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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

Energy variance criterion and threshold tuning scheme for high impedance fault detection  

Microsoft Academic Search

Summary form only given as follows. This paper presents a new approach to the detection of high impedance fault (HIF). The proposed approach (or detector which implements this approach) has four distinct features. First, the detector input signal is the three-phase unbalanced current (or feeder 3I0), rather than the conventional three individual phase-currents. Secondly, the detector is designed by monitoring

Keng-Yu Lien; Shi-Lin Chen; Ching-Jung Liao; Tzong-Yih Guo; Tsair-Ming Lin; Jer-Sheng Shen

1999-01-01

3

Detection and discrimination thresholds for auditory periodicity.  

PubMed

Complex periodic auditory signals, produced by the Guttman-Julesz procedure of repeating segments of random noise, were employed to address the low region of auditory periodicity. Periodicity detection and discrimination tasks were examined with a common experimental procedure and a common measure of thresholds. Typically, detection and discrimination performance suffer at extremely low periodicities, presumably because of the extremely close spacing of harmonics throughout the auditory spectrum. Interaural phase effects are extremely weak for these signals, being largely confined to threshold-detection tasks. Despite qualitative phenomenological differences for different periodicity regions, detection and discrimination functions show no sharp discontinuities over a wide range of periodicities. PMID:2304808

Pollack, I

1990-02-01

4

ESTIMATION OF DETECTION THRESHOLDS FOR REDIRECTED WALKING TECHNIQUES 1 Estimation of Detection Thresholds for  

E-print Network

ESTIMATION OF DETECTION THRESHOLDS FOR REDIRECTED WALKING TECHNIQUES 1 Estimation of Detection Thresholds for Redirected Walking Techniques Frank Steinicke, Member, IEEE, Gerd Bruder, Student Member, IEEE they believe they are walking straight. Index Terms--Virtual reality, virtual locomotion, redirected walking

Hinrichs, Klaus

5

Reconstructing the WIMP Velocity Distribution from Direct Dark Matter Detection Data with a Non-negligible Threshold Energy  

E-print Network

In this paper, we investigate the modification of our expressions developed for the model-independent data analysis procedure of the reconstruction of the (time-averaged) one-dimensional velocity distribution of Galactic Weakly Interacting Massive Particles (WIMPs) with a non-negligible experimental threshold energy. Our numerical simulations show that, for a minimal reconstructable velocity of as high as O(200) km/s, our model-independent modification of the estimator for the normalization constant could provide precise reconstructed velocity distribution points to match the true WIMP velocity distribution with a <~ 10% bias.

Shan, Chung-Lin

2015-01-01

6

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

7

Failure of direction discrimination at detection threshold for both fast  

E-print Network

Failure of direction discrimination at detection threshold for both fast and slow chromatic motion West, H 4-14, Montreal, Quebec, H3A 1A1 Canada Received April 20, 1998; accepted June 30, 1998; revised at detection threshold, whereas at higher temporal rates detection and direction discrimination threshold

Mullen, Kathy T.

8

Cryostat for Ultra-low-energy Threshold Germanium Spectrometers  

SciTech Connect

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

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

2013-04-01

9

Cryostat for Ultra-low-energy Threshold Germanium Spectrometers  

E-print Network

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

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

2012-10-08

10

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

11

Energy Switching Threshold for Climatic Benefits  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

12

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

13

Determinants and detection of anaerobic threshold and consequences of exercise above it.  

PubMed

During exercise, the level of oxygen consumption (VO2) above which aerobic energy production is supplemented by anaerobic mechanisms causing a sustained increase in lactate and metabolic acidosis is termed the anaerobic threshold. The VO2 at which the anaerobic threshold occurs is influenced by the factors that affect oxygen delivery to the tissues, being increased when oxygen flow is enhanced and decreased when oxygen flow is diminished. The anaerobic threshold is an important functional demarcation since the physiologic responses to exercise are different above the anaerobic threshold as compared with below the anaerobic threshold. Above the anaerobic threshold, in addition to the development of metabolic acidosis, exercise endurance is reduced, VO2 kinetics are slowed so that a steady state is delayed, and minute ventilation increases disproportionately to the metabolic requirement and a progressive tachypnea develops. The anaerobic threshold can be measured directly from lactate concentration with good threshold detection from a log-log transformation of lactate and VO2. This threshold defines the VO2 at which the lactate/pyruvate ratio increases. As bicarbonate changes reciprocally with lactate, its measurement can also be used to estimate the lactate threshold. But most conveniently, changes in gas exchange caused by the physical-chemical event of buffering of lactic acid by bicarbonate can be used to detect the anaerobic threshold during exercise. PMID:3315297

Wasserman, K

1987-12-01

14

IMAGE THRESHOLDING FOR LANDSLIDE DETECTION BY GENETIC PROGRAMMING  

E-print Network

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

Martin, Ralph R.

15

Mammographic calcification cluster detection and threshold gold thickness measurements  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

16

Scheme of Whole Detecting Cheaters in Threshold Secret Sharing  

Microsoft Academic Search

?Abstract?So far, methods of whole detecting cheaters in threshold secret sharing are few. If another participant canjoin in the tparticipants, t+1 participants in total, according to the scheme proposed in this paper, the existence of cheaters can be checked out only calculating equations once, requiring no other information. This scheme is a perfect sharing scheme. Its information rate is 1.

ZHANG Yi; CHEN Wen-xing

2009-01-01

17

Carbon monoxide exposure and human visual detection thresholds  

SciTech Connect

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

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

1989-01-01

18

Variable threshold method for ECG R-peak detection.  

PubMed

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

Kew, Hsein-Ping; Jeong, Do-Un

2011-10-01

19

Detection thresholds for 60 Hz electric fields by nonhuman primates  

SciTech Connect

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

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

1995-12-31

20

Effect of lateral perturbations on psychophysical acceleration detection thresholds  

PubMed Central

Background In understanding how the human body perceives and responds to small slip-like motions, information on how one senses the slip is essential. The effect of aging and plantar sensory loss on detection of a slip can also be studied. Using psychophysical procedures, acceleration detection thresholds of small lateral whole-body perturbations were measured for healthy young adults (HYA), healthy older adults (HOA) and older adults with diabetic neuropathy (DOA). It was hypothesized that young adults would require smaller accelerations than HOA's and DOA's to detect perturbations at a given displacement. Methods Acceleration detection thresholds to whole-body lateral perturbations of 1, 2, 4, 8, and 16 mm were measured for HYAs, HOAs, and DOAs using psychophysical procedures including a two-alternative forced choice protocol. Based on the subject's detection of the previous trial, the acceleration magnitude of the subsequent trial was increased or decreased according to the parameter estimation by sequential testing methodology. This stair-stepping procedure allowed acceleration thresholds to be measured for each displacement. Results Results indicate that for lateral displacements of 1 and 2 mm, HOAs and DOAs have significantly higher acceleration detection thresholds than young adults. At displacements of 8 and 16 mm, no differences in threshold were found among groups or between the two perturbation distances. The relationship between the acceleration threshold and perturbation displacement is of particular interest. Peak acceleration thresholds of approximately 10 mm/s2 were found at displacements of 2, 4, 8, and 16 mm for HYAs; at displacements of 4, 8, and 16 mm for HOAs; and at displacements of 8 and 16 mm for DOAs. Thus, 2, 4, and 8 mm appear to be critical breakpoints for HYAs, HOAs, and DOAs respectively, where the psychometric curve deviated from a negative power law relationship. These critical breakpoints likely indicate a change in the physiology of the system as it responds to the stimuli. Conclusion As a function of age, the displacement at which the group deviates from a negative power law relationship increases from 2 mm to 4 mm. Additionally, the displacement at which subjects with peripheral sensory deficits deviate from the negative power law relations increases to 8 mm. These increases as a function of age and peripheral sensory loss may help explain the mechanism of falls in the elderly and diabetic populations. PMID:16433916

Richerson, Samantha J; Morstatt, Scott M; O'Neal, Kristopher K; Patrick, Gloria; Robinson, Charles J

2006-01-01

21

Threshold power and energy confinement for ITER  

SciTech Connect

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

Takizuka, T.

1996-12-31

22

Orion MPCV Touchdown Detection Threshold Development and Testing  

NASA Technical Reports Server (NTRS)

A robust method of detecting Orion Multi-Purpose Crew Vehicle (MPCV) splashdown is necessary to ensure crew and hardware safety during descent and after touchdown. The proposed method uses a triple redundant system to inhibit Reaction Control System (RCS) thruster firings, detach parachute risers from the vehicle, and transition to the post-landing segment of the Flight Software (FSW). An in-depth trade study was completed to determine optimal characteristics of the touchdown detection method resulting in an algorithm monitoring filtered, lever-arm corrected, 200 Hz Inertial Measurement Unit (IMU) vehicle acceleration magnitude data against a tunable threshold using persistence counter logic. Following the design of the algorithm, high fidelity environment and vehicle simulations, coupled with the actual vehicle FSW, were used to tune the acceleration threshold and persistence counter value to result in adequate performance in detecting touchdown and sufficient safety margin against early detection while descending under parachutes. An analytical approach including Kriging and adaptive sampling allowed for a sufficient number of finite element analysis (FEA) impact simulations to be completed using minimal computation time. The combination of a persistence counter of 10 and an acceleration threshold of approximately 57.3 ft/s2 resulted in an impact performance factor of safety (FOS) of 1.0 and a safety FOS of approximately 2.6 for touchdown declaration. An RCS termination acceleration threshold of approximately 53.1 ft/s(exp)2 with a persistence counter of 10 resulted in an increased impact performance FOS of 1.2 at the expense of a lowered under-parachutes safety factor of 2.2. The resulting tuned algorithm was then tested on data from eight Capsule Parachute Assembly System (CPAS) flight tests, showing an experimental minimum safety FOS of 6.1. The formulated touchdown detection algorithm will be flown on the Orion MPCV FSW during the Exploration Flight Test 1 (EFT-1) mission in the second half of 2014.

Daum, Jared; Gay, Robert

2013-01-01

23

Threshold-related effects on the high energy plateau in above-threshold detachment  

NASA Astrophysics Data System (ADS)

We present results of a nonperturbative Floquet study of above-threshold detachment (ATD) of the H- and F- negative ions. Pronounced enhancements of ATD rates in the high-energy plateau region are found as the laser field intensity passes across ponderomotively shifted multiphoton thresholds. Depending on the symmetry of the initial state ( s or p symmetry), the enhancement is found to be most pronounced for even-or odd-channel closures, which is consistent with threshold laws applicable at the closing of particular multiphoton channels. Variations of ATD photoelectron angular distributions as functions of laser intensity near multiphoton thresholds are also investigated.

Krajewska, K.; Fabrikant, I. I.; Starace, A. F.

2007-04-01

24

Determination of Odor Detection Threshold in the Göttingen Minipig  

PubMed Central

The aim of the study was to examine the ability of Göttingen minipigs to acquire an olfaction-based operant conditioning task and to determine the detection threshold for ethyl acetate and ethanol. We used an automated olfactometer developed for rodents to train and test 14 pigs. Odor sampling and reliable responding were obtained after three to fifteen 160-trial sessions. Successful transfer of the task from ethyl acetate to ethanol was achieved in 1–4 sessions. Detection threshold for ethyl acetate varied between 10?2% and 10?6% v/v and for ethanol between 0.1% and 5 × 10?6% v/v. The results provide evidence that minipigs can successfully acquire 2-odorant discrimination using a food-rewarded instrumental conditioning paradigm for testing olfactory function. This olfactory discrimination paradigm provides reliable measures of olfactory sensitivity and thereby enables detection of changes in olfaction in a porcine model of Alzheimer's disease currently being developed. PMID:20693277

Holm, Ida E.; Herskin, Mette S.; Dagnæs-Hansen, Frederik; Johansen, Marianne G.; Jørgensen, Arne Lund; Ladewig, Jan

2010-01-01

25

Threshold energy effect on avalanche breakdown voltage in semiconductor junctions  

Microsoft Academic Search

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

Y. Okuto; C. R. Crowell

1975-01-01

26

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

NASA Technical Reports Server (NTRS)

Precipitation, including rain and snow, is a critical part of the Earth's energy and hydrology cycles. In order to collect information on the complete global precipitation cycle and to understand the energy budget in terms of precipitation, uniform global estimates of both liquid and frozen precipitation must be collected. Active observations of falling snow are somewhat easier to estimate since the radar will detect the precipitation particles and one only needs to know surface temperature to determine if it is liquid rain or snow. The challenges of estimating falling snow from passive spaceborne observations still exist though progress is being made. While these challenges are still being addressed, knowledge of their impact on expected retrieval results is an important key for understanding falling snow retrieval estimations. Important information to assess falling snow retrievals includes knowing thresholds of detection for active and passive sensors, various sensor channel configurations, snow event system characteristics, snowflake particle assumptions, and surface types. For example, can a lake effect snow system with low (2.5 km) cloud tops having an ice water content (Iwe) at the surface of 0.25 g m-3 and dendrite snowflakes be detected? If this information is known, we can focus retrieval efforts on detectable storms and concentrate advances on achievable results. Here, the focus is to determine thresholds of detection for falling snow for various snow conditions over land and lake surfaces. The analysis relies on simulated Weather Research Forecasting (WRF) simulations of falling snow cases since simulations provide all the information to determine the measurements from space and the ground truth. Results are presented for active radar at Ku, Ka, and W-band and for passive radiometer channels from 10 to 183 GHz (Skofronick-Jackson, et al. submitted to IEEE TGRS, April 2012). The notable results show: (1) the W-Band radar has detection thresholds more than an order of magnitude lower than the future GPM sensors, (2) the cloud structure macrophysics influences the thresholds of detection for passive channels, (3) the snowflake microphysics plays a large role in the detection threshold for active and passive instruments, (4) with reasonable assumptions, the passive 166 GHz channel has detection threshold values comparable to the GPM DPR Ku and Ka band radars with 0.05 g m-3 detected at the surface, or an 0.5-1 mm hr-l melted snow rate (equivalent to 0.5-2 cm hr-l solid fluffy snowflake rate).

Jackson, Gail

2012-01-01

27

Orion MPCV Touchdown Detection Threshold Development and Testing  

NASA Technical Reports Server (NTRS)

A robust method of detecting Orion Multi ]Purpose Crew Vehicle (MPCV) splashdown is necessary to ensure crew and hardware safety during descent and after touchdown. The proposed method uses a triple redundant system to inhibit Reaction Control System (RCS) thruster firings, detach parachute risers from the vehicle, and transition to the post ]landing segment of the Flight Software (FSW). The vehicle crew is the prime input for touchdown detection, followed by an autonomous FSW algorithm, and finally a strictly time based backup timer. RCS thrusters must be inhibited before submersion in water to protect against possible damage due to firing these jets under water. In addition, neglecting to declare touchdown will not allow the vehicle to transition to post ]landing activities such as activating the Crew Module Up ]righting System (CMUS), resulting in possible loss of communication and difficult recovery. A previous AIAA paper gAssessment of an Automated Touchdown Detection Algorithm for the Orion Crew Module h concluded that a strictly Inertial Measurement Unit (IMU) based detection method using an acceleration spike algorithm had the highest safety margins and shortest detection times of other methods considered. That study utilized finite element simulations of vehicle splashdown, generated by LS ]DYNA, which were expanded to a larger set of results using a Kriging surface fit. The study also used the Decelerator Systems Simulation (DSS) to generate flight dynamics during vehicle descent under parachutes. Proto ]type IMU and FSW MATLAB models provided the basis for initial algorithm development and testing. This paper documents an in ]depth trade study, using the same dynamics data and MATLAB simulations as the earlier work, to further develop the acceleration detection method. By studying the combined effects of data rate, filtering on the rotational acceleration correction, data persistence limits and values of acceleration thresholds, an optimal configuration was determined. The lever arm calculation, which removes the centripetal acceleration caused by vehicle rotation, requires that the vehicle angular acceleration be derived from vehicle body rates, necessitating the addition of a 2nd order filter to smooth the data. It was determined that using 200 Hz data directly from the vehicle IMU outperforms the 40 Hz FSW data rate. Data persistence counter values and acceleration thresholds were balanced in order to meet desired safety and performance. The algorithm proved to exhibit ample safety margin against early detection while under parachutes, and adequate performance upon vehicle splashdown. Fall times from algorithm initiation were also studied, and a backup timer length was chosen to provide a large safety margin, yet still trigger detection before CMUS inflation. This timer serves as a backup to the primary acceleration detection method. Additionally, these parameters were tested for safety on actual flight test data, demonstrating expected safety margins.

Daum, Jared; Gay, Robert

2013-01-01

28

Spin-system dynamics and fault detection in threshold networks  

SciTech Connect

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

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

2011-01-15

29

Ultrasonic flaw detection using threshold modified S-transform.  

PubMed

Interference noising originating from the ultrasonic testing defect signal seriously influences the accuracy of the signal extraction and defect location. Time-frequency analysis methods are mainly used to improve the defects detection resolution. In fact, the S-transform, a hybrid of the Short time Fourier transform (STFT) and wavelet transform (WT), has a time frequency resolution which is far from ideal. In this paper, a new modified S-transform based on thresholding technique, which offers a better time frequency resolution compared to the original S-transform is proposed. The improvement is achieved by the introduction of a new scaling rule for the Gaussian window used in S-transform. Simulation results are presented and show correct time frequency information of multiple Gaussian echoes under low signal-to-noise ratio (SNR) environment. In addition, experimental results demonstrate better and reliable detection of close echoes drowned in the noise. PMID:24120270

Benammar, Abdessalem; Drai, Redouane; Guessoum, Abderrezak

2014-02-01

30

Spin-system dynamics and fault detection in threshold networks  

NASA Astrophysics Data System (ADS)

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

Kirkland, Steve; Severini, Simone

2011-01-01

31

Dynamic multiple thresholding breast boundary detection algorithm for mammograms  

SciTech Connect

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

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

2010-01-15

32

Sub-Threshold Design: The Challenges of Minimizing Circuit Energy  

E-print Network

Sub-Threshold Design: The Challenges of Minimizing Circuit Energy B. H. Calhoun1 , A. Wang2 , N identify the key challenges that oppose sub- threshold circuit design and describe fabricated chips that verify techniques for overcoming the challenges. Categories and Subject Descriptors B.7.1 [ICs]: Types

Calhoun, Benton H.

33

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

34

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

35

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

36

Comparison of signal and gap-detection thresholds for focused and broad cochlear implant electrode configurations.  

PubMed

Cochlear implant (CI) users usually exhibit marked across-electrode differences in detection thresholds with "focused" modes of stimulation, such as partial-tripolar (pTP) mode. This may reflect differences either in local neural survival or in the distance of the electrodes from the modiolus. To shed light on these two explanations, we compared stimulus-detection thresholds and gap-detection thresholds (GDTs) at comfortably loud levels for at least four electrodes in each of ten Advanced Bionics CI users, using 1031-pps pulse trains. The electrodes selected for each user had a wide range of stimulus-detection thresholds in pTP mode. We also measured across-electrode variations in both stimulus-detection and gap-detection tasks in monopolar (MP) mode. Both stimulus-detection and gap-detection thresholds correlated across modes. However, there was no significant correlation between stimulus-detection and gap-detection thresholds in either mode. Hence, gap-detection thresholds likely tap a source of across-electrode variation additional to, or different from, that revealed by stimulus-detection thresholds. Stimulus-detection thresholds were significantly lower for apical than for basal electrodes in both modes; this was only true for gap detection in pTP mode. Finally, although the across-electrode standard deviation in stimulus-detection thresholds was greater in pTP than in MP mode, the reliability of these differences-assessed by dividing the across-electrode standard deviation by the standard deviation across adaptive runs for each electrode-was similar for the two modes; this metric was also similar across modes for gap detection. Hence across-electrode differences can be revealed using clinically available MP stimulation, with a reliability comparable to that observed with focused stimulation. PMID:25644786

Bierer, Julie Arenberg; Deeks, John M; Billig, Alexander J; Carlyon, Robert P

2015-04-01

37

ON THE THRESHOLD OF NEW HOUSING DEVELOPMENTS: ZERO ENERGY HOUSING  

Microsoft Academic Search

Apart from the growing need for housing production in the world, the crucial problem is, as cited in literature, the quality of housing planning and design as well as the approach towards water usage and energy consumption. At this point, being on the threshold in terms of environmental sustainability and energy efficiency, zero energy housing(ZEH) concept, newly introduced to the

Merve Bedir

2007-01-01

38

An Algorithm for 353 Odor Detection Thresholds in Humans  

PubMed Central

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

Sánchez-Moreno, Ricardo; Cometto-Muñiz, J. Enrique; Cain, William S.

2012-01-01

39

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

40

Efficient Shadow Detection of Color Aerial Images Based on Successive Thresholding Scheme  

Microsoft Academic Search

Recently, Tsai presented an efficient algorithm which uses the ratio value of the hue over the intensity to construct the ratio map for detecting shadows of color aerial images. Instead of only using the global thresholding process in Tsai's algorithm, this paper presents a novel successive thresholding scheme (STS) to detect shadows more accurately. In our proposed STS, the modified

Kuo-Liang Chung; Yi-Ru Lin; Yong-Huai Huang

2009-01-01

41

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

PubMed Central

Thresholding is an often-used method of spike detection for implantable neural signal processors due to its computational simplicity. A means for automatically selecting the threshold is desirable, especially for high channel count data acquisition systems. Estimating the noise level and setting the threshold to a multiple of this level is a computationally simple means of automatically selecting a threshold. We present an analysis of this method as it is commonly applied to neural waveforms. Four different operators were used to estimate the noise level in neural waveforms and set thresholds for spike detection. An optimal multiplier was identified for each noise measure using a metric appropriate for a brain-machine interface application. The commonly used root-mean-square operator was found to be least advantageous for setting the threshold. Investigators using this form of automatic threshold selection or developing new unsupervised methods can benefit from the optimization framework presented here. PMID:19205769

Rizk, Michael; Wolf, Patrick D.

2009-01-01

42

Thresholds for detection and awareness of masked facial stimuli.  

PubMed

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

Heeks, Frances; Azzopardi, Paul

2015-03-01

43

Pooling optimal combinations of energy thresholds in spectroscopic CT  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

44

Lowering the Gamma Ray Energy Threshold at Thaemis  

NASA Astrophysics Data System (ADS)

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

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

1994-12-01

45

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

PubMed

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

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

2015-02-01

46

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

PubMed

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 low pass-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 A; Salvi, Richard J; Dent, Micheal L

2009-10-01

47

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

PubMed

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

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

2013-09-01

48

The impact model of cumulative damage on the detection threshold of space optical communication  

NASA Astrophysics Data System (ADS)

In order to improve the radiation hardness of free-space optical communication system, this paper theoretically deduces the radiation damage model of laser diodes' output power. For this model, the theory of Gaussian distribution is used to study the radiation influence on detection threshold of free-space optical communication on the condition that the bit error rate keeps invariable. The result shows that both the output power and detection threshold are the linear functions of total dose.

Chang, Guolong; Zhou, Yanping; Ma, Jing; Zhou, Jianqiang; Zhao, Bingnan; Wang, Xiaoming; Zhou, Yu; Lv, Xiaofang

2010-10-01

49

Adaptive Threshold Spike Detection using Stationary Wavelet Transform for Neural Recording Implants  

E-print Network

) is described. The method enables spike detection with 90% accuracy even when the signal- to-noise is -1d for spike detection, and the system then chooses either absolute threshold method or the SWT method. The primary challenge in detecting spikes is interference due to background noise, which is high impedance

Mason, Andrew

50

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

PubMed

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

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

2015-01-28

51

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

NASA Technical Reports Server (NTRS)

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

LaFontaine Frank J.; Jedlovec, Gary J.

2015-01-01

52

Limitations in the spectral method for graph partitioning: detectability threshold and localization of eigenvectors  

E-print Network

Investigating the performance of different methods is a fundamental problem in graph partitioning. In this paper, we estimate the so-called detectability threshold for the spectral method with both unnormalized and normalized Laplacians in sparse graphs. The detectability threshold is the critical point at which the result of the spectral method is completely uncorrelated to the planted partition. We also analyze whether the localization of eigenvectors affects the partitioning performance in the detectable region. We use the replica method, which is often used in the field of spin-glass theory, and focus on the case of bisection. We show that the gap between the estimated threshold for the spectral method and the threshold obtained from Bayesian inference is considerable in sparse graphs, even without eigenvector localization. This gap closes in a dense limit.

