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Sample records for avalanche distributions recorded

  1. Subsampling effects in neuronal avalanche distributions recorded in vivo

    Directory of Open Access Journals (Sweden)

    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

  2. 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...

  3. 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.

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

  6. 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.

  7. 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.

  8. 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.

  9. Information Measure for Size Distribution of Avalanches in the Bak-Sneppen Evolution Model

    Institute of Scientific and Technical Information of China (English)

    LI Wei; CAI Xu

    2003-01-01

    Information of avalanche size distribution is measured by calculating information entropy (IE) in the Bak-Sneppen evolution model. It is found that the IE increases as the model evolves. Specifically, we establish the relation between the IE and the self-organized threshold fc ? The variation of the IE near the critical point yields an exponent entropy index E = (T - l)/avalanche size distribution and avalanche size cutoff, respectively. A new quantity DT(g) (g = 1 - (fc - G)'r-1' , where G is the gap of the current state), denned as 1 - IT(g)/IT(l), with IT(g) and /T(l) being the IE for the current state and the critical one respectively, is suggested that it represents the distance between the state with gap G and the critical one.

  10. PULSE AMPLITUDE DISTRIBUTION RECORDER

    Science.gov (United States)

    Cowper, G.

    1958-08-12

    A device is described for automatica1ly recording pulse annplitude distribution received from a counter. The novelty of the device consists of the over-all arrangement of conventional circuit elements to provide an easy to read permanent record of the pulse amplitude distribution during a certain time period. In the device a pulse analyzer separates the pulses according to annplitude into several channels. A scaler in each channel counts the pulses and operates a pen marker positioned over a drivable recorder sheet. Since the scalers in each channel have the sanne capacity, the control circuitry permits counting of the incoming pulses until one scaler reaches capacity, whereupon the input is removed and an internal oscillator supplies the necessary pulses to fill up the other scalers. Movement of the chart sheet is initiated wben the first scaler reaches capacity to thereby give a series of marks at spacings proportional to the time required to fill the remaining scalers, and accessory equipment marks calibration points on the recorder sheet to facilitate direct reading of the number of external pulses supplied to each scaler.

  11. 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.

  12. 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.

  13. Recent progress in high gain InAs avalanche photodiodes (Presentation Recording)

    Science.gov (United States)

    Bank, Seth; Maddox, Scott J.; Sun, Wenlu; Nair, Hari P.; Campbell, Joe C.

    2015-08-01

    InAs possesses nearly ideal material properties for the fabrication of near- and mid-infrared avalanche photodiodes (APDs), which result in strong electron-initiated impact ionization and negligible hole-initiated impact ionization [1]. Consequently, InAs multiplication regions exhibit several appealing characteristics, including extremely low excess noise factors and bandwidth independent of gain [2], [3]. These properties make InAs APDs attractive for a number of near- and mid-infrared sensing applications including remote gas sensing, light detection and ranging (LIDAR), and both active and passive imaging. Here, we discuss our recent advances in the growth and fabrication of high gain, low noise InAs APDs. Devices yielded room temperature multiplication gains >300, with much reduced (~10x) lower dark current densities. We will also discuss a likely key contributor to our current performance limitations: silicon diffusion into the intrinsic (multiplication) region from the underlying n-type layer during growth. Future work will focus on increasing the intrinsic region thickness, targeting gains >1000. This work was supported by the Army Research Office (W911NF-10-1-0391). [1] A. R. J. Marshall, C. H. Tan, M. J. Steer, and J. P. R. David, "Electron dominated impact ionization and avalanche gain characteristics in InAs photodiodes," Applied Physics Letters, vol. 93, p. 111107, 2008. [2] A. R. J. Marshall, A. Krysa, S. Zhang, A. S. Idris, S. Xie, J. P. R. David, and C. H. Tan, "High gain InAs avalanche photodiodes," in 6th EMRS DTC Technical Conference, Edinburgh, Scotland, UK, 2009. [3] S. J. Maddox, W. Sun, Z. Lu, H. P. Nair, J. C. Campbell, and S. R. Bank, "Enhanced low-noise gain from InAs avalanche photodiodes with reduced dark current and background doping," Applied Physics Letters, vol. 101, no. 15, pp. 151124-151124-3, Oct. 2012.

  14. Temporal correlations in neuronal avalanche occurrence.

    Science.gov (United States)

    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.

  15. Temporal correlations in neuronal avalanche occurrence

    Science.gov (United States)

    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.

  16. Distribution of joint local and total size and of extension for avalanches in the Brownian force model.

    Science.gov (United States)

    Delorme, Mathieu; Le Doussal, Pierre; Wiese, Kay Jörg

    2016-05-01

    The Brownian force model is a mean-field model for local velocities during avalanches in elastic interfaces of internal space dimension d, driven in a random medium. It is exactly solvable via a nonlinear differential equation. We study avalanches following a kick, i.e., a step in the driving force. We first recall the calculation of the distributions of the global size (total swept area) and of the local jump size for an arbitrary kick amplitude. We extend this calculation to the joint density of local and global sizes within a single avalanche in the limit of an infinitesimal kick. When the interface is driven by a single point, we find new exponents τ_{0}=5/3 and τ=7/4, depending on whether the force or the displacement is imposed. We show that the extension of a "single avalanche" along one internal direction (i.e., the total length in d=1) is finite, and we calculate its distribution following either a local or a global kick. In all cases, it exhibits a divergence P(ℓ)∼ℓ^{-3} at small ℓ. Most of our results are tested in a numerical simulation in dimension d=1.

  17. Distribution of joint local and total size and of extension for avalanches in the Brownian force model

    Science.gov (United States)

    Delorme, Mathieu; Le Doussal, Pierre; Wiese, Kay Jörg

    2016-05-01

    The Brownian force model is a mean-field model for local velocities during avalanches in elastic interfaces of internal space dimension d , driven in a random medium. It is exactly solvable via a nonlinear differential equation. We study avalanches following a kick, i.e., a step in the driving force. We first recall the calculation of the distributions of the global size (total swept area) and of the local jump size for an arbitrary kick amplitude. We extend this calculation to the joint density of local and global sizes within a single avalanche in the limit of an infinitesimal kick. When the interface is driven by a single point, we find new exponents τ0=5 /3 and τ =7 /4 , depending on whether the force or the displacement is imposed. We show that the extension of a "single avalanche" along one internal direction (i.e., the total length in d =1 ) is finite, and we calculate its distribution following either a local or a global kick. In all cases, it exhibits a divergence P (ℓ ) ˜ℓ-3 at small ℓ . Most of our results are tested in a numerical simulation in dimension d =1 .

  18. 21 CFR 211.196 - Distribution records.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 4 2010-04-01 2010-04-01 false Distribution records. 211.196 Section 211.196 Food... Distribution records. Distribution records shall contain the name and strength of the product and description... number of the drug product. For compressed medical gas products, distribution records are not required...

  19. 21 CFR 225.110 - Distribution records.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 4 2010-04-01 2010-04-01 false Distribution records. 225.110 Section 225.110 Food...: GENERAL CURRENT GOOD MANUFACTURING PRACTICE FOR MEDICATED FEEDS Records and Reports § 225.110 Distribution records. (a) Distribution records permit the manufacturer to relate complaints to specific batches...

  20. 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.

  1. Analysis of one-dimensional Yut-Nori game: winning strategy and avalanche-size distribution

    CERN Document Server

    Park, Hye Jin; Jo, Hang-Hyun; Kim, Beom Jun

    2013-01-01

    In the Korean traditional board game Yut-Nori, teams compete by moving their pieces on the two-dimensional game board, and the team whose all pieces complete a round trip on the board wins. In every round, teams throw four wooden sticks of the shape of half-cut cylinder and the number of sticks that show belly sides, i.e., the flat sides, determines the number of steps the team's piece can advance on the board. It is possible to pile up one team's pieces if their sites are identical so that pieces as a group can move together afterwards (piling). If a piece of the opponent team is at the new site of one team's piece, the piece is caught and removed from the board, and the team is given one more chance to throw sticks and proceed (catching). For a simplicity, we simulate this game on one-dimensional board with the same number of sites as the original game, and show that catching is more advantageous strategy than piling to win. We also study the avalanche-size distribution in thermodynamic limit to find that i...

  2. 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.

  3. Record Values of a Pareto Distribution.

    Science.gov (United States)

    Ahsanullah, M.

    The record values of the Pareto distribution, labelled Pareto (II) (alpha, beta, nu), are reviewed. The best linear unbiased estimates of the parameters in terms of the record values are provided. The prediction of the sth record value based on the first m (s>m) record values are obtained. A classical Pareto distribution provides reasonably…

  4. Record Values of a Pareto Distribution.

    Science.gov (United States)

    Ahsanullah, M.

    The record values of the Pareto distribution, labelled Pareto (II) (alpha, beta, nu), are reviewed. The best linear unbiased estimates of the parameters in terms of the record values are provided. The prediction of the sth record value based on the first m (s>m) record values are obtained. A classical Pareto distribution provides reasonably good…

  5. A terrestrial record of Last Interglacial climate preserved by voluminous debris avalanche inundation in Taranaki, New Zealand

    Science.gov (United States)

    Newnham, Rewi; Alloway, Brent

    2004-03-01

    At Airedale Reef, western North Island, New Zealand, a ca. 4 m thick volcanogenic debris avalanche deposit has facilitated the preservation of an enveloping sequence of peats with interbedded andesitic tephras spanning marine isotope (MIS) 5. The sequence closely overlies a wave-cut terrace correlated to MIS 5e and, in turn, is overlain by andic beds with tephra interbeds including the Rotoehu and Kawakawa tephras deposited during early MIS 3 and mid-MIS 2, respectively. Pollen analysis of the organic sequence shows a coherent pattern of fluctuating climate for the Last Interglacial-Last Glacial transition that corresponds with marine isotope stratigraphy and supports the contention that orbital variations were a primary factor in late Quaternary southern mid-latitude climate change. A five-stage subdivision of MIS 5 is clearly recognised, with marine isotope substage (MISS) 5b drier than MISS 5d, and the cooling transition from 5a to MIS 4 also may have been comparatively dry and characterised by natural fire, perhaps associated with volcanism. Several other examples of volcanic impact on vegetation and the landscape are evident. The Airedale Reef sequence exhibits strong similarities with fragmentary MIS 5 pollen records preserved elsewhere in New Zealand and enables the proxy record of southern mid-latitude climatic variability during the Last Interglacial-Glacial cycle to be extended. Copyright

  6. 21 CFR 226.110 - Distribution records.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 4 2010-04-01 2010-04-01 false Distribution records. 226.110 Section 226.110 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DRUGS... Distribution records. Complete records shall be maintained for each shipment of Type A medicated article(s)...

  7. Error diagrams and temporal correlations in a fracture model with characteristic and power-law distributed avalanches

    DEFF Research Database (Denmark)

    Moreno, Y.; Vázquez-Prada, M.; Pacheco, A.F.

    2003-01-01

    Forecasting failure events is one of the most important problems in fracture mechanics and related sciences. In this paper, we use the Molchan scheme to investigate the error diagrams in a fracture model which has the notable advantage of displaying two completely different regimes according to t......, there are non-trivial temporal correlations associated to clustering of large events. Finally, we extend the discussion to seismology, where both kinds of avalanche size distributions can be seen. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003....

  8. Avalanche Distribution Analysis in Anjoula Mountain to Guxiang Section of Sichuan-Tibet Highway%川藏公路安久拉山至古乡段雪崩分布规律

    Institute of Scientific and Technical Information of China (English)

    赵鑫; 程尊兰; 李亚军; 杨天军; 强巴

    2015-01-01

    The characteristics of avalanche distribution. We counted and analyzed the 90 avalanche locations. And found the characteristics of avalanche distribution on space. Further,we analyzed the relationship between ava-lanche distribution and topographic factors,such as altitude,slope,aspect,relative elevation. Through statistical analysis,we obtain the characteristics of avalanche distribution:Avalanche geomorphology effect,that avalanche is mainly distributed in the upper reaches of the canyon area;Avalanche altitude effect,that the avalanche is mainly distributed in the 4 300~4 900 m height range,the area where too high and too low avalanche are less developed;( Relative elevation of the avalanche effect,that the majority of avalanche relative elevation between 300 ~1 100 m,accounting for 74. 44%,the relative elevation is a concrete manifestation of the avalanche of matter and energy;Avalanche slope effect,that avalanche of the study area are most distribute in the range of 30°~ 40°,avalanche on larger or smaller slope than this interregional are less developed;Avalanche aspect effect,that shady significantly compared to the number of sunny slope avalanche dominant.%根据对川藏公路安久拉山至古乡段调查所得的90处雪崩资料,运用统计方法得出研究区雪崩的分布情况。通过对该区灾害的发育与流域地貌的相关关系分析,发现安久拉山至古乡段的雪崩分布规律与地貌特征因子之间具有以下特性:1.雪崩主要分布在上游4300~4900 m峡谷地貌区段,海拔过高和过低较少发育;2.雪崩分布相对高差在300~1100 m,占总数的74.44%;3.雪崩主要分布地形坡度为30°~40°,大于或小于这个范围较少发育;4.雪崩主要分布在阳坡。

  9. 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)].

  10. 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.

  11. 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...

  12. Analysis of the one-dimensional Yut-Nori game: Winning strategy and avalanche-size distribution

    Science.gov (United States)

    Park, Hye Jin; Sim, Hasung; Jo, Hang-Hyun; Kim, Beom Jun

    2013-10-01

    In the Korean traditional board game Yut-Nori, teams compete by moving their pieces on a two-dimensional game board, and the team whose all pieces complete a round trip on the board wins. In every round, teams throw four wooden sticks of the shape of half-cut cylinders and the number of sticks that show belly sides, i.e., the flat sides, determines the number of steps the team's piece can advance on the board. It is possible to pile up one team's pieces if their sites are identical so that pieces as a group can move together afterwards (piling). If a team's piece(s) arrives at a site occupied by an opponent's piece(s), it is caught and removed from the board, and the team is given one more chance to throw the sticks and proceed (catching). For simplicity, we simulate this game on a one-dimensional board with the same number of sites as the original game and show that catching is a more advantageous strategy than piling to win. We also study the avalanche-size distribution in the thermodynamic limit and find that it follows an exponential form.

  13. Aging Avalanches

    Science.gov (United States)

    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.

  14. 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.

  15. 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

  16. 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

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

    Science.gov (United States)

    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.

  18. 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.

  19. 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.

  20. Neuronal avalanches in spontaneous activity in vivo.

    Science.gov (United States)

    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.

  1. On the temporal organization of neuronal avalanches.

    Science.gov (United States)

    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.

  2. 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.

  3. 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.

  4. High-performance AlGaN-based solar-blind avalanche photodiodes with dual-periodic III–nitride distributed Bragg reflectors

    Science.gov (United States)

    Yao, Chujun; Ye, Xuanchao; Sun, Rui; Yang, Guofeng; Wang, Jin; Lu, Yanan; Yan, Pengfei; Cao, Jintao; Gao, Shumei

    2017-03-01

    Separate absorption and multiplication AlGaN solar-blind avalanche photodiodes with dual-periodic III–nitride distributed Bragg reflectors (DBRs) are numerically demonstrated. The designed devices exhibit an improved solar-blind characteristic with a maximum spectral responsivity of 0.184 A/W at λ = 284 nm owing to the optimized optical properties of the dual-periodic III–nitride DBRs. Compared with their conventional counterparts, an increased multiplication gain and a reduced breakdown voltage are achieved by using p-type Al0.15Ga0.85N layers with a lower Al content and multiplication layers. These improvements are attributed to the high p-doping efficiency and large hole ionization coefficient.

  5. Record values from a family of J-shaped distributions

    Directory of Open Access Journals (Sweden)

    Ahmad A. Zghoul

    2013-05-01

    Full Text Available A family of J-shaped distributions has applications in life testing modeling. In this paper we study record values from this family of distributions. Based on lower records, recurrence relations and bounds as well as expressions for moments and product moments of record values are obtained, the maximum likelihood estimator of the shape parameter is derived and shown to be consistent, sufficient, complete and UMVU estimator. In addition, an application in reliability is given.

  6. 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. 

  7. 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...

  8. Design considerations of high-performance InGaAs/InP single-photon avalanche diodes for quantum key distribution

    CERN Document Server

    Ma, Jian; Wang, Liu-Jun; Tong, Cun-Zhu; Jin, Ge; Zhang, Jun; Pan, Jian-Wei

    2016-01-01

    InGaAs/InP single-photon avalanche diodes (SPADs) are widely used in practical applications requiring near-infrared photon counting such as quantum key distribution (QKD). Photon detection efficiency and dark count rate are the intrinsic parameters of InGaAs/InP SPADs, due to the fact that their performances cannot be improved using different quenching electronics given the same operation conditions. After modeling these parameters and developing a simulation platform for InGaAs/InP SPADs, we investigate the semiconductor structure design and optimization. The parameters of photon detection efficiency and dark count rate highly depend on the variables of absorption layer thickness, multiplication layer thickness, excess bias voltage and temperature. By evaluating the decoy-state QKD performance, the variables for SPAD design and operation can be globally optimized. Such optimization from the perspective of specific applications can provide an effective approach to design high-performance InGaAs/InP SPADs.

  9. 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.

  10. 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...

  11. Measuring for thickness distribution of recording layer of PLH

    Science.gov (United States)

    Zhang, Xiao-Chun; Guo, Lurong; Guo, Yongkang

    1991-07-01

    An interference microscope is employed to take a photo of the interfering fringes, and its density is analyzed by a computer image system to measure the thickness distribution of a photolithographic hologram (PLH). This method is much more simple than that of SEM. The theory of measuring is presented in the paper. The authors measured the distributions of photolithographic gratings before and after the etching process. Comparing both the thickness distributions of corresponding recording layers, some primary rules of pattern transfer process by etching were identified.

  12. 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...

  13. On Generalized Upper(kRecord Values From Weibull Distribution

    Directory of Open Access Journals (Sweden)

    Jerin Paul

    2015-09-01

    Full Text Available In this paper we study the generalized upper(krecord values arising from Weibull distribution. Expressions for the moments and product moments of those generalized upper(krecord values  are derived. Some properties of generalized upper(krecord values which characterize the Weibull distribution  have been established. Also some distributional properties of generalized upper(krecord values arising from Weibull distribution are considered and used for suggesting an estimator for the shape parameter of Weibull distribution. The location and scale parameters are estimated using the Best Linear Unbiased Estimation procedure. Prediction of a future record using Best Linear Unbiased Predictor has been studied. A real life data is used to illustrate the results generated in this work.

  14. 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.

  15. 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

  16. 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.

  17. 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...

  18. 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.

  19. Full-depth avalanches and soil erosion: an experimental site in NW Italy

    Science.gov (United States)

    Ceaglio, Elisabetta; Freppaz, Michele; Maggioni, Margherita; Filippa, Gianluca; Godone, Danilo; Zanini, Ermanno

    2010-05-01

    In the future the combined effect of changes in climate and land use could contribute to the intensification of soil erosion, related to snowpack movements as snow gliding and full-depth avalanches. Often, with particular meteorological conditions, the snow movement along a slope is associated with erosion and transport of the upper soil horizons, with the release of significant amount of material in the runout zone. Moreover the chemical composition of the snow in the deposition zone is usually different from the snow in the starting zone, revealing a potential release of ionic species mainly by the organic debris transported by the avalanche itself. The aim of this work is to characterize the quantity and quality of the material released by full-depth avalanches in the deposition zone. The study area is located in Aosta Valley (NW-Italy), on a SW exposed avalanche path, running from 2000 m a.s.l. of the triggering zone to 1200 m a.s.l. of the deposition zone. At this site, snow gliding and glide cracks, generally followed by full-depth avalanches, have been frequently observed. In the starting area, two plots located at the same elevation, slope and aspect, but with different soil moisture content, are equipped with moisture and temperature sensors, located at different depth in the soil, at the snow-soil interface and in the basal snowpack layer, and with glide shoes. The recorded data are related to the snow physical properties, measured by periodical investigations. In the deposition area, after a full-depth avalanche event occurred in March 2009, the mixed material was collected through snow avalanche coring, and a snow pit was dug in the deposit, in order to evaluate the quantity and the distribution of the material transported by the avalanche. First results show that the average density of the snow in the deposition zone was 624 kg m-3. The solid material was distributed mainly in the upper 5 cm of the avalanche deposit, with a mean concentration of the

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. Spike avalanches in vivo suggest a driven, slightly subcritical brain state.

    Science.gov (United States)

    Priesemann, Viola; Wibral, Michael; Valderrama, Mario; Pröpper, Robert; Le Van Quyen, Michel; Geisel, Theo; Triesch, Jochen; Nikolić, Danko; Munk, Matthias H J

    2014-01-01

    In self-organized critical (SOC) systems avalanche size distributions follow power-laws. Power-laws have also been observed for neural activity, and so it has been proposed that SOC underlies brain organization as well. Surprisingly, for spiking activity in vivo, evidence for SOC is still lacking. Therefore, we analyzed highly parallel spike recordings from awake rats and monkeys, anesthetized cats, and also local field potentials from humans. We compared these to spiking activity from two established critical models: the Bak-Tang-Wiesenfeld model, and a stochastic branching model. We found fundamental differences between the neural and the model activity. These differences could be overcome for both models through a combination of three modifications: (1) subsampling, (2) increasing the input to the model (this way eliminating the separation of time scales, which is fundamental to SOC and its avalanche definition), and (3) making the model slightly sub-critical. The match between the neural activity and the modified models held not only for the classical avalanche size distributions and estimated branching parameters, but also for two novel measures (mean avalanche size, and frequency of single spikes), and for the dependence of all these measures on the temporal bin size. Our results suggest that neural activity in vivo shows a mélange of avalanches, and not temporally separated ones, and that their global activity propagation can be approximated by the principle that one spike on average triggers a little less than one spike in the next step. This implies that neural activity does not reflect a SOC state but a slightly sub-critical regime without a separation of time scales. Potential advantages of this regime may be faster information processing, and a safety margin from super-criticality, which has been linked to epilepsy.

  5. Spike avalanches in vivo suggest a driven, slightly subcritical brain state

    Directory of Open Access Journals (Sweden)

    Viola ePriesemann

    2014-06-01

    Full Text Available In self-organized critical (SOC systems avalanche size distributions follow power-laws. Power-laws have also been observed for neural activity, and so it has been proposed that SOC underlies brain organization as well. Surprisingly, for spiking activity in vivo, evidence for SOC is still lacking. Therefore we analyzed highly parallel spike recordings from awake rats and monkeys, anaesthetized cats, and also local field potentials from humans. We compared these to spiking activity from two established critical models: the Bak-Tang-Wiesenfeld model, and a stochastic branching model. We found fundamental differences between the neural and the model activity. These differences could be overcome for both models through a combination of three modifications: (1 subsampling, (2 increasing the input to the model (this way eliminating the separation of time scales, which is fundamental to SOC and its avalanche definition, and (3 making the model slightly sub-critical. The match between the neural activity and the modified models held not only for the classical avalanche size distributions and estimated branching parameters, but also for two novel measures (mean avalanche size, and frequency of single spikes, and for the dependence of all these measures on the temporal bin size.Our results suggest that neural activity in vivo shows a mélange of avalanches, and not temporally separated ones, and that their global activity propagation can be approximated by the principle that one spike on average triggers a little less than one spike in the next step. This implies that neural activity does not reflect a SOC state but a slightly sub-critical regime without a separation of time scales. Potential advantages of this regime may be faster information processing, and a safety margin from super-criticality, which has been linked to epilepsy.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 37 CFR 201.27 - Initial notice of distribution of digital audio recording devices or media.

    Science.gov (United States)

    2010-07-01

    ... distribution of digital audio recording devices or media. 201.27 Section 201.27 Patents, Trademarks, and... Initial notice of distribution of digital audio recording devices or media. (a) General. This section..., any digital audio recording device or digital audio recording medium in the United States....

  17. 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.

  18. 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.

  19. 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

  20. Recording real case data of earth faults in distribution lines

    Energy Technology Data Exchange (ETDEWEB)

    Haenninen, S. [VTT Energy, Espoo (Finland)

    1996-12-31

    The most common fault type in the electrical distribution networks is the single phase to earth fault. According to the earlier studies, for instance in Nordic countries, about 80 % of all faults are of this type. To develop the protection and fault location systems, it is important to obtain real case data of disturbances and faults which occur in the networks. For example, the earth fault initial transients can be used for earth fault location. The aim of this project was to collect and analyze real case data of the earth fault disturbances in the medium voltage distribution networks (20 kV). Therefore, data of fault occurrences were recorded at two substations, of which one has an unearthed and the other a compensated neutral, measured as follows: (a) the phase currents and neutral current for each line in the case of low fault resistance (b) the phase voltages and neutral voltage from the voltage measuring bay in the case of low fault resistance (c) the neutral voltage and the components of 50 Hz at the substation in the case of high fault resistance. In addition, the basic data of the fault occurrences were collected (data of the line, fault location, cause and so on). The data will be used in the development work of fault location and earth fault protection systems

  1. 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...

  2. 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.

  3. 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.

  4. 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.

  5. NEW DISTRIBUTION RECORD OF Cryptotermes brevis (ISOPTERA, KALOTERMITIDAE IN ARGENTINA

    Directory of Open Access Journals (Sweden)

    Juan Manuel Coronel

    2014-01-01

    Full Text Available  The first record of the West Indian drywood termite Cryptotermes brevis  (Walker, 1853 in the city of Corrientes (Argentina is reported. Several C. brevis  colonies were detected inside a local deposit, from wooden crates used for carrying fresh fruits. The observed damage consisted of small rounded holes, partially hollowed wood pieces and presence of debris. The importance of weather factors and the type of material of vegetable and fruit containers in the colonization and dispersion of C. brevis  in this region of Argentina are discussed. Illustrations of soldiers and reproductive C. brevis , and an updated map of the distribution of this termite in Argentina are given.Nuevo registro de distribución de Cryptotermes brevis (Isoptera, Kalotermitidae en Argentina Se presenta el primer registro de Cryptotermes brevis  (Walker, 1853 en la ciudad de Corrientes (Argentina. Se detectaron varias colonias de esta termita dentro de un edificio en contenedores de madera empleados para el transporte de fruta fresca. Los daños observados consistieron en orificios redondos, piezas de madera parcialmente excavadas y presencia de debris fecales. Se discute la importancia de factores climatológicos y del tipo de material de contenedores de fruta, en la colonización y dispersión de C. brevis  en esta región de Argentina. Se presentan ilustraciones de soldados y reproductores de C. brevis  y un mapa actualizado de la distribución de esta termita en Argentina

  6. 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.

  7. 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.

  8. 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.

  9. Determination of snow avalanche return periods using a tree-ring based reconstruction in the French Alps: cross validation with the predictions of a statistical-dynamical model

    Science.gov (United States)

    Schläppy, Romain; Eckert, Nicolas; Jomelli, Vincent; Grancher, Delphine; Brunstein, Daniel; Stoffel, Markus; Naaim, Mohamed

    2013-04-01

    Documenting past avalanche activity represents an indispensable step in avalanche hazard assessment. Nevertheless, (i) archival records of past avalanche events do not normally yield data with satisfying spatial and temporal resolution and (ii) precision concerning runout distance is generally poorly defined. In addition, historic documentation is most often (iii) biased toward events that caused damage to structure or loss of life on the one hand and (iv) undersampled in unpopulated areas on the other hand. On forested paths dendrogeomorphology has been demonstrated to represent a powerful tool to reconstruct past activity of avalanches with annual resolution and for periods covering the past decades to centuries. This method is based on the fact that living trees may be affected by snow avalanches during their flow and deposition phases. Affected trees will react upon these disturbances with a certain growth response. An analysis of the responses recorded in tree rings coupled with an evaluation of the position of reacting trees within the path allows the dendrogeomorphic expert to identify past snow avalanche events and deduced their minimum runout distance. The objective of the work presented here is firstly to dendrochronogically -reconstruct snow avalanche activity in the Château Jouan path located near Montgenèvre in the French Alps. Minimal runout distances are then determined for each reconstructed event by considering the point of further reach along the topographic profile. Related empirical return intervals are evaluated, combining the extent of each event with the average local frequency of the dendrological record. In a second step, the runout distance distribution derived from dendrochronological reconstruction is compared to the one derived from historical archives and to high return period avalanches predicted by an up-to-date locally calibrated statistical-numerical model. It appears that dendrochronological reconstructions correspond mostly to

  10. 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.

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

    Directory of Open Access Journals (Sweden)

    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.

  12. 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.)

  13. New distribution record of the endemic and rare Ficus dalhousiae Miq. (Moraceae

    Directory of Open Access Journals (Sweden)

    K.K.S. Kumara

    2013-09-01

    Full Text Available The present sighting of the endemic and rare Ficus dalhousiae Miq. (Moraceae in Kunthi Betta near Pandavapura forms a new distribution record for Karnataka. It is briefly described here with phenological data and its distribution.

  14. Avalanches in a stochastic model of spiking neurons.

    Directory of Open Access Journals (Sweden)

    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.

  15. Avalanches in a stochastic model of spiking neurons.

    Science.gov (United States)

    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.

  16. The dynamics of surges in the 3 February 2015 avalanches in Vallée de la Sionne

    Science.gov (United States)

    Köhler, A.; McElwaine, J. N.; Sovilla, B.; Ash, M.; Brennan, P.

    2016-11-01

    Five avalanches were artificially released at the Vallée de la Sionne test site in the west of Switzerland on 3 February 2015 and recorded by the GEOphysical flow dynamics using pulsed Doppler radAR Mark 3 radar system. The radar beam penetrates the dilute powder cloud and measures reflections from the underlying denser avalanche features allowing the tracking of the flow at 111 Hz with 0.75 m downslope resolution. The data show that the avalanches contain many internal surges. The large or "major" surges originate from the secondary release of slabs. These slabs can each contain more mass than the initial release, and thus can greatly affect the flow dynamics, by unevenly distributing the mass. The small or "minor" surges appear to be a roll wave-like instability, and these can greatly influence the front dynamics as they can repeatedly overtake the leading edge. We analyzed the friction acting on the fronts of minor surges using a Voellmy-like, simple one-dimensional model with frictional resistance and velocity-squared drag. This model fits the data of the overall velocity, but it cannot capture the dynamics and especially the slowing of the minor surges, which requires dramatically varying effective friction. Our findings suggest that current avalanche models based on Voellmy-like friction laws do not accurately describe the physics of the intermittent frontal region of large mixed avalanches. We suggest that these data can only be explained by changes in the snow surface, such as the entrainment of the upper snow layers and the smoothing by earlier flow fronts.

  17. 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.

  18. 21 CFR 606.165 - Distribution and receipt; procedures and records.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 7 2010-04-01 2010-04-01 false Distribution and receipt; procedures and records. 606.165 Section 606.165 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) BIOLOGICS CURRENT GOOD MANUFACTURING PRACTICE FOR BLOOD AND BLOOD COMPONENTS Records and Reports § 606.165 Distribution...

  19. 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.

  20. 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.

  1. 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.

  2. Distributional records of shrews (Mammalia, Soricomorpha, Soricidae) from Northern Central America with the first record of Sorex from Honduras

    Science.gov (United States)

    Woodman, Neal; Matson, John O.; McCarthy, Timothy J.; Eckerlin, Ralph P.; Bulmer, Walter; Ordonez-Garza, Nicte

    2012-01-01

    Short term surveys for small mammals in Guatemala and Honduras during 1992–2009 provided important new records for 12 taxa of shrews from 24 localities. These locality records expand the known geographic distributions for five species and for the genus Sorex Linnaeus, 1758: the geographic range of Cryptotis goodwini Jackson, 1933, now includes the Sierra de las Minas, Guatemala, and several isolated highlands in western Honduras; the known distribution of Cryptotis mayensis (Merriam, 1901) is increased with the first definite modern record for this shrew from Guatemala; Cryptotis merriami Choate, 1970, is now known to occur in the Sierra de las Minas and the Sierra del Merendon, Guatemala, as well as the isolated Sierra de Omoa and Montana de La Muralla in Honduras, and its documented elevational range (600–1720 m) is expanded; records of Sorex veraepacis Alston, 1877, expand the known distribution of this species to include the Sierra de Yalijux, Guatemala; and discovery of Sorex salvini Merriam, 1897, at Celaque, Honduras (1825–3110 m), represents a considerable extension of the geographic range of the species, and it is the first record of the genus Sorex from Honduras. In addition, the first record of potential syntopy among C. goodwini, C merriami, and Cryptotis orophilus (J.A. Allen, 1895), is reported at an elevation of 1430 m in the Sierra de Celaque, Honduras. Information associated with these records contributes substantially to knowledge of habitat use, elevational distributions, reproductive patterns, diet, and parasites of the species encountered. General patterns include the first evidence that Neotropical species of soricids have smaller litters than their temperate congeners.

  3. Characterizations of the power distribution by record values

    Indian Academy of Sciences (India)

    Min-Young Lee

    2016-05-01

    Let $\\{ X_n, n \\geq 1\\}$ be a sequence of i.i.d. random variables which has absolutely continuous distribution function $F(x)$ with probability density function $f(x)$ and $F(0) = 0$. Assume that $X_n$ belongs to the class $C^\\ast_1$ or $C_2$. Then $X_k$ has the power distribution if and only if $X_k$ and $\\frac{X_{L(n+1)}}{X_{L(n)}}$ or $\\frac{X_{L(n+1)}}{X_{L(n)}}$ and $\\frac{X_{L(n)}}{X_{L(n--1)}}$ are identically distributed, respectively. Suppose that $X_n$ belongs to the class $C_3$. Also, $X_k$ has the power distribution if and only if $X_{L(n+1)}$ and $X_{L(n)}\\cdot V$ are identically distributed, where $V$ is independent of $X_{L(n)}$ and $X_{L(n+1)}$ and is distributed as $X_n$’s.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  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. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. Distributing questionnaires about smoking to patients: impact on general practitioners' recording of smoking advice

    Directory of Open Access Journals (Sweden)

    Wynne Alison

    2007-09-01

    Full Text Available Abstract Background Little is known about the impact of questionnaire-based data collection methods on the consulting behaviour of general practitioners (family physicians who participate in research. Here data collected during a research project which involved questionnaires on smoking being distributed to patients before and after appointments with general practitioners (GPs is analyzed to investigate the impact of this data collection method on doctors' documenting of smoking advice in medical records. Methods Researchers distributed questionnaires on smoking behaviour to 6775 patients who attended consultations during surgery sessions with 32 GPs based in Leicestershire, UK. We obtained the medical records for patients who had attended these surgery sessions and also for a comparator group, during which no researcher had been present. We compared the documenting of advice against smoking in patient's medical records for consultations within GPs' surgery sessions where questionnaires had been distributed with those which occurred when no questionnaires had been given out. Results We obtained records for 77.9% (5276/6775 of all adult patients who attended GPs' surgery sessions, with 51.9% (2739 being from sessions during which researchers distributed questionnaires. Discussion of smoking was recorded in 8.0% (220/2739 of medical records when questionnaires were distributed versus 4.6% (116/2537 where these were not. After controlling for relevant potential confounders including patients' age, gender, the odds ratio for recording of information in the presence of questionnaire distribution (versus none was 1.78 (95% CI, 1.36 to 2.34. Conclusion Distributing questionnaires about smoking to patients before and after they consult with doctors significantly increases GPs' recording of discussions about smoking medical records. This has implications for the design of some types of research into addictive behaviours and further research into how data

  15. 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.

