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1

Energy model for contrast detection: spatiotemporal characteristics of threshold vision  

Microsoft Academic Search

.   A model for contrast detection of spatiotemporal stimuli is proposed which consists of a spatiotemporal linear filter, an\\u000a energy device and a threshold device. Assuming the existence of independent intrinsic noise, the probability of stimulus detection\\u000a was approximated by a Weibull function of the response energy. With this assumption, the stimulus energy is a constant at\\u000a fixed detection probability.

V. Manahilov; W. Simpson

1999-01-01

2

Detection Threshold Modelling Explained.  

National Technical Information Service (NTIS)

This document presents expressions for modeling the detection threshold for narrowband and broadband passive sonars using either power or amplitude detection, cross correlation sonars, CW and FM active sonars with or without replica correlation, as well a...

R. L. Dawe

1997-01-01

3

On computational Gestalt detection thresholds  

Microsoft Academic Search

The aim of this paper is to show some recent developments of computational Gestalt theory, as pioneered by Desolneux, Moisan and Morel. The new results allow to predict much more accurately the detection thresholds. This step is unavoidable if one wants to analyze visual detection thresholds in the light of computational Gestalt theory. The paper first recalls the main elements

Rafael Grompone von Gioi; Jérémie Jakubowicz

2009-01-01

4

Optimizing Systems of Threshold Detection Sensors.  

National Technical Information Service (NTIS)

When implementing a system of sensors, one of the biggest challenges is to establish a threshold at which a signal is generated. All signals that exceed this detection threshold are then investigated to determine whether the signal was due to an event of ...

D. C. Banschbach

2008-01-01

5

Ionization threshold energies for metal clusters  

NASA Astrophysics Data System (ADS)

We have measured the ionization threshold energies as a function of cluster size for V, Nb, and Fe clusters. The metal clusters are produced by laser vaporization of a metal substrate inside the throat of a pulsed nozzle. The clusters are detected by photoionization TOF mass spectrometry. Using tunable UV lasers, the ionization thresholds are measured as a function of cluster size. In addition, ionization thresholds for clusters with dissociatively chemisorbed hydrogen are found to increase significantly over that of the corresponding bare cluster.

Cox, D. M.; Whetten, R. L.; Zakin, M. R.; Trevor, D. J.; Reichmann, K. C.; Kaldor, A.

1986-08-01

6

Detection Threshold Calculations for Cross Correlation Processing.  

National Technical Information Service (NTIS)

Detection threshold calculations are performed for cross correlation processing of the received signals from two fixed omnidirectional sensors of a moving source generating an arbitrary random power spectrum. The effects of doppler decorrelation and volum...

P. N. Mikhalevsky

1980-01-01

7

Chemical sensing thresholds for mine detection dogs  

NASA Astrophysics Data System (ADS)

Mine detection dogs have been found to be an effective method to locate buried landmines. The capabilities of the canine olfaction method are from a complex combination of training and inherent capacity of the dog for odor detection. The purpose of this effort was to explore the detection thresholds of a limited group of dogs that were trained specifically for landmine detection. Soils were contaminated with TNT and 2,4-DNT to develop chemical vapor standards to present to the dogs. Soils contained ultra trace levels of TNT and DNT, which produce extremely low vapor levels. Three groups of dogs were presented the headspace vapors from the contaminated soils in work environments for each dog group. One positive sample was placed among several that contained clean soils and, the location and vapor source (strength, type) was frequently changed. The detection thresholds for the dogs were determined from measured and extrapolated dilution of soil chemical residues and, estimated soil vapor values using phase partitioning relationships. The results showed significant variances in dog sensing thresholds, where some dogs could sense the lowest levels and others had trouble with even the highest source. The remarkable ultra-trace levels detectable by the dogs are consistent with the ultra-trace chemical residues derived from buried landmines; however, poor performance may go unnoticed without periodic challenge tests at levels consistent with performance requirements.

Phelan, James M.; Barnett, James L.

2002-08-01

8

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

9

Adaptive Threshold for QRS Complex Detection Based on Wavelet Transform  

Microsoft Academic Search

This paper presents a novel approach, adaptive threshold algorithm, for QRS complex detection. It is based on two-to-four scales in COIFLET wavelet transform. Two initial thresholds are defined as up-limited-threshold (ULT) and down-limited-threshold (DLT) at the beginning of the detection. The system then automatically adjusts the values of the threshold to achieve optimal QRS detection. Simulation work shows that adaptive

Xiaomin Xu; Ying Liu

2005-01-01

10

Thresholding Video Images for Text Detection  

Microsoft Academic Search

Thresholding video images is very challenging due to the fact that image background generally has low resolution and is also more complicated and highly distorted than document images. As a result, thresholding methods that work well for document images may not work effectively for video images in some applications. This paper investigates the issue of thresholding video images for text

Eliza Yingzi Du; Chein-i Chang; P. D. Thouin

2002-01-01

11

Threshold variability in subliminal perception experiments: fixed threshold estimates reduce power to detect subliminal effects.  

PubMed

In studies of subliminal perception, a threshold for awareness is usually estimated for each S (e.g., the stimulus duration that yields chance discrimination performance). This article shows that if the S's true threshold varies randomly from trial to trial, estimation of a fixed threshold has important consequences. Specifically, the estimated threshold approaches the minimum of the distribution of true thresholds, and the power of an experiment to detect subliminal perception is reduced. Because there is much evidence that true thresholds vary across trials, threshold variability may have seriously weakened previous experiments that tested for subliminal perception. Fortunately, it is possible to estimate the maximum power loss resulting from threshold variability and therefore to design an experiment with acceptable power even in the presence of variability. PMID:1834795

Miller, J

1991-08-01

12

Radiographic threshold detection levels of aluminum weld defects  

NASA Technical Reports Server (NTRS)

Test program is used in the design and fabrication of special graduated aluminum penetrometers. The program evaluates the threshold detection capabilities of a fixed radiographic technique in detecting surface and subsurface cracks in one-quarter inch aluminum welds. The radiographic films were evaluated and the threshold detection capabilities defined.

Tryon, R. W.

1969-01-01

13

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

14

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

15

Cryostat for Ultra-Low-Energy Threshold Germanium Spectrometers  

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

16

Estimating thresholds in occupancy when species detection is imperfect.  

PubMed

Identification of thresholds (state changes over a narrow range of values) is of basic and applied ecological interest. However, current methods of estimating thresholds in occupancy ignore variation in the observation process and may lead to erroneous conclusions about ecological relationships or to the development of inappropriate conservation targets. We present a model to estimate a threshold in occupancy while accounting for imperfect species detection. The threshold relationship is described by a break-point (threshold) and the change in slope (threshold effect). Imperfect species detection is incorporated by jointly modeling species occurrence and species detection. We used WinBUGS to evaluate the model through simulation and to fit the model to avian occurrence data for three species from 212 sites with two replicate surveys in 2007-2008. To determine if accounting for imperfect detection changed the inference about thresholds in avian occupancy in relation to habitat structure, we compared our model to results from a commonly used threshold model (segmented logistic regression). We fit this model in both frequentist and Bayesian modes of inference. Results of the simulation study showed that 95% posterior intervals contained the true value of the parameter in approximately 95% of the simulations. As expected, the simulations indicated more precise threshold and parameter estimates as sample size increased. In the empirical study, we found evidence for threshold relationships for four species by covariate combinations when ignoring species detection. However, when we included variation from the observation process, threshold relationships were not supported in three of those four cases (95% posterior intervals included 0). In general, confidence intervals for the threshold effect were larger when we accounted for species nondetection than when we ignored nondetection. This model can be extended to investigate abundance thresholds as a function of ecological and anthropogenic factors, as well as multispecies hierarchical models. PMID:22352169

Jones, Jay E; Kroll, Andrew J; Giovanini, Jack; Duke, Steven D; Betts, Matthew G

2011-12-01

17

Experimental and environmental factors affect spurious detection of ecological thresholds.  

PubMed

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 (tau) 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. PMID:22486082

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

2012-01-01

18

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

19

The Detection Threshold at the Montana Lasa.  

National Technical Information Service (NTIS)

Short-period P arrivals on LASA beamformed traces for 56 teleseismic events were used to compute event magnitudes and corresponding threshold magnitudes. The average event magnitude reported differed by less than 0.1 from the average magnitude computed at...

E. F. Chiburis R. A. Hartenberger

1967-01-01

20

Adaptive threshold QRS detection algorithm for ambulatory ECG  

Microsoft Academic Search

The authors have developed an algorithm for detection of QRS complexes of ambulatory electrocardiogram (ECG) signals. The threshold, which is obtained from a distribution function of the amplitude of the filtered ECG signal, changes with time, adapting to changes in the QRS morphology, levels of noise, and artifacts. The threshold extracts the period which include the QRS complex, and then

K. Akazawa; K. Motoda; A. Sasamori; T. Ishizawa; E. Harasawa

1991-01-01

21

Threshold Detection of Geodetic Satellite Images.  

National Technical Information Service (NTIS)

A literature survey and study has been made on the photographic detection of stellar images. Photographic detection theory in the literature was extended as required by the special conditions of geodetic satellite photography. These conditions include the...

S. Ackerman

1966-01-01

22

Automatic DarkAdaptation Threshold Detection Algorithm.  

PubMed

This paper describes an algorithm used to automatically determine the threshold sensitivity in a new dark adaptometer. The new instrument is controlled by a personal computer and can be used in the investigation of several retinal diseases. The stimulus field is delivered to the eye through the modified optics of a fundus camera. An automated light stimulus source was developed to operate together with this fundus camera. New control parameters were developed in this instrument to improve the traditional Goldmann-Weekers dark adaptometer. PMID:17282613

G de Azevedo, Dario; Helegda, Sergio; Glock, Flavio; Russomano, Thais

2005-01-01

23

Effect of model uncertainty on failure detection - The threshold selector  

NASA Technical Reports Server (NTRS)

The performance of all failure detection, isolation, and accomodation (DIA) algorithms is influenced by the presence of model uncertainty. A unique framework is presented to incorporate a knowledge of modeling error in the analysis and design of failure detection systems. The tools being used are very similar to those in robust control theory. A concept is introduced called the threshold selector, which is a nonlinear inequality whose solution defines the set of detectable sensor failure signals. The threshold selector represents an innovative tool for analysis and synthesis of DIA algorithms. It identifies the optimal threshold to be used in innovations-based DIA algorithms. The optimal threshold is shown to be a function of the bound on modeling errors, the noise properties, the speed of DIA filters, and the classes of reference and failure signals. The size of the smallest detectable failure is also determined. The results are applied to a multivariable turbofan jet engine example, which demonstrates improvements compared to previous studies.

Emami-Naeini, Abbas; Akhter, Muhammad M.; Rock, Stephen M.

1988-01-01

24

Threshold energies in the artificial retina  

Microsoft Academic Search

Laser threshold energies for artificial retinal damage from ultrashort (i.e. less than or equal to 1 ns) laser pulses are investigated as a function of both pulse width and spot size. A piece of film acts as the absorbing layer and is positioned at the focus of the Cain artificial eye (17 mm in water). We performed experiments at the

Dale J. Payne; Richard A. Hopkins; Brent Eilert; Gary D. Noojin; Benjamin A. Rockwell

1998-01-01

25

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

26

Auto-Threshold Peak Detection in Physiological Signals.  

National Technical Information Service (NTIS)

In processing physiological signals, it is often necessary to detect periodic, local maxima. There are a variety of peak detection algorithms, but most require a threshold value in order to distinguish peaks from the rest of the data. This brief paper pre...

M. L. Jacobson

2001-01-01

27

Optimal discrimination threshold for the detection of singlet oxygen luminescence  

NASA Astrophysics Data System (ADS)

Direct detection of singlet oxygen (1O2) luminescence around 1270 nm is the golden standard of 1O2 identification. In this study, the effect of the discrimination threshold on the detection of 1O2 luminescence that generated from the photoirradiation of Rose Bengal (RB) was evaluated by using a self-developed photon-counting detection system. The obtained results show that the discrimination threshold for photon counting has a significant impact on the intensity and shape of the measured 1O2 luminescence, which resulted in the variation of 1O2 lifetimes. The optimal discrimination threshold is determined to be about -0.0412 V, and the corresponding 1O2 lifetime in air-saturated distilled water is 4.26±0.06 ?s.

Chen, Defu; Lin, Huiyun; Shen, Yi; Li, Buhong; Xie, Shusen

2011-01-01

28

Mammographic calcification cluster detection and threshold gold thickness measurements  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

29

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

30

Variable threshold method for ECG R-peak detection.  

PubMed

In this paper, a wearable belt-type ECG electrode worn around the chest by measuring the real-time ECG is produced in order to minimize the inconvenient in wearing. ECG signal is detected using a potential instrument system. The measured ECG signal is transmits via an ultra low power consumption wireless data communications unit to personal computer using Zigbee-compatible wireless sensor node. ECG signals carry a lot of clinical information for a cardiologist especially the R-peak detection in ECG. R-peak detection generally uses the threshold value which is fixed. There will be errors in peak detection when the baseline changes due to motion artifacts and signal size changes. Preprocessing process which includes differentiation process and Hilbert transform is used as signal preprocessing algorithm. Thereafter, variable threshold method is used to detect the R-peak which is more accurate and efficient than fixed threshold value method. R-peak detection using MIT-BIH databases and Long Term Real-Time ECG is performed in this research in order to evaluate the performance analysis. PMID:21695499

Kew, Hsein-Ping; Jeong, Do-Un

2011-10-01

31

Instantaneous phase threshold for reflector detection in ultrasonic images.  

PubMed

A method for reflector detection, based on the instantaneous phase of the aperture data for ultrasonic images, is proposed. The instantaneous phase (IP) image is obtained by replacing the amplitude information by the instantaneous phase in the delay-and-sum (DAS) beamforming. From the analysis of the IP image, a threshold level is defined in terms of the number of signals used for imaging. This threshold is applied to the IP image, resulting in a two-level image which gives a statistical indication of whether the pixels of a region in the image are related to a reflector or noise/artifacts. Because the proposed method uses only the instantaneous phase of the signals, it is less sensitive to attenuation than conventional DAS amplitude images. The point spread function of a 32-element array with half-wavelength pitch at 5 MHz in water is simulated and the reflector is detected for signal-to-noise ratio values larger than -29.6 dB. A phantom and an aluminum plate with artificial defects are tested with the proposed technique, using linear arrays of 64 and 16 elements, respectively. When compared with DAS amplitude images and with two-level images obtained by thresholding the amplitude images using empirical threshold values, the proposed technique reduced artifacts and dead zone, and detected all reflectors, increasing reflectors' detectability and decreasing the occurrence of false indication of reflectors. The proposed technique can be used as additional information for amplitude image analysis, with the advantages that it does not need time-gain compensation and that it considers an objective threshold value. PMID:24960709

Prado, Vander; Higuti, Ricardo; Kitano, Claudio; Martinez-Graullera, Oscar

2014-07-01

32

Detection Threshold Effects on GRBs as a Cosmological Standard Candle  

NASA Astrophysics Data System (ADS)

GRB satellites do not detect all GRBs with equal efficiency. Specifically, most GRB satellites are relatively inefficient detectors of dim hard bursts because they trigger on photon counts, which are number-biased against hard photons. Therefore, 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 detector bias can distort or even create an apparent correlation where increasingly hard GRBs appear increasingly bright. Although such correlations may be obfuscated by a middle step where GRBs need to be bright enough to have their actual redshifts determined, it is found that the bias is generally pervasive. This result is derived here through simulations convolving a wide variety of possible GRB brightnesses and spectra with the BATSE Large Area Detectors (LAD) detection thresholds. The presented analyses indicate that the peak of the ? F? distribution in the frame of the GRB, Epeak, has biases when used as a cosmological standard candle. Therefore, the appearance of Epeak in seeming correlations such as the Amati (Eisotropic - Epeak), Ghirlanda (E? - Epeak, and Lisotropic - Epeak relations are statistically real but strongly influenced by GRB detector thresholds.

Nemiroff, Robert J.; Shahmoradi, A.

2010-01-01

33

Trend of contrast detection threshold with and without localization.  

PubMed

Published information on contrast detection threshold is based primarily on research using a location-known methodology. In previous work on testing the Digital Imaging and Communications in Medicine (DICOM) Grayscale Standard Display Function (GSDF) for perceptual linearity, this research group used a location-unknown methodology to more closely reflect clinical practice. A high false-positive rate resulted in a high variance leading to the conclusion that the impact on results of employing a location-known methodology needed to be explored. Fourteen readers reviewed two sets of simulated mammographic background images, one with the location-unknown and one with the location-known methodology. The results of the reader study were analyzed using Reader Operating Characteristic (ROC) methodology and a paired t test. Contrast detection threshold was analyzed using contingency tables. No statistically significant difference was found in GSDF testing, but a highly statistical significant difference (p value <0.0001) was seen in the ROC (AUC) curve between the location-unknown and the location-known methodologies. Location-known methodology not only improved the power of the GSDF test but also affected the contrast detection threshold which changed from +3 when the location was unknown to +2 gray levels for the location-known images. The selection of location known versus unknown in experimental design must be carefully considered to ensure that the conclusions of the experiment reflect the study's objectives. PMID:23503988

Leong, David L; Rainford, Louise; Haygood, Tamara Miner; Whitman, Gary J; Geiser, William R; Adrada, Beatriz E; Santiago, Lumarie; Brennan, Patrick C

2013-12-01

34

Spatially Varying Spectrally Thresholds for MODIS Cloud Detection  

NASA Technical Reports Server (NTRS)

The EOS science team has developed an elaborate global MODIS cloud detection procedure, and the resulting MODIS product (MOD35) is used in the retrieval process of several geophysical parameters to mask out clouds. While the global application of the cloud detection approach appears quite robust, the product has some shortcomings on the regional scale, often over determining clouds in a variety of settings, particularly at night. This over-determination of clouds can cause a reduction in the spatial coverage of MODIS derived clear-sky products. To minimize this problem, a new regional cloud detection method for use with MODIS data has been developed at NASA's Global Hydrology and Climate Center (GHCC). The approach is similar to that used by the GHCC for GOES data over the continental United States. Several spatially varying thresholds are applied to MODIS spectral data to produce a set of tests for detecting clouds. The thresholds are valid for each MODIS orbital pass, and are derived from 20-day composites of GOES channels with similar wavelengths to MODIS. This paper and accompanying poster will introduce the GHCC MODIS cloud mask, provide some examples, and present some preliminary validation.

Haines, S. L.; Jedlovec, G. J.; Lafontaine, F.

2004-01-01

35

Tactile and thermal detection thresholds of the scalp skin.  

PubMed

The tactile and thermal sensitivity of diverse regions of the human body have been documented extensively, with one exception being the scalp. Additionally, sensory changes may accompany the hair loss from the scalp in androgen-related alopecia (ARA), but formal quantitative sensory testing (QST) has not been reported in respect of this. Therefore, light touch detection thresholds were obtained at nine scalp sites and one forehead site, using Semmes-Weinstein filaments (Von Frey hairs), and for warming and cooling from skin baseline temperature, using 28 and 256 mm(2) thermodes. Affective, thermal, and nociceptive sensations experienced at thermal detection threshold were quantified. Thirty-two male participants were recruited, 10 of whom had normal hair coverage, 12 of whom had shaved scalp but with potentially normal hair coverage, and 10 of whom exhibited ARA to some extent. The scalp was relatively insensitive to tactile and thermal stimulation at all tested sites, especially so along the midline and near the apex of the skull. Threshold level warm stimuli were rated less pleasant, the less sensitive the test site. After correction for age-related changes in sensitivity, bald scalp sites were found more sensitive to cooling than the same sites when shaved, consistent with prior informal reports of increased sensitivity for some scalp sensations in ARA. QST on hair-covered sites was subject to methodological issues that render such testing non-ideal, such as bias in measurement of resting skin temperatures, and the near impossibility of delivering filament stimuli to the scalp skin without disturbing neighboring hairs. PMID:21879989

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

2011-01-01

36

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

37

Dynamic multiple thresholding breast boundary detection algorithm for mammograms  

PubMed Central

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

2010-01-01

38

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.

2009-01-01

39

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

40

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

41

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 has been 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 has been analyzed, and semi-empirical relationships to predict the optimum detection threshold have been 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 have also been investigated.

Webb, W. E.; Marino, J. T., Jr.

1975-01-01

42

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-emperical 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. Bit error probabilities for non-optimum threshold detection system were also investigated.

Webb, W. E.; Marino, J. T., Jr.

1974-01-01

43

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

44

Finding a detection threshold for Fisher Detector applied to beamforming  

NASA Astrophysics Data System (ADS)

The so called F-stat function of test (FoT) is a commonly used detector of signal of interest (SOI) received by sensors with additive white Gaussian noise [1], [3]. This FoT is related to the generalized likelihood ratio test based on the Gaussian assumption and on the parametrization of the planar propagation of the wave carrying the SOI by a slowness vector. The detection test is obtained by comparing the FoT to some threshold or by providing the p-value which is directly compared to the targeted type-I error. In both cases, we need to compute the distribution of the FoT under the null hypothesis i.e. in the absence of the SOI. Unfortunately when the FoT is maximized over a set of various possible slowness vectors for the SOI propagation, the distribution under the null hypothesis is no longer the expected Fisher distribution [4]. In this study we present a new approach to approximate the null distribution when this maximization is performed over a finite set of slowness parameters, which corresponds to the most encountered practical setting. To this end, we derive the asymptotic (Gaussian) behavior of the finite dimensional distributions of the FoT seen as a process indexed by the set of delays that appear in its computation. This approach, although asymptotic, provides a practical way to tune the type-I error of the detection test in a consistent and efficient way, which performs quite well on simulations.

Nouvellet, Adrien; Roueff, François; Charbit, Maurice; Le Pichon, Alexis

2014-05-01

45

Modeling Associative Recognition: A Comparison of Two-High-Threshold, Two-High-Threshold Signal Detection, and Mixture Distribution Models  

ERIC Educational Resources Information Center

A 2-high-threshold signal detection (HTSDT) model, a mixture distribution (SON) model, and 2-highthreshold (HT) models with responses distributed over 1 or several response categories were fit to results of 6 experiments from 2 studies on associative recognition: R. Kelley and J. T. Wixted (2001) and A. P. Yonelinas (1997). HTSDT assumes that…

Macho, Siegfried

2004-01-01

46

Colour detection thresholds in faces and colour patches.  

PubMed

Human facial skin colour reflects individuals' underlying health (Stephen et al 2011 Evolution & Human Behavior 32 216-227); and enhanced facial skin CIELab b* (yellowness), a* (redness), and L* (lightness) are perceived as healthy (also Stephen et al 2009a International Journal of Primatology 30 845-857). Here, we examine Malaysian Chinese participants' detection thresholds for CIELab L* (lightness), a* (redness), and b* (yellowness) colour changes in Asian, African, and Caucasian faces and skin coloured patches. Twelve face photos and three skin coloured patches were transformed to produce four pairs of images of each individual face and colour patch with different amounts of red, yellow, or lightness, from very subtle (deltaE = 1.2) to quite large differences (deltaE = 9.6). Participants were asked to decide which of sequentially displayed, paired same-face images or colour patches were lighter, redder, or yellower. Changes in facial redness, followed by changes in yellowness, were more easily discriminated than changes in luminance. However, visual sensitivity was not greater for redness and yellowness in nonface stimuli, suggesting red facial skin colour special salience. Participants were also significantly better at recognizing colour differences in own-race (Asian) and Caucasian faces than in African faces, suggesting the existence of cross-race effect in discriminating facial colours. Humans' colour vision may have been selected for skin colour signalling (Changizi et al 2006 Biology Letters 2 217-221), enabling individuals to perceive subtle changes in skin colour, reflecting health and emotional status. PMID:24344549

Tan, Kok Wei; Stephen, Ian D

2013-01-01

47

Re-examination of the threshold energy surface in copper  

SciTech Connect

Radiation-induced defect production in copper has been studied using in-situ electrical resistivity damage-rate measurements in the HVEM and molecular dynamics simulations. Analysis of the results yields a threshold energy surface characterized by two isolated pockets of low threshold energy centered at <100> and <110> surrounded by regions of much higher threshold energy; the corresponding damage function exhibits a plateau at 0.65 Frenkel pairs. A Frenkel pair resistivity of (2.75/sub -0.2//sup +0/ /sup 6/) x 10/sup -4/ ..cap omega..-cm is proposed. A model damage function is constructed and compared to results from ion irradiation damage-rate measurements. 7 figures.

King, W.E.; Benedek, R.; Merkle, K.L.; Meshii, M.

1981-01-01

48

Optimizing the Automatic Selection of Spike Detection Thresholds Using a Multiple of the Noise Level  

PubMed Central

Thresholding is an often-used method of spike detection for implantable neural signal processors due to its computational simplicity. A means for automatically selecting the threshold is desirable, especially for high channel count data acquisition systems. Estimating the noise level and setting the threshold to a multiple of this level is a computationally simple means of automatically selecting a threshold. We present an analysis of this method as it is commonly applied to neural waveforms. Four different operators were used to estimate the noise level in neural waveforms and set thresholds for spike detection. An optimal multiplier was identified for each noise measure using a metric appropriate for a brain-machine interface application. The commonly used root-mean-square operator was found to be least advantageous for setting the threshold. Investigators using this form of automatic threshold selection or developing new unsupervised methods can benefit from the optimization framework presented here.

Rizk, Michael; Wolf, Patrick D.

2009-01-01

49

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

50

Threshold Detection in an on-off Binary Communications Channel with Atmospheric Scintillation.  

National Technical Information Service (NTIS)

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 ...

W. E. Webb

1975-01-01

51

Threshold Detection in an on-off Binary Communications Channel with Atmospheric Scintillation.  

National Technical Information Service (NTIS)

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 ...

W. E. Webb J. T. Marino

1974-01-01

52

Using a combined localization\\/detection model to simulate human localization performance near the masked detection threshold level  

Microsoft Academic Search

Recently, the perceptual lateralization of a partly masked target has been successfully simulated using the interaural cross-correlation difference (ICCD) model [Braasch, J. Acoust. Soc. Am. 108, 2597 (2000)]. However, in the accompanying listening tests, the target level was often found to be below the masked detection threshold level. To improve the model performance, a detection threshold model has been implemented

Jonas Braasch

2002-01-01

53

Threshold energy for sub-barrier fusion hindrance phenomenon  

NASA Astrophysics Data System (ADS)

The relationship between the threshold energy for a deep sub-barrier fusion hindrance phenomenon and the energy at which the regime of interaction changes (the turning-off of the nuclear forces and friction) in the sub-barrier capture process is studied within the quantum diffusion approach. The quasielastic barrier distribution is shown to be a useful tool to clarify whether the slope of capture cross section changes at sub-barrier energies.

Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.; Zhang, H. Q.

2013-02-01

54

Neutral Kaon Photo-Production in the Threshold Energy Region  

NASA Astrophysics Data System (ADS)

We have been conducting an experimental program to study strangeness photoproduc-tions on the deuteron by measuring K0 and ? in the threshold energy region. The ?-?+ from K0 and ?-p from ? are detected by use of large acceptance magnetic spectrometers. At the first stage of the program, we started with Neutral Kaon Spectrometer (NKS), which consisted of timing counters and tracking devices in the magnetic field. The NKS spectrometer was employed to measure K0 photoproductions from deuteron and carbon target for the first time. A newly constructed spectrometer (NKS2) has been employed for the second stage experiment. It consists of a 110 ton dipole magnet and a combination of detectors. The momentum distributions of K0 and A from ?+d process were observed, and compared with the calculations based on the isobar models. The NKS2 spectrometer has been upgraded by installing a three dimensional tracking device in the central region. This improvement enables to explore the simultaneous measurement of the K0-A with reasonable statistics.

Beckford, B.; Bydzovsky, P.; Fujibayashi, J.; Fujii, T.; Fujii, Y.; Futatsukawa, K.; Gogami, T.; Hashimoto, O.; Han, Y. C.; Hirose, K.; Hosomi, K.; Iguchi, A.; Ishikawa, T.; Kanda, H.; Kaneta, M.; Kawama, D.; Kawasaki, T.; Kiyokawa, S.; Koike, T.; Maeda, K.; Maruyama, N.; Miwa, K.; Miyagi, Y.; Nakamura, S. N.; Sasaki, A.; Shimizu, H.; Shirotori, K.; Suzuki, K.; Tamae, T.; Tamura, H.; Terada, N.; Tsukada, K.; Yamazaki, H.

2011-10-01

55

Lowering the Gamma Ray Energy Threshold at Thaemis  

NASA Astrophysics Data System (ADS)

The power-law spectra of the 0.1 < E_gamma < 30 GeV point sources detected by EGRET on the Compton GRO have softened at the energies of the atmospheric Cherenkov telescopes (E_gamma > 300 GeV), to the point that only one AGN and two pulsars are visible with current ground-based instruments. Measurement of the spectra in the roll-over range probes details of pulsar and AGN acceleration models, and probes extragalactic infrared photon densities through the absorption of gamma rays. Measurement requires lowering the ground-based energy thresholds to the Egret energy range, and several groups are studying the design of a very large area mirror or mirror array (few thousand M(2) ). Solar power plants built in the 1980's to focus sunlight on boilers in central receiver towers may provide the basic instrument at low cost. This talk describes efforts to use the solar farm at Th\\a'emis in the French Pyrenees for a proof-of-principle prototype for a large area Cherenkov telescope. (Similar feasibility studies are underway at the Solar One site in southern California.) Simulations show that cosmic ray backgrounds mostly vanish below 50 GeV. Electron backgrounds can be reduced by optimizing angular resolution. Excellent flux sensitivity should be obtainable. Secondary optics and electronic timing corrections have been studied and tests to measure Cherenkov pulses will be made this winter. The tests will complement data from the ASGAT and THEMISTOCLE experiments and from the CAT imaging telescope now under construction at Th\\a'emis.

Smith, David A.; Fleury, Patrick; Parae, Eric; Quebert, Jean

1994-12-01

56

THE STATISTICAL DETECTION OF THRESHOLD SIGNALS IN THE RETINA  

Microsoft Academic Search

For the human retina, Hecht, Shlaer, and Pireune (1942) concluded that statistical fluctuations in response to brief flashes at the absolute threshold could be accounted for entirely by random fluctuations in the number of photons absorbed by the photoreceptors at each flash, and that \\

R. Fitzhugh

1957-01-01

57

Threshold computations for detection of failures in SISO systems with transfer function errors  

NASA Technical Reports Server (NTRS)

The author considers the problem of detecting failures in SISO systems using analytic redundancy concepts. Since the models used are subject to error, a method of determining the detection thresholds that account for these errors is sought. The methodology presented utilizes a straightforward application of Parseval's relation to develop a threshold computation that is performed online as a function of the input signal. The threshold is set at a quiescent value to account for sensor noise and is adjusted (upward) according to the activity of the input signal. An application to detection of actuator failures is presented.

Weiss, Jerold L.

1988-01-01

58

Real time electrocardiogram QRS detection using combined adaptive threshold  

Microsoft Academic Search

BACKGROUND: QRS and ventricular beat detection is a basic procedure for electrocardiogram (ECG) processing and analysis. Large variety of methods have been proposed and used, featuring high percentages of correct detection. Nevertheless, the problem remains open especially with respect to higher detection accuracy in noisy ECGs METHODS: A real-time detection method is proposed, based on comparison between absolute values of

Ivaylo I Christov

2004-01-01

59

Elevated visual motion detection thresholds in adults with acquired ophthalmoplegia  

Microsoft Academic Search

AIMSTo test the hypothesis that in patients with acquired chronic bilateral ophthalmoplegia, abnormal retinal image slippage during head movements would result in abnormal thresholds for visual perception of motion.METHODSFive patients (two males and three females) with ophthalmoplegia were included in the study. The average age was 44 years (range 30–69 years). The aetiology of ophthalmoplegia was myasthenia gravis (MG; n=2),

J F Acheson; L Cassidy; E A Grunfeld; J A Shallo-Hoffman; A M Bronstein

2001-01-01

60

Thresholds for detection of constant rotary acceleration during vibratory rotary acceleration  

NASA Technical Reports Server (NTRS)

The effects of vibratory angular acceleration on detection thresholds for constant angular acceleration in a dynamic flight simulator are reported in three experiments. Detection thresholds were determined for 10 pilots and four nonpilots using a random, double-staircase procedure while the subjects sat erect in a device which rotated about an earth-vertical axis. Constant angular acceleration were presented for 0.5 and 1.0 s with concurrent, vibratory angular acceleration at 1 and 5 Hz, and thresholds with no vibratory angular acceleration were established. The thresholds were obtained while the subjects observed a visual reference in the enclosed cockpit in two experiments and in total darkness in a third. The results confirmed earlier experiments showing an inverse relationship between the duration of constant angular acceleration and detection threshold and showed that the detection thresholds in darkness were higher than with a visual reference present. Two analyses of variance revealed no significant differences in thresholds across the three vibration conditions. These results indicate that vibratory angular acceleration of fairly high levels can be present in a dynamic flight simulator without masking the pilot's ability to detect either maneuver or disturbance motions.

Clark, B.; Stewart, J. D.; Phillips, N. H.

1980-01-01

61

Threshold optimization for distributed order-statistic CFAR signal detection  

Microsoft Academic Search

Distributed signal detection schemes have received significant attention recently, but usually under the assumption of stationary observations which are independent from sensor to sensor. Here, order statistics based constant false alarm rate (OS-CFAR) detection techniques are applied to a distributed detection system with nonstationary observations where the signal observations are assumed to be dependent from sensor to sensor. Cases are

RICK S. BLUM; Jinfen Qiao

1996-01-01

62

Target Detection with Adaptive Power Regression Thresholding for HF Radar  

Microsoft Academic Search

High frequency (HF) radars are capable to detect and track targets at extremely long ranges. But the signal environment that includes external noise, different kinds of clutter and interference will significantly limit the detection performance and system capability. This paper considers a new approach to solve the target detection problem in a complex HF radar signal environment. It uses a

A. L. Dzvonkovskaya; H. Rohling

2006-01-01

63

Effects of visual erotic stimulation on vibrotactile detection thresholds in men.  