Kawamoto, Tatsuro

2015-01-01

53

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

PubMed

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

Cronin, John B; Rumpf, Michael C

2014-10-01

54

A method for detection of foreign body in cotton based on threshold segment  

NASA Astrophysics Data System (ADS)

In order to extract foreign body from the complex channel background and cotton layers, a detection method which combined improved Otsu threshold with background estimation threshold is presented. Firstly, the original image which containing multiple foreign fibers is divided into two new images which containing only two substances by Otsu threshold. And then using the estimated value of the means and the standard deviations of the two new images a background estimation threshold was determined. The foreign fibers are extracted by the estimation threshold. Simulation results show that this method can overcome the effect which caused by the channel background interference and diversity of the foreign fibers in the actual working environment and can extract foreign bodies quickly and effectively.

Sha, Tao; Xie, Tingting; Wang, Mengxue; Yang, Chaoyu

2013-10-01

55

A preliminary evaluation of a speed threshold incident detection algorithm  

E-print Network

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

Kolb, Stephanie Lang

1996-01-01

56

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

PubMed Central

It is commonly agreed that one needs to use a threshold value in the detection of muscle activity timing in electromyographic (EMG) signal analysis. However, the algorithm for threshold determination lacks an agreement between the investigators. In this study we aimed to determine a proper threshold value in an incremental cycling exercise for accurate EMG signal analysis. Nine healthy recreationally active male subjects cycled until exhaustion. EMG recordings were performed on four low extremity muscle groups; gastrocnemius lateralis (GL), gastrocnemius medialis (GM), soleus (SOL) and vastus medialis (VM). We have analyzed our data using three different threshold levels: 25%, 35% and 45% of the mean RMS EMG value. We compared the appropriateness of these threshold values using two criteria: (1) significant correlation between the actual and estimated number of bursts and (2) proximity of the regression line of the actual and estimated number of bursts to the line of identity. It had been possible to find a significant correlation between the actual and estimated number of bursts with the 25, 35 and 45% threshold values for the GL muscle. Correlation analyses for the VM muscle had shown that the number of bursts estimated with the 35% threshold value was found to be significantly correlated with the actual number of bursts. For the GM muscle, it had been possible to predict the burst number by using either the 35% or 45% threshold value and for the SOL muscle the 25% threshold value was found as the best predictor for actual number of burst estimation. Detailed analyses of the actual and estimated number of bursts had shown that success of threshold estimation may differ among muscle groups. Evaluation of our data had clearly shown that it is important to select proper threshold values for correct EMG signal analyses. Using a single threshold value for different exercise intensities and different muscle groups may cause misleading results. Key points ? priori accepted threshold value may cause erroneous results in EMG analysis. Using a single threshold value for different exercise intensities and different muscle groups may cause misleading results. The investigators may need to use different threshold selection strategies for different workloads. The investigators have to justify the choice of threshold selection with valid arguments before detailed EMG signal analyses. PMID:24149789

Özgünen, Kerem Tuncay; Çelik, Umut; Kurdak, Sanl? Sadi

2010-01-01

57

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

58

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

59

Influence of detection methods on chloride threshold value for the corrosion of steel reinforcement  

Microsoft Academic Search

The aim of this study is to evaluate the influence of depassivation detection methods on chloride threshold value for the corrosion of steel reinforcement in a concrete. The detection methods of depasstivating steel reinforcement have been examined including electrochemical impedance spectra (EIS), potentiodynamic polarization (PP) in a simulated concrete pore solution and half-cell potential, linear polarization (LP) and electrochemical impedance

Jinxia Xu; Linhua Jiang; Jingxiang Wang

2009-01-01

60

Wavelet-based acoustic emission detection method with adaptive thresholding  

NASA Astrophysics Data System (ADS)

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

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

2000-06-01

61

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

62

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

PubMed Central

Amplitude modulation (AM) is a pervasive feature of natural sounds. Neural detection and processing of modulation cues is behaviourally important across species. Although most ecologically relevant sounds are not fully modulated, physiological studies have usually concentrated on fully modulated (100% modulation depth) signals. Psychoacoustic experiments mainly operate at low modulation depths, around detection threshold (?5% AM). We presented sinusoidal amplitude-modulated tones, systematically varying modulation depth between zero and 100%, at a range of modulation frequencies, to anaesthetised guinea-pigs while recording spikes from neurons in the ventral cochlear nucleus (VCN). The cochlear nucleus is the site of the first synapse in the central auditory system. At this locus significant signal processing occurs with respect to representation of AM signals. Spike trains were analysed in terms of the vector strength of spike synchrony to the amplitude envelope. Neurons showed either low-pass or band-pass temporal modulation transfer functions, with the proportion of band-pass responses increasing with increasing sound level. The proportion of units showing a band-pass response varies with unit type: sustained chopper (CS) > transient chopper (CT) > primary-like (PL). Spike synchrony increased with increasing modulation depth. At the lowest modulation depth (6%), significant spike synchrony was only observed near to the unit's best modulation frequency for all unit types tested. Modulation tuning therefore became sharper with decreasing modulation depth. AM detection threshold was calculated for each individual unit as a function of modulation frequency. Chopper units have significantly better AM detection thresholds than do primary-like units. AM detection threshold is significantly worse at 40 dB vs. 10 dB above pure-tone spike rate threshold. Mean modulation detection thresholds for sounds 10 dB above pure-tone spike rate threshold at best modulation frequency are (95% CI) 11.6% (10.0–13.1) for PL units, 9.8% (8.2–11.5) for CT units, and 10.8% (8.4–13.2) for CS units. The most sensitive guinea-pig VCN single unit AM detection thresholds are similar to human psychophysical performance (?3% AM), while the mean neurometric thresholds approach whole animal behavioural performance (?10% AM). PMID:23629508

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

2013-01-01

63

Orientation tuning in human colour vision at detection threshold  

PubMed Central

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

Gheiratmand, Mina; Mullen, Kathy T.

2014-01-01

64

Sensitivity of the threshold displacement energy to temperature and time  

NASA Astrophysics Data System (ADS)

The impact of temperature and time scale on the threshold displacement energy (Ed) has been investigated using molecular dynamics simulation. Employing a systematic approach to simulating low energy displacement cascades, defect formation probability has been quantified and precise values of Ed have been calculated at temperatures of 50, 300, 750, and 1200 K. In application to rutile TiO2, the thermal activation of Frenkel pairs at elevated temperatures is found to significantly reduce defect formation probability and cause an increase in the oxygen value of Ed. Relating the high-temperature, picosecond simulations to experimental measurement conditions, we find that thermally activated processes are responsible for discrepancies in values of Ed reported by various techniques. This work establishes that Ed is not an intrinsic material property but depends on the conditions in which it is measured and the context in which it is to be used.

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

2012-10-01

65

Signal detection theory and vestibular thresholds: I. Basic theory and practical considerations.  

PubMed

Detection theory has been applied to the measurement of vestibular thresholds and vestibular sensory integration. Yet, a formal detection theory analysis of vestibular responses has not been published. Such a de novo analysis seems warranted because the vestibular system has characteristics that differ from other sensory systems, which impacts the application of detection theory. For example, the physical stimuli evoking vestibular responses are typically bidirectional (e.g., leftward/rightward); this bidirectional nature of vestibular responses leads to another characteristic-what is sometimes called vestibular bias-that must also be considered, since it can impact threshold measurements, including thresholds found using staircase procedures. This paper develops a basic model of vestibular noise and then analyzes this model for four standard paradigms-one-interval recognition, one-interval detection, two-interval detection, and two-interval recognition. While any of these paradigms might be justified for a specific application, it is concluded that one-interval recognition paradigms have advantages over other paradigms for many vestibular applications. One-interval recognition is favored over one-interval detection because it lends itself to a fixed detection boundary, is more efficient, and is less impacted by device vibration. One-interval recognition is generally favored over two-interval recognition because it assesses vestibular bias and can require substantially less time than two-interval tasks. PMID:21359662

Merfeld, Daniel M

2011-05-01

66

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

67

Reduced Complexity Detection for Ricean MIMO Channels Based on Condition Number Thresholding  

E-print Network

Reduced Complexity Detection for Ricean MIMO Channels Based on Condition Number Thresholding transmit and receive antenna elements is presented. Our prime aim is to reduce the extensive complexity of the adaptive detector (AD) is a hard- decision criterion based on the condition number of the MIMO correlation

Wang, Cheng-Xiang

68

Determination of Detection Thresholds to Allow Safe Operation of Television Band \\  

Microsoft Academic Search

The purpose of this study is to determine a range of detection thresholds at which new dynamic spectrum access (DSA) devices can safely operate in unoccupied spectrum allocated to terrestrial television (TV) broadcasting and other services (i.e., the TV \\

M. A. McHenry; K. Steadman; M. Lofquist

2008-01-01

69

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

70

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

PubMed

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

71

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

PubMed

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

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

2013-01-01

72

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

73

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

74

Threshold value-based detection of relevant force inputs onto vehicle skin panels with piezoelectric signals  

NASA Astrophysics Data System (ADS)

This article describes and compares autonomous threshold value-based processes for detecting force inputs onto vehicle skin panels. For this purpose, 13 piezoelectric foil sensors made from polyvinylidene fluoride are applied to the inside of the outer skin panels as sensors. Applied forces give rise to mechanical vibrations in the material, which, in the form of expansions in the sensor, result in a proportional output signal. On the basis of these signals, two static and two adaptive threshold value processes are presented and evaluated for differentiating between relevant events (including scratches, parking bumps) and irrelevant events (including wind, rain). At the same time, the central issue of optimum configuration of the threshold value is investigated, and solutions proposed.

Mueller, Maik; Wiedmann, Karsten; Beikirch, Helmut

2012-07-01

75

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

76

A detection threshold in the amplitude spectra calculated from Kepler data obtained during K2 mission  

NASA Astrophysics Data System (ADS)

We present our analysis of simulated data in order to derive a detection threshold which can be used in the pre-whitening process of amplitude spectra. In case of ground-based data of pulsating stars, this threshold is conventionally taken to be four times the mean noise level in an amplitude spectrum. This threshold is questionable when space-based data are analysed. Our effort is aimed at revising this threshold in the case of continuous 90-d Kepler K2 phase observations. Our result clearly shows that a 95 per cent confidence level, common for ground observations, can be reached at 5.4 times the mean noise level and is coverage dependent. In addition, this threshold varies between 4.8 and 5.7, if the number of cadences is changed. This conclusion should secure further pre-whitening and helps to avoid over-interpretation of spectra of pulsating stars observed with the Kepler spacecraft during K2 phase. We compare our results with the standard approach widely used in the literature.

Baran, A. S.; Koen, C.; Pokrzywka, B.

2015-03-01

77

The Emergence of HIV Transmitted Resistance in Botswana: “When Will the WHO Detection Threshold Be Exceeded?”  

PubMed Central

Background The Botswana antiretroviral program began in 2002 and currently treats 42,000 patients, with a goal of treating 85,000 by 2009. The World Health Organization (WHO) has begun to implement a surveillance system for detecting transmitted resistance that exceeds a threshold of 5%. However, the WHO has not determined when this threshold will be reached. Here we model the Botswana government's treatment plan and predict, to 2009, the likely stochastic evolution of transmitted resistance. Methods We developed a model of the stochastic evolution of drug-resistant strains and formulated a birth-death Master equation. We analyzed this equation to obtain an analytical solution of the probabilistic evolutionary trajectory for transmitted resistance, and used treatment and demographic data from Botswana. We determined the temporal dynamics of transmitted resistance as a function of: (i) the transmissibility (i.e., fitness) of the drug-resistant strains that may evolve and (ii) the rate of acquired resistance. Results Transmitted resistance in Botswana will be unlikely to exceed the WHO's threshold by 2009 even if the rate of acquired resistance is high and the strains that evolve are half as fit as the wild-type strains. However, we also found that transmission of drug-resistant strains in Botswana could increase to ?15% by 2009 if the drug-resistant strains that evolve are as fit as the wild-type strains. Conclusions Transmitted resistance will only be detected by the WHO (by 2009) if the strains that evolve are extremely fit and acquired resistance is high. Initially after a treatment program is begun a threshold lower than 5% should be used; and we advise that predictions should be made before setting a threshold. Our results indicate that it may be several years before the WHO's surveillance system is likely to detect transmitted resistance in other resource-poor countries that have significantly less ambitious treatment programs than Botswana. PMID:17225857

Vardavas, Raffaele; Blower, Sally

2007-01-01

78

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

PubMed Central

Visual perception in schizophrenia is attracting a broad interest given the deep knowledge that we have about the visual system in healthy populations. One example is the class of effects known collectively as visual surround suppression. For example, the visibility of a grating located in the visual periphery is impaired by the presence of a surrounding grating of the same spatial frequency and orientation. Previous studies have suggested abnormal visual surround suppression in patients with schizophrenia. Given that schizophrenia patients have cortical alterations including hypofunction of NMDA receptors and reduced concentration of GABA neurotransmitter, which affect lateral inhibitory connections, then they should be relatively better than controls at detecting visual stimuli that are usually suppressed. We tested this hypothesis by measuring contrast detection thresholds using a new stimulus configuration. We tested two groups: 21 schizophrenia patients and 24 healthy subjects. Thresholds were obtained using Bayesian staircases in a four-alternative forced-choice detection task where the target was a grating within a 3? Butterworth window that appeared in one of four possible positions at 5? eccentricity. We compared three conditions, (a) target with no-surround, (b) target embedded within a surrounding grating of 20? diameter and 25% contrast with same spatial frequency and orthogonal orientation, and (c) target embedded within a surrounding grating with parallel (same) orientation. Previous results with healthy populations have shown that contrast thresholds are lower for orthogonal and no-surround (NS) conditions than for parallel surround (PS). The log-ratios between parallel and NS thresholds are used as an index quantifying visual surround suppression. Patients performed poorly compared to controls in the NS and orthogonal-surround conditions. However, they performed as well as controls when the surround was parallel, resulting in significantly lower suppression indices in patients. To examine whether the difference in suppression was driven by the lower NS thresholds for controls, we examined a matched subgroup of controls and patients, selected to have similar thresholds in the NS condition. Patients performed significantly better in the PS condition than controls. This analysis therefore indicates that a PS raised contrast thresholds less in patients than in controls. Our results support the hypothesis that inhibitory connections in early visual cortex are impaired in schizophrenia patients. PMID:25540631

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

2014-01-01

79

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

80

Signal-detection, threshold, and dual-process models of recognition memory: ROCs and conscious recollection.  

PubMed

Threshold- and signal-detection-based models have dominated theorizing about recognition memory. Building upon these theoretical frameworks, we have argued for a dual-process model in which conscious recollection (a threshold process) and familiarity (a signal-detection process) contribute to memory performance. In the current paper we assessed several memory models by examining the effects of levels of processing and the number of presentations on recognition memory receiver operating characteristics (ROCs). In general, when the ROCs were plotted in probability space they exhibited an inverted U shape; however, when they were plotted in z space they exhibited a U shape. An examination of the ROCs showed that the dual-process model could account for the observed ROCs, but that models based solely on either threshold or signal-detection processes failed to provide a sufficient account of the data. Furthermore, an examination of subjects' introspective reports using the remember/know procedure showed that subjects were aware of recollection and familiarity and were able to consistently report on their occurrence. The remember/know data were used to accurately predict the shapes of the ROCs, and estimates of recollection and familiarity derived from the ROC data mirrored the subjective reports of these processes. PMID:9063609

Yonelinas, A P; Dobbins, I; Szymanski, M D; Dhaliwal, H S; King, L

1996-12-01

81

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

82

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

PubMed Central

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

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

2012-01-01

83

Vibratory stimulation increase the electro-cutaneous sensory detection and pain thresholds in women but not in men  

PubMed Central

Background Vibratory stimulation is a potential method for the treatment of pain. Methods The effect of vibration on the forearm on detection (DT) and pain thresholds (PT) induced by electro-cutaneous stimulation were investigated in healthy male and female volunteers. Results Women have lower baseline detection and pain thresholds as compared to men. Furthermore, women but not men report increased detection and pain thresholds after vibratory stimulation. Conclusion Our findings indicate the potential usefulness of vibratory stimulation for pain treatment, and that gender differences should be considered in future evaluation of the method. PMID:16719906

Dahlin, Lisbeth; Lund, Irene; Lundeberg, Thomas; Molander, Carl

2006-01-01

84

Design and Synthesis of Ultralow Energy Spin-Memristor Threshold Logic  

NASA Astrophysics Data System (ADS)

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

Fan, Deliang; Sharad, Mrigank; Roy, Kaushik

2014-05-01

85

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

PubMed

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

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

2014-03-12

86

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

NASA Technical Reports Server (NTRS)

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

Leach, Rodman N.

1991-01-01

87

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

88

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

Microsoft Academic Search

The delay jitter discrimination threshold in bats is a disputed subject. Some investigators have obtained results indicating\\u000a that bats are able to discriminate alternations in delay down to 10 ns, which appears incredible for purely physical reasons.\\u000a Using actual bat echolocation sequences recorded during an easy detection task to measure simulated delay jitter, it is shown\\u000a here that jitter detection thresholds

Kristian Beedholm

2006-01-01

89

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

90

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

PubMed

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

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

2007-12-01

91

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

SciTech Connect

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

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

2013-05-20

92

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,

93

Spatial and Temporal Varying Thresholds for Cloud Detection in Satellite Imagery  

NASA Technical Reports Server (NTRS)

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

Jedlovec, Gary; Haines, Stephanie

2007-01-01

94

Bio-inspired target detection in natural scenes: optimal thresholds and ego-motion  

NASA Astrophysics Data System (ADS)

We have developed a numerical model of Small Target Motion Detector neurons, bio-inspired from electrophysiological experiments in the fly brain. These neurons respond selectively to small moving features within complex moving surrounds. Interestingly, these cells still respond robustly when the targets are embedded in the background, without relative motion cues. This model contains representations of neural elements along a proposed pathway to the target-detecting neuron and the resultant processing enhances target discrimination in moving scenes. The model encodes high dynamic range luminance values from natural images (via adaptive photoreceptor encoding) and then shapes the transient signals required for target discrimination (via adaptive spatiotemporal high-pass filtering). Following this, a model for Rectifying Transient Cells implements a nonlinear facilitation between rapidly adapting, and independent polarity contrast channels (an 'on' and an 'off' pathway) each with center-surround antagonism. The recombination of the channels results in increased discrimination of small targets, of approximately the size of a single pixel, without the need for relative motion cues. This method of feature discrimination contrasts with traditional target and background motion-field computations. We improve the target-detecting output with inhibition from correlation-type motion detectors, using a form of antagonism between our feature correlator and the more typical motion correlator. We also observe that a changing optimal threshold is highly correlated to the value of observer ego-motion. We present an elaborated target detection model that allows for implementation of a static optimal threshold, by scaling the target discrimination mechanism with a model-derived velocity estimation of ego-motion.

Wiederman, Steven D.; Brinkworth, Russell S. A.; O'Carroll, David C.

2008-08-01

95

Energy scan by $?$ mesons and threshold energy for the confinement-deconfinement phase transition  

E-print Network

We argue that the ratio of $\\phi$ mesons multiplicity over cube of the mean $p_T$ is proportional to the degeneracy of the medium produced in ultra-relativistic heavy ion collisions. The ratio extracted from the existing $\\phi$ meson data in the energy range $\\sqrt{s}$=6.3-200 GeV, indicate that beyond a threshold energy $\\sqrt{s}_{th}=15.74\\pm 8.10$ GeV, the medium crosses over from a confined phase to a deconfined phase.

A. K. Chaudhuri

2010-05-18

96

Error Probabilities and Threshold Selection in Networked Nuclear Detection Chetan D. Pahlajani, Jianxin Sun, Ioannis Poulakakis, Herbert G. Tanner  

E-print Network

of nuclear detection relates to the problem of using radiation sensor data to decide, within a given time. Another challenge is that the signal recorded by the radiation detectors contains, in addition to possibleError Probabilities and Threshold Selection in Networked Nuclear Detection Chetan D. Pahlajani

Poulakakis, Ioannis

97

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

NASA Astrophysics Data System (ADS)

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

Hansen, Anja; Krueger, Alexander; Ripken, Tammo

2013-03-01

98

Threshold effects in strong-field ionization: Energy shifts and Rydberg structures  

NASA Astrophysics Data System (ADS)

The behavior of strong-field ionization rates of neutral atoms in the vicinity of multiphoton ionization thresholds is analyzed using formal collision theory. Our approach, which accounts nonperturbatively for effects of an intense laser field, shows that the ionization rates have a nearly constant behavior below and above each multiphoton threshold and that between such thresholds there are an apparently finite number of rapid oscillations due to resonances with laser-field-modified Rydberg states. This pattern is typical for any atomic target, as we illustrate specifically for hydrogen and neon atoms. The flat behavior of the ionization yield near multiphoton thresholds gives the appearance of an energy shift of the ionization thresholds, which have been postulated in a number of recent studies concerning diverse aspects of above-threshold ionization and high-harmonic generation of atoms. The flat behaviors of the rates near threshold exhibit only a rather weak dependence on the laser-field intensity. Other aspects of the near-threshold behavior of ionization rates and their dependence on the laser-field parameters are also discussed.

Krajewska, K.; Fabrikant, I. I.; Starace, A. F.

2012-11-01

99

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

100

Detection vs. grouping thresholds for elements differing in spacing, size and luminance. An alternative approach towards the psychophysics of Gestalten.  

PubMed

Three experiments were performed to compare thresholds for the detection of non-uniformity in spacing, size and luminance with thresholds for grouping. In the first experiment a row of 12 black equi-spaced dots was used and the spacing after the 3rd, 6th, and 9th dot increased in random steps to determine the threshold at which the observer detected an irregularity in the size of the gaps. Thereafter, spacing in the same locations was increased further to find the threshold at which the observer perceived four groups of three dots each (triplets). In the second experiment, empty circles were used instead of dots and the diameter of the circles in the first and second triplet increased until the difference in size gave rise either to a detection or grouping response. In the third experiment, the dots in the second and fourth triplet were increased in luminance. The aim again was to compare the difference in brightness required for detection or grouping, respectively. Results demonstrate that the threshold for perceiving stimuli as irregularly spaced or dissimilar in size or brightness is much smaller than the threshold for grouping. In order to perceive stimuli as grouped, stimulus differences had to be 5.2 times (for dot spacing), 7.4 times (for size) and 6.6 times (for luminance) larger than for detection. Two control experiments demonstrated that the difference between the two kinds of thresholds persisted even when only two gaps were used instead of three and when gap position was randomized. PMID:20363241

Gori, Simone; Spillmann, Lothar

2010-06-11

101

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

2012-01-01

102

Adaptive Thresholding Technique for Retinal Vessel Segmentation Based on GLCM-Energy Information.  

PubMed

Although retinal vessel segmentation has been extensively researched, a robust and time efficient segmentation method is highly needed. This paper presents a local adaptive thresholding technique based on gray level cooccurrence matrix- (GLCM-) energy information for retinal vessel segmentation. Different thresholds were computed using GLCM-energy information. An experimental evaluation on DRIVE database using the grayscale intensity and Green Channel of the retinal image demonstrates the high performance of the proposed local adaptive thresholding technique. The maximum average accuracy rates of 0.9511 and 0.9510 with maximum average sensitivity rates of 0.7650 and 0.7641 were achieved on DRIVE and STARE databases, respectively. When compared to the widely previously used techniques on the databases, the proposed adaptive thresholding technique is time efficient with a higher average sensitivity and average accuracy rates in the same range of very good specificity. PMID:25802550

Mapayi, Temitope; Viriri, Serestina; Tapamo, Jules-Raymond

2015-01-01

103

Adaptive Thresholding Technique for Retinal Vessel Segmentation Based on GLCM-Energy Information  

PubMed Central

Although retinal vessel segmentation has been extensively researched, a robust and time efficient segmentation method is highly needed. This paper presents a local adaptive thresholding technique based on gray level cooccurrence matrix- (GLCM-) energy information for retinal vessel segmentation. Different thresholds were computed using GLCM-energy information. An experimental evaluation on DRIVE database using the grayscale intensity and Green Channel of the retinal image demonstrates the high performance of the proposed local adaptive thresholding technique. The maximum average accuracy rates of 0.9511 and 0.9510 with maximum average sensitivity rates of 0.7650 and 0.7641 were achieved on DRIVE and STARE databases, respectively. When compared to the widely previously used techniques on the databases, the proposed adaptive thresholding technique is time efficient with a higher average sensitivity and average accuracy rates in the same range of very good specificity.

