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Sample records for adaptive variable-ratio threshold

  1. Adaptive Thresholds

    SciTech Connect

    Bremer, P. -T.

    2014-08-26

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

  2. Adaptive thresholding of digital subtraction angiography images

    NASA Astrophysics Data System (ADS)

    Sang, Nong; Li, Heng; Peng, Weixue; Zhang, Tianxu

    2005-10-01

    In clinical practice, digital subtraction angiography (DSA) is a powerful technique for the visualization of blood vessels in the human body. Blood vessel segmentation is a main problem for 3D vascular reconstruction. In this paper, we propose a new adaptive thresholding method for the segmentation of DSA images. Each pixel of the DSA images is declared to be a vessel/background point with regard to a threshold and a few local characteristic limits depending on some information contained in the pixel neighborhood window. The size of the neighborhood window is set according to a priori knowledge of the diameter of vessels to make sure that each window contains the background definitely. Some experiments on cerebral DSA images are given, which show that our proposed method yields better results than global thresholding methods and some other local thresholding methods do.

  3. An Adaptive Threshold in Mammalian Neocortical Evolution

    PubMed Central

    Kalinka, Alex T.; Tomancak, Pavel; Huttner, Wieland B.

    2014-01-01

    Expansion of the neocortex is a hallmark of human evolution. However, determining which adaptive mechanisms facilitated its expansion remains an open question. Here we show, using the gyrencephaly index (GI) and other physiological and life-history data for 102 mammalian species, that gyrencephaly is an ancestral mammalian trait. We find that variation in GI does not evolve linearly across species, but that mammals constitute two principal groups above and below a GI threshold value of 1.5, approximately equal to 109 neurons, which may be characterized by distinct constellations of physiological and life-history traits. By integrating data on neurogenic period, neuroepithelial founder pool size, cell-cycle length, progenitor-type abundances, and cortical neuron number into discrete mathematical models, we identify symmetric proliferative divisions of basal progenitors in the subventricular zone of the developing neocortex as evolutionarily necessary for generating a 14-fold increase in daily prenatal neuron production, traversal of the GI threshold, and thus establishment of two principal groups. We conclude that, despite considerable neuroanatomical differences, changes in the length of the neurogenic period alone, rather than any novel neurogenic progenitor lineage, are sufficient to explain differences in neuron number and neocortical size between species within the same principal group. PMID:25405475

  4. Adaptive Spike Threshold Enables Robust and Temporally Precise Neuronal Encoding

    PubMed Central

    Resnik, Andrey; Celikel, Tansu; Englitz, Bernhard

    2016-01-01

    Neural processing rests on the intracellular transformation of information as synaptic inputs are translated into action potentials. This transformation is governed by the spike threshold, which depends on the history of the membrane potential on many temporal scales. While the adaptation of the threshold after spiking activity has been addressed before both theoretically and experimentally, it has only recently been demonstrated that the subthreshold membrane state also influences the effective spike threshold. The consequences for neural computation are not well understood yet. We address this question here using neural simulations and whole cell intracellular recordings in combination with information theoretic analysis. We show that an adaptive spike threshold leads to better stimulus discrimination for tight input correlations than would be achieved otherwise, independent from whether the stimulus is encoded in the rate or pattern of action potentials. The time scales of input selectivity are jointly governed by membrane and threshold dynamics. Encoding information using adaptive thresholds further ensures robust information transmission across cortical states i.e. decoding from different states is less state dependent in the adaptive threshold case, if the decoding is performed in reference to the timing of the population response. Results from in vitro neural recordings were consistent with simulations from adaptive threshold neurons. In summary, the adaptive spike threshold reduces information loss during intracellular information transfer, improves stimulus discriminability and ensures robust decoding across membrane states in a regime of highly correlated inputs, similar to those seen in sensory nuclei during the encoding of sensory information. PMID:27304526

  5. Improved visual background extractor using an adaptive distance threshold

    NASA Astrophysics Data System (ADS)

    Han, Guang; Wang, Jinkuan; Cai, Xi

    2014-11-01

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

  6. Adaptive threshold harvesting and the suppression of transients.

    PubMed

    Segura, Juan; Hilker, Frank M; Franco, Daniel

    2016-04-21

    Fluctuations in population size are in many cases undesirable, as they can induce outbreaks and extinctions or impede the optimal management of populations. We propose the strategy of adaptive threshold harvesting (ATH) to control fluctuations in population size. In this strategy, the population is harvested whenever population size has grown beyond a certain proportion in comparison to the previous generation. Taking such population increases into account, ATH intervenes also at smaller population sizes than the strategy of threshold harvesting. Moreover, ATH is the harvesting version of adaptive limiter control (ALC) that has recently been shown to stabilize population oscillations in both experiments and theoretical studies. We find that ATH has similar stabilization properties as ALC and thus offers itself as a harvesting alternative for the control of pests, exploitation of biological resources, or when restocking interventions required from ALC are unfeasible. We present numerical simulations of ATH to illustrate its performance in the presence of noise, lattice effect, and Allee effect. In addition, we propose an adjustment to both ATH and ALC that restricts interventions when control seems unnecessary, i.e. when population size is too small or too large, respectively. This adjustment cancels prolonged transients. PMID:26854876

  7. Adaptations to training at the individual anaerobic threshold.

    PubMed

    Keith, S P; Jacobs, I; McLellan, T M

    1992-01-01

    The individual anaerobic threshold (Th(an)) is the highest metabolic rate at which blood lactate concentrations can be maintained at a steady-state during prolonged exercise. The purpose of this study was to test the hypothesis that training at the Th(an) would cause a greater change in indicators of training adaptation than would training "around" the Th(an). Three groups of subjects were evaluated before, and again after 4 and 8 weeks of training: a control group, a group which trained continuously for 30 min at the Th(an) intensity (SS), and a group (NSS) which divided the 30 min of training into 7.5-min blocks at intensities which alternated between being below the Th(an) [Th(an) -30% of the difference between Th(an) and maximal oxygen consumption (VO2max)] and above the Th(an) (Th(an) +30% of the difference between Th(an) and VO2max). The VO2max increased significantly from 4.06 to 4.27 l.min-1 in SS and from 3.89 to 4.06 l.min-1 in NSS. The power output (W) at Th(an) increased from 70.5 to 79.8% VO2max in SS and from 71.1 to 80.7% VO2max in NSS. The magnitude of change in VO2max, W at Th(an), % VO2max at Th(an) and in exercise time to exhaustion at the pretraining Th(an) was similar in both trained groups. Vastus lateralis citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase activities increased to the same extent in both trained groups. While all of these training-induced adaptations were statistically significant (P < 0.05), there were no significant changes in any of these variables for the control subjects.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1425631

  8. Spike-Threshold Adaptation Predicted by Membrane Potential Dynamics In Vivo

    PubMed Central

    Fontaine, Bertrand; Peña, José Luis; Brette, Romain

    2014-01-01

    Neurons encode information in sequences of spikes, which are triggered when their membrane potential crosses a threshold. In vivo, the spiking threshold displays large variability suggesting that threshold dynamics have a profound influence on how the combined input of a neuron is encoded in the spiking. Threshold variability could be explained by adaptation to the membrane potential. However, it could also be the case that most threshold variability reflects noise and processes other than threshold adaptation. Here, we investigated threshold variation in auditory neurons responses recorded in vivo in barn owls. We found that spike threshold is quantitatively predicted by a model in which the threshold adapts, tracking the membrane potential at a short timescale. As a result, in these neurons, slow voltage fluctuations do not contribute to spiking because they are filtered by threshold adaptation. More importantly, these neurons can only respond to input spikes arriving together on a millisecond timescale. These results demonstrate that fast adaptation to the membrane potential captures spike threshold variability in vivo. PMID:24722397

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

    NASA Astrophysics Data System (ADS)

    Xu, Jian; Wang, Huaisuo; Huang, Hua

    2015-12-01

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

  10. Adaptive local thresholding for robust nucleus segmentation utilizing shape priors

    NASA Astrophysics Data System (ADS)

    Wang, Xiuzhong; Srinivas, Chukka

    2016-03-01

    This paper describes a novel local thresholding method for foreground detection. First, a Canny edge detection method is used for initial edge detection. Then, tensor voting is applied on the initial edge pixels, using a nonsymmetric tensor field tailored to encode prior information about nucleus size, shape, and intensity spatial distribution. Tensor analysis is then performed to generate the saliency image and, based on that, the refined edge. Next, the image domain is divided into blocks. In each block, at least one foreground and one background pixel are sampled for each refined edge pixel. The saliency weighted foreground histogram and background histogram are then created. These two histograms are used to calculate a threshold by minimizing the background and foreground pixel classification error. The block-wise thresholds are then used to generate the threshold for each pixel via interpolation. Finally, the foreground is obtained by comparing the original image with the threshold image. The effective use of prior information, combined with robust techniques, results in far more reliable foreground detection, which leads to robust nucleus segmentation.

  11. Adaptive thresholding for reliable topological inference in single subject fMRI analysis.

    PubMed

    Gorgolewski, Krzysztof J; Storkey, Amos J; Bastin, Mark E; Pernet, Cyril R

    2012-01-01

    Single subject fMRI has proved to be a useful tool for mapping functional areas in clinical procedures such as tumor resection. Using fMRI data, clinicians assess the risk, plan and execute such procedures based on thresholded statistical maps. However, because current thresholding methods were developed mainly in the context of cognitive neuroscience group studies, most single subject fMRI maps are thresholded manually to satisfy specific criteria related to single subject analyzes. Here, we propose a new adaptive thresholding method which combines Gamma-Gaussian mixture modeling with topological thresholding to improve cluster delineation. In a series of simulations we show that by adapting to the signal and noise properties, the new method performs well in terms of total number of errors but also in terms of the trade-off between false negative and positive cluster error rates. Similarly, simulations show that adaptive thresholding performs better than fixed thresholding in terms of over and underestimation of the true activation border (i.e., higher spatial accuracy). Finally, through simulations and a motor test-retest study on 10 volunteer subjects, we show that adaptive thresholding improves reliability, mainly by accounting for the global signal variance. This in turn increases the likelihood that the true activation pattern can be determined offering an automatic yet flexible way to threshold single subject fMRI maps.

  12. Adaptive thresholding for reliable topological inference in single subject fMRI analysis.

    PubMed

    Gorgolewski, Krzysztof J; Storkey, Amos J; Bastin, Mark E; Pernet, Cyril R

    2012-01-01

    Single subject fMRI has proved to be a useful tool for mapping functional areas in clinical procedures such as tumor resection. Using fMRI data, clinicians assess the risk, plan and execute such procedures based on thresholded statistical maps. However, because current thresholding methods were developed mainly in the context of cognitive neuroscience group studies, most single subject fMRI maps are thresholded manually to satisfy specific criteria related to single subject analyzes. Here, we propose a new adaptive thresholding method which combines Gamma-Gaussian mixture modeling with topological thresholding to improve cluster delineation. In a series of simulations we show that by adapting to the signal and noise properties, the new method performs well in terms of total number of errors but also in terms of the trade-off between false negative and positive cluster error rates. Similarly, simulations show that adaptive thresholding performs better than fixed thresholding in terms of over and underestimation of the true activation border (i.e., higher spatial accuracy). Finally, through simulations and a motor test-retest study on 10 volunteer subjects, we show that adaptive thresholding improves reliability, mainly by accounting for the global signal variance. This in turn increases the likelihood that the true activation pattern can be determined offering an automatic yet flexible way to threshold single subject fMRI maps. PMID:22936908

  13. Reinforcement learning for adaptive threshold control of restorative brain-computer interfaces: a Bayesian simulation.

    PubMed

    Bauer, Robert; Gharabaghi, Alireza

    2015-01-01

    Restorative brain-computer interfaces (BCI) are increasingly used to provide feedback of neuronal states in a bid to normalize pathological brain activity and achieve behavioral gains. However, patients and healthy subjects alike often show a large variability, or even inability, of brain self-regulation for BCI control, known as BCI illiteracy. Although current co-adaptive algorithms are powerful for assistive BCIs, their inherent class switching clashes with the operant conditioning goal of restorative BCIs. Moreover, due to the treatment rationale, the classifier of restorative BCIs usually has a constrained feature space, thus limiting the possibility of classifier adaptation. In this context, we applied a Bayesian model of neurofeedback and reinforcement learning for different threshold selection strategies to study the impact of threshold adaptation of a linear classifier on optimizing restorative BCIs. For each feedback iteration, we first determined the thresholds that result in minimal action entropy and maximal instructional efficiency. We then used the resulting vector for the simulation of continuous threshold adaptation. We could thus show that threshold adaptation can improve reinforcement learning, particularly in cases of BCI illiteracy. Finally, on the basis of information-theory, we provided an explanation for the achieved benefits of adaptive threshold setting. PMID:25729347

  14. Reinforcement learning for adaptive threshold control of restorative brain-computer interfaces: a Bayesian simulation.

    PubMed

    Bauer, Robert; Gharabaghi, Alireza

    2015-01-01

    Restorative brain-computer interfaces (BCI) are increasingly used to provide feedback of neuronal states in a bid to normalize pathological brain activity and achieve behavioral gains. However, patients and healthy subjects alike often show a large variability, or even inability, of brain self-regulation for BCI control, known as BCI illiteracy. Although current co-adaptive algorithms are powerful for assistive BCIs, their inherent class switching clashes with the operant conditioning goal of restorative BCIs. Moreover, due to the treatment rationale, the classifier of restorative BCIs usually has a constrained feature space, thus limiting the possibility of classifier adaptation. In this context, we applied a Bayesian model of neurofeedback and reinforcement learning for different threshold selection strategies to study the impact of threshold adaptation of a linear classifier on optimizing restorative BCIs. For each feedback iteration, we first determined the thresholds that result in minimal action entropy and maximal instructional efficiency. We then used the resulting vector for the simulation of continuous threshold adaptation. We could thus show that threshold adaptation can improve reinforcement learning, particularly in cases of BCI illiteracy. Finally, on the basis of information-theory, we provided an explanation for the achieved benefits of adaptive threshold setting.

  15. Reinforcement learning for adaptive threshold control of restorative brain-computer interfaces: a Bayesian simulation

    PubMed Central

    Bauer, Robert; Gharabaghi, Alireza

    2015-01-01

    Restorative brain-computer interfaces (BCI) are increasingly used to provide feedback of neuronal states in a bid to normalize pathological brain activity and achieve behavioral gains. However, patients and healthy subjects alike often show a large variability, or even inability, of brain self-regulation for BCI control, known as BCI illiteracy. Although current co-adaptive algorithms are powerful for assistive BCIs, their inherent class switching clashes with the operant conditioning goal of restorative BCIs. Moreover, due to the treatment rationale, the classifier of restorative BCIs usually has a constrained feature space, thus limiting the possibility of classifier adaptation. In this context, we applied a Bayesian model of neurofeedback and reinforcement learning for different threshold selection strategies to study the impact of threshold adaptation of a linear classifier on optimizing restorative BCIs. For each feedback iteration, we first determined the thresholds that result in minimal action entropy and maximal instructional efficiency. We then used the resulting vector for the simulation of continuous threshold adaptation. We could thus show that threshold adaptation can improve reinforcement learning, particularly in cases of BCI illiteracy. Finally, on the basis of information-theory, we provided an explanation for the achieved benefits of adaptive threshold setting. PMID:25729347

  16. Baseline Adaptive Wavelet Thresholding Technique for sEMG Denoising

    NASA Astrophysics Data System (ADS)

    Bartolomeo, L.; Zecca, M.; Sessa, S.; Lin, Z.; Mukaeda, Y.; Ishii, H.; Takanishi, Atsuo

    2011-06-01

    The surface Electromyography (sEMG) signal is affected by different sources of noises: current technology is considerably robust to the interferences of the power line or the cable motion artifacts, but still there are many limitations with the baseline and the movement artifact noise. In particular, these sources have frequency spectra that include also the low-frequency components of the sEMG frequency spectrum; therefore, a standard all-bandwidth filtering could alter important information. The Wavelet denoising method has been demonstrated to be a powerful solution in processing white Gaussian noise in biological signals. In this paper we introduce a new technique for the denoising of the sEMG signal: by using the baseline of the signal before the task, we estimate the thresholds to apply to the Wavelet thresholding procedure. The experiments have been performed on ten healthy subjects, by placing the electrodes on the Extensor Carpi Ulnaris and Triceps Brachii on right upper and lower arms, and performing a flexion and extension of the right wrist. An Inertial Measurement Unit, developed in our group, has been used to recognize the movements of the hands to segment the exercise and the pre-task baseline. Finally, we show better performances of the proposed method in term of noise cancellation and distortion of the signal, quantified by a new suggested indicator of denoising quality, compared to the standard Donoho technique.

  17. Reinforcement learning by Hebbian synapses with adaptive thresholds.

    PubMed

    Pennartz, C M

    1997-11-01

    A central problem in learning theory is how the vertebrate brain processes reinforcing stimuli in order to master complex sensorimotor tasks. This problem belongs to the domain of supervised learning, in which errors in the response of a neural network serve as the basis for modification of synaptic connectivity in the network and thereby train it on a computational task. The model presented here shows how a reinforcing feedback can modify synapses in a neuronal network according to the principles of Hebbian learning. The reinforcing feedback steers synapses towards long-term potentiation or depression by critically influencing the rise in postsynaptic calcium, in accordance with findings on synaptic plasticity in mammalian brain. An important feature of the model is the dependence of modification thresholds on the previous history of reinforcing feedback processed by the network. The learning algorithm trained networks successfully on a task in which a population vector in the motor output was required to match a sensory stimulus vector presented shortly before. In another task, networks were trained to compute coordinate transformations by combining different visual inputs. The model continued to behave well when simplified units were replaced by single-compartment neurons equipped with several conductances and operating in continuous time. This novel form of reinforcement learning incorporates essential properties of Hebbian synaptic plasticity and thereby shows that supervised learning can be accomplished by a learning rule similar to those used in physiologically plausible models of unsupervised learning. The model can be crudely correlated to the anatomy and electrophysiology of the amygdala, prefrontal and cingulate cortex and has predictive implications for further experiments on synaptic plasticity and learning processes mediated by these areas.

  18. Unipolar terminal-attractor based neural associative memory with adaptive threshold

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang (Inventor); Barhen, Jacob (Inventor); Farhat, Nabil H. (Inventor); Wu, Chwan-Hwa (Inventor)

    1993-01-01

    A unipolar terminal-attractor based neural associative memory (TABAM) system with adaptive threshold for perfect convergence is presented. By adaptively setting the threshold values for the dynamic iteration for the unipolar binary neuron states with terminal-attractors for the purpose of reducing the spurious states in a Hopfield neural network for associative memory and using the inner product approach, perfect convergence and correct retrieval is achieved. Simulation is completed with a small number of stored states (M) and a small number of neurons (N) but a large M/N ratio. An experiment with optical exclusive-OR logic operation using LCTV SLMs shows the feasibility of optoelectronic implementation of the models. A complete inner-product TABAM is implemented using a PC for calculation of adaptive threshold values to achieve a unipolar TABAM (UIT) in the case where there is no crosstalk, and a crosstalk model (CRIT) in the case where crosstalk corrupts the desired state.

  19. Unipolar Terminal-Attractor Based Neural Associative Memory with Adaptive Threshold

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang (Inventor); Barhen, Jacob (Inventor); Farhat, Nabil H. (Inventor); Wu, Chwan-Hwa (Inventor)

    1996-01-01

    A unipolar terminal-attractor based neural associative memory (TABAM) system with adaptive threshold for perfect convergence is presented. By adaptively setting the threshold values for the dynamic iteration for the unipolar binary neuron states with terminal-attractors for the purpose of reducing the spurious states in a Hopfield neural network for associative memory and using the inner-product approach, perfect convergence and correct retrieval is achieved. Simulation is completed with a small number of stored states (M) and a small number of neurons (N) but a large M/N ratio. An experiment with optical exclusive-OR logic operation using LCTV SLMs shows the feasibility of optoelectronic implementation of the models. A complete inner-product TABAM is implemented using a PC for calculation of adaptive threshold values to achieve a unipolar TABAM (UIT) in the case where there is no crosstalk, and a crosstalk model (CRIT) in the case where crosstalk corrupts the desired state.

  20. Adapting to a changing environment: non-obvious thresholds in multi-scale systems.

    PubMed

    Perryman, Clare; Wieczorek, Sebastian

    2014-10-01

    Many natural and technological systems fail to adapt to changing external conditions and move to a different state if the conditions vary too fast. Such 'non-adiabatic' processes are ubiquitous, but little understood. We identify these processes with a new nonlinear phenomenon-an intricate threshold where a forced system fails to adiabatically follow a changing stable state. In systems with multiple time scales, we derive existence conditions that show such thresholds to be generic, but non-obvious, meaning they cannot be captured by traditional stability theory. Rather, the phenomenon can be analysed using concepts from modern singular perturbation theory: folded singularities and canard trajectories, including composite canards. Thus, non-obvious thresholds should explain the failure to adapt to a changing environment in a wide range of multi-scale systems including: tipping points in the climate system, regime shifts in ecosystems, excitability in nerve cells, adaptation failure in regulatory genes and adiabatic switching in technology. PMID:25294963

  1. Adapting to a changing environment: non-obvious thresholds in multi-scale systems

    PubMed Central

    Perryman, Clare; Wieczorek, Sebastian

    2014-01-01

    Many natural and technological systems fail to adapt to changing external conditions and move to a different state if the conditions vary too fast. Such ‘non-adiabatic’ processes are ubiquitous, but little understood. We identify these processes with a new nonlinear phenomenon—an intricate threshold where a forced system fails to adiabatically follow a changing stable state. In systems with multiple time scales, we derive existence conditions that show such thresholds to be generic, but non-obvious, meaning they cannot be captured by traditional stability theory. Rather, the phenomenon can be analysed using concepts from modern singular perturbation theory: folded singularities and canard trajectories, including composite canards. Thus, non-obvious thresholds should explain the failure to adapt to a changing environment in a wide range of multi-scale systems including: tipping points in the climate system, regime shifts in ecosystems, excitability in nerve cells, adaptation failure in regulatory genes and adiabatic switching in technology. PMID:25294963

  2. Fixed- and Variable-Ratio Reinforcement of Reading Performance.

    ERIC Educational Resources Information Center

    George, John E.

    The effects of fixed-ratio and variable-ratio reinforcement classroom reading performance was investigated. Subjects were 50 boys and 50 girls from four grade-2 classrooms of one elementary school. The subjects were divided into three reading levels, above-average, average, and below-average, and were randomly assigned to (1) a no-reinforcement…

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

    ERIC Educational Resources Information Center

    Tavassoli, T.; Baron-Cohen, S.

    2012-01-01

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

  4. Severe Obesity Shifts Metabolic Thresholds but Does Not Attenuate Aerobic Training Adaptations in Zucker Rats

    PubMed Central

    Rosa, Thiago S.; Simões, Herbert G.; Rogero, Marcelo M.; Moraes, Milton R.; Denadai, Benedito S.; Arida, Ricardo M.; Andrade, Marília S.; Silva, Bruno M.

    2016-01-01

    Severe obesity affects metabolism with potential to influence the lactate and glycemic response to different exercise intensities in untrained and trained rats. Here we evaluated metabolic thresholds and maximal aerobic capacity in rats with severe obesity and lean counterparts at pre- and post-training. Zucker rats (obese: n = 10, lean: n = 10) were submitted to constant treadmill bouts, to determine the maximal lactate steady state, and an incremental treadmill test, to determine the lactate threshold, glycemic threshold and maximal velocity at pre and post 8 weeks of treadmill training. Velocities of the lactate threshold and glycemic threshold agreed with the maximal lactate steady state velocity on most comparisons. The maximal lactate steady state velocity occurred at higher percentage of the maximal velocity in Zucker rats at pre-training than the percentage commonly reported and used for training prescription for other rat strains (i.e., 60%) (obese = 78 ± 9% and lean = 68 ± 5%, P < 0.05 vs. 60%). The maximal lactate steady state velocity and maximal velocity were lower in the obese group at pre-training (P < 0.05 vs. lean), increased in both groups at post-training (P < 0.05 vs. pre), but were still lower in the obese group at post-training (P < 0.05 vs. lean). Training-induced increase in maximal lactate steady state, lactate threshold and glycemic threshold velocities was similar between groups (P > 0.05), whereas increase in maximal velocity was greater in the obese group (P < 0.05 vs. lean). In conclusion, lactate threshold, glycemic threshold and maximal lactate steady state occurred at similar exercise intensity in Zucker rats at pre- and post-training. Severe obesity shifted metabolic thresholds to higher exercise intensity at pre-training, but did not attenuate submaximal and maximal aerobic training adaptations. PMID:27148063

  5. A Threshold-Adaptive Reputation System on Mobile Ad Hoc Networks

    NASA Astrophysics Data System (ADS)

    Tsai, Hsiao-Chien; Lo, Nai-Wei; Wu, Tzong-Chen

    In recent years huge potential benefits from novel applications in mobile ad hoc networks (MANET) have been discussed extensively. However, without robust security mechanisms and systems to provide safety shell through the MANET infrastructure, MANET applications can be vulnerable and hammered by malicious attackers easily. In order to detect misbehaved message routing and identify malicious attackers in MANET, schemes based on reputation concept have shown their advantages in this area in terms of good scalability and simple threshold-based detection strategy. We observed that previous reputation schemes generally use predefined thresholds which do not take into account the effect of behavior dynamics between nodes in a period of time. In this paper, we propose a Threshold-Adaptive Reputation System (TARS) to overcome the shortcomings of static threshold strategy and improve the overall MANET performance under misbehaved routing attack. A fuzzy-based inference engine is introduced to evaluate the trustiness of a node's one-hop neighbors. Malicious nodes whose trust values are lower than the adaptive threshold, will be detected and filtered out by their honest neighbors during trustiness evaluation process. The results of network simulation show that the TARS outperforms other compared schemes under security attacks in most cases and at the same time reduces the decrease of total packet delivery ratio by 67% in comparison with MANET without reputation system.

  6. Future temperature in southwest Asia projected to exceed a threshold for human adaptability

    NASA Astrophysics Data System (ADS)

    Pal, Jeremy S.; Eltahir, Elfatih A. B.

    2016-02-01

    A human body may be able to adapt to extremes of dry-bulb temperature (commonly referred to as simply temperature) through perspiration and associated evaporative cooling provided that the wet-bulb temperature (a combined measure of temperature and humidity or degree of `mugginess’) remains below a threshold of 35 °C. (ref. ). This threshold defines a limit of survivability for a fit human under well-ventilated outdoor conditions and is lower for most people. We project using an ensemble of high-resolution regional climate model simulations that extremes of wet-bulb temperature in the region around the Arabian Gulf are likely to approach and exceed this critical threshold under the business-as-usual scenario of future greenhouse gas concentrations. Our results expose a specific regional hotspot where climate change, in the absence of significant mitigation, is likely to severely impact human habitability in the future.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  8. Impact of sub and supra-threshold adaptation currents in networks of spiking neurons.

    PubMed

    Colliaux, David; Yger, Pierre; Kaneko, Kunihiko

    2015-12-01

    Neuronal adaptation is the intrinsic capacity of the brain to change, by various mechanisms, its dynamical responses as a function of the context. Such a phenomena, widely observed in vivo and in vitro, is known to be crucial in homeostatic regulation of the activity and gain control. The effects of adaptation have already been studied at the single-cell level, resulting from either voltage or calcium gated channels both activated by the spiking activity and modulating the dynamical responses of the neurons. In this study, by disentangling those effects into a linear (sub-threshold) and a non-linear (supra-threshold) part, we focus on the the functional role of those two distinct components of adaptation onto the neuronal activity at various scales, starting from single-cell responses up to recurrent networks dynamics, and under stationary or non-stationary stimulations. The effects of slow currents on collective dynamics, like modulation of population oscillation and reliability of spike patterns, is quantified for various types of adaptation in sparse recurrent networks.

  9. Impact of sub and supra-threshold adaptation currents in networks of spiking neurons.

    PubMed

    Colliaux, David; Yger, Pierre; Kaneko, Kunihiko

    2015-12-01

    Neuronal adaptation is the intrinsic capacity of the brain to change, by various mechanisms, its dynamical responses as a function of the context. Such a phenomena, widely observed in vivo and in vitro, is known to be crucial in homeostatic regulation of the activity and gain control. The effects of adaptation have already been studied at the single-cell level, resulting from either voltage or calcium gated channels both activated by the spiking activity and modulating the dynamical responses of the neurons. In this study, by disentangling those effects into a linear (sub-threshold) and a non-linear (supra-threshold) part, we focus on the the functional role of those two distinct components of adaptation onto the neuronal activity at various scales, starting from single-cell responses up to recurrent networks dynamics, and under stationary or non-stationary stimulations. The effects of slow currents on collective dynamics, like modulation of population oscillation and reliability of spike patterns, is quantified for various types of adaptation in sparse recurrent networks. PMID:26400658

  10. Comparison of different automatic adaptive threshold selection techniques for estimating discharge from river width

    NASA Astrophysics Data System (ADS)

    Elmi, Omid; Javad Tourian, Mohammad; Sneeuw, Nico

    2015-04-01

    The importance of river discharge monitoring is critical for e.g., water resource planning, climate change, hazard monitoring. River discharge has been measured at in situ gauges for more than a century. Despite various attempts, some basins are still ungauged. Moreover, a reduction in the number of worldwide gauging stations increases the interest to employ remote sensing data for river discharge monitoring. Finding an empirical relationship between simultaneous in situ measurements of discharge and river widths derived from satellite imagery has been introduced as a straightforward remote sensing alternative. Classifying water and land in an image is the primary task for defining the river width. Water appears dark in the near infrared and infrared bands in satellite images. As a result low values in the histogram usually represent the water content. In this way, applying a threshold on the image histogram and separating into two different classes is one of the most efficient techniques to build a water mask. Beside its simple definition, finding the appropriate threshold value in each image is the most critical issue. The threshold is variable due to changes in the water level, river extent, atmosphere, sunlight radiation, onboard calibration of the satellite over time. These complexities in water body classification are the main source of error in river width estimation. In this study, we are looking for the most efficient adaptive threshold algorithm to estimate the river discharge. To do this, all cloud free MODIS images coincident with the in situ measurement are collected. Next a number of automatic threshold selection techniques are employed to generate different dynamic water masks. Then, for each of them a separate empirical relationship between river widths and discharge measurements are determined. Through these empirical relationships, we estimate river discharge at the gauge and then validate our results against in situ measurements and also

  11. Impact of slow K(+) currents on spike generation can be described by an adaptive threshold model.

    PubMed

    Kobayashi, Ryota; Kitano, Katsunori

    2016-06-01

    A neuron that is stimulated by rectangular current injections initially responds with a high firing rate, followed by a decrease in the firing rate. This phenomenon is called spike-frequency adaptation and is usually mediated by slow K(+) currents, such as the M-type K(+) current (I M ) or the Ca(2+)-activated K(+) current (I AHP ). It is not clear how the detailed biophysical mechanisms regulate spike generation in a cortical neuron. In this study, we investigated the impact of slow K(+) currents on spike generation mechanism by reducing a detailed conductance-based neuron model. We showed that the detailed model can be reduced to a multi-timescale adaptive threshold model, and derived the formulae that describe the relationship between slow K(+) current parameters and reduced model parameters. Our analysis of the reduced model suggests that slow K(+) currents have a differential effect on the noise tolerance in neural coding. PMID:27085337

  12. Fine tuning of the threshold of T cell selection by the Nck adapters.

    PubMed

    Roy, Edwige; Togbe, Dieudonnée; Holdorf, Amy; Trubetskoy, Dmitry; Nabti, Sabrina; Küblbeck, Günter; Schmitt, Sabine; Kopp-Schneider, Annette; Leithäuser, Frank; Möller, Peter; Bladt, Friedhelm; Hämmerling, Günter J; Arnold, Bernd; Pawson, Tony; Tafuri, Anna

    2010-12-15

    Thymic selection shapes the T cell repertoire to ensure maximal antigenic coverage against pathogens while preventing autoimmunity. Recognition of self-peptides in the context of peptide-MHC complexes by the TCR is central to this process, which remains partially understood at the molecular level. In this study we provide genetic evidence that the Nck adapter proteins are essential for thymic selection. In vivo Nck deletion resulted in a reduction of the thymic cellularity, defective positive selection of low-avidity T cells, and impaired deletion of thymocytes engaged by low-potency stimuli. Nck-deficient thymocytes were characterized by reduced ERK activation, particularly pronounced in mature single positive thymocytes. Taken together, our findings identify a crucial role for the Nck adapters in enhancing TCR signal strength, thereby fine-tuning the threshold of thymocyte selection and shaping the preimmune T cell repertoire.

  13. Fine tuning of the threshold of T cell selection by the Nck adapters.

    PubMed

    Roy, Edwige; Togbe, Dieudonnée; Holdorf, Amy; Trubetskoy, Dmitry; Nabti, Sabrina; Küblbeck, Günter; Schmitt, Sabine; Kopp-Schneider, Annette; Leithäuser, Frank; Möller, Peter; Bladt, Friedhelm; Hämmerling, Günter J; Arnold, Bernd; Pawson, Tony; Tafuri, Anna

    2010-12-15

    Thymic selection shapes the T cell repertoire to ensure maximal antigenic coverage against pathogens while preventing autoimmunity. Recognition of self-peptides in the context of peptide-MHC complexes by the TCR is central to this process, which remains partially understood at the molecular level. In this study we provide genetic evidence that the Nck adapter proteins are essential for thymic selection. In vivo Nck deletion resulted in a reduction of the thymic cellularity, defective positive selection of low-avidity T cells, and impaired deletion of thymocytes engaged by low-potency stimuli. Nck-deficient thymocytes were characterized by reduced ERK activation, particularly pronounced in mature single positive thymocytes. Taken together, our findings identify a crucial role for the Nck adapters in enhancing TCR signal strength, thereby fine-tuning the threshold of thymocyte selection and shaping the preimmune T cell repertoire. PMID:21078909

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

    PubMed

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

    2015-11-01

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

  15. Positive–negative corresponding normalized ghost imaging based on an adaptive threshold

    NASA Astrophysics Data System (ADS)

    Li, G. L.; Zhao, Y.; Yang, Z. H.; Liu, X.

    2016-11-01

    Ghost imaging (GI) technology has attracted increasing attention as a new imaging technique in recent years. However, the signal-to-noise ratio (SNR) of GI with pseudo-thermal light needs to be improved before it meets engineering application demands. We therefore propose a new scheme called positive–negative correspondence normalized GI based on an adaptive threshold (PCNGI-AT) to achieve a good performance with less amount of data. In this work, we use both the advantages of normalized GI (NGI) and positive–negative correspondence GI (P–NCGI). The correctness and feasibility of the scheme were proved in theory before we designed an adaptive threshold selection method, in which the parameter of object signal selection conditions is replaced by the normalizing value. The simulation and experimental results reveal that the SNR of the proposed scheme is better than that of time-correspondence differential GI (TCDGI), avoiding the calculation of the matrix of correlation and reducing the amount of data used. The method proposed will make GI far more practical in engineering applications.

  16. Survival thresholds and mortality rates in adaptive dynamics: conciliating deterministic and stochastic simulations.

    PubMed

    Perthame, Benoît; Gauduchon, Mathias

    2010-09-01

    Deterministic population models for adaptive dynamics are derived mathematically from individual-centred stochastic models in the limit of large populations. However, it is common that numerical simulations of both models fit poorly and give rather different behaviours in terms of evolution speeds and branching patterns. Stochastic simulations involve extinction phenomenon operating through demographic stochasticity, when the number of individual 'units' is small. Focusing on the class of integro-differential adaptive models, we include a similar notion in the deterministic formulations, a survival threshold, which allows phenotypical traits in the population to vanish when represented by few 'individuals'. Based on numerical simulations, we show that the survival threshold changes drastically the solution; (i) the evolution speed is much slower, (ii) the branching patterns are reduced continuously and (iii) these patterns are comparable to those obtained with stochastic simulations. The rescaled models can also be analysed theoretically. One can recover the concentration phenomena on well-separated Dirac masses through the constrained Hamilton-Jacobi equation in the limit of small mutations and large observation times. PMID:19734200

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

    PubMed

    Wonjune Kang; Kyunguen Byun; Hong-Goo Kang

    2015-08-01

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

  18. Developing Bayesian adaptive methods for estimating sensitivity thresholds (d') in Yes-No and forced-choice tasks.

    PubMed

    Lesmes, Luis A; Lu, Zhong-Lin; Baek, Jongsoo; Tran, Nina; Dosher, Barbara A; Albright, Thomas D

    2015-01-01

    Motivated by Signal Detection Theory (SDT), we developed a family of novel adaptive methods that estimate the sensitivity threshold-the signal intensity corresponding to a pre-defined sensitivity level (d' = 1)-in Yes-No (YN) and Forced-Choice (FC) detection tasks. Rather than focus stimulus sampling to estimate a single level of %Yes or %Correct, the current methods sample psychometric functions more broadly, to concurrently estimate sensitivity and decision factors, and thereby estimate thresholds that are independent of decision confounds. Developed for four tasks-(1) simple YN detection, (2) cued YN detection, which cues the observer's response state before each trial, (3) rated YN detection, which incorporates a Not Sure response, and (4) FC detection-the qYN and qFC methods yield sensitivity thresholds that are independent of the task's decision structure (YN or FC) and/or the observer's subjective response state. Results from simulation and psychophysics suggest that 25 trials (and sometimes less) are sufficient to estimate YN thresholds with reasonable precision (s.d. = 0.10-0.15 decimal log units), but more trials are needed for FC thresholds. When the same subjects were tested across tasks of simple, cued, rated, and FC detection, adaptive threshold estimates exhibited excellent agreement with the method of constant stimuli (MCS), and with each other. These YN adaptive methods deliver criterion-free thresholds that have previously been exclusive to FC methods.

  19. Adaptive Threshold Neural Spike Detector Using Stationary Wavelet Transform in CMOS.

    PubMed

    Yang, Yuning; Boling, C Sam; Kamboh, Awais M; Mason, Andrew J

    2015-11-01

    Spike detection is an essential first step in the analysis of neural recordings. Detection at the frontend eases the bandwidth requirement for wireless data transfer of multichannel recordings to extra-cranial processing units. In this work, a low power digital integrated spike detector based on the lifting stationary wavelet transform is presented and developed. By monitoring the standard deviation of wavelet coefficients, the proposed detector can adaptively set a threshold value online for each channel independently without requiring user intervention. A prototype 16-channel spike detector was designed and tested in an FPGA. The method enables spike detection with nearly 90% accuracy even when the signal-to-noise ratio is as low as 2. The design was mapped to 130 nm CMOS technology and shown to occupy 0.014 mm(2) of area and dissipate 1.7 μW of power per channel, making it suitable for implantable multichannel neural recording systems. PMID:25955990

  20. Adaptive Threshold Neural Spike Detector Using Stationary Wavelet Transform in CMOS.

    PubMed

    Yang, Yuning; Boling, C Sam; Kamboh, Awais M; Mason, Andrew J

    2015-11-01

    Spike detection is an essential first step in the analysis of neural recordings. Detection at the frontend eases the bandwidth requirement for wireless data transfer of multichannel recordings to extra-cranial processing units. In this work, a low power digital integrated spike detector based on the lifting stationary wavelet transform is presented and developed. By monitoring the standard deviation of wavelet coefficients, the proposed detector can adaptively set a threshold value online for each channel independently without requiring user intervention. A prototype 16-channel spike detector was designed and tested in an FPGA. The method enables spike detection with nearly 90% accuracy even when the signal-to-noise ratio is as low as 2. The design was mapped to 130 nm CMOS technology and shown to occupy 0.014 mm(2) of area and dissipate 1.7 μW of power per channel, making it suitable for implantable multichannel neural recording systems.

  1. Motion Estimation Based on Mutual Information and Adaptive Multi-Scale Thresholding.

    PubMed

    Xu, Rui; Taubman, David; Naman, Aous Thabit

    2016-03-01

    This paper proposes a new method of calculating a matching metric for motion estimation. The proposed method splits the information in the source images into multiple scale and orientation subbands, reduces the subband values to a binary representation via an adaptive thresholding algorithm, and uses mutual information to model the similarity of corresponding square windows in each image. A moving window strategy is applied to recover a dense estimated motion field whose properties are explored. The proposed matching metric is a sum of mutual information scores across space, scale, and orientation. This facilitates the exploitation of information diversity in the source images. Experimental comparisons are performed amongst several related approaches, revealing that the proposed matching metric is better able to exploit information diversity, generating more accurate motion fields.

  2. Implementation for temporal noise identification using adaptive threshold of infrared imaging system

    NASA Astrophysics Data System (ADS)

    Lim, Inok

    2007-10-01

    Bad pixels are spatial or temporal noise which arise from dead pixels by fixed signal levels or blinking pixels by variable signal levels that go beyond the bounds of normal pixel levels at the temperature. Because bad pixels are the false targets over infrared imaging system for tracking, those must be corrected. Main contribution to the number of bad pixels is fixed pattern noise (FPN) according to increasing array size. And it is more simple to establish whether FPN is or not through analyzing of accumulated frames. But it needs to calculate with more complex implementation such standard deviation from frame to frame in case of the temporal noise. Both cases it is very important to establish the threshold levels for identifying at variable operating temperatures. In this paper, we propose a more efficient data analysis method and a temporal noise identification method using adaptive threshold for infrared imaging system, and the hardware is implemented to identify and replace bad pixels. And its result is confirmed visually by bad pixel map images.

  3. Hybrid threshold adaptable quantum secret sharing scheme with reverse Huffman-Fibonacci-tree coding.

    PubMed

    Lai, Hong; Zhang, Jun; Luo, Ming-Xing; Pan, Lei; Pieprzyk, Josef; Xiao, Fuyuan; Orgun, Mehmet A

    2016-01-01

    With prevalent attacks in communication, sharing a secret between communicating parties is an ongoing challenge. Moreover, it is important to integrate quantum solutions with classical secret sharing schemes with low computational cost for the real world use. This paper proposes a novel hybrid threshold adaptable quantum secret sharing scheme, using an m-bonacci orbital angular momentum (OAM) pump, Lagrange interpolation polynomials, and reverse Huffman-Fibonacci-tree coding. To be exact, we employ entangled states prepared by m-bonacci sequences to detect eavesdropping. Meanwhile, we encode m-bonacci sequences in Lagrange interpolation polynomials to generate the shares of a secret with reverse Huffman-Fibonacci-tree coding. The advantages of the proposed scheme is that it can detect eavesdropping without joint quantum operations, and permits secret sharing for an arbitrary but no less than threshold-value number of classical participants with much lower bandwidth. Also, in comparison with existing quantum secret sharing schemes, it still works when there are dynamic changes, such as the unavailability of some quantum channel, the arrival of new participants and the departure of participants. Finally, we provide security analysis of the new hybrid quantum secret sharing scheme and discuss its useful features for modern applications. PMID:27515908

  4. Hybrid threshold adaptable quantum secret sharing scheme with reverse Huffman-Fibonacci-tree coding.

    PubMed

    Lai, Hong; Zhang, Jun; Luo, Ming-Xing; Pan, Lei; Pieprzyk, Josef; Xiao, Fuyuan; Orgun, Mehmet A

    2016-01-01

    With prevalent attacks in communication, sharing a secret between communicating parties is an ongoing challenge. Moreover, it is important to integrate quantum solutions with classical secret sharing schemes with low computational cost for the real world use. This paper proposes a novel hybrid threshold adaptable quantum secret sharing scheme, using an m-bonacci orbital angular momentum (OAM) pump, Lagrange interpolation polynomials, and reverse Huffman-Fibonacci-tree coding. To be exact, we employ entangled states prepared by m-bonacci sequences to detect eavesdropping. Meanwhile, we encode m-bonacci sequences in Lagrange interpolation polynomials to generate the shares of a secret with reverse Huffman-Fibonacci-tree coding. The advantages of the proposed scheme is that it can detect eavesdropping without joint quantum operations, and permits secret sharing for an arbitrary but no less than threshold-value number of classical participants with much lower bandwidth. Also, in comparison with existing quantum secret sharing schemes, it still works when there are dynamic changes, such as the unavailability of some quantum channel, the arrival of new participants and the departure of participants. Finally, we provide security analysis of the new hybrid quantum secret sharing scheme and discuss its useful features for modern applications.

  5. Hybrid threshold adaptable quantum secret sharing scheme with reverse Huffman-Fibonacci-tree coding

    PubMed Central

    Lai, Hong; Zhang, Jun; Luo, Ming-Xing; Pan, Lei; Pieprzyk, Josef; Xiao, Fuyuan; Orgun, Mehmet A.

