daryan, Ara; Melkumyan, Laura; Pokhsraryan, David; Sargsyan, David

2013-02-01

277

The electronic states of but-2-yne studied by VUV absorption, near-threshold electron energy-loss spectroscopy and ab initio configuration interaction methods  

NASA Astrophysics Data System (ADS)

The photoabsorption spectrum of but-2-yne in the range 5.5-11 eV (225-110 nm) has been recorded using a synchrotron radiation source. The spectrum is dominated by three d-type Rydberg series, converging to the first ionisation energy (IE) (? -1, 9.562 eV). Origins of the ?3d members are 7.841, 7.977 and 8.018 eV, respectively. Transitions of low intensity, arising from excitation of the ?3s state (origin, 6.35 eV) and two ?3p Rydberg states (7.38 and 7.51 eV, respectively) have also been identified in the spectrum. Near-threshold electron energy-loss spectra reveal valence excited triplet states at about 5.2 and 5.8 eV, respectively. Electronic excitation energies for valence and Rydberg-type states have been computed using ab initio multi-reference multi-root CI methods. These studies used a triple zeta + polarisation basis set, augmented by diffuse (Rydberg) orbitals, to generate the theoretical singlet and triplet energy manifolds. The correlation of theory and experiment shows the nature of the more intense Rydberg state types, and identification of the main valence and Rydberg bands. Calculated energies for Rydberg states are close to those expected, and there is generally a good correlation between the theoretical and experimental envelopes. It was possible to generate singlet Rydberg states which relate to the 5-lowest IEs of but-2-yne; furthermore, the separation of these sequences shows that the IE order (under D 3h symmetry) is: 2e<5a1'<1e<1e<4a2?, also supported by direct calculation of the IEs by CI. The lowest valence singlet states are ?? ?, optically forbidden, and calculated to lie near 7.3 and 7.6 eV. The states which contribute strongly to the observed spectrum are ?? ?(1E+1A2?) near 7.9 eV having 2e6a1'? excitation, followed by several ?? ? and ?? ? states (1E+1A2?) between 10.0 and 10.5 eV; an 1E' antisymmetric combination(2e'2e? - 2e'2e?) is by far the strongest in intensity. A further group of symmetry-allowed valence states are calculated to lie near 12.3 and 12.9 eV. The two lowest triplet states, both of E' symmetry (?? ?), have vertical excitation energies of 5.7 and 6.2 eV, but are strongly bent with a trans-CCCC unit (C S and C 2h). The theoretical work confirms that, on intensity grounds, valence excited states do not contribute significantly to the spectrum. CI calculations of the ionic states give the ionisation energy sequence (D): 2E<2A1'<2E<2E<2A2?. Adiabatic structures for the first cation, two triplets, and a singlet (C 2h) were obtained; these show shortening of C-C, and lengthening of C tbnd C, in a trans-CCCC, as is found with ethyne.

Palmer, Michael H.; Walker, Isobel C.

2007-11-01

278

Comparison of Two Statistical Approaches to Detect Abnormal Building Energy Consumption with Simulation Test  

E-print Network

Comparison?of?Two?Statistical?Approaches? to?Detect?Abnormal?Building?Energy? Consumption?with?Simulation?Test 12th International?Conference?for?Enhanced?Building?Operations 23rd ? 26th October?2012? Manchester,?England Guanjing...:?How?to?keep?the?optimal?building?energy? performance?after?Cx? ? Solution:?Whole?building?fault?detection? ? A?process?of?identifying?abnormal?energy?consumption ? Alert?operators?early?after?the?onset?of?significant? increases/decreases?in?consumption 2 Paper Model Fault Detection Dodier and...

Lin, G.; Claridge, D.

2012-01-01

279

Seeking to Improve Low Energy Neutral Atom Detection in Space  

NASA Technical Reports Server (NTRS)

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.

Shappirio, M.; Coplan, M.; Chornay, D.; Collier, M.; Herrero, F.; Ogilvie, K.; Williams, E.

2007-01-01

280

A low threshold EAS (extensive-air-shower) array for gamma-ray astronomy at Los Alamos  

SciTech Connect

A new type of extensive-air-shower (EAS) array is described that achieves a low energy threshold, large area, high duty factor and large muon coverage. By placing a regularly-spaced grid of phototubes just below the surface of a shallow pond, the Cherenkov light of particles in an air shower striking the water can be detected, resulting in a primary energy threshold of less than 1 TeV. This highly sensitive array can thus be used to span the gap of information between the existing air Cherenkov techniques at 1 TeV and the existing EAS arrays at 100 TeV. 5 refs., 3 figs.

Burman, R.L.; Hoffman, C.M.; Nagle, D.E.; Potter, M.E.; Sandberg, V.; Berley, D.; Dingus, B.L.; Goodman, J.A.; Haines, T.J.; Stark, M.; Ellsworth, R.W.; Alexandreas, D.E.; Biller, S.; Dion, G.; Lu, X.Q.; Vishwanath, P.R.; Yodh, G.B.; Tumer, T.; White, S.; Zych, A.; Freedman, S.; Krakauer, D.; Lamb, R. (Los Alamos National Lab., NM (USA); Maryland Univ., College Park, MD (USA); George Mason Univ., Fairfax, VA (USA); Ca

1990-01-01

281

Low Energy Nuclear Recoil Response in Xenon Gas for Low Mass Dark Matter WIMP Search  

E-print Network

to the detection of relatively higher mass WIMPs because of detector threshold limits, background effects, or a lack of fundamental understanding of very low energy nuclear recoils (nuclear recoil energies...

Sofka, Clement James

2014-04-16

282

Melanin microcavitation threshold in the near infrared  

NASA Astrophysics Data System (ADS)

Thresholds for microcavitation of isolated bovine and porcine melanosomes were determined using single nanosecond (ns) laser pulses in the NIR (1000 - 1319 nm) wavelength regime. Average fluence thresholds for microcavitation increased non-linearly with increasing wavelength. Average fluence thresholds were also measured for 10-ns pulses at 532 nm, and found to be comparable to visible ns pulse values published in previous reports. Fluence thresholds were used to calculate melanosome absorption coefficients, which decreased with increasing wavelength. This trend was found to be comparable to the decrease in retinal pigmented epithelial (RPE) layer absorption coefficients reported over the same wavelength region. Estimated corneal total intraocular energy (TIE) values were determined and compared to the current and proposed maximum permissible exposure (MPE) safe exposure levels. Results from this study support the proposed changes to the MPE levels.

Schmidt, Morgan S.; Kennedy, Paul K.; Vincelette, Rebecca L.; Schuster, Kurt J.; Noojin, Gary D.; Wharmby, Andrew W.; Thomas, Robert J.; Rockwell, Benjamin A.

2014-02-01

283

Fibonacci thresholding: signal representation and morphological filters  

NASA Astrophysics Data System (ADS)

A new weighted thresholding concept is presented, which is used for the set-theoretical representation of signals, the producing new signals containing a large number of key features that are in the original signals and the design new morphological filters. Such representation maps many operations of non binary signal and image processing to the union of the simple operations over the binary signals and images. The weighted thresholding is invariant under the morphological transformations, including the basic ones, erosion and dilation. The main idea of using the weighted thresholding is in the choice of the special level of thresholding on which we can concentrate all our attention for the future processing. Together with arithmetical thresholding the so-called Fibonacci levels are chosen because of many interesting properties; one of them is the effective decomposition of the median filter. Experimental results show that the Fibonacci thresholding is much promised and can be used for many applications, including the image enhancement, segmentation, and edge detection.

Grigoryan, Artyom M.; Agaian, Sos S.

2014-02-01

284

Detecting dark energy with wavelets on the sphere Jason D. McEwen  

E-print Network

Detecting dark energy with wavelets on the sphere Jason D. McEwen Astrophysics Group, Cavendish Laboratory, Cambridge CB3 0HE, UK ABSTRACT 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

McEwen, Jason

285

Threshold quantum cryptograph based on Grover's algorithm  

E-print Network

Grover's operator in the two-qubit case can transform a basis into its conjugated basis. A permutation operator can transform a state in the two conjugated bases into its orthogonal state. These properties are included in a threshold quantum protocol. The proposed threshold quantum protocol is secure based the proof that the legitimate participators can only eavesdrop 2 bits of 3 bits operation information on one two-qubit with error probability 3/8. We propose a scheme to detect the Trojan horse attack without destroying the legal qubit.

Jian-Zhong Du; Su-Juan Qin; Qiao-Yan Wen; Fu-Chen Zhu

2006-06-27

286

Dual-energy X-ray radiography for automatic high- Z material detection  

NASA Astrophysics Data System (ADS)

There is an urgent need for high- Z material detection in cargo. Materials with Z > 74 can indicate the presence of fissile materials or radiation shielding. Dual (high) energy X-ray material discrimination is based on the fact that different materials have different energy dependence in X-ray attenuation coefficients. This paper introduces the basic physics and analyzes the factors that affect dual-energy material discrimination performance. A detection algorithm is also discussed.

Chen, Gongyin; Bennett, Gordon; Perticone, David

2007-08-01

287

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)

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.

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

288

Absolute detection efficiencies for keV energy atoms incident on a microchannel plate detector  

NASA Astrophysics Data System (ADS)

The absolute detection efficiencies of a microchannel plate detector (MCP) were determined experimentally for neutral hydrogen, carbon, and tungsten atoms with impact energies of 0.5-4.5 keV. We measured detection efficiencies using our recently developed method, which uses coincidence counting between neutralized incident ions and ionized target atoms in single-electron capture collisions. The obtained detection efficiencies showed similar impact-energy and mass dependence to those of rare gas atoms (Ne, Ar, Kr, and Xe), measured previously using our method. The detection efficiencies increased with increasing impact energy and converged to the open area ratio (?50%) of the MCP used. The efficiencies at fixed energies decreased as the mass of the incident atom increased. The absolute detection efficiencies obtained for H, C, W, Ne, Ar, Kr, and Xe atoms could be scaled according to the average electron emission yield estimated using the formulas for electronic and nuclear stopping powers.

Takahashi, N.; Adachi, Y.; Saito, M.; Haruyama, Y.

2013-11-01

289

16O resonances near 4? threshold through 12C (6Li,d ) reaction  

NASA Astrophysics Data System (ADS)

Several narrow alpha resonant 16O states were detected through the 12C (6Li,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 So Paulo Pelletron-Enge-Spectrograph facility and the nuclear emulsion technique. Experimental angular distributions associated with natural parity quasi-bound states around the 4? threshold are presented and compared to DWBA predictions. The upper limit for the resonance widths obtained is near the energy resolution (15 keV).

Rodrigues, M. R. D.; Borello-Lewin, T.; Miyake, H.; Horodynski-Matsushigue, L. B.; Duarte, J. L. M.; Rodrigues, C. L.; de Faria, P. Neto; Cunsolo, A.; Cappuzzello, F.; Foti, A.; Agodi, C.; Cavallaro, M.; di Napoli, M.; Ukita, G. M.

2014-11-01

290

Measuring the speed of dark: Detecting dark energy perturbations  

SciTech Connect

The nature of dark energy can be probed not only through its equation of state but also through its microphysics, characterized by the sound speed of perturbations to the dark energy density and pressure. As the sound speed drops below the speed of light, dark energy inhomogeneities increase, affecting both cosmic microwave background and matter power spectra. We show that current data can put no significant constraints on the value of the sound speed when dark energy is purely a recent phenomenon, but can begin to show more interesting results for early dark energy models. For example, the best fit model for current data has a slight preference for dynamics [w(a){ne}-1], degrees of freedom distinct from quintessence (c{sub s{ne}}1), and early presence of dark energy [{Omega}{sub de}(a<<1){ne}0]. Future data may open a new window on dark energy by measuring its spatial as well as time variation.

Putter, Roland de [Berkeley Lab and University of California, Berkeley, California 94720 (United States); Huterer, Dragan [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan, 48109 (United States); Linder, Eric V. [Berkeley Lab and University of California, Berkeley, California 94720 (United States); Institute for the Early Universe, Ewha Womans University, Seoul (Korea, Republic of)

2010-05-15

291

Threshold behavior of double-pion electroproduction from nuclei  

NASA Astrophysics Data System (ADS)

The leading contribution of threshold double-pion production to inelastic electron scattering from nuclei through a given angle and with a given energy loss is calculated in a Fermi gas model of the nuclear spectrum. The isobar model characterized by the threshold creation of a ?-? pair constitutes the one-body input with the contact term providing the dominant contribution. The cross sections are found to have an ?5 dependence near threshold, where ?=(?1-?2-2m?)m? for initial and final electron energies, ?1 and ?2. The technique utilized of Fermi averaging near threshold is shown to reproduce the threshold behaviors of the various components of the analogous incoherent electroproduction cross section found earlier by Czyz and Walecka. NUCLEAR REACTIONS Threshold double-pion electroproduction cross section d2?d?e'd?e' calculated, Fermi gas model of nucleus, ?-? production mechanism.

Rockmore, R.; Kamal, A. N.

1983-07-01

292

Network problem threshold  

NASA Technical Reports Server (NTRS)

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.

Gejji, Raghvendra, R.

1992-01-01

293

Detecting Protein-Protein Interaction Decoys using Fast Free Energy Calculations  

E-print Network

Detecting Protein-Protein Interaction Decoys using Fast Free Energy Calculations Christopher James, Generalized Belief Propagation, Free Energy, Protein- Protein Interactions #12;Abstract We present a physics for a given complex, and Generalized Belief Propa- gation to perform the free energy calculation. Our method

Langmead, Christopher James

294

Threshold and state concepts used in ESDs: Needs and applications  

E-print Network

of process that produces a transition Can be detected with cover values, stubble height, gap size Ludwig et Perspective, 1991 #12;Recent grassland loss, A horizon present Crossed a pattern- process threshold Grassland

295

TPC in ?-ray astronomy above pair-creation threshold  

NASA Astrophysics Data System (ADS)

We examine the performance of a TPC as a ?-ray telescope above the pair-creation threshold. The contributions to the photon angular resolution are studied and their dependence on energy is obtained. The effective area per detector unit mass for such a thin detector is the conversion mass attenuation coefficient. The differential sensitivity for the detection of a point-like source is then derived. Finally, the measurement of track momentum from deflections due to multiple scattering is optimized.These analytical results are exemplified numerically for a few sets of detector parameters. TPCs show an impressive improvement in sensitivity with respect to existing pair-creation-based telescopes in the [MeV-GeV] energy range, even with the modest detector parameters of this study. In addition, gas TPCs allow an improvement in angular resolution of about one order of magnitude.

Bernard, D.

2013-02-01

296

Detection of explosives, nerve agents, and illicit substances by zero-energy electron attachment  

NASA Technical Reports Server (NTRS)

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.

Chutjian, A.; Darrach, M. R.

2000-01-01

297

Making Diagnostic Thresholds Less Arbitrary  

E-print Network

The application of diagnostic thresholds plays an important role in the classification of mental disorders. Despite their importance, many diagnostic thresholds are set arbitrarily, without much empirical support. This paper seeks to introduce...