Mapayi, Temitope; Viriri, Serestina; Tapamo, Jules-Raymond

2015-01-01

104

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

105

An Accurate Measurement of the O Threshold Energy  

E-print Network

-uniform proton energy loss, and the loss of energy due to ionisation of the 14 N atoms. This value of the amount of gas released into the target chamber. These measurements can be easily converted into results

Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group

106

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

107

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

PubMed

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

de Nazaré Silva, Joberth; de Carvalho Filho, Antonio Oseas; Corrêa Silva, Aristófanes; Cardoso de Paiva, Anselmo; Gattass, Marcelo

2014-10-01

108

Milagro: A low energy threshold extensive air shower array  

SciTech Connect

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

Sinnis, C.

1994-12-31

109

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

110

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

111

Macroscopic detection of the strong stochasticity threshold in Fermi-Pasta-Ulam chains of oscillators  

E-print Network

The largest Lyapunov exponent of a system composed by a heavy impurity embedded in a chain of anharmonic nearest-neighbor Fermi-Pasta-Ulam oscillators is numerically computed for various values of the impurity mass $M$. A crossover between weak and strong chaos is obtained at the same value $\\epsilon_{_T}$ of the energy density $\\epsilon$ (energy per degree of freedom) for all the considered values of the impurity mass $M$. The threshold $\\epsi lon_{_T}$ coincides with the value of the energy density $\\epsilon$ at which a change of scaling of the relaxation time of the momentum autocorrelation function of the impurity ocurrs and that was obtained in a previous work ~[M. Romero-Bastida and E. Braun, Phys. Rev. E {\\bf65}, 036228 (2002)]. The complete Lyapunov spectrum does not depend significantly on the impurity mass $M$. These results suggest that the impurity does not contribute significantly to the dynamical instability (chaos) of the chain and can be considered as a probe for the dynamics of the system to which the impurity is coupled. Finally, it is shown that the Kolmogorov-Sinai entropy of the chain has a crossover from weak to strong chaos at the same value of the energy density that the crossover value $\\epsilon_{_T}$ of largest Lyapunov exponent. Implications of this result are discussed.

M. Romero-Bastida

2004-02-16

112

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

PubMed Central

Taste sensitivity is assessed with various techniques, including absolute detection and quality recognition. For any stimulus, one might expect individual differences in sensitivity to be reflected in all measures, but they are often surprisingly independent. Here, we focus on sensitivity to sour and salty taste, in part because processing of these qualities is poorly understood relative to other tastes. In Study 1, we measured retest reliability for detection (modified, forced-choice staircase method) and recognition (modified Harris–Kalmus procedure) for both citric acid (CA) and sodium chloride (NaCl). Despite good retest reliability, individual differences in detection and recognition were weakly correlated, suggesting that detection and recognition of sour and salty stimuli may reflect different physiological processes. In Study 2, a subset of subjects returned to contribute full detection (psychometric) functions for CA and NaCl. Thresholds estimated from full detection functions correlated with both staircase and recognition thresholds, suggesting that both tasks may reflect absolute sensitivity to some extent. However, the ranges of individual differences were systematically compressed for staircase thresholds relative to those from full detection functions. Thus, individual differences in sensitivity appear to interact with different test methodologies in lawful ways. More work will be required to understand how different taste phenotypes relate to one another. PMID:23413310

2013-01-01

113

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

PubMed

Taste sensitivity is assessed with various techniques, including absolute detection and quality recognition. For any stimulus, one might expect individual differences in sensitivity to be reflected in all measures, but they are often surprisingly independent. Here, we focus on sensitivity to sour and salty taste, in part because processing of these qualities is poorly understood relative to other tastes. In Study 1, we measured retest reliability for detection (modified, forced-choice staircase method) and recognition (modified Harris-Kalmus procedure) for both citric acid (CA) and sodium chloride (NaCl). Despite good retest reliability, individual differences in detection and recognition were weakly correlated, suggesting that detection and recognition of sour and salty stimuli may reflect different physiological processes. In Study 2, a subset of subjects returned to contribute full detection (psychometric) functions for CA and NaCl. Thresholds estimated from full detection functions correlated with both staircase and recognition thresholds, suggesting that both tasks may reflect absolute sensitivity to some extent. However, the ranges of individual differences were systematically compressed for staircase thresholds relative to those from full detection functions. Thus, individual differences in sensitivity appear to interact with different test methodologies in lawful ways. More work will be required to understand how different taste phenotypes relate to one another. PMID:23413310

Wise, Paul M; Breslin, Paul A S

2013-05-01

114

A novel thresholding method for automatically detecting stars in astronomical images Alejandro Cristo, Antonio Plaza, David Valencia  

E-print Network

A novel thresholding method for automatically detecting stars in astronomical images Alejandro-Tracking the position of stars or bright bodies in astronomical images. In such techniques, all pixels above a images specifically de- a star. Also, there is always some degree of noise present in veloped for astronomical

Plaza, Antonio J.

115

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

116

The development of an adaptive threshold for model-based fault detection of a nonlinear electro-hydraulic system  

Microsoft Academic Search

This paper presents a practical approach to combine model-based fault detection with an adaptive threshold. The suitability of the proposed technique is illustrated through its application to the condition monitoring of a nonlinear electro-hydraulic plant. The paper begins by outlining the difficulties associated with modelling the plant and the steps taken to identify the uncertain factors that influence the accuracy

Z. Shi; F. Gu; B. Lennox; A. D. Ball

2005-01-01

117

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

PubMed Central

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

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

1987-01-01

118

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

PubMed Central

High resolution (HR) multi-electrode mapping is increasingly being used to evaluate gastrointestinal slow wave behaviors. To create the HR-activation maps from gastric serosal electrode recordings that quantify slow wave propagation, it is first necessary to identify the activation time (AT) of each individual slow wave event. Identifying these ATs has been a time consuming task, because there has previously been no reliable automated detection method. We have developed an automated AT detection method termed falling-edge, variable threshold (FEVT) detection. It computes a detection signal transform to accentuate the high ‘energy’ content of the falling edges in the serosal recording, and uses a running median estimator of the noise to set the time-varying detection threshold. The FEVT method was optimized, validated, and compared to other potential algorithms using in-vivo HR recordings from a porcine model. FEVT properly detects ATs in a wide range of waveforms, making its performance substantially superior to the other methods, especially for low signal-to-noise ratio (SNR) recordings. The algorithm offered a substantial time savings (>100 times) over manual-marking whilst achieving a highly satisfactory sensitivity (0.92) and positive-prediction value (0.89). PMID:20024624

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

2010-01-01

119

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.

120

Energy conservation using face detection  

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

121

Relationship between vibrotactile detection threshold in the Pacinian channel and complex mechanical modulus of the human glabrous skin.  

PubMed

The goal of this study was to investigate the relationship between the psychophysical vibrotactile thresholds of the Pacinian (P) channel and the mechanical properties of the skin at the fingertip. Seven healthy adult subjects (age: 23-30) participated in the study. The mechanical stimuli were 250-Hz sinusoidal bursts and applied with cylindrical contactor probes of radii 1, 2, and 3.5?mm on three locations at the fingertip. The duration of each burst was 0.5?s (rise and fall time: 50?ms). The subjects performed a two-interval forced-choice task while the stimulus levels changed for tracking the threshold at 75% probability of detection. There were significant main effects of contactor radius and location (two-way ANOVA, values of p?thresholds decreased as the contactor radius increased (i.e., spatial summation effect) at all locations. The thresholds were lowest near the whorl at the fingertip. Additionally, we measured the mechanical impedance (specifically, the storage and loss moduli) at the contact locations. The storage moduli did not change with the contactor location, but the loss moduli were lowest near the whorl. While the loss moduli decreased, the storage moduli increased (e.g., more springiness) as the contactor radius increased. There was moderate and barely significant correlation between the absolute thresholds and the storage moduli (r?=?0.650, p?=?0.058). However, the correlation between the absolute thresholds and the loss moduli was high and very significant (r?=?0.951, p?detection thresholds, which would otherwise be expected to be constant due to uniform Pacinian innervention density at the fingertip. PMID:23323828

Yildiz, Mustafa Zah?d; Güçlü, Burak

2013-01-01

122

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

PubMed Central

Normal brain function requires constant adaptation, as an organism learns to associate important sensory stimuli with appropriate motor actions. Neurological disorders may disrupt these learned associations, and require the nervous system to reorganize itself. As a consequence, neural plasticity is a crucial component of normal brain function and a critical mechanism for recovery from injury. Associative, or Hebbian pairing of pre- and postsynaptic activity has been shown to alter stimulus-evoked responses in vivo, however, to date, such protocols have not been shown to affect the animal’s subsequent behavior. We paired stimulus trains separated by a brief time delay to two electrodes in rat sensorimotor cortex, which changed the statistical pattern of spikes during subsequent behavior. These changes were consistent with strengthened functional connections from the leading electrode to the lagging electrode. We then trained rats to respond to a microstimulation cue, and repeated the paradigm using the cue electrode as the leading electrode. This pairing lowered the rat’s ICMS detection threshold, with the same dependence on intra-electrode time lag that we found for the functional connectivity changes. The timecourse of the behavioral effects was very similar to that of the connectivity changes. We propose that the behavioral changes were a consequence of strengthened functional connections from the cue electrode to other regions of sensorimotor cortex. Such paradigms might be used to augment recovery from stroke, or to promote adaptation in a bidirectional brain machine interface. PMID:21252415

Rebesco, James M.; Miller, Lee E.

2011-01-01

123

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

124

Canal-otolith interactions and detection thresholds of linear and angular components during curved-path self-motion.  

PubMed

Gravitational signals arising from the otolith organs and vertical plane rotational signals arising from the semicircular canals interact extensively for accurate estimation of tilt and inertial acceleration. Here we used a classical signal detection paradigm to examine perceptual interactions between otolith and horizontal semicircular canal signals during simultaneous rotation and translation on a curved path. In a rotation detection experiment, blindfolded subjects were asked to detect the presence of angular motion in blocks where half of the trials were pure nasooccipital translation and half were simultaneous translation and yaw rotation (curved-path motion). In separate, translation detection experiments, subjects were also asked to detect either the presence or the absence of nasooccipital linear motion in blocks, in which half of the trials were pure yaw rotation and half were curved path. Rotation thresholds increased slightly, but not significantly, with concurrent linear velocity magnitude. Yaw rotation detection threshold, averaged across all conditions, was 1.45 +/- 0.81 degrees/s (3.49 +/- 1.95 degrees/s(2)). Translation thresholds, on the other hand, increased significantly with increasing magnitude of concurrent angular velocity. Absolute nasooccipital translation detection threshold, averaged across all conditions, was 2.93 +/- 2.10 cm/s (7.07 +/- 5.05 cm/s(2)). These findings suggest that conscious perception might not have independent access to separate estimates of linear and angular movement parameters during curved-path motion. Estimates of linear (and perhaps angular) components might instead rely on integrated information from canals and otoliths. Such interaction may underlie previously reported perceptual errors during curved-path motion and may originate from mechanisms that are specialized for tilt-translation processing during vertical plane rotation. PMID:20554843

MacNeilage, Paul R; Turner, Amanda H; Angelaki, Dora E

2010-08-01

125

Low-energy structure of above-threshold-ionization electron spectra: Role of the Coulomb threshold effect  

E-print Network

Recent experimental observations of above-threshold ionization of rare gas atoms and diatomic molecules by midinfrared laser fields [C. I. Blaga et al., Nat. Phys. 5, 335 (2009); W. Quan et al., Phys. Rev. Lett. 103, 093001 ...

Telnov, Dmitry A.; Chu, Shih-I

2011-06-10

126

Resonance and Threshold Phenomena in Low-Energy Electron Collisions with Molecules and Clusters  

NASA Astrophysics Data System (ADS)

A survey of resonance and threshold phenomena in low-energy electron collisions with molecules and clusters is presented. Following an introduction into the role of resonances to promote vibrational excitation and anion formation through electron attachment, we discuss recent progress in achieving high energy resolution, using optimized conventional setups and photoelectron methods (the latter achieving sub-meV energy widths in attachment studies). Discussing selected cases, we highlight threshold and resonance phenomena in electron scattering and attachment channels, as observed in recent high resolution experiments and characterized by improved theoretical models. The threshold behaviour for dissociative electron attachment proceeding through s-wave and p-wave capture is demonstrated for CCl4 and Cl2, respectively. Threshold peaks, vibrational Feshbach and outer-well resonances as well as boomerang-type oscillatory structures are discussed for the polar molecules HF, HCl, and CH3I. Narrow vibrational Feshbach resonances, observed in cluster anion formation due to electron attachment to molecular clusters of CO2 and N2O, and their size-dependent redshifts, illustrating the effects of solvation, are discussed and explained as diffuse weakly-bound electron states. We briefly address the recent observation and the relevance of vibrational resonances in positron-molecule collisions at energies below 0.5 eV, as observed in positron annihilation. We conclude with a brief summary and mention some perspectives for future work.

Hotop, H.; Rul, M.-W.; Fabrikant, I. I.

127

The threshold energy for defect production in SiC: A molecular dynamic study  

SciTech Connect

We discuss the results of molecular dynamics computer simulation studies of the threshold energy for defect production in {beta}-SiC. The simulations are performed with the Tersoff potential for SiC which provides accurate values of many of its defect properties. In addition, we show that it properly describes the melting behavior of SiC. Simulations were carried out for Si and C recoils in 3 dimensional cubic computational cells with periodic boundary conditions and up to 4096 atoms. The results show anisotropy in the threshold for Si and C recoils as well as for the recoil direction. The lowest threshold is 25 eV for C recoils along [111] and the highest is 85 eV for Si recoils along [110]. Details of the defect configurations obtained will be discussed.

Wong, J.; Diaz de la Rubia, T.; Guinan, M.W.; Tobin, M. [Lawrence Livermore National Lab., CA (United States); Perlado, J.M.; Perez, A.S.; Sanz, J. [Universidad Politecnica de Madrid (Spain). Instituto de Fusion Nuclear

1993-10-01

128

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

129

Separable effects of inversion and contrast-reversal on face detection thresholds and response functions: A sweep VEP study.  

PubMed

The human brain rapidly detects faces in the visual environment. We recently presented a sweep visual evoked potential approach to objectively define face detection thresholds as well as suprathreshold response functions (Ales, Farzin, Rossion, & Norcia, 2012). Here we determined these parameters are affected by orientation (upright vs. inverted) and contrast polarity (positive vs. negative), two manipulations that disproportionately disrupt the perception of faces relative to other object categories. Face stimuli parametrically increased in visibility through phase -descrambling while alternating with scrambled images at a fixed presentation rate of 3 Hz (6 images/s). The power spectrum and mean luminance of all stimuli were equalized. As a face gradually emerged during a stimulation sequence, EEG responses at 3 Hz appeared at ?35% phase coherence over right occipito-temporal channels, replicating previous observations. With inversion and contrast-reversal, the 3-Hz amplitude decreased by ?20%-50% and the face detection threshold increased by ?30%-60% coherence. Furthermore, while the 3-Hz response emerged abruptly and saturated quickly for normal faces, suggesting a categorical neural response, the response profile for inverted and negative polarity faces was shallower and more linear, indicating gradual and continuously increasing activation of the underlying neural population. These findings demonstrate that inversion and contrast-reversal increase the threshold and modulate the suprathreshold response function of face detection. PMID:25761329

Liu-Shuang, Joan; Ales, Justin; Rossion, Bruno; Norcia, Anthony M

2015-01-01

130

Gap detection threshold in the rat before and after auditory cortex ablation.  

PubMed

Gap detection threshold (GDT) was measured in adult female pigmented rats (strain Long-Evans) by an operant conditioning technique with food reinforcement, before and after bilateral ablation of the auditory cortex. GDT was dependent on the frequency spectrum and intensity of the continuously present noise in which the gaps were embedded. The mean values of GDT for gaps embedded in white noise or low-frequency noise (upper cutoff frequency 3 kHz) at 70 dB sound pressure level (SPL) were 1.57+/-0.07 ms and 2.9+/-0.34 ms, respectively. Decreasing noise intensity from 80 dB SPL to 20 dB SPL produced a significant increase in GDT. The increase in GDT was relatively small in the range of 80-50 dB SPL for white noise and in the range of 80-60 dB for low-frequency noise. The minimal intensity level of the noise that enabled GDT measurement was 20 dB SPL for white noise and 30 dB SPL for low-frequency noise. Mean GDT values at these intensities were 10.6+/-3.9 ms and 31.3+/-4.2 ms, respectively. Bilateral ablation of the primary auditory cortex (complete destruction of the Te1 and partial destruction of the Te2 and Te3 areas) resulted in an increase in GDT values. The fifth day after surgery, the rats were able to detect gaps in the noise. The values of GDT observed at this time were 4.2+/-1.1 ms for white noise and 7.4+/-3.1 ms for low-frequency noise at 70 dB SPL. During the first month after cortical ablation, recovery of GDT was observed. However, 1 month after cortical ablation GDT still remained slightly higher than in controls (1.8+/-0.18 for white noise, 3.22+/-0.15 for low-frequency noise, P<0.05). A decrease in GDT values during the subsequent months was not observed. PMID:12361878

Syka, J; Rybalko, N; Mazelová, J; Druga, R

2002-10-01

131

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

132

Systematics of threshold incident energy for deep sub-barrier fusion hindrance  

SciTech Connect

We systematically evaluate the potential energy at the touching configuration for heavy-ion reactions using various potential models. We point out that the energy at the touching point, especially that estimated with the Krappe-Nix-Sierk (KNS) potential, strongly correlates with the threshold incident energy for steep falloff of fusion cross sections observed recently for several systems at extremely low energies. This clearly indicates that the steep fall-off phenomenon can be attributed to the dynamics after the target and projectile touch with each other, e.g., the tunneling process and the nuclear saturation property in the overlap region.

Ichikawa, Takatoshi [RIKEN Nishina Center, RIKEN, Wako, Saitama 351-0198 (Japan); Hagino, Kouichi [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Iwamoto, Akira [Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan)

2007-06-15

133

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

134

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

135

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

136

$J/?$ suppression in the threshold model at RHIC and LHC energy  

E-print Network

In the QGP based threshold model \\cite{Blaizot:2000ev,Blaizot:1996nq}, in addition to the normal nuclear absorption, $J/\\psi$'s are subjected to an 'anomalous' suppression such that above a threshold density $n_{J/\\psi}$, all the $J/\\psi$'s are melted. In the threshold model we have analysed the recent PHENIX data on the centrality dependence of $J/\\psi$ suppression in Au+Au collisions at RHIC. Feedback from decay of the state $\\chi$ is accounted for. $J/\\psi$'s are anomalously suppressed above a threshold density, $n_{J/\\psi}=3.57\\pm 0.17$ $fm^{-2}$. Threshold density for anomalous suppression of the state $\\chi$ is uncertain to a large extent, $n_\\chi=0.32 \\pm 0.32$ $fm^{-2}$. The fraction $F$ of the state $\\chi$ can not be determined unambiguously, depending on the nuclear absorption, it can vary from 20% to 40%. We have also predicted for the suppression in Pb+Pb collisions at LHC energy. In central Pb+Pb collisions, $J/\\psi$'s are suppressed by a factor of 3-4. Suppression pattern is rather similar to that in Au+Au collisions, if not slighty less in central collisions. Using the PHENIX data on the participant number dependence of the Bjorken energy density, we have also estimated the QGP formation time. For critical temperature $T_c$=192 MeV, estimated QGP formation time ranges between 0.07-0.09 fm/c.

A. K. Chaudhuri

2007-11-14

137

Empirical bayesian random censoring threshold model improves detection of differentially abundant proteins.  

PubMed

A challenge in proteomics is that many observations are missing with the probability of missingness increasing as abundance decreases. Adjusting for this informative missingness is required to assess accurately which proteins are differentially abundant. We propose an empirical Bayesian random censoring threshold (EBRCT) model that takes the pattern of missingness in account in the identification of differential abundance. We compare our model with four alternatives, one that considers the missing values as missing completely at random (MCAR model), one with a fixed censoring threshold for each protein species (fixed censoring model) and two imputation models, k-nearest neighbors (IKNN) and singular value thresholding (SVTI). We demonstrate that the EBRCT model bests all alternative models when applied to the CPTAC study 6 benchmark data set. The model is applicable to any label-free peptide or protein quantification pipeline and is provided as an R script. PMID:25102230

Koopmans, Frank; Cornelisse, L Niels; Heskes, Tom; Dijkstra, Tjeerd M H

2014-09-01

138

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

PubMed

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

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

2014-09-01

139

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

E-print Network

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

Nabile Boussaid; Sylvain Golénia

2009-06-08

140

Observation of a translational energy threshold for a highly exoergic ion?molecule reaction  

E-print Network

of 1 Januarv 1974 for a fuller description of Letters to the Editor. COMMUNICATIONS Observation of a translational energy threshold for a highly exoergic ion-molecule reaction * J. R. Wyattt, L. W. Strattan, S. C. Snyder, and P. M. Hierl Department...V (c. m.). The beam instrument (single beam-collision chamber configuration with product velocity and angular analysis) used in this study has been described. 2 The product velocity vector distributions peak considerably forward of the center...

Wyatt, J. R.; Strattan, L. W.; Snyder, S. C.; Hierl, Peter M.

1974-01-01

141

DETECTION AND IDENTIFICATION THRESHOLD VALUES FOR KEY FLAVOR COMPONENTS IN AN ORANGE JUICE MATRIX  

Technology Transfer Automated Retrieval System (TEKTRAN)

Due to the complex nature of orange juice, threshold values for key flavor components could differ significantly from those values reported in simpler systems, like water. In order to provide the citrus industry with reference values closer to the real situation in orange juice, different orange ju...

142

Changes to somatosensory detection and pain thresholds following high frequency repetitive TMS of the motor cortex in individuals suffering from chronic pain  

Microsoft Academic Search

Research has shown that transcranial magnetic stimulation (TMS) results in a transient reduction in the experience of chronic pain. The present research aimed to investigate whether a single session of high frequency TMS is able to change the sensory thresholds of individuals suffering from chronic pain. Detection and pain thresholds for cold and heat sensations were measured before and after

Sama Johnson; Jeff Summers; Saxby Pridmore

2006-01-01

143

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

144

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

145

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

146

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

NASA Astrophysics Data System (ADS)

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

Gómez Camacho, A.; Aguilera, E. F.

2014-12-01

147

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

E-print Network

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

Davide Faranda; Valerio Lucarini; Paul Manneville; Jeroen Wouters

2014-03-21

148

Blur detection thresholds in childhood myopia: single and dual target presentation  

Microsoft Academic Search

There is some suggestion that the ability to detect blur may be altered in adults with myopia. Here, we address the question of whether children with myopia have worse blur detection than other children, and whether blur detection in myopic children is related to the rate of myopia progression. We recruited 20 myopes and 20 non-myopes aged between 8 and

Katrina L Schmid; D Robert Iskander; Roger W. H Li; Marion H Edwards; John K. F Lew

2002-01-01

149

A Bragg curve counter with an active cathode to improve the energy threshold in fragment measurements  

NASA Astrophysics Data System (ADS)

We have developed a Bragg curve counter (BCC) equipped with an active cathode to extend the energy acceptance to lower energies than for a conventional BCC to measure differential cross-sections of fragment production reactions induced by tens of MeV protons. The signal from the active cathode providing the timing signal of fragment incidence and the time difference signal between the cathode and anode gives information on the fragment range in the BCC on the basis of electron drift time. Utilization of the range information made possible identification of fragments less than 0.5 MeV/u that is lower than the identification threshold of a conventional BCC technique. After investigations on fundamental properties of a newly constructed BCC using heavy ion beams and alpha-particles, this method was applied successfully to a fragment production measurement for 70 MeV proton-induced reactions on carbon. With this technique, the energy threshold of the BCC was improved without introducing an additional detector or energy loss.

Sanami, T.; Hagiwara, M.; Oishi, T.; Baba, M.; Takada, M.

2008-05-01

150

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

NASA Technical Reports Server (NTRS)

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

Bhatia, Anand

2008-01-01

151

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

NASA Technical Reports Server (NTRS)

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

Bhatia, A. K.; Temkin, A.