    2016-01-01

    With prevalent attacks in communication, sharing a secret between communicating parties is an ongoing challenge. Moreover, it is important to integrate quantum solutions with classical secret sharing schemes with low computational cost for the real world use. This paper proposes a novel hybrid threshold adaptable quantum secret sharing scheme, using an m-bonacci orbital angular momentum (OAM) pump, Lagrange interpolation polynomials, and reverse Huffman-Fibonacci-tree coding. To be exact, we employ entangled states prepared by m-bonacci sequences to detect eavesdropping. Meanwhile, we encode m-bonacci sequences in Lagrange interpolation polynomials to generate the shares of a secret with reverse Huffman-Fibonacci-tree coding. The advantages of the proposed scheme is that it can detect eavesdropping without joint quantum operations, and permits secret sharing for an arbitrary but no less than threshold-value number of classical participants with much lower bandwidth. Also, in comparison with existing quantum secret sharing schemes, it still works when there are dynamic changes, such as the unavailability of some quantum channel, the arrival of new participants and the departure of participants. Finally, we provide security analysis of the new hybrid quantum secret sharing scheme and discuss its useful features for modern applications. PMID:27515908

  6. Hybrid threshold adaptable quantum secret sharing scheme with reverse Huffman-Fibonacci-tree coding

    NASA Astrophysics Data System (ADS)

    Lai, Hong; Zhang, Jun; Luo, Ming-Xing; Pan, Lei; Pieprzyk, Josef; Xiao, Fuyuan; Orgun, Mehmet A.

    2016-08-01

    With prevalent attacks in communication, sharing a secret between communicating parties is an ongoing challenge. Moreover, it is important to integrate quantum solutions with classical secret sharing schemes with low computational cost for the real world use. This paper proposes a novel hybrid threshold adaptable quantum secret sharing scheme, using an m-bonacci orbital angular momentum (OAM) pump, Lagrange interpolation polynomials, and reverse Huffman-Fibonacci-tree coding. To be exact, we employ entangled states prepared by m-bonacci sequences to detect eavesdropping. Meanwhile, we encode m-bonacci sequences in Lagrange interpolation polynomials to generate the shares of a secret with reverse Huffman-Fibonacci-tree coding. The advantages of the proposed scheme is that it can detect eavesdropping without joint quantum operations, and permits secret sharing for an arbitrary but no less than threshold-value number of classical participants with much lower bandwidth. Also, in comparison with existing quantum secret sharing schemes, it still works when there are dynamic changes, such as the unavailability of some quantum channel, the arrival of new participants and the departure of participants. Finally, we provide security analysis of the new hybrid quantum secret sharing scheme and discuss its useful features for modern applications.

  7. Developing Bayesian adaptive methods for estimating sensitivity thresholds (d′) in Yes-No and forced-choice tasks

    PubMed Central

    Lesmes, Luis A.; Lu, Zhong-Lin; Baek, Jongsoo; Tran, Nina; Dosher, Barbara A.; Albright, Thomas D.

    2015-01-01

    Motivated by Signal Detection Theory (SDT), we developed a family of novel adaptive methods that estimate the sensitivity threshold—the signal intensity corresponding to a pre-defined sensitivity level (d′ = 1)—in Yes-No (YN) and Forced-Choice (FC) detection tasks. Rather than focus stimulus sampling to estimate a single level of %Yes or %Correct, the current methods sample psychometric functions more broadly, to concurrently estimate sensitivity and decision factors, and thereby estimate thresholds that are independent of decision confounds. Developed for four tasks—(1) simple YN detection, (2) cued YN detection, which cues the observer's response state before each trial, (3) rated YN detection, which incorporates a Not Sure response, and (4) FC detection—the qYN and qFC methods yield sensitivity thresholds that are independent of the task's decision structure (YN or FC) and/or the observer's subjective response state. Results from simulation and psychophysics suggest that 25 trials (and sometimes less) are sufficient to estimate YN thresholds with reasonable precision (s.d. = 0.10–0.15 decimal log units), but more trials are needed for FC thresholds. When the same subjects were tested across tasks of simple, cued, rated, and FC detection, adaptive threshold estimates exhibited excellent agreement with the method of constant stimuli (MCS), and with each other. These YN adaptive methods deliver criterion-free thresholds that have previously been exclusive to FC methods. PMID:26300798

  8. A fast and efficient adaptive threshold rate control scheme for remote sensing images.

    PubMed

    Chen, Xiao; Xu, Xiaoqing

    2012-01-01

    The JPEG2000 image compression standard is ideal for processing remote sensing images. However, its algorithm is complex and it requires large amounts of memory, making it difficult to adapt to the limited transmission and storage resources necessary for remote sensing images. In the present study, an improved rate control algorithm for remote sensing images is proposed. The required coded blocks are sorted downward according to their numbers of bit planes prior to entropy coding. An adaptive threshold computed from the combination of the minimum number of bit planes, along with the minimum rate-distortion slope and the compression ratio, is used to truncate passes of each code block during Tier-1 encoding. This routine avoids the encoding of all code passes and improves the coding efficiency. The simulation results show that the computational cost and working buffer memory size of the proposed algorithm reach only 18.13 and 7.81%, respectively, of the same parameters in the postcompression rate distortion algorithm, while the peak signal-to-noise ratio across the images remains almost the same. The proposed algorithm not only greatly reduces the code complexity and buffer requirements but also maintains the image quality.

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

    NASA Astrophysics Data System (ADS)

    Bagwari, A.; Tomar, G. S.

    2014-04-01

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

  10. The linear system theory's account of behavior maintained by variable-ratio schedules.

    PubMed

    McDowell, J J; Wixted, J T

    1988-01-01

    The mathematical theory of linear systems, which has been used successfully to describe behavior maintained by variable-interval schedules, is extended to describe behavior maintained by variable-ratio schedules. The result of the analysis is a pair of equations, one of which expresses response rate on a variable-ratio schedule as a function of the mean ratio requirement (n) that the schedule arranges. The other equation expresses response rate on a variable-ratio schedule as a function of reinforcement rate. Both equations accurately describe existing data from variable-ratio schedules. The theory accounts for two additional characteristics of behavior maintained by variable-ratio schedules; namely, the appearance of strained, two-valued (i.e., zero or very rapid) responding at large ns, and the abrupt cessation of responding at a boundary n. The theory also accounts for differences between behavior on variable-interval and variable-ratio schedules, including (a) the occurrence of strained responding on variable-ratio but not on variable-interval schedules, (b) the abrupt cessation of responding on occurrence of higher response rates on variable-ratio than on variable-interval schedules. Furthermore, given data from a series of variable-interval schedules and from a series of concurrent variable-ratio variable-interval schedules, the theory permits quantitative prediction of many properties of behavior on single-alternative variable-ratio schedules. The linear system theory's combined account of behavior on variable-interval and variable-ratio schedules is superior to existing versions of six other mathematical theories of variable-interval and variable-ratio responding.

  11. The linear system theory's account of behavior maintained by variable-ratio schedules.

    PubMed Central

    McDowell, J J; Wixted, J T

    1988-01-01

    The mathematical theory of linear systems, which has been used successfully to describe behavior maintained by variable-interval schedules, is extended to describe behavior maintained by variable-ratio schedules. The result of the analysis is a pair of equations, one of which expresses response rate on a variable-ratio schedule as a function of the mean ratio requirement (n) that the schedule arranges. The other equation expresses response rate on a variable-ratio schedule as a function of reinforcement rate. Both equations accurately describe existing data from variable-ratio schedules. The theory accounts for two additional characteristics of behavior maintained by variable-ratio schedules; namely, the appearance of strained, two-valued (i.e., zero or very rapid) responding at large ns, and the abrupt cessation of responding at a boundary n. The theory also accounts for differences between behavior on variable-interval and variable-ratio schedules, including (a) the occurrence of strained responding on variable-ratio but not on variable-interval schedules, (b) the abrupt cessation of responding on occurrence of higher response rates on variable-ratio than on variable-interval schedules. Furthermore, given data from a series of variable-interval schedules and from a series of concurrent variable-ratio variable-interval schedules, the theory permits quantitative prediction of many properties of behavior on single-alternative variable-ratio schedules. The linear system theory's combined account of behavior on variable-interval and variable-ratio schedules is superior to existing versions of six other mathematical theories of variable-interval and variable-ratio responding. PMID:3279150

  12. Presepsin (sCD14-ST) in emergency department: the need for adapted threshold values?

    PubMed

    Chenevier-Gobeaux, Camille; Trabattoni, Eloise; Roelens, Marie; Borderie, Didier; Claessens, Yann-Erick

    2014-01-01

    Presepsin is elevated in patients developing infections and increases in a severity-dependent manner. We aimed to evaluate circulating values of this new biomarker in a population free of any acute infectious disorder. We recruited 144 consecutive patients presenting at the emergency department (ED) without acute infection or acute/unstable disorder, and 54 healthy participants. Presepsin plasmatic concentrations were measured on the PATHFAST point-of-care analyzer. The 95th percentile of presepsin values in the ED population is 750ng/L. Presepsin was significantly increased in patients aged ≥70years vs. younger patients (470 [380-601] ng/L vs. 300 [201-457] ng/L, p<0.001). Prevalence of elevated presepsin values was increased in patients in comparison to controls (80% vs.13%, p<0.001), and in patients aged ≥70years in comparison to younger patients (87% vs. 47%, p<0.001). Presepsin concentrations were significantly increased in patients with kidney dysfunction. Aging was an independent predictor of an elevated presepsin value. In conclusion, presepsin concentrations increase with age and kidney dysfunction. Therefore interpretation of presepsin concentrations might be altered in the elderly or in patients with impaired renal function. Adapted thresholds are needed for specific populations.

  13. Multichannel spike detector with an adaptive threshold based on a Sigma-delta control loop.

    PubMed

    Gagnon-Turcotte, G; Gosselin, B

    2015-08-01

    In this paper, we present a digital spike detector using an adaptive threshold which is suitable for real time processing of 32 electrophysiological channels in parallel. Such a new scheme is based on a Sigma-delta control loop that precisely estimates the standard deviation of the amplitude of the noise of the input signal to optimize the detection rate. Additionally, it is not dependent on the amplitude of the input signal thanks to a robust algorithm. The spike detector is implemented inside a Spartan-6 FPGA using low resources, only FPGA basic logic blocks, and is using a low clock frequency under 6 MHz for minimal power consumption. We present a comparison showing that the proposed system can compete with a dedicated off-line spike detection software. The whole system achieves up to 100% of true positive detection rate for SNRs down to 5 dB while achieving 62.3% of true positive detection rate for an SNR as low as -2 dB at a 150 AP/s firing rate. PMID:26737934

  14. Interresponse Time Structures in Variable-Ratio and Variable-Interval Schedules

    ERIC Educational Resources Information Center

    Bowers, Matthew T.; Hill, Jade; Palya, William L.

    2008-01-01

    The interresponse-time structures of pigeon key pecking were examined under variable-ratio, variable-interval, and variable-interval plus linear feedback schedules. Whereas the variable-ratio and variable-interval plus linear feedback schedules generally resulted in a distinct group of short interresponse times and a broad distribution of longer…

  15. The Random-Threshold Generalized Unfolding Model and Its Application of Computerized Adaptive Testing

    ERIC Educational Resources Information Center

    Wang, Wen-Chung; Liu, Chen-Wei; Wu, Shiu-Lien

    2013-01-01

    The random-threshold generalized unfolding model (RTGUM) was developed by treating the thresholds in the generalized unfolding model as random effects rather than fixed effects to account for the subjective nature of the selection of categories in Likert items. The parameters of the new model can be estimated with the JAGS (Just Another Gibbs…

  16. Adaptive thresholding of chest temporal subtraction images in computer-aided diagnosis of pathologic change

    NASA Astrophysics Data System (ADS)

    Harrison, Melanie; Looper, Jared; Armato, Samuel G.

    2016-03-01

    Radiologists frequently use chest radiographs acquired at different times to diagnose a patient by identifying regions of change. Temporal subtraction (TS) images are formed when a computer warps a radiographic image to register and then subtract one image from the other, accentuating regions of change. The purpose of this study was to create a computeraided diagnostic (CAD) system to threshold chest TS images and identify candidate regions of pathologic change. Each thresholding technique created two different candidate regions: light and dark. Light regions have a high gray-level mean, while dark regions have a low gray-level mean; areas with no change appear as medium-gray pixels. Ten different thresholding techniques were examined and compared. By thresholding light and dark candidate regions separately, the number of properly thresholded regions improved. The thresholding of light and dark regions separately produced fewer overall candidate regions that included more regions of actual pathologic change than global thresholding of the image. Overall, the moment-preserving method produced the best results for light regions, while the normal distribution method produced the best results for dark regions. Separation of light and dark candidate regions by thresholding shows potential as the first step in creating a CAD system to detect pathologic change in chest TS images.

  17. Simulation of mid-infrared clutter rejection. 1: One-dimensional LMS spatial filter and adaptive threshold algorithms.

    PubMed

    Longmire, M S; Milton, A F; Takken, E H

    1982-11-01

    Several 1-D signal processing techniques have been evaluated by simulation with a digital computer using high-spatial-resolution (0.15 mrad) noise data gathered from back-lit clouds and uniform sky with a scanning data collection system operating in the 4.0-4.8-microm spectral band. Two ordinary bandpass filters and a least-mean-square (LMS) spatial filter were evaluated in combination with a fixed or adaptive threshold algorithm. The combination of a 1-D LMS filter and a 1-D adaptive threshold sensor was shown to reject extreme cloud clutter effectively and to provide nearly equal signal detection in a clear and cluttered sky, at least in systems whose NEI (noise equivalent irradiance) exceeds 1.5 x 10(-13) W/cm(2) and whose spatial resolution is better than 0.15 x 0.36 mrad. A summary gives highlights of the work, key numerical results, and conclusions.

  18. An adaptive threshold method for improving astrometry of space debris CCD images

    NASA Astrophysics Data System (ADS)

    Sun, Rong-yu; Zhao, Chang-yin

    2014-06-01

    Optical survey is a main technique for observing space debris, and precisely measuring the positions of space debris is of great importance. Due to several factors, e.g. the angle object normal to the observer, the shape as well as the attitude of the object, the variations of observed characteristics for low earth orbital space debris are distinct. When we look at optical CCD images of observed objects, the size and brightness are varying, hence it’s difficult to decide the threshold during centroid measurement and precise astrometry. Traditionally the threshold is given empirically and constantly in data reduction, and obviously it’s not suitable for data reduction of space debris. Here we offer a solution to provide the threshold. Our method assumes that the PSF (point spread function) is Gaussian and estimates the signal flux by a directly two-dimensional Gaussian fit, then a cubic spline interpolation is performed to divide each initial pixel into several sub-pixels, at last the threshold is determined by the estimation of signal flux and the sub-pixels above threshold are separated to estimate the centroid. A trail observation of the fast spinning satellite Ajisai is made and the CCD frames are obtained to test our algorithm. The calibration precision of various threshold is obtained through the comparison between the observed equatorial position and the reference one, the latter are obtained from the precise ephemeris of the satellite. The results indicate that our method reduces the total errors of measurements, it works effectively in improving the centering precision of space debris images.

  19. An Active Contour Model Based on Adaptive Threshold for Extraction of Cerebral Vascular Structures.

    PubMed

    Wang, Jiaxin; Zhao, Shifeng; Liu, Zifeng; Tian, Yun; Duan, Fuqing; Pan, Yutong

    2016-01-01

    Cerebral vessel segmentation is essential and helpful for the clinical diagnosis and the related research. However, automatic segmentation of brain vessels remains challenging because of the variable vessel shape and high complex of vessel geometry. This study proposes a new active contour model (ACM) implemented by the level-set method for segmenting vessels from TOF-MRA data. The energy function of the new model, combining both region intensity and boundary information, is composed of two region terms, one boundary term and one penalty term. The global threshold representing the lower gray boundary of the target object by maximum intensity projection (MIP) is defined in the first-region term, and it is used to guide the segmentation of the thick vessels. In the second term, a dynamic intensity threshold is employed to extract the tiny vessels. The boundary term is used to drive the contours to evolve towards the boundaries with high gradients. The penalty term is used to avoid reinitialization of the level-set function. Experimental results on 10 clinical brain data sets demonstrate that our method is not only able to achieve better Dice Similarity Coefficient than the global threshold based method and localized hybrid level-set method but also able to extract whole cerebral vessel trees, including the thin vessels. PMID:27597878

  20. An Active Contour Model Based on Adaptive Threshold for Extraction of Cerebral Vascular Structures

    PubMed Central

    Wang, Jiaxin; Zhao, Shifeng; Liu, Zifeng; Duan, Fuqing; Pan, Yutong

    2016-01-01

    Cerebral vessel segmentation is essential and helpful for the clinical diagnosis and the related research. However, automatic segmentation of brain vessels remains challenging because of the variable vessel shape and high complex of vessel geometry. This study proposes a new active contour model (ACM) implemented by the level-set method for segmenting vessels from TOF-MRA data. The energy function of the new model, combining both region intensity and boundary information, is composed of two region terms, one boundary term and one penalty term. The global threshold representing the lower gray boundary of the target object by maximum intensity projection (MIP) is defined in the first-region term, and it is used to guide the segmentation of the thick vessels. In the second term, a dynamic intensity threshold is employed to extract the tiny vessels. The boundary term is used to drive the contours to evolve towards the boundaries with high gradients. The penalty term is used to avoid reinitialization of the level-set function. Experimental results on 10 clinical brain data sets demonstrate that our method is not only able to achieve better Dice Similarity Coefficient than the global threshold based method and localized hybrid level-set method but also able to extract whole cerebral vessel trees, including the thin vessels.

  1. An Active Contour Model Based on Adaptive Threshold for Extraction of Cerebral Vascular Structures

    PubMed Central

    Wang, Jiaxin; Zhao, Shifeng; Liu, Zifeng; Duan, Fuqing; Pan, Yutong

    2016-01-01

    Cerebral vessel segmentation is essential and helpful for the clinical diagnosis and the related research. However, automatic segmentation of brain vessels remains challenging because of the variable vessel shape and high complex of vessel geometry. This study proposes a new active contour model (ACM) implemented by the level-set method for segmenting vessels from TOF-MRA data. The energy function of the new model, combining both region intensity and boundary information, is composed of two region terms, one boundary term and one penalty term. The global threshold representing the lower gray boundary of the target object by maximum intensity projection (MIP) is defined in the first-region term, and it is used to guide the segmentation of the thick vessels. In the second term, a dynamic intensity threshold is employed to extract the tiny vessels. The boundary term is used to drive the contours to evolve towards the boundaries with high gradients. The penalty term is used to avoid reinitialization of the level-set function. Experimental results on 10 clinical brain data sets demonstrate that our method is not only able to achieve better Dice Similarity Coefficient than the global threshold based method and localized hybrid level-set method but also able to extract whole cerebral vessel trees, including the thin vessels. PMID:27597878

  2. The Isolation, Primacy, and Recency Effects Predicted by an Adaptive LTD/LTP Threshold in Postsynaptic Cells.

    PubMed

    Sikström, Sverker

    2006-03-01

    An item that stands out (is isolated) from its context is better remembered than an item consistent with the context. This isolation effect cannot be accounted for by increased attention, because it occurs when the isolated item is presented as the first item, or by impoverished memory of nonisolated items, because the isolated item is better remembered than a control list consisting of equally different items. The isolation effect is seldom experimentally or theoretically related to the primacy or the recency effects-that is, the improved performance on the first few and last items, respectively, on the serial position curve. The primacy effect cannot easily be accounted for by rehearsal in short-term memory because it occurs when rehearsal is eliminated. This article suggests that the primacy, the recency, and the isolation effects can be accounted for by experience-dependent synaptic plasticity in neural cells. Neurological empirical data suggest that the threshold that determines whether cells will show long-term potentiation (LTP) or long-term depression (LTD) varies as a function of recent postsynaptic activity and that synaptic plasticity is bounded. By implementing an adaptive LTP-LTD threshold in an artificial neural network, the various aspects of the isolation, the primacy, and the recency effects are accounted for, whereas none of these phenomena are accounted for if the threshold is constant. This theory suggests a possible link between the cognitive and the neurological levels.

  3. Informativeness of the threshold adaptation and fatigue for assessment of the auditory health risk.

    PubMed

    Tzaneva, L

    1997-09-01

    The management and control of modern automated productions evidence the elevated role of the auditory system as one of the distant sensor communication systems. The present study informs about the auditory adaptation and fatigue at the end of the working shift of 385 operators at control boards in "Kremikovtzi" State Company. The results of the monitoring of the dynamic changes show significant changes, expressed in aggravation of the auditory fatigue manifestation by moderate to significant disturbance of the adaptation-recovery processes. The analysis established a significant positive correlation between the changes in auditory fatigue and the duration of service. The frequencies of the speech range are preserved for a long time. The elevated auditory fatigue is observed in the injured hearing band 4,000 Hz, followed by 6,000 Hz and continuous dissemination to the middle frequencies of the speech band-2,000 and 1,000 Hz. The results of the study of the adaptation-recovery processes are characterised by statistically significant reliability, single direction and reproducibility and can be applied as informative criteria for assessment of the auditory health risk.

  4. Real time algorithm invariant to natural lighting with LBP techniques through an adaptive thresholding implemented in GPU processors

    NASA Astrophysics Data System (ADS)

    Orjuela-Vargas, S. A.; Triana-Martinez, J.; Yañez, J. P.; Philips, W.

    2014-03-01

    Video analysis in real time requires fast and efficient algorithms to extract relevant information from a considerable number, commonly 25, of frames per second. Furthermore, robust algorithms for outdoor visual scenes may retrieve correspondent features along the day where a challenge is to deal with lighting changes. Currently, Local Binary Pattern (LBP) techniques are widely used for extracting features due to their robustness to illumination changes and the low requirements for implementation. We propose to compute an automatic threshold based on the distribution of the intensity residuals resulting from the pairwise comparisons when using LBP techniques. The intensity residuals distribution can be modelled by a Generalized Gaussian Distribution (GGD). In this paper we compute the adaptive threshold using the parameters of the GGD. We present a CUDA implementation of our proposed algorithm. We use the LBPSYM technique. Our approach is tested on videos of four different urban scenes with mobilities captured during day and night. The extracted features can be used in a further step to determine patterns, identify objects or detect background. However, further research must be conducted for blurring correction since the scenes at night are commonly blurred due to artificial lighting.

  5. Fast parallel MR image reconstruction via B1-based, adaptive restart, iterative soft thresholding algorithms (BARISTA).

    PubMed

    Muckley, Matthew J; Noll, Douglas C; Fessler, Jeffrey A

    2015-02-01

    Sparsity-promoting regularization is useful for combining compressed sensing assumptions with parallel MRI for reducing scan time while preserving image quality. Variable splitting algorithms are the current state-of-the-art algorithms for SENSE-type MR image reconstruction with sparsity-promoting regularization. These methods are very general and have been observed to work with almost any regularizer; however, the tuning of associated convergence parameters is a commonly-cited hindrance in their adoption. Conversely, majorize-minimize algorithms based on a single Lipschitz constant have been observed to be slow in shift-variant applications such as SENSE-type MR image reconstruction since the associated Lipschitz constants are loose bounds for the shift-variant behavior. This paper bridges the gap between the Lipschitz constant and the shift-variant aspects of SENSE-type MR imaging by introducing majorizing matrices in the range of the regularizer matrix. The proposed majorize-minimize methods (called BARISTA) converge faster than state-of-the-art variable splitting algorithms when combined with momentum acceleration and adaptive momentum restarting. Furthermore, the tuning parameters associated with the proposed methods are unitless convergence tolerances that are easier to choose than the constraint penalty parameters required by variable splitting algorithms.

  6. Fast Parallel MR Image Reconstruction via B1-based, Adaptive Restart, Iterative Soft Thresholding Algorithms (BARISTA)

    PubMed Central

    Noll, Douglas C.; Fessler, Jeffrey A.

    2014-01-01

    Sparsity-promoting regularization is useful for combining compressed sensing assumptions with parallel MRI for reducing scan time while preserving image quality. Variable splitting algorithms are the current state-of-the-art algorithms for SENSE-type MR image reconstruction with sparsity-promoting regularization. These methods are very general and have been observed to work with almost any regularizer; however, the tuning of associated convergence parameters is a commonly-cited hindrance in their adoption. Conversely, majorize-minimize algorithms based on a single Lipschitz constant have been observed to be slow in shift-variant applications such as SENSE-type MR image reconstruction since the associated Lipschitz constants are loose bounds for the shift-variant behavior. This paper bridges the gap between the Lipschitz constant and the shift-variant aspects of SENSE-type MR imaging by introducing majorizing matrices in the range of the regularizer matrix. The proposed majorize-minimize methods (called BARISTA) converge faster than state-of-the-art variable splitting algorithms when combined with momentum acceleration and adaptive momentum restarting. Furthermore, the tuning parameters associated with the proposed methods are unitless convergence tolerances that are easier to choose than the constraint penalty parameters required by variable splitting algorithms. PMID:25330484

  7. Fast Hearing-Threshold Estimation Using Multiple Auditory Steady-State Responses with Narrow-Band Chirps and Adaptive Stimulus Patterns

    PubMed Central

    Mühler, Roland; Mentzel, Katrin; Verhey, Jesko

    2012-01-01

    This paper describes the estimation of hearing thresholds in normal-hearing and hearing-impaired subjects on the basis of multiple-frequency auditory steady-state responses (ASSRs). The ASSR was measured using two new techniques: (i) adaptive stimulus patterns and (ii) narrow-band chirp stimuli. ASSR thresholds in 16 normal-hearing and 16 hearing-impaired adults were obtained simultaneously at both ears at 500, 1000, 2000, and 4000 Hz, using a multiple-frequency stimulus built up of four one-octave-wide narrow-band chirps with a repetition rate of 40 Hz. A statistical test in the frequency domain was used to detect the response. The recording of the steady-state responses was controlled in eight independent recording channels with an adaptive, semiautomatic algorithm. The average differences between the behavioural hearing thresholds and the ASSR threshold estimate were 10, 8, 13, and 15 dB for test frequencies of 500, 1000, 2000, and 4000 Hz, respectively. The average overall test duration of 18.6 minutes for the threshold estimations at the four frequencies and both ears demonstrates the benefit of an adaptive recording algorithm and the efficiency of optimised narrow-band chirp stimuli. PMID:22619622

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

    PubMed

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

    2013-06-01

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

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

    PubMed

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

    2013-06-01

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

  10. Hearing threshold estimation by auditory steady-state responses with narrow-band chirps and adaptive stimulus patterns: implementation in clinical routine.

    PubMed

    Seidel, David Ulrich; Flemming, Tobias Angelo; Park, Jonas Jae-Hyun; Remmert, Stephan

    2015-01-01

    Objective hearing threshold estimation by auditory steady-state responses (ASSR) can be accelerated by the use of narrow-band chirps and adaptive stimulus patterns. This modification has been examined in only a few clinical studies. In this study, clinical data is validated and extended, and the applicability of the method in audiological diagnostics routine is examined. In 60 patients (normal hearing and hearing impaired), ASSR and pure tone audiometry (PTA) thresholds were compared. ASSR were evoked by binaural multi-frequent narrow-band chirps with adaptive stimulus patterns. The precision and required testing time for hearing threshold estimation were determined. The average differences between ASSR and PTA thresholds were 18, 12, 17 and 19 dB for normal hearing (PTA ≤ 20 dB) and 5, 9, 9 and 11 dB for hearing impaired (PTA > 20 dB) at the frequencies of 500, 1,000, 2,000 and 4,000 Hz, respectively, and the differences were significant in all frequencies with the exception of 1 kHz. Correlation coefficients between ASSR and PTA thresholds were 0.36, 0.47, 0.54 and 0.51 for normal hearing and 0.73, 0.74, 0.72 and 0.71 for hearing impaired at 500, 1,000, 2,000 and 4,000 Hz, respectively. Mean ASSR testing time was 33 ± 8 min. In conclusion, auditory steady-state responses with narrow-band-chirps and adaptive stimulus patterns is an efficient method for objective frequency-specific hearing threshold estimation. Precision of threshold estimation is most limited for slighter hearing loss at 500 Hz. The required testing time is acceptable for the application in everyday clinical routine. PMID:24305781

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

    PubMed Central

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

    2013-01-01

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

  12. Variable-ratio versus variable-interval schedules: response rate, resistance to change, and preference.

    PubMed

    Nevin, J A; Randolph; Holland, S; McLean, A P

    2001-07-01

    Two experiments asked whether resistance to change depended on variable-ratio as opposed to variable-interval contingencies of reinforcement and the different response rates they establish. In Experiment 1, pigeons were trained on multiple random-ratio random-interval schedules with equated reinforcer rates. Baseline response rates were disrupted by intercomponent food, extinction, and prefeeding. Resistance to change relative to baseline was greater in the interval component, and the difference was correlated with the extent to which baseline response rates were higher in the ratio component. In Experiment 2, pigeons were trained on multiple variable-ratio variable-interval schedules in one half of each session and on concurrent chains in the other half in which the terminal links corresponded to the multiple-schedule components. The schedules were varied over six conditions, including two with equated reinforcer rates. In concurrent chains, preference strongly overmatched the ratio of obtained reinforcer rates. In multiple schedules, relative resistance to response-independent food during intercomponent intervals, extinction, and intercomponent food plus extinction depended on the ratio of obtained reinforcer rates but was less sensitive than was preference. When reinforcer rates were similar, both preference and relative resistance were greater for the variable-interval schedule, and the differences were correlated with the extent to which baseline response rates were higher on the variable-ratio schedule, confirming the results of Experiment 1. These results demonstrate that resistance to change and preference depend in part on response rate as well as obtained reinforcer rate, and challenge the independence of resistance to change and preference with respect to response rate proposed by behavioral momentum theory.

  13. Variable-ratio versus variable-interval schedules: response rate, resistance to change, and preference.

    PubMed Central

    Nevin, J A; Randolph; Holland, S; McLean, A P

    2001-01-01

    Two experiments asked whether resistance to change depended on variable-ratio as opposed to variable-interval contingencies of reinforcement and the different response rates they establish. In Experiment 1, pigeons were trained on multiple random-ratio random-interval schedules with equated reinforcer rates. Baseline response rates were disrupted by intercomponent food, extinction, and prefeeding. Resistance to change relative to baseline was greater in the interval component, and the difference was correlated with the extent to which baseline response rates were higher in the ratio component. In Experiment 2, pigeons were trained on multiple variable-ratio variable-interval schedules in one half of each session and on concurrent chains in the other half in which the terminal links corresponded to the multiple-schedule components. The schedules were varied over six conditions, including two with equated reinforcer rates. In concurrent chains, preference strongly overmatched the ratio of obtained reinforcer rates. In multiple schedules, relative resistance to response-independent food during intercomponent intervals, extinction, and intercomponent food plus extinction depended on the ratio of obtained reinforcer rates but was less sensitive than was preference. When reinforcer rates were similar, both preference and relative resistance were greater for the variable-interval schedule, and the differences were correlated with the extent to which baseline response rates were higher on the variable-ratio schedule, confirming the results of Experiment 1. These results demonstrate that resistance to change and preference depend in part on response rate as well as obtained reinforcer rate, and challenge the independence of resistance to change and preference with respect to response rate proposed by behavioral momentum theory. PMID:11516115

  14. Control system and method for a power delivery system having a continuously variable ratio transmission

    DOEpatents

    Frank, A.A.

    1984-07-10

    A control system and method for a power delivery system, such as in an automotive vehicle, having an engine coupled to a continuously variable ratio transmission (CVT). Totally independent control of engine and transmission enable the engine to precisely follow a desired operating characteristic, such as the ideal operating line for minimum fuel consumption. CVT ratio is controlled as a function of commanded power or torque and measured load, while engine fuel requirements (e.g., throttle position) are strictly a function of measured engine speed. Fuel requirements are therefore precisely adjusted in accordance with the ideal characteristic for any load placed on the engine. 4 figs.

  15. Control system and method for a power delivery system having a continuously variable ratio transmission

    DOEpatents

    Frank, Andrew A.

    1984-01-01

    A control system and method for a power delivery system, such as in an automotive vehicle, having an engine coupled to a continuously variable ratio transmission (CVT). Totally independent control of engine and transmission enable the engine to precisely follow a desired operating characteristic, such as the ideal operating line for minimum fuel consumption. CVT ratio is controlled as a function of commanded power or torque and measured load, while engine fuel requirements (e.g., throttle position) are strictly a function of measured engine speed. Fuel requirements are therefore precisely adjusted in accordance with the ideal characteristic for any load placed on the engine.

  16. Delay reduction and optimal foraging: variable-ratio search in a foraging analogue.

    PubMed

    Williams, W A; Fantino, E

    1994-05-01

    The present study investigated conditions under which the conditioned reinforcement principles of delay-reduction theory and views based on simple maximization of reinforcement rate make ordinally opposing predictions with respect to foraging-related choice behavior. The use of variable-ratio schedules in the choice phase also represents an extension of delay-reduction theory to schedules that may better mimic the effort involved in searching. Pigeons responded on modified concurrent-chains schedules in which equal variable-ratio schedules led to unequal variable-interval outcomes and unequal reinforcer amounts. All 4 subjects completed a minimum of two replications of conditions for which the predictions of delay-reduction theory and a simple rate-maximizing theory were opposed. Results were consistent with delay reduction's ordinal predictions in 11 of 11 replications of the divergent predictions favoring the smaller, more immediate alternative. The predictions of rate maximization were upheld only when they were consistent with those of delay reduction. Results are discussed in terms of conditioned reinforcement, sensitivity to reductions in delay to food, and possible rules of thumb that may be useful in characterizing foraging.

  17. Air and Bone Conduction Click and Tone-burst Auditory Brainstem Thresholds using Kalman Adaptive Processing in Non-sedated Normal Hearing Infants

    PubMed Central

    Elsayed, Alaaeldin M.; Hunter, Lisa L.; Keefe, Douglas H.; Feeney, M. Patrick; Brown, David K.; Meinzen-Derr, Jareen K.; Baroch, Kelly; Sullivan-Mahoney, Maureen; Francis, Kara; Schaid, Leigh G.

    2015-01-01

    Objective To study normative thresholds and latencies for click and tone-burst auditory brainstem response (TB-ABR) for air and bone conduction in normal infants and those discharged from neonatal intensive care units (NICU), who passed newborn hearing screening and follow-up DPOAE. An evoked potential system (Vivosonic Integrity™) that incorporates Bluetooth electrical isolation and Kalman-weighted adaptive processing to improve signal to noise ratios was employed for this study. Results were compared with other published data. Research Design One hundred forty-five infants who passed two-stage hearing screening with transient-evoked otoacoustic emission (OAE) or automated ABR were assessed with clicks at 70 dB nHL and threshold TB-ABR. Tone-bursts at frequencies between 500 to 4000 Hz were employed for air and bone conduction ABR testing using a specified staircase threshold search to establish threshold levels and Wave V peak latencies. Results Median air conduction hearing thresholds using TB-ABR ranged from 0-20 dB nHL, depending on stimulus frequency. Median bone conduction thresholds were 10 dB nHL across all frequencies, and median air-bone gaps were 0 dB across all frequencies. There was no significant threshold difference between left and right ears and no significant relationship between thresholds and hearing loss risk factors, ethnicity or gender. Older age was related to decreased latency for air conduction. Compared to previous studies, mean air conduction thresholds were found at slightly lower (better) levels, while bone conduction levels were better at 2000 Hz and higher at 500 Hz. Latency values were longer at 500 Hz than previous studies using other instrumentation. Sleep state did not affect air or bone conduction thresholds. Conclusions This study demonstrated slightly better Wave V thresholds for air conduction than previous infant studies. The differences found in the current study, while statistically significant, were within the test

  18. An all fiber apparatus for microparticles selective manipulation based on a variable ratio coupler and a microfiber

    NASA Astrophysics Data System (ADS)

    Li, Baoli; Luo, Wei; Xu, Fei; Lu, Yanqing

    2016-09-01

    We propose an all fiber apparatus based on a variable ratio coupler which can transport microparticles controllably and trap particles one by one along a microfiber. By connecting two output ports of a variable ratio coupler with two end pigtails of a microfiber and launching a 980 nm laser into the variable ratio coupler, particles in suspension were trapped to the waist of microfiber due to a gradient force and then transported along the microfiber due to a total scattering force generated by two counter-propagating beams. The direction of transportation was controlled by altering the coupling ratio of the variable ratio coupler. When the intensities of two output ports were equivalent, trapped particles stayed at fixed positions. With time going, another particle around the micro fiber was trapped onto the microfiber. There were three particles trapped in total in our experiment. This technique combines with the function of conventional tweezers and optical conveyor.

  19. Investigation of Adaptive-threshold Approaches for Determining Area-Time Integrals from Satellite Infrared Data to Estimate Convective Rain Volumes

    NASA Technical Reports Server (NTRS)

    Smith, Paul L.; VonderHaar, Thomas H.

    1996-01-01

    The principal goal of this project is to establish relationships that would allow application of area-time integral (ATI) calculations based upon satellite data to estimate rainfall volumes. The research is being carried out as a collaborative effort between the two participating organizations, with the satellite data analysis to determine values for the ATIs being done primarily by the STC-METSAT scientists and the associated radar data analysis to determine the 'ground-truth' rainfall estimates being done primarily at the South Dakota School of Mines and Technology (SDSM&T). Synthesis of the two separate kinds of data and investigation of the resulting rainfall-versus-ATI relationships is then carried out jointly. The research has been pursued using two different approaches, which for convenience can be designated as the 'fixed-threshold approach' and the 'adaptive-threshold approach'. In the former, an attempt is made to determine a single temperature threshold in the satellite infrared data that would yield ATI values for identifiable cloud clusters which are closely related to the corresponding rainfall amounts as determined by radar. Work on the second, or 'adaptive-threshold', approach for determining the satellite ATI values has explored two avenues: (1) attempt involved choosing IR thresholds to match the satellite ATI values with ones separately calculated from the radar data on a case basis; and (2) an attempt involved a striaghtforward screening analysis to determine the (fixed) offset that would lead to the strongest correlation and lowest standard error of estimate in the relationship between the satellite ATI values and the corresponding rainfall volumes.

  20. Variable-ratio schedules as variable-interval schedules with linear feedback loops.

    PubMed

    McDowell, J J; Wixted, J T

    1986-11-01

    The mathematical theory of linear systems has been used successfully to describe responding on variable-interval (VI) schedules. In the simplest extension of the theory to the variable-ratio (VR) case, VR schedules are treated as if they were VI schedules with linear feedback loops. The assumption entailed by this approach, namely, that VR and VI-plus-linear-feedback schedules are equivalent, was tested by comparing responding on the two types of schedule. Four human subjects' lever pressing produced monetary reinforcers on five VR schedules, and on five VI schedules with linear feedback loops that reproduced the feedback properties of the VR schedules. Pressing was initiated by instructions in 2 subjects, and was shaped by successive approximation in the other 2. The different methods of response initiation did not have differential effects on behavior. For each of the 4 subjects, the VR and the comparable VI-plus-linear-feedback schedules generated similar average response rates and similar response patterns. The subjects' behavior on both types of schedule was similar to that of avian and rodent species on VR schedules. These results indicate that the assumption entailed by the VI-plus-linear-feedback approach to the VR case is valid and, consequently, that the approach is worth pursuing. The results also confute interresponse-time theories of schedule performance, which require interval and ratio contingencies to produce different response rates.

  1. Behavioral economics of concurrent ethanol-sucrose and sucrose reinforcement in the rat: effects of altering variable-ratio requirements.

    PubMed Central

    Petry, N M; Heyman, G M

    1995-01-01

    These experiments examined the own-price and cross-price elasticities of a drug (ethanol mixed with 10% sucrose) and a nondrug (10% sucrose) reinforcer. Rats were presented with ethanol-sucrose and sucrose, both available on concurrent independent variable-ratio (VR) 8 schedules of reinforcement. In Experiment 1, the variable ratio for the ethanol mix was systematically raised to 10, 12, 14, 16, 20, and 30, while the variable ratio for sucrose remained at 8. Five of the 6 rats increased ethanol-reinforced responding at some of the increments and defended baseline levels of ethanol intake. However, the rats eventually ceased ethanol-reinforced responding at the highest variable ratios. Sucrose-reinforced responding was not systematically affected by the changes in variable ratio for ethanol mix. In Experiment 2, the variable ratio for sucrose was systematically increased while the ethanol-sucrose response requirement remained constant. The rats decreased sucrose-reinforced responding and increased ethanol-sucrose-reinforced responding, resulting in a two- to 10-fold increase in ethanol intake. Experiment 3 examined the substitutability of qualitatively identical reinforcers: 10% sucrose versus 10% sucrose. Increases in variable-ratio requirements at the preferred lever resulted in a switch in lever preference. Experiment 4 examined whether 10% ethanol mix substituted for 5% ethanol mix, with increasing variable-ratio requirements of the 5% ethanol. All rats eventually responded predominantly for the 10% ethanol mix, but total amount of ethanol consumed per session did not systematically change. In Experiment 5, the variable-ratio requirements for both ethanol and sucrose were simultaneously raised to VR 120; 7 of 8 rats increased ethanol-reinforced responding while decreasing sucrose-reinforced responding. These data suggest that, within this ethanol-induction procedure and within certain parameters, demand for ethanol-sucrose was relatively inelastic, and sucrose

  2. A de-noising algorithm based on wavelet threshold-exponential adaptive window width-fitting for ground electrical source airborne transient electromagnetic signal

    NASA Astrophysics Data System (ADS)

    Ji, Yanju; Li, Dongsheng; Yu, Mingmei; Wang, Yuan; Wu, Qiong; Lin, Jun

    2016-05-01

    The ground electrical source airborne transient electromagnetic system (GREATEM) on an unmanned aircraft enjoys considerable prospecting depth, lateral resolution and detection efficiency, etc. In recent years it has become an important technical means of rapid resources exploration. However, GREATEM data are extremely vulnerable to stationary white noise and non-stationary electromagnetic noise (sferics noise, aircraft engine noise and other human electromagnetic noises). These noises will cause degradation of the imaging quality for data interpretation. Based on the characteristics of the GREATEM data and major noises, we propose a de-noising algorithm utilizing wavelet threshold method and exponential adaptive window width-fitting. Firstly, the white noise is filtered in the measured data using the wavelet threshold method. Then, the data are segmented using data window whose step length is even logarithmic intervals. The data polluted by electromagnetic noise are identified within each window based on the discriminating principle of energy detection, and the attenuation characteristics of the data slope are extracted. Eventually, an exponential fitting algorithm is adopted to fit the attenuation curve of each window, and the data polluted by non-stationary electromagnetic noise are replaced with their fitting results. Thus the non-stationary electromagnetic noise can be effectively removed. The proposed algorithm is verified by the synthetic and real GREATEM signals. The results show that in GREATEM signal, stationary white noise and non-stationary electromagnetic noise can be effectively filtered using the wavelet threshold-exponential adaptive window width-fitting algorithm, which enhances the imaging quality.

  3. Second-order schedules of token reinforcement with pigeons: effects of fixed- and variable-ratio exchange schedules.

    PubMed

    Foster, T A; Hackenberg, T D; Vaidya, M

    2001-09-01

    Pigeons' key pecks produced food under second-order schedules of token reinforcement, with light-emitting diodes serving as token reinforcers. In Experiment 1, tokens were earned according to a fixed-ratio 50 schedule and were exchanged for food according to either fixed-ratio or variable-ratio exchange schedules, with schedule type varied across conditions. In Experiment 2, schedule type was varied within sessions using a multiple schedule. In one component, tokens were earned according to a fixed-ratio 50 schedule and exchanged according to a variable-ratio schedule. In the other component, tokens were earned according to a variable-ratio 50 schedule and exchanged according to a fixed-ratio schedule. In both experiments, the number of responses per exchange was varied parametrically across conditions, ranging from 50 to 400 responses. Response rates decreased systematically with increases in the fixed-ratio exchange schedules, but were much less affected by changes in the variable-ratio exchange schedules. Response rates were consistently higher under variable-ratio exchange schedules than tinder comparable fixed-ratio exchange schedules, especially at higher exchange ratios. These response-rate differences were due both to greater pre-ratio pausing and to lower local rates tinder the fixed-ratio exchange schedules. Local response rates increased with proximity to food under the higher fixed-ratio exchange schedules, indicative of discriminative control by the tokens. PMID:11599637

  4. Second-order schedules of token reinforcement with pigeons: effects of fixed- and variable-ratio exchange schedules.

    PubMed Central

    Foster, T A; Hackenberg, T D; Vaidya, M

    2001-01-01

    Pigeons' key pecks produced food under second-order schedules of token reinforcement, with light-emitting diodes serving as token reinforcers. In Experiment 1, tokens were earned according to a fixed-ratio 50 schedule and were exchanged for food according to either fixed-ratio or variable-ratio exchange schedules, with schedule type varied across conditions. In Experiment 2, schedule type was varied within sessions using a multiple schedule. In one component, tokens were earned according to a fixed-ratio 50 schedule and exchanged according to a variable-ratio schedule. In the other component, tokens were earned according to a variable-ratio 50 schedule and exchanged according to a fixed-ratio schedule. In both experiments, the number of responses per exchange was varied parametrically across conditions, ranging from 50 to 400 responses. Response rates decreased systematically with increases in the fixed-ratio exchange schedules, but were much less affected by changes in the variable-ratio exchange schedules. Response rates were consistently higher under variable-ratio exchange schedules than tinder comparable fixed-ratio exchange schedules, especially at higher exchange ratios. These response-rate differences were due both to greater pre-ratio pausing and to lower local rates tinder the fixed-ratio exchange schedules. Local response rates increased with proximity to food under the higher fixed-ratio exchange schedules, indicative of discriminative control by the tokens. PMID:11599637

  5. Adaptive thresholding algorithm based on SAR images and wind data to segment oil spills along the northwest coast of the Iberian Peninsula.

