Science.gov

Sample records for outburst thermonuclear runaways

  1. The Thermonuclear Runaway and the Classical Nova Outburst

    NASA Astrophysics Data System (ADS)

    Starrfield, S.; Iliadis, C.; Hix, W. R.

    2016-05-01

    Nova explosions occur on the white dwarf component of a cataclysmic variable binary stellar system that is accreting matter lost by its companion. When sufficient material has been accreted by the white dwarf, a thermonuclear runaway occurs and ejects material in what is observed as a classical nova explosion. We describe both the recent advances in our understanding of the progress of the outburst and outline some of the puzzles that are still outstanding. We report on the effects of improving both the nuclear reaction rate library and including a modern nuclear reaction network in our one-dimensional, fully implicit, hydrodynamic computer code. In addition, there has been progress in observational studies of supernovae Ia with implications about the progenitors, and we discuss that in this review.

  2. The Nova Outburst: Thermonuclear Runaways on Degenerated Dwarfs

    SciTech Connect

    Starrfield, S.; Truran, J.W.; Sparks, W.M.

    1999-07-08

    Observational and theoretical studies of the outbursts of classical novae have provided critical insights into a broad range of astrophysical phenomena. Thermonuclear runaways (TNRs) in accreted hydrogen-rich envelopes on the white dwarf (WD) components of close binary systems constitute not only the outburst mechanism for a classical nova explosion, but also the recurrent novae and a fraction of the symbiotic novae explosions. Studies of the general characteristics of these explosions, both in our own galaxy and in neighboring galaxies of varying metallicity, can teach us about binary stellar evolution, while studies of the evolution of nova binary systems can constrain models for the (as yet unidentified) progenitors of Type Ia supernovae. Further, the empirical relation between the peak luminosity of a nova and the rate of decline, which presents a challenge to theoretical models, allows novae to be utilized as standard candles for distance determinations out to the Virgo Cluster. E xtensive studies of novae with IUE and the resulting abundance determinations have revealed the existence of oxygen-neon white dwarfs in some systems. The high levels of enrichment of novae ejecta in elements ranging from carbon to sulfur confirm that there is significant dredge-up of matter from the core of the underlying white dwarf and enable novae to contribute to the chemical enrichment of the interstellar medium. Observations of the epoch of dust formation in the expanding shells of novae allow important constraints to be placed on the dust formation process and confirm that graphite, SiC, and SiO{sub 2} grains are formed by the outburst. It is possible that grains from novae were injected into the pre-solar nebula and can be identified with some of the pre-solar grains or ''stardust'' found in meteorites. Finally, g-ray observations during the first several years of their outburst, using the next generation of satellite observatories, could confirm

  3. Thermonuclear runaways in nova outbursts. 2: Effect of strong, instantaneous, local fluctuations

    NASA Technical Reports Server (NTRS)

    Shankar, Anurag; Arnett, David

    1994-01-01

    In an attempt to understand the manner in which nova outbursts are initiated on the surface of a white dwarf, we investigate the effects fluctuations have on the evolution of a thermonuclear runaway. Fluctuations in temperature density, or the composition of material in the burning shell may arise due to the chaotic flow field generated by convection when it occurs, or by the accretion process itself. With the aid of two-dimensional reactive flow calculations, we consider cases where a strong fluctutation in temperature arises during the early, quiescent accretion phase or during the later, more dynamic, explosion phase. In all cases we find that an instantaneous, local temperature fluctuation causes the affected material to become Rayleigh-Taylor unstable. The rapid rise and subsequent expansion of matter immediately cools the hot blob, which prevents the lateral propagation of burning. This suggests that local temperature fluctuations do not play a significant role in directly initiating the runaway, especially during the early stages. However, they may provide an efficient mechanism of mixing core material into the envelope (thereby pre-enriching the fuel for subsequent episodes of explosive hydrogen burning) and of mixing substantial amounts of the radioactive nucleus N-13 into the surface layers, making novae potential gamma-ray sources. This suggests that it is the global not the local, evolution of the core-envelope interface to high temperatures which dominates the development of the runaway. We also present a possible new scenario for the initiation of nova outbursts based on our results.

  4. A hydrodynamic study of a slow nova outburst. [computerized simulation of thermonuclear runaway in white dwarf envelope

    NASA Technical Reports Server (NTRS)

    Sparks, W. M.; Starrfield, S.; Truran, J. W.

    1978-01-01

    The paper reports use of a Lagrangian implicit hydrodynamics computer code incorporating a full nuclear-reaction network to follow a thermonuclear runaway in the hydrogen-rich envelope of a 1.25 solar-mass white dwarf. In this evolutionary sequence the envelope was assumed to be of normal (solar) composition and the resulting outburst closely resembles that of the slow nova HR Del. In contrast, previous CNO-enhanced models resemble fast nova outbursts. The slow-nova model ejects material by radiation pressure when the high luminosity of the rekindled hydrogen shell source exceeds the local Eddington luminosity of the outer layers. This is in contrast to the fast nova outburst where ejection is caused by the decay of the beta(+)-unstable nuclei. Nevertheless, radiation pressure probably plays a major role in ejecting material from the fast nova remnants. Therefore, the sequence from slow to fast novae can be interpreted as a sequence of white dwarfs with increasing amounts of enhanced CNO nuclei in their hydrogen envelopes, although other parameters such as the white-dwarf mass and accretion rate probably contribute to the observed variation between novae.

  5. A burst from a thermonuclear runaway on an ONeMg white dwarf

    NASA Technical Reports Server (NTRS)

    Starrfield, S.; Politano, M.; Truran, J. W.; Sparks, W. M.

    1992-01-01

    Studies which examine the consequences of accretion, at rates of 10(exp -9) solar mass/yr and 10(exp -10) solar mass/yr, onto an ONeMg white dwarf with a mass of 1.35 solar masses are performed. In these studies, a Lagrangian, hydrodynamic, one-dimensional computer code was used. The code now includes a network with 89 nuclei up to Ca-40, elemental diffusion, new opacities, and new equation of state. The initial abundance distribution corresponded to a mixture that was enriched to either 25, 50, or 75 percent in products of carbon burning. The remaining material in each case is assumed to have a solar composition. The evolution of the thermonuclear runaway in the 1.35 solar mass white dwarf, with M = 10(exp -9) solar mass, produced peak temperatures in the shell source exceeding 300 million degrees. The sequence produced significant amounts of Na-22 from proton captures onto Ne-20 and significant amounts of Al-26 from proton captures on Mg-24. This sequence ejected 5.2 x 10(exp -6) solar mass moving with speeds from approximately 100 km/s to 2300 km/s. When the mass accretion rate was decreased to 10(exp -10) solar mass, the resulting thermonuclear runaway produced a shock that moved through the outer envelope of the white dwarf and raised the surface luminosity to L greater than 10(exp 7) solar luminosity and the effective temperature to values exceeding 10(exp 7) K. The interaction of the material expanding from off of the white dwarf with the accretion disk should produce a burst of gamma-rays.

  6. CNO nucleosynthesis and the nova outburst

    NASA Technical Reports Server (NTRS)

    Starrfield, S.; Truran, J.; Sparks, W.

    1977-01-01

    Predictions for CNO nucleosynthesis by the classical nova outburst are presented. Properties of the nova phenomenon pertinent to the production of CNO isotopes are discussed, the effect of beta(+) unstable nuclei on outburst evolution is examined, and the need for enhanced CNO nuclei in the envelope is described. Possible mechanisms for producing such enhancement are considered, and recent observations of enhanced CNO nuclei in nova ejecta are reviewed. Results of model evolutionary calculations are outlined which show that a thermonuclear runaway in the hydrogen envelope of a carbon-oxygen white dwarf can reproduce the gross features of the classical nova outburst, that the behavior of the outburst depends at least on the hydrogen-envelope mass and the degree of CNO enhancement, and that all degrees of isotopic enhancement result in an outburst that may be compared with observed events. Two enhancement mechanisms are identified, both of which involve mixing in the envelope.

  7. Nova outbursts in the case of mild hibernation

    SciTech Connect

    Livio, M.; Shankar, A.; Truran, J.W.

    1988-02-01

    The necessary conditions for the production of strong thermonuclear runaways in the hibernation scenario are identified and explored. It is found that a reduction in the accretion rate by a factor of about 100, for a period longer than a few thousand years, is generally sufficient to ensure nova-type outbursts, even in the presence of rather high preoutburst accretion rates. Nova outbursts can be obtained under mild hibernation conditions on 1 solar mass white dwarfs as well as on very massive ones. A reduction in the accretion rate by a factor of 10 only is insufficient to produce a nova outburst, if the preoutburst accretion rate is as high as 10 to the -8th solar mass/yr. 28 references.

  8. Numerical Simulations of a Prompt Hard X-ray Emission During its Bright Outburst

    NASA Astrophysics Data System (ADS)

    Filippova, Ekaterina V.; Revnivtsev, M.; Lutovinov, A.

    2007-08-01

    We present a simple numerical model of the X-ray emission of the system XTE J0421+560/CI Cam during its bright outburst on 31 March 1998. Basing on the spectral and timing behavior of the object we argue that this outburst is a prompt X-ray/hard X-ray emission of a classical nova-type explosion (thermonuclear runaway on the surface of the white dwarf) unlike many other outbursts of X-ray binary systems. The thermonuclear runaway on the surface of the white dwarf leads to the formation of fast ejecta which moves through the dense stellar wind of the optical companion (B giant). Shock waves, which are formed in the material of the wind and that of the ejecta heats the matter up to X-ray temperatures. We use the spherically symmetric Lagrangian hydro- simulation to follow the evolution of the explosion. Up to now we have extensively simulated early phases of the outburst and showed that using of physically motivated simulations one can put constrains on the velocity of the ejecta and the stellar companion mass loss rate. In order to follow X-ray evolution throughout the whole outburst we develop a fully adaptive code.

  9. Target of Opportunity Observations of TOADS: Finding the Dust in Super-Outburst Ejecta

    NASA Astrophysics Data System (ADS)

    Hoard, Donald; Ciardi, David; Howell, Steve

    2008-03-01

    Tremendous Outburst Amplitude Dwarf novae (TOADs) consist of a white dwarf primary star and an extremely low mass main sequence or brown dwarf-like secondary star. The latter fills its Roche lobe and transfers matter to the white dwarf through the inner Lagrange point into an accretion disk. TOADs undergo non-thermonuclear (i.e., disk instability) super-outbursts on timescales of decades. During the decline from super-outburst peak they display a characteristic dip in light curves at visible wavelengths, reminiscent of what is observed in slow classical (i.e., thermonuclear runaway) novae. In classical novae, the visible light dip is attributed to the formation of dust in the nova ejecta but, until now, the cause of the dip in TOAD light curves has remained unclear. In 2004, a previously unknown TOAD was discovered as it went into super-outburst, and our team was granted a Spitzer DDT program with which we have detected the likely formation of dust in the outburst ejecta. We now propose a Target of Opportunity program with Spitzer to observe an additional super-outbursting TOAD, in order to address the following questions: 1) Do all TOADs produce dust during their outbursts?; 2) What is the timescale for dust formation and dissipation?; 3) How much dust is produced during a super-outburst?; and 4) How does the dust production scale with the outburst amplitude? Spitzer is uniquely capable of detecting and characterizing the dust formed in the ejecta during super-outbursts and fundamentally changing the understanding of TOADs, their super-outbursts, and their contribution to the recycling of the interstellar medium.

  10. Swift observations of the 2015 outburst of AG Peg - from slow nova to classical symbiotic outburst

    NASA Astrophysics Data System (ADS)

    Ramsay, Gavin; Sokoloski, J. L.; Luna, G. J. M.; Nuñez, N. E.

    2016-10-01

    Symbiotic stars often contain white dwarfs with quasi-steady shell burning on their surfaces. However, in most symbiotics, the origin of this burning is unclear. In symbiotic slow novae, however, it is linked to a past thermonuclear runaway. In 2015 June, the symbiotic slow nova AG Peg was seen in only its second optical outburst since 1850. This recent outburst was of much shorter duration and lower amplitude than the earlier eruption, and it contained multiple peaks - like outbursts in classical symbiotic stars such as Z And. We report Swift X-ray and UV observations of AG Peg made between 2015 June and 2016 January. The X-ray flux was markedly variable on a time-scale of days, particularly during four days near optical maximum, when the X-rays became bright and soft. This strong X-ray variability continued for another month, after which the X-rays hardened as the optical flux declined. The UV flux was high throughout the outburst, consistent with quasi-steady shell burning on the white dwarf. Given that accretion discs around white dwarfs with shell burning do not generally produce detectable X-rays (due to Compton-cooling of the boundary layer), the X-rays probably originated via shocks in the ejecta. As the X-ray photoelectric absorption did not vary significantly, the X-ray variability may directly link to the properties of the shocked material. AG Peg's transition from a slow symbiotic nova (which drove the 1850 outburst) to a classical symbiotic star suggests that shell burning in at least some symbiotic stars is residual burning from prior novae.

  11. A pre-outburst signal in the long-term optical light curve of the recurrent nova RS Ophiuchi

    NASA Astrophysics Data System (ADS)

    Adamakis, S.; Eyres, S. P. S.; Sarkar, A.; Walsh, R. W.

    2011-07-01

    Recurrent novae are binary stars in which a white dwarf accretes matter from a less evolved companion, either a red giant or a main-sequence star. They have dramatic optical brightenings of around 5-6 mag in V in less than a day, several times a century. These occur at variable and unpredictable intervals, and are followed by an optical decline over several weeks and activity from the X-ray to the radio. The unpredictability of recurrent novae and related stellar types can hamper systematic study of their outbursts. Here we analyse the long-term light curve of RS Ophiuchi, a recurrent nova with six confirmed outbursts, most recently in 2006 February. We confirm the previously suspected 1945 outburst, largely obscured in a seasonal gap. We also find a signal via wavelet analysis that can be used to predict an incipient outburst up to a few hundred days before hand. This has never before been possible. In addition, this may suggest that the preferred thermonuclear runaway mechanism for the outbursts will have to be modified, as no pre-outburst signal is anticipated in that case. If our result indeed points to gaps in our understanding of how outbursts are driven, we will need to study such objects carefully to determine if the white dwarf is growing in mass, an essential factor if these systems are to become Type Ia supernovae. Determining the likelihood of recurrent novae being an important source population will have implications for stellar and galaxy evolution.

  12. Synthesis of C-rich dust in CO nova outbursts

    NASA Astrophysics Data System (ADS)

    José, Jordi; Halabi, Ghina M.; El Eid, Mounib F.

    2016-09-01

    Context. Classical novae are thermonuclear explosions that take place in the envelopes of accreting white dwarfs in stellar binary systems. The material transferred onto the white dwarf piles up under degenerate conditions, driving a thermonuclear runaway. In these outbursts, about 10-7-10-3 M⊙, enriched in CNO and sometimes other intermediate-mass elements (e.g., Ne, Na, Mg, or Al for ONe novae) are ejected into the interstellar medium. The large concentrations of metals spectroscopically inferred in the nova ejecta reveal that the solar-like material transferred from the secondary mixes with the outermost layers of the underlying white dwarf. Aims: Most theoretical models of nova outbursts reported to date yield, on average, outflows characterized by O > C, from which, in principle, only oxidized condensates (e.g., O-rich grains) would be expected. Methods: To specifically address whether CO novae can actually produce C-rich dust, six different hydrodynamic nova models have been evolved, from accretion to the expansion and ejection stages, with different choices for the composition of the substrate with which the solar-like accreted material mixes. Updated chemical profiles inside the H-exhausted core have been used, based on stellar evolution calculations for a progenitor of 8 M⊙ through H- and He-burning phases. Results: We show that these profiles lead to C-rich ejecta after the nova outburst. This extends the possible contribution of novae to the inventory of presolar grains identified in meteorites, particularly in a number of carbonaceous phases (i.e., nanodiamonds, silicon carbides, and graphites).

  13. Outbursts in Symbiotic Binaries

    NASA Technical Reports Server (NTRS)

    Sonneborn, George (Technical Monitor); Kenyon, Scott J.

    2004-01-01

    Two models have been proposed for the outbursts of symbiotic stars. In the thermonuclear model, outbursts begin when the hydrogen burning shell of a hot white dwarf reaches a critical mass. After a rapid increase in the luminosity and effective temperature, the white dwarf evolves at constant luminosity to lower effective temperatures, remains at optical maximum for several years, and then returns to quiescence along a white dwarf cooling curve. In disk instability models, the brightness rises when the accretion rate from the disk onto the central white dwarf abruptly increases by factors of 5-20. After a few month to several year period at maximum, both the luminosity and the effective temperature of the disk decline as the system returns to quiescence. If most symbiotic stars undergo thermonuclear eruptions, then symbiotics are probably poor candidates for type I supernovae. However, they can then provide approx. 10% of the material which stars recycle back into the interstellar medium. If disk instabilities are the dominant eruption mechanism, symbiotics are promising type Ia candidates but recycle less material into the interstellar medium.

  14. Outburst activity of the symbiiotic binary AG Dra

    NASA Astrophysics Data System (ADS)

    Gális, R.; Hric, L.; Leedjärv, L.; Merc, J.

    2016-03-01

    The outburst activity of the symbiotic system AG Dra has been studied using extensive spectroscopic observational material. High luminosity and temperature of the hot component of AG Dra indicate that quasi-steady thermonuclear shell burning takes place on the surface of the white dwarf. The major (cool) outbursts at the beginning of active phases might occur due to enhanced thermonuclear burning triggered by disk instability. Smaller scale hot outbursts might be explained by the accretion disc instability model like in dwarf novae. We discovered significant similarities in photometric and spectroscopic behaviour of AG Dra and prototypical symbiotic star Z And.

  15. Merging white dwarfs and thermonuclear supernovae.

    PubMed

    van Kerkwijk, M H

    2013-06-13

    Thermonuclear supernovae result when interaction with a companion reignites nuclear fusion in a carbon-oxygen white dwarf, causing a thermonuclear runaway, a catastrophic gain in pressure and the disintegration of the whole white dwarf. It is usually thought that fusion is reignited in near-pycnonuclear conditions when the white dwarf approaches the Chandrasekhar mass. I briefly describe two long-standing problems faced by this scenario, and the suggestion that these supernovae instead result from mergers of carbon-oxygen white dwarfs, including those that produce sub-Chandrasekhar-mass remnants. I then turn to possible observational tests, in particular, those that test the absence or presence of electron captures during the burning. PMID:23630372

  16. Merging white dwarfs and thermonuclear supernovae.

    PubMed

    van Kerkwijk, M H

    2013-06-13

    Thermonuclear supernovae result when interaction with a companion reignites nuclear fusion in a carbon-oxygen white dwarf, causing a thermonuclear runaway, a catastrophic gain in pressure and the disintegration of the whole white dwarf. It is usually thought that fusion is reignited in near-pycnonuclear conditions when the white dwarf approaches the Chandrasekhar mass. I briefly describe two long-standing problems faced by this scenario, and the suggestion that these supernovae instead result from mergers of carbon-oxygen white dwarfs, including those that produce sub-Chandrasekhar-mass remnants. I then turn to possible observational tests, in particular, those that test the absence or presence of electron captures during the burning.

  17. Nucleosynthesis in Thermonuclear Supernovae

    SciTech Connect

    Claudia, Travaglio; Hix, William Raphael

    2013-01-01

    We review our understanding of the nucleosynthesis that occurs in thermonuclear supernovae and their contribution to Galactic Chemical evolution. We discuss the prospects to improve the modeling of the nucleosynthesis within simulations of these events.

  18. Thermonuclear land of plenty

    NASA Astrophysics Data System (ADS)

    Gasior, P.

    2014-11-01

    Since the process of energy production in the stars has been identified as the thermonuclear fusion, this mechanism has been proclaimed as a future, extremely modern, reliable and safe for sustaining energetic needs of the humankind. However, the idea itself was rather straightforward and the first attempts to harness thermonuclear reactions have been taken yet in 40s of the twentieth century, it quickly appeared that physical and technical problems of domesticating exotic high temperature medium known as plasma are far from being trivial. Though technical developments as lasers, superconductors or advanced semiconductor electronics and computers gave significant contribution for the development of the thermonuclear fusion reactors, for a very long time their efficient performance was out of reach of technology. Years of the scientific progress brought the conclusions that for the development of the thermonuclear power plants an enormous interdisciplinary effort is needed in many fields of science covering not only plasma physics but also material research, superconductors, lasers, advanced diagnostic systems (e.g. spectroscopy, interferometry, scattering techniques, etc.) with huge amounts of data to be processed, cryogenics, measurement-control systems, automatics, robotics, nanotechnology, etc. Due to the sophistication of the problems with plasma control and plasma material interactions only such a combination of the research effort can give a positive output which can assure the energy needs of our civilization. In this paper the problems of thermonuclear technology are briefly outlined and it is shown why this domain can be a broad field for the experts dealing with electronics, optoelectronics, programming and numerical simulations, who at first glance can have nothing common with the plasma or nuclear physics.

  19. Relativistic Runaway Electrons

    NASA Astrophysics Data System (ADS)

    Breizman, Boris

    2014-10-01

    This talk covers recent developments in the theory of runaway electrons in a tokamak with an emphasis on highly relativistic electrons produced via the avalanche mechanism. The rapidly growing population of runaway electrons can quickly replace a large part of the initial current carried by the bulk plasma electrons. The magnetic energy associated with this current is typically much greater than the particle kinetic energy. The current of a highly relativistic runaway beam is insensitive to the particle energy, which separates the description of the runaway current evolution from the description of the runaway energy spectrum. A strongly anisotropic distribution of fast electrons is generally prone to high-frequency kinetic instabilities that may cause beneficial enhancement of runaway energy losses. The relevant instabilities are in the frequency range of whistler waves and electron plasma waves. The instability thresholds reported in earlier work have been revised considerably to reflect strong dependence of collisional damping on the wave frequency and the role of plasma non-uniformity, including radial trapping of the excited waves in the plasma. The talk also includes a discussion of enhanced scattering of the runaways as well as the combined effect of enhanced scattering and synchrotron radiation. A noteworthy feature of the avalanche-produced runaway current is a self-sustained regime of marginal criticality: the inductive electric field has to be close to its critical value (representing avalanche threshold) at every location where the runaway current density is finite, and the current density should vanish at any point where the electric field drops below its critical value. This nonlinear Ohm's law enables complete description of the evolving current profile. Work supported by the U.S. Department of Energy Contract No. DEFG02-04ER54742 and by ITER contract ITER-CT-12-4300000273. The views and opinions expressed herein do not necessarily reflect those of

  20. ICPP: Scale size of of magnetic turbulence as probed with 30 MeV runaway electrons

    NASA Astrophysics Data System (ADS)

    Jaspers, Roger

    2000-10-01

    This paper reviews results concerning generation, confinement and transport of runaway electrons in the energy range 20-30 MeV in the TEXTOR tokamak. For future fusion reactors, it is of major importance to know the processes of runaway generation and runaway loss after disruptions, because of the potential damage to first wall components. Second, since the runaway electrons are effectively collisionless, their confinement is determined by the magnetic field turbulence. In this way the runaway transport provides a unique opportunity to probe turbulence in the core of a thermonuclear plasma. Runaway electrons above 20 MeV emit synchrotron radiation in the (near) infrared, which can easily be detected by thermographic cameras. This technique is developed and exploited at the TEXTOR-94 tokamak and has resulted in some spectacular results. These include: the experimental evidence of the secondary (`knock-on') runaway generation; the discovery of the runaway snake; the observation of disruption generated runaways; the probing of magnetic turbulence in the core of the plasma in Ohmic and additionally heated plasmas. The paper reviews these results with special emphasis on the subject of probing magnetic turbulence in the core of the plasma. Measurements in the TEXTOR-94 tokamak show that after switching on Neutral Beam Injection, the runaway population decays. The decay only starts with a significant delay, which decreases with increasing NBI heating power. This delay provides direct evidence of the energy dependence of runaway confinement, which is expected if magnetic modes govern the loss of runaway electrons. These observations allow to estimate the mode width δ of the magnetic perturbations:δ smaller than 0.5 cm in Ohmic discharges, increasing to δ=3D 4.4 cm for 0.6 MW NBI power.

  1. National Runaway Safeline

    MedlinePlus

    ... Asked Questions Leadership Financials Events Media Resource Center Work at NRS Visit the Blog Youth & Teens Do you need help? The National Runaway Safeline (NRS) is here to listen whether you are ...

  2. Runaways in History

    ERIC Educational Resources Information Center

    Lipschutz, Mark R.

    1977-01-01

    Although running away is a glorified part of American folk tradition, today's runaway runs afoul of a host of laws, including those which make the act itself illegal. This article examines the history of the social and legal status of youth and why they run away. (Author)

  3. Velocity Distributions of Runaway Stars Produced by Supernovae in the Galaxy

    NASA Astrophysics Data System (ADS)

    Yisikandeer, Abudusaimaitijiang; Zhu, Chunhua; Wang, Zhaojun; Lü, Guoliang

    2016-09-01

    Using a method of population synthesis, we investigate the runaway stars produced by disrupted binaries via asymmetric core collapse supernova explosions (CC-RASs) and thermonuclear supernova explosions (TN-RASs). We find the velocities of CC-RASs in the range of about 30-100 km s -1. The runaway stars observed in the galaxy are possibly CC-RASs. Due to differences in stellar chemical components and structures, TN-RASs are divided into hydrogen-rich TN-RASs and helium-rich TN-RASs. The velocities of the former are about 100-500 km s -1, while the velocities of the latter are mainly between 600 and 1100 km s -1. The hypervelocity stars observed in the galaxy may originate from thermonuclear supernova explosions. Our results possibly cover the US 708 which is a compact helium star and travels with a velocity of 1157 ±53 km s-1 in our galaxy.

  4. Runaway losses in ergodized plasmas

    NASA Astrophysics Data System (ADS)

    Finken, K. H.; Abdullaev, S. S.; Jakubowski, M. W.; Jaspers, R.; Lehnen, M.; Schlickeiser, R.; Spatschek, K. H.; Wingen, A.; Wolf, R.; TEXTOR Team

    2007-02-01

    New results from the generation of runaways and the loss of runaway electrons in an ergodized magnetic field are presented. For the generation process, a clear difference between a 'normal' and a clean, freshly boronized wall condition has been found. Under clean wall conditions, one observes at low densities not only the runaway electrons with energies up to 30 MeV and at discharges with even lower electron density one finds more runaway electrons but at an energy in the low-MeV regime. The runaway electrons are utilized as test particles for revealing the ergodized magnetic field line structure. For the measurements the m/n = 6/2 base mode configuration of the dynamic ergodic divertor (DED), has been applied. One observes a clear modification of the radial runaway profile with preferential losses in the ergodized zone. From the loss rate of the runaway electrons due to ergodization and from the redistribution of the runaways after the DED phase, the diffusion rate is estimated to be of the order of 0.1 m2 s-1.

  5. Thermonuclear model for x-ray transients

    SciTech Connect

    Wallace, R.K.; Woosley, S.E.; Weaver, T.A.

    1982-01-01

    The thermonuclear evolution of a 1.41 M sub solar neutron star accreting both solar and metal-deficient mixtures of hydrogen, helium, and heavy elements at rates ranging from about 10/sup -11/ to 10/sup -10/ M sub solar per year is examined using a one-dimensional numerical model. The metal deficient compositions may result either from placement of the neutron star in a binary system with a Population II red giant or from gravitational settling of heavy ions in the accreted material. For such accretion rates and metallicities, hydrogen burning, mediated by the ..beta..-limited CNO cycle, is stable and leads to the accumulation of a thick helium layer with mass 10/sup 23/ to 10/sup 25/ g and temperature 0.7 less than or equal to T/sub 8/ less than or equal to 1.2. Helium ignition occurs under extremely degenerate circumstances and is catastrophically violent. In the lower t helium shells this runaway is propagated as a convective deflagration, for the thicker layers a detonation front is set up which steepens into a strong relativistic shock wave in the neutron star envelope. In all models greatly super-Eddington luminosities in the outer layers of the neutron star lead to a sustained epoch of radiatively driven mass loss. Observationally, such models may correspond to rapid x-ray transients. The hopeless prospect for constructing a one-dimensional model for ..gamma..-ray bursts without magnetic field confinement is discussed and uncertainties pointed out in the strong screening correction for helium burning reaction.

  6. Runaway cultural niche construction.

    PubMed

    Rendell, Luke; Fogarty, Laurel; Laland, Kevin N

    2011-03-27

    Cultural niche construction is a uniquely potent source of selection on human populations, and a major cause of recent human evolution. Previous theoretical analyses have not, however, explored the local effects of cultural niche construction. Here, we use spatially explicit coevolutionary models to investigate how cultural processes could drive selection on human genes by modifying local resources. We show that cultural learning, expressed in local niche construction, can trigger a process with dynamics that resemble runaway sexual selection. Under a broad range of conditions, cultural niche-constructing practices generate selection for gene-based traits and hitchhike to fixation through the build up of statistical associations between practice and trait. This process can occur even when the cultural practice is costly, or is subject to counteracting transmission biases, or the genetic trait is selected against. Under some conditions a secondary hitchhiking occurs, through which genetic variants that enhance the capability for cultural learning are also favoured by similar dynamics. We suggest that runaway cultural niche construction could have played an important role in human evolution, helping to explain why humans are simultaneously the species with the largest relative brain size, the most potent capacity for niche construction and the greatest reliance on culture.

  7. Pellet interaction with runaway electrons

    SciTech Connect

    James, A. N.; Hollmann, E. M.; Yu, J.H.; Austin, M. E.; Commaux, Nicolas JC; Evans, T.E.; Humphrey, D. A.; Jernigan, T. C.; Parks, P. B.; Putvinski, S.; Strait, E. J.; Tynan, G. R.; Wesley, J. C.

    2011-01-01

    We describe results from recent experiments studying interaction of solid polystyrene pellets with a runaway electron current channel generated after cryogenic argon pellet rapid shutdown of DIII-D. Fast camera imaging shows the pellet trajectory and continuum emission from the subsequent explosion, with geometric calibration providing detailed explosion analysis and runaway energy. Electron cyclotron emission also occurs, associated with knock-on electrons broken free from the pellet by RE which then accelerate and runaway, and also with a short lived hot plasma blown off the pellet surface. In addition, we compare heating and explosion times from observations and a model of pellet heating and breakdown by runaway interaction. (C) 2011 Elsevier B.V. All rights reserved

  8. A Detailed Photometric and Spectroscopic Study of the 2011 Outburst of the Recurrent Nova T Pyxidis from 0.8 to 250 Days after Discovery

    NASA Astrophysics Data System (ADS)

    Surina, F.; Hounsell, R. A.; Bode, M. F.; Darnley, M. J.; Harman, D. J.; Walter, F. M.

    2014-05-01

    We investigated the optical light curve of T Pyx during its 2011 outburst by compiling a database of Solar Mass Ejection Imager (SMEI) and AAVSO observations. The SMEI light curve, providing unprecedented detail covering t = 1.5-49 days post-discovery, was divided into four phases based on the idealized nova optical light curve: the initial rise (1.5-3.3 days), the pre-maximum halt (3.3-13.3 days), the final rise (14.7-27.9 days), and the early decline (27.9+ days). The SMEI light curve contains a strongly detected period of 1.44 ± 0.05 days during the pre-maximum halt phase. These oscillations resemble those found in recent thermonuclear runaway models arising from instabilities in the expanding envelope. No spectral variations that mirror the light curve periodicity were found, however. The marked dip at t ~ 22-24 days just before the light curve maximum at t = 27.9 days may represent the same (shorter duration) phenomenon seen in other novae observed by SMEI and present in some model light curves. The spectra from the 2 m Liverpool Telescope and SMARTS 1.5 m telescope were obtained from t = 0.8-80.7 and 155.1-249.9 days, covering the major phases of development. The nova was observed very early in its rise where a distinct high-velocity ejection phase was evident with initially derived V ej ~ 4000 km s-1. A marked drop occurred at t = 5.7 days, and then a gradual increase in derived V ej to stabilize at ~1500 km s-1 at the pre-maximum halt. Here, we propose two different stages of mass loss, a short-lived phase occurring immediately after outburst and lasting ~6 days, followed by a more steadily evolving and higher mass loss phase. The overall spectral development follows that typical of a classical nova and comparison with the photometric behavior reveals consistencies with the simple evolving pseudo-photosphere model of the nova outburst. Comparing optical spectra to X-ray and radio light curves, weak [Fe X] 6375 Å emission was marginally detected before the

  9. A detailed photometric and spectroscopic study of the 2011 outburst of the recurrent nova T Pyxidis from 0.8 to 250 days after discovery

    SciTech Connect

    Surina, F.; Bode, M. F.; Darnley, M. J.; Harman, D. J.; Hounsell, R. A.; Walter, F. M.

    2014-05-01

    We investigated the optical light curve of T Pyx during its 2011 outburst by compiling a database of Solar Mass Ejection Imager (SMEI) and AAVSO observations. The SMEI light curve, providing unprecedented detail covering t = 1.5-49 days post-discovery, was divided into four phases based on the idealized nova optical light curve: the initial rise (1.5-3.3 days), the pre-maximum halt (3.3-13.3 days), the final rise (14.7-27.9 days), and the early decline (27.9+ days). The SMEI light curve contains a strongly detected period of 1.44 ± 0.05 days during the pre-maximum halt phase. These oscillations resemble those found in recent thermonuclear runaway models arising from instabilities in the expanding envelope. No spectral variations that mirror the light curve periodicity were found, however. The marked dip at t ∼ 22-24 days just before the light curve maximum at t = 27.9 days may represent the same (shorter duration) phenomenon seen in other novae observed by SMEI and present in some model light curves. The spectra from the 2 m Liverpool Telescope and SMARTS 1.5 m telescope were obtained from t = 0.8-80.7 and 155.1-249.9 days, covering the major phases of development. The nova was observed very early in its rise where a distinct high-velocity ejection phase was evident with initially derived V {sub ej} ∼ 4000 km s{sup –1}. A marked drop occurred at t = 5.7 days, and then a gradual increase in derived V {sub ej} to stabilize at ∼1500 km s{sup –1} at the pre-maximum halt. Here, we propose two different stages of mass loss, a short-lived phase occurring immediately after outburst and lasting ∼6 days, followed by a more steadily evolving and higher mass loss phase. The overall spectral development follows that typical of a classical nova and comparison with the photometric behavior reveals consistencies with the simple evolving pseudo-photosphere model of the nova outburst. Comparing optical spectra to X-ray and radio light curves, weak [Fe X] 6375

  10. Probing thermonuclear flame spreading on neutron stars using burst rise oscillations

    NASA Astrophysics Data System (ADS)

    Chakraborty, Manoneeta; Bhattacharyya, Sudip

    2016-07-01

    Intense X-ray bursts (type-I bursts), originated from runaway thermonuclear processes, are observed from the surfaces of many accreting neutron star Low Mass X-ray Binary (LMXB) systems and they provide an important tool to constrain the neutron star equation of state. Periodic intensity variations during these bursts, termed burst oscillations, are observed in about 10% of thermonuclear bursts. Oscillations during the rising phases of thermonuclear bursts are hypothesized to originate from an expanding hot-spot on the surface of the neutron star. We studied the evolution of oscillations during the rising phase of a large sample of thermonuclear bursts from 10 bursting neutron stars in order to probe the process of burning front propagation during an X-ray burst. Our results show observational evidences of expanding hot-spot with spin modulated flame speeds, possibly due to the effects of the Coriolis force present as a result of the high stellar spin (270-620 Hz). This implies that the flame propagation is latitude-dependent and we address the factors affecting the detection and non-detection of burst rise oscillations in the light of this Coriolis force modulated flame spreading scenario.

  11. Thermonuclear ignition criterion in ICF

    NASA Astrophysics Data System (ADS)

    Cheng, Baolian

    2010-11-01

    The Lawson criterion, which determines the onset of thermonuclear ignition in inertial confinement fusion (ICF), is re-derived in terms of physical measurable quantities: the hot spot ion temperature T and the areal density (ρR) of the deuterium-tritium (DT) gas. From this criterion, an ignition curve is generated in the ρR -T plane. In addition, a minimal required implosion energy for laser-drive and a minimal DT gas mass for a sustainable ignition with respect to the condition are derived.

  12. A quiver of many runaways

    NASA Astrophysics Data System (ADS)

    Argurio, Riccardo; Closset, Cyril

    2007-09-01

    We study the quantum corrections to the moduli space of the quiver gauge theory corresponding to regular and fractional D3-branes at the dP1 singularity. We find that besides the known runaway behavior at the lowest step of the duality cascade, there is a runaway direction along a mesonic branch at every higher step of the cascade. Moreover, the algebra of the chiral operators which obtain the large expectation values is such that we reproduce Altmann's first order deformation of the dP1 cone.

  13. A Theoretical Light-Curve Model for the 1999 Outburst of U Scorpii

    NASA Astrophysics Data System (ADS)

    Hachisu, Izumi; Kato, Mariko; Kato, Taichi; Matsumoto, Katsura

    2000-01-01

    A theoretical light curve for the 1999 outburst of U Scorpii is presented in order to obtain various physical parameters of the recurrent nova. Our U Sco model consists of a very massive white dwarf (WD) with an accretion disk and a lobe-filling, slightly evolved, main-sequence star (MS). The model includes a reflection effect by the companion and the accretion disk together with a shadowing effect on the companion by the accretion disk. The early visual light curve (with a linear phase of t~1-15 days after maximum) is well reproduced by a thermonuclear runaway model on a very massive WD close to the Chandrasekhar limit (MWD=1.37+/-0.01 Msolar), in which optically thick winds blowing from the WD play a key role in determining the nova duration. The ensuing plateau phase (t~15-30 days) is also reproduced by the combination of a slightly irradiated MS and a fully irradiated flaring-up disk with a radius ~1.4 times the Roche lobe size. The cooling phase (t~30-40 days) is consistent with a low-hydrogen content of X~0.05 of the envelope for the 1.37 Msolar WD. The best-fit parameters are the WD mass of MWD~1.37 Msolar, the companion mass of MMS~1.5 Msolar (0.8-2.0 Msolar is acceptable), the inclination angle of the orbit (i~80deg), and the flaring-up edge, the vertical height of which is ~0.30 times the accretion disk radius. The duration of the strong wind phase (t~0-17 days) is very consistent with the BeppoSAX supersoft X-ray detection at t~19-20 days because supersoft X-rays are self-absorbed by the massive wind. The envelope mass at the peak is estimated to be ~3×10-6 Msolar, which is indicates an average mass accretion rate of ~2.5×10-7 Msolar yr-1 during the quiescent phase between 1987 and 1999. These quantities are exactly the same as those predicted in a new progenitor model of Type Ia supernovae.

  14. Infrared outburst in Arp 299

    NASA Astrophysics Data System (ADS)

    Mattila, Seppo; Meikle, Peter; Kotak, Rubina; Perez-Torres, Miguel; Romero-Canizales, Cristina; Alberdi, Antxon

    2011-05-01

    Arp 299 is one of the nearest examples of a luminous infrared galaxy. We discovered a strong outburst in Arp 299 which is apparent at infrared (IR) wavelengths but not in the optical indicating emission from warm dust and a high extinction. This source could originate from an IR 'dust echo' resulting either from a highly obscured outburst in an active galactic nucleus or an energetic supernova. To continue our study of the origin of this outburst we propose short IRAC observations.

  15. Remote Shutoff Stops Runaway Lawnmower

    ERIC Educational Resources Information Center

    Grambo, Alan A.

    2007-01-01

    In this article, the author describes how electronics students at Central Nine Career Center designed a kill switch circuit to stop a runaway lawnmower. This project is ideal for a career center since the electronics/robotics, small engines and horticulture classes can all work together on their respective parts of the modification, installation…

  16. Runaway Reaction: Solving for X.

    ERIC Educational Resources Information Center

    Bartz, Solveig A.

    2003-01-01

    This article examines the runaway reaction as it was displayed by Barry, a 14-year-old eighth-grade boy with learning disabilities. It identifies some of the common characteristics of this response and proposes school intervention methods. Functional behavioral assessments and strength-based assessments are encouraged, along with using strategy…

  17. Personality Profile of Adolescent Runaways.

    ERIC Educational Resources Information Center

    Rohr, Michael E.

    An overview of the history of adolescent runaway behavior indicates that it has become a social and psychological problem of significant proportions. This study investigated the use of a personality measure that was hypothesized to be representative of a cluster of behaviors associated with running away. The study also sought to determine a…

  18. Tidally-Induced Thermonuclear Supernovae

    SciTech Connect

    Rosswog, S.; Ramirez-Ruiz, E.; Hix, William Raphael

    2009-01-01

    We discuss the results of 3D simulations of tidal disruptions of white dwarfs by moderate-mass black holes as they may exist in the cores of globular clusters or dwarf galaxies. Our simulations follow self-consistently the hydrodynamic and nuclear evolution from the initial parabolic orbit over the disruption to the build-up of an accretion disk around the black hole. For strong enough encounters (pericentre distances smaller than about 1/3 of the tidal radius) the tidal compression is reversed by a shock and finally results in a thermonuclear explosion. These explosions are not restricted to progenitor masses close to the Chandrasekhar limit, we find exploding examples throughout the whole white dwarf mass range. There is, however, a restriction on the masses of the involved black holes: black holes more massive than 2x105M{circle_dot} swallow a typical 0.6M{circle_dot} white dwarf before their tidal forces can overwhelm the star's selfgravity. Therefore, this mechanism is characteristic for black holes of moderate masses. The material that remains bound to the black hole settles into an accretion disk and produces an Xray flare close to the Eddington limit of L{sub Edd} {approx} 10{sup 41}erg/s (Mbh/1000M{circle_dot}), typically lasting for a few months. The combination of a peculiar thermonuclear supernova together with an X-ray flare thus whistle-blows the existence of such moderate-mass black holes. The next generation of wide field space-based instruments should be able to detect such events.

  19. Experimental investigation of the 30S(α, p) thermonuclear reaction in x-ray bursts

    NASA Astrophysics Data System (ADS)

    Kahl, D.; Chen, A. A.; Kubono, S.; Yamaguchi, H.; Binh, D. N.; Chen, J.; Cherubini, S.; Duy, N. N.; Hashimoto, T.; Hayakawa, S.; Iwasa, N.; Jung, H. S.; Kato, S.; Kwon, Y. K.; Nishimura, S.; Ota, S.; Setoodehnia, K.; Teranishi, T.; Tokieda, H.; Yamada, T.; Yun, C. C.; Zhang, L. Y.

    2016-02-01

    We performed the first measurement of 30S+α resonant elastic scattering to experimentally examine the 30S(α, p) stellar reaction rate in type I x-ray bursts. These bursts are the most frequent thermonuclear explosions in the galaxy, resulting from thermonuclear runaway on the surface of accreting neutron star binaries. The 30S(α, p) reaction plays a critical role in burst models, yet very little is known about the compound nucleus 34Ar at these energies nor the reaction rate itself. We performed a measurement of alpha elastic scattering with a radioactive beam of 30S to experimentally probe the entrance channel. Utilizing a gaseous active target system and silicon detector array, we extracted the excitation function from 1.8 to 5.5 MeV near 160° in the center-of-mass frame. The experimental data were analyzed with an R-Matrix calculation, and we discovered several new resonances and extracted their quantum properties (resonance energy, width, spin, and parity). Finally, we calculated the narrow resonant thermonuclear reaction rate of 30S(α, p) for these new resonances.

  20. Runaway electron generation in tokamak disruptions

    NASA Astrophysics Data System (ADS)

    Smith, H. M.; Fehér, T.; Fülöp, T.; Gál, K.; Verwichte, E.

    2009-12-01

    Runaway electrons can be generated in disruptions by the Dreicer, hot tail and avalanche mechanisms. Analytical and numerical results for hot tail runaway generation are included in a one-dimensional model of electric field, temperature and runaway current, which is applied to simulate disruptions and fast shutdown. The peaked shape of the runaway current density profile may cause tearing modes to become unstable. Fast shutdown is studied by prescribing varying amounts of injected impurities. Large argon content suppresses runaways in JET simulations but causes hot tail generation in ITER. A pellet code is coupled to the runaway model, and it is extended to enable simulations of carbon doped deuterium pellet injection. Such pellets are seen not to give enough cooling for a fast current quench.

  1. A Risk Profile Comparison of Runaway and Non-Runaway Youth.

    ERIC Educational Resources Information Center

    Yates, Gary L.; And Others

    1988-01-01

    Examination of data from 1985 visits by 110 runaway and 655 non-runaway youth to an outpatient medical clinic reveals that runaway youth are at greater risk for a wide variety of medical problems and of health-compromising behaviors including suicide, depression, prostitution, and drug use. (Author/BJV)

  2. Losses of runaway electrons during ergodization

    NASA Astrophysics Data System (ADS)

    Finken, K. H.; Abdullaev, S. S.; Jakubowski, M.; Jaspers, R.; Lehnen, M.; Zimmermann, O.

    2006-04-01

    The dynamic ergodic divertor (DED) of TEXTOR has been applied to runaway discharges. The runaway electrons (ɛ < 30 MeV) are developed as probes for investigating the internal magnetic field line structure in the plasma. Complementary diagnostics are used, namely neutron measurements for the loss of the runaways and synchrotron radiation for the detection inside the plasma. During the DED phase, three features of the runaway electrons are found: a sudden loss from the just formed ergodic layer, an enhanced diffusive transport and very sudden loss events which may be related to field line reconnection processes.

  3. Mechanism of instantaneous coal outbursts

    SciTech Connect

    Guan, P.; Wang, H.Y.; Zhang, Y.X.

    2009-10-15

    Thousands of mine workers die every year from mining accidents, and instantaneous coal outbursts in underground coal mines are one of the major killers. Various models for these outbursts have been proposed, but the precise mechanism is still unknown. We hypothesize that the mechanism of coal outbursts is similar to magma fragmentation during explosive volcanic eruptions; i.e., it is caused by high gas pressure inside coal but low ambient pressure on it, breaking coal into pieces and releasing the high-pressure gas in a shock wave. Hence, coal outbursts may be regarded as another type of gas-driven eruption, in addition to explosive volcanic, lake, and possible ocean eruptions. We verify the hypothesis by experiments using a shock-tube apparatus. Knowing the mechanism of coal outbursts is the first step in developing prediction and mitigation measures. The new concept of gas-driven solid eruption is also important to a better understanding of salt-gas outbursts, rock-gas outbursts, and mud volcano eruptions.

  4. Intense soft x-rays from RS Ophiuchi during the 1985 outburst

    SciTech Connect

    Mason, K.O.; Cordova, F.A.; Bode, M.F.; Barr, P.

    1985-01-01

    Intense soft x-ray emission with a characteristic temperature of a few million degrees has been detected from the recurrent nova RS Oph approximately two months after its January 1985 optical outburst. This is the first detection of x-rays from such a system at outburst. The x-radiation is interpreted as emission from circumstellar gas that is shock heated by the passage of the blast wave from the nova explosion. The rapid decline of the x-ray flux between about 60 and 90 days after the outburst probably occurs because the blast wave has reached the edge of the volume filled, between outbursts, by the stellar wind of the red giant component of the binary system. Residual x-ray emission detected from RS Oph 250 days after the outburst is interpreted as coming from the surface of a white dwarf, at a temperature of approx.300,000K, where thermonuclear burning is persisting. 7 refs., 3 figs.

  5. Runaways: A Review of the Literature.

    ERIC Educational Resources Information Center

    Taylor, Jennifer; Mosteller, Frederick

    More than half of runaway adolescents cite poor family communication and conflict as the primary reasons for running. Runaways (.5-1.5 million annually) generally arrive on the streets with few survival skills and little money. They are often subject to abuse of various sorts, and many eventually resort to criminal activity or use drugs in efforts…

  6. Runaway Slave Advertisements: Teaching from Primary Documents

    ERIC Educational Resources Information Center

    Costa, Tom; Doyle, Brooke

    2004-01-01

    In this article, the authors discuss how children can learn from runaway slave advertisements. The advertisements for runaway slaves that masters placed in eighteenth- and nineteenth-century newspapers are among the documentary sources available to teachers for studying the lives of African-American slaves. Such advertisements often describe a…

  7. Trapped-electron runaway effect

    NASA Astrophysics Data System (ADS)

    Nilsson, E.; Decker, J.; Fisch, N. J.; Peysson, Y.

    2015-08-01

    In a tokamak, trapped electrons subject to a strong electric field cannot run away immediately, because their parallel velocity does not increase over a bounce period. However, they do pinch toward the tokamak center. As they pinch toward the center, the trapping cone becomes more narrow, so eventually they can be detrapped and run away. When they run away, trapped electrons will have a very different signature from circulating electrons subject to the Dreicer mechanism. The characteristics of what are called trapped-electron runaways are identified and quantified, including their distinguishable perpendicular velocity spectrum and radial extent.

  8. On extended thermonuclear functions through pathway model

    NASA Astrophysics Data System (ADS)

    Kumar, Dilip

    when α → 1. The beauty of the result is that these different families of three different functional forms are covered through the pathway parameter α. In a physical set up if f (x) in (3) is the stable or limiting form, the Maxwell-Boltzmann approach to thermonuclear functions, then f (x) in (1) and (2) will contain a large variety of unstable or chaotic situations which will all tend to (3) in the limit. Thus we get a clear idea of all the stable and unstable situations around the Maxwell-Boltzmann approach. Thus the current theory is given a mathematical extension and physical interpretations can be found to situations in (1) and (2). Incidently Tsallis statistics is a special case of (1) for γ = 0, a = 1, δ = 1, η = 1. The Beck-Cohen superstatistics, discussed in current statistical mechanics literature is a special case of (2) for a = 1, η = 1, α > 1. The main purpose of the present paper is to investigate in some more detail, mathematically, the extended thermonuclear functions for Maxwell-Boltzmann statistics and in the cut-off case. The extended thermonuclear functions will be evaluated in closed form for all convenient values of the parameter by means of residue calculus. A comparison of the standard thermonuclear functions with the extended thermonuclear functions is also done. The results and derivations in this paper are new and these will be of interest to physicists, mathematicians, probabilists, and statisticians.

  9. ACCRETION OUTBURSTS IN CIRCUMPLANETARY DISKS

    SciTech Connect

    Lubow, S. H.; Martin, R. G.

    2012-04-20

    We describe a model for the long-term evolution of a circumplanetary disk that is fed mass from a circumstellar disk and contains regions of low turbulence (dead zones). We show that such disks can be subject to accretion-driven outbursts, analogous to outbursts previously modeled in the context of circumstellar disks to explain FU Ori phenomena. Circumplanetary disks around a proto-Jupiter can undergo outbursts for infall accretion rates onto the disks in the range M-dot{sub infall} approx. 10{sup -9} to 10{sup -7} M{sub Sun} yr{sup -1}, typical of accretion rates in the T Tauri phase. During outbursts, the accretion rate and disk luminosity increases by several orders of magnitude. Most of the planet mass growth during planetary gas accretion may occur via disk outbursts involving gas that is considerably hotter than predicted by steady state models. For low infall accretion rates M-dot{sub infall} {approx}< 10{sup -10} M{sub sun} yr{sup -1} that occur in late stages of disk accretion, disk outbursts are unlikely to occur, even if dead zones are present. Such conditions are favorable for the formation of icy satellites.

  10. Spreading of thermonuclear flames on the neutron star in SAX J1808.4-3658: an observational tool

    NASA Technical Reports Server (NTRS)

    Bhattacharyya, Sudip; Strohmayer, Tod E.

    2005-01-01

    We analyse archival Rossi X-Ray Timing Explorer (RXTE) proportional counter array (PCA) data of thermonuclear X-ray bursts from the 2002 outburst of the accreting millisecond pulsar SAX 51808.4-3658. We present evidence of a complex frequency modulation of oscillations during burst rise, and correlations among the time evolution of the oscillation frequency, amplitude, and the inferred burning region area. We discuss these findings in the context of a model, based on thermonuclear flame spreading on the neutron star surface, that can qualitatively explain these features. From our model, we infer that for the 2002 Oct. 15 thermonuclear burst, the ignition likely occurred in the mid-latitudes, the burning region took approx. 0.2 s to nearly encircle the equatorial region of the neutron star, and after that the lower amplitude oscillation originated from the remaining asymmetry of the burning front in the same hemisphere where the burst ignited. We emphasize that studies of the evolution of burst oscillation properties during burst rise can provide a powerful tool to understand thermonuclear flame spreading on neutron star surfaces under extreme physical conditions.

  11. Runaway Stars in Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Pannicke, Anna; Neuhaeuser, Ralph; Dinçel, Baha

    2016-07-01

    Half of all stars and in particular 70 % of the massive stars are a part of a multiple system. A possible development for the system after the core collapse supernova (SN) of the more massive component is as follows: The binary is disrupted by the SN. The formed neutron star is ejected by the SN kick whereas the companion star either remains within the system and is gravitationally bounded to the neutron star, or is ejected with a spatial velocity comparable to its former orbital velocity (up to 500 km/s). Such stars with a large peculiar space velocity are called runaway stars. We present our observational results of the supernova remnants (SNRs) G184.6-5.8, G74.0-8.5 and G119.5+10.2. The focus of this project lies on the detection of low mass runaway stars. We analyze the spectra of a number of candidates and discuss their possibility of being the former companions of the SN progenitor stars. The spectra were obtained with INT in Tenerife, Calar Alto Astronomical Observatory and the University Observatory Jena. Also we investigate the field stars in the neighborhood of the SNRs G74.0-8.5 and G119.5+10.2 and calculate more precise distances for these SNRs.

  12. Enigma of Runaway Stars Solved

    NASA Astrophysics Data System (ADS)

    1997-01-01

    Supernova Propels Companion Star through Interstellar Space The following success story is a classical illustration of scientific progress through concerted interplay of observation and theory. It concerns a 35-year old mystery which has now been solved by means of exciting observations of a strange double star. An added touch is the successive involvement of astronomers connected to the European Southern Observatory. For many years, astronomers have been puzzled by the fact that, among the thousands of very young, hot and heavy stars which have been observed in the Milky Way, there are some that move with exceptionally high velocities. In some cases, motions well above 100 km/sec, or ten times more than normal for such stars, have been measured. How is this possible? Which mechanism is responsible for the large amounts of energy needed to move such heavy bodies at such high speeds? Could it be that these stars are accelerated during the powerful explosion of a companion star as a supernova? Such a scenario was proposed in 1961 by Adriaan Blaauw [1], but until now, observational proof has been lacking. Now, however, strong supporting evidence for this mechanism has become available from observations obtained at the ESO La Silla observatory. The mysterious runaway stars OB-runaway stars [2] are heavy stars that travel through interstellar space with an anomalously high velocity. They have been known for several decades, but it has always been a problem to explain their high velocities. Although most OB-runaway stars are located at distances of several thousands of lightyears, their high velocity results in a measurable change in position on sky photos taken several years apart. The velocity component in the direction of the Earth can be measured very accurately from a spectrogram. From a combination of such observations, it is possible to measure the space velocity of OB-runaways. Bow shocks reveal runaway stars It has also been found that some OB-runaways display

  13. Runaway Children Twelve Years Later: A Follow-Up.

    ERIC Educational Resources Information Center

    Olson, Lucy; And Others

    1980-01-01

    This study was based on intensive interviews with former runaways, nonrunaway siblings, parents, and other relatives. Differences in outcome were found between: (1) runaways and siblings; (2) runaway repeaters and nonrepeaters; and (3) runaways from working-class and middle-class backgrounds. (Author)

  14. Neutron Stars and Thermonuclear X-ray Bursts

    NASA Technical Reports Server (NTRS)

    Bhattacharyya, Supid

    2007-01-01

    This viewgraph presentation describes neutron stars and thermonuclear x ray bursts. The contents include: 1) Neutron Stars: why do we care?; 2) Thermonuclear Bursts: why do we care?; 3) Neutron Stars: Mass, Radius and Spin: a. Continuum Spectroscopy of Bursts b. Spectral Lines from Bursts c. Timing Properties of Bursts; 4) Neutron Star Atmosphere: Thermonuclear Flame Spreading; and 5) Future Prospects and Conclusions.

  15. The polonium-210 problem in thermonuclear reactor

    SciTech Connect

    Shchipakhin, O.L.; Borisov, N.B.; Churkin, S.L.

    1993-12-31

    Polonium 210 forms in the lithium-lead eutectic blanket of a thermonuclear reactor. On the basis of obtained experimental data some estimates have been calculated on the ITER blanket accident consequences. The LOCA type accident represents the failure of eutectic circuit in the process of transfusion of liquid eutectic from blanket to the tritium reprocessing plant.

  16. Plasma physics and controlled thermonuclear fusion

    SciTech Connect

    Krikorian, R. )

    1989-01-01

    This proceedings contains papers on plasma physics and controlled thermonuclear fusion. Included are the following topics: Plasma focus and Z-pinch, Review of mirror fusion research, Progress in studies of x-ray and ion-beam emission from plasma focus facilities.

  17. Laser Fusion - A New Thermonuclear Concept

    ERIC Educational Resources Information Center

    Cooper, Ralph S.

    1975-01-01

    Describes thermonuclear processes induced by interaction of a laser beam with the surface of a fuel pellet. An expanding plasma is formed which results in compression of the element. Laser and reactor technology are discussed. Pictures and diagrams are included. (GH)

  18. Thermonuclear milestones: (1) The American effort

    SciTech Connect

    Goncharov, G.A.

    1996-11-01

    It took a decade for scientists in America to develop the first ideas for a {open_quote}Super{close_quote} bomb into a device that ignited {open_quote}the first small thermonuclear flame ever to burn on Earth.{close_quote} {copyright} {ital 1996 American Institute of Physics.}

  19. Theory of runaway collisional transport

    SciTech Connect

    Tessarotto, M. ); White, R.B. )

    1993-11-01

    The purpose of this paper is to formulate the transport problem for a multispecies rotating toroidal magnetoplasma in the so-called runaway regime, which is defined by an appropriate ordering of relevant characteristic frequencies, in particular, the Larmor frequency, the characteristic acceleration frequency due to the applied electric field and the effective collision frequency, all evaluated at some characteristic speed [ital v][sub 0]. A suitable form of the gyrokinetic equation is obtained to describe the time-dependent, multispecies plasma response to an applied electric field, in toroidal geometry and for a strongly rotating, quiescent, and collisional plasma. Its moment equations are proven to imply the reduction of the energy equation to Joule's law, as well as consequences on the form of Ohm's law and of the Grad--Shafranov equation. To construct an approximate solution of the gyrokinetic equation and to evaluate all relevant fluxes, appearing in the moment equations, a general variational solution method is developed.

  20. On the inward drift of runaway electrons during the plateau phase of runaway current

    DOE PAGESBeta

    Hu, Di; Qin, Hong

    2016-03-29

    The well observed inward drift of current carrying runaway electrons during runaway plateau phase after disruption is studied by considering the phase space dynamic of runaways in a large aspect ratio toroidal system. We consider the case where the toroidal field is unperturbed and the toroidal symmetry of the system is preserved. The balance between the change in canonical angular momentum and the input of mechanical angular momentum in such a system requires runaways to drift horizontally in configuration space for any given change in momentum space. The dynamic of this drift can be obtained by integrating the modified Euler-Lagrangemore » equation over one bounce time. It is then found that runaway electrons will always drift inward as long as they are decelerating. This drift motion is essentially non-linear, since the current is carried by runaways themselves, and any runaway drift relative to the magnetic axis will cause further displacement of the axis itself. A simplified analytical model is constructed to describe such inward drift both in the ideal wall case and no wall case, and the runaway current center displacement as a function of parallel momentum variation is obtained. The time scale of such displacement is estimated by considering effective radiation drag, which shows reasonable agreement with the observed displacement time scale. Furthermore, this indicates that the phase space dynamic studied here plays a major role in the horizontal displacement of runaway electrons during plateau phase. (C) 2016 AIP Publishing LLC.« less

  1. Runaway electron generation in a cooling plasma

    SciTech Connect

    Smith, H.; Helander, P.; Eriksson, L.-G.; Fueloep, T.

    2005-12-15

    The usual calculation of Dreicer [Phys. Rev. 115, 238 (1959); 117, 329 (1960)] generation of runaway electrons assumes that the plasma is in a steady state. In a tokamak disruption this is not necessarily true since the plasma cools down quickly and the collision time for electrons at the runaway threshold energy can be comparable to the cooling time. The electron distribution function then acquires a high-energy tail which can easily be converted to a burst of runaways by the rising electric field. This process is investigated and simple criteria for its importance are derived. If no rapid losses of fast electrons occur, this can be a more important source of runaway electrons than ordinary Dreicer generation in tokamak disruptions.

  2. Energy source for comet outbursts

    NASA Technical Reports Server (NTRS)

    Patashnick, H.; Schuerman, D. W.; Rupprecht, G.

    1974-01-01

    Development of a mechanism explaining the internal source of energy of comet outbursts. A mechanism is proposed which automatically provides a source of particulate matter which creates a huge surface area which contains a substantial percentage of amorphous ice, so that the phase transition of the amorphous ice to a cubic structure provides a release of energy which may be responsible for the outbursts observed in many comets. In addition, the volume into which the transition can propagate is estimated for a spherical comet with a radius of 5 km.

  3. Defining Strategic Methods with Which To Access Runaway Youth into a Runaway Program.

    ERIC Educational Resources Information Center

    Bray, Sheldon

    Thousands of children run away from home or placements each year. The many programs for these children require evaluation to determine effectiveness; one runaway program for at-risk children is examined here. It was felt that if the runaway youth could receive some counseling, then it might help these children and families to solve some of their…

  4. What is the fate of runaway positrons in tokamaks?

    SciTech Connect

    Liu, Jian; Qin, Hong; Fisch, Nathaniel J.; Teng, Qian; Wang, Xiaogang

    2014-06-19

    In this study, massive runaway positrons are generated by runaway electrons in tokamaks. The fate of these positrons encodes valuable information about the runaway dynamics. The phase space dynamics of a runaway position is investigated using a Lagrangian that incorporates the tokamak geometry, loop voltage, radiation and collisional effects. It is found numerically that runaway positrons will drift out of the plasma to annihilate on the first wall, with an in-plasma annihilation possibility less than 0.1%. The dynamics of runaway positrons provides signatures that can be observed as diagnostic tools.

  5. Energetics of runaway electrons during tokamak disruptions

    NASA Astrophysics Data System (ADS)

    Riemann, J.; Smith, H. M.; Helander, P.

    2012-01-01

    In a tokamak disruption, a substantial fraction of the plasma current can be converted into runaway electrons. Although these are usually highly relativistic, their total energy is initially much smaller than that of the pre-disruption plasma. However, following a suggestion by Putvinski et al. [Plasma Phys. Controlled Fusion 39, B157 (1997)], it is shown that as the post-disruption plasma drifts toward the first wall, a non-negligible part of the energy contained in the poloidal magnetic field can be converted into kinetic energy of the runaway electrons. This process is simulated numerically, and it is found that in an ITER-like tokamak runaway electrons can gain kinetic energies up to about 70 MJ by this mechanism.

  6. Runaway sexual selection leads to good genes.

    PubMed

    Chandler, Christopher H; Ofria, Charles; Dworkin, Ian

    2013-01-01

    Mate choice and sexual displays are widespread in nature, but their evolutionary benefits remain controversial. Theory predicts these traits can be favored by runaway sexual selection, in which preference and display reinforce one another due to genetic correlation; or by good genes benefits, in which mate choice is advantageous because extreme displays indicate a well-adapted genotype. However, these hypotheses are not mutually exclusive, and the adaptive benefits underlying mate choice can themselves evolve. In particular, examining how and why sexual displays become indicators of good genes is challenging in natural systems. Here, we use experimental evolution in "digital organisms" to demonstrate the origins of condition-dependent indicator displays following their spread due to a runaway process. Surprisingly, handicap-like costs are not necessary for displays to become indicators of male viability. Instead, a pleiotropic genetic architecture underlies both displays and viability. Runaway sexual selection and good genes benefits should thus be viewed as interacting mechanisms that reinforce one another.