  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. 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

  19. 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).

  20. 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.

  1. 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.

  2. 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}.

  3. Description of the female of Ctenodontina nairae Vieira (Diptera, Asilidae, Asilinae, with new distribution records

    Directory of Open Access Journals (Sweden)

    Rodrigo Vieira

    2014-12-01

    Full Text Available Description of the female of Ctenodontina nairae Vieira (Diptera, Asilidae, Asilinae, with new distribution records. The female of Ctenodontina nairae Vieira, 2012 is described for the first time. Description and illustrations of the habitus, wing and terminalia of the female are provided. The distribution is extended to Bolivia and Peru.

  4. New records and geographical distribution of ctenid spiders (Araneae: Ctenidae) in Colombia.

    Science.gov (United States)

    Hazzi, Nicolás A; Valderrama-Ardila, Carlos; Brescovit, Antonio D; Polotow, Daniele; Simó, Miguel

    2013-01-01

    This study provides new records, geographical distribution extensions and a checklist of the current ctenids species in Colombia based on the review of four arachnological collections and published literature. A total of 15 new records for Ctenidae in Colombia are reported; nine of these species are new records for the country and the distribution of the remaining six is expanded. The genus Centroctenus Mello-Leitão, 1929 (C. ocelliventer Strand, 1909) is recorded for first time in Colombia and Cupiennius coccineus (F.O. Pickard-Cambridge, 1901) for South America. Due to the strategic geographic position of Colombia, which is a transition zone between Southern and Central American biotas, species inventories in different localities are important to fill distributional gaps. The number of known species of ctenids in Colombia is increased from 16 to 25 and these data will be useful for future studies in taxonomy, systematics and biogeography of this family.

  5. Studies in Hawaiian Diptera I: New Distributional Records for Endemic Asteia (Asteiidae

    Directory of Open Access Journals (Sweden)

    Patrick O'Grady

    2014-02-01

    Full Text Available New island records are reported for five species of Asteia endemic to the Hawaiian Islands (A. hawaiiensis, A. mauiensis, A. molokaiensis, A. palikuensis, A. sabroskyi. These new records expand our understanding of distributions in Asteia, change the percentage of single island endemics from 78% to 33%, and have significance in how we view the process of diversification acting in this lineage. We also present a list of the known rearing records for two species in this group. Asteia montgomeryi has been recorded from Erythrina and A. sabroskyi has been reared from Pisonia, Urera, Charpentiera and Hibiscadelphus.

  6. Studies in hawaiian Diptera I: new distributional records for endemic asteia (asteiidae).

    Science.gov (United States)

    O'Grady, Patrick M; Magnacca, Karl Nicholas

    2014-01-01

    New island records are reported for five species of Asteia endemic to the Hawaiian Islands (Asteiahawaiiensis, Asteiamauiensis, Asteiamolokaiensis, Asteiapalikuensis, Asteiasabroskyi). These new records expand our understanding of distributions in Asteia, change the percentage of single island endemics from 78% to 33%, and have significance in how we view the process of diversification acting in this lineage. We also present a list of the known rearing records for two species in this group. Asteiamontgomeryi has been recorded from Erythrina and Asteiasabroskyi has been reared from Pisonia, Urera, Charpentiera and Hibiscadelphus.

  7. 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...

  8. 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.

  9. Characterization of the artificially triggered avalanches in the MonterosaSki resort (North-western Italian Alps)

    Science.gov (United States)

    Maggioni, Margherita; Brulport, A.; Freppaz, M.; Welf, A.; Purves, R.

    2010-05-01

    Artificially triggering methods are nowadays commonly used for avalanche prevention within ski-resorts. The knowledge of possible relations between the characteristics of the avalanche events and the snowpack and weather conditions might help to foresee the avalanche release probability after a favorable weather cycle. The forecast might be helped by models, like for example snowpack evolution models or nearest neighbor models. The latters are based on statistics performed on large databases where the avalanche events, together with the related snow and weather conditions, are well recorded. Within the Operational programme 'Italy - France (Alps - ALCOTRA)', Project "Gestion en sécurité des territories de montagne transfrontalière - Risk-Nat", from winter 2009-2010, in the MonterosaSki resort all the artificially triggered avalanches are registered with their characteristics (e.g. outline, type of avalanches, elevation, aspect), the triggering method (e.g. explosive, Daisy-Bell) and the snow and weather conditions. The aim of this project is to create a well documented database in order to perform some simple statistical analysis to find possible relation between the characteristics of the avalanches (e.g. type, size, run-out distance), the topography of the site (e.g. slope angle, aspect), snowpack condition (e.g. snow crystal type, snow temperature, density) and meteorological parameters (e.g. new snow, air temperature, wind). Moreover, the avalanche release method and the result of the triggering are recorded, in order to understand which are the most favorable conditions for avalanche release. This project is at its first operational winter, therefore in this work we present preliminary data concerning the study area, the methodology and the results from the first winter season, which might be useful to improve our knowledge about artificially triggered avalanches and to help the ski-piste security personnel to take decisions about the avalanche situation

  10. 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.

  11. 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.

  12. 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.

  13. Analysis of the dynamic avalanche of carrier stored trench bipolar transistor (CSTBT) during clamped inductive turn-off transient

    Science.gov (United States)

    Xue, Peng; Fu, Guicui

    2017-03-01

    The dynamic avalanche has a huge impact on the switching robustness of carrier stored trench bipolar transistor (CSTBT). The purpose of this work is to investigate the CSTBT's dynamic avalanche mechanism during clamped inductive turn-off transient. At first, with a Mitsubishi 600 V/150 A CSTBT and a Infineon 600 V/200 A field stop insulated gate bipolar transistor (FS-IGBT) utilized, the clamped inductive turn-off characteristics are obtained by double pulse test. The unclamped inductive switching (UIS) test is also utilized to identify the CSTBT's clamping voltage under dynamic avalanche condition. After the test data analysis, it is found that the CSTBT's dynamic avalanche is abnormal and can be triggered under much looser condition than the conventional buffer layer IGBT. The comparison between the FS-IGBT and CSTBT's experimental results implies that the CSTBT's abnormal dynamic avalanche phenomenon may be induced by the carrier storage (CS) layer. Based on the semiconductor physics, the electric field distribution and dynamic avalanche generation in the depletion region are analyzed. The analysis confirms that the CS layer is the root cause of the CSTBT's abnormal dynamic avalanche mechanism. Moreover, the CSTBT's negative gate capacitance effect is also investigated to clarify the underlying mechanism of the gate voltage bump observed in the test. In the end, the mixed-mode numerical simulation is utilized to reproduce the CSTBT's dynamic avalanche behavior. The simulation results validate the proposed dynamic avalanche mechanisms.

  14. 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

  15. Temporal distribution of favourite books, movies, and records: differential encoding and re-sampling.

    Science.gov (United States)

    Janssen, Steve M J; Chessa, Antonio G; Murre, Jaap M J

    2007-10-01

    The reminiscence bump is the effect that people recall more personal events from early adulthood than from childhood or adulthood. The bump has been examined extensively. However, the question of whether the bump is caused by differential encoding or re-sampling is still unanswered. To examine this issue, participants were asked to name their three favourite books, movies, and records. Furthermore,they were asked when they first encountered them. We compared the temporal distributions and found that they all showed recency effects and reminiscence bumps. The distribution of favourite books had the largest recency effect and the distribution of favourite records had the largest reminiscence bump. We can explain these results by the difference in rehearsal. Books are read two or three times, movies are watched more frequently, whereas records are listened to numerous times. The results suggest that differential encoding initially causes the reminiscence bump and that re-sampling increases the bump further.

  16. High definition in minimally invasive surgery: a review of methods for recording, editing, and distributing video.

    Science.gov (United States)

    Kelly, Christopher R; Hogle, Nancy J; Landman, Jaime; Fowler, Dennis L

    2008-09-01

    The use of high-definition cameras and monitors during minimally invasive procedures can provide the surgeon and operating team with more than twice the resolution of standard definition systems. Although this dramatic improvement in visualization offers numerous advantages, the adoption of high definition cameras in the operating room can be challenging because new recording equipment must be purchased, and several new technologies are required to edit and distribute video. The purpose of this review article is to provide an overview of the popular methods for recording, editing, and distributing high-definition video. This article discusses the essential technical concepts of high-definition video, reviews the different kinds of equipment and methods most often used for recording, and describes several options for video distribution.

  17. 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.

  18. 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.

  19. New distribution record of Cybocephalus kathrynae (Coleoptera, Cybocephalidae on Mona Island, Puerto Rico

    Directory of Open Access Journals (Sweden)

    Jean Carlos Curbelo-Rodríguez

    2012-03-01

    Full Text Available New distribution record of Cybocephalus Kathrynae (Coleoptera, Cybocephalidae on Mona Island, Puerto Rico. A new record of Cybocephalus kathrynae T.R. Smith (Cybocephalidae is reported for Puerto Rico. Adults were collected from the flowers of Mammillaria nivosa (Cactaceae on Mona Island Reserve. Prior to this study, this beetle species was only reported for Monroe and Miami-Dade Counties, Florida, USA.

  20. Spatial reconstructions and comparisons of historic snow avalanche frequency and extent using tree rings in Glacier National Park, Montana, U.S.A.

    Science.gov (United States)

    Reardon, B.A.; Pederson, G.T.; Caruso, C.J.; Fagre, D.B.

    2008-01-01

    Natural snow avalanches have periodically damaged infrastructure and disrupted railroad and highway traffic at the southwestern corner of Glacier National Park, Montana. The 94-year history of these disruptions constitutes an uncommon record of natural avalanches spanning over nine decades and presents a unique opportunity to examine how natural avalanche frequency and minimum extent have varied over time due to climatic or biophysical changes. This study compared the historic record of natural avalanches in one avalanche path with tree-ring evidence of avalanches from 109 cross sections and increment cores collected in the same path. Results from combined historic and tree-ring records yielded 27 avalanche years in the 1910-2003 chronology, with the historic record alone underestimating avalanche years by half. Mean return period was 3.2 years. Interpolated maps allowed for more spatially precise estimates of return periods throughout the runout zone than previous studies. The maps show return periods increase rapidly downslope from 2.3 to 25 years. Avalanche years were associated with positive Snow Water Equivalent anomalies at a nearby snow course. Minimum avalanche extent was highly variable but not associated with snowpack anomalies. Most avalanche years coincided with years in which the mean January-February Pacific Decadal Oscillation (PDO) and El Nin??o-Southern Oscillation (ENSO) 3.4 indices were neutral. The findings suggest that changes in Pacific climate patterns that influence snowfall could also alter the frequency of natural snow avalanches and could thus change disturbance patterns in the montane forests of the canyon. ?? 2008 Regents of the University of Colorado.

  1. [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.

  2. A CORBA-based integration of distributed electronic healthcare records using the synapses approach.

    Science.gov (United States)

    Grimson, J; Grimson, W; Berry, D; Stephens, G; Felton, E; Kalra, D; Toussaint, P; Weier, O W

    1998-09-01

    The ability to exchange in a meaningful, secure, and simple fashion relevant healthcare data about patients is seen as vital in the context of efficient and cost-effective shared or team-based care. The electronic healthcare record (EHCR) lies at the heart of this information exchange, and it follows that there is an urgent need to address the ability to share EHCR's or parts of records between carers and across distributed health information systems. This paper presents the Synapses approach to sharing based on a standardized shared record, the Federated Healthcare Record, which is implemented in an open and flexible manner using the Common Object Request Broker Architecture (CORBA). The architecture of the Federated Healthcare Record is based on the architecture proposed by the Technical Committee 251 of the European Committee for Standardization.

  3. 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.

  4. The scorpions of Yunnan (China: updated identification key, new record, and distributions (Arachnida: Scorpiones

    Directory of Open Access Journals (Sweden)

    Zhiyong Di

    2011-02-01

    Full Text Available This is an identification key to the Scorpiones species of Yunnan (China with notes on the distribution and habitats of these species. E. kubani is one new record species to China. The number of known species of Scorpiones from Yunnan is raised to nine. The redescriptions of E. shidian and E. kubani are provided. Features and distribution of these species provided as additional information for identification.

  5. 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.

  6. 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

  7. 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 ...

  8. New records, distribution and status of six seabird species in Brazil

    Directory of Open Access Journals (Sweden)

    Rafael Antunes Dias

    2010-12-01

    Full Text Available Distribution records of poorly-known species are currently the most explored theme in the Brazilian seabird literature. If properly evaluated, this kind of information can improve our knowledge on distribution, migration and status of occurrence of these species. In this note we present new records for six species of poorly-known seabirds in the Brazilian coast, reviewing distribution records and defining their status of occurrence in the country. We consider Chionis albus (Gmelin, 1789 a pseudo-vagrant in Brazil and define its status as a scarce seasonal visitor from southern South America. We present the first records of Leucophaeus atricilla (Linnaeus, 1758 for Trindade Island, and of Leucophaeus pipixcan (Wagler, 1831 for the state of Rio Grande do Sul, and determined that the former is a vagrant in eastern Brazil and the latter a vagrant across the country. Anous stolidus (Linnaeus, 1758 is a vagrant in southernmost Brazil. We were unable to determine if records of Chlidonias niger (Linnaeus, 1758 for Brazil and southern South America refer to vagrancy or pseudo-vagrancy. Additionally, we verified the occurrence of breeding individuals of Anous minutus Boie, 1844 on Martin Vaz Island and confirmed that there is no evidence of breeding on neighboring Trindade Island.

  9. Estimation of the location parameter of distributions with known coefficient of variation by record values

    Directory of Open Access Journals (Sweden)

    N. K. Sajeevkumar

    2014-09-01

    Full Text Available In this article, we derived the Best Linear Unbiased Estimator (BLUE of the location parameter of certain distributions with known coefficient of variation by record values. Efficiency comparisons are also made on the proposed estimator with some of the usual estimators. Finally we give a real life data to explain the utility of results developed in this article.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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…

  15. VBORNET gap analysis: Mosquito vector distribution models utilised to identify areas of potential species distribution in areas lacking records.

    Directory of Open Access Journals (Sweden)

    Francis Schaffner

    2016-12-01

    Full Text Available This is the second of a number of planned data papers presenting modelled vector distributions produced originally during the ECDC funded VBORNET project. This work continues under the VectorNet project now jointly funded by ECDC and EFSA. Further data papers will be published after sampling seasons when more field data will become available allowing further species to be modelled or validation and updates to existing models.  The data package described here includes those mosquito species first modelled in 2013 & 2014 as part of the VBORNET gap analysis work which aimed to identify areas of potential species distribution in areas lacking records. It comprises three species models together with suitability masks based on land class and environmental limits. The species included as part of this phase are the mosquitoes 'Aedes vexans', 'Anopheles plumbeus' and 'Culex modestus'. The known distributions of these species within the area covered by the project (Europe, the ­Mediterranean Basin, North Africa, and Eurasia are currently incomplete to a greater or lesser degree. The models are designed to fill the gaps with predicted distributions, to provide a assistance in ­targeting surveys to collect distribution data for those areas with no field validated information, and b a first indication of the species distributions within the project areas.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Motion of a Granular Avalanche in an Exponentially Curved Chute: Experiments and Theoretical Predictions

    Science.gov (United States)

    Hutter, Kolumban; Koch, Thilo

    1991-01-01

    This paper describes a model to predict the flow of an initially stationary mass of cohesionless granular material down a rough curved bed, and checks it against laboratory experiments that were conducted with several cohesionless granular materials that are released from rest and travel in an exponentially curved chute. This work is of interest in connection with the motion of rock and ice avalanches and dense flow snow avalanches. We use the depth-averaged field equations of balance of mass and linear momentum as presented by Savage & Hutter (1990). These equations are evolution equations for the transversely averaged streamwise velocity and the distribution of avalanche depths and involve two phenomenological parameters, the internal angle of friction, φ , and a bed friction angle, δ , both as constitutive properties of Coulomb-type behaviour. We present the model but do not derive its equations, which are presented in two variants that incorporate weak and strong curvature effects. For granular avalanches which start as parabolic piles, the governing equations (incorporating weak curvature effects) permit similarity solutions. These solutions preserve the parabolic shape and have simple velocity distributions. We present the equations again without detailed explanations. Experiments were performed with seven different granular materials (two classes of glass beads, Vestolen plastic particles, two samples of quartz granules and two types of crunched marmor particles). Piles of finite masses of such granular materials with various initial geometries were released from rest in a 100 mm wide chute having an exponentially curved bed that was lined with Makrolon (a plexiglass), drawing-paper and sandpaper. The granular masses under motion were photographed and video filmed and thus the geometry of the avalanche was recorded as a function of position and time. With all materials and for all the bed linings, the angle of repose and the bed friction angle were

  1. Ficus sur (Moraceae and Gymnanthemum coloratum (Asteraceae: Vernonieae – first distribution records for Namibia

    Directory of Open Access Journals (Sweden)

    Wessel Swanepoel

    2015-03-01

    Full Text Available Background: The distribution of Ficus sur includes most of tropical Africa, but whilst this species was suspected to occur in Namibia, this has not been verified. Gymnanthemum coloratum is a tropical African savannah shrub or tree that has been recorded for Botswana, Swaziland and South Africa, but which has not previously been recorded for Namibia.Objectives: To formally document the first records of two plant species from Namibia and provide habitat details of the localities from which these species were recorded.Method: The data presented have resulted from botanical expeditions to the poorly known Baynes Mountains in the Koakoveld region of Namibia. Specimens of the two species in the National Herbarium, Pretoria were examined to verify the identity in the case of G. coloratum, and to document additional records in Namibia for F. sur.Results: Ficus sur was recorded from two localities, and a third locality based on a specimen in the National Herbarium, Pretoria, was verified. Gymnanthemum coloratum, a member of the Asteraceae, was recorded from a single locality.Conclusion: The fact that F. sur was collected at more than one location in the Kaokoveld suggests that it is probably more widespread in suitable microhabitats. Ficus sur also occurs further north in Angola, suggesting that the Kaokoveld plants represent a cross-border outlier of the much more widespread Angolan population. Gymnanthemum coloratum was only recorded from the one locality in the Koakoveld. The species also occurs in Angola, which suggests that the Kaokoveld plant represents a cross-border outlier of the population in that country.

  2. Review on Order Statistics and Record Values from F^{α} Distributions

    Directory of Open Access Journals (Sweden)

    Mohammad Shakil

    2012-01-01

    Full Text Available v\\:* {behavior:url(#default#VML;} o\\:* {behavior:url(#default#VML;} w\\:* {behavior:url(#default#VML;} .shape {behavior:url(#default#VML;} Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Abstract: Both order statistics and records arise naturally in many fields of studies such as climatology, sports, science, engineering, medicine, traffic, and industry, among others. Studies of their properties and applications play important roles in many areas of statistical research, for example, statistical inference, nonparametric statistics, among others. In recent years, the F^{α} distributions have been widely studied in statistics because of their wide applicability in the modeling and analysis of life time data. An absolutely continuous positive random variable X is said to have an F^{α} or exponentiated distribution if its cumulative distribution function (cdf is given by G(x=F^{α}(x=[F(x]^{α}, α>0, x>0, which is the αth power of the base line distribution function F(x. Many researchers and authors have developed various classes of F^{α} distributions. It appears from the literature that not much attention has been paid to the analysis of record values and order statistics from these members of F^{α} family of distributions, and, therefore, need

  3. Quantifying changes of wind speed distributions in the historical record of Atlantic tropical cyclones

    Directory of Open Access Journals (Sweden)

    K. Chen

    2009-10-01

    Full Text Available Here we re-examine the official Atlantic basin tropical cyclone (hurricane database HURDAT (1851–2008 and quantify differences between wind speed distributions in the early historical (1851–1943 record and more recent observations. Analyses were performed at three different geographical levels: for all six-hourly track segments of all Atlantic basin events, all segments of all events that crossed the US mainland, and US landfalling segments alone. At all three geographical levels of study, distributions of windspeeds over the last two, four and six decades display negligible dispersion or systematic change over time. On the other hand and relative to wind speed frequencies for subsequent years, the 1851–1943 record has a marked and statistically significant over-representation of wind speeds largely corresponding to Saffir-Simpson Categories 1 and 2 and under-representation of Categories 4 and 5 events; importantly, no single Category 5 event is recorded prior to 1924. The stability of the distribution of windspeeds at landfall over the last six decades, the dataset in which we can have most confidence, suggests that the differences in the earlier record are most likely explained by well-known measurement and observational deficiencies. Moreover by disaggregating the Power Dissipation Index (PDI, we demonstrate that the upward trend in Atlantic basin PDI since 1970s does not imply stronger and longer duration Category 5 windspeeds despite a warming climate. These results have implications for hurricane catastrophe loss modeling for the insurance industry and long-term trend analyses of the historical wind speed record, especially those related to the attribution of the role of Global Climate Change.

  4. 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.

  5. Gun muzzle flash detection using a single photon avalanche diode array in 0.18µm CMOS technology

    Science.gov (United States)

    Savuskan, Vitali; Jakobson, Claudio; Merhav, Tomer; Shoham, Avi; Brouk, Igor; Nemirovsky, Yael

    2015-05-01

    In this study, a CMOS Single Photon Avalanche Diode (SPAD) 2D array is used to record and sample muzzle flash events in the visible spectrum, from representative weapons. SPADs detect the emission peaks of alkali salts, potassium or sodium, with spectral emission lines around 769nm and 589nm, respectively. The alkali salts are included in the gunpowder to suppress secondary flashes ignited during the muzzle flash event. The SPADs possess two crucial properties for muzzle flash imaging: (i) very high photon detection sensitivity, (ii) a unique ability to convert the optical signal to a digital signal at the source pixel, thus practically eliminating readout noise. The sole noise sources are the ones prior to the readout circuitry (optical signal distribution, avalanche initiation distribution and nonphotonic generation). This enables high sampling frequencies in the kilohertz range without significant SNR degradation, in contrast to regular CMOS image sensors. This research will demonstrate the SPAD's ability to accurately sample and reconstruct the temporal behavior of the muzzle flash in the visible wavelength, in the presence of sunlight. The reconstructed signal is clearly distinguishable from background clutter, through exploitation of flash temporal characteristics and signal processing, which will be reported. The frame rate of ~16 KHz was chosen as an optimum between SNR degradation and temporal profile recognition accuracy. In contrast to a single SPAD, the 2D array allows for multiple events to be processed simultaneously. Moreover, a significant field of view is covered, enabling comprehensive surveillance and imaging.

  6. New distribution records of Mesoclemmys vanderhaegei (Testudines: Chelidae from southeastern Brazil, including observations on reproduction

    Directory of Open Access Journals (Sweden)

    Fábio Maffei

    2016-09-01

    Full Text Available Mesoclemmys vanderhaegei is a poorly known freshwater turtle widely distributed in central South America, where it occurs in Argentina, Paraguay, Brazil, and probably Bolivia.  It is considered “Near Threatened” by the IUCN Red List and “Data Deficient” by other local lists. Herein, we present new records and data on the reproductive biology of Mesoclemmys vanderhaegei in southeastern Brazil. 

  7. 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.

  8. Procedure for recording the simultaneous activity of single neurons distributed across cortical areas during sensory discrimination

    Science.gov (United States)

    Hernández, Adrián; Nácher, Verónica; Luna, Rogelio; Alvarez, Manuel; Zainos, Antonio; Cordero, Silvia; Camarillo, Liliana; Vázquez, Yuriria; Lemus, Luis; Romo, Ranulfo

    2008-01-01

    We report a procedure for recording the simultaneous activity of single neurons distributed across five cortical areas in behaving monkeys. The procedure consists of a commercially available microdrive adapted to a commercially available neural data collection system. The critical advantage of this procedure is that, in each cortical area, a configuration of seven microelectrodes spaced 250–500 μm can be inserted transdurally and each can be moved independently in the z axis. For each microelectrode, the data collection system can record the activity of up to five neurons together with the local field potential (LFP). With this procedure, we normally monitor the simultaneous activity of 70–100 neurons while trained monkeys discriminate the difference in frequency between two vibrotactile stimuli. Approximately 20–60 of these neurons have response properties previously reported in this task. The neuronal recordings show good signal-to-noise ratio, are remarkably stable along a 1-day session, and allow testing several protocols. Microelectrodes are removed from the brain after a 1-day recording session, but are reinserted again the next day by using the same or different x-y microelectrode array configurations. The fact that microelectrodes can be moved in the z axis during the recording session and that the x-y configuration can be changed from day to day maximizes the probability of studying simultaneous interactions, both local and across distant cortical areas, between neurons associated with the different components of this task. PMID:18946031

  9. New distribution records for the southern semiornate snake, Meizodon s. semiornatus (Peters, 1854, with a first record from the Kruger National Park and Transvaal

    Directory of Open Access Journals (Sweden)

    G.V. Haagner

    1990-09-01

    Full Text Available The southern semiornate snake, Meizodon s. semiornatus, has a fairly wide distribution in south-east Africa, but due to its secretive habits, it is seldom seen or collected. In South Africa, this species was previously known from only one specimen collected in Zululand during 1965. A second specimen was collected near Crocodile Bridge in the Kruger National Park on 8 November 1987 and constitutes the first record of the species in the Transvaal. Other distribution records for the species were obtained from museums and an updated distribution map was compiled.

  10. Infrasound array criteria for automatic detection and front velocity estimation of snow avalanches: towards a real-time early-warning system

    Directory of Open Access Journals (Sweden)

    E. Marchetti

    2015-04-01

    Full Text Available Avalanche risk management is strongly related to the ability to identify and timely report the occurrence of snow avalanches. Infrasound has been applied to avalanche research and monitoring for the last 20 years but it never turned into an operational tool for the ambiguity to identify clear signals related to avalanches. We present here a new method based on the analysis of infrasound signals recorded by a small aperture array in Ischgl (Austria, which overcome now this limit. The method is based on array derived wave parameters, such as back-azimuth and apparent velocity. The method defines threshold criteria for automatic avalanche identification considering avalanches as a moving source of infrasound. We validate efficiency of the automatic infrasound detection with continuous observations with Doppler Radar and we show how dynamics parameters such as the velocity of a snow avalanche in any given path around the array can be efficiently derived. Our results indicate that a proper infrasound array analysis allows a robust, real-time, remote detection of snow avalanches that could thus contribute significantly to avalanche forecast and risk management.

  11. 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.

  12. 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.

  13. Different Avalanche Behaviors in Different Specific Areas of a System Based on Neural Networks

    Institute of Scientific and Technical Information of China (English)

    ZHAOXiao-Wei; CHENTian-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 model neural populations. We find power-law distribution behavior of avalanche size in our model. But more importantly, we find there are different avalanche distribution behaviors in different specific areas of our system, which are formed by the topological learning process of the SOM net.

  14. Room temperature single-photon detectors for high bit rate quantum key distribution

    Energy Technology Data Exchange (ETDEWEB)

    Comandar, L. C.; Patel, K. A. [Toshiba Research Europe Ltd., 208 Cambridge Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Engineering Department, Cambridge University, 9 J J Thomson Ave., Cambridge CB3 0FA (United Kingdom); Fröhlich, B., E-mail: bernd.frohlich@crl.toshiba.co.uk; Lucamarini, M.; Sharpe, A. W.; Dynes, J. F.; Yuan, Z. L.; Shields, A. J. [Toshiba Research Europe Ltd., 208 Cambridge Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Penty, R. V. [Engineering Department, Cambridge University, 9 J J Thomson Ave., Cambridge CB3 0FA (United Kingdom)

    2014-01-13

    We report room temperature operation of telecom wavelength single-photon detectors for high bit rate quantum key distribution (QKD). Room temperature operation is achieved using InGaAs avalanche photodiodes integrated with electronics based on the self-differencing technique that increases avalanche discrimination sensitivity. Despite using room temperature detectors, we demonstrate QKD with record secure bit rates over a range of fiber lengths (e.g., 1.26 Mbit/s over 50 km). Furthermore, our results indicate that operating the detectors at room temperature increases the secure bit rate for short distances.

  15. Hylid frogs from Mount Ayanganna, Guyana: new species, redescriptions, and distributional records

    Directory of Open Access Journals (Sweden)

    Ross D. MacCulloch

    2005-10-01

    Full Text Available A new species of Osteocephalus, one species of Hyla, three species of Hypsiboas and one of Myersiohyla were collected on Mount Ayanganna, a sandstone Guiana Shield tepui. Hyla warreni, Hypsiboas roraima, H. sibleszi, Myersiohyla kanaima and the new Osteocephalus were collected in high-tepui forest at 1500 m elevation, while Hypsiboas lemai, H. roraima and M. kanaima were also collected in lower montane forest at 870 m. Supplementary descriptions of adults of all species of Hyla, Hypsiboas and Myersiohyla based on the newly collected specimens are provided. Tadpoles of M. kanaima are described. The specimens from Ayanganna represent significant distributional records for several species. This is the first record of Osteocephalus as a member of the Guiana Shield high-tepui herpetofauna.

  16. Scaling behavior of individual barkhausen avalanches in nucleation-mediated magnetization reversal processes

    Energy Technology Data Exchange (ETDEWEB)

    Im, Mi-Young; Fischer, Peter; Kim, Dong-Hyun; Shin, Sung-Chul

    2009-11-09

    We report the scaling behavior of Barkhausen avalanches along the hysteresis loop of a CoCrPt alloy film with perpendicular magnetic anisotropy for every field step of 200 Oe. Individual Barkhausen avalanches are directly observed via high-resolution soft X-ray microscopy with a spatial resolution of 15 nm. The Barkhausen avalanches exhibit a power-law scaling behavior, where the scaling exponent of the power-law distribution drastically changes from 1 {+-} 0.04 to 1.47 {+-} 0.03 as the applied magnetic field approaches the coercivity of the CoCrPt film. We infer that this is due to the coupling of adjacent domains.

  17. Plasmonic field confinement for separate absorption-multiplication in InGaAs nanopillar avalanche photodiodes

    Science.gov (United States)

    Farrell, Alan C.; Senanayake, Pradeep; Hung, Chung-Hong; El-Howayek, Georges; Rajagopal, Abhejit; Currie, Marc; Hayat, Majeed M.; Huffaker, Diana L.

    2015-12-01

    Avalanche photodiodes (APDs) are essential components in quantum key distribution systems and active imaging systems requiring both ultrafast response time to measure photon time of flight and high gain to detect low photon flux. The internal gain of an APD can improve system signal-to-noise ratio (SNR). Excess noise is typically kept low through the selection of material with intrinsically low excess noise, using separate-absorption-multiplication (SAM) heterostructures, or taking advantage of the dead-space effect using thin multiplication regions. In this work we demonstrate the first measurement of excess noise and gain-bandwidth product in III-V nanopillars exhibiting substantially lower excess noise factors compared to bulk and gain-bandwidth products greater than 200 GHz. The nanopillar optical antenna avalanche detector (NOAAD) architecture is utilized for spatially separating the absorption region from the avalanche region via the NOA resulting in single carrier injection without the use of a traditional SAM heterostructure.

  18. Dynamical critical behavior in a cellular model of superconducting vortex avalanches

    Science.gov (United States)

    Vadakkan, Tegy John

    Bak, Tang, and Wiesenfeld showed that certain driven dissipative systems with many degrees of freedom organize into a critical state characterized by avalanche dynamics and power law distribution of avalanche sizes and durations. They called this phenomenon self-organized criticality and sandpile became the prototype of such dynamical systems. Universality in these systems is not yet well established. Forty years ago, de Gennes noted that the Bean state in a type-II superconductor is similar to a sandpile. Motivated by strong experimental evidences, Bassler and Paczuski (BP) proposed a 2D sandpile model to study self-organization in the dynamics of vortices in superconductors. In this dissertation, the effect of anisotropy in the vortex-vortex interaction, stochasticity in the vortex toppling rule, and the configuration of the pinning centers on the scaling properties of the avalanches in the BP model is studied. Also, universality in the cellular model of vortex dynamics is investigated.

  19. Comprehensive understanding of dark count mechanisms of single-photon avalanche diodes fabricated in deep sub-micron CMOS technologies

    Science.gov (United States)

    Xu, Yux; Xiang, Ping; Xie, Xiaopeng

    2017-03-01

    The dark count noise mechanisms of single-photon avalanche diodes (SPADs) fabricated in deep sub-micron (DSM) CMOS technologies are investigated in depth. An electric field dependence of tunneling model combined with carrier thermal generation is established for dark count rate (DCR) prediction. Applying the crucial parameters provided by Geiger mode TCAD simulation such as avalanche triggering probability and electric field distribution in the SPAD avalanche region, the individual contribution of each noise source to DCR is calculated for several SPADs in DSM CMOS technologies. The model calculation results reveal that the trap-assisted tunneling is the main DCR generation source for these DSM CMOS SPADs. With the increase of doping levels in the device avalanche region, the band-to-band tunneling will be the dominant factor that could lead to the higher DCR in scaled DSM CMOS technologies.

  20. Cosmic Ray Measurements by Scintillators with Metal Resistor Semiconductor Avalanche Photo Diodes

    Science.gov (United States)

    Blanco, Francesco; La Rocca, Paola; Riggi, Francesco; Akindinov, Alexandre; Mal'kevich, Dmitry

    2008-01-01

    An educational set-up for cosmic ray physics experiments is described. The detector is based on scintillator tiles with a readout through metal resistor semiconductor (MRS) avalanche photo diode (APD) arrays. Typical measurements of the cosmic angular distribution at sea level and a study of the East-West asymmetry obtained by such a device are…

  1. 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...

  2. Possible effects of ongoing and predicted climate change on snow avalanche activity in western Norway

    Science.gov (United States)

    Laute, Katja; Beylich, Achim A.

    2016-04-01

    As snow avalanche formation is mainly governed by meteorological conditions as, e.g., air temperature fluctuations, heavy precipitation and wind conditions, it is likely that the frequency and magnitude of both ordinary and extreme snow avalanche events is modified through the documented effects of current and future climate change. In the Northern Hemisphere, 1983-2013 was likely the warmest 30-year period of the last 1400 years (IPCC, 2013). Meteorological records of western Norway show the general trend that the last 100 years, especially the last three decades, have been warmer and wetter than the time periods before. However, it is not evident that snow avalanche activity will increase in the near future. Today, the number of studies assessing the impact of climate change on the occurrence and magnitude of snow avalanches is limited. This work focuses on recent and possible future effects of climate change on snow avalanche activity along the western side of the Jostedalsbreen ice cap representing one of the areas with the highest snow avalanche activity in entire Norway. We have analyzed long-term homogenized meteorological data from five meteorological stations in different elevations above sea level, three of them with a long-term record of 120 years (1895-2015). In addition to the statistical analyses of long-term datasets, gained results and insights from a four-year (2009-2012) high-resolution snow avalanche monitoring study conducted in the same study area are incorporated. The statistical analyses of mean monthly air temperature, monthly precipitation sums and mean monthly snow depths showed that there is a trend of increasing air temperatures and precipitation sums whereas no clear trend was found for mean snow depths. Magnitude-frequency analyses conducted for three defined time intervals (120, 90, 60 years) of monthly precipitation sums exhibit an increase of precipitation especially during the last 30 years with the tendency that more precipitation

  3. 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.

