WorldWideScience

Sample records for burst distance indicators

  1. HOST GALAXIES AS GAMMA-RAY BURST DISTANCE INDICATORS

    Energy Technology Data Exchange (ETDEWEB)

    D. BAND; ET AL

    2001-01-01

    We calculate the distributions of the total burst energy, the peak luminosity and the X-ray afterglow energy using burst observations and distances to the associated host galaxies. To expand the sample, we include redshift estimates for host galaxies without spectroscopic redshifts. The methodology requires a model of the host galaxy population; we find that in the best model the burst rate is proportional to the host galaxy luminosity at the time of the burst.

  2. Investigating the properties of gamma ray bursts and gravitational wave standard sirens as high redshift distance indicators

    Science.gov (United States)

    Speirits, Fiona Claire

    In a discipline commonly faulted for ad hoc assumptions and models with very little discriminating observational evidence, cosmologists are continually trying, and in many cases succeeding, to improve both the data and models. However, the desire to support currently favoured models often dominates research and may lead to a systematic bias being introduced in favour of a model before a strong body of supporting evidence has been accumulated. This is perhaps most evident in literature supporting the viability of Gamma Ray Bursts as cosmological distance indicators, where aside from subjective data-selection, the basic statistical methods are at best questionable and at worst incorrect. To this end, we construct a simple cosmology-independent illustration of the effect that the application of these methods has on parameter estimation and discuss the correct method to apply to current data. We also investigate the constraints potential future Gamma Ray Burst data may place on alternatives to the status quo Concordance Model in the shape of Conformal Gravity and Unified Dark Matter through a widely applicable and transferable Bayesian model comparison technique and the development of a representative mock data set. Finally, we investigate gravitational wave standard sirens as an alternative high-redshift distance indicator. We first illustrate their strong diagnostic potential through a Bayesian model comparison between the standard Unified Dark Matter model and a variant in which the dark component is redshift dependent. By drawing mock data from a known cosmological model, thus fixing the expected values of the model parameters, we find that while 182 Type 1a Supernovae are readily confused between constant and evolving models, just 2 standard sirens are able to successfully identify the correct model. Having established standard sirens as an effective tool in cosmological model comparison, we then address the potential confusion of models with dynamical dark energy

  3. Constraints on cosmological models and reconstructing the acceleration history of the Universe with gamma-ray burst distance indicators

    Science.gov (United States)

    Liang, Nan; Wu, Puxun; Zhang, Shuang Nan

    2010-04-01

    Gamma-ray bursts (GRBs) have been regarded as standard candles at very high redshift for cosmology research. We have proposed a new method to calibrate GRB distance indicators with Type Ia supernova (SNe Ia) data in a completely cosmology-independent way to avoid the circularity problem that had limited the direct use of GRBs to probe cosmology [N. Liang, W. K. Xiao, Y. Liu, and S. N. Zhang, Astrophys. J. 685, 354 (2008).ASJOAB0004-637X10.1086/590903]. In this paper, a simple method is provided to combine GRB data into the joint observational data analysis to constrain cosmological models; in this method those SNe Ia data points used for calibrating the GRB data are not used to avoid any correlation between them. We find that the ΛCDM model is consistent with the joint data in the 1-σ confidence region, using the GRB data at high redshift calibrated with the interpolating method, the Constitution set of SNe Ia, the cosmic microwave background radiation from Wilkinson Microwave Anisotropy Probe five year observation, the baryonic acoustic oscillation from the spectroscopic Sloan Digital Sky Survey Data Release 7 galaxy sample, the x-ray baryon mass fraction in clusters of galaxies, and the observational Hubble parameter versus redshift data. Comparing to the joint constraints with GRBs and without GRBs, we find that the contribution of GRBs to the joint cosmological constraints is a slight shift in the confidence regions of cosmological parameters to better enclose the ΛCDM model. Finally, we reconstruct the acceleration history of the Universe up to z>6 with the distance moduli of SNe Ia and GRBs and find some features that deviate from the ΛCDM model and seem to favor oscillatory cosmology models; however, further investigations are needed to better understand the situation.

  4. Powerful Radio Burst Indicates New Astronomical Phenomenon

    Science.gov (United States)

    2007-09-01

    Astronomers studying archival data from an Australian radio telescope have discovered a powerful, short-lived burst of radio waves that they say indicates an entirely new type of astronomical phenomenon. Region of Strong Radio Burst Visible-light (negative greyscale) and radio (contours) image of Small Magellanic Cloud and area where burst originated. CREDIT: Lorimer et al., NRAO/AUI/NSF Click on image for high-resolution file ( 114 KB) "This burst appears to have originated from the distant Universe and may have been produced by an exotic event such as the collision of two neutron stars or the death throes of an evaporating black hole," said Duncan Lorimer, Assistant Professor of Physics at West Virginia University (WVU) and the National Radio Astronomy Observatory (NRAO). The research team led by Lorimer consists of Matthew Bailes of Swinburne University in Australia, Maura McLaughlin of WVU and NRAO, David Narkevic of WVU, and Fronefield Crawford of Franklin and Marshall College in Lancaster, Pennsylvania. The astronomers announced their findings in the September 27 issue of the online journal Science Express. The startling discovery came as WVU undergraduate student David Narkevic re-analyzed data from observations of the Small Magellanic Cloud made by the 210-foot Parkes radio telescope in Australia. The data came from a survey of the Magellanic Clouds that included 480 hours of observations. "This survey had sought to discover new pulsars, and the data already had been searched for the type of pulsating signals they produce," Lorimer said. "We re-examined the data, looking for bursts that, unlike the usual ones from pulsars, are not periodic," he added. The survey had covered the Magellanic Clouds, a pair of small galaxies in orbit around our own Milky Way Galaxy. Some 200,000 light-years from Earth, the Magellanic Clouds are prominent features in the Southern sky. Ironically, the new discovery is not part of these galaxies, but rather is much more distant

  5. Q-bursts from various distances on the Earth

    Science.gov (United States)

    Ogawa, Toshio; Komatsu, Masayuki

    2009-02-01

    The mechanism of the Q-burst is investigated in the time and frequency domains. Electric fields in the ELF (extremely low frequency) to VLF (very low frequency) range have been observed with a ball antenna since 2003 in Kochi City, Japan (latitude 33.3°north, longitude 133.4°east). Source-to-observer distances (SODs) of Q-bursts are estimated by analyzing the waveforms. It is found as a result that the Q-burst is produced by combination of direct and antipodal pulses from a source lightning stroke occurring all over the world.

  6. Measuring the cosmic proper distance from fast radio bursts

    Science.gov (United States)

    Yu, H.; Wang, F. Y.

    2017-09-01

    The cosmic proper distance dP is a fundamental distance in the Universe. Unlike the luminosity and angular diameter distances, which correspond to the angular size, the proper distance is the length of light path from the source to observer. However, the proper distance has not been measured before. The recent redshift measurement of a repeat fast radio burst (FRB) can shed light on the proper distance. We show that the proper distance-redshift relation can indeed be derived from dispersion measures (DMs) of FRBs with measured redshifts. From Monte Carlo simulations, we find that about 500 FRBs with DM and redshift measurements can tightly constrain the proper distance-redshift relation. We also show that the curvature of our Universe can be constrained with a model-independent method using this derived proper distance-redshift relation and the observed angular diameter distances. Owing to the high event rate of FRBs, hundreds of FRBs can be discovered in the future by upcoming instruments. The proper distance will play an important role in investigating the accelerating expansion and the geometry of the Universe.

  7. A simple empirical redshift indicator for gamma-ray bursts

    OpenAIRE

    Atteia, J-L

    2003-01-01

    We propose a new empirical redshift indicator for gamma-ray bursts. This indicator is easily computed from the gamma-ray burst spectral parameters, and its duration, and it provides ``pseudo-redshifts'' accurate to a factor two. Possible applications of this redshift indicator are briefly discussed.

  8. Burst-Suppression Ratio on Electrocorticography Depends on Interelectrode Distance

    DEFF Research Database (Denmark)

    Moldovan, Mihai; Calin, Alexandru; Kumaraswamy, Vishakhadatta M.

    2016-01-01

    Introduction: With deepening of anesthesia-induced comatose states, the EEG becomes fragmented by increasing periods of suppression. When measured from conventional EEG recordings, the binary burst-suppression signal (BS) appears similar across the scalp. As such, the BS ratio (BSR), quantifying...

  9. Leukocytes respiratory burst activity as indicator of innate immunity of pacu Piaractus mesopotamicus

    Directory of Open Access Journals (Sweden)

    JD Biller-Takahashi

    Full Text Available The present study evaluated the assay to quantify the respiratory burst activity of blood leukocytes of pacu as an indicator of the innate immune system, using the reduction of nitroblue tetrazolium (NBT to formazan as a measure of the production of reactive oxygen species (ROS. In order to assess the accuracy of the assay, fish were challenged by Aeromonas hydrophila and sampled one week after challenge. The A. hydrophila infection increased the leukocyte respiratory burst activity. The protocol showed a reliable and easy assay, appropriate to determine the respiratory burst activity of blood leukocytes of pacu, a neotropical fish, in the present experimental conditions.

  10. A primer on quality indicators of distance education.

    Science.gov (United States)

    Chaney, Beth H; Eddy, James M; Dorman, Steve M; Glessner, Linda L; Green, B Lee; Lara-Alecio, Rafael

    2009-04-01

    In the past decade, there has been an enormous growth of distance education courses and programs in higher education. The growth of distance education is particularly evident in the field of health education. However, the enormous potential of distance education is tempered by one overriding question: How does one ensure that distance education coursework and degrees are of high quality? To this end, the purpose of this study is twofold: to identify quality indicators of distance education and to provide implications of the identified quality indicators for health education researchers and practitioners. The results of the study reveal common benchmarks and quality indicators that all parties deem important in designing, implementing, and evaluating distance education courses and programs.

  11. New method for distance-based close following safety indicator.

    Science.gov (United States)

    Sharizli, A A; Rahizar, R; Karim, M R; Saifizul, A A

    2015-01-01

    The increase in the number of fatalities caused by road accidents involving heavy vehicles every year has raised the level of concern and awareness on road safety in developing countries like Malaysia. Changes in the vehicle dynamic characteristics such as gross vehicle weight, travel speed, and vehicle classification will affect a heavy vehicle's braking performance and its ability to stop safely in emergency situations. As such, the aim of this study is to establish a more realistic new distance-based safety indicator called the minimum safe distance gap (MSDG), which incorporates vehicle classification (VC), speed, and gross vehicle weight (GVW). Commercial multibody dynamics simulation software was used to generate braking distance data for various heavy vehicle classes under various loads and speeds. By applying nonlinear regression analysis to the simulation results, a mathematical expression of MSDG has been established. The results show that MSDG is dynamically changed according to GVW, VC, and speed. It is envisaged that this new distance-based safety indicator would provide a more realistic depiction of the real traffic situation for safety analysis.

  12. Indication of radio frequency interference (RFI) sources for solar burst monitoring in Malaysia

    Science.gov (United States)

    Hamidi, Z. S.; Abidin, Z. Z.; Ibrahim, Z. A.; Shariff, N. N. M.

    2012-06-01

    Apart of monitoring the Sun project, the Radio Frequency Interference (RFI) surveying in the region of (1-1200) MHz has been conducted. The main objective of this surveying is to test and qualify the potential of monitoring a continuous radio emission of Solar in Malaysia. This work is also an initiative of International Space Weather Initiative (ISWI) project where Malaysia is one of the country that participate a e-Callisto Spectrometer network in order to study the behavior of Solar radio burst in frequency of (45-800) MHz region which will be install in this October. Detail results will indicate the potential of monitoring a solar in Malaysia.

  13. A New Redshift Indicator of Gamma-Ray Bursts to Measure the Cosmos

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    Zhibin Zhang

    2007-06-01

    Full Text Available Using 64 ms count data of long gamma-ray bursts (LBs, T90 > 2.6 s, we analyze the quantity named relative spectral lag (RSL, τ31/FWHM (1 =τrel, 31. We investigate in detail the properties of the RSL for a sample of nine LBs, using the general cross-correlation technique that includes the lag between two different energy bands. We find that the distribution of RSLs is normal and has a mean value of 0.1. Our important discovery is that redshift (z and peak luminosity (Lp are strongly correlated with the RSL, which can be measured easily and directly, making the RSL a good redshift and peak luminosity indicator. In addition, we find that the redshift and luminosity estimator can also hold for short gamma-ray bursts (SBs, T90 < 2.6 s. With it, we estimate the median of redshift and peak luminosity of SBs to be about z≤0.06 and Lp ∼1.68×1048 erg/s, which are in excellent agreement with the results suggested by some previous authors. We thus argue that the sources including SBs and LBs with positive spectral lags might be one united category with the same physical process.

  14. Radius expansion bursts from the neutron star transient XTE J1701-462; a new distance estimate

    NARCIS (Netherlands)

    Lin, D.; Homan, J.; Remillard, R.; Wijnands, R.

    2007-01-01

    A detailed spectral analysis of the second and third type-I X- ray bursts from the neutron star transient XTE J1701-462 (detected on July 20 and July 25, see also ATel #1165) reveals clear photospheric radius expansion in both of them. The bursts show radius expansion for about 2-3 seconds, with the

  15. Machine-z: Rapid Machine-Learned Redshift Indicator for Swift Gamma-Ray Bursts

    Science.gov (United States)

    Ukwatta, T. N.; Wozniak, P. R.; Gehrels, N.

    2016-01-01

    Studies of high-redshift gamma-ray bursts (GRBs) provide important information about the early Universe such as the rates of stellar collapsars and mergers, the metallicity content, constraints on the re-ionization period, and probes of the Hubble expansion. Rapid selection of high-z candidates from GRB samples reported in real time by dedicated space missions such as Swift is the key to identifying the most distant bursts before the optical afterglow becomes too dim to warrant a good spectrum. Here, we introduce 'machine-z', a redshift prediction algorithm and a 'high-z' classifier for Swift GRBs based on machine learning. Our method relies exclusively on canonical data commonly available within the first few hours after the GRB trigger. Using a sample of 284 bursts with measured redshifts, we trained a randomized ensemble of decision trees (random forest) to perform both regression and classification. Cross-validated performance studies show that the correlation coefficient between machine-z predictions and the true redshift is nearly 0.6. At the same time, our high-z classifier can achieve 80 per cent recall of true high-redshift bursts, while incurring a false positive rate of 20 per cent. With 40 per cent false positive rate the classifier can achieve approximately 100 per cent recall. The most reliable selection of high-redshift GRBs is obtained by combining predictions from both the high-z classifier and the machine-z regressor.

  16. Ultralong-period Cepheids: a possible primary distance indicator?

    Science.gov (United States)

    Fiorentino, G.; Annibali, F.; Clementini, G.; Ramos, R. Contreras; Marconi, M.; Musella, I.; Saha, A.; Tosi, M.; Aloisi, A.; van der Marel, R.

    2013-02-01

    We present a project that aims to provide a complete theoretical and observational framework for an as yet unexplored class of variable stars, the ultralong-period Cepheids (P longer than 80-100 days). Given their very high luminosities (MV up to -7 mag), with the Hubble Space Telescope we will be able to observe them easily in stellar systems located at large distances (~ 100 Mpc). This limit will be further increased, out to the Hubble flow (~ 350 Mpc), using future ground-based facilities such as the European Extremely Large Telescope. The nature of their pulsation is as yet unclear, as is their evolutionary status, which seems different from the central helium-burning phase generally associated with classical Cepheids. These objects have been found to cover a very large metallicity range, from [Fe/H] ~ -2 dex to solar values, and they are located in heterogeneous stellar systems, from dwarf to spiral galaxies. Once completely characterized, they could provide a crucial test, since they have been found in all Type Ia supernova host spiral galaxies that have been monitored for variability over long periods and that currently offer sound constraints on the estimated value of the Hubble constant.

  17. Interpreting the gamma statistic in phylogenetic diversification rate studies: a rate decrease does not necessarily indicate an early burst.

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    James A Fordyce

    Full Text Available BACKGROUND: Phylogenetic hypotheses are increasingly being used to elucidate historical patterns of diversification rate-variation. Hypothesis testing is often conducted by comparing the observed vector of branching times to a null, pure-birth expectation. A popular method for inferring a decrease in speciation rate, which might suggest an early burst of diversification followed by a decrease in diversification rate is the gamma statistic. METHODOLOGY: Using simulations under varying conditions, I examine the sensitivity of gamma to the distribution of the most recent branching times. Using an exploratory data analysis tool for lineages through time plots, tree deviation, I identified trees with a significant gamma statistic that do not appear to have the characteristic early accumulation of lineages consistent with an early, rapid rate of cladogenesis. I further investigated the sensitivity of the gamma statistic to recent diversification by examining the consequences of failing to simulate the full time interval following the most recent cladogenic event. The power of gamma to detect rate decrease at varying times was assessed for simulated trees with an initial high rate of diversification followed by a relatively low rate. CONCLUSIONS: The gamma statistic is extraordinarily sensitive to recent diversification rates, and does not necessarily detect early bursts of diversification. This was true for trees of various sizes and completeness of taxon sampling. The gamma statistic had greater power to detect recent diversification rate decreases compared to early bursts of diversification. Caution should be exercised when interpreting the gamma statistic as an indication of early, rapid diversification.

  18. A photospheric radius-expansion burst observed from XTE J1701-407 by INTEGRAL: an update on distance

    DEFF Research Database (Denmark)

    Chenevez, Jérôme; Maurizio, F.; Brandt, Søren Kristian

    2010-01-01

    V), with an exponential decay time of 118s. The peak flux was about 4 Crab (1e-7 erg/cm2/s) in the 3-30 keV energy band (JEM-X) and 0.35 Crab (3.4 e-9 erg/cm2/s) in the 18-40 keV band (IBIS/ISGRI). The JEM-X light curve shows evidence for photosperic radius expansion, with a 2s precursor starting about 4s before the main.......7-3946 (PI R. Terrier). As part of our monitoring of long thermonuclear X-ray bursts with INTEGRAL, we have analysed both the JEM-X and ISGRI data covering this event, and we identify it as another type I (thermonuclear) X-ray burst. The duration of the burst was about 3 minutes (3-30 ke...

  19. Perspectives of observing the color indices of optical afterglows of gamma-ray bursts with ESA Gaia

    Science.gov (United States)

    Šimon, Vojtěch; Hudec, René; Pizzichini, Graziella

    2017-10-01

    We propose a strategy for detecting and analyzing optical afterglows (OAs) of long gamma-ray bursts (GRBs) without the need to obtain their light curves. This approach is useful for the Gaia satellite, which provides sampled optical ultra-low-dispersion spectroscopic observations of the sky. For this purpose, we show that most OAs of long GRBs display specific values of some of their color indices, representing synchrotron emission of the jet. They are stable in time during the event. These indices, which can be determined from the spectra, are very similar for the ensemble of OAs with redshift z Gaia instruments also gives us a hope to search for the so-called orphan afterglows, which, according to some authors, can be considerably more numerous than OAs of the observed GRBs. We also show how to resolve OAs from other transients in the Gaia data. The color indices and the properties of the quiescent sources (host galaxies of OAs detectable later by the large ground-based telescopes at the co-ordinates of the OA determined by Gaia) would tell us which one, among transients detected by Gaia, is a GRB OA.

  20. REDESIGNING THE GLOBAL FOOD SECURITY INDEX: A MULTIVARIATE COMPOSITE I-DISTANCE INDICATOR APPROACH

    Directory of Open Access Journals (Sweden)

    Milica Maricic

    2016-01-01

    Full Text Available tract The topic of food security has gained significant attention and importance due to its impact on political, economic, and humanitarian decisions governments make. Although composite indexes that measure food security have proliferated in the last decade, many questions regarding their methodologies remain unanswered. Among several composite indexes that aim to measure food security, the Global Food Security Index (GFSI stands out for its solid methodology and reliable data sources. However, its weighting scheme can be categorized as biased. This paper attempts to overcome the issue of subjectively assigned weights to indicators and categories within the GFSI. Namely, we propose a statistical methodology, the Composite I-distance Indicator (CIDI, which is based on the I-distance method, for obtaining an unbiased weighting scheme. Our approach can serve as a foundation for future research on weighting schemes, which are enveloped with subjectivity.

  1. Running Performance as an Indicator of VO(2max): A Replication of Distance Effects

    Science.gov (United States)

    2001-07-23

    An earlier review showed that run test validity as an indicator of aerobic capacity increased with test distance up to 2 km and with test duration up...model of run test validity. The range of constant validity in the PW model was surprising in light of physiological and mathematical models of running...evidence, a I 2-min run test maximizes validity while minimizing demands on the runners.

  2. Phenotypic distances of parental components as a possible indicator of heterosis

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    Babić Vojka

    2010-01-01

    Full Text Available Although the reveal of heterotic groups in maize significantly increased testing efficiency, field trials are still unreplaceable and most time and fund consumable in the process of the hybrid development. The efficiency of breeding programmes could be significantly increased if the hybrid performance could be predicted prior to the field evaluation. Although different marker techniques have been developed and included into current breeding programmes, the satisfactory results have not been obtained yet. The present study is an attempt to inexpensively and rapidly discover indicators that could even partially facilitate the selection of parental pairs in the process of the hybrid development prior to the field evaluation. The phenotypic description of inbred lines according to the UPOV Descriptor was used for the estimation of the phenotypic distances for which it had been assumed that they could, to a certain degree, be an indicator of heterosis. The phenotypic characterization according to the UPOV Descriptor was done for 28 elite inbreds, that are often used in our commercial breeding programmes, and for 24 inbreds originating from the same source, as well as, for an inbred of the unknown origin and their phenotypic distances were estimated. The cluster analysis resulted in the classification that was in high compliance with known information on the origin. It was empirically concluded that great distances of parent inbreds result in good hybrids. Furthermore, high values among certain inbreds belonging to the same heterotic groups are observed on the morphological distance matrix and crosses among them should indeed be tested in the field prior to making any general conclusion on the reliability of the morphological distance in the prediction of heterosis.

  3. Information Management Processes for Extraction of Student Dropout Indicators in Courses in Distance Mode

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    Renata Maria Abrantes Baracho

    2016-04-01

    Full Text Available This research addresses the use of information management processes in order to extract student dropout indicators in distance mode courses. Distance education in Brazil aims to facilitate access to information. The MEC (Ministry of Education announced, in the second semester of 2013, that the main obstacles faced by institutions offering courses in this mode were students dropping out and the resistance of both educators and students to this mode. The research used a mixed methodology, qualitative and quantitative, to obtain student dropout indicators. The factors found and validated in this research were: the lack of interest from students, insufficient training in the use of the virtual learning environment for students, structural problems in the schools that were chosen to offer the course, students without e-mail, incoherent answers to activities to the course, lack of knowledge on the part of the student when using the computer tool. The scenario considered was a course offered in distance mode called Aluno Integrado (Integrated Student

  4. Honing Type Ia Supernovae as Distance Indicators, Exploiting Environmental Bias for H0 and w.

    Science.gov (United States)

    Rigault, Michkael

    2015-10-01

    Type Ia supernovae are excellent distance indicators and provide a uniqueprobe for measuring the expansion history of the Universe. They playkey roles both in measuring the Hubble Constant, H0, and the dark energyequation of state, w. However their exact nature remains uncertain andastrophysical dependencies have been identified and shown to significantlyaffect the measurements of H0 and w. Recently we have used a uniquesample having local host information to demonstrate that, far from beinga problem, correlations between standardized SN Ia brightnesses andproperties of their local environmental can be used to improve SNe Iaas distance indicators. These correlations can be used to both reducethe dispersion in standardized brightnesses and correct existing biases.This proposal aims to analyze both global and local properties usingUV-to-optical photometry in order to understand the source of the SNastrophysical biases found so far, and to use that knowledge to developtools with which future high-redshift SN Ia surveys can correct or exploitthese correlations. The UV data necessary to break the degeneracy betweenstellar ages and dust extinction is only accessible from space, and inthe UV, only HST can provide the angular resolution necessary to study theenvironments of nearby smooth Hubble-flow SN Ia hosts on the kpc scale.

  5. Indicators of competitive activity of the oarswomen on kayaks at the Olympic distance.

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    Chychkan O.A.

    2010-08-01

    Full Text Available The frame of competitive activity of sportsmen on kayaks different sports qualification on a distance of 500 meters is construed. 20 sportsmen of different sports qualification have been inspected. During competitions were fixed: number paddle boat and a road clearance time of a distance. It is exhibited variances in a level of competitive activity. Competitive activity expediently to value on parameters of a road clearance time of a distance, an amount paddle boat on a distance, roads of a boat for 1 paddle boat, an average velocity of a boat, average rate, average duration paddle boat, an average velocity of a boat in a cycle paddle boat, to factor mechanics.

  6. A repeating fast radio burst

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    Spitler, L. G.; Scholz, P.; Hessels, J. W. T.; Bogdanov, S.; Brazier, A.; Camilo, F.; Chatterjee, S.; Cordes, J. M.; Crawford, F.; Deneva, J.; Ferdman, R. D.; Freire, P. C. C.; Kaspi, V. M.; Lazarus, P.; Lynch, R.; Madsen, E. C.; McLaughlin, M. A.; Patel, C.; Ransom, S. M.; Seymour, A.; Stairs, I. H.; Stappers, B. W.; van Leeuwen, J.; Zhu, W. W.

    2016-03-01

    Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.

  7. Ground contact time as an indicator of metabolic cost in elite distance runners.

    Science.gov (United States)

    Chapman, Robert F; Laymon, Abigail S; Wilhite, Daniel P; McKenzie, James M; Tanner, David A; Stager, Joel M

    2012-05-01

    Differences in running economy at common speeds have been demonstrated between male and female distance runners, as well as between middle-distance (MD) and long-distance (LD) specialists. Whether measures of foot ground contact time (tc), known to be proportional to the mass-specific cost of locomotion, follows the same running economy relationships in these groups is unknown. This study examined if differences in tc and selected gait kinematic variables exist between elite male and female distance runners, as well as between elite MD and LD specialists, as running speed increases. Twelve male and six female elite distance runners completed multiple 30-s trials on a treadmill at common competitive racing velocities. Wireless triaxial 10-g accelerometers, sampling at 1024 Hz, were securely attached to the laces of each shoe. Values of tc, swing time, stride length, and stride frequency were determined from accelerometric output corresponding to foot strike and toe-off events obtained from a minimum of 20 consecutive steps of each foot. A proportional estimate of metabolic cost was obtained by using 1/tc. Women displayed shorter tc, swing time, and stride length with greater stride frequency compared with men at common speeds; however, these differences were largely negated by normalizing to standing height. At common speeds, women demonstrated smaller measures of tc compared with men, suggesting an increased metabolic cost, paralleling published oxygen uptake data. MD specialists displayed smaller increases in 1/tc as speed increased, compared with LD specialists. Elite distance runners demonstrate ground contact measures that suggest that known differences in running economy between sexes and event specialties may be a result of differences in running gait.

  8. Multirhythmic bursting

    Science.gov (United States)

    Butera, Robert J.

    1998-03-01

    A complex modeled bursting neuron [C. C. Canavier, J. W. Clark, and J. H. Byrne, J. Neurophysiol. 66, 2107-2124 (1991)] has been shown to possess seven coexisting limit cycle solutions at a given parameter set [Canavier et al., J. Neurophysiol 69, 2252-2259 (1993); 72, 872-882 (1994)]. These solutions are unique in that the limit cycles are concentric in the space of the slow variables. We examine the origin of these solutions using a minimal 4-variable bursting cell model. Poincaré maps are constructed using a saddle-node bifurcation of a fast subsystem such as our Poincaré section. This bifurcation defines a threshold between the active and silent phases of the burst cycle in the space of the slow variables. The maps identify parameter spaces with single limit cycles, multiple limit cycles, and two types of chaotic bursting. To investigate the dynamical features which underlie the unique shape of the maps, the maps are further decomposed into two submaps which describe the solution trajectories during the active and silent phases of a single burst. From these findings we postulate several necessary criteria for a bursting model to possess multiple stable concentric limit cycles. These criteria are demonstrated in a generalized 3-variable model. Finally, using a less direct numerical procedure, similar return maps are calculated for the original complex model [C. C. Canavier, J. W. Clark, and J. H. Byrne, J. Neurophysiol. 66, 2107-2124 (1991)], with the resulting mappings appearing qualitatively similar to those of our 4-variable model. These multistable concentric bursting solutions cannot occur in a bursting model with one slow variable. This type of multistability arises when a bursting system has two or more slow variables and is viewed as an essentially second-order system which receives discrete perturbations in a state-dependent manner.

  9. Astrophysical tests of modified gravity: Constraints from distance indicators in the nearby universe

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Bhuvnesh; Vikram, Vinu [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States); Sakstein, Jeremy [Department of Applied Mathematics and Theoretical Physics, Cambridge CB3 0WA (United Kingdom)

    2013-12-10

    We use distance measurements in the nearby universe to carry out new tests of gravity, surpassing other astrophysical tests by over two orders of magnitude for chameleon theories. The three nearby distance indicators—cepheids, tip of the red giant branch (TRGB) stars, and water masers—operate in gravitational fields of widely different strengths. This enables tests of scalar-tensor gravity theories because they are screened from enhanced forces to different extents. Inferred distances from cepheids and TRGB stars are altered (in opposite directions) over a range of chameleon gravity theory parameters well below the sensitivity of cosmological probes. Using published data, we have compared cepheid and TRGB distances in a sample of unscreened dwarf galaxies within 10 Mpc. We use a comparable set of screened galaxies as a control sample. We find no evidence for the order unity force enhancements expected in these theories. Using a two-parameter description of the models (the coupling strength and background field value), we obtain constraints on both the chameleon and symmetron screening scenarios. In particular we show that f(R) models with background field values f {sub R0} above 5 × 10{sup –7} are ruled out at the 95% confidence level. We also compare TRGB and maser distances to the galaxy NGC 4258 as a second test for larger field values. While there are several approximations and caveats in our study, our analysis demonstrates the power of gravity tests in the local universe. We discuss the prospects for additional improved tests with future observations.

  10. Language Learning Activities of Distance EFL Learners in the Turkish Open Education System as the Indicator of Their Learner Autonomy

    Science.gov (United States)

    Altunay, Dilek

    2013-01-01

    This study investigates the noncompulsory language learning activities performed by a group of distance EFL learners in the Turkish Open Education System. Performance of these activities has been considered as an indicator of their learner autonomy. The data were collected through an online questionnaire and interviews. The study shows that in…

  11. A Burst to See

    Science.gov (United States)

    2008-04-01

    On 19 March, Nature was particularly generous and provided astronomers with the wealth of four gamma-ray bursts on the same day. But that was not all: one of them is the most luminous object ever observed in the Universe. Despite being located in a distant galaxy, billions of light years away, it was so bright that it could have been seen, for a brief while, with the unaided eye. ESO PR Photo 08a/08 ESO PR Photo 08a/08 The REM Telescope and TORTORA Camera Gamma-ray bursts (GRBs) are short flashes of energetic gamma-rays lasting from less than a second to several minutes. They release a tremendous quantity of energy in this short time making them the most powerful events since the Big Bang. It is now widely accepted that the majority of the gamma-ray bursts signal the explosion of very massive, highly evolved stars that collapse into black holes. Gamma-ray bursts, which are invisible to our eyes, are discovered by telescopes in space. After releasing their intense burst of high-energy radiation, they become detectable for a short while in the optical and in the near-infrared. This 'afterglow' fades very rapidly, making detailed analysis possible for only a few hours after the gamma-ray detection. This analysis is important in particular in order to determine the GRB's distance and, hence, intrinsic brightness. The gamma-ray burst GRB 080319B was detected by the NASA/STFC/ASI Swift satellite. "It was so bright that it almost blinded the Swift instruments for a while," says Guido Chincarini, Italian principal investigator of the mission. A bright optical counterpart was soon identified in the Boötes Constellation (the "Bear Driver" or "Herdsman"). A host of ground-based telescopes reacted promptly to study this new object in the sky. In particular, the optical emission was detected by a few wide-field cameras on telescopes that constantly monitor a large fraction of the sky, including the TORTORA camera in symbiosis with the 0.6-m REM telescope located at La Silla

  12. J-band Red Giant Branch Tip Magnitudes for the Distance Indicator

    Science.gov (United States)

    Lee, Hyun-chul; Garcia, Cedar; Pena, Ivana

    2017-12-01

    The tip of the red giant branch is one of the widely used distance measurement methods for the relatively nearby galaxies where the bright individual stars are resolved. Most of the earlier works have used the Photometry in the I-band such as HST ACS/WFC F814W or F850LP for the RGB tip method. Here we look into the RGB tip magnitudes in J-band such as HST WFC3/IR F110W and JWST NIRCam/WF F115W for a wide range of age and metallicity. We find that the J-band (HST WFC3/IR F110W and JWST NIRCam/WF F115W) RGB tip magnitudes do not significantly change compared to that of the I-band (HST ACS/WFC F814W, F850LP) for a wide range of metallicity at given age. Moreover, HST WFC3/IR F110W RGB tip magnitudes stay constant within 0.005 magnitudes for stellar populations with old ages (age > 5 Gyr) at given metallicity.

  13. New conformity indices based on the calculation of distances between the target volume and the volume of reference isodose

    Science.gov (United States)

    Park, J M; Park, S-Y; Ye, S-J; Kim, J H; Carlson, J

    2014-01-01

    Objective: To present conformity indices (CIs) based on the distance differences between the target volume (TV) and the volume of reference isodose (VRI). Methods: The points on the three-dimensional surfaces of the TV and the VRI were generated. Then, the averaged distances between the points on the TV and the VRI were calculated (CIdistance). The performance of the presented CIs were evaluated by analysing six situations, which were a perfect match, an expansion and a reduction of the distance from the centroid to the VRI compared with the distance from the centroid to the TV by 10%, a lateral shift of the VRI by 3 cm, a rotation of the VRI by 45° and a spherical-shaped VRI having the same volume as the TV. The presented CIs were applied to the clinical prostate and head and neck (H&N) plans. Results: For the perfect match, CIdistance was 0 with 0 as the standard deviation (SD). When expanding and reducing, CIdistance was 10 and −10 with SDs 11. The average value of the CIdistance in the prostate and H&N plans was 0.13 ± 7.44 and 6.04 ± 23.27, respectively. Conclusion: The performance of the CIdistance was equal or better than those of the conventional CIs. Advances in knowledge: The evaluation of target conformity by the distances between the surface of the TV and the VRI could be more accurate than evaluation with volume information. PMID:25225915

  14. LANGUAGE LEARNING ACTIVITIES OF DISTANCE EFL LEARNERS IN THE TURKISH OPEN EDUCATION SYSTEM AS THE INDICATOR OF THEIR LEARNER AUTONOMY

    Directory of Open Access Journals (Sweden)

    Dilek ALTUNAY

    2013-10-01

    Full Text Available This study investigates the noncompulsory language learning activities performed by a group of distance EFL learners in the Turkish Open Education System. Performance of these activities has been considered as an indicator of their learner autonomy. The data were collected through an online questionnaire and interviews. The study shows that in general learners do not demonstrate autonomous language learning behaviour. They prefer learning English in a relaxed environment particularly by engaging in entertaining activities, and through note-taking. However, they do not have sufficient interaction with their facilitator, other learners or speakers. Although the participants are distance learners, they do not prefer Internet-based activities. Conditions stemming from adulthood, lack of skills necessary to perform an activity, lack of awareness of some activities and learners’ experiences in their previous years of education are some of the reasons for their unautonomous behaviour. The article also includes suggestions for teaching and future research.

  15. Observations of Gamma-Ray Bursts

    Science.gov (United States)

    Fishman, Gerald J.

    1999-01-01

    Gamma-ray bursts are now generally believed to originate from cosmological distances and represent the largest known explosions in the Universe. These lectures will describe the temporal and spectral characteristic of gamma-ray bursts, their intensity and sky distribution, and other observed characteristics in the gamma-ray region, primarily from data obtained with the BATSE experiment on the Compton Observatory. A summary of recent discoveries and observations in other wavelength regions will also be presented, along with their implications for models of the burst emission mechanism. Various possibilities and models for the energy source(s) of gamma-ray bursts will be described.

  16. The Double Firing Burst

    Science.gov (United States)

    2008-09-01

    this nearly head-on alignment to occur is only about once a decade," added his colleague Cristiano Guidorzi. GRB 080319B was detected by the NASA/STFC/ASI Swift satellite towards the constellation of Boötes, the "Herdsman". A host of ground-based telescopes reacted promptly to study this new object in the sky, including ESO's Very Large Telescope, which was the first to provide the distance of the object, 7.5 billion light-years. The visible light from the burst was detected by a handful of wide-field cameras worldwide that are mounted on telescopes constantly monitoring a large fraction of the sky. One of these was the TORTORA camera mounted on the 0.6-m REM telescope at ESO's La Silla Observatory (ESO 26/07). TORTORA's rapid imaging provides the most detailed look yet at the visible light associated with the initial blast of a gamma-ray burst. "We've been waiting a long time for this one," says TORTORA senior scientist Grigory Beskin of Russia's Special Astrophysical Observatory. The data collected simultaneously by TORTORA and the Swift satellite allowed astronomers to explain the properties of this burst.

  17. An Artificial Intelligence Classification Tool and Its Application to Gamma-Ray Bursts

    Science.gov (United States)

    Hakkila, Jon; Haglin, David J.; Roiger, Richard J.; Giblin, Timothy; Paciesas, William S.; Pendleton, Geoffrey N.; Mallozzi, Robert S.

    2004-01-01

    Despite being the most energetic phenomenon in the known universe, the astrophysics of gamma-ray bursts (GRBs) has still proven difficult to understand. It has only been within the past five years that the GRB distance scale has been firmly established, on the basis of a few dozen bursts with x-ray, optical, and radio afterglows. The afterglows indicate source redshifts of z=1 to z=5, total energy outputs of roughly 10(exp 52) ergs, and energy confined to the far x-ray to near gamma-ray regime of the electromagnetic spectrum. The multi-wavelength afterglow observations have thus far provided more insight on the nature of the GRB mechanism than the GRB observations; far more papers have been written about the few observed gamma-ray burst afterglows in the past few years than about the thousands of detected gamma-ray bursts. One reason the GRB central engine is still so poorly understood is that GRBs have complex, overlapping characteristics that do not appear to be produced by one homogeneous process. At least two subclasses have been found on the basis of duration, spectral hardness, and fluence (time integrated flux); Class 1 bursts are softer, longer, and brighter than Class 2 bursts (with two second durations indicating a rough division). A third GRB subclass, overlapping the other two, has been identified using statistical clustering techniques; Class 3 bursts are intermediate between Class 1 and Class 2 bursts in brightness and duration, but are softer than Class 1 bursts. We are developing a tool to aid scientists in the study of GRB properties. In the process of developing this tool, we are building a large gamma-ray burst classification database. We are also scientifically analyzing some GRB data as we develop the tool. Tool development thus proceeds in tandem with the dataset for which it is being designed. The tool invokes a modified KDD (Knowledge Discovery in Databases) process, which is described as follows.

  18. Metric distances between hippocampal shapes indicate different rates of change over time in nondemented and demented subjects.

    Science.gov (United States)

    Ceyhan, Elvan; Beg, Mirza Faisal; Ceritoğlu, Can; Wang, Lei; Morris, John C; Csernansky, John G; Miller, Michael I; Ratnanather, J Tilak

    2012-10-01

    In this article, we use longitudinal morphometry (shape and size) measures of hippocampus in subjects with mild dementia of Alzheimer type (DAT) and nondemented controls in logistic discrimination. The morphometric measures we use are volume and metric distance measures at baseline and follow-up (two years apart from baseline). Morphometric differences with respect to a template hippocampus were measured by the metric distance obtained from the large deformation diffeomorphic metric mapping (LDDMM) algorithm. LDDMM assigns metric distances on the space of anatomical images, thereby allowing for the direct comparison and quantization of morphometric changes. We also apply principal component analysis (PCA) on volume and metric distance measures to obtain principal components that capture some salient aspect of morphometry. We construct classifiers based on logistic regression to distinguish diseased and healthy hippocampi (hence potentially diagnose the mild form of DAT). We consider logistic classifiers based on volume and metric distance change over time (from baseline to follow-up), on the raw volumes and metric distances, and on principal components from various types of PCA analysis. We provide a detailed comparison of the performance of these classifiers and guidelines for their practical use. Moreover, combining the information conveyed by volume and metric distance measures by PCA can provide a better biomarker for detection of dementia compared to volume, metric distance, or both.

  19. Observing a Burst with Sunglasses

    Science.gov (United States)

    2003-11-01

    Unique Five-Week VLT Study of the Polarisation of a Gamma-Ray Burst Afterglow "Gamma-ray bursts (GRBs)" are certainly amongst the most dramatic events known in astrophysics. These short flashes of energetic gamma-rays, first detected in the late 1960's by military satellites, last from less than one second to several minutes. GRBs have been found to be situated at extremely large ("cosmological") distances. The energy released in a few seconds during such an event is larger than that of the Sun during its entire lifetime of more than 10,000 million years. The GRBs are indeed the most powerful events since the Big Bang known in the Universe, cf. ESO PR 08/99 and ESO PR 20/00. During the past years circumstantial evidence has mounted that GRBs signal the collapse of extremely massive stars, the so-called hypernovae. This was finally demonstrated some months ago when astronomers, using the FORS instrument on ESO's Very Large Telescope (VLT), documented in unprecedented detail the changes in the spectrum of the light source ("the optical afterglow") of the gamma-ray burst GRB 030329 (cf. ESO PR 16/03). A conclusive and direct link between cosmological gamma-ray bursts and explosions of very massive stars was provided on this occasion. Gamma-Ray Burst GRB 030329 was discovered on March 29, 2003 by NASA's High Energy Transient Explorer spacecraft. Follow-up observations with the UVES spectrograph at the 8.2-m VLT KUEYEN telescope at the Paranal Observatory (Chile) showed the burst to have a redshift of 0.1685 [1]. This corresponds to a distance of about 2,650 million light-years, making GRB 030329 the second-nearest long-duration GRB ever detected. The proximity of GRB 030329 resulted in very bright afterglow emission, permitting the most extensive follow-up observations of any afterglow to date. A team of astronomers [2] led by Jochen Greiner of the Max-Planck-Institut für extraterrestrische Physik (Germany) decided to make use of this unique opportunity to study the

  20. Walking Behavior of Zoo Elephants: Associations between GPS-Measured Daily Walking Distances and Environmental Factors, Social Factors, and Welfare Indicators

    Science.gov (United States)

    Holdgate, Matthew R.; Meehan, Cheryl L.; Hogan, Jennifer N.; Miller, Lance J.; Soltis, Joseph; Andrews, Jeff; Shepherdson, David J.

    2016-01-01

    Research with humans and other animals suggests that walking benefits physical health. Perhaps because these links have been demonstrated in other species, it has been suggested that walking is important to elephant welfare, and that zoo elephant exhibits should be designed to allow for more walking. Our study is the first to address this suggestion empirically by measuring the mean daily walking distance of elephants in North American zoos, determining the factors that are associated with variations in walking distance, and testing for associations between walking and welfare indicators. We used anklets equipped with GPS data loggers to measure outdoor daily walking distance in 56 adult female African (n = 33) and Asian (n = 23) elephants housed in 30 North American zoos. We collected 259 days of data and determined associations between distance walked and social, housing, management, and demographic factors. Elephants walked an average of 5.3 km/day with no significant difference between species. In our multivariable model, more diverse feeding regimens were correlated with increased walking, and elephants who were fed on a temporally unpredictable feeding schedule walked 1.29 km/day more than elephants fed on a predictable schedule. Distance walked was also positively correlated with an increase in the number of social groupings and negatively correlated with age. We found a small but significant negative correlation between distance walked and nighttime Space Experience, but no other associations between walking distances and exhibit size were found. Finally, distance walked was not related to health or behavioral outcomes including foot health, joint health, body condition, and the performance of stereotypic behavior, suggesting that more research is necessary to determine explicitly how differences in walking may impact elephant welfare. PMID:27414411

  1. Walking Behavior of Zoo Elephants: Associations between GPS-Measured Daily Walking Distances and Environmental Factors, Social Factors, and Welfare Indicators.

    Directory of Open Access Journals (Sweden)

    Matthew R Holdgate

    Full Text Available Research with humans and other animals suggests that walking benefits physical health. Perhaps because these links have been demonstrated in other species, it has been suggested that walking is important to elephant welfare, and that zoo elephant exhibits should be designed to allow for more walking. Our study is the first to address this suggestion empirically by measuring the mean daily walking distance of elephants in North American zoos, determining the factors that are associated with variations in walking distance, and testing for associations between walking and welfare indicators. We used anklets equipped with GPS data loggers to measure outdoor daily walking distance in 56 adult female African (n = 33 and Asian (n = 23 elephants housed in 30 North American zoos. We collected 259 days of data and determined associations between distance walked and social, housing, management, and demographic factors. Elephants walked an average of 5.3 km/day with no significant difference between species. In our multivariable model, more diverse feeding regimens were correlated with increased walking, and elephants who were fed on a temporally unpredictable feeding schedule walked 1.29 km/day more than elephants fed on a predictable schedule. Distance walked was also positively correlated with an increase in the number of social groupings and negatively correlated with age. We found a small but significant negative correlation between distance walked and nighttime Space Experience, but no other associations between walking distances and exhibit size were found. Finally, distance walked was not related to health or behavioral outcomes including foot health, joint health, body condition, and the performance of stereotypic behavior, suggesting that more research is necessary to determine explicitly how differences in walking may impact elephant welfare.

  2. Walking Behavior of Zoo Elephants: Associations between GPS-Measured Daily Walking Distances and Environmental Factors, Social Factors, and Welfare Indicators.

    Science.gov (United States)

    Holdgate, Matthew R; Meehan, Cheryl L; Hogan, Jennifer N; Miller, Lance J; Soltis, Joseph; Andrews, Jeff; Shepherdson, David J

    2016-01-01

    Research with humans and other animals suggests that walking benefits physical health. Perhaps because these links have been demonstrated in other species, it has been suggested that walking is important to elephant welfare, and that zoo elephant exhibits should be designed to allow for more walking. Our study is the first to address this suggestion empirically by measuring the mean daily walking distance of elephants in North American zoos, determining the factors that are associated with variations in walking distance, and testing for associations between walking and welfare indicators. We used anklets equipped with GPS data loggers to measure outdoor daily walking distance in 56 adult female African (n = 33) and Asian (n = 23) elephants housed in 30 North American zoos. We collected 259 days of data and determined associations between distance walked and social, housing, management, and demographic factors. Elephants walked an average of 5.3 km/day with no significant difference between species. In our multivariable model, more diverse feeding regimens were correlated with increased walking, and elephants who were fed on a temporally unpredictable feeding schedule walked 1.29 km/day more than elephants fed on a predictable schedule. Distance walked was also positively correlated with an increase in the number of social groupings and negatively correlated with age. We found a small but significant negative correlation between distance walked and nighttime Space Experience, but no other associations between walking distances and exhibit size were found. Finally, distance walked was not related to health or behavioral outcomes including foot health, joint health, body condition, and the performance of stereotypic behavior, suggesting that more research is necessary to determine explicitly how differences in walking may impact elephant welfare.

  3. Fast radio bursts: the last sign of supramassive neutron stars

    OpenAIRE

    Falcke, H.; Rezzolla, L.

    2014-01-01

    Several fast radio bursts have been discovered recently, showing a bright, highly dispersed millisecond radio pulse. The pulses do not repeat and are not associated with a known pulsar or gamma-ray burst. The high dispersion suggests sources at cosmological distances, hence implying an extremely high radio luminosity, far larger than the power of single pulses from a pulsar. We suggest that a fast radio burst represents the final signal of a supramassive rotating neutron star that collapses t...

  4. Unusual Solar Decameter Radio Bursts with High Frequency Cut off

    Science.gov (United States)

    Brazhenko, A. I.; Melnik, V. M.; Frantsuzenko, A. V.; Rucker, H. O.; Panchenko, M.

    2015-03-01

    Solar bursts with high frequency cut off were observed by the URAN-2 radio telescope (Poltava, Ukraine) on 18 August, 2012 in the frequency range 8-32 MHz. Durations of these bursts changed from 30 to 70 s. It is much longer than that for standard type III bursts. Drift rates are much smaller than those of type III bursts are, though much larger than those for decameter type II bursts. In some cases, the drift rate sign changes from the negative to positive one. Some of these bursts have fine structures. Stripes of the fine structures have small drift rates of 20-40 kHz/s. Polarizations of these bursts made about 10 % that apparently indicates that they are generated at the second harmonic of the local plasma frequency. The connection of bursts with the high frequency cut off with compact ejections from the behind-limb active regions is confirmed.

  5. Adaptive Optical Burst Switching

    OpenAIRE

    Bonald, Thomas; Indre, Raluca-Maria; Oueslati, Sara

    2012-01-01

    International audience; We propose a modified version of Optical Burst Switching (OBS) that adapts the size of switched data units to the network load. Specifically, we propose a two-way reservation OBS scheme in which every active source-destination pair attempts to reserve a lightpath and for every successful reservation, transmits an optical burst whose size is proportional to the number of active data flows. We refer to this technique as Adaptive Optical Burst Switching. We prove that the...

  6. Representing distance, consuming distance

    DEFF Research Database (Denmark)

    Larsen, Gunvor Riber

    Title: Representing Distance, Consuming Distance Abstract: Distance is a condition for corporeal and virtual mobilities, for desired and actual travel, but yet it has received relatively little attention as a theoretical entity in its own right. Understandings of and assumptions about distance...... to mobility and its social context. Such an understanding can be approached through representations, as distance is being represented in various ways, most noticeably in maps and through the notions of space and Otherness. The question this talk subsequently asks is whether these representations of distance...

  7. On the nature of gamma-ray burst time dilations

    Science.gov (United States)

    Wijers, Ralph A. M. J.; Paczynski, Bohdan

    1994-01-01

    The recent discovery that faint gamma-ray bursts are stretched in time relative to bright ones has been interpreted as support for cosmological distances: faint bursts have their durations redshifted relative to bright ones. It was pointed out, however, that the relative time stretching can also be produced by an intrinsic correlation bewteen duration and luminosity of gamma-ray bursts in a nearby, bounded distribution. While both models can explain the average amount of time stretching, we find a difference between them in the way the duration distribution of faint bursts deviates from that of bright ones, assuming the luminosity function of gamma-ray bursts is independent of distance. This allows us to distinguish between these two broad classes of model on the basis of the duration distributions of gamma-ray bursts, leading perhaps to an unambiguous determination of the distance scale of gamma-ray bursts. We apply our proposed test to the second Burst and Transient Source Experiment (BATSE) catalog and conclude, with some caution, that the data favor a cosmological interpretation of the time dilation.

  8. Searching gamma-ray bursts for gravitational lensing echoes - Implications for compact dark matter

    Science.gov (United States)

    Nemiroff, R. J.; Norris, J. P.; Wickramasinghe, W. A. D. T.; Horack, J. M.; Kouveliotou, C.; Fishman, G. J.; Meegan, C. A.; Wilson, R. B.; Paciesas, W. S.

    1993-01-01

    The first available 44 gamma-ray bursts (GRBs) detected by the Burst and Transient Source Experiment on board the Compton Gamma-Ray Observatory have been inspected for echo signals following shortly after the main signal. No significant echoes have been found. Echoes would have been expected were the GRBs distant enough and the universe populated with a sufficient density of compact objects composing the dark matter. Constraints on dark matter abundance and GRB redshifts from the present data are presented and discussed. Based on these preliminary results, a universe filled to critical density of compact objects between 10 exp 6.5 and 10 exp 8.1 solar masses are now marginally excluded, or the most likely cosmological distance paradigm for GRBs is not correct. We expect future constraints to be able either to test currently popular cosmological dark matter paradigms or to indicate that GRBs do not lie at cosmological distances.

  9. The Drift Burst Hypothesis

    DEFF Research Database (Denmark)

    Christensen, Kim; Oomen, Roel; Renò, Roberto

    The Drift Burst Hypothesis postulates the existence of short-lived locally explosive trends in the price paths of financial assets. The recent US equity and Treasury flash crashes can be viewed as two high profile manifestations of such dynamics, but we argue that drift bursts of varying magnitude....... We then develop a non-parametric test statistic that allows for the identification of drift bursts from noisy high-frequency data. We apply this methodology to a comprehensive set of tick data and show that drift bursts form an integral part of the price dynamics across equities, fixed income......, currencies and commodities. We find that the majority of identified drift bursts are accompanied by strong price reversals and these can therefore be regarded as “flash crashes” that span brief periods of severe market disruption without any material longer term price impacts....

  10. The Most Remote Gamma-Ray Burst

    Science.gov (United States)

    2000-10-01

    . Technical information about these photos is available below. A gamma-ray burst was detected on January 31, 2000, by an international network of satellites ( Ulysses , NEAR and Konus ) via the InterPlanetary Network (IPN) [2]. It was designated GRB 000131 according to the date of the event. From geometric triangulation by means of the measured, exact arrival times of the signal at the individual satellites, it was possible to determine the direction from which the burst came. It was found to be from a point within a comparatively small sky area (about 50 arcmin 2 or 1/10 of the apparent size of the Moon), just inside the border of the southern constellation Carina (The Keel). Follow-up observations were undertaken by a group of European astronomers [1] with the ESO Very Large Telescope at the Paranal Observatory. A comparison of several exposures with the FORS1 multi-mode instrument at the 8.2-m VLT ANTU telescope during the nights of February 3-4 and 5-6 revealed a faint, point-like object that was fading rapidly - this was identified as the optical counterpart of the gamma-ray burst (the "afterglow"). On the second night, the R-magnitude (brightness) was found to be only 24.4, or 30 million times fainter than visible with the unaided eye in a dark sky. It was also possible to observe it with a camera at the 1.54-m Danish Telescope at the La Silla Observatory , albeit only in a near-infrared band and with a 1-hour exposure. Additional observations were made on February 8 with the SOFI multi-mode instrument at the ESO 3.58-m New Technology Telescope (NTT) at La Silla. The observations were performed partly by the astronomers from the group, partly in "service mode" by ESO staff at La Silla and Paranal. The observations showed that the light from the afterglow was very red, without blue and green light. This indicated a comparatively large distance and, assuming that the light from the explosion would originally have had the same colour (spectral distribution) as that of

  11. A booming economy means a bursting trauma system: association between hospital admission for major injury and indicators of economic activity in a large Canadian health region.

    Science.gov (United States)

    Roberts, Derek J; Das, Debanjana; Mercado, Michelle; Vis, Christine; Kortbeek, John B; Kirkpatrick, Andrew W; Ball, Chad G

    2014-05-01

    Injury epidemiology fluctuates with economic activity in many countries. These relationships remain unclear in Canada. The annual risk of admission for major injury (Injury Severity Score ≥12) to a high-volume, level-1 Canadian trauma center was compared with indicators of economic activity over a 16-year period using linear regression. An increased risk of injured patient admissions was associated with rising mean gross domestic product (GDP [millions of chained 2002 dollars]) (.36 person increase per 100,000 population/$1,000 increase in GDP; P = .001) and annual gasoline prices (.47 person increase per 100,000 population/cent increase in gasoline price; P = .001). Recreation-related vehicle injuries were also associated with economic affluence. The risk of trauma patient mortality with increasing mean annual GDP (P = .72) and gasoline prices (P = .32) remained unchanged. Hospital admissions for major injury, but not trauma patient mortality, were associated with economic activity in a large Canadian health care region. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Optimal Codes for the Burst Erasure Channel

    Science.gov (United States)

    Hamkins, Jon

    2010-01-01

    Deep space communications over noisy channels lead to certain packets that are not decodable. These packets leave gaps, or bursts of erasures, in the data stream. Burst erasure correcting codes overcome this problem. These are forward erasure correcting codes that allow one to recover the missing gaps of data. Much of the recent work on this topic concentrated on Low-Density Parity-Check (LDPC) codes. These are more complicated to encode and decode than Single Parity Check (SPC) codes or Reed-Solomon (RS) codes, and so far have not been able to achieve the theoretical limit for burst erasure protection. A block interleaved maximum distance separable (MDS) code (e.g., an SPC or RS code) offers near-optimal burst erasure protection, in the sense that no other scheme of equal total transmission length and code rate could improve the guaranteed correctible burst erasure length by more than one symbol. The optimality does not depend on the length of the code, i.e., a short MDS code block interleaved to a given length would perform as well as a longer MDS code interleaved to the same overall length. As a result, this approach offers lower decoding complexity with better burst erasure protection compared to other recent designs for the burst erasure channel (e.g., LDPC codes). A limitation of the design is its lack of robustness to channels that have impairments other than burst erasures (e.g., additive white Gaussian noise), making its application best suited for correcting data erasures in layers above the physical layer. The efficiency of a burst erasure code is the length of its burst erasure correction capability divided by the theoretical upper limit on this length. The inefficiency is one minus the efficiency. The illustration compares the inefficiency of interleaved RS codes to Quasi-Cyclic (QC) LDPC codes, Euclidean Geometry (EG) LDPC codes, extended Irregular Repeat Accumulate (eIRA) codes, array codes, and random LDPC codes previously proposed for burst erasure

  13. Larval Behavior and Longevity in the Cold-Water Coral Lophelia pertusa Indicate Potential for Long Distance Dispersal

    Directory of Open Access Journals (Sweden)

    Susanna M. Strömberg

    2017-12-01

    Full Text Available The life cycle of many marine benthic species includes a pelagic larval stage that governs the connectivity between populations. Larval transport is a function of hydrodynamic and biological processes. Knowledge of how larval traits affect dispersal will increase the accuracy of biophysical models used to predict connectivity, and is of paramount importance for management and conservation. This study examines the larval traits of the cold-water coral Lophelia pertusa that forms widespread and highly diverse ecosystems in the deep ocean. We monitored development, swimming behavior, and survival under different environmental conditions. We found that the embryonic development rate doubled when the rearing temperature was increased from normal conditions of 7–8°C to 11–12°C. Pre-competent planulae migrated vertically upwards at a speed of 0.5–0.7 mm s−1 and crossed salinity gradients with a maximum tested difference of 5 psu with no hesitation. At 3 weeks, planulae had a fully developed mouth and started feeding on animal derivatives, picoplankton, and possibly smaller size microalgae. Presence of food significantly altered the swimming pattern, and feeding was corroborated by direct observation. Planulae survived for up to 10 months in a salinity of 25 psu, which together with the vertical migration pattern and feeding indicates that larvae may spend a period of their pelagic phase in the photic zone. After 50 days, larvae were still in a very good condition as deduced by maintained high swimming speed. Survival rate of developed planulae was on average 60% over a 3-month period, and maximum longevity was a full year, in laboratory cultures.

  14. GIS modelling of seismic vulnerability of residential fabrics considering geotechnical, structural, social and physical distance indicators in Tehran city using multi-criteria decision-making (MCDM) techniques

    Science.gov (United States)

    Rezaie, F.; Panahi, M.

    2014-09-01

    The main issue in determining the seismic vulnerability is having a comprehensive view to all probable damages related to earthquake occurrence. Therefore, taking factors such as peak ground acceleration (PGA) in the time of earthquake occurrence, the type of structures, population distribution among different age groups, level of education, the physical distance to a hospitals (or medical care centers), etc. into account and categorized under four indicators of geotechnical, structural, social and physical distance to needed facilities and distance from dangerous ones will provide us with a better and more exact outcome. To this end in this paper using analytic hierarchy process (AHP), the amount of importance of criteria or alternatives are determined and using geographical information system (GIS), the vulnerability of Tehran metropolitan as a result of an earthquake, is studied. This study focuses on the fact that Tehran is surrounded by three active and major faults of the Mosha, North Tehran and Rey. In order to comprehensively determine the vulnerability, three scenarios are developed. In each scenario, seismic vulnerability of different areas in Tehran city is analysed and classified into four levels including high, medium, low and safe. The results show that regarding seismic vulnerability, the faults of Mosha, North Tehran and Rey respectively make 6, 16 and 10% of Tehran area highly vulnerable and also 34, 14 and 27% are safe.

  15. Gamma-Ray Bursts: A Radio Perspective

    Directory of Open Access Journals (Sweden)

    Poonam Chandra

    2016-01-01

    Full Text Available Gamma-ray bursts (GRBs are extremely energetic events at cosmological distances. They provide unique laboratory to investigate fundamental physical processes under extreme conditions. Due to extreme luminosities, GRBs are detectable at very high redshifts and potential tracers of cosmic star formation rate at early epoch. While the launch of Swift and Fermi has increased our understanding of GRBs tremendously, many new questions have opened up. Radio observations of GRBs uniquely probe the energetics and environments of the explosion. However, currently only 30% of the bursts are detected in radio bands. Radio observations with upcoming sensitive telescopes will potentially increase the sample size significantly and allow one to follow the individual bursts for a much longer duration and be able to answer some of the important issues related to true calorimetry, reverse shock emission, and environments around the massive stars exploding as GRBs in the early Universe.

  16. Interplanetary Shocks Lacking Type 2 Radio Bursts

    Science.gov (United States)

    Gopalswamy, N.; Xie, H.; Maekela, P.; Akiyama, S.; Yashiro, S.; Kaiser, M. L.; Howard, R. A.; Bougeret, J.-L.

    2010-01-01

    We report on the radio-emission characteristics of 222 interplanetary (IP) shocks detected by spacecraft at Sun-Earth L1 during solar cycle 23 (1996 to 2006, inclusive). A surprisingly large fraction of the IP shocks (approximately 34%) was radio quiet (RQ; i.e., the shocks lacked type II radio bursts). We examined the properties of coronal mass ejections (CMEs) and soft X-ray flares associated with such RQ shocks and compared them with those of the radio-loud (RL) shocks. The CMEs associated with the RQ shocks were generally slow (average speed approximately 535 km/s) and only approximately 40% of the CMEs were halos. The corresponding numbers for CMEs associated with RL shocks were 1237 km/s and 72%, respectively. Thus, the CME kinetic energy seems to be the deciding factor in the radio-emission properties of shocks. The lower kinetic energy of CMEs associated with RQ shocks is also suggested by the lower peak soft X-ray flux of the associated flares (C3.4 versus M4.7 for RL shocks). CMEs associated with RQ CMEs were generally accelerating within the coronagraph field of view (average acceleration approximately +6.8 m/s (exp 2)), while those associated with RL shocks were decelerating (average acceleration approximately 3.5 m/s (exp 2)). This suggests that many of the RQ shocks formed at large distances from the Sun, typically beyond 10 Rs, consistent with the absence of metric and decameter-hectometric (DH) type II radio bursts. A small fraction of RL shocks had type II radio emission solely in the kilometric (km) wavelength domain. Interestingly, the kinematics of the CMEs associated with the km type II bursts is similar to those of RQ shocks, except that the former are slightly more energetic. Comparison of the shock Mach numbers at 1 AU shows that the RQ shocks are mostly subcritical, suggesting that they were not efficient in accelerating electrons. The Mach number values also indicate that most of these are quasi-perpendicular shocks. The radio-quietness is

  17. Method and apparatus for coherent burst ranging

    Science.gov (United States)

    Wachter, Eric A.; Fisher, Walter G.

    1998-01-01

    A high resolution ranging method is described utilizing a novel modulated waveform, hereafter referred to as coherent burst modulation. In the coherent burst method, high frequency modulation of an acoustic or electromagnetic transmitter, such as a laser, is performed at a modulation frequency. This modulation frequency is transmitted quasi-continuously in the form of interrupted bursts of radiation. Energy from the transmitter is directed onto a target, interacts with the target, and the returning energy is collected. The encoded burst pattern contained in the collected return signal is detected coherently by a receiver that is tuned so as to be principally sensitive to the modulation frequency. The receiver signal is processed to determine target range using both time-of-flight of the burst envelope and phase shift of the high frequency modulation. This approach effectively decouples the maximum unambiguous range and range resolution relationship of earlier methods, thereby allowing high precision ranging to be conducted at arbitrarily long distances using at least one burst of encoded energy. The use of a receiver tuned to the high frequency modulation contained within the coherent burst vastly improves both sensitivity in the detection of the target return signal and rejection of background interferences, such as ambient acoustic or electromagnetic noise. Simultaneous transmission at several energies (or wavelengths) is possible by encoding each energy with a separate modulation frequency or pattern; electronic demodulation at the receiver allows the return pattern for each energy to be monitored independently. Radial velocity of a target can also be determined by monitoring change in phase shift of the return signal as a function of time.

