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1

Double Threshold Energy Detection Based Cooperative Spectrum Sensing for Cognitive Radio Networks with QoS Guarantee  

NASA Astrophysics Data System (ADS)

Cooperative spectrum sensing, which can greatly improve the ability of discovering the spectrum opportunities, is regarded as an enabling mechanism for cognitive radio (CR) networks. In this paper, we employ a double threshold detection method in energy detector to perform spectrum sensing, only the CR users with reliable sensing information are allowed to transmit one bit local decision to the fusion center. Simulation results will show that our proposed double threshold detection method could not only improve the sensing performance but also save the bandwidth of the reporting channel compared with the conventional detection method with one threshold. By weighting the sensing performance and the consumption of system resources in a utility function that is maximized with respect to the number of CR users, it has been shown that the optimal number of CR users is related to the price of these Quality-of-Service (QoS) requirements.

Hu, Hang; Yu, Hong; Zhang, Yongzhi

2013-03-01

2

Joint optimization of sensing threshold and transmission power in wideband cognitive radio with energy detection  

NASA Astrophysics Data System (ADS)

this paper, we consider a wideband cognitive radio system that operates over multiple idle subchannels. A joint optimization of sensing threshold and transmission power is proposed, which maximizes the total throughput subject to the constraints on the total interference, the total power, and the probabilities of false alarm and detection of each subchannel. An alternative joint optimization is proposed, which minimizes the total interference under the constraint of the total throughput. The bilevel optimization method is used to solve the proposed optimization problems with a minimized iteration complexity. The mixed-variable optimization problem is divided into two single-variable convex optimization subproblems: the upper level for threshold optimization and the lower level for power optimization. Weighed cooperative sensing is proposed to maximize the detection probability by choosing the optimal weighed factors. The simulations show that the proposed joint optimization algorithm can achieve desirable improvement on the throughput of cognitive radio at the same interference level to primary user, or vice versa within the limits on the probabilities of false alarm and miss detection, and the weighed cooperative sensing can considerably improve sensing performance compared with the unweighed cooperative sensing and single-user sensing.

Liu, Xin; Bi, Guoan; Jia, Min; Guan, Yong Liang; Zhong, Weizhi; Lin, Rui

2013-07-01

3

Breast Cancer Detection Using Multilevel Thresholding  

E-print Network

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

Rejani, Y Ireaneus Anna

2009-01-01

4

Detection thresholds for small haptic effects  

NASA Astrophysics Data System (ADS)

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

Dosher, Jesse A.; Hannaford, Blake

2002-02-01

5

Adaptive Threshold for QRS Complex Detection Based on Wavelet Transform.  

PubMed

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 threshold algorithm can give more accurate results than fixed algorithms. By means of weights of missing and fault detection, ULT and DLT are adapted to get more accurate detecting results. More important for this algorithm is that it can increase the recognition efficiency greatly. PMID:17281961

Xu, Xiaomin; Liu, Ying

2005-01-01

6

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

7

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

8

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

9

Target detection with randomized thresholds for lidar applications.  

PubMed

Light detection and ranging (lidar) systems use binary hypothesis tests to detect the presence of a target in a range interval. For systems that count photon detections, hypothesis test thresholds are normally set so that a target detection is declared if the number of detections exceeds a particular number. When this method is employed, the false alarm probability can not be selected arbitrarily. In this paper, a hypothesis test that uses randomized thresholds is described. This randomized method of thresholding allows lidar operation at any false alarm probability. When there is a maximum allowable false alarm probability, the hypothesis test that uses randomized thresholds generally produces higher target detection probabilities than the conventional (nonrandom) hypothesis test. PMID:22722291

Johnson, Steven E

2012-06-20

10

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

11

Quantum key distribution system using dual-threshold homodyne detection  

Microsoft Academic Search

In this work we present the principles of a flexible quantum key distribution (QKD) system using quadrature-phase-shift-keying (QPSK) base and symbol encoding and dual-threshold balanced homodyne detection (BHD) scheme. We give its security proofs and we compare its performance experimentally with a photon counting detection scheme.

Qing Xu; Manuel Sabban; Philippe Gallion; Francisco Mendieta

2008-01-01

12

Fault-tolerant adaptive FIR filters using variable detection threshold  

NASA Astrophysics Data System (ADS)

Adaptive filters are widely used in many digital signal processing applications, where tap weight of the filters are adjusted by stochastic gradient search methods. Block adaptive filtering techniques, such as block least mean square and block conjugate gradient algorithm, were developed to speed up the convergence as well as improve the tracking capability which are two important factors in designing real-time adaptive filter systems. Even though algorithm-based fault tolerance can be used as a low-cost high level fault-tolerant technique to protect the aforementioned systems from hardware failures with minimal hardware overhead, the issue of choosing a good detection threshold remains a challenging problem. First of all, the systems usually only have limited computational resources, i.e., concurrent error detection and correction is not feasible. Secondly, any prior knowledge of input data is very difficult to get in practical settings. We propose a checksum-based fault detection scheme using two-level variable detection thresholds that is dynamically dependent on the past syndromes. Simulations show that the proposed scheme reduces the possibility of false alarms and has a high degree of fault coverage in adaptive filter systems.

Lin, L. K.; Redinbo, G. R.

1994-10-01

13

Information transmission and detection thresholds in the vestibular nuclei: single neurons vs. population encoding  

E-print Network

Information transmission and detection thresholds in the vestibular nuclei: single neurons vs. Information transmission and detection thresholds in the vestibular nuclei: single neurons vs. population. Peripheral vestibular afferents display differential variability that is correlated with the importance

Chacron, Maurice

14

Prewhitening of colored noise fields for detection of threshold sources  

NASA Astrophysics Data System (ADS)

This report presents an algorithm for the estimation of noise correlations for an array of sensors. The algorithm assumes a mixed spectra model composed of discrete sinusoidal sources and continuous noise components. A spatial autoregressive (AR) process models the continuous component. Previous methods use spatial AR models with real coefficients, restricting the utility of the model to noise sources that impinge on an array at broadside. The complex formulation presented here solves the general problem of arbitrarily oriented noise sources. The technique uses a gradient algorithm for maximization of a likelihood functional to solve for the complex AR coefficients. Once the algorithm determines the noise covariance matrix, prewhitening techniques allow detection of threshold sources. The multiple signal classification (MUSIC) direction finder when applied to the prewhitened observed correlation matrix illustrates the usefulness in detecting low signal-to-noise ratio (SNR) sources. Computational examples use the standardized test case (STC), a realistic model with a challenging range of SNR and difficult source locations.

Barthelemy, Alain C.

1993-11-01

15

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

16

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

17

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

18

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

19

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

20

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

21

Threshold energy surface and Frenkel-pair resistivity for Cu  

SciTech Connect

In-situ electrical resistivity damage-rate measurements in the high voltage electron microscope have been used to study electron-irradiation-induced defect production in copper single crystals at T < 10/sup 0/K. Analysis of the directional and energy dependence yields a threshold energy surface that is significantly different from those of previous investigations: two 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 of 0.6 Frenkel pairs. the present results imply a Frenkel pair resistivity for C of (2.75/sub -0.2//sup +0.6/) x ..cap omega..-cm.

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

1982-01-01

22

An efficient blood vessel detection algorithm for retinal images using local entropy thresholding  

Microsoft Academic Search

This paper presents an efficient method for automatic detection and extraction of blood vessels in retinal images. Specifically, we also delineate vascular intersections\\/crossovers. The proposed algorithm is composed of four steps: matched filtering, local entropy thresholding, length filtering, and vascular intersection detection. The purpose of matched filtering is to enhance the blood vessels. Entropy-based thresholding can well keep the spatial

Thitiporn Chanwimaluang; Guoliang Fan

2003-01-01

23

Failure of direction discrimination at detection threshold for both fast  

E-print Network

Andrew B. Metha and Kathy T. Mullen McGill Vision Research, Department of Ophthalmology, 687 Pine Avenue'' pathway with a high sensitivity to chromatic tar- gets that signals the direction of slowly moving, have noted that at higher speeds the threshold gap disappears for RG tar- gets, signifying correct

Mullen, Kathy T.

24

Automated Coronal Hole Detection Using Local Intensity Thresholding Techniques  

NASA Astrophysics Data System (ADS)

We identify coronal holes using a histogram-based intensity thresholding technique and compare their properties to fast solar wind streams at three different points in the heliosphere. The thresholding technique was tested on EUV and X-ray images obtained using instruments onboard STEREO, SOHO and Hinode. The full-disk images were transformed into Lambert equal-area projection maps and partitioned into a series of overlapping sub-images from which local histograms were extracted. The histograms were used to determine the threshold for the low intensity regions, which were then classified as coronal holes or filaments using magnetograms from the SOHO/MDI. For all three instruments, the local thresholding algorithm was found to successfully determine coronal hole boundaries in a consistent manner. Coronal hole properties extracted using the segmentation algorithm were then compared with in situ measurements of the solar wind at ˜ 1 AU from ACE and STEREO. Our results indicate that flux tubes rooted in coronal holes expand super-radially within 1 AU and that larger (smaller) coronal holes result in longer (shorter) duration high-speed solar wind streams.

Krista, Larisza D.; Gallagher, Peter T.

2009-05-01

25

Blood Vessel Detection in Retinal Images by Shape-Based Multi-threshold Probing  

Microsoft Academic Search

We propose a novel approach to blood vessel detection in retinal images using shape-based multi-threshold probing. On an image\\u000a set with hand-labeled ground truth our algorithm quantitatively demonstrates superior performance over the basic thresholding\\u000a and another method recently reported in the literature. The core of our algorithm, classification-based multi-threshold probing,\\u000a represents a general framework of segmentation that has not been

Xiaoyi Jiangand; Daniel Mojon

2001-01-01

26

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

PubMed

Cronin, JB and Rumpf, MC. Effect of four different step detection thresholds on nonmotorized treadmill sprint measurement. J Strength Cond Res 28(10): 2996-3000, 2014-The purpose of this study was to investigate the effect of 4 different step detection thresholds (10, 15, 20, and 30% body mass [BM]) on the kinetics and kinematics of a youth population sprinting on a Woodway nonmotorized treadmill (NMT). A total of 16 male youth athletes sprinted 30 m from a split start position. Of the 15 variables measured, significant differences (p ? 0.05) were found in the measurement of 5 kinematic (step length, vertical displacement, contact time, eccentric, and concentric time) and 2 kinetic (vertical and leg stiffness) variables between the 10 vs. 20 and 30% BM step detection thresholds. Contact time was also significantly different (12%) between 15 vs. 30% BM step detection thresholds. In terms of reliability, the 15 and 30% BM step detection thresholds were found the most stable across all variables (average coefficient of variation ?6.0%). Given this information, a step detection threshold of 15% BM is recommended for quantifying kinematic and kinetic variables on a NMT, as this threshold seems to account for signal variability appropriately without compromising reliability. PMID:25250860

Cronin, John B; Rumpf, Michael C

2014-10-01

27

Behaviorally Measured Audiograms and Gap Detection Thresholds in CBA/CaJ Mice  

PubMed Central

Tone detection and temporal gap detection thresholds were determined in CBA/CaJ mice using a Go/No-go procedure and the psychophysical Method of Constant Stimuli. In the first experiment, audiograms were constructed for five CBA/CaJ mice. Thresholds were obtained for eight pure tones ranging in frequency from 1 to 42 kHz. Audiograms showed peak sensitivity between 8 and 24 kHz, with higher thresholds at lower and higher frequencies. In the second experiment, thresholds for gap detection in broadband and narrowband noise bursts were measured at several sensation levels. For broadband noise, gap thresholds were between 1 and 2 ms, except at very low sensation levels, where thresholds increased significantly. Gap thresholds also increased significantly for lowpass-filtered noise bursts with a cutoff frequency below 18 kHz. Our experiments revised absolute auditory thresholds in the CBA/CaJ mouse strain and demonstrated excellent gap detection ability in the mouse. These results add to the baseline behavioral data from normal-hearing mice which have become increasingly important for assessing auditory abilities in genetically altered mice. PMID:19756650

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

2010-01-01

28

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

29

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

30

Detection thresholds for phenyl ethyl alcohol using serial dilutions in different solvents.  

PubMed

Detection thresholds are typically obtained by presenting a subject with serial dilutions of an odorant. Many factors, including the solvent used to dilute the odorant, can influence the measurement of detection thresholds. Differences have been reported in detection thresholds for phenyl ethyl alcohol (PEA) when different solvents are used. In this study we used gas chromatography (GC) to investigate further the effect of solvent on odor detection thresholds. We used a single ascending method and serial dilutions of PEA in four different solvents--liquid paraffin (LP), mineral oil (MO), propylene glycol (PG) and dipropylene glycol (DPG)--to determine the PEA thresholds for 31 adult subjects. For each solvent, we prepared eight serial log base 10 step dilutions (1-8), with corresponding liquid PEA concentrations of 6.3 x 10(1)-6.3 x 10(-6) (% v/v). We found that the threshold concentrations for PEA in LP (step 6.5) and PEA in MO (step 5.5) were significantly lower (P < 0.05) than for PEA in PG (step 4.0) and DPG (step 4.0) We then used GC to measure both the liquid and gas PEA concentrations for the dilution steps prepared with LP and PG. Although there were large threshold differences in the liquid concentrations of PEA in LP and PG, the headspace gas concentrations of PEA were the same. These results demonstrate the importance of determining the gas concentration of odorant stimuli when performing odor threshold measurements, in particular when comparing odor detection thresholds obtained using different solvents. PMID:12502521

Tsukatani, Toshiaki; Miwa, Takaki; Furukawa, Mitsuru; Costanzo, Richard M

2003-01-01

31

A preliminary evaluation of a speed threshold incident detection algorithm  

E-print Network

and California algorithm #8 using Fuzzy Logic to evaluate the new algorithm's effectiveness in detecting incidents on freeways. To test these algorithms, real data from TransGuide were run through the algorithms. Algorithm output were compared with CCTV (closed...

Kolb, Stephanie Lang

2012-06-07

32

Dynamo threshold detection in the von Kármán sodium experiment.  

PubMed

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

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

2013-07-01

33

Threshold detection of aromatic compounds in wine with an electronic nose and a human sensory panel  

NASA Astrophysics Data System (ADS)

An electronic nose (e-nose) based on thin film semiconductor sensors has been developed in order to compare the performance with a trained human sensory panel. The panel had 25 members and was trained to detect concentration thresholds of some compounds of interest present in wine. Typical red wine compounds such as whiskylactone and white wine compounds such as 3-methyl butanol were measured at different concentrations starting from the detection threshold found in literature (in the micrograms to milligrams per liter range). Pattern recognition methods (principal component analisys and neural networks) were used to process the data. The results showed that the performance of the e-nose for threshold detection was much better than the human panel. The compounds were detected by the e-nose at concentrations up to ten times lower than the panel. Moreover the e-nose was able to identify correctly each concentration level therefore quantitative applications are devised for this system.

Santos, José Pedro; Lozano, Jesús; Aleixandre, Manuel; Arroyo, Teresa; Cabellos, Juan Mariano; Gil, Mar; del Carmen Horrillo, Maria

2009-05-01

34

Pressure Systems Stored-Energy Threshold Risk Analysis  

SciTech Connect

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

Paulsen, Samuel S.

2009-08-25

35

New Dynamic Model-Based Fault Detection Thresholds for Robot Manipulators  

Microsoft Academic Search

Autonomous robotic fault detection is becoming increasingly important as robots are used in more inaccessible and hazardous environments. Detection algorithms, however, are adversely effected by the model simplification, parameter uncertainty, and computational inaccuracy inherent in robotic control, leading to an unacceptable number of false alarms and overzealous fault tolerance. The algorithms must use thresholds to mask out these errors. Typically,

M. L. Visinsky; Ian D. Walker; Joseph R. Cavallaro

1994-01-01

36

Nuclear Elastic Scattering of Photons near the Particle Threshold Energy (I)  

Microsoft Academic Search

The elastic scattering of photons near the particle threshold energy was studied for Al, Si, S, K, Ca, Ni, Cu, Cd, Sn, Pb and Bi. The bremsstrahlung x-rays from a 25 Mev betatron were used. The pulse of the primary x-rays was expanded up to about 30 mu sec to decrease the pile-up effect. The scattered photons were detected at

Tsutomu Tohei; Masumi Sugawara; Shigeki Mori; Motoharu Kimura

1961-01-01

37

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

PubMed

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

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

2014-04-01

38

Dual-Threshold Balanced Homodyne Detection at 1550 nm Optical Fiber Quantum Key Distribution System  

Microsoft Academic Search

We present a flexible quantum key distribution (QKD) system implementation using quadrature phase-shift keying (QPSK) encoding. Two detection techniques are implemented and compared: a photon counting detection scheme using single photon avalanche diodes (SPAD) and a dual-threshold balanced homodyne detection (BHD) using standard PIN diodes in which the weak signal is time-multiplexed with a strong reference. The interferometer instability and

Q. Xu; M. Sabban; M. B. Costa e Silva; P. Gallion; F. J. Mendieta

2009-01-01

39

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

PubMed

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, measuring pitch and roll angular velocities, and a threshold-based algorithm. Data analysis was performed using Matlab to determine the angular accelerations, angular velocities and changes in trunk angle recorded, during eight different fall and ADL types. Three thresholds were identified so that a fall could be distinguished from an ADL: if the resultant angular velocity is greater than 3.1 rads/s (Fall Threshold 1), the resultant angular acceleration is greater than 0.05 rads/s(2) (Fall Threshold 2), and the resultant change in trunk-angle is greater than 0.59 rad (Fall Threshold 3), a fall is detected. Results show that falls can be distinguished from ADL with 100% accuracy, for a total data set of 480 movements. PMID:17222579

Bourke, A K; Lyons, G M

2008-01-01

40

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

NASA Astrophysics Data System (ADS)

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

Morantes, Gaudi; Fernández, Gerardo; Altuve, Miguel

2013-11-01

41

Within, but not between hands interactions in vibrotactile detection thresholds reflect somatosensory receptive field organization.  

PubMed

Detection of a tactile stimulus on one finger is impaired when a concurrent stimulus (masker) is presented on an additional finger of the same or the opposite hand. This phenomenon is known to be finger-specific at the within-hand level. However, whether this specificity is also maintained at the between hand level is not known. In four experiments, we addressed this issue by combining a Bayesian adaptive staircase procedure quick estimation of threshold (QUEST) with a two-interval forced choice (2IFC) design in order to establish threshold for detecting 200 ms, 100 Hz sinusoidal vibrations applied to the index or little fingertip of either hand (targets). We systematically varied the masker finger (index, middle, ring, or little finger of either hand), while controlling the spatial location of the target and masker stimuli. Detection thresholds varied consistently as a function of the masker finger when the latter was on the same hand (Experiments 1 and 2), but not when on different hands (Experiments 3 and 4). Within the hand, detection thresholds increased for masker fingers closest to the target finger (i.e., middle > ring when the target was index). Between the hands, detection thresholds were higher only when the masker was present on any finger as compared to when the target was presented in isolation. The within hand effect of masker finger is consistent with the segregation of different fingers at the early stages of somatosensory processing, from the periphery to the primary somatosensory cortex (SI). We propose that detection is finger-specific and reflects the organization of somatosensory receptive fields in SI within, but not between the hands. PMID:24592252

Tamè, Luigi; Moles, Andrew; Holmes, Nicholas P

2014-01-01

42

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

43

A Hybrid Clustering Algorithm for Fire Detection in Video and Analysis with Color Based Thresholding Method  

Microsoft Academic Search

In this study an unsupervised way of fire pixel detection from video frames is depicted. A hybrid clustering algorithm is proposed, depending on color samples in video frames. A modified k-mean clustering algorithm is used here. In this algorithm hierarchical and partition clustering are used to build the hybrid. The results are analyzed with color base threshold method by considering

Ishita Chakraborty; Tanoy Kr. Paul

2010-01-01

44

[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

45

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

PubMed Central

Lameness is common in commercially reared broiler chickens but relationships between lameness and pain (and thus bird welfare) have proved complex, partly because lameness is often partially confounded with factors such as bodyweight, sex and pathology. Thermal nociceptive threshold (TNT) testing explores the neural processing of noxious stimuli, and so can contribute to our understanding of pain. Using an acute model of experimentally induced articular pain, we recently demonstrated that TNT was reduced in lame broiler chickens, and was subsequently attenuated by administration of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs). This study extended these findings to a large sample of commercial broilers. It examined factors affecting thermal threshold (Part 1) and the effect of an NSAID drug (meloxicam, 5 mg/kg) and of an opioid (butorphanol; 4 mg/kg) (Part 2). Spontaneously lame and matched non-lame birds (n?=?167) from commercial farms were exposed to ramped thermal stimulations via a probe attached to the lateral aspect of the tarsometatarsus. Baseline skin temperature and temperature at which a behavioural avoidance response occurred (threshold) were recorded. In Part 1 bird characteristics influencing threshold were modelled; In Part 2 the effect of subcutaneous administration of meloxicam or butorphanol was investigated. Unexpectedly, after accounting for other influences, lameness increased threshold significantly (Part 1). In Part 2, meloxicam affected threshold differentially: it increased further in lame birds and decreased in non-lame birds. No effect of butorphanol was detected. Baseline skin temperature was also consistently a significant predictor of threshold. Overall, lameness significantly influenced threshold after other bird characteristics were taken into account. This, and a differential effect of meloxicam on lame birds, suggests that nociceptive processing may be altered in lame birds, though mechanisms for this require further investigation. PMID:24847799

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

2014-01-01

46

The detection, removal and effect on damage thresholds of cerium impurities on fused silica  

SciTech Connect

We describe the detection, by resonance ionization mass spectrometry (RIMS), of cerium impurities on fused silica optical substrates. The impurity is desorbed into the gas phase by an infrared laser (1.06..mu..m), and detected, as both free cerium atoms and cerium oxide, by RIMS. In addition, we describe an acid wash procedure that both improves the damage threshold, and reduces significantly the measured levels of near-surface cerium. 14 refs., 5 figs.

Estler, R.C.; Nogar, N.S.; Schmell, R.A.

1988-01-01

47

Motion-Detection Threshold and Measures of Balance in Older Adults: The SEE Project  

Microsoft Academic Search

balance (measured by a reduction in the anterior-posterior sway) was strongly associated with the ability to detect small movements (motion-detection thresholds). Balance-associated vision variables were also identified in a population-based study of 782 older adults. West and col- leagues17 identified the vision variables that were associated with the ability to maintain a full tandem stance (one foot behind the other)

Ellen E. Freeman; Aimee T. Broman; Kathleen A. Turano; Sheila K. West

2008-01-01

48

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

PubMed

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 experimental reclamation pond (Pond 9). Using the three-alternative forced choice method, a concentration series of NAs were presented to the sensory panels in phosphate buffer (pH 8) and in steamed fish (Sander vitreus). In buffer, the odor detection thresholds of Acros, Merichem and Pond 9 NAs, as evaluated by the trained panelists, were 1.5, 0.04, and 1.0 mg L(-1), respectively. Only the detection threshold for the Merichem NAs was significantly different (p<0.01) than the other two sources. Based on the general population assessments, all three odor detection thresholds were significantly different from one another; 4.8, 0.2, and 2.5 mg L(-1) for Acros, Merichem, and Pond 9 NAs, respectively (p<0.01). The odor detection thresholds of Merichem and Pond 9 NAs in steamed fish were 0.6 and 12 mg kg(-1), respectively and were significantly different from each other (p<0.01). The detection threshold of Acros NAs was estimated to be >21 mg kg(-1). For the steamed fish evaluations, the odor descriptors of all three of the NAs preparations was given as chemical in nature (Acros: oil, plastic; Merichem: gasoline; Pond 9: gasoline, tar). Exposure of live rainbow trout to a non-lethal concentration of Merichem NAs (3 mg L(-1) for 10 d) imparted an odor to the fish flesh. Analyses of the three NAs preparations by gas chromatography-mass spectrometry showed that each had a unique distribution of acids. We conclude that the source of the NAs is important when interpreting odor threshold data and that the two commercial preparations of NAs that were tested do not represent oil sands waters' tainting potential. PMID:20801486

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

2010-11-01

49

Fusion of threshold rules for target detection in wireless sensor networks  

SciTech Connect

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

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

2010-03-01

50

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

51

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

52

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

NASA Astrophysics Data System (ADS)

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

Bagwari, A.; Tomar, G. S.

2014-04-01

53

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

PubMed Central

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

Hammer, Michael J.; Krueger, Mallory A.

2014-01-01

54

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

PubMed

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

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

2013-04-01

55

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

PubMed Central

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

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

2010-01-01

56

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

PubMed Central

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

Buran, Bradley N.; von Trapp, Gardiner

2014-01-01

57

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

58

Evaluation of the Validity of a Maximum Likelihood Adaptive Staircase Procedure for Measurement of Olfactory Detection Threshold in Mice  

Microsoft Academic Search

Threshold is defined as the stimulus intensity necessary for a subject to reach a specified percent correct on a detection test. MLPEST (maximum likelihood parameter estimation by sequential testing) is a method that is able to determine threshold accurately and more rapidly than many other methods. Originally developed for human auditory and visual tasks, it has been adapted for human

Amy C. Clevenger; Diego Restrepo

2006-01-01

59

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. PMID:23717293

Zoefel, Benedikt; Heil, Peter

2013-01-01

60

Seismicity and detection/location threshold in the Southern Great Basin Seismic Network  

NASA Astrophysics Data System (ADS)

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. Such a model is required to unambiguously identify regions that are aseismic due to natural processes rather than to limited detection and/or location capabilities. Accounting for spatial variations in detection/location threshold is also important for studies in which magnitude-frequency distributions are interpreted in terms of source scaling properties. The characteristics of the spatial distribution of earthquakes, where earthquake clusters and aseismic regions locate, appear to be stable at all magnitude levels so that inferences about where strain is being accommodated will be the same whether numbers of earthquakes or strain estimated from seismic moments are examined. For the southern Great Basin region these principal characteristics include clusters at the northern end of the Furnace Creek fault and in the Pahranagat Shear Zone, and a relatively large number of earthquakes in the northern and southeastern portions of the Nevada Test Site. These clusters cover regions much larger than the surface projections of any of the mapped faults. The extent to which seismicity is induced by nuclear testing is unclear. The predominantly aseismic regions include the area west of the Death Valley/Furnace Creek fault system and an almost complete absence of events at Yucca Mountain. Finally, a considerable number of isolated events in the SGBSN catalog cannot be correlated with mapped faults.

Gomberg, Joan

1991-09-01

61

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. PMID:20550244

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

2010-01-01

62

Ultra low power, harsh environment SOI-CMOS design of temperature sensor based threshold detection and wake-up IC  

Microsoft Academic Search

An ultra-low-power temperature-sensor-based silicon-on-insulator (SOI) CMOS Integrated Circuit (IC) for harsh environment application is presented. It first detects a temperature threshold, secondly generates a wake-up signal that turns on a data-acquisition microprocessor once the threshold has been detected and thirdly operates as a temperature sensor in a harsh environment while being wired to the microprocessor kept in a safe area.

M. Assaad; P. Ge?rard; L. A. Francis; D. Flandre

2010-01-01

63

Measurement of Cooling Detection Thresholds for Identification of Diabetic Sensorimotor Polyneuropathy in Type 1 Diabetes  

PubMed Central

Objective Compared to recently-studied novel morphological measures, conventional small nerve fiber functional tests have not been systematically studied for identification of diabetic sensorimotor polyneuropathy (DSP). We aimed to determine and compare the diagnostic performance of cooling detection thresholds (CDT) in a cross-sectional type 1 diabetes cohort. Research Design and Methods 136 subjects with type 1 diabetes and 52 healthy volunteers underwent clinical and electrophysiological examination for DSP classification concomitantly with the Toronto Clinical Neuropathy Score (TCNS) and three small fiber function tests: CDT, heart rate variability (HRV), and laser doppler imaging of axon-mediated neurogenic flare responses to cutaneous heating (LDIFLARE). Area under the curve (AUC) and optimal thresholds were determined by receiver operating characteristic (ROC) curves in the type 1 diabetes cohort. Results Type 1 diabetes subjects were 42±17 years of age with mean HbA1c 7.9±1.7%. Fifty-nine (45%) met the case definition for DSP. CDT values were lowest in cases with DSP (18.3±8.4°C) compared to controls without DSP (28.4±3.5°C) and to healthy volunteers (29.6±1.8°C; p-value for both comparisons<0.0001). AUCCDT was 0.863 which was similar to AUCTCNS (0.858, p?=?0.24) and AUCHRV (0.788, p?=?0.05), but exceeded AUCLDIFLARE (0.750, p?=?0.001). The threshold of <25.1°C was equivalent to the lower bound of the healthy volunteer 95% distribution [25.1, 30.8°C] and performed with 83% sensitivity and 82% specificity. Conclusions Akin to novel small fiber morphological measures, CDT is a functional test that identifies DSP with very good diagnostic performance. These findings support further research that revisits the role of CDT in early DSP detection. PMID:25216179

Lysy, Zoe; Lovblom, Leif E.; Halpern, Elise M.; Ngo, Mylan; Ng, Eduardo; Orszag, Andrej; Breiner, Ari; Bril, Vera; Perkins, Bruce A.

2014-01-01

64

Beyond stacking: a maximum-likelihood method to constrain radio source counts below the detection threshold  

NASA Astrophysics Data System (ADS)

We present a statistical method based on a maximum-likelihood approach to constrain the number counts of extragalactic sources below the nominal flux-density limit of continuum imaging surveys. We extract flux densities from a radio map using positional information from an auxiliary catalogue and show that we can model the number counts of this undetected population down to flux-density levels well below the detection threshold of the radio survey. We demonstrate the capabilities that our method will have with future generation wide-area radio surveys by performing simulations over various sky areas. We show that it is possible to accurately constrain the number counts of the simulated distribution down to one-tenth of the flux noise rms with just a sky area of 100 deg2. We then test the application of our method using data from the Faint Images of the Radio Sky at Twenty-Centimetres survey (FIRST). We extract flux densities from the FIRST map, sensitive to 150 ?Jy beam-1 (1 ?), using the positional information from a catalogue in the same field, also acquired at the same frequency, sensitive to 12 ?Jy beam-1 (1 ?). Implementing our method, with known source positions, we are able to recover the right differential number counts of the noise-dominated FIRST map fluxes down to a flux-density level which is one-tenth the FIRST detection threshold.

Mitchell-Wynne, Ketron; Santos, Mário G.; Afonso, José; Jarvis, Matt J.