Unger, Alexis Ariana

2012-07-16

298

Experimental determination of laser induced breakdown thresholds of metals under nanosecond Q-switched laser operation  

NASA Astrophysics Data System (ADS)

Laser-induced breakdown thresholds for several pure metals were determined using a nanosecond laser. A Q-switched pulsed Nd:YAG laser operating at infrared (1064 nm), visible (532 nm) and ultraviolet (266 nm) wavelengths has been used. The plasma was generated by focusing the Nd:YAG laser on the target in air at atmospheric pressure. The dispersed plasma light was detected using a two-dimensional intensified charge-coupled device (CCD) detector. The studied elements were chosen according to their different thermal and physical properties, particularly boiling point, melting point and thermal conductivity. The effect of wavelength on the plasma threshold has been discussed. Laser fluence thresholds in the ultraviolet were larger than those obtained using visible and infrared radiation, while the energy threshold is larger using infrared radiation. Correlations between the plasma threshold of metal targets and the melting point and boiling point at 266, 532 and 1064 nm have been established. The results indicate that thermal effects have an important influence on the ablation behavior of metals at the three wavelengths used.

Cabaln, L. M.; Laserna, J. J.

1998-05-01

299

Energy efficient data representation and aggregation with event region detection in wireless sensor networks  

NASA Astrophysics Data System (ADS)

Unlike conventional networks, wireless sensor networks (WSNs) are limited in power, have much smaller memory buffers, and possess relatively slower processing speeds. These characteristics necessitate minimum transfer and storage of information in order to prolong the network lifetime. In this dissertation, we exploit the spatio-temporal nature of sensor data to approximate the current values of the sensors based on readings obtained from neighboring sensors and itself. We propose a Tree based polynomial REGression algorithm, (TREG) that addresses the problem of data compression in wireless sensor networks. Instead of aggregated data, a polynomial function (P) is computed by the regression function, TREG. The coefficients of P are then passed to achieve the following goals: (i) The sink can get attribute values in the regions devoid of sensor nodes, and (ii) Readings over any portion of the region can be obtained at one time by querying the root of the tree. As the size of the data packet from each tree node to its parent remains constant, the proposed scheme scales very well with growing network density or increased coverage area. Since physical attributes exhibit a gradual change over time, we propose an iterative scheme, UPDATE_COEFF, which obviates the need to perform the regression function repeatedly and uses approximations based on previous readings. Extensive simulations are performed on real world data to demonstrate the effectiveness of our proposed aggregation algorithm, TREG. Results reveal that for a network density of 0.0025 nodes/m2, a complete binary tree of depth 4 could provide the absolute error to be less than 6%. A data compression ratio of about 0.02 is achieved using our proposed algorithm, which is almost independent of the tree depth. In addition, our proposed updating scheme makes the aggregation process faster while maintaining the desired error bounds. We also propose a Polynomial-based scheme that addresses the problem of Event Region Detection (PERD) for WSNs. When a single event occurs, a child of the tree sends a Flagged Polynomial (FP) to its parent, if the readings approximated by it falls outside the data range defining the existing phenomenon. After the aggregation process is over, the root having the two polynomials, P and FP can be queried for FP (approximating the new event region) instead of flooding the whole network. For multiple such events, instead of computing a polynomial corresponding to each new event, areas with same data range are combined by the corresponding tree nodes and the aggregated coefficients are passed on. Results reveal that a new event can be detected by PERD while error in detection remains constant and is less than a threshold of 10%. As the node density increases, accuracy and delay for event detection are found to remain almost constant, making PERD highly scalable. Whenever an event occurs in a WSN, data is generated by closeby sensors and relaying the data to the base station (BS) make sensors closer to the BS run out of energy at a much faster rate than sensors in other parts of the network. This gives rise to an unequal distribution of residual energy in the network and makes those sensors with lower remaining energy level die at much faster rate than others. We propose a scheme for enhancing network Lifetime using mobile cluster heads (CH) in a WSN. To maintain remaining energy more evenly, some energy-rich nodes are designated as CHs which move in a controlled manner towards sensors rich in energy and data. This eliminates multihop transmission required by the static sensors and thus increases the overall lifetime of the WSN. We combine the idea of clustering and mobile CH to first form clusters of static sensor nodes. A collaborative strategy among the CHs further increases the lifetime of the network. Time taken for transmitting data to the BS is reduced further by making the CHs follow a connectivity strategy that always maintain a connected path to the BS. Spatial correlation of sensor data can be further exploited for dynamic channel selection

Banerjee, Torsha

300

K SHELL INTERNAL CONVERSION COEFFICIENTS AT THRESHOLD  

Microsoft Academic Search

Coulomb field effects on K shell internal conversion coefficients for ; threshold values of the gamma-ray energy are investigated using exact wave ; functions to describe both the bound and the continuum state electrons. Exact ; results for the internal conversion coefficients are obtained in terms of gamma ; functions and confluent hypergeometric functions. To facilitate numerical ; evaluation, the

OConnell

1963-01-01

301

Lidocaine-Related Increase in Defibrillation Threshold  

Microsoft Academic Search

ith the growing reliance on the implantable cardioverter defibrillator (ICD) for the pri- mary treatment of life-threatening ventricular arrhythmias, interactions between these devices and antiarrhythmic drugs has assumed increased clinical importance. The effects of antiarrhythmic drugs on defibrillation threshold (DFT) have been investigated (1). Lidocaine, a commonly used antiarrhythmic drug, has generally been reported to increase DFT (requires more energy

Robert W. Peters; Timothy B. Gilbert; Stefany Johns-Walton; Michael R. Gold

1997-01-01

302

Research on Life-Detection Based on Electromagnetic Energy  

Microsoft Academic Search

Base on Maxwell equations, a life-detector's theoretic background is discussed, consisting of energy conversion of EM (electromagnetic) wave transmission and reception, and human body's influence on energy conversion in the EM field. Then the detector has been constructed and some experiments are accomplished. The experimental results show that the detector can not only catch living signals of human beings, when

Wen Xiao-qin; Wu Qing-jia; You Lin-ru; Bi Shu-e

2010-01-01

303

DETECTION OF LARGE ACOUSTIC ENERGY FLUX IN THE SOLAR ATMOSPHERE  

SciTech Connect

We study the energy flux carried by acoustic waves excited by convective motions at sub-photospheric levels. The analysis of high-resolution spectropolarimetric data taken with IMaX/SUNRISE provides a total energy flux of {approx}6400-7700 W m{sup -2} at a height of {approx}250 km in the 5.2-10 mHz range, i.e., at least twice the largest energy flux found in previous works. Our estimate lies within a factor of two of the energy flux needed to balance radiative losses from the chromosphere according to the estimates of Anderson and Athay and revives interest in acoustic waves for transporting energy to the chromosphere. The acoustic flux is mainly found in the intergranular lanes but also in small rapidly evolving granules and at the bright borders, forming dark dots and lanes of splitting granules.

Bello Gonzalez, N.; Franz, M.; Schmidt, W.; Berkefeld, T. [Kiepenheuer-Institut fuer Sonnenphysik, Schoeneckstr. 6, 79110 Freiburg (Germany); MartInez Pillet, V.; Bonet, J. A. [Instituto de Astrofisica de Canarias, Avd. Via Lactea s/n, La Laguna (Spain); Solanki, S. K.; Gandorfer, A.; Barthol, P. [Max-Planck-Institut fuer Sonnensystemforschung, Max-Planck-Strasse 2, 37191 Katlenburg-Lindau (Germany); Del Toro Iniesta, J. C.; Domingo, V. [Instituto de Astrofisica de AndalucIa (CSIC), Apdo. de Correos 3004, 18080 Granada (Spain); Knoelker, M., E-mail: nbello@kis.uni-freiburg.d [High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80307 (United States)

2010-11-10

304

Detection of Large Acoustic Energy Flux in the Solar Atmosphere  

NASA Astrophysics Data System (ADS)

We study the energy flux carried by acoustic waves excited by convective motions at sub-photospheric levels. The analysis of high-resolution spectropolarimetric data taken with IMaX/SUNRISE provides a total energy flux of ~6400-7700 W m-2 at a height of ~250 km in the 5.2-10 mHz range, i.e., at least twice the largest energy flux found in previous works. Our estimate lies within a factor of two of the energy flux needed to balance radiative losses from the chromosphere according to the estimates of Anderson & Athay and revives interest in acoustic waves for transporting energy to the chromosphere. The acoustic flux is mainly found in the intergranular lanes but also in small rapidly evolving granules and at the bright borders, forming dark dots and lanes of splitting granules.

Bello Gonzlez, N.; Franz, M.; Martnez Pillet, V.; Bonet, J. A.; Solanki, S. K.; del Toro Iniesta, J. C.; Schmidt, W.; Gandorfer, A.; Domingo, V.; Barthol, P.; Berkefeld, T.; Knlker, M.

2010-11-01

305

RE2-CD: Robust and Energy Efficient Cut Detection in Wireless Sensor Networks  

NASA Astrophysics Data System (ADS)

Reliable network connectivity in wireless sensor networks (WSN) is difficult to achieve. Harsh, unattended, low-security environments and resource-constrained nodes exacerbate the problem. An ability to detect connectivity disruptions, due to either security or environmental problems, allows WSN to conserve power and memory while reducing network congestion. We propose RE2-CD, an integrated solution incorporating both robustness to attack and energy-efficiency. To enhance security, a robust outlier detection algorithm assists nodes in detecting a specific threat in their environment. To improve energy-efficiency, a cluster-based cut detection algorithm recognizes and reacts to disrupted connectivity. Extensive simulations across a range of network sizes and densities indicate that energy-efficiency can be improved by an order of magnitude in denser networks while malicious nodes are detected at deviations of 1% from expected behavior.

Won, Myounggyu; George, Stephen M.; Stoleru, Radu

306

A near infrared fluorescence resonance energy transfer based aptamer biosensor for insulin detection in human plasma.  

PubMed

A new FRET model using near-infrared quantum-dots (NIR-QDs) and oxidized carbon nanoparticles (OCNPs) as the energy donor and acceptor was constructed and designed for insulin detection in complex human plasma. PMID:24292147

Wang, Yuhui; Gao, Duyang; Zhang, Pengfei; Gong, Ping; Chen, Chi; Gao, Guanhui; Cai, Lintao

2014-01-25

307

Whole Building Energy Performance Anomaly Detections at TU/e  

E-print Network

will also incorporate expert knowledge to couple energy analysis with analysis regarding system maintenance and failure risk. Proposed research will seek to develop an advanced retro-commissioning analysis methodology to assist with the initial assessment...

Hensen, J. L. M.; Bynum, J. D.

2013-01-01

308

Broken Bar Detection in Synchronous Machines Based Wind Energy Conversion System  

E-print Network

BROKEN BAR DETECTION IN SYNCHRONOUS MACHINES BASED WIND ENERGY CONVERSION SYSTEM A Dissertation by MINA MASHHADI RAHIMIAN Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment... of the requirements for the degree of DOCTOR OF PHILOSOPHY August 2011 Major Subject: Electrical Engineering BROKEN BAR DETECTION IN SYNCHRONOUS MACHINES BASED WIND ENERGY CONVERSION SYSTEM A Dissertation by MINA MASHHADI RAHIMIAN...

Rahimian, Mina Mashhadi

2012-10-19

309

Grossman's Missing Health Threshold?  

PubMed Central

We present a generalized solution to Grossman's model of health capital (1972), relaxing the widely used assumption that individuals can adjust their health stock instantaneously to an optimal level without adjustment costs. The Grossman model then predicts the existence of a health threshold above which individuals do not demand medical care. Our generalized solution addresses a significant criticism: the model's prediction that health and medical care are positively related is consistently rejected by the data. We suggest structural- and reduced-form equations to test our generalized solution and contrast the predictions of the model with the empirical literature. PMID:21775003

Galama, Titus; Kapteyn, Arie

2011-01-01

310

Nuclear materials detection using high-energy ?-rays  

NASA Astrophysics Data System (ADS)

The FIGARO technique uses 6-7 MeV ?-rays produced in the 19F(p, ??) 16O reaction to detect materials used in nuclear weapons or associated with their production. These ?-rays induce neutron emission via the photoneutron and photofission processes in nuclear materials. Previous experiments have shown that FIGARO gives responses specific to nuclear materials with little or no response to common benign materials. The technique is also resistant to both photon and neutron shielding countermeasures. We present preliminary results from modeling studies of neutron detection rates with simulated air cargo and intermodal shipping containers. A general methodology to compare operating performance based on receiver-operator-characteristic curves is also discussed.

Micklich, Bradley J.; Smith, Donald L.

2005-12-01

311

Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products  

DOEpatents

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.

Norman, Eric B. (Oakland, CA); Prussin, Stanley G. (Kensington, CA)

2009-01-27

312

Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products  

DOEpatents

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.

Norman, Eric B. (Oakland, CA); Prussin, Stanley G. (Kensington, CA)

2009-01-06

313

Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products  

DOEpatents

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.

Norman, Eric B [Oakland, CA; Prussin, Stanley G [Kensington, CA

2009-05-05

314

Detecting dark energy in long baseline neutrino oscillations  

E-print Network

In this paper, we discuss a possibility of studying properties of dark energy in long baseline neutrino oscillation experiments. We consider two types of models of neutrino dark energy. For one type of models the scalar field is taken to be quintessence-like and for the other phantom-like. In these models the scalar fields couple to the neutrinos to give rise to a spatially varying neutrino masses. We will show that the two types of models predict different behaviors of the spatial variation of the neutrino masses inside Earth and consequently result in different signals in long baseline neutrino oscillation experiments.

Pei-Hong Gu; Xiao-Jun Bi; Bo Feng; Bing-Lin Young; Xinmin Zhang

2005-12-06

315

A "test of concept" comparison of aerodynamic and mechanical resuspension mechanisms for particles deposited on field rye grass ( Secale cercele).Part 2. Threshold mechanical energies for resuspension particle fluxes  

NASA Astrophysics Data System (ADS)

Kinetic energy from the oscillatory impacts of the grass stalk against a stationary object was measured with a kinetic energy measuring device. These energy inputs were measured as part of a resuspension experiment of uniform latex microspheres deposited on a single rye grass seed pod in a wind tunnel. The experiment was designed to measure resuspension from aerodynamic (viscous and turbulent) mechanisms compared to that from mechanisms from mechanical resuspension resulting from the oscillatory impact of the grass hitting a stationary object. The experiment was run for deposited spherical latex particles with diameters from 2 to 8.1 ?m. Wind tunnel tests were run for wind speeds from 2 to 18.5 m s -1 and a turbulence intensity (root-mean-square fluctuation wind speed/mean wind speed) of 0.1. Our experiments showed the following: Threshold mechanical energy input rates increased from 0.04 to 0.2 ?J s -1 for resuspension of spherical polystyrene latex particles from 2 to 8.1 ?m diameter. Kinetic energy flux generated by mechanical impact of the wind-driven oscillating grass was found to be highly sensitive to slightly different placements and grass morphology. The kinetic energy input by impaction of the grass against a stationary cylinder is roughly proportional to the kinetic energy flux of the wind.