  18. Gamma-ray bursts

    National Research Council Canada - National Science Library

    Gehrels, Neil; Mészáros, Péter

    2012-01-01

    Gamma-ray bursts (GRBs) are bright flashes of gamma rays coming from the cosmos. They occur roughly once per day, typically last for tens of seconds, and are the most luminous events in the universe...

  19. Detection of signature consistent with cosmological time dilation in gamma-ray bursts

    Science.gov (United States)

    Norris, J. P.; Nemiroff, R. J.; Scargle, J. D.; Kouveliotou, C.; Fishman, G. J.; Meegan, C. A.; Paciesas, W. S.; Bonnel, J. T.

    1994-01-01

    If gamma ray bursts are at cosmological distances-as suggested by their isotropic distribution on the sky and by their number-intensity relation-then the burst profiles will be stretched in time, by an amount proportional to the redshift, 1 + Z. We have tested data from the Compton Gamma Ray Observatory's (CGRO's) Burst and Transient Source Experiment (BATSE) for such time dilation. Out of 590 bursts observed by BATSE, 131 bursts were analyzed; bursts with durations shorter than 1.5 s were excluded. We used three tests to compare the timescales of bright and dim bursts, the latter, on average, being more distant than the former. Our measures of timescale are constructed to avoid selection effects arising from intensity differences by rescaling all bursts to fiducial levels of peak intensity and noise bias. (1) We found that the total rescaled count above background for the dim burst ensemble is approximately twice that for the brightest bursts-translating into longer durations for the dim bursts. (2) Wavelet-transform decompositions of the burst profiles confirmed that this dilation operates over a broad range of timescales. (3) Structure on the shortest timescales was examined using a procedure which aligns the highest peaks of profiles from which the noise has been optimally removed using a wavelet threshold technique. In all three tests, the dim bursts are stretched by a factor of approximately 2 relative to the bright ones, over seven octaves of timescale. We calibrated the measurements by dilating synthetic bursts that approximate the temporal characteristics of bright BATSE bursts. Results are consistent with bursts at BATSE's peak-flux completeness limit being at cosmological distances corresponding to Z approximately equal to 1, and thus with independent cosmological interpretations of the BATSE number-intensity relation. Alternative explanations of our results, arising from the nature of physical processes in bursts, are still possible.

  20. GIS modeling of seismic vulnerability of residential fabrics considering geotechnical, structural, social and physical distance indicators in Tehran using multi-criteria decision-making techniques

    Science.gov (United States)

    Rezaie, F.; Panahi, M.

    2015-03-01

    The main issue in determining seismic vulnerability is having a comprehensive view of all probable damages related to earthquake occurrence. Therefore, taking into account factors such as peak ground acceleration at the time of earthquake occurrence, the type of structures, population distribution among different age groups, level of education and the physical distance to hospitals (or medical care centers) and categorizing them into four indicators of geotechnical, structural, social and physical distance to needed facilities and from dangerous ones will provide us with a better and more exact outcome. To this end, this paper uses the analytic hierarchy process to study the importance of criteria or alternatives and uses the geographical information system to study the vulnerability of Tehran to an earthquake. This study focuses on the fact that Tehran is surrounded by three active and major faults: Mosha, North Tehran and Rey. In order to comprehensively determine the vulnerability, three scenarios are developed. In each scenario, seismic vulnerability of different areas in Tehran is analyzed and classified into four levels: high, medium, low and safe. The results show that, regarding seismic vulnerability, the faults of Mosha, North Tehran and Rey make, respectively, 6, 16 and 10% of Tehran highly vulnerable, while 34, 14 and 27% is safe.

  1. Type III Radio Burst Duration and SEP Events

    Science.gov (United States)

    Gopalswamy, N.; Makela, P.; Xie, H.

    2010-01-01

    Long-duration (>15 min), low-frequency (SEP events of solar cycle 23. The Type III durations are distributed symmetrically at 1 MHz yielding a mean value of approximately 33 min (median = 32 min) for the large SEP events. When the SEP events with ground level enhancement (GLE,) are considered, the distribution is essentially unchanged (mean = 32 min, median = 30 min). To test the importance of type III bursts in indicating SEP events, we considered a set of six type III bursts from the same active region (AR 10588) whose durations fit the "long duration" criterion. We analyzed the coronal mass ejections (CMEs), flares, and type II radio bursts associated with the type III bursts. The CMEs were of similar speeds and the flares are also of similar size and duration. All but one of the type III bursts was not associated with a type II burst in the metric or longer wavelength domains. The burst without type II burst also lacked a solar energetic particle (SEP) event at energies >25 MeV. The 1-MHz duration of the type III burst (28 rein) is near the median value of type III durations found for gradual SEP events and ground level enhancement (GLE) events. Yet, there was no sign of SEP events. On the other hand, two other type III bursts from the same active region had similar duration but accompanied by WAVES type 11 bursts; these bursts were also accompanied by SEP events detected by SOHO/ERNE. This study suggests that the type III burst duration may not be a good indicator of an SEP event, consistent with the statistical study of Cliver and Ling (2009, ApJ ).

  2. Large tundra methane burst during onset of freezing

    DEFF Research Database (Denmark)

    Mastepanov, Mikhail; Sigsgaard, Charlotte; Dlugokencky, Edward J.

    2008-01-01

    of global atmospheric methane concentrations indicate that the observed early winter emission burst improves the agreement between the simulated seasonal cycle and atmospheric data from latitudes north of 60N. Our findings suggest that permafrost-associated freeze-in bursts of methane missions from tundra...

  3. CONTENTION RESOLUTION IN OPTICAL BURST SWITCHES USING FIBER DELAY LINE BUFFERS

    Directory of Open Access Journals (Sweden)

    SHIVANGI DUBEY

    2017-02-01

    Full Text Available Optical burst switching (OBS is a circuit switching paradigm that provides very high throughput with reasonable delay. In OBS, the data burst size is not uniform and can be of any length. As the size of the data burst cannot be estimated in advance, several burst assembly techniques have been proposed. In this work, an estimation of data burst is done in advance which enable us to store the data burst. In this process, buffering of the data burst reduces average latency as well as it helps to improve the burst loss probability (BLP. Finally, the investigation indicates that the deflection routing along-with buffering of contending bursts provide an effective solution by decreasing the loss probability nearly 100 times.

  4. Genotyping-by-sequencing approach indicates geographic distance as the main factor affecting genetic structure and gene flow in Brazilian populations of Grapholita molesta (Lepidoptera, Tortricidae).

    Science.gov (United States)

    Silva-Brandão, Karina Lucas; Silva, Oscar Arnaldo Batista Neto E; Brandão, Marcelo Mendes; Omoto, Celso; Sperling, Felix A H

    2015-06-01

    The oriental fruit moth Grapholita molesta is one of the major pests of stone and pome fruit species in Brazil. Here, we applied 1226 SNPs obtained by genotyping-by-sequencing to test whether host species associations or other factors such as geographic distance structured populations of this pest. Populations from the main areas of occurrence of G. molesta were sampled principally from peach and apple orchards. Three main clusters were recovered by neighbor-joining analysis, all defined by geographic proximity between sampling localities. Overall genetic structure inferred by a nonhierarchical amova resulted in a significant ΦST value = 0.19109. Here, we demonstrate for the first time that SNPs gathered by genotyping-by-sequencing can be used to infer genetic structure of a pest insect in Brazil; moreover, our results indicate that those markers are very informative even over a restricted geographic scale. We also demonstrate that host plant association has little effect on genetic structure among Brazilian populations of G. molesta; on the other hand, reduced gene flow promoted by geographic isolation has a stronger impact on population differentiation.

  5. Scientific Applications Performance Evaluation on Burst Buffer

    KAUST Repository

    Markomanolis, George S.

    2017-10-19

    Parallel I/O is an integral component of modern high performance computing, especially in storing and processing very large datasets, such as the case of seismic imaging, CFD, combustion and weather modeling. The storage hierarchy includes nowadays additional layers, the latest being the usage of SSD-based storage as a Burst Buffer for I/O acceleration. We present an in-depth analysis on how to use Burst Buffer for specific cases and how the internal MPI I/O aggregators operate according to the options that the user provides during his job submission. We analyze the performance of a range of I/O intensive scientific applications, at various scales on a large installation of Lustre parallel file system compared to an SSD-based Burst Buffer. Our results show a performance improvement over Lustre when using Burst Buffer. Moreover, we show results from a data hierarchy library which indicate that the standard I/O approaches are not enough to get the expected performance from this technology. The performance gain on the total execution time of the studied applications is between 1.16 and 3 times compared to Lustre. One of the test cases achieved an impressive I/O throughput of 900 GB/s on Burst Buffer.

  6. Distance Learning

    National Research Council Canada - National Science Library

    Braddock, Joseph

    1997-01-01

    A study reviewing the existing Army Distance Learning Plan (ADLP) and current Distance Learning practices, with a focus on the Army's training and educational challenges and the benefits of applying Distance Learning techniques...

  7. Gamma-ray bursts

    CERN Document Server

    Wijers, Ralph A M J; Woosley, Stan

    2012-01-01

    Cosmic gamma ray bursts (GRBs) have fascinated scientists and the public alike since their discovery in the late 1960s. Their story is told here by some of the scientists who participated in their discovery and, after many decades of false starts, solved the problem of their origin. Fourteen chapters by active researchers in the field present a detailed history of the discovery, a comprehensive theoretical description of GRB central engine and emission models, a discussion of GRB host galaxies and a guide to how GRBs can be used as cosmological tools. Observations are grouped into three sets from the satellites CGRO, BeppoSAX and Swift, and followed by a discussion of multi-wavelength observations. This is the first edited volume on GRB astrophysics that presents a fully comprehensive review of the subject. Utilizing the latest research, Gamma-ray Bursts is an essential desktop companion for graduate students and researchers in astrophysics.

  8. Rock burst governance of working face under igneous rock

    Science.gov (United States)

    Chang, Zhenxing; Yu, Yue

    2017-01-01

    As a typical failure phenomenon, rock burst occurs in many mines. It can not only cause the working face to cease production, but also cause serious damage to production equipment, and even result in casualties. To explore how to govern rock burst of working face under igneous rock, the 10416 working face in some mine is taken as engineering background. The supports damaged extensively and rock burst took place when the working face advanced. This paper establishes the mechanical model and conducts theoretical analysis and calculation to predict the fracture and migration mechanism and energy release of the thick hard igneous rock above the working face, and to obtain the advancing distance of the working face when the igneous rock fractures and critical value of the energy when rock burst occurs. Based on the specific conditions of the mine, this paper put forward three kinds of governance measures, which are borehole pressure relief, coal seam water injection and blasting pressure relief.

  9. Probing Intrinsic Properties of Short Gamma-Ray Bursts with Gravitational Waves

    Science.gov (United States)

    Fan, Xilong; Messenger, Christopher; Heng, Ik Siong

    2017-11-01

    Progenitors of short gamma-ray bursts are thought to be neutron stars coalescing with their companion black hole or neutron star, which are one of the main gravitational wave sources. We have devised a Bayesian framework for combining gamma-ray burst and gravitational wave information that allows us to probe short gamma-ray burst luminosities. We show that combined short gamma-ray burst and gravitational wave observations not only improve progenitor distance and inclination angle estimates, they also allow the isotropic luminosities of short gamma-ray bursts to be determined without the need for host galaxy or light-curve information. We characterize our approach by simulating 1000 joint short gamma-ray burst and gravitational wave detections by Advanced LIGO and Advanced Virgo. We show that ˜90 % of the simulations have uncertainties on short gamma-ray burst isotropic luminosity estimates that are within a factor of two of the ideal scenario, where the distance is known exactly. Therefore, isotropic luminosities can be confidently determined for short gamma-ray bursts observed jointly with gravitational waves detected by Advanced LIGO and Advanced Virgo. Planned enhancements to Advanced LIGO will extend its range and likely produce several joint detections of short gamma-ray bursts and gravitational waves. Third-generation gravitational wave detectors will allow for isotropic luminosity estimates for the majority of the short gamma-ray burst population within a redshift of z ˜1 .

  10. Spatial patterns of AFLP diversity in Bulbophyllum occultum (Orchidaceae) indicate long-term refugial isolation in Madagascar and long-distance colonization effects in La Réunion.

    Science.gov (United States)

    Jaros, U; Fischer, G A; Pailler, T; Comes, H P

    2016-05-01

    Bulbophyllum occultum, an epiphytic orchid mainly distributed in the rainforests of (north)eastern Madagascar and La Réunion, represents an interesting model case for testing the effects of anthropogenic vs historical (e.g., climate induced) habitat isolation and long-distance colonization on the genetic structure of plant species with disjunct distributions in the Madagascan region. To this aim, we surveyed amplified fragment length polymorphisms (AFLPs) across 13 populations in Madagascar and nine in La Réunion (206 individuals in total). We found overall high levels of population subdivision (Φ(PT)=0.387) and low within-population diversity (H(E), range: 0.026-0.124), indicating non-equilibrium conditions in a mainly selfing species. There was no impact of recent deforestation (Madagascar) or habitat disturbance (La Réunion) detectable on AFLP diversity. K-means clustering and BARRIER analyses identified multiple gene pools and several genetic breaks, both within and among islands. Inter-island levels of population genetic diversity and subdivision were similar, whereby inter-individual divergence in flower colour explained a significant part of gene pool divergence in La Réunion. Our results suggest that (i) B. occultum persisted across multiple isolated ('refugial') regions along the eastern rainforest corridor of Madagascar over recent climatic cycles and (ii) populations in La Réunion arose from either single or few independent introductions from Madagascar. High selfing rates and sufficient time for genetic drift likely promoted unexpectedly high population genetic and phenotypic (flower colour) differentiation in La Réunion. Overall, this study highlights a strong imprint of history on the genetic structure of a low-gene-dispersing epiphytic orchid from the Madagascan region.

  11. Robust statistical properties of the size of large burst events in AE

    OpenAIRE

    Hush, Philip; Chapman, Sandra C.; Dunlop, M. W.; Watkins, Nicholas W.

    2015-01-01

    Geomagnetic indices provide a comprehensive data set with which to quantify space climate, that is, how the statistical likelihood of activity varies with the solar cycle. We characterize space climate by the AE index burst distribution. Burst sizes are constructed by thresholding the AE time series; a burst is the sum of the excess in the time series for each time interval over which the threshold is exceeded. The distribution of burst sizes is two component with a crossover in behavior at t...

  12. Gamma-Ray Bursts and Cosmology

    Science.gov (United States)

    Norris, Jay P.

    2003-01-01

    The unrivalled, extreme luminosities of gamma-ray bursts (GRBs) make them the favored beacons for sampling the high redshift Universe. To employ GRBs to study the cosmic terrain -- e.g., star and galaxy formation history -- GRB luminosities must be calibrated, and the luminosity function versus redshift must be measured or inferred. Several nascent relationships between gamma-ray temporal or spectral indicators and luminosity or total energy have been reported. These measures promise to further our understanding of GRBs once the connections between the luminosity indicators and GRB jets and emission mechanisms are better elucidated. The current distribution of 33 redshifts determined from host galaxies and afterglows peaks near z $\\sim$ 1, whereas for the full BATSE sample of long bursts, the lag-luminosity relation predicts a broad peak z $\\sim$ 1--4 with a tail to z $\\sim$ 20, in rough agreement with theoretical models based on star formation considerations. For some GRB subclasses and apparently related phenomena -- short bursts, long-lag bursts, and X-ray flashes -- the present information on their redshift distributions is sparse or entirely lacking, and progress is expected in Swift era when prompt alerts become numerous.

  13. Wolf-Rayet stars as gamma-ray burst progenitors

    NARCIS (Netherlands)

    Langer, N.|info:eu-repo/dai/nl/304829498; van Marle, A. -J; Yoon, S.C.|info:eu-repo/dai/nl/266576753

    2010-01-01

    It became clear in the last few years that long gamma-ray bursts are associated with the endpoints of massive star evolution. They occur in star forming regions at cosmological distances (Jakobsson et al., 2005), and are associated with supernova-type energies. The collapsar model explains gamma-ray

  14. Optothermally actuated capillary burst valve

    Science.gov (United States)

    Eriksen, Johan; Bilenberg, Brian; Kristensen, Anders; Marie, Rodolphe

    2017-04-01

    We demonstrate the optothermal actuation of individual capillary burst valves in an all-polymer microfluidic device. The capillary burst valves are realised in a planar design by introducing a fluidic constriction in a microfluidic channel of constant depth. We show that a capillary burst valve can be burst by raising the temperature due to the temperature dependence of the fluid surface tension. We address individual valves by using a local heating platform based on a thin film of near infrared absorber dye embedded in the lid used to seal the microfluidic device [L. H. Thamdrup et al., Nano Lett. 10, 826-832 (2010)]. An individual valve is burst by focusing the laser in its vicinity. We demonstrate the capture of single polystyrene 7 μm beads in the constriction triggered by the bursting of the valve.

  15. Introduction to Optical Burst Switching

    OpenAIRE

    KERNÁCS János; Szilágyi, Szabolcs

    2010-01-01

    Optical Burst Switching (OBS) isconsidered a popular switching paradigm for therealization of all-optical networks due to the balance itoffers between the coarse-grained Optical CircuitSwitching (OSC) and fine-grained Optical PacketSwitching (OPS). Given that the data are switched allopticallyat the burst level, Optical Burst Switchingcombines the transparency of Optical CircuitSwitching with the benefits of statistical multiplexingin Optical Packet Switching.

  16. Gamma-ray bursts.

    Science.gov (United States)

    Gehrels, Neil; Mészáros, Péter

    2012-08-24

    Gamma-ray bursts (GRBs) are bright flashes of gamma rays coming from the cosmos. They occur roughly once per day, typically last for tens of seconds, and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this Review, we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglow.

  17. NEW BURST ASSEMBLY AND SCHEDULING TECHNIQUE FOR OPTICAL BURST SWITCHING NETWORKS

    OpenAIRE

    Kavitha, V.; V.Palanisamy

    2013-01-01

    The Optical Burst Switching is a new switching technology that efficiently utilizes the bandwidth in the optical layer. The key areas to be concentrated in Optical Burst Switching (OBS) networks are the burst assembly and burst scheduling i.e., assignment of wavelengths to the incoming bursts. This study presents a New Burst Assembly and Scheduling (NBAS) technique in a simultaneous multipath transmission for burst loss recovery in OBS networks. A Redundant Burst Segmentation (RBS) is used fo...

  18. Fast radio bursts: the last sign of supramassive neutron stars

    Science.gov (United States)

    Falcke, Heino; Rezzolla, Luciano

    2014-02-01

    Context. Several fast radio bursts have been discovered recently, showing a bright, highly dispersed millisecond radio pulse. The pulses do not repeat and are not associated with a known pulsar or gamma-ray burst. The high dispersion suggests sources at cosmological distances, hence implying an extremely high radio luminosity, far larger than the power of single pulses from a pulsar. Aims: We suggest that a fast radio burst represents the final signal of a supramassive rotating neutron star that collapses to a black hole due to magnetic braking. The neutron star is initially above the critical mass for non-rotating models and is supported by rapid rotation. As magnetic braking constantly reduces the spin, the neutron star will suddenly collapse to a black hole several thousand to million years after its birth. Methods: We discuss several formation scenarios for supramassive neutron stars and estimate the possible observational signatures making use of the results of recent numerical general-relativistic calculations. Results: While the collapse will hide the stellar surface behind an event horizon, the magnetic-field lines will snap violently. This can turn an almost ordinary pulsar into a bright radio "blitzar": accelerated electrons from the travelling magnetic shock dissipate a significant fraction of the magnetosphere and produce a massive radio burst that is observable out to z > 0.7. Only a few per cent of the neutron stars need to be supramassive in order to explain the observed rate. Conclusions: We suggest the intriguing possibility that fast radio bursts might trace the solitary and almost silent formation of stellar mass black holes at high redshifts. These bursts could be an electromagnetic complement to gravitational-wave emission and reveal a new formation and evolutionary channel for black holes and neutron stars that are not seen as gamma-ray bursts. If supramassive neutron stars are formed at birth and not by accretion, radio observations of these

  19. Short duration gamma ray bursts

    Indian Academy of Sciences (India)

    Abstract. After a short review of gamma ray bursts (GRBs), we discuss the physical implications of strong statistical correlations seen among some of the parameters of short duration bursts (90 < 2 s). Finally, we conclude with a brief sketch of a new unified model for long and short GRBs.

  20. Short duration gamma ray bursts

    Indian Academy of Sciences (India)

    Gamma ray bursts (GRBs) are transient extragalactic events appearing randomly in the sky as localized flashes of electromagnetic radiation, consisting predominantly of photons with energy in the range of ~0.1–1 MeV. These sporadic bursts, occurring at the rate of ~600 per year, are isotropically distributed in the sky, ...

  1. SK channels participate in the formation of after burst hyperpolarization and partly inhibit the burst strength of epileptic ictal discharges.

    Science.gov (United States)

    Huang, Yian; Liu, Xu; Wang, Guoxiang; Wang, Yun

    2018-01-01

    rat cortical EEG recordings also exhibited a similar positive correlation between the duration of epileptic burst and after burst depression. Collectively, the results indicate that ABH may serve in the physiological feedback system to reduce the strength of epileptic hyperexcitation, a process in which SK channels are important.

  2. [The effect of anesthetic concentration on burst-suppression of the EEG in rats].

    Science.gov (United States)

    Zhang, Dandan; Jia, Xiaofeng; Ding, Haiyan

    2012-04-01

    The term "burst-suppression" is used to describe the electroencephalogram (EEG) pattern characterized by theta or delta waves, at times intermixed with faster waves, and intervening periods of relative quiescence. Burst-suppression pattern can reflect the seriously suppressed brain activity under deep anesthesia. To investigate the relationship between burst-suppression features and anesthetic concentration, we adopted four straightforward indexes, i. e., burst-suppression ratio (BSR), burst frequency, burst amplitude and suppression amplitude, and used them to analyze the EEG recordings in ten isoflurane-anesthetized rats. It was found that all the four burst-suppression indexes changed along with anesthetic concentration, that BSR and burst amplitude increased with higher concentration of isoflurane while burst frequency and suppression amplitude decreased, and that BSR was the most sensitive and consistent measurement to indicate isoflurane concentration so it constituted a valuable tool for timely evaluation of burst-suppression feature under deep anesthesia. The result also showed that the composition of carrier gas (i. e. pure oxygen vs. mixed oxygen) did not influence the effect of anesthesia significantly; and the four indexes of burst-suppression features could keep relatively stable within 60 min under the isoflurane concentration of 2%. The present study provides quantitative information of burst-suppression features under different anesthetic depth and may help to develop a clinically satisfied system that could quantify the characteristics of EEG and rigorously evaluate the cerebral state of patients.

  3. Bursts de raios gama

    Science.gov (United States)

    Braga, J.

    2003-02-01

    Nos últimos anos, graças principalmente aos dados obtidos pelo Compton Gamma-Ray Observatory e pelo satélite ítalo-holandês BeppoSAX, grandes avanços foram obtidos no nosso conhecimento sobre os fascinantes e enigmáticos fenômenos conhecidos por "bursts"de raios gama. Neste trabalho é feita uma revisão sobre a fenomenologia desses misteriosos objetos e são apresentados os desenvolvimentos recentes nessa área palpitante da astrofísica moderna, ressaltando tanto os resultados observacionais obtidos até o momento quanto os modelos teóricos propostos para explixá-los.

  4. A Near-Infrared Triggered Nanophotosensitizer Inducing Domino Effect on Mitochondrial Reactive Oxygen Species Burst for Cancer Therapy.

    Science.gov (United States)

    Yu, Zhengze; Sun, Qiaoqiao; Pan, Wei; Li, Na; Tang, Bo

    2015-11-24

    Photodynamic therapy (PDT) is a well-established modality for cancer therapy, which locally kills cancer cells when light irradiates a photosensitizer. However, conventional PDT is often limited by the extremely short lifespan and severely limited diffusion distance of reactive oxygen species (ROS) generated by photosensitizer, as well as the penetration depth of visible light activation. Here, we develop a near-infrared (NIR) triggered nanophotosensitizer based on mitochondria targeted titanium dioxide-coated upconversion nanoparticles for PDT against cancer. When irradiated by NIR laser, the nanophotosensitizer could produce ROS in mitochondria, which induced the domino effect on ROS burst. The overproduced ROS accumulated in mitochondria, resulting in mitochondrial collapse and irreversible cell apoptosis. Confocal fluorescence imaging indicated that the mitochondrial targeting and real-time imaging of ROS burst could be achieved in living cells. The complete removal of tumor in vivo confirmed the excellent therapeutic effect of the nanophotosensitizer.

  5. Quantum key based burst confidentiality in optical burst switched networks.

    Science.gov (United States)

    Balamurugan, A M; Sivasubramanian, A

    2014-01-01

    The optical burst switching (OBS) is an emergent result to the technology concern that could achieve a feasible network in future. They are endowed with the ability to meet the bandwidth requirement of those applications that require intensive bandwidth. There are more domains opening up in the OBS that evidently shows their advantages and their capability to face the future network traffic. However, the concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution, and quality of service (QoS). This paper deals with employing RC4 (stream cipher) to encrypt and decrypt bursts thereby ensuring the confidentiality of the burst. Although the use of AES algorithm has already been proposed for the same issue, by contrasting the two algorithms under the parameters of burst encryption and decryption time, end-to-end delay, it was found that RC4 provided better results. This paper looks to provide a better solution for the confidentiality of the burst in OBS networks.

  6. Quantum Key Based Burst Confidentiality in Optical Burst Switched Networks

    Directory of Open Access Journals (Sweden)

    A. M. Balamurugan

    2014-01-01

    Full Text Available The optical burst switching (OBS is an emergent result to the technology concern that could achieve a feasible network in future. They are endowed with the ability to meet the bandwidth requirement of those applications that require intensive bandwidth. There are more domains opening up in the OBS that evidently shows their advantages and their capability to face the future network traffic. However, the concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution, and quality of service (QoS. This paper deals with employing RC4 (stream cipher to encrypt and decrypt bursts thereby ensuring the confidentiality of the burst. Although the use of AES algorithm has already been proposed for the same issue, by contrasting the two algorithms under the parameters of burst encryption and decryption time, end-to-end delay, it was found that RC4 provided better results. This paper looks to provide a better solution for the confidentiality of the burst in OBS networks.

  7. Resistance of mine roadway supports to dynamic loads under conditions of rock burst hazards in the Katowice Mine Union

    Energy Technology Data Exchange (ETDEWEB)

    Filipek, M.; Syrek, B.; Sarnek, R. (Katowickie Gwarectwo Weglowe, Katowice (Poland))

    1988-01-01

    Analyzes 77 seismic events (rock bursts) that occurred in mine roadways in areas not directly influenced by working faces. The roadways were supported by V or LP yielding arched supports spaced at 0.8 to 1.0 m. Rock burst energy is analyzed. Indices used in describing rock burst energy are comparatively evaluated. Support failures caused by rock bursts are described. Rock bursts in coal seams, in the floor and in the roof are analyzed. Formulae used to describe the forecast effects of a rock burst are derived. 7 refs.

  8. Burst Oscillation Studies with NICER

    Science.gov (United States)

    Mahmoodifar, Simin; Strohmayer, Tod E.

    2017-08-01

    Type I X-ray bursts are thermonuclear flashes observed from the surfaces of accreting neutron stars in Low Mass X-ray Binaries. Oscillations have been observed during the rise and/or decay of some of these X-ray bursts. Those seen during the rise can be well explained by a spreading hot spot model, but large amplitude oscillations in the decay phase remain mysterious because of the absence of a clear-cut source of asymmetry. Here we present the results of our computations of the light curves and amplitudes of oscillations in X-ray burst models that realistically account for both flame spreading and subsequent cooling. For the cooling phase of the burst we use two simple phenomenological models. The first considers asymmetric cooling that can achieve high amplitudes in the tail. The second considers a sustained temperature pattern on the stellar surface that is produced by r-modes propagating in the surface fluid ocean of the star. We will present some simulated burst light curves/spectra using these models and NICER response files, and will show the capabilities of NICER to detect and study burst oscillations. NICER will enable us to study burst oscillations in the energy band below ~3 keV, where there has been no previous measurements of these phenomena.

  9. Transient optical emission from the error box of the gamma-ray burst of 28 February 1997

    DEFF Research Database (Denmark)

    van Paradijs, J.; Groot, P.J.; Galama, T.

    1997-01-01

    For almost a quarter of a century(1), the origin of gamma-ray bursts-brief, energetic bursts of high-energy photons-has remained unknown. The detection of a counterpart at another wavelength has long been thought to be a key to understanding the nature of these bursts (see, for example, ref. 2......), but intensive searches have not revealed such a counterpart. The distribution and properties of the bursts(3) are explained naturally if they lie at cosmological distances (a few Gpc)(4), but there is a countervailing view that they are relatively local objects(5), perhaps distributed in a very large halo...... around our Galaxy. Here we report the detection of a transient and fading optical source in the error box associated with the burst GRB970228, less than 21 hours after the burst(6,7). The optical transient appears to be associated with a faint galaxy(7,8), suggesting that the burst occurred...

  10. Properties of gamma-ray burst progenitor stars.

    Science.gov (United States)

    Kumar, Pawan; Narayan, Ramesh; Johnson, Jarrett L

    2008-07-18

    We determined some basic properties of stars that produce spectacular gamma-ray bursts at the end of their lives. We assumed that accretion of the outer portion of the stellar core by a central black hole fuels the prompt emission and that fall-back and accretion of the stellar envelope later produce the plateau in the x-ray light curve seen in some bursts. Using x-ray data for three bursts, we estimated the radius of the stellar core to be approximately (1 - 3) x 10(10) cm and that of the stellar envelope to be approximately (1 - 2) x 10(11) cm. The density profile in the envelope is fairly shallow, with rho approximately r(-2) (where rho is density and r is distance from the center of the explosion). The rotation speeds of the core and envelope are approximately 0.05 and approximately 0.2 of the local Keplerian speed, respectively.

  11. Distribution of forces and frequency of seismic activity close to a caved face liable to rock bursts

    Energy Technology Data Exchange (ETDEWEB)

    Syrek, B.

    1985-01-01

    The average force distribution and frequency spread of seismic activity as a function of the distance from a face with stowing or caving are investigated. The results obtained close to faces not liable to rock burst are compared with those of faces having a high risk of rock burst and interesting possibilities are demonstrated for assessing the danger of rock bursts as well as the validity of caving. 4 references.

  12. Numerical simulations of trailing vortex bursting

    Science.gov (United States)

    Beran, Philip S.

    1987-01-01

    Solutions of the steady-state Navier-Stokes equations for the axisymmetric bursting of a laminar trailing vortex are computed with Newton's method and the pseudo-arc length continuation method for wide ranges of vortex strength and Reynolds number. The results indicate that a trailing vortex can undergo a transition from a state in which the core slowly diffuses to a state marked by large amplitude, spatial oscillations of core radius and core axial velocity. At the transition point the core grows rapidly in size. This event is interpreted as vortex bursting. The results also suggest that when the maximum core swirl velocity is sufficiently large the centerline axial flow downstream of transition will be reversed.

  13. Management options in thoracolumbar burst fractures.

    Science.gov (United States)

    Hitchon, P W; Torner, J C; Haddad, S F; Follett, K A

    1998-06-01

    Both surgery and recumbency have been adopted in the treatment of spinal fractures. Herein we present the indications for each, and our experience with thoracolumbar junction (T12, L1 and L2) burst fractures. Sixty-eight patients with thoracolumbar burst fractures were treated operatively in 36 cases, and nonoperatively in 32 with recumbency for 1-6 weeks. Treatment was based on clinical and radiological criteria. Eighty-one percent of the recumbency patients, but only 14% of the surgical patients were intact on admission. Patients were followed for a mean+/-SD of 9+/-10 months in the recumbency group, and 21+/-21 months in the surgical group. Neurological improvement and progressive angular deformity occurred in both groups. The cost of recumbency in our patients was nearly half that of those who required surgery, though the length of hospitalization between the two groups was similar at 1 month +/-2 weeks. The above study emphasizes that the selection of operative versus nonoperative treatment in burst fractures should not be random but based on clinical as well as radiological criteria. Recumbency is favored in patients who are intact, with angular deformity less than 20 degrees , a residual spinal canal greater than 50% of normal, and an anterior body height exceeding 50% of the posterior height. Surgical intervention is generally indicated in patients with partial neurological deficit, and those with severe instability.

  14. Real-time observation of liposome bursting induced by acetonitrile.

    Science.gov (United States)

    Yoshida, Kazunari; Horii, Keitaro; Fujii, Yasuhiro; Nishio, Izumi

    2014-10-06

    We show the bursting process of dioleoylphosphatidylcholine (DOPC) liposomes in response to the addition of acetonitrile, a small toxic molecule widely used in the fields of chemistry and industry. The percentage of destroyed liposomes is reduced upon decreasing the acetonitrile fraction in the aqueous solution and vesicle bursting is not observed at volume ratios of 4:6 and below. This indicates that a high fraction of acetonitrile causes the bursting of liposomes, and it is proposed that this occurs through insertion of the molecules into outer leaflet of the lipid bilayer. The elapsed time between initial addition of acetonitrile and liposome bursting at each vesicle is also measured and demonstrated to be dependent on the volume fraction of acetonitrile and the vesicle size. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Wake bursting: A computational and experimental investigation for application to high-lift multielement airfoil design

    Science.gov (United States)

    Pomeroy, Brent William

    environments and the weaknesses of computational solvers. Results for a three-element airfoil, consisting of a main element and a double-slotted flap, were determined using various experimental methods. Experimental results included aerodynamic polars, flow visualization, and wake surveys with both split-film and 7-hole probes. The split-film probe yielded two-dimensional unsteady velocity measurements while the 7-hole probe was use to capture time-averaged velocity vector, static pressure, and total pressure. The burst-wake region consisted of increased turbulence intensities and extremely-high turbulence production when compared to the flow outside of the wake. An increase in wake thickness with increasing downstream distance was captured from each probe, and the relationship between the wake thickness and freestream conditions was established. Low Reynolds numbers and increased angle of attack yielded the thickest wakes of all tested freestream conditions. In addition, flaps with extremely small gap sizes also yielded increased wake bursting than the large-gap airfoils. In general, minimal differences in the burst-wake flowfield were observed for small- or large-overhang simulations, and the results are found in the experiment. Three novel criterion are proposed such that burst-wake flowfields can be readily compared to other flowfields. These thresholds are applied to determine the existence of wake bursting, the spatial point at which the wake bursts, and the severity of the wake bursting. Two-dimensional computational results were captured for low-order and higher-order methods including both a panel code and a RANS program. In general, the RANS solver indicated larger and thicker wakes than the wakes predicted by the panel code or captured in the wake surveys. This result of larger and thicker wakes was found to be independent of the selected turbulence model. Further investigation suggested a large vortex resulted from the junction between the airfoil and the wind

  16. 30 CFR 57.3461 - Rock bursts.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Rock bursts. 57.3461 Section 57.3461 Mineral...-Underground Only § 57.3461 Rock bursts. (a) Operators of mines which have experienced a rock burst shall— (1) Within twenty four hours report to the nearest MSHA office each rock burst which: (i) Causes persons to...

  17. Analysis of the Difficulty and Discrimination Indices of Multiple-Choice Questions According to Cognitive Levels in an Open and Distance Learning Context

    Science.gov (United States)

    Koçdar, Serpil; Karadag, Nejdet; Sahin, Murat Dogan

    2016-01-01

    This is a descriptive study which intends to determine whether the difficulty and discrimination indices of the multiple-choice questions show differences according to cognitive levels of the Bloom's Taxonomy, which are used in the exams of the courses in a business administration bachelor's degree program offered through open and distance…

  18. Gamma-Ray Bursts: Characteristics and Prospects

    Science.gov (United States)

    Azzam, W. J.; Zitouni, H.; Guessoum, N.

    2017-06-01

    Gamma-ray bursts (GRBs) are the most powerful explosions in the universe. They have remained the object of intense research ever since their discovery was declassified in the early 1970s. Several space-borne missions have been dedicated to their study, including the Compton Gamma-Ray Burst Observatory (CGRO) in the 1990s and the current Swift and Fermi satellites. However, despite several decades of focused research, the precise mechanisms behind these enigmatic explosions have not been fully established. In the first part of this paper, we review what is currently known about GRBs. This includes: GRB light-curves and spectra; the different progenitor models, i.e., the "collapsar" and "merger" models; and the afterglow characteristics, including external shocks and the surrounding medium. In the second part of the paper, we present our work, which focuses on utilizing GRBs as cosmological probes. GRBs are ideal cosmological tools, because they have been observed to great distances (redshifts up to z = 9.4) and their radiation is unencumbered by any intervening dust. Although GRBs are not standard candles, the discovery of several energy and luminosity correlations, like the Amati relation which correlates the intrinsic spectral peak energy, Ep,i to the equivalent isotropic energy, Eiso , has ushered in a new era in which GRBs are used to investigate cosmological issues like the star formation rate and the value of the matter-density parameter, ΩM.

  19. Decameter Type III-Like Bursts

    Science.gov (United States)

    Melnik, V. N.; Konovalenko, A. A.; Rutkevych, B. P.; Rucker, H. O.; Dorovskyy, V. V.; Abranin, E. P.; Lecacheux, A.; Brazhenko, A. I.; Stanislavskyy, A. A.

    2007-12-01

    Starting from 1960s Type III-like bursts (Type III bursts with high drift rates) in a wide frequency range from 300 to 950MHz have been observed. These new bursts observed at certain frequency being compared to the usual Type III bursts at the same frequency show similar behaviour but feature frequency drift 2-6 times higher than the normal bursts. In this paper we report the first observations of Type III-like bursts in decameter range, carried out during summer campaigns 2002 - 2004 at UTR-2 radio telescope. The circular polarization of the bursts was measured by the radio telescope URAN-2 in 2004. The observed bursts are analyzed and compared with usual Type III bursts in the decameter range. From the analysis of over 1100 Type III-like bursts, their main parameters have been found. Characteristic feature of the observed bursts is similar to Type III-like bursts at other frequencies, i.e. measured drift rates (5-10 MHz/s) of this bursts are few times larger than that for usual Type III bursts, and their durations (1-2 s) are few times smaller than that for usual Type III bursts in this frequency band.

  20. Light Dawns on Dark Gamma-ray Bursts

    Science.gov (United States)

    2010-12-01

    Gamma-ray bursts are among the most energetic events in the Universe, but some appear curiously faint in visible light. The biggest study to date of these so-called dark gamma-ray bursts, using the GROND instrument on the 2.2-metre MPG/ESO telescope at La Silla in Chile, has found that these gigantic explosions don't require exotic explanations. Their faintness is now fully explained by a combination of causes, the most important of which is the presence of dust between the Earth and the explosion. Gamma-ray bursts (GRBs), fleeting events that last from less than a second to several minutes, are detected by orbiting observatories that can pick up their high energy radiation. Thirteen years ago, however, astronomers discovered a longer-lasting stream of less energetic radiation coming from these violent outbursts, which can last for weeks or even years after the initial explosion. Astronomers call this the burst's afterglow. While all gamma-ray bursts [1] have afterglows that give off X-rays, only about half of them were found to give off visible light, with the rest remaining mysteriously dark. Some astronomers suspected that these dark afterglows could be examples of a whole new class of gamma-ray bursts, while others thought that they might all be at very great distances. Previous studies had suggested that obscuring dust between the burst and us might also explain why they were so dim. "Studying afterglows is vital to further our understanding of the objects that become gamma-ray bursts and what they tell us about star formation in the early Universe," says the study's lead author Jochen Greiner from the Max-Planck Institute for Extraterrestrial Physics in Garching bei München, Germany. NASA launched the Swift satellite at the end of 2004. From its orbit above the Earth's atmosphere it can detect gamma-ray bursts and immediately relay their positions to other observatories so that the afterglows could be studied. In the new study, astronomers combined Swift

  1. Heterogeneity in Short Gamma-Ray Bursts

    Science.gov (United States)

    Norris, Jay P.; Gehrels Neil; Scargle, Jeffrey D.

    2011-01-01

    We analyze the Swift/BAT sample of short gamma-ray bursts, using an objective Bayesian Block procedure to extract temporal descriptors of the bursts' initial pulse complexes (IPCs). The sample comprises 12 and 41 bursts with and without extended emission (EE) components, respectively. IPCs of non-EE bursts are dominated by single pulse structures, while EE bursts tend to have two or more pulse structures. The medians of characteristic timescales - durations, pulse structure widths, and peak intervals - for EE bursts are factors of approx 2-3 longer than for non-EE bursts. A trend previously reported by Hakkila and colleagues unifying long and short bursts - the anti-correlation of pulse intensity and width - continues in the two short burst groups, with non-EE bursts extending to more intense, narrower pulses. In addition we find that preceding and succeeding pulse intensities are anti-correlated with pulse interval. We also examine the short burst X-ray afterglows as observed by the Swift/XRT. The median flux of the initial XRT detections for EE bursts (approx 6 X 10(exp -10) erg / sq cm/ s) is approx > 20 x brighter than for non-EE bursts, and the median X-ray afterglow duration for EE bursts (approx 60,000 s) is approx 30 x longer than for non-EE bursts. The tendency for EE bursts toward longer prompt-emission timescales and higher initial X-ray afterglow fluxes implies larger energy injections powering the afterglows. The longer-lasting X-ray afterglows of EE bursts may suggest that a significant fraction explode into more dense environments than non-EE bursts, or that the sometimes-dominant EE component efficiently p()wers the afterglow. Combined, these results favor different progenitors for EE and non-EE short bursts.

  2. A Retroactive-Burst Framework for Automated Intrusion Response System

    Directory of Open Access Journals (Sweden)

    Alireza Shameli-Sendi

    2013-01-01

    Full Text Available The aim of this paper is to present an adaptive and cost-sensitive model to prevent security intrusions. In most automated intrusion response systems, response selection is performed locally based on current threat without using the knowledge of attacks history. Another challenge is that a group of responses are applied without any feedback mechanism to measure the response effect. We address these problems through retroactive-burst execution of responses and a Response Coordinator (RC mechanism, the main contributions of this work. The retroactive-burst execution consists of several burst executions of responses with, at the end of each burst, a mechanism for measuring the effectiveness of the applied responses by the risk assessment component. The appropriate combination of responses must be considered for each burst execution to mitigate the progress of the attack without necessarily running the next round of responses, because of the impact on legitimate users. In the proposed model, there is a multilevel response mechanism. To indicate which level is appropriate to apply based on the retroactive-burst execution, we get help from a Response Coordinator mechanism. The applied responses can improve the health of Applications, Kernel, Local Services, Network Services, and Physical Status. Based on these indexes, the RC gives a general overview of an attacker’s goal in a distributed environment.

  3. Speech Clarity Index (Ψ): A Distance-Based Speech Quality Indicator and Recognition Rate Prediction for Dysarthric Speakers with Cerebral Palsy

    Science.gov (United States)

    Kayasith, Prakasith; Theeramunkong, Thanaruk

    It is a tedious and subjective task to measure severity of a dysarthria by manually evaluating his/her speech using available standard assessment methods based on human perception. This paper presents an automated approach to assess speech quality of a dysarthric speaker with cerebral palsy. With the consideration of two complementary factors, speech consistency and speech distinction, a speech quality indicator called speech clarity index (Ψ) is proposed as a measure of the speaker's ability to produce consistent speech signal for a certain word and distinguished speech signal for different words. As an application, it can be used to assess speech quality and forecast speech recognition rate of speech made by an individual dysarthric speaker before actual exhaustive implementation of an automatic speech recognition system for the speaker. The effectiveness of Ψ as a speech recognition rate predictor is evaluated by rank-order inconsistency, correlation coefficient, and root-mean-square of difference. The evaluations had been done by comparing its predicted recognition rates with ones predicted by the standard methods called the articulatory and intelligibility tests based on the two recognition systems (HMM and ANN). The results show that Ψ is a promising indicator for predicting recognition rate of dysarthric speech. All experiments had been done on speech corpus composed of speech data from eight normal speakers and eight dysarthric speakers.

  4. A “Cosmic Comb” Model of Fast Radio Bursts

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Bing [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States)

    2017-02-20

    Recent observations of fast radio bursts (FRBs) indicate a perplexing, inconsistent picture. We propose a unified scenario to interpret diverse FRBs observed. A regular pulsar, otherwise unnoticeable at a cosmological distance, may produce a bright FRB if its magnetosphere is suddenly “combed” by a nearby, strong plasma stream toward the anti-stream direction. If the Earth is to the night side of the stream, the combed magnetic sheath would sweep across the direction of Earth and make a detectable FRB. The stream could be an AGN flare, a GRB or supernova blastwave, a tidal disruption event, or even a stellar flare. Since it is the energy flux received by the pulsar rather than the luminosity of the stream origin that defines the properties of the FRB, this model predicts a variety of counterparts of FRBs, including a possible connection between FRB 150418 and an AGN flare, a possible connection between FRB 131104 and a weak GRB, a steady radio nebula associated with the repeating FRB 121102, and probably no bright counterparts for some FRBs.

  5. Bursts in intermittent aeolian saltation

    CERN Document Server

    Carneiro, M V; Herrmann, H J

    2014-01-01

    Close to the onset of Aeolian particle transport through saltation we find in wind tunnel experiments a regime of intermittent flux characterized by bursts of activity. Scaling laws are observed in the time delay between each burst and in the measurements of the wind fluctuations at the critical Shields number $\\theta_c$. The time delay between each burst decreases on average with the increase of the Shields number until saltation becomes non-intermittent and the sand flux becomes continuous. A numerical model for saltation including the wind-entrainment from the turbulent fluctuations can reproduce these observations and gives insight about their origin. We present here also for the first time measurements showing that with feeding it becomes possible to sustain intermittent flux even below the threshold $\\theta_c$ for natural saltation initiation.

  6. INTEGRAL Results on Gamma-Ray Bursts

    Science.gov (United States)

    Hurley, Kevin C.

    2008-03-01

    Prompt, precise localizations of gamma-ray bursts imaged by IBIS are being disseminated at a rate of about 10 per year (49 to date). The INTEGRAL Burst Alert System (IBAS) produces automated alerts within 10's of seconds, giving positions which are accurate to several arcminutes for events as weak as 5.7 x 10-8 erg cm-2. IBIS is also a very sensitive detector of soft gamma repeaters (SGRs). It has detected well over 200 bursts from SGR1806-20, down to a fluence of 7×10-9 erg cm-2. An unexpected discovery is that the quiescent X-ray emission of this source and SGR 1900+14 is considerably harder than previous measurements indicated, and extends to 200 keV, a property which SGRs share with the AXP's. In addition, the SPI anti-coincidence shield (ACS) system is an extremely useful component of the interplanetary network. With its isotropic response, it detects about 66 confirmed bursts/year ( 450 to date) down to a threshold of 4.8×10-8 erg cm-2, many of which can be localized by triangulation. Most of these events are not detected by Swift or IBIS due to their limited fields of view. The triangulation results are currently being used to search for coincident neutrino emission, for gravitational radiation simultaneous with GRBs, and for coincidences between Type Ic supernovae and bursts, among other things. The SPI ACS has recently played a key role in localizing and identifying two events which are believed to be extragalactic giant magnetar flares (EMFs), from M81 and M31. LIGO was operating at the time of one of these events, and their observations support the EMF hypothesis. SPI is also being used as a Compton-scatter polarimeter for GRBs. Kalemci et al. (2007) and McGlynn et al. (2007) studied its response to GRB041219a, and obtained polarizations of 98% +/- 33%, and 63% (+31%,-30%) respectively.

  7. Testing and Improving the Luminosity Relations for Gamma-Ray Bursts

    Science.gov (United States)

    Collazzi, Andrew

    2011-08-01

    Gamma Ray Bursts (GRBs) have several luminosity relations where a measurable property of a burst light curve or spectrum is correlated with the burst luminosity. These luminosity relations are calibrated for the fraction of bursts with spectroscopic redshifts and hence the known luminosities. GRBs have thus become known as a type of 'standard candle'; where standard candle is meant in the usual sense that their luminosities can be derived from measurable properties of the bursts. GRBs can therefore be used for the same cosmology applications as Type Ia supernovae, including the construction of the Hubble Diagram and measuring massive star formation rate. The greatest disadvantage of using GRBs as standard candles is that their accuracy is lower than desired. With the recent advent of GRBs as a new standard candle, every effort must be made to test and improve the distance measures. Here, several methods are employed to do just that. First, generalized forms of two tests are performed on all of the luminosity relations. All the luminosity relations pass the second of these tests, and all but two pass the first. Even with this failure, the redundancy in using multiple luminosity relations allows all the luminosity relations to retain value. Next, the 'Firmani relation' is shown to have poorer accuracy than first advertised. In addition, it is shown to be exactly derivable from two other luminosity relations. For these reasons, the Firmani relation is useless for cosmology. The Amati relation is then revisited and shown to be an artifact of a combination of selection effects. Therefore, the Amati relation is also not good for cosmology. Fourthly, the systematic errors involved in measuring a popular luminosity indicator (Epeak ) are measured. The result is that an irreducible systematic error of 28% exists. After that, a preliminary investigation into the usefulness of breaking GRBs into individual pulses is conducted. The results of an 'ideal' set of data do not

  8. Mahalanobis Distance

    Indian Academy of Sciences (India)

    and G 2 might represent girls and boys, respectively or, in a medical diagnosis ... Representation of. Mahalanobis distance for the univariate case. GENERAL I ARTICLE. If the variables in X were uncorrelated in each group and were scaled so that they had ... have been proposed, and about thirty are known in the literature.

  9. DISTANCE EDUCATION

    African Journals Online (AJOL)

    take a longer period to get a degree and a greater number of learners can be reached than is possi- ble through .... distance learners and available funds, in short, a collection development policy. Infrastructure. In the long ..... gional centres could double as administrators. journal of science and technology, volume 25, no.

  10. Distance Education.

    Science.gov (United States)

    Feasley, Charles E.

    The magnitude, diversity, and impact of distance education are discussed in this international review of its implementation in economically diverse countries. Uses of the following media are described: (1) print--correspondence study, programmed instruction, modularized instruction, newspaper; (2) audio media--telephone, radio, subsidiary…

  11. [Distance Education.

    Science.gov (United States)

    Wallace, Teri, Ed.; Weatherman, Dick, Ed.

    1995-01-01

    This newsletter theme issue on distance education serving individuals with disabilities considers historical developments, technology, staff training strategies, and staff training materials. It is noted that improving access to training for staff members can improve the quality of services for individuals with disabilities. The following articles…

  12. Pulsar kicks and γ-ray burst

    Science.gov (United States)

    Cui, X. H.; Wang, H. G.; Xu, R. X.; Qiao, G. J.

    2007-09-01

    Aims:We use the supernova-GRB (γ-ray burst) association and assume that the GRB asymmetric explosions produce pulsars in order to test the consistency of distributions of modeled and observed pulsar-kick velocities. Methods: The deduced distribution of kick velocity from the model of GRB and the observed kick distribution of radio pulsars are checked by a K-S test. Results: These two distributions are found to come from the same parent population. Conclusions: This result may indicate that GRBs could really be related to supernova and that the asymmetry of GRB associated with supernova would cause the pulsar kick.

  13. EXIST's Gamma-Ray Burst Sensitivity

    Science.gov (United States)

    Band, D. L.; Grindlay, J. E.; Hong, J.; Fishman, G.; Hartmann, D. H.; Garson, A., III; Krawczynski, H.; Barthelmy, S.; Gehrels, N.; Skinner, G.

    2008-02-01

    We use semianalytic techniques to evaluate the burst sensitivity of designs for the EXIST hard X-ray survey mission. Applying these techniques to the mission design proposed for the Beyond Einstein program, we find that with its very large field of view and faint gamma-ray burst detection threshold, EXIST will detect and localize approximately two bursts per day, a large fraction of which may be at high redshift. We estimate that EXIST's maximum sensitivity will be ~4 times greater than that of Swift's Burst Alert Telescope. Bursts will be localized to better than 40'' at threshold, with a burst position as good as a few arcseconds for strong bursts. EXIST's combination of three different detector systems will provide spectra from 3 keV to more than 10 MeV. Thus, EXIST will enable a major leap in the understanding of bursts, their evolution, environment, and utility as cosmological probes.

  14. Optothermally actuated capillary burst valve

    DEFF Research Database (Denmark)

    Eriksen, Johan; Bilenberg, Brian; Kristensen, Anders

    2017-01-01

    be burst by raising the temperature due to the temperature dependence of the fluid surface tension. We address individual valves by using a local heating platform based on a thin film of near infrared absorber dye embedded in the lid used to seal the microfluidic device [L. H. Thamdrup et al., Nano Lett...

  15. Respiratory burst oxidase of fertilization.

    Science.gov (United States)

    Heinecke, J W; Shapiro, B M

    1989-02-01

    Partially reduced oxygen species are toxic, yet sea urchin eggs synthesize H2O2 in a "respiratory burst" at fertilization, as an extracellular oxidant to crosslink their protective surface envelopes. To study the biochemical mechanism for H2O2 production, we have isolated an NADPH-specific oxidase fraction from homogenates of unfertilized Strongylocentrotus purpuratus eggs that produces H2O2 when stimulated with Ca2+ and MgATP2-. Concentrations of free Ca2+ previously implicated in regulation of egg activation modulate the activity of the oxidase. Inhibitors were used to test the relevance of this oxidase to the respiratory burst of fertilization. Procaine, two phenothiazines, and N-ethylmaleimide (but not iodoacetamide) inhibited H2O2 production by the oxidase fraction and oxygen consumption by activated eggs. The ATP requirement suggested that protein kinase activity might regulate the respiratory burst of fertilization; consonant with this hypothesis, H-7 and staurosporine were inhibitory. The respiratory burst oxidase of fertilization is an NADPH:O2 oxidoreductase that appears to be regulated by a protein kinase; although it bears a remarkable resemblance to the neutrophil oxidase, unlike the latter it does not form O2- as its initial product.

  16. FERMIGBRST - Fermi GBM Burst Catalog

    Data.gov (United States)

    National Aeronautics and Space Administration — This table lists all of the triggers observed by a subset of the 14 GBM detectors (12 NaI and 2 BGO) which have been classified as gamma-ray bursts (GRBs). Note that...

  17. Distance learning

    Directory of Open Access Journals (Sweden)

    Katarina Pucelj

    2006-12-01

    Full Text Available I would like to underline the role and importance of knowledge, which is acquired by individuals as a result of a learning process and experience. I have established that a form of learning, such as distance learning definitely contributes to a higher learning quality and leads to innovative, dynamic and knowledgebased society. Knowledge and skills enable individuals to cope with and manage changes, solve problems and also create new knowledge. Traditional learning practices face new circumstances, new and modern technologies appear, which enable quick and quality-oriented knowledge implementation. The centre of learning process at distance learning is to increase the quality of life of citizens, their competitiveness on the workforce market and ensure higher economic growth. Intellectual capital is the one, which represents the biggest capital of each society and knowledge is the key factor for succes of everybody, who are fully aware of this. Flexibility, openness and willingness of people to follow new IT solutions form suitable environment for developing and deciding to take up distance learning.

  18. Strict limit on CPT violation from polarization of γ-ray bursts.

    Science.gov (United States)

    Toma, Kenji; Mukohyama, Shinji; Yonetoku, Daisuke; Murakami, Toshio; Gunji, Shuichi; Mihara, Tatehiro; Morihara, Yoshiyuki; Sakashita, Tomonori; Takahashi, Takuya; Wakashima, Yudai; Yonemochi, Hajime; Toukairin, Noriyuki

    2012-12-14

    We report the strictest observational verification of CPT invariance in the photon sector, as a result of γ-ray polarization measurement of distant gamma-ray bursts (GRBs), which are the brightest stellar-sized explosions in the Universe. We detected γ-ray polarization of three GRBs with high significance levels, and the source distances may be constrained by a well-known luminosity indicator for GRBs. For the Lorentz- and CPT-violating dispersion relation E(±)(2) = p(2) ± 2ξp(3)/M(Pl), where ± denotes different circular polarization states of the photon, the parameter ξ is constrained as |ξ|

  19. Detecting pipe bursts by monitoring water demand

    NARCIS (Netherlands)

    Bakker, M.; Vreeburg, J.H.G.; Van der Roer, M.; Sperber, V.

    2012-01-01

    An algorithm which compares measured and predicted water demands to detect pipe bursts was developed and tested on three data sets of water demand and reported pipe bursts of three years. The algorithm proved to be able to detect bursts where the water loss exceeds 30% of the average water demand in

  20. What did we learn from gamma-ray burst 080319B?

    Energy Technology Data Exchange (ETDEWEB)

    Panaitescu, Alin [Los Alamos National Laboratory; Kumar, Pawan [UNIV OF TEXAS

    2008-01-01

    The optical and gamma-ray observations of GRB 080319B allow us to provide a broad-brush picture for this remarkable burst. The data indicate that the prompt optical and gamma-ray photons were possibly produced at the same location but by different radiation processes: synchrotron and synchrotron self-Compton, respectively (but we note that this interpretation of the gamma-ray data faces some difficulties). We find that the burst prompt optical emission was produced at a distance of 10{sup 16.3} cm by an ultrarelativistic source moving at Lorentz factor of -500. A straightforward inference is that about 10 times more energy must have been radiated at tens of GeV than that released at 1 MeV. Assuming that the GRB outflow was baryonic and the gamma-ray source was shock-heated plasma, the collimation-corrected kinetic energy of the jet powering GRB 080319B was larger than 10{sup 52.3} erg. The decay of the early afterglow optical emission (up to 1 ks) is too fast to be attributed to the reverse-shock crossing the GRB ejecta but is consistent with the expectations for the 'large-angle' emission released during the burst. The pure power-law decay of the optical afterglow flux from 1 ks to 10 d is most naturally identified with the (synchrotron) emission from the shock propagating into a wind-like medium. However, the X-ray afterglow requires a departure from the standard blast-wave model.

  1. Partition of aerobic and anaerobic swimming costs and their correlation to tail-beat frequency and burst activity in Sparus aurata

    DEFF Research Database (Denmark)

    Steffensen, John Fleng

    2012-01-01

    until fatigue at 10°C. The anaerobic swimming cost was measured as the excess postexercise oxygen consumption (EPOC) following each swimming speed. To determine tail-beat frequency, amplitude and burst and coast behaviour, the peduncle position was determined at 25 s·' by video tracking. The data showed......, and resulted in a total anaerobic capacity of 170 mg O2 kg·'. Normalized tail-beat amplitude and frequency both predicted the swimming speed but only tail-beat frequency was able to predict the aerobic swimming cost. The change to burst and coast swimming was correlated to the first measurements of EPOC...... and both the burst frequency (bursts min·') and burst distance (percentage burst distance) were found to predict EPOC by linear regressions. The low temperature used in the present study resulted in a prolonged recovery time, which increased with the anaerobic contribution to 10 hours after fatigue. Due...

  2. Electronic implementation of optical burst switching techniques

    Science.gov (United States)

    Albanese, Ilijc; Darcie, Thomas E.; Ganti, Sudhakar

    2013-10-01

    Extensive research effort is ongoing in energy-efficient Internet-based communications. Optical Flow Switching (OFS) and Optical Burst Switching (OBS) offer potentially efficient alternatives to IP-router-based networks for large data transactions, but significant challenges remain. OFS requires each user to install expensive core network technology, limiting application to highly specialized nodes. OBS can achieve higher scalability but burst assembly/disassembly procedures reduce power efficiency. Finally both OFS and OBS use all-optical switching technologies for which energy efficiency and flexibility remain subject to debate. Our study aims at combining the advantages of both OBS and OFS while avoiding their shortcomings. We consider using a two-way resource reservation protocol for periodic concatenations of large (e.g. 1 Mb) packets or Media Frames (MFs). These chains of MFs (MFCs) are semi-transparent with a periodicity referred to as the "transparency degree". Each MFC is assembled and stored at an end-user machine during the resource reservation procedure and is then switched and buffered electronically along its path. The periodic configuration of each MFC enables interleaving of several chains using buffering only to align the MFs in each MFC in time, largely reducing the buffer requirements with respect to OBS. This periodicity also enables a simple scheduling algorithm to schedule large transactions with minimal control plane processing, achieving link utilization approaching 99.9%. In summary, results indicate that implementing optical burst switching techniques in the electronic domain is a compelling path forward to high-throughput power-efficient networking.

  3. LOCALIZATION OF GAMMA-RAY BURSTS USING THE FERMI GAMMA-RAY BURST MONITOR

    Energy Technology Data Exchange (ETDEWEB)

    Connaughton, V.; Briggs, M. S.; Burgess, J. M. [CSPAR and Physics Department, University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35899 (United States); Goldstein, A.; Wilson-Hodge, C. A. [Astrophysics Office, ZP12, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Meegan, C. A.; Jenke, P.; Pelassa, V.; Xiong, S.; Bhat, P. N. [CSPAR, University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35899 (United States); Paciesas, W. S. [Universities Space Research Association, Huntsville, AL (United States); Preece, R. D. [Department of Space Science, University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35899 (United States); Gibby, M. H. [Jacobs Technology, Inc., Huntsville, AL (United States); Greiner, J.; Yu, H.-F. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Gruber, D. [Planetarium Südtirol, Gummer 5, I-39053 Karneid (Italy); Kippen, R. M. [Los Alamos National Laboratory, NM 87545 (United States); Byrne, D.; Fitzpatrick, G.; Foley, S., E-mail: valerie@nasa.gov [School of Physics, University College Dublin, Belfield, Stillorgan Road, Dublin 4 (Ireland); and others

    2015-02-01

    The Fermi Gamma-ray Burst Monitor (GBM) has detected over 1400 gamma-ray bursts (GRBs) since it began science operations in 2008 July. We use a subset of over 300 GRBs localized by instruments such as Swift, the Fermi Large Area Telescope, INTEGRAL, and MAXI, or through triangulations from the InterPlanetary Network, to analyze the accuracy of GBM GRB localizations. We find that the reported statistical uncertainties on GBM localizations, which can be as small as 1°, underestimate the distance of the GBM positions to the true GRB locations and we attribute this to systematic uncertainties. The distribution of systematic uncertainties is well represented (68% confidence level) by a 3.°7 Gaussian with a non-Gaussian tail that contains about 10% of GBM-detected GRBs and extends to approximately 14°. A more complex model suggests that there is a dependence of the systematic uncertainty on the position of the GRB in spacecraft coordinates, with GRBs in the quadrants on the Y axis better localized than those on the X axis.

  4. Localization of Gamma-Ray Bursts Using the Fermi Gamma-Ray Burst Monitor

    Science.gov (United States)

    Connaughton, V.; Briggs, M. S.; Goldstein, A.; Meegan, C. A.; Paciesas, W. S.; Preece, R. D.; Wilson-Hodge, C. A.; Gibby, M. H.; Greiner, J.; Gruber, D.; Jenke, P.; Kippen, R. M.; Pelassa, V.; Xiong, S.; Yu, H.-F.; Bhat, P. N.; Burgess, J. M.; Byrne, D.; Fitzpatrick, G.; Foley, S.; Giles, M. M.; Guiriec, S.; van der Horst, A. J.; von Kienlin, A.; McBreen, S.; McGlynn, S.; Tierney, D.; Zhang, B.-B.

    2015-02-01

    The Fermi Gamma-ray Burst Monitor (GBM) has detected over 1400 gamma-ray bursts (GRBs) since it began science operations in 2008 July. We use a subset of over 300 GRBs localized by instruments such as Swift, the Fermi Large Area Telescope, INTEGRAL, and MAXI, or through triangulations from the InterPlanetary Network, to analyze the accuracy of GBM GRB localizations. We find that the reported statistical uncertainties on GBM localizations, which can be as small as 1°, underestimate the distance of the GBM positions to the true GRB locations and we attribute this to systematic uncertainties. The distribution of systematic uncertainties is well represented (68% confidence level) by a 3.°7 Gaussian with a non-Gaussian tail that contains about 10% of GBM-detected GRBs and extends to approximately 14°. A more complex model suggests that there is a dependence of the systematic uncertainty on the position of the GRB in spacecraft coordinates, with GRBs in the quadrants on the Y axis better localized than those on the X axis.

  5. Imaging spectroscopy of type U and J solar radio bursts with LOFAR

    Science.gov (United States)

    Reid, Hamish A. S.; Kontar, Eduard P.

    2017-10-01

    bursts to be more frequently observed. The large instability distances required before Langmuir waves are produced by some electron beams, and the small magnitude of the background density gradients makes closed loops less facilitative for radio emission than loops that extend into interplanetary space.