2014-01-01

65

MOA-2010-BLG-311: A Planetary Candidate below the Threshold of Reliable Detection  

NASA Astrophysics Data System (ADS)

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

Yee, J. C.; Hung, L.-W.; Bond, I. A.; Allen, W.; Monard, L. A. G.; Albrow, M. D.; Fouqué, P.; Dominik, M.; Tsapras, Y.; Udalski, A.; Gould, A.; Zellem, R.; Bos, M.; Christie, G. W.; DePoy, D. L.; Dong, Subo; Drummond, J.; Gaudi, B. S.; Gorbikov, E.; Han, C.; Kaspi, S.; Klein, N.; Lee, C.-U.; Maoz, D.; McCormick, J.; Moorhouse, D.; Natusch, T.; Nola, M.; Park, B.-G.; Pogge, R. W.; Polishook, D.; Shporer, A.; Shvartzvald, Y.; Skowron, J.; Thornley, G.; ?FUN Collaboration; Abe, F.; Bennett, D. P.; Botzler, C. S.; Chote, P.; Freeman, M.; Fukui, A.; Furusawa, K.; Harris, P.; Itow, Y.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Miyake, N.; Ohnishi, K.; Rattenbury, N. J.; Saito, To.; Sullivan, D. J.; Sumi, T.; Suzuki, D.; Sweatman, W. L.; Tristram, P. J.; Wada, K.; Yock, P. C. M.; MOA Collaboration; Szyma?ski, M. K.; Soszy?ski, I.; Kubiak, M.; Poleski, R.; Ulaczyk, K.; Pietrzy?ski, G.; Wyrzykowski, ?.; The OGLE Collaboration; Bachelet, E.; Batista, V.; Beatty, T. G.; Beaulieu, J.-P.; Bennett, C. S.; Bowens-Rubin, R.; Brillant, S.; Caldwell, J. A. R.; Cassan, A.; Cole, A. A.; Corrales, E.; Coutures, C.; Dieters, S.; Dominis Prester, D.; Donatowicz, J.; Greenhill, J.; Henderson, C. B.; Kubas, D.; Marquette, J.-B.; Martin, R.; Menzies, J. W.; Shappee, B.; Williams, A.; Wouters, D.; van Saders, J.; Zub, M.; The PLANET Collaboration; Street, R. A.; Horne, K.; Bramich, D. M.; Steele, I. A.; The RoboNet Collaboration; Alsubai, K. A.; Bozza, V.; Browne, P.; Burgdorf, M. J.; Calchi Novati, S.; Dodds, P.; Finet, F.; Gerner, T.; Hardis, S.; Harpsøe, K.; Hessman, F. V.; Hinse, T. C.; Hundertmark, M.; Jørgensen, U. G.; Kains, N.; Kerins, E.; Liebig, C.; Mancini, L.; Mathiasen, M.; Penny, M. T.; Proft, S.; Rahvar, S.; Ricci, D.; Sahu, K. C.; Scarpetta, G.; Schäfer, S.; Schönebeck, F.; Snodgrass, C.; Southworth, J.; Surdej, J.; Wambsganss, J.; MiNDSTEp Consortium, The

2013-05-01

66

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. PMID:23825884

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

2013-01-01

67

Effects of threshold displacement energy on defect production by displacement cascades in ?, ? and ?-LiAlO2  

NASA Astrophysics Data System (ADS)

Threshold displacement energy evaluation and a series of displacement cascade simulations in ?, ?, and ?-LiAlO2 were performed using molecular dynamics. Threshold displacement energy evaluations indicated that higher absolute ionic charge values and larger densities both increase threshold displacement energy. The displacement cascade simulations suggest that the influence of different crystal structures on the number of interstitial atoms generated in a displacement cascade is explainable almost entirely by the difference of the threshold displacement energy.

Tsuchihira, H.; Oda, T.; Tanaka, S.

2013-11-01

68

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

NASA Astrophysics Data System (ADS)

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

Nguyen, Duy; Tran, Giang

2012-07-01

69

The intrapleural volume threshold for ultrasound detection of pneumothoraces: An experimental study on porcine models  

PubMed Central

Background Small pneumothoraxes (PTXs) may not impart an immediate threat to trauma patients after chest injuries. However, the amount of pleural air may increase and become a concern for patients who require positive pressure ventilation or air ambulance transport. Lung ultrasonography (US) is a reliable tool in finding intrapleural air, but the performance characteristics regarding the detection of small PTXs need to be defined. The study aimed to define the volume threshold of intrapleural air when PTXs are accurately diagnosed with US and compare this volume with that for chest x-ray (CXR). Methods Air was insufflated into a unilateral pleural catheter in seven incremental steps (10, 25, 50, 100, 200, 350 and 500 mL) in 20 intubated porcine models, followed by a diagnostic evaluation with US and a supine anteroposterior CXR. The sonographers continued the US scanning until the PTXs could be ruled in, based on the pathognomonic US “lung point” sign. The corresponding threshold volume was noted. A senior radiologist interpreted the CXR images. Results The mean threshold volume to confirm the diagnosis of PTX using US was 18 mL (standard deviation of 13 mL). Sixty-five percent of the PTXs were already diagnosed at 10 mL of intrapleural air; 25%, at 25 mL; and the last 10%, at 50 mL. At an air volume of 50 mL, the radiologist only identified four out of 20 PTXs in the CXR pictures; i.e., a sensitivity of 20% (95% CI: 7%, 44%). The sensitivity of CXR increased as a function of volume but leveled off at 67%, leaving one-third (1/3) of the PTXs unidentified after 500 mL of insufflated air. Conclusion Lung US is very accurate in diagnosing even small amounts of intrapleural air and should be performed by clinicians treating chest trauma patients when PTX is among the differential diagnoses. PMID:23453044

2013-01-01

70

Probing nuclear symmetry energy with the sub-threshold pion production  

E-print Network

Within the framework of semiclassical Boltzmann-Uehling-Uhlenbeck (BUU) transport model, we investigated the effects of symmetry energy on the sub-threshold pion using the isospin MDI interaction with the stiff and soft symmetry energies in the central collision of $^{48}$Ca + $^{48}$Ca at the incident beam energies of 100, 150, 200, 250 and 300 MeV/nucleon, respectively. We find that the ratio of $\\pi^{-}/\\pi^{+}$ of sub-threshold charged pion production is greatly sensitive to the symmetry energy, particularly around 100 MeV/nucleon energies. Large sensitivity of sub-threshold charged pion production to nuclear symmetry energy may reduce uncertainties of probing nuclear symmetry energy via heavy-ion collision.

Fang Zhang; Yang Liu; Gao-Chan Yong; Wei Zuo

2012-04-04

71

Effects of presentation method and duration on alarm detection threshold in the presence of loud pink noise.  

PubMed

Detection of pure tone signals in the presence of noise has been thoroughly studied. Most of these studies have used monaural presentation of audio stimuli. Also, studies testing alarm detection in the presence of noise are limited. In 2013, Karunarathne et al., conducted a study and found out that human listeners were able to detect an alarm in negative signal-to-noise ratios (SNRs), as low as -24 dB. This study aims to investigate the effects of presentation method and duration of the alarms on detection threshold. Eight conditions varied by presentation method (monaural vs spatial) and alarm duration were tested. Sixteen human subjects with normal hearing were given the task of identifying which one of two sound intervals contained an alarm along with 80dBA pink noise. Thresholds were estimated as the 79.4% points on the psychometric functions, using adaptive 2-Interval Forced Choice (2IFC) procedure with a 3-down 1-up rule. Results indicated that detection thresholds were statistically significantly lower in spatial condition compared to monaural. The effect of alarm duration was not significant in both spatial and monaural conditions. Thresholds lower than -30 dB SNR were observed in the spatial condition, which agreed with the findings of Karunarathne et al. and further extended threshold boundaries. PMID:25235188

Karunarathne, Buddhika; So, Richard; Kam, Anna

2014-04-01

72

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. PMID:22737023

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

2012-01-01

73

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

E-print Network

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

Thumm, Uwe

74

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

75

Evaluation of the validity of a maximum likelihood adaptive staircase procedure for measurement of olfactory detection threshold in mice.  

PubMed

Threshold is defined as the stimulus intensity necessary for a subject to reach a specified percent correct on a detection test. MLPEST (maximum likelihood parameter estimation by sequential testing) is a method that is able to determine threshold accurately and more rapidly than many other methods. Originally developed for human auditory and visual tasks, it has been adapted for human olfactory and gustatory tests. In order to utilize this technique for olfactory testing in mice, we have adapted MLPEST methodology for use with computerized olfactometry as a tool to estimate odor detection thresholds. Here we present Monte Carlo simulations and operant conditioning data that demonstrate the potential utility of this technique in mice, we explore the ramifications of altering MLPEST test parameters on performance, and we discuss the advantages and disadvantages of using MLPEST compared to other methods for the estimation of thresholds in rodents. Using MLPEST, we find that olfactory detection thresholds in mice deficient for the cyclic nucleotide-gated channel subunit A2 are similar to those of wild-type animals for odorants the knockout animals are able to detect. PMID:16306319

Clevenger, Amy C; Restrepo, Diego

2006-01-01

76

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

E-print Network

Results are reported from a joint analysis of Phase I and Phase II data from the Sudbury Neutrino Observatory. The effective electron kinetic energy threshold used is Teff=3.5 MeV, the lowest analysis threshold yet achieved ...

Monroe, Jocelyn

77

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

PubMed

Earlier spatial orientation studies used both motion-detection (e.g., did I move?) and direction-recognition (e.g., did I move left/right?) paradigms. The purpose of our study was to compare thresholds measured with motion-detection and direction-recognition tasks on a standard Moog motion platform to see whether a substantial fraction of the reported threshold variation might be explained by the use of different discrimination tasks in the presence of vibrations that vary with motion. Thresholds for the perception of yaw rotation about an earth-vertical axis and for interaural translation in an earth-horizontal plane were determined for four healthy subjects with standard detection and recognition paradigms. For yaw rotation two-interval detection thresholds were, on average, 56 times smaller than two-interval recognition thresholds, and for interaural translation two-interval detection thresholds were, on average, 31 times smaller than two-interval recognition thresholds. This substantive difference between recognition thresholds and detection thresholds is one of our primary findings. For motions near our measured detection threshold, we measured vibrations that matched previously established vibration thresholds. This suggests that vibrations contribute to whole body motion detection. We also recorded yaw rotation thresholds on a second motion device with lower vibration and found direction-recognition and motion-detection thresholds that were not significantly different from one another or from the direction-recognition thresholds recorded on our Moog platform. Taken together, these various findings show that yaw rotation recognition thresholds are relatively unaffected by vibration when moderate (up to ? 0.08 m/s(2)) vibration cues are present. PMID:24068754

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

2013-12-01

78

Quantitative prediction of perceptual decisions during near-threshold fear detection  

NASA Astrophysics Data System (ADS)

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

Pessoa, Luiz; Padmala, Srikanth

2005-04-01

79

Determination of threshold energy dose for ultrasound-induced transdermal drug transport  

Microsoft Academic Search

Low-frequency (20 kHz) ultrasound has been shown to enhance transdermal transport of drugs, a phenomenon referred to as sonophoresis. In this paper, we report the threshold energy dose for ultrasound-induced transdermal drug transport. The threshold was determined by in vitro measurements of the dependence of sonophoretic enhancement on ultrasound parameters, including intensity, duty cycle, and exposure time. While the enhancement

Samir Mitragotri; Joanne Farrell; Hua Tang; Takaaki Terahara; Joseph Kost; Robert Langer

2000-01-01

80

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

NASA Astrophysics Data System (ADS)

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

Dobrovolsky, V.

2014-10-01

81

Nuclear Elastic Scattering of Photons near the Particle Threshold Energy (II)  

Microsoft Academic Search

Elastic scattering cross section of photons by a nucleus near the particle threshold energy was studied at 120 degrees for Mg, Fe, Zn, As, Cd, Sb and Bi using bremsstrahlung gamma rays. Each element has a gross peak in this energy range. This is consistent with the earlier results reported by Tohei et al. The peak values are 0.5, 1.3,

Masumi Sugawara; Shigeki Mori; Atsuwo Ono; Akio Hotta; Motoharu Kimura

1963-01-01

82

NUCLEAR ELASTIC SCATTERING OF PHOTONS NEAR THE PARTICLE THRESHOLD ENERGY. PART II  

Microsoft Academic Search

Elastic scattering cross section of photons by a nucleus near the ; particle threshold energy was studied at 120 degrees for Mg, Fe, Zn, As, Cd, Sb. ; and Bi using bremsstrahlung gamma rays. Each element has a gross peak in this ; energy range. This is consistent with the earlier results reported by Tohei et ; al. The peak

M. Sugawara; S. Mori; A. Ono; A. Hotta; M. Kimura

1963-01-01

83

Meson synchrotron radiation threshold for ultra-high energy cosmic ray protons  

Microsoft Academic Search

High energy protons in uniform circular motion can emit the equivalent of synchrotron radiation composed by mesons. Here, we consider this process in an astrophysical context. We show, in particular, that astrophysical sources of cosmic rays endowed with a magnetic field B> 1012 Gauss cannot accelerate protons to energies higher than E? 1015 eV since, in this situation, the threshold

Douglas Fregolente

84

Fine resolution measurements of the L-dependent energy threshold for isotropy at the trapping boundary  

Microsoft Academic Search

The fluxes of trapped and precipitating particles are often near equal at the trapping boundary in the radiation belts at low satellite altitudes. Near midnight this isotropy phenomenon was previously discovered frequently to occur only above an energy threshold which decreases rapidly with increasing L value. Now, much finer energy resolution measurements of the phenomenon for electrons have been performed

W. L. Imhof

1988-01-01

85

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

86

Electroreception of catfish Ictalurus nebulosus in uniform and non-uniform DC fields: detection threshold and body length  

Microsoft Academic Search

Catfish are able to detect electric fields with their electroreceptor organs. It goes without saying that the electrodetection threshold depends on the sensitivity of the electroreceptor organs. The sensitivity in turn depends on a variety of extrinsic factors such as water temperature, conductivity, and electric field fre- quency. The aim of this study was to determine the effect of an

Lonneke B. M. Eeuwes; Robert C. Peters; Franklin Bretschneider; Wim J. G. Loos

2001-01-01

87

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

PubMed

Hearing-aid noise reduction should reduce background noise, but not disturb the target speech. This objective is difficult because noise reduction suffers from a trade-off between the amount of noise removed and signal distortion. It is unknown if this important trade-off differs between normal-hearing (NH) and hearing-impaired (HI) listeners. This study separated the negative effect of noise reduction (distortion) from the positive effect (reduction of noise) to allow the measurement of the detection threshold for noise-reduction (NR) distortion. Twelve NH subjects and 12 subjects with mild to moderate sensorineural hearing loss participated in this study. The detection thresholds for distortion were determined using an adaptive procedure with a three-interval, two-alternative forced-choice paradigm. Different levels of distortion were obtained by changing the maximum amount of noise reduction. Participants were also asked to indicate their preferred NR strength. The detection threshold for overall distortion was higher for HI subjects than for NH subjects, suggesting that stronger noise reduction can be applied for HI listeners without affecting the perceived sound quality. However, the preferred NR strength of HI listeners was closer to their individual detection threshold for distortion than in NH listeners. This implies that HI listeners tolerate fewer audible distortions than NH listeners. PMID:25190410

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

2014-09-01

88

Optical damage threshold and energy deposition in the embedded nanostructures  

NASA Astrophysics Data System (ADS)

Results of energy deposition measurement in interaction between an ultra-short laser pulse and nanostructured target are described. As a target we used carbon nanotubes and multilayer graphene deposited on a sapphire wafer surface and embedded in a layer of protein. A 25 fs, p-polarised pulses from a 1 kHz-Ti;sapphire laser of energy up to 3 mJ were focused to give intensity up to 2×1016 W/cm2 on a target positioned within an integrating sphere. The absorption measured showed a level in excess of 80 %, increasing with the intensity. The results suggest that the host material (lysozyme) is responsible for the breakdown while the embedded material contributes dominantly to the absorption.

Janulewicz, Karol A.; Lee, Hak Jae; Hapiddin, Asep; Matouš, Bohuslav; Kim, Chul Min; Joseph, Dickson; Geckeler, K. E.; Nickles, Peter V.

2012-11-01

89

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

2011-03-01

90

An objective method for measuring face detection thresholds using the sweep steady-state visual evoked response.  

PubMed

We introduce a sensitive method for measuring face detection thresholds rapidly, objectively, and independently of low-level visual cues. The method is based on the swept parameter steady-state visual evoked potential (ssVEP), in which a stimulus is presented at a specific temporal frequency while parametrically varying ("sweeping") the detectability of the stimulus. Here, the visibility of a face image was increased by progressive derandomization of the phase spectra of the image in a series of equally spaced steps. Alternations between face and fully randomized images at a constant rate (3/s) elicit a robust first harmonic response at 3 Hz specific to the structure of the face. High-density EEG was recorded from 10 human adult participants, who were asked to respond with a button-press as soon as they detected a face. The majority of participants produced an evoked response at the first harmonic (3 Hz) that emerged abruptly between 30% and 35% phase-coherence of the face, which was most prominent on right occipito-temporal sites. Thresholds for face detection were estimated reliably in single participants from 15 trials, or on each of the 15 individual face trials. The ssVEP-derived thresholds correlated with the concurrently measured perceptual face detection thresholds. This first application of the sweep VEP approach to high-level vision provides a sensitive and objective method that could be used to measure and compare visual perception thresholds for various object shapes and levels of categorization in different human populations, including infants and individuals with developmental delay. PMID:23024355

Ales, Justin M; Farzin, Faraz; Rossion, Bruno; Norcia, Anthony M

2012-01-01

91

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

E-print Network

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

Farantos, Stavros C.

92

Molecular-dynamics simulation of threshold displacement energies in lithium aluminate  

NASA Astrophysics Data System (ADS)

Threshold displacement energies in LiAlO2 were evaluated using molecular dynamics technique. A pairwise potential model was adopted for simplicity, with reliance on high ionicity of LiAlO2. In all the three elements, the threshold displacement energy varied considerably depending on the displacement direction of the primary knock-on atom. The average displacement energies of Li, O and Al over 342 displacement directions were evaluated to be 22, 37 and 84 eV, respectively. The order of these values are consistent with the number of generated defects in displacement cascade simulation with initial PKA energy of 1-5 keV, where the number of generated defects was the largest in Li and the smallest in Al in proportion to the number of atoms included in the system, regardless of the initial PKA energy.

Tsuchihira, H.; Oda, T.; Tanaka, S.

2011-07-01

93

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

PubMed

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 D(0) 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. PMID:22852673

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

2012-07-01

94

NUCLEAR ELASTIC SCATTERING OF PHOTONS NEAR THE PARTICLE THRESHOLD ENERGY PART I  

Microsoft Academic Search

The elastic scattering of photons near the particle threshold energy was ; studied for Al, Si, S, K, Ca, Ni, Cu, Cd, Sn, Pb, and Bi. The bremsstrahlung x ; rays from a 25 Mev betatron were used. The pulse of the primary x rays was ; expanded up to about 30 mu sec to decrease the pile-up effect. The

T. Tohei; M. Sugawara; S. Mori; M. Kimura

1961-01-01

95

SAM Thresholding and False Discovery Rates for Detecting Differential Gene Expression in DNA Microarrays  

Microsoft Academic Search

SAM is a computer package for correlating gene expression with an outcome parameter such as treatment, survival time, or diagnostic class. It thresholds an appropriate test statistic and reports the q-value of each test based on a set of sample permutations. SAM works as a Microsoft Excel add-in and has additional features for fold-change thresholding and block permutations. Here, we

John D. Storey; Robert Tibshirani

96

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

E-print Network

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

Zhe Chang; Xin Li

2008-09-27

97

Effect of molecular size on the threshold energy producing a 51 Cr hot atom  

Microsoft Academic Search

The lowest retention values of51Cr hot atom in various forms of the -diketonetype complexes, Cr(bzac)3, Cr(dpm)3 and Cr(dbm)3, as well as Cr(acac)3 as a reference, were obtained in the experimental condition in which they are regarded as the primary retentions. From these retention values, the threshold energies for producing a hot atom, the appearance energies, were estimated using the calculated

T. Matsuura; H. Takenawa; T. Suzuki; R. Hirota; K. Sasaki

1990-01-01

98

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

99

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

100

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

101

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

102

Determination of ortho- and retronasal detection thresholds and odor impact of 2,5-dimethyl-3-methoxypyrazine in wine.  

PubMed

2,5-Dimethyl-3-methoxypyrazine (DMMP) has been recently identified in both Coccinellidae-tainted (by either Coccinella septempunctata or Harmonia axyridis beetles) and untainted wines; however, little is known regarding its impact on wine aroma and flavor. The aims of this study were to obtain an accurate estimate of both the ortho- and retronasal detection thresholds of DMMP in red wine and to understand how DMMP contributes to the aroma profile of red wine. In the first study, thresholds were determined for 21 individuals using the ASTM E679 ascending forced choice method of limits. The orthonasal group best estimate threshold (BET) was 31 ng/L and the retronasal group BET was 70 ng/L. A moderate variation in individual thresholds was observed for the orthonasal modality (standard deviation (SD) = 19.8) and a larger variation was noted for retronasal thresholds (SD = 111.8). In the second study, a panel of 8 assessors performed descriptive sensory analysis on 3 red wines containing various concentrations of added DMMP (0, 50, and 120 ng/L). Results show significant changes in aroma characteristics in the 120 ng/L wine and smaller effects at the 50 ng/L level. Overall, wines spiked with DMMP generated lower intensity ratings for cherry and red berry descriptors and higher ratings for earthy/musty and green/vegetal descriptors. When considered with other recent results on DMMP concentrations found in wine, DMMP can be considered a hitherto undescribed impact odorant in some wine styles. PMID:23057415

Botezatu, Andreea; Pickering, Gary J

2012-11-01

103

Spatial beam shaping for lowering the threshold energy for femtosecond laser pulse photodisruption  

NASA Astrophysics Data System (ADS)

High precision femtosecond laser surgery is achieved by focusing femtosecond (fs) laser pulses in transparent tissues to create an optical breakdown leading to tissue dissection through photodisruption. For moving applications in ophthalmology from corneal or lental applications in the anterior eye to vitreal or retinal surgery in the posterior eye the applied pulse energy needs to be minimized in order to avoid harm to the retina. However, the aberrations of the anterior eye elements cause a distortion of the wave front and consequently an increase in size of the irradiated area and a decrease in photon density in the focal volume. Therefore, higher pulse energy is required to still surpass the threshold irradiance. In this work, aberrations in an eye model consisting of a plano-convex lens for focusing and 2-hydroxyethylmethacrylate (HEMA) in a water cuvette as eye tissue were corrected with 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. A reduction of the threshold energy was shown in the aberration-corrected case and the spatial confinement raised the irradiance at constant pulse energy. As less energy is required for photodisruption when correcting for wave front aberrations the potential risk of peripheral damage is reduced, especially for the retina during laser surgery in the posterior eye segment. This offers new possibilities for high precision fs-laser surgery in the treatment of several vitreal and retinal pathologies.

Hansen, Anja; Ripken, Tammo; Heisterkamp, Alexander

2011-10-01

104

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

E-print Network

Vacuum ultraviolet mass-analyzed threshold ionization spectroscopy of p-, m-, and o-difluorobenzenes. Ionization energies and vibrational frequencies and structures of the cations Chan Ho Kwon, Hong Lae Kim been measured by vacuum ultraviolet mass-analyzed threshold ionization VUV-MATI spectroscopy. From

Kim, Myung Soo

105

Silicon displacement threshold energy determined by electron paramagnetic resonance and positron annihilation spectroscopy in cubic and hexagonal polytypes of silicon carbide  

NASA Astrophysics Data System (ADS)

Both for electronic and nuclear applications, it is of major interest to understand the properties of point defects into silicon carbide (SiC). Low energy electron irradiations are supposed to create primary defects into materials. SiC single crystals have been irradiated with electrons at two beam energies in order to investigate the silicon displacement threshold energy into SiC. This paper presents the characterization of the electron irradiation-induced point defects into both polytypes hexagonal (6H) and cubic (3C) SiC single crystals by using both positron annihilation spectroscopy (PAS) and electron paramagnetic resonance (EPR). The nature and the concentration of the generated point defects depend on the energy of the electron beam and the polytype. After an electron irradiation at an energy of 800 keV v Si mono-vacancies and v Si-v C di-vacancies are detected in both 3C and 6H-SiC polytypes. On the contrary, the nature of point defects detected after an electron irradiation at 190 keV strongly depends on the polytype. Into 6H-SiC crystals, silicon Frenkel pairs v Si-Si are detected whereas only carbon vacancy related defects are detected into 3C-SiC crystals. The difference observed in the distribution of defects detected into the two polytypes can be explained by the different values of the silicon displacement threshold energies for 3C and 6H-SiC. By comparing the calculated theoretical numbers of displaced atoms with the defects numbers measured using EPR, the silicon displacement threshold energy has been estimated to be slightly lower than 20 eV in the 6H polytype and close to 25 eV in the 3C polytype.

Kerbiriou, X.; Barthe, M.-F.; Esnouf, S.; Desgardin, P.; Blondiaux, G.; Petite, G.

2007-05-01

106

Threshold-based Detection of P and T-wave in ECG using New Feature Signal  

Microsoft Academic Search

Summary Detection of P and T waves is an important part in the analysis and interpretation of ECG. The presented algorithm detects and delineates both P and T-waves simultaneously. It employs a modified definition of slope, of ECG signal, as the feature for detection of ECG wave components. A number of transformations of the filtered and baseline drift corrected ECG

V. S. Chouhan; S. S. Mehta

2008-01-01

107

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

108

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

NASA Astrophysics Data System (ADS)

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

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

1987-05-01

109

Fine resolution measurements of the L-dependent energy threshold for isotropy at the trapping boundary  

SciTech Connect

The fluxes of trapped and precipitating particles are often near equal at the trapping boundary in the radiation belts at low satellite altitudes. Near midnight this isotropy phenomenon was previously discovered frequently to occur only above an energy threshold which decreases rapidly with increasing L value. Now, much finer energy resolution measurements of the phenomenon for electrons have been performed with much lower backgrounds and higher sampling rates, and hence better statistical accuracies in the energy spectra. Here we present details on the strong dependence of the measured ratios of precipitating to trapped electrons on the gyroradius of the particles. Published theoretical calculations for the L dependences of the magnetic rigidity of the onset of isotropy for both electrons and protons near midnight are compared with the present measurements under both very quiet and very disturbed magnetic activity conditions. The measured curves are generally steeper than the theoretical ones except for a few at very disturbed times when reasonable agreement is achieved. The frequency of occurrence of an energy selective threshold for isotropy at the trapping boundary is presented as a function of magnetic local time; it was observed on 34% of the passes near midnight and seldom near noon. copyright American Geophysical Union 1988

Imhof, W.L.

1988-09-01

110

Study of the anisotropy of the threshold energy in copper using in-situ electrical resistivity measurements in the HVEM  

SciTech Connect

In the past, electrical-resistivity measurements and high voltage electron microscopy-(HVEM) have been used separately to investigate the anisotropy of the threshold energy for Frenkel-pair production. Electrical resistivity, measured in a conventional electron accelerator, has been used to observe small changes in the concentration of isolated Frenekel pairs at low temperatures, while HVEM experiments have focussed on the observation of measurable changes in visible defect clusters, primarily at elevated temperatures. However, quantitative comparison of the threshold energies obtained with the two techniques has proved difficult. As a first step toward resolving this dilemma, the threshold-energy surface for copper was determined by in-situ electrical-resistivity measurements below 10 K in the HVEM. By combining the advantages of both techniques, this approach allowed a precise and detailed study of the anisotropy of the threshold energy for Frenkel-pair production.

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

1980-01-01

111

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

112

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

E-print Network

.e. transdermal and transcranial) cavitation detection during BBB opening. After the intravenous administration a formidable challenge in drug delivery. The blood­brain barrier (BBB) prevents most neurological drugs from

Konofagou, Elisa E.

113

Infrared image dim small target detection based on double energy accumulation  

Microsoft Academic Search

Detection of dim moving small targets at low signal noise ratio is a very important issue and difficult problem in infrared searching and tracking system. Based on analysis of the character of infrared images, a new double energy accumulating method is proposed. Firstly, images are denoised by wavelet transformation with soft threshold. Then, object motion area is detected according to

Yuqiu Sun; Sheng Zheng; Jinwen Tian; Jian Liu

2005-01-01

114

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

115

Detection of low energy solar neutrinos with HPGermanium  

E-print Network

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

L. Baudis; H. V. Klapdor-Kleingrothaus

1999-06-30

116

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

117

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

PubMed

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

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

2013-01-01

118

Atomistic simulations of threshold displacement energies in SiO 2  

NASA Astrophysics Data System (ADS)

Silica is one of the candidate materials for final focusing mirrors in inertial fusion reactors. This material will be exposed to high neutron irradiation fluxes during operation. Radiation damage results in point defects that can lead to obscuration of this material; that is, degradation of the optical properties of silica. In this paper, we present molecular dynamic simulations of defect production in silica glass. Results on the threshold displacement energies due to oxygen primary knock-on atoms (PKA) are reported concluding that a range of energies (20-40 eV) exists in which the defects have a probability to be created. In addition, we determine a range of distances for a PKA to become a stable defect from its original position. Our present analysis is focused on the formation of oxygen deficient centers (ODC).

Mota, F.; Caturla, M.-J.; Perlado, J. M.; Dominguez, E.; Kubota, A.

2004-08-01

119

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

E-print Network

Within the framework of the improved isospin dependent quantum molecular dynamics (ImIQMD) model, the dynamics of strangeness (K$^{0,+}$, $\\Lambda$ and $\\Sigma^{-,0,+}$) production in heavy-ion collisions near threshold energies is investigated systematically, in which the strange particles are considered to be mainly produced by the inelastic collisions of baryon-baryon and pion-baryon. The collisions in the region of supra-saturation densities of the dense baryonic matter formed in heavy-ion collisions dominate the yields of strangeness production. The 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 the K$^{+}$ production in the reactions $^{12}$C+$^{12}$C and $^{197}$Au+$^{197}$Au.