  7. The origin of OB runaway stars.

    PubMed

    Fujii, Michiko S; Portegies Zwart, Simon

    2011-12-01

    About 20% of all massive stars in the Milky Way have unusually high velocities, the origin of which has puzzled astronomers for half a century. We argue that these velocities originate from strong gravitational interactions between single stars and binaries in the centers of star clusters. The ejecting binary forms naturally during the collapse of a young (≤1 million years old) star cluster. This model replicates the key characteristics of OB runaways in our galaxy, and it explains the presence of runaway stars of ≥100 solar masses (M(⊙)) around young star clusters, such as R136 and Westerlund 2. The high proportion and the distributions in mass and velocity of runaways in the Milky Way are reproduced if the majority of massive stars are born in dense and relatively low-mass (5000 to 10,000 M(⊙)) clusters. PMID:22096104

  8. A risk profile comparison of runaway and non-runaway youth.

    PubMed Central

    Yates, G L; MacKenzie, R; Pennbridge, J; Cohen, E

    1988-01-01

    All initial visits (N = 765) to an outpatient medical clinic during calendar year 1985 were analyzed. Six hundred and fifty-five of these visits made by non-runaway youth were compared to 110 visits made by runaways. Based on data from the Childrens Hospital Adolescent Risk Profile Interview, runaway street youth are at greater risk for a wide variety of medical problems and of health-compromising behaviors including suicide and depression, prostitution, and drug use. The implications for public health and social policy are discussed. PMID:3381958

  9. Runaway electrons and magnetic island confinement

    NASA Astrophysics Data System (ADS)

    Boozer, Allen H.

    2016-08-01

    The breakup of magnetic surfaces is a central feature of ITER planning for the avoidance of damage due to runaway electrons. Rapid thermal quenches, which lead to large accelerating voltages, are thought to be due to magnetic surface breakup. Impurity injection to avoid and to mitigate both halo and runaway electron currents utilizes massive gas injection or shattered pellets. The actual deposition is away from the plasma center, and the breakup of magnetic surfaces is thought to spread the effects of the impurities across the plasma cross section. The breakup of magnetic surfaces would prevent runaway electrons from reaching relativistic energies were it not for the persistence of non-intercepting flux tubes. These are tubes of magnetic field lines that do not intercept the walls. In simulations and in magnetic field models, non-intercepting flux tubes are found to persist near the magnetic axis and in the cores of magnetic islands even when a large scale magnetic surface breakup occurs. As long as a few magnetic surfaces reform before all of the non-intercepting flux tubes dissipate, energetic electrons confined and accelerated in these flux tubes can serve as the seed electrons for a transfer of the overall plasma current from thermal to relativistic carriers. The acceleration of electrons is particularly strong because of the sudden changes in the poloidal flux that naturally occur in a rapid magnetic relaxation. The physics of magnetic islands as non-intercepting flux tubes is studied. Expressions are derived for (1) the size of islands required to confine energetic runaway electrons, (2) the accelerating electric field in an island, (3) the increase or reduction in the size of an island by the runaway electron current, (4) the approximate magnitude of the runaway current in an island, and (5) the time scale for the evolution of an island.

  10. The pre-outburst flare of the A 0535+26 August/September 2005 outburst

    NASA Astrophysics Data System (ADS)

    Caballero, I.; Santangelo, A.; Kretschmar, P.; Staubert, R.; Postnov, K.; Klochkov, D.; Camero-Arranz, A.; Finger, M. H.; Kreykenbohm, I.; Pottschmidt, K.; Rothschild, R. E.; Suchy, S.; Wilms, J.; Wilson, C. A.

    2008-03-01

    Aims:We study the spectral and temporal behavior of the High Mass X-ray Binary A 0535+26 during a “pre-outburst flare” which took place 5 d before the peak of a normal (type I) outburst in August/September 2005. We compare the studied behavior with that observed during the outburst. Methods: We analyse RXTEobservations that monitored A 0535+26 during the outburst. We complete spectral and timing analyses of the data. We study the evolution of the pulse period, present energy-dependent pulse profiles both at the initial pre-outburst flare and close to outburst maximum, and measure how the cyclotron resonance-scattering feature (hereafter CRSF) evolves. Results: We present three main results: a constant period P = 103.3960(5) sis measured until periastron passage, followed by a spin-up with a decreasing period derivative of dot{P} = (-1.69 ±0.04) ×10-8 ss-1 at MJD 53 618, and P remains constant again at the end of the main outburst. The spin-up provides evidence for the existence of an accretion disk during the normal outburst. We measure a CRSF energy of Ecyc 50 keV during the pre-outburst flare, and Ecyc 46 keVduring the main outburst. The pulse shape, which varies significantly during both pre-outburst flare and main outburst, evolves strongly with photon energy.

  11. Compton scattering in ignited thermonuclear plasmas.

    PubMed

    Hartemann, F V; Siders, C W; Barty, C P J

    2008-03-28

    Inertially confined, ignited thermonuclear D-T plasmas will produce intense blackbody radiation at temperatures T greater, similar20 keV; it is shown that the injection of GeV electrons into the burning core can efficiently generate high-energy Compton scattering photons. Moreover, the spectrum scattered in a small solid angle can be remarkably monochromatic, due to kinematic pileup; a peak brightness in excess of 10;{30} photons/(mm(2) mrad(2) s 0.1% bandwidth) is predicted. These results are discussed within the context of the Schwinger field and the Sunyaev-Zel'dovich effect.

  12. Measuring Cooling Curves Following Magnetar Outbursts

    NASA Astrophysics Data System (ADS)

    Kaspi, Victoria

    2012-09-01

    Magnetars have been observed to increase their flux output by several orders of magnitude in outbursts. Following outbursts they cool on timescales of months to years. We propose to observe two magnetars, Swift J1822.3-1606 and 1E 1547.0-5408, using Chandra as they approach their quiescent state following their recent outbursts in 2011 and 2009, respectively. We will apply a newly developed crustal cooling model to these cooling curves to constrain the properties of the magnetars, such as the crust thickness and heat capacity, and of their outbursts, such as the location of energy deposition.

  13. RUNAWAY STARS, HYPERVELOCITY STARS, AND RADIAL VELOCITY SURVEYS

    SciTech Connect

    Bromley, Benjamin C.; Kenyon, Scott J.; Brown, Warren R.; Geller, Margaret J. E-mail: skenyon@cfa.harvard.ed E-mail: mgeller@cfa.harvard.ed

    2009-12-01

    Runaway stars ejected from the Galactic disk populate the halo of the Milky Way. To predict the spatial and kinematic properties of runaways, we inject stars into a Galactic potential, compute their trajectories through the Galaxy, and derive simulated catalogs for comparison with observations. Runaways have a flattened spatial distribution, with higher velocity stars at Galactic latitudes less than 30{sup 0}. Due to their shorter stellar lifetimes, massive runaway stars are more concentrated toward the disk than low mass runaways. Bound (unbound) runaways that reach the halo probably originate from distances of 6-12 kpc (10-15 kpc) from the Galactic center, close to the estimated origin of the unbound runaway star HD 271791. Because runaways are brighter and have smaller velocities than hypervelocity stars (HVSs), radial velocity surveys are unlikely to confuse runaway stars with HVSs. We estimate that at most one runaway star contaminates the current sample. We place an upper limit of 2% on the fraction of A-type main-sequence stars ejected as runaways.

  14. Runaway breakdown and electrical discharges in thunderstorms

    NASA Astrophysics Data System (ADS)

    Milikh, Gennady; Roussel-Dupré, Robert

    2010-12-01

    This review considers the precise role played by runaway breakdown (RB) in the initiation and development of lightning discharges. RB remains a fundamental research topic under intense investigation. The question of how lightning is initiated and subsequently evolves in the thunderstorm environment rests in part on a fundamental understanding of RB and cosmic rays and the potential coupling to thermal runaway (as a seed to RB) and conventional breakdown (as a source of thermal runaways). In this paper, we describe the basic mechanism of RB and the conditions required to initiate an observable avalanche. Feedback processes that fundamentally enhance RB are discussed, as are both conventional breakdown and thermal runaway. Observations that provide clear evidence for the presence of energetic particles in thunderstorms/lightning include γ-ray and X-ray flux intensifications over thunderstorms, γ-ray and X-ray bursts in conjunction with stepped leaders, terrestrial γ-ray flashes, and neutron production by lightning. Intense radio impulses termed narrow bipolar pulses (or NBPs) provide indirect evidence for RB particularly when measured in association with cosmic ray showers. Our present understanding of these phenomena and their enduring enigmatic character are touched upon briefly.

  15. On the avalanche generation of runaway electrons during tokamak disruptions

    SciTech Connect

    Martín-Solís, J. R.; Loarte, A.; Lehnen, M.

    2015-08-15

    A simple zero dimensional model for a tokamak disruption is developed to evaluate the avalanche multiplication of a runaway primary seed during the current quench phase of a fast disruptive event. Analytical expressions for the plateau runaway current, the energy of the runaway beam, and the runaway energy distribution function are obtained allowing the identification of the parameters dominating the formation of the runaway current during disruptions. The effect of the electromagnetic coupling to the vessel and the penetration of the external magnetic energy during the disruption current quench as well as of the collisional dissipation of the runaway current at high densities are investigated. Current profile shape effects during the formation of the runaway beam are also addressed by means of an upgraded one-dimensional model.

  16. Synchrotron radiation from a runaway electron distribution in tokamaks

    SciTech Connect

    Stahl, A.; Fülöp, T.; Landreman, M.; Papp, G.; Hollmann, E.

    2013-09-15

    The synchrotron radiation emitted by runaway electrons in a fusion plasma provides information regarding the particle momenta and pitch-angles of the runaway electron population through the strong dependence of the synchrotron spectrum on these parameters. Information about the runaway density and its spatial distribution, as well as the time evolution of the above quantities, can also be deduced. In this paper, we present the synchrotron radiation spectra for typical avalanching runaway electron distributions. Spectra obtained for a distribution of electrons are compared with the emission of mono-energetic electrons with a prescribed pitch-angle. We also examine the effects of magnetic field curvature and analyse the sensitivity of the resulting spectrum to perturbations to the runaway distribution. The implications for the deduced runaway electron parameters are discussed. We compare our calculations to experimental data from DIII-D and estimate the maximum observed runaway energy.

  17. Heterosynaptic Plasticity Prevents Runaway Synaptic Dynamics

    PubMed Central

    Chen, Jen-Yung; Lonjers, Peter; Lee, Christopher; Chistiakova, Marina; Volgushev, Maxim

    2013-01-01

    Spike timing-dependent plasticity (STDP) and other conventional Hebbian-type plasticity rules are prone to produce runaway dynamics of synaptic weights. Once potentiated, a synapse would have higher probability to lead to spikes and thus to be further potentiated, but once depressed, a synapse would tend to be further depressed. The runaway synaptic dynamics can be prevented by precisely balancing STDP rules for potentiation and depression; however, experimental evidence shows a great variety of potentiation and depression windows and magnitudes. Here we show that modifications of synapses to layer 2/3 pyramidal neurons from rat visual and auditory cortices in slices can be induced by intracellular tetanization: bursts of postsynaptic spikes without presynaptic stimulation. Induction of these heterosynaptic changes depended on the rise of intracellular calcium, and their direction and magnitude correlated with initial state of release mechanisms. We suggest that this type of plasticity serves as a mechanism that stabilizes the distribution of synaptic weights and prevents their runaway dynamics. To test this hypothesis, we develop a cortical neuron model implementing both homosynaptic (STDP) and heterosynaptic plasticity with properties matching the experimental data. We find that heterosynaptic plasticity effectively prevented runaway dynamics for the tested range of STDP and input parameters. Synaptic weights, although shifted from the original, remained normally distributed and nonsaturated. Our study presents a biophysically constrained model of how the interaction of different forms of plasticity—Hebbian and heterosynaptic—may prevent runaway synaptic dynamics and keep synaptic weights unsaturated and thus capable of further plastic changes and formation of new memories. PMID:24089497

  18. Eclipse Mapping Experiments in Dwarf Novae Outbursts

    NASA Astrophysics Data System (ADS)

    Borges, B. W.; Baptista, R.

    2006-06-01

    In this work, we report the eclipse mapping analysis of CCD photometric data of two short period dwarf novae - V4140 Sgr (Borges & Baptista 2005) and HT Cas (Borges, Baptista & Catalán, in preparation) - during observed outburst events. The analysis of the observations of V4140 Sgr, done between 1991 and 2001, reveals that the object was in the decline from an outburst in 1992 and again in outburst in 2001. A distance of d = 170+/-30 pc is obtained from a method similar to that used to constrain the distance to open clusters. From this distance, disc radial brightness temperature distributions are determined, and the disc temperatures remain below the critical effective temperature T_{crit} at all disc radii during the outburst. The distributions in quiescence and in outburst are significantly different from those of other dwarf novae of similar orbital period. These results cannot be explained within the framework of the disc instability model and the small amplitude outbursts of V4140 Sgr can be due bursts of enhanced mass transfer rate from the secondary star. Our HT Cas data consist of V and R CCD photometric observations done in 2005 November with the 0.95-m James Gregory Telescope (JGT) and cover a outburst cycle. We used the entropy associated to the eclipse maps to obtain the semi-opening disc angle α evolution throught the outburst. The obtained angles are systematically lower than those obtained by Ioannou et al. (1999) and we can conclude that the outburst radial profiles must be flatter than the the T ∝ r^{-3/4} law of steady state dics, against the expectations of the disc instability model. Our intensity radial distributions presents the same ``outside-in'' outburst behavior as obtained by the referred author.

  19. Tokomak disruption runaway electron beam energy deposition

    NASA Astrophysics Data System (ADS)

    Lei, Yian

    2012-10-01

    Disruption is one of the major concerns in magnetic confinement fusion (MCF) research. People believe the energetic runaway electron beam can damage the first wall by depositing most of its energy to certain region as heat, melting the wall. However, as the energy of the beam electron is very high (up to 50 MeV), most of the beam energy should be converted as gamma radiation and escape, and the fraction of thermal energy deposition is relatively small. We will calculate the runaway electron energy deposition in typical first wall configurations in ITER disruption scenario, and give the temperature profile of the wall. We will also calculate the bremsstrahlung gamma ray spectra of the beam and discuss the consequences.

  20. Numerical calculation of ion runaway distributions

    SciTech Connect

    Embréus, O.; Stahl, A.; Hirvijoki, E.; Fülöp, T.; Newton, S.

    2015-05-15

    Ions accelerated by electric fields (so-called runaway ions) in plasmas may explain observations in solar flares and fusion experiments; however, limitations of previous analytic work have prevented definite conclusions. In this work, we describe a numerical solver of the 2D non-relativistic linearized Fokker-Planck equation for ions. It solves the initial value problem in velocity space with a spectral-Eulerian discretization scheme, allowing arbitrary plasma composition and time-varying electric fields and background plasma parameters. The numerical ion distribution function is then used to consider the conditions for runaway ion acceleration in solar flares and tokamak plasmas. Typical time scales and electric fields required for ion acceleration are determined for various plasma compositions, ion species, and temperatures, and the potential for excitation of toroidal Alfvén eigenmodes during tokamak disruptions is considered.

  1. ON THE EFFECT OF EXPLOSIVE THERMONUCLEAR BURNING ON THE ACCRETED ENVELOPES OF WHITE DWARFS IN CATACLYSMIC VARIABLES

    SciTech Connect

    Sion, Edward M.; Sparks, Warren E-mail: warrensparks@comcast.net

    2014-11-20

    The detection of heavy elements at suprasolar abundances in the atmospheres of some accreting white dwarfs in cataclysmic variables (CVs), coupled with the high temperatures needed to produce these elements, requires explosive thermonuclear burning. The central temperatures of any formerly more massive secondary stars in CVs undergoing hydrostatic CNO burning are far too low to produce these elements. Evidence is presented that at least some CVs contain donor secondaries that have been contaminated by white dwarf remnant burning during the common envelope phase and are transferring this material back to the white dwarf. This scenario does not exclude the channel in which formerly more massive donor stars underwent CNO processing in systems with thermal timescale mass transfer. Implications for the progenitors of CVs are discussed and a new scenario for the white dwarf's accretion-nova-outburst is given.

  2. The reproducible radio outbursts of SS Cygni

    NASA Astrophysics Data System (ADS)

    Russell, T. D.; Miller-Jones, J. C. A.; Sivakoff, G. R.; Altamirano, D.; O'Brien, T. J.; Page, K. L.; Templeton, M. R.; Körding, E. G.; Knigge, C.; Rupen, M. P.; Fender, R. P.; Heinz, S.; Maitra, D.; Markoff, S.; Migliari, S.; Remillard, R. A.; Russell, D. M.; Sarazin, C. L.; Waagen, E. O.

    2016-08-01

    We present the results of our intensive radio observing campaign of the dwarf nova SS Cyg during its 2010 April outburst. We argue that the observed radio emission was produced by synchrotron emission from a transient radio jet. Comparing the radio light curves from previous and subsequent outbursts of this system (including high-resolution observations from outbursts in 2011 and 2012) shows that the typical long and short outbursts of this system exhibit reproducible radio outbursts that do not vary significantly between outbursts, which is consistent with the similarity of the observed optical, ultraviolet and X-ray light curves. Contemporaneous optical and X-ray observations show that the radio emission appears to have been triggered at the same time as the initial X-ray flare, which occurs as disc material first reaches the boundary layer. This raises the possibility that the boundary region may be involved in jet production in accreting white dwarf systems. Our high spatial resolution monitoring shows that the compact jet remained active throughout the outburst with no radio quenching.

  3. Rust catalyzed ethylene hydrogenation causes temperature runaway

    SciTech Connect

    Halle, R.T. ); Vadekar, M. )

    1991-06-17

    During early operation of one of Exxon Chemical Co.'s ethane cracking plants, a temperature runaway in a small shell-and-tube heat exchanger upstream of the hydrogen methanator reactor resulted in rupture of the exchanger shell. Exxon has concluded that the overtemperature resulted from the exothermic heat of reaction of ethylene and hydrogen. This hydrogenation reaction unexpectedly initiated at a temperature well under 300{degree}C.

  4. On the Production of Relativistic Runaway Electrons in Damavand Tokamak

    NASA Astrophysics Data System (ADS)

    Moslehi-Fard, Mahmoud

    2013-02-01

    Experimental observations in Damavand tokamak show that hard X-ray is produced by either disruption with I p < 20 kA or by shots with I p > 20 kA. Hard X-ray also persists from the initiation of plasma discharge to the end. Occurrence of multiple spikes in hard X-ray during the discharge is evident. The propagation of hard X-ray is attributed to runaway electrons. We observe runaway electrons in two regimes with different characteristics. Regime (RADI) is similar to the observations of other Tokamak during disruption on that the plasma current is reduced abruptly and interpreted by Dreicer theory. In the regime of RADII, hard X-ray and subsequently runaway electrons are observed from starting of plasma discharge which provides the condition that the most of runaway electrons contain the toroidal plasma current. Runaway electron beam excites whistler waves and scattered electrons in velocity space and prevent growing the runaway electrons beam.

  5. Are Comet Outbursts the Result of Avalanches?

    NASA Astrophysics Data System (ADS)

    Steckloff, Jordan; Melosh, H. Jay

    2016-10-01

    Recently, Rosetta became the first spacecraft to make high-resolution observations of a comet outburst (a rapid, ephemeral increase in dust production) emerging from the surface of a comet nucleus. These outbursts occurred near perihelion, lasted only a few minutes, and produced a highly collimated outburst plume without any corresponding increase in H2O or CO2 gas production (See abstract by Rinaldi et al.). These observations cannot be explained by proposed driving outburst mechanisms (such as crystallization of amorphous ice, cryovolcanic gas exsolution, or explosive outgasing of subsurface chambers), all of which are driven by gas, and would therefore lead to an increase in the gas production.We propose instead that the observed outbursts on Comet 67P/Churyumov-Gerasimenko (hereafter 67P) are the result of cometary avalanches. The surface of 67P contains many cliffs and scarps, with dusty surface layers blanketing the shallower slopes above and below these steep surfaces. The Rosetta spacecraft returned clear evidence of mass wasting, which form icy talus fields that are the source of much of 67P's cometary activity. Additionally, Rosetta observed morphological changes over time in the shallower, dusty surface layers above these steep slopes, which suggest that avalanches periodically release dusty materials onto these active talus fields.Here we present the results of a numerical simulation of dusty material avalanching into an active area (active talus field). These simulations show that such avalanches will generate a transient, highly collimated outburst plume that closely matches the observed morphology of the outbursts emanating from the surface of 67P. This mechanism predicts that cometary outbursting should not be directly associated with any increase in gas production, consistent with observations. Additionally, we show that regions of the nucleus that have sourced outburst plumes contain steep surfaces (above the angle of repose), which is required

  6. Understanding Neutron Stars using Thermonuclear X-ray Bursts

    NASA Technical Reports Server (NTRS)

    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.).

  7. Neutron Stars and Thermonuclear X-ray Bursts

    NASA Technical Reports Server (NTRS)

    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.).

  8. Does Turbulence in the Iron Convection Zone Cause the Massive Outbursts of Eta Carinae?

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.

    1999-01-01

    Taken at face value, the observed properties of the central object in Eta-Car suggest a very massive, hot main-sequence star, only slightly evolved. If this is so, the star's extraordinarily high steady rate of mass loss must dynamically perturb its outer envelope down to the iron convection zone, where the kinetic energy associated with turbulent convection can be directly fed into mass ejection. Runaway mass loss, triggered by either internal (pulsational, rotational) or external (tidal) forcing, would produce a secular oscillation of the outer envelope. In either case, the oscillation is potentially able to account for the observed approximately 5 yr cycles of visual outbursts in Eta-Car, including the giant eruption of 1843.

  9. The impact of angular scattering on the runaway threshold definition, consequences on the thermal runaway acceleration mechanism.

    NASA Astrophysics Data System (ADS)

    Chanrion, O.; Bonaventura, Z.; Neubert, T.; Bourdon, A.

    2015-12-01

    The discovery of Terrestrial Gamma-ray Flashes (TGFs) by the Compton Gamma-ray Observatory in 1991 is now understood as X- and Gamma-rays emissions associated with thunderstorms. This interest led to a better understanding of the emissions, now explained by bremsstrahlung from high energy electrons which run away in electric fields associated with thunderstorms. In this presentation we discuss the influence of the scattering for the runaway mechanism and the runaway threshold. We compare the outcome of different models with increasing complexity in the description of the scattering. The results show that the inclusion of the scattering in the model firstly reduces the runaway production by allowing some electrons to diffuse out of the runaway regime before they reach energy high enough to justify a forward scattering model. Secondly they affect the definition of the runaway threshold itself. We purpose a alternative definition applicable for sub-MeV electrons and discuss the impact on runaway rates.

  10. Protoplanetary Formation and the FU Orionis Outburst

    NASA Technical Reports Server (NTRS)

    Bodenheimer, P. H.

    1996-01-01

    The following three publications which reference the above grant from the NASA Origins of Solar Systems program are attached and form the final technical report for this project. The research involved comparisons of the spectral energy distributions of FU Orionis objects with theoretical models and associated studies of the structure of the outbursting accretion disks, as well as related studies on the effects of magnetic fields in disks, which will lead in the future to models of FU Orionis outbursts which include the effects of magnetic fields. The project was renewed under a new grant NAGW-4456, entitled 'Effects of FU Orionis Outbursts on Protoplanetary Disks'. Work now being prepared for publication deals more specifically with the issue of the effects of the outbursts on protoplanetary formation. Models of the spectral energy distribution of FU Orionis stars. A simple model of a buoyant magnetic dynamo in accretion disks and a numerical study of magnetic buoyancy in an accretion disk have been submitted.

  11. Energy Balance of Controlled Thermonuclear Fusion

    NASA Astrophysics Data System (ADS)

    Hashmi, M.; Staudenmaier, G.

    It is shown that a discrepancy and incompatibility persist between basic physics and fusion-literature regarding the radiation losses from a thermonuclear plasma. Whereas the fusion-literature neglects the excitation or line radiation completely, according to basic physics it depends upon the prevailing conditions and cannot be neglected in general. Moreover, for a magnetized plasma, while the fusion-literature assumes a self-absorption or reabsorption of cyclotron or synchrotron radiation emitted by the electrons spiraling along the magnetic field, the basic physics does not allow any effective reabsorption of cyclotron or synchrotron radiation. As is demonstrated, fallacious assumptions and notions, which somehow or other crept into the fusion-literature, are responsible for this discrepancy. In the present work, the theory is corrected. On the grounds of basic physics, a complete energy balance of magnetized and non-magnetized plasmas is presented for pulsed, stationary and self-sustaining operations by taking into account the energy release by reactions of light nuclei as well as different kinds of diffusive (conduction) and radiative (bremsstrahlung, cyclotron or synchrotron radiation and excitation radiation) energy losses. Already the energy losses by radiation make the energy balance negative. Hence, a fusion reactor - an energy producing device - seems to be beyond the realms of realization.

  12. Operating large controlled thermonuclear fusion research facilities

    SciTech Connect

    Gaudreau, M.P.J.; Tarrh, J.M.; Post, R.S.; Thomas, P.

    1987-10-01

    The MIT Tara Tandem Mirror is a large, state of the art controlled thermonuclear fusion research facility. Over the six years of its design, implementation, and operation, every effort was made to minimize cost and maximize performance by using the best and latest hardware, software, and scientific and operational techniques. After reviewing all major DOE fusion facilities, an independent DOE review committee concluded that the Tara operation was the most automated and efficient of all DOE facilities. This paper includes a review of the key elements of the Tara design, construction, operation, management, physics milestones, and funding that led to this success. We emphasize a chronological description of how the system evolved from the proposal stage to a mature device with an emphasis on the basic philosophies behind the implementation process. This description can serve both as a qualitative and quantitative database for future large experiment planning. It includes actual final costs and manpower spent as well as actual run and maintenance schedules, number of data shots, major system failures, etc. The paper concludes with recommendations for the next generation of facilities. 13 refs., 15 figs., 3 tabs.

  13. Bayesian Estimation of Thermonuclear Reaction Rates

    NASA Astrophysics Data System (ADS)

    Iliadis, C.; Anderson, K. S.; Coc, A.; Timmes, F. X.; Starrfield, S.

    2016-11-01

    The problem of estimating non-resonant astrophysical S-factors and thermonuclear reaction rates, based on measured nuclear cross sections, is of major interest for nuclear energy generation, neutrino physics, and element synthesis. Many different methods have been applied to this problem in the past, almost all of them based on traditional statistics. Bayesian methods, on the other hand, are now in widespread use in the physical sciences. In astronomy, for example, Bayesian statistics is applied to the observation of extrasolar planets, gravitational waves, and Type Ia supernovae. However, nuclear physics, in particular, has been slow to adopt Bayesian methods. We present astrophysical S-factors and reaction rates based on Bayesian statistics. We develop a framework that incorporates robust parameter estimation, systematic effects, and non-Gaussian uncertainties in a consistent manner. The method is applied to the reactions d(p,γ)3He, 3He(3He,2p)4He, and 3He(α,γ)7Be, important for deuterium burning, solar neutrinos, and Big Bang nucleosynthesis.

  14. Dwarf Nova Outbursts with Magnetorotational Turbulence

    NASA Astrophysics Data System (ADS)

    Coleman, M. S. B.; Kotko, I.; Blaes, O.; Lasota, J.-P.; Hirose, S.

    2016-08-01

    The phenomenological Disc Instability Model has been successful in reproducing the observed light curves of dwarf nova outbursts by invoking an enhanced Shakura-Sunyaev α parameter ˜0.1 - 0.2 in outburst compared to a low value ˜0.01 in quiescence. Recent thermodynamically consistent simulations of magnetorotational (MRI) turbulence with appropriate opacities and equation of state for dwarf nova accretion discs have found that thermal convection enhances α in discs in outburst, but only near the hydrogen ionization transition. At higher temperatures, convection no longer exists and α returns to the low value comparable to that in quiescence. In order to check whether this enhancement near the hydrogen ionization transition is sufficient to reproduce observed light curves, we incorporate this MRI-based variation in α into the Disc Instability Model, as well as simulation-based models of turbulent dissipation and convective transport. These MRI-based models can successfully reproduce observed outburst and quiescence durations, as well as outburst amplitudes, albeit with different parameters from the standard Disc Instability Models. The MRI-based model lightcurves exhibit reflares in the decay from outburst, which are not generally observed in dwarf novae. However, we highlight the problematic aspects of the quiescence physics in the Disc Instability Model and MRI simulations that are responsible for this behavior.

  15. Dwarf nova outbursts with magnetorotational turbulence

    NASA Astrophysics Data System (ADS)

    Coleman, M. S. B.; Kotko, I.; Blaes, O.; Lasota, J.-P.; Hirose, S.

    2016-11-01

    The phenomenological disc instability model has been successful in reproducing the observed light curves of dwarf nova outbursts by invoking an enhanced Shakura-Sunyaev α parameter ˜0.1-0.2 in outburst compared to a low value ˜0.01 in quiescence. Recent thermodynamically consistent simulations of magnetorotational instability (MRI) turbulence with appropriate opacities and equation of state for dwarf nova accretion discs have found that thermal convection enhances α in discs in outburst, but only near the hydrogen ionization transition. At higher temperatures, convection no longer exists and α returns to the low value comparable to that in quiescence. In order to check whether this enhancement near the hydrogen ionization transition is sufficient to reproduce observed light curves, we incorporate this MRI-based variation in α into the disc instability model, as well as simulation-based models of turbulent dissipation and convective transport. These MRI-based models can successfully reproduce observed outburst and quiescence durations, as well as outburst amplitudes, albeit with different parameters from the standard disc instability models. The MRI-based model light curves exhibit reflares in the decay from outburst, which are not generally observed in dwarf novae. However, we highlight the problematic aspects of the quiescence physics in the disc instability model and MRI simulations that are responsible for this behaviour.

  16. A comparison of drug involvement between runaways and school youths.

    PubMed

    Fors, S W; Rojek, D G

    1991-01-01

    Problems related to homeless/runaway youths have received increased attention in recent years. Homeless/runaway youths manifest many problems in addition to being absent from home and without supervision of a parent or guardian. The purpose of the study was to determine drug use and abuse patterns of homeless/runaway youths and to compare those patterns, along with attitudes toward selected illicit behaviors, with similar data collected from adolescents in school. Data were collected from persons (n = 253) in homeless/runaway shelters in the southeast United States. Comparisons made with data from other studies of runaways and of youths in school indicate that drug use and abuse is two-three times more prevalent for runaways than with the school youths. Runaways' attitudes toward selected illicit behaviors are more tolerant than those of school youths. Intervention programs for runaway/homeless youths should reflect an understanding of the complexity of the psycho-social and behavioral history of the clients which is much different than that of those who are in school.

  17. Runaway greenhouse atmospheres: Applications to Earth and Venus

    NASA Technical Reports Server (NTRS)

    Kasting, James F.

    1991-01-01

    Runaway greenhouse atmospheres are discussed from a theoretical standpoint and with respect to various practical situation in which they might occur. The following subject areas are covered: (1) runaway greenhouse atmospheres; (2) moist greenhouse atmospheres; (3) loss of water from Venus; (4) steam atmosphere during accretion; and (5) the continuously habitable zone.

  18. Nowhere to Run: HIV Prevention for Runaway and Homeless Youth.

    ERIC Educational Resources Information Center

    Posner, Marc

    This volume is a guide to providing effective Human Immunodeficiency Virus (HIV) and substance abuse prevention services to runaway and homeless youth. The guide is based on current research and the best programs in this field. Chapters 1 and 2 summarize what is known about runaway and homeless youth, the services these youth require if they are…

  19. Kinetic modelling of runaway electrons in dynamic scenarios

    NASA Astrophysics Data System (ADS)

    Stahl, A.; Embréus, O.; Papp, G.; Landreman, M.; Fülöp, T.

    2016-11-01

    Improved understanding of runaway-electron formation and decay processes are of prime interest for the safe operation of large tokamaks, and the dynamics of the runaway electrons during dynamical scenarios such as disruptions are of particular concern. In this paper, we present kinetic modelling of scenarios with time-dependent plasma parameters; in particular, we investigate hot-tail runaway generation during a rapid drop in plasma temperature. With the goal of studying runaway-electron generation with a self-consistent electric-field evolution, we also discuss the implementation of a collision operator that conserves momentum and energy and demonstrate its properties. An operator for avalanche runaway-electron generation, which takes the energy dependence of the scattering cross section and the runaway distribution into account, is investigated. We show that the simplified avalanche model of Rosenbluth and Putvinskii (1997 Nucl. Fusion 37 1355) can give inaccurate results for the avalanche growth rate (either lower or higher) for many parameters, especially when the average runaway energy is modest, such as during the initial phase of the avalanche multiplication. The developments presented pave the way for improved modelling of runaway-electron dynamics during disruptions or other dynamic events.

  20. Becoming a Runaway: From the Accounts of Youthful Runners.

    ERIC Educational Resources Information Center

    Ek, Carl A.; Steelman, Lala Carr

    1988-01-01

    Interviews with runaways reveals the following stages of a runaway episode: (1) problematic relationships at home, characterized by violence, power struggles, sibling favoritism, and a lack of love; (2) the fight, which includes a transgression and a parental threat; and (3) running away, where the youth must manage fear and handle logistical…

  1. Predictors of Trauma-Related Symptoms among Runaway Adolescents

    ERIC Educational Resources Information Center

    McCarthy, Michael D.; Thompson, Sanna J.

    2010-01-01

    Little is known about trauma-related symptoms among runaway adolescents. Precocious departure from familial homes often exposes youth to traumatic victimization. This study examined the extent to which runaway adolescents present trauma symptomotology and assessed factors that predict trauma symptoms. Participants (N = 350) were 12-18 years of age…

  2. Runaway electron drift orbits in magnetostatic perturbed fields

    NASA Astrophysics Data System (ADS)

    Papp, G.; Drevlak, M.; Fülöp, T.; Helander, P.

    2011-04-01

    Disruptions in large tokamaks can lead to the generation of a relativistic runaway electron beam that may cause serious damage to the first wall. To mitigate the disruption and suppress the runaway beam the application of resonant magnetic perturbations has been suggested. In this work we investigate the effect of resonant magnetic perturbations on the confinement of runaway electrons by simulating their drift orbits in magnetostatic perturbed fields and calculating the orbit losses for various initial energies and magnetic perturbation magnitudes. In the simulations we use a TEXTOR-like configuration and solve the relativistic, gyro-averaged drift equations for the runaway electrons including synchrotron radiation and collisions. The results indicate that runaway electrons are well confined in the core of the device, but the onset time of runaway losses closer to the edge is dependent on the magnetic perturbation level and thereby can affect the maximum runaway current. However, the runaway current damping rate is not sensitive to the magnetic perturbation level, in agreement with experimental observations.

  3. An Impact Triggered Runaway Greenhouse on Mars

    NASA Technical Reports Server (NTRS)

    Segura, T. L.; McKay, C. P.; Toon, O. B.

    2004-01-01

    When a planet is in radiative equilibrium, the incoming solar flux balances the outgoing longwave flux. If something were to perturb the system slightly, say the incoming solar flux increased, the planet would respond by radiating at a higher surface temperature. Since any radiation that comes in must go out, if the incoming is increased, the outgoing must also increase, and this increase manifests itself as a warmer equilibrium temperature. The increase in solar flux would correspond to an increase in temperature, which would increase the amount of water vapor in the atmosphere due to increased evaporation. Since water vapor is a greenhouse gas, it would absorb more radiation in the atmosphere leading to a yet warmer equilibrium temperature. The planet would reach radiative equilibrium at this new temperature. There exists a point, however, past which this positive feedback leads to a "runaway" situation. In this case, the planet does not simply evaporate a little more water and eventually come to a slightly higher equilibrium temperature. Instead, the planet keeps evaporating more and more water until all of the planet's available liquid and solid water is in the atmosphere. The reason for this is generally understood. If the planet's temperature increases, evaporation of water increases, and the absorption of radiation increases. This increases the temperature and the feedback continues until all water is in the atmosphere. The resulting equilibrium temperature is very high, much higher than the equilibrium temperature of a point with slightly lower solar flux. One can picture that as solar flux increases, planetary temperature also increases until the runaway point where temperature suddenly "jumps" to a higher value, in response to all the available water now residing in the atmosphere. This new equilibrium is called a "runaway greenhouse" and it has been theorized that this is what happened to the planet Venus, where the surface temperature is more than 700 K

  4. Runaway electron dynamics in tokamak plasmas with high impurity content

    SciTech Connect

    Martín-Solís, J. R.; Loarte, A.; Lehnen, M.

    2015-09-15

    The dynamics of high energy runaway electrons is analyzed for plasmas with high impurity content. It is shown that modified collision terms are required in order to account for the collisions of the relativistic runaway electrons with partially stripped impurity ions, including the effect of the collisions with free and bound electrons, as well as the scattering by the full nuclear and the electron-shielded ion charge. The effect of the impurities on the avalanche runaway growth rate is discussed. The results are applied, for illustration, to the interpretation of the runaway electron behavior during disruptions, where large amounts of impurities are expected, particularly during disruption mitigation by massive gas injection. The consequences for the electron synchrotron radiation losses and the resulting runaway electron dynamics are also analyzed.

  5. Runaway electron dynamics in tokamak plasmas with high impurity content

    NASA Astrophysics Data System (ADS)

    Martín-Solís, J. R.; Loarte, A.; Lehnen, M.

    2015-09-01

    The dynamics of high energy runaway electrons is analyzed for plasmas with high impurity content. It is shown that modified collision terms are required in order to account for the collisions of the relativistic runaway electrons with partially stripped impurity ions, including the effect of the collisions with free and bound electrons, as well as the scattering by the full nuclear and the electron-shielded ion charge. The effect of the impurities on the avalanche runaway growth rate is discussed. The results are applied, for illustration, to the interpretation of the runaway electron behavior during disruptions, where large amounts of impurities are expected, particularly during disruption mitigation by massive gas injection. The consequences for the electron synchrotron radiation losses and the resulting runaway electron dynamics are also analyzed.

  6. The Be X-ray Binary Outburst Zoo II

    NASA Astrophysics Data System (ADS)

    Kuehnel, M.; Kretschmar, P.; Nespoli, E.; Okazaki, A. T.; Schoenherr, G.; Wilson-Hodge, C. A.; Falkner, S.; Brand, T.; Anders, F.; Schwarm, F.-W.; Kreykenbohm, I.; Mueller, S.; Pottschmidt, K.; Fuerst, F.; Grinberg, V.; Wilms, J.

    2015-03-01

    We have continued our recently started systematic study of Be X-ray binary (BeXRB) outbursts. Specifically, we are developing a catalogue of outbursts including their basic properties based on nearly all available X-ray all-sky-monitors. These properties are derived by fitting asymmetric Gaussians to the outburst lightcurves. This model describes most of the outbursts covered by our preliminary catalogue well; only 13% of all datasets show more complex outburst shapes. Analyzing the basic properties, we reveal a strong correlation between the outburst length and the reached peak flux. As an example, we discuss possible models describing the observed correlation in EXO 2030+375.

  7. Reductions in HIV risk among runaway youth.

    PubMed

    Rotheram-Borus, Mary Jane; Song, Juwon; Gwadz, Marya; Lee, Martha; Van Rossem, Ronan; Koopman, Cheryl

    2003-09-01

    Runaway youth are 6-12 times more likely to become infected with HIV than other youth. Using a quasi-experimental design, the efficacy of an HIV prevention program was evaluated over 2 years among 2 groups of runaways: (1) those at 2 shelters who received Street Smart, an intensive HIV intervention program, and (2) youth at 2 control shelters. Street Smart provided youth with access to health care and condoms and delivered a 10-session skill-focused prevention program based on social learning theory to youth. Prior to analysis of the intervention's outcomes, propensity scores were used to identify comparable subgroups of youth in the intervention (n = 101) and control conditions (n = 86). Compared to females in the control condition, females in the intervention condition significantly reduced their unprotected sexual acts at 2 years and alcohol use, marijuana use, and the number of drugs used over 12 months. Male adolescents in the intervention condition showed significant reductions in marijuana use over 6 months compared to control youth. Adolescent HIV prevention programs must proactively identify mechanisms for maintaining behavior change over the long-term, and innovative research designs are needed to allow examination of agency-level interventions.

  8. Kinetic modelling of runaway electron avalanches in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Nilsson, E.; Decker, J.; Peysson, Y.; Granetz, R. S.; Saint-Laurent, F.; Vlainic, M.

    2015-09-01

    Runaway electrons can be generated in tokamak plasmas if the accelerating force from the toroidal electric field exceeds the collisional drag force owing to Coulomb collisions with the background plasma. In ITER, disruptions are expected to generate runaway electrons mainly through knock-on collisions (Hender et al 2007 Nucl. Fusion 47 S128-202), where enough momentum can be transferred from existing runaways to slow electrons to transport the latter beyond a critical momentum, setting off an avalanche of runaway electrons. Since knock-on runaways are usually scattered off with a significant perpendicular component of the momentum with respect to the local magnetic field direction, these particles are highly magnetized. Consequently, the momentum dynamics require a full 3D kinetic description, since these electrons are highly sensitive to the magnetic non-uniformity of a toroidal configuration. For this purpose, a bounce-averaged knock-on source term is derived. The generation of runaway electrons from the combined effect of Dreicer mechanism and knock-on collision process is studied with the code LUKE, a solver of the 3D linearized bounce-averaged relativistic electron Fokker-Planck equation (Decker and Peysson 2004 DKE: a fast numerical solver for the 3D drift kinetic equation Report EUR-CEA-FC-1736, Euratom-CEA), through the calculation of the response of the electron distribution function to a constant parallel electric field. The model, which has been successfully benchmarked against the standard Dreicer runaway theory now describes the runaway generation by knock-on collisions as proposed by Rosenbluth (Rosenbluth and Putvinski 1997 Nucl. Fusion 37 1355-62). This paper shows that the avalanche effect can be important even in non-disruptive scenarios. Runaway formation through knock-on collisions is found to be strongly reduced when taking place off the magnetic axis, since trapped electrons can not contribute to the runaway electron population. Finally, the

  9. Alfvénic instabilities driven by runaways in fusion plasmas

    SciTech Connect

    Fülöp, T.; Newton, S.

    2014-08-15

    Runaway particles can be produced in plasmas with large electric fields. Here, we address the possibility that such runaway ions and electrons excite Alfvénic instabilities. The magnetic perturbation induced by these modes can enhance the loss of runaways. This may have important implications for the runaway electron beam formation in tokamak disruptions.

  10. Nucleosynthesis and the nova outburst

    NASA Technical Reports Server (NTRS)

    Starrfield, S.; Truran, J.W.; Wiescher, M.; Sparks, W.M.

    1995-01-01

    A nova outburst is the consequence of the accretion of hydrogen rich material onto a white dwarf and it can be considered as the largest hydrogen bomb in the Universe. The fuel is supplied by a secondary star in a close binary system while the strong degeneracy of the massive white dwarf acts to contain the gas during the early stages of the explosion. The containment allows the temperature in the nuclear burning region to exceed 10(sup 8)K under all circumstances. As a result a major fraction of CNO nuclei in the envelope are transformed into (beta)(sup +)-unstable nuclei. We discuss the effects of these nuclei on the evolution. Recent observational studies have shown that there are two compositional classes of novae; one which occurs on carbon-oxygen white dwarfs, and a second class that occurs on oxygen-neon-magnesium white dwarfs. In this review we will concentrate on the latter explosions since they produce the most interesting nucleosynthesis. We report both on the results of new observational determinations of nova abundances and, in addition, new hydrodynamic calculations that examine the consequences of the accretion process on 1.0M(sub (circle dot)), 1.25M(sub (circle dot)), and 1.35M(sub (circle dot)) white dwarfs. Our results show that novae can produce (sup 22)Na, (sup 26)Al, and other intermediate mass nuclei in interesting amounts. We will present the results of new calculations, done with updated nuclear reaction rates and opacities, which exhibit quantitative differences with respect to published work.

  11. Nucleosynthesis and the nova outburst

    SciTech Connect

    Starrfield, S.; Truran, J.W.; Wiescher, M.; Sparks, W.M.

    1995-12-31

    A nova outburst is the consequence of the accretion of hydrogen rich material onto a white dwarf and it can be considered as the largest hydrogen bomb in the Universe. The fuel is supplied by a secondary star in a close binary system while the strong degeneracy of the massive white dwarf acts to contain the gas during the early stages of the explosion. The containment allows the temperature in the nuclear burning region to exceed 10{sup 8}K under all circumstances. As a result a major fraction of CNO nuclei in the envelope are transformed into {beta}{sup +}-unstable nuclei. We discuss the effects of these nuclei on the evolution. Recent observational studies have shown that there are two compositional classes of novae; one which occurs on carbon-oxygen white dwarfs, and a second class that occurs on oxygen-neon-magnesium white dwarfs. In this review we will concentrate on the latter explosions since they produce the most interesting nucleosynthesis. We report both on the results of new observational determinations of nova abundances and, in addition, new hydrodynamic calculations that examine the consequences of the accretion process on 1.0M{sub {circle_dot}}, 1.25M{sub {circle_dot}}, and 1.35M{sub {circle_dot}} white dwarfs. Our results show that novae can produce {sup 22}Na, {sup 26}Al, and other intermediate mass nuclei in interesting amounts. We will present the results of new calculations, done with updated nuclear reaction rates and opacities, which exhibit quantitative differences with respect to published work.

  12. Do spherical tokamaks have a thermonuclear future?

    NASA Astrophysics Data System (ADS)

    Mirnov, S. V.

    2012-12-01

    the potential possibility of their use in thermonuclear research.

  13. Measurements of the runaway electron energy during disruptions in the tokamak TEXTOR

    SciTech Connect

    Forster, M.; Finken, K. H.; Willi, O.; Lehnen, M.; Xu, Y.; Collaboration: TEXTOR Team

    2012-05-15

    Calorimetric measurements of the total runaway electron energy are carried out using a reciprocating probe during induced TEXTOR disruptions. A comparison with the energy inferred from runaway energy spectra, which are measured with a scintillator probe, is used as an independent check of the results. A typical runaway current of 100 kA at TEXTOR contains 30 to 35 kJ of runaway energy. The dependencies of the runaway energy on the runaway current, the radial probe position, the toroidal magnetic field and the predisruptive plasma current are studied. The conversion efficiency of the magnetic plasma energy into runaway energy is calculated to be up to 26%.

  14. Measurements of the runaway electron energy during disruptions in the tokamak TEXTOR

    NASA Astrophysics Data System (ADS)

    Forster, M.; Finken, K. H.; Lehnen, M.; Willi, O.; Xu, Y.; the TEXTOR Team

    2012-05-01

    Calorimetric measurements of the total runaway electron energy are carried out using a reciprocating probe during induced TEXTOR disruptions. A comparison with the energy inferred from runaway energy spectra, which are measured with a scintillator probe, is used as an independent check of the results. A typical runaway current of 100 kA at TEXTOR contains 30 to 35 kJ of runaway energy. The dependencies of the runaway energy on the runaway current, the radial probe position, the toroidal magnetic field and the predisruptive plasma current are studied. The conversion efficiency of the magnetic plasma energy into runaway energy is calculated to be up to 26%.

  15. Runaway studies in the ATF (Advanced Toroidal Facility) torsatron

    SciTech Connect

    England, A.C.; DeVan, W.R.; Eberle, C.C.; Fowler, R.H.; Gabbard, W.A.; Glowienka, J.C.; Harris, J.H.; Haste, G.R.; Kindsfather, R.R.; Morris, R.N.

    1989-01-01

    Pulsed torsatrons and heliotrons are susceptible to runaway electron formation and confinement resulting from the inherent good containment in the vacuum fields and the high loop voltages during the initiation and termination of the helical and vertical fields (''field ramping''). Because runaway electrons can cause an unacceptable level of hard X rays near the machine, a runaway suppression system was designed and included in the initial operation of the Advanced Toroidal Facility (ATF). The main component of the system is a rotating paddle that is normally left in the vacuum chamber during the field ramps. This device proved to be very effective in reducing the runaway population. Measurements of hard X rays from ATF have shown that the runaways are produced primarily during the field ramping but that usually a small steady-state runaway component is also present during the ''flat-top'' portion of the fields. The paddle is the main source of the hard X rays (thick-target bremsstrahlung), although other objects in the vacuum chamber also serve as targets for the runaways at various times. The maximum X-ray energy found by pulse height analysis is /approximately/12--15 MeV; the mean energy appears to be a few mega-electron-volts. A noticeable forward peaking of the bremsstrahlung from the paddle is evident. The limiters do not appear to be major sources of bremsstrahlung. 17 refs., 14 figs.

  16. Study of runaway electron generation during major disruptions in JET

    NASA Astrophysics Data System (ADS)

    Plyusnin, V. V.; Riccardo, V.; Jaspers, R.; Alper, B.; Kiptily, V. G.; Mlynar, J.; Popovichev, S.; de La Luna, E.; Andersson, F.; EFDA contributors, JET

    2006-02-01

    Extensive analysis of disruptions in JET has helped advance the understanding of trends of disruption-generated runaway electrons. Tomographic reconstruction of the soft x-ray emission has made possible a detailed observation of the magnetic flux geometry evolution during disruptions. With the aid of soft and hard x-ray diagnostics runaway electrons have been detected at the very beginning of disruptions. A study of runaway electron parameters has shown that an approximate upper bound for the conversion efficiency of pre-disruptive plasma currents into runaways is about 60% over a wide range of plasma currents in JET. Runaway generation has been simulated with a test particle model in order to verify the results of experimental data analysis and to obtain the background for extrapolation of the existing results onto larger devices such as ITER. It was found that close agreement between the modelling results and experimental data could be achieved if in the calculations the post-disruption plasma electron temperature was assumed equal to 10 eV and if the plasma column geometry evolution is taken into account in calculations. The experimental trends and numerical simulations show that runaway electrons are a critical issue for ITER and, therefore, the development of mitigation methods, which suppress runaway generation, is an essential task.

  17. Review of the classical nova outburst

    SciTech Connect

    Starrfield, S.; Sparks, W.M.

    1986-06-01

    Observational studies have not only identified a new class of novae but theoretical simulations of this class have been found to be in excellent agreement with the observations. This new class consists of outbursts occurring on ONeMg white dwarfs in close binar systems in contrast to the other outbursts which are occurring on CO white dwarfs. We also review the effects of the ..beta../sup +/-unstable nuclei and show how their presence has a major effect on the evolution. 77 refs.

  18. Runaway Geneeration In Disruptions Of Plasmas In TFTR

    SciTech Connect

    Fredrickson, E. D.; Bell, M. G.; Taylor, G.; Medley, S. S.

    2014-03-31

    Many disruptions in the Tokamak Fusion Test Reactor (TFTR) [D. Meade and the TFTR Group, in Proceedings of the International Conference on Plasma Physics and Controlled Nuclear Fusion, Washington, DC, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 1, pp. 9-24] produced populations of runaway electrons which carried a significant fraction of the original plasma current. In this paper, we describe experiments where, following a disruption of a low-beta, reversed shear plasma, currents of up to 1 MA carried mainly by runaway electrons were controlled and then ramped down to near zero using the ohmic transformer. In the longer lasting runaway plasmas, Parail-Pogutse instabilities were observed.

  19. Control of disruption-generated runaway plasmas in TFTR

    NASA Astrophysics Data System (ADS)

    Fredrickson, E. D.; Bell, M. G.; Taylor, G.; Medley, S. S.

    2015-01-01

    Many disruptions in the Tokamak Fusion Test Reactor (TFTR) (Meade and the TFTR Group 1991 Proc. Int. Conf. on Plasma Physics and Controlled Nuclear Fusion (Washington, DC, 1990) vol 1 (Vienna: IAEA) pp 9-24) produced populations of runaway electrons which carried a significant fraction of the original plasma current. In this paper, we describe experiments where, following a disruption of a low-beta, reversed-shear plasma, currents of up to 1 MA carried mainly by runaway electrons were controlled and then ramped down to near zero using the ohmic transformer. In the longer lasting runaway plasmas, events resembling Parail-Pogutse instabilities were observed.

  20. Project Runaway: Calibrating the Spectroscopic Distance Scale Using Runaway O and Wolf-Rayet Stars

    NASA Astrophysics Data System (ADS)

    Hartkopf, William I.; Mason, B. D.

    2009-05-01

    Well-determined O star masses are notoriously difficult to obtain, due to such factors as broad spectral lines, larger and less-reliable average distances, high multiplicity rates, crowded fields, and surrounding nebulosity. Some of these difficulties are reduced for the subset of O stars known as runaways, however. They have escaped some of the nebulosity and crowding, and the event leading to their ejection virtually guarantees that these objects are either single stars or extremely hard spectroscopic binaries. The goal of this project is to increase the sample of known runaway stars, using updated proper motions from the soon-to-be-released UCAC3 catalog, as well as published radial velocities and data from recent duplicity surveys of massive stars using AO and speckle interferometry. Input files include the Galactic O Star Catalog of Maiz-Apellaniz et al. (2004 ApJSS 151, 103) as well as the Seventh Catalogue of Galactic Wolf-Rayet Stars and its more recent Annex (van der Hucht 2001 NewAR 45, 135; 2006 A&A 458, 453). The new runaway star sample will form the basis for a list of SIM targets aimed at improving the distances of Galactic O and WR stars, calibrating the spectroscopic distance scale and leading to more accurate mass estimates for these massive stars.

  1. RUNAWAY MASSIVE STARS FROM R136: VFTS 682 IS VERY LIKELY A 'SLOW RUNAWAY'

    SciTech Connect

    Banerjee, Sambaran; Kroupa, Pavel; Oh, Seungkyung E-mail: pavel@astro.uni-bonn.de

    2012-02-10

    We conduct a theoretical study on the ejection of runaway massive stars from R136-the central massive, starburst cluster in the 30 Doradus complex of the Large Magellanic Cloud. Specifically, we investigate the possibility of the very massive star (VMS) VFTS 682 being a runaway member of R136. Recent observations of the above VMS, by virtue of its isolated location and its moderate peculiar motion, have raised the fundamental question of whether isolated massive star formation is indeed possible. We perform the first realistic N-body computations of fully mass-segregated R136-type star clusters in which all the massive stars are in primordial binary systems. These calculations confirm that the dynamical ejection of a VMS from an R136-like cluster, with kinematic properties similar to those of VFTS 682, is common. Hence, the conjecture of isolated massive star formation is unnecessary to account for this VMS. Our results are also quite consistent with the ejection of 30 Dor 016, another suspected runaway VMS from R136. We further note that during the clusters' evolution, mergers of massive binaries produce a few single stars per cluster with masses significantly exceeding the canonical upper limit of 150 M{sub Sun }. The observations of such single super-canonical stars in R136, therefore, do not imply an initial mass function with an upper limit greatly exceeding the accepted canonical 150 M{sub Sun} limit, as has been suggested recently, and they are consistent with the canonical upper limit.

  2. Thermonuclear supernovae: simulations of the deflagration stage and their implications.

    PubMed

    Gamezo, Vadim N; Khokhlov, Alexei M; Oran, Elaine S; Chtchelkanova, Almadena Y; Rosenberg, Robert O

    2003-01-01

    Large-scale, three-dimensional numerical simulations of the deflagration stage of a thermonuclear supernova explosion show the formation and evolution of a highly convoluted turbulent flame in the gravitational field of an expanding carbon-oxygen white dwarf. The flame dynamics are dominated by the gravity-induced Rayleigh-Taylor instability that controls the burning rate. The thermonuclear deflagration releases enough energy to produce a healthy explosion. The turbulent flame, however, leaves large amounts of unburned and partially burned material near the star center, whereas observations that imply these materials are present only in outer layers. This disagreement could be resolved if the deflagration triggers a detonation. PMID:12446871

  3. Thermonuclear supernovae: simulations of the deflagration stage and their implications.

    PubMed

    Gamezo, Vadim N; Khokhlov, Alexei M; Oran, Elaine S; Chtchelkanova, Almadena Y; Rosenberg, Robert O

    2003-01-01

    Large-scale, three-dimensional numerical simulations of the deflagration stage of a thermonuclear supernova explosion show the formation and evolution of a highly convoluted turbulent flame in the gravitational field of an expanding carbon-oxygen white dwarf. The flame dynamics are dominated by the gravity-induced Rayleigh-Taylor instability that controls the burning rate. The thermonuclear deflagration releases enough energy to produce a healthy explosion. The turbulent flame, however, leaves large amounts of unburned and partially burned material near the star center, whereas observations that imply these materials are present only in outer layers. This disagreement could be resolved if the deflagration triggers a detonation.

  4. Runaway breakdown and hydrometeors in lightning initiation.

    PubMed

    Gurevich, A V; Karashtin, A N

    2013-05-01

    The particular electric pulse discharges are observed in thunderclouds during the initiation stage of negative cloud-to-ground lightning. The discharges are quite different from conventional streamers or leaders. A detailed analysis reveals that the shape of the pulses is determined by the runaway breakdown of air in the thundercloud electric field initiated by extensive atmospheric showers (RB-EAS). The high amplitude of the pulse electric current is due to the multiple microdischarges at hydrometeors stimulated and synchronized by the low-energy electrons generated in the RB-EAS process. The series of specific pulse discharges leads to charge reset from hydrometeors to the free ions and creates numerous stretched ion clusters, both positive and negative. As a result, a wide region in the thundercloud with a sufficiently high fractal ion conductivity is formed. The charge transport by ions plays a decisive role in the lightning leader preconditioning. PMID:23683210

  5. Runaway electron generation as possible trigger for enhancement of magnetohydrodynamic plasma activity and fast changes in runaway beam behavior

    SciTech Connect

    Pankratov, I. M. E-mail: rjzhou@ipp.ac.cn; Zhou, R. J. E-mail: rjzhou@ipp.ac.cn; Hu, L. Q.

    2015-07-15

    Peculiar phenomena were observed during experiments with runaway electrons: rapid changes in the synchrotron spot and its intensity that coincided with stepwise increases in the electron cyclotron emission (ECE) signal (cyclotron radiation of suprathermal electrons). These phenomena were initially observed in TEXTOR (Tokamak Experiment for Technology Oriented Research), where these events only occurred in the current decay phase or in discharges with thin stable runaway beams at a q = 1 drift surface. These rapid changes in the synchrotron spot were interpreted by the TEXTOR team as a fast pitch angle scattering event. Recently, similar rapid changes in the synchrotron spot and its intensity that coincided with stepwise increases in the non-thermal ECE signal were observed in the EAST (Experimental Advanced Superconducting Tokamak) runaway discharge. Runaway electrons were located around the q = 2 rational magnetic surface (ring-like runaway electron beam). During the EAST runaway discharge, stepwise ECE signal increases coincided with enhanced magnetohydrodynamic (MHD) activity. This behavior was peculiar to this shot. In this paper, we show that these non-thermal ECE step-like jumps were related to the abrupt growth of suprathermal electrons induced by bursting electric fields at reconnection events during this MHD plasma activity. Enhancement of the secondary runaway electron generation also occurred simultaneously. Local changes in the current-density gradient appeared because of local enhancement of the runaway electron generation process. These current-density gradient changes are considered to be a possible trigger for enhancement of the MHD plasma activity and the rapid changes in runaway beam behavior.

  6. A Failed outburst of H1743-322

    NASA Astrophysics Data System (ADS)

    Capitanio, F.; Belloni, T.; Del Santo, M.; Ubertini, P.

    2010-07-01

    H1743-322 is a bright BHC observed by HEAO-1 in 1977. The source underwent again in outburst in 2003 after about 25 years. After the 2003 outburst (the brightest one) the source exhibited other 5 outbursts. We report a brief summary of the results found during a campaign of X-ray observations performed with RXTE during the two 2008 outbursts. In particular the October 2008 outburst showed a singular behaviour that has been rarely observed in transient X-ray binaries.

  7. AC operation and runaway electron behaviour in HT-7 tokamak

    NASA Astrophysics Data System (ADS)

    Lu, Hong-Wei; Hu, Li-Qun; Zhou, Rui-Jie; Lin, Shi-Yao; Zhong, Guo-Qiang; Wang, Shao-Feng; Chen, Kai-Yun; Xu, Ping; Zhang, Ji-Zong; Ling, Bi-Li; Mao, Song-Tao; Duan, Yan-Min

    2010-06-01

    Operation of HT-7 tokamak in a multicycle alternating square wave plasma current regime is reported. A set of AC operation experiments, including LHW heating to enhance plasma ionization during the current transition and current sustainment, is described. The behaviour of runaway electrons is analysed by four HXR detectors tangentially viewing the plasma in the equatorial plane, within energy ranges 0.3-1.2 MeV and 0.3-7 MeV, separately. High energy runaway electrons (~MeV) are found to circulate predominantly in the opposite direction to the plasma current, while the number of low energy runaway electrons (~tens to hundreds of keV) circulating along the plasma current is comparable to that in the direction opposite to the plasma current. AC operation with lower hybrid current drive (LHCD) is observed to have an additional benefit of suppressing the runaway electrons if the drop of the loop voltage is large enough.

  8. Mitigating Thermal Runaway Risk in Lithium Ion Batteries

    NASA Technical Reports Server (NTRS)

    Darcy, Eric; Jeevarajan, Judy; Russell, Samuel

    2014-01-01

    The JSC/NESC team has successfully demonstrated Thermal Runaway (TR) risk reduction in a lithium ion battery for human space flight by developing and implementing verifiable design features which interrupt energy transfer between adjacent electrochemical cells. Conventional lithium ion (li-Ion) batteries can fail catastrophically as a result of a single cell going into thermal runaway. Thermal runaway results when an internal component fails to separate electrode materials leading to localized heating and complete combustion of the lithium ion cell. Previously, the greatest control to minimize the probability of cell failure was individual cell screening. Combining thermal runaway propagation mitigation design features with a comprehensive screening program reduces both the probability, and the severity, of a single cell failure.

  9. Dual and multiple diagnosis among substance using runaway youth.

    PubMed

    Slesnick, Natasha; Prestopnik, Jillian

    2005-01-01

    Although research on runaway and homeless youth is increasing, relatively little is known about the diagnostic profile of runaway adolescents. The current study examined patterns of psychiatric dual and multiple diagnosis among a sample (N=226) of treatment-engaged substance-abusing youth (ages 13 to 17) who were residing at a runaway shelter. As part of a larger treatment outcome study, the youths' psychiatric status was assessed using the DSM-IV based computerized diagnostic interview schedule for children [CDISC; (1)]. The majority of the youth in our sample met criteria for dual or multiple diagnosis (60%) with many having more than one substance-use diagnosis (56%). The severity of mental-health and substance-use problems in this sample of substance-abusing runaways suggests the need for continued development of comprehensive services. The range and intensity of diagnoses seen indicates a need for greater focus on treatment development and strategies to address their multiple areas of risk.

  10. Reaction of runaway electron distributions to radiative processes

    NASA Astrophysics Data System (ADS)

    Stahl, Adam; Embréus, Ola; Hirvijoki, Eero; Pusztai, István; Decker, Joan; Newton, Sarah L.; Fülöp, Tünde

    2015-11-01

    The emission of electromagnetic radiation by a charged particle in accelerated motion is associated with a reduction in its energy, accounted for by the inclusion of a radiation reaction force in the kinetic equation. For runaway electrons in plasmas, the dominant radiative processes are the emission of bremsstrahlung and synchrotron radiation. In this contribution, we investigate the impact of the associated radiation reaction forces on the runaway electron distribution, using both analytical and numerical studies, and discuss the corresponding change to the runaway electron growth rate, which can be substantial. We also report on the formation of non-monotonic features in the runaway electron tail as a consequence of the more complicated momentum-space dynamics in the presence of radiation reaction.

  11. Outbursts in ultracompact X-ray binaries

    NASA Astrophysics Data System (ADS)

    Hameury, J.-M.; Lasota, J.-P.

    2016-10-01

    Context. Very faint X-ray binaries appear to be transient in many cases with peak luminosities much fainter than that of usual soft X-ray transients, but their nature still remains elusive. Aims: We investigate the possibility that this transient behaviour is due to the same thermal/viscous instability which is responsible for outbursts of bright soft X-ray transients, occurring in ultracompact binaries for adequately low mass-transfer rates. More generally, we investigate the observational consequences of this instability when it occurs in ultracompact binaries. Methods: We use our code for modelling the thermal-viscous instability of the accretion disc, assumed here to be hydrogen poor. We also take into account the effects of disc X-ray irradiation, and consider the impact of the mass-transfer rate on the outburst brightness. Results: We find that one can reproduce the observed properties of both the very faint and the brighter short transients (peak luminosity, duration, recurrence times), provided that the viscosity parameter in quiescence is slightly smaller (typically a factor of between two and four) than in bright soft X-ray transients and normal dwarf nova outbursts, the viscosity in outburst being unchanged. This possibly reflects the impact of chemical composition on non-ideal magnetohydrodynamic effects affecting magnetically driven turbulence in poorly ionized discs.

  12. Numerical modelling of the classical nova outburst

    SciTech Connect

    Kutter, G.S.; Sparks, W.M.

