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Sample records for neuronal avalanches generically

  1. Neuronal avalanches and learning

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    Arcangelis, Lucilla de, E-mail: dearcangelis@na.infn.it [Department of Information Engineering and CNISM, Second University of Naples, 81031 Aversa (Italy)

    2011-05-01

    Networks of living neurons represent one of the most fascinating systems of biology. If the physical and chemical mechanisms at the basis of the functioning of a single neuron are quite well understood, the collective behaviour of a system of many neurons is an extremely intriguing subject. Crucial ingredient of this complex behaviour is the plasticity property of the network, namely the capacity to adapt and evolve depending on the level of activity. This plastic ability is believed, nowadays, to be at the basis of learning and memory in real brains. Spontaneous neuronal activity has recently shown features in common to other complex systems. Experimental data have, in fact, shown that electrical information propagates in a cortex slice via an avalanche mode. These avalanches are characterized by a power law distribution for the size and duration, features found in other problems in the context of the physics of complex systems and successful models have been developed to describe their behaviour. In this contribution we discuss a statistical mechanical model for the complex activity in a neuronal network. The model implements the main physiological properties of living neurons and is able to reproduce recent experimental results. Then, we discuss the learning abilities of this neuronal network. Learning occurs via plastic adaptation of synaptic strengths by a non-uniform negative feedback mechanism. The system is able to learn all the tested rules, in particular the exclusive OR (XOR) and a random rule with three inputs. The learning dynamics exhibits universal features as function of the strength of plastic adaptation. Any rule could be learned provided that the plastic adaptation is sufficiently slow.

  2. On the temporal organization of neuronal avalanches.

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    Lombardi, Fabrizio; Herrmann, Hans J; Plenz, Dietmar; De Arcangelis, Lucilla

    2014-01-01

    Spontaneous activity of cortex in vitro and in vivo has been shown to organize as neuronal avalanches. Avalanches are cascades of neuronal activity that exhibit a power law in their size and duration distribution, typical features of balanced systems in a critical state. Recently it has been shown that the distribution of quiet times between consecutive avalanches in rat cortex slice cultures displays a non-monotonic behavior with a power law decay at short time scales. This behavior has been attributed to the slow alternation between up and down-states. Here we further characterize the avalanche process and investigate how the functional behavior of the quiet time distribution depends on the fine structure of avalanche sequences. By systematically removing smaller avalanches from the experimental time series we show that size and quiet times are correlated and highlight that avalanche occurrence exhibits the characteristic periodicity of θ and β/γ oscillations, which jointly emerge in most of the analyzed samples. Furthermore, our analysis indicates that smaller avalanches tend to be associated with faster β/γ oscillations, whereas larger ones are associated with slower θ and 1-2 Hz oscillations. In particular, large avalanches corresponding to θ cycles trigger cascades of smaller ones, which occur at β/γ frequency. This temporal structure follows closely the one of nested θ - β/γ oscillations. Finally we demonstrate that, because of the multiple time scales characterizing avalanche dynamics, the distributions of quiet times between avalanches larger than a certain size do not collapse onto a unique function when rescaled by the average occurrence rate. However, when considered separately in the up-state and in the down-state, these distributions are solely controlled by the respective average rate and two different unique function can be identified.

  3. Temporal correlations in neuronal avalanche occurrence

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    Lombardi, F.; Herrmann, H. J.; Plenz, D.; de Arcangelis, L.

    2016-04-01

    Ongoing cortical activity consists of sequences of synchronized bursts, named neuronal avalanches, whose size and duration are power law distributed. These features have been observed in a variety of systems and conditions, at all spatial scales, supporting scale invariance, universality and therefore criticality. However, the mechanisms leading to burst triggering, as well as the relationship between bursts and quiescence, are still unclear. The analysis of temporal correlations constitutes a major step towards a deeper understanding of burst dynamics. Here, we investigate the relation between avalanche sizes and quiet times, as well as between sizes of consecutive avalanches recorded in cortex slice cultures. We show that quiet times depend on the size of preceding avalanches and, at the same time, influence the size of the following one. Moreover we evidence that sizes of consecutive avalanches are correlated. In particular, we show that an avalanche tends to be larger or smaller than the following one for short or long time separation, respectively. Our analysis represents the first attempt to provide a quantitative estimate of correlations between activity and quiescence in the framework of neuronal avalanches and will help to enlighten the mechanisms underlying spontaneous activity.

  4. Temporal correlations in neuronal avalanche occurrence.

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    Lombardi, F; Herrmann, H J; Plenz, D; de Arcangelis, L

    2016-04-20

    Ongoing cortical activity consists of sequences of synchronized bursts, named neuronal avalanches, whose size and duration are power law distributed. These features have been observed in a variety of systems and conditions, at all spatial scales, supporting scale invariance, universality and therefore criticality. However, the mechanisms leading to burst triggering, as well as the relationship between bursts and quiescence, are still unclear. The analysis of temporal correlations constitutes a major step towards a deeper understanding of burst dynamics. Here, we investigate the relation between avalanche sizes and quiet times, as well as between sizes of consecutive avalanches recorded in cortex slice cultures. We show that quiet times depend on the size of preceding avalanches and, at the same time, influence the size of the following one. Moreover we evidence that sizes of consecutive avalanches are correlated. In particular, we show that an avalanche tends to be larger or smaller than the following one for short or long time separation, respectively. Our analysis represents the first attempt to provide a quantitative estimate of correlations between activity and quiescence in the framework of neuronal avalanches and will help to enlighten the mechanisms underlying spontaneous activity.

  5. Neuronal avalanches in spontaneous activity in vivo.

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    Hahn, Gerald; Petermann, Thomas; Havenith, Martha N; Yu, Shan; Singer, Wolf; Plenz, Dietmar; Nikolic, Danko

    2010-12-01

    Many complex systems give rise to events that are clustered in space and time, thereby establishing a correlation structure that is governed by power law statistics. In the cortex, such clusters of activity, called "neuronal avalanches," were recently found in local field potentials (LFPs) of spontaneous activity in acute cortex slices, slice cultures, the developing cortex of the anesthetized rat, and premotor and motor cortex of awake monkeys. At present, it is unclear whether neuronal avalanches also exist in the spontaneous LFPs and spike activity in vivo in sensory areas of the mature brain. To address this question, we recorded spontaneous LFPs and extracellular spiking activity with multiple 4 × 4 microelectrode arrays (Michigan Probes) in area 17 of adult cats under anesthesia. A cluster of events was defined as a consecutive sequence of time bins Δt (1-32 ms), each containing at least one LFP event or spike anywhere on the array. LFP cluster sizes consistently distributed according to a power law with a slope largely above -1.5. In two thirds of the corresponding experiments, spike clusters also displayed a power law that displayed a slightly steeper slope of -1.8 and was destroyed by subsampling operations. The power law in spike clusters was accompanied with stronger temporal correlations between spiking activities of neurons that spanned longer time periods compared with spike clusters lacking power law statistics. The results suggest that spontaneous activity of the visual cortex under anesthesia has the properties of neuronal avalanches.

  6. Statistical analyses support power law distributions found in neuronal avalanches.

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    Andreas Klaus

    Full Text Available The size distribution of neuronal avalanches in cortical networks has been reported to follow a power law distribution with exponent close to -1.5, which is a reflection of long-range spatial correlations in spontaneous neuronal activity. However, identifying power law scaling in empirical data can be difficult and sometimes controversial. In the present study, we tested the power law hypothesis for neuronal avalanches by using more stringent statistical analyses. In particular, we performed the following steps: (i analysis of finite-size scaling to identify scale-free dynamics in neuronal avalanches, (ii model parameter estimation to determine the specific exponent of the power law, and (iii comparison of the power law to alternative model distributions. Consistent with critical state dynamics, avalanche size distributions exhibited robust scaling behavior in which the maximum avalanche size was limited only by the spatial extent of sampling ("finite size" effect. This scale-free dynamics suggests the power law as a model for the distribution of avalanche sizes. Using both the Kolmogorov-Smirnov statistic and a maximum likelihood approach, we found the slope to be close to -1.5, which is in line with previous reports. Finally, the power law model for neuronal avalanches was compared to the exponential and to various heavy-tail distributions based on the Kolmogorov-Smirnov distance and by using a log-likelihood ratio test. Both the power law distribution without and with exponential cut-off provided significantly better fits to the cluster size distributions in neuronal avalanches than the exponential, the lognormal and the gamma distribution. In summary, our findings strongly support the power law scaling in neuronal avalanches, providing further evidence for critical state dynamics in superficial layers of cortex.

  7. Statistical analyses support power law distributions found in neuronal avalanches.

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    Klaus, Andreas; Yu, Shan; Plenz, Dietmar

    2011-01-01

    The size distribution of neuronal avalanches in cortical networks has been reported to follow a power law distribution with exponent close to -1.5, which is a reflection of long-range spatial correlations in spontaneous neuronal activity. However, identifying power law scaling in empirical data can be difficult and sometimes controversial. In the present study, we tested the power law hypothesis for neuronal avalanches by using more stringent statistical analyses. In particular, we performed the following steps: (i) analysis of finite-size scaling to identify scale-free dynamics in neuronal avalanches, (ii) model parameter estimation to determine the specific exponent of the power law, and (iii) comparison of the power law to alternative model distributions. Consistent with critical state dynamics, avalanche size distributions exhibited robust scaling behavior in which the maximum avalanche size was limited only by the spatial extent of sampling ("finite size" effect). This scale-free dynamics suggests the power law as a model for the distribution of avalanche sizes. Using both the Kolmogorov-Smirnov statistic and a maximum likelihood approach, we found the slope to be close to -1.5, which is in line with previous reports. Finally, the power law model for neuronal avalanches was compared to the exponential and to various heavy-tail distributions based on the Kolmogorov-Smirnov distance and by using a log-likelihood ratio test. Both the power law distribution without and with exponential cut-off provided significantly better fits to the cluster size distributions in neuronal avalanches than the exponential, the lognormal and the gamma distribution. In summary, our findings strongly support the power law scaling in neuronal avalanches, providing further evidence for critical state dynamics in superficial layers of cortex.

  8. Avalanches in a stochastic model of spiking neurons.

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    Marc Benayoun

    Full Text Available Neuronal avalanches are a form of spontaneous activity widely observed in cortical slices and other types of nervous tissue, both in vivo and in vitro. They are characterized by irregular, isolated population bursts when many neurons fire together, where the number of spikes per burst obeys a power law distribution. We simulate, using the Gillespie algorithm, a model of neuronal avalanches based on stochastic single neurons. The network consists of excitatory and inhibitory neurons, first with all-to-all connectivity and later with random sparse connectivity. Analyzing our model using the system size expansion, we show that the model obeys the standard Wilson-Cowan equations for large network sizes ( neurons. When excitation and inhibition are closely balanced, networks of thousands of neurons exhibit irregular synchronous activity, including the characteristic power law distribution of avalanche size. We show that these avalanches are due to the balanced network having weakly stable functionally feedforward dynamics, which amplifies some small fluctuations into the large population bursts. Balanced networks are thought to underlie a variety of observed network behaviours and have useful computational properties, such as responding quickly to changes in input. Thus, the appearance of avalanches in such functionally feedforward networks indicates that avalanches may be a simple consequence of a widely present network structure, when neuron dynamics are noisy. An important implication is that a network need not be "critical" for the production of avalanches, so experimentally observed power laws in burst size may be a signature of noisy functionally feedforward structure rather than of, for example, self-organized criticality.

  9. Avalanches in a stochastic model of spiking neurons.

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    Benayoun, Marc; Cowan, Jack D; van Drongelen, Wim; Wallace, Edward

    2010-07-08

    Neuronal avalanches are a form of spontaneous activity widely observed in cortical slices and other types of nervous tissue, both in vivo and in vitro. They are characterized by irregular, isolated population bursts when many neurons fire together, where the number of spikes per burst obeys a power law distribution. We simulate, using the Gillespie algorithm, a model of neuronal avalanches based on stochastic single neurons. The network consists of excitatory and inhibitory neurons, first with all-to-all connectivity and later with random sparse connectivity. Analyzing our model using the system size expansion, we show that the model obeys the standard Wilson-Cowan equations for large network sizes ( neurons). When excitation and inhibition are closely balanced, networks of thousands of neurons exhibit irregular synchronous activity, including the characteristic power law distribution of avalanche size. We show that these avalanches are due to the balanced network having weakly stable functionally feedforward dynamics, which amplifies some small fluctuations into the large population bursts. Balanced networks are thought to underlie a variety of observed network behaviours and have useful computational properties, such as responding quickly to changes in input. Thus, the appearance of avalanches in such functionally feedforward networks indicates that avalanches may be a simple consequence of a widely present network structure, when neuron dynamics are noisy. An important implication is that a network need not be "critical" for the production of avalanches, so experimentally observed power laws in burst size may be a signature of noisy functionally feedforward structure rather than of, for example, self-organized criticality.

  10. Background activity drives criticality of neuronal avalanches

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    Juanico, D E; Monterola, C [National Institute of Physics, University of the Philippines, Diliman, Quezon City 1101 (Philippines)

    2007-08-03

    We establish a general framework that explains how leaky, dissipative systems, such as neuronal networks (NN), can exhibit robust self-organized criticality (SOC). Consistent with recent experiments, we propose that persistent membrane potential fluctuations allow NNs to transform from a sub-critical to a critical state. Our results also account for the tendency in small networks to tip towards an epileptiform state (the case of largely synchronized neurons) when background activity is strong.

  11. Subsampling effects in neuronal avalanche distributions recorded in vivo

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    Munk Matthias HJ

    2009-04-01

    Full Text Available Abstract Background Many systems in nature are characterized by complex behaviour where large cascades of events, or avalanches, unpredictably alternate with periods of little activity. Snow avalanches are an example. Often the size distribution f(s of a system's avalanches follows a power law, and the branching parameter sigma, the average number of events triggered by a single preceding event, is unity. A power law for f(s, and sigma = 1, are hallmark features of self-organized critical (SOC systems, and both have been found for neuronal activity in vitro. Therefore, and since SOC systems and neuronal activity both show large variability, long-term stability and memory capabilities, SOC has been proposed to govern neuronal dynamics in vivo. Testing this hypothesis is difficult because neuronal activity is spatially or temporally subsampled, while theories of SOC systems assume full sampling. To close this gap, we investigated how subsampling affects f(s and sigma by imposing subsampling on three different SOC models. We then compared f(s and sigma of the subsampled models with those of multielectrode local field potential (LFP activity recorded in three macaque monkeys performing a short term memory task. Results Neither the LFP nor the subsampled SOC models showed a power law for f(s. Both, f(s and sigma, depended sensitively on the subsampling geometry and the dynamics of the model. Only one of the SOC models, the Abelian Sandpile Model, exhibited f(s and sigma similar to those calculated from LFP activity. Conclusion Since subsampling can prevent the observation of the characteristic power law and sigma in SOC systems, misclassifications of critical systems as sub- or supercritical are possible. Nevertheless, the system specific scaling of f(s and sigma under subsampling conditions may prove useful to select physiologically motivated models of brain function. Models that better reproduce f(s and sigma calculated from the physiological

  12. Synaptic plasticity and neuronal refractory time cause scaling behaviour of neuronal avalanches

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    Michiels van Kessenich, L.; de Arcangelis, L.; Herrmann, H. J.

    2016-08-01

    Neuronal avalanches measured in vitro and in vivo in different cortical networks consistently exhibit power law behaviour for the size and duration distributions with exponents typical for a mean field self-organized branching process. These exponents are also recovered in neuronal network simulations implementing various neuronal dynamics on different network topologies. They can therefore be considered a very robust feature of spontaneous neuronal activity. Interestingly, this scaling behaviour is also observed on regular lattices in finite dimensions, which raises the question about the origin of the mean field behavior observed experimentally. In this study we provide an answer to this open question by investigating the effect of activity dependent plasticity in combination with the neuronal refractory time in a neuronal network. Results show that the refractory time hinders backward avalanches forcing a directed propagation. Hebbian plastic adaptation plays the role of sculpting these directed avalanche patterns into the topology of the network slowly changing it into a branched structure where loops are marginal.

  13. Neuronal avalanches of a self-organized neural network with active-neuron-dominant structure.

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    Li, Xiumin; Small, Michael

    2012-06-01

    Neuronal avalanche is a spontaneous neuronal activity which obeys a power-law distribution of population event sizes with an exponent of -3/2. It has been observed in the superficial layers of cortex both in vivo and in vitro. In this paper, we analyze the information transmission of a novel self-organized neural network with active-neuron-dominant structure. Neuronal avalanches can be observed in this network with appropriate input intensity. We find that the process of network learning via spike-timing dependent plasticity dramatically increases the complexity of network structure, which is finally self-organized to be active-neuron-dominant connectivity. Both the entropy of activity patterns and the complexity of their resulting post-synaptic inputs are maximized when the network dynamics are propagated as neuronal avalanches. This emergent topology is beneficial for information transmission with high efficiency and also could be responsible for the large information capacity of this network compared with alternative archetypal networks with different neural connectivity.

  14. Synaptic plasticity and neuronal refractory time cause scaling behaviour of neuronal avalanches.

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    Michiels van Kessenich, L; de Arcangelis, L; Herrmann, H J

    2016-08-18

    Neuronal avalanches measured in vitro and in vivo in different cortical networks consistently exhibit power law behaviour for the size and duration distributions with exponents typical for a mean field self-organized branching process. These exponents are also recovered in neuronal network simulations implementing various neuronal dynamics on different network topologies. They can therefore be considered a very robust feature of spontaneous neuronal activity. Interestingly, this scaling behaviour is also observed on regular lattices in finite dimensions, which raises the question about the origin of the mean field behavior observed experimentally. In this study we provide an answer to this open question by investigating the effect of activity dependent plasticity in combination with the neuronal refractory time in a neuronal network. Results show that the refractory time hinders backward avalanches forcing a directed propagation. Hebbian plastic adaptation plays the role of sculpting these directed avalanche patterns into the topology of the network slowly changing it into a branched structure where loops are marginal.

  15. Are dragon-king neuronal avalanches dungeons for self-organized brain activity?

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    de Arcangelis, L.

    2012-05-01

    Recent experiments have detected a novel form of spontaneous neuronal activity both in vitro and in vivo: neuronal avalanches. The statistical properties of this activity are typical of critical phenomena, with power laws characterizing the distributions of avalanche size and duration. A critical behaviour for the spontaneous brain activity has important consequences on stimulated activity and learning. Very interestingly, these statistical properties can be altered in significant ways in epilepsy and by pharmacological manipulations. In particular, there can be an increase in the number of large events anticipated by the power law, referred to herein as dragon-king avalanches. This behaviour, as verified by numerical models, can originate from a number of different mechanisms. For instance, it is observed experimentally that the emergence of a critical behaviour depends on the subtle balance between excitatory and inhibitory mechanisms acting in the system. Perturbing this balance, by increasing either synaptic excitation or the incidence of depolarized neuronal up-states causes frequent dragon-king avalanches. Conversely, an unbalanced GABAergic inhibition or long periods of low activity in the network give rise to sub-critical behaviour. Moreover, the existence of power laws, common to other stochastic processes, like earthquakes or solar flares, suggests that correlations are relevant in these phenomena. The dragon-king avalanches may then also be the expression of pathological correlations leading to frequent avalanches encompassing all neurons. We will review the statistics of neuronal avalanches in experimental systems. We then present numerical simulations of a neuronal network model introducing within the self-organized criticality framework ingredients from the physiology of real neurons, as the refractory period, synaptic plasticity and inhibitory synapses. The avalanche critical behaviour and the role of dragon-king avalanches will be discussed in

  16. Neuronal avalanches, epileptic quakes and other transient forms of neurodynamics.

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    Milton, John G

    2012-07-01

    Power-law behaviors in brain activity in healthy animals, in the form of neuronal avalanches, potentially benefit the computational activities of the brain, including information storage, transmission and processing. In contrast, power-law behaviors associated with seizures, in the form of epileptic quakes, potentially interfere with the brain's computational activities. This review draws attention to the potential roles played by homeostatic mechanisms and multistable time-delayed recurrent inhibitory loops in the generation of power-law phenomena. Moreover, it is suggested that distinctions between health and disease are scale-dependent. In other words, what is abnormal and defines disease it is not the propagation of neural activity but the propagation of activity in a neural population that is large enough to interfere with the normal activities of the brain. From this point of view, epilepsy is a disease that results from a failure of mechanisms, possibly located in part in the cortex itself or in the deep brain nuclei and brainstem, which truncate or otherwise confine the spatiotemporal scales of these power-law phenomena.

  17. Network dynamics in nociceptive pathways assessed by the neuronal avalanche model

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    Wu José

    2012-04-01

    Full Text Available Abstract Background Traditional electroencephalography provides a critical assessment of pain responses. The perception of pain, however, may involve a series of signal transmission pathways in higher cortical function. Recent studies have shown that a mathematical method, the neuronal avalanche model, may be applied to evaluate higher-order network dynamics. The neuronal avalanche is a cascade of neuronal activity, the size distribution of which can be approximated by a power law relationship manifested by the slope of a straight line (i.e., the α value. We investigated whether the neuronal avalanche could be a useful index for nociceptive assessment. Findings Neuronal activity was recorded with a 4 × 8 multichannel electrode array in the primary somatosensory cortex (S1 and anterior cingulate cortex (ACC. Under light anesthesia, peripheral pinch stimulation increased the slope of the α value in both the ACC and S1, whereas brush stimulation increased the α value only in the S1. The increase in α values was blocked in both regions under deep anesthesia. The increase in α values in the ACC induced by peripheral pinch stimulation was blocked by medial thalamic lesion, but the increase in α values in the S1 induced by brush and pinch stimulation was not affected. Conclusions The neuronal avalanche model shows a critical state in the cortical network for noxious-related signal processing. The α value may provide an index of brain network activity that distinguishes the responses to somatic stimuli from the control state. These network dynamics may be valuable for the evaluation of acute nociceptive processes and may be applied to chronic pathological pain conditions.

  18. Scale-invariant neuronal avalanche dynamics and the cut-off in size distributions.

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    Shan Yu

    Full Text Available Identification of cortical dynamics strongly benefits from the simultaneous recording of as many neurons as possible. Yet current technologies provide only incomplete access to the mammalian cortex from which adequate conclusions about dynamics need to be derived. Here, we identify constraints introduced by sub-sampling with a limited number of electrodes, i.e. spatial 'windowing', for well-characterized critical dynamics-neuronal avalanches. The local field potential (LFP was recorded from premotor and prefrontal cortices in two awake macaque monkeys during rest using chronically implanted 96-microelectrode arrays. Negative deflections in the LFP (nLFP were identified on the full as well as compact sub-regions of the array quantified by the number of electrodes N (10-95, i.e., the window size. Spatiotemporal nLFP clusters organized as neuronal avalanches, i.e., the probability in cluster size, p(s, invariably followed a power law with exponent -1.5 up to N, beyond which p(s declined more steeply producing a 'cut-off' that varied with N and the LFP filter parameters. Clusters of size s≤N consisted mainly of nLFPs from unique, non-repeated cortical sites, emerged from local propagation between nearby sites, and carried spatial information about cluster organization. In contrast, clusters of size s>N were dominated by repeated site activations and carried little spatial information, reflecting greatly distorted sampling conditions. Our findings were confirmed in a neuron-electrode network model. Thus, avalanche analysis needs to be constrained to the size of the observation window to reveal the underlying scale-invariant organization produced by locally unfolding, predominantly feed-forward neuronal cascades.

  19. Avalanche dynamics of idealized neuron function in the brain on an uncorrelated random scale-free network

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    Lee, K. E.; Lee, J. W.

    2006-03-01

    We study a simple model for a neuron function in a collective brain system. The neural network is composed of an uncorrelated configuration model (UCM) for eliminating the degree correlation of dynamical processes. The interaction of neurons is assumed to be isotropic and idealized. These neuron dynamics are similar to biological evolution in extremal dynamics with locally isotropic interaction but has a different time scale. The functioning of neurons takes place as punctuated patterns based on avalanche dynamics. In our model, the avalanche dynamics of neurons exhibit self-organized criticality which shows power-law behavior of the avalanche sizes. For a given network, the avalanche dynamic behavior is not changed with different degree exponents of networks, γ≥2.4 and various refractory periods referred to the memory effect, Tr. Furthermore, the avalanche size distributions exhibit power-law behavior in a single scaling region in contrast to other networks. However, return time distributions displaying spatiotemporal complexity have three characteristic time scaling regimes Thus, we find that UCM may be inefficient for holding a memory.

  20. Efficient network reconstruction from dynamical cascades identifies small-world topology of neuronal avalanches.

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    Sinisa Pajevic

    2009-01-01

    Full Text Available Cascading activity is commonly found in complex systems with directed interactions such as metabolic networks, neuronal networks, or disease spreading in social networks. Substantial insight into a system's organization can be obtained by reconstructing the underlying functional network architecture from the observed activity cascades. Here we focus on Bayesian approaches and reduce their computational demands by introducing the Iterative Bayesian (IB and Posterior Weighted Averaging (PWA methods. We introduce a special case of PWA, cast in nonparametric form, which we call the normalized count (NC algorithm. NC efficiently reconstructs random and small-world functional network topologies and architectures from subcritical, critical, and supercritical cascading dynamics and yields significant improvements over commonly used correlation methods. With experimental data, NC identified a functional and structural small-world topology and its corresponding traffic in cortical networks with neuronal avalanche dynamics.

  1. Biological modelling of a computational spiking neural network with neuronal avalanches

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    Li, Xiumin; Chen, Qing; Xue, Fangzheng

    2017-05-01

    In recent years, an increasing number of studies have demonstrated that networks in the brain can self-organize into a critical state where dynamics exhibit a mixture of ordered and disordered patterns. This critical branching phenomenon is termed neuronal avalanches. It has been hypothesized that the homeostatic level balanced between stability and plasticity of this critical state may be the optimal state for performing diverse neural computational tasks. However, the critical region for high performance is narrow and sensitive for spiking neural networks (SNNs). In this paper, we investigated the role of the critical state in neural computations based on liquid-state machines, a biologically plausible computational neural network model for real-time computing. The computational performance of an SNN when operating at the critical state and, in particular, with spike-timing-dependent plasticity for updating synaptic weights is investigated. The network is found to show the best computational performance when it is subjected to critical dynamic states. Moreover, the active-neuron-dominant structure refined from synaptic learning can remarkably enhance the robustness of the critical state and further improve computational accuracy. These results may have important implications in the modelling of spiking neural networks with optimal computational performance. This article is part of the themed issue `Mathematical methods in medicine: neuroscience, cardiology and pathology'.

  2. Can power-law scaling and neuronal avalanches arise from stochastic dynamics?

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    Jonathan Touboul

    Full Text Available The presence of self-organized criticality in biology is often evidenced by a power-law scaling of event size distributions, which can be measured by linear regression on logarithmic axes. We show here that such a procedure does not necessarily mean that the system exhibits self-organized criticality. We first provide an analysis of multisite local field potential (LFP recordings of brain activity and show that event size distributions defined as negative LFP peaks can be close to power-law distributions. However, this result is not robust to change in detection threshold, or when tested using more rigorous statistical analyses such as the Kolmogorov-Smirnov test. Similar power-law scaling is observed for surrogate signals, suggesting that power-law scaling may be a generic property of thresholded stochastic processes. We next investigate this problem analytically, and show that, indeed, stochastic processes can produce spurious power-law scaling without the presence of underlying self-organized criticality. However, this power-law is only apparent in logarithmic representations, and does not survive more rigorous analysis such as the Kolmogorov-Smirnov test. The same analysis was also performed on an artificial network known to display self-organized criticality. In this case, both the graphical representations and the rigorous statistical analysis reveal with no ambiguity that the avalanche size is distributed as a power-law. We conclude that logarithmic representations can lead to spurious power-law scaling induced by the stochastic nature of the phenomenon. This apparent power-law scaling does not constitute a proof of self-organized criticality, which should be demonstrated by more stringent statistical tests.

  3. Aging Avalanches

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    Boettcher, Stefan; Paczuski, Maya

    1997-03-01

    We have shown that in an analytically solvable model of Self-Organized Criticality (SOC)(S. Boettcher & M. Paczuski, Phys. Rev. Lett. 76), 348 (1996). the evolving avalanche is governed by an equation of motion with a memory term that ranges over all past events.(S. Boettcher & M. Paczuski, Phys. Rev. E 54), 1082 (1996). The solution for the propagator shows sub-diffusive behavior with a broad exponential tail. Numerical studies of the temporal correlations during avalanches in a variety of SOC systems indicate that history dependence and hierarchical structures are generic features which emerge dynamically from simple local update rules. In particular, we find(S. Boettcher & M. Paczuski, ``Off-Equilibrium Behavior and Aging in Self-Organized Criticality'', (in preparation).) ``aging'' similar to the slow relaxation behavior in disordered systems that move through ``rugged landscapes'' in phase space, such as spin glasses.

  4. Avalanche Statistics of Driven Granular Slides in a Miniature Mound

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    Juanico, D E; Batac, R; Monterola, C

    2008-01-01

    We examine avalanche statistics of rain- and vibration-driven granular slides in miniature soil mounds using experimental and numerical approaches. A crossover from power-law to non power-law avalanche-size statistics is demonstrated as a generic driving rate $\

  5. [Avalanche accidents and treatment of avalanche victims].

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    Skaiaa, Sven Christjar; Thomassen, Øyvind

    2016-03-15

    Avalanches may be provoked spontaneously or as a result of human activity, and they trigger the need for considerable rescue resources. Avalanche search and rescue operations are complex and characterised by physical and mental stress. The guidelines for resuscitation of avalanche victims may be perceived as complex and abstruse, which can lead to suboptimal treatment and an increased strain on rescue teams. The purpose of this article is to summarise the principles for medical treatment of avalanche victims.

  6. Co-emergence of multi-scale cortical activities of irregular firing, oscillations and avalanches achieves cost-efficient information capacity

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    Zhou, Hai-Jun; Zhou, Changsong

    2017-01-01

    The brain is highly energy consuming, therefore is under strong selective pressure to achieve cost-efficiency in both cortical connectivities and activities. However, cost-efficiency as a design principle for cortical activities has been rarely studied. Especially it is not clear how cost-efficiency is related to ubiquitously observed multi-scale properties: irregular firing, oscillations and neuronal avalanches. Here we demonstrate that these prominent properties can be simultaneously observed in a generic, biologically plausible neural circuit model that captures excitation-inhibition balance and realistic dynamics of synaptic conductance. Their co-emergence achieves minimal energy cost as well as maximal energy efficiency on information capacity, when neuronal firing are coordinated and shaped by moderate synchrony to reduce otherwise redundant spikes, and the dynamical clusterings are maintained in the form of neuronal avalanches. Such cost-efficient neural dynamics can be employed as a foundation for further efficient information processing under energy constraint. PMID:28192429

  7. Neuronal avalanches in complex networks

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    Victor Hernandez-Urbina

    2016-12-01

    Full Text Available Brain networks are neither regular nor random. Their structure allows for optimal information processing and transmission across the entire neural substrate of an organism. However, for topological features to be appropriately harnessed, brain networks should implement a dynamical regime which prevents phase-locked and chaotic behaviour. Critical neural dynamics refer to a dynamical regime in which the system is poised at the boundary between regularity and randomness. It has been reported that neural systems poised at this boundary achieve maximum computational power. In this paper, we review recent results regarding critical neural dynamics that emerge from systems whose underlying structure exhibits complex network properties.

  8. Negative feedback avalanche diode

    Science.gov (United States)

    Itzler, Mark Allen (Inventor)

    2010-01-01

    A single-photon avalanche detector is disclosed that is operable at wavelengths greater than 1000 nm and at operating speeds greater than 10 MHz. The single-photon avalanche detector comprises a thin-film resistor and avalanche photodiode that are monolithically integrated such that little or no additional capacitance is associated with the addition of the resistor.

  9. Avalanche speed in thin avalanche photodiodes

    Science.gov (United States)

    Ong, D. S.; Rees, G. J.; David, J. P. R.

    2003-04-01

    The duration of the avalanche multiplication process in thin GaAs avalanche photodiodes is investigated using a full band Monte Carlo (FBMC) model. The results are compared with those of a simple random path length (RPL) model which makes the conventional assumptions of a displaced exponential for the ionization path length probability distribution function and that carriers always travel at their saturated drift velocities. We find that the avalanche duration calculated by the RPL model is almost twice of that predicted by the FBMC model, although the constant drift velocities used in the former model are estimated using the latter. The faster response predicted by FBMC model arises partly from the reduced dead space but mainly from the velocity overshoot of ionizing carriers. While the feedback multiplication processes forced by the effects of dead space extend the avalanche duration in short structures, the effects of velocity overshoot in the realistic model more than compensate, significantly improving multiplication bandwidth.

  10. Dealing with the white death: avalanche risk management for traffic routes.

    Science.gov (United States)

    Rheinberger, Christoph M; Bründl, Michael; Rhyner, Jakob

    2009-01-01

    This article discusses mitigation strategies to protect traffic routes from snow avalanches. Up to now, mitigation of snow avalanches on many roads and railways in the Alps has relied on avalanche sheds, which require large initial investments resulting in high opportunity costs. Therefore, avalanche risk managers have increasingly adopted organizational mitigation measures such as warning systems and closure policies instead. The effectiveness of these measures is, however, greatly dependent on human decisions. In this article, we present a method for optimizing avalanche mitigation for traffic routes in terms of both their risk reduction impact and their net benefit to society. First, we introduce a generic framework for assessing avalanche risk and for quantifying the impact of mitigation. This allows for sound cost-benefit comparisons between alternative mitigation strategies. Second, we illustrate the framework with a case study from Switzerland. Our findings suggest that site-specific characteristics of avalanche paths, as well as the economic importance of a traffic route, are decisive for the choice of optimal mitigation strategies. On routes endangered by few avalanche paths with frequent avalanche occurrences, structural measures are most efficient, whereas reliance on organizational mitigation is often the most appropriate strategy on routes endangered by many paths with infrequent or fuzzy avalanche risk. Finally, keeping a traffic route open may be very important for tourism or the transport industry. Hence, local economic value may promote the use of a hybrid strategy that combines organizational and structural measures to optimize the resource allocation of avalanche risk mitigation.

  11. Rock avalanches on glaciers

    OpenAIRE

    Shugar, Daniel

    2011-01-01

    This thesis examines relations between rock avalanches and the glaciers on which they are deposited. I have attempted to understand a geophysical phenomenon from two viewpoints: sedimentology and glaciology. The contributions are both methodological, and practical. I have used a GIS to quantify debris sheet geomorphology. A thorough characterization of rock avalanche debris is a necessary step in understanding the flow mechanics of large landslide. I have also developed a technique for solvin...

  12. Saturated logistic avalanche model

    Science.gov (United States)

    Aielli, G.; Camarri, P.; Cardarelli, R.; Di Ciaccio, A.; Liberti, B.; Paoloni, A.; Santonico, R.

    2003-08-01

    The search for an adequate avalanche RPC working model evidenced that the simple exponential growth can describe the electron multiplication phenomena in the gas with acceptable accuracy until the external electric field is not perturbed by the growing avalanche. We present here a model in which the saturated growth induced by the space charge effects is explained in a natural way by a constant coefficient non-linear differential equation, the Logistic equation, which was originally introduced to describe the evolution of a biological population in a limited resources environment. The RPCs, due to the uniform and intense field, proved to be an ideal device to test experimentally the presented model.

  13. Dune Avalanche Scars

    Science.gov (United States)

    2004-01-01

    05 August 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows large, low albedo (dark) sand dunes in Kaiser Crater near 47.2oS, 340.4oW. The dunes are--ever so slowly--moving east to west (right to left) as sand avalanches down the steeper, slip face slopes of each. Avalanching sand in the Kaiser dune field has left deep scars on these slopes, suggesting that the sand is not loose but is instead weakly cemented. The image covers an area approximately 3 km (1.9 mi) wide and is illuminated by sunlight from the upper left.

  14. QSpike Tools: a Generic Framework for Parallel Batch Preprocessing of Extracellular Neuronal Signals Recorded by Substrate Microelectrode Arrays

    Directory of Open Access Journals (Sweden)

    Mufti eMahmud

    2014-03-01

    Full Text Available Micro-Electrode Arrays (MEAs have emerged as a mature technique to investigate brain (dysfunctions in vivo and in in vitro animal models. Often referred to as smart Petri dishes, MEAs has demonstrated a great potential particularly for medium-throughput studies in vitro, both in academic and pharmaceutical industrial contexts. Enabling rapid comparison of ionic/pharmacological/genetic manipulations with control conditions, MEAs are often employed to screen compounds by monitoring non-invasively the spontaneous and evoked neuronal electrical activity in longitudinal studies, with relatively inexpensive equipment. However, in order to acquire sufficient statistical significance, recordings last up to tens of minutes and generate large amount of raw data (e.g., 60 channels/MEA, 16 bits A/D conversion, 20kHz sampling rate: ~8GB/MEA,h uncompressed. Thus, when the experimental conditions to be tested are numerous, the availability of fast, standardized, and automated signal preprocessing becomes pivotal for any subsequent analysis and data archiving. To this aim, we developed an in-house cloud-computing system, named QSpike Tools, where CPU-intensive operations, required for preprocessing of each recorded channel (e.g., filtering, multi-unit activity detection, spike-sorting, etc., are decomposed and batch-queued to a multi-core architecture or to computer cluster. With the commercial availability of new and inexpensive high-density MEAs, we believe that disseminating QSpike Tools might facilitate its wide adoption and customization, and possibly inspire the creation of community-supported cloud-computing facilities for MEAs users.

  15. QSpike tools: a generic framework for parallel batch preprocessing of extracellular neuronal signals recorded by substrate microelectrode arrays.

    Science.gov (United States)

    Mahmud, Mufti; Pulizzi, Rocco; Vasilaki, Eleni; Giugliano, Michele

    2014-01-01

    Micro-Electrode Arrays (MEAs) have emerged as a mature technique to investigate brain (dys)functions in vivo and in in vitro animal models. Often referred to as "smart" Petri dishes, MEAs have demonstrated a great potential particularly for medium-throughput studies in vitro, both in academic and pharmaceutical industrial contexts. Enabling rapid comparison of ionic/pharmacological/genetic manipulations with control conditions, MEAs are employed to screen compounds by monitoring non-invasively the spontaneous and evoked neuronal electrical activity in longitudinal studies, with relatively inexpensive equipment. However, in order to acquire sufficient statistical significance, recordings last up to tens of minutes and generate large amount of raw data (e.g., 60 channels/MEA, 16 bits A/D conversion, 20 kHz sampling rate: approximately 8 GB/MEA,h uncompressed). Thus, when the experimental conditions to be tested are numerous, the availability of fast, standardized, and automated signal preprocessing becomes pivotal for any subsequent analysis and data archiving. To this aim, we developed an in-house cloud-computing system, named QSpike Tools, where CPU-intensive operations, required for preprocessing of each recorded channel (e.g., filtering, multi-unit activity detection, spike-sorting, etc.), are decomposed and batch-queued to a multi-core architecture or to a computers cluster. With the commercial availability of new and inexpensive high-density MEAs, we believe that disseminating QSpike Tools might facilitate its wide adoption and customization, and inspire the creation of community-supported cloud-computing facilities for MEAs users.

  16. Abelian avalanches and Tutte polynomials

    Science.gov (United States)

    Gabrielov, Andrei

    1993-04-01

    We introduce a class of deterministic lattice models of failure, Abelian avalanche (AA) models, with continuous phase variables, similar to discrete Abelian sandpile (ASP) models. We investigate analytically the structure of the phase space and statistical properties of avalanches in these models. We show that the distributions of avalanches in AA and ASP models with the same redistribution matrix and loading rate are identical. For an AA model on a graph, statistics of avalanches is linked to Tutte polynomials associated with this graph and its subgraphs. In the general case, statistics of avalanches is linked to an analog of a Tutte polynomial defined for any symmetric matrix.

  17. Reuyl Crater Dust Avalanches

    Science.gov (United States)

    2002-01-01

    (Released 13 May 2002) The Science The rugged, arcuate rim of the 90 km crater Reuyl dominates this THEMIS image. Reuyl crater is at the southern edge of a region known to be blanketed in thick dust based on its high albedo (brightness) and low thermal inertia values. This thick mantle of dust creates the appearance of snow covered mountains in the image. Like snow accumulation on Earth, Martian dust can become so thick that it eventually slides down the face of steep slopes, creating runaway avalanches of dust. In the center of this image about 1/3 of the way down is evidence of this phenomenon. A few dozen dark streaks can be seen on the bright, sunlit slopes of the crater rim. The narrow streaks extend downslope following the local topography in a manner very similar to snow avalanches on Earth. But unlike their terrestrial counterparts, no accumulation occurs at the bottom. The dust particles are so small that they are easily launched into the thin atmosphere where they remain suspended and ultimately blow away. The apparent darkness of the avalanche scars is due to the presence of relatively dark underlying material that becomes exposed following the passage of the avalanche. Over time, new dust deposition occurs, brightening the scars until they fade into the background. Although dark slope streaks had been observed in Viking mission images, a clear understanding of this dynamic phenomenon wasn't possible until the much higher resolution images from the Mars Global Surveyor MOC camera revealed the details. MOC images also showed that new avalanches have occurred during the time MGS has been in orbit. THEMIS images will allow additional mapping of their distribution and frequency, contributing new insights about Martian dust avalanches. The Story The stiff peaks in this image might remind you of the Alps here on Earth, but they really outline the choppy edge of a large Martian crater over 50 miles wide (seen in the context image at right). While these aren

  18. Generic variation?

    DEFF Research Database (Denmark)

    Jensen, Torben Juel

    2009-01-01

    Abstract In modern Danish, a handful of pronouns may be used to refer to a generic referent. In recent decades, the second person singular pronoun du has gained ground, apparently in parallel to similar recent developments in other languages. Even though generic du may not be as old as the tradit...

  19. Repertoires of spike avalanches are modulated by behavior and novelty

    Directory of Open Access Journals (Sweden)

    Tiago Lins Ribeiro

    2016-03-01

    Full Text Available Neuronal avalanches measured as consecutive bouts of thresholded field potentials represent a statistical signature that the brain operates near a critical point. In theory, criticality optimizes stimulus sensitivity, information transmission, computational capability and mnemonic repertoires size. Field potential avalanches recorded via multielectrode arrays from cortical slice cultures are repeatable spatiotemporal activity patterns. It remains unclear whether avalanches of action potentials observed in forebrain regions of freely-behaving rats also form recursive repertoires, and whether these have any behavioral relevance. Here we show that spike avalanches, recorded from hippocampus and sensory neocortex of freely-behaving rats, constitute distinct families of recursive spatiotemporal patterns. A significant number of those patterns were specific to a behavioral state. Although avalanches produced during sleep were mostly similar to others that occurred during waking, the repertoire of patterns recruited during sleep differed significantly from that of waking. More importantly, exposure to novel objects increased the rate at which new patterns arose, also leading to changes in post-exposure repertoires, which were significantly different from those before the exposure. A significant number of families occurred exclusively during periods of whisker contact with objects, but few were associated with specific objects. Altogether, the results provide original evidence linking behavior and criticality at the spike level: spike avalanches form repertoires that emerge in waking, recur during sleep, are diversified by novelty and contribute to object representation.

  20. Repertoires of Spike Avalanches Are Modulated by Behavior and Novelty.

    Science.gov (United States)

    Ribeiro, Tiago L; Ribeiro, Sidarta; Copelli, Mauro

    2016-01-01

    Neuronal avalanches measured as consecutive bouts of thresholded field potentials represent a statistical signature that the brain operates near a critical point. In theory, criticality optimizes stimulus sensitivity, information transmission, computational capability and mnemonic repertoires size. Field potential avalanches recorded via multielectrode arrays from cortical slice cultures are repeatable spatiotemporal activity patterns. It remains unclear whether avalanches of action potentials observed in forebrain regions of freely-behaving rats also form recursive repertoires, and whether these have any behavioral relevance. Here, we show that spike avalanches, recorded from hippocampus (HP) and sensory neocortex of freely-behaving rats, constitute distinct families of recursive spatiotemporal patterns. A significant number of those patterns were specific to a behavioral state. Although avalanches produced during sleep were mostly similar to others that occurred during waking, the repertoire of patterns recruited during sleep differed significantly from that of waking. More importantly, exposure to novel objects increased the rate at which new patterns arose, also leading to changes in post-exposure repertoires, which were significantly different from those before the exposure. A significant number of families occurred exclusively during periods of whisker contact with objects, but few were associated with specific objects. Altogether, the results provide original evidence linking behavior and criticality at the spike level: spike avalanches form repertoires that emerge in waking, recur during sleep, are diversified by novelty and contribute to object representation.

  1. Statistical theory of hierarchical avalanche ensemble

    OpenAIRE

    Olemskoi, Alexander I.

    1999-01-01

    The statistical ensemble of avalanche intensities is considered to investigate diffusion in ultrametric space of hierarchically subordinated avalanches. The stationary intensity distribution and the steady-state current are obtained. The critical avalanche intensity needed to initiate the global avalanche formation is calculated depending on noise intensity. The large time asymptotic for the probability of the global avalanche appearance is derived.

  2. AVALANCHES - EXTREME WINTER EVENTS. MONITORING AND AVALANCHE RISK

    Directory of Open Access Journals (Sweden)

    NARCISA MILIAN

    2012-03-01

    Full Text Available This paper presents the avalanches monitored by the National Meteorological Administration within the nivo-meteorological program since february 2004. Daily observations and weekly snow measurements are made at the weather stations from Bucegi Mountains - Vârful Omu (2504 m, Sinaia (1500 m şi Predeal (1100m and Făgăraş Mountains – Bâlea-Lac (2055m, to provide data for avalanche risk estimation using the european avalanche danger scale. Increasing winter sport activities had led to several avalanche accidents, some of them fatal.

  3. Characteristics of avalanche accidents and a overview of avalanche equipment

    Directory of Open Access Journals (Sweden)

    Mateusz Biela

    2015-12-01

    Full Text Available Avalanches are one of the most spectacular phenomena which may occur in the mountains. Unfortunately they are often caused by humans and pose for him a big danger. In the Polish Tatras alone they represent 18% of all causes of death among 1996-2013. One fourth of the people caught by an avalanche dies, and their chances of survival depends on the depth of burial, burial time, the presence of an air pocket and the degree of injuries. The most common cause of death is asphyxiation, the next is injuries and hypothermia is the rarest cause of death. The fate of the buried people depends on their equipment such as avalanche transceiver, ABS backpack and AvaLung, and also from the equipment of the people who are seeking (avalanche probes, avalanche transceiver and shovels, which has been proven in practice and research.

  4. Avalanches in UGe 2

    Science.gov (United States)

    Lhotel, E.; Paulsen, C.; Huxley, A. D.

    2004-05-01

    In UGe 2 ferromagnetism and superconductivity co-exist for pressures in the range 1.0- 1.6 GPa. The magnetic state, however, has several unusual properties. Here we report measurements of hysteresis loops for fields parallel to the easy-axis at low temperature and ambient pressure, measured for two separate UGe 2 single crystals. Steps in the magnetization as the field is changed at low temperature are observed for both crystals. The general phenomenology associated with the steps strongly suggests that they correspond to avalanches of domain-wall motion.

  5. Integrated avalanche photodiode arrays

    Science.gov (United States)

    Harmon, Eric S.

    2015-07-07

    The present disclosure includes devices for detecting photons, including avalanche photon detectors, arrays of such detectors, and circuits including such arrays. In some aspects, the detectors and arrays include a virtual beveled edge mesa structure surrounded by resistive material damaged by ion implantation and having side wall profiles that taper inwardly towards the top of the mesa structures, or towards the direction from which the ion implantation occurred. Other aspects are directed to masking and multiple implantation and/or annealing steps. Furthermore, methods for fabricating and using such devices, circuits and arrays are disclosed.

  6. Controlling avalanche criticality in 2D nano arrays.

    Science.gov (United States)

    Zohar, Y C; Yochelis, S; Dahmen, K A; Jung, G; Paltiel, Y

    2013-01-01

    Many physical systems respond to slowly changing external force through avalanches spanning broad range of sizes. Some systems crackle even without apparent external force, such as bursts of neuronal activity or charge transfer avalanches in 2D molecular layers. Advanced development of theoretical models describing disorder-induced critical phenomena calls for experiments probing the dynamics upon tuneable disorder. Here we show that isomeric structural transitions in 2D organic self-assembled monolayer (SAM) exhibit critical dynamics with experimentally tuneable disorder. The system consists of field effect transistor coupled through SAM to illuminated semiconducting nanocrystals (NCs). Charges photoinduced in NCs are transferred through SAM to the transistor surface and modulate its conductivity. Avalanches of isomeric structural transitions are revealed by measuring the current noise I(t) of the transistor. Accumulated surface traps charges reduce dipole moments of the molecules, decrease their coupling, and thus decrease the critical disorder of the SAM enabling its tuning during experiments.

  7. Technological advances in avalanche survival.

    Science.gov (United States)

    Radwin, Martin I; Grissom, Colin K

    2002-01-01

    Over the last decade, a proliferation of interest has emerged in the area of avalanche survival, yielding both an improved understanding of the pathophysiology of death after avalanche burial and technological advances in the development of survival equipment. The dismal survival statistics born out of the modern era of winter recreation unmistakably reveal that elapsed time and depth of burial are the most critical variables of survival and the focus of newer survival devices on the market. Although blunt trauma may kill up to one third of avalanche victims, early asphyxiation is the predominant mechanism of death, and hypothermia is rare. A survival plateau or delay in asphyxiation may be seen in those buried in respiratory communication with an air pocket until a critical accumulation of CO2 or an ice lens develops. The newest survival devices available for adjunctive protection, along with a transceiver and shovel, are the artificial air pocket device (AvaLung), the avalanche air bag system (ABS), and the Avalanche Ball. The artificial air pocket prolongs adequate respiration during snow burial and may improve survival by delaying asphyxiation. The ABS, which forces the wearer to the surface of the avalanche debris by inverse segregation to help prevent burial, has been in use in Europe for the last 10 years with an impressive track record. Finally, the Avalanche Ball is a visual locator device in the form of a spring-loaded ball attached to a tether, which is released from a fanny pack by a rip cord. Despite the excitement surrounding these novel technologies, avalanche avoidance through knowledge and conservative judgment will always be the mainstay of avalanche survival, never to be replaced by any device.

  8. Family Genericity

    DEFF Research Database (Denmark)

    Ernst, Erik

    2006-01-01

    Type abstraction in object-oriented languages embody two techniques, each with its own strenghts and weaknesses. The first technique is extension, yielding abstraction mechanisms with good support for gradual specification. The prime example is inheritance. The second technique is functional abst...... the result as family genericity. The presented language design has been implemented....

  9. Family Genericity

    DEFF Research Database (Denmark)

    Ernst, Erik

    2006-01-01

    Type abstraction in object-oriented languages embody two techniques, each with its own strenghts and weaknesses. The first technique is extension, yielding abstraction mechanisms with good support for gradual specification. The prime example is inheritance. The second technique is functional abst...... the result as family genericity. The presented language design has been implemented....

  10. Imaging findings of avalanche victims

    Energy Technology Data Exchange (ETDEWEB)

    Grosse, Alexandra B.; Grosse, Claudia A.; Anderson, Suzanne [University Hospital of Berne, Inselspital, Department of Diagnostic, Pediatric and Interventional Radiology, Berne (Switzerland); Steinbach, Lynne S. [University of California San Francisco, Department of Radiology, San Francisco, CA (United States); Zimmermann, Heinz [University Hospital of Berne, Inselspital, Department of Trauma and Emergency Medicine, Berne (Switzerland)

    2007-06-15

    Skiing and hiking outside the boundaries remains an attractive wilderness activity despite the danger of avalanches. Avalanches occur on a relatively frequent basis and may be devastating. Musculoskeletal radiologists should be acquainted with these injuries. Fourteen avalanche victims (11 men and 3 women; age range 17-59 years, mean age 37.4 years) were air transported to a high-grade trauma centre over a period of 2 years. Radiographs, CT and MR images were prospectively evaluated by two observers in consensus. Musculoskeletal findings (61%) were more frequent than extraskeletal findings (39%). Fractures were most commonly seen (36.6%), involving the spine (14.6%) more frequently than the extremities (9.8%). Blunt abdominal and thoracic trauma were the most frequent extraskeletal findings. A wide spectrum of injuries can be found in avalanche victims, ranging from extremity fractures to massive polytrauma. Asphyxia remains the main cause of death along with hypoxic brain injury and hypothermia. (orig.)

  11. Nanopillar Optical Antenna Avalanche Detectors

    Science.gov (United States)

    2014-08-30

    68 , (11), 10. 51. Adachi, S., Properties of aluminium gallium ...bandwidth products > 100 GHz. 2 UNIVERSITY OF CALIFORNIA Los Angeles Nanopillar Optical Antenna Avalanche Detectors A dissertation... products > 100 GHz. 6 iii The dissertation of Pradeep

  12. Spike avalanches exhibit universal dynamics across the sleep-wake cycle.

    Directory of Open Access Journals (Sweden)

    Tiago L Ribeiro

    Full Text Available BACKGROUND: Scale-invariant neuronal avalanches have been observed in cell cultures and slices as well as anesthetized and awake brains, suggesting that the brain operates near criticality, i.e. within a narrow margin between avalanche propagation and extinction. In theory, criticality provides many desirable features for the behaving brain, optimizing computational capabilities, information transmission, sensitivity to sensory stimuli and size of memory repertoires. However, a thorough characterization of neuronal avalanches in freely-behaving (FB animals is still missing, thus raising doubts about their relevance for brain function. METHODOLOGY/PRINCIPAL FINDINGS: To address this issue, we employed chronically implanted multielectrode arrays (MEA to record avalanches of action potentials (spikes from the cerebral cortex and hippocampus of 14 rats, as they spontaneously traversed the wake-sleep cycle, explored novel objects or were subjected to anesthesia (AN. We then modeled spike avalanches to evaluate the impact of sparse MEA sampling on their statistics. We found that the size distribution of spike avalanches are well fit by lognormal distributions in FB animals, and by truncated power laws in the AN group. FB data surrogation markedly decreases the tail of the distribution, i.e. spike shuffling destroys the largest avalanches. The FB data are also characterized by multiple key features compatible with criticality in the temporal domain, such as 1/f spectra and long-term correlations as measured by detrended fluctuation analysis. These signatures are very stable across waking, slow-wave sleep and rapid-eye-movement sleep, but collapse during anesthesia. Likewise, waiting time distributions obey a single scaling function during all natural behavioral states, but not during anesthesia. Results are equivalent for neuronal ensembles recorded from visual and tactile areas of the cerebral cortex, as well as the hippocampus. CONCLUSIONS

  13. Avalanche effects near nanojunctions

    Science.gov (United States)

    Nandigana, Vishal V. R.; Aluru, N. R.

    2016-07-01

    In this article, we perform a computational investigation of a nanopore connected to external fluidic reservoirs of asymmetric geometries. The asymmetry between the reservoirs is achieved by changing the cross-sectional areas, and the reservoirs are designated as the micropore reservoir and macropore reservoir. When an electric field is applied, which is directed from the macropore towards the micropore reservoir, we observe local nonequilibrium chaotic current oscillations. The current oscillations originate at the micropore-nanopore interface owing to the local cascade of ions; we refer to this phenomenon as the "avalanche effects." We mathematically quantify chaos in terms of the maximum Lyapunov exponent. The maximum Lyapunov exponent exhibits a monotonic increase with the applied voltage and the macropore reservoir diameter. The temporal power spectra maps of the chaotic currents depict a low-frequency "1 /f "-type dynamics for the voltage chaos and "1 /f2 "-type dynamics for the macropore reservoir chaos. The results presented here offer avenues to manipulate ionic diodes and fluidic pumps.

  14. Ultraviolet avalanche photodiodes

    Science.gov (United States)

    McClintock, Ryan; Razeghi, Manijeh

    2015-08-01

    The III-Nitride material system is rapidly maturing; having proved itself as a material for LEDs and laser, and now finding use in the area of UV photodetectors. However, many UV applications are still dominated by the use of photomultiplier tubes (PMT). PMTs are capable of obtaining very high sensitivity using internal electron multiplication gain (typically ~106). It is highly desirable to develop a compact semiconductor-based photodetector capable of realizing this level of sensitivity. In principle, this can be obtained in III-Nitrides by taking advantage of avalanche multiplication under high electric fields - typically 2.7 MV/cm, which with proper design can correspond to an external reverse bias of less than 100 volts. In this talk, we review the current state-of-the-art in III-Nitride solar- and visible-blind APDs, and present our latest results on GaN APDs grown on both conventional sapphire and low dislocation density free-standing c- and m-plane GaN substrates. Leakage current, gain, and single photon detection efficiency (SPDE) of these APDs were compared. The spectral response and Geiger-mode photon counting performance of UV APDs are studied under low photon fluxes, with single photon detection capabilities as much as 30% being demonstrated in smaller devices. Geiger-mode operation conditions are optimized for enhanced SPDE.

  15. Avalanche risk assessment in Russia

    Science.gov (United States)

    Komarov, Anton; Seliverstov, Yury; Sokratov, Sergey; Glazovskaya, Tatiana; Turchaniniva, Alla

    2017-04-01

    The avalanche prone area covers about 3 million square kilometers or 18% of total area of Russia and pose a significant problem in most mountain regions of the country. The constant growth of economic activity, especially in the North Caucasus region and therefore the increased avalanche hazard lead to the demand of the large-scale avalanche risk assessment methods development. Such methods are needed for the determination of appropriate avalanche protection measures as well as for economic assessments during all stages of spatial planning of the territory. The requirement of natural hazard risk assessments is determined by the Federal Law of Russian Federation. However, Russian Guidelines (SP 11-103-97; SP 47.13330.2012) are not clearly presented concerning avalanche risk assessment calculations. A great size of Russia territory, vast diversity of natural conditions and large variations in type and level of economic development of different regions cause significant variations in avalanche risk values. At the first stage of research the small scale avalanche risk assessment was performed in order to identify the most common patterns of risk situations and to calculate full social risk and individual risk. The full social avalanche risk for the territory of country was estimated at 91 victims. The area of territory with individual risk values lesser then 1×10(-6) covers more than 92 % of mountain areas of the country. Within these territories the safety of population can be achieved mainly by organizational activities. Approximately 7% of mountain areas have 1×10(-6) - 1×10(-4) individual risk values and require specific mitigation measures to protect people and infrastructure. Territories with individual risk values 1×10(-4) and above covers about 0,1 % of the territory and include the most severe and hazardous mountain areas. The whole specter of mitigation measures is required in order to minimize risk. The future development of such areas is not recommended

  16. Observations and modelling of snow avalanche entrainment

    OpenAIRE

    2002-01-01

    In this paper full scale avalanche dynamics measurements from the Italian Pizzac and Swiss Vallée de la Sionne test sites are used to develop a snowcover entrainment model. A detailed analysis of three avalanche events shows that snowcover entrainment at the avalanche front appears to dominate over bed erosion at the basal sliding surface. Furthermore, the distribution of mass within the avalanche body is primarily a function of basal fric...

  17. Correlations in avalanche critical points

    Science.gov (United States)

    Cerruti, Benedetta; Vives, Eduard

    2009-07-01

    Avalanche dynamics and related power-law statistics are ubiquitous in nature, arising in phenomena such as earthquakes, forest fires, and solar flares. Very interestingly, an analogous behavior is associated with many condensed-matter systems, such as ferromagnets and martensites. Bearing it in mind, we study the prototypical random-field Ising model at T=0 . We find a finite correlation between waiting intervals and the previous avalanche size. This correlation is not found in other models for avalanches but it is experimentally found in earthquakes and in forest fires. Our study suggests that this effect occurs in critical points that are at the end of a first-order discontinuity separating two regimes: one with high activity from another with low activity.

  18. Lumped transmission line avalanche pulser

    Science.gov (United States)

    Booth, Rex

    1995-01-01

    A lumped linear avalanche transistor pulse generator utilizes stacked transistors in parallel within a stage and couples a plurality of said stages, in series with increasing zener diode limited voltages per stage and decreasing balanced capacitance load per stage to yield a high voltage, high and constant current, very short pulse.

  19. Avalanche dynamics on a rough inclined plane.

    Science.gov (United States)

    Börzsönyi, Tamás; Halsey, Thomas C; Ecke, Robert E

    2008-07-01

    The avalanche behavior of gravitationally forced granular layers on a rough inclined plane is investigated experimentally for different materials and for a variety of grain shapes ranging from spherical beads to highly anisotropic particles with dendritic shape. We measure the front velocity, area, and height of many avalanches and correlate the motion with the area and height. We also measure the avalanche profiles for several example cases. As the shape irregularity of the grains is increased, there is a dramatic qualitative change in avalanche properties. For rough nonspherical grains, avalanches are faster, bigger, and overturning in the sense that individual particles have down-slope speeds u p that exceed the front speed uf as compared with avalanches of spherical glass beads that are quantitatively slower and smaller and where particles always travel slower than the front speed. There is a linear increase of three quantities: (i) dimensionless avalanche height, (ii) ratio of particle to front speed, and (iii) the growth rate of avalanche speed with increasing avalanche size with increasing tan theta r where theta r is the bulk angle of repose, or with increasing beta P, the slope of the depth averaged flow rule, where both theta r and beta P reflect the grain shape irregularity. These relations provide a tool for predicting important dynamical properties of avalanches as a function of grain shape irregularity. A relatively simple depth-averaged theoretical description captures some important elements of the avalanche motion, notably the existence of two regimes of this motion.