  4. Classification of 5-S Epileptic EEG Recordings Using Distribution Entropy and Sample Entropy

    Science.gov (United States)

    Li, Peng; Karmakar, Chandan; Yan, Chang; Palaniswami, Marimuthu; Liu, Changchun

    2016-01-01

    Epilepsy is an electrophysiological disorder of the brain, the hallmark of which is recurrent and unprovoked seizures. Electroencephalogram (EEG) measures electrical activity of the brain that is commonly applied as a non-invasive technique for seizure detection. Although a vast number of publications have been published on intelligent algorithms to classify interictal and ictal EEG, it remains an open question whether they can be detected using short-length EEG recordings. In this study, we proposed three protocols to select 5 s EEG segment for classifying interictal and ictal EEG from normal. We used the publicly-accessible Bonn database, which consists of normal, interical, and ictal EEG signals with a length of 4097 sampling points (23.6 s) per record. In this study, we selected three segments of 868 points (5 s) length from each recordings and evaluated results for each of them separately. The well-studied irregularity measure—sample entropy (SampEn)—and a more recently proposed complexity measure—distribution entropy (DistEn)—were used as classification features. A total of 20 combinations of input parameters m and τ for the calculation of SampEn and DistEn were selected for compatibility. Results showed that SampEn was undefined for half of the used combinations of input parameters and indicated a large intra-class variance. Moreover, DistEn performed robustly for short-length EEG data indicating relative independence from input parameters and small intra-class fluctuations. In addition, it showed acceptable performance for all three classification problems (interictal EEG from normal, ictal EEG from normal, and ictal EEG from interictal) compared to SampEn, which showed better results only for distinguishing normal EEG from interictal and ictal. Both SampEn and DistEn showed good reproducibility and consistency, as evidenced by the independence of results on analysing protocol. PMID:27148074

  5. Cryptotermes colombianus a new drywood termite and distribution record of Cryptotermes in Colombia.

    Science.gov (United States)

    Casalla, Robin; Scheffrahn, Rudolf; Korb, Judith

    2016-01-01

    A new species of drywood termite (Kalotermitidae), Cryptotermes colombianus, is described and new records for Cryptotermes cylindroceps and Cryptotermes mangoldi are presented from the Caribbean coast of Colombia. Cryptotermes colombianus is described from two soldiers and genetic sequences. This unusual species differs noticeably from other regional Cryptotermes species for its weak and inconspicuous definition of the frontal and genal horns and its acute angle of the frons with respect to the vertex. Cryptotermes colombianus clustered with species from the Ethiopian and Oriental region and it is closely related to Cryptotermes havilandi. Cryptotermes cylindroceps is widely distributed along the Colombian Caribbean coast, commonly associated with dead wood in mangrove habitats. It also is commonly found in wooden furniture, constituting an important household pest. Cryptotermes mangoldi is reported from the Caribbean mainland for the first time. With these new records, there are now five Cryptotermes species for Colombia, including the pest species Cryptotermes brevis and Cryptotermes dudleyi. This new description raises the numbers of Neotropical Cryptotermes to a total of 34 species, of which 2 are fossils, 4 introduced, and 28 endemic.

  6. Comparison of minute distribution frequency for anesthesia start and end times from an anesthesia information management system and paper records.

    Science.gov (United States)

    Phelps, Michael; Latif, Asad; Thomsen, Robert; Slodzinski, Martin; Raghavan, Rahul; Paul, Sharon Leigh; Stonemetz, Jerry

    2016-06-07

    Use of an anesthesia information management system (AIMS) has been reported to improve accuracy of recorded information. We tested the hypothesis that analyzing the distribution of times charted on paper and computerized records could reveal possible rounding errors, and that this effect could be modulated by differences in the user interface for documenting certain event times with an AIMS. We compared the frequency distribution of start and end times for anesthesia cases completed with paper records and an AIMS. Paper anesthesia records had significantly more times ending with "0" and "5" compared to those from the AIMS (p distribution of minutes recorded with AIMS was almost evenly distributed, unlike those from paper records that still showed significant end-digit preference. The accuracy of anesthesia case start times and case end times, as inferred by statistical analysis of the distribution of the times, is enhanced with the use of an AIMS. Furthermore, the differences in AIMS user interface for documenting case start and case end times likely affects the degree of end-digit preference, and likely accuracy, of those times.

  7. 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

  8. California dragonfly and damselfly (Odonata) database: temporal and spatial distribution of species records collected over the past century.

    Science.gov (United States)

    Ball-Damerow, Joan E; Oboyski, Peter T; Resh, Vincent H

    2015-01-01

    The recently completed Odonata database for California consists of specimen records from the major entomology collections of the state, large Odonata collections outside of the state, previous literature, historical and recent field surveys, and from enthusiast group observations. The database includes 32,025 total records and 19,000 unique records for 106 species of dragonflies and damselflies, with records spanning 1879-2013. Records have been geographically referenced using the point-radius method to assign coordinates and an uncertainty radius to specimen locations. In addition to describing techniques used in data acquisition, georeferencing, and quality control, we present assessments of the temporal, spatial, and taxonomic distribution of records. We use this information to identify biases in the data, and to determine changes in species prevalence, latitudinal ranges, and elevation ranges when comparing records before 1976 and after 1979. The average latitude of where records occurred increased by 78 km over these time periods. While average elevation did not change significantly, the average minimum elevation across species declined by 108 m. Odonata distribution may be generally shifting northwards as temperature warms and to lower minimum elevations in response to increased summer water availability in low-elevation agricultural regions. The unexpected decline in elevation may also be partially the result of bias in recent collections towards centers of human population, which tend to occur at lower elevations. This study emphasizes the need to address temporal, spatial, and taxonomic biases in museum and observational records in order to produce reliable conclusions from such data.

  9. Gryporhynchidae (Cestoda: Cyclophyllidea) in Mexico: species list, hosts, distribution and new records.

    Science.gov (United States)

    Ortega-Olivares, Mirza P; García-Prieto, Luis; García-Varela, Martín

    2014-05-12

    As a result of this study, 8 new host (Botaurus lentiginosus for Glossocercus caribaensis and Valipora mutabilis; Egretta caerulea for Valipora minuta; Egretta thula for Glossocercus cyprinodontis; Egretta tricolor and Nycticorax nycticorax for Glossocercus caribaensis; Pelecanus occidentalis and Platalea ajaja for Paradilepis caballeroi) and 31 new locality records for gryporhynchid cestode species in Mexico are presented. With these data, the total number of species of this group of helminths in Mexico becomes 25 (19 named species and 6 unidentified taxa), which have been registered as parasites of fishes (47 host species) and (or) birds (20 host species). This information comes from 102 localities, pertaining to 20 of 32 Mexican states. Five of the 25 taxa have been exclusivelly collected in fishes, 7 in fish-eating birds, and 13 in both groups of hosts. The most frequent metacestodes found in Mexican fishes are the merocercoids of Cyclustera ralli, Valipora mutabilis, Parvitaenia cochlearii and Valipora campylancristrota; in adult stage, Glossocercus caribaensis was the species with the largest host spectrum, while Paradilepis caballeroi has the widest distribution range. The work includes parasite/host lists, as well as habitat, distribution, references and information on specimens' deposition.

  10. The cassava mealybug (Phenacoccus manihoti in Asia: first records, potential distribution, and an identification key.

    Directory of Open Access Journals (Sweden)

    Soroush Parsa

    Full Text Available Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae, one of the most serious pests of cassava worldwide, has recently reached Asia, raising significant concern over its potential spread throughout the region. To support management decisions, this article reports recent distribution records, and estimates the climatic suitability for its regional spread using a CLIMEX distribution model. The article also presents a taxonomic key that separates P. manihoti from all other mealybug species associated with the genus Manihot. Model predictions suggest P. manihoti imposes an important, yet differential, threat to cassava production in Asia. Predicted risk is most acute in the southern end of Karnataka in India, the eastern end of the Ninh Thuan province in Vietnam, and in most of West Timor in Indonesia. The model also suggests P. manihoti is likely to be limited by cold stress across Vietnam's northern regions and in the entire Guangxi province in China, and by high rainfall across the wet tropics in Indonesia and the Philippines. Predictions should be particularly important to guide management decisions for high risk areas where P. manihoti is absent (e.g., India, or where it has established but populations remain small and localized (e.g., South Vietnam. Results from this article should help decision-makers assess site-specific risk of invasion, and develop proportional prevention and surveillance programs for early detection and rapid response.

  11. 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.

  12. Superior bit error rate and jitter due to improved switching field distribution in exchange spring magnetic recording media.

    Science.gov (United States)

    Suess, D; Fuger, M; Abert, C; Bruckner, F; Vogler, C

    2016-06-01

    We report two effects that lead to a significant reduction of the switching field distribution in exchange spring media. The first effect relies on a subtle mechanism of the interplay between exchange coupling between soft and hard layers and anisotropy that allows significant reduction of the switching field distribution in exchange spring media. This effect reduces the switching field distribution by about 30% compared to single-phase media. A second effect is that due to the improved thermal stability of exchange spring media over single-phase media, the jitter due to thermal fluctuation is significantly smaller for exchange spring media than for single-phase media. The influence of this overall improved switching field distribution on the transition jitter in granular recording and the bit error rate in bit-patterned magnetic recording is discussed. The transition jitter in granular recording for a distribution of Khard values of 3% in the hard layer, taking into account thermal fluctuations during recording, is estimated to be a = 0.78 nm, which is similar to the best reported calculated jitter in optimized heat-assisted recording media.

  13. Analogue modelling of rock avalanches and structural analysis of the deposits

    Science.gov (United States)

    Longchamp, C.; Charrière, M.; Jaboyedoff, M.

    2012-04-01

    Rock avalanches are catastrophic events in which granular masses of rock debris flow at high speeds, commonly with unusual runout. A great volume of material (>106 m3) is involved and the flowing mass can reach velocities up to ten meters per second. Rock avalanches can travel long distances on the order of kilometres and covering an area over 0.1 km2. These are extremely destructive and uncontrollable events. Due to the rarity of these events, analogue modelling plays a fundamental role in the understanding of the behaviour such events. The main objective of this research is to link the granular physics with the modelling of rock avalanches. Firstly, we attempt to model the debris avalanche and its spreading on a slope with different substratum to understand the relationship between the volume and the reach angle, or Fahrböschung, i.e. angle of the line joining the top of the scar and the end of the deposit. For a better understanding of the sliding mass motion and its spreading, the deposit is scanned with a micro Lidar Minolta. The different datasets are compared in order to see how the grainsize and volume influence a debris avalanche. In a general way, the travel distance is greater with coarse material and varies between 32° for the coarser grainsize and 37° for the finer one. It is interesting to note that the highest Fahrböschung, 41°, is reached for the highest slope angle (60°) and varies between 32 and 34.5° for a slope of 40°. Secondly, a detailed structural analysis of the deposit is performed in order to understand how the sliding mass stops. Several authors (e.g. Shea and van Wyk de Vries (2008)) highlighted that faults and folds are present in rock avalanches deposits and reproduced these features in analogue modelling. Our experiments are recorded by a height speed precision camera to see the development of these structures during the flowing of the mass. The most important impacts of this study is a better understanding of the effects of

  14. Fish geographic distribution range shifts as recorded in the eastern Mediterranean during the last 5 Ma

    Science.gov (United States)

    Agiadi, Konstantina; Karakitsios, Vasileios

    2013-04-01

    Marine fish species geographic distribution is known to reflect the individuals' response to changes in oceanic circulation, temperature, salinity, local geography, other species presence and/or abundance, food availability and other biotic and abiotic factors1. New and published records on the eastern Mediterranean fish, from the end of the Messinian salinity crisis to the present, are here examined, in correlation with palaeoenvironmental data, in order to draw conclusions regarding the abiotic parameters most affecting the fish distribution during the last 5 Ma in this area. This investigation shows that the environmental variables do not affect the fish fauna in a uniform way. Rather, three faunal components may be separated, each occupying a different depth range in the water column. Pelagic fish dwell for the most part on the uppermost 200 m, and their distribution seems to be affected mainly by climatic variability. Mesopelagic fish occupy mostly intermediate depths and their distribution is regulated by the prevailing water circulation patterns. Benthic and benthopelagic fish, which live close or in contact with the sea bottom, are mostly affected by the nature and depth of the substratum. Furthermore, examples from the Ionian2,3 and the Aegean Sea indicate that, during the last 5 Ma, large-scale range shifts, similar to those occurring today, frequently took place in this area. This observation significantly alters previously views on the stability of fish assemblages and the processes occurring today. Acknowledgments. This research has been co-financed by the European Union (European Social Fund - ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program: Heracleitus II. Investing in knowledge society through the European Social Fund. References 1 Wooton RJ. 1998. Ecology of teleost fishes,Fish and Fisheries Series,24.Kluwers.392p. 2

  15. 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.

  16. Cataloguing in the open - the disintegration and distribution of the record

    Directory of Open Access Journals (Sweden)

    Martin Malmsten

    2013-01-01

    Full Text Available As part of a strategic investment in openness the Swedish National Library has released the National Bibliography and accompanying authority file as open data with a Creative Commons Zero license effectively putting it in the public domain. The data has been available  as linked open data since 2008 but is now also released in its original, complete form making it fit for re-use by other library systems. An important principle of linked data is to link out the other datasets. However, as data becomes more interconnected and distributed the need for ways to track and respond to changes in other datasets, even ones outside our area of control, becomes bigger. The issue of who to trust of course becomes vitally important. This paper details the motivation behind the release as well as the technology used to support it. Also, a consequence of exposing and using linked data is that the idea of the record as a self contained and delimited entity starts to fall apart.

  17. Correlation between calculated stress distribution and recorded seismicity in Northern Israel and its surrounding

    Science.gov (United States)

    Wetzler, N.; Kurzon, I.; Rosenthal, M.; Segev, A.; Rybakov, M.; Ben-Avraham, Z.; Lyakhovsky, V.

    2015-12-01

    We study the relationship between crustal structure, tectonic slip, and seismicity. A detailed 3-D layered crustal model is constructed including the geometry and mechanical properties of the main geological units of the study area, Northern Israel and its surrounding. Boundary condition of the 3-D model had been set according to the regional GPS measurements and including localized weak zones extrapolated from the mapped faults. The regional crustal model is converted to 1-D seismic velocity model that was applied in second order relocation software (hypoDD), to obtain more accurate earthquake location. We compare earthquake record of the past 30 years with areas of uplifted shear stress in the crustal model, and compare it with a reference 3-D model with flat layers and similar rock properties. Numerical simulation shows spatial distribution of the zones with increased shear stress associated with differential gravitational load, weak zones geometry, and tectonic load. The obtained zones with high stress are well correlated with earthquake locations. Our results and interpretation highlight the importance and advantages of utilizing detailed crustal structure for assessment of regional seismic hazards.

  18. 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.

  19. Avalanche dynamics of granular materials under the slumping regime in a rotating drum as revealed by speckle visibility spectroscopy.

    Science.gov (United States)

    Yang, H; Li, R; Kong, P; Sun, Q C; Biggs, M J; Zivkovic, V

    2015-04-01

    We used speckle visibility spectroscopy to measure the time-resolved dynamcis of avalanching down the inclined surface of a granular material in a half-full rotating drum operating in the slumping regime. The distribution of the avalanche period, t(d), rest time between them, t(r), and peak particle velocity fluctuation, δv(p)(2), are all normally distributed. While the distributions of the two times at the top and bottom of the free surface are very similar, the particle velocity fluctuation is greater at the bottom of the free surface than at the top. The rest time is observed to be inversely related to the drum speed. Combining this with the relation of t(r) and the difference of the upper and lower angle of repose for the granular material, Δθ, we find that the latter decreases linearly with increasing rotational speed. We also observe that t(d) increases in a linear fashion with the drum speed. Using the relation of t(r) and the distance that particles have to move during an avalanche, we further find that a new scaling relation of the mean number of avalanches required to traverse the free surface with drum speed. We find that the slumping frequency increases with the rotating speed before becoming constant in the slumping-to-rolling transition region. Finally, we find that the average peak of the fluctuation speed of the avalanche, δv(p)(2), increases linearly with the drum speed.

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

    Directory of Open Access Journals (Sweden)

    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.

  1. A two-dimensional model for the dynamics of granular avalanches

    OpenAIRE

    2005-01-01

    Zoning of avalanche risk areas is one important task of land-use planning in alpine areas. The lack of records, due to the low frequency of these events, makes it dicult to implement a statistical analysis. Simulations made with physical and mathematical models can improve the knowledge of the dynamics of these events. In this thesis three didifferent mathematical and numerical models, based on the rheological theory of Savage and Hutter for granular flows, are introduced. A one dimensi...

  2. California dragonfly and damselfly (Odonata database: temporal and spatial distribution of species records collected over the past century

    Directory of Open Access Journals (Sweden)

    Joan E. Ball-Damerow

    2015-02-01

    Full Text Available The recently completed Odonata database for California consists of specimen records from the major entomology collections of the state, large Odonata collections outside of the state, previous literature, historical and recent field surveys, and from enthusiast group observations. The database includes 32,025 total records and 19,000 unique records for 106 species of dragonflies and damselflies, with records spanning 1879–2013. Records have been geographically referenced using the point-radius method to assign coordinates and an uncertainty radius to specimen locations. In addition to describing techniques used in data acquisition, georeferencing, and quality control, we present assessments of the temporal, spatial, and taxonomic distribution of records. We use this information to identify biases in the data, and to determine changes in species prevalence, latitudinal ranges, and elevation ranges when comparing records before 1976 and after 1979. The average latitude of where records occurred increased by 78 km over these time periods. While average elevation did not change significantly, the average minimum elevation across species declined by 108 m. Odonata distribution may be generally shifting northwards as temperature warms and to lower minimum elevations in response to increased summer water availability in low-elevation agricultural regions. The unexpected decline in elevation may also be partially the result of bias in recent collections towards centers of human population, which tend to occur at lower elevations. This study emphasizes the need to address temporal, spatial, and taxonomic biases in museum and observational records in order to produce reliable conclusions from such data.

  3. 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.

  4. 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.

  5. Controls and geomorphic effects of a high-magnitude/low-frequency snow avalanche event in the proglacial area of the Bødalsbreen glacier, Nordfjord, western Norway

    Science.gov (United States)

    Laute, Katja; Beylich, Achim A.

    2014-05-01

    Due to the interactions between the prevalent climatic factors and the local topography snow avalanches are a common phenomena especially in western and northern Norway. Compared to the annually occurring snow avalanches (low-magnitude/high-frequency events) so-called extreme snow avalanches (high-magnitude/low-frequency) are more difficult to record as they are characterized by recurrence intervals often larger than a decade. During the winter-spring period 2011/2012 an extreme snow avalanche occurred within the upper valley part of a steep mountain catchment (Bødalen) in western Norway. The snow avalanche run-out zone was located directly in front of the Bødalsbreen glacier which had a substantial effect with respect to the reworking and remobilization of exposed sediment and debris within the proglacial area. Due to the ongoing glacier retreat of the Bødalsbreen glacier freshly exposed areas are enlarged which e.g. exhibit a comparably higher sediment availability enabling active sediment reworking and re-deposition by secondary transfers (e.g. by snow avalanches or fluvial processes). This study focuses on (i) morphometric and meteorological controls of this specific snow avalanche extreme event and (ii) its related relative role in mass transport as compared to the annually monitored snow avalanche activity within the Bødalen valley. Mapping of the extension and run-out distance of this extreme snow avalanche event is combined with spatial data analysis of possible morphometric controls. The timing and meteorological controls of this event are explored based on meteorological data from two different climate stations located nearby. The volume of the entire snow avalanche, its speed and possible pressure effects are estimated and the total transferred sediment mass is calculated. First results show that this extreme snow avalanche was initiated by a large breakup of the snowpack developed along the cliff of an E-facing rockwall located above the B

  6. 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.

  7. Transformation of the critical state in hard superconductors resulting from thermomagnetic avalanches

    Science.gov (United States)

    Chabanenko, V. V.; Kuchuk, E. I.; Rusakov, V. F.; Abaloszewa, I.; Nabiałek, A.; Pérez-Rodríguez, F.

    2016-04-01

    The results of experimental studies of magnetic flux dynamics in finite-size superconductors, obtained using integral and local measurements methods, are presented. Local methods were aimed at clarifying the role of the demagnetizing factor in the dynamic formation of a complex magnetic structure of the critical state of hard superconductors. To understand the reasons for drastic transformation of the magnetic induction, we further analyzed the literature data on the visualization of flux dynamics in the presence of avalanches, obtained by magneto-optical methods. New features in the behavior of the magnetic flux during and after an avalanche were revealed and characterized: two stages in the formation of the magnetic induction distribution inside the avalanche region were established—homogeneous and heterogeneous filling with magnetic flux; the mechanism of inversion of the induction profile; velocity oscillations in the propagating magnetic flux front; transformation of the critical state band near the edge of the sample; and the role of the thermal effects and demagnetizing factor in the dissipative flux dynamics. The generalized information allowed us to present, within the framework of the Bean concept, a model of the transformation of the patterns of magnetic induction in the critical state and superconducting currents in a finite superconductor occurring as a result of flux avalanches in two different regimes—shielding and trapping of magnetic flux.

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

    Science.gov (United States)

    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.

  9. 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...

  10. First demonstration of THGEM/GAPD-matrix optical readout in a two-phase Cryogenic Avalanche Detector in Ar

    Energy Technology Data Exchange (ETDEWEB)

    Bondar, A. [Budker Institute of Nuclear Physics, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogov Street 2, 630090 Novosibirsk (Russian Federation); Buzulutskov, A., E-mail: a.f.buzulutskov@inp.nsk.su [Budker Institute of Nuclear Physics, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogov Street 2, 630090 Novosibirsk (Russian Federation); Dolgov, A. [Novosibirsk State University, Pirogov Street 2, 630090 Novosibirsk (Russian Federation); Grebenuk, A. [Budker Institute of Nuclear Physics, 630090 Novosibirsk (Russian Federation); Shemyakina, E.; Sokolov, A. [Budker Institute of Nuclear Physics, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogov Street 2, 630090 Novosibirsk (Russian Federation); Breskin, A. [Weizmann Institute of Science, 76100 Rehovot (Israel); Thers, D. [SUBATECH, Ecole des Mines de Nantes, CNRS/In2p3, Université de Nantes, 44307 Nantes Cedex 3 (France)

    2013-12-21

    The multi-channel optical readout of a THGEM multiplier coupled to a matrix of 3×3 Geiger-mode APDs (GAPDs) was demonstrated in a two-phase Cryogenic Avalanche Detector (CRAD) in Ar. The GAPDs recorded THGEM-hole avalanches in the Near Infrared (NIR) spectral range. At an avalanche charge gain of 160, the yield of the combined THGEM/GAPD-matrix multiplier amounted to ∼80 photoelectrons per 20 keV X-ray absorbed in the liquid phase. A spatial resolution of 2.5 mm (FWHM) has been measured for the impinging X-rays. This technique has potential applications in coherent neutrino-nucleus scattering and in dark matter search experiments.

  11. Effect of tunneling current on the noise characteristics of a 4H-SiC Read Avalanche diode

    Institute of Scientific and Technical Information of China (English)

    Deepak K.Karan; Pranati Panda; G.N.Dash

    2013-01-01

    Noise characteristics of a Read Avalanche diode are analyzed by incorporating the tunneling mechanism of the electron into the avalanche mechanism.Analytical expressions are presented for the mean square noise voltage and noise measure in MITATT (mixed tunneling and avalanche transit time) mode operation.A wide band gap semiconductor (4H-SiC) based MITATT diode is considered to study the effect of tunneling on the noise characteristics and negative conductance.While exhibiting enough potential for 4H-SiC to be used as a terahertz source of power in the MITATT mode,our results record a noise measure of 35.18 dB at a frequency of 1.5 THz.

  12. First demonstration of THGEM/GAPD-matrix optical readout in two-phase Cryogenic Avalanche Detector in Ar

    CERN Document Server

    Bondar, A; Dolgov, A; Grebenuk, A; Shemyakina, E; Sokolov, A; Breskin, A; Thers, D

    2013-01-01

    The multi-channel optical readout of a THGEM multiplier coupled to a matrix of 3x3 Geiger-mode APDs (GAPDs) was demonstrated in a two-phase Cryogenic Avalanche Detector (CRAD) in Ar. The GAPDs recorded THGEM-hole avalanches in the Near Infrared (NIR). At an avalanche charge gain of 160, the yield of the combined THGEM/GAPD-matrix multiplier amounted at ~80 photoelectrons per 20 keV X-ray absorbed in the liquid phase. A spatial resolution of 2.5 mm (FWHM) has been measured for the impinging X-rays. This technique has potential applications in coherent neutrino-nucleus scattering and dark matter search experiments.

  13. 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.

  14. Potential distribution and new records of Trinomys species (Rodentia: Echimyidae in the state of Rio de Janeiro

    Directory of Open Access Journals (Sweden)

    Nina Attias

    2009-06-01

    Full Text Available The spiny rats of the genus Trinomys Thomas, 1921 have a broad distribution in the Atlantic Forests of southeastern Brazil. However, some species are known only from their type locality and adjacent areas. In our study, nine areas in the state of Rio de Janeiro were surveyed and three species of the genus were captured - Trinomys dimidiatus (Günther, 1877, T. setosus (Desmarest, 1817 and T. gratiosus bonafidei (MOOJEN, 1948. We extended the distribution of T. gratiosus bonafidei in 100 km, in a straight line to the northwest, and into an area of Semidecidual Seasonal Forest. We captured T. setosus, which had not been previously recorded in the state, in the municipality of Cambuci, extending its distribution 150 km, in a straight line to the east of its closest record, in Juiz de Fora, state of Minas Gerais. The state of Rio de Janeiro has now six recognized species of Trinomys, however none of them were collected above 1300 m of altitude. We used occurrence points provided by our inventories data and from the literature to model the potential distribution of Trinomys species. We used climatic, topographic and phytogeographic variables to prepare the potential distribution maps. The algorithm used for modeling was provided by the software Maxent, version 3.2.1. Although species boundaries within Trinomys in Rio de Janeiro State are not yet clear, their distributions seem to be parapatric, except for T. iheringi and T. dimidiatus.

  15. New distribution record of the Forest Owlet Heteroglaux blewitti Hume, 1873, (Aves: Strigiformes: Strigidae in Purna Wildlife Sanctuary, Gujarat, India

    Directory of Open Access Journals (Sweden)

    Jenis R. Patel

    2015-10-01

    Full Text Available Little is known about the distribution of the endemic forest owlet Heteroglaux Blewitti in India. Its presence has been always dubious in the past in Gujarat. Earlier surveys failed to confirm its occurrence in Gujarat. We present the photographic evidence of the forest owlet from the Purna Wildlife Sanctuary, Gujarat. Two individuals were observed in the same locality. This record presents the first record of Forest owlet from northernmost Western Ghats. A species targeted study is recommended to generate information for the conservation of this threatened species in its range in Gujarat.

  16. A preprocessing tool for removing artifact from cardiac RR interval recordings using three-dimensional spatial distribution mapping.

    Science.gov (United States)

    Stapelberg, Nicolas J C; Neumann, David L; Shum, David H K; McConnell, Harry; Hamilton-Craig, Ian

    2016-04-01

    Artifact is common in cardiac RR interval data that is recorded for heart rate variability (HRV) analysis. A novel algorithm for artifact detection and interpolation in RR interval data is described. It is based on spatial distribution mapping of RR interval magnitude and relationships to adjacent values in three dimensions. The characteristics of normal physiological RR intervals and artifact intervals were established using 24-h recordings from 20 technician-assessed human cardiac recordings. The algorithm was incorporated into a preprocessing tool and validated using 30 artificial RR (ARR) interval data files, to which known quantities of artifact (0.5%, 1%, 2%, 3%, 5%, 7%, 10%) were added. The impact of preprocessing ARR files with 1% added artifact was also assessed using 10 time domain and frequency domain HRV metrics. The preprocessing tool was also used to preprocess 69 24-h human cardiac recordings. The tool was able to remove artifact from technician-assessed human cardiac recordings (sensitivity 0.84, SD = 0.09, specificity of 1.00, SD = 0.01) and artificial data files. The removal of artifact had a low impact on time domain and frequency domain HRV metrics (ranging from 0% to 2.5% change in values). This novel preprocessing tool can be used with human 24-h cardiac recordings to remove artifact while minimally affecting physiological data and therefore having a low impact on HRV measures of that data.

  17. Study of frequency and time responses of a separated absorption and multiplication region avalanche photodiode

    CERN Document Server

    Banoushi, A; Setayeshi, S

    2003-01-01

    In this paper, the frequency and time responses of a separated absorption and multiplication avalanche photodiode are studied by solving the carrier continuity equations, in the low gain regime. The discrepancy between the carrier velocities in different layers is considered for the first time. It is shown that considerable error occurs, if the device d characteristics are calculated assuming uniformly distributed velocities in the depletion layer, especially when the different layers have almost equal thickness.

  18. Jamming transitions and avalanches in the game of Dots-and-Boxes

    Science.gov (United States)

    Metzler, Richard; Engel, Andreas

    2002-06-01

    We study the game of Dots-and-Boxes from a statistical point of view. The early game can be treated as a case of random sequential adsorption, with a jamming transition that marks the beginning of the end game. We derive a set of differential equations to make predictions about the state of the lattice at the transition, and thus about the distribution of avalanches in the end game.

  19. 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

  20. 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.

  1. Minimum required number of specimen records to develop accurate species distribution models

    NARCIS (Netherlands)

    Proosdij, van A.S.J.; Sosef, M.S.M.; Wieringa, J.J.; Raes, N.

    2016-01-01

    Species distribution models (SDMs) are widely used to predict the occurrence of species. Because SDMs generally use presence-only data, validation of the predicted distribution and assessing model accuracy is challenging. Model performance depends on both sample size and species’ prevalence, being t

  2. 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.

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

    CERN Document Server

    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 $\

  4. 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.

  5. New distributional records and conservation implications for the critically endangered greater bamboo lemur Prolemur simus.

    Science.gov (United States)

    Rakotonirina, Laingoniaina; Rajaonson, Andry; Ratolojanahary, Tianasoa; Rafalimandimby, Jean; Fanomezantsoa, Prosper; Ramahefasoa, Bellarmin; Rasolofoharivelo, Tovonanahary; Ravaloharimanitra, Maholy; Ratsimbazafy, Jonah; Dolch, Rainer; King, Tony

    2011-01-01

    To improve our knowledge of the distribution of the critically endangered greater bamboo lemur Prolemur simus, we surveyed 6 sites in eastern Madagascar. We found its characteristic feeding signs at 5 sites and made a direct sighting at one of these. One site represents a northern extension of 45 km of the known extant range of the species. Two sites are located in a forest corridor approximately halfway between the previously known southern and northern populations, therefore suggesting a broadly continuous distribution of the species within its range rather than the previously suspected distribution of two distinct populations separated by a distance of over 200 km. Our results illustrate the benefit of species-focussed surveys in determining the true distribution of endangered species, a realistic measure which is necessary in order to assess their current status and to prioritise long-term conservation interventions.

  6. Investigating ion channel distribution using a combination of spatially limited photolysis, Ca(2+) imaging, and patch clamp recording.

    Science.gov (United States)

    Almassy, Janos; Yule, David I

    2013-01-01

    The production of saliva by parotid acinar cells is stimulated by Ca(2+) activation of Cl(-) and K(+) channels located in the apical plasma membrane of these polarized cells. Here, we utilize a combination of spatially limited flash photolysis, Ca(2+) imaging, and electrophysiological recording to investigate the distinct distribution of Ca(2+)-dependent ion channels in the plasma membrane (PM) of enzymatically isolated murine parotid acinar cells. In these experiments, the aim of photolysis is to selectively target and modify the activity of ion channels, thereby revealing membrane-domain-specific differences in distribution. Specifically, the relative distribution of channels to either apical or basal PM can be investigated. Since there is substantial evidence that Ca(2+)-dependent Cl(-) channels are exclusively localized to the apical membrane of acinar cells, this provides an important electrophysiological verification that a particular membrane has been specifically targeted.

  7. A simulated avalanche search and rescue mission induces temporary physiological and behavioural changes in military dogs.

    Science.gov (United States)

    Diverio, Silvana; Barbato, Olimpia; Cavallina, Roberta; Guelfi, Gabriella; Iaboni, Martina; Zasso, Renato; Di Mari, Walter; Santoro, Michele Matteo; Knowles, Toby G

    2016-09-01

    observers' opinions on a dog's search mission ability was found only for motivation, signalling behaviour, signs of stress and possessive reward playing. More time signalling was related to shorter search time. In conclusion, despite extreme environmental and training conditions only temporary physiological and behavioural changes were recorded in the avalanche dogs. Their excellent performance in successful simulated SASR may be attributable to extensive training and good dog-handler relationships. Simulated SASR did not seem to impair SAGF dogs' performance or welfare.

  8. New Records for Distribution of Invasive Topmouth gudgeon (Pseudorasbora parva Temminck & Schlegel, 1846 in Anatolia

    Directory of Open Access Journals (Sweden)

    Vedat YEĞEN

    2015-04-01

    Full Text Available The topmouth gudgeon Pseudorasbora parva is described as most invasive fish in Europe. It’s a small cyprinid fish native to East Asia. In 1982, the existence of this species was first recorded from the Thrace region of Türkiye. Todays it is recorded from Thrace to Ceyhan region. In this study was carried out Afyonkarahisar, Bilecik, Burdur, Denizli, Eskişehir, Isparta, Konya, Kütahya and Uşak provinces between 2001 and 2013. Specimens collected from various localities in these provinces. Our results are shown P. parva has invaded many freshwater systems in Türkiye. This species has a potential threat to the diversity of the ichthyofauna of Anatolia and fish farms because of causing an increased mortality pressure on some salmonids and cyprinids, and totally inhibiting spawning of existing native fish.

  9. Cryptotermes colombianus a new drywood termite and distribution record of Cryptotermes in Colombia

    OpenAIRE

    Casalla, Robin; Scheffrahn,Rudolf; Korb, Judith

    2016-01-01

    Abstract A new species of drywood termite ( Kalotermitidae ), Cryptotermes colombianus , is described and new records for Cryptotermes cylindroceps and Cryptotermes mangoldi are presented from the Caribbean coast of Colombia. Cryptotermes colombianus is described from two soldiers and genetic sequences. This unusual species differs noticeably from other regional Cryptotermes species for its weak and inconspicuous definition of the frontal and genal horns and its acute angle of the frons with ...

  10. Evaluating avalanche generation by 2-D finite element analysis at Pico de Orizaba, Mexico

    Science.gov (United States)

    Concha Dimas, A.; Watters, R. J.

    2003-04-01

    Pico de Orizaba, at the eastern Mexican Volcanic Belt, has collapse twice during its evolution (250 ka and 20 ka ago). In case of collapse of the present day cone, the run out distance of the moving mass represents a hazard for the surrounding population. We evaluate, by using finite element, two geological aspects that have been recognized in the present cone of Pico de Orizaba as possible triggering mechanisms for avalanches: 1) Extensive hydrothermal alteration (argillic), and 2) normal faulting at the volcano basement. Two dimensional finite element analyses were carried out in a profile trending NE40SW, perpendicular to the trend of dikes and volcanic flank eruptions. We evaluate effects of extension of hydrothermal alteration and amount of fault displacement needed for triggering the avalanche. We compare the shape of failure surface (which reflects the volume of the resulting failing mass) through distribution of velocity contours and displacement vectors.