Gillette, Dale A.; Lawson, Robert E.; Thompson, Roger S.

316

Energy efficient sampling for event detection in wireless sensor networks  

Microsoft Academic Search

ABSTRACT Compressive Sensing (CS) is a recently developed mecha- nism that allows signal acquisition and compression to be performed in one inexpensive step so that the sampling pro- cess itself produces a compressed version of the signal. This signicantly,improves systemic energy eciency,because the average sampling rate can be considerably reduced and ex- plicit compression eliminated. In this paper, we introduce

Zainul Charbiwala; Younghun Kim; Sadaf Zahedi; Jonathan Friedman; Mani B. Srivastava

2009-01-01

317

Optimising threshold levels for information transmission in binary threshold networks: Independent multiplicative noise on each threshold  

NASA Astrophysics Data System (ADS)

The problem of optimising the threshold levels in multilevel threshold system subject to multiplicative Gaussian and uniform noise is considered. Similar to previous results for additive noise, we find a bifurcation phenomenon in the optimal threshold values, as the noise intensity changes. This occurs when the number of threshold units is greater than one. We also study the optimal thresholds for combined additive and multiplicative Gaussian noise, and find that all threshold levels need to be identical to optimise the system when the additive noise intensity is a constant. However, this identical value is not equal to the signal mean, unlike the case of additive noise. When the multiplicative noise intensity is instead held constant, the optimal threshold levels are not all identical for small additive noise intensity but are all equal to zero for large additive noise intensity. The model and our results are potentially relevant for sensor network design and understanding neurobiological sensory neurons such as in the peripheral auditory system.

Zhou, Bingchang; McDonnell, Mark D.

2015-02-01

318

EMD and Teager-Kaiser energy applied to hydrocarbon detection in a carbonate reservoir  

NASA Astrophysics Data System (ADS)

Oil and gas reservoirs can cause anomalies in the energy and frequency of seismic signals. We can take advantage of these anomalies for hydrocarbon detection. Based on the Teager-Kaiser (TK) energy characteristics, a method that uses this energy in association with the Empirical Mode Decomposition (EMD) method is proposed for hydrocarbon detection in carbonate reservoirs. The EMD method, which can decompose the original seismic signals into a finite number of monocomponent intrinsic mode functions (IMFs) in the temporal domain, is used for multiband filtering. A TK energy separation algorithm is used to estimate the instantaneous frequency and amplitude of the selected IMFs from the EMD method. The proposed method can generate a joint time-frequency representation that can reflect the energy tracking of the seismic signals. The instantaneous spectrums produced by the EMD/TK method have the capability to detect hydrocarbon. The model results to the gas field, which located in the eastern Ordos Basin, China, show that the EMD/TK method can be adopted and they detect the gas-bearing reservoir efficiently. Application of the EMD/TK method in hydrocarbon detection in a gas field located in the Eastern Ordos Basin shows its effectiveness. The EMD/TK method can be used as a new analysis tool to determine the instantaneous spectral properties of a reservoir to detect hydrocarbon.

Xue, Ya-juan; Cao, Jun-xing; Tian, Ren-fei

2014-04-01

319

Measurements of the Suitability of Large Rock Salt Formations for Radio Detection of High Energy Neutrinos  

Microsoft Academic Search

We have investigated the possibility that large rock salt formations might be suitable as target masses for detection of neutrinos of energies about 10 PeV and above. In neutrino interactions at these energies, the secondary electromagnetic cascade produces a coherent radio pulse well above ambient thermal noise via the Askaryan effect. We describe measurements of radio-frequency attenuation lengths and ambient

Peter Gorham; David Saltzberg; Allen Odian; Dawn Williams; David Besson; George Frichter; Sami Tantawi

2001-01-01

320

Detecting W/Z pairs and Higgs at high energy pp colliders: Main experimental issues  

SciTech Connect

The main detection issues implied by the search for W and Z/sup 0/ pairs and Higgs in a high energy pp collider context are discussed here. It includes: precise electron identification, missing energy measurement, multilepton recognition, sophisticated jet pattern recognition, and pile-up. The study uses, as much as possible, a ''realistic simulation of life.''

Alverson, G.; Bengtsson, H.U.; Hauptman, J.; Hedin, D.; Herrero, M.J.; Wang, E.; Linn, S.; Young, C.; Milliken, B.; Paige, F.

1987-03-01

321

Generalized Analysis of a Distributed Energy Efficient Algorithm for Change Detection  

E-print Network

Generalized Analysis of a Distributed Energy Efficient Algorithm for Change Detection Taposh. of ECE, Indian Institute of Science Bangalore, India vinod@ece.iisc.ernet.in ABSTRACT An energy efficient­29, 2009, Tenerife, Canary Islands, Spain Copyright 2009 ACM 978-1-60558-616-9/09/10 ...$10.00. model finds

Sharma, Vinod

322

A detection system for very low-energy protons from ?-delayed proton decay  

NASA Astrophysics Data System (ADS)

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 ?-delayed p-decay with reduced beta background and improved energy resolution. The detector was tested using the ?-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 80 keV. The low energy (206 keV, 267 keV) proton peaks were positively identified, well separated, and the resolution was improved.

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.

2012-11-01

323

Detecting Gamma-Ray Bursts with Ultra-High Energy Neutrinos  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts are candidate sources of ultra-high energy cosmic rays and neutrinos. While cosmic rays are scattered in the intervening magnetic field, neutrinos point back to their sources being charge neutral and make neutrino astronomy possible. Detection of ultrahigh energy neutrinos by future experiments such as ANITA, ANTARES, Ice-Cube and RICE can provide useful information such as particle acceleration, radiation mechanism and magnetic field about the sources and their progenitors. Detection of ultrahigh energy neutrinos which point back to their sources may establish gamma-ray bursts as the sources of GZK cosmic rays.

Razzaque, Soebur; Mszros, Peter; Waxman, Eli

324

Oscillatory Threshold Logic  

PubMed Central

In the 1940s, the first generation of modern computers used vacuum tube oscillators as their principle components, however, with the development of the transistor, such oscillator based computers quickly became obsolete. As the demand for faster and lower power computers continues, transistors are themselves approaching their theoretical limit and emerging technologies must eventually supersede them. With the development of optical oscillators and Josephson junction technology, we are again presented with the possibility of using oscillators as the basic components of computers, and it is possible that the next generation of computers will be composed almost entirely of oscillatory devices. Here, we demonstrate how coupled threshold oscillators may be used to perform binary logic in a manner entirely consistent with modern computer architectures. We describe a variety of computational circuitry and demonstrate working oscillator models of both computation and memory. PMID:23173034

Borresen, Jon; Lynch, Stephen

2012-01-01

325

Can dark energy viscosity be detected with the Euclid survey?  

E-print Network

Recent work has demonstrated that it is important to constrain the dynamics of cosmological perturbations, in addition to the evolution of the background, if we want to distinguish among different models of the dark sector. Especially the anisotropic stress of the (possibly effective) dark energy fluid has been shown to be an important discriminator between modified gravity and dark energy models. In this paper we use approximate analytical solutions of the perturbation equations in the presence of viscosity to study how the anisotropic stress affects the weak lensing and galaxy power spectrum. We then forecast how sensitive the photometric and spectroscopic Euclid surveys will be to both the speed of sound and the viscosity of our effective dark energy fluid when using weak lensing tomography and the galaxy power spectrum. We find that Euclid alone can only constrain models with very small speed of sound and viscosity, while it will need the help of other observables in order to give interesting constraints on models with a sound speed close to one. This conclusion is also supported by the expected Bayes factor between models.

Domenico Sapone; Elisabetta Majerotto; Martin Kunz; Bianca Garilli

2013-05-08

326

NOSTOS: a spherical TPC to detect low energy neutrinos  

SciTech Connect

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.

Aune, S.; Colas, P.; Ribas, E. Ferrer; Giomataris, Y.; Irastorza, I. G. [DAPNIA, Centre d'Etudes Nucleaires de Saclay (CEA-Saclay), Gif-sur-Yvette (France); Dolbeau, J.; Gorodetzky, P.; Patzak, T.; Salin, P. [APC, Universite Paris 7 Denis Diderot, Paris (France); Fanourakis, G.; Geralis, T.; Kousouris, K. [National Center for Scientific Research 'Demokritos', Athens (Greece); Gounaris, G. J.; Savvidis, I. [Aristotle University of Thessaloniki (Greece); Lepeltier, V. [Laboratoire de l'Accelerateur Lineaire, Orsay (France); Paschos, E.A. [University of Dortmunt, Dortmunt (Germany); Vergados, J.D. [University of Ioannina, Ioannina (Greece)

2005-09-08

327

Tunnel catch from potential wells and energy detection  

E-print Network

We consider the one-dimensional Schr\\"{o}dinger operator in the semiclassical regime assuming that its double-well potential is the sum of a finite "physically given" well and a square shape probing well whose width or depth can be varied (tuned). We study the dynamics of initial state localized in the physical well. It is shown that if the probing well is not too close to the physical one and if its parameters are specially tuned, then the {\\it tunnel catch effect} appears, i.e. the initial state starts tunneling oscillations between the physical and probing wells. The asymptotic formula for the probability of finding the state in the probing well is obtained. We show that the observation of the tunnel catch effect can be used to determine the energy level of the initial state, and we obtain the corresponding asymptotic formula for the initial state energy. We also calculate the leading term of the tunneling splitting of energy levels in this double well potential.

M. V. Karasev; E. V. Vybornyi

2014-11-17

328

Low energy conversion electron detection in superfluid He3 at ultra-low temperature  

E-print Network

We report on the first results of the MACHe3 (MAtrix of Cells of Helium 3) prototype experiment concerning the measurement of low energy conversion electrons at ultra-low temperature. For the first time, the feasibility of the detection of low energy electrons is demonstrated in superfluid He3-B cooled down to 100 microK. Low energy electrons at 7.3 keV coming from the K shell conversion of the 14.4 keV nuclear transition of a low activity Co57 source are detected, opening the possibility to use a He3-based detector for the detection of Weakly Interacting Massive Particles (WIMPs) which are expected to release an amount of energy higher-bounded by 5.6 keV.

E. Moulin; C. Winkelmann; J. F. Macias-Perez; Yu. M. Bunkov; H. Godfrin; D. Santos

2005-04-12

329

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  

NASA Astrophysics Data System (ADS)

On the basis of the Bargmann representation of the S matrix, the pole approximation is obtained for the effective-range function k cot ?. This approximation is optimal for describing the neutron-deuteron system in the doublet spin state. The values of r 0 = 412.469 fm and v 2 = -35 495.62 fm3 for the doublet low-energy parameters of neutron-deuteron scattering and the value of D = 172.678 fm2 for the respective pole parameter are deduced by using experimental results for the triton binding energy E T , the doublet neutron-deuteron scattering length a 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 v = 0.608 MeV for the virtuallevel position and C {/T 2} = 2.866 and C {/v 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 2. The effective triton radii in the ground ( ? T = 1.711 fm) and virtual ( ? v = 74.184 fm) states are calculated for the first time.

Babenko, V. A.; Petrov, N. M.

2008-01-01

330

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

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.

Babenko, V. A.; Petrov, N. M., E-mail: pet@online.com.ua [National Academy of Sciences of Ukraine, Bogolyubov Institute for Theoretical Physics (Ukraine)

2008-01-15

331

Learning foraging thresholds for lizards  

SciTech Connect

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.

Goldberg, L.A. [Univ. of Warwick, Coventry (United Kingdom). Dept. of Computer Science; Hart, W.E. [Sandia National Labs., Albuquerque, NM (United States); Wilson, D.B. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1996-01-12

332

Volumetric detection of flat lesions for minimal-preparation dual-energy CT colonography  

NASA Astrophysics Data System (ADS)

Computer-aided detection (CAD) systems for computed tomographic colonography (CTC) tend to miss many flat lesions. We developed a volumetric method for automated detection of lesions with dual-energy CTC (DECTC). The target region for the detection is defined in terms of a distance transform of the colonic lumen. To detect lesions, volumetric shape features are calculated at the image scale defined by the thickness of the target region. False-positive (FP) detections are reduced by use of a random-forest classifier based on shape, texture, and dual-energy features of the detected lesion candidates. For pilot evaluation, 37 patients were examined by use of DE-CTC with a reduced one-day bowel preparation. The CAD scheme was trained with the DE-CTC data of 12 patients, and it was tested with the DE-CTC data of 25 patients. The detection sensitivity was assessed at multiple thicknesses of the target region. There were 39 lesions >=6 mm in 15 patients, including 8 flat lesions >=10 mm. The thickness of the target region had a statistically significant effect on the detection sensitivity. At the optimal thickness of the target region, the per-lesion and per-patient sensitivities for flat lesions were 100% at a median of 4 FPs per patient.

Nppi, Janne J.; Kim, Se Hyung; Yoshida, Hiroyuki

2013-02-01

333

High Energy Resolution Fluorescence Detection X-Ray Absorption Spectroscopy: Detection of Adsorption Sites in Supported Metal Catalysts  

NASA Astrophysics Data System (ADS)

High energy resolution fluorescence detection (HERFD) X-ray adsorption spectroscopy (XAS) is demonstrated as a new tool to identify the geometry of metal adsorption sites and the orbitals involved in bonding. The type of CO adsorption site on a nanoparticular Pt-Al2O3 catalyst is determined. The orbitals involved in the Pt CO bonding are identified using theoretical FEFF8.0 calculations. In situ application of HERFD XAS is applicable to a large number of catalytic systems and will provide fundamental insights in structure performance relationships.

Tromp, Moniek; van Bokhoven, Jeroen A.; Safonova, Olga V.; De Groot, Frank M. F.; Evans, John; Glatzel, Pieter

2007-02-01

334

On energy transfer by detection of a tunneling atom  

E-print Network

We are in the process of building an experiment to study the tunneling of laser-cooled Rubidium atoms through an optical barrier. A particularly thorny set of questions arises when one considers the possibility of observing a tunneling particle while it is in the ``forbidden'' region. In earlier work, we have discussed how one might probe a tunneling atom ``weakly,'' so as to prevent collapse. Here we make some observations about the implications of a more traditional quantum measurement. Considerations of energy conservation suggest that attempts to observe tunneling atoms will enhance inelastic scattering, but not in a way which can be directly observed. It is possible that attempts to make such measurements may lead to experimentally realizable ``observationally assisted barrier penetration.''

A. M. Steinberg

1999-04-28

335

Exhaustive Thresholds and Resistance Checkpoints  

NASA Technical Reports Server (NTRS)

Once deployed, all intricate systems that operate for a long time (such as an airplane or chemical processing plant) experience degraded performance during operational lifetime. These can result from losses of integrity in subsystems and parts that generally do not materially impact the operation of the vehicle (e.g., the light behind the button that opens the sliding door of the minivan). Or it can result from loss of more critical parts or subsystems. Such losses need to be handled quickly in order to avoid loss of personnel, mission, or part of the system itself. In order to manage degraded systems, knowledge of its potential problem areas and the means by which these problems are detected should be developed during the initial development of the system. Once determined, a web of sensors is employed and their outputs are monitored with other system parameters while the system is in preparation or operation. Just gathering the data is only part of the story. The interpretation of the data itself and the response of the system must be carefully developed as well to avoid a mishap. Typically, systems use a test-threshold-response paradigm to process potential system faults. However, such processing sub-systems can suffer from errors and oversights of a consistent type, causing system aberrant behavior instead of expected system and recovery operations. In our study, we developed a complete checklist for determining the completeness of a fault system and its robustness to common processing and response difficulties.