  20. STUDY ON SIMULATION METHOD OF AVALANCHE : FLOW ANALYSIS OF AVALANCHE USING PARTICLE METHOD

    OpenAIRE

    2015-01-01

    In this paper, modeling for the simulation of the avalanche by a particle method is discussed. There are two kinds of the snow avalanches, one is the surface avalanche which shows a smoke-like flow, and another is the total-layer avalanche which shows a flow like Bingham fluid. In the simulation of the surface avalanche, the particle method in consideration of a rotation resistance model is used. The particle method by Bingham fluid is used in the simulation of the total-layer avalanche. At t...

  1. Avalanche hazard and control in Kazakhstan

    Directory of Open Access Journals (Sweden)

    V. P. Blagoveshchensky

    2014-01-01

    Full Text Available In Kazakhstan, area of 124 thousand km2 is prone to the avalanche hazard. Avalanches are released down in mountain regions situated along the eastern boundary of Kazakhstan. Systematic studies of avalanches here were started in 1958 by explorer I.S. Sosedov; later on, I.V. Seversky continued these investigations in Institute of Geography of the Kazakh Soviet Republic. Actually, he founded the Kazakh school of the avalanche studies. In 1970–1980s, five snow-avalanche stations operated in Kazakhstan: two in Il’ Alatau, two in Zhetysu Alatau, and one in the Altai. At the present time, only two stations and two snow-avalanche posts operate, and all of them are located in Il’ Alatau.Since 1951 to 2013, 75 avalanches took place in Kazakhstan, releases of them caused significant damages. For this period 172 people happened to be under avalanches, among them 86 perished. Large avalanche catastrophes causing human victims and destructions took place in Altai in 1977 and in Karatau in 1990. In spring of 1966, only in Il’ Alatau avalanches destroyed more 600 ha of mature fir (coniferous forest, and the total area of forest destroyed here by avalanches amounts to 2677 ha or 7% of the total forest area.For 48 years of the avalanche observations, there were 15 winters with increased avalanche activity in the river Almatinka basin when total volume of released snow exceeded annual mean value of 147 thousand m3. During this period, number of days with winter avalanches changed from three (in season of 1973/1974 to 28 (1986/1987, the average for a year is 16 days for a season. Winter with the total volume of snow 1300 thousand m3 occur once in 150 years. Individual avalanches with maximal volume of 350 thousand m3 happen once in 80 years.Preventive avalanche releases aimed at protection of roads and settlements are used in Kazakhstan since 1974. These precautions are taken in Il’ Alatau, Altai, and on Kalbinsky Range. Avalanches are released with the

  2. The prehospital management of avalanche victims.

    Science.gov (United States)

    Kornhall, Daniel K; Martens-Nielsen, Julie

    2016-12-01

    Avalanche accidents are frequently lethal events with an overall mortality of 23%. Mortality increases dramatically to 50% in instances of complete burial. With modern day dense networks of ambulance services and rescue helicopters, health workers often become involved during the early stages of avalanche rescue. Historically, some of the most devastating avalanche accidents have involved military personnel. Armed forces are frequently deployed to mountain regions in order to train for mountain warfare or as part of ongoing conflicts. Furthermore, military units are frequently called to assist civilian organised rescue in avalanche rescue operations. It is therefore important that clinicians associated with units operating in mountain regions have an understanding of, the medical management of avalanche victims, and of the preceding rescue phase. The ensuing review of the available literature aims to describe the pathophysiology particular to avalanche victims and to outline a structured approach to the search, rescue and prehospital medical management.

  3. Avalanche ecology and large magnitude avalanche events: Glacier National Park, Montana, USA

    Science.gov (United States)

    Fagre, Daniel B.; Peitzsch, Erich H.

    2010-01-01

    Large magnitude snow avalanches play an important role ecologically in terms of wildlife habitat, vegetation diversity, and sediment transport within a watershed. Ecological effects from these infrequent avalanches can last for decades. Understanding the frequency of such large magnitude avalanches is also critical to avalanche forecasting for the Going-to-the-Sun Road (GTSR). In January 2009, a large magnitude avalanche cycle occurred in and around Glacier National Park, Montana. The study site is the Little Granite avalanche path located along the GTSR. The study is designed to quantify change in vegetative cover immediately after a large magnitude event and document ecological response over a multi-year period. GPS field mapping was completed to determine the redefined perimeter of the avalanche path. Vegetation was inventoried using modified U.S. Forest Service Forest Inventory and Analysis plots, cross sections were taken from over 100 dead trees throughout the avalanche path, and an avalanche chronology was developed. Initial results indicate that the perimeter of this path was expanded by 30%. The avalanche travelled approximately 1200 vertical meters and 3 linear kilometers. Stands of large conifers as old as 150 years were decimated by the avalanche, causing a shift in dominant vegetation types in many parts of the avalanche path. Woody debris is a major ground cover up to 3 m in depth on lower portions of the avalanche path and will likely affect tree regrowth. Monitoring and measuring the post-avalanche vegetation recovery of this particular avalanche path provides a unique dataset for determining the ecological role of avalanches in mountain landscapes.

  4. [Avalanche emergencies. Review of the current situation].

    Science.gov (United States)

    Paal, P; Beikircher, W; Brugger, H

    2006-03-01

    In North America and Europe around 140 persons die every year due to avalanches, approximately 35 in North America, 100 in the European Alps, and 5 in other parts of Europe. Most of the victims are skiers and snowboarders. This article outlines the specific pathophysiology of avalanche burials, such as hypoxia, hypercapnia, and hypothermia and also other factors which influence survival. Strategies to minimize the mortality due to avalanches and the on-site treatment of buried persons are discussed. Finally, possibilities to reduce the number of avalanche deaths are pointed out.

  5. Remote detection of artificially triggered avalanches below a fixed avalanche control installation

    Science.gov (United States)

    van Herwijnen, Alec; Simioni, Stephan; Schweizer, Juerg

    2014-05-01

    Avalanche control by explosives is widely used as a temporary preventive measure to reduce avalanche hazard. The goal is to artificially trigger smaller less destructive avalanches, by detonating charges either above or on the snow surface. Hand charges are most often used, whereby the explosives are deployed by manually hand tossing or lowering onto the snow slope. Given the inherent dangers and limitations of this type of avalanche control, fixed avalanche control installations are increasingly used. These consist of strategically placed remote controlled installations that generate an explosion above the snow pack in an avalanche starting zone. While fixed installations can be used at any time and minimize the risk to avalanche control personnel, visual confirmation is still required to verify if an avalanche released. In order to remotely detect artificially triggered avalanches, we therefore developed a low-cost seismic monitoring system. We deployed the monitoring system in a ski area above the town of Davos , in the eastern Swiss Alps, below a Gazex installation, a remote controlled installation that generates an air blast by detonating a fuel-air explosive above the snow pack. The monitoring system consists of three vertical component geophones inserted in the ground at approximately 14, 27 and 46 meters from the Gazex installation. Our results show that, despite the relatively low precision of the monitoring equipment, both the detonation and the resulting avalanches can clearly be identified in the seismic data. Specifically, detonations are characterized by short, high amplitude broadband signals, while avalanches generate much longer, low frequency signals. Furthermore, information on the size of the artificially triggered avalanches is also obtained as it directly relates to the duration of the generated seismic signal. The overall goal is to assess the effectiveness of the fixed avalanche control installation with regards to yield (i.e. number of

  6. Triaging multiple victims in an avalanche setting: the Avalanche Survival Optimizing Rescue Triage algorithmic approach.

    Science.gov (United States)

    Bogle, Lee B; Boyd, Jeff J; McLaughlin, Kyle A

    2010-03-01

    As winter backcountry activity increases, so does exposure to avalanche danger. A complicated situation arises when multiple victims are caught in an avalanche and where medical and other rescue demands overwhelm resources in the field. These mass casualty incidents carry a high risk of morbidity and mortality, and there is no recommended approach to patient care specific to this setting other than basic first aid principles. The literature is limited with regard to triaging systems applicable to avalanche incidents. In conjunction with the development of an electronic avalanche rescue training module by the Canadian Avalanche Association, we have designed the Avalanche Survival Optimizing Rescue Triage algorithm to address the triaging of multiple avalanche victims to optimize survival and disposition decisions.

  7. Silicon Geiger mode avalanche photodiodes

    Institute of Scientific and Technical Information of China (English)

    M. Mazzillo; S. Billotta; G. Bonanno; A. Campisi; L. Cosentino; P. Finocchiaro; F. Musumeci; S.Privitera; S. Tudisco; G. Condorelli; D. Sanfilippo; G. Fallica; E. Sciacca; S. Aurite; S. Lombardo; E. Rlmini; M. Belluso

    2007-01-01

    In this letter we present the results regarding the electrical and optical characterization of Geiger mode silicon avalanche photodiodes (GMAP) fabricated by silicon standard planar technology. Low dark count rates, negligible afterpulsing effects,good timing resolution and high quantum detection efficiency in all the visible range have been measured. The very good electro-optical performances of our photodiodes make them attractive for the fabrication of arrays with a large number of GMAP to be used both in the commercial and the scientific fields, as telecommunications and nuclear medical imaging.

  8. Avalanche!--Teachable Moments in Outdoor Education

    Science.gov (United States)

    Galloway, Shayne

    2005-01-01

    Rarely do outdoor educators get the opportunity to safely incorporate an avalanche while the topic of the day is actually avalanche awareness and forecasting. Many similar possibilities exist in the expeditionary context, but even brief excursions may result in incredible learning experiences. These "teachable moments" occur regularly in the…

  9. Chaos and Correlated Avalanches in Excitatory Neural Networks with Synaptic Plasticity

    Science.gov (United States)

    Pittorino, Fabrizio; Ibáñez-Berganza, Miguel; di Volo, Matteo; Vezzani, Alessandro; Burioni, Raffaella

    2017-03-01

    A collective chaotic phase with power law scaling of activity events is observed in a disordered mean field network of purely excitatory leaky integrate-and-fire neurons with short-term synaptic plasticity. The dynamical phase diagram exhibits two transitions from quasisynchronous and asynchronous regimes to the nontrivial, collective, bursty regime with avalanches. In the homogeneous case without disorder, the system synchronizes and the bursty behavior is reflected into a period doubling transition to chaos for a two dimensional discrete map. Numerical simulations show that the bursty chaotic phase with avalanches exhibits a spontaneous emergence of persistent time correlations and enhanced Kolmogorov complexity. Our analysis reveals a mechanism for the generation of irregular avalanches that emerges from the combination of disorder and deterministic underlying chaotic dynamics.

  10. Observations and modelling of snow avalanche entrainment

    Directory of Open Access Journals (Sweden)

    B. Sovilla

    2002-01-01

    Full Text Available In this paper full scale avalanche dynamics measurements from the Italian Pizzac and Swiss Vallée de la Sionne test sites are used to develop a snowcover entrainment model. A detailed analysis of three avalanche events shows that snowcover entrainment at the avalanche front appears to dominate over bed erosion at the basal sliding surface. Furthermore, the distribution of mass within the avalanche body is primarily a function of basal friction. We show that the mass distribution in the avalanche changes the flow dynamics significantly. Two different dynamical models, the Swiss Voellmy-fluid model and the Norwegian NIS model, are used to back calculate the events. Various entrainment methods are investigated and compared to measurements. We demon-strate that the Norwegian NIS model is clearly better able to simulate the events once snow entrainment has been included in the simulations.

  11. Finding generically stable measures

    CERN Document Server

    Simon, Pierre

    2010-01-01

    We discuss two constructions for obtaining generically stable Keisler measures in an NIP theory. First, we show how to symmetrize an arbitrary invariant measure to obtain a generically stable one from it. Next, we show that suitable sigma-additive probability measures give rise to generically stable measures. Also included is a proof that generically stable measures over o-minimal theories and the p-adics are smooth.

  12. The generic article

    NARCIS (Netherlands)

    Farkas, D.F.; Swart, Henriëtte de

    2005-01-01

    We take a fresh look at the connection between genericity and (in)definiteness by reconsidering a long-standing puzzle concerning the relation between definiteness and genericity. We contrast English on the one hand and Romance languages and Hungarian on the other, focusing on generic sentences invo

  13. Thermal energy in dry snow avalanches

    Science.gov (United States)

    Steinkogler, W.; Sovilla, B.; Lehning, M.

    2015-09-01

    Avalanches can exhibit many different flow regimes from powder clouds to slush flows. Flow regimes are largely controlled by the properties of the snow released and entrained along the path. Recent investigations showed the temperature of the moving snow to be one of the most important factors controlling the mobility of the flow. The temperature of an avalanche is determined by the temperature of the released and entrained snow but also increases by frictional processes with time. For three artificially released avalanches, we conducted snow profiles along the avalanche track and in the deposition area, which allowed quantifying the temperature of the eroded snow layers. This data set allowed to calculate the thermal balance, from release to deposition, and to discuss the magnitudes of different sources of thermal energy of the avalanches. For the investigated dry avalanches, the thermal energy increase due to friction was mainly depending on the effective elevation drop of the mass of the avalanche with a warming of approximately 0.3 °C per 100 vertical metres. Contrarily, the temperature change due to entrainment varied for the individual avalanches, from -0.08 to 0.3 °C, and depended on the temperature of the snow along the path and the erosion depth. Infrared radiation thermography (IRT) was used to assess the surface temperature before, during and just after the avalanche with high spatial resolution. This data set allowed to identify the warmest temperatures to be located in the deposits of the dense core. Future research directions, especially for the application of IRT, in the field of thermal investigations in avalanche dynamics are discussed.

  14. Thermal energy in dry snow avalanches

    Directory of Open Access Journals (Sweden)

    W. Steinkogler

    2014-11-01

    Full Text Available Avalanches can exhibit many different flow regimes from powder clouds to slush flows. Flow regimes are largely controlled by the properties of the snow released and entrained along the path. Recent investigations showed the temperature of the moving snow to be one of the most important factors controlling the mobility of the flow. The temperature of an avalanche is determined by the temperature of the released and entrained snow but also increases by frictional and collisional processes with time. For three artificially released avalanches, we conducted snow profiles along the avalanche track and in the deposition area, which allowed quantifying the temperature of the eroded snow layers. Infrared radiation thermography (IRT was used to assess the surface temperature before, during and just after the avalanche with high spatial resolution. This data set allowed to calculate the thermal balance, from release to deposition, and to discuss the magnitudes of different sources of thermal energy of the avalanches. We could confirm that, for the investigated dry avalanches, the thermal energy increase due to friction was mainly depending on the elevation drop of the avalanche with a warming of approximately 0.5 °C per 100 height meters. Contrary, warming due to entrainment was very specific to the individual avalanche and depended on the temperature of the snow along the path and the erosion depth ranging from nearly no warming to a maximum observed warming of 1 °C. Furthermore, we could observe the warmest temperatures are located in the deposits of the dense core. Future research directions, especially for the application of IRT, in the field of thermal investigations in avalanche dynamics are discussed.

  15. Equilibrium avalanches in spin glasses

    Science.gov (United States)

    Le Doussal, Pierre; Müller, Markus; Wiese, Kay Jörg

    2012-06-01

    We study the distribution of equilibrium avalanches (shocks) in Ising spin glasses which occur at zero temperature upon small changes in the magnetic field. For the infinite-range Sherrington-Kirkpatrick (SK) model, we present a detailed derivation of the density ρ(ΔM) of the magnetization jumps ΔM. It is obtained by introducing a multicomponent generalization of the Parisi-Duplantier equation, which allows us to compute all cumulants of the magnetization. We find that ρ(ΔM)˜ΔM-τ with an avalanche exponent τ=1 for the SK model, originating from the marginal stability (criticality) of the model. It holds for jumps of size 1≪ΔMmodel. For finite-range models, using droplet arguments, we obtain the prediction τ=(df+θ)/dm where df,dm, and θ are the fractal dimension, magnetization exponent, and energy exponent of a droplet, respectively. This formula is expected to apply to other glassy disordered systems, such as the random-field model and pinned interfaces. We make suggestions for further numerical investigations, as well as experimental studies of the Barkhausen noise in spin glasses.

  16. Hummock alignment in Japanese volcanic debris avalanches controlled by pre-avalanche slope of depositional area

    Science.gov (United States)

    Yoshida, Hidetsugu

    2014-10-01

    This paper investigates the relationship of hummock orientation to the flow dynamics of volcanic debris avalanches. There are opposing views on whether hummocks are systematically aligned along debris avalanche paths, or not. To investigate this geomorphologically fundamental question, I investigated hummock orientation for six Japanese debris avalanches of two simple styles: four "freely spreading" debris avalanches, and two "valley-filling" debris avalanches. Quantitative GIS-based data analysis revealed that hummock orientation along the avalanche flow path alternated between dominantly parallel to and dominantly perpendicular to the flow direction. These changes of alignment reflect dynamic changes of the local stress field within the avalanche, alternating between extensional and compressional in response to changes of the slope of the pre-avalanche ground surface. Changes of hummock alignment from perpendicular to parallel indicate that the local stress regime has changed from compressional to extensional. Conversely, changes of hummock alignment from parallel to perpendicular indicate that the local stress regime has changed from extensional to compressional. Thus, this research demonstrated a clear relationship between hummock orientation and dynamic changes of stress regime within avalanches that are related to changes of the slope of the pre-avalanche ground surface.

  17. Avalanche Initiaition Mechanism - A Finite-element Approach

    Directory of Open Access Journals (Sweden)

    S. Senthil

    2003-01-01

    Full Text Available The Himalayas, the longest chain of mountains in the world, experiences extensive snowfall and avalanche activity during winter. Some of these areas are densely populated, and death and destruction on large scale due to avalanche activity has been reported in these areas. One of the ways of reducing the loss of life and material due to avalanches is through prediction of avalanches. An understanding of weather forecasting, terrain, and avalanche initiation mechanism is a prerequisite for avalanche prediction. In the present paper mathematical modelling of avalanche initiation mechanism has been discussed.

  18. InAs/InAsSb Avalanche Photodiode (APD) for applicaions in long-wavelength infrared region

    Institute of Scientific and Technical Information of China (English)

    P.K.Maurya; H.Agarwal; A.Singh; P.Chakrabarti

    2008-01-01

    A generic numerical model of a long-wavelength Avalanche Photodiode (APD) based on narrow bandgap semiconductor InAsSb on lnAs substrate is reported for the first time. This model has been applied for theoretical characterization of a proposed N+ InAS/P-InAsSb avalanche photodiode structure for possible application in 2-5 μm wavelength region. The parameters such as gain, excess noise factor and their trade-offwith variation of doping concentration and bias voltage have been estimated for the APD taking into account history-dependent theory of avalanche multiplication process. The LWIR APD is expected to find application in optical gas sensor and in future generation of optical communication system.

  19. Ionization avalanching in clusters ignited by extreme-ultraviolet driven seed electrons

    CERN Document Server

    Schütte, Bernd; Mermillod-Blondin, Alexandre; Vrakking, Marc J J; Rouzée, Arnaud; Fennel, Thomas

    2016-01-01

    We study the ionization dynamics of Ar clusters exposed to ultrashort near-infrared (NIR) laser pulses for intensities well below the threshold at which tunnel ionization could ignite the nanoplasma formation. We find that the emission of highly charged ions up to Ar$^{8+}$ can be switched on with unit contrast by generating only a few seed electrons with an ultrashort extreme ultraviolet (XUV) pulse prior to the NIR field. Molecular dynamics simulations can explain the experimental observations and predict a generic scenario where efficient heating via inverse bremsstrahlung and NIR avalanching are followed by resonant collective nanoplasma heating. The temporally and spatially well-controlled injection of the XUV seed electrons opens new routes for controlling avalanching and heating phenomena in nanostructures and solids, with implications for both fundamental and applied laser-matter science.

  20. Monitoring and modelling snow avalanches in Svalbard

    Science.gov (United States)

    Humlum, O.; Christiansen, H.; Neumann, U.; Eckerstorfer, M.; Sjöblom, A.; Stalsberg, K.; Rubensdotter, L.

    2009-04-01

    Monitoring and modelling snow avalanches in Svalbard Ole Humlum 1,3, Hanne H. Christiansen 1, Ulrich Neumann 1, Markus Eckerstorfer 1, Anna Sjöblom 1, Knut Stalsberg 2 and Lena Rubensdotter 2. 1: The University Centre in Svalbard (UNIS). 2: Geological Survey of Norway (NGU) 3: University of Oslo Ground based transportation in Svalbard landscape all takes place across mountainous terrain affected by different geomorphological slope processes. Traffic in and around the Svalbard settlements is increasing, and at the same time global climate models project substantial increases in temperature and precipitation in northern high latitudes for coming century. Therefore improved knowledge on the effect of climatic changes on slope processes in such high arctic landscapes is becoming increasingly important. Motivated by this, the CRYOSLOPE Svalbard research project since 2007 has carried out field observations on snow avalanche frequency and associated meteorological conditions. Snow avalanches are important geomorphic agents of erosion and deposition, and have long been a source of natural disasters in many mid-latitude mountain areas. Avalanches as a natural hazard has thereby been familiar to inhabitants of the Alps and Scandinavia for centuries, while it is a more recent experience in high arctic Svalbard. In addition, overall climate, topography and especially high winter wind speeds makes it difficult to apply snow avalanche models (numerical or empirical) developed for use at lower latitudes, e.g. in central Europe. In the presentation we examplify results from the ongoing (since winter 2006-07) monitoring of snow avalanches in Svalbard along a 70 km long observational route in the mountains. In addition, we present observations on the geomorphological impact of avalanches, with special reference to the formation of rock glaciers. Finally, we also present some initial results from numerical attempts of snow avalanche risk modelling within the study area.

  1. Statistics of Electron Avalanches and Streamers

    Directory of Open Access Journals (Sweden)

    T. Ficker

    2007-01-01

    Full Text Available We have studied the severe systematic deviations of populations of electron avalanches from the Furry distribution, which has been held to be the statistical law corresponding to them, and a possible explanation has been sought. A  new theoretical concept based on fractal avalanche multiplication has been proposed and is shown to be a convenient candidate for explaining these deviations from Furry statistics. 

  2. Catastrophic avalanches and methods of their control

    Directory of Open Access Journals (Sweden)

    N. A. Volodicheva

    2014-01-01

    Full Text Available Definition of such phenomenon as “catastrophic avalanche” is presented in this arti-cle. Several situations with releases of catastrophic avalanches in mountains of Caucasus, Alps, and Central Asia are investigated. Materials of snow-avalanche ob-servations performed since 1960s at the Elbrus station of the Lomonosov Moscow State University (Central Caucasus were used for this work. Complex-valued measures of engineering protection demonstrating different efficiencies are consid-ered.

  3. Evolution of the average avalanche shape with the universality class.

    Science.gov (United States)

    Laurson, Lasse; Illa, Xavier; Santucci, Stéphane; Tore Tallakstad, Ken; Måløy, Knut Jørgen; Alava, Mikko J

    2013-01-01

    A multitude of systems ranging from the Barkhausen effect in ferromagnetic materials to plastic deformation and earthquakes respond to slow external driving by exhibiting intermittent, scale-free avalanche dynamics or crackling noise. The avalanches are power-law distributed in size, and have a typical average shape: these are the two most important signatures of avalanching systems. Here we show how the average avalanche shape evolves with the universality class of the avalanche dynamics by employing a combination of scaling theory, extensive numerical simulations and data from crack propagation experiments. It follows a simple scaling form parameterized by two numbers, the scaling exponent relating the average avalanche size to its duration and a parameter characterizing the temporal asymmetry of the avalanches. The latter reflects a broken time-reversal symmetry in the avalanche dynamics, emerging from the local nature of the interaction kernel mediating the avalanche dynamics.

  4. Bioequivalence of generic drugs.

    Science.gov (United States)

    Andrade, Chittaranjan

    2015-09-01

    Generic drugs are bioequivalent to the original brand; this is a prerequisite for marketing approval. It is theoretically possible that one generic drug may overestimate the pharmacokinetic (PK) parameters of the original and another generic may underestimate these PK parameters; in consequence, these 2 generics may not be bioequivalent between themselves. The result could be loss of efficacy or development of drug-related adverse effects if these generics are interchanged in stable patients. In a recent study involving 292 indirect comparisons of generic formulations of 9 different drugs, mathematical modeling showed that in most cases (87.0% for maximum concentration, 90.1% for area under the curve, and 80.5% for both) generic drugs are bioequivalent to each other. These reassuring findings notwithstanding, prudence dictates that, in stable patients, generic drugs should be interchanged only if there is a good reason for it. This is because bioequivalent brands of drugs may differ in their excipient content, and this can result in variations in safety profiles.

  5. Generic Fortran Containers (GFC)

    Energy Technology Data Exchange (ETDEWEB)

    2016-09-01

    The Fortran language does not provide a standard library that implements generic containers, like linked lists, trees, dictionaries, etc. The GFC software provides an implementation of generic Fortran containers natively written in Fortran 2003/2008 language. The following containers are either already implemented or planned: Stack (done), Linked list (done), Tree (done), Dictionary (done), Queue (planned), Priority queue (planned).

  6. Avalanche analysis from multi-electrode ensemble recordings in cat, monkey and human cerebral cortex during wakefulness and sleep.

    Directory of Open Access Journals (Sweden)

    Nima eDehghani

    2012-08-01

    Full Text Available Self-organized critical states are found in many natural systems, from earthquakes to forest fires, they have also been observed in neural systems, particularly, in neuronal cultures. However, the presence of critical states in the awake brain remains controversial. Here, we compared avalanche analyses performed on different in vivo preparations during wakefulness, slow-wave sleep and REM sleep, using high-density electrode arrays in cat motor cortex (96 electrodes, monkey motor cortex and premotor cortex and human temporal cortex (96 electrodes in epileptic patients. In neuronal avalanches defined from units (up to 160 single units, the size of avalanches never clearly scaled as power-law, but rather scaled exponentially or displayed intermediate scaling. We also analyzed the dynamics of local field potentials (LFPs and in particular LFP negative peaks (nLFPs among the different electrodes (up to 96 sites in temporal cortex or up to 128 sites in adjacent motor and pre-motor cortices. In this case, the avalanches defined from nLFPs displayed power-law scaling in double logarithmic representations, as reported previously in monkey. However, avalanche defined as positive LFP (pLFP peaks, which are less directly related to neuronal firing, also displayed apparent power-law scaling. Closer examination of this scaling using the more reliable cumulative distribution function (CDF and other rigorous statistical measures, did not confirm power-law scaling. The same pattern was seen for cats, monkey and human, as well as for different brain states of wakefulness and sleep. We also tested other alternative distributions. Multiple exponential fitting yielded optimal fits of the avalanche dynamics with bi-exponential distributions. Collectively, these results show no clear evidence for power-law scaling or self-organized critical states in the awake and sleeping brain of mammals, from cat to man.

  7. Rock avalanches: significance and progress (Invited)

    Science.gov (United States)

    Davies, T. R.

    2013-12-01

    1. The probability distribution of landslide volumes follows a power-law indicating that large rock avalanches dominate the terrestrial sediment supply from mountains, and that their source area morphologies dominate mountain topography. 2. Large rock slope failures (~ 106 m3 or greater) often mobilise into rock avalanches, which can travel extraordinarily long distances with devastating effect. This hypermobility has been the subject of many investigations; we have demonstrated that it can be explained quantitatively and accurately by considering the energetics of the intense rock fragmentation that always occurs during motion of a large rock mass. 3. Study of rock avalanche debris psd shows that the energy used in creating new rock surface area during fragmentation is not lost to surface energy, but is recycled generating a high-frequency elastic energy field that reduces the frictional resistance to motion during runout. 4. Rock avalanches that deposit on glaciers can eventually form large terminal moraines that have no connection with any climatic event; unless these are identified as rock-avalanche-influenced they can confuse palaeoclimatic inferences drawn from moraine ages. Rock-avalanche-derived fines, however, can be identified in moraine debris up to ten thousand years old by the characteristic micron-scale agglomerates that form during intense fragmentation, and which are absent from purely climatically-induced moraines; there is thus a strong case for re-examining existing palaeoclimatic databases to eliminate potentially rock-avalanche-influenced moraine ages. 5. Rock avalanches (especially coseismic ones) are a serious hazard, being very destructive in their own right; they also block river valleys, forming landslide dams and potentially devastating dambreak floods, and subsequent severe decade-scale aggradation of downstream fans and floodplains. Rock avalanches falling into lakes or fiords can cause catastrophic tsunami that pose a serious risk to

  8. Electron avalanches in liquid argon mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J.G.; Dardin, S.M.; Kadel, R.W.; Kadyk, J.A.; Wenzel, W.B.; Peskov, V.

    2004-03-19

    We have observed stable avalanche gain in liquid argon when mixed with small amounts of xenon in the high electric field (>7 MV/cm) near the point of a chemically etched needle in a point-plane geometry. We identify two gain mechanisms, one pressure dependent, and the other independent of the applied pressure. We conclude that the pressure dependent signals are from avalanche gain in gas bubbles at the tip of the needle, while the pressure independent pulses are from avalanche gain in liquid. We measure the decay time spectra of photons from both types of avalanches. The decay times from the pressure dependent pulses decrease (increase) with the applied pressure (high voltage), while the decay times from the pressure independent pulses are approximately independent of pressure or high voltage. For our operating conditions, the collected charge distribution from avalanches is similar for 60 keV or 122 keV photon sources. With krypton additives, instead of Xe, we measure behavior consistent with only the pressure dependent pulses. Neon and TMS were also investigated as additives, and designs for practical detectors were tested.

  9. Deterministically Driven Avalanche Models of Solar Flares

    Science.gov (United States)

    Strugarek, Antoine; Charbonneau, Paul; Joseph, Richard; Pirot, Dorian

    2014-08-01

    We develop and discuss the properties of a new class of lattice-based avalanche models of solar flares. These models are readily amenable to a relatively unambiguous physical interpretation in terms of slow twisting of a coronal loop. They share similarities with other avalanche models, such as the classical stick-slip self-organized critical model of earthquakes, in that they are driven globally by a fully deterministic energy-loading process. The model design leads to a systematic deficit of small-scale avalanches. In some portions of model space, mid-size and large avalanching behavior is scale-free, being characterized by event size distributions that have the form of power-laws with index values, which, in some parameter regimes, compare favorably to those inferred from solar EUV and X-ray flare data. For models using conservative or near-conservative redistribution rules, a population of large, quasiperiodic avalanches can also appear. Although without direct counterparts in the observational global statistics of flare energy release, this latter behavior may be relevant to recurrent flaring in individual coronal loops. This class of models could provide a basis for the prediction of large solar flares.

  10. Deterministically Driven Avalanche Models of Solar Flares

    CERN Document Server

    Strugarek, Antoine; Joseph, Richard; Pirot, Dorian

    2014-01-01

    We develop and discuss the properties of a new class of lattice-based avalanche models of solar flares. These models are readily amenable to a relatively unambiguous physical interpretation in terms of slow twisting of a coronal loop. They share similarities with other avalanche models, such as the classical stick--slip self-organized critical model of earthquakes, in that they are driven globally by a fully deterministic energy loading process. The model design leads to a systematic deficit of small scale avalanches. In some portions of model space, mid-size and large avalanching behavior is scale-free, being characterized by event size distributions that have the form of power-laws with index values, which, in some parameter regimes, compare favorably to those inferred from solar EUV and X-ray flare data. For models using conservative or near-conservative redistribution rules, a population of large, quasiperiodic avalanches can also appear. Although without direct counterparts in the observational global st...

  11. High Resolution Radar Measurements of Snow Avalanches

    Science.gov (United States)

    McElwaine, Jim; Sovilla, Betty; Vriend, Nathalie; Brennan, Paul; Ash, Matt; Keylock, Chris

    2013-04-01

    Geophysical mass flows, such as snow avalanches, are a major hazard in mountainous areas and have a significant impact on the infrastructure, economy and tourism of such regions. Obtaining a thorough understanding of the dynamics of snow avalanches is crucial for risk assessment and the design of defensive structures. However, because the underlying physics is poorly understood there are significant uncertainties concerning current models, which are poorly validated due to a lack of high resolution data. Direct observations of the denser core of a large avalanche are particularly difficult, since it is frequently obscured by the dilute powder cloud. We have developed and installed a phased array FMCW radar system that penetrates the powder cloud and directly images the dense core with a resolution of around 1 m at 50 Hz over the entire slope. We present data from recent avalanches at Vallee de la Sionne that show a wealth of internal structure and allow the tracking of individual fronts, roll waves and surges down the slope for the first time. We also show good agreement between the radar results and existing measurement systems that record data at particular points on the avalanche track.

  12. Avalanche dynamics in silicon avalanche single- and few-photon sensitive photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Blazej, J; Prochazka, I, E-mail: blazej@fjfi.cvut.c [Czech Technical University in Prague, Brehova 7, 115 19 Prague 1 (Czech Republic)

    2009-11-15

    We are presenting the results of the study of the Single Photon Avalanche Diode (SPAD) avalanche pulse response rise-time and its dependence on several key parameters. We were investigating the unique properties of K14 type SPAD with its high delay uniformity of 200 {mu}m active area, the character of avalanche, and the correlation between the avalanche build-up time and the photon number involved in the avalanche trigger. The detection chip was operated with bias higher then breakdown voltage, ie. in Geiger mode. The detection chip was operated in a passive quenching circuit with active gating. This set-up enabled us to monitor both the diode reverse current using an electrometer and a fast digitizing oscilloscope. The electrometer reading enabled to estimate the photon number per detection event, the avalanche build up was recorded on the oscilloscope and processed by custom designed waveform analysis package. The correlation of avalanche build up to the photon number, bias above break, photon absorption location, optical pulse length and photon energy was investigated in detail. The experimental results are presented.

  13. Assessment of the Perchertal avalanche in Tyrol, Austria

    OpenAIRE

    KURT, Tayfun

    2014-01-01

    The present study has been conducted to analyze the Perchertal avalanche area near Bärenkopf Mountain, which has several avalanche-prone areas on its slopes, within the area of Pertisau, Tyrol, in Austria. The main focus is on identifying the characteristics of the avalanche process itself to determine the potential risk to endangered objects, which include an important road and a hotel. Another focus is to evaluate the current local hazard map. Based on the dynamic avalanche models (Samos-AT...

  14. Practicing the Generic (City)

    DEFF Research Database (Denmark)

    Hansen, Lone Koefoed

    2010-01-01

    Flanagan proposes that most locative media artworks neglect the particularities of spaces, their historical and political layers. Koolhaas, on the other hand, states that all urban areas are alike, that we are facing a global Generic City. The paper analyses digital media artist Esther Polak......’s NomadicMILK project in light of the generic and particular properties of space as laid out by Flanagan and Koolhaas in order to discuss the possible reconfiguring practices of locative media....

  15. Relating rock avalanche morphology to emplacement processes

    Science.gov (United States)

    Dufresne, Anja; Prager, Christoph; Bösmeier, Annette

    2015-04-01

    The morphology, structure and sedimentological characteristics of rock avalanche deposits reflect both internal emplacement processes and external influences, such as runout path characteristics. The latter is mainly predisposed by topography, substrate types, and hydrogeological conditions. Additionally, the geological setting at the source slope controls, e.g. the spatial distribution of accumulated lithologies and hence material property-related changes in morphology, or the maximum clast size and amount of fines of different lithological units. The Holocene Tschirgant rock avalanche (Tyrol, Austria) resulted from failure of an intensely deformed carbonate rock mass on the southeast face of a 2,370-m-high mountain ridge. The initially sliding rock mass rapidly fragmented as it moved towards the floor of the Inn River valley. Part of the 200-250 x 106 m3 (Patzelt 2012) rock avalanche debris collided with and moved around an opposing bedrock ridge and flowed into the Ötz valley, reaching up to 6.3 km from source. Where the Tschirgant rock avalanche spread freely it formed longitudinal ridges aligned along motion direction as well as smaller hummocks. Encountering high topography, it left runup ridges, fallback patterns (i.e. secondary collapse), and compressional morphology (successively elevated, transverse ridges). Further evidence for the mechanical landslide behaviour is given by large volumes of mobilized valley-fill sediments (polymict gravels and sands). These sediments indicate both shearing and compressional faulting within the rock avalanche mass (forming their own morphological units through, e.g. in situ bulldozing or as distinctly different hummocky terrain), but also indicate extension of the spreading landslide mass (i.e. intercalated/injected gravels encountered mainly in morphological depressions between hummocks). Further influences on its morphology are given by the different lithological units. E.g. the transition from massive dolomite

  16. Adjoint method and runaway electron avalanche

    Science.gov (United States)

    Liu, Chang; Brennan, Dylan P.; Boozer, Allen H.; Bhattacharjee, Amitava

    2017-02-01

    The adjoint method for the study of runaway electron dynamics in momentum space Liu et al (2016 Phys. Plasmas 23 010702) is rederived using the Green’s function method, for both the runaway probability function (RPF) and the expected loss time (ELT). The RPF and ELT obtained using the adjoint method are presented, both with and without the synchrotron radiation reaction force. The adjoint method is then applied to study the runaway electron avalanche. Both the critical electric field and the growth rate for the avalanche are calculated using this fast and novel approach.

  17. Assessing the importance of terrain parameters on glide avalanche release

    Science.gov (United States)

    Peitzsch, Erich H.; Hendrikx, Jordy; Fagre, Daniel B.

    2014-01-01

    Glide snow avalanches are dangerous and difficult to predict. Despite recent research there is still a lack of understanding regarding the controls of glide avalanche release. Glide avalanches often occur in similar terrain or the same locations annually and observations suggest that topography may be critical. Thus, to gain an understanding of the terrain component of these types of avalanches we examined terrain parameters associated with glide avalanche release as well as areas of consistent glide crack formation but no subsequent avalanches. Glide avalanche occurrences visible from the Going-to-the-Sun Road corridor in Glacier National Park, Montana from 2003-2013 were investigated using an avalanche database derived of daily observations each year from April 1 to June 15. This yielded 192 glide avalanches in 53 distinct avalanche paths. Each avalanche occurrence was digitized in a GIS using satellite, oblique, and aerial imagery as reference. Topographical parameters such as area, slope, aspect, elevation and elevation were then derived for the entire dataset utilizing GIS tools and a 10m DEM. Land surface substrate and surface geology were derived from National Park Service Inventory and Monitoring maps and U.S. Geological Survey surface geology maps, respectively. Surface roughness and glide factor were calculated using a four level classification index. . Then, each avalanche occurrence was aggregated to general avalanche release zones and the frequencies were compared. For this study, glide avalanches released in elevations ranging from 1300 to 2700 m with a mean aspect of 98 degrees (east) and a mean slope angle of 38 degrees. The mean profile curvature for all glide avalanches was 0.15 and a plan curvature of -0.01, suggesting a fairly linear surface (i.e. neither convex nor concave). The glide avalanches occurred in mostly bedrock made up of dolomite and limestone slabs and talus deposits with very few occurring in alpine meadows. However, not all glide

  18. Scale-free avalanches in disordered systems of localized charges with long-range Coulomb interaction

    Science.gov (United States)

    Palassini, Matteo; Goethe, Martin

    2012-02-01

    We study theoretically and numerically the charge avalanches created by a perturbation in disordered systems of localized charges with unscreened Coulomb interaction (the so-called electron glass model), in two and three dimensions. Starting from a low-lying local energy minimum, we perturb the system by inserting an extra charge or an extra dipole, and let it relax via one-particle hops until a new minimum is reached. We find that the size distribution of the avalanches created in this process displays generically a power-law tail with an exponent close to the mean-field value 3/2 both in 2D and 3D, without requiring any parameter tuning. We provide a qualitative explanation of these results in terms of the density of states of elementary charge and dipole excitations and the associated Coulomb gap, which shows that the power-law tail arises from arbitrarily long hops, without requiring to assume the existence of a glass phase. Finally, we discuss the experimental relevance of these results and compare our picture to similar scale-free avalanches observed in mean field spin glasses, in which they are are associated to a marginal glass phase.

  19. High temperature and wavelength dependence of avalanche gain of AlAsSb avalanche photodiodes.

    Science.gov (United States)

    Sandall, Ian C; Xie, Shiyu; Xie, Jingjing; Tan, Chee Hing

    2011-11-01

    The evolution of the dark currents and breakdown at elevated temperatures of up to 450  K are studied using thin AlAsSb avalanche regions. While the dark currents increase rapidly as the temperature is increased, the avalanche gain is shown to only have a weak temperature dependence. Temperature coefficients of breakdown voltage of 0.93 and 1.93  mV/K were obtained from the diodes of 80 and 230  nm avalanche regions (i-regions), respectively. These values are significantly lower than for other available avalanche materials at these temperatures. The wavelength dependence of multiplication characteristics of AlAsSb p-i-n diodes has also been investigated, and it was found that the ionization coefficients for electrons and holes are comparable within the electric field and wavelength ranges measured.

  20. Nano-multiplication region avalanche photodiodes and arrays

    Science.gov (United States)

    Zheng, Xinyu (Inventor); Pain, Bedabrata (Inventor); Cunningham, Thomas J. (Inventor)

    2011-01-01

    An avalanche photodiode with a nano-scale reach-through structure comprising n-doped and p-doped regions, formed on a silicon island on an insulator, so that the avalanche photodiode may be electrically isolated from other circuitry on other silicon islands on the same silicon chip as the avalanche photodiode. For some embodiments, multiplied holes generated by an avalanche reduces the electric field in the depletion region of the n-doped and p-doped regions to bring about self-quenching of the avalanche photodiode. Other embodiments are described and claimed.

  1. The avalanche-mode superjunction LED

    NARCIS (Netherlands)

    Dutta, Satadal; Steeneken, Peter G.; Agarwal, Vishal Vishal; Schmitz, Jurriaan; Annema, Anne J.; Hueting, Raymond Josephus Engelbart

    2017-01-01

    Avalanche-mode light-emitting diodes (AMLEDs) in silicon (Si) are potential light sources to enable monolithic optical links in standard CMOS technology, due to the large overlap of their electroluminescent (EL) spectra with the responsivity of Si photodiodes. These EL spectra depend on the reverse

  2. Measuring acoustic emissions in an avalanche slope

    Science.gov (United States)

    Reiweger, Ingrid; Schweizer, Jürg

    2014-05-01

    Measurements of acoustic emissions are a common technique for monitoring damage and predicting imminent failure of a material. Within natural hazards it has already been used to successfully predict the break-off of a hanging glacier. To explore the applicability of the acoustic emission (AE) technique for avalanche prediction, we installed two acoustic sensors (with 30 kHz and 60 kHz resonance frequency) in an avalanche prone slope at the Mittelgrat in the Parsenn ski area above Davos, Switzerland. The slope is north-east facing, frequently wind loaded, and approximately 35° steep. The AE signals - in particular the event energy and waiting time distributions - were compared with slope stability. The latter was determined by observing avalanche activity. The results of two winter's measurements yielded that the exponent β of the inverse cumulative distribution of event energy showed a significant drop (from a value of 3.5 to roughly 2.5) at very unstable conditions, i.e. on the three days during our measurement periods when spontaneous avalanches released on our study slope.

  3. Simulations of avalanche breakdown statistics: probability and timing

    Science.gov (United States)

    Ng, Jo Shien; Tan, Chee Hing; David, John P. R.

    2010-04-01

    Important avalanche breakdown statistics for Single Photon Avalanche Diodes (SPADs), such as avalanche breakdown probability, dark count rate, and the distribution of time taken to reach breakdown (providing mean time to breakdown and jitter), were simulated. These simulations enable unambiguous studies on effects of avalanche region width, ionization coefficient ratio and carrier dead space on the avalanche statistics, which are the fundamental limits of the SPADs. The effects of quenching resistor/circuit have been ignored. Due to competing effects between dead spaces, which are significant in modern SPADs with narrow avalanche regions, and converging ionization coefficients, the breakdown probability versus overbias characteristics from different avalanche region widths are fairly close to each other. Concerning avalanche breakdown timing at given value of breakdown probability, using avalanche material with similar ionization coefficients yields fast avalanche breakdowns with small timing jitter (albeit higher operating field), compared to material with dissimilar ionization coefficients. This is the opposite requirement for abrupt breakdown probability versus overbias characteristics. In addition, by taking band-to-band tunneling current (dark carriers) into account, minimum avalanche region width for practical SPADs was found to be 0.3 and 0.2 μm, for InP and InAlAs, respectively.

  4. Generic Airspace Survey

    Science.gov (United States)

    Mogford, Richard H.; Bridges, Wayne; Gujarl, Vimmy; Lee, Paul U.; Preston, William

    2013-01-01

    This paper reports on an extension of generic airspace research to explore the amount of memorization and specialized skills required to manage sectors with specific characteristics or factors. Fifty-five retired controllers were given an electronic survey where they rated the amount of memorization or specialized skills needed for sixteen generic airspace factors. The results suggested similarities in the pattern of ratings between different areas of the US (East, Central, and West). The average of the ratings for each area also showed some differences between regions, with ratings being generally higher in the East area. All sixteen factors were rated as moderately to highly important and may be useful for future research on generic airspace, air traffic controller workload, etc.

  5. Generic robot architecture

    Science.gov (United States)

    Bruemmer, David J [Idaho Falls, ID; Few, Douglas A [Idaho Falls, ID

    2010-09-21

    The present invention provides methods, computer readable media, and apparatuses for a generic robot architecture providing a framework that is easily portable to a variety of robot platforms and is configured to provide hardware abstractions, abstractions for generic robot attributes, environment abstractions, and robot behaviors. The generic robot architecture includes a hardware abstraction level and a robot abstraction level. The hardware abstraction level is configured for developing hardware abstractions that define, monitor, and control hardware modules available on a robot platform. The robot abstraction level is configured for defining robot attributes and provides a software framework for building robot behaviors from the robot attributes. Each of the robot attributes includes hardware information from at least one hardware abstraction. In addition, each robot attribute is configured to substantially isolate the robot behaviors from the at least one hardware abstraction.

  6. Rethinking generic skills

    Directory of Open Access Journals (Sweden)

    Roy Canning

    2013-10-01

    Full Text Available The paper provides a critical analysis of the notion of generic or transversal skillscontained with European Union policy discourses. The author presents a conceptualframework that challenges the idea that generic skills are universal, transferable andautonomous. An alternative analysis is put forward that argues the case forcontextualising skills and knowledge within particular understandings and cultures thatare more collective than individualistic in nature. The arguments are framed withinwider cross-disciplinary debates in linguistics, geosemiotics and social-cultural theoryand build upon an earlier paper exploring core skills in the UK (Canning, 2007.

  7. Generic Kalman Filter Software

    Science.gov (United States)

    Lisano, Michael E., II; Crues, Edwin Z.

    2005-01-01

    The Generic Kalman Filter (GKF) software provides a standard basis for the development of application-specific Kalman-filter programs. Historically, Kalman filters have been implemented by customized programs that must be written, coded, and debugged anew for each unique application, then tested and tuned with simulated or actual measurement data. Total development times for typical Kalman-filter application programs have ranged from months to weeks. The GKF software can simplify the development process and reduce the development time by eliminating the need to re-create the fundamental implementation of the Kalman filter for each new application. The GKF software is written in the ANSI C programming language. It contains a generic Kalman-filter-development directory that, in turn, contains a code for a generic Kalman filter function; more specifically, it contains a generically designed and generically coded implementation of linear, linearized, and extended Kalman filtering algorithms, including algorithms for state- and covariance-update and -propagation functions. The mathematical theory that underlies the algorithms is well known and has been reported extensively in the open technical literature. Also contained in the directory are a header file that defines generic Kalman-filter data structures and prototype functions and template versions of application-specific subfunction and calling navigation/estimation routine code and headers. Once the user has provided a calling routine and the required application-specific subfunctions, the application-specific Kalman-filter software can be compiled and executed immediately. During execution, the generic Kalman-filter function is called from a higher-level navigation or estimation routine that preprocesses measurement data and post-processes output data. The generic Kalman-filter function uses the aforementioned data structures and five implementation- specific subfunctions, which have been developed by the user on

  8. X-ray imaging using avalanche multiplication in amorphous selenium: investigation of depth dependent avalanche noise.

    Science.gov (United States)

    Hunt, D C; Tanioka, Kenkichi; Rowlands, J A

    2007-03-01

    The past decade has seen the swift development of the flat-panel detector (FPD), also known as the active matrix flat-panel imager, for digital radiography. This new technology is applicable to other modalities, such as fluoroscopy, which require the acquisition of multiple images, but could benefit from some improvements. In such applications where more than one image is acquired less radiation is available to form each image and amplifier noise becomes a serious problem. Avalanche multiplication in amorphous selenium (a-Se) can provide the necessary amplification prior to read out so as to reduce the effect of electronic noise of the FPD. However, in direct conversion detectors avalanche multiplication can lead to a new source of gain fluctuation noise called depth dependent avalanche noise. A theoretical model was developed to understand depth dependent avalanche noise. Experiments were performed on a direct imaging system implementing avalanche multiplication in a layer of a-Se to validate the theory. For parameters appropriate for a diagnostic imaging FPD for fluoroscopy the detective quantum efficiency (DQE) was found to drop by as much as 50% with increasing electric field, as predicted by the theoretical model. This drop in DQE can be eliminated by separating the collection and avalanche regions. For example by having a region of low electric field where x rays are absorbed and converted into charge that then drifts into a region of high electric field where the x-ray generated charge undergoes avalanche multiplication. This means quantum noise limited direct conversion FPD for low exposure imaging techniques are a possibility.

  9. Nearest neighbour models for local and regional avalanche forecasting

    Directory of Open Access Journals (Sweden)

    M. Gassner

    2002-01-01

    Full Text Available This paper presents two avalanche forecasting applications NXD2000 and NXD-REG which were developed at the Swiss Federal Institute for Snow and Avalanche Re-search (SLF. Even both are based on the nearest neighbour method they are targeted to different scales. NXD2000 is used to forecast avalanches on a local scale. It is operated by avalanche forecasters responsible for snow safety at snow sport areas, villages or cross country roads. The area covered ranges from 10 km2 up to 100 km2 depending on the climatological homogeneity. It provides the forecaster with ten most similar days to a given situation. The observed avalanches of these days are an indication of the actual avalanche danger. NXD-REG is used operationally by the Swiss avalanche warning service for regional avalanche forecasting. The Nearest Neighbour approach is applied to the data sets of 60 observer stations. The results of each station are then compiled into a map of current and future avalanche hazard. Evaluation of the model by cross-validation has shown that the model can reproduce the official SLF avalanche forecasts in about 52% of the days.

  10. Exploring Generic Haskell

    NARCIS (Netherlands)

    Löh, A.

    2004-01-01

    This thesis is an exploration -- an exploration of a language extension of the functional programming language Haskell. The extension is called Generic Haskell, albeit the name has been used to refer to different objects over the last several years: Many papers have described different proposals, fe

  11. Generic Market Models

    NARCIS (Netherlands)

    R. Pietersz (Raoul); M. van Regenmortel

    2005-01-01

    textabstractCurrently, there are two market models for valuation and risk management of interest rate derivatives, the LIBOR and swap market models. In this paper, we introduce arbitrage-free constant maturity swap (CMS) market models and generic market models featuring forward rates that span perio

  12. Avalanches in functional materials and geophysics

    CERN Document Server

    Saxena, Avadh; Planes, Antoni

    2017-01-01

    This book provides the state-of-the art of the present understanding of avalanche phenomena in both functional materials and geophysics. The main emphasis of the book is analyzing these apparently different problems within the common perspective of out-of-equilibrium phenomena displaying spatial and temporal complexity that occur in a broad range of scales. Many systems, when subjected to an external force, respond intermittently in the form of avalanches that often span over a wide range of sizes, energies and durations. This is often related to a class of critical behavior characterized by the absence of characteristic scales. Typical examples are magnetization processes, plastic deformation and failure occuring in functional materials. These phenomena share many similarities with seismicity arising from the earth crust failure due to stresses that originate from plate tectonics.

  13. Fractal properties of LED avalanche breakdown

    Directory of Open Access Journals (Sweden)

    Antonina S. Shashkina

    2016-12-01

    Full Text Available The conventional model of the processes occurring in the course of a p–n-junction's partial avalanche breakdown has been analyzed in this paper. Microplasma noise spectra of industrially produced LEDs were compared with those predicted by the model. It was established that the data obtained experimentally on reverse-biased LEDs could not be described in terms of this model. The degree to which the fractal properties were pronounced was shown to be variable by changing the reverse voltage. The discovered fractal properties of microplasma noise can serve as the basis for further studies which are bound to explain the breakdown characteristics of real LEDs and to correct the conventional model of p–n-junction's avalanche breakdown.

  14. Single electron multiplication distribution in GEM avalanches

    CERN Document Server

    Laszlo, Andras; Kiss, Gabor; Varga, Dezso

    2016-01-01

    In this paper measurement results and experimental methodology is presented on the determination of multiplication distributions of avalanches in GEM foils initiated by a single electron. The measurement relies on the amplification of photoelectrons by the GEM under study, which is subsequently amplified in an MWPC. The intrinsic detector resolution, namely the sigma over mean ratio of this distribution is also elaborated. Small gain dependence of the avalanche size is observed in the range of net effective gain of 15 to 100. The distribution has an exponentially decaying tail at large amplitudes, whereas the applied working gas is seen to have a well visible effect on the shape of the multiplication distribution at low amplitudes; or equivalently, the working gas has an influence on the intrinsic detector resolution of GEMs via suppression of the low amplitude responses. A sigma over mean ratio down to 0.75 was reached using neon based mixture, whereas other gases provided an intrinsic detector resolution cl...

  15. Do Neural Avalanches Indicate Criticality After All?

    CERN Document Server

    Dehghani, Mohammad; Shahbazi, Farhad

    2016-01-01

    Neural avalanches in size and duration exhibit a power law distribution illustrating as a straight line when plotted on the logarithmic scales. The power-law exponent is interpreted as the signature of criticality and it is assumed that the resting brain operates near criticality. However, there is no clear evidence that supports this assumption, and even there are extensive research studies conflicting one another. The model of the current paper is an extension of a previous publication wherein we used an integrate-and-fire model on a regular lattice with periodic boundary conditions and introduced the temporal complexity as a genuine signature of criticality. However, in that model the power-law distribution of neural avalanches were manifestation of super-criticality rather than criticality. Here, however, we show that replacing the discrete noise in the model with a Gaussian noise and continuous time solution of the equation leads to coincidence of temporal complexity and spatiotemporal patterns of neural...

  16. Electrothermal simulation of superconducting nanowire avalanche photodetectors

    Science.gov (United States)

    Marsili, Francesco; Najafi, Faraz; Herder, Charles; Berggren, Karl K.

    2011-02-01

    We developed an electrothermal model of NbN superconducting nanowire avalanche photodetectors (SNAPs) on sapphire substrates. SNAPs are single-photon detectors consisting of the parallel connection of N superconducting nanowires. We extrapolated the physical constants of the model from experimental data and we simulated the time evolution of the device resistance, temperature and current by solving two coupled electrical and thermal differential equations describing the nanowires. The predictions of the model were in good quantitative agreement with the experimental results.

  17. Shot noise suppression in avalanche photodiodes.

    Science.gov (United States)

    Ma, Feng; Wang, Shuling; Campbell, Joe C

    2005-10-21

    We identify a new shot noise suppression mechanism in a thin (approximately 100 nm) heterostructure avalanche photodiode. In the low-gain regime the shot noise is suppressed due to temporal correlations within amplified current pulses. We demonstrate in a Monte Carlo simulation that the effective excess noise factors can be < 1, and reconcile the apparent conflict between theory and experiments. This shot noise suppression mechanism is independent of known mechanisms such as Coulomb interaction, or reflection at heterojunction interfaces.

  18. Edge effect on the power law distribution of granular avalanches.

    Science.gov (United States)

    Lorincz, Kinga A; Wijngaarden, Rinke J

    2007-10-01

    Many punctuated phenomena in nature are claimed [e.g., by the theory of self-organized criticality (SOC)] to be power-law distributed. In our experiments on a three-dimensional pile of long-grained rice, we find that by only changing the boundary condition of the system, we switch from such power-law-distributed avalanche sizes to quasiperiodic system-spanning avalanches. Conversely, by removing ledges the incidence of system-spanning avalanches is significantly reduced. This may offer a perspective on new avalanche prevention schemes. In addition, our findings may help to explain why the archetype of SOC, the sandpile, was found to have power-law-distributed avalanches in some experiments, while in other experiments quasiperiodic system-spanning avalanches were found.

  19. Generic and biosimilar medicines: quid?

    Directory of Open Access Journals (Sweden)

    Steven Simoens

    2012-12-01

    Full Text Available Once intellectual property protection, data and marketing exclusivity of reference medicines have expired, generic medicines and biosimilar medicines can enter the off-patent market. This market entry is conditional on the approval of marketing authorization, pricing and reimbursement. Given that there tends to be confusion surrounding generic and biosimilar medicines, this Editorial introduces basic concepts related to generic and biosimilar medicines and presents the different studies and articles included in this supplement dedicated to generic and biosimilar medicines.

  20. Monte Carlo investigation of avalanche multiplication process in thin InP avalanche photodiodes

    Institute of Scientific and Technical Information of China (English)

    WANG Gang; MA YuXiang

    2009-01-01

    An ensemble Monte Carlo simulation is presented to investigate the avalanche multiplication process in thin InP avalanche photodiodes (APDs). Analytical band structures are applied to the description of the conduction and valence band, and impact ionization is treated as an additional scattering mecha-nism with the Keldysh formula. Multiplication gain and excess noise factor of InP p~+-i-n~+ APDs aresimulated and obvious excess noise reduction is found in the thinner devices. The effect of dead space on excess noise in thin APD structures is investigated by the distribution of impact ionization events within the multiplication region. It is found that the dead space can suppress the feedback ionization events resulting in a more deterministic avalanche multiplication process and reduce the excess noise in thinner APDs.

  1. Modelling avalanche danger and understanding snow depth variability

    OpenAIRE

    2010-01-01

    This thesis addresses the causes of avalanche danger at a regional scale. Modelled snow stratigraphy variables were linked to [1] forecasted avalanche danger and [2] observed snowpack stability. Spatial variability of snowpack parameters in a region is an additional important factor that influences the avalanche danger. Snow depth and its change during individual snow fall periods are snowpack parameters which can be measured at a high spatial resolution. Hence, the spatial distribution of sn...

  2. Determining avalanche modelling input parameters using terrestrial laser scanning technology

    OpenAIRE

    2013-01-01

    International audience; In dynamic avalanche modelling, data about the volumes and areas of the snow released, mobilized and deposited are key input parameters, as well as the fracture height. The fracture height can sometimes be measured in the field, but it is often difficult to access the starting zone due to difficult or dangerous terrain and avalanche hazards. More complex is determining the areas and volumes of snow involved in an avalanche. Such calculations require high-resolution spa...

  3. New advances for modelling the debris avalanches

    Science.gov (United States)

    Cuomo, Sabatino; Cascini, Leonardo; Pastor, Manuel; Castorino, Giuseppe Claudio

    2013-04-01

    Flow-like landslides are a major global hazard and they occur worldwide causing a large number of casualties, significant structural damages to property and infrastructures as well as economic losses. When involving open slopes, these landslides often occur in triangular source areas where initial slides turn into avalanches through further failures and/or eventual soil entrainment. This paper deals with the numerical modelling of the propagation stage of debris avalanches which provides information such as the propagation pattern of the mobilized material, its velocity, thickness and run-out distance. In the paper, a "depth integrated" model is used which allows: i) adequately taking into account the irregular topography of real slopes which greatly affect the propagation stage and ii) using a less time consuming model than fully 3D approaches. The used model is named "GeoFlow_SPH" and it was formerly applied to theoretical, experimental and real case histories (Pastor et al., 2009; Cascini et al., 2012). In this work the behavior of debris avalanches is analyzed with special emphasis on the apical angle, one of the main features of this type of landslide, in relation to soil rheology, hillslope geometry and features of triggering area. Furthermore, the role of erosion has been investigated with reference to the uppermost parts of open slopes with a different steepness. These analyses are firstly carried out for simplified benchmark slopes, using both water-like materials (with no shear strength) and debris type materials. Then, three important case studies of Campania region (Cervinara, Nocera Inferiore e Sarno) are analyzed where debris avalanches involved pyroclastic soils originated from the eruptive products of Vesusius volcano. The results achieved for both benchmark slopes and real case histories outline the key role played by the erosion on the whole propagation stage of debris avalanches. The results are particularly satisfactory since they indicate the

  4. Generic wormhole throats

    CERN Document Server

    Visser, M; Visser, Matt; Hochberg, David

    1997-01-01

    Wormholes and black holes have traditionally been treated a quite separate objects with relatively little overlap. The possibility of a connection arises in that wormholes, if they exist, might have profound influence on black holes, their event horizons, and their internal structure. After discussing some connections, we embark on an overview of what can generally be said about traversable wormhole throats. We discuss the violations of the energy conditions that typically occur at and near the throat of any traversable wormhole and emphasize the generic nature of this result. We discuss the original Morris-Thorne wormhole and its generalization to a spherically symmetric time-dependent wormhole, and also discuss spherically symmetric Brans-Dicke wormholes. We also discuss the relationship with the topological censorship theorem. Finally we turn to a rather general class of wormholes that permit explicit analysis: generic static traversable wormholes (without any symmetry). We define the wormhole throat in te...

  5. Correcting for accidental correlations in saturated avalanche photodiodes

    National Research Council Canada - National Science Library

    Grieve, J A; Chandrasekara, R; Tang, Z; Cheng, C; Ling, A

    2016-01-01

    .... As an example, we provide a detailed high-level model for the behaviour of passively quenched avalanche photodiodes, and demonstrate effective background subtraction at rates commonly associated...

  6. Generic safety documentation model

    Energy Technology Data Exchange (ETDEWEB)

    Mahn, J.A.