Zhao-Qing Feng; Gen-Ming Jin

2010-10-13

120

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

Microsoft Academic Search

Results are reported from a joint analysis of Phase I and Phase II data from the Sudbury Neutrino Observatory. The effective electron kinetic energy threshold used is Teff=3.5 MeV, the lowest analysis threshold yet achieved with water Cherenkov detector data. In units of 106 cm-2 s-1, the total flux of active-flavor neutrinos from B8 decay in the Sun measured using

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

2010-01-01

121

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

122

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

Code of Federal Regulations, 2010 CFR

...operator must, within 30 calendar days of receiving evidence or confirmation of a standard threshold shift, unless a physician or audiologist determines the standard threshold shift is neither work-related nor aggravated by occupational noise exposure:...

2010-07-01

123

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

E-print Network

We consider the so-called Keplerian periodogram, in which the putative detectable signal is modelled by a highly non-linear Keplerian radial velocity function, appearing in Doppler exoplanetary surveys. We demonstrate that for planets on high-eccentricity orbits the Keplerian periodogram is far more efficient than the classic Lomb-Scargle periodogram and even the multiharmonic periodograms, in which the periodic signal is approximated by a truncated Fourier series. We provide new numerical algorithm for computation of the Keplerian periodogram. This algorithm adaptively increases the parameteric resolution where necessary, in order to uniformly cover all local optima of the Keplerian fit. Thanks to this improvement, the algorithm provides more smooth and reliable results with minimized computing demands. We also derive a fast analytic approximation to the false alarm probability levels of the Keplerian periodogram. This approximation has the form $(P z^{3/2} + Q z) W \\exp(-z)$, where $z$ is the observed perio...

Baluev, Roman V

2014-01-01

124

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

125

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

E-print Network

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

Guo, Wen-Mei; Liu, Hang; Zuo, Wei

2014-01-01

126

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

PubMed Central

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

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

2014-01-01

127

Threshold Improvements in Scintillation Experiments by Photon Individuation  

NASA Astrophysics Data System (ADS)

Dark matter experiments face two main challenges: low rate and low energy detection. Background reduction techniques are widely in development in order to improve sensitivity. Energy threshold is more technique-dependent and so it requires specific efforts for each detection approach. In this work we present some improvements in this line that open the possibility of further reduction in the energy threshold of scintillation experiments. Some preliminary results within the projected NaI(Tl) experiment ANAIS are reported.

Pobes, C.; Amaré, J.; Borjabad, S.; Calleja, A.; García, E.; Martínez, M.; Morales, J.; de Solórzano, A. Ortiz; Puimedón, J.; Sarsa, M. L.; Villar, J. A.

2007-08-01

128

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

129

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

130

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

PubMed Central

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

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

2014-01-01

131

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

PubMed Central

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

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

2014-01-01

132

Highly sensitive colour change system within slight differences in metal ion concentrations based on homo–binuclear complex formation equilibrium for visual threshold detection of trace metal ions  

Microsoft Academic Search

A new technique of expressing slight differences in metal ion concentrations by clear difference in colour was established for visual threshold detection of trace metal ions. The proposed method is based on rapid change of the mole fraction of the homo–binuclear complex (M2L) about a ligand in a narrow range of the total metal ion concentration (MT) in a small

Hitoshi Mizuguchi; Hiroshi Atsumi; Keigo Hashimoto; Yasuhiro Shimada; Yuki Kudo; Masatoshi Endo; Fumihiko Yokota; Junichi Shida; Takao Yotsuyanagi

2004-01-01

133

Quantitative encoding of a partial agonist effect on individual opioid receptors by multi-site phosphorylation and threshold detection  

PubMed Central

Many drugs act as partial agonists of seven-transmembrane signaling receptors when compared to endogenous ligands. Partial agonism is well described as a 'macroscopic' property manifest at the level of physiological systems or cell populations, but it is not known whether partial agonists encode discrete regulatory information at the 'microscopic' level of individual receptors. We addressed this question by focusing on morphine, a partial agonist drug for µ-type opioid peptide receptors, and combining quantitative mass spectrometry with cell biological analysis to investigate morphine's reduced efficacy for promoting receptor endocytosis when compared to a peptide full agonist. We show that these chemically distinct ligands produce a complex, and qualitatively similar mixture of phosphorylated opioid receptor forms in intact cells. Quantitatively, however, the agonists promote markedly disproportional production of multi-site phosphorylation involving a specific Ser/Thr motif, whose modification at more than one residue is essential for efficient recruitment of the adaptor protein ?-arrestin to clathrin-coated pits that mediate subsequent endocytosis of MORs. These results reveal quantitative encoding of agonist-selective endocytosis at the level of individual opioid receptors, based on the conserved biochemical principles of multi-site phosphorylation and threshold detection. PMID:21868358

Lau, Elaine K.; Trester-Zedlitz, Michelle; Trinidad, Jonathan C.; Kotowski, Sarah J.; Krutchinsky, Andrew N.; Burlingame, Alma L.; von Zastrow, Mark

2013-01-01

134

Electron cloud overlap related to specific energy threshold and breakdown at high temperature, short time and nano distance  

Microsoft Academic Search

An electron cloud overlap model is developed to reflect the integrity of the electron arrangements for a system with two adjoining atoms excited by high temperature. This is accomplished with the aid of an anticipated specific energy threshold breakdown transitional region that spanned approximately one-half order of magnitude in the absolute temperature. Moderate overlap is assumed such that the interference

G. C. Sih

2008-01-01

135

Infrared image dim small target detection based on double energy accumulation  

NASA Astrophysics Data System (ADS)

Detection of dim moving small targets at low signal noise ratio is a very important issue and difficult problem in infrared searching and tracking system. Based on analysis of the character of infrared images, a new double energy accumulating method is proposed. Firstly, images are denoised by wavelet transformation with soft threshold. Then, object motion area is detected according to difference images and the target intensity is well enhanced by accumulating energy two times with addition and product operation. Finally, target candidates are separated from background by thresholding process with the selected threshold. Computer experiments are carried out with an infrared image sequence and the experimental results illustrate that the proposed method is effective and efficient.

Sun, Yuqiu; Zheng, Sheng; Tian, Jinwen; Liu, Jian

2005-11-01

136

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

137

Estimates of the DT Fusion Gamma Spectrum Using an Energy Thresholding Gas Cherenkov Detector  

NASA Astrophysics Data System (ADS)

In addition to alphas and neutrons, the DT fusion reaction also produces gamma rays from the intermediate excited 5He nucleus with a small branching ratio 10E-5 gamma/n. The very small branching ratio of the gamma-rays are mitigated by the very large yields that are expected on NIF (10E+19 ). The excited 5He can produce gamma-rays by decay to the ground state, emitting a 16.75 MeV gamma-ray (width 0.5 MeV), or to a broad first excited state emitting a 12 MeV gamma ray (width 5 MeV). Knowledge of the relative gamma-ray BR of these two states, from which we infer the DT gamma ray spectrum, is important to making absolutely calibrated measurements on a variety of experiments. We have carried out an energy thresh-holding experiment for DT ICF implosions on the Omega laser using a Gas Cherenkov Detector, and compared the relative intensities at various thresholds with theoretical gamma spectra folded with detector response as calculated by ACCEPT and GEANT4 codes. We present recent results from this experiment, our estimate of the precision of the DT fusion gamma spectrum and the implications for the future determination of the DT gamma/n BR.

Horsfield, Colin; Rubery, Michael; Hans, Herrmann; Mack, Joseph; Young, Carl; Caldwell, Steven; Scott, Evans; Sedillo, Thomas; Kim, Yongho; Hale, Gerry; Shah, Rahul; Kirk, Miller; Wolfgang, Stoefll

2011-11-01

138

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

139

The perils of thresholding  

E-print Network

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

Font-Clos, Francesc; Deluca, Anna; Moloney, Nicholas R

2014-01-01

140

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

141

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

142

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

143

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

144

Threshold Bound States  

E-print Network

Relationships between the coupling constant and the binding energy of threshold bound states are obtained in a simple manner from an iterative algorithm for solving the eigenvalue problem. The absence of threshold bound states in higher dimensions can be easily understood.

W. A. Berger; H. G. Miller; D. Waxman

2007-02-08

145

Parametrically excited MEMS vibration energy harvesters with design approaches to overcome the initiation threshold amplitude  

NASA Astrophysics Data System (ADS)

Resonant-based vibration harvesters have conventionally relied upon accessing the fundamental mode of directly excited resonance to maximize the conversion efficiency of mechanical-to-electrical power transduction. This paper explores the use of parametric resonance, which unlike the former, the resonant-induced amplitude growth, is not limited by linear damping and wherein can potentially offer higher and broader nonlinear peaks. A numerical model has been constructed to demonstrate the potential improvements over the convention. Despite the promising potential, a damping-dependent initiation threshold amplitude has to be attained prior to accessing this alternative resonant phenomenon. Design approaches have been explored to passively reduce this initiation threshold. Furthermore, three representative MEMS designs were fabricated with both 25 and 10 ?m thick device silicon. The devices include electrostatic cantilever-based harvesters, with and without the additional design modification to overcome initiation threshold amplitude. The optimum performance was recorded for the 25 ?m thick threshold-aided MEMS prototype with device volume ˜0.147 mm3. When driven at 4.2 ms-2, this prototype demonstrated a peak power output of 10.7 nW at the fundamental mode of resonance and 156 nW at the principal parametric resonance, as well as a 23-fold decrease in initiation threshold over the purely parametric prototype. An approximate doubling of the half-power bandwidth was also observed for the parametrically excited scenario.

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

2013-11-01

146

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

PubMed Central

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

Doi, Takahiro; Fujita, Ichiro

2014-01-01

147

Resonance ?'-meson photoproduction on protons at photon energies from the reaction threshold to 3700 MeV  

NASA Astrophysics Data System (ADS)

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

Tryasuchev, V. A.

2013-06-01

148

Gaseous Detector with sub keV Threshold to Study Neutrino Scattering at Low Recoil Energies  

E-print Network

Gaseous detector with a sub keV electron equivalent threshold is a very perspective tool for the precision measurement of the neutrino magnetic moment and to observe coherent scattering of neutrinos on nuclei. The progress in the development of low noise electronics makes it possible to register the rare events at the threshold less than 100 eV. The construction of the gaseous detector is given and the typical pulses with amplitudes of a few eV observed on a bench scale installation are presented. The possible implications for future experiments are discussed.

Kopylov, A V; Petukhov, V V; Solomatin, A E

2014-01-01

149

Detection of meteors and sub-relativistic dust grains by the fluorescence detectors of ultra high energy cosmic rays  

Microsoft Academic Search

Fluorescence detectors of ultra high energy cosmic rays (UHECR) allow to record not only the extensive air showers, initiated by the UHECR particles, but also to detect light, produced by meteors and by the fast dust grains. It is shown that the fluorescence detector operated at the mountain site can register signals from meteors with kinetic energy threshold of about

B. A. Khrenov; V. P. Stulov

2006-01-01

150

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

151

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

152

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

NASA Technical Reports Server (NTRS)

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

Miles, Jeffrey Hilton

2010-01-01

153

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

PubMed Central

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

2013-01-01

154

Detection of negative energy: 4-dimensional examples  

E-print Network

We study the response of switched particle detectors to static negative energy densities and negative energy fluxes. It is demonstrated how the switching leads to excitation even in the vacuum and how negative energy can lead to a suppression of this excitation. We obtain quantum inequalities on the detection similar to those obtained for the energy density by Ford and co-workers and in an `operational' context by Helfer. We revisit the question `Is there a quantum equivalence principle?' in terms of our model. Finally, we briefly address the issue of negative energy and the second law of thermodynamics.

P. C. W. Davies; Adrian C. Ottewill

2002-03-01

155

Determination of ion-ligand bond energies and ion fragmentation energies of electrospray-produced ions by collision-induced dissociation threshold measurements  

Microsoft Academic Search

A triple quadrupole mass spectrometer adapted for the determination of collision-induced dissociation (CID) threshold energies of ions produced by electrospray (ES) is described. The ES-produced ions are transferred from 1 atm atm a low pressure source, 10 Torr, where they can be partially declustered and after that thermalized by gas collisions. The ions entering the vacuum of the triple quadrupole

Stephen G. Anderson; Arthur T. Blades; John Klassen; Paul Kebarle

1995-01-01

156

Ultra-low-energy electron scattering cross section measurements of Ar, Kr and Xe employing the threshold photoelectron source  

NASA Astrophysics Data System (ADS)

A new experimental technique for the measurements of the total cross section for electron scattering from atoms and molecules at very low energy is described. Momentum transfer cross sections for scattering from Ar, Kr and Xe at very low energies were carefully derived using the modified effective range theory from the recently measured total cross sections, which were obtained with a new experimental technique utilizing the threshold photoelectron source. A significant discrepancy between the momentum cross sections derived from the present analysis and those determined in the previous electron swarm studies was found at energies below 100 meV. The findings emphasize the need of further high precision experiments in the very low energy region as well as re-analysis of the previous swarm data.

Kitajima, M.; Kurokawa, M.; Kishino, T.; Toyoshima, K.; Odagiri, T.; Kato, H.; Anzai, K.; Hoshino, M.; Tanaka, H.; Ito, K.

2012-05-01

157

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

SciTech Connect

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

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

2013-06-15

158

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

PubMed Central

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 the detection of MCC in prenatal diagnosis of inborn errors by biochemical analysis. Methods: The threshold of each biochemical assay was assessed by co-cultivating fibroblasts from known affected and normal individuals. Genotypes for three polymorphic loci were determined by PCR and GeneScan analysis. The sensitivity of the molecular test was determined by DNA mixing experiments and isolation of DNA from co-cultivated fibroblasts. Results: MCC was detected in 2.5% of at risk CVS cultures (n = 79). Co-cultivation of defective and normal fibroblasts demonstrated that the peroxisomal biochemical assays were accurate at 25% contamination. Very low level DNA or cell contamination (1–5%) was detectable by genotyping, but an allele did not yield a definitive peak based on morphology until ?10% contamination. Furthermore, we demonstrated that other inborn errors of metabolism might be more susceptible to diagnostic error by low level MCC. Conclusion: The sensitivity of the microsatellite analysis (?10%) is well within the threshold of peroxisomal biochemical assays. Although peroxisomal biochemical assays would not be predicted to introduce a false positive or negative result if MCC <10% were present but not recognised by molecular analysis, the same may not be true for other inborn errors of metabolism. PMID:15635073

Steinberg, S; Katsanis, S; Moser, A; Cutting, G

2005-01-01

159

Energy model for contrast detection: spatial-frequency and orientation selectivity in grating summation  

Microsoft Academic Search

Models of spatial vision usually assume a 'front-end' of spatial-frequency and orientation selective channels. Subthreshold-sum- mation studies have provided some of the strongest support for this notion. We applied a single-channel energy model and a multiple-channels probability-summation model to explore subthreshold-summation phenomena. We measured the contrast thresholds for detection of two superimposed Gabor patches as a function of the spatial-frequency

Velitchko Manahilov; William A. Simpson

2001-01-01

160

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

161

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

162

Detecting salient contours using orientation energy distribution  

Microsoft Academic Search

How does our visual system detect prominent contours? Our investigation begins with the observation that neurons in the visual cortex have receptive fields similar to oriented Gabor filters. Unlike plain gray-level intensity histograms which greatly vary across images, we found that Gabor orientation-response (or orientation-energy) histograms of natural images have a fairly uniform shape. Based on this observation, we derived

Hyeon-Cheol Lee; Yoonsuck Choe

2003-01-01

163

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

164

An integrated system for multichannel neuronal recording with spike/LFP separation, integrated A/D conversion and threshold detection.  

PubMed

A mixed-signal front-end processor for multichannel neuronal recording is described. It receives 12 differential-input channels of implanted recording electrodes. A programmable cutoff High Pass Filter (HPF) blocks dc and low-frequency input drift at about 1 Hz. The signals are band-split at about 200 Hz to low-frequency Local Field Potential (LFP) and high-frequency spike data (SPK), which is band limited by a programmable-cutoff LPF, in a range of 8-13 kHz. Amplifier offsets are compensated by 5-bit calibration digital-to-analog converters (DACs). The SPK and LFP channels provide variable amplification rates of up to 5000 and 500, respectively. The analog signals are converted into 10-bit digital form, and streamed out over a serial digital bus at up to 8 Mbps. A threshold filter suppresses inactive portions of the signal and emits only spike segments of programmable length. A prototype has been fabricated on a 0.35-microm CMOS process and tested successfully, demonstrating a 3-microV noise level. Special interface system incorporating an embedded CPU core in a programmable logic device accompanied by real-time software has been developed to allow connectivity to a computer host. PMID:17260864

Perelman, Yevgeny; Ginosar, Ran

2007-01-01

165

Threshold based load balancing protocol for energy efficient routing in WSN  

Microsoft Academic Search

A sensible and foresighted planned routing protocol has a vital role to add life to the sensor network. Concentrated and iterative path routing, unbalanced load emphasizing, non-scalability property and frequent beacon exchange squeezes the life of stringent energy constraint Wireless Sensor Network. WSN is a special type of Adhoc network with energy, memory and processing constraint factors for sensing the

Sohail Jabbar; Ayesha Ejaz Butt; Najm us Sahar; Abid Ali Minhas

2011-01-01

166

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

167

Doppler tuning vuv spectroscopy of D- over an extended photon-energy range around the n=2 threshold  

NASA Astrophysics Data System (ADS)

The giant (or shape) resonance in the photodetachment cross section of D- above the n=2 threshold has been subjected to high-resolution vacuum ultraviolet spectroscopy performed by Doppler tuning of ions stored in the ASTRID storage ring. In order to prevent changes in the overlap between laser and ion beams over the large kinetic-energy range employed in the experiment, a new ion-beam-positioning method based on a quadrupole-shunt technique was applied. The study presents an accurate measurement of parameters for the resonance, which is also denoted {0}22+P1o . The resonance has a width of 26(2) meV while the asymmetry parameter q of the Fano profile is 3.2(0.4), which is at variance with the most recent theoretical calculations.

Balling, P.; Raarup, M. K.; Elstrøm, U. V.; Martinussen, R.; Petrunin, V. V.; Andersen, T.

2007-10-01

168

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

169

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

170

Temporary hearing threshold shifts and restitution after energy-equivalent exposures to industrial noise and classical music.  

PubMed

In order to investigate whether the energy-equivalence principle is at least acceptable for exposures with a duration in the range of hours and in order to disclose the actual physiological responses to exposures which varied with respect to the time structure and the semantic quality of sounds, a series of tests was carried out where physiological costs associated with varying exposures were measured audiometrically. In a cross-over test design, 10 Subjects (Ss) participated in test series with 3 energetically equal sound exposures on different days. The exposures corresponded with a tolerable rating level of 85 dB / 8 h. In a first test series (TS I), the Ss were exposed to a prototype of industrial noise with a sound pressure level of 94 dB(A) / 1 h. In a second test series (TS II), the same type of noise was applied, but the exposure time of a reduced level of 91 dB(A) was increased to 2 hours. In a third test series (TS III), classical music was provided also for 2 h at a mean level of 91 dB(A). The physiological responses to the 3 exposures were recorded audiometrically via the temporary threshold shift TTS2, the restitution time t(0 dB), and the IRTTS-value. IRTTS is the integrated restitution temporary threshold shift which is calculated by the sum of all threshold shifts. It represents the total physiological costs the hearing must "pay" for the sound exposure. Physiological responses of the hearing to the industrial noise exposures in TS I and TS II, all in all, were identical in the 3 parameters. Maximum threshold shifts of approximately 25 dB occurred which did not dissipate completely until 2.5 h after the end of the exposure and IRTTS-values of about 800 dBmin were calculated. Therefore, at least for exposure times in the range of hours, the equilibration of intensity and duration of sound exposures according to the energy-equivalence principle seems to have no influence on the hearing. Classical music was associated with the least severe TTS of less than 10 dB which disappeared much more quickly. IRTTS added up to just about 100 dBmin and, in comparison with 800 dBmin as specific responses to industrial noise, amounted to only about 12%. The substantially lower physiological costs of classical music apparently indicate a decisive influence of the type of sound exposures. Making inferences from the results of the study, the conventional approach of rating sound exposures exclusively by the principle of energy equivalence can lead to gravely misleading assessments of their actual physiological costs. PMID:14558895

Strasser, H; Irle, H; Legler, R

2003-01-01

171

Surface energy balance and melt thresholds over 11 years at Taylor Glacier, Antarctica  

Microsoft Academic Search

In the McMurdo Dry Valleys, Victoria Land, Antarctica, melting of glacial ice is the primary source of water to streams, lakes, and associated ecosystems. To understand geochemical fluxes and ecological responses to past and future climates requires a physically based energy balance model. We applied a one-dimensional model to one site on Taylor Glacier using 11 years of daily meteorological

Matthew J. Hoffman; Andrew G. Fountain; Glen E. Liston

2008-01-01

172

Photoluminescence determination of valence-band symmetry and Auger-1 threshold energy in biaxially compressed InAsSb layers  

SciTech Connect

InAsSb/InGaAs strained-layer superlattices (SLSs) and InAsSb quantum wells, both with biaxially compressed InAsSb layers, were characterized using magneto-photoluminescence and compared with unstained InAsSb and InAs alloys. In heterostructures with biaxially compressed InAsSb, the holes exhibited a decrease in effective mass, approaching that of the electrons. Correcting the data for the magneto-exciton binding energy, we obtain electron-hole reduced mass values in the range, {mu}=0.010--0.015, for the InAsSb heterostructures, whereas {mu}=0.026 and {mu}-0.023 for unstrained InAsSb and InAs alloys respectively. In the 2-dimensional limit, a large increase in the Auger-1 threshold energy accompanies this strain-induced change in valence-band symmetry. Correspondingly, the activation energy for nonradiative recombination in the SLSs displayed a marked increase compared with that of the unstrained alloys.

Kurtz, S.R.; Biefeld, R.M.; Dawson, L.R.

1994-08-01

173

Determination of the threshold-energy surface for copper using in-situ electrical-resistivity measurements in the high-voltage electron microscope  

SciTech Connect

A detailed study of the anisotropy of the threshold energy for Frenkel-pair production in copper was carried out experimentally, using in-situ electrical-resistivity measurements in the high-voltage electron microscope. These electrical-resistivity measurements, which are sensitive to small changes in point-defect concentration, were used to determine the damage or defect production rate. Damage-rate measurements in copper single crystals were carried out for approx.40 incident electron-beam directions and six electron energies from 0.4 to 1.1 MeV. The total cross section for Frenkel-pair production is proportional to the measured damage rate and can be theoretically calculated if the form of the threshold-energy surface is known. Trial threshold-energy surfaces were systematically altered until a ''best fit'' of the calculated to the measured total cross sections for Frenkel-pair production was obtained. The average threshold energy of this surface is 28.5 eV. The minimum threshold energy is 18 +- 2 eV and is located near <100>. A ring of very high threshold energy (>50 eV) surrounds the <111> direction. A damage function for single-defect production was derived from this surface and was applied to defect-production calculations at higher recoil energies. This function rises rather sharply from a value of zero at 17 eV to 0.8 at 42 eV. It has the value of 0.5 at 24.5 eV. Above 30 eV the slope of the curve begins to decrease, reflecting the presence of the high-energy regions of the threshold-energy surface. Both topographical and quantitative comparisons of the present surface with those in the literature were presented. Based on a chi/sup 2/ goodness-of-fit test, the present surface was found to predict the experimentally observed total cross sections for Frenkel-pair production significantly better than the other available surfaces. Also, the goodness of fit varied substantially less with energy and direction for the present surface.

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

1981-06-15

174

Determination of the threshold-energy surface for copper using in-situ electrical-resistivity measurements in the high-voltage electron microscope  

NASA Astrophysics Data System (ADS)

A detailed study of the anisotropy of the threshold energy for Frenkel-pair production in copper was carried out experimentally, using in-situ electrical-resistivity measurements in the high-voltage electron microscope. These electrical-resistivity measurements, which are sensitive to small changes in point-defect concentration, were used to determine the damage or defect production rate. Damage-rate measurements in copper single crystals were carried out for ~40 incident electron-beam directions and six electron energies from 0.4 to 1.1 MeV. The total cross section for Frenkel-pair production is proportional to the measured damage rate and can be theoretically calculated if the form of the threshold-energy surface is known. Trial threshold-energy surfaces were systematically altered until a "best fit" of the calculated to the measured total cross sections for Frenkel-pair production was obtained. The average threshold energy of this surface is 28.5 eV. The minimum threshold energy is 18 +/- 2 eV and is located near <100>. A ring of very high threshold energy (> 50 eV) surrounds the <111> direction. A damage function for singledefect production was derived from this surface and was applied to defect-production calculations at higher recoil energies. This function rises rather sharply from a value of zero at 17 eV to 0.8 at 42 eV. It has the value of 0.5 at 24.5 eV. Above 30 eV the slope of the curve begins to decrease, reflecting the presence of the high-energy regions of the threshold-energy surface. Both topographical and quantitative comparisons of the present surface with those in the literature were presented. Based on a ?2 goodness-of-fit test, the present surface was found to predict the experimentally observed total cross sections for Frenkel-pair production significantly better than the other available surfaces. Also, the goodness of fit varied substantially less with energy and direction for the present surface.

King, Wayne E.; Merkle, K. L.; Meshii, M.

1981-06-01

175

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

E-print Network

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

Paul Smith

2010-12-18

176

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 two smaller than previously published results. Also presented are the spectra of recoil electrons from the charged current reaction of neutrinos on deuterons and the elastic scattering of electrons. A fit to the SNO data in which the free parameters directly describe the total {sup 8}B neutrino flux and the energy-dependent Ve survival probability provides a measure of the total {sup 8}B neutrino flux {Phi}{sub 8{sub B}} = 5.046{sub -0.152}{sup +0.159}(stat){sub -0.123}{sup +0.107}(syst). Combining these new results with results of all other solar experiments and the KamLAND reactor experiment yields best-fit values of the mixing parameters of {theta}{sub 12} = 34.06{sub -0.84}{sup +1.16} degrees and {Delta}m{sub 21}{sup 2} = 7.59{sub -0.21}{sup +0.20} x 10{sup -5} eV{sup 2}. The global value of {Phi}{sub 8{sub B}} is extracted to a precision of {sub -2.95}{sup +2.38}%. In a three-flavor analysis the best fit value of sin{sup 2} {theta}{sub 13} is 2.00{sub -1.63}{sup +2.09} x 10{sup -2}. Interpreting this as a limit implies an upper bound of sin{sup 2} {theta}{sub 13} < 0.057 (95% C. L.).

Seibert, S R [Los Alamos National Laboratory; Hime, A [Los Alamos National Laboratory; Elliott, S R [Los Alamos National Laboratory; Rielage, K [Los Alamos National Laboratory

2009-01-01

177

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

178

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

E-print Network

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

Wolter, Benjamin; Baudisch, Matthias; Pullen, Michael G; Tong, Xiao-Min; Hemmer, Michaël; Senftleben, Arne; Schröter, Claus Dieter; Ullrich, Joachim; Moshammer, Robert; Biegert, Jens; Burgdörfer, Joachim

2014-01-01

179

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

PubMed

Ionization energies and cationic structures of pyridine were intensively investigated utilizing one-photon mass-analyzed threshold ionization (MATI) spectroscopy with vacuum ultraviolet radiation generated by four-wave difference frequency mixing in Kr. The present one-photon high-resolution MATI spectrum of pyridine demonstrated a much finer and richer vibrational structure than that of the previously reported two-photon MATI spectrum. From the MATI spectrum and photoionization efficiency curve, the accurate ionization energy of the ionic ground state of pyridine was confidently determined to be 73?570 ± 6 cm(-1) (9.1215 ± 0.0007 eV). The observed spectrum was almost completely assigned by utilizing Franck-Condon factors and vibrational frequencies calculated through adjustments of the geometrical parameters of cationic pyridine at the B3LYP/cc-pVTZ level. A unique feature unveiled through rigorous analysis was the prominent progression of the 10 vibrational mode, which corresponds to in-plane ring bending, and the combination of other totally symmetric fundamentals with the ring bending overtones, which contribute to the geometrical change upon ionization. Notably, the remaining peaks originate from the upper electronic state ((2)A2), as predicted by high-resolution photoelectron spectroscopy studies and symmetry-adapted cluster configuration interaction calculations. Based on the quantitatively good agreement between the experimental and calculated results, it was concluded that upon ionization the pyridine cation in the ground electronic state should have a planar structure of C2v symmetry through the C-N axis. PMID:25381510

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

2014-11-01

180

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

NASA Astrophysics Data System (ADS)

Ionization energies and cationic structures of pyridine were intensively investigated utilizing one-photon mass-analyzed threshold ionization (MATI) spectroscopy with vacuum ultraviolet radiation generated by four-wave difference frequency mixing in Kr. The present one-photon high-resolution MATI spectrum of pyridine demonstrated a much finer and richer vibrational structure than that of the previously reported two-photon MATI spectrum. From the MATI spectrum and photoionization efficiency curve, the accurate ionization energy of the ionic ground state of pyridine was confidently determined to be 73 570 ± 6 cm-1 (9.1215 ± 0.0007 eV). The observed spectrum was almost completely assigned by utilizing Franck-Condon factors and vibrational frequencies calculated through adjustments of the geometrical parameters of cationic pyridine at the B3LYP/cc-pVTZ level. A unique feature unveiled through rigorous analysis was the prominent progression of the 10 vibrational mode, which corresponds to in-plane ring bending, and the combination of other totally symmetric fundamentals with the ring bending overtones, which contribute to the geometrical change upon ionization. Notably, the remaining peaks originate from the upper electronic state (2A2), as predicted by high-resolution photoelectron spectroscopy studies and symmetry-adapted cluster configuration interaction calculations. Based on the quantitatively good agreement between the experimental and calculated results, it was concluded that upon ionization the pyridine cation in the ground electronic state should have a planar structure of C2v symmetry through the C-N axis.