  11. Additions to the Encyrtidae and Mymaridae (Chalcidoidea) of India with new distribution and host records for some species

    Science.gov (United States)

    Rameshkumar, A.; V, Naveen

    2015-01-01

    Abstract Background Encyrtidae and Mymaridae of India have not been surveyed in depth and hosts are not known for most of the species as the methods of collections used are passive and do not yield firsthand information on the hosts. Based on our ongoing surveys on the Encyrtidae and Mymaridae of India, we report here new distribution and host records for some species. New information Acmopolynema campylurum Xu and Lin, Litus cynipseus Haliday, Omyomymar glabrum Lin and Chiappini and Platystethynium Ogloblin (Mymaridae), and Rhytidothorax purpureiscutellum (Girault) (Encyrtidae) are reported for the first time from India. Anagyrus aquilonaris (Noyes and Hayat) is recorded as new to Arunachal Pradesh and Meghalaya. Paraphaenodiscus indicus Singh and Agarwal and Paraphaenodiscus monawari Bhuiya are recorded from south India for the first time, the latter on a new host, Pulvinaria polygonata. Chorizococcus sorghi Williams (Pseudococcidae) is reported as a host for Cryptanusia ajmerensis (Fatma & Shafee), for which no hosts are hitherto known and the male of Cryptanusia is documented for the first time. Aclerda sp. is recorded as a new host for Neastymachus axillaris Singh, Agarwal and Basha. PMID:26069438

  12. Antiaris toxic aria (Moraceae - a new distribution record to the Eastern Ghats

    Directory of Open Access Journals (Sweden)

    K. Ravikumar

    2009-01-01

    Full Text Available Antiaris toxicaria (Pers. Lesch. (Moraceae - a paleotropical species has so far been reported only from the Western Ghats and Andaman islands in India. The present collections from Tamil Nadu and Andhra Pradesh form a new report to the entire Eastern Ghats. Provided here are the latest nomenclature, brief description and some notes on its distribution.

  13. Perilestes eustaquioi sp. nov. and new distributional records of Perilestidae (Odonata in Brazil

    Directory of Open Access Journals (Sweden)

    Angelo B. M. Machado

    2015-10-01

    Full Text Available ABSTRACT Perilestes eustaquioi sp. nov. (holotype male deposited in ABMM collection from the state of Bahia (municipality of Una, northeastern Brazil, is described and illustrated based on one male specimen. It differs from the other species of the genus mainly by the larger size of the anteclypeus in relations to the postclypeus. Together with P. fragilis Hagen in Selys, 1862 from the state of Sergipe and P. solutus Williamson & Williamson, 1924 from the state of Ceará, these are the first records of Perilestidae from northeastern Brazil.

  14. A new experimental site for the study of snow avalanches in the Aosta Valley (NW-Italy)

    Science.gov (United States)

    Segor, Valerio; Barbero, Monica; Barpi, Fabrizio; Borri Brunetto, Mauro; Bovet, Eloise; Brulport, Antoine; Ceaglio, Elisabetta; Chiaia, Bernardino; Fassin, Daniele; Freppaz, Michele; Frigo, Barbara; Godone, Danilo; Maggioni, Margherita; Pallara, Oronzo; Torretta, Franco; Viglietti, Davide; Welf, Arnoldo

    2010-05-01

    Within the Operational programme 'Italy - France (Alps - ALCOTRA)', Project "DynAval - Dynamique des avalanches: départ et interactions écoulement/obstacles", a new experimental site is proposed in the Aosta Valley (NW-Italy) to study small-medium size snow avalanches. In the past the attention has been mainly posed over extreme events, which can destroy villages and infrastructures and modify the landscape; scientists tried to understand their dynamics and potential destructive effects. Only recently the scientific world has started to study more in details the dynamics of smaller avalanches, which might be characterized by different relevant processes than those typical of extreme events. The paper describes the new experimental site that will be built to study the behavior of this kind of snow avalanches from several points of view. The test site is located in Aosta Valley (North-western Italian Alps) within the MonterosaSki resort (410171, 5078440) on the Monte Rosa Massif. The slope, with an altitude difference of about 300 m (from 2300 to 2570 m a.s.l.), has a dip direction of 350° and a mean dip of about 38°. The rock mass is constituted of a surface debris layer about 10 m thick on a highly fractured bedrock. Two instability phenomena can occur in the slope: superficial sliding in the debris layer and rock falls. The main objectives of the studies are: 1. the dynamics of small-medium size avalanches; 2. the interaction between avalanche flows and obstacles; 3. the mass balance of avalanches; 4. the characteristics of the snow in the deposition zone compared to those of the release zone; 5. the release process produced by explosives. To achieve the objectives, from winter 2009-2010, it is planned to artificially release avalanches along the slope according to the snow and weather conditions. In that occasion, the research team records the event measuring different variables of the avalanche. It is planned to film the event from the opposite side of the

  15. A mineralogical and granulometric study of Cayambe volcano debris avalanche deposit

    Science.gov (United States)

    Detienne, M.; Delmelle, P.; Guevara, A.; Samaniego, P.; Bustillos, J.; Sonnet, P.; Opfergelt, S.

    2013-12-01

    Volcano flank/sector collapse represents one of the most catastrophic volcanic hazards. Various volcanic and non-volcanic processes are known to decrease the stability of a volcanic cone, eventually precipitating its gravitational failure. Among them, hydrothermal alteration of volcanic rocks leading to clay mineral formation is recognized as having a large negative impact on rock strength properties. Furthermore, the presence of hydrothermal clays in the collapsing mass influences the behavior of the associated volcanic debris avalanche. In particular, clay-containing debris avalanches seem to travel farther and spread more widely than avalanches of similar volume but which do not incorporate hydrothermally-altered materials. However, the relationship between hydrothermal alteration, flank collapse and debris avalanche behavior is not well understood. The objective of this study is to better determine the volume and composition of hydrothermal clay minerals in the poorly characterized debris avalanche deposit (DAD) of Cayambe composite volcano, located in a densely populated area ~70 km northeast of Quito, Ecuador. Cayambe DAD originated from a sector collapse, which occurred less than 200 ka ago. The DAD is 10-20 m thick and has an estimated total volume of ~0.85 Km3. The H/L ratio (where H is the vertical drop and L is the travel distance of the avalanche) for Cayambe DAD is ~0.095, suggesting a high mobility. In the medial-distal zone, at 9-20 km from its source, the DAD consists of an unstratified and unsorted matrix supporting millimetric to metric clasts. It has a matrix facies (i.e. rich in particles < 2 mm) enriched in hydrothermally-altered materials. Preliminary results of granulometry measurements indicate that the matrix corresponds to ~55 wt.% of the deposit and suggest that the DAD behaved as a cohesive debris flow. Analysis of 13 matrix samples reveals a large variability in particle size distribution. This may reflect poor mixing of the collapsed

  16. Records and Distribution of New World Phlebotomine Sand Flies (Psychodidae, Diptera), With Special Emphasis on Primary Types and Species Diversity.

    Science.gov (United States)

    Rueda, Leopoldo M; Foley, Desmond H; Pecor, David; Wolkoff, Matthew

    2015-01-01

    This article includes the records and distribution of Phlebotomine sand flies (Psychodidae, Diptera) in the New World based on the specimen collections housed in 2 repositories, the US National Museum of Natural History and the Museum of Entomology, Florida State Collection of Arthropods. Approximately 128 species have primary types housed in the 2 repositories, including holotypes (47 species, 3 subspecies), "types" (7 species), allotypes (52 species, 6 subspecies), lectotypes (4 species), paratypes (93 species, 10 subspecies), and neoallotype (1 species), mounted on slides, with a total of 1,107 type slides. For species diversity, collection data from 24 countries in the sand fly database were analyzed according to the number of species present, specimen records, decade of collections, and countries where collections were conducted.

  17. The cross-shore distribution of plankton and particles southwest of Iceland observed with a Video Plankton Recorder

    Science.gov (United States)

    Gislason, Astthor; Logemann, Kai; Marteinsdottir, Gudrun

    2016-07-01

    The high resolution distribution of plankton and particles along a transect extending from the coast and across the shelf southwest of Iceland was studied in relation to hydrographic features and chlorophyll a fluorescence in late May 2010-2013 with a Video Plankton Recorder. The different groups of plankton and particles showed distinctive distributional pattern. Decaying organic matter (marine snow) was a very significant component of the system. Calanus finmarchicus stayed generally shallower than egg carrying Pseudocalanus spp. Diel variability in depth distribution of C. finmarchicus was not evident. Ctenophores, jellies and fish larvae were most abundant above ~50 m depth. Ctenophores were relatively abundant across the whole transect, while jellies and fish larvae were mainly seen on the landward half of the transect. The data on distribution of copepods (mainly C. finmarchicus) were combined with the results of a numerical circulation model (CODE), thus obtaining an estimate of fluxes of copepods in the area. The results show that C. finmarchicus may be transported by currents both eastwards and westwards along the south coast, while retention on the bank is also possible. Based on the results of the synthesis of the distributional data and the CODE model, it is hypothesized that the populations off the south coast are at least partly self-sustained in the region.

  18. 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.

  19. Avalanche related damage potential - changes of persons and mobile values since the mid-twentieth century, case study Galtür

    Directory of Open Access Journals (Sweden)

    M. Keiler

    2005-01-01

    Full Text Available When determining risk related to natural hazard processes, many studies neglect the investigations of the damage potential or are limited to the assessment of immobile values like buildings. However, persons as well as mobile values form an essential part of the damage potential. Knowledge of the maximum number of exposed persons in an endangered area is of great importance for elaborating evacuation plans and immediate measures in case of catastrophes. In addition, motor vehicles can also be highly damaged, as was shown by the analysis of avalanche events. With the removal of mobile values in time as a preventive measure this kind of damage can be minimised. This study presents a method for recording the maximum number of exposed persons and monetarily assessing motor vehicles in the municipality of Galtür (Tyrol, Austria. Moreover, general developments of the damage potential due to significant socio-economic changes since the mid-twentieth century are pointed out in the study area. The present situation of the maximum number of persons and mobile values in the official avalanche hazard zones of the municipality is described in detail. Information on the number of persons is derived of census data, tourism and employment statistics. During the winter months, a significant increase overlaid by strong short-term fluctuation in the number of persons can be noted. These changes result from a higher demand of tourism related manpower as well as from varying occupancy rates. The number of motor vehicles in endangered areas is closely associated to the number of exposed persons. The potential number of motor vehicles is investigated by means of mapping, statistics on the stock of motor vehicles and the density distribution. Diurnal and seasonal fluctuations of the investigated damage potential are pointed out. The recording of the number of persons and mobile values in endangered areas is vital for any disaster management.

  20. 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.

  1. Angiosperm n-alkane distribution patterns and the geologic record of C4 grassland evolution

    Science.gov (United States)

    Henderson, A.; Graham, H. V.; Patzkowsky, M.; Fox, D. L.; Freeman, K. H.

    2012-12-01

    n-Alkane average chain-length (ACL) patterns vary regionally with community composition and climate. To clarify the influence of phylogenetic and community patterns, we compiled and analyzed a global database of published n-alkane abundance for n-C27 to C35 homologs in modern plant specimens (n=205). ACL for waxes in C4 non-woody plants are longer than for woody plants, suggesting ACL can serve as an indicator of the three-dimensional structure of local vegetation. Further, these findings suggest compound-specific isotopic data for longer alkane homologs (C31, C33, C35) will proportionately represent non-woody vegetation and isotope measurements of C29 are more representative of woody vegetation. Thus, the combination of ACL and carbon isotope compositions should allow us to disentangle C3 woody, C3 non-woody, and C4 non-woody signals in terrestrial paleorecords. Application of this approach to the geologic record of Miocene C4 grassland expansion in the US Great Plains and the Siwaliks in Pakistan illustrate two very different transition scenarios. Alkane-specific isotopic data indicate C4 grasslands appeared 2.5 Ma in the Great Plains and 6.5 Ma in the Siwaliks, and ACL analysis indicates that this transition involved the replacement of woody vegetation in the US and the replacement of C3 grasses in Pakistan. Our analysis illustrates that, consistent with differences in the timing of C4 grassland, the drivers of change were likely not the same in these regions. Oxygen isotope records suggest that the more recent transition in the Great Plains was associated with climate cooling and possibly changes in disturbance regimes and that the transition in the Siwaliks was likely associated with warming and drying.

  2. Synopsis of Paxillus MacLeay, 1819 (Coleoptera: Passalidae): distributional records and descriptions of four new species from Brazil.

    Science.gov (United States)

    Mattos, Ingrid; Mermudes, José Ricardo M

    2013-01-01

    Paxillus MacLeay, 1819 (Coleoptera: Passalidae) is redescribed, with new distributional records and descriptions of four species from Brazil. Paxillus reyesi new species is characterized by the first antennomere of antennal club reduced, slightly longer than half of the second antennomere; mesosternal scar straight, wide and deep. Paxillus chapadensis new species from the Chapada dos Guimarães (Mato Grosso, Brazil) has prostenal process centrally impressed with an opaque depression; and the scape of the antenna with a subapical dorsal spine, shallow ventral depression, and few erect setae. Paxillus manausensis new species from Manaus (Amazonas, Brazil) has high frontal ridges; mid-frontal tubercles high, acuminate and larger than the internal tubercles; and the central tubercle short. Paxillus uaupesensis new species from Uaupes (Amazonas, Brazil) has the mesosternal scar opaque, elongate and depressed; and the scutellum depressed. Diagnostic redescriptions and illustrations of known species from Brazil, a key to all known species, and a checklist with distributional data are provided.

  3. The Large-Scale Debris Avalanche From The Tancitaro Volcano (Mexico): Characterization And Modeling

    Science.gov (United States)

    Morelli, S.; Gigli, G.; Falorni, G.; Garduno Monroy, V. H.; Arreygue, E.

    2008-12-01

    The Tancitaro is an andesitic-dacitic stratovolcano located in the Michoacán Guanajuato volcanic field within the west-central portion of the trans-Mexican Volcanic Belt. The volcanism in this area is characterized by two composite volcanoes, the highest of which is the Tancitaro volcanic edifice (3840 m), some low angle lava cones and more than 1,000 monogenetic cinder cones. The distribution of the cinder cones is controlled by NE-SW active faults, although there are also additional faults with NNW-SSE trends along which some cones are aligned. The Tancitaro stratovolcano is located at the intersection of the tectonical structures that originate these alignments. All this geological activity has contributed to the gravitational instability of the volcano, leading to a huge sector collapse which produced the investigated debris avalanche. The collapse structure is an east-facing horseshoe-shaped crater (4 km wide and 5.3 km long), related with a large fan that was deposited within the Tepalcatepec depression. The deposit starts only 7 km downslope from the failure scar, it is 66 km long and covers an area of approximately 1155 km2. The landslide magnitude is about 20 km3 and it was firstly determined by the reconstruction of the paleo-edifice using a GIS software and then validated by the observation of significant outcrops. The fan was primarily formed by the deposit of this huge debris avalanche and subsequently by debris flow and fluvial deposits. Field investigations on the fan area highlighted the presence of two texturally distinct parts, which are referred to the 'block facies' and the 'matrix facies'. The first sedimentary structure is responsible for the typical hummock morphologies in the proximal area, as seen in many other debris avalanche deposits. Instead in the distal zones, the deposit is made up by the 'mixed block and matrix facies'. Blocks and megablocks, some of which are characterized by a jigsaw puzzle texture, gradually decrease in size

  4. 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...

  5. Statistics of avalanches with relaxation and Barkhausen noise: A solvable model

    Science.gov (United States)

    Dobrinevski, Alexander; Le Doussal, Pierre; Wiese, Kay Jörg

    2013-09-01

    We study a generalization of the Alessandro-Beatrice-Bertotti-Montorsi (ABBM) model of a particle in a Brownian force landscape, including retardation effects. We show that under monotonous driving the particle moves forward at all times, as it does in absence of retardation (Middleton's theorem). This remarkable property allows us to develop an analytical treatment. The model with an exponentially decaying memory kernel is realized in Barkhausen experiments with eddy-current relaxation and has previously been shown numerically to account for the experimentally observed asymmetry of Barkhausen pulse shapes. We elucidate another qualitatively new feature: the breakup of each avalanche of the standard ABBM model into a cluster of subavalanches, sharply delimited for slow relaxation under quasistatic driving. These conditions are typical for earthquake dynamics. With relaxation and aftershock clustering, the present model includes important ingredients for an effective description of earthquakes. We analyze quantitatively the limits of slow and fast relaxation for stationary driving with velocity v>0. The v-dependent power-law exponent for small velocities, and the critical driving velocity at which the particle velocity never vanishes, are modified. We also analyze nonstationary avalanches following a step in the driving magnetic field. Analytically, we obtain the mean avalanche shape at fixed size, the duration distribution of the first subavalanche, and the time dependence of the mean velocity. We propose to study these observables in experiments, allowing a direct measurement of the shape of the memory kernel and tracing eddy current relaxation in Barkhausen noise.

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

    Science.gov (United States)

    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.

  7. Rapid motions of free-surface avalanches down curved and twisted channels and their numerical simulation.

    Science.gov (United States)

    Pudasaini, Shiva P; Wang, Yongqi; Hutter, Kolumban

    2005-07-15

    This paper presents a new model and discussions about the motion of avalanches from initiation to run-out over moderately curved and twisted channels of complicated topography and its numerical simulations. The model is a generalization of a well established and widely used depth-averaged avalanche model of Savage & Hutter and is published with all its details in Pudasaini & Hutter (Pudasaini & Hutter 2003 J. Fluid Mech. 495, 193-208). The intention was to be able to describe the flow of a finite mass of snow, gravel, debris or mud, down a curved and twisted corrie of nearly arbitrary cross-sectional profile. The governing equations for the distribution of the avalanche thickness and the topography-parallel depth-averaged velocity components are a set of hyperbolic partial differential equations. They are solved for different topographic configurations, from simple to complex, by applying a high-resolution non-oscillatory central differencing scheme with total variation diminishing limiter. Here we apply the model to a channel with circular cross-section and helical talweg that merges into a horizontal channel which may or may not become flat in cross-section. We show that run-out position and geometry depend strongly on the curvature and twist of the talweg and cross-sectional geometry of the channel, and how the topography is shaped close to run-out zones.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  10. Neural avalanches at the critical point between replay and non-replay of spatiotemporal patterns.

    Science.gov (United States)

    Scarpetta, Silvia; de Candia, Antonio

    2013-01-01

    We model spontaneous cortical activity with a network of coupled spiking units, in which multiple spatio-temporal patterns are stored as dynamical attractors. We introduce an order parameter, which measures the overlap (similarity) between the activity of the network and the stored patterns. We find that, depending on the excitability of the network, different working regimes are possible. For high excitability, the dynamical attractors are stable, and a collective activity that replays one of the stored patterns emerges spontaneously, while for low excitability, no replay is induced. Between these two regimes, there is a critical region in which the dynamical attractors are unstable, and intermittent short replays are induced by noise. At the critical spiking threshold, the order parameter goes from zero to one, and its fluctuations are maximized, as expected for a phase transition (and as observed in recent experimental results in the brain). Notably, in this critical region, the avalanche size and duration distributions follow power laws. Critical exponents are consistent with a scaling relationship observed recently in neural avalanches measurements. In conclusion, our simple model suggests that avalanche power laws in cortical spontaneous activity may be the effect of a network at the critical point between the replay and non-replay of spatio-temporal patterns.

  11. Neural avalanches at the critical point between replay and non-replay of spatiotemporal patterns.

    Directory of Open Access Journals (Sweden)

    Silvia Scarpetta

    Full Text Available We model spontaneous cortical activity with a network of coupled spiking units, in which multiple spatio-temporal patterns are stored as dynamical attractors. We introduce an order parameter, which measures the overlap (similarity between the activity of the network and the stored patterns. We find that, depending on the excitability of the network, different working regimes are possible. For high excitability, the dynamical attractors are stable, and a collective activity that replays one of the stored patterns emerges spontaneously, while for low excitability, no replay is induced. Between these two regimes, there is a critical region in which the dynamical attractors are unstable, and intermittent short replays are induced by noise. At the critical spiking threshold, the order parameter goes from zero to one, and its fluctuations are maximized, as expected for a phase transition (and as observed in recent experimental results in the brain. Notably, in this critical region, the avalanche size and duration distributions follow power laws. Critical exponents are consistent with a scaling relationship observed recently in neural avalanches measurements. In conclusion, our simple model suggests that avalanche power laws in cortical spontaneous activity may be the effect of a network at the critical point between the replay and non-replay of spatio-temporal patterns.

  12. 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.

  13. Functioning of the avalanche starting zones which undergo snow-transport by wind: Field observations and computer modeling

    Science.gov (United States)

    Sivardière, F.; Castelle, T.; Guyomarc'h, G.; Mérindol, L.; Buisson, L.

    1995-11-01

    For two years, three French and Swiss laboratories have been making field observations and measurements on two high altitude slopes in a Northern French Alps site. The aim of this work is to study the functioning of the avalanche sites which, in their starting zones, undergo snow-transport by wind. The experimental site is located in the French Alps, at 2,800 m, above Grenoble. It is an open area, equipped with an automatic meteorological station and an altitude laboratory. The two slopes that are studied face East. One of them is artificially released but the other has a natural avalanche activity. The investigations concern: -snow deposition in avalanche starting zones; -temporal evolution of the snowpack characteristics; -avalanche release. For the field observations and measurements, continuous recording of the meteorological conditions on the site, photogrammetrical techniques and two snow depth profiles, as well as stratigraphical snow profiles and video are used. The computer modeling is based on existing computer models developed by the CEMAGREF-Nivologie (ELSA) and the CEN/Météo-France (SAFRAN-CROCUS-MEPRA), which analyse the snowpack and its stability. The field observations and measurements aim at improving snow-transport by wind modeling modules, in order to improve their whole analysis.

  14. Geological history and within-island diversity: a debris avalanche and the Tenerife lizard Gallotia galloti.

    Science.gov (United States)

    Brown, Richard P; Hoskisson, Paul A; Welton, John-Henry; Báez, Marcos

    2006-10-01

    Several processes have been described that could explain geographical variation and speciation within small islands, including fragmentation of populations through volcanic eruptions. Massive landslides, or debris avalanches, could cause similar effects. Here we analyse the potential impact of the 0.8 million-year-ago (Ma) Güimar valley debris avalanche on the phylogeography of the lizard Gallotia galloti on the Canary Island of Tenerife. Distributions of mitochondrial DNA lineages (based on cytochrome b sequences) were analysed on a 60-km southeastern coast transect centred on this area. Three main clades were detected, which can be divided into northern (one clade) and southern (two clades) groups that introgress across the valley. Maximum-likelihood estimates of migration rates (scaled for mutation rate) revealed highly asymmetric patterns, indicating that long-term gene flow into this region from both the northern and the southern populations greatly exceeded that in the opposite directions, consistent with recolonization of the area. The ancestral Tenerife node on the G. galloti tree is estimated at 0.80 Ma, matching closely with the geological estimate for the debris avalanche. Morphological variation (body dimensions and scalation) was also analysed and indicated a stepped cline in female scalation across the valley, although the patterns for male scalation and male and female body dimensions were not as clear. Together these findings provide support for the hypothesis that the debris avalanche has shaped the phylogeography of G. galloti and may even have been a primary cause of the within-island cladogenesis through population fragmentation and isolation. Current estimates of timing of island unification mean that the original hypothesis that within-island diversity is explained by the secondary contact of populations from the two ancient precursor islands of Teno and Anaga is less plausible for this and some other Tenerife species. Large-scale landslides

  15. Snow Mass Quantification and Avalanche Victim Search By Ground Penetrating Radar

    Science.gov (United States)

    Jaedicke, C.

    Ground penetrating radar (GPR) systems can be used in many applications of snow and ice research. The information from the GPR is interpreted to identify layers, ob- ject and different structures in the snow. A commercially available GPR system was further developed to work in the rough environment of snow and ice. The applied GPR is a 900 MHz system that easily reaches snow depths of ten meters. The system is cal- ibrated by several manual snow depth measurements during each survey. The depth resolution is depending on the snow type and ranges around +/- 0.1 m. The GPR sys- tem carried along a line of interest and is triggered by an odometer wheel at regular adjustable steps. All equipment is mounted in a sledge and is moved by a snow mo- bile over the surface. This setup allows the efficient coverage of several kilometers of profiles. The radar profiles give a real time two-dimensional impression of structures and objects and the interface between snow and underlying ground. The actual radar profile is shown on a screen on the sledge allowing the immediate marking of objects and structures. During the past three years the instrument was successfully used for the study of snow distributions, for the detection of glacier crevasses under the snow cover and for the search of avalanche victims in avalanche debris. The results show the capability of the instrument to detect persons and objects in the snow cover. In the future this could be new tool for avalanche rescue operations. Today the size and weight of the system prevents the access to very steep slopes and areas not accessible for snowmobile. Further development will decrease the size of the system and make it a valuable tool to quantify the snow mass in avalanche release zones and run out areas.

  16. Cloudwave: distributed processing of "big data" from electrophysiological recordings for epilepsy clinical research using Hadoop.

    Science.gov (United States)

    Jayapandian, Catherine P; Chen, Chien-Hung; Bozorgi, Alireza; Lhatoo, Samden D; Zhang, Guo-Qiang; Sahoo, Satya S

    2013-01-01

    Epilepsy is the most common serious neurological disorder affecting 50-60 million persons worldwide. Multi-modal electrophysiological data, such as electroencephalography (EEG) and electrocardiography (EKG), are central to effective patient care and clinical research in epilepsy. Electrophysiological data is an example of clinical "big data" consisting of more than 100 multi-channel signals with recordings from each patient generating 5-10GB of data. Current approaches to store and analyze signal data using standalone tools, such as Nihon Kohden neurology software, are inadequate to meet the growing volume of data and the need for supporting multi-center collaborative studies with real time and interactive access. We introduce the Cloudwave platform in this paper that features a Web-based intuitive signal analysis interface integrated with a Hadoop-based data processing module implemented on clinical data stored in a "private cloud". Cloudwave has been developed as part of the National Institute of Neurological Disorders and Strokes (NINDS) funded multi-center Prevention and Risk Identification of SUDEP Mortality (PRISM) project. The Cloudwave visualization interface provides real-time rendering of multi-modal signals with "montages" for EEG feature characterization over 2TB of patient data generated at the Case University Hospital Epilepsy Monitoring Unit. Results from performance evaluation of the Cloudwave Hadoop data processing module demonstrate one order of magnitude improvement in performance over 77GB of patient data. (Cloudwave project: http://prism.case.edu/prism/index.php/Cloudwave).

  17. Spatial distribution and historical records of mercury sedimentation in urban lakes under urbanization impacts.

    Science.gov (United States)

    Li, Hong-Bo; Yu, Shen; Li, Gui-Lin; Deng, Hong; Xu, Bo; Ding, Jing; Gao, Jin-Bo; Hong, You-Wei; Wong, Ming-Hung

    2013-02-15

    China is assumed one of the largest contributors to the world's total mercury (Hg) emissions, with a rapid increase in anthropogenic Hg emissions. However, little is known about Hg fate and transport in urban areas of China. In this study, total Hg contents in surface (0-5 cm) sediments from lakes in 14 parks (3 in the central urban core (CUC) area, 5 in the developed urban (DDU) area, 2 in the developing urban (DIU) area, and 4 in the suburban (SU) area) and (210)Pb-dated sediment cores from lakes in 5 parks (3 in the CUC and 2 in the DDU) in Shanghai were assessed to compare current patterns (urbanization effect) with the historical records of Hg emissions over the past century. Total Hg content in surface sediments showed a clear urbanization pattern. Dated sediment cores revealed a 2-3 fold increase in total Hg content, while Hg fluxes exponentially increased from ~1900 to present and accelerated since 1990 when China's economy and urbanization booms started. Anthropogenic Hg fluxes in post-2000 ranged from 253 to 1452 μg m(-2) yr(-1), 2-7 times greater than preindustrial (pre-1900) Hg fluxes. Total Hg and Pb contents in both surface sediments and sediment cores were highly correlated and Hg flux in sediment cores also significantly correlated with annual coal consumption in the period 1949-2008. The significant correlations suggest that coal combustion is a major source of Hg emission in Shanghai.

  18. Digital holography wavefront sensing in the pupil-plane recording geometry for distributed-volume atmospheric aberrations

    Science.gov (United States)

    Banet, Matthias T.; Spencer, Mark F.; Raynor, Robert A.; Marker, Dan K.

    2016-09-01

    Digital holography in the pupil-plane recording geometry shows promise as a wavefront sensor for use in adaptive-optics systems. Because current wavefront sensors suffer from decreased performance in the presence of turbulence and thermal blooming, there is a need for a more robust wavefront sensor in such distributed-volume atmospheric conditions. Digital holography fulfills this roll by accurately estimating the wrapped phase of the complex optical field after propagation through the atmosphere to the pupil plane of an optical system. This paper examines wave-optics simulations of spherical-wave propagation through both turbulence and thermal blooming; it also quantifies the performance of digital holography as a wavefront sensor by generating field-estimated Strehl ratios as a function of the number of pixels in the detector array, the Rytov number, and the Fried coherence diameter. Altogether the results indicate that digital holography wavefront sensing in the pupil-plane recording geometry is a valid and accurate method for estimating the wrapped phase of the complex optical field in the presence of distributed-volume atmospheric aberrations.

  19. 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.

  20. 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.

  1. 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...

  2. 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.

  3. Security of the distributed electronic patient record: a case-based approach to identifying policy issues.

    Science.gov (United States)

    Anderson, J G

    2000-11-01

    The growth of managed care and integrated delivery systems has created a new commodity, health information and the technology that it requires. Surveys by Deloitte and Touche indicate that over half of the hospitals in the US are in the process of implementing electronic patient record (EPR) systems. The National Research Council has established that industry spends as much as $15 billion on information technology (IT), an amount that is expanding by 20% per year. The importance of collecting, electronically storing, and using the information is undisputed. This information is needed by consumers to make informed choices; by physicians to provide appropriate quality clinical care: and by health plans to assess outcomes, control costs and monitor quality. The collection, storage and communication of a large variety of personal patient data, however, present a major dilemma. How can we provide the data required by the new forms of health care delivery and at the same time protect the personal privacy of patients? Recent debates concerning medical privacy legislation, software regulation, and telemedicine suggest that this dilemma will not be easily resolved. The problem is systemic and arises out of the routine use and flow of information throughout the health industry. Health care information is primarily transferred among authorized users. Not only is the information used for patient care and financial reimbursement, secondary users of the information include medical, nursing, and allied health education, research, social services, public health, regulation, litigation, and commercial purposes such as the development of new medical technology and marketing. The main threats to privacy and confidentiality arise from within the institutions that provide patient care as well as institutions that have access to patient data for secondary purposes.

  4. 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.

  5. 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.

  6. 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.

  7. CEPF Western Ghats Special Series: Range extension of Malabar Tree Nymph Idea malabarica (Moore (Lepidoptera: Nymphalidae to northern Western Ghats of Maharashtra and a review of distribution records

    Directory of Open Access Journals (Sweden)

    M. Jadhav

    2013-01-01

    Full Text Available Barring a single record of Ghosh et al. (1990 from Raigarh District as a new report for Maharashtra State, no further records of Idea malabarica from any of the districts of Maharashtra, northern Western Ghats is available. The occurrence of Malabar Tree Nymph, an endemic butterfly of southern Western Ghats in the new geographical area is interesting to study. A distribution map for Idea malabarica in Western Ghats is provided based on the published records.

  8. Spatio-temporal avalanche forecasting with Support Vector Machines

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    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.

  9. Addition of a spider family for Uruguay: First record of Iviraiva pachyura (Mello-Leitão, 1935 (Araneae: Hersiliidae, with notes on its natural history and distribution

    Directory of Open Access Journals (Sweden)

    Álvaro Laborda

    2015-08-01

    Full Text Available This is the first record for the species Iviraiva pachyura and for the family Hersiliidae in Uruguay.  Data presented represent the southernmost record for the species.  Figures of living specimens, copulatory organs and a description of the egg sac are provided. The distribution of the species is shown and discussed. 

  10. Describing the interannual variability of precipitation with the derived distribution approach: effects of record length and resolution

    Science.gov (United States)

    Meier, Claudio I.; Sebastián Moraga, Jorge; Pranzini, Geri; Molnar, Peter

    2016-10-01

    Interannual variability of precipitation is traditionally described by fitting a probability model to yearly precipitation totals. There are three potential problems with this approach: a long record (at least 25-30 years) is required in order to fit the model, years with missing rainfall data cannot be used, and the data need to be homogeneous, i.e., one has to assume stationarity. To overcome some of these limitations, we test an alternative methodology proposed by Eagleson (1978), based on the derived distribution (DD) approach. It allows estimation of the probability density function (pdf) of annual rainfall without requiring long records, provided that continuously gauged precipitation data are available to derive external storm properties. The DD approach combines marginal pdfs for storm depths and inter-arrival times to obtain an analytical formulation of the distribution of annual precipitation, under the simplifying assumptions of independence between events and independence between storm depth and time to the next storm. Because it is based on information about storms and not on annual totals, the DD can make use of information from years with incomplete data; more importantly, only a few years of rainfall measurements should suffice to estimate the parameters of the marginal pdfs, at least at locations where it rains with some regularity. For two temperate locations in different climates (Concepción, Chile, and Lugano, Switzerland), we randomly resample shortened time series to evaluate in detail the effects of record length on the DD, comparing the results with the traditional approach of fitting a normal (or lognormal) distribution. Then, at the same two stations, we assess the biases introduced in the DD when using daily totalized rainfall, instead of continuously gauged data. Finally, for randomly selected periods between 3 and 15 years in length, we conduct full blind tests at 52 high-quality gauging stations in Switzerland, analyzing the ability

  11. 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

  12. Utilizing distributional analytics and electronic records to assess timeliness of inpatient blood glucose monitoring in non-critical care wards

    Directory of Open Access Journals (Sweden)

    Ying Chen

    2016-04-01

    Full Text Available Abstract Background Regular and timely monitoring of blood glucose (BG levels in hospitalized patients with diabetes mellitus is crucial to optimizing inpatient glycaemic control. However, methods to quantify timeliness as a measurement of quality of care are lacking. We propose an analytical approach that utilizes BG measurements from electronic records to assess adherence to an inpatient BG monitoring protocol in hospital wards. Methods We applied our proposed analytical approach to electronic records obtained from 24 non-critical care wards in November and December 2013 from a tertiary care hospital in Singapore. We applied distributional analytics to evaluate daily adherence to BG monitoring timings. A one-sample Kolmogorov-Smirnov (1S-KS test was performed to test daily BG timings against non-adherence represented by the uniform distribution. This test was performed among wards with high power, determined through simulation. The 1S-KS test was coupled with visualization via the cumulative distribution function (cdf plot and a two-sample Kolmogorov-Smirnov (2S-KS test, enabling comparison of the BG timing distributions between two consecutive days. We also applied mixture modelling to identify the key features in daily BG timings. Results We found that 11 out of the 24 wards had high power. Among these wards, 1S-KS test with cdf plots indicated adherence to BG monitoring protocols. Integrating both 1S-KS and 2S-KS information within a moving window consisting of two consecutive days did not suggest frequent potential change from or towards non-adherence to protocol. From mixture modelling among wards with high power, we consistently identified four components with high concentration of BG measurements taken before mealtimes and around bedtime. This agnostic analysis provided additional evidence that the wards were adherent to BG monitoring protocols. Conclusions We demonstrated the utility of our proposed analytical approach as a monitoring

  13. MAAC: a software tool for user authentication and access control to the electronic patient record in an open distributed environment

    Science.gov (United States)

    Motta, Gustavo H.; Furuie, Sergio S.