    1994-04-01

    This document is intended to be a resource for preparers of safety documentation for Sandia National Laboratories, New Mexico facilities. It provides standardized discussions of some topics that are generic to most, if not all, Sandia/NM facilities safety documents. The material provides a ``core`` upon which to develop facility-specific safety documentation. The use of the information in this document will reduce the cost of safety document preparation and improve consistency of information.

  7. Generic Network Location Service

    Directory of Open Access Journals (Sweden)

    Laban Mwansa

    2010-11-01

    Full Text Available This work presents the Generic Network Location Service based on the Chord implementation utilizing data structures called distributed hash tables (DHT or structured overlay networks, which are used to build scalable self-managing distributed systems. The provided algorithms guarantee resilience in the presence of dynamism: they guarantee consistent lookup results in the presence of nodes failing and leaving. Generic Network Location Service provides a Location Service system based on DHT technology, which is storing device location records in nodes within a Chord DHT. Location records are consisting of network device identification keys as attributes, which are used to create replicas of additional location records through established Chord hashing mechanisms. Storing device location records, in places address-able (using the DHT lookup by individual location record keys provides a simple way of implementing transla¬tion functions similar to well¬ known network services (e.g. ARP, DNS, ENUM. The generic network location ser¬vice presented in the paper is not supposed to be a substitu¬tion of the existing translation techniques (e.g. ARP, DNS, ENUM, but it is considered as an overlay service that uses data available in existing systems and provides some translations currently unavailable.

  8. Radiation damage effect on avalanche photodiodes

    CERN Document Server

    Baccaro, S; Cavallari, F; Da Ponte, V; Deiters, K; Denes, P; Diemoz, M; Kirn, Th; Lintern, A L; Longo, E; Montecchi, M; Musienko, Y; Pansart, J P; Renker, D; Reucroft, S; Rosi, G; Rusack, R; Ruuska, D; Stephenson, R; Torbet, M J

    1999-01-01

    Avalanche Photodiodes have been chosen as photon sensors for the electromagnetic calorimeter of the CMS experiment at the LHC. These sensors should operate in the 4T magnetic field of the experiment. Because of the high neutron radiation in the detector extensive studies have been done by the CMS collaboration on the APD neutron radiation damage. The characteristics of these devices after irradiation have been analized, with particular attention to the quantum efficiency and the dark current. The recovery of the radiation induced dark current has been studied carefully at room temperature and at slightly lower and higher temperatures. The temperature dependence of the defects decay-time has been evaluated.

  9. Photon detection with cooled avalanche photodiodes

    Science.gov (United States)

    Robinson, D. L.; Metscher, B. D.

    1987-01-01

    Commercial avalanche photodiodes have been operated as single-photon detectors at an optimum operating temperature and bias voltage. These detectors were found to be 1.5-3 times more sensitive than presently available photomultiplier tubes (PMTs). Both single-photon detection probability and detector noise increase with bias voltage; detection probabilities greater than twice that of a PMT were obtained with detector noise levels below 100 counts per second. Higher probabilities were measured at higher noise levels. The sources of noise and their dependence on temperature and bias voltage are discussed.

  10. Cooled avalanche photodiode used for photon detection

    Science.gov (United States)

    Robinson, Deborah L.; Metscher, Brian D.

    1987-01-01

    Commercial avalanche photodiodes have been operated as single-photon detectors at an optimum operating temperature and bias voltage. These detectors were found to be 1.5 to 3 times more sensitive than presently-available photomultiplier tubes (PPMTs). Both single-photon detection probability and detector noise increase with bias voltage; detection probabilities greater than 25 percent were obtained with detector noise levels comparable to the noise of a PMT; higher probabilities were measured at higher noise levels. The sources of noise and their dependence on temperature and bias voltage are discussed.

  11. Avalanche Photodiode Arrays for Optical Communications Receivers

    Science.gov (United States)

    Srinivasan, M.; Vilnrotter, V.

    2001-01-01

    An avalanche photodiode (APD) array for ground-based optical communications receivers is investigated for the reception of optical signals through the turbulent atmosphere. Kolmogorov phase screen simulations are used to generate realistic spatial distributions of the received optical field. It is shown that use of an APD array for pulse-position modulation detection can improve performance by up to 4 dB over single APD detection in the presence of turbulence, but that photon-counting detector arrays yield even greater gains.

  12. Avalanches in UGe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Lhotel, E. E-mail: lhotel@grenoble.cnrs.fr; Paulsen, C.; Huxley, A.D

    2004-05-01

    In UGe{sub 2} ferromagnetism and superconductivity co-exist for pressures in the range 1.0-1.6 GPa. The magnetic state, however, has several unusual properties. Here we report measurements of hysteresis loops for fields parallel to the easy-axis at low temperature and ambient pressure, measured for two separate UGe{sub 2} single crystals. Steps in the magnetization as the field is changed at low temperature are observed for both crystals. The general phenomenology associated with the steps strongly suggests that they correspond to avalanches of domain-wall motion.

  13. TCAD simulation of Low Gain Avalanche Detectors

    Science.gov (United States)

    Dalal, Ranjeet; Jain, Geetika; Bhardwaj, Ashutosh; Ranjan, Kirti

    2016-11-01

    In the present work, detailed simulation using Technology Computer Aided Design (TCAD) tool, Silvaco for non-irradiated and irradiated LGAD (Low Gain Avalanche Detector) devices has been carried out. The effects of different design parameters and proton irradiation on LGAD operation are discussed in detail. An already published effective two trap bulk damage model is used to simulate the radiation damage without implementing any acceptor removal term. The TCAD simulation for irradiated LGAD devices produce decreasing gain with increasing fluence, similar to the measurement results. The space charge density and electric field distribution are used to illustrate the possible reasons for the degradation of gain of the irradiated LGAD devices.

  14. Avalanche Effect in Improperly Initialized CAESAR Candidates

    Directory of Open Access Journals (Sweden)

    Martin Ukrop

    2016-12-01

    Full Text Available Cryptoprimitives rely on thorough theoretical background, but often lack basic usability features making them prone to unintentional misuse by developers. We argue that this is true even for the state-of-the-art designs. Analyzing 52 candidates of the current CAESAR competition has shown none of them have an avalanche effect in authentication tag strong enough to work properly when partially misconfigured. Although not directly decreasing their security profile, this hints at their security usability being less than perfect. Paper details available at crcs.cz/papers/memics2016

  15. Bilayer avalanche spin-diode logic

    Energy Technology Data Exchange (ETDEWEB)

    Friedman, Joseph S., E-mail: joseph.friedman@u-psud.fr; Querlioz, Damien [Institut d’Electronique Fondamentale, Univ. Paris-Sud, CNRS, 91405 Orsay (France); Fadel, Eric R. [Department of Materials Science, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Wessels, Bruce W. [Department of Electrical Engineering & Computer Science, Northwestern University, Evanston, IL 60208 (United States); Department of Materials Science & Engineering, Northwestern University, Evanston, IL 60208 (United States); Sahakian, Alan V. [Department of Electrical Engineering & Computer Science, Northwestern University, Evanston, IL 60208 (United States); Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208 (United States)

    2015-11-15

    A novel spintronic computing paradigm is proposed and analyzed in which InSb p-n bilayer avalanche spin-diodes are cascaded to efficiently perform complex logic operations. This spin-diode logic family uses control wires to generate magnetic fields that modulate the resistance of the spin-diodes, and currents through these devices control the resistance of cascaded devices. Electromagnetic simulations are performed to demonstrate the cascading mechanism, and guidelines are provided for the development of this innovative computing technology. This cascading scheme permits compact logic circuits with switching speeds determined by electromagnetic wave propagation rather than electron motion, enabling high-performance spintronic computing.

  16. Generic medications in ophthalmology.

    Science.gov (United States)

    Zore, Matt; Harris, Alon; Tobe, Leslie Abrams; Siesky, Brent; Januleviciene, Ingrida; Behzadi, Jennifer; Amireskandari, Annahita; Egan, Patrick; Garff, Kevin; Wirostko, Barbara

    2013-03-01

    The purpose of this review is to discuss the process of genericisation of medications in the US and Europe with a focus on ophthalmic drugs. Regulatory guidelines of the US Food and Drug Administration and the European Medicines Agency will be discussed, and the advantages and concerns of genericisation will be explored. We will look at various studies concerning the safety and efficacy of generic drugs compared to their branded counterparts. In particular, the challenges of assuring bioequivalence and therapeutic equivalence in topical ophthalmic drugs will be examined.

  17. Generic patch inference

    DEFF Research Database (Denmark)

    Andersen, Jesper; Lawall, Julia

    2010-01-01

    A key issue in maintaining Linux device drivers is the need to keep them up to date with respect to evolutions in Linux internal libraries. Currently, there is little tool support for performing and documenting such changes. In this paper we present a tool, spdiff, that identifies common changes...... developers can use it to extract an abstract representation of the set of changes that others have made. Our experiments on recent changes in Linux show that the inferred generic patches are more concise than the corresponding patches found in commits to the Linux source tree while being safe with respect...

  18. A cooled avalanche photodiode with high photon detection probability

    Science.gov (United States)

    Robinson, D. L.; Metscher, B. D.

    1986-01-01

    An avalanche photodiode has been operated as a photon-counting detector with 2 to 3 times the sensitivity of currently-available photomultiplier tubes. APD (avalanche photodiodes) detection probabilities that exceed 27% and approach 50% have been measured at an optimum operating temperature which minimizes noise. The sources of noise and their dependence on operating temperature and bias voltage are discussed.

  19. Radiation and Temperature Hard Multi-Pixel Avalanche Photodiodes

    Science.gov (United States)

    Bensaoula, Abdelhak (Inventor); Starikov, David (Inventor); Pillai, Rajeev (Inventor)

    2017-01-01

    The structure and method of fabricating a radiation and temperature hard avalanche photodiode with integrated radiation and temperature hard readout circuit, comprising a substrate, an avalanche region, an absorption region, and a plurality of Ohmic contacts are presented. The present disclosure provides for tuning of spectral sensitivity and high device efficiency, resulting in photon counting capability with decreased crosstalk and reduced dark current.

  20. Validation of DEM prediction for granular avalanches on irregular terrain

    Science.gov (United States)

    Mead, Stuart R.; Cleary, Paul W.

    2015-09-01

    Accurate numerical simulation can provide crucial information useful for a greater understanding of destructive granular mass movements such as rock avalanches, landslides, and pyroclastic flows. It enables more informed and relatively low cost investigation of significant risk factors, mitigation strategy effectiveness, and sensitivity to initial conditions, material, or soil properties. In this paper, a granular avalanche experiment from the literature is reanalyzed and used as a basis to assess the accuracy of discrete element method (DEM) predictions of avalanche flow. Discrete granular approaches such as DEM simulate the motion and collisions of individual particles and are useful for identifying and investigating the controlling processes within an avalanche. Using a superquadric shape representation, DEM simulations were found to accurately reproduce transient and static features of the avalanche. The effect of material properties on the shape of the avalanche deposit was investigated. The simulated avalanche deposits were found to be sensitive to particle shape and friction, with the particle shape causing the sensitivity to friction to vary. The importance of particle shape, coupled with effect on the sensitivity to friction, highlights the importance of quantifying and including particle shape effects in numerical modeling of granular avalanches.

  1. Avalanches mediate crystallization in a hard-sphere glass.

    Science.gov (United States)

    Sanz, Eduardo; Valeriani, Chantal; Zaccarelli, Emanuela; Poon, Wilson C K; Cates, Michael E; Pusey, Peter N

    2014-01-07

    By molecular-dynamics simulations, we have studied the devitrification (or crystallization) of aged hard-sphere glasses. First, we find that the dynamics of the particles are intermittent: Quiescent periods, when the particles simply "rattle" in their nearest-neighbor cages, are interrupted by abrupt "avalanches," where a subset of particles undergo large rearrangements. Second, we find that crystallization is associated with these avalanches but that the connection is not straightforward. The amount of crystal in the system increases during an avalanche, but most of the particles that become crystalline are different from those involved in the avalanche. Third, the occurrence of the avalanches is a largely stochastic process. Randomizing the velocities of the particles at any time during the simulation leads to a different subsequent series of avalanches. The spatial distribution of avalanching particles appears random, although correlations are found among avalanche initiation events. By contrast, we find that crystallization tends to take place in regions that already show incipient local order.

  2. Avalanche behavior of power MOSFETs under different temperature conditions

    Institute of Scientific and Technical Information of China (English)

    Lu Jiang; Wang Lixin; Lu Shuojin; Wang Xuesheng; Han Zhengsheng

    2011-01-01

    The ability of high-voltage power MOSFETs to withstand avalanche events under different temperature conditions are studied by experiment and two-dimensional device simulation. The experiment is performed to investigate dynamic avalanche failure behavior of the domestic power MOSFETs which can occur at the rated maximum operation temperature range (-55 to 150 ℃). An advanced ISE TCAD two-dimensional mixed mode simulator with thermodynamic non-isothermal model is used to analyze the avalanche failure mechanism. The unclamped inductive switching measurement and simulation results show that the parasitic components and thermal effect inside the device will lead to the deterioration of the avalanche reliability of power MOSFETs with increasing temperature. The main failure mechanism is related to the parasitic bipolar transistor activity during the occurrence of the avalanche behavior.

  3. Recent Sand Avalanching on Rabe Crater Dunes

    Science.gov (United States)

    2000-01-01

    Dark streaks on the steep, down-wind slopes of sand dunes in Rabe Crater are seen at several locations in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image. These streaks indicate relatively recent (i.e., in the past few years or less) movement of sand down these slopes.Sand dunes move forward by the combined action of wind that drives sand up the shallow slope on the windward side of the dune (in this case, the slopes that face toward the lower right) and the avalanching of this sand down the steeper, lee-side slope. The steep slope is also known as the slip face. The dark streaks indicated by arrows are evidence for sand avalanches that occurred within a few months or years of the time when the picture was taken in March 1999. Other streaks which are seen criss-crossing the dunes may be the result of passing dust devils. This image is illuminated from the upper left and located in Rabe Crater of the Hellespontus-Noachis region near 44.2oS, 325.6oW.

  4. NET 40 Generics Beginner's Guide

    CERN Document Server

    Mukherjee, Sudipta

    2012-01-01

    This is a concise, practical guide that will help you learn Generics in .NET, with lots of real world and fun-to-build examples and clear explanations. It is packed with screenshots to aid your understanding of the process. This book is aimed at beginners in Generics. It assumes some working knowledge of C# , but it isn't mandatory. The following would get the most use out of the book: Newbie C# developers struggling with Generics. Experienced C++ and Java Programmers who are migrating to C# and looking for an alternative to other generic frameworks like STL and JCF would find this book handy.

  5. Generic Quantum Fourier Transforms

    CERN Document Server

    Moore, Cristopher; Russell, A; Moore, Cristopher; Rockmore, Daniel; Russell, Alexander

    2003-01-01

    The quantum Fourier transform (QFT) is the principal algorithmic tool underlying most efficient quantum algorithms. We present a generic framework for the construction of efficient quantum circuits for the QFT by ``quantizing'' the separation of variables technique that has been so successful in the study of classical Fourier transform computations. Specifically, this framework applies the existence of computable Bratteli diagrams, adapted factorizations, and Gel'fand-Tsetlin bases to offer efficient quantum circuits for the QFT over a wide variety a finite Abelian and non-Abelian groups, including all group families for which efficient QFTs are currently known and many new group families. Moreover, the method gives rise to the first subexponential-size quantum circuits for the QFT over the linear groups GL_k(q), SL_k(q), and the finite groups of Lie type, for any fixed prime power q.

  6. Dimensional regularization is generic

    CERN Document Server

    Fujikawa, Kazuo

    2016-01-01

    The absence of the quadratic divergence in the Higgs sector of the Standard Model in the dimensional regularization is usually regarded to be an exceptional property of a specific regularization. To understand what is going on in the dimensional regularization, we illustrate how to reproduce the results of the dimensional regularization for the $\\lambda\\phi^{4}$ theory in the more conventional regularization such as the higher derivative regularization; the basic postulate involved is that the quadratically divergent induced mass, which is independent of the scale change of the physical mass, is kinematical and unphysical. This is consistent with the derivation of the Callan-Symanzik equation, which is a comparison of two theories with slightly different masses, for the $\\lambda\\phi^{4}$ theory without encountering the quadratic divergence. We thus suggest that the dimensional regularization is generic in a bottom-up approach starting with a successful low-energy theory. We also define a modified version of t...

  7. Generic torus canards

    Science.gov (United States)

    Vo, Theodore

    2017-10-01

    Torus canards are special solutions of fast/slow systems that alternate between attracting and repelling manifolds of limit cycles of the fast subsystem. A relatively new dynamic phenomenon, torus canards have been found in neural applications to mediate the transition from tonic spiking to bursting via amplitude-modulated spiking. In R3, torus canards are degenerate: they require one-parameter families of 2-fast/1-slow systems in order to be observed and even then, they only occur on exponentially thin parameter intervals. The addition of a second slow variable unfolds the torus canard phenomenon, making it generic and robust. That is, torus canards in fast/slow systems with (at least) two slow variables occur on open parameter sets. So far, generic torus canards have only been studied numerically, and their behaviour has been inferred based on averaging and canard theory. This approach, however, has not been rigorously justified since the averaging method breaks down near a fold of periodics, which is exactly where torus canards originate. In this work, we combine techniques from Floquet theory, averaging theory, and geometric singular perturbation theory to show that the average of a torus canard is a folded singularity canard. In so doing, we devise an analytic scheme for the identification and topological classification of torus canards in fast/slow systems with two fast variables and k slow variables, for any positive integer k. We demonstrate the predictive power of our results in a model for intracellular calcium dynamics, where we explain the mechanisms underlying a novel class of elliptic bursting rhythms, called amplitude-modulated bursting, by constructing the torus canard analogues of mixed-mode oscillations. We also make explicit the connection between our results here with prior studies of torus canards and torus canard explosion in R3, and discuss how our methods can be extended to fast/slow systems of arbitrary (finite) dimension.

  8. Disordered artificial spin ices: Avalanches and criticality (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Reichhardt, Cynthia J. Olson, E-mail: cjrx@lanl.gov; Chern, Gia-Wei; Reichhardt, Charles [Center for Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Libál, Andras [Faculty of Mathematics and Computer Science, Babes-Bolyai University, RO-400591 Cluj-Napoca (Romania)

    2015-05-07

    We show that square and kagome artificial spin ices with disconnected islands exhibit disorder-induced nonequilibrium phase transitions. The critical point of the transition is characterized by a diverging length scale and the effective spin reconfiguration avalanche sizes are power-law distributed. For weak disorder, the magnetization reversal is dominated by system-spanning avalanche events characteristic of a supercritical regime, while at strong disorder, the avalanche distributions have subcritical behavior and are cut off above a length scale that decreases with increasing disorder. The different type of geometrical frustration in the two lattices produces distinct forms of critical avalanche behavior. Avalanches in the square ice consist of the propagation of locally stable domain walls separating the two polarized ground states, and we find a scaling collapse consistent with an interface depinning mechanism. In the fully frustrated kagome ice, however, the avalanches branch strongly in a manner reminiscent of directed percolation. We also observe an interesting crossover in the power-law scaling of the kagome ice avalanches at low disorder. Our results show that artificial spin ices are ideal systems in which to study a variety of nonequilibrium critical point phenomena as the microscopic degrees of freedom can be accessed directly in experiments.

  9. Weak avalanche discrimination for gated-mode single-photon avalanche photodiodes.

    Science.gov (United States)

    Cho, Seok-Beom; Kang, Sae-Kyoung

    2011-09-12

    The after-pulsing effect is a common problem that needs to be overcome for high-speed single-photon detection based on gated-mode single-photon avalanche photodiodes (SPADs). This paper presents a simple and practical method for suppression of the after-pulsing probability using an auxiliary signal to discriminate quite weak avalanches. The detection efficiency and after-pulse probability of an InGaAs/InP SPAD are investigated with a 10 MHz gating for conventional and proposed methods, and a sharp decrease of after-pulse probability is demonstrated with the application of the proposed method. At a gating frequency of 100 MHz, a detection efficiency of 10.4% is achieved with an after-pulse probability of 5.6% without dead time.

  10. Typed combinators for generic traversal

    NARCIS (Netherlands)

    Lämmel, R.; Vonk, J.

    2001-01-01

    Lacking support for generic traversal, functional programming languages suffer from a scalability problem when applied to large-scale program transformation problems. As a solution, we introduce emph{functional strategies: typeful generic functions that not only can be applied to terms of any type,

  11. Article choice in plural generics

    NARCIS (Netherlands)

    Farkas, D.F.; Swart, Henriëtte de

    2007-01-01

    We discuss two groups of languages where article use contrasts in generic plural sentences but is otherwise essentially similar. The languages in the first group (English and Dutch) use bare plurals in the expression of kind reference (‘Dinosaurs are extinct’) and in generic generalizations (‘Dogs a

  12. IFKIS a basis for organizational measures in avalanche risk management

    Science.gov (United States)

    Bründl, M.; Etter, H.-J.; Klingler, Ch.; Steiniger, M.; Rhyner, J.; Ammann, W.

    2003-04-01

    The avalanche winter 1999 in Switzerland showed that the combination of protection measures like avalanche barriers, hazard zone mapping, artificial avalanche release and organisational measures (closure of roads, evacuation etc.) proved to perform well. However, education as well as information and communication between the involved organizations proved to be a weak link in the crisis management. In the first part of the project IFKIS we developed a modular education and training course program for security responsibles of settlements and roads. In the second part an information system was developed which improves on the one hand the information fluxes between the national center for avalanche forecasting, the Swiss Federal Institute for Snow and Avalanche Research SLF, and the local forecasters. On the other hand the communication between the avalanche security services in the communities can be enhanced. During the last two years an information system based on Internet technology has been developed for this purpose. This system allows the transmission of measured data and observations to a central database at SLF and visualization of the data for different users. It also provides the possibility to exchange information on organizational measures like closure of roads, artificial avalanche release etc. on a local and regional scale. This improves the information fluxes and the coordination of safety-measures because all users, although at different places, are on the same information level. Inconsistent safety-measures can be avoided and information and communication concerning avalanche safety becomes much more transparent for all persons involved in hazard management. The training program as well the concept for the information-system are important basics for an efficient avalanche risk management but also for other natural processes and catastrophes.

  13. III-V alloy heterostructure high speed avalanche photodiodes

    Science.gov (United States)

    Law, H. D.; Nakano, K.; Tomasetta, L. R.

    1979-01-01

    Heterostructure avalanche photodiodes have been successfully fabricated in several III-V alloy systems: GaAlAs/GaAs, GaAlSb/GaAlSb, and InGaAsP/InP. These diodes cover optical wavelengths from 0.4 to 1.8 micron. Early stages of development show very encouraging results. High speed response of less than 35 ps and high quantum efficiency more than 95 percent have been obtained. The dark currents and the excess avalanche noise are also dicussed. A direct comparison of GaAlSb, GaAlAsSb, and In GaAsP avalanche photodiodes is given.

  14. Characterization of avalanche photodiodes for lidar atmospheric return signal detectors

    Science.gov (United States)

    Antill, C. W., Jr.; Holloway, R. M.

    1988-01-01

    Results are presented from tests to characterize noise, dark current, overload, and gain versus bias, relationships of ten avalanche photodiodes. The advantages of avalanche photodiodes over photomultiplier tubes for given laser wavelengths and return signal amplitudes are outlined. The relationship between responsivity and temperature and dark current and temperature are examined. Also, measurements of the noise equivalent power, the excess noise factor, and linearity are given. The advantages of using avalanche photodiodes in the Lidar Atmospheric Sensing Experiment and the Lidar In-Space Technology Experiment are discussed.

  15. Anthropogenic effect on avalanche and debris flow activity

    Directory of Open Access Journals (Sweden)

    S. A. Sokratov

    2013-01-01

    Full Text Available The paper presents examples of the change in snow avalanches and debris flows activity due to the anthropogenic pressure on vegetation and relief. The changes in dynamical characteristics of selected snow avalanches and debris flows due to the anthropogenic activity are quantified. The conclusion is made that the anthropogenic effects on the snow avalanches and debris flows activity are more pronounced than the possible effects of the climate change. The necessity is expressed on the unavoidable changes of the natural environment as the result of a construction and of use of the constructed infrastructure to be account for in corresponding planning of the protection measures.

  16. Seeded excitation avalanches in off-resonantly driven Rydberg gases

    CERN Document Server

    Simonelli, Cristiano; Masella, Guido; Asteria, Luca; Arimondo, Ennio; Ciampini, Donatella; Morsch, Oliver

    2016-01-01

    We report an experimental investigation of the facilitated excitation dynamics in off-resonantly driven Rydberg gases by separating the initial off-resonant excitation phase from the facilitation phase, in which successive facilitation events lead to excitation avalanches. We achieve this by creating a controlled number of initial seed excitations. Greater insight into the avalanche mechanism is obtained from an analysis of the full counting distributions. We also present simple mathematical models and numerical simulations of the excitation avalanches that agree well with our experimental results.

  17. Noise-induced phase transitions in neuronal networks

    CERN Document Server

    Lee, K -E; Goltsev, A V

    2013-01-01

    Using an exactly solvable cortical model of a neuronal network, we show that, by increasing the intensity of shot noise (flow of random spikes bombarding neurons), the network undergoes first- and second-order non-equilibrium phase transitions. We study the nature of the transitions, bursts and avalanches of neuronal activity. Saddle-node and supercritical Hopf bifurcations are the mechanisms of emergence of sustained network oscillations. We show that the network stimulated by shot noise behaves similar to the Morris-Lecar model of a biological neuron stimulated by an applied current.

  18. Avalanche of particles in evaporating coffee drops

    CERN Document Server

    Marin, Alvaro G; Snoeijer, Jacco; Lohse, Detlef

    2010-01-01

    The pioneering work of Deegan et al. [Nature 389, (1997)] showed how a drying sessile droplet suspension of particles presents a maximum evaporating flux at its contact line which drags liquid and particles creating the well known coffee stain ring. In this Fluid Dynamics Video, measurements using micro Particle Image Velocimetry and Particle Tracking clearly show an avalanche of particles being dragged in the last moments, for vanishing contact angles and droplet height. This explains the different characteristic packing of the particles in the layers of the ring: the outer one resembles a crystalline array, while the inner one looks more like a jammed granular fluid. Using the basic hydrodynamic model used by Deegan et al. [Phys. Rev. E 62, (2000)] it will be shown how the liquid radial velocity diverges as the droplet life comes to an end, yielding a good comparison with the experimental data.

  19. Photon counting techniques with silicon avalanche photodiodes.

    Science.gov (United States)

    Dautet, H; Deschamps, P; Dion, B; Macgregor, A D; Macsween, D; McIntyre, R J; Trottier, C; Webb, P P

    1993-07-20

    The properties of avalanche photodiodes and associated electronics required for photon counting in the Geiger and the sub-Geiger modes are reviewed. When the Geiger mode is used, there are significant improvements reported in overall photon detection efficiencies (approaching 70% at 633 nm), and a timing jitter (under 200 ps) is achieved with passive quenching at high overvoltages (20-30 V). The results obtained by using an active-mode fast quench circuit capable of switching overvoltages as high as 15 V (giving photon detection efficiencies in the 50% range) with a dead time of less than 50 ns are reported. Larger diodes (up to 1 mm in diameter) that are usable in the Geiger mode and that have quantum efficiencies over 80% in the 500-800-nm range are also reported.

  20. Avalanche photodiodes now and possible developments

    CERN Document Server

    Britvitch, I; Ingram, Q; Kuznetsov, A; Musienko, Y; Renker, D; Reucroft, S; Sakhelashvili, T M; Swain, J

    2004-01-01

    Avalanche Photodiodes (APDs) are now out of their infancy and are used in large numbers in the electromagnetic calorimeter of CMS where they have to stand the extremely hostile environment of LHC. This type - with smaller sensitive area and arranged in monolithic arrays - is an excellent candidate for the read out of scintillating crystals in medical imaging and a PET scanner operates already successfully since more than 3 years. We present the properties of the device used in CMS and possible improvements of the structure, which could open the door for new applications. Operating APDs at low temperatures or in Geiger mode will allow single photon counting and in future they could replace photomultiplier tubes.

  1. Overspill avalanching in a dense reservoir network

    CERN Document Server

    Mamede, G L; Schneider, C M; de Araújo, J C; Herrmann, H J

    2012-01-01

    Sustainability of communities, agriculture, and industry is strongly dependent on an effective storage and supply of water resources. In some regions the economic growth has led to a level of water demand which can only be accomplished through efficient reservoir networks. Such infrastructures are not always planned at larger scale but rather made by farmers according to their local needs of irrigation during droughts. Based on extensive data from the upper Jaguaribe basin, one of the world's largest system of reservoirs, located in the Brazilian semiarid northeast, we reveal that surprisingly it self-organizes into a scale-free network exhibiting also a power-law in the distribution of the lakes and avalanches of discharges. With a new self-organized-criticality-type model we manage to explain the novel critical exponents. Implementing a flow model we are able to reproduce the measured overspill evolution providing a tool for catastrophe mitigation and future planning.

  2. Lautaret avalanche test site: outcomes from the 11th april 2012 event

    OpenAIRE

    2012-01-01

    International audience; The Lautaret full-scale avalanche test site has been used by Cemagref-Irstea since the early 70's. The first studies were dedicated to avalanche released systems. Later, experiments focused on avalanche dynamics and avalanche impact pressures both in relation with the fundamental knowledge of snow flow rheology and the engineering of defense structures and avalanche hazard zoning. Recent instrumentation developments now provide rich-documented in situ measurements of a...

  3. Encouraging generic use can yield significant savings.

    Science.gov (United States)

    Zimmerman, Christina

    2012-11-01

    Key findings. (1) Zero copayment for generic drugs is the greatest influencer of generic statin utilization. (2) Both higher copayments for generic drugs and lower copayments for competing brands are associated with a decreased probability of using generic statins. (3) Prior authorization and step therapy requirements for brand-name statins are associated with an increased use of generic drugs. (4) Greater use of generic statins should reduce costs for patients, plans, and Medicare.

  4. A Generic Dynamic Emulator

    CERN Document Server

    Albert, Carlo

    2011-01-01

    In applied sciences, we often deal with deterministic simulation models that are too slow for simulation-intensive tasks such as calibration or real-time control. In this paper, an emulator for a generic dynamic model, given by a system of ordinary non-linear differential equations, is developed. The non-linear differential equations are linearized and Gaussian white noise is added to account for the non-linearities. The resulting linear stochastic system is conditioned on a set of solutions of the non-linear equations that have been calculated prior to the emulation. A path-integral approach is used to derive the Gaussian distribution of the emulated solution. The solution reveals that most of the computational burden can be shifted to the conditioning phase of the emulator and the complexity of the actual emulation step only scales like $\\mathcal O(Nnm^2)$, where $N$ is the number of time-points at which the solution is to be emulated, $n$ the number of solutions the emulator is conditioned on and $m$ the n...

  5. SiC Avalanche Photodiodes and Arrays Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Aymont Technology, Inc. (Aymont) will demonstrate the feasibility of SiC p-i-n avalanche photodiodes (APD) arrays. Aymont will demonstrate 4 x 4 arrays of 2 mm2 APDs...

  6. Relative degradation of near infrared avalanche photodiodes from proton irradiation

    Science.gov (United States)

    Becker, Heidi; Johnston, Allan H.

    2004-01-01

    InGaAs and Ge avalanche photodiodes are compared for the effects of 63-MeV protons on dark current. Differences in displacement damage factors are discussed as they relate to structural differences between devices.

  7. Relative degradation of near infrared avalanche photodiodes from proton irradiation

    Science.gov (United States)

    Becker, Heidi; Johnston, Allan H.

    2004-01-01

    InGaAs and Ge avalanche photodiodes are compared for the effects of 63-MeV protons on dark current. Differences in displacement damage factors are discussed as they relate to structural differences between devices.

  8. Non-linear behaviour of large-area avalanche photodiodes

    CERN Document Server

    Fernandes, L M P; Monteiro, C M B; Santos, J M; Morgado, R E

    2002-01-01

    The characterisation of photodiodes used as photosensors requires a determination of the number of electron-hole pairs produced by scintillation light. One method involves comparing signals produced by X-ray absorptions occurring directly in the avalanche photodiode with the light signals. When the light is derived from light-emitting diodes in the 400-600 nm range, significant non-linear behaviour is reported. In the present work, we extend the study of the linear behaviour to large-area avalanche photodiodes, of Advanced Photonix, used as photosensors of the vacuum ultraviolet (VUV) scintillation light produced by argon (128 nm) and xenon (173 nm). We observed greater non-linearities in the avalanche photodiodes for the VUV scintillation light than reported previously for visible light, but considerably less than the non-linearities observed in other commercially available avalanche photodiodes.

  9. Dynamic intermittency in discrete erodible-bed avalanches

    Science.gov (United States)

    Arran, Matthew; Vriend, Nathalie

    2016-11-01

    The coexistence of fluid-like and solid-like behaviour in granular matter allows avalanches of grains to flow on the surface of a static but erodible bed. For sufficiently slow inflow, these avalanches are discrete, with previous experimentalists reporting that avalanche fronts pass a given point quasi-periodically. We report instead observations of dynamic intermittency between two regimes, one in which avalanches occur quasi-periodically and another in which the intervals between them are irregular. Finding the first regime consistent with existing models, we introduce a model for the second regime within the framework of Self-Organised Criticality, and describe the transition between the regimes with reference to the state of the erodible bed.

  10. Avalanche statistics from data with low time resolution.

    Science.gov (United States)

    LeBlanc, Michael; Nawano, Aya; Wright, Wendelin J; Gu, Xiaojun; Uhl, J T; Dahmen, Karin A

    2016-11-01

    Extracting avalanche distributions from experimental microplasticity data can be hampered by limited time resolution. We compute the effects of low time resolution on avalanche size distributions and give quantitative criteria for diagnosing and circumventing problems associated with low time resolution. We show that traditional analysis of data obtained at low acquisition rates can lead to avalanche size distributions with incorrect power-law exponents or no power-law scaling at all. Furthermore, we demonstrate that it can lead to apparent data collapses with incorrect power-law and cutoff exponents. We propose new methods to analyze low-resolution stress-time series that can recover the size distribution of the underlying avalanches even when the resolution is so low that naive analysis methods give incorrect results. We test these methods on both downsampled simulation data from a simple model and downsampled bulk metallic glass compression data and find that the methods recover the correct critical exponents.

  11. UNIQUENESS OF SOLUTIONS FOR SEMICONDUCTOR EQUATIONS WITH AVALANCHE TERM

    Institute of Scientific and Technical Information of China (English)

    Xing Jiasheng; Wang Yuanming

    2000-01-01

    In this paper, we consider the initial and mixed boundary value problems for the semiconductor equations with avalanche term, the uniqueness of the weak solution for the semiconductor equation has been proved.

  12. Generic substitution - comparing the clinical efficacy of a generic ...

    African Journals Online (AJOL)

    1998-03-03

    Mar 3, 1998 ... Departments of Psychiatry and Biostatistics, University of the. Orange Free State ... industry has expanded rapidly during the last 2 decades! The need to contain the ... Substitution of a generic drug product for an innovator.

  13. Geiger-Mode Avalanche Photodiodes in Particle Detection

    OpenAIRE

    Vilella, E.; Alonso, O.; Trenado, J.; Vilà, A.; De Vos, M.; Garrido, L.; Diéguez, A.

    2012-01-01

    It is well known that avalanche photodiodes operated in the Geiger mode above the breakdown voltage offer a virtually infinite sensitivity and time accuracy in the picosecond range that can be used for single photon detection. However, their performance in particle detection remains still unexplored. In this contribution, we are going to expose the different steps that we have taken in order to prove the efficiency of Geiger mode avalanche photodiodes in the aforementioned field. In particula...

  14. Wavelength dependence of silicon avalanche photodiode fabricated by CMOS process

    Science.gov (United States)

    Mohammed Napiah, Zul Atfyi Fauzan; Hishiki, Takuya; Iiyama, Koichi

    2017-07-01

    Avalanche photodiodes fabricated by CMOS process (CMOS-APDs) have features of high avalanche gain below 10 V, wide bandwidth over 5 GHz, and easy integration with electronic circuits. In CMOS-APDs, guard ring structure is introduced for high-speed operation by canceling photo-generated carriers in the substrate at the sacrifice of the responsivity. We describe here wavelength dependence of the responsivity and the bandwidth of the CMOS-APDs with shorted and opened guard ring structure.

  15. Influence of snow-cover properties on avalanche dynamics

    Science.gov (United States)

    Steinkogler, W.; Sovilla, B.; Lehning, M.

    2012-04-01

    Snow avalanches with the potential of reaching traffic routes and settlements are a permanent winter threat for many mountain communities. Snow safety officers have to take the decision whether to close a road, a railway line or a ski slope. Those decisions are often very difficult as they demand the ability to interpret weather forecasts, to establish their implication for the stability and the structure of the snow cover and to evaluate the influence of the snow cover on avalanche run-out distances. In the operational programme 'Italy-Switzerland, project STRADA' we focus on the effects of snow cover on avalanche dynamics, and thus run-out distance, with the aim to provide a better understanding of this influence and to ultimately develop tools to support snow safety officers in their decision process. We selected five avalanches, measured at the Vallée de la Sionne field site, with similar initial mass and topography but different flow dynamics and run-out distances. Significant differences amongst the individual avalanches could be observed for front and internal velocities, impact pressures, flow regimes, deposition volumes and run-out distances. For each of these avalanches, the prevailing snow conditions at release were reconstructed using field data from local snowpits or were modeled with SNOWPACK. Combining flow dynamical data with snow cover properties shows that erodible snow depth, snow density and snow temperature in the snow pack along the avalanche track are among the decisive variables that appear to explain the observed differences. It is further discussed, how these influencing factors can be quantified and used for improved predictions of site and time specific avalanche hazard.

  16. Effect of volume fraction on granular avalanche dynamics.

    Science.gov (United States)

    Gravish, Nick; Goldman, Daniel I

    2014-09-01

    We study the evolution and failure of a granular slope as a function of prepared volume fraction, ϕ(0). We rotated an initially horizontal layer of granular material (0.3-mm-diam glass spheres) to a 45° angle while we monitor the motion of grains from the side and top with high-speed video cameras. The dynamics of grain motion during the tilt process depended sensitively on ϕ(0)∈[0.58-0.63] and differed above or below the granular critical state, ϕ(c), defined as the onset of dilation as a function of increasing volume fraction. For ϕ(0)-ϕ(c)avalanche. Precursor compaction events began at an initial angle θ(0)=7.7±1.4° and occurred intermittently prior to the onset of an avalanche. Avalanches occurred at the maximal slope angle θ(m)=28.5±1.0°. Granular material at ϕ(0)-ϕ(c)>0 did not experience precursor compaction prior to avalanche flow, and instead experienced a single dilational motion at θ(0)=32.1±1.5° prior to the onset of an avalanche at θ(m)=35.9±0.7°. Both θ(0) and θ(m) increased with ϕ(0) and approached the same value in the limit of random close packing. The angle at which avalanching grains came to rest, θ(R)=22±2°, was independent of ϕ(0). From side-view high-speed video, we measured the velocity field of intermittent and avalanching flow. We found that flow direction, depth, and duration were affected by ϕ(0), with ϕ(0)-ϕ(c)0. Our study elucidates how initial conditions-including volume fraction-are important determinants of granular slope stability and the onset of avalanches.

  17. Avalanche Phenomenon of Runaway Electrons During Additional Fuelling

    Institute of Scientific and Technical Information of China (English)

    杨进蔚; 曹建勇; 曾庆希; 张炜; 唐年益; 董贾福; 邓中朝; 肖正贵; 姚良骅

    2002-01-01

    During pellet injection and supersonic molecular beam injection, we have observed the increase of electron density and the enhancement of hard x-ray radiation, but the runaway electrons normally decrease without additional fuelling when the density of plasma increases. This phenomenon may come from the synergetic effects of Dreicer and avalanche runaway electrons. The experimental results are consistent with the calculation based on the theory of avalanche runaway in the HL-1M tokamak.

  18. Avalanche robustness of SiC Schottky diode

    OpenAIRE

    Dchar, Ilyas; Buttay, Cyril; Morel, Hervé

    2016-01-01

    International audience; Reliability is one of the key issues for the application of Silicon carbide (SiC) diode in high power conversion systems. For instance, in high voltage direct current (HVDC) converters, the devices can be submitted to high voltage transients which yield to avalanche. This paper presents the experimental evaluation of SiC diodes submitted to avalanche, and shows that the energy dissipation in the device can increase quickly and will not be uniformly distributed across t...

  19. Spatio-temporal avalanche forecasting with Support Vector Machines

    Directory of Open Access Journals (Sweden)

    A. Pozdnoukhov

    2011-02-01

    Full Text Available This paper explores the use of the Support Vector Machine (SVM as a data exploration tool and a predictive engine for spatio-temporal forecasting of snow avalanches. Based on the historical observations of avalanche activity, meteorological conditions and snowpack observations in the field, an SVM is used to build a data-driven spatio-temporal forecast for the local mountain region. It incorporates the outputs of simple physics-based and statistical approaches used to interpolate meteorological and snowpack-related data over a digital elevation model of the region. The interpretation of the produced forecast is discussed, and the quality of the model is validated using observations and avalanche bulletins of the recent years. The insight into the model behaviour is presented to highlight the interpretability of the model, its abilities to produce reliable forecasts for individual avalanche paths and sensitivity to input data. Estimates of prediction uncertainty are obtained with ensemble forecasting. The case study was carried out using data from the avalanche forecasting service in the Locaber region of Scotland, where avalanches are forecast on a daily basis during the winter months.

  20. A revision of the Haiming rock avalanche (Eastern Alps)

    Science.gov (United States)

    Dufresne, Anja; Ostermann, Marc; Kelfoun, Karim; Ring, Max; Asam, Dario; Prager, Christoph

    2016-04-01

    The carbonate Haiming rock avalanche is directly neighbouring the larger Tschirgant rock avalanche deposit, both located in the upper Inn valley (Tyrol, Austria). Based on detailed morpho-lithologic mapping of the deposit, which has not been done at Haiming before, the sedimentology of the Holocene landslide debris is characterised. Structural-tectonic elements of the bedrock units at the scarp area are supplemented with borehole data from drillings at the source area giving valuable insights into the complex geological bedrock composition and structure. New source and runout reconstructions allow updated volumetric calculations, which are subsequently integrated into numerical runout modelling. Haiming is one of few topographically unobstructed rock avalanches, yet its morphology was greatly influenced by fluvial terraces, which are still discernible through the deposit on LiDAR hillshade images. We also address the influence of the rock avalanche on the valley floor and local river system as a short-lived dam and its interaction with fluvial incision. Finally, we discuss the Haiming rock avalanche in view of the other massive rock slope failures in the area ("Fernpass cluster"), their spatio-temporal distribution, and point out further highlights of this simple(?) rock avalanche deposit.

  1. Avalanches, plasticity, and ordering in colloidal crystals under compression.

    Science.gov (United States)

    McDermott, D; Reichhardt, C J Olson; Reichhardt, C

    2016-06-01

    Using numerical simulations we examine colloids with a long-range Coulomb interaction confined in a two-dimensional trough potential undergoing dynamical compression. As the depth of the confining well is increased, the colloids move via elastic distortions interspersed with intermittent bursts or avalanches of plastic motion. In these avalanches, the colloids rearrange to minimize their colloid-colloid repulsive interaction energy by adopting an average lattice constant that is isotropic despite the anisotropic nature of the compression. The avalanches take the form of shear banding events that decrease or increase the structural order of the system. At larger compression, the avalanches are associated with a reduction of the number of rows of colloids that fit within the confining potential, and between avalanches the colloids can exhibit partially crystalline or anisotropic ordering. The colloid velocity distributions during the avalanches have a non-Gaussian form with power-law tails and exponents that are consistent with those found for the velocity distributions of gliding dislocations. We observe similar behavior when we subsequently decompress the system, and find a partially hysteretic response reflecting the irreversibility of the plastic events.

  2. Avalanches and hysteresis in frustrated superconductors and XY spin glasses.

    Science.gov (United States)

    Sharma, Auditya; Andreanov, Alexei; Müller, Markus

    2014-10-01

    We study avalanches along the hysteresis loop of long-range interacting spin glasses with continuous XY symmetry, which serves as a toy model of granular superconductors with long-range and frustrated Josephson couplings. We identify sudden jumps in the T=0 configurations of the XY phases as an external field is increased. They are initiated by the softest mode of the inverse susceptibility matrix becoming unstable, which induces an avalanche of phase updates (or spin alignments). We analyze the statistics of these events and study the correlation between the nonlinear avalanches and the soft mode that initiates them. We find that the avalanches follow the directions of a small fraction of the softest modes of the inverse susceptibility matrix, similarly as was found in avalanches in jammed systems. In contrast to the similar Ising spin glass (Sherrington-Kirkpatrick) studied previously, we find that avalanches are not distributed with a scale-free power law but rather have a typical size which scales with the system size. We also observe that the Hessians of the spin-glass minima are not part of standard random matrix ensembles as the lowest eigenvector has a fractal support.

  3. Modeling of snow avalanches for protection measures designing

    Science.gov (United States)

    Turchaninova, Alla; Lazarev, Anton; Loginova, Ekaterina; Seliverstov, Yuri; Glazovskaya, Tatiana; Komarov, Anton

    2017-04-01

    Avalanche protection structures such as dams have to be designed using well known standard engineering procedures that differ in different countries. Our intent is to conduct a research on structural avalanche protection measures designing and their reliability assessment during the operation using numerical modeling. In the Khibini Mountains, Russia, several avalanche dams have been constructed at different times to protect settlements and mining. Compared with other mitigation structures dams are often less expensive to construct in mining regions. The main goal of our investigation was to test the capabilities of Swiss avalanche dynamics model RAMMS and Russian methods to simulate the interaction of avalanches with mitigation structures such as catching and reflecting dams as well as to reach the observed runout distances after the transition through a dam. We present the RAMMS back-calculation results of an artificially triggered and well-documented catastrophic avalanche occurred in the town of Kirovsk, Khibini Mountains in February 2016 that has unexpectedly passed through a system of two catching dams and took the lives of 3 victims. The estimated volume of an avalanche was approximately 120,000 m3. For the calculation we used a 5 m DEM including catching dams generated from field measurements in summer 2015. We simulated this avalanche (occurred below 1000 m.a.s.l.) in RAMMS having taken the friction parameters (µ and ζ) from the upper altitude limit (above 1500 m.a.s.l.) from the table recommended for Switzerland (implemented into RAMMS) according to the results of our previous research. RAMMS reproduced the observed avalanche behavior and runout distance. No information is available concerning the flow velocity; however, calculated values correspond in general to the values measured in this avalanche track before. We applied RAMMS using an option of adding structures to DEM (including a dam in GIS) in other to test other operating catching dams in

  4. Generic interpreters and microprocessor verification

    Science.gov (United States)

    Windley, Phillip J.

    1990-01-01

    The following topics are covered in viewgraph form: (1) generic interpreters; (2) Viper microprocessors; (3) microprocessor verification; (4) determining correctness; (5) hierarchical decomposition; (6) interpreter theory; (7) AVM-1; (8) phase-level specification; and future work.

  5. Generic ISIS Transport Module Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The purpose of the Generic ISIS Transport Module is to provide a means to bring living specimens to and from orbit. In addition to living specimens, the module can...

  6. Hanford Generic Interim Safety Basis

    Energy Technology Data Exchange (ETDEWEB)

    Lavender, J.C.

    1994-09-09

    The purpose of this document is to identify WHC programs and requirements that are an integral part of the authorization basis for nuclear facilities that are generic to all WHC-managed facilities. The purpose of these programs is to implement the DOE Orders, as WHC becomes contractually obligated to implement them. The Hanford Generic ISB focuses on the institutional controls and safety requirements identified in DOE Order 5480.23, Nuclear Safety Analysis Reports.

  7. The Generic Data Capture Facility

    Science.gov (United States)

    Connell, Edward B.; Barnes, William P.; Stallings, William H.

    The Generic Data Capture Facility, which can provide data capture support for a variety of different types of spacecraft while enabling operations costs to be carefully controlled, is discussed. The data capture functions, data protection, isolation of users from data acquisition problems, data reconstruction, and quality and accounting are addressed. The TDM and packet data formats utilized by the system are described, and the development of generic facilities is considered.

  8. Knowledge Development Generic Framework Concept

    Science.gov (United States)

    2008-12-18

    Branch This is the final MNE 5 document on Knowledge Development. Contact ZTransfBw Abt II CDE@bundeswehr.org for inquiries regarding...subsequent updates beyond MNE 5 efforts. VERSION 1.30 18. December 2008 Knowledge Development Generic Framework Concept Draft Report...2. REPORT TYPE Final 3. DATES COVERED - 4. TITLE AND SUBTITLE Knowledge Development Generic Framework Concept 5a. CONTRACT NUMBER 5b

  9. Skier triggering of backcountry avalanches with skilled route selection

    Science.gov (United States)

    Sinickas, Alexandra; Haegeli, Pascal; Jamieson, Bruce

    2015-04-01

    Jamieson (2009) provided numerical estimates for the baseline probabilities of triggering an avalanche by a backcountry skier making fresh tracks without skilled route selection as a function of the North American avalanche danger scale (i.e., hazard levels Low, Moderate, Considerable, High and Extreme). Using the results of an expert survey, he showed that triggering probabilities while skiing directly up, down or across a trigger zone without skilled route selection increase roughly by a factor of 10 with each step of the North American avalanche danger scale (i.e. hazard level). The objective of the present study is to examine the effect of skilled route selection on the relationship between triggering probability and hazard level. To assess the effect of skilled route selection on triggering probability by hazard level, we analysed avalanche hazard assessments as well as reports of skiing activity and triggering of avalanches from 11 Canadian helicopter and snowcat operations during two winters (2012-13 and 2013-14). These reports were submitted to the daily information exchange among Canadian avalanche safety operations, and reflect professional decision-making and route selection practices of guides leading groups of skiers. We selected all skier-controlled or accidentally triggered avalanches with a destructive size greater than size 1 according to the Canadian avalanche size classification, triggered by any member of a guided group (guide or guest). These operations forecast the avalanche hazard daily for each of three elevation bands: alpine, treeline and below treeline. In contrast to the 2009 study, an exposure was defined as a group skiing within any one of the three elevation bands, and consequently within a hazard rating, for the day (~4,300 ratings over two winters). For example, a group that skied below treeline (rated Moderate) and treeline (rated Considerable) in one day, would receive one count for exposure to Moderate hazard, and one count for

  10. Avalanches in a granular stick-slip experiment: detection using wavelets

    Science.gov (United States)

    Abed Zadeh, Aghil; Barés, Jonathan; Behringer, Robert P.

    2017-06-01

    Avalanches have been experimentally investigated in a wide range of physical systems from granular physics to friction. Here, we measure and detect avalanches in a 2D granular stick-slip experiment. We discuss the conventional way of signal processing for avalanche extraction and how statistics depend on several parameters that are chosen in the analysis process. Then, we introduce another way of detecting avalanches using wavelet transformations that can be applied in many other systems. We show that by using this method and measuring Lipschitz exponents, we can intelligently detect noise in a signal, which leads to a better avalanche extraction and more reliable avalanche statistics.

  11. First approximations in avalanche model validations using seismic information

    Science.gov (United States)

    Roig Lafon, Pere; Suriñach, Emma; Bartelt, Perry; Pérez-Guillén, Cristina; Tapia, Mar; Sovilla, Betty

    2017-04-01

    Avalanche dynamics modelling is an essential tool for snow hazard management. Scenario based numerical modelling provides quantitative arguments for decision-making. The software tool RAMMS (WSL Institute for Snow and Avalanche Research SLF) is one such tool, often used by government authorities and geotechnical offices. As avalanche models improve, the quality of the numerical results will depend increasingly on user experience on the specification of input (e.g. release and entrainment volumes, secondary releases, snow temperature and quality). New model developments must continue to be validated using real phenomena data, for improving performance and reliability. The avalanches group form University of Barcelona (RISKNAT - UB), has studied the seismic signals generated from avalanches since 1994. Presently, the group manages the seismic installation at SLF's Vallée de la Sionne experimental site (VDLS). At VDLS the recorded seismic signals can be correlated to other avalanche measurement techniques, including both advanced remote sensing methods (radars, videogrammetry) and obstacle based sensors (pressure, capacitance, optical sender-reflector barriers). This comparison between different measurement techniques allows the group to address the question if seismic analysis can be used alone, on more additional avalanche tracks, to gain insight and validate numerical avalanche dynamics models in different terrain conditions. In this study, we aim to add the seismic data as an external record of the phenomena, able to validate RAMMS models. The seismic sensors are considerable easy and cheaper to install than other physical measuring tools, and are able to record data from the phenomena in every atmospheric conditions (e.g. bad weather, low light, freezing make photography, and other kind of sensors not usable). With seismic signals, we record the temporal evolution of the inner and denser parts of the avalanche. We are able to recognize the approximate position

  12. Avalanche outbreaks emerging in cooperative contagions

    Science.gov (United States)

    Cai, Weiran; Chen, Li; Ghanbarnejad, Fakhteh; Grassberger, Peter

    2015-11-01

    The spreading of contagions can exhibit a percolation transition, which separates transitory prevalence from outbreaks that reach a finite fraction of the population. Such transitions are commonly believed to be continuous, but empirical studies have shown more violent spreading modes when the participating agents are not limited to one type. Striking examples include the co-epidemic of the Spanish flu and pneumonia that occurred in 1918 (refs , ), and, more recently, the concurrent prevalence of HIV/AIDS and a host of diseases. It remains unclear to what extent an outbreak in the presence of interacting pathogens differs from that due to an ordinary single-agent process. Here we study a mechanistic model for understanding contagion processes involving inter-agent cooperation. Our stochastic simulations reveal the possible emergence of a massive avalanche-like outbreak right at the threshold, which is manifested as a discontinuous phase transition. Such an abrupt change arises only if the underlying network topology supports a bottleneck for cascaded mutual infections. Surprisingly, all these discontinuous transitions are accompanied by non-trivial critical behaviours, presenting a rare case of hybrid transition. The findings may imply the origin of catastrophic occurrences in many realistic systems, from co-epidemics to financial contagions.

  13. The structure of powder snow avalanches

    Science.gov (United States)

    Sovilla, Betty; McElwaine, Jim N.; Louge, Michel Y.

    2015-01-01

    Powder snow avalanches (PSAs) can be hundreds of metres high and descend at astonishing speeds. This review paints a composite picture of PSAs from data acquired at the Vallée de la Sionne test site in Switzerland, including time-histories of snow cover thickness from buried RADAR and, at several elevations on a pylon, impact pressures from load cells, air pressure, particle velocity from optical sensors, and cloud density and particle cluster size from capacitance probes. PSAs feature distinct flow regions with stratification in mean density. At the head, highly fluctuating impact pressures weaken with elevation, while vertical velocity profiles evolve rapidly along the flow, suggesting that surface snow layers of light, cold, cohesionless snow erupt into a turbulent, inhomogeneous, recirculating frontal cloud region. For hundreds of metres behind the head, cloud stratification sharpens with the deposition of suspended cloud particles, while a denser basal flow of increasing thickness forms as deeper, warmer and heavier parts of the weakened snow cover are entrained. Toward the tail, vertical velocity profiles are more uniform, impact pressures become lower and steadier as the flow becomes thinner, and snow pack entrainment is negligible.

  14. Granular avalanches down inclined and vibrated planes

    Science.gov (United States)

    Gaudel, Naïma; Kiesgen de Richter, Sébastien; Louvet, Nicolas; Jenny, Mathieu; Skali-Lami, Salaheddine

    2016-09-01

    In this article, we study granular avalanches when external mechanical vibrations are applied. We identify conditions of flow arrest and compare with the ones classically observed for nonvibrating granular flows down inclines [Phys. Fluids 11, 542 (1999), 10.1063/1.869928]. We propose an empirical law to describe the thickness of the deposits with the inclination angle and the vibration intensity. The link between the surface velocity and the depth of the flow highlights a competition between gravity and vibrations induced flows. We identify two distinct regimes: (a) gravity-driven flows at large angles where vibrations do not modify dynamical properties but the deposits (scaling laws in this regime are in agreement with the literature for nonvibrating granular flows) and (b) vibrations-driven flows at small angles where no flow is possible without applied vibrations (in this last regime, the flow behavior can be properly described by a vibration induced activated process). We show, in this study, that granular flows down inclined planes can be finely tuned by external mechanical vibrations.

  15. Infrasonic monitoring of snow avalanches in the Alps

    Science.gov (United States)

    Marchetti, E.; Ulivieri, G.; Ripepe, M.; Chiambretti, I.; Segor, V.

    2012-04-01

    Risk assessment of snow avalanches is mostly related to weather conditions and snow cover. However a robust risk validation requires to identify all avalanches occurring, in order to compare predictions to real effects. For this purpose on December 2010 we installed a permanent 4-element, small aperture (100 m), infrasound array in the Alps, after a pilot experiment carried out in Gressonay during the 2009-2010 winter season. The array has been deployed in the Ayas Valley, at an elevation of 2000 m a.s.l., where natural avalanches are expected and controlled events are regularly performed. The array consists into 4 Optimic 2180 infrasonic microphones, with a sensitivity of 10-3 Pa in the 0.5-50 Hz frequency band and a 4 channel Guralp CMG-DM24 A/D converter, sampling at 100 Hz. Timing is achieved with a GPS receiver. Data are transmitted to the Department of Earth Sciences of the University of Firenze, where data is recorded and processed in real-time. A multi-channel semblance is carried out on the continuous data set as a function of slowness, back-azimuth and frequency of recorded infrasound in order to detect all avalanches occurring from the back-ground signal, strongly affected by microbarom and mountain induced gravity waves. This permanent installation in Italy will allow to verify the efficiency of the system in short-to-medium range (2-8 km) avalanche detection, and might represent an important validation to model avalanches activity during this winter season. Moreover, the real-time processing of infrasonic array data, might strongly contribute to avalanche risk assessments providing an up-to-description of ongoing events.

  16. Sediment Transport by Spring Avalanches in the Southern Swiss Alps

    Science.gov (United States)

    Egloff, J. M.; Hunziker, M.; Moore, J. R.; Christen, M.

    2010-12-01

    Dense wet-snow avalanches breaking through to the base of the snow pack or overriding snow-free surfaces can entrain basal material and act as important agents of sediment transport in steep Alpine catchments. As part of an ongoing study, we investigated two debris fans in the Matter Valley of southern Switzerland during spring 2009 and 2010, with emphasis on quantifying avalanche sediment transport. Deposited debris ranged from soil parcels and plant material to cobbles and boulders greater than 1 m3. Large boulders were generally angular and fresh with clear signs of recent impacts. The seasonal sediment load transported by avalanches was estimated at one fan by sampling the debris content within a number of representative areas, and then extrapolating the cumulative volume. Results reveal a total transported sediment volume of ~150 m3 in 2009 and ~15 m3 in 2010, which likely reflects varying snowfall and avalanche frequency between years. When distributed over the deposition area on the fan, these results imply an average accumulated sediment thickness of 12 mm in 2009 and 3 mm in 2010. Calculated catchment-wide erosion rates are ~0.1 mm/yr for 2009 and ~0.01 mm/yr for 2010. Cross-sections through avalanche debris revealed that transported sediment generally resides on top of the snow surface. As the avalanches melt, entrained sediment is set down gently, often resulting in precariously balanced boulders and rows of blocks perched on the walls of the fan’s channels. In flat lying areas, snowmelt resulted in sparse sediment deposits with no clear structure or sorting. Observations show that the fan surface is usually protected from erosion by snow and older avalanche deposits, which provide a smooth gliding plane for new events. Within the bedrock gulley adjacent to the fan, and in the avalanche source region above, signs of abrasive wear were evident on exposed bedrock surfaces. These include rounded and scoured bedrock, fresh signs of boulder impacts, and

  17. Implications of Grainfall for Avalanches and Barchan Dune Morphodynamics

    Science.gov (United States)

    Nield, J. M.; Wiggs, G.; Baddock, M. C.; Hipondoka, M.