    1987-01-01

    We describe a mechanism that promises to explain how nova outbursts take place on white dwarf of 1 Msub solar or less and for accretion rates of 4 x 10/sup -10/ Msub solar yr/sup -1/ or greater. 7 refs.

  13. Experimental modelling of outburst flood - bed interactions

    NASA Astrophysics Data System (ADS)

    Carrivick, J. L.; Xie, Z.; Sleigh, A.; Hubbard, M.

    2009-04-01

    Outburst floods are a sudden release and advancing wave of water and sediment, with a peak discharge that is often several orders of magnitude greater than perennial flows. Common outburst floods from natural sources include those from glacial and moraine-impounded lakes, freshwater dyke and levee bursts, volcanic debris dams, landslides, avalanches, coastal bay-bars, and those from tree or vegetation dams. Outburst flood hazards are regularly incorporated into risk assessments for urban, coastal and mountainous areas, for example. Outburst flood hazards are primarily due to direct impacts, caused by a frontal surge wave, from debris within a flow body, and from the mass and consistency of the flows. A number of secondary impacts also pose hazards, including widespread deposition of sediment and blocked tributary streams. It is rapid landscape change, which is achieved the mobilization and redistribution of sediment that causes one of the greatest hazards due to outburst floods. The aim of this project is therefore to parameterise hydrodynamic - sedimentary interactions in experimental outburst floods. Specifically, this project applies laboratory flume modelling, which offers a hitherto untapped opportunity for examining complex interactions between water and sediment within outburst floods. The experimental set-up is of a tradition lock-gate design with a straight 4 m long tank. Hydraulics are scaled at 1:20 froude scale and the following controls on frontal wave flow-bed interactions and hence on rapid landscape change are being investigated: 1. Pre-existing mobile sediment effects, fixed bed roughness effects, sediment concentration effects, mobile bed effects. An emphasis is being maintained on examining the downstream temporal and spatial change in physical character of the water / sediment frontal wave. Facilities are state-of-the-art with a fully-automated laser bed-profiler to measure bed elevation after a run, Seatek arrays to measure transient flow

  14. Empirical Quantification of the Runaway Greenhouse Limit on Earth

    NASA Astrophysics Data System (ADS)

    Goldblatt, C.; Dewey, M. C.

    2015-12-01

    There have been many modeling studies of the runaway greenhouse effect and the conditions required to produce one on an Earth-like planet, however these models have not been verified with empirical evidence. It has been suggested that the Earth's tropics may be near a state of localized runaway greenhouse, meaning the surface temperature and atmospheric composition in those areas could cause runaway greenhouse, were it not for the tempering effects of meridional heat transport and circulation (Pierrehumbert, 1995). Using the assumption that some areas of the Earth's tropics may be under these conditions, this study uses measurements of the atmospheric properties, surface properties, and radiation budgets of these areas to quantify a radiation limit for runaway greenhouse on Earth, by analyzing the dependence of outgoing longwave radiation (OLR) at the top of the atmosphere on surface temperature and total column water vapour. An upper limit on OLR for clear-sky conditions was found between 289.8 W/m2 and 292.2 W/m2, which occurred at surface temperatures near 300K. For surface temperatures above this threshold, total column water vapour increased, but OLR initially decreased and then remained relatively constant, between 273.6 W/m2 and 279.7 W/m2. These limits are in good agreement with recent modeling results (Goldblatt et al., 2013), supporting the idea that some of the Earth's tropics may be in localized runaway greenhouse, and that radiation limits for runaway greenhouse on Earth can be empirically derived. This research was done as part of Maura Dewey's undergraduate honours thesis at the University of Victoria. Refs: Robert T. Pierrehumbert. Thermostats, radiator fins, and the local runaway greenhouse. Journal of Atmospheric Sciences, 52(10):1784-1806, 1995. Colin Goldblatt, Tyler D. Robinson, Kevin J. Zahnle, and David Crisp. Low simulated radiation limit for runaway greenhouse climates. Nature Geoscience, 6:661-667, 2013.

  15. Runaway generation during disruptions in JET and TEXTOR

    NASA Astrophysics Data System (ADS)

    Lehnen, M.; Abdullaev, S. S.; Arnoux, G.; Bozhenkov, S. A.; Jakubowski, M. W.; Jaspers, R.; Plyusnin, V. V.; Riccardo, V.; Samm, U.; Jet Efda Contributors; Textor Team

    2009-06-01

    Runaway electrons generated during ITER disruptions are of concern for the integrity of the plasma facing components. It is expected that a power of up to 8 GW is exposed to ITER PFCs. We present in this article observations from JET and TEXTOR on the generation of runaways and the heat load deposition. Suppression techniques like massive gas injection and resonant magnetic perturbations are discussed.

  16. Thermonuclear Fusion: An Energy Source for the Future

    ERIC Educational Resources Information Center

    Drummond, William E.

    1973-01-01

    Discusses current research in thermonuclear fusion with particular emphasis on the problem of confining hot plasma. Recent experiments indicate that magnetic bottles called tokamaks may achieve the necessary confinement times, and this break-through has given renewed optimism to the feasibility of commercial fusion power by the turn of the…

  17. Enhancement of runaway production by resonant magnetic perturbation on J-TEXT

    NASA Astrophysics Data System (ADS)

    Chen, Z. Y.; Huang, D. W.; Izzo, V. A.; Tong, R. H.; Jiang, Z. H.; Hu, Q. M.; Wei, Y. N.; Yan, W.; Rao, B.; Wang, S. Y.; Ma, T. K.; Li, S. C.; Yang, Z. J.; Ding, D. H.; Wang, Z. J.; Zhang, M.; Zhuang, G.; Pan, Y.; J-TEXT Team

    2016-07-01

    The suppression of runaways following disruptions is key for the safe operation of ITER. The massive gas injection (MGI) has been developed to mitigate heat loads, electromagnetic forces and runaway electrons (REs) during disruptions. However, MGI may not completely prevent the generation of REs during disruptions on ITER. Resonant magnetic perturbation (RMP) has been applied to suppress runaway generation during disruptions on several machines. It was found that strong RMP results in the enhancement of runaway production instead of runaway suppression on J-TEXT. The runaway current was about 50% pre-disruption plasma current in argon induced reference disruptions. With moderate RMP, the runway current decreased to below 30% pre-disruption plasma current. The runaway current plateaus reach 80% of the pre-disruptive current when strong RMP was applied. Strong RMP may induce large size magnetic islands that could confine more runaway seed during disruptions. This has important implications for runaway suppression on large machines.

  18. Verification of runaway migration in a massive disk

    SciTech Connect

    Li, Shengtai

    2009-01-01

    Runaway migration of a proto-planet was first proposed and observed by Masset and Papaloizou (2003). The semi-major axis of the proto-planet varies by 50% over just a few tens of orbits when runaway migration happens. More recent work by D'Angelo et al. (2005) solved the same problem with locally refined grid and found that the migration rate is sharply reduced and no runaway occurs when the grid cells surrounding the planet are refined enough. To verify these two seemly contradictory results, we independently perform high-resolution simulations, solving the same problem as Masset and Papaloizou (2003), with and without self-gravity. We find that the migration rate is highly dependent on the softening used in the gravitational force between thd disk and planet. When a small softening is used in a 2D massive disk, the mass of the circumplanetary disk (CPD) increases with time with enough resolution in the CPD region. It acts as the mass is continually accreted to the CPD, which cannot be settled down until after thousands of orbits. If the planet is held on a fixed orbit long enough, the mass of CPD will become so large that the condition for the runaway migration derived in Masset (2008) will not be satisfied, and hence the runaway migration will not be triggered. However, when a large softening is used, the mass of the CPD will begin to decrease after the initial increase stage. Our numerical results with and without disk-gravity confirm that the runaway migration indeed exists when the mass deficit is larger than the total mass of the planet and CPD. Our simulations results also show that the torque from the co-orbital region, in particular the planet's Hill sphere, is the main contributor to the runaway migration, and the CPD which is lagged behind by the planet becomes so asymmetric that it accelerates the migration.

  19. Origin of the 2006 Orionid Outburst

    NASA Astrophysics Data System (ADS)

    Sato, Mikiya; Watanabe, Jun-Ichi

    2007-08-01

    The Orionid outburst observed in 2006 resulted in strong activity, continuing for about four days. We have found that this activity was caused by the dust trails formed by meteoroids ejected from 1P/Halley in -1265, -1197, and -910. These meteoroids had six times the Jovian orbital period, and their orbit was able to intersect the Earth's orbit at the present day because of this mean motion resonance with Jupiter.

  20. Comet outbursts and the meteor showers

    NASA Astrophysics Data System (ADS)

    Guliyev, A. S.; Kokhirova, G. I.; Poladova, U. D.

    2014-07-01

    The features of 116 comets that have shown an outbursts in their brightness, are considered in the paper. The hypothesis on that the outburst in activity of comets are caused by their passing through meteoroid streams is studied. For this purpose the orbital elements of such comets relative to the planes of motion of 68 meteor showers from Cook's catalogue are analyzed. It was found that four of the nearest and distant nodes of comet orbits relative to the planes of motion of nine meteor showers exceeds the average statistical background with confidence probability from 0.90 to 0.95, and more than 0.95, respectively. The October Draconids, Aurigids, kappa-Serpentids, delta-Draconids, sigma-Hydrids}, Coma Berenicids, Leonids, Leo Minorids, and Perseids showers are the most effective. The results of calculation show that often, the comets outbursts may be caused by collisions of comets with meteoroids under the passing through the meteoroid streams that are producing listed meteor showers as well as solar activity.

  1. VARIABLE ACCRETION OUTBURSTS IN PROTOSTELLAR EVOLUTION

    SciTech Connect

    Bae, Jaehan; Hartmann, Lee; Zhu, Zhaohuan; Gammie, Charles E-mail: lhartm@umich.edu E-mail: gammie@illinois.edu

    2013-02-20

    We extend the one-dimensional, two-zone models of long-term protostellar disk evolution with infall of Zhu et al. to consider the potential effects of a finite viscosity in regions where the ionization is too low for the magnetorotational instability (MRI) to operate (the {sup d}ead zone{sup )}. We find that the presence of a small but finite dead zone viscosity, as suggested by simulations of stratified disks with MRI-active outer layers, can trigger inside-out bursts of accretion, starting at or near the inner edge of the disk, instead of the previously found outside-in bursts with zero dead zone viscosity, which originate at a few AU in radius. These inside-out bursts of accretion bear a qualitative resemblance to the outburst behavior of one FU Ori object, V1515 Cyg, in contrast to the outside-in burst models, which more closely resemble the accretion events in FU Ori and V1057 Cyg. Our results suggest that the type and frequency of outbursts are potentially a probe of transport efficiency in the dead zone. Simulations must treat the inner disk regions, R {approx}< 0.5 AU, to show the detailed time evolution of accretion outbursts in general and to observe the inside-out bursts in particular.

  2. Outbursts in Two New Cool Pulsating DA White Dwarfs

    NASA Astrophysics Data System (ADS)

    Bell, Keaton J.; Hermes, J. J.; Montgomery, M. H.; Gentile Fusillo, N. P.; Raddi, R.; Gänsicke, B. T.; Winget, D. E.; Dennihy, E.; Gianninas, A.; Tremblay, P.-E.; Chote, P.; Winget, K. I.

    2016-10-01

    The unprecedented extent of coverage provided by Kepler observations recently revealed outbursts in two hydrogen-atmosphere pulsating white dwarfs (DAVs) that cause hours-long increases in the overall mean flux of up to 14%. We have identified two new outbursting pulsating white dwarfs in K2, bringing the total number of known outbursting white dwarfs to four. EPIC 211629697, with {T}{eff} = 10,780 ± 140 K and {log} g = 7.94 ± 0.08, shows outbursts recurring on average every 5.0 days, increasing the overall flux by up to 15%. EPIC 229227292, with {T}{eff} = 11,190 ± 170 K and {log} g = 8.02 ± 0.05, has outbursts that recur roughly every 2.4 days with amplitudes up to 9%. We establish that only the coolest pulsating white dwarfs within a small temperature range near the cool, red edge of the DAV instability strip exhibit these outbursts.

  3. On thermonuclear ignition criterion at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Cheng, Baolian; Kwan, Thomas J. T.; Wang, Yi-Ming; Batha, Steven H.

    2014-10-01

    Sustained thermonuclear fusion at the National Ignition Facility remains elusive. Although recent experiments approached or exceeded the anticipated ignition thresholds, the nuclear performance of the laser-driven capsules was well below predictions in terms of energy and neutron production. Such discrepancies between expectations and reality motivate a reassessment of the physics of ignition. We have developed a predictive analytical model from fundamental physics principles. Based on the model, we obtained a general thermonuclear ignition criterion in terms of the areal density and temperature of the hot fuel. This newly derived ignition threshold and its alternative forms explicitly show the minimum requirements of the hot fuel pressure, mass, areal density, and burn fraction for achieving ignition. Comparison of our criterion with existing theories, simulations, and the experimental data shows that our ignition threshold is more stringent than those in the existing literature and that our results are consistent with the experiments.

  4. Thermonuclear Burning as a Probe of Neutron Star

    NASA Technical Reports Server (NTRS)

    Strohmayer, Tod

    2008-01-01

    Thermonuclear fusion is a fundamental process taking place in the matter transferred onto neutron stars in accreting binary systems. The heat deposited by nuclear reactions becomes readily visible in the X-ray band when the burning is either unstable or marginally stable, and results in the rich phenomenology of X-ray bursts, superbursts, and mHz quasiperiodic oscillations. Fast X-ray timing observations with NASA's Rossi X-ray Timing Explorer (RXTE) over the past decade have revealed a wealth of new phenomena associated with thermonuclear burning on neutron stars, including the discovery of nuclear powered pulsations during X-ray bursts and superbursts. I will briefly review our current observational and theoretical understanding of these new phenomena, with an emphasis on recent findings, and discuss what they are telling us about the structure of neutron stars.

  5. Sonoluminescence, shock waves, and micro-thermonuclear fusion

    SciTech Connect

    Moss, W.C.; Clarke, D.B.; White, J.W.; Young, D.A.

    1995-08-01

    We have performed numerical hydrodynamic simulations of the growth and collapse of a sonoluminescing bubble in a liquid. Our calculations show that spherically converging shock waves are generated during the collapse of the bubble. The combination of the shock waves and a realistic equation of state for the gas in the bubble provides an explanation for the measured picosecond optical pulse widths and indicates that the temperatures near the center of the bubble may exceed 3O eV. This leads naturally to speculation about obtaining micro-thermonuclear fusion in a bubble filled with deuterium (D{sub 2}) gas. Consequently, we performed numerical simulations of the collapse of a D{sub 2} bubble in D{sub 2}0. A pressure spike added to the periodic driving amplitude creates temperatures that may be sufficient to generate a very small, but measurable number of thermonuclear D-D fusion reactions in the bubble.

  6. Shock ignition of thermonuclear fuel with high areal density.

    PubMed

    Betti, R; Zhou, C D; Anderson, K S; Perkins, L J; Theobald, W; Solodov, A A

    2007-04-13

    A novel method by C. Zhou and R. Betti [Bull. Am. Phys. Soc. 50, 140 (2005)] to assemble and ignite thermonuclear fuel is presented. Massive cryogenic shells are first imploded by direct laser light with a low implosion velocity and on a low adiabat leading to fuel assemblies with large areal densities. The assembled fuel is ignited from a central hot spot heated by the collision of a spherically convergent ignitor shock and the return shock. The resulting fuel assembly features a hot-spot pressure greater than the surrounding dense fuel pressure. Such a nonisobaric assembly requires a lower energy threshold for ignition than the conventional isobaric one. The ignitor shock can be launched by a spike in the laser power or by particle beams. The thermonuclear gain can be significantly larger than in conventional isobaric ignition for equal driver energy.

  7. On thermonuclear ignition criterion at the National Ignition Facility

    SciTech Connect

    Cheng, Baolian; Kwan, Thomas J. T.; Wang, Yi-Ming; Batha, Steven H.

    2014-10-15

    Sustained thermonuclear fusion at the National Ignition Facility remains elusive. Although recent experiments approached or exceeded the anticipated ignition thresholds, the nuclear performance of the laser-driven capsules was well below predictions in terms of energy and neutron production. Such discrepancies between expectations and reality motivate a reassessment of the physics of ignition. We have developed a predictive analytical model from fundamental physics principles. Based on the model, we obtained a general thermonuclear ignition criterion in terms of the areal density and temperature of the hot fuel. This newly derived ignition threshold and its alternative forms explicitly show the minimum requirements of the hot fuel pressure, mass, areal density, and burn fraction for achieving ignition. Comparison of our criterion with existing theories, simulations, and the experimental data shows that our ignition threshold is more stringent than those in the existing literature and that our results are consistent with the experiments.

  8. Thermal Runaway Severity Reduction Assessment and Implementation: On Li-Ion Batteries

    NASA Technical Reports Server (NTRS)

    Darcy, Eric

    2015-01-01

    Preventing cell-cell thermal runaway propagation and flames/sparks from exiting battery enclosure is possible with proper thermal & electrical design and cell thermal runaway ejecta/effluent management and can be had with minimal mass/volume penalty.

  9. Care of thermally injured victims of a thermonuclear explosion

    SciTech Connect

    Kaplan, J.Z.

    1983-04-29

    Nuclear war or accidental non-hostile nuclear explosion would obviously rank among the greatest disasters to affect mankind. In addition to massive numbers of casualties, depending on the circumstances, our ability to care for these casualties might also be affected. Despite the predictions of doomsday soothsayers, nothing is accomplished by burying one's head in the sand. Therefore, we must give consideration to how victims of a thermo-nuclear explosion would be cared for.

  10. Outburst-related period changes of recurrent nova CI aquilae

    SciTech Connect

    Wilson, R. E.; Honeycutt, R. K. E-mail: rewilson@ufl.edu

    2014-11-01

    Pre-outburst and post-outburst light curves and post-outburst eclipse timings are analyzed to measure any period (P) change related to nova CI Aql's outburst of early 2000 and a mean post-outburst dP/dt, which then lead to estimates of the accreting component's rate of mass (M) change and its overall outburst-related change of mass over roughly a decade of observations. We apply a recently developed procedure for unified analysis of three timing-related data types (light curves, radial velocities, and eclipse timings), although with only light curves and timings in this case. Fits to the data are reasonably good without need for a disk in the light-curve model, although the disk certainly exists and has an important role in our post-outburst mass flow computations. Initial experiments showed that, although there seems to be an accretion hot spot, it has essentially no effect on derived outburst-related ΔP or on post-outburst dP/dt. Use of atomic time (HJED) in place of HJD also has essentially nil effect on ΔP and dP/dt. We find ΔP consistently negative in various types of solutions, although at best only marginally significant statistically in any one experiment. Pre-outburst HJD {sub 0} and P results are given, as are post-outburst HJD {sub 0}, P, and dP/dt, with light curves and eclipse times as joint input, and also with only eclipse time input. Post-outburst dP/dt is negative at about 2.4σ. Explicit formulae for mass transfer rates and epoch-to-epoch mass change are developed and applied. A known offset in the magnitude zero point for 1991-1994 is corrected.

  11. Efficient GPU Accelerationfor Integrating Large Thermonuclear Networks in Astrophysics

    NASA Astrophysics Data System (ADS)

    Guidry, Mike

    2016-02-01

    We demonstrate the systematic implementation of recently-developed fast explicit kinetic integration algorithms on modern graphics processing unit (GPU) accelerators. We take as representative test cases Type Ia supernova explosions with extremely stiff thermonuclear reaction networks having 150-365 isotopic species and 1600-4400 reactions, assumed coupled to hydrodynamics using operator splitting. In such examples we demonstrate the capability to integrate independent thermonuclear networks from ~250-500 hydro zones (assumed to be deployed on CPU cores) in parallel on a single GPU in the same wall clock time that standard implicit methods can integrate the network for a single zone. This two or more orders of magnitude increase in efficiency for solving systems of realistic thermonuclear networks coupled to fluid dynamics implies that important coupled, multiphysics problems in various scientific and technical disciplines that were intractable, or could be simulated only with highly schematic kinetic networks, are now computationally feasible. As examples of such applications I will discuss our ongoing deployment of these new methods for Type Ia supernova explosions in astrophysics and for simulation of the complex atmospheric chemistry entering into weather and climate problems.

  12. Method of achieving the controlled release of thermonuclear energy

    DOEpatents

    Brueckner, Keith A.

    1986-01-01

    A method of achieving the controlled release of thermonuclear energy by illuminating a minute, solid density, hollow shell of a mixture of material such as deuterium and tritium with a high intensity, uniformly converging laser wave to effect an extremely rapid build-up of energy in inwardly traveling shock waves to implode the shell creating thermonuclear conditions causing a reaction of deuterons and tritons and a resultant high energy thermonuclear burn. Utilizing the resulting energy as a thermal source and to breed tritium or plutonium. The invention also contemplates a laser source wherein the flux level is increased with time to reduce the initial shock heating of fuel and provide maximum compression after implosion; and, in addition, computations and an equation are provided to enable the selection of a design having a high degree of stability and a dependable fusion performance by establishing a proper relationship between the laser energy input and the size and character of the selected material for the fusion capsule.

  13. Glacier lake outburst floods - modelling process chains

    NASA Astrophysics Data System (ADS)

    Schaub, Yvonne; Huggel, Christian; Haeberli, Wilfried

    2013-04-01

    New lakes are forming in high-mountain areas all over the world due to glacier recession. Often they will be located below steep, destabilized flanks and are therefore exposed to impacts from rock-/ice-avalanches. Several events worldwide are known, where an outburst flood has been triggered by such an impact. In regions such as in the European Alps or in the Cordillera Blanca in Peru, where valley bottoms are densely populated, these far-travelling, high-magnitude events can result in major disasters. For appropriate integral risk management it is crucial to gain knowledge on how the processes (rock-/ice-avalanches - impact waves in lake - impact on dam - outburst flood) interact and how the hazard potential related to corresponding process chains can be assessed. Research in natural hazards so far has mainly concentrated on describing, understanding, modeling or assessing single hazardous processes. Some of the above mentioned individual processes are quite well understood in their physical behavior and some of the process interfaces have also been investigated in detail. Multi-hazard assessments of the entire process chain, however, have only recently become subjects of investigations. Our study aims at closing this gap and providing suggestions on how to assess the hazard potential of the entire process chain in order to generate hazard maps and support risk assessments. We analyzed different types of models (empirical, analytical, physically based) for each process regarding their suitability for application in hazard assessments of the entire process chain based on literature. Results show that for rock-/ice-avalanches, dam breach and outburst floods, only numerical, physically based models are able to provide the required information, whereas the impact wave can be estimated by means of physically based or empirical assessments. We demonstrate how the findings could be applied with the help of a case study of a recent glacier lake outburst event at Laguna

  14. The behavior of runaway current in massive gas injection fast shutdown plasmas in J-TEXT

    NASA Astrophysics Data System (ADS)

    Chen, Z. Y.; Huang, D. W.; Luo, Y. H.; Tang, Y.; Dong, Y. B.; Zeng, L.; Tong, R. H.; Wang, S. Y.; Wei, Y. N.; Wang, X. H.; Jian, X.; Li, J. C.; Zhang, X. Q.; Rao, B.; Yan, W.; Ma, T. K.; Hu, Q. M.; Yang, Z. J.; Gao, L.; Ding, Y. H.; Wang, Z. J.; Zhang, M.; Zhuang, G.; Pan, Y.; Jiang, Z. H.; J-TEXT Team

    2016-11-01

    Runaway currents following disruptions have an important effect on the first wall in current tokamaks and will be more severe in next generation tokamaks. The behavior of runaway currents in massive gas injection (MGI) induced disruptions have been investigated in the J-TEXT tokamak. The cold front induced by the gas jet penetrates helically along field lines, preferentially toward the high field side and stops at a location near the q  =  2 surface before the disruption. When the cold front reaches the q  =  2 surface it initiates magnetohydrodynamic activities and results in disruption. It is found that the MGI of He or Ne results in runaway free shutdown in a large range of gas injections. Mixture injection of He and Ar (90% He and 10%Ar) consistently results in runaway free shutdown. A moderate amount of Ar injection could produce significant runaway current. The maximum runaway energy in the runaway plateau is estimated using a simplified model which neglects the drag forces and other energy loss mechanisms. The maximum runaway energy increases with decreasing runaway current. Imaging of the runaway beam using a soft x-ray array during the runaway current plateau indicates that the runaway beam is located in the center of the plasma. Resonant magnetic perturbation (RMP) is applied to reduce the runaway current successfully during the disruption phase in a small scale tokamak, J-TEXT. When the runaway current builds up, the application of RMP cannot decouple the runaway beam due to the lower sensitivity of the energetic runaway electrons to the magnetic perturbation.

  15. AG Pegasi - now a classical symbiotic star in outburst?

    NASA Astrophysics Data System (ADS)

    Tomov, T. V.; Stoyanov, K. A.; Zamanov, R. K.

    2016-11-01

    Optical spectroscopy study of the recent AG Pegasi (AG Peg) outburst observed during the second half of 2015 is presented. Considerable variations of the intensity and the shape of the spectral features as well as the changes of the hot component parameters, caused by the outburst, are discussed and certain similarities between the outburst of AG Peg and the outburst of a classical symbiotic stars are shown. It seems that after the end of the symbiotic nova phase, AG Peg became a member of the classical symbiotic stars group.

  16. AG Pegasi - now a classical symbiotic star in outburst?

    NASA Astrophysics Data System (ADS)

    Tomov, T. V.; Stoyanov, K. A.; Zamanov, R. K.

    2016-08-01

    Optical spectroscopy study of the recent AG Peg outburst observed during the second half of 2015 is presented. Considerable variations of the intensity and the shape of the spectral features as well as the changes of the hot component parameters, caused by the outburst, are discussed and certain similarities between the outburst of AG Peg and the outburst of a classical symbiotic stars are shown. It seems that after the end of the symbiotic nova phase, AG Peg became a member of the classical symbiotic stars group.

  17. Runaway Electron Suppression by ECRH and RMP in KSTAR

    NASA Astrophysics Data System (ADS)

    C. England, A.; Y. Chen, Z.; C. Seo, D.; Chung, J.; S. Leev, Y.; W. Yoo, J.; C. Kim, W.; S. Bae, Y.; M. Jeonv, Y.; G. Kwak, J.; M., Kwon; the Kstar Team

    2013-02-01

    We have observed reduction of the runaway electron synchrotron radiation, hard X-ray (HXR) intensity, and HXR energy after applying 110 GHz 2nd harmonic electron cyclotron resonant heating (ECRH) during runaway electron (RE) discharges at low density with startup runaway electrons. However, we did not see a significant reduction of X-rays from 170 GHz 2nd harmonic ECRH at a higher field. A recently installed IR TV camera was used to observe the forward cone of synchrotron radiation from high energy REs in KSTAR. We have observed changes to the synchrotron images and reduction of the HXR by application of resonant magnetic perturbations (RMP) from in-vessel control coils (IVCC) installed inside KSTAR in the n = 1 configuration.

  18. Effects of Spatial Gradients on Electron Runaway Acceleration

    NASA Technical Reports Server (NTRS)

    MacNeice, Peter; Ljepojevic, N. N.

    1996-01-01

    The runaway process is known to accelerate electrons in many laboratory plasmas and has been suggested as an acceleration mechanism in some astrophysical plasmas, including solar flares. Current calculations of the electron velocity distributions resulting from the runaway process are greatly restricted because they impose spatial homogeneity on the distribution. We have computed runaway distributions which include consistent development of spatial gradients in the energetic tail. Our solution for the electron velocity distribution is presented as a function of distance along a finite length acceleration region, and is compared with the equivalent distribution for the infinitely long homogenous system (i.e., no spatial gradients), as considered in the existing literature. All these results are for the weak field regime. We also discuss the severe restrictiveness of this weak field assumption.

  19. Ecologically based family therapy outcome with substance abusing runaway adolescents.

    PubMed

    Slesnick, Natasha; Prestopnik, Jillian L

    2005-04-01

    Runaway youth report a broader range and higher severity of substance-related, mental health and family problems relative to non-runaway youth. Most studies to date have collected self-report data on the family and social history; virtually no research has examined treatment effectiveness with this population. This study is a treatment development project in which 124 runaway youth were randomly assigned to (1) ecologically based family therapy (EBFT) or (2) service as usual (SAU) through a shelter. Youth completed an intake, posttreatment, 6 and 12 months follow-up assessment. Youth assigned to EBFT reported greater reductions in overall substance abuse compared to youth assigned to SAU while other problem areas improved in both conditions. Findings suggest that EBFT is an efficacious intervention for this relatively severe population of youth.

  20. Numerical characterization of bump formation in the runaway electron tail

    NASA Astrophysics Data System (ADS)

    Decker, J.; Hirvijoki, E.; Embreus, O.; Peysson, Y.; Stahl, A.; Pusztai, I.; Fülöp, T.

    2016-02-01

    Runaway electrons are generated in a magnetized plasma when the parallel electric field exceeds a critical value. For such electrons with energies typically reaching tens of MeV, the Abraham-Lorentz-Dirac (ALD) radiation force, in reaction to the synchrotron emission, is significant and can be the dominant process limiting electron acceleration. The effect of the ALD force on runaway electron dynamics in a homogeneous plasma is investigated using the relativistic finite-difference Fokker-Planck codes LUKE (Decker and Peysson 2004 Report EUR-CEA-FC-1736, Euratom-CEA), and CODE (Landreman et al 2014 Comput. Phys. Commun. 185 847). The time evolution of the distribution function is analyzed as a function of the relevant parameters: parallel electric field, background magnetic field, and effective charge. Under the action of the ALD force, we find that runaway electrons are subject to an energy limit, and that the electron distribution evolves towards a steady-state. In addition, a bump is formed in the tail of the electron distribution function if the electric field is sufficiently strong. The mechanisms leading to the bump formation and energy limit involve both the parallel and perpendicular momentum dynamics; they are described in detail. An estimate for the bump location in momentum space is derived. We observe that the energy of runaway electrons in the bump increases with the electric field amplitude, while the population increases with the bulk electron temperature. The presence of the bump divides the electron distribution into a runaway beam and a bulk population. This mechanism may give rise to beam-plasma types of instabilities that could, in turn, pump energy from runaway electrons and alter their confinement.

  1. Chandra Discovers Eruption and Pulsation in Nova Outburst

    NASA Astrophysics Data System (ADS)

    2001-09-01

    NASA's Chandra X-ray Observatory has discovered a giant outburst of X-rays and unusual cyclical pulsing from a white dwarf star that is closely orbiting another star -- the first time either of these phenomena has been seen in X-rays. The observations are helping scientists better understand the thermonuclear explosions that occur in certain binary star systems. The observations of Nova Aquilae were reported today at the "Two Years of Science with Chandra" symposium by an international team led by Sumner Starrfield of Arizona State University. "We found two important results in our Chandra observations. The first was an underlying pulsation every 40 minutes in the X-ray brightness, which we believe comes from the cyclical expansion and contraction of the outer layers of the white dwarf," said Starrfield. "The other result was an enormous flare of X-rays that lasted for 15 minutes. Nothing like this has been seen before from a nova, and we don't know how to explain it." Novas occur on a white dwarf (a star which used up all its nuclear fuel and shrank to roughly the size of the Earth) that is orbiting a normal size star. Strong gravity tides drag hydrogen gas off the normal star and onto the white dwarf, where it can take more than 100,000 years for enough hydrogen to accumulate to ignite nuclear fusion reactions. Gradually, these reactions intensify until a cosmic-sized hydrogen bomb blast results. The outer layers of the white dwarf are then blown away, producing a nova outburst that can be observed for a period of months to years as the material expands into space. "Chandra has allowed us to see deep into the gases ejected by this giant explosion and extract unparalleled information on the evolution of the white dwarf whose surface is exploding," said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics. The brightening of Nova Aquilae was first detected by optical astronomers in December 1999. "Although this star is at a distance of more than 6

  2. Cherenkov neutron detector for fusion reaction and runaway electron diagnostics

    SciTech Connect

    Cheon, MunSeong Kim, Junghee

    2015-08-15

    A Cherenkov-type neutron detector was newly developed and neutron measurement experiments were performed at Korea Superconducting Tokamak Advanced Research. It was shown that the Cherenkov neutron detector can monitor the time-resolved neutron flux from deuterium-fueled fusion plasmas. Owing to the high temporal resolution of the detector, fast behaviors of runaway electrons, such as the neutron spikes, could be observed clearly. It is expected that the Cherenkov neutron detector could be utilized to provide useful information on runaway electrons as well as fusion reaction rate in fusion plasmas.

  3. An in situ runaway electron diagnostic for DIII-D

    SciTech Connect

    Wurden, G. A. Oertel, J. A.; Evans, T. E.

    2014-11-15

    We are designing a new diagnostic based on laser inverse Compton scattering to study the dynamics of runaway electron formation during killer-pellet triggered disruptions in DIII-D, and their subsequent loss. We can improve the expected S/N ratio by using a high-intensity short-pulse laser combined with gated x-ray imagers. With 80 ps sampling, time-of-flight spatial resolution within the laser chord can be obtained. We will measure the time-resolved spatial profile and energy distribution of the runaway electrons while they are in the core of the tokamak plasma.

  4. Runaway domain wall and space-time varying α

    SciTech Connect

    Chiba, Takeshi; Yamaguchi, Masahide E-mail: gucci@phys.titech.ac.jp

    2011-03-01

    Recently spatial as well as temporal variations of the fine structure constant α have been reported. We show that a ''runaway domain wall{sup ,} which arises for the scalar field potential without minima, can account for such variations simultaneously. The time variation is induced by a runaway potential and the spatial variation is induced by the formation of a domain wall. The model is consistent with the current cosmological data and can be tested by the future experiments to test the equivalence principle.

  5. Symbiotic variable V4018 Sgr in outburst

    NASA Astrophysics Data System (ADS)

    Elizabeth O. Waagen

    2012-09-01

    The symbiotic variable V4018 Sgr is undergoing an outburst, according to observations reported to the AAVSO and confirmed by spectroscopy by Ulisse Munari et al. Prompted by an observation and comment from John Bortle (Stormville, NY) (16 June 2012, visual magnitude 12.2) about a possible outburst, Steven O'Connor (St. George's, Bermuda) obtained an observation (10 August 2012, 11.44V) that confirmed V4018 Sgr was bright. His subsequent BVRI observations in September and visual observations by Bortle and Andrew Pearce (Nedlands, Western Australia) show the system brightening and at V magnitude 11.07 as of 2012 Sep. 17.091 UT. Ulisse Munari (INAF Astr. Obs. Padua, Italy) and colleagues Paolo Valisa and Sergio Dallaporta (ANS Collaboration), after being informed by the AAVSO of the bright state of V4018 Sgr, carried out spectroscopy. Munari writes: "A low resolution, absolutely fluxed 4000-8650 Ang spectrum of V4018 Sgr was obtained on Sept 13.90 UT with the 0.6m telescope ! of the Schiaparelli Observatory in Varese (Italy). It shows the spectrum of the M giant overwhelmed by a blue continuum up to 6000 Ang, and all high ionization emission lines typical of quiescence are gone, leaving only hydrogen Balmer and weak HeI lines in emission. The spectrum looks like a template one for a symbiotic star in outburst. CCD photometry was obtained on Sept 13.79 UT and provides V=11.027 ± 0.002, B-V=+0.621 ± 0.003. The B-V color is appreciably bluer and the V magnitude much brighter than typical in quiescence (on average V=13.3, B-V=+1.09; Henden and Munari 2008, Baltic Astronomy 17, 293), and support the idea V4018 Sgr is undergoing an outburst." According to Munari, the last bright outburst of V4018 Sgr was underway in June 1990. Observations in the AAVSO International Database from Albert Jones (Nelson, New Zealand) beginning in May 1992 show the variable at visual magnitude 11.0, with fluctuations between 10.5 and 11.9 through October 1995. Numerous ! other observers

  6. MCNeil's Nebula in Orion: The Outburst History

    NASA Astrophysics Data System (ADS)

    Briceño, C.; Vivas, A. K.; Hernández, J.; Calvet, N.; Hartmann, L.; Megeath, T.; Berlind, P.; Calkins, M.; Hoyer, S.

    2004-05-01

    We present a sequence of I-band images obtained at the Venezuela 1 m Schmidt telescope during the outburst of the nebula recently discovered by J. W. McNeil in the Orion L1630 molecular cloud. We derive photometry spanning the preoutburst state and the brightening itself, which is a unique record including 14 epochs and spanning a timescale of ~5 years. We constrain the beginning of the outburst at some time between 2003 October 28 and November 15. The light curve of the object at the vertex of the nebula, the likely exciting source of the outburst, reveals that it has brightened ~5 mag in about 4 months. The timescale for the nebula to develop is consistent with the light-travel time, indicating that we are observing light from the central source scattered by the ambient cloud into the line of sight. We also show recent FLWO optical spectroscopy of the exciting source and of the nearby HH 22. The spectrum of the source is highly reddened; in contrast, the spectrum of HH 22 shows a shock spectrum superposed on a continuum, most likely the result of reflected light from the exciting source reaching the HH object through a much less reddened path. The blue portion of this spectrum is consistent with an early B spectral type, similar to the early outburst spectrum of the FU Orionis variable star V1057 Cygni; we estimate a luminosity of L~219 Lsolar. The eruptive behavior of McNeil's Nebula, its spectroscopic characteristics and luminosity, suggest that we may be witnessing an FU Ori event on its way to maximum. By further monitoring this object, we will be able decide whether or not it qualifies as a member of this rare class of objects. Based on observations obtained at the Llano del Hato National Astronomical Observatory of Venezuela, operated by CIDA for the Ministerio de Ciencia y Tecnología, and at the Fred Lawrence Whipple Observatory (FLWO) of the Smithsonian Institution.

  7. Temporal and spectral evolution of runaway electron bursts in TEXTOR disruptions

    SciTech Connect

    Forster, M.; Finken, K. H.; Kudyakov, T.; Willi, O.; Lehnen, M.; Xu, Y.; Zeng, L.; Collaboration: TEXTOR Team

    2012-09-15

    Novel observations of the burst-like runaway electron losses in tokamak disruptions are reported. The runaway bursts are temporally resolved and first-time measurements of the corresponding runaway energy spectra are presented. A characteristic shape and burst to burst changes of the spectra are found. The runaway energy content of the disruptions and the conversion of the predisruptive magnetic energy are estimated. The radial decay of the runaways can be approximated by an exponential distribution. Deriving from the measurements, resistive tearing modes or kink modes are suggested to trigger the formation of the bursts.

  8. The experience of aggressive outbursts in intermittent explosive disorder

    PubMed Central

    Kulper, Daniel A.; Kleiman, Evan M.; McCloskey, Michael S.; Berman, Mitchell E.; Coccaro, Emil F.

    2014-01-01

    Conceptualizations of Intermittent Explosive Disorder (IED) have suffered from a scarcity of research investigating the subjective experience and phenomenology of the aggressive outbursts among those with IED relative to those who partake in more normative forms of aggression. Furthermore, though some studies have shown that individuals with IED are more impaired and have a poorer quality of life, few studies looked at negative outcomes specific to an individual with IED’s aggressive behavior. The purpose of this study was to examine the subjective experience and social, occupational, and legal consequences of aggressive outbursts in IED. We assessed individuals with IED (n = 410), psychiatric controls (n = 133), and healthy controls (n = 154) in the experiential correlates present before, during, and after an aggressive outburst as well as the consequences of aggressive outbursts. Results indicated that before and during aggressive outbursts, individuals with IED experienced more intense anger, physiological reactivity, and feelings of dyscontrol as well as more remorse after an aggressive outburst. Furthermore, individuals with IED report more negative consequences of their aggressive outbursts. These results provide an account of how the subjective experience and consequences of aggressive outbursts in IED differ from those with more normative forms of aggression. PMID:25541537

  9. The prototype symbiotic star AX Per is in outburst

    NASA Astrophysics Data System (ADS)

    Munari, U.; Dallaporta, S.; Righetti, G. L.; Castellani, F.; Cherini, G.

    2014-08-01

    The prototype symbiotic star AX Per is in outburst. This is the third such event in the current series of outbursts, the previous two peaking at V=10.41 on 2009 May 26 and at V=10.03 on 2012 Aug 28, according to ANS Collaboration intensive monitoring.

  10. Simulation of runaway electrons, transport affected by J-TEXT resonant magnetic perturbation

    NASA Astrophysics Data System (ADS)

    Jiang, Z. H.; Wang, X. H.; Chen, Z. Y.; Huang, D. W.; Sun, X. F.; Xu, T.; Zhuang, G.

    2016-09-01

    The topology of a magnetic field and transport properties of runaway electrons can be changed by a resonant magnetic perturbation field. The J-TEXT magnetic topology can be effectively altered via static resonant magnetic perturbation (SRMP) and dynamic resonant magnetic perturbation (DRMP). This paper studies the effect of resonant magnetic perturbation (RMP) on the confinement of runaway electrons via simulating their drift orbits in the magnetic perturbation field and calculating the orbit losses for different runaway initial energies and different runaway electrons, initial locations. The model adopted is based on Hamiltonian guiding center equations for runaway electrons, and the J-TEXT magnetic turbulences and RMP are taken into account. The simulation indicates that the loss rate of runaway electrons is sensitive to the radial position of electrons. The loss of energetic runaway beam is dominated by the shrinkage of the confinement region. Outside the shrinkage region of the runaway electrons are lost rapidly. Inside the shrinkage region the runaway beam is confined very well and is less sensitive to the magnetic perturbation. The experimental result on the response of runaway transport to the application RMP indicates that the loss of runaway electrons is dominated by the shrinkage of the confinement region, other than the external magnetic perturbation.

  11. Successful Transitions of Runaway/Homeless Youth from Shelter Care

    ERIC Educational Resources Information Center

    Nebbitt, Von E.; House, Laura E.; Thompson, Sanna J.; Pollio, David E.

    2007-01-01

    Previous research indicates that runaway and homeless youth often achieve positive outcomes after shelter stays however few studies have examined how these outcomes are achieved. This study employs qualitative methods to explicate this phenomenon. Twenty-five providers and 21 youth from four shelters participated in this study. Youth were…

  12. Gang Involvement and Membership among Homeless and Runaway Youth.

    ERIC Educational Resources Information Center

    Yoder, Kevin A.; Whitbeck, Les B.; Hoyt, Dan R.

    2003-01-01

    Assessed the extent of gang involvement among homeless and runaway youth, comparing gang members, gang-involved youth (not members), and non-gang youth on several dimensions. Interview data indicated that 15.4 percent of the youth were gang members and 32.2 percent were involved in gangs. These youth reported more family problems and school…

  13. Low Simulated Radiation Limit for Runaway Greenhouse Climates

    NASA Technical Reports Server (NTRS)

    Goldblatt, Colin; Robinson, Tyler D.; Zahnle, Kevin J.; Crisp, David

    2013-01-01

    Terrestrial planet atmospheres must be in long-term radiation balance, with solar radiation absorbed matched by thermal radiation emitted. For hot moist atmospheres, however, there is an upper limit on the thermal emission which is decoupled from the surface temperature. If net absorbed solar radiation exceeds this limit the planet will heat uncontrollably, the so-called \\runaway greenhouse". Here we show that a runaway greenhouse induced steam atmosphere may be a stable state for a planet with the same amount of incident solar radiation as Earth has today, contrary to previous results. We have calculated the clear-sky radiation limits at line-by-line spectral resolution for the first time. The thermal radiation limit is lower than previously reported (282 W/sq m rather than 310W/sq m) and much more solar radiation would be absorbed (294W/sq m rather than 222W/sq m). Avoiding a runaway greenhouse under the present solar constant requires that the atmosphere is subsaturated with water, and that cloud albedo forcing exceeds cloud greenhouse forcing. Greenhouse warming could in theory trigger a runaway greenhouse but palaeoclimate comparisons suggest that foreseeable increases in greenhouse gases will be insufficient to do this.

  14. Conditions for electron runaway under leader breakdown of long gaps

    SciTech Connect

    Ul'yanov, K. N.

    2008-04-15

    An original hydrodynamic model in which inelastic collisions in the equations of motion and energy balance play a decisive role is developed and applied to simulate electron avalanches in strong electric fields. The mean energy and drift velocity of electrons, as well as the ionization coefficient and electric field in a wide range of mean electron energies, are determined for helium and xenon. A criterion is derived for the runaway of the average electron in discharges with ionization multiplication. It is shown that runaway can take place at any value of E/p, provided that the momentum mean free path exceeds the gap length. The voltage corresponding to electron runaway is found for helium, xenon, and air as a function of the electric field, the electron mean energy, and the parameter pd. Conditions for the formation of a precursor in electronegative gases are analyzed. It is shown that the presence of a precursor with a high electric conductance is necessary for the formation of a new leader step. The voltage and time ranges corresponding to efficient electron runaway and X-ray generation during leader breakdown in air are determined.

  15. Shelters for Runaway and Homeless Youths: Capacity and Occupancy.

    ERIC Educational Resources Information Center

    Greene, Jody M.; And Others

    1997-01-01

    Data from a nationally representative sample of shelters for runaway and homeless youths (n=160) were analyzed to determine shelter capacity, occupancy, and occupancy ratios. Analysis focused in particular on occupancy ratios by funding status, shelter size, metropolitan statistical area, season, and day of the week. Results showed a relatively…

  16. A Family Systems Approach for Preventing Adolescent Runaway Behavior.

    ERIC Educational Resources Information Center

    Coco, E. Lane; Courtney, Linda J.

    1998-01-01

    Utilizes a family therapy approach to restructure family relationships in order to prevent further runaway behavior of a 15-year-old Mexican-American female. The approach involves a family interview, genogram, and family therapy. The Family Satisfaction Scale was administered to evaluate the effectiveness of the approach. (Author/MKA)

  17. Runaway implantable defibrillator--a rare complication of radiation therapy.

    PubMed

    Nemec, Jan

    2007-05-01

    A case of a patient with runaway implantable cardioverter defibrillator (ICD) due to radiation therapy of a lung cancer is reported. This manifested as poorly tolerated wide complex tachycardia due to inappropriate rapid ventricular pacing, The event terminated with polymorphic VT, which inhibited pacing and ceased spontaneously before ICD discharge. The likely cause was corruption of device random access memory by ionizing radiation.

  18. Runaway House: A Youth-Run Service Project.

    ERIC Educational Resources Information Center

    Butler, Dodie; And Others

    This booklet describes Special Approaches in Juvenile Assistance (SAJA), a nonprofit corporation that consists of: (1) the Runaway House, a temporary shelter and counseling program for people under the age of 18 who have run away from home; (2) two foster group homes in which the workers and young people share responsibility for cooking, cleaning…

  19. The 1987 outburst of the BL Lacertid AO 0235 + 164

    NASA Astrophysics Data System (ADS)

    Webb, J. R.; Smith, A. G.

    1989-08-01

    The violently variable BL Lacertid AO 0235 + 164 displayed a 3.24 magnitude outburst in early 1987. This outburst was observed intensively from Rosemary Hill Observatory in three colors. Long term monitoring observations made at Rosemary Hill are examined in an effort to find any recurring timescales associated with this outburst and previous large amplitude outbursts. The energetics of the 1987 outburst are analyzed in terms of the Shields and Wheeler model of a magnetized accretion disk. The timescales identified in the power spectrum (2.8 and 1.6 yr) are input into the model as the storage timescales. Since the emitted energy calculated from the optical burst cannot be stored in a magnetized disk at an allowable radius, it is concluded that either the storage timescales are longer than those identified in the power spectrum, or relativistic beaming effects must be considered, with a Doppler factor of 1.3 to 1.6.

  20. Runaway transient simulation of a model Kaplan turbine

    NASA Astrophysics Data System (ADS)

    Liu, S.; Zhou, D.; Liu, D.; Wu, Y.; Nishi, M.

    2010-08-01

    The runaway transient is a typical transient process of a hydro power unit, where the rotational speed of a turbine runner rapidly increases up to the runaway speed under a working head as the guide vanes cannot be closed due to some reason at the load rejection. In the present paper, the characteristics of the runaway transient of a model Kaplan turbine having ns = 479(m-kW) is simulated by using a time-dependent CFD technique where equation of rotational motion of runner, continuity equation and unsteady RANS equations with RNG k-epsilon turbulence model are solved iteratively. In the calculation, unstructured mesh is used to the whole flow passage, which consists of several sub-domains: entrance, casing, stay vanes + guide vanes, guide section, runner and draft tube. And variable speed sliding mesh technique is used to exchange interface flow information between moving part and stationary part, and three-dimensional unstructured dynamic mesh technique is also adopted to ensure mesh quality. Two cases were treated in the simulation of runaway transient characteristics after load rejection: one is the rated operating condition as the initial condition, and the other is the condition at the maximum head. Regarding the runaway speed, the experimental speed is 1.45 times the initial speed and the calculation is 1.47 times the initial for the former case. In the latter case, the experiment and the calculation are 1.67 times and 1.69 times respectively. From these results, it is recognized that satisfactorily prediction will be possible by using the present numerical method. Further, numerical results show that the swirl in the draft-tube flow becomes stronger in the latter part of the transient process so that a vortex rope will occur in the draft tube and its precession will cause the pressure fluctuations which sometimes affect the stability of hydro power system considerably.

  1. Thermonuclear Supernova Explosions From Hybrid White Dwarf Progenitors

    NASA Astrophysics Data System (ADS)

    Willcox, Donald E.; Townsley, Dean; Calder, Alan; Denissenkov, Pavel; Herwig, Falk

    2016-01-01

    Motivated by recent results in stellar evolution in which convective boundary mixing in SAGB stars can give rise to hybrid white dwarf (WD) stars with a C-O core inside an O-Ne shell, we simulate thermonuclear (Type Ia) supernovae from these hybrid progenitors. We use the FLASH code to perform multidimensional simulations in the deflagration to detonation transition (DDT) explosion paradigm from progenitor models produced with the MESA stellar evolution code that include the thermal energetics of the Urca process. We performed a suite of DDT simulations over a range of ignition conditions and compare to previous results from a suite of C-O white dwarfs. Despite significant variability within each suite, distinguishing trends are apparent in their Ni-56 yields and the kinetic properties of their ejecta. We comment on the feasibility of these hybrid WD explosions as the source of some classes of observed subluminous events. This research was supported in part by the U.S. Department of Energy under grant DE-FG02-87ER40317 and by resources at the Institute for Advanced Computational Science at Stony Brook University. The software used in this work was in part developed by the DOE-supported ASC/Alliances Center for Astrophysical Thermonuclear Flashes at the University of Chicago.

  2. The classification of magnetohydrodynamic regimes of thermonuclear combustion

    SciTech Connect

    Remming, Ian S.; Khokhlov, Alexei M.

    2014-10-10

    Physical properties of magnetohydrodynamic (MHD) reaction fronts are studied as functions of the thermodynamic conditions, and the strength and orientation of the magnetic field in the unburned matter through which the fronts propagate. We determine the conditions for the existence of the various types of MHD reaction fronts and the character of the changes in physical quantities across these reaction fronts. The analysis is carried out in general for a perfect gas equation of state and a constant energy release, and then extended to thermonuclear reaction fronts in degenerate carbon-oxygen mixtures and degenerate helium in conditions typical of Type Ia supernova explosions. We find that as unburned matter enters perpendicular to a reaction front, the release of energy through burning generates shear velocity in the reacting gas that, depending on the type of reaction front, strengthens or weakens the magnetic field. In addition, we find that the steady-state propagation of a reaction front is impossible for certain ranges of magnetic field direction. Our results provide insight into the phenomena of MHD thermonuclear combustion that is relevant to the interpretation of future simulations of SN Ia explosions that have magnetic fields systematically incorporated.

  3. Statistical analysis of properties of dwarf novae outbursts

    NASA Astrophysics Data System (ADS)

    Otulakowska-Hypka, Magdalena; Olech, Arkadiusz; Patterson, Joseph

    2016-08-01

    We present a statistical study of all measurable photometric features of a large sample of dwarf novae during their outbursts and superoutbursts. We used all accessible photometric data for all our objects to make the study as complete and up to date as possible. Our aim was to check correlations between these photometric features in order to constrain theoretical models which try to explain the nature of dwarf novae outbursts. We managed to confirm a few of the known correlations, that is the Stolz and Schoembs relation, the Bailey relation for long outbursts above the period gap, the relations between the cycle and supercycle lengths, amplitudes of normal and superoutbursts, amplitude and duration of superoutbursts, outburst duration and orbital period, outburst duration and mass ratio for short and normal outbursts, as well as the relation between the rise and decline rates of superoutbursts. However, we question the existence of the Kukarkin-Parenago relation but we found an analogous relation for superoutbursts. We also failed to find one presumed relation between outburst duration and mass ratio for superoutbursts. This study should help to direct theoretical work dedicated to dwarf novae.

  4. Prevalence and clinical correlates of explosive outbursts in Tourette syndrome.

    PubMed

    Chen, Kevin; Budman, Cathy L; Diego Herrera, Luis; Witkin, Joanna E; Weiss, Nicholas T; Lowe, Thomas L; Freimer, Nelson B; Reus, Victor I; Mathews, Carol A

    2013-02-28

    The aim of this study was to examine the prevalence and clinical correlates of explosive outbursts in two large samples of individuals with Tourette syndrome (TS), including one collected primarily from non-clinical sources. Participants included 218 TS-affected individuals who were part of a genetic study (N=104 from Costa Rica (CR) and N=114 from the US). The relationships between explosive outbursts and comorbid attention deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), tic severity, and prenatal and perinatal complications were examined using regression analyses. Twenty percent of participants had explosive outbursts, with no significant differences in prevalence between the CR (non-clinical) and the US (primarily clinical) samples. In the overall sample, ADHD, greater tic severity, and lower age of tic onset were strongly associated with explosive outbursts. ADHD, prenatal exposure to tobacco, and male gender were significantly associated with explosive outbursts in the US sample. Lower age of onset and greater severity of tics were significantly associated with explosive outbursts in the CR sample. This study confirms previous studies that suggest that clinically significant explosive outbursts are common in TS and associated with ADHD and tic severity. An additional potential risk factor, prenatal exposure to tobacco, was also identified.

  5. YOUNG AGN OUTBURST RUNNING OVER OLDER X-RAY CAVITIES

    SciTech Connect

    Bogdán, Ákos; Van Weeren, Reinout J.; Kraft, Ralph P.; Forman, William R.; Randall, Scott; Jones, Christine; Giacintucci, Simona; Churazov, Eugene; O'Dea, Christopher P.; Baum, Stefi A.; Noell-Storr, Jacob

    2014-02-20

    Although the energetic feedback from active galactic nuclei (AGNs) is believed to have a profound effect on the evolution of galaxies and clusters of galaxies, details of AGN heating remain elusive. Here, we study NGC 193—a nearby lenticular galaxy—based on X-ray (Chandra) and radio (Very Large Array and Giant Meter-wave Radio Telescope) observations. These data reveal the complex AGN outburst history of the galaxy: we detect a pair of inner X-ray cavities, an outer X-ray cavity, a shock front, and radio lobes extending beyond the inner cavities. We suggest that the inner cavities were produced ∼78 Myr ago by a weaker AGN outburst, while the outer cavity, the radio lobes, and the shock front are due to a younger (13-26 Myr) and 4-8 times more powerful outburst. Combining this with the observed morphology of NGC 193, we conclude that NGC 193 likely represents the first example of a second, more powerful, AGN outburst overrunning an older, weaker outburst. These results help us to understand how the outburst energy is dissipated uniformly in the core of galaxies, and therefore may play a crucial role in resolving how AGN outbursts suppress the formation of large cooling flows at cluster centers.

  6. Young AGN Outburst Running over Older X-Ray Cavities

    NASA Astrophysics Data System (ADS)

    Bogdan, Akos; van Weeren, Reinout Johannes; Kraft, Ralph; Forman, William; Scott, Randall; Giacintucci, Simona; Churazov, Eugene; O'Dea, Christopher; Baum, Stefi; Noell-Storr, Jacob; Jones, Christine

    2015-08-01

    Although the energetic feedback from active galactic nuclei (AGNs) is believed to have a profound effect on the evolution of galaxies and clusters of galaxies, details of AGN heating remain elusive. Here, we study NGC 193 -- a nearby lenticular galaxy in a group -- based on X-ray and radio observations. These data reveal the complex AGN outburst history of the galaxy: we detect a pair of inner X-ray cavities, an outer X-ray cavity, a shock front, and radio lobes extending beyond the inner cavities. We suggest that the inner cavities were produced about 78 Myr ago by a weaker AGN outburst, while the outer cavity, the radio lobes, and the shock front are due to a younger (13-26 Myr) and 4-8 times more powerful outburst. Combining this with the observed morphology of NGC 193, we conclude that NGC 193 likely represents the first example of a second, more powerful, AGN outburst overrunning an older, weaker outburst. These results help us to understand how the outburst energy is dissipated uniformly in the core of galaxies, and therefore may play a crucial role in resolving how AGN outbursts suppress the formation of large cooling flows at cluster centers.

  7. GIANT OUTBURSTS IN Be/X-RAY BINARIES

    SciTech Connect

    Martin, Rebecca G.; Nixon, Chris; Armitage, Philip J.; Lubow, Stephen H.; Price, Daniel J.

    2014-08-01

    Be/X-ray binary systems exhibit both periodic (Type I) X-ray outbursts and giant (Type II) outbursts, whose origins have remained elusive. We suggest that Type II X-ray outbursts occur when a highly misaligned decretion disk around the Be star becomes eccentric, allowing the compact object companion to capture a large amount of material at periastron. Using three-dimensional smoothed particle hydrodynamics simulations, we model the long-term evolution of a representative Be/X-ray binary system. We find that periodic (Type I) X-ray outbursts occur when the neutron star is close to periastron for all disk inclinations. Type II outbursts occur for large misalignment angles and are associated with eccentricity growth which occurs on a timescale of about 10 orbital periods. Mass capture from the eccentric decretion disk results in an accretion disk around the neutron star whose estimated viscous time is long enough to explain the extended duration of Type II outbursts. Previous studies suggested that the outbursts are caused by a warped disk but our results suggest that this is not sufficient; the disk must be both highly misaligned and eccentric to initiate a Type II accretion event.

  8. V1331 Cyg- An outburst of results

    NASA Astrophysics Data System (ADS)

    Choudhary, Arpita; Stecklum, Bringfried; Stapelfeldt, Karl

    2013-07-01

    FU Orionis objects are a class of young stars with large brightness outbursts in the optical. The outbursts lead to strong increase in luminosity due to enhanced accretion and dust removal by the accompanying wind. All FUors have large infrared excess emission from circumstellar dust, and some drive bipolar jets and outflows. V1331 Cyg is a pre-outburst FUor candidate: At distance of ~ 550 pc, at the border of the dark cloud LDN 981. It is associated with an arc-like reflection nebula. It has two nested rings of 9000 and 3300 AU radii respectively, encircled by an expanding CO ring. The HST-WFPC2 imaging was done in 2000 and 2009. The first epoch images were obtained for F606W and F814W filters. The second epoch observations were deeper with one more filter, F450W introduced. Wind-driven expansion has an imprint on the colour profile of the ring, the study of which will be the next step to do. There is a missing ring section to the NW not due to extinction by the dark cloud but represent a shadow, originating close to the star. Our PSF -subtracted planetary camera frames disclosed a knot at ~0.4" from the star in the same direction. Also our analysis of archival Subaru coronagraphic H-band imaging reveals scattered light associated with this feature which was not seen before. Both findings suggest increased height of the matter at distances of ~300 AU which casts the shadow. This might be related to planet formation in the circumstellar disk. The scattering knot is associated with two spiral arms which stretch further out. The UKIDSS JHK images show faint reddened stars in the gap, confirming the presence of dense matter from probably both the protostellar environment and the molecular cloud. Herschel and SCUBA data confirm that V1331 Cyg is the most luminous object in the surroundings, ONLY possible young stellar candidate responsible for the outflow. Narrow-band imaging in the Hα and [SII] line revealed a bipolar outflow, presumed to have a substantial

  9. Experimental and theoretical analysis of a method to predict thermal runaway in Li-ion cells

    NASA Astrophysics Data System (ADS)

    Shah, Krishna; Chalise, Divya; Jain, Ankur

    2016-10-01

    Thermal runaway is a well-known safety concern in Li-ion cells. Methods to predict and prevent thermal runaway are critically needed for enhanced safety and performance. While much work has been done on understanding the kinetics of various heat generation processes during thermal runaway, relatively lesser work exists on understanding how heat removal from the cell influences thermal runaway. Through a unified analysis of heat generation and heat removal, this paper derives and experimentally validates a non-dimensional parameter whose value governs whether or not thermal runaway will occur in a Li-ion cell. This parameter is named the Thermal Runaway Number (TRN), and comprises contributions from thermal transport within and outside the cell, as well as the temperature dependence of heat generation rate. Experimental data using a 26650 thermal test cell are in good agreement with the model, and demonstrate the dependence of thermal runaway on various thermal transport and heat generation parameters. This parameter is used to predict the thermal design space in which the cell will or will not experience thermal runaway. By combining all thermal processes contributing to thermal runaway in a single parameter, this work contributes towards a unified understanding of thermal runaway, and provides the fundamental basis for design tools for safe, high-performance Li-ion batteries.

  10. EUVE photometry of SS Cygni: Dwarf nova outbursts and oscillations

    SciTech Connect

    Mauche, C.W.

    1995-05-15

    The authors present EUVE Deep Survey photometry and AAVSO optical measurements of the 1993 August and 1994 June/July outbursts of the dwarf nova SS Cygni. The EUV and optical light curves are used to illustrate the different response of the accretion disk to outbursts which begin at the inner edge and propagate outward, and those which begin at the outer edge and propagate inward. Furthermore, the authors describe the properties of the quasi-coherent 7--9 s sinusoidal oscillations in the EUV flux detected during the rise and plateau stages of these outbursts.

  11. A POWERFUL AGN OUTBURST IN RBS 797

    SciTech Connect

    Cavagnolo, K. W.; McNamara, B. R.; Wise, M. W.; Nulsen, P. E. J.; Gitti, M.; Brueggen, M.; Rafferty, D. A.

    2011-05-10

    Utilizing {approx}50 ks of Chandra X-Ray Observatory imaging, we present an analysis of the intracluster medium (ICM) and cavity system in the galaxy cluster RBS 797. In addition to the two previously known cavities in the cluster core, the new and deeper X-ray image has revealed additional structure associated with the active galactic nucleus (AGN). The surface brightness decrements of the two cavities are unusually large and are consistent with elongated cavities lying close to our line of sight. We estimate a total AGN outburst energy and mean jet power of {approx}(3-6) x 10{sup 60} erg and {approx}(3-6) x 10{sup 45} erg s{sup -1}, respectively, depending on the assumed geometrical configuration of the cavities. Thus, RBS 797 is apparently among the most powerful AGN outbursts known in a cluster. The average mass accretion rate needed to power the AGN by accretion alone is {approx}1 M{sub sun} yr{sup -1}. We show that accretion of cold gas onto the AGN at this level is plausible, but that Bondi accretion of the hot atmosphere is probably not. The brightest cluster galaxy (BCG) harbors an unresolved, non-thermal nuclear X-ray source with a bolometric luminosity of {approx}2 x 10{sup 44} erg s{sup -1}. The nuclear emission is probably associated with a rapidly accreting, radiatively inefficient accretion flow. We present tentative evidence that star formation in the BCG is being triggered by the radio jets and suggest that the cavities may be driving weak shocks (M {approx} 1.5) into the ICM, similar to the process in the galaxy cluster MS 0735.6+7421.

  12. The 2010 outburst and pre-outburst optical spectrum of the recurrent nova U Scorpii

    NASA Astrophysics Data System (ADS)

    Anupama, G. C.; Kamath, U. S.; Ramaprakash, A. N.; Kantharia, N. G.; Hegde, M.; Mohan, V.; Kulkarni, M.; Bode, M. F.; Eyres, S. P. S.; Evans, A.; O'Brien, T. J.