Easton, Charles; Khuzadi, Mbuyi

2008-01-01

336

Diagnostic Thresholds with Three Ordinal Groups  

PubMed Central

Summary In practice, there exist many disease processes with three ordinal disease classes; for example in the detection of Alzheimers disease (AD) a patient can be classified as healthy (disease free stage), mild cognitive impairment (early disease stage) or AD (full disease stage). The treatment interventions and effectiveness of such disease processes will depend on the disease stage. Therefore it is important to develop diagnostic tests with the ability to discriminate between the three disease stages. Measuring the overall ability of diagnostic tests to discriminate between the three classes has been discussed extensively in the literature. However there has been little proposed on how to select clinically meaningful thresholds for such diagnostic tests, except for a method based on the generalized Youden index by Nakas et al. (2010). In this paper, we propose two new criterion for selecting diagnostic thresholds in the three class setting. The numerical study demonstrated that the proposed methods may provide thresholds with less variability and more balance among the correct classification rates for the three stages. The proposed methods are applied to two real examples: the clinical diagnosis of AD from the Washington University Alzheimers Disease Research Center and on the detection of liver cancer (LC) using protein segments. PMID:24707966

Attwood, Kristopher; Tian, Lili; Xiong, Chengjie

2015-01-01

337

Low-threshold bidirectional air lasing.  

PubMed

Air lasing refers to the remote optical pumping of the constituents of ambient air that results in a directional laserlike emission from the pumped region. Intense current investigations of this concept are motivated by the potential applications in remote atmospheric sensing. Different approaches to air lasing are being investigated, but, so far, only the approach based on dissociation and resonant two-photon pumping of air molecules by deep-UV laser pulses has produced measurable lasing energies in real air and in the backward direction, which is of the most relevance for applications. However, the emission had a high pumping threshold, in hundreds of GW/cm^{2}. We demonstrate that the threshold can be virtually eliminated through predissociation of air molecules with an additional nanosecond laser. We use a single tunable pump laser system to generate backward-propagating lasing in both oxygen and nitrogen in air, with energies of up to 1???J per pulse. PMID:25554881

Laurain, Alexandre; Scheller, Maik; Polynkin, Pavel

2014-12-19

338

Low-Threshold Bidirectional Air Lasing  

NASA Astrophysics Data System (ADS)

Air lasing refers to the remote optical pumping of the constituents of ambient air that results in a directional laserlike emission from the pumped region. Intense current investigations of this concept are motivated by the potential applications in remote atmospheric sensing. Different approaches to air lasing are being investigated, but, so far, only the approach based on dissociation and resonant two-photon pumping of air molecules by deep-UV laser pulses has produced measurable lasing energies in real air and in the backward direction, which is of the most relevance for applications. However, the emission had a high pumping threshold, in hundreds of GW /cm2. We demonstrate that the threshold can be virtually eliminated through predissociation of air molecules with an additional nanosecond laser. We use a single tunable pump laser system to generate backward-propagating lasing in both oxygen and nitrogen in air, with energies of up to 1 ? J per pulse.

Laurain, Alexandre; Scheller, Maik; Polynkin, Pavel

2014-12-01

339

Automatic detection of bone fragments in poultry using multi-energy x-rays  

DOEpatents

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.

Gleason, Shaun S. (Knoxville, TN); Paulus, Michael J. (Knoxville, TN); Mullens, James A. (Knoxville, TN)

2002-04-09

340

Preliminary results utilizing high-energy fission product ?-rays to detect fissionable material in cargo  

Microsoft Academic Search

A concept for detecting the presence of special nuclear material (235U or 239Pu) concealed in intermodal cargo containers is described. It is based on interrogation with a pulsed beam of 7MeV neutrons that produce fission events and their ?-delayed neutron emission or ?-delayed high-energy ? radiation between beam pulses provide the detection signature. Fission product ?-delayed ?-rays above 3MeV are

D. R. Slaughter; M. R. Accatino; A. Bernstein; J. A. Church; M. A. Descalle; T. B. Gosnell; J. M. Hall; A. Loshak; D. R. Manatt; G. J. Mauger; T. L. Moore; E. B. Norman; B. A. Pohl; J. A. Pruet; D. C. Petersen; R. S. Walling; D. L. Weirup; S. G. Prussin; M. McDowell

2005-01-01

341

Early results utilizing high-energy fission product (gamma) rays to detect fissionable material in cargo  

Microsoft Academic Search

A concept for detecting the presence of special nuclear material (U or Pu) concealed in intermodal cargo containers is described. It is based on interrogation with a pulsed beam of 7 MeV neutrons that produce fission events and their -delayed neutron emission or -delayed high-energy -radiation between beam pulses provide the detection signature. Fission product -delayed -rays above 3 MeV

D R Slaughter; M R Accatino; A Bernstein; J A Church; M A Descalle; T B Gosnell; J M Hall; A Loshak; D R Manatt; G J Mauger; M McDowell; T M Moore; E B Norman; B A Pohl; J A Pruet; D C Petersen; R S Walling; D L Weirup; S G Prussin

2004-01-01

342

Adaptive Harmonic Detection Control of Grid Interfaced Solar Photovoltaic Energy System with Power Quality Improvement  

NASA Astrophysics Data System (ADS)

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.

Singh, B.; Goel, S.

2014-07-01

343

Probabilistic Threshold Criterion  

SciTech Connect

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.

Gresshoff, M; Hrousis, C A

2010-03-09

344

Near threshold studies of photoelectron satellites  

SciTech Connect

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.

Heimann, P.A.

1986-11-01

345

Threshold Concepts and Information Literacy  

ERIC Educational Resources Information Center

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

Townsend, Lori; Brunetti, Korey; Hofer, Amy R.

2011-01-01

346

Synchronisation of Resonances with Thresholds  

Microsoft Academic Search

The mechanism by which a resonance may be attracted to a sharp threshold is described with several examples. It involves a threshold cusp interfering constructively with either or both (i) a resonance produced via confinement, (ii) attractive t- and u-channel exchanges. More generally, it is suggested that resonances are eigenstates generated by mixing between confined states and long-range meson and

David V. Bugg

2009-01-01

347

Threshold Hypothesis: Fact or Artifact?  

ERIC Educational Resources Information Center

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

Karwowski, Maciej; Gralewski, Jacek

2013-01-01

348

Early results utilizing high-energy fission product (gamma) rays to detect fissionable material in cargo  

SciTech Connect

A concept for detecting the presence of special nuclear material ({sup 235}U or {sup 239}Pu) concealed in intermodal cargo containers is described. It is based on interrogation with a pulsed beam of 7 MeV neutrons that produce fission events and their {beta}-delayed neutron emission or {beta}-delayed high-energy {gamma}-radiation between beam pulses provide the detection signature. Fission product {beta}-delayed {gamma}-rays above 3 MeV are nearly ten times more abundant than {beta}-delayed neutrons and are distinct from natural radioactivity and from nearly all of the induced activity in a normal cargo. Detector backgrounds and potential interferences with the fission signature radiation have been identified and quantified. An important goal in the US is the detection of nuclear weapons or special nuclear material (SNM) concealed in intermodal cargo containers. This must be done with high detection probability, low false alarm rates, and without impeding commerce, i.e. about one minute for an inspection. The concept for inspection has been described before and its components are now being evaluated. While normal radiations emitted from plutonium may allow its detection, the majority of {sup 235}U {gamma} ray emission is at 186 keV, is readily attenuated by cargo, and thus not a reliable detection signature for passive detection. Delayed neutron detection following a neutron or photon beam pulse has been used successfully to detect lightly or unshielded SNM targets. While delayed neutrons can be easily distinguished from beam neutrons they have relatively low yield in fission, approximately 0.008 per fission in {sup 239}Pu and 0.017 per fission in {sup 235}U, and are rapidly attenuated in hydrogenous materials making that technique unreliable when challenged by thick hydrogenous cargo overburden. They propose detection of {beta}-delayed high-energy {gamma} radiation as a more robust signature characteristic of SNM.

Slaughter, D R; Accatino, M R; Bernstein, A; Church, J A; Descalle, M A; Gosnell, T B; Hall, J M; Loshak, A; Manatt, D R; Mauger, G J; McDowell, M; Moore, T M; Norman, E B; Pohl, B A; Pruet, J A; Petersen, D C; Walling, R S; Weirup, D L; Prussin, S G

2004-09-30

349

s-wave threshold in electron attachment - Results in 2-C4F6 and CFCl3 at ultra-low electron energies  

NASA Technical Reports Server (NTRS)

Electron attachment lineshapes and cross sections are reported for the processes 2-C4F6(-)/2-C4F6 and Cl(-)/CFCl3 at electron energies of 0-120 and 0-140 meV, and at resolutions of 6 and 7 meV (FWHM), respectively. As in previous measurements in CCl4 and SF6, the results show resolution-limited narrow structure in the cross section at electron energies below 15 meV. This structure arises from the divergence of the s-wave cross section in the limit of zero electron energy. Comparisons are given with swarm-measured results, and with collisional ionization (high-Rydberg attachment) data in this energy range.

Chutjian, A.; Alajajian, S. H.; Ajello, J. M.; Orient, O. J.

1984-01-01

350

Identification of Low-Dimensional Energy Containing\\/Flux Transporting Eddy Motion in the Atmospheric Surface Layer Using Wavelet Thresholding Methods  

Microsoft Academic Search

The partitioning of turbulent perturbations into a `low-dimensional' active part responsible for much of the turbulent energy and fluxes and a `high-dimensional' passive part that contributes little to turbulent energy and transport dynamics is investigated using atmospheric surface-layer (ASL) measurements. It is shown that such a partitioning scheme can be achieved by transforming the ASL measurements into a domain that

Gabriel Katul; Brani Vidakovic

1998-01-01

351

Threshold enhancement in eta photoproduction from 2H and 4He  

E-print Network

The photoproduction of eta-mesons from 2H and 4He has been studied for energies close to the production thresholds. The experiments were carried out with the tagged photon beam of the Mainz MAMI accelerator. The eta-mesons were detected via their two photon decays with the electromagnetic calorimeter TAPS. Total cross sections, angular and momentum distributions of the eta-mesons have been determined for both reactions. The total cross sections in the threshold region show a large enhancement over the predictions of a participant - spectator model, indicating significant final state interaction effects. The results are compared to recent model calculations taking into account nucleon-nucleon and nucleon-eta final state interaction effects on different levels of sophistication.

V. Hejny; J. Weiss; P. Achenbach; J. Ahrens; J. R. M. Annand; R. Beck; M. Kotulla; B. Krusche; V. Kuhr; R. Leukel; I. J. D. MacGregor; V. Metag; R. Novotny; V. Olmos de Leon; F. Rambo; A. Schmidt; M. Schumacher; U. Siodlaczek; H. Stroeher; F. Wissmann; M. Wolf

2003-04-02

352

The twin threshold model: risk-intermediate foraging by rufous hummingbirds, Selasphorus rufus  

Microsoft Academic Search

I developed two versions of the twin threshold model (TTM) to assess risk-sensitive foraging decisions by rufous hummingbirds. The model incorporates energy thresholds for both starvation and reproduction and assesses how three reward distributions with a common mean but different levels of variance interact with these critical thresholds to determine fitness. Fitness, a combination of survival and reproduction, is influenced

Andrew T. Hurly

2003-01-01

353

Detection of high energy X-rays from the galactic center region  

NASA Technical Reports Server (NTRS)

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.

Dennis, B. R.; Beall, J. H.; Cutler, E. P.; Crannell, C. J.; Dolan, J. G.; Frost, K. J.; Orwig, L. E.

1979-01-01

354

Methods of sequencing and detection using energy transfer labels with cyanine dyes as donor chromophores  

DOEpatents

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.

Glazer, Alexander N. (Orinda, CA); Mathies, Richard A. (Moraga, CA); Hung, Su-Chun (Richmond, CA); Ju, Jingyue (Redwood City, CA)

2000-01-01

355

Electron-emission processes in highly charged Ar and Xe ions impinging on highly ordered pyrolytic graphite at energies just above the kinetic threshold  

NASA Astrophysics Data System (ADS)

At keV energies, many electronic processes contribute to the emission of secondary electrons in the interaction of highly charged ions on surfaces. To unravel contributions resulting from isolated hollow atoms in front of the surface or embedded in the electron gas of the target, heavy highly charged Ar and Xe ions are collided on highly ordered pyrolytic graphite (HOPG). A light target material as HOPG assures straight-line trajectories in the subsurface range. By a systematic change of incidence angle and energy of low-charged Ar and Xe ions, the kinetic electron emission component is determined. Separating out the kinetic energy contribution for the highly charged ions yields pure potential-energy-driven secondary-electron yields. From these yields it is concluded that in contrast to metallic targets, only a small fraction of the secondary electrons stem from above the surface. The lack of above-surface emission is likely due to the semimetallic electronic structure of HOPG. The subsurface emission is found to scale with the increase in binding energy of the inner-shell hole when incrementing the charge state of the projectile Ar or Xe ions.

Bodewits, E.; Hoekstra, R.; Dobes, K.; Aumayr, F.

2014-11-01

356

Bayesian estimation of dose thresholds  

NASA Technical Reports Server (NTRS)

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.

Groer, P. G.; Carnes, B. A.

2003-01-01

357

The role and detectability of the charm contribution to ultra high energy neutrino fluxes  

SciTech Connect

It is widely believed that charm meson production and decay may play an important role in high energy astrophysical sources of neutrinos, especially those that are baryon-rich, providing an environment conducive to pp interactions. Using slow-jet supernovae (SJS) as an example of such a source, we study the detectability of high-energy neutrinos, paying particular attention to those produced from charmed-mesons. We highlight important distinguishing features in the ultra-high energy neutrino flux which would act as markers for the role of charm in the source. In particular, charm leads to significant event rates at higher energies, after the conventional (?,K) neutrino fluxes fall off. We calculate event rates both for a nearby single source and for diffuse SJS fluxes for an IceCube-like detector. By comparing muon event rates for the conventional and prompt fluxes in different energy bins, we demonstrate the striking energy dependence in the rates induced by the presence of charm. We also show that it leads to an energy dependant flux ratio of shower to muon events, providing an additional important diagnostic tool for the presence of prompt neutrinos. Motivated by the infusion of high energy anti-electron neutrinos into the flux by charm decay, we also study the detectability of the Glashow resonance due to these sources.