PubMed

This study examined the effects of sexual arousal on vibration detection thresholds in the right index finger of 30 healthy, heterosexual males who reported no sexual dysfunction. Vibrotactile detection thresholds at frequencies of 30, 60, and 100 Hz were assessed before and after watching erotic and control videos using a forced-choice, staircase method. A mechanical stimulator was used to produce the vibratory stimulus. Results were analyzed using repeated measures analysis of variance. After watching the erotic video, the vibrotactile detection thresholds at 30, 60, and 100 Hz were significantly reduced (p < .01). No changes in thresholds were detected at any frequency following exposure to the non-erotic stimulus. The results show that sexual arousal resulted in an increase in vibrotactile sensitivity to low frequency stimuli in the index finger of sexually functional men. PMID:17713850

Jiao, Chuanshu; Knight, Peter K; Weerakoon, Patricia; Turman, A Bulent

2007-12-01

64

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

65

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

Verfuß, Ursula K; Dähne, Michael; Gallus, Anja; Jabbusch, Martin; Benke, Harald

2013-09-01

66

Variable threshold detection for 3D page-oriented optical data storage systems  

NASA Astrophysics Data System (ADS)

We propose a new method to determine dynamically the threshold in volumetric (3D) page-oriented optical data storage (PODS) systems that use an incoherent (non-holographic) imaging format. In these systems, the inter-symbol interference (ISI) and inter-page interference (IPI) that occurs with very high data packing density are two major sources of error during data retrieval. Traditional readout systems based on a fixed binary decision threshold provide poor results. Our variable threshold detection method identifies the amount of interference from three dimensions for each data element (pixel) and adjusts the threshold value based on that information. In simulation results, the variable threshold method exhibits significant improvement over traditional detection methods.

Ho, Tawei; Intharasombat, Nopparit; Sawchuk, Alexander A.

2006-01-01

67

Signal-Detection, Threshold, and Dual-Process Models of Recognition Memory: ROCs and Conscious Recollection  

Microsoft Academic Search

Threshold- and signal-detection-based models have dominated theorizing about recognition memory. Building upon these theoretical frameworks, we have argued for a dual-process model in which conscious recollection (a threshold process) and familiarity (a signal-detection process) contribute to memory performance. In the current paper we assessed several memory models by examining the effects of levels of processing and the number of presentations

Andrew P. Yonelinas; Ian Dobbins; Michael D. Szymanski; Harpreet S. Dhaliwal; Ling King

1996-01-01

68

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 42 kHz. Audiograms showed peak sensitivity between 8 and 24 kHz, 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

69

A Robust QRS Complex Detection Algorithm Using Dynamic Thresholds  

Microsoft Academic Search

Automatic QRS complex detection is important in ECG signal analysis. QRS detection methods are affected by the quality of the ECG recordings and the abnormalities in the ECG signals. In this paper, a generic algorithm is introduced to improve the detection of QRS complexes in arrhythmia ECG signals that suffer from: (1) non-stationary effects, (2) low signal-to-noise ratio, (3) negative

Mohamed Elgendi; Sivaram Mahalingam; Mirjam Jonkman; Friso De Boer

2008-01-01

70

A neural network-based detection thresholding scheme for active sonar signal tracking  

Microsoft Academic Search

Intensity thresholding is an effective technique to cut off the low energy noises and cut down the computational load in an underwater target tracking system. A neural network based adaptive intensity thresholding scheme with a constant false alarm rate (CFAR) for an active sonar signal tracking situation in a realistic sea environment is proposed in this paper. The proposed system

Y. Sun; M. Farooq

1996-01-01

71

A complex relationship among chemical concentration, detection threshold, and suprathreshold intensity of bitter compounds.  

PubMed

Detection thresholds and psychophysical curves were established for caffeine, quinine-HCl (QHCl), and propylthiouracil (PROP) in a sample of 33 subjects (28 female mean age 24 +/- 4). The mean detection threshold (+/-standard error) for caffeine, QHCl, and PROP was 1.2 +/- 0.12, 0.0083 +/- 0.001, and 0.088 +/- 0.07 mM, respectively. Pearson product-moment analysis revealed no significant correlations between detection thresholds of the compounds. Psychophysical curves were constructed for each bitter compound over 6 concentrations. There were significant correlations between incremental points of the individual psychophysical curves for QHCl and PROP. Regarding caffeine, there was a specific concentration (6 mM) below and above which the incremental steps in bitterness were correlated. Between compounds, analysis of psychophysical curves revealed no correlations with PROP, but there were significant correlations between the bitterness of caffeine and QHCl at higher concentrations on the psychophysical curve (P<0.05). Correlation analysis of detection threshold and suprathreshold intensity within a compound revealed a significant correlation between PROP threshold and suprathreshold intensity (r=0.46-0.4, P<0.05), a significant negative correlation for QHCl (r=-0.33 to -0.4, P<0.05), and no correlation for caffeine. The results suggest a complex relationship between chemical concentration, detection threshold, and suprathreshold intensity. PMID:17220518

Keast, Russell S J; Roper, Jessica

2007-03-01

72

High energy E11 excitons above the continuum threshold in semiconducting single-walled carbon nanotubes  

Microsoft Academic Search

Although the excitonic nature of the primary photoexcitation has been firmly established in semiconducting single-walled carbon nanotubes (S-SWCNTs), the magnitude of the exciton binding energy is still being debated. Recent photoluminescence excitation experiments have detected excitons above the threshold of the continuum band predicted from two-photon absorption measurements in the (10,6) S-SWCNT footnotetextJ. Lefebvre and P. Finnie, Nano Lett. 8,

Hongbo Zhao; Sumit Mazumdar

2010-01-01

73

Determination of an Optimal Threshold Value for Muscle Activity Detection in EMG Analysis  

PubMed Central

It is commonly agreed that one needs to use a threshold value in the detection of muscle activity timing in electromyographic (EMG) signal analysis. However, the algorithm for threshold determination lacks an agreement between the investigators. In this study we aimed to determine a proper threshold value in an incremental cycling exercise for accurate EMG signal analysis. Nine healthy recreationally active male subjects cycled until exhaustion. EMG recordings were performed on four low extremity muscle groups; gastrocnemius lateralis (GL), gastrocnemius medialis (GM), soleus (SOL) and vastus medialis (VM). We have analyzed our data using three different threshold levels: 25%, 35% and 45% of the mean RMS EMG value. We compared the appropriateness of these threshold values using two criteria: (1) significant correlation between the actual and estimated number of bursts and (2) proximity of the regression line of the actual and estimated number of bursts to the line of identity. It had been possible to find a significant correlation between the actual and estimated number of bursts with the 25, 35 and 45% threshold values for the GL muscle. Correlation analyses for the VM muscle had shown that the number of bursts estimated with the 35% threshold value was found to be significantly correlated with the actual number of bursts. For the GM muscle, it had been possible to predict the burst number by using either the 35% or 45% threshold value and for the SOL muscle the 25% threshold value was found as the best predictor for actual number of burst estimation. Detailed analyses of the actual and estimated number of bursts had shown that success of threshold estimation may differ among muscle groups. Evaluation of our data had clearly shown that it is important to select proper threshold values for correct EMG signal analyses. Using a single threshold value for different exercise intensities and different muscle groups may cause misleading results. Key points ? priori accepted threshold value may cause erroneous results in EMG analysis. Using a single threshold value for different exercise intensities and different muscle groups may cause misleading results. The investigators may need to use different threshold selection strategies for different workloads. The investigators have to justify the choice of threshold selection with valid arguments before detailed EMG signal analyses.

Ozgunen, Kerem Tuncay; Celik, Umut; Kurdak, Sanl? Sadi

2010-01-01

74

Optimizing Biosurveillance Systems that Use Threshold-based Event Detection Methods.  

National Technical Information Service (NTIS)

We describe a methodology for optimizing a threshold detection-based biosurveillance system. The goal is to maximize the system-wide probability of detecting an 'event of interest' against a noisy background, subject to a constraint on the expected number...

D. Banschbach J. R. Fricker

2009-01-01

75

Lower TGF Detection Threshold for Fermi GBM: Sample Properties  

NASA Astrophysics Data System (ADS)

From shortly after the launch of Fermi in 2008 the Gamma-ray Burst Monitor has detected TGFs by the flight software monitoring the detector rates. The sensitivity of this method is limited by the 16 ms resolution of the in-orbit data, which is far longer than the durations of TGFs. Since the summer of 2010 individual photon data has been downlinked for selected portions of the orbit, from TGF active regions and seasons. An offline search of this data at high temporal resolution has increased the TGF detection rate by a factor of ten. The reliability of the sample was verified using control regions and VLF observations of the World Wide Lightning Location Network (WWLLN). In this sample, we find TGFs that are shorter than those in the triggered population, and TGFs at greater distances from the spacecraft nadir. Maps of the source locations, as determined with WWLLN, show distinct geographic and meteorological features.

Briggs, M. S.; Xiong, S.; Connaughton, V.; Grove, J.; Chekhtman, A.; Holzworth, R. H.; Hutchins, M. L.

2012-12-01

76

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.

Gheiratmand, Mina; Mullen, Kathy T.

2014-01-01

77

Thresholding for biological material detection in real-time multispectral imaging  

NASA Astrophysics Data System (ADS)

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

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

2005-09-01

78

Using a combined localization/detection model to simulate human localization performance near the masked detection threshold level  

NASA Astrophysics Data System (ADS)

Recently, the perceptual lateralization of a partly masked target has been successfully simulated using the interaural cross-correlation difference (ICCD) model [Braasch, J. Acoust. Soc. Am. 108, 2597 (2000)]. However, in the accompanying listening tests, the target level was often found to be below the masked detection threshold level. To improve the model performance, a detection threshold model has been implemented in the localization model so that the localization process is triggered only when the target level is above a threshold. Otherwise, the position of the sound source is determined according to a behavioral pattern. The detection stage is based on an on- and offset detection algorithm that analyzes the derivative in time. For the simulation of the binaural conditions, the equalization-cancellation algorithm of Durlach [J. Acoust. Soc. Am. 35, 1206-1218 (1963)] has been included in the model. It has been shown that for target levels above the masked detection threshold, the on-/offset detection algorithm is accurate enough to trigger the subtraction process of the ICCD algorithm. Furthermore, the improved model has resulted in better simulations of human localization patterns in the presence of a distracting sound.

Braasch, Jonas

2002-05-01

79

Selection of intrusion detection system threshold bounds for effective sensor fusion  

NASA Astrophysics Data System (ADS)

The motivation behind the fusion of Intrusion Detection Systems was the realization that with the increasing traffic and increasing complexity of attacks, none of the present day stand-alone Intrusion Detection Systems can meet the high demand for a very high detection rate and an extremely low false positive rate. Multi-sensor fusion can be used to meet these requirements by a refinement of the combined response of different Intrusion Detection Systems. In this paper, we show the design technique of sensor fusion to best utilize the useful response from multiple sensors by an appropriate adjustment of the fusion threshold. The threshold is generally chosen according to the past experiences or by an expert system. In this paper, we show that the choice of threshold bounds according to the Chebyshev inequality priciple performs better. This approach also helps to solve the problem of scalability and has the advantage of failsafe capability. This paper theoretically models the fusion of Intrusion Detection Systems for the purpose of proving the improvement in performance, supplemented with the empirical evaluation. The combination of complementary sensors is shown to detect more attacks than the individual components. Since the individual sensors chosen detect sufficiently different attacks, their result can be merged for improved performance. The combination is done in different ways like (i) taking all the alarms from each system and avoiding duplications, (ii) taking alarms from each system by fixing threshold bounds, and (iii) rule-based fusion with a priori knowledge of the individual sensor performance. A number of evaluation metrics are used, and the results indicate that there is an overall enhancement in the performance of the combined detector using sensor fusion incorporating the threshold bounds and significantly better performance using simple rule-based fusion.

Thomas, Ciza; Balakrishnan, Narayanaswamy

2007-04-01

80

Detection of low energy solar neutrinos with HPGermanium  

Microsoft Academic Search

The potential of the GENIUS proposal [1] to measure the spectrum of low energy solar neutrinos in real time is studied. The detection reaction is elastic neutrino-electron scattering 9 + e M 9 + e. 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

L. Baudis; H. V. Klapdor--Kleingrothaus

1999-01-01

81

Systematic calculation of threshold displacement energies: Case study in rutile  

NASA Astrophysics Data System (ADS)

A generalized and systematic method of calculating threshold displacement energies (Ed) using molecular dynamics simulations has been developed and applied to rutile TiO2. Statistically representative results have been achieved through fine sampling of impact energy and trajectory for each atomic species. Each impact trajectory is drawn from a uniform distribution of points on a unit sphere, along which, primary knock-on atoms (PKAs) with kinetic energies in the range of 20-200 eV were introduced into lattices equilibrated to 300 K. Various definitions of Ed are explored, with values presented as probabilities of defect formation. Results for the Ti PKA agree well with experimental data with a value of Ed at around 69 eV. Simulations of O PKAs contrast greatly with Ti PKAs, with displacements occurring at significantly lower energies, resulting in an O value of Ed at 19 eV. Analysis shows that replacement chains on the O sublattice are a common feature and play a significant role in governing defect formation in rutile.

Robinson, M.; Marks, N. A.; Whittle, K. R.; Lumpkin, G. R.

2012-03-01

82

Odor detection thresholds of naphthenic acids from commercial sources and oil sands process-affected water  

Microsoft Academic Search

Naphthenic acids (NAs) occur naturally in various petroleums and in oil sands tailings waters and have been implicated as potential fish tainting compounds. In this study, trained sensory panels and the general population from a university were used to determine the odor detection thresholds of two commercial NAs preparations (Acros and Merichem) and of NAs extracted from an oil sands

Kristyn Edge; Brenda Barona; Rozlyn F. Young; Phillip M. Fedorak; Wendy V. Wismer

2010-01-01

83

Use of a quality index in threshold contrast detail detection measurements in television fluoroscopy  

Microsoft Academic Search

The use of a single index to assist in quality control procedures of X-ray television fluoroscopy systems was investigated. A single quality index was devised incorporating a measure of threshold contrast detail detectability (TCDD) performance and taking into account image intensifier input kerma rate, field size, differences in radiation beam quality, and pulsed fluoroscopy. This was applied to a number

D J Gallacher; S BATCHELOR; J LYNCH; J E SAUNDERS

2003-01-01

84

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

85

Improving Magnitude Detection Thresholds Using Multi-Station Multi- Event, and Multi-Phase Methods.  

National Technical Information Service (NTIS)

We report on the results of both a semi-empirical analysis and a case study in Xiuyan, China, that demonstrated that a correlation detector can lower magnitude detection thresholds by over one full unit for similar events as compared to a standard STA/LTA...

D. Schaff F. Waldhauser

2008-01-01

86

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

PubMed

An improved method for detecting cloud combining Kmeans clustering and the multi-spectral threshold approach is described. On the basis of landmark spectrum analysis, MODIS data is categorized into two major types initially by Kmeans method. The first class includes clouds, smoke and snow, and the second class includes vegetation, water and land. Then a multi-spectral threshold detection is applied to eliminate interference such as smoke and snow for the first class. The method is tested with MODIS data at different time under different underlying surface conditions. By visual method to test the performance of the algorithm, it was found that the algorithm can effectively detect smaller area of cloud pixels and exclude the interference of underlying surface, which provides a good foundation for the next fire detection approach. PMID:21714260

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

2011-04-01

87

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.

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

2014-01-01

88

A dual-threshold ATI-SAR approach for detecting slow moving targets  

Microsoft Academic Search

The high false alarm associated with conventional along-track interferometric synthetic aperture radar (ATI-SAR) is a big concern for any valuable military radar. To reduce the false alarm rate, this paper proposes a dual-threshold approach that combines the conventional interferometric phase detection with the SAR image amplitude detection. This yields two results: (1) the interferometric phase map (including target velocity information)

Yuhong Zhang; A. Hajjari; Kyungjung Kim; B. Himed

2005-01-01

89

Sexually dimorphic enhancement by estradiol of male urinary odor detection thresholds in mice  

PubMed Central

We asked whether sex and adult estrogen exposure influence the detection thresholds for urinary odors used by mice to guide their social behaviors. Gonadectomized (GDX) male and female mice were trained on a two-choice food-motivated task to determine detection thresholds for male urinary odors. There was no significant sex difference in the detection of these odors by GDX subjects without hormone replacement. However, during treatment with estradiol benzoate (EB), GDX females, but not GDX males, showed an enhanced ability to detect these odors. To investigate a possible mechanism for this effect, we measured GDX females’ odor-sampling behavior (sniffing) by monitoring intranasal pressure transients during performance of the urinary odor detection task with and without EB treatment. Under both hormone conditions females decreased their sniffing frequency as the urinary odor concentration decreased, with this decrease being significantly greater while GDX females received EB. Thus, estradiol enhanced detection thresholds for male urine in a sex-specific manner, and this enhanced sensitivity in females was correlated with altered odor-sampling behavior.

Sorwell, Krystina G.; Wesson, Daniel W.; Baum, Michael J.

2010-01-01

90

Detection thresholds of structured noise in the presence of shot noise  

NASA Astrophysics Data System (ADS)

An observer study was run to determine the detection thresholds of several representative examples of column fixed pattern noise, in the presence of varying levels of shot noise, which is known to mask structured noise. The data obtained were fit well at relevant shot noise levels by a simple model based on signal detection theory. Individual metrics of fixed pattern noise and shot noise, used in the masking equation, were computed from one dimensional integrations involving the capture noise power spectra (mapped to CIELAB space); the modulation transfer function of the display; the display pixel pitch; the viewing distance; and the S-CIELAB luminance contrast sensitivity function. The results of this work can be used to predict detection thresholds that can be added to photon transfer curves for the purpose of determining whether fixed pattern noise will be visible.

Li, Feng; Keelan, Brian; Jenkin, Robin; Dokoutchaev, Alex

2012-01-01

91

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.

2014-06-01

92

Stochastic Resonance and Optimal Detection of Pulse Trains by Threshold Devices  

Microsoft Academic Search

The nonlinear detection by a threshold device of a periodic train of soliton-like pulses embedded in arbitrarily distributed white noise is studied. A theoretical model is developed which provides expressions for the signal-to-noise ratio at the output of the detector and for the input–output gain in signal-to-noise ratio. We analyze the properties and conditions of optimality for these quantities as

François Chapeau-Blondeau

1999-01-01

93

Olfactory Detection Thresholds and Adaptation in Adults with Autism Spectrum Condition  

Microsoft Academic Search

Sensory issues have been widely reported in Autism Spectrum Conditions (ASC). Since olfaction is one of the least investigated\\u000a senses in ASC, the current studies explore olfactory detection thresholds and adaptation to olfactory stimuli in adults with\\u000a ASC. 80 participants took part, 38 (18 females, 20 males) with ASC and 42 control participants (20 males, 22 females). A subgroup\\u000a of

T. Tavassoli; S. Baron-Cohen

94

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

95

Thresholds of Passive Microwave Snowfall Detection Determined Using A-Train Observations  

NASA Astrophysics Data System (ADS)

In this study we explore a database of CloudSat+AMSU-B coincident overpasses to determine the minimum threshold of passive microwave detection of snowfall using the high-frequency channels available on GMI. Using the Advanced Infrared Sounder (AIRS) temperature and water vapor profiles along with a surface emissivity database developed from AMSU-B and MHS observations, clear-sky radiances are simulated and compared to AMSU-B observed radiances for all profiles with a maximum temperature less than 271 K. The ability of a scattering signal (observed brightness tempertaure colder than clear-sky brightness temperature by a threshold T) to detect snowfall (CloudSat reflectivity greater than threshold Z) is quantified using the Heidke Skill Score. The 183+/-1 and 183+/-3 GHz channels have the highest skill scores, while those channels that are sensitive to the surface (89, 150 and 183+/-7 GHz) have zero or even negative skill (depending on Z and T), implying that an emission signal (presumably from cloud water) is as good or better for detecting precipitation than a scattering signal. These results emphasize the need for proper characterization of surface emissivity and adequate representation of cloud water in cold season precipitation profiles that form the databases used for Bayesian retrievals from GMI and other GPM constellation radiometers.

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

2011-12-01

96

High energy E11 excitons above the continuum threshold in semiconducting single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Although the excitonic nature of the primary photoexcitation has been firmly established in semiconducting single-walled carbon nanotubes (S-SWCNTs), the magnitude of the exciton binding energy is still being debated. Recent photoluminescence excitation experiments have detected excitons above the threshold of the continuum band predicted from two-photon absorption measurements in the (10,6) S-SWCNT footnotetextJ. Lefebvre and P. Finnie, Nano Lett. 8, 1890 (2008). One interpretation of this experiment is that the exciton binding energy is much larger than previous estimates footnotetextJ. Deslippe et al., Nano Lett. 9, 1330 (2009). We have performed configuration interaction calculations for the (10,6) S-SWCNT within the molecular PPP model that quantitatively reproduces the earlier estimate for the exciton binding energy and also finds excitons deep inside the continuum. A similar observation has previously been made for the conjugated polymer PPV.

Zhao, Hongbo; Mazumdar, Sumit

2010-03-01

97

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

PubMed

A key problem in unconscious perception research is ruling out the possibility that weak conscious awareness of stimuli might explain the results. In the present study, signal detection theory was compared with the objective threshold/strategic model as explanations of results for detection and identification sensitivity in a commonly used unconscious perception task. In the task, 64 undergraduate participants detected and identified one of four briefly displayed, visually masked letters. Identification was significantly above baseline (i.e., proportion correct > .25) at the highest detection confidence rating. This result is most consistent with signal detection theory's continuum of sensory states and serves as a possible index of conscious perception. However, there was limited support for the other model in the form of a predicted "looker's inhibition" effect, which produced identification performance that was significantly below baseline. One additional result, an interaction between the target stimulus and type of mask, raised concerns for the generality of unconscious perception effects. PMID:21987923

Haase, Steven J; Fisk, Gary D

2011-08-01

98

Lowering Threshold by Energy Transfer between Two Dyes in Cholesteric Liquid Crystal Distributed Feedback Lasers  

Microsoft Academic Search

Lowering lasing threshold based on the Förster-type energy transfer process has been studied in distributed feedback (DFB) lasers of cholesteric liquid crystals (CLCs) containing two dyes. We found that the lasing threshold in the energy transfer process was lowered to less than half of that in direct excitation processes. This effect is attributed to the suppression of self-absorption of a

Koji Sonoyama; Yoichi Takanishi; Ken Ishikawa; Hideo Takezoe

2008-01-01

99

Detection and recognition threshold values of odorants used in the odorization of natural gas  

SciTech Connect

This study was designed to determine if odorization practices provide adequate warning for detecting and reacting to gas leakage and involves direct sensory measurements under totally controlled conditions with experienced panelists, indirect measurements by randomly selected panelists exposed to varying odorant levels inside a specially built chamber, and other-directed measurements that test the of the other measurements. This paper reports the findings of the direct sensory measurements and also measurements of odor detection and recognition threshold values, dose-response curves and an assessment of the capabilities of currently used odorants to serve as warning agents.

Moschundreas, D.J.; Jones, D.; Martinus, J.

1982-06-01

100

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

101

Detection threshold of sensory panels for mealiiness of baked potatoes as related to specific gravity differences  

Microsoft Academic Search

Summary  Thresholds of mealiness detection in baked potatoes were demonstrated in three series of tests each representing three specific\\u000a gavity levels within a broad range of 1.096 to 1.056.\\u000a \\u000a Only one of 15 contrasts of 0.002 differences in specific gravity was detected significantly by 29-member panels in three\\u000a 6-sample tests of stored Russet Burbank potatoes.\\u000a \\u000a \\u000a \\u000a With comparable potatoes differing by 0.004

Elizabeth F. Murphy; Ruth H. True; John M. Hogan

1967-01-01

102

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

PubMed

The echolocating bat, Eptesicus fuscus, detects sonar echoes with a sensitivity that changes according to the time elapsed between broadcasting of each sonar signal and reception of echoes. When tested in an electronic target simulator on a two-choice echo-detection task, the bat's threshold improved by 11.5 dB as echo delay changed from 2.3 to 4.6 ms (target ranges of 40 and 80 cm). Earlier experiments measured the change in detection threshold for delays from 1 to 6.4 ms (target ranges from about 17 to 110 cm) and obtained about 11 dB of improvement per doubling of delay. The new experiments used electronic delay lines to simulate echo delay, thus avoiding movement of loudspeakers to different distances and the possible creation of delay-dependent backward masking between stimulus echoes and cluttering echoes from the loudspeaker surfaces. The slope of the threshold shift defines an echo gain control that keeps echoes from point targets at a fixed sensation level--reducing sensitivity by 11 to 12 dB as echo amplitude increases by 12 dB per halving of range during the bat's approach to the target. A recent experiment using loudness discrimination of echoes at 70 to 80 dB SPL (roughly 50 dB above threshold) found a slope of about 6 dB per halving of range, so the gain-control effect may be level dependent. The observed effect is operationally equivalent to forward masking of echoes by the transmission, but any events correlated with vocalization which impair hearing sensitivity for a short interval following transmissions could cause a decline in sensitivity to echoes. Contractions of the bat's middle-ear muscles synchronized to transmissions may account for the observed threshold shift, at least for a span of echo delays associated with the most critical portion of the approach stage of pursuit. Forward masking by the sonar transmissions may contribute to the threshold shift, too, but middle-ear muscle contractions do occur and must be a significant part of the cause. PMID:1556314

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

1992-02-01

103

Application of new advanced CNN structure with adaptive thresholds to color edge detection  

NASA Astrophysics Data System (ADS)

Color edge detection is much more efficient than gray scale detection when edges exist at the boundary between regions of different colors with no change in intensity. This paper presents adaptive templates, which are capable of detecting various color and intensity changes in color image. To avoid conception of multilayer proposed in literatures, modification has been done to the CNN structure. This modified structure allows a matrix C, which carries the change information of pixels, to replace the control parts in the basic CNN equation. This modification is necessary because in multilayer structure, it faces the challenge of how to represent the intrinsic relationship among each primary layer. Additionally, in order to enhance the accuracy of edge detection, adaptive detection threshold is employed. The adaptive thresholds are considered to be alterable criteria in designing matrix C. The proposed synthetic system not only avoids the problem which is engendered by multi-layers but also exploits full information of pixels themselves. Experimental results prove that the proposed method is efficient.

Deng, Shaojiang; Tian, Yuan; Hu, Xipeng; Wei, Pengcheng; Qin, Mingfu

2012-04-01

104

Electrical microstimulation thresholds for behavioral detection and saccades in monkey frontal eye fields.  

PubMed

The frontal eye field (FEF) is involved in the transformation of visual signals into saccadic eye movements. Although it is often considered an oculomotor structure, several lines of evidence suggest that the FEF also contributes to visual perception and attention. To better understand the range of behaviors to which the FEF can contribute, we tested whether monkeys could detect activation of their FEF by electrical microstimulation with currents below those that cause eye movements. We found that stimulation of FEF neurons could almost always be detected at levels below those needed to generate saccades and that the electrical current needed for detection was highly correlated with that needed to generate a saccade. This relationship between detection and saccade thresholds can be explained if FEF neurons represent preparation to make particular saccades and subjects can be aware of such preparations without acting on them when the representation is not strong. PMID:18477698

Murphey, Dona K; Maunsell, John H R

2008-05-20

105

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

USGS Publications Warehouse

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

Gomberg, J.

1991-01-01

106

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

107

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

108

Automated threshold determination for a family of matched subspace filters for target detection in hyperspectral images  

NASA Astrophysics Data System (ADS)

The detection of subpixel targets in hyperspectral images is complicated by interference arising from other background materials. This paper describes three target detection algorithms implemented in Data Fusion Corporation's HYPERTOOLS, a suite of hyperspectral image analysis tools. The matched subspace filter (MSF) is a generalized likelihood ratio test designed to detect target signatures while suppressing known interference signatures in a hyperspectral image. The fill-factor matched subspace filter (FFMSF) and the mixture-modeled matched subspace filter (MMMSF) extend the MSF by fusing geometrical (i.e., material abundance) and statistical (i.e., an assessment of the applicability of a linear replacement mixture model) information with the MSF output. The MSF, FFMSF, and MMMSF require one, two, and three thresholds, respectively. Automated means of determining these thresholds are proposed and justified. The MSF is further designed to allow the processing of multirank target and interference spectral matrices. As more information about a target or targets is included in the MSF, the detection performance of the MSF is expected to improve. If the target and/or interference matrices are singular or nearly singular, however, the performance of the MSF may instead be degraded. Singular value decomposition (SVD) may be employed to prepare spectral data matrices for optimal performance of the MSF. Although the use of singular value decomposition for preprocessing data matrices is well-known in signal processing, the determination of thresholds for the selection of left-singular vectors spanning the data space remains more of "an art." An automated method for determining the number of useful left-singular vectors is proposed based on an interpretation of the singular values and on the analysis of the dimensions of the measurement space.

Reynolds, Lewis; Kober, Woody

2005-05-01

109

A study of the unimolecular decomposition of internal-energy-selected furan molecular ions by threshold-photoelectron–photoion coincidence spectroscopy  

Microsoft Academic Search

The unimolecular decomposition of internal-energy-selected furan molecular ions has been studied by means of threshold-photoelectron–photoion coincidence spectroscopy. Monochromatic synchrotron radiation was used as the ionisation source, and the molecular ion internal energy was established through the detection of a threshold electron. A pulsed electric field was applied to extract the ions from the interaction region and direct them towards a

E. E. Rennie; L. Cooper; C. A. F. Johnson; J. E. Parker; R. A. Mackie; L. G. Shpinkova; D. M. P. Holland; D. A. Shaw; M. A. Hayes

2001-01-01

110

Methods for Detecting and Estimating Population Threshold Concentrations for Air Pollution–Related Mortality with Exposure Measurement Error  

Microsoft Academic Search

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 we considered methods to detect

Sabit Cakmak; Richard T. Burnett; Daniel Krewski

1999-01-01

111

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

PubMed Central

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

Zoefel, Benedikt; Heil, Peter

2013-01-01

112

A dynamic multiple thresholding method for automated breast boundary detection in digitized mammograms  

NASA Astrophysics Data System (ADS)

We have previously developed a breast boundary detection method by using a gradient-based method to search for the breast boundary (GBB). In this study, we developed a new dynamic multiple thresholding based breast boundary detection system (MTBB). The initial breast boundary (MTBB-Initial) is obtained based on the analysis of multiple thresholds on the image. The final breast boundary (MTBB-Final) is obtained based on the initial breast boundary and the gradient information from horizontal and the vertical Sobel filtering. In this way, it is possible to accurately segment the breast area from the background region. The accuracy of the breast boundary detection algorithm was evaluated by comparison with an experienced radiologist's manual segmentation using three performance metrics: the Hausdorff distance (HDist), the average minimum Euclidean distance (AMinDist), and the area overlap (AOM). It was found that 68%, 85%, and 90% of images have HDist errors less than 6 mm for GBB, MTBB-Initial, and MTBB-Final, respectively. Ninety-five percent, 96%, and 97% of the images have AMinDist errors less than 1.5 mm for GBB, MTBB-Initial, and MTBB-Final, respectively. Ninety-six percent, 97%, and 99% of the images have AOM values larger than 0.9 for GBB, MTBB-Initial, and MTBB-Final, respectively. It was found that the performance of the proposed method was improved in comparison to our previous method.

Wu, Yi-Ta; Zhou, Chuan; Hadjiiski, Lubomir M.; Shi, Jiazheng; Wei, Jun; Paramagul, Chintana; Sahiner, Berkman; Chan, Heang-Ping

2007-03-01

113

Human odor detectability: new methodology used to determine threshold and variation.  

PubMed

Current ambiguity concerning the related issues of optimal means for measurement of odor sensitivity and the functional properties of the olfactory system hinders progress in basic and applied research on the human sense of smell. To address these needs, we selected n-amyl acetate (nAA) as a test odorant and developed a methodology in which participants (Ps) receive multiple presentations each session of several concentrations. Yes-no responses as to whether odor was detected are analyzed using binomial statistics, with the probability that a given proportion of yes responses (or greater) would occur by chance alone being treated as the inverse of detectability. Over the course of multiple sessions, this information is also used to maximize the collection of data in the peri-threshold region. Surprisingly, data collected over as many as 14 sessions were fit well by a single logistic regression model relating probability and concentration. Threshold concentrations, defined as those corresponding to a probability of 0.05, varied from 7.11 to 167.53 p.p.b. (v/v) for 11 Ps. Our approach and findings, if shown to be representative of other combinations of Ps and odorants, could accelerate the pace of research in human olfaction by providing a comprehensive operational definition of the limit of the olfactory system to detect odorant molecules. PMID:14654450

Walker, James C; Hall, Sandra B; Walker, Dianne B; Kendal-Reed, Martin S; Hood, Alison F; Niu, Xu-Feng

2003-11-01

114

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

115

Determination of postexcitation thresholds for single ultrasound contrast agent microbubbles using double passive cavitation detection  

PubMed Central

This work presents experimental responses of single ultrasound contrast agents to short, large amplitude pulses, characterized using double passive cavitation detection. In this technique, two matched, focused receive transducers were aligned orthogonally to capture the acoustic response of a microbubble from within the overlapping confocal region. The microbubbles were categorized according to a classification scheme based on the presence or absence of postexcitation signals, which are secondary broadband spikes following the principle oscillatory response of the ultrasound contrast agent and are indicative of the transient collapse of the microbubble. Experiments were conducted varying insonifying frequencies (0.9, 2.8, 4.6, and 7.1 MHz) and peak rarefactional pressures (200 kPa to 6.2 MPa) for two types of contrast agents (Definity® and Optison™). Results were fit using logistic regression analysis to define pressure thresholds where at least 5% and 50% of the microbubble populations collapsed for each frequency. These thresholds were found to occur at lower pressures for Definity than for Optison over the range of frequencies studied; additionally, the thresholds occurred at lower pressures with lower frequencies for both microbubble types in most cases, though this trend did not follow a mechanical index scaling.

King, Daniel A.; Malloy, Michael J.; Roberts, Alayna C.; Haak, Alexander; Yoder, Christian C.; O'Brien, William D.

2010-01-01

116

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

PubMed Central

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

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

2013-01-01

117

Automatic multiple sclerosis lesion detection in brain MRI by FLAIR thresholding.  