2007-01-01

152

Automatic threshold-setting method for iris detection for brown eyes in an eye-gaze interface system with a visible light camera  

NASA Astrophysics Data System (ADS)

This study describes the improvement of an eye-gaze interface system with a visible light camera. The current system detects the center of the iris from a captured eye image using image processing. During the initial stages of system use, a display window is provided to set the threshold values of the image's saturation and intensity, which is used to manually adjust the appearance of the iris region. In this study, we propose an automatic threshold setting method. The optimum threshold value for the saturation is obtained by discriminant analysis and that for the intensity is determined by finding the value that yields the same number of accumulated pixels in the detected region as threshold processing of the saturation. In our experiments with subjects with brown eyes, the automatic method obtained good threshold values in most cases. Furthermore, an adjustment function to overcome under- or over-estimated saturation threshold values is also proposed. This function provides a more robust automatic threshold setting. In experiments, we compared our automatic setting method with conventional manual techniques, which showed that the automatic method is useful for reducing the time required for threshold setting and its pointing accuracy is comparable to that of the manual approach.

Ogata, Kohichi; Niino, Shingo

2015-03-01

153

Pressure and particle motion detection thresholds in fish: a re-examination of salient auditory cues in teleosts.  

PubMed

The auditory evoked potential technique has been used for the past 30 years to evaluate the hearing ability of fish. The resulting audiograms are typically presented in terms of sound pressure (dB re. 1 ?Pa) with the particle motion (dB re. 1 m s(-2)) component largely ignored until recently. When audiograms have been presented in terms of particle acceleration, one of two approaches has been used for stimulus characterisation: measuring the pressure gradient between two hydrophones or using accelerometers. With rare exceptions these values are presented from experiments using a speaker as the stimulus, thus making it impossible to truly separate the contribution of direct particle motion and pressure detection in the response. Here, we compared the particle acceleration and pressure auditory thresholds of three species of fish with differing hearing specialisations, goldfish (Carassius auratus, weberian ossicles), bigeye (Pempheris adspersus, ligamentous hearing specialisation) and a third species with no swim bladder, the common triplefin (Forstergyian lappillum), using three different methods of determining particle acceleration. In terms of particle acceleration, all three fish species have similar hearing thresholds, but when expressed as pressure thresholds goldfish are the most sensitive, followed by bigeye, with triplefin the least sensitive. It is suggested here that all fish have a similar ability to detect the particle motion component of the sound field and it is their ability to transduce the pressure component of the sound field to the inner ear via ancillary hearing structures that provides the differences in hearing ability. Therefore, care is needed in stimuli presentation and measurement when determining hearing ability of fish and when interpreting comparative hearing abilities between species. PMID:22693030

Radford, Craig A; Montgomery, John C; Caiger, Paul; Higgs, Dennis M

2012-10-01

154

The detection threshold for extremely low frequency magnetic fields may be below 1000 nT-Hz in mice.  

PubMed

Previous experiments with mice have shown that a repeated 1 h daily exposure to an ambient magnetic field shielded environment induces analgesia (anti-nociception). This shielding reduces ambient static and extremely low frequency magnetic fields (ELF-MF) by approximately 100 times for frequencies below 120 Hz. To determine the threshold of ELF-MF amplitude that would attenuate or abolish this effect, 30 and 120 Hz magnetic fields were introduced into the shielded environment at peak amplitudes of 25, 50, 100 and 500 nT. At 30 Hz, peak amplitudes of 50, 100, and 500 nT attenuated this effect in proportion to the amplitude magnitude. At 120 Hz, significant attenuation was observed at all amplitudes. Exposures at 10, 60, 100, and 240 Hz with peak amplitudes of 500, 300, 500, and 300 nT, respectively, also attenuated the induced analgesia. No exposure abolished this effect except perhaps at 120 Hz, 500 nT. If the peak amplitude frequency product was kept constant at 6000 nT-Hz for frequencies of 12.5, 25, 50, and 100 Hz, the extent of attenuation was constant, indicating that the detection mechanism is dependent on the nT-Hz product. A plot of effect versus the induced current metric nT-Hz suggests a threshold of ELF-MF detection in mice at or below 1000 nT-Hz. PMID:21381048

Prato, Frank S; Desjardins-Holmes, Dawn; Keenliside, Lynn D; DeMoor, Janice M; Robertson, John A; Stodilka, Robert Z; Thomas, Alex W

2011-10-01

155

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

PubMed

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

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

2013-03-01

156

DYNAMIC THRESHOLDING METHOD FOR IMPROVING CONTAMINANT DETECTION ACCURACY WITH HYPERSPECTRAL IMAGES  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

157

A Dynamic Threshold Approach to Fault Detection in Uninhabited Aerial Vehicles  

Microsoft Academic Search

The integration of UAVs into civil airspace is hampered by the inability to asses and guarantee safety and reliability properties of these systems. The paper outlines a software oriented approach for the real-time detection of faults in multi-modal hybrid systems. Online model generation of continuous variables enables the detection of multiple faults, while managing computational complexity. The aileron control loop

Andres E. Ortiz; Natasha A. Neogi

158

Threshold quantum cryptography  

SciTech Connect

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

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

2005-01-01

159

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

160

Threshold effect in the energy loss of slow protons and deuterons channeled in Au crystals  

NASA Astrophysics Data System (ADS)

Measurements of the energy loss of protons and deuterons channeled in a very thin single-crystal foil of gold were performed, covering the range of very low velocities. The experimental results provide clear evidence of the deviation of the energy loss from the proportionality with ion velocity predicted theoretically, showing a transition between two well-defined regimes. We explain this behavior by a theoretical analysis that takes into account the electronic band structure properties of the medium, separating the contribution of the conduction band (described as a free Fermi gas) from the contribution of the nearly free d electrons of gold, which are affected by a threshold behavior due to the shift of the density of states of this band with respect to the Fermi level. The theoretical model yields a very good description of the experimental findings.

Figueroa, E. A.; Cantero, E. D.; Eckardt, J. C.; Lantschner, G. H.; Valdés, J. E.; Arista, N. R.

2007-01-01

161

Unconstrained Respiration Measurement and Respiratory Arrest Detection Method by Dynamic Threshold in Transferring Patients by Stretchers  

NASA Astrophysics Data System (ADS)

General anesthesia used for surgical operations may cause unstable conditions of the patients after the operations, which could lead to respiratory arrests. Under such circumstances, nurses could fail in finding the change of the conditions, and other malpractices could also occur. It is highly possible that such malpractices may occur while transferring a patient from ICU to the room using a stretcher. Monitoring the change in the blood oxygen saturation concentration and other vital signs to detect a respiratory arrest is not easy when transferring a patient on a stretcher. Here we present several noise reduction system and algorithm to detect respiratory arrests in transferring a patient, based on the unconstrained air pressure method that the authors presented previously. As the result, when the acceleration level of the stretcher noise was 0.5G, the respiratory arrest detection ratio using this novel method was 65%, while that with the conventional method was 0%.

Kurihara, Yosuke; Watanabe, Kajiro; Kobayashi, Kazuyuki; Tanaka, Hiroshi

162

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

163

The effect of white and filtered noise on contrast detection thresholds  

Microsoft Academic Search

Models of the dipper effect seen in contrast discrimination experiments predict that small amounts of noise should facilitate detection of a subthreshold sinusoidal grating. Although facilitation of chromatic sine waves has been measured with chromatic or luminance noise, a facilitory effect of luminance sinusoidal gratings has not been measured, most likely because the stimulus characteristics were not tuned for revealing

Kim T. Blackwell

1998-01-01

164

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

PubMed Central

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

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

2013-01-01

165

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

166

Variability-Aware Design of Energy-Delay Optimal Linear Pipelines Operating in the Near-Threshold Regime and Above  

E-print Network

of Electrical Engineering Los Angeles, California, United States, 90089 {xqing, yanzhiwa, pedram and substrate temperature changes. This paper thus addresses the issue of variability-aware design of energy operation, in particular, near-threshold (NT) operation, is very effective in minimizing energy consumption

Pedram, Massoud

167

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

NASA Astrophysics Data System (ADS)

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

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

2009-10-01

168

Stiffness and strain energy criteria to evaluate the threshold of injury to an intervertebral joint.  

PubMed

This study is focused to evaluate the threshold of injury to an intervertebral joint based on its mechanical response. The load-deflection behavior of the intervertebral joint indicated non-linear and sigmoidal characteristics with continuously changing stiffness (a measure of the ability to withstand external force). The load corresponding to the point of zero stiffness was identified, according to the classical theories of mechanics, as the maximum load carrying capacity. Further, the initiation of trauma was defined to occur at the point on the load-deflection curve at which the stiffness begins to decrease for the first time. The load, stiffness and energy absorbing capabilities of normal and degenerated intervertebral joints at the initiation of trauma was determined. Axial compressive load experiments were conducted on nine intervertebral joints of fresh human male cadavers and the resulting load-deflection responses were transformed into stiffness-deflection responses using the derivative principle. Energy characteristics were also derived. Load, stiffness and energy at the initiation of trauma were found to be 9.0 kN, 2850 N mm-1, and 10.2 J for normal and 4.4 kN, 1642 N mm-1, and 5.8 J for degenerated segments, respectively. The load and energy values at failure were 11.0 kN, and 18.0 J for normal and 5.3 kN and 5.7 J for degenerated intervertebral joints, respectively. PMID:2708393

Yoganandan, N; Ray, G; Pintar, F A; Myklebust, J B; Sances, A

1989-01-01

169

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

170

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

Code of Federal Regulations, 2011 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:...

2011-07-01

171

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

Code of Federal Regulations, 2013 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:...

2013-07-01

172

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

Code of Federal Regulations, 2012 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:...

2012-07-01

173

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

Code of Federal Regulations, 2014 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:...

2014-07-01

174

Visible Contrast Energy Metrics for Detection and Discrimination  

NASA Technical Reports Server (NTRS)

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

Ahumada, Albert; Watson, Andrew

2013-01-01

175

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

176

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

177

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

178

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

NASA Astrophysics Data System (ADS)

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

Song, Taesoo; Ko, Che Ming

2015-01-01

179

Threshold effect in the energy-loss straggling of protons channeled in Au?100? at very low velocities  

NASA Astrophysics Data System (ADS)

The energy-loss straggling of protons channeled in gold crystals in the ?100? direction has been experimentally and theoretically studied at the low-velocity limit. The experimental results show a threshold effect in the straggling values, which is similar to that observed earlier in the energy loss. This effect is described by a theoretical model which explains the velocity dependence by considering the individual features of the contributions of free electrons in the conduction band and the nearly free (5d10) electrons which generate a threshold effect at low energies due to their binding energy. The model predicts a deviation of proportionality with ion velocity of the energy-loss spread and yields a good description of the obtained experimental data.

Figueroa, E. A.; Cantero, E. D.; Eckardt, J. C.; Lantschner, G. H.; Arista, N. R.

2007-06-01

180

High-energy above-threshold ionization revisited within an alternative strong-field approach.  

NASA Astrophysics Data System (ADS)

The highly-nonlinear multiphoton phenomenon of high-energy above-threshold ionization (HATI) of an atomic system by an intense laser field is considered theoretically and studied numerically within frame of a new fully quantum-mechanical strong-field approach developed earlier for effective numerical calculation of high-order harmonic generation spectra [1]. The proposed strong-field approach is based on the standard Keldysh approximation combined with a specific making use of the ``essential states'' method (see, e.g., [2] for details) and related the ``pole approximation'' that both applied together allow to derive of the final expressions for total ATI probability rates in closed and compact analytical (so-called the factorized) form quite transparent for interpretation and available for direct numerical calculations. To demonstrate the model availability, a number of certain HATI spectra produced by various atomic systems (mostly noble gas atoms and hydrogen negative ion) and respective rescattered ATI electron angular distributions (viz., side-lobes or so-called ``rings'') corresponding to a certain ATI peaks within a high-energy plateau region have been calculated and shown that they all are well consistent with typical ones measured in experiments or calculated within frame of different (but, more sophisticated analytically or computation demanding) approaches and methods developed earlier. Moreover, with a fairly good accuracy, the calculated HATI photoelectron spectra all reproduce the conventional phenomenological rule for the extent of high-energy plateau and position of its cut-off energy. References [1] V. I. Usachenko and V. A. Pazdzersky, ''High-order harmonic generation in a strong laser field: An alternative quantum-mechanical SFA-model'', J.Phys. B: At. Mol. Opt. Phys. (2002) (in press). [2] M.V. Fedorov, Atomic and Free Electrons in a Strong Light Field, ed. (World Sci., Singapore, 1997).

Usachenko, Vladimir; Pazdzersky, Vladimir; McIver, John

2002-05-01

181

Tunnel effect wave energy detection  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

182

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

NASA Astrophysics Data System (ADS)

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

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

2009-10-01

183

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

184

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

PubMed

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

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

2014-11-01

185

The influence of microhydration on the ionization energy thresholds of uracil and thymine.  

PubMed

In the present study the ionization energy thresholds (IET's) of uracil and thymine have been calculated (with the B3LYP, PMP2, and P3 levels of theory using the standard 6-31++G(d,p) basis set) with one to three water molecules placed in the first hydration shell. Then (B3LYP) polarizable continuum model (PCM) calculations were performed with one to three waters of the hydration shell included. Calculations show there is a distinct effect of microhydration on uracil and thymine. For uracil, one added water results in a decrease in the IET of about 0.15 eV. The second and third water molecules cause a further decrease by about 0.07 eV each. For thymine, the first water molecule is seen to decrease the IET by about 0.1 eV, while the second and third water molecules cause a further decrease of less than 0.1 eV each. The changes in IET calculated here for thymine with one to three waters of hydration are smaller than the experimental values determined by Kim et al. (Kim, S. K.; Lee, W.; Herschbach, D. R. J. Phys. Chem. 1996, 100, 7933). Preliminary results presented here indicate that the experimental results may involve keto-enol tautomers of thymine. The results of placing the microhydrated structures of uracil and thymine in a PCM cavity was seen to make very little difference in the IET when compared to the IET of ordinary uracil or thymine in a PCM cavity. The implications are that accurate calculations of the IET's of uracil and thymine can be obtained by simply considering long-range solvation effects. PMID:16833269

Close, David M; Crespo-Hernández, Carlos E; Gorb, Leonid; Leszczynski, Jerzy

2005-10-20

186

High Energy Polarization of Blazars: Detection Prospects  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

187

Resonance phenomena near thresholds  

SciTech Connect

The trapping effect is investigated close to the elastic threshold. The nucleus is described as an open quantum mechanical many-body system embedded in the continuum of decay channels. An ensemble of compound nucleus states with states below and above threshold is investigated in an energy-dependent formalism. It is shown that the states below threshold can trap the resonance ones and also that they can directly influence the scattering cross section. {copyright} {ital 1996 The American Physical Society.}

Persson, E.; Mueller, M.; Rotter, I. [Forschungszentrum Rossendorf, Institut fuer Kern- und Hadronenphysik, D-01314 Dresden (Germany)] [Forschungszentrum Rossendorf, Institut fuer Kern- und Hadronenphysik, D-01314 Dresden (Germany); [Technische Universitaet Dresden, Institut fuer Theoretische Physik, D-01062 Dresden (Germany)

1996-06-01

188

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

NASA Astrophysics Data System (ADS)

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

Miloševi?, D. B.

2014-12-01

189

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

NASA Astrophysics Data System (ADS)

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

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

2000-11-01

190

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. PMID:25360107

Doi, Takahiro; Fujita, Ichiro

2014-01-01

191

Design of an energy management strategy for parallel hybrid electric vehicles using a logic threshold and instantaneous optimization method  

Microsoft Academic Search

A novel parallel hybrid electric vehicle (PHEV) configuration consisting of an extra one-way clutch and an automatic mechanical\\u000a transmission (AMT) is taken as the study subject of this paper. An energy management strategy (EMS) combining a logic threshold\\u000a approach and an instantaneous optimization algorithm is developed for the investigated PHEV. The objective of this EMS is\\u000a to achieve acceptable vehicle

Y.-J. Huang; C.-L. Yin; J.-W. Zhang

2009-01-01

192

Alternative Detection Methods for Highest Energy Neutrinos  

E-print Network

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

Rolf Nahnhauer

2004-11-26

193

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

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

194

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

195

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

SciTech Connect

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

Gallup, Gordon A.; Fabrikant, Ilya I. [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588-0111 (United States)

2007-03-15

196

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

NASA Astrophysics Data System (ADS)

Cross sections for elastic and inelastic electron collisions with CH3X (X=Cl, Br, I) molecules are calculated. For the lowest partial wave the resonance R-matrix theory, and for the higher partial waves the theory of scattering by dipolar plus polarization potential, are used. It is shown that the rotationally elastic scattering amplitude for a polar molecule in the fixed-nuclei approximation is logarithmically divergent for the forward direction, and a new closure formula is derived to speed up the convergence at small angles. The dipole moment as a function of the C--X distance is modeled semiempirically. This is supplemented by ab initio calculations of the dipole moment function for CH3Br using the multi-configurational valence bond method. The results for scattering cross sections show pronounced features caused by vibrational Feshbach resonances and threshold cusps. The features are most noticeable at the v=6, 7, and 8 thresholds in CH3Cl, at the v=3 and 4 thresholds in CH3Br and at the v=1 threshold in CH3I. The authors are grateful to H. Hotop for many stimulating discussions.

Fabrikant, Ilya; Gallup, Gordon

2007-06-01

197

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

NASA Astrophysics Data System (ADS)

Cross sections for elastic and inelastic electron collisions with CH3X (X=Cl,Br,I) molecules are calculated. For the lowest partial wave, the resonance R -matrix theory, and for the higher partial waves, the theory of scattering by dipolar plus polarization potential, are used. It is shown that the rotationally elastic scattering amplitude for a polar molecule in the fixed-nuclei approximation is logarithmically divergent for the forward direction, and a closure formula is derived to speed up the convergence at small angles. In treating the nuclear motion, only C-X stretch vibrations are taken into account. The dipole moment as a function of the C-X distance is modeled by a function incorporating the experimental value of the molecular dipole moments at the equilibrium distance and the derivatives of the dipole moments extracted from the experimental data on infrared intensities. This is supplemented by ab initio calculations of the dipole moment function for CH3Br using the multiconfigurational valence bond method. The results for scattering cross sections show pronounced features caused by vibrational Feshbach resonances and threshold cusps. The features are most noticeable at the v=6 , 7, and 8 thresholds in CH3Cl , at the v=3 and 4 thresholds in CH3Br , and at the v=1 threshold in CH3I .

Gallup, Gordon A.; Fabrikant, Ilya I.

2007-03-01

198

Theoretical model calculation of dosimetry cross-sections for cobalt from threshold energy to 50 MeV  

SciTech Connect

Dosimetry cross-sections of the threshold reactions for cobalt have been calculated by the GNASH code in the energy region up to 50 MeV for the application in accelerator-based high energy neutron fields. The dosimetry cross-sections of (n,2n), (n,3n), (n,4n), (n,p), (n, {alpha}), (n,2n {alpha} ) as well as helium accumulation cross-section (n,He) were calculated. The (n,2n {alpha} ) reaction can be a new, promising dosimetry reaction in the region from 30 to 50 MeV.

Iwasaki, S. [Tohoku Univ., Sendai (Japan); Odano, N. [Ship Research Institute, Ibaragi-ken (Japan)

1994-12-31

199

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

200

High Energy Polarization of Blazars : Detection Prospects  

E-print Network

Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (wit...

Chakraborty, Nachiketa; Fields, Brian

2015-01-01

201

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

202

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

203

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

204

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

E-print Network

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

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

2015-01-07

205

Frequency-locking and threshold current-lowering effects of a quantum cascade laser and an application in gas detection field  

NASA Astrophysics Data System (ADS)

In this paper, the frequency-locking and threshold current-lowering effects of a quantum cascade laser are studied and achieved. Combined with cavity-enhanced absorption spectroscopy, the noninvasive detection of H2 with a prepared concentration of 500 ppm in multiple dissolved gases is performed and evaluated. The high frequency selectivity of 0.0051 cm?1 at an acquisition time of 1 s allows the sensitive detection of the (1-0) S(1) band of H2 with a high accuracy of (96.53±0.29)% and shows that the detection limit to an absorption line of 4712.9046 cm?1 is approximately (17.26±0.63) ppm at an atmospheric pressure and a temperature of 20 °C. Project supported by the Special Funds for the Development of National Major Scientific Instruments and Equipment, China (Grant No. 2012YQ160007) and the National Natural Science Foundation of China (Grant No. 51277185).

Chen, Wei-Gen; Wan, Fu; Zou, Jing-Xin; Gu, Zhao-Liang; Zhou, Qu

2015-02-01

206

Spatial Variable Thresholding for SCALES  

Microsoft Academic Search

The Stochastic Coherent Adaptive Large Eddy Simulation (SCALES) is a novel wavelet-based approach that resolves energy containing turbulent motions using wavelet multiresolution decomposition and self-adaptivity. The extraction of the most energetic structures is achieved using wavelet thresholding filter with a priori prescribed threshold level. This strategy, although successful, has a major drawback: the thresholding criterion is global and does not

Alireza Nejadmalayeri; Oleg V. Vasilyev; Alexei Vezolainen; Giuliano de Stefano

2009-01-01

207

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

208

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

Microsoft Academic Search

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

ANNE B. LOUCKS; JEAN R. THUMA

2010-01-01

209

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

PubMed

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

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

2013-06-01

210

[Empirical mode of combination of the wavelet threshold filtering and empirical mode decomposition (EMD) based on energy estimate].  

PubMed

According to the frequency overlapping of intrinsic mode function (IMF) based on the temporal and spatial filtering of empirical mode decomposition (EMD), which will lead to the question of useful signals and noises filtered together, we proposed a method that numbers of IMF is determined by energy estimate, temporal and spatial filtering combing wavelet threshold and EMD integrating wavelet local signal characteristics of time and scale domain. This method not only used multi-resolution wavelet transform features, but also combined the EMD and Hilbert decomposition of the adaptive spectral analysis of instantaneous frequency and significance of the relationship between energy, so as to solve the problem of useful signal being weakened. With MIT/BIH ECG database standard data subjects, experimental results showed it was an effective method of data processing for handling this type of physiological signals under strong noise. PMID:22295693

Li, Xin; Wang, Huihui; Wang, Yueru; Zhao, Fangfang

2011-12-01

211

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

Microsoft Academic Search

Solving the key issue of sustainability of battery-powered sensors continues to attract significant research attention. The prevailing theme of this research is to address this concern using energy-efficient protocols based on a form of simple cooperative transmission (CT) called the opportunistic large arrays (OLAs), and intelligent exploitation of energy harvesting and hybrid energy storage systems (HESSs). The two key contributions

Aravind Kailas

2010-01-01

212

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

PubMed

Falls in the elderly population are a major problem for today's society. The immediate automatic detection of such events would help reduce the associated consequences of falls. This paper describes the development of an accurate, accelerometer-based fall detection system to distinguish between Activities of Daily Living (ADL) and falls. It has previously been shown that falls can be distinguished from normal ADL through vertical velocity thresholding using an optical motion capture system. In this study however accurate vertical velocity profiles of the trunk were generated by simple signal processing of the signals from a tri-axial accelerometer (TA). By recording simulated falls onto crash mats and ADL performed by 5 young healthy subjects, using both a single chest mounted TA and using an optical motion capture system, the accuracy of the vertical velocity profiles was assessed. Data analysis was performed using MATLAB to determine the peak velocities recorded and RMS error during four different fall and six ADL types. Results show high correlations and low percentage errors between the vertical velocity profiles generated by the TA to those recorded using the optical motion capture system. In addition, through thresholding of the vertical velocity profiles generated using the TA at -1.3m/s, falls can be distinguished from normal ADL with 100% sensitivity and specificity. PMID:19163295

Bourke, Alan K; O'Donovan, Karol J; Nelson, John; OLaighin, Gearóid M

2008-01-01

213

Prediction of threshold impact energy for onset of delamination in quasi-isotropic carbon\\/epoxy composite laminates under low-velocity impact  

Microsoft Academic Search

This paper describes a procedure for the prediction of the threshold impact energy for the onset of delamination in fibre-reinforced quasi-isotropic laminates under low-velocity impact. It is primarily based upon two models. One is the energy-balance model which equates the kinetic energy of the impactor with the static deformation energy of the laminate. The geometrical non-linearity of the deformation of

G. A. O. Davies; D. Hitchings; J. Wang

2000-01-01

214

Thermal Detection Thresholds of A?- and C-Fibre Afferents Activated by Brief CO2 Laser Pulses Applied onto the Human Hairy Skin  

PubMed Central

Brief high-power laser pulses applied onto the hairy skin of the distal end of a limb generate a double sensation related to the activation of A?- and C-fibres, referred to as first and second pain. However, neurophysiological and behavioural responses related to the activation of C-fibres can be studied reliably only if the concomitant activation of A?-fibres is avoided. Here, using a novel CO2 laser stimulator able to deliver constant-temperature heat pulses through a feedback regulation of laser power by an online measurement of skin temperature at target site, combined with an adaptive staircase algorithm using reaction-time to distinguish between responses triggered by A?- and C-fibre input, we show that it is possible to estimate robustly and independently the thermal detection thresholds of A?-fibres (46.9±1.7°C) and C-fibres (39.8±1.7°C). Furthermore, we show that both thresholds are dependent on the skin temperature preceding and/or surrounding the test stimulus, indicating that the A?- and C-fibre afferents triggering the behavioural responses to brief laser pulses behave, at least partially, as detectors of a change in skin temperature rather than as pure level detectors. Most importantly, our results show that the difference in threshold between A?- and C-fibre afferents activated by brief laser pulses can be exploited to activate C-fibres selectively and reliably, provided that the rise in skin temperature generated by the laser stimulator is well-controlled. Our approach could constitute a tool to explore, in humans, the physiological and pathophysiological mechanisms involved in processing C- and A?-fibre input, respectively. PMID:22558230

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

2012-01-01

215

Interference Analysis and Sensing Threshold of Detect and Avoid (DAA) for UWB Coexistence with WiMax  

Microsoft Academic Search

Although ultra wideband (UWB) is a promising wireless technology for the future due to its high data rate, low power consumption, and low cost, its worldwide acceptance is conditioned by coexistence issues because of the frequency overlap with other wireless standards such as WiMax. In many countries, a detect and avoid (DAA) scheme has been promoted as a means to

Kwan-woo Kim; Jongmin Park; Jinyoun Cho; Kyutae Lim; Charles J. Razzell; Kihong Kim; Chang-ho Lee; Haksun Kim; Joy Laskar

2007-01-01

216

EVA space suit proton and electron threshold energy measurements by XCT and range shifting  

Microsoft Academic Search

Construction of the International Space Station (ISS) will require more than 1000h of extravehicular activity (EVA). Outside of the ISS during EVA, astronauts and cosmonauts are likely to be exposed to a large fluence of electrons and protons. Development of radiation protection guidelines and mitigation of risks requires the determination of the minimum energy of electrons and protons that penetrate

M. F. Moyers; P. B. Saganti; G. A. Nelson

2006-01-01

217

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

218

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

E-print Network

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

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

2011-03-23

219

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

220

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

221

K-shell ionization of Al induced by ions near the threshold energy  

NASA Astrophysics Data System (ADS)

The K-shell ionization cross sections of Al induced by H+ and Ne7+ were studied. The ionization cross sections obtained are compared with the predictions of ECPSSR theory (based on the perturbed-stationary-state approach including Coulomb deflection, energy loss and relativistic corrections), BEA (binary encounter approximation) and 1s? molecular-orbital ionization. It is found that the ECPSSR theoretical results agree with the experimental data very well for proton impact, while the BEA model with correction of Coulomb deflection shows good agreement with experimental results.

