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Sample records for bursts blue horizontal

  1. Blue Horizontal Branch Stars in M92

    CERN Document Server

    Cohen, J G

    1997-01-01

    We have analyzed high dispersion and high precision spectra of 5 blue horizontal branch stars in the globular cluster M92 to establish that the projected rotational velocity for these stars ranges from 15 to 40 \\kms. This is larger than that expected based on the rotation of their main sequence progenitors, the spin down of rotation with age, and the conservation of angular momentum. Possible explanations include a rapidly rotating stellar core. An abundance analysis of these spectra of these blue HB stars in M92 yields the same results as have been obtained from the giants in this cluster. There is a hint of a trend of higher abundance as the projected surface rotational velocity increases, which could be chance and requires confirmation.

  2. The Chemical Compositions of Non-Variable Red and Blue Field Horizontal Branch Stars

    CERN Document Server

    For, Bi-Qing

    2010-01-01

    We present a new detailed abundance study of field red horizontal branch (RHB) and blue horizontal branch (BHB) non-variable stars. High resolution and high S/N echelle spectra of 11 RHB and 12 BHB were obtained with the McDonald 2.7 m telescope, and the RHB sample was augmented by reanalysis of spectra of 25 stars from a recent survey. We derived stellar atmospheric parameters based on spectroscopic constraints, and computed relative abundance ratios for 24 species of 19 elements. The species include Si II and Ca II, which have not been previously studied in RHB and BHB (Teff ~ [Fe/H] >~ -2.5. This yielded effective temperatures estimates of 5900K and 7400 K for the red and blue edges of the RR Lyrae instability strip.

  3. Spectroscopy of blue horizontal branch stars in NGC 6656 (M22)

    CERN Document Server

    Salgado, C; Villanova, S; Geisler, D; Catelan, M

    2013-01-01

    Recent investigations revealed very peculiar properties of blue horizontal branch (HB) stars in \\omega Centauri, which show anomalously low surface gravity and mass compared to other clusters and to theoretical models. \\omega Centauri, however, is a very unusual object, hosting a complex mix of multiple stellar populations with different metallicity and chemical abundances. We measured the fundamental parameters (temperature, gravity, and surface helium abundance) of a sample of 71 blue HB stars in M22, with the aim of clarifying if the peculiar results found in \\omega Cen are unique to this cluster. M22 also hosts multiple sub-populations of stars with a spread in metallicity, analogous to \\omega Cen. The stellar parameters were measured on low-resolution spectra fitting the Balmer and helium lines with a grid of synthetic spectra. From these parameters, the mass and reddening were estimated. Our results on the gravities and masses agree well with theoretical expectations, matching the previous measurements ...

  4. Striking Photospheric Abundance Anomalies in Blue Horizontal-Branch Stars in Globular Cluster M13

    CERN Document Server

    Behr, B B; McCarthy, J K; Djorgovski, S G; Behr, Bradford B.; Cohen, Judith G.; Carthy, James K. Mc

    1999-01-01

    High-resolution optical spectra of thirteen blue horizontal-branch (BHB) stars in the globular cluster M13 show enormous deviations in element abundances from the expected cluster metallicity. In the hotter stars (T_eff > 12000 K), helium is depleted by factors of 10 to 100 below solar, while iron is enhanced to three times the solar abundance, two orders of magnitude above the canonical metallicity [Fe/H] ~= -1.5 dex for this globular cluster. Nitrogen, phosphorus, and chromium exhibit even more pronounced enhancements, and other metals are also mildly overabundant, with the exception of magnesium, which stays very near the expected cluster metallicity. These photospheric anomalies are most likely due to diffusion --- gravitational settling of helium, and radiative levitation of the other elements --- in the stable radiative atmospheres of these hot stars. The effects of these mechanisms may have some impact on the photometric morphology of the cluster's horizontal branch and on estimates of its age and dist...

  5. THE ULTRA-LONG GAMMA-RAY BURST 111209A: THE COLLAPSE OF A BLUE SUPERGIANT?

    Energy Technology Data Exchange (ETDEWEB)

    Gendre, B.; Cutini, S.; D' Elia, V. [ASI Science Data Center, via Galileo Galilei, I-00044 Frascati (Italy); Stratta, G. [Osservatorio Astronomico di Roma, OAR-INAF, via Frascati 33, I-00040, Monte Porzio Catone (Italy); Atteia, J. L.; Klotz, A. [Universite de Toulouse, UPS-OMP, IRAP, Toulouse (France); Basa, S. [Aix Marseille Universite, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France); Boeer, M. [CNRS, ARTEMIS, UMR 7250, Boulevard de l' Observatoire, BP 4229, F-06304 Nice Cedex 4 (France); Coward, D. M.; Howell, E. J [University of Western Australia, School of Physics, University of Western Australia, Crawley WA 6009 (Australia); Piro, L., E-mail: bruce.gendre@gmail.com [Istituto di Astrofisica e Planetologia Spaziali di Roma, INAF, via fosso del cavaliere 100, I-00133 Roma (Italy)

    2013-03-20

    We present optical, X-ray and gamma-ray observations of GRB 111209A, observed at a redshift of z = 0.677. We show that this event was active in its prompt phase for about 25000 s, making it the longest burst ever observed. This rare event could have been detected up to z {approx} 1.4 in gamma-rays. Compared to other long gamma-ray bursts (GRBs), GRB 111209A is a clear outlier in the energy-fluence and duration plane. The high-energy prompt emission shows no sign of a strong blackbody component, the signature of a tidal disruption event, or a supernova shock breakout. Given the extreme longevity of this event, and lack of any significant observed supernova signature, we propose that GRB 111209A resulted from the core-collapse of a low-metallicity blue supergiant star. This scenario is favored because of the necessity to supply enough mass to the central engine over a duration of thousands of seconds. Hence, we suggest that GRB 111209A could have more in common with population III stellar explosions, rather than those associated with normal long GRBs.

  6. The ultra-long Gamma-Ray Burst 111209A: the collapse of a blue supergiant?

    CERN Document Server

    Gendre, B; Atteia, J L; Basa, S; Boër, M; Coward, D M; Cutini, S; D'Elia, V; Howell, E; Klotz, A; Piro, L

    2012-01-01

    We present optical, X-ray and gamma-ray observations of GRB 111209A, at a redshift of z = 0.677. We show that this event was active in its prompt phase for about 25000 seconds, making it the longest burst ever observed. This rare event could have been detected up to z ~ 1.4. Compared to other long GRBs, GRB 111209A is a clear outlier in the energy-fluence and duration plane. The high-energy prompt emission shows no sign of a strong black body component, as expected if the event was caused by a tidal disruption event or a supernova shock breakout. Given the extreme longevity of this event, and a lack of a supernova signature, we propose that GRB 111209A is a relatively rare stellar collapse of a low metallicity blue super giant star. Only this progenitor can supply mass to the central engine over a duration of thousands of seconds. Hence, GRB 111209A could have more in common with population III stellar explosions, rather than normal long gamma ray bursts.

  7. Chemical Abundances and Rotation Velocities of Blue Horizontal-Branch Stars in Six Globular Clusters

    CERN Document Server

    Behr, B B

    2003-01-01

    High-resolution spectroscopic measurements of blue horizontal-branch stars in six metal-poor globular clusters -- M3, M13, M15, M68, M92, and NGC 288 -- reveal remarkable variations in photospheric composition and rotation velocity as a function of a star's position along the horizontal branch. For the cooler stars (Teff < 11200 K), the derived abundances are in good agreement with the canonical cluster metallicities, and we find a wide range of v sin i rotation velocities, some as high as 40 km/s. In the hotter stars, however, most metal species are strongly enhanced, by as much as 3 dex, relative to the expected cluster metallicity, while helium is depleted by 2 dex or more. In addition, the hot stars all rotate slowly, with v sin i < 8 km/s. The anomalous abundances appear to be due to atomic diffusion mechanisms -- gravitational settling of helium, and radiative levitation of metals -- in the non-convective atmospheres of these hot stars. We discuss the influence of these photospheric metal enhancem...

  8. Guided Growth of Horizontal ZnSe Nanowires and their Integration into High-Performance Blue-UV Photodetectors.

    Science.gov (United States)

    Oksenberg, Eitan; Popovitz-Biro, Ronit; Rechav, Katya; Joselevich, Ernesto

    2015-07-15

    Perfectly aligned horizontal ZnSe nano-wires are obtained by guided growth, and easily integrated into high-performance blue-UV photodetectors. Their crystal phase and crystallographic orientation are controlled by the epitaxial relations with six different sapphire planes. Guided growth paves the way for the large-scale integration of nanowires into optoelectronic devices. PMID:26011601

  9. Chronography of the Milky Way's Halo System with Field Blue Horizontal-Branch Stars

    CERN Document Server

    Santucci, R M; Placco, V M; Carollo, D; Rossi, S; Lee, Y S; Denissenkov, P; Tumlinson, J; Tissera, P B

    2015-01-01

    In a pioneering effort, Preston et al. reported that the colors of blue horizontal-branch (BHB) stars in the halo of the Galaxy shift with distance, from regions near the Galactic center to about 12 kpc away, and interpreted this as a correlated variation in the ages of halo stars, from older to younger, spanning a range of a few Gyrs. We have applied this approach to a sample of some 4700 spectroscopically confirmed BHB stars selected from the Sloan Digital Sky Survey to produce the first "chronographic map" of the halo of the Galaxy. We demonstrate that the mean de-reddened g$-$r color, , increases outward in the Galaxy from $-$0.22 to $-$0.08 (over a color window spanning [$-$0.3:0.0]) from regions close to the Galactic center to ~40 kpc, independent of the metallicity of the stars. Models of the expected shift in the color of the field BHB stars based on modern stellar evolutionary codes confirm that this color gradient can be associated with an age difference of roughly 2-2.5 Gyrs, with the oldest stars ...