  6. Prompt Optical Observations of Gamma-Ray Bursts.

    Science.gov (United States)

    Akerlof; Balsano; Barthelmy; Bloch; Butterworth; Casperson; Cline; Fletcher; Frontera; Gisler; Heise; Hills; Hurley; Kehoe; Lee; Marshall; McKay; Pawl; Piro; Szymanski; Wren

    2000-03-20

    The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs). A search for optical counterparts to six GRBs with localization errors of 1 deg2 or better produced no detections. The earliest limiting sensitivity is mROTSE>13.1 at 10.85 s (5 s exposure) after the gamma-ray rise, and the best limit is mROTSE>16.0 at 62 minutes (897 s exposure). These are the most stringent limits obtained for the GRB optical counterpart brightness in the first hour after the burst. Consideration of the gamma-ray fluence and peak flux for these bursts and for GRB 990123 indicates that there is not a strong positive correlation between optical flux and gamma-ray emission.

  7. Evolution of gamma-ray burst progenitors at low metallicity

    NARCIS (Netherlands)

    Yoon, S.C.; Langer, N.

    2005-01-01

    Despite the growing evidence that long Gamma-Ray Bursts (GRBs) are associated with deaths of Wolf-Rayet stars, the evolutionary path of massive stars to GRBs and the exact nature of GRB progenitors remain poorly known. However, recent massive star evolutionary models indicate that — for sufficiently

  8. Gamma Ray Bursts and Their Links With Supernovae and Cosmology

    Science.gov (United States)

    Meszaros, Peter; Gehrels, Neil

    2012-01-01

    Gamma-ray bursts are the most luminous explosions in the Universe, whose origin and mechanism is the focus of intense interest. They appear connected to supernova remnants from massive stars or the merger of their remnants, and their brightness makes them temporarily detectable out to the largest distances yet explored in the Universe. After pioneering breakthroughs from space and ground experiments, their study is entering a new phase with observations from the recently launched Fermi satellite, as well as the prospect of detections or limits from large neutrino and gravitational wave detectors. The interplay between such observations and theoretical models of gamma-ray bursts is reviewed, as well as their connections to supernovae and cosmology.

  9. Respiratory burst oxidase of fertilization.

    OpenAIRE

    Heinecke, J W; Shapiro, B M

    1989-01-01

    Partially reduced oxygen species are toxic, yet sea urchin eggs synthesize H2O2 in a "respiratory burst" at fertilization, as an extracellular oxidant to crosslink their protective surface envelopes. To study the biochemical mechanism for H2O2 production, we have isolated an NADPH-specific oxidase fraction from homogenates of unfertilized Strongylocentrotus purpuratus eggs that produces H2O2 when stimulated with Ca2+ and MgATP2-. Concentrations of free Ca2+ previously implicated in regulation...

  10. On the neutron bursts origin.

    CERN Document Server

    Stenkin, Yu V

    2002-01-01

    The origin of the neutron bursts in Extensive Air Showers (EAS) is explained using results of the experiments and CORSIKA based Monte-Carlo simulations. It is shown that events with very high neutron multiplicity observed last years in neutron monitors as well as in surrounding detectors, are caused by usual EAS core with primary energies > 1 PeV. No exotic processes were needed for the explanation.

  11. Distance hijacking attacks on distance bounding protocols

    OpenAIRE

    Cremers, Cas; Rasmussen, Kasper Bonne; Čapkun, Srdjan

    2011-01-01

    Distance bounding protocols are typically analyzed with respect to three types of attacks: Distance Fraud, Mafia Fraud, and Terrorist Fraud. We define and analyze a fourth main type of attack on distance bounding protocols, called Distance Hijacking. We show that many proposed distance bounding protocols are vulnerable to this type of attack, and we propose solutions to make these protocols resilient to Distance Hijacking. We further show that verifying distance bounding protocols using exist...

  12. Distance hijacking attacks on distance bounding protocols

    OpenAIRE

    Cremers, Cas; Rasmussen, Kasper Bonne; Čapkun, Srdjan

    2011-01-01

    Distance bounding protocols are typically analyzed with respect to three types of attacks: Distance Fraud, Mafia Fraud, and Terrorist Fraud. We define a fourth main type of attacks on distance bounding protocols, called Distance Hijacking attacks. We show that many proposed distance bounding protocols are vulnerable to these attacks, and we propose solutions to make these protocols resilient to Distance Hijacking. Additionally, we generalize Distance Hijacking to Location Hijacking, to which ...

  13. Simultaneous X-Ray, Gamma-Ray, and Radio Observations of the Repeating Fast Radio Burst FRB 121102

    Science.gov (United States)

    Scholz, P.; Bogdanov, S.; Hessels, J. W. T.; Lynch, R. S.; Spitler, L. G.; Bassa, C. G.; Bower, G. C.; Burke-Spolaor, S.; Butler, B. J.; Chatterjee, S.; Cordes, J. M.; Gourdji, K.; Kaspi, V. M.; Law, C. J.; Marcote, B.; McLaughlin, M. A.; Michilli, D.; Paragi, Z.; Ransom, S. M.; Seymour, A.; Tendulkar, S. P.; Wharton, R. S.

    2017-09-01

    We undertook coordinated campaigns with the Green Bank, Effelsberg, and Arecibo radio telescopes during Chandra X-ray Observatory and XMM-Newton observations of the repeating fast radio burst FRB 121102 to search for simultaneous radio and X-ray bursts. We find 12 radio bursts from FRB 121102 during 70 ks total of X-ray observations. We detect no X-ray photons at the times of radio bursts from FRB 121102 and further detect no X-ray bursts above the measured background at any time. We place a 5σ upper limit of 3 × 10‑11 erg cm‑2 on the 0.5–10 keV fluence for X-ray bursts at the time of radio bursts for durations < 700 ms, which corresponds to a burst energy of 4 × 1045 erg at the measured distance of FRB 121102. We also place limits on the 0.5–10 keV fluence of 5 × 10‑10 and 1 × 10‑9 erg cm‑2 for bursts emitted at any time during the XMM-Newton and Chandra observations, respectively, assuming a typical X-ray burst duration of 5 ms. We analyze data from the Fermi Gamma-ray Space Telescope Gamma-ray Burst Monitor and place a 5σ upper limit on the 10–100 keV fluence of 4 × 10‑9 erg cm‑2 (5 × 1047 erg at the distance of FRB 121102) for gamma-ray bursts at the time of radio bursts. We also present a deep search for a persistent X-ray source using all of the X-ray observations taken to date and place a 5σ upper limit on the 0.5–10 keV flux of 4 × 10‑15 erg s‑1 cm‑2 (3 × 1041 erg s‑1 at the distance of FRB 121102). We discuss these non-detections in the context of the host environment of FRB 121102 and of possible sources of fast radio bursts in general.

  14. Fuzzy-Based Adaptive Hybrid Burst Assembly Technique for Optical Burst Switched Networks

    Directory of Open Access Journals (Sweden)

    Abubakar Muhammad Umaru

    2014-01-01

    Full Text Available The optical burst switching (OBS paradigm is perceived as an intermediate switching technology for future all-optical networks. Burst assembly that is the first process in OBS is the focus of this paper. In this paper, an intelligent hybrid burst assembly algorithm that is based on fuzzy logic is proposed. The new algorithm is evaluated against the traditional hybrid burst assembly algorithm and the fuzzy adaptive threshold (FAT burst assembly algorithm via simulation. Simulation results show that the proposed algorithm outperforms the hybrid and the FAT algorithms in terms of burst end-to-end delay, packet end-to-end delay, and packet loss ratio.

  15. Analysis of variability in the burst oscillations of the accreting millisecond pulsar XTE J1814-338

    Science.gov (United States)

    Watts, Anna L.; Strohmayer, Tod E.; Markwardt, Craig B.

    2005-01-01

    The accreting millisecond pulsar XTE J1814-338 exhibits oscillations at the known spin frequency during Type I X-ray bursts. The properties of the burst oscillations reflect the nature of the thermal asymmetry on the stellar surface. We present an analysis of the variability of the burst oscillations of this source, focusing on three characteristics: fractional amplitude, harmonic content and frequency. Fractional amplitude and harmonic content constrain the size, shape and position of the emitting region, whilst variations in frequency indicate motion of the emitting region on the neutron star surface. We examine both long-term variability over the course of the outburst, and short-term variability during the bursts. For most of the bursts, fractional amplitude is consistent with that of the accretion pulsations, implying a low degree of fuel spread. There is however a population of bursts whose fractional amplitudes are substantially lower, implying a higher degree of fuel spread, possibly forced by the explosive burning front of a precursor burst. For the first harmonic, substantial differences between the burst and accretion pulsations suggest that hotspot geometry is not the only mechanism giving rise to harmonic content in the latter. Fractional amplitude variability during the bursts is low; we can only rule out the hypothesis that the fractional amplitude remains constant at the l(sigma) level for bursts that do not exhibit photospheric radius expansion (PRE). There are no significant variations in frequency in any of the bursts except for the one burst that exhibits PRE. This burst exhibits a highly significant but small (= 0.1Hz) drop in frequency in the burst rise. The timescale of the frequency shift is slower than simple burning layer expansion models predict, suggesting that other mechanisms may be at work.

  16. X-Ray Reflection and an Exceptionally Long Thermonuclear Helium Burst from IGR J17062-6143

    Science.gov (United States)

    Keek, L.; Iwakiri, W.; Serino, M.; Ballantyne, D. R.; in’t Zand, J. J. M.; Strohmayer, T. E.

    2017-01-01

    Thermonuclear X-ray bursts from accreting neutron stars power brief but strong irradiation of their surroundings, providing a unique way to study accretion physics. We analyze MAXI/Gas Slit Camera and Swift/XRT spectra of a day-long flash observed from IGR J17062-6143 in 2015. It is a rare case of recurring bursts at a low accretion luminosity of 0.15% Eddington. Spectra from MAXI, Chandra, and NuSTAR observations taken between the 2015 burst and the previous one in 2012 are used to determine the accretion column. We find it to be consistent with the burst ignition column of 5x10(exp 10) g cm (exp -2), which indicates that it is likely powered by burning in a deep helium layer. The burst flux is observed for over a day, and decays as a straight power law: F gamma t (exp -1.15). The burst and persistent spectra are well described by thermal emission from the neutron star, Comptonization of this emission in a hot optically thin medium surrounding the star, and reflection off the photoionized accretion disk. At the burst peak, the Comptonized component disappears, when the burst may dissipate the Comptonizing gas, and it returns in the burst tail. The reflection signal suggests that the inner disk is truncated at approximately 102 gravitational radii before the burst, but may move closer to the star during the burst. At the end of the burst, the flux drops below the burst cooling trend for 2 days, before returning to the pre-burst level.

  17. Method of induced seismo-acoustic activity and its application in evaluation of rock burst hazards

    Energy Technology Data Exchange (ETDEWEB)

    Kornowski, J.; Sokolowski, H.

    1987-03-01

    Describes a method of induced seismic activity, its physical principles, use of the PAS-2 portable apparatus and result interpretation. Discusses criteria of rock burst hazards valid for rock burst endangered regions. A low pulse number before blasting and no increase after it testifies to a low rock mass effort. Up to 5 pulses per 2 minutes before blasting and below 30 pulses for 6 minutes after it, but not longer than for 16 minutes, points to low burst hazards. Above 5 pulses per 2 minutes before blasting and above 30 pulses per 2 minutes after blasting, for longer than 126 minutes, indicates high rock burst hazards. A computer-aided parametric version of rock burst hazard criteria has also been developed.

  18. A New Population of Ultra-long Duration Gamma-Ray Bursts

    NARCIS (Netherlands)

    Levan, A.J.; Tanvir, N.R.; Starling, R.L.C.; Wiersema, K.; Page, K.L.; Perley, D.A.; Schulze, S.; Wynn, G.A.; Chornock, R.; Hjorth, J.; Cenko, S.B.; Fruchter, A.S.; O'Brien, P.T.; Brown, G.C.; Tunnicliffe, R.L.; Malesani, D.; Jakobsson, P.; Watson, D.; Berger, E.; Bersier, D.; Cobb, B.E.; Covino, S.; Cucchiara, A.; de Ugarte Postigo, A.; Fox, D.B.; Gal-Yam, A.; Goldoni, P.; Gorosabel, J.; Kaper, L.; Krühler, T.; Karjalainen, R.; Osborne, J.P.; Pian, E.; Sánchez-Ramírez, R.; Schmidt, B.; Skillen, I.; Tagliaferri, G.; Thöne, C.; Vaduvescu, O.; Wijers, R.A.M.J.; Zauderer, B.A.

    2014-01-01

    We present comprehensive multiwavelength observations of three gamma-ray bursts (GRBs) with durations of several thousand seconds. We demonstrate that these events are extragalactic transients; in particular, we resolve the long-standing conundrum of the distance of GRB 101225A (the "Christmas-day

  19. Hardness/intensity correlations among BATSE bursts

    Science.gov (United States)

    Paciesas, William S.; Pendleton, Geoffrey N.; Kouveliotou, Chryssa; Fishman, Gerald J.; Meegan, Charles A.; Wilson, Robert B.

    1992-01-01

    Conclusions about the nature of gamma-ray bursts derived from the size-frequency distribution may be altered if a significant correlation exists between burst intensity and spectral shape. Moreover, if gamma-ray bursts have a cosmological origin, such a correlation may be expected to result from the expansion of the universe. We have performed a rudimentary search of the BATSE bursts for hardness/intensity correlations. The range of spectral shapes was determined for each burst by computing the ratio of the intensity in the range 100-300 keV to that in 55-300 keV. We find weak evidence for the existence of a correlation, the strongest effect being present when comparing the maximum hardness ratio for each burst with its maximum rate.

  20. Quark nova model for fast radio bursts

    Science.gov (United States)

    Shand, Zachary; Ouyed, Amir; Koning, Nico; Ouyed, Rachid

    2016-05-01

    Fast radio bursts (FRBs) are puzzling, millisecond, energetic radio transients with no discernible source; observations show no counterparts in other frequency bands. The birth of a quark star from a parent neutron star experiencing a quark nova - previously thought undetectable when born in isolation - provides a natural explanation for the emission characteristics of FRBs. The generation of unstable r-process elements in the quark nova ejecta provides millisecond exponential injection of electrons into the surrounding strong magnetic field at the parent neutron star's light cylinder via β-decay. This radio synchrotron emission has a total duration of hundreds of milliseconds and matches the observed spectrum while reducing the inferred dispersion measure by approximately 200 cm-3 pc. The model allows indirect measurement of neutron star magnetic fields and periods in addition to providing astronomical measurements of β-decay chains of unstable neutron rich nuclei. Using this model, we can calculate expected FRB average energies (˜ 1041 erg) and spectral shapes, and provide a theoretical framework for determining distances.

  1. Estimation of distances of recorded sounds presented through headphones.

    Science.gov (United States)

    Lounsbury, B F; Butler, R A

    1979-01-01

    Intermittent sounds generated at 270 degrees azimuth and from distances ranging from 2 to 10 feet were recorded on magnetic tape and played back to listeners via headphones. Loudness cues for relative distance were eliminated at the time of recording. Listeners were required to estimate the apparent distance of the recorded sounds when heard monoaurally and binaurally. Most subjects estimated the order of distances correctly. Distance estimations were as proficient when listening monaurally as when listening binaurally. Performance was more accurate for high-pass (greater than 4.0 kHz) noise bursts than for low-pass (less than 1.0 kHz) noise bursts. In a second study, broad-band noise bursts were recorded from azimuthal positions of 360 degrees, 330 degrees, 300 degrees and 270 degrees again at distances ranging from 2 to 10 feet. Estimations of the distances of the sounds, presented via headphones, were most proficient when azimuthal position of the original stimuli was 330 degrees.

  2. Computational Developments for Distance Determination of Stellar ...

    Indian Academy of Sciences (India)

    On the other hand, the determination of distances within our galaxy allows us to cali- brate the distance indicators (Shanks 1997; Tanvir 1997; Brochkhadze & Kogoshvili. 1999) used to estimate distances outside it. Moreover, determining distances would also help astronomers in their quest to understand the size and the ...

  3. The new intermediate long-bursting source XTE J1701-407

    DEFF Research Database (Denmark)

    Falanga, M.; Cumming, A.; Bozzo, E.

    2009-01-01

    Aims. XTE J1701-407 is a newly discovered X-ray transient source. We investigate its flux variability and study the intermediate long-and short-bursts discovered by Swift on July 17, and 27, 2008, respectively. Methods. Only one intermediate long-burst, of duration approximate to 18 min and ten....... Results. The intermediate long-burst may have exhibited a photospheric radius expansion, allowing us to derive the source distance at 6.2 kpc, assuming the empirically derived Eddington luminosity for pure helium. The intermediate long-burst decay was described most accurately by using two exponential...... functions with e-folding times of tau(1) = 40 +/- 3 s and tau(2) = 221 +/- 9 s. The bursts occurred at a persistent luminosity of L-per = 8.3 x 10(36) erg s(-1) (approximate to 2.2% of the Eddington luminosity). For the intermediate long-burst, the mass accretion rate per unit area onto the neutron star...

  4. The thermonuclear model for γ-ray bursts

    Science.gov (United States)

    Woosley, S. E.

    1982-01-01

    The evolution of magnetized neutron stars with field strengths of ~1012 gauss that are accreting mass onto kilometer-sized polar regions at a rate of ~10-13 Msolar yr-1 is examined. Based on the results of one-dimensional calculations, one finds that stable hydrogen burning, mediated by the ``hot'' CNO-cycle, will lead to a critical helium mass in the range 1020 to 1022 g km-2. Owing to the extreme degeneracy of the electron gas providing pressure support, helium burning occurs as a violent thermonuclear runaway which may propagate either as a convective deflagration (Type I burst) or as a detonation wave (Type II burst). Complete combustion of helium into 56Ni releases from 1038 to 1040 erg km-2 and pushes hot plasma with β>~1 above the surface of the neutron star. Rapid expansion of the plasma channels a substantial fraction of the explosion energy into magnetic field stress. Spectral properties are expected to be complex with emission from both thermal and non-thermal processes. The hard γ-outburst of several seconds softens as the event proceeds and is followed by a period, typically of several minutes duration, of softer x-ray emission as the subsurface ashes of the thermonuclear explosion cool. In this model, most γ-ray bursts currently being observed are located at a distance of several hundred parsecs and should recur on a timescale of months to centuries with convective deflagrations (Type I bursts) being the more common variety. An explanation for ``Jacobson-like'' transients is also offered.

  5. Bursting as a source of non-linear determinism in the firing patterns of nigral dopamine neurons.

    Science.gov (United States)

    Jeong, Jaeseung; Shi, Wei-Xing; Hoffman, Ralph; Oh, Jihoon; Gore, John C; Bunney, Benjamin S; Peterson, Bradley S

    2012-11-01

    Nigral dopamine (DA) neurons in vivo exhibit complex firing patterns consisting of tonic single-spikes and phasic bursts that encode information for certain types of reward-related learning and behavior. Non-linear dynamical analysis has previously demonstrated the presence of a non-linear deterministic structure in complex firing patterns of DA neurons, yet the origin of this non-linear determinism remains unknown. In this study, we hypothesized that bursting activity is the primary source of non-linear determinism in the firing patterns of DA neurons. To test this hypothesis, we investigated the dimension complexity of inter-spike interval data recorded in vivo from bursting and non-bursting DA neurons in the chloral hydrate-anesthetized rat substantia nigra. We found that bursting DA neurons exhibited non-linear determinism in their firing patterns, whereas non-bursting DA neurons showed truly stochastic firing patterns. Determinism was also detected in the isolated burst and inter-burst interval data extracted from firing patterns of bursting neurons. Moreover, less bursting DA neurons in halothane-anesthetized rats exhibited higher dimensional spiking dynamics than do more bursting DA neurons in chloral hydrate-anesthetized rats. These results strongly indicate that bursting activity is the main source of low-dimensional, non-linear determinism in the firing patterns of DA neurons. This finding furthermore suggests that bursts are the likely carriers of meaningful information in the firing activities of DA neurons. © 2012 The Authors. European Journal of Neuroscience © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

  6. Gamma-Ray Burst at the Extreme: "The Naked-Eye Burst" GRB 080319B

    Science.gov (United States)

    Woźniak, P. R.; Vestrand, W. T.; Panaitescu, A. D.; Wren, J. A.; Davis, H. R.; White, R. R.

    2009-01-01

    On 2008 March 19, the northern sky was the stage of a spectacular optical transient that for a few seconds remained visible to the naked eye. The transient was associated with GRB 080319B, a gamma-ray burst (GRB) at a luminosity distance of about 6 Gpc (standard cosmology), making it the most luminous optical object ever recorded by humankind. We present comprehensive sky monitoring and multicolor optical follow-up observations of GRB 080319B collected by the RAPTOR telescope network covering the development of the explosion and the afterglow before, during, and after the burst. The extremely bright prompt optical emission revealed features that are normally not detectable. The optical and gamma-ray variability during the explosion are correlated, but the optical flux is much greater than can be reconciled with single-emission mechanism and a flat gamma-ray spectrum. This extreme optical behavior is best understood as synchrotron self-Compton model (SSC). After a gradual onset of the gamma-ray emission, there is an abrupt rise of the prompt optical flux, suggesting that variable self-absorption dominates the early optical light curve. Our simultaneous multicolor optical light curves following the flash show spectral evolution consistent with a rapidly decaying red component due to large-angle emission and the emergence of a blue forward-shock component from interaction with the surrounding environment. While providing little support for the reverse shock that dominates the early afterglow, these observations strengthen the case for the universal role of the SSC mechanism in generating GRBs.

  7. High-z Universe with Gamma Ray Bursts

    Science.gov (United States)

    Kouveliotou, C.

    2011-01-01

    Gamma-Ray Bursts (GRBs) are the most luminous explosions in space and trace the cosmic star formation history back to the first generations of stars. Their bright afterglows allow us to trace the abundances of heavy elements to large distances, thereby measuring cosmic chemical evolution. To date GRBs have been detected up to distances of z=8.23 and possibly even beyond z9. This makes GRBs a unique and powerful tool to probe the high-z Universe up to the re-ionization era. We discuss the current status of the field, place it in context with other probes, and also discuss new mission concepts that have been planned to utilize GRBs as probes.

  8. Coupling and noise induced spiking-bursting transition in a parabolic bursting model

    Science.gov (United States)

    Ji, Lin; Zhang, Jia; Lang, Xiufeng; Zhang, Xiuhui

    2013-03-01

    The transition from tonic spiking to bursting is an important dynamic process that carry physiologically relevant information. In this work, coupling and noise induced spiking-bursting transition is investigated in a parabolic bursting model with specific discussion on their cooperation effects. Fast/slow analysis shows that weak coupling may help to induce the bursting by changing the geometric property of the fast subsystem so that the original unstable periodical solution are stabilized. It turned out that noise can play the similar stabilization role and induce bursting at appropriate moderate intensity. However, their cooperation may either strengthen or weaken the overall effect depending on the choice of noise level.

  9. Photospheric radius expansion during magnetar bursts

    NARCIS (Netherlands)

    Watts, A.L.; Kouveliotou, C.; van der Horst, A.J.; Göğüş, E.; Kaneko, Y.; van der Klis, M.; Wijers, R.A.M.J.; Harding, A.K.; Baring, M.G.

    2010-01-01

    On 2008 August 24 the new magnetar SGR 0501+4516 (discovered by Swift) emitted a bright burst with a pronounced double-peaked structure in hard X-rays, reminiscent of the double-peaked temporal structure seen in some bright thermonuclear bursts on accreting neutron stars. In the latter case this is

  10. A theory of gamma-ray bursts

    NARCIS (Netherlands)

    Brown, G.E.; Lee, C.-H.; Wijers, R.A.M.J.; Lee, H.K.; Israelian, G.; Bethe, H.A.

    2000-01-01

    Recent observations and theoretical considerations have linked gamma-ray bursts with ultra-bright type Ibc supernovae (`hypernovae'). We here work out a specific scenario for this connection. Based on earlier work, we argue that especially the longest bursts must be powered by the Blandford-Znajek

  11. A New Clue in the Mystery of Fast Radio Bursts

    Science.gov (United States)

    Kohler, Susanna

    2017-06-01

    .Bassa and collaborators also found that the properties of the host galaxy are consistent with those of a type of galaxy known as extreme emission line galaxies. This provides a tantalizing clue, as these galaxies are known to host both hydrogen-poor superluminous supernovae and long-duration gamma-ray bursts.Linking to the CauseWhat can this tell us about the cause of FRB 121102? The fact that this burst repeats already eliminates cataclysmic events as the origin. But the projected location of FRB 121102 within a star-forming region especially in a host galaxy thats similar to those typically hosting superluminous supernovae and long gamma-ray bursts strongly suggests theres a relation between these events.Artists impression of a gamma-ray burst in a star-forming region. [NASA/Swift/Mary Pat Hrybyk-Keith and John Jones]The authors propose that this observed coincidence, supported by models of magnetized neutron star birth, indicate an evolutionary link between fast radio bursts and neutron stars. In this picture, neutron stars or magnetars are born as long gamma-ray bursts or hydrogen-poor supernovae, and then evolve into fast-radio-burst-emitting sources.This picture may finally explain the cause of fast radio bursts but Bassa and collaborators caution that its also possible that this model applies only to FRB 121102. Since FRB 121102 is unique in being the only burst discovered to repeat, its cause may also be unique. The authors suggest that targeted searches of star-forming regions in galaxies similar to FRB 121102s host may reveal other repeating burst candidates, helping us to unravel the ongoing mystery of fast radio bursts.CitationC. G. Bassa et al 2017 ApJL 843 L8. doi:10.3847/2041-8213/aa7a0c

  12. TECHNIQUE OF ESTIMATION OF ERROR IN THE REFERENCE VALUE OF THE DOSE DURING THE LINEAR ACCELERATOR RADIATION OUTPUT CALIBRATION PROCEDURE. Part 2. Dependence on the characteristics of collimator, optical sourse-distance indicator, treatment field, lasers and treatment couch

    Directory of Open Access Journals (Sweden)

    Y. V. Tsitovich

    2016-01-01

    Full Text Available To ensure the safety of radiation oncology patients needed to provide consistent functional characteristics of the medical linear accelerators, which affect the accuracy of dose delivery. To this end, their quality control procedures, which include the calibration of radiation output of the linac, the error in determining the dose reference value during which must not exceed 2 %, is provided. The aim is to develop a methodology for determining the error (difference between a measured value of quantity and its true value in determining this value, depending on the characteristics of the collimator, the source to surface distance pointer, lasers, radiation field and treatment table. To achieve the objectives have been carried out dosimetric measurements of Trilogy S/N 3567 linac dose distributions, on the basis of which dose errors depending on the accuracy setting the zero position of the collimator, the deviation of the collimator rotation isocenter, the sourcesurface distance pointer accuracy, field size accuracy, the accuracy of lasers and treatment table positioning were obtained. It was found that the greatest impact on the value of the error has the error in the optical SSD indication and the error in the lasers position in the plane perpendicular to the plane of incidence of the radiation beam (up to 3.64 % for the energy of 6 MV. Dose errors caused by error in the field size were different for two photon energies, and reached 2.54 % for 6 MeV and 1.33% for 18 MeV. Errors caused by the rest of the characteristic do not exceed 1 %. Thus, it is possible to express the results of periodic quality control of these devices integrated in linac in terms of dose and use them to conduct a comprehensive assessment of the possibility of clinical use of a linear accelerator for oncology patients irradiation on the basis of the calibration of radiation output in case of development of techniques that allow to analyze the influence dosimetric

  13. The oxidative burst reaction in mammalian cells depends on gravity.

    Science.gov (United States)

    Adrian, Astrid; Schoppmann, Kathrin; Sromicki, Juri; Brungs, Sonja; von der Wiesche, Melanie; Hock, Bertold; Kolanus, Waldemar; Hemmersbach, Ruth; Ullrich, Oliver

    2013-12-20

    Gravity has been a constant force throughout the Earth's evolutionary history. Thus, one of the fundamental biological questions is if and how complex cellular and molecular functions of life on Earth require gravity. In this study, we investigated the influence of gravity on the oxidative burst reaction in macrophages, one of the key elements in innate immune response and cellular signaling. An important step is the production of superoxide by the NADPH oxidase, which is rapidly converted to H2O2 by spontaneous and enzymatic dismutation. The phagozytosis-mediated oxidative burst under altered gravity conditions was studied in NR8383 rat alveolar macrophages by means of a luminol assay. Ground-based experiments in "functional weightlessness" were performed using a 2 D clinostat combined with a photomultiplier (PMT clinostat). The same technical set-up was used during the 13th DLR and 51st ESA parabolic flight campaign. Furthermore, hypergravity conditions were provided by using the Multi-Sample Incubation Centrifuge (MuSIC) and the Short Arm Human Centrifuge (SAHC). The results demonstrate that release of reactive oxygen species (ROS) during the oxidative burst reaction depends greatly on gravity conditions. ROS release is 1.) reduced in microgravity, 2.) enhanced in hypergravity and 3.) responds rapidly and reversible to altered gravity within seconds. We substantiated the effect of altered gravity on oxidative burst reaction in two independent experimental systems, parabolic flights and 2D clinostat / centrifuge experiments. Furthermore, the results obtained in simulated microgravity (2D clinorotation experiments) were proven by experiments in real microgravity as in both cases a pronounced reduction in ROS was observed. Our experiments indicate that gravity-sensitive steps are located both in the initial activation pathways and in the final oxidative burst reaction itself, which could be explained by the role of cytoskeletal dynamics in the assembly and function

  14. Emergence of spatially heterogeneous burst suppression in a neural field model of electrocortical activity

    Directory of Open Access Journals (Sweden)

    Ingo eBojak

    2015-02-01

    Full Text Available Burst suppression in the electroencephalogram (EEG is a well described phenomenon that occurs during deep anaesthesia, as well as in a variety of congenital and acquired brain insults. Classically it is thought of as spatially synchronous, quasi-periodic bursts of high amplitude EEG separated by low amplitude activity. However, its characterisation as a ``global brain state'' has been challenged by recent results obtained with intracranial electrocortigraphy. Not only does it appear that burst suppression activity is highly asynchronous across cortex, but also that it may occur in isolated regions of circumscribed spatial extent. Here we outline a realistic neural field model for burst suppression by adding a slow process of synaptic resource depletion and recovery, which is able to reproduce qualitatively the empirically observed features during general anaesthesia at the whole cortex level. Simulations reveal heterogeneous bursting over the model cortex and complex spatiotemporal dynamics during simulated anaesthetic action, and provide forward predictions of neuroimaging signals for subsequent empirical comparisons and more detailed characterisation.Because burst suppression corresponds to a dynamical end-point of brain activity, theoretically accounting for its spatiotemporal emergence will vitally contribute to efforts aimed at clarifying whether a common physiological trajectory is induced by the actions of general anaesthetic agents. We have taken a first step in this direction by showing that a neural field model can qualitatively match recent experimental data that indicate spatial differentiation of burst suppression activity across cortex.

  15. Bursting thalamic responses in awake monkey contribute to visual detection and are modulated by corticofugal feedback

    Directory of Open Access Journals (Sweden)

    Tania eOrtuno

    2014-05-01

    Full Text Available The lateral geniculate nucleus is the gateway for visual information en route to the visual cortex. Neural activity is characterized by the existence of 2 firing modes: burst and tonic. Originally associated with sleep, bursts have now been postulated to be a part of the normal visual response, structured to increase the probability of cortical activation, able to act as a wake-up call to the cortex. We investigated a potential role for burst in the detection of novel stimuli by recording neuronal activity in the LGN of behaving monkeys during a visual detection task. Our results show that bursts are often the neuron’s first response, and are more numerous in the response to attended target stimuli than to unattended distractor stimuli. Bursts are indicators of the task novelty, as repetition decreased bursting. Because the primary visual cortex is the major modulatory input to the LGN, we compared the results obtained in control conditions with those observed when cortical activity was reduced by TMS. This cortical deactivation reduced visual response related bursting by 90%. These results highlight a novel role for the thalamus, able to code higher order image attributes as important as novelty early in the thalamo-cortical conversation.

  16. Observational properties of decameter type IV bursts

    Science.gov (United States)

    Melnik, Valentin; Brazhenko, Anatoly; Rucker, Helmut; Konovalenko, Alexander; Briand, Carine; Dorovskyy, Vladimir; Zarka, Philippe; Frantzusenko, Anatoly; Panchenko, Michael; Poedts, Stefan; Zaqarashvili, Teimuraz; Shergelashvili, Bidzina

    2013-04-01

    Oscillations of decameter type IV bursts were registered during observations of solar radio emission by UTR-2, URAN-2 and NDA in 2011-2012. Large majority of these bursts were accompanied by coronal mass ejections (CMEs), which were observed by SOHO and STEREO in the visible light. Only in some cases decameter type IV bursts were not associated with CMEs. The largest periods of oscillations P were some tens of minutes. There were some modes of long periods of oscillations simultaneously. Periods of oscillations in flux and in polarization profiles were close. Detailed properties of oscillations at different frequencies were analyzed on the example of two type IV bursts. One of them was observed on April 7, 2011 when a CME happened. Another one (August 1, 2011) was registered without any CME. The 7 April type IV burst had two periods in the frames 75-85 and 35-85 minutes. Interesting feature of these oscillations is decreasing periods with time. The observed decreasing rates dP/dt equaled 0.03-0.07. Concerning type IV burst observed on August 1, 2011 the period of its oscillations increases from 17 min. at 30 MHz to 44 min. at 10 MHz. Connection of type IV burst oscillations with oscillations of magnetic arches and CMEs at corresponding altitudes are discussed. The work is fulfilled in the frame of FP7 project "SOLSPANET".

  17. Bursting neurons and ultrasound avoidance in crickets

    Directory of Open Access Journals (Sweden)

    Gary eMarsat

    2012-07-01

    Full Text Available Decision making in invertebrates often relies on simple neural circuits composed of only a few identified neurons. The relative simplicity of these circuits makes it possible to identify the key computation and neural properties underlying decisions. In this review, we summarize recent research on the neural basis of ultrasound avoidance in crickets, a response that allows escape from echolocating bats. The key neural property shaping behavioral output is high-frequency bursting of an identified interneuron, AN2, which carries information about ultrasound stimuli from receptor neurons to the brain. AN2's spike train consists of clusters of spikes –bursts– that may be interspersed with isolated, non-burst spikes. AN2 firing is necessary and sufficient to trigger avoidance steering but only high-rate firing, such as occurs in bursts, evokes this response. AN2 bursts are therefore at the core of the computation involved in deciding whether or not to steer away from ultrasound. Bursts in AN2 are triggered by synaptic input from nearly synchronous bursts in ultrasound receptors. Thus the population response at the very first stage of sensory processing –the auditory receptor- already differentiates the features of the stimulus that will trigger a behavioral response from those that will not. Adaptation, both intrinsic to AN2 and within ultrasound receptors, scales the burst-generating features according to the stimulus statistics, thus filtering out background noise and ensuring that bursts occur selectively in response to salient peaks in ultrasound intensity. Furthermore AN2’s sensitivity to ultrasound varies adaptively with predation pressure, through both developmental and evolutionary mechanisms. We discuss how this key relationship between bursting and the triggering of avoidance behavior is also observed in other invertebrate systems such as the avoidance of looming visual stimuli in locusts or heat avoidance in beetles.

  18. Burst Oscillations: Watching Neutron Stars Spin

    Science.gov (United States)

    Strohmayer, Tod

    2010-01-01

    It is now almost 15 years since the first detection of rotationally modulated emission from X-ray bursting neutron stars, "burst oscillations," This phenomenon enables us to see neutron stars spin, as the X-ray burst flux asymmetrically lights up the surface. It has enabled a new way to probe the neutron star spin frequency distribution, as well as to elucidate the multidimensional nature of nuclear burning on neutron stars. I will review our current observational understanding of the phenomenon, with an eye toward highlighting some of the interesting remaining puzzles, of which there is no shortage.

  19. Space 'beachballs' generate pulsar bursts

    CERN Multimedia

    Wasowicz, L

    2003-01-01

    Researchers have analyzed radio emissions from a pulsar at the center of the Crab Nebula and have found 'subpulses' that last around 2 nanoseconds. They speculate this means the regions in which these ultra-short pulses are generated can be no larger than about 2 feet across - the distance light travels in 2 nanoseconds (2 pages).

  20. The October 30, 1994, seismic disturbance in South Africa: Earthquake or large rock burst?

    Science.gov (United States)

    Bowers, David

    1997-05-01

    The relative amplitude method is applied to body waves recorded at teleseismic distances from the October 30, 1994, mb 5.6 seismic disturbance, in South Africa, to determine the source depth and moment tensor. The results indicate that the source is shallow and that moment tensors with a positive volume change component are inconsistent with the observations. Observations of Rg in the frequency range 0.5-2.0 Hz at two regional distance stations also indicate that the source is shallow (less than about 3 km deep). Three-component broadband and long-period seismograms recorded at regional distances show strong Love wave excitation and a lobed Rayleigh radiation pattern, observations that are inconsistent with collapse mechanisms recently proposed for some large rock bursts (mine tremors). Modeling of teleseismic broadband P and regional distance surface waves shows that the source depth is shallow (2-3 km) and that the observed source radiation is consistent with that expected from a 45° normal dip-slip fault. The results of the modeling are confirmed by reports from the mining region that the disturbance was a mine tremor caused by slip on the Stuirmanspan Fault in the President Brand mine at a depth of between 2 and 3 km. The close match between observed and synthetic P and Rayleigh wave amplitudes suggests that the explosion-like mb: Ms of the mine tremor (mb 5.6, Ms 4.7) is attributable to the effect of the mechanism and the shallow depth of the source. The above results are at odds with those of Fan and Wallace [1995], who interpreted this disturbance as an earthquake at a depth of 12 km, based on a broadband inversion of three-component waveforms from two regional distance stations. This study confirms the need to interpret both broadband waveforms (to match amplitude and polarity) and short-period waveforms (to confirm (relative) onset times in the model structure) if inversion of regional broadband waveforms is to provide a reliable estimate of the moment

  1. Distance Education Success Factors.

    Science.gov (United States)

    Wagner, Ellen D.

    1995-01-01

    Anticipating and supporting the needs of users of technologies, programs, and services are critical to the success of distance education programs. Principal stakeholders are instructors who teach at a distance, learners pursuing distance education courses, site facilitators, and administrators. (JOW)

  2. Distance from a distance: psychological distance reduces sensitivity to any further psychological distance.

    Science.gov (United States)

    Maglio, Sam J; Trope, Yaacov; Liberman, Nira

    2013-08-01

    What is the difference between far and further? Investigations into such psychological distancing--removal from an egocentric reference point--have suggested similarities between geographical space, time, probability, and social distance. We draw on these similarities to propose that experiencing any kind of distance will reduce sensitivity to any other distance. Nine studies varied the initial distance of an event and assessed sensitivity to a second distance. Consistently, people were less responsive to a given span of distance when it was distal versus proximal. This effect held using each of the four distances as the initial instantiation of distance; it also held using each dimension to assess sensitivity to distance (i.e., as the second distance dimension). These findings suggest that the dimensions of psychological distance share a common, interchangeable meaning and that the cross-dimension difference between far and further is less than that between near and far. PsycINFO Database Record (c) 2013 APA, all rights reserved.

  3. On Gamma-Ray Bursts

    CERN Document Server

    Ruffini, Remo; Bianco, Carlo Luciano; Caito, Letizia; Chardonnet, Pascal; Cherubini, Christian; Dainotti, Maria Giovanna; Fraschetti, Federico; Geralico, Andrea; Guida, Roberto; Patricelli, Barbara; Rotondo, Michael; Hernandez, Jorge Armando Rueda; Vereshchagin, Gregory; Xue, She-Sheng

    2008-01-01

    (Shortened) We show by example how the uncoding of Gamma-Ray Bursts (GRBs) offers unprecedented possibilities to foster new knowledge in fundamental physics and in astrophysics. After recalling some of the classic work on vacuum polarization in uniform electric fields by Klein, Sauter, Heisenberg, Euler and Schwinger, we summarize some of the efforts to observe these effects in heavy ions and high energy ion collisions. We then turn to the theory of vacuum polarization around a Kerr-Newman black hole, leading to the extraction of the blackholic energy, to the concept of dyadosphere and dyadotorus, and to the creation of an electron-positron-photon plasma. We then present a new theoretical approach encompassing the physics of neutron stars and heavy nuclei. It is shown that configurations of nuclear matter in bulk with global charge neutrality can exist on macroscopic scales and with electric fields close to the critical value near their surfaces. These configurations may represent an initial condition for the...

  4. Intermediate long X-ray bursts from the ultra-compact binary candidate SLX1737-282

    DEFF Research Database (Denmark)

    Falanga, M.; Chenevez, Jérôme; Cumming, A.

    2008-01-01

    Aims. The low persistent flux X-ray burster source SLX 1737-282 is classified as an ultra-compact binary candidate. We compare the data on SLX 1737-282 with the other similar objects and attempt to derive constraints on the physical processes responsible for the formation of intermediate long...... bursts. Methods: Up to now only four bursts, all with duration between ≃15{-}30 min, have been recorded for SLX 1737-282. The properties of three of these intermediate long X-ray bursts observed by INTEGRAL are investigated and compared to other burster sources. The broadband spectrum of the persistent...... emission in the 3-100 keV energy band is studied with the INTEGRAL data. Results: The persistent emission is measured to be 0.5% Eddington luminosity. From the photospheric radius expansion observed during at least one burst we derive the source distance at 7.3 kpc assuming a pure helium atmosphere...

  5. Long Burst Error Correcting Codes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Long burst error mitigation is an enabling technology for the use of Ka band for high rate commercial and government users. Multiple NASA, government, and commercial...

  6. POPULATION SYNTHESIS AND GAMMA RAY BURST PROGENITORS

    Energy Technology Data Exchange (ETDEWEB)

    C. L. FREYER

    2000-12-11

    Population synthesis studies of binaries are always limited by a myriad of uncertainties from the poorly understood effects of binary mass transfer and common envelope evolution to the many uncertainties that still remain in stellar evolution. But the importance of these uncertainties depends both upon the objects being studied and the questions asked about these objects. Here I review the most critical uncertainties in the population synthesis of gamma-ray burst progenitors. With a better understanding of these uncertainties, binary population synthesis can become a powerful tool in understanding, and constraining, gamma-ray burst models. In turn, as gamma-ray bursts become more important as cosmological probes, binary population synthesis of gamma-ray burst progenitors becomes an important tool in cosmology.

  7. Impact responses, compressive and burst tests of glass/epoxy (GRE) composite pipes

    Science.gov (United States)

    Abrar, F. S. B.; Majid, M. S. A.; Ridzuan, M. J. M.; Syayuthi, A. R. A.

    2017-10-01

    The paper presents the impact responses, compression and burst tests of glass reinforced epoxy (GRE) composites pipes. Impact loadings of three different energy levels (5 J, 7.5 J, and 10 J) were applied, followed by monotonic burst tests. Uniaxial compressive tests were conducted GRE samples using a universal testing machine in accordance with ASTM D695-10. In addition, the tests were also repeated with samples of different winding angles of ±45 ° and ±55 ° and tested at room temperature, and elevated temperatures of 45 °C and 65 °C. The result shows that the higher the impact energy applied to the pipes, the lower the burst strength of the pipes. The maximum burst strength found decreased with an increase in the impact energy level. The results also indicate that the strength of the GRE pipes significantly decreases with increase in temperature though, they are also found to increase as the winding angles decrease.

  8. A quantitative measure of the structure of gamma-ray burst time profiles

    Science.gov (United States)

    Lestrade, John P.; Fishman, G.; Horack, J.; Meegan, C.; Moore, P.; Paciesas, W.; Wilson, R.

    1992-01-01

    A cursory examination of cosmic gamma-ray burst time profiles indicates an inhomogeneous distribution of structure. In the first approximation, there seem to be two types of profiles; smooth ones with little structure and highly variable ones with lots of structure. To put this observation to the test, we have examined the statistical nature of the profile derivative to choose which parameter might best be called the burst 'spikiness'. We have found that a good estimator is given by a count of the number of 'spikes' (defined by a specific numerical recipe) and not by the rms deviations from either a pre-burst background or any type of moving average background. The application of this parameter to 30 burst time histories shows it to be consistent over a wide range of profile types. The analysis also reveals a preferred average time between spikes of approximately 1.5 seconds.

  9. Dilated and unreactive pupils and burst-suppression on electroencephalography due to buproprion overdose.

    Science.gov (United States)

    Mundi, Jyoti Pathria; Betancourt, Jaime; Ezziddin, Omar; Tremayne, Brandie; Majic, Tamara; Mosenifar, Zab

    2012-01-01

    Burst-suppression pattern on electroencephalography (EEG) occurs upon dissociation of the cortex from underlying brain structures. Unless the pattern is a physiologic consequence of administered sedatives, this electroencephalographic pattern is indicative of a poor neurologic outcome and high mortality. We report a case of a 29-year-old female thought to be brain dead based on initial physical examination and EEG findings of burst-suppression, who was later found to have supratherapeutic serum levels of bupropion. This is the second documented case of burst-suppression pattern on EEG in a patient who overdosed on bupropion. We propose that burst-suppression in the setting of bupropion toxicity may revert with drug clearance.

  10. THE DISTANCE TO M104

    Energy Technology Data Exchange (ETDEWEB)

    McQuinn, Kristen B. W. [University of Texas at Austin, McDonald Observatory, 2515 Speedway, Stop C1400 Austin, TX 78712 (United States); Skillman, Evan D. [Minnesota Institute for Astrophysics, School of Physics and Astronomy, 116 Church Street, SE, University of Minnesota, Minneapolis, MN 55455 (United States); Dolphin, Andrew E. [Raytheon Company, 1151 E. Hermans Road, Tucson, AZ 85756 (United States); Berg, Danielle [Center for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin Milwaukee, 1900 East Kenwood Boulevard, Milwaukee, WI 53211 (United States); Kennicutt, Robert, E-mail: kmcquinn@astro.as.utexas.edu [Institute for Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)

    2016-11-01

    M104 (NGC 4594; the Sombrero galaxy) is a nearby, well-studied elliptical galaxy included in scores of surveys focused on understanding the details of galaxy evolution. Despite the importance of observations of M104, a consensus distance has not yet been established. Here, we use newly obtained Hubble Space Telescope optical imaging to measure the distance to M104 based on the tip of the red giant branch (TRGB) method. Our measurement yields the distance to M104 to be 9.55 ± 0.13 ± 0.31 Mpc equivalent to a distance modulus of 29.90 ± 0.03 ± 0.07 mag. Our distance is an improvement over previous results as we use a well-calibrated, stable distance indicator, precision photometry in a optimally selected field of view, and a Bayesian maximum likelihood technique that reduces measurement uncertainties. The most discrepant previous results are due to Tully–Fisher method distances, which are likely inappropriate for M104 given its peculiar morphology and structure. Our results are part of a larger program to measure accurate distances to a sample of well-known spiral galaxies (including M51, M74, and M63) using the TRGB method.

  11. The Distance to M51

    Science.gov (United States)

    McQuinn, Kristen. B. W.; Skillman, Evan D.; Dolphin, Andrew E.; Berg, Danielle; Kennicutt, Robert

    2016-07-01

    Great investments of observing time have been dedicated to the study of nearby spiral galaxies with diverse goals ranging from understanding the star formation process to characterizing their dark matter distributions. Accurate distances are fundamental to interpreting observations of these galaxies, yet many of the best studied nearby galaxies have distances based on methods with relatively large uncertainties. We have started a program to derive accurate distances to these galaxies. Here we measure the distance to M51—the Whirlpool galaxy—from newly obtained Hubble Space Telescope optical imaging using the tip of the red giant branch method. We measure the distance modulus to be 8.58 ± 0.10 Mpc (statistical), corresponding to a distance modulus of 29.67 ± 0.02 mag. Our distance is an improvement over previous results as we use a well-calibrated, stable distance indicator, precision photometry in a optimally selected field of view, and a Bayesian Maximum Likelihood technique that reduces measurement uncertainties. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  12. Gamma-ray burst standard sirens: Precision cosmology from gravitational waves

    Science.gov (United States)

    Holz, Daniel; Nissanke, Samaya; Hughes, Scott; Dalal, Neal; Sievers, Jonathan

    2011-04-01

    It has long been hypothesized that at least some gamma-ray bursts are associated with the merger of binary neutron stars, or with the merger of a neutron star with a black hole. Recent observations have accumulated compelling evidence supporting this hypothesis, at least for short-hard gamma-ray bursts. These bursts should then be accompanied by a gravitational-wave signal corresponding to the ?nal inspiral of the compact binary. Simultaneous observation of the gravitational and electromagnetic waves from these bursts would allow us to directly and independently determine both luminosity distance and redshift to the binary, thereby providing an absolutely calibrated, high accuracy standard siren (the gravitational wave analog of a standard candle). We examine the cosmological measurements to be expected from observations of gamma-ray burst standard sirens with a ground-based gravitational wave detector network (including LIGO and Virgo, and possible extensions with AIGO and LCGT). We find that these measurements should be able to map the low-redshift Hubble ?ow with excellent accuracy.

  13. Compact solar UV burst triggered in a magnetic field with a fan-spine topology

    Science.gov (United States)

    Chitta, L. P.; Peter, H.; Young, P. R.; Huang, Y.-M.

    2017-09-01

    Context. Solar ultraviolet (UV) bursts are small-scale features that exhibit intermittent brightenings that are thought to be due to magnetic reconnection. They are observed abundantly in the chromosphere and transition region, in particular in active regions. Aims: We investigate in detail a UV burst related to a magnetic feature that is advected by the moat flow from a sunspot towards a pore. The moving feature is parasitic in that its magnetic polarity is opposite to that of the spot and the pore. This comparably simple photospheric magnetic field distribution allows for an unambiguous interpretation of the magnetic geometry leading to the onset of the observed UV burst. Methods: We used UV spectroscopic and slit-jaw observations from the Interface Region Imaging Spectrograph (IRIS) to identify and study chromospheric and transition region spectral signatures of said UV burst. To investigate the magnetic topology surrounding the UV burst, we used a two-hour-long time sequence of simultaneous line-of-sight magnetograms from the Helioseismic and Magnetic Imager (HMI) and performed data-driven 3D magnetic field extrapolations by means of a magnetofrictional relaxation technique. We can connect UV burst signatures to the overlying extreme UV (EUV) coronal loops observed by the Atmospheric Imaging Assembly (AIA). Results: The UV burst shows a variety of extremely broad line profiles indicating plasma flows in excess of ±200 km s-1 at times. The whole structure is divided into two spatially distinct zones of predominantly up- and downflows. The magnetic field extrapolations show a persistent fan-spine magnetic topology at the UV burst. The associated 3D magnetic null point exists at a height of about 500 km above the photosphere and evolves co-spatially with the observed UV burst. The EUV emission at the footpoints of coronal loops is correlated with the evolution of the underlying UV burst. Conclusions: The magnetic field around the null point is sheared by

  14. Blockwise Repeated Burst Error Correcting Linear Codes

    Directory of Open Access Journals (Sweden)

    B.K. Dass

    2010-12-01

    Full Text Available This paper presents a lower and an upper bound on the number of parity check digits required for a linear code that corrects a single sub-block containing errors which are in the form of 2-repeated bursts of length b or less. An illustration of such kind of codes has been provided. Further, the codes that correct m-repeated bursts of length b or less have also been studied.

  15. Supernovae and gamma-ray bursts connection

    Energy Technology Data Exchange (ETDEWEB)

    Valle, Massimo Della [INAF-Napoli, Capodimonte Observatory, Salita Moiariello, 16, I-80131 Napoli (Italy); International Center for Relativistic Astrophysics Network, Piazzale della Repubblica 10, I-65122, Pescara (Italy)

    2015-12-17

    I’ll review the status of the Supernova/Gamma-Ray Burst connection. Several pieces of evidence suggest that long duration Gamma-ray Bursts are associated with bright SNe-Ic. However recent works suggest that GRBs might be produced in tight binary systems composed of a massive carbon-oxygen cores and a neutron star companion. Current estimates of the SN and GRB rates yield a ratio GRB/SNe-Ibc in the range ∼ 0.4% − 3%.

  16. Giant sparks at cosmological distances?

    Energy Technology Data Exchange (ETDEWEB)

    Kulkarni, S. R. [Caltech Optical Observatories 249-17, California Institute of Technology, Pasadena, CA 91125 (United States); Ofek, E. O. [Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100 (Israel); Neill, J. D. [Space Radiation Laboratory 290-17, California Institute of Technology, Pasadena, CA 91125 (United States); Zheng, Z. [Department of Physics and Astronomy, University of Utah, 115 South 1400 East 201, Salt Lake City, UT 84112 (United States); Juric, M. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)

    2014-12-10

    Millisecond-duration bright radio pulses at 1.4 GHz with high dispersion measures (DMs) were reported by Lorimer et al., Keane et al., and Thornton et al. Their all-sky rate is ≈10{sup 4} day{sup –1} above ∼1 Jy. Related events are 'Perytons'–similar pulsed, dispersed sources, but most certainly local. Suggested models of fast radio bursts (FRBs) can originate in Earth's atmosphere, in stellar coronae, in other galaxies, and even at cosmological distances. Using physically motivated assumptions combined with observed properties, we explore these models. In our analysis, we focus on the Lorimer event: a 30 Jy, 5 ms duration burst with DM = 375 cm{sup –3} pc, exhibiting a steep frequency-dependent pulse width (the Sparker). To be complete, we drop the assumption that high DMs are produced by plasma propagation and assume that the source produces pulses with frequency-dependent arrival time ('chirped signals'). Within this framework, we explore a scenario in which Perytons, the Sparker, and the FRBs are all atmospheric phenomena occurring at different heights. This model is ad hoc in that we cannot explain why Perytons at higher altitudes show greater DMs or exhibit narrower pulses. Nonetheless, we argue that the Sparker may be a Peryton. We end with two remarks. First, the detection of a single FRB by an interferometer with a kilometer (or longer) baseline will prove that FRBs are of extraterrestrial origin. Second, we urge astronomers to pursue observations and understanding of Perytons since they form (at least) a formidable foreground for the FRBs.

  17. Alfvenic accelerated electrons and short burst auroral kilometric radiations observed by the FAST satellite

    Science.gov (United States)

    Ma, Lun

    This investigation is motivated by previous study of short burst radiations (S- bursts) reported by Ergun et al. [2006], who suggested two generation mechanisms of S-bursts: one is the electron cyclotron maser instability due to an unstable ring distribution; the other is an upward electron beam generating upper hybrid resonance. The simulation results reported by Su et al. [2007] support the former mechanism. Only one Earth-based S-burst event was reported prior to our study. A systematic study was performed on particle and field observations from the FAST spacecraft to search for events of S-bursts and Alfvén waves. Eight events involving coexistence were identified and are presented in this thesis. All of them were observed at altitudes greater than 2500 km during winter months. In addition, S-bursts associated with Alfvénic perturbations were detected during periods when the AE indices were high, indicating a possible association with substorms. Furthermore, 24 dayside Alfvénic events and 20 nightside events were examined in detail. We found that the electron phase space density peaks along the magnetic field line for the nightside, which supports the concept of field-aligned acceleration by inertial Alfvén waves. However, the electron anisotropies involving the phase space densities peaked perpendicular to the magnetic field were observed on the dayside.

  18. Phase analysis method for burst onset prediction

    Science.gov (United States)

    Stellino, Flavio; Mazzoni, Alberto; Storace, Marco

    2017-02-01

    The response of bursting neurons to fluctuating inputs is usually hard to predict, due to their strong nonlinearity. For the same reason, decoding the injected stimulus from the activity of a bursting neuron is generally difficult. In this paper we propose a method describing (for neuron models) a mechanism of phase coding relating the burst onsets with the phase profile of the input current. This relation suggests that burst onset may provide a way for postsynaptic neurons to track the input phase. Moreover, we define a method of phase decoding to solve the inverse problem and estimate the likelihood of burst onset given the input state. Both methods are presented here in a unified framework, describing a complete coding-decoding procedure. This procedure is tested by using different neuron models, stimulated with different inputs (stochastic, sinusoidal, up, and down states). The results obtained show the efficacy and broad range of application of the proposed methods. Possible applications range from the study of sensory information processing, in which phase-of-firing codes are known to play a crucial role, to clinical applications such as deep brain stimulation, helping to design stimuli in order to trigger or prevent neural bursting.

  19. Encyclopedia of distances

    CERN Document Server

    Deza, Michel Marie

    2016-01-01

    This 4th edition of the leading reference volume on distance metrics is characterized by updated and rewritten sections on some items suggested by experts and readers, as well a general streamlining of content and the addition of essential new topics. Though the structure remains unchanged, the new edition also explores recent advances in the use of distances and metrics for e.g. generalized distances, probability theory, graph theory, coding theory, data analysis. New topics in the purely mathematical sections include e.g. the Vitanyi multiset-metric, algebraic point-conic distance, triangular ratio metric, Rossi-Hamming metric, Taneja distance, spectral semimetric between graphs, channel metrization, and Maryland bridge distance. The multidisciplinary sections have also been supplemented with new topics, including: dynamic time wrapping distance, memory distance, allometry, atmospheric depth, elliptic orbit distance, VLBI distance measurements, the astronomical system of units, and walkability distance. Lea...

  20. Dispersion Measure Variation of Repeating Fast Radio Burst Sources

    Science.gov (United States)

    Yang, Yuan-Pei; Zhang, Bing

    2017-09-01

    The repeating fast radio burst (FRB) 121102 was recently localized in a dwarf galaxy at a cosmological distance. The dispersion measure (DM) derived for each burst from FRB 121102 so far has not shown significant evolution, even though an apparent increase was recently seen with newly detected VLA bursts. It is expected that more repeating FRB sources may be detected in the future. In this work, we investigate a list of possible astrophysical processes that might cause DM variation of a particular FRB source. The processes include (1) cosmological scale effects such as Hubble expansion and large-scale structure fluctuations; (2) FRB local effects such as gas density fluctuation, expansion of a supernova remnant (SNR), a pulsar wind nebula, and an H ii region; and (3) the propagation effect due to plasma lensing. We find that the DM variations contributed by the large-scale structure are extremely small, and any observable DM variation is likely caused by the plasma local to the FRB source. In addition to mechanisms that decrease DM over time, we suggest that an FRB source in an expanding SNR around a nearly neutral ambient medium during the deceleration (Sedov-Taylor and snowplow) phases or in a growing H ii region can increase DM. Some effects (e.g., an FRB source moving in an H ii region or plasma lensing) can produce either positive or negative DM variations. Future observations of DM variations of FRB 121102 and other repeating FRB sources can provide important clues regarding the physical origin of these sources.

  1. Photon Mass Limits from Fast Radio Bursts

    CERN Document Server

    Bonetti, Luca; Mavromatos, Nikolaos E.; Sakharov, Alexander S.; Sarkisyan-Grinbaum, Edward K.G.; Spallicci, Alessandro D.A.M.

    2016-06-10

    The frequency-dependent time delays in fast radio bursts (FRBs) can be used to constrain the photon mass, if the FRB redshifts are known, but the similarity between the frequency dependences of dispersion due to plasma effects and a photon mass complicates the derivation of a limit on $m_\\gamma$. The redshift of FRB 150418 has been measured to $\\sim 2$% and its dispersion measure (DM) is known to $\\sim 0.1$%, but the strength of the constraint on $m_\\gamma$ is limited by uncertainties in the modelling of the host galaxy and the Milky Way, as well as possible inhomogeneities in the intergalactic medium (IGM). Allowing for these uncertainties, the recent data on FRB 150418 indicate that $m_\\gamma \\lesssim 1.7 \\times 10^{-14}$ eV c$^{-2}$ ($4.6 \\times 10^{-50}$ kg). In the future, the different redshift dependences of the plasma and photon mass contributions to DM can be used to improve the sensitivity to $m_\\gamma$ if more FRB redshifts are measured. For a fixed fractional uncertainty in the extra-galactic cont...

  2. Propagation and Interaction Properties of Successive Coronal Mass Ejections in Relation to a Complex Type II Radio Burst

    Science.gov (United States)

    Liu, Ying D.; Zhao, Xiaowei; Zhu, Bei

    2017-11-01

    We examine the propagation and interaction properties of three successive coronal mass ejections (CMEs) from 2001 November 21-22, with a focus on their connection with the behaviors of the associated long-duration complex type II radio burst. In combination with coronagraph and multi-point in situ observations, the long-duration type II burst provides key features for resolving the propagation and interaction complexities of the three CMEs. The two CMEs from November 22 interacted first and then overtook the November 21 CME at a distance of about 0.85 au from the Sun. The timescale for the shock originally driven by the last CME to propagate through the preceding two CMEs is estimated to be about 14 and 6 hr, respectively. We present a simple analytical model without any free parameters to characterize the whole Sun-to-Earth propagation of the shock, which shows a remarkable consistency with all the available data and MHD simulations even out to the distance of Ulysses (2.34 au). The coordination of in situ measurements at the Earth and Ulysses, which were separated by about 71.°4 in latitude, gives important clues for the understanding of shock structure and the interpretation of in situ signatures. The results also indicate a means by which to increase geo-effectiveness with multiple CMEs, which can be considered as another manifestation of the “perfect storm” scenario proposed by Liu et al., although the current case is not “super” in the same sense as the 2012 July 23 event.

  3. On Gamma-Ray Bursts

    Science.gov (United States)

    Ruffini, R.; Bernardini, M. G.; Bianco, C. L.; Caito, L.; Chardonnet, P.; Cherubini, C.; Dainotti, M. G.; Fraschetti, F.; Geralico, A.; Guida, R.; Patricelli, B.; Rotondo, M.; Rueda Hernandez, J. A.; Vereshchagin, G.; Xue, S.-S.

    2008-09-01

    We show by example how the uncoding of Gamma-Ray Bursts (GRBs) offers unprecedented possibilities to foster new knowledge in fundamental physics and in astrophysics. After recalling some of the classic work on vacuum polarization in uniform electric fields by Klein, Sauter, Heisenberg, Euler and Schwinger, we summarize some of the efforts to observe these effects in heavy ions and high energy ion collisions. We then turn to the theory of vacuum polarization around a Kerr-Newman black hole, leading to the extraction of the blackholic energy, to the concept of dyadosphere and dyadotorus, and to the creation of an electron-positron-photon plasma. We then present a new theoretical approach encompassing the physics of neutron stars and heavy nuclei. It is shown that configurations of nuclear matter in bulk with global charge neutrality can exist on macroscopic scales and with electric fields close to the critical value near their surfaces. These configurations may represent an initial condition for the process of gravitational collapse, leading to the creation of an electron-positron-photon plasma: the basic self-accelerating system explaining both the energetics and the high energy Lorentz factor observed in GRBs. We then turn to recall the two basic interpretational paradigms of our GRB model: 1) the Relative Space-Time Transformation (RSTT) paradigm and 2) the Interpretation of the Burst Structure (IBS) paradigm. These paradigms lead to a "canonical" GRB light curve formed from two different components: a Proper-GRB (P-GRB) and an extended afterglow comprising a raising part, a peak, and a decaying tail. When the P-GRB is energetically predominant we have a "genuine" short GRB, while when the afterglow is energetically predominant we have a so-called long GRB or a "fake" short GRB. We compare and contrast the description of the relativistic expansion of the electron-positron plasma within our approach and within the other ones in the current literature. We then turn

  4. Time Resolved Spectroscopy of SGR J1550-5418 Bursts Detected with Fermi/Gamma-Ray Burst Monitor

    NARCIS (Netherlands)

    Younes, G.; Kouveliotou, C.; van der Horst, A.J.; Baring, M.G.; Granot, J.; Watts, A.L.; Bhat, P.N.; Collazzi, A.; Gehrels, N.; Gorgone, N.; Göğüş, E.; Gruber, D.; Grunblatt, S.; Huppenkothen, D.; Kaneko, Y.; von Kienlin, A.; van der Klis, M.; Lin, L.; Mcenery, J.; van Putten, T.; Wijers, R.A.M.J.