    2016-12-01

    Sediment accumulation on aeolian dunes is predominately though avalanching (or grainflow). This grainflow is initiated by the accumulation of grainfall deposits, close to the dune brink. When the accumulation, or `bulge', exceeds an angle of repose, avalanches are initiated and sediment is transported down the lee of the dune. The location of sediment accumulation, or avalanche initiation point, is determined by the distance that grainfall can travel from the dune brink. While previous studies have focused on determining angles at which avalanches occur, along with depositional flux rates, technical constraints have limited the testing of models to predict grainfall zone dynamics under varying wind conditions. Here we use terrestrial laser scanning (TLS) to measure both grainfall distance and associated lee slope surface change of a 5 m high barchan dune under variable wind speeds, on the Skeleton Coast, Namibia. We find that under stronger winds, the distance that grainfall can travel from the brink expands (by up to 0.45 m for a 3 m/s increase in wind speed). Along with this expansion of the grainfall distance there is an increase in saltation flux over the brink. The increased grainfall distance shifts sand further from the brink resulting in dominant avalanche initiation point locations expanding from 0.3 m to 0.4 m for wind speeds above 6 m/s. This shift also corresponds to the appearance of secondary avalanches, which are initiated by primary avalanche lobe deposits extending outside of the main grainfall zone. Ultimately, under stronger winds the expansion of the grainfall distance contributes to the destabilisation and movement of increased sediment volumes down the lee slope. Avalanches under stronger wind speeds, therefore, increase in thickness, width and length, while during weaker wind speeds, most of the grainfall and grainflow is limited to the upper section of the lee slope. The implication of this dual avalanche behaviour under variable wind

  18. Dynamics of the Bingham Canyon rock avalanches (Utah, USA) resolved from topographic, seismic, and infrasound data: Bingham Canyon Rock Avalanches

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Jeffrey R. [Department of Geology and Geophysics, University of Utah, Salt Lake City Utah USA; Pankow, Kristine L. [Department of Geology and Geophysics, University of Utah, Salt Lake City Utah USA; Ford, Sean R. [Atmospheric, Earth, and Energy Division, Lawrence Livermore National Laboratory, Livermore California USA; Koper, Keith D. [Department of Geology and Geophysics, University of Utah, Salt Lake City Utah USA; Hale, J. Mark [Department of Geology and Geophysics, University of Utah, Salt Lake City Utah USA; Aaron, Jordan [Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver British Columbia Canada; Larsen, Chris F. [Geophysical Institute, University of Alaska Fairbanks, Fairbanks Alaska USA

    2017-03-01

    The 2013 Bingham Canyon Mine rock avalanches represent one of the largest cumulative landslide events in recorded U.S. history and provide a unique opportunity to test remote analysis techniques for landslide characterization. Here we combine aerial photogrammetry surveying, topographic reconstruction, numerical runout modeling, and analysis of broadband seismic and infrasound data to extract salient details of the dynamics and evolution of the multiphase landslide event. Our results reveal a cumulative intact rock source volume of 52 Mm3, which mobilized in two main rock avalanche phases separated by 1.5 h. We estimate that the first rock avalanche had 1.5–2 times greater volume than the second. Each failure initiated by sliding along a gently dipping (21°), highly persistent basal fault before transitioning to a rock avalanche and spilling into the inner pit. The trajectory and duration of the two rock avalanches were reconstructed using runout modeling and independent force history inversion of intermediate-period (10–50 s) seismic data. Intermediate- and shorter-period (1–50 s) seismic data were sensitive to intervals of mass redirection and constrained finer details of the individual slide dynamics. Back projecting short-period (0.2–1 s) seismic energy, we located the two rock avalanches within 2 and 4 km of the mine. Further analysis of infrasound and seismic data revealed that the cumulative event included an additional 11 smaller landslides (volumes ~104–105 m3) and that a trailing signal following the second rock avalanche may result from an air-coupled Rayleigh wave. Our results demonstrate new and refined techniques for detailed remote characterization of the dynamics and evolution of large landslides.

  19. Solid-state flat panel imager with avalanche amorphous selenium

    Science.gov (United States)

    Scheuermann, James R.; Howansky, Adrian; Goldan, Amir H.; Tousignant, Olivier; Levéille, Sébastien; Tanioka, K.; Zhao, Wei

    2016-03-01

    Active matrix flat panel imagers (AMFPI) have become the dominant detector technology for digital radiography and fluoroscopy. For low dose imaging, electronic noise from the amorphous silicon thin film transistor (TFT) array degrades imaging performance. We have fabricated the first prototype solid-state AMFPI using a uniform layer of avalanche amorphous selenium (a-Se) photoconductor to amplify the signal to eliminate the effect of electronic noise. We have previously developed a large area solid-state avalanche a-Se sensor structure referred to as High Gain Avalanche Rushing Photoconductor (HARP) capable of achieving gains of 75. In this work we successfully deposited this HARP structure onto a 24 x 30 cm2 TFT array with a pixel pitch of 85 μm. An electric field (ESe) up to 105 Vμm-1 was applied across the a-Se layer without breakdown. Using the HARP layer as a direct detector, an X-ray avalanche gain of 15 +/- 3 was achieved at ESe = 105 Vμm-1. In indirect mode with a 150 μm thick structured CsI scintillator, an optical gain of 76 +/- 5 was measured at ESe = 105 Vμm-1. Image quality at low dose increases with the avalanche gain until the electronic noise is overcome at a constant exposure level of 0.76 mR. We demonstrate the success of a solid-state HARP X-ray imager as well as the largest active area HARP sensor to date.

  20. Snow avalanche friction relation based on extended kinetic theory

    Science.gov (United States)

    Rauter, Matthias; Fischer, Jan-Thomas; Fellin, Wolfgang; Kofler, Andreas

    2016-11-01

    Rheological models for granular materials play an important role in the numerical simulation of dry dense snow avalanches. This article describes the application of a physically based model from the field of kinetic theory to snow avalanche simulations. The fundamental structure of the so-called extended kinetic theory is outlined and the decisive model behavior for avalanches is identified. A simplified relation, covering the basic features of the extended kinetic theory, is developed and implemented into an operational avalanche simulation software. To test the obtained friction relation, simulation results are compared to velocity and runout observations of avalanches, recorded from different field tests. As reference we utilize a classic phenomenological friction relation, which is commonly applied for hazard estimation. The quantitative comparison is based on the combination of normalized residuals of different observation variables in order to take into account the quality of the simulations in various regards. It is demonstrated that the extended kinetic theory provides a physically based explanation for the structure of phenomenological friction relations. The friction relation derived with the help of the extended kinetic theory shows advantages to the classic phenomenological friction, in particular when different events and various observation variables are investigated.

  1. Solitary granular avalanches: stability, fingering and theoretical modeling

    Science.gov (United States)

    Malloggi, Florent; Andreotti, Bruno; Clément, Eric; Aronson, Igor; Tsimring, Lev

    2008-03-01

    Avalanching processes do not only occur in the air as we know of snow avalanches, mud flows and land-slides. Such events frequently happen below the see level as they take many forms from turbidity currents to thick sediment waves. In this study we report results on laboratory scale avalanche experiments taking place both in the air and under-water. In both cases a family of stable solitary erosion/deposition waves is observed [1]. At higher inclination angles, we show the existence of a long wavelength transverse instability followed by a coarsening and the onset of a fingering pattern. While the experiments strongly differ by the spatial and time scales, the agreement between the stability diagrams, the wavelengths selection and the avalanche morphology suggest a common erosion/deposition scenario. We also use these erosion/deposition waves to investigate the dynamics of granular flow and jamming in the frame work of the Partial Fluidization Theory (PFT) proposed by Aronson et al. to describe the dynamics of granular matter near jamming [2]. [1] F. Malloggi et al. Europhysics Letters, 2006, Erosion waves: Transverse instabilities and fingering 75, 825-831 [2] I. S. Aranson et al.. Transverse instability of avalanches in granular flows down an incline. Physical Review E, 2006, 73, 050302; I.S.Aronson et al., Non rheological properties of granular flows: exploring the near jamming limit, preprint (2007).

  2. Infrasound monitoring of snow avalanches in the Italian Alps

    Science.gov (United States)

    Ripepe, Maurizio; Ulivieri, Giacomo; Marchetti, Emanuele; Chiambretti, Igor; Segor, Valerio; Pitet, Luca

    2010-05-01

    Risk assessment of snow avalanches is mostly related to weather conditions and snow cover. However a robust risk validation requires to identify all avalanches occurring, in order to compare predictions to real effects. For this purpose on December 2009 we installed a temporary 4-element, small aperture (100 m), infrasound array in the Alps. The array has been deployed south of Mt. Rosa, at an elevation of 2000 m a.s.l. in the valley of Gressoney, where natural avalanches are expected and triggered ones are regularly programmed. The array consists into 4 absolute pressure transducers with a sensitivity of 0.01 Pa in the 0.1-50 Hz frequency band and a 7 channel Guralp CMG-DM24 A/D converter, sampling at 100 Hz. Timing is achieved with a GPS receiver. The array is completely buried in snow. Gel cell batteries and 200 W solar panels provide the array power requirements (~3 W) and should allow a continuous operation during the winter season. A multi-channel semblance is carried out on the continuous data set as a function of slowness, back-azimuth and frequency of recorded infrasound in order to detect all avalanches occurring from the back-ground signal, strongly affected by microbarom and mountain induced gravity waves. This pilot experiment in Italy will allow to verify the efficiency of the system, and might represent an important validation to modeled avalanches activity during this winter season.

  3. The effectiveness of mean-field theory for avalanche distributions

    Science.gov (United States)

    Lee, Edward; Raju, Archishman; Sethna, James

    We explore the mean-field theory of the pseudogap found in avalanche systems with long-range anisotropic interactions using analytical and numerical tools. The pseudogap in the density of low-stability states emerges from the competition between stabilizing interactions between spins in an avalanche and the destabilizing random movement towards the threshold caused by anisotropic couplings. Pazmandi et al. have shown that for the Sherrington-Kirkpatrick model, the pseudogap scales linearly and produces a distribution of avalanche sizes with exponent t=1 in contrast with that predicted from RFIM t=3/2. Lin et al. have argued that the scaling exponent ? of the pseudogap depends on the tail of the distribution of couplings and on non-universal values like the strain rate and the magnitude of the coupling strength. Yet others have argued that the relationship between the pseudogap scaling and the distribution of avalanche sizes is dependent on dynamical details. Despite the theoretical arguments, the class of RFIM mean-field models is surprisingly good at predicting the distribution of avalanche sizes in a variety of different magnetic systems. We investigate these differences with a combination of theory and simulation.

  4. Segregation induced fingering instabilities in granular avalanches

    Science.gov (United States)

    Woodhouse, Mark; Thornton, Anthony; Johnson, Chris; Kokelaar, Pete; Gray, Nico

    2013-04-01

    It is important to be able to predict the distance to which a hazardous natural granular flows (e.g. snow slab avalanches, debris-flows and pyroclastic flows) might travel, as this information is vital for accurate assessment of the risks posed by such events. In the high solids fraction regions of these flows the large particles commonly segregate to the surface, where they are transported to the margins to form bouldery flow fronts. In many natural flows these bouldery margins experience a much greater frictional force, leading to frontal instabilities. These instabilities create levees that channelize the flow vastly increasing the run-out distance. A similar effect can be observed in dry granular experiments, which use a combination of small round and large rough particles. When this mixture is poured down an inclined plane, particle size segregation causes the large particles to accumulate near the margins. Being rougher, the large particles experience a greater friction force and this configuration (rougher material in front of smoother) can be unstable. The instability causes the uniform flow front to break up into a series of fingers. A recent model for particle size-segregation has been coupled to existing avalanche models through a particle concentration dependent friction law. In this talk numerical solutions of this coupled system are presented and compared to both large scale experiments carried out at the USGS flume and more controlled small scale laboratory experiments. The coupled depth-averaged model captures the accumulation of large particles at the flow front. We show this large particle accumulation at the head of the flow can lead to the break-up of the initially uniform front into a series of fingers. However, we are unable to obtain a fully grid-resolved numerical solution; the width of the fingers decreases as the grid is refined. By considering the linear stability of a steady, fully-developed, bidisperse granular layer it is shown that

  5. Precision Blasting Techniques For Avalanche Control

    Science.gov (United States)

    Powell, Kevin M.

    Experimental firings sponsored by the Center For Snow Science at Alta, Utah have demonstrated the potential of a unique prototype shaped charge device designed to stimulate snow pack and ice. These studies, conducted against stable snow pack, demonstrated a fourfold increase in crater volume yield and introduced a novel application of Shock Tube technology to facilitate position control, detonation and dud recovery of manually deployed charges. The extraordinary penetration capability of the shaped charge mechanism has been exploited in many non-military applications to meet a wide range of rapidpiercing and/or cutting requirements. The broader exploitation of the potential of the shaped charge mechanism has nevertheless remained confined to defence based applications. In the studies reported in this paper, the inimitable ability of the shaped charge mechanism to project shock energy, or a liner material, into a highly focussed energetic stream has been applied uniquely to the stimulation of snow pack. Recent research and development work, conducted within the UK, has resulted in the integration of shaped charge technology into a common Avalauncher and hand charge device. The potential of the common charge configuration and spooled Shock Tube fire and control system to improve the safety and cost effectiveness of explosives used in avalanche control operations was successfully demonstrated at Alta in March 2001. Future programmes of study will include focussed shock/blast mechanisms for suspended wire traverse techniques, application of the shaped charge mechanism to helibombing, and the desig n and development of non-fragmenting shaped charge ammunition formilitary artillery gun systems.

  6. Modeling and monitoring avalanches caused by rain-on-snow events

    Science.gov (United States)

    Havens, S.; Marshall, H. P.; Trisca, G. O.; Johnson, J. B.; Nicholson, B.

    2014-12-01

    Direct-action avalanches occur during large storm cycles in mountainous regions, when stresses on the snowpack increase rapidly due to the load of new snow and outpace snow strengthening due to compaction. If temperatures rise above freezing during the storm and snowfall turns to rain, the near-surface snow undergoes rapid densification caused by the introduction of liquid water. This shock to the snowpack, if stability is near critical, can cause widespread immediate avalanching due to the large induced strain rates in the slab, followed by secondary delayed avalanches due to both the increased load as well as water percolation to the depth of a weak layer. We use the semi-empirical SNOow Slope Stability model (SNOSS) to estimate the evolution of stability prior to large avalanches during rain-on-snow events on Highway 21 north of Boise, Idaho. We have continuously monitored avalanche activity using arrays of infrasound sensors in the avalanche-prone section of HW21 near Stanley, in collaboration with the Idaho Transportation Department's avalanche forecasting program. The autonomous infrasound avalanche monitoring system provides accurate timing of avalanche events, in addition to capturing avalanche dynamics during some major releases adjacent to the array. Due to the remote location and low winter traffic volume, the highway is typically closed for multiple days during major avalanche cycles. Many major avalanches typically release naturally and reach the road, but due the complex terrain and poor visibility, manual observations are often not possible until several days later. Since most avalanche programs typically use explosives on a regular basis to control slope stability, the infrasound record of avalanche activity we have recorded on HW21 provides a unique opportunity to study large naturally triggered avalanches. We use a first-order physically based stability model to estimate the importance of precipitation phase, amount, and rate during major rain

  7. Towards an automated detection of avalanche deposits using their directional properties

    OpenAIRE

    2009-01-01

    Snow avalanches killed more people in the Swiss alpine area during the past decades than any other natural hazard. To further improve the avalanche prediction and the protection of people and infrastructure, information about the occurrence and the distribution of avalanche activity is crucial. Nevertheless this information is missing for large parts of the Alpine area. The surface roughness of avalanche deposits differs considerably from the adjacent undisturbed snow cover and is an impor...

  8. Elementary excitations and avalanches in the Coulomb glass

    Science.gov (United States)

    Palassini, Matteo; Goethe, Martin

    2012-07-01

    We study numerically the statistics of elementary excitations and charge avalanches in the classical Coulomb glass model of localized charges with unscreened Coulomb interaction and disorder. We compute the single-particle density of states with an energy minimization algorithm for systems of up to 1003 sites. The shape of the Coulomb gap is consistent with a power-law with exponent δ simeq 2.4 and marginally consistent with exponential behavior. The results are also compared with a recently proposed self-consistent approach. We then analyze the size distribution of the charge avalanches produced by a small perturbation of the system. We show that the distribution decays as a power law in the limit of large system size, and explain this behavior in terms of the elementary excitations. Similarities and differences with the scale-free avalanches observed in mean-field spin glasses are discussed.

  9. Studies of Electron Avalanche Behavior in Liquid Argon

    CERN Document Server

    Kim, J G; Jackson, K H; Kadel, R W; Kadyk, J A; Peskov, Vladimir; Wenzel, W A

    2002-01-01

    Electron avalanching in liquid argon is being studied as a function of voltage, pressure, radiation intensity, and the concentrations of certain additives, especially xenon. The avalanches produced in an intense electric field at the tip of a tungsten needle are initiated by ionization from a moveable americium (241Am) gamma ray source. Photons from xenon excimers are detected as photomultiplier signals in coincidence with the current pulse from the needle. In pure liquid argon the avalanche behavior is erratic, but the addition of even a small amount of xenon (>100ppm) stabilizes the performance. Similar attempts with neon (30%) as an additive to argon have been unsuccessful. Tests with higher energy gamma rays (57Co) yield spectra and other performance characteristics quite similar to those using the 241Am source. Two types of signal pulses are commonly observed: a set of pulses that are sensitive to ambient pressure, and a set of somewhat smaller pulses that are not pressure dependent.

  10. Precise method for determining avalanche breakdown voltage of silicon photomultipliers

    Science.gov (United States)

    Chirikov-Zorin, I.

    2017-07-01

    A physically motivated method is proposed for determining the avalanche breakdown voltage of silicon photomultipliers (SiPM). The method is based on measuring the dependence of the relative photon detection efficiency (PDErel) on the bias voltage when one type of carriers (electron or hole) is injected into the avalanche multiplication zone of the p-n junction. The injection of electrons or holes from the base region of the SiPM semiconductor structure is performed using short-wave or long-wave light. At a low overvoltage (1-2 V) the detection efficiency is linearly dependent on the bias voltage; therefore, extrapolation to zero PDErel value determines the SiPM avalanche breakdown voltage with an accuracy within a few millivolts.

  11. Model of single-electron performance of micropixel avalanche photodiodes

    CERN Document Server

    Sadygov, Z; Akhmedov, G; Akhmedov, F; Khorev, S; Mukhtarov, R; Sadigov, A; Sidelev, A; Titov, A; Zerrouk, F; Zhezher, V

    2014-01-01

    An approximate iterative model of avalanche process in a pixel of micropixel avalanche photodiode initiated by a single photoelectron is presented. The model describes development of the avalanche process in time, taking into account change of electric field within the depleted region caused by internal discharge and external recharge currents. Conclusions obtained as a result of modelling are compared with experimental data. Simulations show that typical durations of the front and rear edges of the discharge current have the same magnitude of less than 50 ps. The front of the external recharge current has the same duration, however duration of the rear edge depends on value of the quenching micro-resistor. It was found that effective capacitance of the pixel calculated as the slope of linear dependence of the pulse charge on bias voltage exceeds its real capacitance by a factor of two.

  12. [Death by avalanche in the minor mountain range].

    Science.gov (United States)

    Geisenberger, Dorothee; Kramer, Lena; Pircher, Rebecca; Pollak, Stefan

    2015-01-01

    On 30 Jan 2015, two avalanche accidents happened in the Black Forest (at the foot of the 1493 m high Feldberg and the Herzogenhorn situated next to it), in which experienced ski tourers--a 58-year-old woman and a 20-year-old man--were completely buried by snow masses. Both victims were recovered dead after nearly 2 hours under the snow. The avalanches were promoted by strong snowfalls, snowdrift by the wind and steep downwind slopes. One of the victims, the 20-year-old man, underwent a forensic autopsy. The findings suggested death by protracted asphyxiation with agonal hypothermia. A mechanical traumatization with internal injuries suspected by the emergency doctor at the scene could not be confirmed at autopsy. The possible causes of death in the avalanche are discussed using the reported case as an example and in reference to the relevant literature.

  13. Flux avalanches in Nb superconducting shifted strip arrays

    Science.gov (United States)

    Tsuchiya, Y.; Mawatari, Y.; Ibuka, J.; Tada, S.; Pyon, S.; Nagasawa, S.; Hidaka, M.; Maezawa, M.; Tamegai, T.

    2013-09-01

    Flux penetrations into three-dimensional Nb superconducting strip arrays, where two layers of strip arrays are stacked by shifting a half period, are studied using a magneto-optical imaging method. Flux avalanches are observed when the overlap between the top and bottom layers is large even if the width of each strip is well below the threshold value. In addition, anomalous linear avalanches perpendicular to the strip are observed in the shifted strip array when the overlap is very large and the thickness of the superconductor is greater than the penetration depth. We discuss possible origins for the flux avalanches, including linear ones, by considering flux penetration calculated by the Campbell method assuming the Bean model.

  14. Experimental method to predict avalanches based on neural networks

    Directory of Open Access Journals (Sweden)

    V. V. Zhdanov

    2016-01-01

    Full Text Available The article presents results of experimental use of currently available statistical methods to classify the avalanche‑dangerous precipitations and snowfalls in the Kishi Almaty river basin. The avalanche service of Kazakhstan uses graphical methods for prediction of avalanches developed by I.V. Kondrashov and E.I. Kolesnikov. The main objective of this work was to develop a modern model that could be used directly at the avalanche stations. Classification of winter precipitations into dangerous snowfalls and non‑dangerous ones was performed by two following ways: the linear discriminant function (canonical analysis and artificial neural networks. Observational data on weather and avalanches in the gorge Kishi Almaty in the gorge Kishi Almaty were used as a training sample. Coefficients for the canonical variables were calculated by the software «Statistica» (Russian version 6.0, and then the necessary formula had been constructed. The accuracy of the above classification was 96%. Simulator by the authors L.N. Yasnitsky and F.М. Cherepanov was used to learn the neural networks. The trained neural network demonstrated 98% accuracy of the classification. Prepared statistical models are recommended to be tested at the snow‑avalanche stations. Results of the tests will be used for estimation of the model quality and its readiness for the operational work. In future, we plan to apply these models for classification of the avalanche danger by the five‑point international scale.

  15. Spectral method for characterization of avalanche photodiode working as single-photon detector.

    Science.gov (United States)

    Cavalcanti, Maria Daniela Santabaia; Mendonça, Fábio Alencar; Ramos, Rubens Viana

    2011-09-01

    In this Letter, a new method for avalanche photodiode characterization, based on the spectral analysis of the photocurrent produced during an avalanche, is proposed. The theory is developed, and an experimental characterization of an avalanche photodiode working in the Geiger mode with CW laser is performed.

  16. Practical methods for using vegetation patterns to estimate avalanche frequency and magnitude

    Science.gov (United States)

    Simonson, S.; Fassnacht, S. R.

    2011-12-01

    Practitioners working in avalanche terrain may never witness an extreme event, but understanding extreme events is important for categorizing avalanches that occur within a given season. Historical records of avalanche incidents and direct observations are the most reliable evidence of avalanche activity, but patterns in vegetation can be used to further quantify and map the frequency and magnitude of past events. We surveyed published literature to synthesize approaches for using vegetation sampling to characterize avalanche terrain, and developed examples to identify the benefits and caveats of using different practical field methods to estimate avalanche frequency and magnitude. Powerful avalanches can deposit massive piles of snow, rocks, and woody debris in runout zones. Large avalanches (relative to the path) can cut fresh trimlines, widening their tracks by uprooting, stripping, and breaking trees. Discs and cores can be collected from downed trees to detect signals of past avalanche disturbance recorded in woody plant tissue. Signals of disturbance events recorded in tree rings can include direct impact scars from the moving snow and wind blast, development of reaction wood in response to tilting, and abrupt variation in the relative width of annual growth rings. The relative ages of trees in avalanche paths and the surrounding landscape can be an indicator of the area impacted by past avalanches. Repeat photography can also be useful to track changes in vegetation over time. For Colorado, and perhaps elsewhere, several vegetation ecology methods can be used in combination to accurately characterize local avalanche frequency and magnitude.

  17. SNOW AVALANCHE ACTIVITY IN PARÂNG SKI AREA REVEALED BY TREE-RINGS

    Directory of Open Access Journals (Sweden)

    F. MESEȘAN

    2014-11-01

    Full Text Available Snow Avalanche Activity in Parâng Ski Area Revealed by Tree-Rings. Snow avalanches hold favorable conditions to manifest in Parâng Mountains but only one event is historically known, without destructive impact upon infrastructure or fatalities and this region wasn’t yet the object of avalanche research. The existing ski infrastructure of Parâng resort located in the west of Parâng Mountains is proposed to be extended in the steep slopes of subalpine area. Field evidence pinpoints that these steep slopes were affected by snow avalanches in the past. In this study we analyzed 11 stem discs and 31 increment cores extracted from 22 spruces (Picea abies (L. Karst impacted by avalanches, in order to obtain more information about past avalanches activity. Using the dendrogeomorphological approach we found 13 avalanche events that occurred along Scărița avalanche path, since 1935 until 2012, nine of them produced in the last 20 years. The tree-rings data inferred an intense snow avalanche activity along this avalanche path. This study not only calls for more research in the study area but also proves that snow avalanches could constitute an important restrictive factor for the tourism infrastructure and related activities in the area. It must be taken into consideration by the future extension of tourism infrastructure. Keywords: snow avalanche, Parâng Mountains, dendrogeomorphology, ski area.

  18. Progress in simulations of micropattern gas avalanche detectors

    CERN Document Server

    Cwetanski, Peter

    2000-01-01

    Helpful for a better understanding of the intrinsic processes in the various gas avalanche detectors are simulations, involving three- dimensional Finite Element Method (FEM) field map computations in order to describe the more and more complex geometries. Drift, multiplication and attachment procedures are simulated using Monte Carlo techniques. Recent results show a remarkable agreement with gain and energy resolution measurements thanks to the refined computations of gas transport properties and improved avalanching models. As examples the influence of wire eccentricity on gas gain and energy resolution in the ATLAS TRT straws is shown as well as performed studies of the Micromegas detector. 8 Refs.

  19. High gain multigap avalanche detectors for Cerenkov ring imaging

    Energy Technology Data Exchange (ETDEWEB)

    Gilmore, R.S.; Lavender, W.M.; Leith, D.W.G.S.; Williams, S.H.

    1980-10-01

    We report on a continuing study of multigap parallel plate avalanche chambers, primarily as photoelectron detectors for use with Cerenkov ring imaging counters. By suitable control of the fields in successive gaps and by introducing screens to reduce photon feedback to the cathode the gain many be increased considerably. We have obtained gains in excess of 6 x 10/sup 7/ for photoelectrons with a good pulse height spectrum and expect to increase this further. We discuss the use of resistive anodes to give avalanche positions in two dimensions by charge division.

  20. Geiger-Mode Avalanche Photodiodes in Particle Detection

    CERN Document Server

    Vilella, E; Trenado, J; Vila, A; Vos, M; Garrido, L; Dieguez, A

    2012-01-01

    It is well known that avalanche photodiodes operated in the Geiger mode above the breakdown voltage offer a virtually infinite sensitivity and time accuracy in the picosecond range that can be used for single photon detection. However, their performance in particle detection remains still unexplored. In this contribution, we are going to expose the different steps that we have taken in order to prove the efficiency of Geiger mode avalanche photodiodes in the aforementioned field. In particular, we will present an array of pixels of 1mmx1mm fabricated with a standard CMOS technology for characterization in a test beam.

  1. Negative Avalanche Feedback Detectors for Photon-Counting Optical Communications

    Science.gov (United States)

    Farr, William H.

    2009-01-01

    Negative Avalanche Feedback photon counting detectors with near-infrared spectral sensitivity offer an alternative to conventional Geiger mode avalanche photodiode or phototube detectors for free space communications links at 1 and 1.55 microns. These devices demonstrate linear mode photon counting without requiring any external reset circuitry and may even be operated at room temperature. We have now characterized the detection efficiency, dark count rate, after-pulsing, and single photon jitter for three variants of this new detector class, as well as operated these uniquely simple to use devices in actual photon starved free space optical communications links.

  2. Negative Avalanche Feedback Detectors for Photon-Counting Optical Communications

    Science.gov (United States)

    Farr, William H.

    2009-01-01

    Negative Avalanche Feedback photon counting detectors with near-infrared spectral sensitivity offer an alternative to conventional Geiger mode avalanche photodiode or phototube detectors for free space communications links at 1 and 1.55 microns. These devices demonstrate linear mode photon counting without requiring any external reset circuitry and may even be operated at room temperature. We have now characterized the detection efficiency, dark count rate, after-pulsing, and single photon jitter for three variants of this new detector class, as well as operated these uniquely simple to use devices in actual photon starved free space optical communications links.

  3. Test of BESⅢ RPC in the avalanche mode

    Institute of Scientific and Technical Information of China (English)

    HAN Ji-Feng; ZHANG Jia-Wen; CHEN Jin; ZHANG Qing-Min; LIU Qian; XIE Yu-Guang; QIAN Sen; MA Lie-Hua

    2008-01-01

    The installation of the BESⅢ RPC system has been completed.Cosmic ray test results show that they perform very well in streamer mode and meet the BESⅢ requirements.We have tested several RPCs in the avalanche mode with the addition of extra SF6 in the gas mixture.We find an efficiency plateau that reaches~95%.and a time resolution of 1.8 ns.This demonstrates that the BESⅢ-type RPC can work in the avalanche mode as well.

  4. Magnetar Outbursts from Avalanches of Hall Waves and Crustal Failures

    CERN Document Server

    Li, Xinyu; Belovorodov, Andrei M

    2016-01-01

    We explore the interaction between Hall waves and mechanical failures inside a magnetar crust, using detailed one-dimentional models that consider temperature-sensitive plastic flow, heat transport and cooling by neutrino emission, as well as the coupling of the crustal motion to the magnetosphere. We find that the dynamics is enriched and accelerated by the fast, short-wavelength Hall waves that are emitted by each failure. The waves propagate and cause failures elsewhere, triggering avalanches. We argue that these avalanches are the likely sources of outbursts in transient magnetars.

  5. Assessing risk based on uncertain avalanche activity patterns

    Science.gov (United States)

    Zeidler, Antonia; Fromm, Reinhard

    2015-04-01

    Avalanches may affect critical infrastructure and may cause great economic losses. The planning horizon of infrastructures, e.g. hydropower generation facilities, reaches well into the future. Based on the results of previous studies on the effect of changing meteorological parameters (precipitation, temperature) and the effect on avalanche activity we assume that there will be a change of the risk pattern in future. The decision makers need to understand what the future might bring to best formulate their mitigation strategies. Therefore, we explore a commercial risk software to calculate risk for the coming years that might help in decision processes. The software @risk, is known to many larger companies, and therefore we explore its capabilities to include avalanche risk simulations in order to guarantee a comparability of different risks. In a first step, we develop a model for a hydropower generation facility that reflects the problem of changing avalanche activity patterns in future by selecting relevant input parameters and assigning likely probability distributions. The uncertain input variables include the probability of avalanches affecting an object, the vulnerability of an object, the expected costs for repairing the object and the expected cost due to interruption. The crux is to find the distribution that best represents the input variables under changing meteorological conditions. Our focus is on including the uncertain probability of avalanches based on the analysis of past avalanche data and expert knowledge. In order to explore different likely outcomes we base the analysis on three different climate scenarios (likely, worst case, baseline). For some variables, it is possible to fit a distribution to historical data, whereas in cases where the past dataset is insufficient or not available the software allows to select from over 30 different distribution types. The Monte Carlo simulation uses the probability distribution of uncertain variables

  6. Rectification of two generic names

    NARCIS (Netherlands)

    Büttikofer, J.

    1896-01-01

    I am sorry to say that amongst the new generic names, occurring in my recent paper on the genus Pycnonotus and some allied Genera (N. L. M. XVII), Centrolophus and Gymnocrotaphus are already preoccupied among the Fishes, the first being used by Lacépède, the second by Günther. I propose, therefore,

  7. GENERIC model for multiphase systems

    NARCIS (Netherlands)

    Sagis, L.M.C.

    2010-01-01

    GENERIC is a nonequilibrium thermodynamic formalism in which the dynamic behavior of a system is described by a single compact equation involving two types of brackets: a Poisson bracket and a dissipative bracket. This formalism has proved to be a very powerful instrument to model the dynamic behavi

  8. Generic Hurricane Extreme Seas State

    DEFF Research Database (Denmark)

    Wehmeyer, Christof; Skourup, Jesper; Frigaard, Peter

    2012-01-01

    the US east coast and the Gulf of Mexico (1851 - 2009) and Japanese east coast (1951 -2009) form the basis for Weibull extreme value analyses to determine return period respective maximum wind speeds. Unidirectional generic sea state spectra are obtained by application of the empirical models...

  9. Generic Software Architecture for Launchers

    Science.gov (United States)

    Carre, Emilien; Gast, Philippe; Hiron, Emmanuel; Leblanc, Alain; Lesens, David; Mescam, Emmanuelle; Moro, Pierre

    2015-09-01

    The definition and reuse of generic software architecture for launchers is not so usual for several reasons: the number of European launcher families is very small (Ariane 5 and Vega for these last decades); the real time constraints (reactivity and determinism needs) are very hard; low levels of versatility are required (implying often an ad hoc development of the launcher mission). In comparison, satellites are often built on a generic platform made up of reusable hardware building blocks (processors, star-trackers, gyroscopes, etc.) and reusable software building blocks (middleware, TM/TC, On Board Control Procedure, etc.). If some of these reasons are still valid (e.g. the limited number of development), the increase of the available CPU power makes today an approach based on a generic time triggered middleware (ensuring the full determinism of the system) and a centralised mission and vehicle management (offering more flexibility in the design and facilitating the long term maintenance) achievable. This paper presents an example of generic software architecture which could be envisaged for future launchers, based on the previously described principles and supported by model driven engineering and automatic code generation.

  10. Electric field distribution and simulation of avalanche formation due to the passage of heavy ions in a parallel grid avalanche counter

    Indian Academy of Sciences (India)

    D Kanjilal; S Saha

    2009-05-01

    Electric field distributions and their role in the formation of avalanche due to the passage of heavy ions in parallel grid avalanche type wire chamber detectors are evaluated using a Monte Carlo simulation. The relative merits and demerits of parallel and crossed wire grid configurations are studied. It is found that the crossed grid geometry has marginally higher gain at larger electric fields close to the avalanche region. The spatial uniformity of response in the two wire grid configurations is also compared.

  11. Mylan to Offer Generic EpiPen

    Science.gov (United States)

    ... news/fullstory_160669.html Mylan to Offer Generic EpiPen Manufacturer responds to mounting criticism about price hikes ... cheaper generic version of the emergency allergy treatment EpiPen will be made available within the next few ...

  12. Gridded snow maps supporting avalanche forecasting in Norway

    Science.gov (United States)

    Müller, K.; Humstad, T.; Engeset, R. V.; Andersen, J.

    2012-04-01

    We present gridded maps indicating key parameters for avalanche forecasting with a 1 km x 1 km resolution. Based on the HBV hydrology model, snow parameters are modeled based on observed and interpolated precipitation and temperature data. Modeled parameters include for example new snow accumulated the last 24 and 72 hours, snow-water equivalent, and snow-water content. In addition we use meteorological parameters from the UK weather prediction model "Unified Model" such as wind and radiation to model snow-pack properties. Additional loading in lee-slopes by wind-transport is modeled based on prevailing wind conditions, snow-water content and snow age. A depth hoar index accounts for days with considerable negative temperature gradients in the snow pack. A surface hoar index based on radiation and humidity is currently under development. The maps are tested against field reports from avalanche observers throughout Norway. All data is available via a web-platform that combines maps for geo-hazards such as floods, landslides and avalanches. The maps are used by the Norwegian avalanche forecasting service, which is currently in a test phase. The service will be operational by winter 2012/2013.

  13. Catastrophic debris avalanche deposit of Socompa volcano, northern Chile

    Science.gov (United States)

    Francis, P. W.; Gardeweg, M.; Ramirez, C. F.; Rothery, D. A.

    1985-01-01

    Between 10,000 and 500 yr ago the Socompa volcano in northern Chile experienced a catastrophic collapse of a 70 deg sector of the original cone, causing a debris avalanche that descended nearly 3000 m vertically and traveled more than 35 km from the volcano. The deposits cover some 490 sq km and have a minimum volume of 15 cu km. Parts of the original cone slumped in a nearly coherent form and are now preserved as large blocks more than 400 m high. The primary avalanche traveled northwestward over sloping ground before coming to rest transiently, forming a prominent marginal ridge, and then slid away northeastward to form a secondary flow, overriding much of the primary avalanche deposit. Abundant, prismatic, jointed dacite blocks within the debris avalanche deposit and a thin, fine-grained pumiceous deposit beneath it suggest that the collapse was triggered by magmatic activity and may have been accompanied by a violent lateral blast. Collapse was followed by eruption of pumiceous pyroclastic flows and extrusion of voluminous dacite domes.

  14. High quantum efficiency GaP avalanche photodiodes.

    Science.gov (United States)

    McIntosh, Dion; Zhou, Qiugui; Chen, Yaojia; Campbell, Joe C

    2011-09-26

    Gallium Phosphide (GaP) reach-through avalanche photodiodes (APDs) are reported. The APDs exhibited dark current less than a pico-ampere at unity gain. A quantum efficiency of 70% was achieved with a recessed window structure; this is almost two times higher than previous work. © 2011 Optical Society of America

  15. Electron avalanche structure determined by random walk theory

    Science.gov (United States)

    Englert, G. W.

    1973-01-01

    A self-consistent avalanche solution which accounts for collective long range Coulomb interactions as well as short range elastic and inelastic collisions between electrons and background atoms is made possible by a random walk technique. Results show that the electric field patterns in the early formation stages of avalanches in helium are close to those obtained from theory based on constant transport coefficients. Regions of maximum and minimum induced electrostatic potential phi are located on the axis of symmetry and within the volume covered by the electron swarm. As formation time continues, however, the region of minimum phi moves to slightly higher radii and the electric field between the extrema becomes somewhat erratic. In the intermediate formation periods the avalanche growth is slightly retarded by the high concentration of ions in the tail which oppose the external electric field. Eventually the formation of ions and electrons in the localized regions of high field strength more than offset this effect causing a very abrupt increase in avalanche growth.

  16. Hybrid phase transition into an absorbing state: Percolation and avalanches.

    Science.gov (United States)

    Lee, Deokjae; Choi, S; Stippinger, M; Kertész, J; Kahng, B

    2016-04-01

    Interdependent networks are more fragile under random attacks than simplex networks, because interlayer dependencies lead to cascading failures and finally to a sudden collapse. This is a hybrid phase transition (HPT), meaning that at the transition point the order parameter has a jump but there are also critical phenomena related to it. Here we study these phenomena on the Erdős-Rényi and the two-dimensional interdependent networks and show that the hybrid percolation transition exhibits two kinds of critical behaviors: divergence of the fluctuations of the order parameter and power-law size distribution of finite avalanches at a transition point. At the transition point global or "infinite" avalanches occur, while the finite ones have a power law size distribution; thus the avalanche statistics also has the nature of a HPT. The exponent β_{m} of the order parameter is 1/2 under general conditions, while the value of the exponent γ_{m} characterizing the fluctuations of the order parameter depends on the system. The critical behavior of the finite avalanches can be described by another set of exponents, β_{a} and γ_{a}. These two critical behaviors are coupled by a scaling law: 1-β_{m}=γ_{a}.

  17. Avalanches in dry and saturated disordered media at fracture.

    Science.gov (United States)

    Milanese, Enrico; Yılmaz, Okan; Molinari, Jean-François; Schrefler, Bernhard

    2016-04-01

    This paper analyzes fracturing in inhomogeneous media under dry and fully saturated conditions. We adopt a central force model with continuous damage to study avalanche behavior in a two-dimensional truss lattice undergoing dilation. Multiple fractures can develop at once and a power-law distribution of the avalanche size is observed. The values for the power-law exponent are compared with the ones found in the literature and scale-free behavior is suggested. The fracture evolves intermittently in time because only some avalanches correspond to fracture advancement. A fully saturated model with continuous damage based on the extended Biot's theory is developed and avalanche behavior is studied in the presence of fluid, varying the fluid boundary conditions. We show that power-law behavior is destroyed when the fluid flux governs the problem. Fluid pressure behavior during intermittent crack tip advancement is studied for the continuous-damage fully saturated model. It is found that when mechanical loading prevails, the pressure rises when the crack advances, while when fluid loading prevails, the pressure drops when the crack advances.

  18. Group Dynamics and Decision Making: Backcountry Recreationists in Avalanche Terrain

    Science.gov (United States)

    Bright, Leslie Shay

    2010-01-01

    The purpose of this study was to describe and determine the prevalence of decision-making characteristics of recreational backcountry groups when making a decision of where to travel and ride in avalanche terrain from the perspective of individuals. Decision-making characteristics encompassed communication, decision-making processes, leadership,…

  19. Teaching Avalanche Safety Courses: Instructional Techniques and Field Exercises.

    Science.gov (United States)

    Watters, Ron

    This paper discusses course structure, teaching techniques, and field exercises for enhancing winter travelers' avalanche knowledge and skills. In two class sessions, the course typically consists of a historical perspective; a section on snow physics (clouds, types of snow crystals, effects of riming, identification of precipitated snow crystals,…

  20. Reducing the Odds: Backcountry Powder Skiing in Avalanche Terrain.

    Science.gov (United States)

    Daffern, Tony

    This paper provides information and strategies to reduce the risk of encountering an avalanche when skiing or climbing on steep slopes. Skiers must recognize that the risk exists, be aware of their own tolerance for risk, and not allow companions to pressure them into taking more risk than they can tolerate. Ideally, one should ski with a small…

  1. THE SNOW CONDITION, THE AVALANCHES CAUSED AND THE DYNAMIC OF THE AVALANCHES CORRIDORS DURING THE WINTER 2007-2008. CASE STUDY, PADINILE FRUMOASE (PIATRA CRAIULUI MOUNTAINS, ROMANIA

    Directory of Open Access Journals (Sweden)

    ANCA MUNTEANU

    2013-04-01

    Full Text Available The snow condition, the avalanches caused and the dynamic of the avalanches corridors during the winter 2007-2008. Case study, Padinile Frumoase (Piatra Craiului Mountains, Romania. In this paper we aim to present in detail the situations generated by meteorological and morphological parameters, which determined the generation of avalanches of different intensities, on five avalanches corridors in the winter 2007-2008. These are situated in the area named Padinile Frumoase, in the north-eastern part of the Piatra Craiului Mountains, which are situated in the central part of Romania and which belong to the Meridional Carpathians. The relief is represented by a calcareous- conglomeratic ridge, in the high part, the peak reaches over 2000 m altitude. Local conditions determine the forming of avalanches, which are oriented on well defined corridors, along the temporary hydrographic network. By studying the evolution of meteorological parameters and their overlapping with local morphological parameters, the existence of some favourable conditions for the apparition of avalanches were detected. There were noticed both active corridors with traces of avalanches, and inactive corridors on which it was not noticed the manifestation of these phenomena. The material adds up to the data base about the avalanches from this massif, being the second situation of analysed avalanches for this mountainous space totally situated in the National Park Piatra Craiului.

  2. Rock-avalanche dynamics revealed by large-scale field mapping and seismic signals at a highly mobile avalanche in the West Salt Creek valley, western Colorado

    Science.gov (United States)

    Coe, Jeffrey A.; Baum, Rex L.; Allstadt, Kate; Kochevar, Bernard; Schmitt, Robert G.; Morgan, Matthew L.; White, Jonathan L.; Stratton, Benjamin T.; Hayashi, Timothy A.; Kean, Jason W.

    2016-01-01

    On 25 May 2014, a rain-on-snow–induced rock avalanche occurred in the West Salt Creek valley on the northern flank of Grand Mesa in western Colorado (United States). The avalanche mobilized from a preexisting rock slide in the Green River Formation and traveled 4.6 km down the confined valley, killing three people. The avalanche was rare for the contiguous United States because of its large size (54.5 Mm3) and high mobility (height/length = 0.14). To understand the avalanche failure sequence, mechanisms, and mobility, we conducted a forensic analysis using large-scale (1:1000) structural mapping and seismic data. We used high-resolution, unmanned aircraft system imagery as a base for field mapping, and analyzed seismic data from 22 broadband stations (distances avalanche exerted on the earth and tracked these forces using curves in the avalanche path. Our results revealed that the rock avalanche was a cascade of landslide events, rather than a single massive failure. The sequence began with an early morning landslide/debris flow that started ∼10 h before the main avalanche. The main avalanche lasted ∼3.5 min and traveled at average velocities ranging from 15 to 36 m/s. For at least two hours after the avalanche ceased movement, a central, hummock-rich core continued to move slowly. Since 25 May 2014, numerous shallow landslides, rock slides, and rock falls have created new structures and modified avalanche topography. Mobility of the main avalanche and central core was likely enhanced by valley floor material that liquefied from undrained loading by the overriding avalanche. Although the base was likely at least partially liquefied, our mapping indicates that the overriding avalanche internally deformed predominantly by sliding along discrete shear surfaces in material that was nearly dry and had substantial frictional strength. These results indicate that the West Salt Creek avalanche, and probably other long-traveled avalanches, could be modeled as two

  3. Rock avalanches clusters along the northern Chile coastal scarp

    Science.gov (United States)

    Crosta, G. B.; Hermanns, R. L.; Dehls, J.; Lari, S.; Sepulveda, S.

    2017-07-01

    Rock avalanche clusters can be relevant indicators of the evolution of specific regions. They can be used to define: the type and intensity of triggering events, their recurrence and potential probability of occurrence, the progressive damage of the rock mass, the mechanisms of transport and deposition, as well as the environmental conditions at the time of occurrence. This paper tackles these subjects by analyzing two main clusters of rock avalanches (each event between 0.6 and 30 Mm3), separated by few kilometers and located along the coastal scarp of Northern Chile, south of Iquique. It lies, hence, within a seismic area characterized by a long seismic gap that ended on April 1st, 2014 with a Mw 8.2 earthquake. The scar position, high along the coastal cliff, supports seismic triggering for these clusters. The deposits' relative positions are used to obtain the sequence of rock avalanching events for each cluster. The progressive decrease of volume in the sequence of rock avalanches forming each cluster fits well the theoretical models for successive slope failures. These sequences seem to agree with those derived by dating the deposits with ages spanning between 4 kyr and 60 kyr. An average uplift rate of 0.2 mm/yr in the last 40 kyr is estimated for the coastal plain giving a further constraint to the rock avalanche deposition considering the absence of reworking of the deposits. Volume estimates and datings allow the estimation of an erosion rate contribution of about 0.098-0.112 mm km- 2 yr- 1 which is well comparable to values presented in the literature for earthquake induced landslides. We have carried out numerical modeling in order to analyze the mobility of the rock avalanches and examine the environmental conditions that controlled the runout. In doing so, we have considered the sequence of individual rock avalanches within the specific clusters, thus including in the models the confining effect caused by the presence of previous deposits. Bingham

  4. Single and few photon avalanche photodiode detection process study

    Science.gov (United States)

    Blazej, Josef; Prochazka, Ivan

    2009-07-01

    We are presenting the results of the study of the Single Photon Avalanche Diode (SPAD) pulse response risetime and its dependence on several key parameters. We were investigating the unique properties of K14 type SPAD with its high delay uniformity of 200 μm active area and the correlation between the avalanche buildup time and the photon number involved in the avalanche trigger. The detection chip was operated in a passive quenching circuit with active gating. This setup enabled us to monitor the diode reverse current using an electrometer, a fast digitizing oscilloscope, and using a custom design comparator circuit. The electrometer reading enabled to estimate the photon number per detection event, independently on avalanche process. The avalanche build up was recorded on the oscilloscope and processed by custom designed waveform analysis package. The correlation of avalanche build up to the photon number, bias above break, photon absorption location, optical pulse length and photon energy was investigated in detail. The experimental results are presented. The existing solid state photon counting detectors have been dedicated for picosecond resolution and timing stability of single photon events. However, the high timing stability is maintained for individual single photons detection, only. If more than one photon is absorbed within the detector time resolution, the detection delay will be significantly affected. This fact is restricting the application of the solid state photon counters to cases where single photons may be guaranteed, only. For laser ranging purposes it is highly desirable to have a detector, which detects both single photon and multi photon signals with picoseconds stability. The SPAD based photon counter works in a purely digital mode: a uniform output signal is generated once the photon is detected. If the input signal consists of several photons, the first absorbed one triggers the avalanche. Obviously, for multiple photon signals, the

  5. Snow avalanche detection and identification for near real-time application

    Science.gov (United States)

    Havens, S.; Johnson, J. B.; Marshall, H.; Nicholson, B.; Trisca, G. O.

    2013-12-01

    A near real-time avalanche detection system will provide highway avalanche forecasters with a tool to remotely monitor major avalanche paths and provide information about regional avalanche activity and timing. For the last three winters, a network of infrasound arrays has been remotely monitoring both avalanche and non-avalanche events along a 10 mile section of Highway 21 in Idaho. To provide the best results to avalanche forecasters, the system must be robust and detect all major avalanche events of interest that affect the highway. Over the last three winters, the infrasound arrays recorded multiple avalanche cycles and we explore different methods of event detection for both large dry avalanches (strong infrasound signal) and small wet avalanches (weak infrasound signal). We compare the F-statistic and cross-correlation techniques (i.e. PMCC) to determine the most robust method and develop computationally efficient algorithms to implement in near-real time using parallel processing and GPU computing. Once an event has been detected, we use the artificial intelligence method of recursive neural networks to classify based on similar characteristics to past known signals.

  6. Use of a magnetic field to modify and detect avalanche behavior on a conical bead pile

    Science.gov (United States)

    Johnson, Nathan; Lehman, Susan

    2015-03-01

    A conical bead pile subject to slow driving and an external magnetic field is used to test the effects of drop height and cohesion on avalanche statistics. Magnetically susceptible beads were dropped onto a pile from different heights and into different strengths of magnetic field. Avalanches were recorded by the change in mass as beads fall off the pile. For beads dropped from a low drop height with no cohesion, the avalanche size distribution follows a power law. As cohesion increases, we observe an increase in the probability of very large avalanches and decreases in the mid-size avalanches. The resulting bump in the avalanche distribution moves to larger avalanche size as the cohesion in the system is increased, matching the prediction by an analytic theory from a mean-field model of slip avalanches. The model also makes predictions for avalanche duration, which is not measurable with our current system. Since the steel beads are magnetized while in the applied magnetic field, their motion during an avalanche creates a change in magnetic flux. To detect this motion, we have placed a large-diameter pick-up coil around the pile. Results of the testing and calibration of this coil to measure avalanche duration are presented.

  7. Compositional Design of a Generic Design Agent

    NARCIS (Netherlands)

    Brazier, F.M.T.; Jonker, C.M.; Treur, J.; Wijngaards, N.J.E.

    2001-01-01

    This paper presents a generic architecture for a design agent, to be used in an Internet environment. The design agent is based on an existing generic agent model, and includes a refinement of a generic model for design, in which strategic reasoning

  8. Comparing approaches to generic programming in Haskell

    NARCIS (Netherlands)

    Hinze, R.; Jeuring, J.T.; Löh, A.

    2007-01-01

    The last decade has seen a number of approaches to data- type-generic programming: PolyP, Functorial ML, `Scrap Your Boiler- plate', Generic Haskell, `Generics for the Masses', etc. The approaches vary in sophistication and target audience: some propose full-blown pro- gramming languages, some sugge

  9. Development in the design and performance of gas avalanche microdetectors (MSGC, MGC, and MDOT)

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Hyo-Sung [Univ. of California, Berkeley, CA (United States). Dept. of Nuclear Enginering

    1997-12-01

    There has been continuing development of generic classes of microstrip gas chambers (MSGCs), microgap gas chambers (MGCs) and microdot gas chambers (MDOTs) at Lawrence Berkeley National Laboratory (LBNL) over the past few years, to improve such detectors beyond their present capabilities, to produce detectors suitable for use in current or upcoming experiments, and to allow a basis for new R&D developments which may incorporate these detectors as part of the system. All of these new detectors are collectively referred to as "gas avalanche microdetectors". The MSGC, which was motivated by the pioneering work of A. Oed, has many attractive features, especially excellent spatial resolution (~30 μm rms at normal incidence) and high rate capability (~106 mm-2∙s-1). Moreover, the MGC seems to have certain advantages over the MSGC in speed, stability and simplicity, and the MDOT has larger gain (>104) and the intrinsic advantages of two-dimensional readout. Because of these attractive properties, they have received a great deal of attention for nuclear and high energy physics experiments, medical X-ray imaging and many other fields requiring radiation detection and measurement.

  10. Laboratory study of avalanches in a magnetized plasma

    Science.gov (United States)

    van Compernolle, Bart

    2015-11-01

    Results of a basic heat transport experiment [] involving an off-axis heat source are presented. Experiments are performed in the Large Plasma Device (LAPD) at UCLA. A ring-shaped electron beam source injects low energy electrons (below ionization energy) along a strong magnetic field into a preexisting, large and cold plasma. The injected electrons are thermalized by Coulomb collisions within a short distance and provide an off-axis heat source that results in a long, hollow, cylindrical region of elevated electron temperature embedded in a colder plasma, and far from the machine walls. It is demonstrated that this heating configuration provides an ideal environment to study avalanche phenomena under controlled conditions. The avalanches are identified as sudden rearrangements of the pressure profile following the growth of fluctuations from ambient noise. The intermittent collapses of the plasma pressure profile are associated with unstable drift-Alfvén waves and exhibit both radial and azimuthal dynamics. After each collapse the plasma enters a quiescent phase in which the pressure profile slowly recovers and steepens until a threshold is exceeded, and the process repeats. The use of reference probes as time markers allows for the visualization of the 2D spatio-temporal evolution of the avalanche events. Avalanches are only observed for a limited combination of heating powers and magnetic fields. At higher heating powers the system transitions from the avalanche regime into a regime dominated by sustained drift-Alfvén wave activity. The pressure profile then transitions to a near steady-state in which anomalous transport balances the external pressure source. Performed at the Basic Plasma Science Facility at UCLA, supported jointly by DOE and NSF.

  11. Forensic Analysis of the May 2014 West Salt Creek Rock Avalanche in Western Colorado

    Science.gov (United States)

    Coe, J. A.; Baum, R. L.; Allstadt, K.; Kochevar, B. F.; Schmitt, R. G.; Morgan, M. L.; White, J. L.; Stratton, B. T.; Hayashi, T. A.; Kean, J. W.

    2015-12-01

    The rain-on-snow induced West Salt Creek rock avalanche occurred on May 25, 2014 on the northern flank of Grand Mesa. The avalanche was rare for the contiguous U.S. because of its large size (59 M m3) and high mobility (Length/Height=7.2). To understand the avalanche failure sequence, mechanisms, and mobility, we conducted a forensic analysis using large-scale (1:1000) structural mapping and seismic data. We used high-resolution, Unmanned Aircraft System (UAS) imagery as a base for our field mapping and analyzed seismic data from 22 broadband stations (distances avalanche exerted on the earth and tracked these forces using curves in the avalanche path. Our results revealed that the rock avalanche was a cascade of landslide events, rather than a single massive failure. The sequence began with a landslide/debris flow that started about 10 hours before the main avalanche. The main avalanche lasted just over 3 minutes and traveled at average velocities ranging from 15 to 36 m/s. For at least two hours after the avalanche ceased movement, a central, hummock-rich, strike-slip bound core continued to move slowly. Following movement of the core, numerous shallow landslides, rock slides, and rock falls created new structures and modified topography. Mobility of the main avalanche and central core were likely enhanced by valley floor material that liquefied from undrained loading by the overriding avalanche. Although the base was likely at least partially liquefied, our mapping indicates that the overriding avalanche internally deformed predominantly by sliding along discrete shear surfaces in material that was nearly dry and had substantial frictional strength. These results indicate that the West Salt Creek avalanche, and probably other long-traveled avalanches, could be modeled as two layers: a liquefied basal layer; and a thicker and stronger overriding layer.

  12. Avalanche Debris Detection Using Satellite- and Drone Based Radar and Optical Remote Sensing

    Science.gov (United States)

    Eckerstorfer, M.; Malnes, E.; Vickers, H.; Solbø, S. A.; Tøllefsen, A.

    2014-12-01

    The mountainous fjord landscape in the county of Troms, around its capital Tromsø in Northern Norway is prone to high avalanche activity during the snow season. Large avalanches pose a hazard to infrastructure, such as buildings and roads, located between the steep mountainsides and the fjords. A prolonged cold spell during January and February 2014 was followed by rapid new-snow loading during March 2014, inducing a significant avalanche cycle with many spontaneous, size D4 avalanches that affected major transport veins. During and shortly after the avalanche cycle of March 2014, we obtained 11 Radarsat-2 Ultrafine mode scenes, chosen according to reported avalanche activity. We further collected four Radarsat-2 ScanSAR mode scenes and two Landsat-8 scenes covering the entire county of Troms. For one particular avalanche, we obtained a drone-based orthophoto, from which a DEM of the avalanche debris surface was derived, using structure-from-motion photogrammetry. This enabled us to calculate the debris volume accurately. We detected avalanche debris in the radar images visually, by applying two detection algorithms that make use of the increased backscatter in avalanche debris. This backscatter increase is a product of increased snow water equivalent and surface roughness, roughly of the order of 3 dB. In addition, we applied a multi-temporal approach by repeatedly detecting avalanche debris at different acquisition times, as well as a multi-sensor approach, covering similar areas with different sensors. This multi-temporal and multi-sensor approach enabled us to map the spatial extent and magnitude of the March 2014 avalanche cycle in the county Troms. With ESA's Sentinel-1 satellite, providing high-resolution, large swath radar images with a short repeat cycle, a complete avalanche record for a forecasting region could become feasible. In this first test season, we detected more than 550 avalanches that were released during a one-month period over an area of

  13. Automated identification of potential snow avalanche release areas based on digital elevation models

    Directory of Open Access Journals (Sweden)

    Y. Bühler

    2013-05-01

    Full Text Available The identification of snow avalanche release areas is a very difficult task. The release mechanism of snow avalanches depends on many different terrain, meteorological, snowpack and triggering parameters and their interactions, which are very difficult to assess. In many alpine regions such as the Indian Himalaya, nearly no information on avalanche release areas exists mainly due to the very rough and poorly accessible terrain, the vast size of the region and the lack of avalanche records. However avalanche release information is urgently required for numerical simulation of avalanche events to plan mitigation measures, for hazard mapping and to secure important roads. The Rohtang tunnel access road near Manali, Himachal Pradesh, India, is such an example. By far the most reliable way to identify avalanche release areas is using historic avalanche records and field investigations accomplished by avalanche experts in the formation zones. But both methods are not feasible for this area due to the rough terrain, its vast extent and lack of time. Therefore, we develop an operational, easy-to-use automated potential release area (PRA detection tool in Python/ArcGIS which uses high spatial resolution digital elevation models (DEMs and forest cover information derived from airborne remote sensing instruments as input. Such instruments can acquire spatially continuous data even over inaccessible terrain and cover large areas. We validate our tool using a database of historic avalanches acquired over 56 yr in the neighborhood of Davos, Switzerland, and apply this method for the avalanche tracks along the Rohtang tunnel access road. This tool, used by avalanche experts, delivers valuable input to identify focus areas for more-detailed investigations on avalanche release areas in remote regions such as the Indian Himalaya and is a precondition for large-scale avalanche hazard mapping.

  14. Enhancing Safety through Generic Competencies

    Directory of Open Access Journals (Sweden)

    S. Mockel

    2014-03-01

    Full Text Available This article provides insights into proactive safety management and mitigation. An analysis of accident reports reveals categories of supervening causes of accidents which can be directly linked to the concept of generic competencies (information management, communication and coordination, problem solving, and effect control. These findings strongly suggest adding the human element as another safety-constituting pillar to the concept of ship safety next to technology and regulation. We argue that the human element has unique abilities in dealing with critical and highly dynamic situations which can contribute to the system's recovery from non-routine or critical situations. By educating seafarers in generic competencies we claim to enable the people onboard to successfully deal with critical situations.

  15. Efficient Generation of Generic Entanglement

    CERN Document Server

    Oliveira, R; Plenio, M B

    2006-01-01

    We find that generic entanglement is physical, in the sense that it can be generated in polynomial time from two-qubit gates picked at random. We prove as the main result that such a process generates the average entanglement of the uniform (Haar) measure in at most $O(N^3)$ steps for $N$ qubits. This is despite an exponentially growing number of such gates being necessary for generating that measure fully on the state space. Numerics furthermore show a variation cut-off allowing one to associate a specific time with the achievement of the uniform measure entanglement distribution. Various extensions of this work are discussed. The results are relevant to entanglement theory and to protocols that assume generic entanglement can be achieved efficiently.

  16. A multi path, weather independent avalanche monitoring tool using distributed acoustic fiber optic sensing

    Science.gov (United States)

    Prokop, Alexander; Wirbel, Anna

    2013-04-01

    Information on avalanche activity is a paramount parameter in avalanche forecasting. When avalanches are released spontaneously, the risk of avalanches is very high. Triggering avalanches by artificial means, such as explosives launched from helicopter or avalanche towers, can also give information on the stability of the snow pack. Hence, monitoring of avalanches released naturally or artificially, is an important quantity in avalanche forecasting. This information is also needed when deciding whether to close or not endangered ski runs, roads or railway lines. So far monitoring systems lack certain benefits. Either they monitor only large avalanches, can only be used for single avalanche tracks or are weather/sight dependant. Therefore a new tool for avalanche- monitoring, a distributed fiber optic system, is for the first time installed and adapted for the purpose of monitoring snow avalanche activity. The method is based on an optical time domain reflectometer (OTDR) system, which dates back to the 1970`s and detects seismic vibrations and acoustic signals on a fiber optic cable that can have a length of up to 30 km. An appropriate test slope for this configuration has been found in the ski area of "Lech am Arlberg". In this work a detailed description of the theoretical background, the system implementation, the field installation, realization of tests and an investigation of the recorded data is presented. We conducted 100 tests and triggered 41 avalanches so far with a runout distances ranging from a few meters to approximately 250 meters, all of which were detected by the system, as well as the 59 not successful attempts of artificial triggering. Moreover we measured properly if critical infrastructure (in our case a ski run) was reached by the avalanches or not. The spatial distributed sensing approach allowed us to relate the amplitude and spectral content of the signals to avalanche size, avalanche speed and snow properties of the avalanches. In

  17. Self-Organized Criticality in a Simple Neuron Model Based on Scale-Free Networks

    Institute of Scientific and Technical Information of China (English)

    LIN Min; WANG Gang; CHEN Tian-Lun

    2006-01-01

    A simple model for a set of interacting idealized neurons in scale-free networks is introduced. The basic elements of the model are endowed with the main features of a neuron function. We find that our model displays powerlaw behavior of avalanche sizes and generates long-range temporal correlation. More importantly, we find different dynamical behavior for nodes with different connectivity in the scale-free networks.