    2004-04-01

    Designing proper models for authorization and access control for the electronic patient record (EPR) is essential to wide scale use of the EPR in large health organizations. This work presents MAAC (Middleware for Authentication and Access Control), a tool that implements a contextual role-based access control (RBAC) authorization model. RBAC regulates user"s access to computers resources based on their organizational roles. A contextual authorization uses environmental information available at access-request time, like user/patient relationship, in order to decide whether a user has the right to access an EPR resource. The software architecture where MAAC is implemented uses Lightweight Directory Access Protocol, Java programming language and the CORBA/OMG standards CORBA Security Service and Resource Access Decision Facility. With those open and distributed standards, heterogeneous EPR components can request user authentication and access authorization services in a unified and consistent fashion across multiple platforms.

  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. 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.

  16. 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.

  17. New records and detailed distribution and abundance of selected arthropod species collected between 1999 and 2011 in Azorean native forests

    Science.gov (United States)

    Gaspar, Clara; Crespo, Luís Carlos Fonseca; Rigal, François; Cardoso, Pedro; Pereira, Fernando; Rego, Carla; Amorim, Isabel R.; Melo, Catarina; Aguiar, Carlos; André, Genage; Mendonça, Enésima P.; Ribeiro, Sérvio; Hortal, Joaquín; Santos, Ana M.C.; Barcelos, Luís; Enghoff, Henrik; Mahnert, Volker; Pita, Margarida T.; Ribes, Jordi; Baz, Arturo; Sousa, António B.; Vieira, Virgílio; Wunderlich, Jörg; Parmakelis, Aristeidis; Whittaker, Robert J.; Quartau, José Alberto; Serrano, Artur R.M.; Triantis, Kostas A.

    2016-01-01

    Abstract Background In this contribution we present detailed distribution and abundance data for arthropod species identified during the BALA – Biodiversity of Arthropods from the Laurisilva of the Azores (1999-2004) and BALA2 projects (2010-2011) from 18 native forest fragments in seven of the nine Azorean islands (all excluding Graciosa and Corvo islands, which have no native forest left). New information Of the total 286 species identified, 81% were captured between 1999 and 2000, a period during which only 39% of all the samples were collected. On average, arthropod richness for each island increased by 10% during the time frame of these projects. The classes Arachnida, Chilopoda and Diplopoda represent the most remarkable cases of new island records, with more than 30% of the records being novelties. This study stresses the need to expand the approaches applied in these projects to other habitats in the Azores, and more importantly to other less surveyed taxonomic groups (e.g. Diptera and Hymenoptera). These steps are fundamental for getting a more accurate assessment of biodiversity in the archipelago. PMID:28174509

  18. Numerical modeling of debris avalanches at Nevado de Toluca (Mexico): implications for hazard evaluation and mapping

    Science.gov (United States)

    Grieco, F.; Capra, L.; Groppelli, G.; Norini, G.

    2007-05-01

    The present study concerns the numerical modeling of debris avalanches on the Nevado de Toluca Volcano (Mexico) using TITAN2D simulation software, and its application to create hazard maps. Nevado de Toluca is an andesitic to dacitic stratovolcano of Late Pliocene-Holocene age, located in central México near to the cities of Toluca and México City; its past activity has endangered an area with more than 25 million inhabitants today. The present work is based upon the data collected during extensive field work finalized to the realization of the geological map of Nevado de Toluca at 1:25,000 scale. The activity of the volcano has developed from 2.6 Ma until 10.5 ka with both effusive and explosive events; the Nevado de Toluca has presented long phases of inactivity characterized by erosion and emplacement of debris flow and debris avalanche deposits on its flanks. The largest epiclastic events in the history of the volcano are wide debris flows and debris avalanches, occurred between 1 Ma and 50 ka, during a prolonged hiatus in eruptive activity. Other minor events happened mainly during the most recent volcanic activity (less than 50 ka), characterized by magmatic and tectonic-induced instability of the summit dome complex. According to the most recent tectonic analysis, the active transtensive kinematics of the E-W Tenango Fault System had a strong influence on the preferential directions of the last three documented lateral collapses, which generated the Arroyo Grande and Zaguàn debris avalanche deposits towards E and Nopal debris avalanche deposit towards W. The analysis of the data collected during the field work permitted to create a detailed GIS database of the spatial and temporal distribution of debris avalanche deposits on the volcano. Flow models, that have been performed with the software TITAN2D, developed by GMFG at Buffalo, were entirely based upon the information stored in the geological database. The modeling software is built upon equations

  19. Volcanic debris avalanche transport and emplacement: water content and fragmentation vs disaggregation

    Science.gov (United States)

    Roverato, Matteo

    2016-04-01

    conditions with chaotically distributed zones of shear developing where softer lithologies occur in the collapsing mass, through to a distal homogenous and well-mixed mud-dominated flow. The aim of this work is to describe the textural features from proximal to distal reaches within the DAD. The textural analysis of the unit from field descriptions, granulometric investigations, and microscopic analysis of particle forms enables a reconstruction of the transitions in flow conditions during the emplacement of a debris avalanche, which are applicable to the understanding of the mobility and hazards associated with large-scale stratovolcanoes.

  20. Auditory Power-Law Activation Avalanches Exhibit a Fundamental Computational Ground State

    Science.gov (United States)

    Stoop, Ruedi; Gomez, Florian

    2016-07-01

    The cochlea provides a biological information-processing paradigm that we are only beginning to understand in its full complexity. Our work reveals an interacting network of strongly nonlinear dynamical nodes, on which even a simple sound input triggers subnetworks of activated elements that follow power-law size statistics ("avalanches"). From dynamical systems theory, power-law size distributions relate to a fundamental ground state of biological information processing. Learning destroys these power laws. These results strongly modify the models of mammalian sound processing and provide a novel methodological perspective for understanding how the brain processes information.

  1. New distribution records of the savanna specialist fungus-farming ant Cyatta Sosa-Calvo et al. (Hymenoptera: Formicidae: Myrmicinae)

    Science.gov (United States)

    Feitosa, Rodrigo Machado; Vasconcelos, Heraldo Luis; Maravalhas, Jonas

    2016-01-01

    Abstract Background The fungus-farming ant genus Cyatta (Formicidae: Myrmicinae) is represented by a single species, C. abscondita Sosa-Calvo et al., known from a few localities in Brazil (in the states of Ceará, Minas Gerais, São Paulo and the Distrito Federal), and a single locality in the Misiones province, Argentina. Cyatta is known to occur predominantly in savanna habitats and occasionally in the transition zones between the Atlantic Forest and Cerrado. New information The new records reported here significantly expand the previously known distribution of Cyatta abscondita and provide further support for the intimate relation between this species and the savannas of South America. We report the first occurrence of the genus in southern Brazil (Paraná state) and the westernmost occurrence (Bolivia) of Cyatta abscondita, which extend its distribution approximately 1450 km to the west. Finally, we discuss the importance of mapping inconspicuous species in order to develop strategies for protecting endangered areas and to increase our understanding of the evolutionary history of organisms and biomes. PMID:27932931

  2. Notes on the geographic distribution and subspecific taxonomy of Sais rosalia (Cramer (Lepidoptera, Nymphalidae, Ithomiini, including the first records in Paraguay

    Directory of Open Access Journals (Sweden)

    Sergio D. Ríos Díaz

    2014-03-01

    Full Text Available Notes on the geographic distribution and subspecific taxonomy of Sais rosalia (Cramer (Lepidoptera, Nymphalidae, Ithomiini, including the first records in Paraguay. This paper provides comments on the subspecific taxonomy and geographic distribution of Sais rosalia (Cramer, 1779 (Lepidoptera, Nymphalidae, Ithomiini, as well as an up-to-date distributional map, complemented with unpublished distributional data based on specimens deposited in the Coleção Entomológica Pe. Jesus S. Moure, Curitiba, Brazil and the Museo de Historia Natural, Lima, Peru. The following synonyms are proposed: Sais rosalia camariensis Haensch, 1905 syn. rev. as junior subjective synonym of Papilio rosalia Cramer, 1779 and Sais rosalia brasiliensis Talbot, 1928 syn. rev. as junior subjective synonym of Sais rosalia rosalinde Weymer, 1890. Additionally, the first country records of Sais rosalia in Paraguay, including the southernmost record of the species, are documented.

  3. Avalanches, branching ratios, and clustering of attractors in random Boolean networks and in the segment polarity network of Drosophila

    Energy Technology Data Exchange (ETDEWEB)

    Berdahl, Andrew; Shreim, Amer; Sood, Vishal; Davidsen, Joern; Paczuski, Maya [Complexity Science Group, Department of Physics and Astronomy, University of Calgary, Calgary, Alberta T2N 1N4 (Canada)], E-mail: aberdahl@phas.ucalgary.ca

    2008-06-15

    We discuss basic features of emergent complexity in dynamical systems far from equilibrium by focusing on the network structure of their state space. We start by measuring the distributions of avalanche and transient times in random Boolean networks (RBNs) and in the Drosophila polarity network by exact enumeration. A transient time is the duration of the transient from a starting state to an attractor. An avalanche is a special transient which starts as a single Boolean element perturbation of an attractor state. Significant differences at short times between the avalanche and the transient times for RBNs with small connectivity K-compared to the number of elements N-indicate that attractors tend to cluster in configuration space. In addition, one bit flip has a non-negligible chance to put an attractor state directly onto another attractor. This clustering is also present in the segment polarity gene network of Drosophila melanogaster, suggesting that this may be a robust feature of biological regulatory networks. We also define and measure a branching ratio for the state space networks and find evidence for a new timescale that diverges roughly linearly with N for 2{<=}K<avalanche durations exhibit no characteristic scale within our statistical resolution. Hence, we propose that the branching ratio and the avalanche duration are new indicators for scale-free behavior that may or may not be found simultaneously with other indicators of emergent complexity in extended, deterministic dynamical systems.

  4. Cosmogenic Nuclide Exposure Dating of the Tiltill Rock Avalanche, Yosemite National Park

    Science.gov (United States)

    Ford, K. R.; Pluhar, C. J.; Stone, J. O.; Stock, G. M.; Zimmerman, S. R.

    2013-12-01

    Yosemite National Park serves as an excellent natural laboratory for studying rock falls and rock avalanches because these are the main processes modifying the nearly vertical slopes of this recently glaciated landscape. Mass wasting represents a significant hazard in the region and the database of previous rock falls and other mass wasting events in Yosemite is extensive, dating back to the mid-1800s. However, this record is too short to capture the recurrence characteristics and triggering mechanisms of the very largest events, necessitating studies of the geologic record of mass wasting. Rock falls and rock avalanches are readily dated by cosmogenic nuclide methods due to their instantaneous formation, and results can be tied to triggering events such as seismic activity (e.g. Stock et al., 2009). Here, we apply exposure dating to the Holocene Tiltill rock avalanche north of Hetch Hetchy Reservoir. The deposit comprises what appear to be two separate lobes of rock and debris, yielding a total volume of ~3.1 x 106 m3. Assuming an erosion rate of 0.0006 cm/yr and neglecting snowpack shielding, preliminary data suggest a mean exposure age of 11,000 + 600 year B.P. for both deposits, indicating that they were emplaced in a single event. The age of the Tiltill 'slide' is similar to earthquakes on the Owens Valley Fault between 10,800 + 600 and 10,200 + 200 cal year B.P. (Bacon, 2007) and the White Mountain Fault, ~10,000 cal year B.P. (Reheis, 1996; DePolo, 1989). Given that movement on the Owens Valley fault in 1872 caused a number of rock falls in Yosemite and the coincidence of ages between the Tiltill 'slide' and paleoseismic events, a large earthquake in Eastern Sierra Nevada may have triggered this event. Other trigger events are also possibilities, but only through compilation of a database of large rock avalanches can statistically significant groupings of events begin to demonstrate whether seismic triggering is a dominant process.

  5. Cold seeps associated with a submarine debris avalanche deposit at Kick'em Jenny volcano, Grenada (Lesser Antilles)

    Science.gov (United States)

    Carey, Steven; Ballard, Robert; Bell, Katherine L. C.; Bell, Richard J.; Connally, Patrick; Dondin, Frederic; Fuller, Sarah; Gobin, Judith; Miloslavich, Patricia; Phillips, Brennan; Roman, Chris; Seibel, Brad; Siu, Nam; Smart, Clara

    2014-11-01

    Remotely operated vehicle (ROV) exploration at the distal margins of a debris avalanche deposit from Kick'em Jenny submarine volcano in Grenada has revealed areas of cold seeps with chemosynthetic-based ecosystems. The seeps occur on steep slopes of deformed, unconsolidated hemipelagic sediments in water depths between 1952 and 2042 m. Two main areas consist of anastomosing systems of fluid flow that have incised local sediments by several tens of centimeters. No temperature anomalies were observed in the vent areas and no active flow was visually observed, suggesting that the venting may be waning. An Eh sensor deployed on a miniature autonomous plume recorder (MAPR) recorded a positive signal and the presence of live organisms indicates at least some venting is still occurring. The chemosynthetic-based ecosystem included giant mussels (Bathymodiolus sp.) with commensal polychaetes (Branchipolynoe sp.) and cocculinid epibionts, other bivalves, Siboglinida (vestimentiferan) tubeworms, other polychaetes, and shrimp, as well as associated heterotrophs, including gastropods, anemones, crabs, fish, octopods, brittle stars, and holothurians. The origin of the seeps may be related to fluid overpressure generated during the collapse of an ancestral Kick'em Jenny volcano. We suggest that deformation and burial of hemipelagic sediment at the front and base of the advancing debris avalanche led to fluid venting at the distal margin. Such deformation may be a common feature of marine avalanches in a variety of geological environments especially along continental margins, raising the possibility of creating large numbers of ephemeral seep-based ecosystems.

  6. 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.

  7. 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

  8. The effect of inertia on sheared disordered solids: Critical scaling of avalanches in two and three dimensions

    OpenAIRE

    Salerno, K. Michael; Robbins, Mark O.

    2013-01-01

    Molecular dynamics simulations with varying damping are used to examine the effects of inertia and spatial dimension on sheared disordered solids in the athermal, quasistatic limit. In all cases the distribution of avalanche sizes follows a power law over at least three orders of magnitude in dissipated energy or stress drop. Scaling exponents are determined using finite-size scaling for systems with thousands to millions of particles. Three distinct universality classes are identified corres...

  9. Snowpack displacement measured by terrestrial radar interferometry as precursor for wet snow avalanches

    Science.gov (United States)

    Caduff, Rafael; Wiesmann, Andreas; Bühler, Yves

    2016-04-01

    patches distributed over the entire slope. Typically, patches showing (full depth) snow gliding reach extensions from 5x10 metres up to 40x60 metres. Using a sampling interval of 1-3 minutes, the temporal displacement of such snow glide-hot spots can be tracked and thus revealing the individual signature of deformation. Nearly linear behaviour over several days, peaking in a final acceleration releasing an avalanche was observed as well characteristic acceleration and deceleration cycles during day and night could be captured. These cycles sometimes trigger an avalanche and sometimes reach a full stop of the differential snow glide movement. Findings of the different campaigns will be presented. We put them in the context for possible future campaigns that could be used to solve scientific questions regarding the mechanical properties of the snow pack. We evaluate the possibilities for the use of terrestrial radar interferometry for hazard management and avalanche forecast.

  10. 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.

  11. Inventory of large landslides and rock avalanches in the European Alps

    Science.gov (United States)

    Crosta, Giovanni B.; Frattini, Paolo; Agliardi, Federico

    2013-04-01

    Large deep-seated landslides include a broad range of instability phenomena (e.g. rockslide, rock slump, lateral spread, rock mass creep and sackung, rock avalanche) which in some cases can be found as combined or sequential processes, representing the progressive evolution of a complex slope instability. Complementing the orogen-scale inventory of DSGSD that has been recently presented for the European Alps (Crosta et al 2008, Agliardi et al 2012), we created an orogen scale inventory of large landslides (mainly rockslides) and rock avalanches. The inventory includes 1701 large landslides ranging in area between 0.1 and 17 km2, and 81 rock avalanches ranging between 0.09 and 15.5 km2. The inventory covers an area of about 110,000 km2 extending over the alpine territories of Italy, France, Switzerland, and Austria, and was prepared by using available satellite imagery (multi-temporal, Google Earth, Google, Inc.) and topographic data at different resolutions (DEMs from 1 m x 1m up to 20 m x 20 m for different areas). The inventory was validated against local or regional landslide inventories already available at different scales prepared by different subjects and using different means.. Geometrical features and geomorphological parameters have been collected and related to the different phenomena and local settings. The frequency-area relationship for the mapped features is presented. The inventory shows that large landslides are widespread in the Alps. Their spatial distribution has been analysed though bivariate and multivariate analysis (mainly Principal Component Analysis and Discriminant Analysis) against a variety of factors, including: lithology, proximity to tectonic structures, seismicity, uplift and exhumation rates, position within the mountain belt and along main and tributary valleys, slope morphometry (e.g. relief, elevation, gradient, etc.), ice thickness of glaciers during LGM, and mean annual rainfall. The analysis allowed a preliminary assessment

  12. 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.

  13. 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.

  14. [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.

  15. 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.

  16. 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.

  17. 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.

  18. Recent records and distribution of the Indian Brown Mongoose Herpestes fuscus Gray, 1837 (Mammalia: Carnivora: Herpestidae from the southern Western Ghats, India

    Directory of Open Access Journals (Sweden)

    R. Sreehari

    2016-09-01

    Full Text Available We are reporting four new records of Brown Mongoose Herpestes fuscus Gray, 1837 from four protected areas in Western Ghats including Peppara Wildlife Sanctuary, Shendurney Wildlife Sanctuary, Periyar Tiger Reserve and Pampadum Shola National Park and one new site record outside a protected area from Pambanar Tea plantation in Idukki dt. situated in Kerala part of southern Western Ghats. An updated distribution map of Brown Mongoose in Western Ghats is presented here.  

  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. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Testing the hypothesis of the Earth's magnetosphere behaving like an avalanching system

    Directory of Open Access Journals (Sweden)

    A. T. Y. Lui

    2004-01-01

    Full Text Available The global auroral dissipation power as observed by the imager on the Polar spacecraft is used as a proxy for the power dissipation of the Earth's magnetosphere to examine whether or not the magnetosphere is an avalanching system. It is found that the probability density distributions for the area and power of auroral activity sites have a power law component within a finite scale range, suggestive of a scale-free nature in this finite-size system. This property is robust, prevailing with variations in the threshold used to define auroral activity sites and in the strength of the external driver, namely, the solar wind. The statistical characteristics on the temporal evolution of auroral sites are then examined, which leads to a criterion that can be used to predict about 42min in advance the total energy dissipation during the lifetime of an auroral activity site. The scale-free characteristics of auroral activity appears to be an intrinsic feature of the magnetosphere based on a comparison of the probability density distribution in the total auroral brightness power with that of the solar wind power input parameters in the same period as the auroral observations. These results are consistent with the hypothesis of the magnetosphere behaving like an avalanching system.

  5. Data Distribution and Documenting Uncertainty Information for the Earth System Data Record: The Global Terrestrial Water Cycle

    Science.gov (United States)

    MacCracken, R. F.; Wood, E. F.; Sheffield, J.; Lettenmaier, D. P.; Houser, P.; Pinker, R. T.; Kummerow, C.; Pan, M.; Gao, H.; Sahoo, A. K.; Bytheway, J. L.

    2012-12-01

    A new balanced global terrestrial water cycle dataset is being created for the NASAs' Making Earth Science Data Records for use in Research Environments (MEaSURE) project. This dataset will be comprised of multiple remotely-sensed datasets and model generated data, and will be merged into a single unified multi-decade, high spatial resolution, climate consistent Earth Science Data Record (ESDR). In addition to the final unified ESDR, the seven remotely-sensed and model generated input datasets will also be available as ESDRs. These input datasets are: (1) VIC model derived water cycle variables, (3 hourly, from 1948 - 2010, on a 0.25 degree grid); (2) Satellite derived precipitation data from two separate sources: (a) GPCC data, (monthly, from 1983 - 1998, on a 0.5 degree grid), and (b) TRMM TMPA data, (3 hourly, from 1998 - 2010, on a 0.25 degree grid); (3) Satellite derived evapotranspiration data, based on the SRB/ISCCP radiation forcings, ( 3 hourly, from 1983 - 2007, on a 0.5 degree spatial resolution; (4) Satellite based soil moisture is derived from multiple satellite sensors, but, primarily the TRMM TMI and AMSR-E, (daily, from 1998 - 2011, on a 0.25 degree grid); (5) Satellite derived water management variables (monthly, from 1992 - 2010, on a variable degree grid); (6) Satellite derived surface radiations, based on ISCCP-DX data, (3 hourly, from 1983 - 2007, on a 0.5 degree grid) (7) Model derived Surface Meteorological Forcing Fields (3 hourly, from 1948 - 2010, on a 0.25 degree grid). Along with these ESDRs, it is also necessary to distribute uncertainty information about the data. Including this information will assist the data users with how much error there is in the estimations in the data, the limitations in the data, as well as knowing how the final merged components of the water balance equation was weighted in order to obtain a balanced equation. This uncertainty information was generated from either the producers of the individual datatsets and

  6. A new modeling and simulation method for important statistical performance prediction of single photon avalanche diode detectors

    Science.gov (United States)

    Xu, Yue; Xiang, Ping; Xie, Xiaopeng; Huang, Yang

    2016-06-01

    This paper presents a new modeling and simulation method to predict the important statistical performance of single photon avalanche diode (SPAD) detectors, including photon detection efficiency (PDE), dark count rate (DCR) and afterpulsing probability (AP). Three local electric field models are derived for the PDE, DCR and AP calculations, which show analytical dependence of key parameters such as avalanche triggering probability, impact ionization rate and electric field distributions that can be directly obtained from Geiger mode Technology Computer Aided Design (TCAD) simulation. The model calculation results are proven to be in good agreement with the reported experimental data in the open literature, suggesting that the proposed modeling and simulation method is very suitable for the prediction of SPAD statistical performance.

  7. MPPC versus MRS APD in two-phase Cryogenic Avalanche Detectors

    CERN Document Server

    Bondar, A; Dolgov, A; Shemyakina, E; Sokolov, A

    2015-01-01

    Two-phase Cryogenic Avalanche Detectors (CRADs) with combined THGEM/GAPD multiplier have become an emerging potential technique for dark matter search and coherent neutrino-nucleus scattering experiments. In such a multiplier the THGEM hole avalanches are optically recorded in the Near Infrared (NIR) using a matrix of Geiger-mode APDs (GAPDs). To select the proper sensor, the performances of six GAPD types manufactured by different companies, namely by Hamamatsu (MPPCs), CPTA (MRS APDs) and SensL (SiPMs), have been comparatively studied at cryogenic temperatures when operated in two-phase CRADs in Ar at 87 K. While the GAPDs with ceramic packages failed to operate properly at cryogenic temperatures, those with plastic packages, namely MPPC S10931-100P and MRS APD 149-35, showed satisfactory performances at 87 K. In addition, MPPC S10931-100P turned out to be superior in terms of the higher detection efficiency, lower nose rate, lower pixel quenching resistor and better characteristics reproducibility.

  8. Biodiversity's big wet secret: the global distribution of marine biological records reveals chronic under-exploration of the deep pelagic ocean.

    Directory of Open Access Journals (Sweden)

    Thomas J Webb

    Full Text Available BACKGROUND: Understanding the distribution of marine biodiversity is a crucial first step towards the effective and sustainable management of marine ecosystems. Recent efforts to collate location records from marine surveys enable us to assemble a global picture of recorded marine biodiversity. They also effectively highlight gaps in our knowledge of particular marine regions. In particular, the deep pelagic ocean--the largest biome on Earth--is chronically under-represented in global databases of marine biodiversity. METHODOLOGY/PRINCIPAL FINDINGS: We use data from the Ocean Biogeographic Information System to plot the position in the water column of ca 7 million records of marine species occurrences. Records from relatively shallow waters dominate this global picture of recorded marine biodiversity. In addition, standardising the number of records from regions of the ocean differing in depth reveals that regardless of ocean depth, most records come either from surface waters or the sea bed. Midwater biodiversity is drastically under-represented. CONCLUSIONS/SIGNIFICANCE: The deep pelagic ocean is the largest habitat by volume on Earth, yet it remains biodiversity's big wet secret, as it is hugely under-represented in global databases of marine biological records. Given both its value in the provision of a range of ecosystem services, and its vulnerability to threats including overfishing and climate change, there is a pressing need to increase our knowledge of Earth's largest ecosystem.

  9. 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,…

  10. 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,…

  11. 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…

  12. 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.

  13. 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.

  14. 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.

  15. A Record Holder Female Athlete’s Train ing Loads and its Distribution in Women 400 meter Hurdle Running

    Directory of Open Access Journals (Sweden)

    Sibel DÜNDAR

    2015-07-01

    Full Text Available The purpose of this study was to investigate the effects on 400 mt characteristics of women training load used in the hurdle runnig , the distribution and performance according to the period. At this study female athlete’s, who won second place at the European Champion Clubs' Cup Competitions and had a record - breaking six times in a country, five - year training loads and degrees were investigated. In this study, athlete’s degrees an d training loads were analyzed between the years of 1982 - 1987. Atlete’s best 100m,200m,400m,400m hurdle degrees and some training loads (sprint, andurance, weight lifting were assessed by the means and satandart deviations. Athlete’s sprint and training l oads mean and standard deviation values were calculated as 100 m ( 11.96 ± 0.17 , 200m ( 25.0 ± 0.38 , 400m ( 56.07 ± 0.91 and 400 m hurdle running ( 60.38 ± 1.88 and for the training loads of 0 - 150 m sprint ( 66.85 ± 18.95 m, endurance ( 2 02.55 ± 57.56 miles and weightlifting( 151.88 ± 68.2 tons. It was observed that percentage of change of the value of training loads and the running performance changes were not increase at the same rate. Regarding the relationship between the best run ning degree and training load, it was found a significant relationship between only 60 m sprint and 150 - 450 m sprint degrees.

  16. 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

  17. A preliminary checklist of polypores of Peru, with notes on distribution in the Andes-Amazon region and new records for the country

    Directory of Open Access Journals (Sweden)

    Janovec JP

    2012-05-01

    Full Text Available A checklist of 33 polypore species (Hymenochaetales and Polyporales from the Camanti-Marcapata Biological Corridor (CMBC of Cusco, Peru, is provided with data about distribution in the Andes-Amazon region. More than 90% of polypore species reported herein are new records to the country.

  18. 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.

  19. Geological and geotechnical characterization of the debris avalanche and pyroclastic deposits of Cotopaxi Volcano (Ecuador). A contribute to instability-related hazard studies

    Science.gov (United States)

    Vezzoli, L.; Apuani, T.; Corazzato, C.; Uttini, A.

    2017-02-01

    The huge volcanic debris avalanche occurred at 4.5 ka is a major event in the evolution of the Cotopaxi volcano, Ecuador. The present volcanic hazard in the Cotopaxi region is related to lahars generated by volcanic eruptions and concurrent ice melting. This paper presents the geological and geotechnical field and laboratory characterization of the 4.5 ka Cotopaxi debris avalanche deposit and of the younger unconsolidated pyroclastic deposits, representing the probable source of future shallow landslides. The debris avalanche formed a deposit with a well-developed hummocky topography, and climbed a difference in height of about 260 m along the slopes of the adjacent Sincholagua volcano. The debris avalanche deposit includes four lithofacies (megablock, block, mixed, and sheared facies) that represent different flow regimes and degrees of substratum involvement. The facies distribution suggests that, in the proximal area, the debris avalanche slid predominantly confined to the valleys along the N and NE flank of the volcanic cone, emplacing a stack of megablocks. When the flow reached the break in slope at the base of the edifice, it became unconfined and spread laterally over most of the area of the Rio Pita valley. A dynamic block fragmentation and dilation occurred during the debris avalanche transport, emplacing the block facies. The incorporation of the older Chalupas Ignimbrite is responsible for the mixed facies and the sheared facies. Geotechnical results include a full-range grain size characterization, which enabled to make broader considerations on possible variability among the sampled facies. Consolidated drained triaxial compression tests, carried out on the fine fraction Failure surfaces are always well developed, indicating that the poorly consolidated pyroclastic cover could undergo failure leading to the formation of a gravity driven instability phenomena, like granular or debris flows, which are mainly controlled by the fine fraction. This work

  20. 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.

  1. New records and detailed distribution and abundance of selected arthropod species collected between 1999 and 2011 in Azorean native forests

    DEFF Research Database (Denmark)

    Borges, Paulo A. V.; Gaspar, Clara; Crespo, Luís Carlos Fonseca

    2016-01-01

    by 10% during the time frame of these projects. The classes Arachnida, Chilopoda and Diplopoda represent the most remarkable cases of new island records, with more than 30% of the records being novelties. This study stresses the need to expand the approaches applied in these projects to other habitats...

  2. A study of the runaway relativistic electron avalanche and the feedback theory using GEANT4

    Science.gov (United States)

    Broberg Skeltved, Alexander; Østgaard, Nikolai; Carlson, Brant; Gjesteland, Thomas

    2014-05-01

    This study investigate the Runaway Relativistic Electron Avalanche (RREA) and the feedback process as well as the production of Bremsstrahlung photons from Runaway Electrons (REs). These processes are important to understand the production of the intense bursts of gamma-rays known as Terrestrial Gamma-Ray Flashes (TGFs). Results are obtained from Monte Carlo (MC) simulations using the GEometry ANd Tracking 4 (GEANT4) programming toolkit. The simulations takes into account the effects of electron ionisation, electron by electron scattering (Møller scattering) as well as positron and photon interactions, in the 250 eV-100 GeV energy range. Several physics libraries or 'physics lists' are provided with GEANT4 to implement these physics processes in the simulations. We give a detailed analysis of the electron and the feedback multiplication, in particular the avalanche lengths, Λ, the energy distribution and the feedback factor, γ. We also find that our results vary significantly depending on which physics list we implement. In order to verify our results and the GEANT4 programming toolkit, we compare them to previous results from existing models. In addition we present the ratio of the production of bremsstrahlung photons to runaway electrons. From this ratio we obtain the parameter, α, which describe the electron to photon relation.

  3. Comparison of Measurement And Modeling Of Current Profile Changes Due To Neutral Bean Ion Redistribution During TAE Avalanches in NSTX

    Energy Technology Data Exchange (ETDEWEB)

    Darrow, Douglas

    2013-07-09

    Brief "avalanches" of toroidal Alfven eigenmodes (TAEs) are observed in NSTX plasmas with several different n numbers simultaneously present. These affect the neutral beam ion distribution as evidenced by a concurrent drop in the neutron rate and, sometimes, beam ion loss. Guiding center orbit modeling has shown that the modes can transiently render portions of the beam ion phase space stochastic. The resulting redistribution of beam ions can also create a broader beam-driven current profile and produce other changes in the beam ion distribution function

  4. 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

  5. Integrated snow and avalanche monitoring syatem for Indian Himalaya using multi-temporal satellite imagery and ancillary data

    Science.gov (United States)

    Sharma, S. S.; Mani, Sneh; Mathur, P.

    . Different methods have been used for the analysis of the temporal changes in satellite images. Multi-sensor data fusion techniques have been applied to increase the accuracy of classification, and also for extraction of necessary information about characteristics of snow and avalanches and the ground conditions. The results of the analysis of time series of last two winters are reported. The study confirms that significant changes in snow characteristics and wetness are mainly due to large variations in temperature at these altitudes, which contribute towards avalanche activities in early winter. A definite relationship has been observed between snow wetness, altitude and period of the year with respect to the probability of an avalanche occurrence. Snow wetness is found to be inversely proportional to the altitude, whereas probability of an avalanche is directly proportional to the wetness of snow, lying either over thin grass or boulder-covered ground. The results were verified through extensive field measurements. The emphasis has been laid on establishment of a dense network of Automatic Weather Stations (AWS), Upper Air Stations (UAS) and observatories in entire Himalaya; development of GIS based data bases using satellite imageries and other ancillary data for weather, snow and land cover monitoring. Records of past years will provide base information for realistic estimation of the impact of climatic changes and confidence to predict the weather and avalanches in various regions of Himalaya. Key Words: Integrated Monitoring System, Time series multi-sensor/multi-temporal Satellite Imageries, Multi-sensor Data Fusion, Change Detection, Snow characteristics

  6. Integrated snow and avalanche monitoring system for Indian Himalaya using multi-temporal satellite imagery and ancillary data

    Science.gov (United States)

    Sharma, S. S.; Mani, Sneh; Mathur, P.

    . Different methods have been used for the analysis of the temporal changes in satellite images. Multi-sensor data fusion techniques have been applied to increase the accuracy of classification, and also for extraction of necessary information about characteristics of snow and avalanches and the ground conditions. The results of the analysis of time series of last two winters are reported. The study confirms that significant changes in snow characteristics and wetness are mainly due to large variations in temperature at these altitudes, which contribute towards avalanche activities in early winter. A definite relationship has been observed between snow wetness, altitude and period of the year with respect to the probability of an avalanche occurrence. Snow wetness is found to be inversely proportional to the altitude, whereas probability of an avalanche is directly proportional to the wetness of snow, lying either over thin grass or boulder-covered ground. The results were verified through extensive field measurements. The emphasis has been laid on establishment of a dense network of Automatic Weather Stations (AWS), Upper Air Stations (UAS) and observatories in entire Himalaya; development of GIS based data bases using satellite imageries and other ancillary data for weather, snow and land cover monitoring. Records of past years will provide base information for realistic estimation of the impact of climatic changes and confidence to predict the weather and avalanches in various regions of Himalaya. Key Words: Integrated Monitoring System, Time series multi-sensor/multi-temporal Satellite Imageries, Multi-sensor Data Fusion, Change Detection, Snow characteristics

  7. The Montesbelos mass-flow (southern Amazonian craton, Brazil): a Paleoproterozoic volcanic debris avalanche deposit?

    Science.gov (United States)

    Roverato, M.

    2016-07-01

    The present contribution documents the extremely well-preserved Paleoproterozoic architecture of the Montesbelos breccia (named here for the first time), which is interpreted as a rare example of a subaerial paleoproterozoic (>1.85 Ga) granular-dominated mass-flow deposit, few of which are recorded in the literature. Montesbelos deposit is part of the andesitic Sobreiro Formation located in the São Felix do Xingu region, southern Amazonian craton, northern Brazil. The large volume, high variability of textural features, presence of broken clasts, angular low sphericity fragments, mono- to heterolithic character, and the size of the outcrops point to a volcanic debris avalanche flow. Fluviatile sandy material and debris flows are associated with the deposit as a result of post-depositional reworking processes.