    2013-11-01

    Aims: We study the evolution of the recurrent nova U Scorpii during its outburst in 2010. Methods: Optical spectroscopic observations of the nova were obtained during 0.83-162.5 days after outburst maximum. Optical linear polarisation observations were made before the onset of the super soft X-ray source (SSS) phase and during the SSS phase. Radio continuum observations were made in the 1280 MHz band during the early decline phase, and in the 610 MHz band at the onset and end of the SSS phase. We also present optical spectra obtained in the pre-outburst quiescence phase. Results: The overall spectral evolution during the 2010 outburst is similar to the previous outbursts. However, the dense temporal coverage, especially during the early phases, reveals several short term variations not reported previously. The early phase emission line widths indicate extremely high velocities for the nova ejecta, ~10 000 km s-1. The line profiles are broad, boxy and structured. Narrow P-Cygni absorptions, at ~500 km s-1 are seen associated with the He I lines, and also the Ca II, N I and hydrogen lines (at wavelengths >8000 Å) in the spectrum of day 6.83, obtained immediately after an optical flare. This absorption component could be arising in the plasma emitting the Nitrogen lines seen in X-rays, that probably lies outside the binary orbit. Rapid variations are detected in the strength of the 4660 Å N III feature, which shows a significant increase in the line strength on days 8.83 and 13.82, at orbital phases of 0.75 and 0.25, respectively. Instrinsic polarisation is detected just before the onset, and during the SSS phase, with pv ~ 1.4% during the SSS phase. The flux variations of the N III feature and the intrinsic polarisation are most likely associated with the reforming accretion disc/stream. We estimate the mass of the ejected (hydrogen) shell to be ~4.6 × 10-6 M⊙, for a spherical shell geometry. The non-detection of U Sco in the 1280 MHz and 610 MHz radio bands is

  13. Relativistic outflow from two thermonuclear shell flashes on neutron stars

    NASA Astrophysics Data System (ADS)

    in't Zand, J. J. M.; Keek, L.; Cavecchi, Y.

    2014-08-01

    We study the exceptionally short (32-43 ms) precursors of two intermediate-duration thermonuclear X-ray bursts observed with the Rossi X-ray Timing Explorer from the neutron stars in 4U 0614+09 and 2S 0918-549. They exhibit photon fluxes that surpass those at the Eddington limit later in the burst by factors of 2.6 to 3.1. We are able to explain both the short duration and the super-Eddington flux by mildly relativistic outflow velocities of 0.1c to 0.3c subsequent to the thermonuclear shell flashes on the neutron stars. These are the highest velocities ever measured from any thermonuclear flash. The precursor rise times are also exceptionally short: about 1 ms. This is inconsistent with predictions for nuclear flames spreading laterally as deflagrations and suggests detonations instead. This is the first time that a detonation is suggested for such a shallow ignition column depth (yign ≈ 1010 g cm-2). The detonation would possibly require a faster nuclear reaction chain, such as bypassing the α-capture on 12C with the much faster 12C(p,γ)13N(α,p)16O process previously proposed. We confirm the possibility of a detonation, albeit only in the radial direction, through the simulation of the nuclear burning with a large nuclear network and at the appropriate ignition depth, although it remains to be seen whether the Zel'dovich criterion is met. A detonation would also provide the fast flame spreading over the surface of the neutron star to allow for the short rise times. This needs to be supported by future two-dimensional calculations of flame spreading at the relevant column depth. As an alternative to the detonation scenario, we speculate on the possibility that the whole neutron star surface burns almost instantly in the auto-ignition regime. This is motivated by the presence of 150 ms precursors with 30 ms rise times in some superexpansion bursts from 4U 1820-30 at low ignition column depths of ~108 g cm-2.

  14. Runaway electrification of friable self-replicating granular matter.

    PubMed

    Cartwright, Julyan H E; Escribano, Bruno; Grothe, Hinrich; Piro, Oreste; Sainz Díaz, C Ignacio; Tuval, Idan

    2013-10-15

    We establish that the nonlinear dynamics of collisions between particles favors the charging of an insulating, friable, self-replicating granular material that undergoes nucleation, growth, and fission processes; we demonstrate with a minimal dynamical model that secondary nucleation produces a positive feedback in an electrification mechanism that leads to runaway charging. We discuss ice as an example of such a self-replicating granular material: We confirm with laboratory experiments in which we grow ice from the vapor phase in situ within an environmental scanning electron microscope that charging causes fast-growing and easily breakable palmlike structures to form, which when broken off may form secondary nuclei. We propose that thunderstorms, both terrestrial and on other planets, and lightning in the solar nebula are instances of such runaway charging arising from this nonlinear dynamics in self-replicating granular matter. PMID:24041221

  15. Runaway Electrification of Friable Self-Replicating Granular Matter

    PubMed Central

    2013-01-01

    We establish that the nonlinear dynamics of collisions between particles favors the charging of an insulating, friable, self-replicating granular material that undergoes nucleation, growth, and fission processes; we demonstrate with a minimal dynamical model that secondary nucleation produces a positive feedback in an electrification mechanism that leads to runaway charging. We discuss ice as an example of such a self-replicating granular material: We confirm with laboratory experiments in which we grow ice from the vapor phase in situ within an environmental scanning electron microscope that charging causes fast-growing and easily breakable palmlike structures to form, which when broken off may form secondary nuclei. We propose that thunderstorms, both terrestrial and on other planets, and lightning in the solar nebula are instances of such runaway charging arising from this nonlinear dynamics in self-replicating granular matter. PMID:24041221

  16. Positron creation and annihilation in tokamak plasmas with runaway electrons.

    PubMed

    Helander, P; Ward, D J

    2003-04-01

    It is shown that electron-positron pair production is expected to occur in post-disruption plasmas in large tokamaks, including JET and JT-60U, where up to about 10(14) positrons may be created in collisions between multi-MeV runaway electrons and thermal particles. If the loop voltage is large enough, they are accelerated and form a beam of long-lived runaway positrons in the direction opposite to that of the electrons; if the loop voltage is smaller, the positrons have a lifetime of a few hundred ms, in which they are slowed down to energies comparable to that of the cool ( less, similar 10 eV) background plasma before being annihilated.

  17. Runaway Stars in the Galactic Halo: Their Origin and Kinematics

    NASA Astrophysics Data System (ADS)

    Duarte de Vasconcelos Silva, Manuel

    2012-03-01

    Star formation in the Milky Way is confined to star-forming regions (OB associ- ation, HII regions, and open clusters) in the Galactic plane. It is usually assumed that these regions are found preferably along spiral arms, as is observed in other spiral galaxies. However, young early-type stars are often found at high Galactic latitudes, far away from their birthplaces in the Galactic disc. These stars are called runaway stars, and it is believed that they were ejected from their birth- places early in their lifetimes by one of two mechanisms: ejection from a binary system following the destruction of the massive companion in a supernova type II event (the binary ejection mechanism), or ejection from a dense cluster following a close gravitational encounter between two close binaries (the dynamical ejection mechanism). The aims of our study were: to improve the current understanding of the nature of high Galactic latitude runaway stars, in particular by investigating whether the theoretical ejection mechanisms could explain the more extreme cases; to show the feasibility of using high Galactic latitude stars as tracers of the spiral arms. The main technique used in this investigation was the tracing of stellar orbits back in time, given their present positions and velocities in 3D space. This technique allowed the determination of the ejection velocities, flight times and birthplaces of a sample of runaway stars. In order to obtain reasonable velocity estimates several recent catalogues of proper motion data were used. We found that the evolutionary ages of the vast majority of runaway stars is consistent with the disc ejection scenario. However, we identified three outliers which would need flight times much larger then their estimated ages in order to reach their present positions in the sky. Moreover, the ejection velocity distribution appears to be bimodal, showing evidence for two populations of runaway stars: a "low" velocity population (89 per cent of the

  18. Breakdown and discharges in dense gases governed by runaway electrons

    SciTech Connect

    Babich, L.P.

    1996-03-01

    The phenomenon of runaway electrons (REs) at high values of the ratio field intensity/gas number density {ital E}/{ital N} and {ital N} up to the Loshmidt number {ital N}{sub {ital L}}{approx_equal}2.7{times}10{sup 19} cm{sup {minus}3} is described. REs are shown to govern the breakdown and discharges at such condition. {copyright} {ital 1996 American Institute of Physics.}

  19. Detection of runaway electrons - a journey 100 years long

    NASA Astrophysics Data System (ADS)

    Chilingarian, Ashot

    2013-04-01

    In the beginning of last century C.T.R. Wilson proposes that strong electrical field of the thunderclouds might accelerate electrons to very high energies. However, this and many other electromagnetic processes in our atmosphere are poorly understood till now; the key questions about the thundercloud electrification and lightning initiation remain unanswered. During recent decades several observations of gamma ray, electron and neutron fluxes correlated with thunderstorms were reported. Nonetheless, the origin of these fluxes is under debate till now. The direct registration of the particle showers initiated by the runaway electrons (the most popular theory) was missing. We present the experimental evidence of the microsecond duration electron bursts originated from runaway electrons accelerated in thunderclouds. The first direct experimental observation of the RREA process was made at Aragats in 2009 with a network of 16 plastic scintillators distributing on the area of ~ 1000 m2 registering 8-fold enhancement of particle showers during maximal flux of TGE. The statistical analysis of ~200 detected particle showers reveals their systematic difference from the Extensive Air Shower (EAS) events: the density was much lower and spatial spread of the electrons was much more uniform (particle distribution in EAS has characteristic bell-like form). The particle showers from the thunderclouds were named - Cloud extensive showers (CESs). A SEC phenomenon is very rare: only 3 largest TGEs from 300 were accompanied by SEC observation. CESs originated from individual runaway electrons accelerated in the cloud just above the detector. RREA (CES) phenomenon is very local and depends on the height of cloud above detector and on the strength of electric field in it. Both parameters are fast changing and only during several minutes cascades from runaway electrons can be developed enough to cover several thousand square meters of surface. Only very suitable location and large sizes

  20. Note: Measurement of the runaway electrons in the J-TEXT tokamak

    SciTech Connect

    Chen, Z. Y.; Zhang, Y.; Zhang, X. Q.; Luo, Y. H.; Jin, W.; Li, J. C.; Chen, Z. P.; Wang, Z. J.; Yang, Z. J.; Zhuang, G.

    2012-05-15

    The runaway electrons have been measured by hard x-ray detectors and soft x-ray array in the J-TEXT tokamak. The hard x-ray radiations in the energy ranges of 0.5-5 MeV are measured by two NaI detectors. The flux of lost runaway electrons can be obtained routinely. The soft x-ray array diagnostics are used to monitor the runaway beam generated in disruptions since the soft x-ray is dominated by the interaction between runaway electrons and metallic impurities inside the plasma. With the aid of soft x-ray array, runaway electron beam has been detected directly during the formation of runaway current plateau following the disruptions.

  1. Observation of runaway electrons by infrared camera in J-TEXT

    NASA Astrophysics Data System (ADS)

    Tong, R. H.; Chen, Z. Y.; Zhang, M.; Huang, D. W.; Yan, W.; Zhuang, G.

    2016-11-01

    When the energy of confined runaway electrons approaches several tens of MeV, the runaway electrons can emit synchrotron radiation in the range of infrared wavelength. An infrared camera working in the wavelength of 3-5 μm has been developed to study the runaway electrons in the Joint Texas Experimental Tokamak (J-TEXT). The camera is located in the equatorial plane looking tangentially into the direction of electron approach. The runaway electron beam inside the plasma has been observed at the flattop phase. With a fast acquisition of the camera, the behavior of runaway electron beam has been observed directly during the runaway current plateau following the massive gas injection triggered disruptions.

  2. The dynamic mutation characteristics of thermonuclear reaction in Tokamak.

    PubMed

    Li, Jing; Quan, Tingting; Zhang, Wei; Deng, Wei

    2014-01-01

    The stability and bifurcations of multiple limit cycles for the physical model of thermonuclear reaction in Tokamak are investigated in this paper. The one-dimensional Ginzburg-Landau type perturbed diffusion equations for the density of the plasma and the radial electric field near the plasma edge in Tokamak are established. First, the equations are transformed to the average equations with the method of multiple scales and the average equations turn to be a Z 2-symmetric perturbed polynomial Hamiltonian system of degree 5. Then, with the bifurcations theory and method of detection function, the qualitative behavior of the unperturbed system and the number of the limit cycles of the perturbed system for certain groups of parameter are analyzed. At last, the stability of the limit cycles is studied and the physical meaning of Tokamak equations under these parameter groups is given.

  3. Current drive at plasma densities required for thermonuclear reactors.

    PubMed

    Cesario, R; Amicucci, L; Cardinali, A; Castaldo, C; Marinucci, M; Panaccione, L; Santini, F; Tudisco, O; Apicella, M L; Calabrò, G; Cianfarani, C; Frigione, D; Galli, A; Mazzitelli, G; Mazzotta, C; Pericoli, V; Schettini, G; Tuccillo, A A

    2010-08-10

    Progress in thermonuclear fusion energy research based on deuterium plasmas magnetically confined in toroidal tokamak devices requires the development of efficient current drive methods. Previous experiments have shown that plasma current can be driven effectively by externally launched radio frequency power coupled to lower hybrid plasma waves. However, at the high plasma densities required for fusion power plants, the coupled radio frequency power does not penetrate into the plasma core, possibly because of strong wave interactions with the plasma edge. Here we show experiments performed on FTU (Frascati Tokamak Upgrade) based on theoretical predictions that nonlinear interactions diminish when the peripheral plasma electron temperature is high, allowing significant wave penetration at high density. The results show that the coupled radio frequency power can penetrate into high-density plasmas due to weaker plasma edge effects, thus extending the effective range of lower hybrid current drive towards the domain relevant for fusion reactors.

  4. NASA superconducting magnetic mirror facility. [for thermonuclear research

    NASA Technical Reports Server (NTRS)

    Reinmann, J. J.; Swanson, M. C.; Nichols, C. R.; Bloy, S. J.; Nagy, L. A.; Brady, F. J.

    1973-01-01

    The design details and initial test results of a superconducting magnetic mirror facility that has been constructed at NASA Lewis Research Center for use in thermonuclear research are summarized. The magnet system consists of four solenoidal coils which are individually rated at 5.0 T. Each coll is composed of an inner, middle, and outer winding. The inner winding is wound of stabilized Nb3Sn superconducting ribbon, and the middle and outer windings are wound of stabilized Nb-Ti superconducting wire. When arranged in the mirror geometry, the four coils will produce 8.7 T at the mirrors and a 1.8 mirror ratio. The magnet has a 41-cm diameter clear bore which is open to atmosphere. Distance between the mirrors is 111 cm. Presently there are only three magnets in the facility; the fourth magnet is being rebuilt.

  5. A compilation of charged-particle induced thermonuclear reaction rates

    NASA Astrophysics Data System (ADS)

    Angulo, C.; Arnould, M.; Rayet, M.; Descouvemont, P.; Baye, D.; Leclercq-Willain, C.; Coc, A.; Barhoumi, S.; Aguer, P.; Rolfs, C.; Kunz, R.; Hammer, J. W.; Mayer, A.; Paradellis, T.; Kossionides, S.; Chronidou, C.; Spyrou, K.; degl'Innocenti, S.; Fiorentini, G.; Ricci, B.; Zavatarelli, S.; Providencia, C.; Wolters, H.; Soares, J.; Grama, C.; Rahighi, J.; Shotter, A.; Lamehi Rachti, M.

    1999-08-01

    Low-energy cross section data for 86 charged-particle induced reactions involving light (1 <=Z <=14), mostly stable, nuclei are compiled. The corresponding Maxwellian-averaged thermonuclear reaction rates of relevance in astrophysical plasmas at temperatures in the range from 106 K to 1010 K are calculated. These evaluations assume either that the target nuclei are in their ground state, or that the target states are thermally populated following a Maxwell-Boltzmann distribution, except in some cases involving isomeric states. Adopted values complemented with lower and upper limits of the rates are presented in tabular form. Analytical approximations to the adopted rates, as well as to the inverse/direct rate ratios, are provided.

  6. Hot subdwarf stars and their connection to thermonuclear supernovae

    NASA Astrophysics Data System (ADS)

    Geier, S.; Kupfer, T.; Ziegerer, E.; Heber, U.; Németh, P.; Irrgang, A.; pre=", team

    2016-07-01

    Hot subdwarf stars (sdO/Bs) are evolved core helium-burning stars with very thin hydrogen envelopes, which can be formed by common envelope ejection. Close sdB binaries with massive white dwarf (WD) companions are potential progenitors of thermonuclear supernovae type Ia (SN Ia). We discovered such a progenitor candidate as well as a candidate for a surviving companion star, which escapes from the Galaxy. More candidates for both types of objects have been found by crossmatching known sdB stars with proper motion and light curve catalogues. The Gaia mission will provide accurate astrometry and light curves of all the stars in our hot subdwarf sample and will allow us to compile a much larger all-sky catalogue of those stars. In this way we expect to find hundreds of progenitor binaries and ejected companions.

  7. Influence of thermonuclear effects on the collapse of supermassive stars

    NASA Astrophysics Data System (ADS)

    Montero, Pedro J.; Janka, H.-T.; Müller, E.; Müller, B.

    2011-09-01

    We present results of general relativistic simulations of collapsing supermassive stars using the two-dimensional general relativistic numerical code Nada, which solves the Einstein equations written in the BSSN formalism and the general relativistic hydrodynamic equations with high resolution shock capturing schemes. These numerical simulations use a tabulated equation of state which includes effects of radiation and gas pressure, and those associated with the electron-positron pairs. We also take into account the effect of thermonuclear energy released by hydrogen and helium burning. We find that objects with mass ≈ 5 × 105M and initial metallicity greater than ZCNO ≈ 0.004 do explode if non-rotating, while the threshold metallicity for an explosion is reduced to ZCNO ≈ 0.002 for objects uniformly rotating.

  8. The Dynamic Mutation Characteristics of Thermonuclear Reaction in Tokamak

    PubMed Central

    Li, Jing; Quan, Tingting; Zhang, Wei; Deng, Wei

    2014-01-01

    The stability and bifurcations of multiple limit cycles for the physical model of thermonuclear reaction in Tokamak are investigated in this paper. The one-dimensional Ginzburg-Landau type perturbed diffusion equations for the density of the plasma and the radial electric field near the plasma edge in Tokamak are established. First, the equations are transformed to the average equations with the method of multiple scales and the average equations turn to be a Z2-symmetric perturbed polynomial Hamiltonian system of degree 5. Then, with the bifurcations theory and method of detection function, the qualitative behavior of the unperturbed system and the number of the limit cycles of the perturbed system for certain groups of parameter are analyzed. At last, the stability of the limit cycles is studied and the physical meaning of Tokamak equations under these parameter groups is given. PMID:24892099

  9. The September 1996 outbursts of Comet Hale-Bopp

    NASA Astrophysics Data System (ADS)

    Larson, S. M.; Samarasinha, N.; Tao, J.; Hergenrother, C.

    2000-10-01

    Digitally enhanced pre-perihelion groundbased images of Comet Hale-Bopp taken in September 1996 show intersting morphology resulting from at least two outbursts. During that apparition, the coma was dominated by radial ``porcupine" morphology. However, a 2 magnitude outburst starting on 1996 September 9.5 UT (Tao et al., 2000, Plan. Sp. Sci. 48, 153-161) resulted in two expanding dust shells with apparent expansion speeds of 112 and 225 m/s and an arc in the NW quadrant. This morphology is very similar to that seen in post-perihelion NICMOS images of a similar outburst on 1997 August 27 (see Campins et al., DPS 2000 abstract). Similar, but less pronounced outburst activity can be seen later in the month and include evidence for ejection of discrete fragments. We explore the possible mechanisms for the observed morphology. This work is supported in part by the NASA Planetary Atmospheres Program.

  10. Prominent outburst of the blazar CTA 102 in 2012

    NASA Astrophysics Data System (ADS)

    Larionov, V. M.; Blinov, D. A.; Jorstad, S. G.; Marscher, A. P.; Villata, M.; Raiteri, C. M.; Agudo, I.; Smith, P. S.; Morozova, D. A.; Troitsky, I. S.; Clemens, D. P.

    2013-12-01

    After a few years of quiescence, the blazar CTA 102 underwent a large outburst in the fall of 2012. The flare has been tracked from γ-rays to near-infrared, including Fermi and Swift data as well as polarimetric data from several observatories. An intensive GASP-WEBT collaboration campaign in optical and NIR bands, with the addition of previously unpublished archival data, allows comparison of this outburst with the previous activity period of this blazar in the early 2000s. We find remarkable similarity between the optical and γ-ray behavior of CTA 102 during the outburst, without any time lag between the two light curves, indicating co-spatiality of the optical and γ-ray emission regions. A strong harder-when-brighter spectral dependence is seen both in γ-rays and optical. The polarimetric behavior of CTA 102 during the outburst conforms with a shock-in-jet interpretation.

  11. Precession of parent bodies from historical meteor outbursts

    NASA Astrophysics Data System (ADS)

    Ahn, S.-H.

    2015-01-01

    We collect records of meteor outbursts from world-wide historical archives, and analyzed them to see which meteor outbursts have existed during the last two millennia. We calculate the dates of occurrence within the sidereal year for each record, and find four prominent major meteor streams having existed continuously. The prominent and continuous meteor streams are the Lyrids, the Perseids, the Leonids, and the eta- Aquariids/Orionids pair. We also check the regression of nodal points of these streams, and find that both the Leonids and the eta-Aquariids/Orionids pair have relatively large precession rates, while the other streams have small rates. We discuss that the near-type outbursts have occurred more frequently than the far-type outbursts.

  12. New Outburst of Centaur Comet (60558) 174P/Echeclus

    NASA Astrophysics Data System (ADS)

    Choi, Young-Jun; Ishiguro, Masateru; Moon, Hong-Kyu

    2015-03-01

    We report observations of new outburst of Centaur (60558) 174P/Echeclus, using Suprime-Cam of Subaru tele-scope. The outburst was detected by Jager on May 30, 2011 (Jaeger et al., 2011). We made several follow-up observations for this outburst with 1m telescope at Mt. Lemon Optical Astronomy Observatory located in US and 60cm telescope at Sobaeksan Optical Astronomy Observatory in Korea. The very first presence of coma around (60558) 2000 EC98 has been detected by Choi and Weissman (2006) on 2005 December 30.50 UT with the Palomar 5m telescope. Soon after, the object was given the periodic comet designa-tion 174P/Echeclus. We will present the characterstics and discuss the reason of this recursive outburst.

  13. Physical Mechanism of Comet (and Asteroid) Outbursts: The Movie

    NASA Astrophysics Data System (ADS)

    Hartmann, W. K.

    2015-07-01

    A film made during impact experiments at NASA Ames illustrates a mechanism in which regolith can become gas charged and then erupt to create outbursts as observed on comets (and "asteroids" such as 2060 Chiron).

  14. An impact-induced, stable, runaway climate on Mars

    NASA Astrophysics Data System (ADS)

    Segura, Teresa L.; McKay, Christopher P.; Toon, Owen B.

    2012-07-01

    Large asteroid and comet impacts on Mars, such as the one that formed the Argyre basin, delivered considerable amounts of kinetic energy to the planet and raised the surface temperature hundreds of degrees. The impact that formed the Argyre basin occurred 3.8-3.9 byr ago (Werner, S.C. [2008]. Icarus 195, 45-60; Fassett, C.I., Head, J.W. [2011]. Icarus 211, 1204-1214), during the time of formation of fluvial features on the early martian surface, and was capable of causing global-scale precipitation and warming of the surface. Dual solutions to the climate of early Mars, one cold like present Mars and the other in a hot runaway state, exist for the pressure range of 0.006-1 bar of CO2, and for water inventories 6.5 bars or greater. A large impact event may have pushed Mars to a long-lasting hot runaway state. The runaway state would persist until escape processes reduced water vapor and forced the planet to return to a cold climate.

  15. Can increased atmospheric CO2 levels trigger a runaway greenhouse?

    PubMed

    Ramirez, Ramses M; Kopparapu, Ravi Kumar; Lindner, Valerie; Kasting, James F

    2014-08-01

    Recent one-dimensional (globally averaged) climate model calculations by Goldblatt et al. (2013) suggest that increased atmospheric CO(2) could conceivably trigger a runaway greenhouse on present Earth if CO(2) concentrations were approximately 100 times higher than they are today. The new prediction runs contrary to previous calculations by Kasting and Ackerman (1986), which indicated that CO(2) increases could not trigger a runaway, even at Venus-like CO(2) concentrations. Goldblatt et al. argued that this different behavior is a consequence of updated absorption coefficients for H(2)O that make a runaway more likely. Here, we use a 1-D climate model with similar, up-to-date absorption coefficients, but employ a different methodology, to show that the older result is probably still valid, although our model nearly runs away at ∼12 preindustrial atmospheric levels of CO(2) when we use the most alarmist assumptions possible. However, we argue that Earth's real climate is probably stable given more realistic assumptions, although 3-D climate models will be required to verify this result. Potential CO(2) increases from fossil fuel burning are somewhat smaller than this, 10-fold or less, but such increases could still cause sufficient warming to make much of the planet uninhabitable by humans.

  16. THE NATURE OF THE HYPER-RUNAWAY CANDIDATE HIP 60350

    SciTech Connect

    Irrgang, Andreas; Przybilla, Norbert; Heber, Ulrich; Fernanda Nieva, M.; Schuh, Sonja

    2010-03-01

    Young, massive stars in the Galactic halo are widely supposed to be the result of an ejection event from the Galactic disk forcing some stars to leave their place of birth as so-called runaway stars. Here, we present a detailed spectroscopic and kinematic analysis of the runaway B star HIP 60350 to determine which runaway scenario-a supernova explosion disrupting a binary system or dynamical interaction in star clusters-may be responsible for HIP 60350's peculiar orbit. Based on a non-local thermodynamic equilibrium approach, a high-resolution optical echelle spectrum was examined to revise spectroscopic quantities and for the first time to perform a differential chemical abundance analysis with respect to the B-type star 18 Peg. The results together with proper motions from the Hipparcos Catalog further allowed the three-dimensional kinematics of the star to be studied numerically. The abundances derived for HIP 60350 are consistent with a slightly supersolar metallicity agreeing with the kinematically predicted place of birth {approx}6 kpc away from the Galactic center. However, they do not exclude the possibility of an alpha-enhanced abundance pattern expected in the case of the supernova scenario. Its outstanding high Galactic rest-frame velocity of 530 +- 35 km s{sup -1} is a consequence of ejection in the direction of Galactic rotation and slightly exceeds the local Galactic escape velocity in a standard Galactic potential. Hence, HIP 60350 may be unbound to the Galaxy.

  17. Can increased atmospheric CO2 levels trigger a runaway greenhouse?

    PubMed

    Ramirez, Ramses M; Kopparapu, Ravi Kumar; Lindner, Valerie; Kasting, James F

    2014-08-01

    Recent one-dimensional (globally averaged) climate model calculations by Goldblatt et al. (2013) suggest that increased atmospheric CO(2) could conceivably trigger a runaway greenhouse on present Earth if CO(2) concentrations were approximately 100 times higher than they are today. The new prediction runs contrary to previous calculations by Kasting and Ackerman (1986), which indicated that CO(2) increases could not trigger a runaway, even at Venus-like CO(2) concentrations. Goldblatt et al. argued that this different behavior is a consequence of updated absorption coefficients for H(2)O that make a runaway more likely. Here, we use a 1-D climate model with similar, up-to-date absorption coefficients, but employ a different methodology, to show that the older result is probably still valid, although our model nearly runs away at ∼12 preindustrial atmospheric levels of CO(2) when we use the most alarmist assumptions possible. However, we argue that Earth's real climate is probably stable given more realistic assumptions, although 3-D climate models will be required to verify this result. Potential CO(2) increases from fossil fuel burning are somewhat smaller than this, 10-fold or less, but such increases could still cause sufficient warming to make much of the planet uninhabitable by humans. PMID:25061956

  18. Relativistic runaway breakdown in low-frequency radio

    NASA Astrophysics Data System (ADS)

    Füllekrug, Martin; Roussel-Dupré, Robert; Symbalisty, Eugene M. D.; Chanrion, Olivier; Odzimek, Anna; van der Velde, Oscar; Neubert, Torsten

    2010-01-01

    The electromagnetic radiation emitted by an electron avalanche beam resulting from relativistic runaway breakdown within the Earth's atmosphere is investigated. It is found from theoretical modeling with a computer simulation that the electron beam emits electromagnetic radiation which is characterized by consecutive broadband pulses in the low-frequency radio range from ˜10 to 300 kHz at a distance of ˜800 km. Experimental evidence for the existence of consecutive broadband pulses is provided by low-frequency radio observations of sprite-producing lightning discharges at a distance of ˜550 km. The measured broadband pulses occur ˜4-9 ms after the sprite-producing lightning discharge, they exhibit electromagnetic radiation which mainly spans the frequency range from ˜50 to 350 kHz, and they exhibit complex waveforms without the typical ionospheric reflection of the first hop sky wave. Two consecutive pulses occur ˜4.5 ms and ˜3 ms after the causative lightning discharge and coincide with the sprite luminosity. It is concluded that relativistic runaway breakdown within the Earth's atmosphere can emit broadband electromagnetic pulses and possibly generates sprites. The source location of the broadband pulses can be determined with an interferometric network of wideband low-frequency radio receivers to lend further experimental support to the relativistic runaway breakdown theory.

  19. Demonstration of thermonuclear conditions in magnetized liner inertial fusion experiments

    DOE PAGESBeta

    Gomez, Matthew R.; Slutz, Stephen A.; Sefkow, Adam B.; Hahn, Kelly D.; Hansen, Stephanie B.; Knapp, Patrick F.; Schmit, Paul F.; Ruiz, Carlos L.; Sinars, Daniel Brian; Harding, Eric C.; et al

    2015-04-29

    In this study, the magnetized liner inertial fusion concept [S. A. Slutz et al., Phys. Plasmas17, 056303 (2010)] utilizes a magnetic field and laser heating to relax the pressure requirements of inertial confinement fusion. The first experiments to test the concept [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] were conducted utilizing the 19 MA, 100 ns Z machine, the 2.5 kJ, 1 TW Z Beamlet laser, and the 10 T Applied B-field on Z system. Despite an estimated implosion velocity of only 70 km/s in these experiments, electron and ion temperatures at stagnation were as highmore » as 3 keV, and thermonuclear deuterium-deuterium neutron yields up to 2 × 1012 have been produced. X-ray emission from the fuel at stagnation had widths ranging from 50 to 110 μm over a roughly 80% of the axial extent of the target (6–8 mm) and lasted approximately 2 ns. X-ray yields from these experiments are consistent with a stagnation density of the hot fuel equal to 0.2–0.4 g/cm3. In these experiments, up to 5 ×1010 secondary deuterium-tritium neutrons were produced. Given that the areal density of the plasma was approximately 1–2 mg/cm2, this indicates the stagnation plasma was significantly magnetized, which is consistent with the anisotropy observed in the deuterium-tritium neutron spectra. Control experiments where the laser and/or magnetic field were not utilized failed to produce stagnation temperatures greater than 1 keV and primary deuterium-deuterium yields greater than 1010. An additional control experiment where the fuel contained a sufficient dopant fraction to substantially increase radiative losses also failed to produce a relevant stagnation temperature. The results of these experiments are consistent with a thermonuclear neutron source.« less

  20. Detonating Failed Deflagration Model of Thermonuclear Supernovae. I. Explosion Dynamics

    NASA Astrophysics Data System (ADS)

    Plewa, Tomasz

    2007-03-01

    We present a detonating failed deflagration model of Type Ia supernovae. In this model, the thermonuclear explosion of a massive white dwarf follows an off-center deflagration. We conduct a survey of asymmetric ignition configurations initiated at various distances from the stellar center. In all cases studied, we find that only a small amount of stellar fuel is consumed during deflagration phase, no explosion is obtained, and the released energy is mostly wasted on expanding the progenitor. Products of the failed deflagration quickly reach the stellar surface, polluting and strongly disturbing it. These disturbances eventually evolve into small and isolated shock-dominated regions that are rich in fuel. We consider these regions as seeds capable of forming self-sustained detonations that, ultimately, result in the thermonuclear supernova explosion. Preliminary nucleosynthesis results indicate that the model supernova ejecta are typically composed of about 0.1-0.25 Msolar of silicon group elements and 0.9-1.2 Msolar of iron group elements and are essentially carbon-free. The ejecta have a composite morphology, are chemically stratified, and display a modest amount of intrinsic asymmetry. The innermost layers are slightly egg shaped with the axis ratio ~1.2-1.3 and dominated by the products of silicon burning. This central region is surrounded by a shell of silicon group elements. The outermost layers of ejecta are highly inhomogeneous and contain products of incomplete oxygen burning with only small admixture of unburned stellar material. The explosion energies are ~(1.3-1.5)×1051 ergs.

  1. Outburst of the recurrent nova V745 Sco

    NASA Astrophysics Data System (ADS)

    Waagen, Elizabeth O.

    2014-02-01

    The outburst of the recurrent nova V745 Sco (Nova Sco 1937) by Rod Stubbings (Tetoora Road, VIC, Australia) at visual magnitude 9.0 on 2014 February 6.694 UT is reported. This recurrent nova is fading quickly. Follow-up observations of all types (visual, CCD, DSLR) are strongly encouraged, as is spectroscopy; fast time-series of this nova may be useful to detect possible flaring activity as was observed during the outburst of U Scorpii in 2010. Coincident time-series by multiple observers would be most useful for such a study, with a V-filter being preferred. Observations reported to the AAVSO International Database show V745 Sco at visual mag. 10.2 on 2014 Feb. 07.85833 UT (A. Pearce, Nedlands, W. Australia). Finder charts with sequence may be created using the AAVSO Variable Star Plotter (http://www.aavso.org/vsp). Observations should be submitted to the AAVSO International Database. Previous outbursts occurred in 1937 and 1989. The 1937 outburst was detected in 1958 (in decline at magnitude 11.0 on 1937 May 11.1 UT; outburst had occurred within the previous 19 days) by Lukas Plaut on plates taken by Hendrik van Gent at the Leiden Observatory; the object was announced as Nova Sco 1937 and later assigned the GCVS name V745 Sco. The 1989 outburst was detected on 1989 August 1.55 UT by Mati Morel (MMAT, Thornton, NSW, Australia) at visual magnitude 10.4 and in decline. Dr. Bradley Schaefer (Louisiana State University) reports (2010ApJS..187..275S) in his comprehensive analysis of the 10 known galactic recurrent novae (including V745 Sco) that the median interval between recurrent novae outbursts is 24 years. The interval since the 1989 outburst of V745 Sco is 24.10 years. See the Alert Notice for additional visual and multicolor photometry and for more details.

  2. Optical and EUV light curves of dwarf nova outbursts

    SciTech Connect

    Mauche, C W; Mattei, J A; Bateson, F M

    2000-11-15

    We combine AAVSO and VSS/RASNZ optical and Extreme Ultraviolet Explorer EUV light curves of dwarf novae in outburst to place constraints on the nature of dwarf nova outbursts. From the observed optical-EUV time delays of {approx} 0.75-1.5 days, we show that the propagation velocity of the dwarf nova instability heating wave is {approx} 3 km s{sup -1}.

  3. A rare case of "runaway" pacemaker in a modern CPU-controlled pacemaker.

    PubMed

    Makaryus, Amgad N; Patrick, Carol; Maccaro, Paul

    2005-09-01

    "Runaway" pacemaker is a rare entity that occurs when a malfunctioning artificial cardiac pacemaker abruptly accelerates its pacing rate above the set upper rate limit. This can result in life-threatening dysrhythmia. Runaway pacemaker used to occur more frequently in older model pacemakers, but now with newer pacemaker generators, runaway pacemaker is a rare entity. We report the case of a runaway pacemaker in a modern CPU-controlled pacemaker in a 79-year-old man presenting with lightheadedness and review the literature regarding this rare entity.

  4. The Runaway Greenhouse Effect on Earth and other Planets

    NASA Technical Reports Server (NTRS)

    Rabbette, Maura; Pilewskie, Peter; McKay, Christopher; Young, Robert

    2001-01-01

    Water vapor is an efficient absorber of outgoing longwave infrared radiation on Earth and is the primary greenhouse gas. Since evaporation increases with increasing sea surface temperature, and the increase in water vapor further increases greenhouse warming, there is a positive feedback. The runaway greenhouse effect occurs if this feedback continues unchecked until all the water has left the surface and enters the atmosphere. For Mars and the Earth the runaway greenhouse was halted when water vapor became saturated with respect to ice or liquid water respectively. However, Venus is considered to be an example of a planet where the runaway greenhouse effect did occur, and it has been speculated that if the solar luminosity were to increase above a certain limit, it would also occur on the Earth. Satellite data acquired during the Earth Radiation Budget Experiment (ERBE) under clear sky conditions shows that as the sea surface temperature (SST) increases, the rate of outgoing infrared radiation at the top of the atmosphere also increases, as expected. Over the pacific warm pool where the SST exceeds 300 K the outgoing radiation emitted to space actually decreases with increasing SST, leading to a potentially unstable system. This behavior is a signature of the runaway greenhouse effect on Earth. However, the SST never exceeds 303K, thus the system has a natural cap which stops the runaway. According to Stefan-Boltzmann's law the amount of heat energy radiated by the Earth's surface is proportional to (T(sup 4)). However, if the planet has a substantial atmosphere, it can absorb all infrared radiation from the lower surface before the radiation penetrates into outer space. Thus, an instrument in space looking at the planet does not detect radiation from the surface. The radiation it sees comes from some level higher up. For the earth#s atmosphere the effective temperature (T(sub e)) has a value of 255 K corresponding to the middle troposphere, above most of the

  5. Outbursts In Symbiotic Binaries (FUSE 2000)

    NASA Technical Reports Server (NTRS)

    Kenyon, Scott J.; Sonneborn, George (Technical Monitor)

    2002-01-01

    During the past year, we made good progress on analysis of FUSE observations of the symbiotic binary Z And. For background, Z And is a binary system composed of a red giant and a hot component of unknown status. The orbital period is roughly 750 days. The hot component undergoes large-scale eruptions every 10-20 yr. An outburst began several years ago, triggering this FUSE opportunity. First, we obtained an excellent set of ground-based optical data in support, of the FUSE observations. We used FAST, a high throughput low resolution spectrograph on the 1.5-m telescope at Mt. Hopkins, Arizona. A 300 g/ mm grating blazed at 4750 A, a 3 in. slit, and a thinned Loral 512 x 2688 CCD gave us spectra covering 3800-7500 A at a resolution of 6 A. The wavelength solution for each spectrum has a probable error of +/- 0.5 A or better. Most of the resulting spectra have moderate signal-to-noise, S/.N approx. greater than 30 per pixel. The time coverage for these spectra is excellent. Typically, we acquired spectra every 1-2 nights during dark runs at Mt. Hopkins. These data cover most of the rise and all of the decline of the recent outburst. The spectra show a wealth of emission lines, including H I, He I, He II, [Fe V11], and the Raman scattering bands at 6830 A and 7088 A. The Raman bands and other high ionization features vary considerably throughout the outburst. These features will enable us to correlate variations in the FUSE spectra with variations in the optical spectra. Second, we began an analysis of FUSE spectra of Z And. We have carefully examined the spectra, identifying real features and defects. We have identified and measured fluxes for all strong emission lines, including the O VI doublet at 1032 A and 1038 A. These and several other strong emission lines display pronounced P Cygni absorption components indicative of outgrowing gas. We will attempt to correlate these velocities with similar profiles observed on optical spectra. The line velocities - together

  6. Draconid 2011 outburst observations from Slovenia

    NASA Astrophysics Data System (ADS)

    Kac, Javor

    2015-06-01

    The 2011 Draconid outburst results are presented based on visual, video and photographic observations. A population index of r = 2.6 ± 0.1 and a maximum zenithal hourly rate of 460 ± 60 on 2011 October 8 at 20h11m UT are obtained from the visual observations. Twelve double-station Draconids form an average geocentric radiant at α = 262°4 ± 0°8, δ = +55°4 ± 0°4, with a velocity v_∞ = 22.4 ± 0.4 km/s. Single-station video observations indicate a radiant at α = 261°4 ± 1°4, δ = +55°8 ± 1°4, and a velocity of v_∞ = 20.6 ± 0.5 km/s. A flux profile is presented based on 358 video Draconids, and a maximum flux of 87 Draconids per 1000 km^{2} per hour is found on 2011 October 8 at 20h15m UT.

  7. Persistent Energetic Ion Outbursts from the Sun

    NASA Astrophysics Data System (ADS)

    Bucik, R.; Innes, D.; Mason, G. M.

    2014-12-01

    Following the greatest elongation in 2011, STEREO-A and -B, along with the near-Earth Solar Dynamics Observatory, have provided for the first time a view of the full solar surface. This allows continual tracking of solar active regions for their entire lifetime. With the advantage of a wide angular separation between the two STEREOs and the near-Earth Advanced Composition Explorer, we present the first report of multiple 3He-rich solar energetic particle (SEP) outbursts occurring in single active regions for relatively long time periods, lasting at least a quarter of a solar rotation. We identified several long-lasting 3He- or Fe-rich SEP sources with particle emissions successively observed at least on two of STEREO-B, ACE and STEREO-A spacecraft. Previous single spacecraft observations showed such energetic ion bursts over a limited time interval (about one day) presumably due to the loss of magnetic connection to the flare sites. These new observations reveal that the physical processes responsible for particle acceleration and escape from the Sun appear to be more continuous than previously thought. We discuss conditions in the solar sources which could lead to the reappearance of 3He-rich SEPs by comparing with the cases showing no such feature.

  8. Multiband Microvariability of BL Lac During Outburst

    NASA Astrophysics Data System (ADS)

    Clements, S. D.; Carini, M. T.; Noble, J. C.

    1998-01-01

    The blazar BL Lac recently underwent a major outburst. A search for microvariability was made with the 0.76 m telescope at the University of Florida's Rosemary Hill Observatory. Nearly 300 CCD observations in V and R were made over ten nights in July. During that time, BL Lac varied by more than 1.5 magnitudes and exhibited substantial microvariability. In fact, it exhibited microvariability each of the eight nights multiple exposures were made, being most active when brightest on July 29. On this night, four mini-flares were seen within 7 hours. During one of these flares, BL Lac brightened by more than 0.5 magnitude in less than 2.5 hours. The variations in V and R were simultaneous within the limits of the observations. However, the V and R magnitudes did not always change at the same rate. On July 3, BL Lac brightened in R faster than in V. Then on July 4, it dimmed in V faster than in R. Yet over the ten nights observed, BL Lac became bluer as it brightened. Another interesting difference between the V and R data was seen on July 4 when a mini-flare was seen in V but not in R. Clearly, while the V and R variations are highly correlated, there are compelling differences. Here we present these observations and discuss them in relation to models intended to explain microvariability. The authors gratefully acknowledge the support of NASA grant NCC5-228.

  9. Outburst of a Black Hole X-ray Binary V4641 Sgr in 2004 July

    NASA Astrophysics Data System (ADS)

    Uemura, M.; Mennickent, R.; Stubbings, R.; Bolt, G.; Monard, B.; Cook, L. M.; Williams, P.; Ishioka, R.; Imada, A.; Kato, T.; Nogami, D.; Starkey, D.; Maehara, H.; Nakajima, K.; Meszaros, Sz.; Szekely, P.; Kiss, L. L.; Lindstrom, C.; Griffin, J.

    2005-05-01

    We report an outburst of a black hole X-ray binary, V4641 Sgr in 2004 July. We succeeded in performing time-series photometry during the outburst, which showed repetitive short flares having a timescale of 10 min. Even after the outburst, it remained active for 17 d, as observed after an outburst in 2002. In conjunction with a low X-ray flux, we suggest that the 2004 outburst has the same nature as those in 2002 and 2003, though the total released energy during the outburst seems to be less in 2004.

  10. Cryogenic thermonuclear fuel implosions on the National Ignition Facility

    SciTech Connect

    Glenzer, S. H.; Callahan, D. A.; MacKinnon, A. J.; Alger, E. T.; Berger, R. L.; Bernstein, L. A.; Bleuel, D. L.; Bradley, D. K.; Burkhart, S. C.; Burr, R.; Caggiano, J. A.; Castro, C.; Choate, C.; Clark, D. S.; Celliers, P.; Cerjan, C. J.; Collins, G. W.; Dewald, E. L.; DiNicola, P.; DiNicola, J. M.; and others

    2012-05-15

    The first inertial confinement fusion implosion experiments with equimolar deuterium-tritium thermonuclear fuel have been performed on the National Ignition Facility. These experiments use 0.17 mg of fuel with the potential for ignition and significant fusion yield conditions. The thermonuclear fuel has been fielded as a cryogenic layer on the inside of a spherical plastic capsule that is mounted in the center of a cylindrical gold hohlraum. Heating the hohlraum with 192 laser beams for a total laser energy of 1.6 MJ produces a soft x-ray field with 300 eV temperature. The ablation pressure produced by the radiation field compresses the initially 2.2-mm diameter capsule by a factor of 30 to a spherical dense fuel shell that surrounds a central hot-spot plasma of 50 {mu}m diameter. While an extensive set of x-ray and neutron diagnostics has been applied to characterize hot spot formation from the x-ray emission and 14.1 MeV deuterium-tritium primary fusion neutrons, thermonuclear fuel assembly is studied by measuring the down-scattered neutrons with energies in the range of 10 to 12 MeV. X-ray and neutron imaging of the compressed core and fuel indicate a fuel thickness of (14 {+-} 3) {mu}m, which combined with magnetic recoil spectrometer measurements of the fuel areal density of (1 {+-} 0.09) g cm{sup -2} result in fuel densities approaching 600 g cm{sup -3}. The fuel surrounds a hot-spot plasma with average ion temperatures of (3.5 {+-} 0.1) keV that is measured with neutron time of flight spectra. The hot-spot plasma produces a total fusion neutron yield of 10{sup 15} that is measured with the magnetic recoil spectrometer and nuclear activation diagnostics that indicate a 14.1 MeV yield of (7.5{+-}0.1) Multiplication-Sign 10{sup 14} which is 70% to 75% of the total fusion yield due to the high areal density. Gamma ray measurements provide the duration of nuclear activity of (170 {+-} 30) ps. These indirect-drive implosions result in the highest areal densities

  11. Cryogenic thermonuclear fuel implosions on the National Ignition Facilitya)

    NASA Astrophysics Data System (ADS)

    Glenzer, S. H.; Callahan, D. A.; MacKinnon, A. J.; Kline, J. L.; Grim, G.; Alger, E. T.; Berger, R. L.; Bernstein, L. A.; Betti, R.; Bleuel, D. L.; Boehly, T. R.; Bradley, D. K.; Burkhart, S. C.; Burr, R.; Caggiano, J. A.; Castro, C.; Casey, D. T.; Choate, C.; Clark, D. S.; Celliers, P.; Cerjan, C. J.; Collins, G. W.; Dewald, E. L.; DiNicola, P.; DiNicola, J. M.; Divol, L.; Dixit, S.; Döppner, T.; Dylla-Spears, R.; Dzenitis, E.; Eckart, M.; Erbert, G.; Farley, D.; Fair, J.; Fittinghoff, D.; Frank, M.; Frenje, L. J. A.; Friedrich, S.; Casey, D. T.; Gatu Johnson, M.; Gibson, C.; Giraldez, E.; Glebov, V.; Glenn, S.; Guler, N.; Haan, S. W.; Haid, B. J.; Hammel, B. A.; Hamza, A. V.; Haynam, C. A.; Heestand, G. M.; Hermann, M.; Hermann, H. W.; Hicks, D. G.; Hinkel, D. E.; Holder, J. P.; Holunda, D. M.; Horner, J. B.; Hsing, W. W.; Huang, H.; Izumi, N.; Jackson, M.; Jones, O. S.; Kalantar, D. H.; Kauffman, R.; Kilkenny, J. D.; Kirkwood, R. K.; Klingmann, J.; Kohut, T.; Knauer, J. P.; Koch, J. A.; Kozioziemki, B.; Kyrala, G. A.; Kritcher, A. L.; Kroll, J.; La Fortune, K.; Lagin, L.; Landen, O. L.; Larson, D. W.; LaTray, D.; Leeper, R. J.; Le Pape, S.; Lindl, J. D.; Lowe-Webb, R.; Ma, T.; McNaney, J.; MacPhee, A. G.; Malsbury, T. N.; Mapoles, E.; Marshall, C. D.; Meezan, N. B.; Merrill, F.; Michel, P.; Moody, J. D.; Moore, A. S.; Moran, M.; Moreno, K. A.; Munro, D. H.; Nathan, B. R.; Nikroo, A.; Olson, R. E.; Orth, C. D.; Pak, A. E.; Patel, P. K.; Parham, T.; Petrasso, R.; Ralph, J. E.; Rinderknecht, H.; Regan, S. P.; Robey, H. F.; Ross, J. S.; Rosen, M. D.; Sacks, R.; Salmonson, J. D.; Saunders, R.; Sater, J.; Sangster, C.; Schneider, M. B.; Séguin, F. H.; Shaw, M. J.; Spears, B. K.; Springer, P. T.; Stoeffl, W.; Suter, L. J.; Thomas, C. A.; Tommasini, R.; Town, R. P. J.; Walters, C.; Weaver, S.; Weber, S. V.; Wegner, P. J.; Whitman, P. K.; Widmann, K.; Widmayer, C. C.; Wilde, C. H.; Wilson, D. C.; Van Wonterghem, B.; MacGowan, B. J.; Atherton, L. J.; Edwards, M. J.; Moses, E. I.

    2012-05-01

    The first inertial confinement fusion implosion experiments with equimolar deuterium-tritium thermonuclear fuel have been performed on the National Ignition Facility. These experiments use 0.17 mg of fuel with the potential for ignition and significant fusion yield conditions. The thermonuclear fuel has been fielded as a cryogenic layer on the inside of a spherical plastic capsule that is mounted in the center of a cylindrical gold hohlraum. Heating the hohlraum with 192 laser beams for a total laser energy of 1.6 MJ produces a soft x-ray field with 300 eV temperature. The ablation pressure produced by the radiation field compresses the initially 2.2-mm diameter capsule by a factor of 30 to a spherical dense fuel shell that surrounds a central hot-spot plasma of 50 μm diameter. While an extensive set of x-ray and neutron diagnostics has been applied to characterize hot spot formation from the x-ray emission and 14.1 MeV deuterium-tritium primary fusion neutrons, thermonuclear fuel assembly is studied by measuring the down-scattered neutrons with energies in the range of 10 to 12 MeV. X-ray and neutron imaging of the compressed core and fuel indicate a fuel thickness of (14 ± 3) μm, which combined with magnetic recoil spectrometer measurements of the fuel areal density of (1 ± 0.09) g cm-2 result in fuel densities approaching 600 g cm-3. The fuel surrounds a hot-spot plasma with average ion temperatures of (3.5 ± 0.1) keV that is measured with neutron time of flight spectra. The hot-spot plasma produces a total fusion neutron yield of 1015 that is measured with the magnetic recoil spectrometer and nuclear activation diagnostics that indicate a 14.1 MeV yield of (7.5±0.1)×1014 which is 70% to 75% of the total fusion yield due to the high areal density. Gamma ray measurements provide the duration of nuclear activity of (170 ± 30) ps. These indirect-drive implosions result in the highest areal densities and neutron yields achieved on laser facilities to date

  12. Clinical Features of Young Children Referred for Impairing Temper Outbursts

    PubMed Central

    Klein, Rachel G.; Angelosante, Aleta; Bar-Haim, Yair; Leibenluft, Ellen; Hulvershorn, Leslie; Dixon, Erica; Dodds, Alice; Spindel, Carrie

    2013-01-01

    Abstract Objective In light of the current controversy about whether severe temper outbursts are diagnostic of mania in young children, we conducted a study to characterize such children, focusing on mania and other mood disorders, emotion regulation, and parental psychiatric history. Methods Study participants included 51 5–9-year-old children with frequent, impairing outbursts (probands) and 24 non-referred controls without outbursts. Parents completed a lifetime clinical interview about their child, and rated their child's current mood and behavior. Teachers completed a behavior rating scale. To assess emotion regulation, children were administered the Balloons Game, which assesses emotion expressivity in response to frustration, under demands of high and low regulation. Parental lifetime diagnoses were ascertained in blind clinical interviews. Results No child had bipolar disorder, bipolar disorder not otherwise specified (NOS), or major depression (MDD). The most prevalent disorder was oppositional defiant disorder (88.2%), followed by attention-deficit/hyperactivity disorder (74.5%), anxiety disorders (49.0%), and non-MDD depressive disorders (33.3%). Eleven probands (21.6%) met criteria for severe mood dysregulation. During the Balloons Game, when there were no demands for self-regulation, children with severe outbursts showed reduced positive expressivity, and also showed significant deficits in controlling negative facial expressions when asked to do so. Anxiety disorders were the only diagnoses significantly elevated in probands' mothers. Conclusions Overall, young children with severe temper outbursts do not present with bipolar disorder. Rather, disruptive behavior disorders with anxiety and depressive mood are common. In children with severe outbursts, deficits in regulating emotional facial expressions may reflect deficits controlling negative affect. This work represents a first step towards elucidating mechanisms underlying severe outbursts in

  13. 45 CFR 1351.10 - What is the purpose of the Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... existing or proposed community-based runaway and homeless youth projects to provide temporary shelter and care to runaway or otherwise homeless youth who are in need of temporary shelter, counseling...

  14. Demonstration of thermonuclear conditions in magnetized liner inertial fusion experiments

    SciTech Connect

    Gomez, Matthew R.; Slutz, Stephen A.; Sefkow, Adam B.; Hahn, Kelly D.; Hansen, Stephanie B.; Knapp, Patrick F.; Schmit, Paul F.; Ruiz, Carlos L.; Sinars, Daniel Brian; Harding, Eric C.; Jennings, Christopher A.; Awe, Thomas James; Geissel, Matthias; Rovang, Dean C.; Smith, Ian C.; Chandler, Gordon A.; Cooper, Gary Wayne; Cuneo, Michael Edward; Harvey-Thompson, Adam James; Herrmann, Mark C.; Mark Harry Hess; Lamppa, Derek C.; Martin, Matthew R.; McBride, Ryan D.; Peterson, Kyle J.; Porter, John L.; Rochau, Gregory A.; Savage, Mark E.; Schroen, Diana G.; Stygar, William A.; Vesey, Roger Alan

    2015-04-29

    In this study, the magnetized liner inertial fusion concept [S. A. Slutz et al., Phys. Plasmas17, 056303 (2010)] utilizes a magnetic field and laser heating to relax the pressure requirements of inertial confinement fusion. The first experiments to test the concept [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] were conducted utilizing the 19 MA, 100 ns Z machine, the 2.5 kJ, 1 TW Z Beamlet laser, and the 10 T Applied B-field on Z system. Despite an estimated implosion velocity of only 70 km/s in these experiments, electron and ion temperatures at stagnation were as high as 3 keV, and thermonuclear deuterium-deuterium neutron yields up to 2 × 1012 have been produced. X-ray emission from the fuel at stagnation had widths ranging from 50 to 110 μm over a roughly 80% of the axial extent of the target (6–8 mm) and lasted approximately 2 ns. X-ray yields from these experiments are consistent with a stagnation density of the hot fuel equal to 0.2–0.4 g/cm3. In these experiments, up to 5 ×1010 secondary deuterium-tritium neutrons were produced. Given that the areal density of the plasma was approximately 1–2 mg/cm2, this indicates the stagnation plasma was significantly magnetized, which is consistent with the anisotropy observed in the deuterium-tritium neutron spectra. Control experiments where the laser and/or magnetic field were not utilized failed to produce stagnation temperatures greater than 1 keV and primary deuterium-deuterium yields greater than 1010. An additional control experiment where the fuel contained a sufficient dopant fraction to substantially increase radiative losses also failed to produce a relevant stagnation temperature. The results of these experiments are consistent with a thermonuclear neutron source.

  15. Demonstration of thermonuclear conditions in magnetized liner inertial fusion experiments

    SciTech Connect

    Gomez, M. R.; Slutz, S. A.; Sefkow, A. B.; Hahn, K. D.; Hansen, S. B.; Knapp, P. F.; Schmit, P. F.; Ruiz, C. L.; Sinars, D. B.; Harding, E. C.; Jennings, C. A.; Awe, T. J.; Geissel, M.; Rovang, D. C.; Smith, I. C.; Chandler, G. A.; Cooper, G. W.; Cuneo, M. E.; Harvey-Thompson, A. J.; Hess, M. H.; and others

    2015-05-15

    The magnetized liner inertial fusion concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)] utilizes a magnetic field and laser heating to relax the pressure requirements of inertial confinement fusion. The first experiments to test the concept [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] were conducted utilizing the 19 MA, 100 ns Z machine, the 2.5 kJ, 1 TW Z Beamlet laser, and the 10 T Applied B-field on Z system. Despite an estimated implosion velocity of only 70 km/s in these experiments, electron and ion temperatures at stagnation were as high as 3 keV, and thermonuclear deuterium-deuterium neutron yields up to 2 × 10{sup 12} have been produced. X-ray emission from the fuel at stagnation had widths ranging from 50 to 110 μm over a roughly 80% of the axial extent of the target (6–8 mm) and lasted approximately 2 ns. X-ray yields from these experiments are consistent with a stagnation density of the hot fuel equal to 0.2–0.4 g/cm{sup 3}. In these experiments, up to 5 × 10{sup 10} secondary deuterium-tritium neutrons were produced. Given that the areal density of the plasma was approximately 1–2 mg/cm{sup 2}, this indicates the stagnation plasma was significantly magnetized, which is consistent with the anisotropy observed in the deuterium-tritium neutron spectra. Control experiments where the laser and/or magnetic field were not utilized failed to produce stagnation temperatures greater than 1 keV and primary deuterium-deuterium yields greater than 10{sup 10}. An additional control experiment where the fuel contained a sufficient dopant fraction to substantially increase radiative losses also failed to produce a relevant stagnation temperature. The results of these experiments are consistent with a thermonuclear neutron source.

  16. 30 CFR 56.9302 - Protection against moving or runaway railroad equipment.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Protection against moving or runaway railroad... MINES Loading, Hauling, and Dumping Safety Devices, Provisions, and Procedures for Roadways, Railroads, and Loading and Dumping Sites § 56.9302 Protection against moving or runaway railroad...

  17. 30 CFR 56.9302 - Protection against moving or runaway railroad equipment.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Protection against moving or runaway railroad... MINES Loading, Hauling, and Dumping Safety Devices, Provisions, and Procedures for Roadways, Railroads, and Loading and Dumping Sites § 56.9302 Protection against moving or runaway railroad...

  18. 30 CFR 56.9302 - Protection against moving or runaway railroad equipment.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Protection against moving or runaway railroad... MINES Loading, Hauling, and Dumping Safety Devices, Provisions, and Procedures for Roadways, Railroads, and Loading and Dumping Sites § 56.9302 Protection against moving or runaway railroad...

  19. 30 CFR 56.9302 - Protection against moving or runaway railroad equipment.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Protection against moving or runaway railroad... MINES Loading, Hauling, and Dumping Safety Devices, Provisions, and Procedures for Roadways, Railroads, and Loading and Dumping Sites § 56.9302 Protection against moving or runaway railroad...

  20. Propensity for Violence among Homeless and Runaway Adolescents: An Event History Analysis

    ERIC Educational Resources Information Center

    Crawford, Devan M.; Whitbeck, Les B.; Hoyt, Dan R.

    2011-01-01

    Little is known about the prevalence of violent behaviors among homeless and runaway adolescents or the specific behavioral factors that influence violent behaviors across time. In this longitudinal study of 300 homeless and runaway adolescents aged 16 to 19 at baseline, the authors use event history analysis to assess the factors associated with…

  1. An Adjustment to Get a Clear Image: Focus-Runaway Hostel.

    ERIC Educational Resources Information Center

    Gang, Bill

    Runaways have become a concern to Congress, law enforcement agencies, courts, and parents. Since running away is a juvenile offense, it has serious legal consequences for the young people involved. This publication describes one community's successful effort to divert runaways from the juvenile justice system and to strengthen services to troubled…

  2. 30 CFR 57.9302 - Protection against moving or runaway railroad equipment.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Protection against moving or runaway railroad... LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND..., Railroads, and Loading and Dumping Sites § 57.9302 Protection against moving or runaway railroad...

  3. 30 CFR 57.9302 - Protection against moving or runaway railroad equipment.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Protection against moving or runaway railroad... LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND..., Railroads, and Loading and Dumping Sites § 57.9302 Protection against moving or runaway railroad...

  4. 30 CFR 57.9302 - Protection against moving or runaway railroad equipment.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Protection against moving or runaway railroad... LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND..., Railroads, and Loading and Dumping Sites § 57.9302 Protection against moving or runaway railroad...

  5. 30 CFR 57.9302 - Protection against moving or runaway railroad equipment.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Protection against moving or runaway railroad... LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND..., Railroads, and Loading and Dumping Sites § 57.9302 Protection against moving or runaway railroad...

  6. RUNAWAY STARS AND THE ESCAPE OF IONIZING RADIATION FROM HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Conroy, Charlie; Kratter, Kaitlin M.

    2012-08-20

    Approximately 30% of all massive stars in the Galaxy are runaways with velocities exceeding 30 km s{sup -1}. Their high speeds allow them to travel {approx}0.1-1 kpc away from their birthplace before they explode at the end of their several Myr lifetimes. At high redshift, when galaxies were much smaller than in the local universe, runaways could venture far from the dense inner regions of their host galaxies. From these large radii, and therefore low column densities, much of their ionizing radiation is able to escape into the intergalactic medium. Runaways may therefore significantly enhance the overall escape fraction of ionizing radiation, f{sub esc}, from small galaxies at high redshift. We present simple models of the high-redshift runaway population and its impact on f{sub esc} as a function of halo mass, size, and redshift. We find that the inclusion of runaways enhances f{sub esc} by factors of Almost-Equal-To 1.1-8, depending on halo mass, galaxy geometry, and the mechanism of runaway production, implying that runaways may contribute 50%-90% of the total ionizing radiation escaping from high-redshift galaxies. Runaways may therefore play an important role in reionizing the universe.

  7. Model Experiment of Thermal Runaway Reactions Using the Aluminum-Hydrochloric Acid Reaction

    ERIC Educational Resources Information Center

    Kitabayashi, Suguru; Nakano, Masayoshi; Nishikawa, Kazuyuki; Koga, Nobuyoshi

    2016-01-01

    A laboratory exercise for the education of students about thermal runaway reactions based on the reaction between aluminum and hydrochloric acid as a model reaction is proposed. In the introductory part of the exercise, the induction period and subsequent thermal runaway behavior are evaluated via a simple observation of hydrogen gas evolution and…

  8. 30 CFR 56.9302 - Protection against moving or runaway railroad equipment.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Protection against moving or runaway railroad... MINES Loading, Hauling, and Dumping Safety Devices, Provisions, and Procedures for Roadways, Railroads, and Loading and Dumping Sites § 56.9302 Protection against moving or runaway railroad...

  9. 30 CFR 57.9302 - Protection against moving or runaway railroad equipment.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Protection against moving or runaway railroad equipment. 57.9302 Section 57.9302 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF..., Railroads, and Loading and Dumping Sites § 57.9302 Protection against moving or runaway railroad...

  10. Generation and suppression of runaway electrons in disruption mitigation experiments in TEXTOR

    NASA Astrophysics Data System (ADS)

    Bozhenkov, S. A.; Lehnen, M.; Finken, K. H.; Jakubowski, M. W.; Wolf, R. C.; Jaspers, R.; Kantor, M.; Marchuk, O. V.; Uzgel, E.; Van Wassenhove, G.; Zimmermann, O.; Reiter, D.; TEXTOR Team

    2008-10-01

    Runaway electrons represent a serious problem for the reliable operation of the future experimental tokamak ITER. Due to the multiplication factor of exp(50) in the avalanche even a few seed runaway electrons will result in a beam of high energetic electrons that is able to damage the machine. Thus suppression of runaway electrons is a task of great importance, for which we present here a systematic study of runaway electrons following massive gas injection in TEXTOR. Argon injection can cause the generation of runaways carrying up to 30% of the initial plasma current, while disruptions triggered by injection of helium or of mixtures of argon (5%, 10%, 20%) with deuterium are runaway free. Disruptions caused by argon injection finally become runaway free for very large numbers of injected atoms. The appearance/absence of runaway electrons is related to the fraction of atoms delivered to the plasma centre. This so-called mixing efficiency is deduced from a 0D model of the current quench. The estimated mixing efficiency is 3% for argon, 15% for an argon/deuterium mixture and about 40% for helium. A low mixing efficiency of high-Z impurities can have a strong implication for the design of the disruption mitigation system for ITER. However, a quantitative prediction requires a better understanding of the mixing mechanism.