PubMed

Magnetic resonance imaging (MRI) is frequently used to detect and segment multiple sclerosis lesions due to the detailed and rich information provided. We present a modified expectation-maximisation algorithm to segment brain tissues (white matter, grey matter, and cerebro-spinal fluid) as well as a partial volume class containing fluid and grey matter. This algorithm provides an initial segmentation in which lesions are not separated from tissue, thus a second step is needed to find them. This second step involves the thresholding of the FLAIR image, followed by a regionwise refinement to discard false detections. To evaluate the proposal, we used a database with 45 cases comprising 1.5T imaging data from three different hospitals with different scanner machines and with a variable lesion load per case. The results for our database point out to a higher accuracy when compared to two of the best state-of-the-art approaches. PMID:24813718

Cabezas, Mariano; Oliver, Arnau; Roura, Eloy; Freixenet, Jordi; Vilanova, Joan C; Ramió-Torrentà, Lluís; Rovira, Alex; Lladó, Xavier

2014-07-01

118

When minimal detectable change exceeds a diagnostic test-based threshold change value for an outcome measure: resolving the conflict.  

PubMed

Assessing patient progress is an integral part of physical therapist practice. In an attempt to assist clinical decision making regarding a patient's change status, researchers have offered study-based threshold change values. Often researchers have provided reliability and diagnostic test-based estimates of threshold change values obtained from the same patient sample. A potential dilemma occurs when the reliability (ie, the minimal detectable change [MDC])-based threshold change value exceeds the diagnostic test-based threshold value. How can a change be detected if the threshold change value falls within the limits of error? In this situation, researchers have recommended using the larger MDC threshold change value. In this perspective article, we describe the interpretation of the threshold values provided by each of these estimation methods and consider which one offers information that is more meaningful to the challenge faced by physical therapists when making decisions concerning the change status of patients. The context for our discussion is a clinical vignette that depicts the dilemma outlined above. We conclude this perspective with suggestions for researchers concerning essential information to include when reporting threshold estimates obtained from reliability-based and diagnostic test-based studies of outcome measures. PMID:22767887

Stratford, Paul W; Riddle, Daniel L

2012-10-01

119

Macaque thresholds for detecting increases in intensity: effects of formant structure.  

PubMed

Macaque monkeys, like humans, are more sensitive to differences in formant frequency than to differences in the frequency of pure tones (see Sinnott et al. (1987) J. Comp. Psychol. 94, 401-415; Pfingst (1993) J. Acoust. Soc. Am. 93, 2124-2129; Prosen et al. (1990) J. Acoust. Soc. Am. 88, 2152-2158; Sinnott et al. (1985) J. Acoust. Soc. Am. 78, 1977-1985; Sinnott and Kreiter (1991) J. Acoust. Soc. Am. 89, 2421-2429; for summary, see May et al. (1996) Aud. Neurosci. 3, 135-162). In the discrimination of formant frequency, it appears that the relevant cue for macaque monkeys is relative level differences of the component frequencies (Sommers et al. (1992) J. Acoust. Soc. Am. 91, 3499-3510). To further explore the result of Sommers et al., we trained macaque monkeys (Macaca fuscata) to report detection of a change in the spectral shape of multi-component harmonic complexes. Spectral shape changes were produced by the addition of intensity increments. When the amplitude spectrum of the comparison stimulus was modeled after the /ae/ vowel sound, thresholds for detecting a change from the comparison stimulus were lowest when intensity increments were added at spectral peaks. These results parallel previous data from human subjects, suggesting that both human and monkey subjects may process vowel spectra through simultaneous comparisons of component levels across the spectrum. When the subjects were asked to detect a change from a comparison stimulus with a flat amplitude spectrum, the subjects showed sensitivity that was relatively comparable to that of human subjects tested in other investigations (e.g. Zera et al. (1993) J. Acoust. Soc. Am. 93, 3431-3441). In additional experiments, neither increasing the dynamic range of the /ae/ spectrum nor dynamically varying the amplitude of the increment during the stimulus presentation reliably affected detection thresholds. PMID:11707349

Le Prell, C G; Niemiec, A J; Moody, D B

2001-12-01

120

Energy threshold effects in the collisionless dissociation of polyatomic molecules by ir laser radiation  

NASA Technical Reports Server (NTRS)

The threshold for collisionless dissociation of SF6, SiF4, and CF2Cl2 by focused CO2 laser radiation has been measured. This threshold is a laser pulse energy effect and, within experimental error, is found to be the same for all three gases. Provided collisions cannot occur during the laser pulse, the degree of dissociation produced depends only on the energy in the pulse, which is consistent with simple adiabatic vibrational heating of the molecules by the laser.

Gower, M. C.; Billman, K. W.

1977-01-01

121

Physics and astrophysics with a ground-based gamma-ray telescope of low energy threshold  

Microsoft Academic Search

Ground-based Cherenkov telescopes have made in recent years important contributions to high energy gamma-ray astronomy. A lower energy threshold, considerably below 100GeV, and improved sensitivity will be key parameters to extend their role. A lower threshold will permit these instruments to cover wavelengths with good overlap with satellite experiments, thus providing essential complementary information.The latest generation of Imaging Air Cherenkov

J. Albert i Fort; A. Armada; C. Baixeras; H. Bartko; D. Bastieri; W. Bednarek; C. Bigongiari; A. Biland; E. Bisesi; O. Blanch; R. K. Bock; T. Bretz; A. Chilingarian; S. Ciprini; S. Commichau; J. L. Contreras; J. Cortina; V. Danielyan; F. Dazzi; A. De Angelis; B. De Lotto; E. Domingo; D. Dorner; M. Doro; O. Epler; D. Ferenc; E. Fernández; R. Firpo; J. Flix; M. V. Fonseca; N. Galante; M. Garczarczyk; M. Gaug; J. Gebauer; R. Giannitrapani; M. Giller; F. Goebel; T. Hengstebeck; P. Jacon; O. C. de Jager; O. Kalekin; D. Kranich; A. Laille; T. Lenisa; E. Lindfors; F. Longo; M. López; J. López; E. Lorenz; F. Lucarelli; K. Mannheim; M. Mariotti; M. Martinez; K. Mase; D. Mazin; C. Merck; M. Merck; M. Meucci; M. Meyer; R. Mirzoyan; S. Mizobuchi; A. Moralejo; E. Oña-Wilhelmi; R. Orduña; N. Otte; D. Paneque; R. Paoletti; M. Pasanen; D. Pascoli; F. Pauss; N. Pavel; R. Pegna; L. Peruzzo; A. Piccioli; M. Pin; R. de los Reyes; J. Rico; D. Renker; A. Robert; G. Rossato; A. Saggion; A. Sánchez; P. Sartori; V. Scalzotto; T. Schweizer; M. Shayduk; K. Shinozaki; A. Sillanpää; D. Sobczynska; A. Stamerra; L. Stark; L. Takalo; M. Teshima; N. Tonello; A. Torres; N. Turini; G. Viertel; V. Vitale; S. Volkov; R. Wagner; T. Wibig; W. Wittek

2005-01-01

122

Flood extent mapping for Namibia using change detection and thresholding with SAR  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

123

Spatial and Temporal Varying Thresholds for Cloud Detection in Satellite Imagery  

NASA Technical Reports Server (NTRS)

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

Jedlovec, Gary; Haines, Stephanie

2007-01-01

124

Near their thresholds for detection, shapes are discriminated by the angular separation of their corners.  

PubMed

Observers make sense of scenes by parsing images on the retina into meaningful objects. This ability is retained for line drawings, demonstrating that critical information is concentrated at object boundaries. Information theoretic studies argue for further concentration at points of maximum curvature, or corners, on such boundaries [1]-[3] suggesting that the relative positions of such corners might be important in defining shape. In this study we use patterns subtly deformed from circular, by a sinusoidal modulation of radius, in order to measure threshold sensitivity to shape change. By examining the ability of observers to discriminate between patterns of different frequency and/or number of cycles of modulation in a 2x2 forced choice task we were able to show, psychophysically, that difference in a single cue, the periodicity of the corners (specifically the polar angle between two points of maximum curvature) was sufficient to allow discrimination of two patterns near their thresholds for detection. We conclude that patterns could be considered as labelled for this measure. These results suggest that a small number of such labels might be sufficient to identify an object. PMID:23741521

Dickinson, J Edwin; Bell, Jason; Badcock, David R

2013-01-01

125

Low tube voltage CT for improved detection of pancreatic cancer: detection threshold for small, simulated lesions  

PubMed Central

Background Pancreatic ductal adenocarcinoma is associated with dismal prognosis. The detection of small pancreatic tumors which are still resectable is still a challenging problem. The aim of this study was to investigate the effect of decreasing the tube voltage from 120 to 80?kV on the detection of pancreatic tumors. Methods Three scanning protocols was used; one using the standard tube voltage (120?kV) and current (160?mA) and two using 80?kV but with different tube currents (500 and 675?mA) to achieve equivalent dose (15?mGy) and noise (15 HU) as that of the standard protocol. Tumors were simulated into collected CT phantom images. The attenuation in normal parenchyma at 120?kV was set at 130 HU, as measured previously in clinical examinations, and the tumor attenuation was assumed to differ 20 HU and was set at 110HU. By scanning and measuring of iodine solution with different concentrations the corresponding tumor and parenchyma attenuation at 80?kV was found to be 185 and 219 HU, respectively. To objectively evaluate the differences between the three protocols, a multi-reader multi-case receiver operating characteristic study was conducted, using three readers and 100 cases, each containing 0–3 lesions. Results The highest reader averaged figure-of-merit (FOM) was achieved for 80?kV and 675?mA (FOM?=?0,850), and the lowest for 120?kV (FOM?=?0,709). There was a significant difference between the three protocols (p?

2012-01-01

126

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

127

Detection of masses in mammograms via statistically based enhancement, multilevel-thresholding segmentation, and region selection.  

PubMed

A method for automatic detection of mammographic masses is presented. As part of this method, an enhancement algorithm that improves image contrast based on local statistical measures of the mammograms is proposed. After enhancement, regions are segmented via thresholding at multiple levels, and a set of features is computed from each of the segmented regions. A region-ranking system is also presented that identifies the regions most likely to represent abnormalities based on the features computed. The method was tested on 57 mammographic images of masses from the Mini-MIAS database, and achieved a sensitivity of 80% at 2.3 false-positives per image (average of 0.32 false-positives per image). PMID:18358699

Rojas Domínguez, Alfonso; Nandi, Asoke K

2008-06-01

128

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; Abächerli, Roger

2012-09-01

129

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

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

2012-01-01

130

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

131

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 Geográfico Nacional. This array currently comprises 120 seismic stations distributed throughout Spanish territory (mainland and islands). Basically, we are interested in checking the noise conditions, reliability, and seismic detection capability of the Spanish network by analyzing the background noise level affecting the array stations, errors in hypocentral location, and detection threshold, which provides knowledge about network performance. It also enables testing of the suitability of the velocity model used in the routine process of earthquake location. To perform this study we use a method that relies on P and S wave travel times, which are computed by simulation of seismic rays from virtual seismic sources placed at the nodes of a regular grid covering the study area. Given the characteristics of the seismicity of Spain, we drew maps for M L magnitudes 2.0, 2.5, and 3.0, at a focal depth of 10 km and a confidence level 95 %. The results relate to the number of stations involved in the hypocentral location process, how these stations are distributed spatially, and the uncertainties of focal data (errors in origin time, longitude, latitude, and depth). To assess the extent to which principal seismogenic areas are well monitored by the network, we estimated the average error in the location of a seismic source from the semiaxes of the ellipsoid of confidence by calculating the radius of the equivalent sphere. Finally, the detection threshold was determined as the magnitude of the smallest seismic event detected at least by four stations. The northwest of the peninsula, the Pyrenees, especially the westernmost segment, 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, José; D'Anna, Giuseppe; Papanastassiou, Dimitris; Baskoutas, Ioannis; Özel, Nurcan M.

2013-11-01

132

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; Demattè, Fabrizio

2011-09-01

133

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

134

N2 band oscillator strengths at near-threshold energies  

NASA Astrophysics Data System (ADS)

Band oscillator strengths for 58 bands in the near-threshold region of N2, i.e., from 116 200 to 125 400 cm-1, are derived from measured band-integrated optical depths. The complexity of the absorption spectrum demands that the measurements be carried out on rotationally cold supersonic jet expansions. The column density N in the absorbing path of the jet cannot be measured directly. Instead, the room temperature f values of selected calibration bands are used to convert the band-integrated optical depths of the jet-cooled calibration bands to preliminary column densities [N], which, plotted as a function of jet reservoir pressure p, scatter around a straight line passing through the origin of the graph. From the slope of the line, first estimates of the effective column density N can be derived for any value of p. Second estimates are obtained by repeating the same procedure using ab initio calculated f values based on the work of Spelsberg and Meyer [J. Chem. Phys. 115, 6438 (2001)]. Depending on the jet configuration, the two estimates differ by 3%-15% their average is accepted as the best approximation to N. The derived band oscillator strengths are compatible with ab initio results of Spelsberg and Meyer and reproduce the observations reasonably well, even where two or more transitions combine in the formation of complex band structures. They also clarify the analysis of the absorption spectrum in the region of the 7p(0) complex [Jungen, Huber, Jungen, and Stark, J. Chem. Phys. 118, 4517 (2003)] and lead to a plausible interpretation of the spectrum in the 124 680-124 880 cm-1 range. As a result, the lowest three vibronic levels of both the 3'd'? and the 4's'? core excited states have now been identified.

Huber, Klaus P.; Chan, Man-Chor; Stark, Glenn; Ito, Kenji; Matsui, Takashi

2009-08-01

135

Energy transfer and temperature-gradient thresholds in plasma.  

National Technical Information Service (NTIS)

Generic constraints on energy transfer in inhomogeneous magnetized plasmas and on plasma stability are derived within the context of the quasiparticle description. Their relation to the problem of turbulent fluctuations driven by temperature gradients is ...

P. P. Sosenko J. Weiland

1995-01-01

136

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

137

Relationship between gap detection thresholds and loudness in cochlear-implant users.  

PubMed

Gap detection threshold (GDT) is a commonly used measure of temporal acuity in cochlear-implant (CI) recipients. This measure, like other measures of temporal acuity, shows considerable variation across subjects and also varies across stimulation sites within subjects. The aims of this study were (1) to determine whether across-site variation in GDTs would be reduced or maintained with increased stimulation levels; (2) to determine whether across-site variation in GDTs at low stimulation levels was related to differences in loudness percepts at those same levels; and (3) to determine whether matching loudness levels could reduce across-site differences in GDTs. Thresholds and maximum comfortable loudness levels were measured in postlingually deaf adults using all available sites in their electrode arrays. All sites were then surveyed at 30% of the dynamic range (DR) to examine across-site variation. Two sites with the largest difference in GDTs were then selected and for those two sites GDTs were measured at multiple levels of the DR (10%, 30%, 50%, 70%, and 90%). Stimuli consisted of 500 ms trains of symmetric-biphasic pulses, 40 ?s/phase, presented at a rate of 1000 pps using a monopolar (MP1+2) electrode configuration. To examine perceptual differences in loudness, the selected sites were loudness-matched at the same levels of the DR. Variations in GDTs and loudness patterns were observed across stimulation sites and across subjects. Variations in GDTs across sites tended to decrease with increasing stimulation levels. For the majority of the subjects, stimuli at a given level in %DR were perceived louder at sites with better GDTs than those presented at the same level in %DR at sites with poorer GDTs. These results suggest that loudness is a contributing factor to across-site variation in GDTs and that CI fittings based on more detailed loudness matching could reduce across-site variation and improve perceptual acuity. PMID:21168479

Garadat, Soha N; Pfingst, Bryan E

2011-05-01

138

Pulsed laser damage thresholds and laser treatment energy parameters, in vivo, of human aphakic intraocular membranes.  

PubMed

Energy and power density damage thresholds were determined for the perforation of human aphakic pupillary membranes and intraocular lens implants, in vivo, at the focal point of Neodymium-YAG ophthalmic laser systems, at 1,064 nm, which produced Q-switched nanosecond pulses (TEMoo, pulse duration; 20 ns) and mode-locked pulse trains (TEMoo, 9-11 pulses, pulse duration; 30 ps, entire pulse train delivered in 50-70 ns). Pulse energies bracketing the damage thresholds and focal diameter were tabulated. The energy density and power density thresholds for perforation of the pupillary membranes (hereafter referred to as perforation threshold) were slightly lower and power density damage thresholds higher for shorter duration pulses, eg--66 J/cm2 (2,200 GW/cm2) with the picosecond pulse trains vs 80 J/cm2 (2.7 GW/cm2) with the nanosecond pulses and were similar in pseudophakics and aphakics; 78 J/cm2 for pseudophakics vs 83 J/cm2 aphakics, both treated with single nanosecond Nd-YAG pulses, and 68 J/cm2 for pseudophakic vs 66 J/cm2 for aphakic patients treated with picosecond Nd-YAG laser pulse trains. The number of laser pulses and pulse energies required for successful discussion of the pupillary membranes depended not only on the pulse parameters but also on the characteristics of the membrane, such as thickness, nonuniformity, capsular haze, or capsular haze combined with fibrosis. PMID:3807631

Davi, S K

1986-01-01

139

Dynamic Route and Threshold Level Selection in Energy Efficient WSN  

Microsoft Academic Search

Sensor nodes are hardware devices and their source of energy is battery power . Nodes store, forward, report various environment related parameters to the sink, which is normally a base station, thus monitor the environment using co-operative information. A dynamic approach is suggested to regulate and decide broadcast radius . It can reduce collision . It can improve life span

Bhushan N. Mahajan; V. M. Thakare; R. V. Dharaskar

2010-01-01

140

Lowering threshold energy for femtosecond laser pulse photodisruption through turbid media using adaptive optics  

NASA Astrophysics Data System (ADS)

Focussed femtosecond laser pulses are applied in ophthalmic tissues to create an optical breakdown and therefore a tissue dissection through photodisruption. The threshold irradiance for the optical breakdown depends on the photon density in the focal volume which can be influenced by the pulse energy, the size of the irradiated area (focus), and the irradiation time. For an application in the posterior eye segment the aberrations of the anterior eye elements cause a distortion of the wavefront and therefore an increased focal volume which reduces the photon density and thus raises the required energy for surpassing the threshold irradiance. The influence of adaptive optics on lowering the pulse energy required for photodisruption by refining a distorted focus was investigated. A reduction of the threshold energy can be shown when using adaptive optics. The spatial confinement with adaptive optics furthermore raises the irradiance at constant pulse energy. The lowered threshold energy allows for tissue dissection with reduced peripheral damage. This offers the possibility for moving femtosecond laser surgery from corneal or lental applications in the anterior eye to vitreal or retinal applications in the posterior eye.

Hansen, A.; Ripken, Tammo; Krueger, Ronald R.; Lubatschowski, Holger

2011-02-01

141

Dissociation Thresholds of Low-Energy Molecular Ions on a Cu(111) Surface  

NASA Astrophysics Data System (ADS)

The dissociation thresholds of polyatomic SF5+ and BF2+ ions on Cu(111) surface have been investigated in the incident energy range of 2 200 eV. The mass and kinetic energy of scattered ions were analyzed simultaneously using a quadrupole mass analyzer equipped with a 45° sector field energy filter. For SF5+ ion irradiation, dissociated species (SF4+ and F-) began to emerge at an energy of 15±2 eV, and the irradiated ions further dissociated into SF3+ at 50±2 eV. These energies are substantially higher than the bond strength of S F for free SF6 molecules (3.3 eV). These results suggest that the translational-vibrational energy transfer during the collision process greatly affects the observed dissociation threshold. Similar results are also observed for BF2+ irradiation.

Yamamoto, Hiroyuki; Baba, Yuji; Sasaki, Teikichi

1998-09-01

142

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 Harris–Kalmus procedure) for both citric acid (CA) and sodium chloride (NaCl). Despite good retest reliability, individual differences in detection and recognition were weakly correlated, suggesting that detection and recognition of sour and salty stimuli may reflect different physiological processes. In Study 2, a subset of subjects returned to contribute full detection (psychometric) functions for CA and NaCl. Thresholds estimated from full detection functions correlated with both staircase and recognition thresholds, suggesting that both tasks may reflect absolute sensitivity to some extent. However, the ranges of individual differences were systematically compressed for staircase thresholds relative to those from full detection functions. Thus, individual differences in sensitivity appear to interact with different test methodologies in lawful ways. More work will be required to understand how different taste phenotypes relate to one another.

2013-01-01

143

An Artificial Immune System for Temporal Anomaly Detection Using Cell Activation Thresholds and Clonal Size Regulation with Homeostasis  

Microsoft Academic Search

This paper presents an artificial immune system (AIS) based on Grossman's tunable activation threshold (TAT) for anomaly detection. We describe the immunological metaphor and the algorithm adopted for T-cells, emphasizing two important features: the temporal dynamic adjustment of T-cells clonal size and its associated homeostasis mechanism. We present some promising results obtained with artificially generated data sets, aiming to test

Mário João Gonçalves Antunes; Manuel Eduardo Correia

2009-01-01

144

Threshold displacement energies and defect formation energies in Y2Ti2O7  

SciTech Connect

Ab initio molecular dynamics simulations have been carried out to determine the threshold displacement energies Ed and the corresponding defect configurations, and ab initio methods have been used to accurately determine their formation energies in Y2Ti2O7. The minimum Ed is found to be 27 eV for a Y recoil along the <100> direction, 31.5 eV for Ti atoms along the <100> direction, 14.5 eV for O48f atoms along the <110> direction and 13 eV for O8b atoms along the <111> direction. The average Ed value determined is 32.7, 34.2, 14.2 and 16.1 eV for yttrium, titanium, O48f and O8b atoms, respectively. Cation interstitials at vacant 8a sites, which are generally occupied by oxygen anions, and at the bridge sites between two neighboring cations along the <010> direction are observed after low energy recoil events. A systematic study of defect formation energies suggests that cation interstitials, which are located at 8a sites and bridge sites along the <010> direction, and in split configurations along the <010>, <110> or <111> direction, are all stable with low defect formation energies. It is suggested that the relative stability of cation interstitials may provide a pathway of driving ion-irradiation induced amorphization in Y2Ti2O7.

Xiao, Haiyan [Pacific Northwest National Laboratory (PNNL); Gao, Fei [Pacific Northwest National Laboratory (PNNL); Weber, William J [ORNL

2010-01-01

145

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

146

Effect of Functional Group and Carbon Chain Length on the Odor Detection Threshold of Aliphatic Compounds  

PubMed Central

Odor detection thresholds (ODTs) are used for assessing outdoor and indoor air quality. They are obtained experimentally by olfactometry and psychophysical methods, and large compilations are available in the literature. A non-linear regression equation was fitted to describe the ODT variability of 114 aliphatic compounds based on the alkyl chain length for different homologous series (carboxylic acids, aldehydes, 2-ketones, esters, 1-alcohols, amines, thiols, thioethers and hydrocarbons). The resulting equation reveals an effect of the functional group, molecular size and also an interaction between both factors. Although the mechanistic interpretation of results is uncertain, the relatively high goodness-of-fit (R2 = 0.90) suggests that ODT values of aliphatic compounds can be predicted rather accurately, which is not the case for rigid molecules. This equation may serve as a basis for the development of more complex ODT models taking into account diverse structural features of odorants. The variability of power-law exponents was also investigated for the homologous series.

Zarzo, Manuel

2012-01-01

147

[Boundary threshold value method used in crystalline material internal defect detection by short wavelength X-ray diffraction].  

PubMed

There are few references about crystalline material internal defect detected by X-ray diffraction tomography using common X-ray source. Short wavelength X-ray diffractometer (SWXRD), invented by Institute of Southwest Technology Engineering, is a relatively small and inexpensive instrument compared to synchrotron radiation or neutron reactor. Boundary determination of defect affects the imaging quality and the distinguishing of defect in X-ray diffraction tomography using SWXRD. In the present paper, threshold value method of diffracted intensity is put forward to process the test data, so the boundary of defect is legible. In order to study how the factors influence the threshold value, Gauss function is used in fitting the test data. The influence of varisized image quality indicator pressed in powdered aluminum on threshold value has been studied. The result shows that 91% of the diffraction intensity of substrate can be regarded as the threshold value. The experiment of slit in aluminum alloy sheet further verified the threshold value method. It's useful in detecting the defect boundary. PMID:21847964

Mu, Jian-Lei; Zhang, Jin; Gao, Zheng-Huan; Zheng, Lin; He, Chang-Guang

2011-06-01

148

Threshold Tracking Pacing Based on Beat by Beat Evoked Response Detection: Clinical Benefits and Potential Problems  

Microsoft Academic Search

Continuous monitoring of pacemaker stimulation thresholds and automatic adjustment of pacemaker outputs were among the longstanding goals of the pacing community. The first clinically successful implementation of threshold tracking pacing was the Autocapture feature which has accomplished automatic ventricular capture verification for every single stimulus by monitoring the Evoked Response (ER) signal resulting from myocardial depolarization. The Autocapture feature not

F?rat Duru; Urs Bauersfeld; Hans Schüller; Reto Candinas

2000-01-01

149

Falling-Edge, Variable Threshold (FEVT) Method for the Automated Detection of Gastric Slow Wave Events in High-Resolution Serosal Electrode Recordings  

PubMed Central

High resolution (HR) multi-electrode mapping is increasingly being used to evaluate gastrointestinal slow wave behaviors. To create the HR-activation maps from gastric serosal electrode recordings that quantify slow wave propagation, it is first necessary to identify the activation time (AT) of each individual slow wave event. Identifying these ATs has been a time consuming task, because there has previously been no reliable automated detection method. We have developed an automated AT detection method termed falling-edge, variable threshold (FEVT) detection. It computes a detection signal transform to accentuate the high ‘energy’ content of the falling edges in the serosal recording, and uses a running median estimator of the noise to set the time-varying detection threshold. The FEVT method was optimized, validated, and compared to other potential algorithms using in-vivo HR recordings from a porcine model. FEVT properly detects ATs in a wide range of waveforms, making its performance substantially superior to the other methods, especially for low signal-to-noise ratio (SNR) recordings. The algorithm offered a substantial time savings (>100 times) over manual-marking whilst achieving a highly satisfactory sensitivity (0.92) and positive-prediction value (0.89).

Erickson, Jonathan C; O'Grady, Gregory; Du, Peng; Obioha, Chibuike; Qiao, Wenlian; Richards, William O; Bradshaw, L Alan; Pullan, Andrew J.; Cheng, Leo K.

2010-01-01

150

First demonstration of a sub-keV electron recoil energy threshold in a liquid argon ionization chamber  

NASA Astrophysics Data System (ADS)

We describe the first demonstration of a sub-keV electron recoil energy threshold in a dual-phase liquid argon time projection chamber. This is an important step in an effort to develop a detector capable of identifying the ionization signal resulting from nuclear recoils with energies of order a few keV and below. We obtained this result by observing the peaks in the energy spectrum at 2.82 keV and 0.27 keV, following the K- and L-shell electron capture decay of 37Ar respectively. The 37Ar source preparation is described in detail, since it enables calibration that may also prove useful in dark matter direct detection experiments. An internally placed 55Fe x-ray source simultaneously provided another calibration point at 5.9 keV. We discuss the ionization yield and electron recombination in liquid argon at those three calibration energies.

Sangiorgio, S.; Joshi, T. H.; Bernstein, A.; Coleman, J.; Foxe, M.; Hagmann, C.; Jovanovic, I.; Kazkaz, K.; Mavrokoridis, K.; Mozin, V.; Pereverzev, S.; Sorensen, P.

2013-11-01

151

Threshold displacement energies and defect formation energies in Y2Ti2O7  

SciTech Connect

Ab initio molecular dynamics simulations have been carried out to determine both the threshold displacement energies Ed and corresponding defect configurations, and ab initio methods have been used to accurately determine the formation energies in Y2Ti2O7. The minimum Ed is found to be 27 eV for a Y recoil along the <100> direction, 31.5 eV for Ti atoms along the <100> direction, 14.5 eV for O48f atoms along the <110> direction and 13 eV for O8b atoms along the <111> direction. The average Ed value along three directions determined is 35.1, 35.4, 17.0 and 16.2 eV for yttrium, titanium, O48f and O8b atoms, respectively. Cation interstitials at vacant 8a sites, which are generally occupied by oxygen anions, and at the bridge sites between two neighboring cations along the <010> direction are observed after low energy recoil events. A systematic study of the defect formation energies suggests that cation interstitials, which are located at 8a sites and bridge sites along the <010> direction, and in split configurations along the <010>, <110> or <111> direction, are all stable in these configurations. It is suggested that the relative stability of cation interstitials may provide a pathway of driving ion-irradiation induced amorphization in Y2Ti2O7.

Xiao, Haiyan Y.; Gao, Fei; Weber, William J.

2010-10-20

152

Threshold displacement energies and defect formation energies in Y2Ti2O7.  

PubMed

Ab initio molecular dynamics simulations have been carried out to determine both threshold displacement energies, E(d), and corresponding defect configurations, and ab initio methods have been used to determine defect formation energies in Y(2)Ti(2)O(7). The minimum E(d) is found to be 27 eV for a Y recoil along the {100} direction, 31.5 eV for Ti atoms along the {100} direction, 14.5 eV for O(48f) atoms along the {110} direction and 13 eV for O(8b) atoms along the {111} direction. The average E(d) values along three directions determined here are 35.1, 35.4, 17.0 and 16.2 eV for yttrium, titanium, O(48f) and O(8b) atoms, respectively. Cation interstitials are observed occupying vacant 8a anion sites and bridge sites between two neighboring cations along the {010} direction after low energy recoil events. A systematic study of the defect formation energies suggests that cation interstitials that are located at 8a sites, at bridge sites along the {010} direction and in split configurations along the {010}, {110} or {111} direction are all stable configurations. It is suggested that the relative stability of cation interstitials may provide a pathway for driving irradiation induced amorphization in Y(2)Ti(2)O(7). PMID:21386601

Xiao, H Y; Gao, F; Weber, W J

2010-10-20

153

Threshold displacement energies and defect formation energies in Y2Ti2O7  

NASA Astrophysics Data System (ADS)

Ab initio molecular dynamics simulations have been carried out to determine both threshold displacement energies, Ed, and corresponding defect configurations, and ab initio methods have been used to determine defect formation energies in Y2Ti2O7. The minimum Ed is found to be 27 eV for a Y recoil along the lang100rang direction, 31.5 eV for Ti atoms along the lang100rang direction, 14.5 eV for O48f atoms along the lang110rang direction and 13 eV for O8b atoms along the lang111rang direction. The average Ed values along three directions determined here are 35.1, 35.4, 17.0 and 16.2 eV for yttrium, titanium, O48f and O8b atoms, respectively. Cation interstitials are observed occupying vacant 8a anion sites and bridge sites between two neighboring cations along the lang010rang direction after low energy recoil events. A systematic study of the defect formation energies suggests that cation interstitials that are located at 8a sites, at bridge sites along the lang010rang direction and in split configurations along the lang010rang, lang110rang or lang111rang direction are all stable configurations. It is suggested that the relative stability of cation interstitials may provide a pathway for driving irradiation induced amorphization in Y2Ti2O7.

Xiao, H. Y.; Gao, F.; Weber, W. J.

2010-10-01

154

Threshold Energy Density of Lower Hybrid Waves in the Freja Experiment  

SciTech Connect

Data from the Freja satellite experiment on the lower hybrid turbulence in the Earth's magnetosphere are analyzed. It is shown that the observed threshold energy density of lower hybrid waves required for the excitation of localized wave packets is in good agreement with theoretical predictions.

Popel, S. I. [Institute of Geosphere Dynamics (Russian Federation)] [Institute of Geosphere Dynamics (Russian Federation)

2001-05-15

155

A PET scatter correction using simultaneous acquisitions with low and high lower energy thresholds  

Microsoft Academic Search

The authors propose a new method for scatter correction using two sinograms acquired simultaneously with a low and a high lower energy threshold (LLD). The high LLD is chosen such that the corresponding sinogram contains no or few scatter counts. The information in each data set are combined to produce a sinogram corrected for scatter. The method is described in

B. Bendriem; R. Trebossen; V. Frouin; A. Syrota

1993-01-01

156

Comparative study of laser damage threshold energies in the artificial retina  

Microsoft Academic Search

Laser damage threshold energies produced from ultrashort (i.e.,

Dale J. Payne; Richard A. Hopkins; Brent Eilert; Gary D. Noojin; David J. Stolarski; Robert J. Thomas; Clarence P. Cain; Gordon T. Hengst; Paul K. Kennedy; Thomas R. Jost; Benjamin A. Rockwell

1999-01-01

157

A threshold-based approach to calorimetry in helium droplets: Measurement of binding energies of water clusters  

NASA Astrophysics Data System (ADS)

Helium droplet beam methods have emerged as a versatile technique that can be used to assemble a wide variety of atomic and molecular clusters. We have developed a method to measure the binding energies of clusters assembled in helium droplets by determining the minimum droplet sizes required to assemble and detect selected clusters in the spectrum of the doped droplet beam. The differences in the droplet sizes required between the various multimers are then used to estimate the incremental binding energies. We have applied this method to measure the binding energies of cyclic water clusters from the dimer to the tetramer. We obtain measured values of D0 that are in agreement with theoretical estimates to within ~20%. Our results suggest that this threshold-based approach should be generally applicable using either mass spectrometry or optical spectroscopy techniques for detection, provided that the clusters selected for study are at least as strongly bound as those of water, and that a peak in the overall spectrum of the beam corresponding only to the cluster chosen (at least in the vicinity of the threshold) can be located.

Lewis, William K.; Harruff-Miller, Barbara A.; Gord, Michael A.; Gord, Joseph R.; Guliants, Elena A.; Bunker, Christopher E.

2012-07-01

158

A vertical-energy-thresholding procedure for data reduction with multiple complex curves.  