Gandhi, Raj; Samanta, Abhijit; Watanabe, Atsushi, E-mail: raj@hri.res.in, E-mail: abhijit@hri.res.in, E-mail: watanabe@higgs.phys.kyushu-u.ac.jp [Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211019 (India)

2009-09-01

358

Harmonic Analysis of Polynomial Threshold Functions  

Microsoft Academic Search

The analysis of linear threshold Boolean functions has recently attracted the attention of those interested in circuit complexity as well as of those interested in neural networks. Here a generalization of linear threshold functions is defined, namely, polynomial threshold functions, and its relation to the class of linear threshold functions is investigated. A Boolean function is polynomial threshold if it

Jehoshua Bruck

1990-01-01

359

Detection  

E-print Network

In this work, we focus on the mainly detection of buildings.. As input data, we use LIDAR data and multispectral aerial images of two different test sites. One is from Zurich airport and the other one is from Vaihingen region close to Stuttgart. Quality assessment has been performed by comparing our results with existing reference data which are generated using commercial photogrammetric software and manual stereo measurement. 1.

unknown authors

360

Improving Weapon Detection in Single Energy X-Ray Images Through Pseudocoloring  

Microsoft Academic Search

This paper describes a series of linear and nonlinear pseudocoloring maps designed and applied to single energy X-ray luggage scans to assist airport screeners in identifying and detecting threat items, particularly hard to see low-density weapons in luggage. Considerations of the psychological and physiological processing involved in the human perception of color as well as the effects of using various

Besma R. Abidi; Yue Zheng; Andrei V. Gribok; Mongi A. Abidi

2006-01-01

361

30TH INTERNATIONAL COSMIC RAY CONFERENCE Radio Detection of UltraHigh Energy Cosmic Rays  

E-print Network

30TH INTERNATIONAL COSMIC RAY CONFERENCE Radio Detection of Ultra­High Energy Cosmic Rays HEINO from cosmic rays, confirmed the geosynchrotron effect for extensive air showers, and provided a good rays and the usage of the LOFAR radio telescope (and later the SKA) as a cosmic ray detector. Here

Falcke, Heino

362

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...

363

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...

364

An Alternative Energy Detection Using Sliding Window for Cognitive Radio System  

Microsoft Academic Search

Cognitive radio is one of the most effective techniques to improve the spectrum utilization efficiency. To implement the cognitive radio, spectrum sensing is considered as the key functionality because secondary users should identify the spectrum holes and utilize them efficiently without causing interference to primary users. In generally, there are three major spectrum sensing methods, including matched filter, energy detection

Young Min Kim; Guanbo Zheng; Sung Hwan Sohn; Jae Moung Kim

2008-01-01

365

Automated lung nodule detection and segmentation  

NASA Astrophysics Data System (ADS)

A computer-aided detection (CAD) system for lung nodules in CT scans was developed. For the detection of lung nodules two different methods were applied and only pixels which were detected by both methods are marked as true positives. The first method uses a multi-threshold algorithm, which detect connected regions within the lung that have an intensity between specified threshold values. The second is a multi-scale detection method. The data are searched for points located in spherical objects. The image data were smoothed with a 3D Gaussian filter and computed the Hessian matrix and eigenvectors and eigenvalues for all pixels detected by the first algorithm. By analyzing the eigenvalues points that lie within a spherical structure can be located. For segmentation of the detected nodules an active contour model was used. A two-dimensional active contour with four energy terms describing form and position of the contour in the image data was implemented. In addition balloon energy to get the active contour was used growing out from one point. The result of our detection part is used as input for the segmentation part. To test the detection algorithms we used 19 CT volume data sets from a low-dose CT studies. Our CAD system detected 58% of the nodules with a falsepositive rate of 1.38. Additionally we take part at the ANODE09 study whose results will be presented at the SPIE meeting in 2009.

Schneider, Christian; Amjadi, Azad; Richter, Anja; Fiebich, Martin

2009-02-01

366

Threshold meson production and cosmic ray transport  

E-print Network

An interesting accident of nature is that the peak of the cosmic ray spectrum, for both protons and heavier nuclei, occurs near the pion production threshold. The Boltzmann transport equation contains a term which is the cosmic ray flux multiplied by the cross section. Therefore when considering pion and kaon production from proton-proton reactions, small cross sections at low energy can be as important as larger cross sections at higher energy. This is also true for subthreshold kaon production in nuclear collisions, but not for subthreshold pion production.

John W. Norbury; Lawrence W. Townsend; Ryan B. Norman

2006-12-11

367

An energy kurtosis demodulation technique for signal denoising and bearing fault detection  

NASA Astrophysics Data System (ADS)

Rolling element bearings are commonly used in rotary machinery. Reliable bearing fault detection techniques are very useful in industries for predictive maintenance operations. Bearing fault detection still remains a very challenging task especially when defects occur on rotating bearing components because the fault-related features are non-stationary in nature. In this work, an energy kurtosis demodulation (EKD) technique is proposed for bearing fault detection especially for non-stationary signature analysis. The proposed EKD technique firstly denoises the signal by using a maximum kurtosis deconvolution filter to counteract the effect of signal transmission path so as to highlight defect-associated impulses. Next, the denoised signal is modulated over several frequency bands; a novel signature integration strategy is proposed to enhance feature characteristics. The effectiveness of the proposed EKD fault detection technique is verified by a series of experimental tests corresponding to different bearing conditions.

Wang, Wilson; Lee, Hewen

2013-02-01

368

Nuclear recoil energy scale in liquid xenon with application to the direct detection of dark matter  

SciTech Connect

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.

Sorensen, P; Dahl, C E

2011-02-14

369

Comparison of current and energy X-ray measurement methods in contrast media detection  

NASA Astrophysics Data System (ADS)

X-ray spectra were measured using a CdZnTe detector for the various combinations of water phantom thickness (15-25 cm), iodine contrast media thickness (3-60 ?m in a 1 cm thick simulated tumour), La filter thickness (0, 100, and 160 ?m), and X-ray tube voltage (50, 65, and 80 kV). The iodine thickness was obtained as a contrast using energy information from the X-ray spectra and current, which was calculated as the summed products of X-ray energy and events. The most sensitive method of iodine detection is the energy measurement method with 65 kV tube voltage.

Kanno, I.; Uesaka, A.; Nomiya, S.; Onabe, H.

2007-09-01

370

Automatic Classification of Kepler Threshold Crossing Events  

NASA Astrophysics Data System (ADS)

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 NASAs Science Mission Directorate.

McCauliff, Sean; Catanzarite, Joseph; Jenkins, Jon Michael

2014-06-01

371

Detection of occult, undisplaced hip fractures with a dual-energy CT algorithm targeted to detection of bone marrow edema.  

PubMed

The purpose of this study is to describe our initial clinical experience with dual-energy computed tomography (DECT) virtual non-calcium (VNC) images for the detection of bone marrow (BM) edema in patients with suspected hip fracture following trauma. Twenty-five patients presented to the emergency department at a level 1 trauma center between January 1, 2011 and January 1, 2013 with clinical suspicion of hip fracture and normal radiographs were included. All CT scans were performed on a dual-source, dual-energy CT system. VNC images were generated using prototype software and were compared to regular bone reconstructions by two musculoskeletal radiologists in consensus. Radiological and/or clinical diagnosis of fracture at 30-day follow-up was used as the reference standard. Twenty-one patients were found to have DECT-VNC signs of bone marrow edema. Eighteen of these 21 patients were true positive and three were false positive. A concordant fracture was clearly seen on bone reconstruction images in 15 of the 18 true positive cases. In three cases, DECT-VNC was positive for bone marrow edema where bone reconstruction CT images were negative. Four patients demonstrated no DECT-VNC signs of bone marrow edema: two cases were true negative, two cases were false negative. When compared with the gold standard of hip fracture determined at retrospective follow-up, the sensitivity of DECT-VNC images of the hip was 90%, specificity was 40%, positive predictive value was 86%, and negative predictive value was 50%. Our initial experience would suggest that DECT-VNC is highly sensitive but poorly specific in the diagnosis of hip fractures in patients with normal radiographs. The value of DECT-VNC primarily lies in its ability to help detect fractures which may be subtle or undetectable on bone reconstruction CT images. PMID:24985783

Reddy, T; McLaughlin, P D; Mallinson, P I; Reagan, A C; Munk, P L; Nicolaou, S; Ouellette, H A

2015-02-01

372

Resilience, Triggers, Feedbacks and Thresholds  

E-print Network

Resilience, Triggers, Feedbacks and Thresholds: A Western Juniper Model Steven Petersen Tamzen #12;Ecological Resilience Ecological resilience describes the degree of ecosystem modification resilience and function" (Bestelmeyer et al. 2003). Negative feedbacks maintain ecosystem stability

373

Possible Effects of Dark Energy on the Detection of Dark Matter Particles  

E-print Network

We study in this paper the possible influence of the dark energy on the detection of the dark matter particles. In models of dark energy described by a dynamical scalar field such as the Quintessence, its interaction with the dark matter will cause the dark matter particles such as the neutralino vary as a function of space and time. Given a specific model of the Quintessence and its interaction in this paper we calculate numerically the corrections to the neutralino masses and the induced spectrum of the neutrinos from the annihilation of the neutralinos pairs in the core of the Sun. This study gives rise to a possibility of probing for dark energy in the experiments of detecting the dark matter particles.

Peihong Gu; Xiao-Jun Bi; Zhi-Hai Lin; Xinmin Zhang

2005-03-14

374

A detection system for very low-energy protons from {beta}-delayed proton decay  

SciTech Connect

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.

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. [Cyclotron Institute, Texas A and M University, College Station, TX 77843-3366 (United States); CEA/IRFU Saclay, Gif-sur-Yvette (France); Cyclotron Institute, Texas A and M University, College Station, TX 77843-3366 (United States); Institut fuer Kernphysik der Universitaet zu Koeln, D-50937 Koeln (Germany); CEA/IRFU Saclay, Gif-sur-Yvette (France)

2012-11-20

375

A study of the energy dependence of the detection efficiency of a microchannel plate for low energy H?? ions  

E-print Network

/RE CRANAELS Fig. 1. Cutaway view of a microchannel plate [3]. When an NCP is placed in vacuum and a voltage is applied between the surfaces, each channel becomes a continuous electron multiplier. Particles, which strike the walls of one of the channels...V. Another measurement [12] with a different channel multiplier results in a totally different efficiency (fig. 26 b): The detection efficiency rises fast with ion energy and reaches its maximum value of about 60 below an ion energy of 1 keV. For higher...

Holzscheiter, Karin Elisabeth Martha

1987-01-01

376

Synchonisation of Resonances with Thresholds  

E-print Network

The mechanism by which a resonance may be attracted to a sharp threshold is described with several examples. It involves a threshold cusp interfering constructively with either or both (i) a resonance produced via confinement, (ii) attractive t- and u-channel exchanges. More generally, it is suggested that resonances are eigenstates generated by mixing between confined states and long-range meson and baryon exchanges.

D. V. Bugg

2008-07-05

377

Threshold models in radiation carcinogenesis  

SciTech Connect

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.

Hoel, D.G.; Li, P. [Medical Univ. of South Carolina, Charleston, SC (United States). Dept. of Biometry and Epidemiology

1998-09-01

378

Energy Detectives! Introduce Students to a Promising Career in Energy Auditing  

ERIC Educational Resources Information Center

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

Helmholdt, Nick

2012-01-01

379

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

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}

Eder, K.; Semrad, D.; Bauer, P. [Institut fuer Experimentalphysik, Johannes-Kepler Universitaet Linz, A-4040 Linz (Austria)] [Institut fuer Experimentalphysik, Johannes-Kepler Universitaet Linz, A-4040 Linz (Austria); Golser, R. [Institut fuer Radiumforschung und Kernphysik, Universitaet Wien, A-1090 Wien (Austria)] [Institut fuer Radiumforschung und Kernphysik, Universitaet Wien, A-1090 Wien (Austria); Maier-Komor, P. [Target Laboratory, Technical University Munich, D-85748 Garching (Germany)] [Target Laboratory, Technical University Munich, D-85748 Garching (Germany); Aumayr, F. [Institut fuer Allgemeine Physik, Technische Universitaet Wien, A-1040 Wien (Austria)] [Institut fuer Allgemeine Physik, Technische Universitaet Wien, A-1040 Wien (Austria); Penalba, M. [Departamento de Fisica Aplicada I, E.T.S.I.I. y T., Universidad del Pais Vasco, Bilbao (Spain)] [Departamento de Fisica Aplicada I, E.T.S.I.I. y T., Universidad del Pais Vasco, Bilbao (Spain); Arnau, A.; Ugalde, J.M.; Echenique, P.M. [Departamento de Fisica de Materiales, Universidad del Pais Vasco, Apartado 1072, San Sebastian 20080 (Spain)] [Departamento de Fisica de Materiales, Universidad del Pais Vasco, Apartado 1072, San Sebastian 20080 (Spain)

1997-11-01

380

Nanostructure formation on tungsten exposed to low-pressure rf helium plasmas: A study of ion energy threshold and early stage growth  

NASA Astrophysics Data System (ADS)

Nanostructure formation on W targets is explored as a function of He+ impact energy, &z.epsiv;i, in the range 20 ? &z.epsiv;i ? 57 eV. Six targets are exposed at 1120 K for 6 h to pure He plasmas, generated by a low-pressure rf Helicon source. One target is additionally exposed to Ar plasma pre-treatment. It is found that He ions of impact energy 32-37 eV are necessary for nanostructure formation to be observed in this type of plasma, as determined by SEM. At 57 eV a nanostructured surface forms readily (similar to that observed by Baldwin and Doerner, Nuclear Fusion 48 (2008) 035001 in the PISCES-B device), but growth is retarded in the Ar pre-treatment case. Thermal desorption shows that nanostructuring is accompanied by increased trapping of He in degenerate vacancies and clusters, but is reduced by a factor of 8 as a result of Ar pre-treatment.

Baldwin, M. J.; Lynch, T. C.; Doerner, R. P.; Yu, J. H.

2011-08-01

381

The e+e-?3(?+?-), 2(?+?-?0) and K+K-2(?+?-) cross sections at center-of-mass energies from production threshold to 4.5 GeV measured with initial-state radiation  

NASA Astrophysics Data System (ADS)

We study the processes e+e-?3(?+?-)?, 2(?+?-?0)? and K+K-2(?+?-)?, with the photon radiated from the initial state. About 20 000, 33 000 and 4000 fully reconstructed events, respectively, have been selected from 232 fb-1 of BABAR data. The invariant mass of the hadronic final state defines the effective e+e- center-of-mass energy, so that these data can be compared with the corresponding direct e+e- measurements. From the 3(?+?-), 2(?+?-?0) and K+K-2(?+?-) mass spectra, the cross sections for the processes e+e-?3(?+?-), e+e-?2(?+?-?0) and e+e-?K+K-2(?+?-) are measured for center-of-mass energies from production threshold to 4.5 GeV. The uncertainty in the cross section measurement is typically 6% 15%. We observe a structure at 1.9 GeV in both cross sections and a resonance structure with mass 16450.008 GeV/c2 and width 0.1140.014 GeV when the ?(782)? final state is extracted. We observe the J/? in all these final states and measure the corresponding branching fractions.

Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Tisserand, V.; Zghiche, A.; Grauges, E.; Palano, A.; Pappagallo, M.; Chen, J. C.; Qi, N. D.; Rong, G.; Wang, P.; Zhu, Y. S.; Eigen, G.; Ofte, I.; Stugu, B.; Abrams, G. S.; Battaglia, M.; Best, D. S.; Brown, D. N.; Button-Shafer, J.; Cahn, R. N.; Charles, E.; Day, C. T.; Gill, M. S.; Gritsan, A. V.; Groysman, Y.; Jacobsen, R. G.; Kadel, R. W.; Kadyk, J. A.; Kerth, L. T.; Kolomensky, Yu. G.; Kukartsev, G.; Lynch, G.; Mir, L. M.; Oddone, P. J.; Orimoto, T. J.; Pripstein, M.; Roe, N. A.; Ronan, M. T.; Wenzel, W. A.; Barrett, M.; Ford, K. E.; Harrison, T. J.; Hart, A. J.; Hawkes, C. M.; Morgan, S. E.; Watson, A. T.; Fritsch, M.; Goetzen, K.; Held, T.; Koch, H.; Lewandowski, B.; Pelizaeus, M.; Peters, K.; Schroeder, T.; Steinke, M.; Boyd, J. T.; Burke, J. P.; Cottingham, W. N.; Walker, D.; Cuhadar-Donszelmann, T.; Fulsom, B. G.; Hearty, C.; Knecht, N. S.; Mattison, T. S.; McKenna, J. A.; Khan, A.; Kyberd, P.; Saleem, M.; Teodorescu, L.; Blinov, V. E.; Bukin, A. D.; Druzhinin, V. P.; Golubev, V. B.; Kravchenko, E. A.; Onuchin, A. P.; Serednyakov, S. I.; Skovpen, Yu. I.; Solodov, E. P.; Todyshev, K. Yu; Bondioli, M.; Bruinsma, M.; Chao, M.; Curry, S.; Eschrich, I.; Kirkby, D.; Lankford, A. J.; Lund, P.; Mandelkern, M.; Mommsen, R. K.; Roethel, W.; Stoker, D. P.; Abachi, S.; Buchanan, C.; Foulkes, S. D.; Gary, J. W.; Long, O.; Shen, B. C.; Wang, K.; Zhang, L.; Del Re, D.; Hadavand, H. K.; Hill, E. J.; Paar, H. P.; Rahatlou, S.; Sharma, V.; Berryhill, J. W.; Campagnari, C.; Cunha, A.; Dahmes, B.; Hong, T. M.; Richman, J. D.; Beck, T. W.; Eisner, A. M.; Flacco, C. J.; Heusch, C. A.; Kroseberg, J.; Lockman, W. S.; Nesom, G.; Schalk, T.; Schumm, B. A.; Seiden, A.; Spradlin, P.; Williams, D. C.; Wilson, M. G.; Albert, J.; Chen, E.; Dubois-Felsmann, G. P.; Dvoretskii, A.; Hitlin, D. G.; Narsky, I.; Piatenko, T.; Porter, F. C.; Ryd, A.; Samuel, A.; Andreassen, R.; Mancinelli, G.; Meadows, B. T.; Sokoloff, M. D.; Blanc, F.; Bloom, P. C.; Chen, S.; Ford, W. T.; Hirschauer, J. F.; Kreisel, A.; Nauenberg, U.; Olivas, A.; Ruddick, W. O.; Smith, J. G.; Ulmer, K. A.; Wagner, S. R.; Zhang, J.; Chen, A.; Eckhart, E. A.; Soffer, A.; Toki, W. H.; Wilson, R. J.; Winklmeier, F.; Zeng, Q.; Altenburg, D. D.; Feltresi, E.; Hauke, A.; Jasper, H.; Spaan, B.; Brandt, T.; Dickopp, M.; Klose, V.; Lacker, H. M.; Nogowski, R.; Otto, S.; Petzold, A.; Schubert, J.; Schubert, K. R.; Schwierz, R.; Sundermann, J. E.; Volk, A.; Bernard, D.; Bonneaud, G. R.; Grenier, P.; Latour, E.; Schrenk, S.; Thiebaux, Ch.; Vasileiadis, G.; Verderi, M.; Bard, D. J.; Clark, P. J.; Gradl, W.; Muheim, F.; Playfer, S.; Xie, Y.; Andreotti, M.; Bettoni, D.; Bozzi, C.; Calabrese, R.; Cibinetto, G.; Luppi, E.; Negrini, M.; Piemontese, L.; Anulli, F.; Baldini-Ferroli, R.; Calcaterra, A.; de Sangro, R.; Finocchiaro, G.; Pacetti, S.; Patteri, P.; Peruzzi, I. M.; Piccolo, M.; Zallo, A.; Buzzo, A.; Capra, R.; Contri, R.; Vetere, M. Lo; Macri, M. M.; Monge, M. R.; Passaggio, S.; Patrignani, C.; Robutti, E.; Santroni, A.; Tosi, S.; Brandenburg, G.; Chaisanguanthum, K. S.; Morii, M.; Wu, J.; Dubitzky, R. S.; Marks, J.; Schenk, S.; Uwer, U.; Bhimji, W.; Bowerman, D. A.; Dauncey, P. D.; Egede, U.; Flack, R. L.; Gaillard, J. R.; Nash, J.; Nikolich, M. B.; Vazquez, W. Panduro; Chai, X.; Charles, M. J.; Mader, W. F.; Mallik, U.; Ziegler, V.; Cochran, J.; Crawley, H. B.; Dong, L.; Eyges, V.; Meyer, W. T.; Prell, S.; Rosenberg, E. I.; Rubin, A. E.; Schott, G.; Arnaud, N.; Davier, M.; Grosdidier, G.; Hcker, A.; Diberder, F. Le; Lepeltier, V.; Lutz, A. M.; Oyanguren, A.; Petersen, T. C.; Pruvot, S.; Rodier, S.; Roudeau, P.; Schune, M. H.; Stocchi, A.; Wang, W. F.; Wormser, G.; Cheng, C. H.; Lange, D. J.; Wright, D. M.; Bevan, A. J.; Chavez, C. A.; Forster, I. J.; Fry, J. R.; Gabathuler, E.; Gamet, R.; George, K. A.; Hutchcroft, D. E.; Payne, D. J.; Schofield, K. C.; Touramanis, C.; Lodovico, F. Di; Menges, W.; Sacco, R.; Brown, C. L.; Cowan, G.; Flaecher, H. U.; Green, M. G.; Hopkins, D. A.; Jackson, P. S.; McMahon, T. R.; Ricciardi, S.; Salvatore, F.; Brown, D. N.; Davis, C. L.; Allison, J.; Barlow, N. R.; Barlow, R. J.; Chia, Y. M.; Edgar, C. L.; Kelly, M. P.; Lafferty, G. D.; Naisbit, M. T.; Williams, J. C.; Yi, J. I.; Chen, C.; Hulsbergen, W. D.; Jawahery, A.; Kovalskyi, D.; Lae, C. K.; Roberts, D. A.; Simi, G.; Blaylock, G.; Dallapiccola, C.; Hertzbach, S. S.; Kofler, R.; Li, X.; Moore, T. B.; Saremi, S.; Staengle, H.; Willocq, S. Y.; Cowan, R.; Koeneke, K.; Sciolla, G.; Sekula, S. J.; Spitznagel, M.; Taylor, F.; Yamamoto, R. K.; Kim, H.; Patel, P. M.; Potter, C. T.; Robertson, S. H.; Lazzaro, A.; Lombardo, V.; Palombo, F.; Bauer, J. M.; Cremaldi, L.; Eschenburg, V.

2006-03-01

382

Structural Variability of Nucleosomes Detected by Single-Pair Forster Resonance Energy Transfer: Histone Acetylation, Sequence Variation, and Salt Effects  

E-print Network

Structural Variability of Nucleosomes Detected by Single-Pair Fo¨rster Resonance Energy Transfer¨rster resonance energy transfer (spFRET) measurements of the distance between fluorescently labeled bases detuned detection" (D3 ). This permits the separation of subpopulations in the samples even for the low

Langowski, Jörg

383

Radio surf in polar ice: A new method of ultrahigh energy neutrino detection  

NASA Astrophysics Data System (ADS)

We explore a new mechanism for detection of neutrino-induced showers via surface waves at radio frequencies. Air-dielectric surface waves exist on a plane boundaries that have attenuation lengths 2.82 that of the dielectric, and their amplitudes fall only by the inverse square root of propagation distance. Allowing for substantial coupling uncertainties, surface waves may provide a useful mechanism for neutrino detection in polar ice, promoting the development of neutrino telescopes in the energy regime above 1015eV.

Ralston, John P.

2005-01-01

384

Preliminary results utilizing high-energy fission product ?-rays to detect fissionable material in cargo  

NASA Astrophysics Data System (ADS)

A concept for detecting the presence of special nuclear material ( 235U or 239Pu) concealed in intermodal cargo containers is described. It is based on interrogation with a pulsed beam of 7 MeV neutrons that produce fission events and their ?-delayed neutron emission or ?-delayed high-energy ? radiation between beam pulses provide the detection signature. Fission product ?-delayed ?-rays above 3 MeV are nearly 10 times more abundant than ?-delayed neutrons and are distinct from natural radioactivity and from nearly all of the induced activity in a normal cargo. Detector backgrounds and potential interferences with the fission signature radiation have been identified and quantified.

Slaughter, D. R.; Accatino, M. R.; Bernstein, A.; Church, J. A.; Descalle, M. A.; Gosnell, T. B.; Hall, J. M.; Loshak, A.; Manatt, D. R.; Mauger, G. J.; Moore, T. L.; Norman, E. B.; Pohl, B. A.; Pruet, J. A.; Petersen, D. C.; Walling, R. S.; Weirup, D. L.; Prussin, S. G.; McDowell, M.

2005-12-01

385

Negative-ion contribution to threshold peaks observed in vibrational excitation spectra of molecules by electron impact  

Microsoft Academic Search

The contribution of negative ions, formed by dissociative attachment, to threshold peaks reported in the vibrational excitation spectra of some molecules is discussed. It is concluded that negative ions formed in the energy range of the vibrational levels of a neutral molecule with no kinetic energy and a large cross section contribute significantly to threshold peaks or simulate threshold peaks

R. Azria; Y. LeCoat; J. P. Guillotin

1980-01-01

386

High-Damage-Threshold Pinhole for Glass Fusion Laser Applications  

SciTech Connect

We are investigating methods to fabricate high-damage-threshold spatial-filter pinholes that might not be susceptible to plasma closure for relatively high energies and long pulses. These are based on the observation that grazing-incidence reflection from glass can withstand in excess of 5 kJ/cm{sup 2} (normal to the beam) without plasma formation. The high damage threshold results from both the cos q spreading of the energy across the surface and the reflection of a large fraction of the energy from the surface, thereby greatly reducing the field strength within the medium.

Kumit, N.A.; Letzring, S.A.; Johnson, R.P.

1998-06-07

387

Threshold photodetachment spectroscopy of negative ions  

SciTech Connect

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.

Kitsopoulos, T.N.

1991-12-01

388

New measurement of the scintillation efficiency of low-energy nuclear recoils in liquid xenon  

Microsoft Academic Search

Particle detectors that use liquid xenon (LXe) as detection medium are among the leading technologies in the search for dark matter weakly interacting massive particles (WIMPs). A key enabling element has been the low-energy detection threshold for recoiling nuclei produced by the interaction of WIMPs in LXe targets. In these detectors, the nuclear recoil energy scale is based on the

G. Plante; E. Aprile; R. Budnik; B. Choi; K.-L. Giboni; L. W. Goetzke; R. F. Lang; K. E. Lim; A. J. Melgarejo Fernandez

2011-01-01

389

Hybrid aptamer-antibody linked fluorescence resonance energy transfer based detection of trinitrotoluene.  

PubMed

Combining synthetic macromolecules and biomolecular recognition units are promising in developing novel diagnostic and analysis techniques for detecting environmental and/or clinically important substances. Fluorescence resonance energy transfer (FRET) apta-immunosensor for explosive detection is reported using 2,4,6-trinitrotoluene (TNT) specific aptamer and antibodies tagged with respective FRET pair dyes in a sandwich immunoassay format. FITC-labeled aptamer was used as a binder molecule in the newly developed apta-immunoassay format where the recognition element was specific anti-TNT antibody labeled with rhodamine isothiocyanate. The newly developed sensing platform showed excellent sensitivity with a detection limit of the order of 0.4 nM presenting a promising candidate for routine screening of TNT in samples. PMID:25008849

Sabherwal, Priyanka; Shorie, Munish; Pathania, Preeti; Chaudhary, Shilpa; Bhasin, K K; Bhalla, Vijayender; Suri, C Raman

2014-08-01

390

Cascaded systems analysis of noise and detectability in dual-energy cone-beam CT  

PubMed Central

Purpose: Dual-energy computed tomography and dual-energy cone-beam computed tomography (DE-CBCT) are promising modalities for applications ranging from vascular to breast, renal, hepatic, and musculoskeletal imaging. Accordingly, the optimization of imaging techniques for such applications would benefit significantly from a general theoretical description of image quality that properly incorporates factors of acquisition, reconstruction, and tissue decomposition in DE tomography. This work reports a cascaded systems analysis model that includes the Poisson statistics of x rays (quantum noise), detector model (flat-panel detectors), anatomical background, image reconstruction (filtered backprojection), DE decomposition (weighted subtraction), and simple observer models to yield a task-based framework for DE technique optimization. Methods: The theoretical framework extends previous modeling of DE projection radiography and CBCT. Signal and noise transfer characteristics are propagated through physical and mathematical stages of image formation and reconstruction. Dual-energy decomposition was modeled according to weighted subtraction of low- and high-energy images to yield the 3D DE noise-power spectrum (NPS) and noise-equivalent quanta (NEQ), which, in combination with observer models and the imaging task, yields the dual-energy detectability index (d?). Model calculations were validated with NPS and NEQ measurements from an experimental imaging bench simulating the geometry of a dedicated musculoskeletal extremities scanner. Imaging techniques, including kVp pair and dose allocation, were optimized using d? as an objective function for three example imaging tasks: (1) kidney stone discrimination; (2) iodine vs bone in a uniform, soft-tissue background; and (3) soft tissue tumor detection on power-law anatomical background. Results: Theoretical calculations of DE NPS and NEQ demonstrated good agreement with experimental measurements over a broad range of imaging conditions. Optimization results suggest a lower fraction of total dose imparted by the low-energy acquisition, a finding consistent with previous literature. The selection of optimal kVp pair reveals the combined effect of both quantum noise and contrast in the kidney stone discrimination and soft-tissue tumor detection tasks, whereas the K-edge effect of iodine was the dominant factor in determining kVp pairs in the iodine vs bone task. The soft-tissue tumor task illustrated the benefit of dual-energy imaging in eliminating anatomical background noise and improving detectability beyond that achievable by single-energy scans. Conclusions: This work established a task-based theoretical framework that is predictive of DE image quality. The model can be utilized in optimizing a broad range of parameters in image acquisition, reconstruction, and decomposition, providing a useful tool for maximizing DE-CBCT image quality and reducing dose. PMID:22894440

Gang, Grace J.; Zbijewski, Wojciech; Webster Stayman, J.; Siewerdsen, Jeffrey H.