  10. Vertical abundance stratification in the blue horizontal branch star HD135485

    CERN Document Server

    Khalack, V R; Bohlender, D A; Wade, G A; Behr, B B

    2007-01-01

    It is commonly believed that the observed overabundances of many chemical species relative to the expected cluster metallicity in blue horizontal branch (BHB) stars appear as a result of atomic diffusion in the photosphere. The slow rotation of BHB stars (with T_eff > 11,500K), typically v sin{i} < 10 km/s, is consistent with this idea. In this work we search for observational evidence of vertical chemical stratification in the atmosphere of HD135485. If this evidence exists, it will demonstrate the importance of atomic diffusion processes in the atmospheres of BHB stars. We undertake an extensive abundance stratification analysis of the atmosphere of HD135485, based on recently acquired high resolution and S/N CFHT ESPaDOnS spectra and a McDonald-CE spectrum. Our numerical simulations show that nitrogen and sulfur reveal signatures of vertical abundance stratification in the stellar atmosphere. It appears that the abundances of these elements increase toward the upper atmosphere. This fact cannot be expla...

  11. Characterizing stellar halo populations II: The age gradient in blue horizontal-branch stars

    CERN Document Server

    Das, Payel; Binney, James

    2016-01-01

    The distribution of Milky Way halo blue horizontal-branch (BHB) stars is examined using action-based extended distribution functions (EDFs) that describe the locations of stars in phase space, metallicity, and age. The parameters of the EDFs are fitted using stars observed in the Sloan Extension for Galactic Understanding and Exploration-II (SEGUE-II) survey that trace the phase-space kinematics and chemistry out to ~70 kpc. A maximum a posteriori probability (MAP) estimate method and a Markov Chain Monte Carlo method are applied, taking into account the selection function in positions, distance, and metallicity for the survey. The best-fit EDF declines with actions less steeply at actions characteristic of the inner halo than at the larger actions characteristic of the outer halo, and older ages are found at smaller actions than at larger actions. In real space, the radial density profile steepens smoothly from -2 at ~2 kpc to -4 in the outer halo, with an axis ratio ~0.7 throughout. There is no indication f...

  12. Vertical stratification of iron in atmospheres of blue horizontal-branch stars

    CERN Document Server

    Khalack, V; Behr, B B

    2010-01-01

    The aim of this study is to search for observational evidence of vertical iron stratification in the atmosphere of fourteen blue horizontal-branch (BHB) stars. We have found from our numerical simulations that five BHB stars: B22, B186 in the globular cluster NGC 288, WF2-820, WF2-2692 in M13 and B203 in M15 show clear signatures of the vertical stratification of iron whose abundance increases toward the lower atmosphere. Two other BHB stars (B334 in M15 and B176 in M92) also show possible iron stratification in their atmosphere. A dependence of the slope of iron stratification on the effective temperature was also discovered. It is found that the vertical stratification of iron is strongest in BHB stars with Teff around 11,500K. The slope of iron abundance decreases as Teff increases and becomes negligible for the BHB stars with Teff= 14,000K. These results support the hypothesis regarding the efficiency of atomic diffusion in the stellar atmospheres of BHB stars with Teff > 11,500K.

  13. Optical Guiding of Trapped Atoms by a Blue-Detuned Hollow Laser Beam in the Horizontal Direction

    Institute of Scientific and Technical Information of China (English)

    JIANG Kai-Jun; LI Ke; WANG Jin; ZHAN Ming-Sheng

    2005-01-01

    @@ Optical guiding of 85 Rb atoms in a magneto-optical trap (MOT) by a blue-detuned horizontal hollow laser beam is demonstrated experimentally. The guiding efficiency and the velocity distribution of the guided atoms are found to have strong dependence on the detuning of the guiding laser. In particular, the optimum guiding occurs when the blue detuning of the hollow laser beam is approximately equal to the hyperfine structure splitting of the 85Rb ground states, in good agreement with the theoretical analysis based on a three-level model.

  14. Characterizing stellar halo populations II: The age gradient in blue horizontal-branch stars

    Science.gov (United States)

    Das, Payel; Williams, Angus; Binney, James

    2016-08-01

    The distribution of Milky Way halo blue horizontal-branch (BHB) stars is examined using action-based extended distribution functions (EDFs) that describe the locations of stars in phase space, metallicity, and age. The parameters of the EDFs are fitted using stars observed in the Sloan Extension for Galactic Understanding and Exploration-II (SEGUE-II) survey that trace the phase-space kinematics and chemistry out to ˜70 kpc. A maximum a posteriori probability (MAP) estimate method and a Markov Chain Monte Carlo method are applied, taking into account the selection function in positions, distance, and metallicity for the survey. The best-fit EDF declines with actions less steeply at actions characteristic of the inner halo than at the larger actions characteristic of the outer halo, and older ages are found at smaller actions than at larger actions. In real space, the radial density profile steepens smoothly from -2 at ˜2 kpc to -4 in the outer halo, with an axis ratio ˜0.7 throughout. There is no indication for rotation in the BHBs, although this is highly uncertain. A moderate level of radial anisotropy is detected, with βs varying from isotropic to between ˜0.1 and ˜0.3 in the outer halo depending on latitude. The BHB data are consistent with an age gradient of -0.03 Gyr kpc-1, with some uncertainty in the distribution of the larger ages. These results are consistent with a scenario in which older, larger systems contribute to the inner halo, whilst the outer halo is primarily comprised of younger, smaller systems.

  15. Highly efficient non-doped deep blue fluorescent emitters with horizontal emitting dipoles using interconnecting units between chromophores.

    Science.gov (United States)

    Kim, Kwon-Hyeon; Baek, Jang Yeol; Cheon, Chan Woo; Moon, Chang-Ki; Sim, Bomi; Choi, Myeong Yong; Kim, Jang-Joo; Kim, Yun-Hi

    2016-09-21

    New deep blue fluorescent emitters composed of anthracene as an electron rich unit, a diphenyltriazine as a strong electron acceptor unit, and phenyl or xylene as interconnecting units were synthesised. The interconnecting unit between chromophores increased the singlet transition energy and the ratio of horizontal emitting dipoles. As a result, a non-doped blue fluorescent organic light-emitting diode (OLED) using a new emitter was demonstrated, with an external quantum efficiency (EQE) of 6.6% and Commision Internationale de l'Eclairage (CIE) colour coordinates of (0.145, 0.068). This device performance has been the highest EQE observed in deep blue non-doped OLEDs with CIE coordinates less than (0.145, 0.068) to date. PMID:27524501

  16. Horizontal

    Institute of Scientific and Technical Information of China (English)

    ZHONG; Chunping

    2005-01-01

    [1]Wu, H., Bochner technique in differential geometry, Advance in Math. (in Chinese), 1981, 10(1): 57-76.[2]Morrow, J., Kodaira, K., Complex Manifolds, New York: Holt, Rinehart & Winston, 1971.[3]Abate, M., Aikou, T., Patrizio, G., Preface for Complex Finsler Geometry, Cont. Math., Vol. 196, Providence,RI: Amer. Math. Soc., 1996, 97-100.[4]Abate, M., Patrizio, G., Finsler Metrics-A global approach with applications to geometric function theory,Lecture Notes in Mathematics, Vol. 1591, Bedin: Springer-Verlag, 1994.[5]Antonelli, P. L., Lackey, B.(eds.), The Theory of Finslerian Laplacians and Applications, MAIA 459, Dordrecht:Kluwer Academic Publishers, 1998.[6]Bao, D., Lackey, B., A Hodge decomposition theorem for Finsler spaces, C. R. Acad. Sci. Paris, t. 323, Serie 1,1996, 51-56.[7]Munteanu, O., Weitzenbock formulas for horizontal and vertical Laplacians, Houston Journal of Mathematics,2003, 29(4): 889-900.[8]Faran, J. J., The equivalence problem for complex Finsler Hamiltonians, Cont. Math.,Vol. 196, Providence, RI:Amer. Math. Soc., 1996, 133-144.[9]Kobayashi, S., Complex Finsler vector bundles, Cont. Math., Vol. 196, Providence, RI: Amer. Math. Soc.,1996,145-153.[10]Aikou, T., On complex Finsler manifolds, Rep. Fac. Sci. Kagoshima Univ. (Math. Phys. & Chem.), 1991, 24:9-25.

  17. Blue Horizontal-Branch Stars The "Jump" in Strömgren u, Low Gravities, and Radiative Levitation of Metals

    CERN Document Server

    Grundahl, F; Landsman, W B; Stetson, P B; Andersen, M I

    1999-01-01

    We study the ``jump'' in the blue horizontal--branch (BHB) distribution first detected by Grundahl et al. (1998) in the Galactic globular cluster (GC) M13. On the basis of Stromgren photometry for a sample of fourteen GC's we show that: 1) The jump is best characterized as a systematic shift, on a (u, u-y) color-magnitude diagram, from canonical zero-age HB (ZAHB) models, in the sense that the stars appear brighter and/or hotter than the models; 2) the jump is a ubiquitous phenomenon, ocurring over the temperature range 11,500 < Teff < 20,000K; 3) An analogous feature is present in (log g, log Teff) diagrams -- indicating a common physical origin for the two phenomena; 4) The physical mechanism responsible for the jump phenomenon is most likely radiative levitation of iron and other

  18. Mapping the Galactic Halo with blue horizontal branch stars from the 2dF quasar redshift survey

    CERN Document Server

    De Propris, Roberto; Mares, Peter J; CTIO,; University, Cornell

    2010-01-01

    We use 666 blue horizontal branch (BHB) stars from the 2Qz redshift survey to map the Galactic halo in four dimensions (position, distance and velocity). We find that the halo extends to at least 100 kpc in Galactocentric distance, and obeys a single power-law density profile of index ~-2.5 in two different directions separated by 150 degrees on the sky. This suggests that the halo is spherical. Our map shows no large kinematically coherent structures (streams, clouds or plumes) and appears homogeneous. However, we find that at least 20% of the stars in the halo reside in substructures and that these substructures are dynamically young. The velocity dispersion profile of the halo appears to increase towards large radii while the stellar velocity distribution is non Gaussian beyond 60 kpc. We argue that the outer halo consists of a multitude of low luminosity overlapping tidal streams from recently accreted objects.