PubMed

Due to the development of sensing and computer technology, measurements of many process variables are available in current manufacturing processes. It is very challenging, however, to process a large amount of information in a limited time in order to make decisions about the health of the processes and products. This paper develops a "preprocessing" procedure for multiple sets of complicated functional data in order to reduce the data size for supporting timely decision analyses. The data type studied has been used for fault detection, root-cause analysis, and quality improvement in such engineering applications as automobile and semiconductor manufacturing and nanomachining processes. The proposed vertical-energy-thresholding (VET) procedure balances the reconstruction error against data-reduction efficiency so that it is effective in capturing key patterns in the multiple data signals. The selected wavelet coefficients are treated as the "reduced-size" data in subsequent analyses for decision making. This enhances the ability of the existing statistical and machine-learning procedures to handle high-dimensional functional data. A few real-life examples demonstrate the effectiveness of our proposed procedure compared to several ad hoc techniques extended from single-curve-based data modeling and denoising procedures. PMID:17036818

Jung, Uk; Jeong, Myong K; Lu, Jye-Chyi

2006-10-01

159

Threshold displacement energies in rutile TiO2: A molecular dynamics simulation study  

SciTech Connect

Threshold displacement energies are determined for Ti and O in rutile TiO2 using molecular dynamics simulations with an empirical model. The simulations involve the introduction of a primary knock-on atom (PKA) with a range of energies (30- 150 eV) in various crystallographic directions at 160 K. We observe the formation of stable Frenkel defects, as well as defect recovery via low-energy interstitial migration mechanisms. The latter causes significant statistical variation between simulation outcomes, which leads to the definition of a defect formation probability. This probability is characterized as a function of PKA energy in order to define the threshold displacement energy and compare with experimental results. Using a probability of 10%, the average threshold displacement energy is around 40 eV for oxygen (comparable to experiment) and 105 eV for titanium. Using a probability of 50%, the values are 65 eV and 130 eV respectively, which may be more appropriate for use in TRIM calculations. In addition, we run a parallel set of calculations using a second empirical model, finding that the detailed results are highly model-dependent, particularly the oxygen defect structures and energies, which are compared to new ab initio data.

Thomas, Bronwyn S.; Marks, Nigel A.; Corrales, Louis R.; Devanathan, Ram

2005-09-01

160

Silicon threshold displacement energy determined by photoluminescence in electron-irradiated cubic silicon carbide  

SciTech Connect

In view of the potential use of silicon carbide (SiC) in the nuclear industry, it is of major interest to understand point defect formation in this material. This work is a contribution to the determination of the silicon threshold displacement energy in the cubic polytype of SiC using electron irradiations with increasing energies from 275 to 680 keV. The photoluminescence signal of the silicon vacancy was related to the number of displacements per atom in the silicon sublattice. This quantity was calculated taking into account the energy loss and angular dispersion of electrons in the target. A best fit of experimental data was obtained for a displacement cross section using a threshold displacement energy of 25 eV along the [100] lattice direction. We checked the relevance of this result by comparing the experimental concentration of silicon single vacancies measured by electron paramagnetic resonance spectroscopy with the theoretical number of displaced silicon atoms.

Lefevre, Jeremie; Esnouf, Stephane; Petite, Guillaume [Laboratoire des Solides Irradies, CEA-IRAMIS, CNRS, Ecole Polytechnique, F-91128 Palaiseau Cedex (France); Costantini, Jean-Marc [CEA, DEN, SRMA, F-91191 Gif-sur-Yvette Cedex (France)

2009-01-15

161

Parametric resonance for vibration energy harvesting with design techniques to passively reduce the initiation threshold amplitude  

NASA Astrophysics Data System (ADS)

A vibration energy harvester designed to access parametric resonance can potentially outperform the conventional direct resonant approach in terms of power output achievable given the same drive acceleration. Although linear damping does not limit the resonant growth of parametric resonance, a damping dependent initiation threshold amplitude exists and limits its onset. Design approaches have been explored in this paper to passively overcome this limitation in order to practically realize and exploit the potential advantages. Two distinct design routes have been explored, namely an intrinsically lower threshold through a pendulum-lever configuration and amplification of base excitation fed into the parametric resonator through a cantilever-initial-spring configuration. Experimental results of the parametric resonant harvesters with these additional enabling designs demonstrated an initiation threshold up to an order of magnitude lower than otherwise, while attaining a much higher power peak than direct resonance.

Jia, Yu; Yan, Jize; Soga, Kenichi; Seshia, Ashwin A.

2014-06-01

162

Effect of Electron Energy Sharing on the Double Photoionization of Helium Near Threshold  

Microsoft Academic Search

Energy and angle resolved measurements have been performed in the double photoionization of helium. Whereas the angular distributions do not depend much on the energy sharing \\\\(E1,E2\\\\) at 4 eV above threshold, a strong effect is observed at E = 18.6 eV. These results can be analyzed qualitatively if the total amplitude is split into two parts which are, respectively,

P. Lablanquie; J. Mazeau; L. Andric; P. Selles; A. Huetz

1995-01-01

163

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

164

A STATISTICAL MODELING METHODOLOGY FOR THE DETECTION, QUANTIFICATION, AND PREDICTION OF ECOLOGICAL THRESHOLDS  

EPA Science Inventory

This study will provide a general methodology for integrating threshold information from multiple species ecological metrics, allow for prediction of changes of alternative stable states, and provide a risk assessment tool that can be applied to adaptive management. The integr...

165

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

NASA Technical Reports Server (NTRS)

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

Temkin, A.

1974-01-01

166

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 (13.6±0.6)keV. Interpretation of the results depends on the response to fluorine and carbon recoils, but in general we find agreement with the predictions of the classical bubble-nucleation theory. 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.; Vázquez-Jáuregui, E.; Rivera, R. A.; Uplegger, L.

2013-07-01

167

Low-threshold neutron detection for proton-transfer reactions with VANDLE  

NASA Astrophysics Data System (ADS)

Proton-transfer studies with radioactive beams are a useful tool for constraining astrophysical proton-capture rates and probing the single-particle structure of exotic nuclei. Measurements from (d,n) reactions on radioactive beams require an efficient large- area neutron detector array. The Versatile Array of Neutron Detectors at Low Energy (VANDLE) is being developed at ORNL for both (d,n) and beta-delayed neutron spectroscopy measurements. Digital electronics and optimized materials make VANDLE sensitive to neutron--proton scattering for neutrons above 100 keV, and also to elastically scattered carbon from neutrons above 1 MeV. This carbon sensitivity supplements the detection efficiency at those energies. Measured efficiencies from an ^27Al(d,n) study at Ohio University and from a ^252Cf source will be presented, along with plans and simulated responses for (d,n) measurements of astrophysicaly important proton-capture reactions.

Peters, William; Grzywacz, R.; Madurga, M.; Paulauskas, S.; Cizewski, J. A.; Howard, M. E.; O'Malley, P. D.; Manning, B.; Merino, E.; Massey, T. N.; Brune, C.; Sarazin, F.; Ilyuskin, S.; Walter, D.; Blackmon, J.; Bardayan, D. W.; Spassova, I.; Matei, C.

2011-10-01

168

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

169

Thresholds to chromatic spots of cells in the macaque geniculate nucleus as compared to detection sensitivity in man.  

PubMed Central

1. The relation between wavelength and psychophysical threshold for chromatic spots on a white background provides evidence for the existence of chromatic channels in the primate visual system. To find the physiological substrate of this task, we compared increment thresholds of different cell types in the macaque lateral geniculate nucleus with human psychophysical thresholds to the same stimuli, using two spot sizes, 4 and 0.4 deg. 2. At different wavelengths, different opponent cell classes in the parvocellular layers of the nucleus were most sensitive, so that at long wavelengths (greater than 600 nm) red on-centre cells were most sensitive, while at short wavelengths (less than 500 nm) S-cone, blue on-centre cells were most sensitive, from 500 to about 550 nm green on-centre cells being most sensitive. A rare cell type with inhibition from S-cones was most sensitive at about 570 nm, although its maximum contrast increment sensitivity was poor compared with that of other cell types. Variation in strength of cone opponency caused a considerable range in threshold in each of the opponent cell classes of the parvocellular layers. 3. On- and off-centre cells from the magnocellular layers were more sensitive than opponent cells to white and yellow spots (as is the case with achromatic gratings). 4. With different wavelengths and spot sizes, the most sensitive cells found approached (to within 0.1-0.3 log units) human psychophysical sensitivity, suggesting that the most sensitive cells available may underlie detection. 5. Measurements of psychophysical chromatic discrimination thresholds, both with nearly monochromatic spots and with spots of differing saturation (purity), support this hypothesis. When magnocellular cell sensitivity corresponded to psychophysical threshold, a suprathreshold stimulus, capable of activating opponent cells, was required for chromatic discrimination.

Crook, J M; Lee, B B; Tigwell, D A; Valberg, A

1987-01-01

170

Ab initio molecular dynamics simulations of threshold displacement energies in SrTiO3  

SciTech Connect

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

Liu, Bin [ORNL] [ORNL; Xiao, Haiyan [University of Tennessee, Knoxville (UTK)] [University of Tennessee, Knoxville (UTK); Zhang, Yanwen [ORNL] [ORNL; Aidhy, Dilpuneet S [ORNL] [ORNL; Weber, William J [ORNL] [ORNL

2013-01-01

171

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

PubMed

Ab initio molecular dynamics simulations have been carried out to study low energy recoil events in SrTiO3. The threshold displacement energies are shown to be strongly dependent on both the orientation and the corresponding atomic arrangement. The minimum threshold displacement energies are 13 eV for an O recoil along the <100> O-O chain, 25 eV for a Sr recoil along the <100> Sr-Sr chain and 38 eV for a Ti recoil along the <110> Ti-Ti chain. The weighted average threshold displacement energies along the primary crystallographic directions are 35.7, 53.5 and >64.9 eV for O, Sr and Ti, respectively. The interstitial configurations produced by the recoil events are <100> and <111> split interstitials for O and Sr, respectively, together with a Ti interstitial occupying a distorted bridge position between two Sr sites. It is found that the recoil events in SrTiO3 are partial-charge transfer assisted processes, and the partial-charge transfer plays an important role in these recoil events. PMID:24162447

Liu, B; Xiao, H Y; Zhang, Y; Aidhy, D S; Weber, W J

2013-12-01

172

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

173

Signal Detection Theory and Vestibular Perception: II. Fitting Perceptual Thresholds as a Function of Frequency  

PubMed Central

Vestibular perceptual thresholds are defined by a dynamic sensory system. To capture these dynamics, thresholds were previously fit as a function of frequency. In this paper, we compare fits using two published models with two new models. Furthermore, a new fitting method that utilizes vestibular perceptual dynamics is developed to improve fit quality and overcome problems associated with the conventional approach. Combinations of the four models and two fitting methods are tested using both simulated data and previously published experimental data. Simulations reveal that the conventional approach underestimates thresholds when the number of trials at each frequency is limited (circa 50); this underestimation is reduced fivefold by the new fitting method that simultaneously utilizes data across frequencies. The new fitting method also scored best for goodness of fit for both the simulations and experimental data. In fact, the new approach of fitting simultaneously across frequencies proved more accurate, more precise, more robust, and more efficient than the conventional approach of fitting the responses at each frequency individually and then fitting these threshold data across frequency. The revised fit of published yaw rotation threshold data show that these are best fit by a first-order high-pass filter having a plateau of 0.5°/s (roughly a factor of 4 higher than the motion platform vibration) at frequencies above the cut-off frequency of 0.26 Hz, which is well above the cut-off frequency of the semicircular canals (circa 0.03 Hz). This dynamic analysis suggests the contributions of a velocity leakage mechanism to human yaw rotation thresholds.

Lim, Koeun; Merfeld, Daniel M.

2012-01-01

174

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

PubMed

A Fabry-Perot interferometer fiber-optic hydrophone (FOH) was investigated for use as an acoustic cavitation detector and compared with a piezo-ceramic passive cavitation detector (PCD). Both detectors were used to measure negative pressure thresholds for broadband emissions in 3% agar and ex vivo bovine liver simultaneously. FOH-detected half- and fourth-harmonic emissions were also studied. Three thresholds were defined and investigated: (i) onset of cavitation; (ii) 100% probability of cavitation; and (iii) a time-integrated threshold where broadband signals integrated over a 3-s exposure duration, averaged over 5-10 repeat exposures, become statistically significantly greater than noise. The statistical sensitiviy of FOH broadband detection was low compared with that of the PCD (0.43/0.31 in agar/liver). FOH-detected fourth-harmonic data agreed best with PCD broadband (sensitivity: 0.95/0.94, specificity: 0.89/0.76 in agar/liver). The FOH has potential as a cavitation detector, particularly in applications where space is limited or during magnetic resonance-guided studies. PMID:24035410

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

2013-12-01

175

Effects of experimental configuration on the detection threshold of hysteretic elastic nonlinearity.  

PubMed

Nonlinear elastic signature of granular consolidated or damaged media is often very small and might easily fall within the noise level. Therefore, it is important to determine an excitation amplitude threshold above which nonlinear measurements start to be meaningful. In this paper, we analyze the way this threshold is influenced by some parameters of the experimental configuration, such as the receiver position, and of the data analysis, such as the considered reference amplitude. Furthermore, this contribution shows that extracting absolute values of the nonlinear parameters often requires the a priori knowledge of the resonance structure of the medium. PMID:24457031

Idjimarene, S; Bentahar, M; El Guerjouma, R; Scalerandi, M

2014-09-01

176

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

177

Threshold displacement and interstitial-atom formation energies in Ni sub 3 Al  

SciTech Connect

Threshold displacement energies for atomic displacements along {l angle}110{r angle}, {l angle}100{r angle} and {l angle}111{r angle} directions, and formation enthalpies of several symmetric interstitial atom configurations were calculated for Ni{sub 3}Al by computer simulation using embedded atom method'' potentials. The Ni-Ni(100) dumbbell in the plane containing only Ni atoms has the lowest interstitial-atom enthalpy although the enthalpies of other configurations are similar. Interstitial configurations involving Al atoms all have much higher enthalpies. The anisotropy of the threshold energies in Ni{sub 3}Al is similar to pure metals and no significant difference in threshold energy was observed for {l angle}110{r angle} replacement chains in rows containing all Ni atoms or alternating Ni-Al atoms. Various metastable interstitial atom configurations were observed, including crowd-ions. In addition, the spontaneous recombination volume for some configurations can be much smaller than in pure metals. The consequences of these results for radiation induced segregation and amorphization {ital are} {ital discussed}.

Caro, A.; Victoria, M. (Paul Scherrer Institute, CH-5232 Villingen (Switzerland)); Averback, R.S. (Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL (USA))

1990-07-01

178

Defining Ploidy-Specific Thresholds in Array Comparative Genomic Hybridization to Improve the Sensitivity of Detection of Single Copy Alterations in Cell Lines  

PubMed Central

Array comparative genomic hybridization (CGH) is being widely used to screen for recurrent genomic copy number alterations in neoplasms, with imbalances typically detected through the application of gain and loss thresholds. Review of array CGH publications for the year 2005 showed that a wide range of thresholds are used. However, the effect of sample ploidy on the sensitivity of these thresholds for single copy alterations (SCAs) has not been evaluated. Here, we describe a method to evaluate the detection accuracy of thresholds for detecting SCAs in cell line array CGH data. By applying a hidden Markov model-based method, we segmented array CGH data from well-karyotyped cell lines and generated ploidy-specific sensitivity-specificity plots, from which we identified optimum thresholds relevant to sample ploidy. We demonstrate that commonly used nonploidy-specific thresholds are suboptimal in their ability to call SCAs, particularly when applied to hypertriploid or tetraploid cell lines. We conclude that the use of ploidy-specific thresholds improves the sensitivity of thres-hold-based array CGH for detecting SCAs in cell lines. Because polyploidy is a common feature of cancer cells, the application of ploidy-specific thresholds to cell lines (and potentially to clinical samples) may improve the detection sensitivity of SCAs of biological significance.

Ng, Grace; Huang, Jingxiang; Roberts, Ian; Coleman, Nicholas

2006-01-01

179

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

PubMed Central

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

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

2013-01-01

180

Improved Double Threshold Detector for Spatially Distributed Target  

NASA Astrophysics Data System (ADS)

The double threshold detecting strategy is widely used for spatially distributed target detection in practical systems. However, the detector is limited in terms of robustness and effectiveness. In this paper, an improved double threshold detector is proposed that avoids these shortcomings. In the proposed detector, the energy in range cells that exceed the first threshold is accumulated and then the output of the accumulator is compared with the second threshold for detection. The threshold selection strategy is derived to guarantee the constant false-alarm rate (CFAR) property. A simulation shows that the proposed detector is superior to the conventional approach in terms of both robustness and effectiveness.

Long, Teng; Zheng, Le; Li, Yang; Yang, Xiaopeng

181

Double ionization of O2 via single photon at energy below double ionization threshold  

NASA Astrophysics Data System (ADS)

We studied the double ionization of O2 molecule at photon energies below the double ionization threshold (about 41.5 eV). At this energy the double ionization is a two-step process. A highly excited cation state is produced by the interaction of the neutral molecule with the photon. The cation autoionizes subsequently. We try to elucidate the dissociative intermediate states of this singly charged ion during this double ionization processes. Therefore we performed a kinematically complete experiment measuring the 3d-momentum vectors of two electrons and two oxygen ions in coincidence following the excitation of O2, dissociation of O2^+ and the subsequent autoionization of the excited neutral oxygen atom. We present the ionic kinetic energy release as a function of electron energies (energy maps), electron angular distributions in the body fixed frame and compare our results to previous time-resolved studies [A. Sandhu et al., Science, 322, 1081, (2008)].

Bocharova, I. A.; Stuck, C.; Schoeffler, M.; Belkacem, A.; Weber, Th.; Doerner, R.; Jahnke, T.; Landers, A.; Cocke, C. L.

2011-06-01

182

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

183

Hydration Energies of Zinc(II): Threshold Collision-Induced Dissociation Experiments and Theoretical Studies  

NASA Astrophysics Data System (ADS)

The first experimentally determined sequential bond dissociation energies of Zn2+(H2O)n complexes, where n = 6-10, are measured using threshold collision-induced dissociation in a guided ion beam tandem mass spectrometer coupled with an electrospray ionization source. Kinetic energy dependent cross sections are obtained and analyzed to yield 0 K threshold measurements for the loss of one and two water ligands after accounting for multiple collisions, kinetic shifts, and energy distributions. The threshold measurements are then converted from 0 to 298 K values to give the hydration energies for sequentially losing one water from each parent complex. Theoretical geometry optimizations and single-point energy calculations are performed using several levels of theory for comparison to experiment. Although different levels of theory disagree on the ground-state conformation of most complexes examined here leading to potential ambiguities in the final thermochemical values, calculations at the MP2(full) level provide the best agreement with experiment. On this basis, the present experiments are most consistent with the inner solvent shell of Zn2+ being five waters, except for Zn2+(H2O)6 where all waters bind directly to the metal ion. The charge separation process, Zn2+(H2O)n ? ZnOH+(H2O)m + H+(H2O)n-m-1, which is in competition with the loss of water from the parent complex, is also observed for n = 6-8. These processes are analyzed in detail in the following paper.

Cooper, Theresa E.; Carl, D. R.; Armentrout, P. B.

2009-11-01

184

Hydration energies of zinc(II): threshold collision-induced dissociation experiments and theoretical studies.  

PubMed

The first experimentally determined sequential bond dissociation energies of Zn(2+)(H(2)O)(n) complexes, where n = 6-10, are measured using threshold collision-induced dissociation in a guided ion beam tandem mass spectrometer coupled with an electrospray ionization source. Kinetic energy dependent cross sections are obtained and analyzed to yield 0 K threshold measurements for the loss of one and two water ligands after accounting for multiple collisions, kinetic shifts, and energy distributions. The threshold measurements are then converted from 0 to 298 K values to give the hydration energies for sequentially losing one water from each parent complex. Theoretical geometry optimizations and single-point energy calculations are performed using several levels of theory for comparison to experiment. Although different levels of theory disagree on the ground-state conformation of most complexes examined here leading to potential ambiguities in the final thermochemical values, calculations at the MP2(full) level provide the best agreement with experiment. On this basis, the present experiments are most consistent with the inner solvent shell of Zn(2+) being five waters, except for Zn(2+)(H(2)O)(6) where all waters bind directly to the metal ion. The charge separation process, Zn(2+)(H(2)O)(n) --> ZnOH(+)(H(2)O)(m) + H(+)(H(2)O)(n-m-1), which is in competition with the loss of water from the parent complex, is also observed for n = 6-8. These processes are analyzed in detail in the following paper. PMID:19904969

Cooper, Theresa E; Carl, D R; Armentrout, P B

2009-12-10

185

Automated threshold determination for a family of matched subspace filters for target detection in hyperspectral images  

Microsoft Academic Search

The detection of subpixel targets in hyperspectral images is complicated by interference arising from other background materials. This paper describes three target detection algorithms implemented in Data Fusion Corporation's HYPERTOOLS, a suite of hyperspectral image analysis tools. The matched subspace filter (MSF) is a generalized likelihood ratio test designed to detect target signatures while suppressing known interference signatures in a

Lewis Reynolds; Woody Kober

2005-01-01

186

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

187

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

188

Adaptive thresholding and dynamic windowing method for automatic centroid detection of digital Shack-Hartmann wavefront sensor  

SciTech Connect

A Shack-Hartmann wavefront sensor (SWHS) splits the incident wavefront into many subsections and transfers the distorted wavefront detection into the centroid measurement. The accuracy of the centroid measurement determines the accuracy of the SWHS. Many methods have been presented to improve the accuracy of the wavefront centroid measurement. However, most of these methods are discussed from the point of view of optics, based on the assumption that the spot intensity of the SHWS has a Gaussian distribution, which is not applicable to the digital SHWS. In this paper, we present a centroid measurement algorithm based on the adaptive thresholding and dynamic windowing method by utilizing image processing techniques for practical application of the digital SHWS in surface profile measurement. The method can detect the centroid of each focal spot precisely and robustly by eliminating the influence of various noises, such as diffraction of the digital SHWS, unevenness and instability of the light source, as well as deviation between the centroid of the focal spot and the center of the detection area. The experimental results demonstrate that the algorithm has better precision, repeatability, and stability compared with other commonly used centroid methods, such as the statistical averaging, thresholding, and windowing algorithms.

Yin Xiaoming; Li Xiang; Zhao Liping; Fang Zhongping

2009-11-10

189

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

PubMed

Contrast detection thresholds for moving sine wave gratings were obtained at the fovea and at eccentricities of 6 degrees, 21 degrees, and 50 degrees on the nasal horizontal meridian. The targets subtended from 30 X 30 minutes of arc up to 16 degrees X 16 degrees. Mean retinal illuminance was varied between 10 and 0.01 trolands. The transition from the de Vries-Rose to the Weber region occurs in the far peripheral visual field at a 2-3 decades lower illuminance level than at the fovea. The spatio-temporal contrast detection thresholds become comparable over the whole visual field if the mean distance between retinal ganglion cells is taken as a yardstick, and field width, spatial frequency, and quantum density are scaled accordingly. This means that at scotopic illuminance levels coarse or medium gratings are preferentially detected at other than foveal locations. (The fine gratings cannot be resolved at all at such levels.) It is argued that both electrophysiological and psychophysical evidence indicates that Weber behavior starts whenever some small fixed number of quantum absorptions occur within an area of 1 mean interganglion cell distance across. Or, equivalently, if a fixed small number of "neural quanta" enters a 100 X 100 micron2 area of the visual cortex. PMID:702225

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

1978-06-01

190

EEG amplitude spectra before near threshold visual presentations differentially predict detection/omission and short-long reaction time outcomes.  

PubMed

Performance in simple stimulus detection manifests as both probability of detection and speed of signaling detected stimuli. These two dimensions of performance across trials were examined with respect to brain states just prior to stimulus delivery, using near threshold stimuli targeting the magnocellular or the parvocellular visual streams in an attempt to isolate differential perceptual preparation. The EEG amplitude of 12 university students was analyzed in spectral bands from 2 to 50 Hz at 9 bilateral channel pairs in a window covering -450 ms to +50 ms relative to stimulus onset. A hierarchical statistical procedure was applied to control false positive results. EEG power in the 2, 4, 8 and 10 Hz bands was found significantly lower at the F7-F8 channel pair both before detected compared to omitted stimuli and before the fastest compared to slowest reaction time quartiles, with no stimulus type effect. In addition, the 22 and 24 Hz band activity was lower prior to better performance frontally (F3-F4, F7-F8) in reaction time but not in detection, while it was larger centro-parietally (CP1-CP2, P3-P4) in detection but not in reaction times. Spectral analysis thus shows stimulus detection and response speed to depend partly on common and partly on distinct pre-stimulus brain states. PMID:23747426

Achim, André; Bouchard, Julie; Braun, Claude M J

2013-07-01

191

Optimal energy thresholds and weights for separating materials using photon counting x-ray detectors with energy discriminating capabilities  

NASA Astrophysics Data System (ADS)

It is well known that decomposing an object into attenuation or material basis functions provides additional imaging benefits such as contrast enhancement or material subtraction. This can be accomplished with photon counting x-ray detectors (PCXDs) with energy discriminating capabilities, which enable us to count x-ray photons and classify them based on their energies. The richness of the information contained in these measurements can depend heavily on how these photons are binned together. In this paper, our goal is to identify a method that yields the optimal energy thresholds and/or weights for binning data from energy discriminating PCXDs. Additional energy information from these PCXDs allows us to use maximum-likelihood to estimate the amount of the basis materials penetrated by the beam. However, due to inherent quantum noise, these estimates are themselves noisy. We show that for PCXDs that discriminate between low and high energy photons, it is beneficial to have a gap between the thresholds. Photons with energies that fall into this gap should either be discarded or counted separately to improve material separability. Furthermore, if the PCXD can discern the energy of each photon, we show that when estimating the amount of each of two material basis functions, two appropriately weighted sums of the photon counts provide as much information as knowing the number of counts at each energy.

Wang, Adam S.; Pelc, Norbert J.

2009-02-01

192

The Edge Detection of Oil Spills Image Using Self-Adaptive Dynamic Block Threshold Algorithm Based on Non-Maximal Suppression  

Microsoft Academic Search

Edge detection technology of oil spills image on the sea is one of most key technologies to monitor oil spills on the sea. This paper presents a novel method to detect edge of oil spills image on the sea. The algorithm is composed of two parts: nonmaximal suppression realizes candidate edge detection of oil spills image, self-adaptive dynamic block threshold

Yu Jing; Jubai An; Li Li

2009-01-01

193

Threshold photoelectron studies of isoxazole over the energy range 9.9-30 eV  

NASA Astrophysics Data System (ADS)

The threshold photoelectron spectrum of the isoxazole molecule, C 3H 3NO has been measured over the photon energy range 9.9-30 eV with the use of synchrotron radiation. In the 9.9-10.8 eV range, corresponding to photoionization from the highest occupied molecular orbital 3a?(? 3), seven well resolved vibrational series have been observed and their modes are tentatively assigned. A strong adiabatic ionization, with an energy of 11.132 ± 0.003 eV corresponding to the 2a?(? 2) band, has also been observed. This is followed by a single vibrational series of the ?C-H stretching mode. Photoelectron bands in the energy region 13-30 eV have also been identified, some for the first time.

Dampc, Marcin; Mielewska, Brygida; Siggel-King, Michele R. F.; King, George C.; Sivaraman, Bhalamurugan; Ptasi?ska, Sylwia; Mason, Nigel; Zubek, Mariusz

2010-02-01

194

Construction of energy-independent potentials above inelastic thresholds in quantum field theories  

NASA Astrophysics Data System (ADS)

We construct energy-independent but nonlocal potentials above inelastic thresholds, in terms of Nambu-Bethe-Salpeter wave functions defined in quantum field theories such as QCD. As an explicit example, we consider NN?NN+n? scattering processes for n=0,1,2,…. We show the existence of energy-independent coupled channel potentials with a nonrelativistic approximation, where momenta of all particles are small compared with their own masses. In the case of two-body inelastic scatterings such as ?????, N?, ??, on the other hand, we show that energy-independent potentials can be constructed without relying on nonrelativistic approximations. We also propose a method to extract these potentials using time dependence of general correlation functions.

Aoki, Sinya; Charron, Bruno; Doi, Takumi; Hatsuda, Tetsuo; Inoue, Takashi; Ishii, Noriyoshi

2013-02-01

195

In vivo transcranial cavitation threshold detection during ultrasound-induced blood-brain barrier opening in mice  

PubMed Central

The in vivo cavitation response associated with blood–brain barrier (BBB) opening as induced by transcranial focused ultrasound (FUS) in conjunction with microbubbles was studied in order to better identify the underlying mechanism in its noninvasive application. A cylindrically focused hydrophone, confocal with the FUS transducer, was used as a passive cavitation detector (PCD) to identify the threshold of inertial cavitation (IC) in the presence of Definity® microbubbles (mean diameter range: 1.1–3.3 ?m, Lantheus Medical Imaging, MA, USA). A vessel phantom was first used to determine the reliability of the PCD prior to in vivo use. A cerebral blood vessel was simulated by generating a cylindrical channel of 610 ?m in diameter inside a polyacrylamide gel and by saturating its volume with microbubbles. The microbubbles were sonicated through an excised mouse skull. Second, the same PCD setup was employed for in vivo noninvasive (i.e. transdermal and transcranial) cavitation detection during BBB opening. After the intravenous administration of Definity® microbubbles, pulsed FUS was applied (frequency: 1.525 or 1.5 MHz, peak-rarefactional pressure: 0.15–0.60 MPa, duty cycle: 20%, PRF: 10 Hz, duration: 1 min with a 30 s interval) to the right hippocampus of twenty-six (n = 26) mice in vivo through intact scalp and skull. T1 and T2-weighted MR images were used to verify the BBB opening. A spectrogram was generated at each pressure in order to detect the IC onset and duration. The threshold of BBB opening was found to be at a 0.30 MPa peak-rarefactional pressure in vivo. Both the phantom and in vivo studies indicated that the IC pressure threshold had a peak-rarefactional amplitude of 0.45 MPa. This indicated that BBB opening may not require IC at or near the threshold. Histological analysis showed that BBB opening could be induced without any cellular damage at 0.30 and 0.45 MPa. In conclusion, the cavitation response could be detected without craniotomy in mice and IC may not be required for BBB opening at relatively low pressures.

Tung, Yao-Sheng; Vlachos, Fotios; Choi, James J; Deffieux, Thomas; Selert, Kirsten; Konofagou, Elisa E

2014-01-01

196

In vivo transcranial cavitation threshold detection during ultrasound-induced blood-brain barrier opening in mice  

NASA Astrophysics Data System (ADS)

The in vivo cavitation response associated with blood-brain barrier (BBB) opening as induced by transcranial focused ultrasound (FUS) in conjunction with microbubbles was studied in order to better identify the underlying mechanism in its noninvasive application. A cylindrically focused hydrophone, confocal with the FUS transducer, was used as a passive cavitation detector (PCD) to identify the threshold of inertial cavitation (IC) in the presence of Definity® microbubbles (mean diameter range: 1.1-3.3 µm, Lantheus Medical Imaging, MA, USA). A vessel phantom was first used to determine the reliability of the PCD prior to in vivo use. A cerebral blood vessel was simulated by generating a cylindrical channel of 610 µm in diameter inside a polyacrylamide gel and by saturating its volume with microbubbles. The microbubbles were sonicated through an excised mouse skull. Second, the same PCD setup was employed for in vivo noninvasive (i.e. transdermal and transcranial) cavitation detection during BBB opening. After the intravenous administration of Definity® microbubbles, pulsed FUS was applied (frequency: 1.525 or 1.5 MHz, peak-rarefactional pressure: 0.15-0.60 MPa, duty cycle: 20%, PRF: 10 Hz, duration: 1 min with a 30 s interval) to the right hippocampus of twenty-six (n = 26) mice in vivo through intact scalp and skull. T1 and T2-weighted MR images were used to verify the BBB opening. A spectrogram was generated at each pressure in order to detect the IC onset and duration. The threshold of BBB opening was found to be at a 0.30 MPa peak-rarefactional pressure in vivo. Both the phantom and in vivo studies indicated that the IC pressure threshold had a peak-rarefactional amplitude of 0.45 MPa. This indicated that BBB opening may not require IC at or near the threshold. Histological analysis showed that BBB opening could be induced without any cellular damage at 0.30 and 0.45 MPa. In conclusion, the cavitation response could be detected without craniotomy in mice and IC may not be required for BBB opening at relatively low pressures.

Tung, Yao-Sheng; Vlachos, Fotios; Choi, James J.; Deffieux, Thomas; Selert, Kirsten; Konofagou, Elisa E.

2010-10-01

197

Determination of simple thresholds for accelerometry-based parameters for fall detection  

Microsoft Academic Search

The increasing population of elderly people is mainly living in a home-dwelling environment and needs applications to support their independency and safety. Falls are one of the major health risks that affect the quality of life among older adults. Body attached accelerometers have been used to detect falls. The placement of the accelerometric sensor as well as the fall detection

Maarit Kangas; Antti Konttila; Ilkka Winblad; Timo Jämsä

2007-01-01

198

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

199

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.

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

2012-01-01

200

Energy dependence of the pp->K{sup +}nSIGMA{sup +} reaction close to threshold  

SciTech Connect

Production of the SIGMA{sup +} hyperon through the pp->K{sup +}nSIGMA{sup +} reaction has been investigated at four energies close to threshold, 1.826,1.920,1.958, and 2.020 GeV. At low energies, correlated K{sup +}pi{sup +} pairs can only originate from SIGMA{sup +} production so their measurement allows the total cross section for the reaction to be determined. The results obtained are completely consistent with the values extracted from the study of the K{sup +}-proton correlation spectra obtained in the same experiment. These spectra, as well as the inclusive K{sup +} momentum distributions, also provide conservative upper limits on SIGMA{sup +} production rates. The measurements show a SIGMA{sup +} production cross section that varies roughly like phase space, and, in particular, none of the three experimental approaches used supports the anomalously high, near-threshold pp->K{sup +}nSIGMA{sup +} total cross section previously reported [T. Rozek et al., Phys. Lett. B 643, 251 (2006)].