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

2014-11-01

181

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

NASA Astrophysics Data System (ADS)

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

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

2006-08-01

182

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

PubMed

An evaluation of mono-energetic proton energies ranging from 1.885 MeV to 1.920 MeV was carried out to determine the viability of these near threshold energies in producing neutrons for BNCT via the (7)Li(p,n)(7)Be reaction. Neutron fields generated at these proton energies were assessed using the treatable protocol depth (TPD) and the maximum TPD (TPD(max)) as evaluation indices. The heavy charged particle (HCP) dose rate to tumour was likewise applied as a figure of merit in order to account for irradiation time and required proton current. Incident proton energies closer to the reaction threshold generated deeper TPDs compared to higher energy protons when no boron dose enhancers (BDE) were placed in the irradiation field. Introducing a BDE resulted in improved TPDs for high proton energies but their achievable TPD(max) were comparatively lower than that obtained for lower proton energies. In terms of the HCP dose rate to tumour, higher proton energies generated neutron fields that yielded higher dose rates both at TPD(max) and at fixed depths of comparison. This infers that higher currents are required to deliver the prescribed treatment dose to tumours for proton beams with energies closer to the (7)Li(p,n)(7)Be reaction threshold and more achievable proton currents of around 10 mA or less for proton energies from 1.900 MeV and above. The dependence on incident proton energy of the TPD, TPD(max) and the HCP dose rate to tumour with respect to the (10)B concentration in tumour and healthy tissues were also clarified in this study. Increasing the (10)B concentration in tumour while maintaining a constant T/N ratio resulted in deeper TPD(max) where a greater change in TPD(max) was obtained for proton energies closer to the (7)Li(p,n)(7)Be reaction threshold. The HCP dose rates to tumour for all proton energies also went up, with the higher proton energies benefiting more from the increased (10)B concentration. PMID:16885627

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

2006-08-21

183

Low-energy ion induced Auger electron spectra and energy thresholds for some pure elements, compounds, and alloys  

Microsoft Academic Search

By improvements of experimental method, ion induced Auger electron spectra (IAES) of pure elements, compounds, and alloys for 23 samples have been obtained successfully using a combined scanning Auger microscopy\\/secondary ion mass spectrometry instrument. Ar\\/sup +\\/ with energy up to 5 keV was the incident ion. The spectra measured are different from that obtained by electron-stimulated Auger, and correspondent Auger

Chuizhen Fan; Zhenjiang Yu; Xuekang Chen

1987-01-01

184

How Real Detector Thresholds Create False Standard Candles  

SciTech Connect

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

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

2009-05-25

185

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

186

Imaging of magnetospheric dynamics using low energy neutral atom detection  

Microsoft Academic Search

Recent advances in low energy neutral atom (LENA) detection technology show that imaging of magnetospheric dynamics is achievable with 4°×4° resolution and can distinguish numerous features of the magnetosphere. A critical factor in detecting low energy neutrals is their removal from the ambient UV background. One technique to accomplish this is by ionizing the neutrals by their transmission through an

H. O. Funsten; D. J. McComas; K. R. Moore; E. E. Scime; M. F. Thomsen

1994-01-01

187

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

Microsoft Academic Search

The absolute heats of formation of 1,2-, 1,3-, and 1,4-dehydrobenzene (ortho, meta-, and para-benzyne) have been determined from measurements of the threshold energies for collision-induced dissociation (CID) of ortho, meta-, and para-chlorophenyl anions in a flowing afterglow-triple quadrupole apparatus. The 298 K heats of formation for ortho-, meta-, and para-benzyne derived in this manner are 106.6 [+-] 3.0, 122.0 [+-

Paul G. Wenthold; Robert R. Squires

1994-01-01

188

Determination of the threshold-energy surface for copper using in-situ electrical-resistivity measurements in the high-voltage electron microscope  

Microsoft Academic Search

A detailed study of the anisotropy of the threshold energy for Frenkel-pair production in copper was carried out experimentally, using in-situ electrical-resistivity measurements in the high-voltage electron microscope. These electrical-resistivity measurements, which are sensitive to small changes in point-defect concentration, were used to determine the damage or defect production rate. Damage-rate measurements in copper single crystals were carried out for

Wayne E. King; K. L. Merkle; M. Meshii

1981-01-01

189

Detecting dark energy with wavelets on the sphere  

E-print Network

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

J. D. McEwen

2007-08-29

190

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

191

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

192

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

193

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

194

Can the Existence of Dark Energy be Directly Detected?  

SciTech Connect

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

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

2011-11-23

195

Online Fault Detection and Tolerance for Photovoltaic Energy Harvesting Systems  

E-print Network

effects of fossil fuels, human society is in desperate need of renewable energy sources (e.g., solar, wind shorten the PV system lifespan. Manual PV cell fault detection and elimination are expensive and nearly PV systems (e.g., PV systems for satellites), manual fault detection and elimination is expensive

Pedram, Massoud

196

Ubiquitous MIMO radar energy integration detection based on range synthesis  

Microsoft Academic Search

During such long-term time, the problem of target range-walk, Doppler-slide, beam-crossing must be considered, in the processing of the ubiquitous multiple-input multiple-output (MIMO) radar energy integration detection. Commonly, keystone transform is adopted for the completion of the migration compensation, and then the integration is finally carried out by motion target detection or joint time-frequency analysis, the result of energy integration

Wu-Xing Mao; Zhao Zhang; Xiang-Ru Li

2011-01-01

197

Imaging of magnetospheric dynamics using low energy neutral atom detection  

Microsoft Academic Search

Recent advances in low energy neutral atom (LENA) detection technology show that magnetospheric imaging is achievable with 4[sub o][times]4[sub o] resolution and can distinguish numerous features of the magnetosphere. A critical factor in detecting low energy neutrals is their removal from the ambient UV background. One technique to accomplish this is by ionizing the neutrals by their transmission through an

H. O. Funsten; D. J. McComas; K. R. Moore; E. E. Scime

1993-01-01

198

Imaging of magnetospheric dynamics using low energy neutral atom detection  

Microsoft Academic Search

Recent advances in low energy neutral atom (LENA) detection technology show that magnetospheric imaging is achievable with 4{sub o}Ã4{sub o} resolution and can distinguish numerous features of the magnetosphere. A critical factor in detecting low energy neutrals is their removal from the ambient UV background. One technique to accomplish this is by ionizing the neutrals by their transmission through an

H. O. Funsten; D. J. McComas; K. R. Moore; E. E. Scime

1993-01-01

199

Determination of threshold energies for displacements of Fe and Rh atoms in Fe-50 at.%Rh intermetallic compound by using energetic electron irradiation at low temperatures  

NASA Astrophysics Data System (ADS)

Changes in electrical resistivity induced by irradiation with energetic electrons were measured for Fe-50 at.%Rh alloy as a function of electron energy in the range from 0.5 to 2.0 MeV. The irradiation was carried out below 20 K and the resistivity was measured at 10 K. The electron energy dependence of the resistivity change rate was analysed by using a simple displacement theory, and the average threshold energies for atomic displacements, E d, were determined as 30 eV for Fe and 45 eV for Rh. The analysis also revealed that resistivity values for Frenkel pairs, ? F (in units of ?? cm per at.%) were 128 and 181 for Fe atom and Rh atom, respectively. The experimentally determined values of E d and ? F can be used for the quantitative estimate of defect concentration in Fe-50 at.%Rh irradiated with energetic particles.

Kosugi, S.; Ishikawa, N.; Saitoh, Y.; Hori, F.; Iwase, A.

2011-04-01

200

Observational study of erythrocyte protoporphyrin screening test for detecting low lead exposure in children: Impact of lowering the blood lead action threshold  

SciTech Connect

We examined a retrospective sample of 1800 children on whom both erythrocyte protoporphyrin (EP) and blood lead (BPb) measurements were taken. The primary objective was to ascertain whether EP is a cost-effective screening test for low but increased BPb concentrations and to establish the optimal thresholds. The data did not provide evidence of an EP threshold at low BPb concentrations; however, the data did show a significant age effect. A subset of 500 children for whom both EP and hematocrit data were available showed no correlation between those variables. Age-specific operating characteristic curves, total error, and cost analyses are presented. The latter sets bounds on the relative cost of EP testing, above which only BPb determination should be performed. The implications of these findings are discussed in light of impending changes in U.S. federal guidelines for preventing lead poisoning in young children.

Parsons, P.J.; Reilly, A.A.; Hussain, A. (New York State Department of Health, Albany (USA))

1991-02-01

201

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

202

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

203

The Acoustic Detection of Ultra High Energy Neutrinos  

E-print Network

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

J. Perkin

2008-01-07

204

Whole-body vibration perception thresholds  

NASA Astrophysics Data System (ADS)

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

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

1988-03-01

205

LAT Perspectives in Detection of High Energy Cosmic Ray Electrons  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

206

Computed tomography with energy-resolved detection: a feasibility study  

Microsoft Academic Search

The feasibility of computed tomography (CT) with energy-resolved x-ray detection has been investigated. A breast CT design with multi slit multi slice (MSMS) data acquisition was used for this study. The MSMS CT includes linear arrays of photon counting detectors separated by gaps. This CT configuration allows for efficient scatter rejection and 3D data acquisition. The energy-resolved CT images were

Polad M. Shikhaliev

2008-01-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

208

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

PubMed

The usable range of thickness for the solid lithium target in the accelerator-based neutron production for BNCT via the near-threshold (7)Li(p,n)(7)Be reaction was investigated. While the feasibility of using a (7)Li-target with thickness equal to that which is required to slow down a mono-energetic 1.900 MeV incident proton to the 1.881 MeV threshold of the (7)Li(p,n)(7)Be reaction (i.e., t(min) = 2.33 microm) has already been demonstrated, dosimetric properties of neutron fields from targets greater than t(min) were assessed as thicker targets would last longer and offer more stable neutron production. Additionally, the characteristics of neutron fields generated by (7)Li(p,n)(7)Be for Gaussian incident protons with mean energy of 1.900 MeV were evaluated at a (7)Li-target thickness t(min). The main evaluation index applied in this study was the treatable protocol depth (TPD) which corresponds to the depth in an irradiated medium that satisfies the requirements of the adapted dose protocol. A maximum TPD (TPD(max)) was obtained for each irradiation condition from the relationship between the TPD and the thickness of boron dose enhancer (BDE) used. For a mono-energetic 1.900 MeV proton beam, the deepest TPD(max) of 3.88 cm was attained at the (7)Li-target thickness of t(min) and a polyethylene BDE of 1.10 cm. When the intended TPD for a BNCT clinical treatment is shallower than the deepest TPD(max), the usable (7)Li-target thickness would be between t(min) and an upper limit t(upper) whose value depends on the BDE thickness used. In terms of the effect of stability of the incident proton energy, Gaussian incident proton energies stable to within +/-10 keV of 1.900 MeV were found to be feasible for the neutron production via the near-threshold (7)Li(p,n)(7)Be reaction for BNCT provided that a suitable BDE is used. PMID:17228111

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

2007-02-01

209

SUSY Thresholds at a Muon Collider  

E-print Network

One of the useful features of muon colliders is the naturally narrow spread in beam energies. Measurements of threshold cross sections then become a prime candidate for precision measurements of particle masses, widths, and couplings as well as determining particle spin. We describe the potential for measuring cross sections near threshold in supersymmetric theories.

M. S. Berger

2000-03-14

210

Absolute neutron detection efficiency calibration of a stilbene organic scintillator in the energy range 2 to 20 MeV with the associated particle technique  

Microsoft Academic Search

The associated particle technique (APT) has been used with neutrons from D(d, n)3He and T(d, n)4He reactions to measure the absolute neutron detection efficiency of a stilbene detector (3.81 cm diameter, 1.27 cm thick) in the energy range 2-20 MeV as a function of the light collection threshold. The measurements have been carried out using thin Ti-T and home made

R. Cherubini; G. Moschini; R. Nino; R. Policroniades; A. Varela

1988-01-01

211

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

SciTech Connect

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

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

2012-11-26

212

Directed energy active illumination for near-Earth object detection  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

213

Energy-driven detection scheme with guaranteed accuracy  

Microsoft Academic Search

This is our first step towards a holistic investigation of the minimum energy for wireless sensor network (WSN) to perform a specific function. We consider wireless sensor net works that perform an event detection function. Each sensor node will repetitively collect a 1-bit information regarding whether the event occurs or not in its neighborhood. A fusion center will make the

Lige Yu; Lin Yuan; Gang Qu; Anthony Ephremides

2006-01-01

214

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

1991-07-01

215

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

216

Induction of low-T3 syndrome in exercising women occurs at a threshold of energy availability.  

PubMed

To investigate the relationship between energy availability (dietary energy intake minus energy expended during exercise) and thyroid metabolism, we studied 27 untrained, regularly menstruating women who performed approximately 30 kcal.kg lean body mass (LBM)-1.day-1 of supervised ergometer exercise at 70% of aerobic capacity for 4 days in the early follicular phase. A clinical dietary product was used to set energy availability in four groups (10.8, 19.0, 25.0, 40.4 kcal.kg LBM-1.day-1). For 9 days beginning 3 days before treatments, blood was sampled once daily at 8 A.M. Initially, thyroxine (T4) and free T4 (fT4), 3,5,3'-triiodothyronine (T3) and free T3 (fT3), and reverse T3 (rT3) were in the normal range for all subjects. Repeated-measures one-way analysis of variance followed by one-sided, two-sample post hoc Fischer's least significant difference tests of changes by treatment day 4 revealed that reductions in T3 (16%, P < 0.00001) and fT3 (9%, P < 0.01) occurred abruptly between 19.0 and 25.0 kcal.kg LBM-1.day-1 and that increases in fT4 (11%, P < 0.05) and rT3 (22%, P < 0.01) occurred abruptly between 10.8 and 19.0 kcal.kg LBM-1.day-1. Changes in T4 could not be distinguished. If energy deficiency suppresses reproductive as well as thyroid function, athletic amenorrhea might be prevented or reversed by increasing energy availability through dietary reform to 25 kcal.kg LBM-1.day-1, without moderating the exercise regimen. PMID:8160876

Loucks, A B; Heath, E M

1994-03-01

217

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

SciTech Connect

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

Ostafin, A.E.; Lipsky, S. (Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455 (United States))

1993-04-01

218

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

219

Low energy electron and nuclear recoil thresholds in the DRIFT-II negative ion TPC for dark matter searches  

NASA Astrophysics Data System (ADS)

Understanding the ability to measure and discriminate particle events at the lowest possible energy is an essential requirement in developing new experiments to search for weakly interacting massive particle (WIMP) dark matter. In this paper we detail an assessment of the potential sensitivity below 10 keV in the 1 m3 DRIFT-II directionally sensitive, low pressure, negative ion time projection chamber (NITPC), based on event-by-event track reconstruction and calorimetry in the multiwire proportional chamber (MWPC) readout. By application of a digital smoothing polynomial it is shown that the detector is sensitive to sulfur and carbon recoils down to 2.9 and 1.9 keV respectively, and 1.2 keV for electron induced events. The energy sensitivity is demonstrated through the 5.9 keV gamma spectrum of 55Fe, where the energy resolution is sufficient to identify the escape peak. The effect of a lower energy sensitivity on the WIMP exclusion limit is demonstrated. In addition to recoil direction reconstruction for WIMP searches this sensitivity suggests new prospects for applications also in KK axion searches.

Burgos, S.; Daw, E.; Forbes, J.; Ghag, C.; Gold, M.; Hagemann, C.; Kudryavtsev, V. A.; Lawson, T. B.; Loomba, D.; Majewski, P.; Muna, D.; Murphy, A. St. J.; Paling, S. M.; Petkov, A.; Plank, S. J. S.; Robinson, M.; Sanghi, N.; Snowden-Ifft, D. P.; Spooner, N. J. C.; Turk, J.; Tziaferi, E.

2009-04-01

220

Mass selected pulsed field threshold ionization and coherent ion dip spectroscopy of van der Waal's complexes  

NASA Astrophysics Data System (ADS)

Mass selected pulsed field threshold ionization of optically excited high Rydberg states is a new method for the production of state-selected molecular and cluster ions. Exclusive detection of state-selected threshold ions is achieved by the kinetic energy analysis of ions in a reflectron mass spectrometer. This leads to vibrationally resolved spectra of molecular ions, like benzene, xylene, carbazole, etc. and ionic complexes of these molecules with noble gas atoms. The detected threshold cluster ions are state-selected with different internal energies depending on the excited vibrational state. Above a certain vibrational excess energy their decay is observed by the disappearance of vibrational peaks in the threshold ion spectrum at the parent mass and the simultaneous appearance of threshold daughter ions. Upper and lower bounds for the dissociation energies of the neutral and ionic complexes are deduced and compared with recent theoretical results. The coherent interaction of two narrowband Fourier- transform limited nanosecond laser pulses with gas phase molecular systems leads to the new technique of coherent ion dip spectroscopy (CIS) for rotationally resolved spectroscopy of polyatomic molecules and clusters. It is based on coherent effects with a special time sequence of the two pulses and yields a population dynamic in a three level system which is different from that of incoherent excitation experiments: At resonance, for different time sequences of the two pulses no or a complete population transfer from an initial to a final state is achieved and nearly 100% deep ion dips are observed in spectroscopic investigations.

Neusser, Hans-Jurgen; Krause, Hans-Joachim; Grebner, Thomas L.; Sussmann, Ralf; Neuhauser, Ralph

1995-09-01

221

Woods-Saxon and São Paulo optical model calculations of the threshold anomaly of the 6,7Li+28Si systems near Coulomb barrier energies  

NASA Astrophysics Data System (ADS)

Two types of optical model interactions, namely the double-folding density dependent São Paulo potential (SPP) and the Woods-Saxon potential (WSP) are used to study the appearance of the Theshold Anomaly (TA) or the Breakup Threshold Anomaly (BTA) for the nuclear systems 6,7Li+28Si for energies around the Coulomb barrier. In the first case, the presence of the anomaly is determined from the energy dependence of the normalization parameters NR and NI as found from fittings to elastic scattering angular distributions. In the second case, the presence of the anomaly is investigated by the energy variation of the fusion and direct reaction parts of the Woods-Saxon potential. In this case, the parameters of the fusion and direct reaction potentials are calculated by a simultaneous analysis of elastic scattering, fusion and total reaction cross sections. It is found in both cases that the BTA appears for the 6Li+28Si reaction. As for 7Li+28Si, the calculation with the SPP shows that the usual TA appears but the dispersion relation is not satisfied, however the WSP indicates that indeed the BTA shows up.

Gómez Camacho, A.; Gomes, P. R. S.; Lubian, J.

2011-10-01

222

Limit on the detectability of the energy scale of inflation.  

PubMed

We show that the polarization of the cosmic microwave background can be used to detect gravity waves from inflation if the energy scale of inflation is above 2x10(15) GeV. These gravity waves generate polarization patterns with a curl, whereas (to first order in perturbation theory) density perturbations do not. The limiting "noise" arises from the second-order generation of curl from density perturbations, or rather residuals from its subtraction. We calculate optimal sky coverage and detectability limits as a function of detector sensitivity and observing time. PMID:12097027

Knox, Lloyd; Song, Yong-Seon

2002-07-01

223

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

224

Low energy electron and nuclear recoil thresholds in the DRIFT-II negative ion TPC for dark matter searches  

Microsoft Academic Search

Understanding the ability to measure and discriminate particle events at the lowest possible energy is an essential requirement in developing new experiments to search for weakly interacting massive particle (WIMP) dark matter. In this paper we detail an assessment of the potential sensitivity below 10 keV in the 1 m3 DRIFT-II directionally sensitive, low pressure, negative ion time projection chamber

S. Burgos; E. Daw; J. Forbes; C. Ghag; M. Gold; C. Hagemann; V. A. Kudryavtsev; T. B. Lawson; D. Loomba; P. Majewski; D. Muna; A. St. J. Murphy; S. M. Paling; A. Petkov; S. J. S. Plank; M. Robinson; N. Sanghi; D. P. Snowden-Ifft; N. J. C. Spooner; J. Turk; E. Tziaferi

2009-01-01

225

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

226

Computed tomography with energy-resolved detection: a feasibility study.  

PubMed

The feasibility of computed tomography (CT) with energy-resolved x-ray detection has been investigated. A breast CT design with multi slit multi slice (MSMS) data acquisition was used for this study. The MSMS CT includes linear arrays of photon counting detectors separated by gaps. This CT configuration allows for efficient scatter rejection and 3D data acquisition. The energy-resolved CT images were simulated using a digital breast phantom and the design parameters of the proposed MSMS CT. The phantom had 14 cm diameter and 50/50 adipose/glandular composition, and included carcinoma, adipose, blood, iodine and CaCO3 as contrast elements. The x-ray technique was 90 kVp tube voltage with 660 mR skin exposure. Photon counting, charge (energy) integrating and photon energy weighting CT images were generated. The contrast-to-noise (CNR) improvement with photon energy weighting was quantified. The dual energy subtracted images of CaCO3 and iodine were generated using a single CT scan at a fixed x-ray tube voltage. The x-ray spectrum was electronically split into low- and high-energy parts by a photon counting detector. The CNR of the energy weighting CT images of carcinoma, blood, adipose, iodine, and CaCO3 was higher by a factor of 1.16, 1.20, 1.21, 1.36 and 1.35, respectively, as compared to CT with a conventional charge (energy) integrating detector. Photon energy weighting was applied to CT projections prior to dual energy subtraction and reconstruction. Photon energy weighting improved the CNR in dual energy subtracted CT images of CaCO3 and iodine by a factor of 1.35 and 1.33, respectively. The combination of CNR improvements due to scatter rejection and energy weighting was in the range of 1.71-2 depending on the type of the contrast element. The tilted angle CZT detector was considered as the detector of choice. Experiments were performed to test the effect of the tilting angle on the energy spectrum. Using the CZT detector with 20 degrees tilting angle decreased the tailing of the measured x-ray spectrum as compared to a conventional CZT detector. It was concluded that the energy-resolved MSMS CT with tilted angle CZT detector is potentially feasible and could provide a unique combination of photon counting, energy weighting, scatter rejection and single kVp dual energy subtraction CT imaging. PMID:18296774

Shikhaliev, Polad M

2008-03-01

227

Computed tomography with energy-resolved detection: a feasibility study  

NASA Astrophysics Data System (ADS)

The feasibility of computed tomography (CT) with energy-resolved x-ray detection has been investigated. A breast CT design with multi slit multi slice (MSMS) data acquisition was used for this study. The MSMS CT includes linear arrays of photon counting detectors separated by gaps. This CT configuration allows for efficient scatter rejection and 3D data acquisition. The energy-resolved CT images were simulated using a digital breast phantom and the design parameters of the proposed MSMS CT. The phantom had 14 cm diameter and 50/50 adipose/glandular composition, and included carcinoma, adipose, blood, iodine and CaCO3 as contrast elements. The x-ray technique was 90 kVp tube voltage with 660 mR skin exposure. Photon counting, charge (energy) integrating and photon energy weighting CT images were generated. The contrast-to-noise (CNR) improvement with photon energy weighting was quantified. The dual energy subtracted images of CaCO3 and iodine were generated using a single CT scan at a fixed x-ray tube voltage. The x-ray spectrum was electronically split into low- and high-energy parts by a photon counting detector. The CNR of the energy weighting CT images of carcinoma, blood, adipose, iodine, and CaCO3 was higher by a factor of 1.16, 1.20, 1.21, 1.36 and 1.35, respectively, as compared to CT with a conventional charge (energy) integrating detector. Photon energy weighting was applied to CT projections prior to dual energy subtraction and reconstruction. Photon energy weighting improved the CNR in dual energy subtracted CT images of CaCO3 and iodine by a factor of 1.35 and 1.33, respectively. The combination of CNR improvements due to scatter rejection and energy weighting was in the range of 1.71-2 depending on the type of the contrast element. The tilted angle CZT detector was considered as the detector of choice. Experiments were performed to test the effect of the tilting angle on the energy spectrum. Using the CZT detector with 20° tilting angle decreased the tailing of the measured x-ray spectrum as compared to a conventional CZT detector. It was concluded that the energy-resolved MSMS CT with tilted angle CZT detector is potentially feasible and could provide a unique combination of photon counting, energy weighting, scatter rejection and single kVp dual energy subtraction CT imaging.

Shikhaliev, Polad M.

2008-03-01

228

Threshold for Radiation Effects in Silica  

Microsoft Academic Search

Data are given for the initial compaction (negative dilatation) of vitreous silica per incident bombarding ion for 40- and 140-keV H+, D+, He+, Ne+, Ar+, and 80-keV He+. The slope of the logarithm of these data plotted against the logarithm of the energy above a threshold value dissipated in nuclear scattering indicates that the threshold energy for the compaction process

William Primak

1972-01-01

229

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

230

Imaging of magnetospheric dynamics using low energy neutral atom detection  

SciTech Connect

Recent advances in low energy neutral atom (LENA) detection technology show that magnetospheric imaging is achievable with 4[sub o][times]4[sub o] resolution and can distinguish numerous features of the magnetosphere. A critical factor in detecting low energy neutrals is their removal from the ambient UV background. One technique to accomplish this is by ionizing the neutrals by their transmission through an untrathin charge modification foil and subsequent electrostatic deflection. In this type of instrument, the driving factor for resolution and sensitivity is scattering in the foil and the ionization probability of transiting neutrals. We describe results of a prototype LENA imager using a collimated beam of 10 key H. Additionally, we illustrate model results of anticipated LENA images of the magnetosphere based on the Rice Convection Model and show that plasma variations resulting from geomagnetic storm disturbances can be observed using a LENA imager.

Funsten, H.O.; McComas, D.J.; Moore, K.R.; Scime, E.E.

1993-01-01

231

Imaging of magnetospheric dynamics using low energy neutral atom detection  

SciTech Connect

Recent advances in low energy neutral atom (LENA) detection technology show that magnetospheric imaging is achievable with 4{sub o}{times}4{sub o} resolution and can distinguish numerous features of the magnetosphere. A critical factor in detecting low energy neutrals is their removal from the ambient UV background. One technique to accomplish this is by ionizing the neutrals by their transmission through an untrathin charge modification foil and subsequent electrostatic deflection. In this type of instrument, the driving factor for resolution and sensitivity is scattering in the foil and the ionization probability of transiting neutrals. We describe results of a prototype LENA imager using a collimated beam of 10 key H. Additionally, we illustrate model results of anticipated LENA images of the magnetosphere based on the Rice Convection Model and show that plasma variations resulting from geomagnetic storm disturbances can be observed using a LENA imager.

Funsten, H.O.; McComas, D.J.; Moore, K.R.; Scime, E.E.

1993-05-01

232

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

233

Dual energy detection of weapons of mass destruction  

NASA Astrophysics Data System (ADS)

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

Budner, Gregory J.

2006-03-01

234

AUDIBILITY THRESHOLDS OF THE BLUE JAY  

Microsoft Academic Search

The audibility thresholds of two Blue Jays were measured behaviorally using operant conditioning and psychophysical techniques. The jays responded to pure tones between 0.25 and 10 kHz. Their thresholds are similar to those reported for seven other passerines. This indicates that passerines are somewhat less sensitive than man in the detection of sounds in the 1 to 4 kHz range

STEVEN M. COHEN; WILLIAM C. STEBBINS; DAVID B. MOODY

1978-01-01

235

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

236

Threshold voltage extraction circuit  

E-print Network

A novel optimally self-biasing MOSFET threshold-voltage (V[]) extractor circuit is presented. It implements the most popular industrial extraction algorithm of biasing a saturated MOSFET to the linear portion of its [] versus [] characteristic...

Hoon, Siew Kuok

2012-06-07

237

Efficient threshold cryptosystems  

E-print Network

A threshold signature or decryption scheme is a distributed implementation of a cryptosystem, in which the secret key is secret-shared among a group of servers. These servers can then sign or decrypt messages by following ...

Jarecki, Stanisł aw (Stanisł aw Michal), 1971-

2001-01-01

238

Threshold cross section measurements  

E-print Network

Accurate measurements of particles masses, couplings and widths are possible by measuring production cross sections near threshold. We discuss the prospects for performing such measurements at a high luminosity muon collider.

M. S. Berger

1998-02-02

239

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

240

A curved detection-slit to improve ERD (Elastic Recoil Detection) energy/depth resolution  

SciTech Connect

Recoil atoms detected in Elastic Recoil Detection (ERD) experiments emerge from an initial collision area along cones of constant energy due to the cylindrical symmetry of the elastic scattering cross section. The constant energy cones therefore intercept planar slit plates placed before the detectors in conic sections. For ease of fabrication slits are typically configured as long narrow rectangles, and as a result energy resolution is adversely affected. It has been shown that the kinematic broadening caused by using rectangular slits is minimized when L = 2 (W z tan/Theta//sub recoil/)/sup 1/2/ where W is the slit width, L is the slit length, z is the slit-target distance and /Theta//sub recoil/ is the lab-frame recoil angle. The improved energy resolution which results when rectangular slits are replaced by appropriate curved slits is examined here. Formulas are given for the conic sections associated with the curved slits as a function of experimental geometry. When slit dimensions are small compared with the full extent of the conic section slit geometry can be accurately approximated as the arc of a circle with radius R/sub c/ = z tan/Theta//sub recoil/. Energy loss effects on the resolution are also accounted for in our treatment. The use of curved slits with L = 4 (W z tan/Theta//sub recoil/)/sup 1/2/ is shown to improve kinematic broadening by /approximately/50% as compared to optimized rectangular slits of the same area. 2 refs., 5 figs.

Brice, D.K.; Doyle, B.L.

1989-01-01

241

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

242

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

243

Intra-individual variation of GH-dependent markers in athletes: comparison of population based and individual thresholds for detection of GH abuse in sports.  

PubMed

The GH-2000 discriminant functions, using insulin-like growth factor I (IGF-I) and the N-terminal propeptide of type III procollagen (PIIINP), enabled the detection of growth hormone (GH) doping despite the broad inter-individual normal range of both peptides. The sensitivity of the discriminant function-based methodology may perhaps be further increased in future by applying individual athlete profiles. The purpose of the present study was to evaluate the intra-individual variability of IGF-I, PIIINP and the GH-2000 scores in athletes. For this purpose a total of eight blood samples were taken from each of fifty male and female elite athletes over a period of up to 18 months. The IGF-I and PIIINP levels, we found, lay predominantly within the reference range for elite athletes. The intra-individual variability for IGF-I ranged between 6 and 26%, while that for PIIINP ranged between 6 and 33%. The intra-individual variations of both parameters were higher in female than in male subjects and were found to be mostly moderate. We found that the intra-individual variations of the GH-2000 test scores, expressed as CV, ranged from 4 to 36% and were in most of the subjects markedly smaller than the inter-individual variation. Individual cut-offs for the GH-2000 scores would be lower than population based ones in most of the cases. PMID:23850935

Kniess, Astrid; Ziegler, Eckart; Thieme, Detlef; Müller, R Klaus

2013-10-01

244

The ttbar threshold at a muon collider  

E-print Network

The beam energy spread is a major issue in future attempts to study the $t\\overline{t}$ threshold at $e^+e^-$ colliders. Muon colliders are expected to naturally have narrow band beams making them an ideal place to study the excitation curve. We present the parameter determinations that are possible from measuring the total cross section near threshold at a $\\mu ^+\\mu ^-$ collider.