  8. Two-phase Cryogenic Avalanche Detector with electroluminescence gap operated in argon doped with nitrogen

    Science.gov (United States)

    Bondar, A.; Buzulutskov, A.; Dolgov, A.; Nosov, V.; Shekhtman, L.; Shemyakina, E.; Sokolov, A.

    2017-02-01

    A two-phase Cryogenic Avalanche Detector (CRAD) with electroluminescence (EL) gap, operated in argon doped with a minor (49±7 ppm) admixture of nitrogen, has been studied. The EL gap was optically read out using cryogenic PMTs located on the perimeter of the gap. We present the results of the measurements of the N2 content, detector sensitivity to X-ray-induced signals, EL gap yield and electron lifetime in the liquid. The detector sensitivity, at a drift field in liquid Ar of 0.6 kV/cm, was measured to be 9 and 16 photoelectrons recorded at the PMTs per keV of deposited energy at 23 and 88 keV respectively. Such two-phase detectors, with enhanced sensitivity to the S2 (ionization-induced) signal, are relevant in the field of argon detectors for dark matter search and low energy neutrino detection.

  9. Two-phase Cryogenic Avalanche Detector with electroluminescence gap operated in argon doped with nitrogen

    CERN Document Server

    Bondar, A; Dolgov, A; Nosov, V; Shekhtman, L; Shemyakina, E; Sokolov, A

    2016-01-01

    A two-phase Cryogenic Avalanche Detector (CRAD) with electroluminescence (EL) gap, operated in argon doped with a minor (49$\\pm$7 ppm) admixture of nitrogen, has been studied. The EL gap was optically read out using cryogenic PMTs located on the perimeter of the gap. We present the results of the measurements of the N$_2$ content, detector sensitivity to X-ray-induced signals, EL gap yield and electron lifetime in the liquid. The detector sensitivity, at a drift field in liquid Ar of 0.6 kV/cm, was measured to be 9 and 16 photoelectrons recorded at the PMTs per keV of deposited energy at 23 and 88 keV respectively. Such two-phase detectors, with enhanced sensitivity to the S2 (ionization-induced) signal, are relevant in the field of argon detectors for dark matter search and low energy neutrino detection.

  10. An annotated checklist of the scale insects of Iran (Hemiptera, Sternorrhyncha, Coccoidea with new records and distribution data

    Directory of Open Access Journals (Sweden)

    Masumeh Moghaddam

    2013-09-01

    Full Text Available A list of scale insects (Hemiptera: Sternorrhyncha: Coccoidea of Iran is present based mainly on the literature records since 1902. In total, 13 families and 275 species have been recorded and these are listed along with their locality data and host plants. The families are as follows: Asterolecaniidae, Cerococcidae, Coccidae, Diaspididae, Eriococcidae, Kermesidae, Margarodidae, Monophlebidae, Ortheziidae, Phoenicococcidae, Pseudococcidae, Putoidae and Rhizoecidae. The following ten species are recorded for the first time from Iran: Diaspidiotus lenticularis (Lindinger, D. wuenni (Lindinger, Fiorinia proboscidaria Green, Koroneaspis lonicerae Borchsenius, Eriococcus cingulatus Kiritchenko, E. pamiricus (Bazarov, E. reynei Schmutterer, E. sanguinairensis Goux and E. saxidesertus (Borchsenius and Porphyrophora victoriae Jashenko.

  11. An annotated checklist of the scale insects of Iran (Hemiptera, Sternorrhyncha, Coccoidea) with new records and distribution data.

    Science.gov (United States)

    Moghaddam, Masumeh

    2013-01-01

    A list of scale insects (Hemiptera: Sternorrhyncha: Coccoidea) of Iran is present based mainly on the literature records since 1902. In total, 13 families and 275 species have been recorded and these are listed along with their locality data and host plants. The families are as follows: Asterolecaniidae, Cerococcidae, Coccidae, Diaspididae, Eriococcidae, Kermesidae, Margarodidae, Monophlebidae, Ortheziidae, Phoenicococcidae, Pseudococcidae, Putoidae and Rhizoecidae. The following ten species are recorded for the first time from Iran: Diaspidiotus lenticularis (Lindinger), Diaspidiotus wuenni (Lindinger), Fiorinia proboscidaria Green, Koroneaspis lonicerae Borchsenius, Eriococcus cingulatus Kiritchenko, Eriococcus pamiricus (Bazarov), Eriococcus reynei Schmutterer, Eriococcus sanguinairensis Goux and Eriococcus saxidesertus (Borchsenius) and Porphyrophora victoriae Jashenko.

  12. Records of the endemic and threatened catfish, Hemibagrus punctuates from the southern Western Ghats with notes on its distribution, ecology and conservation status

    Directory of Open Access Journals (Sweden)

    A. Ali

    2013-07-01

    Full Text Available The Nilgiri Mystus, Hemibagrus punctatus, a rare bagrid catfish endemic to the Western Ghats, has been currently listed in the IUCN Red List, as Critically Endangered with a possibility that it could be extinct. The last validated record of H. punctatus was known to be in 1998, and several surveys since then have not been able to collect the species from its native range. In this paper, we provide information on new records of this rare catfish from the Western Ghats after a period of 14 years, and discuss its distribution, ecology and conservation. An updated conservation assessment of this species following the IUCN Red List Criteria is also provided.

  13. A novel camera type for very high energy gamma-ray astronomy based on Geiger-mode avalanche photodiodes

    CERN Document Server

    Anderhub, H; Biland, A; Boller, A; Braun, I; Bretz, T; Commichau, S; Commichau, V; Dorner, D; Gendotti, A; Grimm, O; von Gunten, H; Hildebrand, D; Horisberger, U; Krähenbühl, T; Kranich, D; Lorenz, E; Lustermann, W; Mannheim, K; Neise, D; Pauss, F; Renker, D; Rhode, W; Rissi, M; Röser, U; Rollke, S; Stark, L S; Stucki, J -P; Viertel, G; Vogler, P; Weitzel, Q

    2009-01-01

    Geiger-mode avalanche photodiodes (G-APD) are promising new sensors for light detection in atmospheric Cherenkov telescopes. In this paper, the design and commissioning of a 36-pixel G-APD prototype camera is presented. The data acquisition is based on the Domino Ring Sampling (DRS2) chip. A sub-nanosecond time resolution has been achieved. Cosmic-ray induced air showers have been recorded using an imaging mirror setup, in a self-triggered mode. This is the first time that such measurements have been carried out with a complete G-APD camera.

  14. A novel camera type for very high energy gamma-ray astronomy based on Geiger-mode avalanche photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Anderhub, H; Biland, A; Boller, A; Braun, I; Commichau, S; Commichau, V; Dorner, D; Gendotti, A; Grimm, O; Gunten, H von; Hildebrand, D; Horisberger, U; Kraehenbuehl, T; Kranich, D; Lorenz, E; Lustermann, W [Institute for Particle Physics, ETH Zurich, Schafmattstr. 20, 8093 Zurich (Switzerland); Backes, M; Neise, D [TU Dortmund University, Otto-Hahn-Str. 4, 44227 Dortmund (Germany); Bretz, T; Mannheim, K [University of Wuerzburg Am Hubland, 97074 Wuerzburg (Germany)], E-mail: qweitzel@phys.ethz.ch (and others)

    2009-10-15

    Geiger-mode avalanche photodiodes (G-APD) are promising new sensors for light detection in atmospheric Cherenkov telescopes. In this paper, the design and commissioning of a 36-pixel G-APD prototype camera is presented. The data acquisition is based on the Domino Ring Sampling (DRS2) chip. A sub-nanosecond time resolution has been achieved. Cosmic-ray induced air showers have been recorded using an imaging mirror setup, in a self-triggered mode. This is the first time that such measurements have been carried out with a complete G-APD camera.

  15. 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.

  16. 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.

  17. Fauna of Simuliidae (Diptera from the state of Espírito Santo, Brazil: distribution, new records and list of species

    Directory of Open Access Journals (Sweden)

    Karina Bertazo

    2013-03-01

    Full Text Available Fauna of Simuliidae (Diptera from the state of Espírito Santo, Brazil: Distribution, new records and list of species. The fauna of Simuliidae in Brazil is composed of 87 species, 17 of which are recorded from the state of Espírito Santo. Entomological collections were carried out in 2010-2011 with the objective of increasing the knowledge of the species richness of this family in the state. Ninety three rivers and streams were sampled, each collection being carried out in a 50m transect. During the study period 30 species were collected, 13 of which represent new records for the state, 12 of the genus Simulium and one of the genus Lutzsimulium. Among these new state records one, Simulium lobatoi, also represents a new record from southeastern Brazil. The other newly recorded species are: Lutzsimulium hirticosta, Simulium distinctum, Simulium exiguum, Simulium oyapockense, Simulium botulibranchium, Simulium petropoliense, Simulium clavibranchium, Simulium rappae, Simulium minusculum, Simulium dinellii, Simulium ochraceum and Simulium scutistriatum.

  18. 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.

  19. 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...

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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...

  7. New distribution records of the gall crab Opecarcinus cathyae van der Meij, 2014 (Decapoda: Brachyura: Cryptochiridae) from the Red Sea, Maldives and Japan

    KAUST Repository

    Meij, Sancia E. T.

    2016-11-12

    The gall crab Opecarcinus cathyae van der Meij, 2014 has been reported from various localities in Indonesia and Malaysia. Recent surveys in the Red Sea, Maldives and Japan yielded additional specimens of O. cathyae, considerably expanding the known distribution range of this species to the east and west. The identity of O. cathyae was confirmed based on COI sequence data, revealing identical haplotypes for the Red Sea, Maldivian and Japanese material and three haplotypes in the Indonesian material. Opecarcinus cathyae has one of the widest known recorded distribution ranges for all gall crab species.

  8. LOCAL CONDITIONS AND IMPACTS OF THE AVALANCHES. CASE STUDIES IN REPRESENTATIVE SECTORS WITHIN PIATRA CRAIULUI AND FĂGĂRAȘ MOUNTAINS

    Directory of Open Access Journals (Sweden)

    ANCA MUNTEANU

    2014-05-01

    Full Text Available Genesis conditions and effects of avalanches. Case studies in representative sectors within Piatra Craiului and Fagars mountains. The present paper aims at investigating the avalanches and their impact on the environment components. Snow avalanches are natural phenomena, which are controlled by the specific features of the mountain realm. They start suddenly due to the combination of meteorological and non-meteorological factors, which make the loose materials (snow, ice, detritus, vegetation or soil collapse or slide down along the slope. In consequence, erosion is increased or facilitated because of the impact they have on the other components of the environment (thalwegs deepening, forest destruction. The distribution of avalanches is hard to be highlighted, because of the inaccessible lands and the adverse meteorological conditions. From this reason, one needs to know their complex features, namely the morphology, vegetation and spatial dynamics of the areas prone to such phenomena. The effects on the environment can be easily identified in the mountain realm, inasmuch as they create typical corridors along the streams crossing the forests. At the same time, however, they have certain effects on the slope deposits, too. These will be further presented with examples for the eastern slope of the Piatra Craiului Mts. and the Suru – Negoiu section in the Făgăraș Mts. These areas are deemed representative for each of the mentioned mountain massifs.

  9. 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 ...

  10. 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.

  11. 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.

  12. 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.

  13. Geographical distribution of the space-weaving spider, Chibchea salta, from northwestern Argentina: New records and bioclimatic modeling.

    Science.gov (United States)

    Rubio, Gonzalo D; Acosta, Luis E

    2011-01-01

    New records of the spider Chibchea salta Huber 2000 (Araneae, Pholcidae) from northwestern Argentina are provided, and the potential range of this species is modeled. Two presence-only methods, Maxent and Bioclim, were run using 19 bioclimatic parameters at a resolution of 30 arc seconds. The climatic profile of C. salta is described, and the relative importance of the bioclimatic variables is explored. Temperature variables proved to be more decisive to the final range shape. The range predicted with Maxent is slightly larger than with Bioclim, but the latter appears to be more sensitive to the record set bias. Both methods performed well, resulting in predictive ranges consistent with the yungas ecoregion. These results provide an initial insight into the bioclimatic tolerance of C. salta, and by identifying potential areas with no records, such as the sierras on the Salta-Jujuy border, they also help in identifying sites for future sampling efforts.

  14. 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.

  15. Three new species and new distributional records of Oecetis McLachlan 1877 (Trichoptera: Leptoceridae: Leptocerinae) from Brazil.

    Science.gov (United States)

    Henriques-Oliveira, Ana Lucia; Dumas, Leandro Lourenço; Nessimian, Jorge Luiz

    2014-01-07

    The genus Oecetis is widespread over the world, being most diverse in tropical areas, especially in the Australian Region. Of about 400 described species, only 34 occur in the Neotropical Region. Herein, we describe and illustrate three new species of Oecetis from Brazil: Oecetis angelae sp. nov., O. danielae sp. nov. and O. iara sp. nov. Furthermore, O. doesburgi, O. dominguezi, and O. knutsoni are recorded for the first time in Brazil. Also, we provide new state records for 7 species: O. amazonica, O. connata, O. excisa, O. fibra, O. iguazu, O. inconspicua, and O. paranensis.

  16. Two-dimensional simulation research of secondary electron emission avalanche discharge on vacuum insulator surface

    Science.gov (United States)

    Cai, Libing; Wang, Jianguo; Zhu, Xiangqin; Wang, Yue; Zhang, Dianhui

    2015-01-01

    Based on the secondary electron emission avalanche (SEEA) model, the SEEA discharge on the vacuum insulator surface is simulated by using a 2D PIC-MCC code developed by ourselves. The evolutions of the number of discharge electrons, insulator surface charge, current, and 2D particle distribution are obtained. The effects of the strength of the applied electric field, secondary electron yield coefficient, rise time of the pulse, length of the insulator on the discharge are investigated. The results show that the number of the SEEA electrons presents a quadratic dependence upon the applied field strength. The SEEA current, which is on the order of Ampere, is directly proportional to the field strength and secondary electron yield coefficient. Finally, the electron-stimulated outgassing is included in the simulation code, and a three-phase discharge curve is presented by the simulation, which agrees with the experimental data.

  17. High-pressure pulsed avalanche discharges: Formulas for required preionization density and rate for homogeneity

    Energy Technology Data Exchange (ETDEWEB)

    Brenning, N.; Axnaes, I.; Nilsson, J.O.; Eninger, J.E. [Royal Inst. of Tech., Stockholm (Sweden)

    1997-02-01

    The requirements on preionization for the formation of spatially homogeneous pulsed avalanche discharges are examined. The authors derive two formulas which apply in the case of a slowly rising electric field, one which gives the required preionization density at breakdown, and one which gives the required preionization rate. These quantities are expressed as functions of the electrochemical properties of the gas, the neutral density, and the electric field rise time. They also treat the statistical effect that the electrons tend to form groups, in contrast to being randomly distributed in space, during the prebreakdown phase. This process is found to increase the required preionization rate significantly, typically by a factor of five for a discharge at atmospheric pressure. Homogeneous high-pressure discharges have been used for laser excitation, and have also been proposed for chemical plasma processing (ozone production) because of their good scaling properties and high efficiency.

  18. Quick single-photon detector with many avalanche photo diodes working on the time division

    Institute of Scientific and Technical Information of China (English)

    Jian Peng; Yifei Fu; Li Yao; Xudong Shang; Zhixin Lu; Bojun Yang; Li Yu

    2008-01-01

    Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.

  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. Twelve new species and fifty-three new provincial distribution records of Aleocharinae rove beetles of Saskatchewan, Canada (Coleoptera, Staphylinidae).

    Science.gov (United States)

    Klimaszewski, Jan; Larson, David J; Labrecque, Myriam; Bourdon, Caroline

    2016-01-01

    One hundred twenty species of aleocharine beetles (Staphylinidae) are recognized in the province of Saskatchewan. Sixty-five new provincial records, including twelve new species and one new North American record, are presented. Oligota inflata (Mannerheim), a Palearctic species, is newly recorded for North America. The following twelve species are described as new to science: Acrotona pseudopygmaea Klimaszewski & Larson, sp. n., Agaricomorpha pulchra Klimaszewski & Larson, sp. n. (new genus record for Canadian fauna), Aleochara elisabethae Klimaszewski & Larson, sp. n., Atheta (Dimetrota) larsonae Klimaszewski & Larson, sp. n., Atheta (Microdota) pseudopittionii Klimaszewski & Larson, sp. n., Atheta (Microdota) spermathecorum Klimaszewski & Larson, sp. n., Atheta (sensu lato) richardsoni Klimaszewski & Larson, sp. n., Brachyusa saskatchewanae Klimaszewski & Larson, sp. n., Dochmonota langori Klimaszewski & Larson, sp. n., Dochmonota simulans Klimaszewski & Larson, sp. n., Dochmonota websteri Klimaszewski & Larson, sp. n., and Oxypoda domestica Klimaszewski & Larson, sp. n. Colour images of habitus and black and white images of the median lobe of the aedeagus, spermatheca, and tergite and sternite VIII are presented for all new species, Oligota inflata Mannerheim and Dochmonota rudiventris (Eppelsheim). A new synonymy is established: Tetralina filitarsus Casey, syn. n. = Tetralina helenae Casey, now placed in the genus Brachyusa Mulsant & Rey.

  1. The Phalacridae (Coleoptera, Cucujoidea of Canada: new records, distribution, and bionomics with a particular focus on the Atlantic Canadian fauna

    Directory of Open Access Journals (Sweden)

    Christopher Majka

    2008-09-01

    Full Text Available The Canadian Phalacridae are briefly surveyed. Two species, Phalacrus politus Melsheimer and Olibrus vittatus LeConte, are newly recorded in Canada. As a result, eight phalacrids are now known to occur in Canada. Thirteen new provincial records are reported including one from Saskatchewan, two from Manitoba, two from New Brunswick, three from Nova Scotia, two from Prince Edward Island, and three from Newfoundland and Labrador. The four species and ten provincial records of Phalacridae reported from provinces in Atlantic Canada are the first records of this family in the region. Information on the bionomics of these species is briefly summarized. The species include Phalacrus penicillatus Say, Phalacrus politus Melsheimer (a smut-feeding species associated with corn, sorghum, and other grasses, Olibrus vittatus LeConte, Olibrus semistriatus LeConte (an abundant floricolous species found in the heads of several genera of Asteraceae, Acylomus pugetanus Casey (an ergot-feeding beetle associated with various grains and wild grasses, and Stilbus apicalis (Melsheimer (an apparently surface-feeding, mold-grazing, facultatively parthenogenic species. The discovery of P. politus on insular Newfoundland is particularly noteworthy and represents a range extension of about 1,260 km. The possible origins of this apparently isolated and disjunct population are discussed, focusing on the glacial history of the region.

  2. 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

  3. 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

  4. 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...

  5. 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...

  6. 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.

  7. Iterative inversion of global magnetospheric ion distributions using energetic neutral atom (ENA images recorded by the NUADU/TC2 instrument

    Directory of Open Access Journals (Sweden)

    L. Lu

    2008-06-01

    Full Text Available A method has been developed for extracting magnetospheric ion distributions from Energetic Neutral Atom (ENA measurements made by the NUADU instrument on the TC-2 spacecraft. Based on a constrained linear inversion, this iterative technique is suitable for use in the case of an ENA image measurement, featuring a sharply peaked spatial distribution. The method allows for magnetospheric ion distributions to be extracted from a low-count ENA image recorded over a short integration time (5 min. The technique is demonstrated through its application to a set of representative ENA images recorded in energy Channel~2 (hydrogen: 50–81 keV, oxygen: 138–185 keV of the NUADU instrument during a geomagnetic storm. It is demonstrated that this inversion method provides a useful tool for extracting ion distribution information from ENA data that are characterized by high temporal and spatial resolution. The recovered ENA images obtained from inverted ion fluxes match most effectively the measurements made at maximum ENA intensity.

  8. Flank collapse at Mount Wrangell, Alaska, recorded by volcanic mass-flow deposits in the Copper River lowland

    Science.gov (United States)

    Waythomas, C.F.; Wallace, K.L.

    2002-01-01

    An areally extensive volcanic mass-flow deposit of Pleistocene age, known as the Chetaslina volcanic mass-flow deposit, is a prominent and visually striking deposit in the southeastern Copper River lowland of south-central Alaska. The mass-flow deposit consists of a diverse mixture of colorful, variably altered volcanic rocks, lahar deposits, glaciolacustrine diamicton, and till that record a major flank collapse on the southwest flank of Mount Wrangell. The deposit is well exposed near its presumed source, and thick, continuous, stratigraphic exposures have permitted us to study its sedimentary characteristics as a means of better understanding the origin, significance, and evolution of the deposit. Deposits of the Chetaslina volcanic mass flow in the Chetaslina River drainage are primary debris-avalanche deposits and consist of two principal facies types, a near-source block facies and a distal mixed facies. The block facies is composed entirely of block-supported, shattered and fractured blocks with individual blocks up to 40 m in diameter. The mixed facies consists of block-sized particles in a matrix of poorly sorted rock rubble, sand, and silt generated by the comminution of larger blocks. Deposits of the Chetaslina volcanic mass flow exposed along the Copper, Tonsina, and Chitina rivers are debris-flow deposits that evolved from the debris-avalanche component of the flow and from erosion and entrainment of local glacial and glaciolacustrine diamicton in the Copper River lowland. The debris-flow deposits were probably generated through mixing of the distal debris avalanche with the ancestral Copper River, or through breaching of a debris-avalanche dam across the ancestral river. The distribution of facies types and major-element chemistry of clasts in the deposit indicate that its source was an ancestral volcanic edifice, informally known as the Chetaslina vent, on the southwest side of Mount Wrangell. A major sector collapse of the Chetaslina vent initiated

  9. 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.

  10. Icequakes as precursors of ice avalanches

    CERN Document Server

    Faillettaz, J; Sornette, D

    2009-01-01

    A hanging glacier at the east face of Weisshorn broke off in 2005. We were able to monitor and measure surface motion and icequake activity for 21 days up to three days prior to the break-off. Results are presented from the analysis of seismic waves generated by the glacier during the rupture maturation process. Three types of precursory signals of the imminent catastrophic rupture were identified: (i) an increasing seismic activity within the glacier, (ii) a change in the size-frequency distribution of icequake energy, and (iii) a log-periodic oscillating behavior superimposed on power law acceleration of the inverse of waiting time between two icequakes. The analysis of the seismic activity gave indications of the rupture process and led to the identification of two regimes: a stable one where events are isolated and non correlated which is characteristic of diffuse damage, and an unstable and dangerous one in which events become synchronized and large icequakes are triggered.

  11. Avalanche criticalities and elastic and calorimetric anomalies of the transition from cubic Cu-Al-Ni to a mixture of 18 R and 2 H structures

    Science.gov (United States)

    Vives, Eduard; Baró, Jordi; Gallardo, María Carmen; Martín-Olalla, José-María; Romero, Francisco Javier; Driver, Sarah L.; Carpenter, Michael A.; Salje, Ekhard K. H.; Stipcich, Marcelo; Romero, Ricardo; Planes, Antoni

    2016-07-01

    We studied the two-step martensitic transition of a Cu-Al-Ni shape-memory alloy by calorimetry, acoustic emission (AE), and resonant ultrasound spectroscopy (RUS) measurements. The transition occurs under cooling from the cubic (β , F m 3 m ) parent phase near 242 K to a mixture of orthorhombic 2 H and monoclinic 18 R phases. Heating leads first to the back transformation of small 18 R domains to β and/or 2 H near 255 K, and then to the transformation 2 H to β near 280 K. The total transformation enthalpy is Δ HT=328 ±10 J/mol and is observed as one large latent heat peak under cooling. The back-transformation entropy under heating breaks down into a large component 18 R to β at 255 K and a smaller, smeared component of the transformation 2 H to β near 280 K. The proportions inside the phase mixture depend on the thermal history of the sample. The elastic response of the sample is dominated by large elastic softening during cooling. The weakening of the elastic shear modulus shows a peak at 242 K, which is typical for the formation of complex microstructures. Cooling the sample further leads to additional changes of the microstructure and domain wall freezing, which is seen by gradual elastic hardening and increasing damping of the RUS signal. Heating from 220 K to room temperature leads to elastic anomalies due to the initial transformation, which is now shifted to high temperatures. The transition is smeared over a wider temperature interval and shows strong elastic damping. The shear modulus of the cubic phase is recovered at 280 K. The phase transformation leads to avalanches, which were recorded by AE and by time-resolved calorimetry. The cooling transition shows very extended avalanche signals in calorimetry with power-law distributions. Cooling and heating runs show AE signals over a large temperature interval above 260 K. Splitting the transformation into two martensite phases leads to power-law exponents ɛ ˜2 (β ↔ 18 R ) and ɛ ˜1.5 (β ↔ 2

  12. New records and distribution modeling of Gryne orensis (Sørensen) (Opiliones: Cosmetidae) support the Mesopotamian-Yungas disjunction in subtropical Argentina.

    Science.gov (United States)

    Acosta, Luis E; Vergara, Julia

    2013-11-12

    The presence of Gryne orensis (Sørensen) (Opiliones: Cosmetidae) in a Yungas locality (northwestern Argentina) is reported for the first time, providing new evidence for the Mesopotamian-Yungas disjunct pattern. Combining a total of 19 new Mesopotamian records with previous, reliable citations from the literature, a dataset of 45 points was used to model the potential distribution of the species, using the presence-only methods BIOCLIM and MAXENT. Models supported the existence of a distributional gap across the Semiarid Chaco. The imprecise literature record from "El Impenetrable", province of Chaco, is assigned to three tentative locations to evaluate if models are affected by their inclusion; in all cases, the disjunction was maintained. It was thereby estimated that the actual record might have originated in a site closer to the Humid Chaco and/or associated to streams. This paper also provides a statement of the bioclimatic profile and identification of major environmental constraints that define the range of G. orensis. 

  13. Dark-current characteristics of GaN-based UV avalanche photodiodes

    Science.gov (United States)

    Xu, Jintong; Chang, Chao; Li, Xiangyang

    2015-04-01

    For UV detecting, it needs high ratio of signal to noise, which means high responsibility and low noise. GaN-based avalanche photodiodes can provide a high internal photocurrent gain. In this paper, we report the testing and characterization of GaN based thin film materials, optimization design of device structure, the device etching and passivation technology, and the photoelectric characteristics of the devices. Also, uniformity of the device was obtained. The relationship between dark current and material quality or device processes was the focus of this study. GaN based material with high aluminum components have high density defects. Scanning electron microscope, cathodoluminescence spectra, X-ray double crystal diffraction and transmission spectroscopy testing were employed to evaluate the quality of GaN-based material. It shows that patterned sapphire substrate or thick AlN buffer layer is more effective to get high quality materials. GaN-based materials have larger hole ionization coefficient, so back incident structure were adopted to maximize the hole-derived multiplication course and it was helped to get a smaller multiplication noise. The device with separate absorption and multiplication regions is also prospective to reduce the avalanche noise. According to AlGaN based material characteristics and actual device fabrication, device structure was optimized further. Low physical damage inductively coupled plasma (ICP) etching method was used to etch mesa and wet etching method was employed to treat mesa damage. Silica is passivation material of device mesa. For solar-blind ultraviolet device, it is necessary to adopt a wider bandgap material than AlGaN material. The current-voltage characteristics under reverse bias were measured in darkness and under UV illumination. The distribution of dark current and response of different devices was obtained. In short, for GaN-based UV avalanche photodiode, dark current was related to high density dislocation of

  14. 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%. 

  15. First record of Saga pedo (Orthoptera, Tettigoniidae in Suceava County with notes on its distribution in Eastern Romania

    Directory of Open Access Journals (Sweden)

    Emilian Pricop

    2012-12-01

    Full Text Available The predatory bush-cricket Saga pedo Pallas, 1771 is mentioned for the first time from“Fâneţele Seculare Ponoare” Bosanci Natural Reserve, located few kilometers south of Suceava city,Suceava county (Romania. The general distribution of this species in eastern Romania is also discussedin this paper.

  16. New Records of Rosaceae Plants Distributed in Jiangxi Province%江西蔷薇科植物新记录

    Institute of Scientific and Technical Information of China (English)

    季春峰

    2012-01-01

    Five newly recorded Rosaceae plants in Jiangxi Province are reported in this paper, i. e. Spiraea schneideriana Rehd. , Cerasus schneideriana ( Koehne ) Yu et Li, Laurocerasus fordiana (Dunn ) Yu et Lu, Pygeum topengii Merr. , and Maddenia fujianensis Y. T. Chang.%报道5种江西新纪录的蔷薇科植物,即川滇绣线菊Spiraea schneideriana Rehd.、浙闽樱桃Cerasus schneideriana (Koehne) Yu et Li、华南桂樱Laurocerasus fordiana (Dunn) Yu et Lu、臀形果Pygeum topengii Merr.、福建假稠李Maddenia fujianensis Y.T.Chang.

  17. New records of Oleaceae plants distributed in Jiangxi province%江西木犀科植物新记录

    Institute of Scientific and Technical Information of China (English)

    季春峰

    2012-01-01

    Five newly recorded Oleaceae plants in Jiangxi province were reported in the paper, I. E. Osmanthus armatus Diels, Olea dioica Roxb. , Jasminum floridum Bunge. , J. Urophyllum Hemsl. , and J. Seguinii Levl.%报道了江西省木犀科植物分布新记录5种,即红柄木犀(Osmanthus armatus Diels)、异株木犀榄(Olea dioica Roxb.)、探春花(Jasminum floridum Bunge.)、川素馨(J.urophyllum Hemsl.)、亮叶素馨(J.seguinii Levl.).

  18. An updated and annotated list of Indian lizards (Reptilia: Sauria based on a review of distribution records and checklists of Indian reptiles

    Directory of Open Access Journals (Sweden)

    P.D. Venugopal

    2010-03-01

    Full Text Available Over the past two decades many checklists of reptiles of India and adjacent countries have been published. These publications have furthered the growth of knowledge on systematics, distribution and biogeography of Indian reptiles, and the field of herpetology in India in general. However, the reporting format of most such checklists of Indian reptiles does not provide a basis for direct verification of the information presented. As a result, mistakes in the inclusion and omission of species have been perpetuated and the exact number of reptile species reported from India still remains unclear. A verification of the current listings based on distributional records and review of published checklists revealed that 199 species of lizards (Reptilia: Sauria are currently validly reported on the basis of distributional records within the boundaries of India. Seventeen other lizard species have erroneously been included in earlier checklists of Indian reptiles. Omissions of species by these checklists have been even more numerous than erroneous inclusions. In this paper, I present a plea to report species lists as annotated checklists which corroborate the inclusion and omission of species by providing valid source references or notes.

  19. Taxonomic key for the genera of Elmidae (Coleoptera, Byrrhoidea occurring in Goiás State, Brazil, including new records and distributional notes

    Directory of Open Access Journals (Sweden)

    Felipe F. Barbosa

    2013-06-01

    Full Text Available A taxonomic key for the genera of Elmidae (Coleoptera, Byrrhoidea occurring in Goiás State, Brazil, including new records and distributional notes. Despite their great diversity and high abundance in Neotropical aquatic environments, the fauna of Elmidae remains practically unknown in some areas and even entire biomes in this region. In this work we bring, for the first time, faunistic data for the Elmidae of central Brazil. The aim of this work was to inventory the Elmidae fauna in central, southwestern and southeastern Goiás State, Brazil and to produce a taxonomic key, at genus level, for adults from the studied region. The taxonomic key presented herein offers means for the identification of all the 13 genera known to occur in Goiás, 11 of them being new records for the State. Moreover, the number of named species registered for Goiás increased from one to nine.

  20. 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.

  1. 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.

  2. Avalanche risk assessment for mountain roads - a comparison of case studies from Iceland and the Alps

    Science.gov (United States)

    Wastl, M.; Stötter, J.

    2009-04-01

    While the management of alpine natural hazards in settlements follows highly developed operational standardised procedures in many countries, there are very few approaches for a systematic survey and assessment of these natural hazard processes and the related risks and for a sustainable planning of measures for roads. This is even more surprising against the background of the ongoing increase of traffic in Europe and its economic importance. This contribution compares the results of a regional scale assessment of the avalanche risk on mountain roads for case studies from Austria, Italy and Iceland. It provides the first assessment of the natural hazard situation for roads outside closed settlements in Iceland and discusses the applicability of regional scale risk based approaches developed in the Alps to the specific natural, economic and social situation. It also compares the role of risk in the assessment and management of natural hazards in these countries. The assessment of the risk by natural hazard processes for roads follows approaches developed by Wilhelm (1997, 1998, 1999) and Borter (1999a, 1999b) in the Alps adapted to comply with the data availability of the regional scale. These approaches distinguish between the individual risk on the one hand and the collective risk for the society on the other hand for each process area as well as the cumulative risk for the investigated road section. As the spatial and temporal distribution of avalanches is relatively well documented in some of the Alpine countries practical approaches have been developed for the assessment of this natural hazard process. These have been successfully applied e.g. to roads in inner Oetz and inner Stubai Valley, Tyrol, Austria by Huttenlau (2004) and Gufler (2007) and Sulden road, Ortles Alps, Southern Tyrol, Italy by Zischg et al. (2004). On the basis of these investigations the individual, collective and cumulative death risk for avalanches was determined for Siglufjar

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. Data processing of high-rate low-voltage distribution grid recordings for smart grid monitoring and analysis

    Science.gov (United States)

    Maaß, Heiko; Cakmak, Hüseyin Kemal; Bach, Felix; Mikut, Ralf; Harrabi, Aymen; Süß, Wolfgang; Jakob, Wilfried; Stucky, Karl-Uwe; Kühnapfel, Uwe G.; Hagenmeyer, Veit

    2015-12-01

    Power networks will change from a rigid hierarchic architecture to dynamic interconnected smart grids. In traditional power grids, the frequency is the controlled quantity to maintain supply and load power balance. Thereby, high rotating mass inertia ensures for stability. In the future, system stability will have to rely more on real-time measurements and sophisticated control, especially when integrating fluctuating renewable power sources or high-load consumers like electrical vehicles to the low-voltage distribution grid.

  9. An integration of historical records and genetic data to the assessment of global distribution and population structure in Octopus vulgaris

    Directory of Open Access Journals (Sweden)

    Daniele eDe Luca

    2014-09-01

    Full Text Available The common octopus (Octopus vulgaris Cuvier, 1797 is one of the most widely distributed species belonging to the genus Octopus as well as an important commercially harvested species and a model organism for behavioral biology of invertebrates. It has been described for the first time in the Mediterranean Sea but it is considered a cosmopolitan species inhabiting the temperate and tropical sea of the northern and southern hemispheres. In the last few years, several species previously considered as O. vulgaris have been recognized as new species, limiting the distributional range of vulgaris and reinforcing the thesis of a species complex. Where it is an important fishery resource, numerous studies have been conducted in order to define its genetic structure with the purpose of managing different stocks. However, many locations are still poorly investigated from this point of view and others are under taxonomic revision to exclude or confirm its occurrence. Here we provide a summary of the current status of knowledge on distribution and genetic structure in this species in the different oceanic regions.

  10. 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.

  11. 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...

  12. 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...