Valdau, Yu.; Mikirtychiants, S. [High Energy Physics Department, Petersburg Nuclear Physics Institute, RU-188350 Gatchina (Russian Federation); Institut fuer Kernphysik and Juelich Centre for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); Barsov, S.; Dzyuba, A.; Koptev, V. [High Energy Physics Department, Petersburg Nuclear Physics Institute, RU-188350 Gatchina (Russian Federation); Buescher, M.; Hartmann, M.; Kacharava, A.; Nekipelov, M.; Ohm, H.; Rathmann, F.; Stroeher, H. [Institut fuer Kernphysik and Juelich Centre for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); Chiladze, D. [Institut fuer Kernphysik and Juelich Centre for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); High Energy Physics Institute, Tbilisi State University, 0186 Tbilisi, Georgia (United States); Dymov, S. [Physikalisches Institut II, Universitaet Erlangen-Nuernberg, D-91058 Erlangen (Germany); Laboratory of Nuclear Problems, JINR, RU-141980 Dubna (Russian Federation); Keshelashvili, I. [High Energy Physics Institute, Tbilisi State University, 0186 Tbilisi, Georgia (United States); Physics Department, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Khoukaz, A.; Mielke, M.; Papenbrock, M. [Institut fuer Kernphysik, Universitaet Muenster, D-48149 Muenster (Germany); Kulessa, P. [H. Niewodniczanski Institute of Nuclear Physics PAN, PL-31342 Cracow (Poland); Merzliakov, S. [Institut fuer Kernphysik and Juelich Centre for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); Laboratory of Nuclear Problems, JINR, RU-141980 Dubna (Russian Federation)

2010-04-15

201

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

202

Novel Approach for Sub-Threshold Detection and Prevention of Laser Injury in Ocular Tissue.  

National Technical Information Service (NTIS)

Aim I. Development of a novel fluorescence imaging technique, for in vivo detection of retinal pigment epithelium lesions following exposure to laser radiation. We acquired a new custom-built multi wavelength scanning laser ophthalmoscope (SLO) for multi ...

F. Van Kuijk M. Motamedi

2009-01-01

203

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

204

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

SciTech Connect

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

Feng Zhaoqing; Jin Genming [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2010-11-15

205

Maximum approximate entropy and r threshold: A new approach for regularity changes detection  

NASA Astrophysics Data System (ADS)

Approximate entropy (ApEn) has been widely used as an estimator of regularity in many scientific fields. It has proved to be a useful tool because of its ability to distinguish different system’s dynamics when there is only available short-length noisy data. Incorrect parameter selection (embedding dimension m, threshold r and data length N) and the presence of noise in the signal can undermine the ApEn discrimination capacity. In this work we show that rmax (ApEn(m,rmax,N)=ApEnmax) can also be used as a feature to discern between dynamics. Moreover, the combined use of ApEnmax and rmax allows a better discrimination capacity to be accomplished, even in the presence of noise. We conducted our studies using real physiological time series and simulated signals corresponding to both low- and high-dimensional systems. When ApEnmax is incapable of discerning between different dynamics because of the noise presence, our results suggest that rmax provides additional information that can be useful for classification purposes. Based on cross-validation tests, we conclude that, for short length noisy signals, the joint use of ApEnmax and rmax can significantly decrease the misclassification rate of a linear classifier in comparison with their isolated use.

Restrepo, Juan F.; Schlotthauer, Gastón; Torres, María E.

2014-09-01

206

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

PubMed

Interpretation of DNA evidence depends upon the ability of the analyst to accurately compare the DNA profile obtained from an item of evidence and the DNA profile of a standard. This interpretation becomes progressively more difficult as the number of 'drop-out' and 'drop-in' events increase. Analytical thresholds (AT) are typically selected to ensure the false detection of noise is minimized. However, there exists a tradeoff between the erroneous labeling of noise as alleles and the false non-detection of alleles (i.e. drop-out). In this study, the effect ATs had on both types of error was characterized. Various ATs were tested, where three relied upon the analysis of baseline signals obtained from 31 negative samples. The fourth AT was determined by utilizing the relationship between RFU signal and DNA input. The other ATs were the commonly employed 50, 150 and 200 RFU thresholds. Receiver Operating Characteristic (ROC) plots showed that although high ATs completely negated the false labeling of noise, DNA analyzed with ATs derived using analysis of the baseline signal exhibited the lowest rates of drop-out and the lowest total error rates. In another experiment, the effect small changes in ATs had on drop-out was examined. This study showed that as the AT increased from ?10 to 60 RFU, the number of heterozygous loci exhibiting the loss of one allele increased. Between ATs of 60 and 150 RFU, the frequency of allelic drop-out remained constant at 0.27 (±0.02) and began to decrease when ATs of 150 RFU or greater were utilized. In contrast, the frequency of heterozygous loci exhibiting the loss of both alleles consistently increased with AT. In summary, for samples amplified with less than 0.5ng of DNA, ATs derived from baseline analysis of negatives were shown to decrease the frequency of drop-out by a factor of 100 without significantly increasing rates of erroneous noise detection. PMID:22796031

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

2012-12-01

207

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

208

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.

Macias, Miguel Macias; Manso, Antonio Garcia; Orellana, Carlos Javier Garcia; Velasco, Horacio Manuel Gonzalez; Caballero, Ramon Gallardo; Chamizo, Juan Carlos Peguero

2013-01-01

209

Apriori-LLR-Threshold-Assisted K-Best Sphere Detection for MIMO Channels  

Microsoft Academic Search

When the maximum number of best candidates retained at each tree search level of the K-Best Sphere Detection (SD) is kept low for the sake of maintaining a low memory requirement and computational complexity, the SD may result in a considerable performance degradation in comparison to the full-search based Maximum Likelihood (ML) detector. In order to circumvent this problem, in

Li Wang; Lei Xu; Sheng Chen; Lajos Hanzo

2008-01-01

210

Threshold-based intrusion detection in ad hoc networks and secure AODV  

Microsoft Academic Search

Mobile ad hoc networks (MANETs) play an important role in connecting devices in pervasive environments. MANETs provide inexpensive and versatile communication, yet several challenges remain in addressing their security. So far, numerous schemes have been proposed for secure routing and intrusion detection, with only simulations to validate them; little work exists, in implementing such schemes on small handheld devices. In

Anand Patwardhan; Jim Parker; Michaela Iorga; Anupam Joshi; Tom Karygiannis; Yelena Yesha

2008-01-01

211

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. Larzillière

1999-01-01

212

Continuation-based numerical detection of after-depolarization and spike-adding thresholds.  

PubMed

The changes in neuronal firing pattern are signatures of brain function, and it is of interest to understand how such changes evolve as a function of neuronal biophysical properties. We address this important problem by the analysis and numerical investigation of a class of mechanistic mathematical models. We focus on a hippocampal pyramidal neuron model and study the occurrence of bursting related to the after-depolarization (ADP) that follows a brief current injection. This type of burst is a transient phenomenon that is not amenable to the classical bifurcation analysis done, for example, for periodic bursting oscillators. In this letter, we show how to formulate such transient behavior as a two-point boundary value problem (2PBVP), which can be solved using well-known continuation methods. The 2PBVP is formulated such that the transient response is represented by a finite orbit segment for which onsets of ADP and additional spikes in a burst can be detected as bifurcations during a one-parameter continuation. This in turn provides us with a direct method to approximate the boundaries of regions in a two-parameter plane where certain model behavior of interest occurs. More precisely, we use two-parameter continuation of the detected onset points to identify the boundaries between regions with and without ADP and bursts with different numbers of spikes. Our 2PBVP formulation is a novel approach to parameter sensitivity analysis that can be applied to a wide range of problems. PMID:23339609

Nowacki, Jakub; Osinga, Hinke M; Tsaneva-Atanasova, Krasimira T

2013-04-01

213

A differentially amplified motion in the ear for near-threshold sound detection  

PubMed Central

The ear is a remarkably sensitive pressure fluctuation detector. In guinea pigs, behavioral measurements indicate a minimum detectable sound pressure of ~20 ?Pa at 16 kHz. Such faint sounds produce 0.1 nm basilar membrane displacements, a distance smaller than conformational transitions in ion channels. It seems that noise within the auditory system would swamp such tiny motions, making weak sounds imperceptible. Here, a new mechanism contributing to a resolution of this problem is proposed and validated through direct measurement. We hypothesize that vibration at the apical end of hair cells is enhanced compared to the commonly measured basilar membrane side. Using in vivo optical coherence tomography, we demonstrated that apical-side vibrations peak at a higher frequency, had different timing, and were enhanced compared to the basilar membrane. These effects depend nonlinearly on the stimulus level. The timing difference and enhancement are important for explaining how the noise problem is circumvented.

Chen, Fangyi; Zha, Dingjun; Fridberger, Anders; Zheng, Jiefu; Choudhury, Niloy; Jacques, Steven L.; Wang, Ruikang K.; Shi, Xiaorui; Nuttall, Alfred L.

2011-01-01

214

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

215

Measurement of Inclusive Radiative B-Meson Decays with a Photon Energy Threshold of 1.7 GeV  

NASA Astrophysics Data System (ADS)

Using 605fb-1 of data collected at the ?(4S) resonance we present a measurement of the inclusive radiative B-meson decay channel, B?Xs?. For the lower photon energy thresholds of 1.7, 1.8, 1.9, and 2.0 GeV, as defined in the rest frame of the B meson, we measure the partial branching fraction and the mean and variance of the photon energy spectrum. At the 1.7 GeV threshold we obtain the partial branching fraction BF(B?Xs?)=(3.45±0.15±0.40)×10-4, where the errors are statistical and systematic.

Limosani, A.; Aihara, H.; Arinstein, K.; Aushev, T.; Bakich, A. M.; Balagura, V.; Barberio, E.; Bay, A.; Belous, K.; Bischofberger, M.; Bondar, A.; Bozek, A.; Bra?ko, M.; Browder, T. E.; Chang, P.; Chao, Y.; Chen, A.; Cheon, B. G.; Choi, Y.; Dalseno, J.; Danilov, M.; Drutskoy, A.; Dungel, W.; Eidelman, S.; Goldenzweig, P.; Golob, B.; Ha, H.; Hayashii, H.; Hoshi, Y.; Hou, W.-S.; Hyun, H. J.; Inami, K.; Itoh, R.; Iwasaki, Y.; Julius, T.; Kah, D. H.; Kim, H. O.; Kim, S. K.; Kim, Y. I.; Kim, Y. J.; Kinoshita, K.; Ko, B. R.; Korpar, S.; Kreps, M.; Križan, P.; Krokovny, P.; Kuhr, T.; Kumar, R.; Kwon, Y.-J.; Kyeong, S.-H.; Lesiak, T.; Li, J.; Liu, C.; Liventsev, D.; Louvot, R.; Matyja, A.; Miyabayashi, K.; Miyata, H.; Miyazaki, Y.; Mizuk, R.; Mori, T.; Nakao, M.; Nakazawa, H.; Nishida, S.; Nishimura, K.; Nitoh, O.; Nozaki, T.; Ogawa, S.; Ohshima, T.; Okuno, S.; Ozaki, H.; Pakhlova, G.; Park, C. W.; Park, H.; Piilonen, L. E.; Rozanska, M.; Sahoo, H.; Sakai, Y.; Schneider, O.; Schümann, J.; Schwanda, C.; Schwartz, A. J.; Senyo, K.; Sevior, M. E.; Shapkin, M.; Shebalin, V.; Shen, C. P.; Shiu, J.-G.; Singh, J. B.; Stani?, S.; Stari?, M.; Sumisawa, K.; Sumiyoshi, T.; Suzuki, S.; Taylor, G. N.; Teramoto, Y.; Trabelsi, K.; Tsuboyama, T.; Uehara, S.; Unno, Y.; Uno, S.; Urquijo, P.; Ushiroda, Y.; Varner, G.; Varvell, K. E.; Vervink, K.; Wang, C. H.; Wang, M.-Z.; Wang, P.; Watanabe, Y.; Wedd, R.; Wicht, J.; Won, E.; Yabsley, B. D.; Yamamoto, H.; Yamashita, Y.; Zhang, Z. P.; Zivko, T.; Zupanc, A.

2009-12-01

216

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

217

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 108±7 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

218

Local energy pattern for texture classification using self-adaptive quantization thresholds.  

PubMed

Local energy pattern, a statistical histogram-based representation, is proposed for texture classification. First, we use normalized local-oriented energies to generate local feature vectors, which describe the local structures distinctively and are less sensitive to imaging conditions. Then, each local feature vector is quantized by self-adaptive quantization thresholds determined in the learning stage using histogram specification, and the quantized local feature vector is transformed to a number by N-nary coding, which helps to preserve more structure information during vector quantization. Finally, the frequency histogram is used as the representation feature. The performance is benchmarked by material categorization on KTH-TIPS and KTH-TIPS2-a databases. Our method is compared with typical statistical approaches, such as basic image features, local binary pattern (LBP), local ternary pattern, completed LBP, Weber local descriptor, and VZ algorithms (VZ-MR8 and VZ-Joint). The results show that our method is superior to other methods on the KTH-TIPS2-a database, and achieving competitive performance on the KTH-TIPS database. Furthermore, we extend the representation from static image to dynamic texture, and achieve favorable recognition results on the University of California at Los Angeles (UCLA) dynamic texture database. PMID:22910113

Zhang, Jun; Liang, Jimin; Zhao, Heng

2013-01-01

219

Potential energy threshold of surface erosion on GaN by impact of slow highly charged heavy ions  

NASA Astrophysics Data System (ADS)

In the present work the erosion behavior on the surface of GaN epi-layer by the impact of various slow highly charged heavy ions (SHCIs, including Ar q+, Xe q+ and Pb q+, in two incidence geometries) was investigated. Atomic force microscopy reveals a well-defined threshold of potential energy carried by the incident heavy ions accounting for the surface erosion. This threshold also depends on the projected range of the SHCIs, the longer the projected range, the higher the potential energy required for the onset of surface erosion. And the etched depth is close to a linear function of potential energy deposited, increasing with the potential energy increases. Moreover, the etching rate for 60° off normal incidence is by more than a factor of 2 larger than etching rate for normal incidence, and the etch rate by Xe q+ is larger than by Pb q+ under the same potential energy and incident direction. And a mechanism is discussed.

Zhang, L. Q.; Zhang, C. H.; Yang, Y. T.; Han, L. H.; Li, B. S.; Song, S. J.; Sun, Y. M.; Jin, Y. F.

2011-02-01

220

Variable-Threshold Threshold Elements.  

National Technical Information Service (NTIS)

A threshold element is a mathematical model of certain types of logic gates and of a biological neuron. Much work has been done on the subject of threshold elements with fixed thresholds; this study concerns itself with elements in which the threshold may...

W. S. Meisel

1967-01-01

221

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

222

Thresholds for igniting exothermic reactions in Al/Ni multilayers using pulses of electrical, mechanical, and thermal energy  

NASA Astrophysics Data System (ADS)

We use pulses of electrical, mechanical, and thermal energy to determine the ignition thresholds of self-propagating reactions in Al/(Ni-7 V) and Al/Inconel multilayers. The energy density and power density required to initiate reactions in a Al/(Ni-7 V) foil with a 50 nm bilayer is compared for all three techniques to demonstrate the importance of heat loss on ignition thresholds and its dependence on the test volume and the surrounding thermal resistance. In addition, ignition is shown to occur at temperatures as low as 232 °C when heat losses are very small suggesting that ignition can be controlled by atomic mixing in the solid state. The experiments demonstrate that the ignition threshold drops with increasing ignition volume, and it rises with increasing bilayer spacing and with increasing intermixed thickness. These trends are also supported by an analytical model we derive to predict the effects of ignition volume, multilayer microstructure, and physical properties on the ignition threshold. We calculate an activation energy of 77.3 +/- 1.3 kJ/mol for solid state mixing based on measured ignition temperatures.

Fritz, Gregory M.; Spey, Stephen J.; Grapes, Michael D.; Weihs, Timothy P.

2013-01-01

223

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

224

A comparative analysis of a fixed thresholding vs. a classification tree approach for operational burn scar detection and mapping  

NASA Astrophysics Data System (ADS)

The scope of this paper is to demonstrate, evaluate and compare two burn scar mapping (BSM) approaches developed and applied operationally in the framework of the RISK-EOS service element project within the Global Monitoring for Environment and Security (GMES) program funded by ESA ( http://www.risk-eos.com). The first method is the BSM_NOA, a fixed thresholding method using a set of specifically designed and combined image enhancements, whilst the second one is the BSM_ITF, a decision tree classification approach based on a wide range of biophysical parameters. The two methods were deployed and compared in the framework of operational mapping conditions set by RISK-EOS standards, based either on sets of uni- or multi-temporal satellite images acquired by Landsat 5 TM and SPOT 4 HRV. The evaluation of the performance of the two methods showed that either in uni- or multi-temporal acquisition mode, the two methods reach high detection capability rates ranging from 80% to 91%. At the same time, the minimum burnt area detected was of 0.9-1.0 ha, despite the coarser spatial resolution of Landsat 5 TM sensor. Among the advantages of the satellite-based approaches compared to conventional burn scar mapping, are cost-efficiency, repeatability, flexibility, and high spatial and thematic accuracy from local to country level. Following the catastrophic fire season of 2007, burn scar maps were generated using BSM_NOA for the entirety of Greece and BSM_ITF for south France in the framework of the RISK-EOS/GMES Services Element project.

Kontoes, C. C.; Poilvé, H.; Florsch, G.; Keramitsoglou, I.; Paralikidis, S.

2009-10-01

225

Threshold Photoionization Spectroscopy with Heavy Rydberg States  

NASA Astrophysics Data System (ADS)

We have shown that it is possible to excite and detect Rydberg-like states just below the threshold for dissociation into ion pairs in a molecule. (J.D.D. Martin and J.W. Hepburn, Phys. Rev. Lett. 79 , 3154 (1997)) This type of threshold spectroscopy, called TIPPS for threshold ion-pair production spectroscopy, can be used to determine dissociation energies to very high accuracy (<1cm-1) and to record the spectra of fragment ions. In this talk some of the applications of TIPPS will be discussed, including a recent determination of the Born-Oppenheimer breakdown in HCl and HF.

Hepburn, John W.

2002-05-01

226

Dual energy computed tomography for explosive detection  

Microsoft Academic Search

Single energy computed tomography (CT) scanners use measurements of densities to detect explosives in luggage. It is desirable to apply dual energy techniques to these CT scanners to obtain atomic number measurements to reduce false alarm rates. However, the direct application of existing dual energy techniques has practical problems, such as, approximation errors and lack of boundary constraints in dual

Zhengrong Ying; Ram Naidu; Carl R. Crawford

2006-01-01

227

Threshold collision-induced dissociation: A guided ion beam study of energy transfer dynamics, lifetime effects, and applications  

NASA Astrophysics Data System (ADS)

A guided ion beam tandem mass spectrometer (GIB-TMS) instrument is used to study the dynamics and kinetics of collision induced dissociation (CID) processes in the threshold energy region. The dynamics of CID in the threshold energy region is investigated through integral and differential cross section measurements on the sequential dissociation of the Cr(CO)6+ system. The implementation of the method of measuring differential cross sections on this instrument is presented in detail. Energy transfer dynamics is discussed on the basis of differential cross section data. Experimental deposited energy distributions are compared to the predictions of the modified line-of-centers model used in modeling the kinetic energy dependence of CID. The kinetic shift effects encountered in the CID of C6H 4C12+ and n-C4H9C 6H5+ with Xe are investigated. Ab initio calculations are performed in order to complement the available information about the potential energy surfaces of these systems. CID threshold values are obtained by modeling the energy dependence of integral cross sections and accounting for kinetic and competitive shifts by using the RRKM theory. The selection of parameters used for calculation of dissociation rates by RRKM theory is discussed by comparing the energy dependence of the calculated rates with experimental data from literature. The energy dependencies of CID integral cross sections of the [OCS:C 2H2]+ system are analyzed using the present modeling procedures that account for kinetic and competitive shifts. The potential energy surface of the system is characterized in great detail by CID experiments with Xe and Ar, and by ab initio calculations.

Muntean, Felician

228

Sequential Distributed Detection in Energy-Constrained Wireless Sensor Networks  

NASA Astrophysics Data System (ADS)

The recently proposed sequential distributed detector based on level-triggered sampling operates as simple as the decision fusion techniques and at the same time performs as well as the data fusion techniques. Hence, it is well suited for resource-constrained wireless sensor networks. However, in practical cases where sensors observe discrete-time signals, the random overshoot above or below the sampling thresholds considerably degrades the performance of the considered detector. We propose, for systems with stringent energy constraints, a novel approach to tackle this problem by encoding the overshoot into the time delay between the sampling time and the transmission time. Specifically, each sensor computes the local log-likelihood ratio (LLR) and samples it using level-triggered sampling. Then, it transmits a single pulse to the fusion center (FC) after a transmission delay that is proportional to the overshoot, as in pulse position modulation (PPM). The FC, upon receiving a bit decodes the corresponding overshoot and recovers the transmitted LLR value. It then updates the approximate global LLR and compares it with two threshold to either make a decision or to continue the sequential process. We analyze the asymptotic average detection delay performance of the proposed scheme. We then apply the proposed sequential scheme to target detection in wireless sensor networks under the four Swerling fluctuating target models. It is seen that the proposed sequential distributed detector offers significant performance advantage over conventional decision fusion techniques.

Yilmaz, Yasin; Wang, Xiaodong

2014-06-01

229

Threshold collision-induced dissociation and theoretical studies of hydrated Fe(II): binding energies and Coulombic barrier heights.  

PubMed

The first experimentally determined bond dissociation energies for losing water from Fe(2+)(H(2)O)(n) complexes, n = 4-11, are measured using threshold collision-induced dissociation (TCID) in a guided ion beam tandem mass spectrometer coupled to an electrospray ionization source that forms thermalized complexes. In this technique, absolute cross-sections for dissociation induced by collisions with Xe at systematically varied kinetic energies are obtained. After accounting for multiple collisions, kinetic shifts, and energy distributions, these cross-sections are analyzed to yield the energy thresholds for losing one, two, or three water ligands at 0 K. The 0 K threshold measurements are converted to 298 K values to give the hydration enthalpies and free energies for sequentially losing water ligands from each complex. Comparisons to previous results for hydration of Zn(2+) indicate that the bond energies are dominated by electrostatic interactions, with no obvious variations associated with the open shell of Fe(2+). Theoretical geometry optimizations and single-point energy calculations are performed using several levels of theory for comparison to experiment, with generally good agreement. In addition to water loss channels, the charge separation process generating hydrated FeOH(+) and protons is observed for multiple reactant complexes. Energies of the rate-limiting transition states are calculated at several levels of theory with density functional approaches (B3LYP and B3P86) disagreeing with MP2(full) results. Comparisons to our kinetic energy dependent cross-sections suggest that the energetics of the MP2(full) level are most accurate. PMID:22812673

Hofstetter, Theresa E; Armentrout, P B

2013-02-14

230

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.

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

2014-01-01

231

Adaptive Local Thresholding by Verification-Based Multithreshold Probing with Application to Vessel Detection in Retinal Images  

Microsoft Academic Search

In this paper, we propose a general framework of adaptive local thresholding based on a verification-based multithreshold probing scheme. Object hypotheses are generated by binarization using hypothetic thresholds and accepted\\/rejected by a verification procedure. The application-dependent verification procedure can be designed to fully utilize all relevant informations about the objects of interest. In this sense, our approach is regarded as

Xiaoyi Jiang; Daniel Mojon

2003-01-01

232

Tunnel effect wave energy detection  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

233

Measurement of Inclusive Radiative B-Meson Decays with a Photon Energy Threshold of 1.7 GeV  

SciTech Connect

Using 605 fb{sup -1} of data collected at the UPSILON(4S) resonance we present a measurement of the inclusive radiative B-meson decay channel, B->X{sub s}gamma. For the lower photon energy thresholds of 1.7, 1.8, 1.9, and 2.0 GeV, as defined in the rest frame of the B meson, we measure the partial branching fraction and the mean and variance of the photon energy spectrum. At the 1.7 GeV threshold we obtain the partial branching fraction BF(B->X{sub s}gamma)=(3.45+-0.15+-0.40)x10{sup -4}, where the errors are statistical and systematic.

Limosani, A.; Barberio, E.; Julius, T.; Sevior, M. E.; Taylor, G. N.; Urquijo, P.; Wedd, R. [University of Melbourne, School of Physics, Victoria 3010 (Australia); Aihara, H. [Department of Physics, University of Tokyo, Tokyo (Japan); Arinstein, K.; Bondar, A.; Eidelman, S.; Shebalin, V. [Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation); Novosibirsk State University, Novosibirsk (Russian Federation); Aushev, T. [Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne (Switzerland); Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Bakich, A. M.; Varvell, K. E.; Yabsley, B. D. [University of Sydney, Sydney, New South Wales (Australia); Balagura, V.; Danilov, M.; Liventsev, D.; Mizuk, R. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation)

2009-12-11

234

A new trigger provides a lower energy threshold for the MAGIC Cherenkov telescope  

Microsoft Academic Search

We have designed and implemented a new trigger concept (hereafter called sumtrigger) for Cherenkov telescopes, which allowed us to lower the trigger threshold of the MAGIC telescope by a factor of two to 25 GeV. For the new trigger, we subdivided the camera in 24 overlapping patches, each patch consisting of 18 pixels. In each patch the clipped analog signals

M. Rissi; N. Otte; T. Schweizer; M. Shayduk

2008-01-01

235

Effect of a finite-energy spread of the positron beam on the threshold behavior of the positron annihilation cross section  

SciTech Connect

In a recent paper [Phys. Rev. Lett. 88, 163202 (2002)] we established the threshold behavior of the cross section of positron-atom annihilation into two {gamma} quanta near the positronium (Ps)-formation threshold. Here, the near-threshold behavior of the positron 3{gamma} annihilation cross section and its relation to the ortho-Ps-formation cross section are determined. We also analyze the feasibility of observing these effects by examining the effect of the finite-energy resolution of a positron beam on the threshold behavior.

Ludlow, J.; Gribakin, G.F. [Department of Applied Mathematics and Theoretical Physics, Queen's University, Belfast BT7 1NN, Northern Ireland (United Kingdom)

2002-12-01

236

Application of supervised range-constrained thresholding to extract lung pleura for automated detection of pleural thickenings from thoracic CT images  

NASA Astrophysics Data System (ADS)

We develop an image analysis system to automatically detect pleural thickenings and assess their characteristic values from patients' thoracic spiral CT images. Algorithms are described to carry out the segmentation of pleural contours and to find the pleural thickenings. The method of thresholding was selected as the technique to separate lung's tissue from other. Instead thresholding based only on empirical considerations, the so-called "supervised range-constrained thresholding" is applied. The automatic detection of pleural thickenings is carried out based on the examination of its concavity and on the characteristic Hounsfield unit of tumorous tissue. After detection of pleural thickenings, in order to assess their growth rate, a spline-based interpolation technique is used to create a model of healthy pleura. Based on this healthy model, the size of the pleural thickenings is calculated. In conjunction with the spatio-temporal matching of CT images acquired at different times, the oncopathological assessment of morbidity can be documented. A graphical user interface is provided which is also equipped with 3D visualization of the pleura. Our overall aim is to develop an image analysis system for an efficient and reliable diagnosis of early stage pleural mesothelioma in order to ease the consequences of the expected peak of malignant pleural mesothelioma caused by asbestos exposure.

Chaisaowong, K.; Knepper, A.; Kraus, T.; Aach, T.

2007-03-01

237

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

PubMed

RNA polymerase (RNAP) melts promoter DNA to form transcription-competent open promoter complex (RPo). Interaction of the RNAP ? subunit with non-template strand bases of a conserved -10 element (consensus sequence T-12A-11T-10A-9A-8T-7) is an important source of energy-driving localized promoter melting. Here, we used an RNAP molecular beacon assay to investigate interdependencies of RNAP interactions with -10 element nucleotides. The results reveal a strong cooperation between RNAP interactions with individual -10 element non-template strand nucleotides and indicate that recognition of the -10 element bases occurs only when free energy of the overall RNAP -10 element binding reaches a certain threshold level. The threshold-like mode of the -10 element recognition may be related to the energetic cost of attaining a conformation of the -10 element that is recognizable by RNAP. The RNAP interaction with T/A-12 base pair was found to be strongly stimulated by RNAP interactions with other -10 element bases and with promoter spacer between the -10 and -35 promoter elements. The data also indicate that unmelted -10 promoter element can impair RNAP interactions with promoter DNA upstream of the -11 position. We suggest that cooperativity and threshold effects are important factors guiding the dynamics and selectivity of RPo formation. PMID:23771146

Mekler, Vladimir; Severinov, Konstantin

2013-08-01

238

The Patient Health Questionnaire-9 for detection of major depressive disorder in primary care: consequences of current thresholds in a crosssectional study  

PubMed Central

Background There is a need for brief instruments to ascertain the diagnosis of major depressive disorder. In this study, we present the reliability, construct validity and accuracy of the PHQ-9 and PHQ-2 to detect major depressive disorder in primary care. Methods Cross-sectional analyses within a large prospective cohort study (PREDICT-NL). Data was collected in seven large general practices in the centre of the Netherlands. 1338 subjects were recruited in the general practice waiting room, irrespective of their presenting complaint. The diagnostic accuracy (the area under the ROC curve and sensitivities and specificities for various thresholds) was calculated against a diagnosis of major depressive disorder determined with the Composite International Diagnostic Interview (CIDI). Results The PHQ-9 showed a high degree of internal consistency (ICC = 0.88) and test-retest reliability (correlation = 0.94). With respect to construct validity, it showed a clear association with functional status measurements, sick days and number of consultations. The discriminative ability was good for the PHQ-9 (area under the ROC curve = 0.87, 95% CI: 0.84-0.90) and the PHQ-2 (ROC area = 0.83, 95% CI 0.80-0.87). Sensitivities at the recommended thresholds were 0.49 for the PHQ-9 at a score of 10 and 0.28 for a categorical algorithm. Adjustment of the threshold and the algorithm improved sensitivities to 0.82 and 0.84 respectively but the specificity decreased from 0.95 to 0.82 (threshold) and from 0.98 to 0.81 (algorithm). Similar results were found for the PHQ-2: the recommended threshold of 3 had a sensitivity of 0.42 and lowering the threshold resulted in an improved sensitivity of 0.81. Conclusion The PHQ-9 and the PHQ-2 are useful instruments to detect major depressive disorder in primary care, provided a high score is followed by an additional diagnostic work-up. However, often recommended thresholds for the PHQ-9 and the PHQ-2 resulted in many undetected major depressive disorders.

2010-01-01

239

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

PubMed

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

Miles, Jeffrey Hilton

2011-05-01

240

Scintillators for Photon Detection at Medium Energies  

Microsoft Academic Search

In a comparative study the performance of sub-arrays consisting of large CeF3 and PbWO4 crystals has been investigated with high energy photons below 1GeV. Energy and time resolutions are determined and compared to the corresponding values for BaF2 based on the experience of operating the electromagnetic calorimeter TAPS. Since clean photon detection relies on the discrimination and identification of charged

R. Novotny

2002-01-01

241

Inhibition of the human eyeblink reflex: An evaluation of the sensitivity of the Wendt-Yerkes method of threshold detection  

Microsoft Academic Search

In 2 experiments, 14 college students showed a reduced eyewink reflex to an airpuff (S-sub-2) if it was preceded by a light flash or a noise burst (S-sub-1). Exp I showed that a light inhibited the blink maximally at a 100-msec lag. In Exp III, thresholds for noise pips were established with the method of limits. The pips were then

Levi A. Reiter; James R. Ison

1977-01-01

242

Audiometric Threshold Screening Method Using Envelope Detection Filters of Intensity Ramping Click Auditory Steady-State Responses  

Microsoft Academic Search

The auditory steady-state responses (ASSR) elicited by click stimuli can be utilized for hearing screening as is traditionally done with click-evoked auditory brainstem responses (ABR). In a typical ASSR or ABR hearing screening, several recordings at different intensities are required to find the response threshold. In this study the use of binaural click stimulus with time ramping intensity produces dual-ear

N. Acikgoz; O. Ozdamar; R. E. Delgado; J. Bohorquez

2006-01-01

243

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

244

A lucky drift model, including a soft threshold energy, for the relation between gate and substrate currents in MOSFETs  

NASA Astrophysics Data System (ADS)

Substrate and gate currents in MOSFETs are formulated by interpreting the lucky drift model with a soft threshold energy from the distribution function point of view. A modified Keldysh formula is introduced to the ionization relaxation time. Unknown parameters in the formulation are determined by fitting the calculation to the measured relations between gate and substrate currents in MOSFETs. Impact ionization coefficient reported by Lee et al. [16], is also subsidiarily used for determining the parameters. The model can eliminate the nonphysical fitting parameter on the Schottky barrier lowering effect, which was necessary in past models. Fitting parameters concerning the ionization relaxation time, thus obtained, are compared with various theoretical calculations. It is recognized that the relation between gate and substrate currents in MOSFETs reflects the energy dependent ionization rate which originates from electron-electron interaction in the complicated energy band structure of silicon.

Tanaka, Sumio

1989-11-01

245

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

246

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 glacier—RAMAND-type, (2) in holes in the ice at depths of several hundred meters—RICE-type or (3) on board of a stratospheric balloon at an altitude of 40 km—ANITA-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

247

Sensitivity and specificity of the 76suprathreshold visual field test to detect eyes with visual field defect by Humphrey threshold testing in a population-based setting: the Thessaloniki eye study  

Microsoft Academic Search

PurposeTo evaluate the screening performance of the 76-Suprathreshold (76-STHR) visual field test to detect eyes with visual field defect (VFD) as measured by Humphrey threshold testing in a population-based setting.

Fotis Topouzis; Anne L. Coleman; Fei Yu; Leonidas Mavroudis; Eleftherios Anastasopoulos; Archimidis Koskosas; Theofanis Pappas; Stavros Dimitrakos; M. Roy Wilson

2004-01-01

248

Energy- and angle-dependent threshold photoemission magnetic circular dichroism from an ultrathin Co/Pt(111) film  

NASA Astrophysics Data System (ADS)

Threshold photoemission magnetic circular dichroism (TPMCD) in one-photon photoemission (1PPE) and two-photon photoemission (2PPE) is measured at an ultrathin Co film grown on Pt(111). Energy-dependent measurements reveal maximum asymmetries directly at the photoemission threshold (1.90% for 1PPE and 11.7% for 2PPE) which weakly decrease with increasing photon energy. The measured TPMCD asymmetries are discussed in two excitation models on the basis of spin-resolved band-structure calculations. For the model of direct band-to-band transitions in other k directions than the direction of observation (?-L) ab initio calculations for 1PPE and 2PPE are performed. The theory is in reasonable agreement with the measured TPMCD responses. An explanation of the large 2PPE TPMCD signal is provided in terms of specific interband excitations within the first excitation step. In the case of 2PPE angle-dependent measurements reveal a continuous drop of the asymmetry with increasing angle of incidence that agrees perfectly well with a calculation using the Fresnel equations. For 1PPE a deviation from the Fresnel-field approximation is obvious.