    PubMed

    Mera, David; Cotos, José M; Varela-Pet, José; Garcia-Pineda, Oscar

    2012-10-01

    Satellite Synthetic Aperture Radar (SAR) has been established as a useful tool for detecting hydrocarbon spillage on the ocean's surface. Several surveillance applications have been developed based on this technology. Environmental variables such as wind speed should be taken into account for better SAR image segmentation. This paper presents an adaptive thresholding algorithm for detecting oil spills based on SAR data and a wind field estimation as well as its implementation as a part of a functional prototype. The algorithm was adapted to an important shipping route off the Galician coast (northwest Iberian Peninsula) and was developed on the basis of confirmed oil spills. Image testing revealed 99.93% pixel labelling accuracy. By taking advantage of multi-core processor architecture, the prototype was optimized to get a nearly 30% improvement in processing time.

  6. On the Primacy of Molecular Processes in Determining Response Rates under Variable-Ratio and Variable-Interval Schedules

    ERIC Educational Resources Information Center

    Tanno, Takayuki; Sakagami, Takayuki

    2008-01-01

    This study focused on variables that may account for response-rate differences under variable-ratio (VR) and variable-interval (VI) schedules of reinforcement. Four rats were exposed to VR, VI, tandem VI differential- reinforcement-of-high-rate, regulated-probability-interval, and negative-feedback schedules of reinforcement that provided the same…

  7. Numerical simulation on the adaptation of forms in trabecular bone to mechanical disuse and basic multi-cellular unit activation threshold at menopause

    NASA Astrophysics Data System (ADS)

    Gong, He; Fan, Yubo; Zhang, Ming

    2008-04-01

    The objective of this paper is to identify the effects of mechanical disuse and basic multi-cellular unit (BMU) activation threshold on the form of trabecular bone during menopause. A bone adaptation model with mechanical- biological factors at BMU level was integrated with finite element analysis to simulate the changes of trabecular bone structure during menopause. Mechanical disuse and changes in the BMU activation threshold were applied to the model for the period from 4 years before to 4 years after menopause. The changes in bone volume fraction, trabecular thickness and fractal dimension of the trabecular structures were used to quantify the changes of trabecular bone in three different cases associated with mechanical disuse and BMU activation threshold. It was found that the changes in the simulated bone volume fraction were highly correlated and consistent with clinical data, and that the trabecular thickness reduced significantly during menopause and was highly linearly correlated with the bone volume fraction, and that the change trend of fractal dimension of the simulated trabecular structure was in correspondence with clinical observations. The numerical simulation in this paper may help to better understand the relationship between the bone morphology and the mechanical, as well as biological environment; and can provide a quantitative computational model and methodology for the numerical simulation of the bone structural morphological changes caused by the mechanical environment, and/or the biological environment.

  8. Non-parametric permutation thresholding for adaptive nonlinear beamformer analysis on MEG revealed oscillatory neuronal dynamics in human brain.

    PubMed

    Ishii, Ryouhei; Canuet, Leonides; Aoki, Yasunori; Ikeda, Shunichiro; Hata, Masahiro; Iwase, Masao; Takeda, Masatoshi

    2013-01-01

    Adaptive nonlinear beamformer technique for analyzing magnetoencephalography (MEG) data has been proved to be powerful tool for both brain research and clinical applications. A general method of analyzing multiple subject data with a formal statistical treatment for the group data has been developed and applied for various types of MEG data. Our latest application of this method was frontal midline theta rhythm (Fmθ), which indicates focused attention and appears widely distributed over medial prefrontal areas in EEG recordings. To localize cortical generators of the magnetic counterpart of Fmθ precisely and identify cortical sources and underlying neural activity associated with mental calculation processing (i.e., arithmetic subtraction), we applied adaptive nonlinear beamformer and permutation analysis on MEG data. As a result, it was indicated that Fmθ is generated in the dorsal anterior cingulate and adjacent medial prefrontal cortex. Gamma event-related synchronization is as an index of activation in right parietal regions subserving mental subtraction associated with basic numerical processing and number-based spatial attention. Gamma desynchronization appeared in the right lateral prefrontal cortex, likely representing a mechanism to interrupt neural activity that can interfere with the ongoing cognitive task. We suggest that the combination of adaptive nonlinear beamformer and permutation analysis on MEG data is quite powerful tool to reveal the oscillatory neuronal dynamics in human brain. PMID:24110810

  9. [Effects of variable-interval punishment on lever pressing maintained by variable-ratio reinforcement in the rat].

    PubMed

    Iida, Naritoshi; Kimura, Hiroshi

    2007-12-01

    The effects of reinforcement and punishment on response suppression under variable-ratio reinforcement and variable-interval punishment schedules were investigated. In the baseline period, lever pressing in rats was maintained by a variable-ratio food reinforcement schedule. In the punishment condition, responding was punished by a grid shock under a variable-interval schedule. Baseline and punishment conditions alternated, and were continued until the response stabilized. Three rats were given five or six punishment rates with a fixed reinforcement rate and another three rats were given four or five reinforcement rates with a fixed punishment rate. The results indicated that the responses were either completely suppressed or not suppressed at all. When the punishment rate increased or the reinforcement rate decreased, the response was suppressed completely. Whereas when the punishment rate decreased or the reinforcement rate increased, the responses were not suppressed. These results agree with the predictions of the molar theory.

  10. Identification of Molecular Fingerprints in Human Heat Pain Thresholds by Use of an Interactive Mixture Model R Toolbox (AdaptGauss).

    PubMed

    Ultsch, Alfred; Thrun, Michael C; Hansen-Goos, Onno; Lötsch, Jörn

    2015-10-28

    Biomedical data obtained during cell experiments, laboratory animal research, or human studies often display a complex distribution. Statistical identification of subgroups in research data poses an analytical challenge. Here were introduce an interactive R-based bioinformatics tool, called "AdaptGauss". It enables a valid identification of a biologically-meaningful multimodal structure in the data by fitting a Gaussian mixture model (GMM) to the data. The interface allows a supervised selection of the number of subgroups. This enables the expectation maximization (EM) algorithm to adapt more complex GMM than usually observed with a noninteractive approach. Interactively fitting a GMM to heat pain threshold data acquired from human volunteers revealed a distribution pattern with four Gaussian modes located at temperatures of 32.3, 37.2, 41.4, and 45.4 °C. Noninteractive fitting was unable to identify a meaningful data structure. Obtained results are compatible with known activity temperatures of different TRP ion channels suggesting the mechanistic contribution of different heat sensors to the perception of thermal pain. Thus, sophisticated analysis of the modal structure of biomedical data provides a basis for the mechanistic interpretation of the observations. As it may reflect the involvement of different TRP thermosensory ion channels, the analysis provides a starting point for hypothesis-driven laboratory experiments.

  11. Validation of various adaptive threshold methods of segmentation applied to follicular lymphoma digital images stained with 3,3’-Diaminobenzidine&Haematoxylin

    PubMed Central

    2013-01-01

    The comparative study of the results of various segmentation methods for the digital images of the follicular lymphoma cancer tissue section is described in this paper. The sensitivity and specificity and some other parameters of the following adaptive threshold methods of segmentation: the Niblack method, the Sauvola method, the White method, the Bernsen method, the Yasuda method and the Palumbo method, are calculated. Methods are applied to three types of images constructed by extraction of the brown colour information from the artificial images synthesized based on counterpart experimentally captured images. This paper presents usefulness of the microscopic image synthesis method in evaluation as well as comparison of the image processing results. The results of thoughtful analysis of broad range of adaptive threshold methods applied to: (1) the blue channel of RGB, (2) the brown colour extracted by deconvolution and (3) the ’brown component’ extracted from RGB allows to select some pairs: method and type of image for which this method is most efficient considering various criteria e.g. accuracy and precision in area detection or accuracy in number of objects detection and so on. The comparison shows that the White, the Bernsen and the Sauvola methods results are better than the results of the rest of the methods for all types of monochromatic images. All three methods segments the immunopositive nuclei with the mean accuracy of 0.9952, 0.9942 and 0.9944 respectively, when treated totally. However the best results are achieved for monochromatic image in which intensity shows brown colour map constructed by colour deconvolution algorithm. The specificity in the cases of the Bernsen and the White methods is 1 and sensitivities are: 0.74 for White and 0.91 for Bernsen methods while the Sauvola method achieves sensitivity value of 0.74 and the specificity value of 0.99. According to Bland-Altman plot the Sauvola method selected objects are segmented without

  12. An adaptive technique for multiscale approximate entropy (MAEbin) threshold (r) selection: application to heart rate variability (HRV) and systolic blood pressure variability (SBPV) under postural stress.

    PubMed

    Singh, Amritpal; Saini, Barjinder Singh; Singh, Dilbag

    2016-06-01

    Multiscale approximate entropy (MAE) is used to quantify the complexity of a time series as a function of time scale τ. Approximate entropy (ApEn) tolerance threshold selection 'r' is based on either: (1) arbitrary selection in the recommended range (0.1-0.25) times standard deviation of time series (2) or finding maximum ApEn (ApEnmax) i.e., the point where self-matches start to prevail over other matches and choosing the corresponding 'r' (rmax) as threshold (3) or computing rchon by empirically finding the relation between rmax, SD1/SD2 ratio and N using curve fitting, where, SD1 and SD2 are short-term and long-term variability of a time series respectively. None of these methods is gold standard for selection of 'r'. In our previous study [1], an adaptive procedure for selection of 'r' is proposed for approximate entropy (ApEn). In this paper, this is extended to multiple time scales using MAEbin and multiscale cross-MAEbin (XMAEbin). We applied this to simulations i.e. 50 realizations (n = 50) of random number series, fractional Brownian motion (fBm) and MIX (P) [1] series of data length of N = 300 and short term recordings of HRV and SBPV performed under postural stress from supine to standing. MAEbin and XMAEbin analysis was performed on laboratory recorded data of 50 healthy young subjects experiencing postural stress from supine to upright. The study showed that (i) ApEnbin of HRV is more than SBPV in supine position but is lower than SBPV in upright position (ii) ApEnbin of HRV decreases from supine i.e. 1.7324 ± 0.112 (mean ± SD) to upright 1.4916 ± 0.108 due to vagal inhibition (iii) ApEnbin of SBPV increases from supine i.e. 1.5535 ± 0.098 to upright i.e. 1.6241 ± 0.101 due sympathetic activation (iv) individual and cross complexities of RRi and systolic blood pressure (SBP) series depend on time scale under consideration (v) XMAEbin calculated using ApEnmax is correlated with cross-MAE calculated using ApEn (0.1-0.26) in steps of 0

  13. Adapt

    NASA Astrophysics Data System (ADS)

    Bargatze, L. F.

    2015-12-01

    Active Data Archive Product Tracking (ADAPT) is a collection of software routines that permits one to generate XML metadata files to describe and register data products in support of the NASA Heliophysics Virtual Observatory VxO effort. ADAPT is also a philosophy. The ADAPT concept is to use any and all available metadata associated with scientific data to produce XML metadata descriptions in a consistent, uniform, and organized fashion to provide blanket access to the full complement of data stored on a targeted data server. In this poster, we present an application of ADAPT to describe all of the data products that are stored by using the Common Data File (CDF) format served out by the CDAWEB and SPDF data servers hosted at the NASA Goddard Space Flight Center. These data servers are the primary repositories for NASA Heliophysics data. For this purpose, the ADAPT routines have been used to generate data resource descriptions by using an XML schema named Space Physics Archive, Search, and Extract (SPASE). SPASE is the designated standard for documenting Heliophysics data products, as adopted by the Heliophysics Data and Model Consortium. The set of SPASE XML resource descriptions produced by ADAPT includes high-level descriptions of numerical data products, display data products, or catalogs and also includes low-level "Granule" descriptions. A SPASE Granule is effectively a universal access metadata resource; a Granule associates an individual data file (e.g. a CDF file) with a "parent" high-level data resource description, assigns a resource identifier to the file, and lists the corresponding assess URL(s). The CDAWEB and SPDF file systems were queried to provide the input required by the ADAPT software to create an initial set of SPASE metadata resource descriptions. Then, the CDAWEB and SPDF data repositories were queried subsequently on a nightly basis and the CDF file lists were checked for any changes such as the occurrence of new, modified, or deleted

  14. Thresholds of cutaneous afferents related to perceptual threshold across the human foot sole.

    PubMed

    Strzalkowski, Nicholas D J; Mildren, Robyn L; Bent, Leah R

    2015-10-01

    Perceptual thresholds are known to vary across the foot sole, despite a reported even distribution in cutaneous afferents. Skin mechanical properties have been proposed to account for these differences; however, a direct relationship between foot sole afferent firing, perceptual threshold, and skin mechanical properties has not been previously investigated. Using the technique of microneurography, we recorded the monofilament firing thresholds of cutaneous afferents and associated perceptual thresholds across the foot sole. In addition, receptive field hardness measurements were taken to investigate the influence of skin hardness on these threshold measures. Afferents were identified as fast adapting [FAI (n = 48) or FAII (n = 13)] or slowly adapting [SAI (n = 21) or SAII (n = 20)], and were grouped based on receptive field location (heel, arch, metatarsals, toes). Overall, perceptual thresholds were found to most closely align with firing thresholds of FA afferents. In contrast, SAI and SAII afferent firing thresholds were found to be significantly higher than perceptual thresholds and are not thought to mediate monofilament perceptual threshold across the foot sole. Perceptual thresholds and FAI afferent firing thresholds were significantly lower in the arch compared with other regions, and skin hardness was found to positively correlate with both FAI and FAII afferent firing and perceptual thresholds. These data support a perceptual influence of skin hardness, which is likely the result of elevated FA afferent firing threshold at harder foot sole sites. The close coupling between FA afferent firing and perceptual threshold across foot sole indicates that small changes in FA afferent firing can influence perceptual thresholds.

  15. The Limits to Adaptation; A Systems Approach

    EPA Science Inventory

    The Limits to Adaptation: A Systems Approach. The ability to adapt to climate change is delineated by capacity thresholds, after which climate damages begin to overwhelm the adaptation response. Such thresholds depend upon physical properties (natural processes and engineering...

  16. Variable ratio regenerative braking device

    DOEpatents

    Hoppie, Lyle O.

    1981-12-15

    Disclosed is a regenerative braking device (10) for an automotive vehicle. The device includes an energy storage assembly (12) having a plurality of rubber rollers (26, 28) mounted for rotation between an input shaft (36) and an output shaft (42), clutches (38, 46) and brakes (40, 48) associated with each shaft, and a continuously variable transmission (22) connectable to a vehicle drivetrain and to the input and output shafts by the respective clutches. The rubber rollers are torsionally stressed to accumulate energy from the vehicle when the input shaft is clutched to the transmission while the brake on the output shaft is applied, and are torsionally relaxed to deliver energy to the vehicle when the output shaft is clutched to the transmission while the brake on the input shaft is applied. The transmission ratio is varied to control the rate of energy accumulation and delivery for a given rotational speed of the vehicle drivetrain.

  17. Can rare SAT formulae be easily recognized? On the efficiency of message-passing algorithms for K-SAT at large clause-to-variable ratios

    NASA Astrophysics Data System (ADS)

    Altarelli, Fabrizio; Monasson, Rémi; Zamponi, Francesco

    2007-02-01

    For large clause-to-variable ratios, typical K-SAT instances drawn from the uniform distribution have no solution. We argue, based on statistical mechanics calculations using the replica and cavity methods, that rare satisfiable instances from the uniform distribution are very similar to typical instances drawn from the so-called planted distribution, where instances are chosen uniformly between the ones that admit a given solution. It then follows, from a recent article by Feige, Mossel and Vilenchik (2006 Complete convergence of message passing algorithms for some satisfiability problems Proc. Random 2006 pp 339-50), that these rare instances can be easily recognized (in O(log N) time and with probability close to 1) by a simple message-passing algorithm.

  18. CARA Risk Assessment Thresholds

    NASA Technical Reports Server (NTRS)

    Hejduk, M. D.

    2016-01-01

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

  19. The Limits to Adaptation: A Systems Approach

    EPA Science Inventory

    The ability to adapt to climate change is delineated by capacity thresholds, after which climate damages begin to overwhelm the adaptation response. Such thresholds depend upon physical properties (natural processes and engineering parameters), resource constraints (expressed th...

  20. Threshold quantum cryptography

    SciTech Connect

    Tokunaga, Yuuki; Okamoto, Tatsuaki; Imoto, Nobuyuki

    2005-01-01

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

  1. Threshold Concepts in Biochemistry

    ERIC Educational Resources Information Center

    Loertscher, Jennifer

    2011-01-01

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

  2. Bayesian Threshold Estimation

    ERIC Educational Resources Information Center

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

    2009-01-01

    Bayesian estimation of a threshold time (hereafter simply threshold) for the receipt of impulse signals is accomplished given the following: 1) data, consisting of the number of impulses received in a time interval from zero to one and the time of the largest time impulse; 2) a model, consisting of a uniform probability density of impulse time…

  3. Pausing at the Threshold

    ERIC Educational Resources Information Center

    Morgan, Patrick K.

    2015-01-01

    Since about 2003, the notion of threshold concepts--the central ideas in any field that change how learners think about other ideas--have become difficult to escape at library conferences and in general information literacy discourse. Their visibility will likely only increase because threshold concepts figure prominently in the Framework for…

  4. Threshold Concepts in Economics

    ERIC Educational Resources Information Center

    Shanahan, Martin

    2016-01-01

    Purpose: The purpose of this paper is to examine threshold concepts in the context of teaching and learning first-year university economics. It outlines some of the arguments for using threshold concepts and provides examples using opportunity cost as an exemplar in economics. Design/ Methodology/Approach: The paper provides an overview of the…

  5. The perils of thresholding

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  6. Double Photoionization Near Threshold

    NASA Technical Reports Server (NTRS)

    Wehlitz, Ralf

    2007-01-01

    The threshold region of the double-photoionization cross section is of particular interest because both ejected electrons move slowly in the Coulomb field of the residual ion. Near threshold both electrons have time to interact with each other and with the residual ion. Also, different theoretical models compete to describe the double-photoionization cross section in the threshold region. We have investigated that cross section for lithium and beryllium and have analyzed our data with respect to the latest results in the Coulomb-dipole theory. We find that our data support the idea of a Coulomb-dipole interaction.

  7. Auditory thresholds in the rat measured by an operant technique.

    PubMed

    GOUREVITCH, G; HACK, M H; HAWKINS, J E

    1960-04-01

    An adaptation of the Ratliff and Blough technique has been developed for auditory measurement in rats. Thresholds for a 2000-cy/sec tone were determined over a period of weeks. Kanamycin, an ototoxic agent, was then administered, and the gradual rise in threshold was followed.

  8. Hydrodynamics of sediment threshold

    NASA Astrophysics Data System (ADS)

    Ali, Sk Zeeshan; Dey, Subhasish

    2016-07-01

    A novel hydrodynamic model for the threshold of cohesionless sediment particle motion under a steady unidirectional streamflow is presented. The hydrodynamic forces (drag and lift) acting on a solitary sediment particle resting over a closely packed bed formed by the identical sediment particles are the primary motivating forces. The drag force comprises of the form drag and form induced drag. The lift force includes the Saffman lift, Magnus lift, centrifugal lift, and turbulent lift. The points of action of the force system are appropriately obtained, for the first time, from the basics of micro-mechanics. The sediment threshold is envisioned as the rolling mode, which is the plausible mode to initiate a particle motion on the bed. The moment balance of the force system on the solitary particle about the pivoting point of rolling yields the governing equation. The conditions of sediment threshold under the hydraulically smooth, transitional, and rough flow regimes are examined. The effects of velocity fluctuations are addressed by applying the statistical theory of turbulence. This study shows that for a hindrance coefficient of 0.3, the threshold curve (threshold Shields parameter versus shear Reynolds number) has an excellent agreement with the experimental data of uniform sediments. However, most of the experimental data are bounded by the upper and lower limiting threshold curves, corresponding to the hindrance coefficients of 0.2 and 0.4, respectively. The threshold curve of this study is compared with those of previous researchers. The present model also agrees satisfactorily with the experimental data of nonuniform sediments.

  9. Neural nets for adaptive filtering and adaptive pattern recognition

    SciTech Connect

    Widrow, B.; Winter, R.

    1988-03-01

    The fields of adaptive signal processing and adaptive neural networks have been developing independently but have that adaptive linear combiner (ALC) in common. With its inputs connected to a tapped delay line, the ALC becomes a key component of an adaptive filter. With its output connected to a quantizer, the ALC becomes an adaptive threshold element of adaptive neuron. Adaptive threshold elements, on the other hand, are the building blocks of neural networks. Today neural nets are the focus of widespread research interest. Areas of investigation include pattern recognition and trainable logic. Neural network systems have not yet had the commercial impact of adaptive filtering. The commonality of the ALC to adaptive signal processing and adaptive neural networks suggests the two fields have much to share with each other. This article describes practical applications of the ALC in signal processing and pattern recognition.

  10. Crossing the Writing Threshold.

    ERIC Educational Resources Information Center

    Clark, Carol Lea

    What pushes a writer over the edge of thought into text production--over what may be called "the writing threshold?" This is the moment when the thoughts in a writer's mind, the writing situation, and personal motivations create a momentum that results in a pattern of written words. There is evidence that not everyone crosses the writing threshold…

  11. Elaborating on Threshold Concepts

    ERIC Educational Resources Information Center

    Rountree, Janet; Robins, Anthony; Rountree, Nathan

    2013-01-01

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

  12. [Taste thresholds and above-threshold responses to fructose solution in relation to diet in Callitrichidae primates].

    PubMed

    Simmen, B

    1992-01-01

    Taste thresholds and consumption responses to above-threshold concentrations of fructose solutions were determined in eight callitrichid primate species using the "two-bottle preference test". Although taste thresholds are relatively similar across species, above-threshold responses may differ considerably between marmosets and tamarins. As fructose concentration increases, the rate of consumption increases less for most marmoset species (Cebuella and Callithrix spp.) than for Goeldi's monkey (Callimico) and tamarins (Saguinus and Leontopithecus spp.). It is proposed that distinct shapes of the curves illustrating these responses characterize species in terms of global taste system adaptations to different diets.

  13. Network problem threshold

    NASA Technical Reports Server (NTRS)

    Gejji, Raghvendra, R.

    1992-01-01

    Network transmission errors such as collisions, CRC errors, misalignment, etc. are statistical in nature. Although errors can vary randomly, a high level of errors does indicate specific network problems, e.g. equipment failure. In this project, we have studied the random nature of collisions theoretically as well as by gathering statistics, and established a numerical threshold above which a network problem is indicated with high probability.

  14. High correlation between absolute psychophysical threshold and the scotopic threshold response to the same stimulus.

    PubMed Central

    Graham, S. L.; Vaegan

    1991-01-01

    The scotopic threshold response (STR) is a negative potential to low intensity light recorded from the dark-adapted retina. It reflects inner retinal function. The STR is now recorded routinely as part of our electroretinography protocol. The projected absolute threshold calculated from the amplitude versus intensity function for the STR has been found to correlate well (r = 0.59) with the absolute subjective threshold to the same stimulus. The correlation holds for about 1.5 log units above normal. With further elevation the STR is usually abnormal or absent as b wave threshold is approached. The correlation would have been much greater were it not for this truncated range over which both are recordable. This report includes our findings in 127 patients and examines several disease groups. When the STR had a reduced and abnormal intensity series or was absent, the subjective threshold was elevated in almost all cases (92.2%). The converse relationship also held. When there was a discrepancy, recording problems were usually identified. Since the STR requires difficult, time consuming signal averaging for reliable recording, it may be adequate to record the subjective threshold alone to provide a relatively easily recordable indicator of inner retinal function. Additional STR recording will seldom be warranted. PMID:1954209

  15. Coloring geographical threshold graphs

    SciTech Connect

    Bradonjic, Milan; Percus, Allon; Muller, Tobias

    2008-01-01

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

  16. Laser threshold magnetometry

    NASA Astrophysics Data System (ADS)

    Jeske, Jan; Cole, Jared H.; Greentree, Andrew D.

    2016-01-01

    We propose a new type of sensor, which uses diamond containing the optically active nitrogen-vacancy (NV-) centres as a laser medium. The magnetometer can be operated at room-temperature and generates light that can be readily fibre coupled, thereby permitting use in industrial applications and remote sensing. By combining laser pumping with a radio-frequency Rabi-drive field, an external magnetic field changes the fluorescence of the NV- centres. We use this change in fluorescence level to push the laser above threshold, turning it on with an intensity controlled by the external magnetic field, which provides a coherent amplification of the readout signal with very high contrast. This mechanism is qualitatively different from conventional NV--based magnetometers which use fluorescence measurements, based on incoherent photon emission. We term our approach laser threshold magnetometer (LTM). We predict that an NV--based LTM with a volume of 1 mm3 can achieve shot-noise limited dc sensitivity of 1.86 fT /\\sqrt{{{Hz}}} and ac sensitivity of 3.97 fT /\\sqrt{{{Hz}}}.

  17. Excitable neurons, firing threshold manifolds and canards.

    PubMed

    Mitry, John; McCarthy, Michelle; Kopell, Nancy; Wechselberger, Martin

    2013-01-01

    We investigate firing threshold manifolds in a mathematical model of an excitable neuron. The model analyzed investigates the phenomenon of post-inhibitory rebound spiking due to propofol anesthesia and is adapted from McCarthy et al. (SIAM J. Appl. Dyn. Syst. 11(4):1674-1697, 2012). Propofol modulates the decay time-scale of an inhibitory GABAa synaptic current. Interestingly, this system gives rise to rebound spiking within a specific range of propofol doses. Using techniques from geometric singular perturbation theory, we identify geometric structures, known as canards of folded saddle-type, which form the firing threshold manifolds. We find that the position and orientation of the canard separatrix is propofol dependent. Thus, the speeds of relevant slow synaptic processes are encoded within this geometric structure. We show that this behavior cannot be understood using a static, inhibitory current step protocol, which can provide a single threshold for rebound spiking but cannot explain the observed cessation of spiking for higher propofol doses. We then compare the analyses of dynamic and static synaptic inhibition, showing how the firing threshold manifolds of each relate, and why a current step approach is unable to fully capture the behavior of this model. PMID:23945278

  18. Adaptation improves discrimination of face identity.

    PubMed

    Oruç, Ipek; Barton, Jason J S

    2011-09-01

    Whether face adaptation confers any advantages to perceptual processing remains an open question. We investigated whether face adaptation can enhance the ability to make fine discriminations in the vicinity of the adapted face. We compared face discrimination thresholds in three adapting conditions: (i) same-face: where adapting and test faces were the same, (ii) different-face: where adapting and test faces differed, and (iii) baseline: where the adapting stimulus was a blank. Discrimination thresholds for morphed identity changes involving the adapted face (same-face) improved compared with those from both the baseline (no-adaptation) and different-face conditions. Since adapting to a face did not alter discrimination performance for other faces, this effect is selective for the facial identity that is adapted. These results indicate a form of gain control to heighten perceptual sensitivity in the vicinity of a currently viewed face, analogous to forms of adaptive gain control at lower levels of the visual system.

  19. Thresholds for Coral Bleaching: Are Synergistic Factors and Shifting Thresholds Changing the Landscape for Management? (Invited)

    NASA Astrophysics Data System (ADS)

    Eakin, C.; Donner, S. D.; Logan, C. A.; Gledhill, D. K.; Liu, G.; Heron, S. F.; Christensen, T.; Rauenzahn, J.; Morgan, J.; Parker, B. A.; Hoegh-Guldberg, O.; Skirving, W. J.; Strong, A. E.

    2010-12-01

    As carbon dioxide rises in the atmosphere, climate change and ocean acidification are modifying important physical and chemical parameters in the oceans with resulting impacts on coral reef ecosystems. Rising CO2 is warming the world’s oceans and causing corals to bleach, with both alarming frequency and severity. The frequent return of stressful temperatures has already resulted in major damage to many of the world’s coral reefs and is expected to continue in the foreseeable future. Warmer oceans also have contributed to a rise in coral infectious diseases. Both bleaching and infectious disease can result in coral mortality and threaten one of the most diverse ecosystems on Earth and the important ecosystem services they provide. Additionally, ocean acidification from rising CO2 is reducing the availability of carbonate ions needed by corals to build their skeletons and perhaps depressing the threshold for bleaching. While thresholds vary among species and locations, it is clear that corals around the world are already experiencing anomalous temperatures that are too high, too often, and that warming is exceeding the rate at which corals can adapt. This is despite a complex adaptive capacity that involves both the coral host and the zooxanthellae, including changes in the relative abundance of the latter in their coral hosts. The safe upper limit for atmospheric CO2 is probably somewhere below 350ppm, a level we passed decades ago, and for temperature is a sustained global temperature increase of less than 1.5°C above pre-industrial levels. How much can corals acclimate and/or adapt to the unprecedented fast changing environmental conditions? Any change in the threshold for coral bleaching as the result of acclimation and/or adaption may help corals to survive in the future but adaptation to one stress may be maladaptive to another. There also is evidence that ocean acidification and nutrient enrichment modify this threshold. What do shifting thresholds mean

  20. Probabilistic Threshold Criterion

    SciTech Connect

    Gresshoff, M; Hrousis, C A

    2010-03-09

    The Probabilistic Shock Threshold Criterion (PSTC) Project at LLNL develops phenomenological criteria for estimating safety or performance margin on high explosive (HE) initiation in the shock initiation regime, creating tools for safety assessment and design of initiation systems and HE trains in general. Until recently, there has been little foundation for probabilistic assessment of HE initiation scenarios. This work attempts to use probabilistic information that is available from both historic and ongoing tests to develop a basis for such assessment. Current PSTC approaches start with the functional form of the James Initiation Criterion as a backbone, and generalize to include varying areas of initiation and provide a probabilistic response based on test data for 1.8 g/cc (Ultrafine) 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) and LX-17 (92.5% TATB, 7.5% Kel-F 800 binder). Application of the PSTC methodology is presented investigating the safety and performance of a flying plate detonator and the margin of an Ultrafine TATB booster initiating LX-17.

  1. Threshold fatigue and information transfer

    PubMed Central

    Lindner, Benjamin; Longtin, André

    2016-01-01

    Neurons in vivo must process sensory information in the presence of significant noise. It is thus plausible to assume that neural systems have developed mechanisms to reduce this noise. Theoretical studies have shown that threshold fatigue (i.e. cumulative increases in the threshold during repetitive firing) could lead to noise reduction at certain frequencies bands and thus improved signal transmission as well as noise increases and decreased signal transmission at other frequencies: a phenomenon called noise shaping. There is, however, no experimental evidence that threshold fatigue actually occurs and, if so, that it will actually lead to noise shaping. We analyzed action potential threshold variability in intracellular recordings in vivo from pyramidal neurons in weakly electric fish and found experimental evidence for threshold fatigue: an increase in instantaneous firing rate was on average accompanied by an increase in action potential threshold. We show that, with a minor modification, the standard Hodgkin–Huxley model can reproduce this phenomenon. We next compared the performance of models with and without threshold fatigue. Our results show that threshold fatigue will lead to a more regular spike train as well as robustness to intrinsic noise via noise shaping. We finally show that the increased/reduced noise levels due to threshold fatigue correspond to decreased/increased information transmission at different frequencies. PMID:17436067

  2. Learning foraging thresholds for lizards

    SciTech Connect

    Goldberg, L.A.; Hart, W.E.; Wilson, D.B.

    1996-01-12

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

  3. Life below the threshold.

    PubMed

    Castro, C

    1991-01-01

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

  4. The Nature of Psychological Thresholds

    ERIC Educational Resources Information Center

    Rouder, Jeffrey N.; Morey, Richard D.

    2009-01-01

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

  5. Threshold Concepts and Information Literacy

    ERIC Educational Resources Information Center

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

    2011-01-01

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

  6. Threshold Hypothesis: Fact or Artifact?

    ERIC Educational Resources Information Center

    Karwowski, Maciej; Gralewski, Jacek

    2013-01-01

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

  7. Bayesian estimation of dose thresholds

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  8. Carbon monoxide exposure and human visual detection thresholds

    SciTech Connect

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

    1989-01-01

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

  9. Parton distributions with threshold resummation

    NASA Astrophysics Data System (ADS)

    Bonvini, Marco; Marzani, Simone; Rojo, Juan; Rottoli, Luca; Ubiali, Maria; Ball, Richard D.; Bertone, Valerio; Carrazza, Stefano; Hartland, Nathan P.

    2015-09-01

    We construct a set of parton distribution functions (PDFs) in which fixed-order NLO and NNLO calculations are supplemented with soft-gluon (threshold) resummation up to NLL and NNLL accuracy respectively, suitable for use in conjunction with any QCD calculation in which threshold resummation is included at the level of partonic cross sections. These resummed PDF sets, based on the NNPDF3.0 analysis, are extracted from deep-inelastic scattering, Drell-Yan, and top quark pair production data, for which resummed calculations can be consistently used. We find that, close to threshold, the inclusion of resummed PDFs can partially compensate the enhancement in resummed matrix elements, leading to resummed hadronic cross-sections closer to the fixed-order calculations. On the other hand, far from threshold, resummed PDFs reduce to their fixed-order counterparts. Our results demonstrate the need for a consistent use of resummed PDFs in resummed calculations.

  10. Threshold models in radiation carcinogenesis

    SciTech Connect

    Hoel, D.G.; Li, P.

    1998-09-01

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

  11. Face verification with balanced thresholds.

    PubMed

    Yan, Shuicheng; Xu, Dong; Tang, Xiaoou

    2007-01-01

    The process of face verification is guided by a pre-learned global threshold, which, however, is often inconsistent with class-specific optimal thresholds. It is, hence, beneficial to pursue a balance of the class-specific thresholds in the model-learning stage. In this paper, we present a new dimensionality reduction algorithm tailored to the verification task that ensures threshold balance. This is achieved by the following aspects. First, feasibility is guaranteed by employing an affine transformation matrix, instead of the conventional projection matrix, for dimensionality reduction, and, hence, we call the proposed algorithm threshold balanced transformation (TBT). Then, the affine transformation matrix, constrained as the product of an orthogonal matrix and a diagonal matrix, is optimized to improve the threshold balance and classification capability in an iterative manner. Unlike most algorithms for face verification which are directly transplanted from face identification literature, TBT is specifically designed for face verification and clarifies the intrinsic distinction between these two tasks. Experiments on three benchmark face databases demonstrate that TBT significantly outperforms the state-of-the-art subspace techniques for face verification.

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

    NASA Astrophysics Data System (ADS)

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

    2000-06-01

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

  13. Guidelines for Auditory Threshold Measurement for Significant Threshold Shift.

    PubMed

    Campbell, Kathleen; Hammill, Tanisha; Hoffer, Michael; Kil, Jonathan; Le Prell, Colleen

    2016-09-01

    The purpose of this article is to provide guidelines for determining a Significant Noise-Induced Threshold Shift in clinical trials involving human populations. The article reviews recommendations for the standards to be referenced for human subjects, equipment, test environment, and personnel. Additional guidelines for military populations are provided. Guidelines for the calibration of audiometers, sound booth noise levels, and immitance equipment are provided. In addition the guidance provides specific suggestions for the subjects history before study onset, and otoscopy.Test frequencies for threshold determination and methods of threshold determination are reviewed for both air conduction and bone conduction for both baseline testing and later determination of either a temporary (TTS) or permanent threshold shift (PTS). Once a Significant Noise-Induced Threshold Shift has been determined, subjects should be retested, conductive component should be ruled out or addressed, and the subject should be counseled or referred for additional medical evaluation. Guidance for reporting procedures and the computerized study database are described. Finally, experimental designs suggested for noise-induced otoprotection clinical trials are described.

  14. Guidelines for Auditory Threshold Measurement for Significant Threshold Shift.

    PubMed

    Campbell, Kathleen; Hammill, Tanisha; Hoffer, Michael; Kil, Jonathan; Le Prell, Colleen

    2016-09-01

    The purpose of this article is to provide guidelines for determining a Significant Noise-Induced Threshold Shift in clinical trials involving human populations. The article reviews recommendations for the standards to be referenced for human subjects, equipment, test environment, and personnel. Additional guidelines for military populations are provided. Guidelines for the calibration of audiometers, sound booth noise levels, and immitance equipment are provided. In addition the guidance provides specific suggestions for the subjects history before study onset, and otoscopy.Test frequencies for threshold determination and methods of threshold determination are reviewed for both air conduction and bone conduction for both baseline testing and later determination of either a temporary (TTS) or permanent threshold shift (PTS). Once a Significant Noise-Induced Threshold Shift has been determined, subjects should be retested, conductive component should be ruled out or addressed, and the subject should be counseled or referred for additional medical evaluation. Guidance for reporting procedures and the computerized study database are described. Finally, experimental designs suggested for noise-induced otoprotection clinical trials are described. PMID:27518134

  15. Statistical mechanics analysis of thresholding 1-bit compressed sensing

    NASA Astrophysics Data System (ADS)

    Xu, Yingying; Kabashima, Yoshiyuki

    2016-08-01

    The one-bit compressed sensing framework aims to reconstruct a sparse signal by only using the sign information of its linear measurements. To compensate for the loss of scale information, past studies in the area have proposed recovering the signal by imposing an additional constraint on the l 2-norm of the signal. Recently, an alternative strategy that captures scale information by introducing a threshold parameter to the quantization process was advanced. In this paper, we analyze the typical behavior of thresholding 1-bit compressed sensing utilizing the replica method of statistical mechanics, so as to gain an insight for properly setting the threshold value. Our result shows that fixing the threshold at a constant value yields better performance than varying it randomly when the constant is optimally tuned, statistically. Unfortunately, the optimal threshold value depends on the statistical properties of the target signal, which may not be known in advance. In order to handle this inconvenience, we develop a heuristic that adaptively tunes the threshold parameter based on the frequency of positive (or negative) values in the binary outputs. Numerical experiments show that the heuristic exhibits satisfactory performance while incurring low computational cost.

  16. Taste Detection Thresholds of Resveratrol.

    PubMed

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

    2015-09-01

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

  17. Flash Expansion Threshold in Whirligig Swarms

    PubMed Central

    Romey, William L.; Lamb, Alicia R.

    2015-01-01

    In the selfish herd hypothesis, prey animals move toward each other to avoid the likelihood of being selected by a predator. However, many grouped animals move away from each other the moment before a predator attacks. Very little is known about this phenomenon, called flash expansion, such as whether it is triggered by one individual or a threshold and how information is transferred between group members. We performed a controlled experiment with whirligig beetles in which the ratio of sighted to unsighted individuals was systematically varied and emergent flash expansion was measured. Specifically, we examined: the percentage of individuals in a group that startled, the resulting group area, and the longevity of the flash expansion. We found that one or two sighted beetles in a group of 24 was not enough to cause a flash expansion after a predator stimulus, but four sighted beetles usually initiated a flash expansion. Also, the more beetles that were sighted the larger the resulting group area and the longer duration of the flash expansion. We conclude that flash expansion is best described as a threshold event whose adaptive value is to prevent energetically costly false alarms while quickly mobilizing an emergent predator avoidance response. This is one of the first controlled experiments of flash expansion, an important emergent property that has applications to understanding collective motion in swarms, schools, flocks, and human crowds. Also, our study is a convincing demonstration of social contagion, how the actions of one individual can pass through a group. PMID:26301958

  18. Flash Expansion Threshold in Whirligig Swarms.

    PubMed

    Romey, William L; Lamb, Alicia R

    2015-01-01

    In the selfish herd hypothesis, prey animals move toward each other to avoid the likelihood of being selected by a predator. However, many grouped animals move away from each other the moment before a predator attacks. Very little is known about this phenomenon, called flash expansion, such as whether it is triggered by one individual or a threshold and how information is transferred between group members. We performed a controlled experiment with whirligig beetles in which the ratio of sighted to unsighted individuals was systematically varied and emergent flash expansion was measured. Specifically, we examined: the percentage of individuals in a group that startled, the resulting group area, and the longevity of the flash expansion. We found that one or two sighted beetles in a group of 24 was not enough to cause a flash expansion after a predator stimulus, but four sighted beetles usually initiated a flash expansion. Also, the more beetles that were sighted the larger the resulting group area and the longer duration of the flash expansion. We conclude that flash expansion is best described as a threshold event whose adaptive value is to prevent energetically costly false alarms while quickly mobilizing an emergent predator avoidance response. This is one of the first controlled experiments of flash expansion, an important emergent property that has applications to understanding collective motion in swarms, schools, flocks, and human crowds. Also, our study is a convincing demonstration of social contagion, how the actions of one individual can pass through a group.

  19. On computational Gestalt detection thresholds.

    PubMed

    Grompone von Gioi, Rafael; Jakubowicz, Jérémie

    2009-01-01

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

  20. Thresholds in chemical respiratory sensitisation.

    PubMed

    Cochrane, Stella A; Arts, Josje H E; Ehnes, Colin; Hindle, Stuart; Hollnagel, Heli M; Poole, Alan; Suto, Hidenori; Kimber, Ian

    2015-07-01

    There is a continuing interest in determining whether it is possible to identify thresholds for chemical allergy. Here allergic sensitisation of the respiratory tract by chemicals is considered in this context. This is an important occupational health problem, being associated with rhinitis and asthma, and in addition provides toxicologists and risk assessors with a number of challenges. In common with all forms of allergic disease chemical respiratory allergy develops in two phases. In the first (induction) phase exposure to a chemical allergen (by an appropriate route of exposure) causes immunological priming and sensitisation of the respiratory tract. The second (elicitation) phase is triggered if a sensitised subject is exposed subsequently to the same chemical allergen via inhalation. A secondary immune response will be provoked in the respiratory tract resulting in inflammation and the signs and symptoms of a respiratory hypersensitivity reaction. In this article attention has focused on the identification of threshold values during the acquisition of sensitisation. Current mechanistic understanding of allergy is such that it can be assumed that the development of sensitisation (and also the elicitation of an allergic reaction) is a threshold phenomenon; there will be levels of exposure below which sensitisation will not be acquired. That is, all immune responses, including allergic sensitisation, have threshold requirement for the availability of antigen/allergen, below which a response will fail to develop. The issue addressed here is whether there are methods available or clinical/epidemiological data that permit the identification of such thresholds. This document reviews briefly relevant human studies of occupational asthma, and experimental models that have been developed (or are being developed) for the identification and characterisation of chemical respiratory allergens. The main conclusion drawn is that although there is evidence that the

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

    NASA Technical Reports Server (NTRS)

    Webb, W. E.

    1975-01-01

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

  2. Binarization and multi-thresholding of document images using connectivity

    SciTech Connect

    O`Gorman, L.

    1994-12-31

    Thresholding is a common image processing operation applied to gray-scale images to obtain binary or multi-level images. A thresholding method is described here that is global in approach, but uses a measure of local information, namely connectivity. Thresholds are found at the intensity levels that best preserve the connectivity of regions within the image. Thus, this method has advantages of both global and locally adaptive approaches. Experimental comparisons for document images show that the connectivity-preserving method improves subsequent OCR recognition rates from about 95% to 97.5% and reduces the number of binarization failures (where text is so poorly binarized as to be totally unrecognizable by a commercial OCR system) from 33% to 6% on difficult images.

  3. New states above charm threshold

    SciTech Connect

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

    2005-11-01

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

  4. Threshold Concepts and Pedagogic Representation

    ERIC Educational Resources Information Center

    Meyer, Jan H. F.

    2016-01-01

    Purpose: The purpose of this paper is to present a brief exposure to the development of the threshold concepts framework (TCF), the intention being to illuminate for interested readers a broader landscape of research activity than that perhaps conveyed by the individual contributions to this special edition. Design/Methodology/Approach: There is…

  5. Crossing Thresholds in Academic Reading

    ERIC Educational Resources Information Center

    Abbott, Rob

    2013-01-01

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

  6. Threshold enhancement of diphoton resonances

    NASA Astrophysics Data System (ADS)

    Bharucha, Aoife; Djouadi, Abdelhak; Goudelis, Andreas

    2016-10-01

    We revisit a mechanism to enhance the decay width of (pseudo-)scalar resonances to photon pairs when the process is mediated by loops of charged fermions produced near threshold. Motivated by the recent LHC data, indicating the presence of an excess in the diphoton spectrum at approximately 750 GeV, we illustrate this threshold enhancement mechanism in the case of a 750 GeV pseudoscalar boson A with a two-photon decay mediated by a charged and uncolored fermion having a mass at the 1/2MA threshold and a small decay width, < 1 MeV. The implications of such a threshold enhancement are discussed in two explicit scenarios: i) the Minimal Supersymmetric Standard Model in which the A state is produced via the top quark mediated gluon fusion process and decays into photons predominantly through loops of charginos with masses close to 1/2MA and ii) a two Higgs doublet model in which A is again produced by gluon fusion but decays into photons through loops of vector-like charged heavy leptons. In both these scenarios, while the mass of the charged fermion has to be adjusted to be extremely close to half of the A resonance mass, the small total widths are naturally obtained if only suppressed three-body decay channels occur. Finally, the implications of some of these scenarios for dark matter are discussed.