    2014-01-01

    We report on a time-resolved spectroscopy of the 63 brightest bursts of SGR J1550-5418, detected with the Fermi/Gamma-ray Burst Monitor during its 2008-2009 intense bursting episode. We performed spectral analysis down to 4 ms timescales to characterize the spectral evolution of the bursts. Using a

  5. Hierarchical traits distances explain grassland Fabaceae species’ ecological niches distances

    Directory of Open Access Journals (Sweden)

    Florian eFort

    2015-02-01

    Full Text Available Fabaceae species play a key role in ecosystem functioning through their capacity to fix atmospheric nitrogen via their symbiosis with Rhizobium bacteria. To increase benefits of using Fabaceae in agricultural systems, it is necessary to find ways to evaluate species or genotypes having potential adaptations to sub-optimal growth conditions. We evaluated the relevance of phylogenetic distance, absolute trait distance and hierarchical trait distance for comparing the adaptation of 13 grassland Fabaceae species to different habitats, i.e. ecological niches. We measured a wide range of functional traits (root traits, leaf traits and whole plant traits in these species. Species phylogenetic and ecological distances were assessed from a species-level phylogenetic tree and species’ ecological indicator values, respectively. We demonstrated that differences in ecological niches between grassland Fabaceae species were related more to their hierarchical trait distances than to their phylogenetic distances. We showed that grassland Fabaceae functional traits tend to converge among species with the same ecological requirements. Species with acquisitive root strategies (thin roots, shallow root systems are competitive species adapted to non-stressful meadows, while conservative ones (coarse roots, deep root systems are able to tolerate stressful continental climates. In contrast, acquisitive species appeared to be able to tolerate low soil-P availability, while conservative ones need high P availability. Finally we highlight that traits converge along the ecological gradient, providing the assumption that species with similar root-trait values are better able to coexist, regardless of their phylogenetic distance.

  6. Coronas Mass Ejections, Shocks, and Type II Radio Bursts

    Science.gov (United States)

    Gopalswamy, Natchimuthuk

    2010-01-01

    Coronal mass ejections (CMEs) are the most energetic phenomena in the interplanetary medium. Type II radio bursts are the earliest indicators of particle acceleration by CME-driven shocks. There is one-to-one correspondence between large solar energetic particle (SEP) events and long wavelength type II bursts because the same CME-driven shock is supposed to accelerate electrons and ions. However, there are some significant deviations: some CMEs lacking type II bursts (radio-quiet or RQ CMEs) are associated with small SEP events while some radioloud (RL) CMEs are not associated with SEP events, suggesting subtle differences in the acceleration of electrons and protons. Not all CME-driven shocks are radio loud: more than one third of the interplanetary shocks during solar cycle 23 were radio quiet. Some RQ shocks were associated with energetic storm particle (ESP) events, which are detected when the shocks arrive at the observing spacecraft. This paper attempts to explain these contradictory results in terms of the properties of CMEs, shocks, and the ambient medium.

  7. Dynamics of gamma bursts in local field potentials.

    Science.gov (United States)

    Greenwood, Priscilla E; McDonnell, Mark D; Ward, Lawrence M

    2015-01-01

    In this letter, we provide a stochastic analysis of, and supporting simulation data for, a stochastic model of the generation of gamma bursts in local field potential (LFP) recordings by interacting populations of excitatory and inhibitory neurons. Our interest is in behavior near a fixed point of the stochastic dynamics of the model. We apply a recent limit theorem of stochastic dynamics to probe into details of this local behavior, obtaining several new results. We show that the stochastic model can be written in terms of a rotation multiplied by a two-dimensional standard Ornstein-Uhlenbeck (OU) process. Viewing the rewritten process in terms of phase and amplitude processes, we are able to proceed further in analysis. We demonstrate that gamma bursts arise in the model as excursions of the modulus of the OU process. The associated pair of stochastic phase and amplitude processes satisfies their own pair of stochastic differential equations, which indicates that large phase slips occur between gamma bursts. This behavior is mirrored in LFP data simulated from the original model. These results suggest that the rewritten model is a valid representation of the behavior near the fixed point for a wide class of models of oscillatory neural processes.

  8. Influence of suspension on the oxidative burst by rat neutrophils

    Science.gov (United States)

    Miller, E. S.; Koebel, D. A.; Davis, S. A.; Klein, J. B.; McLeish, K. R.; Goldwater, D.; Sonnenfeld, G.

    1994-01-01

    The influence of spaceflight on the oxidative burst of neutrophils is not known. The present study was designed to evaluate the influence of antiorthostatic suspension, a ground-based modeling system designed to simulate certain aspects of weightlessness that occur after spaceflight, on the capacity of rat neutrophils to express the oxidative burst, an important host defense mechanism against microbial pathogens. Rats were suspended in whole body harnesses in the antiorthostatic orientation for a 3- or 7-day period. Control rats were suspended orthostatically or allowed to remain in vivarium cages without the attachment of any suspension materials. After suspension, peripheral blood was harvested and neutrophils were isolated by density gradient centrifugation. The enriched neutrophil preparations were stimulated with N-formyl-methionyl-leucine-phenylalanine and phorbol myristic acid to induce the oxidative burst. It was found that neutrophils isolated from suspended animals released the same levels of superoxide anion as did vivarium control animals that were not suspended, indicating that whole body suspension did not alter this aspect of rat neutrophil function.

  9. On the origin of gamma-ray bursts.

    Science.gov (United States)

    Ryde, Felix

    2008-12-13

    Gamma-ray bursts are the most energetic explosions in the Universe, occurring at cosmological distances. The initial phase of the emission from these bursts is predominantly of gamma rays and stems from a highly relativistic outflow. The nature of this emission is still under debate. Here, I present the interpretation that the peak in the photon spectrum can be attributed to the black-body emission of the photosphere of the outflow, having a temperature of approximately 109K. An additional non-thermal spectral component can be attributed to additional dissipation of the kinetic energy in the outflow. This two-component model can be well fitted to most instantaneous spectra. Interestingly, the thermal component exhibits a recurring behaviour over emission pulse structures. Both the temperature and the energy flux vary as broken power laws. During the pre-break phase, the temperature is approximately constant while the energy flux rises. Furthermore, the ratio of the observed thermal flux to the emergent flux increases as a power law over the whole pulse. It is argued that these observations hold the key to our understanding of the prompt emission and the properties of the site from which it emanates.

  10. Fast radio burst event rate counts - I. Interpreting the observations

    Science.gov (United States)

    Macquart, J.-P.; Ekers, R. D.

    2018-02-01

    The fluence distribution of the fast radio burst (FRB) population (the `source count' distribution, N (>F) ∝Fα), is a crucial diagnostic of its distance distribution, and hence the progenitor evolutionary history. We critically reanalyse current estimates of the FRB source count distribution. We demonstrate that the Lorimer burst (FRB 010724) is subject to discovery bias, and should be excluded from all statistical studies of the population. We re-examine the evidence for flat, α > -1, source count estimates based on the ratio of single-beam to multiple-beam detections with the Parkes multibeam receiver, and show that current data imply only a very weak constraint of α ≲ -1.3. A maximum-likelihood analysis applied to the portion of the Parkes FRB population detected above the observational completeness fluence of 2 Jy ms yields α = -2.6_{-1.3}^{+0.7 }. Uncertainties in the location of each FRB within the Parkes beam render estimates of the Parkes event rate uncertain in both normalizing survey area and the estimated post-beam-corrected completeness fluence; this uncertainty needs to be accounted for when comparing the event rate against event rates measured at other telescopes.

  11. AN ABSENCE OF FAST RADIO BURSTS AT INTERMEDIATE GALACTIC LATITUDES

    Energy Technology Data Exchange (ETDEWEB)

    Petroff, E.; Van Straten, W.; Bailes, M.; Barr, E. D.; Coster, P.; Flynn, C.; Keane, E. F. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, VIC 3122 (Australia); Johnston, S. [CSIRO Astronomy and Space Science, Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710 (Australia); Bates, S. D.; Keith, M. J.; Kramer, M.; Stappers, B. W. [Jodrell Bank Centre for Astrophysics, University of Manchester, Alan Turing Building, Oxford Road, Manchester M13 9PL (United Kingdom); Bhat, N. D. R. [ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), 44 Rosehill Street, Redfern, NSW 2016 (Australia); Burgay, M.; Possenti, A.; Tiburzi, C. [INAF—Osservatorio Astronomico di Cagliari, Via della Scienza, I-09047 Selargius (Italy); Burke-Spolaor, S. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91104 (United States); Champion, D.; Ng, C. [Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Levin, L., E-mail: epetroff@astro.swin.edu.au [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); and others

    2014-07-10

    Fast radio bursts (FRBs) are an emerging class of bright, highly dispersed radio pulses. Recent work by Thornton et al. has revealed a population of FRBs in the High Time Resolution Universe (HTRU) survey at high Galactic latitudes. A variety of progenitors have been proposed, including cataclysmic events at cosmological distances, Galactic flare stars, and terrestrial radio frequency interference. Here we report on a search for FRBs at intermediate Galactic latitudes (–15° bursts.

  12. Visual Distance Cues Amplify Neuromagnetic Auditory N1m Responses

    Directory of Open Access Journals (Sweden)

    Christian F Altmann

    2011-10-01

    Full Text Available Ranging of auditory objects relies on several acoustic cues and is possibly modulated by additional visual information. Sound pressure level can serve as a cue for distance perception because it decreases with increasing distance. In this agnetoencephalography (MEG experiment, we tested whether psychophysical loudness judgment and N1m MEG responses are modulated by visual distance cues. To this end, we paired noise bursts at different sound pressure levels with synchronous visual cues at different distances. We hypothesized that noise bursts paired with far visual cues will be perceived louder and result in increased N1m amplitudes compared to a pairing with close visual cues. The rationale behind this was that listeners might compensate the visually induced object distance when processing loudness. Psychophysically, we observed no significant modulation of loudness judgments by visual cues. However, N1m MEG responses at about 100 ms after stimulus onset were significantly stronger for far versus close visual cues in the left auditory cortex. N1m responses in the right auditory cortex increased with increasing sound pressure level, but were not modulated by visual distance cues. Thus, our results suggest an audio-visual interaction in the left auditory cortex that is possibly related to cue integration for auditory distance processing.

  13. ASKAP Joins the Hunt for Mysterious Bursts

    Science.gov (United States)

    Kohler, Susanna

    2017-05-01

    A new telescope, the Australian Square Kilometre Array Pathfinder (ASKAP), has joined the search for energetic and elusive fast radio bursts. And in just a few days of looking, its already had success!Elusive TransientsThe Parkes radio telescope, which has detected all but five of the fast radio bursts published to date, has a very narrow field of view. [CSIRO]Fast radio bursts are mysterious millisecond-duration radio pulses that were first discovered around a decade ago. Since that time particularly in recent years weve made some progress toward the goal of localizing them. Were now fairly convinced that fast radio bursts come from outside of the galaxy, and yet theyre enormously bright orders of magnitude more luminous than any pulse seen from the Milky Way.Better identification of where these mysterious bursts come from would help us to determine what they are. But so far, weve discovered only around 30 such bursts, despite the fact that theyre estimated to occur at a rate of 3,000 events per day across the whole sky.Why are they so hard to find? Due to their short duration, effective detection would require instantaneous coverage of a very large fraction of the sky. The Parkes radio telescope which has detected all but five of the fast radio bursts published to date has a field of view spanning less than a square degree,significantly limiting our ability to rapidly survey for these transients.FRB 170107s band-averaged pulse (top) and dynamic spectrum (bottom). [Bannister et al. 2017]A New Array in TownA new player is now on the scene, however, and its already had huge success. ASKAP is a wide-field radio telescope made up of an array of 12-meter antennas. Using phased-array-feed technology, ASKAP is able to instantaneously observe an effective area of 160 square degrees an enormous field compared to Parkes 0.6 square degrees! This capability significantly increases our chances of being able to detect fast radio bursts.In a new study led by Keith Bannister

  14. Localization of Gamma-Ray Bursts Using the Fermi Gamma-Ray Burst Monitor

    NARCIS (Netherlands)

    Connaughton, V.; Briggs, M.S.; Goldstein, A.; Meegan, C.A.; Paciesas, W.S.; Preece, R.D.; Wilson-Hodge, C.A.; Gibby, M.H.; Greiner, J.; Gruber, D.; Jenke, P.; Kippen, R.M.; Pelassa, V.; Xiong, S.; Yu, H-F.; Bhat, P.N.; Burgess, J.M.; Byrne, D.; Fitzpatrick, G.; Foley, S.; Giles, M.M.; Guiriec, S.; van der Horst, A.J.; von Kienlin, A.; McBreen, S.; McGlynn, S.; Tierney, D.; Zhang, B..B.

    2015-01-01

    The Fermi Gamma-ray Burst Monitor (GBM) has detected over 1400 gamma-ray bursts (GRBs) since it began science operations in 2008 July. We use a subset of over 300 GRBs localized by instruments such as Swift, the Fermi Large Area Telescope, INTEGRAL, and MAXI, or through triangulations from the

  15. Apparent distance of sounds recorded in echoic and anechoic chambers.

    Science.gov (United States)

    Butler, R A; Levy, E T; Neff, W D

    1980-11-01

    With miniature microphones inserted into the external ear canals of a model and the sound source 90 degrees to left of midline, low-pass, and broadband noise bursts were picked up and recorded on magnetic tape. The bursts were generated in two highly contrasting acoustic environments: an anechoic and an echoic chamber. The taped sounds were played back monaurally and binaurally via headphones to 16 listeners seated in an acoustically neutral setting. They were instructed to estimate the distance of the stimuli. Apparent distances of bursts recorded in the echoic or reverberant chamber far exceeded those recorded in the anechoic chamber. It mattered not whether the sounds were presented monaurally or binaurally. What did influence distance estimates dramatically was the frequency composition of the stimuli. Low-pass sounds recorded in either acoustic environment were consistently judged to be further removed than high-pass sounds recorded in the same setting. They were also more likely to appear from behind the listener. In our moment-to-moment transaction with the acoustic environment, distant sounds generally have less acoustic energy in the higher audio frequency. We suggest that this lifetime of auditory experience influenced our listeners' scale of relative distance.

  16. Strategies for Studying the Sources of Gamma Ray Bursts

    Science.gov (United States)

    Cline, T. L.; Norris, J. P.; Hurley, K. C.

    2003-01-01

    The study of gamma ray bursts (GRBs) has rapidly evolved in recent years with the discovery of their cosmological nature and with BATSE, BeppoSAX, HETE and the IPN enabling a wide variety of associated . afterglow measurements. Multiwavelength observations ranging through the radio, optical, soft and hard x-ray, and gamma-ray regimes have exploded the field of GRB interpretation. Also, the Amanda, Milagro and LIGO experiments can search for related neutrino, cosmic-ray photon, and gravitational radiation events, even with the delayed alerts, such as from the IPN. The infrared region, where the optical emissions from sources at the extreme distances may be shifted, will become important but is undersubscribed. The soon-to-be launched Swift mission will greatly broaden the GRB discipline, and a strategy for associated ground-based measurements is outlined. The need for the improved global distribution of all instruments, in particular, robotic infrared detectors, is cited.

  17. Spatial Distribution of Gamma-Ray Burst Sources

    Science.gov (United States)

    Shirokov, S. I.; Raikov, A. A.; Baryshev, Yu. V.

    2017-12-01

    The spatial distribution of sources of gamma-ray bursts (GRB) with known red shifts is analyzed by the conditional density and pairwise distance methods. The sample of GRB is based on data from the Swift program and contains fluxes, coordinates, and red shifts for 384 GRB sources. Selection effects that distort the true source distribution are taken into account by comparing the observed distribution with fractal and uniform model catalogs. The Malmqvist effect is modeled using an approximation for the visible luminosity function of the GRB. The case of absorption in the galactic plane is also examined. This approach makes it possible to study the spatial structure of the entire sample at one time without artificial truncations. The estimated fractal dimensionality is D = 2.55 ± 0.06 on scales of 2-6 Gpc.

  18. INDUCED SCATTERING LIMITS ON FAST RADIO BURSTS FROM STELLAR CORONAE

    Energy Technology Data Exchange (ETDEWEB)

    Lyubarsky, Yuri [Physics Department, Ben-Gurion University, P.O.B. 653, Beer-Sheva 84105 (Israel); Ostrovska, Sofiya [Department of Mathematics, Atilim University, Incek 06836, Ankara (Turkey)

    2016-02-10

    The origin of fast radio bursts remains a puzzle. Suggestions have been made that they are produced within the Earth’s atmosphere, in stellar coronae, in other galaxies, or at cosmological distances. If they are extraterrestrial, the implied brightness temperature is very high, and therefore the induced scattering places constraints on possible models. In this paper, constraints are obtained on flares from coronae of nearby stars. It is shown that the radio pulses with the observed power could not be generated if the plasma density within and in the nearest vicinity of the source is as high as is necessary to provide the observed dispersion measure. However, one cannot exclude the possibility that the pulses are generated within a bubble with a very low density and pass through the dense plasma only in the outer corona.

  19. A study of the temporal and spectral characteristics of gamma ray bursts. Ph.D. Thesis - Maryland Univ.

    Science.gov (United States)

    Norris, J.

    1983-01-01

    Gamma-ray burst data obtained from the ISEE-3 Gamma Ray Burst Spectrometer and the Solar Maximum Mission's Hard X-ray Burst Spectrometer (HXRBS) were analyzed to yield information on burst temporal and spectral characteristics. A Monte Carlo approach was used to simulate the HXRBS response to candidate spectral models. At energies above about 100 keV, the spectra are well fit by exponential forms. At lower energies, 30 keV to 60 keV, depressions below the model continua are apparent in some bursts. The depressions are not instrumental or data-reduction artifacts. The event selection criterion of the ISEE-3 experiment is based on the time to accumulate a present number of photons rather than the photon count per unit time and is consequently independent of event duration for a given burst intensity, unlike most conventional systems. As a result, a significantly greater percentage of fast, narrow events have been detected. The ratio of count rates from two ISEE-3 detectors indicates that bursts with durations or approx. one second have much softer spectra than longer bursts.

  20. Probing the Cosmic Gamma-Ray Burst Rate with Trigger Simulations of the Swift Burst Alert Telescope

    Science.gov (United States)

    Lien, Amy; Sakamoto, Takanori; Gehrels, Neil; Palmer, David M.; Barthelmy, Scott D.; Graziani, Carlo; Cannizzo, John K.

    2013-01-01

    The gamma-ray burst (GRB) rate is essential for revealing the connection between GRBs, supernovae and stellar evolution. Additionally, the GRB rate at high redshift provides a strong probe of star formation history in the early universe. While hundreds of GRBs are observed by Swift, it remains difficult to determine the intrinsic GRB rate due to the complex trigger algorithm of Swift. Current studies of the GRB rate usually approximate the Swift trigger algorithm by a single detection threshold. However, unlike the previously own GRB instruments, Swift has over 500 trigger criteria based on photon count rate and additional image threshold for localization. To investigate possible systematic biases and explore the intrinsic GRB properties, we develop a program that is capable of simulating all the rate trigger criteria and mimicking the image threshold. Our simulations show that adopting the complex trigger algorithm of Swift increases the detection rate of dim bursts. As a result, our simulations suggest bursts need to be dimmer than previously expected to avoid over-producing the number of detections and to match with Swift observations. Moreover, our results indicate that these dim bursts are more likely to be high redshift events than low-luminosity GRBs. This would imply an even higher cosmic GRB rate at large redshifts than previous expectations based on star-formation rate measurements, unless other factors, such as the luminosity evolution, are taken into account. The GRB rate from our best result gives a total number of 4568 +825 -1429 GRBs per year that are beamed toward us in the whole universe.

  1. QKD-Based Secured Burst Integrity Design for Optical Burst Switched Networks

    Science.gov (United States)

    Balamurugan, A. M.; Sivasubramanian, A.; Parvathavarthini, B.

    2016-03-01

    The field of optical transmission has undergone numerous advancements and is still being researched mainly due to the fact that optical data transmission can be done at enormous speeds. It is quite evident that people prefer optical communication when it comes to large amount of data involving its transmission. The concept of switching in networks has matured enormously with several researches, architecture to implement and methods starting with Optical circuit switching to Optical Burst Switching. Optical burst switching is regarded as viable solution for switching bursts over networks but has several security vulnerabilities. However, this work exploited the security issues associated with Optical Burst Switching with respect to integrity of burst. This proposed Quantum Key based Secure Hash Algorithm (QKBSHA-512) with enhanced compression function design provides better avalanche effect over the conventional integrity algorithms.

  2. Cosmic Forensics Confirms Gamma-Ray Burst And Supernova Connection

    Science.gov (United States)

    2003-03-01

    Scientists announced today that they have used NASA's Chandra X-ray Observatory to confirm that a gamma-ray burst was connected to the death of a massive star. This result is an important step in understanding the origin of gamma-ray bursts, the most violent events in the present-day universe. "If a gamma-ray burst were a crime, then we now have strong circumstantial evidence that a supernova explosion was at the scene," said Nathaniel Butler of Massachusetts Institute of Technology in Cambridge, lead author of a paper presented today at the meeting of the High Energy Division of the American Astronomical Society. Chandra was able to obtain an unusually long observation (approximately 21 hours) of the afterglow of GRB 020813 (so named because the High-Energy Transient Explorer, HETE, discovered it on August 13, 2002.) A grating spectrometer aboard Chandra revealed an overabundance of elements characteristically dispersed in a supernova explosion. Narrow lines, or bumps, due to silicon and sulfur ions (atoms stripped of most of their electrons) were clearly identified in the X-ray spectrum of GRB 020813. "Our observation of GRB 020813 supports two of the most important features of the popular supra-nova model for gamma-ray bursts," said Butler. "An extremely massive star likely exploded less than two months prior to the gamma-ray burst, and the radiation from the gamma-ray burst was beamed into a narrow cone." An analysis of the data showed that the ions were moving away from the site of the gamma-ray burst at a tenth the speed of light, probably as part of a shell of matter ejected in the supernova explosion. The line features were observed to be sharply peaked, indicating that they were coming from a narrow region of the expanding shell. This implies that only a small fraction of the shell was illuminated by the gamma-ray burst, as would be expected if the burst was beamed into a narrow cone. The observed duration of the afterglow suggests a delay of about 60 days

  3. Non-Equilibrium Thermodynamics of Transcriptional Bursts

    Science.gov (United States)

    Hernández-Lemus, Enrique

    Gene transcription or Gene Expression (GE) is the process which transforms the information encoded in DNA into a functional RNA message. It is known that GE can occur in bursts or pulses. Transcription is irregular, with strong periods of activity, interspersed by long periods of inactivity. If we consider the average behavior over millions of cells, this process appears to be continuous. But at the individual cell level, there is considerable variability, and for most genes, very little activity at any one time. Some have claimed that GE bursting can account for the high variability in gene expression occurring between cells in isogenic populations. This variability has a big impact on cell behavior and thus on phenotypic conditions and disease. In view of these facts, the development of a thermodynamic framework to study gene expression and transcriptional regulation to integrate the vast amount of molecular biophysical GE data is appealing. Application of such thermodynamic formalism is useful to observe various dissipative phenomena in GE regulatory dynamics. In this chapter we will examine at some detail the complex phenomena of transcriptional bursts (specially of a certain class of anomalous bursts) in the context of a non-equilibrium thermodynamics formalism and will make some initial comments on the relevance of some irreversible processes that may be connected to anomalous transcriptional bursts.

  4. Encyclopedia of distances

    CERN Document Server

    Deza, Michel Marie

    2014-01-01

    This updated and revised third edition of the leading reference volume on distance metrics includes new items from very active research areas in the use of distances and metrics such as geometry, graph theory, probability theory and analysis. Among the new topics included are, for example, polyhedral metric space, nearness matrix problems, distances between belief assignments, distance-related animal settings, diamond-cutting distances, natural units of length, Heidegger’s de-severance distance, and brain distances. The publication of this volume coincides with intensifying research efforts into metric spaces and especially distance design for applications. Accurate metrics have become a crucial goal in computational biology, image analysis, speech recognition and information retrieval. Leaving aside the practical questions that arise during the selection of a ‘good’ distance function, this work focuses on providing the research community with an invaluable comprehensive listing of the main available di...

  5. Pulsar-Driven Jets in Supernovae, Gamma-Ray Bursts, and the Universe

    Directory of Open Access Journals (Sweden)

    John Middleditch

    2012-01-01

    Full Text Available The bipolarity of Supernova 1987A can be understood through its very early light curve from the CTIO 0.4 m telescope and IUE FES and following speckle observations of the “Mystery Spot”. These indicate a beam/jet of light/particles, with initial collimation factors >104 and velocities >0.95 c, involving up to 10−5 M⊙ interacting with circumstellar material. These can be produced by a model of pulsar emission from polarization currents induced/(modulated faster than c beyond the pulsar light cylinder by the periodic electromagnetic field (supraluminally induced polarization currents (SLIP. SLIP accounts for the disruption of supernova progenitors and their anomalous dimming at cosmological distances, jets from Sco X-1 and SS 433, the lack/presence of pulsations from the high-/low-luminosity low-mass X-ray binaries, and long/short gamma-ray bursts, and it predicts that their afterglows are the pulsed optical-/near-infrared emission associated with these pulsars. SLIP may also account for the TeV e+/e− results from PAMELA and ATIC, the WMAP “Haze”/Fermi “Bubbles,” and the r-process. SLIP jets from SNe of the first stars may allow galaxies to form without dark matter and explain the peculiar nongravitational motions between pairs of distant galaxies observed by GALEX.

  6. Bursting activity spreading through asymmetric interactions

    CERN Document Server

    Onaga, Tomokatsu

    2014-01-01

    People communicate with those who have the same background or share a common interest by using a social networking service (SNS). News or messages propagate through inhomogeneous connections in an SNS by sharing or facilitating additional comments. Such human activity is known to lead to endogenous bursting in the rate of message occurrences. We analyze a multi-dimensional self-exciting process to reveal dependence of the bursting activity on the topology of connections and the distribution of interaction strength on the connections. We determine the critical conditions for the cases where interaction strength is regulated at either the point of input or output for each person. In the input regulation condition, the network may exhibit bursting with infinitesimal interaction strength, if the dispersion of the degrees diverges as in the scale-free networks. In contrast, in the output regulation condition, the critical value of interaction strength, represented by the average number of events added by a single ...

  7. Burst Searches for Compact Binary Coalescences

    Science.gov (United States)

    Klimenko, Sergey

    2014-03-01

    Compact Binary coalescences (CBC) are the most promising sources of gravitational waves (GW) for the first detection with advanced GW detectors. Being the most efficient GW emitters among anticipated GW sources, they are also well understood theoretically in the framework of General Relativity. In the talk I'll discuss different flavors of CBC sources and two types of search methods employed in the GW data analysis: template and excess power. While template methods are the most optimal for CBC sources, I will concentrate on the excess power methods, which are typical for searches of generic GW transients (bursts). How to use burst searches for CBC sources? Why would we do this? What can we learn about CBC sources from a burst search? - these and other questions will be discussed in the talk. Supported by NSF grant PHY-1205512.

  8. CONSERVATIVE TREATMENT FOR THORACOLUMBAR SPINE BURST FRACTURES

    Directory of Open Access Journals (Sweden)

    Barajas Vanegas Raymundo

    Full Text Available ABSTRACT Objective: To identify the category of evidence and the strength of recommendation for the conservative treatment of thoracolumbar spine burst fractures. Method: A systematic review was conducted from April 2014 to June 2015, selecting articles according to their prospective design, related to thoracolumbar spine burst fractures and their treatment. These studies were published in the electronic bibliographic databases from January 2009 to January 2015. Results: A total of 9,504 articles were found in a free search, of which 7 met the selection criteria and were included for analysis in a study of a total of 435 patients, of whom 72 underwent surgical treatment and 363 received some type of conservative treatment, showing predominantly level of evidence "1b", with strength of recommendation type "A". Conclusions: According to the evidence obtained, the conservative treatment is a choice for patients with stable burst fracture in a single level of thoracolumbar spine and with no neurological injury.

  9. Gamma Ray Bursts Observations and Theoretical Conjectures

    CERN Document Server

    Alagoz, E; Carrillo, C; Golup, G T; Grimes, M; Herrera, Mora C; Gallo, Palomino J L; López, Vega A; Wicht, J

    2008-01-01

    Gamma Ray Bursts (GRBs) are short bursts of very high energy photons which were discovered in the late 1960s. Ever since their discovery, scientists have wondered about their origin. Nowadays it is known that they originate outside the Milky Way because of their high red shift rst measured in the afterglows thanks to the Beppo-SAX satellite and ground-based observations. However, theoreticians still do not agree about the mechanism that generates the bursts, and different competing models are animatedly debated. Current GRB experiments include the Swift satellite and the Pierre Auger Observatory that could detect GRBs with an increase of the background. A forthcoming dedicated experiment is GLAST, a satellite observatory for detecting gamma rays with energies up to 300 GeV, whose launch is scheduled for early 2008.

  10. Mechanism behind Erosive Bursts In Porous Media

    Science.gov (United States)

    Jäger, R.; Mendoza, M.; Herrmann, H. J.

    2017-09-01

    Erosion and deposition during flow through porous media can lead to large erosive bursts that manifest as jumps in permeability and pressure loss. Here we reveal that the cause of these bursts is the reopening of clogged pores when the pressure difference between two opposite sites of the pore surpasses a certain threshold. We perform numerical simulations of flow through porous media and compare our predictions to experimental results, recovering with excellent agreement shape and power-law distribution of pressure loss jumps, and the behavior of the permeability jumps as a function of particle concentration. Furthermore, we find that erosive bursts only occur for pressure gradient thresholds within the range of two critical values, independent of how the flow is driven. Our findings provide a better understanding of sudden sand production in oil wells and breakthrough in filtration.

  11. Height of Shock Formation in the Solar Corona Inferred from Observations of Type II Radio Bursts and Coronal Mass Ejections

    Science.gov (United States)

    Gopalswamy, N.; Xie, H.; Makela, P.; Yashiro, S.; Akiyama, S.; Uddin, W.; Srivastava, A. K.; Joshi, N. C.; Chandra, R.; Manoharan, P. K.

    2013-01-01

    Employing coronagraphic and EUV observations close to the solar surface made by the Solar Terrestrial Relations Observatory (STEREO) mission, we determined the heliocentric distance of coronal mass ejections (CMEs) at the starting time of associated metric type II bursts. We used the wave diameter and leading edge methods and measured the CME heights for a set of 32 metric type II bursts from solar cycle 24. We minimized the projection effects by making the measurements from a view that is roughly orthogonal to the direction of the ejection. We also chose image frames close to the onset times of the type II bursts, so no extrapolation was necessary. We found that the CMEs were located in the heliocentric distance range from 1.20 to 1.93 solar radii (Rs), with mean and median values of 1.43 and 1.38 Rs, respectively. We conclusively find that the shock formation can occur at heights substantially below 1.5 Rs. In a few cases, the CME height at type II onset was close to 2 Rs. In these cases, the starting frequency of the type II bursts was very low, in the range 25-40 MHz, which confirms that the shock can also form at larger heights. The starting frequencies of metric type II bursts have a weak correlation with the measured CME/shock heights and are consistent with the rapid decline of density with height in the inner corona.

  12. X-ray bursts observed with JEM-X

    DEFF Research Database (Denmark)

    Brandt, Søren Kristian; Chenevez, Jérôme; Lund, Niels

    2006-01-01

    We report on the search for X-ray bursts in the JEM-X X-ray monitor on INTEGRAL during the first two years of operations. More than 350 bursts from 25 different type-I X-ray burst sources were found.......We report on the search for X-ray bursts in the JEM-X X-ray monitor on INTEGRAL during the first two years of operations. More than 350 bursts from 25 different type-I X-ray burst sources were found....

  13. A Repeating Fast Radio Burst: Radio and X-ray Follow-up Observations of FRB 121102

    Science.gov (United States)

    Scholz, Paul; Spitler, Laura; Hessels, Jason; Bogdanov, Slavko; Brazier, Adam; Camilo, Fernando; Chatterjee, Shami; Cordes, James M.; Crawford, Fronefield; Deneva, Julia S.; Ferdman, Robert; Freire, Paulo; Kaspi, Victoria M.; Lazarus, Patrick; Lynch, Ryan; Madsen, Erik; McLaughlin, Maura; Patel, Chitrang; Ransom, Scott M.; Seymour, Andrew; Stairs, Ingrid H.; Stappers, Benjamin; van Leeuwen, Joeri; Zhu, Weiwei

    2016-04-01

    A new phenomenon has emerged in high-energy astronomy in the past few years: the Fast Radio Burst. Fast Radio Bursts (FRBs) are millisecond-duration radio bursts whose dispersion measures imply that they originate from far outside of the Galaxy. Their origin is as yet unknown; their durations and energetics imply that they involve compact objects, such as neutron stars or black holes. Due to their extreme luminosities implied by their distances and the previous absence of any repeat burst in follow-up observations, many potential explanations involve one-time cataclysmic events. However, in our Arecibo telescope follow-up observations of FRB 121102 (discovered in the PALFA survey; Spitler et al. 2014), we find additional bursts at the same location and dispersion measure as the original burst. We also present the results of Swift and Chandra X-ray observations of the field. This result shows that, for at least a sub-set of the FRB population, the source can repeat and thus cannot be explained by a cataclysmic origin.

  14. Broadband Spectral Investigations of Magnetar Bursts

    Science.gov (United States)

    Kırmızıbayrak, Demet; Şaşmaz Muş, Sinem; Kaneko, Yuki; Göğüş, Ersin

    2017-09-01

    We present our broadband (2-250 keV) time-averaged spectral analysis of 388 bursts from SGR J1550-5418, SGR 1900+14, and SGR 1806-20 detected with the Rossi X-ray Timing Explorer (RXTE) here and as a database in a companion web-catalog. We find that two blackbody functions (BB+BB), the sum of two modified blackbody functions (LB+LB), the sum of a blackbody function and a power-law function (BB+PO), and a power law with a high-energy exponential cutoff (COMPT) all provide acceptable fits at similar levels. We performed numerical simulations to constrain the best fitting model for each burst spectrum and found that 67.6% of burst spectra with well-constrained parameters are better described by the Comptonized model. We also found that 64.7% of these burst spectra are better described with the LB+LB model, which is employed in the spectral analysis of a soft gamma repeater (SGR) for the first time here, than with the BB+BB and BB+PO models. We found a significant positive lower bound trend on photon index, suggesting a decreasing upper bound on hardness, with respect to total flux and fluence. We compare this result with bursts observed from SGR and AXP (anomalous X-ray pulsar) sources and suggest that the relationship is a distinctive characteristic between the two. We confirm a significant anticorrelation between burst emission area and blackbody temperature, and find that it varies between the hot and cool blackbody temperatures differently than previously discussed. We expand on the interpretation of our results in the framework of a strongly magnetized neutron star.

  15. Broadband Spectral Investigations of Magnetar Bursts

    Energy Technology Data Exchange (ETDEWEB)

    Kırmızıbayrak, Demet; Şaşmaz Muş, Sinem; Kaneko, Yuki; Göğüş, Ersin, E-mail: demetk@sabanciuniv.edu [Faculty of Engineering and Natural Sciences, Sabancı University, Orhanlı Tuzla, Istanbul 34956 (Turkey)

    2017-09-01

    We present our broadband (2–250 keV) time-averaged spectral analysis of 388 bursts from SGR J1550−5418, SGR 1900+14, and SGR 1806−20 detected with the Rossi X-ray Timing Explorer ( RXTE ) here and as a database in a companion web-catalog. We find that two blackbody functions (BB+BB), the sum of two modified blackbody functions (LB+LB), the sum of a blackbody function and a power-law function (BB+PO), and a power law with a high-energy exponential cutoff (COMPT) all provide acceptable fits at similar levels. We performed numerical simulations to constrain the best fitting model for each burst spectrum and found that 67.6% of burst spectra with well-constrained parameters are better described by the Comptonized model. We also found that 64.7% of these burst spectra are better described with the LB+LB model, which is employed in the spectral analysis of a soft gamma repeater (SGR) for the first time here, than with the BB+BB and BB+PO models. We found a significant positive lower bound trend on photon index, suggesting a decreasing upper bound on hardness, with respect to total flux and fluence. We compare this result with bursts observed from SGR and AXP (anomalous X-ray pulsar) sources and suggest that the relationship is a distinctive characteristic between the two. We confirm a significant anticorrelation between burst emission area and blackbody temperature, and find that it varies between the hot and cool blackbody temperatures differently than previously discussed. We expand on the interpretation of our results in the framework of a strongly magnetized neutron star.

  16. A 3rd Class of Gamma Ray Bursts?

    OpenAIRE

    Horvath, I.

    1998-01-01

    Two classes of Gamma Ray Bursts have been identified so far, characterized by T_90 durations shorter and longer than approximately 2 seconds. We show here that the BATSE 3B data allow a good fit with three Gaussian distributions in log T_90. The chi^2 statistic indicates a 40 % probability for two Gaussians, whereas the three-Gaussian fit probability is 98 %. Using another statistical method, it is argued that the probability that the third class is a random fluctuation is less than 0.02 %.

  17. Simmer analysis of prompt burst energetics experiments

    Energy Technology Data Exchange (ETDEWEB)

    Hitchcock, J.T.

    1982-03-01

    The Prompt Burst Energetics experiments are designed to measure the pressure behavior of fuel and coolant as working fluids during a hypothetical prompt burst disassembly in an LMFBR. The work presented in this report consists of a parametric study of PBE-5S, a fresh oxide fuel experiment, using SIMMER-II. The various pressure sources in the experiment are examined, and the dominant source identified as incondensable contaminant gasses in the fuel. The important modeling uncertainties and limitations of SIMMER-II as applied to these experiments are discussed.

  18. Noise-induced bursting in Rulkov model

    Science.gov (United States)

    Ryashko, L.; Slepukhina, E.; Nasyrova, V.

    2016-10-01

    A problem of mathematical modeling and analysis of the stochastic phenomena in neuronal activity is considered. As a basic example, we use the nonlinear Rulkov map-based neuron model with random disturbances. In deterministic case, this one-dimensional model demonstrates quiescence, tonic and chaotic spiking regimes. We show that due to presence of random disturbances, a new regime of noise-induced bursting is generated not only in bistability zones, but also in monostability zones. To estimate noise intensity corresponding to the onset of bursting, the stochastic sensitivity technique and confidence domains method are applied. An effciency of our approach is confirmed by the statistics of interspike intervals.

  19. Supernovae and Gamma-Ray Bursts

    Science.gov (United States)

    Livio, Mario; Panagia, Nino; Sahu, Kailash

    2001-07-01

    Participants; Preface; Gamma-ray burst-supernova relation B. Paczynski; Observations of gamma-ray bursts G. Fishman; Fireballs T. Piran; Gamma-ray mechanisms M. Rees; Prompt optical emission from gamma-ray bursts R. Kehoe, C. Akerlof, R. Balsano, S. Barthelmy, J. Bloch, P. Butterworth, D. Casperson, T. Cline, S. Fletcher, F. Frontera, G. Gisler, J. Heise, J. Hills, K. Hurley, B. Lee, S. Marshall, T. McKay, A. Pawl, L. Piro, B. Priedhorsky, J. Szymanski and J. Wren; X-ray afterglows of gamma-ray bursts L. Piro; The first year of optical-IR observations of SN1998bw I. Danziger, T. Augusteijn, J. Brewer, E. Cappellaro, V. Doublier, T. Galama, J. Gonzalez, O. Hainaut, B. Leibundgut, C. Lidman, P. Mazzali, K. Nomoto, F. Patat, J. Spyromilio, M. Turatto, J. Van Paradijs, P. Vreeswijk and J. Walsh; X-ray emission of Supernova 1998bw in the error box of GRB980425 E. Pian; Direct analysis of spectra of type Ic supernovae D. Branch; The interaction of supernovae and gamma-ray bursts with their surroundings R. Chevalier; Magnetars, soft gamma-ray repeaters and gamma-ray bursts A. Harding; Super-luminous supernova remnants Y. -H. Chu, C. -H. Chen and S. -P. Lai; The properties of hypernovae: SNe Ic 1998bw, 1997ef, and SN IIn 1997cy K. Nomoto, P. Mazzali, T. Nakamura, K. Iwanmoto, K. Maeda, T. Suzuki, M. Turatto, I. Danziger and F. Patat; Collapsars, Gamma-Ray Bursts, and Supernovae S. Woosley, A. MacFadyen and A. Heger; Pre-supernova evolution of massive stars N. Panagia and G. Bono; Radio supernovae and GRB 980425 K. Weiler, N. Panagia, R. Sramek, S. Van Dyk, M. Montes and C. Lacey; Models for Ia supernovae and evolutionary effects P. Hoflich and I. Dominguez; Deflagration to detonation A. Khokhlov; Universality in SN Iae and the Phillips relation D. Arnett; Abundances from supernovae F. -K. Thielemann, F. Brachwitz, C. Freiburghaus, S. Rosswog, K. Iwamoto, T. Nakamura, K. Nomoto, H. Umeda, K. Langanke, G. Martinez-Pinedo, D. Dean, W. Hix and M. Strayer; Sne, GRBs, and the

  20. Polyrhythmic synchronization in bursting networking motifs.

    Science.gov (United States)

    Shilnikov, Andrey; Gordon, René; Belykh, Igor

    2008-09-01

    We study the emergence of polyrhythmic dynamics of motifs which are the building block for small inhibitory-excitatory networks, such as central pattern generators controlling various locomotive behaviors of animals. We discover that the pacemaker determining the specific rhythm of such a network composed of realistic Hodgkin-Huxley-type neurons is identified through the order parameter, which is the ratio of the neurons' burst durations or of duty cycles. We analyze different configurations of the motifs and describe the universal mechanisms for synergetics of the bursting patterns. We discuss also the multistability of inhibitory networks that results in polyrhythmicity of its emergent synchronous behaviors. (c) 2008 American Institute of Physics.

  1. Flux decay during thermonuclear X-ray bursts analysed with the dynamic power-law index method

    Science.gov (United States)

    Kuuttila, J.; Kajava, J. J. E.; Nättilä, J.; Motta, S. E.; Sánchez-Fernández, C.; Kuulkers, E.; Cumming, A.; Poutanen, J.

    2017-08-01

    The cooling of type-I X-ray bursts can be used to probe the nuclear burning conditions in neutron star envelopes. The flux decay of the bursts has been traditionally modelled with an exponential, even if theoretical considerations predict power-law-like decays. We have analysed a total of 540 type-I X-ray bursts from five low-mass X-ray binaries observed with the Rossi X-ray Timing Explorer. We grouped the bursts according to the source spectral state during which they were observed (hard or soft), flagging those bursts that showed signs of photospheric radius expansion (PRE). The decay phase of all the bursts were then fitted with a dynamic power-law index method. This method provides a new way of probing the chemical composition of the accreted material. Our results show that in the hydrogen-rich sources the power-law decay index is variable during the burst tails and that simple cooling models qualitatively describe the cooling of presumably helium-rich sources 4U 1728-34 and 3A 1820-303. The cooling in the hydrogen-rich sources 4U 1608-52, 4U 1636-536, and GS 1826-24, instead, is clearly different and depends on the spectral states and whether PRE occurred or not. Especially the hard state bursts behave differently than the models predict, exhibiting a peculiar rise in the cooling index at low burst fluxes, which suggests that the cooling in the tail is much faster than expected. Our results indicate that the drivers of the bursting behaviour are not only the accretion rate and chemical composition of the accreted material, but also the cooling that is somehow linked to the spectral states. The latter suggests that the properties of the burning layers deep in the neutron star envelope might be impacted differently depending on the spectral state.

  2. Achromatic late-time variability in thermonuclear X-ray bursts - an accretion disk disrupted by a nova-like shell?

    OpenAIRE

    Zand, J. J. M. in 't; Galloway, D. K.; Ballantyne, D. R.

    2010-01-01

    An unusual Eddington-limited thermonuclear X-ray burst was detected from the accreting neutron star in 2S 0918-549 with the Rossi X-ray Timing Explorer. The burst commenced with a brief (40 ms) precursor and maintained near-Eddington fluxes during the initial 77 s. These characteristics are indicative of a nova-like expulsion of a shell from the neutron star surface. Starting 122 s into the burst, the burst shows strong (87 +/- 1% peak-to-peak amplitude) achromatic fluctuations for 60 s. We s...

  3. ESA's Integral detects closest cosmic gamma-ray burst

    Science.gov (United States)

    2004-08-01

    should emit similar amounts of gamma-ray energy. The fraction of it detected at Earth should then depend on the 'width' (opening angle) and orientation of the beam as well as on the distance. The energy received should be larger when the beam is narrow or points towards us and smaller when the beam is broad or points away from us. New data collected with ESA's high energy observatories, Integral and XMM-Newton, now show that this picture is not so clear-cut and that the amount of energy emitted by GRBs can vary significantly. "The idea that all GRBs spit out the same amount of gamma rays, or that they are 'standard candles' as we call them, is simply ruled out by the new data," said Dr Sergey Sazonov, from the Space Research Institute of the Russian Academy of Sciences, Moscow (Russia) and the Max-Planck Institute for Astrophysics, Garching near Munich (Germany). Sazonov and an international team of researchers studied the GRB detected by Integral on 3 December 2003 and given the code-name of GRB 031203. Within a record 18 seconds of the burst, the Integral Burst Alert System had pinpointed the approximate position of GRB 031203 in the sky and sent the information to a network of observatories around the world. A few hours later one of them, ESA's XMM-Newton, determined a much more precise position for GRB 031203 and detected a rapidly fading X-ray source, which was subsequently seen by radio and optical telescopes on the ground. This wealth of data allowed astronomers to determine that GRB 031203 went off in a galaxy less than 1300 million light years away, making it the closest GRB ever observed. Even so, the way in which GRB 031203 dimmed with time and the distribution of its energy were not different from those of distant GRBs. Then, scientists started to realise that the concept of the 'standard candle' may not hold. "Being so close should make GRB 031203 appear very bright, but the amount of gamma-rays measured by Integral is about one thousand times less than what

  4. INTEGRAL monitoring of unusually long X-ray bursts

    DEFF Research Database (Denmark)

    -rich bursting regime to a pure helium regime. Moreover, a handful of long bursts have shown, before the extended decay phase, an initial spike similar to a normal short X-ray burst. Such twofold bursts might be a sort of link between short and super-bursts, where the premature ignition of a carbon layer could......Thermonuclear bursts on the surface of accreting neutron stars in low mass X-ray binaries have been studied for many years and have in a few cases confirmed theoretical models of nuclear ignition and burning mechanisms. The large majority of X-ray bursts last less than 100s. A good number...... of the known X-ray bursters are frequently observed by INTEGRAL, in particular in the frame of the Key Programmes. Taking advantage of the INTEGRAL instrumentation, an international collaboration led by the JEM-X team at the Danish National Space Institute has been monitoring the occurrence of uncommon burst...

  5. On the Nature of the Gamma-ray Bursts

    Directory of Open Access Journals (Sweden)

    Kyung-Ai Hong

    1987-12-01

    Full Text Available Review of the γ-ray burst phenomena are presented. History of the γ-ray bursts, characteristics, and three radiation mechanisms of thermal bremsstrahlung, thermal synchrotron, and inverse Compton scattering processes are considered.

  6. THE FERMI-GBM X-RAY BURST MONITOR: THERMONUCLEAR BURSTS FROM 4U 0614+09

    Energy Technology Data Exchange (ETDEWEB)

    Linares, M.; Chakrabarty, D. [Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, Cambridge, MA 02139 (United States); Connaughton, V.; Bhat, P. N.; Briggs, M. S.; Preece, R. [CSPAR and Physics Department, University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Jenke, P.; Kouveliotou, C.; Wilson-Hodge, C. A. [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Van der Horst, A. J. [Astronomical Institute ' Anton Pannekoek' , University of Amsterdam, NL-1090-GE Amsterdam (Netherlands); Camero-Arranz, A.; Finger, M.; Paciesas, W. S. [Universities Space Research Association, Huntsville, AL 35805 (United States); Beklen, E. [Physics Department, Suleyman Demirel University, 32260 Isparta (Turkey); Von Kienlin, A. [Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, Postfach 1312, D-85748 Garching (Germany)

    2012-12-01

    Thermonuclear bursts from slowly accreting neutron stars (NSs) have proven difficult to detect, yet they are potential probes of the thermal properties of the NS interior. During the first year of a systematic all-sky search for X-ray bursts using the Gamma-ray Burst Monitor aboard the Fermi Gamma-ray Space Telescope we have detected 15 thermonuclear bursts from the NS low-mass X-ray binary 4U 0614+09 when it was accreting at nearly 1% of the Eddington limit. We measured an average burst recurrence time of 12 {+-} 3 days (68% confidence interval) between 2010 March and 2011 March, classified all bursts as normal duration bursts and placed a lower limit on the recurrence time of long/intermediate bursts of 62 days (95% confidence level). We discuss how observations of thermonuclear bursts in the hard X-ray band compare to pointed soft X-ray observations and quantify such bandpass effects on measurements of burst radiated energy and duration. We put our results for 4U 0614+09 in the context of other bursters and briefly discuss the constraints on ignition models. Interestingly, we find that the burst energies in 4U 0614+09 are on average between those of normal duration bursts and those measured in long/intermediate bursts. Such a continuous distribution in burst energy provides a new observational link between normal and long/intermediate bursts. We suggest that the apparent bimodal distribution that defined normal and long/intermediate duration bursts during the last decade could be due to an observational bias toward detecting only the longest and most energetic bursts from slowly accreting NSs.

  7. Spectral Lag Evolution among -Ray Burst Pulses

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... We analyse the spectral lag evolution of -ray burst (GRB) pulses with observations by CGRO/BATSE. No universal spectral lag evolution feature and pulse luminosity-lag relation within a GRB is observed.Our results suggest that the spectral lag would be due to radiation physics and dynamics of a given ...

  8. Radio Afterglows of Gamma Ray Bursts

    Indian Academy of Sciences (India)

    Lekshmi Resmi

    2017-09-12

    Sep 12, 2017 ... Gamma Ray Bursts (GRBs) were serendipitously discovered in late 1960s by the Vela military satel- lites. In the following years, dedicated scanning instru- ments on-board high energy missions like BeppoSAX1,. CGRO2, HETE3, Swift4 and Fermi5 have increased the number of GRB detections to several ...

  9. Interface Simulation Distances

    Directory of Open Access Journals (Sweden)

    Pavol Černý

    2012-10-01

    Full Text Available The classical (boolean notion of refinement for behavioral interfaces of system components is the alternating refinement preorder. In this paper, we define a distance for interfaces, called interface simulation distance. It makes the alternating refinement preorder quantitative by, intuitively, tolerating errors (while counting them in the alternating simulation game. We show that the interface simulation distance satisfies the triangle inequality, that the distance between two interfaces does not increase under parallel composition with a third interface, and that the distance between two interfaces can be bounded from above and below by distances between abstractions of the two interfaces. We illustrate the framework, and the properties of the distances under composition of interfaces, with two case studies.

  10. Is there cosmological time dilation in gamma-ray bursts?

    Science.gov (United States)

    Band, David L.

    1994-01-01

    Norris et al. report that the temporal structure of faint gamma-ray bursts is longer than that of bright bursts, as expected for time dilation in the cosmological models of burst origin. I show that the observed trends can easily be produced by a burst luminosity function and thus may not result from cosmological effects. A cosmological signature may be present, but the tests Norris et al. present are not powerful enough to detect these signatures.

  11. BurstMem: A High-Performance Burst Buffer System for Scientific Applications

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Teng [Auburn University, Auburn, Alabama; Oral, H Sarp [ORNL; Wang, Yandong [Auburn University, Auburn, Alabama; Settlemyer, Bradley W [ORNL; Atchley, Scott [ORNL; Yu, Weikuan [Auburn University, Auburn, Alabama

    2014-01-01

    The growth of computing power on large-scale sys- tems requires commensurate high-bandwidth I/O system. Many parallel file systems are designed to provide fast sustainable I/O in response to applications soaring requirements. To meet this need, a novel system is imperative to temporarily buffer the bursty I/O and gradually flush datasets to long-term parallel file systems. In this paper, we introduce the design of BurstMem, a high- performance burst buffer system. BurstMem provides a storage framework with efficient storage and communication manage- ment strategies. Our experiments demonstrate that BurstMem is able to speed up the I/O performance of scientific applications by up to 8.5 on leadership computer systems.

  12. Long-term relationships between cholinergic tone, synchronous bursting and synaptic remodeling.

    Directory of Open Access Journals (Sweden)

    Maya Kaufman

    Full Text Available Cholinergic neuromodulation plays key roles in the regulation of neuronal excitability, network activity, arousal, and behavior. On longer time scales, cholinergic systems play essential roles in cortical development, maturation, and plasticity. Presumably, these processes are associated with substantial synaptic remodeling, yet to date, long-term relationships between cholinergic tone and synaptic remodeling remain largely unknown. Here we used automated microscopy combined with multielectrode array recordings to study long-term relationships between cholinergic tone, excitatory synapse remodeling, and network activity characteristics in networks of cortical neurons grown on multielectrode array substrates. Experimental elevations of cholinergic tone led to the abrupt suppression of episodic synchronous bursting activity (but not of general activity, followed by a gradual growth of excitatory synapses over hours. Subsequent blockage of cholinergic receptors led to an immediate restoration of synchronous bursting and the gradual reversal of synaptic growth. Neither synaptic growth nor downsizing was governed by multiplicative scaling rules. Instead, these occurred in a subset of synapses, irrespective of initial synaptic size. Synaptic growth seemed to depend on intrinsic network activity, but not on the degree to which bursting was suppressed. Intriguingly, sustained elevations of cholinergic tone were associated with a gradual recovery of synchronous bursting but not with a reversal of synaptic growth. These findings show that cholinergic tone can strongly affect synaptic remodeling and synchronous bursting activity, but do not support a strict coupling between the two. Finally, the reemergence of synchronous bursting in the presence of elevated cholinergic tone indicates that the capacity of cholinergic neuromodulation to indefinitely suppress synchronous bursting might be inherently limited.

  13. α-Calcium calmodulin kinase II modulates the temporal structure of hippocampal bursting patterns.

    Directory of Open Access Journals (Sweden)

    Jeiwon Cho

    Full Text Available The alpha calcium calmodulin kinase II (α-CaMKII is known to play a key role in CA1/CA3 synaptic plasticity, hippocampal place cell stability and spatial learning. Additionally, there is evidence from hippocampal electrophysiological slice studies that this kinase has a role in regulating ion channels that control neuronal excitability. Here, we report in vivo single unit studies, with α-CaMKII mutant mice, in which threonine 305 was replaced with an aspartate (α-CaMKII(T305D mutants, that indicate that this kinase modulates spike patterns in hippocampal pyramidal neurons. Previous studies showed that α-CaMKII(T305D mutants have abnormalities in both hippocampal LTP and hippocampal-dependent learning. We found that besides decreased place cell stability, which could be caused by their LTP impairments, the hippocampal CA1 spike patterns of α-CaMKII(T305D mutants were profoundly abnormal. Although overall firing rate, and overall burst frequency were not significantly altered in these mutants, inter-burst intervals, mean number of intra-burst spikes, ratio of intra-burst spikes to total spikes, and mean intra-burst intervals were significantly altered. In particular, the intra burst intervals of place cells in α-CaMKII(T305D mutants showed higher variability than controls. These results provide in vivo evidence that besides its well-known function in synaptic plasticity, α-CaMKII, and in particular its inhibitory phosphorylation at threonine 305, also have a role in shaping the temporal structure of hippocampal burst patterns. These results suggest that some of the molecular processes involved in acquiring information may also shape the patterns used to encode this information.

  14. Media in Distance Learning: The Nigerian National Teachers Instute Distance Education Programme

    OpenAIRE

    Mudasiru Olalere YUSUF; FALADE, Ayotunde Atanda

    2005-01-01

    This study investigated the use of media by distance learners enrolled in the NTI distance education programme. Two hundred and fifty five distance learners drawn from Oyo State, Nigeria, completed a questionnaire to determine the use of media, and factors militating against their effective use by distance learners. Research data were analyzed using percentages. The findings indicated that face-to-face contact and print related media were the major media used for learning. The findings also i...

  15. Detailed spectroscopic analysis of SN 1987A: The distance to the LMC using the SEAM method

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, Robert C.; Baron, E.; Branch, David; Hauschildt, Peter H.; Nugent, Peter E.; Lundqvist, Peter; Blinnikov, Sergei; Pun, Chun S.J.

    2002-05-21

    Supernova 1987A remains the most well-studied supernova to date. Observations produced excellent broad-band photometric and spectroscopic coverage over a wide wavelength range at all epochs. We model the observed spectra from Day 1 to Day 81 using a hydrodynamical model. We show that good agreement can be obtained at times up to about 60 days, if we allow for extended nickel mixing. Later than about 60 days the observed Balmer lines become stronger than our models can reproduce. We show that this is likely due to a more complicated distribution of gamma-rays than we allow for in our spherically symmetric calculations. We present synthetic light curves in UBVRIJHK and a synthetic bolometric light curve. Using this broad baseline of detailed spectroscopic models we find a distance modulus mu = 18.5 +/- 0.2 using the SEAM method of determining distances to supernovae. We find that the explosion time agrees with that of the neutrino burst and is constrained at 68 percent confidence to within +/- 0.9 days. We argue that the weak Balmer lines of our detailed model calculations casts doubt on the accuracy of the purely photometric EPM method. We also suggest that Type IIP supernovae will be most useful as distance indicators at early times due to a variety of effects.

  16. Heuristic burst detection method using flow and pressure measurements

    NARCIS (Netherlands)

    Bakker, M.; Vreeburg, J.H.G.; Roer, Van de M.; Rietveld, L.C.

    2014-01-01

    Pipe bursts in a drinking water distribution system lead to water losses, interruption of supply, and damage to streets and houses due to the uncontrolled water flow. To minimize the negative consequences of pipe bursts, an early detection is necessary. This paper describes a heuristic burst

  17. Detecting Pipe Bursts Using Heuristic and CUSUM Methods

    NARCIS (Netherlands)

    Bakker, M.; Jung, D.; Vreeburg, J.; Van de Roer, M.; Lansey, K.; Rierveld, L.

    2014-01-01

    Pipe bursts in a drinking water distribution system lead to water losses, interruption of supply, and damage to streets and houses due to the uncontrolled water flow. To minimize the negative consequences of pipe bursts, an early detection is necessary. This paper describes a heuristic burst

  18. IGR J17254-3257, a new bursting neutron star

    DEFF Research Database (Denmark)

    Chenevez, Jérôme; Falanga, M.; Kuulkers, E.

    2007-01-01

    Aims. The study of the observational properties of uncommonly long bursts from low luminosity sources is important when investigating the transition from a hydrogen - rich bursting regime to a pure helium regime and from helium burning to carbon burning as predicted by current burst theories. On ...

  19. Observations of gamma-ray burst afterglows with the AEOS Burst Camera

    Science.gov (United States)

    Flewelling, Heather Anne

    Gamma-ray bursts (GRBs), are variable bursts of gamma-ray radiation, that lasts from milliseconds to hundreds of seconds. These bursts of gamma rays are detected in other wavelengths (optical, IR, radio, X-ray), because the afterglow lasts much longer, and this enables us to learn more about GRBs. The AEOS Burst Camera (ABC) is a 6'x6' field of view camera designed to observe the optical afterglows of GRBs, and is mounted on the 3.67m Advanced Electro- Optical System (AEOS) telescope, located at 10,000ft on Haleakala, Hawaii. There are 45 hours of Target of Opportunity (ToO) time to observe GRBs detected by Swift and other GRB satellites. Observations are started within minutes after a suitable GRB is detected, and continue for an hour or two. During this project, 21 GRBs were observed, and of those, 10 had detected afterglows, and 4 had interesting limits. About half of the bursts fit the fireball model, and half did not, which is similar to what ROTSE has found. Roughly half of the ABC bursts fall in the dark category, with b ox Akerlof Sr, Swan (2007) found, that roughly 70% of all GRBs brighter than 22nd mag at 1000s should be detectable.

  20. Path correlation considered prioritized burst segmentation for quality of service support in optical burst switching networks

    Science.gov (United States)

    Hou, Rui; Changyue, Jiana; He, Tingting; Yu, Jianwei; Lei, Bo; Mao, Tengyue

    2013-04-01

    Burst segmentation (BS) is a high-efficiency contention resolution scheme in bufferless optical burst switching (OBS) networks. A prioritized BS scheme for quality of service (QoS) support is developed. Unlike the existing work on the BS scheme, the proposed BS model considers path-correlated factors, such as path length, the adjoining paths carrying traffic on a given path, and the multipriority traffic coming from all paths. Byte loss probability for high-priority and low-priority bursts under the time-based assembly approach and the length-based assembly approach to estimate the performance of the proposed BS scheme by comparing the cumulative distribution function of a burst length in an OBS ingress node (source) with that in an egress node (destination) is introduced. A preemptive BS policy for different priority bursts is proposed to support the QoS of the OBS network. Finally, a simulation is given to validate the proposed analytical model in an existing OBS network with two priority bursts. It is shown that the proposed BS scheme can realize the service differentiation for multipriority traffic under the consideration of network topology-dependent parameters.

  1. The first interferometric detections of fast radio bursts

    Science.gov (United States)

    Caleb, M.; Flynn, C.; Bailes, M.; Barr, E. D.; Bateman, T.; Bhandari, S.; Campbell-Wilson, D.; Farah, W.; Green, A. J.; Hunstead, R. W.; Jameson, A.; Jankowski, F.; Keane, E. F.; Parthasarathy, A.; Ravi, V.; Rosado, P. A.; van Straten, W.; Venkatraman Krishnan, V.

    2017-07-01

    We present the first interferometric detections of fast radio bursts (FRBs), an enigmatic new class of astrophysical transient. In a 180-d survey of the Southern sky, we discovered three FRBs at 843 MHz with the UTMOST array, as a part of commissioning science during a major ongoing upgrade. The wide field of view of UTMOST (≈9 deg2) is well suited to FRB searches. The primary beam is covered by 352 partially overlapping fan-beams, each of which is searched for FRBs in real time with pulse widths in the range 0.655-42 ms, and dispersion measures ≤2000 pc cm-3. Detections of FRBs with the UTMOST array place a lower limit on their distances of ≈104 km (limit of the telescope near-field) supporting the case for an astronomical origin. Repeating FRBs at UTMOST or an FRB detected simultaneously with the Parkes radio telescope and UTMOST would allow a few arcsec localization, thereby providing an excellent means of identifying FRB host galaxies, if present. Up to 100 h of followup for each FRB has been carried out with the UTMOST, with no repeating bursts seen. From the detected position, we present 3σ error ellipses of 15 arcsec × 8.4° on the sky for the point of origin for the FRBs. We estimate an all-sky FRB rate at 843 MHz above a fluence F_lim of 11 Jy ms of ˜78 events sky-1 d-1 at the 95 per cent confidence level. The measured rate of FRBs at 843 MHz is two times higher than we had expected, scaling from the FRB rate at the Parkes radio telescope, assuming that FRBs have a flat spectral index and a uniform distribution in Euclidean space. We examine how this can be explained by FRBs having a steeper spectral index and/or a flatter logN-logF distribution than expected for a Euclidean Universe.

  2. Identifying gamma-ray bursts at very high redshifts

    Science.gov (United States)

    Tanvir, Nial

    2017-08-01

    Gamma-ray bursts are bright enough to be seen to very great distances and their afterglows can provide redshifts and positions for their host galaxies, and in some cases details of the ISM and the IGM close to the burst, irrespective of the host magnitude itself. Thus GRBs, despite their small numbers, offer a unique and powerful tracer of early star formation and the galaxy populations in the era of reionization. Our efforts to identify high-z GRBs have been rewarded with the discoveries of GRB 090423 and GRB 120923A at spectroscopic redshifts of 8.2 and 7.8 respectively. However, it remains the case that some good candidate high-z GRBs cannot be followed up quickly or deeply enough with ground-based IR spectroscopy, and indeed for others the Ly-alpha break may fall in regions of the IR spectrum difficult to access from the ground. GRB 090429B is an example, which had a photo-z of 9.4, but for which spectroscopy was curtailed due to bad weather. WFC3/IR on HST can obtain redshifts based on the location of the Ly-alpha break via slitless grism spectroscopy to considerably deeper limits (and hence later times) than is possible from the ground, thus offering a solution to this problem. This proposal aims to continue to build the sample of z>7 GRBs by obtaining spectroscopy for up to two candidates for which photometry suggests a very high redshift, but where the redshift could not be secured from the ground. This will provide an important legacy of host galaxy targets with known redshifts for future studies with JWST. The low rate of z>7 GRBs leads us to request a long-term ToO program, spanning cycles 25 and 26.