M. S. Berger

1995-08-01

245

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

246

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

247

Regional Seismic Threshold Monioring  

E-print Network

A database comprising a total of 45 events, selected to provide the best possible ray path coverage of the Barents Sea and adjacent areas, was compiled and reanalyzed in a consistent manner. This resulted in new regional attenuation relations for Pn and Sn, together with a preferred average velocity model to be used for predicting the travel times of regional phases. We have now applied these attenuation relations to investigate a regional threshold monitoring scheme for the Barents Sea area. A grid system with an approximately 100-km grid spacing was deployed for the Barents Sea region, and the observations at the arrays, ARCES, SPITS, FINES and NORES, were then used for calculating threshold magnitudes for each of the grid points. During an interval without seismic signals, the threshold magnitudes showed large variations over the region, and, in particular, in the vicinity of each array. However, for the region around the island of Novaya Zemlya, the variations are modest, varying around a mean of magnitude 2.1-2.2. In order to investigate in more detail the variations in threshold magnitudes for the Novaya Zemlya region, we deployed a dense grid with an areal extent of about 500 x 500 km around the former Novaya Zemlya nuclear test site. For each of the grid nodes, we calculated magnitude thresholds for the two-hour time interval 00:00 - 02:00 on 23 February 2002. At 01:21:12.1 there was an event with a magnitude of about 3, located about 100 km northeast of the former nuclear test site. Regions of different sizes were constructed by selecting grid points within different radii from the former nuclear test site. Average, minimum and maximum threshold magnitudes were calculated for circular regions with radii of 20, 50, 100 and 200 km, respectively. The most importan...

T. Kv& aelig; rna; T. Kvrna; E. Hicks; J. Schweitzer; F. Ringdal

2002-01-01

248

Measurement of the 13C(?, n)16O reaction at astrophysical energies using the Trojan Horse Method. Focus on the -3 keV sub-threshold resonance  

NASA Astrophysics Data System (ADS)

Most of the nuclei in the mass range 90 ? A ? 208 are produced through the so-called s-process, namely through a series of neutron capture reactions on seed nuclei followed by ?-decays. The 13C(?, n)16O reaction is the neutron source for the main component of the s-process. It is active inside the helium-burning shell of asymptotic giant branch stars, at temperatures ? 108 K, corresponding to an energy interval of 140 - 230 keV. In this region, the astrophysical S(E)-factor is dominated by the -3 keV sub-threshold resonance due to the 6.356 MeV level in 17O. Direct measurements could not soundly establish its contribution owing to the cross section suppression at astrophysical energies determined by the Coulomb barrier between interacting nuclei. Indirect measurements and extrapolations yielded inconsistent results, calling for further investigations. The Trojan Horse Method turns out to be very suited for the study of the 13C(?, n)16O reaction as it allows us to access the low as well as the negative energy re- gion, in particular in the case of resonance reactions. We have applied the Trojan HorseMethod to the 13C(6Li, n16O)d quasi-free reaction. By using the modified R-matrix approach, the asymptotic normalization coefficient {( {tilde C{? 13{{C}}}17{{O(1/}{{{2}}{ + }}{{)}}}} )^2} of the 6.356 MeV level has been deduced as well as the n-partial width, allowing to attain an unprecedented accuracy for the 13C(?, n)16O astrophysical factor. A preliminary analysis of a partial data set has lead to {( {tilde C{? 13{{C}}}17{{O(1/}{{{2}}{ + }}{{)}}}} )^2} = 6.7 - 0.6 + 0.9 {{f}}{{{m}} - 1}, slightly larger than the values in the literature, determining a 13C(?, n)16O reaction rate in agreement with the most results in the literature at ˜ 108 K, with enhanced accuracy thanks to this innovative approach.

La Cognata, M.; Spitaleri, C.; Trippella, O.; Kiss, G. G.; Rogachev, G. V.; Mukhamedzhanov, A. M.; Avila, M.; Guardo, G. L.; Koshchiy, E.; Kuchera, A.; Lamia, L.; Puglia, S. M. R.; Romano, S.; Santiago, D.; Spartà, R.

2014-03-01

249

Elaborating on Threshold Concepts  

ERIC Educational Resources Information Center

We propose an expanded definition of Threshold Concepts (TCs) that requires the successful acquisition and internalisation not only of knowledge, but also its practical elaboration in the domains of applied strategies and mental models. This richer definition allows us to clarify the relationship between TCs and Fundamental Ideas, and to account…

Rountree, Janet; Robins, Anthony; Rountree, Nathan

2013-01-01

250

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

251

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

252

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

253

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

254

Threshold optimization of cooperative spectrum sensing in cognitive radio networks  

NASA Astrophysics Data System (ADS)

We consider the threshold optimization problem of cooperative spectrum sensing for cognitive radio (CR) and investigate the threshold optimization algorithm for both single-channel and multichannel cooperative spectrum sensing. In order to obtain the optimal threshold for single-channel cooperative spectrum sensing, we deploy the fusion rules AND Logic, OR Logic, and K-OUT-N Logic. Moreover, an iterative optimization algorithm is proposed to obtain optimal CRs in cooperative spectrum sensing and their optimal thresholds. In multichannel cooperative spectrum sensing, two threshold optimization methods—namely nonrestrained multichannel threshold optimization (NRMTO) and restrained multichannel threshold optimization (RMTO)—have been proposed in order to decrease the total error detection probability of all the subchannels. The simulation results show that in single-channel cooperative spectrum sensing the proposed algorithm outperforms traditional cooperative spectrum sensing with the uniform threshold if the SNR is different, while decreasing the detection performance slightly if the SNR is identical. The results also indicate that the NRMTO can achieve the minimal total error detection probability of multichannel cooperative spectrum sensing, while the RMTO can guarantee the detection performance of each subchannel but with a higher total error detection probability.

Liu, Xin; Jia, Min; Tan, Xuezhi

2013-01-01

255

Direct Detection Rates of Dark Matter Coupled to Dark Energy  

E-print Network

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

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

2006-09-07

256

Algorithm for detecting energy diversion. [Appendix contains an annotated bibliography  

SciTech Connect

The objective of this project was to investigate those factors influencing energy consumption and to develop advanced statistical algorithms and a corresponding computer program to aid utilities in identifying energy diversion by analyzing patterns of energy consumption and other factors readily available to the utility. This final report documents the development of the algorithms, the methodologies used in analyzing their validity, and the advantages and disadvantages of these methods that resulted from these analyses. In the internal study, the algorithms appear to discriminate diverters from the rest of the population. Problems were found that decreased the efficiency of the algorithms during the field investigation. These included the quality of the data used by the algorithms, and the incomplete description of diverters. For the external study 300 potential diverters were submitted to the participating utility for field investigation. They found many cases of vacancies, seasonal use, two cases of tampering, several of suspect nature, irregularities in billing, and a number of meter problems. The code development was not undertaken due to the inconclusive nature of the results obtained in the external validation of the algorithms. Two final recommendations are presented. The first, to create better profiles for diverters and nondiverters, a large sample investigation of electric utility customers should be conducted. This would eliminate selection bias problems perceived to be present in current data. The second provides a list of action items that can be taken by the utilities, to improve both present detection methods and any algorithms that may be developed in the future. 64 refs., 39 figs., 32 figs.

Altschul, R.E.; Janky, D.G.; Scholz, F.W.; Tjoelker, R.A.; Tosch, T.J.; Tosch, T.J. (Boeing Computer Services Co., Seattle, WA (United States))

1991-08-01

257

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

258

Gas threshold Cerenkov counters  

NASA Technical Reports Server (NTRS)

The report describes two designs are reported of gas threshold Cerenkov counters for recording electrons of primary cosmic rays without recording protons. Also presented are design and technological measures which ensure maximum light collection of the Cerenkov radiation originating on the photocathode of the photomultiplier inside the radiator. The dependence of the reflection factor on the length of the light wave for different coatings is shown as well as for the throughput of the different optical materials employed. A range of methods for determining the efficiency of the counters during the recording of cosmic ray nucons and ways of increasing it further are given.

Logachev, V. I.; Sinitsyna, V. G.; Chukin, V. S.

1975-01-01

259

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

260

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

261

Transthoracic defibrillation threshold of sine and trapezoidal waveforms in defibrillation.  

PubMed

The transthoracic defibrillation threshold of trapezoidal (2.5-, 5-, 10-, 15-, 20-, 40-, and 55-msec duration) and damped sine waveforms were established in groups of anesthetized greyhounds. Of the seven trapezoidal waveforms, the threshold current was lowest for the 20-msec pulse but was not significantly different for the 5-20-msec pulses (p greater than 0.05). The threshold delivered energy was not significantly different for the 2.5-20-msec waveforms. The 40- and 55-msec pulses had significantly greater delivered energies than the shorter pulses (p less than 0.01). The transthoracic defibrillation threshold of two trapezoidal (5- and 20-msec) and three damped sine waves (Lown, Edmark, and Belfast) showed that the threshold transthoracic current and energy were not significantly different for the 5-msec trapezoid and three sine waves (p greater than 0.05). The threshold transthoracic energy for the 20-msec trapezoid was significantly greater than that of the four other waveforms. The threshold current for the 20-msec trapezoid was significantly less than that of the Belfast and Edmark waveforms only. Thus, none of the three damped sine waveforms was superior, with the 5-msec trapezoid producing similar results. Although the 20-msec trapezoid had the lowest threshold current, it had the highest delivery energy. PMID:2760559

Wilson, C M; Bailey, A; Allen, J D; Anderson, J; Adgey, A A

1989-07-01

262

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

E-print Network

Detecting dark energy with wavelets on the sphere Jason D. McEwen Astrophysics Group, Cavendish Laboratory, Cambridge CB3 0HE, UK ABSTRACT Dark energy dominates the energy density of our Universe, yet we know very little about its nature and origin. Although strong evidence in support of dark energy

McEwen, Jason

263

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

264

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

265

High energy muon number spectrum detected at the Baksan Underground Scintillation Telescope  

NASA Astrophysics Data System (ADS)

Integral muon number spectrum has been measured at the Baksan Underground Scintillation Telescope (BUST) for near vertical directions (??20°, effective muon threshold energy is 230 GeV). The analyzed range of the number of muon tracks crossing BUST is 2 170. It corresponds to the primary energy range 3?10 eV 10 eV. Muon number spectrum calculations have been carried out for different primary compositions. For EAS simulations CORSIKA code (v.6.030, QGSJET01 model) has been used. Our data agree with a composition lighter than the standard one before the knee with the knee position at Z?2.0?10 eV.

Petkov, V. B.; Szabelski, J.; Smirnov, D. V.; Novoseltseva, R. V.

2008-01-01

266

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

267

Electroproduction of single pions near threshold  

Microsoft Academic Search

Inelastic electron scattering cross sections from hydrogen have been measured near the pion production threshold at electron four-momentum transfers squared of 0.10, 0.14. 0.19 and 0.31 (GeV\\/c)2 using a beam of 2 GeV\\/c electrons from the Daresbury electron synchrotron and a magnetic spectrometer to detect the scattered electron. The results are analysed phenomenologically, and compared with theoretical calculations, using current

V. P. R. Nuthakki; O. T. Tumer; B. Dickinson; M. Ibbotson; W. J. Shuttleworth; R. Siddle; A. Sofair; J. Fannon; J. Allison; A. B. Clegg; F. Foster; R. D. Hellings

1971-01-01

268

A determination of the ionization threshold for the Mg(3 s3 p3P0) · Ar( 3? 0 -) metastable state: The bond energy of MgAr +  

NASA Astrophysics Data System (ADS)

The ionization threshold for the metastable Mg(3 s3 p3P0) · Ar( 3? 0 -) state has been determined to be 38744 ± 5 cm -1 by two-color photoionization via Mg(3 s4 s3S1) · Ar( 3? +, ?') resonance states. From several experimental measurements and an ab initio calculation, D 0( Mg(3 s3 p3P0) · Ar( 3? 0 -)) = 160 ± 40 cm-1, from which D0(MgAr +) is calculated to be 1237 ± 40 cm -. This value is consistent with, but more accurate than, previous experimental and ab initio estimates of D0(MgAr +).

Massick, Steven; Breckenridge, W. H.

1996-08-01

269

Earnings Management to Exceed Thresholds  

Microsoft Academic Search

Earnings provide important information for investment decisions. Thus, executives--who are monitored by investors, directors, customers, and suppliers--acting in self-interest and at times for shareholders, have strong incentives to manage earnings. The authors introduce behavioral thresholds for earnings management. A model shows how thresholds induce specific types of earnings management. Empirical explorations identify earnings management to exceed each of three thresholds:

Francois Degeorge; Jayendu Patel; Richard Zeckhauser

1999-01-01

270

Tracking of nociceptive thresholds using adaptive psychophysical methods.  

PubMed

Psychophysical thresholds reflect the state of the underlying nociceptive mechanisms. For example, noxious events can activate endogenous analgesic mechanisms that increase the nociceptive threshold. Therefore, tracking thresholds over time facilitates the investigation of the dynamics of these underlying mechanisms. Threshold tracking techniques should use efficient methods for stimulus selection and threshold estimation. This study compares, in simulation and in human psychophysical experiments, the performance of different combinations of adaptive stimulus selection procedures and threshold estimation methods. Monte Carlo simulations were first performed to compare the bias and precision of threshold estimates produced by three different stimulus selection procedures (simple staircase, random staircase, and minimum entropy procedure) and two estimation methods (logistic regression and Bayesian estimation). Logistic regression and Bayesian estimations resulted in similar precision only when the prior probability distributions (PDs) were chosen appropriately. The minimum entropy and simple staircase procedures achieved the highest precision, while the random staircase procedure was the least sensitive to different procedure-specific settings. Next, the simple staircase and random staircase procedures, in combination with logistic regression, were compared in a human subject study (n = 30). Electrocutaneous stimulation was used to track the nociceptive perception threshold before, during, and after a cold pressor task, which served as the conditioning stimulus. With both procedures, habituation was detected, as well as changes induced by the conditioning stimulus. However, the random staircase procedure achieved a higher precision. We recommend using the random staircase over the simple staircase procedure, in combination with logistic regression, for nonstationary threshold tracking experiments. PMID:23835651

Doll, Robert J; Buitenweg, Jan R; Meijer, Hil G E; Veltink, Peter H

2014-03-01

271

The use of Schottky CdTe detectors for high-energy astronomy: application to the detection plane of the instrument SVOM/ECLAIRs  

NASA Astrophysics Data System (ADS)

Ohmic CdZnTe and CdTe detectors have been successfully used in high-energy missions such as IBIS on-board INTEGRAL and the Swift-BAT in the past two decades. Such detectors provide very good quantum efficiency in the hard X-ray band. For the future generation of hard X-ray coded mask detectors, a higher sensitivity will be required. A way to achieve this is to increase the effective area of the pixilated detection plane, to change the mask pattern and/or the properties of the semi-conductors paving the detection plane. For the future Chinese-French Gamma-ray burst mission SVOM, the GRB trigger camera ECLAIRs will make use of a new type of high-energy detectors, the Schottky CdTe detectors. Such detectors, when reversely biased, are known to present very low leakage current, resulting in lower values of the low-energy threshold (down to 4 keV or less) than for previous missions (i.e. > 10 keV for the Swift-BAT and INTEGRAL/IBIS). Such low values will enable ECLAIRs with a moderate geometrical area of 1024 cm2 and a low-energy threshold of 4 keV to be more sensitive to high-redshift GRBs (emitting mainly in X-rays) than the Swift-BAT with a higher effective area and low-energy threshold. However, the spectral performance of such detectors are known to degrade over time, once polarized, due to the polarization effect that strongly depends on the temperature and the bias voltage applied to the detectors. In this paper, we present an intensive study of the properties of Schottky CdTe detectors as used on SVOM/ECLAIRs such as I-V characteristics, polarization effect, activation energy and low temperature annealing effects. We discuss the implications of these measurements on the use of this type of detectors in future high-energy instruments.

Nasser, G.; Godet, O.; Atteia, J.-L.; Amoros, C.; Barret, D.; Bordon, S.; Cordier, B.; Gevin, O.; Gonzalez, F.; Houret, B.; Lacombe, K.; Mandrou, P.; Marty, W.; Mercier, K.; Pons, R.; Rambaud, D.; Ramon, P.; Rouaix, G.; Waegebaert, V.

2014-07-01

272

Measuring the speed of dark: Detecting dark energy perturbations  

SciTech Connect

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

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

2010-05-15

273

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

274

Analysis of the hadronic energy spectrum in high-energy cosmic-ray families detected by emulsion chambers  

SciTech Connect

We analyze the hadronic energy spectrum for cosmic-ray families detected by emulsion chambers in the high-energy region, by means of the solution of diffusion equations for the hadronic cascade induced by one single nucleon in the atmosphere, assuming three different models for the energy distribution function in multiple pion production. We describe the experimental data for the energy of three high-energy families detected in emulsion chamber of Brazil-Japan Colloboration (BJC) at Mt. Chacaltaya and of two families detected by Pamir Collaboration (PC). We look also for consistency of the rapidity-density distribution, obtained for the different hypotheses for multiple pion production above, with accelerator data in the ISR and Collider regions. Finally, the Models are analysed with respect to the energy dependence of the mean inelasticity.

Bellandi, J.; Costa, C.G.S.; Covolan, R.J.M.; Dobrigkeit, C.; Guzzo, M.M.; Mundim, L.M. (Departamento de Raios Cosmicos e Cronologia, IFGW Unicamp, C. Postal 6165, Campinas, SP 13081-970 (Brazil))

1993-06-15

275

Exhaustive Thresholds and Resistance Checkpoints  

NASA Technical Reports Server (NTRS)

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

Easton, Charles; Khuzadi, Mbuyi

2008-01-01

276

An Efficient Energy based Detection of Malicious Node in Mobile Wireless Sensor Networks  

NASA Astrophysics Data System (ADS)

Mobile wireless sensor networks (MWSN) are composed of a large number of wireless sensors and they require a careful consumption of available energy to prolong the life of the network. From the security point of view, existing detection schemes consumes node energy and thus reduces the life time of the network. This paper focuses on energy based scheme for detecting the malicious node in the forward routing path. This detection scheme suits any standard routing protocol. The forward route selection path is identified by using dynamic source routing protocol. The proposed scheme is simulated in glomosim and evaluated using packet throughput, percentage of byte overheads, energy consumption, and the accuracy of detection. The network with moderate mobility is used and the proposed scheme consumes 20 % of node energy.

Sharmila, S.; Umamaheswari, G.

2012-03-01

277

Detecting Protein-Protein Interaction Decoys using Fast Free Energy Calculations  

E-print Network

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

Langmead, Christopher James

278

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

NASA Astrophysics Data System (ADS)

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

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

279

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

280

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

281

Threshold Hypothesis: Fact or Artifact?  

ERIC Educational Resources Information Center

The threshold hypothesis (TH) assumes the existence of complex relations between creative abilities and intelligence: linear associations below 120 points of IQ and weaker or lack of associations above the threshold. However, diverse results have been obtained over the last six decades--some confirmed the hypothesis and some rejected it. In this…

Karwowski, Maciej; Gralewski, Jacek

2013-01-01

282

In-band spectrum sensing in cognitive radio networks: energy detection or feature detection?  

Microsoft Academic Search

In a cognitive radio network (CRN), in-band spectrum sens- ing is essential for the protection of legacy spectrum users, with which the presence of primary users (PUs) can be de- tected promptly, allowing secondary users (SUs) to vacate the channels immediately. For in-band sensing, it is impor- tant to meet the detectability requirements, such as the max- imum allowed latency

Hyoil Kim; Kang G. Shin

2008-01-01

283

Life below the threshold.  

PubMed

This article explains that malnutrition, poor health, and limited educational opportunities plague Philippine children -- especially female children -- from families living below the poverty threshold. Nearly 70% of households in the Philippines do not meet the required daily level of nutritional intake. Because it is often -- and incorrectly -- assumed that women's nutritional requirements are lower than men's, women suffer higher rates of malnutrition and poor health. A 1987 study revealed that 11.7% of all elementary students were underweight and 13.9% had stunted growths. Among elementary-school girls, 17% were malnourished and 40% suffered from anemia (among lactating mothers, more than 1/2 are anemic). A 1988 Program for Decentralized Educational Development study showed that grade VI students learn only about 1/2 of what they are supposed to learn. 30% of the children enrolled in grade school drop out before they reach their senior year. The Department of Education, Culture and Sports estimates that some 2.56 million students dropped out of school in l989. That same year, some 3.7 million children were counted as part of the labor force. In Manila alone, some 60,000 children work the streets, whether doing odd jobs or begging, or turning to crime or prostitution. the article tells the story of a 12 year-old girl named Ging, a 4th grader at a public school and the oldest child in a poor family of 6 children. The undernourished Ging dreams of a good future for her family and sees education as a way out of poverty; unfortunately, her time after school is spend working in the streets or looking after her family. She considers herself luckier than many of the other children working in the streets, since she at least has a family. PMID:12285009

Castro, C

1991-01-01

284

DETECTION OF LARGE ACOUSTIC ENERGY FLUX IN THE SOLAR ATMOSPHERE  

SciTech Connect

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

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

2010-11-10

285

Diagnostic thresholds with three ordinal groups.  

PubMed

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

Attwood, Kristopher; Tian, Lili; Xiong, Chengjie

2014-01-01

286

A sub-threshold cell library and methodology  

E-print Network

Sub-threshold operation is a compelling approach for energy-constrained applications where speed is of secondary concern, but increased sensitivity to process variation must be mitigated in this regime. With scaling of ...

Kwong, Joyce Y. S. (Joyce Yui Si)

2006-01-01

287

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

288

Generalized constrained energy minimization approach to subpixel target detection  

E-print Network

with a dimensionality expansion (DE) approach resulting from a gener- alized orthogonal subspace projection (GOSP dimensionality. Experiments show that the proposed GCEM detects targets more effectively than GOSP and CEM, Ren and Chang3 recently proposed a generalized orthogonal subspace projection GOSP approach, which

Chang, Chein-I

289

Multiple photon detection and the localization of light energy  

E-print Network

It is shown that probabilities of photon detection can be found on the basis of consideration of the phase space sells filling for an ideal photon gas, which led Bose to the derivation of the Planks law. These probabilities are directly connected to photon localization properties consistent with the entropy of a dilute photon gas found by Einstein.

M. V. Lebedev

2013-12-31

290

Near threshold studies of photoelectron satellites  

SciTech Connect

Photoelectron spectroscopy and synchrotron radiation have been used to study correlation effects in the rare gases: He, Ne, Ar, Kr, and Xe. Two kinds of time-of-flight electron analyzers were employed to examine photoionization very close to threshold and at higher kinetic energies. Partial cross sections and angular distributions have been measured for a number of photoelectron satellites. The shake-off probability has been determined at some inner-shell resonances. 121 refs., 28 figs., 13 tabs.

Heimann, P.A.

1986-11-01

291

Superlinear threshold detectors in quantum cryptography  

E-print Network

We introduce the concept of a superlinear threshold detector, a detector that has a higher probability to detect multiple photons if it receives them simultaneously rather than at separate times. Highly superlinear threshold detectors in quantum key distribution systems allow eavesdropping the full secret key without being revealed. Here, we generalize the detector control attack, and analyze how it performs against quantum key distribution systems with moderately superlinear detectors. We quantify the superlinearity in superconducting single-photon detectors based on earlier published data, and gated avalanche photodiode detectors based on our own measurements. The analysis shows that quantum key distribution systems using detector(s) of either type can be vulnerable to eavesdropping. The avalanche photodiode detector becomes superlinear towards the end of the gate, allowing eavesdropping using trigger pulses containing less than 120 photons per pulse. Such an attack would be virtually impossible to catch with an optical power meter at the receiver entrance.

Lars Lydersen; Nitin Jain; Christoffer Wittmann; Øystein Marøy; Johannes Skaar; Christoph Marquardt; Vadim Makarov; Gerd Leuchs

2011-06-10

292

Threshold magnitude for Ionospheric TEC response to earthquakes  

NASA Astrophysics Data System (ADS)

We have analyzed ionospheric response to earthquakes with magnitudes of 4.1-8.8 which occurred under quiet geomagnetic conditions in different regions of the world (the Baikal region, Kuril Islands, Japan, Greece, Indonesia, China, New Zealand, Salvador, and Chile). This investigation relied on measurements of total electron content (TEC) variations made by ground-based dual-frequency GPS receivers. To perform the analysis, we selected earthquakes with permanent GPS stations installed close by. Data processing has revealed that after 4.1-6.3-magnitude earthquakes wave disturbances in TEC variations are undetectable. We have thoroughly analyzed publications over the period of 1965-2013 which reported on registration of wave TIDs after earthquakes. This analysis demonstrated that the magnitude of the earthquakes having a wave response in the ionosphere was no less than 6.5. Based on our results and on the data from other researchers, we can conclude that there is a threshold magnitude (near 6.5) below which there are no pronounced earthquake-induced wave TEC disturbances. The probability of detection of post-earthquake TIDs with a magnitude close to the threshold depends strongly on geophysical conditions. In addition, reliable identification of the source of such TIDs generally requires many GPS stations in an earthquake zone. At low magnitudes, seismic energy is likely to be insufficient to generate waves in the neutral atmosphere which are able to induce TEC disturbances observable at the level of background fluctuations.

Perevalova, N. P.; Sankov, V. A.; Astafyeva, E. I.; Zhupityaeva, A. S.

2014-02-01

293

NOSTOS: a spherical TPC to detect low energy neutrinos  

Microsoft Academic Search

A novel low-energy (~few keV) neutrino-oscillation experiment NOSTOS, combining a strong tritium source and a high pressure spherical Time Projection Chamber (TPC) detector 10 m in radius has been recently proposed. The oscillation of neutrinos of such energies occurs within the size of the detector itself, potentially allowing for a very precise (and rather systematics-free) measure of the oscillation parameters,

S. Aune; P. Colas; J. Dolbeau; G. Fanourakis; E. Ferrer Ribas; T. Geralis; Y. Giomataris; P. Gorodetzky; G. J. Gounaris; I. G. Irastorza; K. Kousouris; V. Lepeltier; T. Patzak; E. A. Paschos; P. Salin; I. Savvidis; J. D. Vergados

2005-01-01

294

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

295

High-resolution threshold photoelectron spectroscopy by electron attachment  

NASA Technical Reports Server (NTRS)

A new technique for measuring high-resolution threshold photoelectron spectra of atoms, molecules, and radicals is described. It involves photoionization of a gaseous species, attachment of the threshold, or nearly zero electron to some trapping molecule (here SF6 or CFCl3), and mass detection of the attachment product (SF6/-/ or Cl/-/ respectively). This technique of threshold photoelectron spectroscopy by electron attachment was used to measure the spectra of argon and xenon at 11 meV (FWHM) resolution, and was also applied to CFCl3.

Ajello, J. M.; Chutjian, A.

1976-01-01

296

Generalized constrained energy minimization approach to subpixel detection for multispectral imagery  

Microsoft Academic Search

Subpixel detection for multispectral imagery presents a challenging problem due to relatively low spectral resolution. This paper proposes a Generalized Constrained Energy Minimization (GCEM) approach to detecting objects in multispectral imagery at subpixel level. GCEM is a combination of a dimensionality expansion (DE) approach resulting from a generalized orthogonal subspace projection (GOSP) developed for multispectral image classification and a CEM

JihMing Liu; ChunMu Wang; BinChang Chieu; Chein-I. Chang; Hsuan Ren; Ching-Wen Yang

1999-01-01

297

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

E-print Network

Comparison?of?Two?Statistical?Approaches? to?Detect?Abnormal?Building?Energy? Consumption?with?Simulation?Test 12th International?Conference?for?Enhanced?Building?Operations 23rd ? 26th October?2012? Manchester,?England Guanjing...Comparison?of?Two?Statistical?Approaches? to?Detect?Abnormal?Building?Energy? Consumption?with?Simulation?Test 12th International?Conference?for?Enhanced?Building?Operations 23rd ? 26th October?2012? Manchester,?England Guanjing...

Lin, G.; Claridge, D.

2012-01-01

298

Indirect Detection of Dark Matter in km-size Neutrino Telescopes  

E-print Network

Neutrino telescopes of kilometer size are currently being planned. They will be two or three orders of magnitude larger than presently operating detectors, but they will have a much higher muon energy threshold. We discuss the trade-off between area and energy threshold for indirect detection of neutralino dark matter captured in the Sun and in the Earth and annihilating into high energy neutrinos. We also study the effect of a higher threshold on the complementarity of different searches for supersymmetric dark matter.

Lars Bergstrom; Joakim Edsjo; Paolo Gondolo

1999-06-02

299

Threshold collision-induced dissociation of Sr(2+)(H(2)O)(x) complexes (x=1-6): An experimental and theoretical investigation of the complete inner shell hydration energies of Sr(2+).  

PubMed

The sequential bond energies of Sr(2+)(H(2)O)(x) complexes, where x=1-6, are determined by threshold collision-induced dissociation using a guided ion beam tandem mass spectrometer equipped with an electrospray ionization source. The electrospray source produces an initial distribution of Sr(2+)(H(2)O)(x) complexes, where x=6-9. Smaller Sr(2+)(H(2)O)(x) complexes, where x=1-5, are accessed using a recently developed in-source fragmentation technique that takes place in the high pressure region of a rf-only hexapole ion guide. This work constitutes the first experimental study for the complete inner shell of any multiply charged ion. The kinetic energy dependent cross sections are determined over a wide energy range to monitor all possible dissociation products and are modeled to obtain 0 and 298 K binding energies for loss of a single water molecule. These binding energies decrease monotonically for the Sr(2+)(H(2)O) complex to Sr(2+)(H(2)O)(6). Our experimental results agree well with previous literature results obtained by equilibrium and kinetic studies for x=5 and 6. Because there has been limited theory for the hydration of Sr(2+), we also present an in-depth theoretical study on the energetics of the Sr(2+)(H(2)O)(x) systems by employing several levels of theory with multiple effective core potentials for Sr and different basis sets for the water molecules. PMID:20113029

Carl, D R; Chatterjee, B K; Armentrout, P B

2010-01-28

300

Detecting dark energy in long baseline neutrino oscillations  

E-print Network

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

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

2005-12-06

301

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

DOEpatents

A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

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

2009-05-05

302

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

DOEpatents

A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

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

2009-01-06

303

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

DOEpatents

A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

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

2009-01-27

304

High energy neutron flux detection with dielectric plastics  

Microsoft Academic Search

Dielectric plastics were irradiated with high energy neutrons to investigate their usefulness as flux detectors. Shields thick to heavy particles and of varying composition were placed in front of the plastics to test their effectiveness as radiators. Track producing particles resulted from (n, 4He) reactions and from recoils of light nuclei. Elements possessing high (n, 4He) cross sections were chosen

A. L. Frank; E. V. Benton

1970-01-01

305

Definition and measurement of dust aeolian thresholds  

Microsoft Academic Search

Dust suspension and particle “saltation threshold” speeds were measured in an environmental boundary layer wind tunnel located at the University of California, Davis. The results indicate that dust suspension threshold speeds occur at substantially lower friction speeds than “saltation threshold” speeds. Many of the dust suspension threshold values are half of the “saltation threshold” values. For example, surface soils from

Jason A. Roney; Bruce R. White

2004-01-01

306

Summing tree graphs at threshold  

NASA Astrophysics Data System (ADS)

The solution of the classical field equation generates the sum of all tree graphs. We show that the classical equation reduces to an easily solved ordinary differential equation for certain multiparticle threshold amplitudes and compute these amplitudes.