  19. The Century Survey Galactic Halo Project II: Global Properties and the Luminosity Function of Field Blue Horizontal Branch Stars

    CERN Document Server

    Brown, W R; Kenyon, S J; Kurtz, M J; Allende-Prieto, C; Beers, T C; Wilhelm, R; Brown, Warren R.; Geller, Margaret J.; Kenyon, Scott J.; Kurtz, Michael J.; Prieto, Carlos Allende; Beers, Timothy C.; Wilhelm, Ronald

    2005-01-01

    We discuss a 175 deg^2 spectroscopic survey for blue horizontal branch (BHB) stars in the Galactic halo. We use the Two Micron All Sky Survey (2MASS) and the Sloan Digital Sky Survey (SDSS) to select BHB candidates, and find that the 2MASS and SDSS color-selection is 38% and 50% efficient, respectively, for BHB stars. Our samples include one likely run-away B7 star 6 kpc below the Galactic plane. The global properties of the BHB samples are consistent with membership in the halo population: the median metallicity is [Fe/H]=-1.7, the velocity dispersion is 108 km/s, and the mean Galactic rotation of the BHB stars 3<|z|<15 kpc is -4 +- 30 km/s. We discuss the theoretical basis of the Preston, Shectman & Beers M_V-color relation for BHB stars, and conclude that intrinsic shape of the BHB M_V-color relation results from the physics of stars on the horizontal branch. We calculate the luminosity function for the field BHB star samples using the Efstathiou, Ellis, & Peterson maximum-likelihood method w...

  20. KINEMATICS OF THE STELLAR HALO AND THE MASS DISTRIBUTION OF THE MILKY WAY USING BLUE HORIZONTAL BRANCH STARS

    International Nuclear Information System (INIS)

    Here, we present a kinematic study of the Galactic halo out to a radius of ∼60 kpc, using 4664 blue horizontal branch stars selected from the SDSS/SEGUE survey to determine key dynamical properties. Using a maximum likelihood analysis, we determine the velocity dispersion profiles in spherical coordinates (σr, σθ, σφ) and the anisotropy profile (β). The radial velocity dispersion profile (σr) is measured out to a galactocentric radius of r ∼ 60 kpc, but due to the lack of proper-motion information, σθ, σφ, and β could only be derived directly out to r ∼ 25 kpc. From a starting value of β ≈ 0.5 in the inner parts (9 circ) of the Galaxy out to r ∼ 25 kpc. The mass of the Galaxy within r ∼11 M☉, and with a three-component fit to vcirc(r), we determine the virial mass of the Milky Way dark matter halo to be Mvir = 0.9+0.4–0.3 × 1012 M☉ (Rvir = 249+34–31 kpc).

  1. KINEMATICS OF THE STELLAR HALO AND THE MASS DISTRIBUTION OF THE MILKY WAY USING BLUE HORIZONTAL BRANCH STARS

    Energy Technology Data Exchange (ETDEWEB)

    Kafle, Prajwal R.; Sharma, Sanjib; Lewis, Geraint F.; Bland-Hawthorn, Joss, E-mail: p.kafle@physics.usyd.edu.au [Sydney Institute for Astronomy, School of Physics, A28, University of Sydney, NSW 2006 (Australia)

    2012-12-20

    Here, we present a kinematic study of the Galactic halo out to a radius of {approx}60 kpc, using 4664 blue horizontal branch stars selected from the SDSS/SEGUE survey to determine key dynamical properties. Using a maximum likelihood analysis, we determine the velocity dispersion profiles in spherical coordinates ({sigma}{sub r}, {sigma}{sub {theta}}, {sigma}{sub {phi}}) and the anisotropy profile ({beta}). The radial velocity dispersion profile ({sigma}{sub r}) is measured out to a galactocentric radius of r {approx} 60 kpc, but due to the lack of proper-motion information, {sigma}{sub {theta}}, {sigma}{sub {phi}}, and {beta} could only be derived directly out to r {approx} 25 kpc. From a starting value of {beta} Almost-Equal-To 0.5 in the inner parts (9 < r/kpc < 12), the profile falls sharply in the range r Almost-Equal-To 13-18 kpc, with a minimum value of {beta} = -1.2 at r = 17 kpc, rising sharply at larger radius. In the outer parts, in the range 25 < r/kpc < 56, we predict the profile to be roughly constant with a value of {beta} Almost-Equal-To 0.5. The newly discovered kinematic anomalies are shown not to arise from halo substructures. We also studied the anisotropy profile of simulated stellar halos formed purely by accretion and found that they cannot reproduce the sharp dip seen in the data. From the Jeans equation, we compute the stellar rotation curve (v{sub circ}) of the Galaxy out to r {approx} 25 kpc. The mass of the Galaxy within r {approx}< 25 kpc is determined to be 2.1 Multiplication-Sign 10{sup 11} M{sub Sun }, and with a three-component fit to v{sub circ}(r), we determine the virial mass of the Milky Way dark matter halo to be M{sub vir} = 0.9{sup +0.4}{sub -0.3} Multiplication-Sign 10{sup 12} M{sub Sun} (R{sub vir} = 249{sup +34}{sub -31} kpc).

  2. Are Ultra-long Gamma-Ray Bursts Caused by Blue Supergiant Collapsars, Newborn Magnetars, or White Dwarf Tidal Disruption Events?

    CERN Document Server

    Ioka, Kunihito; Piran, Tsvi

    2016-01-01

    Ultra-long gamma-ray bursts (ulGRBs) are a new population of GRBs with an extreme duration $\\sim 10^{4}$ s. Leading candidates for their origin are blue supergiant Collapsars, magnetars, and white dwarf tidal disruption events (WD-TDEs) by massive black holes (BHs). Recent observations of supernova-like (SN-like) bumps associated with ulGRBs challenged both the WD-TDE and the blue supergiant models because of the detection of SNe and the absence of hydrogen lines, respectively. We propose that WD-TDEs can accommodate the observed SN-like bumps if the fallback WD matter releases energy into the unbound WD ejecta. The observed ejecta energy, luminosity, and velocity are explained by the gravitational energy, Eddington luminosity, and escape velocity of the formed accretion disk, respectively. We also show that the observed X-rays can ionize the ejecta, eliminating lines. The SN-like light curves (SN 2011kl) for the ulGRB 111209A are consistent with all three models, although a magnetar model is unnatural in whi...

  3. Statistical Properties of Blue Horizontal Branch Stars in the Spheroid: Detection of a Moving Group approximately 50 kpc from the Sun

    CERN Document Server

    Harrigan, Matthew J; Newberg, Lee A; Yanny, Brian; Beers, Timothy C; Lee, Young Sun; Fiorentin, Paola Re

    2010-01-01

    A new moving group comprising at least four Blue Horizontal Branch (BHB) stars is identified at (l,b) = (65 deg, 48 deg). The horizontal branch at g0=18.9 magnitude implies a distance of 50 kpc from the Sun. The heliocentric radial velocity is RV = -157 +/- 4 km/s, corresponding to V(gsr) = -10 km/s; the dispersion in line-of-sight velocity is consistent with the instrumental errors for these stars. The mean metallicity of the moving group is [Fe/H] approximately -2.4, which is significantly more metal poor than the stellar spheroid. We estimate that the BHB stars in the outer halo have a mean metallicity of [Fe/H] = -2.0, with a wide scatter and a distribution that does not change much as a function of distance from the Sun. We explore the systematics of SDSS DR7 surface gravity metallicity determinations for faint BHB stars, and present a technique for estimating the significance of clumps discovered in multidimensional data. This moving group cannot be distinguished in density, and highlights the need to c...

  4. Blue Supergiant Model for Ultra-Long Gamma-Ray Burst with Superluminous-Supernova-Like Bump

    CERN Document Server

    Nakauchi, Daisuke; Suwa, Yudai; Nakamura, Takashi

    2013-01-01

    Long GRBs (LGRBs) have typical duration of $\\sim 30\\ {\\rm s}$ and some of them are associated with hypernovae, like Type Ic SN 1998bw. Wolf-Rayet stars are the most plausible LGRB progenitors, since the free-fall time of the envelope is consistent with the duration, and the natural outcome of the progenitor is a Type Ic SN. While a new population of ultra-long GRBs (ULGRBs), GRB 111209A, GRB 101225A, and GRB 121027A, has a duration of $\\sim 10^4$ s, two of them are accompanied by superluminous-supernova (SLSN) like bumps, which are $\\lesssim 10$ times brighter than typical hypernovae. Wolf-Rayet progenitors cannot explain ULGRBs because of too long duration and too bright SN-like bump. A blue supergiant (BSG) progenitor model, however, can explain the duration of ULGRBs. Moreover, SLSN-like bump can be attributed to the so-called cocoon-fireball photospheric emissions (CFPEs). Since a large cocoon is inevitably produced during the relativistic jet piercing though the BSG envelope, this component can be a smok...

  5. The Century Survey Galactic Halo Project III: A Complete 4300 deg^2 Survey of Blue Horizontal Branch Stars in the Metal-Weak Thick Disk and Inner Halo

    CERN Document Server

    Brown, Warren R; Wilhelm, Ronald; Prieto, Carlos Allende; Geller, Margaret J; Kenyon, Scott J; Kurtz, Michael J

    2007-01-01

    We present a complete spectroscopic survey of 2414 2MASS-selected blue horizontal branch (BHB) candidates selected over 4300 deg^2 of the sky. We identify 655 BHB stars in this non-kinematically selected sample. We calculate the luminosity function of field BHB stars and find evidence for very few hot BHB stars in the field. The BHB stars located at a distance from the Galactic plane |Z|<4 kpc trace what is clearly a metal-weak thick disk population, with a mean metallicity of [Fe/H]= -1.7, a rotation velocity gradient of dv_{rot}/d|Z|= -28+-3.4 km/s in the region |Z|<6 kpc, and a density scale height of h_Z= 1.26+-0.1 kpc. The BHB stars located at 5<|Z|<9 kpc are a predominantly inner-halo population, with a mean metallicity of [Fe/H]= -2.0 and a mean Galactic rotation of -4+-31 km/s. We infer the density of halo and thick disk BHB stars is 104+-37 kpc^-3 near the Sun, and the relative normalization of halo to thick-disk BHB stars is 4+-1% near the Sun.