Hild, K.; Schönhense, G.; Elmers, H. J.; Nakagawa, T.; Yokoyama, T.; Tarafder, K.; Oppeneer, P. M.

2010-11-01

249

Relations Between the Arrhenius Activation Energy and Threshold Energy for Simple Models of the Reactive Cross Sections in a Dilute Gas  

NASA Astrophysics Data System (ADS)

The Arrhenius activation energy for the reaction A + A leftrightarrows B + B in a dilute gas is calculated from a temperature dependence of the rate constant obtained from the perturbation solution of the Boltzmann equation. The first and the second approximation to the velocity distribution function are used in an analysis of nonequilibrium effects. Results obtained for the line-of-centers model and the Prigogine--Xhrouet model of reactive differential cross sections are presented. The Arrhenius activation energy is represented as a function of appropriate threshold energies.

Cukrowski, A. S.

2006-06-01

250

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

PubMed

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

2013-06-01

251

Scintillators for Photon Detection at Medium Energies  

NASA Astrophysics Data System (ADS)

In a comparative study the performance of sub-arrays consisting of large CeF3 and PbWO4 crystals has been investigated with high energy photons below 1GeV. Energy and time resolutions are determined and compared to the corresponding values for BaF2 based on the experience of operating the electromagnetic calorimeter TAPS. Since clean photon detection relies on the discrimination and identification of charged and neutral particles, the response to hadrons including time-of-flight and pulse-shape techniques are discussed in detail.

Novotny, R.

2002-11-01

252

Correlator bank detection of gravitational wave chirps--False-alarm probability, template density, and thresholds: Behind and beyond the minimal-match issue  

SciTech Connect

The general problem of computing the false-alarm probability vs the detection-threshold relationship for a bank of correlators is addressed, in the context of maximum-likelihood detection of gravitational waves in additive stationary Gaussian noise. Specific reference is made to chirps from coalescing binary systems. Accurate (lower-bound) approximants for the cumulative distribution of the whole-bank supremum are deduced from a class of Bonferroni-type inequalities. The asymptotic properties of the cumulative distribution are obtained, in the limit where the number of correlators goes to infinity. The validity of numerical simulations made on small-size banks is extended to banks of any size, via a Gaussian-correlation inequality. The result is used to readdress the problem of relating the template density to the fraction of potentially observable sources which could be dismissed as an effect of template space discreteness.

Croce, R.P.; Demma, Th.; Pierro, V.; Pinto, I.M. [Wavesgroup, University of Sannio at Benevento, Piazza Roma, Pal. Bosco Lucarelli, 82100 Benevento (Italy); Longo, M.; Marano, S.; Matta, V. [Dipartimento di Ingegneria dell' Informazione e Ingegneria Elettrica, University of Salerno, Via Ponte don Melillo, 84084 Fisciano, SA (Italy)

2004-12-15

253

Probing the Unusual Thresholds of AlH+/AlD+ formation by Molecular Dynamic Simulations on MRCI Potential Energy Surfaces  

NASA Astrophysics Data System (ADS)

In an experiment performed by P. Armentrout (Int. Rev. Phys. Chem. 1990, 9, 115), the Al^+ cation was accelerated into the various isotopic combinations of H2 to form AlH^+ and AlD^+. It was found that the product-forming reactions proceed very inefficiently. The experiments also showed a reduction of ˜29% in the threshold for the formation of AlD^+ from the HD reactant whereas all other AlH^+ and AlD^+ products formed at the same energetic threshold. Four previous theoretical attempts at capturing this unusual phenomenon have not been successful. The lowest energy singlet surfaces for the reaction of Al^+ with H2 have been calculated at the multi-reference configuration interaction (MRCI) level of theory. The real/imaginary boundary of the symmetry-breaking b2 vibrational mode was examined in three dimensions using Hessian matrices computed at a multi-configurational self-consistent field (MCSCF) level of theory. Molecular dynamic simulations numbering on the order of 10^7 were performed, sampling initial conditions reflective of the experiments. The simulations were run until they reached the location where the b2 vibrational mode became unbound. A dissociation model was applied at these greatly compressed geometries to model the dissociation into AlH^+ and AlD^+ products.

Brewer, Nathan

2008-04-01

254

Energy Dependent Partial Wave Analysis of (pi+)p yields (Kappa+)(Sigma+) between Threshold and 2.35GeV.  

National Technical Information Service (NTIS)

An energy dependent partial wave analysis of the reaction given in the title has been carried out between threshold and 2.35GeV centre of mass energy using recently published, high statistical precision, data. A single solution giving a satisfactory fit t...

D. J. Candlin D. C. Lowe K. J. Peach L. R. Scotland

1983-01-01

255

Tunnelling coordinates of high-energy photoelectrons in above-threshold ionization  

NASA Astrophysics Data System (ADS)

With a three-dimensional semiclassical ensemble simulation, we comprehensively analyse the underlying dynamics of the photoelectron energy plateau (with an energy ranging from 2Up to 10Up, Up is the ponderomotive energy) from the single ionization of atoms in strong linearly polarized laser fields. We study the initial tunnelling coordinates at the tunnel exit (tunnelling phase and initial transverse momentum) of those high-energy photoelectrons. The rescattering process is very sensitive to the initial transverse momentum at the tunnel exit. We further identify the significant role of the long-range Coulomb potential on the rescattering process, which is usually ignored for those high-energy plateau electrons. Depending on the initial tunnelling coordinates, multiple forward scattering plus a hard collision has a significant contribution to the yield of the high-energy photoelectrons. By analysing the tunnelling coordinates of rescattering electrons, this provides sophisticated information for other related rescattering processes, i.e., high-harmonic generation and nonsequential double ionization.

Yuan, Jialei; Li, Min; Sun, Xufei; Gong, Qihuang; Liu, Yunquan

2014-01-01

256

The 8Li(p,?)5He reaction at low energies, and 9Be spectroscopy around the proton threshold  

NASA Astrophysics Data System (ADS)

We present a direct measurement of the low-energy 8Li(p,?)5He cross section, using a radioactive 8Li beam impinging on a thick target. With four beam energies, we cover the energy range between Ec.m.=0.2 and 2.1 MeV. An R-matrix analysis of the data is performed and suggests the existence of two broad overlapping resonances (5/2+ at Ec.m.=1.69 MeV and 7/2+ at Ec.m.=1.76 MeV). At low energies our data are sensitive to the properties of a subthreshold state (Ex=16.67 MeV) and of two resonances above threshold. These resonances were observed in previous experiments. The R-matrix fit confirms spin assignments, and provides partial widths. We propose a new 8Li(p,?)5He reaction rate and briefly discuss its influence in nuclear astrophysics.

Mendes, D. R., Jr.; Lépine-Szily, A.; Descouvemont, P.; Lichtenthäler, R.; Guimarães, V.; de Faria, P. N.; Barioni, A.; Pires, K. C. C.; Morcelle, V.; Pampa Condori, R.; Morais, M. C.; Leistenschneider, E.; Lima, C. E. F.; Zamora, J. C.; Alcantara, J. A.; Zagatto, V.; Assunção, M.; Shorto, J. M. B.

2012-12-01

257

A Novel Integrated Approach Using Dynamic Thresholding and Edge Detection (IDTED) for Automatic Detection of Exudates in Digital Fundus Retinal Images  

Microsoft Academic Search

The automatic screening of patients for early detection and prevention of diabetic retinopathy (DR) has been the prime focus in recent times due to the large ratio of patients to medical ophthalmologists. Exudate detection is one of the main steps of DR. A reliable method for detection of exudates is presented in this paper. Optic disc (OD) is localized by

Anantha Vidya Sagar; S. Balasubramaniam; V. Chandrasekaran

2007-01-01

258

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

259

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

PubMed

The mouse visual system is immature when the eyes open two weeks after birth. As in other mammals, some of the maturation that occurs in the subsequent weeks is known to depend on visual experience. Development of the retina, which as the first stage of vision provides the visual information to the brain, also depends on light-driven activity for proper development but has been less well studied than visual cortical development. The critical properties for retinal encoding of images include detection of contrast and responsiveness to the broad range of temporal stimulus frequencies present in natural stimuli. Here we show that contrast detection threshold and temporal frequency response characteristics of ON and OFF retinal ganglion cells (RGCs), which are poor at eye opening, subsequently undergo maturation, improving RGC performance. Further, we find that depriving mice of visual experience from before birth by rearing them in the dark causes ON and OFF RGCs to have smaller receptive field centers but does not affect their contrast detection threshold development. The modest developmental increase in temporal frequency responsiveness of RGCs in mice reared on a normal light cycle was inhibited by dark rearing only in ON but not OFF RGCs. Thus, these RGC response characteristics are in many ways unaffected by the experience-dependent changes to synaptic and spontaneous activity known to occur in the mouse retina in the two weeks after eye opening, but specific differences are apparent in the ON vs. OFF RGC populations. © 2014 Wiley Periodicals, Inc. Develop Neurobiol 74: 692-706, 2014. PMID:24408883

Akimov, Nikolay P; Rentería, René C

2014-07-01

260

Threshold for detection of diabetic peripheral sensory neuropathy using a range of research grade monofilaments in persons with Type 2 diabetes mellitus  

PubMed Central

Aims To identify the threshold of reduced sensory perception in Type 2 diabetes mellitus (Type 2 DM) using a range of research grade monofilaments. Methods Three groups of participants were recruited into a between subject, cross-sectional study. Group 1(NEW), persons with Type 2 DM diagnosed for less than 2 years (n = 80); Group 2 (EST) persons with Type 2 DM diagnosed for more than 2 years (n = 91), and Group 3, a Comparison group without Type 2 DM (n = 73), resulted in a total study population, n = 244. Research grade monofilaments (2, 4, 6, 8 and 10-gram) were employed using standardised protocol, at 6 sites on the plantar aspect of both feet. The demographic and anthropometric measures of gender, age, height, weight, body mass index (BMI), blood pressure and duration of Type 2 DM since diagnosis (if applicable) of the participants were analysed. Results Perception of the research grade monofilaments differed significantly between the 3 groups (p < 0.05). The 6-gram monofilament was found to be the threshold of normal perception, based on 90% of the Comparison group perceiving the 6-gram monofilament at all sites in contrast to 64% of NEW and 48% of EST groups. Conclusion The 6-gram monofilament was identified as the threshold of normal sensory perception. Inability to perceive the 6-gram monofilament indicates, when using the method described in this study, that diminution of sensory perception is evident. Employing a range of monofilaments, 6, 8 and 10-grams in Type 2 DM foot screening would allow the clinical detection of deteriorating sensory perception and enable implementation of foot protection strategies at an earlier stage than is currently practised.

Thomson, Mary P; Potter, Julia; Finch, Paul M; Paisey, Richard B

2008-01-01

261

Photon scattering from heavy nuclei up to energies well above particle emission thresholds  

Microsoft Academic Search

At the new superconducting electron accelerator ELBE at Dresden - Rossendorf various eorts on the identication and reduction of back- ground in nuclear resonance uorescence photon spectra were successful such that reasonably clean spectra could be accumulated even at end- point energies above the isovector giant dipole resonance (IVGDR). The dipole strength distribution below and in the IVGDR of 208Pb

M. Erhard; E. Grosse; A. R. Junghans; K. Kosev; G. Rusev; K. D. Schilling; R. Schwengner; A. Wagner

262

Ovipositional preferences, damage thresholds, and detection of the tomato-potato psyllid Bactericera cockerelli (Homoptera: Psyllidae) on selected tomato accessions.  

PubMed

The tomato-potato psyllid Bactericera [Paratrioza] cockerelli (Sulc) has recently caused losses exceeding 50% on fresh market tomatoes in California and Baja, Mexico by injecting a toxin that results in a condition known as 'psyllid yellows'. The objectives of this study were to: (i) document oviposition preferences on a range of tomato cultivars; (ii) determine threshold levels for psyllid densities that would cause psyllid yellows on tomatoes within the first three weeks following transplanting; and (iii) identify the most important 'psyllid yellows' symptoms that might be used in surveying and monitoring for this pest. Plant lines tested included the commonly-planted commercial cultivars 'Shady Lady' and 'QualiT 21', an older, previously commercial cultivar '7718 VFN', a common cultivar planted by consumers 'Yellow Pear', and a wild type plant accession, PI 134417. When given a choice, psyllids significantly preferred 'Yellow Pear' and avoided PI 134417 for oviposition. Under no-choice conditions psyllids laid significantly fewer eggs on PI 134417, but all the other plant lines were equally good substrates for laying eggs. Thus, oviposition preference is not likely to provide a functional management strategy in large plantings. On 'Shady Lady', psyllids preferred to oviposit on plants already infested with adults. On both 'Shady Lady' and '7718 VFN' oviposition was significantly greater on plants previously infested by nymphs as compared to uninfested control plants. This suggests that, at least for some cultivars, there is a physiological change in plant attractiveness following psyllid feeding. 'Yellow Pear' and 'QualiT 21' were relatively tolerant of psyllids, requiring 18 nymphs per plant to produce the disease symptoms. Only eight nymphs per plant were needed on 'Shady Lady' and '7718 VFN'. For all cultivars, the pest density showed strong correlations with measurements such as the number of yellowing leaves and leaflets and distorted leaves, which were as good as or better than the first factor extracted from principal component analysis. Therefore, such measurements have the potential to simplify field surveys. PMID:16556341

Liu, D; Trumble, J T

2006-04-01

263

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

264

The nature of the vectorial photoelectric effect in the threshold energy region  

Microsoft Academic Search

Summary  An immediate correlation has been proved to exist between the vectorial photoelectric effect and electronic surface structure\\u000a modified due to adsorption. Experimental studies were performed for Cs overlayers on W(110) and Si(111) faces using visible\\u000a exciting photons with energies below those of both bulk and surface plasmons. Considerable (more than 20 fold) growth of the\\u000a effect was observed forp-polarized light

G. V. Benemanskaya; M. N. Lapushkin; Yu. N. Gnedin; G. W. Fraser

1994-01-01

265

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, (2000–125?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

266

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

SciTech Connect

Results are reported from a joint analysis of Phase I and Phase II data from the Sudbury Neutrino Observatory. The effective electron kinetic energy threshold used is T{sub eff}=3.5 MeV, the lowest analysis threshold yet achieved with water Cherenkov detector data. In units of 10{sup 6} cm{sup -2} s{sup -1}, the total flux of active-flavor neutrinos from {sup 8}B decay in the Sun measured using the neutral current (NC) reaction of neutrinos on deuterons, with no constraint on the {sup 8}B neutrino energy spectrum, is found to be PHI{sub NC}=5.140{sub -0.158}{sup +0.160}(stat){sub -0.117}{sup +0.132}(syst). These uncertainties are more than a factor of 2 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 Sudbury Neutrino Observatory data in which the free parameters directly describe the total {sup 8}B neutrino flux and the energy-dependent nu{sub e} survival probability provides a measure of the total {sup 8}B neutrino flux PHI{sub {sup 8}{sub B}}=5.046{sub -0.152}{sup +0.159}(stat){sub -0.123}{sup +0.107}(syst). Combining these new results with results of all other solar experiments and the KamLAND reactor experiment yields best-fit values of the mixing parameters of theta{sub 12}=34.06{sub -0.84}{sup +1.16} degrees and DELTAm{sub 21}{sup 2}=7.59{sub -0.21}{sup +0.20}x10{sup -5} eV{sup 2}. The global value of PHI{sup 8}{sub B} is extracted to a precision of {sub -2.95}{sup +2.38}%. In a three-flavor analysis the best fit value of sin{sup 2}theta{sub 13} is 2.00{sub -1.63}{sup +2.09}x10{sup -2}. This implies an upper bound of sin{sup 2}theta{sub 13}<0.057 (95% C.L.).

Aharmim, B.; Chauhan, D.; Fleurot, F.; Hallman, E. D.; Schwendener, M. H.; Virtue, C. J. [Department of Physics and Astronomy, Laurentian University, Sudbury, Ontario P3E 2C6 (Canada); Ahmed, S. N.; Boulay, M. G.; Cai, B.; Chen, M.; DiMarco, M.; Earle, E. D.; Evans, H. C.; Ewan, G. T.; Guillian, E.; Harvey, P. J.; Kormos, L. L.; Kos, M.; Kraus, C.; Leslie, J. R. [Department of Physics, Queen's University, Kingston, Ontario K7L 3N6 (Canada)

2010-05-15

267

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

PubMed

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, (2000-125000 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 decelerate at an average of 0.47 m/s2 while the participant either looked at the car in front (control), continuously dialed series of three random integers on a numeric keypad (divided visual attention), or performed a memory and addition task (non-visual attention). The results indicated that drivers' detection ability was impaired by about 0.5 s in terms of brake reaction time and almost 1 s in terms of time-to-collision, when they were doing the non-visual task whilst driving. This impairment was similar to when the drivers were dividing their visual attention between the road ahead and dialing numbers on the keypad. It was concluded that neither a hands-free option nor a voice controlled interface removes the safety problems associated with the use of mobile phones in a car. PMID:10487336

Lamble, D; Kauranen, T; Laakso, M; Summala, H

1999-11-01

268

Mitochondrial threshold effects.  

PubMed Central

The study of mitochondrial diseases has revealed dramatic variability in the phenotypic presentation of mitochondrial genetic defects. To attempt to understand this variability, different authors have studied energy metabolism in transmitochondrial cell lines carrying different proportions of various pathogenic mutations in their mitochondrial DNA. The same kinds of experiments have been performed on isolated mitochondria and on tissue biopsies taken from patients with mitochondrial diseases. The results have shown that, in most cases, phenotypic manifestation of the genetic defect occurs only when a threshold level is exceeded, and this phenomenon has been named the 'phenotypic threshold effect'. Subsequently, several authors showed that it was possible to inhibit considerably the activity of a respiratory chain complex, up to a critical value, without affecting the rate of mitochondrial respiration or ATP synthesis. This phenomenon was called the 'biochemical threshold effect'. More recently, quantitative analysis of the effects of various mutations in mitochondrial DNA on the rate of mitochondrial protein synthesis has revealed the existence of a 'translational threshold effect'. In this review these different mitochondrial threshold effects are discussed, along with their molecular bases and the roles that they play in the presentation of mitochondrial diseases.

Rossignol, Rodrigue; Faustin, Benjamin; Rocher, Christophe; Malgat, Monique; Mazat, Jean-Pierre; Letellier, Thierry

2003-01-01

269

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

270

The absolute threshold of cone vision  

PubMed Central

We report measurements of the absolute threshold of cone vision, which has been previously underestimated due to sub-optimal 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 msec), 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 units 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.

Koeing, Darran; Hofer, Heidi

2013-01-01

271

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

PubMed

Headspace (HS) analysis has been recommended as one of the most optimal methods for extracting and analyzing volatile organic compounds from samples in diverse media such as soil and water. Short-chain volatile fatty acids (VFA, C3-C7) with strong adsorptivity were selected as the target compounds to assess the basic characteristics of the HS analysis through simulation of HS conditions by in-vial vaporization of liquid-phase standards (VL) in 25 mL glass vials. The reliability of the VL approach was assessed by apportioning the in-vial VFA mass into three classes: (1) vaporized fraction, (2) dynamic adsorption on the vial walls (intermediate stage between vaporization and irreversible absorption), and (3) irreversible absorptive loss (on the vial wall). The dynamic adsorption partitioning inside the vial increased with n-VFA carbon number, e.g., 43% (C2: acetic acid, extrapolated value), 65% (C3: propanoic acid), and 98% (C7: heptanoic acid). The maximum irreversible losses for the studied n-VFAs exhibited a quadratic relationship with carbon number. If the detection threshold limit (DTL: the onset of mass detection after attaining the maximum irreversible loss) is estimated, the DTL values for target VFAs were in the range of 101 ng for i-valeric acid to 616 ng for propionic acid, which are larger than the method detection limit by about 3 orders of magnitude. Consequently, quantitation of VFAs using the VL approach should be critically assessed by simultaneously considering the DTL criterion and the initial VFA masses loaded into the vial. PMID:24881858

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

2014-07-01

272

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

273

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

PubMed

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 ?G(C)(Ni(II)-InrS·DNA) are sufficiently high, relative to other metal sensors, for InrS to detect Ni(II), while the equivalent parameters for copper may be insufficient for copper-sensing in Synechocystis (at 48?h). InrS K(Zn(II)) (5.6?×?10(-13) ?M) is comparable to the sensory sites of ZiaR (and Zur), but ?G(C)(Zn(II)-InrS·DNA) is less than ?G(C)(Zn(II)-ZiaR·DNA) implying that relative to other sensors, ?G(C)(Zn(II)-Sensor·DNA) rather than K(Zn(II)) determines the final detection threshold for Zn(II). PMID:24666373

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

2014-05-01

274

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

PubMed

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

Böhm, R; Sedlák, A; Bulko, M; Holý, K

2014-07-01

275

Low Energy Solar Neutrino Detection by using Liquid Xenon  

NASA Astrophysics Data System (ADS)

Possibility to use ultra pure liquid Xenon as a low energy solar neutrino detector by means of ?+e scattering is evaluated. A possible detector with 10 tons of fiducial volume will give ~14 events for pp-neutrinos and ~6 events for 7Be neutrinos with the energy threshold at 50 keV. The detector can be built with known and established technologies. High density of the liquid- Xe would provide self-shields against the incoming backgrounds originating from the container and outer environments.

Suzuki, Y.

2001-01-01

276

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

277

A reconfigurable SITITO boost\\/buck regulator with sub-threshold cross-regulation-free dual-mode control for energy-harvesting applications  

Microsoft Academic Search

This paper describes a reconfigurable single-inductor triple- input triple-output regulator that is able to obtain power from three independent sources and provide multiple output regulations for energy-harvesting applications. A sub-threshold dual-mode controller can minimize power dissipation, avoid cross regulation between outputs, and provide predictable output noise spectrum. Implemented in a standard 0.35µm CMOS, the proposed regulator provides high power efficiency

Mengmeng Du; Hoi Lee; Jin Liu

2011-01-01

278

Ioninduced elongation of gold nanoparticles in silica by irradiation with Ag and Cu swift heavy ions: track radius and energy loss threshold  

Microsoft Academic Search

Systematic investigations of the energy loss threshold above which the irradiation-induced elongation of spherical Au nanoparticles occurs are reported. Silica films containing Au nanoparticles with average diameters of 15-80 nm embedded within a single plane were irradiated with 12-54 MeV Ag and 10-45 MeV Cu ions at 300 K and at normal incidence. We demonstrate that the efficiency of the

E. A. Dawi; A. M. Vredenberg; G. Rizza; M. Toulemonde

2011-01-01

279

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.

280

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.

281

? meson photoproduction on hydrogen near threshold  

NASA Astrophysics Data System (ADS)

The total cross section for ?p-->?p near threshold has been measured using the PHOENICS tagging system at the ELSA electron facility of the Physikalisches Institut der Universität Bonn. The photons are created by bremsstrahlung, and are tagged by measuring the momentum of each electron after the photon has been emitted. The recoil proton from ?p-->?p is detected by the AMADEUS counter setup in coincidence with the tagging system. Data were taken with AMADEUS at 3.3° in the laboratory, where the large Jacobian increases our event rate so that we obtain the cross section from threshold (E?=707.2 MeV) to E?~=720 MeV with adequate statistics. The ?p-->?p events are identified by kinematics, dE/dx, and timing information. We find that in our energy region the production cross section is consistent with S-wave production.

Price, J. W.; Anton, G.; Arends, J.; Beulertz, W.; Bock, A.; Breuer, M.; Büchler, K.; Clajus, M.; Detemple, P.; Hey, J.; Krämer, D.; Meyer, W.; Nefkens, B. M.; Nöldeke, G.; Schneider, W.; Zucht, B.

1995-05-01

282

Multiple-laser-energy detection system  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

283

Detecting Energy Patterns in Software Development  

Microsoft Academic Search

With the advent of increased computing on mobile devices such as phones and tablets, it has become crucial to pay attention to the energy consumption of mobile applications. The software engineering field is now faced with a whole new spectrum of energy-related challenges, ranging from power budgeting to testing and debugging the energy consumption. To the best of our knowledge

Ashish Gupta; Thomas Zimmermann; Christian Bird; Nachiappan Nagappan; Thirumalesh Bhat; Syed Emran

2011-01-01

284

Threshold Logic Drempellogica.  

National Technical Information Service (NTIS)

The theory is discussed of presently available threshold logic circuits, and an analysis of threshold functions is presented. An operational threshold gate adding circuit in TTL technology is described, and the difficulty of improving logic in complex cir...

C. Vader J. W. M. Wasser

1973-01-01

285

Modulation and Coding Detection of Energy Absorption.  

National Technical Information Service (NTIS)

This report discusses the theory of modulation and coding detection schemes. Applications of these techniques in active radiation dosimetry measurements would appear to be particularly promising. Modern integrated circuits provide ready made modulation an...

P. R. Moran

1976-01-01

286

Measurement of the solar B8 neutrino rate with a liquid scintillator target and 3 MeV energy threshold in the Borexino detector  

Microsoft Academic Search

We report the measurement of nu-e elastic scattering from B8 solar neutrinos with 3 MeV energy threshold by the Borexino detector in Gran Sasso (Italy). The rate of solar neutrino-induced electron scattering events above this energy in Borexino is 0.22±0.04(stat)±0.01(syst)cpd\\/100t, which corresponds to PhiB8ES=2.4±0.4±0.1×106cm-2s-1, in good agreement with measurements from SNO and SuperKamiokaNDE. Assuming the B8 neutrino flux predicted by

G. Bellini; J. Benziger; S. Bonetti; M. Buizza Avanzini; B. Caccianiga; L. Cadonati; F. Calaprice; C. Carraro; A. Chavarria; A. Chepurnov; F. Dalnoki-Veress; D. D'Angelo; S. Davini; H. de Kerret; A. Derbin; A. Etenko; K. Fomenko; D. Franco; C. Galbiati; S. Gazzana; C. Ghiano; M. Giammarchi; M. Goeger-Neff; A. Goretti; E. Guardincerri; S. Hardy; Aldo Ianni; Andrea Ianni; M. Joyce; G. Korga; D. Kryn; M. Laubenstein; M. Leung; T. Lewke; E. Litvinovich; B. Loer; P. Lombardi; L. Ludhova; I. Machulin; S. Manecki; W. Maneschg; G. Manuzio; Q. Meindl; E. Meroni; L. Miramonti; M. Misiaszek; D. Montanari; V. Muratova; L. Oberauer; M. Obolensky; F. Ortica; M. Pallavicini; L. Papp; L. Perasso; S. Perasso; A. Pocar; R. S. Raghavan; G. Ranucci; A. Razeto; A. Re; P. Risso; A. Romani; D. Rountree; A. Sabelnikov; R. Saldanha; C. Salvo; S. Schönert; H. Simgen; M. Skorokhvatov; O. Smirnov; A. Sotnikov; S. Sukhotin; Y. Suvorov; R. Tartaglia; G. Testera; D. Vignaud; R. B. Vogelaar; F. von Feilitzsch; J. Winter; M. Wojcik; A. Wright; M. Wurm; J. Xu; O. Zaimidoroga; S. Zavatarelli; G. Zuzel

2010-01-01

287

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

288

Master equation analysis of thermal activation reactions: Energy-transfer constraints on falloff behavior in the decomposition of reactive intermediates with low thresholds  

SciTech Connect

This paper deals with the high-temperature decomposition of reactive intermediates with low reaction thresholds. If these intermediates are created in situ, for example, through radical chain processes, their initial molecular distribution functions may be characteristic of the bath temperature and, under certain circumstances, peak at energies above the reaction threshold. Such an ordering of reaction thresholds and distribution functions has some similarities to that found during chemical activation. This leads to consequences that are essentially the inverse (larger rate constants than those deduced from steady-state distributions) of the situation for stable compounds under shock-heated conditions and hence reduces falloff effects. To study this behavior, rate constants for the unimolecular decomposition of ally, ethyl, n-propyl, and n-hexyl radicals have been determined on the basis of the solution of the time-dependent master equation with specific rate constants from RRKM calculations. The time required for the molecules to attain steady-state distribution functions has been determined as a function of the energy-transfer parameter (the step size down) molecular size (heat capacity), high-pressure rate parameters, temperature, and pressure. At 101 kPa (1atm) pressure, unimolecular rate constants near 10{sup 7} s{sup -1} represent a lower boundary, above which steady-state assumptions become increasingly questionable. 21 refs., 7 figs., 1 tab.

Tsang, W.; Bedanov, V.; Zachariah, M.R. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)] [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1996-03-07

289

Threshold electron impact spectrum of N2O  

NASA Astrophysics Data System (ADS)

Using a high-resolution electron impact monochromator combined with a penetrating-field analyzer for efficient detection of electrons of nearly zero energy, the first high-resolution electron impact spectrum of N2O was obtained. The threshold spectrum is presented over a wide energy range from 1.5 to 17.5 eV. Decay of a low-energy shape resonance into the vibrationally excited ground state was observed. Several new optically forbidden and previously unobserved Rydberg states were detected.

Cubric, D.; Cvejanovic, D.; Jureta, J.; Cvejanovic, S.; Hammond, P.

1986-12-01

290

Randomness fault detection system  

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

291

Anomaly detection in premise energy consumption data  

Microsoft Academic Search

Demand Response (DR) programs are designed to reduce energy consumption for relatively short time periods (e.g., a few hours per event). It has been widely recognized that DR can help to meet both reliability and market needs. In order for DR programs to achieve their full benefits, however, it is critical for utilities to accurately predict the reduction in energy

Yi Zhang; Weiwei Chen; Jason Black

2011-01-01

292

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

293

High Energy Electron Detection with ATIC  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

294

Sequential bond energies of Fe+ (CO2)n, n = 1-5, determined by threshold collision-induced dissociation and ab initio theory.  

PubMed

Collision-induced dissociation of the Fe+ (CO2)n complexes for n = 1-5 is studied using kinetic energy dependent guided ion beam mass spectrometry. In all cases, the primary products are endothermic loss of an intact neutral ligand from the complex. The cross section thresholds are interpreted to yield 0 K bond energies after accounting for the effects of multiple ion-molecule collisions, internal energy of the complexes, and unimolecular decay rates. These values are compared with density functional theoretical values for all five complexes. Theory provides bond energies in reasonable agreement with experiment for n = 1-4 and predictions for the infrared spectroscopy of these complexes that agree nicely with experimental results of Gregoire and Duncan (J. Chem. Phys. 2002, 117, 2120). Our thermochemical results are also compared with the Fe+ (CO)n and Fe+ (N2)n complexes, previously studied. PMID:16354023

Armentrout, P B; Koizumi, Hideya; MacKenna, Meghan

2005-12-22

295

Ion-induced elongation of gold nanoparticles in silica by irradiation with Ag and Cu swift heavy ions: track radius and energy loss threshold  

NASA Astrophysics Data System (ADS)

Systematic investigations of the energy loss threshold above which the irradiation-induced elongation of spherical Au nanoparticles occurs are reported. Silica films containing Au nanoparticles with average diameters of 15-80 nm embedded within a single plane were irradiated with 12-54 MeV Ag and 10-45 MeV Cu ions at 300 K and at normal incidence. We demonstrate that the efficiency of the ion-induced nanoparticle elongation increases linearly with the electronic energy transferred per ion track length unit from the energetic ions to the silica film. Ion beam shaping occurs above a threshold value of the specific electronic energy transfer. Three relevant regions are identified with respect to the original size of the Au nanoparticles. For 15 and 30 nm diameter particles, elongation occurs for electronic stopping power larger than 3.5 keV nm - 1. For Au nanoparticles with 40-50 nm diameter an electronic stopping power above 5.5 keV nm - 1 is required for elongation to be observed. Elongation of Au nanoparticles with 80 nm diameter is observed for electronic stopping between ~ 7-8 keV nm - 1. For all combinations of ions and energies, the ion track temperature profiles are calculated within the framework of the thermal spike model. The correlation between experimental results and simulated data indicates a thermal origin of the increase in the elongation rate with increasing the track diameter.

Dawi, E. A.; Vredenberg, A. M.; Rizza, G.; Toulemonde, M.

2011-05-01

296

Ion-induced elongation of gold nanoparticles in silica by irradiation with Ag and Cu swift heavy ions: track radius and energy loss threshold.  

PubMed

Systematic investigations of the energy loss threshold above which the irradiation-induced elongation of spherical Au nanoparticles occurs are reported. Silica films containing Au nanoparticles with average diameters of 15-80 nm embedded within a single plane were irradiated with 12-54 MeV Ag and 10-45 MeV Cu ions at 300 K and at normal incidence. We demonstrate that the efficiency of the ion-induced nanoparticle elongation increases linearly with the electronic energy transferred per ion track length unit from the energetic ions to the silica film. Ion beam shaping occurs above a threshold value of the specific electronic energy transfer. Three relevant regions are identified with respect to the original size of the Au nanoparticles. For 15 and 30 nm diameter particles, elongation occurs for electronic stopping power larger than 3.5 keV nm(-1). For Au nanoparticles with 40-50 nm diameter an electronic stopping power above 5.5 keV nm(-1) is required for elongation to be observed. Elongation of Au nanoparticles with 80 nm diameter is observed for electronic stopping between ? 7-8 keV nm(-1). For all combinations of ions and energies, the ion track temperature profiles are calculated within the framework of the thermal spike model. The correlation between experimental results and simulated data indicates a thermal origin of the increase in the elongation rate with increasing the track diameter. PMID:21451236

Dawi, E A; Vredenberg, A M; Rizza, G; Toulemonde, M

2011-05-27

297

Psychophysical evaluation of the image quality of a dynamic flat-panel digital x-ray image detector using the threshold contrast detail detectability (TCDD) technique  

NASA Astrophysics Data System (ADS)

We are currently in an era of active development of the digital X-ray imaging detectors that will serve the radiological communities in the new millennium. The rigorous comparative physical evaluations of such devices are therefore becoming increasingly important from both the technical and clinical perspectives. The authors have been actively involved in the evaluation of a clinical demonstration version of a flat-panel dynamic digital X-ray image detector (or FDXD). Results of objective physical evaluation of this device have been presented elsewhere at this conference. The imaging performance of FDXD under radiographic exposure conditions have been previously reported, and in this paper a psychophysical evaluation of the FDXD detector operating under continuous fluoroscopic conditions is presented. The evaluation technique employed was the threshold contrast detail detectability (TCDD) technique, which enables image quality to be measured on devices operating in the clinical environment. This approach addresses image quality in the context of both the image acquisition and display processes, and uses human observers to measure performance. The Leeds test objects TO[10] and TO[10+] were used to obtain comparative measurements of performance on the FDXD and two digital spot fluorography (DSF) systems, one utilizing a Plumbicon camera and the other a state of the art CCD camera. Measurements were taken at a range of detector entrance exposure rates, namely 6, 12, 25 and 50 (mu) R/s. In order to facilitate comparisons between the systems, all fluoroscopic image processing such as noise reduction algorithms, were disabled during the experiments. At the highest dose rate FDXD significantly outperformed the DSF comparison systems in the TCDD comparisons. At 25 and 12 (mu) R/s all three-systems performed in an equivalent manner and at the lowest exposure rate FDXD was inferior to the two DSF systems. At standard fluoroscopic exposures, FDXD performed in an equivalent manner to the DSF systems for the TCDD comparisons. This would suggest that FDXD would therefore perform adequately in a clinical fluoroscopic environment and our initial clinical experiences support this. Noise reduction processing of the fluoroscopic data acquired on FDXD was also found to further improve TCDD performance for FDXD. FDXD therefore combines acceptable fluoroscopic performance with excellent radiographic (snap shot) imaging fidelity, allowing the possibility of a universal x-ray detector to be developed, based on FDXD's technology. It is also envisaged that fluoroscopic performance will be improved by the development of digital image enhancement techniques specifically tailored to the characteristics of the FDXD detector.