Brown, Lowell S.

1992-11-01

307

Image thresholding using standard deviation  

NASA Astrophysics Data System (ADS)

Threshold selection using the within-class variance in Otsu's method is generally moderate, yet inappropriate for expressing class statistical distributions. Otsu uses a variance to represent the dispersion of each class based on the distance square from the mean to any data. However, since the optimal threshold is biased toward the larger variance among two class variances, variances cannot be used to denote the real class statistical distributions. Therefore, to express more accurate class statistical distributions, this paper proposes the within-class standard deviation as a criterion for threshold selection, and the optimal threshold is then determined by minimizing the within-class standard deviation. Experimental results confirm that the proposed method produced a better performance than existing algorithms.

Sung, Jung-Min; Kim, Dae-Chul; Choi, Bong-Yeol; Ha, Yeong-Ho

2014-03-01

308

Structural Threshold Regression Andros Kourtellos  

E-print Network

Structural Threshold Regression Andros Kourtellos University of Cyprus Thanasis Stengos University, and 23rd (EC)2 conference. Department of Economics, P.O. Box 537, CY 1678 Nicosia, Cyprus,email: andros

Nesterov, Yurii

309

DNA energy landscapes via calorimetric detection of microstate ensembles of metastable macrostates and triplet repeat diseases  

Microsoft Academic Search

Biopolymers exhibit rough energy landscapes, thereby allowing biological processes to access a broad range of kinetic and thermodynamic states. In contrast to proteins, the energy landscapes of nucleic acids have been the subject of relatively few experimental investigations. In this study, we use calorimetric and spectroscopic observables to detect, resolve, and selectively enrich energetically discrete ensembles of microstates within metastable

Jens Völker; Horst H. Klump; Kenneth J. Breslauer

2008-01-01

310

DNA Energy Landscapes via Calorimetric Detection of Microstate Ensembles of Metastable Macrostates and Triplet Repeat Diseases  

Microsoft Academic Search

Biopolymers exhibit rough energy landscapes, thereby allowing biological processes to access a broad range of kinetic and thermodynamic states. In contrast to proteins, the energy landscapes of nucleic acids have been the subject of relatively few experimental investigations. In this study, we use calorimetric and spectroscopic observables to detect, resolve, and selectively enrich energetically discrete ensembles of microstates within metastable

Jens Völker; Horst H. Klump; Kenneth J. Breslauer

2008-01-01

311

OWL 2 Reasoning To Detect Energy-Efficient Software Variants From Context  

E-print Network

, but differing in the realization. A feasible approach to component-based self-adaptive systems are contractOWL 2 Reasoning To Detect Energy-Efficient Software Variants From Context Sebastian G¨otz1 , Julian to achieve energy-efficiency. For optimizing the system configuration at runtime, the early recognition

Baader, Franz

312

Threshold models in radiation carcinogenesis.  

PubMed

Cancer incidence and mortality data from the atomic bomb survivors cohort has been analyzed to allow for the possibility of a threshold dose response. The same dose-response models as used in the original papers were fit to the data. The estimated cancer incidence from the fitted models over-predicted the observed cancer incidence in the lowest exposure group. This is consistent with a threshold or non-linear dose-response at low-doses. Thresholds were added to the dose-response models and the range of possible thresholds is shown for both solid tumor cancers as well as the different leukemia types. This analysis suggests that the A-bomb cancer incidence data agree more with a threshold or non-linear dose-response model than a purely linear model although the linear model is statistically equivalent. This observation is not found with the mortality data. For both the incidence data and the mortality data the addition of a threshold term significantly improves the fit to the linear or linear-quadratic dose response for both total leukemias and also for the leukemia subtypes of ALL, AML, and CML. PMID:9721832

Hoel, D G; Li, P

1998-09-01

313

Threshold models in radiation carcinogenesis  

SciTech Connect

Cancer incidence and mortality data from the atomic bomb survivors cohort has been analyzed to allow for the possibility of a threshold dose response. The same dose-response models as used in the original papers were fit to the data. The estimated cancer incidence from the fitted models over-predicted the observed cancer incidence in the lowest exposure group. This is consistent with a threshold or nonlinear dose-response at low-doses. Thresholds were added to the dose-response models and the range of possible thresholds is shown for both solid tumor cancers as well as the different leukemia types. This analysis suggests that the A-bomb cancer incidence data agree more with a threshold or nonlinear dose-response model than a purely linear model although the linear model is statistically equivalent. This observation is not found with the mortality data. For both the incidence data and the mortality data the addition of a threshold term significantly improves the fit to the linear or linear-quadratic dose response for both total leukemias and also for the leukemia subtypes of ALL, AML, and CML.

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

1998-09-01

314

Detecting plasmon resonance energy transfer with differential interference contrast microscopy.  

PubMed

Gold nanoparticles are ideal probes for studying intracellular environments and energy transfer mechanisms due to their plasmonic properties. Plasmon resonance energy transfer (PRET) relies on a plasmonic nanoparticle to donate energy to a nearby resonant acceptor molecule, a process which can be observed due to the plasmonic quenching of the donor nanoparticle. In this study, a gold nanosphere was used as the plasmonic donor, while the metalloprotein cytochrome c was used as the acceptor molecule. Differential interference contrast (DIC) microscopy allows for simultaneous monitoring of complex environments and noble metal nanoparticles in real time. Using DIC and specially designed microfluidic channels, we were able to monitor PRET at the single gold particle level and observe the reversibility of PRET upon the introduction of phosphate-buffered saline to the channel. In an additional experiment, single gold particles were internalized by HeLa cells and were subsequently observed undergoing PRET as the cell hosts underwent morphological changes brought about by ethanol-induced apoptosis. PMID:24377308

Augspurger, Ashley E; Stender, Anthony S; Han, Rui; Fang, Ning

2014-01-21

315

Detecting Plasmon Resonance Energy Transfer with Differential Interference Contrast Microscopy  

SciTech Connect

Gold nanoparticles are ideal probes for studying intracellular environments and energy transfer mechanisms due to their plasmonic properties. Plasmon resonance energy transfer (PRET) relies on a plasmonic nanoparticle to donate energy to a nearby resonant acceptor molecule, a process which can be observed due to the plasmonic quenching of the donor nanoparticle. In this study, a gold nanosphere was used as the plasmonic donor, while the metalloprotein cytochrome c was used as the acceptor molecule. Differential interference contrast (DIC) microscopy allows for simultaneous monitoring of complex environments and noble metal nanoparticles in real time. Using DIC and specially designed microfluidic channels, we were able to monitor PRET at the single gold particle level and observe the reversibility of PRET upon the introduction of phosphate-buffered saline to the channel. In an additional experiment, single gold particles were internalized by HeLa cells and were subsequently observed undergoing PRET as the cell hosts underwent morphological changes brought about by ethanol-induced apoptosis.

Augspurger, Ashley E. [Ames Laboratory; Stender, Anthony S. [Ames Laboratory; Han, Rui [Ames Laboratory; Fang, Ning [Ames Laboratory

2013-12-30

316

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

Microsoft Academic Search

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

Andrew T. Hurly

2003-01-01

317

Threshold laws for collisional reorientation of electronic angular momentum Roman V. Krems* and Alexander Dalgarno  

E-print Network

Threshold laws for collisional reorientation of electronic angular momentum Roman V. Krems it here. We derive threshold laws for the energy dependence of cross sections for projection flipping in paramagnetic atoms or molecules in collisions with struc- tureless targets. Wigner presented threshold laws

Krems, Roman

318

Automatic Classification of Kepler Threshold Crossing Events  

NASA Astrophysics Data System (ADS)

Over the course of its 4-year primary mission the Kepler mission has discovered numerous planets. Part of the process of planet discovery has involved generating threshold crossing events (TCEs); a light curve with a repeating exoplanet transit-like feature. The large number of diagnostics 100) makes it difficult to examine all the information available for each TCE. The effort required for vetting all threshold-crossing events (TCEs) takes several months by many individuals associated with the Kepler Threshold Crossing Event Review Team (TCERT). The total number of objects with transit-like features identified in the light curves has increased to as many as 18,000, just examining the first three years of data. In order to accelerate the process by which new planet candidates are classified, we propose a machine learning approach to establish a preliminary list of planetary candidates ranked from most credible to least credible. The classifier must distinguish between three classes of detections: non-transiting phenomena, astrophysical false positives, and planet candidates. We use random forests, a supervised classification algorithm to this end. We report on the performance of the classifier and identify diagnostics that are important for discriminating between these classes of TCEs.Funding for this mission is provided by NASA’s Science Mission Directorate.

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

2014-06-01

319

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

E-print Network

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

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

2005-04-12

320

Relationship between canine transthoracic impedance and defibrillation threshold. Evidence for current-based defibrillation.  

PubMed Central

The electrical parameter used to define defibrillation strength is energy. Peak current, however, may more accurately reflect the field quantities (i.e., electric field strength and current density) that mediate defibrillation and therefore should be a better clinical descriptor of threshold than energy. Though transthoracic impedance is a major determinant of energy-based threshold and is sensitive to operator-dependent changes in impedance (electrode-subject interface), an ideal threshold descriptor should be invariant with respect to these changes in impedance. We therefore compared the relative invariance of energy- and current-based thresholds when transthoracic impedance was altered by one of two methods: (a) change in electrode size (protocol A) or (b) change in electrode force (protocol B). In protocol A, impedance was altered in each dog by a mean of 95%. Energy thresholds determined at both low and high impedance were 44 +/- 21 J (mean +/- SD) and 105 +/- 35 J, respectively, P less than 0.0001. In contrast, peak current (A) thresholds were independent of transthoracic impedance, 22 +/- 5 A (low impedance) vs. 24 +/- 6 A (high impedance), P = NS. Energy and current thresholds showed a similar relationship for animals tested in protocol B. Therefore, current-based thresholds, in contrast to energy thresholds are independent of operator-dependent variables of transthoracic impedance and are invariant for a given animal. These results suggest that redefining defibrillation threshold in terms of peak current rather than energy provides a superior method of defibrillation. Images PMID:3624489

Lerman, B B; Halperin, H R; Tsitlik, J E; Brin, K; Clark, C W; Deale, O C

1987-01-01

321

The thawing dark energy dynamics: Can we detect it?  

NASA Astrophysics Data System (ADS)

We consider different classes of scalar field models including quintessence and tachyon scalar fields with a variety of generic potentials belonging to the thawing type. We focus on observational quantities like Hubble parameter, luminosity distance as well as quantities related to the Baryon Acoustic Oscillation measurement. Our study shows that with present state of observations, one cannot distinguish amongst various models which in turn cannot be distinguished from cosmological constant. Our analysis indicates that there is a small chance to observe the dark energy metamorphosis in near future.

Sen, S.; Sen, A. A.; Sami, M.

2010-03-01

322

Detection of high-energy delayed gammas for nuclear waste packages characterization  

NASA Astrophysics Data System (ADS)

Methods based on photon activation analysis (PAA) have been developed by CEA LIST for several years, in order to assay actinides inside nuclear waste packages. These techniques were primarily based on the detection of delayed neutrons emitted by fission products. To overcome some limitations related to neutrons, CEA LIST has worked on the detection of high-energy delayed gammas ( E>3 MeV), which are simultaneously emitted by fission products along with delayed neutrons. Since the emission yield is more important for high-energy delayed gammas than delayed neutrons and because they are less sensitive to hydrogenous material, high-energy delayed gammas are a solution of interest in order to improve the accuracy of these techniques. In this article, we present new experimental results demonstrating the feasibility of high-energy delayed gamma detection for nuclear waste packages characterization. Experiments have been carried out in the PAA facility called SAPHIR, which is located in CEA Saclay. The most important part of our work has been carried out on an 870 l mock-up package. Some experimental techniques, initially based on delayed neutron detection (altitude scan, photofission tomography), have been successfully applied for the first time using high-energy delayed gamma detection.

Carrel, F.; Agelou, M.; Gmar, M.; Lainé, F.

2011-10-01

323

Threshold collision-induced dissociation of hydrated magnesium: experimental and theoretical investigation of the binding energies for Mg(2+)(H2O)x complexes (x=2-10).  

PubMed

The sequential bond energies of Mg(2+)(H2O)x complexes, in which x=2-10, are measured by threshold collision-induced dissociation in a guided ion beam tandem mass spectrometer. From an electrospray ionization source that produces an initial distribution of Mg(2+)(H2O)x complexes in which x=7-10, complexes down to x=3 are formed by using an in-source fragmentation technique. Complexes smaller than Mg(2+)(H2O)3 cannot be formed in this source because charge separation into MgOH(+)(H2O) and H3O(+) is a lower-energy pathway than simple water loss from Mg(2+)(H2O)3. The kinetic energy dependent cross sections for dissociation of Mg(2+)(H2O)x complexes, in which x=3-10, are examined over a wide energy range to monitor all dissociation products and are modeled to obtain 0 and 298 K binding energies. Analysis of both primary and secondary water molecule losses from each sized complex provides thermochemistry for the sequential hydration energies of Mg(2+) for x=2-10 and the first experimental values for x=2-4. Additionally, the thermodynamic onsets leading to the charge-separation products from Mg(2+)(H2O)3 and Mg(2+)(H2O)4 are determined for the first time. Our experimental results for x=3-7 agree well with quantum chemical calculations performed here and previously calculated binding enthalpies, as well as previous measurements for x=6. The present values for x=7-10 are slightly lower than previous experimental results and theory, but within experimental uncertainties. PMID:23239534

Carl, Damon R; Armentrout, Peter B

2013-03-18

324

Experimental investigation of the complete inner shell hydration energies of Ca2+: threshold collision-induced dissociation of Ca(2+)(H2O)x Complexes (x = 2-8).  

PubMed

The sequential bond energies of Ca(2+)(H(2)O)(x) complexes, where x = 1-8, are measured by threshold collision-induced dissociation (TCID) in a guided ion beam tandem mass spectrometer. From an electrospray ionization source that produces an initial distribution of Ca(2+)(H(2)O)(x) complexes where x = 6-8, complexes down to x = 2 are formed using an in-source fragmentation technique. Ca(2+)(H(2)O) cannot be formed in this source because charge separation into CaOH(+) and H(3)O(+) is a lower energy pathway than simple water loss from Ca(2+)(H(2)O)(2). The kinetic energy dependent cross sections for dissociation of Ca(2+)(H(2)O)(x) complexes, where x = 2-9, are examined over a wide energy range to monitor all dissociation products and are modeled to obtain 0 and 298 K binding energies. Analysis of both primary and secondary water molecule losses from each sized complex provides thermochemistry for the sequential hydration energies of Ca(2+) for x = 1-8 and the first experimental values for x = 1-4. Additionally, the thermodynamic onsets leading to the charge separation products from Ca(2+)(H(2)O)(2) and Ca(2+)(H(2)O)(3) are determined for the first time. Our experimental results for x = 1-6 agree well with previously calculated binding enthalpies as well as quantum chemical calculations performed here. Agreement for x = 1 is improved when the basis set on calcium includes core correlation. PMID:22452741

Carl, Damon R; Armentrout, P B

2012-04-19

325

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

326

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

DOEpatents

At least two linear arrays of x-ray detectors are placed below a conveyor belt in a poultry processing plant. Multiple-energy x-ray sources illuminate the poultry and are detected by the detectors. Laser profilometry is used to measure the poultry thickness as the x-ray data is acquired. The detector readout is processed in real time to detect the presence of small highly attenuating fragments in the poultry, i.e., bone, metal, and cartilage.

Gleason, Shaun S [Knoxville, TN; Paulus, Michael J [Knoxville, TN; Mullens, James A [Knoxville, TN

2002-04-09

327

Learning saliency by MRF and differential threshold.  

PubMed

Saliency detection has been an attractive topic in recent years. The reliable detection of saliency can help a lot of useful processing without prior knowledge about the scene, such as content-aware image compression, segmentation, etc. Although many efforts have been spent in this subject, the feature expression and model construction are far from perfect. The obtained saliency maps are therefore not satisfying enough. In order to overcome these challenges, this paper presents a new psychologic visual feature based on differential threshold and applies it in a supervised Markov-random-field framework. Experiments on two public data sets and an image retargeting application demonstrate the effectiveness, robustness, and practicability of the proposed method. PMID:23757590

Zhu, Guokang; Wang, Qi; Yuan, Yuan; Yan, Pingkun

2013-12-01

328

Automated detection of colorectal lesions with dual-energy CT colonography  

NASA Astrophysics Data System (ADS)

Conventional single-energy computed tomography colonography (CTC) tends to miss polyps 6 - 9 mm in size and flat lesions. Dual-energy CTC (DE-CTC) provides more complete information about the chemical composition of tissue than does conventional CTC. We developed an automated computer-aided detection (CAD) scheme for detecting colorectal lesions in which dual-energy features were used to identify different bowel materials and their partial-volume artifacts. Based on these features, the dual-energy CAD (DE-CAD) scheme extracted the region of colon by use of a lumen-tracking method, detected lesions by use of volumetric shape features, and reduced false positives by use of a statistical classifier. For validation, 20 patients were prepared for DE-CTC by use of reduced bowel cleansing and orally administered fecal tagging with iodine and/or barium. The DE-CTC was performed in dual positions by use of a dual-energy CT scanner (SOMATOM Definition, Siemens) at 140 kVp and 80 kVp energy levels. The lesions identified by subsequent same-day colonoscopy were correlated with the DE-CTC data. The detection accuracies of the DE-CAD and conventional CAD schemes were compared by use of leave-one-patient-out evaluation and a bootstrap analysis. There were 25 colonoscopy-confirmed lesions: 22 were 6 - 9 mm and 3 were flat lesions >=10 mm in size. The DE-CAD scheme detected the large flat lesions and 95% of the 6 - 9 mm lesions with 9.9 false positives per patient. The improvement in detection accuracy by the DE-CAD was statistically significant.

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

2012-03-01

329

Detection of dark energy near the Local Group with the Hubble Space Telescope  

E-print Network

We report the detection of dark energy near the Milky Way made with precision observations of the local Hubble flow of expansion. We estimate the local density of dark energy and find that it is near, if not exactly equal to, the global dark energy density. The result is independent of, compatible with, and complementary to the horizon-scale observations in which dark energy was first discovered. Together with the cosmological concordance data, our result forms direct observational evidence for the Einstein antigravity as a universal phenomenon -- in the same sense as the Newtonian universal gravity.

Chernin, A D; Teerikorpi, P; Valtonen, M J; Byrd, G G; Efremov, Yu N; Dolgachev, V P; Domozhilova, L M; Makarov, D I; Baryshev, Yu V

2007-01-01

330

Detection of dark energy near the Local Group with the Hubble Space Telescope  

E-print Network

We report the detection of dark energy near the Milky Way made with precision observations of the local Hubble flow of expansion. We estimate the local density of dark energy and find that it is near, if not exactly equal to, the global dark energy density. The result is independent of, compatible with, and complementary to the horizon-scale observations in which dark energy was first discovered. Together with the cosmological concordance data, our result forms direct observational evidence for the Einstein antigravity as a universal phenomenon -- in the same sense as the Newtonian universal gravity.

A. D. Chernin; I. D. Karachentsev; P. Teerikorpi; M. J. Valtonen; G. G. Byrd; Yu. N. Efremov; V. P. Dolgachev; L. M. Domozhilova; D. I. Makarov; Yu. V. Baryshev

2007-06-27

331

Generalized constrained energy minimization approach to subpixel detection for multispectral imagery  

NASA Astrophysics Data System (ADS)

Subpixel detection for multispectral imagery presents a challenging problem due to relatively low spectral resolution. This paper proposes a Generalized Constrained Energy Minimization (GCEM) approach to detecting objects in multispectral imagery at subpixel level. GCEM is a combination of a dimensionality expansion (DE) approach resulting from a generalized orthogonal subspace projection (GOSP) developed for multispectral image classification and a CEM method developed for hyperspectral image classification. DE allows us to generate additional bands from original multispectral images while CEM is used for subpixel detection to extract objects embedded in multispectral images. CEM has been successfully applied to hyperspectral target detection and image classification. Its applicability to multispectral imagery has not been investigated. A potential limitation of CEM on multispectral imagery is the effectiveness of interference elimination due to the lack of sufficient dimensionality. DE is introduced to mitigate this problem. Experiments have shown that the proposed GCEM detects objects more effectively than CEM without dimensionality expansion and GOSP.

Liu, JihMing; Wang, ChunMu; Chieu, BinChang; Chang, Chein-I.; Ren, Hsuan; Yang, Ching-Wen

1999-12-01

332

Threshold of hierarchical percolating systems  

NASA Astrophysics Data System (ADS)

Many modern nanostructured materials and doped polymers are morphologically too complex to be interpreted by classical percolation theory. Here, we develop the concept of a hierarchical percolating (percolation-within-percolation) system to describe such complex materials and illustrate how to generalize the conventional percolation to double-level percolation. Based on Monte Carlo simulations, we find that the double-level percolation threshold is close to, but definitely larger than, the product of the local percolation thresholds for the two enclosed single-level systems. The deviation may offer alternative insights into physics concerning infinite clusters and open up new research directions for percolation theory.

Li, Jiantong; Ray, Biswajit; Alam, Muhammad A.; Östling, Mikael

2012-02-01

333

Calculations of atomic sputtering and displacement cross-sections in solid elements by electrons with energies from threshold to 1. 5 MV  

SciTech Connect

The kinetics of knock-on collisions of relativistic electrons with nuclei and details of the numerical evaluation of differential, recoil, and total Mott cross-sections are reviewed and discussed. The effects of electron beam induced displacement and sputtering, in the transmission electron microscope (TEM) environment, on microanalysis are analyzed with particular emphasis placed on the removal of material by knock-on sputtering. The mass loss predicted due to transmission knock-on sputtering is significant for many elements under conditions frequently encountered in microanalysis. Total Mott cross-sections are tabulated for all naturally occurring solid elements up to Z = 92 at displacement energies of one, two, four, and five times the sublimation energy and for accelerating voltages accessible in the transmission electron microscope. Fortran source code listings for the calculation of the differential Mott cross-section as a function of electron scattering angle (dMottCS), as a function of nuclear recoil angle (RECOIL), and the total Mott cross-section (TOTCS) are included. 48 refs., 21 figs., 12 tabs.

Bradley, C.R.

1988-12-01

334

Particle Detection in Superfluid Helium: R&D for Low Energy Solar Neutrinos  

SciTech Connect

This report presents a summary of the results from R&D conducted as a feasibility study in the Department of Physics of Brown University for detection of low energy solar neutrinos utilizing a superfluid helium target. The report outlines the results in several areas: 1) development of experimental facilities, 2) energy deposition by electrons and alphas in superfluid helium, 3) development of wafer and metallic magnetic calorimeters, 4) background studies, 5) coded apertures and conceptual design, 6) Detection of single electrons and 7) a simulation of expected performance of a full scale device. Recommendations for possible future work are also presented. A bibliography of published papers and unpublished doctoral theses is included.

Lanou, Robert E., Jr.

2006-03-31

335

X-ray reflectivity measurements of surface roughness using energy dispersive detection  

SciTech Connect

We describe a new technique for measuring x-ray reflectivity using energy dispersive x-ray detection. The benefits of this method are the use of a fixed scattering angle and parallel detection of all energies simultaneously. These advantages make the technique more readily useable with laboratory x-ray sources and more compatible with growth chambers. We find excellent agreement between the calculated Fresnel reflectivity and the reflectivity obtained from a smooth Ge (001) surface. Reflectivities obtained during 500 eV Xe ion bombardment of Ge surfaces demonstrate the sensitivity of the technique to be better than 1 {angstrom}. 9 refs., 4 figs.

Chason, E.; Warwick, D.T.

1990-01-01

336

High-Damage-Threshold Pinhole for Glass Fusion Laser Applications  

SciTech Connect

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

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

1998-06-07

337

Quark mass thresholds in QCD thermodynamics  

E-print Network

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

M. Laine; Y. Schroder

2006-03-06

338

Gray Level Thresholding in Badly Illuminated Images  

Microsoft Academic Search

The thresholding method involves first locating objects in an image by using the intensity gradient, then noting the levels that correspond to the objects in various areas of the image, and finally using these levels as initial guesses at a threshold. This method is capable of thresholding images that have been produced in the context of variable illumination. The thresholding

J. R. Parker

1991-01-01

339

Computational study of plutonium-neodymium fluorobritholite Ca 9Nd 0.5Pu 0.5(SiO 4)(PO 4) 5F 2 thermodynamic properties and threshold displacement energies  

NASA Astrophysics Data System (ADS)

A force field for the modelling of neodymium fluorobritholites, having the general composition Ca 10- yNd y(SiO 4) y(PO 4) 6- yF 2, is derived. The validity of the established analytical potentials is tested by calculating the crystallographic parameters of the compositions for 0? y?6 and comparing to the experimental values. The validity is further tested by calculating the variation of the phonon spectra when transitioning from the fluoroapatite Ca 10(PO 4) 6F 2 to the full silicate neodymium fluorobritholite Ca 4Nd 6(SiO 4) 6F 2. Trivalent plutonium ions are introduced into the mono-silicate neodymium fluorobritholite using transferable potentials in order to obtain the composition Ca 9Pu 0.5Nd 0.5(SiO 4)(PO 4) 5F 2, which corresponds to a Pu concentration of about 10 wt%. The thermodynamic properties of the resulting structure are calculated, and the threshold displacement energies of various sublattices are estimated by applying the sudden approximation (SA) method. The activation energies for Frenkel defect annealing are also calculated using the rational function optimisation (RFO) procedure for the saddle point research.

Meis, C.

2001-02-01

340

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

DOEpatents

Cyanine dyes are used as the donor fluorophore in energy transfer labels in which light energy is absorbed by a donor fluorophore and transferred to an acceptor fluorophore which responds to the transfer by emitting fluorescent light for detection. The cyanine dyes impart an unusually high sensitivity to the labels thereby improving their usefulness in a wide variety of biochemical procedures, particularly nucleic acid sequencing, nucleic acid fragment sizing, and related procedures.

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

2000-01-01

341

Crossing Thresholds in Academic Reading  

ERIC Educational Resources Information Center

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

Abbott, Rob

2013-01-01

342

MACHINE MONITORING USING PROBABILITY THRESHOLDS  

E-print Network

MACHINE MONITORING USING PROBABILITY THRESHOLDS AND SYSTEM OPERATING CHARACTERISTICS Stephen M a discrete-part production machine, with the objective of effectively determining when to shut the machine analysis: a) There is an underlying time interval that characterizes the operation of the machine, most

Pollock, Stephen

343

Fractal Superconductivity near Localization Threshold  

E-print Network

Fractal Superconductivity near Localization Threshold Mikhail Feigel'man Landau Institute, Moscow-electron states are extended but fractal and populate small fraction of the whole volume How BCS theory should be modified to account for eigenstates fractality ? #12;Mean-Field Eq. for Tc #12;#12;3D Anderson model: = 0

Fominov, Yakov

344

Stochastic threshold for ion heating with beating electrostatic waves.  

PubMed

The stochastic threshold for the heating of ions in a magnetized plasma with two electrostatic waves is experimentally characterized. Two obliquely propagating electrostatic modes are launched in a magnetized plasma with frequencies that differ by the ion cyclotron frequency. The values of the wave amplitudes where a rapid increase in the local ion temperature occurs is then parametrically investigated. It is found that the two threshold wave amplitudes are linearly related and that this dependence translates to a lower required energy density for the onset of heating when compared to the case of a single electrostatic wave. Agreement also is demonstrated between the experimentally observed threshold for stochastic heating and an analytical prediction [B. Jorns and E.?Y. Choueiri, Phys. Rev. E 87, 013107 (2013)] for this threshold. PMID:25165933

Jorns, B; Choueiri, E Y

2013-06-14

345

Dynamical fusion thresholds in macroscopic and microscopic theories  

SciTech Connect

Macroscopic and microscopic results demonstrating the existence of dynamical fusion thresholds are presented. For macroscopic theories, it is shown that the extra-push dynamics is sensitive to some details of the models used, e.g. the shape parametrization and the type of viscosity. The dependence of the effect upon the charge and angular momentum of the system is also studied. Calculated macroscopic results for mass-symmetric systems are compared to experimental mass-asymmetric results by use of a tentative scaling procedure, which takes into account both the entrance-channel and the saddle-point regions of configuration space. Two types of dynamical fusion thresholds occur in TDHF studies: (1) the microscopic analogue of the macroscopic extra push threshold, and (2) the relatively high energy at which the TDHF angular momentum window opens. Both of these microscopic thresholds are found to be very sensitive to the choice of the effective two-body interaction.

Davies, K.T.R.; Sierk, A.J.; Nix, J.R.

1983-01-01

346

Handling of BLM abort thresholds in the LHC  

E-print Network

The Beam Loss Monitoring system (BLM) for the LHC consists of about 3600 Ionization Chambers (IC) located around the ring. Its main purpose is to request a beam abort when the measured losses exceed a certain threshold. The BLM detectors integrate the measured signals in 12 different time intervals (running from 40us to 83.8s) enabling for a different set of abort thresholds depending on the duration of the beam loss. Furthermore, 32 energy levels running from 450GeV to 7TeV account for the fact that the energy density of a particle shower increases with the energy of the primary particle, i.e. the beam energy. Thus, a set of ! 3600 × 12 × 32 = 1.3 · 106 thresholds must be handled. These thresholds are highly critical for the safety of the machine and depend to a large part on human judgment, which cannot be replaced by automatic test procedures. The BLM team has defined well established procedures to compute, set and check new BLM thresholds, in order to avoid and/or find non-conformities due to manipulat...