  6. How Long does a Burst Burst?

    CERN Document Server

    Zhang, Bin-Bin; Murase, Kohta; Connaughton, Valerie; Briggs, Michael S

    2013-01-01

    Several gamma-ray bursts (GRBs) last much longer (~ hours) in gamma-rays than typical long GRBs (~ minutes), and recently it was proposed that these "ultra-long GRBs" may form a distinct population, probably with a different (e.g. blue supergiant) progenitor than typical GRBs. However, Swift observations have suggested that many GRBs have extended central engine activities manifested as flares and internal plateaus in X-rays. We perform a comprehensive study on a large sample of Swift GRBs with XRT observations to investigate GRB central engine activity duration and to check whether ultra-long GRBs are special. We define burst duration t_{burst} based on both gamma-ray and X-ray light curves rather than using gamma-ray observations only. We show that the distribution of t_{burst} peaks at ~ 320s for the entire sample, with 17.6% GRBs having t_{burst} > 10^3 s and 5.4% GRBs having t_{burst} > 10^4 s. The distribution shows a tail at the long t_{burst} end. The existence of a separate population is not ruled ou...

  7. Magnetar Bursts

    Science.gov (United States)

    Kouveliotou, Chryssa

    2014-01-01

    The Fermi/Gamma-ray Burst Monitor (GBM) was launched in June 2008. During the last five years the instrument has observed several hundreds of bursts from 8 confirmed magnetars and 19 events from unconfirmed sources. I will discuss the results of the GBM magnetar burst catalog, expand on the different properties of their diverse source population, and compare these results with the bursting activity of past sources. I will then conclude with thoughts of how these properties fit the magnetar theoretical models.

  8. Postpartum Blues

    Medline Plus

    Full Text Available ... blues The postpartum blues E-mail to a friend Please fill in all fields. Please enter a ... blues: Talk to your partner or a good friend about how you feel Get plenty of rest ...

  9. Postpartum Blues

    Medline Plus

    Full Text Available ... Quality Collaboratives Launch Prematurity research centers What is team science? More than 75 years of solving problems ... delivery cause the postpartum blues. How can you manage the baby blues? The American College of Obstetricians ...

  10. Postpartum Blues

    Medline Plus

    Full Text Available ... with this condition are happy most of the time. But compared to how she usually feels, the ... the "blues" usually lessens and goes away over time. What causes the baby blues? Medical experts believe ...

  11. Postpartum Blues

    Medline Plus

    Full Text Available ... Postpartum care > The postpartum blues The postpartum blues E-mail to a friend Please fill in all fields. Please enter a valid e-mail address. Your information: Your recipient's information: Your ...

  12. Postpartum Blues

    Medline Plus

    Full Text Available ... can you manage the baby blues? The American College of Obstetricians and Gynecologists recommends that women do ... can you manage the baby blues? The American College of Obstetricians and Gynecologists recommends that women do ...

  13. Postpartum Blues

    Medline Plus

    Full Text Available ... Feels sad Feels confused The postpartum blues peak three to five days after delivery. They usually end ... Feels sad Feels confused The postpartum blues peak three to five days after delivery. They usually end ...

  14. Postpartum Blues

    Medline Plus

    Full Text Available ... postpartum blues The postpartum blues E-mail to a friend Please fill in all fields. Please enter ... hear about breakthroughs for babies and families. Ask a question Our health experts can answer questions about ...

  15. Postpartum Blues

    Medline Plus

    Full Text Available ... Medical experts believe that changes in the woman's hormones after delivery cause the postpartum blues. How can ... Medical experts believe that changes in the woman's hormones after delivery cause the postpartum blues. How can ...

  16. Kind of Blue - Europa Blues

    DEFF Research Database (Denmark)

    Mortensen, Tore; Kirkegaard, Peter

    2009-01-01

    Bidraget reflekterer over sammenhænge mellem to værker fra det musikalske og litterære område. Det drejer sig om Miles Davis' Kind of Blue fra 1959 og Arne Dahls krimi, Europa Blues fra 2001. Den grundlæggende indfaldsvinkel er det performative, den frie, men samtidigt disciplinerede musikalske...

  17. Postpartum Blues

    Medline Plus

    Full Text Available ... leader Partner Spotlight Become a partner World Prematurity Day Your support helps babies We are determined to ... confused The postpartum blues peak three to five days after delivery. They usually end by the tenth ...

  18. Postpartum Blues

    Medline Plus

    Full Text Available ... Saving Just a moment, please. You've saved this page It's been added to your dashboard . After ... blues" is not really correct since women with this condition are happy most of the time. But ...

  19. Postpartum Blues

    Medline Plus

    Full Text Available ... dashboard . After the baby is born, many new mothers have the postpartum blues (also called the baby ... compared to how she usually feels, the new mother: Is more irritable Cries more easily Feels sad ...

  20. Postpartum Blues

    Medline Plus

    Full Text Available ... for your baby Feeding your baby Common illnesses New parents Family health & safety Complications & Loss Pregnancy complications ... your dashboard . After the baby is born, many new mothers have the postpartum blues (also called the ...

  1. NUMERICAL SIMULATION OF BED DEFORMATION IN DIKE BURST

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The key point in the numerical simulation of breach growth and bed deformation process in a dike burst is the accurate computation of flow and sediment transport. A numerical model for horizontal 2-D non-uniform sediment was developed to simulate the bed deformation process in the dike burst. The first-order scheme was used in computation. Several simulated results were worked out to demonstrate the applicability of the numerical model.

  2. Blue gods, blue oil, and blue people.

    Science.gov (United States)

    Fairbanks, V F

    1994-09-01

    Studies of the composition of coal tar, which began in Prussia in 1834, profoundly affected the economies of Germany, Great Britain, India, and the rest of the world, as well as medicine and surgery. Such effects include the collapse of the profits of the British indigo monopoly, the growth in economic power of Germany based on coal tar chemistry, and an economic crisis in India that led to more humane tax laws and, ultimately, the independence of India and the end of the British Empire. Additional consequences were the development of antiseptic surgery and the synthesis of a wide variety of useful drugs that have eradicated infections and alleviated pain. Many of these drugs, particularly the commonly used analgesics, sulfonamides, sulfones, and local anesthetics, are derivatives of aniline, originally called "blue oil" or "kyanol." Some of these aniline derivatives, however, have also caused aplastic anemia, agranulocytosis, and methemoglobinemia (that is, "blue people"). Exposure to aniline drugs, particularly when two or three aniline drugs are taken concurrently, seems to be the commonest cause of methemoglobinemia today. PMID:8065194

  3. The Most Remote Gamma-Ray Burst

    Science.gov (United States)

    2000-10-01

    seconds is larger than that of the Sun during its entire life time (about 10,000 million years). "Gamma-ray bursts" are in fact by far the most powerful events since the Big Bang that are known in the Universe. While there are indications that gamma-ray bursts originate in star-forming regions within distant galaxies, the nature of such explosions remains a puzzle. Recent observations with large telescopes, e.g. the measurement of the degree of polarization of light from a gamma-ray burst in May 1999 with the VLT ( ESO PR 08/99), are now beginning to cast some light on this long-standing mystery. The afterglow of GRB 000131 ESO PR Photo 28a/00 ESO PR Photo 28a/00 [Preview - JPEG: 400 x 475 pix - 41k] [Normal - JPEG: 800 x 949 pix - 232k] [Full-Res - JPEG: 1200 x 1424 pix - 1.2Mb] ESO PR Photo 28b/00 ESO PR Photo 28b/00 [Preview - JPEG: 400 x 480 pix - 67k] [Normal - JPEG: 800 x 959 pix - 288k] [Full-Res - JPEG: 1200 x 1439 pix - 856k] Caption : PR Photo 28a/00 is a colour composite image of the sky field around the position of the gamma-ray burst GRB 000131 that was detected on January 31, 2000. It is based on images obtained with the ESO Very Large Telescope at Paranal. The object is indicated with an arrow, near a rather bright star (magnitude 9, i.e., over 1 million times brighter than the faintest objects visible on this photo). This and other bright objects in the field are responsible for various unavoidable imaging effects, caused by optical reflections (ring-shaped "ghost images", e.g. to the left of the brightest star) and detector saturation effects (horizontal and vertical straight lines and coloured "coronae" at the bright objects, and areas of "bleeding", e.g. below the bright star). PR Photo 28b/00 shows the rapid fading of the optical counterpart of GRB 000131 (slightly left of the centre), by means of exposures with the VLT on February 4 (upper left), 6 (upper right), 8 (lower left) and March 5 (lower right). It is no longer visible on the last photo

  4. Posthuman blues

    CERN Document Server

    Tonnies, Mac

    2013-01-01

    Posthuman Blues, Vol. I is first volume of the edited version of the popular weblog maintained by author Mac Tonnies from 2003 until his tragic death in 2009. Tonnies' blog was a pastiche of his original fiction, reflections on his day-to-day life, trenchant observations of current events, and thoughts on an eclectic range of material he culled from the Internet. What resulted was a remarkably broad portrait of a thoughtful man and the complex times in which he lived, rendered with intellige...

  5. CAPITAL GAINS: BLUE MACHINES AND RED MACHINES

    OpenAIRE

    LUÍS AGUIAR-CONRARIA; KARL SHELL

    2005-01-01

    Capital gains play an essential role in the intertemporal allocation of resources, but they can also fuel self-fulfilling bubbles. The simple case of 2 "identical" capitals is analyzed in an overlapping generations model. The only trajectory in which expectations are realized at every date is the one in which blue machines and red machines have the same price. If ever their prices differ, then there is a "bubble" which must burst in finite time.

  6. Interplanetary Type IV Bursts

    CERN Document Server

    Hillaris, Alexander; Nindos, Alexander

    2016-01-01

    In this work we study the characteristics of moving type IV radio bursts which extend to the hectometric wavelengths (interplanetary type IV or type IV IP bursts) and their relationship with energetic phenomena on the Sun. Our dataset comprised 48 Interplanetary type IV bursts observed by the Wind/WAVES in the 13.825 MHz?20 KHz frequency range. The dynamic spec tra of the RSTN, DAM, ARTEMIS-IV, CULGOORA, Hiraiso and IZMIRAN Radio-spectrographs were used to track the evolution of the events in the low corona; these were supplemented with SXR ?ux recordings from GOES and CME data from LASCO. Positional information for the coronal bursts were obtained by the Nan\\c{c}ay radioheliograph (NRH). We examined the relationship of the type IV events with coronal radio bursts, CMEs and SXR ?ares. The majority of the events (45) were characterized as compact; their duration was on average 106 min. This type of events were, mostly, associated with M and X class ?ares (40 out of 45) and fast CMEs; 32 of these events had CME...