  11. Runaway electron beam generation and mitigation during disruptions at JET-ILW

    NASA Astrophysics Data System (ADS)

    Reux, C.; Plyusnin, V.; Alper, B.; Alves, D.; Bazylev, B.; Belonohy, E.; Boboc, A.; Brezinsek, S.; Coffey, I.; Decker, J.; Drewelow, P.; Devaux, S.; de Vries, P. C.; Fil, A.; Gerasimov, S.; Giacomelli, L.; Jachmich, S.; Khilkevitch, E. M.; Kiptily, V.; Koslowski, R.; Kruezi, U.; Lehnen, M.; Lupelli, I.; Lomas, P. J.; Manzanares, A.; De Aguilera, A. Martin; Matthews, G. F.; Mlynář, J.; Nardon, E.; Nilsson, E.; Perez von Thun, C.; Riccardo, V.; Saint-Laurent, F.; Shevelev, A. E.; Sips, G.; Sozzi, C.; contributors, JET

    2015-09-01

    Disruptions are a major operational concern for next generation tokamaks, including ITER. They may generate excessive heat loads on plasma facing components, large electromagnetic forces in the machine structures and several MA of multi-MeV runaway electrons. A more complete understanding of the runaway generation processes and methods to suppress them is necessary to ensure safe and reliable operation of future tokamaks. Runaway electrons were studied at JET-ILW showing that their generation dependencies (accelerating electric field, avalanche critical field, toroidal field, MHD fluctuations) are in agreement with current theories. In addition, vertical stability plays a key role in long runaway beam formation. Energies up to 20 MeV are observed. Mitigation of an incoming runaway electron beam triggered by massive argon injection was found to be feasible provided that the injection takes place early enough in the disruption process. However, suppressing an already accelerated runaway electron beam in the MA range was found to be difficult even with injections of more than 2 kPa.m3 high-Z gases such as krypton or xenon. This may be due to the presence of a cold background plasma weakly coupled to the runaway electron beam which prevents neutrals from penetrating in the electron beam core. Following unsuccessful mitigation attempts, runaway electron impacts on beryllium plasma-facing components were observed, showing localized melting with toroidal asymmetries.

  12. 78 FR 64153 - Direct Certification and Certification of Homeless, Migrant and Runaway Children for Free School...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-28

    ..., 2011, at 76 FR 22785, were approved by OMB on April 19, 2013 under OMB Control Number 0584-0026 and... of Homeless, Migrant and Runaway Children for Free School Meals; Approval of Information Collection... Homeless, Migrant and Runaway Children for Free School Meals was published on April 25, 2011. The ICR...

  13. HOPS 383: AN OUTBURSTING CLASS 0 PROTOSTAR IN ORION

    SciTech Connect

    Safron, Emily J.; Megeath, S. Thomas; Booker, Joseph; Fischer, William J.; Furlan, Elise; Rebull, Luisa M.; Stutz, Amelia M.; Stanke, Thomas; Billot, Nicolas; Tobin, John J.; Ali, Babar; Allen, Lori E.; Watson, Dan M.; Wilson, T. L.

    2015-02-10

    We report the dramatic mid-infrared brightening between 2004 and 2006 of Herschel Orion Protostar Survey (HOPS) 383, a deeply embedded protostar adjacent to NGC 1977 in Orion. By 2008, the source became a factor of 35 brighter at 24 μm with a brightness increase also apparent at 4.5 μm. The outburst is also detected in the submillimeter by comparing APEX/SABOCA to SCUBA data, and a scattered-light nebula appeared in NEWFIRM K{sub s} imaging. The post-outburst spectral energy distribution indicates a Class 0 source with a dense envelope and a luminosity between 6 and 14 L{sub ⊙}. Post-outburst time-series mid- and far-infrared photometry show no long-term fading and variability at the 18% level between 2009 and 2012. HOPS 383 is the first outbursting Class 0 object discovered, pointing to the importance of episodic accretion at early stages in the star formation process. Its dramatic rise and lack of fading over a 6 year period hint that it may be similar to FU Ori outbursts, although the luminosity appears to be significantly smaller than the canonical luminosities of such objects.

  14. 45 CFR 1351.15 - What costs are supportable under a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Homeless Youth Program grant? 1351.15 Section 1351.15 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.15 What costs are supportable under a Runaway and...

  15. 45 CFR 1351.15 - What costs are supportable under a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Homeless Youth Program grant? 1351.15 Section 1351.15 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.15 What costs are supportable under a Runaway and...

  16. 45 CFR 1351.11 - Who is eligible to apply for a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Homeless Youth Program grant? 1351.11 Section 1351.11 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.11 Who is eligible to apply for a Runaway and...

  17. 45 CFR 1351.16 - What costs are not allowable under a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Homeless Youth Program grant? 1351.16 Section 1351.16 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.16 What costs are not allowable under a Runaway...

  18. 45 CFR 1351.12 - Who gets priority for the award of a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Homeless Youth Program grant? 1351.12 Section 1351.12 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.12 Who gets priority for the award of a Runaway...

  19. 45 CFR 1351.10 - What is the purpose of the Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Youth Program grant? 1351.10 Section 1351.10 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.10 What is the purpose of the Runaway and Homeless...

  20. 45 CFR 1351.16 - What costs are not allowable under a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Homeless Youth Program grant? 1351.16 Section 1351.16 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.16 What costs are not allowable under a Runaway...

  1. 45 CFR 1351.15 - What costs are supportable under a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Homeless Youth Program grant? 1351.15 Section 1351.15 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.15 What costs are supportable under a Runaway and...

  2. 45 CFR 1351.17 - How is application made for a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Youth Program grant? 1351.17 Section 1351.17 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.17 How is application made for a Runaway and...

  3. 45 CFR 1351.11 - Who is eligible to apply for a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Homeless Youth Program grant? 1351.11 Section 1351.11 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.11 Who is eligible to apply for a Runaway and...

  4. 45 CFR 1351.12 - Who gets priority for the award of a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Homeless Youth Program grant? 1351.12 Section 1351.12 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.12 Who gets priority for the award of a Runaway...

  5. 45 CFR 1351.17 - How is application made for a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Youth Program grant? 1351.17 Section 1351.17 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.17 How is application made for a Runaway and...

  6. 45 CFR 1351.12 - Who gets priority for the award of a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Homeless Youth Program grant? 1351.12 Section 1351.12 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.12 Who gets priority for the award of a Runaway...

  7. 45 CFR 1351.16 - What costs are not allowable under a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Homeless Youth Program grant? 1351.16 Section 1351.16 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.16 What costs are not allowable under a Runaway...

  8. 45 CFR 1351.11 - Who is eligible to apply for a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Homeless Youth Program grant? 1351.11 Section 1351.11 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.11 Who is eligible to apply for a Runaway and...

  9. 45 CFR 1351.12 - Who gets priority for the award of a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Homeless Youth Program grant? 1351.12 Section 1351.12 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.12 Who gets priority for the award of a Runaway...

  10. 45 CFR 1351.10 - What is the purpose of the Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Youth Program grant? 1351.10 Section 1351.10 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.10 What is the purpose of the Runaway and Homeless...

  11. 45 CFR 1351.17 - How is application made for a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Youth Program grant? 1351.17 Section 1351.17 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.17 How is application made for a Runaway and...

  12. 45 CFR 1351.16 - What costs are not allowable under a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Homeless Youth Program grant? 1351.16 Section 1351.16 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.16 What costs are not allowable under a Runaway...

  13. 45 CFR 1351.15 - What costs are supportable under a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Homeless Youth Program grant? 1351.15 Section 1351.15 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.15 What costs are supportable under a Runaway and...

  14. 45 CFR 1351.10 - What is the purpose of the Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Youth Program grant? 1351.10 Section 1351.10 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.10 What is the purpose of the Runaway and Homeless...

  15. 45 CFR 1351.17 - How is application made for a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Youth Program grant? 1351.17 Section 1351.17 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.17 How is application made for a Runaway and...

  16. 45 CFR 1351.11 - Who is eligible to apply for a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Homeless Youth Program grant? 1351.11 Section 1351.11 Public Welfare Regulations Relating to Public Welfare... FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.11 Who is eligible to apply for a Runaway and...

  17. Thermonuclear inverse magnetic pumping power cycle for stellarator reactors

    NASA Astrophysics Data System (ADS)

    Ho, D. D. M.; Kulsrud, R. M.

    1985-09-01

    A novel power cycle for direct conversion of alpha-particle energy into electricity is proposed for an ignited plasma in a stellerator reactor. The plasma column is alternately compressed and expanded in minor radius by periodic variation of the toroidal magnetic field strength. As a result of the way a stellarator is expected to work, the plasma pressure during expansion is greater than the corresponding pressure during compression. Therefore, negative work is done on the plasma during a complete cycle. This work manifests itself as a back-voltage in the toroidal field coils, and direct electrical energy is obtained from this voltage. For a typical reactor, the average power obtained from this cycle (with a minor radius compression factor on the order of 50%) can be as much as 50% of the electrical power obtained from the thermonuclear neutrons without compressing the plasma. Thus, if it is feasible to vary the toroidal field strength, the power cycle provides an alternative scheme of energy conversion for a deuterium-tritium fueled reactor. The cycle may become an important method of energy conversion for advanced neutron-lean fueled reactors. By operating two or more reactors in tandem, the cycle can be made self-sustaining.

  18. Thermonuclear dynamo inside ultracentrifuge with supersonic plasma flow stabilization

    NASA Astrophysics Data System (ADS)

    Winterberg, F.

    2016-01-01

    Einstein's general theory of relativity implies the existence of virtual negative masses in the rotational reference frame of an ultracentrifuge with the negative mass density of the same order of magnitude as the positive mass density of a neutron star. In an ultracentrifuge, the repulsive gravitational field of this negative mass can simulate the attractive positive mass of a mini-neutron star, and for this reason can radially confine a dense thermonuclear plasma placed inside the centrifuge, very much as the positive mass of a star confines its plasma by its own attractive gravitational field. If the centrifuge is placed in an externally magnetic field to act as the seed field of a magnetohydrodynamic generator, the configuration resembles a magnetar driven by the release of energy through nuclear fusion, accelerating the plasma to supersonic velocities, with the magnetic field produced by the thermomagnetic Nernst effect insulating the hot plasma from the cold wall of the centrifuge. Because of the supersonic flow and the high plasma density the configuration is stable.

  19. Cryogenic thermonuclear fuel implosions on the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Glenzer, Siegfried

    2011-10-01

    The first inertial confinement fusion implosion experiments with cryogenic fuel layers have been fielded in preparation for ignition experiments on the National Ignition Facility. These experiments use mega joule laser energies that compress fusion capsules in indirect dive hohlraums to test initial hot spot formation and thermonuclear fuel assembly. Hydrogen-rich fuel (THD) provides a relatively low yield and diagnostics rich environment that allows us to measure the implosion core, neutron yield, temperatures and fuel areal density from a suite of x-ray and neutron diagnostics. These experiments have successfully demonstrated the control of the implosion shape using ignition grade cryogenic fuel layers, laser pulse shaping, and nonlinear plasma optics. The implosions show scaling of the DT fusion yield with ion temperature over more than one order of magnitude to a yield in excess of 1014 neutrons. Recent implosion performance improvements due to shock timing tuning have led to high Lawson confinement parameters. Additional tuning experiments are being performed with the goal to increase hot spot temperatures and to observe alpha particle heating with pure DT fuel. Prepared by LLNL under Contract DE-AC52-07NA27344.

  20. Current drive for stability of thermonuclear plasma reactor

    NASA Astrophysics Data System (ADS)

    Amicucci, L.; Cardinali, A.; Castaldo, C.; Cesario, R.; Galli, A.; Panaccione, L.; Paoletti, F.; Schettini, G.; Spigler, R.; Tuccillo, A.

    2016-01-01

    To produce in a thermonuclear fusion reactor based on the tokamak concept a sufficiently high fusion gain together stability necessary for operations represent a major challenge, which depends on the capability of driving non-inductive current in the hydrogen plasma. This request should be satisfied by radio-frequency (RF) power suitable for producing the lower hybrid current drive (LHCD) effect, recently demonstrated successfully occurring also at reactor-graded high plasma densities. An LHCD-based tool should be in principle capable of tailoring the plasma current density in the outer radial half of plasma column, where other methods are much less effective, in order to ensure operations in the presence of unpredictably changes of the plasma pressure profiles. In the presence of too high electron temperatures even at the periphery of the plasma column, as envisaged in DEMO reactor, the penetration of the coupled RF power into the plasma core was believed for long time problematic and, only recently, numerical modelling results based on standard plasma wave theory, have shown that this problem should be solved by using suitable parameter of the antenna power spectrum. We show here further information on the new understanding of the RF power deposition profile dependence on antenna parameters, which supports the conclusion that current can be actively driven over a broad layer of the outer radial half of plasma column, thus enabling current profile control necessary for the stability of a reactor.

  1. High energy components and collective modes in thermonuclear plasmas

    SciTech Connect

    Coppi, B.; Cowley, S.; Detragiache, P.; Kulsrud, R.; Pegoraro, F.

    1986-02-01

    The theory of a class of collective modes of a thermonuclear magnetically confined plasma, with frequencies in the range of the ion cyclotron frequency and of its harmonics, is presented. These modes can be excited by their resonant cyclotron interaction with a plasma component of relatively high energy particles characterized by a strongly anisotropic distribution in velocity space. Normal modes that are spatially localized by the inhomogeneity of the plasma density are found. This ensures that the energy gained by their resonant interaction is not convected away. The mode spatial localization can be significantly altered by the magnetic field inhomogeneity for a given class of plasma density profiles. Special attention is devoted to the case of a spin polarized plasma, where the charged products of fusion reactions are anisotropically distributed. We show that for the mode of polarization that enhances nuclear reaction rates the tritium will be rapidly depolarized to toroidal configurations with relatively mild gradients of the confining magnetic field. 18 refs., 9 figs.

  2. Wideband Heterodyne QWIP Receiver Development for Thermonuclear Fusion Measurements

    SciTech Connect

    Bennett, C.A.; Buchanan, M.; Hutchinson, D.P.; Liu, H.C.; Richards, R.K.; Simpson, M.L.

    1998-11-01

    Oak Ridge National Laboratory (ORNL) has been developing heterodyne receivers for plasma diagnostic applications for over 20 years. One area of this work has been the development of a diagnostic system for the measurement of the energy of alpha particles created in a thermonuclear fusion reactor. These particles originate with an energy of 3.5 MeV and cool to the thermal energy of the plasma (around 15 keV) after several seconds. To measure the velocity distribution of these alpha particles, a Thomson scattering diagnostic is under development based on a high power CO{sub 2} laser at 10 microns with a heterodyne receiver. The Doppler shift generated by Thomson scattering of the alpha particles requires a wideband heterodyne receiver (greater than 10 GHz). Because Mercury-Cadimum-Telluride (MCT) detectors are limited to a bandwidth of approximately 2 GHz, a Quantum Well Infrared Photodetector (QWIP) detector was obtained from the National Research Council of Canada (NRC) and evaluated for its heterodyne performance using the heterodyne testing facility developed at ORNL.

  3. Evidence of Spreading Layer Emission in a Thermonuclear Superburst

    NASA Astrophysics Data System (ADS)

    Koljonen, K. I. I.; Kajava, J. J. E.; Kuulkers, E.

    2016-10-01

    When a neutron star (NS) accretes matter from a companion star in a low-mass X-ray binary, the accreted gas settles onto the stellar surface through a boundary/spreading layer. On rare occasions the accumulated gas undergoes a powerful thermonuclear superburst powered by carbon burning deep below the NS atmosphere. In this paper, we apply the non-negative matrix factorization spectral decomposition technique to show that the spectral variations during a superburst from 4U 1636-536 can be explained by two distinct components: (1) the superburst emission characterized by a variable temperature blackbody radiation component and (2) a quasi-Planckian component with a constant, ˜2.5 keV, temperature varying by a factor of ˜15 in flux. The spectrum of the quasi-Planckian component is identical in shape and characteristics to the frequency-resolved spectra observed in the accretion/persistent spectrum of NS low-mass X-ray binaries and agrees well with the predictions of the spreading layer model by Inogamov & Sunyaev. Our results provide yet more observational evidence that superbursts—and possibly also normal X-ray bursts—induce changes in the disc-star boundary.

  4. Quasi-linear analysis of the extraordinary electron wave destabilized by runaway electrons

    SciTech Connect

    Pokol, G. I.; Kómár, A.; Budai, A.; Stahl, A.; Fülöp, T.

    2014-10-15

    Runaway electrons with strongly anisotropic distributions present in post-disruption tokamak plasmas can destabilize the extraordinary electron (EXEL) wave. The present work investigates the dynamics of the quasi-linear evolution of the EXEL instability for a range of different plasma parameters using a model runaway distribution function valid for highly relativistic runaway electron beams produced primarily by the avalanche process. Simulations show a rapid pitch-angle scattering of the runaway electrons in the high energy tail on the 100–1000 μs time scale. Due to the wave-particle interaction, a modification to the synchrotron radiation spectrum emitted by the runaway electron population is foreseen, exposing a possible experimental detection method for such an interaction.

  5. The production and confinement of runaway electrons with impurity killer pellets in DIII-D

    SciTech Connect

    Evans, T.E.; Taylor, P.L.; Whyte, D.G.

    1998-12-01

    Prompt runaway electron bursts, generated by rapidly cooling DIII-D plasmas with argon killer pellets, are used to test a recent knock-on avalanche theory describing the growth of multi-MeV runaway electron currents during disruptions in tokamaks. Runaway current amplitudes, observed during some but not all DIII-D current quenches, are consistent with growth rates predicted by the theory assuming a pre-current quench runaway electron density of approximately 10{sup 15} m{sup {minus}3}. Argon killer pellet modeling yields runaway densities of between 10{sup 15}--10{sup 16} m{sup {minus}3} in these discharges. Although knock-on avalanching appears to agree rather well with the measurements, relatively small avalanche amplification factors combined with uncertainties in the spatial distribution of pellet mass and cooling rates make it difficult to unambiguously confirm the proposed theory with existing data.

  6. Observation of the avalanche of runaway electrons in air in a strong electric field.

    PubMed

    Gurevich, A V; Mesyats, G A; Zybin, K P; Yalandin, M I; Reutova, A G; Shpak, V G; Shunailov, S A

    2012-08-24

    The generation of an avalanche of runaway electrons is demonstrated for the first time in a laboratory experiment. Two flows of runaway electrons are formed sequentially in an extended air discharge gap at the stage of delay of a pulsed breakdown. The first, picosecond, runaway electron flow is emitted in the cathode region where the field is enhanced. Being accelerated in the gap, this beam generates electrons due to impact ionization. These secondary electrons form a delayed avalanche of runaway electrons if the field is strong enough. The properties of the avalanche correspond to the existing notions about the runaway breakdown in air. The measured current of the avalanche exceeds up to an order the current of the initiating electron beam. PMID:23002751

  7. Electromagnetic waves destabilized by runaway electrons in near-critical electric fields

    SciTech Connect

    Komar, A.; Pokol, G. I.; Fueloep, T.

    2013-01-15

    Runaway electron distributions are strongly anisotropic in velocity space. This anisotropy is a source of free energy that may destabilize electromagnetic waves through a resonant interaction between the waves and the energetic electrons. In this work, we investigate the high-frequency electromagnetic waves that are destabilized by runaway electron beams when the electric field is close to the critical field for runaway acceleration. Using a runaway electron distribution appropriate for the near-critical case, we calculate the linear instability growth rate of these waves and conclude that the obliquely propagating whistler waves are most unstable. We show that the frequencies, wave numbers, and propagation angles of the most unstable waves depend strongly on the magnetic field. Taking into account collisional and convective damping of the waves, we determine the number density of runaways that is required to destabilize the waves and show its parametric dependences.

  8. Observation of the Avalanche of Runaway Electrons in Air in a Strong Electric Field

    NASA Astrophysics Data System (ADS)

    Gurevich, A. V.; Mesyats, G. A.; Zybin, K. P.; Yalandin, M. I.; Reutova, A. G.; Shpak, V. G.; Shunailov, S. A.

    2012-08-01

    The generation of an avalanche of runaway electrons is demonstrated for the first time in a laboratory experiment. Two flows of runaway electrons are formed sequentially in an extended air discharge gap at the stage of delay of a pulsed breakdown. The first, picosecond, runaway electron flow is emitted in the cathode region where the field is enhanced. Being accelerated in the gap, this beam generates electrons due to impact ionization. These secondary electrons form a delayed avalanche of runaway electrons if the field is strong enough. The properties of the avalanche correspond to the existing notions about the runaway breakdown in air. The measured current of the avalanche exceeds up to an order the current of the initiating electron beam.

  9. Observation of the avalanche of runaway electrons in air in a strong electric field.

    PubMed

    Gurevich, A V; Mesyats, G A; Zybin, K P; Yalandin, M I; Reutova, A G; Shpak, V G; Shunailov, S A

    2012-08-24

    The generation of an avalanche of runaway electrons is demonstrated for the first time in a laboratory experiment. Two flows of runaway electrons are formed sequentially in an extended air discharge gap at the stage of delay of a pulsed breakdown. The first, picosecond, runaway electron flow is emitted in the cathode region where the field is enhanced. Being accelerated in the gap, this beam generates electrons due to impact ionization. These secondary electrons form a delayed avalanche of runaway electrons if the field is strong enough. The properties of the avalanche correspond to the existing notions about the runaway breakdown in air. The measured current of the avalanche exceeds up to an order the current of the initiating electron beam.

  10. Structure of the runaway electron loss during induced disruptions in TEXTOR

    NASA Astrophysics Data System (ADS)

    Wongrach, K.; Finken, K. H.; Abdullaev, S. S.; Willi, O.; Zeng, L.; Xu, Y.

    2015-10-01

    The loss of runaway electrons during an induced disruption is recorded by a synchrotron imaging technique using a fast infrared CCD camera. The loss is predominantly diffuse. During the "spiky-loss phase", when the runaway beam moves close to the wall, a narrow channel between the runaway column and a scintillator probe is formed and lasts until the runaway beam is terminated. In some cases, the processed images show a stripe pattern at the plasma edge. A comparison between the MHD dominated disruptions and the MHD-free disruption is performed. A new mechanism of plasma disruptions with the runaway electron generation and a novel model which reproduces many characteristic features of the plasma beam evolution during a disruption is briefly described.

  11. A Simple, Unifying Model of the Extreme Ultraviolet Spectra of Dwarf Novae in Outburst

    SciTech Connect

    Mauche, C W

    2003-12-31

    A simple model of the boundary layer and accretion disk wind of dwarf novae in outburst is briefly described and applied to the Chandra Low Energy Transmission Grating spectra of WZ Sge and SS Cyg in outburst.

  12. A Review of Cometary Outbursts at Large Heliocentric Distances

    NASA Astrophysics Data System (ADS)

    Gronkowski, P.; Wesołowski, M.

    2016-10-01

    The outbursts of comets, sudden large increases in their luminosity, are still very interesting and mysterious signs of activity of this celestial bodies. Most of the cometary outbursts are taking place at heliocentric distances where sublimation of water ice plays an important role in the activity of comets. However, the phenomenon is also observed far away from the Sun (i.e. ≃5-20 au) where the sublimation of water ice is negligible and the activity of comets is dominated by more volatile chemicals. Not only typical comets show `cometary-like' activity but also Centaurs. In addition to the long-term changes in brightness related to heliocentric distances and short-periodic variations connected with the rotation of the nucleus, they also exhibit a random variations in luminosity which are similar to the cometary outbursts. Paper presents an overview of the most likely hypotheses and models which try to explain this phenomenon.

  13. Monitoring of the Latest Stages of Neutron Star Transient Outbursts

    NASA Astrophysics Data System (ADS)

    Campana, Sergio

    Binary transients vary their X-ray luminosity over many orders of magnitude, allowing to probe different accretion regimes that are unaccessible to persistent sources. This is the main drive of the present proposal that aims at observing the latest stages of transient outbursts, looking for spectral and timing properties changes. We propose to monitor the final stages of two HXRT and two SXRT outbursts. We will complemement these data with approved (AO1) INTEGRAL data on a sample of SXRTs and with IR/optical data taken with REM at La Silla. RXTE is particularly well suited due to its schedule flexibility and unrivalled capability of exploring fast variability and it provides a unique opportunity to gain insight in the physics of the outburst latest stages.

  14. Mass transfer rate and outburst cycle of SS Cygni

    NASA Astrophysics Data System (ADS)

    Hempelmann, Alexander; Kurths, Juergen

    1993-07-01

    From an analysis of the SS Cygni light curve, we have recently shown (Hempelmann & Kurths, 1990) that the rate of mass transfer, M-dot(T), from the secondary star to the white dwarf primary is inversely correlated with the outburst cycle, t(c). This has been criticized as being of a trivial nature by Cannizzo & Mattei (1992). We demonstrate the nontrivial character of our finding by means of a gedankenexperiment which is based on the static outburst parameters observed. We show in this experiment that a positive M-dot(T)-t(c) correlation is possible. The negative correlation found by Hempelmann & Kurths (1990) is a consequence of the dynamics of small and strong outbursts.

  15. Quantification of Lithium-ion Cell Thermal Runaway Energetics

    SciTech Connect

    Orendorff, Christopher J.; Lamb, Joshua; Steele, Leigh Anna Marie; Spangler, Scott Wilmer; Langendorf, Jill Louise

    2016-01-01

    Much of what is known about lithium-ion cell thermal runaway energetics has been measured and extrapolated from data acquired on relatively small cells (< 3 Ah). This work is aimed at understanding the effects of cell size on thermal runaway energetics on cells from 3 to 50 Ah of both LiFePO4 (LFP) and LiNi0.80Co0.15Al0.05O2 (NCA) chemistries. Results show that for both LFP and NCA cells, the normalized heating rate (W/Ah) increases roughly linearly for cells from 3-38 Ah while the normalized total heat released (kJ/Ah) is relatively constant over that cell size range. The magnitude of the normalized heating rate is on the order of 2x greater for NCA relative to LFP chemistries for 2-3 Ah cells, while that difference is on the order of 10x for 30-40 Ah cells. The total normalized heat release is ~ 15-20% greater for NCA relative to LFP cells across the entire size range studied 3-38 Ah.

  16. Massive runaway stars in the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Gvaramadze, V. V.; Pflamm-Altenburg, J.; Kroupa, P.

    2011-01-01

    Using archival Spitzer Space Telescope data, we identified for the first time a dozen runaway OB stars in the Small Magellanic Cloud (SMC) through the detection of their bow shocks. The geometry of detected bow shocks allows us to infer the direction of motion of the associated stars and to determine their possible parent clusters and associations. One of the identified runaway stars, AzV 471, was already known as a high-velocity star on the basis of its high peculiar radial velocity, which is offset by ≃ 40 km s-1 from the local systemic velocity. We discuss implications of our findings for the problem of the origin of field OB stars. Several of the bow shock-producing stars are found in the confines of associations, suggesting that these may be “alien” stars contributing to the age spread observed for some young stellar systems. We also report the discovery of a kidney-shaped nebula attached to the early WN-type star SMC-WR3 (AzV 60a). We interpreted this nebula as an interstellar structure created owing to the interaction between the stellar wind and the ambient interstellar medium.

  17. MULTIWAVELENGTH OBSERVATIONS OF THE RUNAWAY BINARY HD 15137

    SciTech Connect

    McSwain, M. Virginia; Aragona, Christina; Marsh, Amber N.; Roettenbacher, Rachael M.; De Becker, Michael; Roberts, Mallory S. E.; Boyajian, Tabetha S.; Gies, Douglas R.; Grundstrom, Erika D. E-mail: cha206@lehigh.edu E-mail: rmr207@lehigh.edu E-mail: malloryr@gmail.com E-mail: gies@chara.gsu.edu

    2010-03-15

    HD 15137 is an intriguing runaway O-type binary system that offers a rare opportunity to explore the mechanism by which it was ejected from the open cluster of its birth. Here, we present recent blue optical spectra of HD 15137 and derive a new orbital solution for the spectroscopic binary and physical parameters of the O star primary. We also present the first XMM-Newton observations of the system. Fits of the EPIC spectra indicate soft, thermal X-ray emission consistent with an isolated O star. Upper limits on the undetected hard X-ray emission place limits on the emission from a proposed compact companion in the system, and we rule out a quiescent neutron star (NS) in the propeller regime or a weakly accreting NS. An unevolved secondary companion is also not detected in our optical spectra of the binary, and it is difficult to conclude that a gravitational interaction could have ejected this runaway binary with a low mass optical star. HD 15137 may contain an elusive NS in the ejector regime or a quiescent black hole with conditions unfavorable for accretion at the time of our observations.

  18. Density Dependence Triggers Runaway Selection of Reduced Senescence

    PubMed Central

    Seymour, Robert M; Doncaster, C. Patrick

    2007-01-01

    In the presence of exogenous mortality risks, future reproduction by an individual is worth less than present reproduction to its fitness. Senescent aging thus results inevitably from transferring net fertility into younger ages. Some long-lived organisms appear to defy theory, however, presenting negligible senescence (e.g., hydra) and extended lifespans (e.g., Bristlecone Pine). Here, we investigate the possibility that the onset of vitality loss can be delayed indefinitely, even accepting the abundant evidence that reproduction is intrinsically costly to survival. For an environment with constant hazard, we establish that natural selection itself contributes to increasing density-dependent recruitment losses. We then develop a generalized model of accelerating vitality loss for analyzing fitness optima as a tradeoff between compression and spread in the age profile of net fertility. Across a realistic spectrum of senescent age profiles, density regulation of recruitment can trigger runaway selection for ever-reducing senescence. This novel prediction applies without requirement for special life-history characteristics such as indeterminate somatic growth or increasing fecundity with age. The evolution of nonsenescence from senescence is robust to the presence of exogenous adult mortality, which tends instead to increase the age-independent component of vitality loss. We simulate examples of runaway selection leading to negligible senescence and even intrinsic immortality. PMID:18166075

  19. The inter-outburst behavior of cataclysmic variables

    NASA Technical Reports Server (NTRS)

    Szkody, Paula; Mattei, Janet A.; Waagen, Elizabeth O.; Stablein, Clay

    1990-01-01

    Existing International Ultraviolet Explorer (IUE) and American Association of Variable Star Observers (AAVSO) archive data was used to accomplish a large scale study of what happens to the ultraviolet flux of accretion disk systems during the quiescent intervals between outbursts and how it relates to the preceding outburst characteristics of amplitude and width. The data sample involved multiple IUE observations for 16 dwarf novae and 8 novae along with existing optical coverage. Results indicate that most systems show correlated ultraviolet (UV) flux behavior with interoutburst phase, with 60 percent of the dwarf novae and 50 percent of the novae having decreasing flux trends while 33 percent of the dwarf novae and 38 percent of the novae show rising UV flux during the quiescent interval. All of the dwarf novae with decreasing UV fluxes at 1475A have orbital periods longer than 4.4 hours, while all (except BV Cen) with flat or rising fluxes at 1475A have orbital periods less than two hours. There are not widespread correlations of the UV fluxes with the amplitude of the preceding outburst and no correlations with the width of the outburst. From a small sample (7) that have relatively large quiescent V magnitude changes between the IUE observations, most show a strong correlation between the UV and optical continuum. Interpretation of the results is complicated by not being able to determine how much the white dwarf contributes to the ultraviolet flux. However, it is now evident that noticeable changes are occurring in the hot zones in accreting systems long after the outburst, and not only for systems that are dominated by the white dwarf. Whether these differences are due to different outburst mechanisms or to changes on white dwarfs which provide varying contributions to the UV flux remains to be determined.

  20. Water outburst activity in Comet 17P/Holmes

    NASA Astrophysics Data System (ADS)

    de Almeida, Amaury A.; Boice, Daniel C.; Picazzio, Enos; Huebner, Walter F.

    2016-08-01

    Cometary outbursts are sporadic events whose mechanisms are not well known where the activity and consequently the brightness can increase hundreds of thousands of times within a few hours to several days. This indicates a dramatic departure from thermal equilibrium between the comet and interplanetary space and is usually documented by "light curves". In a typical cometary outburst, the brightness can increase by 2-5 magnitudes (Whitney, 1955; Gronkowski and Wesolowski, 2015). In only 42 h, Comet 17P/Holmes was reported to brighten from a magnitude of about 17 to about 2.4 at the height of the burst, representing the largest known outburst by a comet. We present the H2O production rate of Holmes for the megaburst occurring between 23 and 24 October 2007. For this, we selected more than 1900 photometric observations from the International Comet Quarterly Archive of Photometric Data (Green, 2007) and use the Semi-Empirical Method of Visual Magnitudes (SEMVM; de Almeida et al., 2007). We clearly show that the comet achieved an average water production rate of 5 × 1029 molecules s-1, corresponding to a water gas loss rate of 14,960 kg s-1, in very good agreement with Schleicher (2009) who derived the water production rate using OH measurements on 1 Nov 2007 (about 8 days after the outburst). We discuss possible physical processes that might cause cometary outbursts and propose a new qualitative mechanism, the Pressurized Obstructed Pore (POP) model. The key feature of POP is the recrystallization of water in the surface regolith as it cools, plugging pores and blocking the release of subsurface gas flow. As the interior gas pressure increases, an outburst is eventually triggered. POP is consistent with current observations and can be tested in the future with observations (e.g., Rosetta in situ measurements) and detailed simulations.

  1. Experimental Study of Coal and Gas Outbursts Related to Gas-Enriched Areas

    NASA Astrophysics Data System (ADS)

    Tu, Qingyi; Cheng, Yuanping; Guo, Pinkun; Jiang, Jingyu; Wang, Liang; Zhang, Rong

    2016-09-01

    A coal and gas outburst can lead to a catastrophic failure in a coal mine. These outbursts usually occur where the distribution of coal seam gas is abnormal, commonly in tectonic belts. To study the effects of the abnormal distribution of this gas on outbursts, an experimental apparatus to collect data on simulated coal seam outbursts was constructed. Experiments on specimens containing discrete gas-enriched areas were run to induce artificial gas outbursts and further study of these outbursts using data from the experiment was conducted. The results suggest that more gas and outburst energy are contained in gas-enriched areas and this permits these areas to cause an outburst easily, even though the gas pressure in them is lower. During mining, the disappearance of the sealing effect of a coal pillar establishes the occurrence conditions for an outburst. When the enriched gas and outburst energy in the gas-enriched area is released suddenly, a reverse unloading wave and a high gas pressure gradient are formed, which have tension effects on the coal. Under these effects, the fragmentation degree of the coal intensifies and the intensity of the outburst increases. Because a high gas pressure gradient is maintained near the exposed surface and the enriched energy release reduces the coal strength, the existence of a gas-enriched area in coal leads to a faster outburst and the average thickness of the spall is smaller than where is no gas-enriched area.

  2. Vaporization in Comets; outbursts from Comet Schwassmann-Wachmann 1

    NASA Technical Reports Server (NTRS)

    Cowan, J. J.; Ahearn, M. F.

    1982-01-01

    Revised estimates are presented which show that the total mass and kinetic energy in a typical Comet P/Schassmann-Wachmann 1 outburst are lower than previously estimated, and that this mass is comparable to the mass of gas vaporized, as inferred from recent observations of CO(+) in this comet. The storage of energy suggested by many authors is therefore not neccessary. A simple equilibrium vaporization of CO2 or CO which is suddenly exposed, on a nucleus that is otherwise primarily composed of H2O, is proposed. Under these conditions, calculations of the variation of vaporization with rotational phase indicate that the mechanism can quantitatively produce outbursts of the size observed.

  3. FUSE Observations of Galactic and LMC Novae in Outburst

    NASA Technical Reports Server (NTRS)

    Huschildt, P. H.

    2001-01-01

    This document is a collection of five abstracts from papers written on the 'FUSE Observations of Galactic and LMC Novae in Outburst'. The titles are the following: (1) Analyzing FUSE Observations of Galactic and LMC Novae; (2) Detailed NLTE Model Atmospheres for Novae during Outburst: Modeling Optical and Ultraviolet Observations for Nova LMC 1988; (3) Numerical Solution of the Expanding Stellar Atmosphere Problem; (4) A Non-LTE Line-Blanketed Expanding Atmosphere Model for A-supergiant Alpha Cygni; and (5) Non-LTE Model Atmosphere Analysis of the Early Ultraviolet Spectra of Nova Andromedae 1986. A list of journal publications is also included.

  4. The response of Jupiter's magnetosphere to an outburst on Io.

    PubMed

    Brown, M E; Bouchez, A H

    1997-10-10

    A 6-month-long monitoring campaign of the Io plasma torus and neutral cloud was conducted to determine the characteristics of their interaction. During the observations, a large outburst of material from Io-inferred to be caused by the eruption of a volcanic plume on Io-caused a transient increase in the neutral cloud and plasma torus masses. The response of the plasma torus to this outburst shows that the interaction between Io and Jupiter's magnetosphere is stabilized by a feedback mechanism in which increases in the plasma torus mass cause a nonlinear increase in loss from the plasma torus, limiting plasma buildup.

  5. Theory of supercompression of vapor bubbles and nanoscale thermonuclear fusion

    SciTech Connect

    Nigmatulin, Robert I.; Akhatov, Iskander Sh.; Topolnikov, Andrey S.; Bolotnova, Raisa Kh.; Vakhitova, Nailya K.; Lahey, Richard T. Jr.; Taleyarkhan, Rusi P.

    2005-10-01

    This paper provides the theoretical basis for energetic vapor bubble implosions induced by a standing acoustic wave. Its primary goal is to describe, explain, and demonstrate the plausibility of the experimental observations by Taleyarkhan et al. [Science 295, 1868 (2002); Phys. Rev. E 69, 036109 (2004)] of thermonuclear fusion for imploding cavitation bubbles in chilled deuterated acetone. A detailed description and analysis of these data, including a resolution of the criticisms that have been raised, together with some preliminary HYDRO code simulations, has been given by Nigmatulin et al. [Vestnik ANRB (Ufa, Russia) 4, 3 (2002); J. Power Energy 218-A, 345 (2004)] and Lahey et al. [Adv. Heat Transfer (to be published)]. In this paper a hydrodynamic shock (i.e., HYDRO) code model of the spherically symmetric motion for a vapor bubble in an acoustically forced liquid is presented. This model describes cavitation bubble cluster growth during the expansion period, followed by a violent implosion during the compression period of the acoustic cycle. There are two stages of the bubble dynamics process. The first, low Mach number stage, comprises almost all the time of the acoustic cycle. During this stage, the radial velocities are much less than the sound speeds in the vapor and liquid, the vapor pressure is very close to uniform, and the liquid is practically incompressible. This process is characterized by the inertia of the liquid, heat conduction, and the evaporation or condensation of the vapor. The second, very short, high Mach number stage is when the radial velocities are the same order, or higher, than the sound speeds in the vapor and liquid. In this stage high temperatures, pressures, and densities of the vapor and liquid take place. The model presented herein has realistic equations of state for the compressible liquid and vapor phases, and accounts for nonequilibrium evaporation/condensation kinetics at the liquid/vapor interface. There are interacting

  6. Theory of supercompression of vapor bubbles and nanoscale thermonuclear fusion

    NASA Astrophysics Data System (ADS)

    Nigmatulin, Robert I.; Akhatov, Iskander Sh.; Topolnikov, Andrey S.; Bolotnova, Raisa Kh.; Vakhitova, Nailya K.; Lahey, Richard T.; Taleyarkhan, Rusi P.

    2005-10-01

    This paper provides the theoretical basis for energetic vapor bubble implosions induced by a standing acoustic wave. Its primary goal is to describe, explain, and demonstrate the plausibility of the experimental observations by Taleyarkhan et al. [Science 295, 1868 (2002); Phys. Rev. E 69, 036109 (2004)] of thermonuclear fusion for imploding cavitation bubbles in chilled deuterated acetone. A detailed description and analysis of these data, including a resolution of the criticisms that have been raised, together with some preliminary HYDRO code simulations, has been given by Nigmatulin et al. [Vestnik ANRB (Ufa, Russia) 4, 3 (2002); J. Power Energy 218-A, 345 (2004)] and Lahey et al. [Adv. Heat Transfer (to be published)]. In this paper a hydrodynamic shock (i.e., HYDRO) code model of the spherically symmetric motion for a vapor bubble in an acoustically forced liquid is presented. This model describes cavitation bubble cluster growth during the expansion period, followed by a violent implosion during the compression period of the acoustic cycle. There are two stages of the bubble dynamics process. The first, low Mach number stage, comprises almost all the time of the acoustic cycle. During this stage, the radial velocities are much less than the sound speeds in the vapor and liquid, the vapor pressure is very close to uniform, and the liquid is practically incompressible. This process is characterized by the inertia of the liquid, heat conduction, and the evaporation or condensation of the vapor. The second, very short, high Mach number stage is when the radial velocities are the same order, or higher, than the sound speeds in the vapor and liquid. In this stage high temperatures, pressures, and densities of the vapor and liquid take place. The model presented herein has realistic equations of state for the compressible liquid and vapor phases, and accounts for nonequilibrium evaporation/condensation kinetics at the liquid/vapor interface. There are interacting

  7. Thermonuclear Fusion Research Progress and the Way to the Reactor

    NASA Astrophysics Data System (ADS)

    Koch, Raymond

    2006-06-01

    The paper reviews the progress of fusion research and its prospects for electricity generation. It starts with a reminder of the principles of thermonuclear fusion and a brief discussion of its potential role in the future of the world energy production. The reactions allowing energy production by fusion of nuclei in stars and on earth and the conditions required to sustain them are reviewed. At the high temperatures required for fusion (hundred millions kelvins), matter is completely ionized and has reached what is called its 4th state: the plasma state. The possible means to achieve these extreme temperatures is discussed. The remainder of the paper focuses on the most promising of these approaches, magnetic confinement. The operating principles of the presently most efficient machine of this type — the tokamak — is described in some detail. On the road to producing energy with fusion, a number of obstacles have to be overcome. The plasma, a fluid that reacts to electromagnetic forces and carries currents and charges, is a complex medium. Fusion plasma is strongly heated and is therefore a good example of a system far from equilibrium. A wide variety of instabilities can grow in this system and lead to self-organized structures and spontaneous cycles. Turbulence is generated that degrades the confinement and hinders easy achievement of long lasting hot plasmas. Physicists have learned how to quench turbulence, thereby creating sort of insulating bottles inside the plasma itself to circumvent this problem. The recent history of fusion performance is outlined and the prospect of achieving power generation by fusion in a near future is discussed in the light of the development of the "International Tokamak Experimental Reactor" project ITER.

  8. Maverick Comet Splits during Dramatic Outburst

    NASA Astrophysics Data System (ADS)

    1996-01-01

    New ESO Observations of P/Schwassmann-Wachmann 3 A few months ago, Periodic Comet Schwassmann-Wachmann 3 underwent a dramatic and completely unexpected, thousand-fold brightening. At that time, the cause for this interesting event was unknown. However, observations with the two largest ESO telescopes have now shown that the ``dirty snowball'' nucleus of this comet has recently split into at least four individual pieces [1]. There is little doubt that the outburst and the splitting event(s) are closely related and that the greatly increased dust and gas production is due to ``fresh'' material of the icy cometary nucleus becoming exposed to the surrounding space for the first time. A Comet with a Troubled History Comet Schwassmann-Wachmann 3 was discovered on May 2, 1930, on a photographic plate obtained at the Hamburg Observatory (Germany) by two astronomers at this institution, Arnold Schwassmann and Arthur Arno Wachmann. The subsequent observations showed that the comet moved in an elliptical orbit with a revolution period of somewhat more than 5 years. Great efforts were expended to observe the comet during the next returns, but it was not recovered until nearly 50 years and eight revolutions later, when its faint image was found of a plate obtained in August 1979 with a telescope at the Perth Observatory in Western Australia. It was missed in 1984, but was sighted again in 1989 and most recently in 1994. Thus this comet has only been observed during four out of thirteen approaches since 1930. While this may be partly due to a less advantageous location in the sky at some returns, it is also a strong indication that the comet behaves unpredictably and must have a quite variable brightness. For the sake of convenience this comet is often referred to as ``SW-3'' by professional astronomers. Recent orbital calculations have shown that it was inserted into the present, short-period orbit by the strong gravitational pull of Jupiter during several, relatively close

  9. Physical Mechanism of Comet Outbursts: The Movie

    NASA Astrophysics Data System (ADS)

    Hartmann, William K.

    2014-11-01

    predicted for the Deep Impact experiment in Comet Tempel 1.The film is posted on the Planetary Science Institute website, www.psi.edu/hartmann. [1] Hartmann, W. K. 1993 Physical Mechanism of Comet Outbursts: An Experimental Result. Icarus 104, 226-233.

  10. Experimental observation of increased threshold electric field for runaway generation due to synchrotron radiation losses in the FTU tokamak

    SciTech Connect

    Martin-Solis, Jose Ramon; Sanchez, Raul; Esposito, Basilio

    2010-01-01

    The threshold electric field for runaway generation has been investigated during runaway suppression experiments by means of electron-cyclotron-resonance heating in the flattop phase of FTU discharges. Runaway suppression has been experimentally found to occur at electric fields substantially larger than those predicted by the relativistic collisional theory of runaway generation, E{sub R} = n{sub e}e{sup 3}ln{Lambda}/4{pi}{var_epsilon}{sub 0}{sup 2}m{sub e}c{sup 2}. These experimental results are consistent with an increase of the critical electric field due to the electron synchrotron radiation losses. No runaway electrons are found in FTU experiments below the radiation threshold. These results support evidence for a new threshold electric field for runaway generation that accounts for the effect of the synchrotron losses, and which should be considered when making predictions on runaway generation and mitigation in devices such as ITER.

  11. Visible imaging and spectroscopy of disruption runaway electrons in DIII-D

    SciTech Connect

    Yu, J. H.; Hollmann, E. M.; Moyer, R. A.; Commaux, N.; Jernigan, T. C.; Eidietis, N. W.; Humphreys, D. A.; James, A. N.

    2013-04-15

    The first visible light images of synchrotron emission from disruption runaway electrons are presented. The forward-detected continuum radiation from runaways is identified as synchrotron emission by comparing two survey spectrometers and two visible fast cameras viewing in opposite toroidal directions. Analysis of the elongation of 2D synchrotron images of oval-shaped runaway beams indicates that the velocity pitch angle v{sub Up-Tack }/v{sub ||} ranges from 0.1 to 0.2 for the detected electrons, with energies above 25 MeV. Analysis of synchrotron intensity from a camera indicates that the tail of the runaway energy distribution reaches energies up to 60 MeV, which agrees with 0D modeling of electron acceleration in the toroidal electric field generated during the current quench. A visible spectrometer provides an independent estimate of the upper limit of runaway electron energy which is roughly consistent with energy determined from camera data. Synchrotron spectra reveal that approximately 1% of the total post-thermal quench plasma current is carried by the detected high-energy runaway population with energies in the range of 25-60 MeV; the bulk of the plasma current thus appears to be carried by relativistic electrons with energy less than 25 MeV. In addition to stable oval shapes, runaway beams with other shapes and internal structure are sometimes observed.

  12. The runaway greenhouse: implications for future climate change, geoengineering and planetary atmospheres.

    PubMed

    Goldblatt, Colin; Watson, Andrew J

    2012-09-13

    The ultimate climate emergency is a 'runaway greenhouse': a hot and water-vapour-rich atmosphere limits the emission of thermal radiation to space, causing runaway warming. Warming ceases only after the surface reaches approximately 1400 K and emits radiation in the near-infrared, where water is not a good greenhouse gas. This would evaporate the entire ocean and exterminate all planetary life. Venus experienced a runaway greenhouse in the past, and we expect that the Earth will in around 2 billion years as solar luminosity increases. But could we bring on such a catastrophe prematurely, by our current climate-altering activities? Here, we review what is known about the runaway greenhouse to answer this question, describing the various limits on outgoing radiation and how climate will evolve between these. The good news is that almost all lines of evidence lead us to believe that is unlikely to be possible, even in principle, to trigger full a runaway greenhouse by addition of non-condensible greenhouse gases such as carbon dioxide to the atmosphere. However, our understanding of the dynamics, thermodynamics, radiative transfer and cloud physics of hot and steamy atmospheres is weak. We cannot therefore completely rule out the possibility that human actions might cause a transition, if not to full runaway, then at least to a much warmer climate state than the present one. High climate sensitivity might provide a warning. If we, or more likely our remote descendants, are threatened with a runaway greenhouse, then geoengineering to reflect sunlight might be life's only hope. Injecting reflective aerosols into the stratosphere would be too short-lived, and even sunshades in space might require excessive maintenance. In the distant future, modifying Earth's orbit might provide a sustainable solution. The runaway greenhouse also remains relevant in planetary sciences and astrobiology: as extrasolar planets smaller and nearer to their stars are detected, some will be in

  13. The runaway greenhouse: implications for future climate change, geoengineering and planetary atmospheres.

    PubMed

    Goldblatt, Colin; Watson, Andrew J

    2012-09-13

    The ultimate climate emergency is a 'runaway greenhouse': a hot and water-vapour-rich atmosphere limits the emission of thermal radiation to space, causing runaway warming. Warming ceases only after the surface reaches approximately 1400 K and emits radiation in the near-infrared, where water is not a good greenhouse gas. This would evaporate the entire ocean and exterminate all planetary life. Venus experienced a runaway greenhouse in the past, and we expect that the Earth will in around 2 billion years as solar luminosity increases. But could we bring on such a catastrophe prematurely, by our current climate-altering activities? Here, we review what is known about the runaway greenhouse to answer this question, describing the various limits on outgoing radiation and how climate will evolve between these. The good news is that almost all lines of evidence lead us to believe that is unlikely to be possible, even in principle, to trigger full a runaway greenhouse by addition of non-condensible greenhouse gases such as carbon dioxide to the atmosphere. However, our understanding of the dynamics, thermodynamics, radiative transfer and cloud physics of hot and steamy atmospheres is weak. We cannot therefore completely rule out the possibility that human actions might cause a transition, if not to full runaway, then at least to a much warmer climate state than the present one. High climate sensitivity might provide a warning. If we, or more likely our remote descendants, are threatened with a runaway greenhouse, then geoengineering to reflect sunlight might be life's only hope. Injecting reflective aerosols into the stratosphere would be too short-lived, and even sunshades in space might require excessive maintenance. In the distant future, modifying Earth's orbit might provide a sustainable solution. The runaway greenhouse also remains relevant in planetary sciences and astrobiology: as extrasolar planets smaller and nearer to their stars are detected, some will be in

  14. After runaway: The trans-Hill stage of planetesimal growth

    SciTech Connect

    Lithwick, Yoram

    2014-01-01

    When planetesimals begin to grow by coagulation, they first enter an epoch of runaway, during which the biggest bodies grow faster than all the others. The questions of how runaway ends and what comes next have not been answered satisfactorily. We show that runaway is followed by a new stage—the 'trans-Hill stage'—that commences when the bodies that dominate viscous stirring ('big bodies') become trans-Hill, i.e., when their Hill velocity matches the random speed of the small bodies they accrete. Subsequently, the small bodies' random speed grows in lockstep with the big bodies' sizes, such that the system remains in the trans-Hill state. Trans-Hill growth is crucial for determining the efficiency of growing big bodies, as well as their growth timescale and size spectrum. Trans-Hill growth has two sub-stages. In the earlier one, which occurs while the stirring bodies remain sufficiently small, the evolution is collisionless, i.e., collisional cooling among all bodies is irrelevant. The efficiency of forming big bodies in this collisionless sub-stage is very low, ∼10α << 1, where α ∼ 0.005(a/AU){sup –1} is the ratio between the physical size of a body and its Hill radius. Furthermore, the size spectrum is flat (equal mass per size decade, i.e., q = 4). This collisionless trans-Hill solution explains results from previous coagulation simulations for both the Kuiper Belt and the asteroid belt. The second trans-Hill sub-stage commences once the stirring bodies grow big enough (>α{sup –1} × the size of the accreted small bodies). After that time, collisional cooling among small bodies controls the evolution. The efficiency of forming big bodies rises and the size spectrum becomes more top heavy. Trans-Hill growth can terminate in one of two ways, depending on the sizes of the small bodies. First, mutual accretion of big bodies can become significant and conglomeration proceeds until half of the total mass is converted into big bodies. This mode of growth

  15. After Runaway: The Trans-Hill Stage of Planetesimal Growth

    NASA Astrophysics Data System (ADS)

    Lithwick, Yoram

    2014-01-01

    When planetesimals begin to grow by coagulation, they first enter an epoch of runaway, during which the biggest bodies grow faster than all the others. The questions of how runaway ends and what comes next have not been answered satisfactorily. We show that runaway is followed by a new stage—the "trans-Hill stage"—that commences when the bodies that dominate viscous stirring ("big bodies") become trans-Hill, i.e., when their Hill velocity matches the random speed of the small bodies they accrete. Subsequently, the small bodies' random speed grows in lockstep with the big bodies' sizes, such that the system remains in the trans-Hill state. Trans-Hill growth is crucial for determining the efficiency of growing big bodies, as well as their growth timescale and size spectrum. Trans-Hill growth has two sub-stages. In the earlier one, which occurs while the stirring bodies remain sufficiently small, the evolution is collisionless, i.e., collisional cooling among all bodies is irrelevant. The efficiency of forming big bodies in this collisionless sub-stage is very low, ~10α Lt 1, where α ~ 0.005(a/AU)-1 is the ratio between the physical size of a body and its Hill radius. Furthermore, the size spectrum is flat (equal mass per size decade, i.e., q = 4). This collisionless trans-Hill solution explains results from previous coagulation simulations for both the Kuiper Belt and the asteroid belt. The second trans-Hill sub-stage commences once the stirring bodies grow big enough (>α-1 × the size of the accreted small bodies). After that time, collisional cooling among small bodies controls the evolution. The efficiency of forming big bodies rises and the size spectrum becomes more top heavy. Trans-Hill growth can terminate in one of two ways, depending on the sizes of the small bodies. First, mutual accretion of big bodies can become significant and conglomeration proceeds until half of the total mass is converted into big bodies. This mode of growth may explain the

  16. Double-peak structure in the cyclic optical outbursts of blazar OJ 287.

    NASA Astrophysics Data System (ADS)

    Sillanpaa, A.; Takalo, L. O.; Pursimo, T.; Nilsson, K.; Heinamaki, P.; Katajainen, S.; Pietila, H.; Hanski, M.; Rekola, R.; Kidger, M.; Boltwood, P.; Turner, G. W.; Robertson, J. W.; Honeycut, R. K.; Efimov, Yu. S.; Shakhovskoy, N.; Fiorucci, M.; Tosti, G.; Ghisellini, G.; Raiteri, C. M.; Villata, M.; de Francesco, G.; Lanteri, L.; Chiaberge, M.; Peila, A.; Heidt, J.

    1996-11-01

    An international monitoring project, called OJ-94, was set up with the aim of monitoring blazar OJ 287 during the predicted optical outburst (in fall 1994, Sillanpaa et al. 1988ApJ...325..628S) and the predicted secondary outburst (in winter 1995-1996, Sillanpaa et al. 1996A&A...305L..17S). The most prominent features in the OJ 287 light curve during the period covered by the project are the large outburst in September-December 1994, reaching the maximum at the beginning of November, and the secondary outburst peaking just at Christmas 1995. Both these outbursts occurred almost exactly at the predicted times.

  17. Quenching electron runaway in positive high-voltage-impulse discharges in air by laser filaments.

    PubMed

    Eto, S; Zhidkov, A; Oishi, Y; Miki, M; Fujii, T

    2012-03-15

    Strong hard (ε>100 keV) x rays being observed from impulse atmospheric discharges with maximal voltages from U=0.5 to 0.9 MV just before the breakdown were completely stopped with the use of femtosecond-laser-filament plasma. Runaway electrons generating such x rays and being estimated to achieve their maximal energy, ε~U, near the positive electrode disappear if a laser filament plasma is ignited perpendicularly to the runaway near the positive electrode. A preheating mechanism for formation of the electron runaway in air is proposed.

  18. An energetic stellar outburst accompanied by circumstellar light echoes.

    PubMed

    Bond, Howard E; Henden, Arne; Levay, Zoltan G; Panagia, Nino; Sparks, William B; Starrfield, Sumner; Wagner, R Mark; Corradi, R L M; Munari, U

    2003-03-27

    Some classes of stars, including novae and supernovae, undergo explosive outbursts that eject stellar material into space. In 2002, the previously unknown variable star V838 Monocerotis brightened suddenly by a factor of approximately 10(4). Unlike a supernova or nova, it did not explosively eject its outer layers; rather, it simply expanded to become a cool supergiant with a moderate-velocity stellar wind. Superluminal light echoes were discovered as light from the outburst propagated into the surrounding, pre-existing circumstellar dust. Here we report high-resolution imaging and polarimetry of those light echoes, which allow us to set direct geometric distance limits to the object. At a distance of >6 kpc, V838 Mon at its maximum brightness was temporarily the brightest star in the Milky Way. The presence of the circumstellar dust implies that previous eruptions have occurred, and spectra show it to be a binary system. When combined with the high luminosity and unusual outburst behaviour, these characteristics indicate that V838 Mon represents a hitherto unknown type of stellar outburst, for which we have no completely satisfactory physical explanation. PMID:12660776

  19. SMC X-3 in outburst: Swift XRT Timing and Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kennea, J. A.; Coe, M. J.; Evans, P. A.

    2016-08-01

    As a result of the detection of SMC X-3 having entered outburst by S-CUBED (Kennea et al., ATEL #9362) and MAXI (Negoro et al., ATEL #9362), at 22:10UT on August 10, 2016, Swift began a 5ks Target of Opportunity observation.

  20. Herschel Observations of Circinus X-1 during Outburst and Quiescence

    NASA Astrophysics Data System (ADS)

    Harrison, Thomas E.; Gelino, Dawn M.; Buxton, Michelle; Fost, Tyler

    2014-07-01

    We have used the Photodetector Array Camera and Spectrometer and Spectral and Photometric Imaging REceiver instruments on the Herschel Space Observatory to observe Cir X-1 both in and out of outburst. We detected Cir X-1 during outburst at 70 μm. Unfortunately, a cold background source dominates Cir X-1 at longer wavelengths. We have assembled optical and infrared (IR) data for Cir X-1 to model its spectral energy distribution (SED) in both quiescence and outburst and find that in both states it is consistent with a heavily reddened, 10,000 K blackbody. We believe this behavior is completely consistent with previous suggestions that these outbursts are due to accretion disk events, not unlike those of dwarf novae. To explore the behavior of other low-mass X-ray binaries with reported synchrotron jets, we have extracted and/or compiled optical and near- and mid-IR data sets for five such systems to construct their SEDs. The Z-source GX 349+2 and the black hole system GRS 1915+105 have strong and variable mid-IR excesses that suggest synchrotron emission. The other Z-sources have rather weak (or no) IR excesses that can be explained as reddened blackbody spectra with the addition of either synchrotron or bremsstrahlung components. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  1. Herschel observations of Circinus X-1 during outburst and quiescence

    SciTech Connect

    Harrison, Thomas E.; Gelino, Dawn M.; Buxton, Michelle; Fost, Tyler E-mail: dawn@ipac.caltech.edu E-mail: tyler.fost@gmail.com

    2014-07-01

    We have used the Photodetector Array Camera and Spectrometer and Spectral and Photometric Imaging REceiver instruments on the Herschel Space Observatory to observe Cir X-1 both in and out of outburst. We detected Cir X-1 during outburst at 70 μm. Unfortunately, a cold background source dominates Cir X-1 at longer wavelengths. We have assembled optical and infrared (IR) data for Cir X-1 to model its spectral energy distribution (SED) in both quiescence and outburst and find that in both states it is consistent with a heavily reddened, 10,000 K blackbody. We believe this behavior is completely consistent with previous suggestions that these outbursts are due to accretion disk events, not unlike those of dwarf novae. To explore the behavior of other low-mass X-ray binaries with reported synchrotron jets, we have extracted and/or compiled optical and near- and mid-IR data sets for five such systems to construct their SEDs. The Z-source GX 349+2 and the black hole system GRS 1915+105 have strong and variable mid-IR excesses that suggest synchrotron emission. The other Z-sources have rather weak (or no) IR excesses that can be explained as reddened blackbody spectra with the addition of either synchrotron or bremsstrahlung components.

  2. An energetic stellar outburst accompanied by circumstellar light echoes.

    PubMed

    Bond, Howard E; Henden, Arne; Levay, Zoltan G; Panagia, Nino; Sparks, William B; Starrfield, Sumner; Wagner, R Mark; Corradi, R L M; Munari, U

    2003-03-27

    Some classes of stars, including novae and supernovae, undergo explosive outbursts that eject stellar material into space. In 2002, the previously unknown variable star V838 Monocerotis brightened suddenly by a factor of approximately 10(4). Unlike a supernova or nova, it did not explosively eject its outer layers; rather, it simply expanded to become a cool supergiant with a moderate-velocity stellar wind. Superluminal light echoes were discovered as light from the outburst propagated into the surrounding, pre-existing circumstellar dust. Here we report high-resolution imaging and polarimetry of those light echoes, which allow us to set direct geometric distance limits to the object. At a distance of >6 kpc, V838 Mon at its maximum brightness was temporarily the brightest star in the Milky Way. The presence of the circumstellar dust implies that previous eruptions have occurred, and spectra show it to be a binary system. When combined with the high luminosity and unusual outburst behaviour, these characteristics indicate that V838 Mon represents a hitherto unknown type of stellar outburst, for which we have no completely satisfactory physical explanation.

  3. Outburst from SS 433 observed with BOOTES-2/COLORES

    NASA Astrophysics Data System (ADS)

    Caballero-Garcia, M. D.; Castro-Tirado, A.; Jelinek, M.; et al.

    2014-08-01

    In light of the recent extreme outburst of SS 433 (ATELs #6347, #6355) and follow-up by SWIFT (ATEL #6364) the 0.6m TELMA robotic telescope at the BOOTES-2 (+COLORES) astronomical station in Malaga (Spain), obtained optical 4000-9000 A spectra starting at 2014-08-01 and ending at 2014-08-07.

  4. A DOUBLE-PEAKED OUTBURST OF A 0535+26 OBSERVED WITH INTEGRAL, RXTE, AND SUZAKU

    SciTech Connect

    Caballero, I.; Barragan, L.; Wilms, J.; Kreykenbohm, I.; Ferrigno, C.; Klochkov, D.; Suchy, S.; Santangelo, A.; Staubert, R.; Zurita Heras, J. A.; Kretschmar, P.; Fuerst, F.; Rothschild, R.; Finger, M. H.; Camero-Arranz, A.; Makishima, K.; Enoto, T.; Iwakiri, W.; and others

    2013-02-20

    The Be/X-ray binary A 0535+26 showed a normal (type I) outburst in 2009 August. It is the fourth in a series of normal outbursts associated with the periastron, but is unusual because it presented a double-peaked light curve. The two peaks reached a flux of {approx}450 mCrab in the 15-50 keV range. We present results of the timing and spectral analysis of INTEGRAL, RXTE, and Suzaku observations of the outburst. The energy-dependent pulse profiles and their evolution during the outburst are studied. No significant differences with respect to other normal outbursts are observed. The centroid energy of the fundamental cyclotron line shows no significant variation during the outburst. A spectral hardening with increasing luminosity is observed. We conclude that the source is accreting in the sub-critical regime. We discuss possible explanations for the double-peaked outburst.

  5. Abuse, support, and depression among homeless and runaway adolescents.

    PubMed

    Bao, W N; Whitbeck, L B; Hoyt, D R

    2000-12-01

    This study examines the effectiveness of social support networks on psychological well-being among 602 homeless and runaway adolescents. The respondents were interviewed in shelters, drop-in centers, and on the streets in cities of four Midwestern states (Missouri, Iowa, Nebraska, and Kansas). The path model was used to test the direct effect of family abuse and precocious independence on adolescent depressive symptoms and indirect effects through social support networks. Results indicate that although abusive family origins contribute directly to depressive symptoms there are indirect effects of family abuse and early independence through social support networks. Family abuse and early independence drive homeless adolescents to rely on peers for social support. While support from friends on the street reduces depression, association with deviant peers increases depression.

  6. Laser action in runaway electron pre-ionized diffuse discharges

    NASA Astrophysics Data System (ADS)

    Panchenko, Alexei N.; Lomaev, Mikhail I.; Panchenko, Nikolai A.; Tarasenko, Viktor F.; Suslov, Alexei I.

    2015-12-01

    Formation features of run-away electron preionized diffuse discharge (REP DD) and REP DD properties in different experimental conditions are studied. It was shown that sufficient uniformity of REP DD allows its application as an excitation source of lasers on different gas mixtures at elevated pressure. Promising results of REP DD application for development of gas lasers are shown. Stimulated radiation in the IR, visible and UV spectral ranges was obtained in the diffuse discharge. Ultimate efficiency of non-chain HF(DF) chemical and nitrogen lasers on mixtures of SF6 with H2(D2) and N2 was achieved. New operation mode of nitrogen laser is demonstrated under REP DD excitation. Kinetic model of the REP DD in mixtures of nitrogen with SF6 is developed allowing to predict the radiation parameters of nitrogen laser at λ = 337,1 nm. Long-pulse operation of rare gas halide lasers was achieved.