Wang, Xing; Zhao, Yongtao; Cheng, Rui; Zhou, Xianming; Lei, Yu; Sun, Yuanbo; Wang, Yuyu; Ren, Jieru; Yu, Yang; Li, Yongfeng; Xu, Ge; Zhang, Xiaoan; Li, Yaozong; Liang, Changhui; Xiao, Guoqing

2013-09-01

222

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

2013-01-28

223

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

PubMed Central

Despite their important role in security, little is known about the energy requirements of working dogs such as odor, explosive and human detection dogs. Previous researchers have evaluated the energy requirements of individual canine breeds as well as dogs in exercise roles such as sprint racing. This study is the first to evaluate the energy requirements of working dogs trained in odor, explosive and human detection. This retrospective study evaluated twenty adult dogs who maintained consistent body weights over a six month period. During this time, the average energy consumption was \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$136\\pm 38~\\mathrm{kcal}\\cdot {\\mathrm{BW}}_{\\mathrm{kg}}^{0.75}$\\end{document}136±38kcal?BWkg0.75 or two times the calculated resting energy requirement (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$\\mathrm{RER}=70~\\mathrm{kcal}\\cdot {\\mathrm{BW}}_{\\mathrm{kg}}^{0.75}$\\end{document}RER=70kcal?BWkg0.75). No statistical differences were found between breeds, age or sex, but a statistically significant association (p = 0.0033, R-square = 0.0854) was seen between the number of searches a dog performs and their energy requirement. Based on this study’s population, it appears that working dogs have maintenance energy requirements similar to the 1974 National Research Council’s (NRC) maintenance energy requirement of \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$132~\\mathrm{kcal}\\cdot {\\mathrm{BW}}_{\\mathrm{kg}}^{0.75}$\\end{document}132kcal?BWkg0.75 (National Research Council (NRC), 1974) and the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$139\\pm 42~\\mathrm{kcal}\\cdot {\\mathrm{BW}}_{\\mathrm{kg}}^{0.75}$\\end{document}139±42kcal?BWkg0.75 reported for young laboratory beagles (Rainbird & Kienzle, 1990). Additional research is needed to determine if these data can be applied to all odor, explosive and human detection dogs and to determine if other types of working dogs (tracking, search and rescue etc.) have similar energy requirements. PMID:25755919

Witzel, Angela L.; Price, Joshua

2015-01-01

224

Master Equation Analysis of Thermal Activation Reactions: Energy-Transfer Constraints on Falloff Behavior in the Decomposition of Reactive Intermediates with Low Thresholds  

E-print Network

with the high-temperature decomposition of reactive intermediates with low reaction thresholds) molecular size (heat capacity), high-pressure rate parameters, temperature, and pressure. At 101 kPa (1 atm temperatures or low pressures, unimo- lecular decompositions begin to be affected by energy-transfer effects

Zachariah, Michael R.

225

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

226

Electrophysiological correlates of the threshold to detection of passive motion: an investigation in professional volleyball athletes with and without atrophy of the infraspinatus muscle.  

PubMed

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

Salles, José Inácio; Cossich, Victor Rodrigues Amaral; Amaral, Marcus Vinicius; Monteiro, Martim T; Cagy, Maurício; Motta, Geraldo; Velasques, Bruna; Piedade, Roberto; Ribeiro, Pedro

2013-01-01

227

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

PubMed Central

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

Salles, José Inácio; Cossich, Victor Rodrigues Amaral; Amaral, Marcus Vinicius; Monteiro, Martim T.; Cagy, Maurício; Motta, Geraldo; Velasques, Bruna; Piedade, Roberto; Ribeiro, Pedro

2013-01-01

228

Detection and Analysis of Threats to the Energy Sector: DATES  

Microsoft Academic Search

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

Alfonso Valdes

2010-01-01

229

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

230

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

PubMed

Individual variability in the effects of opioid analgesics such as fentanyl remains a major challenge for tailored pharmacological treatment including postoperative analgesia. This study aimed to establish a new real-time method for detecting the effects of fentanyl and their individual differences in the preoperative period, using the pressure pain threshold (PPT) and Narcotrend index (NTI) test.Eighty women undergoing elective surgery under general anesthesia were enrolled in this randomized, double-blinded, placebo-controlled study to receive either intravenous fentanyl (Group F) or saline (Group S). Before (T1) and 5 (T2) and 10?min (T3) after intravenous injection, the PPT, NTI, respiratory rate, heart rate, blood pressure, and pulse oxygen saturation were measured. The initial time at which the Narcotrend index showed a decline was also recorded.In total, 40 patients in Group S and 38 patients in Group F were included in the final analysis. At 5?min and 10?min after intravenous fentanyl administration, the analgesic effect was determined by measuring the PPT, which was significantly increased (P?detected using the NTI, which was significantly decreased (P?detect the effects of fentanyl and their individual differences in real time before induction of anesthesia in the operation room. This method could potentially be applied to preoperatively determine patients' sensitivity to fentanyl. PMID:25569647

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

2015-01-01

231

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

232

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

SciTech Connect

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

Lee, Yu Ran; Kang, Do Won; Kim, Hong Lae, E-mail: chkwon@kangwon.ac.kr, E-mail: hlkim@kangwon.ac.kr; Kwon, Chan Ho, E-mail: chkwon@kangwon.ac.kr, E-mail: hlkim@kangwon.ac.kr [Department of Chemistry and Institute for Molecular Science and Fusion Technology, College of Natural Sciences, Kangwon National University, Chuncheon 200-701 (Korea, Republic of)

2014-11-07

233

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

234

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

235

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

236

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

SciTech Connect

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

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

2014-01-28

237

CERES Detects Earth's Heat and Energy  

NASA Technical Reports Server (NTRS)

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

2002-01-01

238

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

239

High Energy Electron Detection with ATIC  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

240

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

241

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

Microsoft Academic Search

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

Mengmeng Du; Hoi Lee; Jin Liu

2011-01-01

242

Resonance energy transfer methods of RNA detection  

Microsoft Academic Search

Quantitation of RNA is important in diagnostics, environmental science, and basic biomedical research. RNA is considered a\\u000a signature for pathogen identification, and its expression profile is linked with disease pathogenesis, allowing for biomarker\\u000a identification. RNA-based diagnostics is an emerging field of research. This expansion of interest in studying RNA has generated\\u000a demand for its accurate and sensitive detection. Several methods

Kyle A. Cissell; Eric A. Hunt; Sapna K. Deo

2009-01-01

243

A comparison of various strategies to equalize the lower energy thresholds of a CdTe Medipix2 hexa detector for X-ray imaging applications  

NASA Astrophysics Data System (ADS)

Technological advances have made possible the development of pixelized photon counting semiconductor detectors, many of which are used in X-ray imaging to resolve the spectral composition of the incident photons. Here, in a so-called Hexa detector, we employ a 3 × 2 array of Medipix2 MXR readout chips, bump bonded to a cadmium telluride sensor of 1 mm thickness with a pixel pitch of 165 ?m. Each pixel in this assembly offers two variable energy thresholds, which enables counting of only those photons within an energy range of interest. As manufacturing tolerances cause deviations in each of the pixel's responses, the two thresholds can be calibrated for every pixel to render their response to radiation more homogeneous. In this work, we compare various methods that we chose to equalize the lower thresholds: a) the noise edge of the detector electronics, the characteristic X-rays from b) silver and c) tantalum foils as well as flat fields obtained at d) 40 and e) 120 kVp. It will be shown that the energy dependence in the resulting adjustment bit maps are only small, whereas the question as to which strategy to choose (peak position vs. image homogeneity) will have a greater influence on the resulting corrections. Additionally, we observed a decrease in the mean adjustment values with increasing distance from the central axis of the Hexa detector under study.

Koenig, T.; Zuber, M.; Zwerger, A.; Schuenke, P.; Nill, S.; Fauler, A.; Fiederle, M.; Oelfke, U.

2011-01-01

244

Decentralized Computation of Threshold Crossing Alerts  

Microsoft Academic Search

Threshold crossing alerts (TCAs) indicate to a management system that a management variable, associated with the state, performance or health of the network, has crossed a certain threshold. The timely detection of TCAs is essential to proactive management. This paper focuses on detecting TCAs for network-level variables, which are computed from device-level variables using aggregation functions, such as SUM, MAX,

Fetahi Wuhib; Mads Dam; Rolf Stadler; Alexander Clemm

2005-01-01

245

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

NASA Technical Reports Server (NTRS)

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

Beal, R. C.

1980-01-01

246

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

PubMed

The double-differential cross sections (energy spectra) for the (n, px), (n, dx), (n, tx) and (n, rx) reactions on oxygen have been measured for nine incident neutron energies in the range 25 to 65 MeV at lab angles between 20 degrees and 160 degrees in steps of 10 degrees. From these measurements, the energy differential cross sections have been determined and consequently the partial and total kerma factors. Based on the obtained experimental partial kerma factors in the incident neutron energy range 25-65 MeV, a procedure is proposed for the extrapolation of these values to the reaction threshold energy of each measured reaction channel. Results of the experimental double-differential, energy differential and total cross sections are presented. The deduced partial and total kerma factors of the present work are compared with results of previous measurements and theoretical predictions. PMID:9869022

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

1998-12-01

247

Observation and analysis of structural changes in fused silica by continuous irradiation with femtosecond laser light having an energy density below the laser-induced damage threshold  

PubMed Central

Summary The laser-induced damage threshold (LIDT) is widely used as an index for evaluating an optical component’s resistance to laser light. However, a degradation in the performance of an optical component is also caused by continuous irradiation with laser light having an energy density below the LIDT. Therefore, here we focused on the degradation in performance of an optical component caused by continuous irradiation with femtosecond laser light having a low energy density, i.e., laser-induced degradation. We performed an in situ observation and analysis of an increase in scattering light intensity in fused silica substrates. In experiments conducted using a pulsed laser with a wavelength of 800 nm, a pulse width of 160 fs and pulse repetition rate of 1 kHz, we found that the scattered light intensity increased starting from a specific accumulated fluence, namely, that the laser-induced degradation had a threshold. We evaluated the threshold fluence F t as 6.27 J/cm2 and 9.21 J/cm2 for the fused silica substrates with surface roughnesses of 0.20 nm and 0.13 nm in R a value, respectively, showing that the threshold decreased as the surface roughness increased. In addition, we found that the reflected light spectrum changed as degradation proceeded. We analyzed the details of the degradation by measuring instantaneous reflectance changes with a pump–probe method; we observed an increase in the generation probability of photogenerated carriers in a degraded silica substrate and a damaged silica substrate and observed a Raman signal originating from a specific molecular structure of silica. From these findings, we concluded that compositional changes in the molecular structure occurred during degradation due to femtosecond laser irradiation having an energy density below the LIDT. PMID:25247116

Kawazoe, Tadashi; Yatsui, Takashi; Naruse, Makoto; Ohtsu, Motoichi

2014-01-01

248

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

249

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

PubMed Central

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

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

2014-01-01

250

Surface characterizations of color threshold  

NASA Technical Reports Server (NTRS)

The paper evaluates how well three different parametric shapes, ellipsoids, rectangles, and parallelograms, serve as models of three-dimentional detection contours. The constraints of the procedures for deriving the best-fitting shapes on inferences about the theoretical visual detection mechanisms are described. Results of two statistical tests show that only the parallelogram fits the data with more precision than the variance in repeated threshold measurements, and thus provides a slightly better fit than the other two shapes. Nevertheless it does not serve as a better guide than the ellipsoidal model for interpolating from the measurements to thresholds in novel color directions.

Poirson, Allen B.; Wandell, Brian A.; Varner, Denise C.; Brainard, David H.

1990-01-01

251

Threshold photodetachment in a repulsive potential  

E-print Network

We report on the first experimental observation of a new threshold behavior observed in the 5g partial channel in photodetachment of K-. It arises from the repulsive polarization interaction between the detached electron and the residual K(5g) atom, which has a large negative dipole polarizability. In order to account for the observation in the K(5g) channel, we have developed a semiclassical model that predicts an exponential energy dependence for the cross section. The measurements were made with collinear laser-ion beams and a resonance ionization detection scheme.

Lindahl, Anton O; Hultgren, Hannes; Kiyan, Igor Yu; Pegg, David J; Walter, C Wesley; Hanstorp, Dag; 10.1103/PhysRevLett.108.033004

2012-01-01

252

INDRA, a 4? charged product detection array at GANIL  

Microsoft Academic Search

INDRA, a new and innovative highly segmented detector for light charged particles and fragments is described. It covers geometrically 90% of the 4? solid angle and has very low detection thresholds. The detector, operated under vacuum, is axially symmetric and segmented in 336 independent cells allowing efficient detection of high multiplicity events. Nucleus identification down to very low energy threshold

J. Pouthas; B. Borderie; R. Dayras; E. Plagnol; M. F. Rivet; F. Saint-Laurent; J. C. Steckmeyer; G. Auger; C. O. Bacri; S. Barbey; A. Barbier; A. Benkirane; J. Benlliure; B. Berthier; E. Bougamont; P. Bourgault; P. Box; R. Bzyl; B. Cahan; Y. Cassagnou; D. Charlet; J. L. Charvet; A. Chbihi; T. Clerc; N. Copinet; D. Cussol; M. Engrand; J. M. Gautier; Y. Huguet; O. Jouniaux; J. L. Laville; P. Le Botlan; A. Leconte; R. Legrain; P. Lelong; M. Le Guay; L. Martina; C. Mazur; P. Mosrin; L. Olivier; J. P. Passerieux; S. Pierre; B. Piquet; E. Plaige; E. C. Pollacco; B. Raine; A. Richard; J. Ropert; C. Spitaels; L. Stab; D. Sznajderman; L. Tassan-Got; J. Tillier; M. Tripon; P. Vallerand; C. Volant; P. Volkov; J. P. Wieleczko; G. Wittwer

1995-01-01

253

The effect of signal duration on the underwater detection thresholds of a harbor porpoise (Phocoena phocoena) for single frequency-modulated tonal signals between 0.25 and 160 kHz.  

PubMed

The underwater hearing sensitivity of a young male harbor porpoise for tonal signals of various signal durations was quantified by using a behavioral psychophysical technique. The animal was trained to respond only when it detected an acoustic signal. Fifty percent detection thresholds were obtained for tonal signals (15 frequencies between 0.25-160 kHz, durations 0.5-5000 ms depending on the frequency; 134 frequency-duration combinations in total). Detection thresholds were quantified by varying signal amplitude by the 1-up 1-down staircase method. The hearing thresholds increased when the signal duration fell below the time constant of integration. The time constants, derived from an exponential model of integration [Plomp and Bouman, J. Acoust. Soc. Am. 31, 749-758 (1959)], varied from 629 ms at 2 kHz to 39 ms at 64 kHz. The integration times of the porpoises were similar to those of other mammals including humans, even though the porpoise is a marine mammal and a hearing specialist. The results enable more accurate estimations of the distances at which porpoises can detect short-duration environmental tonal signals. The audiogram thresholds presented by Kastelein et al. [J. Acoust. Soc. Am. 112, 334-344 (2002)], after correction for the frequency bandwidth of the FM signals, are similar to the results of the present study for signals of 1500 ms duration. Harbor porpoise hearing is more sensitive between 2 and 10 kHz, and less sensitive above 10 kHz, than formerly believed. PMID:21110616

Kastelein, Ronald A; Hoek, Lean; de Jong, Christ A F; Wensveen, Paul J

2010-11-01

254

Frequency dependence of vestibuloocular reflex thresholds  

PubMed Central

How the brain processes signals in the presence of noise impacts much of behavioral neuroscience. Thresholds provide one way to assay noise. While perceptual thresholds have been widely investigated, vestibuloocular reflex (VOR) thresholds have seldom been studied and VOR threshold dynamics have never, to our knowledge, been reported. Therefore, we assessed VOR thresholds as a function of frequency. Specifically, we measured horizontal VOR thresholds evoked by yaw rotation in rhesus monkeys, using standard signal detection approaches like those used in earlier human vestibular perceptual threshold studies. We measured VOR thresholds ranging between 0.21 and 0.76°/s; the VOR thresholds increased slightly with frequency across the measured frequency range (0.2–3 Hz). These results do not mimic the frequency response of human perceptual thresholds that have been shown to increase substantially as frequency decreases below 0.5 Hz. These reported VOR threshold findings could indicate a qualitative difference between vestibular responses of humans and nonhuman primates, but a more likely explanation is an additional dynamic neural mechanism that does not influence the VOR but, rather, influences perceptual thresholds via a decision-making process included in direction recognition tasks. PMID:22072512

Haburcakova, Csilla; Lewis, Richard F.

2012-01-01

255

Near Threshold Coincident Electrofission of Uranium -238.  

NASA Astrophysics Data System (ADS)

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

Dowell, David Harry

256

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

257

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

258

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

Microsoft Academic Search

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

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

2008-01-01

259

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

NASA Astrophysics Data System (ADS)

The present contribution is devoted to the analysis of three extremely weak A-type bands of 16O3 recorded near 7686, 7739 and 7860 cm-1i.e. only a few % below the dissociation limit, D0, at about 8560 cm-1. They correspond to the most excited vibration-rotation states of ozone observed so far via high-resolution absorption spectroscopy. They were detected by high sensitivity CW-cavity ring down spectroscopy with a typical noise equivalent absorption, ?min, on the order of 2×10-10 cm-1 and modelled using the effective operator approach. The derived band centres and rotational constants show a very good agreement with recent theoretical predictions based on a new ab initio potential energy surface.

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

2015-02-01

260

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

SciTech Connect

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

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

2014-04-07

261

High-Energy Threshold Reaction Rates on 0.8 GeV Proton-Irradiated Thick W and W-Na Targets  

E-print Network

Threshold activation reaction rates in 12C, 19F, 27Al, 59Co, 63Cu, 65Cu, 64Zn, 93Nb, 115In, 169Tm, 181Ta, 197Au, and 209Bi experimental samples placed along the axis inside and outside the 0.8 GeV proton-irradiated 92-cm thick W-Na and 4-cm thick W targets where measured at the ITEP proton synchrotron. 158 reactions of up to +AH4-0.5 GeV thresholds have been measured in 123 activation samples for W-Na target, and 157 reactions in 36 activation samples for W target. The reaction rates were determined using the gamma-spectrometry method. In total, more than 1000 values of activation reactions were determined in the experiments. In both cases the measured reaction rates were compared with the LAHET code simulated rates and using several nuclear databases for the respective excitation functions, namely, ENDF/B6 for cross section of neutrons at energies below 20 MeV and MENDL2 together with MENDL2P for cross sections of protons and neutrons of 20 to 100 MeV energies. A general satisfactory agreement between simulated and experimental data has been found.

Yu. E. Titarenko; V. F. Batyaev; E. I. Karpikhin; V. M. Zhivun; A. B. Koldobsky; R. D. Mulambetov; S. V. Mulambetova; S. L. Zaitsev; S. G. Mashnik; R. E. Prael

2004-01-26

262

Resonant energy transfer based biosensor for detection of multivalent proteins.  

SciTech Connect

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

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

2001-01-01

263

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

264

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

265

A theory for calculating the surface-adsorbate bond dissociation energy from collision-induced desorption threshold measurements  

E-print Network

A theory for calculating the surface-adsorbate bond dissociation energy from collision is presented for determining the bond dissociation energy, Do, of a surface-adsorbate complex from collision-induced desorption measurements. D, is calculated from the minimum collision energy required for desorption

Levis, Robert J.

266

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

267

Accuracy threshold for postselected quantum computation  

Microsoft Academic Search

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

Panos Aliferis; Daniel Gottesman; John Preskill

2007-01-01

268

Is the dynamics of scaling dark energy detectable?  

SciTech Connect

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

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

2008-07-15

269

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

270

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

271

A hydrophone prototype for ultra high energy neutrino acoustic detection  

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

272

Detecting energy-greedy anomalies and mobile malware variants  

Microsoft Academic Search

Mobile users of computation and communication services have been rapidly adopting battery-powered mobile hand- helds, such as PocketPCs and SmartPhones, for their work. However, the limited battery-lifetime of these devices re- stricts their portability and applicability, and this weak- ness can be exacerbated by mobile malware targeting de- pletion of battery energy. Such malware are usually di-- cult to detect

Hahnsang Kim; Joshua Smith; Kang G. Shin

2008-01-01

273

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

274

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

E-print Network

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

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

2007-05-08

275

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

NASA Astrophysics Data System (ADS)

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

Brühl, S.; Kochur, A. G.

2012-07-01

276

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

277

Local visual energy mechanisms revealed by detection of global patterns.  

PubMed

A central goal of visual neuroscience is to relate the selectivity of individual neurons to perceptual judgments, such as detection of a visual pattern at low contrast or in noise. Since neurons in early areas of visual cortex carry information only about a local patch of the image, detection of global patterns must entail spatial pooling over many such neurons. Physiological methods provide access to local detection mechanisms at the single-neuron level but do not reveal how neural responses are combined to determine the perceptual decision. Behavioral methods provide access to perceptual judgments of a global stimulus but typically do not reveal the selectivity of the individual neurons underlying detection. Here we show how the existence of a nonlinearity in spatial pooling does allow properties of these early mechanisms to be estimated from behavioral responses to global stimuli. As an example, we consider detection of large-field sinusoidal gratings in noise. Based on human behavioral data, we estimate the length and width tuning of the local detection mechanisms and show that it is roughly consistent with the tuning of individual neurons in primary visual cortex of primate. We also show that a local energy model of pooling based on these estimated receptive fields is much more predictive of human judgments than competing models, such as probability summation. In addition to revealing underlying properties of early detection and spatial integration mechanisms in human cortex, our findings open a window on new methods for relating system-level perceptual judgments to neuron-level processing. PMID:22423090

Morgenstern, Yaniv; Elder, James H

2012-03-14

278

Research on energy transmission calculation problem on laser detecting submarine  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

279

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

280

Measurement of the solar {sup 8}B neutrino rate with a liquid scintillator target and 3 MeV energy threshold in the Borexino detector  

SciTech Connect

We report the measurement of {nu}-e elastic scattering from {sup 8}B solar neutrinos with 3 MeV energy threshold by the Borexino detector in Gran Sasso (Italy). The rate of solar neutrino-induced electron scattering events above this energy in Borexino is 0.22{+-}0.04(stat){+-}0.01(syst) cpd/100 t, which corresponds to {Phi}{sub {sup 8}B}{sup ES}=2.4{+-}0.4{+-}0.1x10{sup 6} cm{sup -2} s{sup -1}, in good agreement with measurements from SNO and SuperKamiokaNDE. Assuming the {sup 8}B neutrino flux predicted by the high metallicity standard solar model, the average {sup 8}B {nu}{sub e} survival probability above 3 MeV is measured to be 0.29{+-}0.10. The survival probabilities for {sup 7}Be and {sup 8}B neutrinos as measured by Borexino differ by 1.9{sigma}. These results are consistent with the prediction of the MSW-LMA solution of a transition in the solar {nu}{sub e} survival probability P{sub ee} between the low-energy vacuum-driven and the high-energy matter-enhanced solar neutrino oscillation regimes.