  7. Color vision: retinal blues.

    Science.gov (United States)

    Johnston, Jamie; Esposti, Federico; Lagnado, Leon

    2012-08-21

    Two complementary studies have resolved the circuitry underlying green-blue color discrimination in the retina. A blue-sensitive interneuron provides the inhibitory signal required for computing green-blue color opponency.

  8. A Burst to See

    Science.gov (United States)

    2008-04-01

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

  9. Interplanetary Type IV Bursts

    Science.gov (United States)

    Hillaris, A.; Bouratzis, C.; Nindos, A.

    2016-08-01

    We study the characteristics of moving type IV radio bursts that extend to hectometric wavelengths (interplanetary type IV or type {IV}_{{IP}} bursts) and their relationship with energetic phenomena on the Sun. Our dataset comprises 48 interplanetary type IV bursts observed with the Radio and Plasma Wave Investigation (WAVES) instrument onboard Wind in the 13.825 MHz - 20 kHz frequency range. The dynamic spectra of the Radio Solar Telescope Network (RSTN), the Nançay Decametric Array (DAM), the Appareil de Routine pour le Traitement et l' Enregistrement Magnetique de l' Information Spectral (ARTEMIS-IV), the Culgoora, Hiraso, and the Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN) Radio Spectrographs were used to track the evolution of the events in the low corona. These were supplemented with soft X-ray (SXR) flux-measurements from the Geostationary Operational Environmental Satellite (GOES) and coronal mass ejections (CME) data from the Large Angle and Spectroscopic Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). Positional information of the coronal bursts was obtained by the Nançay Radioheliograph (NRH). We examined the relationship of the type IV events with coronal radio bursts, CMEs, and SXR flares. The majority of the events (45) were characterized as compact, their duration was on average 106 minutes. This type of events was, mostly, associated with M- and X-class flares (40 out of 45) and fast CMEs, 32 of these events had CMEs faster than 1000 km s^{-1}. Furthermore, in 43 compact events the CME was possibly subjected to reduced aerodynamic drag as it was propagating in the wake of a previous CME. A minority (three) of long-lived type {IV}_{{IP}} bursts was detected, with durations from 960 minutes to 115 hours. These events are referred to as extended or long duration and appear to replenish their energetic electron content, possibly from electrons escaping from the corresponding coronal

  10. A Repeating Fast Radio Burst

    CERN Document Server

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

    2016-01-01

    Fast Radio Bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measures (i.e. integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of the fast radio bursts has led several authors to hypothesise that they originate in cataclysmic astrophysical events. Here we report the detection of ten additional bursts from the direction of FRB121102, using the 305-m Arecibo telescope. These new bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and wh...

  11. Bursts of star formation in computer simulations of dwarf galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Comins, N.F.

    1984-09-01

    A three-dimensional Stochastic Self-Propagating Star Formation (SSPSF) model of compact galacies is presented. Two phases of gas, active and inactive, are present, and permanent depletion of gas in the form of long lived, low mass stars and remnants occurs. Similarly, global infall of gas from a galactic halo or through galactic cannibalism is permitted. We base our parameters on the observed properties of the compact blue galaxy I Zw 36. Our results are that bursts of star formation occur much more frequently in these runs than continuous nonbursting star formation, suggesting that the blue compact galaxies are probably undergoing bursts rather than continuous, nonbursting low-level star formation activity.

  12. The Double Firing Burst

    Science.gov (United States)

    2008-09-01

    Astronomers from around the world combined data from ground- and space-based telescopes to paint a detailed portrait of the brightest explosion ever seen. The observations reveal that the jets of the gamma-ray burst called GRB 080319B were aimed almost directly at the Earth. Uncovering the disc ESO PR Photo 28/08 A Gamma-Ray Burst with Two Jets Read more on this illuminating blast in the additional story. GRB 080319B was so intense that, despite happening halfway across the Universe, it could have been seen briefly with the unaided eye (ESO 08/08). In a paper to appear in the 11 September issue of Nature, Judith Racusin of Penn State University, Pennsylvania (USA), and a team of 92 co-authors report observations across the electromagnetic spectrum that began 30 minutes before the explosion and followed it for months afterwards. "We conclude that the burst's extraordinary brightness arose from a jet that shot material almost directly towards Earth at almost the speed of light - the difference is only 1 part in 20 000," says Guido Chincarini, a member of the team. Gamma-ray bursts are the Universe's most luminous explosions. Most occur when massive stars run out of fuel. As a star collapses, it creates a black hole or neutron star that, through processes not fully understood, drives powerful gas jets outward. As the jets shoot into space, they strike gas previously shed by the star and heat it, thereby generating bright afterglows. The team believes the jet directed toward Earth contained an ultra-fast component just 0.4 degrees across (this is slightly smaller than the apparent size of the Full Moon). This jet is contained within another slightly less energetic jet about 20 times wider. The broad component is more typical of other bursts. "Perhaps every gamma-ray burst has a narrow jet, but astronomers miss it most of the time," says team member Stefano Covino. "We happened to view this monster down the barrel of the very narrow and energetic jet, and the chance for

  13. Estudio del horizonte local

    OpenAIRE

    Ros Ferré, Rosa Maria

    2009-01-01

    El estudio del horizonte es fundamental para poder facilitar las primeras observaciones de los alumnos en un centro educativo. Un simple modelo, que debe realizarse para cada centro, nos permite facilitar el estudio y la comprensión de los primeros rudimentos astronómicos. El modelo construido se presenta a su vez como un sencillo modelo de reloj ecuatorial y a partir de él se pueden construir otros modelos (horizontal y vertical).

  14. A repeating fast radio burst

    Science.gov (United States)

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

    2016-03-01

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

  15. Blue cures blue but be cautious

    Directory of Open Access Journals (Sweden)

    Pranav Sikka

    2011-01-01

    Full Text Available Methemoglobinemia is a disorder characterized by the presence of >1% methemoglobin (metHb in the blood. Spontaneous formation of methemoglobin is normally counteracted by protective enzyme systems, for example, nicotinamide adenine dinucleotide phosphate (NADPH methemoglobin reductase. Methemoglobinemia is treated with supplemental oxygen and methylene blue (1-2 mg/kg administered slow intravenously, which acts by providing an artificial electron acceptor for NADPH methemoglobin reductase. But known or suspected glucose-6-phosphate dehydrogenase (G6PD deficiency is a relative contraindication to the use of methylene blue because G6PD is the key enzyme in the formation of NADPH through pentose phosphate pathway and G6PD-deficient individuals generate insufficient NADPH to efficiently reduce methylene blue to leukomethylene blue, which is necessary for the activation of the NADPH-dependent methemoglobin reductase system. So, we should be careful using methylene blue in methemoglobinemia patient before G6PD levels.

  16. Horizontal carbon nanotube alignment.

    Science.gov (United States)

    Cole, Matthew T; Cientanni, Vito; Milne, William I

    2016-09-21

    The production of horizontally aligned carbon nanotubes offers a rapid means of realizing a myriad of self-assembled near-atom-scale technologies - from novel photonic crystals to nanoscale transistors. The ability to reproducibly align anisotropic nanostructures has huge technological value. Here we review the present state-of-the-art in horizontal carbon nanotube alignment. For both in and ex situ approaches, we quantitatively assess the reported linear packing densities alongside the degree of alignment possible for each of these core methodologies. PMID:27546174

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

    Science.gov (United States)

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

    2015-03-01

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

  18. Introduction to Optical Burst Switching

    OpenAIRE

    KERNÁCS János; SZILÁGYI Szabolcs

    2010-01-01

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

  19. Gamma-ray burst spectra

    Science.gov (United States)

    Teegarden, B. J.

    1982-01-01

    A review of recent results in gamma-ray burst spectroscopy is given. Particular attention is paid to the recent discovery of emission and absorption features in the burst spectra. These lines represent the strongest evidence to date that gamma-ray bursts originate on or near neutron stars. Line parameters give information on the temperature, magnetic field and possibly the gravitational potential of the neutron star. The behavior of the continuum spectrum is also discussed. A remarkably good fit to nearly all bursts is obtained with a thermal-bremsstrahlung-like continuum. Significant evolution is observed of both the continuum and line features within most events.

  20. Dark Gamma Ray Bursts

    OpenAIRE

    Brdar, Vedran; Kopp, Joachim; Liu, Jia

    2016-01-01

    Many theories of dark matter (DM) predict that DM particles can be captured by stars via scattering on ordinary matter. They subsequently condense into a DM core close to the center of the star and eventually annihilate. In this work, we trace DM capture and annihilation rates throughout the life of a massive star and show that this evolution culminates in an intense annihilation burst coincident with the death of the star in a core collapse supernova. The reason is that, along with the stell...

  1. Gamma Ray Bursts

    Science.gov (United States)

    Gehrels, Neil; Meszaros, Peter

    2012-01-01

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

  2. Gamma-Ray Bursts

    Science.gov (United States)

    Gehrels, Neil; Mészáros, Péter

    2012-08-01

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

  3. Gamma Ray Bursts

    CERN Document Server

    Gehrels, Neil; 10.1126/science.1216793

    2012-01-01

    Gamma-ray bursts (GRBs) are bright flashes of gamma-rays coming from the cosmos. They occur roughly once per day, last typically 10s of seconds and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this review we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglows.

  4. Horizontal Connection and Horizontal Mean Curvature in Carnot Groups

    Institute of Scientific and Technical Information of China (English)

    Kang Hai TAN; Xiao Ping YANG

    2006-01-01

    In this paper we give a geometric interpretation of the notion of the horizontal mean curvature which is introduced by Danielli-Garofalo-Nhieu and Pauls who recently introduced sub-Riemannian minimal surfaces in Carnot groups. This will be done by introducing a natural nonholonomic connection which is the restriction (projection) of the natural Riemannian connection on the horizontal bundle. For this nonholonomic connection and (intrinsic) regular hypersurfaces we introduce the notions of the horizontal second fundamental form and the horizontal shape operator. It turns out that the horizontal mean curvature is the trace of the horizontal shape operator.