Davies, Andrew G.; Cowen, Arnold R.; Bruijns, Tom J. C.

1999-05-01

298

Detection and tracking of a low energy swell system off the U.S. East Coast with the Seasat SAR  

NASA Technical Reports Server (NTRS)

It is noted that on the morning of September 28, 1978, at 1520 GMT, Seasat approached the East Coast of the U.S. with the 100 km swath of its synthetic aperture radar (SAR) running approximately parallel to the coast but displayed eastward by about 20 km. This pass is analyzed and the following conclusions are drawn: (1) the SAR can successfully detect low-energy swell systems with wave heights under 1 m (actually 0.65 + or - 0.25 m); (2) the refraction of low-energy but well-organized swells deriving from changes in the local depth of the ocean is clearly detectable in both wavelength and direction; and (3) the complexity of the ocean spectrum (whether composed of more than one system or spread in direction and wave number) appears to have little bearing on the threshold detection limits.

Beal, R. C.

1980-01-01

299

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

300

Threshold for detection of diabetic peripheral sensory neuropathy using a range of research grade monofilaments in persons with Type 2 diabetes mellitus  

Microsoft Academic Search

AIMS: To identify the threshold of reduced sensory perception in Type 2 diabetes mellitus (Type 2 DM) using a range of research grade monofilaments. METHODS: Three groups of participants were recruited into a between subject, cross-sectional study. Group 1(NEW), persons with Type 2 DM diagnosed for less than 2 years (n = 80); Group 2 (EST) persons with Type 2

Mary P Thomson; Julia Potter; Paul M Finch; Richard B Paisey

2008-01-01

301

Biochemical analysis of cultured chorionic villi for the prenatal diagnosis of peroxisomal disorders: biochemical thresholds and molecular sensitivity for maternal cell contamination detection  

Microsoft Academic Search

Objectives: The prenatal diagnosis of peroxisomal disorders is most often performed by biochemical analysis of cultured chorionic villus sample (CVS) or amniocytes. We aimed to (a) highlight the risk of maternal cell contamination (MCC) in biochemical prenatal diagnosis, (b) establish the threshold of these biochemical assays to MCC, and (c) document the sensitivity of PCR based genotyping of microsatellites for

S Steinberg; S Katsanis; A Moser; G Cutting

2005-01-01

302

Absorption detection in capillary electrophoresis by fluorescence energy transfer  

SciTech Connect

Normally, only highly fluorescent materials can be detected at low concentrations in the small detection volumes typical of capillary electrophoresis in a laser-based fluorometer. The authors report here the detection of absorbing but nonfluorescing analytes by laser-excited fluorescence. This is possible if the excited analytes transfer their energy to a fluorescent additive in the running buffer to increase the background fluorescence level. Two different fluorophores and four different absorbing analytes were tested in this detection scheme. Concentrations as low as 6 {times} 10{sup {minus}9} M and amounts as small as 4 amol at injection are detectable. The data support a long-range energy-transfer scheme, but the transfer efficiency is much larger than those reported for other donor-acceptor pairs.

Garner, T.W.; Yeung, E.S. (Iowa State Univ., Ames (USA))

1990-10-15

303

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

PubMed

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

304

Near-threshold Photoproduction of Phi Mesons from Deuterium  

SciTech Connect

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

Qian, X; Chen, W; Hicks, K; Kramer, K; Laget, J M; Mibe, T; Qiang, Y; Stepanyan, Syed; Tedeschi, D J; Xu, W; Adhikari, K P; Amaryan, Mak; Anghinolfi, M; Ball, J; Battaglieri, M; Batourine, V; Bedlinskiy, I; Bellis, M; Biselli, A S; Bookwalter, C; Branford, D; Briscoe, W J; Brooks, W K; Burkert, V D; Careccia, S L; Carman, D S; Cole, P L; Collins, P; Crede, V; D& #x27; Angelo, A; Daniel, A; Dashyan, N; De Vita, R; De Sanctis, E; Deur, A; Dey, B; Dhamija, S; Djalali, C; Doughty, D; Dupre, R; Egiyan, H; El Alaoui, A; Eugenio, P; Fegan, S; Gabrielyan, M Y; Gevorgyan, N; Gilfoyle, G P; Giovanetti, K L; Girod, F X; Goetz, J T; Gohn, W; Gothe, R W; Graham, L; Griffioen, K A; Guidal, M; Guo, L; Hafidi, K; Hakobyan, H; Hanretty, C; Hassall, N; Holtrop, M; Ilieva, Y; Ireland, D G; Jawalker, S S; Jo, H S; Joo, K; Keller, D; Khandaker, M; Khetarpal, P; Kim, A; Kim, W; Klein, F J; Konczykowski, P; Kubarovsky, V; Kuleshov, S V; Kuznetsov, V; Livingston, K; Martinez, D; Mayer, M; McAndrew, J; McCracken, M E; McKinnon, B; Meyer, C A; Mikhailov, K; Mineeva, T; Mirazita, M; Mokeev, V; Moreno, B; Moriya, K; Morrison, B; Moutarde, H; Munevar, E; Nadel-Turonski, P; Ni, A; Niccolai, S; Niculescu, I; Niroula, M R; Osipenko, M; Ostrovidov, A I; Paremuzyan, R; Park, K; Park, S; Anefalos Pereira, S; Pisano, S; Pogorelko, O; Pozdniakov, S; Price, J W; Procureur, S; Protopopescu, D; Ricco, G; Ripani, M; Ritchie, B G; Rosner, G; Rossi, P; Sabatie, F; Saini, M S; Salgado, C; Schott, D; Schumacher, R A; Seder, E; Seraydaryan, H; Sharabian, Y G; Smith, E S; Smith, G D; Sober, D I; Sokhan, D; Stepanyan, S S; Stoler, P; Strakovsky, I I; Strauch, S; Taiuti, M; Taylor, C E; Tkachenko, S; Ungaro, M; Vernarsky, B; Vineyard, M F; Voutier, E; Weinstein, L B; Weygand, D P; Wood, M H; Zachariou, N; Zana, L; Zhang, J; Zhao, B

2011-02-01

305

Variation of the bulk damage threshold of optical glasses upon repetitive exposure to pulsed laser radiation  

NASA Astrophysics Data System (ADS)

It is shown that exposure of optical glasses free of absorbing microinhomogeneities to below-threshold nanosecond laser radiation induces residual changes in their optical properties; these reduce the bulk damage threshold upon repetitive exposure to laser pulses. Residual changes in the nonlinear refractive index were detected. These were induced upon exposure to below-threshold radiation at wavelengths of 0.53 and 1.06 microns under conditions where the quantum energy is less than Eg/2, where Eg is the glass matrix ionizaton potential.

Balitskas, S. K.; Bal'Kiavichus, P. I.; Lukoshius, I. P.; Maldutis, E. K.; Sakalauskas, S. V.

1988-05-01

306

Threshold photoelectron spectroscopy of H 2O and D 2O over the photon energy range 12-40 eV  

NASA Astrophysics Data System (ADS)

The threshold photoelectron spectra of H 2O and D 2O have been recorded over the ionization region (12-40 eV) under high-resolution conditions using synchrotron radiation. Extensive vibrational 'filling-in' is found in the Franck-Condon gap regions between the three lowest ionic-state band systems that is attributed to autoionization of Rydberg states lying in these binding-energy regions. Vibronic coupling effects are found in the A 2A 1 band system of H 2O + and D 2O + in general agreement with a previous experiment. An unusual intensity enhancement is found in the B 2B 2 band system in the threshold photoelectron spectra of H 2O and D 2O that is attributed to an enhanced production of H 2O + and D 2O + ions due to the autoionization of Rydberg states lying in the binding energy region of this electronic state. In the inner valence ionization region two broad features have been found that are attributed to the (2a 1) -1 'main-line' state and the (1b)14a1? resonant state.

Truong, S. Y.; Yencha, A. J.; Juarez, A. M.; Cavanagh, S. J.; Bolognesi, P.; King, G. C.

2009-01-01

307

Threshold modulation for continuous energy resolution with two channels per pixel in a photon counting X-ray image detector  

NASA Astrophysics Data System (ADS)

The introduction of energy resolution in X-ray image detectors will lead to tradeoffs between circuit complexity and spatial/energy resolution in the pixel design. The proposed method provides continuous energy resolution with only two energy channels per pixel, which is a comparable complexity to that of a window discriminator pixel like Medipix2. The paper illustrates the method and validates the method through analytical analysis and through simulation of real and synthetic data.

O'Nils, Mattias; Thim, Jan; Norlin, Börje; Oelmann, Bengt

2009-08-01

308

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

309

Threshold Concepts in Biochemistry  

ERIC Educational Resources Information Center

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

Loertscher, Jennifer

2011-01-01

310

HRS Threshold Adjustment Test  

NASA Astrophysics Data System (ADS)

This test will determine the optimal, non-standard discriminator thresholds for the few anomalous channels on each HRS detector. A 15 second flat field observation followed by a 210 second dark count is performed at each of 10 discriminator threshold values for each detector. The result of the test will be the optimal threshold values to be entered into the PDB.

Troeltzsch, John

1990-07-01

311

Automatic Threshold Circuit.  

National Technical Information Service (NTIS)

An automatic threshold circuit to establish a threshold that is a specified number of db above the input's rms frequency weighted noise value is described. The input is compared with the feedback threshold value, the result of which is coupled to a limite...

J. H. Bumgardner

1976-01-01

312

New states above charm threshold  

SciTech Connect

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

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

2005-11-01

313

Threshold States in Schematic Model.  

National Technical Information Service (NTIS)

In an extended Brown-Bolsterli schematic model the possibility of strength decoupling from the giant dipole resonance is shown. A part of the particle-hole excited states, the threshold states are supposed to have lower energy than the other normal states...

L. P. Csernai

1977-01-01

314

Reexamination of the improved strong-field approximation: Low-energy structures in the above-threshold-ionization spectra for short-range potentials  

NASA Astrophysics Data System (ADS)

The improved strong-field approximation (ISFA) is a version of the strong-field approximation which takes into account an additional interaction of the ionized electron with the parent ion within the first Born approximation. The ISFA describes well the middle- and high-energy parts of the electron spectra in the above-threshold ionization process. We show, using an example of a short-range potential, that the ISFA is able to describe the low-energy structure in the energy spectra if it is calculated without additional approximations. We introduce two different forms of the T-matrix element which are appropriate for application of two widely used approximations: the saddle-point approximation [i.e., its more advanced version, the uniform approximation (UA)] and the pole approximation (PA). We show that both the PA and UA are not able to describe the low-energy structure. Furthermore, the UA describes better the plateau of the spectrum than the PA. We also identify the origin of a very-low-energy structure; it is connected to the laser-free (i.e., without exchange of the laser photons) electron forward scattering.

Miloševi?, D. B.

2013-08-01

315

Monte Carlo simulation of the cascade decay processes in gaseous boron initiated by photons with energies scanned through L- and K-ionization thresholds  

NASA Astrophysics Data System (ADS)

The Monte Carlo technique is applied to simulate the processes of the cascade relaxation of gaseous boron at atomic density of 2.5 × 1022 m-3 ionized by photons with the energies of 0.7-25 Ryd passing through a cylindrical interaction zone along its axis. The trajectories of electrons are simulated based on photoionization and electron-impact ionization cross sections calculated in the one-electron configuration-average Pauli-Fock approximation. Numbers of electrons and photons leaving the interaction zone per one initial photoionization, their energy spectra, the energy transferred to the medium and the probabilities of final ion formations are shown to change noticeably as the incident photon energy is scanned through boron atom ionization thresholds. These variations can be explained only if secondary electron-impact-produced processes are considered. The density of secondary events decreases when going from the zone axis to its border, and the profiles of the density along the radial direction are found to be similar for all the initial exciting photon energies.

Brühl, S.; Kochur, A. G.

2012-07-01

316

Photodetachment of O- from threshold to 1.2 eV electron kinetic energy using velocity-map imaging  

NASA Astrophysics Data System (ADS)

High-resolution photoelectron imaging from O- with excess energies between 0.5 meV and 1.2 eV is reported. With electron energy resolutions ranging from 266 ?eV to 3 meV, branching ratios and angular-distribution asymmetry parameters for each of the fine-structure transitions were measured. Preliminary data for a subset of these measurements showing possible effects due to electron correlation at low excess energy are presented, in the hope of stimulating further theoretical calculations for this species.

Cavanagh, S. J.; Gibson, S. T.; Lewis, B. R.

2010-02-01

317

Nuclear reactions in deuterated palladium and rhenium irradiated by ? quanta with a continuous spectrum at a threshold energy of 23 MeV in dense deuterium gas  

NASA Astrophysics Data System (ADS)

The element composition of Pd and Re samples in dense deuterium gas irradiated by ? quanta with a continuous spectrum and a threshold energy of 23 MeV has been studied. Considerable anomalies are discovered in the structure and element composition of irradiated samples. Substantial changes are observed at both ends of the Pd and Re wires in the form of blowouts of molten metal with a complex chemical composition resembling congealed solar protuberances. The surface of Pd and Re wires proved to be covered with 1-2-?m particles predominantly composed of rhenium oxide Re2O7. Near the cracks on the surface, these particles are crystallized in the form of small hexagonal crystallites composed of rhenium, carbon, and oxygen. The entire surface of rhenium is cracked and covered by a thick layer of the Re x C y compound. A brief description of the phenomenological model of nuclear reactions leading to the observed anomalies is given.

Didyk, A. Yu.; Wi?niewski, R.

2013-07-01

318

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

319

Water and energy gradients produce resilience and thresholds in ecosystem function in the western Sierra Nevada Mountains  

NASA Astrophysics Data System (ADS)

Energy and water availability are fundamental controls on ecosystem properties such as ecosystem type, water use, phenology, and carbon uptake, allocation, and turnover. How availability of energy and water interact to produce stepwise changes in ecosystem properties across linear climate gradients remains an important question for ecology and predicting impacts of climate change. Previous work has focused on the climatic factors that determine individual species' mortality or locations of individual ecotones, but research is lacking that examines role of energy and water availability in controlling patterns of ecosystem trait shifts across a broad climatic gradient. We studied a 2600-m elevation gradient along the western slope of the Sierra Nevada Mountains in the Southern Sierra Critical Zone Observatory (SSCZO) to understand how water and energy availability interact to influence ecosystem properties across a broad range of climate conditions and ecosystem types. Eddy covariance, vegetation type, forest biomass and production, sap flux, and soil moisture were measured to understand nonlinear ecosystem responses to gradients in energy and water availability. We describe the small differences in temperature and water availability that produce sharp transitions in ecosystem type, productivity, water use, and phenology. Conversely, we describe how broad ranges of temperature and water availability produce stability in ecosystem properties and demonstrate ecosystem resilience to climate change. These findings can better inform predictions of impacts of a changing climate on ecosystem range shifts, mortality, seasonality, carbon cycling, and water use.

Kelly, A. E.; Goulden, M.; Bales, R. C.; Meadows, M. W.; Winston, G.

2012-12-01

320

PREFACE: Sixth Symposium on Large TPCs for Low Energy Rare Event Detection  

NASA Astrophysics Data System (ADS)

For the sixth time the International Symposium on large TPCs for Low-Energy Rare-Event Detection has been organized in Paris on 17-19 December 2012. As for the previous conference, we were welcomed in the Astroparticle and Cosmology Laboratory (APC). Around one hundred physicists from all over the world gathered to discuss progress in the dark matter and low-energy neutrino search. The new results from the LHC were also widely discussed. The Higgs discovery at 125 GeV, without any sign of other new heavy particles, does not provide us with any information on the nature of dark mater. Alternatives to the favored SUSY model, in which the role of the WIMP is played by a stable neutralino, predict low mass candidates below a few GeV. Developing low threshold detectors at sub-keV energies becomes mandatory, and interest for Axion or Axion-like particles as dark matter is revived. We have seen increasing activity in the field and new infrastructures for these searches have been developed. We heard news of activities in the Canfranc laboratory in Spain, Jinping in China, SURF in the USA and about the extension project of Fréjus (LSM) laboratory. We would like to thank the organizing and advisory committees as well as the session chairpersons: J Zinn-Justin, G Wormser, D Nygren, G Chardin, F Vannucci, D Attié, T Patzak and S Jullian. I Giomataris, P Colas and I G Irastorza Group picture

Irastorza, Igor G.; Colas, Paul; Giomataris, Ioannis

2013-10-01

321

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

322

The reinfection threshold.  

PubMed

Thresholds in transmission are responsible for critical changes in infectious disease epidemiology. The epidemic threshold indicates whether infection invades a totally susceptible population. The reinfection threshold indicates whether self-sustained transmission occurs in a population that has developed a degree of partial immunity to the pathogen (by previous infection or vaccination). In models that combine susceptible and partially immune individuals, the reinfection threshold is technically not a bifurcation of equilibria as correctly pointed out by Breban and Blower. However, we show that a branch of equilibria to a reinfection submodel bifurcates from the disease-free equilibrium as transmission crosses this threshold. Consequently, the full model indicates that levels of infection increase by two orders of magnitude and the effect of mass vaccination becomes negligible as transmission increases across the reinfection threshold. PMID:15967188

Gomes, M Gabriela M; White, Lisa J; Medley, Graham F

2005-09-01

323

Fall-detection through vertical velocity thresholding using a tri-axial accelerometer characterized using an optical motion-capture system  

Microsoft Academic Search

Falls in the elderly population are a major problem for today's society. The immediate automatic detection of such events would help reduce the associated consequences of falls. This paper describes the development of an accurate, accelerometer-based fall detection system to distinguish between Activities of Daily Living (ADL) and falls. It has previously been shown that falls can be distinguished from

Alan K. Bourke; Karol J. O'Donovan; John Nelson; Gearoid M. OLaighin

2008-01-01

324

HRS Threshold Adjustment Test  

NASA Astrophysics Data System (ADS)

This test will determine the optimal, non-standard discriminator thresholds for the few anomalous channels on each HRS detector. A 15 second flat field observation followed by a 210 second dark count is performed at each of 10 discriminator threshold values for each detector. The result of the test will be the optimal threshold values to be entered into the PDB. Edited 4/30/91 to add comments to disable/re-enable cross-talk tables.

Skapik, Joe

1992-07-01

325

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

326

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

PubMed

Time-over-threshold (ToT) is attractive as a method of combined timing and energy encoding in positron emission tomography (PET) due to its simplicity in implementation and readout. However, conventional single threshold ToT has a nonlinear response and generally suffers from a tradeoff between timing and energy resolution. The resulting poor performance is not fit for applications requiring fast timing, such as time-of-flight (ToF) PET. In this work it is shown experimentally that by replacing single threshold ToT with a dual threshold method in a new compact circuit, excellent time resolution can be achieved (154 ps FWHM for 3 × 3 × 5 mm(3) LYSO crystals), suitable for ToF. Dual threshold ToT timing results have been compared to a similar single threshold design, demonstrating that dual threshold ToT performance is far superior to that of single threshold ToT (154 ps versus 418 ps coincidence time resolution for the dual and single threshold cases, respectively). A method of correcting for nonlinearity in dual threshold ToT energy spectra is also demonstrated. PMID:24889105

Grant, Alexander M; Levin, Craig S

2014-07-01

327

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

NASA Astrophysics Data System (ADS)

Time-over-threshold (ToT) is attractive as a method of combined timing and energy encoding in positron emission tomography (PET) due to its simplicity in implementation and readout. However, conventional single threshold ToT has a nonlinear response and generally suffers from a tradeoff between timing and energy resolution. The resulting poor performance is not fit for applications requiring fast timing, such as time-of-flight (ToF) PET. In this work it is shown experimentally that by replacing single threshold ToT with a dual threshold method in a new compact circuit, excellent time resolution can be achieved (154 ps FWHM for 3 × 3 × 5 mm3 LYSO crystals), suitable for ToF. Dual threshold ToT timing results have been compared to a similar single threshold design, demonstrating that dual threshold ToT performance is far superior to that of single threshold ToT (154 ps versus 418 ps coincidence time resolution for the dual and single threshold cases, respectively). A method of correcting for nonlinearity in dual threshold ToT energy spectra is also demonstrated.

Grant, Alexander M.; Levin, Craig S.

2014-07-01

328

High-energy neutrino astronomy: detection methods and first achievements  

NASA Astrophysics Data System (ADS)

In the last century, astronomy evolved from optical observation to the multi-wavelength study of celestial objects from radio waves up to x- and ?-rays, leading to a wealth of new discoveries and opening the way to high-energy astroparticle physics. In particular, the recent success of ground-based very-high-energy ?-ray telescopes has opened a new window on the most powerful and violent objects of the Universe, giving a new insight into the physical processes at work in such sources. In the context of high-energy astronomy, neutrinos constitute a unique probe since they escape from their sources, travel undisturbed on virtually cosmological distances and are produced in high-energy hadronic processes. In particular they would allow a direct detection and unambiguous identification of the sites of acceleration of high-energy baryonic cosmic rays, which remain unknown. This report discusses the physics potential of the domain and reviews the experimental techniques relevant for the detection of high-energy (>=TeV) neutrinos. The results obtained by the first generation of such detectors are presented, along with the perspectives opened by new projects and prototypes being currently developed.

Baret, B.; Van Elewyck, V.

2011-04-01

329

Resonant photonuclear isotope detection using medium-energy photon beam  

NASA Astrophysics Data System (ADS)

Resonant photonuclear isotope detection (RPID) is a nondestructive detection/assay of nuclear isotopes by measuring ? rays following photonuclear reaction products. Medium-energy wideband photons of E?=12-16MeV are used for the photonuclear (?,n) reactions and ? rays characteristic of the reaction products are measured by means of high-sensitivity Ge detectors. Impurities of stable and radioactive isotopes of the orders of ?gr—ngr and ppm—ppb are investigated. RPID is used to study nuclear isotopes of astronuclear and particle physics interests and those of geological and historical interests. It is used to identify radioactive isotopes of fission products as well.

Ejiri, Hiroyasu; Shima, Tatsushi

2012-02-01

330

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

331

Radar CFAR thresholding in clutter and multiple target situations  

Microsoft Academic Search

Radar detection procedures involve the comparison of the received signal amplitude to a threshold. In order to obtain a constant false-alarm rate (CFAR), an adaptive threshold must be applied reflecting the local clutter situation. The cell averaging approach, for example, is an adaptive procedure. A CFAR method is discussed using as the CFAR threshold one single value selected from the

Hermann Rohling

1983-01-01

332

A comparative analysis of frequency modulation threshold extension techniques  

NASA Technical Reports Server (NTRS)

FM threshold extension for system performance improvement, comparing impulse noise elimination, correlation detection and delta modulation signal processing techniques implemented at demodulator output

Arndt, G. D.; Loch, F. J.

1970-01-01

333

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

334

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

335

Threshold Selection, 4.  

National Technical Information Service (NTIS)

If a picture contains dark objects on a light background, or vice versa, the objects can be separated from the background by thresholding the picture. A good place to choose the threshold is at the average gray level of those picture points where the valu...

J. S. Weszka A. Rosenfeld

1974-01-01

336

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

337

Electron Energy Distribution Detection in Symmetrically Driven RF Argon Discharge  

NASA Astrophysics Data System (ADS)

The electron energy distribution function (EEDF) is measured with a Langmuir probe in a symmetrically driven capacitively coupled rf argon discharge. The distortion of the probe current-voltage characteristics by rf plasma potential fluctuation, which is suppressed by electric circuit resonance among an inductance, the electrode-plasma sheath and the plasma-ground stray capacitances, is finally eliminated by applying the remaining fluctuation to the probe. The detected EEDF differs from the theoretical one obtained from the Boltzmann equation.

Kimura, Takashi; Ohe, Kazuyuki

1993-08-01

338

Electron energy distribution detection in symmetrically driven RF argon discharge  

NASA Astrophysics Data System (ADS)

The electron energy distribution function (EEDF) is measured with a Langmuir probe in a symmetrically driven capacitively coupled RF argon discharge. The distortion of the probe current-voltage characteristics by RF plasma potential fluctuation, which is suppressed by electric circuit resonance among an inductance, the electrode-plasma sheath and the plasma-ground stray capacitances, is finally eliminated by applying the remaining fluctuation to the probe. The detected EEDF differs from the theoretical one obtained from the Boltzmann equation.

Kimura, Takashi; Ohe, Kazuyuki

1993-08-01

339

Energy detection under narrowband interference in UWB systems  

Microsoft Academic Search

Non-coherent UWB receivers are cost-effective and robust against multipath propagation. However the analog-front end of such receivers is highly susceptible to narrowband interference (NBI), which could undermine the overall performance of the receiver. To cope with this, we propose a multichannel energy detection scheme. The receiver uses a bank of correlators with different short delays to capture and suppress the

Yohannes D. Alemseged; Klaus Witrisal

2007-01-01

340

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.

2006-04-01

341

PCR and direct fluorescent-antibody staining confirm Chlamydia trachomatis antigens in swabs and urine below the detection threshold of Chlamydiazyme enzyme immunoassay.  

PubMed Central

In order to test the hypothesis that specimens blocking with a neutralizing reagent below the cutoff of the Chlamydiazyme enzyme immunoassay represent infected patients, we used direct fluorescent-antibody staining for elementary bodies (EBs) and PCR to confirm results for cervical swabs collected from 55,963 women and urethral swabs or first-void urine (FVU) samples collected from 5,781 men attending physicians' offices in the Toronto, Canada, area. Within a grey zone arbitrarily selected to represent values up to 40% below the positive threshold of the test run, 134 cervical swabs, 44 urethral swabs, and 39 FVU specimens exhibited a blocking response ( > 50% reduction in signal). Three or more EBs were observed in each of 98 cervical swabs (73.1%), 38 urethral swabs (86.4%), and 21 FVU specimens (53.8%). Of the 36 cervical swabs with fewer than three EBs, 33 were PCR positive; the positive PCR results for male specimens were 6 of 6 urethral swabs and 17 of 18 FVU samples. Application of the blocking test to specimens negative in the Chlamydiazyme enzyme immunoassay but having optical densities within 40% of the cutoff added 14.2% (217 of 1,531 specimens) more positive results to the survey. A total of 213 of 217 samples (98.2%) were reconfirmed as having EBs or DNA.

Krepel, J; Laur, I; Sproston, A; Luinstra, K; Jang, D; Mahony, J; Chernesky, M

1995-01-01

342

PCR and direct fluorescent-antibody staining confirm Chlamydia trachomatis antigens in swabs and urine below the detection threshold of Chlamydiazyme enzyme immunoassay.  

PubMed

In order to test the hypothesis that specimens blocking with a neutralizing reagent below the cutoff of the Chlamydiazyme enzyme immunoassay represent infected patients, we used direct fluorescent-antibody staining for elementary bodies (EBs) and PCR to confirm results for cervical swabs collected from 55,963 women and urethral swabs or first-void urine (FVU) samples collected from 5,781 men attending physicians' offices in the Toronto, Canada, area. Within a grey zone arbitrarily selected to represent values up to 40% below the positive threshold of the test run, 134 cervical swabs, 44 urethral swabs, and 39 FVU specimens exhibited a blocking response ( > 50% reduction in signal). Three or more EBs were observed in each of 98 cervical swabs (73.1%), 38 urethral swabs (86.4%), and 21 FVU specimens (53.8%). Of the 36 cervical swabs with fewer than three EBs, 33 were PCR positive; the positive PCR results for male specimens were 6 of 6 urethral swabs and 17 of 18 FVU samples. Application of the blocking test to specimens negative in the Chlamydiazyme enzyme immunoassay but having optical densities within 40% of the cutoff added 14.2% (217 of 1,531 specimens) more positive results to the survey. A total of 213 of 217 samples (98.2%) were reconfirmed as having EBs or DNA. PMID:8576331

Krepel, J; Laur, I; Sproston, A; Luinstra, K; Jang, D; Mahony, J; Chernesky, M

1995-11-01

343

Setting the Triggering Thresholds on Swift  

SciTech Connect

The Burst Alert Telescope (BAT) on Swift has two main types of 'rate' triggers: short and long. Short trigger time scales range from 4ms to 64ms, while long triggers are 64ms to {approx_equal} 16 seconds. While both short and long trigger have criteria with one background sample (traditional 'one-sided' triggers), the long triggers can also have criteria with two background samples ('bracketed' triggers) which remove trends in the background. Both long and short triggers can select energy ranges of 15-25, 15-50, 25-100 and 50-350 KeV. There are more than 180 short triggering criteria and approximately 500 long triggering criteria used to detect gamma ray bursts. To fully utilize these criteria, the thresholds must be set correctly. The optimum thresholds are determined by a tradeoff between avoiding false triggers and capturing as many bursts as possible. We use realistic simulated orbital variations, which are the prime cause of false triggers.

McLean, Kassandra M. [Los Alamos National Laboratory (United States); University of Texas at Dallas (United States); Fenimore, E.E.; Palmer, David [Los Alamos National Laboratory (United States); Barthelmy, S.; Gehrels, N.; Krimm, H.; Markwardt, C.; Parsons, A. [Goddard Space Flight Center (United States)

2004-09-28

344

Threshold bubble chamber for measurement of knock-on DT neutron tails from magnetic and inertial confinement experiments  

SciTech Connect

We propose a new {open_quotes}threshold{close_quotes} bubble chamber detector for measurement of knock-on neutron tails. These energetic neutrons result from fusion reactions involving energetic fuel ions created by alpha knock-on collisions in tokamak and other magnetic confinement experiments, and by both alpha and neutron knock-on collisions in inertial confinement fusion (ICF) experiments. The energy spectrum of these neutrons will yield information on the alpha population and energy distribution in tokamaks, and on alpha target physics and {rho}R measurements in ICF experiments. The bubble chamber should only detect neutrons with energies above a selectable threshold energy controlled by the bubble chamber pressure. The bubble chamber threshold mechanism, detection efficiency, and proposed applications to the International Thermonuclear Experimental Reactor (ITER) and National Ignition Facility (NIF) experiments will be discussed.

Fisher, R.K. [General Atomics, San Diego, CA (United States); Zaveryaev, V.S. [Russian Research Centre, Moscow (Russian Federation). Kurchatov Institute; Trusillo, S.V. [Russian Federal Nuclear Centre, Arzamas (Russian Federation). Experimental Physics Institute

1996-07-01

345

Evidence for both Lytic Replication and Tightly Regulated Human Herpesvirus 8 Latency in Circulating Mononuclear Cells, with Virus Loads Frequently below Common Thresholds of Detection  

Microsoft Academic Search

To address whether human herpesvirus 8 (HHV-8) DNA in peripheral blood mononuclear cells (PBMCs) might be the product of latent or lytic infection and to shed light on sporadic detection of HHV-8 DNA in individuals seropositive for the virus, we studied the frequency of infected cells, total virus load, and virus load per infected cell in PBMCs from men coinfected

Elisa Martro; Michael J. Cannon; Sheila C. Dollard; Thomas J. Spira; A. Scott Laney; Chin-Yih Ou; Philip E. Pellett

2004-01-01

346

Concentrating lightguide for threshold Cherenkov counters.  

National Technical Information Service (NTIS)

A method of manufacturing light guides (Winston lenses) is proposed to increase the effective area of light collection on photodetectors (with diameter of detection area from 45 to 120 mm) and to broaden angular range of radiation detection in threshold C...

O. P. Gavrishchuk V. A. Onuchin V. K. Semenov V. I. Suzdalev

1991-01-01

347

Effect of dissipation on dynamical fusion thresholds  

SciTech Connect

The existence of dynamical thresholds to fusion in heavy nuclei (A greater than or equal to 200) due to the nature of the potential-energy surface is shown. These thresholds exist even in the absence of dissipative forces, due to the coupling between the various collective deformation degrees of freedom. Using a macroscopic model of nuclear shape dynamics, It is shown how three different suggested dissipation mechanisms increase by varying amounts the excitation energy over the one-dimensional barrier required to cause compound-nucleus formation. The recently introduced surface-plus-window dissipation may give a reasonable representation of experimental data on fusion thresholds, in addition to properly describing fission-fragment kinetic energies and isoscalar giant multipole widths. Scaling of threshold results to asymmetric systems is discussed. 48 refs., 10 figs.

Sierk, A.J.

1986-01-01

348

Towards a Low Threshold SuperCDMS Experiment  

NASA Astrophysics Data System (ADS)

Astrophysical evidence points to the existence of particle dark matter that comprises the majority of the mass of the universe. A natural candidate for these particles are Weakly Interacting Massive Particles, or WIMPs. Lately there has been much interest in dark matter search experiments for low mass WIMPs. Detection of WIMP dark matter with mass below 20 GeV/c^2 requires a low-energy trigger threshold. However, lowering the trigger threshold also makes us sensitive to triggering on random noise which can hamper livetime. In order to minimize triggering on this random noise the original trigger filters for SuperCDMS were replaced with improved filters that reduce the amplitude of random noise substantially compared to an event-generated signal, thus allowing us to lower the trigger thresholds without the livetime penalty we would otherwise accrue. An overview of how this was accomplished as well as post-triggering methods of noise discrimination will be discussed. Predictions for the improved low thresholds will be compared to data, and the impact on a low mass WIMP search will be described.