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Non-Geiger-Mode Single-Photon Avalanche Detector with Low Excess Noise

    Science.gov (United States)

    Zhao, Kai; Lo, YuHwa; Farr, William

    2010-01-01

    This design constitutes a self-resetting (gain quenching), room-temperature operational semiconductor single-photon-sensitive detector that is sensitive to telecommunications optical wavelengths and is scalable to large areas (millimeter diameter) with high bandwidth and efficiencies. The device can detect single photons at a 1,550-nm wavelength at a gain of 1 x 10(exp 6). Unlike conventional single photon avalanche detectors (SPADs), where gain is an extremely sensitive function to the bias voltage, the multiplication gain of this device is stable at 1 x 10(exp 6) over a wide range of bias from 30.2 to 30.9 V. Here, the multiplication gain is defined as the total number of charge carriers contained in one output pulse that is triggered by the absorption of a single photon. The statistics of magnitude of output signals also shows that the device has a very narrow pulse height distribution, which demonstrates a greatly suppressed gain fluctuation. From the histograms of both pulse height and pulse charge, the equivalent gain variance (excess noise) is between 1.001 and 1.007 at a gain of 1 x 10(exp 6). With these advantages, the device holds promise to function as a PMT-like photon counter at a 1,550- nm wavelength. The epitaxial layer structure of the device allows photons to be absorbed in the InGaAs layer, generating electron/hole (e-h) pairs. Driven by an electrical field in InGaAs, electrons are collected at the anode while holes reach the multiplication region (InAlAs p-i-n structure) and trigger the avalanche process. As a result, a large number of e-h pairs are created, and the holes move toward the cathode. Holes created by the avalanche process gain large kinetic energy through the electric field, and are considered hot. These hot holes are cooled as they travel across a p -InAlAs low field region, and are eventually blocked by energy barriers formed by the InGaAsP/ InAlAs heterojunctions. The composition of the InGaAsP alloy was chosen to have an 80 me

  19. 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 ...

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Analysis and modeling of optical crosstalk in InP-based Geiger-mode avalanche photodiode FPAs

    Science.gov (United States)

    Chau, Quan; Jiang, Xudong; Itzler, Mark A.; Entwistle, Mark; Piccione, Brian; Owens, Mark; Slomkowski, Krystyna

    2015-05-01

    Optical crosstalk is a major factor limiting the performance of Geiger-mode avalanche photodiode (GmAPD) focal plane arrays (FPAs). This is especially true for arrays with increased pixel density and broader spectral operation. We have performed extensive experimental and theoretical investigations on the crosstalk effects in InP-based GmAPD FPAs for both 1.06-μm and 1.55-μm applications. Mechanisms responsible for intrinsic dark counts are Poisson processes, and their inter-arrival time distribution is an exponential function. In FPAs, intrinsic dark counts and cross talk events coexist, and the inter-arrival time distribution deviates from purely exponential behavior. From both experimental data and computer simulations, we show the dependence of this deviation on the crosstalk probability. The spatial characteristics of crosstalk are also demonstrated. From the temporal and spatial distribution of crosstalk, an efficient algorithm to identify and quantify crosstalk is introduced.

  7. Extracting magnetic cluster size and its distributions in advanced perpendicular recording media with shrinking grain size using small angle x-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Mehta, Virat; Ikeda, Yoshihiro; Takano, Ken; Terris, Bruce D.; Hellwig, Olav [San Jose Research Center, HGST a Western Digital company, 3403 Yerba Buena Rd., San Jose, California 95135 (United States); Wang, Tianhan [Department of Materials Science and Engineering, Stanford University, Stanford, California 94035 (United States); Stanford Institute for Materials and Energy Science (SIMES), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Wu, Benny; Graves, Catherine [Stanford Institute for Materials and Energy Science (SIMES), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Department of Applied Physics, Stanford University, Stanford, California 94035 (United States); Dürr, Hermann A.; Scherz, Andreas; Stöhr, Jo [Stanford Institute for Materials and Energy Science (SIMES), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States)

    2015-05-18

    We analyze the magnetic cluster size (MCS) and magnetic cluster size distribution (MCSD) in a variety of perpendicular magnetic recording (PMR) media designs using resonant small angle x-ray scattering at the Co L{sub 3} absorption edge. The different PMR media flavors considered here vary in grain size between 7.5 and 9.5 nm as well as in lateral inter-granular exchange strength, which is controlled via the segregant amount. While for high inter-granular exchange, the MCS increases rapidly for grain sizes below 8.5 nm, we show that for increased amount of segregant with less exchange the MCS remains relatively small, even for grain sizes of 7.5 and 8 nm. However, the MCSD still increases sharply when shrinking grains from 8 to 7.5 nm. We show evidence that recording performance such as signal-to-noise-ratio on the spin stand correlates well with the product of magnetic cluster size and magnetic cluster size distribution.

  8. Nuevos registros y distribución de mosquitos de la Argentina (Diptera: Culicidae New records and distribution of mosquitoes from Argentina (Diptera: Culicidae

    Directory of Open Access Journals (Sweden)

    Gustavo C. Rossi

    2006-12-01

    Full Text Available Se presentan 21 nuevos registros de especies y se amplía la distribución de otras 12 especies de los géneros Anopheles Meigen, Coquillettidia Dyar, Culex L., Haemagogus Williston, Ochlerotatus Lynch Arribalzaga, Onirion Harbach y Peyton, Orthopodomyia Theobald, Psorophora Robineau-Desvoidy, Sabethes Robineau-Desvoidy, Stegomyia Theobald, Toxorhynchites Theobald. Se incluyen comentarios y cambios de estatus para especies de Howardina Theobald, Ochlerotatus y Lutzia (Theobald. Actualmente, en la Argentina se hallan presentes 226 especies distribuidas en 23 géneros.Twenty one new records and 12 new distributional records of species of the genus Anopheles Meigen, Coquillettidia Dyar, Culex L., Haemagogus Williston, Ochlerotatus Lynch Arribalzaga, Onirion Harbach & Peyton, Orthopodomyia Theobald, Psorophora Robineau-Desvoidy, Sabethes Robineau-Desvoidy, Stegomyia Theobald, Toxorhynchites Theobald are reported. Comments and changes in the status of species of Howardina Theobald, Ochelrotatus and Lutzia Theobald are included. Currently, in Argentina are present 226 species distributed in 23 genera.

  9. Distribution of tetraether lipids in the 25-ka sedimentary record of Lake Challa: extracting reliable TEX86 and MBT/CBT palaeotemperatures from an equatorial African lake

    Science.gov (United States)

    Sinninghe Damsté, Jaap S.; Ossebaar, Jort; Schouten, Stefan; Verschuren, Dirk

    2012-09-01

    The distribution of isoprenoid and branched glycerol dialkyl glycerol tetraether (GDGT) lipids was studied in the sedimentary record of Lake Challa, a permanently stratified, partly anoxic crater lake on the southeastern slope of Mt. Kilimanjaro (Kenya/Tanzania), to examine if the GDGTs could be used to reconstruct past variation in regional temperature. The study material comprised 230 samples from a continuous sediment sequence spanning the last 25 ka with excellent age control based on high-resolution AMS 14C dating. The distribution of GDGTs showed large variation through time. In some time intervals (i.e., from 20.4 to 15.9 ka BP and during the Younger Dryas, 12.9-11.7 ka BP) crenarchaeol was the most abundant GDGT, whereas at other times (i.e., during the Early Holocene) branched GDGTs and GDGT-0 were the major GDGT constituents. In some intervals of the sequence the relative abundance of GDGT-0 and GDGT-2 was too high to be derived exclusively from lacustrine Thaumarchaeota, suggesting a sizable contribution from methanogens and other archaea. This severely complicated application of TEX86 palaeothermometry in this lake, and limited reliable reconstruction of lake water temperature to the time interval 25-13 ka BP, i.e. the Last Glacial Maximum and the period of post-glacial warming. The TEX86-inferred timing of this warming is similar to that recorded previously in two of the large African rift lakes, while its magnitude is slightly or much higher than that recorded at these other sites, depending on which lake-based TEX86 calibration is used. Application of calibration models based on distributions of branched GDGTs developed for lakes inferred temperatures of 15-18 °C for the Last Glacial Maximum and 19-22 °C for the Holocene. However, the MBT/CBT palaeothermometer reconstructs temperatures as low as 12 °C for a Lateglacial period centred on 15 ka BP. Variation in down-core values of the BIT index are mainly determined by the varying production rate of

  10. Development of the Damage Potential resulting from Avalanche Risks, Case Study Galtür (Tyrol, Austria)

    Science.gov (United States)

    Keiler, M.

    2003-04-01

    Reports on catastrophes with high damage caused by natural hazards seem to have increased in number recently. A new trend in dealing with these natural processes leads to the integration of risk into natural hazards evaluations and approaches of integral risk management. The risk resulting from natural hazards can be derived from the combination of parameters of physical processes (intensity and recurrence probability) and damage potential (probability of presence and expected damage value). Natural hazard research focuses mainly on the examination, modelling and estimation of individual geomorphological processes as well as on future developments caused by climate change. Even though damage potential has been taken into account more frequently, quantifying statements are still missing. Due to the changes of the socio-economic structures in mountain regions (urban sprawl, population growth, increased mobility and tourism) these studies are mandatory. This study presents a conceptual method that records the damage potential (probability of physical presence, evaluation of buildings) and shows the development of the damage potential resulting from avalanches since 1950. The study area is the community of Galtür, Austria. 36 percent of the existing buildings are found in officially declared avalanche hazard zones. The majority of these buildings are either agricultural or accommodation facilities. Additionally, the effects of physical planning and/or technical measures on the spatial development of the potential damage are illustrated. The results serve to improve risk determination and point out an unnoticed increase of damage potential and risk in apparently safe settlement areas.

  11. An impaired metabolic response to hydrostatic pressure explains Alcanivorax borkumensis recorded distribution in the deep marine water column

    KAUST Repository

    Scoma, Alberto

    2016-08-12

    Alcanivorax borkumensis is an ubiquitous model organism for hydrocarbonoclastic bacteria, which dominates polluted surface waters. Its negligible presence in oil-contaminated deep waters (as observed during the Deepwater Horizon accident) raises the hypothesis that it may lack adaptive mechanisms to hydrostatic pressure (HP). The type strain SK2 was tested under 0.1, 5 and 10 MPa (corresponding to surface water, 500 and 1000 m depth, respectively). While 5 MPa essentially inactivated SK2, further increase to 10 MPa triggered some resistance mechanism, as indicated by higher total and intact cell numbers. Under 10 MPa, SK2 upregulated the synthetic pathway of the osmolyte ectoine, whose concentration increased from 0.45 to 4.71 fmoles cell-1. Central biosynthetic pathways such as cell replication, glyoxylate and Krebs cycles, amino acids metabolism and fatty acids biosynthesis, but not β-oxidation, were upregulated or unaffected at 10 MPa, although total cell number was remarkably lower with respect to 0.1 MPa. Concomitantly, expression of more than 50% of SK2 genes was downregulated, including genes related to ATP generation, respiration and protein translation. Thus, A. borkumensis lacks proper adaptation to HP but activates resistance mechanisms. These consist in poorly efficient biosynthetic rather than energy-yielding degradation-related pathways, and suggest that HP does represent a major driver for its distribution at deep-sea.

  12. An impaired metabolic response to hydrostatic pressure explains Alcanivorax borkumensis recorded distribution in the deep marine water column

    Science.gov (United States)

    Scoma, Alberto; Barbato, Marta; Borin, Sara; Daffonchio, Daniele; Boon, Nico

    2016-08-01

    Alcanivorax borkumensis is an ubiquitous model organism for hydrocarbonoclastic bacteria, which dominates polluted surface waters. Its negligible presence in oil-contaminated deep waters (as observed during the Deepwater Horizon accident) raises the hypothesis that it may lack adaptive mechanisms to hydrostatic pressure (HP). The type strain SK2 was tested under 0.1, 5 and 10 MPa (corresponding to surface water, 500 and 1000 m depth, respectively). While 5 MPa essentially inactivated SK2, further increase to 10 MPa triggered some resistance mechanism, as indicated by higher total and intact cell numbers. Under 10 MPa, SK2 upregulated the synthetic pathway of the osmolyte ectoine, whose concentration increased from 0.45 to 4.71 fmoles cell‑1. Central biosynthetic pathways such as cell replication, glyoxylate and Krebs cycles, amino acids metabolism and fatty acids biosynthesis, but not β-oxidation, were upregulated or unaffected at 10 MPa, although total cell number was remarkably lower with respect to 0.1 MPa. Concomitantly, expression of more than 50% of SK2 genes was downregulated, including genes related to ATP generation, respiration and protein translation. Thus, A. borkumensis lacks proper adaptation to HP but activates resistance mechanisms. These consist in poorly efficient biosynthetic rather than energy-yielding degradation-related pathways, and suggest that HP does represent a major driver for its distribution at deep-sea.

  13. Pyrite framboid size distribution as a record for relative variations in sedimentation rate: An example on the Toarcian Oceanic Anoxic Event in Southiberian Palaeomargin

    Science.gov (United States)

    Gallego-Torres, David; Reolid, Matías; Nieto-Moreno, Vanesa; Martínez-Casado, Francisco Javier

    2015-12-01

    The Early Toarcian Oceanic Anoxic Event (T-OAE) represents one of the major alterations of the carbon cycle of the Mesozoic period. Despite being globally recognized, and particularly represented within the Tethys realm, its expression in the sedimentary record is highly variable depending on the studied section, which suggests local environmental factors exert a major control on the resulting lithological appearance of the event. We investigated the Fuente Vidriera section, in the eastern External Subbetic of the Betic Cordillera (Spain), where the Lower Jurassic is represented by alternate layers of marls and marly limestones, and the T-OAE is identified by a major δ13C excursion, micropalaeontological, ichnofacies and geochemical evidences. For this study, we analyzed pyrite framboid size distribution of the sedimentary sequence in Fuente Vidriera. The outcome, according to previous studies on pyrite framboid distribution, is contradictory when compared to all other evidences, suggesting oxygen depletion during the T-OAE. The results have been reinterpreted in the light of Crystal Size Distribution Theory and we conclude that not only growth time but also geochemical environment controls pyrite formation. Since growth time is directly related to burial rates, this approach allows us to reconstruct relative variations of sedimentation rates during the Early Jurassic in this location. Based on the obtained results, we provide new evidences for wide-spread transgression during the Early Toarcian in the South Iberian palaeomargin, which induced low sedimentation rate and lower energetic conditions, as well as favored oxygen impoverished bottom waters.

  14. 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.

  15. 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.

  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. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. Geomorphological analysis, monitoring and modeling of large rock avalanches in northern Chile (Iquique area) for regional hazard assessment.

    Science.gov (United States)

    Yugsi Molina, F. X.; Hermanns, R. L.; Crosta, G. B.; Dehls, J.; Sosio, R.; Sepúlveda, S. A.

    2012-04-01

    mapped characterized by well defined lateral levees and clear internal morphological features (ridges and furrows, hummocks). Rock avalanche run out simulations have been carried out to back analyze the sites using DAN 3D and a 3 m pixel resolution digital elevation model (DEM) obtained from stereoscopic Geoeye-1 images to assess parameters that controlled propagation mechanism and impact area extent of the events. The older lobes were dated by radiocarbon methods. Results indicate ages higher than 40,000 yr BP for the northern site. The second site could only be dated relatively with an underlying terrace that resulted older than the age limit of radiocarbon dating (43.500 yr BP). All the deposits are positioned well above (40-70 m) the present sea level rise, and at the reported uplift rates for the area, they could be associated to events older than some hundreds of thousand years. A more complete record of the failure history of the sites will be obtained when results of cosmogenic nuclides (CN) and luminescence dating will become available later this year. Several other smaller rock avalanches have been mapped in the study area. Satellite-based radar interferometry (InSAR) was performed using ERS-1 and ERS-2 scenes from 1995-2000 as well as ENVISAT ASAR scenes from 2004-2010. Both datasets show only small deformation in the area. This deformation includes sliding of small surficial slope deposits and subsidence apparently due to local groundwater withdrawal. No deformation of bedrock along the escarpment edge is observed. Results show that only major rock avalanches could reach the main access roads to Iquique and currently no large slope segments show signs of large displacement rates. Moreover, there is no strong correlation between M > 8 earthquakes return periods and age of the dated deposits, which implies that large rock avalanches could have been triggered by other factors. Hence, from a hazard and risk perspective, it is unlikely that large rock avalanches

  3. 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.

  4. 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.

  5. 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

  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. 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.

  8. 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.

  9. 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.

  10. 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.

  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. 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

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. Low noise InGaAs/InP single-photon negative feedback avalanche diodes: characterization and applications

    Science.gov (United States)

    Boso, Gianluca; Korzh, Boris; Lunghi, Tommaso; Zbinden, Hugo

    2015-05-01

    In recent years, many applications have been proposed that require detection of light signals in the near-infrared range with single-photon sensitivity and time resolution down to few hundreds of picoseconds. InGaAs/InP singlephoton avalanche diodes (SPADs) are a viable choice for these tasks thanks to their compactness and ease-of-use. Unfortunately, their performance is traditionally limited by high dark count rates (DCRs) and afterpulsing effects. However, a recent demonstration of negative feedback avalanche diodes (NFADs), operating in the free-running regime, achieved a DCR down to 1 cps at 10 % photon detection efficiency (PDE) at telecom wavelengths. Here we present our recent results on the characterization of NFAD detectors for temperatures down to approximately 150 K. A FPGA controlled test-bench facilitates the acquisition of all the parameters of interest like PDE, DCR, afterpulsing probability etc. We also demonstrate the performance of the detector in different applications: In particular, with low-temperature NFADs, we achieved high secret key rates with quantum key distribution over fiber links between 100-300 km. But low noise InGaAs/InP SPADs will certainly find applications in yet unexplored fields like photodynamic therapy, near infrared diffuse optical spectroscopy and many more. For example with a large area detector, we made time-resolved measurements of singlet-oxygen luminescence from a standard Rose Bengal dye in aqueous solution.

  19. High-performance timing electronics for single photon avalanche diode arrays

    Science.gov (United States)

    Acconcia, G.; Crotti, M.; Rech, I.; Ghioni, M.

    2015-05-01

    Time correlated photon counting techniques have been proved to be very effective, especially when very fast and faint optical signals have to be recorded with extremely high precision. Nowadays, a steadily increasing number of applications require not only high performance in terms of photon detection efficiency, time resolution and linearity but also a high number of pixels operating in parallel. In order to combine the features of the most performing detectors and state of art timing electronics, an innovative architecture has been conceived and the main circuits have been designed. The system will employ dense arrays of custom technology Single Photon Avalanche Diode (SPAD) detectors, in order to perform a truly concurrent analysis of the sample, while it will have only a small number of acquisition chains with the ultimate purpose of obtaining very high performance while limiting area occupation and power dissipation. To this aim, three main circuits have been designed: first of all, a pick-up circuit capable of directly reading the signal coming from the sensor; secondly, a timing circuit to measure the arrival time of the each photon with picoseconds resolution and very high linearity and finally, a circuit to perform a dynamic binding between the many sensors and the few conversion chains.

  20. Avalanches of coalescence events and local extensional flows--stabilisation or destabilisation due to surfactant.

    Science.gov (United States)

    Gunes, Deniz Z; Clain, Xavier; Breton, Olivier; Mayor, Guy; Burbidge, Adam S

    2010-03-01

    From two-drop collision experiments, it is known that local extensional flow favors coalescence. Recently, Bremond et al. used microfluidic methods to evidence this point. Similarly, we used specific microfluidic geometries to impose sudden extensional flow, following drop collision under controlled conditions, and coalescence events were recorded with a high-speed camera. In this study we focus on the effect of surfactant on the coalescence, or stabilisation against it, between drops flowing apart due to either imposed external flow or capillary forces related to drop shape relaxation. Coalescence can be induced even when drops are initially separated by an intersticial lubricating film by far thicker than the critical thickness for rupturing under the action of Van der Waals forces. This is particularly relevant to avalanches of coalescence events, in flowing or even quiescent emulsions or foams. When non-ionic surfactant was used, it was observed that small concentrations apparently enhance coalescence in extension. But at higher concentrations it provides stabilisation through a specific mechanism of thread formation and rupture; the stabilisation mechanism can be complex.

  1. Short-Range Temporal Interactions in Sleep; Hippocampal Spike Avalanches Support a Large Milieu of Sequential Activity Including Replay.

    Directory of Open Access Journals (Sweden)

    J Matthew Mahoney

    Full Text Available Hippocampal neural systems consolidate multiple complex behaviors into memory. However, the temporal structure of neural firing supporting complex memory consolidation is unknown. Replay of hippocampal place cells during sleep supports the view that a simple repetitive behavior modifies sleep firing dynamics, but does not explain how multiple episodes could be integrated into associative networks for recollection during future cognition. Here we decode sequential firing structure within spike avalanches of all pyramidal cells recorded in sleeping rats after running in a circular track. We find that short sequences that combine into multiple long sequences capture the majority of the sequential structure during sleep, including replay of hippocampal place cells. The ensemble, however, is not optimized for maximally producing the behavior-enriched episode. Thus behavioral programming of sequential correlations occurs at the level of short-range interactions, not whole behavioral sequences and these short sequences are assembled into a large and complex milieu that could support complex memory consolidation.

  2. A nineteenth century avalanche episode reconstruction via historic newspapers: from unstructured information to standardized information

    Science.gov (United States)

    García, Cristina; Ruíz, Jesús; Gallinar, David; Sánchez de Posada, Covadonga

    2014-05-01

    Several climatic risks studies based on the analysis of data recorded in newspapers have been published to date. These studies deal with both general (Moltó, 2000; García y Martí, 2000; Hernández Varela et al., 2003; Olcina, 2005) and specific risks such as landslides (Domínguez et al., 1999; Devoli et al., 2007; Polemio y Petrucci, 2010) seastorms (Yanes y Marzol, 2009) and snowstorms (Olcina y Moltó, 2002) among others. The purpose of this paper is to report on the methodology and results of the study of an extreme historical event happened in the Asturian Massif (Northern Spain) in 1888. Special attention has been paid to methodological aspects and to the difficulties found in the goal of devising a method that would enable the reconstruction of this kind of phenomena on the basis of nivometheorogical conditions, geographical location and socio-economic impact. To a great deal we focused our efforts on designing a logical database structure and a set of tables that would allow us to store and cross the information for statistical analysis. This includes outlier detection in order to ensure the quality of the results. The information sources used in our study have been the issues of the daily newspaper 'El Carbayón' and the weekly newspaper 'El Oriente de Asturias' published in Oviedo and Llanes (Asturias) between the 20th of January and 30th of May 1888. A total of 92 issues have been collected via the hard copy microfilm housed in the Central Library of Asturias. We reviewed 70 reports relating to avalanche events happened in the aforementioned period of time. We grouped the consequences of the events into 3 main categories (personal injuries, material damages and absence of both) and 5 child categories (deaths, wounded, house and attached building damage, livestock injuries, damage to infrastructures and communications). We gathered data about the thickness of snow-cover, the number of consecutive snowstorms and, in order to facilitate a territorial

  3. Characteristics of the spatiotemporal distribution of daily extreme temperature events in China: Minimum temperature records in different climate states against the background of the most probable temperature

    Institute of Scientific and Technical Information of China (English)

    Qian Zhong-Hua; Hu Jing-Guo; Feng Guo-Lin; Cao Yong-Zhong

    2012-01-01

    Based on the skewed function,the most probable temperature is defined and the spatiotemporal distributions of the frequencies and strengths of extreme temperature events in different climate states over China are investigated,where the climate states are referred to as State Ⅰ,State Ⅱ and State Ⅲ,i.e.,the daily minimum temperature records of 1961-1990,1971-2000,and 1981-2009.The results show that in space the frequency of high temperature events in summer decreases clearly in the lower and middle reaches of the Yellow River in State Ⅰ and that low temperature events decrease in northern China in State Ⅱ.In the present state,the frequency of high temperature events increases significantly in most areas over China except the north east,while the frequency of low temperature events decreases mainly in north China and the regions between the Yangtze River and the Yellow River.The distributions of frequencies and strengths of extreme temperature events are consistent in space.The analysis of time evolution of extreme events shows that the occurrence of high temperature events become higher with the change in state,while that of low temperature events decreases.High temperature events are becoming stronger as well and deserve to be paid special attention.

  4. 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...

  5. 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...

  6. 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.

  7. 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.

  8. 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...

  9. 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.

  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. 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

  12. 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.

  13. 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...

  14. 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.

  15. 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.

  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. Reinforced concrete structures loaded by snow avalanches : numerical and experimental approaches.

    Science.gov (United States)

    Ousset, I.; Bertrand, D.; Brun, M.; Limam, A.; Naaim, M.

    2012-04-01

    Today, due to the extension of occupied areas in mountainous regions, new strategies for risk mitigation have to be developed. In the framework of risk analysis, these latter have to take into account not only the natural hazard description but also the physical vulnerability of the exposed structures. From a civil engineering point of view, the dynamic behavior of column or portico was widely investigated especially in the case of reinforced concrete and steel. However, it is not the case of reinforced concrete walls for which only the in-plan dynamic behavior (shear behavior) has been studied in detail in the field of earthquake engineering. Therefore, the aim of this project is to study the behavior of reinforced concrete civil engineering structures submitted to out-of-plan dynamic loadings coming from snow avalanche interaction. Numerical simulations in 2D or 3D by the finite element method (FEM) are presented. The approach allows solving mechanical problems in dynamic condition involving none linearities (especially none linear materials). Thus, the structure mechanical response can be explored in controlled conditions. First, a reinforced concrete wall with a L-like shape is considered. The structure is supposed to represent a French defense structure dedicated to protect people against snow avalanches. Experimental pushover tests have been performed on a physical model. The experimental tests consisted to apply a uniform distribution of pressure until the total collapse of the wall. A 2D numerical model has been developed to simulate the mechanical response of the structure under quasi-static loading. Numerical simulations have been compared to experimental datas and results gave a better understanding of the failure mode of the wall. Moreover, the influence of several parameters (geometry and the mechanical properties) is also presented. Secondly, punching shear experimental tests have also been carried out. Reinforced concrete slabs simply supported have

  1. Avalanche-like fluidization of a non-Brownian particle gel

    Science.gov (United States)

    Kurokawa, Aika; Vidal, Valérie; Kurita, Kei; Divoux, Thibaut; Manneville, Sébastien

    We report on the fluidization dynamics of an attractive gel composed of non-Brownian particles made of fused silica colloids. Extensive rheology coupled to ultrasonic velocimetry allows us to characterize the global stress response together with the local dynamics of the gel during shear startup experiments. In practice, after being rejuvenated by a preshear, the gel is left to age during a time tw before being submitted to a constant shear rate γ˙. We investigate in detail the effects of both tw and γ˙ on the fluidization dynamics and build a detailed state diagram of the gel response to shear startup flows. The gel may either display transient shear banding towards complete fluidization, or steady-state shear banding. In the former case, we unravel that the progressive fluidization occurs by successive steps that appear as peaks on the global stress relaxation signal. Flow imaging reveals that the shear band grows up to complete fluidization of the material by sudden avalanche-like events which are distributed heterogeneously along the vorticity direction and correlated to large peaks in the slip velocity at the moving wall. PRC CNRS/JSPS RheoVolc, IUF & ERC Grant Agreement No. 258803.

  2. 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

  3. 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...

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

    Science.gov (United States)

    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.

  5. Interaction of Avalanche Photodiodes (APDs Devices With Thermal Irradiation Environments

    Directory of Open Access Journals (Sweden)

    Ahmed Nabih Zaki Rashed

    2012-04-01

    Full Text Available This paper has been examined the high temperature irradiation variations testing in order to be used to determine avalanche photodiode lifetime, even though APD failure mechanisms are more sensitive to increases in current density. As a measured parameter of degradation, the current density is of great significance when searching for failure modes in APD. Raising the current density however, is not really indicative of lifetime since it is more likely a situation to be avoided than one that simulates normal lifetime degradation. The reliability of semiconductor detectors is very dependent on the degradation modes. This paper has investigated deeply some of the degradation performance and capabilities of typical APDs currently used in many communication and sensing systems over wide range of the affecting parameters. APDs are used in systems that require coherent and often single mode light such as high data rate communications and sensing applications. APDs are an attractive receiver choice for photon-starved (low signal applications, because their internal gain mechanism can improve signal to noise ratio. An optical receiver must also be appropriate for the laser wavelength being used. The near infrared is the preferred wavelength regime for deep space optical communications largely due to the wavelengths of available laser technologies that meet the optical power requirements of a deep space optical link

  6. DEM modeling of flexible structures against granular material avalanches

    Science.gov (United States)

    Lambert, Stéphane; Albaba, Adel; Nicot, François; Chareyre, Bruno

    2016-04-01

    This article presents the numerical modeling of flexible structures intended to contain avalanches of granular and coarse material (e.g. rock slide, a debris slide). The numerical model is based on a discrete element method (YADE-Dem). The DEM modeling of both the flowing granular material and the flexible structure are detailed before presenting some results. The flowing material consists of a dry polydisperse granular material accounting for the non-sphericity of real materials. The flexible structure consists in a metallic net hanged on main cables, connected to the ground via anchors, on both sides of the channel, including dissipators. All these components were modeled as flexible beams or wires, with mechanical parameters defined from literature data. The simulation results are presented with the aim of investigating the variability of the structure response depending on different parameters related to the structure (inclination of the fence, with/without brakes, mesh size opening), but also to the channel (inclination). Results are then compared with existing recommendations in similar fields.

  7. Transport, hysteresis and avalanches in artificial spin ice systems

    Energy Technology Data Exchange (ETDEWEB)

    Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, Cynthia J [Los Alamos National Laboratory; Libal, A [BABES-BOLYAI UNIV.

    2010-01-01

    We examine the hopping dynamics of an artificial spin ice system constructed from colloids on a kagome optical trap array where each trap has two possible states. By applying an external drive from an electric field which is analogous to a biasing applied magnetic field for real spin systems, we can create polarized states that obey the spin-ice rules of two spins in and one spin out at each vertex. We demonstrate that when we sweep the external drive and measure the fraction of the system that has been polarized, we can generate a hysteresis loop analogous to the hysteretic magnetization versus external magnetic field curves for real spin systems. The disorder in our system can be readily controlled by changing the barrier that must be overcome before a colloid can hop from one side of a trap to the other. For systems with no disorder, the effective spins all flip simultaneously as the biasing field is changed, while for strong disorder the hysteresis curves show a series of discontinuous jumps or avalanches similar to Barkhausen noise.

  8. New gamma detector modules based on micropixel avalanche photodiode

    Science.gov (United States)

    Ahmadov, F.; Ahmadov, G.; Guliyev, E.; Madatov, R.; Sadigov, A.; Sadygov, Z.; Suleymanov, S.; Akberov, R.; Nuriyev, S.; Zerrouk, F.

    2017-01-01

    In this paper presented the results of the ionizing radiation detector modules, which developed on the basis of a new generation of micropixel avalanche photodiode (MAPD) of MAPD-3NK type. The samples were produced in cooperation with the Zecotek Photonics and characterized by the following parameters: sensitive area—3.7 mm × 3.7 mm, density of pixels—10000 pixels/mm2, photon detection efficiency—35-40% (at wavelength of 450-550 nm) and operation voltage—91 V. The beta particle and gamma ray detection performance of MAPD with different single scintillation crystal such as NaI, LFS and p-terphenyl was investigated. The gamma ray detector modules demonstrated a perfect linear behavior of detected signal amplitudes as a function of the gamma ray energy (from 26.3 keV up to 1.33 MeV). Energy resolution for 662 keV gamma rays was 11.2% and the minimum detectable energy was 26.3 keV.

  9. Global Avalanche Characteristics of Boolean Functions by Concatenation

    Institute of Scientific and Technical Information of China (English)

    Mingsheng Ren

    2016-01-01

    In order to measure the correlation propeties of two Boolean functions, the global avalanche characteristics of Boolean functions constructed by concatenation are discussed, i.e., f1‖f2 and f1‖f2‖f3‖f4. Firstly, for the function f = f1‖f2 , the cross⁃correlation function of f1 , f2 in the special condition are studied. In this case, f, f1 , f2 must be in desired form. By computing their sum⁃of⁃squares indicators, the cross⁃correlation function between f1 , f2 is obtained. Secondly, for the function g = f1‖f2‖f3‖f4 , by analyzing the relation among their auto⁃correlation functions, their sum⁃of⁃squares indicators are investigated. Based on them, the sum⁃of⁃squares indicators of functions obtained by Canteaut et al. are investigated. The results show that the correlation property of g is good when the correlation properties of Boolean functions f1 , f2 , f3 , f4 are good.

  10. Recent advances in very large area avalanche photodiodes

    Science.gov (United States)

    Squillante, Michael R.; Christian, James; Entine, Gerald; Farrell, Richard; Karger, Arieh M.; McClish, Mickel; Myers, Richard; Shah, Kanai S.; Taylor, David; Vanderpuye, Kofi; Waer, Peter; Woodring, Mitchell

    2003-09-01

    The Avalanche Photodiode (APD) is a unique device that combines the advantages of solid state photodetectors with those of high gain devices such as photomultiplier tubes (PMTs). APDs have internal gain that provides a high signal-to-noise ratio. APDs have high quantum efficiency, are fast, compact, and rugged. These properties make them suitable detectors for important applications such as LADAR, detection and identification toxic chemicals and bio-warfare agents, LIDAR fluorescence detection, stand-off laser induced breakdown spectroscopy (LIBS), and nuclear detectors and imagers. Recently there have been significant technical breakthroughs in fabricating very large APDs, APD arrays, and position sensitive APD arrays (PSAPD). Signal gain of over 10,000 has been achieved, single element APDs have been fabricated with active area greater than 40 cm2, monolithic pixelated arrays with up to 28 x 28 elements have been fabricated, and position sensitive APDs have been developed and tested. Additionally, significant progress has been made in improving the fabrication process to provide better uniformity and high yield, permitting cost effective manufacturing of APDs for reduced cost.

  11. Review of the fossil matamata turtles: earliest well-dated record and hypotheses on the origin of their present geographical distribution

    Science.gov (United States)

    Ferreira, Gabriel S.; Rincón, Ascanio D.; Solórzano, Andrés; Langer, Max C.

    2016-04-01

    The matamata ( Chelus fimbriatus) is a highly aquatic chelid turtle known exclusively from northern South America. Due to its extremely modified morphology, it is well circumscribed among living taxa, but that is not the case of the two extinct species ascribed to the taxon, Chelus colombianus and Chelus lewisi. These were originally described for the Miocene of Colombia and Venezuela, respectively, and are known mostly from post-cranial material. Few traits have been considered diagnostic for these fossil taxa, and their shared geographic and temporal distributions raise doubts about their distinctiveness. Here, we describe new turtle remains from the early Miocene Castillo Formation, at Cerro la Cruz, northwestern Venezuela, assigning them to C. colombianus. We also review the taxonomy and diagnostic features of the fossil species of Chelus, comparing them with the variation recognized within C. fimbriatus. All alleged differences between the fossil Chelus species were found in our sample of the extant species, and may represent intraspecific variation of a single fossil species. Further, we reviewed the fossil record of Chelus spp. and proposed a paleobiogeographic hypothesis to explain its present geographic range.