Bellini, G.; Bonetti, S.; Buizza Avanzini, M.; Caccianiga, B.; D'Angelo, D.; Franco, D.; Giammarchi, M.; Lombardi, P.; Ludhova, L.; Meroni, E.; Miramonti, L.; Perasso, L.; Ranucci, G.; Re, A. [Dipartimento di Fisica, Universita degli Studi e INFN, 20133 Milano (Italy); Benziger, J. [Chemical Engineering Department, Princeton University, Princeton, New Jersey 08544 (United States); Cadonati, L.; Pocar, A. [Physics Department, University of Massachusetts, Amherst, Massachusetts 01003 (United States); Calaprice, F.; Chavarria, A.; Dalnoki-Veress, F. [Physics Department, Princeton University, Princeton, New Jersey 08544 (United States)

2010-08-01

281

Low-energy spectrum of N = 4 super-Yang-Mills on T^3: flat connections, bound states at threshold, and S-duality  

E-print Network

We study (3+1)-dimensional N=4 supersymmetric Yang-Mills theory on a spatial three-torus. The low energy spectrum consists of a number of continua of states of arbitrarily low energies. Although the theory has no mass-gap, it appears that the dimensions and discrete abelian magnetic and electric 't Hooft fluxes of the continua are computable in a semi-classical approximation. The wave-functions of the low-energy states are supported on submanifolds of the moduli space of flat connections, at which various subgroups of the gauge group are left unbroken. The field theory degrees of freedom transverse to such a submanifold are approximated by supersymmetric matrix quantum mechanics with 16 supercharges, based on the semi-simple part of this unbroken group. Conjectures about the number of normalizable bound states at threshold in the latter theory play a crucial role in our analysis. In this way, we compute the low-energy spectra in the cases where the simply connected cover of the gauge group is given by SU(n), Spin(2n+1) or Sp(2n). We then show that the constraints of S-duality are obeyed for unique values of the number of bound states in the matrix quantum mechanics. In the cases based on Spin(2n+1) and Sp(2n), the proof involves surprisingly subtle combinatorial identities, which hint at a rich underlying structure.

Mans Henningson; Niclas Wyllard

2007-06-10

282

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

283

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

284

Underwater Acoustic Detection of Ultra High Energy Neutrinos  

E-print Network

We investigate the acoustic detection method of 10^18-20 eV neutrinos in a Mediterranean Sea environment. The acoustic signal is re-evaluated according to dedicated cascade simulations and a complex phase dependant absorption model, and compared to previous studies. We detail the evolution of the acoustic signal as function of the primary shower characteristics and of the acoustic propagation range. The effective volume of detection for a single hydrophone is given taking into account the limitations due to sea bed and surface boundaries as well as refraction effects. For this 'benchmark detector' we present sensitivity limits to astrophysical neutrino fluxes, from which sensitivity bounds for a larger acoustic detector can be derived. Results suggest that with a limited instrumentation the acoustic method would be more efficient at extreme energies, above 10^20 eV.

V. Niess; V. Bertin

2006-04-21

285

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

E-print Network

- form IR or Raman spectroscopy of gas phase ions.1,2 Optical emission spectroscopy is seldom applicable be performed by using commercial pulsed dye lasers, utilization of the spectroscopic data of the intermedi- ate state and dye laser output. Since ionization energies of most of the molecules lie in the range 9­12 e

Kim, Myung Soo

286

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

287

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

288

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

289

Automated detection and delineation of lung tumors in PET-CT volumes using a lung atlas and iterative mean-SUV threshold  

NASA Astrophysics Data System (ADS)

Automated segmentation for the delineation of lung tumors with PET-CT is a challenging task. In PET images, primary lung tumors can have varying degrees of tracer uptake, which sometimes does not differ markedly from normal adjacent structures such as the mediastinum, heart and liver. In addition, separation of tumor from adjacent soft tissues and bone in the chest wall is problematic due to limited resolution. For CT, the tumor soft tissue density can be similar to that in the blood vessels and the chest wall; and although CT provides better boundary definition, exact tumor delineation is also difficult when the tumor density is similar to adjacent structures. We propose an innovative automated adaptive method to delineate lung tumors in PET-CT images in conjunction with a lung atlas in which an iterative mean-SUV (Standardized Uptake Value) threshold is used to gradually define the tumor region in PET. Tumor delineation in the CT data is performed using region growing and seeds obtained autonomously from the PET tumor regions. We evaluated our approach in 13 patients with non-small cell lung cancer (NSCLC) and found it could delineate tumors of different size, shape and location, even when when the NSCLC involved the chest wall.

Ballangan, Cherry; Wang, Xiuying; Eberl, Stefan; Fulham, Michael; Feng, Dagan

2009-02-01

290

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

291

Implied Mortgage Refinancing Thresholds  

Microsoft Academic Search

The optimal prepayment model asserts that rational homeowners will refinance if they can reduce the current value of their liabilities by an amount greater than the refinancing threshold, defined as the cost of carrying the transaction plus the time value of the embedded call option. To compute the notional value of the refinancing threshold, researchers have traditionally relied on discrete-

Paul Bennett; Richard Peach; Stavros Peristiani

2000-01-01

292

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

293

Rotationally resolved threshold photoionization of H2S  

NASA Astrophysics Data System (ADS)

Threshold spectroscopy based on pulsed field ionization (PFI) has been used in conjunction with a VUV laser source to obtain the rovibronic distributions of molecular cations following single photon ionization. The technique selectively detects electrons produced from field ionization of very high-n Rydberg levels (n >= 200) which lie within 1 - 2 cm-1 of each rovibronic threshold. Since the oscillator strength is continuous across an ionization threshold, the PFI spectrum reflects the rovibronic state population at threshold. The nascent rotational state distribution of the molecular ion reflects the exchanges of energy and angular momentum in the `scattering' of the photoexcited electron with the anisotropic molecular ion potential. Rotationally resolved studies on several molecular systems (O2, HCl, OH(OD), H2O and N2O) have shown that photoionization can lead to large changes in core rotation, e.g., (Delta) J equals J+ - J' = 3). For photoionization of nonlinear molecules (H2O), transitions between asymmetric top levels involving the rotational angular momentum projections, Ka,Kb,Kc, permit resolution of the photoelectron continua according to symmetry. PFI studies on the van der Waals dimer, Xe2, demonstrate the utility of this technique for investigating low frequency vibrations in molecular cations and for studying minor species (

Wiedmann, Ralph T.; White, Michael G.

1992-04-01

294

Towards a Low Threshold SuperCDMS Experiment  

NASA Astrophysics Data System (ADS)

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

Welliver, Bradford

2013-04-01

295

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

296

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

297

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

SciTech Connect

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

Middleton, D.

1996-05-02

298

Snapshot molecular imaging using coded energy-sensitive detection.  

PubMed

We demonstrate a technique for measuring the range-resolved coherent scatter form factors of different objects from a single snapshot. By illuminating the object with an x-ray pencil beam and placing a coded aperture in front of a linear array of energy-sensitive detector elements, we record the coherently scattered x-rays. This approach yields lateral, range, and momentum transfer resolutions of 1 mm, 5 mm, and 0.2 nm?¹, respectively, which is sufficient for the distinguishing a variety of solids and liquids. These results indicate a path toward real-time volumetric molecular imaging for non-destructive examination in a variety of applications, including medical diagnostics, quality inspection, and security detection. PMID:24150387

Greenberg, Joel A; Krishnamurthy, Kalyani; Brady, David

2013-10-21

299

A Mobility and Energy-aware Hierarchical Intrusion Detection System for Mobile ad hoc Networks  

E-print Network

A Mobility and Energy-aware Hierarchical Intrusion Detection System for Mobile ad hoc Networks the energy consumption in a fair and efficient manner. Keywords. Intrusion Detection System, IDS, mobile ad, sufficient protection from them is fundamental requirement. The implemen- tation of an Intrusion Detection

Stavrakakis, Ioannis

300

Methods for threshold determination in multiplexed assays  

DOEpatents

Methods for determination of threshold values of signatures comprised in an assay are described. Each signature enables detection of a target. The methods determine a probability density function of negative samples and a corresponding false positive rate curve. A false positive criterion is established and a threshold for that signature is determined as a point at which the false positive rate curve intersects the false positive criterion. A method for quantitative analysis and interpretation of assay results together with a method for determination of a desired limit of detection of a signature in an assay are also described.

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

2014-06-24

301

Quantum threshold group signature  

NASA Astrophysics Data System (ADS)

In most situations, the signer is generally a single person. However, when the message is written on behalf of an organization, a valid message may require the approval or consent of several persons. Threshold signature is a solution to this problem. Generally speaking, as an authority which can be trusted by all members does not exist, a threshold signature scheme without a trusted party appears more attractive. Following some ideas of the classical Shamir’s threshold signature scheme, a quantum threshold group signature one is proposed. In the proposed scheme, only t or more of n persons in the group can generate the group signature and any t - 1 or fewer ones cannot do that. In the verification phase, any t or more of n signature receivers can verify the message and any t - 1 or fewer receivers cannot verify the validity of the signature.

Yang, Yuguang; Wen, Qiaoyan

2008-10-01

302

Threshold behaviour in hydrological systems as (human) geo-ecosystems: manifestations, controls, implications  

NASA Astrophysics Data System (ADS)

In this paper we review threshold behaviour in environmental systems, which are often associated with the onset of floods, contamination and erosion events, and other degenerative processes. Key objectives of this review are to a) suggest indicators for detecting threshold behavior, b) discuss their implications for predictability, c) distinguish different forms of threshold behavior and their underlying controls, and d) hypothesise on possible reasons for why threshold behaviour might occur. Threshold behaviour involves a fast qualitative change of either a single process or the response of a system. For elementary phenomena this switch occurs when boundary conditions (e.g., energy inputs) or system states as expressed by dimensionless quantities (e.g. the Reynolds number) exceed threshold values. Mixing, water movement or depletion of thermodynamic gradients becomes much more efficient as a result. Intermittency is a very good indicator for detecting event scale threshold behavior in hydrological systems. Predictability of intermittent processes/system responses is inherently low for combinations of systems states and/or boundary conditions that push the system close to a threshold. Post hoc identification of "cause-effect relations" to explain when the system became critical is inherently difficult because of our limited ability to perform observations under controlled identical experimental conditions. In this review, we distinguish three forms of threshold behavior. The first one is threshold behavior at the process level that is controlled by the interplay of local soil characteristics and states, vegetation and the rainfall forcing. Overland flow formation, particle detachment and preferential flow are examples of this. The second form of threshold behaviour is the response of systems of intermediate complexity - e.g., catchment runoff response and sediment yield - governed by the redistribution of water and sediments in space and time. These are controlled by the topological architecture of the catchments that interacts with system states and the boundary conditions. Crossing the response thresholds means to establish connectedness of surface or subsurface flow paths to the catchment outlet. Subsurface stormflow in humid areas, overland flow and erosion in semi-arid and arid areas are examples, and explain that crossing local process thresholds is necessary but not sufficient to trigger a system response threshold. The third form of threshold behaviour involves changes in the "architecture" of human geo-ecosystems, which experience various disturbances. As a result substantial change in hydrological functioning of a system is induced, when the disturbances exceed the resilience of the geo-ecosystem. We present examples from savannah ecosystems, humid agricultural systems, mining activities affecting rainfall runoff in forested areas, badlands formation in Spain, and the restoration of the Upper Rhine river basin as examples of this phenomenon. This functional threshold behaviour is most difficult to predict, since it requires extrapolations far away from our usual experience and the accounting of bidirectional feedbacks. However, it does not require the development of more complicated model, but on the contrary, only models with the right level of simplification, which we illustrate with an instructive example. Following Prigogine, who studied structure formation in open thermodynamic systems, we hypothesise that topological structures which control response thresholds in the landscape might be seen as dissipative structures, and the onset of threshold processes/response as a switch to more efficient ways of depleting strong gradients that develop in the case of extreme boundary conditions.

Zehe, E.; Sivapalan, M.

2009-07-01

303

Pion photoproduction on 3He at threshold  

NASA Astrophysics Data System (ADS)

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

Tiator, L.

1981-07-01

304

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

305

Lucid Dreaming: Reliable Analog Event Detection for Energy-Constrained Applications  

E-print Network

Lucid Dreaming: Reliable Analog Event Detection for Energy-Constrained Applications Sasha Jevtic vibrations in buildings and bridges, we have designed, implemented, and evaluated lucid dreaming, a hardware

306

[open quotes]Magic[close quotes] energies for detecting light elements with resonant alpha particle backscattering  

SciTech Connect

Resonant backscattering is widely used to improve the detection limit of the light elements such as B, C, N and O. One disadvantage, however, is that several incident energies are normally needed if the sample contains a number of the light elements. There are [open quotes]magic[close quotes] energies at which several light elements can be detected simultaneously with suitable sensitivities. When these energies are used along with the elastic recoil detection of hydrogen, multiple elements can be detected without changing the beam energy, and the analysis time is greatly reduced. These reactions along with examples will be discussed. [copyright] [ital 1999 American Institute of Physics.

Wetteland, C.J.; Maggiore, C.J.; Tesmer, J.R. (Center for Materials Science, Materials Science and Technology Division, Los Alamos National Laboratory (United States)); He, X.; Lee, D. (Structure/Property Relations, Materials Science and Technology Division, Los Alamos National Laboratory (United States))

1999-06-01

307

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

308

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

309

Detection of Medium-Sized Polycyclic Aromatic Hydrocarbons via Fluorescence Energy Transfer  

PubMed Central

Reported herein is the use of proximity-induced non-covalent energy transfer for the detection of medium-sized polycyclic aromatic hydrocarbons (PAHs). This energy transfer occurs within the cavity of ?-cyclodextrin in various aqueous environments, including human plasma and coconut water. Highly efficient energy transfer was observed, and the efficiency of the energy transfer is independent of the concentration of ?-cyclodextrin used, demonstrating the importance of hydrophobic binding in facilitating such energy transfer. Low limits of detection were also observed for many of the PAHs investigated, which is promising for the development of fluorescence-based detection schemes.

Serio, Nicole; Prignano, Lindsey; Peters, Sean; Levine, Mindy

2015-01-01

310

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

311

Empirical threshold values for quantitative trait mapping  

Microsoft Academic Search

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

G. A. Churchill; R. W. Doerge

1994-01-01

312

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

313

Melanin microcavitation threshold in the near infrared  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

314

Detection of sperm whale clicks based on the TeagerKaiser energy operator  

E-print Network

Detection of sperm whale clicks based on the Teager­Kaiser energy operator V. Kandia a,*, Y of an algorithm for automatic detection of sperm whale clicks in large recordings is described. It is based and robust. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Sperm whale; Click; Teager­Kaiser energy

Stylianou, Yannis

315

Detecting Energy-Greedy Anomalies and Mobile Malware Hahnsang Kim, Joshua Smith, Kang G. Shin  

E-print Network

Detecting Energy-Greedy Anomalies and Mobile Malware Variants Hahnsang Kim, Joshua Smith, Kang G-powered mobile hand- helds, such as PocketPCs and SmartPhones, for their work. However, the limited battery malware targeting de- pletion of battery energy. Such malware are usually diffi- cult to detect

Shihada, Basem

316

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

317

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

318

Silicon micromachined threshold accelerometers  

NASA Astrophysics Data System (ADS)

A threshold accelerometer, also known as a g-switch, was developed for sensing very high acceleration levels. The design follows the concept of a cantilever beam as the sensing element with a metal line running along its length. Under applied acceleration, the beam deflects upwards across a small gap and makes contact with a second electrode, thus closing a switch. The structural material chosen for the beam was silicon dioxide, due to its flexibility and ease in fabrication. The theory of the electrostatic and inertial forces are analyzed and a threshold acceleration level is derived. It is shown that this level is very sensitive to beam length. Fabrication steps are described, including chemical vapor deposition, chemical etching, and fabrication and assembly of the top glass plate. Electrostatic testing that involved voltages representative of threshold acceleration levels of 400 to 100,000 gravities was performed on over 150 beams. Under static centrifuge testing involving over 100 beams, threshold acceleration levels from 400 to 20,000 gravities were measured. Most of the experimental results are within the predicted tolerance limits set by the processing parameters.

Loke, Y.; McKinnon, G. H.; Brett, M. J.

319

Animation with Threshold Textures  

Microsoft Academic Search

We present a method for frame coherent texturing and hatching of 3D models with a discrete set of colors. Our technique is inspired by various artistic styles that use a limited set of colors to convey surface shape and texture. In previous research discrete color shading was produced by modifying smooth shading with a threshold function. We extend this approach

Oleg Veryovka

2002-01-01

320

Charmonium spectroscopy above thresholds  

E-print Network

We present a systematic and selfconsistent analysis of four-quark charmonium states and applied it to study compact four-quark systems and meson-meson molecules. Our results are robust and should serve to clarify the situation of charmonium spectroscopy above the threshold production of charmed mesons.

T. Fernandez-Carames; A. Valcarce; J. Vijande

2010-01-25

321

Near-threshold deuteron photodisintegration: An indirect determination of the Gerasimov-Drell-Hearn sum rule and forward spin polarizability (?0) for the deuteron at low energies  

NASA Astrophysics Data System (ADS)

It is shown that a measurement of the analyzing power obtained with linearly polarized ?-rays and an unpolarized target can provide an indirect determination of two physical quantities. These are the Gerasimov-Drell-Hearn (GDH) sum rule integrand for the deuteron and the sum rule integrand for the forward spin polarizability (?0) near photodisintegration threshold. An analysis of data for the d(??,n)p reaction and other experiments is presented. A fit to the world data analyzed in this manner gives a GDH integral value of -603±43?b between the photodisintegration threshold and 6 MeV. This result is the first confirmation of the large contribution of the 1S0(M1) transition predicted for the deuteron near photodisintegration threshold. In addition, a sum rule value of 3.75±0.18 fm4 for ?0 is obtained between photodisintegration threshold and 6 MeV. This is a first indirect confirmation of the leading-order effective field theory prediction for the forward spin-polarizability of the deuteron.

Ahmed, M. W.; Blackston, M. A.; Perdue, B. A.; Tornow, W.; Weller, H. R.; Norum, B.; Sawatzky, B.; Prior, R. M.; Spraker, M. C.

2008-04-01

322

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

323

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

324

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

E-print Network

A STUDY OF THE ENERGY DEPENDENCE OF THE DETECTION EFFICIENCY OF A MICROCHANNEL PLATE FOR LOW ENERGY H2 IONS A Thesis by KARIN ELISABETH MARTHA HOLZSCHEITER Submitted to the Graduate College of Texas A&M University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE December 1987 Major Subject: Physics A STUDY OF THE ENERGY DEPENDENCE OF THE DETECTION EFFICIENCY OF A MICROCHANNEL PLATE FOR LOW ENERGY H2 IONS A Thesis by KARIN ELISABETH MARTHA HOLZSCHEITER Approved...

Holzscheiter, Karin Elisabeth Martha

1987-01-01

325

Contraction threshold and the \\  

Microsoft Academic Search

The delayed component of intramembranous charge movement (hump, Iv) was studied around the contraction threshold in cut skeletal muscle fibers of the frog (Rana esculenta) in a single Vaseline-gap voltage clamp. Charges (Q) were computed as 50-ms integrals of the ON (QoN) and OFF (QoFr) of the asymmetric currents after subtracting a baseline. The hump appeared in parallel with an

G. Szffcs; L. CSERNOCH; J. MAGYAR; L. KovAcs

1991-01-01

326

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

NASA Astrophysics Data System (ADS)

Several narrow alpha resonant 16O states were detected through the 12C (6Li,d ) reaction, in the range of 13.5 to 17.5 MeV of excitation energy. The reaction was measured at a bombarding energy of 25.5 MeV employing the São Paulo Pelletron-Enge-Spectrograph facility and the nuclear emulsion technique. Experimental angular distributions associated with natural parity quasi-bound states around the 4? threshold are presented and compared to DWBA predictions. The upper limit for the resonance widths obtained is near the energy resolution (15 keV).

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

2014-11-01

327

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

328

AI and GIS together on Energy Fraud Detection  

Microsoft Academic Search

Abstract The task of fraud,detection,was,always,an issue,for Credit Cards and,Telecom,Companies. The issue became,also a serious problem,in Brazil for Power Distribution Companies.,Detecting fraud is not a simple,task and,requires,a careful exam,on a huge,amount,of data,collected through,out years of operation. The numbers,involving fraud are always,impressive,and we can easily expect,a resource recover that goes,around,the millions of dollars. This paper,aims,to show,a business,case,that combines,the use of GIS and,AI

Rodrigo Mendonça Queiroga

329

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

330

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

331

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

332

Instantaneous energy density as a feature for gear fault detection  

NASA Astrophysics Data System (ADS)

In this work, energy-based features for gear fault diagnosis and prediction are proposed. The instantaneous energy density is shown to obtain high values when defected teeth are engaged. Three methods are compared in terms of sensitivity, reliability and computation effectiveness. The Wigner-Ville distribution is contrasted to the wavelet transform and the newly proposed empirical mode decomposition scheme. It is shown that all three methods are capable of a reliable prediction. An empirical law, which relates the energy content to the crack magnitude is established.

Loutridis, S. J.

2006-07-01

333

Threshold photoelectron source for the study of low-energy electron scattering: Total cross section for electron scattering from krypton in the energy range from 14 meV to 20 eV  

SciTech Connect

An experimental technique for the measurement of the total cross section for electron scattering from atoms and molecules at high resolution is described. The total cross sections for electron scattering from Kr in the energy range from 14 meV to 20 eV obtained with the technique are also reported. The present technique employs a combination of the penetrating field technique and the threshold photoionization of rare-gas atoms using synchrotron radiation as an electron source in order to produce a high-resolution electron beam at very low energy. The characteristics of the electron sources were determined by measuring the ionizing photon energy dependence of photoelectron yield. Absolute total cross sections for electron scattering are obtained by the attenuation method. The measured absolute values of the total cross sections for electron scattering from Kr agree with those obtained by other groups down to 175 meV, above which several experimental works have been reported. Below 175 meV, the present results generally agree with theoretical cross sections down to 14 meV. The resonant structures in the total cross sections due to Kr{sup -} (4p{sup 5}5s{sup 2} {sup 2}P{sub 3/2}) and the Kr{sup -} (4p{sup 5}5s{sup 2} {sup 2}P{sub 1/2}) Feshbach resonances are also reported. The resolution of the present setup has been estimated from a fit of the measured profile of the Kr{sup -} (4p{sup 5}5s{sup 2} {sup 2}P{sub 3/2}) resonance by the theoretical curve obtained from the resonant scattering theory.

Kurokawa, M.; Kitajima, M.; Toyoshima, K.; Odagiri, T. [Department of Chemistry, Tokyo Institute of Technology, Tokyo 152-8551 (Japan); Kato, H.; Kawahara, H.; Hoshino, M.; Tanaka, H. [Department of Physics, Sophia University, Tokyo 102-8554 (Japan); Ito, K. [Photon Factory, Institute of Materials Structure Science, Tsukuba 305-0801 (Japan)

2010-12-15

334

An Energy Efficient FPGA Hardware Architecture for the Acceleration of OpenCV Object Detection  

E-print Network

An Energy Efficient FPGA Hardware Architecture for the Acceleration of OpenCV Object Detection for the Acceleration of OpenCV Object Detection Braiden Brousseau Master of Applied Science Graduate Department . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.4 OpenCV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.5 Multi

Rose, Jonathan

335

Pacing technology: advances in pacing threshold management.  