  5. Dark Gamma Ray Bursts

    CERN Document Server

    Brdar, Vedran; Liu, Jia

    2016-01-01

    Many theories of dark matter (DM) predict that DM particles can be captured by stars via scattering on ordinary matter. They subsequently condense into a DM core close to the center of the star and eventually annihilate. In this work, we trace DM capture and annihilation rates throughout the life of a massive star and show that this evolution culminates in an intense annihilation burst coincident with the death of the star in a core collapse supernova. The reason is that, along with the stellar interior, also its DM core heats up and contracts, so that the DM density increases rapidly during the final stages of stellar evolution. We argue that, counterintuitively, the annihilation burst is more intense if DM annihilation is a p-wave process than for s-wave annihilation because in the former case, more DM particles survive until the supernova. If among the DM annihilation products are particles like dark photons that can escape the exploding star and decay to Standard Model particles later, the annihilation bu...

  6. Burst Mode Transmission in GPON

    Institute of Scientific and Technical Information of China (English)

    LI Liang-chuan; ZHANG Yan-gan; LI Ling; XU Da-xiong

    2004-01-01

    In this paper, a newly approved standard G.984 for Gigabit-capable Passive Optical Networks (GPON) is introduced. Technical challenges about high-speed burst-mode data transmission in GPON are discussed and key issues such as Forward Error Correction (FEC), timing to uplink performance of burst mode are high-lighted.

  7. Short duration gamma ray bursts

    Indian Academy of Sciences (India)

    Patrick Das Gupta

    2004-10-01

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

  8. Horizontally mounted solar collector

    Science.gov (United States)

    Black, D. H. (Inventor)

    1979-01-01

    Solar energy is collected by using a vertical deflector assembly, a stationary reflector and a horizontally mounted solar collector. The deflector assembly contains a plurality of vanes which change the direction of the solar energy to the vertical, while constantly keeping the same side of the deflector facing the sun. The vertical rays are then reflected off the stationary reflector and are then absorbed by the collector.

  9. Conceptualising horizontal politics

    OpenAIRE

    Harding, Eloise Mary

    2012-01-01

    This project investigates the likelihood of a distinctive ideology emerging from what are known as ‘horizontal’ political movements – those which, in brief, aim to operate non-hierarchically guided by principles such as affinity – and furthermore to identify the potential components of such an ideology. The methodology is broadly based on that developed by Freeden, namely an analysis of the conceptual morphology of the ideas put out by horizontal movements. The sources used derive largely fro...

  10. Bursts de raios gama

    Science.gov (United States)

    Braga, J.

    2003-02-01

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

  11. Horizontal drilling activity in Manitoba

    Energy Technology Data Exchange (ETDEWEB)

    Fox, J.

    1997-04-01

    An update of horizontal well drilling in Manitoba was provided. Manitoba`s productive formations are: (1) the Bakken Formation, (2) the Lodgepole Formation, (3) the Mission Canyon Formation, (4) the Amaranth Formation, and (5) the Melita Formation. A total of 28 exploratory wells and 29 development wells, including 11 horizontal wells were drilled in 1996. The 11 horizontal wells accounted for 30 per cent of the drilling meterage. The leading drillers for horizontal wells in Manitoba are Tundra Oil and Gas, Chevron, Anderson and HCO. Production from horizontal wells in 1996 totaled 310 cubic meter per day. To date, no horizontal wells have been drilled in the Bakken Formation. The least successful horizontal well application has been in the Lodgepole Formation. A summary of horizontal well production was provided for each Formation. 4 tabs., 10 figs.

  12. Blue and White Pot

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    Many recent archaeological studies have proven that the earliest blue and white porcelain was produced from the kiln in Gongxian County, Henan Province in the Tang Dynasty (618-907). It was an important variety of porcelain available for export then. The early blue and white porcelain in the Yuan Dynasty appeared dark and gray. During the reign of Zhizheng, clear blue and white porcelain was produced, indicating

  13. Concept for LEU Burst Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Steven Karl [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kimpland, Robert Herbert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-03-07

    Design and performance of a proposed LEU burst reactor are sketched. Salient conclusions reached are the following: size would be ~1,500 kg or greater, depending on the size of the central cavity; internal stresses during burst require split rings for relief; the reactor would likely require multiple control and safety rods for fine control; the energy spectrum would be comparable to that of HEU machines; and burst yields and steady-state power levels will be significantly greater in an LEU reactor.

  14. Feeling blue? Blue phosphors for OLEDs

    Directory of Open Access Journals (Sweden)

    Hungshin Fu

    2011-10-01

    Full Text Available Research on organic light emitting diodes (OLEDs has been revitalized, partly due to the debut of the OLED TV by SONY in 2008. While there is still plenty of room for improvement in efficiency, cost-effectiveness and longevity, it is timely to report on the advances of light emitting materials, the core of OLEDs, and their future perspectives. The focus of this account is primarily to chronicle the blue phosphors developed in our laboratory. Special attention is paid to the design strategy, synthetic novelty, and their OLED performance. The report also underscores the importance of the interplay between chemistry and photophysics en route to true-blue phosphors.

  15. SWIFT and BATSE bursts' classification

    CERN Document Server

    Horvath, I; Balazs, L G; Tusnady, G; Veres, P

    2009-01-01

    Two classes of gamma-ray bursts were identified in the BATSE catalogs characterized by their durations. There were also some indications for the existence of a third type of gamma-ray bursts. Swift satellite detectors have different spectral sensitivity than pre-Swift ones for GRBs. Therefore in this paper we analyze the bursts' duration distribution and also the duration-hardness bivariate distribution, published in The First BAT Catalog. Similarly to the BATSE data, to explain the BAT GRBs' duration distribution three components are needed. Although, the relative frequencies of the groups are different than they were in the BATSE GRB sample, the difference in the instrument spectral sensitivities can explain this bias in a natural way. This means theoretical models may have to explain three different type of gamma-ray bursts.

  16. FERMIGBRST - Fermi GBM Burst Catalog

    Data.gov (United States)

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

  17. Chimera states in bursting neurons

    OpenAIRE

    Bera, Bidesh K.; Ghosh, Dibakar; Lakshmanan, M.

    2015-01-01

    We study the existence of chimera states in pulse-coupled networks of bursting Hindmarsh-Rose neurons with nonlocal, global and local (nearest neighbor) couplings. Through a linear stability analysis, we discuss the behavior of stability function in the incoherent (i.e. disorder), coherent, chimera and multi-chimera states. Surprisingly, we find that chimera and multi-chimera states occur even using local nearest neighbor interaction in a network of identical bursting neurons alone. This is i...

  18. Disinhibition Bursting of Dopaminergic Neurons

    Directory of Open Access Journals (Sweden)

    Collin J Lobb

    2011-05-01

    Full Text Available Substantia nigra pars compacta (SNpc dopaminergic neurons receive strong tonic inputs from GABAergic neurons in the substantia nigra pars reticulata (SNpr and globus pallidus (GP, and glutamatergic neurons in the subthalamic nucleus. The presence of these tonic inputs raises the possibility that phasic disinhibition may trigger phasic bursts in dopaminergic neurons. We first applied constant NMDA and GABAA conductances onto a two-compartment single cell model of the dopaminergic neuron (Kuznetsov et al., 2006. The model exhibited disinhibition bursting upon stepwise removal of inhibition. A further bifurcation analysis suggests that disinhibition may be more robust than excitation alone in that for most levels of NMDA conductance, the cell remains capable of bursting even after a complete removal of inhibition, whereas too much excitatory input will drive the cell into depolarization block. To investigate the network dynamics of disinhibition, we used a modified version of an integrate-and-fire based model of the basal ganglia (Humphries et al., 2006. Synaptic activity generated in the network was delivered to the two-compartment single cell dopaminergic neuron. Phasic activation of the D1-expressing medium spiny neurons in the striatum (D1STR produced disinhibition bursts in dopaminergic neurons through the direct pathway (D1STR to SNpr to SNpc. Anatomical studies have shown that D1STR neurons have collaterals that terminate in GP. Adding these collaterals to the model, we found that striatal activation increased the intra-burst firing frequency of the disinhibition burst as the weight of this connection was increased. Our studies suggest that striatal activation is a robust means by which disinhibition bursts can be generated by SNpc dopaminergic neurons, and that recruitment of the indirect pathway via collaterals may enhance disinhibition bursting.

  19. Light Dawns on Dark Gamma-ray Bursts

    Science.gov (United States)

    2010-12-01

    [1] Gamma-ray bursts lasting longer than two seconds are referred to as long bursts and those with a shorter duration are known as short bursts. Long bursts, which were observed in this study, are associated with the supernova explosions of massive young stars in star-forming galaxies. Short bursts are not well understood, but are thought to originate from the merger of two compact objects such as neutron stars. [2] The Gamma-Ray burst Optical and Near-infrared Detector (GROND) was designed and built at the Max-Planck Institute for Extraterrestrial Physics in collaboration with the Tautenburg Observatory, and has been fully operational since August 2007. [3] Other studies relating to dark gamma-ray bursts have been released. Early this year, astronomers used the Subaru Telescope to observe a single gamma-ray burst, from which they hypothesised that dark gamma-ray bursts may indeed be a separate sub-class that form through a different mechanism, such as the merger of binary stars. In another study published last year using the Keck Telescope, astronomers studied the host galaxies of 14 dark GRBs, and based on the derived low redshifts they infer dust as the likely mechanism to create the dark bursts. In the new work reported here, 39 GRBs were studied, including nearly 20 dark bursts, and it is the only study in which no prior assumptions have been made and the amount of dust has been directly measured. [4] Because the afterglow light of very distant bursts is redshifted due to the expansion of the Universe, the light that left the object was originally bluer than the light we detect when it gets to Earth. Since the reduction of light intensity by dust is greater for blue and ultraviolet light than for red, this means that the overall dimming effect of dust is greater for the more distant gamma-ray bursts. This is why GROND's ability to observe near-infrared radiation makes such a difference. More information This research is presented in a paper to appear in the

  20. Blue Willow Story Plates

    Science.gov (United States)

    Fontes, Kris

    2009-01-01

    In the December 1997 issue of "SchoolArts" is a lesson titled "Blue Willow Story Plates" by Susan Striker. In this article, the author shares how she used this lesson with her middle-school students many times over the years. Here, she describes a Blue Willow plate painting project that her students made.