Welliver, Bradford

2013-04-01

349

Catastrophic defeat in war, weapon system life cycles, energy threshold advancement and political change: A case study of Brandenburg-Prussia, 928-1815  

SciTech Connect

This dissertation examines the effects of catastrophic defeat in war in stimulating political change. A catastrophic defeat is a crisis causing event for a political community. It results in the prevailing concept of the soldier, which serves as an inhibitor to military change, being destroyed. Change comes to the military system of the polity by means of weapons system developments, witnessed by weapon system life cycles, generate changes in the entire structure of the military system. Change is in turn transmitted to the administrative and economic systems of the political community. The political community ultimately rebuilds itself, both materially and ideologically, around a more advanced energy threshold than the one which existed before the catastrophic defeat. This results in more energy output generated which translates into a greater level of work potential harnessed by the polity. This rebuilding process stimulates change through power redistribution within the political community because some social classes gain power and others lose it during each period of rebuilding. To support this research query, a case study based on Brandenburg-Prussia from 928 to 1815 has been utilized. Five episodes of catastrophic defeat followed by political change have been isolated. To measure the political changes in these episodes, representative structures have been created which allow changes in weapon systems, the army, the administration and the economy of the political community to be portrayed. Qualitative indicators are utilized which portray structural changes by tracking variables which define their components. While some quantitative indicators such as increases in energy output are utilized, in essence this is a study in [open quotes]qualitative causality[close quotes] through an examination of history.

Bunker, R.J.

1993-01-01

350

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

351

Threshold detection of radar signals off the sea surface in non-Gaussian clutter and deterministic interference: II - statistical analysis of ROI surface data  

SciTech Connect

The purpose of this report is to motivate and outline a program of data analysis, for data obtained from radar returns from ocean surfaces perturbed by internal waves and wind-wave interactions. The ultimate aims of this analysis are to provide the appropriate statistics of the signals returned from these ocean surfaces for: (1) use in implementing and evaluating optimum and near-optimum signal processing procedures for detecting and evaluating (i.e., measuring) these internal wave effects and, (2) to provide quantitative physical insight into both the surface scatter and subsurface mechanisms which determine the received radar signals. Here the focus is initially on the needed statistics of the radar returns. These are primarily: (i) the (instantaneous) amplitude and envelope probability densities, (pdf`s) and distributions (PDFS) of the returns and, (ii) analogous statistics for the intensities (associated with the pixel data). Also required are: (iii) space-time covariance data of the returns, for further improvement of detection capabilities. Preliminary evidence and earlier experiments suggest that these data [(i), (ii)] are nongaussian and strongly so at times. This in turn, if not properly taken into account, can greatly degrade signal detection in the usual weak-signal regimes [1],[2].

Middleton, D.

1996-05-02

352

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

Böser, Sebastian

2013-06-01

353

Ventricular pacing threshold variations in the young.  

PubMed

Ventricular Capture Management (VCM) is a Medtronic Kappa pacemakers (PM) feature that automatically measures pacing threshold through detection of the evoked response after a pacing stimulus. The aim of this study was to evaluate the range of variation of ventricular pacing threshold in pediatric patients with endocardial and epicardial pacing leads. Thirty-one patients (median age 6.5 years) were implanted with a Kappa 901 PM for atrioventricular block or sinus node dysfunction. Congenital heart defects (CHD) were present in 58% of patients. Ventricular leads were epicardial in 52% of patients. VCM was programmed to automatically measure threshold every 2 hours. In a median follow-up of 12 months, 27,110 threshold measurements, 72% of which were successful, have been taken in 94% of patients. Measurement success was 99% in the endocardial leads group (age at implantation 12 +/- 6 years) and 31% in epicardial leads (age 4 +/- 5 years) (P < 0.05). Main reasons for unsuccessful measurements were high heart rate and, in a patient with an endocardial lead, competition with intrinsic rhythm. Undersensing or oversensing of the evoked responses was not detected. In all successful VCM measurements, epicardial pacing and CHD contributed to stability of thresholds (multivariate analysis). Pacing threshold showed specific circadian patterns: higher thresholds were found between 00.00 and 06.00 a.m., but the variation was low, 0.03 +/- 0.01 V. In conclusion, children and young patients show stable ventricular thresholds, especially in presence of CHD, and epicardial leads are at least as stable as endocardial leads. Ventricular pacing threshold showed a circadian variability similar to that described in adults, that does not seem to influence VCM functioning and PM programming. PMID:17338712

Silvetti, Massimo Stefano; De Santis, Antonella; Grovale, Nicoletta; Grutter, Giorgia; Baccarini, Andrea; Drago, Fabrizio

2007-02-01

354

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

355

Tuning of threshold voltage in organic field-effect transistors with hydrophobic gate dielectric using monoenergetic low-energy electron beams and triode corona  

NASA Astrophysics Data System (ADS)

We report organic field-effect transistors (OFETs) with the hydrophobic gate dielectric exposed to an electron beam before semiconductor deposition, shifting the threshold voltage toward positive gate bias for a p-channel semiconductor. A 1 ?m Cytop film was irradiated with defined doses of electron beams with different energies. The charges/polarizations embedded in the dielectric by the irradiation have effective charge densities of ~10-8 C/cm2. OFETs were completed using 5,5'-bis(4-hexylphenyl)-2,2'-bithiophene as the semiconductor, and showed corresponding shifts in Vth. Other OFETs were made where the gate dielectric was treated with a corona discharge. Both types of devices showed similar shifts in Vth and transfer characteristics. There is no change in mobility of the charge carriers after either charging process. The charges do not contribute to the gate capacitance but induce changes in the onset of capacitance increase caused by accumulation of mobile channel charge during capacitance-voltage experiments in two-terminal metal-insulator-semiconductor-metal configurations.

Deshmukh, K. D.; Reuter, K.; Kempa, H.; West, J. E.; Katz, H. E.

2009-09-01

356

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

González-Recio, Oscar; de Maturana, Evangelina López; Vega, Andrés T; Engelman, Corinne D; Broman, Karl W

2009-01-01

357

Threshold concepts: implications for the management of natural resources  

USGS Publications Warehouse

Threshold concepts can have broad relevance in natural resource management. However, the concept of ecological thresholds has not been widely incorporated or adopted in management goals. This largely stems from the uncertainty revolving around threshold levels and the post hoc analyses that have generally been used to identify them. Natural resource managers have a need for new tools and approaches that will help them assess the existence and detection of conditions that demand management actions. Recognition of additional threshold concepts include: utility thresholds (which are based on human values about ecological systems) and decision thresholds (which reflect management objectives and values and include ecological knowledge about a system) as well as ecological thresholds. All of these concepts provide a framework for considering the use of threshold concepts in natural resource decision making.

Guntenspergen, Glenn R.; Gross, John

2014-01-01

358

Energy Nonlinearity in Radiation Detection Materials: Causes and Consequences  

SciTech Connect

The phenomenology and present theoretical understanding of energy nonlinearity (nonproportionality) in radiation detection materials is reviewed, with emphasis on gamma-ray spectroscopy. Semiconductor detectors are extremely linear, while scintillators display varying degrees and patterns of nonlinearity, and gas detectors show a characteristic form of nonproportionality associated with core levels. The relation between nonlinear response (to both primary particles and secondary electrons) and spectrometer resolution is also discussed. We review the qualitative ideas about the origin of nonlinearity in scintillators that have been proposed to date, with emphasis on transport and recombination of information carriers. Recent computational and experimental work on the basic physics of scintillators is leading towards a better understanding of energy nonlinearity and should result in new, more linear scintillator materials in the near future.

Jaffe, John E.; Jordan, David V.; Peurrung, Anthony J.

2007-01-01

359

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 modulating means for continuously varying the temperature of the filament (and hence the reaction rate) between two values sufficient to produce the chemical reaction. In response to this thermal modulation, the sensor produces a modulated output signal, the modulation of which is a function of the activation energy of the chemical reaction, which activation energy is specific to the particular component of interest and its concentration. Microprocessor means compares the modulated output signal with standard responses for a plurality of components to identify and quantify the particular component of interest. 4 figs.

Stetter, J.R.; Otagawa, T.

1985-05-20

360

Pion photoproduction on 3He at threshold  

NASA Astrophysics Data System (ADS)

The reaction 3He(?, ? +) 3H is studied in the impulse approximation using realistic wave functions for photon energies up to 5 MeV above threshold. The calculation is performed with Blomqvist-Laget amplitudes and Fermi motion is taken into account. At threshold we obtain the reduced cross section a( 3He) = 120 ?b , which is in good agreement with the recent experiment of Argan et al.

Tiator, L.

1981-07-01

361

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

362

Detecting Tau Neutrino Oscillations at EeV Energies  

NASA Astrophysics Data System (ADS)

It is suggested that a large scale UHE cosmic ray detector of the fluorescence type (Fly's Eye style as implemented in Hi-Res or the Auger Project, or from space as with OWL or Airwatch) may be able to observe a unique signature due to tau neutrinos. This signature comes about due to the initial charged current tau neutrino interaction producing a large shower, flying some distance, and then decaying in a second larger shower with typically twice the energy. Near horizontally incoming tau neutrinos provide the best change for this observation, where long flight paths in the atmosphere serve to discriminate between tau events, strongly interacting showers, and showers generated by either electron or muon neutrino interactions. Tau neutrinos are generally expected at the energies under study for resolving the SHE cosmic ray anomaly, because many suggested processes which produce the observed cosmic rays beyond the G-Z-K cutoff also produce copious neutrinos. We now have good evidence that the muon neutrino oscillates, and probably the electron neutrino as well. Despite the probable lack of source production of tau neutrinos, generation of tau neutrinos via oscillations, given the long flight distances, seems likely (though not inescapable, as for example if the oscillations presently seen are to sterile neutrinos). We present estimates of detection rates which demonstrate that if the tau neutrinos are present in the cosmic ray beam at a substantial fraction of the total, then experiments may well detect them.

Learned, John G.; Pakvasa, Sandi; Stanev, Todor

363

Hyperon and Charged Kaon Pair Production Close to Threshold  

SciTech Connect

Close-to-threshold data on the elementary kaon and antikaon production channels in the proton{endash}proton interaction have been taken using the COSY-11 installation at the cooler synchrotron COSY Juelich. The experimental technique applied at the internal COSY-11 facility{emdash}designed for meson production studies at small excess energy{emdash}is outlined. The threshold excitation functions for the kaon{endash}hyperon production via the reactions pp {yields} pK{sup +}{Lambda} and pp {yields} pK{sup +}{Sigma}{sup 0} are presented. The magnitude of the production amplitudes is compared at equal excess energies, and physical implications of the observed {Sigma}{sup 0} suppression in the threshold region are discussed. In addition, within a Dalitz plot analysis the spin-averaged S-wave scattering parameters could be extracted for the {Lambda}{endash}p channel. With the possibility of detecting all final state particles the elementary antikaon production in the reaction pp {yields} ppK{sup +}k{sup {minus}} has been investigated. Results on the exclusive total cross section fix the scale of the strangeness dissociation into two kaons.

Wolke, M.; Adam, H.H.; Balewski, J.T.; Budzanowski, A.; Goodman, C.; Grzonka, D. Jarczyk, L.; Jochmann, M.; Khoukaz, A.; Kilian, K.; Koehler, M.; Kowina, P.; Lister, T.; Moskal, P.; Lang, N.; Oelert, W.; Quentmeier, C.; Santo, R.; Schepers, G.; Seddik, U.; Sefzick, T.; Sewerin, S.; Siemaszko, M.; Smyrski, J.; Strzalkowski, A.; Wuestner, P.; Zipper, W.

2000-12-31

364

Direct measurement of the energy thresholds to conformational isomerization. II. 3-indole-propionic acid and its water-containing complex.  

PubMed

The methods of stimulated emission pumping-hole-filling spectroscopy (SEP-HFS) and population transfer spectroscopy (SEP-PTS) were used to place direct experimental bounds on the energetic barriers to conformational isomerization in 3-indole-propionic acid (IPA) and its water-containing complex. By contrast with tryptamine (Paper I), IPA has only two conformations with significant population in them. The structures of the two conformers are known from previous work [P. M. Felker, J. Phys. Chem. 96, 7844 (1992)]. The energy thresholds for A-->B and B-->A isomerizations are placed at 854 and 754 cm(-1), respectively. Lower bounds on the isomerization barrier in the two directions are determined from the last transition not observed in the SEP-PT spectra. These are placed at 800 and 644 cm(-1) for A-->B and B-->A, respectively. The combined results place bounds on the relative energies of the A and B minima, with E(B)-E(A)=46-210 cm(-1). Like the IPA monomer, the IPA-H2O complex forms two conformational isomers. Both these isomers incorporate the water molecule as a bridge between the carbonyl and OH groups of the carboxylic acid. Previous rotational coherence measurements (L. L. Connell, Ph.D. thesis, UCLA, 1991) have determined that these complexes retain the same IPA conformational structure as the monomers. SEP-PTS and SEP-HFS were carried out on the IPA-H2O complexes. It was demonstrated that it is possible to use SEP to drive conformational isomerization between the two conformational isomers of IPA-H2O. Bounds on the energy barriers to conformational isomerization are not effected greatly by the presence of the water molecule, with Ebarrier(A-->B)=771-830 cm(-1) and Ebarrier(B-->A)=583-750 cm(-1). This is a simple consequence of the fact that the barrier is an intramolecular barrier, and the water molecule is held fixed in the COOH pocket, where it interacts with the ring only peripherally during the isomerization process. Finally, changes in the SEP-PT spectral intensity in transitions near the top of the barrier to isomerization as a function of the position of SEP excitation relative to the pulsed valve exit provide some insight to the competition between vibrational relaxation and isomerization in a molecule the size of IPA. PMID:15974743

Clarkson, Jasper R; Baquero, Esteban; Zwier, Timothy S

2005-06-01

365

Threshold resonances in ultracold chemical reactions  

NASA Astrophysics Data System (ADS)

We analyze the effects of near threshold resonances on the low energy behavior of cross sections for reactive scattering systems with reaction a barrier (e.g. Cl + H2, D + H2). We find an anomalous behavior when a resonance pole is very close to the threshold of the entrance channel. For inelastic processes, including reactive ones, the anomalous energy dependence of the cross sections is given by ?˜E-3/2. However, at vanishingly low energies, the standard Wigner's threshold behavior (?˜E-1/2) is eventually recovered, but limiting to much narrower range of energies. When the cross sections are averaged to obtain rate coefficients, the anomalous behavior persists; indeed, we find an intermediate regime of ultralow temperatures, where the inelastic rate coefficients behave as K˜1/T.

Côté, Robin; Simbotin, Ionel; Ghosal, Subhas

2012-06-01

366

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

367

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

368

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

369

Definition of thresholds for stereoscopic depth.  

PubMed Central

In the laboratory, thresholds for stereoscopic depth perception are usually determined by asking observers to discriminate between a stimulus with a given depth offset and its mirror image. Threshold is most often defined as the disparity difference that yields 75% or 83% correct responses. Disparities used for clinical tests of stereopsis are much higher. Here it is argued that, among other factors, this is because of the fact that clinical tests usually require the detection of a depth difference (offset versus no offset), rather than the discrimination between two directions of depth difference (in front versus behind). From a formal comparison of the two tasks, the data show that discrimination, or classification is easier by at least a factor of 2 than detection. The contribution of variations of the threshold criterion and learning to the differences between stereoacuity as measured in laboratory and clinic is also discussed. These differences are relevant to the design of tests for clinical use.

Fahle, M; Henke-Fahle, S; Harris, J

1994-01-01

370

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

371

Threshold Group Testing  

Microsoft Academic Search

We introduce a natural generalization of the well-studied group testing prob- lem: A test gives a positive (negative) answer if the pool contains at least u (at most l) positive elements, and an arbitrary answer if the number of positive elements is between these fixed thresholds l and u. We show that the p posi- tive elements can be determined

Peter Damaschke

2006-01-01

372

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

373

Empirical threshold values for quantitative trait mapping  

Microsoft Academic Search

The detection of genes that control quantitative characters is a problem of great interest to the genetic mapping community. Methods for locating these quantitative trait loci (QTL) relative to maps of genetic markers are now widely used. This paper addresses an issue common to all QTL mapping methods, that of determining an appropriate threshold value for declaring significant QTL effects.

G. A. Churchill; R. W. Doerge

1994-01-01

374

Weighting/Threshold Approach to Sensor Fusion.  

National Technical Information Service (NTIS)

A weighting/threshold-based sensor fusion algorithm to decrease the false alarm rate (FAR) while maintaining a high probability of detection (PD) is being tested in the Remote Security Station (RSS). The RSS is being developed to provide temporary intrusi...

W. A. Amai

1988-01-01

375

Supply and threshold voltage scaling for low power CMOS  

Microsoft Academic Search

This paper investigates the effect of lowering the supply and threshold voltages on the energy efficiency of CMOS circuits. Using a first-order model of the energy and delay of a CMOS circuit, we show that lowering the supply and threshold voltage is generally advantageous, especially when the transistors are velocity saturated and the nodes have a high activity factor, In

Ricardo Gonzalez; Benjamin M. Gordon; Mark A. Horowitz

1997-01-01

376

Probabilistic Deviation Detection and Optimal Thresholds.  

National Technical Information Service (NTIS)

The PDDOT program is to provide a method of continuously monitoring military plans during execution for deviations from expected performance. Determining such deviations in critical to the success of military operations where the complexity of the battle ...

J. Fahey J. Smith

2014-01-01

377

The effects of surround contrast on contrast thresholds, perceived contrast and contrast discrimination  

Microsoft Academic Search

Perceived contrast, contrast detection thresholds and contrast discrimination thresholds were measured in the presence and absence of surrounding patterns of a similar spatio-temporal makeup. In the foveal retina we found that the perceived contrast of the central pattern was reduced by the presence of the contrast surrounds with the effect being greatest at low test contrast. Detection thresholds were not

Robert J Snowden; Stephen T Hammett

1998-01-01

378

Threshold properties of a microcavity laser with submicroampere threshold current  

SciTech Connect

We report the threshold characteristics of small oxide-confined vertical-cavity surface emitting lasers. Abrupt threshold transitions 105 times the spontaneous emission background are obtained at injection currents as low as 470 nanoampere.

Choquette, K.D.; Hou, H.Q.; Lear, K.L.; Chow, W.W.; Mar, A.; Geib, K.M.; Hammons, B.E.

1996-02-01

379

Transport near stochastic threshold  

SciTech Connect

Transport in a magnetic field configuration near stochastic threshold is investigated. The waiting time distribution near magnetic islands, and the size distribution of these islands are identified as the two fundamental functions which determine both the short time subdiffusive behavior, and the regular diffusive regime. These time and length distributions are studied, the mean square displacement is expressed in terms of these functions, and the result is compared to direct numerical simulation.

White, R.B.; Rax, J.M.; Wu, Y.

1992-12-01

380

Threshold Concepts in Research Education and Evidence of Threshold Crossing  

ERIC Educational Resources Information Center

Most work on threshold concepts has hitherto related to discipline-specific undergraduate education, however, the idea of generic doctoral-level threshold concepts appeared to us to provide a strong and useful framework to support research learning and teaching at the graduate level. The early work regarding research-level threshold concepts is…

Kiley, Margaret; Wisker, Gina

2009-01-01

381

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

382

Detection, Diagnosis and Prognosis: Contribution to the energy challenge: Proceedings of the Meeting of the Mechanical Failures Prevention Group  

NASA Technical Reports Server (NTRS)

The contribution of failure detection, diagnosis and prognosis to the energy challenge is discussed. Areas of special emphasis included energy management, techniques for failure detection in energy related systems, improved prognostic techniques for energy related systems and opportunities for detection, diagnosis and prognosis in the energy field.

Shives, T. R. (editor); Willard, W. A. (editor)

1981-01-01

383

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.

Galama, Titus; Kapteyn, Arie

2011-01-01

384

Threshold dependence in the electronic sputtering of condensed sulfur  

SciTech Connect

An apparent threshold is found for ejection of neutral sulfur from condensed sulfur due to electronic energy deposited by fast, light ions. This effect is important for understanding experiments on electronically stimulated sputtering (desorption) of large molecules. The threshold is determined by the density of ''ionization'' events deposited in the solid, and the nature of the threshold measured is affected by a material alteration process.

Torrisi, L.; Coffa, S.; Foti, G.; Johnson, R.E.; Chrisey, D.B.; Boring, J.W.

1988-07-15

385

Energy-Driven Statistical Sampling: Detecting Software Hotspots  

Microsoft Academic Search

Abstract Energy is a critical resource in many computing systems, motivating the need for energy - efficient software design This work proposes a new approach, energy - driven statistical profiling , to help software developers reason about the energy impact of software design decisions We describe a prototype implementation of this approach for the Itsy pocket computing platform Our experimental

Fay Chang; Keith I. Farkas; Parthasarathy Ranganathan

2002-01-01

386

Linear and bilinear fault detection and diagnosis based on mass and energy balance equations  

Microsoft Academic Search

Processes combining heat and material flows involve non-linear relationships that complicate fault detection and diagnosis (FDD) procedures. This paper proposes two model-based methods for detecting and diagnosing faults in process models as well as in measurements. The models involved in both methods consist of stationary mass and energy conservation equations. The ?2 detection test and the generalized likelihood ratio diagnosis

Antoine Berton; Daniel Hodouin

2003-01-01

387

Energy efficient learning solution for intrusion detection in Wireless Sensor Networks  

Microsoft Academic Search

The protocols in Wireless Sensor Networks (WSN) have a unique requirement for being of low complexity and energy-efficient. Due to their possible deployment in remote locations for civil, educational, scientific and military purposes, security, which includes intrusion detection and intrusion prevention, is of utmost importance. In this paper, we propose a simple, low complexity and energy-aware protocol for intrusion detection

Sudip Misra; P. Venkata Krishna; Kiran Isaac Abraham

2010-01-01

388

Coloring geographical threshold graphs  

SciTech Connect

We propose a coloring algorithm for sparse random graphs generated by the geographical threshold graph (GTG) model, a generalization of random geometric graphs (RGG). In a GTG, nodes are distributed in a Euclidean space, and edges are assigned according to a threshold function involving the distance between nodes as well as randomly chosen node weights. The motivation for analyzing this model is that many real networks (e.g., wireless networks, the Internet, etc.) need to be studied by using a 'richer' stochastic model (which in this case includes both a distance between nodes and weights on the nodes). Here, we analyze the GTG coloring algorithm together with the graph's clique number, showing formally that in spite of the differences in structure between GTG and RGG, the asymptotic behavior of the chromatic number is identical: {chi}1n 1n n / 1n n (1 + {omicron}(1)). Finally, we consider the leading corrections to this expression, again using the coloring algorithm and clique number to provide bounds on the chromatic number. We show that the gap between the lower and upper bound is within C 1n n / (1n 1n n){sup 2}, and specify the constant C.

Bradonjic, Milan [Los Alamos National Laboratory; Percus, Allon [Los Alamos National Laboratory; Muller, Tobias [EINDHOVEN UNIV. OF TECH

2008-01-01

389

Threshold resonance effects in reactive processes  

NASA Astrophysics Data System (ADS)

We investigate the effect of near threshold resonances in reactive scattering at low energy. We find a general type of anomalous behavior of the cross sections, and illustrate it with a real system (H2+Cl). For inelastic processes, the anomalous energy dependence of the total cross section is given by ? ˜k-3 (with k ??? ). The standard threshold behavior given by Wigner's law (? ˜k-1) is eventually recovered at vanishing energies, but its validity is now limited to a much narrower range of energies. The anomalous behavior leads to reaction rate coefficients behaving as K ˜1/T instead of the expected constant rate of the Wigner regime. We also provide analytical expressions for s-wave cross sections, and discuss the implication in ultracold physics and chemistry.

Simbotin, I.; Ghosal, S.; Côté, R.

2014-04-01

390

Threshold pion photoproduction in chiral perturbation theory  

NASA Astrophysics Data System (ADS)

We analyze threshold pion photoproduction in the framework of baryon chiral perturbation theory. In case of neutral pion photoproduction, virtual pions generate infrared singularities which modify the familiar form of the low-energy theorem for the electric dipole amplitude E0+. In particular, we predict E0+?0p( sth)=-(1.33±0.09)× -3/ M?+ . We also find a satisfactory description of the recently measured total cross section for ?p? ?0p in the threshold region. The process ?n? ?0n is entirely given by the loop and counterterm contributions. It would be interesting to have an experimental determination of the corresponding cross section in the threshold region. In case of the charged channels, the loop corrections are much more tame.

Bernard, Véronique; Kaiser, Norbert; Meißner, Ulf-G.

1992-09-01

391

Air temperature thresholds for indoor comfort and perceived air quality  

Microsoft Academic Search

Air temperature thresholds are investigated and proposed for acceptable comfort in air-conditioned buildings. Using the ASHRAE database of field studies in which acceptability votes were obtained from occupants, it is shown that within the thresholds the acceptability is indistinguishable. Therefore, there is little gain from conditioning spaces to an ‘optimum’ air temperature, a practice that involves significant energy cost. However,

Hui Zhang; Edward Arens; Wilmer Pasut

2011-01-01

392

Adaptive Thresholding and Parameter Estimation for PPM  

NASA Technical Reports Server (NTRS)

A method of adaptive setting of a threshold level for the detection of pulses in a pulse-position modulation (PPM) free-space optical communication system has been developed. In simplified terms, it is desirable to set a threshold value high enough to greatly reduce the probability (PFA as defined below) of erroneously detecting noise as signal pulses but not so high as to greatly reduce the probability (PD as defined below) of detecting any signal pulses that may be present along with noise. In the present method, the threshold level is varied with time, in response to changing conditions in the optical-communication channel, in an effort to maintain a balance between the aforesaid competing requirements. An integral part of this adaptation scheme is a scheme for estimating key parameters of the optical-communication channel in particular, parameters that describe the fading and total attenuation in the channel, and parameters that characterize spreading of pulses by atmospheric and other effects. The method can be implemented by software processing of digitized optoelectronic-detector output, and has been tested by computational simulation. In the first stage of processing by this method, the digitized values of the detector output during noise-only time slots of received PPM symbols are averaged to obtain a background level. This background level is subtracted from the detector output in the hope of reducing or eliminating the noise component in the remaining signal. (This background level should not be confused with the detection threshold, which is computed in the last stage of processing.) Next, the remaining signal - in effect, a vector of pulse samples - is normalized by dividing it by its L1 norm (in general, the L1 norm of a vector is defined as the sum of absolute magnitudes of its orthogonal components).

Arabshahi, Payman; Mulai, Ryan; Yan, Tsun-Yee

2005-01-01

393

[Testing method of human body's current threshold for perception based on EEG analysis].  

PubMed

Electric and electronic products are required to pass through the certification on electrical safety performance before entering into the market in order to reduce electrical shock and electrical fire so as to protect the safety of people and property. The leakage current is the most important factor in testing the electrical safety performance and the test theory is based on the perception current effect and threshold. The traditional method testing the current threshold for perception only depends on the sensing of the human body and is affected by psychological factors. Some authors filter the effect of subjective sensation by using physiological and psychological statistical algorithm in recent years and the reliability and consistency of the experiment data are improved. We established an experiment system of testing the human hody's current threshold for perception based on EEG feature analysis, and obtained 967 groups of data. We used wavelet packet analysis to detect a wave from EEG, and used FFT to do spectral analysis on alpha wave before and after the current flew through the human body. The study has shown that about 97.72% alpha wave energy changes significantly when electrical stimulation occurs. It is well proved that when the EEG feature identification is applied to test the human body current threshold for perception, and meanwhile alpha wave energy change and human body sensing are used together to confirm if the current flowing through the human body reaches the perception threshold, the measurement of the human body current threshold for perception could be carried out objectively and accurately. PMID:24804476

Wang, Xiaofei; Shi, Lijuan; Li, Dong; Zhao, Xu; Shao, Haiming

2014-02-01

394

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

395

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

396

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

397

Development of a Cerenkov radiation sensor to detect low-energy beta-particles.  

PubMed

We fabricated a novel fiber-optic Cerenkov radiation sensor using a Cerenkov radiator for measuring beta-particles. Instead of employing a scintillator, transparent liquids having various refractive indices were used as a Cerenkov radiator to serve as a sensing material. The experimental results showed that the amount of Cerenkov radiation due to the interaction with beta-particles increased as the refractive index of the Cerenkov radiator was increased as a results of a decrease of the Cerenkov threshold energy for electrons. PMID:23582496

Yoo, Wook Jae; Han, Ki-Tek; Shin, Sang Hun; Seo, Jeong Ki; Jeon, Dayeong; Lee, Bongsoo

2013-11-01

398

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

399

A method to detect ultra high energy electrons using earth's magnetic field as a radiator  

NASA Technical Reports Server (NTRS)

It is pointed out that the detection of electrons with energies exceeding a few TeV, which lose energy rapidly through synchrotron and inverse Compton processes, would provide valuable information on the distribution of sources and on the propagation of cosmic rays in the solar neighborhood. However, it would not be possible to measure the energy spectrum beyond a few TeV with any of the existing experimental techniques. The present investigation is, therefore concerned with the possibility of detecting electrons with energies exceeding a few TeV on the basis of the photons emitted through synchrotron radiation in the earth's magnetic field. Attention is given to the synchrotron radiation of electrons in the earth's magnetic field, detector response and energy estimation, and the characteristics of an ideal detector, capable of detecting photons with energies equal to or greater than 20 keV.

Stephens, S. A.; Balasubrahmanyan, V. K.

1983-01-01

400

Capability to detect wimps with a high energy neutrino telescope.  

National Technical Information Service (NTIS)

We studied the potential of the proposed ANTARES undersea neutrino telescope to detect muons coming from from neutralinos annihilating at the center of the Earth. First results show that the full 1 cu km-scale detector can indicate, after a few years of o...

F. Blondeau

1998-01-01

401

Energy measurement device wiring detection and examination training system design  

Microsoft Academic Search

To heighten the electrical measurement device wrong wiring detection speed and improve inspectors' working efficiency, analyzing the request of electrical measurement device wiring testing and examination training system, there put forward a whole design scheme and data collection device framework, PC Analysis system framework, and also gives a main algorithm of wrong wiring. The system has run in a ShanXi

Xingzhong Zhang; Gaoyun Liu

2009-01-01

402

High Energy Electron and Gamma - Ray Detection with ATIC  

NASA Technical Reports Server (NTRS)

The Advanced Thin Ionization Calorimeter (ATIC) balloon borne ionization calorimeter is well suited to record and identify high energy cosmic ray electrons, and at very high energies gamma-ray photons as well. We have simulated the performance of the instrument, and compare the simulations with actual high energy electron exposures at the CERN accelerator. Simulations and measurements do not compare exactly, in detail, but overall the simulations have predicted actual measured behavior quite well. ATIC has had its first 16 day balloon flight at the turn of the year over Antarctica, and first results obtained using the analysis methods derived from simulations and calibrations will be reported.

Chang, J.; Schmidt, W. K. H.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

403

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

404

Anomalous thresholds of reaction amplitudes  

Microsoft Academic Search

Summary  Anomalous thresholds of reaction amplitudes are studied without recourse to a partial wave expansion. Ft is shown that the\\u000a behavior of the amplitudes is quite similar to that of the partial wave projections even though the Legendre series does not\\u000a converge near the anomalous threshold.

P. G. O. Freund; R. Karplus

1961-01-01

405

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

406

Approaching the O- photodetachment threshold with velocity-map imaging  

NASA Astrophysics Data System (ADS)

A series of photodetachment spectra from O- has been measured from near threshold to several eV using the technique of velocity-map imaging. With a resolving power of ?E/E <= 0.38%, the energy and angular dependences for the six fine-structure transitions have been determined. For the first time, the energy and angular dependences of the cross section within a few meV of threshold have been determined.

Cavanagh, S. J.; Gibson, S. T.; Lewis, B. R.

2009-11-01

407

First simultaneous detection of PeV energy burst from the Crab Nebula  

NASA Astrophysics Data System (ADS)

The simultaneous detection of a PeV burst from the Crab Nebula is reported. The detection was made on February 23, 1989 by experiments in the Kolar Gold Fields in southern India and the Baksan Valley in the northern Caucasus mountains. These findings lend support to the theory that supernovae are the sources of cosmic rays with energies up to 10 to the 20th eV. The methods used to make the present detection are described.

Acharya, B. S.; Rao, M. V. S.; Sivaprasad, K.; Sreekantan, B. V.; Vishwanath, P. R.

1990-09-01

408

Fluorescent silica nanoparticle-based probe for the detection of ozone via fluorescence resonance energy transfer.  

PubMed

A fluorescence resonance energy transfer (FRET) platform for the detection of ozone was developed by combining the overlap of the fluorescence spectrum of Ru(bpy)3(2+)-doped silica nanoparticles with the absorption spectrum of indigo carmine at around 600 nm. This FRET system can be used to detect ozone simply within 10 min. Simple qualitative ozone detection methods using cotton swabs or paper were also developed. PMID:24049767

Qi, Wenjing; Wu, Di; Zhao, Jianming; Liu, Zhongyuan; Xu, Min; Anjum, Saima; Xu, Guobao

2013-11-01

409

Critical line in random-threshold networks with inhomogeneous thresholds.  

PubMed

We calculate analytically the critical connectivity K_{c} of random-threshold networks (RTNs) for homogeneous and inhomogeneous thresholds, and confirm the results by numerical simulations. We find a superlinear increase of K_{c} with the (average) absolute threshold mid R:hmid R: , which approaches K_{c}(mid R:hmid R:) approximately h;{2}(2lnmid R:hmid R:) for large mid R:hmid R: , and show that this asymptotic scaling is universal for RTNs with Poissonian distributed connectivity and threshold distributions with a variance that grows slower than h;{2} . Interestingly, we find that inhomogeneous distribution of thresholds leads to increased propagation of perturbations for sparsely connected networks, while for densely connected networks damage is reduced; the crossover point yields a characteristic connectivity K_{d} , that has no counterpart in Boolean networks with transition functions not restricted to threshold-dependent switching. Last, local correlations between node thresholds and in-degree are introduced. Here, numerical simulations show that even weak (anti)correlations can lead to a transition from ordered t