  7. Threshold magnitudes for a multichannel correlation detector in background seismicity

    DOE PAGES

    Carmichael, Joshua D.; Hartse, Hans

    2016-04-01

    Colocated explosive sources often produce correlated seismic waveforms. Multichannel correlation detectors identify these signals by scanning template waveforms recorded from known reference events against "target" data to find similar waveforms. This screening problem is challenged at thresholds required to monitor smaller explosions, often because non-target signals falsely trigger such detectors. Therefore, it is generally unclear what thresholds will reliably identify a target explosion while screening non-target background seismicity. Here, we estimate threshold magnitudes for hypothetical explosions located at the North Korean nuclear test site over six months of 2010, by processing International Monitoring System (IMS) array data with a multichannelmore » waveform correlation detector. Our method (1) accounts for low amplitude background seismicity that falsely triggers correlation detectors but is unidentifiable with conventional power beams, (2) adapts to diurnally variable noise levels and (3) uses source-receiver reciprocity concepts to estimate thresholds for explosions spatially separated from the template source. Furthermore, we find that underground explosions with body wave magnitudes mb = 1.66 are detectable at the IMS array USRK with probability 0.99, when using template waveforms consisting only of P -waves, without false alarms. We conservatively find that these thresholds also increase by up to a magnitude unit for sources located 4 km or more from the Feb.12, 2013 announced nuclear test.« less

  8. A threshold for dissipative fission

    SciTech Connect

    Thoennessen, M.; Bertsch, G.F.

    1993-09-21

    The empirical domain of validity of statistical theory is examined as applied to fission data on pre-fission data on pre-fission neutron, charged particle, and {gamma}-ray multiplicities. Systematics are found of the threshold excitation energy for the appearance of nonstatistical fission. From the data on systems with not too high fissility, the relevant phenomenological parameter is the ratio of the threshold temperature T{sub thresh} to the (temperature-dependent) fission barrier height E{sub Bar}(T). The statistical model reproduces the data for T{sub thresh}/E{sub Bar}(T) < 0.26 {plus_minus} 0.05, but underpredicts the multiplicities at higher T{sub thresh}/E{sub Bar}(T) independent of mass and fissility of the systems.

  9. Roots at the Percolation Threshold

    NASA Astrophysics Data System (ADS)

    Kroener, E.; Ahmed, M. A.; Kaestner, A.; Vontobel, P.; Zarebanadkouki, M.; Carminati, A.

    2014-12-01

    Much of the carbon assimilated by plants during photosynthesis is lost to the soil via rhizodepositions. One component of rhizopdeposition is mucilage, a hydrogel that dramatically alters the soil physical properties. Mucilage was assumed to explain unexpectedly low rhizosphere rewetting rates during irrigation (Carminati et al. 2010) and temporarily water repellency in the rhizosphere after severe drying (Moradi et al. 2012).Here, we present an experimental and theoretical study for the rewetting behaviour of a soil mixed with mucilage, which was used as an analogue of the rhizosphere. Our samples were made of two layers of untreated soils separated by a thin layer (ca. 1 mm) of soil treated with mucilage. We prepared soil columns of varying particle size, mucilage concentration and height of the middle layer above the water table. The dry soil columns were re-wetted by capillary rise from the bottom.The rewetting of the middle layer showed a distinct dual behavior. For mucilage concentrations lower than a certain threshold, water could cross the thin layer almost immediately after rewetting of bulk soil. At slightly higher mucilage concentrations, the thin layer was almost impermeable. The mucilage concentration at the threshold strongly depended on particle size: the smaller the particle size the larger the soil specific surface and the more mucilage was needed to cover the entire particle surface and to induce water repellency.We applied a classic pore network model to simulate the experimental observations. In the model a certain fraction of nodes were randomly disconnected to reproduce the effect of mucilage in temporarily blocking the flow. The percolation model could qualitatively reproduce well the threshold characteristics of the experiments. Our experiments, together with former observations of water dynamics in the rhizosphere, suggest that the rhizosphere is near the percolation threshold, where small variations in mucilage concentration sensitively

  10. Definition of temperature thresholds: the example of the French heat wave warning system.

    PubMed

    Pascal, Mathilde; Wagner, Vérène; Le Tertre, Alain; Laaidi, Karine; Honoré, Cyrille; Bénichou, Françoise; Beaudeau, Pascal

    2013-01-01

    Heat-related deaths should be somewhat preventable. In France, some prevention measures are activated when minimum and maximum temperatures averaged over three days reach city-specific thresholds. The current thresholds were computed based on a descriptive analysis of past heat waves and on local expert judgement. We tested whether a different method would confirm these thresholds. The study was set in the six cities of Paris, Lyon, Marseille, Nantes, Strasbourg and Limoges between 1973 and 2003. For each city, we estimated the excess in mortality associated with different temperature thresholds, using a generalised additive model, controlling for long-time trends, seasons and days of the week. These models were used to compute the mortality predicted by different percentiles of temperatures. The thresholds were chosen as the percentiles associated with a significant excess mortality. In all cities, there was a good correlation between current thresholds and the thresholds derived from the models, with 0°C to 3°C differences for averaged maximum temperatures. Both set of thresholds were able to anticipate the main periods of excess mortality during the summers of 1973 to 2003. A simple method relying on descriptive analysis and expert judgement is sufficient to define protective temperature thresholds and to prevent heat wave mortality. As temperatures are increasing along with the climate change and adaptation is ongoing, more research is required to understand if and when thresholds should be modified.

  11. 40 CFR 98.361 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Manure Management § 98.361 Reporting threshold. Livestock facilities must report GHG emissions under this subpart if the facility meets the reporting threshold as defined in...

  12. USE OF THRESHOLDS IN LANDSCAPE ASSESSMENTS

    EPA Science Inventory

    Identification and use of thresholds are potentially important additions to interpretations of ecological monitoring data. However, there are a number of issues related to defining and using thresholds in interpreting ecological data. Most of these issues center around the pauc...

  13. Thresholds for impaired species recovery

    PubMed Central

    Hutchings, Jeffrey A.

    2015-01-01

    Studies on small and declining populations dominate research in conservation biology. This emphasis reflects two overarching frameworks: the small-population paradigm focuses on correlates of increased extinction probability; the declining-population paradigm directs attention to the causes and consequences of depletion. Neither, however, particularly informs research on the determinants, rate or uncertainty of population increase. By contrast, Allee effects (positive associations between population size and realized per capita population growth rate, rrealized, a metric of average individual fitness) offer a theoretical and empirical basis for identifying numerical and temporal thresholds at which recovery is unlikely or uncertain. Following a critique of studies on Allee effects, I quantify population-size minima and subsequent trajectories of marine fishes that have and have not recovered following threat mitigation. The data suggest that threat amelioration, albeit necessary, can be insufficient to effect recovery for populations depleted to less than 10% of maximum abundance (Nmax), especially when they remain depleted for lengthy periods of time. Comparing terrestrial and aquatic vertebrates, life-history analyses suggest that population-size thresholds for impaired recovery are likely to be comparatively low for marine fishes but high for marine mammals. Articulation of a ‘recovering population paradigm’ would seem warranted. It might stimulate concerted efforts to identify generic impaired recovery thresholds across species. It might also serve to reduce the confusion of terminology, and the conflation of causes and consequences with patterns currently evident in the literature on Allee effects, thus strengthening communication among researchers and enhancing the practical utility of recovery-oriented research to conservation practitioners and resource managers. PMID:26213739

  14. Thresholds for impaired species recovery.

    PubMed

    Hutchings, Jeffrey A

    2015-06-22

    Studies on small and declining populations dominate research in conservation biology. This emphasis reflects two overarching frameworks: the small-population paradigm focuses on correlates of increased extinction probability; the declining-population paradigm directs attention to the causes and consequences of depletion. Neither, however, particularly informs research on the determinants, rate or uncertainty of population increase. By contrast, Allee effects (positive associations between population size and realized per capita population growth rate, r(realized), a metric of average individual fitness) offer a theoretical and empirical basis for identifying numerical and temporal thresholds at which recovery is unlikely or uncertain. Following a critique of studies on Allee effects, I quantify population-size minima and subsequent trajectories of marine fishes that have and have not recovered following threat mitigation. The data suggest that threat amelioration, albeit necessary, can be insufficient to effect recovery for populations depleted to less than 10% of maximum abundance (N(max)), especially when they remain depleted for lengthy periods of time. Comparing terrestrial and aquatic vertebrates, life-history analyses suggest that population-size thresholds for impaired recovery are likely to be comparatively low for marine fishes but high for marine mammals.Articulation of a 'recovering population paradigm' would seem warranted. It might stimulate concerted efforts to identify generic impaired recovery thresholds across species. It might also serve to reduce the confusion of terminology, and the conflation of causes and consequences with patterns currently evident in the literature on Allee effects, thus strengthening communication among researchers and enhancing the practical utility of recovery-oriented research to conservation practitioners and resource managers. PMID:26213739

  15. Compositional threshold for Nuclear Waste Glass Durability

    SciTech Connect

    Kruger, Albert A.; Farooqi, Rahmatullah; Hrma, Pavel R.

    2013-04-24

    Within the composition space of glasses, a distinct threshold appears to exist that separates "good" glasses, i.e., those which are sufficiently durable, from "bad" glasses of a low durability. The objective of our research is to clarify the origin of this threshold by exploring the relationship between glass composition, glass structure and chemical durability around the threshold region.

  16. Threshold Concepts in Finance: Student Perspectives

    ERIC Educational Resources Information Center

    Hoadley, Susan; Kyng, Tim; Tickle, Leonie; Wood, Leigh N.

    2015-01-01

    Finance threshold concepts are the essential conceptual knowledge that underpin well-developed financial capabilities and are central to the mastery of finance. In this paper we investigate threshold concepts in finance from the point of view of students, by establishing the extent to which students are aware of threshold concepts identified by…

  17. Uncertainty Estimates of Psychoacoustic Thresholds Obtained from Group Tests

    NASA Technical Reports Server (NTRS)

    Rathsam, Jonathan; Christian, Andrew

    2016-01-01

    Adaptive psychoacoustic test methods, in which the next signal level depends on the response to the previous signal, are the most efficient for determining psychoacoustic thresholds of individual subjects. In many tests conducted in the NASA psychoacoustic labs, the goal is to determine thresholds representative of the general population. To do this economically, non-adaptive testing methods are used in which three or four subjects are tested at the same time with predetermined signal levels. This approach requires us to identify techniques for assessing the uncertainty in resulting group-average psychoacoustic thresholds. In this presentation we examine the Delta Method of frequentist statistics, the Generalized Linear Model (GLM), the Nonparametric Bootstrap, a frequentist method, and Markov Chain Monte Carlo Posterior Estimation and a Bayesian approach. Each technique is exercised on a manufactured, theoretical dataset and then on datasets from two psychoacoustics facilities at NASA. The Delta Method is the simplest to implement and accurate for the cases studied. The GLM is found to be the least robust, and the Bootstrap takes the longest to calculate. The Bayesian Posterior Estimate is the most versatile technique examined because it allows the inclusion of prior information.

  18. Epidemic threshold in directed networks.

    PubMed

    Li, Cong; Wang, Huijuan; Van Mieghem, Piet

    2013-12-01

    Epidemics have so far been mostly studied in undirected networks. However, many real-world networks, such as the online social network Twitter and the world wide web, on which information, emotion, or malware spreads, are directed networks, composed of both unidirectional links and bidirectional links. We define the directionality ξ as the percentage of unidirectional links. The epidemic threshold τ(c) for the susceptible-infected-susceptible (SIS) epidemic is lower bounded by 1/λ(1) in directed networks, where λ(1), also called the spectral radius, is the largest eigenvalue of the adjacency matrix. In this work, we propose two algorithms to generate directed networks with a given directionality ξ. The effect of ξ on the spectral radius λ(1), principal eigenvector x(1), spectral gap (λ(1)-|λ(2)|), and algebraic connectivity μ(N-1) is studied. Important findings are that the spectral radius λ(1) decreases with the directionality ξ, whereas the spectral gap and the algebraic connectivity increase with the directionality ξ. The extent of the decrease of the spectral radius depends on both the degree distribution and the degree-degree correlation ρ(D). Hence, in directed networks, the epidemic threshold is larger and a random walk converges to its steady state faster than that in undirected networks with the same degree distribution. PMID:24483506

  19. Computational gestalts and perception thresholds.

    PubMed

    Desolneux, Agnès; Moisan, Lionel; Morel, Jean-Michel

    2003-01-01

    In 1923, Max Wertheimer proposed a research programme and method in visual perception. He conjectured the existence of a small set of geometric grouping laws governing the perceptual synthesis of phenomenal objects, or "gestalt" from the atomic retina input. In this paper, we review this set of geometric grouping laws, using the works of Metzger, Kanizsa and their schools. In continuation, we explain why the Gestalt theory research programme can be translated into a Computer Vision programme. This translation is not straightforward, since Gestalt theory never addressed two fundamental matters: image sampling and image information measurements. Using these advances, we shall show that gestalt grouping laws can be translated into quantitative laws allowing the automatic computation of gestalts in digital images. From the psychophysical viewpoint, a main issue is raised: the computer vision gestalt detection methods deliver predictable perception thresholds. Thus, we are set in a position where we can build artificial images and check whether some kind of agreement can be found between the computationally predicted thresholds and the psychophysical ones. We describe and discuss two preliminary sets of experiments, where we compared the gestalt detection performance of several subjects with the predictable detection curve. In our opinion, the results of this experimental comparison support the idea of a much more systematic interaction between computational predictions in Computer Vision and psychophysical experiments. PMID:14766147

  20. Epidemic threshold in directed networks.

    PubMed

    Li, Cong; Wang, Huijuan; Van Mieghem, Piet

    2013-12-01

    Epidemics have so far been mostly studied in undirected networks. However, many real-world networks, such as the online social network Twitter and the world wide web, on which information, emotion, or malware spreads, are directed networks, composed of both unidirectional links and bidirectional links. We define the directionality ξ as the percentage of unidirectional links. The epidemic threshold τ(c) for the susceptible-infected-susceptible (SIS) epidemic is lower bounded by 1/λ(1) in directed networks, where λ(1), also called the spectral radius, is the largest eigenvalue of the adjacency matrix. In this work, we propose two algorithms to generate directed networks with a given directionality ξ. The effect of ξ on the spectral radius λ(1), principal eigenvector x(1), spectral gap (λ(1)-|λ(2)|), and algebraic connectivity μ(N-1) is studied. Important findings are that the spectral radius λ(1) decreases with the directionality ξ, whereas the spectral gap and the algebraic connectivity increase with the directionality ξ. The extent of the decrease of the spectral radius depends on both the degree distribution and the degree-degree correlation ρ(D). Hence, in directed networks, the epidemic threshold is larger and a random walk converges to its steady state faster than that in undirected networks with the same degree distribution.

  1. Epidemic threshold in directed networks

    NASA Astrophysics Data System (ADS)

    Li, Cong; Wang, Huijuan; Van Mieghem, Piet

    2013-12-01

    Epidemics have so far been mostly studied in undirected networks. However, many real-world networks, such as the online social network Twitter and the world wide web, on which information, emotion, or malware spreads, are directed networks, composed of both unidirectional links and bidirectional links. We define the directionality ξ as the percentage of unidirectional links. The epidemic threshold τc for the susceptible-infected-susceptible (SIS) epidemic is lower bounded by 1/λ1 in directed networks, where λ1, also called the spectral radius, is the largest eigenvalue of the adjacency matrix. In this work, we propose two algorithms to generate directed networks with a given directionality ξ. The effect of ξ on the spectral radius λ1, principal eigenvector x1, spectral gap (λ1-λ2), and algebraic connectivity μN-1 is studied. Important findings are that the spectral radius λ1 decreases with the directionality ξ, whereas the spectral gap and the algebraic connectivity increase with the directionality ξ. The extent of the decrease of the spectral radius depends on both the degree distribution and the degree-degree correlation ρD. Hence, in directed networks, the epidemic threshold is larger and a random walk converges to its steady state faster than that in undirected networks with the same degree distribution.

  2. Computational gestalts and perception thresholds.

    PubMed

    Desolneux, Agnès; Moisan, Lionel; Morel, Jean-Michel

    2003-01-01

    In 1923, Max Wertheimer proposed a research programme and method in visual perception. He conjectured the existence of a small set of geometric grouping laws governing the perceptual synthesis of phenomenal objects, or "gestalt" from the atomic retina input. In this paper, we review this set of geometric grouping laws, using the works of Metzger, Kanizsa and their schools. In continuation, we explain why the Gestalt theory research programme can be translated into a Computer Vision programme. This translation is not straightforward, since Gestalt theory never addressed two fundamental matters: image sampling and image information measurements. Using these advances, we shall show that gestalt grouping laws can be translated into quantitative laws allowing the automatic computation of gestalts in digital images. From the psychophysical viewpoint, a main issue is raised: the computer vision gestalt detection methods deliver predictable perception thresholds. Thus, we are set in a position where we can build artificial images and check whether some kind of agreement can be found between the computationally predicted thresholds and the psychophysical ones. We describe and discuss two preliminary sets of experiments, where we compared the gestalt detection performance of several subjects with the predictable detection curve. In our opinion, the results of this experimental comparison support the idea of a much more systematic interaction between computational predictions in Computer Vision and psychophysical experiments.

  3. Full-Field Pupillary Light Responses, Luminance Thresholds, and Light Discomfort Thresholds in CEP290 Leber Congenital Amaurosis Patients

    PubMed Central

    Collison, Frederick T.; Park, Jason C.; Fishman, Gerald A.; McAnany, J. Jason; Stone, Edwin M.

    2015-01-01

    Purpose To investigate visual function in patients with CEP290 Leber congenital amaurosis (LCA-CEP290), using three full-field tests that can be performed by patients with poor fixation. Methods Six patients (age range, 9–39 years) with LCA-CEP290 participated in the study. Stimuli for all three tests (full-field stimulus test [FST], pupillometry, and light discomfort threshold [LDT] testing) were generated by the Diagnosys ColorDome ganzfeld, by using achromatic stimuli as well as long- and short-wavelength stimuli to target rod and cone photoreceptors with all three tests and, in the latter two tests, melanopsin photoreceptors. Results Dark-adapted FST thresholds in LCA-CEP290 patients were cone mediated and elevated between 4.8 and 6.2 log units above the normal achromatic threshold. The FST threshold was not measurable in one patient. The rod-mediated transient pupillary light reflex (PLR) was absent in all but the youngest patient, where unreliable responses precluded PLR quantification. Cone-mediated transient PLRs were subnormal in five patients, and absent in another. Sustained melanopsin-mediated PLRs were measurable in all patients. Full-field LDT thresholds were elevated compared to normal controls, and were lower for short-wavelengh than for long-wavelength stimuli. Conclusions The FST thresholds and transient PLRs were cone mediated in our cohort LCA-CEP290 patients. Rod-mediated PLRs were undetectable, whereas melanopsin-mediated sustained responses were detected in all patients, suggesting a relative preservation of inner-retina function. The LDT elevations for the patients are somewhat paradoxical, given their subjective perception of photoaversion. Relative aversion to short-wavelength light suggests influence from melanopsin on LDTs in these patients. PMID:26529047

  4. Optimizing threshold for extreme scale analysis

    NASA Astrophysics Data System (ADS)

    Maynard, Robert; Moreland, Kenneth; Atyachit, Utkarsh; Geveci, Berk; Ma, Kwan-Liu

    2013-01-01

    As the HPC community starts focusing its efforts towards exascale, it becomes clear that we are looking at machines with a billion way concurrency. Although parallel computing has been at the core of the performance gains achieved until now, scaling over 1,000 times the current concurrency can be challenging. As discussed in this paper, even the smallest memory access and synchronization overheads can cause major bottlenecks at this scale. As we develop new software and adapt existing algorithms for exascale, we need to be cognizant of such pitfalls. In this paper, we document our experience with optimizing a fairly common and parallelizable visualization algorithm, threshold of cells based on scalar values, for such highly concurrent architectures. Our experiments help us identify design patterns that can be generalized for other visualization algorithms as well. We discuss our implementation within the Dax toolkit, which is a framework for data analysis and visualization at extreme scale. The Dax toolkit employs the patterns discussed here within the framework's scaffolding to make it easier for algorithm developers to write algorithms without having to worry about such scaling issues.

  5. Human contrast threshold and astronomical visibility

    NASA Astrophysics Data System (ADS)

    Crumey, Andrew

    2014-08-01

    The standard visibility model in light-pollution studies is the formula of Hecht, as used e.g. by Schaefer. However, it is applicable only to point sources and is shown to be of limited accuracy. A new visibility model is presented for uniform achromatic targets of any size against background luminances ranging from zero to full daylight, produced by a systematic procedure applicable to any appropriate data set (e.g. Blackwell's), and based on a simple but previously unrecognized empirical relation between contrast threshold and adaptation luminance. The scotopic luminance correction for variable spectral radiance (colour index) is calculated. For point sources, the model is more accurate than Hecht's formula and is verified using telescopic data collected at Mount Wilson in 1947, enabling the sky brightness at that time to be determined. The result is darker than the calculation by Garstang, implying that light pollution grew more rapidly in subsequent decades than has been supposed. The model is applied to the nebular observations of William Herschel, enabling his visual performance to be quantified. Proposals are made regarding sky quality indicators for public use.

  6. A review of thresholding strategies applied to human chromosome segmentation.

    PubMed

    Poletti, Enea; Zappelli, Francesca; Ruggeri, Alfredo; Grisan, Enrico

    2012-11-01

    Karyotype analysis is a widespread procedure in cytogenetics to assess the presence of genetic defects by the visualization of the structure of chromosomes. The procedure is lengthy and repetitive and an effective automatic analysis would greatly help the cytogeneticist routine work. Still, automatic segmentation and the full disentangling of chromosomes are open issues. The first step in every automatic procedure is the thresholding step, which detect blobs that represent either single chromosomes or clusters of chromosomes. The better the thresholding step, the easier is the subsequent disentanglement of chromosome clusters into single entities. We implemented eleven thresholding methods, i.e. the ones that appear in the literature as the best performers, and compared their performance in segmenting chromosomes and chromosome clusters in cytogenetic Q-band images. The images are affected by the presence of hyper- or hypo-fluorescent regions and by a contrast variability between the stained chromosomes and the background. A thorough analysis of the results highlights that, although every single algorithm shows peculiar strong/weak points, Adaptive Threshold and Region Based Level Set have the overall best performance. In order to provide the scientific community with a public dataset, the data and manual segmentation used in this paper are available for public download at http://bioimlab.dei.unipd.it.

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

    NASA Astrophysics Data System (ADS)

    Friedman, Melvin

    2016-05-01

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

  8. Thresholds for conservation and management: structured decision making as a conceptual framework

    USGS Publications Warehouse

    Nichols, James D.; Eaton, Mitchell J.; Martin, Julien; Edited by Guntenspergen, Glenn R.

    2014-01-01

    changes in system dynamics. They are frequently incorporated into ecological models used to project system responses to management actions. Utility thresholds are components of management objectives and are values of state or performance variables at which small changes yield substantial changes in the value of the management outcome. Decision thresholds are values of system state variables at which small changes prompt changes in management actions in order to reach specified management objectives. Decision thresholds are derived from the other components of the decision process.We advocate a structured decision making (SDM) approach within which the following components are identified: objectives (possibly including utility thresholds), potential actions, models (possibly including ecological thresholds), monitoring program, and a solution algorithm (which produces decision thresholds). Adaptive resource management (ARM) is described as a special case of SDM developed for recurrent decision problems that are characterized by uncertainty. We believe that SDM, in general, and ARM, in particular, provide good approaches to conservation and management. Use of SDM and ARM also clarifies the distinct roles of ecological thresholds, utility thresholds, and decision thresholds in informed decision processes.

  9. Adaptive Management

    EPA Science Inventory

    Adaptive management is an approach to natural resource management that emphasizes learning through management where knowledge is incomplete, and when, despite inherent uncertainty, managers and policymakers must act. Unlike a traditional trial and error approach, adaptive managem...

  10. Threshold phenomena in soft matter

    NASA Astrophysics Data System (ADS)

    Huang, Zhibin

    Although two different fields are covered, this thesis is mainly focused on some threshold behaviors in both liquid crystal field and fluid dynamic systems. A method of rubbed polyimide is used to obtain pretilt. Sufficiently strong rubbing of a polyimide (SE-1211) results in a large polar pretilt of liquid crystal director with respect to the homeotropic orientation. There exists a threshold rubbing strength required to induce nonzero pretilt. For the homologous liquid crystal series alkyl-cyanobyphenyl, we found that the threshold rubbing strength is a monotonic function of the number of methylene units. A dual easy axis model is then used to explain the results. Freedericksz transition measurements have been used to determine the quadratical and quartic coefficients associated with the molecules' tilt with respect to the layer normal in surface-induced smectic layers in the nematic phase above the smectic-A-nematic phase transition temperature. Both the quadratic and quartic coefficients are consistent with the scaling relationship as predicted in theory, and their ratio is approximately constant. A Rayleigh-Taylor instability experiment is performed by using a magnetic field gradient to draw down a low density but highly paramagnetic fluid below a more dense fluid in a Hele-Shaw cell. When turning off the magnetic field, the RT instability occurs in situ and the growth of the most unstable wavevector is measured as a function of time. The wavelength of the RT instability along with the growth rate was measured as a function of capillary number (which is related to the density difference and interfacial tension between two fluids). A theory for the instability that permits different viscosities for two immiscible fluids was developed, and good agreement was found with the experimental results. The technique of magnetic levitation promises to broaden significantly the accessible parameter space of gravitational interfacial instability experiments. A method is

  11. Comparison of thresholding schemes for visible light communication using mobile-phone image sensor.

    PubMed

    Liu, Yang; Chow, Chi-Wai; Liang, Kevin; Chen, Hung-Yu; Hsu, Chin-Wei; Chen, Chung-Yen; Chen, Shih-Hao

    2016-02-01

    Based on the rolling shutter effect of the complementary metal-oxide-semiconductor (CMOS) image sensor, bright and dark fringes can be observed in each received frame. By demodulating the bright and dark fringes, the visible light communication (VLC) data logic can be retrieved. However, demodulating the bright and dark fringes is challenging as there is a high data fluctuation and large extinction ratio (ER) variation in each frame due. Hence proper thresholding scheme is needed. In this work, we propose and compare experimentally three thresholding schemes; including third-order polynomial curve fitting, iterative scheme and quick adaptive scheme. The evaluation of these three thresholding schemes is performed.

  12. The uncertainty threshold principle - Fundamental limitations of optimal decision making under dynamic uncertainty

    NASA Technical Reports Server (NTRS)

    Athans, M.; Ku, R.; Gershwin, S. B.

    1976-01-01

    The fundamental limitations of the optimal control of dynamic systems with random parameters are analyzed by studying a scalar linear-quadratic optimal control example. It is demonstrated that optimum long-range decision making is possible only if the dynamic uncertainty (quantified by the means and covariances of the random parameters) is below a certain threshold. If this threshold is exceeded, there do not exist optimum decision rules. This phenomenon is called the 'uncertainty threshold principle'. The implications of this phenomenon to the field of modelling, identification, and adaptive control are discussed.

  13. Detection thresholds of macaque otolith afferents.

    PubMed

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

    2012-06-13

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

  14. Epidemic thresholds for bipartite networks

    NASA Astrophysics Data System (ADS)

    Hernández, D. G.; Risau-Gusman, S.

    2013-11-01

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

  15. Fireplace adapters

    SciTech Connect

    Hunt, R.L.

    1983-12-27

    An adapter is disclosed for use with a fireplace. The stove pipe of a stove standing in a room to be heated may be connected to the flue of the chimney so that products of combustion from the stove may be safely exhausted through the flue and outwardly of the chimney. The adapter may be easily installed within the fireplace by removing the damper plate and fitting the adapter to the damper frame. Each of a pair of bolts has a portion which hooks over a portion of the damper frame and a threaded end depending from the hook portion and extending through a hole in the adapter. Nuts are threaded on the bolts and are adapted to force the adapter into a tight fit with the adapter frame.

  16. Embracing thresholds for better environmental management

    PubMed Central

    Kelly, Ryan P.; Erickson, Ashley L.; Mease, Lindley A.; Battista, Willow; Kittinger, John N.; Fujita, Rod

    2015-01-01

    Three decades of study have revealed dozens of examples in which natural systems have crossed biophysical thresholds (‘tipping points’)—nonlinear changes in ecosystem structure and function—as a result of human-induced stressors, dramatically altering ecosystem function and services. Environmental management that avoids such thresholds could prevent severe social, economic and environmental impacts. Here, we review management measures implemented in ecological systems that have thresholds. Using Ostrom's social–ecological systems framework, we analysed key biophysical and institutional factors associated with 51 social–ecological systems and associated management regimes, and related these to management success defined by ecological outcomes. We categorized cases as instances of prospective or retrospective management, based upon whether management aimed to avoid a threshold or to restore systems that have crossed a threshold. We find that smaller systems are more amenable to threshold-based management, that routine monitoring is associated with successful avoidance of thresholds and recovery after thresholds have been crossed, and that success is associated with the explicit threshold-based management. These findings are powerful evidence for the policy relevance of information on ecological thresholds across a wide range of ecosystems.

  17. Whole-body vibration perception thresholds

    NASA Astrophysics Data System (ADS)

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

    1988-03-01

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

  18. Thresholds for Cenozoic bipolar glaciation.

    PubMed

    Deconto, Robert M; Pollard, David; Wilson, Paul A; Pälike, Heiko; Lear, Caroline H; Pagani, Mark

    2008-10-01

    The long-standing view of Earth's Cenozoic glacial history calls for the first continental-scale glaciation of Antarctica in the earliest Oligocene epoch ( approximately 33.6 million years ago), followed by the onset of northern-hemispheric glacial cycles in the late Pliocene epoch, about 31 million years later. The pivotal early Oligocene event is characterized by a rapid shift of 1.5 parts per thousand in deep-sea benthic oxygen-isotope values (Oi-1) within a few hundred thousand years, reflecting a combination of terrestrial ice growth and deep-sea cooling. The apparent absence of contemporaneous cooling in deep-sea Mg/Ca records, however, has been argued to reflect the growth of more ice than can be accommodated on Antarctica; this, combined with new evidence of continental cooling and ice-rafted debris in the Northern Hemisphere during this period, raises the possibility that Oi-1 represents a precursory bipolar glaciation. Here we test this hypothesis using an isotope-capable global climate/ice-sheet model that accommodates both the long-term decline of Cenozoic atmospheric CO(2) levels and the effects of orbital forcing. We show that the CO(2) threshold below which glaciation occurs in the Northern Hemisphere ( approximately 280 p.p.m.v.) is much lower than that for Antarctica ( approximately 750 p.p.m.v.). Therefore, the growth of ice sheets in the Northern Hemisphere immediately following Antarctic glaciation would have required rapid CO(2) drawdown within the Oi-1 timeframe, to levels lower than those estimated by geochemical proxies and carbon-cycle models. Instead of bipolar glaciation, we find that Oi-1 is best explained by Antarctic glaciation alone, combined with deep-sea cooling of up to 4 degrees C and Antarctic ice that is less isotopically depleted (-30 to -35 per thousand) than previously suggested. Proxy CO(2) estimates remain above our model's northern-hemispheric glaciation threshold of approximately 280 p.p.m.v. until approximately 25 Myr

  19. Thresholds for Cenozoic bipolar glaciation.

    PubMed

    Deconto, Robert M; Pollard, David; Wilson, Paul A; Pälike, Heiko; Lear, Caroline H; Pagani, Mark

    2008-10-01

    The long-standing view of Earth's Cenozoic glacial history calls for the first continental-scale glaciation of Antarctica in the earliest Oligocene epoch ( approximately 33.6 million years ago), followed by the onset of northern-hemispheric glacial cycles in the late Pliocene epoch, about 31 million years later. The pivotal early Oligocene event is characterized by a rapid shift of 1.5 parts per thousand in deep-sea benthic oxygen-isotope values (Oi-1) within a few hundred thousand years, reflecting a combination of terrestrial ice growth and deep-sea cooling. The apparent absence of contemporaneous cooling in deep-sea Mg/Ca records, however, has been argued to reflect the growth of more ice than can be accommodated on Antarctica; this, combined with new evidence of continental cooling and ice-rafted debris in the Northern Hemisphere during this period, raises the possibility that Oi-1 represents a precursory bipolar glaciation. Here we test this hypothesis using an isotope-capable global climate/ice-sheet model that accommodates both the long-term decline of Cenozoic atmospheric CO(2) levels and the effects of orbital forcing. We show that the CO(2) threshold below which glaciation occurs in the Northern Hemisphere ( approximately 280 p.p.m.v.) is much lower than that for Antarctica ( approximately 750 p.p.m.v.). Therefore, the growth of ice sheets in the Northern Hemisphere immediately following Antarctic glaciation would have required rapid CO(2) drawdown within the Oi-1 timeframe, to levels lower than those estimated by geochemical proxies and carbon-cycle models. Instead of bipolar glaciation, we find that Oi-1 is best explained by Antarctic glaciation alone, combined with deep-sea cooling of up to 4 degrees C and Antarctic ice that is less isotopically depleted (-30 to -35 per thousand) than previously suggested. Proxy CO(2) estimates remain above our model's northern-hemispheric glaciation threshold of approximately 280 p.p.m.v. until approximately 25 Myr

  20. Structured decision making as a conceptual framework to identify thresholds for conservation and management

    USGS Publications Warehouse

    Martin, J.; Runge, M.C.; Nichols, J.D.; Lubow, B.C.; Kendall, W.L.

    2009-01-01

    component, and ecological thresholds may be embedded in models projecting consequences of management actions. Decision thresholds are determined by the above-listed components of a structured decision process. These components may themselves vary over time, inducing variation in the decision thresholds inherited from them. These dynamic decision thresholds can then be determined using adaptive management. We provide numerical examples (that are based on patch occupancy models) of structured decision processes that include all three kinds of thresholds. ?? 2009 by the Ecological Society of America.

  1. Adaptive SPECT

    PubMed Central

    Barrett, Harrison H.; Furenlid, Lars R.; Freed, Melanie; Hesterman, Jacob Y.; Kupinski, Matthew A.; Clarkson, Eric; Whitaker, Meredith K.

    2008-01-01

    Adaptive imaging systems alter their data-acquisition configuration or protocol in response to the image information received. An adaptive pinhole single-photon emission computed tomography (SPECT) system might acquire an initial scout image to obtain preliminary information about the radiotracer distribution and then adjust the configuration or sizes of the pinholes, the magnifications, or the projection angles in order to improve performance. This paper briefly describes two small-animal SPECT systems that allow this flexibility and then presents a framework for evaluating adaptive systems in general, and adaptive SPECT systems in particular. The evaluation is in terms of the performance of linear observers on detection or estimation tasks. Expressions are derived for the ideal linear (Hotelling) observer and the ideal linear (Wiener) estimator with adaptive imaging. Detailed expressions for the performance figures of merit are given, and possible adaptation rules are discussed. PMID:18541485

  2. Colour thresholding in video imaging.

    PubMed Central

    Fermin, C D; Degraw, S

    1995-01-01

    The basic aspects of video imaging are reviewed as they relate to measurements of histological and anatomical features, with particular emphasis on the advantages and disadvantages of colour and black-and-white imaging modes. In black-and-white imaging, calculations are based on the manipulation of picture elements (pixels) that contain 0-255 levels of information. Black is represented by the absence of light (0) and white by 255 grades of light. In colour imaging, the pixels contain variation of hues for the primary (red, green and blue) and secondary (magenta, yellow, cyan, pink) colours. Manipulation of pixels with colour information is more computer intense than that for black-and-white pixels, because there are over 16 million possible combinations of colour in a system with a 24-bit resolution. The narrow 128 possible grades of separation in black and white often makes distinction between pixels with overlapping intensities difficult. Such difficulty is greatly reduced by colour thresholding of systems that base the representation of colour on a combination of hue-saturation-intensity (HSI) format. Images Fig. 3 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Fig. 15 Fig. 16 Fig. 17 Fig. 18 Fig. 19 Fig. 20 PMID:7559121

  3. Roots at the percolation threshold

    NASA Astrophysics Data System (ADS)

    Kroener, Eva; Ahmed, Mutez Ali; Carminati, Andrea

    2015-04-01

    The rhizosphere is the layer of soil around the roots where complex and dynamic interactions between plants and soil affect the capacity of plants to take up water. The physical properties of the rhizosphere are affected by mucilage, a gel exuded by roots. Mucilage can absorb large volumes of water, but it becomes hydrophobic after drying. We use a percolation model to describe the rewetting of dry rhizosphere. We find that at a critical mucilage concentration the rhizosphere becomes impermeable. The critical mucilage concentration depends on the radius of the soil particle size. Capillary rise experiments with neutron radiography prove that for concentrations below the critical mucilage concentration water could easily cross the rhizosphere, while above the critical concentration water could no longer percolate through it. Our studies, together with former observations of water dynamics in the rhizosphere, suggest that the rhizosphere is near the percolation threshold, where small variations in mucilage concentration sensitively alter the soil hydraulic conductivity. Is mucilage exudation a plant mechanism to efficiently control the rhizosphere conductivity and the access to water?

  4. Efficient threshold for volumetric segmentation

    NASA Astrophysics Data System (ADS)

    Burdescu, Dumitru D.; Brezovan, Marius; Stanescu, Liana; Stoica Spahiu, Cosmin; Ebanca, Daniel

    2015-07-01

    Image segmentation plays a crucial role in effective understanding of digital images. However, the research on the existence of general purpose segmentation algorithm that suits for variety of applications is still very much active. Among the many approaches in performing image segmentation, graph based approach is gaining popularity primarily due to its ability in reflecting global image properties. Volumetric image segmentation can simply result an image partition composed by relevant regions, but the most fundamental challenge in segmentation algorithm is to precisely define the volumetric extent of some object, which may be represented by the union of multiple regions. The aim in this paper is to present a new method to detect visual objects from color volumetric images and efficient threshold. We present a unified framework for volumetric image segmentation and contour extraction that uses a virtual tree-hexagonal structure defined on the set of the image voxels. The advantage of using a virtual tree-hexagonal network superposed over the initial image voxels is that it reduces the execution time and the memory space used, without losing the initial resolution of the image.

  5. Roots at the percolation threshold.

    PubMed

    Kroener, Eva; Ahmed, Mutez Ali; Carminati, Andrea

    2015-04-01

    The rhizosphere is the layer of soil around the roots where complex and dynamic interactions between plants and soil affect the capacity of plants to take up water. The physical properties of the rhizosphere are affected by mucilage, a gel exuded by roots. Mucilage can absorb large volumes of water, but it becomes hydrophobic after drying. We use a percolation model to describe the rewetting of dry rhizosphere. We find that at a critical mucilage concentration the rhizosphere becomes impermeable. The critical mucilage concentration depends on the radius of the soil particle size. Capillary rise experiments with neutron radiography prove that for concentrations below the critical mucilage concentration water could easily cross the rhizosphere, while above the critical concentration water could no longer percolate through it. Our studies, together with former observations of water dynamics in the rhizosphere, suggest that the rhizosphere is near the percolation threshold, where small variations in mucilage concentration sensitively alter the soil hydraulic conductivity. Is mucilage exudation a plant mechanism to efficiently control the rhizosphere conductivity and the access to water? PMID:25974526

  6. Percolation Threshold in Polycarbonate Nanocomposites

    NASA Astrophysics Data System (ADS)

    Ahuja, Suresh

    2014-03-01

    Nanocomposites have unique mechanical, electrical, magnetic, optical and thermal properties. Many methods could be applied to prepare polymer-inorganic nanocomposites, such as sol-gel processing, in-situ polymerization, particle in-situ formation, blending, and radiation synthesis. The analytical composite models that have been put forth include Voigt and Reuss bounds, Polymer nanocomposites offer the possibility of substantial improvements in material properties such as shear and bulk modulus, yield strength, toughness, film scratch resistance, optical properties, electrical conductivity, gas and solvent transport, with only very small amounts of nanoparticles Experimental results are compared against composite models of Hashin and Shtrikman bounds, Halpin-Tsai model, Cox model, and various Mori and Tanaka models. Examples of numerical modeling are molecular dynamics modeling and finite element modeling of reduced modulus and hardness that takes into account the modulus of the components and the effect of the interface between the hard filler and relatively soft polymer, polycarbonate. Higher nanoparticle concentration results in poor dispersion and adhesion to polymer matrix which results in lower modulus and hardness and departure from the existing composite models. As the level of silica increases beyond a threshold level, aggregates form which results in weakening of the structure. Polymer silica interface is found to be weak as silica is non-interacting promoting interfacial slip at silica-matrix junctions. Our experimental results compare favorably with those of nanocomposites of polyesters where the effect of nanoclay on composite hardness and modulus depended on dispersion of nanoclay in polyester.

  7. Invasion Threshold in Heterogeneous Metapopulation Networks

    NASA Astrophysics Data System (ADS)

    Colizza, Vittoria; Vespignani, Alessandro

    2007-10-01

    We study the dynamics of epidemic and reaction-diffusion processes in metapopulation models with heterogeneous connectivity patterns. In susceptible-infected-removed-like processes, along with the standard local epidemic threshold, the system exhibits a global invasion threshold. We provide an explicit expression of the threshold that sets a critical value of the diffusion/mobility rate below, which the epidemic is not able to spread to a macroscopic fraction of subpopulations. The invasion threshold is found to be affected by the topological fluctuations of the metapopulation network. The results presented provide a general framework for the understanding of the effect of travel restrictions in epidemic containment.

  8. Impact of Fast Sodium Channel Inactivation on Spike Threshold Dynamics and Synaptic Integration

    PubMed Central

    Platkiewicz, Jonathan; Brette, Romain

    2011-01-01

    Neurons spike when their membrane potential exceeds a threshold value. In central neurons, the spike threshold is not constant but depends on the stimulation. Thus, input-output properties of neurons depend both on the effect of presynaptic spikes on the membrane potential and on the dynamics of the spike threshold. Among the possible mechanisms that may modulate the threshold, one strong candidate is Na channel inactivation, because it specifically impacts spike initiation without affecting the membrane potential. We collected voltage-clamp data from the literature and we found, based on a theoretical criterion, that the properties of Na inactivation could indeed cause substantial threshold variability by itself. By analyzing simple neuron models with fast Na inactivation (one channel subtype), we found that the spike threshold is correlated with the mean membrane potential and negatively correlated with the preceding depolarization slope, consistent with experiments. We then analyzed the impact of threshold dynamics on synaptic integration. The difference between the postsynaptic potential (PSP) and the dynamic threshold in response to a presynaptic spike defines an effective PSP. When the neuron is sufficiently depolarized, this effective PSP is briefer than the PSP. This mechanism regulates the temporal window of synaptic integration in an adaptive way. Finally, we discuss the role of other potential mechanisms. Distal spike initiation, channel noise and Na activation dynamics cannot account for the observed negative slope-threshold relationship, while adaptive conductances (e.g. K+) and Na inactivation can. We conclude that Na inactivation is a metabolically efficient mechanism to control the temporal resolution of synaptic integration. PMID:21573200

  9. Adaptive Computing.

    ERIC Educational Resources Information Center

    Harrell, William

    1999-01-01

    Provides information on various adaptive technology resources available to people with disabilities. (Contains 19 references, an annotated list of 129 websites, and 12 additional print resources.) (JOW)

  10. Contour adaptation.

    PubMed

    Anstis, Stuart

    2013-01-01

    It is known that adaptation to a disk that flickers between black and white at 3-8 Hz on a gray surround renders invisible a congruent gray test disk viewed afterwards. This is contrast adaptation. We now report that adapting simply to the flickering circular outline of the disk can have the same effect. We call this "contour adaptation." This adaptation does not transfer interocularly, and apparently applies only to luminance, not color. One can adapt selectively to only some of the contours in a display, making only these contours temporarily invisible. For instance, a plaid comprises a vertical grating superimposed on a horizontal grating. If one first adapts to appropriate flickering vertical lines, the vertical components of the plaid disappears and it looks like a horizontal grating. Also, we simulated a Cornsweet (1970) edge, and we selectively adapted out the subjective and objective contours of a Kanisza (1976) subjective square. By temporarily removing edges, contour adaptation offers a new technique to study the role of visual edges, and it demonstrates how brightness information is concentrated in edges and propagates from them as it fills in surfaces.

  11. A New Adaptive Image Denoising Method Based on Neighboring Coefficients

    NASA Astrophysics Data System (ADS)

    Biswas, Mantosh; Om, Hari

    2016-03-01

    Many good techniques have been discussed for image denoising that include NeighShrink, improved adaptive wavelet denoising method based on neighboring coefficients (IAWDMBNC), improved wavelet shrinkage technique for image denoising (IWST), local adaptive wiener filter (LAWF), wavelet packet thresholding using median and wiener filters (WPTMWF), adaptive image denoising method based on thresholding (AIDMT). These techniques are based on local statistical description of the neighboring coefficients in a window. These methods however do not give good quality of the images since they cannot modify and remove too many small wavelet coefficients simultaneously due to the threshold. In this paper, a new image denoising method is proposed that shrinks the noisy coefficients using an adaptive threshold. Our method overcomes these drawbacks and it has better performance than the NeighShrink, IAWDMBNC, IWST, LAWF, WPTMWF, and AIDMT denoising methods.

  12. Error-thresholds for qudit-based topological quantum memories

    NASA Astrophysics Data System (ADS)

    Andrist, Ruben S.; Wootton, James R.; Katzgraber, Helmut G.