  3. The Fermi-GBM X-Ray Burst Monitor: Thermonuclear Bursts from 4U 0614+09

    NARCIS (Netherlands)

    Linares, M.; Connaughton, V.; Jenke, P.; van der Horst, A.J.; Camero-Arranz, A.; Kouveliotou, C.; Chakrabarty, D.; Beklen, E.; Bhat, P.N.; Briggs, M.S.; Finger, M.; Paciesas, W.S.; Preece, R.; von Kienlin, A.; Wilson-Hodge, C.A.

    2012-01-01

    Thermonuclear bursts from slowly accreting neutron stars (NSs) have proven difficult to detect, yet they are potential probes of the thermal properties of the NS interior. During the first year of a systematic all-sky search for X-ray bursts using the Gamma-ray Burst Monitor aboard the Fermi

  4. Self-organized criticality in type I X-ray bursts

    Science.gov (United States)

    Wang, J. S.; Wang, F. Y.; Dai, Z. G.

    2017-11-01

    Type I X-ray bursts in a low-mass X-ray binary are caused by unstable nuclear burning of accreted materials. Semi-analytical and numerical studies of unstable nuclear burning have successfully reproduced the partial properties of this kind of burst. However, some other properties (e.g. the waiting time) are not well explained. In this paper, we find that the probability distributions of fluence, peak count, rise time, duration and waiting time can be described as power-law-like distributions. This indicates that type I X-ray bursts may be governed by a self-organized criticality (SOC) process. The power-law index of the waiting time distribution (WTD) is around -1, which is not predicted by any current waiting time model. We propose a physical burst rate model, in which the mean occurrence rate is inversely proportional to time: λ ∝ t-1. In this case, the WTD is explained well by a non-stationary Poisson process within the SOC theory. In this theory, the burst size is also predicted to follow a power-law distribution, which requires that the emission area covers only part of the neutron star surface. Furthermore, we find that the WTDs of some astrophysical phenomena can also be described by similar occurrence rate models.

  5. INTERPLANETARY NETWORK LOCALIZATIONS OF KONUS SHORT GAMMA-RAY BURSTS

    Energy Technology Data Exchange (ETDEWEB)

    Pal' shin, V. D.; Svinkin, D. S.; Aptekar, R. L.; Golenetskii, S. V.; Frederiks, D. D.; Mazets, E. P.; Oleynik, P. P.; Ulanov, M. V. [Ioffe Physical Technical Institute, St. Petersburg, 194021 (Russian Federation); Hurley, K. [Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, CA 94720-7450 (United States); Cline, T.; Trombka, J.; McClanahan, T. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Mitrofanov, I. G.; Golovin, D. V.; Kozyrev, A. S.; Litvak, M. L.; Sanin, A. B. [Space Research Institute, 84/32, Profsoyuznaya, Moscow 117997 (Russian Federation); Boynton, W.; Fellows, C.; Harshman, K., E-mail: val@mail.ioffe.ru [Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721 (United States); and others

    2013-08-15

    Between the launch of the Global Geospace Science Wind spacecraft in 1994 November and the end of 2010, the Konus-Wind experiment detected 296 short-duration gamma-ray bursts (including 23 bursts which can be classified as short bursts with extended emission). During this period, the Interplanetary Network (IPN) consisted of up to 11 spacecraft, and using triangulation, the localizations of 271 bursts were obtained. We present the most comprehensive IPN localization data on these events. The short burst detection rate, {approx}18 yr{sup -1}, exceeds that of many individual experiments.

  6. Search for gravitational waves associated with γ-ray bursts detected by the interplanetary network.

    Science.gov (United States)

    Aasi, J; Abbott, B P; Abbott, R; Abbott, T; Abernathy, M R; Acernese, F; Ackley, K; Adams, C; Adams, T; Addesso, P; Adhikari, R X; Affeldt, C; Agathos, M; Aggarwal, N; Aguiar, O D; Ajith, P; Alemic, A; Allen, B; Allocca, A; Amariutei, D; Andersen, M; Anderson, R A; Anderson, S B; Anderson, W G; Arai, K; Araya, M C; Arceneaux, C; Areeda, J S; Ast, S; Aston, S M; Astone, P; Aufmuth, P; Augustus, H; Aulbert, C; Aylott, B E; Babak, S; Baker, P T; Ballardin, G; Ballmer, S W; Barayoga, J C; Barbet, M; Barish, B C; Barker, D; Barone, F; Barr, B; Barsotti, L; Barsuglia, M; Barton, M A; Bartos, I; Bassiri, R; Basti, A; Batch, J C; Bauchrowitz, J; Bauer, Th S; Baune, C; Bavigadda, V; Behnke, B; Bejger, M; Beker, M G; Belczynski, C; Bell, A S; Bell, C; Bergmann, G; Bersanetti, D; Bertolini, A; Betzwieser, J; Bilenko, I A; Billingsley, G; Birch, J; Biscans, S; Bitossi, M; Biwer, C; Bizouard, M A; Black, E; Blackburn, J K; Blackburn, L; Blair, D; Bloemen, S; Bock, O; Bodiya, T P; Boer, M; Bogaert, G; Bogan, C; Bond, C; Bondu, F; Bonelli, L; Bonnand, R; Bork, R; Born, M; Boschi, V; Bose, Sukanta; Bosi, L; Bradaschia, C; Brady, P R; Braginsky, V B; Branchesi, M; Brau, J E; Briant, T; Bridges, D O; Brillet, A; Brinkmann, M; Brisson, V; Brooks, A F; Brown, D A; Brown, D D; Brückner, F; Buchman, S; Buikema, A; Bulik, T; Bulten, H J; Buonanno, A; Burman, R; Buskulic, D; Buy, C; Cadonati, L; Cagnoli, G; Calderón Bustillo, J; Calloni, E; Camp, J B; Campsie, P; Cannon, K C; Canuel, B; Cao, J; Capano, C D; Carbognani, F; Carbone, L; Caride, S; Castaldi, G; Caudill, S; Cavaglià, M; Cavalier, F; Cavalieri, R; Celerier, C; Cella, G; Cepeda, C; Cesarini, E; Chakraborty, R; Chalermsongsak, T; Chamberlin, S J; Chao, S; Charlton, P; Chassande-Mottin, E; Chen, X; Chen, Y; Chincarini, A; Chiummo, A; Cho, H S; Cho, M; Chow, J H; Christensen, N; Chu, Q; Chua, S S Y; Chung, S; Ciani, G; Clara, F; Clark, D E; Clark, J A; Clayton, J H; Cleva, F; Coccia, E; Cohadon, P-F; Colla, A; Collette, C; Colombini, M; Cominsky, L; Constancio, M; Conte, A; Cook, D; Corbitt, T R; Cornish, N; Corsi, A; Costa, C A; Coughlin, M W; Coulon, J-P; Countryman, S; Couvares, P; Coward, D M; Cowart, M J; Coyne, D C; Coyne, R; Craig, K; Creighton, J D E; Croce, R P; Crowder, S G; Cumming, A; Cunningham, L; Cuoco, E; Cutler, C; Dahl, K; Dal Canton, T; Damjanic, M; Danilishin, S L; D'Antonio, S; Danzmann, K; Dattilo, V; Daveloza, H; Davier, M; Davies, G S; Daw, E J; Day, R; Dayanga, T; DeBra, D; Debreczeni, G; Degallaix, J; Deléglise, S; Del Pozzo, W; Denker, T; Dent, T; Dereli, H; Dergachev, V; De Rosa, R; DeRosa, R T; DeSalvo, R; Dhurandhar, S; Díaz, M; Dickson, J; Di Fiore, L; Di Lieto, A; Di Palma, I; Di Virgilio, A; Dolique, V; Dominguez, E; Donovan, F; Dooley, K L; Doravari, S; Douglas, R; Downes, T P; Drago, M; Drever, R W P; Driggers, J C; Du, Z; Ducrot, M; Dwyer, S; Eberle, T; Edo, T; Edwards, M; Effler, A; Eggenstein, H-B; Ehrens, P; Eichholz, J; Eikenberry, S S; Endrőczi, G; Essick, R; Etzel, T; Evans, M; Evans, T; Factourovich, M; Fafone, V; Fairhurst, S; Fan, X; Fang, Q; Farinon, S; Farr, B; Farr, W M; Favata, M; Fazi, D; Fehrmann, H; Fejer, M M; Feldbaum, D; Feroz, F; Ferrante, I; Ferreira, E C; Ferrini, F; Fidecaro, F; Finn, L S; Fiori, I; Fisher, R P; Flaminio, R; Fournier, J-D; Franco, S; Frasca, S; Frasconi, F; Frede, M; Frei, Z; Freise, A; Frey, R; Fricke, T T; Fritschel, P; Frolov, V V; Fulda, P; Fyffe, M; Gair, J R; Gammaitoni, L; Gaonkar, S; Garufi, F; Gehrels, N; Gemme, G; Gendre, B; Genin, E; Gennai, A; Ghosh, S; Giaime, J A; Giardina, K D; Giazotto, A; Gleason, J; Goetz, E; Goetz, R; Gondan, L; González, G; Gordon, N; Gorodetsky, M L; Gossan, S; Goßler, S; Gouaty, R; Gräf, C; Graff, P B; Granata, M; Grant, A; Gras, S; Gray, C; Greenhalgh, R J S; Gretarsson, A M; Groot, P; Grote, H; Grover, K; Grunewald, S; Guidi, G M; Guido, C J; Gushwa, K; Gustafson, E K; Gustafson, R; Ha, J; Hall, E D; Hamilton, W; Hammer, D; Hammond, G; Hanke, M; Hanks, J; Hanna, C; Hannam, M D; Hanson, J; Harms, J; Harry, G M; Harry, I W; Harstad, E D; Hart, M; Hartman, M T; Haster, C-J; Haughian, K; Heidmann, A; Heintze, M; Heitmann, H; Hello, P; Hemming, G; Hendry, M; Heng, I S; Heptonstall, A W; Heurs, M; Hewitson, M; Hild, S; Hoak, D; Hodge, K A; Hofman, D; Holt, K; Hopkins, P; Horrom, T; Hoske, D; Hosken, D J; Hough, J; Howell, E J; Hu, Y; Huerta, E; Hughey, B; Husa, S; Huttner, S H; Huynh, M; Huynh-Dinh, T; Idrisy, A; Ingram, D R; Inta, R; Islas, G; Isogai, T; Ivanov, A; Iyer, B R; Izumi, K; Jacobson, M; Jang, H; Jaranowski, P; Ji, Y; Jiménez-Forteza, F; Johnson, W W; Jones, D I; Jones, R; Jonker, R J G; Ju, L; Haris, K; Kalmus, P; Kalogera, V; Kandhasamy, S; Kang, G; Kanner, J B; Karlen, J; Kasprzack, M; Katsavounidis, E; Katzman, W; Kaufer, H; Kaufer, S; Kaur, T; Kawabe, K; Kawazoe, F; Kéfélian, F; Keiser, G M; Keitel, D; Kelley, D B; Kells, W; Keppel, D G

    2014-07-04

    We present the results of a search for gravitational waves associated with 223 γ-ray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 2005-2010 during LIGO's fifth and sixth science runs and Virgo's first, second, and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significantly from degree scale to hundreds of square degrees. We search for both a well-modeled binary coalescence signal, the favored progenitor model for short GRBs, and for generic, unmodeled gravitational wave bursts. Both searches use the event time and sky localization to improve the gravitational wave search sensitivity as compared to corresponding all-time, all-sky searches. We find no evidence of a gravitational wave signal associated with any of the IPN GRBs in the sample, nor do we find evidence for a population of weak gravitational wave signals associated with the GRBs. For all IPN-detected GRBs, for which a sufficient duration of quality gravitational wave data are available, we place lower bounds on the distance to the source in accordance with an optimistic assumption of gravitational wave emission energy of 10(-2)M⊙c(2) at 150 Hz, and find a median of 13 Mpc. For the 27 short-hard GRBs we place 90% confidence exclusion distances to two source models: a binary neutron star coalescence, with a median distance of 12 Mpc, or the coalescence of a neutron star and black hole, with a median distance of 22 Mpc. Finally, we combine this search with previously published results to provide a population statement for GRB searches in first-generation LIGO and Virgo gravitational wave detectors and a resulting examination of prospects for the advanced gravitational wave detectors.

  7. Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by the Interplanetary Network

    Science.gov (United States)

    Aasi, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Acernese, F.; Blackbum, L.; Camp, J. B.; Gehrels, N.; Graff, P. B.; hide

    2014-01-01

    We present the results of a search for gravitational waves associated with 223 gamma ray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 2005-2010 during LIGO's fifth and sixth science runs and Virgo's first, second, and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significantly from degree scale to hundreds of square degrees. We search for both a well-modeled binary coalescence signal, the favored progenitor model for short GRBs, and for generic, unmodeled gravitational wave bursts. Both searches use the event time and sky localization to improve the gravitational wave search sensitivity as compared to corresponding all-time, all-sky searches. We find no evidence of a gravitational wave signal associated with any of the IPN GRBs in the sample, nor do we find evidence for a population of weak gravitational wave signals associated with the GRBs. For all IPN-detected GRBs, for which a sufficient duration of quality gravitational wave data are available, we place lower bounds on the distance to the source in accordance with an optimistic assumption of gravitational wave emission energy of 10(exp-2) solar mass c(exp 2) at 150 Hz, and find a median of 13 Mpc. For the 27 short-hard GRBs we place 90% confidence exclusion distances to two source models: a binary neutron star coalescence, with a median distance of 12 Mpc, or the coalescence of a neutron star and black hole, with a median distance of 22 Mpc. Finally, we combine this search with previously published results to provide a population statement for GRB searches in first-generation LIGO and Virgo gravitational wave detectors and a resulting examination of prospects for the advanced gravitational wave detectors.

  8. Numerical distance protection

    CERN Document Server

    Ziegler, Gerhard

    2011-01-01

    Distance protection provides the basis for network protection in transmission systems and meshed distribution systems. This book covers the fundamentals of distance protection and the special features of numerical technology. The emphasis is placed on the application of numerical distance relays in distribution and transmission systems.This book is aimed at students and engineers who wish to familiarise themselves with the subject of power system protection, as well as the experienced user, entering the area of numerical distance protection. Furthermore it serves as a reference guide for s

  9. Tourists consuming distance

    DEFF Research Database (Denmark)

    Larsen, Gunvor Riber

    The environmental impact of tourism mobility is linked to the distances travelled in order to reach a holiday destination, and with tourists travelling more and further than previously, an understanding of how the tourists view the distance they travel across becomes relevant. Based on interviews...... contribute to an understanding of how it is possible to change tourism travel behaviour towards becoming more sustainable. How tourists 'consume distance' is discussed, from the practical level of actually driving the car or sitting in the air plane, to the symbolic consumption of distance that occurs when...

  10. An origin in the local Universe for some short gamma-ray bursts.

    Science.gov (United States)

    Tanvir, N R; Chapman, R; Levan, A J; Priddey, R S

    2005-12-15

    Gamma-ray bursts (GRBs) divide into two classes: 'long', which typically have initial durations of T90 > 2 s, and 'short', with durations of T90 origin of short bursts has remained mysterious until recently. A subsecond intense 'spike' of gamma-rays during a giant flare from the Galactic soft gamma-ray repeater, SGR 1806-20, reopened an old debate over whether some short GRBs could be similar events seen in galaxies out to approximately 70 Mpc (refs 6-10; redshift z approximately 0.016). Shortly after that, localizations of a few short GRBs (with optical afterglows detected in two cases) have shown an apparent association with a variety of host galaxies at moderate redshifts. Here we report a correlation between the locations of previously observed short bursts and the positions of galaxies in the local Universe, indicating that between 10 and 25 per cent of short GRBs originate at low redshifts (z < 0.025).

  11. Forming a constant density medium close to long gamma-ray burst

    NARCIS (Netherlands)

    Marle, A.J.; Langer, N.; Achterberg, A; Garia-Segura, G.

    2006-01-01

    Aims. The progenitor stars of long Gamma-Ray Bursts (GRBs) are thought to be Wolf-Rayet stars, which generate a massive and energetic wind. Nevertheless, about 25 percent of all GRB afterglows light curves indicate a constant density medium close to the exploding star. We explore various ways to

  12. Gamma-Ray Bursts and Their Links with Supernovae and Cosmology

    Science.gov (United States)

    Meszaros, Peter; Gehrels, Neil

    2012-01-01

    Gamma-ray bursts are the most luminous explosions in the Universe, whose origin and mechanism are the focus of intense interest. They appear connected to supernova remnants from massive stars or the merger of their remnants, and their brightness makes them temporarily detectable out to the largest distances yet explored in the universe. After pioneering breakthroughs from space and ground experiments, their study is entering a new phase with observations from the recently launched Fermi satellite, as well as the prospect of detections or limits from large neutrino and gravitational wave detectors. The interplay between such observations and theoretical models of gamma-ray bursts is reviewed, as well as their connections to supernovae and cosmology.

  13. Consistency of time dilation in temporal profiles and spectra of gamma-ray bursts

    Science.gov (United States)

    Noriss, J. P.; Nemiroff, R. J.; Bonnell, J. T.; Scargle, J. D.; Davis, S. P.; Kouveliotou, C.; Pendleton, G.; Fishman, G. J.; Meegan, C. A.; Paciesas, W. S.

    1995-01-01

    If gamma-ray bursters are at cosmological distances-a possibility suggested by their isotropic distribution and spatial inhomogeneity-then the temporal profiles and spectra of more distant sources will be time dilated compared to those of relatively nearby sources. Analyses of bright and dim Burst and Transient Source Experiment (BATSE) gamma-ray bursts yield a relative time-dilation factor of 2.3 on timescales of pulses and event durations. We redshift the spectra of time intervals near the intensity peaks of the bright sample on a trial grid and compare with spectra of the dim sample. A redshift factor of order two-with wide latitude permitted-brings the spectra of the two brightness groups into alignment. Thus there is coarse agreement with the time-dilation factor found in the temporal domain.

  14. Production of gamma-ray bursts near rapidly rotating accreting black holes

    Energy Technology Data Exchange (ETDEWEB)

    Piran, T.; Shaham, J.

    1977-05-15

    A model for the production of ..gamma..-rays during the occurrence of instabilities in accretion of matter onto rapidly rotating black holes is described. Gamma rays are produced by Compton scattering of infalling X-ray photons, whenever the optical depth in the deep ergosphere is of the order of the gravitational distance. The initial photons are produced farther away by viscous processes in the infalling plasma, and contribute to the lower-energy regime of the burst spectrum, along with low-energy photons produced in the deep ergosphere. Calculated spectra for that specific Compton scattering may account for burst spectra in the range approx.300 keV--3 MeV.

  15. Formation and characterization of the vortices generated by a DBD plasma actuator in burst mode

    Science.gov (United States)

    Mishra, Bal Krishan; Panigrahi, P. K.

    2017-02-01

    The present study reports the formation and evolution characteristics of the continuously generated vortical structure and resulting flow field in quiescent air induced by a dielectric-barrier-discharge (DBD) plasma actuator in burst mode operation. A starting vortex is formed during the initial actuation period, which disappears after a small time interval for continuous mode operation of the DBD plasma actuator. A burst input signal to the actuator generates a train of self-similar vortices. The behaviour of vortices and the average flow field induced by the actuator has been studied using high speed schlieren visualization and particle image velocimetry technique for different actuation amplitude and duty cycle parameters. These repeating vortices travel faster than the starting vortex, and the vortex core velocity of these repeating vortices increases with increase in duty cycle parameter. Fuller u-velocity profile, higher v-velocity near the edge of the outer shear layer region, and higher growth of the wall jet thickness is observed due to enhanced entrainment by repeating vortices for burst mode operation. The repeating vortices travel at an angle of 21° relative to the wall surface for duty cycle parameter of 90.9% in comparison to 31° for the starting vortex. Self-similarity of the velocity profile is delayed in the streamwise direction for burst mode operation in comparison to that for the continuous mode of operation. This can be attributed to delay in attaining the maximum velocity of the wall jet profile and presence of coherent structures for the burst mode operation. The non-dimensional vortex core location and size for repeating vortices follow power law fit similar to the starting vortex with difference in value of the power law exponent. The phase difference between the input voltage and current drawn is in the range of π/12 to π/9 (in radians) for both continuous and burst mode operation indicating identical electrical behaviour of the

  16. A simple model of burst nucleation.

    Science.gov (United States)

    Baronov, Alexandr; Bufkin, Kevin; Shaw, Dan W; Johnson, Brad L; Patrick, David L

    2015-08-28

    We introduce a comprehensive quantitative treatment for burst nucleation (BN)-a kinetic pathway toward self-assembly or crystallization defined by an extended post-supersaturation induction period, followed by a burst of nucleation, and finally the growth of existing stable assemblages absent the formation of new ones-based on a hybrid mean field rate equation model incorporating thermodynamic treatment of the saturated solvent from classical nucleation theory. A key element is the inclusion of a concentration-dependent critical nucleus size, determined self-consistently along with the subcritical cluster population density. The model is applied to an example experimental study of crystallization in tetracene films prepared by organic vapor-liquid-solid deposition, where good agreement is observed with several aspects of the experiment using a single, physically well-defined adjustable parameter. The model predicts many important features of the experiment, and can be generalized to describe other self-organizing systems exhibiting BN kinetics.

  17. New approach to rock burst forecasting

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, V.V.; Fokin, A.N.; Pimonov, A.G. (Kuzbasskii Politekhnicheskii Institut (USSR))

    1990-10-01

    Deals with the problem of rock burst forecasting that departs from the concept of solid body strength and breaking and from equations that relate endurance of a solid body to continuous stress. A formula is derived that permits the lifetime of a rock volume under stress to be calculated. A block diagram of a laboratory automatic system is presented that is capable of monitoring the stress state of a rock sample and of forecasting the time to sample destruction. The system consists of a loading fixture, electromagnetic emission sensor, frequency meter, microprocessor and plotter. An example of a plot of the rate of fissure formation as a function of time is shown and a monitor screen display of a sample life versus time is also presented. It is maintained that the system creates a basis for developing a system that would monitor and forecast rock burst hazards in a continuous manner. 4 refs.

  18. A review of gamma ray bursts

    CERN Document Server

    Rees, Martin J

    2000-01-01

    Gamma-ray bursts, an enigma for more than 25 years, are now coming into focus. They involve extraordinary power outputs, and highly relativistic dynamics. The 'trigger' involves stellar-mass compact objects. The most plausible progenitors, ranging from neutron star binary mergers to collapsars (sometimes called 'hypernovae') eventually lead to the formation of a black hole with a torus of hot neutron-density material around it, the extractable energy being up to 10 sup 5 sup 4 ergs. Magnetic fields may exceed 10 sup 1 sup 5 G and particles may be accelerated up to > or approx. 10 sup 2 sup 0 eV. Details of the afterglow may be easier to understand than the initial trigger. Bursts at very high redshift can be astronomically-important as probes of the distant universe.

  19. Coherent combining pulse bursts in time domain

    Energy Technology Data Exchange (ETDEWEB)

    Galvanauskas, Almantas

    2018-01-09

    A beam combining and pulse stacking technique is provided that enhances laser pulse energy by coherent stacking pulse bursts (i.e. non-periodic pulsed signals) in time domain. This energy enhancement is achieved by using various configurations of Fabry-Perot, Gires-Tournois and other types of resonant cavities, so that a multiple-pulse burst incident at either a single input or multiple inputs of the system produces an output with a solitary pulse, which contains the summed energy of the incident multiple pulses from all beams. This disclosure provides a substantial improvement over conventional coherent-combining methods in that it achieves very high pulse energies using a relatively small number of combined laser systems, thus providing with orders of magnitude reduction in system size, complexity, and cost compared to current combining approaches.

  20. The Chase to Capture Gamma Ray Bursts

    Science.gov (United States)

    Gehrels, Neil

    2008-01-01

    Gamma-ray bursts are the most powerful explosions in the universe, thought to be the birth cries of black holes. It has taken 40 years of international cooperation and competition to begin to unravel the mystery of their origin. The most recent chapter in this field is being written by the SWIFT mission, a fast-response satellite with 3 power telescopes. An international team from countries all over the world participates in the chase to capture the fading light of bursts detected by SWIFT. This talk will discuss the challenges and excitement of building this space observatory. New results will be presented on our growing understanding of exploding stars and fiery mergers of orbiting stars.

  1. Bursting of sensitive polymersomes induced by curling.

    Science.gov (United States)

    Mabrouk, Elyes; Cuvelier, Damien; Brochard-Wyart, Françoise; Nassoy, Pierre; Li, Min-Hui

    2009-05-05

    Polymersomes, which are stable and robust vesicles made of block copolymer amphiphiles, are good candidates for drug carriers or micro/nanoreactors. Polymer chemistry enables almost unlimited molecular design of responsive polymersomes whose degradation upon environmental changes has been used for the slow release of active species. Here, we propose a strategy to remotely trigger instantaneous polymersome bursting. We have designed asymmetric polymer vesicles, in which only one leaflet is composed of responsive polymers. In particular, this approach has been successfully achieved by using a UV-sensitive liquid-crystalline copolymer. We study experimentally and theoretically this bursting mechanism and show that it results from a spontaneous curvature of the membrane induced by the remote stimulus. The versatility of this mechanism should broaden the range of applications of polymersomes in fields such as drug delivery, cosmetics and material chemistry.

  2. Wave disturbances in the polar ionosphere after a Vitim meteorite burst

    Science.gov (United States)

    Tereshchenko, V. D.; Ogloblina, O. F.; Tereshchenko, V. A.; Chernyakov, S. M.

    On September 24th, 2002, at 16:49 UT in the Mamsko-Chuisk region of the Irkutsk oblast of Russia it was a fall of a big meteorite. The fall was accompanied with light, acoustic, geomagnetic, seismic and mechanical phenomena which were recorded by ground and space means of observations. The meteorite has burst in the air at the altitude of 30 km with coordinates of the burst: 58.23 N, 113.46 E. After 17:00 UT there was recorded a sequence of small disturbances of the geomagnetic field and wavelike changes of amplitude of medium wave radioreflections at heights from 47 till 129 km in Tumanny (Murmansk oblast, Russia; 69.0 N, 35.7 E) which was situated at a distance of 4000 km from a place of the burst. It was gotten that after the burst three types of waves (magnetoacoustic, acoustic-gravitational and infraacoustic) spread in the polar mesosphere and lower ionosphere. Observable disturbances had periods of oscillations about 3-4, 5-6 and more than 9-10 minutes. A similarity characteristics of the wave indignations with analogous ones which were gotten earlier during investigations of effects of the Tungusk meteorite and the American space station "Skylab" falls and also a fact of a registration of a pressure wave on a net of microbarographs of PGI in Apatity permit to maintain that the source of the indignations in the polar ionosphere is the meteorite explosion. The hypothesis about wavequide spreading of atmospheric waves to large distance was confirmed.

  3. Media in Distance Learning: The Nigerian National Teachers Institude Distance Education Programme

    Directory of Open Access Journals (Sweden)

    Mudasiru Olalere YUSUF

    2005-10-01

    Full Text Available Media in Distance Learning: The Nigerian National Teachers Institude Distance Education Programme Mudasiru Olalere YUSUF (Ph.DSenior lecturer (Educational Technology Ayotunde Atanda FALADEGraduate Student Department of Curriculum Studies and Educational Technology, Faculty of Education University of Ilorin, Ilorin NIGERIA ABSTRACT This study investigated the use of media by distance learners enrolled in the NTI distance education programme. Two hundred and fifty five distance learners drawn from Oyo State, Nigeria, completed a questionnaire to determine the use of media, and factors militating against their effective use by distance learners. Research data were analyzed using percentages. The findings indicated that face-to-face contact and print related media were the major media used for learning. The findings also indicated that lack of fund, ICT facilities, electricity, among others; militate against the use of technology media. Recommendations were made for the provision of basic infrastructures to facilitate the integration of technology in distance education, in Nigeria.

  4. The cannonball model of gamma ray bursts

    CERN Document Server

    Dar, Arnon

    2003-01-01

    The cannonball model (CB) of gamma ray bursts (GRBs) is incredibly more successful than the standard blast-wave models (SM) of GRBs, which suffer from profound inadequacies and limited predictive power. The CB model is falsifiable in its hypothesis and results. Its predictions are summarized in simple analytical expressions, derived, in fair approximations, from first principles. It provides a good description on a universal basis of the properties of long-duration GRBs and of their afterglows (AGs).

  5. A History of Distance Education in Mexico

    Science.gov (United States)

    Castaneda, Manuel Moreno

    2005-01-01

    Research on distance education in Mexico is still in the embryonic stage, in spite of its long history. One indication is that among the lines of research defined by the Mexican Council on Educational Research, the leading organization in the field in Mexico, distance education does not even appear. Only recently, in the last few years, has an…

  6. Who Graduates from Irish Distance University Education?

    Science.gov (United States)

    Delaney, Lorraine

    2015-01-01

    This paper outlines results from an online survey of recent distance graduates. The study, based in Dublin City University (DCU) addresses a gap in the research on this cohort of graduates. Findings indicate that distance graduates are primarily from lower socio economic backgrounds, a group largely under-represented in full-time university…

  7. Normalized information distance

    NARCIS (Netherlands)

    Vitányi, P.M.B.; Balbach, F.J.; Cilibrasi, R.L.; Li, M.

    2008-01-01

    The normalized information distance is a universal distance measure for objects of all kinds. It is based on Kolmogorov complexity and thus uncomputable, but there are ways to utilize it. First, compression algorithms can be used to approximate the Kolmogorov complexity if the objects have a string

  8. Distance Education in Turkey

    Directory of Open Access Journals (Sweden)

    Dr. Nursel Selver RUZGAR,

    2004-04-01

    Full Text Available Distance Education in Turkey Assistant Professor Dr. Nursel Selver RUZGAR Technical Education Faculty Marmara University, TURKEY ABSTRACT Many countries of the world are using distance education with various ways, by internet, by post and by TV. In this work, development of distance education in Turkey has been presented from the beginning. After discussing types and applications for different levels of distance education in Turkey, the distance education was given in the cultural aspect of the view. Then, in order to create the tendencies and thoughts of graduates of Higher Education Institutions and Distance Education Institutions about being competitors in job markets, sufficiency of education level, advantages for education system, continuing education in different Institutions, a face-to-face survey was applied to 1284 graduates, 958 from Higher Education Institutions and 326 from Distance Education Institutions. The results were evaluated and discussed. In the last part of this work, suggestions to become widespread and improve the distance education in the country were made.

  9. Encyclopedia of distances

    CERN Document Server

    Deza, Michel Marie

    2009-01-01

    Distance metrics and distances have become an essential tool in many areas of pure and applied Mathematics. This title offers both independent introductions and definitions, while at the same time making cross-referencing easy through hyperlink-like boldfaced references to original definitions.

  10. Normalized information distance

    NARCIS (Netherlands)

    Vitányi, P.M.B.; Balbach, F.J.; Cilibrasi, R.L.; Li, M.; Emmert-Streib, F.; Dehmer, M.

    2009-01-01

    The normalized information distance is a universal distance measure for objects of all kinds. It is based on Kolmogorov complexity and thus uncomputable, but there are ways to utilize it. First, compression algorithms can be used to approximate the Kolmogorov complexity if the objects have a string

  11. Duty and Distance

    NARCIS (Netherlands)

    C. Binder (C.); C. Heilmann (Conrad)

    2017-01-01

    markdownabstractEver since the publication of Peter Singer’s article ‘‘Famine, Affluence, and Morality’’ has the question of whether the (geographical) distance to people in need affects our moral duties towards them been a hotly debated issue. Does geographical distance affect our moral

  12. Applicability of modified burst test data to reactivity initiated accident

    Science.gov (United States)

    Yueh, K.

    2017-05-01

    A comprehensive irradiated cladding mechanical property dataset was generated by a recently developed modified burst test (MBT) under reactivity initiated accident (RIA) loading conditions [1,2]. The test data contains a wide range of test conditions that could bridge the gap between fast transient test reactor data (short pulse and/or low temperature) and prototypical commercial reactor conditions. This paper documents an evaluation performed to demonstrate the applicability of the MBT data to fuel cladding performance under RIA conditions. The current effort includes a comparison of calculated fuel cladding failure/burst strain for tests conducted at the Japan Atomic Energy Agency's (JAEA) Nuclear Safety Research Reactor (NSRR) to the MBT dataset, and an evaluation of potential mechanisms on how some NSRR tests survived beyond the cladding loading capacity. A simple shell model, coupled with temperature output from the Falcon fuel performance code, was used to calculate the fuel pellet thermal expansion of NSRR tests at the point of failure. The calculated fuel pellet thermal expansion correlates well directly with the MBT data at similar loading conditions. A 3-dimensional (3D) finite element analysis (FEA) model was used to evaluate fuel movement potential during a RIA. The evaluation indicates fuel relocation into the pellet chamfer and later into the dish is possible once a temperature threshold is reached before cladding failure and thus could significantly increase the fuel rod energy absorption capacity in a RIA event.

  13. Coronal extension of flaring region magnetic fields inferred from high-resolution microwave and type III burst observations

    Science.gov (United States)

    Lantos, P.; Pick, M.; Kundu, M. R.

    1984-01-01

    Observations of three solar radio bursts, obtained with the Very Large Array of the National Radio Astronomy Observatory at 6 cm wavelength, have been combined with meter observations from the Mark III Nancay Radioheliograph. There is a good correlation between solar activity observed at the two wavelength domains. A small change by about 10 sec in the centimetric burst location corresponds to a large change, by about 0.5 solar radius, in the related metric type III burst location. This indicates discrete injection/acceleration regions and the presence of very divergent magnetic fields. The bursts come from two distinct active regions. With two-dimensional spatial resolution, it is shown that, in this sample, each active region possesses a coronal extension that is separated from that of the neighboring active region.

  14. Direct Observations of GPS L1 Signal-to-Noise Degradation due to Solar Radio Bursts

    Science.gov (United States)

    Cerruti, A. P.; Kintner, P. M.; Gary, D.; Lanzerotti, L.

    2006-05-01

    GPS signals, systems, and navigation accuracy are vulnerable to a variety of space weather effects mostly caused by the ionosphere. This paper considers a different class of space weather effects on GPS signals: solar radio bursts. We present the first direct observations of GPS L1 (1.6 GHz) carrier-to-noise degradation on two different models of GPS receivers due to the solar radio burst associated with the 7 September, 2005 solar flare. The solar radio burst consisted of two periods of 1.6 GHz activity at approximately 17:40 UT and again at 18:30 UT. All the receivers that were affected by the solar radio burst were in the sun-lit hemisphere: three identical receivers were collocated at the Arecibo Observatory, and four identical receivers of a different model were located in Brazil. For both models, all GPS satellites in view were affected similarly. In some cases the decrease in the GPS L1 signal-to-noise agreed perfectly with the solar radio burst amplitudes, while in other cases there was no association. Further analysis indicated that only the right hand circularly polarized (RHCP) emissions affected the GPS signals. Since GPS signals are RHCP and GPS antennas are also RHCP, the null effect of the LHCP power confirms our hypothesis that the solar radio bursts are causal. The maximum solar radio burst power associated with the 7 September 2005 flare had a peak intensity of about 8,700 solar flux units (SFU) RHCP at 1,600 MHz, which caused a corresponding decrease in the signal- to-noise of about 2.5 dB across all visible satellites. Furthermore, an event with a peak intensity of 5,000 SFU RHCP at 1,600 MHz caused a 2 dB fade for nearly 15 minutes. To further investigate the effect of solar radio bursts, we also examined the emissions associated with the 28 October 2003 flare. Although polarization data was not available for this even, a similar association was found between 1,400 MHz solar radio power and GPS signal-to-noise degradation. The maximum

  15. Automatic Cloud Bursting under FermiCloud

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Hao [Fermilab; Shangping, Ren [IIT; Garzoglio, Gabriele [Fermilab; Timm, Steven [Fermilab; Bernabeu, Gerard [Fermilab; Kim, Hyun Woo; Chadwick, Keith; Jang, Haengjin [KISTI, Daejeon; Noh, Seo-Young [KISTI, Daejeon

    2013-01-01

    Cloud computing is changing the infrastructure upon which scientific computing depends from supercomputers and distributed computing clusters to a more elastic cloud-based structure. The service-oriented focus and elasticity of clouds can not only facilitate technology needs of emerging business but also shorten response time and reduce operational costs of traditional scientific applications. Fermi National Accelerator Laboratory (Fermilab) is currently in the process of building its own private cloud, FermiCloud, which allows the existing grid infrastructure to use dynamically provisioned resources on FermiCloud to accommodate increased but dynamic computation demand from scientists in the domains of High Energy Physics (HEP) and other research areas. Cloud infrastructure also allows to increase a private cloud’s resource capacity through “bursting” by borrowing or renting resources from other community or commercial clouds when needed. This paper introduces a joint project on building a cloud federation to support HEP applications between Fermi National Accelerator Laboratory and Korea Institution of Science and Technology Information, with technical contributions from the Illinois Institute of Technology. In particular, this paper presents two recent accomplishments of the joint project: (a) cloud bursting automation and (b) load balancer. Automatic cloud bursting allows computer resources to be dynamically reconfigured to meet users’ demands. The load balance algorithm which the cloud bursting depends on decides when and where new resources need to be allocated. Our preliminary prototyping and experiments have shown promising success, yet, they also have opened new challenges to be studied

  16. Black Hole Accretion in Gamma Ray Bursts

    Directory of Open Access Journals (Sweden)

    Agnieszka Janiuk

    2017-02-01

    Full Text Available We study the structure and evolution of the hyperaccreting disks and outflows in the gamma ray bursts central engines. The torus around a stellar mass black hole is composed of free nucleons, Helium, electron-positron pairs, and is cooled by neutrino emission. Accretion of matter powers the relativistic jets, responsible for the gamma ray prompt emission. The significant number density of neutrons in the disk and outflowing material will cause subsequent formation of heavier nuclei. We study the process of nucleosynthesis and its possible observational consequences. We also apply our scenario to the recent observation of the gravitational wave signal, detected on 14 September 2015 by the two Advanced LIGO detectors, and related to an inspiral and merger of a binary black hole system. A gamma ray burst that could possibly be related with the GW150914 event was observed by the Fermi satellite. It had a duration of about 1 s and appeared about 0.4 s after the gravitational-wave signal. We propose that a collapsing massive star and a black hole in a close binary could lead to the event. The gamma ray burst was powered by a weak neutrino flux produced in the star remnant’s matter. Low spin and kick velocity of the merged black hole are reproduced in our simulations. Coincident gravitational-wave emission originates from the merger of the collapsed core and the companion black hole.

  17. RADIO FLARES FROM GAMMA-RAY BURSTS

    Energy Technology Data Exchange (ETDEWEB)

    Kopač, D.; Mundell, C. G.; Kobayashi, S.; Virgili, F. J. [Astrophysics Research Institute, Liverpool John Moores University, Liverpool, L3 5RF (United Kingdom); Harrison, R. [Department of Astrophysics, School of Physics and Astronomy, Tel Aviv University, 69978 Tel Aviv (Israel); Japelj, J.; Gomboc, A. [Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana (Slovenia); Guidorzi, C. [Department of Physics and Earth Sciences, University of Ferrara, Via Saragat, 1, I-44122 Ferrara (Italy); Melandri, A., E-mail: D.Kopac@ljmu.ac.uk [INAF/Brera Astronomical Observatory, via Bianchi 46, I-23807, Merate (Italy)

    2015-06-20

    We present predictions of centimeter and millimeter radio emission from reverse shocks (RSs) in the early afterglows of gamma-ray bursts (GRBs) with the goal of determining their detectability with current and future radio facilities. Using a range of GRB properties, such as peak optical brightness and time, isotropic equivalent gamma-ray energy, and redshift, we simulate radio light curves in a framework generalized for any circumburst medium structure and including a parameterization of the shell thickness regime that is more realistic than the simple assumption of thick- or thin-shell approximations. Building on earlier work by Mundell et al. and Melandri et al. in which the typical frequency of the RS was suggested to lie at radio rather than optical wavelengths at early times, we show that the brightest and most distinct RS radio signatures are detectable up to 0.1–1 day after the burst, emphasizing the need for rapid radio follow-up. Detection is easier for bursts with later optical peaks, high isotropic energies, lower circumburst medium densities, and at observing frequencies that are less prone to synchrotron self-absorption effects—typically above a few GHz. Given recent detections of polarized prompt gamma-ray and optical RS emission, we suggest that detection of polarized radio/millimeter emission will unambiguously confirm the presence of low-frequency RSs at early time.

  18. Secured Hash Based Burst Header Authentication Design for Optical Burst Switched Networks

    Science.gov (United States)

    Balamurugan, A. M.; Sivasubramanian, A.; Parvathavarthini, B.

    2017-12-01

    The optical burst switching (OBS) is a promising technology that could meet the fast growing network demand. They are featured with the ability to meet the bandwidth requirement of applications that demand intensive bandwidth. OBS proves to be a satisfactory technology to tackle the huge bandwidth constraints, but suffers from security vulnerabilities. The objective of this proposed work is to design a faster and efficient burst header authentication algorithm for core nodes. There are two important key features in this work, viz., header encryption and authentication. Since the burst header is an important in optical burst switched network, it has to be encrypted; otherwise it is be prone to attack. The proposed MD5&RC4-4S based burst header authentication algorithm runs 20.75 ns faster than the conventional algorithms. The modification suggested in the proposed RC4-4S algorithm gives a better security and solves the correlation problems between the publicly known outputs during key generation phase. The modified MD5 recommended in this work provides 7.81 % better avalanche effect than the conventional algorithm. The device utilization result also shows the suitability of the proposed algorithm for header authentication in real time applications.

  19. Content Aware Burst Assembly - Supporting Telesurgery and Telemedicine in Optical Burst Switching Networks

    Directory of Open Access Journals (Sweden)

    Henry Orosco

    2010-08-01

    Full Text Available The emerging Telemedicine and Telesurgery technologies allow patients to share medical experts remotely through communication networks. However, network bandwidth, network latency and jitter (variation of latency, are the obstacles to the widespread use of this technology remotely. Optical Burst Switching (OBS networks greatly expand network bandwidth in existing network infrastructure by utilizing multiple DWDM channels within a single fiber, enabling high bandwidth applications. However, the burst assembly process in OBS networks introduces latency and jitter, making it unsuitable for high bandwidth, latency sensitive applications such as telesurgery and telemedicine. In this paper, we propose a content aware burst assembly scheme which dynamically adjusts the burst assembly parameters based on the content being assembled. The proposed content aware burst assembly minimizes the latency and jitter within a video frame, as well as across the left-view and right-view frames for 3D vision generation. Simulation results have shown that the proposed scheme can effectively reduce the latency and jitter experienced by video streams, making OBS a promising candidate for supporting telesurgery and telemedicine applications.

  20. Burst-suppression is reactive to photic stimulation in comatose children with acquired brain injury

    DEFF Research Database (Denmark)

    Nita, Dragos A.; Moldovan, Mihai; Sharma, Roy

    2016-01-01

    Objective: Burst-suppression is an electroencephalographic pattern observed during coma. In individuals without known brain pathologies undergoing deep general anesthesia, somatosensory stimulation transiently increases the occurrence of bursts. We investigated the reactivity of burst-suppression......Objective: Burst-suppression is an electroencephalographic pattern observed during coma. In individuals without known brain pathologies undergoing deep general anesthesia, somatosensory stimulation transiently increases the occurrence of bursts. We investigated the reactivity of burst...... reactivity. We quantified reactivity by measuring the change in the burst ratio (fraction of time in burst) following photic stimulation. Results: Photic stimulation evoked bursts in all patients, resulting in a transient increase in the burst ratio, while the mean heart rate remained unchanged....... The regression slope of the change in burst ratio, referred to as the standardized burst ratio reactivity, correlated with subjects' Glasgow Coma Scale scores. Conclusions: Reactivity of the burst-suppression pattern to photic stimulation occurs across diverse coma etiologies. Standardized burst ratio reactivity...

  1. Dynamic encoding of natural luminance sequences by LGN bursts.

    Directory of Open Access Journals (Sweden)

    Nicholas A Lesica

    2006-07-01

    Full Text Available In the lateral geniculate nucleus (LGN of the thalamus, visual stimulation produces two distinct types of responses known as tonic and burst. Due to the dynamics of the T-type Ca(2+ channels involved in burst generation, the type of response evoked by a particular stimulus depends on the resting membrane potential, which is controlled by a network of modulatory connections from other brain areas. In this study, we use simulated responses to natural scene movies to describe how modulatory and stimulus-driven changes in LGN membrane potential interact to determine the luminance sequences that trigger burst responses. We find that at low resting potentials, when the T channels are de-inactivated and bursts are relatively frequent, an excitatory stimulus transient alone is sufficient to evoke a burst. However, to evoke a burst at high resting potentials, when the T channels are inactivated and bursts are relatively rare, prolonged inhibitory stimulation followed by an excitatory transient is required. We also observe evidence of these effects in vivo, where analysis of experimental recordings demonstrates that the luminance sequences that trigger bursts can vary dramatically with the overall burst percentage of the response. To characterize the functional consequences of the effects of resting potential on burst generation, we simulate LGN responses to different luminance sequences at a range of resting potentials with and without a mechanism for generating bursts. Using analysis based on signal detection theory, we show that bursts enhance detection of specific luminance sequences, ranging from the onset of excitatory sequences at low resting potentials to the offset of inhibitory sequences at high resting potentials. These results suggest a dynamic role for burst responses during visual processing that may change according to behavioral state.

  2. Localization of Gamma-Ray Bursts using the Fermi Gamma-Ray Burst Monitor

    OpenAIRE

    Connaughton, V.; Briggs, M. S.; Goldstein, A.; Meegan, C. A.; Paciesas, W. S.; Preece, R. D.; Wilson-Hodge, C.A.; Gibby, M. H.; Greiner, J.; Gruber, D.; Jenke, P.; Kippen, R. M.; Pelassa, V.; Xiong, S.; Yu, H-F

    2014-01-01

    The Fermi Gamma-ray Burst Monitor (GBM) has detected over 1400 Gamma-Ray Bursts (GRBs) since it began science operations in July, 2008. We use a subset of over 300 GRBs localized by instruments such as Swift, the Fermi Large Area Telescope, INTEGRAL, and MAXI, or through triangulations from the InterPlanetary Network (IPN), to analyze the accuracy of GBM GRB localizations. We find that the reported statistical uncertainties on GBM localizations, which can be as small as 1 degree, underestimat...

  3. Burst segmentation for void-filling scheduling and its performance evaluation in optical burst switching.

    Science.gov (United States)

    Tan, Wei; Wang, Sheng; Li, Lemin

    2004-12-27

    As a promising solution for the next generation optical Internet, optical burst switching still has much to be improved, especially the design of core routers. This paper mainly focuses on channel scheduling algorithms of core routers and proposes a new practical scheduling algorithm. In the new algorithm, burst segmentation, one of the contention resolution schemes that are another major concern in core router design, is introduced. The proposed algorithm is analyzed theoretically and evaluated by computer simulations. The results show that the new algorithm, compared with existing traditional scheduling algorithms, can lower the packet loss probability and enhance the link utilization and network performance.

  4. Exploring the Pulse Structure of the Gamma-Ray Bursts from the Swift Burst Alert Telescop

    Science.gov (United States)

    Martinez, Juan-Carlos; Team 1: Jon Hakkila, Amy Lien, Judith, Racusin, Team 2: Antonino Cucchiara, David Morris

    2018-01-01

    Gamma-ray bursts (GRBs) are one of the brightest and most intense explosions in our universe. For this project, we studied the shape of 400 single pulse GRBs using data gathered from Swift's Burst Alert Telescope (BAT). Hakkila et al. (2015) have discovered a mathematical Model that describes the GRB’s pulse shapes. Following the method in Hakkila et al. (2015), we fit GRB pulses with the Norris function and examined the residual in the fitting, to see whether the results are consistent with the one reported in Hakkila et al. (2015).

  5. Weighted Feature Distance

    DEFF Research Database (Denmark)

    Ortiz-Arroyo, Daniel; Yazdani, Hossein

    2017-01-01

    The accuracy of machine learning methods for clustering depends on the optimal selection of similarity functions. Conventional distance functions for the vector space might cause an algorithm to being affected by some dominant features that may skew its final results. This paper introduces a flexible...... environment for mining algorithms that uses the most suitable similarity functions to cover the diversity of both vector and feature spaces. The paper describes some well known conventional distance functions and introduces Weighted Feature Distance (WFD) and Prioritized Weighted Feature Distance (PWFD......). These novel functions attempt to balance the impact of the dominant features by covering both feature and vector spaces, additionally to optionally allowing us to increase or decrease the impact of some features. We evaluate and compare the accuracy of our proposed WFD(s) on conventional fuzzy...

  6. Motivation in Distance Leaming

    Directory of Open Access Journals (Sweden)

    Daniela Brečko

    1996-12-01

    Full Text Available It is estimated that motivation is one of the most important psychological functions making it possible for people to leam even in conditions that do not meet their needs. In distance learning, a form of autonomous learning, motivation is of outmost importance. When adopting this method in learning an individual has to stimulate himself and take learning decisions on his or her own. These specific characteristics of distance learning should be taken into account. This all different factors maintaining the motivation of partici­pants in distance learning are to be included. Moreover, motivation in distance learning can be stimulated with specific learning materials, clear instructions and guide-lines, an efficient feed back, personal contact between tutors and parti­cipants, stimulating learning letters, telephone calls, encouraging letters and through maintaining a positive relationship between tutor and participant.

  7. Benchmarking Distance Education.

    Science.gov (United States)

    Novak, Richard J.

    2002-01-01

    Identifies and discusses the myriad perspectives on measures of quality and benchmarking in distance education. Reviews the standards or benchmarks of quality that have been promulgated by various stakeholder groups. (EV)

  8. Long distance quantum teleportation

    Science.gov (United States)

    Xia, Xiu-Xiu; Sun, Qi-Chao; Zhang, Qiang; Pan, Jian-Wei

    2018-01-01

    Quantum teleportation is a core protocol in quantum information science. Besides revealing the fascinating feature of quantum entanglement, quantum teleportation provides an ultimate way to distribute quantum state over extremely long distance, which is crucial for global quantum communication and future quantum networks. In this review, we focus on the long distance quantum teleportation experiments, especially those employing photonic qubits. From the viewpoint of real-world application, both the technical advantages and disadvantages of these experiments are discussed.

  9. Improved Heterogeneous Distance Functions

    OpenAIRE

    Wilson, D. R.; Martinez, T. R.

    1996-01-01

    Instance-based learning techniques typically handle continuous and linear input values well, but often do not handle nominal input attributes appropriately. The Value Difference Metric (VDM) was designed to find reasonable distance values between nominal attribute values, but it largely ignores continuous attributes, requiring discretization to map continuous values into nominal values. This paper proposes three new heterogeneous distance functions, called the Heterogeneous Value Difference M...

  10. Inland Waters - Navigation Distance Mark - Minnesota River (Non-Navigable)

    Data.gov (United States)

    Army Corps of Engineers, Department of the Army, Department of Defense — A distance mark indicates the distance measured from an origin and consists of a distinct location without special installation, used to serve as a reference along...

  11. The Truncated Lognormal Distribution as a Luminosity Function for SWIFT-BAT Gamma-Ray Bursts

    Directory of Open Access Journals (Sweden)

    Lorenzo Zaninetti

    2016-11-01

    Full Text Available The determination of the luminosity function (LF in Gamma ray bursts (GRBs depends on the adopted cosmology, each one characterized by its corresponding luminosity distance. Here, we analyze three cosmologies: the standard cosmology, the plasma cosmology and the pseudo-Euclidean universe. The LF of the GRBs is firstly modeled by the lognormal distribution and the four broken power law and, secondly, by a truncated lognormal distribution. The truncated lognormal distribution fits acceptably the range in luminosity of GRBs as a function of the redshift.

  12. Gamma-Ray Burst Formation Rate Inferred from the Spectral Peak EnergyndashPeak Luminosity Relation

    OpenAIRE

    Yonetoku, D.; Murakami, T.; Nakamura, T.; Yamazaki, Ryo; Inoue, A.K.; Ioka, K.

    2004-01-01

    We estimate a gamma-ray burst (GRB) formation rate based on the new relation between the spectral peak energy (Ep) and the peak luminosity. The new relation is derived by combining the data of Ep and the peak luminosities by BeppoSAX and BATSE, and it looks considerably tighter and more reliable than the relations suggested by the previous works. Using the new Ep-luminosity relation, we estimate redshifts of the 689 GRBs without known distances in the BATSE catalog and derive a GRB formation ...

  13. Neutrino and cosmic-ray emission from multiple internal shocks in gamma-ray bursts

    DEFF Research Database (Denmark)

    Bustamante, Mauricio; Baerwald, Philipp; Murase, Kohta

    2014-01-01

    Gamma-ray bursts are short-lived, luminous explosions at cosmological distances, thought to originate from relativistic jets launched at the deaths of massive stars. They are among the prime candidates to produce the observed cosmic rays at the highest energies. Recent neutrino data have, however...... and cosmic-ray emission from multiple emission regions since these internal collisions must occur at very different radii, from below the photosphere all the way out to the circumburst medium, as a consequence of the efficient dissipation of kinetic energy. We demonstrate that the different messengers...

  14. A Biomechanical Assessment of Kyphoplasty as a Stand-Alone Treatment in a Human Cadaveric Burst Fracture Model.

    Science.gov (United States)

    Wong, Edwin King Yat; Whyne, Cari Marisa; Singh, Devin; Ford, Michael

    2015-07-15

    In vitro biomechanics study. To determine whether kyphoplasty is an adequate stand-alone treatment for restoring biomechanical stability in the spine after experiencing high-energy vertebral burst fractures. Kyphoplasty in the treatment of high-energy vertebral burst fractures has been shown by previous studies to significantly improve stiffness when used in conjunction with pedicle screw instrumentation. However, it is not known whether kyphoplasty as a stand-alone treatment may be an acceptable method for restoring biomechanical stability of a spinal motion segment post-burst fracture while allowing flexibility of the motion segment through the intervertebral discs. Young cadaveric spines (15-50 yr old; 3 males and 1 female; bone mineral density 0.27-0.31 gHA/cm) were divided into motion segments consisting of 3 intact vertebrae separated by 2 intervertebral discs (T11-L1 and L2-L4). Mechanical testing in axial, flexion/extension, lateral bending, and torsion was performed on each specimen in an intact state, after an experimentally simulated burst fracture and postkyphoplasty. Computed tomography was used to confirm the burst fractures and quantify cement placement. Between the intact and burst-fractured states significant decreases in stiffness were seen in all loading modes (63%-69%). Burst fracture increased the average angulation of the vertebral endplates 147% and decreased vertebral body height by an average of 40%. Postkyphoplasty, only small recoveries in stiffness were seen in axial, flexion/extension, and lateral bending (4%-12%), with no improvement in torsional stiffness. Large angular deformations (85%) and height loss (31%) remained postkyphoplasty as compared with the intact state. Lack of overall improvement in biomechanical stiffness indicates failure of kyphoplasty to sufficiently restore stability as a stand-alone treatment after high-energy burst fracture. The lack of stability can be explained by an inability to biomechanically repair the

  15. Emergent synchronous bursting of oxytocin neuronal network.

    Directory of Open Access Journals (Sweden)

    Enrico Rossoni

    2008-07-01

    Full Text Available When young suckle, they are rewarded intermittently with a let-down of milk that results from reflex secretion of the hormone oxytocin; without oxytocin, newly born young will die unless they are fostered. Oxytocin is made by magnocellular hypothalamic neurons, and is secreted from their nerve endings in the pituitary in response to action potentials (spikes that are generated in the cell bodies and which are propagated down their axons to the nerve endings. Normally, oxytocin cells discharge asynchronously at 1-3 spikes/s, but during suckling, every 5 min or so, each discharges a brief, intense burst of spikes that release a pulse of oxytocin into the circulation. This reflex was the first, and is perhaps the best, example of a physiological role for peptide-mediated communication within the brain: it is coordinated by the release of oxytocin from the dendrites of oxytocin cells; it can be facilitated by injection of tiny amounts of oxytocin into the hypothalamus, and it can be blocked by injection of tiny amounts of oxytocin antagonist. Here we show how synchronized bursting can arise in a neuronal network model that incorporates basic observations of the physiology of oxytocin cells. In our model, bursting is an emergent behaviour of a complex system, involving both positive and negative feedbacks, between many sparsely connected cells. The oxytocin cells are regulated by independent afferent inputs, but they interact by local release of oxytocin and endocannabinoids. Oxytocin released from the dendrites of these cells has a positive-feedback effect, while endocannabinoids have an inhibitory effect by suppressing the afferent input to the cells.

  16. On the Structure of the Burst and Afterglow of Gamma-Ray Bursts I

    Science.gov (United States)

    Ruffini, Remo; Bianco, Carlo Luciano; Xue, She-Sheng; Chardonnet, Pascal; Fraschetti, Federico

    We have recently proposed three paradigms for the theoretical interpretation of gamma-ray bursts (GRBs). (1) The relative space time transformation (RSTT) paradigm emphasizes how the knowledge of the entire world-line of the source from the moment of gravitational collapse is a necessary condition in order to interpret GRB data.1 (2) The interpretation of the burst structure (IBS) paradigm differentiates in all GRBs between an injector phase and a beam-target phase.2 (3) The GRB-supernova time sequence (GSTS) paradigm introduces the concept of induced supernova explosion in the supernovae-GRB association.3 The RSTT and IBS paradigms are enunciated and illustrated using our theory based on the vacuum polarization process occurring around an electromagnetic black hole (EMBH) theory. The results are summarized using figures, diagrams and a complete table with the space time grid, the fundamental parameters and the corresponding values of the Lorentz gamma factor for GRB 991216 used as a prototype. In the following sections the detailed treatment of the EMBH theory needed to understand the results of the three above paradigms is presented. We start from the considerations on the dyadosphere formation. We then review the basic hydrodynamic and rate equations, the equations leading to the relative space time transformations as well as the adopted numerical integration techniques. We then illustrate the five fundamental eras of the EMBH theory: the self acceleration of the e+e- pair-electromagnetic plasma (PEM pulse), its interaction with the baryonic remnant of the progenitor star, the further self acceleration of the e+e- pair-electromagnetic radiation and baryon plasma (PEMB pulse). We then study the approach of the PEMB pulse to transparency, the emission of the proper GRB (P-GRB) and its relation to the "short GRBs". Particular attention is given to the free parameters of the theory and to the values of the thermodynamical quantities at transparency. Finally

  17. Auroral kilometric radiation triggered by type II solar radio bursts

    Science.gov (United States)

    Calvert, W.

    1985-01-01

    The previously-reported triggering of auroral kilometric radiation (AKR) during type III solar radio bursts was attributed to the incoming radio waves rather than other aspects of the burst's causative solar flare. This conclusion has now been confirmed by ISEE-1 and ISEE-3 observations showing AKR which seems to have been triggered also by a subsequent type II solar radio burst, up to eleven hours after the flare.

  18. The bursting of housing bubble as jamming phase transition

    Science.gov (United States)

    Nishinari, Katsuhiro; Iwamura, Mitsuru; Umeno Saito, Yukiko; Watanabe, Tsutomu

    2010-04-01

    In this paper, we have proposed a bubble burst model by focusing on transaction volume incorporating a traffic model that represents spontaneous traffic jam. We find that the phenomenon of bubble burst shares many similar properties with traffic jam formation on highway by comparing data taken from the U.S. housing market. Our result suggests that transaction volume could be a driving force of bursting phenomenon.

  19. Detecting Pipe Bursts Using Heuristic and CUSUM Methods

    OpenAIRE

    Bakker, M.; Jung, D; Vreeburg, J.; van de Roer, M.; Lansey, K.; Rietveld, L.

    2014-01-01

    Pipe bursts in a drinking water distribution system lead to water losses, interruption of supply, and damage to streets and houses due to the uncontrolled water flow. To minimize the negative consequences of pipe bursts, an early detection is necessary. This paper describes a heuristic burst detection method, which continuously compares forecasted and measured values of the water demand. The forecasts of the water demand were generated by an adaptive water demand forecasting model. To test th...

  20. Bursting in Cellular Automata and Cardiac Arrhythmias

    Science.gov (United States)

    Bub, Gil; Shrier, Alvin; Glass, Leon

    2013-01-01

    The mechanisms underlying the initiation and continuation of abnormal cardiac arrhythmias are incompletely understood. In this chapter, we summarize work that shows how simple cellular automata models of excitable media can display a range of interesting dynamical behavior including spontaneous bursts of reentrant spiral activity. Since the model incorporates basic physiological properties of excitability, heterogeneity, localized pacemakers, and fatigue in a schematic way, the model captures generic physiological dynamics that should be broadly observed in experimental and clinical settings as well as in more realistic mathematical models.

  1. Burst-Mode Asynchronous Controllers on FPGA

    Directory of Open Access Journals (Sweden)

    Duarte L. Oliveira

    2008-01-01

    Full Text Available FPGAs have been mainly used to design synchronous circuits. Asynchronous design on FPGAs is difficult because the resulting circuit may suffer from hazard problems. We propose a method that implements a popular class of asynchronous circuits, known as burst mode, on FPGAs based on look-up table architectures. We present two conditions that, if satisfied, guarantee essential hazard-free implementation on any LUT-based FPGA. By doing that, besides all the intrinsic advantages of asynchronous over synchronous circuits, they also take advantage of the shorter design time and lower cost associated with FPGA designs.

  2. Encephalopathies epileptogenes precoces avec suppression burst ...

    African Journals Online (AJOL)

    L'EEG de sommeil réalisé au moment du diagnostic a montré un pattern de suppression burst. Aucune étiologie n'a été retenue du fait de la limitation du bilan complémentaire à visée étiologique tel que l'IRM cérébrale ou les bilans métaboliques. L'évolution électro-clinique est favorable pour certains patients avec le ...

  3. A cognitively grounded measure of pronunciation distance.

    Directory of Open Access Journals (Sweden)

    Martijn Wieling

    Full Text Available In this study we develop pronunciation distances based on naive discriminative learning (NDL. Measures of pronunciation distance are used in several subfields of linguistics, including psycholinguistics, dialectology and typology. In contrast to the commonly used Levenshtein algorithm, NDL is grounded in cognitive theory of competitive reinforcement learning and is able to generate asymmetrical pronunciation distances. In a first study, we validated the NDL-based pronunciation distances by comparing them to a large set of native-likeness ratings given by native American English speakers when presented with accented English speech. In a second study, the NDL-based pronunciation distances were validated on the basis of perceptual dialect distances of Norwegian speakers. Results indicated that the NDL-based pronunciation distances matched perceptual distances reasonably well with correlations ranging between 0.7 and 0.8. While the correlations were comparable to those obtained using the Levenshtein distance, the NDL-based approach is more flexible as it is also able to incorporate acoustic information other than sound segments.

  4. Coexistence of tonic firing and bursting in cortical neurons

    Science.gov (United States)

    Fröhlich, Flavio; Bazhenov, Maxim

    2006-09-01

    Sustained neuronal activity can be broadly classified as either tonic firing or bursting. These two major patterns of neuronal oscillations are state dependent and may coexist. The dynamics and intracellular mechanisms of transitions between tonic firing and bursting in cortical networks remain poorly understood. Here we describe a detailed two-compartment conductance-based cortical neuron model which exhibits bistability with hysteresis between tonic firing and bursting for elevated extracellular potassium concentration. The study explains the ionic and dynamical mechanisms of burst generation and reveals the conditions underlying coexistence of two different oscillatory modes as a function of neuronal excitability.

  5. Review of GRANAT observations of gamma-ray bursts

    DEFF Research Database (Denmark)

    Terekhov, O.; Denissenko, D.; Sunyaev, R.

    1995-01-01

    of the observations of the time histories and spectral evolution of the detected events provided by the different instruments in different energy ranges. Short Gamma-Ray Bursts (histories. They have harder energy spectra than the long (> 2 s) events. Evidence of the existence...... of four differently behaving componenents in gamma-ray burst spectra is discussed. Statistical properties of the gamma-ray burst sources based on the 5 years of observations with (∼ 10−6 erg/cm2) sensitivity as well as the results of high sensitivity (∼ 10−8 erg/cm2) search for Gamma-Ray Bursts within...