2012-01-01

391

Prospects for Lunar Satellite Detection of Radio Pulses from Ultrahigh Energy Neutrinos Interacting with the Moon  

E-print Network

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^{20} eV, i.e. near and above the interesting GZK limit, at the very low fluxes predicted in different scenarios.

O. Stl; J. E. S. Bergman; B. Thid; L. K. S. Daldorff; G. Ingelman

2007-02-15

392

Detection of a flaring low-energy gamma-ray source  

NASA Technical Reports Server (NTRS)

We report the detection of a flaring gamma-ray source by the University of New Hampshire (UNH) balloon-borne coded aperture gamma-ray telescope (DGT) on 1984 October 2. The source was detected at the significance level of 7.2 sigma over the energy range 160-2000 keV. The intensity in the range (160-200) keV was 1.1 Crab. The best-fit position of the source is given by R.A. = 3h 25.8m and Decl. = 67 deg 653 min and is located in the constellation of Camelopardia. The source was visible within the Field of View (FOV) of the telescope for approximately = 2 hr and exhibited signs of flaring. The derived photon spectrum can be equally fitted by an optically thin bremsstrahlung distribution of kT approximately = 52 keV or a power law of the form, dN(E)/dE = 3.7 x 10(exp -6) (E/400)(exp -4.5) photons/sq cm/keV. We compare its spectral characteristics ad energy output to various types of fast X-ray transients. No measurable flux could be detected from CG 135+1, the COS B source which was in the FOV and therefore, we present 2 sigma upper flux limits on its spectral emission over the energy range 160 keV to 9.3 MeV.

Bhattacharya, Dipen; Owens, Alan

1994-01-01

393

Analysis of MODIS imagery for detection of clear cuts in the boreal forest in north-west Russia  

Microsoft Academic Search

This study examines the feasibility of using MODIS images (MOD02 products) for the detection and monitoring of forest clear cuts in the boreal forest in north-west Russia. The proposed approach combines three change detection methods, including Change Vector Analysis, Textural Analysis using the coefficient of variation, and Constrained Energy Minimization analysis. For each individual method a series of thresholds was

Tom Bucha; Hans-Jrgen Stibig

2008-01-01

394

Predicting percolation thresholds in networks  

NASA Astrophysics Data System (ADS)

We consider different methods, which do not rely on numerical simulations of the percolation process, to approximate percolation thresholds in networks. We perform a systematic analysis on synthetic graphs and a collection of 109 real networks to quantify their effectiveness and reliability as prediction tools. Our study reveals that the inverse of the largest eigenvalue of the nonbacktracking matrix of the graph often provides a tight lower bound for true percolation threshold. However, in more than 40 % of the cases, this indicator is less predictive than the naive expectation value based solely on the moments of the degree distribution. We find that the performance of all indicators becomes worse as the value of the true percolation threshold grows. Thus, none of them represents a good proxy for the robustness of extremely fragile networks.

Radicchi, Filippo

2015-01-01

395

Technology Thresholds for Microgravity: Status and Prospects  

NASA Technical Reports Server (NTRS)

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.

Noever, D. A.

1996-01-01

396

Quark mass thresholds in QCD thermodynamics  

E-print Network

We discuss radiative corrections to how quark mass thresholds are crossed, as a function of the temperature, in basic thermodynamic observables such as the pressure, the energy and entropy densities, and the heat capacity of high temperature QCD. The indication from leading order that the charm quark plays a visible role at surprisingly low temperatures, is confirmed. We also sketch a way to obtain phenomenological estimates relevant for generic expansion rate computations at temperatures between the QCD and electroweak scales, pointing out where improvements over the current knowledge are particularly welcome.

M. Laine; Y. Schroder

2006-03-06

397

Detection of a weak gamma-ray burst from the direction of Ursa Major  

SciTech Connect

An 80-second gamma-ray burst was detected over the energy range 42-205 keV by a balloon-borne gamma-ray telescope at 23:00:22 UT on May 11, 1988. Assuming a uniformly distributed source model, a 30 keV energy threshold, and a 3 delta detection threshold, it is estimated that the burst rate is 39,000 + 90,000 - 32,000/yr. It is found that the emission originated from the direction of Ursa Major. The event displays a marginal periodicity with a fundamental period 2.17 + or - 0.12 s. 34 refs.

Owens, A.; Sembay, S.; Bhattacharya, D. (NASA, Goddard Space Flight Center, Greenbelt, MD (USA) New Hampshire Univ., Durham (USA))

1990-04-01

398

Micro-Holographic Storage and Threshold Holographic Recording Materials  

NASA Astrophysics Data System (ADS)

This paper presents a new injection-molded holographic recording media with a threshold optical response that is specifically designed for single-bit holographic data storage. The concept of a threshold response in a holographic recording material is discussed and the benefits of such a material relative to standard linear materials are evaluated. Micro-holograms are recorded in the new material and the performance is compared to similar measurements in a linear material. The results show that the material has a threshold recording energy of approximately 1 J/pulse in a low-numerical-aperture (NA) test system, corresponding to 50 nJ/pulse in a high-NA system. In addition, the threshold material shows a 1000-fold improvement in continuous-wave (CW) read-out stability and a 25% reduction in hologram size as compared to the linear material.

Ostroverkhov, Victor; Lawrence, Brian L.; Shi, Xiaolei; Boden, Eugene P.; Erben, Christoph

2009-03-01

399

Energy-Efficient Data Reduction Techniques for Wireless Seizure Detection Systems  

PubMed Central

The emergence of wireless sensor networks (WSNs) has motivated a paradigm shift in patient monitoring and disease control. Epilepsy management is one of the areas that could especially benefit from the use of WSN. By using miniaturized wireless electroencephalogram (EEG) sensors, it is possible to perform ambulatory EEG recording and real-time seizure detection outside clinical settings. One major consideration in using such a wireless EEG-based system is the stringent battery energy constraint at the sensor side. Different solutions to reduce the power consumption at this side are therefore highly desired. The conventional approach incurs a high power consumption, as it transmits the entire EEG signals wirelessly to an external data server (where seizure detection is carried out). This paper examines the use of data reduction techniques for reducing the amount of data that has to be transmitted and, thereby, reducing the required power consumption at the sensor side. Two data reduction approaches are examined: compressive sensing-based EEG compression and low-complexity feature extraction. Their performance is evaluated in terms of seizure detection effectiveness and power consumption. Experimental results show that by performing low-complexity feature extraction at the sensor side and transmitting only the features that are pertinent to seizure detection to the server, a considerable overall saving in power is achieved. The battery life of the system is increased by 14 times, while the same seizure detection rate as the conventional approach (95%) is maintained. PMID:24469356

Chiang, Joyce; Ward, Rabab K.

2014-01-01

400

Energy-efficient data reduction techniques for wireless seizure detection systems.  

PubMed

The emergence of wireless sensor networks (WSNs) has motivated a paradigm shift in patient monitoring and disease control. Epilepsy management is one of the areas that could especially benefit from the use of WSN. By using miniaturized wireless electroencephalogram (EEG) sensors, it is possible to perform ambulatory EEG recording and real-time seizure detection outside clinical settings. One major consideration in using such a wireless EEG-based system is the stringent battery energy constraint at the sensor side. Different solutions to reduce the power consumption at this side are therefore highly desired. The conventional approach incurs a high power consumption, as it transmits the entire EEG signals wirelessly to an external data server (where seizure detection is carried out). This paper examines the use of data reduction techniques for reducing the amount of data that has to be transmitted and, thereby, reducing the required power consumption at the sensor side. Two data reduction approaches are examined: compressive sensing-based EEG compression and low-complexity feature extraction. Their performance is evaluated in terms of seizure detection effectiveness and power consumption. Experimental results show that by performing low-complexity feature extraction at the sensor side and transmitting only the features that are pertinent to seizure detection to the server, a considerable overall saving in power is achieved. The battery life of the system is increased by 14 times, while the same seizure detection rate as the conventional approach (95%) is maintained. PMID:24469356

Chiang, Joyce; Ward, Rabab K

2014-01-01

401

[Application of wavelet threshold denoising model to infrared spectral signal processing].  

PubMed

Aimed at noise interference of infrared spectra, an example of using infrared spectra to detect fat content value on the surface of cashmere was applied to evaluate the effect of wavelet threshold denoising. The denoising capabilities of three wavelet threshold denoising models (penalty threshold denoising model, Brige-Massart threshold denoising model and default threshold denoising model) were compared and analyzed. Denoised spectra and measured cashmere fat content values were used for calibration and validation with multivariate analysis (partial least squares combined with support vector machine). The authors analyzed and evaluated denoising effects of these three wavelet threshold denoising models by comparing parameters (R2, RMSEC and RMSEP) obtained through calibration and validation of denoised spectra with these three wavelet threshold denoising models respectively. The results show that the three wavelet threshold denoising models all can denoise the infrared spectral signal, increase signal to noise ratio and improve precision of prediction model to some extent; Among these three wavelet threshold denoising models, the denoising effect of Brige-Massart threshold denoising model and default threshold denoising model were significantly better than that of default threshold denoising model; Compared with the prediction precision (R2 = 0.793, RMSEC = 0.233, RMSEP = 0.225) of multivariate analysis model established with original spectra, the prediction precision (R2 = 0.882, RMSEC = 0.144, RMSEP = 0.136) of multivariate analysis model established with spectra denoised by Brige-Massart threshold denoising model and the prediction precision (R2 = 0.876, RMSEC = 0.151, RMSEP = 0.142) both had much more improvements. All the above illustrates that wavelet threshold denoising models can denoise infrared spectral signal effectively, make multivariate analysis model of spectral data and measured cashmere fat values more representative and robust, and so it can improve detection precision of infrared spectral technique. PMID:20210142

Wu, Gui-Fang; He, Yong

2009-12-01

402

Computerized Detection of Lung Nodules by Means of Virtual Dual-Energy Radiography  

PubMed Central

Major challenges in current computer-aided detection (CADe) schemes for nodule detection in chest radiographs (CXRs) are to detect nodules that overlap with ribs and/or clavicles and to reduce the frequent false positives (FPs) caused by ribs. Detection of such nodules by a CADe scheme is very important, because radiologists are likely to miss such subtle nodules. Our purpose in this study was to develop a CADe scheme with improved sensitivity and specificity by use of virtual dual-energy (VDE) CXRs where ribs and clavicles are suppressed with massive-training artificial neural networks (MTANNs). To reduce rib-induced FPs and detect nodules overlapping with ribs, we incorporated the VDE technology in our CADe scheme. The VDE technology suppressed rib and clavicle opacities in CXRs while maintaining soft-tissue opacity by use of the MTANN technique that had been trained with real dual-energy imaging. Our scheme detected nodule candidates on VDE images by use of a morphologic filtering technique. Sixty morphologic and gray-level-based features were extracted from each candidate from both original and VDE CXRs. A nonlinear support vector classifier was employed for classification of the nodule candidates. A publicly available database containing 140 nodules in 140 CXRs and 93 normal CXRs was used for testing our CADe scheme. All nodules were confirmed by computed tomography examinations, and the average size of the nodules was 17.8 mm. Thirty percent (42/140) of the nodules were rated extremely subtle or very subtle by a radiologist. The original scheme without VDE technology achieved a sensitivity of 78.6% (110/140) with 5 (1165/233) FPs per image. By use of the VDE technology, more nodules overlapping with ribs or clavicles were detected and the sensitivity was improved substantially to 85.0% (119/140) at the same FP rate in a leave-one-out cross-validation test, whereas the FP rate was reduced to 2.5 (583/233) per image at the same sensitivity level as the original CADe scheme obtained (Difference between the specificities of the original and the VDE-based CADe schemes was statistically significant). In particular, the sensitivity of our VDE-based CADe scheme for subtle nodules (66.7% = 28/42) was statistically significantly higher than that of the original CADe scheme (57.1% = 24/42). Therefore, by use of VDE technology, the sensitivity and specificity of our CADe scheme for detection of nodules, especially subtle nodules, in CXRs were improved substantially. PMID:23193306

Chen, Sheng; Suzuki, Kenji

2014-01-01

403

Improved visual background extractor using an adaptive distance threshold  

NASA Astrophysics Data System (ADS)

Camouflage is a challenging issue in moving object detection. Even the recent and advanced background subtraction technique, visual background extractor (ViBe), cannot effectively deal with it. To better handle camouflage according to the perception characteristics of the human visual system (HVS) in terms of minimum change of intensity under a certain background illumination, we propose an improved ViBe method using an adaptive distance threshold, named IViBe for short. Different from the original ViBe using a fixed distance threshold for background matching, our approach adaptively sets a distance threshold for each background sample based on its intensity. Through analyzing the performance of the HVS in discriminating intensity changes, we determine a reasonable ratio between the intensity of a background sample and its corresponding distance threshold. We also analyze the impacts of our adaptive threshold together with an update mechanism on detection results. Experimental results demonstrate that our method outperforms ViBe even when the foreground and background share similar intensities. Furthermore, in a scenario where foreground objects are motionless for several frames, our IViBe not only reduces the initial false negatives, but also suppresses the diffusion of misclassification caused by those false negatives serving as erroneous background seeds, and hence shows an improved performance compared to ViBe.

Han, Guang; Wang, Jinkuan; Cai, Xi

2014-11-01

404

Quantitative design and evaluation of enhancement\\/thresholding edge detectors  

Microsoft Academic Search

Quantitative design and performance evaluation techniques are developed for the enhancement\\/thresholding class of image edge detectors. The design techniques are based on statistical detection theory and deterministic pattern-recognition classification procedures. The performance evaluation methods developed include: a)deterministic measurement of the edge gradient amplitude; b)comparison of the probabilities of correct and false edge detection; and c) figure of merit computation. The

I. E. Abdou; W. K. Pratt

1979-01-01

405

Real-Time Building Energy Modeling, fault Detection and Diagnostic for a DoD Building  

E-print Network

ME 4343 HVAC Design Real-Time Building Energy Modeling and Fault Detection and Diagnostics for a DoD Building Bing Dong1, Zheng ONeill2 1 University of Texas, San Antonio, TX, USA 2 University of Alabama, AL, USA The work was done at the United... Pie Chart Interface ESL-KT-13-12-18 CATEE 2013: Clean Air Through Energy Efficiency Conference, San Antonio, Texas Dec. 16-18 Results 11 ? Real-time Energy Simulation 07/06 07/07 07/08 07/09 07/10 07/11 0 500 1000 BL D G 71 14 W at er Si de Lo...

Dong, B.