  18. Complex Behavior in a Selective Aging Neuron Model Based on Small World Networks

    Institute of Scientific and Technical Information of China (English)

    LUO Min-Jie; ZHANG Gui-Qing; LIU Qiu-Yu; CHEN Tian-Lun

    2008-01-01

    Complex behavior in a selective aging simple neuron model based on small world networks is investigated. The basic elements of the model are endowed with the main features of a neuron function. The structure of the selective aging neuron model is discussed. We also give some properties of the new network and find that the neuron model displays a power-law behavior. If the brain network is small world-like network, the mean avalanche size is almost the same unless the aging parameter is big enough.

  19. Maximum speeds and alpha angles of flowing avalanches

    Science.gov (United States)

    McClung, David; Gauer, Peter

    2016-04-01

    A flowing avalanche is one which initiates as a slab and, if consisting of dry snow, will be enveloped in a turbulent snow dust cloud once the speed reaches about 10 m/s. A flowing avalanche has a dense core of flowing material which dominates the dynamics by serving as the driving force for downslope motion. The flow thickness typically on the order of 1 -10 m which is on the order of about 1% of the length of the flowing mass. We have collected estimates of maximum frontal speed um (m/s) from 118 avalanche events. The analysis is given here with the aim of using the maximum speed scaled with some measure of the terrain scale over which the avalanches ran. We have chosen two measures for scaling, from McClung (1990), McClung and Schaerer (2006) and Gauer (2012). The two measures are the √H0-;√S0-- (total vertical drop; total path length traversed). Our data consist of 118 avalanches with H0 (m)estimated and 106 with S0 (m)estimated. Of these, we have 29 values with H0 (m),S0 (m)and um (m/s)estimated accurately with the avalanche speeds measured all or nearly all along the path. The remainder of the data set includes approximate estimates of um (m/s)from timing the avalanche motion over a known section of the path where approximate maximum speed is expected and with either H0or S0or both estimated. Our analysis consists of fitting the values of um/√H0--; um/√S0- to probability density functions (pdf) to estimate the exceedance probability for the scaled ratios. In general, we found the best fits for the larger data sets to fit a beta pdf and for the subset of 29, we found a shifted log-logistic (s l-l) pdf was best. Our determinations were as a result of fitting the values to 60 different pdfs considering five goodness-of-fit criteria: three goodness-of-fit statistics :K-S (Kolmogorov-Smirnov); A-D (Anderson-Darling) and C-S (Chi-squared) plus probability plots (P-P) and quantile plots (Q-Q). For less than 10% probability of exceedance the results show that

  20. Generic drugs in dermatology: part II.

    Science.gov (United States)

    Payette, Michael; Grant-Kels, Jane M

    2012-03-01

    In part I, we discussed new drug development, reviewed the history of the generic drug industry, described how generic drugs are approved by the US Food and Drug Administration, and defined the concepts of bioequivalence and therapeutic equivalence. Herein, we explore various factors impacting generic drug use across the different parties involved: the prescriber, the pharmacist, the patient, and the payer. We also include original cost analysis of dermatologic brand name and generic drugs and show the potential cost savings that can be achieved through generic substitution. We conclude with a review of the data addressing potential differences in the effectiveness of brand name versus generic drugs in dermatology. The cost of brand name and generic medications is highly variable by pharmacy, state, and payer. We used one source (www.drugstore.com) as an example and for consistency across all medications discussed herein. Prices included here may not reflect actual retail prices across the United States.

  1. Generic Graph Grammar: A Simple Grammar for Generic Procedural Modelling

    DEFF Research Database (Denmark)

    Christiansen, Asger Nyman; Bærentzen, Jakob Andreas

    2012-01-01

    in a directed cyclic graph. Furthermore, the basic productions are chosen such that Generic Graph Grammar seamlessly combines the capabilities of L-systems to imitate biological growth (to model trees, animals, etc.) and those of split grammars to design structured objects (chairs, houses, etc.). This results......Methods for procedural modelling tend to be designed either for organic objects, which are described well by skeletal structures, or for man-made objects, which are described well by surface primitives. Procedural methods, which allow for modelling of both kinds of objects, are few and usually...

  2. Structural vulnerability assessment using reliability of slabs in avalanche area

    Science.gov (United States)

    Favier, Philomène; Bertrand, David; Eckert, Nicolas; Naaim, Mohamed

    2013-04-01

    Improvement of risk assessment or hazard zoning requires a better understanding of the physical vulnerability of structures. To consider natural hazard issue such as snow avalanches, once the flow is characterized, highlight on the mechanical behaviour of the structure is a decisive step. A challenging approach is to quantify the physical vulnerability of impacted structures according to various avalanche loadings. The main objective of this presentation is to introduce methodology and outcomes regarding the assessment of vulnerability of reinforced concrete buildings using reliability methods. Reinforced concrete has been chosen as it is one of the usual material used to build structures exposed to potential avalanche loadings. In avalanche blue zones, structures have to resist to a pressure up to 30kPa. Thus, by providing systematic fragility relations linked to the global failure of the structure, this method may serve the avalanche risk assessment. To do so, a slab was numerically designed. It represented the avalanche facing wall of a house. Different configuration cases of the element in stake have been treated to quantify numerical aspects of the problem, such as the boundary conditions or the mechanical behaviour of the structure. The structure is analysed according to four different limit states, semi-local and global failures are considered to describe the slab behaviour. The first state is attained when cracks appear in the tensile zone, then the two next states are described consistent with the Eurocode, the final state is the total collapse of the structure characterized by the yield line theory. Failure probability is estimated in accordance to the reliability framework. Monte Carlo simulations were conducted to quantify the fragility to different loadings. Sensitivity of models in terms of input distributions were defined with statistical tools such as confidence intervals and Sobol's indexes. Conclusion and discussion of this work are established to

  3. Hummocks: how they form and evolve in debris avalanches (Invited)

    Science.gov (United States)

    Paguican, E. R.; van Wyk de Vries, B.; Lagmay, A.

    2013-12-01

    Hummocks are topographic features of large landslides and rockslide-debris avalanches common in volcanic settings. We use scaled analog models to study hummock formation and explore their importance in understanding landslide kinematics and dynamics. The models are designed to replicate large-scale volcanic collapses but are relevant also to non-volcanic settings. We characterize hummocks in terms of their evolution, spatial distribution, and internal structure from slide initiation to final arrest. Hummocks initially form by extensional faulting as a landslide begins to move. During motion, individual large blocks develop and spread, creating an initial distribution, with small hummocks at the landslide front and larger ones at the back. As the mass spreads, hummocks remain as discrete entities. They can get wider but may decrease in height, break up, or merge to form bigger and long anticlinal hummocks when confined. In areas of transverse movement within a landslide, elongate hummocks develop between strike-slip flower structures. Absence of hummocks and fault-like features in the deposit may imply a more fluidal flow of emplacement or very low cohesion of lithologies. Hummock size depends on their position in the initial mass, modified by subsequent breakup or coalescence. Hummock size, shape and spatial distribution vary between and within deposits. Such a universal structure with clear connection to the deformation process should provide a framework with which to study avalanche emplacement dynamics and conditions. We study well-preserved and well-sectioned hummocks in the Mt Iriga rockslide-debris avalanches (Philippines), to characterise the internal structure and relate hummocks to the landslide-avalanche behaviour. All the model structures are consistent with field observations and suggest a general brittle-slide emplacement for most landslide avalanches. The upper and outer hummock surface is destabilised by minor slumps and scree formation forming a

  4. A new web-based system to improve the monitoring of snow avalanche hazard in France

    Science.gov (United States)

    Bourova, Ekaterina; Maldonado, Eric; Leroy, Jean-Baptiste; Alouani, Rachid; Eckert, Nicolas; Bonnefoy-Demongeot, Mylene; Deschatres, Michael

    2016-05-01

    Snow avalanche data in the French Alps and Pyrenees have been recorded for more than 100 years in several databases. The increasing amount of observed data required a more integrative and automated service. Here we report the comprehensive web-based Snow Avalanche Information System newly developed to this end for three important data sets: an avalanche chronicle (Enquête Permanente sur les Avalanches, EPA), an avalanche map (Carte de Localisation des Phénomènes d'Avalanche, CLPA) and a compilation of hazard and vulnerability data recorded on selected paths endangering human settlements (Sites Habités Sensibles aux Avalanches, SSA). These data sets are now integrated into a common database, enabling full interoperability between all different types of snow avalanche records: digitized geographic data, avalanche descriptive parameters, eyewitness reports, photographs, hazard and risk levels, etc. The new information system is implemented through modular components using Java-based web technologies with Spring and Hibernate frameworks. It automates the manual data entry and improves the process of information collection and sharing, enhancing user experience and data quality, and offering new outlooks to explore and exploit the huge amount of snow avalanche data available for fundamental research and more applied risk assessment.

  5. A method for automated snow avalanche debris detection through use of synthetic aperture radar (SAR) imaging

    Science.gov (United States)

    Vickers, H.; Eckerstorfer, M.; Malnes, E.; Larsen, Y.; Hindberg, H.

    2016-11-01

    Avalanches are a natural hazard that occur in mountainous regions of Troms County in northern Norway during winter and can cause loss of human life and damage to infrastructure. Knowledge of when and where they occur especially in remote, high mountain areas is often lacking due to difficult access. However, complete, spatiotemporal avalanche activity data sets are important for accurate avalanche forecasting, as well as for deeper understanding of the link between avalanche occurrences and the triggering snowpack and meteorological factors. It is therefore desirable to develop a technique that enables active mapping and monitoring of avalanches over an entire winter. Avalanche debris can be observed remotely over large spatial areas, under all weather and light conditions by synthetic aperture radar (SAR) satellites. The recently launched Sentinel-1A satellite acquires SAR images covering the entire Troms County with frequent updates. By focusing on a case study from New Year 2015 we use Sentinel-1A images to develop an automated avalanche debris detection algorithm that utilizes change detection and unsupervised object classification methods. We compare our results with manually identified avalanche debris and field-based images to quantify the algorithm accuracy. Our results indicate that a correct detection rate of over 60% can be achieved, which is sensitive to several algorithm parameters that may need revising. With further development and refinement of the algorithm, we believe that this method could play an effective role in future operational monitoring of avalanches within Troms and has potential application in avalanche forecasting areas worldwide.

  6. Rescue missions for totally buried avalanche victims: conclusions from 12 years of experience.

    Science.gov (United States)

    Hohlrieder, Matthias; Thaler, Stephanie; Wuertl, Walter; Voelckel, Wolfgang; Ulmer, Hanno; Brugger, Hermann; Mair, Peter

    2008-01-01

    The planning and execution of avalanche rescue missions to search for totally buried avalanche victims are mostly based on personal experience and preference, as evidence-based information from literature is almost completely missing. Hence, the aim of this study was to identify major factors determining the survival probability of totally buried victims during avalanche rescue missions carried out by organized rescue teams (Austrian Mountain Rescue Service, Tyrol). During the 12-year period studied, 109 totally buried persons (56 off-piste, 53 backcountry), were rescued or recovered; 18.3% survived to hospital discharge. Median depth of burial was 1.25 m; median duration of burial was 85 min. The majority (61.6%) of the rescue missions were conducted under considerably dangerous avalanche conditions. The probability of survival was highest when located visually and lowest for those located by avalanche transceiver; survival did not significantly differ between those found by rescue dogs and those located with avalanche probes. Multivariate analysis revealed short duration of burial and off-piste terrain to be the two independent predictors of survival. Whenever companion rescue fails, snow burial in an avalanche is associated with extraordinarily high mortality. Searching the avalanche debris with probe lines seems to be equally effective as compared to searching with rescue dogs. The potential hazard for rescuers during avalanche rescue missions comes mainly from self-triggered avalanches, hence thorough mission planning and critical risk-benefit assessment are of utmost importance for risk reduction.

  7. Direct observation of avalanche scintillations in a THGEM-based two-phase Ar avalanche detector using Geiger-mode APD

    CERN Document Server

    Bondar, A; Grebenuk, A; Sokolov, A; Akimov, D; Alexandrov, I; Breskin, A

    2010-01-01

    A novel concept of optical signal recording in two-phase avalanche detectors, with Geiger-mode Avalanche Photodiodes (G-APD) is described. Avalanche-scintillation photons were measured in a thick Gas Electron Multiplier (THGEM) in view of potential applications in rare-event experiments. The effective detection of avalanche scintillations in THGEM holes has been demonstrated in two-phase Ar with a bare G-APD without wavelength shifter, i.e. insensitive to VUV emission of Ar. At gas-avalanche gain of 400 and under \\pm 70^\\circ viewing-angle, the G-APD yielded 640 photoelectrons (pe) per 60 keV X-ray converted in liquid Ar; this corresponds to 0.7 pe per initial (prior to multiplication) electron. The avalanche-scintillation light yield measured by the G-APD was about 0.7 pe per avalanche electron, extrapolated to 4pi acceptance. The avalanche scintillations observed occurred presumably in the near infrared (NIR) where G-APDs may have high sensitivity. The measured scintillation yield is similar to that observe...

  8. Arrest of Avalanche Propagation by Discontinuities on Snow Cover

    Science.gov (United States)

    Frigo, B.; Chiaia, B.

    2009-04-01

    Considering the spatial variability of the snow cover, the paper analyses, in the framework of Fracture Mechanics, the Mode II fracture propagation on snow cover that leads to large dry slab avalanches. Under the hypothesis of a perfectly brittle phenomenon, avalanche triggering is usually investigated numerically by means of Linear Elastic Fracture Mechanics (McClung, 1979; Chiaia et al., 2008). Since, however, the real phenomenon is intrinsically dynamical, another aspect to investigate is represented by dynamic fracture propagation. In this paper, we model dynamic crack propagation into a dry snow slab, to assess the possibility of crack arrest due to the presence of weak zones distributed along the snow slope. As a consequence of the first triggering mechanism (the Mode II fracture propagation on the weak plane), the secondary Mode I crack propagation in the crown is studied by means of numerical simulations based on Dynamic Elastic Fracture Mechanics and on the theory of crack arresters. By taking into account kinetic energy and using the FEM software FRANC 2D (Wawrzynek and Ingraffea, 1993), several paths of crown fracture propagation and their stability have been investigated. The snowpack is considered as a linear-elastic plate (2D problem), whose physical and mechanical parameters are chosen according to classical literature values. To investigate the possible arrest of crown fracture, we apply the theory of crack arresters, usually adopted for pipelines and perforated steel sheets fracture problems. To study crack arrest, different crack paths are simulated, in discontinuous (equipped with different shapes and geometries of artificial voids) snowpacks. The simulations show the effectiveness of these weak zones, to reduce substantially the crack driving force of the propagating fracture. This means that, increasing spatial variability tends to stabilize the snow slope, eventually splitting a major avalanche event into smaller, independent avalanches. Our

  9. Generic Crystalline Disposal Reference Case

    Energy Technology Data Exchange (ETDEWEB)

    Painter, Scott Leroy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, Shaoping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harp, Dylan Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Perry, Frank Vinton [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wang, Yifeng [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-02-20

    A generic reference case for disposal of spent nuclear fuel and high-level radioactive waste in crystalline rock is outlined. The generic cases are intended to support development of disposal system modeling capability by establishing relevant baseline conditions and parameters. Establishment of a generic reference case requires that the emplacement concept, waste inventory, waste form, waste package, backfill/buffer properties, EBS failure scenarios, host rock properties, and biosphere be specified. The focus in this report is on those elements that are unique to crystalline disposal, especially the geosphere representation. Three emplacement concepts are suggested for further analyses: a waste packages containing 4 PWR assemblies emplaced in boreholes in the floors of tunnels (KBS-3 concept), a 12-assembly waste package emplaced in tunnels, and a 32-assembly dual purpose canister emplaced in tunnels. In addition, three failure scenarios were suggested for future use: a nominal scenario involving corrosion of the waste package in the tunnel emplacement concepts, a manufacturing defect scenario applicable to the KBS-3 concept, and a disruptive glaciation scenario applicable to both emplacement concepts. The computational approaches required to analyze EBS failure and transport processes in a crystalline rock repository are similar to those of argillite/shale, with the most significant difference being that the EBS in a crystalline rock repository will likely experience highly heterogeneous flow rates, which should be represented in the model. The computational approaches required to analyze radionuclide transport in the natural system are very different because of the highly channelized nature of fracture flow. Computational workflows tailored to crystalline rock based on discrete transport pathways extracted from discrete fracture network models are recommended.

  10. Spontaneous avalanche ionization of a strongly blockaded Rydberg gas

    CERN Document Server

    Robert-de-Saint-Vincent, M; Schempp, H; Günter, G; Whitlock, S; Weidemüller, M

    2012-01-01

    We report the sudden and spontaneous evolution of an initially correlated gas of repulsively interacting Rydberg atoms to an ultracold plasma. Under continuous laser coupling we create a Rydberg ensemble in the strong blockade regime, which at longer times undergoes an ionization avalanche. By combining optical imaging and ion detection, we access the full information on the dynamical evolution of the system, including the rapid increase in the number of ions and a sudden depletion of the Rydberg and ground state densities. Rydberg-Rydberg interactions are observed to strongly affect the dynamics of plasma formation. Using a coupled rate-equation model to describe our data, we extract the average energy of electrons trapped in the plasma, and an effective cross-section for ionizing collisions between Rydberg atoms and atoms in low-lying states. Our results suggest that the initial correlations of the Rydberg ensemble should persist through the avalanche. This would provide the means to overcome disorder-induc...

  11. Avalanche effect and gain saturation in high harmonic generation

    CERN Document Server

    Serrat, Carles; Budesca, Josep M; Seres, Jozsef; Seres, Enikoe; Aurand, Bastian; Hoffmann, Andreas; Namba, Shinichi; Kuehl, Thomas; Spielmann, Christian

    2015-01-01

    Optical amplifiers in all ranges of the electromagnetic spectrum exhibit two essential characteristics: i) the input signal during the propagation in the medium is multiplied by the avalanche effect of the stimulated emission to produce exponential growth and ii) the amplification saturates at increasing input signal. We demonstrate that the strong-field theory in the frame of high harmonic generation fully supports the appearance of both the avalanche and saturation effects in the amplification of extreme ultraviolet attosecond pulse trains. We confirm that the amplification takes place only if the seed pulses are perfectly synchronized with the driving strong field in the amplifier. We performed an experimental study and subsequent model calculation on He gas driven by intense 30-fs-long laser pulses, which was seeded with an attosecond pulse train at 110 eV generated in a separated Ne gas jet. The comparison of the performed calculations with the measurements clearly demonstrates that the pumped He gas med...

  12. Stability of the discretization of the electron avalanche phenomenon

    Energy Technology Data Exchange (ETDEWEB)

    Villa, Andrea, E-mail: andrea.villa@rse-web.it [Ricerca Sul Sistema Energetico (RSE), Via Rubattino 50, 20134, Milano (Italy); Barbieri, Luca, E-mail: luca.barbieri@rse-web.it [Ricerca Sul Sistema Energetico (RSE), Via Rubattino 50, 20134, Milano (Italy); Gondola, Marco, E-mail: marco.gondola@rse-web.it [Ricerca Sul Sistema Energetico (RSE), Via Rubattino 50, 20134, Milano (Italy); Leon-Garzon, Andres R., E-mail: andresricardo.leon@polimi.it [CMIC Department “Giulio Natta”, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano (Italy); Malgesini, Roberto, E-mail: roberto.malgesini@rse-web.it [Ricerca Sul Sistema Energetico (RSE), Via Rubattino 50, 20134, Milano (Italy)

    2015-09-01

    The numerical simulation of the discharge inception is an active field of applied physics with many industrial applications. In this work we focus on the drift-reaction equation that describes the electron avalanche. This phenomenon is one of the basic building blocks of the streamer model. The main difficulty of the electron avalanche equation lies in the fact that the reaction term is positive when a high electric field is applied. It leads to exponentially growing solutions and this has a major impact on the behavior of numerical schemes. We analyze the stability of a reference finite volume scheme applied to this latter problem. The stability of the method may impose a strict mesh spacing, therefore a proper stabilized scheme, which is stable whatever spacing is used, has been developed. The convergence of the scheme is treated as well as some numerical experiments.

  13. Magnetic avalanches in granular ferromagnets: thermal activated collective behavior

    Science.gov (United States)

    Chern, Gia-Wei

    2017-02-01

    We present a numerical study on the thermal activated avalanche dynamics in granular materials composed of ferromagnetic clusters embedded in a non-magnetic matrix. A microscopic dynamical simulation based on the reaction-diffusion process is developed to model the magnetization process of such systems. The large-scale simulations presented here explicitly demonstrate inter-granular collective behavior induced by thermal activation of spin tunneling. In particular, we observe an intriguing criticality controlled by the rate of energy dissipation. We show that thermal activated avalanches can be understood in the framework of continuum percolation and the emergent dissipation induced criticality is in the universality class of 3D percolation transition. Implications of these results to the phase-separated states of colossal magnetoresistance materials and other artificial granular magnetic systems are also discussed.

  14. Photon avalanche up-conversion in holmium doped fluoride glasses

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y.H.; Liu, G.K.; Beitz, J.V. [Argonne National Lab., IL (United States). Chemistry Division; Jie Wang [Shanghai Institute of Optics and Fine Mechanics, Shanghai (China)

    1996-08-01

    Photon avalanche green up-conversion emission centered at 545 nm has been observed in Ho{sup 3+} doped and Ho{sup 3+}, Tm{sup 3+} co-doped ZrF{sub 4}-based fluoride glasses when excited near 585 nm which is off resonance with any ground state absorption bands of either Ho{sup 3+} or Tm{sup 3+} ions. Detailed spectral measurements and analysis suggest that the 545 nm emission occurs from the {sup 5}S{sub 2},{sup 5}F{sub 4} states of Ho{sup 3+} that are populated by excited state absorption from the {sup 5}I{sub 7} state of Ho{sup 3+}. Strong cross-relaxation that efficiently populates the {sup 5}I{sub 7} state makes the photon avalanche process possible in this system.

  15. Robust Quantum Random Number Generator Based on Avalanche Photodiodes

    Science.gov (United States)

    Wang, Fang-Xiang; Wang, Chao; Chen, Wei; Wang, Shuang; Lv, Fu-Sheng; He, De-Yong; Yin, Zhen-Qiang; Li, Hong-Wei; Guo, Guang-Can; Han, Zheng-Fu

    2015-08-01

    We propose and demonstrate a scheme to realize a high-efficiency truly quantum random number generator (RNG) at room temperature (RT). Using an effective extractor with simple time bin encoding method, the avalanche pulses of avalanche photodiode (APD) are converted into high-quality random numbers (RNs) that are robust to slow varying noise such as fluctuations of pulse intensity and temperature. A light source is compatible but not necessary in this scheme. Therefor the robustness of the system is effective enhanced. The random bits generation rate of this proof-of-principle system is 0.69 Mbps with double APDs and 0.34 Mbps with single APD. The results indicate that a high-speed RNG chip based on the scheme is potentially available with an integrable APD array.

  16. Generic behaviours in impact fragmentation

    Energy Technology Data Exchange (ETDEWEB)

    Sator, N.; Mechkov, S.; Sausset, F. [Paris-6 Univ. Pierre et Marie Curie, Lab. de Physique Theorique de la Matiere Condensee, UMR CNRS 7600, 75 - Paris (France); Mechkov, S. [Ecole Normale Superieure, Lab. de Physique Statistique, 75 - Paris (France)

    2008-02-15

    From atomic nuclei to supernovae, including plates and rocks, every cohesive system can be broken into fragments, provided that the deposited energy is sufficiently large compared to its cohesive energy. We present a simple numerical model for investigating the general properties of fragmentation. By use of molecular dynamics simulations, we study the impact fragmentation of a solid disk of interacting particles with a wall. Regardless of the particular form of the interaction potential, the fragment size distribution exhibits a power law behaviour with an exponent that increases logarithmically with the energy deposited in the system, in agreement with experiments. We expect this behaviour to be generic in fragmentation phenomena. (authors)

  17. Generic maximum likely scale selection

    DEFF Research Database (Denmark)

    Pedersen, Kim Steenstrup; Loog, Marco; Markussen, Bo

    2007-01-01

    The fundamental problem of local scale selection is addressed by means of a novel principle, which is based on maximum likelihood estimation. The principle is generally applicable to a broad variety of image models and descriptors, and provides a generic scale estimation methodology. The focus...... on second order moments of multiple measurements outputs at a fixed location. These measurements, which reflect local image structure, consist in the cases considered here of Gaussian derivatives taken at several scales and/or having different derivative orders....

  18. Investigation of avalanche photodiodes radiation hardness for baryonic matter studies

    CERN Document Server

    Kushpil, V; Ladygin, V P; Kugler, A; Kushpil, S; Svoboda, O; Tlustý, P

    2015-01-01

    Modern avalanche photodiodes (APDs) with high gain are good device candidates for light readout from detectors applied in relativistic heavy ion collisions experiments. The results of the investigations of the APDs properties from Zecotek, Ketek and Hamamatsu manufacturers after irradiation using secondary neutrons from cyclotron facility U120M at NPI of ASCR in \\v{R}e\\v{z} are presented. The results of the investigations can be used for the design of the detectors for the experiments at NICA and FAIR.

  19. Simulation of a flowing snow avalanche using molecular dynamics

    OpenAIRE

    2010-01-01

    Ankara : The Department of Computer Engineering and the Institute of Engineering and Science of Bilkent University, 2010. Thesis (Master's) -- Bilkent University, 2010. Includes bibliographical references leaves 45-50. This thesis presents an approach for modeling and simulation of a flowing snow avalanche, which is formed of dry and liquefied snow that slides down a slope, by using molecular dynamics and discrete element method. A particle system is utilized as a base method for th...

  20. A micropixel avalanche phototransistor for time of flight measurements

    Science.gov (United States)

    Sadigov, A.; Suleymanov, S.; Ahmadov, F.; Ahmadov, G.; Abdullayev, K.; Akberov, R.; Heydarov, N.; Madatov, R.; Mukhtarov, R.; Nazarov, M.; Valiyev, R.

    2017-02-01

    This paper presents results of studies of the silicon based new micropixel avalanche phototransistor (MAPT). MAPT is a modification of well-known silicon photomultipliers (SiPMs) and differs since each photosensitive pixel of the MAPT operates in Geiger mode and comprises an individual micro-transistor operating in binary mode. This provides a high amplitude single photoelectron signal with significantly shorter rise time. The obtained results are compared with appropriate parameters of known SiPMs.

  1. Sixteen-year follow-up of childhood avalanche survivors

    Science.gov (United States)

    Thordardottir, Edda Bjork; Valdimarsdottir, Unnur Anna; Hansdottir, Ingunn; Hauksdóttir, Arna; Dyregrov, Atle; Shipherd, Jillian C.; Elklit, Ask; Resnick, Heidi; Gudmundsdottir, Berglind

    2016-01-01

    Background Every year a substantial number of children are affected by natural disasters worldwide. However, data are scarce on long-term psychological impact of natural disasters on children's health. Identifying risk factors and outcomes associated with the long-term sequelae of posttraumatic stress disorder (PTSD) can provide a gateway to recovery as well as enhancement of preventive measures. Objective Among childhood avalanche survivors, we aimed to investigate risk factors for PTSD symptoms and the relationship between socioeconomic status (SES) and PTSD symptoms in adulthood. Methods Childhood survivors (aged 2–19 at the time of exposure) of two avalanches were identified through nationwide registers 16 years later. The Posttraumatic Diagnostic Scale was used to assess current PTSD symptoms. One-way ANOVA was used to explore PTSD symptoms by background and trauma-specific factors, as well as associations with current SES. Predictors of PTSD symptoms were examined by multivariable regression analysis. Results Response rate was 66% (108/163). Results from univariate ANOVA analysis revealed that female sex was associated with PTSD symptoms (F=5.96, punemployment and/or disability (F=3.04, p<0.05). In a multivariable regression model, when adjusting for age and sex, lack of social support (t=4.22, p<0.001) and traumatic reactions of caregivers (t=2.49, p<0.05) in the aftermath of the disaster independently predicted PTSD 16 years post-trauma. Conclusions Lingering PTSD symptoms after childhood exposure to a disaster may negatively influence socioeconomic development in adulthood. Strengthening children's support systems post-disaster may prevent the long-term sequelae of symptoms. Highlights of the article PTSD symptoms following avalanche exposure during childhood were associated with poorer socioeconomic status in adulthood. Lack of social support and traumatic reactions of caregivers in the aftermath of avalanches predicted PTSD symptoms among childhood

  2. Photon detection efficiency of Geiger-mode avalanche photodiodes

    OpenAIRE

    Gentile, Simonetta; Kuznetsova, Ekaterina; Meddi, Franco

    2010-01-01

    The photon detection efficiencies of multi-pixel Geiger-mode avalanche photodiodes manufactured by different produ cers are estimated. A new fit method of the response spectra to low-intensity light, taking into ac count after-pulse and cross-talk effects is proposed to yield the initial number of photons. The value of photon detection efficiency is calculated using a calibrated photodetector as a reference.

  3. Automated characterization of single-photon avalanche photodiode

    CERN Document Server

    Ghazali, Aina M M; Sauge, Sebastien; Makarov, Vadim

    2012-01-01

    We report an automated characterization of a single-photon detector based on commercial silicon avalanche photodiode (PerkinElmer C30902SH). The photodiode is characterized by I-V curves at different illumination levels (darkness, 10 pW and 10 uW), dark count rate and photon detection efficiency at different bias voltages. The automated characterization routine is implemented in C++ running on a Linux computer.

  4. Receiver characteristics of laser altimeters with avalanche photodiodes

    Science.gov (United States)

    Sun, Xiaoli; Davidson, Frederic M.; Boutsikaris, Leo; Abshire, James B.

    1992-01-01

    The receiver characteristics of a laser altimeter system containing an avalanche photodiode photodetector are analyzed using the Gaussian approximation, the saddle-point approximation, and a nearly exact analysis. The last two methods are shown to yield very similar results except when the background noise is extremely low and the probability of false alarm is high. However, the Gaussian approximation method is shown to cause significant errors even under relatively high levels of background noise and received signal energy.

  5. Gullies and avalanche scars on Martian dark dunes

    OpenAIRE

    Reiss, D.; Jaumann, Ralf; Kereszturi, A.,; Sik, A.; Neukum, G.

    2007-01-01

    Gullies on Mars occur on slopes of impact craters, pits, valleys and hills. However, in some cases gullies are cut into dark dune slopes. Other mass movement features on dark dune slopes are avalanche scars which occur on most dune fields beside the gully features. We classified the mass movement features based on their morphology and analyzed them with respect to their distribution, slope angle, orientation and seasonal climatic conditions to constrain the possible formation process causing ...

  6. Particle-size segregation in dense granular avalanches

    Science.gov (United States)

    Gray, John Mark Nicholas Timm; Gajjar, Parmesh; Kokelaar, Peter

    2015-01-01

    Particles of differing sizes are notoriously prone to segregate, which is a chronic problem in the manufacture of a wide variety of products that are used by billions of people worldwide every day. Segregation is the single most important factor in product non-uniformity, which can lead to significant handling problems as well as complete batches being discarded at huge financial loss. It is generally regarded that the most important mechanism for segregation is the combination of kinetic sieving and squeeze expulsion in shallow granular avalanches. These free-surface flows are more common than one might expect, often forming part of more complicated flows in drums, heaps and silos, where there is mass exchange with underlying regions of static or slowly moving grains. The combination of segregation and solid-fluid granular phase transitions creates incredibly complicated and beautiful patterns in the resulting deposits, but a full understanding of such effects lies beyond our capabilities at present. This paper reviews recent advances in our ability to model the basic segregation processes in a single avalanche (without mass exchange) and the subtle feedback effects that they can have on the bulk flow. This is particularly important for geophysical applications, where segregation can spontaneously self-channelize and lubricate the flow, significantly enhancing the run-out of debris-flows, pyroclastic flows, rock-falls and snow-slab avalanches.

  7. Meshfree simulation of avalanches with the Finite Pointset Method (FPM)

    Science.gov (United States)

    Michel, Isabel; Kuhnert, Jörg; Kolymbas, Dimitrios

    2017-04-01

    Meshfree methods are the numerical method of choice in case of applications which are characterized by strong deformations in conjunction with free surfaces or phase boundaries. In the past the meshfree Finite Pointset Method (FPM) developed by Fraunhofer ITWM (Kaiserslautern, Germany) has been successfully applied to problems in computational fluid dynamics such as water crossing of cars, water turbines, and hydraulic valves. Most recently the simulation of granular flows, e.g. soil interaction with cars (rollover), has also been tackled. This advancement is the basis for the simulation of avalanches. Due to the generalized finite difference formulation in FPM, the implementation of different material models is quite simple. We will demonstrate 3D simulations of avalanches based on the Drucker-Prager yield criterion as well as the nonlinear barodesy model. The barodesy model (Division of Geotechnical and Tunnel Engineering, University of Innsbruck, Austria) describes the mechanical behavior of soil by an evolution equation for the stress tensor. The key feature of successful and realistic simulations of avalanches - apart from the numerical approximation of the occurring differential operators - is the choice of the boundary conditions (slip, no-slip, friction) between the different phases of the flow as well as the geometry. We will discuss their influences for simplified one- and two-phase flow examples. This research is funded by the German Research Foundation (DFG) and the FWF Austrian Science Fund.

  8. Automated Characterization of Single-Photon Avalanche Photodiode

    Directory of Open Access Journals (Sweden)

    Aina Mardhiyah M. Ghazali

    2012-01-01

    Full Text Available We report an automated characterization of a single-photon detector based on commercial silicon avalanche photodiode (PerkinElmer C30902SH. The photodiode is characterized by I-V curves at different illumination levels (darkness, 10 pW and 10 µW, dark count rate and photon detection efficiency at different bias voltages. The automated characterization routine is implemented in C++ running on a Linux computer. ABSTRAK: Kami melaporkan pencirian pengesan foton tunggal secara automatik berdasarkan kepada diod foto runtuhan silikon (silicon avalanche photodiode (PerkinElmer C30902SH komersial. Pencirian  diod foto adalah berdasarkan kepada plot arus-voltan (I-V pada tahap pencahayaan yang berbeza (kelam - tanpa cahaya, 10pW, dan 10µW, kadar bacaan latar belakang, kecekapan pengesanan foton pada voltan picuan yang berbeza. Pengaturcaraan C++ digunakan di dalam rutin pencirian automatik melalui komputer dengan sistem pengendalian LINUX.KEYWORDS: avalanche photodiode (APD; single photon detector; photon counting; experiment automation

  9. AN MHD AVALANCHE IN A MULTI-THREADED CORONAL LOOP

    Energy Technology Data Exchange (ETDEWEB)

    Hood, A. W.; Cargill, P. J.; Tam, K. V. [School of Mathematics and Statistics, University of St Andrews, St Andrews, Fife, KY16 9SS (United Kingdom); Browning, P. K., E-mail: awh@st-andrews.ac.uk [School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom)

    2016-01-20

    For the first time, we demonstrate how an MHD avalanche might occur in a multithreaded coronal loop. Considering 23 non-potential magnetic threads within a loop, we use 3D MHD simulations to show that only one thread needs to be unstable in order to start an avalanche even when the others are below marginal stability. This has significant implications for coronal heating in that it provides for energy dissipation with a trigger mechanism. The instability of the unstable thread follows the evolution determined in many earlier investigations. However, once one stable thread is disrupted, it coalesces with a neighboring thread and this process disrupts other nearby threads. Coalescence with these disrupted threads then occurs leading to the disruption of yet more threads as the avalanche develops. Magnetic energy is released in discrete bursts as the surrounding stable threads are disrupted. The volume integrated heating, as a function of time, shows short spikes suggesting that the temporal form of the heating is more like that of nanoflares than of constant heating.

  10. Scale-free avalanches in the multifractal random walk

    CERN Document Server

    Bartolozzi, M

    2007-01-01

    Avalanches, or Avalanche-like, events are often observed in the dynamical behaviour of many complex systems which span from solar flaring to the Earth's crust dynamics and from traffic flows to financial markets. Self-organized criticality (SOC) is one of the most popular theories able to explain this intermittent charge/discharge behaviour. Despite a large amount of theoretical work, empirical tests for SOC are still in their infancy. In the present paper we address the common problem of revealing SOC from a simple time series without having much information about the underlying system. As a working example we use a modified version of the multifractal random walk originally proposed as a model for the stock market dynamics. The study reveals, despite the lack of the typical ingredients of SOC, an avalanche-like dynamics similar to that of many physical systems. While, on one hand, the results confirm the relevance of cascade models in representing turbulent-like phenomena, on the other, they also raise the ...

  11. Scale-free avalanches in the multifractal random walk

    Science.gov (United States)

    Bartolozzi, M.

    2007-06-01

    Avalanches, or Avalanche-like, events are often observed in the dynamical behaviour of many complex systems which span from solar flaring to the Earth's crust dynamics and from traffic flows to financial markets. Self-organized criticality (SOC) is one of the most popular theories able to explain this intermittent charge/discharge behaviour. Despite a large amount of theoretical work, empirical tests for SOC are still in their infancy. In the present paper we address the common problem of revealing SOC from a simple time series without having much information about the underlying system. As a working example we use a modified version of the multifractal random walk originally proposed as a model for the stock market dynamics. The study reveals, despite the lack of the typical ingredients of SOC, an avalanche-like dynamics similar to that of many physical systems. While, on one hand, the results confirm the relevance of cascade models in representing turbulent-like phenomena, on the other, they also raise the question about the current state of reliability of SOC inference from time series analysis.

  12. Avalanche photodiodes and quenching circuits for single-photon detection.

    Science.gov (United States)

    Cova, S; Ghioni, M; Lacaita, A; Samori, C; Zappa, F

    1996-04-20

    Avalanche photodiodes, which operate above the breakdown voltage in Geiger mode connected with avalanche-quenching circuits, can be used to detect single photons and are therefore called singlephoton avalanche diodes SPAD's. Circuit configurations suitable for this operation mode are critically analyzed and their relative merits in photon counting and timing applications are assessed. Simple passive-quenching circuits (PQC's), which are useful for SPAD device testing and selection, have fairly limited application. Suitably designed active-quenching circuits (AQC's) make it possible to exploit the best performance of SPAD's. Thick silicon SPAD's that operate at high voltages (250-450 V) have photon detection efficiency higher than 50% from 540- to 850-nm wavelength and still ~3% at 1064 nm. Thin silicon SPAD's that operate at low voltages (10-50 V) have 45% efficiency at 500 nm, declining to 10% at 830 nm and to as little as 0.1% at 1064 nm. The time resolution achieved in photon timing is 20 ps FWHM with thin SPAD's; it ranges from 350 to 150 ps FWHM with thick SPAD's. The achieved minimum counting dead time and maximum counting rate are 40 ns and 10 Mcps with thick silicon SPAD's, 10 ns and 40 Mcps with thin SPAD's. Germanium and III-V compound semiconductor SPAD's extend the range of photon-counting techniques in the near-infrared region to at least 1600-nm wavelength.

  13. A novel stream encryption scheme with avalanche effect

    Science.gov (United States)

    Min, Lequan; Chen, Guanrong

    2013-11-01

    This paper proposes a novel stream encryption scheme with avalanche effect (SESAE). Using this scheme and an ideal pseudorandom number generator (PRNG) to generate d-bit segment binary key streams, one can encrypt a plaintext such that by using any key stream generated from a different seed to decrypt the ciphertext, the decrypted plaintext will become an avalanche-like text which has 2 d - 1 consecutive one's with a high probability. As a cost, the required bits of the ciphertext are d times those of the plaintext. A corresponding avalanche-type encryption theorem is established. Two chaotic 12-bit segment PRNGs are designed. A generalized FIPS140 test and SESAE test for the two chaotic PRNGs, RC4 12-bit segment PRNG and 12-bit segment Matlab PRNG are implemented. The SESAE tests for 16-bit segment PRNGs are also compared. The results suggest that those PRNGs are able to generate the SESAEs which are similar to those generated via ideal PRNGs.

  14. Avalanche photodiodes and quenching circuits for single-photon detection

    Science.gov (United States)

    Cova, S.; Ghioni, M.; Lacaita, A.; Samori, C.; Zappa, F.

    1996-04-01

    Avalanche photodiodes, which operate above the breakdown voltage in Geiger mode connected with avalanche-quenching circuits, can be used to detect single photons and are therefore called single-photon avalanche diodes SPAD's. Circuit configurations suitable for this operation mode are critically analyzed and their relative merits in photon counting and timing applications are assessed. Simple passive-quenching circuits (PQC's), which are useful for SPAD device testing and selection, have fairly limited application. Suitably designed active-quenching circuits (AQC's) make it possible to exploit the best performance of SPAD's. Thick silicon SPAD's that operate at high voltages (250-450 V) have photon detection efficiency higher than 50% from 540-to 850-nm wavelength and still approximately 3% at 1064 nm. Thin silicon SPAD's that operate at low voltages (10-50 V) have 45% efficiency at 500 nm, declining to 10% at 830 nm and to as little as 0.1% at 1064 nm. The time resolution achieved in photon timing is 20 ps FWHM with thin SPAD's; it ranges from 350 to 150 ps FWHM with thick SPAD's. The achieved minimum counting dead time and maximum counting rate are 40 ns and 10 Mcps with thick silicon SPAD's, 10 ns and 40 Mcps with thin SPAD's. Germanium and III-V compound semiconductor SPAD's extend the range of photon-counting techniques in the near-infrared region to at least 1600-nm wavelength.

  15. Turn-on and turn-off voltages of an avalanche p—n junction

    Science.gov (United States)

    Guoqing, Zhang; Dejun, Han; Changjun, Zhu; Xuejun, Zhai

    2012-09-01

    Characteristics of the turn-on and turn-off voltage of avalanche p—n junctions were demonstrated and studied. As opposed to existing reports, the differences between the turn-on and turn-off voltage cannot be neglected when the size of the p—n junction is in the order of microns. The difference increases inversely with the area of a junction, exerting significant influences on characterizing some parameters of devices composed of small avalanche junctions. Theoretical analyses show that the mechanism for the difference lies in the increase effect of the threshold multiplication factor at the turn-on voltage of a junction when the area of a junction decreases. Moreover, the “breakdown voltage" in the formula of the avalanche asymptotic current is, in essence, the avalanche turn-off voltage, and consequently, the traditional expression of the avalanche asymptotic current and the gain of a Geiger mode avalanche photodiode were modified.

  16. Estimating the avalanche contribution to the mass balance of debris covered glaciers

    Directory of Open Access Journals (Sweden)

    A. Banerjee

    2014-01-01

    Full Text Available Avalanche from high head walls dominates the net accumulation in many debris covered glaciers in the Himalaya. These avalanche contributions are difficult to directly measure and may cause a systematic bias in glaciological mass balance measurements. In this paper we develop a method to estimate the avalanche contribution using available data, within the context of an idealised flowline model of the glacier. We focus on Hamtah glacier in Western Himalaya and estimate the magnitude of the avalanche accumulation to its specific mass balance profile. Our estimate explains the reported discrepancy between values of recent glaciological and geodetic net mass balance for this glacier. Model estimate of accumulation area ratio (AAR for this glacier is small (0.1 even at a steady state. This shows that empirical mass balance–AAR relationships derived from glaciers which do not have a significant avalanche contribution will not apply to a large region containing a significant fraction avalanche fed ones.

  17. Skin rash during treatment with generic itraconazole

    Directory of Open Access Journals (Sweden)

    Antonio De Vuono

    2014-01-01

    Full Text Available Generic drugs have the same active substance, the same pharmaceutical form, the same therapeutic indications and a similar bioequivalence with the reference medicinal product (branded. Although a similar efficacy is postulated, some cases of clinical inefficacy during treatment with generic formulations have been reported. In this case, we describe a woman with onychomycosis that developed a skin rash during treatment with a generic formulation of itraconazole. Drug administration and its re-challenge confirmed the association between itraconazole and skin rash. Both Naranjo probability scale and World Health Organization causality assessment scale documented a probable association between generic-itraconazole and skin rash. The switch from generic formulation to brand one induced an improvement of symptoms. Since we are unable to evaluate the role of each excipient in the development of skin rash, we cannot rule out their involvement. However, more data are necessary to better define the similarities or differences between branded and generic formulations.

  18. Toward a generic UGV autopilot

    Science.gov (United States)

    Moore, Kevin L.; Whitehorn, Mark; Weinstein, Alejandro J.; Xia, Junjun

    2009-05-01

    Much of the success of small unmanned air vehicles (UAVs) has arguably been due to the widespread availability of low-cost, portable autopilots. While the development of unmanned ground vehicles (UGVs) has led to significant achievements, as typified by recent grand challenge events, to date the UGV equivalent of the UAV autopilot is not available. In this paper we describe our recent research aimed at the development of a generic UGV autopilot. Assuming we are given a drive-by-wire vehicle that accepts as inputs steering, brake, and throttle commands, we present a system that adds sonar ranging sensors, GPS/IMU/odometry, stereo camera, and scanning laser sensors, together with a variety of interfacing and communication hardware. The system also includes a finite state machine-based software architecture as well as a graphical user interface for the operator control unit (OCU). Algorithms are presented that enable an end-to-end scenario whereby an operator can view stereo images as seen by the vehicle and can input GPS waypoints either from a map or in the vehicle's scene-view image, at which point the system uses the environmental sensors as inputs to a Kalman filter for pose estimation and then computes control actions to move through the waypoint list, while avoiding obstacles. The long-term goal of the research is a system that is generically applicable to any drive-by-wire unmanned ground vehicle.

  19. On possibilities of application of Miller formula for determination of parameters of Micropixel Avalanche Photodiodes

    CERN Document Server

    Sadygov, Z; Akhmedov, G; Akhmedov, F; Mukhtarov, R; Sadygov, A; Titov, A; Zhezher, V

    2014-01-01

    Miller formula modified to take into account voltage drop on serial resistor of an avalanche photodiode is considered. It is proven by experimental data that modified Miller formula can describe operation of both regular and micropixel avalanche photodiodes with good enough precision. It is shown that operation parameters of the devices can be determined using a linear extrapolation of the voltage-current curve for both regular avalanche photodiode and the one operating in Geiger mode.

  20. On possibilities of application of Miller formula for determination of parameters of Micropixel Avalanche Photodiodes

    OpenAIRE

    Sadygov, Z.; Abdullaev, Kh.; Akhmedov, G.; Akhmedov, F.; Mukhtarov, R.; Sadygov, A.; Titov, A.; Zhezher, V.

    2014-01-01

    Miller formula modified to take into account voltage drop on serial resistor of an avalanche photodiode is considered. It is proven by experimental data that modified Miller formula can describe operation of both regular and micropixel avalanche photodiodes with good enough precision. It is shown that operation parameters of the devices can be determined using a linear extrapolation of the voltage-current curve for both regular avalanche photodiode and the one operating in Geiger mode.

  1. Exponential time response in analogue and Geiger mode avalanche photodiodes\\ud

    OpenAIRE

    Groves, C.; Tan, C H; David, J.P.R.; Rees, G J; Hayat, M.M.

    2005-01-01

    The mean avalanche current impulse response in an\\ud avalanche photodiode exhibits an initial transient and then grows or decays, above or below breakdown, at exponential rates which depend only on the probability distributions of the electron and hole ionization events. The process continues while the electric field profile remains unchanged by the applied bias or the evolving space\\ud charge. Below breakdown the distribution in the avalanche duration also exhibits an initial transient and t...

  2. PROBLEM OF GENERIC REPLACEMENT: ADVANTAGES AND DISADVANTAGES

    Directory of Open Access Journals (Sweden)

    S. N. Tolpygina

    2009-01-01

    Full Text Available The main differences between original and generic drugs as well as registration criteria for generics are described. Possible reasons of discrepancy in bioequivalence and therapeutic equivalence of original and generic drugs are reviewed. The examples of such a discrepancy as a result of comparative clinical trails (enalapril maleate are discussed. Approaches to planning of comparative trails on drug therapeutic equivalence are presented. 

  3. Generic domain models in software engineering

    Science.gov (United States)

    Maiden, Neil

    1992-01-01

    This paper outlines three research directions related to domain-specific software development: (1) reuse of generic models for domain-specific software development; (2) empirical evidence to determine these generic models, namely elicitation of mental knowledge schema possessed by expert software developers; and (3) exploitation of generic domain models to assist modelling of specific applications. It focuses on knowledge acquisition for domain-specific software development, with emphasis on tool support for the most important phases of software development.

  4. GENERIC COMMODITY PROMOTION AND PRODUCT DIFFERENTIATION

    OpenAIRE

    1999-01-01

    This paper considers whether generic promotion lowers the differentiation among competing brands as claimed in the 1997 Supreme Court case (Wileman et al. v. Glickman). Commodity promotion is modeled as a multi-stage game where products are vertically differentiated. Analytical results show that if the benefits of generic advertising from increased demand are outweighed by the costs from lower product differentiation then high-quality producers will not benefit from generic promotion but prod...

  5. Determinants of generic drug substitution in Switzerland

    Directory of Open Access Journals (Sweden)

    Lufkin Thomas M

    2011-01-01

    Full Text Available Abstract Background Since generic drugs have the same therapeutic effect as the original formulation but at generally lower costs, their use should be more heavily promoted. However, a considerable number of barriers to their wider use have been observed in many countries. The present study examines the influence of patients, physicians and certain characteristics of the generics' market on generic substitution in Switzerland. Methods We used reimbursement claims' data submitted to a large health insurer by insured individuals living in one of Switzerland's three linguistic regions during 2003. All dispensed drugs studied here were substitutable. The outcome (use of a generic or not was modelled by logistic regression, adjusted for patients' characteristics (gender, age, treatment complexity, substitution groups and with several variables describing reimbursement incentives (deductible, co-payments and the generics' market (prices, packaging, co-branded original, number of available generics, etc.. Results The overall generics' substitution rate for 173,212 dispensed prescriptions was 31%, though this varied considerably across cantons. Poor health status (older patients, complex treatments was associated with lower generic use. Higher rates were associated with higher out-of-pocket costs, greater price differences between the original and the generic, and with the number of generics on the market, while reformulation and repackaging were associated with lower rates. The substitution rate was 13% lower among hospital physicians. The adoption of the prescribing practices of the canton with the highest substitution rate would increase substitution in other cantons to as much as 26%. Conclusions Patient health status explained a part of the reluctance to substitute an original formulation by a generic. Economic incentives were efficient, but with a moderate global effect. The huge interregional differences indicated that prescribing behaviours and

  6. PROBLEM OF GENERIC REPLACEMENT: ADVANTAGES AND DISADVANTAGES

    Directory of Open Access Journals (Sweden)

    S. N. Tolpygina

    2016-01-01

    Full Text Available The main differences between original and generic drugs as well as registration criteria for generics are described. Possible reasons of discrepancy in bioequivalence and therapeutic equivalence of original and generic drugs are reviewed. The examples of such a discrepancy as a result of comparative clinical trails (enalapril maleate are discussed. Approaches to planning of comparative trails on drug therapeutic equivalence are presented. 

  7. Spatial aspects of vulnerability and risk resulting from snow avalanches

    Science.gov (United States)

    Fuchs, S.; Koltermann, P.; Sokratov, S.; Seliverstov, Y.; Shnyparkov, A.

    2012-04-01

    Mountain regions provide a significant proportion of areas used for human settlements, economic purpose, and recreation. Simultaneously, due to steep vertical gradients mountain areas are prone to mass movement processes. The intersection of such processes with areas used by human action turns them into hazards. In particular in arctic regions, which show a greater susceptibility to disturbances than many landscapes, considerable efforts have been undertaken in recent decades to reduce the adverse effects of mountain hazards. The concept of risk supplemented the traditional engineering approaches of technical mitigation since the 1990s to comprehensively manage these threats, and to develop strategies for a sustainable use of these areas. The concept of risk is based on a mathematical combination of hazards and consequences, but is static over time. However, three major dynamic systems interact in the field of mountain hazard risk management: the physical environment, which includes hazardous events; the social and demographic characteristics of the communities that experience them; and the values at risk such as buildings, roads, and other components of the built environment. These dynamics have not sufficiently been taken into account so far in natural hazard risk management, in particular with respect to industrialised artic regions. Within the city of Kirovsk, Kola Peninsula, Russian Federation, these dynamics were assessed by taking snow avalanche risk as an example. The test site is exposed to multiple avalanche tracks with repeated releases during individual winter seasons, endangering the built environment and any kind of infrastructure lines. The aim was to contribute to the development of a spatial risk model for mountain regions on different temporal scales. The spatial characteristics of the long-term avalanche risk, as a result of the evolution of the built environment, was analysed on an annual as well as inter-annual level. This long-term development

  8. The Tancitaro Debris Avalanche: Characterization, propagation and modeling

    Science.gov (United States)

    Morelli, Stefano; Monroy, Victor Hugo Garduño; Gigli, Giovanni; Falorni, Giacomo; Rocha, Eleazar Arreygue; Casagli, Nicola

    2010-06-01

    The Tancitaro volcano (3860 m) is an andesitic-dacitic stratovolcano located in the western portion of the Trans-Mexican Volcanic Belt within the state of Michoacán (Mexico). The tectonic activity of this area has likely contributed to a large sector collapse of the volcano. The first findings of a multidisciplinary investigation into this debris avalanche are presented here. Geomorphological analyses, based on the interpretation of orthophotos, satellite imagery and on GIS elaborations, had the objective of determining the main morphometric features of the landslide. The collapse structure is an east-facing horseshoe-shaped crater (4 km wide and 5.3 km long), while the deposit forms a large fan that is 66 km long, covers an area of approximately 1155 km 2 and has an estimated volume of 18 km 3. Event volume was established by reconstructing the paleo-edifice in a GIS and taking into account volumetric expansion. Cross sections measured in the field were also used for this purpose. Field investigations also highlighted the presence of two texturally distinct units, which are referred to as the "block facies" and the "matrix facies", respectively. The first is responsible for the typical hummock morphologies found in the proximal area. A transitional zone contains a "mixed block and matrix facies" while in the distal portion blocks and megablocks, some of which have a jigsaw puzzle texture, gradually decrease in size until they disappear entirely. A number of matrix samples were collected to conduct direct shear tests, granulometric analyses and classification of the materials. The data and analyses described above were used to discuss the mechanism controlling the long runout of the avalanche. Based on the comparison between the Tancitaro debris avalanche and similar events we propose that mechanical fluidization was the mechanism responsible for the remarkable mobility of the landslide. The predisposing factors leading to the collapse were also considered. Field

  9. Reference pricing with endogenous generic entry.

    OpenAIRE

    Kurt R. Brekke; Canta, Chiara; Straume, Odd Rune

    2015-01-01

    In this paper we study the effect of reference pricing on pharmaceutical prices and ex-penditures when generic entry is endogenously determined. We develop a Salop-type model where a brand-name producer competes with generic producers in terms of prices. In the market there are two types of consumers: (i) brand biased consumers who choose between brand-name and generic drugs, and (ii) brand neutral consumers who choose between the different generic drugs. We find that, for a given number of ...

  10. Generic modules for trivial extension algebras

    Institute of Scientific and Technical Information of China (English)

    杜先能

    1995-01-01

    Let A be a finite-dimensional algebra over an algebraically closed field. An indecomposable (right) ,4-module M is called generic provided M is infinite k-dimensional but finite length as (left) EndA(M)-module. Let R = A DA be the trivial extension algebra of A- Generic R-modules are constructed from generic A-modules using some functors between Mod A and Mod R. it is also proved that if A is a tame hereditary algebra, then R has only two generic modules.

  11. "Generic Entry and the Pricing of Pharmaceuticals"

    OpenAIRE

    Frank, Richard G.; David S. Salkever

    1995-01-01

    During the 1980s the share of prescriptions sold by retail pharmacies that was accounted for by generic products roughly doubled. The price response to generic entry of brand-name products has been a source of controversy. In this paper we estimate models of price responses to generic entry in the market for brand-name and generic drugs. We study a sample of 32 drugs that lost patent protection during the early to mid-1980s. Our results provide strong evidence that brand-name prices increase ...

  12. Rational use of generic psychotropic drugs.

    Science.gov (United States)

    Carbon, Maren; Correll, Christoph U

    2013-05-01

    For economic reasons, the generic substitution of branded medications is common and welcome. These replacements are based on the concept of bioequivalence, which is considered equal to therapeutic equivalence. Regulatory standards for bioequivalence require the 90 % confidence intervals of group averages of pharmacokinetic measures of a generic and the original drug to overlap within ±20 %. However, therapeutic equivalence has been challenged for several psychotropic agents by retrospective studies and case reports. To evaluate the degree of bioequivalence and therapeutic equivalence of branded and generic psychotropic drugs, we performed an electronic search (from database inception until 24 May 2012 and without language restrictions) in PubMed/MEDLINE, Cochrane Library, and Web of Science. Search terms were "(generic) AND (psychotropic OR psychoactive OR antipsychotic OR antiepileptic OR antidepressant OR stimulant OR benzodiazepine)" or the respective individual substances. We included clinical studies, regardless of design, comparing branded with generic psychotropic drug formulations, identifying 35 such studies. We also included case reports/series reporting on outcomes after a switch between brand and generic psychotropics, identifying 145 clinical cases. Bioequivalence studies in healthy controls or animals, in-vitro studies, and health economics studies without medical information were excluded. An overview of the few randomized controlled studies supports that US FDA regulations assure clinically adequate drug delivery in the majority of patients switched from brand to generic. However, with a growing number of competing generic products for one substance, and growing economic pressure to substitute with the currently cheapest generic, frequent generic-generic switches, often unbeknownst to prescribing clinicians, raise concerns, particularly for antiepileptics/mood stabilizers. Generic-generic switches may vary by more than ±20 % from each other in

  13. Information processing occurs via critical avalanches in a model of the primary visual cortex

    Science.gov (United States)

    Bortolotto, G. S.; Girardi-Schappo, M.; Gonsalves, J. J.; Pinto, L. T.; Tragtenberg, M. H. R.

    2016-01-01

    We study a new biologically motivated model for the Macaque monkey primary visual cortex which presents power-law avalanches after a visual stimulus. The signal propagates through all the layers of the model via avalanches that depend on network structure and synaptic parameter. We identify four different avalanche profiles as a function of the excitatory postsynaptic potential. The avalanches follow a size-duration scaling relation and present critical exponents that match experiments. The structure of the network gives rise to a regime of two characteristic spatial scales, one of which vanishes in the thermodynamic limit.

  14. Snow Avalanche Disturbance Ecology: Examples From the San Juan Mountains, Colorado.

    Science.gov (United States)

    Simonson, S.; Fassnacht, S. R.

    2008-12-01

    We evaluated landscape ecology approaches to characterize snow avalanche paths based on patterns of plant species composition and evidence of disturbance. Historical records of avalanche incidents, patterns in the annual growth layers of woody plants, and distributions of plant species can be used to quantify and map the frequency and magnitude of snow slide events. Near Silverton, Colorado, a series of snow storms in January of 2005 resulted in many avalanche paths running full track at 30 and 100 year return frequency. Many avalanches cut fresh trimlines, widening their tracks by uprooting, stripping, and breaking mature trees. Powerful avalanches deposited massive piles of snow, rocks, and woody debris in their runout zones. We used cross-section discs and cores of representative downed trees to detect dendro-ecological signals of past snow avalanche disturbance. Avalanche signals included impact scars from the moving snow and associated wind blast, relative width of annual growth rings, and development of reaction wood in response to tilting. Initial measurements of plant diversity and disturbance along the elevation gradient of an avalanche path near Silverton indicate that avalanche activity influences patterns of forest cover, contributes to the high local plant species diversity, and provides opportunities for new seedling establishment.

  15. Large-Area Superconducting Nanowire Single-Photon Detector with Double-Stage Avalanche Structure

    OpenAIRE

    2016-01-01

    We propose a novel design of superconducting nanowire avalanche photodetectors (SNAPs), which combines the advantages of multi-stage avalanche SNAPs to lower the avalanche current I_AV and that of series-SNAPs to reduce the reset time. As proof of principle, we fabricated 800 devices with large detection area (15 um * 15 um) and five different designs on a single silicon chip for comparison, which include standard SNSPDs, series-3-SNAPs and our modified series-SNAPs with double-stage avalanch...

  16. IFKIS - a basis for managing avalanche risk in settlements and on roads in Switzerland

    Directory of Open Access Journals (Sweden)

    M. Bründl

    2004-01-01

    Full Text Available After the avalanche winter of 1999 in Switzerland, which caused 17 deaths and damage of over CHF 600 mill. in buildings and on roads, the project IFKIS, aimed at improving the basics of organizational measures (closure of roads, evacuation etc. in avalanche risk management, was initiated. The three main parts of the project were the development of a compulsory checklist for avalanche safety services, a modular education and training course program and an information system for safety services. The information system was developed in order to improve both the information flux between the national centre for avalanche forecasting, the Swiss Federal Institute for Snow and Avalanche Research SLF, and the local safety services on the one hand and the communication between avalanche safety services in the communities on the other hand. The results of this project make a valuable contribution to strengthening organizational measures in avalanche risk management and to closing the gaps, which became apparent during the avalanche winter of 1999. They are not restricted to snow avalanches but can also be adapted for dealing with other natural hazard processes and catastrophes.

  17. Highly efficient avalanche multiphoton luminescence from coupled Au nanowires in the visible region

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We report highly efficient avalanche multiphoton luminescence(MPL)from ordered-arrayed gold nanowires(NWs).The time-average excitation intensity I_(exc) is as low as 5.0-9.1 kW/cm~2.The intensity of avalanche MPL I_(MPL) is about 10~4 times larger than that of three-photon luminescence,the slope ■logI_(MPL)/■logI_(exc) of avalanche MPL reaches as high as 18.3 and the corresponding polarization dependence of I_(MPL) has a form of cos~(50)■_p.The emission dynamics of avalanche MPL and three-photon luminesc...