  7. Effects of acetone on methyl ethyl ketone peroxide runaway reaction.

    PubMed

    Lin, Yan-Fu; Tseng, Jo-Ming; Wu, Tsung-Chih; Shu, Chi-Min

    2008-05-30

    Runaway reactions by methyl ethyl ketone peroxide (MEKPO) are an important issue in Asia, due to its unstable structure and extensive heat release during upset situations. This study employed differential scanning calorimetry (DSC) to draw the experimental data for MEKPO 31 mass% and with acetone 99 mass% on three types of heating rate of 2, 4, and 10 degrees C/min; the kinetic and safety parameters were then evaluated via curve fitting. Through the reproducible tests in each condition, the results show that acetone is not a contaminant, because it could increase the activation energy (Ea) and onset temperature (To) when combined with MEKPO, which differs from the hazard information of the material safety data sheet (MSDS).

  8. Black Hole X Ray Nova Outburst with XTE and HST

    NASA Technical Reports Server (NTRS)

    Patterson, Joseph; Haswell, Carole

    1998-01-01

    We obtained multiwavelength coverage of the soft X-ray transient. GRO J1655-40 during its 1996 outburst, using HST (Hubble Space Telescope), RXTE (Rossi X Ray Timing Explorer), CGRO (Compton Gamma Ray Observatory), and ground-based facilities. This outburst was qualitatively different from other SXT (Soft X Ray Telescope) outbursts and from previous outbursts of this source. The onset of hard X-ray activity occurred very slowly, over several months, and was delayed relative to the soft X-ray rise. During this period, the optical fluxes declined steadily. This apparent anticorrelation is not consistent with with the standard disk instability model of SXT outbursts, nor is it expected if the optical output is dominated by reprocessed X-rays, as in persistent low-mass X-ray binaries. Based on the strength of the 2175-A interstellar absorption feature, we constrain the reddening to be E(B - V) = 1.2 plus or minus 0.1, a result which is consistent with the known properties of the source and with the strength of other interstellar absorption lines. After this dereddening we find that the spectra are dominated by a component peaking in the optical, with the expected v (sup l/3) disk spectrum seen only in the ultraviolet. Bowen fluorescence lines of NIII and OIII are also seen, as well as possible P Cyg profiles in the ultraviolet resonance lines. These features suggest an accretion-disk wind. The X-ray spectra broadly resemble the high/soft state commonly seen in black hole candidates, but evolve through two substates.

  9. The maximal runaway temperature of Earth-like planets

    NASA Astrophysics Data System (ADS)

    Shaviv, Nir J.; Shaviv, Giora; Wehrse, Rainer

    2011-12-01

    In Simpson’s (Simpson, G.C. [1927]. Mem. R. Meteorol. Soc. II (16), 69-95) classical derivation of the temperature of the Earth in the semi-gray model, the surface temperature diverges as the fourth root of the thermal radiation’s optical depth. No resolution to this apparent paradox was yet obtained under the strict semi-gray approximation. Using this approximation and a simplified approach, we study the saturation of the runaway greenhouse effect. First we generalize the problem of the semi-gray model to cases in which a non-negligible fraction of the stellar radiation falls on the long-wavelength range, and/or that the planetary long-wavelength emission penetrates into the transparent short wavelength domain of the absorption. Second, applying the most general assumptions and independently of any particular properties of an absorber, we show that the greenhouse effect saturates and that any Earth-like planet has a maximal temperature which depends on the type of and distance to its main-sequence star, its albedo and the primary atmospheric components which determine the cutoff frequency below which the atmosphere is optically thick. For example, a hypothetical convection-less planet similar to Venus, that is optically thin in the visible, could have at most a surface temperature of 1200-1300 K irrespective of the nature of the greenhouse gas. We show that two primary mechanisms are responsible for the saturation of the runaway greenhouse effect, depending on the value of λcut, the wavelength above which the atmosphere becomes optically thick. Unless λcut is small and resides in the optical region, saturation is achieved by radiating the thermal flux of the planet through the short wavelength tail of the thermal distribution. This has an interesting observational implication, the radiation from such a planet should be skewed towards the NIR. Otherwise, saturation takes place by radiating through windows in the FIR.

  10. Runaway M Dwarf Candidates from the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Favia, Andrej; West, Andrew A.; Theissen, Christopher A.

    2015-11-01

    We present a sample of 20 runaway M dwarf candidates (RdMs) within 1 kpc of the Sun whose Galactocentric (GC) velocities exceed 400 km s-1. The candidates were selected from the Sloan Digital Sky Survey (SDSS) DR7 M Dwarf Catalog of West et al. Our RdMs have SDSS+USNO-B proper motions that are consistent with those recorded in the PPMXL, LSPM, and combined Wide-field Infrared Survey Explorer+SDSS+Two-micron All-sky Survey catalogs. Sixteen RdMs are classified as dwarfs, while the remaining four RdMs are subdwarfs. We model the Galactic potential using a bulge-disk-halo profile. Our fastest RdM, with a GC velocity of 658.5 ± 236.9 km s-1, is a possible hypervelocity candidate, as it is unbound in 77% of our simulations. About half of our RdMs have kinematics that are consistent with ejection from the Galactic center. Seven of our RdMs have kinematics consistent with an ejection scenario from M31 or M32 to within 2σ, although our distance-limited survey makes such a realization unlikely. No more than four of our RdMs may have originated from the Leo stream. We propose that to within measurement errors, most of our bound RdMs are likely disk runaways or halo objects, and may have been accelerated through a series of multi-body interactions within the Galactic disk or possibly supernovae explosions.

  11. Parents, teachers, and peers and early adolescent runaway in Hong Kong.

    PubMed

    Cheung, Chan-Kiu; Liu, Suk-Ching; Lee, Tak-yan

    2005-01-01

    Parental monitoring, teacher support, classmate support, and friend relationship presumably affect adolescents' runaway from home. According to social control theory, social control based on conventional social norms would prevent adolescent runaway, but association with friends may erode such control. This expectation appears to hold true in a sample of Grade 7 students in Hong Kong; parental monitoring and classmate support reduced runaway risk whereas friend relationship raised the risk. These findings emerged from a causal model that controlled for a latent predisposition that commonly affected parental monitoring, friend relationship, and runaway risk. Further analysis indicates that the preventive effect of parental monitoring was stronger on adolescents born on the Chinese mainland than in Hong Kong, and the effect of friend relationship was stronger on the Hong Kong born than the mainland born. Conceivably, a socially controlling culture bolsters the preventive effect of social control.

  12. Two-year predictors of runaway and homeless episodes following shelter services among substance abusing adolescents.

    PubMed

    Slesnick, Natasha; Guo, Xiamei; Brakenhoff, Brittany; Feng, Xin

    2013-10-01

    Given high levels of health and psychological costs associated with the family disruption of homelessness, identifying predictors of runaway and homeless episodes is an important goal. The current study followed 179 substance abusing, shelter-recruited adolescents who participated in a randomized clinical trial. Predictors of runaway and homeless episodes were examined over a two year period. Results from the hierarchical linear modeling analysis showed that family cohesion and substance use, but not family conflict or depressive symptoms, delinquency, or school enrollment predicted future runaway and homeless episodes. Findings suggest that increasing family support, care and connection and reducing substance use are important targets of intervention efforts in preventing future runaway and homeless episodes amongst a high risk sample of adolescents. PMID:24011094

  13. Dynamics of runaway tails with time-dependent sub-Dreicer dc fields in magnetized plasmas

    NASA Technical Reports Server (NTRS)

    Moghaddam-Taaheri, E.; Vlahos, L.

    1987-01-01

    The evolution of runaway tails driven by sub-Dreicer time-dependent dc fields in a magnetized plasma are studied numerically using a quasi-linear code based on the Ritz-Galerkin method and finite elements. It is found that the runaway tail maintained a negative slope during the dc field increase. Depending on the values of the dc electric field at t = 0 and the electron gyrofrequency to the plasma frequency ratio the runaway tail became unstable to the anomalous Doppler resonance or remained stable before the saturation of the dc field at some maximum value. The systems that remained stable during this stage became unstable to the anomalous Doppler or the Cerenkov resonances when the dc field was kept at the saturation level or decreased. Once the instability is triggered, the runaway tail is isotropized.

  14. Interaction of runaway electrons with lower hybrid waves via anomalous Doppler broadening

    NASA Astrophysics Data System (ADS)

    Martín-Solís, J. R.; Sánchez, R.; Esposito, B.

    2002-05-01

    Due to the relativistic decrease of the electron cyclotron frequency, a cyclotron resonance may appear between runaway electrons and lower hybrid waves. A single particle description of the runaway dynamics [J. R. Martín-Solís et al., Phys. Plasmas 5, 2370 (1998)] is extended to analyze the effect of the interaction of runaway electrons with lower hybrid waves via anomalous Doppler broadening. The conditions under which the resonant interaction can play a role in limiting the runaway energy are established and it is shown that, under typical lower hybrid current drive operation parameters, an efficient wave-particle coupling may occur. Observations of a fast pitch angle scattering event during the current decay phase of Ohmic discharges in the Toroidal Experiment for Technically Oriented Research (TEXTOR) [R. J. E. Jaspers, Ph.D. thesis, Technical University Eindhoven (1995)] are interpreted in terms of such interaction.

  15. Runaway electron damage to the Tore Supra Phase III outboard pump limiter

    SciTech Connect

    Nygren, R.; Lutz, T.; Walsh, D.; Martin, G.; Chatelier, M.; Loarer, T.; Guilhem, D.

    1996-08-01

    Operation of the Phase III outboard pump limiter (OPL) in Tore Supra in 1994 was terminated prematurely when runaway electrons during the current decay following a disruption pierced leading edge tube on the electron side and caused a water leak. The location, about 20 mm outside the last closed flux surface during normal operation, and the infrared (IR) images of the limiter indicate that the runaways moved in large outward steps, i.e. tens of millimeters, in one toroidal revolution. For plasma (runaway) currents in the range of 155 to 250 kA, the drift orbits open to the outside. Basic trajectory computations suggest that such motion is possible under the conditions present for this experiment. Activation measurements made on sections of the tube to indicate the area of local damage are presented here. An understanding of this event may provide important guidance regarding the potential damage from runaways in future tokamaks.

  16. Dramatic Outburst Reveals Nearest Black Hole

    NASA Astrophysics Data System (ADS)

    2000-01-01

    Scientists have discovered the closest black hole yet, a mere 1,600 light years from Earth. Its discovery was heralded by four of the most dramatic rapid X-ray intensity changes ever seen from one star. Astronomers from the Massachusetts Institute of Technology (MIT) and the National Science Foundation's National Radio Astronomy Observatory (NRAO) announced their findings at the American Astronomical Society's meeting in Atlanta. The black hole in the constellation Sagittarius, along with a normal star dubbed V4641 Sgr, form a violent system that briefly flooded part of our Milky Way Galaxy with X-rays and ejected subatomic particles moving at nearly the speed of light one day last September. At the peak of its X-ray output, V4641 Sgr was the brightest X-ray emitter in the sky. Astronomers call this type of system an X-ray nova because it suddenly becomes a bright source of X-rays, but this object shows characteristics never seen in an X-ray nova. "V4641 Sgr turns on and off so fast that it seems to represent a new subclass of X-ray novae," said Donald A. Smith, postdoctoral associate in MIT's Center for Space Research. Smith worked on data from this object with MIT principal research scientist Ronald Remillard and NRAO astronomer Robert Hjellming. "In X-rays, the intensity rose by a factor of more than 1,000 in seven hours, then dropped by a factor of 100 in two hours," Remillard said. The radio emission was seen as an image of an expanding "jet" of particles shooting out from the binary system. After reaching a maximum, the radio intensity dropped by a factor of nearly 40 within two days. "Radio telescopes give us a quick glimpse of something moving at a fantastically high velocity," Hjellming said. Black holes harbor enormous gravitational force that can literally rip the gas away from a nearby star. This transfer of gas is visible in many forms of radiation. Both orbiting X-ray telescopes and ground-based radio and optical telescopes saw the outburst of V4641

  17. Epidemiology of a thermonuclear bomb-burst over Nashville, Tennessee: a theoretic study.

    PubMed

    Quinn, R W

    1983-07-01

    A thermonuclear bomb explosion over any city in the world would have a devastating effect on the population and environment. For those who survive, with or without injuries, life would become primitive with little or no uncontaminated food or water, and with inadequate housing, fuel, and medical care, resulting in a breakdown of family and interpersonal relationships. This theoretic study of the potential outcome of a thermonuclear bomb-burst over Nashville, Tennessee, discusses epidemiologically the wide range of medical and psychologic effects from the direct trauma of blast and fire, widespread epidemics of otherwise controlled disease, long-term chronic illness, genetic damage, and catastrophic environmental havoc.

  18. Theoretical determination of the strength characteristics of multilayer materials intended for nuclear and thermonuclear engineering

    NASA Astrophysics Data System (ADS)

    Vitkovskii, I. V.; Leshukov, A. Yu.; Romashin, S. N.; Shorkin, V. S.

    2015-12-01

    A method is developed to estimate the integrity of multilayer structures. This method is based on the version of the theory of adhesion and cohesion interactions of structure elements that only takes into account their thermomechanical properties. The structures to be studied are the material of the multilayer wall of the liquid-metal thermonuclear reactor blanket and a heat-resistant magnet wire with a bimetallic conductor, which is the base of the windings of the magnetohydrodynamic machines and electric motors intended for operation at high temperatures under ionizing radiation in, e.g., the machines and facilities in nuclear and thermonuclear reactors.

  19. From Planetesimals to Planets in Turbulent Protoplanetary Disks. I. Onset of Runaway Growth

    NASA Astrophysics Data System (ADS)

    Kobayashi, Hiroshi; Tanaka, Hidekazu; Okuzumi, Satoshi

    2016-02-01

    When planetesimals grow via collisions in a turbulent disk, stirring through density fluctuation caused by turbulence effectively increases the relative velocities between planetesimals, which suppresses the onset of runaway growth. We investigate the onset of runaway growth in a turbulent disk through simulations that calculate the mass and velocity evolution of planetesimals. When planetesimals are small, the average relative velocity between planetesimals, {v}{{r}}, is much greater than their surface escape velocity, {v}{{esc}}, so that runaway growth does not occur. As planetesimals become large via collisional growth, {v}{{r}} approaches {v}{{esc}}. When {v}{{r}}≈ 1.5{v}{{esc}}, runaway growth of the planetesimals occurs. During the oligarchic growth subsequent to runaway growth, a small number of planetary embryos produced via runaway growth become massive through collisions with planetesimals with radii of that at the onset of runaway growth, {r}{{p,run}}. We analytically derive {r}{{p,run}} as a function of the turbulent strength. Growing ∼ 10 {M}\\oplus embryos that are suitable to become the cores of Jupiter and Saturn requires {r}{{p,run}}∼ 100 km, which is similar to the proposed fossil feature in the size distribution of main belt asteroids. In contrast, the formation of Mars as quickly as suggested from Hf-W isotope studies requires small planetesimals at the onset of runaway growth. Thus, the conditions required to form Mars, Jupiter, and Saturn and the size distribution of the main-belt asteroids indicate that the turbulence increased in amplitude relative to the sound speed with increasing distance from the young Sun.

  20. Influence of the angular scattering of electrons on the runaway threshold in air

    NASA Astrophysics Data System (ADS)

    Chanrion, O.; Bonaventura, Z.; Bourdon, A.; Neubert, T.

    2016-04-01

    The runaway electron mechanism is of great importance for the understanding of the generation of x- and gamma rays in atmospheric discharges. In 1991, terrestrial gamma-ray flashes (TGFs) were discovered by the Compton Gamma-Ray Observatory. Those emissions are bremsstrahlung from high energy electrons that run away in electric fields associated with thunderstorms. In this paper, we discuss the runaway threshold definition with a particular interest in the influence of the angular scattering for electron energy close to the threshold. In order to understand the mechanism of runaway, we compare the outcome of different Fokker-Planck and Monte Carlo models with increasing complexity in the description of the scattering. The results show that the inclusion of the stochastic nature of collisions smooths the probability to run away around the threshold. Furthermore, we observe that a significant number of electrons diffuse out of the runaway regime when we take into account the diffusion in angle due to the scattering. Those results suggest using a runaway threshold energy based on the Fokker-Planck model assuming the angular equilibrium that is 1.6 to 1.8 times higher than the one proposed by [1, 2], depending on the magnitude of the ambient electric field. The threshold also is found to be 5 to 26 times higher than the one assuming forward scattering. We give a fitted formula for the threshold field valid over a large range of electric fields. Furthermore, we have shown that the assumption of forward scattering is not valid below 1 MeV where the runaway threshold usually is defined. These results are important for the thermal runaway and the runaway electron avalanche discharge mechanisms suggested to participate in the TGF generation.

  1. Substance use among runaway and homeless youth in three national samples.

    PubMed Central

    Greene, J M; Ennett, S T; Ringwalt, C L

    1997-01-01

    OBJECTIVES: Standardized estimates of the prevalence of substance use by runaway and homeless youth between the ages of 12 and 21 in various settings were compared with each other and with estimates for youth in the general population. METHODS: Four surveys were used: (1) a nationally representative survey of runaway and homeless youth residing in federally and non-federally funded shelters; (2) a multicity survey of street youth; (3) a nationally representative household survey of youth with and without recent runaway and homeless experiences; and (4) a nationally representative household survey of youth whose previous runaway/homeless status was unknown. RESULTS: For almost every substance, substance use prevalence was highest among street youth. Shelter youth and household youth with recent runaway/homeless experiences reported similar rates. In the household surveys, substance use rates were lowest and were generally comparable. CONCLUSIONS: Many homeless and runaway youth use tobacco, alcohol, and other drugs at rates substantially higher than nonrunaway and nonhomeless youth, indicating a need for comprehensive and intensive substance abuse prevention and treatment services for these youth. PMID:9103102

  2. Influence of the angular scattering on the thermal runaway acceleration mechanism.

    NASA Astrophysics Data System (ADS)

    Chanrion, Olivier; Bonaventura, Zdenek; Bourdon, Anne; Neubert, Torsten

    2015-04-01

    The runaway electron acceleration mechanism is of great importance for the understanding of the generation of X- and Gamma-rays in atmospheric discharges. Recently, Terrestrial Gamma-ray Flashes (TGFs) were discovered by the Compton Gamma-ray Observatory in 1991. Those emissions are bremsstrahlung from high energy electrons which run away in electric fields associated with thunderstorms. In this presentation we focus on the theory of acceleration of thermal electrons to the runaway regime and discuss the influence of the scattering for electron energy close to the runaway threshold. We compare the outcome of different models with increasing complexity in the description of the scattering. The results show that the inclusion of the scattering in the model reduces the runaway production by allowing some electrons to diffuse out of the runaway regime before they reach energy high enough to justify a forward scattering model. The outcome of the present work emphasizes the importance of the set of cross section or model used to describe the angular scattering in electron-neutral collision when studying the runaway acceleration mechanism.

  3. Experiments in DIII-D toward achieving rapid shutdown with runaway electron suppression

    SciTech Connect

    Hollmann, E. M.; Commaux, Nicolas JC; Eidietis, N. W.; Evans, T. E.; Humphreys, D. A.; James, A. N.; Jernigan, T. C.; Parks, P. B.; Strait, E. J.; Wesley, J. C.; Yu, J.H.; Austin, M. E.; Baylor, Larry R; Brooks, N. H.; Izzo, V. A.; Jackson, G. L.; Van Zeeland, M. A.; Wu, W.

    2010-01-01

    Experiments have been performed in the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] toward understanding runaway electron formation and amplification during rapid discharge shutdown, as well as toward achieving complete collisional suppression of these runaway electrons via massive delivery of impurities. Runaway acceleration and amplification appear to be well explained using the zero-dimensional (0D) current quench toroidal electric field. 0D or even one-dimensional modeling using a Dreicer seed term, however, appears to be too small to explain the initial runaway seed formation. Up to 15% of the line-average electron density required for complete runaway suppression has been achieved in the middle of the current quench using optimized massive gas injection with multiple small gas valves firing simultaneously. The novel rapid shutdown techniques of massive shattered pellet injection and shell pellet injection have been demonstrated for the first time. Experiments using external magnetic perturbations to deconfine runaways have shown promising preliminary results. (C) 2010 American Institute of Physics. [doi:10.1063/1.3309426

  4. Control of post-disruption runaway electron beams in DIII-D

    SciTech Connect

    Eidietis, N. W.; Commaux, Nicolas JC; Hollmann, E. M.; Humphrey, D. A.; Jernigan, T. C.; Moyer, R.A.; Strait, E. J.; Van Zeeland, M. A.; Wesley, J. C.

    2012-01-01

    Recent experiments in the DIII-D tokamak have demonstrated real-time control and dissipation of post-disruption runaway electron (RE) beams. In the event that disruption avoidance, control, and mitigation schemes fail to avoid or suppress RE generation, active control of the RE beam may be an important line of defense to prevent the rapid, localized deposition of RE beam energy onto vulnerable vessel sections. During and immediately after the current quench, excessive radial compression of the runaway beams is avoided by a combination of techniques, improving the likelihood of the beams surviving this dynamic period without a fast termination. Once stabilized, the runaway beams are held in a steady state (out to the ohmic flux limit) with the application of active plasma current and position controls. Beam interaction with the vessel wall is minimized by avoiding distinct thresholds for enhanced wall interaction at small and large radii, corresponding to inner wall and outer limiter interaction, respectively. Staying within the 'safe zone' between those radial thresholds allows for the sustainment of long-lived, quiescent runaway beams. The total beam energy and runaway electron population are then dissipated gradually by a controlled ramp-down of the runaway current.

  5. Theoretical z -pinch scaling relations for thermonuclear-fusion experiments.

    PubMed

    Stygar, W A; Cuneo, M E; Vesey, R A; Ives, H C; Mazarakis, M G; Chandler, G A; Fehl, D L; Leeper, R J; Matzen, M K; McDaniel, D H; McGurn, J S; McKenney, J L; Muron, D J; Olson, C L; Porter, J L; Ramirez, J J; Seamen, J F; Speas, C S; Spielman, R B; Struve, K W; Torres, J A; Waisman, E M; Wagoner, T C; Gilliland, T L

    2005-08-01

    implosion time tau(i). For an accelerator coupled to a double-pinch-driven hohlraum that drives the implosion of an ICF fuel capsule, we find that the accelerator power and energy required to achieve high-yield fusion scale as tau(i)0.36 and tau(i)1.36, respectively. Thus the accelerator requirements decrease as the implosion time is decreased. However, the x-ray-power and thermonuclear-yield efficiencies of such a coupled system increase with tau(i). We also find that increasing the anode-cathode gap of the pinch from 2 to 4 mm increases the requisite values of P(a) and E(a) by as much as a factor of 2.

  6. The effect of a tectonic stress field on coal and gas outbursts.

    PubMed

    An, Fenghua; Cheng, Yuanping

    2014-01-01

    Coal and gas outbursts have always been a serious threat to the safe and efficient mining of coal resources. Ground stress (especially the tectonic stress) has a notable effect on the occurrence and distribution of outbursts in the field practice. A numerical model considering the effect of coal gas was established to analyze the outburst danger from the perspective of stress conditions. To evaluate the outburst tendency, the potential energy of yielded coal mass accumulated during an outburst initiation was studied. The results showed that the gas pressure and the strength reduction from the adsorbed gas aggravated the coal mass failure and the ground stress altered by tectonics would affect the plastic zone distribution. To demonstrate the outburst tendency, the ratio of potential energy for the outburst initiation and the energy consumption was used. Increase of coal gas and tectonic stress could enhance the potential energy accumulation ratio, meaning larger outburst tendency. The component of potential energy for outburst initiation indicated that the proportion of elastic energy was increased due to tectonic stress. The elastic energy increase is deduced as the cause for a greater outburst danger in a tectonic area from the perspective of stress conditions. PMID:24991648

  7. The Effect of a Tectonic Stress Field on Coal and Gas Outbursts

    PubMed Central

    An, Fenghua; Cheng, Yuanping

    2014-01-01

    Coal and gas outbursts have always been a serious threat to the safe and efficient mining of coal resources. Ground stress (especially the tectonic stress) has a notable effect on the occurrence and distribution of outbursts in the field practice. A numerical model considering the effect of coal gas was established to analyze the outburst danger from the perspective of stress conditions. To evaluate the outburst tendency, the potential energy of yielded coal mass accumulated during an outburst initiation was studied. The results showed that the gas pressure and the strength reduction from the adsorbed gas aggravated the coal mass failure and the ground stress altered by tectonics would affect the plastic zone distribution. To demonstrate the outburst tendency, the ratio of potential energy for the outburst initiation and the energy consumption was used. Increase of coal gas and tectonic stress could enhance the potential energy accumulation ratio, meaning larger outburst tendency. The component of potential energy for outburst initiation indicated that the proportion of elastic energy was increased due to tectonic stress. The elastic energy increase is deduced as the cause for a greater outburst danger in a tectonic area from the perspective of stress conditions. PMID:24991648

  8. Understanding the timing behavior of magnetars during outburst

    NASA Astrophysics Data System (ADS)

    Tong, Hao

    2016-07-01

    Magnetars show various kinds of variabilities during their outbursts: (1)decreasing spin-down torque during the decrease of X-ray flux by Swift J1822.3-1606; (2) increasing spin-down torque during the decrease of X-ray flux by the Galactic center magnetar; (3) anti-glitch during an outburst of AXP 1E2259+586, etc. All these timing behaviors of magnetars can be understood uniformly in the wind braking model of magnetars. Furthermore, a possible hard X-ray cutoff at about 130 keV is found. Future spectra observations may help us to distinguish between the magnetar model and fallback disk model for AXPs and SGRs.

  9. Swift/BAT detects an outburst from UX Ari

    NASA Astrophysics Data System (ADS)

    Krimm, H. A.; Barthelmy, S. D.; Baumgartner, W.; Cummings, J.; Gehrels, N.; Lien, A. Y.; Markwardt, C. B.; Palmer, D.; Sakamoto, T.; Stamatikos, M.; Ukwatta, T.

    2014-02-01

    The RS Canum Venaticorum type variable star UX Ari is currently in outburst as detected in the Swift/BAT hard X-ray transient monitor in the 15-50 keV band. The current outburst began on 2014 February 14 (MJD 56702) when it had a count rate of 0.004 +/- 0.002 ct/s/cm^2 (~20 mCrab). It continued to brighten, reaching a rate of 0.013 +/- 0.003 ct/s/cm^2 (~60 mCrab) on 2014 February 17. It has since faded somewhat, with a rate of 0.005 +/- 0.002 ct/s/cm^2 (~20 mCrab) on 2014 February 19.

  10. Intranight Variability During the 1997 Outburst of BL Lac

    NASA Astrophysics Data System (ADS)

    Clements, Sandra D.; Carini, Michael T.; Noble, John C.

    1998-02-01

    The blazar BL Lac underwent a major outburst this summer. To search for intranight variability during the outburst, observations of BL Lac were made with the 30 inch telescope at the University of Florida's Rosemary Hill Observatory. During ten nights in July, nearly 300 CCD observations were made. BL Lac was seen to vary by more than 1.5 magnitudes over those ten nights. Substantial intranight variability was also observed. For example, on July 29, BL Lac increased in brightness by more than 0.5 magnitude in less than 2.5 hours. The observations of BL Lac taken in July are reported here and discussed in relation to the models intended to explain intranight variability.

  11. Model Atmospheres for Novae in Outburst: Summary of Research

    NASA Technical Reports Server (NTRS)

    Hauschildt, Peter H.

    1999-01-01

    This paper presents a final report and summary of research on Model Atmospheres for Novae in Outburst. Some of the topics include: 1) Detailed NLTE (non-local thermodynamic equilibrium) Model Atmospheres for Novae during Outburst: II. Modeling optical and ultraviolet observations of Nova LMC 1988 #1; 2) A Non-LTE Line-Blanketed Stellar Atmosphere Model of the Early B Giant epsilon CMa; 3) Spectroscopy of Low Metallicity Stellar atmospheres; 4) Infrared Colors at the Stellar/Substellar Boundary; 5) On the abundance of Lithium in T CrB; 6) Numerical Solution of the Expanding Stellar Atmosphere Problem; and 7) The NextGen Model Atmosphere grid for 3000 less than or equal to T (sub eff) less than or equal to 10000K.

  12. Thermal runaway in VRLAB-Phenomena, reaction mechanisms and monitoring

    NASA Astrophysics Data System (ADS)

    Pavlov, D.; Monahov, B.; Kirchev, A.; Valkovska, D.

    During operation of the oxygen cycle water decomposes forming O 2 at the lead dioxide electrode, while at the lead electrode O 2 is reduced forming water. The mechanism of these processes is related with thermal phenomena as a result of which heat is released. When the cell temperature increases substantially the battery can be damaged. This phenomenon is often called thermal runaway (TRA). The present work investigates the changes in positive and negative plate potentials, temperature, current, and gassing rate during thermal runaway. It is established that during TRA maximums in the transient curves of positive plate potential, current, and finally cell temperature appear. These maximums mark four periods in the development of the TRA phenomenon. The processes that take place during each of these periods are elucidated. On ground of the experimental results a model of the electrochemical and chemical reactions that take place in the system is proposed. The thermal effects of these reactions lead to increase of the cell temperature. Water decomposition at the positive plate and water formation at the negative one cause changes in the concentration of H 2SO 4 at the plate interfaces. When the applied cell voltage is high the increase of the temperature and the changes in H 2SO 4 concentration lead to changes in the structure and phase composition of the electrodes interfaces. This results in changes of the type of the reactions that proceed at the two interfaces. Exothermic chemical reactions take place at the negative plate. Due to the increased temperature and H 2SO 4 concentration the positive plate partially passivates and the current goes through maximum and starts to decrease. The changes in Pb/solution interface and the decreased O 2 flow lead to a maximum in the cell temperature. Problems appear when the value of this maximum becomes higher than the temperature limit below which the battery operates normally. On ground of this model of the thermal phenomena

  13. Outburst Activity of the Symbiotic System AG Dra

    NASA Astrophysics Data System (ADS)

    Gális, R.; Hric, L.; Leedjärv, L.; Kundra, E.

    2015-07-01

    AG Dra is one of the best studied symbiotic systems. A period analysis of new and historical photometric data, as well as radial velocities, confirmed the presence of the two periods — about 550 days, caused by orbital motion, and around 350 days, related to pulsations of the cool component of AG Dra. In addition, the active stages change distinctively, but the outbursts recur with periods from 359 to 375 days.

  14. New type I outburst of GRO J1008-57

    NASA Astrophysics Data System (ADS)

    Kretschmar, P.; Kuehnel, M.; Nakajima, M.; Rothschild, R. E.; Laplace, E.; Salazar, E.; Mihara, T.; Kreykenbohm, I.; Wilson-Hodge, C. A.

    2016-01-01

    The Be X-ray binary GRO J1008-57 has begun another regular outburst. At the time of writing, daily averaged flux levels were 41 & plusmn; 11 mCrab (0.15 & plusmn; 0.04 counts/sec/cm^2, 2-20 keV) in MAXI and ~60 mCrab (~0.013 count/cm^2/s) in the Swift BAT monitor data.

  15. EVN detection of Aql X-1 in outburst

    NASA Astrophysics Data System (ADS)

    Tudose, V.; Paragi, Z.; Miller-Jones, J.; Garrett, M.; Fender, R.; Rushton, A.; Spencer, R.

    2009-11-01

    The X-ray binary Aql X-1 has been in outburst in the last few weeks (ATEL #2288, #2296, #2299, #2302, #2303). We observed the system on 2009 November 19 between 14:30-19:00 UT at 5 GHz with the European VLBI Network (EVN) using the e-VLBI technique. The participating radio telescopes were Effelsberg (1 Gbps), Medicina (896 Mbps), Onsala 25m (1 Gbps), Torun (1 Gbps), Westerbork (1 Gbps), Yebes (896 Mbps), and Cambridge (128 Mbps).

  16. The Role of Outburst Shock Heating in AGN Feedback

    NASA Astrophysics Data System (ADS)

    Randall, Scott W.; Nulsen, Paul; Jones, Christine; Forman, William R.

    2016-04-01

    One of the major discoveries of modern X-ray observatories is that central AGN in galaxies, groups, and clusters can regulate cooling in the diffuse X-ray emitting gas. This connection is demonstrated by the presence of large cavities in the diffuse gas, usually filled with radio-emitting plasma, that have been evacuated by jets from the AGN. This AGN feedback has important consequences for star formation, galaxy evolution, super-massive black hole growth, galaxy/black hole scaling relations, cluster scaling relations, and the growth of structure. Although it has generally been found that the kinetic output of central AGN scales with the gas cooling rate and is energetic enough to offset cooling, the details of how and where this energy is transferred to heat the gas are poorly understood. I will discuss the role of weak AGN outburst shocks in heating the diffuse gas, and present some results from a very deep (650 ks) Chandra observation of the galaxy group NGC 5813. With three three pairs of collinear cavities, each pair associated with an elliptical AGN outburst shock, NGC 5813 is uniquely well-suited to studying the outburst history of the AGN and the mean shock heating rate.

  17. GW Librae: Still Hot Eight Years Post-outburst

    NASA Astrophysics Data System (ADS)

    Szkody, Paula; Mukadam, Anjum S.; Gänsicke, Boris T.; Chote, Paul; Nelson, Peter; Myers, Gordon; Toloza, Odette; Waagen, Elizabeth O.; Sion, Edward M.; Sullivan, Denis J.; Townsley, Dean M.

    2016-08-01

    We report continued Hubble Space Telescope (HST) ultraviolet spectra and ground-based optical photometry and spectroscopy of GW Librae eight years after its largest known dwarf nova outburst in 2007. This represents the longest cooling timescale measured for any dwarf nova. The spectra reveal that the white dwarf still remains about 3000 K hotter than its quiescent value. Both ultraviolet and optical light curves show a short period of 364-373 s, similar to one of the non-radial pulsation periods present for years prior to the outburst, and with a similar large UV/optical amplitude ratio. A large modulation at a period of 2 hr (also similar to that observed prior to outburst) is present in the optical data preceding and during the HST observations, but the satellite observation intervals did not cover the peaks of the optical modulation, and so it is not possible to determine its corresponding UV amplitude. The similarity of the short and long periods to quiescent values implies that the pulsating, fast spinning white dwarf in GW Lib may finally be nearing its quiescent configuration.

  18. The Swift Supergiant Fast X-ray Transients outburst factory

    NASA Astrophysics Data System (ADS)

    Romano, Patrizia; Kennea, Jamie; Barthelmy, Scott Douglas; Bozzo, Enrico; Burrows, David N.; Ducci, Lorenzo; Esposito, Paolo; Evans, Phil; Gehrels, Neil; Krimm, Hans A.; Vercellone, Stefano

    2016-04-01

    We present the Swift Supergiant Fast X-ray Transients project, which has been exploiting Swift's capabilities in a systematic study of SFXTs and classical supergiant X-ray binaries (SGXBs) since 2007. We performed an efficient long-term monitoring of 16 sources including both SFXTs and classical SGXBs and followed source activity across more than 4 orders of magnitude in X-ray luminosity, sampling the light curves on timescales spanning from few hundred seconds to years. We use our measurements of dynamic ranges, duty cycles as a function of luminosity, and luminosity distributions to highlight systematic differences that help discriminate between different theoretical models proposed to explain the differences between the wind accretion processes in SFXTs and classical SGXBs. Our follow-ups of the SFXT outbursts provide a steady advancement in the comprehension of the mechanisms triggering the high X-ray level emission of these sources. In particular, the recent observations of the outburst of the SFXT prototype IGR J17544-2619 on 2014 October 10, when the source reached a peak luminosity of 3x1038 erg s-1, challenged, for the first time, the maximum theoretical luminosity achievable by a wind-fed neutron star high mass X-ray binary. We propose that this giant outburst was due to the formation of a transient accretion disc around the compact object.

  19. GW Librae: Still Hot Eight Years Post-outburst

    NASA Astrophysics Data System (ADS)

    Szkody, Paula; Mukadam, Anjum S.; Gänsicke, Boris T.; Chote, Paul; Nelson, Peter; Myers, Gordon; Toloza, Odette; Waagen, Elizabeth O.; Sion, Edward M.; Sullivan, Denis J.; Townsley, Dean M.

    2016-08-01

    We report continued Hubble Space Telescope (HST) ultraviolet spectra and ground-based optical photometry and spectroscopy of GW Librae eight years after its largest known dwarf nova outburst in 2007. This represents the longest cooling timescale measured for any dwarf nova. The spectra reveal that the white dwarf still remains about 3000 K hotter than its quiescent value. Both ultraviolet and optical light curves show a short period of 364–373 s, similar to one of the non-radial pulsation periods present for years prior to the outburst, and with a similar large UV/optical amplitude ratio. A large modulation at a period of 2 hr (also similar to that observed prior to outburst) is present in the optical data preceding and during the HST observations, but the satellite observation intervals did not cover the peaks of the optical modulation, and so it is not possible to determine its corresponding UV amplitude. The similarity of the short and long periods to quiescent values implies that the pulsating, fast spinning white dwarf in GW Lib may finally be nearing its quiescent configuration.

  20. Multi-wavelength coverage of outburst decays of LMXBs

    NASA Astrophysics Data System (ADS)

    Kalemci, Emrah; Tomsick, John; Bailyn, Charles; Dincer, Tolga

    2016-07-01

    Low mass X-ray binaries (LMXB) are dynamic laboratories that are powered by accretion, and under some conditions these systems create strong outflows in the form of highly collimated jets, or winds. Outburst decays of transient LMXBs provide additional information about compact jets and their relation to changes in timing properties. Our group characterizes the multi-wavelength evolution of Galactic black hole transients during their outburst decays using simultaneous X-ray (RXTE, Swift, and INTEGRAL), optical/infrared (SMARTS) and radio (VLA, ATCA, VLBI). By characterizing the X-ray spectral and timing evolution of these systems, and merging this information with the evolution in the near-infrared and radio, we obtain the conditions necessary to launch stable compact jets, and discuss how jets can be influencing and/or influenced by X-ray timing and spectral properties of these systems. In this presentation, I will summarize recent results regarding multi-wavelength observations of not only black hole systems, but also neutron star X-ray binaries during outburst decays, and discuss models that explain not only the broad spectral energy distribution, but also some of the timing properties of these systems.

  1. THE OUTBURST OF COMET 17P/HOLMES

    SciTech Connect

    Lin Zhongyi; Lara, Luisa M.; Lin, C.-S.; Ip, W.-H.

    2009-08-15

    Comet 17P/Holmes had a massive outburst at approximately 2007 October 23.8 and its total brightness reached maximum (from m = 17 to m = 2.5) around 2007 October 25, about 1.7 days (42 hr) after the event. Following the first report of this extraordinary cometary outburst, comprehensive observations were obtained at the Lulin Observatory until early 2008 January by using broadband filters and narrowband cometary filters. The separation velocity, as projected on the plane of the sky, between the nucleus and the coma blob produced by the outburst has been estimated to be 0.132 {+-} 0.004 km s{sup -1} from October 25.8 to November 1.6. The expansion speed, also projected on the plane of the sky of the dust shell has been found to be constant at a rate of approximately 0.554 {+-} 0.005 km s{sup -1} from October 25.8 to November 1.6. The color on December 10 is slightly redder than that of the Sun. Our narrowband observations provide information on the production rates of gas species on October 31: log Q (CN) = 27.103 and log Q (C{sub 2}) = 27.349. The resulting abundance ratios show that the comet 17P can be classified as a 'typical comet' in terms of composition.

  2. Disk instability and outburst properties of the intermediate polar GK Persei

    NASA Technical Reports Server (NTRS)

    Kim, Soon-Wook; Wheeler, J. C.; Mineshige, Shin

    1992-01-01

    The present study reproduces the observed recurrence time scales and duration of the 1981-1989 dwarf nova-type outbursts of the intermediate polar GK Per with a model based on the time-dependent disk instability model. The model gives approximately symmetric (type B, inside-out) outbursts, as observed. This agreement suggests that the outbursts cannot result from a mass transfer instability. A modest variation of the mass transfer rate from the companion is sufficient to account for the variable outburst recurrence time scale. Contamination from the companion and the hot spot dominate the light from the disk except during a bright outburst. An intermediate temperature stagnation wave followed by a full heating wave is consistent with the observed rapid rise and double-peaked structure in the UV and optical light curves. It is argued that the hard X-ray efficiency is dime-dependent, and it is found to be much smaller in outburst than in quiescence.

  3. [Human life and energy production. Prospects opened up by controlled thermonuclear fusion].

    PubMed

    Escande, D

    1997-03-18

    The massive and presently increasing energy production is going to confront mankind with a very important problem in the forthcoming decades, in particular due to the vanishing of resources and to the greenhouse effect. The share of fossil fuels in the energy production will have to decrease, and other energy sources will be needed. Among them controlled thermonuclear fusion has may assets due to its non-radioactive fuel with plentiful supply, its non radioactive and non polluting ashes, its safety, its weak environmental impact, and its irrelevance to nuclear proliferation in a normal setting. During the last three decades, physicists have made a series of steps toward the peaceful use of the dominant source of energy in the Universe. They have learned how to confine by magnetic fields plasmas at temperatures of 200 millions degrees centigrade, and they have developed several specific technologies. This way, they produced 11 million watts of nuclear power by fusing two isotopes of hydrogen. These investigations are conducted in a responsible spirit, that of ecoproduction, where possible negative consequences are anticipated, are made as low as reasonably achievable, and their management is studied. Yet several fundamental issues still have to be solved before on economically efficient industrial thermonuclear power plant be operated. A huge international collaboration involving Japan, the USA, the Russian Federation, and the European Union joined with Switzerland and Canada, is presently designing the first experimental thermonuclear reactor, the International Thermonuclear Experimental Reactor (ITER). It would cost 9 billion dollars, a cost similar to other large scientific projects. This is an important step toward an electricity producing thermonuclear reactor that would be both safe and respectful of human health and of environment. PMID:9203740

  4. [Human life and energy production. Prospects opened up by controlled thermonuclear fusion].

    PubMed

    Escande, D

    1997-03-18

    The massive and presently increasing energy production is going to confront mankind with a very important problem in the forthcoming decades, in particular due to the vanishing of resources and to the greenhouse effect. The share of fossil fuels in the energy production will have to decrease, and other energy sources will be needed. Among them controlled thermonuclear fusion has may assets due to its non-radioactive fuel with plentiful supply, its non radioactive and non polluting ashes, its safety, its weak environmental impact, and its irrelevance to nuclear proliferation in a normal setting. During the last three decades, physicists have made a series of steps toward the peaceful use of the dominant source of energy in the Universe. They have learned how to confine by magnetic fields plasmas at temperatures of 200 millions degrees centigrade, and they have developed several specific technologies. This way, they produced 11 million watts of nuclear power by fusing two isotopes of hydrogen. These investigations are conducted in a responsible spirit, that of ecoproduction, where possible negative consequences are anticipated, are made as low as reasonably achievable, and their management is studied. Yet several fundamental issues still have to be solved before on economically efficient industrial thermonuclear power plant be operated. A huge international collaboration involving Japan, the USA, the Russian Federation, and the European Union joined with Switzerland and Canada, is presently designing the first experimental thermonuclear reactor, the International Thermonuclear Experimental Reactor (ITER). It would cost 9 billion dollars, a cost similar to other large scientific projects. This is an important step toward an electricity producing thermonuclear reactor that would be both safe and respectful of human health and of environment.

  5. E-ELT constraints on runaway dilaton scenarios

    SciTech Connect

    Martinelli, M.; Calabrese, E.; Martins, C.J.A.P. E-mail: erminia.calabrese@physics.ox.ac.uk

    2015-11-01

    We use a combination of simulated cosmological probes and astrophysical tests of the stability of the fine-structure constant α, as expected from the forthcoming European Extremely Large Telescope (E-ELT), to constrain the class of string-inspired runaway dilaton models of Damour, Piazza and Veneziano. We consider three different scenarios for the dark sector couplings in the model and discuss the observational differences between them. We improve previously existing analyses investigating in detail the degeneracies between the parameters ruling the coupling of the dilaton field to the other components of the universe, and studying how the constraints on these parameters change for different fiducial cosmologies. We find that if the couplings are small (e.g., α{sub b} = α{sub V} ∼ 0) these degeneracies strongly affect the constraining power of future data, while if they are sufficiently large (e.g., α{sub b} ∼> 10{sup −5}−α{sub V} ∼> 0.05, as in agreement with current constraints) the degeneracies can be partially broken. We show that E-ELT will be able to probe some of this additional parameter space.

  6. A study of runaway electrons on a university scale generator

    NASA Astrophysics Data System (ADS)

    Ouart, Nicholas; Giuliani, John; Dasgupta, Arati; Petrov, George; Ampleford, David; Hansen, Stephanie; Safronova, Alla; Kantsyrev, Victor; Shrestha, Ishor

    2014-10-01

    Wire array implosions have produced characteristic K-shell emission. These K-alpha and K-beta photons are a result of high energy electrons removing an n = 1 bound electron from lower ionization stages (e.g. Ne-like). The motivation for studying this emission is the possibility of producing an alternative plasma radiation source with photon energies above 10 keV. However, the mechanism producing these fast runaway electrons still remains elusive. We show results from following electrons in uniform cylindrical plasma with an axial electric field and an azimuthal magnetic field. Elastic and inelastic collisions are included via Monte Carlo techniques. Comparison with experimental Zebra data previously reported will be discussed. Work supported by DOE/NNSA. This work is partially funded by Sandia LDRD Project 165733. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  7. Runaway beam studies during disruptions at JET-ILW

    NASA Astrophysics Data System (ADS)

    Reux, C.; Plyusnin, V.; Alper, B.; Alves, D.; Bazylev, B.; Belonohy, E.; Brezinsek, S.; Decker, J.; Devaux, S.; de Vries, P.; Fil, A.; Gerasimov, S.; Lupelli, I.; Jachmich, S.; Khilkevitch, E. M.; Kiptily, V.; Koslowski, R.; Kruezi, U.; Lehnen, M.; Manzanares, A.; Mlynář, J.; Nardon, E.; Nilsson, E.; Riccardo, V.; Saint-Laurent, F.; Shevelev, A. E.; Sozzi, C.

    2015-08-01

    Runaway electrons (RE) during disruptions are a concern for future tokamaks including ITER with its metallic wall. Although RE are rare in spontaneous disruptions with the JET ITER-like Wall (JET-ILW), RE beams up to 380 kA were obtained using massive injection (MGI) of argon in JET-ILW divertor discharges. Entry points into the RE domain defined by operational parameters (toroidal field, argon fraction in MGI) are unchanged but higher RE currents have been obtained inside the JET-ILW MGI-generated RE domain when compared to JET-C. This might be due to the influence of the metallic wall on the current quench plasma. Temperatures of 900 °C have been observed following RE impacts on beryllium tiles. Heat deposition depth of ∼2 mm has to be assumed to match the tile cooling time. 3D simulations of the RE energy deposition using the ENDEP/MEMOS codes show that material melting is unlikely with 100 kA RE beams.

  8. Accretion outbursts in self-gravitating protoplanetary disks

    SciTech Connect

    Bae, Jaehan; Hartmann, Lee; Zhu, Zhaohuan; Nelson, Richard P. E-mail: lhartm@umich.edu E-mail: r.p.nelson@qmul.ac.uk

    2014-11-01

    We improve on our previous treatments of the long-term evolution of protostellar disks by explicitly solving disk self-gravity in two dimensions. The current model is an extension of the one-dimensional layered accretion disk model of Bae et al. We find that gravitational instability (GI)-induced spiral density waves heat disks via compressional heating (i.e., PdV work), and can trigger accretion outbursts by activating the magnetorotational instability (MRI) in the magnetically inert disk dead zone. The GI-induced spiral waves propagate well inside of the gravitationally unstable region before they trigger outbursts at R ≲ 1 AU where GI cannot be sustained. This long-range propagation of waves cannot be reproduced with the previously used local α treatments for GI. In our standard model where zero dead-zone residual viscosity (α{sub rd}) is assumed, the GI-induced stress measured at the onset of outbursts is locally as large as 0.01 in terms of the generic α parameter. However, as suggested in our previous one-dimensional calculations, we confirm that the presence of a small but finite α{sub rd} triggers thermally driven bursts of accretion instead of the GI + MRI-driven outbursts that are observed when α{sub rd} = 0. The inclusion of non-zero residual viscosity in the dead zone decreases the importance of GI soon after mass feeding from the envelope cloud ceases. During the infall phase while the central protostar is still embedded, our models stay in a 'quiescent' accretion phase with M-dot {sub acc}∼10{sup −8}--10{sup −7} M{sub ⊙} yr{sup −1} over 60% of the time and spend less than 15% of the infall phase in accretion outbursts. While our models indicate that episodic mass accretion during protostellar evolution can qualitatively help explain the low accretion luminosities seen in most low-mass protostars, detailed tests of the mechanism will require model calculations for a range of protostellar masses with some constraint on the initial core

  9. Hot Spot in Eclipsing Dwarf Nova IY Ursae Majoris during Quiescence and Normal Outburst

    NASA Astrophysics Data System (ADS)

    Bąkowska, K.; Olech, A.

    2015-12-01

    We present the analysis of hot spot brightness in light curves of the eclipsing dwarf nova IY UMa during its normal outburst in March 2013 and in quiescence in April 2012 and in October 2015. Examination of four reconstructed light curves of the hot spot eclipses showed directly that the brightness of the hot spot changed significantly only during the outburst. The brightness of the hot spot, before and after the outburst, was on the same level. Thus, based on the behavior of the hot spot, IY UMa during its normal outburst follows the disk-instability model.

  10. A steady-state simulation methodology for predicting runaway speed in Francis turbines

    NASA Astrophysics Data System (ADS)

    Hosseinimanesh, H.; Vu, T. C.; Devals, C.; Nennemann, B.; Guibault, F.

    2014-03-01

    Runaway speed is an important performance factor for the safe operation of hydropower systems. In turbine design, the manufacturers must conduct several model tests to calculate the accurate value of runaway speed for the complete range of operating conditions, which are expensive and time-consuming. To study runaway conditions, the application of numerical tools such as unsteady CFD simulations can help to better understand the complex flow physics during transient processes. However, unsteady simulations require significant computational effort to compute accurate values of runaway speed due to difficulties related to unsteady turbulent flow modelling and instabilities. The present study presents a robust methodology based on steady-state RANS flow simulations capable of predicting the runaway speed of a Francis turbine with an adequate level of accuracy and in a reasonable simulation time. The simulations are implemented using a commercial flow solver and an iterative algorithm that relies on a smooth relation between turbine torque and speed coefficient. The impact of friction has been considered when estimating turbine torque, in order to improve the accuracy. The results of this study show good agreement with experiments.

  11. Relativistic Runaway Electron Avalanches in the Presence of an External Magnetic Field

    NASA Astrophysics Data System (ADS)

    Cramer, E. S.; Dwyer, J. R.; Liu, N.; Rassoul, H.; Briggs, M. S.

    2015-12-01

    Relativistic runaway electron avalanches are known to be produced inside the high electric field regions of thunderstorms. In this work, we include the effects of an external static magnetic field. Previous studies have shown that the magnetic field has a great influence on the electron motion at higher altitudes, e.g. Lehtinen et al., 1997, and Gurevich et al., 1996. This result proves important when studying phenomena such as Terrestrial Gamma-ray Flashes, and their effects on the upper atmosphere. Therefore, electron avalanche rates, feedback rates, and electron energy distribution functions will be analyzed and compared to the results of previous studies that did not include a magnetic field. The runaway electron avalanche model (REAM) is a Monte Carlo code that simulates the generation, interactions, and propagation of relativistic runaway electrons in air [Dwyer, 2003, 2004, 2007]. We use this simulation for varying strengths and angles between the electric and magnetic fields to calculate avalanche lengths and angular distribution functions of the relativistic runaway electrons. We will also show electron distribution functions in momentum space. Finally, we will discuss the important regimes for which the magnetic field becomes significant in studying the properties of runaway electron avalanches and relativistic feedback.

  12. Bounce-averaged Fokker-Planck Simulation of Runaway Avalanche from Secondary Knock-on Production

    NASA Astrophysics Data System (ADS)

    Chiu, S. C.; Chan, V. S.; Harvey, R. W.; Rosenbluth, M. N.

    1996-11-01

    It has been pointed out that secondary production of runaway electrons by knock-on collisions with very energetic confined electrons can significantly change the runaway rate,(M.N. Rosenbluth, Bull. Amer. Phys. Soc. 40), 1804 (1995).^,(N.T. Besedin, I.M. Pankratov, Nucl. Fusion 26), 807 (1986).^,(R. Jaspers, K.H. Finden, G. Mank et al.), Nucl. Fusion 33, 1775 (1993). and is potentially a serious problem in reactors. Previous calculations of the effect have only partially included important effects such as toroidal trapping, synchrotron radiation, and bremsstrahlung. Furthermore, in a normal constant current operation, the increase of the density of runaway electrons causes a decrease of the ohmic field and all these effects can balance to a steady-state. The purpose of the present paper is to present results on bounce-averaged Fokker-Planck simulations of knock-on avalanching runaways including these effects. Initially, an energetic seed component is inserted to initiate knock-on avalanching. Results on the dependence of the steady-state runaway current on Z_eff, density, and radial location will be presented.

  13. Onset of Conduct Disorder, Use of Delinquent Subsistence Strategies, and Street Victimization among Homeless and Runaway Adolescents in the Midwest

    ERIC Educational Resources Information Center

    Chen, Xiaojin; Thrane, Lisa; Whitbeck, Les B.; Johnson, Kurt D.; Hoyt, Dan R.

    2007-01-01

    This study examines the effects of childhood-onset conduct disorder on later antisocial behavior and street victimization among a group of homeless and runaway adolescents. Four hundred twenty-eight homeless and runaway youth were interviewed directly on the streets and in shelters from four Midwestern states. Key findings include the following.…

  14. 45 CFR 1351.20 - What are the additional requirements under a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Runaway and Homeless Youth Program grant? 1351.20 Section 1351.20 Public Welfare Regulations Relating to... THE ADMINISTRATION FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Additional Requirements § 1351.20 What are the additional requirements under...

  15. 45 CFR 1351.18 - What criteria has HHS established for deciding which Runaway and Homeless Youth Program grant...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... adequate facilities and resources; (i) Whether the proposed project design, if well executed, is capable of... otherwise homeless youth in the area in which the runaway and homeless youth project is or will be located... runaway and homeless youth project is located; (d) Whether there is a minimum residential capacity of...

  16. The mechanism of thermal runaway due to continuous local disturbances in the YBCO-coated conductor coil winding

    NASA Astrophysics Data System (ADS)

    Yanagisawa, Y.; Okuyama, E.; Nakagome, H.; Takematsu, T.; Takao, T.; Hamada, M.; Matsumoto, S.; Kiyoshi, T.; Takizawa, A.; Takahashi, M.; Maeda, H.

    2012-07-01

    Though YBCO coils are stable against transient disturbances such as conductor motion, they suffer from thermal runaway at a current below the coil critical current due to continuous local disturbances attributed to partial degradation of the conductor in the coil winding. Continuous heat generation in the degraded layer induces thermal runaway in adjacent layers; thermal runaway does not occur in the degraded layer spontaneously due to the small n index of the degraded YBCO-coated conductor. The thermal runaway current depends on the cooling conditions of the winding. For a paraffin-impregnated YBCO coil under quasi-adiabatic conditions, the thermal runaway current is far below the coil critical current, while it is close to the coil critical current in the case of a dry-wound coil. The permissible temperature rise following a thermal runaway for YBCO conductors in the degraded layer is demonstrated to be 340 K. If the YBCO coils are operated at a temperature below 20 K, the current density, typically 600-800 A mm-2, is much higher than that at 77 K. Therefore, the time interval between thermal runaway initiation and the melting temperature becomes less than 0.5 s, posing a difficult problem for protection; i.e., thermal runaway due to continuous local disturbances is hazardous to the safe operation of high current density YBCO coils.

  17. Numerical study of the generation of runaway electrons in a gas diode with a hot channel

    SciTech Connect

    Lisenkov, V. V.; Shklyaev, V. A.

    2015-11-15

    A new method for increasing the efficiency of runaway electron beam generation in atmospheric pressure gas media has been suggested and theoretically proved. The method consists of creating a hot region (e.g., a spark channel or a laser plume) with a decreased numerical density of gas molecules (N) near the cathode. In this method, the ratio E/N (E—electric field strength) is increased by decreasing N instead of increasing E, as has been done in the past. The numerical model that is used allows the simultaneous calculation of the formation of a subnanosecond gas discharge and the generation of runaway electrons in gas media. The calculations have demonstrated the possibility of obtaining current pulses of runaway electrons with amplitudes of hundred of amperes and durations of more than 100 ps. The influence of the hot channel geometry on the parameters of the generated beam has been investigated.

  18. New mechanism of runaway electron diffusion due to microturbulence in tokamaks

    SciTech Connect

    Abdullaev, S. S.; Finken, K. H.; Forster, M.

    2012-07-15

    Chaotic transport of runaway electrons in a toroidal system in the presence of a weak small-scale magnetic turbulent field with a wide mode spectrum is studied. Using a fast running mapping, the radial profiles of turbulent diffusion coefficients are calculated. It is found that at large Kubo numbers the chaotic transport of the electrons is described by a fractal-like radial dependence of the diffusion coefficients with reduced or zero values near low-order rational drift surfaces which form transport barriers. The latter can be one of the main reasons of the improved confinement of runaway electrons in tokamaks. One can expect that this effect may lead to the formation of the nested beams of runaway electrons.

  19. Ecologically-Based Family Therapy Outcome with Substance Abusing Runaway Adolescents

    PubMed Central

    Slesnick, Natasha; Prestopnik, Jillian L.

    2007-01-01

    Runaway youth report a broader range and higher severity of substance-related, mental health and family problems relative to non-runaway youth. Most studies to date have collected self-report data on the family and social history; virtually no research has examined treatment effectiveness with this population. This study is a treatment development project in which 124 runaway youth were randomly assigned to 1) Ecologically-Based Family Therapy (EBFT) or 2) Service as Usual (SAU) through a shelter. Youth completed an intake, posttreatment, 6 and 12 month follow-up assessment. Youth assigned to EBFT reported greater reductions in overall substance abuse compared to youth assigned to SAU while other problem areas improved in both conditions. Findings suggest that EBFT is an efficacious intervention for this relatively severe population of youth. PMID:15878048

  20. Simulation of a runaway electron avalanche developing in an atmospheric pressure air discharge

    SciTech Connect

    Oreshkin, E. V.; Barengolts, S. A.; Chaikovsky, S. A.; Oreshkin, V. I.

    2015-12-15

    To gain a better understanding of the operation of atmospheric pressure air discharges, the formation of a runaway electron beam at an individual emission site on the cathode has been numerically simulated. The model provides a description of the dynamics of the fast electrons emitted into an air gap from the surface of the emission zone by solving numerically two-dimensional equations for the electrons. It is supposed that the electric field at the surface of the emission zone is enhanced, providing conditions for continuous acceleration of the emitted electrons. It is shown that the formation of a runaway electron beam in a highly overvolted discharge is largely associated with avalanche-type processes and that the number of electrons in the avalanche reaches 50% of the total number of runaway electrons.

  1. Predictors of posttraumatic stress symptoms among runaway youth utilizing two service sectors.

    PubMed

    Thompson, Sanna J; Maccio, Elaine M; Desselle, Sherry K; Zittel-Palamara, Kimberly

    2007-08-01

    Youth who run away often experience situations that produce symptoms of traumatic distress. This exploratory study assessed predictors of trauma symptomatology among runaway youth who had been admitted to youth emergency shelter services or juvenile detention. Findings demonstrated high levels of trauma-related symptoms for both groups. Worry about family, greater runaway episodes, and living with a father who abused alcohol/drugs significantly predicted higher posttraumatic stress symptoms in detained youth, whereas only worry about family relationships predicted higher trauma symptom scores among youth in emergency shelter care. Findings suggest distressful family life may induce complex emotional responses in youth. Although services to runaway youth must continue to focus on safe, short-term residential care, trauma issues must be acknowledged.

  2. Comparisons of Runaway Electron Production in DIII--D with the CQL3D Model

    NASA Astrophysics Data System (ADS)

    Harvey, R. W.; Chan, V. S.; Chiu, S. C.; Evans, T. E.; Whyte, D. G.; Rosenbluth, M. N.

    1997-11-01

    The time-dependent CQL3D relativistic, bounce-averaged Fokker-Planck code is well suited to modeling the electron runaway generation by ``tail slideaway'' and ``knockon'' processes associated with rapid plasma temperature drop as occurs during plasma disruption and pellet injection. ``Rapid temperure drop'' means in a time short compared to the resistive time thus leading to large inductive electric field; and also short compared to tail electron slowing down time thereby providing a significant number of high velocity electrons. The tail electrons find themselves beyond the critical velocity for runaway. During DIII--D pellet injection experiments, in the plasma interior we calculate nearly 100 percent of the plasma current is transferred to runaway electrons by tail slideaway. This effect diminishes towards the plasma edge, where the knockon process can become dominant on a longer time scale. These computational results will be benchmarked against the experimental results.

  3. High performance gamma-ray spectrometer for runaway electron studies on the FT-2 tokamak

    NASA Astrophysics Data System (ADS)

    Shevelev, A. E.; Khilkevitch, E. M.; Lashkul, S. I.; Rozhdestvensky, V. V.; Altukhov, A. B.; Chugunov, I. N.; Doinikov, D. N.; Esipov, L. A.; Gin, D. B.; Iliasova, M. V.; Naidenov, V. O.; Nersesyan, N. S.; Polunovsky, I. A.; Sidorov, A. V.; Kiptily, V. G.

    2016-09-01

    A gamma-ray spectrometer based on LaBr3(Ce) scintillator has been used for measurements of hard X-ray emission generated by runaway electrons in the FT-2 tokamak plasmas. Using of the fast LaBr3(Ce) has allowed extending count rate range of the spectrometer by a factor of 10. A developed digital processing algorithm of the detector signal recorded with a digitizer sampling rate of 250 MHz has provided a pulse height analysis at count rates up to 107 s-1. A spectrum deconvolution code DeGaSum has been applied for inferring the energy distribution of runaway electrons escaping from the plasma and interacting with materials of the FT-2 limiter in the vacuum chamber. The developed digital signal processing technique for LaBr3(Ce) spectrometer has allowed studying the evolution of runaways energy distribution in the FT-2 plasma discharges with time resolution of 1-5 ms.

  4. Imaging the water snow-line during a protostellar outburst.

    PubMed

    Cieza, Lucas A; Casassus, Simon; Tobin, John; Bos, Steven P; Williams, Jonathan P; Perez, Sebastian; Zhu, Zhaohuan; Caceres, Claudio; Canovas, Hector; Dunham, Michael M; Hales, Antonio; Prieto, Jose L; Principe, David A; Schreiber, Matthias R; Ruiz-Rodriguez, Dary; Zurlo, Alice

    2016-07-13

    A snow-line is the region of a protoplanetary disk at which a major volatile, such as water or carbon monoxide, reaches its condensation temperature. Snow-lines play a crucial role in disk evolution by promoting the rapid growth of ice-covered grains. Signatures of the carbon monoxide snow-line (at temperatures of around 20 kelvin) have recently been imaged in the disks surrounding the pre-main-sequence stars TW Hydra and HD163296 (refs 3, 10), at distances of about 30 astronomical units (au) from the star. But the water snow-line of a protoplanetary disk (at temperatures of more than 100 kelvin) has not hitherto been seen, as it generally lies very close to the star (less than 5 au away for solar-type stars). Water-ice is important because it regulates the efficiency of dust and planetesimal coagulation, and the formation of comets, ice giants and the cores of gas giants. Here we report images at 0.03-arcsec resolution (12 au) of the protoplanetary disk around V883 Ori, a protostar of 1.3 solar masses that is undergoing an outburst in luminosity arising from a temporary increase in the accretion rate. We find an intensity break corresponding to an abrupt change in the optical depth at about 42 au, where the elevated disk temperature approaches the condensation point of water, from which we conclude that the outburst has moved the water snow-line. The spectral behaviour across the snow-line confirms recent model predictions: dust fragmentation and the inhibition of grain growth at higher temperatures results in soaring grain number densities and optical depths. As most planetary systems are expected to experience outbursts caused by accretion during their formation, our results imply that highly dynamical water snow-lines must be considered when developing models of disk evolution and planet formation.