  6. CME-Associated Radio Bursts from Satellite Observations

    Science.gov (United States)

    Gopalswamy, Nat

    2012-01-01

    Coronal mass ejections (CMEs) are closely associated with various types of radio bursts from the Sun. All radio bursts are due to nonthermal electrons, which are accelerated during the eruption of CMEs. Radio bursts at frequencies below about 15 MHz are of particular interest because they are associated with energetic CMEs that contribute to severe space weather. The low-frequency bursts need to be observed primarily from space because of the ionospheric cutoff. The main CME-related radio bursts are associated are: type III bursts due to accelerated electrons propagating along open magnetic field lines, type II bursts due to electrons accelerated in shocks, and type IV bursts due to electrons trapped in post-eruption arcades behind CMEs. This paper presents a summary of results obtained during solar cycle 23 primarily using the white-light coronagraphic observations from the Solar Heliospheric Observatory (SOHO) and the WAVES experiment on board Wind. Particular emphasis will be placed on what we can learn about particle acceleration in the coronal and interplanetary medium by analyzing the CMEs and the associated radio bursts.

  7. BATSE Observations of Gamma-Ray Burst Tails

    Science.gov (United States)

    Connaughton, Valerie

    2002-01-01

    With the observation of low-energy radiation coming from the site of gamma-ray bursts in the hours to weeks after the initial gamma ray burst, it appears that astronomers have discovered a cosmological imprint made by the burster on its surroundings. This paper discusses the phenomenon of postburst emission in Burst and Transient Source Experiment (BATSE) gamma-ray bursts at energies usually associated with prompt emission. After summing up the background-subtracted signals from hundreds of bursts, it is found that tails out to hundreds of seconds after the trigger could be a common feature of events of a duration greater than 2 seconds, and perhaps of the shorter bursts at a lower and shorter-lived level. The tail component may be softer and seems independent of the duration (within the long-GRB sample) and brightness of the prompt burst emission. Some individual bursts have visible tails at gamma-ray energies, and the spectrum in a few cases differs from that of the prompt emission. For one of these bursts, GRB 991216, afterglow at lower energies was detected, which raised the possibility of seeing afterglow observations over large energy ranges using the next generation of GRB detectors in addition to sensitive space- or ground-based telescopes.

  8. Gamma-ray burst interaction with dense interstellar medium

    OpenAIRE

    Barkov, Maxim; Bisnovatyi-Kogan, Gennady

    2004-01-01

    Interaction of cosmological gamma ray burst radiation with the dense interstellar medium of host galaxy is considered. Gas dynamical motion of interstellar medium driven by gamma ray burst is investigated in 2D approximation for different initial density distributions of host galaxy matter and different total energy of gamma ray burst. The maximum velocity of motion of interstellar medium is $1.8\\cdot10^4$ km/s. Light curves of gamma ray burst afterglow are calculated for set of non homogeneo...

  9. Energy sources in gamma-ray burst models

    Science.gov (United States)

    Taam, Ronald E.

    1987-01-01

    The current status of energy sources in models of gamma-ray bursts is examined. Special emphasis is placed on the thermonuclear flash model which has been the most developed model to date. Although there is no generally accepted model, if the site for the gamma-ray burst is on a strongly magnetized neutron star, the thermonuclear model can qualitatively explain the energetics of some, but probably not all burst events. The critical issues that may differentiate between the possible sources of energy for gamma-ray bursts are listed and briefly discussed.

  10. Burst-Compression And -Expansion For TDMA Communication

    Science.gov (United States)

    Budinger, James M.

    1991-01-01

    Burst-compression and -expansion technique enables interconnection of users transmitting and receiving data at rates asynchronous with respect to clocks within ground terminals of satellite-switched, time-division-multiple-access (TDMA) communication network. Matrix switch aboard satellite routes bursts of data from source users received on uplink antennas to downlink antennas illuminating ground areas containing destination users. TDMA ground terminal compresses streams of data from source users into rapid bursts for transmission and reexpands bursts of received data into slower streams of data for delivery to destination users. Greater flexibility in interconnecting widely dispersed users achieved by use of hopping beams.

  11. The psychological distance of climate change.

    Science.gov (United States)

    Spence, Alexa; Poortinga, Wouter; Pidgeon, Nick

    2012-06-01

    Avoiding dangerous climate change is one of the most urgent social risk issues we face today and understanding related public perceptions is critical to engaging the public with the major societal transformations required to combat climate change. Analyses of public perceptions have indicated that climate change is perceived as distant on a number of different dimensions. However, to date there has been no in-depth exploration of the psychological distance of climate change. This study uses a nationally representative British sample in order to systematically explore and characterize each of the four theorized dimensions of psychological distance--temporal, social, and geographical distance, and uncertainty--in relation to climate change. We examine how each of these different aspects of psychological distance relate to each other as well as to concerns about climate change and sustainable behavior intentions. Results indicate that climate change is both psychologically distant and proximal in relation to different dimensions. Lower psychological distance was generally associated with higher levels of concern, although perceived impacts on developing countries, as an indicator of social distance, was also significantly related to preparedness to act on climate change. Our findings clearly point to the utility of risk communication techniques designed to reduce psychological distance. However, highlighting the potentially very serious distant impacts of climate change may also be useful in promoting sustainable behavior, even among those already concerned. © 2011 Society for Risk Analysis.

  12. Statistical Distance For Chaotic Maps

    CERN Document Server

    Johal, R S

    1998-01-01

    The purpose of this letter is to define a distance on the underlying phase space of a chaotic map, based on natural invariant density of the map. It is observed that for logistic map this distance is equivalent to Wootters' statistical distance. This distance becomes the Euclidean distance for a map with constant invariant density.

  13. Bursting Events in Pressure Flushing with Expanding Bottom Outlet Channel within Dam Reservoir

    Directory of Open Access Journals (Sweden)

    soheila Tofighi

    2017-01-01

    each experiment, the bed level of scouring was measured using laser meters, and the volume of flushing cone was calculated by Surfer software. For investigation of turbulence parameters, the measurement of flow velocity in 0.5cm from the bed of flushing cone in the central axis of the outlet channel in the flow rate of 3 liters per second and water level of 47.5cm for three expansion sizes of the outlet channel (10, 20, and 30cm was performed. The flow velocity measurement was done using an Acoustic Doppler Velocimeter. This device is capable of measuring instantaneous velocity in three directions. Results and Discussion: The results indicated that the relative amount of bottom outlet channel expansion for 0.5, 1 and 1.5 times height of the sediments in the reservoir, leads to increase in flushing cone length for an average of 48, 83 and 113% and flushing cone volume for the average amount of 50, 74 and 96% compared to the case when the outlet channel is not developed. Also the analysis of the turbulence parameters showed that in the nearest axis to the inlet of the bottom outlet channel in which the maximum depth of flushing cone, the occurrence probability of sweep and ejection are maximum and impact angle of moment force due to these events is minimized. However the dominant event here is ejected which was also observed in laboratory experiments the particles were transferred into the channel as suspended load. By increasing the distance from the inlet opening of the channel the occurrence probability of sweep and ejection are decreased and impact angle of moment force due to these events is increased, but again, these two events are the dominant events in this regions and sweep is more important than ejection, that the observations also verify the particles transferred as bed load in these region. Ultimately, it comes to a region where the probabilities of all four events are the same and where the sediment flushing cone reaches the primary sedimentation level that

  14. Measuring Cosmological Parameters with Gamma Ray Bursts

    Science.gov (United States)

    Amati, Lorenzo; Della Valle, Massimo

    2013-12-01

    In a few dozen seconds, gamma ray bursts (GRBs) emit up to 1054 erg in terms of an equivalent isotropically radiated energy Eiso, so they can be observed up to z 10. Thus, these phenomena appear to be very promising tools to describe the expansion rate history of the universe. Here, we review the use of the Ep,i-Eiso correlation of GRBs to measure the cosmological density parameter ΩM. We show that the present data set of GRBs, coupled with the assumption that we live in a flat universe, can provide independent evidence, from other probes, that ΩM 0.3. We show that current (e.g. Swift, Fermi/GBM, Konus-WIND) and forthcoming gamma ray burst (GRB) experiments (e.g. CALET/GBM, SVOM, Lomonosov/UFFO, LOFT/WFM) will allow us to constrain ΩM with an accuracy comparable to that currently exhibited by Type Ia supernovae (SNe-Ia) and to study the properties of dark energy and their evolution with time.

  15. Gamma-ray bursts as cosmological probes

    Science.gov (United States)

    Vergani, S. D.

    2013-11-01

    Gamma-ray bursts (GRBs) are short, intense burstsof gamma-rays which during seconds to minutes outshine all other sources of gamma-ray emission in the sky.Following the prompt gamma-ray emission, an `afterglow' of emission from the X-ray range to radio wavelengthspersists up to months after the initial burst. The association of the class of long GRBs with the explosion of broad-line type Ic SNe GRBs allow galaxies to be selected independently oftheir emission properties (independently of dust obscuration and, uniquely, independently of their brightnesses atany wavelength) and they also permit the study of the gas in the interstellar medium (ISM) systematically and at anyredshift by the absorption lines present in the afterglow spectra. Moreover, the fading nature of GRBs and theprecise localization of the afterglow allow a detailed investigation of the emission properties of the GRB hostgalaxy once the afterglow has vanished. GRBs therefore constitute a unique tool to understand the link between theproperties of the ISM in the galaxy and the star formation activity, and this at any redshift. This is a unique wayto reveal the physical processes that trigger galaxy formation. The SVOM space mission project is designed to improve the use GRBs as cosmological probes.

  16. Neutron star mass and radius measurements from atmospheric model fits to X-ray burst cooling tail spectra

    Science.gov (United States)

    Nättilä, J.; Miller, M. C.; Steiner, A. W.; Kajava, J. J. E.; Suleimanov, V. F.; Poutanen, J.

    2017-12-01

    Observations of thermonuclear X-ray bursts from accreting neutron stars (NSs) in low-mass X-ray binary systems can be used to constrain NS masses and radii. Most previous work of this type has set these constraints using Planck function fits as a proxy: the models and the data are both fit with diluted blackbody functions to yield normalizations and temperatures that are then compared with each other. For the first time, we here fit atmosphere models of X-ray bursting NSs directly to the observed spectra. We present a hierarchical Bayesian fitting framework that uses current X-ray bursting NS atmosphere models with realistic opacities and relativistic exact Compton scattering kernels as a model for the surface emission. We test our approach against synthetic data and find that for data that are well described by our model, we can obtain robust radius, mass, distance, and composition measurements. We then apply our technique to Rossi X-ray Timing Explorer observations of five hard-state X-ray bursts from 4U 1702-429. Our joint fit to all five bursts shows that the theoretical atmosphere models describe the data well, but there are still some unmodeled features in the spectrum corresponding to a relative error of 1-5% of the energy flux. After marginalizing over this intrinsic scatter, we find that at 68% credibility, the circumferential radius of the NS in 4U 1702-429 is R = 12.4±0.4 km, the gravitational mass is M = 1.9±0.3 M⊙, the distance is 5.1 < D/ kpc < 6.2, and the hydrogen mass fraction is X < 0.09.

  17. The electron-cyclotron maser instability as a source of plasma radiation. [Solar radio bursts

    Science.gov (United States)

    Winglee, R. M.; Dulk, G. A.

    1986-01-01

    The generation of continuum bursts from the sun at dm and m wavelengths (in particular, type IV bursts) via the electron-cyclotron-maser instability is examined. The maser instability can be driven by an electron distribution with either a loss-cone anisotropy or a peak at large pitch angles. For omega(p)/Omega(e) much greater than 1, the maser emission is produced by electrons interacting through a harmonic (cyclotron) resonance and is electrostatic, being in the upper hybrid mode at frequencies approximately equal to omega(p). Coalescence processes are required to convert the electrostatic waves into transverse radiation which can escape from the source region. Whether the resultant spectrum is nearly a smooth continuum or has a zebra-stripe pattern (both of which occur in type IV bursts) depends on the form of the electron distribution, inhomogeneities in the density and magnetic field, and whether the maser reaches saturation. For at least the case of some type IV dm bursts with fine structure, comparison with observations seems to indicate that the electrons producing the emission are more likely to have a loss-cone distribution, and that the maser instability is not at saturation.

  18. One-dimensional Turbulence Models of Type I X-ray Bursts

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Chen [Univ. of Minnesota, Minneapolis, MN (United States)

    2016-01-06

    Type I X-ray bursts are caused by thermonuclear explosions occurring on the surface of an accreting neutron star in a binary star system. Observations and simulations of these phenomena are of great importance for understanding the fundamental properties of neutron stars and dense matter because the equation of state for cold dense matter can be constrained by the mass-radius relationship of neutron stars. During the bursts, turbulence plays a key role in mixing the fuels and driving the unstable nuclear burning process. This dissertation presents one-dimensional models of photospheric radius expansion bursts with a new approach to simulate turbulent advection. Compared with the traditional mixing length theory, the one-dimensional turbulence (ODT) model represents turbulent motions by a sequence of maps that are generated according to a stochastic process. The light curves I obtained with the ODT models are in good agreement with those of the KEPLER model in which the mixing length theory and various diffusive processes are applied. The abundance comparison, however, indicates that the differences in turbulent regions and turbulent diffusivities result in more 12C survival during the bursts in the ODT models, which can make a difference in the superbursts phenomena triggered by unstable carbon burning.

  19. Cannabinoid receptor activation reverses kainate-induced synchronized population burst firing in rat hippocampus

    Directory of Open Access Journals (Sweden)

    Rob Mason

    2009-06-01

    Full Text Available Cannabinoids have been shown to possess anticonvulsant properties in whole animal models of epilepsy. The present investigation sought to examine the effects of cannabinoid receptor activation on kainic acid (KA-induced epileptiform neuronal excitability. Under urethane anesthesia, acute KA treatment (10 mg/kg, i.p. entrained the spiking mode of simultaneously recorded neurons from random firing to synchronous bursting (% change in burst rate. Injection of the high-affinity cannabinoid agonist (--11-hydroxy-8-tetrahydrocannabinol-dimethyl-heptyl (HU210, 100 µg/kg, i.p. following KA markedly reduced the burst frequency (% decrease in burst frequency and reversed synchronized firing patterns back to baseline levels. Pre-treatment with the central cannabinoid receptor (CB1 antagonist N-piperidino-5-(4-clorophenyl-1-(2,4-dichlorophenyl-4-methyl-3-pyrazole-carboxamide (rimonabant, SR141716A 3 mg/kg, i.p. completely prevented the actions of HU210. The present results indicate that cannabinoids exert their antiepileptic effects by impeding pathological synchronization of neuronal networks in the hippocampus.

  20. Front-Side Type II Radio Bursts Without Shocks Near Earth

    Science.gov (United States)

    Gopalswamy, N.; Makela, P.; Xie, H.; Yashiro, S.; Akiyama, S.

    2011-01-01

    Type II radio bursts are due to shocks driven by coronal mass ejections (CMEs), so the shocks are expected to arrive at Earth in 2-3 days if the source is on the front-side of the Sun. However, a significant fraction of front-side CMEs producing type II bursts did not result in shocks at 1 AU. On can think of several possibilities for the lack of shocks: (1) CMEs originating at large central meridian distances may be driving a shock, but the shock may not be extended sufficiently to reach to the Sun-Earth line. (2) CME cannibalism results in the merger of shocks so that one observes a single shock at Earth even though there are two type II bursts near the Sun. (3) CME-driven shocks may become weak and dissipate before reaching 1 AU. We examined a set of 30 type II bursts observed by the Wind/WAVES experiment that had the solar sources very close to the disk center (within a CMD of 15 degrees), but did not have shock at Earth. We find that the near-Sun speeds of the associated CMEs average to approx.600 km/s, only slightly higher than the average speed of CM Es associated with radio-quiet shocks. However, the fraction of halo CMEs is only -28%, compared to 40% for radio-quiet shocks and 72% for all radio-loud shocks. We conclude that the disk-center radio loud CMEs with no shocks at 1 AU are generally of lower energy and they drive shocks only close to the Sun.

  1. Functional Imaging of Human Vestibular Cortex Activity Elicited by Skull Tap and Auditory Tone Burst

    Science.gov (United States)

    Noohi, F.; Kinnaird, C.; Wood, S.; Bloomberg, J.; Mulavara, A.; Seidler, R.

    2016-01-01

    tone burst elicited vestibular evoked myogenic potentials, indicated by eye muscle responses. We further assessed subjects' postural control and its correlation with vestibular cortical activity. Our results provide the first evidence of using skull taps to elicit vestibular activity inside the MRI scanner. By conducting conjunction analyses we showed that skull taps elicit the same activation pattern as auditory tone bursts (superior temporal gyrus), and both modes of stimulation activate previously identified vestibular cortical regions. Additionally, we found that skull taps elicit more robust vestibular activity compared to auditory tone bursts, with less reported aversive effects. This further supports that the skull tap could replace auditory tone burst stimulation in clinical interventions and basic science research. Moreover, we observed that greater vestibular activation is associated with better balance control. We showed that not only the quality of balance (indicated by the amount of body sway) but also the ability to maintain balance for a longer time (indicated by the balance time) was associated with individuals' vestibular cortical excitability. Our findings support an association between vestibular cortical activity and individual differences in balance. In sum, we found that the skull tap stimulation results in activation of canonical vestibular cortex, suggesting an equally valid, but more tolerable stimulation method compared to auditory tone bursts. This is of high importance in longitudinal vestibular assessments, in which minimizing aversive effects may contribute to higher protocol adherence.

  2. Gamma ray bursts observed with WATCH‐EURECA

    DEFF Research Database (Denmark)

    Brandt, Søren; Lund, Niels; Castro-Tirado, A. J.

    1994-01-01

    The WATCH wide field x‐ray monitor has the capability of independently locating bright Gamma Ray Bursts to 1° accuracy. We report the preliminary positions of 12 Gamma Ray Bursts observed with the WATCH monitor flown on the ES spacecraft EURECA during its 11 month mission. Also the recurrence...

  3. Jet simulations and gamma-ray burst afterglow jet breaks

    NARCIS (Netherlands)

    van Eerten, H. J.; Meliani, Z.; Wijers, Ramj; Keppens, R.

    2011-01-01

    The conventional derivation of the gamma-ray burst afterglow jet break time uses only the blast wave fluid Lorentz factor and therefore leads to an achromatic break. We show that in general gamma-ray burst afterglow jet breaks are chromatic across the self-absorption break. Depending on

  4. Jet simulations and gamma-ray burst afterglow jet breaks

    NARCIS (Netherlands)

    van Eerten, H. J.; Meliani, Z.; Wijers, R.A.M.J.; Keppens, R.

    2010-01-01

    The conventional derivation of the gamma-ray burst afterglow jet break time uses only the blast wave fluid Lorentz factor and therefore leads to an achromatic break. We show that in general gamma-ray burst afterglow jet breaks are chromatic across the self-absorption break. Depending on

  5. Stochastic bursting synchronization in a population of subthreshold Izhikevich neurons

    Science.gov (United States)

    Kim, Sang-Yoon; Kim, Youngnam; Hong, Duk-Geun; Kim, Jean; Lim, Woochang

    2012-05-01

    We consider a population of subthreshold Izhikevich neurons that cannot fire spontaneously without noise. As the coupling strength passes a threshold, individual neurons exhibit noise-induced burstings ( i.e., discrete groups or bursts of noise-induced spikes). We investigate stochastic bursting synchronization by varying the noise intensity. Through competition between the constructive and the destructive roles of noise, collective coherence between noise-induced burstings is found to occur over a large range of intermediate noise intensities. This kind of stochastic bursting synchronization is well characterized by using the techniques of statistical mechanics and nonlinear dynamics, such as the order parameter, the raster plot of neural spikes, the time series of the ensemble-averaged global potential, and the phase portraits of limit cycles. In contrast to spiking neurons showing only spike synchronization (characterizing a temporal relationship between spikes), bursting neurons are found to exhibit both spike synchronization and burst synchronization (characterizing a temporal relationship between the onset times of the active phases of repetitive spikings). The degree of stochastic bursting synchronization is also measured in terms of a synchronization measure that reflects the resemblance of the global potential to the individual potential.

  6. Observations of cosmic gamma ray bursts with WATCH on EURECA

    DEFF Research Database (Denmark)

    Brandt, Søren; Lund, N.; Castro-Tirado, A. J.

    1995-01-01

    19 Cosmic Gamma-Ray Bursts were detected by the WATCH wide field X-ray monitor during the 11 months flight of EURECA. The identification of the bursts were complicated by a high frequency of background of events caused by high energy cosmic ray interactions in the detector and by low energy, trap...

  7. Statistical properties of SGR 1806-20 bursts

    NARCIS (Netherlands)

    Göğüş, E.; Woods, P.M.; Kouveliotou, C.; van Paradijs, J.; Briggs, M.S.; Duncan, R.C.; Thompson, C.

    2000-01-01

    We present statistics of SGR 1806-20 bursts, combining 290 events detected with the Rossi X-Ray Timing Explorer/Proportional Counter Array, 111 events detected with the Burst and Transient Source Experiment, and 134 events detected with the International Cometary Explorer. We find that the fluence

  8. Nanoemulsions obtained via bubble bursting at a compound interface

    NARCIS (Netherlands)

    Feng, J.; Roche, M.; Vigolo, D.; Arnaudov, L.N.; Stoyanov, S.D.; Gurkov, T.D.; Tsutsumanova, G.G.; Stone, H.A.

    2014-01-01

    Bursting of bubbles at an air/liquid interface is a familiar occurrence relevant to foam stability, cell cultures in bioreactors and ocean–atmosphere mass transfer. In the latter case, bubble-bursting leads to the dispersal of sea-water aerosols in the surrounding air. Here we show that bubbles

  9. Supernova sheds light on gamma-ray bursts

    CERN Multimedia

    2003-01-01

    On 29 March the HETE-II satellite detected the most violent explosion in the universe to date - an enormous burst of gamma rays. Observers across the world recorded and studied the event. It appears to prove that gamma ray bursts originate in supernovae (1 page)

  10. Multiparameter Monitoring and Prevention of Fault-Slip Rock Burst

    Directory of Open Access Journals (Sweden)

    Shan-chao Hu

    2017-01-01

    Full Text Available Fault-slip rock burst is one type of the tectonic rock burst during mining. A detailed understanding of the precursory information of fault-slip rock burst and implementation of monitoring and early warning systems, as well as pressure relief measures, are essential to safety production in deep mines. This paper first establishes a mechanical model of stick-slip instability in fault-slip rock bursts and then reveals the failure characteristics of the instability. Then, change rule of mining-induced stress and microseismic signals before the occurrence of fault-slip rock burst are proposed, and multiparameter integrated early warning methods including mining-induced stress and energy are established. Finally, pressure relief methods targeting large-diameter boreholes and coal seam infusion are presented in accordance with the occurrence mechanism of fault-slip rock burst. The research results have been successfully applied in working faces 2310 of the Suncun Coal Mine, and the safety of the mine has been enhanced. These research results improve the theory of fault-slip rock burst mechanisms and provide the basis for prediction and forecasting, as well as pressure relief, of fault-slip rock bursts.

  11. WATCH observations of gamma ray bursts during 1990–1992

    DEFF Research Database (Denmark)

    Castro-Tirado, A.; Brandt, Søren; Lund, Niels

    1994-01-01

    The first WATCH/GRANAT Gamma‐Ray Burst Catalogue comprises 70 events which have been detected by WATCH during the period December 1989–September 1992. 32 GRBs could be localized within a 3σ error radii of 1°. We have found a weak (2.2σ) clustering of these 32 bursts towards the Galactic Center...

  12. The width of the gamma-ray burst luminosity function

    NARCIS (Netherlands)

    Ulmer, A.; Wijers, R.A.M.J.

    1995-01-01

    We examine the width of the gamma-ray burst (GRB) luminosity function through the distribution of GRB peak count rates, Cpeak, as detected by Burst and Transient Source Experiment (BATSE) (1993). In the context of Galactic corona spatial distribution models, we attempt to place constaints on the

  13. 80537 based distance relay

    DEFF Research Database (Denmark)

    Pedersen, Knud Ole Helgesen

    1999-01-01

    A method for implementing a digital distance relay in the power system is described.Instructions are given on how to program this relay on a 80537 based microcomputer system.The problem is used as a practical case study in the course 53113: Micocomputer applications in the power system.The relay...

  14. Electromagnetic distance measurement

    CERN Document Server

    1967-01-01

    This book brings together the work of forty-eight geodesists from twenty-five countries. They discuss various new electromagnetic distance measurement (EDM) instruments - among them the Tellurometer, Geodimeter, and air- and satellite-borne systems - and investigate the complex sources of error.

  15. Determining average yarding distance.

    Science.gov (United States)

    Roger H. Twito; Charles N. Mann

    1979-01-01

    Emphasis on environmental and esthetic quality in timber harvesting has brought about increased use of complex boundaries of cutting units and a consequent need for a rapid and accurate method of determining the average yarding distance and area of these units. These values, needed for evaluation of road and landing locations in planning timber harvests, are easily and...

  16. 76 FR 28460 - Agency Information Collection Activities; Submission for OMB Review; Comment Request; Rock Burst...

    Science.gov (United States)

    2011-05-17

    ...; Rock Burst Control Plan--Pertains to Underground Metal and Nonmetal Mines ACTION: Notice. SUMMARY: The... rock burst plan within 90 days after a rock burst has been experienced. Stress data are normally...

  17. Usefulness of seismic monitoring around longwall faces mined with caving for rock burst hazard estimation

    Energy Technology Data Exchange (ETDEWEB)

    Filipek, M.; Syrek, B.

    1987-04-01

    Considers seismic energy distribution in dependence of distance from the face of a closing longwall in seam 501 at the Wujek mine. Describes geologic and mining conditions and rock burst hazards. Seismic activity was monitored there in 1984 along with two series of stress-relaxing blasting using 60-100 kg explosive charges. Three instances of stress relaxation with energy of 10/sup 4/ J were noted during the first series of 66 blasts, and four during the second series. Seismic activity was monitored using geophones installed in ventilation headings. Shocks with energy of 10/sup 4/-10/sup 6/ J were analyzed. Exploratory drilling was carried out by 10 m long holes and the measured volume of drillings was 3.5-4.5 l/m. The distance of maximum seismic energy from longwall face provides information on the actual state of extreme stresses in the immediate vicinity of exploitation. The analyses performed allowed a new method of rock burst hazard prediction to be formulated. 10 refs.

  18. Analyses of resource reservation schemes for optical burst switching networks

    Science.gov (United States)

    Solanska, Michaela; Scholtz, Lubomir; Ladanyi, Libor; Mullerova, Jarmila

    2017-12-01

    With growing demands of Internet Protocol services for transmission capacity and speed, the Optical Burst Switching presents the solution for future high-speed optical networks. Optical Burst Switching is a technology for transmitting large amounts of data bursts through a transparent optical switching network. To successfully transmit bursts over OBS network and reach the destination node, resource reservation schemes have to be implemented to allocate resources and configure optical switches for that burst at each node. The one-way resource reservation schemes and the performance evaluation of reservation schemes are presented. The OBS network model is performed using OMNeT++ simulation environment. During the reservation of network resources, the optical cross-connect based on semiconductor optical amplifier is used as the core node. Optical switches based on semiconductor optical amplifiers are a promising technology for high-speed optical communication networks.

  19. Cosmology and the Subgroups of Gamma-ray Bursts

    Directory of Open Access Journals (Sweden)

    A. Mészáros

    2011-01-01

    Full Text Available Both short and intermediate gamma-ray bursts are distributed anisotropically in the sky (Mészáros, A. et al. ApJ, 539, 98 (2000, Vavrek, R. et al. MNRAS, 391, 1 741 (2008. Hence, in the redshift range, where these bursts take place, the cosmological principle is in doubt. It has already been noted that short bursts should be mainly at redshifts smaller than one (Mészáros, A. et al. Gamma-ray burst: Sixth Huntsville Symp., AIP, Vol. 1 133, 483 (2009; Mészáros, A. et al. Baltic Astron., 18, 293 (2009. Here we show that intermediate bursts should be at redshifts up to three.

  20. Long X-ray burst monitoring with INTEGRAL

    DEFF Research Database (Denmark)

    X-ray bursts are thermonuclear explosions on the surface of accreting neutron stars in low mass X-ray binary systems. In the frame of the INTEGRAL observational Key Programme over the Galactic Center a good number of the known X-ray bursters are frequently being monitored. An international...... collaboration lead by the JEM-X team at the Danish National Space Center has proposed to exploit the improved sensitivity of the INTEGRAL instruments to investigate the observational properties and physics up to high energies of exceptional burst events lasting between a few tens of minutes and several hours....... Of special interest are low luminosity bursting sources that exhibit X-ray bursts of very different durations allowing to study the transition from a hydrogen-rich bursting regime to a pure helium regime and from helium burning to carbon burning. I will present results obtained from INTEGRAL archive data...

  1. Statistical Properties of SGR J1550-5418 Bursts

    Science.gov (United States)

    Gorgone, Nicholas M.

    2010-01-01

    Magnetars are slowly rotating neutron stars with extreme magnetic fields, over 10(exp 15) Gauss. Only few have been discovered in the last 30 years. These sources are dormant most of their lifetimes and become randomly active emitting multiple soft gamma-ray bursts. We present here our results on the temporal analysis of 300 bursts from Soft Gamma Repeater SGR J1550-5418 recorded with the Gamma-ray Burst Monitor (GBM) onboard the Fermi Observatory during its activation on January 22-29, 2009. We employed an un-triggered burst search in the energy range 8-100keV to collect all events from the source, besides the ones that triggered GBM. For the entire sample of bursts we determined their durations, rise and decay times. We study here the statistical properties of these characteristics and discuss how these may help us better understand the physical characteristics of the magnetar model.

  2. Gamma-ray bursts observed by the watch experiment

    DEFF Research Database (Denmark)

    Lund, Niels; Brandt, Søren; Castro-Tirado, A. J.

    1991-01-01

    After two years in orbit the WATCH instruments on the GRANAT space observatory have localized seven gamma burst sources with better than 1° accuracy. In several cases, follow‐up observations with Schmidt telescopes have been made within a few days. Some of the bursts have also been detected by th...... by the distant space probes PVO and ULYSSES and there are, therefore, good prospects for obtaining much improved positions using the burst arrival times. The existence of the almost concurrent Schmidt plates could then become particularly interesting.......After two years in orbit the WATCH instruments on the GRANAT space observatory have localized seven gamma burst sources with better than 1° accuracy. In several cases, follow‐up observations with Schmidt telescopes have been made within a few days. Some of the bursts have also been detected...

  3. Distance Training as Part of a Distance Consulting Solution.

    Science.gov (United States)

    Fulantelli, Giovanni; Chiazzese, Giuseppe; Allegra, Mario

    "Distance Training" models, when integrated in a more complex framework, such as a "Distance Consulting" model, present specific features and impose a revision of the strategies commonly adopted in distance training experiences. This paper reports on the distance training strategies adopted in a European funded project aimed at…

  4. Design and Characterization of Thin Stainless Steel Burst Disks for Increasing Two-Stage Light Gas Launcher Efficiency

    Science.gov (United States)

    Tylka, Jonathan M.; Johnson, Kenneth L.; Henderson, Donald; Rodriguez, Karen

    2012-01-01

    indicated by transgranular microvoid coalescence, non-fragmenting rupture and mixed tensile and shear failure modes, regardless of the material states tested. More testing is underway to determine the relationship between SSBD burst pressure and projectile velocity.

  5. Soap Films Burst Like Flapping Flags

    Science.gov (United States)

    Lhuissier, Henri; Villermaux, Emmanuel

    2009-07-01

    When punctured, a flat soap film bursts by opening a hole driven by liquid surface tension. The hole rim does not, however, remain smooth but soon develops indentations at the tip of which ligaments form, ultimately breaking and leaving the initially connex film into a mist of disjointed drops. We report on original observations showing that these indentations result from a flaglike instability between the film and the surrounding atmosphere inducing an oscillatory motion out of its plane. Just like a flag edge flaps in the wind, the film is successively accelerated on both sides perpendicularly to its plane, inducing film thickness modulations and centrifuging liquid ligaments that finally pinch off to form the observed spray. This effect exemplifies how the dynamics of fragile objects such as thin liquid films is sensitive to their embedding medium.

  6. The Theory of Gamma-Ray Bursts

    Science.gov (United States)

    Dai, Zigao; Daigne, Frédéric; Mészáros, Peter

    2017-10-01

    This chapter gives a brief review on the theory of gamma-ray bursts (GRBs), including the models of multi-messengers (e.g., prompt multiwavelength electromagnetic emissions, high-energy neutrinos, ultra-high-energy cosmic rays, and gravitational waves) and central engines (in particular, mergers of binary neutron stars for short GRBs). For detailed reviews, please see (Piran in Phys. Rep. 314:575, 1999; Rev. Mod. Phys. 76:1143, 2004; Mészáros in Annu. Rev. Astron. Astrophys. 40:137, 2002; Rep. Prog. Phys. 69:2259, 2006; Zhang and Mészáros in Int. J. Mod. Phys. A 19:2385, 2004; Zhang in Chin. J. Astron. Astrophys. 7:1, 2007; Nakar in Phys. Rep. 442:166, 2007; Kumar and Zhang in Phys. Rep. 561:1, 2015).

  7. The ``Christmas burst'' GRB 101225A revisited

    Science.gov (United States)

    Thöne, C. C.; de Ugarte Postigo, A.; Fryer, C. L.; Kann, D. A.

    2015-03-01

    Long GRBs are related to the death of massive stars and reveal themselves through synchrotron emission from highly relativistic jets. The `Christmas Burst' GRB 101225A was an exceptionally long GRB with a thermal afterglow, very different from the standard GRB. Initially, no spectroscopic redshift could be obtained and SED modeling yielded z=0.33. A plausible model was a He-NS star merger where the He-star had ejected part of its envelope in the common envelope phase during inspiral. The interaction between the jet and the previously ejected shell can explains the thermal emission. We obtained deep spectroscopy of the host galaxy which leads to a correction of the redshift to z=0.847. Despite the higher redshift, our model is still valid and theoretically better justified than the alternative suggestion of a blue supergiant progenitor proposed by Levan et al. (2014) for several ``ultra-long'' GRBs.

  8. Gamma-Ray Burst Prompt Correlations

    Directory of Open Access Journals (Sweden)

    M. G. Dainotti

    2018-01-01

    Full Text Available The mechanism responsible for the prompt emission of gamma-ray bursts (GRBs is still a debated issue. The prompt phase-related GRB correlations can allow discriminating among the most plausible theoretical models explaining this emission. We present an overview of the observational two-parameter correlations, their physical interpretations, and their use as redshift estimators and possibly as cosmological tools. The nowadays challenge is to make GRBs, the farthest stellar-scaled objects observed (up to redshift z=9.4, standard candles through well established and robust correlations. However, GRBs spanning several orders of magnitude in their energetics are far from being standard candles. We describe the advances in the prompt correlation research in the past decades, with particular focus paid to the discoveries in the last 20 years.

  9. Soap films burst like flapping flags.

    Science.gov (United States)

    Lhuissier, Henri; Villermaux, Emmanuel

    2009-07-31

    When punctured, a flat soap film bursts by opening a hole driven by liquid surface tension. The hole rim does not, however, remain smooth but soon develops indentations at the tip of which ligaments form, ultimately breaking and leaving the initially connex film into a mist of disjointed drops. We report on original observations showing that these indentations result from a flaglike instability between the film and the surrounding atmosphere inducing an oscillatory motion out of its plane. Just like a flag edge flaps in the wind, the film is successively accelerated on both sides perpendicularly to its plane, inducing film thickness modulations and centrifuging liquid ligaments that finally pinch off to form the observed spray. This effect exemplifies how the dynamics of fragile objects such as thin liquid films is sensitive to their embedding medium.

  10. Measuring spectra using burst-mode LDA

    Science.gov (United States)

    Velte, Clara; George, William; Tutkun, Murat; Frohnapfel, Bettina

    2008-11-01

    The phrase ``burst-mode LDA'' refers to an LDA which operates with at most one particle present in the measuring volume at a time. For the signal to be interpreted correctly to avoid velocity bias, one must apply residence time-weighing to all statistical analysis. In addition, for time-series analysis, even though the randomly arriving particles eliminate aliasing, the self-noise from the random arrivals must be removed or it will dominate the spectra and correlations. A flaw in the earlier theory [1],[2], the goal of which was to provide an unbiased and unaliased spectral estimator from the random samples, is identified and corrected. The new methodology is illustrated using recent experiments in a round jet and a turbulent boundary layer. 1. Buchhave, P. PhD Thesis, SUNY/Buffalo, 1979. 2. George, W.K. Proc. Marseille.-Balt. Dyn. Flow Conf. 1978,757-800.

  11. Origin of Radio Enhancements in Type II Bursts in the Outer Corona

    Science.gov (United States)

    Al-Hamadani, Firas; Pohjolainen, Silja; Valtonen, Eino

    2017-09-01

    We study interplanetary (IP) solar radio type II bursts from 2011 - 2014 in order to determine the cause of the intense enhancements in their radio emission. Type II bursts are known to be due to propagating shocks that are often associated with fast halo-type coronal mass ejections (CMEs). We analysed the radio spectral data and the white-light coronagraph data from 16 selected events to obtain directions and heights for the propagating CMEs and the type II bursts. CMEs preceding the selected events were included in the analysis to verify whether CME interaction was possible. As a result, we were able to classify the events into five different groups. 1) Events where the heights of the CMEs and type II bursts are consistent, indicating that the shock is located at the leading front of the CME. The radio enhancements are superposed on the type II lanes, and they are probably formed when the shock meets remnant material from earlier CMEs, but the shock continues to propagate at the same speed. 2) Events where the type II heights agree with the CME leading front and an earlier CME is located at a height that suggests interaction. The radio enhancements and frequency jumps could be due to the merging process of the CMEs. 3) Events where the type II heights are significantly lower than the CME heights almost from the start. Interaction with close-by streamers is probably the cause for the enhanced radio emission, which is located at the CME flank region. 4) Events where the radio enhancements are located within wide-band type II bursts and the causes for the radio enhancements are not clear. 5) Events where the radio enhancements are associated with later-accelerated particles (electron beams, observed as type III bursts) that stop at the type II burst emission lane, and no other obvious reason for the enhancement can be identified. Most of the events (38%) were due to shock-streamer interaction, while one quarter of the events was due to possible CME-CME interaction

  12. Infrasonic harmonic tremor and degassing bursts from Halema'uma'u Crater, Kilauea Volcano, Hawaii

    Science.gov (United States)

    Fee, David; Garcés, Milton; Patrick, Matt; Chouet, Bernard; Dawson, Phil; Swanson, Donald A.

    2010-01-01

    The formation, evolution, collapse, and subsequent resurrection of a vent within Halema'uma'u Crater, Kilauea Volcano, produced energetic and varied degassing signals recorded by a nearby infrasound array between 2008 and early 2009. After 25 years of quiescence, a vent-clearing explosive burst on 19 March 2008 produced a clear, complex acoustic signal. Near-continuous harmonic infrasonic tremor followed this burst until 4 December 2008, when a period of decreased degassing occurred. The tremor spectra suggest volume oscillation and reverberation of a shallow gas-filled cavity beneath the vent. The dominant tremor peak can be sustained through Helmholtz oscillations of the cavity, while the secondary tremor peak and overtones are interpreted assuming acoustic resonance. The dominant tremor frequency matches the oscillation frequency of the gas emanating from the vent observed by video. Tremor spectra and power are also correlated with cavity geometry and dynamics, with the cavity depth estimated at ~219 m and volume ~3 x 106 m3 in November 2008. Over 21 varied degassing bursts were observed with extended burst durations and frequency content consistent with a transient release of gas exciting the cavity into resonance. Correlation of infrasound with seismicity suggests an open system connecting the atmosphere to the seismic excitation process at depth. Numerous degassing bursts produced very long period (0.03-0.1 Hz) infrasound, the first recorded at Kilauea, indicative of long-duration atmospheric accelerations. Kilauea infrasound appears controlled by the exsolution of gas from the magma, and the interaction of this gas with the conduits and cavities confining it.

  13. Anterior Z-plate and titanic mesh fixation for acute burst thoracolumbar fracture.

    Science.gov (United States)

    Xu, Jian-Guang; Zeng, Bing-Fang; Zhou, Wei; Kong, Wei-Qing; Fu, Yi-Shan; Zhao, Bi-Zeng; Zhang, Tao; Lian, Xiao-Feng

    2011-04-01

    A retrospective study. To evaluate the clinical outcome, effectiveness, and security of the surgical management of acute thoracolumbar burst fracture with corpectomy, titanic mesh autograft, and Z-plate fixation by anterior approach. Many surgical methods were adopted to treat acute burst thoracolumbar fracture. But the optimal surgical management remains controversial. A retrospective review of a consecutive series of 48 patients with thoracolumbar burst fracture treated with anterior corpectomy, titanic mesh autograft, and Z-plate internal fixation was carried out. Preoperative clinical and radiographic data of all cases were originally collected. Surgical indications were motor neurologic deficit and thoracolumbar column instability. Twenty-two patients (45.8%) with acute thoracolumbar burst fractures presented with a neurologic deficit. The postoperative recovery of neural function, restoration of anterior cortex collapse, kyphotic angle, and spinal canal compromise were observed. The preoperative kyphotic angle was improved to a mean of 5.6°, radiographic height restored to 95.8% of the adjacent normal levels, and canal compromise was 0%. None of the patients had neurologic deterioration. Mean follow-up time was 32.4 months (range, 24-47 months). All 22 patients with neurologic deficit demonstrated at least one Frankel grade improvement on final observation, with 16 (73%) patients had accomplished complete neurologic recovery. Forty-six (96%) patients reported minimal or no pain at final follow-up observation, and 40 (83%) patients who had been working before injury returned to original work. The authors considered spinal cord decompression with anterior corpectomy and stability reconstruction with titanic mesh autograft and Z-plate fixation at same time in one incision as an effective technique for unstable thoracolumbar burst fracture with and without neurologic deficit.

  14. Does Twitter trigger bursts in signature collections?

    Science.gov (United States)

    Yamaguchi, Rui; Imoto, Seiya; Kami, Masahiro; Watanabe, Kenji; Miyano, Satoru; Yuji, Koichiro

    2013-01-01

    The quantification of social media impacts on societal and political events is a difficult undertaking. The Japanese Society of Oriental Medicine started a signature-collecting campaign to oppose a medical policy of the Government Revitalization Unit to exclude a traditional Japanese medicine, "Kampo," from the public insurance system. The signature count showed a series of aberrant bursts from November 26 to 29, 2009. In the same interval, the number of messages on Twitter including the keywords "Signature" and "Kampo," increased abruptly. Moreover, the number of messages on an Internet forum that discussed the policy and called for signatures showed a train of spikes. In order to estimate the contributions of social media, we developed a statistical model with state-space modeling framework that distinguishes the contributions of multiple social media in time-series of collected public opinions. We applied the model to the time-series of signature counts of the campaign and quantified contributions of two social media, i.e., Twitter and an Internet forum, by the estimation. We found that a considerable portion (78%) of the signatures was affected from either of the social media throughout the campaign and the Twitter effect (26%) was smaller than the Forum effect (52%) in total, although Twitter probably triggered the initial two bursts of signatures. Comparisons of the estimated profiles of the both effects suggested distinctions between the social media in terms of sustainable impact of messages or tweets. Twitter shows messages on various topics on a time-line; newer messages push out older ones. Twitter may diminish the impact of messages that are tweeted intermittently. The quantification of social media impacts is beneficial to better understand people's tendency and may promote developing strategies to engage public opinions effectively. Our proposed method is a promising tool to explore information hidden in social phenomena.

  15. Does Twitter trigger bursts in signature collections?

    Directory of Open Access Journals (Sweden)

    Rui Yamaguchi

    Full Text Available INTRODUCTION: The quantification of social media impacts on societal and political events is a difficult undertaking. The Japanese Society of Oriental Medicine started a signature-collecting campaign to oppose a medical policy of the Government Revitalization Unit to exclude a traditional Japanese medicine, "Kampo," from the public insurance system. The signature count showed a series of aberrant bursts from November 26 to 29, 2009. In the same interval, the number of messages on Twitter including the keywords "Signature" and "Kampo," increased abruptly. Moreover, the number of messages on an Internet forum that discussed the policy and called for signatures showed a train of spikes. METHODS AND FINDINGS: In order to estimate the contributions of social media, we developed a statistical model with state-space modeling framework that distinguishes the contributions of multiple social media in time-series of collected public opinions. We applied the model to the time-series of signature counts of the campaign and quantified contributions of two social media, i.e., Twitter and an Internet forum, by the estimation. We found that a considerable portion (78% of the signatures was affected from either of the social media throughout the campaign and the Twitter effect (26% was smaller than the Forum effect (52% in total, although Twitter probably triggered the initial two bursts of signatures. Comparisons of the estimated profiles of the both effects suggested distinctions between the social media in terms of sustainable impact of messages or tweets. Twitter shows messages on various topics on a time-line; newer messages push out older ones. Twitter may diminish the impact of messages that are tweeted intermittently. CONCLUSIONS: The quantification of social media impacts is beneficial to better understand people's tendency and may promote developing strategies to engage public opinions effectively. Our proposed method is a promising tool to explore

  16. Calibration of the Extragalactic Distance Scale

    Science.gov (United States)

    Madore, B. F.; Freedman, W. L.

    Introduction to the lectures Cepheids Brief summary of the observed properties of cepheid variables Simple physical considerations Observational considerations Advances driven by new technology CCDs and multiwavelength coverage Obtaining accurate cepheid distances Local Group galaxies Beyond the Local Group The Hubble constant The future Contrasting aspects of the PL and PLC A reddening-free formulation of the PL relation Comments on reddening determinations Comparisons with other distance indicators The key project Other ground-based work Helium core flash and the tip of the red giant branch as a primary distance indicator The ideal distances indicator Some history concerning the red giant branch Concerns and technical issues An overview of the theoretical underpinnings: core helium ignition Recent applications of the TRGB method The scorecard Discussion Implications of the hipparcos observations of galactic cepheids Comparison with V-band period-luminosity relations Multiwavelength period-luminosity relations Discussion Implications of a cepheid distance to the Fornax cluster NGC 1365 and the Fornax cluster HST observations Cepheids in NGC 1365 The Hubble constant The Hubble constant at Fornax The nearby flow field Beyond Fornax: the Tully-Fisher relation Beyond Fornax: other relative distance determinations Beyond Fornax: type Ia supernovae Cosmological implications Conclusions References

  17. The link between coherent burst oscillations, burst spectral evolution and accretion state in 4U 1728-34

    NARCIS (Netherlands)

    Zhang, Guobao; Méndez, Mariano; Zamfir, Michael; Cumming, Andrew

    2016-01-01

    Coherent oscillations and the evolution of the X-ray spectrum during thermonuclear X-ray bursts in accreting neutron-star X-ray binaries have been studied intensively but separately. We analysed all the X-ray bursts of the source 4U 1728-34 with the Rossi X-ray Timing Explorer. We found that the

  18. Monitoring burst (M-burst) — A novel framework of failure localization in all-optical mesh networks

    KAUST Repository

    Ali, Mohammed L.

    2011-10-10

    Achieving instantaneous and precise failure localization in all-optical wavelength division multiplexing (WDM) networks has been an attractive feature of network fault management systems, and is particularly important when failure-dependent protection is employed. The paper introduces a novel framework of real-time failure localization in all-optical WDM mesh networks, called monitoring-burst (m-burst), which aims to initiate a graceful compromise between consumed monitoring resources and monitoring delay. Different from any previously reported solution, the proposed m-burst framework has a single monitoring node (MN) which launches optical bursts along a set of pre-defined close-loop routes, called monitoring cycles (m-cycles), to probe the links along the m-cycles. Bursts along different m-cycles are kept non-overlapping through any link of the network. By identifying the lost bursts due to single link failure events only, the MN can unambiguously localize the failed link in at least 3-connected networks. We will justify the feasibility and applicability of the proposed m-burst framework in the scenario of interest. To avoid possible collision among optical bursts launched by the MN, we define the problem of collision-free scheduling and formulate it into an integer linear program (ILP) in order to minimize the monitoring delay. Numerical results demonstrate the effectiveness of the proposed framework and the proposed solution.

  19. Performance Analysis of Particle Swarm Optimization Based Routing Algorithm in Optical Burst Switching Networks

    Science.gov (United States)

    Hou, Rui; Yu, Junle

    2011-12-01

    Optical burst switching (OBS) has been regarded as the next generation optical switching technology. In this paper, the routing problem based on particle swarm optimization (PSO) algorithm in OBS has been studies and analyzed. Simulation results indicate that, the PSO based routing algorithm will optimal than the conversional shortest path first algorithm in space cost and calculation cost. Conclusions have certain theoretical significances for the improvement of OBS routing protocols.

  20. Multi‐instrument observations from Svalbard of a traveling convection vortex, electromagnetic ion cyclotron wave burst, and proton precipitation associated with a bow shock instability

    DEFF Research Database (Denmark)

    Engebretson, M. J.; Yeoman, T. K.; Oksavik, K.

    2013-01-01

    An isolated burst of 0.35 Hz electromagnetic ion cyclotron (EMIC) waves was observed at four sites on Svalbard from 0947 to 0954 UT 2 January 2011, roughly 1 h after local noon. This burst was associated with one of a series of ~50 nT magnetic impulses observed at the northernmost stations......-based observations of the Hα line at Longyearbyen indicated proton precipitation at the same time as the EMIC wave burst, and NOAA-19, which passed over the west coast of Svalbard between 0951 and 0952, observed a clear enhancement of ring current protons at the same latitude. Electron precipitation from this same...... satellite indicated that the EMIC burst was located on closed field lines, but near to the polar cap boundary. We believe these are the first simultaneous observations of EMIC waves and precipitating energetic protons so near to the boundary of the dayside magnetosphere. Although several spacecraft upstream...

  1. Phantom bursting is highly sensitive to noise and unlikely to account for slow bursting in beta-cells

    DEFF Research Database (Denmark)

    Pedersen, Morten Gram

    2007-01-01

    Pancreatic beta-cells show bursting electrical activity with a wide range of burst periods ranging from a few seconds, often seen in isolated cells, over tens of seconds (medium bursting), usually observed in intact islets, to several minutes. The phantom burster model [Bertram, R., Previte, J......., Sherman, A., Kinard, T.A., Satin, L.S., 2000. The phantom burster model for pancreatic beta-cells. Biophys. J. 79, 2880-2892] provided a framework, which covered this span, and gave an explanation of how to obtain medium bursting combining two processes operating on different time scales. However, single...... cells are subjected to stochastic fluctuations in plasma membrane currents, which are likely to disturb the bursting mechanism and transform medium bursters into spikers or very fast bursters. We present a polynomial, minimal, phantom burster model and show that noise modifies the plateau fraction...

  2. The sound of distance.

    Science.gov (United States)

    Rabaglia, Cristina D; Maglio, Sam J; Krehm, Madelaine; Seok, Jin H; Trope, Yaacov

    2016-07-01

    Human languages may be more than completely arbitrary symbolic systems. A growing literature supports sound symbolism, or the existence of consistent, intuitive relationships between speech sounds and specific concepts. Prior work establishes that these sound-to-meaning mappings can shape language-related judgments and decisions, but do their effects generalize beyond merely the linguistic and truly color how we navigate our environment? We examine this possibility, relating a predominant sound symbolic distinction (vowel frontness) to a novel associate (spatial proximity) in five studies. We show that changing one vowel in a label can influence estimations of distance, impacting judgment, perception, and action. The results (1) provide the first experimental support for a relationship between vowels and spatial distance and (2) demonstrate that sound-to-meaning mappings have outcomes that extend beyond just language and can - through a single sound - influence how we perceive and behave toward objects in the world. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Quantum Minimum Distance Classifier

    OpenAIRE

    Enrica Santucci

    2017-01-01

    We propose a quantum version of the well known minimum distance classification model called Nearest Mean Classifier (NMC). In this regard, we presented our first results in two previous works. First, a quantum counterpart of the NMC for two-dimensional problems was introduced, named Quantum Nearest Mean Classifier (QNMC), together with a possible generalization to any number of dimensions. Secondly, we studied the n-dimensional problem into detail and we showed a new encoding for arbitrary n-...

  4. De-severing distance

    DEFF Research Database (Denmark)

    Jensen, Hanne Louise; de Neergaard, Maja

    2016-01-01

    De-severing Distance This paper draws on the growing body of mobility literature that shows how mobility can be viewed as meaningful everyday practices (Freudendal –Pedersen 2007, Cresswell 2006) this paper examines how Heidegger’s term de-severing can help us understand the everyday coping with ...... of 11 urban families who have moved to the countryside and chosen to commute in order to dwell there....

  5. Ultrametric Distance in Syntax

    Directory of Open Access Journals (Sweden)

    Roberts Mark D.

    2015-04-01

    Full Text Available Phrase structure trees have a hierarchical structure. In many subjects, most notably in taxonomy such tree structures have been studied using ultrametrics. Here syntactical hierarchical phrase trees are subject to a similar analysis, which is much simpler as the branching structure is more readily discernible and switched. The ambiguity of which branching height to choose, is resolved by postulating that branching occurs at the lowest height available. An ultrametric produces a measure of the complexity of sentences: presumably the complexity of sentences increases as a language is acquired so that this can be tested. All ultrametric triangles are equilateral or isosceles. Here it is shown that X̅ structure implies that there are no equilateral triangles. Restricting attention to simple syntax a minimum ultrametric distance between lexical categories is calculated. A matrix constructed from this ultrametric distance is shown to be different than the matrix obtained from features. It is shown that the definition of C-COMMAND can be replaced by an equivalent ultrametric definition. The new definition invokes a minimum distance between nodes and this is more aesthetically satisfying than previous varieties of definitions. From the new definition of C-COMMAND follows a new definition of of the central notion in syntax namely GOVERNMENT.

  6. Managerial Distance and Virtual Ownership

    DEFF Research Database (Denmark)

    Hansmann, Henry; Thomsen, Steen

    Industrial foundations are autonomous nonprofit entities that own and control one or more conventional business firms. These foundations are common in Northern Europe, where they own a number of internationally prominent companies. Previous studies have indicated, surprisingly, that companies con......, but corporate governance and fiduciary behavior more generally.......Industrial foundations are autonomous nonprofit entities that own and control one or more conventional business firms. These foundations are common in Northern Europe, where they own a number of internationally prominent companies. Previous studies have indicated, surprisingly, that companies......-seeking outside owners of the company. Consistent with this hypothesis, our empirical analysis shows a positive, significant, and robust association between managerial distance and the economic performance of foundation owned companies. The findings appear to illuminate not just foundation governance...

  7. Exploring Short Gamma-ray Bursts as Gravitational-wave Standard Sirens

    Science.gov (United States)

    Nissanke, Samaya; Holz, Daniel E.; Hughes, Scott A.; Dalal, Neal; Sievers, Jonathan L.

    2010-12-01

    Recent observations support the hypothesis that a large fraction of "short-hard" gamma-ray bursts (SHBs) are associated with the inspiral and merger of compact binaries. Since gravitational-wave (GW) measurements of well-localized inspiraling binaries can measure absolute source distances, simultaneous observation of a binary's GWs and SHB would allow us to directly and independently determine both the binary's luminosity distance and its redshift. Such a "standard siren" (the GW analog of a standard candle) would provide an excellent probe of the nearby (z <~ 0.3) universe's expansion, independent of the cosmological distance ladder, thereby complementing other standard candles. Previous work explored this idea using a simplified formalism to study measurement by advanced GW detector networks, incorporating a high signal-to-noise ratio limit to describe the probability distribution for measured parameters. In this paper, we eliminate this simplification, constructing distributions with a Markov Chain Monte Carlo technique. We assume that each SHB observation gives source sky position and time of coalescence, and we take non-spinning binary neutron star and black hole-neutron star coalescences as plausible SHB progenitors. We examine how well parameters (particularly distance) can be measured from GW observations of SHBs by a range of ground-based detector networks. We find that earlier estimates overstate how well distances can be measured, even at fairly large signal-to-noise ratio. The fundamental limitation to determining distance proves to be a degeneracy between distance and source inclination. Overcoming this limitation requires that we either break this degeneracy, or measure enough sources to broadly sample the inclination distribution.

  8. Understanding the Generation of Network Bursts by Adaptive Oscillatory Neurons

    Directory of Open Access Journals (Sweden)

    Tanguy Fardet

    2018-02-01

    Full Text Available Experimental and numerical studies have revealed that isolated populations of oscillatory neurons can spontaneously synchronize and generate periodic bursts involving the whole network. Such a behavior has notably been observed for cultured neurons in rodent's cortex or hippocampus. We show here that a sufficient condition for this network bursting is the presence of an excitatory population of oscillatory neurons which displays spike-driven adaptation. We provide an analytic model to analyze network bursts generated by coupled adaptive exponential integrate-and-fire neurons. We show that, for strong synaptic coupling, intrinsically tonic spiking neurons evolve to reach a synchronized intermittent bursting state. The presence of inhibitory neurons or plastic synapses can then modulate this dynamics in many ways but is not necessary for its appearance. Thanks to a simple self-consistent equation, our model gives an intuitive and semi-quantitative tool to understand the bursting behavior. Furthermore, it suggests that after-hyperpolarization currents are sufficient to explain bursting termination. Through a thorough mapping between the theoretical parameters and ion-channel properties, we discuss the biological mechanisms that could be involved and the relevance of the explored parameter-space. Such an insight enables us to propose experimentally-testable predictions regarding how blocking fast, medium or slow after-hyperpolarization channels would affect the firing rate and burst duration, as well as the interburst interval.

  9. Accelerating Science with the NERSC Burst Buffer Early User Program

    Energy Technology Data Exchange (ETDEWEB)

    Bhimji, Wahid [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bard, Debbie [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Romanus, Melissa [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Rutgers Univ., New Brunswick, NJ (United States); Paul, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Ovsyannikov, Andrey [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Friesen, Brian [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bryson, Matt [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Correa, Joaquin [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Lockwood, Glenn K. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Tsulaia, Vakho [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Byna, Suren [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Farrell, Steve [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Gursoy, Doga [Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS); Daley, Chris [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Beckner, Vince [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Van Straalen, Brian [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Trebotich, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Tull, Craig [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Weber, Gunther H. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Wright, Nicholas J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Antypas, Katie [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Prabhat, none [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2016-01-01

    NVRAM-based Burst Buffers are an important part of the emerging HPC storage landscape. The National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory recently installed one of the first Burst Buffer systems as part of its new Cori supercomputer, collaborating with Cray on the development of the DataWarp software. NERSC has a diverse user base comprised of over 6500 users in 700 different projects spanning a wide variety of scientific computing applications. The use-cases of the Burst Buffer at NERSC are therefore also considerable and diverse. We describe here performance measurements and lessons learned from the Burst Buffer Early User Program at NERSC, which selected a number of research projects to gain early access to the Burst Buffer and exercise its capability to enable new scientific advancements. To the best of our knowledge this is the first time a Burst Buffer has been stressed at scale by diverse, real user workloads and therefore these lessons will be of considerable benefit to shaping the developing use of Burst Buffers at HPC centers.

  10. Unusual Solar Radio Burst Observed at Decameter Wavelengths

    Science.gov (United States)

    Melnik, V. N.; Brazhenko, A. I.; Konovalenko, A. A.; Rucker, H. O.; Frantsuzenko, A. V.; Dorovskyy, V. V.; Panchenko, M.; Stanislavskyy, A. A.

    2014-01-01

    An unusual solar burst was observed simultaneously by two decameter radio telescopes UTR-2 (Kharkov, Ukraine) and URAN-2 (Poltava, Ukraine) on 3 June 2011 in the frequency range of 16 - 28 MHz. The observed radio burst had some unusual properties, which are not typical for the other types of solar radio bursts. Its frequency drift rate was positive (about 500 kHz s-1) at frequencies higher than 22 MHz and negative (100 kHz s-1) at lower frequencies. The full duration of this event varied from 50 s up to 80 s, depending on the frequency. The maximum radio flux of the unusual burst reached ≈103 s.f.u. and its polarization did not exceed 10 %. This burst had a fine frequency-time structure of unusual appearance. It consisted of stripes with the frequency bandwidth 300 - 400 kHz. We consider that several accompanied radio and optical events observed by SOHO and STEREO spacecraft were possibly associated with the reported radio burst. A model that may interpret the observed unusual solar radio burst is proposed.

  11. A burst segmentation-deflection routing contention resolution mechanism in OBS networks

    Science.gov (United States)

    Guan, Ai-hong; Wang, Bo-yun

    2012-01-01

    One of the key problems to hinder the realization of optical burst switching (OBS) technology in the core networks is the losses due to the contention among the bursts at the core nodes. Burst segmentation is an effective contention resolution technique used to reduce the number of packets lost due to the burst losses. In our work, a burst segmentation-deflection routing contention resolution mechanism in OBS networks is proposed. When the contention occurs, the bursts are segmented according to the lowest packet loss probability of networks firstly, and then the segmented burst is deflected on the optimum routing. An analytical model is proposed to evaluate the contention resolution mechanism. Simulation results show that high-priority bursts have significantly lower packet loss probability and transmission delay than the low-priority. And the performance of the burst lengths, in which the number of segments per burst distributes geometrically, is more effective than that of the deterministically distributed burst lengths.

  12. Strong sunward propagating flow bursts in the night sector during quiet solar wind conditions: SuperDARN and satellite observations

    Directory of Open Access Journals (Sweden)

    C. Senior

    Full Text Available High-time resolution data from the two Iceland SuperDARN HF radars show very strong nightside convection activity during a prolonged period of low geomagnetic activity and northward interplanetary magnetic field (IMF. Flows bursts with velocities ranging from 0.8 to 1.7 km/s are observed to propagate in the sunward direction with phase velocities up to 1.5 km/s. These bursts occur over several hours of MLT in the 20:00–01:00 MLT sector, in the evening-side sunward convection. Data from a simultaneous DMSP pass and POLAR UVI images show a very contracted polar cap and extended regions of auroral particle precipitation from the magnetospheric boundaries. A DMSP pass over the Iceland-West field-of-view while one of these sporadic bursts of enhanced flow is observed, indicates that the flow bursts appear within the plasma sheet and at its outward edge, which excludes Kelvin-Helmholtz instabilities at the magnetopause boundary as the generation mechanism. In the nightside region, the precipitation is more spot-like and the convection organizes itself as clockwise U-shaped structures. We interpret these flow bursts as the convective transport following plasma injection events from the tail into the night-side ionosphere. We show that during this period, where the IMF clock angle is around 70°, the dayside magnetosphere is not completely closed.

    Key words. Ionosphere (Auroral ionosphere; Ionospheremagnetosphere interactions; Particle precipitation

  13. Strong sunward propagating flow bursts in the night sector during quiet solar wind conditions: SuperDARN and satellite observations

    Directory of Open Access Journals (Sweden)

    C. Senior

    2002-06-01

    Full Text Available High-time resolution data from the two Iceland SuperDARN HF radars show very strong nightside convection activity during a prolonged period of low geomagnetic activity and northward interplanetary magnetic field (IMF. Flows bursts with velocities ranging from 0.8 to 1.7 km/s are observed to propagate in the sunward direction with phase velocities up to 1.5 km/s. These bursts occur over several hours of MLT in the 20:00–01:00 MLT sector, in the evening-side sunward convection. Data from a simultaneous DMSP pass and POLAR UVI images show a very contracted polar cap and extended regions of auroral particle precipitation from the magnetospheric boundaries. A DMSP pass over the Iceland-West field-of-view while one of these sporadic bursts of enhanced flow is observed, indicates that the flow bursts appear within the plasma sheet and at its outward edge, which excludes Kelvin-Helmholtz instabilities at the magnetopause boundary as the generation mechanism. In the nightside region, the precipitation is more spot-like and the convection organizes itself as clockwise U-shaped structures. We interpret these flow bursts as the convective transport following plasma injection events from the tail into the night-side ionosphere. We show that during this period, where the IMF clock angle is around 70°, the dayside magnetosphere is not completely closed.Key words. Ionosphere (Auroral ionosphere; Ionospheremagnetosphere interactions; Particle precipitation

  14. Bullet Ultrasonic Obstruction Detection & Distance Measurement Using AVR Microcontroller

    Directory of Open Access Journals (Sweden)

    Satish Pandey

    2008-08-01

    Full Text Available This paper describes the practical implementation of a short range ultrasonic obstruction detection and distance measurement device. By employing an ultrasonic transducer pair for producing ultrasonic sounds and sensing the reflected sound waves, the obstructions are detected. The hardware interface uses an Atmel ATmega8 AVR microcontroller to facilitate the generation of 40 kHz signal burst which is used in the transmitter circuit, and also to process the received signal for measuring the time of flight of reflected waves and exact distance of the obstruction. The program for this device is developed in WinAVR, and the code generated is dumped into microcontroller using AVR Studio. Educational aspects of this project include the mastery of a programming language and corresponding tools, the design of a functional and intuitive embedded application, and the development of appropriate hardware to build the device.