  18. 76 FR 54507 - Proposed Generic Communication; Draft NRC Generic Letter 2011-XX: Seismic Risk Evaluations for...

    Science.gov (United States)

    2011-09-01

    ... COMMISSION Proposed Generic Communication; Draft NRC Generic Letter 2011-XX: Seismic Risk Evaluations for... the effects of natural phenomena, including earthquakes, without losing the capability to perform... Electric Power Research Institute models to estimate earthquake ground motion and updated models...

  19. Analysis of French generic medicines retail market: why the use of generic medicines is limited.

    Science.gov (United States)

    Dylst, Pieter; Vulto, Arnold; Simoens, Steven

    2014-12-01

    The market share of generic medicines in France is low compared to other European countries. This perspective paper provides an overview of the generic medicines retail market in France and how the current policy environment may affect the long-term sustainability. Looking at the French generic medicines retail market and the surrounding regulatory framework, all conditions seem to be in place to create a healthy generic medicines market: the country has well-respected regulatory authorities, generic medicines enter the market in a timely manner and prices of generic medicines are competitive compared with other European countries. Despite the success of the demand-side policies targeted at pharmacists and patients, those targeted at physicians were less successful due to a lack of enforcement and a lack of trust in generic medicines by French physicians. Recommendations to increase the use of generic medicines in France round off this perspective paper.

  20. An indirect flat-panel detector with avalanche gain for low dose x-ray imaging: SAPHIRE (scintillator avalanche photoconductor with high resolution emitter readout)

    Science.gov (United States)

    Zhao, Wei; Li, Dan; Rowlands, J. A.; Egami, N.; Takiguchi, Y.; Nanba, M.; Honda, Y.; Ohkawa, Y.; Kubota, M.; Tanioka, K.; Suzuki, K.; Kawai, T.

    2008-03-01

    An indirect flat-imager with programmable avalanche gain and field emitter array (FEA) readout is being investigated for low-dose x-ray imaging with high resolution. It is made by optically coupling a structured x-ray scintillator CsI (Tl) to an amorphous selenium (a-Se) avalanche photoconductor called HARP (high-gain avalanche rushing photoconductor). The charge image created by HARP is read out by electron beams generated by the FEA. The proposed detector is called SAPHIRE (Scintillator Avalanche Photoconductor with HIgh Resolution Emitter readout). The avalanche gain of HARP depends on both a-Se thickness and applied electric field E Se. At E Se of > 80 V/μm, the avalanche gain can enhance the signal at low dose (e.g. fluoroscopy) and make the detector x-ray quantum noise limited down to a single x-ray photon. At high exposure (e.g. radiography), the avalanche gain can be turned off by decreasing E Se to < 70 V/μm. In this paper the imaging characteristics of the FEA readout method, including the spatial resolution and noise, were investigated experimentally using a prototype optical HARP-FEA image sensor. The potential x-ray imaging performance of SAPHIRE, especially the aspect of programmable gain to ensure wide dynamic range and x-ray quantum noise limited performance at the lowest exposure in fluoroscopy, was investigated.

  1. Pharmaceutical policy regarding generic drugs in Belgium.

    Science.gov (United States)

    Simoens, Steven; De Bruyn, Kristien; Bogaert, Marc; Laekeman, Gert

    2005-01-01

    Pressure to control pharmaceutical expenditure and price competition among pharmaceutical companies are fuelling the development of generic drug markets in EU countries. However, in Belgium, the market for generic drugs is underdeveloped compared with other countries. To promote the use of generic drugs, the government introduced a reference pricing (RP) scheme in 2001. The aim of this paper is to discuss Belgian pharmaceutical policy regarding generic drugs and to analyse how the Belgian drug market has evolved following initiation of the RP scheme. The market share held by generic drugs increased following implementation of the RP scheme. Focusing on volume, average market share (by semester) for generic drugs amounted to 2.05% of the total pharmaceutical market from January 1998 to June 2001, compared with 6.11% from July 2001 to December 2003. As new generic drugs are introduced, their market share tends to increase in the first couple of months, after which it levels off. Faced with increasing generic competition, some manufacturers have launched new variants of their original drug, thereby effectively extending the period of patent protection. Strategies consisting of price reductions in return for the abolition of prescribing conditions and the launch of new dosages or formulations appear to have been successful in maintaining the market share of original drugs. Nevertheless, the introduction of the RP scheme was associated with savings amounting to 1.8% of pharmaceutical expenditure by the third-party payer in 2001 and 2.1% in 2002. The findings of this paper indicate that the RP scheme has stimulated the Belgian generic drug market. However, existing policy has largely failed to take into account the role that physicians and pharmacists can play in stimulating generic drug use. Therefore, further development of the Belgian generic drug market seems to hinge on the creation of appropriate incentives for physicians to prescribe, and for pharmacists to

  2. Prediction of avalanches on the basis of the 27‐day Solar activity variations

    Directory of Open Access Journals (Sweden)

    N. A. Kazakov

    2015-01-01

    Full Text Available Many natural processes on the Earth are the cyclic ones and they are self-sustaining within a system of the Sun–Earth relations. To verify our hypothesis on a cyclic occurrence of the avalanche processes and to estimate a possibility to predict avalanches as a cyclic process we had analyzed information about avalanches and meteorological processes (number of avalanches per a day, their total and maximal volumes, and daily sums of precipitation using the method of 27-day Sun (solar calendars by A. Chizhevskiy. Analysis of results of such studies obtained in Khibini (Kola peninsula, for 1935–1986 and on a Chamginskiy mountain pass (the Sakhalin Island, Vostochno-Sakhalinskie Mountains, for 1982–1992 had shown that activity of the avalanche processes and the atmospheric precipitation had evident 27-day solar cycle. Cyclicity of appearance and volume of avalanches of both syngenetic and epigenetic types is established as well as of the precipitation in quantitative gradations. Procedures of prediction of number and volume of avalanches and daily precipitation were developed on the basis of their relationship with the Sun cycles. Verification of the method proposed in this article by the data obtained in Khibini (Kukisvum mountain pass, 1987–1988 and on the Sakhalin Island (Chamginskiy mountain pass, 1993–1995; Yuzhno-Sahalinsk; Tomari, 1991–1999 had demonstrated that correctness of such forecast with earliness of 60 days is as follows: for precipitation – 85–90%; the new snow avalanches of new snow – 90–95%; avalanches of recrystallization snow – 75–80%. At that with earliness of 10 days: precipitation – 90–95%; avalanches of new snow – 95%; avalanches of r recrystallization snow – 75–80%. 

  3. Once more the generic name Passerina Vieillot

    NARCIS (Netherlands)

    Oort, van E.D.

    1910-01-01

    The note on the generic name of the Snow-bunting by Dr. E. Hartert in this part of our periodical gives me cause to revert to the subject of my note on the generic name Passerina Vieillot and to state here, that I stand to what I have said about the rejection of this name in Zoology (Notes Leyden Mu

  4. Designing Generic and Efficient Negotiation Strategies

    NARCIS (Netherlands)

    Tykhonov, D.

    2010-01-01

    The central aim of this thesis is the design of generic and efficient automated strategies for two-party negotiations in which negotiating parties do not reveal their preferences explicitly. A strategy for negotiation is the decision mechanism for determining the actions of a negotiator. Generic ref

  5. Typed generic traversals in $S_gamma^'$

    NARCIS (Netherlands)

    Lämmel, R.

    2001-01-01

    A typed model of strategic rewriting is developed. An innovation is that generic traversals are covered. To this end, we define a rewriting calculus $S'_{gamma$. The calculus offers a few strategy combinators for generic traversals. There is, for example, a combinator to apply a strategy to all imme

  6. Generic drugs in dermatology: part I.

    Science.gov (United States)

    Payette, Michael; Grant-Kels, Jane M

    2012-03-01

    The cost of health care in the United States is increasing. In order to help control these rising costs, all parties involved in the delivery of health care, including dermatologists, need to be part of the solution of ethically reducing the cost of delivery of care. One potential means of meeting this goal is to increase the use of generic medications in daily practice. Generic medications can offer equally efficacious therapy at significantly lower prices, which can translate into large scale savings for the individual patient, the payer, and the overall health care system. Herein we provide an overview of new drug development, review the history of the generic drug industry, describe how generic drugs are approved by the US Food and Drug Administration, and define the concepts of bioequivalence and therapeutic equivalence. In part II, we explore various factors impacting generic drug use, provide cost analyses of dermatologic brand name and generic drugs, and review data addressing potential differences in the effectiveness of brand name versus generic drugs in dermatology. The cost of brand name and generic medications is highly variable by pharmacy, state, and payer. We used one source (www.drugstore.com) as an example and for consistency across all medications discussed herein. Prices included here may not reflect actual retail prices across the United States.

  7. [Generic drugs: quality, efficacy, safety and interchangeability].

    Science.gov (United States)

    Tschabitscher, Doris; Platzer, Peter; Baumgärtel, Christoph; Müllner, Marcus

    2008-01-01

    Since the introduction of generic drugs to the pharmaceutical market a sometimes emotional debate exists whether they are well-investigated and of high quality. There is some uncertainty about whether evidence of bioequivalence is enough to guarantee efficacy and safety of generic drugs. Some physicians ask the question if competent authorities are able to ascertain that the pharmaceutical quality of generics is acceptable. Doctors and patients sometimes are ill at ease about the interchangeability of innovator and generic products. This article describes how the European Union legislation ensures that a generic drug is only approved if its risk-benefit relationship is favourable and that it is essentially similar to the innovator product. In this context pharmacokinetic parameters are accepted as surrogates for clinical results because bioequivalence means therapeutic equivalence as well. For most drugs, current bioequivalence testing generally enables clinicians to routinely substitute generic for innovator products. Published findings, however, suggest that particular drugs may not be ideally suited for generic substitution when a patient is already on that drug. These are the so called critical dose medicinal products (drugs with a narrow therapeutic range). When starting a new therapy with any generic drug, however, its similarity to the innovator drug in terms of efficacy, safety and quality is guaranteed.

  8. GENERIC DRUG USER FEE: AN OVERVIEW

    Directory of Open Access Journals (Sweden)

    Darshit S. Patel*, Abhishek R. Patel and Narendra A. Patel

    2012-09-01

    Full Text Available The globalization of generic drug manufacturing, supply and testing, and a growing workload that has far outpaced USFDA’s resources has created new challenges. USFDA & Industry propose generic drug user fee to address the need for globalization of the inspection process, and to speed the timely review of generic product applications. The Generic Drug User Fee (GDUF proposal is agreed by generic industry & USFDA and is focused on three key aims: safety, access, and transparency. Under the program, USFDA will receive nearly $1.5 billion over five years in supplemental funding through generic industry user fees in order to help the agency expedite access to generic drugs, enhance drug quality and safety and ensure inspection parity of both foreign and domestic manufacturing sites. GDUF also will help accelerate the market entry of additional manufacturers of drugs currently in short supply and improve quality, consistency, and availability within the supply chain, further helping to mitigate drug shortages. The GDUF new legislation is a milestone for the generic giants and a major win for American health care consumers.

  9. Defining Generic Skills. At a Glance.

    Science.gov (United States)

    National Centre for Vocational Education Research, Leabrook (Australia).

    Generic skills--skills that apply across a variety of jobs and life contexts--are taking on increased importance in Australia and internationally. There is a high demand for generic skills in the workplace because employers seek to ensure business success by recruiting and retaining employees who have a variety of skills and personal attributes as…

  10. Inhibitory neurons promote robust critical firing dynamics in networks of integrate-and-fire neurons

    Science.gov (United States)

    Lu, Zhixin; Squires, Shane; Ott, Edward; Girvan, Michelle

    2016-12-01

    We study the firing dynamics of a discrete-state and discrete-time version of an integrate-and-fire neuronal network model with both excitatory and inhibitory neurons. When the integer-valued state of a neuron exceeds a threshold value, the neuron fires, sends out state-changing signals to its connected neurons, and returns to the resting state. In this model, a continuous phase transition from non-ceaseless firing to ceaseless firing is observed. At criticality, power-law distributions of avalanche size and duration with the previously derived exponents, -3 /2 and -2 , respectively, are observed. Using a mean-field approach, we show analytically how the critical point depends on model parameters. Our main result is that the combined presence of both inhibitory neurons and integrate-and-fire dynamics greatly enhances the robustness of critical power-law behavior (i.e., there is an increased range of parameters, including both sub- and supercritical values, for which several decades of power-law behavior occurs).

  11. Martian Dust Devil Electron Avalanche Process and Associated Electrochemistry

    Science.gov (United States)

    Jackson, Telana L.; Farrell, William M.; Delory, Gregory T.; Nithianandam, Jeyasingh

    2010-01-01

    Mars' dynamic atmosphere displays localized dust devils and larger, global dust storms. Based on terrestrial analog studies, electrostatic modeling, and laboratory work these features will contain large electrostatic fields formed via triboelectric processes. In the low-pressure Martian atmosphere, these fields may create an electron avalanche and collisional plasma due to an increase in electron density driven by the internal electrical forces. To test the hypothesis that an electron avalanche is sustained under these conditions, a self-consistent atmospheric process model is created including electron impact ionization sources and electron losses via dust absorption, electron dissociation attachment, and electron/ion recombination. This new model is called the Dust Devil Electron Avalanche Model (DDEAM). This model solves simultaneously nine continuity equations describing the evolution of the primary gaseous chemical species involved in the electrochemistry. DDEAM monitors the evolution of the electrons and primary gas constituents, including electron/water interactions. We especially focus on electron dynamics and follow the electrons as they evolve in the E field driven collisional gas. When sources and losses are self-consistently included in the electron continuity equation, the electron density grows exponentially with increasing electric field, reaching an equilibrium that forms a sustained time-stable collisional plasma. However, the character of this plasma differs depending upon the assumed growth rate saturation process (chemical saturation versus space charge). DDEAM also shows the possibility of the loss of atmospheric methane as a function of electric field due to electron dissociative attachment of the hydrocarbon. The methane destruction rates are presented and can be included in other larger atmospheric models.

  12. Magnetic field modification to the relativistic runaway electron avalanche length

    Science.gov (United States)

    Cramer, E. S.; Dwyer, J. R.; Rassoul, H. K.

    2016-11-01

    This paper explores the impact of the geomagnetic field on the relativistic runaway electron avalanche length, λe-. Coleman and Dwyer (2006) developed an analytical fit to Monte Carlo simulations using the Runaway Electron Avalanche Model. In this work, we repeat this process but with the addition of the geomagnetic field in the range of [100,900]/n μT, where n is the ratio of the density of air at altitude to the sea level density. As the ambient electric field approaches the runaway threshold field (Eth≈284 kV/m sea level equivalent), it is shown that the magnetic field has an impact on the orientation of the resulting electron beam. The runaway electrons initially follow the vertically oriented electric field but then are deflected in the v × B direction, and as such, the electrons experience more dynamic friction due to the increase in path length. This will be shown to result in a difference in the avalanche length from the case where B = 0. It will also be shown that the average energy of the runaway electrons will decrease while the required electric field to produce runaway electrons increases. This study is also important in understanding the physics of terrestrial gamma ray flashes (TGFs). Not only will this work impact relativistic feedback rates determined from simulations, it may also be useful in studying spectroscopy of TGFs observed from balloon and aircraft measurements. These models may also be used in determining beaming properties of TGFs originating in the tropical regions seen from orbiting spacecraft.

  13. Martian Dust Devil Electron Avalanche Process and Associated Electrochemistry

    Science.gov (United States)

    Jackson, Telana L.; Farrell, William M.; Delory, Gregory T.; Nithianandam, Jeyasingh

    2010-01-01

    Mars' dynamic atmosphere displays localized dust devils and larger, global dust storms. Based on terrestrial analog studies, electrostatic modeling, and laboratory work these features will contain large electrostatic fields formed via triboelectric processes. In the low-pressure Martian atmosphere, these fields may create an electron avalanche and collisional plasma due to an increase in electron density driven by the internal electrical forces. To test the hypothesis that an electron avalanche is sustained under these conditions, a self-consistent atmospheric process model is created including electron impact ionization sources and electron losses via dust absorption, electron dissociation attachment, and electron/ion recombination. This new model is called the Dust Devil Electron Avalanche Model (DDEAM). This model solves simultaneously nine continuity equations describing the evolution of the primary gaseous chemical species involved in the electrochemistry. DDEAM monitors the evolution of the electrons and primary gas constituents, including electron/water interactions. We especially focus on electron dynamics and follow the electrons as they evolve in the E field driven collisional gas. When sources and losses are self-consistently included in the electron continuity equation, the electron density grows exponentially with increasing electric field, reaching an equilibrium that forms a sustained time-stable collisional plasma. However, the character of this plasma differs depending upon the assumed growth rate saturation process (chemical saturation versus space charge). DDEAM also shows the possibility of the loss of atmospheric methane as a function of electric field due to electron dissociative attachment of the hydrocarbon. The methane destruction rates are presented and can be included in other larger atmospheric models.

  14. Mirror neurons

    National Research Council Canada - National Science Library

    Rubia Vila, Francisco José

    2011-01-01

    Mirror neurons were recently discovered in frontal brain areas of the monkey. They are activated when the animal makes a specific movement, but also when the animal observes the same movement in another animal...

  15. Linking snow depth to avalanche release area size: measurements from the Vallée de la Sionne field site

    OpenAIRE

    2016-01-01

    One of the major challenges in avalanche hazard assessment is the correct estimation of avalanche release area size, which is of crucial importance to evaluate the potential danger that avalanches pose to roads, railways or infrastructure. Terrain analysis plays an important role in assessing the potential size of avalanche releases areas and is commonly based on digital terrain models (DTMs) of a snow-free summer terrain. However, a snow-covered winter terrain can significa...

  16. 400-ps time resolution with a passively quenched avalanche photodiode.

    Science.gov (United States)

    Grayson, T P; Wang, L J

    1993-06-01

    Avalanche photodiodes (APD's) operated in a single-photon-counting Geiger mode are becoming attractive alternatives to photomultiplier tubes for low-light-level detection and signal timing. By paying careful attention to the design and construction of a simple APD passive quenching circuit to reduce stray capacitances, we directly measured a time resolution of 410 ps FWHM for a commercial APD. A more detailed data analysis shows the actual time resolution to be ~ 390 ps FWHM. This is believed to be the most accurate time response for such a simple, inexpensive, and widely available device achieved to date.

  17. Silicon avalanche photodiode operation and lifetime analysis for small satellites.

    Science.gov (United States)

    Tan, Yue Chuan; Chandrasekara, Rakhitha; Cheng, Cliff; Ling, Alexander

    2013-07-15

    Silicon avalanche photodiodes (APDs) are sensitive to operating temperature fluctuations and are also susceptible to radiation flux expected in satellite-based quantum experiments. We introduce a low power voltage adjusting mechanism to overcome the effects of in-orbit temperature fluctuations. We also present data on the performance of Si APDs after irradiation (γ-ray and proton beam). Combined with an analysis of expected orbital irradiation, we propose that a Si APD in a 400 km equatorial orbit may operate beyond the lifetime of the satellite.

  18. Photon counting modules using RCA silicon avalanche photodiodes

    Science.gov (United States)

    Lightstone, Alexander W.; Macgregor, Andrew D.; Macsween, Darlene E.; Mcintyre, Robert J.; Trottier, Claude; Webb, Paul P.

    1989-01-01

    Avalanche photodiodes (APD) are excellent small area, solid state detectors for photon counting. Performance possibilities include: photon detection efficiency in excess of 50 percent; wavelength response from 400 to 1000 nm; count rate to 10 (exp 7) counts per sec; afterpulsing at negligible levels; timing resolution better than 1 ns. Unfortunately, these performance levels are not simultaneously available in a single detector amplifier configuration. By considering theoretical performance predictions and previous and new measurements of APD performance, the anticipated performance of a range of proposed APD-based photon counting modules is derived.

  19. Silicon avalanche photodiode operation and lifetime analysis for small satellites

    CERN Document Server

    Tan, Yue Chuan; Cheng, Cliff; Ling, Alexander

    2013-01-01

    Silicon avalanche photodiodes (APDs) are sensitive to operating temperature fluctuations and are also susceptible to radiation flux expected in satellite-based quantum experiments. We introduce a low power voltage adjusting mechanism to overcome the effects of in-orbit temperature fluctuations. We also present data on the performance of Si APDs after irradiation (gamma-ray and proton beam). Combined with an analysis of expected orbital irradiation, we propose that a Si APD in a 400 km equatorial orbit may operate beyond the lifetime of the satellite.

  20. A 1.06 micrometer avalanche photodiode receiver

    Science.gov (United States)

    Eden, R. C.

    1975-01-01

    The development of a complete solid state 1.06 micron optical receiver which can be used in optical communications at data rates approaching 1.5 Gb/s, or in other applications requiring sensitive, short pulse detection, is reported. This work entailed both the development of a new type of heterojunction III-V semiconductor alloy avalanche photodiode and an extremely charge-sensitive wideband low noise preamp design making use of GaAs Schottky barrier-gate field effect transistors (GAASFET's) operating in in the negative-feedback transimpedance mode. The electrical characteristics of the device are described.

  1. Silicon avalanche photodiodes for direct detection of X-rays.

    Science.gov (United States)

    Baron, Alfred Q R; Kishimoto, Shunji; Morse, John; Rigal, Jean Marie

    2006-03-01

    Silicon avalanche photodiodes (APDs) are discussed as fast X-ray detectors for synchrotron radiation. The emphasis is on ;direct' detection, where the X-ray is absorbed within the silicon APD itself, and, therefore, on use with medium-energy X-rays, <30 keV. The impact of APD structure on device performance is examined, and representative data from many different commercial devices are presented. Specific areas discussed include signal shapes, high-rate behavior, time resolution and pulse-height response. Data from several APD arrays are also presented, as is a detailed description of an integrated package system. Tables are included comparing commercially available devices, including arrays.

  2. Reliability assessment of multiple quantum well avalanche photodiodes

    Science.gov (United States)

    Yun, Ilgu; Menkara, Hicham M.; Wang, Yang; Oguzman, Isamil H.; Kolnik, Jan; Brennan, Kevin F.; May, Gray S.; Wagner, Brent K.; Summers, Christopher J.

    1995-01-01

    The reliability of doped-barrier AlGaAs/GsAs multi-quantum well avalanche photodiodes fabricated by molecular beam epitaxy is investigated via accelerated life tests. Dark current and breakdown voltage were the parameters monitored. The activation energy of the degradation mechanism and median device lifetime were determined. Device failure probability as a function of time was computed using the lognormal model. Analysis using the electron beam induced current method revealed the degradation to be caused by ionic impurities or contamination in the passivation layer.

  3. Energy pumping in electrical circuits under avalanche noise.

    Science.gov (United States)

    Kanazawa, Kiyoshi; Sagawa, Takahiro; Hayakawa, Hisao

    2014-07-01

    We theoretically study energy pumping processes in an electrical circuit with avalanche diodes, where non-Gaussian athermal noise plays a crucial role. We show that a positive amount of energy (work) can be extracted by an external manipulation of the circuit in a cyclic way, even when the system is spatially symmetric. We discuss the properties of the energy pumping process for both quasistatic and finite-time cases, and analytically obtain formulas for the amounts of the work and the power. Our results demonstrate the significance of the non-Gaussianity in energetics of electrical circuits.

  4. Correcting for accidental correlations in saturated avalanche photodiodes

    CERN Document Server

    Grieve, James A; Tang, Zhongkan; Ling, Alexander

    2015-01-01

    In this paper we present a high-level numerical model for estimating rates of accidental correlations between a pair of passively quenched Geiger mode avalanche photodiodes operating in the saturated regime. By considering the recovery time of both the diodes and the detection circuit we introduce the concept of an "effective duty cycle" and show that it may be estimated by numeric simulation. The impact of effective duty cycle on the observed accidental rate is examined and we demonstrate that the updated model leads to an improved correction factor in actual experiments. This will improve the signal-to-noise ratio in applications depending on correlation measurements.

  5. Readout of a scintillating-fiber array by avalanche photodiodes

    CERN Document Server

    Okusawa, T; Yamasaki, M; Yoshida, T

    2000-01-01

    We have evaluated the performance of avalanche photodiodes (APDs) as photosensors for scintillating-fiber tracking detectors, putting emphasis on their temperature dependence. For this purpose, a scintillating-fiber array has been built with 0.5 mm diameter fibers 55 cm long. The array is so structured that an incident particle traverses two fibers coupled to an APD. As temperature of the APD falls, the signal-to-noise (S/N) ratio rises exponentially. It even reaches 90 at -30 deg. C. The detection efficiency exceeds 98% when the temperature decreases until the S/N ratio becomes 30.

  6. Geiger-mode avalanche photodiodes for Cherenkov detectors

    Energy Technology Data Exchange (ETDEWEB)

    Renker, D [Paul Scherrer Institue, 5232 Villigen PSI (Switzerland)], E-mail: dieter.renker@psi.ch

    2010-01-15

    Semiconductor photo sensors have in comparison with other detectors used in the ring image Cherenkov (RICH) and in the internally reflected Cherenkov light (DIRC) technique, photomultipier tubes and their derivates, a number of advantages: they have high photon detection efficiency ( {approx} 50%), are insensitive to magnetic fields, operate at low voltages and allow a compact, light and robust design. Specially the relatively new Geiger-mode avalanche photodiode (also called silicon photomultiplier) is a promising candidate for a detector of Cherenkov photons. The state of the development and the problems of this device will be described.

  7. Double Screening Tests of the CMS ECAL Avalanche Photodiodes

    CERN Document Server

    Deiters, Konrad; Renker, Dieter; Sakhelashvili, Tariel; Britvitch, Ilia; Kuznetsov, Andrey; Musienko, Yuri; Singovsky, Alexander

    2005-01-01

    Specially developed avalanche photo-diodes (APDs) will be used to measure the light from the 61,200 lead tungstate crystals in the barrel part of the CMS electromagnetic calorimeter. To ensure the reliability over the lifetime of the detector, every APD is screened by irradiation and burn-in before it is accepted for CMS. As part of the establishment of the screening procedure and to determine its effectiveness, a large number of APDs were screened twice. The results of these tests suggest that the required reliability will be achieved.

  8. Flowers in flour: avalanches in cohesive granular matter.

    Science.gov (United States)

    Freyssingeas, E; Dalbe, M-J; Géminard, J-C

    2011-05-01

    We report on the intermittent dynamics of the free surface of a cohesive granular material during a silo discharge. In absence of cohesion, one observes the formation and the growth of a conical crater whose angle is well defined and constant in time. When the cohesion is involved the free surface exhibits a complex dynamics and the crater, resulting from a series of individual avalanches, is no longer axisymmetric. However, in spite of the intermittent behavior of the free surface, the flow rate is observed to remain constant throughout the discharge.

  9. The Vaigat Rock Avalanche Laboratory, west-central Greenland

    Science.gov (United States)

    Dunning, S.; Rosser, N. J.; Szczucinski, W.; Norman, E. C.; Benjamin, J.; Strzelecki, M.; Long, A. J.; Drewniak, M.

    2013-12-01

    Rock avalanches have unusually high mobility and pose both an immediate hazard, but also produce far-field impacts associated with dam breach, glacier collapse and where they run-out into water, tsunami. Such secondary hazards can often pose higher risks than the original landslide. The prediction of future threats posed by potential rock avalanches is heavily reliant upon understanding of the physics derived from an interpretation of deposits left by previous events, yet drawing comparisons between multiple events is normally challenging as interactions with complex mountainous terrain makes deposits from each event unique. As such numerical models and the interpretation of the underlying physics which govern landslide mobility is commonly case-specific and poorly suited to extrapolation beyond the single events the model is tuned to. Here we present a high-resolution LiDAR and hyperspectral dataset captured across a unique cluster of large rock avalanche source areas and deposits in the Vaigat straight, west central Greenland. Vaigat offers the unprecedented opportunity to model a sample of > 15 rock avalanches of various age sourced from an 80 km coastal escarpment. At Vaigat many of the key variables (topography, geology, post-glacial history) are held constant across all landslides providing the chance to investigate the variations in dynamics and emplacement style related to variable landslide volume, drop-heights, and thinning/spreading over relatively simple, unrestricted run-out zones both onto land and into water. Our data suggest that this region represents excellent preservation of landslide deposits, and hence is well suited to calibrate numerical models of run out dynamics. We use this data to aid the interpretation of deposit morphology, structure lithology and run-out characteristics in more complex settings. Uniquely, we are also able to calibrate our models using a far-field dataset of well-preserved tsunami run-up deposits, resulting from the 21

  10. AvaDrone: An Autonomous Drone for Avalanche Victim Recovery

    OpenAIRE

    Dickensheets, Benjamin D.

    2015-01-01

    For the 179 Americans that are caught in avalanches each year, timely recovery often means the difference between life and death. The goal of this project was to design and build a prototype drone for a system to quickly and automatically locate a buried victim, using an on-board antenna to receive a signal from industry standard transmitting beacons. The design was based on a quad-rotor platform and uses Arduino hardware to receive a beacon signal and navigate the craft. In broad strokes...

  11. Avalanche mapping and related G.I.S. applications in the Catalan Pyrenees

    Science.gov (United States)

    Furdada, G.; Martí, G.; Oller, P.; García, C.; Mases, M.; Vilaplana, J. M.

    1995-11-01

    The Avalanche Risk Project for the Catalan Pyrenees was started in 1986 by the Servei Geològic de Catalunya and the Dpt. de Geologia Dinàmica, Geofísica i Paleontologia. One of the aims of this project is to carry out the “Map of Probable Avalanche Paths”, which is a thematic map in where the land areas affected by avalanches are represented. This information is the result of: 1) aerial photointerpretation, 2) field work: observations of the avalanche effects and interviews to the inhabitants and people who work in the mountain areas. All the descriptive complementary information about each avalanche zone has been stored in a database, thus constituting the avalanche Cadastre. A Geographic Information System (G.I.S.) is an informatic system which can acquire, store and manipulate data that describe the land surface. The Cadastre and Map of Probable Avalanche Paths constitutes a complex document. It is also a basic document to perform further analysis, risk maps and defense actions, so it must have the following characteristics: easy to update, possibility to combine with other documents and to exploit as a source of diverse informations. Therefore, a G.I.S. is the most appropriate tool to store, manage, analyze and restore this avalanche data. The area of the Catalan Pyrenees that has been mapped and automated until now is also presented.

  12. Analysis of inter-event times for avalanches on a conical bead pile with cohesion

    Science.gov (United States)

    Lehman, Susan; Johnson, Nathan; Tieman, Catherine; Wainwright, Elliot

    2015-03-01

    We investigate the critical behavior of a 3D conical bead pile built from uniform 3 mm steel spheres. Beads are added to the pile by dropping them onto the apex one at a time; avalanches are measured through changes in pile mass. We investigate the dynamic response of the pile by recording avalanches from the pile over tens of thousands of bead drops. We have previously shown that the avalanche size distribution follows a power law for beads dropped onto the pile apex from a low drop height. We are now tuning the critical behavior of the system by adding cohesion from a uniform magnetic field and find an increase in both size and number for very large avalanches and decreases in the mid-size avalanches. The resulting bump in the avalanche distribution moves to larger avalanche size as the cohesion in the system is increased. We compare the experimental inter-event time distribution to both the Brownian passage-time and Weibull distributions, and observe a shift from the Weibull to Brownian passage-time as we raise the threshold from measuring time between events of all sizes to time between only the largest system-spanning events. These results are both consistent with those from a mean-field model of slip avalanches in a shear system [Dahmen, Nat Phys 7, 554 (2011)].

  13. Hole-Initiated-Avalanche, Linear-Mode, Single-Photon-Sensitive Avalanche Photodetector with Reduced Excess Noise and Low Dark Count Rate Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A radiation hard, single photon sensitive InGaAs avalanche photodiode (APD) receiver technology will be demonstrated useful for long range space based optical...

  14. Monitoring and modeling ice-rock avalanches from ice-capped volcanoes: A case study of frequent large avalanches on Iliamna Volcano, Alaska

    Science.gov (United States)

    Huggel, C.; Caplan-Auerbach, J.; Waythomas, C.F.; Wessels, R.L.

    2007-01-01

    Iliamna is an andesitic stratovolcano of the Aleutian arc with regular gas and steam emissions and mantled by several large glaciers. Iliamna Volcano exhibits an unusual combination of frequent and large ice-rock avalanches in the order of 1 ?? 106??m3 to 3 ?? 107??m3 with recent return periods of 2-4??years. We have reconstructed an avalanche event record for the past 45??years that indicates Iliamna avalanches occur at higher frequency at a given magnitude than other mass failures in volcanic and alpine environments. Iliamna Volcano is thus an ideal site to study such mass failures and its relation to volcanic activity. In this study, we present different methods that fit into a concept of (1) long-term monitoring, (2) early warning, and (3) event documentation and analysis of ice-rock avalanches on ice-capped active volcanoes. Long-term monitoring methods include seismic signal analysis, and space-and airborne observations. Landsat and ASTER satellite data was used to study the extent of hydrothermally altered rocks and surface thermal anomalies at the summit region of Iliamna. Subpixel heat source calculation for the summit regions where avalanches initiate yielded temperatures of 307 to 613??K assuming heat source areas of 1000 to 25??m2, respectively, indicating strong convective heat flux processes. Such heat flow causes ice melting conditions and is thus likely to reduce the strength at the base of the glacier. We furthermore demonstrate typical seismic records of Iliamna avalanches with rarely observed precursory signals up to two hours prior to failure, and show how such signals could be used for a multi-stage avalanche warning system in the future. For event analysis and documentation, space- and airborne observations and seismic records in combination with SRTM and ASTER derived terrain data allowed us to reconstruct avalanche dynamics and to identify remarkably similar failure and propagation mechanisms of Iliamna avalanches for the past 45??years

  15. Two examples of expert knowledge based system for avalanche forecasting and protection

    Science.gov (United States)

    Buisson, Laurent; Giraud, Gérald

    1995-11-01

    In avalanche modelling and control and in avalanche forecasting, most of the knowledge is based on scientific theory but the experience of specialists (field practitioners, forecasters...) plays a large role. This paper presents two French computer-based systems dedicated to avalanche modelling and control and to avalanche forecasting. They are both based on expert knowledge. ELSA (Etude et Limites de Sites d'Avalanches), is a computer system dedicated to the modelling of the knowledge of avalanche experts and to the integration of new symbolic computer models with classical numerical models. The basic aim of integration is to build a unique computer system incorporating all these models. After a description of the terrain representation, we present the different scenarios that ELSA takes into account. Then, the methods which deal with some phenomena occurring in avalanches are described. The problems involved in the integration of these methods close this first part. MEPRA is an expert system built to create an objective tool in avalanche risk forecasting. This development allowed us to imagine a processing system for 2 of the most important problems in avalanche risk forecasting: representation of the present snow cover characteristics and evaluation of avalanche instability and risk. In this way, mechanics and thermodynamics play a major role in the system. After a punctual validation at the location of a snow weather station and in order to describe the great variability of the snow pack and the avalanche risk in a massif, the MEPRA expert system was connected with a meteorological analysis system, SAFRAN and a numerical model to simulate the snow cover CROCUS. Then, every day, a MEPRA expert analysis is carried out in different locations with different orientations, slopes and altitudes. Its results were used successfully during the Winter Olympic Games of Albertville and by avalanche forecasters during the 92/93 winter season. The daily avalanche risks

  16. The geomorphological effect of cornice fall avalanches in the Longyeardalen valley, Svalbard

    Science.gov (United States)

    Eckerstorfer, M.; Christiansen, H. H.; Rubensdotter, L.; Vogel, S.

    2013-09-01

    The study of snow avalanches and their geomorphological effect in the periglacial parts of the cryosphere is important for enhanced geomorphological process understanding as well as hazard-related studies. Only a few field studies, and particularly few in the High Arctic, have quantified avalanche sedimentation. Snow avalanches are traditionally ranked behind rockfall in terms of their significance for mass-wasting processes of rockslopes. Cornice fall avalanches are at present the most dominant snow avalanche type at two slope systems, called Nybyen and Larsbreen, in the valley Longyeardalen in central Svalbard. Both slope systems are on northwest-facing lee slopes underneath a large summit plateau, with annual cornices forming on the top. High-frequency and magnitude cornice fall avalanching is observed by daily automatic time-lapse photography. In addition, rock debris sedimentation by cornice fall avalanches was measured directly in permanent sediment traps or by snow inventories. The results from a maximum of seven years of measurements in a total of 13 catchments show maximum mean rock debris sedimentation rates ranging from 8.2 to 38.7 kg m-2 at Nybyen, and from 0.8 to 55.4 kg m-2 at Larsbreen. Correspondingly, avalanche fan surfaces accreted from 2.6 to 8.8 mm yr-1 at Nybyen, and from 0.2 to 13.9 mm yr-1 at Larsbreen. This comparably efficient rockslope mass wasting is due to collapsing cornices producing cornice fall avalanches containing large amounts of rock debris throughout the entire winter. The rock debris of different origin stems from the plateau crests, the adjacent free rock face and the transport pathway, accumulating distinct avalanche fans at both slope systems. Cornice fall avalanche sedimentation also contributed to the development of a rock glacier at the Larsbreen site during the Holocene. We have recorded present maximum rockwall retreat rates of 0.9 mm yr-1 at Nybyen, but as much as 6.7 mm yr-1 at Larsbreen, while average Holocene

  17. The geomorphological effect of cornice fall avalanches in the Longyeardalen valley, Svalbard

    Directory of Open Access Journals (Sweden)

    M. Eckerstorfer

    2013-09-01

    Full Text Available The study of snow avalanches and their geomorphological effect in the periglacial parts of the cryosphere is important for enhanced geomorphological process understanding as well as hazard-related studies. Only a few field studies, and particularly few in the High Arctic, have quantified avalanche sedimentation. Snow avalanches are traditionally ranked behind rockfall in terms of their significance for mass-wasting processes of rockslopes. Cornice fall avalanches are at present the most dominant snow avalanche type at two slope systems, called Nybyen and Larsbreen, in the valley Longyeardalen in central Svalbard. Both slope systems are on northwest-facing lee slopes underneath a large summit plateau, with annual cornices forming on the top. High-frequency and magnitude cornice fall avalanching is observed by daily automatic time-lapse photography. In addition, rock debris sedimentation by cornice fall avalanches was measured directly in permanent sediment traps or by snow inventories. The results from a maximum of seven years of measurements in a total of 13 catchments show maximum mean rock debris sedimentation rates ranging from 8.2 to 38.7 kg m−2 at Nybyen, and from 0.8 to 55.4 kg m−2 at Larsbreen. Correspondingly, avalanche fan surfaces accreted from 2.6 to 8.8 mm yr−1 at Nybyen, and from 0.2 to 13.9 mm yr−1 at Larsbreen. This comparably efficient rockslope mass wasting is due to collapsing cornices producing cornice fall avalanches containing large amounts of rock debris throughout the entire winter. The rock debris of different origin stems from the plateau crests, the adjacent free rock face and the transport pathway, accumulating distinct avalanche fans at both slope systems. Cornice fall avalanche sedimentation also contributed to the development of a rock glacier at the Larsbreen site during the Holocene. We have recorded present maximum rockwall retreat rates of 0.9 mm yr−1 at Nybyen, but as much as 6.7 mm yr−1 at

  18. High-speed, high-voltage pulse generation using avalanche transistor

    Science.gov (United States)

    Yong-sheng, Gou; Bai-yu, Liu; Yong-lin, Bai; Jun-jun, Qin; Xiao-hong, Bai; Bo, Wang; Bing-li, Zhu; Chuan-dong, Sun

    2016-05-01

    In this work, the conduction mechanism of avalanche transistors was demonstrated and the operation condition for generating high-speed pulse using avalanche transistors was illustrated. Based on the above analysis, a high-speed and high-voltage pulse (HHP) generating circuit using avalanche transistors was designed, and its working principle and process were studied. To improve the speed of the output pulse, an approach of reducing the rise time of the leading edge is proposed. Methods for selecting avalanche transistor and reducing the parasitic inductance and capacitance of printed circuit board (PCB) were demonstrated. With these instructions, a PCB with a tapered transmission line was carefully designed and manufactured. Output pulse with amplitude of 2 kV and rise time of about 200 ps was realized with this PCB mounted with avalanche transistors FMMT417, indicating the effectiveness of the HHP generating circuit design.

  19. Assessing wet snow avalanche activity using detailed physics based snowpack simulations

    Science.gov (United States)

    Wever, N.; Vera Valero, C.; Fierz, C.

    2016-06-01

    Water accumulating on microstructural transitions inside a snowpack is often considered a prerequisite for wet snow avalanches. Recent advances in numerical snowpack modeling allow for an explicit simulation of this process. We analyze detailed snowpack simulations driven by meteorological stations in three different climate regimes (Alps, Central Andes, and Pyrenees), with accompanying wet snow avalanche activity observations. Predicting wet snow avalanche activity based on whether modeled water accumulations inside the snowpack locally exceed 5-6% volumetric liquid water content is providing a higher prediction skill than using thresholds for daily mean air temperature, or the daily sum of the positive snow energy balance. Additionally, the depth of the maximum water accumulation in the simulations showed a significant correlation with observed avalanche size. Direct output from detailed snow cover models thereby is able to provide a better regional assessment of dangerous slope aspects and potential avalanche size than traditional methods.

  20. Reevaluation of tsunami formation by debris avalanche at Augustine Volcano, Alaska

    Science.gov (United States)

    Waythomas, C.F.

    2000-01-01

    Debris avalanches entering the sea at Augustine Volcano, Alaska have been proposed as a mechanism for generating tsunamis. Historical accounts of the 1883 eruption of the volcano describe 6- to 9-meter-high waves that struck the coastline at English Bay (Nanwalek), Alaska about 80 kilometers east of Augustine Island. These accounts are often cited as proof that volcanigenic tsunamis from Augustine Volcano are significant hazards to the coastal zone of lower Cook Inlet. This claim is disputed because deposits of unequivocal tsunami origin are not evident at more than 50 sites along the lower Cook Inlet coastline where they might be preserved. Shallow water (Augustine Island, in the run-out zone for debris avalanches, limits the size of an avalanche-caused wave. If the two most recent debris avalanches, Burr Point (A.D. 1883) and West Island (Augustine Volcano appears minor, unless a very large debris avalanche occurs at high tide.

  1. Scaling Behavior of Barkhausen Avalanches along the Hysteresis loop in Nucleation-Mediated Magnetization Reversal Process

    Energy Technology Data Exchange (ETDEWEB)

    Im, Mi-Young; Fischer, Peter; Kim, D.-H.; Shin, S.-C.

    2008-10-14

    We report the scaling behavior of Barkhausen avalanches for every small field step along the hysteresis loop in CoCrPt alloy film having perpendicular magnetic anisotropy. Individual Barkhausen avalanche is directly observed utilizing a high-resolution soft X-ray microscopy that provides real space images with a spatial resolution of 15 nm. Barkhausen avalanches are found to exhibit power-law scaling behavior at all field steps along the hysteresis loop, despite their different patterns for each field step. Surprisingly, the scaling exponent of the power-law distribution of Barkhausen avalanches is abruptly altered from 1 {+-} 0.04 to 1.47 {+-} 0.03 as the field step is close to the coercive field. The contribution of coupling among adjacent domains to Barkhausen avalanche process affects the sudden change of the scaling behavior observed at the coercivity-field region on the hysteresis loop of CoCrPt alloy film.

  2. Averaged model for probabilistic coalescence avalanches in two-dimensional emulsions: Insights into uncertainty propagation

    Science.gov (United States)

    Danny Raj, M.; Rengaswamy, R.

    2017-03-01

    A two-dimensional concentrated emulsion exhibits spontaneous rapid destabilization through an avalanche of coalescence events which propagate through the assembly stochastically. We propose a deterministic model to explain the average dynamics of the avalanching process. The dynamics of the avalanche phenomenon is studied as a function of a composite parameter, the decay time ratio, which characterizes the ratio of the propensity of coalescence to cease propagation to that of propagation. When this ratio is small, the avalanche grows autocatalytically to destabilize the emulsion. Using a scaling analysis, we unravel the relation between a local characteristic of the system and a global system wide effect. The anisotropic nature of local coalescence results in a system size dependent transition from nonautocatalytic to autocatalytic behavior. By incorporating uncertainty into the parameters in the model, several possible realizations of the coalescence avalanche are generated. The results are compared with the Monte Carlo simulations to derive insights into how the uncertainty propagates in the system.

  3. Fitting Neuron Models to Spike Trains

    Science.gov (United States)

    Rossant, Cyrille; Goodman, Dan F. M.; Fontaine, Bertrand; Platkiewicz, Jonathan; Magnusson, Anna K.; Brette, Romain

    2011-01-01

    Computational modeling is increasingly used to understand the function of neural circuits in systems neuroscience. These studies require models of individual neurons with realistic input–output properties. Recently, it was found that spiking models can accurately predict the precisely timed spike trains produced by cortical neurons in response to somatically injected currents, if properly fitted. This requires fitting techniques that are efficient and flexible enough to easily test different candidate models. We present a generic solution, based on the Brian simulator (a neural network simulator in Python), which allows the user to define and fit arbitrary neuron models to electrophysiological recordings. It relies on vectorization and parallel computing techniques to achieve efficiency. We demonstrate its use on neural recordings in the barrel cortex and in the auditory brainstem, and confirm that simple adaptive spiking models can accurately predict the response of cortical neurons. Finally, we show how a complex multicompartmental model can be reduced to a simple effective spiking model. PMID:21415925

  4. Risks and benefits of generic antiepileptic drugs.

    Science.gov (United States)

    Gómez-Alonso, Juan; Kanner, Andrés M; Herranz, José Luis; Molins, Albert; Gil-Nagel, Antonio

    2008-11-01

    In most therapeutic areas, prescribing generic drugs seems to lower costs without sacrificing efficacy. The use of generic drugs for treating epilepsy may, however, be more controversial. A systematic review of the literature on generic antiepileptic drugs has been carried out based primarily on a bibliographical search in the Medline database. Published studies are usually of a descriptive nature and are sometimes based on generic drugs that were approved in times when regulatory agency requirements were not as strict as they are now. Experts claim that a change in pharmaceutical formulations could cause seizure recurrence in cases that had been successfully controlled in the past, with severe effects on patients. Meanwhile, several health organizations have provided inconsistent recommendations on the use of generic antiepileptic drugs. In order to obtain scientific evidence on the potential risks and benefits of interchanging branded and generic antiepileptic drugs, high methodological comparative studies are necessary. These studies could bring consensus about the role of generic drugs for treating epilepsy.

  5. Generic physical protection logic trees

    Energy Technology Data Exchange (ETDEWEB)

    Paulus, W.K.

    1981-10-01

    Generic physical protection logic trees, designed for application to nuclear facilities and materials, are presented together with a method of qualitative evaluation of the trees for design and analysis of physical protection systems. One or more defense zones are defined where adversaries interact with the physical protection system. Logic trees that are needed to describe the possible scenarios within a defense zone are selected. Elements of a postulated or existing physical protection system are tagged to the primary events of the logic tree. The likelihood of adversary success in overcoming these elements is evaluated on a binary, yes/no basis. The effect of these evaluations is propagated through the logic of each tree to determine whether the adversary is likely to accomplish the end event of the tree. The physical protection system must be highly likely to overcome the adversary before he accomplishes his objective. The evaluation must be conducted for all significant states of the site. Deficiencies uncovered become inputs to redesign and further analysis, closing the loop on the design/analysis cycle.

  6. Generic Magnetic Fusion Reactor Revisited

    Science.gov (United States)

    Sheffield, John; Milora, Stanley

    2015-11-01

    The original Generic Magnetic Fusion Reactor paper was published in 1986. This update describes what has changed in 30 years. Notably, the construction of ITER is providing important benchmark numbers for technologies and costs. In addition, we use a more conservative neutron wall flux and fluence. But these cost-increasing factors are offset by greater optimism on the thermal-electric conversion efficiency and potential availability. The main examples show the cost of electricity (COE) as a function of aspect ratio and neutron flux to the first wall. The dependence of the COE on availability, thermo-electric efficiency, electrical power output, and the present day's low interest rates is also discussed. Interestingly, at fixed aspect ratio there is a shallow minimum in the COE at neutron flux around 2.5 MW/m2. The possibility of operating with only a small COE penalty at even lower wall loadings (to 1.0 MW/m2 at larger plant size) and the use of niobium-titanium coils are also investigated. J. Sheffield was supported by ORNL subcontract 4000088999 with the University of Tennessee.

  7. Validating numerical simulations of snow avalanches using dendrochronology: the Cerro Ventana event in Northern Patagonia, Argentina

    Directory of Open Access Journals (Sweden)

    A. Casteller

    2008-05-01

    Full Text Available The damage caused by snow avalanches to property and human lives is underestimated in many regions around the world, especially where this natural hazard remains poorly documented. One such region is the Argentinean Andes, where numerous settlements are threatened almost every winter by large snow avalanches. On 1 September 2002, the largest tragedy in the history of Argentinean mountaineering took place at Cerro Ventana, Northern Patagonia: nine persons were killed and seven others injured by a snow avalanche. In this paper, we combine both numerical modeling and dendrochronological investigations to reconstruct this event. Using information released by local governmental authorities and compiled in the field, the avalanche event was numerically simulated using the avalanche dynamics programs AVAL-1D and RAMMS. Avalanche characteristics, such as extent and date were determined using dendrochronological techniques. Model simulation results were compared with documentary and tree-ring evidences for the 2002 event. Our results show a good agreement between the simulated projection of the avalanche and its reconstructed extent using tree-ring records. Differences between the observed and the simulated avalanche, principally related to the snow height deposition in the run-out zone, are mostly attributed to the low resolution of the digital elevation model used to represent the valley topography. The main contributions of this study are (1 to provide the first calibration of numerical avalanche models for the Patagonian Andes and (2 to highlight the potential of Nothofagus pumilio tree-ring records to reconstruct past snow-avalanche events in time and space. Future research should focus on testing this combined approach in other forested regions of the Andes.

  8. Validating numerical simulations of snow avalanches using dendrochronology: the Cerro Ventana event in Northern Patagonia, Argentina

    Science.gov (United States)

    Casteller, A.; Christen, M.; Villalba, R.; Martínez, H.; Stöckli, V.; Leiva, J. C.; Bartelt, P.

    2008-05-01

    The damage caused by snow avalanches to property and human lives is underestimated in many regions around the world, especially where this natural hazard remains poorly documented. One such region is the Argentinean Andes, where numerous settlements are threatened almost every winter by large snow avalanches. On 1 September 2002, the largest tragedy in the history of Argentinean mountaineering took place at Cerro Ventana, Northern Patagonia: nine persons were killed and seven others injured by a snow avalanche. In this paper, we combine both numerical modeling and dendrochronological investigations to reconstruct this event. Using information released by local governmental authorities and compiled in the field, the avalanche event was numerically simulated using the avalanche dynamics programs AVAL-1D and RAMMS. Avalanche characteristics, such as extent and date were determined using dendrochronological techniques. Model simulation results were compared with documentary and tree-ring evidences for the 2002 event. Our results show a good agreement between the simulated projection of the avalanche and its reconstructed extent using tree-ring records. Differences between the observed and the simulated avalanche, principally related to the snow height deposition in the run-out zone, are mostly attributed to the low resolution of the digital elevation model used to represent the valley topography. The main contributions of this study are (1) to provide the first calibration of numerical avalanche models for the Patagonian Andes and (2) to highlight the potential of textit{Nothofagus pumilio} tree-ring records to reconstruct past snow-avalanche events in time and space. Future research should focus on testing this combined approach in other forested regions of the Andes.

  9. Comparison of seismic and infrasound wave fields generated by snow avalanches

    Science.gov (United States)

    Suriñach, Emma; Tapia, Mar; Pérez-Guillén, Cristina; Khazaradze, Giorgi; Roig, Pere

    2016-04-01

    Snow avalanches are a source of waves that are transmitted through the ground and the air. These wave fields are detected by seismic and infrasound sensors. During the winter seasons 2008 -2016, a good quality database of avalanches was obtained at the VdlS test site with an accurate instrumentation. These avalanches were both natural and artificially triggered and were of varying types and sizes. Distances involved were 0.5 -3 km. Seismic signals were acquired using three seismometers (3-components, 1Hz) spaced 600 m apart along the avalanche track. One infrasound sensor (0.1Hz) and one seismometer (3-components, 1Hz) were placed one next to the other with a common base of time on the slope opposite the path. The database obtained enables us to compare the different signals generated. Differences in the frequency content and shape of the signals depending on the type and size of the avalanche are detected. A clear evolution of the recorded seismic signals along the path is observed. The cross correlation of the infrasound and seismic signals generated by the avalanches allows us to determine different characteristics for powder, transitional and wet avalanches concerning their wave fields. The joint analysis of infrasound and seismic waves enables us to obtain valuable information about the internal parts of the avalanche as a source of each wave field. This study has repercussions on avalanche dynamics and on the selection of the appropriate avalanche detection system. This study is supported by the Spanish Ministry of Science and Innovation project CHARMA: CHAracterization and ContRol of MAss Movements. A Challenge for Geohazard Mitigation (CGL2013-40828-R), and RISKNAT group (2014GR/1243).

  10. Granular avalanches in a two-dimensional rotating drum with imposed vertical vibration.

    Science.gov (United States)

    Amon, Daniel L; Niculescu, Tatiana; Utter, Brian C

    2013-07-01

    We present statistics on granular avalanches in a rotating drum with and without imposed vertical vibration. The experiment consists of a quasi-two-dimensional, vertical drum containing pentagonal particles and rotated at a constant angular velocity. The drum rests on an electromagnetic shaker to allow vibration of the assembly as it rotates. We measure time series of the slope of the interface and find that the critical angle for slope failure θ(c) and the resulting angle of repose θ(r) are broadly distributed with an approximate power-law distribution of avalanches θ(c)-θ(r) for large avalanches. The faceted pentagonal grains used lead to significant interlocking with critical and repose angles (θ(c)≈45° and θ(r)≈39°) larger than experiments using spherical grains, even with vibration, and avalanche magnitudes correlated with the prior build-up and anti-correlated with the prior avalanche. We find that the stability of the assembly increases with small vibrations and is destabilized at vibration amplitudes above a dimensionless acceleration (peak acceleration divided by acceleration due to gravity) of Γ=0.2. We also study history dependence of the avalanches by periodically oscillating the drum to compare the initial avalanche upon reversal of shear to steady-state distributions for avalanches during continuous rotation. We observe history dependence as an initial decrease in critical angle upon reversal of the drum rotation direction, indicating that a texture is induced to resist continued shear such that the surface is weaker to reversals in shear direction. Memory of this history is removed by sufficient external vibration (Γ≥0.8), which leads to compaction and relaxation of the surface layer grains responsible for avalanching dynamics, as initial and steady-state avalanche distributions become indistinguishable.

  11. Relativistic electron avalanches as a thunderstorm discharge competing with lightning.

    Science.gov (United States)

    Kelley, Nicole A; Smith, David M; Dwyer, Joseph R; Splitt, Michael; Lazarus, Steven; Martinez-McKinney, Forest; Hazelton, Bryna; Grefenstette, Brian; Lowell, Alexander; Rassoul, Hamid K

    2015-08-12

    Gamma-ray 'glows' are long duration (seconds to tens of minutes) X-ray and gamma-ray emission coming from thunderclouds. Measurements suggest the presence of relativistic runaway electron avalanches (RREA), the same process underlying terrestrial gamma-ray flashes. Here we demonstrate that glows are relatively a common phenomena near the tops of thunderstorms, when compared with events such as terrestrial gamma-ray flashes. Examining the strongest glow measured by the airborne detector for energetic emissions, we show that this glow is measured near the end of a downward RREA, consistent with occurring between the upper positive charge layer and the negative screening layer above it. The glow discharges the upper positive layer by ≥9.6 mA, strong enough to be an important charging mechanism of the storm. For this glow, the gamma-ray flux observed is close to the value at which relativistic feedback processes become important, with an avalanche multiplication factor of 4,500.

  12. Silicon Avalanche Pixel Sensor for High Precision Tracking

    CERN Document Server

    D'Ascenzo, N; Moon, C S; Morsani, F; Ratti, L; Saveliev, V; Navarro, A Savoy; Xie, Q

    2013-01-01

    The development of an innovative position sensitive pixelated sensor to detect and measure with high precision the coordinates of the ionizing particles is proposed. The silicon avalanche pixel sensors (APiX) is based on the vertical integration of avalanche pixels connected in pairs and operated in coincidence in fully digital mode and with the processing electronics embedded on the chip. The APiX sensor addresses the need to minimize the material budget and related multiple scattering effects in tracking systems requiring a high spatial resolution in the presence of a large occupancy. The expected operation of the new sensor features: low noise, low power consumption and suitable radiation tolerance. The APiX device provides on-chip digital information on the position of the coordinate of the impinging charged particle and can be seen as the building block of a modular system of pixelated arrays, implementing a sparsified readout. The technological challenges are the 3D integration of the device under CMOS ...

  13. An Atomically Layered InSe Avalanche Photodetector.

    Science.gov (United States)

    Lei, Sidong; Wen, Fangfang; Ge, Liehui; Najmaei, Sina; George, Antony; Gong, Yongji; Gao, Weilu; Jin, Zehua; Li, Bo; Lou, Jun; Kono, Junichiro; Vajtai, Robert; Ajayan, Pulickel; Halas, Naomi J

    2015-05-13

    Atomically thin photodetectors based on 2D materials have attracted great interest due to their potential as highly energy-efficient integrated devices. However, photoinduced carrier generation in these media is relatively poor due to low optical absorption, limiting device performance. Current methods for overcoming this problem, such as reducing contact resistances or back gating, tend to increase dark current and suffer slow response times. Here, we realize the avalanche effect in a 2D material-based photodetector and show that avalanche multiplication can greatly enhance the device response of an ultrathin InSe-based photodetector. This is achieved by exploiting the large Schottky barrier formed between InSe and Al electrodes, enabling the application of a large bias voltage. Plasmonic enhancement of the photosensitivity, achieved by patterning arrays of Al nanodisks onto the InSe layer, further improves device efficiency. With an external quantum efficiency approaching 866%, a dark current in the picoamp range, and a fast response time of 87 μs, this atomic layer device exhibits multiple significant advances in overall performance for this class of devices.

  14. pSNOWPACK: a forecasting tool for avalanche warning services

    Directory of Open Access Journals (Sweden)

    S. Bellaire

    2011-08-01

    Full Text Available Avalanche danger is often estimated based on snow cover stratigraphy and snow stability data. In Canada, single forecasting regions are very large (>50 000 km2 and snow cover data are often not available. To provide additional information on the snow cover and its seasonal evolution the Swiss snow cover model SNOWPACK was therefore coupled with a regional weather forecasting model GEM15. We assess the capability of this model chain (pSNOWPACK to forecast three key factors of snow cover instability at a single point: new snow amounts, surface hoar formation and crust formation. The output of GEM15 was compared to meteorological data from Mt. Fidelity, British Columbia, Canada, for five winters between 2005 and 2010. Forecasted precipitation amounts were generally over-estimated. The forecasted data were therefore filtered and used as input for the snow cover model. Comparison between the model output and manual observations showed that after pre-processing the input data the snow depth, new snow events and amounts were well modelled. Relevant critical layers, i.e. melt-freeze crusts and surface hoar layers were reproduced. Overall, the model chain pSNOWPACK shows promising potential as a forecasting tool for avalanche warning services in Canadian data sparse areas and could thus well be applied to similarly large regions elsewhere.

  15. Supershort avalanche electron beam in SF6 and krypton

    Science.gov (United States)

    Zhang, Cheng; Tarasenko, Victor F.; Gu, Jianwei; Baksht, Evgeni Kh.; Beloplotov, Dmitry V.; Burachenko, Alexander G.; Yan, Ping; Lomaev, Mikhail I.; Shao, Tao

    2016-03-01

    Runaway electrons play an important role in the avalanche formation in nanosecond- and subnanosecond- pulse discharges. In this paper, characteristics of a supershort avalanche electron beam (SAEB) generated at the subnanosecond and nanosecond breakdown in sulfur hexafluoride (SF6 ) in an inhomogeneous electric field were studied. One pulser operated at negative polarity with voltage pulse amplitude of ˜130 kV and rise time of 0.3 ns. The other pulser operated at negative polarity with voltage pulse amplitude of 70 kV and rise time of ˜1.6 ns . SAEB parameters in SF6 are compared with those obtained in krypton (Kr), nitrogen (N2 ), air, and mixtures of SF6 with krypton or nitrogen. Experimental results showed that SAEB currents appeared during the rise-time of the voltage pulse for both pulsers. Moreover, amplitudes of the SAEB current in SF6 and Kr approximately ranged from several to tens of milliamps at atmospheric pressure, which were smaller than those in N2 and air (ranging from hundreds of milliamps to several amperes). Furthermore, the concentration of SF6 additive could significantly reduce the SAEB current in N2-SF6 mixture, but it slightly affected the SAEB current in Kr -SF6 mixture because of the atomic/molecular ionization cross section of the gas had a much greater impact on the SAEB current rather than the electronegativity.

  16. Avalanche Structure in the Kadanoff Sand Pile Model

    CERN Document Server

    Perrot, Kevin

    2011-01-01

    Sand pile models are dynamical systems emphasizing the phenomenon of Self Organized Criticality (SOC). From N stacked grains, iterating evolution rules leads to some critical configuration where a small disturbance has deep consequences on the system, involving numerous steps of grain fall. Physicists L. Kadanoff et al. inspire KSPM, a model presenting a sharp SOC behavior, extending the well known Sand Pile Model. In KSPM with parameter D we start from a pile of N stacked grains and apply the rule: D-1 grains can fall from column i onto the D-1 adjacent columns to the right if the difference of height between columns i and i+1 is greater or equal to D. We propose an iterative study of KSPM evolution where one single grain addition is repeated on a heap of sand. The sequence of grain falls following a single grain addition is called an avalanche. From a certain column precisely studied for D=3, we provide a plain process describing avalanches.