    2014-03-01

    Extending the quantum computing paradigm from qubits to higher-dimensional quantum systems allows for increased channel capacity and a more efficient implementation of quantum gates. However, to perform reliable computations an efficient error-correction scheme adapted for these multi-level quantum systems is needed. A promising approach is via topological quantum error correction, where stability to external noise is achieved by encoding quantum information in non-local degrees of freedom. A key figure of merit is the error threshold which quantifies the fraction of physical qudits that can be damaged before logical information is lost. Here we analyze the resilience of generalized topological memories built from d-level quantum systems (qudits) to bit-flip errors. The error threshold is determined by mapping the quantum setup to a classical Potts-like model with bond disorder, which is then investigated numerically using large-scale Monte Carlo simulations. Our results show that topological error correction with qutrits exhibits an improved error threshold in comparison to qubit-based systems.

  13. Double threshold ultrasonic distance measurement technique and its application

    NASA Astrophysics Data System (ADS)

    Li, Weihua; Chen, Qiang; Wu, Jiangtao

    2014-04-01

    The double threshold method realized by hardware circuits and high performance timing chip TDC-GP21 was successfully adapted to solve the key problem of ultrasonic distance measurement, the accurate time-of-flight (TOF) measurement of ultrasonic wave. Compared with other techniques of TOF measurement, the double threshold method presented in this work can suppress noise in the received signal, and achieve a time resolution of around 22 ps and real-time. This method is easy to realize and pertains the advantage of low cost. To compensate temperature and pressure deviations, a temperature measurement module of 10 mK in precision as well as a pressure measurement module of 0.01% in accuracy was developed. The system designed in this work can be exactly used as a two paths ultrasonic gas flowmeter without any adjustment of the hardware circuit. The double threshold method was further corroborated using experiment results of both the ultrasonic distance measurement and ultrasonic gas flow measurement. In distance measurement, the maximum absolute deviation and the maximum relative error are 0.69 mm and 0.28%, respectively, for a target distance range of 100-600 mm. In flow measurement, the maximum absolute deviation and the worst repeatability are 1.16% and 0.65% for a flow in the range of 50-700 m3/h.

  14. Double threshold ultrasonic distance measurement technique and its application.

    PubMed

    Li, Weihua; Chen, Qiang; Wu, Jiangtao

    2014-04-01

    The double threshold method realized by hardware circuits and high performance timing chip TDC-GP21 was successfully adapted to solve the key problem of ultrasonic distance measurement, the accurate time-of-flight (TOF) measurement of ultrasonic wave. Compared with other techniques of TOF measurement, the double threshold method presented in this work can suppress noise in the received signal, and achieve a time resolution of around 22 ps and real-time. This method is easy to realize and pertains the advantage of low cost. To compensate temperature and pressure deviations, a temperature measurement module of 10 mK in precision as well as a pressure measurement module of 0.01% in accuracy was developed. The system designed in this work can be exactly used as a two paths ultrasonic gas flowmeter without any adjustment of the hardware circuit. The double threshold method was further corroborated using experiment results of both the ultrasonic distance measurement and ultrasonic gas flow measurement. In distance measurement, the maximum absolute deviation and the maximum relative error are 0.69 mm and 0.28%, respectively, for a target distance range of 100-600 mm. In flow measurement, the maximum absolute deviation and the worst repeatability are 1.16% and 0.65% for a flow in the range of 50-700 m(3)/h. PMID:24784646

  15. Large Covariance Estimation by Thresholding Principal Orthogonal Complements

    PubMed Central

    Fan, Jianqing; Liao, Yuan; Mincheva, Martina

    2012-01-01

    This paper deals with the estimation of a high-dimensional covariance with a conditional sparsity structure and fast-diverging eigenvalues. By assuming sparse error covariance matrix in an approximate factor model, we allow for the presence of some cross-sectional correlation even after taking out common but unobservable factors. We introduce the Principal Orthogonal complEment Thresholding (POET) method to explore such an approximate factor structure with sparsity. The POET estimator includes the sample covariance matrix, the factor-based covariance matrix (Fan, Fan, and Lv, 2008), the thresholding estimator (Bickel and Levina, 2008) and the adaptive thresholding estimator (Cai and Liu, 2011) as specific examples. We provide mathematical insights when the factor analysis is approximately the same as the principal component analysis for high-dimensional data. The rates of convergence of the sparse residual covariance matrix and the conditional sparse covariance matrix are studied under various norms. It is shown that the impact of estimating the unknown factors vanishes as the dimensionality increases. The uniform rates of convergence for the unobserved factors and their factor loadings are derived. The asymptotic results are also verified by extensive simulation studies. Finally, a real data application on portfolio allocation is presented. PMID:24348088

  16. Managing ecological thresholds in coupled environmental–human systems

    PubMed Central

    Horan, Richard D.; Fenichel, Eli P.; Drury, Kevin L. S.; Lodge, David M.

    2011-01-01

    Many ecosystems appear subject to regime shifts—abrupt changes from one state to another after crossing a threshold or tipping point. Thresholds and their associated stability landscapes are determined within a coupled socioeconomic–ecological system (SES) where human choices, including those of managers, are feedback responses. Prior work has made one of two assumptions about managers: that they face no institutional constraints, in which case the SES may be managed to be fairly robust to shocks and tipping points are of little importance, or that managers are rigidly constrained with no flexibility to adapt, in which case the inferred thresholds may poorly reflect actual managerial flexibility. We model a multidimensional SES to investigate how alternative institutions affect SES stability landscapes and alter tipping points. With institutionally dependent human feedbacks, the stability landscape depends on institutional arrangements. Strong institutions that account for feedback responses create the possibility for desirable states of the world and can cause undesirable states to cease to exist. Intermediate institutions interact with ecological relationships to determine the existence and nature of tipping points. Finally, weak institutions can eliminate tipping points so that only undesirable states of the world remain. PMID:21502517

  17. Climate adaptation

    NASA Astrophysics Data System (ADS)

    Kinzig, Ann P.

    2015-03-01

    This paper is intended as a brief introduction to climate adaptation in a conference devoted otherwise to the physics of sustainable energy. Whereas mitigation involves measures to reduce the probability of a potential event, such as climate change, adaptation refers to actions that lessen the impact of climate change. Mitigation and adaptation differ in other ways as well. Adaptation does not necessarily have to be implemented immediately to be effective; it only needs to be in place before the threat arrives. Also, adaptation does not necessarily require global, coordinated action; many effective adaptation actions can be local. Some urban communities, because of land-use change and the urban heat-island effect, currently face changes similar to some expected under climate change, such as changes in water availability, heat-related morbidity, or changes in disease patterns. Concern over those impacts might motivate the implementation of measures that would also help in climate adaptation, despite skepticism among some policy makers about anthropogenic global warming. Studies of ancient civilizations in the southwestern US lends some insight into factors that may or may not be important to successful adaptation.

  18. Prediction-based threshold for medication alert.

    PubMed

    Kawazoe, Yoshimasa; Miyo, Kengo; Kurahashi, Issei; Sakurai, Ryota; Ohe, Kazuhiko

    2013-01-01

    This study presents a prediction-based approach to determine thresholds for a medication alert in a computerized physician order entry. Traditional static thresholds can sometimes lead to physician's alert fatigue or overlook potentially excessive medication even if the doses are belowthe configured threshold. To address this problem, we applied a random forest algorithm to develop a prediction model for medication doses, and applied a boxplot to determine the thresholds based on the prediction results. An evaluation of the eight drugs most frequently causing alerts in our hospital showed that the performances of the prediction were high, except for two drugs. It was also found that using the thresholds based on the predictions would reduce the alerts to a half of those when using the static thresholds. Notably, some cases were detected only by the prediction thresholds. The significance of the thresholds should be discussed in terms of the trade-offs between gains and losses; however, our approach, which relies on physicians' collective experiences, has practical advantages. PMID:23920550

  19. 40 CFR 98.361 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Reporting threshold. 98.361 Section 98.361 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Manure Management § 98.361 Reporting threshold. Livestock facilities...

  20. 40 CFR 98.361 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Reporting threshold. 98.361 Section 98.361 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Manure Management § 98.361 Reporting threshold. Livestock facilities...

  1. 40 CFR 98.51 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Reporting threshold. 98.51 Section 98.51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Adipic Acid Production § 98.51 Reporting threshold. You must report...

  2. 40 CFR 98.51 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Reporting threshold. 98.51 Section 98.51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Adipic Acid Production § 98.51 Reporting threshold. You must report...

  3. 40 CFR 98.81 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Reporting threshold. 98.81 Section 98.81 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Cement Production § 98.81 Reporting threshold. You must report...

  4. Intelligence and Creativity: Over the Threshold Together?

    ERIC Educational Resources Information Center

    Welter, Marisete Maria; Jaarsveld, Saskia; van Leeuwen, Cees; Lachmann, Thomas

    2016-01-01

    Threshold theory predicts a positive correlation between IQ and creativity scores up to an IQ level of 120 and no correlation above this threshold. Primary school children were tested at beginning (N = 98) and ending (N = 70) of the school year. Participants performed the standard progressive matrices (SPM) and the Test of Creative…

  5. 40 CFR 98.231 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Reporting threshold. 98.231 Section 98.231 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Petroleum and Natural Gas Systems § 98.231 Reporting threshold. (a)...

  6. Applying Threshold Concepts to Finance Education

    ERIC Educational Resources Information Center

    Hoadley, Susan; Wood, Leigh N.; Tickle, Leonie; Kyng, Tim

    2016-01-01

    Purpose: The purpose of this paper is to investigate and identify threshold concepts that are the essential conceptual content of finance programmes. Design/Methodology/Approach: Conducted in three stages with finance academics and students, the study uses threshold concepts as both a theoretical framework and a research methodology. Findings: The…

  7. 40 CFR 98.151 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Reporting threshold. 98.151 Section 98.151 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING HCFC-22 Production and HFC-23 Destruction § 98.151 Reporting threshold. You must report GHG emissions under...

  8. 40 CFR 98.441 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Geologic Sequestration of Carbon Dioxide § 98.441 Reporting threshold. (a... amount of CO2 for long-term containment in subsurface geologic formations. There is no threshold. (b... that current monitoring and model(s) show that the injected CO2 stream is not expected to migrate...

  9. 40 CFR 98.421 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Reporting threshold. 98.421 Section 98.421 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Suppliers of Carbon Dioxide § 98.421 Reporting threshold. Any supplier...

  10. 40 CFR 98.421 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Reporting threshold. 98.421 Section 98.421 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Suppliers of Carbon Dioxide § 98.421 Reporting threshold. Any supplier...

  11. 40 CFR 98.51 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Reporting threshold. 98.51 Section 98.51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Adipic Acid Production § 98.51 Reporting threshold. You must report...

  12. 40 CFR 98.81 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Reporting threshold. 98.81 Section 98.81 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Cement Production § 98.81 Reporting threshold. You must report...

  13. 40 CFR 98.71 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Reporting threshold. 98.71 Section 98.71 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Ammonia Manufacturing § 98.71 Reporting threshold. You must report...

  14. 40 CFR 98.111 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Reporting threshold. 98.111 Section 98.111 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Ferroalloy Production § 98.111 Reporting threshold. You must report...

  15. 40 CFR 98.71 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Reporting threshold. 98.71 Section 98.71 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Ammonia Manufacturing § 98.71 Reporting threshold. You must report...

  16. 40 CFR 98.51 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Reporting threshold. 98.51 Section 98.51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Adipic Acid Production § 98.51 Reporting threshold. You must report...

  17. 40 CFR 98.71 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Reporting threshold. 98.71 Section 98.71 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Ammonia Manufacturing § 98.71 Reporting threshold. You must report...

  18. 40 CFR 98.341 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Reporting threshold. 98.341 Section 98.341 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Municipal Solid Waste Landfills § 98.341 Reporting threshold. You...

  19. Network Motif Basis of Threshold Responses

    EPA Science Inventory

    There has been a long-running debate over the existence of thresholds for adverse effects. The difficulty stems from two fundamental challenges: (i) statistical analysis by itself cannot prove the existence of a threshold, i.e., a dose below which there is no effect; and (ii) the...

  20. Threshold Concepts, Systems and Learning for Sustainability

    ERIC Educational Resources Information Center

    Sandri, Orana Jade

    2013-01-01

    This paper presents a framework for understanding the role that systems theory might play in education for sustainability (EfS). It offers a sketch and critique of Land and Meyer's notion of a "threshold concept", to argue that seeing systems as a threshold concept for sustainability is useful for understanding the processes of…

  1. Methods for automatic trigger threshold adjustment

    DOEpatents

    Welch, Benjamin J; Partridge, Michael E

    2014-03-18

    Methods are presented for adjusting trigger threshold values to compensate for drift in the quiescent level of a signal monitored for initiating a data recording event, thereby avoiding false triggering conditions. Initial threshold values are periodically adjusted by re-measuring the quiescent signal level, and adjusting the threshold values by an offset computation based upon the measured quiescent signal level drift. Re-computation of the trigger threshold values can be implemented on time based or counter based criteria. Additionally, a qualification width counter can be utilized to implement a requirement that a trigger threshold criterion be met a given number of times prior to initiating a data recording event, further reducing the possibility of a false triggering situation.

  2. Pain thresholds are elevated during pseudopregnancy.

    PubMed

    Gintzler, A R; Bohan, M C

    1990-01-22

    Increases in pain thresholds have been observed during gestation in a variety of laboratory animals and humans. The specific events that occur during pregnancy that are responsible for this increase in maternal pain threshold are not known. In order to investigate whether or not the changes in the peripheral concentration of sex steroids that are known to occur during gestation contribute to the analgesia of pregnancy, the effect of pseudopregnancy on jump thresholds was determined. Pseudopregnancy is associated with a significant increase in the mean jump threshold. In contrast, rats treated chronically with the opioid antagonist naltrexone do not manifest an increase in jump threshold during the pseudopregnant condition. These results suggest that peripheral sex steroids whose peripheral concentration profile is altered during pseudopregnancy might be important modulators of opioid systems that regulate responsiveness to aversive stimuli.

  3. A Threshold Continuum for Aeolian Sand Transport

    NASA Astrophysics Data System (ADS)

    Swann, C.; Ewing, R. C.; Sherman, D. J.

    2015-12-01

    The threshold of motion for aeolian sand transport marks the initial entrainment of sand particles by the force of the wind. This is typically defined and modeled as a singular wind speed for a given grain size and is based on field and laboratory experimental data. However, the definition of threshold varies significantly between these empirical models, largely because the definition is based on visual-observations of initial grain movement. For example, in his seminal experiments, Bagnold defined threshold of motion when he observed that 100% of the bed was in motion. Others have used 50% and lesser values. Differences in threshold models, in turn, result is large errors in predicting the fluxes associated with sand and dust transport. Here we use a wind tunnel and novel sediment trap to capture the fractions of sand in creep, reptation and saltation at Earth and Mars pressures and show that the threshold of motion for aeolian sand transport is best defined as a continuum in which grains progress through stages defined by the proportion of grains in creep and saltation. We propose the use of scale dependent thresholds modeled by distinct probability distribution functions that differentiate the threshold based on micro to macro scale applications. For example, a geologic timescale application corresponds to a threshold when 100% of the bed in motion whereas a sub-second application corresponds to a threshold when a single particle is set in motion. We provide quantitative measurements (number and mode of particle movement) corresponding to visual observations, percent of bed in motion and degrees of transport intermittency for Earth and Mars. Understanding transport as a continuum provides a basis for revaluating sand transport thresholds on Earth, Mars and Titan.

  4. Influence of adaptation state and stimulus luminance on peri-saccadic localization.

    PubMed

    Georg, Katharina; Hamker, Fred H; Lappe, Markus

    2008-01-01

    Spatial localization of flashed stimuli across saccades shows transient distortions of perceived position: Stimuli appear shifted in saccade direction and compressed towards the saccade target. The strength and spatial pattern of this mislocalization is influenced by contrast, duration, and spatial and temporal arrangement of stimuli and background. Because mislocalization of stimuli on a background depends on contrast, we asked whether mislocalization of stimuli in darkness depends on luminance. Since dark adaptation changes luminance thresholds, we compared mislocalization in dark-adapted and light-adapted states. Peri-saccadic mislocalization was measured with near-threshold stimuli and above-threshold stimuli in dark-adapted and light-adapted subjects. In both adaptation states, near-threshold stimuli gave much larger mislocalization than above-threshold stimuli. Furthermore, when the stimulus was presented near-threshold, the perceived positions of the stimuli clustered closer together. Stimulus luminance that produced strong mislocalization in the light-adapted state produced very little mislocalization in the dark-adapted state because it was now well above threshold. We conclude that the strength of peri-saccadic mislocalization depends on the strength of the stimulus: stimuli with near-threshold luminance, and hence low visibility, are more mis-localized than clearly visible stimuli with high luminance.

  5. Thresholds for the perception of whole-body linear sinusoidal motion in the horizontal plane

    NASA Technical Reports Server (NTRS)

    Mah, Robert W.; Young, Laurence R.; Steele, Charles R.; Schubert, Earl D.

    1989-01-01

    An improved linear sled has been developed to provide precise motion stimuli without generating perceptible extraneous motion cues (a noiseless environment). A modified adaptive forced-choice method was employed to determine perceptual thresholds to whole-body linear sinusoidal motion in 25 subjects. Thresholds for the detection of movement in the horizontal plane were found to be lower than those reported previously. At frequencies of 0.2 to 0.5 Hz, thresholds were shown to be independent of frequency, while at frequencies of 1.0 to 3.0 Hz, thresholds showed a decreasing sensitivity with increasing frequency, indicating that the perceptual process is not sensitive to the rate change of acceleration of the motion stimulus. The results suggest that the perception of motion behaves as an integrating accelerometer with a bandwidth of at least 3 Hz.

  6. Thresholds for Shifting Visually Perceived Eye Level Due to Incremental Pitches

    NASA Technical Reports Server (NTRS)

    Scott, Donald M.; Welch, Robert; Cohen, M. M.; Hill, Cyndi

    2001-01-01

    Visually perceived eye level (VPEL) was judged by subjects as they viewed a luminous grid pattern that was pitched by 2 or 5 deg increments between -20 deg and +20 deg. Subjects were dark adapted for 20 min and indicated--VPEL by directing the beam of a laser pointer to the rear wall of a 1.25 m cubic pitch box that rotated about a horizontal axis midpoint on the rear wall. Data were analyzed by ANOVA and the Tukey HSD procedure. Results showed a 10.0 deg threshold for pitches P(sub i) above the reference pitch P(sub 0), and a -10.3 deg threshold for pitches P(sub i) below-the reference-pitch P(sub 0). Threshold data for pitches P(sub i) < P(sub 0) suggest an asymmetric threshold for VPEL below and above physical eye level.

  7. Orion MPCV Touchdown Detection Threshold Development and Testing

    NASA Technical Reports Server (NTRS)

    Daum, Jared; Gay, Robert

    2013-01-01

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

  8. User-relevant, threshold-specific observations of climate change

    NASA Astrophysics Data System (ADS)

    Stainforth, Dave; Chapman, Sandra; Watkins, Nicholas

    2014-05-01

    Users of climate information look for details of changing climate at local scales (to inform specific activities) and on the geographical patterns of such changes (to prioritise adaptation investments). They often have user-specific thresholds of vulnerability so the changes of interest must refer to such thresholds or to the related quantile of the climatic distribution. A method for providing such information from timeseries of temperature data has recently been published [1] along with maps of changes at thresholds and quantiles [2] derived from the European Observational dataset E-Obs [3]. In this presentation we will do two things. First we will discuss the opportunities to tailor such methods to provide user-specific information through climate services, using illustrations from the existing methodology applied to daily maximum and minimum temperatures [1,2]. Second we will present new results on threshold specific observed changes in precipitation. The methodology for precipitation is related to that which has been applied to temperature but has been developed to handle the characteristics of precipitation distributions. The results identify some regions with systematic increases in precipitation on the seasonally wettest days and others which show drying across all days, on a seasonal basis. We will present the geographic locations and precipitation thresholds where strong signals of changes are seen across Europe. The coherency of such results and the methodology used to process the observational data will be discussed. We will also highlight the justifications for having confidence in the results in some regions and at some thresholds while having a lack of confidence in others. Such information should be an important element of any climate services. It is worth noting that here "wettest days" refers to events which are uncommon within a season (e.g. one in ~20 wet days). This is in contrast and complementary to, for instance, the one in a hundred year

  9. Sputtering Threshold Energies of Heavy Ions

    NASA Technical Reports Server (NTRS)

    Mantenieks, Maris A.

    1999-01-01

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

  10. Microstructures, percolation thresholds, and rock physical properties

    NASA Astrophysics Data System (ADS)

    Guéguen, Y.; Chelidze, T.; Le Ravalec, M.

    1997-09-01

    The physical properties (transport properties and mechanical properties) of porous/cracked rocks are mainly functions of their microstructure. In this connection the problem of critical (threshold) porosity for transport, elasticity and mechanical strength is especially important. Two dominant mathematical formalisms — effective medium theory (EMT) and percolation theory — pretend to give answers to this problem. Some of the EMT models do not predict any threshold (differential effective medium). Other EMT models (self-consistent models) do predict thresholds, but it is shown that these thresholds are fictitious and result from an extension of a theory beyond its limit of validity. The failure of EMT methods at high pores/crack concentrations is the result of clustering effects. The appropriate formalism to correctly describe the phenomenon of clustering of pores and cracks and the behaviour of a system close to its critical porosity is percolation theory. Percolation thresholds can be predicted in that case from classical site or bond percolation on regular or random lattices. The threshold values depend on the density and average size of pores/cracks so that porosity is not sufficient in general to characterize the threshold for a specific physical property. The general term 'critical porosity' should thus be used with caution and it is preferable to specify which property is concerned and what kind of microstructure is present. This term can be more safely used for a population of rocks which have an identical average shape of pores/cracks and for a given physical property.

  11. Toothbrush Adaptations.

    ERIC Educational Resources Information Center

    Exceptional Parent, 1987

    1987-01-01

    Suggestions are presented for helping disabled individuals learn to use or adapt toothbrushes for proper dental care. A directory lists dental health instructional materials available from various organizations. (CB)

  12. Enhanced Sensitivity to Rapid Input Fluctuations by Nonlinear Threshold Dynamics in Neocortical Pyramidal Neurons.

    PubMed

    Mensi, Skander; Hagens, Olivier; Gerstner, Wulfram; Pozzorini, Christian

    2016-02-01

    The way in which single neurons transform input into output spike trains has fundamental consequences for network coding. Theories and modeling studies based on standard Integrate-and-Fire models implicitly assume that, in response to increasingly strong inputs, neurons modify their coding strategy by progressively reducing their selective sensitivity to rapid input fluctuations. Combining mathematical modeling with in vitro experiments, we demonstrate that, in L5 pyramidal neurons, the firing threshold dynamics adaptively adjust the effective timescale of somatic integration in order to preserve sensitivity to rapid signals over a broad range of input statistics. For that, a new Generalized Integrate-and-Fire model featuring nonlinear firing threshold dynamics and conductance-based adaptation is introduced that outperforms state-of-the-art neuron models in predicting the spiking activity of neurons responding to a variety of in vivo-like fluctuating currents. Our model allows for efficient parameter extraction and can be analytically mapped to a Generalized Linear Model in which both the input filter--describing somatic integration--and the spike-history filter--accounting for spike-frequency adaptation--dynamically adapt to the input statistics, as experimentally observed. Overall, our results provide new insights on the computational role of different biophysical processes known to underlie adaptive coding in single neurons and support previous theoretical findings indicating that the nonlinear dynamics of the firing threshold due to Na+-channel inactivation regulate the sensitivity to rapid input fluctuations. PMID:26907675

  13. 40 CFR 98.281 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Silicon Carbide Production § 98.281 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a silicon carbide production process...

  14. 40 CFR 98.281 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Silicon Carbide Production § 98.281 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a silicon carbide production process...

  15. 40 CFR 98.281 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Silicon Carbide Production § 98.281 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a silicon carbide production process...

  16. 40 CFR 98.281 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Silicon Carbide Production § 98.281 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a silicon carbide production process...

  17. 40 CFR 98.281 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Silicon Carbide Production § 98.281 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a silicon carbide production process...

  18. 40 CFR 98.81 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Cement Production § 98.81 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a cement production process and the facility...

  19. 40 CFR 98.331 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Zinc Production § 98.331 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a zinc production process and the facility meets...

  20. 40 CFR 98.331 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Zinc Production § 98.331 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a zinc production process and the facility meets...

  1. 40 CFR 98.331 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Zinc Production § 98.331 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a zinc production process and the facility meets...

  2. 40 CFR 98.331 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Zinc Production § 98.331 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a zinc production process and the facility meets...

  3. 40 CFR 98.41 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Electricity Generation § 98.41 Reporting threshold. You must report GHG emissions under this subpart if your facility contains one or more electricity generating units and...

  4. 40 CFR 98.41 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Electricity Generation § 98.41 Reporting threshold. You must report GHG emissions under this subpart if your facility contains one or more electricity generating units and...

  5. 40 CFR 98.41 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Electricity Generation § 98.41 Reporting threshold. You must report GHG emissions under this subpart if your facility contains one or more electricity generating units and...

  6. 40 CFR 98.41 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Electricity Generation § 98.41 Reporting threshold. You must report GHG emissions under this subpart if your facility contains one or more electricity generating units and...

  7. 40 CFR 98.41 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Electricity Generation § 98.41 Reporting threshold. You must report GHG emissions under this subpart if your facility contains one or more electricity generating units and...

  8. 40 CFR 98.141 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Glass Production § 98.141 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a glass production process and the facility meets...

  9. 40 CFR 98.141 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Glass Production § 98.141 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a glass production process and the facility meets...

  10. 40 CFR 98.141 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Glass Production § 98.141 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a glass production process and the facility meets...

  11. 40 CFR 98.141 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Glass Production § 98.141 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a glass production process and the facility meets...

  12. 40 CFR 98.141 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Glass Production § 98.141 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a glass production process and the facility meets...

  13. 40 CFR 98.211 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Miscellaneous Uses of Carbonate § 98.211 Reporting threshold. You must report GHG emissions from miscellaneous uses of carbonate if your facility uses carbonates as defined...

  14. 40 CFR 98.391 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Suppliers of Petroleum Products § 98.391 Reporting threshold. Any supplier of petroleum products who meets the requirements of § 98.2(a)(4) must report GHG emissions....

  15. 40 CFR 98.341 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Municipal Solid Waste Landfills § 98.341 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a MSW landfill and the facility...

  16. 40 CFR 98.151 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING HCFC-22 Production and HFC-23 Destruction § 98.151 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an HCFC-22 production...

  17. 40 CFR 98.221 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Nitric Acid Production § 98.221 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a nitric acid train and the facility meets...

  18. 40 CFR 98.271 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Pulp and Paper Manufacturing § 98.271 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a pulp and paper manufacturing...

  19. 40 CFR 98.191 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Lime Manufacturing § 98.191 Reporting threshold. You must report GHG emissions under this subpart if your facility is a lime manufacturing plant as defined in § 98.190 and...

  20. 40 CFR 98.381 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Suppliers of Coal-based Liquid Fuels § 98.381 Reporting threshold. Any supplier of coal-to-liquid products who meets the requirements of § 98.2(a)(4) must report GHG emissions....

  1. 40 CFR 98.31 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING General Stationary Fuel Combustion Sources § 98.31 Reporting threshold. You must report GHG emissions under this subpart if your facility contains one or more stationary...

  2. 40 CFR 98.61 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Aluminum Production § 98.61 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an aluminum production process and the facility...

  3. 40 CFR 98.61 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Aluminum Production § 98.61 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an aluminum production process and the facility...

  4. 40 CFR 98.61 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Aluminum Production § 98.61 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an aluminum production process and the facility...

  5. 40 CFR 98.61 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Aluminum Production § 98.61 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an aluminum production process and the facility...

  6. 40 CFR 98.61 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Aluminum Production § 98.61 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an aluminum production process and the facility...

  7. Laser damage threshold of diamond films

    NASA Technical Reports Server (NTRS)

    Albin, Sacharia; Cropper, Andre D.; Watkins, Linwood C.; Byvik, Charles E.; Buoncristiani, A. Martin

    1989-01-01

    The possibility that diamond films may inhibit laser-induced damage to optical components in laser systems films was investigated by measuring laser damage thresholds of free-standing diamond film windows, diamond films deposited on silicon substrates, and bare silicon substrate. Polycrystalline diamond films were deposited using a dc plasma-enhanced CVD process. It was found that free-standing diamond films had the highest laser damage threshold at 1064 nm. For a diamond film of 630 nm, the damage threshold was found to be 7 J/sq cm, as compared to a damage threshold of 4.5 J/sq cm for bare silicon, and a low value of 1.5 J/sq cm for the film/substrate combination. The damage mechanism is considered to involve melting or dielectric breakdown induced by laser radiation. The low value of the film/substrate combination is attributed to film stress and conditions of film deposition.

  8. 40 CFR 98.471 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Injection of Carbon Dioxide § 98.471 Reporting threshold. (a) You must... purposes of this subpart, any reference to CO2 emissions in § 98.2(i) shall mean CO2 received....

  9. 40 CFR 98.471 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Injection of Carbon Dioxide § 98.471 Reporting threshold. (a) You must... purposes of this subpart, any reference to CO2 emissions in § 98.2(i) shall mean CO2 received....

  10. 40 CFR 98.351 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ....351 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Industrial Wastewater Treatment § 98.351 Reporting threshold. You must... wastewater treatment sludge. (b) Ethanol production and food processing facilities. (1) The facility...

  11. 40 CFR 98.351 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ....351 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Industrial Wastewater Treatment § 98.351 Reporting threshold. You must... wastewater treatment sludge. (b) Ethanol production and food processing facilities. (1) The facility...

  12. 40 CFR 98.351 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ....351 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Industrial Wastewater Treatment § 98.351 Reporting threshold. You must... wastewater treatment sludge. (b) Ethanol production and food processing facilities. (1) The facility...

  13. 40 CFR 98.351 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ....351 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Industrial Wastewater Treatment § 98.351 Reporting threshold. You must... wastewater treatment sludge. (b) Ethanol production and food processing facilities. (1) The facility...

  14. 40 CFR 98.151 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING HCFC-22 Production and HFC-23 Destruction § 98.151 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an HCFC-22 production...

  15. 40 CFR 98.151 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING HCFC-22 Production and HFC-23 Destruction § 98.151 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an HCFC-22 production...

  16. 40 CFR 98.151 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING HCFC-22 Production and HFC-23 Destruction § 98.151 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an HCFC-22 production...

  17. 40 CFR 98.161 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Hydrogen Production § 98.161 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a hydrogen production process and the facility...

  18. 40 CFR 98.241 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Petrochemical Production § 98.241 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a petrochemical process as specified...

  19. 40 CFR 98.241 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Petrochemical Production § 98.241 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a petrochemical process as specified...

  20. 40 CFR 98.241 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Petrochemical Production § 98.241 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a petrochemical process as specified...

  1. 40 CFR 98.241 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Petrochemical Production § 98.241 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a petrochemical process as specified...

  2. 40 CFR 98.241 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Petrochemical Production § 98.241 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a petrochemical process as specified...

  3. 40 CFR 98.331 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Zinc Production § 98.331 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a zinc production process and the facility meets...

  4. 40 CFR 98.71 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Ammonia Manufacturing § 98.71 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an ammonia manufacturing process and the...

  5. 40 CFR 98.71 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Ammonia Manufacturing § 98.71 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an ammonia manufacturing process and the...

  6. 40 CFR 98.201 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Magnesium Production § 98.201 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a magnesium production process and the facility...

  7. 40 CFR 98.201 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Magnesium Production § 98.201 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a magnesium production process and the facility...

  8. 40 CFR 98.201 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Magnesium Production § 98.201 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a magnesium production process and the facility...

  9. 40 CFR 98.201 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Magnesium Production § 98.201 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a magnesium production process and the facility...

  10. 40 CFR 98.411 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Suppliers of Industrial Greenhouse Gases § 98.411 Reporting threshold. Any supplier of industrial greenhouse gases who meets the requirements of § 98.2(a)(4) must report...

  11. 40 CFR 98.411 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Suppliers of Industrial Greenhouse Gases § 98.411 Reporting threshold. Any supplier of industrial greenhouse gases who meets the requirements of § 98.2(a)(4) must report...

  12. 40 CFR 98.411 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Suppliers of Industrial Greenhouse Gases § 98.411 Reporting threshold. Any supplier of industrial greenhouse gases who meets the requirements of § 98.2(a)(4) must report...

  13. 40 CFR 98.411 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Suppliers of Industrial Greenhouse Gases § 98.411 Reporting threshold. Any supplier of industrial greenhouse gases who meets the requirements of § 98.2(a)(4) must report...

  14. 40 CFR 98.411 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Suppliers of Industrial Greenhouse Gases § 98.411 Reporting threshold. Any supplier of industrial greenhouse gases who meets the requirements of § 98.2(a)(4) must report...

  15. 40 CFR 98.311 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Titanium Dioxide Production § 98.311 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a titanium dioxide production process...

  16. 40 CFR 98.311 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Titanium Dioxide Production § 98.311 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a titanium dioxide production process...

  17. 40 CFR 98.311 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Titanium Dioxide Production § 98.311 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a titanium dioxide production process...

  18. 40 CFR 98.311 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Titanium Dioxide Production § 98.311 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a titanium dioxide production process...

  19. 40 CFR 98.311 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Titanium Dioxide Production § 98.311 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a titanium dioxide production process...

  20. 40 CFR 98.261 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Phosphoric Acid Production § 98.261 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a phosphoric acid production process...

  1. 40 CFR 98.261 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Phosphoric Acid Production § 98.261 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a phosphoric acid production process...

  2. 40 CFR 98.261 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Phosphoric Acid Production § 98.261 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a phosphoric acid production process...

  3. 40 CFR 98.181 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Lead Production § 98.181 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a lead production process and the facility meets...

  4. 40 CFR 98.171 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Iron and Steel Production § 98.171 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an iron and steel production process...

  5. Effective theories and thresholds in particle physics

    SciTech Connect

    Gaillard, M.K.

    1991-06-07

    The role of effective theories in probing a more fundamental underlying theory and in indicating new physics thresholds is discussed, with examples from the standard model and more speculative applications to superstring theory. 38 refs.

  6. 40 CFR 98.251 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Petroleum Refineries § 98.251 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a petroleum refineries process and the facility...

  7. 40 CFR 98.251 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Petroleum Refineries § 98.251 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a petroleum refineries process and the facility...

  8. 40 CFR 98.251 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Petroleum Refineries § 98.251 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a petroleum refineries process and the facility...

  9. 40 CFR 98.251 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Petroleum Refineries § 98.251 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a petroleum refineries process and the facility...

  10. 40 CFR 98.251 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Petroleum Refineries § 98.251 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a petroleum refineries process and the facility...

  11. 40 CFR 98.171 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Iron and Steel Production § 98.171 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an iron and steel production process...

  12. 40 CFR 98.171 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Iron and Steel Production § 98.171 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an iron and steel production process...

  13. 40 CFR 98.291 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Soda Ash Manufacturing § 98.291 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a soda ash manufacturing process and the...

  14. 40 CFR 98.291 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Soda Ash Manufacturing § 98.291 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a soda ash manufacturing process and the...

  15. 40 CFR 98.291 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Soda Ash Manufacturing § 98.291 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a soda ash manufacturing process and the...

  16. 40 CFR 98.291 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Soda Ash Manufacturing § 98.291 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a soda ash manufacturing process and the...

  17. 40 CFR 98.291 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Soda Ash Manufacturing § 98.291 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a soda ash manufacturing process and the...

  18. 40 CFR 98.321 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Underground Coal Mines § 98.321 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an active underground coal mine and the...

  19. 40 CFR 98.321 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Underground Coal Mines § 98.321 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an active underground coal mine and the...

  20. 40 CFR 98.321 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Underground Coal Mines § 98.321 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an active underground coal mine and the...

  1. 40 CFR 98.321 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Underground Coal Mines § 98.321 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an active underground coal mine and the...

  2. 40 CFR 98.401 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Suppliers of Natural Gas and Natural Gas Liquids § 98.401 Reporting threshold. Any supplier of natural gas and natural gas liquids that meets the requirements of §...

  3. 40 CFR 98.401 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Suppliers of Natural Gas and Natural Gas Liquids § 98.401 Reporting threshold. Any supplier of natural gas and natural gas liquids that meets the requirements of §...

  4. 40 CFR 98.401 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Suppliers of Natural Gas and Natural Gas Liquids § 98.401 Reporting threshold. Any supplier of natural gas and natural gas liquids that meets the requirements of §...

  5. 40 CFR 98.401 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Suppliers of Natural Gas and Natural Gas Liquids § 98.401 Reporting threshold. Any supplier of natural gas and natural gas liquids that meets the requirements of §...

  6. 40 CFR 98.161 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Hydrogen Production § 98.161 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a hydrogen production process and the facility...

  7. 40 CFR 98.161 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Hydrogen Production § 98.161 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a hydrogen production process and the facility...

  8. 40 CFR 98.161 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Hydrogen Production § 98.161 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a hydrogen production process and the facility...

  9. 40 CFR 98.161 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Hydrogen Production § 98.161 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a hydrogen production process and the facility...

  10. [Nonlinear magnetohydrodynamics]. [Threshold unstable MHD activity

    SciTech Connect

    Not Available

    1992-01-01

    Theoretical predictions were compared with available data from JET on the threshold unstable MHD activity in toroidal confinement devices. In particular, questions arising as to Hartmans number and the selection of a kinematic viscosity are discussed.

  11. 40 CFR 98.261 - Reporting threshold.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Phosphoric Acid Production § 98.261 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a phosphoric acid production process...

  12. 40 CFR 98.261 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Phosphoric Acid Production § 98.261 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a phosphoric acid production process...

  13. No evidence of dioxin cancer threshold.

    PubMed Central

    Mackie, David; Liu, Junfeng; Loh, Yeong-Shang; Thomas, Valerie

    2003-01-01

    The U.S. Environmental Protection Agency (EPA) has developed an estimate of the human cancer risk from dioxin, using the standard low-dose linear extrapolation approach. This estimate has been controversial because of concern that it may overestimate the cancer risk. An alternative approach has been published and was presented to the U.S. EPA Science Advisory Board's Dioxin Review Panel in November 2000. That approach suggests that dioxin is a threshold carcinogen and that the threshold is an order of magnitude above the exposure levels of the general population. We have reexamined the threshold analysis and found that the data have been incorrectly weighted by cohort size. In our reanalysis, without the incorrect weighting, the threshold effect disappears. PMID:12842764

  14. Threshold altitude resulting in decompression sickness

    NASA Technical Reports Server (NTRS)

    Kumar, K. V.; Waligora, James M.; Calkins, Dick S.

    1990-01-01

    A review of case reports, hypobaric chamber training data, and experimental evidence indicated that the threshold for incidence of altitude decompression sickness (DCS) was influenced by various factors such as prior denitrogenation, exercise or rest, and period of exposure, in addition to individual susceptibility. Fitting these data with appropriate statistical models makes it possible to examine the influence of various factors on the threshold for DCS. This approach was illustrated by logistic regression analysis on the incidence of DCS below 9144 m. Estimations using these regressions showed that, under a noprebreathe, 6-h exposure, simulated EVA profile, the threshold for symptoms occurred at approximately 3353 m; while under a noprebreathe, 2-h exposure profile with knee-bends exercise, the threshold occurred at 7925 m.

  15. Nonlinear theory of kinetic instabilities near threshold

    SciTech Connect

    Berk, H.L.; Pekker, M.S.; Breizman, B.N. |

    1997-05-01

    A new nonlinear equation has been derived and solved for the evolution of an unstable collective mode in a kinetic system close to the threshold of linear instability. The resonant particle response produces the dominant nonlinearity, which can be calculated iteratively in the near-threshold regime as long as the mode doe snot trap resonant particles. With sources and classical relaxation processes included, the theory describes both soft nonlinear regimes, where the mode saturation level is proportional to an increment above threshold, and explosive nonlinear regimes, where the mode grows to a level that is independent of the closeness to threshold. The explosive solutions exhibit mode frequency shifting. For modes that exist in the absence of energetic particles, the frequency shift is both upward and downward. For modes that require energetic particles for their existence, there is a preferred direction of the frequency shift. The frequency shift continues even after the mode traps resonant particles.

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

    PubMed

    Grant, Alexander M; Levin, Craig S

    2014-07-01

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

  17. Optimizing Retransmission Threshold in Wireless Sensor Networks.

    PubMed

    Bi, Ran; Li, Yingshu; Tan, Guozhen; Sun, Liang

    2016-01-01

    The retransmission threshold in wireless sensor networks is critical to the latency of data delivery in the networks. However, existing works on data transmission in sensor networks did not consider the optimization of the retransmission threshold, and they simply set the same retransmission threshold for all sensor nodes in advance. The method did not take link quality and delay requirement into account, which decreases the probability of a packet passing its delivery path within a given deadline. This paper investigates the problem of finding optimal retransmission thresholds for relay nodes along a delivery path in a sensor network. The object of optimizing retransmission thresholds is to maximize the summation of the probability of the packet being successfully delivered to the next relay node or destination node in time. A dynamic programming-based distributed algorithm for finding optimal retransmission thresholds for relay nodes along a delivery path in the sensor network is proposed. The time complexity is O n Δ · max 1 ≤ i ≤ n { u i } , where u i is the given upper bound of the retransmission threshold of sensor node i in a given delivery path, n is the length of the delivery path and Δ is the given upper bound of the transmission delay of the delivery path. If Δ is greater than the polynomial, to reduce the time complexity, a linear programming-based ( 1 + p m i n ) -approximation algorithm is proposed. Furthermore, when the ranges of the upper and lower bounds of retransmission thresholds are big enough, a Lagrange multiplier-based distributed O ( 1 ) -approximation algorithm with time complexity O ( 1 ) is proposed. Experimental results show that the proposed algorithms have better performance. PMID:27171092

  18. Computer simulation of the threshold sensitivity determinations

    NASA Technical Reports Server (NTRS)

    Gayle, J. B.

    1974-01-01

    A computer simulation study was carried out to evaluate various methods for determining threshold stimulus levels for impact sensitivity tests. In addition, the influence of a number of variables (initial stimulus level, particular stimulus response curve, and increment size) on the apparent threshold values and on the corresponding population response levels was determined. Finally, a critical review of previous assumptions regarding the stimulus response curve for impact testing is presented in the light of the simulation results.

  19. Optimizing Retransmission Threshold in Wireless Sensor Networks

    PubMed Central

    Bi, Ran; Li, Yingshu; Tan, Guozhen; Sun, Liang

    2016-01-01

    The retransmission threshold in wireless sensor networks is critical to the latency of data delivery in the networks. However, existing works on data transmission in sensor networks did not consider the optimization of the retransmission threshold, and they simply set the same retransmission threshold for all sensor nodes in advance. The method did not take link quality and delay requirement into account, which decreases the probability of a packet passing its delivery path within a given deadline. This paper investigates the problem of finding optimal retransmission thresholds for relay nodes along a delivery path in a sensor network. The object of optimizing retransmission thresholds is to maximize the summation of the probability of the packet being successfully delivered to the next relay node or destination node in time. A dynamic programming-based distributed algorithm for finding optimal retransmission thresholds for relay nodes along a delivery path in the sensor network is proposed. The time complexity is OnΔ·max1≤i≤n{ui}, where ui is the given upper bound of the retransmission threshold of sensor node i in a given delivery path, n is the length of the delivery path and Δ is the given upper bound of the transmission delay of the delivery path. If Δ is greater than the polynomial, to reduce the time complexity, a linear programming-based (1+pmin)-approximation algorithm is proposed. Furthermore, when the ranges of the upper and lower bounds of retransmission thresholds are big enough, a Lagrange multiplier-based distributed O(1)-approximation algorithm with time complexity O(1) is proposed. Experimental results show that the proposed algorithms have better performance. PMID:27171092

  20. Initiation Pressure Thresholds from Three Sources

    SciTech Connect

    Souers, P C; Vitello, P

    2007-02-28

    Pressure thresholds are minimum pressures needed to start explosive initiation that ends in detonation. We obtain pressure thresholds from three sources. Run-to-detonation times are the poorest source but the fitting of a function gives rough results. Flyer-induced initiation gives the best results because the initial conditions are the best known. However, very thick flyers are needed to give the lowest, asymptotic pressure thresholds used in modern models and this kind of data is rarely available. Gap test data is in much larger supply but the various test sizes and materials are confusing. We find that explosive pressures are almost the same if the distance in the gap test spacers are in units of donor explosive radius. Calculated half-width time pulses in the spacers may be used to create a pressure-time curve similar to that of the flyers. The very-large Eglin gap tests give asymptotic thresholds comparable to extrapolated flyer results. The three sources are assembled into a much-expanded set of near-asymptotic pressure thresholds. These thresholds vary greatly with density: for TATB/LX-17/PBX 9502, we find values of 4.9 and 8.7 GPa at 1.80 and 1.90 g/cm{sup 3}, respectively.

  1. Temporal adaptability and the inverse relationship to sensitivity: a parameter identification model.

    PubMed

    Langley, Keith

    2005-01-01

    Following a prolonged period of visual adaptation to a temporally modulated sinusoidal luminance pattern, the threshold contrast of a similar visual pattern is elevated. The adaptive elevation in threshold contrast is selective for spatial frequency, may saturate at low adaptor contrast, and increases as a function of the spatio-temporal frequency of the adapting signal. A model for signal extraction that is capable of explaining these threshold contrast effects of adaptation is proposed. Contrast adaptation in the model is explained by the identification of the parameters of an environmental model: the autocorrelation function of the visualized signal. The proposed model predicts that the adaptability of threshold contrast is governed by unpredicted signal variations present in the visual signal, and thus represents an internal adjustment by the visual system that takes into account these unpredicted signal variations given the additional possibility for signal corruption by additive noise.