  15. A New Model for Iron Emission Lines and Re-Burst in GRB X-Ray Afterglows

    OpenAIRE

    Gao, W. H.; Wei, D. M.

    2005-01-01

    Recently iron emission features have been observed in several X-ray afterglows of GRBs. It is found that the energy obtained from the illuminating continuum which produces the emission lines is much higher than that of the main burst.The observation of SN-GRB association indicates a fallback disk should be formed after the supernovae explosion. The disk is optically thick and advection-dominated and dense. We suggest that the delayed injection energy after the initial main burst, much higher ...

  16. A Fast Radio Burst Every Second?

    Science.gov (United States)

    Kohler, Susanna

    2017-09-01

    How frequently do fast radio busts occur in the observable universe? Two researchers have now developed a new estimate.Extragalactic SignalsIn 2007, scientists looking through archival pulsar data discovered a transient radio pulse a flash that lasted only a few milliseconds. Since then, weve found another 22 such fast radio bursts (FRBs), yet we still dont know what causes these energetic signals.Artists illustration of the Very Large Array pinpointing the location of FRB 121102. [Bill Saxton/NRAO/AUI/NSF/Hubble Legacy Archive/ESA/NASA]Recently, some clues have finally come from FRB 121102, the only FRB ever observed to repeat. The multiple pulses detected from this source over the last five years have allowed us to confirm its extragalactic origin and pinpoint an origin for this FRB: a small, low-mass, metal-poor dwarf galaxy located about three billion light-years away.Is FRB 121102 typical? How frequently do such bursts occur, and how frequently can we hope to be able to detect them in the future? And what might these rates tell us about their origins? Two scientists from the Harvard-Smithsonian Center for Astrophysics, Anastasia Fialkov and Abraham Loeb, have now taken a phenomenological approach to answering these questions.Influencing FactorsFialkov and Loeb arguethat there are three main factors that influence the rate of observable FRBs in the universe:The spectral shape of the individual FRBsFRB 121102 had a Gaussian-like spectral profile, which means it peaks in a narrow range of frequencies and may not be detectable outside of that band. If this is typical for FRBs, then signals of distant FRBs may become redshifted to outside of the frequency band that we observe, making them undetectable.FRB detection rates in the 1.253.5GHz band predicted by the authors models (red and blue solid and dashed lines), as a function of the flux limit for detection (top) and as a function of the FRB hosts redshift (bottom). Grey circles mark our detections of FRBs thus

  17. Research in Distance Education: A Status Report

    Directory of Open Access Journals (Sweden)

    Farhad Saba

    2000-06-01

    Full Text Available Since the 1950s and expansion of social science research, distance education has been studied in comparison to face-to-face or classroom instruction. Although researchers continue to conduct comparative studies, their usefulness in revealing more information has diminished over the years; invariably, they have returned a “no significant difference” result between various forms of instruction. In recent years, researchers have moved beyond atheoretical, experimental comparative studies and have introduced new methods, such as discourse analysis, and in-depth interview of learners. These new methods overcome many methodological and theoretical limitations of the physical science view of distance education. These studies have further revealed the complexity of distance education, indicating the many variables involved in the concept. Starting with the core issue of instructional interaction and grounded on the theory of transactional distance, a new strand of research using methods related to systems dynamics, hierarchy and complexity theories, promises a more comprehensive understanding.

  18. Constraints on the generalized Chaplygin gas model from gamma-ray bursts

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, Rodolfo Camargo; Goncalves, Sergio Vitorino de Borba; Velten, H.E.S. [Universidade Federal do Espirito Santo (UFES), ES (Brazil). Dept. de Fisica. Grupo de Gravitacao e Cosmologia

    2011-07-01

    Full text: One of the most important problems of Modern Cosmology is the determination of the matter content of the Universe. Combining data of the rotation curve of spiral galaxies, the dynamics of galaxy clusters and structure formation indicate that there is about ten times more pressureless matter in the Universe than can be afforded by the baryonic matter. Moreover, the Type Ia supernovae (SNe Ia) data indicates that the Universe is accelerating. Models considering matter content dominated by an exotic fluid whose pressure is negative is one of the proposals to explain this current accelerated phase of the Universe. At the same time, the position of the first acoustic peak in the spectrum of CMB anisotropies, as obtained by WMAP, favours a spatially flat Universe. If we consider the matter content of the Universe dominated by a fluid with negative pressure we have a scenario with a proportion of {Omega}{sub m} {approx} 0.27 and the {Omega}{sub de} {approx} 0.73, with respect to the critical density, for the fractions of the pressureless matter and dark energy, respectively. Much observational data that has been used for comparison with the theoretical cosmological models like the generalized Chaplygin gas model. The spectra of anisotropy of cosmic microwave background radiation, baryonic acoustic oscillations, the integrated Sachs-Wolfe effect, the matter power spectrum, gravitational lenses, X-ray data and ages estimates of high-z objects have been used in this sense. Gamma-ray bursts are jets that release {approx} 10{sup 51} - 10{sup 53} ergs or more for a few seconds and becomes, in this brief period of time, the most bright object in the Universe. The search for a self-consistent method to use the GRBs in cosmological problems is intense and promising. In a recent article Liang et al. employed a method to obtain the distance moduli {approx} of GRBs in the redshift range of SNe Ia and extend this result to very high redshift GRBs (z > 1.4) in a completely

  19. INTEGRAL monitoring of unusually long X-ray bursts

    DEFF Research Database (Denmark)

    Chenevez, Jérôme; Falanga, M.; Kuulkers, E.

    2008-01-01

    X-ray bursts are thermonuclear explosions on the surface of accreting neutron stars in X-ray binaries. As most of the known X-ray bursters are frequently observed by INTEGRAL, an international collaboration have been taking advantage of its instrumentation to specifically monitor the occurrence...... of exceptional burst events lasting more than ~10 minutes. Half of the dozen so-called intermediate long bursts registered so far have been observed by INTEGRAL. The goal is to derive a comprehensive picture of the relationship between the nuclear ignition processes and the accretion states of the system leading...

  20. Neutron Stars and Thermonuclear X-ray Bursts

    Science.gov (United States)

    Bhattacharyya, Sudip

    2007-01-01

    Studies of thermonuclear X-ray bursts can be very useful to constrain the spin rate, mass and radius of a neutron star approaching EOS model of high density cold matter in the neutron star cores. +k Extensive observation and analysis of the data from the rising portions of the bursts - modeling of burst oscillations and thermonuclear flame spreading. +k Theoretical study of thermonuclear flame spreading on the rapidly spinning neutron stars should be done considering all the main physical effects (including magnetic field, nuclear energy generation, Coriolis effect, strong gravity, etc.).

  1. Understanding Neutron Stars using Thermonuclear X-ray Bursts

    Science.gov (United States)

    Bhattacharyya, S.

    2007-01-01

    Studies of thermonuclear X-ray bursts can be very useful to constrain the spin rate, mass and radius of a neutron star = EOS model of high density cold matter in the neutron star cores. Extensive observation and analysis of the data from the rising portions of the bursts = modeling of burst oscillations and thermonuclear flame spreading. Theoretical study of thermonuclear flame spreading on the rapidly spinning neutron stars should be done considering all the main physical effects (including magnetic field, nuclear energy generation, Coriolis effect, strong gravity, etc.).

  2. GRO: Black hole models for gamma-ray bursts

    Science.gov (United States)

    Shaham, Jacob

    1994-01-01

    The possibility of creating gamma ray bursts (GRB's) from accretion flows on to black holes is investigated. The mechanism of initial energy release in the form of a burst is not understood yet. The typical time scales involved in this energy release and the initial distribution of photons as a function of energy are studied. As a first step the problem is formulated in the Minkowski spacetime for a homogeneous and isotropic burst. For an arbitrary initial distribution of photons, the equations of relativistic kinetic theory are formulated for nonequilibrium plasmas which can take into account various particle creation and annihilation processes and various scattering processes.

  3. Shaping bursting by electrical coupling and noise.

    Science.gov (United States)

    Medvedev, Georgi S; Zhuravytska, Svitlana

    2012-02-01

    Gap-junctional coupling is an important way of communication between neurons and other excitable cells. Strong electrical coupling synchronizes activity across cell ensembles. Surprisingly, in the presence of noise synchronous oscillations generated by an electrically coupled network may differ qualitatively from the oscillations produced by uncoupled individual cells forming the network. A prominent example of such behavior is the synchronized bursting in islets of Langerhans formed by pancreatic β-cells, which in isolation are known to exhibit irregular spiking (Sherman and Rinzel, Biophys J 54:411-425, 1988; Sherman and Rinzel, Biophys J 59:547-559, 1991). At the heart of this intriguing phenomenon lies denoising, a remarkable ability of electrical coupling to diminish the effects of noise acting on individual cells. In this paper, building on an earlier analysis of denoising in networks of integrate-and-fire neurons (Medvedev, Neural Comput 21 (11):3057-3078, 2009) and our recent study of spontaneous activity in a closely related model of the Locus Coeruleus network (Medvedev and Zhuravytska, The geometry of spontaneous spiking in neuronal networks, submitted, 2012), we derive quantitative estimates characterizing denoising in electrically coupled networks of conductance-based models of square wave bursting cells. Our analysis reveals the interplay of the intrinsic properties of the individual cells and network topology and their respective contributions to this important effect. In particular, we show that networks on graphs with large algebraic connectivity (Fiedler, Czech Math J 23(98):298-305, 1973) or small total effective resistance (Bollobas, Modern graph theory, Graduate Texts in Mathematics, vol. 184, Springer, New York, 1998) are better equipped for implementing denoising. As a by-product of the analysis of denoising, we analytically estimate the rate with which trajectories converge to the synchronization subspace and the stability of the latter to

  4. Distance to Dark Bodies

    Science.gov (United States)

    2007-01-01

    Using the unique orbit of NASA's Spitzer Space Telescope and a depth-perceiving trick called parallax, astronomers have determined the distance to an invisible Milky Way object called OGLE-2005-SMC-001. This artist's concept illustrates how this trick works: different views from both Spitzer and telescopes on Earth are combined to give depth perception. Our Milky Way galaxy is heavier than it looks, and scientists use the term 'dark matter' to describe all the 'heavy stuff' in the universe that seems to be present but invisible to our telescopes. While much of this dark matter is likely made up of exotic materials, different from the ordinary particles that make up the world around us, some may consist of dark celestial bodies -- like planets, black holes, or failed stars -- that do not produce light or are too faint to detect from Earth. OGLE-2005-SMC-001 is one of these dark celestial bodies. Although astronomers cannot see a dark body, they can sense its presence from the way light acts around it. When a dark body like OGLE-2005-SMC-001 passes in front of a bright star, its gravity causes the background starlight to bend and brighten, a process called gravitational microlensing. When the observing telescope, dark body, and star system are closely aligned, the microlensing event reaches maximum, or peak, brightness. A team of astronomers first sensed OGLE-2005-SMC-001's presence when it passed in front of a star in a neighboring satellite galaxy called the Small Magellanic Cloud. In this artist's rendering, the satellite galaxy is depicted as the fuzzy structure sitting to the left of Earth. Once they detected this microlensing event, the scientists used Spitzer and the principle of parallax to figure out its distance. Humans naturally use parallax to determine distance. Each eye sees the distance of an object differently. The brain takes each eye's perspective and instantaneously calculates how far away the object is. To determine OGLE-2005-SMC-001's distance

  5. An upstream burst-mode equalization scheme for 40 Gb/s TWDM PON based on optimized SOA cascade

    Science.gov (United States)

    Sun, Xiao; Chang, Qingjiang; Gao, Zhensen; Ye, Chenhui; Xiao, Simiao; Huang, Xiaoan; Hu, Xiaofeng; Zhang, Kaibin

    2016-02-01

    We present a novel upstream burst-mode equalization scheme based on optimized SOA cascade for 40 Gb/s TWDMPON. The power equalizer is placed at the OLT which consists of two SOAs, two circulators, an optical NOT gate, and a variable optical attenuator. The first SOA operates in the linear region which acts as a pre-amplifier to let the second SOA operate in the saturation region. The upstream burst signals are equalized through the second SOA via nonlinear amplification. From theoretical analysis, this scheme gives sufficient dynamic range suppression up to 16.7 dB without any dynamic control or signal degradation. In addition, a total power budget extension of 9.3 dB for loud packets and 26 dB for soft packets has been achieved to allow longer transmission distance and increased splitting ratio.

  6. Gamma-ray burst observations with the [ital Compton]/[ital Ulysses]/[ital Pioneer]-[ital Venus] network

    Energy Technology Data Exchange (ETDEWEB)

    Cline, T.L. (NASA/Goddard Space Flight Center, Code 661, Greenbelt, Maryland 20771 (United States)); Hurley, K.C. (University of California, Space Sciences Laboratory, Berkeley, California 94720 (United States)); Sommer, M. (Max-Planck Institut fuer Extraterrestrische Physik, Garching (Germany)); Boer, M.; Niel, M. (Centre d' Etude Spatiale des Rayonnements, Toulouse (France)); Fishman, G.J.; Kouveliotou, C.; Meegan, C.A.; Paciesas, W.S.; Wilson, R.B. (NASA/Marshall Space Flight Center, ES-62, Huntsville, Alabama 35812 (United States)); Fenimore, E.E.; Laros, J.G.; Klebesadel, R.W. (Los Alamos National Laboratory, MS D436, Los Alamos, New Mexico 87545 (United States))

    1993-07-05

    The third and latest interplanetary network for the precise directional analysis of gamma ray bursts consists of the Burst and Transient Source Experiment in [ital Compton] [ital Gamma] [ital Ray] [ital Observatory] and instruments on [ital Pioneer]-[ital Venus] [ital Orbiter] and the deep-space mission [ital Ulysses]. The unsurpassed resolution of the BATSE instrument, the use of refined analysis techniques, and [ital Ulysses]' distance of up to 6 AU all contribute to a potential for greater precision than had been achieved with former networks. Also, the departure of [ital Ulysses] from the ecliptic plane in 1992 avoids any positional alignment of the three instruments that would lessen the source directional accuracy.

  7. Controlled retransmission scheme for prioritized burst segmentation to support quality-of-service in optical burst switching networks

    Science.gov (United States)

    Hou, Rui; He, Tingting; Mao, Tengyue

    2012-10-01

    In optical burst switching (OBS) networks, burst contentions in OBS core nodes may cause data loss. To reduce this data loss, a retransmission scheme has been applied. However, uncontrolled retransmission may significantly increase network load and data loss probability, thus defeating the retransmission purpose. In addition, in a priority traffic existing OBS network, OBS nodes may apply different retransmission mechanisms to priority bursts for quality-of-service (QoS) support. We present a controlled retransmission scheme for prioritized burst segmentation to support QoS in OBS networks. Different from previous work in the literature, we set a different value to retransmission probability at each contention and propose a retransmission analytical model for a burst segmentation contention resolution scheme. In addition, we apply the proposed retransmission scheme to the prioritized burst segmentation for QoS support. We take into account the load at each link due to both the fresh and the retransmitted traffic and calculate the path-blocking probability and the byte loss probability for high-priority and low-priority bursts to evaluate the network performance. An extensive simulation is proposed to validate our analytical model.

  8. Machine Learning Search for Gamma-Ray Burst Afterglows in Optical Images

    Science.gov (United States)

    Topinka, M.

    2016-06-01

    Thanks to the advances in robotic telescopes, time domain astronomy leads to a large number of transient events detected in images every night. Data mining and machine learning tools used for object classification are presented. The goal is to automatically classify transient events for both further follow-up by a larger telescope and for statistical studies of transient events. Special attention is given to the identification of gamma-ray burst afterglows. Machine learning techniques are used to identify GROND gamma-ray burst afterglow among the astrophysical objects present in the SDSS archival images based on the g'-r', r'-i' and i'-z' color indices. The performance of the support vector machine, random forest and neural network algorithms is compared. A joint meta-classifier, built on top of the individual classifiers, can identify GRB afterglows with the overall accuracy of ≳ 90%.

  9. PERBANDINGAN EUCLIDEAN DISTANCE DENGAN CANBERRA DISTANCE PADA FACE RECOGNITION

    Directory of Open Access Journals (Sweden)

    Sendhy Rachmat Wurdianarto

    2014-08-01

    Full Text Available Perkembangan ilmu pada dunia komputer sangatlah pesat. Salah satu yang menandai hal ini adalah ilmu komputer telah merambah pada dunia biometrik. Arti biometrik sendiri adalah karakter-karakter manusia yang dapat digunakan untuk membedakan antara orang yang satu dengan yang lainnya. Salah satu pemanfaatan karakter / organ tubuh pada setiap manusia yang digunakan untuk identifikasi (pengenalan adalah dengan memanfaatkan wajah. Dari permasalahan diatas dalam pengenalan lebih tentang aplikasi Matlab pada Face Recognation menggunakan metode Euclidean Distance dan Canberra Distance. Model pengembangan aplikasi yang digunakan adalah model waterfall. Model waterfall beriisi rangkaian aktivitas proses yang disajikan dalam proses analisa kebutuhan, desain menggunakan UML (Unified Modeling Language, inputan objek gambar diproses menggunakan Euclidean Distance dan Canberra Distance. Kesimpulan yang dapat ditarik adalah aplikasi face Recognation menggunakan metode euclidean Distance dan Canverra Distance terdapat kelebihan dan kekurangan masing-masing. Untuk kedepannya aplikasi tersebut dapat dikembangkan dengan menggunakan objek berupa video ataupun objek lainnya.   Kata kunci : Euclidean Distance, Face Recognition, Biometrik, Canberra Distance

  10. Searching for giga-Jansky fast radio bursts from the Milky Way with a global array of low-cost radio receivers

    Science.gov (United States)

    Maoz, Dan; Loeb, Abraham

    2017-06-01

    If fast radio bursts (FRBs) originate from galaxies at cosmological distances, then their all-sky rate implies that the Milky Way may host an FRB every 30-1500 yr, on average. If many FRBs persistently repeat for decades or more, a local giant FRB could be active now, with 1 GHz radio pulses of flux ˜3 × 1010 Jy, comparable with the fluxes and frequencies detectable by cellular communication devices (cell phones, Wi-Fi and GPS). We propose searching for Galactic FRBs using a global array of low-cost radio receivers. One possibility is the ˜1 GHz communication channel in cellular phones, through a Citizens-Science downloadable application. Participating phones would continuously listen for and record candidate FRBs and would periodically upload information to a central data-processing website which will identify the signature of a real, globe-encompassing, FRB from an astronomical distance. Triangulation of the GPS-based pulse arrival times reported from different Earth locations will provide the FRB sky position, potentially to arcsecond accuracy. Pulse arrival times versus frequency, from reports from phones operating at diverse frequencies, or from fast signal de-dispersion by the application, will yield the dispersion measure (DM). Compared to a Galactic DM model, it will indicate the source distance within the Galaxy. A variant approach uses the built-in ˜100 MHz FM-radio receivers present in cell phones for an FRB search at lower frequencies. Alternatively, numerous 'software-defined radio' devices, costing ˜$10 US each, could be deployed and plugged into USB ports of personal computers (particularly in radio-quiet locations) to establish the global network of receivers.

  11. METHODS OF ESTIMATION AND THE ROLE OF RESPIRATORY BURST IN THE PATHOGENESIS OF INFECTIOUS AND INFLAMMATORY DISEASES

    Directory of Open Access Journals (Sweden)

    A. A. Savchenko

    2017-01-01

    Full Text Available According to the modern concepts the respiratory burst directly related to the processes of phagocytosis characterizes the functional activity of phagocytic cells. This review presents modern methods for assessing the respiratory burst state of phagocytes based on cytofluorometric and chemiluminescent analysis. The sequence and mechanisms of the reactions of reactive oxygen species (ROS synthesis in the process of respiratory cell burst are presented in detail. The sequence of synthesis from ROS with low bactericidal activity to ROS with high bactericidal activity is characterized. The review describes in detail the most popular dyes for cytofluorometric analysis to assess the levels of ROS synthesis. Characteristics and examples of the use of such dyes as dihydroethidine, dichlorodihydrofluorescein and dihydrorhodamine 123 are given. The main stages and mechanisms of the chemiluminescence reaction are presented. The features of the use of the main indicators (luminol and lucigenin of the chemiluminescence reaction are described. A mechanism for estimating the parameters of the chemiluminescence reaction characterizing the features of the state and kinetics of the respiratory burst of phagocytic cells is given. The separate section of the review is devoted to the role of a respiratory burst in phagocytic cells in various immunopathological states. Data on the pathogenetic significance of changes in the intensity and kinetics of respiratory burst of phagocytes in infectious, inflammatory and oncological diseases were presented. Examples of new methods for diagnosing and predicting the course of the immunopathological states characters are presented on the basis of an assessment of the respiratory burst of phagocytic cells. The literature data show that at present, in the diagnosis and evaluation of the nature of the diseases characters the state of a respiratory burst is evaluated in various types of cells of innate immunity: neutrophils

  12. The experimental optical burst switching system

    Science.gov (United States)

    Li, Xinwan; Chen, Jian-Ping; Wu, Guiling; Wang, Hui; Lu, Jialin; Ye, Ailun

    2005-02-01

    The first optical burst switching (OBS) system has been demonstrated in China, which includes three edge routers and one core-node. A kind of fast wavelength selective optical switching was used in the system. The core OBS node consists of a kind of wavelength selective optical switch we developed. It consists of two SOA switches and one wavelength selective thin film filter with centre wavelength at one wavelength. There are one input optical fiber and two output fibers, each fiber carries two wavelengths. The Dell PE2650 servers act as the edge OBS routers. The wavelength of each data channel is located in C-band and the bit rate is at 1.25Gbps. The control channel uses bit rate of 100Mbps at wavelength of 1310 nm. A novel effective scheme for Just-In-Time (JIT) protocol was proposed and implemented. OBS services, such as Video on Demand (VOD) and file transfer protocol (FTP), have been demonstrated. Assembling and scheduling methods that are capable to guarantee the QoS (quality of service) of the transported service are studied.

  13. A modeling perspective for meteor burst communication

    Science.gov (United States)

    Healy, Brian C.

    1988-12-01

    Meteor burst communication (MBC) is well suited for military applications. MBC offers better security compared to other long range communication systems because of its low probability of intercept and antijamming characteristics. MBC, however, has two major drawbacks: low throughout and long message waiting time. In order for MBC to be used effectively, methods need to be developed to predict and optimize system performance. The result of this research is the design and development of a methodology to analyze MBC networks. A decision support system was developed that provides a simulation model for any single or multiple-link MBC network. This model runs on an IBM XT/AT compatible computer and consists of two distinct components. The first component uses engineering parameters to compute intermediate queueing characteristics used by a discrete event simulation component. The simulation component provides point estimates for throughput, message delay, and resource utilization in tabular and graphical form. The MBC process is shown to be a M/G/1 queue with server vacations. Applicable analytical equations are presented and their limitations are discussed. Analytical equations and empirical data were both used to validate the MBC performance model.

  14. Distance collaborations with industry

    Energy Technology Data Exchange (ETDEWEB)

    Peskin, A.; Swyler, K.

    1998-06-01

    The college industry relationship has been identified as a key policy issue in Engineering Education. Collaborations between academic institutions and the industrial sector have a long history and a bright future. For Engineering and Engineering Technology programs in particular, industry has played a crucial role in many areas including advisement, financial support, and practical training of both faculty and students. Among the most important and intimate interactions are collaborative projects and formal cooperative education arrangements. Most recently, such collaborations have taken on a new dimension, as advances in technology have made possible meaningful technical collaboration at a distance. There are several obvious technology areas that have contributed significantly to this trend. Foremost is the ubiquitous presence of the Internet. Perhaps almost as important are advances in computer based imaging. Because visual images offer a compelling user experience, it affords greater knowledge transfer efficiency than other modes of delivery. Furthermore, the quality of the image appears to have a strongly correlated effect on insight. A good visualization facility offers both a means for communication and a shared information space for the subjects, which are among the essential features of both peer collaboration and distance learning.

  15. Distance Teaching on Bornholm

    DEFF Research Database (Denmark)

    Hansen, Finn J. S.; Clausen, Christian

    2001-01-01

    The case study represents an example of a top-down introduction of distance teaching as part of Danish trials with the introduction of multimedia in education. The study is concerned with the background, aim and context of the trial as well as the role and working of the technology and the organi......The case study represents an example of a top-down introduction of distance teaching as part of Danish trials with the introduction of multimedia in education. The study is concerned with the background, aim and context of the trial as well as the role and working of the technology...... and the organisational set-up. It is debated which kind of social learning that has taken place. The innovation process was based on the implementation of an inflexible video-conference system without any proactive considerations of organisational change or pedagocical development. User appropriation of the technology...... was confined to technical problem solving pursued by teachers, students and a limited technical staff. The outcome was a prolonged and troublesome learning and implementation process....

  16. Evaluation of solar radio bursts' effect on GPS receiver signal tracking within International GPS Service network

    Science.gov (United States)

    Chen, Zhiyu; Gao, Yang; Liu, Zhizhao

    2005-06-01

    The direct interference from solar radio bursts (SRB) has not usually been considered as a potential threat to global positioning system (GPS) signal tracking, since the flux densities of most bursts are below 40,000 solar flux units (sfu), a threat threshold to GPS L1 frequency proposed by Klobuchar et al. (1999). Recent analysis indicated that a much lower threshold should be adopted for codeless or semicodeless dual-frequency GPS receivers. In this investigation, severe signal corruptions were found at dayside International GPS Service GPS receiver stations during a large solar radio burst that accompanied the super flare of 28 October 2003. Almost no GPS L2 signals were tracked during the solar flux peak time for areas near the subsolar point. Correlation analysis was performed between the rate of loss of lock on GPS L2 frequency and solar radio flux density at different bands, and a correlation index as high as 0.75 is revealed in the 1415 MHz solar radiation band, which is located between the two GPS operating frequencies L2 (1227.60 MHz) and L1 (1575.42 MHz). The correlation analysis indicates that GPS signal losses of lock were primarily caused by microwave in-band interference and that the threat threshold of SRB effects on the GPS system should be re-evaluated, since the flux density of the burst at 1415 MHz was just 4,000-12,000 sfu, which is far below the previously proposed threat threshold. The signal-tracking performance of different types of GPS receivers during such a super flare event is also presented.

  17. Networks on the Edge of Forever: Examining the Feasibility of using Meteor Burst (MB) Communication Networks on Mars

    Science.gov (United States)

    Charania, A.

    2002-01-01

    The envisioned future may include continuous operating outposts and networks on other worlds supporting human and robotic exploration. Given this possibility, a feasibility analysis is performed of a communications architecture based upon reflection of ion trails from meteors in planetary atmospheres. Meteor Burst (MB) communication systems use meteoritic impacts on planetary atmospheres as two-way, short burst communication nodes. MB systems consist of semi-continuous, low bandwidth networks. These systems possess both long distance capability (hundred of kilometers) and have lower susceptibility to atmospheric perturbations. Every day millions of meteors come into Earth's upper atmosphere with enough energy to ionize gas molecules suitably to reflect radio waves and facilitate communications beyond line of site. The ionized trail occurs at altitudes of 100 km with lengths reaching 30 km. The trial sustains itself long enough to support typical network distances of 1800 km. The initial step to use meteors in this fashion includes detection of a usable ionic trail. A probe signal is sent from one station to another in the network. If there is a meteor trail present, the probe signal is reflected to a receiving station. When another station receives the probe signal, it sends an acknowledgement to the originating station to proceed with transfer on that trail in a high-speed digital data burst. This probe-main signal handshaking occurs each time a burst of data is sent and can occur several times over the course of just one useable meteor trail. Given the need for non-data sending probe signals and error correcting bits; typical transmission data rates vary from a few kilobits per second to over 100 kilobits per second. On Earth, MB links open up hundreds of time per hour depending upon daily and seasonal variations. Meteor bursts were first noticed in detail in the 1930s. With the capabilities of modern computer processing, MB systems have become both technically

  18. A complete sample of long bright Swift gamma ray bursts.

    Science.gov (United States)

    Tagliaferri, Gianpiero; Salvaterra, Ruben; Campana, Sergio; Covino, Stefano; D'Avanzo, Paolo; Fugazza, Dino; Ghirlanda, Giancarlo; Ghisellini, Gabriele; Melandri, Andrea; Nava, Lara; Sbarufatti, Boris; Vergani, Susanna

    2013-06-13

    Complete samples are the basis of any population study. To this end, we selected a complete subsample of Swift long bright gamma ray bursts (GRBs). The sample, made up of 58 bursts, was selected by considering bursts with favourable observing conditions for ground-based follow-up observations and with the 15-150 keV 1 s peak flux above a flux threshold of 2.6 photons cm(-2) s(-1). This sample has a redshift completeness level higher than 90 per cent. Using this complete sample, we investigate the properties of long GRBs and their evolution with cosmic time, focusing in particular on the GRB luminosity function, the prompt emission spectral-energy correlations and the nature of dark bursts.

  19. Study on Monitoring Rock Burst through Drill Pipe Torque

    National Research Council Canada - National Science Library

    Li, Zhonghua; Zhu, Liyuan; Yin, Wanlei; Song, Yanfang

    2015-01-01

      This paper presents a new method to identify the danger of rock burst from the response of drill pipe torque during drilling process to overcome many defects of the conventional volume of drilled coal rubble method...

  20. An Unusual Burst at Decameter Wavelengths. 1. Observations

    Science.gov (United States)

    Brazhenko, A. I.; Melnik, V. M.; Konovalenko, O. O.; Dorovskyy, V. V.; Frantsuzenko, A. V.; Rucker, H. O.; Panchenko, M.; Stanislavsky, A. A.

    2012-06-01

    An unusual burst was observed by the UTR-2 (Kharkiv, Ukraine) and URAN-2 (Poltava, Ukraine) radio telescopes on June 3, 2011. It was recorded in the frequency band 16-28 MHz. Its frequency drift rate (about 500 kHz/s) was positive at frequencies higher than 22 MHz and negative with drift rate 100 kHz/s at lower frequencies. The half-power duration of this burst was about the same at all frequencies and made 17-22 s. The fine frequency-time structure was unusual too. The maximum radio flux of the unusual burst at 24 MHz was about 103 s.f.u. and its polarization was about 10 %. We propose an interpretation of the unusual burst.

  1. Dynamics of electro burst in solids: I. Power characteristics of electro burst

    Energy Technology Data Exchange (ETDEWEB)

    Burkin, V V; Kuznetsova, N S; Lopatin, V V, E-mail: tevn@hvd.tpu.r [High Voltage Research Institute of Tomsk Polytechnical University, Tomsk 634050, 2A Lenina Avenue (Russian Federation)

    2009-09-21

    By means of the developed physical and mathematical model of electro burst, an analysis of the power characteristics of wave disturbances generated by the expanding discharge channel in a solid material has been carried out. The dynamics of the generator energy conversion into the plasma channel and into the wave of mechanical stresses in the solid placed in a liquid has been considered. Conformably to the electro discharge destruction of strong materials, the relation of the discharge circuit parameters with the power characteristics of wave has been analysed. The prediction of a fracture pattern has been made depending on the discharge circuit parameters.

  2. Dynamics of electro burst in solids: I. Power characteristics of electro burst

    Science.gov (United States)

    Burkin, V. V.; Kuznetsova, N. S.; Lopatin, V. V.

    2009-09-01

    By means of the developed physical and mathematical model of electro burst, an analysis of the power characteristics of wave disturbances generated by the expanding discharge channel in a solid material has been carried out. The dynamics of the generator energy conversion into the plasma channel and into the wave of mechanical stresses in the solid placed in a liquid has been considered. Conformably to the electro discharge destruction of strong materials, the relation of the discharge circuit parameters with the power characteristics of wave has been analysed. The prediction of a fracture pattern has been made depending on the discharge circuit parameters.

  3. Burst spinal cord stimulation for limb and back pain.

    Science.gov (United States)

    De Ridder, Dirk; Plazier, Mark; Kamerling, Niels; Menovsky, Tomas; Vanneste, Sven

    2013-11-01

    Spinal cord stimulation via epidurally implanted electrodes is a common treatment for medically intractable neuropathic pain of different origins. Because tonic electrical stimulation evokes paresthesias over the painful area, this method has never been proven scientifically to be superior to placebo. Recently, burst stimulation (in which closely spaced, high-frequency stimuli are delivered to the spinal cord) has been developed, which does not generate paresthesias. A randomized placebo controlled trail in which we compared three stimulation paradigms (burst, tonic, and placebo) was performed on 15 consecutive pain patients. In contrast to tonic stimulation, burst stimulation was able to provide pain relief without the generation of paresthesias, permitting us to use a double-blinded placebo controlled approach. Primary outcome measures were visual analog scale pain scores for back pain, limb pain, and general pain. Secondary outcome measures included the pain vigilance and awareness questionnaire, which is used to measure attention to pain and pain changes, and visual analog scale of the worst, least, and momentary pain. In a subgroup of five patients, a source-localized electroencephalogram was performed under four conditions: baseline, tonic, burst, and placebo stimulation. Burst stimulation was able to improve back, limb, and general pain by 51%, 53%, and 55% and tonic stimulation by 30%, 52%, and 31%, respectively. Pain now, least, and worst pain were improved by 50%, 73%, and 36% by burst stimulation, respectively, and 26%, 46%, and 13% by tonic stimulation. In comparison with placebo, burst, corrected for multiple comparisons, was significantly better for all measurements. However, the greatest differences were obtained in the pain vigilance and awareness questionnaire measurements: burst improved the attention to pain and pain changes, whereas tonic and placebo worsened these measurements. The analysis via encephalogram demonstrates burst stimulation

  4. Visual control of burst priming in the anesthetized lateral geniculate nucleus.

    Science.gov (United States)

    Denning, Kate S; Reinagel, Pamela

    2005-04-06

    Thalamic relay cells fire bursts of action potentials. Once a long hyperpolarization "primes" (deinactivates) the T-type calcium channel, a depolarizing input will "trigger" a calcium spike with a burst of action potentials. During sleep, bursts are frequent, rhythmic, and nonvisual. Bursts have been observed in alert animals, and burst timing is known to carry visual information under light anesthesia. We extend this finding by showing that bursts without visual triggers are rare. Nevertheless, if the channel were primed at random with respect to the stimulus, then bursts would have the same visual significance as single spikes. We find, however, that visual signals influence when the channel is primed. First, natural time-varying stimuli evoke more bursts than white noise. Second, specific visual stimuli reproducibly elicit bursts, whereas others reliably elicit single spikes. Therefore, visual information is encoded by the selective tagging of some responses as bursts. The visual information attributable to visual priming (as distinct from the information attributable to visual triggering of the bursts) was two bits per burst on average. Although bursts are reportedly rare in alert animals, this must be investigated as a function of visual stimulus. Moreover, we propose methods to measure the extent of both visual triggering and visual priming of bursts. Whether or not bursts are rare, our methods could help determine whether bursts in alert animals carry a distinct visual signal.

  5. The underestimated challenges of burst-mode WDM transmission in TWDM-PON

    Science.gov (United States)

    Bonk, R.; Poehlmann, W.; van Veen, D.; Galaro, J.; Farah, R.; Schmuck, H.; Pfeiffer, Th.

    2015-12-01

    In this paper, the underestimated challenges of the burst-mode operation in the upstream path of time-and-wavelength-division-multiplexed passive optical networks are analyzed. Various challenges are disclosed, the influence of the associated physical effects on the signal quality is discussed and mitigation proposals are described: Intra-channel cross-talk can arise from optical network units induced background amplified-spontaneous emission noise and inter-channel cross-talk can be caused by non-ideal filter suppression between wavelength channels at the optical line termination receivers. Such cross-talk effects can be counteracted by reducing the laser burst-signal output power as well as its rival noise power simultaneously, i.e. by applying power leveling. A fast frequency drift in burst-mode operation is inherent to directly modulated lasers, but depends on the specific laser design, the laser output power and the burst length. Mitigation mechanisms are an optimized non-standard laser design or a specific mode of operation, e.g. an increase of the frequency drift during the preamble of the burst. The power dynamic range an optical pre-amplifier as part of the upstream signal receivers needs to handle can be in range of up to 40 dB, because of the multi-wavelength channel operation and of the optical distribution network differential path loss. This power dynamic faced at the receiver can not only cause challenges for the optical amplifier, but also for the burst-mode receivers. Additionally, the physical layer operation and maintenance of the upstream path is challenging too. Each optical network unit laser needs to be either wavelength pre-calibrated, which adds undesired costs or cross-channel synchronization of ranging windows has to be ensured. Otherwise rogue optical network unit behavior in wavelength and time domain will deteriorate system performance with every new optical network unit entering the network. Further, the operation of the optical

  6. Bursts and shocks in a continuum shell model

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Bohr, Tomas; Jensen, M.H.

    1998-01-01

    We study a burst event, i.e., the evolution of an initial condition having support only in a finite interval of k-space, in the continuum shell model due to Parisi. We show that the continuum equation without forcing or dissipation can be explicitly written in characteristic form and that the right...... and left moving parts can be solved exactly. When this is supplemented by the approximate shock condition it is possible to find the symptotic form of the burst....

  7. Real Life Science with Dandelions and Project BudBurst.

    Science.gov (United States)

    Johnson, Katherine A

    2016-03-01

    Project BudBurst is a national citizen-science project that tracks bloom times and other phenological data for plants across the country. Data from Project BudBurst are being used to measure the effects of climate change. Students can participate in this project by watching any of the plants on the list, including the common dandelion, which makes the program easy and accessible to everyone. Journal of Microbiology & Biology Education.

  8. Burst suppression in sleep in a routine outpatient EEG

    Directory of Open Access Journals (Sweden)

    Ammar Kheder

    2014-01-01

    Full Text Available Burst suppression (BS is an electroencephalogram (EEG pattern that is characterized by brief bursts of spikes, sharp waves, or slow waves of relatively high amplitude alternating with periods of relatively flat EEG or isoelectric periods. The pattern is usually associated with coma, severe encephalopathy of various etiologies, or general anesthesia. We describe an unusual case of anoxic brain injury in which a BS pattern was seen during behaviorally defined sleep during a routine outpatient EEG study.

  9. Study on Monitoring Rock Burst through Drill Pipe Torque

    OpenAIRE

    Zhonghua Li; Liyuan Zhu; Wanlei Yin; Yanfang Song

    2015-01-01

    This paper presents a new method to identify the danger of rock burst from the response of drill pipe torque during drilling process to overcome many defects of the conventional volume of drilled coal rubble method. It is based on the relationship of rock burst with coal stress and coal strength. Through theoretic analysis, the change mechanism of drill pipe torque and the relationship of drill pipe torque with coal stress, coal strength, and drilling speed are investigated. In light of the a...

  10. Real Life Science with Dandelions and Project BudBurst

    Directory of Open Access Journals (Sweden)

    Katherine A. Johnson

    2015-12-01

    Full Text Available Project BudBurst is a national citizen-science project that tracks bloom times and other phenological data for plants across the country. Data from Project BudBurst are being used to measure the effects of climate change. Students can participate in this project by watching any of the plants on the list, including the common dandelion, which makes the program easy and accessible to everyone.

  11. An unusual burst at decameter wavelengths. 2. Interpretation

    Science.gov (United States)

    Melnik, V. M.; Brazhenko, A. I.; Konovalenko, O. O.; Dorovskyy, V. V.; Frantsuzenko, A. V.; Rucker, H. O.; Panchenko, M.; Stanislavsky, A. A.

    2012-09-01

    The model which describes appearance and process of radio emission of an unusual burst observed by the UTR-2 (Kharkiv, Ukraine) and URAN-2 (Poltava, Ukraine) radio telescopes at 16-28 MHz is proposed. We suppose that the unusual burst is caused by the small ejection initiated by the active region NOAA1222. This behind-limb region was situated at the heights 2.3R⊙⊙ to 2.8R to 2.8R⊙⊙, when radio emission of the unusual burst at the second harmonic was started. We believe that due to interaction of this ejection with coronal plasma some electrons were accelerated. These electrons propagating towards and outwards the Sun were sources of the UTR-2, URAN-2 and STEREO-A recorded unusual burst. The mechanism of radio emission was plasma one. The proposed model allows explaining such properties of the unusual burst as its positive and negative drift rates, duration, abrupt stopping of radio emission at 27.5 MHz and its fine frequency structure., when radio emission of the unusual burst at the second harmonic was started. We believe that due to interaction of this ejection with coronal plasma some electrons were accelerated. These electrons propagating towards and outwards the Sun were sources of the UTR-2, URAN-2 and STEREO-A recorded unusual burst. The mechanism of radio emission was plasma one. The proposed model allows explaining such properties of the unusual burst as its positive and negative drift rates, duration, abrupt stopping of radio emission at 27.5 MHz and its fine frequency structure.

  12. Cosmic X-ray Flashes Reveal Their Distance

    Science.gov (United States)

    2003-09-01

    Astronomers using X-ray, radio, and optical telescopes have announced a big leap in solving the origin of mysterious objects known as X-ray flashes (XRFs) by finding that they originate from blue star forming galaxies. This discovery of the cosmic distance scale effectively ends the widely-held speculation that XRFs are the death-cries from stars exploding in the infant universe. X-ray flashes resemble a lower energy and longer-duration version of a gamma-ray burst, an energetic explosion thought to signal the death of a massive star. The properties of XRFs led to speculation that they were gamma-ray bursts that occurred less than a few billion years after the Big Bang, and whose light had been subsequently weakened and time-stretched by the expansion of the universe. "Now that the very distant origin has been ruled out, X-ray flashes could be due to exploding massive stars, just like gamma-ray bursts" explained Dr. Joshua Bloom at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author on the paper announcing the results to be published in The Astrophysical Journal. Bloom continued: "But the explosion from an X-ray flash would need to contain less matter or less energy than a typical gamma-ray burst. Alternatively, X-ray flashes could be gamma-ray bursts viewed off-axis." These results are being discussed at the "30th Anniversary of the Discovery of Gamma-ray Bursts" conference currently being held in Sante Fe, New Mexico. The location of the sources studied by Bloom's group required a careful coordination of NASA's Chandra X-ray Observatory and Hubble Space Telescope, along with the National Radio Astronomy Observatory's Very Large Array (VLA) in Socorro, New Mexico. Chandra and the VLA provided a precise location of the fading X-ray and radio "afterglow" of two X-ray flashes known as XRF 011030 and XRF 020427. The Hubble Space Telescope was used to identify and study galaxies at these locations and estimate their distances to between

  13. Synchrotron cooling in energetic gamma-ray bursts observed by the Fermi Gamma-Ray Burst Monitor

    Science.gov (United States)

    Yu, Hoi-Fung; Greiner, Jochen; van Eerten, Hendrik; Burgess, J. Michael; Narayana Bhat, P.; Briggs, Michael S.; Connaughton, Valerie; Diehl, Roland; Goldstein, Adam; Gruber, David; Jenke, Peter A.; von Kienlin, Andreas; Kouveliotou, Chryssa; Paciesas, William S.; Pelassa, Véronique; Preece, Robert D.; Roberts, Oliver J.; Zhang, Bin-Bin

    2015-01-01

    Context. We study the time-resolved spectral properties of energetic gamma-ray bursts (GRBs) with good high-energy photon statistics observed by the Gamma-Ray Burst Monitor (GBM) onboard the Fermi Gamma-Ray Space Telescope. Aims: We aim to constrain in detail the spectral properties of GRB prompt emission on a time-resolved basis and to discuss the theoretical implications of the fitting results in the context of various prompt emission models. Methods: Our sample comprises eight GRBs observed by the Fermi GBM in its first five years of mission, with 1 keV-1 MeV fluence f> 1.0 × 10-4 erg cm-2 and a signal-to-noise ratio level of S/N ≥ 10.0 above 900 keV. We performed a time-resolved spectral analysis using a variable temporal binning technique according to optimal S/N criteria, resulting in a total of 299 time-resolved spectra. We performed Band function fits to all spectra and obtained the distributions for the low-energy power-law index α, the high-energy power-law index β, the peak energy in the observed νFν spectrum Ep, and the difference between the low- and high-energy power-law indices Δs = α - β. We also applied a physically motivated synchrotron model, which is a triple power-law with constrained power-law indices and a blackbody component, to test the prompt emission for consistency with a synchrotron origin and obtain the distributions for the two break energies Eb,1 and Eb,2, the middle segment power-law index β, and the Planck function temperature kT. Results: The Band function parameter distributions are α = -0.73+0.16-0.21, β =ي-2.13+0.28-0.56, Ep = 374.4+307.3-187.7 , , keV (log10Ep = 2.57+0.26-0.30), and Δs = 1.38+0.54-0.31 , with average errors σα ~ 0.1, σβ ~ 0.2, and σEp ~ 0.1Ep. Using the distributions of Δs and β, the electron population index p is found to be consistent with the "moderately fast" scenario, in which fast- and slow-cooling scenarios cannot be distinguished. The physically motivated synchrotron

  14. Bursting of a bubble confined in between two plates

    Science.gov (United States)

    Murano, Mayuko; Kimono, Natsuki; Okumura, Ko

    2015-11-01

    Rupture of liquid thin films, driven by surface tension, has attracted interests of scientists for many years. It is also a daily phenomenon familiar to everyone in the form of the bursting of soap films. In recent years, many studies in confined geometries (e.g. in a Hele-Shaw cell) have revealed physical mechanisms of the dynamics of bubbles and drops. As for a liquid film sandwiched in between another liquid immiscible to the film liquid in the Hele-Shaw cell, it is reported that the thin film bursts at a constant speed and the speed depends on the viscosity of the surrounding liquid when the film is less viscous, although a rim is not formed at the bursting tip; this is because the circular symmetry of the hole in the bursting film is lost. Here, we study the bursting speed of a thin film sandwiched between air instead of the surrounding liquid in the Hele-Shaw cell to seek different scaling regimes. By measuring the bursting velocity and the film thickness of an air bubble with a high speed camera, we have found a new scaling law in viscous regime. This research was partly supported by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).

  15. Probability assessment of burst limit state due to internal corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Hasan, Sikder, E-mail: msh678@mun.ca [Process Engineering, Faculty of Engineering and Applied Science, Memorial University of Newfoundland, St. John' s, NL A1B 3X5 (Canada); Khan, Faisal; Kenny, Shawn [Process Engineering, Faculty of Engineering and Applied Science, Memorial University of Newfoundland, St. John' s, NL A1B 3X5 (Canada)

    2012-01-15

    The failure probability of an oil and gas pipeline, with longitudinally oriented internal corrosion defects, due to burst from internal operating pressure can be estimated through characterization of defect geometry, internal corrosion growth rate, and remaining mechanical hoop strength capacity. A number of candidate models to estimate the corrosion defect depth growth rate were evaluated. Defining a corrosion defect length, the corrosion feature geometry was integrated within burst pressure models, which have been adopted by oil and gas industry standards, codes or recommended practices. On this basis the burst pressure failure probability of a pipeline with internal corrosion defects can be estimated. A comparative analysis of pipe burst limit states and failure estimates were conducted, using Monte Carlo simulation and First Order Second Moment (FOSM) methods. Results from the comparative analysis closely matched and demonstrated consistent trends. Based on the probabilistic assessment, the relative conservatism between burst pressure models was analyzed and recommendations provided to assist designers on model selection. - Highlights: Black-Right-Pointing-Pointer We studied failure probability of pipeline due to internal corrosion defects. Black-Right-Pointing-Pointer We compared the burst pressure models of recommended codes/standard or individual models Black-Right-Pointing-Pointer Discussed relative conservatism of recommended codes/standards or individual models. Black-Right-Pointing-Pointer Recommendations also provided to assist designer on model selection.

  16. 79 Inverted U - Burst Observed on 21 August 2017

    Science.gov (United States)

    Reeve, Witham; Monstein, Christian

    2017-11-01

    Totality of the solar eclipse that occurred 21 August 2017 was observable in a narrow corridor across the United States from Oregon to South Carolina, and a partial eclipse was observable from almost everywhere else in North America. Because the Sun is nearing the minimum of its current solar cycle, we were expecting that radio observations would be of a quiet Sun with possible effects from the eclipse. It turned out that the Sun had two active regions, AR2671 and AR2672, visible from Earth at the time with AR2671 pointed almost directly at Earth(figure 1). We observed numerous Type III radio bursts throughout the day of the eclipse and a rare inverted U-burst (called, simply, U-burst here)during the eclipse. The radio activity was coincidental with but unrelated to the eclipse itself. In this paper we describe observations of the U-burst that were recorded at four stations in the e-Callisto solar radio spectrometer network at 1741 UTC. This burst has both fundamental and harmonic characteristics. Space Weather Prediction Center (SWPC) did not record any radio sweeps at the time of the U-burst (table 1) but we know from experience that SWPC occasionally misses solar radio events.

  17. Aliasing Effects of Q-bursts on Background Spectra of Schumann Resonances

    Science.gov (United States)

    Guha, A.; Mushtak, V. C.; Williams, E.; Neska, M.; Nagy, T. G.; Satori, G.

    2013-12-01

    lightning strokes is essentially identical, especially for lightning strokes large distances, thus producing almost identical time series and spectra at both the stations. As an additional refinement on the selection of Q-bursts, the average energy of the lightning strokes detected by the WWLLN within a 30 ms window is considered. Although, WWLLN has its own limitation in efficiency to detect all large transient events, this additional check minimizes the chance of false detection by an independent check. Only strokes having 1000 Joule average energy are selected as Q-bursts. The search for Q-bursts was performed with the above methodology for May 5, 2009. 22 events were found with an average (median) energy of 6200 (4600) Joules. The maximum stroke energy detected is around 34000 Joule in the African region within 21-22 UT. The majority of qualified events are found to be in the African range of longitude, and their time delays from the usual African background maximum between 14 and 15 UT range from 3 to 11 hours, fully consistent with a mesoscale origin for the African events. Some of these events are likely to strongly alias the South American background SR spectra, dominant in the 22 UT time frames. The achievement of representative background spectra for use in global inversion of multi-station ELF observations requires the removal of the aliasing Q-bursts from raw time series data.

  18. Are fast radio bursts markers of dark core collapse?

    Science.gov (United States)

    Katz, J. I.

    2017-07-01

    Are some neutron stars produced without a supernova, without ejecting mass in a remnant? Theoretical calculations of core collapse in massive stars often predict this. The observation of the repeating FRB 121102, whose dispersion measure has not changed over several years, suggests that dark core collapses are not just failures of computer codes, but may be real. The existence of one repeating fast radio burst (FRB) with unchanging dispersion measure is not conclusive, but within a decade hundreds or thousands of FRB are expected to be discovered, likely including scores of repeaters, permitting useful statistical inferences. A naïve supernova remnant model predicts observable decline in dispersion measure for 100 yr after its formation. If an upper limit on the decline of 2 pc cm-3 yr-1 is set for five repeating FRBs, then the naïve model with nominal parameters is rejected at the 95 per cent level of confidence. This may indicate dark neutron star formation without a supernova or supernova remnant. This hypothesis may also be tested with the Large Synoptic Survey Telescope (LSST) data that would show, if present, a supernova at an interferometric FRB position if it occurred within the LSST epoch.

  19. Statistical Distributions of Optical Flares from Gamma-Ray Bursts

    Science.gov (United States)

    Yi, Shuang-Xi; Yu, Hai; Wang, F. Y.; Dai, Zi-Gao

    2017-07-01

    We statistically study gamma-ray burst (GRB) optical flares from the Swift/UVOT catalog. We compile 119 optical flares, including 77 flares with redshift measurements. Some tight correlations among the timescales of optical flares are found. For example, the rise time is correlated with the decay time, and the duration time is correlated with the peak time of optical flares. These two tight correlations indicate that longer rise times are associated with longer decay times of optical flares and also suggest that broader optical flares peak at later times, which are consistent with the corresponding correlations of X-ray flares. We also study the frequency distributions of optical flare parameters, including the duration time, rise time, decay time, peak time, and waiting time. Similar power-law distributions for optical and X-ray flares are found. Our statistic results imply that GRB optical flares and X-ray flares may share the similar physical origin, and both of them are possibly related to central engine activities.

  20. Characterization of the human burst-forming unit-megakaryocyte.

    Science.gov (United States)

    Briddell, R A; Brandt, J E; Straneva, J E; Srour, E F; Hoffman, R

    1989-07-01

    Two classes of human marrow megakaryocyte progenitor cells are described. Colony-forming unit-megakaryocyte (CFU-MK)-derived colonies appeared in vitro after 12-day incubation; burst-forming unit-megakaryocyte (BFU-MK)-derived colonies appeared after 21 days. CFU-MK-derived colonies were primarily unifocal and composed of 11.6 +/- 1.2 cells/colony; BFU-MK-derived colonies were composed of 2.3 +/- 0.4 foci and 108.6 +/- 4.4 cells/colony. CFU-MK and BFU-MK were separable by counterflow centrifugal elutriation. CFU-MK colony formation was diminished by exposure to 5-fluorouracil (5-FU); BFU-MK colony formation was unaffected. CFU-MK and BFU-MK were immunologically phenotyped. CFU-MK expressed the human progenitor cell antigen-1 (HPCA-1, CD34, clone My10) and a major histocompatibility class II locus, HLA-DR, and BFU-MK expressed only detectable amounts of CD34. BFU-MK colony formation was entirely dependent on addition of exogenous hematopoietic growth factors. Recombinant granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) possessed such colony-stimulating activity, whereas recombinant erythropoietin (Epo), G-CSF, IL-1 alpha, IL-4, and purified thrombocytopoiesis-stimulating factor did not. These studies indicate the existence of a human megakaryocyte progenitor cell, the BFU-MK, which has unique properties allowing it to be distinguished from the CFU-MK.

  1. Evolutionary bursts in Euphorbia (Euphorbiaceae) are linked with photosynthetic pathway.

    Science.gov (United States)

    Horn, James W; Xi, Zhenxiang; Riina, Ricarda; Peirson, Jess A; Yang, Ya; Dorsey, Brian L; Berry, Paul E; Davis, Charles C; Wurdack, Kenneth J

    2014-12-01

    The mid-Cenozoic decline of atmospheric CO2 levels that promoted global climate change was critical to shaping contemporary arid ecosystems. Within angiosperms, two CO2 -concentrating mechanisms (CCMs)-crassulacean acid metabolism (CAM) and C4 -evolved from the C3 photosynthetic pathway, enabling more efficient whole-plant function in such environments. Many angiosperm clades with CCMs are thought to have diversified rapidly due to Miocene aridification, but links between this climate change, CCM evolution, and increased net diversification rates (r) remain to be further understood. Euphorbia (∼2000 species) includes a diversity of CAM-using stem succulents, plus a single species-rich C4 subclade. We used ancestral state reconstructions with a dated molecular phylogeny to reveal that CCMs independently evolved 17-22 times in Euphorbia, principally from the Miocene onwards. Analyses assessing among-lineage variation in r identified eight Euphorbia subclades with significantly increased r, six of which have a close temporal relationship with a lineage-corresponding CCM origin. Our trait-dependent diversification analysis indicated that r of Euphorbia CCM lineages is approximately threefold greater than C3 lineages. Overall, these results suggest that CCM evolution in Euphorbia was likely an adaptive strategy that enabled the occupation of increased arid niche space accompanying Miocene expansion of arid ecosystems. These opportunities evidently facilitated recent, replicated bursts of diversification in Euphorbia. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

  2. Distances with forming environments.

    Science.gov (United States)

    Kelly, Patrick L; Filippenko, Alexei V; Burke, David L; Hicken, Malcolm; Ganeshalingam, Mohan; Zheng, WeiKang

    2015-03-27

    The luminosities of type Ia supernovae (SNe), the thermonuclear explosions of white-dwarf stars, vary systematically with their intrinsic color and the rate at which they fade. From images taken with the Galaxy Evolution Explorer (GALEX), we identified SNe Ia that erupted in environments that have high ultraviolet surface brightness and star-formation surface density. When we apply a steep model extinction law, we calibrate these SNe using their broadband optical light curves to within ~0.065 to 0.075 magnitude, corresponding to <4% in distance. The tight scatter, probably arising from a small dispersion among progenitor ages, suggests that variation in only one progenitor property primarily accounts for the relationship between their light-curve widths, colors, and luminosities. Copyright © 2015, American Association for the Advancement of Science.

  3. Continuing Education for Distance Librarians

    Science.gov (United States)

    Cassner, Mary; Adams, Kate E.

    2012-01-01

    Distance librarians as engaged professionals work in a complex environment of changes in technologies, user expectations, and institutional goals. They strive to keep current with skills and competencies to support distance learners. This article provides a selection of continuing education opportunities for distance librarians, and is relevant…

  4. Relative Timing of Microwave and HXR Bursts

    Science.gov (United States)

    Bastian, T. S.; Aschwanden, M. J.

    1997-05-01

    The close correlation between microwave and hard X-ray (HXR) emission during flares has often been cited as evidence that the same population of energetic electrons is responsible for both types of emission. The two emissions differ in detail, however. Imaging observations have demonstrated that the two are not necessarily cospatial and timing observations have demonstrated that the microwaves are often significantly delayed with respect to HXR emission, typically by several seconds, but occassionally by much longer times. Such delays are in seeming conflict with the thick target model for HXR emission in its simplest form, and with the idea that microwave and HXR emissions result from essentially the same population of electrons. One way to reconcile the delay between microwaves and HXRs in the thick target model is to suppose that that electron trapping is significant (e.g., Cornell et al., ApJ, 279, 875). For a magnetic trap containing a plasma of constant density, high energy electrons have a longer lifetime against collisions than low energy electrons (tau_ {def} ~ E(3/2) ). Hence the energetic electrons responsible for the microwaves remain in the trap longer and the microwave emission they emit peaks later than the HXR emission. Another possibility is that higher energy electrons are accelerated later than lower energy electrons (so-called ``second-step'' acceleration models; e.g., Bai and Dennis 1985, ApJ, 292, 699). To explore the question in detail we have assembled a sample of 16 flares observed simultaneously in microwaves by the Nobeyama radioheliograph and in HXRs by the BATSE instrument on board the CGRO in burst trigger mode. The former imaged the flares at 17 GHz with an angular resolution of ~ 10'' and a time resolution of either 50 msec or 1 sec. The latter obtained medium energy resolution spectra (16 channels) between 20-200 keV with a time resolution of 16 or 64 msec. We present preliminary results of our analysis.

  5. Neuronal networks and energy bursts in epilepsy.

    Science.gov (United States)

    Wu, Y; Liu, D; Song, Z

    2015-02-26

    Epilepsy can be defined as the abnormal activities of neurons. The occurrence, propagation and termination of epileptic seizures rely on the networks of neuronal cells that are connected through both synaptic- and non-synaptic interactions. These complicated interactions contain the modified functions of normal neurons and glias as well as the mediation of excitatory and inhibitory mechanisms with feedback homeostasis. Numerous spread patterns are detected in disparate networks of ictal activities. The cortical-thalamic-cortical loop is present during a general spike wave seizure. The thalamic reticular nucleus (nRT) is the major inhibitory input traversing the region, and the dentate gyrus (DG) controls CA3 excitability. The imbalance between γ-aminobutyric acid (GABA)-ergic inhibition and glutamatergic excitation is the main disorder in epilepsy. Adjustable negative feedback that mediates both inhibitory and excitatory components affects neuronal networks through neurotransmission fluctuation, receptor and transmitter signaling, and through concomitant influences on ion concentrations and field effects. Within a limited dynamic range, neurons slowly adapt to input levels and have a high sensitivity to synaptic changes. The stability of the adapting network depends on the ratio of the adaptation rates of both the excitatory and inhibitory populations. Thus, therapeutic strategies with multiple effects on seizures are required for the treatment of epilepsy, and the therapeutic functions on networks are reviewed here. Based on the high-energy burst theory of epileptic activity, we propose a potential antiepileptic therapeutic strategy to transfer the high energy and extra electricity out of the foci. Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights reserved.

  6. The hyperbolic effect of density and strength of inter beta-cell coupling on islet bursting: a theoretical investigation

    Directory of Open Access Journals (Sweden)

    Wang Xujing

    2008-08-01

    Full Text Available Abstract Background Insulin, the principal regulating hormone of blood glucose, is released through the bursting of the pancreatic islets. Increasing evidence indicates the importance of islet morphostructure in its function, and the need of a quantitative investigation. Recently we have studied this problem from the perspective of islet bursting of insulin, utilizing a new 3D hexagonal closest packing (HCP model of islet structure that we have developed. Quantitative non-linear dependence of islet function on its structure was found. In this study, we further investigate two key structural measures: the number of neighboring cells that each β-cell is coupled to, nc, and the coupling strength, gc. Results β-cell clusters of different sizes with number of β-cells nβ ranging from 1–343, nc from 0–12, and gc from 0–1000 pS, were simulated. Three functional measures of islet bursting characteristics – fraction of bursting β-cells fb, synchronization index λ, and bursting period Tb, were quantified. The results revealed a hyperbolic dependence on the combined effect of nc and gc. From this we propose to define a dimensionless cluster coupling index or CCI, as a composite measure for islet morphostructural integrity. We show that the robustness of islet oscillatory bursting depends on CCI, with all three functional measures fb, λ and Tb increasing monotonically with CCI when it is small, and plateau around CCI = 1. Conclusion CCI is a good islet function predictor. It has the potential of linking islet structure and function, and providing insight to identify therapeutic targets for the preservation and restoration of islet β-cell mass and function.

  7. Persistent sodium currents in mesencephalic v neurons participate in burst generation and control of membrane excitability.

    Science.gov (United States)

    Wu, Nanping; Enomoto, Akifumi; Tanaka, Susumu; Hsiao, Chie-Fang; Nykamp, Duane Q; Izhikevich, Eugene; Chandler, Scott H

    2005-05-01

    The functional and biophysical properties of a persistent sodium current (I(NaP)) previously proposed to participate in the generation of subthreshold oscillations and burst discharge in mesencephalic trigeminal sensory neurons (Mes V) were investigated in brain stem slices (rats, p7-p12) using whole cell patch-clamp methods. I(NaP) activated around -76 mV and peaked at -48 mV, with V1/2 of -58.7 mV. Ramp voltage-clamp protocols showed that I(NaP) undergoes time- as well as voltage-dependent inactivation and recovery from inactivation in the range of several seconds (tau(onset) = 2.04 s, tau(recov) = 2.21 s). Riluzole (model was constructed using Hodgkin-Huxley parameters obtained experimentally for Na+ and K+ currents that simulated the experimentally observed membrane resonance, subthreshold oscillations, bursting, and PIR. Alterations in the model g(NaP) parameters indicate that I(NaP) is critical for control of subthreshold and suprathreshold Mes V neuron membrane excitability and burst generation.

  8. Control of timing, rate and bursts of hippocampal place cells by dendritic and somatic inhibition.

    Science.gov (United States)

    Royer, Sébastien; Zemelman, Boris V; Losonczy, Attila; Kim, Jinhyun; Chance, Frances; Magee, Jeffrey C; Buzsáki, György

    2012-03-25

    A consortium of inhibitory neurons control the firing patterns of pyramidal cells, but their specific roles in the behaving animal are largely unknown. We performed simultaneous physiological recordings and optogenetic silencing of either perisomatic (parvalbumin (PV) expressing) or dendrite-targeting (somatostatin (SOM) expressing) interneurons in hippocampal area CA1 of head-fixed mice actively moving a treadmill belt rich with visual-tactile stimuli. Silencing of either PV or SOM interneurons increased the firing rates of pyramidal cells selectively in their place fields, with PV and SOM interneurons having their largest effect during the rising and decaying parts of the place field, respectively. SOM interneuron silencing powerfully increased burst firing without altering the theta phase of spikes. In contrast, PV interneuron silencing had no effect on burst firing, but instead shifted the spikes' theta phase toward the trough of theta. These findings indicate that perisomatic and dendritic inhibition have distinct roles in controlling the rate, burst and timing of hippocampal pyramidal cells.