  5. Imaging the water snow-line during a protostellar outburst

    NASA Astrophysics Data System (ADS)

    Cieza, Lucas A.; Casassus, Simon; Tobin, John; Bos, Steven P.; Williams, Jonathan P.; Perez, Sebastian; Zhu, Zhaohuan; Caceres, Claudio; Canovas, Hector; Dunham, Michael M.; Hales, Antonio; Prieto, Jose L.; Principe, David A.; Schreiber, Matthias R.; Ruiz-Rodriguez, Dary; Zurlo, Alice

    2016-07-01

    A snow-line is the region of a protoplanetary disk at which a major volatile, such as water or carbon monoxide, reaches its condensation temperature. Snow-lines play a crucial role in disk evolution by promoting the rapid growth of ice-covered grains. Signatures of the carbon monoxide snow-line (at temperatures of around 20 kelvin) have recently been imaged in the disks surrounding the pre-main-sequence stars TW Hydra and HD163296 (refs 3, 10), at distances of about 30 astronomical units (AU) from the star. But the water snow-line of a protoplanetary disk (at temperatures of more than 100 kelvin) has not hitherto been seen, as it generally lies very close to the star (less than 5 AU away for solar-type stars). Water-ice is important because it regulates the efficiency of dust and planetesimal coagulation, and the formation of comets, ice giants and the cores of gas giants. Here we report images at 0.03-arcsec resolution (12 AU) of the protoplanetary disk around V883 Ori, a protostar of 1.3 solar masses that is undergoing an outburst in luminosity arising from a temporary increase in the accretion rate. We find an intensity break corresponding to an abrupt change in the optical depth at about 42 AU, where the elevated disk temperature approaches the condensation point of water, from which we conclude that the outburst has moved the water snow-line. The spectral behaviour across the snow-line confirms recent model predictions: dust fragmentation and the inhibition of grain growth at higher temperatures results in soaring grain number densities and optical depths. As most planetary systems are expected to experience outbursts caused by accretion during their formation, our results imply that highly dynamical water snow-lines must be considered when developing models of disk evolution and planet formation.

  6. Imaging the water snow-line during a protostellar outburst.

    PubMed

    Cieza, Lucas A; Casassus, Simon; Tobin, John; Bos, Steven P; Williams, Jonathan P; Perez, Sebastian; Zhu, Zhaohuan; Caceres, Claudio; Canovas, Hector; Dunham, Michael M; Hales, Antonio; Prieto, Jose L; Principe, David A; Schreiber, Matthias R; Ruiz-Rodriguez, Dary; Zurlo, Alice

    2016-07-14

    A snow-line is the region of a protoplanetary disk at which a major volatile, such as water or carbon monoxide, reaches its condensation temperature. Snow-lines play a crucial role in disk evolution by promoting the rapid growth of ice-covered grains. Signatures of the carbon monoxide snow-line (at temperatures of around 20 kelvin) have recently been imaged in the disks surrounding the pre-main-sequence stars TW Hydra and HD163296 (refs 3, 10), at distances of about 30 astronomical units (au) from the star. But the water snow-line of a protoplanetary disk (at temperatures of more than 100 kelvin) has not hitherto been seen, as it generally lies very close to the star (less than 5 au away for solar-type stars). Water-ice is important because it regulates the efficiency of dust and planetesimal coagulation, and the formation of comets, ice giants and the cores of gas giants. Here we report images at 0.03-arcsec resolution (12 au) of the protoplanetary disk around V883 Ori, a protostar of 1.3 solar masses that is undergoing an outburst in luminosity arising from a temporary increase in the accretion rate. We find an intensity break corresponding to an abrupt change in the optical depth at about 42 au, where the elevated disk temperature approaches the condensation point of water, from which we conclude that the outburst has moved the water snow-line. The spectral behaviour across the snow-line confirms recent model predictions: dust fragmentation and the inhibition of grain growth at higher temperatures results in soaring grain number densities and optical depths. As most planetary systems are expected to experience outbursts caused by accretion during their formation, our results imply that highly dynamical water snow-lines must be considered when developing models of disk evolution and planet formation. PMID:27411631

  7. Spacecraft Risk Posed by the 2016 Perseid Outburst

    NASA Technical Reports Server (NTRS)

    Cooke, W. J.; Moser, D. E.; Moorhead, A. V.

    2016-01-01

    The Perseids are one of the more prolific annual showers, known for high rates and for producing bright meteors. Outbursts of this shower have been noted in the 1860s, the early 1990s, 2004, and 2009, with the 1993 outburst being especially active (peak ZHR above 300). The 1993 Perseids also affected the space-faring nations, as the launch of the STS-51 mission was delayed by NASA until after the shower maximum due to an inability to predict the shower intensity, and the ESA telecommunications satellite Olympus suffered a mission-ending anomaly attributed to a static discharge caused by a Perseid impact [1]. Rates were again high (peak ZHR around 200) in 2009, when the NASA/USGS imaging satellite Landsat-5 experienced a gyro anomaly just before the shower peak; however in this case, the satellite was recovered and normal operations resumed one week later [2]. It is interesting to note that both spacecraft anomalies were not what is typically expected from meteoroid strikes, i.e., physical damage or an attitude displacement due to transfer of momentum. It would appear that the very fast Perseids (59 km s(sup -1) have a marked ability to produce plasma upon impact, which can then serve as a conductive path for discharge currents. The shower is expected to outburst again in 2016, and we present the results from the MSFC Meteoroid Stream Model [4], which predicts enhanced activity on a level similar to that of 2009 as the Earth passes through several debris trails on the night of August 11-12 (UT). We then compare our results to those of other modelers.

  8. 45 CFR 1351.13 - What are the Federal and non-Federal match requirements under a Runaway and Homeless Youth grant?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... requirements under a Runaway and Homeless Youth grant? 1351.13 Section 1351.13 Public Welfare Regulations... SERVICES THE ADMINISTRATION FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.13 What are the Federal and...

  9. 45 CFR 1351.13 - What are the Federal and non-Federal match requirements under a Runaway and Homeless Youth grant?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... requirements under a Runaway and Homeless Youth grant? 1351.13 Section 1351.13 Public Welfare Regulations... SERVICES THE ADMINISTRATION FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.13 What are the Federal and...

  10. 45 CFR 1351.13 - What are the Federal and non-Federal match requirements under a Runaway and Homeless Youth grant?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... requirements under a Runaway and Homeless Youth grant? 1351.13 Section 1351.13 Public Welfare Regulations... SERVICES THE ADMINISTRATION FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.13 What are the Federal and...

  11. 45 CFR 1351.13 - What are the Federal and non-Federal match requirements under a Runaway and Homeless Youth grant?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... requirements under a Runaway and Homeless Youth grant? 1351.13 Section 1351.13 Public Welfare Regulations... SERVICES THE ADMINISTRATION FOR CHILDREN, YOUTH AND FAMILIES, FAMILY AND YOUTH SERVICES BUREAU RUNAWAY AND HOMELESS YOUTH PROGRAM Runaway and Homeless Youth Program Grant § 1351.13 What are the Federal and...

  12. A New Luminous Outburst from SN 2009ip

    NASA Astrophysics Data System (ADS)

    Drake, A. J.; Howerton, S.; McNaught, R.; Djorgovski, S. G.; Mahabal, A. A.; Graham, M. J.; Williams, R.; Prieto, J.; Catelan, M.; Christensen, E.; Larson, S.

    2012-08-01

    Further to Drake et al. (2010, Atel#2897), we report the discovery of a new bright outburst from spectroscopically confirmed LBV (Supernova Impostor) SN 2009ip (Maza et al. 2009; CBET#1928, Berger et al. 2009, ATEL#2184; Smith et al. 2010; Foley et al. 2011) in images taken by the Siding Spring Survey (SSS).

  13. e-VLBI observations of SS 433 in outburst

    NASA Astrophysics Data System (ADS)

    Tudose, V.; Paragi, Z.; Trushkin, S.; Soleri, P.; Fender, R.; Garrett, M.; Spencer, R.; Rushton, A.; Burgess, P.; Kunert-Bajraszewska, M.; Pazderski, E.; Borkowski, K.; Hammargren, R.; Lindqvist, M.; Maccaferri, G.

    2008-11-01

    We have observed the X-ray binary SS 433 on November 6, 2008 between 13:48-18:35 UT at 5 GHz with the European VLBI Network (EVN) using the e-VLBI technique. The radio telescopes participating in the experiment were: Medicina, Onsala 25m, Torun, Jodrell Bank MkII and Cambridge. The X-ray binary SS 433 is in outburst. Trushkin & Nizhelskij (ATel #1819) reported a major flare already active during the RATAN-600 observations in the 1-22 GHz band on 2008 October 28.

  14. Predicted space motions for hypervelocity and runaway stars: proper motions and radial velocities for the Gaia Era

    SciTech Connect

    Kenyon, Scott J.; Brown, Warren R.; Geller, Margaret J.; Bromley, Benjamin C. E-mail: wbrown@cfa.harvard.edu E-mail: bromley@physics.utah.edu

    2014-10-01

    We predict the distinctive three-dimensional space motions of hypervelocity stars (HVSs) and runaway stars moving in a realistic Galactic potential. For nearby stars with distances less than 10 kpc, unbound stars are rare; proper motions alone rarely isolate bound HVSs and runaways from indigenous halo stars. At large distances of 20-100 kpc, unbound HVSs are much more common than runaways; radial velocities easily distinguish both from indigenous halo stars. Comparisons of the predictions with existing observations are encouraging. Although the models fail to match observations of solar-type HVS candidates from SEGUE, they agree well with data for B-type HVS and runaways from other surveys. Complete samples of g ≲ 20 stars with Gaia should provide clear tests of formation models for HVSs and runaways and will enable accurate probes of the shape of the Galactic potential.

  15. Analysis of safety precautions for coal and gas outburst-hazardous strata

    SciTech Connect

    Hudecek, V.

    2008-09-15

    The author analyses coal and gas outbursts and generalizes the available data on the approaches to solving the problematics of these gas-dynamic events in the framework of Czech Republic Grant 'Estimate of the Safety Precautions for Coal and Gas Outburst Hazardous Strata'.

  16. Spectrum of the Runaway Electron Beam Generated During a Nanosecond Discharge in Air at Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Tarasenko, V. F.; Baksht, E. Kh.; Burachenko, A. G.

    2016-04-01

    The spectrum of supershort avalanche runaway electron beam generated in air at atmospheric pressure is experimentally investigated using a time-of-flight spectrometer and attenuation curves. It is shown that the maximum of the electron energy distribution for the main (second) group of electrons is less than the energy eUm, where Um is the maximal voltage across the gap, and the difference between these energies depends on the design of the cathode and the interelectrode gap in a gas diode. It is confirmed that there are three groups of electrons with different energies in the runaway electron beam spectrum.

  17. Sawtooth oscillations in the flux of runaway electrons to the PLT limiter

    SciTech Connect

    Barnes, C.W.; Strachan, J.D.

    1982-03-01

    Increased fluxes of runaway electrons at the PLT limiter are observed in the few milliseconds following internal disruptions. These fluxes have an inverted (outside) sawtooth character. The time for the flux to reach a maximum after the disruption has been studied as a function of the plasma parameters for thousands of PLT discharges. One interpretation is that this delay represents the time for a perturbation to the runaway electron population to travel from the q = 1 region to the plasma boundary. These times are approx. 10/sup -1/ of the electron thermal confinement times and increase with the plasma electron density.

  18. Measurement of the internal magnetic fluctuation by the transport of runaways on J-TEXT

    NASA Astrophysics Data System (ADS)

    Chen, Z. Y.; Huang, D. W.; Tong, R. H.; Yan, W.; Wei, Y. N.; Ma, T. K.; Jiang, Z. H.; Zhang, X. Q.; Chen, Z. P.; Yang, Z. J.; Zhuang, G.

    2016-11-01

    The measurement of internal magnetic fluctuation is important for the study of transport in tokamak plasmas. The runaway electron transport induced by the sawtooth crash can be used to obtain the internal magnetic fluctuation. Inversed sawtooth-like activities on hard x-ray (HXR) fluxes following sawtooth activities were observed after the application of electrode biasing on J-TEXT tokamak. The runaway diffusion coefficient Dr is deduced to be about 30 m2/s according to the time delay of HXR flux peaks to the sawtooth crashes. The averaged value of normalized magnetic fluctuation in the discharges with electrode biasing was increased to the order of 1 × 10-4.

  19. A Deep Search for Prompt Radio Emission from Thermonuclear Supernovae with the Very Large Array

    NASA Astrophysics Data System (ADS)

    Chomiuk, Laura; Soderberg, Alicia M.; Chevalier, Roger A.; Bruzewski, Seth; Foley, Ryan J.; Parrent, Jerod; Strader, Jay; Badenes, Carles; Fransson, Claes; Kamble, Atish; Margutti, Raffaella; Rupen, Michael P.; Simon, Joshua D.

    2016-04-01

    Searches for circumstellar material around Type Ia supernovae (SNe Ia) are some of the most powerful tests of the nature of SN Ia progenitors, and radio observations provide a particularly sensitive probe of this material. Here, we report radio observations for SNe Ia and their lower-luminosity thermonuclear cousins. We present the largest, most sensitive, and spectroscopically diverse study of prompt ({{Δ }}t≲ 1 years) radio observations of 85 thermonuclear SNe, including 25 obtained by our team with the unprecedented depth of the Karl G. Jansky Very Large Array. With these observations, SN 2012cg joins SN 2011fe and SN 2014J as an SN Ia with remarkably deep radio limits and excellent temporal coverage (six epochs, spanning 5-216 days after explosion, implying \\dot{M}/{v}w≲ 5× 10-9 M⊙) yr-1/(100 km s-1), assuming ɛB = 0.1 and ɛe = 0.1). All observations yield non-detections, placing strong constraints on the presence of circumstellar material. We present analytical models for the temporal and spectral evolution of prompt radio emission from thermonuclear SNe as expected from interaction with either wind-stratified or uniform density media. These models allow us to constrain the progenitor mass loss rates, with limits in the range of \\dot{M}≲ 10-9-10-4 M⊙ yr-1, assuming a wind velocity of vw = 100 km s-1. We compare our radio constraints with measurements of Galactic symbiotic binaries to conclude that ≲10% of thermonuclear SNe have red giant companions.

  20. Frontiers in propulsion research: Laser, matter-antimatter, excited helium, energy exchange thermonuclear fusion

    NASA Technical Reports Server (NTRS)

    Papailiou, D. D. (Editor)

    1975-01-01

    Concepts are described that presently appear to have the potential for propulsion applications in the post-1990 era of space technology. The studies are still in progress, and only the current status of investigation is presented. The topics for possible propulsion application are lasers, nuclear fusion, matter-antimatter annihilation, electronically excited helium, energy exchange through the interaction of various fields, laser propagation, and thermonuclear fusion technology.

  1. Black Hole X-Ray Nova Outburst with XTE and HST

    NASA Technical Reports Server (NTRS)

    Patterson, Joseph; Haswell, Carole

    1999-01-01

    We obtained multiwavelength coverage of the soft X-ray transient GRO J1655-40 during its 1996 outburst, using HST, RXTE, CGRO, and ground-based facilities. This outburst was qualitatively different from other SXT outbursts and from previous outbursts of this source. The onset of hard X-ray activity occurred very slowly, over several months, and was delayed relative to the soft X-ray rise. During this period, the optical fluxes declined steadily. This apparent anticorrelation is not consistent with with the standard disk instability model of SXT outbursts, nor is it expected if the optical output is dominated by reprocessed X-rays, as in persistent low-mass X-ray binaries. .

  2. Swift/BAT hard X-ray monitoring: A New Outburst of Black Hole Transient H1743-322

    NASA Astrophysics Data System (ADS)

    Lin, Jie; Yu, Wenfei; Yan, Zhen; Zhang, Hui; Zhang, Wenda

    2016-02-01

    H 1743-322 is one of the a few black hole transients which undergo frequent outbursts in the past decade. From December 2009 to June 2015, it has turned into outbursts for at least eight times (ATEL #2364, #2774, #3277, #3842, #4418, #5241, #6474, and #7607), and its outbursts take place rather regularly with recurrence time of about 7-8 months.

  3. Temper Outbursts in Paediatric Obsessive-Compulsive Disorder and Their Association with Depressed Mood and Treatment Outcome

    ERIC Educational Resources Information Center

    Krebs, Georgina; Bolhuis, Koen; Heyman, Isobel; Mataix-Cols, David; Turner, Cynthia; Stringaris, Argyris

    2013-01-01

    Background: Temper outbursts in youth with obsessive-compulsive disorder (OCD) are a common source of concern, but remain poorly understood. This study examined a set of hypotheses related to: (a) the prevalence of temper outbursts in paediatric OCD, (b) the associations of temper outbursts with OCD severity and depressive symptoms; and (c) the…

  4. 1D-Simulation of Thermonuclear Target Compression and Burning for Laser Facility NIF and LMJ

    NASA Astrophysics Data System (ADS)

    Valiev, R. Zh.; Chizhkov, M. N.; Karlyhanov, N. G.; Lusganova, O. V.; Lykov, V. A.; Netsvetayev, D. S.; Timakova, M. S.

    2006-08-01

    The high-power laser facilities NIF and LMJ with the pulse energy as high as 2 MJ are being created in the USA and France. The basic cryogenic indirect-drive targets for thermonuclear ignition on these facilities are a spherical shell from polystyrene doped with oxygen and bromine. (CH+5%O+0,25%Br), whose inner surface is covered with DT-ice layer. The central region of targets is filled with DT-gas. The targets for NIF and LMJ have different external radii (1,11 and 1,215 mm, correspondingly), masses of DT-fuel (210 и 310 μg), X-ray radiation temperature dependences in time. The thermonuclear yield from the NIF target calculated with LASNEX code is 15 MJ, the yield from the LMJ target calculated with FCI1 code is 25.4 MJ. In RFNC-VNIITF calculations of compression and burning of basic NIF and LMJ targets were performed by using of the 1D ERA code in the spectral diffusion approximation for radiation transfer. We used tabulated opacity calculated by the mean ion model. Thermonuclear yield calculated with ERA code is about 18 MJ for the NIF target and nearly 23 MJ for the LMJ target. Calculated yields are in good agreement with published results. Performed calculations justified the possibility to simulate ICF targets in RFNC-VNIITF. In paper are also presented analysis results of target sensitivity to opacity and X-ray temperature variations.

  5. Rocket propulsion by thermonuclear micro-bombs ignited with intense relativistic electron beams.

    NASA Technical Reports Server (NTRS)

    Winterberg, F.

    1971-01-01

    Discussion of a method for the ignition of a thermonuclear microbomb by means of an intense relativistic electron beam with regard to its potential application to rocket propulsion. With such a system, exhaust velocities up to 1000 km/sec, corresponding to a specific impulse of 100,000 sec, seem to be within the realm of possibility. The rocket is propelled by a chain of thermonuclear microbombs exploded in a concave magnetic mirror produced by superconducting field coils. The magnetic pressure of the field reflects the fireball generated by the explosion. For the large capacitor bank required to generate the intense relativistic electron beam, a desirable lightweight design may be possible through use of ferroelectric materials. Because of the high cost of the T-D and He 3-D thermonuclear material, the system has to be optimized by minimizing the T-D and He 3-D consumption by a proper TD and He 3-D fuel to hydrogen propellant mass ratio, leading to a larger total system mass than would be absolutely necessary.

  6. Measurement of runaway electron energy distribution function during high-Z gas injection into runaway electron plateaus in DIII-D

    SciTech Connect

    Hollmann, E. M.; Moyer, R. A.; Rudakov, D. L.; Parks, P. B.; Eidietis, N. W.; Paz-Soldan, C.; Commaux, N.; Shiraki, D.; Austin, M. E.; Lasnier, C. J.

    2015-05-15

    The evolution of the runaway electron (RE) energy distribution function f{sub ε} during massive gas injection into centered post-disruption runaway electron plateaus has been reconstructed. Overall, f{sub ε} is found to be much more skewed toward low energy than predicted by avalanche theory. The reconstructions also indicate that the RE pitch angle θ is not uniform, but tends to be large at low energies and small θ ∼ 0.1–0.2 at high energies. Overall power loss from the RE plateau appears to be dominated by collisions with background free and bound electrons, leading to line radiation. However, the drag on the plasma current appears to be dominated by collisions with impurity ions in most cases. Synchrotron emission appears not to be significant for overall RE energy dissipation but may be important for limiting the peak RE energy.

  7. Comet 17P/Holmes: contrast in activity between before and after the 2007 outburst

    SciTech Connect

    Ishiguro, Masateru; Kim, Yoonyoung; Warjurkar, Dhanraj S.; Ham, Ji-Beom; Kim, Junhan; Usui, Fumihiko; Vaubaillon, Jeremie J.; Ishihara, Daisuke; Hanayama, Hidekazu; Sarugaku, Yuki; Hasegawa, Sunao; Kasuga, Toshihiro; Watanabe, Jun-ichi; Pyo, Jeonghyun; Kuroda, Daisuke; Ootsubo, Takafumi; Sakamoto, Makoto; Narusawa, Shin-ya; Takahashi, Jun; Akisawa, Hiroki

    2013-11-20

    A Jupiter-family comet, 17P/Holmes, underwent outbursts in 1892 and 2007. In particular, the 2007 outburst is known as the greatest outburst over the past century. However, little is known about the activity before the outburst because it was unpredicted. In addition, the time evolution of the nuclear physical status has not been systematically studied. Here, we study the activity of 17P/Holmes before and after the 2007 outburst through optical and mid-infrared observations. We found that the nucleus was highly depleted in its near-surface icy component before the outburst but that it became activated after the 2007 outburst. Assuming a conventional 1 μm sized grain model, we derived a surface fractional active area of 0.58% ± 0.14% before the outburst whereas the area was enlarged by a factor of ∼50 after the 2007 outburst. We also found that large (≥1 mm) particles could be dominant in the dust tail observed around aphelion. Based on the size of the particles, the dust production rate was ≳170 kg s{sup –1} at a heliocentric distance of r{sub h} = 4.1 AU, suggesting that the nucleus was still active around the aphelion passage. The nucleus color was similar to that of the dust particles and average for a Jupiter-family comet but different from that of most Kuiper Belt objects, implying that color may be inherent to icy bodies in the solar system. On the basis of these results, we concluded that more than 76 m of surface material was blown off by the 2007 outburst.

  8. Effect of Water Invasion on Outburst Predictive Index of Low Rank Coals in Dalong Mine

    PubMed Central

    Jiang, Jingyu; Cheng, Yuanping; Mou, Junhui; Jin, Kan; Cui, Jie

    2015-01-01

    To improve the coal permeability and outburst prevention, coal seam water injection and a series of outburst prevention measures were tested in outburst coal mines. These methods have become important technologies used for coal and gas outburst prevention and control by increasing the external moisture of coal or decreasing the stress of coal seam and changing the coal pore structure and gas desorption speed. In addition, techniques have had a significant impact on the gas extraction and outburst prevention indicators of coal seams. Globally, low rank coals reservoirs account for nearly half of hidden coal reserves and the most obvious feature of low rank coal is the high natural moisture content. Moisture will restrain the gas desorption and will affect the gas extraction and accuracy of the outburst prediction of coals. To study the influence of injected water on methane desorption dynamic characteristics and the outburst predictive index of coal, coal samples were collected from the Dalong Mine. The methane adsorption/desorption test was conducted on coal samples under conditions of different injected water contents. Selective analysis assessed the variations of the gas desorption quantities and the outburst prediction index (coal cutting desorption index). Adsorption tests indicated that the Langmuir volume of the Dalong coal sample is ~40.26 m3/t, indicating a strong gas adsorption ability. With the increase of injected water content, the gas desorption amount of the coal samples decreased under the same pressure and temperature. Higher moisture content lowered the accumulation desorption quantity after 120 minutes. The gas desorption volumes and moisture content conformed to a logarithmic relationship. After moisture correction, we obtained the long-flame coal outburst prediction (cutting desorption) index critical value. This value can provide a theoretical basis for outburst prediction and prevention of low rank coal mines and similar occurrence conditions

  9. A DOUBLE OUTBURST FROM IGR J00291+5934: IMPLICATIONS FOR ACCRETION DISK INSTABILITY THEORY

    SciTech Connect

    Hartman, Jacob M.; Galloway, Duncan K.; Chakrabarty, Deepto

    2011-01-01

    The accretion-powered millisecond pulsar IGR J00291+5934 underwent two {approx}10 day long outbursts during 2008, separated by 30 days in quiescence. Such a short quiescent period between outbursts has never been seen before from a neutron star X-ray transient. X-ray pulsations at the 599 Hz spin frequency are detected throughout both outbursts. For the first time, we derive a pulse phase model that connects two outbursts, providing a long baseline for spin frequency measurement. Comparison with the frequency measured during the 2004 outburst of this source gives a spin-down during quiescence of -(4 {+-} 1) x 10{sup -15} Hz s{sup -1}, approximately an order of magnitude larger than the long-term spin-down observed in the 401 Hz accretion-powered pulsar SAX J1808.4-3658. If this spin-down is due to magnetic dipole radiation, it requires a 2 x 10{sup 8} G field strength, and its high spin-down luminosity may be detectable with the Fermi Large Area Telescope. Alternatively, this large spin-down could be produced by gravitational wave emission from a fractional mass quadrupole moment of Q/I = 1 x 10{sup -9}. The rapid succession of the outbursts also provides a unique test of models for accretion in low-mass X-ray binaries. Disk instability models generally predict that an outburst will leave the accretion disk too depleted to fuel a second outburst after such a brief quiescence. We suggest a modification in which the outburst is shut off by the onset of a propeller effect before the disk is depleted. This model can explain the short quiescence and the unusually slow rise of the light curve of the second 2008 outburst.

  10. Effect of Water Invasion on Outburst Predictive Index of Low Rank Coals in Dalong Mine.

    PubMed

    Jiang, Jingyu; Cheng, Yuanping; Mou, Junhui; Jin, Kan; Cui, Jie

    2015-01-01

    To improve the coal permeability and outburst prevention, coal seam water injection and a series of outburst prevention measures were tested in outburst coal mines. These methods have become important technologies used for coal and gas outburst prevention and control by increasing the external moisture of coal or decreasing the stress of coal seam and changing the coal pore structure and gas desorption speed. In addition, techniques have had a significant impact on the gas extraction and outburst prevention indicators of coal seams. Globally, low rank coals reservoirs account for nearly half of hidden coal reserves and the most obvious feature of low rank coal is the high natural moisture content. Moisture will restrain the gas desorption and will affect the gas extraction and accuracy of the outburst prediction of coals. To study the influence of injected water on methane desorption dynamic characteristics and the outburst predictive index of coal, coal samples were collected from the Dalong Mine. The methane adsorption/desorption test was conducted on coal samples under conditions of different injected water contents. Selective analysis assessed the variations of the gas desorption quantities and the outburst prediction index (coal cutting desorption index). Adsorption tests indicated that the Langmuir volume of the Dalong coal sample is ~40.26 m3/t, indicating a strong gas adsorption ability. With the increase of injected water content, the gas desorption amount of the coal samples decreased under the same pressure and temperature. Higher moisture content lowered the accumulation desorption quantity after 120 minutes. The gas desorption volumes and moisture content conformed to a logarithmic relationship. After moisture correction, we obtained the long-flame coal outburst prediction (cutting desorption) index critical value. This value can provide a theoretical basis for outburst prediction and prevention of low rank coal mines and similar occurrence conditions

  11. Effect of Water Invasion on Outburst Predictive Index of Low Rank Coals in Dalong Mine.

    PubMed

    Jiang, Jingyu; Cheng, Yuanping; Mou, Junhui; Jin, Kan; Cui, Jie

    2015-01-01

    To improve the coal permeability and outburst prevention, coal seam water injection and a series of outburst prevention measures were tested in outburst coal mines. These methods have become important technologies used for coal and gas outburst prevention and control by increasing the external moisture of coal or decreasing the stress of coal seam and changing the coal pore structure and gas desorption speed. In addition, techniques have had a significant impact on the gas extraction and outburst prevention indicators of coal seams. Globally, low rank coals reservoirs account for nearly half of hidden coal reserves and the most obvious feature of low rank coal is the high natural moisture content. Moisture will restrain the gas desorption and will affect the gas extraction and accuracy of the outburst prediction of coals. To study the influence of injected water on methane desorption dynamic characteristics and the outburst predictive index of coal, coal samples were collected from the Dalong Mine. The methane adsorption/desorption test was conducted on coal samples under conditions of different injected water contents. Selective analysis assessed the variations of the gas desorption quantities and the outburst prediction index (coal cutting desorption index). Adsorption tests indicated that the Langmuir volume of the Dalong coal sample is ~40.26 m3/t, indicating a strong gas adsorption ability. With the increase of injected water content, the gas desorption amount of the coal samples decreased under the same pressure and temperature. Higher moisture content lowered the accumulation desorption quantity after 120 minutes. The gas desorption volumes and moisture content conformed to a logarithmic relationship. After moisture correction, we obtained the long-flame coal outburst prediction (cutting desorption) index critical value. This value can provide a theoretical basis for outburst prediction and prevention of low rank coal mines and similar occurrence conditions

  12. Progressive incision of the Channeled Scablands by outburst floods

    NASA Astrophysics Data System (ADS)

    Larsen, Isaac J.; Lamb, Michael P.

    2016-10-01

    The surfaces of Earth and Mars contain large bedrock canyons that were carved by catastrophic outburst floods. Reconstructing the magnitude of these canyon-forming floods is essential for understanding the ways in which floods modify planetary surfaces, the hydrology of early Mars and abrupt changes in climate. Flood discharges are often estimated by assuming that the floods filled the canyons to their brims with water; however, an alternative hypothesis is that canyon morphology adjusts during incision such that bed shear stresses exceed the threshold for erosion by a small amount. Here we show that accounting for erosion thresholds during canyon incision results in near-constant discharges that are five- to ten-fold smaller than full-to-the-brim estimates for Moses Coulee, a canyon in the Channeled Scablands, which was carved during the Pleistocene by the catastrophic Missoula floods in eastern Washington, USA. The predicted discharges are consistent with flow-depth indicators from gravel bars within the canyon. In contrast, under the assumption that floods filled canyons to their brims, a large and monotonic increase in flood discharge is predicted as the canyon was progressively incised, which is at odds with the discharges expected for floods originating from glacial lake outbursts. These findings suggest that flood-carved landscapes in fractured rock might evolve to a threshold state for bedrock erosion, thus implying much lower flood discharges than previously thought.

  13. Convection causes enhanced magnetic turbulence in accretion disks in outburst

    SciTech Connect

    Hirose, Shigenobu; Blaes, Omer; Coleman, Matthew S. B.; Krolik, Julian H.; Sano, Takayoshi

    2014-05-20

    We present the results of local, vertically stratified, radiation magnetohydrodynamic (MHD) shearing box simulations of magneto-rotational instability (MRI) turbulence appropriate for the hydrogen ionizing regime of dwarf nova and soft X-ray transient outbursts. We incorporate the frequency-integrated opacities and equation of state for this regime, but neglect non-ideal MHD effects and surface irradiation, and do not impose net vertical magnetic flux. We find two stable thermal equilibrium tracks in the effective temperature versus surface mass density plane, in qualitative agreement with the S-curve picture of the standard disk instability model. We find that the large opacity at temperatures near 10{sup 4} K, a corollary of the hydrogen ionization transition, triggers strong, intermittent thermal convection on the upper stable branch. This convection strengthens the magnetic turbulent dynamo and greatly enhances the time-averaged value of the stress to thermal pressure ratio α, possibly by generating vertical magnetic field that may seed the axisymmetric MRI, and by increasing cooling so that the pressure does not rise in proportion to the turbulent dissipation. These enhanced stress to pressure ratios may alleviate the order of magnitude discrepancy between the α-values observationally inferred in the outburst state and those that have been measured from previous local numerical simulations of magnetorotational turbulence that lack net vertical magnetic flux.

  14. Recurring middle Pleistocene outburst floods in east-central Alaska

    USGS Publications Warehouse

    Froese, D.G.; Smith, D.G.; Westgate, J.A.; Ager, T.A.; Preece, S.J.; Sandhu, A.; Enkin, R.J.; Weber, F.

    2003-01-01

    Recurring glacial outburst floods from the Yukon-Tanana Upland are inferred from sediments exposed along the Yukon River near the mouth of Charley River in east-central Alaska. Deposits range from imbricate gravel and granules indicating flow locally extending up the Yukon valley, to more distal sediments consisting of at least 10 couplets of planar sands, granules, and climbing ripples with up-valley paleocurrent indicators overlain by massive silt. An interglacial organic silt, occurring within the sequence, indicates at least two flood events are associated with an earlier glaciation, and at least three flood events are associated with a later glaciation which postdates the organic silt. A minimum age for the floods is provided by a glass fission track age of 560,000 ?? 80,000 yr on the GI tephra, which occurs 8 m above the flood beds. A maximum age of 780,000 yr for the floods is based on normal magnetic polarity of the sediments. These age constraints allow us to correlate the flood events to the early-middle Pleistocene. And further, the outburst floods indicate extensive glaciation of the Yukon-Tanana Upland during the early-middle Pleistocene, likely representing the most extensive Pleistocene glaciation of the area. ?? 2003 University of Washington. Published by Elsevier Inc. All rights reserved.

  15. A Large X-Ray Outburst in Mira A

    NASA Astrophysics Data System (ADS)

    Karovska, Margarita; Schlegel, Eric; Hack, Warren; Raymond, John C.; Wood, Brian E.

    2005-04-01

    We report the Chandra ACIS-S detection of a bright soft X-ray transient in the Mira AB interacting symbiotic-like binary. We have resolved the system for the first time in X-rays. Using Chandra and Hubble Space Telescope images, we determine that the unprecedented outburst is likely associated with the cool asymptotic giant branch (AGB) star, Mira A, the prototype of the Mira class of variables. X-rays have never before been detected from an AGB star, and the recent activity signals that the system is undergoing dramatic changes. The total X-ray luminosity of the system is several times higher than the luminosity estimated using previous XMM-Newton and ROSAT observations. The outburst may be caused by a giant flare in Mira A associated with a mass ejection or a jet and may have long-term consequences on the system. We dedicate this paper to the memory of Janet A. Mattei, who inspired this work and made these observations possible for many years.

  16. Sexual Risk Behaviors, AIDS Knowledge, and Beliefs about AIDS among Runaways.

    ERIC Educational Resources Information Center

    Rotheram-Borus, Mary Jane; Koopman, Cheryl

    1991-01-01

    Examined young runaways' current risk behaviors, knowledge of AIDS, and beliefs about preventing AIDS by questioning 130 male and female subjects from shelters in New York City in 1988-89. Results did not explain the 6.7 percent seroprevalence rate reported in l988. Recommends closer inquiries regarding IV drug use and prostitution. (DM)

  17. Predicting runaway reaction in a solid explosive containing a single crack

    SciTech Connect

    Jackson, Scott I; Hill, Larry G

    2009-01-01

    Mechanically damaged high explosive (HE) undergoing defiagration has recently been shown capable of generating combustion pressures and flame speeds dramatically in excess of those observed in undamaged HE. Flame penetration of HE cracks large enough to support the reaction zone serves to increase the burning surface area and the rate of gas production. Cracks confine the product gas, elevating the local pressure and reducing the reaction zone thickness such that the flame can enter smaller-width cracks. As the reaction zone decreases sufficiently to enter the smallest cracks, the flame surface area will grow appreciably, rapidly pressurizing the cracks. This runaway of pressure and burning area, termed combustion bootstrapping, can dramatically accelerate the combustion mode and in the most extreme cases may result in deflagration-to-detonation transition [3, 4]. The current study is intended to help predict the conditions required for the onset of reaction runaway in a narrow slot in HE. We review experiments [5] where flames were observed to propagate though a narrow slot (intended to simulate a well-formed crack) in high explosive at velocities up to 10 km/s, reaching pressures in excess of 1 kbar. Pressurization of the slot due to gas-dynamic choking is then used to predict the onset of runaway reaction. This model agrees with experimental pressure measurements of observed reaction runaway in slots.

  18. Youth with Disabilities Who Are Runaways and/or Homeless: Responding to the Need.

    ERIC Educational Resources Information Center

    Fesko, Sheila Lynch; Graham, Steven; Temelini, David

    This document reports on two studies by the Bridges to Inclusion project concerning issues surrounding runaway and/or homeless youth with disabilities. The first study surveyed emergency adolescent shelter providers funded by the Family and Youth Service Bureau. Findings addressed types of disabilities frequently identified or suspected in…

  19. Mental Disorders, Comorbidity, and Postrunaway Arrests among Homeless and Runaway Adolescents

    ERIC Educational Resources Information Center

    Chen, Xiaojin; Thrane, Lisa; Whitbeck, Les B.; Johnson, Kurt

    2006-01-01

    This study examined the associations between lifetime mental disorder, comorbidity, and self-reported postrunaway arrests among 428 (187 males, 241 females) homeless and runaway youth. The analysis examined the pattern of arrests across five lifetime mental disorders (alcohol abuse, drug abuse, conduct disorder, major depressive episode, and…

  20. Studying the nature of runaway stars using Andromeda's massive stellar population

    NASA Astrophysics Data System (ADS)

    Bulkley, Jordan; Seth, Anil; Johnson, Cliff; Dalcanton, Julianne; Guhathakurta, Raja; Dorman, Claire; Hamren, Katie; Caldwell, Nelson; Williams, Ben

    2016-03-01

    Theory of the formation of massive stars remains incomplete, the question of the environments required have yet to be answered. An agreement on whether all massive stars must form in cluster type environments, or if isolated formation is viable has yet to be reached. This is further complicated by the presence of runaway stars, stellar objects which have been ejected from their host cluster. Studying the nature of these isolated runaway stars becomes paramount in the larger goal of developing a more comprehensive massive star formation theory. Creating a survey of runaway star candidates is possible thanks to Panchromatic Hubble Andromeda Treasury's UV and optical photometry, and the identified clusters from the Andromeda Project. A first glimpse into the data suggests large body of massive stars are 50 parsecs or more from the closest cluster and roughly half of the entire massive stellar population is found outside of defined cluster boundaries. Additional analysts shows a stark difference between the velocity dispersion of massive stars and appropriately young clusters, the stars exhibiting a inflated dispersion. Using this result in conjunction with artificial clusters and star populations, constrains on the percentage of expected runaway objects can be made.

  1. 76 FR 22785 - Direct Certification and Certification of Homeless, Migrant and Runaway Children for Free School...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-25

    ... Food and Nutrition Service 7 CFR Parts 210, 215, 220, 225, 226 and 245 RIN 0584-AD60 Direct Certification and Certification of Homeless, Migrant and Runaway Children for Free School Meals AGENCY: Food and... Program for Children, the Child and Adult Care Food Program and the Summer Food Service Program. The...

  2. Predictors of Substance Use and Family Therapy Outcome among Physically and Sexually Abused Runaway Adolescents

    ERIC Educational Resources Information Center

    Slesnick, Natasha; Bartle-Haring, Suzanne; Gangamma, Rashmi

    2006-01-01

    There is a dearth of research that examines the impact of family systems therapy on problems among sexually and/or physically abused youth. Given this void, differential outcome and predictors of substance use change were evaluated for abused, as compared with nonabused, runaway adolescents who were randomly assigned to family therapy or treatment…

  3. Origin and context of C. T. R. Wilson's ideas on electron runaway in thunderclouds

    NASA Astrophysics Data System (ADS)

    Williams, Earle R.

    2010-08-01

    The publications, research notebooks and personal correspondence of C.T.R. Wilson are reviewed to understand his thinking on the idea of electron runaway in thunderclouds. The expansion cloud chamber, developed and refined over a period of nearly fifty years, is centrally important. Wilson's habit of research is characterized by a pattern of alternating between laboratory work with the cloud chamber and field observations of thunderclouds and the global electrical circuit. The evidence that the ionization tracks of electrons in the cloud chamber straightened with increasing energy was key to the idea of electron runaway, published in 1925. Despite numerous negative results by Wilson's colleagues Schonland, Halliday and others in searching for energetic particles in the vicinity of thunderclouds, Wilson supported the idea from its inception to his final publication in 1956. Wilson's notebooks indicate a conceptual awareness of runaway breakdown in thunderclouds 60 years in advance of contemporary theoretical publications. Definitive observational results on runaway breakdown in contemporary research were likely delayed for 60 years as a result of the unfortunate negative experimental results with inadequate equipment.

  4. Halting a Runaway Train: Reforming Teacher Pensions for the 21st Century

    ERIC Educational Resources Information Center

    Lafferty, Michael B.

    2011-01-01

    When it comes to public-sector pensions, writes lead author Michael B. Lafferty in this report, "A major public-policy (and public-finance) problem has been defined and measured, debated and deliberated, but not yet solved. Except where it has been." As recounted in "Halting a Runaway Train: Reforming Teacher Pensions for the 21st Century", these…

  5. Risk Factors for Sexual Victimization Among Male and Female Homeless and Runaway Youth

    ERIC Educational Resources Information Center

    Tyler, Kimberly A.; Whitbeck, Les B.; Hoyt, Dan R.; Cauce, Ana Mari

    2004-01-01

    Risk factors associated with the likelihood of being sexually victimized by a stranger or friend/acquaintance since being on the street was examined among 372 homeless and runaway youth. Young people were interviewed on the streets and in shelters by outreach workers using a systematic sampling strategy. Youth who engaged in more high-risk…

  6. High altitude atmospheric discharges according to the runaway air breakdown mechanism

    SciTech Connect

    Symbalisty, E.; Roussel-Dupre, R.; Yukhimuk, V.; Taranenko, Y.

    1997-04-01

    High altitude optical transients - red sprites, blue jets, and elves - are modeled in the context of the relativistic electron runaway air breakdown mechanism. These emissions are usually associated with large mesoscale convective systems (hereafter MCS). In thunderstorms cloud electrification proceeds over a time scale long enough to permit the conducting atmosphere above the cloud to polarize and short out the thunderstorm electric field. When a lightning strike rapidly neutralizes a cloud charge layer runaway driving fields can develop in the stratosphere and mesosphere. According to present simulations of the full runaway process the variety of observed optical emissions are due to the nature of the normal lightning event in the MCS that kick starts the runaway avalanche. In this paper the authors describe some details of the model, present the results of the evolution of the primary electron population, and summarize the initial conditions necessary for different types of discharges. Two companion papers present (a) the predicted optical, gamma ray, and radio emissions caused by these electrical discharges, and (b) the time evolution of the secondary electron population and its implications in terms of observables.

  7. Can Cell to Cell Thermal Runaway Propagation be Prevented in a Li-ion Battery Module?

    NASA Technical Reports Server (NTRS)

    Jeevarajan, Judith; Lopez, Carlos; Orieukwu, Josephat

    2014-01-01

    Increasing cell spacing decreased adjacent cell damage center dotElectrically connected adjacent cells drained more than physically adjacent cells center dotRadiant barrier prevents propagation when fully installed between BP cells center dotBP cells vent rapidly and expel contents at 100% SOC -Slower vent with flame/smoke at 50% -Thermal runaway event typically occurs at 160 degC center dotLG cells vent but do not expel contents -Thermal runaway event typically occurs at 200 degC center dotSKC LFP modules did not propagate; fuses on negative terminal of cell may provide a benefit in reducing cell to cell damage propagation. New requirement in NASA-Battery Safety Requirements document: JSC 20793 Rev C 5.1.5.1 Requirements - Thermal Runaway Propagation a. For battery designs greater than a 80-Wh energy employing high specific energy cells (greater than 80 watt-hours/kg, for example, lithium-ion chemistries) with catastrophic failure modes, the battery shall be evaluated to ascertain the severity of a worst-case single-cell thermal runaway event and the propensity of the design to demonstrate cell-to-cell propagation in the intended application and environment. NASA has traditionally addressed the threat of thermal runaway incidents in its battery deployments through comprehensive prevention protocols. This prevention-centered approach has included extensive screening for manufacturing defects, as well as robust battery management controls that prevent abuse-induced runaway even in the face of multiple system failures. This focused strategy has made the likelihood of occurrence of such an event highly improbable. b. The evaluation shall include all necessary analysis and test to quantify the severity (consequence) of the event in the intended application and environment as well as to identify design modifications to the battery or the system that could appreciably reduce that severity. In addition to prevention protocols, programs developing battery designs with

  8. A model of cometary outbursts: a new simple approach to the classical question

    NASA Astrophysics Data System (ADS)

    Gronkowski, P.; Wesołowski, M.

    2015-08-01

    Cometary outbursts, i.e. a sudden increase in brightness, have aroused astronomers' curiosity since the 1920s (Hughes). In 1927, Comet 29P/Schwassmann-Wachmann 1 was discovered, probably at the maximum of one of its outbursts. Many authors have tried to explain the source of cometary outbursts. They formed various models and hypotheses, but none of them have been definitely confirmed and generally accepted. In the present article, we propose a new model for the outburst activity of comets. This model is based on an idea of Ipatov & A'Hearn. This idea is a conclusion from the analysis of time variations in velocity of particles ejected from Comet 9P/Tempel after collision with the Deep Impact impactor. According to this, there are large cavities a few metres below the surface of comet nuclei. These cavities contain material under high gas pressure. In suitable conditions, the surface layers over the cavities can be thrown away and the deeper layers of the nucleus exposed. Finally, an outburst of the comet may be observed. The possible scenario in terms of outbursts is given. The amplitude of the jump in comet luminosity is also calculated. Numerical simulations were carried out for a wide range of cometary physical parameters, which are suitable for comets belonging to the class of Jupiter-family comets. They provide values of jumps in comet brightness that are consistent with those observed during the outbursts of many comets.

  9. On quantified Distribution of Numbers of Cometary Brightness Outbursts with Respect to Heliocentric Distance

    NASA Astrophysics Data System (ADS)

    Chumryumov, K. I.; Filonenko, V. S.

    On the basis of the data of about 180 outbursts of brightness of 129 comets, observed during 1847-1975, distribution of numbers of cometary brightness outbursts from heliocentric distances was investigated. The fine structure in this distribution has been found out. It is characterized by several sharp maxima of numbers of brightness outbursts divided by deep minima. The smoothing of the distribution function has been made by the spline-approximation method. With the help of Pearson- Neyman's, Kolmogorov's and von Mises' criteria it is shown that accidental occurences of maxima in distribution of the brightness outbursts number N from r are hardly probable. Hence, maxima of the brightness outbursts number N of this distribution is an evidence of quite real effects of comet outburst activity, characterized by the fact that brightness outbursts of comets occur at definite heliocentric distances. An analogous effect for the comet P/Tempel 2 in its apparitions in 1967, 1983 and 1987 was found out by the authors earlier.

  10. OUTBURST DUST PRODUCTION OF COMET 29P/SCHWASSMANN-WACHMANN 1

    SciTech Connect

    Hosek, Matthew W. Jr.; Blaauw, Rhiannon C.; Cooke, William J.; Suggs, Robert M.

    2013-05-15

    Multi-aperture photometry of Comet 29P/Schwassmann-Wachmann 1 was conducted on Johnson-Cousins R-band observations spanning 2011 May 1-9 and 2012 June 6-July 3. The comet was observed in outburst on 2011 May 3 and 2012 July 1, during which its brightness increased by 2.2 and 2.1 mag, respectively, as measured through a 10 arcsec aperture. Dust production before and after each outburst is calculated using the parameter Af {rho}, which is converted to a lower limit on the dust production rate based on dust models and derived nuclear properties from other studies. Both outbursts are accompanied by large increases in dust production, Af {rho} by a factor of {approx}6.5-7 and dust production rate by a factor of {approx}18-23. In addition, variations in the dust brightness profile of the coma are examined during the events. The profile is observed to steepen significantly at the beginning of each outburst and then slowly return to pre-outburst values, mirroring the behavior of Af {rho}. The start of an outbound 'ripple' of dust in the profile might be observed as the comet returns to its pre-outburst state, although this cannot be confirmed. Using a simple model of the 2011 May 3 outburst, an estimated lower limit of (2.6 {+-} 0.7) Multiplication-Sign 10{sup 8} kg of dust was released during the event. If this is representative of a typical outburst of 29P, then it is estimated that outbursts account for a lower limit of 80{sub -30}{sup +20}% of the total material ejected by the comet per year.

  11. First INTEGRAL and Swift Observations of a Giant Outburst of A 0535+26

    NASA Technical Reports Server (NTRS)

    Caballero, I.; Mueller, S.; Bordas, P.; Ferrigno, C.; Kuehnel, M.; Pottschmodt, K.; Kretschmar, P.; Wilms, J.; Kreykenbohm, I.; Santangelo, A.; Staubert, R.; Suchy, S.; Rothschild, R.; Camero-Arranz, A.; Finger, M.

    2012-01-01

    The Be/X-ray binary A 0535+26 has shown three giant outbursts since 2005, after a long period of quiescence. The giant outbursts in 2005 (approx.5.2 Crab, 15-50 keY range) and 2009 (approx.5.6 Crab) could not be observed by most X-ray observatories due to Sun observing constraints. Finally, a giant outburst in February 2011, that reached a flux of approx.3.8 Crab, was monitored with INTEGRAL and Swift TOO observations. We present first results these observations, with a special focus on the cyclotron lines present in the X-ray spectrum of the source.

  12. Comparison of outburst danger criteria of coal seams for acoustic spectral and instrumental forecast methods

    NASA Astrophysics Data System (ADS)

    Shadrin, A. V.; Bireva, Yu A.

    2016-10-01

    Outburst danger criteria for the two methods of current coal seam outburst forecast are considered: instrumental - by the initial outgassing rate and chippings outlet during test boreholes drilling, and geo-physical - by relation of high frequency and low frequency components of noise caused by cutting tool of operating equipment probing the face area taking into consideration the outburst criteria correction based on methane concentration at the face area and the coal strength. The conclusion is made on “adjustment” possibility of acoustic spectral forecast method criterion amended by control of methane concentration at the coal face and the coal strength taken from the instrumental method forecast results.

  13. Recent shower outbursts detected by the Canadian Meteor Orbit Radar (CMOR)

    NASA Astrophysics Data System (ADS)

    Brown, P.

    2016-01-01

    We present recent detections of short-duration shower outbursts as measured by the Canadian Meteor Orbit Radar (CMOR) between 2013-2016. In this interval, CMOR detected two strong shower outbursts unlinked to known showers. These included an outburst of the Kappa Cancrids (KCA - IAU 793) on January 5, 2015 and from the Gamma Lyrids (GLY - IAU 794) on February 7, 2015. Both have an orbit consistent with a Halley-type comet (HTC) or nearly isotropic-comet. Analysis of GLY activity also revealed a previously unreported annual shower, the September Ursae Majorids, (SUR - IAU 795).

  14. The outburst sequence of 67/P on 2015 September 13 as seen by VIRTIS/Rosetta

    NASA Astrophysics Data System (ADS)

    Rinaldi, Giovanna; Bockelee-Morvan, Dominique; Leyrat, Cedric; Capaccioni, Fabrizio; Filacchione, Gianrico; Érard, Stéphane; Steckloff, Jordan; Tozzi, Gian-Paolo; Fink, Uwe; Doose, Lyn; Piccioni, Giuseppe; Capria, Maria Teresa; Combi, Michael R.; De Sanctis, Maria Cristina; Kappel, David; Longobardo, Andrea; Migliorini, Alessandra; Palomba, Ernesto; Taylor, Fredric W.; Tosi, Federico; VIRTIS-Team

    2016-10-01

    On 13 September, 2015, the Visual, Infrared and Thermal Imaging Spectrometer (VIRTIS) onboard Rosetta observed strong, anomalous activity of the coma of 67P/Churyumov-Gerasimenko starting at 13:40 UTC, in a range of latitude between -26° and -40° and longitude between 265° and 280°. VIRTIS is an imaging spectrometer in the spectral range 0.25-1 mm (VIRTIS- M) and a high-resolution spectrometer in the range 2-5 mm (VIRTIS- H) on board the Rosetta spacecraft. The instrument observed one large outburst followed by two mini-outbursts that occurred approximately one hour thereafter. This is probably the highest temporally resolved dataset available from a remote sensing instrument of an outburst observed on 67P. The data cover the full spectral range of the two channels and allow studying both dust and gas properties to derive information on the underlying physical mechanism driving the outbursts.The preliminary results of the outburst sequence indicate that they occur on the daylight side of the nucleus. They are characterized by a short duration and decay that lasts typically 15 minutes for the large outburst and 5 minutes for the two mini outbursts. The spatial and temporal distribution of the dust indicates a complex light curve for each event showing internal structures. The large outburst shows a bluer color than the background coma in the range of 2-2.5mm with a value around 1% per 100 nm, which can be interpreted as a change of dust properties and perhaps the presence of icy grains. However, the spectral signature of water ice at 3 mm is not detected in the outburst material, or in the background coma. In the range of 0.45-0.75 mm, the spectral slope shows a redder value in the outburst material (15 % per 100 nm) than in the background (12 % per 100 nm).The dust temperature, measured by fitting the thermal continuum, is much higher for the outburst material than for the background coma. No significant increase in CO2 or H2O production is detected. Both the

  15. Exploitation of Runaways. Hearing before the Subcommittee on Children, Family, Drugs and Alcoholism of the Committee on Labor and Human Resources. United States Senate, Ninety-Ninth Congress, First Session on Examining Alternative Ways to Serve Runaway and Homeless Youths (October 1, 1985).

    ERIC Educational Resources Information Center

    Congress of the U.S., Washington, DC. Senate Committee on Labor and Human Resources.

    This document contains testimonies from witnesses and prepared statements from the Congressional hearing called to examine the exploitation of runaway children and adolescents. Opening statements are included from Senators Hawkins, Dodd, and Grassley which briefly describe runaway statistics, the dangers faced by runaways, and efforts to help…

  16. Ultraviolet spectroscopy of the recurrent nova U Scorpii during outburst

    NASA Technical Reports Server (NTRS)

    Williams, R. E.; Sparks, W. M.; Gallagher, J. S.; Ney, E. P.; Starrfield, S. G.; Truran, J. W.

    1981-01-01

    Observations of the recurrent nova U Sco during the 1979 outburst are presented, and the spectral evolution is found to differ from that of other recurrent novas. Spectra are dominated by emission lines, and the strong forbidden-line emission characteristic is conspicuously absent. A method to determine masses of nova shells is outlined, and an analysis of the emission lines shows an enrichment in N relative to C and O, and that the nova ejecta are rich in He relative to H. Optical spectra of U Sco obtained following its return to quiescence show predominantly He II emission lines, which suggests an enrichment of the preoutburst gas in He, and thus the presence of a highly evolved companion.

  17. Optical, UV, and EUV Oscillations of SS Cygni in Outburst

    SciTech Connect

    Mauche, C W

    2003-12-19

    I provide a review of observations in the optical, UV (HST), and EUV (EUVE and Chandra LETG) of the rapid periodic oscillations of nonmagnetic, disk-accreting, high mass-accretion rate cataclysmic variables (CVs), with particular emphasis on the dwarf nova SS Cyg in outburst. In addition, I drawn attention to a correlation, valid over nearly six orders of magnitude in frequency, between the frequencies of the quasi-periodic oscillations (QPOs) of white dwarf, neutron star, and black hole binaries. This correlation identifies the high frequency quasi-coherent oscillations (so-called ''dwarf nova oscillations'') of CVs with the kilohertz QPOs of low mass X-ray binaries (LMXBs), and the low frequency and low coherence QPOs of CVs with the horizontal branch oscillations (or the broad noise component identified as such) of LMXBs. Assuming that the same mechanisms produce the QPOs of white dwarf, neutron star, and black hole binaries, this correlation has important implications for QPO models.

  18. Physical mechanism of comet outbursts - An experimental result

    NASA Technical Reports Server (NTRS)

    Hartmann, William K.

    1993-01-01

    Attention is given to an experimental investigation of the physical mechanism of comet outbursts which is consistent with the general picture of mantle presence on comets and clarifies the relation of mantles to eruptive activity. The experiment and closeup observation of Comet P/Halley suggest a result different from most mathematical models in that the release of gas pressure does not occur only from uniform gas flow out of the entire surface. In some active comets near perihelion within a few AU of the sun, gas production rates and disturbance of the surface may be so high that the outflow is nearly continuous, with the regolith being entirely stripped away, as in many of the models. The present model provides a cyclic eruption and recharge mechanism which is lacking in most other models.

  19. Observations of the peculiar object MWC 560 in outburst

    SciTech Connect

    Michalitsianos, A.G.; Maran, S.P.; Oliversen, R.J.; Bopp, B.; Kontizas, E. Toledo, University, OH Athens, National Observatory )

    1991-04-01

    The results of ultraviolet spectroscopy, photoelectric photometry, and supplemental high-resolution H(alpha) spectroscopy of a photometric outburst of MWC 560 are discussed. Ultraviolet spectra are shown to be consistent with the ejection of an optically thick shell that produced strong absorption blends of Fe II and Cr II. The velocities reported exceed by far those previously found in symbiotic stars or recurrent novas. In addition to the variable high-velocity system of broad absorption features, a relatively stable system of Mg II, Mg I, Fe II, Cr II, and other ionic absorptions is observed. It is pointed out that the spectroscopic phenomena in MWC 560 resemble those found in XX Ophiuchi, but the velocities in the MWC 560 are an order of magnitude higher than those found in XX Oph. 30 refs.

  20. Observations of the peculiar object MWC 560 in outburst

    NASA Technical Reports Server (NTRS)

    Michalitsianos, A. G.; Maran, S. P.; Oliversen, R. J.; Bopp, B.; Kontizas, E.

    1991-01-01

    The results of ultraviolet spectroscopy, photoelectric photometry, and supplemental high-resolution H(alpha) spectroscopy of a photometric outburst of MWC 560 are discussed. Ultraviolet spectra are shown to be consistent with the ejection of an optically thick shell that produced strong absorption blends of Fe II and Cr II. The velocities reported exceed by far those previously found in symbiotic stars or recurrent novas. In addition to the variable high-velocity system of broad absorption features, a relatively stable system of Mg II, Mg I, Fe II, Cr II, and other ionic absorptions is observed. It is pointed out that the spectroscopic phenomena in MWC 560 resemble those found in XX Ophiuchi, but the velocities in the MWC 560 are an order of magnitude higher than those found in XX Oph.

  1. SIMULTANEOUS MULTIWAVELENGTH OBSERVATIONS OF MARKARIAN 421 DURING OUTBURST

    SciTech Connect

    Acciari, V. A.; Benbow, W.; Aliu, E.; Aune, T.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Boettcher, M.; Bradbury, S. M.; Butt, Y.; Cannon, A.; Celik, O.; Chow, Y. C.; Cesarini, A.; Ciupik, L.; Cogan, P.; Colin, P.; Cui, W.; Duke, C. E-mail: cui@physics.purdue.ed

    2009-09-20

    We report on the results of two coordinated multiwavelength campaigns that focused on the blazar Markarian 421 during its 2006 and 2008 outbursts. These campaigns obtained UV and X-ray data using the XMM-Newton satellite, while the gamma-ray data were obtained utilizing three imaging atmospheric Cerenkov telescopes, the Whipple 10 m telescope and VERITAS, both based in Arizona, as well as the MAGIC telescope, based on La Palma in the Canary Islands. The coordinated effort between the gamma-ray groups allowed for truly simultaneous data in UV/X-ray/gamma-ray wavelengths during a significant portion of the XMM-Newton observations. This simultaneous coverage allowed for a reliable search for correlations between UV, X-ray, and gamma-ray variability over the course of the observations. Investigations of spectral hysteresis and modeling of the spectral energy distributions are also presented.

  2. Observational and theoretical studies of the nova outburst

    SciTech Connect

    Starrfield, S.; Vanlandingham, K.; Schwarz, G.

    1998-04-01

    A nova outburst is one consequence of the accretion of hydrogen rich material onto a white dwarf in a close binary system. The strong electron degeneracy of a massive white dwarf drives the temperatures in the nuclear burning region to values exceeding 108K under all circumstances. As a result, a major fraction of the CNO nuclei in the envelope are transformed into e{sup +}-decay nuclei, which constrains the nuclear energy generation and yields non-solar CNO isotopic abundance ratios. In addition, the observations demonstrate that white dwarf core material is dredged up into the accreted layers and these nuclei are the catalysts for producing peak rates of energy generation that can exceed 10{sup 16} erg gm{sup -1}s{sup -1}. Observations show that there are two compositional classes of novae, one that occurs on a carbon-oxygen white dwarf and the other that occurs on an oxygen-neon-magnesium white dwarf.

  3. Spectral analysis of SMC X-2 during its 2015 outburst

    NASA Astrophysics Data System (ADS)

    La Palombara, N.; Sidoli, L.; Pintore, F.; Esposito, P.; Mereghetti, S.; Tiengo, A.

    2016-05-01

    We report on the results of XMM-Newton and Swift observations of SMC X-2 during its last outburst in 2015 October, the first one since 2000. The source reached a very high luminosity (L ˜ 1038 erg s-1), which allowed us to perform a detailed analysis of its timing and spectral properties. We obtained a pulse period Pspin = 2.372267(5) s and a characterization of the pulse profile also at low energies. The main spectral component is a hard (Γ ≃ 0) power-law model with an exponential cut-off, but at low energies we detected also a soft (with kT ≃ 0.15 keV) thermal component. Several emission lines are present in the spectrum. Their identification with the transition lines of highly ionized N, O, Ne, Si, and Fe suggests the presence of photoionized matter around the accreting source.

  4. Meteor Outbursts and Storms from the Spacecraft Hazard Perspective

    NASA Technical Reports Server (NTRS)

    Cooke, William; Moser, Danielle; Suggs, Rob

    2004-01-01

    The recent Leonid meteor storms have propelled meteor shower forecasting from an idea into the realm of practical application, invoked several times per year by numerous spacecraft. This paper will describe shower activity predictions, which give zenith hourly rate (ZHR) as a function of time, and how these are translated into spacecraft risks. Common spacecraft meteor shower mitigation strategies will also be discussed, and the important issue as to when to implement such operations considered. It should be noted that, while the recent meteor storms did not result in the loss of a vehicle, there were a few spacecraft anomalies attributed to Leonid strikes, and the nature of these will be commented upon. Finally, we assess the current state of the art in shower forecasting, and take a look "down the road" at some possible outbursts in the near future.