PubMed

Over the last five decades, pacemaker therapy has undergone remarkable technological advances with increasing sophistication of pacemaker features. However, device longevity has remained one of the major issues in pacemaker design ever since the first endocardial pacing lead implantation in 1958. In addition to various hardware design to enhance device longevity, software-based solutions to minimize pacing energy and yet with good safety margin have also been developed. Together with desire and need of fully automatic pacing system in increasingly busy pacemaker clinic, several manufacturers have introduced different automatic threshold management algorithm. This article summarizes the current state-of-the-art management in pacing threshold in the modern pacemakers. PMID:20669355

Lau, Chu-pak; Siu, Chung-wah

2010-08-01

336

Threshold voltage extraction circuit  

E-print Network

NMOS transistor obtained via simulation. 27 Simulation P MOS 9. 6/2. 4 9 I I I I B to X 6g C 0 III ) "b 0 -'LfaS NI) Fig. 17. Graph of 4o and 8(V)n)/8(Vcs) versus Vcs of a PMOS transistor obtained via simulation. SIMULATION RESULTS...ltm/2. 4ltm). 33 Temperature ('C) E Cl Qt nt O 'D O ta I -820 -880 Postlayout Simulation TOt S Fig. 21. Temperature dependence of threshold-voltage of a PMOS transistor ( W/I ? 9. 6ltm/2. 4ltm). In the following subsection, chip...

Hoon, Siew Kuok

2000-01-01

337

Threshold resonance effects in reactive processes  

NASA Astrophysics Data System (ADS)

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

Simbotin, I.; Ghosal, S.; Côté, R.

2014-04-01

338

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

339

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

340

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

341

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

342

Wind shear detection using measurement of aircraft total energy change  

NASA Technical Reports Server (NTRS)

Encounters with wind shears are of concern and have caused major accidents, particularly during landing approaches. Changes in the longitudinal component of the wind affect the aircraft by changing its kinetic energy with respect to the air. It is shown that an instrument which will measure and display the rate of change of total energy of the aircraft with respect to the air will give a leading indication of wind shear problems. The concept is outlined and some instrumentation and display considerations are discussed.

Joppa, R. G.

1976-01-01

343

In-situ fault detection apparatus and method for an encased energy storing device  

DOEpatents

An apparatus and method for detecting a breach in an electrically insulating surface of an electrically conductive power system enclosure within which a number of series connected energy storing devices are disposed. The energy storing devices disposed in the enclosure are connected to a series power connection. A detector is coupled to the series connection and detects a change of state in a test signal derived from the series connected energy storing devices. The detector detects a breach in the insulating layer of the enclosure by detecting a state change in the test signal from a nominal state to a non-nominal state. A voltage detector detects a state change of the test signals from a nominal state, represented by a voltage of a selected end energy storing device, to a non-nominal state, represented by a voltage that substantially exceeds the voltage of the selected opposing end energy storing device. Alternatively, the detector may comprise a signal generator that produces the test signal as a time-varying or modulated test signal and injects the test signal into the series connection. The detector detects the state change of the time-varying or modulated test signal from a nominal state, represented by a signal substantially equivalent to the test signal, to a non-nominal state, representative by an absence of the test signal.

Hagen, Ronald A. (Stillwater, MN); Comte, Christophe (Montreal, CA); Knudson, Orlin B. (Vadnais Heights, MN); Rosenthal, Brian (Stillwater, MN); Rouillard, Jean (Saint-Luc, CA)

2000-01-01

344

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

NASA Astrophysics Data System (ADS)

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

Zhou, Bingchang; McDonnell, Mark D.

2015-02-01

345

Detecting Pitch Accent Using Pitch-corrected Energy-based Predictors Andrew Rosenberg, Julia Hirschberg  

E-print Network

Detecting Pitch Accent Using Pitch-corrected Energy-based Predictors Andrew Rosenberg, Julia and bandwidths predict pitch accent with various degrees of accuracy, and pro- duce correct predictions to leverage the predictive power of these energy compo- nents by including pitch and duration features ­ other

Hirschberg, Julia

346

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

SciTech Connect

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

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

1987-03-01

347

Detection of Very High Energy Gamma Rays from the Direction of the Vela Pulsar  

E-print Network

Introduction 1 2 Very High Energy Gamma-Ray Astronomy 5 2.1 Classi#12;cation of Gamma-Ray AstronomyDetection of Very High Energy Gamma Rays from the Direction of the Vela Pulsar A Dissertation : : : : : : : : : : : : : : : : : : : : 5 2.2 VHE Gamma-Ray Production Processes : : : : : : : : : : : : : : : : : : : : 7 2.3 VHE Gamma-Ray

Enomoto, Ryoji

348

Fuzzy logic expert system for automated damage detection from changes in strain energy mode shapes  

Microsoft Academic Search

In recent years, researchers have developed several methods for damage detection in structures employing strain energy or curvature mode shapes. Experience shows that mode shape methods are highly sensitive to measurement noise. Such sensitivity is a direct result of the second derivative applied to the displacement mode shapes, which produces curvature mode shapes. Calculation of strain energy mode shapes includes

EDWARD S. SAZONOVa; Powsiri Klinkhachorn; Hota V. S. Gangarao; Udaya B. Halabe

2002-01-01

349

Stimulus characteristics which lessen the impact of threshold fine structure on estimates of hearing status.  

PubMed

When hearing thresholds are measured with high-frequency resolution there is a pseudo-periodic variation in thresholds across frequency of up to 15-20dB. This variation is called threshold fine structure (previously referred to as threshold microstructure). Consequently, estimates of auditory status based on threshold measures can depend greatly on the specific frequency evaluated. The impact of threshold fine structure on the prediction of auditory status was examined by measuring detection thresholds of pure tones (providing an indication of threshold fine structure) and comparing them with thresholds obtained using linear sweeps, sinusoidally frequency modulated tones, and narrow-band noise. Spontaneous otoacoustic emissions (SOAEs) were also obtained to confirm the established relationship between threshold fine structure and SOAEs. Thresholds obtained using linear sweeps and narrow-band noise provided stable threshold estimates indicating that such threshold estimates were less influenced by threshold fine structure. Consequently, thresholds obtained with these stimuli may provide estimates of cochlear status less dependent of the exact frequency being evaluated, permitting better prediction of performance on other psychoacoustic measures (such as cochlear tuning and loudness perception) and the properties of their more objective measures (such as otoacoustic emissions). PMID:22178980

Lee, Jungmee; Long, Glenis

2012-01-01

350

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

351

Tunnel catch from potential wells and energy detection  

E-print Network

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

M. V. Karasev; E. V. Vybornyi

2014-11-17

352

Detecting Gamma-Ray Bursts with Ultra-High Energy Neutrinos  

NASA Astrophysics Data System (ADS)

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

Razzaque, Soebur; Mészáros, Peter; Waxman, Eli

353

Threshold effects on plateau electron angular distributions in above-threshold detachment  

NASA Astrophysics Data System (ADS)

Rates of above-threshold detachment (ATD) of H- ( s -electron) and F- ( p -electron) ions, calculated using the Sturmian-Floquet quasienergy approach, are investigated as a function of intensity for the case that the laser field intensity passes across ponderomotively shifted detachment thresholds. Pronounced enhancements of both detached electron angular distributions and fixed-angle ATD spectra in the low- and mid-energy plateau region are found at near-threshold laser intensities. These enhancements are sensitive to the initial state symmetry (i.e., the s or p symmetry) of the valence electron and occur in a narrow angular interval that is far from the polarization axis at electron energies near the onset of the plateau and moves toward the polarization axis with increasing electron energy. Although enhancements in detached electron energy distributions have not been observed for energies near the cutoff of the ATD plateau, the corresponding electron angular distributions are found to change shape dramatically as a function of intensity near the closing of ponderomotively shifted detachment thresholds. A comparison of our quantum-mechanically calculated angular distributions and those predicted classically in the high-energy region of the ATD plateau is presented and discussed.

Krajewska, K.; Fabrikant, Ilya I.; Starace, Anthony F.

2008-08-01

354

Volumetric detection of colorectal lesions for noncathartic dual-energy computed tomographic colonography.  

PubMed

Noncathartic computed tomographic colonography (CTC) could significantly increase patient adherence to colorectal screening guidelines. However, radiologists find the interpretation of noncathartic CTC images challenging. We developed a fully automated computer-aided detection (CAD) scheme for assisting radiologists with noncathartic CTC. A volumetric method is used to detect lesions within a thick target region encompassing the colonic wall. Dual-energy CTC (DE-CTC) is used to provide more detailed information about the colon than what is possible with conventional CTC. False-positive detections are reduced by use of a random-forest classifier. The effect of the thickness of the target region on detection performance was assessed by use of 22 clinical noncathartic DE-CTC studies including 27 lesions ?6 mm. The results indicate that the thickness parameter can have significant effect on detection accuracy. Leave-one-patient-out evaluation indicated that the proposed CAD scheme detects colorectal lesions at high accuracy in noncathartic CTC. PMID:23366741

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

2012-01-01

355

Volumetric Detection of Colorectal Lesions for Noncathartic Dual-Energy Computed Tomographic Colonography*  

PubMed Central

Noncathartic computed tomographic colonography (CTC) could significantly increase patient adherence to colorectal screening guidelines. However, radiologists find the interpretation of noncathartic CTC images challenging. We developed a fully automated computer-aided detection (CAD) scheme for assisting radiologists with noncathartic CTC. A volumetric method is used to detect lesions within a thick target region encompassing the colonic wall. Dual-energy CTC (DE-CTC) is used to provide more detailed information about the colon than what is possible with conventional CTC. False-positive detections are reduced by use of a random-forest classifier. The effect of the thickness of the target region on detection performance was assessed by use of 22 clinical noncathartic DE-CTC studies including 27 lesions ?6 mm. The results indicate that the thickness parameter can have significant effect on detection accuracy. Leave-one-patient-out evaluation indicated that the proposed CAD scheme detects colorectal lesions at high accuracy in noncathartic CTC. PMID:23366741

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

2013-01-01

356

Oscillatory Threshold Logic  

PubMed Central

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

Borresen, Jon; Lynch, Stephen

2012-01-01

357

A threshold effect for spacecraft charging  

NASA Technical Reports Server (NTRS)

The borderline case between no charging and large (kV) negative potentials for eclipse charging events on geosynchronous satellites is investigated, and the dependence of this transition on a threshold energy in the ambient plasma is examined. Data from the Applied Technology Satellite 6 and P78-2 (SCATHA) show that plasma sheet fluxes must extend above 10 keV for these satellites to charge in eclipse. The threshold effect is a result of the shape of the normal secondary yield curve, in particular the high energy crossover, where the secondary yield drops below 1. It is found that a large portion of the ambient electron flux must exceed this energy for a negative current to exist.

Olsen, R. C.

1983-01-01

358

Detection of ultrahigh-energy cosmic rays and neutrinos by radio method using artificial lunar satellites  

Microsoft Academic Search

An estimate of the feasibility of the ultrahigh-energy cosmic ray and neutrino detection using a lunar satellite-borne radio\\u000a receiver is presented. The data obtained in the proposed experiment will make resolving the current contradictions in the\\u000a ultrahigh-energy cosmic ray spectra measured with the major ground-based instruments possible. Moreover, they will enable\\u000a us to considerably extend the accessible energy range and

G. A. Gusev; B. N. Lomonosov; K. M. Pichkhadze; N. G. Polukhina; V. A. Ryabov; T. Saito; V. K. Sysoev; E. L. Feinberg; V. A. Tsarev; V. A. Chechin

2006-01-01

359

Helicity dependence and contribution to the Gerasimov-Drell-Hearn sum rule of the ??d???NN reaction channels in the energy region from threshold up to the ?(1232) resonance  

NASA Astrophysics Data System (ADS)

The helicity dependence of the ??d???-pp,??d???+nn, and ??d???0np reaction channels is studied for incident photon energies from threshold up to the ?(1232) resonance with inclusion of leading ?NN effects. The doubly polarized total and differential cross sections for parallel and antiparallel helicity states are predicted. Then the contribution of various channels to the deuteron spin asymmetry and the double polarization E asymmetry is calculated. In addition, the contribution to the Gerasimov-Drell-Hearn (GDH) integral from separate channels is evaluated by explicit integration up to a photon lab energy of 350 MeV. Sizeable effects from final-state interactions, specially for ?0 production, are found. The sensitivity of the results to the elementary pion photoproduction operator is also investigated. Considerable dependence of the results on the elementary amplitude is found. We expect that these results may be useful to interpret the recent measurements from LEGS@BNL, A2, and GDH@MAMI Collaborations.

Darwish, E. M.; Fernández-Ramírez, C.; Guerra, E. Moya De; Udías, J. M.

2007-10-01

360

Learning foraging thresholds for lizards  

SciTech Connect

This work gives a proof of convergence for a randomized learning algorithm that describes how anoles (lizards found in the Carribean) learn a foraging threshold distance. This model assumes that an anole will pursue a prey if and only if it is within this threshold of the anole`s perch. This learning algorithm was proposed by the biologist Roughgarden and his colleagues. They experimentally confirmed that this algorithm quickly converges to the foraging threshold that is predicted by optimal foraging theory our analysis provides an analytic confirmation that the learning algorithm converses to this optimal foraging threshold with high probability.

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

1996-01-12

361

Bayesian analysis of energy and count rate data for detection of low count rate radioactive sources.  

PubMed

A particle counting and detection system is proposed that searches for elevated count rates in multiple energy regions simultaneously. The system analyzes time-interval data (e.g., time between counts), as this was shown to be a more sensitive technique for detecting low count rate sources compared to analyzing counts per unit interval (Luo et al. 2013). Two distinct versions of the detection system are developed. The first is intended for situations in which the sample is fixed and can be measured for an unlimited amount of time. The second version is intended to detect sources that are physically moving relative to the detector, such as a truck moving past a fixed roadside detector or a waste storage facility under an airplane. In both cases, the detection system is expected to be active indefinitely; i.e., it is an online detection system. Both versions of the multi-energy detection systems are compared to their respective gross count rate detection systems in terms of Type I and Type II error rates and sensitivity. PMID:25627949

Klumpp, John; Brandl, Alexander

2015-03-01

362

Analysis of experimental data on doublet neutron-deuteron scattering at energies below the deuteron-breakup threshold on the basis of the pole approximation of the effective-range function  

SciTech Connect

On the basis of the Bargmann representation of the S matrix, the pole approximation is obtained for the effective-range function k cot {delta}. This approximation is optimal for describing the neutron-deuteron system in the doublet spin state. The values of r{sub 0} = 412.469 fm and v{sub 2} = -35 495.62 fm{sup 3} for the doublet low-energy parameters of neutron-deuteron scattering and the value of D = 172.678 fm{sup 2} for the respective pole parameter are deduced by using experimental results for the triton binding energy E{sub T}, the doublet neutron-deuteron scattering length a{sub 2}, and van Oers-Seagrave phase shifts at energies below the deuteron-breakup threshold. With these parameters, the pole approximation of the effective-range function provides a highly precise description (the relative error does not exceed 1%) of the doublet phase shift for neutron-deuteron scattering at energies below the deuteron-breakup threshold. Physical properties of the triton in the ground (T) and virtual (v) states are calculated. The results are B{sub v} = 0.608 MeV for the virtuallevel position and C{sub T}{sup 2} = 2.866 and C{sub v}{sup 2} = 0.0586 for the dimensionless asymptotic normalization constants. It is shown that, in the Whiting-Fuda approximation, the values of physical quantities characterizing the triton virtual state are determined to a high precision by one parameter, the doublet neutron-deuteron scattering length a{sub 2}. The effective triton radii in the ground ({rho}{sub T} = 1.711 fm) and virtual ({rho}{sub v} = 74.184 fm) states are calculated for the first time.

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

2008-01-15

363

Analysis of experimental data on doublet neutron-deuteron scattering at energies below the deuteron-breakup threshold on the basis of the pole approximation of the effective-range function  

NASA Astrophysics Data System (ADS)

On the basis of the Bargmann representation of the S matrix, the pole approximation is obtained for the effective-range function k cot ?. This approximation is optimal for describing the neutron-deuteron system in the doublet spin state. The values of r 0 = 412.469 fm and v 2 = -35 495.62 fm3 for the doublet low-energy parameters of neutron-deuteron scattering and the value of D = 172.678 fm2 for the respective pole parameter are deduced by using experimental results for the triton binding energy E T , the doublet neutron-deuteron scattering length a 2, and van Oers-Seagrave phase shifts at energies below the deuteron-breakup threshold. With these parameters, the pole approximation of the effective-range function provides a highly precise description (the relative error does not exceed 1%) of the doublet phase shift for neutron-deuteron scattering at energies below the deuteron-breakup threshold. Physical properties of the triton in the ground ( T) and virtual ( v) states are calculated. The results are B v = 0.608 MeV for the virtuallevel position and C {/T 2} = 2.866 and C {/v 2} = 0.0586 for the dimensionless asymptotic normalization constants. It is shown that, in the Whiting-Fuda approximation, the values of physical quantities characterizing the triton virtual state are determined to a high precision by one parameter, the doublet neutron-deuteron scattering length a 2. The effective triton radii in the ground ( ? T = 1.711 fm) and virtual ( ? v = 74.184 fm) states are calculated for the first time.

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

2008-01-01

364

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

365

Detection of Infrasonic Energy From Tornado-Producing Storms  

NASA Astrophysics Data System (ADS)

There are numerous reports in the literature on the observation of infrasound emitted from tornadic thunderstorms. Most of these observations have been made from sensors that are several hundreds of kilometers from the location of the storm, and "ground truth" about the tornadic activity is not well established. We report here on a campaign carried out during the summer of 2011 in which 50 infrasound microphones (whose approximate frequency response is 0.01-500 Hz) developed at the University of Mississippi were deployed by members of Hyperion Technology Group and their associates as part of an ongoing multi-university program on hazard detection and alert funded by the National Oceanic and Atmospheric Administration (NOAA). In this campaign, our deployment teams were able to deploy sensors along the paths of developing tornadic storms, including sensors that were located between twin F5 tornados near Oklahoma City on May 24, 2011. For this particular deployment we had sensors located a few kilometers from the northern most F5 tornado, and a second array, composed of three linear element arrays, that was optimally northeast of the storm. (A total of 7 tornados touched down in this area during this particular severe weather outbreak.) Substantial meteorological information, including ground truth about tornados (intensity and size as a function of time), and the relative close proximity of the sensors to the storms, provides us with a level of detail not available in previous storms. We will report on our infrasound measurements and analysis (source strength, frequency content as a function of tornadic intensity) from this outbreak as well as data from two other interceptions of tornadic storms, which occurred on the dates of May 30 and June 19, 2001.

Talmadge, C. L.; Waxler, R.; Kleinert, D. E.; Carter, G. E.; Godbold, G.; Harris, D. R.; Williams, C.

2011-12-01

366

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

367

New photodisintegration threshold observable in  

SciTech Connect

Measurements of the cross section, vector, and tensor analyzing powers, and linear gamma-ray polarization in the radiative capture reactions D(p,y){sup 3} He and p(d,y){sup 3}He at c.m. energies in the range 0-53 keV allow the determination of the reduced matrix elements (RMEs) relevant for these transitions. From these RMEs the value of the integral which determines the Gerasimov-Drell-Hearn sum rule for He is obtained in the threshold region, corresponding to two-body breakup, and compared with the results of an ab initio microscopic three-body model calculation.The theoretical predictions for the value of this integral based on a ''nucleons-only'' assumption are an order of magnitude smaller than experiment. The discrepancy is reduced to about a factor of 2 when two-body currents are taken into account. This factor of 2 is due to an almost exact cancellation between the dominant E1 RMEs in the theoretical calculation. The excess E1 strength observed experimentally could provide useful insights into the nuclear interaction at low energies.

E.A. Wulf; R.S. Canon; Sally J. Gaff; J.H. Kelley; R.M. Prior; E.C. Schreiber; M. Spraker; D.R. Tilley; H.R. Weller; M. Viviani; A. Kievsky; S. Rosati; Rocco Schiavilla

2000-02-01

368

Benefits of texture analysis of dual energy CT for Computer-Aided pulmonary embolism detection.  

PubMed

Pulmonary embolism is an avoidable cause of death if treated immediately but delays in diagnosis and treatment lead to an increased risk. Computer-assisted image analysis of both unenhanced and contrast-enhanced computed tomography (CT) have proven useful for diagnosis of pulmonary embolism. Dual energy CT provides additional information over the standard single energy scan by generating four-dimensional (4D) data, in our case with 11 energy levels in 3D. In this paper a 4D texture analysis method capable of detecting pulmonary embolism in dual energy CT is presented. The method uses wavelet-based visual words together with an automatic geodesic-based region of interest detection algorithm to characterize the texture properties of each lung lobe. Results show an increase in performance with respect to the single energy CT analysis, as well as an accuracy gain compared to preliminary work on a small dataset. PMID:24110602

Foncubierta-Rodríguez, Antonio; Jiménez del Toro, Óscar Alfonso; Platon, Alexandra; Poletti, Pierre-Alexandre; Müller, Henning; Depeursinge, Adrien

2013-01-01

369

Adaptive thresholding and windowing in real-time multispectral correlation  

NASA Astrophysics Data System (ADS)

Both thresholding and windowing are important tools in the reduction of false alarm rates in high sensitivity point source detection and correlation sensor signal processors. In a variable background environment, adaptive thresholding is required to maintain a constant false alarm rate, and in a variable target environment, adaptive windowing is helpful in controlling false alarm rate, while maintaining correlation performance. Several issues arise when applying adaptive detection thresholding and windowing in a scanning infrared sensor processor. Choice of control loops for both thresholding and windowing should be such that instabilities caused by interactions between them are minimized. Instabilities in operation can also occur due to the various states of the system itself, such as scanning state changes or gain mode changes. The current presentation will describe the application of adaptive thresholding and windowing in the sensor subsystem design of the Airborne Surveillance Testbed. Control loop closure choices will be outlined for both thresholding and windowing, and their effect on false alarm rate and correlation will be covered. The correction of scanning state and gain mode effects on thresholding will also be addressed, as well as the impact on correlation performance.

Stephenson, Gary V.; Winterberg, John J.; Bartel, Bart A.; Hedden, Richard L.

1992-08-01

370

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

371

Functions for detecting malposition of transcutaneous energy transmission coils.  

PubMed

A transcutaneous energy transmission system (TETS) for artificial hearts and ventricular assist devices uses electrical coupling of power between external and implanted coils. If the position of coils changes relative to each other, the TETS cannot feed the required power of the implanted device. During activity or sleep, the coils may move accidentally. TETS users and the people around them have to pay attention to this because the range of the position where the required power can be fed efficiently is not wide. Therefore, we added functions for the position changes of the coils to the TETS. Regular, cautious, and irregular positions were introduced, and the ranges of them were decided upon in our experiments. The cautious position was determined by the area where the change of the relative position of the coils was relatively small. When the coils were in the cautious position, the circuit was tuned by way of changing the resonant point. This modulation could give good power efficiency in the cautious position. When the coils were in the irregular position, an alarm switch was turned on. These functions ease the restriction of the coil position and give better quality of life (QOL) than do the conventional TETS. PMID:12918593

Ozeki, Toshinaga; Chinzei, Tsuneo; Abe, Yusuke; Saito, Itsuro; Isoyama, Takashi; Mochizuki, Shuuichi; Ishimaru, Mitsuhiko; Takiura, Koki; Baba, Atsushi; Toyama, Takahiro; Imachi, Kou

2003-01-01

372

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

NASA Astrophysics Data System (ADS)

This paper presents a grid interfaced solar photovoltaic (SPV) energy system with a novel adaptive harmonic detection control for power quality improvement at ac mains under balanced as well as unbalanced and distorted supply conditions. The SPV energy system is capable of compensation of linear and nonlinear loads with the objectives of load balancing, harmonics elimination, power factor correction and terminal voltage regulation. The proposed control increases the utilization of PV infrastructure and brings down its effective cost due to its other benefits. The adaptive harmonic detection control algorithm is used to detect the fundamental active power component of load currents which are subsequently used for reference source currents estimation. An instantaneous symmetrical component theory is used to obtain instantaneous positive sequence point of common coupling (PCC) voltages which are used to derive inphase and quadrature phase voltage templates. The proposed grid interfaced PV energy system is modelled and simulated in MATLAB Simulink and its performance is verified under various operating conditions.

Singh, B.; Goel, S.