  1. Multimodal Distributions along the Horizontal Branch

    CERN Document Server

    Ferraro, F R; Pecci, F F; Dorman, B; Rood, R T; Ferraro, Francesco R.; Paltrinieri, Barbara; Pecci, Flavio Fusi; Dorman, Ben; Rood, Robert T.

    1997-01-01

    We report on HST/WFPC2 U,V and far-ultraviolet observations of two Galactic Globular Clusters (GGCs), NGC 6205 = M13 and NGC 6093 = M80. Both of these clusters have horizontal-branch (HB) tails that extend to the helium-burning main sequence, with the hottest stars reaching theoretical effective temperatures above 35,000 K. In both clusters, groups of stars are found to be separated by narrow gaps along the blue HB sequence. These gaps appear at similar locations in the color-magnitude diagrams of the two clusters. While stochastic effects may give rise to variations in the color distribution along the HB, the coincidence of gaps in different clusters effectively rules this out as the primary cause. The comparison among the clusters strongly suggests that there are separate physical processes operating during the earlier red-giant phase of evolution to produce mass loss.

  2. From blue jeans to blue genes.

    Science.gov (United States)

    Boon, Laurence M; Vikkula, Miikka

    2009-03-01

    Cutaneous venous anomalies are common. They are blue and vary in size, number, and location and account for most consultations at specialized interdisciplinary clinics for vascular anomalies. Venous lesions are clinically important because they cause pain, dysfunction, destruction of adjacent tissues, and esthetic concern. Only resection and sclerotherapy are helpful, although not always curative. Understanding etiopathogenesis could help design animal models and develop novel therapeutic approaches. John B. Mulliken, MD, envisioned a project to uncover the genetic basis of an inherited form of venous malformation in a large New England family. Recruitment of 2 young fellows resulted in a collaborative project that unraveled the searched-for gene and its mutation. This was an opening for a new era in vascular anomalies. Two blue genes' mutations were discovered, which account for most, if not all, of the inherited forms of venous anomalies, but other genes as well, for rheologically diverse lesions. Differential diagnosis and management has improved, and animal models are being made. This was achieved through the help of Dr Mulliken, who inspired 2 young investigators in blue jeans to find 2 blue genes.

  3. Well Spacing for Horizontal Wells

    Directory of Open Access Journals (Sweden)

    C.D.S. Keuengoua

    2011-06-01

    Full Text Available In the developing phase of a hydrocarbon reservoir and planning for drilling the production wells, it is necessary to drill the wells in an appropriate spacing to achieve maximum economic revenues during the reservoir life span. Well spacing which is the real location and interrelationship between producing oil or gas wells in an oil field is an important parameter. It is determined for the maximum ultimate production of a given reservoir and should be taken in consideration during well planning to avoid drilling of unnecessary wells. This study presents the concept of drainage area on horizontal well and horizontal productivity indices with different equations and their applications. A user friendly Excel Spreadsheet program was developed to calculate the productivity values of horizontal wells using three major available productivity equations. Also, the developed spreadsheet program was used to evaluate the effect of well spacing on the productivities of horizontal wells using productivity index approach and drainage area concept. It also helps to review the comparison between vertical and horizontal wells spacing based on drainage area concept. This program was validated, and then was used to study the effect of horizontal well length on the ratio of horizontal well productivity to vertical well productivity. The results show that higher ratio of horizontal well productivity to vertical well productivity values are obtained with increase length of the horizontal well. It is a very useful tool for making decision about the application of well spacing for horizontal wells.

  4. PRODUCTIVITY OF FRACTURED HORIZONTAL WELLS

    Directory of Open Access Journals (Sweden)

    Stjepan Antolović

    2009-12-01

    Full Text Available The interest and performance of horizontal drilling and completions has increased during the last two decades. Horizontal wells are advantageous compared to vertical wells in thin reservoirs, reservoirs with favorable vertical permeability and reservoirs with water and gas coning problems. In many reservoirs, the ratio of horizontal permeability to the vertical permeability is substantially larger than one and often is close to 10. Thus, these reservoirs are very good candidates for hydraulic fracturing. By hydraulic fracturing one or more fractures are created, which can be longitudinal or orthogonal. By that, flow is altered and it mostly conducts horizontally through reservoir toward horizontal wellbore. With this altered flow, fluid is produced faster, with less pressure loss by fluid unit of produced fluid. Some of the existing mathematical models to determine the productivity of multifractured horizontal wells are presented in this work (the paper is published in Croatian.

  5. Blue ocean strategy.

    Science.gov (United States)

    Kim, W Chan; Mauborgne, Renée

    2004-10-01

    Despite a long-term decline in the circus industry, Cirque du Soleil profitably increased revenue 22-fold over the last ten years by reinventing the circus. Rather than competing within the confines of the existing industry or trying to steal customers from rivals, Cirque developed uncontested market space that made the competition irrelevant. Cirque created what the authors call a blue ocean, a previously unknown market space. In blue oceans, demand is created rather than fought over. There is ample opportunity for growth that is both profitable and rapid. In red oceans--that is, in all the industries already existing--companies compete by grabbing for a greater share of limited demand. As the market space gets more crowded, prospects for profits and growth decline. Products turn into commodities, and increasing competition turns the water bloody. There are two ways to create blue oceans. One is to launch completely new industries, as eBay did with online auctions. But it's much more common for a blue ocean to be created from within a red ocean when a company expands the boundaries of an existing industry. In studying more than 150 blue ocean creations in over 30 industries, the authors observed that the traditional units of strategic analysis--company and industry--are of limited use in explaining how and why blue oceans are created. The most appropriate unit of analysis is the strategic move, the set of managerial actions and decisions involved in making a major market-creating business offering. Creating blue oceans builds brands. So powerful is blue ocean strategy, in fact, that a blue ocean strategic move can create brand equity that lasts for decades. PMID:15559577

  6. Blue ocean strategy.

    Science.gov (United States)

    Kim, W Chan; Mauborgne, Renée

    2004-10-01

    Despite a long-term decline in the circus industry, Cirque du Soleil profitably increased revenue 22-fold over the last ten years by reinventing the circus. Rather than competing within the confines of the existing industry or trying to steal customers from rivals, Cirque developed uncontested market space that made the competition irrelevant. Cirque created what the authors call a blue ocean, a previously unknown market space. In blue oceans, demand is created rather than fought over. There is ample opportunity for growth that is both profitable and rapid. In red oceans--that is, in all the industries already existing--companies compete by grabbing for a greater share of limited demand. As the market space gets more crowded, prospects for profits and growth decline. Products turn into commodities, and increasing competition turns the water bloody. There are two ways to create blue oceans. One is to launch completely new industries, as eBay did with online auctions. But it's much more common for a blue ocean to be created from within a red ocean when a company expands the boundaries of an existing industry. In studying more than 150 blue ocean creations in over 30 industries, the authors observed that the traditional units of strategic analysis--company and industry--are of limited use in explaining how and why blue oceans are created. The most appropriate unit of analysis is the strategic move, the set of managerial actions and decisions involved in making a major market-creating business offering. Creating blue oceans builds brands. So powerful is blue ocean strategy, in fact, that a blue ocean strategic move can create brand equity that lasts for decades.

  7. Broadband Spectral Study of Magnetar Bursts

    Science.gov (United States)

    Kirmizibayrak, Demet; Gogus, Ersin; Sasmaz Mus, Sinem; Kaneko, Yuki

    2016-07-01

    Magnetar bursts occur sporadically on random occasions, and every burst-active episode carries unique information about the bursting magnetar. Therefore, in-depth spectral and temporal analyses of each of the magnetar bursts provide new insights into the bursting and radiation mechanisms. There have been a number of studies over the last decade, investigating the spectral and temporal properties of magnetar bursts. The spectra of typical magnetar bursts were generally described with the Comptonized model or the sum of two blackbody functions. However, it was recently shown that the actual spectral nature of these bursts can be conclusively determined if the spectral analysis is performed on a wide energy coverage. We present the results of in-depth systematic broadband (2 - 250 keV) spectral analysis of a large number of bursts originated from three magnetars: SGR 1806-20, SGR 1900+14, and SGR J1550-5418, observed with the Rossi X-ray Timing Explorer.

  8. The Connection among Gamma-ray Burst Host-Galaxies, BL Lacs and Quasars

    OpenAIRE

    Rej, A.

    1999-01-01

    A possible connection among host-galaxies of gamma-ray bursts, BL Lacs and quasars is analysed. It is believed that the gamma-ray bursts, which do not show radio or infrared emission, occur in faint blue dwarf galaxies, that are seen around radio-quiet quasars, which lie in clusters. The GRB counterparts, which show radio emission, may be associated with more evolved starbursting environments, and arise from red galaxies, that are observed around some radio-loud quasars lying in richer cluste...

  9. A codimension-2 bifurcation controlling endogenous bursting activity and pulse-triggered responses of a neuron model.

    Directory of Open Access Journals (Sweden)

    William H Barnett

    Full Text Available The dynamics of individual neurons are crucial for producing functional activity in neuronal networks. An open question is how temporal characteristics can be controlled in bursting activity and in transient neuronal responses to synaptic input. Bifurcation theory provides a framework to discover generic mechanisms addressing this question. We present a family of mechanisms organized around a global codimension-2 bifurcation. The cornerstone bifurcation is located at the intersection of the border between bursting and spiking and the border between bursting and silence. These borders correspond to the blue sky catastrophe bifurcation and the saddle-node bifurcation on an invariant circle (SNIC curves, respectively. The cornerstone bifurcation satisfies the conditions for both the blue sky catastrophe and SNIC. The burst duration and interburst interval increase as the inverse of the square root of the difference between the corresponding bifurcation parameter and its bifurcation value. For a given set of burst duration and interburst interval, one can find the parameter values supporting these temporal characteristics. The cornerstone bifurcation also determines the responses of silent and spiking neurons. In a silent neuron with parameters close to the SNIC, a pulse of current triggers a single burst. In a spiking neuron with parameters close to the blue sky catastrophe, a pulse of current temporarily silences the neuron. These responses are stereotypical: the durations of the transient intervals-the duration of the burst and the duration of latency to spiking-are governed by the inverse-square-root laws. The mechanisms described here could be used to coordinate neuromuscular control in central pattern generators. As proof of principle, we construct small networks that control metachronal-wave motor pattern exhibited in locomotion. This pattern is determined by the phase relations of bursting neurons in a simple central pattern generator