  2. Adaptive Development

    NASA Technical Reports Server (NTRS)

    2005-01-01

    The goal of this research is to develop and demonstrate innovative adaptive seal technologies that can lead to dramatic improvements in engine performance, life, range, and emissions, and enhance operability for next generation gas turbine engines. This work is concentrated on the development of self-adaptive clearance control systems for gas turbine engines. Researchers have targeted the high-pressure turbine (HPT) blade tip seal location for following reasons: Current active clearance control (ACC) systems (e.g., thermal case-cooling schemes) cannot respond to blade tip clearance changes due to mechanical, thermal, and aerodynamic loads. As such they are prone to wear due to the required tight running clearances during operation. Blade tip seal wear (increased clearances) reduces engine efficiency, performance, and service life. Adaptive sealing technology research has inherent impact on all envisioned 21st century propulsion systems (e.g. distributed vectored, hybrid and electric drive propulsion concepts).

  3. Perceptual adaptation helps us identify faces.

    PubMed

    Rhodes, Gillian; Watson, Tamara L; Jeffery, Linda; Clifford, Colin W G

    2010-05-12

    Adaptation is a fundamental property of perceptual processing. In low-level vision, it can calibrate perception to current inputs, increasing coding efficiency and enhancing discrimination around the adapted level. Adaptation also occurs in high-level vision, as illustrated by face aftereffects. However, the functional consequences of face adaptation remain uncertain. Here we investigated whether adaptation can enhance identification performance for faces from an adapted, relative to an unadapted, population. Five minutes of adaptation to an average Asian or Caucasian face reduced identification thresholds for faces from the adapted relative to the unadapted race. We replicated this interaction in two studies, using different participants, faces and adapting procedures. These results suggest that adaptation has a functional role in high-level, as well as low-level, visual processing. We suggest that adaptation to the average of a population may reduce responses to common properties shared by all members of the population, effectively orthogonalizing identity vectors in a multi-dimensional face space and freeing neural resources to code distinctive properties, which are useful for identification.

  4. Adaptive management

    USGS Publications Warehouse

    Allen, Craig R.; Garmestani, Ahjond S.

    2015-01-01

    Adaptive management is an approach to natural resource management that emphasizes learning through management where knowledge is incomplete, and when, despite inherent uncertainty, managers and policymakers must act. Unlike a traditional trial and error approach, adaptive management has explicit structure, including a careful elucidation of goals, identification of alternative management objectives and hypotheses of causation, and procedures for the collection of data followed by evaluation and reiteration. The process is iterative, and serves to reduce uncertainty, build knowledge and improve management over time in a goal-oriented and structured process.

  5. Threshold Values for Identification of Contamination Predicted by Reduced-Order Models

    DOE PAGES

    Last, George V.; Murray, Christopher J.; Bott, Yi-Ju; Brown, Christopher F.

    2014-12-31

    The U.S. Department of Energy’s (DOE’s) National Risk Assessment Partnership (NRAP) Project is developing reduced-order models to evaluate potential impacts on underground sources of drinking water (USDWs) if CO2 or brine leaks from deep CO2 storage reservoirs. Threshold values, below which there would be no predicted impacts, were determined for portions of two aquifer systems. These threshold values were calculated using an interwell approach for determining background groundwater concentrations that is an adaptation of methods described in the U.S. Environmental Protection Agency’s Unified Guidance for Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities.

  6. The variations in visual threshold measurement.

    PubMed

    Hallett, P E

    1969-06-01

    1. This paper presents a statistical analysis of the thresholds of test flashes viewed against zero, steady or transient backgrounds by peripheral vision. The method of threshold measurement is that of the Medical Research Council Report (Pirenne, Marriott & O'Doherty, 1957; Hartline & McDonald, 1943). The data are from the previous paper (Hallett, 1969b) and consist of k days' samples of n threshold measurements on an intensity scale of interval 0.087 log. The collection of a sample required 5-6 min and the samples were spread over a 3-month period.2. The analysis suggests that the nature of biological variations is that the ;instantaneous' frequency-of-seeing curve can occupy a variety of positions, or levels, scattered about its typical position on the log. energy axis. Change of the position of the curve for a given threshold task is most obvious when one compares threshold measurements obtained on different days, but this is not true day-to-day variation; the same sorts of change occur on the same day if the viewing conditions (independent variables) are changed and are perhaps due to shifts in the observer's signal/noise criterion K.3. Two important consequences of the analysis are (i) the errors of visual threshold functions are worse than one method of calculating error suggests and (ii) it is possible to eliminate part of the biological variations from a particular sort of frequency-of-seeing curve and thus obtain a better estimate of the instantaneous curve which is the physiological function of prime interest.4. Some possible causes of the biological variations are considered. The design of experiments is discussed. The method of the M.R.C. Report is to be recommended since it can be applied without prior assumptions about the value of the mean threshold or the nature of the errors. PMID:5784294

  7. Estimating vowel formant discrimination thresholds using a single-interval classification task1

    PubMed Central

    Oglesbee, Eric; Kewley-Port, Diane

    2009-01-01

    Previous research estimating vowel formant discrimination thresholds in words and sentences has often employed a modified two-alternative-forced-choice (2AFC) task with adaptive tracking. Although this approach has produced stable data, the length and number of experimental sessions, as well as the unnaturalness of the task, limit generalizations of results to ordinary speech communication. In this exploratory study, a typical identification task was used to estimate vowel formant discrimination thresholds. Specifically, a signal detection theory approach was used to develop a method to estimate vowel formant discrimination thresholds from a quicker, more natural single-interval classification task. In experiment 1 “classification thresholds” for words in isolation and embedded in sentences were compared to previously collected 2AFC data. Experiment 2 used a within-subjects design to compare thresholds estimated from both classification and 2AFC tasks. Due to instabilities observed in the experiment 1 sentence data, experiment 2 examined only isolated words. Results from these experiments show that for isolated words, thresholds estimated using the classification procedure are comparable to those estimated using the 2AFC task. These results, as well as an analysis of several aspects of the classification procedure, support the viability of this new approach for estimating discrimination thresholds for speech stimuli. PMID:19354407

  8. Enhanced Sensitivity to Rapid Input Fluctuations by Nonlinear Threshold Dynamics in Neocortical Pyramidal Neurons

    PubMed Central

    Mensi, Skander; Hagens, Olivier; Gerstner, Wulfram; Pozzorini, Christian

    2016-01-01

    The way in which single neurons transform input into output spike trains has fundamental consequences for network coding. Theories and modeling studies based on standard Integrate-and-Fire models implicitly assume that, in response to increasingly strong inputs, neurons modify their coding strategy by progressively reducing their selective sensitivity to rapid input fluctuations. Combining mathematical modeling with in vitro experiments, we demonstrate that, in L5 pyramidal neurons, the firing threshold dynamics adaptively adjust the effective timescale of somatic integration in order to preserve sensitivity to rapid signals over a broad range of input statistics. For that, a new Generalized Integrate-and-Fire model featuring nonlinear firing threshold dynamics and conductance-based adaptation is introduced that outperforms state-of-the-art neuron models in predicting the spiking activity of neurons responding to a variety of in vivo-like fluctuating currents. Our model allows for efficient parameter extraction and can be analytically mapped to a Generalized Linear Model in which both the input filter—describing somatic integration—and the spike-history filter—accounting for spike-frequency adaptation—dynamically adapt to the input statistics, as experimentally observed. Overall, our results provide new insights on the computational role of different biophysical processes known to underlie adaptive coding in single neurons and support previous theoretical findings indicating that the nonlinear dynamics of the firing threshold due to Na+-channel inactivation regulate the sensitivity to rapid input fluctuations. PMID:26907675

  9. Photoreceptor processes in visual adaptation.

    PubMed

    Ripps, H; Pepperberg, D R

    1987-01-01

    In this paper we have stressed two experimental results in need of explanation: (i) the reduced efficacy with which (remaining, abundant) rhodopsin in the light-adapted receptor mediates the flash response; and (ii) the disparity in conditions of irradiation (weak background vs. extensive bleaching) leading to equivalent conditions of threshold. The model discussed above suggests, in molecular terms, a possible basis for both properties of receptor adaptation. On the view developed here, property (i) derives from the ability of photoactivated or bleached pigment (R or B) to restrict dramatically the availability of a substance required for phototransduction. Property (ii) derives in large part from the pronounced disparity in the effectiveness of R (during illumination) and B (remaining after illumination) in reducing the availability of this substance. On this view, the "equivalence" of threshold elevation in states of light- vs. dark-adaptation derives from an overall equality of a product of factors (Q, Etot/Es, and J of equation 2). Under all but extreme conditions, this aggregate of factors is dominated by the term Etot/Es, reflecting the functional state of E. PMID:3317149

  10. Commensal bacteria calibrate the activation threshold of innate antiviral immunity.

    PubMed

    Abt, Michael C; Osborne, Lisa C; Monticelli, Laurel A; Doering, Travis A; Alenghat, Theresa; Sonnenberg, Gregory F; Paley, Michael A; Antenus, Marcelo; Williams, Katie L; Erikson, Jan; Wherry, E John; Artis, David

    2012-07-27

    Signals from commensal bacteria can influence immune cell development and susceptibility to infectious or inflammatory diseases. However, the mechanisms by which commensal bacteria regulate protective immunity after exposure to systemic pathogens remain poorly understood. Here, we demonstrate that antibiotic-treated (ABX) mice exhibit impaired innate and adaptive antiviral immune responses and substantially delayed viral clearance after exposure to systemic LCMV or mucosal influenza virus. Furthermore, ABX mice exhibited severe bronchiole epithelial degeneration and increased host mortality after influenza virus infection. Genome-wide transcriptional profiling of macrophages isolated from ABX mice revealed decreased expression of genes associated with antiviral immunity. Moreover, macrophages from ABX mice exhibited defective responses to type I and type II IFNs and impaired capacity to limit viral replication. Collectively, these data indicate that commensal-derived signals provide tonic immune stimulation that establishes the activation threshold of the innate immune system required for optimal antiviral immunity.

  11. Threshold concepts in finance: conceptualizing the curriculum

    NASA Astrophysics Data System (ADS)

    Hoadley, Susan; Tickle, Leonie; Wood, Leigh N.; Kyng, Tim

    2015-08-01

    Graduates with well-developed capabilities in finance are invaluable to our society and in increasing demand. Universities face the challenge of designing finance programmes to develop these capabilities and the essential knowledge that underpins them. Our research responds to this challenge by identifying threshold concepts that are central to the mastery of finance and by exploring their potential for informing curriculum design and pedagogical practices to improve student outcomes. In this paper, we report the results of an online survey of finance academics at multiple institutions in Australia, Canada, New Zealand, South Africa and the United Kingdom. The outcomes of our research are recommendations for threshold concepts in finance endorsed by quantitative evidence, as well as a model of the finance curriculum incorporating finance, modelling and statistics threshold concepts. In addition, we draw conclusions about the application of threshold concept theory supported by both quantitative and qualitative evidence. Our methodology and findings have general relevance to the application of threshold concept theory as a means to investigate and inform curriculum design and delivery in higher education.

  12. Motion parallax thresholds for unambiguous depth perception.

    PubMed

    Holmin, Jessica; Nawrot, Mark

    2015-10-01

    The perception of unambiguous depth from motion parallax arises from the neural integration of retinal image motion and extra-retinal eye movement signals. It is only recently that these parameters have been articulated in the form of the motion/pursuit ratio. In the current study, we explored the lower limits of the parameter space in which observers could accurately perform near/far relative depth-sign discriminations for a translating random-dot stimulus. Stationary observers pursued a translating random dot stimulus containing relative image motion. Their task was to indicate the location of the peak in an approximate square-wave stimulus. We measured thresholds for depth from motion parallax, quantified as motion/pursuit ratios, as well as lower motion thresholds and pursuit accuracy. Depth thresholds were relatively stable at pursuit velocities 5-20 deg/s, and increased at lower and higher velocities. The pattern of results indicates that minimum motion/pursuit ratios are limited by motion and pursuit signals, both independently and in combination with each other. At low and high pursuit velocities, depth thresholds were limited by inaccurate pursuit signals. At moderate pursuit velocities, depth thresholds were limited by motion signals.

  13. Threshold of the precedence effect in noise

    PubMed Central

    Freyman, Richard L.; Griffin, Amanda M.; Zurek, Patrick M.

    2014-01-01

    Three effects that show a temporal asymmetry in the influence of interaural cues were studied through the addition of masking noise: (1) The transient precedence effect—the perceptual dominance of a leading transient over a similar lagging transient; (2) the ongoing precedence effect—lead dominance with lead and lag components that extend in time; and (3) the onset capture effect—determination by an onset transient of the lateral position of an otherwise ambiguous extended trailing sound. These three effects were evoked with noise-burst stimuli and were compared in the presence of masking noise. Using a diotic noise masker, detection thresholds for stimuli with lead/lag interaural delays of 0/500 μs were compared to those with 500/0 μs delays. None of the three effects showed a masking difference between those conditions, suggesting that none of the effects is operative at masked threshold. A task requiring the discrimination between stimuli with 500/0 and 0/500 μs interaural delays was used to determine the threshold for each effect in noise. The results showed similar thresholds in noise (10–13 dB SL) for the transient and ongoing precedence effects, but a much higher threshold (33 dB SL) for onset capture of an ambiguous trailing sound. PMID:24815272

  14. Thresholds for second formant transitions in front vowels

    NASA Astrophysics Data System (ADS)

    Kewley-Port, Diane; Goodman, Shawn S.

    2005-11-01

    Formant dynamics in vowel nuclei contribute to vowel classification in English. This study examined listeners' ability to discriminate dynamic second formant transitions in synthetic high front vowels. Acoustic measurements were made from the nuclei (steady state and 20% and 80% of vowel duration) for the vowels /i,I,e,ɛ,æ/ spoken by a female in /bVd/ context. Three synthesis parameters were selected to yield twelve discrimination conditions: initial frequency value for F2 (2525, 2272, or 2068 Hz), slope direction (rising or falling), and duration (110 or 165 ms). F1 frequency was roved. In the standard stimuli, F0 and F1-F4 were steady state. In the comparison stimuli only F2 frequency varied linearly to reach a final frequency. Five listeners were tested under adaptive tracking to estimate the threshold for frequency extent, the minimal detectable difference in frequency between the initial and final F2 values, called ΔF extent. Analysis showed that initial F2 frequency and direction of movement for some F2 frequencies contributed to significant differences in ΔF extent. Results suggested that listeners attended to differences in the stimulus property of frequency extent (hertz), not formant slope (hertz/second). Formant extent thresholds were at least four times smaller than extents measured in the natural speech tokens, and 18 times smaller than for the diphthongized vowel /e/.

  15. Epidemic threshold and control in a dynamic network

    NASA Astrophysics Data System (ADS)

    Taylor, Michael; Taylor, Timothy J.; Kiss, Istvan Z.

    2012-01-01

    In this paper we present a model describing susceptible-infected-susceptible-type epidemics spreading on a dynamic contact network with random link activation and deletion where link activation can be locally constrained. We use and adapt an improved effective degree compartmental modeling framework recently proposed by Lindquist [J. Math Biol.JMBLAJ0303-681210.1007/s00285-010-0331-2 62, 143 (2010)] and Marceau [Phys. Rev. E1539-3755PLEEE810.1103/PhysRevE.82.036116 82, 036116 (2010)]. The resulting set of ordinary differential equations (ODEs) is solved numerically, and results are compared to those obtained using individual-based stochastic network simulation. We show that the ODEs display excellent agreement with simulation for the evolution of both the disease and the network and are able to accurately capture the epidemic threshold for a wide range of parameters. We also present an analytical R0 calculation for the dynamic network model and show that, depending on the relative time scales of the network evolution and disease transmission, two limiting cases are recovered: (i) the static network case when network evolution is slow and (ii) homogeneous random mixing when the network evolution is rapid. We also use our threshold calculation to highlight the dangers of relying on local stability analysis when predicting epidemic outbreaks on evolving networks.

  16. Climatic and biotic thresholds of coral-reef shutdown

    NASA Astrophysics Data System (ADS)

    Toth, Lauren T.; Aronson, Richard B.; Cobb, Kim M.; Cheng, Hai; Edwards, R. Lawrence; Grothe, Pamela R.; Sayani, Hussein R.

    2015-04-01

    Climate change is now the leading cause of coral-reef degradation and is altering the adaptive landscape of coral populations. Increasing sea temperatures and declining carbonate saturation states are inhibiting short-term rates of coral calcification, carbonate precipitation and submarine cementation. A critical challenge to coral-reef conservation is understanding the mechanisms by which environmental perturbations scale up to influence long-term rates of reef-framework construction and ecosystem function. Here we reconstruct climatic and oceanographic variability using corals sampled from a 6,750-year core from Pacific Panamá. Simultaneous reconstructions of coral palaeophysiology and reef accretion allowed us to identify the climatic and biotic thresholds associated with a 2,500-year hiatus in vertical accretion beginning ~4,100 years ago. Stronger upwelling, cooler sea temperatures and greater precipitation--indicators of La Niña-like conditions--were closely associated with abrupt reef shutdown. The physiological condition of the corals deteriorated at the onset of the hiatus, corroborating theoretical predictions that the tipping points of radical ecosystem transitions should be manifested sublethally in the biotic constituents. Future climate change could cause similar threshold behaviours, leading to another shutdown in reef development in the tropical eastern Pacific.

  17. Analysis of Air Showers at the Trigger Threshold of KASCADE

    NASA Astrophysics Data System (ADS)

    Scholz, J.; Antoni, T.; Apel, W. D.; Bekk, K.; Bercuci, A.; Blümer, H.; Bozdog, H.; Brancus, I. M.; Büttner, C.; Chilingarian, A.; Daumiller, K.; Doll, P.; Engel, R.; Engler, J.; Feßler, F.; Gils, H. J.; Glasstetter, R.; Haungs, A.; Heck, D.; Hörandel, J. R.; Iwan, A.; Kampert, K-H.; Klages, H. O.; Maier, G.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Müller, M.; Obenland, R.; Oehschläger, J.; Ostapchenko, S.; Petcu, M.; Rebel, H.; Risse, M.; Roth, M.; Schatz, G.; Schieler, H.; Thouw, T.; Ulrich, H.; van Buren, J.; Vardanyan, A.; Weindl, A.; Wochele, J.; Zabierowski, J.

    2003-07-01

    The KASCADE experiment measures extensive air showers. It is 100% efficient for showers which are induced by primary particles with energies above 1015 eV to pursue its main goal, the examination of the knee in the flux spectrum at ≈ 5 · 1015 eV. A specially adapted method to calculate two observables (Nch , the number of charged particles and Nµ , the number of muons) by means of a maximum likelihood estimate will be presented. The estimate combines different detector systems and works already at energies around the trigger threshold of KASCADE at ≈ 1014 eV. These observables are used to reconstruct a preliminary energy flux spectrum which is compared with direct measurements and previous measurements of KASCADE at energies above 1015 eV. The reconstruction of energy spectrum and elemental composition around the trigger threshold of KASCADE is important for two reasons. First the estimated spectrum at higher energies has to be congruent with the results of direct measurements. Second it is a cross-check of the interaction models underlying the analysis of extended air showers.

  18. Bird colour vision: behavioural thresholds reveal receptor noise.

    PubMed

    Olsson, Peter; Lind, Olle; Kelber, Almut

    2015-01-15

    Birds have impressive physiological adaptations for colour vision, including tetrachromacy and coloured oil droplets, yet it is not clear exactly how well birds can discriminate the reflecting object colours that they encounter in nature. With behavioural experiments, we determined colour discrimination thresholds of chickens in bright and dim light. We performed the experiments with two colour series, orange and green, covering two parts of chicken colour space. These experiments allowed us to compare behavioural results with model expectations and determine how different noise types limit colour discrimination. At intensities ranging from bright light to those corresponding to early dusk (250-10 cd m(-2)), we describe thresholds accurately by assuming a constant signal-to-noise ratio, in agreement with an invariant Weber fraction of Weber's law. Below this intensity, signal-to-noise ratio decreases and Weber's law is violated because photon-shot noise limits colour discrimination. In very dim light (below 0.05 cd m(-2) for the orange series or 0.2 cd m(-2) for the green series) colour discrimination is possibly constrained by dark noise, and the lowest intensity at which chickens can discriminate colours is 0.025 and 0.08 cd m(-2) for the orange and green series, respectively. Our results suggest that chickens use spatial pooling of cone outputs to mitigate photon-shot noise. Surprisingly, we found no difference between colour discrimination of chickens and humans tested with the same test in bright light. PMID:25609782

  19. Bird colour vision: behavioural thresholds reveal receptor noise.

    PubMed

    Olsson, Peter; Lind, Olle; Kelber, Almut

    2015-01-15

    Birds have impressive physiological adaptations for colour vision, including tetrachromacy and coloured oil droplets, yet it is not clear exactly how well birds can discriminate the reflecting object colours that they encounter in nature. With behavioural experiments, we determined colour discrimination thresholds of chickens in bright and dim light. We performed the experiments with two colour series, orange and green, covering two parts of chicken colour space. These experiments allowed us to compare behavioural results with model expectations and determine how different noise types limit colour discrimination. At intensities ranging from bright light to those corresponding to early dusk (250-10 cd m(-2)), we describe thresholds accurately by assuming a constant signal-to-noise ratio, in agreement with an invariant Weber fraction of Weber's law. Below this intensity, signal-to-noise ratio decreases and Weber's law is violated because photon-shot noise limits colour discrimination. In very dim light (below 0.05 cd m(-2) for the orange series or 0.2 cd m(-2) for the green series) colour discrimination is possibly constrained by dark noise, and the lowest intensity at which chickens can discriminate colours is 0.025 and 0.08 cd m(-2) for the orange and green series, respectively. Our results suggest that chickens use spatial pooling of cone outputs to mitigate photon-shot noise. Surprisingly, we found no difference between colour discrimination of chickens and humans tested with the same test in bright light.

  20. Acceptance threshold theory can explain occurrence of homosexual behaviour.

    PubMed

    Engel, Katharina C; Männer, Lisa; Ayasse, Manfred; Steiger, Sandra

    2015-01-01

    Same-sex sexual behaviour (SSB) has been documented in a wide range of animals, but its evolutionary causes are not well understood. Here, we investigated SSB in the light of Reeve's acceptance threshold theory. When recognition is not error-proof, the acceptance threshold used by males to recognize potential mating partners should be flexibly adjusted to maximize the fitness pay-off between the costs of erroneously accepting males and the benefits of accepting females. By manipulating male burying beetles' search time for females and their reproductive potential, we influenced their perceived costs of making an acceptance or rejection error. As predicted, when the costs of rejecting females increased, males exhibited more permissive discrimination decisions and showed high levels of SSB; when the costs of accepting males increased, males were more restrictive and showed low levels of SSB. Our results support the idea that in animal species, in which the recognition cues of females and males overlap to a certain degree, SSB is a consequence of an adaptive discrimination strategy to avoid the costs of making rejection errors.

  1. Probability Density and CFAR Threshold Estimation for Hyperspectral Imaging

    SciTech Connect

    Clark, G A

    2004-09-21

    implementations to compute the decision threshold r{sub 0}*that will provide the appropriate desired Probability of False Alarm P{sub FA} for the matched filter. The goal is to use prior knowledge of the background data to generate an estimate of the probability density function (pdf) [13] of the matched filter threshold r for the case in which the data measurement contains only background data (we call this case the null hypothesis, or H{sub 0}) [10, 11]. We call the pdf estimate {cflx f}(r|H{sub 0}). In this report, we use histograms and Parzen pdf estimators [14, 15, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27]. Once the estimate is obtained, it can be integrated to compute an estimate of the P{sub FA}as a function of the matched filter detection threshold r. We can then interpolate r vs. P{sub FA} to obtain a curve that gives the threshold r{sub 0}* that will provide the appropriate desired Probability of False Alarm P{sub FA}for the matched filter. Processing results have been computed using both simulated and real LASI data sets. The algorithms and codes have been validated, and the results using LASI data are presented here. Future work includes applying the pdf estimation and CFAR threshold calculation algorithms to the LASI matched filter based upon global background statistics, and developing a new adaptive matched filter algorithm based upon local background statistics. Another goal is to implement the 4-Gamma pdf modeling method proposed by Stocker et. al. [4] and comparing results using histograms and the Parzen pdf estimators.

  2. Effects of pulse duration on magnetostimulation thresholds

    PubMed Central

    Saritas, Emine U.; Goodwill, Patrick W.; Conolly, Steven M.

    2015-01-01

    Purpose: Medical imaging techniques such as magnetic resonance imaging and magnetic particle imaging (MPI) utilize time-varying magnetic fields that are subject to magnetostimulation limits, which often limit the speed of the imaging process. Various human-subject experiments have studied the amplitude and frequency dependence of these thresholds for gradient or homogeneous magnetic fields. Another contributing factor was shown to be number of cycles in a magnetic pulse, where the thresholds decreased with longer pulses. The latter result was demonstrated on two subjects only, at a single frequency of 1.27 kHz. Hence, whether the observed effect was due to the number of cycles or due to the pulse duration was not specified. In addition, a gradient-type field was utilized; hence, whether the same phenomenon applies to homogeneous magnetic fields remained unknown. Here, the authors investigate the pulse duration dependence of magnetostimulation limits for a 20-fold range of frequencies using homogeneous magnetic fields, such as the ones used for the drive field in MPI. Methods: Magnetostimulation thresholds were measured in the arms of six healthy subjects (age: 27 ± 5 yr). Each experiment comprised testing the thresholds at eight different pulse durations between 2 and 125 ms at a single frequency, which took approximately 30–40 min/subject. A total of 34 experiments were performed at three different frequencies: 1.2, 5.7, and 25.5 kHz. A solenoid coil providing homogeneous magnetic field was used to induce stimulation, and the field amplitude was measured in real time. A pre-emphasis based pulse shaping method was employed to accurately control the pulse durations. Subjects reported stimulation via a mouse click whenever they felt a twitching/tingling sensation. A sigmoid function was fitted to the subject responses to find the threshold at a specific frequency and duration, and the whole procedure was repeated at all relevant frequencies and pulse durations

  3. Effects of pulse duration on magnetostimulation thresholds

    SciTech Connect

    Saritas, Emine U.; Goodwill, Patrick W.; Conolly, Steven M.

    2015-06-15

    Purpose: Medical imaging techniques such as magnetic resonance imaging and magnetic particle imaging (MPI) utilize time-varying magnetic fields that are subject to magnetostimulation limits, which often limit the speed of the imaging process. Various human-subject experiments have studied the amplitude and frequency dependence of these thresholds for gradient or homogeneous magnetic fields. Another contributing factor was shown to be number of cycles in a magnetic pulse, where the thresholds decreased with longer pulses. The latter result was demonstrated on two subjects only, at a single frequency of 1.27 kHz. Hence, whether the observed effect was due to the number of cycles or due to the pulse duration was not specified. In addition, a gradient-type field was utilized; hence, whether the same phenomenon applies to homogeneous magnetic fields remained unknown. Here, the authors investigate the pulse duration dependence of magnetostimulation limits for a 20-fold range of frequencies using homogeneous magnetic fields, such as the ones used for the drive field in MPI. Methods: Magnetostimulation thresholds were measured in the arms of six healthy subjects (age: 27 ± 5 yr). Each experiment comprised testing the thresholds at eight different pulse durations between 2 and 125 ms at a single frequency, which took approximately 30–40 min/subject. A total of 34 experiments were performed at three different frequencies: 1.2, 5.7, and 25.5 kHz. A solenoid coil providing homogeneous magnetic field was used to induce stimulation, and the field amplitude was measured in real time. A pre-emphasis based pulse shaping method was employed to accurately control the pulse durations. Subjects reported stimulation via a mouse click whenever they felt a twitching/tingling sensation. A sigmoid function was fitted to the subject responses to find the threshold at a specific frequency and duration, and the whole procedure was repeated at all relevant frequencies and pulse durations

  4. Viral population dynamics and virulence thresholds.

    PubMed

    Lancaster, Karen Z; Pfeiffer, Julie K

    2012-08-01

    Viral factors and host barriers influence virally induced disease, and asymptomatic versus symptomatic infection is governed by a 'virulence threshold'. Understanding modulation of virulence thresholds could lend insight into disease outcome and aid in rational therapeutic and vaccine design. RNA viruses are an excellent system to study virulence thresholds in the context of quasispecies population dynamics. RNA viruses have high error frequencies and our understanding of viral population dynamics has been shaped by quasispecies evolutionary theory. In turn, research using RNA viruses as replicons with short generation times and high mutation rates has been an invaluable tool to test models of quasispecies theory. The challenge and new frontier of RNA virus population dynamics research is to combine multiple theoretical models and experimental data to describe viral population behavior as it changes, moving within and between hosts, to predict disease and pathogen emergence. Several excellent studies have begun to undertake this challenge using novel approaches.

  5. L-H Threshold Studies in NSTX

    SciTech Connect

    Kaye, S M; Battaglia, D; Bell, R E; Chang, C S; Hosea, J; Kugel, H; LeBlanc, B P; Meyer, H; Park, G Y

    2011-09-06

    Recent experiments in the low aspect ratio National Spherical Torus Experiment (NSTX) have been run in support of the high priority ITER and ITPA issue of access to the H-mode. Specifically, a series of experiments showed reduced power threshold values for deuterium vs helium plasmas, and for plasmas with lower current, lower triangularity and with lithium conditioning. Application of n=3 fields at the plasma edge resulted in higher power thresholds. To within the constraints of temporal and spatial resolutions, no systematic difference in T{sub e}, n{sub e}, p{sub e}, T{sub i}, v or their derivatives was found in discharges that transitioned into the H-mode versus those at slightly lower power that did not. Finally, H{sub 98y,2} {approx} 1 confinement quality could be achieved for powers just above the threshold power in ELM-free conditions.

  6. Starvation drives a threshold triggering communication.

    PubMed

    Mailleux, Anne-Catherine; Detrain, Claire; Deneubourg, Jean-Louis

    2006-11-01

    The decision for an ant forager to launch recruitment is governed by an internal response threshold. Here, we demonstrate that this threshold (the desired volume) triggering trail-laying increases under starvation. As a consequence, highly starved foragers lay a recruitment trail and bring back to the nest higher quantities of food from large unlimited resources. In contrast, when the volume of the food source is under their crop capacity, the percentage of trail-communicating foragers is lower following a prolonged period of starvation. Such starvation-dependent changes in the "desired volume" threshold explain how ants optimize recruitment and select liquid food resources in order to prevent collective exploitation of low profitability. PMID:17050837

  7. Predictability of threshold exceedances in dynamical systems

    NASA Astrophysics Data System (ADS)

    Bódai, Tamás

    2015-12-01

    In a low-order model of the general circulation of the atmosphere we examine the predictability of threshold exceedance events of certain observables. The likelihood of such binary events-the cornerstone also for the categoric (as opposed to probabilistic) prediction of threshold exceedances-is established from long time series of one or more observables of the same system. The prediction skill is measured by a summary index of the ROC curve that relates the hit- and false alarm rates. Our results for the examined systems suggest that exceedances of higher thresholds are more predictable; or in other words: rare large magnitude, i.e., extreme, events are more predictable than frequent typical events. We find this to hold provided that the bin size for binning time series data is optimized, but not necessarily otherwise. This can be viewed as a confirmation of a counterintuitive (and seemingly contrafactual) statement that was previously formulated for more simple autoregressive stochastic processes. However, we argue that for dynamical systems in general it may be typical only, but not universally true. We argue that when there is a sufficient amount of data depending on the precision of observation, the skill of a class of data-driven categoric predictions of threshold exceedances approximates the skill of the analogous model-driven prediction, assuming strictly no model errors. Therefore, stronger extremes in terms of higher threshold levels are more predictable both in case of data- and model-driven prediction. Furthermore, we show that a quantity commonly regarded as a measure of predictability, the finite-time maximal Lyapunov exponent, does not correspond directly to the ROC-based measure of prediction skill when they are viewed as functions of the prediction lead time and the threshold level. This points to the fact that even if the Lyapunov exponent as an intrinsic property of the system, measuring the instability of trajectories, determines predictability

  8. Stochastic analysis of epidemics on adaptive time varying networks

    NASA Astrophysics Data System (ADS)

    Kotnis, Bhushan; Kuri, Joy

    2013-06-01

    Many studies investigating the effect of human social connectivity structures (networks) and human behavioral adaptations on the spread of infectious diseases have assumed either a static connectivity structure or a network which adapts itself in response to the epidemic (adaptive networks). However, human social connections are inherently dynamic or time varying. Furthermore, the spread of many infectious diseases occur on a time scale comparable to the time scale of the evolving network structure. Here we aim to quantify the effect of human behavioral adaptations on the spread of asymptomatic infectious diseases on time varying networks. We perform a full stochastic analysis using a continuous time Markov chain approach for calculating the outbreak probability, mean epidemic duration, epidemic reemergence probability, etc. Additionally, we use mean-field theory for calculating epidemic thresholds. Theoretical predictions are verified using extensive simulations. Our studies have uncovered the existence of an “adaptive threshold,” i.e., when the ratio of susceptibility (or infectivity) rate to recovery rate is below the threshold value, adaptive behavior can prevent the epidemic. However, if it is above the threshold, no amount of behavioral adaptations can prevent the epidemic. Our analyses suggest that the interaction patterns of the infected population play a major role in sustaining the epidemic. Our results have implications on epidemic containment policies, as awareness campaigns and human behavioral responses can be effective only if the interaction levels of the infected populace are kept in check.

  9. Recruitment dynamics in adaptive social networks

    PubMed Central

    Shkarayev, Maxim S.; Schwartz, Ira B.; Shaw, Leah B.

    2013-01-01

    We model recruitment in adaptive social networks in the presence of birth and death processes. Recruitment is characterized by nodes changing their status to that of the recruiting class as a result of contact with recruiting nodes. Only a susceptible subset of nodes can be recruited. The recruiting individuals may adapt their connections in order to improve recruitment capabilities, thus changing the network structure adaptively. We derive a mean field theory to predict the dependence of the growth threshold of the recruiting class on the adaptation parameter. Furthermore, we investigate the effect of adaptation on the recruitment level, as well as on network topology. The theoretical predictions are compared with direct simulations of the full system. We identify two parameter regimes with qualitatively different bifurcation diagrams depending on whether nodes become susceptible frequently (multiple times in their lifetime) or rarely (much less than once per lifetime). PMID:25395989

  10. Local adaptation in the ventral photoreceptors of Limulus

    PubMed Central

    1975-01-01

    Local adaptation was demonstrated in the ventral photoreceptors of Lumulus using either flashes or continuous illumination. Spots of light locally desensitized the region of the photoreceptor on which they were focused. In dark-adapted photoreceptors where "quantum bumps" were clearly discernible, local adaptation of the quantum bumps was observed. Local adaptation could induce differences of threshold of 1 decade over distances of 50-80 mum. With continuous local illumination these gradients could be maintained from 2 s to 30 min. In addition, the decrease in time scale associated with light adaptation was also found to be localized to the region of illumination. PMID:1194890

  11. Thresholds in Xeric Hydrology and Biogeochemistry

    NASA Astrophysics Data System (ADS)

    Meixner, T.; Brooks, P. D.; Simpson, S. C.; Soto, C. D.; Yuan, F.; Turner, D.; Richter, H.

    2011-12-01

    Due to water limitation, thresholds in hydrologic and biogeochemical processes are common in arid and semi-arid systems. Some of these thresholds such as those focused on rainfall runoff relationships have been well studied. However to gain a full picture of the role that thresholds play in driving the hydrology and biogeochemistry of xeric systems a full view of the entire array of processes at work is needed. Here a walk through the landscape of xeric systems will be conducted illustrating the powerful role of hydrologic thresholds on xeric system biogeochemistry. To understand xeric hydro-biogeochemistry two key ideas need to be focused on. First, it is important to start from a framework of reaction and transport. Second an understanding of the temporal and spatial components of thresholds that have a large impact on hydrologic and biogeochemical fluxes needs to be offered. In the uplands themselves episodic rewetting and drying of soils permits accelerated biogeochemical processing but also more gradual drainage of water through the subsurface than expected in simple conceptions of biogeochemical processes. Hydrologic thresholds (water content above hygroscopic) results in a stop start nutrient spiral of material across the landscape since runoff connecting uplands to xeric perennial riparian is episodic and often only transports materials a short distance (100's of m). This episodic movement results in important and counter-intuitive nutrient inputs to riparian zones but also significant processing and uptake of nutrients. The floods that transport these biogeochemicals also result in significant input to riparian groundwater and may be key to sustaining these critical ecosystems. Importantly the flood driven recharge process itself is a threshold process dependent on flood characteristics (floods greater than 100 cubic meters per second) and antecedent conditions (losing to near neutral gradients). Floods also appear to influence where arid and semi

  12. Threshold Things That Think: Authorisation for Resharing

    NASA Astrophysics Data System (ADS)

    Peeters, Roel; Kohlweiss, Markulf; Preneel, Bart

    As we are evolving towards ubiquitous computing, users carry an increasing number of mobile devices with sensitive information. The security of this information can be protected using threshold cryptography, in which secret computations are shared between multiple devices. Threshold cryptography can be made more robust by resharing protocols, which allow recovery from partial compromises. This paper introduces user-friendly and secure protocols for the authorisation of resharing protocols. We present both automatic and manual protocols, utilising a group manual authentication protocol to add a new device. We analyse the security of these protocols: our analysis considers permanent and temporary compromises, denial of service attacks and manual authentications errors of the user.

  13. Methods for threshold determination in multiplexed assays

    SciTech Connect

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

    2014-06-24

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

  14. Connector adapter

    NASA Technical Reports Server (NTRS)

    Hacker, Scott C. (Inventor); Dean, Richard J. (Inventor); Burge, Scott W. (Inventor); Dartez, Toby W. (Inventor)

    2007-01-01

    An adapter for installing a connector to a terminal post, wherein the connector is attached to a cable, is presented. In an embodiment, the adapter is comprised of an elongated collet member having a longitudinal axis comprised of a first collet member end, a second collet member end, an outer collet member surface, and an inner collet member surface. The inner collet member surface at the first collet member end is used to engage the connector. The outer collet member surface at the first collet member end is tapered for a predetermined first length at a predetermined taper angle. The collet includes a longitudinal slot that extends along the longitudinal axis initiating at the first collet member end for a predetermined second length. The first collet member end is formed of a predetermined number of sections segregated by a predetermined number of channels and the longitudinal slot.

  15. Adaptive VFH

    NASA Astrophysics Data System (ADS)

    Odriozola, Iñigo; Lazkano, Elena; Sierra, Basi

    2011-10-01

    This paper investigates the improvement of the Vector Field Histogram (VFH) local planning algorithm for mobile robot systems. The Adaptive Vector Field Histogram (AVFH) algorithm has been developed to improve the effectiveness of the traditional VFH path planning algorithm overcoming the side effects of using static parameters. This new algorithm permits the adaptation of planning parameters for the different type of areas in an environment. Genetic Algorithms are used to fit the best VFH parameters to each type of sector and, afterwards, every section in the map is labelled with the sector-type which best represents it. The Player/Stage simulation platform has been chosen for making all sort of tests and to prove the new algorithm's adequateness. Even though there is still much work to be carried out, the developed algorithm showed good navigation properties and turned out to be softer and more effective than the traditional VFH algorithm.

  16. Adaptive sampler

    DOEpatents

    Watson, B.L.; Aeby, I.

    1980-08-26

    An adaptive data compression device for compressing data is described. The device has a frequency content, including a plurality of digital filters for analyzing the content of the data over a plurality of frequency regions, a memory, and a control logic circuit for generating a variable rate memory clock corresponding to the analyzed frequency content of the data in the frequency region and for clocking the data into the memory in response to the variable rate memory clock.

  17. Adaptive sampler

    DOEpatents

    Watson, Bobby L.; Aeby, Ian

    1982-01-01

    An adaptive data compression device for compressing data having variable frequency content, including a plurality of digital filters for analyzing the content of the data over a plurality of frequency regions, a memory, and a control logic circuit for generating a variable rate memory clock corresponding to the analyzed frequency content of the data in the frequency region and for clocking the data into the memory in response to the variable rate memory clock.

  18. Comparison between intensity- duration thresholds and cumulative rainfall thresholds for the forecasting of landslide

    NASA Astrophysics Data System (ADS)

    Lagomarsino, Daniela; Rosi, Ascanio; Rossi, Guglielmo; Segoni, Samuele; Catani, Filippo

    2014-05-01

    This work makes a quantitative comparison between the results of landslide forecasting obtained using two different rainfall threshold models, one using intensity-duration thresholds and the other based on cumulative rainfall thresholds in an area of northern Tuscany of 116 km2. The first methodology identifies rainfall intensity-duration thresholds by means a software called MaCumBA (Massive CUMulative Brisk Analyzer) that analyzes rain-gauge records, extracts the intensities (I) and durations (D) of the rainstorms associated with the initiation of landslides, plots these values on a diagram, and identifies thresholds that define the lower bounds of the I-D values. A back analysis using data from past events can be used to identify the threshold conditions associated with the least amount of false alarms. The second method (SIGMA) is based on the hypothesis that anomalous or extreme values of rainfall are responsible for landslide triggering: the statistical distribution of the rainfall series is analyzed, and multiples of the standard deviation (σ) are used as thresholds to discriminate between ordinary and extraordinary rainfall events. The name of the model, SIGMA, reflects the central role of the standard deviations in the proposed methodology. The definition of intensity-duration rainfall thresholds requires the combined use of rainfall measurements and an inventory of dated landslides, whereas SIGMA model can be implemented using only rainfall data. These two methodologies were applied in an area of 116 km2 where a database of 1200 landslides was available for the period 2000-2012. The results obtained are compared and discussed. Although several examples of visual comparisons between different intensity-duration rainfall thresholds are reported in the international literature, a quantitative comparison between thresholds obtained in the same area using different techniques and approaches is a relatively undebated research topic.

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

    PubMed Central

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

    2010-01-01

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

  20. Adaptive antennas

    NASA Astrophysics Data System (ADS)

    Barton, P.

    1987-04-01

    The basic principles of adaptive antennas are outlined in terms of the Wiener-Hopf expression for maximizing signal to noise ratio in an arbitrary noise environment; the analogy with generalized matched filter theory provides a useful aid to understanding. For many applications, there is insufficient information to achieve the above solution and thus non-optimum constrained null steering algorithms are also described, together with a summary of methods for preventing wanted signals being nulled by the adaptive system. The three generic approaches to adaptive weight control are discussed; correlation steepest descent, weight perturbation and direct solutions based on sample matrix conversion. The tradeoffs between hardware complexity and performance in terms of null depth and convergence rate are outlined. The sidelobe cancellor technique is described. Performance variation with jammer power and angular distribution is summarized and the key performance limitations identified. The configuration and performance characteristics of both multiple beam and phase scan array antennas are covered, with a brief discussion of performance factors.

  1. Dynamics of adaptation at high luminances: adaptation is faster after luminance decrements than after luminance increments.

    PubMed

    Poot, L; Snippe, H P; van Hateren, J H

    1997-09-01

    As is well known, dark adaptation in the human visual system is much slower than is recovery from darkness. We show that at high photopic luminances the situation is exactly opposite. First, we study detection thresholds for a small light flash, at various delays from decrement and increment steps in background luminance. Light adaptation is nearly complete within 100 ms after luminance decrements but takes much longer after luminance increments. Second, we compare sensitivity after equally visible pulses or steps in the adaptation luminance and find that detectability is initially the same but recovers much faster for pulses than for increment steps. This suggests that, whereas any residual threshold elevation after a step shows the incomplete luminance adaptation, the initial threshold elevation is caused by the temporal contrast of the background steps and pulses. This hypothesis is further substantiated in a third experiment, whereby we show that manipulating the contrast of a transition between luminances affects only the initial part of the threshold curve, and not later stages.