2015-03-01

373

Low-Threshold Bidirectional Air Lasing  

NASA Astrophysics Data System (ADS)

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

Laurain, Alexandre; Scheller, Maik; Polynkin, Pavel

2014-12-01

374

Low-threshold bidirectional air lasing.  

PubMed

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

Laurain, Alexandre; Scheller, Maik; Polynkin, Pavel

2014-12-19

375

DONUT: A Threshold Gate Computer  

Microsoft Academic Search

During the past few years there has been a considerable amount of literature concerned with the realization of threshold logic. However, there are a number of questions concerning such factors as sensitivity and component savings which cannot be completely answered by such theoretical studies. DONUT (Digitally Operated Network Using Thresholds) is a small general purpose digital computer which was designed

C. L. Coates; P. M. Lewis

1964-01-01

376

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

377

STEPLENGTH THRESHOLDS FOR INVARIANCE PRESERVING ...  

E-print Network

be obtained by finding the first positive zeros of a finite number of polynomial ... Euler method, the largest steplength threshold for invariance preserving can ... to derive valid thresholds of the steplength in terms of explicit form or ... general rational function type discretization methods, i.e., the coefficient .... The basic ideas.

2014-06-25

378

Threshold Concepts and Information Literacy  

ERIC Educational Resources Information Center

What do we teach when we teach information literacy in higher education? This paper describes a pedagogical approach to information literacy that helps instructors focus content around transformative learning thresholds. The threshold concept framework holds promise for librarians because it grounds the instructor in the big ideas and underlying…

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

2011-01-01

379

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

SciTech Connect

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

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

2004-09-30

380

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

381

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

382

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

383

Boron-layer silicon photodiodes for high-efficiency low-energy electron detection Agata Sakic a,  

E-print Network

for use as low-energy electron detectors have been fabricated using a pure-boron technology to form the pBoron-layer silicon photodiodes for high-efficiency low-energy electron detection Agata Sakic´ a photodiodes Electron detection Low-energy electrons Boron deposition Ultrashallow junctions Responsivity

Technische Universiteit Delft

384

Bioluminescence resonance energy transfer (BRET) for the real-time detection of protein-protein interactions  

Microsoft Academic Search

A substantial range of protein-protein interactions can be readily monitored in real time using bioluminescence resonance energy transfer (BRET). The procedure involves heterologous coexpression of fusion proteins, which link proteins of interest to a bioluminescent donor enzyme or acceptor fluorophore. Energy transfer between these proteins is then detected. This protocol encompasses BRET1, BRET2 and the recently described eBRET, including selection

Ruth M Seeber; Karin A Eidne; Kevin D G Pfleger

2006-01-01

385

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

Microsoft Academic Search

It is widely believed that charm meson production and decay may play an important role in high energy astrophysical sources of neutrinos, especially those that are baryon-rich, providing an environment conducive to pp interactions. Using slow-jet supernovae (SJS) as an example of such a source, we study the detectability of high-energy neutrinos, paying particular attention to those produced from charmed-mesons.

Raj Gandhi; Abhijit Samanta; Atsushi Watanabe

2009-01-01

386

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

387

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

NASA Technical Reports Server (NTRS)

Observations of the galactic center region made with the high energy X-ray detector on OSO-8 are discussed. A strong hard X-ray which was detected during these observations from the vicinity of the galactic center are examined. The counting rate spectrum and the photon number spectrum of the flux are determined. Comparisons with the high energy X-ray fluxes observed from sources in the region by others are discussed.

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

1979-01-01

388

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

T. ANDREW HURLY

2003-01-01

389

Absence of a {open_quote}{open_quote}Threshold Effect{close_quote}{close_quote} in the Energy Loss of Slow Protons Traversing Large-Band-Gap Insulators  

Microsoft Academic Search

The electronic stopping cross section {var_epsilon} of slow hydrogen projectiles in large-band-gap insulators has been measured at energies of a few keV. Even at velocities as low as vâ\\/3 (vâ=c\\/137) , we find no influence of the band gap on the velocity dependence of {var_epsilon} , contrary to the case of gaseous targets with similar minimum excitation energy. The magnitude

K. Eder; D. Semrad; P. Bauer; R. Golser; P. Maier-Komor; F. Aumayr; M. Penalba; A. Arnau; J. M. Ugalde; P. M. Echenique

1997-01-01

390

Bayesian estimation of dose thresholds  

NASA Technical Reports Server (NTRS)

An example is described of Bayesian estimation of radiation absorbed dose thresholds (subsequently simply referred to as dose thresholds) using a specific parametric model applied to a data set on mice exposed to 60Co gamma rays and fission neutrons. A Weibull based relative risk model with a dose threshold parameter was used to analyse, as an example, lung cancer mortality and determine the posterior density for the threshold dose after single exposures to 60Co gamma rays or fission neutrons from the JANUS reactor at Argonne National Laboratory. The data consisted of survival, censoring times and cause of death information for male B6CF1 unexposed and exposed mice. The 60Co gamma whole-body doses for the two exposed groups were 0.86 and 1.37 Gy. The neutron whole-body doses were 0.19 and 0.38 Gy. Marginal posterior densities for the dose thresholds for neutron and gamma radiation were calculated with numerical integration and found to have quite different shapes. The density of the threshold for 60Co is unimodal with a mode at about 0.50 Gy. The threshold density for fission neutrons declines monotonically from a maximum value at zero with increasing doses. The posterior densities for all other parameters were similar for the two radiation types.

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

2003-01-01

391

Cortical evoked response audiometry thresholds and neuroleptic, sedative, hypnotic drugs.  

PubMed

Cortical evoked response audiometry is adequate for approximating hearing threshold levels with frequency specificity when the psychoacoustic responses lack reliability and reproducibility (compensation claim). It is well-known that control of wakefulness is essential for the reliability of slow vertex responses (SVR). Therefore, sedative, hypnotic, and neuroleptic drugs are supposed to have possible adverse effects on the detection of SVR. In contrast, brainstem evoked responses (BER) have proved not to be significantly affected by therapeutic doses of these compounds. The purpose of our study was to assess the reliability of SVR-threshold definition in subjects taking neuroleptic, sedative, and hypnotic drugs. Fifteen subjects examined for occupational hearing loss at the Fund for Occupational Diseases in Brussels and regularly taking one or several of these drugs were compared with 27 comparable controls. In each subject the auditory thresholds were defined with both techniques: SVR (1, 2, and 3 kHz) and BER (clicks). A highly significant difference is observed between the two groups: In the group receiving drugs, the SVR threshold for 3 kHz is 12.1 dB (average) higher than the BER threshold, whereas in the group without drugs, the SVR threshold for 3 kHz is 7.77 dB (average) lower than the BER threshold. In the drug group, large interindividual differences are observed. It may be concluded that the use of neuroleptics, sedatives, and hypnotics renders the auditory threshold definition with SVR completely unreliable. In using SVR for medicolegal threshold definition, controlling the 3-kHz threshold with BER always is necessary. PMID:14689614

Dejonckere, P H; Lebacq, J; Coryn, C

2000-01-01

392

DEVELOPMENT OF A REAL-TIME FLUORESCENCE RESONANCE ENERGY TRANSFER (FRET) PCR TO DETECT ARCOBACTER SPECIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

A real-time PCR targeting the gyrase A subunit gene outside the quinolone resistance-determining region has been developed to detect Arcobacter species. The species identification was made by probe hybridization and melting curve analysis, using the Fluorescence Resonance Energy Transfer technology...

393

DEVELOPMENT OF A REAL-TIME FLUORESCENCE RESONANCE ENERGY TRANSFER PCR TO DETECT ARCOBACTER SPECIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

A real-time PCR targeting the gyrase A subunit gene outside the quinolone resistance-determining region has been developed to detect Arcobacter species. The species identification was made by probe hybridization and melting curve analysis, using Fluorescence Resonance Energy Transfer technology. D...

394

Security versus Energy Tradeoffs in Host-Based Mobile Malware Detection  

E-print Network

Security versus Energy Tradeoffs in Host-Based Mobile Malware Detection Jeffrey Bickford H. Andrés The rapid growth of mobile malware necessitates the presence of robust malware detectors on mobile devices. However, running malware detectors on mobile devices may drain their battery, caus- ing users to disable

Shihada, Basem

395

An Alternative Energy Detection Using Sliding Window for Cognitive Radio System  

Microsoft Academic Search

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

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

2008-01-01

396

Development of an RNA detection system using bioluminescence resonance energy transfer  

Microsoft Academic Search

Here we demonstrate a new RNA detection system using bioluminescence resonance energy transfer (BRET). Recombinant proteins were constructed consisting of enhanced yellow fluorescence protein (EYFP) and Renilla luciferase (RLuc) tethered by Arginine Rich Motif (ARM) peptides, which recognize specific RNA motifs and change their conformation upon binding to them. Conformational transitions of ARM peptides upon RNA binding then trigger a

Takashi Andou; Tamaki Endoh; Masayasu Mie; Eiry Kobatake

2011-01-01

397

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

E-print Network

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

Falcke, Heino

398

Modelling energy flow in the vocal tract with applications to glottal closure and opening detection  

Microsoft Academic Search

The pitch-synchronous analysis that is used in several areas of speech processing often requires robust detection of the instants of glottal closure and opening. In this paper we derive expressions for the flow of acoustic energy in the lossless-tube model of the vocal tract and show how linear predictive analysis may be used to estimate the waveform of acoustic input

D. M. Brookes; H. P. Loke

1999-01-01

399

Identification of packet exchange patterns based on energy detection: the Bluetooth case  

E-print Network

Identification of packet exchange patterns based on energy detection: the Bluetooth case Sergio of Bluetooth packet exchange patterns reveals technology-specific MAC layer procedures, leading-Fi (IEEE Std 802.11), Bluetooth (IEEE Std 802.15.1) and ZigBee (IEEE Std 802.15.4), operate in the ISM 2

Di Benedetto, Maria-Gabriella

400

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

SciTech Connect

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

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

2009-09-01

401

Neutron detection with a NaI spectrometer using high-energy photons  

NASA Astrophysics Data System (ADS)

Neutrons can be indirectly detected by high-energy photons. The performance of a 4?×4?×16? NaI portal monitor was compared to a 3He-based portal monitor with a comparable cross-section of the active volume. Measurements were performed with bare and shielded 252Cf and AmBe sources. With an optimum converter and moderator structure for the NaI detector, the detection efficiencies and minimum detectable activities of the portal monitors were similar. The NaI portal monitor preserved its detection efficiency much better with shielded sources, making the method very interesting for security applications. For heavily shielded sources, the NaI detector was 2-3 times more sensitive than the 3He-based detector.

Holm, Philip; Peräjärvi, Kari; Sihvonen, Ari-Pekka; Siiskonen, Teemu; Toivonen, Harri

2013-01-01

402

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

E-print Network

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 {\\it 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.

Peter Sorensen; Carl Eric Dahl

2011-01-31

403

Magnetic calorimeter with a SQUID for detecting weak radiations and recording the ultralow energy release  

SciTech Connect

The scheme of a magnetic calorimeter for recording extremely low energy releases is developed. The calorimeter is activated by the method of adiabatic demagnetisation and its response to the energy release is measured with a superconducting quantum interference device (SQUID). The estimate of the ultimate sensitivity of the calorimeter with the SQUID demonstrates the possibilities of its application for detecting ultralow radiation intensity, recording single X-ray quanta in the proportional regime and other events with ultralow energy releases. The scheme of the calorimeter with the SQUID on matter waves in superfluid {sup 4}He is proposed. (radiation detectors)

Golovashkin, Aleksander I; Zherikhina, L N; Kuleshova, G V; Tskhovrebov, A M [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Izmailov, G N [Moscow Aviation Institute (State Technical University), Moscow (Russian Federation)

2006-12-31

404

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

405

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

406

On Radio Detection of Ultra-High Energy Neutrinos in Antarctic Ice  

E-print Network

Interactions of ultrahigh energy neutrinos of cosmological origin in large volumes of dense, radio-transparent media can be detected via coherent Cherenkov emission from accompanying electromagnetic showers. Antarctic ice meets the requirements for an efficient detection medium for a radio frequency neutrino telescope. We carefully estimate the sensitivity of realistic antennas embedded deep in the ice to 100 MHz - 1 GHz signals generated by predicted neutrino fluxes from active galactic nuclei. Our main conclusion is that a {\\it single radio receiver} can probe a $\\sim 1$ ${\\rm km}^3$ volume for events with primary energy near 2 PeV and that the total number of events registered would be roughly 200 to 400 ${\\rm year}^{-1}$ in our most conservative estimate. An array of such receivers would increase sensitivity dramatically. A radio neutrino telescope could directly observe and test our understanding of the most powerful particle accelerators in the universe, simultaneously testing the standard theory of particle physics at unprecedented energies.

George M. Frichter; John P. Ralston; Douglas W. McKay

1995-07-21

407

Bone mineral density of the spine and the hip measured with dual energy X-ray absorptiometry: Normal range and fracture threshold for Western European (Belgian) postmenopausal females  

Microsoft Academic Search

Summary Bone mineral density (BMD) of the spine and the different regions of interest (ROI) of the hip were measured by dual energy X-ray absorptiometry in 278 healthy Belgian postmenopausal women and 93 postmenopausal type I osteoporotic females in order to:

J. Y. Reginster; C. Janssen; R. Deroisy; B. Zegels; A. Albert; P. Franchimont

1995-01-01

408

EGRET Spectral Index and the Low-Energy Peak Position in the Spectral Energy Distribution of EGRET-Detected Blazars  

E-print Network

In current theoretical models of the blazar subclass of active galaxies, the broadband emission consists of two components: a low-frequency synchrotron component with a peak in the IR to X-ray band, and a high-frequency inverse Compton component with a peak in the gamma-ray band. In such models, the gamma-ray spectral index should be correlated with the location of the low-energy peak, with flatter gamma-ray spectra expected for blazars with synchrotron peaks at higher photon energies and vice versa. Using the EGRET-detected blazars as a sample, we examine this correlation and possible uncertainties in its construction.

Y. C. Lin

1999-05-12

409

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

410

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

ERIC Educational Resources Information Center

The growing field of energy assessment for buildings presents opportunities for teachers to engage students in topics related to current issues, science, technology, and communication skills. Students who find satisfaction in energy auditing can expand their interests into careers as the demand to stop wasteful practices in homes and businesses…

Helmholdt, Nick

2012-01-01

411

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

412

Direct Detection and Imaging of Low-Energy Electrons with Delta-Doped Charge-Coupled Devices  

NASA Technical Reports Server (NTRS)

We report the use fo delta-doped charge-coupled devices (CCDs) for direct detection of electrons in the 50-1500 eV energy range. These are the first measurements with a solid state device to detect electrons in this energy range.

Nikzad, S.; Yu, Q.; Smith, A. L.; Jones, T. J.; Tombrello, T. A.; Elliott, S. T.

1998-01-01

413

Pulse variations of a conducted energy weapon (similar to the TASER X26 device): effects on muscle contraction and threshold for ventricular fibrillation*.  

PubMed

Conducted energy weapons (such as the Advanced TASER X26 model produced by TASER International), incapacitate individuals by causing muscle contractions. To provide information relevant to development of future potential devices, a "Modifiable Electronic Stimulator" was used to evaluate the effects of changing various parameters of the stimulating pulse. Muscle contraction was affected by pulse power, net/gross charge, pulse duration, and pulse repetition frequency. The contraction force increased linearly as each of these factors was increased. Elimination of a precursor pulse from X26-like pulses did not have a significant effect on the normalized force measured. Muscle-contraction force increased as the spacing increased from 5 to 20 cm, with no further change in force above 20 cm of spacing. Therefore, it is suggested that any future developments of new conducted energy weapons should include placement of electrodes a minimum of 20 cm apart so that efficiency of the system is not degraded. In the current study, the 50% probability of fibrillation level of X26-like pulses ranged from 4 to 5 times higher than the X26 itself. Relatively large variations about the X26 operating level were found not to result in fibrillation or asystole. Therefore, it should be possible to design and build an X26-type device that operates efficiently at levels higher than the X26. PMID:19737245

Beason, Charles W; Jauchem, James R; Clark, C D; Parker, James E; Fines, David A

2009-09-01

414

Absence of a {open_quote}{open_quote}Threshold Effect{close_quote}{close_quote} in the Energy Loss of Slow Protons Traversing Large-Band-Gap Insulators  

SciTech Connect

The electronic stopping cross section {var_epsilon} of slow hydrogen projectiles in large-band-gap insulators has been measured at energies of a few keV. Even at velocities as low as v{sub 0}/3 (v{sub 0}=c/137) , we find no influence of the band gap on the velocity dependence of {var_epsilon} , contrary to the case of gaseous targets with similar minimum excitation energy. The magnitude of {var_epsilon} and its essentially linear velocity dependence allow us to arrive at the following conclusion: Electron promotion processes contribute substantially to stopping due to formation of molecular orbitals. This points towards the existence of a bound electron state at a proton that moves slowly in an insulator. A simple model based on the calculation of molecular orbital correlation diagrams for the H/LiF collision system supports the idea of local reduction of the band gap of an insulating target. {copyright} {ital 1997} {ital The American Physical Society}

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

1997-11-01

415

Helicity dependence and contribution to the Gerasimov-Drell-Hearn sum rule of the {gamma}-vectord-vector{yields}{pi}NN reaction channels in the energy region from threshold up to the {delta}(1232) resonance  

SciTech Connect

The helicity dependence of the {gamma}-vectord-vector{yields}{pi}{sup -}pp,{gamma}-vectord-vector{yields}{pi}{sup +}nn, and {gamma}-vectord-vector{yields}{pi}{sup 0}np reaction channels is studied for incident photon energies from threshold up to the {delta}(1232) resonance with inclusion of leading {pi}NN effects. The doubly polarized total and differential cross sections for parallel and antiparallel helicity states are predicted. Then the contribution of various channels to the deuteron spin asymmetry and the double polarization E asymmetry is calculated. In addition, the contribution to the Gerasimov-Drell-Hearn (GDH) integral from separate channels is evaluated by explicit integration up to a photon lab energy of 350 MeV. Sizeable effects from final-state interactions, specially for {pi}{sup 0} production, are found. The sensitivity of the results to the elementary pion photoproduction operator is also investigated. Considerable dependence of the results on the elementary amplitude is found. We expect that these results may be useful to interpret the recent measurements from LEGS-BNL, A2, and GDH-MAMI Collaborations.

Darwish, E. M. [Physics Department, Faculty of Science, Sohag University, Sohag 82524 (Egypt); Fernandez-Ramirez, C. [Instituto de Estructura de la Materia, CSIC, Serrano 123, E-28006 Madrid (Spain); Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Sevilla, Apdo. 1065, E-41080 Sevilla (Spain); Guerra, E. Moya de [Instituto de Estructura de la Materia, CSIC, Serrano 123, E-28006 Madrid (Spain); Grupo de Fisica Nuclear and Departamento de Fisica Atomica, Molecular y Nuclear, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, Avda. Complutense s/n, E-28040 Madrid (Spain); Udias, J. M. [Grupo de Fisica Nuclear, Departamento de Fisica Atomica, Molecular y Nuclear, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, Avda. Complutense s/n, E-28040 Madrid (Spain)

2007-10-15

416

An energy-based detection algorithm of epileptic seizures in EEG records.  

PubMed

A simple algorithm to automatically detect segments with epileptic seizures in long EEG records has been developed. The main advantages of the proposed method are: the simple algorithm used and the lower computational cost. The algorithm measures the energy of each EEG channel by a sliding window and calculates some features of each patient signal to detect the epileptic seizure. It is also able to distinguish between seizures and noise artifacts. Nine invasive EEG records acquired by Epilepsy Center of the University Hospital of Freiburg were analyzed in this work. In 90 segments studied (39 with epileptic seizures) the sensitivity obtained with the method is 87.18 %. The algorithm is appropriate to detect epileptic seizures, with high sensitivity, in long EEG records to decrease the time used by physicians and specialists in visual inspections. PMID:19964519

Correa, Agustina Garcés; Laciar, Eric; Orosco, Lorena; Gómez, Maria E; Otoya, Raúl; Jané, Raimón

2009-01-01

417

Threshold photodetachment spectroscopy of negative ions  

SciTech Connect

This thesis is concerned with the development and application of high resolution threshold photodetachment spectroscopy of negative ions. Chapter I deals with the principles of our photodetachment technique, and in chapter II a detailed description of the apparatus is presented. The threshold photodetachment spectra of I{sup {minus}}, and SH{sup {minus}}, presented in the last sections of chapter II, indicated that a resolution of 3 cm{sup {minus}1} can be achieved using our technique. In chapter III the threshold photodetachment spectroscopy study of the transition state region of I + HI and I + Di reactions is discussed. Our technique probes the transition state region directly, and the results of our study are the first unambiguous observations of reactive resonances in a chemical reaction. Chapters IV, V and VI are concerned with the spectroscopy of small silicon and carbon clusters. From our spectra we were able to assign electronic state energies and vibrational frequencies for the low lying electronics states of Si{sub n} (n=2,3,4), C{sub 5} and their corresponding anions.

Kitsopoulos, T.N.

1991-12-01

418

Position and energy-resolved particle detection using phonon-mediated microwave kinetic inductance detectors  

NASA Astrophysics Data System (ADS)

We demonstrate position and energy-resolved phonon-mediated detection of particle interactions in a silicon substrate instrumented with an array of microwave kinetic inductance detectors (MKIDs). The relative magnitude and delay of the signal received in each sensor allow the location of the interaction to be determined with <~ 1mm resolution at 30 keV. Using this position information, variations in the detector response with position can be removed, and an energy resolution of ?E = 0.55 keV at 30 keV was measured. Since MKIDs can be fabricated from a single deposited film and are naturally multiplexed in the frequency domain, this technology can be extended to provide highly pixelized athermal phonon sensors for ~1 kg scale detector elements. Such high-resolution, massive particle detectors would be applicable to rare-event searches such as the direct detection of dark matter, neutrinoless double-beta decay, or coherent neutrino-nucleus scattering.

Moore, D. C.; Golwala, S. R.; Bumble, B.; Cornell, B.; Day, P. K.; LeDuc, H. G.; Zmuidzinas, J.

2012-06-01

419

The perceptual threshold for overweight.  

PubMed

Normative, global overweight may play a prominent role in perpetuating the obesity epidemic via its contribution to weight-related norms that describe what is customary in a social environment. These weight-related norms include a perceptual standard determining where body weight shifts from normal to overweight. We introduce the construct of a perceptual threshold for overweight to identify this transition point. The perceptual threshold is measured on 0-100mm scales positioned below adult and child figures. This report presents three studies that evaluate the psychometric properties of this variable. Study 1explored its independence from BMI and body image in factor analyses with diverse samples (Ukrainian, Mexican and US Black, White, and Hispanic). Study 2 was a replication of this factor structure, and Study 3 investigated the reliability of the perceptual threshold using classical test (CT) and generalizability methods (GT). In Studies 1 and 2, two factors were identified (Perceptual Threshold for Overweight and Body Image/BMI) with almost identical factor structures in six analyses. In Study 3 the CT and GT procedures demonstrated adequate reliability. These results indicate that the psychometric properties of the perceptual threshold are sound, and support its use in exploring the social transmission of weight and evaluating obesity prevention and intervention programs. PMID:22664395

Johnson, William G; Stewart, Regan; Pusser, Andrea T

2012-08-01

420

Addressing the Challenges of Anomaly Detection for Cyber Physical Energy Grid Systems  

SciTech Connect

The consolidation of cyber communications networks and physical control systems within the energy smart grid introduces a number of new risks. Unfortunately, these risks are largely unknown and poorly understood, yet include very high impact losses from attack and component failures. One important aspect of risk management is the detection of anomalies and changes. However, anomaly detection within cyber security remains a difficult, open problem, with special challenges in dealing with false alert rates and heterogeneous data. Furthermore, the integration of cyber and physical dynamics is often intractable. And, because of their broad scope, energy grid cyber-physical systems must be analyzed at multiple scales, from individual components, up to network level dynamics. We describe an improved approach to anomaly detection that combines three important aspects. First, system dynamics are modeled using a reduced order model for greater computational tractability. Second, a probabilistic and principled approach to anomaly detection is adopted that allows for regulation of false alerts and comparison of anomalies across heterogeneous data sources. Third, a hierarchy of aggregations are constructed to support interactive and automated analyses of anomalies at multiple scales.

Ferragut, Erik M [ORNL; Laska, Jason A [ORNL; Melin, Alexander M [ORNL; Czejdo, Bogdan [ORNL

2013-01-01

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