2013-01-01

406

Cherenkov light detection as a velocity selector for uranium fission products at intermediate energies  

NASA Astrophysics Data System (ADS)

The in-flight particle separation capability of intermediate-energy radioactive ion (RI) beams produced at a fragment separator can be improved with the Cherenkov light detection technique. The cone angle of Cherenkov light emission varies as a function of beam velocity. This can be exploited as a velocity selector for secondary beams. Using heavy ion beams available at the HIMAC synchrotron facility, the Cherenkov light angular distribution was measured for several thin radiators with high refractive indices (n = 1.9 ~ 2.1). A velocity resolution of ~10-3 was achieved for a 56Fe beam with an energy of 500 MeV/nucleon. Combined with the conventional rigidity selection technique coupled with energy-loss analysis, the present method will enable the efficient selection of an exotic species from huge amounts of various nuclides, such as uranium fission products at the BigRIPS fragment separator located at the RI Beam Factory.

Yamaguchi, T.; Enomoto, A.; Kouno, J.; Yamaki, S.; Matsunaga, S.; Suzaki, F.; Suzuki, T.; Abe, Y.; Nagae, D.; Okada, S.; Ozawa, A.; Saito, Y.; Sawahata, K.; Kitagawa, A.; Sato, S.

2014-12-01

407

Crossing Thresholds in Academic Reading  

ERIC Educational Resources Information Center

This paper looks at the conceptual thresholds in relation to academic reading which might be crossed by undergraduate English Literature students. It is part of a wider study following 16 students through three years of undergraduate study. It uses theoretical ideas from Bakhtin and Foucault to analyse interviews with English lecturers. It

Abbott, Rob

2013-01-01

408

Near threshold femtosecond laser interactions with materials: Ablation thresholds, morphologies, and dynamics  

NASA Astrophysics Data System (ADS)

This dissertation reports the results of femtosecond (fs, 10-15 seconds) laser ablation studies performed on single crystal silicon with oxide thin films and the single crystal Ni-based superalloy, CMSX-4. Emphasis is placed on near threshold ablation (or material removal) phenomena where fs pulsed lasers show significant promise for industrial machining, characterization, materials processing, fabrication of structures, and other applications. Three specific topics are addressed: fs laser ablation thresholds, ablation morphologies, and ablation dynamics. These investigations demonstrate both fundamental aspects of the interaction of fs laser pulses with materials while also introducing novel, previously unobserved phenomena. The fs laser ablation threshold of single crystal silicon was observed to depend on its naturally occurring oxide, the presence of which increased the ablation threshold of silicon by 39% at grazing laser incidence relative to atomically clean silicon. Extension of these studies to ablation threshold measurements on silicon with thermally grown oxide films of varying thickness revealed that despite the high intensities and short timescales of such interactions, the linear optical properties of a surface significantly influence near threshold fs laser ablation. Femtosecond laser induced blistering or buckling of thin oxide films (20--1200 nm) from silicon substrates was observed. Thin film buckling mechanics were used to study the blister features, revealing that the fs laser induced ablation at the oxide film interface participated in the buckling by adding energy to the delaminated oxide film. Furthermore, isolated blisters could be connected together to create linear fluidic channels. A simple device for performing electrophoresis was fabricated with these channels, the characteristic of this device were studied. The dynamics of the ablation event were studied in-situ using the technique of pump-probe microscopy with sub-picosecond resolution. Previously developed models of near threshold fs laser ablation were verified and extended by comparing the dynamics captured from two different viewing angles. Furthermore, the dynamics within the first 10 ns of ablation were found to correlate with the final ablation morphology. Finally, an orthogonal, dual-pulse laser induced breakdown spectroscopy method was used to reduce the surface damage associated with this versatile spectroscopy technique.

McDonald, Joel P.

409

Laser damage thresholds of bone objects  

NASA Astrophysics Data System (ADS)

The main aim of laser cleaning is removal of encrustation without damage of original artwork substrate material. Art object are often made of fragile and breakage vulnerable materials, for which laser cleaning is an irreplaceable technique. The same applies to figures and sculptures made of different kinds of bones, so it is needed to determine damage threshold values of laser fluency. The paper, therefore, presents the results of investigations of pulse laser radiation interaction with bovine bones, ivory and bear tusk, utilizing different harmonic wavelengths of Nd:YAG laser in a wide range of fluences. It includes fundamental wavelength of 1064 nm with maximum energy of 500 mJ and harmonics: 532 nm (250 mJ) and 355 nm (90 mJ), generated by ReNOVALaser 5 system. Laser fluency has been controlled by means of direct energy variations or by radiation focusing at the object (from 8 mm to 300 ?m), using constant pulse duration of 15 ns. Exact determination of bones threshold damage was based on microscopic investigation of the results of laser pulse irradiation.

Ostrowski, Roman; Marczak, Jan; Strzelec, Marek; Koss, Andrzej

2007-07-01

410

Nicking enzyme-assisted biosensor for Salmonella enteritidis detection based on fluorescence resonance energy transfer.  

PubMed

Salmonella enteritidis (S. enteritidis) outbreaks continue to occur, and have increased public awareness of this pathogen. Nicking endonuclease Nb.BbvC I is widely used for the detection of biomolecules and displays activity for specific double-stranded DNA (dsDNA). In this study, we developed a biosensor to detect S. enteritidis based on fluorescence resonance energy transfer (FRET) using nicking enzyme and carbon nanoparticles (CNPs). Because of the quenching effect of black hole quencher 1 (BHQ 1), the CNPs do not fluoresce in the reaction system. When the target bacteria are added, the nicking enzyme recognizes and cleaves the dsDNA fabricated by the interaction between probe and target. As a result, the CNPs dissociate from BHQ 1 and emit strong fluorescence. Using the nicking enzyme, the fluorescence signals of the biosensor are greatly amplified. The biosensor exhibited a linear relationship with the concentration of S. enteritidis ranging from 10(2) to 3 10(3)CFU/mL in water and from 1.5 10(2) to 3 10(3)CFU/mL in milk. The present results indicate that our FRET-based detection system can be widely employed for the effective detection of pathogens. PMID:24434495

Song, Yang; Li, Wenkai; Duan, Yingfen; Li, Zhongjie; Deng, Le

2014-05-15

411

Simulations of a new detection concept for high-energy neutrons based on timing RPCs  

NASA Astrophysics Data System (ADS)

In this manuscript we present a novel concept for the detection of relativistic neutrons (between 100 MeV and 1 GeV) based on Resistive Plate Chambers (RPCs). Its principle relies on the detection of charged particles created in hadronic showers induced by the incoming neutrons on the detector constituent materials. The presented design solely considers glass plates as converters for neutron detection while simultaneously delimiting the active gas. For the optimization of a large area detector based on RPCs, simulations using the Virtual Monte Carlo framework FairRoot have been performed. The resulting detector is designed using timing RPC modules, each with 5 gas gaps, that are sequentially grouped, reaching an efficiency for one neutron detection higher than 90%. We show a systematic study on the counter performance as a function of the thickness of the glass plates, and present the design of a prototype to be tested with quasi-monoenergetic neutrons of energies ranging between 200 MeV and 1.5 GeV in the upcoming future.

Machado, J.; Blanco, A.; Fonte, P.; Galaviz, D.; Lopes, L.; Ferreira Marques, R.; Teubig, P.

2013-07-01

412

Dose and detectability improvements with high energy phase sensitive x-ray imaging in comparison to low energy conventional imaging  

PubMed Central

The objective of this study was to demonstrate the potential benefits of using high energy x-rays for phase sensitive breast imaging through a comparison with conventional mammography imaging. We compared images of a contrast-detail (CD) phantom acquired on a prototype phase sensitive x-ray imaging system with images acquired on a commercial flat panel digital mammography unit. The phase contrast images were acquired using a micro-focus x-ray source with a 50 ?m focal spot at 120 kVp and 4.5 mAs, with a magnification factor of 2.46 and a 50 ?m pixel pitch. A phase attenuation duality (PAD)-based phase retrieval algorithm that requires only a single phase contrast image was applied. Conventional digital mammography images were acquired at 27 kVp, 131 mAs and 28 kVp, 54 mAs. For the same radiation dose, both the observer study and SNR/FOM comparisons indicated a large improvement by the phase retrieved image as compared to the clinical system for the larger disk sizes, but the improvement was not enough to detect the smallest disks. Compared to the double dose image acquired with the clinical system, the observer study also indicated that the phase retrieved image provided improved detection capabilities for all disk sizes except the smallest disks. Thus the SNR improvement provided by phase contrast imaging is not yet enough to offset the noise reduction provided by the clinical system at the doubled dose level. However, the potential demonstrated by this study for high energy phase sensitive x-ray imaging to improve lesion detection and reduce radiation dose in mammography warrants further investigation of this technique. PMID:24732108

Wong, Molly Donovan; Yan, Aimin; Ghani, Muhammad; Li, Yuhua; Fajardo, Laurie; Wu, Xizeng; Liu, Hong

2014-01-01

413

Evoked potential measurement of the masked hearing threshold of a Pacific white-sided dolphin (Lagenorhynchus obliquidens)  

NASA Astrophysics Data System (ADS)

The masked hearing threshold of a Pacific white-sided dolphin (Lagenorhynchus obliquidens) was determined by measuring the animal's auditory brainstem response (ABR). The dolphin was trained to wear surface-contact electrodes embedded in suction cups and to swim into a hoop centered at 1 m below the water surface facing a sound projector 5 m away. Broadband transient signals with center frequencies of 8, 16, 32, 64, 80, and 100 kHz were used as the stimuli. ABR signals were measured by digitizing the electrode signals in 32 point blocks at a sampling rate of 20 kHz. Five hundred blocks were averaged in order to obtain an ABR. The response latency for suprathreshold threshold signals was approximately 1.9 ms with the highest peak-to-peak ABR amplitude of approximately 2.8 uV occurring for a signal frequency of 64 kHz. The spectrum of the ABR signal was similar to that of Tursiops truncatus, with a major peak at 1120 Hz and a secondary peak at 664 Hz. Threshold was determined by progressively reducing the amplitude of the stimulus until an evoked potential could not be detected. The energy signal-to-noise ratio within an integration window at threshold varied between 1 and 8 dB.

Au, Whitlow W. L.; Jeanette, Thomas; Western, A.; Rameriz, Kenneth M.

2003-04-01

414

Threshold Effects in Multi-channel Coupling and Spectroscopic Factors in Exotic Nuclei  

E-print Network

In the threshold region, the cross section and the associated overlap integral obey the Wigner threshold law that results in the Wigner-cusp phenomenon. Due to flux conservation, a cusp anomaly in one channel manifests itself in other open channels, even if their respective thresholds appear at a different energy. The shape of a threshold cusp depends on the orbital angular momentum of a scattered particle; hence, studies of Wigner anomalies in weakly bound nuclei with several low-lying thresholds can provide valuable spectroscopic information. In this work, we investigate the threshold behavior of spectroscopic factors in neutron-rich drip-line nuclei using the Gamow Shell Model, which takes into account many-body correlations and the continuum effects. The presence of threshold anomalies is demonstrated and the implications for spectroscopic factors are discussed.

N. Michel; W. Nazarewicz; M. Ploszajczak

2007-02-08

415

Superlinear threshold detectors in quantum cryptography  

SciTech Connect

We introduce the concept of a superlinear threshold detector, a detector that has a higher probability to detect multiple photons if it receives them simultaneously rather than at separate times. Highly superlinear threshold detectors in quantum key distribution systems allow eavesdropping the full secret key without being revealed. Here, we generalize the detector control attack, and analyze how it performs against quantum key distribution systems with moderately superlinear detectors. We quantify the superlinearity in superconducting single-photon detectors based on earlier published data, and gated avalanche photodiode detectors based on our own measurements. The analysis shows that quantum key distribution systems using detector(s) of either type can be vulnerable to eavesdropping. The avalanche photodiode detector becomes superlinear toward the end of the gate. For systems expecting substantial loss, or for systems not monitoring loss, this would allow eavesdropping using trigger pulses containing less than 120 photons per pulse. Such an attack would be virtually impossible to catch with an optical power meter at the receiver entrance.

Lydersen, Lars; Maroey, Oystein; Skaar, Johannes; Makarov, Vadim [Department of Electronics and Telecommunications, Norwegian University of Science and Technology, NO-7491 Trondheim (Norway); University Graduate Center, NO-2027 Kjeller (Norway); Jain, Nitin; Wittmann, Christoffer; Marquardt, Christoph; Leuchs, Gerd [Max Planck Institute for the Science of Light, Guenther-Scharowsky-Strasse 1/Bau 24, DE-91058 Erlangen (Germany); Institut fuer Optik, Information und Photonik, University of Erlangen-Nuremberg, Staudtstrasse 7/B2, DE-91058 Erlangen (Germany)

2011-09-15

416

Contraband detection using high-energy gamma rays from 16O*  

NASA Astrophysics Data System (ADS)

High-energy monoenergetic gamma rays (6.13 and 7.12 MeV) from the decay of excited states of the 16O* nucleus are highly penetrating and thus offer potential for non- intrusive inspection of loaded containers for narcotics, explosives, and other contraband items. These excited states can be produced by irradiation of water with 14-MeV neutrons from a DT neutron generator or through the 19F(p,alpha)16O* reaction. Resonances in 19F(p,alpha)16O* at proton energies between 340 keV and 2 MeV allow use of a low-energy accelerator to provide a compact, portable gamma source of reasonable intensity. The present work provides estimates of gamma source parameters and suggests how various types of contraband could be detected. Gamma rays can be used to perform transmission or emission radiography of containers or other objects. Through the use of (gamma,n) and (gamma,fission) reactions, this technique is also capable of detecting special nuclear materials such as deuterium, lithium, beryllium, uranium, and plutonium. Analytic and Monte Carlo techniques are used to model empty and loaded container inspection for accelerator-produced gamma, radioisotope, and x-ray sources.

Micklich, Bradley J.; Fink, Charles L.; Sagalovsky, Leonid; Smith, Donald L.

1997-02-01

417

Contraband detection using high-energy gamma rays from {sup 16}O*  

SciTech Connect

High-energy monoenergetic gamma rays (6.13 and 7.12 MeV) from the decay of excited states of the {sup 16}O* nucleus are highly penetrating and thus offer potential for non-intrusive inspection of loaded containers for narcotics, explosives, and other contraband items. These excited states can be produced by irradiation of water with 14-MeV neutrons from a DT neutron generator or through the {sup 19}F(p,{alpha}){sup 16}O* reaction. Resonances in {sup 19}F(p,{alpha}){sup 16}O* at proton energies between 340 keV and 2 MeV allow use of a low-energy accelerator to provide a compact, portable gamma source of reasonable intensity. The present work provides estimates of gamma source parameters and suggests how various types of contraband could be detected. Gamma rays can be used to perform transmission or emission radiography of containers or other objects. Through the use of ({gamma}, n) and ({gamma}, fission) reactions, this technique is also capable of detecting special nuclear materials such as deuterium, lithium, beryllium, uranium, and plutonium. Analytic and Monte Carlo techniques are used to model empty and loaded container inspection for accelerator-produced gamma, radioisotope, and x-ray sources.

Micklich, B.J.; Fink, C.L.; Sagalovsky, L.; Smith, D.L. [Argonne National Lab., IL (United States). Technology Development Div.

1996-12-01