  2. On the two steps threshold selection for over-threshold modelling of extreme events

    NASA Astrophysics Data System (ADS)

    Bernardara, Pietro; Mazas, Franck; Weiss, Jerome; Andreewsky, Marc; Kergadallan, Xavier; Benoit, Michel; Hamm, Luc

    2013-04-01

    The estimation of the probability of occurrence of extreme events is traditionally achieved by fitting a probability distribution on a sample of extreme observations. In particular, the extreme value theory (EVT) states that values exceeding a given threshold converge through a Generalized Pareto Distribution (GPD) if the original sample is composed of independent and identically distributed values. However, the temporal series of sea and ocean variables usually show strong temporal autocorrelation. Traditionally, in order to select independent events for the following statistical analysis, the concept of a physical threshold is introduced: events that excess that threshold are defined as "extreme events". This is the so-called "Peak Over a Threshold (POT)" sampling, widely spread in the literature and currently used for engineering applications among many others. In the past, the threshold for the statistical sampling of extreme values asymptotically convergent toward GPD and the threshold for the physical selection of independent extreme events were confused, as the same threshold was used for both sampling data and to meet the hypothesis of extreme value convergence, leading to some incoherencies. In particular, if the two steps are performed simultaneously, the number of peaks over the threshold can increase but also decrease when the threshold decreases. This is logic in a physical point of view, since the definition of the sample of "extreme events" changes, but is not coherent with the statistical theory. We introduce a two-steps threshold selection for over-threshold modelling, aiming to discriminate (i) a physical threshold for the selection of extreme and independent events, and (ii) a statistical threshold for the optimization of the coherence with the hypothesis of the EVT. The former is a physical events identification procedure (also called "declustering") aiming at selecting independent extreme events. The latter is a purely statistical optimization

  3. Potency matters: thresholds govern endocrine activity.

    PubMed

    Borgert, Christopher J; Baker, Stephen P; Matthews, John C

    2013-10-01

    Whether thresholds exist for endocrine active substances and for endocrine disrupting effects of exogenous chemicals has been posed as a question for regulatory policy by the European Union. This question arises from a concern that the endocrine system is too complex to allow estimations of safe levels of exposure to any chemical with potential endocrine activity, and a belief that any such chemical can augment, retard, or disrupt the normal background activity of endogenous hormones. However, vital signaling functions of the endocrine system require it to continuously discriminate the biological information conveyed by potent endogenous hormones from a more concentrated background of structurally similar, endogenous molecules with low hormonal potential. This obligatory ability to discriminate important hormonal signals from background noise can be used to define thresholds for induction of hormonal effects, without which normal physiological functions would be impossible. From such thresholds, safe levels of exposure can be estimated. This brief review highlights how the fundamental principles governing hormonal effects - affinity, efficacy, potency, and mass action - dictate the existence of thresholds and why these principles also define the potential that exogenous chemicals might have to interfere with normal endocrine functioning.

  4. Anaerobic threshold in total artificial heart animals.

    PubMed

    Chiang, B Y; Pantalos, G; Burns, G L; Long, J W; Khanwilkar, P S; Everett, S D; Mohammad, S F; Olsen, D B

    1994-01-01

    The anaerobic threshold represents an objective measure of functional capacity and is useful in assessment of pulmonary and cardiovascular dysfunction. This study determined the anaerobic threshold in total artificial heart animals and evaluated the performance of the total artificial heart system. Five animals with total artificial hearts were put under incremental exercise testing after exercise training. The intensity of exercise ranged from 2.0 to 4.5 km/hr, with an increment of 0.5 km/hr every 3 min. The anaerobic threshold was 6.72 +/- 0.84 ml/kg/min as detected by the lactate method, and 6.48 +/- 0.79 by the CO2 method. The value of the anaerobic threshold in total artificial heart animals implies that the performance capacity of a total artificial heart is not sufficient to meet the oxygen requirements of vigorously exercising skeletal muscle. The protocol does not allow for driving parameter changes during exercise, and this situation, combined with the manual mode of the control system used, was inadequate to allow the total artificial heart animals to exercise more vigorously. Using an automatic control mode might be helpful, as well as considering the relationship between indices of oxygen metabolism, such as oxygen delivery, oxygen consumption, and oxygen extraction rate, in the control algorithms in total artificial heart control systems.

  5. Speech reception thresholds in various interference conditions

    NASA Astrophysics Data System (ADS)

    Carr, Suzanne P.; Colburn, H. Steven

    2001-05-01

    Speech intelligibility is integral to human verbal communication; however, our understanding of the effects of competing noise, room reverberation, and frequency range restriction is incomplete. Using virtual stimuli, the dependence of intelligibility threshold levels on the extent of room reverberation, the relative locations of speech target and masking noise, and the available frequency content of the speech and the masking noise is explored. Speech-shaped masking noise and target sentences have three spectral conditions: wideband, high pass above 2-kHz, and low pass below 2-kHz. The 2-kHz cutoff was chosen to approximately bisect the range of frequencies most important in speech, and the high pass noise condition simulates high-frequency hearing loss. Reverberation conditions include a pseudo-anechoic case, a moderately reverberant ``classroom'' case, and a very reverberant ``bathroom'' case. Both binaural and monaural intelligibility are measured. Preliminary results show that source separation decreases thresholds, reverberation increases thresholds, and low frequency noise reverberates more in the rooms, contributing to increasing thresholds along with the effects of the upward spread of masking. The energetic effects of reverberation are explored. [Work supported by NIH DC00100.

  6. Auricular electrical stimulation and dental pain threshold.

    PubMed Central

    Simmons, M. S.; Oleson, T. D.

    1993-01-01

    A modified double-blind evaluation of naloxone reversibility of dental analgesia produced by auricular electrical stimulation (AES) was examined in 40 subjects assigned randomly to one of four groups: AES followed by saline (AS), AES followed by naloxone (AN), placebo AES followed by saline (PS), and placebo AES followed by naloxone (PN). Dental pain threshold was tested using a hand-held dental pulp tester. A second investigator administered the true or placebo AES using an electrical stimulator. A third investigator injected intravenously saline or naloxone. The subjects and investigators 1 and 3 were blind to all treatment conditions. A repeated measures analysis of variance revealed a significant difference among the four groups. The AES groups exhibited a statistically significant 18% elevation of pain threshold, whereas the two placebo stimulation groups (PS and PN) remained essentially unchanged. The mean pain threshold increased to more than 23% for group AS, but fell to less than 12% for the subjects in group AN, who were given naloxone. These findings indicate a small but significant elevation of pain threshold by AES, an effect partially blocked by naloxone, suggesting an endogenous opioid system as one mechanism for AES analgesia. Images Figure 1 Figure 2 PMID:8185085

  7. Identification of Threshold Concepts for Biochemistry

    ERIC Educational Resources Information Center

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

    2014-01-01

    Threshold concepts (TCs) are concepts that, when mastered, represent a transformed understanding of a discipline without which the learner cannot progress. We have undertaken a process involving more than 75 faculty members and 50 undergraduate students to identify a working list of TCs for biochemistry. The process of identifying TCs for…

  8. A Cognitive Approach to Threshold Concepts

    ERIC Educational Resources Information Center

    Walker, Guy

    2013-01-01

    This paper asks a fundamental question: what is happening inside the mind of the undergraduate during teaching and learning experiences, and how should curricula be designed to support it? A number of concepts lend themselves to providing an answer, principle among which is the relatively recent idea of Threshold Concepts. In this paper we attempt…

  9. Threshold Concepts in Finance: Conceptualizing the Curriculum

    ERIC Educational Resources Information Center

    Hoadley, Susan; Tickle, Leonie; Wood, Leigh N.; Kyng, Tim

    2015-01-01

    Graduates with well-developed capabilities in finance are invaluable to our society and in increasing demand. Universities face the challenge of designing finance programmes to develop these capabilities and the essential knowledge that underpins them. Our research responds to this challenge by identifying threshold concepts that are central to…

  10. 40 CFR 98.431 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...-Charged Equipment or Closed-Cell Foams § 98.431 Reporting threshold. Any importer or exporter of fluorinated GHGs contained in pre-charged equipment or closed-cell foams who meets the requirements of § 98.2... or closed-cell foams....

  11. 40 CFR 98.431 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...-Charged Equipment or Closed-Cell Foams § 98.431 Reporting threshold. Any importer or exporter of fluorinated GHGs contained in pre-charged equipment or closed-cell foams who meets the requirements of § 98.2... or closed-cell foams....

  12. 40 CFR 98.431 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...-Charged Equipment or Closed-Cell Foams § 98.431 Reporting threshold. Any importer or exporter of fluorinated GHGs contained in pre-charged equipment or closed-cell foams who meets the requirements of § 98.2... or closed-cell foams....

  13. 40 CFR 98.91 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Electronics Manufacturing § 98.91 Reporting threshold. (a) You must report GHG emissions under this subpart if electronics manufacturing production processes, as defined in.... Rather than using the calculation methodologies in § 98.93 to calculate emissions from...

  14. 40 CFR 98.91 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Electronics Manufacturing § 98.91 Reporting threshold. (a) You must report GHG emissions under this subpart if electronics manufacturing production processes, as defined in.... Rather than using the calculation methodologies in § 98.93 to calculate emissions from...

  15. 40 CFR 98.91 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Electronics Manufacturing § 98.91 Reporting threshold. (a) You must report GHG emissions under this subpart if electronics manufacturing production processes, as defined in.... Rather than using the calculation methodologies in § 98.93 to calculate emissions from...

  16. 40 CFR 98.91 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Electronics Manufacturing § 98.91 Reporting threshold. (a) You must report GHG emissions under this subpart if electronics manufacturing production processes, as defined in.... Rather than using the calculation methodologies in § 98.93 to calculate emissions from...

  17. Phi Delta Kappa at the Threshold

    ERIC Educational Resources Information Center

    Walling, Donovan R.

    2006-01-01

    Since its fraternal origins a century ago, Phi Delta Kappa (PDK) International has been foremost a society of individuals joined together in professional collegiality and dedicated to tenets of leadership, service, and research in education. As PDK crosses the threshold into its second century, that early spirit of association lit in 1906, like…

  18. 40 CFR 98.121 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Fluorinated Gas Production § 98.121 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a fluorinated gas production process that... in § 98.2(a)(2), calculate process emissions from fluorinated gas production using uncontrolled...

  19. 40 CFR 98.121 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Fluorinated Gas Production § 98.121 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a fluorinated gas production process that... in § 98.2(a)(2), calculate process emissions from fluorinated gas production using uncontrolled...

  20. 40 CFR 98.431 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Reporting threshold. 98.431 Section 98.431 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Importers and Exporters of Fluorinated Greenhouse Gases Contained in...

  1. 40 CFR 98.121 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Fluorinated Gas Production § 98.121 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a fluorinated gas production process that... in § 98.2(a)(2), calculate process emissions from fluorinated gas production using uncontrolled...

  2. 40 CFR 98.121 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Fluorinated Gas Production § 98.121 Reporting threshold. You must report GHG emissions under this subpart if your facility contains a fluorinated gas production process that... in § 98.2(a)(2), calculate process emissions from fluorinated gas production using uncontrolled...

  3. Gastric Residual Volume: Rethinking the Threshold.

    PubMed

    Emami Zeydi, Amir; Sharafkhani, Mohammad; Armat, Mohammad Reza

    2016-01-01

    There are many challenges related to enteral feedings of the mechanically ventilated patient. Among the most often debated issues is the threshold for gastric residual volume before further feeding. This brief article considers the factors to be considered and reviews current thinking on the topic. PMID:27575801

  4. Photoproduction of the phi (1020) near threshold

    SciTech Connect

    D.J. Tedeschi; M. Huertas

    2000-05-12

    Photoproduction of phi mesons at photon energies below 2 GeV were measured at the CLAS detector in Hall B of Thomas Jefferson National Accelerator Facility. Preliminary differential cross sections are reported from the proton near threshold. The measurement are extended to the region in the variable t where production mechanisms beyond that of diffraction are expected to become significant.

  5. Characterizing the Switching Thresholds of Magnetophoretic Transistors.

    PubMed

    Abedini-Nassab, Roozbeh; Joh, Daniel Y; Van Heest, Melissa A; Yi, John S; Baker, Cody; Taherifard, Zohreh; Margolis, David M; Garcia, J Victor; Chilkoti, Ashutosh; Murdoch, David M; Yellen, Benjamin B

    2015-10-28

    The switching thresholds of magnetophoretic transistors for sorting cells in microfluidic environments are characterized. The transistor operating conditions require short 20-30 mA pulses of electrical current. By demonstrating both attractive and repulsive transistor modes, a single transistor architecture is used to implement the full write cycle for importing and exporting single cells in specified array sites. PMID:26349853

  6. Near threshold behavior of photoelectron satellite intensities

    SciTech Connect

    Shirley, D.A.; Becker, U.; Heimann, P.A.; Langer, B.

    1987-09-01

    The historical background and understanding of photoelectron satellite peaks is reviewed, using He(n), Ne(1s), Ne(2p), Ar(1s), and Ar(3s) as case studies. Threshold studies are emphasized. The classification of electron correlation effects as either ''intrinsic'' or ''dynamic'' is recommended. 30 refs., 7 figs.

  7. 40 CFR 98.461 - Reporting threshold.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) MANDATORY GREENHOUSE GAS REPORTING Industrial Waste Landfills § 98.461 Reporting threshold. You must report GHG emissions under this subpart if your facility contains an industrial waste landfill meeting the...)(2), the emissions from the industrial waste landfill are to be determined using the...

  8. Temperature thresholds to freeze damage in cranberry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sprinkler irrigation is required for frost protection of cranberry and is arguably the most important cultural practice used in production of the crop. A study was initiated in a commercial bed of ‘Stevens’ cranberry located in Langlois, OR. The objectives are to identify temperature thresholds to...

  9. Handwriting Automaticity: The Search for Performance Thresholds

    ERIC Educational Resources Information Center

    Medwell, Jane; Wray, David

    2014-01-01

    Evidence is accumulating that handwriting has an important role in written composition. In particular, handwriting automaticity appears to relate to success in composition. This relationship has been little explored in British contexts and we currently have little idea of what threshold performance levels might be. In this paper, we report on two…

  10. Mandated Reporting Thresholds for Community Professionals

    ERIC Educational Resources Information Center

    Crowell, Kathryn; Levi, Benjamin H.

    2012-01-01

    This study examines how community-based mandated reporters understand and interpret "reasonable suspicion", the standard threshold for mandated reporting of suspected child abuse. Respondents were asked to identify the probability necessary for "suspicion of child abuse" to constitute "reasonable suspicion". Data were analyzed for internal…

  11. Fractal Threshold Behavior in Vacuum Gravitational Collapse

    NASA Astrophysics Data System (ADS)

    Szybka, Sebastian J.; Chmaj, Tadeusz

    2008-03-01

    We present the numerical evidence for fractal threshold behavior in the five dimensional vacuum Einstein equations satisfying the cohomogeneity-two triaxial Bianchi type-IX ansatz. In other words, we show that a flip of the wings of a butterfly may influence the process of the black hole formation.

  12. 40 CFR 98.461 - Reporting threshold.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... generation corrected for oxidation as determined using Equation TT-6 of this subpart times the global warming... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Reporting threshold. 98.461 Section 98.461 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS...

  13. 40 CFR 98.461 - Reporting threshold.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... generation corrected for oxidation as determined using Equation TT-6 of this subpart times the global warming... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Reporting threshold. 98.461 Section 98.461 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS...

  14. 40 CFR 98.461 - Reporting threshold.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... generation corrected for oxidation as determined using Equation TT-6 of this subpart times the global warming... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Reporting threshold. 98.461 Section 98.461 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS...

  15. 20 CFR 418.1105 - What is the threshold?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 2 2010-04-01 2010-04-01 false What is the threshold? 418.1105 Section 418... What is the threshold? (a) The threshold is a level of modified adjusted gross income above which the... gross income threshold is $80,000 for individuals with a Federal income tax filing status of...

  16. 20 CFR 418.2105 - What is the threshold?

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 20 Employees' Benefits 2 2013-04-01 2013-04-01 false What is the threshold? 418.2105 Section 418... Adjustment Amount § 418.2105 What is the threshold? (a) The threshold is a level of modified adjusted gross... years 2011 through and including 2019, the modified adjusted gross income threshold is $85,000...

  17. 20 CFR 418.1105 - What is the threshold?

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 20 Employees' Benefits 2 2013-04-01 2013-04-01 false What is the threshold? 418.1105 Section 418... What is the threshold? (a) The threshold is a level of modified adjusted gross income above which the... gross income threshold is $80,000 for individuals with a Federal income tax filing status of...

  18. Identifying Threshold Concepts in the Careers of Educational Developers

    ERIC Educational Resources Information Center

    Timmermans, Julie A.

    2014-01-01

    The purpose of this multiple case study was to identify threshold concepts in the careers of educational developers. Twenty-one common threshold concepts emerged, with one threshold concept common among all participants: Facilitating a change process. The remaining 20 threshold concepts were captured in the following three categories: (1) Ways of…

  19. [Threshold values for chemicals to prevent disease].

    PubMed

    Schweinsberg, F

    1990-05-01

    Proper interpretation of threshold limit values should always take into account that such limits are not absolute, but rather subject to change depending on advances in scientific knowledge. Threshold limit values derived from toxicologic study are best suited to evaluation of health risks of chemicals in the environment. Although more toxicologic information than is currently available would be desirable for the establishment of limit values, this should not prevent agreement on limits for more substances. "Better" threshold limit values would be forthcoming from epidemiologic studies, which are particularly rare in the FRG. Prospective studies measure current exposure; but appearance of detrimental health effects generally requires a lengthy latency period (e.g., decades in the case of cancer or cardiovascular disease). Threshold limit values permit monitoring and, if necessary, restriction of anthropogenic activity. Such restrictions are necessary, as shown by severe health damage which has occurred in the past (e.g., angiosarcoma due to vinyl chloride or neurogenic damage due to mercury in the workplace, tumors due to arsenic in drinking water, and methemoglobinemia in infants due to nitrite or renal damage due to cadmium in food). Evaluation of potential detrimental health effects for threshold limit values in environmental media is difficult because the effective dose cannot be determined. Monitoring of such limit values, which have already been incorporated into West German law, is relatively easy to implement, however (e.g. continuous outdoor air quality sampling and measurement, and periodic analysis of drinking water and foodstuffs). Since such monitoring may be performed close to the source, preventive measures should be easy to implement. Biological threshold limit values (biological monitoring) are essential to effective evaluation of the health effects of chemicals. Such limits should be established for more substances. When biological limit values

  20. Adherence to thresholds: overdiagnosis of left ventricular noncompaction cardiomyopathy.

    PubMed

    Kini, Vinay; Ferrari, Victor A; Han, Yuchi; Jha, Saurabh

    2015-08-01

    Thresholds derived from quantification in imaging are increasingly used to define disease. This derivation is not an exact science. When one uses a threshold to define a disease, one does not clearly demarcate disease from normality because the threshold includes overlapping spectra of mild disease and normality. Thus, use of the threshold will mislabel normal individuals with disease. In this perspective, we will describe how the threshold has been derived for left ventricular noncompaction cardiomyopathy, the statistical biases in the design of studies used to derive the threshold, and the dangers of overdiagnosis when the threshold is used to rule out left ventricular noncompaction cardiomyopathy.

  1. Rapid evolution of a polyphenic threshold.

    PubMed

    Moczek, Armin P; Nijhout, H Frederik

    2003-01-01

    Polyphenisms are thought to play an important role in the evolution of phenotypic diversity and the origin of morphological and behavioral novelties. However, the extent to which polyphenic developmental mechanisms evolve in natural populations is unknown. Here we contrast patterns of male phenotype expression in native and exotic and ancestral and descendant populations of the horn polyphenic beetle, Onthophagus taurus. Males in this species express two alternative morphologies in response to larval feeding conditions. Favorable conditions cause males to grow larger than a threshold body size and to develop a pair of horns on their heads. Males that encounter relatively poor conditions do not reach this threshold size and remain hornless. We show that exotic and native populations of O. taurus differ significantly in the body size threshold that separates alternative male phenotypes. Comparison with archival museum collections and additional samples obtained from the native range of O. taurus suggests that allometric differences between exotic and native populations do not reflect preexisting variation in the native range of this species. Instead, our data suggest that threshold divergences between exotic and native populations have evolved in less than 40 years since the introduction to a new habitat and have proceeded in opposite directions in two exotic ranges of this species. Finally, we show that the kind and magnitude of threshold divergence between native and exotic populations are similar to differences normally observed between species. Our results support the view that certain components of the developmental control mechanism that underlie polyphenic development can evolve rapidly in natural populations and may provide important avenues for phenotypic differentiation and diversification in nature. We discuss the role of developmental control mechanisms in the origin of allometric diversification and explore potential evolutionary mechanisms that could

  2. Intervention thresholds for osteoporosis in the UK.

    PubMed

    Kanis, John A; Borgstrom, Frederik; Zethraeus, Niklas; Johnell, Olof; Oden, Anders; Jönsson, Bengt

    2005-01-01

    The aim of this study was to determine the threshold of fracture probability at which interventions became cost-effective in women based on data from the UK. We modelled the effects of an intervention costing pound 350 per year given for 5 years that decreased the risk of all osteoporotic fractures by 35% followed by a waning of effect (offset time) for a further 5 years. Sensitivity analyses included a range of treatment duration (3-10 years), intervention costs (pound 300-400/year) and offset times (0-15 years). Data on costs and risks were from the UK. Costs included direct costs, but excluded indirect costs due to morbidity. A threshold for cost-effectiveness of pound 30,000/QALY gained was used. With the base case ( pound 350 per year; 35% efficacy) treatment in women was cost-effective with a 10-year hip fracture probability that ranged from 1.1% at the age of 50 years to 9.0% at the age of 85 years. Intervention thresholds were sensitive to the assumed costs and offset time. The exclusion of osteoporotic fractures other than hip fracture significantly increased the cost-effectiveness ratio because of the substantial morbidity from such other fractures, particularly at younger ages. Cost-effective scenarios were found for women at the threshold for osteoporosis from the age of 60 years. Treatment of established osteoporosis was cost-effective irrespective of age. We conclude that the inclusion of all osteoporotic fractures has a marked effect on intervention thresholds, that these vary with age and that available treatments can be targeted cost-effectively to individuals from the UK at moderately increased fracture risk.

  3. Anomalous threshold reduction from <100> uniaxial strain for a low-threshold Ge laser

    NASA Astrophysics Data System (ADS)

    Sukhdeo, David S.; Kim, Yeji; Gupta, Shashank; Saraswat, Krishna C.; Dutt, Birendra Raj; Nam, Donguk

    2016-11-01

    We theoretically investigate the effect of <100> uniaxial strain on a Ge-on-Si laser. We predict a dramatic ~200x threshold reduction upon applying sufficient uniaxial tensile strain to Ge. This anomalous reduction is explained by how the topmost valence bands split and become anisotropic with uniaxial tensile strain. Approximately 3.2% uniaxial strain is required to achieve this anomalous threshold reduction for 1×1019 cm-3 n-type doping, and a complex interaction between strain and n-type doping is observed. Achieving this critical uniaxial strain level for the anomalous threshold reduction is dramatically more relevant to practical devices than realizing a direct band gap.

  4. Evaluation of thresholding techniques for segmenting scaffold images in tissue engineering

    NASA Astrophysics Data System (ADS)

    Rajagopalan, Srinivasan; Yaszemski, Michael J.; Robb, Richard A.

    2004-05-01

    Tissue engineering attempts to address the ever widening gap between the demand and supply of organ and tissue transplants using natural and biomimetic scaffolds. The regeneration of specific tissues aided by synthetic materials is dependent on the structural and morphometric properties of the scaffold. These properties can be derived non-destructively using quantitative analysis of high resolution microCT scans of scaffolds. Thresholding of the scanned images into polymeric and porous phase is central to the outcome of the subsequent structural and morphometric analysis. Visual thresholding of scaffolds produced using stochastic processes is inaccurate. Depending on the algorithmic assumptions made, automatic thresholding might also be inaccurate. Hence there is a need to analyze the performance of different techniques and propose alternate ones, if needed. This paper provides a quantitative comparison of different thresholding techniques for segmenting scaffold images. The thresholding algorithms examined include those that exploit spatial information, locally adaptive characteristics, histogram entropy information, histogram shape information, and clustering of gray-level information. The performance of different techniques was evaluated using established criteria, including misclassification error, edge mismatch, relative foreground error, and region non-uniformity. Algorithms that exploit local image characteristics seem to perform much better than those using global information.

  5. Vestibular thresholds for yaw rotation about an earth-vertical axis as a function of frequency.

    PubMed

    Grabherr, Luzia; Nicoucar, Keyvan; Mast, Fred W; Merfeld, Daniel M

    2008-04-01

    Perceptual direction detection thresholds for yaw rotation about an earth-vertical axis were measured at seven frequencies (0.05, 0.1, 0.2, 0.5, 1, 2, and 5 Hz) in seven subjects in the dark. Motion stimuli consisted of single cycles of sinusoidal acceleration and were generated by a motion platform. An adaptive two-alternative categorical forced-choice procedure was used. The subjects had to indicate by button presses whether they perceived yaw rotation to the left or to the right. Thresholds were measured using a 3-down, 1-up staircase paradigm. Mean yaw rotation velocity thresholds were 2.8 deg s(-1) for 0.05 Hz, 2.5 deg s(-1) for 0.1 Hz, 1.7 deg s(-1) for 0.2 Hz, 0.7 deg s(-1) for 0.5 Hz, 0.6 deg s(-1) for 1 Hz, 0.4 deg s(-1) for 2 Hz, and 0.6 deg s(-1) for 5 Hz. The results show that motion thresholds increase at 0.2 Hz and below and plateau at 0.5 Hz and above. Increasing velocity thresholds at lower frequencies qualitatively mimic the high-pass characteristics of the semicircular canals, since the increase at 0.2 Hz and below would be consistent with decreased gain/sensitivity observed in the VOR at lower frequencies. In fact, the measured dynamics are consistent with a high pass filter having a threshold plateau of 0.71 deg s(-1) and a cut-off frequency of 0.23 Hz, which corresponds to a time constant of approximately 0.70 s. These findings provide no evidence for an influence of velocity storage on perceptual yaw rotation thresholds.

  6. Storm thresholds for the Spanish Gulf of Cádiz coast

    NASA Astrophysics Data System (ADS)

    Plomaritis, Theocharis; Del Rio, Laura; Benavente, Javier; Valladares, Maria

    2010-05-01

    In this study critical thresholds are defined for storm impacts along the Spanish coast of the Gulf of Cádiz. The thresholds correspond to the minimum wave-tidal conditions necessary to produce significant morphological changes on beaches and dunes and/or damage on coastal infrastructure or human occupation. Threshold definition was performed by computing theoretical sea level variations during storms and comparing them with the topography of the study area and the location of infrastructures at a local level. Specifically, the elevations of the berm, the dune foot and the entrance of existing washovers were selected as threshold parameters. The total sea level variation generated by a storm event was estimated as the sum of the tidal level, the wind-induced setup, the barometric setup and the wave-associated sea level variation (wave setup and runup), assuming a minimum interaction between the different processes. These components were calculated on the basis of parameterisations that were adapted to the specific oceanographic and environmental conditions of the Gulf of Cadiz. Validation of the obtained results was performed for a range of coastal settings over the study area. The obtained thresholds for beach morphological changes in spring tide conditions range between a significant wave height of 2.4 and 3.7 m, while for dune foot erosion are around 4.8 m and for damage to infrastructure around 6.3 m. In case of neap tide conditions these values are increased on average by 50% over the areas with large tidal range. The calculated thresholds constitute snapshots of risk conditions within a certain time framework. Beach and nearshore zones are extremely dynamic, and also the characteristics of occupation on the coast change over time, so critical storm thresholds will change accordingly and therefore will need to be updated.

  7. Measuring Input Thresholds on an Existing Board

    NASA Technical Reports Server (NTRS)

    Kuperman, Igor; Gutrich, Daniel G.; Berkun, Andrew C.

    2011-01-01

    A critical PECL (positive emitter-coupled logic) interface to Xilinx interface needed to be changed on an existing flight board. The new Xilinx input interface used a CMOS (complementary metal-oxide semiconductor) type of input, and the driver could meet its thresholds typically, but not in worst-case, according to the data sheet. The previous interface had been based on comparison with an external reference, but the CMOS input is based on comparison with an internal divider from the power supply. A way to measure what the exact input threshold was for this device for 64 inputs on a flight board was needed. The measurement technique allowed an accurate measurement of the voltage required to switch a Xilinx input from high to low for each of the 64 lines, while only probing two of them. Directly driving an external voltage was considered too risky, and tests done on any other unit could not be used to qualify the flight board. The two lines directly probed gave an absolute voltage threshold calibration, while data collected on the remaining 62 lines without probing gave relative measurements that could be used to identify any outliers. The PECL interface was forced to a long-period square wave by driving a saturated square wave into the ADC (analog to digital converter). The active pull-down circuit was turned off, causing each line to rise rapidly and fall slowly according to the input s weak pull-down circuitry. The fall time shows up as a change in the pulse width of the signal ready by the Xilinx. This change in pulse width is a function of capacitance, pulldown current, and input threshold. Capacitance was known from the different trace lengths, plus a gate input capacitance, which is the same for all inputs. The pull-down current is the same for all inputs including the two that are probed directly. The data was combined, and the Excel solver tool was used to find input thresholds for the 62 lines. This was repeated over different supply voltages and

  8. Differential equation models for sharp threshold dynamics.

    PubMed

    Schramm, Harrison C; Dimitrov, Nedialko B

    2014-01-01

    We develop an extension to differential equation models of dynamical systems to allow us to analyze probabilistic threshold dynamics that fundamentally and globally change system behavior. We apply our novel modeling approach to two cases of interest: a model of infectious disease modified for malware where a detection event drastically changes dynamics by introducing a new class in competition with the original infection; and the Lanchester model of armed conflict, where the loss of a key capability drastically changes the effectiveness of one of the sides. We derive and demonstrate a step-by-step, repeatable method for applying our novel modeling approach to an arbitrary system, and we compare the resulting differential equations to simulations of the system's random progression. Our work leads to a simple and easily implemented method for analyzing probabilistic threshold dynamics using differential equations. PMID:24184349

  9. Is ingested inorganic arsenic a "threshold" carcinogen?

    PubMed

    Abernathy, C O; Chappell, W R; Meek, M E; Gibb, H; Guo, H R

    1996-02-01

    Ingested inorganic arsenic (As) is known to be a human carcinogen. An intriguing question is whether there is a threshold for the carcinogenic effects of As, i.e., is there a level below which it does not induce the development of cancer(s)? This Roundtable will discuss the United States Environmental Protection Agency's As risk assessment using the Taiwan data from different viewpoints. It will also consider the hypothesis that there is a threshold for As and data for or against this hypothesis. For example, some scientists believe that epidemiological data cannot answer this question, while others feel that different study designs and larger sampling will provide adequate data. Reasons for each position are given. This Roundtable discussion demonstrates the controversy surrounding the use of the Taiwan data for risk assessment.

  10. Anomalous threshold laws in quantum sticking.

    PubMed

    Clougherty, Dennis P

    2003-11-28

    It has been stated that for a short-ranged surface interaction, the probability of a low-energy particle sticking to a surface always vanishes as s approximately k with k-->0 where k=sqrt[E]. Deviations from this so-called universal threshold law are derived using a linear model of particle-surface scattering. The Fredholm theory of integral equations is used to find the global conditions necessary for a convergent solution. The exceptional case of a zero-energy resonance is considered in detail. Anomalous threshold laws, where s approximately k(1+alpha),alpha>0 as k-->0, are shown to arise from a soft gap in the weighted density of states of excitations; alpha is determined by the behavior of the weighted density of states near the binding energy. PMID:14683254

  11. Anomalous Threshold Laws in Quantum Sticking

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis P.

    2003-11-01

    It has been stated that for a short-ranged surface interaction, the probability of a low-energy particle sticking to a surface always vanishes as s˜k with k→0 where k=√(E). Deviations from this so-called universal threshold law are derived using a linear model of particle-surface scattering. The Fredholm theory of integral equations is used to find the global conditions necessary for a convergent solution. The exceptional case of a zero-energy resonance is considered in detail. Anomalous threshold laws, where s˜k1+α,α>0 as k→0, are shown to arise from a soft gap in the weighted density of states of excitations; α is determined by the behavior of the weighted density of states near the binding energy.

  12. Anomalous Threshold Laws in Quantum Sticking

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis

    2004-03-01

    It has been stated that for a short-ranged surface interaction, the probability of a low-energy particle sticking to a surface always vanishes as s ˜ k with k→ 0 where k=√E. Deviations from this so-called universal threshold law are derived using a linear model of particle-surface scattering. The Fredholm theory of integral equations is used to find the global conditions necessary for a convergent solution. The exceptional case of a zero-energy resonance is considered in detail. Anomalous threshold laws, where s ˜ k^1+α, α > 0 as k→ 0, are shown to arise from a soft gap in the weighted density of states of excitations; α is determined by the behavior of the weighted density of states near the binding energy.

  13. Semiclassical approaches to below-threshold harmonics

    SciTech Connect

    Hostetter, James A.; Tate, Jennifer L.; Schafer, Kenneth J.; Gaarde, Mette B.

    2010-08-15

    We study the generation of below-threshold harmonics in a model atom by extending the three-step semiclassical model of harmonic generation to include effects of the atomic potential. We explore the generalization of semiclassical trajectories of the electron in the presence of the combined laser-atom potential and calculate the intensity-dependent dipole phase associated with these trajectories. Our results are in good agreement with fully quantum mechanical calculations, as well as with recent experimental observations. We show that the so-called long trajectory readily generalizes to below-threshold harmonic generation and is relatively insensitive to the choice of initial conditions. We also find that the short trajectory can only lead to low-energy harmonics for electrons that have been released close to the ion core in a process that is closer to multiphoton than to tunnel ionization.

  14. Detection thresholds for small haptic effects

    NASA Astrophysics Data System (ADS)

    Dosher, Jesse A.; Hannaford, Blake

    2002-02-01

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

  15. Ku-band radar threshold analysis

    NASA Technical Reports Server (NTRS)

    Weber, C. L.; Polydoros, A.

    1979-01-01

    The statistics of the CFAR threshold for the Ku-band radar was determined. Exact analytical results were developed for both the mean and standard deviations in the designated search mode. The mean value is compared to the results of a previously reported simulation. The analytical results are more optimistic than the simulation results, for which no explanation is offered. The normalized standard deviation is shown to be very sensitive to signal-to-noise ratio and very insensitive to the noise correlation present in the range gates of the designated search mode. The substantial variation in the CFAR threshold is dominant at large values of SNR where the normalized standard deviation is greater than 0.3. Whether or not this significantly affects the resulting probability of detection is a matter which deserves additional attention.

  16. Sub-microWatt threshold nanoisland lasers

    PubMed Central

    Jang, Hoon; Karnadi, Indra; Pramudita, Putu; Song, Jung-Hwan; Soo Kim, Ki; Lee, Yong-Hee

    2015-01-01

    Ultralow threshold nanolasers have been sought after as power efficient light sources in photonic integrated circuits. Here a single-cell nanobeam laser with a nanoisland quantum well is proposed and demonstrated. Continuous operation at 1.5 μm is achieved at room temperature with an ultralow lasing threshold of 210 nW in absorbed power. The size of the active medium is reduced to 0.7 × 0.25 × 0.02 μm3 by removing the absorptive quantum well region surrounding the central cavity. Relatively thick (420 nm) InP slabs are employed to improve the thermal and mechanical characteristics. The nanoisland-based structures will provide a new platform to engineer fundamental light–matter interactions by controlling the size and the location of the nanoemitters, allowing the realization of highly efficient nanophotonic devices. PMID:26391800

  17. Sub-microWatt threshold nanoisland lasers.

    PubMed

    Jang, Hoon; Karnadi, Indra; Pramudita, Putu; Song, Jung-Hwan; Kim, Ki Soo; Lee, Yong-Hee

    2015-01-01

    Ultralow threshold nanolasers have been sought after as power efficient light sources in photonic integrated circuits. Here a single-cell nanobeam laser with a nanoisland quantum well is proposed and demonstrated. Continuous operation at 1.5 μm is achieved at room temperature with an ultralow lasing threshold of 210 nW in absorbed power. The size of the active medium is reduced to 0.7 × 0.25 × 0.02 μm(3) by removing the absorptive quantum well region surrounding the central cavity. Relatively thick (420 nm) InP slabs are employed to improve the thermal and mechanical characteristics. The nanoisland-based structures will provide a new platform to engineer fundamental light-matter interactions by controlling the size and the location of the nanoemitters, allowing the realization of highly efficient nanophotonic devices. PMID:26391800

  18. Differential equation models for sharp threshold dynamics.

    PubMed

    Schramm, Harrison C; Dimitrov, Nedialko B

    2014-01-01

    We develop an extension to differential equation models of dynamical systems to allow us to analyze probabilistic threshold dynamics that fundamentally and globally change system behavior. We apply our novel modeling approach to two cases of interest: a model of infectious disease modified for malware where a detection event drastically changes dynamics by introducing a new class in competition with the original infection; and the Lanchester model of armed conflict, where the loss of a key capability drastically changes the effectiveness of one of the sides. We derive and demonstrate a step-by-step, repeatable method for applying our novel modeling approach to an arbitrary system, and we compare the resulting differential equations to simulations of the system's random progression. Our work leads to a simple and easily implemented method for analyzing probabilistic threshold dynamics using differential equations.

  19. Ultracompact low-threshold organic laser.

    PubMed

    Deotare, Parag B; Mahony, Thomas S; Bulović, Vladimir

    2014-11-25

    We report an ultracompact low-threshold laser with an Alq3:DCM host:guest molecular organic thin film gain layer. The device uses a photonic crystal nanobeam cavity which provides a high quality factor to mode volume (Q/V) ratio and increased spontaneous emission factor along with a small footprint. Lasing is observed with a threshold of 4.2 μJ/cm(2) when pumped by femtosecond pulses of λ = 400 nm wavelength light. We also model the dynamics of the laser and show good agreement with the experimental data. The inherent waveguide geometry of the structure enables easy on-chip integration with potential applications in biochemical sensing, inertial sensors, and data communication.

  20. Global warming, convective threshold and false thermostats

    NASA Astrophysics Data System (ADS)

    Williams, Ian N.; Pierrehumbert, Raymond T.; Huber, Matthew

    2009-11-01

    We demonstrate a theoretically expected behavior of the tropical sea surface temperature probability density function (PDF) in future and past (Eocene) greenhouse climate simulations. To first order this consists of a shift to warmer temperatures as climate warms, without change of shape of the PDF. The behavior is tied to a shift of the temperature for deep convection onset. Consequently, the threshold for appearance of high clouds and associated radiative forcing shifts along with temperature. An excess entropy coordinate provides a reference to which the onset of deep convection is invariant, and gives a compact description of SST changes and cloud feedbacks suitable for diagnostics and as a basis for simplified climate models. The results underscore that the typically skewed appearance of tropical SST histograms, with a sharp drop-off above some threshold value, should not be taken as evidence for tropical thermostats.

  1. Edith Wharton's threshold phobia and two worlds.

    PubMed

    Holtzman, Deanna; Kulish, Nancy

    2014-08-01

    The American novelist Edith Wharton suffered an unusual childhood neurotic symptom, a fear of crossing thresholds, a condition that might be called a "threshold phobia." This symptom is identified and examined in autobiographical material, letters, diaries, and selected literary fiction and nonfiction left by Wharton to arrive at a formulation not previously drawn together. A fascinating theme-living or being trapped between "two worlds"-runs through much of the writer's life and work. The phobia is related to this theme, and both can be linked more broadly to certain sexual conflicts in women. This understanding of Wharton's phobia, it is argued, throws new light on the developmental issues and conflicts related to the female "oedipal" or triadic phase, characterized by the need to negotiate the two worlds of mother and of father. PMID:25059543

  2. Adaptive compressive sensing camera

    NASA Astrophysics Data System (ADS)

    Hsu, Charles; Hsu, Ming K.; Cha, Jae; Iwamura, Tomo; Landa, Joseph; Nguyen, Charles; Szu, Harold

    2013-05-01

    We have embedded Adaptive Compressive Sensing (ACS) algorithm on Charge-Coupled-Device (CCD) camera based on the simplest concept that each pixel is a charge bucket, and the charges comes from Einstein photoelectric conversion effect. Applying the manufactory design principle, we only allow altering each working component at a minimum one step. We then simulated what would be such a camera can do for real world persistent surveillance taking into account of diurnal, all weather, and seasonal variations. The data storage has saved immensely, and the order of magnitude of saving is inversely proportional to target angular speed. We did design two new components of CCD camera. Due to the matured CMOS (Complementary metal-oxide-semiconductor) technology, the on-chip Sample and Hold (SAH) circuitry can be designed for a dual Photon Detector (PD) analog circuitry for changedetection that predicts skipping or going forward at a sufficient sampling frame rate. For an admitted frame, there is a purely random sparse matrix [Φ] which is implemented at each bucket pixel level the charge transport bias voltage toward its neighborhood buckets or not, and if not, it goes to the ground drainage. Since the snapshot image is not a video, we could not apply the usual MPEG video compression and Hoffman entropy codec as well as powerful WaveNet Wrapper on sensor level. We shall compare (i) Pre-Processing FFT and a threshold of significant Fourier mode components and inverse FFT to check PSNR; (ii) Post-Processing image recovery will be selectively done by CDT&D adaptive version of linear programming at L1 minimization and L2 similarity. For (ii) we need to determine in new frames selection by SAH circuitry (i) the degree of information (d.o.i) K(t) dictates the purely random linear sparse combination of measurement data a la [Φ]M,N M(t) = K(t) Log N(t).

  3. Near threshold studies of photoelectron satellites

    SciTech Connect

    Heimann, P.A.

    1986-11-01

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

  4. Monolayer semiconductor nanocavity lasers with ultralow thresholds

    DOE PAGES

    Wu, Sanfeng; Buckley, Sonia; Schaibley, John R.; Feng, Liefeng; Yan, Jiaqiang; Mandrus, David G.; Hatami, Fariba; Yao, Wang; Vučković, Jelena; Majumdar, Arka; et al

    2015-03-16

    Engineering the electromagnetic environment of a nanoscale light emitter by a photonic cavity can significantly enhance its spontaneous emission rate through cavity quantum electrodynamics in the Purcell regime. This effect can greatly reduce the lasing threshold of the emitter1–5, providing the ultimate low-threshold laser system with small footprint, low power consumption and ultrafast modulation. A state-of-the-art ultra-low threshold nanolaser has been successfully developed though embedding quantum dots into photonic crystal cavity (PhCC)6–8. However, several core challenges impede the practical applications of this architecture, including the random positions and compositional fluctuations of the dots7, extreme difficulty in current injection8, and lackmore » of compatibility with electronic circuits7,8. Here, we report a new strategy to lase, where atomically thin crystalline semiconductor, i.e., a tungsten-diselenide (WSe2) monolayer, is nondestructively and deterministically introduced as a gain medium at the surface of a pre-fabricated PhCC. A new type of continuous-wave nanolaser operating in the visible regime is achieved with an optical pumping threshold as low as 27 nW at 130 K, similar to the value achieved in quantum dot PhCC lasers7. The key to the lasing action lies in the monolayer nature of the gain medium, which confines direct-gap excitons to within 1 nm of the PhCC surface. The surface-gain geometry allows unprecedented accessibilities to multi-functionalize the gain, enabling electrically pumped operation. Our scheme is scalable and compatible with integrated photonics for on-chip optical communication technologies.« less

  5. Kitaev's Zd-code threshold estimates

    NASA Astrophysics Data System (ADS)

    Duclos-Cianci, Guillaume; Poulin, David

    2013-06-01

    We study the quantum error correction threshold of Kitaev's toric code over the group Zd subject to a generalized bit-flip noise. This problem requires special decoding techniques, and for this purpose we generalize the renormalization-group method we introduced previously [G. Duclos-Cianci and D. Poulin, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.050504 104, 050504 (2010) and IEEE Information Theory Workshop, Dublin (2010), p. 1] for Z2 topological codes.

  6. Heavy quark masses from production near threshold

    NASA Astrophysics Data System (ADS)

    Maier, Andreas

    2016-08-01

    In this paper, we review the precision determination of the bottom and top quark masses from the total pair-production cross-section near threshold. The theory prediction of the cross-section includes QCD corrections up to third-order. We further discuss the combined impact of Higgs corrections, the QED Coulomb potential, non-resonant production, and P-wave production on the extraction of top quark properties.

  7. Monolayer semiconductor nanocavity lasers with ultralow thresholds

    NASA Astrophysics Data System (ADS)

    Wu, Sanfeng; Buckley, Sonia; Schaibley, John R.; Feng, Liefeng; Yan, Jiaqiang; Mandrus, David G.; Hatami, Fariba; Yao, Wang; Vučković, Jelena; Majumdar, Arka; Xu, Xiaodong

    2015-04-01

    Engineering the electromagnetic environment of a nanometre-scale light emitter by use of a photonic cavity can significantly enhance its spontaneous emission rate, through cavity quantum electrodynamics in the Purcell regime. This effect can greatly reduce the lasing threshold of the emitter, providing a low-threshold laser system with small footprint, low power consumption and ultrafast modulation. An ultralow-threshold nanoscale laser has been successfully developed by embedding quantum dots into a photonic crystal cavity (PCC). However, several challenges impede the practical application of this architecture, including the random positions and compositional fluctuations of the dots, extreme difficulty in current injection, and lack of compatibility with electronic circuits. Here we report a new lasing strategy: an atomically thin crystalline semiconductor--that is, a tungsten diselenide monolayer--is non-destructively and deterministically introduced as a gain medium at the surface of a pre-fabricated PCC. A continuous-wave nanolaser operating in the visible regime is thereby achieved with an optical pumping threshold as low as 27 nanowatts at 130 kelvin, similar to the value achieved in quantum-dot PCC lasers. The key to the lasing action lies in the monolayer nature of the gain medium, which confines direct-gap excitons to within one nanometre of the PCC surface. The surface-gain geometry gives unprecedented accessibility and hence the ability to tailor gain properties via external controls such as electrostatic gating and current injection, enabling electrically pumped operation. Our scheme is scalable and compatible with integrated photonics for on-chip optical communication technologies.

  8. Power threshold for neutral beam current drive

    SciTech Connect

    Politzer, P.A. ); Porter, G.D. )

    1989-10-02

    For fully noninductive current drive in tokamaks using neutral beams, there is a power and density threshold condition, setting a minimum value for P{sup 3/2}/n{sup 2}. If this condition is not met, stationary state cannot occur, and a tokamak discharge will collapse. This is a consequence of the coupling between current and electron temperature, or between current drive efficiency and energy confinement time. 4 figs.