  9. Damage detection and locating using tone burst and continuous excitation modulation method

    Science.gov (United States)

    Li, Zheng; Wang, Zhi; Xiao, Li; Qu, Wenzhong

    2014-03-01

    Among structural health monitoring techniques, nonlinear ultrasonic spectroscopy methods are found to be effective diagnostic approach to detecting nonlinear damage such as fatigue crack, due to their sensitivity to incipient structural changes. In this paper, a nonlinear ultrasonic modulation method was developed to detect and locate a fatigue crack on an aluminum plate. The method is different with nonlinear wave modulation method which recognizes the modulation of low-frequency vibration and high-frequency ultrasonic wave; it recognizes the modulation of tone burst and high-frequency ultrasonic wave. In the experiment, a Hanning window modulated sinusoidal tone burst and a continuous sinusoidal excitation were simultaneously imposed on the PZT array which was bonded on the surface of an aluminum plate. The modulations of tone burst and continuous sinusoidal excitation was observed in different actuator-sensor paths, indicating the presence and location of fatigue crack. The results of experiments show that the proposed method is capable of detecting and locating the fatigue crack successfully.

  10. Inhibition of NMDARs in the nucleus reticularis of the thalamus produces delta frequency bursting

    Directory of Open Access Journals (Sweden)

    Yuchun Zhang

    2009-11-01

    Full Text Available Injection of NMDAR antagonist into the thalamus can produce delta frequency EEG oscillations in the thalamocortical system. It is surprising that an antagonist of an excitatory neurotransmitter should trigger such activity, and the mechanism is unknown. One hypothesis is that the antagonist blocks excitation of GABAergic cells, thus producing disinhibition. To test this hypothesis, we investigated the effect of NMDAR antagonist (APV on cells of the nucleus reticularis (nRT in rat brain slices, a thalamic nucleus that can serve as a pacemaker for thalamocortical delta oscillations and that is composed entirely of GABAergic neurons. We found, unexpectedly, that nRT cells are hyperpolarized by APV. This occurs because these cells have an unusual form of NMDAR (probably NR2C that contributes inward current at resting potential in response to ambient glutamate. The hyperpolarization produced by APV is sufficient to deinactivate T-type calcium channels, and these trigger rhythmic bursting at delta frequency. The APV-induced delta frequency bursting is abolished by dopamine D2 receptor antagonist, indicating that dopamine and NMDAR antagonist work synergistically to stimulate delta frequency bursting. Our results have significant implications concerning the electrophysiological basis of schizophrenia and bring together the NMDAR hypofunction, dopamine, and GABA theories of the disease. Our results suggest that NMDAR hypofunction and dopamine work synergistically on the GABAergic cells of the nRT to generate the delta frequency EEG oscillations, a thalamocortical dysrhythmia (TCD in the awake state that is an established abnormality in schizophrenia.

  11. High-speed noncontact acoustic inspection method for civil engineering structure using multitone burst wave

    Science.gov (United States)

    Sugimoto, Tsuneyoshi; Sugimoto, Kazuko; Kosuge, Nobuaki; Utagawa, Noriyuki; Katakura, Kageyoshi

    2017-07-01

    The noncontact acoustic inspection method focuses on the resonance phenomenon, and the target surface is measured by being vibrated with an airborne sound. It is possible to detect internal defects near the surface layer of a concrete structure from a long distance. However, it requires a fairly long measurement time to achieve the signal-to-noise (S/N) ratio just to find some resonance frequencies. In our method using the conventional waveform “single-tone burst wave”, only one frequency was used for one-sound-wave emission to achieve a high S/N ratio using a laser Doppler vibrometer (LDV) at a safe low power (e.g., He-Ne 1 mW). On the other hand, in terms of the difference in propagation velocity between laser light and sound waves, the waveform that can be used for high-speed measurement was devised using plural frequencies for one-sound-wave emission (“multitone burst wave”). The measurement time at 35 measurement points has been dramatically decreased from 210 to 28 s when using this waveform. Accordingly, 7.5-fold high-speed measurement became possible. By some demonstration experiments, we confirmed the effectiveness of our measurement technique.

  12. Cancer phototherapy via selective photoinactivation of respiratory chain oxidase to trigger a fatal superoxide anion burst.

    Science.gov (United States)

    Wu, Shengnan; Zhou, Feifan; Wei, Yanchun; Chen, Wei R; Chen, Qun; Xing, Da

    2014-02-10

    Here, we develop a novel cancer treatment modality using mitochondria-targeting, high-fluence, low-power laser irradiation (HF-LPLI) in mouse tumor models and explore the mechanism of mitochondrial injury by HF-LPLI. We demonstrated that the initial reaction after photon absorption was photosensitization of cytochrome c oxidase (COX), to inhibit enzymatic activity of COX in situ and cause respiratory chain superoxide anion (O2(-•)) burst. We also found that HF-LPLI exerted its main tumor killing effect through mitochondrial O2(-•) burst via electron transport chain (ETC). These phenomena were completely absent in the respiration-deficient cells and COX knockdown cells. With a carefully selected irradiation protocol, HF-LPLI could efficaciously destroy tumors. The inhibition of enzymatic activity of COX and generation of O2(-•) by HF-LPLI in vivo were also detected. It is the first time that the mechanism involved in the interaction between light and its photoacceptor under HF-LPLI treatment is clarified. Our results clearly indicate that HF-LPLI initiates its effects via targeted COX photoinactivation and that the tumor-killing efficacy is dependent of the subsequent mitochondrial O2(-•) burst via ETC. Based on both in vitro and in vivo results, we conclude that HF-LPLI can selectively photoinactivate respiratory chain oxidase to trigger a fatal mitochondrial O2(-•) burst, producing oxidative damage on cancer cells. This study opens up the possibilities of applications of HF-LPLI as a mitochondria-targeting cancer phototherapy.

  13. Sevoflurane-induced isoelectric EEG and burst suppression: differential and antagonistic effect of added nitrous oxide.

    Science.gov (United States)

    Niu, B; Xiao, J Y; Fang, Y; Zhou, B Y; Li, J; Cao, F; Tian, Y K; Mei, W

    2017-05-01

    The objective of this study was to investigate whether nitrous oxide influenced the ED50 of sevoflurane for induction of isoelectric electroencephalogram (ED50isoelectric ) differently from its influence on the ED50 of sevoflurane for electroencephalogram burst suppression (ED50burst ). In a prospective, randomised, double-blind, parallel group, up-down sequential allocation study, 77 ASA physical status 1 and 2 patients received sevoflurane induction and, after tracheal intubation, were randomly allocated to receive sevoflurane with either 40% oxygen in air (control group) or 60% nitrous oxide in oxygen mixture (nitrous group). The ED50isoelectric in the two groups was determined using Dixon's up and down method, starting at 2.5% with 0.2% step size of end-tidal sevoflurane. The electroencephalogram was considered as isoelectric when a burst suppression ratio of 100% lasted > 1 min. The subsequent concentrations of sevoflurane administered were determined by the presence or absence of isoelectric electroencephalogram in the previous patient in the same group. The ED50isoelectric in the nitrous group 4.08 (95%CI, 3.95-4.38)% was significantly higher than that in the control group 3.68 (95%CI, 3.50-3.78)% (p nitrous group and control group, respectively (p = 0.52). The addition of 60% nitrous oxide increases ED50isoelectric , but not the ED50burst of sevoflurane. Neither result indicates an additive effect of anaesthetic agents, as might be expected, and possible reasons for this are discussed. © 2017 The Authors. Anaesthesia published by John Wiley & Sons Ltd on behalf of Association of Anaesthetists of Great Britain and Ireland.

  14. Are contemporary tourists consuming distance?

    DEFF Research Database (Denmark)

    Larsen, Gunvor Riber

    2012. Background The background for this research, which explores how tourists represent distance and whether or not distance can be said to be consumed by contemporary tourists, is the increasing leisure mobility of people. Travelling for the purpose of visiting friends and relatives is increasing......, and is being seen as an important activity for 'social life conducted at-a-distance' (Larsen et al, 2007: 244), and holidaying away from home has become an integral part of contemporary life (cf: Krippendorf, 1987; Hall, 2008; Urry, 1995; 2002a). Distances to other places are obviously a fundamental part...... by tourists in an increasingly mobile contemporary society. The research questions guiding this inquiry into distance's status in contemporary leisure mobility reflects the aims of the research: • How is distance being represented in the literature? (guiding the literature review) • How is distance being...

  15. Stress Effects on Stop Bursts in Five Languages

    Directory of Open Access Journals (Sweden)

    Marija Tabain

    2016-11-01

    Full Text Available This study examines the effects of stress on the stop burst in five languages differing in number of places of articulation, as reflected in burst duration, spectral centre of gravity, and ­spectral standard deviation. The languages studied are English (three places of articulation /p t k/, the Indonesian language Makasar (four places /p t c k/, and the Central Australian languages ­Pitjantjatjara, Warlpiri (both five places /p t ʈ c k/, and Arrernte (six places /p t̪ t ʈ c k/. We find that languages differ in how they manifest stress on the consonant, with Makasar not ­showing any effect of stress at all, and Warlpiri showing an effect on burst duration, but not on the ­spectral measures. For the other languages, the velar /k/ has a “darker” quality (i.e., lower spectral centre of gravity, and/or a less diffuse spectrum (i.e., lower standard deviation under stress; while the alveolar /t/ has a “lighter” quality under stress. In addition, the dental /t̪/ has a more diffuse spectrum under stress. We suggest that this involves enhancement of the features [grave] and [diffuse] under stress, with velars being [+grave] and [–diffuse], alveolars being [–grave], and dentals being [+diffuse]. We discuss the various possible spectral effects of enhancement of these features. Finally, in the languages with five or six places of articulation, the stop burst is longer only for the palatal /c/ and the velar /k/, which have intrinsically long burst durations, and not for the anterior coronals /t̪ t ʈ/, which have intrinsically short burst durations. We suggest that in these systems, [burst duration] is a feature that separates these two groups of consonants.

  16. Waste indicators

    Energy Technology Data Exchange (ETDEWEB)

    Dall, O.; Lassen, C.; Hansen, E. [Cowi A/S, Lyngby (Denmark)

    2003-07-01

    The Waste Indicator Project focuses on methods to evaluate the efficiency of waste management. The project proposes the use of three indicators for resource consumption, primary energy and landfill requirements, based on the life-cycle principles applied in the EDIP Project. Trial runs are made With the indicators on paper, glass packaging and aluminium, and two models are identified for mapping the Danish waste management, of which the least extensive focuses on real and potential savings. (au)

  17. Quantum Minimum Distance Classifier

    Directory of Open Access Journals (Sweden)

    Enrica Santucci

    2017-12-01

    Full Text Available We propose a quantum version of the well known minimum distance classification model called Nearest Mean Classifier (NMC. In this regard, we presented our first results in two previous works. First, a quantum counterpart of the NMC for two-dimensional problems was introduced, named Quantum Nearest Mean Classifier (QNMC, together with a possible generalization to any number of dimensions. Secondly, we studied the n-dimensional problem into detail and we showed a new encoding for arbitrary n-feature vectors into density operators. In the present paper, another promising encoding is considered, suggested by recent debates on quantum machine learning. Further, we observe a significant property concerning the non-invariance by feature rescaling of our quantum classifier. This fact, which represents a meaningful difference between the NMC and the respective quantum version, allows us to introduce a free parameter whose variation provides, in some cases, better classification results for the QNMC. The experimental section is devoted: (i to compare the NMC and QNMC performance on different datasets; and (ii to study the effects of the non-invariance under uniform rescaling for the QNMC.

  18. Planning with Reachable Distances

    KAUST Repository

    Tang, Xinyu

    2009-01-01

    Motion planning for spatially constrained robots is difficult due to additional constraints placed on the robot, such as closure constraints for closed chains or requirements on end effector placement for articulated linkages. It is usually computationally too expensive to apply sampling-based planners to these problems since it is difficult to generate valid configurations. We overcome this challenge by redefining the robot\\'s degrees of freedom and constraints into a new set of parameters, called reachable distance space (RD-space), in which all configurations lie in the set of constraint-satisfying subspaces. This enables us to directly sample the constrained subspaces with complexity linear in the robot\\'s number of degrees of freedom. In addition to supporting efficient sampling, we show that the RD-space formulation naturally supports planning, and in particular, we design a local planner suitable for use by sampling-based planners. We demonstrate the effectiveness and efficiency of our approach for several systems including closed chain planning with multiple loops, restricted end effector sampling, and on-line planning for drawing/sculpting. We can sample single-loop closed chain systems with 1000 links in time comparable to open chain sampling, and we can generate samples for 1000-link multi-loop systems of varying topology in less than a second. © 2009 Springer-Verlag.

  19. Coping with Distances

    DEFF Research Database (Denmark)

    Bærenholdt, Jørgen Ole

    Coping with distances - Producing Nordic Atlantic Societies Mennesker håndterer afstande og producerer derved samfund. Dette er det grundlæggende synspunkt i en afhandling, hvor samfund ikke tages for givet. Samfund er tværtimod noget som hele tiden må produceres, genproduceres og forandres, og det...... været afgørende. Afhandlingen tages sit afsæt i en teoretisk diskussion af begreberne samfund, håndtering (coping på engelsk), social kapital, territorialitet, mobilitet, bonding (stærke identitetsbærende bånd) og bridging (svage, brobyggende forbindelser). Der gås på tværs af vante skel mellem kultur...... trussel mod samfundsbygningen. Men kap. 6 viser de mange måder hvori gennem turismen bidrager til samfundsbygningen, og det er en historie som indledes med en grundig diskussion af opdagelsesrejsernes grundlæggende betydning, også kulturelt. Begge disse kapitler tilføjer coping tilgangen flere analytiske...

  20. Sensitivity of the High Altitude Water Cherenkov Experiment to observe Gamma-Ray Bursts

    Science.gov (United States)

    González, M. M.

    Ground based telescopes have marginally observed very high energy emission (>100GeV) from gamma-ray bursts(GRB). For instance, Milagrito observed GRB970417a with a significance of 3.7 sigmas over the background. Milagro have not yet observed TeV emission from a GRB with its triggered and untriggered searches or GeV emission with a triggered search using its scalers. These results suggest the need of new observatories with higher sensitivity to transient sources. The HAWC (High Altitute Water Cherenkov) observatory is proposed as a combination of the Milagro tecnology with a very high altitude (>4000m over see level) site. The expected HAWC sensitivity for GRBs is at least >10 times the Milagro sensitivity. In this work HAWC sensitivity for GRBs is discussed for different detector configurations such as altitude, distance between PMTs, depth under water of PMTs, number of PMTs required for a trigger, etc.

  1. Neutrino and cosmic-ray emission from multiple internal shocks in gamma-ray bursts.

    Science.gov (United States)

    Bustamante, Mauricio; Baerwald, Philipp; Murase, Kohta; Winter, Walter

    2015-04-10

    Gamma-ray bursts (GRBs) are short-lived, luminous explosions at cosmological distances, thought to originate from relativistic jets launched at the deaths of massive stars. They are among the prime candidates to produce the observed cosmic rays at the highest energies. Recent neutrino data have, however, started to constrain this possibility in the simplest models with only one emission zone. In the classical theory of GRBs, it is expected that particles are accelerated at mildly relativistic shocks generated by the collisions of material ejected from a central engine. Here we consider neutrino and cosmic-ray emission from multiple emission regions since these internal collisions must occur at very different radii, from below the photosphere all the way out to the circumburst medium, as a consequence of the efficient dissipation of kinetic energy. We demonstrate that the different messengers originate from different collision radii, which means that multi-messenger observations open windows for revealing the evolving GRB outflows.

  2. Quality indicators

    DEFF Research Database (Denmark)

    Hjorth-Andersen, Christian

    1991-01-01

    to the issue of how well these indicators perform, using market data provided by consumer magazines from 3 countries. The results strongly indicate that price is a poor quality indicator. The paper also presents some evidence which suggests that seller reputation and easily observable characteristics are also......In recent literature it has been suggested that consumers need have no knowledge of product quality as a number of quality indicators (or signals) may be used as substitutes. Very little attention has been paid to the empirical verification of these studies. The present paper is devoted...

  3. The Musical Emotional Bursts: A validated set of musical affect bursts to investigate auditory affective processing.

    Directory of Open Access Journals (Sweden)

    Sébastien ePaquette

    2013-08-01

    Full Text Available The Musical Emotional Bursts (MEB consist of 80 brief musical executions expressing basic emotional states (happiness, sadness and fear and neutrality. These musical bursts were designed to be the musical analogue of the Montreal Affective Voices (MAV – a set of brief non-verbal affective vocalizations portraying different basic emotions. The MEB consist of short (mean duration: 1.6 sec improvisations on a given emotion or of imitations of a given MAV stimulus, played on a violin (n:40 or a clarinet (n:40. The MEB arguably represent a primitive form of music emotional expression, just like the MAV represent a primitive form of vocal, nonlinguistic emotional expression. To create the MEB, stimuli were recorded from 10 violinists and 10 clarinetists, and then evaluated by 60 participants. Participants evaluated 240 stimuli (30 stimuli x 4 [3 emotions + neutral] x 2 instruments by performing either a forced-choice emotion categorization task, a valence rating task or an arousal rating task (20 subjects per task; 40 MAVs were also used in the same session with similar task instructions. Recognition accuracy of emotional categories expressed by the MEB (n:80 was lower than for the MAVs but still very high with an average percent correct recognition score of 80.4%. Highest recognition accuracies were obtained for happy clarinet (92.0% and fearful or sad violin (88.0% each MEB stimuli. The MEB can be used to compare the cerebral processing of emotional expressions in music and vocal communication, or used for testing affective perception in patients with communication problems.

  4. Classifying LISA gravitational wave burst signals using Bayesian evidence

    Energy Technology Data Exchange (ETDEWEB)

    Feroz, Farhan; Graff, Philip; Hobson, Michael P; Lasenby, Anthony [Astrophysics Group, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Gair, Jonathan R, E-mail: jgair@ast.cam.ac.u [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom)

    2010-04-07

    We consider the problem of characterization of burst sources detected by the Laser Interferometer Space Antenna (LISA) using the multi-modal nested sampling algorithm, MultiNest. We use MultiNest as a tool to search for modelled bursts from cosmic string cusps, and compute the Bayesian evidence associated with the cosmic string model. As an alternative burst model, we consider sine-Gaussian burst signals, and show how the evidence ratio can be used to choose between these two alternatives. We present results from an application of MultiNest to the last round of the Mock LISA Data Challenge, in which we were able to successfully detect and characterize all three of the cosmic string burst sources present in the release data set. We also present results of independent trials and show that MultiNest can detect cosmic string signals with signal-to-noise ratio (SNR) as low as approx7 and sine-Gaussian signals with SNR as low as approx8. In both cases, we show that the threshold at which the sources become detectable coincides with the SNR at which the evidence ratio begins to favour the correct model over the alternative.

  5. Langmuir Bursts and Filamentary Double Layers in Plasmas.

    Science.gov (United States)

    Theisen, William L.

    1994-01-01

    This thesis reports the results of new studies involving laboratory plasma double layers. Filamentary double layers were created in a triple plasma device. The radial size of the current filament, and central plasma column were varied using a variable aperture R _{rm O}. The scaling of the double layer potential drop V_{ rm dl} with the parameter jd ^2, where j is the current density in the double layer and d is the double layer thickness, was determined for several filament radii. For relatively large values of the filament radius, the one-dimensional (Langmuir) scaling was obeyed. For smaller values of the filament radius, the potential drop became less dependent on the parameter jd^2. Langmuir bursts were observed in the high potential region of anode double layers when a sufficient supply of cold electrons was available to make a bump on tail distribution of electrons. The electric fields of Langmuir bursts were determined by observing deflections of a beam from an electron gun. The electric field of the bursts was strong enough to allow for caviton formation and Langmuir collapse. Other properties of the bursts were also recorded, including characteristic frequencies, burst height, width, and time distributions.

  6. Photocontrol of bud burst involves gibberellin biosynthesis in Rosa sp.

    Science.gov (United States)

    Choubane, Djillali; Rabot, Amélie; Mortreau, Eric; Legourrierec, Jose; Péron, Thomas; Foucher, Fabrice; Ahcène, Youyou; Pelleschi-Travier, Sandrine; Leduc, Nathalie; Hamama, Latifa; Sakr, Soulaiman

    2012-09-01

    Light is a critical determinant of plant shape by controlling branching patterns and bud burst in many species. To gain insight into how light induces bud burst, we investigated whether its inductive effect in rose was related to gibberellin (GA) biosynthesis. In axillary buds of beheaded plants subject to light, the expression of two GA biosynthesis genes (RoGA20ox and RoGA3ox) was promptly and strongly induced, while that of a GA-catabolism genes (RoGA2ox) was reduced. By contrast, lower expression levels of these two GA biosynthesis genes were found in darkness, and correlated with a total inhibition of bud burst. This effect was dependent on both light intensity and quality. In in vitro cultured buds, the inductive effect of light on the growth of preformed leaves and SAM organogenic activity was inhibited by ancymidol and paclobutrazol, two effectors of GA biosynthesis. This effect was concentration-dependent, and negated by GA(3). However, GA(3) alone could not rescue bud burst in the dark. GA biosynthesis was also required for the expression and activity of a vacuolar invertase, and therefore for light-induced sugar metabolism within buds. These findings are evidence that GA biosynthesis contributes to the light effect on bud burst and lay the foundations of a better understanding of its exact role in plant branching. Copyright © 2012 Elsevier GmbH. All rights reserved.

  7. Are There Multiple Populations of Fast Radio Bursts?

    Science.gov (United States)

    Palaniswamy, Divya; Li, Ye; Zhang, Bing

    2018-02-01

    The repeating FRB 121102 (the “repeater”) shows repetitive bursting activities and was localized in a host galaxy at z = 0.193. On the other hand, despite dozens of hours of telescope time spent on follow-up observations, no other fast radio bursts (FRBs) have been observed to repeat. Yet, it has been speculated that the repeater is the prototype of FRBs, and that other FRBs should show similar repeating patterns. Using the published data, we compare the repeater with other FRBs in the observed time interval (Δt)–flux ratio (S i /S i+1) plane. We find that whereas other FRBs occupy the upper (large S i /S i+1) and right (large Δt) regions of the plane due to the non-detections of other bursts, some of the repeater bursts fall into the lower left region of the plot (short interval and small flux ratio) excluded by the non-detection data of other FRBs. The trend also exists even if one only selects those bursts detectable by the Parkes radio telescope. If other FRBs were similar to the repeater, our simulations suggest that the probability that none of them have been detected to repeat with the current searches would be ∼(10‑4–10‑3). We suggest that the repeater is not representative of the entire FRB population, and that there is strong evidence of more than one population of FRBs.

  8. Study on Monitoring Rock Burst through Drill Pipe Torque

    Directory of Open Access Journals (Sweden)

    Zhonghua Li

    2015-01-01

    Full Text Available This paper presents a new method to identify the danger of rock burst from the response of drill pipe torque during drilling process to overcome many defects of the conventional volume of drilled coal rubble method. It is based on the relationship of rock burst with coal stress and coal strength. Through theoretic analysis, the change mechanism of drill pipe torque and the relationship of drill pipe torque with coal stress, coal strength, and drilling speed are investigated. In light of the analysis, a new device for testing drill pipe torque is developed and a series of experiments is performed under different conditions; the results show that drill pipe torque linearly increases with the increase of coal stress and coal strength; the faster the drilling speed, the larger the drill pipe torque, and vice versa. When monitoring rock burst by drill pipe torque method, the index of rock burst is regarded as a function in which coal stress index and coal strength index are principal variables. The results are important for the forecast of rock burst in coal mine.

  9. An internally consistent gamma ray burst time history phenomenology

    Science.gov (United States)

    Cline, T. L.

    1985-01-01

    A phenomenology for gamma ray burst time histories is outlined. Order of their generally chaotic appearance is attempted, based on the speculation that any one burst event can be represented above 150 keV as a superposition of similarly shaped increases of varying intensity. The increases can generally overlap, however, confusing the picture, but a given event must at least exhibit its own limiting characteristic rise and decay times if the measurements are made with instruments having adequate temporal resolution. Most catalogued observations may be of doubtful or marginal utility to test this hypothesis, but some time histories from Helios-2, Pioneer Venus Orbiter and other instruments having one-to several-millisecond capabilities appear to provide consistency. Also, recent studies of temporally resolved Solar Maximum Mission burst energy spectra are entirely compatible with this picture. The phenomenology suggested here, if correct, may assist as an analytic tool for modelling of burst processes and possibly in the definition of burst source populations.

  10. A novel contention solution strategy based on priority for optical burst switching networks

    Science.gov (United States)

    Guan, Ai-Hong; Cui, Fang-Fang

    2010-11-01

    A fundamental issue in optical burst switching (OBS) networks is to solve the burst contention for the core node. In this paper, a novel priority-based contention solution strategy for OBS networks is proposed. When the contention occurs, the burst priority is considered firstly, and then the burst segmentation method is used for the low priority bursts in this strategy. Ensuring the integrity of high priority bursts, part of the segmented bursts can be transmitted to the destination node via combining wavelength conversion and optical buffer method. Simulation results show that the proposed scheme not only ensures the integrity of high priority bursts, but also reduces the packet loss rate of the low priority bursts maximally, so that it can support good quality of service (QoS) for the network.

  11. A Study of Distance of Manipulation on the Responsive Workbench

    OpenAIRE

    Paljic, Alexis; Coquillart, Sabine; Burkhardt, Jean-Marie; Richard, Paul

    2002-01-01

    International audience; Virtual environments such as the Responsive Workbench allow the close manipulation of virtual objects. We define close manipulation as either direct manipulation or manipulation at a relatively small distance. This paper reports on two studies on close manipulation using the Responsive Workbench. The first study investigates the influence of manipulation distance on performance in a 3D location task. The results indicate that direct manipulation and 20 cm distance mani...

  12. Distance : between deixis and perspectivity

    OpenAIRE

    Meermann, Anastasia; Sonnenhauser, Barbara

    2015-01-01

    Discussing exemplary applications of the notion of distance in linguistic analysis, this paper shows that very different phenomena are described in terms of this concept. It is argued that in order to overcome the problems arising from this mixup, deixis, distance and perspectivity have to be distinguished and their interrelations need to be described. Thereby, distance emerges as part of a recursive process mediating between situation-bound deixis and discourse-level perspectivity. This is i...

  13. Solar Indices

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Collection includes a variety of indices related to solar activity contributed by a number of national and private solar observatories located worldwide. This...

  14. RBC indices

    Science.gov (United States)

    ... this. The results are used to diagnose different types of anemia . ... These test results indicate the type of anemia: MCV below normal. Microcytic anemia (may be due to low iron levels, lead poisoning, or thalassemia ). MCV normal. Normocytic anemia (may ...

  15. Geographical Indications

    OpenAIRE

    Anechitoae Constantin; Grigoru? Lavinia-Maria

    2011-01-01

    “The denomination of origin” may be the name of a region, a specific place or country used to describe an agricultural or food product. "The geographical indication" may be the name of a region, a specific place or a country, used to describe an agricultural or food product. The indication of provenance and the denomination of origin serve to identify the source and origin of goods or services.

  16. Bifurcation structure of a model of bursting pancreatic cells

    DEFF Research Database (Denmark)

    Mosekilde, Erik; Lading, B.; Yanchuk, S.

    2001-01-01

    One- and two-dimensional bifurcation studies of a prototypic model of bursting oscillations in pancreatic P-cells reveal a squid-formed area of chaotic dynamics in the parameter plane, with period-doubling bifurcations on one side of the arms and saddle-node bifurcations on the other. The transit......One- and two-dimensional bifurcation studies of a prototypic model of bursting oscillations in pancreatic P-cells reveal a squid-formed area of chaotic dynamics in the parameter plane, with period-doubling bifurcations on one side of the arms and saddle-node bifurcations on the other....... The transition from this structure to the so-called period-adding structure is found to involve a subcritical period-doubling bifurcation and the emergence of type-III intermittency. The period-adding transition itself is not smooth but consists of a saddle-node bifurcation in which (n + 1)-spike bursting...

  17. Nanoemulsions obtained via bubble-bursting at a compound interface

    Science.gov (United States)

    Feng, Jie; Roché, Matthieu; Vigolo, Daniele; Arnaudov, Luben N.; Stoyanov, Simeon D.; Gurkov, Theodor D.; Tsutsumanova, Gichka G.; Stone, Howard A.

    2014-08-01

    Bursting of bubbles at an air/liquid interface is a familiar occurrence relevant to foam stability, cell cultures in bioreactors and ocean-atmosphere mass transfer. In the latter case, bubble-bursting leads to the dispersal of sea-water aerosols in the surrounding air. Here we show that bubbles bursting at a compound air/oil/water-with-surfactant interface can disperse submicrometre oil droplets in water. Dispersal results from the detachment of an oil spray from the bottom of the bubble towards water during bubble collapse. We provide evidence that droplet size is selected by physicochemical interactions between oil molecules and the surfactants rather than by hydrodynamics. We demonstrate the unrecognized role that this dispersal mechanism may play in the fate of the sea surface microlayer and of pollutant spills by dispersing petroleum in the water column. Finally, our system provides an energy-efficient route, with potential upscalability, for applications in drug delivery, food production and materials science.

  18. Creep Burst Testing of a Woven Inflatable Module

    Science.gov (United States)

    Selig, Molly M.; Valle, Gerard D.; James, George H.; Oliveras, Ovidio M.; Jones, Thomas C.; Doggett, William R.

    2015-01-01

    A woven Vectran inflatable module 88 inches in diameter and 10 feet long was tested at the NASA Johnson Space Center until failure from creep. The module was pressurized pneumatically to an internal pressure of 145 psig, and was held at pressure until burst. The external environment remained at standard atmospheric temperature and pressure. The module burst occurred after 49 minutes at the target pressure. The test article pressure and temperature were monitored, and video footage of the burst was captured at 60 FPS. Photogrammetry was used to obtain strain measurements of some of the webbing. Accelerometers on the test article measured the dynamic response. This paper discusses the test article, test setup, predictions, observations, photogrammetry technique and strain results, structural dynamics methods and quick-look results, and a comparison of the module level creep behavior to the strap level creep behavior.

  19. A kinetic model for the burst phase of processive cellulases

    DEFF Research Database (Denmark)

    Præstgaard, Eigil; Olsen, Jens Elmerdahl; Murphy, Leigh

    2011-01-01

    Cellobiohydrolases (exocellulases) hydrolyze cellulose processively, i.e. by sequential cleaving of soluble sugars from one end of a cellulose strand. Their activity generally shows an initial burst, followed by a pronounced slowdown, even when substrate is abundant and product accumulation...... is negligible. Here, we propose an explicit kinetic model for this behavior, which uses classical burst phase theory as the starting point. The model is tested against calorimetric measurements of the activity of the cellobiohydrolase Cel7A from Trichoderma reesei on amorphous cellulose. A simple version...... of the model, which can be solved analytically, shows that the burst and slowdown can be explained by the relative rates of the sequential reactions in the hydrolysis process and the occurrence of obstacles for the processive movement along the cellulose strand. More specifically, the maximum enzyme activity...

  20. Possible mechanism of bursting suppression in nociceptive neurons.

    Science.gov (United States)

    Dick, O E; Krylov, B V; Nozdrachev, A D

    2017-03-01

    The use of the mathematical model of rat nociceptive neuron membrane allowed us to predict a new mechanism of suppression of ectopic bursting discharges, which arise in neurons of dorsal root ganglia and are one of the causes of neuropathic pain. The treatment with comenic acid leads to switching off the ectopic bursting discharges due to a decrease in the effective charge transferring via the activation gating structure of the slow sodium channels (Na V1.8a). Comenic acid is a drug substance of a new non-opioid analgesic [1] Thus, this analgesic not only reduces the frequency of rhythmic discharges of nociceptive neuron membrane [2] but also it suppresses its ectopic bursting discharges.

  1. Dosimetry characterization of the Godiva Reactor under burst conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hickman, D. P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Heinrichs, D. P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hudson, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wong, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ward, D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Wilson, C. [Atomic Weapons Establishment (AWE), Berkshire (United Kingdom); Clark, L. [Atomic Weapons Establishment (AWE), Berkshire (United Kingdom); Trompier, F. [Inst. for Radiation Protection and Nuclear Safety, Fontenay-aux-Roses (France)

    2017-06-22

    A series of sixteen (16) burst irradiations were performed in May 2014, fifteen of which were part of an international collaboration to characterize the Godiva IV fast burst reactor at the National Criticality Experiments Research Center (NCERC). Godiva IV is a bare cylindrical assembly of approximately 65 kg of highly enriched uranium fuel (93.2% 235U metal alloyed with 1.5% molybdenum for strength) and is designed to perform controlled prompt critical excursions (Myers 2010, Goda 2013). Twelve of the irradiations were dedicated to neutron spectral measurements using a Bonner multiple sphere spectrometer. Three irradiations, with core temperature increases of 71.1°C, 136.9°C, and 229.9°C, were performed for generating comparative fluence data, establishing corrections for varying heights, testing linearity with burst temperature, and establishing gamma dose characteristics.

  2. First upper limits from LIGO on gravitational wave bursts

    Energy Technology Data Exchange (ETDEWEB)

    B. Abbott et al.

    2004-03-09

    We report on a search for gravitational wave bursts using data from the first science run of the LIGO detectors. Our search focuses on bursts with durations ranging from 4 ms to 100 ms, and with significant power in the LIGO sensitivity band of 150 to 3000 Hz. We bound the rate for such detected bursts at less than 1.6 events per day at 90% confidence level. This result is interpreted in terms of the detection efficiency for ad hoc waveforms (Gaussians and sine-Gaussians) as a function of their root-sum-square strain h{sub rss}; typical sensitivities lie in the range h{sub rss} {approx} 10{sup -19} - 10{sup -17} strain/{radical}Hz, depending on waveform. We discuss improvements in the search method that will be applied to future science data from LIGO and other gravitational wave detectors.

  3. GRB 120521C at z ∼ 6 and the properties of high-redshift γ-ray bursts

    Energy Technology Data Exchange (ETDEWEB)

    Laskar, Tanmoy; Berger, Edo; Zauderer, B. Ashley; Margutti, Raffaella; Fong, Wen-fai [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Tanvir, Nial; Wiersema, Klaas [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Levan, Andrew [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Perley, Daniel [Department of Astronomy, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Menten, Karl [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Hrudkova, Marie [Isaac Newton Group of Telescopes, Apartado de Correos 321, E-387 00 Santa Cruz de la Palma, Canary Islands (Spain)

    2014-01-20

    We present optical, near-infrared, and radio observations of the afterglow of GRB 120521C. By modeling the multi-wavelength data set, we derive a photometric redshift of z ≈ 6.0, which we confirm with a low signal-to-noise ratio spectrum of the afterglow. We find that a model with a constant-density environment provides a good fit to the afterglow data, with an inferred density of n ≲ 0.05 cm{sup –3}. The radio observations reveal the presence of a jet break at t {sub jet} ≈ 7 d, corresponding to a jet opening angle of θ{sub jet} ≈ 3°. The beaming-corrected γ-ray and kinetic energies are E {sub γ} ≈ E{sub K} ≈ 3 × 10{sup 50} erg. We quantify the uncertainties in our results using a detailed Markov Chain Monte Carlo analysis, which allows us to uncover degeneracies between the physical parameters of the explosion. To compare GRB 120521C to other high-redshift bursts in a uniform manner we re-fit all available afterglow data for the two other bursts at z ≳ 6 with radio detections (GRBs 050904 and 090423). We find a jet break at t {sub jet} ≈ 15 d for GRB 090423, in contrast to previous work. Based on these three events, we find that γ-ray bursts (GRBs) at z ≳ 6 appear to explode in constant-density environments, and exhibit a wide range of energies and densities that span the range inferred for lower redshift bursts. On the other hand, we find a hint for narrower jets in the z ≳ 6 bursts, potentially indicating a larger true event rate at these redshifts. Overall, our results indicate that long GRBs share a common progenitor population at least to z ∼ 8.

  4. A Novel QKD-based Secure Edge Router Architecture Design for Burst Confidentiality in Optical Burst Switched Networks

    Science.gov (United States)

    Balamurugan, A. M.; Sivasubramanian, A.

    2014-06-01

    The Optical Burst Switching (OBS) is an emergent result to the technology issue that could achieve a viable network in future. They have the ability to meet the bandwidth requisite of those applications that call for intensive bandwidth. The field of optical transmission has undergone numerous advancements and is still being researched mainly due to the fact that optical data transmission can be done at enormous speeds. The concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution and quality of service (QoS). This paper proposes a framework based on QKD based secure edge router architecture design to provide burst confidentiality. The QKD protocol offers high level of confidentiality as it is indestructible. The design architecture was implemented in FPGA using diverse models and the results were taken. The results show that the proposed model is suitable for real time secure routing applications of the Optical burst switched networks.

  5. X-ray Bursts from the Accreting Millisecond Pulsar XTE J1814-338

    OpenAIRE

    Strohmayer, Tod E.; Markwardt, Craig B.; Swank, Jean H.; Zand, Jean in 't

    2003-01-01

    Since the discovery of the accreting millisecond pulsar XTE J1814-338 a total of 27 thermonuclear bursts have been observed from the source with the Proportional Counter Array (PCA) onboard the Rossi X-ray Timing Explorer (RXTE). Spectroscopy of the bursts, as well as the presence of continuous burst oscillations, suggests that all but one of the bursts are sub-Eddington. The remaining burst has the largest peak bolometric flux of 2.64 x E^-8 erg/sec/cm^2, as well as a gap in the burst oscill...

  6. Traffic characteristics analysis in optical burst switching networks with optical label processing

    Directory of Open Access Journals (Sweden)

    Edson Moschim

    2007-03-01

    Full Text Available An analysis is carried out with burst-switching optical networks which use label processing consisting of orthogonal optical codes (OOC, considering traffic characteristics such as length/duration and arrival rate of bursts. Main results show that the use of OOC label processing influences on the decrease of burst loss probability, especially for short-lived bursts. Therefore, short bursts that would be blocked in conventional electronic processing networks are transmitted when the OOC label processing is used. Thus, an increase in the network use occurs as well as a decrease in the burst transmission latency, reaching a granularity close to packets networks.

  7. Finite Element Modelling and Retained Life Estimation of Corroded Pipelines in Consideration of Burst Pressures—A Fractural Mechanics Approach

    Directory of Open Access Journals (Sweden)

    Chinedu I. Ossai

    2017-10-01

    Full Text Available This study used Finite Element Modelling (FEM to determine the relationship between the burst pressure (Pb of internally, circumferentially corroded pipelines, with the corrosion defect depth (d, pipe wall thickness (t and the pipe diameter (D. After modelling X46 and X52 grades of pipes, the Pb estimated was compared with those determined experimentally and with industry standard models—ASME B31G (modified, RSTRENG, DNV F101, SHELL92 and FITNET FFS. The comparison specified a Root Mean Square Percentage Error (RMSPE that ranged from 7.06% to 20.4% and a coefficient of determination (R2 that varied from 0.7932 to 0.9813. Multivariate regression was also used to compute a general linear relationship between the burst pressure (Pb and (d/t, (L/D and (L/√Dt. The resulting FEM burst-pressure model, developed with multivariate regression, was later used to estimate the expected allowable operating pressure of a corroded X46 grade pipeline over the lifecycle duration, for low, mild, high and severe corrosion categories. It was observed that the burst pressure retention ratio (Rr, which is an indicator of the reliability of the pipeline, decreased with the increase in (d but did not show distinctive changes with the increase in (L. Considering the robustness of the FEM developed in this study, it can be concluded that it will be very vital for flowline design and pipeline integrity management.

  8. Examining the limits of cellular adaptation bursting mechanisms in biologically-based excitatory networks of the hippocampus.

    Science.gov (United States)

    Ferguson, K A; Njap, F; Nicola, W; Skinner, F K; Campbell, S A

    2015-12-01

    Determining the biological details and mechanisms that are essential for the generation of population rhythms in the mammalian brain is a challenging problem. This problem cannot be addressed either by experimental or computational studies in isolation. Here we show that computational models that are carefully linked with experiment provide insight into this problem. Using the experimental context of a whole hippocampus preparation in vitro that spontaneously expresses theta frequency (3-12 Hz) population bursts in the CA1 region, we create excitatory network models to examine whether cellular adaptation bursting mechanisms could critically contribute to the generation of this rhythm. We use biologically-based cellular models of CA1 pyramidal cells and network sizes and connectivities that correspond to the experimental context. By expanding our mean field analyses to networks with heterogeneity and non all-to-all coupling, we allow closer correspondence with experiment, and use these analyses to greatly extend the range of parameter values that are explored. We find that our model excitatory networks can produce theta frequency population bursts in a robust fashion.Thus, even though our networks are limited by not including inhibition at present, our results indicate that cellular adaptation in pyramidal cells could be an important aspect for the occurrence of theta frequency population bursting in the hippocampus. These models serve as a starting framework for the inclusion of inhibitory cells and for the consideration of additional experimental features not captured in our present network models.

  9. Impact of Bimodal Traffic on Latency in Optical Burst Switching Networks

    Directory of Open Access Journals (Sweden)

    Yuhua Chen

    2008-01-01

    Full Text Available This paper analyzes the impact of bimodal traffic composition on latency in optical burst switching networks. In particular, it studies the performance degradation to short-length packets caused by longer packets, both of which are part of a heterogeneous traffic model. The paper defines a customer satisfaction index for each of the classes of traffic, and a composite satisfaction index. The impact of higher overall utilization of the network as well as that of the ratio of the traffic mix on each of the customer satisfaction indices is specifically addressed.

  10. The afterglow and complex environment of the optically dim burst GRB 980613

    DEFF Research Database (Denmark)

    Hjorth, J.; Thomsen, Bente; Nielsen, S.R.

    2002-01-01

    not exhibit an unusually rapid decay (power-law decay slope alpha X-ray spectral index (beta(RX) approximate to 0.6), indicating a maximal reddening of the afterglow of approximate to0.45 mag in R. Hence, the dimness......We report the identification of the optical afterglow of GRB 980613 in R- and I-band images obtained between 16 and 48 hr after the gamma-ray burst. Early near-infrared (NIR) H and K' observations are also reported. The afterglow was optically faint (R approximate to 23) at discovery but did...

  11. On the bursting of linear polymer melts in inflation processes

    DEFF Research Database (Denmark)

    Rasmussen, Henrik Koblitz; Bach, Anders

    2005-01-01

    Molten LLDPE and HDPE plates (thickness 2 mm) have been inflated into a circular cylinder (inner radius 31 mm) under isothermal conditions. Low deformation rates allow the plates to be inflated considerably into the cylinder, and at high inflation rates an early burst is observed. Axis-symmetric ......Molten LLDPE and HDPE plates (thickness 2 mm) have been inflated into a circular cylinder (inner radius 31 mm) under isothermal conditions. Low deformation rates allow the plates to be inflated considerably into the cylinder, and at high inflation rates an early burst is observed. Axis...

  12. Traffic Grooming on WDM Rings Using Optical Burst Transport

    Science.gov (United States)

    Hsueh, Yu-Li; Kim, Jaedon; Su, Ching-Fong; Rabbat, Richard; Hamada, Takeo; Tian, Cechan; Kazovsky, Leonid G.

    2006-01-01

    A sublambda traffic-grooming scheme on wavelength-division-multiplexed (WDM) rings, which is called optical burst transport (OBT), is proposed. The network protocol and architecture allow increased flexibility to tailor the transport network behavior for efficient delivery of bursty data traffic. Using different network parameters, its performance is analyzed via simulation, and the implementation issues including the media-access-control (MAC) protocol, tunable-filter controller, and burst-mode receiver are addressed. Finally, the feasibility of the OBT with an experimental testbed built by the authors is demonstrated and a streaming-video application is used to present its overall functionality.

  13. Impact of Burst Buffer Architectures on Application Portability

    Energy Technology Data Exchange (ETDEWEB)

    Harms, Kevin [Argonne National Lab. (ANL), Argonne, IL (United States); Oral, H. Sarp [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). National Center for Computational Science; Atchley, Scott [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). National Center for Computational Science; Vazhkudai, Sudharshan S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). National Center for Computational Science

    2016-09-30

    The Oak Ridge and Argonne Leadership Computing Facilities are both receiving new systems under the Collaboration of Oak Ridge, Argonne, and Livermore (CORAL) program. Because they are both part of the INCITE program, applications need to be portable between these two facilities. However, the Summit and Aurora systems will be vastly different architectures, including their I/O subsystems. While both systems will have POSIX-compliant parallel file systems, their Burst Buffer technologies will be different. This difference may pose challenges to application portability between facilities. Application developers need to pay attention to specific burst buffer implementations to maximize code portability.

  14. Testing and Performance of UFFO Burst Alert & Trigger Telescope

    DEFF Research Database (Denmark)

    Rípa, Jakub; Bin Kim, Min; Lee, Jik

    2014-01-01

    The Ultra-Fast Flash Observatory pathfinder (UFFO-p) is a new space mission dedicated to detect Gamma-Ray Bursts (GRBs) and rapidly follow their afterglows in order to provide early optical/ultraviolet measurements. A GRB location is determined in a few seconds by the UFFO Burst Alert & Trigger...... telescope (UBAT) employing the coded mask imaging technique and the detector combination of Yttrium Oxyorthosilicate (YSO) scintillating crystals and multi-anode photomultiplier tubes. The results of the laboratory tests of UBAT’s functionality and performance are described in this article. The detector...

  15. OPTICAL BURST SWITCHING PROTOCOLS IN ALL-OPTICAL NETWORKS

    OpenAIRE

    KIRCI, Pınar; ZAİM, A.Halim

    2012-01-01

    In this paper, all optical network's  general structure  is briefly described  and all optical network's optical switching methods is concantrated on. All  optical network's  classification is presented according to switching methods  and burst switching methods studied carefully.The protocols which are defined for burst switching are studied. One of these protocols JET (Just-Enough-Time) which is mostly studied, is introduced. And the other protocol JIT (Just-In-Time) is prese...

  16. GRO: Black hole models for gamma ray bursts

    Science.gov (United States)

    Shaham, Jacob

    1993-01-01

    This grant deals with the production of gamma-ray bursts (GRB's) close to horizons of black holes (BH's), mainly via accretion of small chunks of matter onto extreme Kerr BH's. In the past year, we laid the ground work for actual calculations close to Kerr BH's. Because of technical reasons, actual work has only started very recently. Following the detailed list of research subprojects as per our original proposal, we have performed research in the following areas: spectrum calculation; burst dynamics; tidal capture and primordial cloud collapse; halo density profile; and capture of other objects.

  17. Iron inhibits respiratory burst of peritoneal phagocytes in vitro

    DEFF Research Database (Denmark)

    Gotfryd, Kamil; Jurek, Aleksandra; Kubit, Piotr

    2011-01-01

    Objective. This study examines the effects of iron ions Fe(3+) on the respiratory burst of phagocytes isolated from peritoneal effluents of continuous ambulatory peritoneal dialysis (CAPD) patients, as an in vitro model of iron overload in end-stage renal disease (ESRD). Material and Methods....... Respiratory burst of peritoneal phagocytes was measured by chemiluminescence method. Results. At the highest used concentration of iron ions Fe(3+) (100 µM), free radicals production by peritoneal phagocytes was reduced by 90% compared to control. Conclusions. Iron overload may increase the risk of infectious...

  18. Manifestation of peripherial coding in the effect of increasing loudness and enhanced discrimination of the intensity of tone bursts before and after tone burst noise

    Science.gov (United States)

    Rimskaya-Korsavkova, L. K.

    2017-07-01

    To find the possible reasons for the midlevel elevation of the Weber fraction in intensity discrimination of a tone burst, a comparison was performed for the complementary distributions of spike activity of an ensemble of space nerves, such as the distribution of time instants when spikes occur, the distribution of interspike intervals, and the autocorrelation function. The distribution properties were detected in a poststimulus histogram, an interspike interval histogram, and an autocorrelation histogram—all obtained from the reaction of an ensemble of model space nerves in response to an auditory noise burst-useful tone burst complex. Two configurations were used: in the first, the peak amplitude of the tone burst was varied and the noise amplitude was fixed; in the other, the tone burst amplitude was fixed and the noise amplitude was varied. Noise could precede or follow the tone burst. The noise and tone burst durations, as well as the interval between them, was 4 kHz and corresponded to the characteristic frequencies of the model space nerves. The profiles of all the mentioned histograms had two maxima. The values and the positions of the maxima in the poststimulus histogram corresponded to the amplitudes and mutual time position of the noise and the tone burst. The maximum that occurred in response to the tone burst action could be a basis for the formation of the loudness of the latter (explicit loudness). However, the positions of the maxima in the other two histograms did not depend on the positions of tone bursts and noise in the combinations. The first maximum fell in short intervals and united intervals corresponding to the noise and tone burst durations. The second maximum fell in intervals corresponding to a tone burst delay with respect to noise, and its value was proportional to the noise amplitude or tone burst amplitude that was smaller in the complex. An increase in tone burst or noise amplitudes was caused by nonlinear variations in the two

  19. Position indicator

    Science.gov (United States)

    Tanner, David E.

    1981-01-01

    A nuclear reactor system is described in which a position indicator is provided for detecting and indicating the position of a movable element inside a pressure vessel. The movable element may be a valve element or similar device which moves about an axis. Light from a light source is transmitted from a source outside the pressure vessel to a first region inside the pressure vessel in alignment with the axis of the movable element. The light is redirected by a reflector prism to a second region displaced radially from the first region. The reflector prism moves in response to movement of the movable element about its axis such that the second region moves arcuately with respect to the first region. Sensors are arrayed in an arc corresponding to the arc of movement of the second region and signals are transmitted from the sensors to the exterior of the reactor vessel to provide indication of the position of the movable element.

  20. Hotspot advance speed - hotspot size/core-hotspot distance relation ...

    African Journals Online (AJOL)

    We examined the evolution of extragalactic radio sources using the observed corehotspot distance and hotspot size. Analysis indicates a fairly strong positive correlation in the ratio of core-hotspot distance to hotspot size between that of the approaching arm and the receding arm with a correlation coefficient of r ~ 0.7.

  1. Openness and Quality in Asian Distance Education Technology ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    It will do so by establishing a set of quality assurance standards and performance indicators for Asian ICT-supported distance education in various settings (formal, ... Openness and quality in Asian distance education : sub-project 7b; evaluation of the effectiveness of RLO-based OER in enhancing the soft skills of students.

  2. Openness and Quality in Asian Distance Education Technology ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    It will do so by establishing a set of quality assurance standards and performance indicators for Asian ICT-supported distance education in various settings (formal, ... education : sub-project 5; development and evaluation of use of distance education technologies for enriching clinical practicum in nursing in the Philippines.

  3. Idealization and Communication in Long-Distance Premarital Relationships.

    Science.gov (United States)

    Stafford, Laura; Reske, James R.

    1990-01-01

    Explored the phenomenon of idealization in college premarital long-distance relationships. Analyzed questionnaire responses of 71 college couples. Findings indicated long-distance couples had more restricted communication and were more idealized than their geographically close counterparts. Found an associative pattern between restricted…

  4. A Model for Scaffolding Traditional Distance Learners in Africa for ...

    African Journals Online (AJOL)

    How can we solve the lull in uptake and usage of online learning amongst traditional distance learners in Africa? Several online learning initiatives are taking place in Africa, but a critical assessment of their impact in terms of increasing access to higher education through distance learning indicates, in most cases, lack of ...

  5. Distance criterion for hydrogen bond

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Distance criterion for hydrogen bond. In a D-H ...A contact, the D...A distance must be less than the sum of van der Waals Radii of the D and A atoms, for it to be a hydrogen bond.

  6. Distance labeling schemes for trees

    DEFF Research Database (Denmark)

    Alstrup, Stephen; Gørtz, Inge Li; Bistrup Halvorsen, Esben

    2016-01-01

    We consider distance labeling schemes for trees: given a tree with n nodes, label the nodes with binary strings such that, given the labels of any two nodes, one can determine, by looking only at the labels, the distance in the tree between the two nodes. A lower bound by Gavoille et al. [Gavoill...

  7. The Psychology of Psychic Distance

    DEFF Research Database (Denmark)

    Håkanson, Lars; Ambos, Björn; Schuster, Anja

    2016-01-01

    and their theoretical underpinnings assume psychic distances to be symmetric. Building on insights from psychology and sociology, this paper demonstrates how national factors and cognitive processes interact in the formation of asymmetric distance perceptions. The results suggest that exposure to other countries...

  8. Virtual Bioinformatics Distance Learning Suite

    Science.gov (United States)

    Tolvanen, Martti; Vihinen, Mauno

    2004-01-01

    Distance learning as a computer-aided concept allows students to take courses from anywhere at any time. In bioinformatics, computers are needed to collect, store, process, and analyze massive amounts of biological and biomedical data. We have applied the concept of distance learning in virtual bioinformatics to provide university course material…

  9. Quality Content in Distance Education

    Science.gov (United States)

    Yildiz, Ezgi Pelin; Isman, Aytekin

    2016-01-01

    In parallel with technological advances in today's world of education activities can be conducted without the constraints of time and space. One of the most important of these activities is distance education. The success of the distance education is possible with content quality. The proliferation of e-learning environment has brought a need for…

  10. Distance transforms: Academics versus industry

    NARCIS (Netherlands)

    van den Broek, Egon; Schouten, Th.E.

    In image and video analysis, distance transformations (DT) are frequently used. They provide a distance image (DI) of background pixels to the nearest object pixel. DT touches upon the core of many applications; consequently, not only science but also industry has conducted a significant body of

  11. Current Trends in Distance Education.

    Science.gov (United States)

    Gaspar, Richard F.; Thompson, Theron D.

    1995-01-01

    Defines distance education; provides a historical background; discusses emerging modes of instruction, including interactive television, computer-mediated communication, electronic mail, and national and international networks; and considers the future of distance education, including the use of the Internet, multimedia, and a new paradigm for…

  12. Distance delivery of nutrition education.

    Science.gov (United States)

    Mazurak, Vera C; Whybrow, Ellen; Varnhagen, Stanley; Field, Catherine J

    2005-01-01

    Questions often arise about the quality of an educational experience in a distance format. Debate exists as to whether the relatively new format of on-line education can offer an equivalent learning experience for students, and the perception remains that virtual learning is impersonal. We examined students' experience in an introductory undergraduate nutrition course that had been remodelled as an asynchronous, active-learning, student-centred model. The investigation used the framework of instructional message design, a concept based on cognitive science principles, to highlight themes in student survey and focus group data. Results indicate that a motivating and accessible quality educational experience is possible in an on-line format through a student-centred model. Such a model provides a means to offer education to a diverse and larger audience. Further investigation is needed to determine faculty professional development needs and cost-effective ways to expand the model. Such a model provides alternatives to expand delivery to encourage interest in the field, and to provide continuing education for allied professionals and the general public.

  13. Distance and Properties of NGC 4993 as the Host Galaxy of the Gravitational-wave Source GW170817

    Science.gov (United States)

    Im, Myungshin; Yoon, Yongmin; Lee, Seong-Kook J.; Lee, Hyung Mok; Kim, Joonho; Lee, Chung-Uk; Kim, Seung-Lee; Troja, Eleonora; Choi, Changsu; Lim, Gu; Ko, Jongwan; Shim, Hyunjin

    2017-11-01

    Recently, the optical counterpart of the gravitational-wave source GW170817 has been identified in the NGC 4993 galaxy. Together with evidence from observations in electromagnetic waves, the event has been suggested as a result of a merger of two neutron stars (NSs). We analyze the multi-wavelength data to characterize the host galaxy property and its distance to examine if the properties of NGC 4993 are consistent with this picture. Our analysis shows that NGC 4993 is a bulge-dominated galaxy with {r}{eff}˜ 2{--}3 {kpc} and a Sérsic index of n=3{--}4 for the bulge component. The spectral energy distribution from 0.15 to 24 μm indicates that this galaxy has no significant ongoing star formation, a mean stellar mass of (0.3{--}1.2)× {10}11 {M}⊙ , a mean stellar age greater than ˜3 Gyr, and a metallicity of about 20%-100% of solar abundance. Optical images reveal dust lanes and extended features that suggest a past merging activity. Overall, NGC 4993 has characteristics of normal, but slightly disturbed elliptical galaxies. Furthermore, we derive the distance to NGC 4993 with the fundamental plane relation using 17 parameter sets of 7 different filters and the central stellar velocity dispersion from the literature, finding an angular diameter distance of 37.7 ± 8.7 Mpc. NGC 4993 is similar to some host galaxies of short gamma-ray bursts (GRBs) but much different from those of long GRBs, supporting the picture of GW170817 as a result of the merger of two NSs.

  14. Distance and Properties of NGC 4993 as the Host Galaxy of the Gravitational-wave Source GW170817

    Science.gov (United States)

    Im, Myungshin; Yoon, Yongmin; Lee, Seong-Kook J.; Lee, Hyung Mok; Kim, Joonho; Lee, Chung-Uk; Kim, Seung-Lee; Troja, Eleonora; Choi, Changsu; Lim, Gu; Ko, Jongwan; Shim, Hyunjin

    2017-11-01

    Recently, the optical counterpart of the gravitational-wave source GW170817 has been identified in the NGC 4993 galaxy. Together with evidence from observations in electromagnetic waves, the event has been suggested as a result of a merger of two neutron stars (NSs). We analyze the multi-wavelength data to characterize the host galaxy property and its distance to examine if the properties of NGC 4993 are consistent with this picture. Our analysis shows that NGC 4993 is a bulge-dominated galaxy with {r}{eff}∼ 2{--}3 {kpc} and a Sérsic index of n=3{--}4 for the bulge component. The spectral energy distribution from 0.15 to 24 μm indicates that this galaxy has no significant ongoing star formation, a mean stellar mass of (0.3{--}1.2)× {10}11 {M}ȯ , a mean stellar age greater than ∼3 Gyr, and a metallicity of about 20%–100% of solar abundance. Optical images reveal dust lanes and extended features that suggest a past merging activity. Overall, NGC 4993 has characteristics of normal, but slightly disturbed elliptical galaxies. Furthermore, we derive the distance to NGC 4993 with the fundamental plane relation using 17 parameter sets of 7 different filters and the central stellar velocity dispersion from the literature, finding an angular diameter distance of 37.7 ± 8.7 Mpc. NGC 4993 is similar to some host galaxies of short gamma-ray bursts (GRBs) but much different from those of long GRBs, supporting the picture of GW170817 as a result of the merger of two NSs.

  15. yield indicators

    African Journals Online (AJOL)

    YIELD INDICATORS. P. NTAWURUHUNGA, P.R. RUBAIHAYOI, J.B.A. WHYTE, A.G.O. DIXONZ and use. osnzu1. International Institute of Tropical Agriculture, East and Southern Africa, Centre, PO. Box 7878, l Kampala ... most important sources of food energy in several ... efficiency in selecting and identifying cassava.

  16. Anthropometric indices

    DEFF Research Database (Denmark)

    Oguoma, V. M.; Nwose, E. U.; Skinner, T. C.

    2016-01-01

    BACKGROUND: The current anthropometric indices used for diagnosis of cardio-metabolic syndrome (CMS) in sub-Saharan Africa are those widely validated in the western world. We hereby aim to compare the sensitivity and specificity of these tools in identifying risk factors for CMS. METHOD: The study...

  17. Distributions of solar drift-pair bursts in frequency from decameter radio observations

    Science.gov (United States)

    Stanislavsky, Aleksander; Volvach, Yaroslav

    2017-04-01

    Statement of the Problem: Solar drift-pair (DP) bursts are one of interesting manifestations of solar activity. Observed during the solar storms of type III bursts, they demonstrate a very simple form on dynamic radio spectra as two short components separated in time, often the second component being the full repetition of the first. As is well known, type III bursts are produced by the accelerated electrons propagating along open magnetic field lines in solar corona. However, no each storm of type III bursts leads to any DP. The role of electron beams in the generation of DPs remains unclear. Solar DPs are detected by ground-based instruments at decameter and meter wavelengths, but each individual DP occupies only a limited bandwidth in the frequency range. The bursts drift in frequency, and their frequency drift rate can be both negative and positive (so-called the forward and reverse DPs), from -2 MHz/s to 6 MHz/s [1]. Besides, there are cases of vertical DPs, which occur simultaneously in all the frequencies within their bandwidth. It is difficult to interpret them by means of a moving source, as any exciting agent responsible for such bursts would travel with velocities faster than velocity of light [2]. Methodology & Experimental Orientation: New features of modern low-frequency radio astronomy allow us to study the empirical properties of DPs more deeply than ever before. Our results are based on the recent radio data (during 10-12 July of 2015) obtained with help of the UTR-2 radio telescope at frequencies 9-33 MHz with the time resolution of 50 ms and the frequency resolution of 4 kHz. We have identified 301 DP bursts in which 209 events were forward (FDP), and the rest were reverse (RDP). Results & Significance: According to the data, the occurrence of FDPs decreased at high frequencies, whereas the number of RDPs had an opposite tendency, they rarely occured at lower frequencies. During the observational session, at 20-25 MHz almost the same amount of

  18. Assessment of Andragogical Attributes of Distance Learners

    Science.gov (United States)

    Hashim, Rugayah Gy; Ahmad, Hashim; Ahmad, Nor'aini

    The purpose of this research was to assess the andragogical attribute of adult students engaged in distance learning, specifically, with regards to the main construct, cognitive engagement versus academic achievement. Five hundred students were sampled and the response rate was 33.8%. From the analyses, the overall mean score for cognitive engagement is 3.75 from a scale of one to seven. The results indicated that knowledge gained through the e-distance learning is low and this evidence correlates to the average academic performance or CGPA of the respondents, which is between 2.50-2.99. The findings indicated a low level of integration and motivation in learning and consequently it is suggested that training programs and additional course revisions be integrated into the curriculum to ensure the chances of student success and reduce attrition rate.

  19. Synchrotron cooling in energetic gamma-ray bursts observed by the Fermi Gamma-Ray Burst Monitor

    OpenAIRE

    Yu, Hoi Fung; Greiner, Jochen; van Eerten, Hendrik; Burgess, J. Michael; P. Narayana Bhat; Briggs, Michael S.; Connaughton, Valerie; Diehl, Roland; Goldstein, Adam; Gruber, David; Jenke, Peter A.; von Kienlin, Andreas; Kouveliotou, Chryssa; Paciesas, William S.; Pelassa, Veronique

    2015-01-01

    Context. We study the time-resolved spectral properties of energetic gamma-ray bursts (GRBs) with good high-energy photon statistics observed by the Gamma-Ray Burst Monitor (GBM) onboard the Fermi Gamma-Ray Space Telescope. Aims. We aim to constrain in detail the spectral properties of GRB prompt emission on a time-resolved basis and to discuss the theoretical implications of the fitting results in the context of various prompt emission models. Methods. Our sample comprises eight GRBs observe...

  20. DO THE FERMI GAMMA-RAY BURST MONITOR AND SWIFT BURST ALERT TELESCOPE SEE THE SAME SHORT GAMMA-RAY BURSTS?

    Energy Technology Data Exchange (ETDEWEB)

    Burns, Eric; Briggs, Michael S. [University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Connaughton, Valerie [Universities Space Research Association, Science and Technology Institute, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Zhang, Bin-Bin [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Lien, Amy [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Goldstein, Adam [NASA Postdoctoral Program, Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Pelassa, Veronique [Smithsonian Astrophysical Observatory, P.O. Box 97, Amado, AZ 85645 (United States); Troja, Eleonora, E-mail: eb0016@uah.edu [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2016-02-20

    Compact binary system mergers are expected to generate gravitational radiation detectable by ground-based interferometers. A subset of these, the merger of a neutron star with another neutron star or a black hole, are also the most popular model for the production of short gamma-ray bursts (GRBs). The Swift Burst Alert Telescope (BAT) and the Fermi Gamma-ray Burst Monitor (GBM) trigger on short GRBs (SGRBs) at rates that reflect their relative sky exposures, with the BAT detecting 10 per year compared to about 45 for GBM. We examine the SGRB populations detected by Swift BAT and Fermi GBM. We find that the Swift BAT triggers on weaker SGRBs than Fermi GBM, providing they occur close to the center of the BAT field of view, and that the Fermi GBM SGRB detection threshold remains flatter across its field of view. Overall, these effects combine to give the instruments the same average sensitivity, and account for the SGRBs that trigger one instrument but not the other. We do not find any evidence that the BAT and GBM are detecting significantly different populations of SGRBs. Both instruments can detect untriggered SGRBs using ground searches seeded with time and position. The detection of SGRBs below the on-board triggering sensitivities of Swift BAT and Fermi GBM increases the possibility of detecting and localizing the electromagnetic counterparts of gravitational wave (GW) events seen by the new generation of GW detectors.