  17. Characterization of midwave infrared InSb avalanche photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Abautret, J., E-mail: johan.abautret@ies.univ-montp2.fr; Evirgen, A. [Université Montpellier, IES, UMR 5214, F-34095 Montpellier (France); CNRS, IES, UMR 5214, F-34095 Montpellier (France); SOFRADIR, BP 21, 38113 Veurey-Voroize (France); Perez, J. P.; Christol, P. [Université Montpellier, IES, UMR 5214, F-34095 Montpellier (France); CNRS, IES, UMR 5214, F-34095 Montpellier (France); Rothman, J. [CEA-LETI, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Cordat, A. [SOFRADIR, BP 21, 38113 Veurey-Voroize (France)

    2015-06-28

    This paper focuses on the InSb material potential for the elaboration of Avalanche Photodiodes (APD) for high performance infrared imaging applications, both in passive or active mode. The first InSb electron-APD structure was grown by molecular beam epitaxy, processed and electrically characterized. The device performances are at the state of the art for the InSb epi-diode technology, with a dark current density J(−50 mV) = 32 nA/cm{sup 2} at 77 K. Then, a pure electron injection was performed, and an avalanche gain, increasing exponentially, was observed with a gain value near 3 at −4 V at 77 K. The Okuto–Crowell model was used to determine the electron ionization coefficient α(E) in InSb, and the InSb gain behavior is compared with the one of InAs and MCT APDs.

  18. Scaling of avalanche queues in directed dissipative sandpiles

    Science.gov (United States)

    Tadic; Priezzhev

    2000-09-01

    Using numerical simulations and analytical methods we study a two-dimensional directed sandpile automaton with nonconservative random defects (concentration c) and varying driving rate r. The automaton is driven only at the top row and driving rate is measured by the number of added particles per time step of avalanche evolution. The probability distribution of duration of elementary avalanches at zero driving rate is exactly given by P1(t,c)=t(-3/2) exp[t ln(1-c)]. For driving rates in the interval 0 server queue in the queue theory. We study scaling properties of the busy period and dissipated energy of sequences of noninterrupted activity. In the limit c-->0 and varying linear system size Lqueues are characterized by a multifractal scaling and we determine the corresponding spectral functions. For L>1/c increasing the driving rate somewhat compensates for the energy losses at defects above the line r approximately sqrt[c]. The scaling exponents of the distributions in this region of phase diagram vary approximately linearly with the driving rate. Using properties of recurrent states and the probability theory we determine analytically the exact upper bound of the probability distribution of busy periods. In the case of conservative dynamics c=0 the probability of a continuous flow increases as F(infinity) approximately r(2) for small driving rates.

  19. Enhanced Avalanche Ionization by RF Fields Creating an Ultracold Plasma

    Science.gov (United States)

    Robinson, M. P.; Gallagher, T. F.; Laburthe Tolra, B.; Pillet, P.

    2001-05-01

    Ultracold plasmas have been shown to evolve from initially frozen Rydberg gases held in magneto-optical traps.(M.P. Robinson, B. Laburthe Tolra, Michael W. Noel, T.F. Gallagher, and P. Pillet, Phys. Rev. Lett. 85), 4466 (2000) We report the enhancement of the avalanche ionization process by application of radiofrequency fields. An initial slow ionization rate is observed in the Rydberg sample due to black body ionization and ionizing collisions with hot Rydberg atoms. This produces an overall posititve space charge of cold ions as the hot electrons leave the sample. Once a threshold density of positive charges is built up, the hot electrons become trapped to the sample, leading to avalance ionization due to electron-Rydberg collisions. The mechanism of the ionization remains unclear. However, the application of radiofrequency fields, in the 1 V/cm, 100 MHz range, dramatically enhances the rate of avalanche ionization without changing the threshold density at which it occurs. Apparently, the limiting parameter is the rate of collisional ionization of Rydberg atoms by electrons.

  20. Generic substitution, financial interests, and imperfect agency.

    Science.gov (United States)

    Rischatsch, Maurus; Trottmann, Maria; Zweifel, Peter

    2013-06-01

    Policy makers around the world seek to encourage generic substitution. In this paper, the importance of prescribing physicians' imperfect agency is tested using the fact that some Swiss jurisdictions allow physicians to dispense drugs on their own account (physician dispensing, PD) while others disallow it. We estimate a model of physician drug choice with the help of drug claim data, finding a significant positive association between PD and the use of generics. While this points to imperfect agency, generics are prescribed more often to patients with high copayments or low incomes.

  1. Morphometric and meteorological controls of snow avalanche distribution and activity at hillslopes in steep mountain valleys in western Norway

    Science.gov (United States)

    Laute, Katja; Beylich, Achim A.

    2013-04-01

    Snow avalanches are common phenomena in Norway due to the interactions between the prevalent climatic factors and local topography. Research on snow avalanches provides insights into possible effects of predicted climate change on avalanche activity and connected sediment transport in mountain areas. This study focuses on (i) controlling factors of avalanche distribution and activity, and (ii) their relative importance regarding mass transfers in two steep, parabolic-shaped and glacier-connected tributary valleys (Erdalen and Bødalen) in western Norway. Mapping of distribution, extension and run-out distances of avalanches is combined with spatial data analysis of morphometric controls. Based on correlation of climate data with monitored avalanche events the timing and frequency of avalanches is explored and debris mass transfer on hillslopes caused by avalanches is estimated. The denudative effect of snow avalanches occurs in two steps: firstly throughout erosion directly on the surface of the rockwall and secondly due to their transport ability which causes significant remobilization and transport of available debris further downslope. The spatial distribution of snow avalanches depends on the valley orientation, slope aspect and rockwall morphometry. Especially distinct laterally convex-shaped leeside upper rockwall areas allow a high accumulation rate of snow during winter which is then released as avalanches during spring. The timing and frequency of avalanches in both valleys depend mainly on snowfall intensity, periods with strong winds combined with a stable wind direction or sudden air temperature changes. Snow avalanche activity leads in some valley areas to significant hillslope-channel coupling because debris is transported far enough by avalanches to reach channels. Snow avalanches represent one of the dominant denudational processes and have a high relative importance regarding mass transfer within the sedimentary budgets of the entire valleys.

  2. Connectivity and dynamics of neuronal networks as defined by the shape of individual neurons

    Energy Technology Data Exchange (ETDEWEB)

    Ahnert, Sebastian E [Theory of Condensed Matter, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom); A N Travencolo, Bruno; Costa, Luciano da Fontoura [Instituto de FIsica de Sao Carlos, Universidade de Sao Paulo, Av. Trabalhador Sao Carlense 400, Caixa Postal 369, CEP 13560-970, Sao Carlos, Sao Paulo (Brazil)], E-mail: luciano@if.sc.usp.br

    2009-10-15

    Biological neuronal networks constitute a special class of dynamical systems, as they are formed by individual geometrical components, namely the neurons. In the existing literature, relatively little attention has been given to the influence of neuron shape on the overall connectivity and dynamics of the emerging networks. The current work addresses this issue by considering simplified neuronal shapes consisting of circular regions (soma/axons) with spokes (dendrites). Networks are grown by placing these patterns randomly in the two-dimensional (2D) plane and establishing connections whenever a piece of dendrite falls inside an axon. Several topological and dynamical properties of the resulting graph are measured, including the degree distribution, clustering coefficients, symmetry of connections, size of the largest connected component, as well as three hierarchical measurements of the local topology. By varying the number of processes of the individual basic patterns, we can quantify relationships between the individual neuronal shape and the topological and dynamical features of the networks. Integrate-and-fire dynamics on these networks is also investigated with respect to transient activation from a source node, indicating that long-range connections play an important role in the propagation of avalanches.

  3. Generic tacrolimus in solid organ transplantation.

    Science.gov (United States)

    Taube, D; Jones, G; O'Beirne, J; Wennberg, L; Connor, A; Rasmussen, A; Backman, L

    2014-05-01

    The availability of a wide range of immunosuppressive therapies has revolutionized the management of patients who have undergone solid organ transplantation (SOT). However, the cost of immunosuppressive drugs remains high. This situation has led to the development of generic equivalents, which are similar in quality, safety, and efficacy to their approved innovator drugs. There are data available for three generic brands, tacrolimus (Intas), tacrolimus (PharOS), and tacrolimus (Sandoz). Bioequivalence has been demonstrated for generic tacrolimus (Sandoz) within a narrow therapeutic range to its innovator tacrolimus drug (Prograf) in both healthy volunteers and kidney transplant patients. Clinical experience with this generic tacrolimus formulation has also been established in both de novo and conversion patients who have undergone kidney and liver transplantation, as well as in conversion of other SOT patients, including lung and heart recipients.

  4. Are generic drugs really inferior medicines?

    Science.gov (United States)

    Moore, N; Berdaï, D; Bégaud, B

    2010-09-01

    In this issue Gagne et al. report an elegant case-crossover study of seizures in patients on antiepileptic drugs. They found that a dispensation episode approximately triples the risk of having a seizure within 21 days, but the risk is not statistically different whether the dispensation was of the same brand-name or generic drug as previously used or a switch from brand-name to a generic or from a generic to a brand name. The cause of the seizure might be a delay in taking medication or late redispensation, among others, but apparently the nature of the product dispensed is not relevant in this study; this may alleviate some of the concerns about generic drugs and epilepsy.

  5. Generic substitution: issues for problematic drugs.

    Science.gov (United States)

    Henderson, J D; Esham, R H

    2001-01-01

    The methodology and criteria for bioequivalence testing have been firmly established by the Food and Drug Administration (FDA). For certain drugs with a narrow therapeutic index (e.g., digoxin, levothyroxine, warfarin), generic substitution may not be advisable or even allowable, depending on the substitution laws of individual states. Digoxin and levothyroxine tablets are examples of drugs for which no New Drug Applications (NDAs) currently exist. However, commercially available generic products for both of these drugs have not been determined by the FDA to be therapeutically equivalent to the innovator products. Generic versions of warfarin have been approved by the FDA as being therapeutically equivalent to the innovator products, as have generic versions of the rescue inhaler albuterol. Yet, misinformation and myths persist regarding the adequacy and proven reliability of the FDA's determination of bioequivalence for these products.

  6. Impacts of Generic Competition and Benefit Management...

    Data.gov (United States)

    U.S. Department of Health & Human Services — According to findings reported in Impacts of Generic Competition and Benefit Management Practices on Spending for Prescription Drugs - Evidence from Medicares Part D...

  7. Impacts of Generic Competition and Benefit Management...

    Data.gov (United States)

    U.S. Department of Health & Human Services — According to findings reported in Impacts of Generic Competition and Benefit Management Practices on Spending for Prescription Drugs - Evidence from Medicares Part D...

  8. Generic User Process Interface for Event Generators

    CERN Document Server

    Boos, E; Giele, W T; Hinchliffe, Ian; Huston, J; Ilyin, V A; Kanzaki, J; Kato, K; Kurihara, Y; Lönnblad, L; Mangano, Michelangelo L; Mrenna, S; Paige, Frank E; Richter-Was, Elzbieta; Seymour, Michael H; Sjöstrand, Torbjörn; Webber, Bryan R; Zeppenfeld, Dieter

    2001-01-01

    Generic Fortran common blocks are presented for use by High Energy Physics event generators for the transfer of event configurations from parton level generators to showering and hadronization event generators.

  9. [Mirror neurons].

    Science.gov (United States)

    Rubia Vila, Francisco José

    2011-01-01

    Mirror neurons were recently discovered in frontal brain areas of the monkey. They are activated when the animal makes a specific movement, but also when the animal observes the same movement in another animal. Some of them also respond to the emotional expression of other animals of the same species. These mirror neurons have also been found in humans. They respond to or "reflect" actions of other individuals in the brain and are thought to represent the basis for imitation and empathy and hence the neurobiological substrate for "theory of mind", the potential origin of language and the so-called moral instinct.

  10. Generic methodology for calibrating profiling nacelle lidars

    DEFF Research Database (Denmark)

    Borraccino, Antoine; Courtney, Michael; Wagner, Rozenn

    is calibrated rather than a reconstructed parameter. This contribution presents a generic methodology to calibrate profiling nacelle-mounted lidars. The application of profiling lidars to wind turbine power performance and corresponding need for calibration procedures is introduced in relation to metrological...... standards. Further, two different calibration procedure concepts are described along with their strengths and weaknesses. The main steps of the generic methodology are then explained and illustrated by calibration results from two types of profiling lidars. Finally, measurement uncertainty assessment...

  11. On the genericity of spacetime singularities

    Indian Academy of Sciences (India)

    Pankaj S Joshi

    2007-07-01

    We consider here the genericity aspects of spacetime singularities that occur in cosmology and in gravitational collapse. The singularity theorems (that predict the occurrence of singularities in general relativity) allow the singularities of gravitational collapse to be either visible to external observers or covered by an event horizon of gravity. It is shown that the visible singularities that develop as final states of spherical collapse are generic. Some consequences of this fact are discussed.

  12. Generic Dynamic Scaling in Kinetic Roughening

    OpenAIRE

    Ramasco, José J.; López, Juan M.; Rodríguez, Miguel A.

    2000-01-01

    We study the dynamic scaling hypothesis in invariant surface growth. We show that the existence of power-law scaling of the correlation functions (scale invariance) does not determine a unique dynamic scaling form of the correlation functions, which leads to the different anomalous forms of scaling recently observed in growth models. We derive all the existing forms of anomalous dynamic scaling from a new generic scaling ansatz. The different scaling forms are subclasses of this generic scali...

  13. On Phases of Generic Toric Singularities

    CERN Document Server

    Sarkar, Tapobrata

    2007-01-01

    We systematically study the phases of generic toric singularities, using methods initiated in hep-th/0612046. These correspond to Gauged Linear Sigma Models with arbitrary charges. We show that complete information about generic $U(1)^r$ GLSMs can be obtained by studying the GLSM Lagrangian, appropriately modified in the different phases of the theory. This can be used to study the different phases of $L^{a,b,c}$ spaces and their non-supersymmetric counterparts.

  14. Developing neuronal networks: self-organized criticality predicts the future.

    Science.gov (United States)

    Pu, Jiangbo; Gong, Hui; Li, Xiangning; Luo, Qingming

    2013-01-01

    Self-organized criticality emerged in neural activity is one of the key concepts to describe the formation and the function of developing neuronal networks. The relationship between critical dynamics and neural development is both theoretically and experimentally appealing. However, whereas it is well-known that cortical networks exhibit a rich repertoire of activity patterns at different stages during in vitro maturation, dynamical activity patterns through the entire neural development still remains unclear. Here we show that a series of metastable network states emerged in the developing and "aging" process of hippocampal networks cultured from dissociated rat neurons. The unidirectional sequence of state transitions could be only observed in networks showing power-law scaling of distributed neuronal avalanches. Our data suggest that self-organized criticality may guide spontaneous activity into a sequential succession of homeostatically-regulated transient patterns during development, which may help to predict the tendency of neural development at early ages in the future.

  15. Comparison of seismic and infrasonic avalanche detection systems: first results from the Dischma valley above Davos, Switzerland

    Science.gov (United States)

    van Herwijnen, Alec; Schweizer, Jürg; Marchetti, Emanuele; Ripepe, Maurizio

    2016-04-01

    The reliable detection of snow avalanches is of crucial importance to better understand triggering mechanisms, identify possible precursors, or improve avalanche forecasting. An avalanche flowing down a mountain is a moving source well coupled with the ground and the atmosphere, which generates seismic and infrasonic waves. Seismic signals are produced by the impact of the dense flowing snow mass on the ground or on obstacles. Infrasonic signals are generated by rapidly accelerating snow particles in the turbulent snow-air flow (powder cloud) of the avalanche. Seismic and infrasound are therefore used as monitoring systems for the remote detection of snow avalanches. However, while it is well known that large avalanches can be detected by both systems over considerable distances, for smaller avalanches the threshold in terms of detection resolution is still unclear. During the winter of 2015-2016 we therefore installed a seismic and an infrasound array in the Dischma valley above Davos, Switzerland. Both arrays were deployed within a distance of 500 m to each other. Several automatic cameras were also installed to provide additional information on the location, type (dry or wet) and size of the avalanches released. The overall goal is to assess the limits of both monitoring systems in terms of avalanche type and size and to assess their resolution to locate avalanches in real-time. We present preliminary results that allow us to define detection capabilities of both methods depending on source-receiver distance as well as the type of the avalanche.

  16. Low dose digital X-ray imaging with avalanche amorphous selenium

    Science.gov (United States)

    Scheuermann, James R.; Goldan, Amir H.; Tousignant, Olivier; Léveillé, Sébastien; Zhao, Wei

    2015-03-01

    Active Matrix Flat Panel Imagers (AMFPI) based on an array of thin film transistors (TFT) have become the dominant technology for digital x-ray imaging. In low dose applications, the performance of both direct and indirect conversion detectors are limited by the electronic noise associated with the TFT array. New concepts of direct and indirect detectors have been proposed using avalanche amorphous selenium (a-Se), referred to as high gain avalanche rushing photoconductor (HARP). The indirect detector utilizes a planar layer of HARP to detect light from an x-ray scintillator and amplify the photogenerated charge. The direct detector utilizes separate interaction (non-avalanche) and amplification (avalanche) regions within the a-Se to achieve depth-independent signal gain. Both detectors require the development of large area, solid state HARP. We have previously reported the first avalanche gain in a-Se with deposition techniques scalable to large area detectors. The goal of the present work is to demonstrate the feasibility of large area HARP fabrication in an a-Se deposition facility established for commercial large area AMFPI. We also examine the effect of alternative pixel electrode materials on avalanche gain. The results show that avalanche gain > 50 is achievable in the HARP layers developed in large area coaters, which is sufficient to achieve x-ray quantum noise limited performance down to a single x-ray photon per pixel. Both chromium (Cr) and indium tin oxide (ITO) have been successfully tested as pixel electrodes.

  17. Multiplication theory for dynamically biased avalanche photodiodes: new limits for gain bandwidth product.

    Science.gov (United States)

    Hayat, Majeed M; Ramirez, David A

    2012-03-26

    Novel theory is developed for the avalanche multiplication process in avalanche photodiodes (APDs) under time-varying reverse-biasing conditions. Integral equations are derived characterizing the statistics of the multiplication factor and the impulse-response function of APDs, as well as their breakdown probability, all under the assumption that the electric field driving the avalanche process is time varying and spatially nonuniform. Numerical calculations generated by the model predict that by using a bit-synchronous sinusoidal biasing scheme to operate the APD in an optical receiver, the pulse-integrated gain-bandwidth product can be improved by a factor of 5 compared to the same APD operating under the conventional static biasing. The bit-synchronized periodic modulation of the electric field in the multiplication region serves to (1) produce large avalanche multiplication factors with suppressed avalanche durations for photons arriving in the early phase of each optical pulse; and (2) generate low avalanche gains and very short avalanche durations for photons arriving in the latter part of each optical pulse. These two factors can work together to reduce intersymbol interference in optical receivers without sacrificing sensitivity.

  18. Antimonide-based Geiger-mode avalanche photodiodes for SWIR and MWIR photon counting

    Science.gov (United States)

    Duerr, Erik K.; Manfra, Michael J.; Diagne, Mohamed A.; Bailey, Robert J.; Zayhowski, John J.; Donnelly, Joseph P.; Connors, Michael K.; Grzesik, Michael J.; Turner, George W.

    2010-04-01

    At MIT Lincoln Laboratory, avalanche photodiodes (APDs) have been developed for both 2-μm and 3.4-μm detection using the antimonide material system. These bulk, lattice-matched detectors operate in Geiger mode at temperatures up to 160 K. The 2-μm APDs use a separate-absorber-multiplier design with an InGaAsSb absorber and electron-initiated avalanching in the multiplier. These APDs have exhibited normalized avalanche probability (product of avalanche probability and photo-carrier-injection probability) of 0.4 and dark count rates of ~150 kHz at 77 K for a 30-μm-diameter device. A 1000- element imaging array of the 2-μm detectors has been demonstrated, which operate in a 5 kg dewar with an integrated Stirling-cycle cooler. The APD array is interfaced with a CMOS readout circuit, which provides photon time-of-arrival information for each pixel, allowing the focal plane array to be used in a photon-counting laser radar system. The 3.4-μm APDs use an InAsSb absorber and hole-initiated avalanching and have shown dark count rates of ~500 kHz at 77 K but normalized avalanche probability of < 1%. Research is ongoing to determine the cause of the low avalanche probability and improve the device performance.

  19. Avalanche Survival After Rescue With the RECCO Rescue System: A Case Report.

    Science.gov (United States)

    Grasegger, Katharina; Strapazzon, Giacomo; Procter, Emily; Brugger, Hermann; Soteras, Inigo

    2016-06-01

    We report a case of survival of a completely buried avalanche victim after being located with the radar-based RECCO Rescue System. In the winter of 2015, 2 off-piste skiers were completely buried in an avalanche near the secured ski area in Baqueira Beret, Spain. The first victim was located with the RECCO Rescue System in less than 35 minutes and was alive and conscious at extrication. This system emits radio waves and requires a specific reflector. It is a portable device that is used by more than 600 rescue organizations worldwide, especially in secured ski areas. The device should be brought to the avalanche site together with electronic avalanche transceivers, a probing team, and avalanche dogs. In the hands of experienced professionals, the device may allow rapid location of victims not carrying an electronic avalanche transceiver. Although it is not the first successful extrication of a victim with the RECCO Rescue System, it is the first case published in the medical literature and is intended to encourage data collection and to increase our understanding of the effectiveness of this device in avalanche rescue.

  20. New Analysis Techniques for Avalanches in a Conical Bead Pile with Cohesion

    Science.gov (United States)

    Tieman, Catherine; Lehman, Susan

    2015-03-01

    Avalanche statistics and pile geometry for 3 mm steel spheres dropped on a conical bead pile were studied at different drop heights and different cohesion strengths. The pile is initially built on a circular base and is subsequently slowly driven by adding one bead at a time to the apex of the pile. We investigate the dynamic response of the pile by recording avalanches off the pile over the course of tens of thousands of bead drops. The level of cohesion is tuned through use of an applied uniform magnetic field. Changes in the pile mass and geometry were investigated to determine the effect of cohesion and drop height on the angle of repose. The angle of repose increased with cohesion strength, and decreased somewhat for higher drop heights. The packing density of beads is expected to decrease as magnetic cohesion increases, but for our 20 000-bead pile, this effect has not been observed. The proportion of beads removed from the pile by different avalanche sizes was also calculated. Although larger avalanches are much rarer occurrences, they carry away a larger fraction of the total avalanched mass than small avalanches. As the pile cohesion increases, the number of small and medium avalanches decreases so that this mass loss distribution shifts more strongly to large sizes.

  1. Recovering the Seismic Energy Transmitted to the Ground by Snow Avalanches.

    Science.gov (United States)

    Mangeney, A.; Surinach, E.; Levy, C.; Roig, P.

    2016-12-01

    The energy transmitted into the ground by flowing snow avalanches was estimated by using the seismic signal recorded at two different sites by UB LE-3D/5s seismic sensors. One sensor was located on the avalanche path, so that the avalanche passes over it. The second one was placed at about 400 m from the runout zone. The energy was recovered at each position of the path taking into account the attenuation factors (intrinsic attenuation and geometrical spreading) as in Vilajosana et al. (2008). Seismic characteristics of the ground, Digital Elevation Model of the area were taking into account for this calculation. The coincidence of the recovered energy at each position coming from the two sensors validates the approach. We then simulated the avalanches that occurred in 2004-2008 at the Ryggfonn experimental site (Norway) (Gauer and Kristensen, 2016) using the data obtained in collaboration with the Norwegian Geotechnical Institute. Dense and Mixed (artificially triggered and spontaneous) avalanches of large and medium size were studied. Video images and characteristics of the snow helped in the determination of the characteristics of the avalanches. The approximate length of the path was 2 km and the vertical drop was 900 m. The transmitted energy shows a good correspondence with the outputs of the SHALTOP numerical model that we used to simulate the snow avalanche along the real topography. We also show a correlation between the seismic energy and the fluctuations of the topography along the avalanche path. Moreover, for the two sites and different parts of the avalanche we recovered similar power laws relating the seismic energy and the signal duration than those observed in a very different environment with different gravitational flows (i. e. rockfalls and pyroclastic flows in La Réunion by Hibert et al., 2011 and Montserrat by Levy et al., 2015).

  2. Slab entrainment and surge dynamics of the 2015 Valleé de la Sionne avalanches

    Science.gov (United States)

    Köhler, Anselm; McElwaine, Jim; Sovilla, Betty

    2016-04-01

    On 3 February 2015 five avalanches were artificially released at the Valleé de la Sionne test site in the west of Switzerland. The dense parts of the avalanches were tracked by the GEODAR Mark 2 radar system at 111 Hz framerate with 0.75 m down slope resolution. The data show that these avalanche contain several internal surges and that the avalanche front is repeatedly overtaken by some of these surges. We show that these surges exist on different scale. While the major surges originates from secondary triggered slab releases and occur all over the avalanche. The minor surges are only found in the energetic part of a well developed powder snow avalanche. The mass of the major surges can be as huge as the initial released mass, this has a dramatic effect on the mass distribution inside the avalanche and effects the front velocity and run out. Furthermore, the secondary released snow slabs are an important entrainment mechanism and up to 50 percent of the mass entered the avalanche via slab entrainment. We analyse the dynamics of the leading edge and the minor surges in more detail using a simple one dimensional model with frictional resistance and quadratic velocity dependent drag. These models fit the data well for the start and middle of avalanche but cannot capture the slowing and overtaking of the minor surge. We find much higher friction coefficients to describe the surging. We propose that this data can only be explained by changes in the snow surface. These effects are not included in current models yet, but the data presented here will enable the development and verification of such models.

  3. Natural avalanches and transportation: A case study from Glacier National Park, Montana, USA

    Science.gov (United States)

    Reardon, B.A.; Fagre, Daniel B.; Steiner, R.W.

    2004-01-01

    In January 2004, two natural avalanches (destructive class 3) derailed a freight train in John F. Stevens Canyon, on the southern boundary of Glacier National Park. The railroad tracks were closed for 29 hours due to cleanup and lingering avalanche hazard, backing up 112km of trains and shutting down Amtrak’s passenger service. The incident marked the fourth time in three winters that natural avalanches have disrupted transportation in the canyon, which is also the route of U.S. Highway 2. It was the latest in a 94-year history of accidents that includes three fatalities and the destruction of a major highway bridge. Despite that history and the presence of over 40 avalanche paths in the 16km canyon, mitigation is limited to nine railroad snow sheds and occasional highway closures. This case study examines natural avalanche cycles of the past 28 winters using data from field observations, a Natural Resources Conservation Service (NRCS) SNOTEL station, and data collected since 2001 at a high-elevation weather station. The avalanches occurred when storms with sustained snowfall buried a persistent near-surface faceted layer and/or were followed by rain-on-snow or dramatic warming (as much as 21oC in 30 minutes). Natural avalanche activity peaked when temperatures clustered near freezing (mean of -1.5oC at 1800m elev.). Avalanches initiated through rapid loading, rain falling on new snow, and/ or temperature-related changes in the mechanical properties of slabs. Lastly, the case study describes how recent incidents have prompted a unique partnership of land management agencies, private corporations and non-profit organizations to develop an avalanche mitigation program for the transportation corridor.

  4. Transport and emplacement mechanisms of channelised long-runout debris avalanches, Ruapehu volcano, New Zealand

    Science.gov (United States)

    Tost, M.; Cronin, S. J.; Procter, J. N.

    2014-12-01

    The steep flanks of composite volcanoes are prone to collapse, producing debris avalanches that completely reshape the landscape. This study describes new insights into the runout of large debris avalanches enhanced by topography, using the example of six debris avalanche deposits from Mount Ruapehu, New Zealand. Individual large flank collapses (>1 km3) produced all of these units, with four not previously recognised. Five major valleys within the highly dissected landscape surrounding Mount Ruapehu channelled the debris avalanches into deep gorges (≥15 m) and resulted in extremely long debris avalanche runouts of up to 80 km from source. Classical sedimentary features of debris avalanche deposits preserved in these units include the following: very poor sorting with a clay-sand matrix hosting large subrounded boulders up to 5 m in diameter, jigsaw-fractured clasts, deformed clasts and numerous rip-up clasts of late-Pliocene marine sediments. The unusually long runouts led to unique features in distal deposits, including a pervasive and consolidated interclast matrix, and common rip-up clasts of Tertiary mudstone, as well as fluvial gravels and boulders. The great travel distances can be explained by the debris avalanches entering deep confined channels (≥15 m), where friction was minimised by a reduced basal contact area along with loading of water-saturated substrates which formed a basal lubrication zone for the overlying flowing mass. Extremely long-runout debris avalanches are most likely to occur in settings where initially partly saturated collapsing masses move down deep valleys and become thoroughly liquified at their base. This happens when pore water is available within the base of the flowing mass or in the sediments immediately below it. Based on their H/L ratio, confined volcanic debris avalanches are two to three times longer than unconfined, spreading flows of similar volume. The hybrid qualities of the deposits, which have some similarities to

  5. Automatic detection of avalanches in seismic data using Hidden Markov Models

    Science.gov (United States)

    Heck, Matthias; Hammer, Conny; van Herwijnen, Alec; Schweizer, Jürg; Fäh, Donat

    2017-04-01

    Seismic monitoring systems are well suited for the remote detection of mass movements, such as landslides, rockfalls and debris flows. For snow avalanches, this has been known since the 1970s and seismic monitoring could potentially provide valuable information for avalanche forecasting. We thus explored continuous seismic data from a string of vertical component geophones in an avalanche starting zone above Davos, Switzerland. The overall goal is to automatically detect avalanches with a Hidden Markov Model (HMM), a statistical pattern recognition tool widely used for speech recognition. A HMM uses a classifier to determine the likelihood that input objects belong to a finite number of classes. These classes are obtained by learning a multidimensional Gaussian mixture model representation of the overall observable feature space. This model is then used to derive the HMM parameters for avalanche waveforms using a single training sample to build the final classifier. We classified data from the winter seasons of 2010 and compared the results to several hundred avalanches manually identified in the seismic data. First results of a classification of a single day have shown, that the model is good in terms of probability of detection while having a relatively low false alarm rate. We further implemented a voting based classification approach to neglect events detected only by one sensor to further improve the model performance. For instance, on 22 March 2010, a day with particular high avalanche activity, 17 avalanches were positively identified by at least three sensors with no false alarms. These results show, that the automatic detection of avalanches in seismic data is feasible, bringing us one step closer to implementing seismic monitoring system in operational forecasting.

  6. Spreading and Deposit Characteristics of a Rapid Dry Granular Avalanche Across 3D Topography: Experimental Study

    Science.gov (United States)

    Wang, Yu-Feng; Xu, Qiang; Cheng, Qian-Gong; Li, Yan; Luo, Zhong-Xu

    2016-11-01

    Aiming to understand the propagation and deposit behaviours of a granular avalanche along a 3D complex basal terrain, a new 3D experimental platform in 1/400 scale was developed according to the natural terrain of the Xiejiadianzi rock avalanche, with a series of laboratory experiments being conducted. Through the conduction of these tests, parameters, including the morphological evolution of sliding mass, run-outs and velocities of surficial particles, thickness contour and centre of final deposit, equivalent frictional coefficient, and energy dissipation, are documented and analysed, with the geomorphic control effect, material grain size effect, drop angle effect, and drop distance effect on rock avalanche mobility being discussed primarily. From the study, some interesting conclusions for a better understanding of rock avalanche along a 3D complex basal topography are reached. (1) For the granular avalanche tested in this study, great differences between the evolutions of the debris along the right and left branch valleys were observed, with an obvious geomorphic control effect on avalanche mobility presented. In addition, some other interesting features, including groove-like trough and superelevation, were also observed under the control of the topographic interferences. (2) The equivalent frictional coefficients of the granular avalanches tested here range from 0.48 to 0.57, which is lower than that reached with a set-up composed of an inclined chute and horizontal plate and higher than that reached using a set-up composed of only an inclined chute. And the higher the drop angle and fine particle content, the higher the equivalent frictional coefficient. The effect of drop distance on avalanche mobility is minor. (3) For a granular avalanche, momentum transfer plays an important role in the motion of mass, which can accelerate the mobility of the front part greatly through delivering the kinetic energy of the rear part to the front.

  7. Forecasting of wet snow avalanche activity: Proof of concept and operational implementation

    Science.gov (United States)

    Gobiet, Andreas; Jöbstl, Lisa; Rieder, Hannes; Bellaire, Sascha; Mitterer, Christoph

    2017-04-01

    State-of-the-art tools for the operational assessment of avalanche danger include field observations, recordings from automatic weather stations, meteorological analyses and forecasts, and recently also indices derived from snowpack models. In particular, an index for identifying the onset of wet-snow avalanche cycles (LWCindex), has been demonstrated to be useful. However, its value for operational avalanche forecasting is currently limited, since detailed, physically based snowpack models are usually driven by meteorological data from automatic weather stations only and have therefore no prognostic ability. Since avalanche risk management heavily relies on timely information and early warnings, many avalanche services in Europe nowadays start issuing forecasts for the following days, instead of the traditional assessment of the current avalanche danger. In this context, the prognostic operation of detailed snowpack models has recently been objective of extensive research. In this study a new, observationally constrained setup for forecasting the onset of wet-snow avalanche cycles with the detailed snow cover model SNOWPACK is presented and evaluated. Based on data from weather stations and different numerical weather prediction models, we demonstrate that forecasts of the LWCindex as indicator for wet-snow avalanche cycles can be useful for operational warning services, but is so far not reliable enough to be used as single warning tool without considering other factors. Therefore, further development currently focuses on the improvement of the forecasts by applying ensemble techniques and suitable post processing approaches to the output of numerical weather prediction models. In parallel, the prognostic meteo-snow model chain is operationally used by two regional avalanche warning services in Austria since winter 2016/2017 for the first time. Experiences from the first operational season and first results from current model developments will be reported.

  8. The role of cornice fall avalanche sedimentation in the valley Longyeardalen, Central Svalbard

    Directory of Open Access Journals (Sweden)

    M. Eckerstorfer

    2012-12-01

    Full Text Available In arctic and alpine high relief landscapes snow avalanches are traditionally ranked behind rockfall in terms of their significance for mass wasting processes of rock slopes. Cornice fall avalanches are at present the most dominant snow avalanche type at two slope systems, called Nybyen and Larsbreen, in the valley Longyeardalen in Central Svalbard. Both slope systems are situated on NW-facing lee slopes underneath large summit plateau, where cornices form annually, and high frequency and magnitude cornice fall avalanching is observed by daily automatic time-lapse photography. In addition, rock debris sedimentation by these cornice fall avalanches was measured directly in either permanent sediment traps or by snow inventories. The results from a maximum of 7 yr of measurements in a total of 13 catchments show maximum avalanche sedimentation rates ranging from 8.2 to 38.7 kg m−2 at Nybyen and from 0.8 to 55.4 kg m−2 at Larsbreen. Correspondingly, the avalanche fan-surfaces accreted annually in a~maximum range from 3.7 to 13 mm yr−1 at Nybyen and from 0.3 to 21.4 mm yr−1 at Larsbreen. This comparably efficient rock slope mass wasting is due to collapsing cornices producing cornice fall avalanche with high rock debris content throughout the entire winter. The rock debris of different origin stems from the plateau crests, the adjacent free rock face and the transport pathway, accumulating distinct avalanche fans at both slope systems and contributing to the development of a rock glacier at the Larsbreen slope system.

  9. Avalanche Statistics Identify Intrinsic Stellar Processes near Criticality in KIC 8462852

    Science.gov (United States)

    Sheikh, Mohammed A.; Weaver, Richard L.; Dahmen, Karin A.

    2016-12-01

    The star KIC8462852 (Tabby's star) has shown anomalous drops in light flux. We perform a statistical analysis of the more numerous smaller dimming events by using methods found useful for avalanches in ferromagnetism and plastic flow. Scaling exponents for avalanche statistics and temporal profiles of the flux during the dimming events are close to mean field predictions. Scaling collapses suggest that this star may be near a nonequilibrium critical point. The large events are interpreted as avalanches marked by modified dynamics, limited by the system size, and not within the scaling regime.

  10. High-Accuracy Measurements of the Centre of Gravity of Avalanches in Proportional Chambers

    Science.gov (United States)

    Charpak, G.; Jeavons, A.; Sauli, F.; Stubbs, R.

    1973-09-24

    In a multiwire proportional chamber the avalanches occur close to the anode wires. The motion of the positive ions in the large electric fields at the vicinity of the wires induces fast-rising positive pulses on the surrounding electrodes. Different methods have been developed in order to determine the position of the centre of the avalanches. In the method we describe, the centre of gravity of the pulse distribution is measured directly. It seems to lead to an accuracy which is limited only by the stability of the spatial distribution of the avalanches generated by the process being measured.

  11. XeCl Avalanche discharge laser employing Ar as a diluent

    Science.gov (United States)

    Sze, Robert C.

    1981-01-01

    A XeCl avalanche discharge exciplex laser which uses a gaseous lasing starting mixture of: (0.2%-0.4% chlorine donor/2.5%-10% Xe/97.3%-89.6% Ar). The chlorine donor normally comprises HCl but can also comprise CCl.sub.4 BCl.sub.3. Use of Ar as a diluent gas reduces operating pressures over other rare gas halide lasers to near atmospheric pressure, increases output lasing power of the XeCl avalanche discharge laser by 30% to exceed KrF avalanche discharge lasing outputs, and is less expensive to operate.

  12. Triple SV: A Bit Level Symmetric Block-Cipher Having High Avalanche Effect

    Directory of Open Access Journals (Sweden)

    Rajdeep Chakraborty

    2011-08-01

    Full Text Available The prolific growth of network communication system entails high risk of breach in information security. This substantiates the need for higher security for electronic information. Cryptography is one of the ways to secure electronic documents. In this paper, we propose a new block cipher, TRIPLE SV (3SV, with 256-bit block size and 112-bit key length. Generally, stream ciphers produce higher avalanche effect but Triple SV shows a substantial rise in avalanche effect with a block cipher implementation. The CBC mode has been used to attain higher avalanche effect. The technique is implemented in C language and has been tested for feasibility

  13. Explosive-residue compounds resulting from snow avalanche control in the Wasatch Mountains of Utah

    Science.gov (United States)

    Naftz, David L.; Kanagy, Leslie K.; Susong, David D.; Wydoski, Duane S.; Kanagy, Christopher J.

    2003-01-01

    A snow avalanche is a powerful force of nature that can play a significant role in developing mountain landscapes (Perla and Martinelli, 1975). More importantly, loss of life can occur when people are caught in the path of snow avalanches (Grossman, 1999). Increasing winter recreation, including skiing, snowboarding, snowmobiling, snowshoeing, and climbing in mountainous areas, has increased the likelihood of people encountering snow avalanches (fig. 1). Explosives are used by most ski areas and State highway departments throughout the Western United States to control the release of snow avalanches, thus minimizing the loss of human life during winter recreation and highway travel (fig. 2).Common explosives used for snow avalanche control include trinitrotoluene (TNT), pentaerythritoltetranitrate (PETN), cyclotrimethylenetrinitramine (RDX), tetrytol, ammonium nitrate, and nitroglycerin (Perla and Martinelli, 1975). During and after snowfall or wind loading of potential avalanche slopes, ski patrollers and Utah Department of Transportation personnel deliver explosive charges onto predetermined targets to artificially release snow avalanches, thereby rendering the slope safer for winter activities. Explosives can be thrown by hand onto target zones or shot from cannons for more remote delivery of explosive charges. Hand-delivered charges typically contain about 2 pounds of TNT or its equivalent (Perla and Martinelli, 1975).Depending on the size of the ski area, acreage of potential avalanche terrain, and weather conditions, the annual quantity of explosives used during a season of snow avalanche control can be substantial. For example, the three ski areas of Alta, Snowbird, and Brighton, plus the Utah Department of Transportation, may use as many as 11,200 hand charges per year (Wasatch Powderbird Guides, unpub. data, 1999) for snow avalanche control in Big and Little Cottonwood Canyons (fig. 3). If each charge is assumed to weigh 2 pounds, this equates to about 22

  14. Avalanche transmission and critical behaviour in load-bearing hierarchical networks

    Indian Academy of Sciences (India)

    Ajay Deep Kachhvah; Neelima Gupte

    2011-11-01

    The strength and stability properties of hierarchical load-bearing networks and their strengthened variants have been discussed in a recent work. Here, we study the avalanche time distributions on these load-bearing networks. The avalanche time distributions of the V-lattice, a unique realization of the networks, show power-law behaviour when tested with certain fractions of its trunk weights. All other avalanche distributions show Gaussian peaked behaviour. Thus the V-lattice is the critical case of the network. We discuss the implications of this result.

  15. 42 CFR 447.506 - Authorized generic drugs.

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 4 2010-10-01 2010-10-01 false Authorized generic drugs. 447.506 Section 447.506... (CONTINUED) MEDICAL ASSISTANCE PROGRAMS PAYMENTS FOR SERVICES Payment for Drugs § 447.506 Authorized generic drugs. (a) Authorized generic drug defined. For the purposes of this subpart, an authorized generic...

  16. The diffusion of generics after patent expiry in Germany.

    Science.gov (United States)

    Fischer, Katharina Elisabeth; Stargardt, Tom

    2016-11-01

    To identify the influences on the diffusion of generics after patent expiry, we analyzed 65 generic entries using prescription data of a large German sickness fund between 2007 and 2012 in a sales model. According to theory, several elements are responsible for technology diffusion: (1) time reflecting the rate of adaption within the social system, (2) communication channels, and (3) the degree of incremental innovation, e.g., the modifications of existing active ingredient's strength. We investigated diffusion in two ways: (1) generic market share (percentage of generic prescriptions of all prescriptions of a substance) and, (2) generic sales quantity (number of units sold) over time. We specified mixed regression models. Generic diffusion takes considerable time. An average generic market share of about 75 % was achieved not until 48 months. There was a positive effect of time since generic entry on generic market share (p innovation influenced generic market share (mostly p < 0.001), but not generic sales quantity. Market structure, e.g., the number of generic manufacturers (p < 0.001) and prices influenced both generic market share and sales. Imperfections in generic uptake through informational cascades seem to be largely present. Third-party payers could enhance means to promote generic diffusion to amplify savings through generic entry.

  17. Generics and the specific features of their regulation

    Directory of Open Access Journals (Sweden)

    E. A. Ushkalova

    2016-01-01

    Full Text Available The article discusses the factors that influence the efficacy and safety of generic drugs, including regular generics, biosimilars, and generic nonbiological complex drugs. It emphasizes the importance of adequate regulatory requirements to provide a comparable therapeutic efficacy and a comparable cost-effectiveness ratio for generics versus brand-name drugs.

  18. Snow drift: acoustic sensors for avalanche warning and research

    Science.gov (United States)

    Lehning, M.; Naaim, F.; Naaim, M.; Brabec, B.; Doorschot, J.; Durand, Y.; Guyomarc'h, G.; Michaux, J.-L.; Zimmerli, M.

    Based on wind tunnel measurements at the CSTB (Jules Verne) facility in Nantes and based on field observations at the SLF experimental site Versuchsfeld Weissfluhjoch, two acoustic wind drift sensors are evaluated against different mechanical snow traps and one optical snow particle counter. The focus of the work is the suitability of the acoustic sensors for applications such as avalanche warning and research. Although the acoustic sensors have not yet reached the accuracy required for typical research applications, they can, however, be useful for snow drift monitoring to help avalanche forecasters. The main problem of the acoustic sensors is a difficult calibration that has to take into account the variable snow properties. Further difficulties arise from snow fall and high wind speeds. However, the sensor is robust and can be operated remotely under harsh conditions. It is emphasized that due to the lack of an accurate reference method for snow drift measurements, all sensors play a role in improving and evaluating snow drift models. Finally, current operational snow drift models and snow drift sensors are compared with respect to their usefulness as an aid for avalanche warning. While drift sensors always make a point measurement, the models are able to give a more representative drift index that is valid for a larger area. Therefore, models have the potential to replace difficult observations such as snow drift in operational applications. Current models on snow drift are either only applicable in flat terrain, are still too complex for an operational application (Lehning et al., 2000b), or offer only limited information on snow drift, such as the SNOWPACK drift index (Lehning et al., 2000a). On the other hand, snow drift is also difficult to measure. While mechanical traps (Mellor 1960; Budd et al., 1966) are probably still the best reference, they require more or less continuous manual operation and are thus not suitable for remote locations or long

  19. Snow drift: acoustic sensors for avalanche warning and research

    Directory of Open Access Journals (Sweden)

    M. Lehning

    2002-01-01

    Full Text Available Based on wind tunnel measurements at the CSTB (Jules Verne facility in Nantes and based on field observations at the SLF experimental site Versuchsfeld Weissfluhjoch, two acoustic wind drift sensors are evaluated against different mechanical snow traps and one optical snow particle counter. The focus of the work is the suitability of the acoustic sensors for applications such as avalanche warning and research. Although the acoustic sensors have not yet reached the accuracy required for typical research applications, they can, however, be useful for snow drift monitoring to help avalanche forecasters. The main problem of the acoustic sensors is a difficult calibration that has to take into account the variable snow properties. Further difficulties arise from snow fall and high wind speeds. However, the sensor is robust and can be operated remotely under harsh conditions. It is emphasized that due to the lack of an accurate reference method for snow drift measurements, all sensors play a role in improving and evaluating snow drift models. Finally, current operational snow drift models and snow drift sensors are compared with respect to their usefulness as an aid for avalanche warning. While drift sensors always make a point measurement, the models are able to give a more representative drift index that is valid for a larger area. Therefore, models have the potential to replace difficult observations such as snow drift in operational applications. Current models on snow drift are either only applicable in flat terrain, are still too complex for an operational application (Lehning et al., 2000b, or offer only limited information on snow drift, such as the SNOWPACK drift index (Lehning et al., 2000a. On the other hand, snow drift is also difficult to measure. While mechanical traps (Mellor 1960; Budd et al., 1966 are probably still the best reference, they require more or less continuous manual operation and are thus not suitable for remote locations

  20. Single Photon Avalanche Diodes: Towards the Large Bidimensional Arrays

    Science.gov (United States)

    Privitera, Simona; Tudisco, Salvatore; Lanzanò, Luca; Musumeci, Francesco; Pluchino, Alessandro; Scordino, Agata; Campisi, Angelo; Cosentino, Luigi; Finocchiaro, Paolo; Condorelli, Giovanni; Mazzillo, Massimo; Lombardo, Salvo; Sciacca, Emilio

    2008-01-01

    Single photon detection is one of the most challenging goals of photonics. In recent years, the study of ultra-fast and/or low-intensity phenomena has received renewed attention from the academic and industrial communities. Intense research activity has been focused on bio-imaging applications, bio-luminescence, bio-scattering methods, and, more in general, on several applications requiring high speed operation and high timing resolution. In this paper we present design and characterization of bi-dimensional arrays of a next generation of single photon avalanche diodes (SPADs). Single photon sensitivity, dark noise, afterpulsing and timing resolution of the single SPAD have been examined in several experimental conditions. Moreover, the effects arising from their integration and the readout mode have also been deeply investigated. PMID:27873777

  1. Single Photon Avalanche Diodes: Towards the Large Bidimensional Arrays

    Directory of Open Access Journals (Sweden)

    Emilio Sciacca

    2008-08-01

    Full Text Available Single photon detection is one of the most challenging goals of photonics. In recent years, the study of ultra-fast and/or low-intensity phenomena has received renewed attention from the academic and industrial communities. Intense research activity has been focused on bio-imaging applications, bio-luminescence, bio-scattering methods, and, more in general, on several applications requiring high speed operation and high timing resolution. In this paper we present design and characterization of bi-dimensional arrays of a next generation of single photon avalanche diodes (SPADs. Single photon sensitivity, dark noise, afterpulsing and timing resolution of the single SPAD have been examined in several experimental conditions. Moreover, the effects arising from their integration and the readout mode have also been deeply investigated.

  2. Avalanche Photodiodes as Fast X-ray Detectors.

    Science.gov (United States)

    Kishimoto, S

    1998-05-01

    An avalanche photodiode (APD) detector provides a sub-nanosecond time resolution and an output rate of more than 10(8) counts s(-1) of synchrotron X-rays. Moreover, the APD has the advantage of low noise. A review of recent developments of detectors using APD devices designed for X-ray experiments is presented in this paper. One of the detectors has an excellent time response of 100 ps resolution and a narrow width on its response function, 1.4 ns at 10(-5) maximum. The other consists of a stack of four diodes and has a transmission structure. The stacked detector improved the efficiency for X-rays, e.g. 55% at 16.53 keV. The output rates reached more than 10(8) counts s(-1) per device.

  3. Temperature Control of Avalanche Photodiode Using Thermoelectric Cooler

    Science.gov (United States)

    Refaat, Tamer F.; Luck, William S., Jr.; DeYoung, Russell J.

    1999-01-01

    Avalanche photodiodes (APDS) are quantum optical detectors that are used for visible and near infrared optical detection applications. Although APDs are compact, rugged, and have an internal gain mechanism that is suitable for low light intensity; their responsivity, and therefore their output, is strongly dependent on the device temperature. Thermoelectric coolers (TEC) offers a suitable solution to this problem. A TEC is a solid state cooling device, which can be controlled by changing its current. TECs are compact and rugged, and they can precisely control the temperature to within 0.1 C with more than a 150 C temperature gradient between its surfaces. In this Memorandum, a proportional integral (PI) temperature controller for APDs using a TEC is discussed. The controller is compact and can successfully cool the APD to almost 0 C in an ambient temperature environment of up to 27 C.

  4. Correcting for accidental correlations in saturated avalanche photodiodes.

    Science.gov (United States)

    Grieve, J A; Chandrasekara, R; Tang, Z; Cheng, C; Ling, A

    2016-02-22

    In this paper we present a general method for estimating rates of accidental coincidence between a pair of single photon detectors operated within their saturation regimes. By folding the effects of recovery time of both detectors and the detection circuit into an "effective duty cycle" we are able to accomodate complex recovery behaviour at high event rates. As an example, we provide a detailed high-level model for the behaviour of passively quenched avalanche photodiodes, and demonstrate effective background subtraction at rates commonly associated with detector saturation. We show that by post-processing using the updated model, we observe an improvement in polarization correlation visibility from 88.7% to 96.9% in our experimental dataset. This technique will be useful in improving the signal-to-noise ratio in applications which depend on coincidence measurements, especially in situations where rapid changes in flux may cause detector saturation.

  5. Systematic afterpulsing-estimation algorithms for gated avalanche photodiodes

    CERN Document Server

    Wiechers, Carlos; Muñiz-Sánchez, Oscar R; Yépiz, Pablo Daniel; Arredondo-Santos, Alejandro; Hirsch, Jorge G; U'Ren, Alfred B

    2016-01-01

    We present a method designed to efficiently extract optical signals from InGaAs avalanche photodiodes (APDs) operated in gated mode. In particular, our method permits an estimation of the fraction of counts which actually results from the signal being measured, as opposed to being produced by noise mechanisms, specifically by afterpulsing. Our method in principle allows the use of InGaAs APDs at high detection efficiencies, with the full operation bandwidth, either with or without resorting to the application of a dead time. As we show below, our method can be used in configurations where afterpulsing exceeds the genuine signal by orders of magnitude, even near saturation. The algorithms which we have developed are suitable to be used either in real-time processing of raw detection probabilities or in post-processing applications, after a calibration step has been performed. The algorithms which we propose here can complement technologies designed for the reduction of afterpulsing.

  6. Avalanche photodiode based time-of-flight mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Ogasawara, Keiichi, E-mail: kogasawara@swri.edu; Livi, Stefano A.; Desai, Mihir I.; Ebert, Robert W.; McComas, David J.; Walther, Brandon C. [Southwest Research Institute, 6220 Culebra Road, San Antonio, Texas 78238 (United States)

    2015-08-15

    This study reports on the performance of Avalanche Photodiodes (APDs) as a timing detector for ion Time-of-Flight (TOF) mass spectroscopy. We found that the fast signal carrier speed in a reach-through type APD enables an extremely short timescale response with a mass or energy independent <2 ns rise time for <200 keV ions (1−40 AMU) under proper bias voltage operations. When combined with a microchannel plate to detect start electron signals from an ultra-thin carbon foil, the APD comprises a novel TOF system that successfully operates with a <0.8 ns intrinsic timing resolution even using commercial off-the-shelf constant-fraction discriminators. By replacing conventional total-energy detectors in the TOF-Energy system, APDs offer significant power and mass savings or an anti-coincidence background rejection capability in future space instrumentation.

  7. Systematic afterpulsing-estimation algorithms for gated avalanche photodiodes.

    Science.gov (United States)

    Wiechers, Carlos; Ramírez-Alarcón, Roberto; Muñiz-Sánchez, Oscar R; Yépiz, Pablo Daniel; Arredondo-Santos, Alejandro; Hirsch, Jorge G; U'Ren, Alfred B

    2016-09-10

    We present a method designed to efficiently extract optical signals from InGaAs avalanche photodiodes (APDs) operated in gated mode. In particular, our method permits an estimation of the fraction of counts that actually results from the signal being measured, as opposed to being produced by noise mechanisms, specifically by afterpulsing. Our method in principle allows the use of InGaAs APDs at high detection efficiencies, with the full operation bandwidth, either with or without resorting to the application of a dead-time. As we show below, our method can be used in configurations where afterpulsing exceeds the genuine signal by orders of magnitude, even near saturation. The algorithms that we have developed are suitable to be used either in real-time processing of raw detection probabilities or in post-processing applications, after a calibration step has been performed. The algorithms that we propose here can complement technologies designed for the reduction of afterpulsing.

  8. Cesium hafnium chloride scintillator coupled with an avalanche photodiode photodetector

    Science.gov (United States)

    Kurosawa, S.; Kodama, S.; Yokota, Y.; Horiai, T.; Yamaji, A.; Shoji, Y.; Král, R.; Pejchal, J.; Ohashi, Y.; Kamada, K.; Nikl, M.; Yoshikawa, A.

    2017-02-01

    Optical and scintillation properties of pure Cs2HfCl6 (CHC) single crystals were investigated. In particular, light output and energy resolution were measured using a Si avalanche photodiode (Si-APD), since the Si-APD has sufficient quantum efficiency of around 70 % at emission wavelength region of CHC around 420 nm. This CHC single crystal grown using the vertical Bridgeman method showed light output of 37,000± 2,000 photons/MeV . The FWHM energy resolution was determined to be 3.7± 0.5× (E/662 keV)-0.85± 0.03[%], where E [keV] is the gamma-ray energy. Moreover, the temperature dependence of the light output was stable from -5 to 30 oC, while the light output increased below -10 oC.

  9. Avalanche photodiode based time-of-flight mass spectrometry.

    Science.gov (United States)

    Ogasawara, Keiichi; Livi, Stefano A; Desai, Mihir I; Ebert, Robert W; McComas, David J; Walther, Brandon C

    2015-08-01

    This study reports on the performance of Avalanche Photodiodes (APDs) as a timing detector for ion Time-of-Flight (TOF) mass spectroscopy. We found that the fast signal carrier speed in a reach-through type APD enables an extremely short timescale response with a mass or energy independent <2 ns rise time for <200 keV ions (1-40 AMU) under proper bias voltage operations. When combined with a microchannel plate to detect start electron signals from an ultra-thin carbon foil, the APD comprises a novel TOF system that successfully operates with a <0.8 ns intrinsic timing resolution even using commercial off-the-shelf constant-fraction discriminators. By replacing conventional total-energy detectors in the TOF-Energy system, APDs offer significant power and mass savings or an anti-coincidence background rejection capability in future space instrumentation.

  10. 10 Gbps silicon waveguide-integrated infrared avalanche photodiode.

    Science.gov (United States)

    Ackert, Jason J; Karar, Abdullah S; Paez, Dixon J; Jessop, Paul E; Cartledge, John C; Knights, Andrew P

    2013-08-26

    We have fabricated monolithic silicon avalanche photodiodes capable of 10 Gbps operation at a wavelength of 1550 nm. The photodiodes are entirely CMOS process compatible and comprise a p-i-n junction integrated with a silicon-on-insulator (SOI) rib waveguide. Photo-generation is initiated via the presence of deep levels in the silicon bandgap, introduced by ion implantation and modified by subsequent annealing. The devices show a small signal 3 dB bandwidth of 2.0 GHz as well as an open eye pattern at 10 Gbps. A responsivity of 4.7 ± 0.5 A/W is measured for a 600 µm device at a reverse bias of 40 V.

  11. A two-fluid model for avalanche and debris flows.

    Science.gov (United States)

    Pitman, E Bruce; Le, Long

    2005-07-15

    Geophysical mass flows--debris flows, avalanches, landslides--can contain O(10(6)-10(10)) m(3) or more of material, often a mixture of soil and rocks with a significant quantity of interstitial fluid. These flows can be tens of meters in depth and hundreds of meters in length. The range of scales and the rheology of this mixture presents significant modelling and computational challenges. This paper describes a depth-averaged 'thin layer' model of geophysical mass flows containing a mixture of solid material and fluid. The model is derived from a 'two-phase' or 'two-fluid' system of equations commonly used in engineering research. Phenomenological modelling and depth averaging combine to yield a tractable set of equations, a hyperbolic system that describes the motion of the two constituent phases. If the fluid inertia is small, a reduced model system that is easier to solve may be derived.

  12. Interevent Correlations from Avalanches Hiding Below the Detection Threshold

    Science.gov (United States)

    Janićević, Sanja; Laurson, Lasse; Mâløy, Knut Jørgen; Santucci, Stéphane; Alava, Mikko J.

    2016-12-01

    Numerous systems ranging from deformation of materials to earthquakes exhibit bursty dynamics, which consist of a sequence of events with a broad event size distribution. Very often these events are observed to be temporally correlated or clustered, evidenced by power-law-distributed waiting times separating two consecutive activity bursts. We show how such interevent correlations arise simply because of a finite detection threshold, created by the limited sensitivity of the measurement apparatus, or used to subtract background activity or noise from the activity signal. Data from crack-propagation experiments and numerical simulations of a nonequilibrium crack-line model demonstrate how thresholding leads to correlated bursts of activity by separating the avalanche events into subavalanches. The resulting temporal subavalanche correlations are well described by our general scaling description of thresholding-induced correlations in crackling noise.

  13. Single-photon avalanche photodiodes with integrated quenching resistor

    Energy Technology Data Exchange (ETDEWEB)

    Mazzillo, M. [STMicroelectronics, IMS R and D Stradale Primosole 50, 95121 Catania (Italy)], E-mail: massimo.mazzillo@st.com; Condorelli, G.; Piazza, A.; Sanfilippo, D.; Valvo, G.; Carbone, B.; Fallica, G. [STMicroelectronics, IMS R and D Stradale Primosole 50, 95121 Catania (Italy); Billotta, S.; Belluso, M.; Bonanno, G. [INAF-Osservatorio Astrofisico di Catania, Via Santa Sofia 78, 95123 Catania (Italy); Pappalardo, A.; Cosentino, L.; Finocchiaro, P. [INFN-Laboratori Nazionali del Sud, Via Santa Sofia 64, 95125 Catania (Italy)

    2008-06-21

    In this paper we present the results of the first electrical and optical characterization performed on STMicroelectronics new photosensor technology based on silicon single-photon avalanche photodiodes (SPAD). On the prospective of the design and the manufacturing of large-area silicon photomultipliers to be used as photodetectors for nuclear medicine imaging applications, we have modified our previous SPAD technology by means of the integration of a high-value quenching resistor to the photodiode. Moreover, an appropriate antireflective coating layer and the reduction of the quasi-neutral region thickness above the thin junction depletion layer have been introduced in the process flow of the device to enhance its spectral response in blue and near ultraviolet wavelength ranges. High gain, low leakage currents, low dark noise, very good quantum detection efficiency in blue-near UV ranges and a good linearity of the photodiode response to the incident luminous flux are the main characterization results.

  14. Motion of current filaments in avalanching PIN diodes

    Science.gov (United States)

    Xingrong, Ren; Changchun, Chai; Zhenyang, Ma; Yintang, Yang; Liping, Qiao; Chunlei, Shi; Lihua, Ren

    2013-04-01

    The motion of current filaments in avalanching PIN diodes has been investigated in this paper by 2D transient numerical simulations. The simulation results show that the filament can move along the length of the PIN diode back and forth when the self-heating effect is considered. The voltage waveform varies periodically due to the motion of the filament. The filament motion is driven by the temperature gradient in the filament due to the negative temperature dependence of the impact ionization rates. Contrary to the traditional understanding that current filamentation is a potential cause of thermal destruction, it is shown in this paper that the thermally-driven motion of current filaments leads to the homogenization of temperature in the diode and is expected to have a positive influence on the failure threshold of the PIN diode.

  15. Self-aligned multi-channel superconducting nanowire avalanche photodetector

    CERN Document Server

    Cheng, Risheng; Ma, Xiaosong; Fan, Linran; Fong, King Y; Poot, Menno; Tang, Hong X

    2016-01-01

    We describe a micromachining process to allow the coupling of an array of single-mode telecommunication fibers to individual superconducting nanowire single photon detectors (SNSPDs). As proof of principle, we show the integration of four detectors on the same silicon chip, including two standard single-section nanowire detectors and two superconducting nanowire avalanche photodetectors (SNAPs) with modified series structure without external inductor, and their performances are compared. The SNAP shows saturated system detection efficiency of 16% while the dark count rate is less than 20 Hz, without the use of photon-recycling reflectors. The SNAP also demonstrates doubled signal-to-noise ratio, reduced reset time (~ 4.9 ns decay time) and improved timing jitter (62 ps FWHM) compared to standard SNSPDs.