Nebot Del Busto, E; Holzer, EB; Zamantzas, C; Kruk, G; Nordt, A; Sapinski, M; Nemcic, M; Orecka, A; Jackson, S; Roderick, C; Skaugen, A

2011-01-01

347

Using Audiometric Thresholds and Word Recognition in a Treatment Study  

Microsoft Academic Search

Objectives: First, to examine a possible limit on significant results imposed by a progressive floor effect for hearing threshold improvement in a treatment study. This floor effect for hearing recovery suggests that if inclusion criteria are not set sufficiently high, the superiority of a treatment group may not be detectable. Second, to examine the outcomes when using two different types

Chris Halpin; Steven D. Rauch

2006-01-01

348

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

E-print Network

ME 4343 HVAC Design Real-Time Building Energy Modeling and Fault Detection and Diagnostics for a DoD Building Bing Dong1, Zheng O’Neill2 1 University of Texas, San Antonio, TX, USA 2 University of Alabama, AL, USA The work was done at the United...

Dong, B.

2013-01-01

349

New method to detect rotation in high-energy heavy-ion collisions  

NASA Astrophysics Data System (ADS)

With increasing beam energies the angular momentum of the fireball in peripheral heavy-ion collisions increases, and the proposed differential Hanbury Brown and Twiss analysis is able to estimate this angular momentum quantitatively. The method detects specific space-time correlation patterns, which are connected to rotation.

Csernai, L. P.; Velle, S.; Wang, D. J.

2014-03-01

350

An eigenvalue approach to enhance energy detection in a mobile spectrum monitoring network  

Microsoft Academic Search

For fulfilling new tasks of the regulator, we propose a novel mobile spectrum monitoring network. The huge amount of measurement data contains besides thermal noise also noise induced by the Automatic Gain Control (AGC). As a result the occupancy results based on normal energy detection are significantly biased. In order to assess the spectrum occupancy more accurately, we employ an

Jan-Willem van Bloem; Anne J. Hendrikse; Roel Schiphorst; Cornelis H. Slump

2011-01-01

351

Closed-Form Approximations for Cooperative LLR-Based Energy Detection in Cognitive Radios  

Microsoft Academic Search

In this paper, we obtain approximations for the optimal Log-Likelihood Ratio (LLR) decision rule in cooperative detection when local energy detectors are assumed. Considering conditional independence, we also show under which bandwidth and sampling frequency regimes these approximations hold best. Furthermore, we present simulations where the performance of the approximated LLR decision rule is compared with other sub- optimal decision

Ibrahim Khalife; Baltasar Beferull-Lozano

2011-01-01

352

What is keeping my phone awake? Characterizing and Detecting No-Sleep Energy Bugs in  

E-print Network

What is keeping my phone awake? Characterizing and Detecting No-Sleep Energy Bugs in Smartphone by their battery life. Preserv- ing this critical resource has driven smartphone OSes to undergo a paradigm shift control APIs by apps or the framework and result in significant and unexpected battery drainage

Shihada, Basem

353

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

Microsoft Academic Search

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

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

2006-01-01

354

Local Reynolds number and thresholds of transition in shear flows  

NASA Astrophysics Data System (ADS)

Recent experimental and numerical investigations reveal that the onset of turbulence in plane-Poiseuille flow and plane-Couette flow has some similar stages separated with different threshold Reynolds numbers. Based on these observations and the energy equation of a disturbed fluid element, a local Reynolds number Re L is derived to represent the maximum ratio of the energy supplement to the energy dissipation in a cross section. It is shown that along the sequence of transition stages, which include transient localized turbulence, "equilibrium" localized turbulence, spatially intermittent but temporally persistent turbulence and uniform turbulence, the corresponding thresholds of Re L for plane-Couette flow, Hagen-Poiseuille flow and plane-Poiseuille flow are consistent, indicating that the critical (threshold) states during the laminar-turbulent transition are determined by the local properties of the base flow and are independent of global features, such as flow geometries (pipe or channel) and types of driving forces (shear driving or pressure driving).

Tao, JianJun; Chen, ShiYi; Su, WeiDong

2013-02-01

355

Static noise margin variation for sub-threshold SRAM in 65-nm CMOS  

Microsoft Academic Search

The increased importance of lowering power in memory design has produced a trend of operating memories at lower supply voltages. Recent explorations into sub-threshold operation for logic show that minimum energy operation is possible in this region. These two trends suggest a meeting point for energy-constrained applications in which SRAM operates at sub-threshold voltages compatible with the logic. Since sub-threshold

Benton H. Calhoun; Anantha P. Chandrakasan

2006-01-01

356

Automatic Intensity-based 3D-to-2D Registration of CT Volume and Dual-energy Digital Radiography for the Detection of Cardiac Calcification  

PubMed Central

We are investigating three-dimensional (3D) to two-dimensional (2D) registration methods for computed tomography (CT) and dual-energy digital radiography (DR) for the detection of coronary artery calcification. CT is an established tool for the diagnosis of coronary artery diseases (CADs). Dual-energy digital radiography could be a cost-effective alternative for screening coronary artery calcification. In order to utilize CT as the “gold standard” to evaluate the ability of DR images for the detection and localization of calcium, we developed an automatic intensity-based 3D-to-2D registration method for 3D CT volumes and 2D DR images. To generate digital rendering radiographs (DRR) from the CT volumes, we developed three projection methods, i.e. Gaussian-weighted projection, threshold-based projection, and average-based projection. We tested normalized cross correlation (NCC) and normalized mutual information (NMI) as similarity measurement. We used the Downhill Simplex method as the search strategy. Simulated projection images from CT were fused with the corresponding DR images to evaluate the localization of cardiac calcification. The registration method was evaluated by digital phantoms, physical phantoms, and clinical data sets. The results from the digital phantoms show that the success rate is 100% with mean errors of less 0.8 mm and 0.2 degree for both NCC and NMI. The registration accuracy of the physical phantoms is 0.34 ± 0.27 mm. Color overlay and 3D visualization of the clinical data show that the two images are registered well. This is consistent with the improvement of the NMI values from 0.20 ± 0.03 to 0.25 ± 0.03 after registration. The automatic 3D-to-2D registration method is accurate and robust and may provide a useful tool to evaluate the dual-energy DR images for the detection of coronary artery calcification. PMID:24386527

Chen, Xiang; Gilkeson, Robert; Fei, Baowei

2013-01-01

357

Automatic intensity-based 3D-to-2D registration of CT volume and dual-energy digital radiography for the detection of cardiac calcification  

NASA Astrophysics Data System (ADS)

We are investigating three-dimensional (3D) to two-dimensional (2D) registration methods for computed tomography (CT) and dual-energy digital radiography (DR) for the detection of coronary artery calcification. CT is an established tool for the diagnosis of coronary artery diseases (CADs). Dual-energy digital radiography could be a cost-effective alternative for screening coronary artery calcification. In order to utilize CT as the "gold standard" to evaluate the ability of DR images for the detection and localization of calcium, we developed an automatic intensity-based 3D-to-2D registration method for 3D CT volumes and 2D DR images. To generate digital rendering radiographs (DRR) from the CT volumes, we developed three projection methods, i.e. Gaussian-weighted projection, threshold-based projection, and average-based projection. We tested normalized cross correlation (NCC) and normalized mutual information (NMI) as similarity measurement. We used the Downhill Simplex method as the search strategy. Simulated projection images from CT were fused with the corresponding DR images to evaluate the localization of cardiac calcification. The registration method was evaluated by digital phantoms, physical phantoms, and clinical data sets. The results from the digital phantoms show that the success rate is 100% with mean errors of less 0.8 mm and 0.2 degree for both NCC and NMI. The registration accuracy of the physical phantoms is 0.34 +/- 0.27 mm. Color overlay and 3D visualization of the clinical data show that the two images are registered well. This is consistent with the improvement of the NMI values from 0.20 +/- 0.03 to 0.25 +/- 0.03 after registration. The automatic 3D-to-2D registration method is accurate and robust and may provide a useful tool to evaluate the dual-energy DR images for the detection of coronary artery calcification.

Chen, Xiang; Gilkeson, Robert; Fei, Baowei

2007-03-01

358

Application of a multichannel detection system to the high-resolution fast electron energy loss spectrometer  

NASA Astrophysics Data System (ADS)

A microchannel-plate based resistive-anode position sensitive detection system is applied to a high-resolution fast electron energy loss spectrometer. The biasing voltage divider network for the detector is investigated. The measurement efficiency is increased by about 20 times, and to some extent, the energy resolution is also improved. The static mode and the scanning mode of the spectrometer are discussed in detail. In the scanning mode, a spectrum with higher energy resolution can be obtained through a coarse scanning. As a testing experiment, the optical oscillator strength spectrum for the Rydberg series of helium is measured and the results are compared.

Liu, Xiao-Jing; Zhu, Lin-Fan; Jiang, Xi-Man; Yuan, Zhen-Sheng; Cai, Bei; Chen, Xiang-Jun; Xu, Ke-Zun

2001-08-01

359

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

SciTech Connect

We show for the first time that the quenching of electronic excitation from nuclear recoils in liquid xenon is well-described by Lindhard theory, if the nuclear recoil energy is reconstructed using the combined (scintillation and ionization) energy scale proposed by Shutt et al.. We argue for the adoption of this perspective in favor of the existing preference for reconstructing nuclear recoil energy solely from primary scintillation. We show that signal partitioning into scintillation and ionization is well-described by the Thomas-Imel box model. We discuss the implications for liquid xenon detectors aimed at the direct detection of dark matter.

Sorensen, P; Dahl, C E

2011-02-14

360

Remote sensing of threshold conditions in an arid ecosystem  

NASA Astrophysics Data System (ADS)

Land management in the arid southwestern USA increasingly addresses thresholds in response to recent concepts adopted by private and public lands agencies and conservation organizations. Vegetation in arid rangelands typically presents as distinctive mosaics of vegetation patches, which persist in dynamic equilibrium with the abiotic environment and facilitative-competitive interactions between organisms. Theory and observation suggest that as an area approaches a threshold in response to disturbance, there is a concomitant change in the spatial arrangement of vegetation patches. This change is readily identifiable on fine spatial resolution aerial photography or satellite sensor imagery. We propose a classification method for identifying threshold-inducing change in vegetation pattern. To illustrate this method, we have applied an object-oriented, supervised classification to subsets of Quickbird imagery (70 cm ground resolution) over the Jornada basin in southern New Mexico. The imagery covers several land management regimes (private, public, federal) and provides spatial variation in ecosystem conditions. Imagery was first segmented to create fine and coarse resolution image objects. Fine resolution image objects are defined as having within-object spectral homogeneity at the scale of the shrub or single patch of grass or soil. Coarse resolution image objects are defined as containing spectral homogeneity at the scale of the vegetation stand. A classification tree was used to classify coarse resolution image objects to high risk of a threshold, low risk of a threshold, or post-threshold according to the content and spatial arrangement of shrub, grass and soil patches within them. Ground-based monitoring to detect localized threshold conditions across broad management areas is intractable so the use of remote sensing is essential to successful prevention of threshold development.

Steele, C. M.; Bestelmeyer, B. T.; Rango, A.; Smith, P. L.; Laliberte, A. S.

2007-12-01

361

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

PubMed

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

Wu, Gui-Fang; He, Yong

2009-12-01

362

Using a CCD for the direct detection of electrons in a low energy space plasma spectrometer  

NASA Astrophysics Data System (ADS)

An E2V CCD64 back-illuminated, ion-implanted CCD (charge-coupled device) has been used as a direct electron imaging detector with CATS (Conceptual And Tiny Spectrometer), a highly miniaturised prototype plasma analyser head. This is in place of an MCP (microchannel plate) with a position sensing anode which would more conventionally be used as a detector in traditional low energy space plasma analyser instruments. The small size of CATS however makes it well matched to the size of the CCD, and the ion implants reduce the depth of the CCD backside electron potential well making it more sensitive to lower energy electrons than standard untreated silicon. Despite ionisation damage from prolonged exposure to excessively energetic electrons, the CCD has been able to detect electrons with energies above 500eV, at temperatures around room temperature. Using both a long integration 'current measuring' mode and a short integration `electron counting' mode it has been used to image the low energy electrons exiting the analyser, enhancing our understanding of the CATS electrostatic optics. The CCD has been selected as the detector for use with CATS for an instrument on a low-altitude student sounding rocket flight. Although it cannot detect the lowest energy electrons that an MCP can detect, and it is more sensitive to stray light, the low voltages required, the lack of vacuum requirements and its novelty and availability made it the most attractive candidate detector.

Bedington, R.; Kataria, D.; Walton, D.

2012-01-01

363

Dark energy with non-adiabatic sound speed: initial conditions and detectability  

SciTech Connect

Assuming that the universe contains a dark energy fluid with a constant linear equation of state and a constant sound speed, we study the prospects of detecting dark energy perturbations using CMB data from Planck, cross-correlated with galaxy distribution maps from a survey like LSST. We update previous estimates by carrying a full exploration of the mock data likelihood for key fiducial models. We find that it will only be possible to exclude values of the sound speed very close to zero, while Planck data alone is not powerful enough for achieving any detection, even with lensing extraction. We also discuss the issue of initial conditions for dark energy perturbations in the radiation and matter epochs, generalizing the usual adiabatic conditions to include the sound speed effect. However, for most purposes, the existence of attractor solutions renders the perturbation evolution nearly independent of these initial conditions.

Ballesteros, Guillermo [Museo Storico della Fisica e Centro Studi e Ricerche ''Enrico Fermi'', Piazza del Viminale 1, I-00184, Rome (Italy); Lesgourgues, Julien, E-mail: ballesteros@pd.infn.it, E-mail: julien.lesgourgues@cern.ch [CERN, Theory Division, CH-1211 Geneva 23 (Switzerland)

2010-10-01

364

Studies of Ar and N2 using threshold photoelectron spectroscopy by electron attachment /TPSA/  

NASA Technical Reports Server (NTRS)

Threshold photoelectron spectra of Ar and N2 are studied by a technique called threshold photoelectron spectroscopy by electron attachment, which involves the attachment of the threshold electron to SF6 followed by the detection of SF6(-). Studies on Ar provide a measure of the rejection ratio for nonthreshold electrons of this technique. A rotational propensity rule is given which states that an autoionizing N2 state prefers to decay to N2(+) states with a minimum change in rotational angular momentum.

Chutjian, A.; Ajello, J. M.

1977-01-01

365

Superlinear threshold detectors in quantum cryptography  

SciTech Connect

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

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

2011-09-15

366

Neural networks with dynamical thresholds  

NASA Astrophysics Data System (ADS)

We incorporate local threshold functions into the dynamics of the Hopfield model. These functions depend on the history of the individual spin (= neuron). They reach a maximal height if the spin remains constant. The resulting one-pattern model has ferromagnetic, paramagnetic, and periodic phases. This model is solved by a master equation and approximated by simplified systems of equations that are substantiated by numerical simulations. When several patterns are included as memories in the model, it exhibits transitions-as well as oscillations-between them. The latter can be excluded by known methods. By introducing threshold functions which affect only spins which remain positive, thus mimicking fatigue of the individual neurons, one can obtain open-ended movement in pattern space. Using couplings which form pointers from one pattern to another, our system leads to self-driven temporal sequences of patterns, resembling the process of associative thinking.

Horn, D.; Usher, M.

1989-07-01

367

Scaling behavior of threshold epidemics  

NASA Astrophysics Data System (ADS)

We study the classic Susceptible-Infected-Recovered (SIR) model for the spread of an infectious disease. In this stochastic process, there are two competing mechanism: infection and recovery. Susceptible individuals may contract the disease from infected individuals, while infected ones recover from the disease at a constant rate and are never infected again. Our focus is the behavior at the epidemic threshold where the rates of the infection and recovery processes balance. In the infinite population limit, we establish analytically scaling rules for the time-dependent distribution functions that characterize the sizes of the infected and the recovered sub-populations. Using heuristic arguments, we also obtain scaling laws for the size and duration of the epidemic outbreaks as a function of the total population. We perform numerical simulations to verify the scaling predictions and discuss the consequences of these scaling laws for near-threshold epidemic outbreaks.

Ben-Naim, E.; Krapivsky, P. L.

2012-05-01

368

On the Pebbling Threshold Spectrum  

Microsoft Academic Search

A configuration of pebbles on the vertices of a graph is solvable if one can\\u000aplace a pebble on any given root vertex via a sequence of pebbling steps. A\\u000afunction is a pebbling threshold for a sequence of graphs if a randomly chosen\\u000aconfiguration of asymptotically more pebbles is almost surely solvable, while\\u000aone of asymptotically fewer pebbles is

Glenn Hurlbert

2001-01-01

369

Minimal transition thresholds in plane Couette flow  

NASA Astrophysics Data System (ADS)

Subcritical transition to turbulence requires finite-amplitude perturbations. Using a nonlinear optimisation technique in a periodic computational domain, we identify the perturbations of plane Couette flow transitioning with least initial kinetic energy for Re ? 3000. We suggest a new scaling law Ec = O(Re-2.7) for the energy threshold vs. the Reynolds number, in quantitative agreement with experimental estimates for pipe flow. The route to turbulence associated with such spatially localised perturbations is analysed in detail for Re = 1500. Several known mechanisms are found to occur one after the other: Orr mechanism, oblique wave interaction, lift-up, streak bending, streak breakdown, and spanwise spreading. The phenomenon of streak breakdown is analysed in terms of leading finite-time Lyapunov exponents of the associated edge trajectory.

Duguet, Yohann; Monokrousos, Antonios; Brandt, Luca; Henningson, Dan S.

2013-08-01

370

Generalized constrained energy minimization approach to subpixel target detection for multispectral imagery  

NASA Astrophysics Data System (ADS)

Subpixel detection in multispectral imagery presents a challenging problem due to relatively low spatial and spectral resolution. We present a generalized constrained energy minimization (GCEM) approach to detecting targets in multispectral imagery at subpixel level. GCEM is a hybrid technique that combines a constrained energy minimization (CEM) method developed for hyperspectral image classification with a dimensionality expansion (DE) approach resulting from a generalized orthogonal subspace projection (GOSP) developed for multispectral image classification. DE enables us to generate additional bands from original multispectral images nonlinearly so that CEM can be used for subpixel detection to extract targets embedded in multispectral images. CEM has been successfully applied to hyperspectral target detection and image classification. Its applicability to multispectral imagery is yet to be investigated. A potential imitation of CEM on multispectral imagery is the effectiveness of interference elimination due to the lack of sufficient dimensionality. DE is introduced to mitigate this problem by expanding the original data dimensionality. Experiments show that the proposed GCEM detects targets more effectively than GOSP and CEM without dimensionality expansion.

Chang, Chein-I.; Liu, JihMing; Chieu, BinChang; Ren, Hsuan; Wang, ChuinMu; Lo, ChienShun; Chung, Pau-Choo; Yang, Ching-Wen; Ma, DyeJyun

2000-05-01

371

Threshold shifts in strong radiation fields: The connection between dc and ac effects  

Microsoft Academic Search

We have studied near-threshold single-photon detachment of a model negative ion, in the presence of a second, intense radiation field. We find a simple, continuous connection between detachment in strong static fields (dc limit) and the increased energy needed to detach an electron into an intense optical field (ac limit). Below this shifted threshold energy, net detachment is suppressed because

L. A. Bloomfield

1989-01-01

372

Probabilistic models for plasma transport in the presence of critical thresholds  

E-print Network

TnTnrVTnTnrr qrq += ),,(),,()( Energy Pinch Thermal conductivity More sophisticated expressions also used, but all intrinsically LOCAL Particle Transport Energy Transport #12;Critical thresholds.Contr. Fusion 46 (2004) 1351] Gyro-Bohm scaling Slow channel Fast channel Critical threshold condition Finds

Martín-Solís, José Ramón

373

Approach to nonparametric cooperative multiband segmentation with adaptive threshold.  

PubMed

We present a new nonparametric cooperative approach to multiband image segmentation. It is based on cooperation between region-growing segmentation and edge segmentation. This approach requires no input data other than the images to be processed. It uses a spectral homogeneity criterion whose threshold is determined automatically. The threshold is adaptive and varies depending on the objects to be segmented. Applying this new approach to very high resolution satellite imagery has yielded satisfactory results. The approach demonstrated its performance on images of varied complexity and was able to detect objects of great spatial and spectral heterogeneity. PMID:19593349

Sebari, Imane; He, Dong-Chen

2009-07-10

374

ELENA MCP detector: absolute detection efficiency for low-energy neutral atoms  

NASA Astrophysics Data System (ADS)

Microchannel Plates (MCP) detectors are frequently used in space instrumentation for detecting a wide range of radiation and particles. In particular, the capability to detect non-thermal low energy neutral species is crucial for the sensor ELENA (Emitted Low-Energy Neutral Atoms), part of the package SERENA (Search for Exospheric Refilling and Emitted Natural Abundances) on board the BepiColombo mission of ESA to Mercury to be launched in 2015. ELENA is a Time of Flight (TOF) sensor, based on a novel concept using an ultra-sonic oscillating shutter (Start section), which is operated at frequencies up to 50 kHz; a MCP detector is used as a Stop detector. The scientific objective of ELENA is to detect energetic neutral atoms in the range 10 eV - 5 keV, within 76° FOV, perpendicular to the S/C orbital plane. ELENA will monitor the emission of neutral atoms from the whole surface of Mercury thanks to the spacecraft motion. The major scientific objectives are the interaction between the plasma environment and the planet’s surface, the global particle loss-rate and the remote sensing of the surface properties. In particular, surface release processes are investigated by identifying particles released from the surface, via solar wind-induced ion sputtering (< 1eV - < 100 eV) as well as Hydrogen back-scattered at hundreds eV. MCP absolute detection efficiency for very low energy neutral atoms (E < 30 eV) is a crucial point for this investigation. At the MEFISTO facility of the Physical Institute of the University of Bern (CH), measurements on three different types of MCP (with and without coating) have been performed providing the detection efficiencies in the energy range 10eV - 1keV. Outcomes from such measurements are discussed here.

Rispoli, R.; De Angelis, E.; Colasanti, L.; Vertolli, N.; Orsini, S.; Scheer, J. A.; Mura, A.; Milillo, A.; Wurz, P.; Selci, S.; Di Lellis, A. M.; Leoni, R.; D'Alessandro, M.; Mattioli, F.; Cibella, S.

2012-09-01

375

Aerospect operations criteria for Mercury thresholds  

NASA Technical Reports Server (NTRS)

The hazards anticipated from a large scale mercury spill during a possible failure in the preflight and early flight stages of the Space Shuttle were studied. Toxicity thresholds were investigated as well as other consequences of mercury interacting with the environment. Three sites of mercury spill were investigated: land, water, and atmosphere. A laboratory study of interactions between mercury vapor and ozone in a low pressure, high ultraviolet radiation environment approximated the conditions of a mercury vapor release in the ozone layer region of the stratosphere. Clear evidence of an interaction leading to the destruction of ozone by conversion to oxygen was obtained. The impact of a spill on the Earth's environment and methods of early detection of a developing hazard wave of primary concern in the study.

Katz, S.

1979-01-01

376

30TH INTERNATIONAL COSMIC RAY CONFERENCE A Search for Prompt Very High Energy Emission from Satellite-detected Gamma-  

E-print Network

30TH INTERNATIONAL COSMIC RAY CONFERENCE A Search for Prompt Very High Energy Emission from Satellite-detected Gamma- ray Bursts using Milagro P. M. SAZ PARKINSON & B. L. DINGUS ¡ FOR THE MILAGRO@scipp.ucsc.edu; dingus@lanl.gov Abstract: Gamma-ray bursts (GRBs) have been detected up to GeV energies and are predicted

California at Santa Cruz, University of

377

Ultrasensitive detection of cellular protein interactions using bioluminescence resonance energy transfer quantum dot-based nanoprobes.  

PubMed

Sensitive detection of protein interactions is a critical step toward understanding complex cellular processes. As an alternative to fluorescence-based detection, Renilla reniformis luciferase conjugated to quantum dots results in self-illuminating bioluminescence resonance energy transfer quantum dot (BRET-Qdot) nanoprobes that emit red to near-infrared bioluminescence light. Here, we report the development of an ultrasensitive technology based on BRET-Qdot conjugates modified with streptavidin ([BRET-Qdot]-SA) to detect cell-surface protein interactions. Transfected COS7 cells expressing human cell-surface proteins were interrogated with a human Fc tagged protein of interest. Specific protein interactions were detected using a biotinylated anti-human Fc region specific antibody followed by incubation with [BRET-Qdot]-SA. The luciferase substrate coelenterazine activated bioluminescence light emission was detected with an ultra-fast and -sensitive imager. Protein interactions barely detectable by the fluorescence-based approach were readily quantified using this technology. The results demonstrate the successful application and the flexibility of the BRET-Qdot-based imaging technology to the ultrasensitive investigation of cell-surface proteins and protein-protein interactions. PMID:22573556

Quiñones, Gabriel A; Miller, Steven C; Bhattacharyya, Sukanta; Sobek, Daniel; Stephan, Jean-Philippe

2012-07-01

378

Kinematics of ? two-body decay near ? threshold at BESIII  

NASA Astrophysics Data System (ADS)

The kinematic properties of two-body decay near ? threshold are studied according to the special capacity of the BEPC II accelerator and the BESIII detector. Explicitly presented are the transformations of energy and momentum of hadronic particles between different reference frames, and the corresponding distributions. A brand new method is proposed to obtain the energy spread of the accelerator by fitting the energy distribution of hadron from ? semi-leptonic decays.

Mo, Xiao-Hu

2010-11-01

379

Discrete peaks in above-threshold double-ionization spectra  

NASA Astrophysics Data System (ADS)

Quantum-mechanical calculations of multiphoton double ionization by intense laser pulses show that the total-kinetic-energy spectrum of the photoelectrons consists of peaks separated by the photon energy, analogous to ordinary above-threshold ionization. Related structures appear in the two-electron and in the recoil-ion momentum distribution. We propose a method to extract the total-kinetic-energy spectrum from the experimental recoil-ion spectrum.

Lein, M.; Gross, E. K.; Engel, V.

2001-08-01

380

The investigation of fast neutron Threshold Activation Detectors (TAD)  

NASA Astrophysics Data System (ADS)

The detection of fast neutrons is usually done by liquid hydrogenous organic scintillators, where the separation between the ever present gamma rays and neutrons is achieved by the pulse shape discrimination (PSD). In many practical situation the detection of fast neutrons has to be carried out while the intense source (be it neutrons, gamma rays or x-rays) that creates these neutrons, for example by the fission process, is present. This source, or ``flash'', usually blinds the neutron detectors and temporarily incapacitates them. By the time the detectors recover the prompt neutron signature does not exist. Thus to overcome the blinding background, one needs to search for processes whereby the desired signature, such as fission neutrons could in some way be measured long after the fission occurred and when the neutron detector is fully recovered from the overload. A new approach was proposed and demonstrated a good sensitivity for the detection of fast neutrons in adverse overload situations where normally it could not be done. A temporal separation of the fission event from the prompt neutrons detection is achieved via the activation process. The main idea, called Threshold Activation Detection (or detector)-TAD, is to find 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 ?-rays) well after the source pulse has ended. The activation material should possess certain properties: a suitable half-life; an energy threshold below which the numerous source neutrons will not activate it (e.g. about 3 MeV); easily detectable activation products and has a usable cross section for the selected reaction. Ideally the substance would be part of the scintillator. There are several good candidates for TAD. The first one we have selected is based on fluorine. One of the major advantages of this element is the fact that it is a major constituent of available scintillators (e.g., BaF2, CaF2, hydrogen free liquid fluorocarbon). Thus the activation products of the fast prompt neutrons, in particular, the beta particles, can be measured with a very high efficiency in the detector. Other detectors and substances were investigated, such as 6Li and even common detectors such as NaI. The principles and experimental results obtained with F, NaI and 6Li based TAD are shown. The various contributing activation products are identified. The insensitivity of the fluorine based TAD to (d,D) neutrons is demonstrated. Ways and means to reduce or subtract the various neutron induced activations of NaI detector are elucidated along with its fast neutron detection capabilities. 6Li could also be a useful TAD.

Gozani, T.; King, M. J.; Stevenson, J.

2012-02-01

381

Effects of diazepam and triazolam on auditory and visual thresholds and reaction times in the baboon  

Microsoft Academic Search

Adult male baboons were trained on a psychophysical procedure that measured detection thresholds and reaction times for pure tone and white light stimuli. Intramuscular injections of diazepam or triazolam were given 30 min before session onset; stimulus intensity was randomly varied from trial to trial, and four to five estimates of sensory thresholds and reaction times were obtained throughout each

Scott E. Lukas; Robert D. Hienz; Joseph V. Brady

1985-01-01

382

Oxygenated-Blood Colour Change Thresholds for Perceived Facial Redness, Health, and Attractiveness  

Microsoft Academic Search

Blood oxygenation level is associated with cardiovascular fitness, and raising oxygenated blood colouration in human faces increases perceived health. The current study used a two-alternative forced choice (2AFC) psychophysics design to quantify the oxygenated blood colour (redness) change threshold required to affect perception of facial colour, health and attractiveness. Detection thresholds for colour judgments were lower than those for health

Daniel E. Re; Ross D. Whitehead; Dengke Xiao; David I. Perrett; Satoru Suzuki

2011-01-01

383

A comparison of different heart rate deflection methods to predict the anaerobic threshold  

Microsoft Academic Search

There is perhaps no greater controversy in exercise physiology than the validity, or lack thereof, of the heart rate breakpoint theory in general, and the Conconi test in particular, in assessing the anaerobic threshold. Three heart rate breakpoint methods have been proposed as methods of detecting the anaerobic threshold have appeared in the literature: (1) a breakpoint in linearity of

Daniel G. Carey; German J. Pliego; Robert L. Raymond

2008-01-01

384

Validation of adaptive threshold spike detector for neural recording.  