  5. Simultaneous Multiwavelength Observations of Markarian 421 During Outburst

    NASA Astrophysics Data System (ADS)

    Acciari, V. A.; Aliu, E.; Aune, T.; Beilicke, M.; Benbow, W.; Böttcher, M.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; Butt, Y.; Cannon, A.; Celik, O.; Cesarini, A.; Chow, Y. C.; Ciupik, L.; Cogan, P.; Colin, P.; Cui, W.; Dickherber, R.; Duke, C.; Falcone, A. D.; Fegan, S. J.; Finley, J. P.; Finnegan, G.; Fortin, P.; Fortson, L.; Furniss, A.; Gall, D.; Gillanders, G. H.; Grube, J.; Guenette, R.; Gyuk, G.; Hanna, D.; Holder, J.; Horan, D.; Hui, C. M.; Humensky, T. B.; Kaaret, P.; Karlsson, N.; Kertzman, M.; Kieda, D.; Kildea, J.; Konopelko, A.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; LeBohec, S.; Maier, G.; McCann, A.; Millis, J.; Moriarty, P.; Ong, R. A.; Otte, A. N.; Pandel, D.; Perkins, J. S.; Pichel, A.; Pohl, M.; Quinn, J.; Ragan, K.; Reyes, L. C.; Reynolds, P. T.; Roache, E.; Rose, H. J.; Schroedter, M.; Sembroski, G. H.; Smith, A. W.; Steele, D.; Swordy, S. P.; Theiling, M.; Toner, J. A.; Varlotta, A.; Vincent, S.; Wakely, S. P.; Ward, J. E.; Weekes, T. C.; Weinstein, A.; Weisgarber, T.; Williams, D. A.; Wissel, S.; Zitzer, B.; VERITAS Collaboration; de la Calle Perez, I.; Ibarra, A.; Anderhub, H.; Rodriguez, P.; Antonelli, L. A.; Antoranz, P.; Backes, M.; Baixeras, C.; Balestra, S.; Barrio, J. A.; Bastieri, D.; Becerra González, J.; Becker, J. K.; Bednarek, W.; Berger, K.; Bernardini, E.; Biland, A.; Bock, R. K.; Bonnoli, G.; Bordas, P.; Borla Tridon, D.; Bosch-Ramon, V.; Bose, D.; Braun, I.; Bretz, T.; Britvitch, I.; Camara, M.; Carmona, E.; Carosi, A.; Commichau, S.; Contreras, J. L.; Cortina, J.; Costado, M. T.; Covino, S.; Curtef, V.; Dazzi, F.; DeAngelis, A.; DeCea del Pozo, E.; Delgado Mendez, C.; Delos Reyes, R.; DeLotto, B.; DeMaria, M.; DeSabata, F.; Dominguez, A.; Dorner, D.; Doro, M.; Elsaesser, D.; Errando, M.; Ferenc, D.; Fernández, E.; Firpo, R.; Fonseca, M. V.; Font, L.; Galante, N.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Goebel, F.; Hadasch, D.; Hayashida, M.; Herrero, A.; Hildebrand, D.; Höhne-Mönch, D.; Hose, J.; Hsu, C. C.; Jogler, T.; Kranich, D.; La Barbera, A.; Laille, A.; Leonardo, E.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Lorenz, E.; Majumdar, P.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Miyamoto, H.; Moldón, J.; Moles, M.; Moralejo, A.; Nieto, D.; Nilsson, K.; Ninkovic, J.; Orito, R.; Oya, I.; Paoletti, R.; Paredes, J. M.; Pasanen, M.; Pascoli, D.; Pauss, F.; Pegna, R. G.; Perez-Torres, M. A.; Persic, M.; Peruzzo, L.; Prada, F.; Prandini, E.; Puchades, N.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Rissi, M.; Robert, A.; Rügamer, S.; Saggion, A.; Saito, T. Y.; Salvati, M.; Sanchez-Conde, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schweizer, T.; Shayduk, M.; Shore, S. N.; Sidro, N.; Sierpowska-Bartosik, A.; Sillanpää, A.; Sitarek, J.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamerra, A.; Stark, L. S.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Tescaro, D.; Teshima, M.; Tluczykont, M.; Torres, D. F.; Turini, N.; Vankov, H.; Wagner, R. M.; Zabalza, V.; Zandanel, F.; Zanin, R.; Zapatero, J.; MAGIC Collaboration

    2009-09-01

    We report on the results of two coordinated multiwavelength campaigns that focused on the blazar Markarian 421 during its 2006 and 2008 outbursts. These campaigns obtained UV and X-ray data using the XMM-Newton satellite, while the gamma-ray data were obtained utilizing three imaging atmospheric Cerenkov telescopes, the Whipple 10 m telescope and VERITAS, both based in Arizona, as well as the MAGIC telescope, based on La Palma in the Canary Islands. The coordinated effort between the gamma-ray groups allowed for truly simultaneous data in UV/X-ray/gamma-ray wavelengths during a significant portion of the XMM-Newton observations. This simultaneous coverage allowed for a reliable search for correlations between UV, X-ray, and gamma-ray variability over the course of the observations. Investigations of spectral hysteresis and modeling of the spectral energy distributions are also presented.

  6. a New Approach of the Deflagration to Detonation Transition in SNIa Thermonuclear Supernovae

    NASA Astrophysics Data System (ADS)

    Chièze, Jean Pierre; Charignon, Camille

    2015-03-01

    A wide class of type Ia thermonuclear supernovae models relies on the transition from the subsonic deflagration combustion regime to the supersonic detonation regime of the carbon and oxygen mixture of an accreting white dwarf, near the Chandrasekhar mass. We show that this can actually be achieved in a cold C+O white dwarf near the Chandrasekhar mass, with seed sound waves of relatively low Mach number M ˜ 0.02. Moreover, even weaker perturbations, with velocity perturbations as low as M ˜ 0.003 can trigger a detonation wave in SNIa progenitors models wich include the presence of a thin helium surface layer.

  7. The use of idle equipment for ITER (International Thermonuclear Engineering Reactor) magnet development

    SciTech Connect

    Miller, J.R.

    1988-07-11

    Test facilities that can be effectively applied to International Thermonuclear Engineering Reactor (ITER) magnet needs are scarce because the costs and the time required to produce them from the ground up tend to be prohibitive. It has been proposed as an option that several unique and valuable pieces of equipment that are already owned by the DOE be consolidated into the Lawrence Livermore National High Field Test Facility (HFTF) which may be uniquely qualified to make effective use of them. 6 figs., 4 tabs.

  8. Fermi-GBM detection of a thermonuclear burst from 4U 1608-52

    NASA Astrophysics Data System (ADS)

    Jenke, P.; Linares, M.; Connaughton, V.; van der Horst, A. J.; Camero-Arranz, A.; Finger, M.; Wilson-Hodge, C.; Kouveliotou, C.

    2012-05-01

    We report the detection with Fermi-GBM (daily CTIME data, 12-25 keV band) of an X-ray burst from a location consistent with the neutron star low-mass X-ray binary and thermonuclear burster 4U 1608-52. The burst peak occurred on May 2, 2012 at 06:47:54 UTC. The Fermi-GBM location of the burst is R.A.(J2000) = 241.3 deg, DEC(J2000) = -51.1 deg (1.8 deg from 4U 1608-52) with a 1 sigma error of 4.7 deg.

  9. Pilot experiments for the International Thermonuclear Experimental Reactor active beam spectroscopy diagnostic

    NASA Astrophysics Data System (ADS)

    Hellermann, M. von; Bock, M. de; Jaspers, R.; Jakubowska, K.; Barnsley, R.; Giroud, C.; Hawkes, N. C.; Zastrow, K. D.; Lotte, P.; Giannella, R.; Malaquias, A.; Rachlew, E.; Tugarinov, S.; Krasilnikov, A.; Litnovsky, A.; Philipps, V.; Wienhold, P.; Oelhafen, P.; Temmerman, G. De; Shmaenok, L.

    2004-10-01

    Supporting pilot experiments and activities which are currently considered or already performed for the development of the International Thermonuclear Experiment Reactor active beam spectroscopy diagnostic are addressed in this article. Four key issues are presented including optimization of spectral instrumentation, feasibility of a motional Stark effect (MSE) evaluation based on line ratios, "first-mirror" test-bed experiments at the tokamak TEXTOR, and finally the role of integrated data analysis for the conceptual layout of the change exchange recombination spectroscopy and MSE diagnostic.

  10. 45 CFR 1351.20 - What are the additional requirements under a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... and Family counseling, and • Crisis intervention techniques. (b) Grantees will be required to... reporting requirements are mandated by the Act which states that “runaway and homeless youth projects...

  11. 45 CFR 1351.20 - What are the additional requirements under a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... and Family counseling, and • Crisis intervention techniques. (b) Grantees will be required to... reporting requirements are mandated by the Act which states that “runaway and homeless youth projects...

  12. 45 CFR 1351.20 - What are the additional requirements under a Runaway and Homeless Youth Program grant?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... and Family counseling, and • Crisis intervention techniques. (b) Grantees will be required to... reporting requirements are mandated by the Act which states that “runaway and homeless youth projects...

  13. That Which Does Not Kill You Makes You Stronger: Runaway Youth’s Resilience to Depression in the Family Context

    PubMed Central

    Erdem, Gizem; Slesnick, Natasha

    2010-01-01

    The present study sought to uncover the relationship between risk and protective factors for depressive symptomatology among runaway youth. To that aim, three models of resiliency - the compensatory, risk-protective, and challenge models - were tested separately on girls and boys. The data came from a cross-sectional survey on a sample of 140 runaway adolescents between the ages of 12 to 17 years who were recruited from the only runaway crisis shelter in a large Midwestern city. Risk factors in the proposed model included primary caretakers’ depressive symptoms, family conflict, and adolescent’s and primary caretaker’s verbal aggression; protective factors included adolescent’s report of task oriented coping and family cohesion. Findings supported the challenge model for predicting adolescent depressive symptoms, suggesting that moderate levels of risk can be beneficial for these runaway adolescents. In addition, risk and protective factors differed by adolescent gender. Implications for preventive interventions and future research are discussed. PMID:20553513

  14. Spectroscopy and photometry of X Ser (Nova Ser 1903) during its current DN stunted outburst

    NASA Astrophysics Data System (ADS)

    Munari, U.; Dallaporta, S.

    2016-09-01

    The old nova X Ser (Nova Ser 1903) is known to display stunted dwarf-nova outbursts (Honeycutt et al. 1998, AJ 115, 2527), for which multiband photometry - and spectroscopy in particular - seem acutely rare.

  15. The impact of IUE on studies of the nova outburst: 1986--1990

    SciTech Connect

    Starrfield, S. . Dept. of Physics Los Alamos National Lab., NM )

    1990-01-01

    In this review I will concentrate on the improvements in our understanding of the nova outburst that have occurred since the IUE meetings in London in 1986 and Goddard in 1988 and those results that have occurred as a direct result of studies with the IUE satellite. These involve the four outbursts that have occurred in the LMC, the numerous recurrent novae outbursts, and a number of archival studies. As a direct result of IUE studies done since 1986, we can now state that fast novae become super-Eddington at maximum, that many novae decline at the same rate, and that neon novae may be more numerous than thought previously. In addition, we have found that there are differences in the outburst characteristics between novae with giant secondaries and those with compact secondaries. 18 refs., 11 figs., 1 tab.

  16. Analysis of the thermal response of plasma facing components during a runaway electron impact

    NASA Astrophysics Data System (ADS)

    Ward, Robert Cameron

    The generation of runaway electrons during a thermal plasma disruption is a concern for the safe and economical operation of a tokamak power system. Runaway electrons have high energy, 10--300 MeV, and may potentially cause extensive damage to plasma facing components through large temperature increases, melting of metallic components, surface erosion, and possible burnout of coolant tubes. The EPQ code system was developed to simulate the thermal response of plasma facing components to a runaway electron impact. The EPQ code system consists of several parts: UNIX scripts which control the operation of an electron-photon monte carlo code to calculate the interaction of the runaway electrons with the plasma facing materials; a finite difference code to calculate the thermal response, melting, and surface erosion of the materials using the modified heat conduction equation; a code to process, scale, transform, and convert the electron monte carlo data to volumetric heating rates for use in the thermal code; and several minor and auxiliary codes for the manipulation and post-processing of the data. The electron-photon monte carlo code used was the Electron-Gamma-Shower (EGS) code, developed and maintained by the National Research Center of Canada. The other codes were written in C++ for this study. The thermal code, called QTTN, solves the two-dimensional cylindrical modified heat conduction equation using the Quickest third-order accurate and stable explicit finite difference method and is capable of tracking melting or surface erosion. The EPQ code system was validated using a series of analytical solutions and simulations of experiments. QTTN and EPQ was verified and validated as able to calculate the temperature distribution, phase change, and surface erosion successfully. EPQ was then employed in a parametric study to simulate a typical runaway electron disruption impact on the FIRE design's plasma facing components. The results of the FIRE parametric study

  17. Outburst from 4U 1145-619: A Transient X-Ray Pulsar

    NASA Technical Reports Server (NTRS)

    Wilson, Colleen; Finger, Mark H.; Scott, Matthew

    1998-01-01

    4U 1145-619, a 293 second Be/X-ray pulsar, was discovered with Uhuru (Forman 1978, ApJS, 38, 357) and first identified as a pulsar in 1977 with Ariel V (White 1978, Nature, 274, 664). From 1991 to 1998, BATSE observed 4U 1145-619 in a series of 12 periodic outbursts, each with durations of 8-30 days. Combining these data with previously published results yielded an outburst ephemeris of T(sub out) = MJD 448871.s (+/- 0.6) +/- 186.68 (+/- 0.05)E(sub out), Where T(sub out) is the time of peak intensity and E(sub out) is the cycle number. Most outbursts occur within phases +/- 0.1 of the outburst ephemeris. Pulse frequency measurements were consistent with a long-term average frequency derivative of the first derivative of v = -3 x 10(exp -14) Hz/s. Most outbursts reached peak total fluxes of approximately equal 100 mCrab (20-50 keV) and had 20-50 keV r.m.s. pulse fractions of about 30%. (A pulse fraction of 70% was observed for one outburst). Two outbursts reached 20-50 keV peak total fluxes of 550 mCrab, but had very different 20-50 keV pulse fractions of about 30% and about 50%. Three outbursts with peak total fluxes of 120, 134, and 180 mCrab, had r.m.s. pulse fractions of about 28%, 34%, and 52%. During the brightest 3 outbursts observed with BATSE, the pulse frequency increased. Fainter outbursts observed with BATSE appeared to reach peak intensity at a later phase (relative to the ephemeris) than brighter outbursts, and were typically not detectable at the expected times of peak intensity. The pulse profile showed significant intensity and energy dependent pulse shape variations. We present histories of pulse frequency, 20-50 keV intensity, and pulse profiles.

  18. Investigation of relativistic runaway electrons in electron cyclotron resonance heating discharges on Korea Superconducting Tokamak Advanced Research

    SciTech Connect

    Kang, C. S.; Lee, S. G.

    2014-07-15

    The behavior of relativistic runaway electrons during Electron Cyclotron Resonance Heating (ECRH) discharges is investigated in the Korea Superconducting Tokamak Advanced Research device. The effect of the ECRH on the runaway electron population is discussed. Observations on the generation of superthermal electrons during ECRH will be reported, which will be shown to be consistent with existing theory for the development of a superthermal electron avalanche during ECRH [A. Lazaros, Phys. Plasmas 8, 1263 (2001)].

  19. ATCA radio observations of Swift J1756.9-2508 in outburst

    NASA Astrophysics Data System (ADS)

    Tudose, V.; Tzioumis, A.; Patruno, A.; Linares, M.; Soleri, P.; Russell, D.

    2009-07-01

    Swift J1756.9-2508 was discovered by the X-ray satellite Swift during an outburst in 2007 (ATEL #1105) and recognized immediately as an accretion-driven millisecond X-ray pulsar (ATEL #1108). No radio pulsations (ATEL #1129) and no continuum radio emission (ATEL #1128) were detected then. While the radio pulsation search was performed during the outburst, the continuum observations were carried out when the X-ray flux levels already decreased below the detection limit of Swift.

  20. New X-ray Outburst in X1744-361 (A1744-36)

    NASA Astrophysics Data System (ADS)

    Remillard, Ronald A.

    2009-11-01

    The recurrent transient and accreting neutron star, X1744-361, has begun the fourth outburst observed with RXTE (see ATel #1587). The ASM data rate for this source is impeded by the angular proximity of the Sun, but the outburst appears to have begun near MJD 55145. The intensity seems to have leveled off quickly, and the the average flux during the last week is 65(7) mCrab at 2-12 keV. Followup observations are encouraged.

  1. Superhumps in a Rarely Outbursting SU UMa-Type Dwarf Nova, HO Delphini

    NASA Astrophysics Data System (ADS)

    Kato, Taichi; Nogami, Daisaku; Moilanen, Marko; Yamaoka, Hitoshi

    2003-10-01

    We observed the 1994, 1996, and 2001 outbursts of HO Del. From the detection of secure superhumps, HO Del is confirmed to be an SU UMa-type dwarf nova with a superhump period of 0.06453(6)d. Based on recent observations and past records, the outbursts of HO Del are found to be relatively rare, with the shortest intervals of superoutbursts being ˜ 740d. Among SU UMa-type dwarf novae with similar outburst intervals, the outburst amplitude (˜ 5.0mag) is unusually small. HO Del showed a rather rapid decay of the superhump amplitudes, and no regrowth of the amplitudes during the later stage, in contrast to the commonly observed behavior in SU UMa-type dwarf novae with long outburst intervals. We positively identified HO Del with a ROSAT X-ray source, and obtained a relatively large X-ray luminosity of 1031.1±0.2erg s-1. We also performed a literature survey of SU UMa-type dwarf novae and presented a new set of basic statistics. The SU UMa-type dwarf novae with a brightening trend or with a regrowth of superhumps near the termination of a superoutburst are found to be rather tightly confined in a small region on the (superhump period-supercycle length) plane. These features may provide a better observational distinction for the previously claimed subgroup of dwarf novae (Tremendous Outburst Amplitude Dwarf Novae).

  2. THE SHAPE OF LONG OUTBURSTS IN U GEM TYPE DWARF NOVAE FROM AAVSO DATA

    SciTech Connect

    Cannizzo, John K.

    2012-10-01

    We search the American Association of Variable Star Observers (AAVSO) archives of the two best-studied dwarf novae in an attempt to find light curves for long outbursts that are extremely well characterized. The systems are U Gem and SS Cyg. Our goal is to search for embedded precursors such as those that have been found recently in the high-fidelity Kepler data for superoutbursts (SOs) of some members of the SU UMa subclass of dwarf novae. For the vast majority of AAVSO data, the combination of low data cadence and large errors associated with individual measurements precludes one from making any strong statement about the shape of the long outbursts. However, for a small number of outbursts, extensive long-term monitoring with digital photometry yields high-fidelity light curves. We report the discovery of embedded precursors in two of three candidate long outbursts. This is the first time that such embedded precursors have been found in dwarf novae above the period gap in other than kepler data, and reinforces van Paradijs' finding that long outbursts in dwarf novae above the period gap and SOs in systems below the period gap constitute a unified class. The thermal-tidal instability to account for SOs in the SU UMa stars predicts embedded precursors only for short orbital period dwarf novae, therefore the presence of embedded precursors in long orbital period systems-U Gem and SS Cyg-argues for a more general mechanism to explain long outbursts.

  3. V899 MON: AN OUTBURSTING PROTOSTAR WITH A PECULIAR LIGHT CURVE, AND ITS TRANSITION PHASES

    SciTech Connect

    Ninan, J. P.; Ojha, D. K.; Baug, T.; Bhatt, B. C.; Anupama, G. C.; Mohan, V.; Ghosh, S. K.; Men’shchikov, A.; Henning, Th.

    2015-12-10

    We present a detailed study of V899 Mon (a new member in the FUors/EXors family of young low-mass stars undergoing outburst), based on our long-term monitoring of the source starting from 2009 November to 2015 April. Our optical and near-infrared photometric and spectroscopic monitoring recorded the source transitioning from its first outburst to a short-duration quiescence phase (<1 yr), and then returning to a second outburst. We report here the evolution of the outflows from the inner region of the disk as the accretion rate evolved in various epochs. Our high-resolution (R ∼ 37,000) optical spectrum could resolve interesting clumpy structures in the outflow traced by various lines. Change in far-infrared flux was also detected between two outburst epochs. Based on our observations, we constrained various stellar and envelope parameters of V899 Mon, as well as the kinematics of its accretion and outflow. The photometric and spectroscopic properties of this source fall between classical FUors and EXors. Our investigation of V899 Mon hints at instability associated with magnetospheric accretion being the physical cause of the sudden short-duration pause of the outburst in 2011. It is also a good candidate to explain similar short-duration pauses in outbursts of some other FUors/EXors sources.

  4. DETECTION OF AN OUTBURST ONE YEAR PRIOR TO THE EXPLOSION OF SN 2011ht

    SciTech Connect

    Fraser, M.; Magee, M.; Kotak, R.; Smartt, S. J.; Smith, K. W.; Polshaw, J.; Drake, A. J.; Boles, T.; Lee, C.-H.; Burgett, W. S.; Chambers, K. C.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Kudritzki, R.-P.; Magnier, E. A.; Tonry, J. L.; Wainscoat, R. J.; Draper, P. W.; Price, P. A.; and others

    2013-12-10

    Using imaging from the Pan-STARRS1 survey, we identify a precursor outburst at 287 and 170 days prior to the reported explosion of the purported Type IIn supernova (SN) 2011ht. In the Pan-STARRS data, a source coincident with SN 2011ht is detected exclusively in the z {sub P1} and y {sub P1}-bands. An absolute magnitude of M{sub z} ≅ –11.8 suggests that this was an outburst of the progenitor star. Unfiltered, archival Catalina Real Time Transient Survey images also reveal a coincident source from at least 258 to 138 days before the main event. We suggest that the outburst is likely to be an intrinsically red eruption, although we cannot conclusively exclude a series of erratic outbursts which were observed only in the redder bands by chance. This is only the fourth detection of an outburst prior to a claimed SN, and lends credence to the possibility that many more interacting transients have pre-explosion outbursts, which have been missed by current surveys.

  5. Spectroscopic view on the outburst activity of the symbiotic binary AG Draconis

    NASA Astrophysics Data System (ADS)

    Leedjärv, L.; Gális, R.; Hric, L.; Merc, J.; Burmeister, M.

    2016-03-01

    Variations of the emission lines in the spectrum of the yellow symbiotic star AG Draconis (AG Dra) have been studied for over 14 yr (1997-2011), using more than 500 spectra obtained with the 1.5-m telescope at Tartu Observatory, Estonia. The time interval covered includes the major (cool) outburst of AG Dra that started in 2006. The main findings can be summarized as follows. (i) The cool and hot outbursts of AG Dra can be distinguished from the variations of optical emission lines. (ii) The Raman scattered emission line of O VI at λ6825 almost disappeared during the cool outburst. (iii) The lower excitation emission lines did not change significantly during the cool outburst, but they do vary in hot outbursts and also follow orbital motion. (iv) The similarity of variations in AG Dra to those in the prototypical symbiotic star Z Andromedae allows us to suggest that a combination nova model proposed for the latter object might also be responsible for the outburst behaviour of AG Dra.

  6. The cooling of the white dwarf in U Geminorum following heating by two different outbursts

    NASA Technical Reports Server (NTRS)

    Huang, Min; Sion, Edward M.; Szkody, Paula

    1995-01-01

    We present the analysis of 13 orbital phase-resolved IUE (large and small aperture) SWP spectra, sampling the quiescent intervals of the proptotype dwarf nova U Geminorum following two individual outbursts, the outburst of 1992, 29 August-14 September, and the outburst of 1993, 19 March-5 April. The quiescent interval following the outburst 29 August 1992 is the longest ever recorded. During quiescence, the photospheric radiation of the exposed white dwarf dominates the far ultrviolet. The variations in absorption line strengths and continum flux levels are analyzed as a function of both orbital phase and elapsed time, since the return to optical quiescence, by fitting the IUE spectra with a grid of high gravity, LTE, model atmospheres with solar composition constructed with TLUSTY and SYNSPEC (Hubeny, I. Tlusty and Synnspec: A Users Guide (1994)). We present evidence from both absorption line variations and continuum variations, as a function of time since the outbursts, that the white dwarf photosphere has cooled by several thousand degrees. Within the signal-to-noise limitations, we find no evidence of a difference in heating and cooling between the two outbursts.

  7. Erratum - the 1989 Outburst of the Recurrent Nova V745-SCORPII

    NASA Astrophysics Data System (ADS)

    Sekiguchi, K.; Whitelock, P. A.; Feast, M. W.; Barrett, P. E.; Caldwell, J. A. R.; Carter, B. S.; Catchpole, R. M.; Laing, J. D.; Laney, C. D.; Marang, F.; van Wyk, F.

    1991-01-01

    The paper "The 1989 Outburst of the Recurrent Nova V745-SCORPII" was published in Mon. Not. R. astr. Soc. (1990) 246, 78-83. The ninth line of the Introduction has been misprinted. The correct version of the Introduction is reproduced below. INTRODUCTION: The first recorded outburst of V745 Sco (α = 17h52m04s.72, δ = -33° 14' 31".8; equinox 1950.0, McNaught 1989) was reported by Plaut (1958) who found the nova at mpυ ˜11.2 on 1937 May 10. It was classified as a nova on the basis of its outburst amplitude and light curve although no spectroscopic observations were reported (Duerbeck 1984, 1987). The second observed outburst was discovered by Liller (1989) on 1989 July 30.08 UT at a ˜9.7 mag. It was at a similar brightness on July 31.02 UT but had been fainter than magnitude 12 on July 29.549 UT (Honda 1989). In the following we will therefore assume that the nova reached maximum light on July 30.0 UT. The 1989 outburst places V745 Sco in the small class of recurrent novae, bringing their numbers up to seven. This paper presents the results of photometric and spectroscopic observations covering the most recent outburst.

  8. THE RETURN OF THE BURSTS: THERMONUCLEAR FLASHES FROM CIRCINUS X-1

    SciTech Connect

    Linares, M.; Homan, J.; Chakrabarty, D.; Watts, A.; Altamirano, D.; Degenaar, N.; Yang, Y.; Wijnands, R.; Armas-Padilla, M.; Cavecchi, Y.; Kalamkar, M.; Kaur, R.; Patruno, A.; Van der Klis, M.; Soleri, P.; Casella, P.; Rea, N.

    2010-08-10

    We report the detection of 15 X-ray bursts with RXTE and Swift observations of the peculiar X-ray binary Circinus X-1 (Cir X-1) during its 2010 May X-ray re-brightening. These are the first X-ray bursts observed from the source after the initial discovery by Tennant and collaborators, 25 years ago. By studying their spectral evolution, we firmly identify nine of the bursts as type I (thermonuclear) X-ray bursts. We obtain an arcsecond location of the bursts that confirms once and for all the identification of Cir X-1 as a type I X-ray burst source, and therefore as a low magnetic field accreting neutron star. The first five bursts observed by RXTE are weak and show approximately symmetric light curves, without detectable signs of cooling along the burst decay. We discuss their possible nature. Finally, we explore a scenario to explain why Cir X-1 shows thermonuclear bursts now but not in the past, when it was extensively observed and accreting at a similar rate.

  9. The TDF System for Thermonuclear Plasma Reaction Rates, Mean Energies and Two-Body Final State Particle Spectra

    SciTech Connect

    Warshaw, S I

    2001-07-11

    The rate of thermonuclear reactions in hot plasmas as a function of local plasma temperature determines the way in which thermonuclear ignition and burning proceeds in the plasma. The conventional model approach to calculating these rates is to assume that the reacting nuclei in the plasma are in Maxwellian equilibrium at some well-defined plasma temperature, over which the statistical average of the reaction rate quantity {sigma}v is calculated, where {sigma} is the cross-section for the reaction to proceed at the relative velocity v between the reacting particles. This approach is well-understood and is the basis for much nuclear fusion and astrophysical nuclear reaction rate data. The Thermonuclear Data File (TDF) system developed at the Lawrence Livermore National Laboratory (Warshaw 1991), which is the topic of this report, contains data on the Maxwellian-averaged thermonuclear reaction rates for various light nuclear reactions and the correspondingly Maxwellian-averaged energy spectra of the particles in the final state of those reactions as well. This spectral information closely models the output particle and energy distributions in a burning plasma, and therefore leads to more accurate computational treatments of thermonuclear burn, output particle energy deposition and diagnostics, in various contexts. In this report we review and derive the theoretical basis for calculating Maxwellian-averaged thermonuclear reaction rates, mean particle energies, and output particle spectral energy distributions for these reactions in the TDF system. The treatment of the kinematics is non-relativistic. The current version of the TDF system provides exit particle energy spectrum distributions for two-body final state reactions only. In a future report we will discuss and describe how output particle energy spectra for three- and four-body final states can be developed for the TDF system. We also include in this report a description of the algorithmic implementation of the

  10. On the Temporal Evolution of Red Sprites, Runaway Theory Versus Data

    NASA Technical Reports Server (NTRS)

    Yukhimuk, V.; Roussel-Dupre, R. A.; Symbalisty, E. M. D.

    1999-01-01

    The results of numerical simulations of red sprite discharges, namely the temporal evolutions of optical emissions, are presented and compared with observations. The simulations are done using the recently recalculated runaway avalanche rates. The temporal evolution of these simulations is in good agreement with ground-based photometer and CCD TV camera observations of red sprites. Our model naturally explains the "hairline" of red sprites as a boundary between the region where the intensity of optical emissions associated with runaway breakdown has a maximum and the region where the intensity of optical emissions caused by conventional breakdown and ambient electron heating has a maximum. We also present for the first time simulations of red sprites with a daytime conductivity profile.

  11. Use of Cherenkov-type detectors for measurements of runaway electrons in the ISTTOK tokamak

    SciTech Connect

    Plyusnin, V. V.; Fernandes, H.; Silva, C.; Duarte, P.

    2008-10-15

    Gas, fluid, or solid Cherenkov-type detectors have been widely used in high-energy physics for determination of parameters of charged particles, which are moving with relativistic velocities. This paper presents experimental results on the detection of runaway electrons using Cherenkov-type detectors in the ISTTOK tokamak discharges. Such detectors have been specially designed for measurements of energetic electrons in tokamak plasma. The technique based on the use of the Cherenkov-type detectors has enabled the detection of energetic electrons (energies higher than 80 keV) and determination of their spatial and temporal parameters in the ISTTOK discharges. Obtained experimental data were found in adequate agreement to the results of numerical modeling of the runaway electron generation in ISTTOK.

  12. Plasma heating and emission of runaway charged particles in a plasma focus device

    NASA Astrophysics Data System (ADS)

    Behbahani, R. A.; Hirose, A.; Xiao, C.

    2016-03-01

    The required experimental E-field across plasma to generate significant runaway electrons and hard X-rays during the pinch phase and the phase with anomalous resistance has been investigated in a dense plasma focus. The plasma voltage and inductance have been measured in a plasma focus with two different anode tip structures. The results show a significant generation of charged particles and hard X-rays at smaller E-field across the plasma column in the phase of anomalous resistances compared to the pinch phase. Plasma heating process may enhance the rate of runaway-charged-particle generation due to the combined effects of a reduced Dreicer field and the avalanche effects during the phase of anomalous resistance.

  13. Comparison of family therapy outcome with alcohol-abusing, runaway adolescents.

    PubMed

    Slesnick, Natasha; Prestopnik, Jillian L

    2009-07-01

    Treatment evaluation for alcohol problem, runaway adolescents and their families is rare. This study recruited primary alcohol problem adolescents (N = 119) and their primary caretakers from two runaway shelters and assigned them to (a) home-based ecologically based family therapy (EBFT), (b) office-based functional family therapy (FFT), or (c) service as usual (SAU) through the shelter. Findings showed that both home-based EBFT and office-based FFT significantly reduced alcohol and drug use compared with SAU at 15-month postbaseline. Measures of family and adolescent functioning improved over time in all groups. However, significant differences among the home- and office-based interventions were found for treatment engagement and moderators of outcome.

  14. Bleak and hopeless no more. Engagement Of reluctant substance-abusing runaway youth and their families.

    PubMed

    Slesnick, N; Meyers, R J; Meade, M; Segelken, D H

    2000-10-01

    Runaway/homeless shelters document high levels of substance abuse among runaway youth, at least double that of school youth. These youth present a constellation of problems and research suggests that this population may be unique in the range and intensity of associated problems. Most studies to date have collected self-report data on these youth; virtually no research has examined treatment effectiveness with the population. Given the void of treatment outcome research with these youths, there is need for identifying potent interventions. Given that issues of engagement and retention must assume prominence in the development of new treatments, this article presents a family-based treatment engagement strategy successfully employed with a sample of substance-abusing youth staying in a southwestern shelter. Youth and primary caretakers are engaged separately by the therapist utilizing motivating factors appropriate to context of the families' lives and to the developmental position of the client.

  15. In-operando high-speed tomography of lithium-ion batteries during thermal runaway

    PubMed Central

    Finegan, Donal P.; Scheel, Mario; Robinson, James B.; Tjaden, Bernhard; Hunt, Ian; Mason, Thomas J.; Millichamp, Jason; Di Michiel, Marco; Offer, Gregory J.; Hinds, Gareth; Brett, Dan J.L.; Shearing, Paul R.

    2015-01-01

    Prevention and mitigation of thermal runaway presents one of the greatest challenges for the safe operation of lithium-ion batteries. Here, we demonstrate for the first time the application of high-speed synchrotron X-ray computed tomography and radiography, in conjunction with thermal imaging, to track the evolution of internal structural damage and thermal behaviour during initiation and propagation of thermal runaway in lithium-ion batteries. This diagnostic approach is applied to commercial lithium-ion batteries (LG 18650 NMC cells), yielding insights into key degradation modes including gas-induced delamination, electrode layer collapse and propagation of structural degradation. It is envisaged that the use of these techniques will lead to major improvements in the design of Li-ion batteries and their safety features. PMID:25919582

  16. Influence of self-gravity on the runaway instability of black-hole-torus systems.

    PubMed

    Montero, Pedro J; Font, José A; Shibata, Masaru

    2010-05-14

    Results from the first fully general relativistic numerical simulations in axisymmetry of a system formed by a black hole surrounded by a self-gravitating torus in equilibrium are presented, aiming to assess the influence of the torus self-gravity on the onset of the runaway instability. We consider several models with varying torus-to-black-hole mass ratio and angular momentum distribution orbiting in equilibrium around a nonrotating black hole. The tori are perturbed to induce the mass transfer towards the black hole. Our numerical simulations show that all models exhibit a persistent phase of axisymmetric oscillations around their equilibria for several dynamical time scales without the appearance of the runaway instability, indicating that the self-gravity of the torus does not play a critical role favoring the onset of the instability, at least during the first few dynamical time scales.

  17. Radiation reaction induced non-monotonic features in runaway electron distributions

    NASA Astrophysics Data System (ADS)

    Hirvijoki, E.; Pusztai, I.; Decker, J.; Embréus, O.; Stahl, A.; Fülöp, T.

    2015-10-01

    > Runaway electrons, which are generated in a plasma where the induced electric field exceeds a certain critical value, can reach very high energies in the MeV range. For such energetic electrons, radiative losses will contribute significantly to the momentum space dynamics. Under certain conditions, due to radiative momentum losses, a non-monotonic feature - a `bump' - can form in the runaway electron tail, creating a potential for bump-on-tail-type instabilities to arise. Here, we study the conditions for the existence of the bump. We derive an analytical threshold condition for bump appearance and give an approximate expression for the minimum energy at which the bump can appear. Numerical calculations are performed to support the analytical derivations.

  18. Can nitrogen cycle feedbacks lead to runaway denitrification and deoxygenation of the ocean?

    NASA Astrophysics Data System (ADS)

    Weber, T. S.; Deutsch, C. A.

    2014-12-01

    Over millennial timescales, the oceanic reservoir of fixed nitrogen (N) is regulated by a balance between N loss in sediments and low oxygen (O2) waters, and N2-fixation by diazotrophic phytoplankton. The two processes are coupled by selection for diazotrophs under N-limited conditions that arise from denitrification, although the spatial scale of this coupling is debated. A strong local coupling has been argued against because the export of newly fixed N would boost nearby denitrification rates, stimulating further N2-fixation in overlying water, resulting in runaway N loss and deoxygenation of the ocean. Using a global ocean circulation model with a prognostic ecosystem and biogeochemical cycles, we show that no such runaway feedback arises. Even when the majority of N2-fixation occurs directly above suboxic zones, N sources and sinks quickly reach a stable equilibrium without widespread N depletion. Taking a systems dynamics approach, we derive a "feedback factor" (f) for the interaction of N inputs and losses, which depends on the stoichiometry of diazotroph biomass, ventilation of the tropical thermocline, and upwelling rate of denitrified waters. Under modern conditions of ocean circulation and O2 solubility, f is much lower than 1 - the value that separates stable and runaway amplification of a system response - and the oceanic N reservoir is remarkably insensitive to spatial proximity of N sources and sinks, as might accompany the alleviation of diazotroph Fe-limitation. Based on these parameters, we identify climatic conditions that might push the system into a runaway feedback regime, allowing for periods of catastrophic N loss and deoxygenation during Earth's history.

  19. Escape fraction of ionizing photons during reionization: Effects due to supernova feedback and runaway ob stars

    SciTech Connect

    Kimm, Taysun; Cen, Renyue

    2014-06-20

    The fraction of hydrogen ionizing photons escaping from galaxies into the intergalactic medium is a critical ingredient in the theory of reionization. We use two zoomed-in, high-resolution (4 pc), cosmological radiation hydrodynamic simulations with adaptive mesh refinement to investigate the impact of two physical mechanisms (supernova, SN, feedback, and runaway OB stars) on the escape fraction (f {sub esc}) at the epoch of reionization (z ≥ 7). We implement a new, physically motivated SN feedback model that can approximate the Sedov solutions at all (from the free expansion to snowplow) stages. We find that there is a significant time delay of about ten million years between the peak of star formation and that of escape fraction, due to the time required for the build-up and subsequent destruction of the star-forming cloud by SN feedback. Consequently, the photon number-weighted mean escape fraction for dwarf galaxies in halos of mass 10{sup 8}-10{sup 10.5} M {sub ☉} is found to be 〈f{sub esc}〉∼11%, although instantaneous values of f {sub esc} > 20% are common when star formation is strongly modulated by the SN explosions. We find that the inclusion of runaway OB stars increases the mean escape fraction by 22% to 〈f{sub esc}〉∼14%. As SNe resulting from runaway OB stars tend to occur in less dense environments, the feedback effect is enhanced and star formation is further suppressed in halos with M{sub vir}≳10{sup 9} M{sub ⊙} in the simulation with runaway OB stars compared with the model without them. While both our models produce enough ionizing photons to maintain a fully ionized universe at z ≤ 7 as observed, a still higher amount of ionizing photons at z ≥ 9 appears necessary to accommodate the high observed electron optical depth inferred from cosmic microwave background observations.

  20. The Effects of Runaway-Homeless Episodes on High School Dropout

    PubMed Central

    Aratani, Yumiko; Cooper, Janice L.

    2013-01-01

    This article uses data from the National Longitudinal Survey of Youth 1997 to examine the relationship between running away from home between the ages of 12 and 14 and dropping from high school among youth. Propensity score matching was conducted in estimating the effect of running away on high school dropout while controlling for confounding factors, such as familial instability and socioemotional health risks. The findings suggest that having runaway-homeless episodes have a detrimental effect on academic achievement. PMID:25641997

  1. Novel approaches for mitigating runaway electrons and plasma disruptions in ADITYA tokamak

    NASA Astrophysics Data System (ADS)

    Tanna, R. L.; Ghosh, J.; Chattopadhyay, P. K.; Dhyani, Pravesh; Purohit, Shishir; Joisa, S.; Rao, C. V. S.; Panchal, V. K.; Raju, D.; Jadeja, K. A.; Bhatt, S. B.; Gupta, C. N.; Chavda, Chhaya; Kulkarni, S. V.; Shukla, B. K.; Praveenlal E., V.; Raval, Jayesh; Amardas, A.; Atrey, P. K.; Dhobi, U.; Manchanda, R.; Ramaiya, N.; Patel, N.; Chowdhuri, M. B.; Jha, S. K.; Jha, R.; Sen, A.; Saxena, Y. C.; Bora, D.; the ADITYA Team

    2015-06-01

    This paper summarizes the results of recent dedicated experiments on disruption control and runaway mitigation carried out in ADITYA, which are of the utmost importance for the successful operation of large size tokamaks, such as ITER. It is quite a well-known fact that disruptions in tokamaks must be avoided. Disruptions, induced by hydrogen gas puffing, are successfully avoided by two innovative techniques in ADITYA using a bias electrode placed inside the last closed flux surface and applying an ion cyclotron resonance pulse with a power of ∼50 to 70 kW. These experiments led to better understanding of the disruption avoidance mechanisms and also can be thought of as one of the options for disruption avoidance in ITER. In both cases, the physical mechanism seems to be the control of magnetohydrodynamic modes due to increased poloidal rotation of edge plasma generated by induced radial electric fields. Real time avoidance of disruption with identifying proper precursors in both the mechanisms is successfully attempted. Further, analysing thoroughly the huge database of different types of spontaneous and deliberately-triggered disruptions from ADITYA, a significant contribution has been made to the international disruption database (ITPA). Furthermore, the mitigation of the runaway electron generated mainly during disruptions remains a challenging topic in present tokamak research as these high-energy electrons can cause severe damage to in-vessel components and the vacuum vessel. A simple technique has been implemented in ADITYA to mitigate the runaway electrons before they can gain high energies using a localized vertical magnetic field perturbation applied at one toroidal location to extract runaway electrons.

  2. Intervention with Substance Abusing Runaway Adolescents and their Families: Results of a Randomized Clinical Trial

    PubMed Central

    Slesnick, Natasha; Erdem, Gizem; Bartle-Haring, Suzanne; Brigham, Gregory S.

    2013-01-01

    Objectives To examine the efficacy of three theoretically distinct interventions among substance-abusing runaway adolescents and to explore individual differences in trajectories of change. Methods Adolescents (N=179) between the ages of 12–17 were recruited from a runaway shelter in a Midwestern city. The sample included 94 females (52.5%) and 85 males (47.5%), the majority of the adolescents were African American (n= 118, 65.9%). Adolescents were randomly assigned to the Community Reinforcement Approach (CRA, n = 57), Motivational Interviewing (MI, n = 61), or Ecologically-Based Family Therapy (EBFT, n = 61). Substance use was assessed at baseline, 3, 6, 9, 12, 18, and 24 months via Form 90 and urine screens. Results Hierarchical linear modeling revealed statistically significant improvement in frequency of substance use among runaways in all three treatment groups with a slight increase at post-treatment. Latent trajectory profile analysis explored individual differences in change trajectories and yielded a 3 class model. The majority of adolescents (n = 136, 76%) showed reductions in substance use over time with a slight increase at follow-up (Class 1: Decreasing). Twenty-four (13.4%) adolescents had shown high levels of substance use over time with patterns of increase and decrease (Class 2: Fluctuating high users), and 19 (10.6%) decreased but returned to baseline levels by two years post-baseline (Class 3: U shaped). Few differences among treatment conditions were noted; within the “decreasing” group, adolescents in MI treatment showed a quicker decline in their substance use but a faster relapse compared to those receiving EBFT. Conclusions These findings suggest that CRA, EBFT and MI are viable treatments for runaway substance-abusing adolescents. PMID:23895088

  3. Hydraulic Reconstructions of Outburst Floods on Earth and Mars

    NASA Astrophysics Data System (ADS)

    Lapotre, M. G. A.; Lamb, M. P.

    2014-12-01

    Large outburst floods on Earth and Mars have carved bedrock canyons in basalt that often have steep sidewalls and amphitheater heads, suggesting erosion by waterfall retreat and block toppling. Two paleohydraulic methods are typically used to reconstruct flood discharges. The first is based on the discharge required to move sediment, which requires rare grain-size data and is necessarily a lower bound. The second assumes bedrock canyons are entirely inundated, which likely greatly overestimates the discharge of canyon carving floods. Here we explore a third hypothesis that canyon width is an indicator of flood discharge. For example, we expect that for large floods relative to the canyon width, the canyon will tend to widen as water spills over and erodes the canyon sidewalls. In contrast, small floods, relative to the canyon size will tend to focus flow into the canyon head, resulting in a narrowing canyon. To test this hypothesis, we need data on how outburst floods focus water into canyons across a wide range of canyon and flood sizes. To fill this data gap, we performed a series of numerical simulations solving the 2D depth-averaged shallow water equations for turbulent flow. We analyzed the effect of five non-dimensional parameters on the shear stress and discharge distributions around head and sidewalls of canyons of different sizes. The Froude number of the flood has the greatest effect on the distribution of shear stresses and discharges around the canyon rim; higher Froude numbers lead to less convergence of the flow towards the canyon, and thus to lower shear stresses (and discharges) on the sides of the canyon. Simulation results show that canyons of constant width were likely carved by floods within a relatively narrow range of discharges. The range of discharges is sensitive to the Froude number and size of blocks that are toppled at the canyon head, both of which can be estimated from field and remotely sensed data. Example applications on Earth and

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  5. Study of runaway electrons using dosimetry of hard x-ray radiations in Damavand tokamak.

    PubMed

    Rasouli, C; Pourshahab, B; Hosseini Pooya, S M; Orouji, T; Rasouli, H

    2014-05-01

    In this work several studies have been conducted on hard x-ray emissions of Damavand tokamak based on radiation dosimetry using the Thermoluminescence method. The goal was to understand interactions of runaway electrons with plasma particles, vessel wall, and plasma facing components. Total of 354 GR-200 (LiF:Mg,Cu,P) thermoluminescence dosimeter (TLD) crystals have been placed on 118 points--three TLDs per point--to map hard x-ray radiation doses on the exterior of the vacuum vessel. Results show two distinctive levels of x-ray radiations doses on the exterior of the vessel. The low-dose area on which measured dose is about 0.5 mSv/shot. In the low-dose area there is no particular component inside the vessel. On the contrary, on high-dose area of the vessel, x-ray radiations dose exceeds 30 mSv/shot. The high-dose area coincides with the position of limiters, magnetic probe ducts, and vacuum vessel intersections. Among the high-dose areas, the highest level of dose is measured in the position of the limiter, which could be due to its direct contact with the plasma column and with runaway electrons. Direct collisions of runaway electrons with the vessel wall and plasma facing components make a major contribution for production of hard x-ray photons in Damavand tokamak.

  6. Runaway electrons as a source of impurity and reduced fusion yield in the dense plasma focus

    SciTech Connect

    Lerner, Eric J.; Yousefi, Hamid R.

    2014-10-15

    Impurities produced by the vaporization of metals in the electrodes may be a major cause of reduced fusion yields in high-current dense plasma focus devices. We propose here that a major, but hitherto-overlooked, cause of such impurities is vaporization by runaway electrons during the breakdown process at the beginning of the current pulse. This process is sufficient to account for the large amount of erosion observed in many dense plasma focus devices on the anode very near to the insulator. The erosion is expected to become worse with lower pressures, typical of machines with large electrode radii, and would explain the plateauing of fusion yield observed in such machines at higher peak currents. Such runaway electron vaporization can be eliminated by the proper choice of electrode material, by reducing electrode radii and thus increasing fill gas pressure, or by using pre-ionization to eliminate the large fields that create runaway electrons. If these steps are combined with monolithic electrodes to eliminate arcing erosion, large reductions in impurities and large increases in fusion yield may be obtained, as the I{sup 4} scaling is extended to higher currents.

  7. Development of thermal runaway preventing ZnO varistor for surge protective device.

    PubMed

    Jeoung, Tae-Hoon; Kim, Young-Sung; Nam, Sung-Pill; Lee, Seung-Hwan; Kang, Jeong-Wook; Kim, Jea-Chul; Lee, Sung-Gap

    2014-12-01

    In this paper, the centre of electrode is suggested for heat conduction. Therefore, the specific reflow soldering process is needed. The comparison of temperature difference among the different areas of ZnO varistors is analyzed. With the nominal surge current, thermal behavior is analyzed. The operation point of temperature for disconnection is proposed. Accordingly, the thermal runaway-preventing ZnO varistors were covered with a fusible alloy, i.e., a thermal fuse, in the process of manufacture, which is expected to ensure there the liability of being resistant to lightning discharge and to ensure stability against thermal runaway in the failure mode. Additionally, it is expected to reduce much more limit voltage than the existing products to which the fuse was separately applied. The thermal runaway-preventing ZnO varistor of the surge protection devices can be widely used as part of the protection provisions of lightning discharge and surge protection demanded in connection with power IT about Green Growth which is nowadays becoming the buzzword in the electric power industry. PMID:25970989

  8. OT2_anoriega_2: SABER: Spectral Analysis of the Bowshock Emission in a Runaway

    NASA Astrophysics Data System (ADS)

    Noriega-Crespo, A.

    2011-09-01

    Bowshocks around runaway OB stars are some of the most spectacular objects in the mid/far infrared, covering in some cases as much as half a degree across the sky. The bowshocks are essentially enormous gas shells contained by ram pressure where the dust trapped in their interiors reprocesses the UV flux from the parent OB stars and re-radiates it in the infrared. The pressure balance between the stellar wind and the ISM, also implies a tight relationship between their physical properties, and therefore, bowshocks from runaway stars provide a powerful tool to probe the interstellar medium and/or the properties of the OB stellar wind. The formation of these shells requires very efficient cooling that is expected to take place through the emission of a wealth of atomic fine structure lines, like [OI] 63.2 or [NII] 205.2 micron. Because the diffuse nature of these shells it has been very difficult to confirm this expectation using spectroscopic observations. In this project we propose to use the PACS spectrometer to observe the zeta Oph bowshock in order to better understand and constrain the physical conditions of its gas shell, its dust properties, its turbulence, and in such a way that will allow to use zeta Oph as a template to make sense of the physical properties of the many more runaway bowshocks are continuously being discovered.

  9. Study of runaway electrons using dosimetry of hard x-ray radiations in Damavand tokamak

    NASA Astrophysics Data System (ADS)

    Rasouli, C.; Pourshahab, B.; Hosseini Pooya, S. M.; Orouji, T.; Rasouli, H.

    2014-05-01

    In this work several studies have been conducted on hard x-ray emissions of Damavand tokamak based on radiation dosimetry using the Thermoluminescence method. The goal was to understand interactions of runaway electrons with plasma particles, vessel wall, and plasma facing components. Total of 354 GR-200 (LiF:Mg,Cu,P) thermoluminescence dosimeter (TLD) crystals have been placed on 118 points - three TLDs per point - to map hard x-ray radiation doses on the exterior of the vacuum vessel. Results show two distinctive levels of x-ray radiations doses on the exterior of the vessel. The low-dose area on which measured dose is about 0.5 mSv/shot. In the low-dose area there is no particular component inside the vessel. On the contrary, on high-dose area of the vessel, x-ray radiations dose exceeds 30 mSv/shot. The high-dose area coincides with the position of limiters, magnetic probe ducts, and vacuum vessel intersections. Among the high-dose areas, the highest level of dose is measured in the position of the limiter, which could be due to its direct contact with the plasma column and with runaway electrons. Direct collisions of runaway electrons with the vessel wall and plasma facing components make a major contribution for production of hard x-ray photons in Damavand tokamak.

  10. Study of runaway electrons using dosimetry of hard x-ray radiations in Damavand tokamak

    SciTech Connect

    Rasouli, C.; Pourshahab, B.; Rasouli, H.; Hosseini Pooya, S. M.; Orouji, T.

    2014-05-15

    In this work several studies have been conducted on hard x-ray emissions of Damavand tokamak based on radiation dosimetry using the Thermoluminescence method. The goal was to understand interactions of runaway electrons with plasma particles, vessel wall, and plasma facing components. Total of 354 GR-200 (LiF:Mg,Cu,P) thermoluminescence dosimeter (TLD) crystals have been placed on 118 points – three TLDs per point – to map hard x-ray radiation doses on the exterior of the vacuum vessel. Results show two distinctive levels of x-ray radiations doses on the exterior of the vessel. The low-dose area on which measured dose is about 0.5 mSv/shot. In the low-dose area there is no particular component inside the vessel. On the contrary, on high-dose area of the vessel, x-ray radiations dose exceeds 30 mSv/shot. The high-dose area coincides with the position of limiters, magnetic probe ducts, and vacuum vessel intersections. Among the high-dose areas, the highest level of dose is measured in the position of the limiter, which could be due to its direct contact with the plasma column and with runaway electrons. Direct collisions of runaway electrons with the vessel wall and plasma facing components make a major contribution for production of hard x-ray photons in Damavand tokamak.

  11. Energy distributions exhibited during thermal runaway of commercial lithium ion batteries used for human spaceflight applications

    NASA Astrophysics Data System (ADS)

    Yayathi, Sandeep; Walker, William; Doughty, Daniel; Ardebili, Haleh

    2016-10-01

    Lithium ion (Li-ion) batteries provide low mass and energy dense solutions necessary for space exploration, but thermal related safety concerns impede the utilization of Li-ion technology for human applications. Experimental characterization of thermal runaway energy release with accelerated rate calorimetry supports safer thermal management systems. 'Standard' accelerated rate calorimetry setup provides means to measure the addition of energy exhibited through the body of a Li-ion cell. This study considers the total energy generated during thermal runaway as distributions between cell body and hot gases via inclusion of a unique secondary enclosure inside the calorimeter; this closed system not only contains the cell body and gaseous species, but also captures energy release associated with rapid heat transfer to the system unobserved by measurements taken on the cell body. Experiments include Boston Power Swing 5300, Samsung 18650-26F and MoliCel 18650-J Li-ion cells at varied states-of-charge. An inverse relationship between state-of-charge and onset temperature is observed. Energy contained in the cell body and gaseous species are successfully characterized; gaseous energy is minimal. Significant additional energy is measured with the heating of the secondary enclosure. Improved calorimeter apparatus including a secondary enclosure provides essential capability to measuring total energy release distributions during thermal runaway.

  12. EQ Lyn and V455 And: Contrasts in Post-Outburst Behavior

    NASA Astrophysics Data System (ADS)

    Szkody, Paula; Mukadam, A. S.; Gaensicke, B. T.

    2013-06-01

    Cataclysmic variables (CVs) that contain accreting, pulsating white dwarfs provide a unique means to study how cooling of the white dwarf affects the pulsation spectrum. In contrast to non-accreting white dwarfs which cool through evolution on timescales of millions of years, the white dwarfs in CVs are heated by infrequent dwarf nova outbursts and then cool on timescales of 3-5 years. Thus, following the cooling and pulsations is very feasible and allows a comparison of how the accretion (which alters the composition, temperature and rotation of the white dwarf) affects the interior of the star. We have followed the pulsation changes of EQ Lyn (SDSSJ070745+45) for 6 years following its outburst in October 2006 and of V455 And (HS2331+39) for 5 years after its September 2007 outburst. While the pulsations disappeared for the year after outburst in each system, the return to quiescent states were quite different in each object. At one year past outburst, EQ Lyn had returned to optical quiescence while the UV showed the white dwarf was still 2000K hotter than quiescence. Pulsations at precisely the same periods as quiescence returned by 3.3 yrs after outburst but they then disappeared the following year, to again return in 2012. The unchanged period combined with the quick return to quiescence imply little accretion happened during outburst with little effect on the white dwarf interior. However, the reason for the disappearance of the pulsations in 2011 is not understood. V455 And did not fully return to optical quiescence until 4 yrs after outburst, even though after 3 yrs it was only 600K above its quiescent temperature. The pulsations that were apparent near 340 sec at quiescence were shifted to shorter periods near 255 sec at 2 years past outburst and gradually lengthened to about 325 sec at the end of 2012. This shortening of the pulsation period at hotter temperatures is similar to what is observed in ZZ Ceti stars in their instability strip. Further cooling

  13. OH maser outburst in the W3 nebula

    NASA Astrophysics Data System (ADS)

    Gosachinskij, I. V.; Grenkov, S. A.; Ipatov, A. V.; Rakhimov, I. A.

    2016-07-01

    We report the results of three-year long observations of OH masers at 1665 MHz in the W3(OH) source carried out with the 32-m antenna of Svetloe Radio Astronomical Observatory.We found that the strongest activity during the period from December 2011 through March 2012 was exhibited by the region at radial velocity -46.2km s-1. The region showed no activity in the ensuing time. The most striking outburst was the event that occurred on January 23, 2013 at UT 03:27. At that time the flux of the region increased by a factor of seven in 90 s, and then decreased down to the initial level. Such a time scale yields the upper estimate of 0.18 AU (2.7 × 1012 cm) for the linear size of the maser dot. In 2013-2014 intensity variations were found the -47.6 and -45.1km s-1 components with time scales on the order of 10 hours and anticorrelated behavior of the left- and right-hand polarization fluxes. This is the first time that such phenomena have been found in the behavior of OH maser emission, and they cannot be explained by any existing models of maser variability.

  14. Evidence for an intense solar outburst in prehistory

    NASA Astrophysics Data System (ADS)

    Peratt, A. L.; Yao, W. F.

    2008-04-01

    A past intense solar outburst and its effect on Earth was proposed by Gold [3] who based his hypotheses on astronomical and geophysical evidence. The discovery that objects from Neolithic or Early Bronze Ages carry patterns of high-current Z-pinches provides insight into the origin and meaning of these ancient symbols produced by mankind. A comparison of graphical and radiation data from high-current Z-pinches to petroglyphs and megaliths is made [1]. These correspond to mankind's visual observations of ancient aurora if the solar wind had increased at times between one and two orders of magnitude, millennia ago [3]. Reference [2] focused on the source of light and its temporal change from a current-increasing Z-Pinch or dense plasma focus aurora. The orientation and field-of-view (FOV) as surveyed and contributed from 139 countries, the latest data coming from a 300 km survey along the Orinoco River Basin in Venezuela, is given. A reconstruction of the auroral form is shown based on existent geophysical evidence. Shown are relativistic electron flows inward at Earth's south polar axis and hypervelocity proton impacts around the north polar axis. 1. A. L. Peratt, Trans. Plasma Sci., 31, 1192, 2003. 2. A. L. Peratt, Trans. Plasma Sci., 35, 778, 2007. 3. T. Gold, Pontificiae Academiae Scientiarvm Scripta Varia 25, 159, 1962.

  15. Cooling of the white dwarf in U Geminorum between outbursts

    NASA Technical Reports Server (NTRS)

    Long, Knox S.; Sion, Edward M.; Huang, Min; Szkody, Paula

    1994-01-01

    We have obtained far-ultraviolet (1150-1610 A) spectra of U Gem with the Faint Object Spectrograph on the Hubble Space Telescope approximately 13 and 70 days after the end of a normal dwarf nova outburst of the system. Both spectra appear dominated by the White Dwarf (WD) in U Gem. At 1400 A, the flux from U Gem declined approximately 28% between the two observations. Detailed comparison of the spectra with solar abundance WD models suggest that average surface temperature of the WD surface cooled from approximately 39,400 K to approximately 32,100 K between the two observations. The main features which are not fitted well by WD models are absorption due to N V lambda lambda-1239, 1243 and emission at Lyman-alpha. These observations provide unambiguous confirmation that the WD in U Gem cools during quiescence, as was suggested by analyses of far-ultraviolet spectra obtained with International Ultraviolet Explorer (IUE) and Hopkins Ultraviolet Telescope (HUT).

  16. {ital EUVE} observations of U Geminorum in outburst

    SciTech Connect

    Long, K.S.; Mauche, C.W.; Raymond, J.C.; Szkody, P.; Mattei, J.A.

    1996-10-01

    We have observed U Gem during the peak and declining phases of a wide outburst in 1993 December with the {ital Extreme} {ital Ultraviolet} {ital Explorer} ({ital EUVE}) satellite. At peak, U Gem was one of the brightest EUV sources in the sky. The spectrum of the source is complex. Fitted to a blackbody spectrum, the apparent temperature at peak is {approximately}140,000 K, the luminosity is {approximately}4{times}10{sup 34}({ital D}/90 pc){sup 2} ergss{sup {minus}1}, and the minimum size of the emitting region is comparable to that of the white dwarf (WD). If the EUV emission arises primarily from the boundary layer, then the boundary layer luminosity in U Gem is comparable to the disk luminosity. The EUV source is partially eclipsed at orbital phases 0.6{endash}0.8. The eclipse spectrum, which we associate with a wind emerging from the vicinity of the white dwarf, is dominated by emission features. The identification of these emission features with transitions expected in a relatively cool ({ital T}{lt}160,000 K), photoionized plasma helps to resolve a controversy concerning the ionization state of winds of dwarf novae. The EUV lines arise from the dominant ionization states of the wind, and their strengths suggest that the wind mass-loss rate, at least in U Gem, is a substantial fraction of the WD accretion rate. {copyright} {ital 1996 The American Astronomical Society.}

  17. The 2014 KCG Meteor Outburst: Clues to a Parent Body

    NASA Technical Reports Server (NTRS)

    Moorhead, Althea V.; Brown, Peter G.; Spurny, Pavel; Cooke, William J.

    2015-01-01

    The Kappa Cygnid (KCG) meteor shower exhibited unusually high activity in 2014, producing ten times the typical number of meteors. The shower was detected in both radar and optical systems and meteoroids associated with the outburst spanned at least five decades in mass. In total, the Canadian Meteor Orbit Radar, European Network, and NASA All Sky and Southern Ontario Meteor Network produced thousands of KCG meteor trajectories. Using these data, we have undertaken a new and improved characterization of the dynamics of this little-studied, variable meteor shower. The Cygnids have a di use radiant and a significant spread in orbital characteristics, with multiple resonances appearing to play a role in the shower dynamics. We conducted a new search for parent bodies and found that several known asteroids are orbitally similar to the KCGs. N-body simulations show that the two best parent body candidates readily transfer meteoroids to the Earth in recent centuries, but neither produces an exact match to the KCG radiant, velocity, and solar longitude. We nevertheless identify asteroid 2001 MG1 as a promising parent body candidate.

  18. The Long-term Post-outburst Spin Down and Flux Relaxation of Magnetar Swift J1822.3-1606

    NASA Astrophysics Data System (ADS)

    Scholz, P.; Kaspi, V. M.; Cumming, A.

    2014-05-01

    The magnetar Swift J1822.3-1606 entered an outburst phase in 2011 July. Previous X-ray studies of its post-outburst rotational evolution yielded inconsistent measurements of the spin-inferred magnetic field. Here we present the timing behavior and flux relaxation from over two years of Swift, RXTE, and Chandra observations following the outburst. We find that the ambiguity in previous timing solutions was due to enhanced spin down that resembles an exponential recovery following a glitch at the outburst onset. After fitting out the effects of the recovery, we measure a long-term spin-down rate of \\dot{\

  19. Two giant outbursts of V0332+53 observed with INTEGRAL

    NASA Astrophysics Data System (ADS)

    Ferrigno, Carlo; Ducci, Lorenzo; Bozzo, Enrico; Kretschmar, Peter; Kühnel, Matthias; Malacaria, Christian; Pottschmidt, Katja; Santangelo, Andrea; Savchenko, Volodymyr; Wilms, Jörn

    2016-10-01

    Context. In July 2015, the high-mass X-ray binary V0332+53 underwent a giant outburst, a decade after the previous one. V0332+53 hosts a strongly magnetized neutron star. During the 2004-2005 outburst, an anti-correlation between the centroid energy of its fundamental cyclotron resonance scattering features (CRSFs) and the X-ray luminosity was observed. Aims: The long (≈100 d) and bright (Lx ≈ 1038 erg s-1) 2015 outburst provided the opportunity to study the unique properties of the fundamental CRSF during another outburst and to study its dependence on the X-ray luminosity. Methods: The source was observed by the INTEGRAL satellite for ~330 ks. We exploit the spectral resolution at high energies of the SPectrometer on INTEGRAL (SPI) and the Joint European X-ray Monitors to characterize its spectral properties, focusing in particular on the CRSF-luminosity dependence. We complement the data of the 2015 outburst with those collected by SPI in 2004-2005, which have so far been left unpublished. Results: We find a highly significant anti-correlation of the centroid energy of the fundamental CRSF and the 3-100 keV luminosity of E1 ∝ -0.095(8)L37 keV. This trend is observed for both outbursts. We confirm the correlation between the width of the fundamental CRSF and the X-ray luminosity previously found in the JEM-X and IBIS dataset of the 2004-2005 outburst. By exploiting the RXTE/ASM and Swift/BAT monitoring data, we also report on the detection of a ~34 d modulation superimposed on the mean profiles and roughly consistent with the orbital period of the pulsar. We discuss possible interpretations of such variability.

  20. Investigation of relationship between barometric pressure and coal and gas outburst events in underground coal mining

    NASA Astrophysics Data System (ADS)

    Yönet, Sinem; Esen, Olgun; Fişne, Abdullah

    2015-04-01

    Coal and gas outburst is a serious risk which occurs during the mine production. This accident results both ejection of high volumes of gas and high amount of coal into the mine production area, and death of mining workers for many years in Turkey. Outburst of gas, coal and rock can be defined as sudden release of coal and rock accompanied by large quantities of gas into the working face or other mine workings. It is a phenomena that influenced by geological structure such as folds, joints of rocks or coal seams, is also still investigated for many years. Zonguldak Coal Basin is the main part of the Upper Carboniferous bituminous coal basin of Turkey. Much of the bituminous coal mining has thus been concentrated in the Zonguldak Basin which is located on the Black Sea coast. The coal field has been disturbed by tectonic activity, first by Hercynian and later by Alpine orogenesis resulting in folding and faulting of strata. This formation has a complex structural geology which consists mostly fault zones, anticlinal and syncline strata and because of this a large amount of methane gases are adsorbed or accumulated in strata or in coal fractures, pores and micropores. There are 5 Collieries exists in Zonguldak Coalfield and coal and gas outbursts were occurred only in two collieries such as Karadon and Kozlu Mines. In addition at a number of 90 coal and gas outburst events were experienced in these collieries. Based on the analysis of data, oscillation at barometric pressure and temperature values at the location of Kozlu and Karadon Mines were seen when coal and gas outburst events were occurred. In this study, barometric pressure and temperature changes are investigated at Kozlu and Karadon Mines. Also the relationship between the variation at temperature with barometric pressure and coal and gas outbursts are evaluated. It can be understand that this investigation depends to field observations and macroscopic considerations and on the purpose of predicting the