  9. Monolayer semiconductor nanocavity lasers with ultralow thresholds.

    PubMed

    Wu, Sanfeng; Buckley, Sonia; Schaibley, John R; Feng, Liefeng; Yan, Jiaqiang; Mandrus, David G; Hatami, Fariba; Yao, Wang; Vučković, Jelena; Majumdar, Arka; Xu, Xiaodong

    2015-04-01

    Engineering the electromagnetic environment of a nanometre-scale light emitter by use of a photonic cavity can significantly enhance its spontaneous emission rate, through cavity quantum electrodynamics in the Purcell regime. This effect can greatly reduce the lasing threshold of the emitter, providing a low-threshold laser system with small footprint, low power consumption and ultrafast modulation. An ultralow-threshold nanoscale laser has been successfully developed by embedding quantum dots into a photonic crystal cavity (PCC). However, several challenges impede the practical application of this architecture, including the random positions and compositional fluctuations of the dots, extreme difficulty in current injection, and lack of compatibility with electronic circuits. Here we report a new lasing strategy: an atomically thin crystalline semiconductor--that is, a tungsten diselenide monolayer--is non-destructively and deterministically introduced as a gain medium at the surface of a pre-fabricated PCC. A continuous-wave nanolaser operating in the visible regime is thereby achieved with an optical pumping threshold as low as 27 nanowatts at 130 kelvin, similar to the value achieved in quantum-dot PCC lasers. The key to the lasing action lies in the monolayer nature of the gain medium, which confines direct-gap excitons to within one nanometre of the PCC surface. The surface-gain geometry gives unprecedented accessibility and hence the ability to tailor gain properties via external controls such as electrostatic gating and current injection, enabling electrically pumped operation. Our scheme is scalable and compatible with integrated photonics for on-chip optical communication technologies. PMID:25778703

  10. What physics does affect the MRI threshold

    SciTech Connect

    Ilgisonis, V. I.; Lakhin, V. P.; Khalzov, I. V.; Smolyakov, A. I.

    2010-06-16

    Several physical effects, which can considerably decrease the magnetorotational instability (MRI) threshold are discussed. First, we show that MRI features are changed significantly in non-uniform magnetic field. Second, the buoyancy effect is shown to can be destabilizing for azimuthal flow of a resistive plasma. Third, we demonstrate that the rotating fluid may be unstable with respect to non-axisymmetric modes at much lower rotation velocities than with respect to usual symmetric modes.

  11. Monolayer semiconductor nanocavity lasers with ultralow thresholds

    SciTech Connect

    Wu, Sanfeng; Buckley, Sonia; Schaibley, John R.; Feng, Liefeng; Yan, Jiaqiang; Mandrus, David G.; Hatami, Fariba; Yao, Wang; Vučković, Jelena; Majumdar, Arka; Xu, Xiaodong

    2015-03-16

    Engineering the electromagnetic environment of a nanoscale light emitter by a photonic cavity can significantly enhance its spontaneous emission rate through cavity quantum electrodynamics in the Purcell regime. This effect can greatly reduce the lasing threshold of the emitter1–5, providing the ultimate low-threshold laser system with small footprint, low power consumption and ultrafast modulation. A state-of-the-art ultra-low threshold nanolaser has been successfully developed though embedding quantum dots into photonic crystal cavity (PhCC)6–8. However, several core challenges impede the practical applications of this architecture, including the random positions and compositional fluctuations of the dots7, extreme difficulty in current injection8, and lack of compatibility with electronic circuits7,8. Here, we report a new strategy to lase, where atomically thin crystalline semiconductor, i.e., a tungsten-diselenide (WSe2) monolayer, is nondestructively and deterministically introduced as a gain medium at the surface of a pre-fabricated PhCC. A new type of continuous-wave nanolaser operating in the visible regime is achieved with an optical pumping threshold as low as 27 nW at 130 K, similar to the value achieved in quantum dot PhCC lasers7. The key to the lasing action lies in the monolayer nature of the gain medium, which confines direct-gap excitons to within 1 nm of the PhCC surface. The surface-gain geometry allows unprecedented accessibilities to multi-functionalize the gain, enabling electrically pumped operation. Our scheme is scalable and compatible with integrated photonics for on-chip optical communication technologies.

  12. Anaerobic Threshold and Salivary α-amylase during Incremental Exercise.

    PubMed

    Akizuki, Kazunori; Yazaki, Syouichirou; Echizenya, Yuki; Ohashi, Yukari

    2014-07-01

    [Purpose] The purpose of this study was to clarify the validity of salivary α-amylase as a method of quickly estimating anaerobic threshold and to establish the relationship between salivary α-amylase and double-product breakpoint in order to create a way to adjust exercise intensity to a safe and effective range. [Subjects and Methods] Eleven healthy young adults performed an incremental exercise test using a cycle ergometer. During the incremental exercise test, oxygen consumption, carbon dioxide production, and ventilatory equivalent were measured using a breath-by-breath gas analyzer. Systolic blood pressure and heart rate were measured to calculate the double product, from which double-product breakpoint was determined. Salivary α-amylase was measured to calculate the salivary threshold. [Results] One-way ANOVA revealed no significant differences among workloads at the anaerobic threshold, double-product breakpoint, and salivary threshold. Significant correlations were found between anaerobic threshold and salivary threshold and between anaerobic threshold and double-product breakpoint. [Conclusion] As a method for estimating anaerobic threshold, salivary threshold was as good as or better than determination of double-product breakpoint because the correlation between anaerobic threshold and salivary threshold was higher than the correlation between anaerobic threshold and double-product breakpoint. Therefore, salivary threshold is a useful index of anaerobic threshold during an incremental workload.

  13. A threshold theory of the humor response.

    PubMed

    Epstein, Robert; Joker, Veronica R

    2007-01-01

    The humor response has long been considered mysterious, and it is given relatively little attention in modern experimental psychology, in spite of the fact that numerous studies suggest that it has substantial benefits for mood and health. Existing theories of humor fail to account for some of the most basic humor phenomena. On most occasions when a humor response occurs, certain verbal or visual stimuli (the "setup" stimuli, which function as an establishing operation) must precede a critical stimulus (such as a "punch line" or the final panel or critical feature of a cartoon), which then occasions a sudden "revelation" or "understanding"; this revelation is often accompanied by the humor response. We suggest that the setup stimuli increase the strength of the revelatory response to a point just below the threshold of awareness and that the critical stimulus, properly designed and timed, edges the revelatory response to a point just above threshold. We also suggest that it is this threshold phenomenon that produces most instances of the humor response. We discuss these issues in the context of some notable humor of Carl Rogers and B. F. Skinner.

  14. Explaining the length threshold of polyglutamine aggregation

    NASA Astrophysics Data System (ADS)

    De Los Rios, Paolo; Hafner, Marc; Pastore, Annalisa

    2012-06-01

    The existence of a length threshold, of about 35 residues, above which polyglutamine repeats can give rise to aggregation and to pathologies, is one of the hallmarks of polyglutamine neurodegenerative diseases such as Huntington’s disease. The reason why such a minimal length exists at all has remained one of the main open issues in research on the molecular origins of such classes of diseases. Following the seminal proposals of Perutz, most research has focused on the hunt for a special structure, attainable only above the minimal length, able to trigger aggregation. Such a structure has remained elusive and there is growing evidence that it might not exist at all. Here we review some basic polymer and statistical physics facts and show that the existence of a threshold is compatible with the modulation that the repeat length imposes on the association and dissociation rates of polyglutamine polypeptides to and from oligomers. In particular, their dramatically different functional dependence on the length rationalizes the very presence of a threshold and hints at the cellular processes that might be at play, in vivo, to prevent aggregation and the consequent onset of the disease.

  15. Threshold photodetachment spectroscopy of negative ions

    SciTech Connect

    Kitsopoulos, T.N.

    1991-12-01

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

  16. Are there threshold numbers for protected forests?

    PubMed

    Bücking, Winfried

    2003-01-01

    Maintenance of forests biodiversity is intimately related on the one hand to the species and community-related ecological needs of flora and fauna living in the forest and on the other hand the disturbance regimes of the specific forest type. Populations of plants and animals need minimum biotopes for their ontogeny; for assuring their survival they depend on a minimum of connected suitable areas. Specific traits of forest types are based upon different disturbance regimes, ranging from small-scale internal processes (e.g. regeneration, growth, senescence, mortality, gap dynamics) generating normal forest cycles (i.e. regular sequences, e.g. regeneration, optimum, decay phases) to potentially chaotic and large-scale, frequently external, disturbances, e.g. fire, landslides, or beetle attacks. Forest protection may meet the needs of these very different demands by varied protected area networks going from small (>100 ha), medium (1000 ha) to large-scale reserves (National Parks, several thousands of ha). According to this triple protection concept not only graduated threshold numbers, but also threshold sizes and threshold areas for forest protection must be defined. To realize this concept the regional and local conditions (forest area, forest cover percentage, forest composition, socio-economic targets) must always be taken in consideration.

  17. Auricular Acupressure Can Modulate Pain Threshold

    PubMed Central

    Santoro, Antonietta; Nori, Stefania Lucia; Lorusso, Letizia; Secondulfo, Carmine; Monda, Marcellino; Viggiano, Andrea

    2015-01-01

    The objective of our study was to investigate if auriculotherapy (AT) can modulate pain threshold. In our experiments, AT consisted of placing Vaccaria seeds over the “fingers point” of one ear. Two groups of healthy volunteers were enrolled for the study. Each subject was asked to perform an autoalgometric test developed by our group on three occasions: before, 1 hour after, AT and 24 hours after AT. Participants of the first group received a 2-minute long session of AT, while participants of the second group received a 2-minute long session of sham treatment, consisting of a puncture/massage above the skin of the neck. The autoalgometric test consisted of applying an increasing pressure with the finger-tips and finger-backs of four fingers by the subjects themselves (i.e., eight sites were evaluated) against a round-shaped needle for two times: until a minimum pain sensation (first time, minimal test) or a maximally tolerable pain sensation (second time, maximal test). Our results showed a significant higher pain threshold in the maximal test at 24 hours after AT compared to sham treatment. This result indicates for the first time that AT can increase pain tolerability, rather than affecting the minimal pain threshold. PMID:26236378

  18. INFLUENCE OF MASS ON DISPLACEMENT THRESHOLD

    SciTech Connect

    Setyawan, Wahyu; Selby, A.; Nandipati, Giridhar; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.

    2014-12-30

    Molecular dynamics simulations are performed to investigate the effect of mass on displacement threshold energy in Cr, Mo, Fe and W. For each interatomic potential, the mass of the atoms is varied among those metals for a total of 16 combinations. The average threshold energy over all crystal directions is calculated within the irreducible crystal directions using appropriate weighting factors. The weighting factors account for the different number of equivalent directions among the grid points and the different solid angle coverage of each grid point. The grid points are constructed with a Miller index increment of 1/24 for a total of 325 points. For each direction, 10 simulations each with a different primary-knock-on atom are performed. The results show that for each interatomic potential, the average threshold energy is insensitive to the mass; i.e., the values are the same within the standard error. In the future, the effect of mass on high-energy cascades for a given interatomic potential will be investigated.

  19. Are there threshold numbers for protected forests?

    PubMed

    Bücking, Winfried

    2003-01-01

    Maintenance of forests biodiversity is intimately related on the one hand to the species and community-related ecological needs of flora and fauna living in the forest and on the other hand the disturbance regimes of the specific forest type. Populations of plants and animals need minimum biotopes for their ontogeny; for assuring their survival they depend on a minimum of connected suitable areas. Specific traits of forest types are based upon different disturbance regimes, ranging from small-scale internal processes (e.g. regeneration, growth, senescence, mortality, gap dynamics) generating normal forest cycles (i.e. regular sequences, e.g. regeneration, optimum, decay phases) to potentially chaotic and large-scale, frequently external, disturbances, e.g. fire, landslides, or beetle attacks. Forest protection may meet the needs of these very different demands by varied protected area networks going from small (>100 ha), medium (1000 ha) to large-scale reserves (National Parks, several thousands of ha). According to this triple protection concept not only graduated threshold numbers, but also threshold sizes and threshold areas for forest protection must be defined. To realize this concept the regional and local conditions (forest area, forest cover percentage, forest composition, socio-economic targets) must always be taken in consideration. PMID:12659802

  20. Automatic Classification of Kepler Threshold Crossing Events

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  1. A threshold theory of the humor response.

    PubMed

    Epstein, Robert; Joker, Veronica R

    2007-01-01

    The humor response has long been considered mysterious, and it is given relatively little attention in modern experimental psychology, in spite of the fact that numerous studies suggest that it has substantial benefits for mood and health. Existing theories of humor fail to account for some of the most basic humor phenomena. On most occasions when a humor response occurs, certain verbal or visual stimuli (the "setup" stimuli, which function as an establishing operation) must precede a critical stimulus (such as a "punch line" or the final panel or critical feature of a cartoon), which then occasions a sudden "revelation" or "understanding"; this revelation is often accompanied by the humor response. We suggest that the setup stimuli increase the strength of the revelatory response to a point just below the threshold of awareness and that the critical stimulus, properly designed and timed, edges the revelatory response to a point just above threshold. We also suggest that it is this threshold phenomenon that produces most instances of the humor response. We discuss these issues in the context of some notable humor of Carl Rogers and B. F. Skinner. PMID:22478488

  2. [Skin temperature and lactate threshold during muscle work in sportsmen].

    PubMed

    Akimov, E B; Son'kin, V D

    2011-01-01

    The purpose of the investigation was to estimate change of a thermal condition of an organism during exhausting work (maximal aerobic test) on cycle ergometer on the basis of studying of dynamics of temperature of a forehead skin. Regularly training 20 men have taken part in the research--sportsmen of various specializations (skiers, rock-climbers, boxers, etc.). Temperature of forehead skin was registered by infrared thermovision chamber Nec TH 9100SL. These results compared with the data of measurements of heart rate, gas exchange, the lactate concentration in peripheral blood, and also with anthropometrical characteristics. It was shown that on dynamics of skin temperature at maximal work load it was possible to divide all subjects into 2 unequal groups: 1 (2/3 subjects, the majority of which trains endurance) - after temperature decrease take place its smooth increase up to refusal ofwork; 2 (1/3 subjects, concerning various sports specializations)--from the moment of the beginning of active evaporation of sweat the temperature decreases to the work termination. In group 1 lactate threshold (lactate concentration in blood--4 mm/l) corresponds to the beginning of rise in temperature after its decrease as a result of sweat evaporation. In group 2 lactate threshold was necessary on a phase of decrease in temperature at the moment of active evaporation of sweat. Distinctions between groups in structure of correlation relationship between the measured indicators are revealed, inversion of a sign ofcorrelation quotient in some cases were shown. Thus significant distinctions between groups in the level of the working capacity indicators were not revealed. All it testifies to existence possibility at least two various successful strategy of urgent adaptation of system of thermoregulation to intense muscular work.

  3. Estimating nerve excitation thresholds to cutaneous electrical stimulation by finite element modeling combined with a stochastic branching nerve fiber model.

    PubMed

    Mørch, Carsten Dahl; Hennings, Kristian; Andersen, Ole Kæseler

    2011-04-01

    Electrical stimulation of cutaneous tissue through surface electrodes is an often used method for evoking experimental pain. However, at painful intensities both non-nociceptive Aβ-fibers and nociceptive Aδ- and C-fibers may be activated by the electrical stimulation. This study proposes a finite element (FE) model of the extracellular potential and stochastic branching fiber model of the afferent fiber excitation thresholds. The FE model described four horizontal layers; stratum corneum, epidermis, dermis, and hypodermal used to estimate the excitation threshold of Aβ-fibers terminating in dermis and Aδ-fibers terminating in epidermis. The perception thresholds of 11 electrodes with diameters ranging from 0.2 to 20 mm were modeled and assessed on the volar forearm of healthy human volunteers by an adaptive two-alternative forced choice algorithm. The model showed that the magnitude of the current density was highest for smaller electrodes and decreased through the skin. The excitation thresholds of the Aδ-fibers were lower than the excitation thresholds of Aβ-fibers when current was applied through small, but not large electrodes. The experimentally assessed perception threshold followed the lowest excitation threshold of the modeled fibers. The model confirms that preferential excitation of Aδ-fibers may be achieved by small electrode stimulation due to higher current density in the dermoepidermal junction. PMID:21207174

  4. Adaptive changes in visual cortex following prolonged contrast reduction

    PubMed Central

    Kwon, MiYoung; Legge, Gordon E.; Fang, Fang; Cheong, Allen M. Y.; He, Sheng

    2009-01-01

    How does prolonged reduction in retinal-image contrast affect visual-contrast coding? Recent evidence indicates that some forms of long-term visual deprivation result in compensatory perceptual and neural changes in the adult visual pathway. It has not been established whether changes due to contrast adaptation are best characterized as “contrast gain” or “response gain.” We present a theoretical rationale for predicting that adaptation to long-term contrast reduction should result in response gain. To test this hypothesis, normally sighted subjects adapted for four hours by viewing their environment through contrast-reducing goggles. During the adaptation period, the subjects went about their usual daily activities. Subjects' contrast-discrimination thresholds and fMRI BOLD responses in cortical areas V1 and V2 were obtained before and after adaptation. Following adaptation, we observed a significant decrease in contrast-discrimination thresholds, and significant increase in BOLD responses in V1 and V2. The observed interocular transfer of the adaptation effect suggests that the adaptation has a cortical origin. These results reveal a new kind of adaptability of the adult visual cortex, an adjustment in the gain of the contrast-response in the presence of a reduced range of stimulus contrasts, which is consistent with a response-gain mechanism. The adaptation appears to be compensatory, such that the precision of contrast coding is improved for low retinal-image contrasts. PMID:19271930

  5. Interaction of noise-induced permanent threshold shift and age-related threshold shift.

    PubMed

    Mills, J H; Boettcher, F A; Dubno, J R

    1997-03-01

    Current medical-legal practices as well as an international standard (ISO 1999) assume the permanent threshold shifts produced by exposure to noise add (in dB) to the threshold shifts caused by increased chronological age (presbyacusis). This assumption, known as the additivity rule, was tested in an animal model. Mongolian gerbils, born and raised in a quiet vivarium, were exposed at age 18 months to a 3.5-kHz pure tone for 1 h at 113 dB SPL. At 6-weeks post-exposure, permanent threshold shifts in the exposed ear were approximately 20 dB in the 4- to 8-kHz region. Thresholds in the nonexposed, control ear were unaffected by the exposure. Animals were then allowed to age in the quiet vivarium until age 36 months and then were retested. Thus in a given animal, aging-only effects were assessed in one ear (internal control) and noise-plus-aging effects were assessed in the other (test) ear. A second control was mean age-related threshold shift measured in 48 gerbils who were born and raised in the quiet vivarium. This group is referred to as a non-noise-exposed population (population control). Using the additivity rule, predictions with either the internal or population control significantly overestimated noise-plus-aging effects. Use of the ISO 1999 compression factor reduced the overestimations by 0-5 dB. The intensity rule produced the most accurate predictions. These results suggest that the interaction of noise-induced permanent threshold shift and age-related threshold shift is not straightforward and that current medical-legal methods using the additivity rule overestimate the contribution of "noise effects". PMID:9069635

  6. Image Watermarking Based on Adaptive Models of Human Visual Perception

    NASA Astrophysics Data System (ADS)

    Khawne, Amnach; Hamamoto, Kazuhiko; Chitsobhuk, Orachat

    This paper proposes a digital image watermarking based on adaptive models of human visual perception. The algorithm exploits the local activities estimated from wavelet coefficients of each subband to adaptively control the luminance masking. The adaptive luminance is thus delicately combined with the contrast masking and edge detection and adopted as a visibility threshold. With the proposed combination of adaptive visual sensitivity parameters, the proposed perceptual model can be more appropriate to the different characteristics of various images. The weighting function is chosen such that the fidelity, imperceptibility and robustness could be preserved without making any perceptual difference to the image quality.

  7. Distribution Characteristics of Normal Pure-Tone Thresholds

    PubMed Central

    Margolis, Robert H.; Wilson, Richard H.; Popelka, Gerald R.; Eikelboom, Robert H.; Swanepoel, De Wet; Saly, George L.

    2016-01-01

    Objective This study examined the statistical properties of normal air-conduction thresholds obtained with automated and manual audiometry to test the hypothesis that thresholds are normally distributed and to examine the distributions for evidence of bias in manual testing. Design Four databases were mined for normal thresholds. One contained audiograms obtained with an automated method. The other three were obtained with manual audiometry. Frequency distributions were examined for four test frequencies (250, 500, 1000, and 2000 Hz). Study Sample The analysis is based on 317,569 threshold determinations of 80,547 subjects from four clinical databases. Results Frequency distributions of thresholds obtained with automated audiometry are normal in form. Corrected for age, the mean thresholds are within 1.5 dB of Reference Equivalent Threshold Sound Pressure Levels. Frequency distributions of thresholds obtained by manual audiometry are shifted toward higher thresholds. Two of the three datasets obtained by manual audiometry are positively skewed. Conclusions The positive shift and skew of the manual audiometry data may result from tester bias. The striking scarcity of thresholds below 0 dB HL suggests that audiologists place less importance on identifying low thresholds than they do for higher-level thresholds. We refer to this as the Good Enough Bias and suggest that it may be responsible for differences in distributions of thresholds obtained by automated and manual audiometry. PMID:25938502

  8. Threshold concepts: implications for the management of natural resources

    USGS Publications Warehouse

    Guntenspergen, Glenn R.; Gross, John

    2014-01-01

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

  9. Category 3 threshold quantities for hazard categorization of nonreactor facilities

    SciTech Connect

    Mandigo, R.L.

    1996-02-13

    This document provides the information necessary to determine Hazard Category 3 threshold quantities for those isotopes of interest not listed in WHC-CM-4-46, Section 4, Table 1.''Threshold Quantities.''

  10. 78 FR 2675 - Revised Jurisdictional Thresholds of the Clayton Act

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-14

    ... From the Federal Register Online via the Government Publishing Office FEDERAL TRADE COMMISSION Revised Jurisdictional Thresholds of the Clayton Act AGENCY: Federal Trade Commission. ACTION: Notice. SUMMARY: The Federal Trade Commission announces the revised thresholds for interlocking...

  11. Patient Perceptions of Osteoporosis Treatment Thresholds

    PubMed Central

    Neuner, Joan; Schapira, Marilyn

    2014-01-01

    Objective Many older patients express concerns about medication risks, and have higher risk thresholds than physicians for cardiovascular preventive medications. We hypothesized that patients have relatively high risk thresholds for fracture preventive medications. Methods Women ≥60 years old were recruited from three primary care internal medicine clinics in Wisconsin. Participants were provided information regarding fracture risks and treatment risks and benefits, followed by a series of vignettes depicting a 70 year old woman at baseline fracture risks between 5–50%. Fracture risks were shown graphically and treatment side effects were provided for each vignette, and participants were asked to respond regarding whether they would accept treatment. The association of vignette treatment acceptance with participant beliefs regarding medication risks was examined in analyses adjusted for perceived risk of medications, patient numeracy and prior respondent experience with osteoporosis. Results The mean age of women in the cohort was 69.4 (S.D. 7.29). 91% were non-Hispanic whites, 34% reported a personal history of fracture, and 20.3% a history of osteoporosis. Subjects varied substantially in their responses to vignettes, but only 51% reported they would accept prescription osteoporosis treatment at the threshold currently recommended by national physician treatment guidelines, and fewer would accept treatment at lower risks. Belief that medications are generally not worth their risks was associated with lower acceptance of treatment at all levels of fracture risk. Conclusions There is substantial variability in preferences for postmenopausal osteoporosis treatment. Presentation of individualized fracture risks as recommended by current guidelines has potential to allow better targeting to higher-risk patients, but further work is needed regarding how to present this information and counsel patients. PMID:24488417

  12. Tissue damage thresholds during therapeutic electrical stimulation

    NASA Astrophysics Data System (ADS)

    Cogan, Stuart F.; Ludwig, Kip A.; Welle, Cristin G.; Takmakov, Pavel

    2016-04-01

    Objective. Recent initiatives in bioelectronic modulation of the nervous system by the NIH (SPARC), DARPA (ElectRx, SUBNETS) and the GlaxoSmithKline Bioelectronic Medicines effort are ushering in a new era of therapeutic electrical stimulation. These novel therapies are prompting a re-evaluation of established electrical thresholds for stimulation-induced tissue damage. Approach. In this review, we explore what is known and unknown in published literature regarding tissue damage from electrical stimulation. Main results. For macroelectrodes, the potential for tissue damage is often assessed by comparing the intensity of stimulation, characterized by the charge density and charge per phase of a stimulus pulse, with a damage threshold identified through histological evidence from in vivo experiments as described by the Shannon equation. While the Shannon equation has proved useful in assessing the likely occurrence of tissue damage, the analysis is limited by the experimental parameters of the original studies. Tissue damage is influenced by factors not explicitly incorporated into the Shannon equation, including pulse frequency, duty cycle, current density, and electrode size. Microelectrodes in particular do not follow the charge per phase and charge density co-dependence reflected in the Shannon equation. The relevance of these factors to tissue damage is framed in the context of available reports from modeling and in vivo studies. Significance. It is apparent that emerging applications, especially with microelectrodes, will require clinical charge densities that exceed traditional damage thresholds. Experimental data show that stimulation at higher charge densities can be achieved without causing tissue damage, suggesting that safety parameters for microelectrodes might be distinct from those defined for macroelectrodes. However, these increased charge densities may need to be justified by bench, non-clinical or clinical testing to provide evidence of device

  13. Nuclear Threshold States: Yesterday, Today, Tomorrow

    SciTech Connect

    Ogloblin, A. A.; Danilov, A. N.; Demyanova, A. S.; Belyaeva, T. L.; Goncharov, S. A.

    2010-04-30

    50 years ago exotic nuclear states with abnormally large radii located close to the thresholds of emission of nucleons or clusters were predicted. Recently a hypothesis of possible existence of alpha-particle Bose condensation was proposed. The 0{sup +}{sub 2}(7.65 MeV) state of {sup 12}C(so-called Hoyle state) is considered to be the prototype of such condensed state and have a dilute structure. We propose two methods for searching the alpha-condensate signatures in the Hoyle state and some other ones near the alpha-thresholds by using inelastic diffractive and rainbow scattering. Inelastic scattering of {sup 2}H, {sup 3}He, {sup 4}He, {sup 6}Li, and {sup 12}C on {sup 12}C was studied and the enhancement of the {sup 12}C radius in the Hoyle state relatively the ground state radius by a factor of 1.2 was demonstrated. Another signature of the condensate structure, 70% probability of all three alpha-particles to be in the s-state, was observed for the Hoyle state by studying the {sup 8}Be transfer reaction. The analogs of the Hoyle state with enhanced radii were identified in {sup 11}B and {sup 13}C. The proposed methods of measuring the nuclear radii allowed observation of neutron halos in the excited states of {sup 9}Be and {sup 13}C. The conception of abnormal dimensions of the threshold states finds its confirmation in many nuclear phenomena both well-known and new ones. One of the perspective domains of its manifestation are the nuclei heavier than {sup 100}Sn with N = Z, which are able to emit several alpha particles.

  14. Threshold power and energy confinement for ITER

    SciTech Connect

    Takizuka, T.

    1996-12-31

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

  15. Percolation threshold on planar Euclidean Gabriel graphs

    NASA Astrophysics Data System (ADS)

    Norrenbrock, Christoph

    2016-04-01

    In the present article, numerical simulations have been performed to find the bond and site percolation thresholds on two-dimensional Gabriel graphs (GG) for Poisson point processes. GGs belong to the family of "proximity graphs" and are discussed, e.g., in context of the construction of backbones for wireless ad-hoc networks. Finite-size scaling analyses have been performed to find the critical points and critical exponents ν, β and γ. The critical exponents obtained this way verify that the associated universality class is that of standard 2D percolation.

  16. Near Threshold Coincident Electrofission of Uranium -238.

    NASA Astrophysics Data System (ADS)

    Dowell, David Harry

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

  17. Technology Thresholds for Microgravity: Status and Prospects

    NASA Technical Reports Server (NTRS)

    Noever, D. A.

    1996-01-01

    The technological and economic thresholds for microgravity space research are estimated in materials science and biotechnology. In the 1990s, the improvement of materials processing has been identified as a national scientific priority, particularly for stimulating entrepreneurship. The substantial US investment at stake in these critical technologies includes six broad categories: aerospace, transportation, health care, information, energy, and the environment. Microgravity space research addresses key technologies in each area. The viability of selected space-related industries is critically evaluated and a market share philosophy is developed, namely that incremental improvements in a large markets efficiency is a tangible reward from space-based research.

  18. Level reduction and the quantum threshold theorem

    NASA Astrophysics Data System (ADS)

    Aliferis, Panagiotis (Panos)

    Computers have led society to the information age revolutionizing central aspects of our lives from production and communication to education and entertainment. There exist, however, important problems which are intractable with the computers available today and, experience teaches us, will remain so even with the more advanced computers we can envision for tomorrow.Quantum computers promise speedups to some of these important but classically intractable problems. Simulating physical systems, a problem of interest in a diverse range of areas from testing physical theories to understanding chemical reactions, and solving number factoring, a problem at the basis of cryptographic protocols that are used widely today on the internet, are examples of applications for which quantum computers, when built, will offer a great advantage over what is possible with classical computer technology.The construction of a quantum computer of sufficient scale to solve interesting problems is, however, especially challenging. The reason for this is that, by its very nature, operating a quantum computer will require the coherent control of the quantum state of a very large number of particles. Fortunately, the theory of quantum error correction and fault-tolerant quantum computation gives us confidence that such quantum states can be created, can be stored in memory and can also be manipulated provided the quantum computer can be isolated to a sufficient degree from sources of noise.One of the central results in the theory of fault-tolerant quantum computation, the quantum threshold theorem shows that a noisy quantum computer can accurately and efficiently simulate any ideal quantum computation provided that noise is weakly correlated and its strength is below a critical value known as the quantum accuracy threshold. This thesis provides a simpler and more transparent non-inductive proof of this theorem based on the concept of level reduction. This concept is also used in proving the

  19. Jost function description of near threshold resonances

    NASA Astrophysics Data System (ADS)

    Simbotin, I.; Shu, D.; Côté, R.

    2015-05-01

    The low energy behavior of cross sections for any scattering problem can be drastically affected by the presence of a resonance near the threshold. In this work, we show that any such strong dependence on energy can be accounted for in terms of the much simpler behavior of the Jost function. Although this is an old idea, see, and despite its advantages, it has not been employed widely. However, this method provides not only a theoretical tool for scattering problems in general, but also a convenient numerical approach in practice. Partially supported by AFOSR (IS), NSF (DS), and ARO (RC).

  20. Is the bitter rejection response always adaptive?

    PubMed

    Glendinning, J I

    1994-12-01

    The bitter rejection response consists of a suite of withdrawal reflexes and negative affective responses. It is generally assumed to have evolved as a way to facilitate avoidance of foods that are poisonous because they usually taste bitter to humans. Using previously published studies, the present paper examines the relationship between bitterness and toxicity in mammals, and then assesses the ecological costs and benefits of the bitter rejection response in carnivorous, omnivorous, and herbivorous (grazing and browsing) mammals. If the bitter rejection response accurately predicts the potential toxicity of foods, then one would expect the threshold for the response to be lower for highly toxic compounds than for nontoxic compounds. The data revealed no such relationship. Bitter taste thresholds varied independently of toxicity thresholds, indicating that the bitter rejection response is just as likely to be elicited by a harmless bitter food as it is by a harmful one. Thus, it is not necessarily in an animal's best interest to have an extremely high or low bitter threshold. Based on this observation, it was hypothesized that the adaptiveness of the bitter rejection response depends upon the relative occurrence of bitter and potentially toxic compounds in an animal's diet. Animals with a relatively high occurrence of bitter and potentially toxic compounds in their diet (e.g., browsing herbivores) were predicted to have evolved a high bitter taste threshold and tolerance to dietary poisons. Such an adaptation would be necessary because a browser cannot "afford" to reject all foods that are bitter and potentially toxic without unduly restricting its dietary options. At the other extreme, animals that rarely encounter bitter and potentially toxic compounds in their diet (e.g., carnivores) were predicted to have evolved a low bitter threshold. Carnivores could "afford" to utilize such a stringent rejection mechanism because foods containing bitter and potentially

  1. Is the bitter rejection response always adaptive?

    PubMed

    Glendinning, J I

    1994-12-01

    The bitter rejection response consists of a suite of withdrawal reflexes and negative affective responses. It is generally assumed to have evolved as a way to facilitate avoidance of foods that are poisonous because they usually taste bitter to humans. Using previously published studies, the present paper examines the relationship between bitterness and toxicity in mammals, and then assesses the ecological costs and benefits of the bitter rejection response in carnivorous, omnivorous, and herbivorous (grazing and browsing) mammals. If the bitter rejection response accurately predicts the potential toxicity of foods, then one would expect the threshold for the response to be lower for highly toxic compounds than for nontoxic compounds. The data revealed no such relationship. Bitter taste thresholds varied independently of toxicity thresholds, indicating that the bitter rejection response is just as likely to be elicited by a harmless bitter food as it is by a harmful one. Thus, it is not necessarily in an animal's best interest to have an extremely high or low bitter threshold. Based on this observation, it was hypothesized that the adaptiveness of the bitter rejection response depends upon the relative occurrence of bitter and potentially toxic compounds in an animal's diet. Animals with a relatively high occurrence of bitter and potentially toxic compounds in their diet (e.g., browsing herbivores) were predicted to have evolved a high bitter taste threshold and tolerance to dietary poisons. Such an adaptation would be necessary because a browser cannot "afford" to reject all foods that are bitter and potentially toxic without unduly restricting its dietary options. At the other extreme, animals that rarely encounter bitter and potentially toxic compounds in their diet (e.g., carnivores) were predicted to have evolved a low bitter threshold. Carnivores could "afford" to utilize such a stringent rejection mechanism because foods containing bitter and potentially

  2. The Importance of Ecosystem Thresholds in Assessing Safe Concentrations of Greenhouse Gases

    NASA Astrophysics Data System (ADS)

    Janetos, A. C.

    2007-12-01

    There is a major strategic challenge in the public debate about global environmental change related to concentrations of greenhouse gases in the atmosphere that might lead to environmentally, socially, and economically unacceptable impacts. This project takes one approach to this problem: avoiding "dangerous anthropogenic interference" and "allowing ecosystems to adapt." But these phrases implicitly assume that the influences of climate change are likely to be gradual and that there will be substantial time for natural resources to adapt or for managers to cope with change. The current state of the science suggests that something quite different may be in the offing. The Intergovernmental Panel on Climate Change (IPCC) and other assessments of possible impacts now agree on two important points. One is that there is already well-documented evidence of the biological and ecological consequences of climate change - in the behavior of migratory birds, in corals bleached from the influence of warming ocean temperatures, in the loss of glaciers to warming air temperatures, and in the loss of sea grass beds to sea level rise. The second is that ecological systems may not in fact change gradually. Modeling studies and the historical record both suggest that changes in ecosystems can be rapid, large, and sometimes irreversible, i.e., there are thresholds that, once crossed, will present serious coping challenges to humans. Moreover, as suggested in a recent National Academy of Sciences (NAS) workshop on "Understanding and Responding to Multiple Environmental Stresses," dealing with threshold responses that may lead to sudden and dramatic change in societal or environmental structure and function will also require that we develop ways to proceed with decision-making despite the many uncertainties associated with thresholds. These observations present serious challenges to the modeling frameworks used in integrated assessment. Not only do the models have to characterize the

  3. Static and Transient Cavitation Threshold Measurements for Mercury

    SciTech Connect

    Moraga, F.; Taleyarkhan, R.P.

    1999-11-14

    Transient and static cavitation thresholds for mercury as a function of the cover gas (helium or air), and pressure are reported. Both static and transient cavitation onset pressure thresholds increase linearly with cover gas pressure. Additionally, the cavitation thresholds as a function of dissolved gases were also measured and are reported.

  4. 36 CFR 1192.117 - Floors, steps and thresholds.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false Floors, steps and thresholds... Intercity Rail Cars and Systems § 1192.117 Floors, steps and thresholds. (a) Floor surfaces on aisles, step.... (b) All step edges and thresholds shall have a band of color(s) running the full width of the step...

  5. 36 CFR 1192.99 - Floors, steps and thresholds.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false Floors, steps and thresholds... Commuter Rail Cars and Systems § 1192.99 Floors, steps and thresholds. (a) Floor surfaces on aisles, step... shall be slip-resistant. (b) All thresholds and step edges shall have a band of color(s) running...

  6. 36 CFR 1192.25 - Doors, steps and thresholds.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 3 2011-07-01 2011-07-01 false Doors, steps and thresholds... Buses, Vans and Systems § 1192.25 Doors, steps and thresholds. (a) Slip resistance. All aisles, steps...) Contrast. All step edges, thresholds, and the boarding edge of ramps or lift platforms shall have a band...

  7. 36 CFR 1192.99 - Floors, steps and thresholds.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 3 2011-07-01 2011-07-01 false Floors, steps and thresholds... Commuter Rail Cars and Systems § 1192.99 Floors, steps and thresholds. (a) Floor surfaces on aisles, step... shall be slip-resistant. (b) All thresholds and step edges shall have a band of color(s) running...

  8. 36 CFR 1192.117 - Floors, steps and thresholds.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 3 2011-07-01 2011-07-01 false Floors, steps and thresholds... Intercity Rail Cars and Systems § 1192.117 Floors, steps and thresholds. (a) Floor surfaces on aisles, step.... (b) All step edges and thresholds shall have a band of color(s) running the full width of the step...

  9. 36 CFR 1192.25 - Doors, steps and thresholds.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false Doors, steps and thresholds... Buses, Vans and Systems § 1192.25 Doors, steps and thresholds. (a) Slip resistance. All aisles, steps...) Contrast. All step edges, thresholds, and the boarding edge of ramps or lift platforms shall have a band...

  10. Threshold Capability Development in Intensive Mode Business Units

    ERIC Educational Resources Information Center

    Crispin, Stuart; Hancock, Phil; Male, Sally Amanda; Baillie, Caroline; MacNish, Cara; Leggoe, Jeremy; Ranmuthugala, Dev; Alam, Firoz

    2016-01-01

    Purpose: The purpose of this paper is to explore: student perceptions of threshold concepts and capabilities in postgraduate business education, and the potential impacts of intensive modes of teaching on student understanding of threshold concepts and development of threshold capabilities. Design/Methodology/Approach: The student experience of…

  11. 45 CFR 149.115 - Cost threshold and cost limit.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 45 Public Welfare 1 2011-10-01 2011-10-01 false Cost threshold and cost limit. 149.115 Section 149... REQUIREMENTS FOR THE EARLY RETIREE REINSURANCE PROGRAM Reinsurance Amounts § 149.115 Cost threshold and cost limit. The following cost threshold and cost limits apply individually, to each early retiree as...

  12. 13 CFR 125.7 - Acquisition-related dollar thresholds.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ..., Government Contracting Programs, contains acquisition-related dollar thresholds subject to inflationary... thresholds. 125.7 Section 125.7 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION GOVERNMENT CONTRACTING PROGRAMS § 125.7 Acquisition-related dollar thresholds. The Federal Acquisition Regulatory...

  13. 13 CFR 125.7 - Acquisition-related dollar thresholds.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ..., Government Contracting Programs, contains acquisition-related dollar thresholds subject to inflationary... thresholds. 125.7 Section 125.7 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION GOVERNMENT CONTRACTING PROGRAMS § 125.7 Acquisition-related dollar thresholds. The Federal Acquisition Regulatory...

  14. 13 CFR 125.7 - Acquisition-related dollar thresholds.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ..., Government Contracting Programs, contains acquisition-related dollar thresholds subject to inflationary... thresholds. 125.7 Section 125.7 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION GOVERNMENT CONTRACTING PROGRAMS § 125.7 Acquisition-related dollar thresholds. The Federal Acquisition Regulatory...

  15. 13 CFR 125.7 - Acquisition-related dollar thresholds.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ..., Government Contracting Programs, contains acquisition-related dollar thresholds subject to inflationary... thresholds. 125.7 Section 125.7 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION GOVERNMENT CONTRACTING PROGRAMS § 125.7 Acquisition-related dollar thresholds. The Federal Acquisition Regulatory...

  16. 13 CFR 125.7 - Acquisition-related dollar thresholds.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ..., Government Contracting Programs, contains acquisition-related dollar thresholds subject to inflationary... thresholds. 125.7 Section 125.7 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION GOVERNMENT CONTRACTING PROGRAMS § 125.7 Acquisition-related dollar thresholds. The Federal Acquisition Regulatory...

  17. User Settings of Cue Thresholds for Binary Categorization Decisions

    ERIC Educational Resources Information Center

    Botzer, Assaf; Meyer, Joachim; Bak, Peter; Parmet, Yisrael

    2010-01-01

    The output of binary cuing systems, such as alerts or alarms, depends on the threshold setting--a parameter that is often user-adjustable. However, it is unknown if users are able to adequately adjust thresholds and what information may help them to do so. Two experiments tested threshold settings for a binary classification task based on binary…

  18. Light Adaptation in the Ventral Photoreceptor of Limulus

    PubMed Central

    Srebro, Richard; Behbehani, Michael

    1974-01-01

    Light adaptation in both the ventral photoreceptor and the lateral eye photoreceptor is a complex process consisting of at least two phases. One phase, which we call the rapid phase of adaptation, occurs whenever there is temporal overlap of the discrete waves that compose a light response. The recovery from the rapid phase of adaptation follows an exponential time-course with a time constant of approximately 75 ms at 21°C. The rapid phase of adaptation occurs at light intensities barely above discrete wave threshold as well as at substantially higher light intensities with the same recovery time-course at all intensities. It occurs in voltage-clamped and unclamped photoreceptors. The kinetics of the rapid phase of adaptation is closely correlated to the photocurrent which appears to initiate it after a short delay. The rapid phase of adaptation is probably identical to what is called the "adapting bump" process. At light intensities greater than about 10 times discrete wave threshold another phase of light adaptation occurs. It develops slowly over a period of ½ s or so, and decays even more slowly over a period of several seconds. It is graded with light intensity and occurs in both voltage-clamped and unclamped photoreceptors. We call this the slow phase of light adaptation. PMID:4846765

  19. Alarm pheromones do not mediate rapid shifts in honey bee guard acceptance threshold.

    PubMed

    Couvillon, Margaret J; Barton, Sarah N; Cohen, Jennifer A; Fabricius, Onna K; Kärcher, Martin H; Cooper, Lee S; Silk, Matthew J; Helanterä, Heikki; Ratnieks, Francis L W

    2010-12-01

    Honey bee (Apis mellifera) guards discriminate nestmates from non-nestmates at the hive entrance. The acceptance threshold of guards is known to change adaptively, for example becoming less permissive when the number of intruder bees from other colonies increases. These adaptive shifts can occur within minutes. What is unknown is the mechanism behind this rapid shift. It was hypothesized that alarm pheromones released by guards may cause the adoption of a less permissive acceptance threshold. Here, we tested this hypothesis on five discriminator hives by using a behavioral assay. We used three amounts each of iso-pentyl acetate (IPA) and 2-heptanone (2H), which are the major components of the pheromones from the sting and the mandibular glands, respectively. Biologically relevant levels of chemicals were delivered to the hive entrance platform via an air pump. We found no effect of either IPA or 2H: there was no change in guard acceptance of either nestmate (on average, 91% accepted) or non-nestmate (on average, 30% accepted) under any of the pheromone treatments compared to the pentane control (98% nestmates accepted and 32% non-nestmates accepted). Therefore, we reject the hypothesis that the presence of IPA or 2H causes a rapid shift of guard acceptance threshold. PMID:21069439

  20. Sub-threshold activation of the superior colliculus drives saccade motor learning

    PubMed Central

    Soetedjo, Robijanto; Fuchs, Albert F.; Kojima, Yoshiko

    2010-01-01

    How the brain learns and maintains accurate precision movements is currently unknown. At times throughout life, rapid gaze shifts (saccades) become inaccurate, but the brain makes gradual adjustments so they again stop on target. Previously, we showed that complex spikes (CSs) in Purkinje cells of the oculomotor cerebellum report the direction and amplitude by which saccades are in error. Anatomical studies indicate that this error signal could originate in the superior colliculus (SC). Here we deliver sub-threshold electrical stimulation of the SC after the saccade lands to signal an apparent error. The size of saccades in the same direction as the simulated error gradually increase; those in the opposite direction decrease. The electrically-adapted saccades endure after stimulation is discontinued, exhibit an adaptation field, can undergo changes in direction and depend on error timing. These electrically-induced adaptations were virtually identical to those produced by the visually-induced adaptations that we report here for comparable visual errors in the same monkeys. Therefore, our experiments reveal that an additional role for the SC in the generation of saccades is to provide a vector error signal that drives dysmetric saccades to adapt. Moreover, the characteristics of the electrically-induced adaptation reflect those of error-related CS activity in the oculomotor cerebellum, suggesting that CS activity serves as the learning signal. We speculate that CS activity may serve as the error signal that drives other kinds of motor learning as well. PMID:19955374