PubMed

We compare the performance of algorithms for automatic spike detection in neural recording applications. Each algorithm sets a threshold based on an estimate of the background noise level. The adaptive spike detection algorithm is suitable for implementation in analog VLSI; results from a proof-of-concept chip using neural data are presented. We also present simulation results of algorithm performance on neural data and compare it to other methods of threshold level adjustment based on the root-mean-square (rms) voltage measured over a finite window. We show that the adaptive spike detection algorithm measures the background noise level accurately despite the presence of large-amplitude action potentials and multi-unit hash. Simulation results enable us to optimize the algorithm parameters, leading to an improved spike detector circuit that is currently being developed. PMID:17271196

Watkins, Paul T; Santhanam, Gopal; Shenoy, Krishna V; Harrison, Reid R

2004-01-01

385

Reduced lasing threshold from organic dye microcavities  

E-print Network

We demonstrate an unexpected tenfold reduction in the lasing threshold of an organic vertical microcavity under subpicosecond optical excitation. In contrast to conventional theory of lasing, we find that the lasing threshold ...

Akselrod, G. M.

386

An alternative method for analyzing the double threshold detector  

NASA Astrophysics Data System (ADS)

An alternative method for analyzing the performance of a double threshold or M-out-of-N detector is discussed. Detection performance for the suggested method is based on the probability that a return crosses the threshold for the Mth time (a detection is declared) on the kth return or look. It is shown that this formulation has many advantages, as compared with the conventional method of analysis which employs the binomial probability distribution, since the upper limit N is not contained in the resulting probability expressions. It is shown that the probability of detection obtained by the alternate method is the same as that obtained if the detection method were analyzed as a Markov chain with M + 1 states. Use of the method results in simple expressions for the mean and variance of the number of looks before detection, provides an alternative way of estimating the probability of a threshold crossing, and leads to computationally simple bounds for the probability of false alarm.

Miller, J. M.

1985-07-01

387

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

PubMed

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

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

2014-08-01

388

Effect of polarization on photodetachment thresholds  

NASA Astrophysics Data System (ADS)

We have measured the near-threshold cross sections for the photodetachment of Li- into the e-(ks,d)-Li(2p1/2) , e-(ks,d)-Li(3p) , e-(kp)-Li(3s) , and e-(kp)-Li(4s) continuum channels and the photodetachment of K- into the e-(ks,d)-K(4p3/2) continuum channel. The data was analyzed using both a top-of-barrier model and a modified effective range theory. Both approaches explicitly take into account the significant polarization potential in the final continuum channels. The study involving both experiment and theory enabled us to investigate the effect of the polarization on near-threshold photodetachment. Furthermore, since photodetachment and electron scattering are related in the half-collision concept, we were able to determine low-energy electron scattering quantities such as phase shifts, elastic cross sections, and s wave scattering lengths for electron scattering on excited Li and K atoms. The results allowed us to predict a virtual state in the e-(ks)-Li(3p) system.

Sandström, J.; Haeffler, G.; Kiyan, I.; Berzinsh, U.; Hanstorp, D.; Pegg, D. J.; Hunnell, J. C.; Ward, S. J.

2004-11-01

389

Magnetized neutron stars as gamma-ray bursters - Detection rates at high energies  

NASA Technical Reports Server (NTRS)

Detailed calculations of the escape of high-energy gamma-rays from the dipolar magnetosphere of general relativistic neutron star models are used to model the detection rate of bursters at high photon energies between 0.3 and 10 MeV. This analysis shows the SMM detection rates to be compatible with a magnetized neutron star origin, with a distribution of magnetic field strengths extending at least up to about 4 x 10 to the 12th G, as expected if the (20-60) keV features reported from Konus and Ginga measurements are interpreted as cyclotron lines. Additional implications are discussed for the emission geometry and the neutron star radius.

Meszaros, P.; Bagoly, Z.; Riffert, H.

1989-01-01

390

Prospective constraints on Lorentz violation from ultrahigh-energy photon detection  

E-print Network

We point out that violation of Lorentz invariance affects the interaction of high-energy photons with the Earth's atmosphere and magnetic field. In certain parameter region this interaction becomes suppressed and the photons escape observation passing through the atmosphere without producing air showers. We argue that a detection of photon-induced air showers with energies above 10^19 eV, implying the absence of suppression as well as the absence of photon decay, will put tight double-sided limits on Lorentz violation in the sector of quantum electrodynamics. These constraints will be by several orders of magnitude stronger than the existing ones and will be robust against any assumptions about the astrophysical origin of the detected photons.

Grigory Rubtsov; Petr Satunin; Sergey Sibiryakov

2013-12-16

391

Comparasion of Energy Detection in Cognitive Radio over different fading channels  

NASA Astrophysics Data System (ADS)

With the advance of wireless communications, the problem of bandwidth scarcity has become more prominent. Cognitive radio technology has come out as a way to solve this problem by allowing the unlicensed users to use the licensed bands opportunistically. To sense the existence of licensed users, many spectrum sensing techniques have been devised. In this paper, energy detection and cyclic prefix is used for spectrum sensing.The comparison of ROC curves has been done for various wireless fading channels using squaring and cubingoperation,the improvement has gone as high as up to 0.6 times for AWGN channel and 0.4 times for Rayleigh channel as we go from squaring to cubing operation in an energy detector. Closed form expressions for Probability of detection for AWGN and Rayleigh channels are described.Nakagami fading channel shows worst results .

Buttar, Simar

2012-07-01

392

? -detected nuclear quadrupole resonance with a low-energy beam of 8Li+  

NASA Astrophysics Data System (ADS)

A nuclear quadrupole resonance (NQR) spectrum of Li8 has been observed in a single crystal of SrTiO3 using a beam of low-energy highly polarized radioactive Li+8 . The resonances were detected by monitoring the ? -decay anisotropy as a function of a small audio frequency magnetic field. These results demonstrate that low energy nuclear spin polarized Li8 can be used as a sensitive probe of the local magnetic and electronic environment in nanostructures and ultrathin films in zero static applied magnetic field.

Salman, Z.; Reynard, E. P.; Macfarlane, W. A.; Chow, K. H.; Chakhalian, J.; Kreitzman, S. R.; Daviel, S.; Levy, C. D. P.; Poutissou, R.; Kiefl, R. F.

2004-09-01

393

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

E-print Network

The Moon provides a huge effective detector volume for ultrahigh energy cosmic neutrinos, which generate coherent radio pulses in the lunar surface layer due to the Askaryan effect. In light of presently considered lunar missions, we propose radio measurements from a Moon-orbiting satellite. First systematic Monte Carlo simulations demonstrate the detectability of Askaryan pulses from neutrinos with energies above 10^{20} eV, i.e. near and above the interesting GZK limit, at the very low fluxes predicted in different scenarios.

O. Stål; J. E. S. Bergman; B. Thidé; L. K. S. Daldorff; G. Ingelman

2006-04-10

394

Gridless retarding potential analyzer for use in very-low-energy charged particle detection  

NASA Technical Reports Server (NTRS)

The theory of the hyperbolic retarding potential analyzer in the electrostatic mode is developed in detail and verified in the laboratory. A monoenergetic electron beam is used for the laboratory investigation. The analyzer (acronym HARP) has advantages over other conventional electrostatic analyzers; among them are less contact potential influence and high throughput because of the symmetry shape of the analyzer. The most useful application of the HARP is in detecting low-energy charged particles. A sample of low-energy particle data obtained in the earth's ionosphere is given.

Shyn, T. W.; Sharp, W. E.; Hays, P. B.

1976-01-01

395

40 CFR 98.91 - Reporting threshold.  

...for comparison to the 25,000 metric ton CO2 e per year emission threshold in...threshold applicability purposes (metric tons CO2 e). S = 100 percent of annual manufacturing...threshold applicability purposes (metric tons Co2 e). S = 100 percent of annual...

2014-07-01

396

Threshold conditions for uniform sediments revisited  

Microsoft Academic Search

The threshold of motion of uniform sediments has been commonly determined using the well-known Shields threshold diagram relating critical dimensionless Shields stress to grain Reynolds number. However, the growing body of experimental data demonstrate an order of magnitude scatter in the Shields diagram suggesting that the diagram in its original form is an inappropriate means of accurately evaluating the threshold

Gareth Pender

397

Probing light WIMPs with directional detection experiments  

E-print Network

The CoGeNT and CRESST WIMP direct detection experiments have recently observed excesses of nuclear recoil events, while the DAMA/LIBRA experiment has a long standing annual modulation signal. It has been suggested that these excesses may be due to light mass, m_chi ~ 5-10 GeV, WIMPs. The Earth's motion with respect to the Galactic rest frame leads to a directional dependence in the WIMP scattering rate, providing a powerful signal of the Galactic origin of any recoil excess. We investigate whether direct detection experiments with directional sensitivity have the potential to observe this anisotropic scattering rate with the elastically scattering light WIMPs proposed to explain the observed excesses. We find that the number of recoils required to detect an anisotropic signal from light WIMPs at 5 sigma significance varies from 7 to more than 190 over the set of target nuclei and energy thresholds expected for directional detectors. Smaller numbers arise from configurations where the detector is only sensitive to recoils from the highest speed, and hence most anisotropic, WIMPs. However, the event rate above threshold is very small in these cases, leading to the need for large experimental exposures to accumulate even a small number of events. To account for this sensitivity to the tail of the WIMP velocity distribution, whose shape is not well known, we consider two exemplar halo models spanning the range of possibilities. We also note that for an accurate calculation the Earth's orbital speed must be averaged over. We find that the exposures required to detect 10 GeV WIMPs at a WIMP-proton cross-section of 10^-4 pb are of order 10^3 kg day for a 20 keV energy threshold, within reach of planned directional detectors. Lower WIMP masses require higher exposures and/or lower energy thresholds for detection.

Ben Morgan; Anne M. Green

2012-08-24

398

Possibility of deriving the Hermean surface composition through low energy neutral atom detection  

NASA Astrophysics Data System (ADS)

The release processes induced by ion sputtering and/or micrometeoroids impacts induces erosion of the Mercury surface. The sputtered neutrals exhibit spectra peaked at low energies (few eV). Nevertheless, a high-energy neutral signal also emerges, due to these release processes. In principle, the directional neutral signal can be detected, providing information on the local surface composition. In this study, we simulate the neutral signal due to ion sputtering below the cusp regions, assuming a highly anisotropic surface composition. The NPA SERENA / ELENA instrument proposed on board the ESA mission BepiColombo is a nadir-pointing 1-D sensor, able to detect neutral atoms, form tens of eV to about 5 keV with a capability of resolving the major species. The ELENA field-of-view (FOV) is ~ 60 degrees, with the FOV plane perpendicular to the MPO orbital plane. Here, we speculate on the possibility of discriminating composition anisotropies by detecting the high-energy portion of the sputtered signal.

Milillo, A.; Orsini, S.; Massetti, S.; Mura, A.; de Angelis, E.; Lammer, H.; Wurz, P.; di Lellis, A. M.

2003-04-01

399

Extreme sensitivity and the practical implications of risk assessment thresholds.  

PubMed

Traditional risk-assessment theory assumes the existence of a threshold for non-cancer health effects. However, a recent trend in environmental regulation rejects this assumption in favor of non-threshold linearity for these endpoints. This trend is driven largely by two related concepts: (1) a theoretical assumption of wide-ranging human sensitivity, and (2) inability to detect thresholds in epidemiologic models. Wide-ranging sensitivity assumes a subpopulation with extreme background vulnerability, so that even trivial environmental exposures are hazardous to someone somewhere. We use examples from the real world of clinical medicine to show that this theoretical assumption is inconsistent with the biology of mammalian systems and the realities of patient care. Using examples from particulate-matter air-pollution research, we further show that failure to reject linearity is usually driven by statistical rather than biological considerations, and that nonlinear/threshold models often have a similar or better fit than their linear counterparts. This evidence suggests the existence of practical, real-world thresholds for most chemical exposures. PMID:23930098

Bukowski, John; Nicolich, Mark; Lewis, R Jeffrey

2013-01-01

400

The Top-Antitop Threshold at Muon Colliders  

E-print Network

Muon colliders are expected to naturally have a small spread in beam energy making them an ideal place to study the excitation curve. We present the parameter determinations that are possible from measuring the total cross section near threshold at a $\\mu ^+\\mu ^-$ collider.

M. S. Berger

1997-12-22

401

Adiabatic theory of Wannier threshold laws and ionization cross sections  

SciTech Connect

The Wannier threshold law for three-particle fragmentation is reviewed. By integrating the Schroedinger equation along a path where the reaction coordinate R is complex, anharmonic corrections to the simple power law are obtained. These corrections are found to be non-analytic in the energy E, in contrast to the expected analytic dependence upon E.

Macek, J.H.; Ovchinnikov, S.Yu.

1994-12-31

402

Energy-Efficient Data Reduction Techniques for Wireless Seizure Detection Systems  

PubMed Central

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

Chiang, Joyce; Ward, Rabab K.

2014-01-01

403

Contrast detection in luminance and chromatic noise.  

PubMed

We measured detection thresholds for a vertically oriented 1.2-cycle-per-degree sine-wave grating embedded in spatiotemporal broadband noise. Noise and signal were modulated in different directions in color space around an equal-energy white point. When signal and noise were modulated in the same direction, we observed a linear relationship between noise spectral density and signal energy at threshold. The slope of this function was the same whether the modulation was along a luminance axis or a red-green axis. If the signal was on one axis and the noise was on the other, no masking was observed. These results support the notion of two independent and equally efficient mechanisms tuned to these directions. We then measured threshold elevations for masks with both chromatic and luminance components. When signal and noise were modulated along the same line (for example, bright red and dark green), thresholds were elevated. When we inverted the phase of the chromatic component of the noise relative to the luminance component (bright green and dark red), the masking effect disappeared, even though the amount of noise in the putative luminance and chromatic mechanisms was exactly the same as before. This implies that detection performance is limited by mechanisms sensitive to both luminance and chromatic contrast signals. We characterized these mechanisms by their spectral tuning curves. PMID:1432339

Gegenfurtner, K R; Kiper, D C

1992-11-01

404

An adaptive threshold detector and channel parameter estimator for deep space optical communications  

NASA Technical Reports Server (NTRS)

This paper presents a method for optimal adaptive setting of ulse-position-modulation pulse detection thresholds, which minimizes the total probability of error for the dynamically fading optical fee space channel.

Arabshahi, P.; Mukai, R.; Yan, T. -Y.

2001-01-01

405

Threshold Assessment of Gear Diagnostic Tools on Flight and Test Rig Data  

NASA Technical Reports Server (NTRS)

A method for defining thresholds for vibration-based algorithms that provides the minimum number of false alarms while maintaining sensitivity to gear damage was developed. This analysis focused on two vibration based gear damage detection algorithms, FM4 and MSA. This method was developed using vibration data collected during surface fatigue tests performed in a spur gearbox rig. The thresholds were defined based on damage progression during tests with damage. The thresholds false alarm rates were then evaluated on spur gear tests without damage. Next, the same thresholds were applied to flight data from an OH-58 helicopter transmission. Results showed that thresholds defined in test rigs can be used to define thresholds in flight to correctly classify the transmission operation as normal.

Dempsey, Paula J.; Mosher, Marianne; Huff, Edward M.

2003-01-01

406

Predicting echo thresholds from speech onset characteristics  

PubMed Central

Echo threshold variability has previously been examined using stimuli that are carefully controlled and artificial (e.g., clicks and noise bursts), while studies using speech stimuli have only reported average thresholds. To begin to understand how echo thresholds might vary among speech sounds, four syllables were selected in pairs that contrasted abruptness vs gradualness of onset envelopes. Fusion and discrimination suppression thresholds, two echo thresholds commonly used to study the precedence effect, differed among syllables. Results were used to evaluate two predictive heuristics adapted from perceptual center (p-center) models. PMID:19354351

Miller, Scott D.; Litovsky, Ruth Y.; Kluender, Keith R.

2009-01-01

407

A new understanding of multiple-pulsed laser-induced retinal injury thresholds.  

PubMed

Laser safety standards committees have struggled for years to formulate adequately a sound method for treating repetitive-pulse laser exposures. Safety standards for lamps and LEDs have ignored this issue because averaged irradiance appeared to treat the issue adequately for large retinal image sizes and skin exposures. Several authors have recently questioned the current approach of three test conditions (i.e., limiting single-pulse exposure, average irradiance, and a single-pulse-reduction factor) as still insufficient to treat pulses of unequal energies or certain pulse groupings. Schulmeister et al. employed thermal modeling to show that a total-on-time pulse (TOTP) rule was conservative. Lund further developed the approach of probability summation proposed by Menendez et al. to explain pulse-additivity, whereby additivity is the result of an increasing probability of detecting injury with multiple pulse exposures. This latter argument relates the increase in detection probability to the slope of the probit curve for the threshold studies. Since the uncertainty in the threshold for producing an ophthalmoscopically detectable minimal visible lesion (MVL) is large for retinal exposure to a collimated laser beam, safety committees traditionally applied large risk reduction factors ("safety factors") of one order of magnitude when deriving intrabeam, "point-source" exposure limits. This reduction factor took into account the probability of visually detecting the low-contrast lesion among other factors. The reduction factor is smaller for large spot sizes where these difficulties are quite reduced. Thus the N??·²? reduction factor may result from the difficulties in detecting the lesion. Recent studies on repetitive pulse exposures in both animal and in vitro (retinal explant) models support this interpretation of the available data. PMID:24562071

Lund, David J; Sliney, David H

2014-04-01

408

Identification of threshold concepts for biochemistry.  

PubMed

Threshold concepts (TCs) are concepts that, when mastered, represent a transformed understanding of a discipline without which the learner cannot progress. We have undertaken a process involving more than 75 faculty members and 50 undergraduate students to identify a working list of TCs for biochemistry. The process of identifying TCs for biochemistry was modeled on extensive work related to TCs across a range of disciplines and included faculty workshops and student interviews. Using an iterative process, we prioritized five concepts on which to focus future development of instructional materials. Broadly defined, the concepts are steady state, biochemical pathway dynamics and regulation, the physical basis of interactions, thermodynamics of macromolecular structure formation, and free energy. The working list presented here is not intended to be exhaustive, but rather is meant to identify a subset of TCs for biochemistry for which instructional and assessment tools for undergraduate biochemistry will be developed. PMID:25185234

Loertscher, Jennifer; Green, David; Lewis, Jennifer E; Lin, Sara; Minderhout, Vicky

2014-01-01

409

Search for supersymmetric baryons near production threshold in terms of the superflavor symmetry  

E-print Network

The supersymmetry (SUSY) may be one of the most favorable extensions of the standard model (SM), however, so far at LHC no evidence of the SUSY particles were observed. An obvious question is whether they have already emerged, but escaped from our detection, or do not exist at all. We propose that the future ILC may provide sufficient energy to produce SUSY particles if they are not too heavy in the low background environment. The superflavor symmetry associates baryons with mesons as long as both of them containing a heavy constituent and a light one. In this work, we estimate the production rate of SUSY baryons near their production threshold in terms of the $B\\bar B$ production data. Our analysis indicates that if the SUSY baryons with masses below $\\sqrt s/2$ ($\\sqrt s$ is the ILC energy) exist, they could be observed at future ILC.

Lian-Bao Jia; Xing-Dao Guo; Hong-Ying Jin; Xue-Qian Li; Ming-Gang Zhao

2014-01-25

410

Search for supersymmetric baryons near production threshold in terms of the superflavor symmetry  

E-print Network

The supersymmetry (SUSY) may be the most favorable extension of the standard model, however, so far at LHC no evidence of the SUSY particles were observed. An obvious question is whether they have already emerged, but escaped from our detection or do not exist at all. We propose that at future ILC which may provide sufficient energy to produce SUSY particles if they are not too heavy as suggested by many authors and low background environment. The superflavor symmetry associates baryons with mesons as long as both of them contain a heavy constituent and a light one. Thus in this work, we are able to calculate the production rate of SUSY baryons near their production threshold in terms of the $B\\bar B$ production data. Our analysis unambiguously indicates that the future ILC data would determine if the SUSY particles with a mass below $\\sqrt s/2$ ($\\sqrt s$ is the ILC energy) indeed exist.

Jia, Lian-Bao; Jin, Hong-Ying; Li, Xue-Qian

2014-01-01

411

Properties of threshold coupled bistable maps  

NASA Astrophysics Data System (ADS)

In this paper we have studied the spatiotemporal behaviour of threshold coupled bistable chaotic maps. We have shown the existence of various cycles of the single map with the variation of threshold value for fixed relaxation time. The effects of variation of relaxation time on the network of threshold coupled maps are presented for different threshold values. Excess propagation through open boundaries is calculated numerically. For a network of three threshold coupled maps, the propagation of excess through open boundaries is calculated analytically. The condition for the existence of the steady state profile of the excess is calculated. The effects of random coupling on spatiotemporal synchronization of the network of threshold coupled maps are investigated. The key observation is that threshold coupling provides an annihilation method of the coexisting chaotic attractors of the local map and stabilizes it to some fixed point or periodic attractor.

Nag, Mayurakshi; Poria, Swarup

2014-09-01

412

Photoproduction of the omega meson off the proton near threshold  

E-print Network

An experimental study of omega photoproduction off the proton has been conducted by using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. The gp-->omega p differential cross sections are measured from threshold to the incident-photon energy Eg=1.4 GeV with ~15 MeV binning and full production-angle coverage. The quality of the present data near threshold gives access to a variety of interesting physics, including an estimation of the omegaN scattering length alpha_{omega p}.

I. I. Strakovsky; S. Prakhov; Ya. I. Azimov; P. Aguar-Bartolome; J. R. M. Annand; H. J. Arends; K. Bantawa; R. Beck; V. Bekrenev; H. Berghaeuser; A. Braghieri; W. J. Briscoe; J. Brudvik; S. Cherepnya; R. F. B. Codling; C. Collicott; S. Costanza; B. T. Demissie; E. J. Downie; P. Drexler; L. V. Fil'kov; D. I. Glazier; R. Gregor; D. J. Hamilton; E. Heid; D. Hornidge; I. Jaegle; O. Jahn; T. C. Jude; V. L. Kashevarov; I. Keshelashvili; R. Kondratiev; M. Korolija; M. Kotulla; A. Koulbardis; S. Kruglov; B. Krusche; V. Lisin; K. Livingston; I. J. D. MacGregor; Y. Maghrbi; D. M. Manley; Z. Marinides; J. C. McGeorge; E. F. McNicoll; D. Mekterovic; V. Metag; D. G. Middleton; A. Mushkarenkov; B. M. K. Nefkens; A. Nikolaev; R. Novotny; H. Ortega; M. Ostrick; P. B. Otte; B. Oussena; P. Pedroni; F. Pheron; A. Polonski; J. Robinson; G. Rosner; T. Rostomyan; S. Schumann; M. H. Sikora; A. Starostin; I. Supek; M. F. Taragin; C. M. Tarbert; M. Thiel; A. Thomas; M. Unverzagt; D. P. Watts; D. Werthmueller; F. Zehr

2014-07-13

413

Calculations of electric fields for radio detection of Ultra-High Energy particles  

E-print Network

The detection of electromagnetic pulses from high energy showers is used as a means to search for Ultra-High Energy cosmic ray and neutrino interactions. An approximate formula has been obtained to numerically evaluate the radio pulse emitted by a charged particle that instantaneously accelerates, moves at constant speed along a straight track and halts again instantaneously. The approximate solution is applied to the particle track after dividing it in smaller subintervals. The resulting algorithm (often referred to as the ZHS algorithm) is also the basis for most of the simulations of the electric field produced in high energy showers in dense media. In this work, the electromagnetic pulses as predicted with the ZHS algorithm are compared to those obtained with an exact solution of the electric field produced by a charged particle track. The precise conditions that must apply for the algorithm to be valid are discussed and its accuracy is addressed. This comparison is also made for electromagnetic showers i...

García-Fernández, Daniel; Carvalho, Washington R; Romero-Wolf, Andrés; Zas, Enrique

2013-01-01

414

Reaction {pi}N {yields} {pi}{pi}N near threshold  

SciTech Connect

The LAMPF E1179 experiment used the {pi}{sup 0} spectrometer and an array of charged particle range counters to detect and record {pi}{sup +}{pi}{sup 0}, {pi}{sup 0}p, and {pi}{sup +}{pi}{sup 0}p coincidences following the reaction {pi}{sup +}p {yields} {pi}{sup 0}{pi}{sup +}p near threshold. The total cross sections for single pion production were measured at the incident pion kinetic energies 190, 200, 220, 240, and 260 MeV. Absolute normalizations were fixed by measuring {pi}{sup +}p elastic scattering at 260 MeV. A detailed analysis of the {pi}{sup 0} detection efficiency was performed using cosmic ray calibrations and pion single charge exchange measurements with a 30 MeV {pi}{sup {minus}} beam. All published data on {pi}N {yields} {pi}{pi}N, including our results, are simultaneously fitted to yield a common chiral symmetry breaking parameter {xi} ={minus}0.25{plus_minus}0.10. The threshold matrix element {vert_bar}{alpha}{sub 0}({pi}{sup 0}{pi}{sup +}p){vert_bar} determined by linear extrapolation yields the value of the s-wave isospin-2 {pi}{pi} scattering length {alpha}{sub 0}{sup 2}({pi}{pi}) = {minus}0.041{plus_minus}0.003 m{sub {pi}}{sup {minus}1}, within the framework of soft-pion theory.

Frlez, E.

1993-11-01

415

Conceptual problems in detecting the evolution of dark energy when using distance measurements  

NASA Astrophysics Data System (ADS)

Context. Dark energy is now one of the most important and topical problems in cosmology. The first step to reveal its nature is to detect the evolution of dark energy or to prove beyond doubt that the cosmological constant is indeed constant. However, in the standard approach to cosmology, the Universe is described by the homogeneous and isotropic Friedmann models. Aims: We aim to show that in the perturbed universe (even if perturbations vanish if averaged over sufficiently large scales) the distance-redshift relation is not the same as in the unperturbed universe. This has a serious consequence when studying the nature of dark energy and, as shown here, can impair the analysis and studies of dark energy. Methods: The analysis is based on two methods: the linear lensing approximation and the non-linear Szekeres Swiss-Cheese model. The inhomogeneity scale is ~50 Mpc, and both models have the same density fluctuations along the line of sight. Results: The comparison between linear and non-linear methods shows that non-linear corrections are not negligible. When inhomogeneities are present the distance changes by several percent. To show how this change influences the measurements of dark energy, ten future observations with 2% uncertainties are generated. It is shown the using the standard methods (i.e. under the assumption of homogeneity) the systematics due to inhomogeneities can distort our analysis, and may lead to a conclusion that dark energy evolves when in fact it is constant (or vice versa). Conclusions: Therefore, if future observations are analysed only within the homogeneous framework then the impact of inhomogeneities (such as voids and superclusters) can be mistaken for evolving dark energy. Since the robust distinction between the evolution and non-evolution of dark energy is the first step to understanding the nature of dark energy a proper handling of inhomogeneities is essential.

Bolejko, K.

2011-01-01

416

Concept and Analysis of a Satellite for Space-Based Radio Detection of Ultra-High Energy Cosmic Rays  

NASA Astrophysics Data System (ADS)

We present a concept for on-orbit radio detection of ultra-high energy cosmic rays (UHECRs) that has the potential to provide collection rates of ~100 events per year for energies above 10^20 eV. The synoptic wideband orbiting radio detector (SWORD) mission's high event statistics at these energies combined with the pointing capabilities of a space-borne antenna array could enable charged particle astronomy. The detector concept is based on ANITA's successful detection UHECRs where the geosynchrotron radio signal produced by the extended air shower is reflected off the Earth's surface and detected in flight.

Romero-Wolf, Andrew; Gorham, P.; Booth, J.; Chen, P.; Duren, R. M.; Liewer, K.; Nam, J.; Saltzberg, D.; Schoorlemmer, H.; Wissel, S.; Zairfian, P.

2014-01-01

417

An implantation and ? detection system applied in ?-decay studies  

NASA Astrophysics Data System (ADS)

To study the ? decays of nuclei far from the ?-stability line, an implantation and ? detection system has been implemented at the Peking University. This detection system covers a wide energy range from keV to GeV while maintaining a good energy resolution and a low detection threshold. By correlating the implantation nuclei with their subsequent ?-decays within the same pixel or adjacent pixels of a double-sided silicon detector (DSSD), the ? decay properties of implanted nuclei can be measured with much less disturbance from other unstable nuclei and the random background.

He, Chao; Li, Xiangqing; Hua, Hui; Li, Zhihuan; Jiang, Dongxing; Ye, Yanlin; Zhang, Shuangquan; Han, Rui; Xu, Chuan; Wang, Enhong; Cheng, Yiyuan; Sun, Junjie; Niu, Chenyang; Tian, Zhengyang; Wang, Shuo; Wang, He; Song, Yushou; Liu, Huilan; Wang, Jiansong; Hu, Zhengguo; Yang, Yanyun; Xu, Hushan

2014-05-01

418

Quantifying Comparisons of Threshold Resummations  

E-print Network

We explore similarities and differences between widely-used threshold resummation formalisms, employing electroweak boson production as an instructive example. Resummations based on both full QCD and soft-collinear effective theory (SCET) share common underlying factorizations and resulting evolution equations. The formalisms differ primarily in their choices of boundary conditions for evolution, in moment space for many treatments based on full QCD, and in momentum space for treatments based on soft-collinear effective theory. At the level of factorized hadronic cross sections, these choices lead to quite different expressions. Nevertheless, we can identify a natural expansion for parton luminosity functions, in which SCET and full QCD resummations agree for the first term, and for which subsequent terms provide differences that are small in most cases. We also clarify the roles of the non-leading resummation constants in the two formalisms, and observe a relationship of the QCD resummation function $D(\\alpha_s)$ to the web expansion.

George Sterman; Mao Zeng

2013-12-19

419

Epidemic thresholds for bipartite networks  

NASA Astrophysics Data System (ADS)

It is well known that sexually transmitted diseases (STD) spread across a network of human sexual contacts. This network is most often bipartite, as most STD are transmitted between men and women. Even though network models in epidemiology have quite a long history now, there are few general results about bipartite networks. One of them is the simple dependence, predicted using the mean field approximation, between the epidemic threshold and the average and variance of the degree distribution of the network. Here we show that going beyond this approximation can lead to qualitatively different results that are supported by numerical simulations. One of the new features, that can be relevant for applications, is the existence of a critical value for the infectivity of each population, below which no epidemics can arise, regardless of the value of the infectivity of the other population.

Hernández, D. G.; Risau-Gusman, S.

2013-11-01

420

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

SciTech Connect

High-energy monoenergetic gamma rays (6.13 and 7.12 MeV) from the decay of excited states of the {sup 16}O* nucleus are highly penetrating and thus offer potential for non-intrusive inspection of loaded containers for narcotics, explosives, and other contraband items. These ex