  16. High-density avalanche chambers for positron emission tomography

    Energy Technology Data Exchange (ETDEWEB)

    Manfrass, P.; Enghardt, W.; Fromm, W.D.; Wohlfarth, D.; Hohmuth, K.

    1988-12-15

    A positron tomograph for radiopharmaceutical and medical research is under construction. In its final stage it will cover six high-density avalanche chambers (HIDAC) in a hexagonal arrangement. Each detector with a sensitive area of 50x28 cm/sup 2/ will consist of a stack of four pairs of multihole photon-to-electron converters with a multiwire proportional counter (MWPC) in between. An experimental investigation of detector properties as time and spatial resolutions as well as detector efficiency in dependence to converter structure, electric field strength and counting gas mixture preceded the final design of these detectors. Results of these studies are outlined. Furthermore, longitudinal tomograms taken with a stationary test camera are presented.

  17. Rapid sequestration of rock avalanche deposits within glaciers.

    Science.gov (United States)

    Dunning, Stuart A; Rosser, Nicholas J; McColl, Samuel T; Reznichenko, Natalya V

    2015-08-19

    Topographic development in mountainous landscapes is a complex interplay between tectonics, climate and denudation. Glaciers erode valleys to generate headwall relief, and hillslope processes control the height and retreat of the peaks. The magnitude-frequency of these landslides and their long-term ability to lower mountains above glaciers is poorly understood; however, small, frequent rockfalls are currently thought to dominate. The preservation of rarer, larger, landslide deposits is exceptionally short-lived, as they are rapidly reworked. The 2013 Mount Haast rock avalanche that failed from the slopes of Aoraki/Mount Cook, New Zealand, onto the glacier accumulation zone below was invisible to conventional remote sensing after just 3 months. Here we use sub-surface data to reveal the now-buried landslide deposit, and suggest that large landslides are the primary hillslope erosion mechanism here. These data show how past large landslides can be identified in accumulation zones, providing an untapped archive of erosive events in mountainous landscapes.

  18. Photon-counting techniques with silicon avalanche photodiodes

    Science.gov (United States)

    Dautet, Henri; Deschamps, P.; Dion, Bruno; MacGregor, Andrew D.; MacSween, D.; McIntyre, Robert J.; Trottier, C.; Webb, Paul P.

    1993-05-01

    Silicon avalanche photodiodes (APD) have been used for photon counting for a number of years. This paper reviews their properties and the associated electronics required for photon counting in the Geiger mode. Significant improvements are reported in overall photon detection efficiencies (approaching 75% at 633 nm), and timing jitter (under 200 ps) achieved at high over-voltages (20 - 30 V). Results obtained using an active-mode fast quench circuit capable of switching over-voltages as high as 20 V (giving photon detection efficiencies in the 50% range), are reported with a dead-time of less than 50 ns. Larger diodes (up to 1 mm diameter), usable in the Geiger mode, which have quantum efficiencies over 80% in the 500 - 800 nm range also are reported.

  19. Nonlinear Dynamical Behavior in Neuron Model Based on Small World Network with Attack and Repair Strategy

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xue; YANG Qiu-Ying; ZHENG Tai-Yu; ZHANG Ying-Yue; ZHENG Li; ZHANG Gui-Qing; CHEN Tian-Lun

    2008-01-01

    In this paper, we investigate the effect due to the change of topology structure of network on the nonlinear dynamical behavior, by virtue of the OFC neuron evolution model with attack and repair strategy based on the small world. In particular, roles of various parameters relating to the dynamical behavior are carefully studied and analyzed. In addition, the avalanche and EEG-like wave activities with attack and repair strategy are also explored in detail in this work.

  20. Gravitational wet-avalanche pressure on pylon-like structures

    Science.gov (United States)

    Sovilla, Betty; Faug, Thierry; Köhler, Anselm; Baroudi, Djebar; Fischer, Jan-Thomas; Thibert, Emmanuel

    2016-04-01

    Low-speed wet-avalanches exert hydrostatic forces on structures which are surface-dependent, however neither the pressure amplification experienced by smaller structure has been quantified and the causes of the amplification understood. In particular, recent wet-snow avalanche pressure measurements, performed with small cells at the "Vallée the la Sionne" test site, indicate significantly higher pressures than those considered by engineering guidelines and common practice rules based only on the contribution of inertial forces. In order to gain a deeper understanding and investigate the relevance of these measurements for structural design, we analyze data collected at the "Vallée the la Sionne" on obstacles of different shapes and dimensions. We show that, the pressure measured on a 1 m2 pressure plate is, on average, 1.8 times smaller than the pressure measured on a 0.008 m2 piezoelectric cell, installed on a 0.60 m wide pylon, and 2.9 times smaller than the pressure measured on a 0.0125 m2 cantilever sensor, extending freely into the snow. The different pressures encountered by the different obstacles is quantitatively explained with a granular force model, assuming the formation of a mobilized volume of snow granules extending from the obstacle upstream. The results underscore the fundamental influence of the dimension of the sensor and the obstacle on pressures. Our study highlights the difficulties that appear in the estimation of forces in the gravitational flow regime, for which force amplification may be caused by this mobilized volume at the scale of the whole structure, but also by plastic wedges, or small dead zones, at the scale of the sensor mounted on a wider structure.

  1. Sixteen-year follow-up of childhood avalanche survivors

    Directory of Open Access Journals (Sweden)

    Edda Bjork Thordardottir

    2016-08-01

    Full Text Available Background: Every year a substantial number of children are affected by natural disasters worldwide. However, data are scarce on long-term psychological impact of natural disasters on children's health. Identifying risk factors and outcomes associated with the long-term sequelae of posttraumatic stress disorder (PTSD can provide a gateway to recovery as well as enhancement of preventive measures. Objective: Among childhood avalanche survivors, we aimed to investigate risk factors for PTSD symptoms and the relationship between socioeconomic status (SES and PTSD symptoms in adulthood. Methods: Childhood survivors (aged 2–19 at the time of exposure of two avalanches were identified through nationwide registers 16 years later. The Posttraumatic Diagnostic Scale was used to assess current PTSD symptoms. One-way ANOVA was used to explore PTSD symptoms by background and trauma-specific factors, as well as associations with current SES. Predictors of PTSD symptoms were examined by multivariable regression analysis. Results: Response rate was 66% (108/163. Results from univariate ANOVA analysis revealed that female sex was associated with PTSD symptoms (F=5.96, p<0.05. When adjusted for age and sex, PTSD symptoms were associated with lower education (F=7.62, p<0.001, poor financial status (F=12.21, p<0.001, and unemployment and/or disability (F=3.04, p<0.05. In a multivariable regression model, when adjusting for age and sex, lack of social support (t=4.22, p<0.001 and traumatic reactions of caregivers (t=2.49, p<0.05 in the aftermath of the disaster independently predicted PTSD 16 years post-trauma. Conclusions: Lingering PTSD symptoms after childhood exposure to a disaster may negatively influence socioeconomic development in adulthood. Strengthening children's support systems post-disaster may prevent the long-term sequelae of symptoms.

  2. Avalanche-to-streamer transition near hydrometeors in thunderstorms

    Science.gov (United States)

    Rutjes, Casper; Dubinova, Anna; Ebert, Ute; Buitink, Stijn; Scholten, Olaf; Trinh, Gia

    2016-04-01

    In the early phase of lightning initiation, streamers must form near water droplets and or ice crystals, collectively called hydrometeors, as it is generally believed that the electric fields in a thunderstorm are below classical breakdown [1]. The hydrometeors, due to their dielectric property, electrically polarize and will enhance the thunderstorm electric field in localized areas just outside the surface, potentially above breakdown. Available electrons, from for example a cosmic ray event, are drawn towards the positive side of the polarized hydrometeor. Some electrons reach the localized area above breakdown, while oxygen molecules have absorbed others. In the area above breakdown electrons begin to multiply in number, creating electron avalanches towards the surface, leaving positive ions behind. This results in a charge separation, which potentially can initiate a positive streamer. The final outcome however strongly depends on several parameters, such as the strength of the thunderstorm electric field, the size and shape of the hydrometeor and the initial amount of electrons. In our letter [1] we introduced a dimensionless quantity M that we call the Meek number, based on the historical and well-used Reather-Meek criterion [2], as a measure of how likely it is to create an avalanche-to-streamer transition near a hydrometeor. Results from simulations showed that streamers can start in a field of only 15% of breakdown from large elongated shaped hydrometeors. Now we extended and generalized our method to arbitrary shaped hydrometeors and we take into account that potentially several electrons can reach the area above breakdown. Due to these effects we can predict smaller hydrometeors to be able to start streamers. We will present the latest results. [1] Dubinova, A., Rutjes, C., Ebert, U., Buitink, S., Scholten, O., & Trinh, G. T. N. (2015). Prediction of lightning inception by large ice particles and extensive air showers. Physical review letters, 115

  3. Advanced active quenching circuits for single-photon avalanche photodiodes

    Science.gov (United States)

    Stipčević, M.; Christensen, B. G.; Kwiat, P. G.; Gauthier, D. J.

    2016-05-01

    Commercial photon-counting modules, often based on actively quenched solid-state avalanche photodiode sensors, are used in wide variety of applications. Manufacturers characterize their detectors by specifying a small set of parameters, such as detection efficiency, dead time, dark counts rate, afterpulsing probability and single photon arrival time resolution (jitter), however they usually do not specify the conditions under which these parameters are constant or present a sufficient description. In this work, we present an in-depth analysis of the active quenching process and identify intrinsic limitations and engineering challenges. Based on that, we investigate the range of validity of the typical parameters used by two commercial detectors. We identify an additional set of imperfections that must be specified in order to sufficiently characterize the behavior of single-photon counting detectors in realistic applications. The additional imperfections include rate-dependence of the dead time, jitter, detection delay shift, and "twilighting." Also, the temporal distribution of afterpulsing and various artifacts of the electronics are important. We find that these additional non-ideal behaviors can lead to unexpected effects or strong deterioration of the system's performance. Specifically, we discuss implications of these new findings in a few applications in which single-photon detectors play a major role: the security of a quantum cryptographic protocol, the quality of single-photon-based random number generators and a few other applications. Finally, we describe an example of an optimized avalanche quenching circuit for a high-rate quantum key distribution system based on time-bin entangled photons.

  4. Asynchronous Rate Chaos in Spiking Neuronal Circuits

    Science.gov (United States)

    Harish, Omri; Hansel, David

    2015-01-01

    The brain exhibits temporally complex patterns of activity with features similar to those of chaotic systems. Theoretical studies over the last twenty years have described various computational advantages for such regimes in neuronal systems. Nevertheless, it still remains unclear whether chaos requires specific cellular properties or network architectures, or whether it is a generic property of neuronal circuits. We investigate the dynamics of networks of excitatory-inhibitory (EI) spiking neurons with random sparse connectivity operating in the regime of balance of excitation and inhibition. Combining Dynamical Mean-Field Theory with numerical simulations, we show that chaotic, asynchronous firing rate fluctuations emerge generically for sufficiently strong synapses. Two different mechanisms can lead to these chaotic fluctuations. One mechanism relies on slow I-I inhibition which gives rise to slow subthreshold voltage and rate fluctuations. The decorrelation time of these fluctuations is proportional to the time constant of the inhibition. The second mechanism relies on the recurrent E-I-E feedback loop. It requires slow excitation but the inhibition can be fast. In the corresponding dynamical regime all neurons exhibit rate fluctuations on the time scale of the excitation. Another feature of this regime is that the population-averaged firing rate is substantially smaller in the excitatory population than in the inhibitory population. This is not necessarily the case in the I-I mechanism. Finally, we discuss the neurophysiological and computational significance of our results. PMID:26230679

  5. FDA Critical Path Initiatives: Opportunities for Generic Drug Development

    OpenAIRE

    Lionberger, Robert A.

    2008-01-01

    FDA’s critical path initiative documents have focused on the challenges involved in the development of new drugs. Some of the focus areas identified apply equally to the production of generic drugs. However, there are scientific challenges unique to the development of generic drugs as well. In May 2007, FDA released a document “Critical Path Opportunities for Generic Drugs” that identified some of the specific challenges in the development of generic drugs. The key steps in generic product de...

  6. Effects of generic versus non-generic feedback on motor learning in children.

    Directory of Open Access Journals (Sweden)

    Suzete Chiviacowsky

    Full Text Available Non-generic feedback refers to a specific event and implies that performance is malleable, while generic feedback implies that task performance reflects an inherent ability. The present study examined the influences of generic versus non-generic feedback on motor performance and learning in 10-year-old children. In the first experiment, using soccer ball kicking at a target as a task, providing participants with generic feedback resulted in worse performance than providing non-generic feedback, after both groups received negative feedback. The second experiment measured more permanent effects. Results of a retention test, performed one day after practicing a throwing task, showed that participants who received non-generic feedback during practice outperformed the generic feedback group, after receiving a negative feedback statement. The findings demonstrate the importance of the wording of feedback. Even though different positive feedback statements may not have an immediate influence on performance, they can affect performance, and presumably individuals' motivation, when performance is (purportedly poor. Feedback implying that performance is malleable, rather than due to an inherent ability, seems to have the potential to inoculate learners against setbacks--a situation frequently encountered in the context of motor performance and learning.

  7. [Analysis of generic drug supply in France].

    Science.gov (United States)

    Taboulet, F; Haramburu, F; Latry, Ph

    2003-09-01

    The list of generic medicines (LGM), published since 1997 by the Agence Française de Sécurité Sanitaire des Produits de Santé (AFFSSaPS), the French Medicine Agency, concerns a special part of the medicines reimbursed by the National Health Insurance (Social Security). The objectives of the present study were: i) to describe the components of this list, based on pharmaceutical, economical and therapeutic characteristics, ii) to study differences between generic and reference products (formulations, excipients, prices, etc.), iii) to analyze information on excipients provided to health care professionals. The 21st version of the LGM (April 2001) was used. Therapeutic value was retrieved from the 2001 AFSSaPS report on the therapeutic value of 4490 reimbursed medicines. Information on excipients in the LGM and the Vidal dictionary (reference prescription book in France) was compared. The products included in the LGM represent 20% of all reimbursed medicines. The mean price differences between generics and their reference products vary between 30 and 50% for more than two thirds of the generic groups. The therapeutic value of the products of the LGM was judged important in 71% of cases (vs 63% for the 4409 assessed medicines) and insufficient in 13% of cases (vs 19%). Information on excipients is often missing and sometimes erroneous. Although the LGM is regularly revised and thus the generic market in perpetual change, the 2001 cross description of this pharmaceutical market provides much informations and raises some concern.

  8. Motor Neurons

    DEFF Research Database (Denmark)

    Hounsgaard, Jorn

    2017-01-01

    Motor neurons translate synaptic input from widely distributed premotor networks into patterns of action potentials that orchestrate motor unit force and motor behavior. Intercalated between the CNS and muscles, motor neurons add to and adjust the final motor command. The identity and functional...... properties of this facility in the path from synaptic sites to the motor axon is reviewed with emphasis on voltage sensitive ion channels and regulatory metabotropic transmitter pathways. The catalog of the intrinsic response properties, their underlying mechanisms, and regulation obtained from motoneurons...... in in vitro preparations is far from complete. Nevertheless, a foundation has been provided for pursuing functional significance of intrinsic response properties in motoneurons in vivo during motor behavior at levels from molecules to systems....

  9. Early warning, warning or alarm systems for natural hazards? A generic classification.

    Science.gov (United States)

    Sättele, Martina; Bründl, Michael; Straub, Daniel

    2013-04-01

    Early warning, warning and alarm systems have gained popularity in recent years as cost-efficient measures for dangerous natural hazard processes such as floods, storms, rock and snow avalanches, debris flows, rock and ice falls, landslides, flash floods, glacier lake outburst floods, forest fires and even earthquakes. These systems can generate information before an event causes loss of property and life. In this way, they mainly mitigate the overall risk by reducing the presence probability of endangered objects. These systems are typically prototypes tailored to specific project needs. Despite their importance there is no recognised system classification. This contribution classifies warning and alarm systems into three classes: i) threshold systems, ii) expert systems and iii) model-based expert systems. The result is a generic classification, which takes the characteristics of the natural hazard process itself and the related monitoring possibilities into account. The choice of the monitoring parameters directly determines the system's lead time. The classification of 52 active systems moreover revealed typical system characteristics for each system class. i) Threshold systems monitor dynamic process parameters of ongoing events (e.g. water level of a debris flow) and incorporate minor lead times. They have a local geographical coverage and a predefined threshold determines if an alarm is automatically activated to warn endangered objects, authorities and system operators. ii) Expert systems monitor direct changes in the variable disposition (e.g crack opening before a rock avalanche) or trigger events (e.g. heavy rain) at a local scale before the main event starts and thus offer extended lead times. The final alarm decision incorporates human, model and organisational related factors. iii) Model-based expert systems monitor indirect changes in the variable disposition (e.g. snow temperature, height or solar radiation that influence the occurrence probability

  10. The properties of ITE's silicon avalanche photodiodes within the spectral range used in scintillation detection

    CERN Document Server

    Wegrzecka, I

    1999-01-01

    The design and properties of 3 mm silicon avalanche photodiodes developed at ITE are presented. Their performance parameters within the spectral range applicable in scintillation detection (400-700 nm) are discussed and compared to those for near infrared radiation.

  11. Landsat Thematic Mapper observations of debris avalanche deposits in the Central Andes

    Science.gov (United States)

    Francis, P. W.; Wells, G. L.

    1988-01-01

    Remote sensing with the Landsat Thematic Mapper of debris avalanche deposits in the Central Andes between 18 and 27 deg S revealed, for the first time, the presence of 28 breached volcanic cones and 11 major volcanic debris avalanche deposits, several of which cover areas in excess of 100 sq km. It is concluded that such avalanche deposits are normal products of the evolution of large composite volcanoes, comparable with lava and pyroclastic flow deposits. A statistical survey of 578 composite volcanoes in the same area indicated that a majority of cones which achieve edifice heights between 2000 and 3000 m may undergo sector collapse. The paper describes morphological criteria for identifying breached composite cones and volcanic debris avalanches using orbital images.

  12. Avalanche diode having reduced dark current and method for its manufacture

    Energy Technology Data Exchange (ETDEWEB)

    Davids, Paul; Starbuck, Andrew Lee; Pomerene, Andrew T. S.

    2017-08-29

    An avalanche diode includes an absorption region in a germanium body epitaxially grown on a silicon body including a multiplication region. Aspect-ratio trapping is used to suppress dislocation growth in the vicinity of the absorption region.

  13. Observation of the Avalanche of Runaway Electrons in Air in a Strong Electric Field

    Science.gov (United States)

    Gurevich, A. V.; Mesyats, G. A.; Zybin, K. P.; Yalandin, M. I.; Reutova, A. G.; Shpak, V. G.; Shunailov, S. A.

    2012-08-01

    The generation of an avalanche of runaway electrons is demonstrated for the first time in a laboratory experiment. Two flows of runaway electrons are formed sequentially in an extended air discharge gap at the stage of delay of a pulsed breakdown. The first, picosecond, runaway electron flow is emitted in the cathode region where the field is enhanced. Being accelerated in the gap, this beam generates electrons due to impact ionization. These secondary electrons form a delayed avalanche of runaway electrons if the field is strong enough. The properties of the avalanche correspond to the existing notions about the runaway breakdown in air. The measured current of the avalanche exceeds up to an order the current of the initiating electron beam.

  14. Inertia and universality of avalanche statistics: The case of slowly deformed amorphous solids.

    Science.gov (United States)

    Karimi, Kamran; Ferrero, Ezequiel E; Barrat, Jean-Louis

    2017-01-01

    By means of a finite elements technique we solve numerically the dynamics of an amorphous solid under deformation in the quasistatic driving limit. We study the noise statistics of the stress-strain signal in the steady-state plastic flow, focusing on systems with low internal dissipation. We analyze the distributions of avalanche sizes and durations and the density of shear transformations when varying the damping strength. In contrast to avalanches in the overdamped case, dominated by the yielding point universal exponents, inertial avalanches are controlled by a nonuniversal damping-dependent feedback mechanism, eventually turning negligible the role of correlations. Still, some general properties of avalanches persist and new scaling relations can be proposed.

  15. Rock avalanche deposits store quantitative evidence on internal shear during runout

    Science.gov (United States)

    Zhang, M.; McSaveney, M. J.

    2017-09-01

    We investigated the quantitative effect of internal shear on grain breakage during rock avalanche runout, by means of 38 ring-shear experiments on identical sand samples at different normal stresses, shear strains and shear strain rates. We compared sample grain-size characteristics before and after shearing. We found that grain size decreased with increase in normal stress and shear strain. Reduction in grain size was inferred to occur through grain breakage associated with grain interactions in strong force chains during strain. The results were consistent with observations of both inverse-grading structure in deep rock avalanche exposures, and fining and grading of particles with increasing rock avalanche travel distance. Our study suggested that with appropriate calibration, variations in grain-size distributions within a rock avalanche deposit would provide quantitative information on the distribution of internal shear during its runout.

  16. Characterization of silicon avalanche photodiodes for photon correlation measurements. 2: Active quenching.

    Science.gov (United States)

    Brown, R G; Jones, R; Rarity, J G; Ridley, K D

    1987-06-15

    We continue examination of the photon correlation properties of silicon avalanche photodiodes operated in photon-counting mode by extending their operation from that of passive quenching(1) to active quenching, yielding shorter dead time and higher frequency operation.

  17. Single Photon Sensitive HgCdTe Avalanche Photodiode Detector (APD) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A linear mode HgCdT electron-initiated avalanche photodiode (EAPD) capable of 1570nm photon detection efficiency (PDE) at >10 MHz will be developed. The Phase I...

  18. Extended Wavelength InP Based Avalanche Diodes for MWIR Response Project

    Data.gov (United States)

    National Aeronautics and Space Administration — For this NASA STTR program, we propose to develop a novel superlattice-based near infrared to midwave infrared avalanche photodetector (APD) grown on InP substrates...

  19. GaN-Based, Low-Voltage Avalanche Photodiodes for Robust and Compact UV Imagers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase I SBIR program is directed toward the development of a novel low-voltage (~10V) AlGaN-based multi-quantum well (MQW) avalanche photodiode (APD) on...

  20. Readout of scintillator light with avalanche photodiodes for positron emission tomography

    CERN Document Server

    Chen, R; Tavernier, Stefaan; Bruyndonckx, P; Clément, D; Loude, J F; Morel, Christian

    1999-01-01

    The noise properties and other relevant characteristics of avalanche photodiodes have been investigated with the perspective of replacing photomultiplier tubes in positron emission tomography. It is clearly demonstrated that they are a valid alternative to photomultiplier tubes in this application.

  1. Dynamic avalanche behavior of power MOSFETs and IGBTs under unclamped inductive switching conditions

    Institute of Scientific and Technical Information of China (English)

    Lu Jiang; Tian Xiaoli; Lu Shuojin; Zhou Hongyu; Zhu Yangjun; Han Zhengsheng

    2013-01-01

    The ability of high-voltage power MOSFETs and IGBTs to withstand avalanche events under unclamped inductive switching (UIS) conditions is measured.This measurement is to investigate and compare the dynamic avalanche failure behavior of the power MOSFETs and the IGBT,which occur at different current conditions.The UIS measurement results at different current conditions show that the main failure reason of the power MOSFETs is related to the parasitic bipolar transistor,which leads to the deterioration of the avalanche reliability of power MOSFETs.However,the results of the IGBT show two different failure behaviors.At high current mode,the failure behavior is similar to the power MOSFETs situation.But at low current mode,the main failure mechanism is related to the parasitic thyristor activity during the occurrence of the avalanche process and which is in good agreement with the experiment result.

  2. Inertia and universality of avalanche statistics: The case of slowly deformed amorphous solids

    Science.gov (United States)

    Karimi, Kamran; Ferrero, Ezequiel E.; Barrat, Jean-Louis

    2017-01-01

    By means of a finite elements technique we solve numerically the dynamics of an amorphous solid under deformation in the quasistatic driving limit. We study the noise statistics of the stress-strain signal in the steady-state plastic flow, focusing on systems with low internal dissipation. We analyze the distributions of avalanche sizes and durations and the density of shear transformations when varying the damping strength. In contrast to avalanches in the overdamped case, dominated by the yielding point universal exponents, inertial avalanches are controlled by a nonuniversal damping-dependent feedback mechanism, eventually turning negligible the role of correlations. Still, some general properties of avalanches persist and new scaling relations can be proposed.

  3. Syn and post- emplacement transformations of the Misti (Peru) volcanic debris avalanches into lahars

    Science.gov (United States)

    Bernard, K.; Van Wyk de Vries, B.; Thouret, J.

    2012-12-01

    We identify stratigraphic, sedimentological and structural variations in lithofacies of debris-avalanche deposits from El Misti volcano in the Quebrada San Lazaro and Río Chili Valley, near the city of Arequipa (south Peru), to determine lithofacies transformations. We describe the internal process associated to the external conditions acting on debris-avalanche deposits in order to assess stages of transformations from the proximal to distal debris-avalanche deposits and the associated epiclastic deposits. Syn-emplacement transformations inside the volcanic debris-avalanche deposits in the upper course of the Rio Chili Valley: within a few meters, the proximal block facies of the sheared debris-avalanche deposit is transformed at the contact of the ash-rich alluvial deposits in thick units comprising a strongly sheared base of the deposit, then stratified matrix dominated beds with normally sorted boulders aligned with the beds. This is interpreted as the effect of strong shearing inside the confined and proximal debris avalanche during motion, which generated a localised stretching near the base of the deposit and the bulking of the thin water saturated basal layers: the bearing capacity of the matrix debris- avalanche is modified, the block facies has been transformed in a stratified matrix facies. The transformations by bulking along a strong sheared contact contribute to reduce the run-out distance of the debris avalanches in the Río Chili valley. Post-deposition evolutions of the debris-avalanche deposits in the Quebrada San Lazaro: in the upper course of the valley, the landslides in the debris- avalanche deposits related to water circulation destabilise the covering scree and volcanic colluvium dipping at 70°. The fragmentation and sorting due to gravity and water are the external processes which separate matrix and block elements; This is the first stage of transformation. The remobilisation of these separated fractions into lahars transforms this

  4. Natural glide slab avalanches, Glacier National Park, USA: A unique hazard and forecasting challenge

    Science.gov (United States)

    Reardon, Blase; Fagre, Daniel B.; Dundas, Mark; Lundy, Chris

    2006-01-01

    In a museum of avalanche phenomena, glide cracks and glide avalanches might be housed in the “strange but true” section. These oddities are uncommon in most snow climates and tend to be isolated to specific terrain features such as bedrock slabs. Many glide cracks never result in avalanches, and when they do, the wide range of time between crack formation and slab failure makes them highly unpredictable. Despite their relative rarity, glide cracks and glide avalanches pose a regular threat and complex forecasting challenge during the annual spring opening of the Going-to-the-Sun Road in Glacier National Park, U.S.A. During the 2006 season, a series of unusual glide cracks delayed snow removal operations by over a week and provided a unique opportunity to record detailed observations of glide avalanches and characterize their occurrence and associated weather conditions. Field observations were from snowpits, crown profiles and where possible, measurements of slab thickness, bed surface slope angle, substrate and other physical characteristics. Weather data were recorded at one SNOTEL site and two automated stations located from 0.6-10 km of observed glide slab avalanches. Nearly half (43%) of the 35 glide slab avalanches recorded were Class D2-2.5, with 15% Class D3-D3.5. The time between glide crack opening and failure ranged from 2 days to over six weeks, and the avalanches occurred in cycles associated with loss of snow water equivalent and spikes in temperature and radiation. We conclude with suggest ions for further study.

  5. Quantification of basal friction for technical and silvicultural glide-snow avalanche mitigation measures

    OpenAIRE

    2014-01-01

    A long-standing problem in avalanche engineering is to design defense structures and manage forest stands such that they can withstand the forces of the natural snow cover. In this way, glide-snow avalanches can be prevented. Ground friction plays a crucial role in this process. To verify existing guidelines, we collected data on the vegetation cover and terrain characteristics of 101 glide-snow release areas in Davos, Switzerland. We quantified the Coulomb friction paramete...

  6. Study of the avalanche to streamer transition in the glass RPC exited by UV light

    CERN Document Server

    Ammosov, V; Kulemzin, A; Semak, A A; Sviridov, Yu; Zaetz, V G; Sviridov, Yu.

    2002-01-01

    A small glass RPC filled with Ar/Isob./Freon mixture has been exposed to a UV laser light. Avalanche and streamer regimes of discharge were reached in a fixed region of the RPC exited by the UV. A dependence of avalanche to streamer transition process on the laser beam intensity and on the applied high voltage was studied. Two types of the streamer signal have been observed. Using a CCD TV camera, pictures on multi-streamer propagation over RPC were obtained.

  7. Some influences of rock strength and strain rate on propagation of rock avalanches

    Science.gov (United States)

    Bowman, Elisabeth; Rait, Kim

    2016-04-01

    Rock avalanches are extreme and destructive mass movements in which large volumes of rock (typically >1 million cubic metres) travel at high speeds, covering large distances, and the occurrence of which is highly unpredictable. The "size effect" in rock avalanches, whereby those with larger volumes produce greater spreading efficiency (as defined by an increase in normalised runout) or lower farboschung angle (defined as the tangent of the ratio of fall height to runout length), is well known. Studies have shown that rock strength is a controlling factor in the mobility of rock avalanches - that is, mass movements involving lower strength rock are generally found to produce greater mobility as evidenced by the spread of deposits or low farboschung angle. However, there are conflicting ideas as to how and why this influence is manifested. This paper discusses different theories of rock comminution in light of numerical simulations of rock clasts undergoing normal and shear induced loading, experimental work on rock avalanche behaviour, and dynamic fracture mechanics. In doing so, we introduce the idea of thresholds of strain rate for the production of dynamic fragmentation (as opposed to pseudo-static clast crushing) that are based, inter alia, on static rock strength. To do this, we refer to data from physical models using rock analogue materials, field data on chalk cliff collapses, and field statistics from documented rock avalanches. The roles of normal and shear loading and loading rate within a rock avalanche are examined numerically using 3D Discrete Element Method models of rock clasts loaded to failure. Results may help to reconcile the observations that large rock avalanches in stronger materials tend not to fragment as much as those in weaker materials and also possess lower mobility, while small cliff collapses (typically > 1000 cubic metres) in weak chalk can exhibit rock avalanche-like behaviour at much smaller volumes.

  8. Two early Holocene rock avalanches in the Bernese Alps (Rinderhorn, Switzerland)

    Science.gov (United States)

    Grämiger, Lorenz M.; Moore, Jeffrey R.; Vockenhuber, Christof; Aaron, Jordan; Hajdas, Irka; Ivy-Ochs, Susan

    2016-09-01

    Large rock avalanches constitute a critical process modulating the evolution of alpine landscapes; however, the relatively infrequent occurrence of these high-magnitude events makes identifying underlying process controls challenging. Here we describe two rock avalanches in the Rinderhorn area of the Bernese Alps, Switzerland, providing new mapping of rock avalanche source areas and deposits, refined volume estimates for each event, runout modeling back-analyses, and absolute age constraint from cosmogenic 36Cl surface exposure dating. Results reveal that the Daubensee rock avalanche released ~ 4 million m3 of limestone sliding from the western crest of the Rinderhorn. Debris ran out across a Lateglacial moraine before reaching the valley bottom and spreading, leaving thin (on average 7 m) deposits across a broad area. The runout resulted in a Fahrböschung angle of 21°. Part of the deposit now lies beneath Lake Daubensee. The Klein Rinderhorn rock avalanche released ~ 37 million m3 of limestone along a dip-slope sliding plane, with a maximum runout distance of 4.3 km and estimated Fahrböschung angle of 14°. Deposits bulked to ~ 47 million m3 running up the opposing slope, with distinct hummocky morphology in the proximal area and a distal longitudinal flow ridge. These deposits were later modified and partly obscured by ice avalanches from the nearby Altels peak. Cosmogenic 36Cl surface exposure dating revealed nearly coincident ages for both rock avalanches of 9.8 ± 0.5 ka. The large lag time between local deglaciation and failure suggests that the events were not directly triggered by deglaciation. Rather, the concurrent exposure ages, also coinciding with the nearby Kander valley rock avalanche as well as paleoseismic records from nearby lakes, strongly suggest seismic triggering.

  9. Snow avalanche activity in the High Tatras Mountains: new data achieved by means of dendrogeomorphic methods

    Science.gov (United States)

    Tichavsky, R.

    2016-12-01

    The High Tatras Mountains are permanently affected by the occurrence of hazardous geomorphic processes. Snow avalanches represent a common hazard that threatens the infrastructure and humans living and visiting the mountains. So far, the spatio-temporal reconstruction of snow avalanche histories was based only on existing archival records, orthophoto interpretation and lichenometric dating in the High Tatras Mountains. Dendrogeomorphic methods allow for the intra-seasonal dating of scars on tree stems and branches and have been broadly used for the dating of snow avalanche events all over the world. We extracted the increment cores and cross sections from 189 individuals of Pinus mugo var. mugo growing on four tali in the Great Cold Valley and dated all the past scars that could correspond with the winter to early spring occurrence of snow avalanches. The dating was supported by the visual analysis of three orthophoto images from 2004, 2009 and 2014. In total, nineteen event years of snow avalanches (10 certain events, and 9 probable events) were identified since 1959. Historical archives provided evidence only for nine event years since 1987, and three of them were confirmed dendrogeomorphically. Geomorphic effect of recent snow avalanches identified by the spatial distribution of scarred trees in individual years corresponds with the extent of events visible from the orthophotos. We can confirm higher frequency of snow avalanche events since 1980s (17 out of 19 events) and significant increase during the last ten years. The future expected climatic changes associated with the changes in temperature and precipitation regime could significantly influence on the frequency of snow avalanches. Therefore, our results can become the starting line for more extensive dendrogeomorphic survey in the High Tatras Mountains in order to create a catalogue of all natural hazards for the future prediction and modelling of these phenomena in context of environmental changes.

  10. Different Avalanche Behaviors in Different Specific Areas of a System Based on Neural Networks

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xiao-Wei; CHEN Tian-Lun

    2003-01-01

    Based on the standard self-organizing map (SOM) neural network model and an integrate-and-fire mecha-nism, we introduce a kind of coupled map lattice system to investigate scale-invariance behavior in the activity of modelneural populations. We find power-law distribution behavior of avalanche size in our model. But more importantly, wefind there are different avalanche distribution behaviors in different specific areas of our system, which are formed by thetopological learning process of the SOM net.

  11. Comparison of risk assessment methods: multiple perspectives of flood and avalanche hazards in North East France

    Science.gov (United States)

    Giacona, Florie; Eleuterio, Julian

    2010-05-01

    Mountainous areas are exposed to several natural hazards such as snow avalanches, debris flows or floods. Such processes may be more frequent and intense in high mountains but they occur in medium-high mountains as well causing loss of life and materials. Thus, the Vosges range, a medium-high mountain located in the north-east of France, is concerned by two kind of natural hazards namely avalanches and floods. While the avalanches constitute the most murderous natural risk in Alsace, its management is paradoxically not a priority. Because it causes more material damages and affects larger places with multiple and complex consequences, the flood risk is more worrying for the administrators. They didn't have the same approach toward these two kinds of risk. So, two different approaches used to assess risk and two study cases are presented: flood risk in the river Bruche (located in the north of the Vosges range, Alsace) and avalanche risk in the Vosges range. The first one is mainly focused on economic aspects of risk. Flood risk analyses are discussed from a hydro-economical perspective. The second one focuses the analysis on human, material and environmental vulnerabilities. Avalanche risk analysis is discussed from a geo-historical point of view. About 300 avalanche events have been reported since the end of the 18th century. The two approaches that we describe illustrate the complementarity of human and physical science to improve the understanding and assessment of hazardous processes in medium-high mountain range. On the one hand, the geo-historical method developed for the avalanche risk could be extended to the flood hazard. Indeed, contrary to high mountains, no service is in charge of the systematic inventory of floods and avalanches in the Vosges mountains. The geo-historical approach could address this lack of data. On the other hand, the methods of damages assessment and vulnerability characterization could be a good tool for the human science.

  12. The Avalanche Catastrophe of El Teniente-chile: August 8 of 1944.

    Science.gov (United States)

    Vergara, J.; Baros, M.

    The avalanche of El Teniente-Chile (~34S) August 8 of 1944, was the most serious avalanche accident in Chile of the last 100 years. On the night of August 8, 1944, a major avalanche impacted a The Sewell, a worked village of the Copper Mine of El Teniente, there were 102 fatalities, 8 building, one school and one bridged de- stroyed. Due to a storm over the central part of Chile where intense precipitation fall over the Andes mountains during nine days. Historical precipitation records near to Sewell shows that total rainfall during the storms was 299mm (La Rufina) and 349mm (Bullileo), and the day before of avalanche the 24 hours rain intensity was 93mm. The Weilbull statistical analysis of monthly snowfall (water equivalent) record in Sewell from 1912-2001 show that the total August 1944 snowfall (621mm) was the larger of the all historical records and the return period is close one events in 180 years, and the annual snowfall during 1944 was 1140mm and return periods was 3.8 years. KEYWRODS: Chile, Avalanches, Andes Mountains, Avalanche Disaster, Historical Snow Records.

  13. Temperature dependence of gain and excess noise in InAs electron avalanche photodiodes.

    Science.gov (United States)

    Ker, Pin Jern; David, John P R; Tan, Chee Hing

    2012-12-31

    Measurement and analysis of the temperature dependence of avalanche gain and excess noise in InAs electron avalanche photodiodes (eAPDs) at 77 to 250 K are reported. The avalanche gain, initiated by pure electron injection, was found to reduce with decreasing temperature. However no significant change in the excess noise was measured as the temperature was varied. For avalanche gain > 3, the InAs APDs with 3.5 µm i-region show consistently low excess noise factors between 1.45 and 1.6 at temperatures of 77 to 250 K, confirming that the eAPD characteristics are exhibited in the measured range of electric field. As the dark current drops much more rapidly than the avalanche gain and the excess noise remains very low, our results confirmed that improved signal to noise ratio can be obtained in InAs eAPDs by reducing the operating temperature. The lack of hole impact ionization, as confirmed by the very low excess noise and the exponentially rising avalanche gain, suggests that hole impact ionization enhancement due to band "resonance" does not occur in InAs APDs at the reported temperatures.

  14. Numerical simulation on the flux avalanche behaviors of microstructured superconducting thin films

    Science.gov (United States)

    Jing, Ze; Yong, Huadong; Zhou, Youhe

    2017-01-01

    Controlling and suppressing the propagation of magnetic flux avalanches is an important issue for the application of type-II superconductors. The effects of engineered pinning centers (antidots) on the guidance of flux avalanche propagation paths in type-II superconducting thin films are numerically investigated by solving the coupled nonlinear Maxwell's equations and the thermal diffusion equations. The field dependence of critical current density is considered in the simulation in this paper. Dynamic propagations of the thermomagnetic avalanches within the superconducting films patterned with different arrangements of antidots (like random, periodic square, and conformal mapping arrays) are presented. We reveal that presence of the antidots significantly modifies the propagation paths of the avalanches. The flux avalanche patterns of the superconducting films change with the variation of the arrangements of antidots. The patterned antidots in the form of conformal mapping arrays within the superconducting film exhibit strong guidance to the thermomagnetic avalanches. In addition, introducing the antidots in the form of conformal mapping arrays into the superconducting film can effectively lower the magnetic flux jump sizes.

  15. Dissipative stochastic sandpile model on small-world networks: Properties of nondissipative and dissipative avalanches

    Science.gov (United States)

    Bhaumik, Himangsu; Santra, S. B.

    2016-12-01

    A dissipative stochastic sandpile model is constructed and studied on small-world networks in one and two dimensions with different shortcut densities ϕ , where ϕ =0 represents regular lattice and ϕ =1 represents random network. The effect of dimension, network topology, and specific dissipation mode (bulk or boundary) on the the steady-state critical properties of nondissipative and dissipative avalanches along with all avalanches are analyzed. Though the distributions of all avalanches and nondissipative avalanches display stochastic scaling at ϕ =0 and mean-field scaling at ϕ =1 , the dissipative avalanches display nontrivial critical properties at ϕ =0 and 1 in both one and two dimensions. In the small-world regime (2-12≤ϕ ≤0.1 ) , the size distributions of different types of avalanches are found to exhibit more than one power-law scaling with different scaling exponents around a crossover toppling size sc. Stochastic scaling is found to occur for s sc . As different scaling forms are found to coexist in a single probability distribution, a coexistence scaling theory on small world network is developed and numerically verified.

  16. Rockfall and snow avalanche impacts leave different anatomical signatures in tree rings of juvenile Larix decidua.

    Science.gov (United States)

    Stoffel, Markus; Hitz, Oliver M

    2008-11-01

    Rockfall and snow avalanche events often cause injury to European larch (Larix decidua Mill.) trees, giving rise to the formation of callus tissue and tangential rows of traumatic resin ducts (TRDs). We analyzed and quantified anatomical reactions of juvenile trees injured before the start of the growing season by snow avalanches (15 trees, 324 cross sections) or rockfalls (18 trees, 270 cross sections). Traumatic resin ducts were observed in the growth ring formed following injury in 94.3% of the rockfall samples and 87.3% of the snow avalanche samples. Traumatic resin ducts were formed at the beginning of the new annual ring around wounds caused by rockfalls. In contrast, in trees injured by snow avalanches, TRDs were not formed until after the formation of several rows of early earlywood (EE) tracheids (mean +/- SD = 4.19 +/- 2.56 rows). The dimensions of the EE tracheids observed in the snow avalanche samples were greatly reduced in the tissues bordering the wound, with radial width reaching an average of only 50% and lumen cross-sectional area an average of only 46% of pre-event values. It is therefore possible to differentiate injuries due to past snow avalanches from injuries due to rockfall based on anatomical growth reactions in the tissues bordering scars.

  17. Is extracorporeal rewarming indicated in avalanche victims with unwitnessed hypothermic cardiorespiratory arrest?

    Science.gov (United States)

    Mair, Peter; Brugger, Hermann; Mair, Birgit; Moroder, Luca; Ruttmann, Elfriede

    2014-12-01

    International guidelines recommend using extracorporeal rewarming in all hypothermic avalanche victims with prolonged cardiac arrest if they have patent airways and a plasma potassium level≤12 mmol/L. The aim of this study was to evaluate outcome data to determine if available experience with extracorporeal rewarming of avalanche victims supports this recommendation. At Innsbruck Medical University Hospital, 28 patients with hypothermic cardiac arrest following an avalanche accident were resuscitated using extracorporeal circulation. Of these patients, 25 were extricated from the snow masses with no vital signs and did not survive to hospital discharge. Three patients had witnessed cardiac arrest after extrication and a core temperature of 21.7°C, 22°C, and 24.0°C, two of whom survived long-term with full neurological recovery. A search of the literature revealed only one asystolic avalanche victim with unwitnessed hypothermic cardiac arrest (core temperature 19°C) surviving long-term. All other avalanche victims in the medical literature surviving prolonged hypothermic cardiac arrest suffered witnessed arrest after extrication with a core temperature below 24°C. Our results suggest that prognosis of hypothermic avalanche victims with unwitnessed asystolic cardiac arrest and a core temperature>24°C is extremely poor. Available outcome data do not support the use of extracorporeal rewarming in these patients.

  18. Artificial kagome spin ice: dimensional reduction, avalanche control and emergent magnetic monopoles.

    Science.gov (United States)

    Hügli, R V; Duff, G; O'Conchuir, B; Mengotti, E; Rodríguez, A Fraile; Nolting, F; Heyderman, L J; Braun, H B

    2012-12-28

    Artificial spin-ice systems consisting of nanolithographic arrays of isolated nanomagnets are model systems for the study of frustration-induced phenomena. We have recently demonstrated that monopoles and Dirac strings can be directly observed via synchrotron-based photoemission electron microscopy, where the magnetic state of individual nanoislands can be imaged in real space. These experimental results of Dirac string formation are in excellent agreement with Monte Carlo simulations of the hysteresis of an array of dipoles situated on a kagome lattice with randomized switching fields. This formation of one-dimensional avalanches in a two-dimensional system is in sharp contrast to disordered thin films, where avalanches associated with magnetization reversal are two-dimensional. The self-organized restriction of avalanches to one dimension provides an example of dimensional reduction due to frustration. We give simple explanations for the origin of this dimensional reduction and discuss the disorder dependence of these avalanches. We conclude with the explicit demonstration of how these avalanches can be controlled via locally modified anisotropies. Such a controlled start and stop of avalanches will have potential applications in data storage and information processing.

  19. Turn-on and turn-off voltages of an avalanche p-n junction

    Institute of Scientific and Technical Information of China (English)

    Zhang Guoqing; Han Dejun; Zhu Changjun; Zhai Xuejun

    2012-01-01

    Characteristics of the turn-on and turn-off voltage of avalanche p-n junctions were demonstrated and studied.As opposed to existing reports,the differences between the turn-on and turn-off voltage cannot be neglected when the size of the p-n junction is in the order of microns.The difference increases inversely with the area of a junction,exerting significant influences on characterizing some parameters of devices composed of small avalanche junctions.Theoretical analyses show that the mechanism for the difference lies in the increase effect of the threshold multiplication factor at the turn-on voltage of a junction when the area of a junction decreases.Moreover,the "breakdown voltage" in the formula of the avalanche asymptotic current is,in essence,the avalanche turn-off voltage,and consequently,the traditional expression of the avalanche asymptotic current and the gain of a Geiger mode avalanche photodiode were modified.

  20. Avalanches and hysteresis in frustrated superconductors and XY spin-glasses

    Science.gov (United States)

    Sharma, Auditya; Andreanov, Alexei; Mueller, Markus

    2014-03-01

    We study avalanches along the hysteresis loop of long-range interacting spin-glasses with continuous XY symmetry - which serves as a toy model of granular superconductors with long-range and frustrated Josephson couplings. We identify sudden jumps in the T = 0 configurations of the XY phases, as an external field is increased. They are initiated by the softest mode of the inverse susceptibility matrix becoming unstable, which induces an avalanche of phase updates (or spin alignments). We analyze the statistics of these events, and study the correlation between the no n-linear avalanches and the soft mode that initiates them. We find that the avalanches follow the directions of a small fraction of the softest modes of the inverse susceptibility matrix, sim ilarly as was found in avalanches in jammed systems. In contrast to the similar Ising spin-glass (Sherrington-Kirkpatrick) studied previously, we find that avalanches are not distributed with a scale-free power law, but rather have a typical size which scales with the system size.

  1. Scaling Analysis And Tuning Parameters For Avalanches On A Slowly-Driven Conical Bead Pile

    Science.gov (United States)

    Lehman, Susan; Christman, Lilianna; Palchoudhuri, Paroma; Jacobs, D. T.

    2014-03-01

    We report the results of our investigation of the dynamic behavior of a 3D conical beadpile composed of 3 mm steel beads. Beads are added to the pile by dropping them onto the apex one at a time; avalanches are measured through changes in pile mass. We have previously shown that the avalanche size distribution generally follows a power law relation for beads dropped onto the pile apex from a low drop height; for higher drop heights or beads dropped over a larger region, the distribution deviates from a power law due to a reduction in the number of larger avalanches. We are now tuning the critical behavior of the system through the addition of cohesion from a uniform magnetic field, and we find an increase in the probability of very large avalanches and decreases in the mid-size avalanches. Similar distributions have been observed previously by other researchers in conical piles of sand, suggesting a possibility that cohesion may have been a factor. All our distributions without cohesion show universality by collapsing onto a common curve in a scaling analysis; so far no scaling has been found in the system with cohesion. The distribution of the time between avalanche events of various size has also been analyzed and shown to depend on both drop height and cohesion strength.

  2. An Internet of Things Generic Reference Architecture

    DEFF Research Database (Denmark)

    Bhalerao, Dipashree M.; Riaz, Tahir; Madsen, Ole Brun

    2013-01-01

    , and keeping track of all these things for monitoring and controlling some information. IoT architecture is studied from software architecture, overall system architecture and network architecture point of view. Paper puts forward the requirements of software architecture along with, its component...... and deployment diagram, process and interface diagram at abstract level. Paper proposes the abstract generic IoT reference and concrete abstract generic IoT reference architectures. Network architecture is also put up as a state of the art. Paper shortly gives overviews of protocols used for IoT. Some...

  3. Generic Rigidity Matroids with Dilworth Truncations

    CERN Document Server

    Tanigawa, Shin-ichi

    2010-01-01

    We prove that the linear matroid that defines generic rigidity of $d$-dimensional body-rod-bar frameworks (i.e., structures consisting of disjoint bodies and rods mutually linked by bars) can be obtained from the union of ${d+1 \\choose 2}$ graphic matroids by applying variants of Dilworth truncation $n_r$ times, where $n_r$ denotes the number of rods. This leads to an alternative proof of Tay's combinatorial characterizations of generic rigidity of rod-bar frameworks and that of identified body-hinge frameworks.

  4. The SENSEI Generic In Situ Interface

    Energy Technology Data Exchange (ETDEWEB)

    Ayachit, Utkarsh [Kitware, Inc., Clifton Park, NY (United States); Whitlock, Brad [Intelligent Light, Rutherford, NJ (United States); Wolf, Matthew [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Loring, Burlen [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Geveci, Berk [Kitware, Inc., Clifton Park, NY (United States); Lonie, David [Kitware, Inc., Clifton Park, NY (United States); Bethel, E. Wes [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2017-04-11

    The SENSEI generic in situ interface is an API that promotes code portability and reusability. From the simulation view, a developer can instrument their code with the SENSEI API and then make make use of any number of in situ infrastructures. From the method view, a developer can write an in situ method using the SENSEI API, then expect it to run in any number of in situ infrastructures, or be invoked directly from a simulation code, with little or no modification. This paper presents the design principles underlying the SENSEI generic interface, along with some simplified coding examples.

  5. Efficient probabilistic inference in generic neural networks trained with non-probabilistic feedback.

    Science.gov (United States)

    Orhan, A Emin; Ma, Wei Ji

    2017-07-26

    Animals perform near-optimal probabilistic inference in a wide range of psychophysical tasks. Probabilistic inference requires trial-to-trial representation of the uncertainties associated with task variables and subsequent use of this representation. Previous work has implemented such computations using neural networks with hand-crafted and task-dependent operations. We show that generic neural networks trained with a simple error-based learning rule perform near-optimal probabilistic inference in nine common psychophysical tasks. In a probabilistic categorization task, error-based learning in a generic network simultaneously explains a monkey's learning curve and the evolution of qualitative aspects of its choice behavior. In all tasks, the number of neurons required for a given level of performance grows sublinearly with the input population size, a substantial improvement on previous implementations of probabilistic inference. The trained networks develop a novel sparsity-based probabilistic population code. Our results suggest that probabilistic inference emerges naturally in generic neural networks trained with error-based learning rules.Behavioural tasks often require probability distributions to be inferred about task specific variables. Here, the authors demonstrate that generic neural networks can be trained using a simple error-based learning rule to perform such probabilistic computations efficiently without any need for task specific operations.

  6. Associations between generic substitution and patients' attitudes, beliefs and experience

    DEFF Research Database (Denmark)

    Østergaard Rathe, Jette; Larsen, Pia Veldt; Andersen, Morten

    2013-01-01

    Abstract Background Generic substitution has been implemented in many countries, but knowledge about patients’ attitudes, beliefs and experiences is still sparse. Aim To assess associations between generic switching and patients’ attitudes, beliefs and experiences with previous generic switching...... on generic medicine and confidence in the healthcare system. Only prescriptions issued by the general practitioners were included. For each patient we focused on one purchase of a generically substitutable drug (index drug). Patients were identified by means of a dispensing database. Results Earlier generic...... switches within the index ATC code were statistically significantly associated with experience of a generic switch (adjusted OR 5.93 95% CI 4.70; 7.49). Having had more than 5 earlier switches within other ATC codes and having negative views on generic medicines reduced the odds of experiencing a generic...

  7. Substorm onset: Current sheet avalanche and stop layer

    Science.gov (United States)

    Haerendel, Gerhard

    2015-03-01

    A new scenario is presented for the onset of a substorm and the nature of the breakup arc. There are two main components, current sheet avalanche and stop layer. The first refers to an earthward flow of plasma and magnetic flux from the central current sheet of the tail, triggered spontaneously or by some unknown interaction with an auroral streamer or a suddenly appearing eastward flow at the end of the growth phase. The second offers a mechanism to stop the flow abruptly at the interface between magnetosphere and tail and extract momentum and energy to be partially processed locally and partially transmitted as Poynting flux toward the ionosphere. The stop layer has a width of the order of the ion inertial length. The different dynamics of the ions entering freely and the magnetized electrons create an electric polarization field which stops the ion flow and drives a Hall current by which flow momentum is transferred to the magnetic field. A simple formalism is used to describe the operation of the process and to enable quantitative conclusions. An important conclusion is that by necessity the stop layer is also highly structured in longitude. This offers a natural explanation for the coarse ray structure of the breakup arc as manifestation of elementary paths of energy and momentum transport. The currents aligned with the rays are balanced between upward and downward directions. While the avalanche is invoked for explaining the spontaneous substorm onset at the inner edge of the tail, the expansion of the breakup arc for many minutes is taken as evidence for a continued formation of new stop layers by arrival of flow bursts from the near-Earth neutral line. This is in line with earlier conclusions about the nature of the breakup arc. Small-scale structure, propagation speed, and energy flux are quantitatively consistent with observations. However, the balanced small-scale currents cannot constitute the substorm current wedge. The source of the latter must be

  8. Should Physicians be Encouraged to use Generic Names and to Prescribe Generic Drugs?

    Science.gov (United States)

    Riaz, Haris; Krasuski, Richard A

    2016-06-01

    While using the brand names seems like a trivial issue at the outset, using these names is inherently problematic. Cardiovascular drugs remain the most commonly prescribed drugs by the physicians. The junior doctors are likely to introject practices of their seniors and consequently to reciprocate from the experiences learnt from their preceptors. Using the generic names may be one way to facilitate prescription of the generic drugs who have a better cost profile and similar efficacy than the more expensive branded drugs. In this editorial, we have outlined several arguments to suggest the importance of using the generic names in academic discussions and clinical documentation.

  9. The importance of being first: evidence from Canadian generic pharmaceuticals.

    Science.gov (United States)

    Hollis, Aidan

    2002-12-01

    This paper uses pooled cross-section data on Canadian ethical drug sales to examine the effect of entry timing on sales of generic drugs. The data is for all drugs for which the first generic competitor entered during the years 1994-1997. It is found that the first generic entrant has a lasting competitive advantage: being first into the market appears to lead to an increase of around 30% in market share (among generics) over a period of at least 4 years. This finding has considerable implications for the current policy of allowing brandname drug companies to issue pseudo-generic equivalents as a preemptive strike against true generic competitors.

  10. The role of initial coherence and path materials in the dynamics of three rock avalanche case histories

    Science.gov (United States)

    Aaron, Jordan; McDougall, Scott; Moore, Jeffrey R.; Coe, Jeffrey A.; Hungr, Oldrich

    2017-01-01

    BackgroundRock avalanches are flow-like landslides that can travel at extremely rapid velocities and impact surprisingly large areas. The mechanisms that lead to the unexpected mobility of these flows are unknown and debated. Mechanisms proposed in the literature can be broadly classified into those that rely on intrinsic characteristics of the rock avalanche material, and those that rely on extrinsic factors such as path material. In this work a calibration-based numerical model is used to back-analyze three rock avalanche case histories. The results of these back-analyses are then used to infer factors that govern rock avalanche motionResultsOur study has revealed two key insights that must be considered when analyzing rock avalanches. Results from two of the case histories demonstrate the importance of accounting for the initially coherent phase of rock avalanche motion. Additionally, the back-analyzed basal resistance parameters, as well as the best-fit rheology, are different for each case history. This suggests that the governing mechanisms controlling rock avalanche motion are unlikely to be intrinsic. The back-analyzed strength parameters correspond well to those that would be expected by considering the path material that the rock avalanches overran.ConclusionOur results show that accurate simulation of rock avalanche motion must account for the initially coherent phase of movement, and that the mechanisms governing rock avalanche motion are unlikely to be intrinsic to the failed material. Interaction of rock avalanche debris with path materials is the likely mechanism that governs the motion of many rock avalanches.

  11. Recent changes in avalanche activity in the French Alps and their links with climatic drivers: an overview

    OpenAIRE

    Eckert, N.; Lavigne, A.; Castebrunet, H.; Giraud, G.; Naaim, M.

    2013-01-01

    International audience; This paper synthetizes our ongoing work on relations between natural avalanche activity and climate change in the French Alps and subregions. Firm results mainly concern occurrences, runout altitudes and high return period avalanches on long time scales (averages over “full” winters and winter-spring sub-seasons) since ~1950. Work in progress concerns extrapolation under future climate, shorter time scales (avalanche cycles), and more generally risk assessment under un...

  12. High resolution tree-ring based spatial reconstructions of snow avalanche activity in Glacier National Park, Montana, USA

    Science.gov (United States)

    Pederson, Gregory T.; Reardon, Blase; Caruso, C.J.; Fagre, Daniel B.

    2006-01-01

    Effective design of avalanche hazard mitigation measures requires long-term records of natural avalanche frequency and extent. Such records are also vital for determining whether natural avalanche frequency and extent vary over time due to climatic or biophysical changes. Where historic records are lacking, an accepted substitute is a chronology developed from tree-ring responses to avalanche-induced damage. This study evaluates a method for using tree-ring chronologies to provide spatially explicit differentiations of avalanche frequency and temporally explicit records of avalanche extent that are often lacking. The study area - part of John F. Stevens Canyon on the southern border of Glacier National Park – is within a heavily used railroad and highway corridor with two dozen active avalanche paths. Using a spatially geo-referenced network of avalanche-damaged trees (n=109) from a single path, we reconstructed a 96-year tree-ring based chronology of avalanche extent and frequency. Comparison of the chronology with historic records revealed that trees recorded all known events as well as the same number of previously unidentified events. Kriging methods provided spatially explicit estimates of avalanche return periods. Estimated return periods for the entire avalanche path averaged 3.2 years. Within this path, return intervals ranged from ~2.3 yrs in the lower track, to ~9-11 yrs and ~12 to >25 yrs in the runout zone, where the railroad and highway are located. For avalanche professionals, engineers, and transportation managers this technique proves a powerful tool in landscape risk assessment and decision making.

  13. Generic tacrolimus in solid organ transplantation

    DEFF Research Database (Denmark)

    Taube, D; Jones, G; O'Beirne, J

    2014-01-01

    The availability of a wide range of immunosuppressive therapies has revolutionized the management of patients who have undergone solid organ transplantation (SOT). However, the cost of immunosuppressive drugs remains high. This situation has led to the development of generic equivalents, which...

  14. Green's Conjecture for the generic canonical curve

    OpenAIRE

    Teixidor-I-Bigas, Montserrat

    1998-01-01

    Green's Conjecture states the following : syzygies of the canonical model of a curve are simple up to the p^th stage if and only if the Clifford index of C is greater than p. We prove that the generic curve of genus g satisfies Green's conjecture.

  15. First-class rules and generic traversal

    NARCIS (Netherlands)

    Dolstra, E.; Visser, Eelco

    2002-01-01

    In this paper we present a functional language supporting first-class rules and generic traversal. This is achieved by generalizing the pattern matching constructs of standard functional languages. The case construct that ties rules together and prevents their reuse, is replaced by separate, firstcl

  16. On generic representation of implicit induction procedures

    NARCIS (Netherlands)

    Naidich, D.

    1996-01-01

    We develop a generic representation of implicit induction proof procedures within the cover set induction framework. Our work further develops the approach of cover set induction on propositional orderings. We show that in order to represent a substantially wide range of implicit induction procedure

  17. Crystallization Kinetics within a Generic Modelling Framework

    DEFF Research Database (Denmark)

    Meisler, Kresten Troelstrup; von Solms, Nicolas; Gernaey, Krist

    2013-01-01

    An existing generic modelling framework has been expanded with tools for kinetic model analysis. The analysis of kinetics is carried out within the framework where kinetic constitutive models are collected, analysed and utilized for the simulation of crystallization operations. A modelling...... procedure is proposed to gain the information of crystallization operation kinetic model analysis and utilize this for faster evaluation of crystallization operations....

  18. Baldrige Theory into Practice: A Generic Model

    Science.gov (United States)

    Arif, Mohammed

    2007-01-01

    Purpose: The education system globally has moved from a push-based or producer-centric system to a pull-based or customer centric system. Malcolm Baldrige Quality Award (MBQA) model happens to be one of the latest additions to the pull based models. The purpose of this paper is to develop a generic framework for MBQA that can be used by…

  19. Matatti’s generic names for fungi

    NARCIS (Netherlands)

    Donk, M.A.

    1975-01-01

    The generic names for fungi used by Maratti in his ‘Flora romana’ must be accepted as validly published. Notes are given on the validly re-published names. Of these Agaricum and Coralloides may cause some difficulties. Conservation of Fomes (Fr.) Fr. against Agaricum [Mich.] Maratti is proposed. To

  20. On the Center of Generic Hecke Algebra

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The concept of norm and cellular algebra are introduced and then the cellular basis is used to replace the Kazhdan-Lusztig basis. So a new base for the center of generic Hecke algebra associated with finite Coxeter group is found. The new base is described by using the notion of cell datum of Graham and Lehrer and the notion of norm.