  12. Cantharellaceae of Guyana II: new species of Craterellus, new South American distribution records for Cantharellus guyanensis and Craterellus excelsus, and a key to the Neotropical taxa.

    Science.gov (United States)

    Henkel, Terry W; Wilson, Andrew W; Aime, M Catherine; Dierks, Janina; Uehling, Jessie K; Roy, Melanie; Schimann, Heidy; Wartchow, Felipe; Mueller, Gregory M

    2014-01-01

    Craterellus olivaceoluteus sp. nov. and Craterellus cinereofimbriatus sp. nov. are described as new to science. These fungi were collected from Guyana in association with ectomycorrhizal host trees in the genera Dicymbe (Fabaceae subfam. Caesalpinioideae) and Pakaraimaea (Dipterocarpaceae). Cantharellus guyanensis Mont., originally described from French Guiana, is redescribed from recent collections from Guyana, with additional range extensions for the species provided based on material examined from French Guiana, Venezuela, and north central, northeastern and southern Brazil, circumscribing nearly the entire Guiana Shield region and beyond. A new distribution record from French Guiana is provided for Craterellus excelsus T.W. Henkel & Aime. Macromorphological, micromorphological and habitat data are provided for the new species and C. guyanensis as well as DNA sequence data from the nuclear ribosomal regions of the internal transcribed spacer (ITS) and 28S large subunit (LSU); additional sequence data is provided for C. guyanensis and C. excelsus specimens collected outside Guyana. The relationships of these taxa within the Cantharellaceae were evaluated with phylogenetic analyses of ITS and LSU sequence data. This work brings the total number of Cantharellaceae species known from Guyana to eight. A key to the Cantharellus and Craterellus species known from the lowland Neotropics and extralimital montane Central and South America is provided.

  13. A report on Lecanidae (Rotifera: Monogononta from Andhra Pradesh, India, including six new distribution records with notes on their contemporary taxonomic nomenclature

    Directory of Open Access Journals (Sweden)

    S.Z. Siddiqi

    2013-07-01

    Full Text Available The Lecane-species complex taxonomy the world over, witnessed a state of flux, causing confusion and controversies, among world taxonomists over the treatment of various subgenera, taxa and sub and or infraspecific categories of the species rich genus Lecane Nitzsch 1827, on the basis of structure/shape of key, morphological features like foot/toes, lorica, etc. The taxonomic scenario in India, relying heavily on the classical, divergent taxonomic approaches presented a picture of more chaos/confusion, following poor accessibility to contemporary revisionary studies until the recent past. Despite revisionary studies across the world, a few notable Indian studies continued to be burdened with old nomenclature. This short communication reports for the first time ever, 33 valid species of lecanid rotifers (Lecanidae, including six new distributional records from Greater Hyderabad region and the entire state of Andhra Pradesh too with comments on their current nomenclature. Further, limnobiological correlation between five physicochemical parameters and rotifer associations revealed, L. bulla, L. closterocerca, L. hamata, L. ludwigi, L. luna and L. papuana as euryokous species, showing tolerance to a wide range of abiotic factors and habitats too.

  14. Video Plankton Recorder estimates of copepod, pteropod and larvacean distributions from a stratified region of Georges Bank with comparative measurements from a MOCNESS sampler

    Science.gov (United States)

    Benfield, Mark C.; Davis, Cabell S.; Wiebe, Peter H.; Gallager, Scott M.; Gregory Lough, R.; Copley, Nancy J.

    A two-vessel exercise was conducted over the southern flank of Georges Bank during the onset of vernal stratification in May 1992. The Video Plankton Recorder (VPR), a towed video system, was used to map out the fine-scale distributions of zooplankton to a depth of 70 m along a trackline which described a regular grid (3.5 × 4.5 km) in Lagrangian space. A second vessel following a parallel course conducted Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) sampling during the last section of the grid, which provided an opportunity to compare data from the two systems. Both the VPR and the MOCNESS provided similar data on the taxonomic composition of the plankton which was numerically dominated by copepods ( Calanus, Pseudocalanus, Oithona), pteropods ( Limacina) and larvaceans ( Oikopleura). The absence of rare (gelatinous taxa were undersampled by the MOCNESS. Estimates of copepod and pteropod concentrations were comparable for the two gear types. While the species composition of the plankton did not change statistically along the grid, abundances of the dominant taxa varied along the transect and each taxon demonstrated pronounced fine-scale vertical patterns that appeared to be related to hydrographic features. The VPR represents a powerful tool for rapid surveys of the micro- to fine-scale structure of zooplankton assemblages either alone, or in conjunction with other sampling techniques.

  15. Discrimination of hot versus cold avalanche deposits: Implications for hazard assessment at Mount Meager, B.C.

    Science.gov (United States)

    Stewart, M. L.; Russell, J. K.; Hickson, C. J.

    The surficial deposits surrounding the Mount Meager volcanic complex include numerous avalanche deposits. These deposits share many attributes: (a) they are nearly monolithologic and comprise mainly intermediate volcanic rock clasts, (b) they lack internal structure, and (c) they are very poorly sorted. Despite these similarities, the avalanche deposits represent two distinct processes. Mass wasting of the Mount Meager volcanic edifice has produced cold rock avalanche deposits, whereas gravitational collapse of active lava domes and flows has produced hot block and ash avalanche deposits. The ability to discriminate between these "hot" and "cold" avalanche deposits is a critical component in the assessment of hazards in volcanic terranes. Hot block and ash avalanche deposits can be distinguished by the presence of radially-oriented joints, breadcrust textures, and incipient welding, which are features indicative of high emplacement temperatures. Conversely, rock avalanche deposits resulting from mass wasting events may be distinguished by the presence of clasts that preserve pre-depositional weathering and jointing surfaces. Volcanic avalanches are mechanically similar to rock avalanches but pose a greater hazard due to high temperatures, increased fluidization from degassing and the potential to decouple highly mobile elutriated ash clouds. The increasing use of hazardous regions such as the Lillooet River valley requires more reliable risk assessment in order to minimize losses from future hazardous events.

  16. Discrimination of hot versus cold avalanche deposits: Implications for hazard assessment at Mount Meager, B.C.

    Directory of Open Access Journals (Sweden)

    M. L. Stewart

    2003-01-01

    Full Text Available The surficial deposits surrounding the Mount Meager volcanic complex include numerous avalanche deposits. These deposits share many attributes: (a they are nearly monolithologic and comprise mainly intermediate volcanic rock clasts, (b they lack internal structure, and (c they are very poorly sorted. Despite these similarities, the avalanche deposits represent two distinct processes. Mass wasting of the Mount Meager volcanic edifice has produced cold rock avalanche deposits, whereas gravitational collapse of active lava domes and flows has produced hot block and ash avalanche deposits. The ability to discriminate between these "hot" and "cold" avalanche deposits is a critical component in the assessment of hazards in volcanic terranes. Hot block and ash avalanche deposits can be distinguished by the presence of radially-oriented joints, breadcrust textures, and incipient welding, which are features indicative of high emplacement temperatures. Conversely, rock avalanche deposits resulting from mass wasting events may be distinguished by the presence of clasts that preserve pre-depositional weathering and jointing surfaces. Volcanic avalanches are mechanically similar to rock avalanches but pose a greater hazard due to high temperatures, increased fluidization from degassing and the potential to decouple highly mobile elutriated ash clouds. The increasing use of hazardous regions such as the Lillooet River valley requires more reliable risk assessment in order to minimize losses from future hazardous events.

  17. Rock-avalanche geomorphological and hydrological impact on an alpine watershed

    Science.gov (United States)

    Frattini, P.; Riva, F.; Crosta, G. B.; Scotti, R.; Greggio, L.; Brardinoni, F.; Fusi, N.

    2016-06-01

    Rock avalanches are large flow-like movements of fragmented rock that can cause extensive and rapid topographic changes, for which very few quantitative data are available. This paper analyses the geomorphological and hydrological impact of the 3 million m3 Thurwieser rock avalanche (2004, Italian Central Alps) by using Terrestrial Laser Scanner, airborne Lidar and GNSS data collected from 2005 to 2014. Sediment yield with respect to the normal valley regime, the dynamic and mass balance of affected glaciers, and the reorganization of superficial and groundwater flow networks are quantified. In the middle portion of the avalanche deposit, a natural sediment trap collected sediments from a new stream channel developed along the upper portion of the deposit and from a lateral drainage basin. This made possible to assess the 10-year impact of the rock avalanche on the sediment yield, which increased from about 120 to about 400 t km- 2·a- 1. The rock avalanche partially covered a glacier with a shallow debris layer that acted as a thermal insulator, limiting ice ablation and producing a 10-m high scarp between the free surface of the glacier and the debris-covered portion. A reduction of 75% of ice ablation was observed due to thermal insulation. The rock avalanche filled a tributary valley, splitting the original drainage basin in two. Under ordinary flows, seepage occurs within the avalanche deposit along the old valley axis. During high flow conditions, a new stream channel is activated along the middle and lower margin of the deposit, which has produced a new alluvial fan on the main valley floor. The fan evolution is described up to the present volume of about 2000 m3.

  18. 1.5 GHz single-photon detection at telecommunication wavelengths using sinusoidally gated InGaAs/InP avalanche photodiode.

    Science.gov (United States)

    Namekata, Naoto; Adachi, Shunsuke; Inoue, Shuichiro

    2009-04-13

    We report a telecom-band single-photon detector for gigahertz clocked quantum key distribution systems. The single-photon detector is based on a sinusoidally gated InGaAs/InP avalanche photodiode. The gate repetition frequency of the single-photon detector reached 1.5 GHz. A quantum efficiency of 10.8 % at 1550 nm was obtained with a dark count probability per gate of 6.3 x 10(-7) and an afterpulsing probability of 2.8 %. Moreover, the maximum detection rate of the detector is 20 MHz.

  19. Optimal design of snow avalanche passive defence structure using reliability approach to quantify buildings vulnerability

    Science.gov (United States)

    Favier, P.; Bertrand, D.; Eckert, N.; Naaim, M.

    2012-04-01

    To protect elements at risk (humans, roads, houses, etc.) against snow avalanches, civil engineering structures, such as dams or mounds, are used. The design of such defence structures is done following a deterministic approach which considers European regulation. The minimization of expected total losses is an interesting alternative that generalizes cost-benefit approach to a continuous decision variable. For this purpose, not only the hazard magnitude but also the buildings vulnerability must be evaluated carefully. The aim of this work is therefore to combine state of the art sub-models for the probabilistic description of avalanche flows and the numerical evaluation of damages to buildings. We defined the risk as the expectation of the cost consequences of avalanches activity. Disposal consequences are quantified thanks to reliability methods. In this formulation, the accuracy of both the hazard estimation and the vulnerability calculation has to be consistent according to precision and computational costs. To do so, a numerical approach has been developed to evaluate the physical vulnerability of concrete buildings submitted to avalanche loadings. The ensuing application illustrates our approach. A reinforced concrete slab is considered to model the building with a finite element method. Reliability approach enables to produce a response spectrum of the structure against avalanche impact. Finally, vulnerability curves are built. Outcomes of the risk calculation are examined to find sensitivity on the optimal design of snow defence structures.

  20. 3-D-numerical approach to simulate an avalanche impact into a reservoir

    Directory of Open Access Journals (Sweden)

    R. Gabl

    2015-06-01

    Full Text Available The impact of an avalanche into a reservoir induces an impulse wave, which poses a threat to population and infrastructure. For a good approximation of the generated wave height and length as well as the resulting outflow volume over structures and dams, formulas, which base on different simplifying assumptions, can be used. Further project-specific investigations by means of a scale model test or numerical simulations are advisable for complex reservoirs as well as the inclusion of hydraulic structures such as spillways. The paper presents a new approach for a 3-D-numerical simulation of an avalanche impact into a reservoir. In this model concept the energy and mass of the avalanche are represented by accelerated water on the real hill slope. Instead of snow, only water and air are used to simulate the moving avalanche with the software FLOW-3D. A significant advantage of this assumption is the self-adaptation of the model avalanche onto the terrain. In order to reach good comparability of the results with existing research at the ETH Zürich, a simplified reservoir geometry is investigated. Thus, a reference case has been analysed including a variation of three geometry parameters (still water depth in the reservoir, freeboard of the dam and reservoir width.

  1. A debris avalanche at Süphan stratovolcano (Turkey) and implications for hazard evaluation

    Science.gov (United States)

    Özdemir, Yavuz; Akkaya, İsmail; Oyan, Vural; Kelfoun, Karim

    2016-02-01

    The Quaternary Süphan debris avalanche deposit is located in Eastern Anatolia, Turkey. The avalanche formed by the sector collapse of a major stratovolcano towards the north, possibly during a single catastrophic event. The deposit has an estimated volume of 4 km3 and ran out over 25 km to cover an area of approximately 200 km2. Products of the collapse are overlain by younger eruptive units from the Süphan volcano. We have tested the numerical code VolcFlow to first reproduce the emplacement of the Quaternary Süphan debris avalanche and then to develop a hazard assessment for potential future sector collapses and subsequent emplacement of debris avalanches and associated tsunami. The numerical model captures the main features of the propagation process, including travel distance, lateral spread, and run up. The best fit obtained for the existing flow has a constant retarding stress of 50 kPa and a collapse scar volume of 4 km3. Analysis of potential future collapse scenarios reveals that northern sector debris avalanches (up to 6 km3) could affect several towns. In the case of a sector collapse towards the south, a tsunami will reach the city of Van and several of the biggest towns on the southern shoreline of Lake Van. Cities most affected by the larger amplitude waves would be Van, Edremit, Gevaş, Tatvan, and, to a lesser extent, Erciş, with wave amplitudes (first waves after the onset of the collapse) between 8 and 10 m.

  2. Non-Markovian property of afterpulsing effect in single-photon avalanche detector

    CERN Document Server

    Wang, Fang-Xiang; Li, Ya-Ping; He, De-Yong; Wang, Chao; Han, Yun-Guang; Wang, Shuang; Yin, Zhen-Qiang; Han, Zheng-Fu

    2016-01-01

    The single-photon avalanche photodiode(SPAD) has been widely used in research on quantum optics. The afterpulsing effect, which is an intrinsic character of SPAD, affects the system performance in most experiments and needs to be carefully handled. For a long time, afterpulsing has been presumed to be determined by the pre-ignition avalanche. We studied the afterpulsing effect of a commercial InGaAs/InP SPAD (The avalanche photodiode model is: Princeton Lightwave PGA-300) and demonstrated that its afterpulsing is non-Markovian, with a memory effect in the avalanching history. Theoretical analysis and experimental results clearly indicate that the embodiment of this memory effect is the afterpulsing probability, which increases as the number of ignition-avalanche pulses increase. This conclusion makes the principle of the afterpulsing effect clearer and is instructive to the manufacturing processes and afterpulsing evaluation of high-count-rate SPADs. It can also be regarded as a fundamental premise to handle ...

  3. Analysis of avalanche risk factors in backcountry terrain based on usage frequency and accident data in Switzerland

    Science.gov (United States)

    Techel, F.; Zweifel, B.; Winkler, K.

    2015-09-01

    Recreational activities in snow-covered mountainous terrain in the backcountry account for the vast majority of avalanche accidents. Studies analyzing avalanche risk mostly rely on accident statistics without considering exposure (or the elements at risk), i.e., how many, when and where people are recreating, as data on recreational activity in the winter mountains are scarce. To fill this gap, we explored volunteered geographic information on two social media mountaineering websites - bergportal.ch and camptocamp.org. Based on these data, we present a spatiotemporal pattern of winter backcountry touring activity in the Swiss Alps and compare this with accident statistics. Geographically, activity was concentrated in Alpine regions relatively close to the main Swiss population centers in the west and north. In contrast, accidents occurred equally often in the less-frequented inner-alpine regions. Weekends, weather and avalanche conditions influenced the number of recreationists, while the odds to be involved in a severe avalanche accident did not depend on weekends or weather conditions. However, the likelihood of being involved in an accident increased with increasing avalanche danger level, but also with a more unfavorable snowpack containing persistent weak layers (also referred to as an old snow problem). In fact, the most critical situation for backcountry recreationists and professionals occurred on days and in regions when both the avalanche danger was critical and when the snowpack contained persistent weak layers. The frequently occurring geographical pattern of a more unfavorable snowpack structure also explains the relatively high proportion of accidents in the less-frequented inner-alpine regions. These results have practical implications: avalanche forecasters should clearly communicate the avalanche danger and the avalanche problem to the backcountry user, particularly if persistent weak layers are of concern. Professionals and recreationists, on the

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

    Science.gov (United States)

    Veitinger, Jochen; Sovilla, Betty

    2016-08-01

    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 significantly differ from its underlying, snow-free terrain. This may lead to different, and/or potentially larger release areas. To investigate this hypothesis, the relation between avalanche release area size, snow depth and surface roughness was investigated using avalanche observations of artificially triggered slab avalanches over a period of 15 years in a high-alpine field site. High-resolution, continuous snow depth measurements at times of avalanche release showed a decrease of mean surface roughness with increasing release area size, both for the bed surface and the snow surface before avalanche release. Further, surface roughness patterns in snow-covered winter terrain appeared to be well suited to demarcate release areas, suggesting an increase of potential release area size with greater snow depth. In this context, snow depth around terrain features that serve as potential delineation borders, such as ridges or trenches, appeared to be particularly relevant for release area size. Furthermore, snow depth measured at a nearby weather station was, to a considerable extent, related to potential release area size, as it was often representative of snow depth around those critical features where snow can accumulate over a long period before becoming susceptible to avalanche release. Snow depth - due to its link to surface roughness - could therefore serve as a highly useful variable with regard to potential release area definition for varying snow cover scenarios, as, for example, the avalanche

  5. Regional evaluation of three day snow depth for avalanche hazard mapping in Switzerland

    Directory of Open Access Journals (Sweden)

    D. Bocchiola

    2008-07-01

    Full Text Available The distribution of the maximum annual three day snow fall depth H72, used for avalanche hazard mapping according to the Swiss procedure (Sp, is investigated for a network of 124 stations in the Alpine part of Switzerland, using a data set dating back to 1931. Stationarity in time is investigated, showing in practice no significant trend for the considered period. Building on previous studies about climatology of Switzerland and using an iterative approach based on statistical tests for regional homogeneity and scaling of H72 with altitude, seven homogenous regions are identified. A regional approach based on the index value is then developed to estimate the T-years return period quantiles of H72 at each single site i, H72i(T. The index value is the single site sample average μH72i. The dimensionless values of H*72i=H72i / μH72i are grouped in one sample for each region and their frequency of occurrence is accommodated by a General Extreme Value, GEV, probability distribution, including Gumbel. The proposed distributions, valid in each site of the homogeneous regions, can be used to assess the T-years return period quantiles of H*72i. It is shown that the value of H72i(T estimated with the regional approach is more accurate than that calculated by single site distribution fitting, particularly for high return periods. A sampling strategy based on accuracy is also suggested to estimate the single site index value, i.e. the sample average μH72i, critical for the evaluation of the distribution of H72i. The proposed regional approach is valuable because it gives more accurate snow depth input to dynamics models than the present procedure based on single site analysis

  6. 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.

  7. Cartographic modeling of snow avalanche path location within Glacier National Park, Montana

    Science.gov (United States)

    Walsh, Stephen J.; Brown, Daniel G.; Bian, Ling; Butler, David R.

    1990-05-01

    Geographic information system (GIS) techniques were applied to the study of snow-avalanche path location within Glacier National Park, Montana. Aerial photointerpretation and field surveys confirmed the location of 121 avalanche paths within the selected study area. Spatial and nonspatial information on each path were integrated using the ARC/INFO GIS. Lithologic, structural, hydrographic, topographic, and land-cover impacts on path location were analyzed. All path frequencies within variable classes were normalized by the area of class occurrence relative to the total area of the study area and were added to the morphometric information contained within INFO tables. The normalized values for each GIS coverage were used to cartographically model, by means of composite factor weightings, avalanche path locations.

  8. Simulation of avalanche electron multiplication in photodetectors with blocked jump conductivity

    CERN Document Server

    Sinitsa, S P

    2002-01-01

    The process of the avalanche electron multiplication in silicon BIB-structure is simulated by Monte Carlo method for the regime single-photon counting. The electron acceleration in the linear electric field, the elastic scattering of electrons on longitudinal acoustic phonons the inelastic scattering of electrons on intervalley phonons and ionization of neutral impurity centers are taken into account during electron motion. The simple algorithm is proposed to calculate coordinates of all ionized centers in the avalanche and the probability function of N electron yield from the avalanche at entering one electron into the multiplication range. It is shown that this function has maximum near the average value that correlates with experimental data

  9. S-boxes generated using Affine Transformation giving Maximum Avalanche Effect

    Directory of Open Access Journals (Sweden)

    Kumara Shama

    2011-09-01

    Full Text Available The Advanced Encryption Standard (AES was published by National Institute of Standards and Technology (NIST in November 2001, to replace DES (Data Encryption Standard and Triple DES. The S-box(Substitution box used in AES is designed to be resistant to known cryptanalytic attacks [1][2]. The property of the S-box is that the output cannot be described as a simple mathematical function of the input. The S-box is designed to provide good avalanche effect. The Avalanche Criteria of S-box depends on the generator matrix A used in affine transformation to construct the S-box. This paper investigates the construction of Sboxes by affine transformation which satisfy maximum Avalanche Criteria.

  10. Cartographic modeling of snow avalanche path location within Glacier National Park, Montana

    Science.gov (United States)

    Walsh, Stephen J.; Brown, Daniel G.; Bian, Ling; Butler, David R.

    1990-01-01

    Geographic information system (GIS) techniques were applied to the study of snow-avalanche path location within Glacier National Park, Montana. Aerial photointerpretation and field surveys confirmed the location of 121 avalanche paths within the selected study area. Spatial and nonspatial information on each path were integrated using the ARC/INFO GIS. Lithologic, structural, hydrographic, topographic, and land-cover impacts on path location were analyzed. All path frequencies within variable classes were normalized by the area of class occurrence relative to the total area of the study area and were added to the morphometric information contained within INFO tables. The normalized values for each GIS coverage were used to cartographically model, by means of composite factor weightings, avalanche path locations.

  11. Modelling wet snow avalanche runout to assess road safety at a high-altitude mine in the central Andes

    Science.gov (United States)

    Valero, Cesar Vera; Wever, Nander; Bühler, Yves; Stoffel, Lukas; Margreth, Stefan; Bartelt, Perry

    2016-11-01

    Mining activities in cold regions are vulnerable to snow avalanches. Unlike operational facilities, which can be constructed in secure locations outside the reach of avalanches, access roads are often susceptible to being cut, leading to mine closures and significant financial losses. In this paper we discuss the application of avalanche runout modelling to predict the operational risk to mining roads, a long-standing problem for mines in high-altitude, snowy regions. We study the 35 km long road located in the "Cajón del rio Blanco" valley in the central Andes, which is operated by the Codelco Andina copper mine. In winter and early spring, this road is threatened by over 100 avalanche paths. If the release and snow cover conditions can be accurately specified, we find that avalanche dynamics modelling is able to represent runout, and safe traffic zones can be identified. We apply a detailed, physics-based snow cover model to calculate snow temperature, density and moisture content in three-dimensional terrain. This information is used to determine the initial and boundary conditions of the avalanche dynamics model. Of particular importance is the assessment of the current snow conditions along the avalanche tracks, which define the mass and thermal energy entrainment rates and therefore the possibility of avalanche growth and long runout distances.

  12. Merging Terrestrial Laser Scanning Technology with Photogrammetric and Total Station Data for the Determination of Avalanche Modeling Parameters

    Science.gov (United States)

    Prokop, Alexander; Schön, Peter; Singer, Florian; Pulfer, Gaëtan; Naaim, Mohamed; Thibert, Emmanuel

    2015-04-01

    Dynamic avalanche modeling requires as input the volumes and areas of the snow released, entrained and deposited, as well as the fracture heights. Determining these parameters requires high-resolution spatial snow surface data from before and after the avalanche. In snow and avalanche research, terrestrial laser scanners are used increasingly to efficiently and accurately map snow surfaces and depths over an area of several km². In practice however, several problems may occur, which must be recognized and accounted for during post-processing and interpretation, especially under the circumstances of surveying an artificially triggered avalanche at a test site, where time pressure due to operational time constraints may also cause less than ideal circumstances and surveying setups. Thus, we combine terrestrial laser scanning with photogrammetry, total station measurements and field snow observations to document and accurately survey an artificially triggered avalanche at the Col du Lautaret test site (2058 m) in the French Alps. The ability of TLS to determine avalanche modeling input parameters efficiently and accurately is shown, and we demonstrate how, merging TLS with the other methods facilitates and improves data post-processing and interpretation. Finally, we present for this avalanche the data required for the parameterization and validation of dynamic avalanche models and discuss using newest data, how the new laser scanning device generation (e.g Riegl VZ6000) further improves such surveying campaigns.

  13. A viscoplastic lubrication model for entrainment by avalanches and debris flows, and comparison with experiments

    Science.gov (United States)

    Bates, Belinda; Ancey, Christophe

    2015-04-01

    Recently, experiments were designed and carried out examining how a viscoplastic avalanche begins to entrain a shallow layer of identical fluid lying in its path, much like a snow avalanche or mud flow which suddenly encounters an entrainable layer, described as a yield stress material. This represents a simplified problem, investigated in order to gain some physical insight into entrainment by avalanches. These experiments serve as a test for mathematical models of entraining gravity currents. Two classes of entrainment behaviour were observed: either the avalanche ``glided'' out over the entrainable bed, immediately shearing it in the downstream direction and progressively incorporating fluid down to the rigid base, or the avalanche seemed to ``roll'' out onto the entrainable bed, with strong motion in the slope-normal direction in the bed after yield. This difference in behaviour was dictated by the magnitude of the flume's slope. For the steeper flows studied (20 and 24 degrees), entrainment was principally in the former class, whereas for shallower slope angle (12 and 16 degrees) entrainment more closely resembled the latter type. This would suggest that there is a competition between the normal and shear stresses exerted on the bed, with bed-yield and entrainment occurring when these stresses exceed a critical value. An interesting phenomenon that was observed in all cases was a sort of buckling of the bed, downstream of the avalanche front. This was far more significant in the flows down shallower slopes, and regular waves were created in the bed with wavelength dependent on the flow depth. Based on theoretical comparisons with non-entraining Herschel Bulkley flows, the physics of entraining flows are investigated numerically for shallow viscoplastic gravity currents on different slopes. The predictions are compared with the experimental values for velocity field and surface height. The model was successful in reproducing velocities of the correct order, but

  14. Particle-size segregation and diffusive remixing in shallow granular avalanches

    Science.gov (United States)

    Gray, J. M. N. T.; Chugunov, V. A.

    2006-12-01

    Segregation and mixing of dissimilar grains is a problem in many industrial and pharmaceutical processes, as well as in hazardous geophysical flows, where the size-distribution can have a major impact on the local rheology and the overall run-out. In this paper, a simple binary mixture theory is used to formulate a model for particle-size segregation and diffusive remixing of large and small particles in shallow gravity-driven free-surface flows. This builds on a recent theory for the process of kinetic sieving, which is the dominant mechanism for segregation in granular avalanches provided the density-ratio and the size-ratio of the particles are not too large. The resulting nonlinear parabolic segregation remixing equation reduces to a quasi-linear hyperbolic equation in the no-remixing limit. It assumes that the bulk velocity is incompressible and that the bulk pressure is lithostatic, making it compatible with most theories used to compute the motion of shallow granular free-surface flows. In steady-state, the segregation remixing equation reduces to a logistic type equation and the ‘S’-shaped solutions are in very good agreement with existing particle dynamics simulations for both size and density segregation. Laterally uniform time-dependent solutions are constructed by mapping the segregation remixing equation to Burgers equation and using the Cole Hopf transformation to linearize the problem. It is then shown how solutions for arbitrary initial conditions can be constructed using standard methods. Three examples are investigated in which the initial concentration is (i) homogeneous, (ii) reverse graded with the coarse grains above the fines, and, (iii) normally graded with the fines above the coarse grains. Time-dependent two-dimensional solutions are also constructed for plug-flow in a semi-infinite chute.

  15. Avalanche-like fluidization of a non-Brownian particle gel.

    Science.gov (United States)

    Kurokawa, Aika; Vidal, Valérie; Kurita, Kei; Divoux, Thibaut; Manneville, Sébastien

    2015-12-14

    We report on the fluidization dynamics of an attractive gel composed of non-Brownian particles made of fused silica colloids. Extensive rheology coupled to ultrasonic velocimetry allows us to characterize the global stress response together with the local dynamics of the gel during shear startup experiments. In practice, after being rejuvenated by a preshear, the gel is left to age for a time tw before being subjected to a constant shear rate [small gamma, Greek, dot above]. We investigate in detail the effects of both tw and [small gamma, Greek, dot above] on the fluidization dynamics and build a detailed state diagram of the gel response to shear startup flows. The gel may display either transient shear banding towards complete fluidization or steady-state shear banding. In the former case, we unravel that the progressive fluidization occurs by successive steps that appear as peaks on the global stress relaxation signal. Flow imaging reveals that the shear band grows until complete fluidization of the material by sudden avalanche-like events which are distributed heterogeneously along the vorticity direction and correlated to large peaks in the slip velocity at the moving wall. These features are robust over a wide range of tw and [small gamma, Greek, dot above] values, although the very details of the fluidization scenario vary with [small gamma, Greek, dot above]. Finally, the critical shear rate [small gamma, Greek, dot above]* that separates steady-state shear-banding from steady-state homogeneous flow depends on the width of the shear cell and exhibits a nonlinear dependence with tw. Our work brings about valuable experimental data on transient flows of attractive dispersions, highlighting the subtle interplay between shear, wall slip and aging whose modeling constitutes a major challenge that has not been met yet.

  16. Dramatic role of critical current anisotropy on flux avalanches in MgB2 films.

    Science.gov (United States)

    Albrecht, J; Matveev, A T; Strempfer, J; Habermeier, H-U; Shantsev, D V; Galperin, Y M; Johansen, T H

    2007-03-16

    Anisotropic penetration of magnetic flux in MgB(2) films grown on vicinal sapphire substrates is investigated using magneto-optical imaging. Regular penetration above 10 K proceeds more easily along the substrate surface steps, the anisotropy of the critical current being 6%. At lower temperatures the penetration occurs via abrupt dendritic avalanches that preferentially propagate perpendicular to the surface steps. This inverse anisotropy in the penetration pattern becomes dramatic very close to 10 K where all flux avalanches propagate in the strongest pinning direction. The observed behavior is fully explained using a thermomagnetic model of the dendritic instability.

  17. Sensitivity Analysis of a Spatio-Temporal Avalanche Forecasting Model Based on Support Vector Machines

    Science.gov (United States)

    Matasci, G.; Pozdnoukhov, A.; Kanevski, M.

    2009-04-01

    The recent progress in environmental monitoring technologies allows capturing extensive amount of data that can be used to assist in avalanche forecasting. While it is not straightforward to directly obtain the stability factors with the available technologies, the snow-pack profiles and especially meteorological parameters are becoming more and more available at finer spatial and temporal scales. Being very useful for improving physical modelling, these data are also of particular interest regarding their use involving the contemporary data-driven techniques of machine learning. Such, the use of support vector machine classifier opens ways to discriminate the ``safe'' and ``dangerous'' conditions in the feature space of factors related to avalanche activity based on historical observations. The input space of factors is constructed from the number of direct and indirect snowpack and weather observations pre-processed with heuristic and physical models into a high-dimensional spatially varying vector of input parameters. The particular system presented in this work is implemented for the avalanche-prone site of Ben Nevis, Lochaber region in Scotland. A data-driven model for spatio-temporal avalanche danger forecasting provides an avalanche danger map for this local (5x5 km) region at the resolution of 10m based on weather and avalanche observations made by forecasters on a daily basis at the site. We present the further work aimed at overcoming the ``black-box'' type modelling, a disadvantage the machine learning methods are often criticized for. It explores what the data-driven method of support vector machine has to offer to improve the interpretability of the forecast, uncovers the properties of the developed system with respect to highlighting which are the important features that led to the particular prediction (both in time and space), and presents the analysis of sensitivity of the prediction with respect to the varying input parameters. The purpose of the

  18. Flexible Retaining Barriers for Prevention of Avalanches on National Highway NH-1A

    Directory of Open Access Journals (Sweden)

    Vinay Chaudhary

    2002-04-01

    Full Text Available "An avalanche hazard Call be reduced by active and passive methods. In an active method, which is a very effective, avalanche control structures are used to mitigate the avalanche danger. These structures can be installed in any of the three zones of an avalanche, viz., formation zone, middle zone and run-out zone. In the formation zone, avalanche can be controlled by supporting structures/retaining barriers, which are installed in the formation zone with a view to prevent formation of an avalanche. Their placement in the formation zone with proper arrangement and layout helps in preventing fracture in the snow mass. The basic concept lies in converting the shear and tensile stresses in snow into compressive stresses which can be conveniently sustained by the snowcover. Such supporting structures/retaining barriers can be categorised into rigid and flexible types of structures. Snow rakes and snow bridges are categorised as rigid structures, whereas wire rope nets are categorised as flexible structures. The Snow & Avalanche Study Establishment, Chandigarh, had developed snow nets in 1988-89, which were installed at D-10 avalanche site on north portal of Jawahar tunnel, Jammu-Srinagar Highway (NH-1A. These nets were designed considering the snow forces acting in the direction parallel to the slope only. Hence, the movement of the swivel post was restricted in one direction only. However, detailed scientific studies carried out for retaining barriers over the last seven year's have revealed that two types of failures occur in these nets. First, a major failure was noticed in hinge joint of swivel post, and second, a failure was noticed in the foundation of the uphill anchor. To overcome these failures, the swivel post joint has been redesigned as articulated ball and socket joint to cater for omni directional movement to the swivel post, and the uphill anchor foundation has been strengthened by providing the reinforcement. This paper deals with

  19. Apparent Cooling Rate of 7°C per Hour in an Avalanche Victim.

    Science.gov (United States)

    Ströhle, Mathias; Putzer, Gabriel; Procter, Emily; Paal, Peter

    2015-12-01

    Avalanche victims can become hypothermic within 35 minutes of snow burial. However, reported cooling rates for avalanche victims are highly variable and it is poorly understood how much cooling is influenced by general factors (body composition, clothing, ambient conditions, duration of burial, and metabolism), unknown inter-individual factors or other phenomena (e.g., afterdrop). We report an apparent cooling rate of ∼7°C in ∼60 minutes in a healthy backcountry skier who was rewarmed with forced air and warm fluids and was discharged after 2 weeks without neurological sequelae.

  20. Avalanche-enhanced photocurrents in pin silicon waveguides at 1550 nm wavelength

    Institute of Scientific and Technical Information of China (English)

    Zhao Yong; Xu Chao; Jiang Xiaoqing; Ge Huiliang

    2013-01-01

    The photocurrent effect in pin silicon waveguides at 1550 nm wavelength is experimentally investigated.The photocurrent is mainly attributed to surface-state absorption,defect-state absorption and/or two-photon absorption.Experimental results show that the photocurrent is enhanced by the avalanche effect.A pin silicon waveguide with an intrinsic region width of 3.4 μm and a length of 2000 μm achieves a responsivity of 4.6 mA/W and an avalanche multiplication factor of about five.