  10. Almost horizontal turbulence

    International Nuclear Information System (INIS)

    The paper is published without modifications. Kolmogorov's manuscript was apparently prepared during his participation in one of expeditions of the ship 'D. Mendeleev' to the Atlantic Ocean (1969) or in a circumnavigation of the world (1971) organized by the Institute for Oceanology led at the time by A.S. Monin. As Kolmogorov himself wrote, the choice of the topic was stimulated by observations concerning '...meanders with horizontal sizes of hundreds of kilometers on a flow involving a layer of hundreds of meters, with subsequent disintegration of these meanders into vortices gradually decreasing in size to several kilometers'. In modern terminology, the paper is devoted to the problem of intensive mixing in pycnoclines, that is, thin layers of stratified fluid, caused by internal waves whose frequencies are less than the Brent-Vaeisaelae frequency. Here I would like to note two circumstances. The first is the scientific insight characteristic for Kolmogorov; this very approach was later reflected in numerous publications (see, for instance, the monograph by V.S. Modevich, V.I. Nikulin, and A.G. Stetsenko 'Dynamics of internal mixing in a stratified medium', Institute for Hydromechanics, Academy of Sciences of Ukraine, Naukova Dumka, Kiev 1988). The second, the more significant in my opinion, is the genuine intellectual curiosity and breadth of thought of this great thinker, who studied not only the most abstract mathematical constructions but also got his head out of the clouds with great interest to solve concrete applied problems

  11. Blue Ribbon Panel Report

    Science.gov (United States)

    An NCI Cancer Currents blog by the NCI acting director thanking the cancer community for contributing to the Cancer Moonshot Blue Ribbon Panel report, which was presented to the National Cancer Advisory Board on September 7.

  12. New York Blue

    Data.gov (United States)

    Federal Laboratory Consortium — New York Blue is used cooperatively by the Laboratory and Stony Brook University as part of the New York Center for Computation Sciences. Ranked as the 28th fastest...

  13. Bursts in intermittent aeolian saltation

    CERN Document Server

    Carneiro, M V; Herrmann, H J

    2014-01-01

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

  14. Chimera states in bursting neurons

    Science.gov (United States)

    Bera, Bidesh K.; Ghosh, Dibakar; Lakshmanan, M.

    2016-01-01

    We study the existence of chimera states in pulse-coupled networks of bursting Hindmarsh-Rose neurons with nonlocal, global, and local (nearest neighbor) couplings. Through a linear stability analysis, we discuss the behavior of the stability function in the incoherent (i.e., disorder), coherent, chimera, and multichimera states. Surprisingly, we find that chimera and multichimera states occur even using local nearest neighbor interaction in a network of identical bursting neurons alone. This is in contrast with the existence of chimera states in populations of nonlocally or globally coupled oscillators. A chemical synaptic coupling function is used which plays a key role in the emergence of chimera states in bursting neurons. The existence of chimera, multichimera, coherent, and disordered states is confirmed by means of the recently introduced statistical measures and mean phase velocity.

  15. US Army Nuclear Burst Detection System (NBDS)

    International Nuclear Information System (INIS)

    The Nuclear Burst Detection System (NBDS) was developed to meet the Army requirements of an unattended, automatic nuclear burst reporting system. It provides pertinent data for battlefield commanders on a timely basis with high reliability

  16. Millisecond extragalactic radio bursts as magnetar flares

    CERN Document Server

    Popov, S B

    2013-01-01

    Properties of the population of millisecond extragalactic radio bursts discovered by Thornton et al. (2013) are in good correspondence with the hypothesis that such events are related to hyperflares of magnetars, as was proposed by us after the first observation of an extragalactic millisecond radio burst by Lorimer et al. (2007). We also point that some of multiple millisecond radio bursts from M31 discovered by Rubio-Herrera et al. (2013) also can be related to weaker magnetar bursts.

  17. The Blues of David Lynch

    OpenAIRE

    Roche, David

    2009-01-01

    This article is an attempt to elaborate a typology of the color blue in the color films of David Lynch up to and including Mulholland Drive (2001). The color blue is considered alternately as light, matter or verbal language. The author studies the use, function, value and meaning of blue lighting, divided into static and flashing light, and of the blue objects in Blue Velvet (1986) and Mulholland Drive. The author shows how Lynch appropriates connotations Western culture, under the influence...

  18. Detecting pipe bursts by monitoring water demand

    NARCIS (Netherlands)

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

    2012-01-01

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

  19. Blue straggler formation at core collapse

    CERN Document Server

    Banerjee, Sambaran

    2016-01-01

    Among the most striking feature of blue straggler stars (BSS) is the presence of multiple sequences of BSSs in the colour-magnitude diagrams (CMDs) of several globular clusters. It is often envisaged that such a multiple BSS sequence would arise due a recent core collapse of the host cluster, triggering a number of stellar collisions and binary mass transfers simultaneously over a brief episode of time. Here we examine this scenario using direct N-body computations of moderately massive star clusters (of order 10^4 Msun ). As a preliminary attempt, these models are initiated with approx. 8-10 Gyr old stellar population and King profiles of high concentrations, being "tuned" to undergo core collapse quickly. BSSs are indeed found to form in a "burst" at the onset of the core collapse and several of such BS-bursts occur during the post-core-collapse phase. In those models that include a few percent primordial binaries, both collisional and binary BSSs form after the onset of the (near) core-collapse. However, t...

  20. How bees distinguish patterns by green and blue modulation

    Directory of Open Access Journals (Sweden)

    Horridge A

    2015-10-01

    Full Text Available Adrian Horridge Biological Sciences, Australian National University, Canberra, ACT, Australia Abstract: In the 1920s, Mathilde Hertz found that trained bees discriminated between shapes or patterns of similar size by something related to total length of contrasting contours. This input is now interpreted as modulation in green and blue receptor channels as flying bees scan in the horizontal plane. Modulation is defined as total contrast irrespective of sign multiplied by length of edge displaying that contrast, projected to vertical, therefore, combining structure and contrast in a single input. Contrast is outside the eye; modulation is a phasic response in receptor pathways inside. In recent experiments, bees trained to distinguish color detected, located, and measured three independent inputs and the angles between them. They are the tonic response of the blue receptor pathway and modulation of small-field green or (less preferred blue receptor pathways. Green and blue channels interacted intimately at a peripheral level. This study explores in more detail how various patterns are discriminated by these cues. The direction of contrast at a boundary was not detected. Instead, bees located and measured total modulation generated by horizontal scanning of contrasts, irrespective of pattern. They also located the positions of isolated vertical edges relative to other landmarks and distinguished the angular widths between vertical edges by green or blue modulation alone. The preferred inputs were the strongest green modulation signal and angular width between outside edges, irrespective of color. In the absence of green modulation, the remaining cue was a measure and location of blue modulation at edges. In the presence of green modulation, blue modulation was inhibited. Black/white patterns were distinguished by the same inputs in blue and green receptor channels. Left–right polarity and mirror images could be discriminated by retinotopic green

  1. Beyond Deep Blue

    CERN Document Server

    Newborn, Monty

    2011-01-01

    More than a decade has passed since IBM's Deep Blue computer stunned the world by defeating Garry Kasparov, the world chess champion at that time. Beyond Deep Blue tells the continuing story of the chess engine and its steady improvement. The book provides analysis of the games alongside a detailed examination of the remarkable technological progress made by the engines - asking which one is best, how good is it, and how much better can it get. Features: presents a total of 118 games, played by 17 different chess engines, collected together for the first time in a single reference; details the

  2. A Blue Lagoon Function

    DEFF Research Database (Denmark)

    Markvorsen, Steen

    2007-01-01

    We consider a specific function of two variables whose graph surface resembles a blue lagoon. The function has a saddle point $p$, but when the function is restricted to any given straight line through $p$ it has a {\\em{strict local minimum}} along that line at $p$.......We consider a specific function of two variables whose graph surface resembles a blue lagoon. The function has a saddle point $p$, but when the function is restricted to any given straight line through $p$ it has a {\\em{strict local minimum}} along that line at $p$....

  3. The Blue Collar Brain

    Directory of Open Access Journals (Sweden)

    Guy eVan Orden

    2012-06-01

    Full Text Available Much effort has gone into elucidating control of the body by the brain, less so the role of the body in controlling the brain. This essay develops the idea that the brain does a great deal of work in the service of behavior that is controlled by the body, a blue collar role compared to the white collar control exercised by the body. The argument that supports a blue collar role for the brain is also consistent with recent discoveries clarifying the white collar role of synergies across the body's tensegrity structure, and the evidence of critical phenomena in brain and behavior.

  4. Gamma-Ray Bursts: The End Game

    Science.gov (United States)

    Lamb, Don

    1997-11-01

    The nature of gamma-ray bursts has been one of the greatest unsolved mysteries in astrophysics for more than a quarter century. A major reason for this is that no definite counterparts to the bursts could be found at other wavelengths, despite intense efforts spanning more than two decades. Consequently, the study of gamma-ray bursts has been isolated from the rest of astronomy. Scientists studying them have had only the laws of physics and the bursts themselves to guide them in attempting to solve the burst mystery. All of this changed dramatically with the discovery earlier this year of fading X-ray and optical sources in the arcminute-sized positional error boxes of several gamma-ray bursts. For the first time, temporal, as well as spatial, coincidence could be used to associate these X-ray and optical sources with the gamma-ray bursts. As a result, the odds are great that the fading X-ray and optical sources are counterparts of the bursts, and that the study of gamma-ray bursts has finally been connected with the rest of astronomy. In this talk, we describe the dramatic new information about the nature of gamma-ray bursts that the X-ray, optical, and radio observations of the fading sources have provided, and emphasize the implications that this information has for the distance scale to the bursts.

  5. Spindle Bursts in Neonatal Rat Cerebral Cortex

    Directory of Open Access Journals (Sweden)

    Jenq-Wei Yang

    2016-01-01

    Full Text Available Spontaneous and sensory evoked spindle bursts represent a functional hallmark of the developing cerebral cortex in vitro and in vivo. They have been observed in various neocortical areas of numerous species, including newborn rodents and preterm human infants. Spindle bursts are generated in complex neocortical-subcortical circuits involving in many cases the participation of motor brain regions. Together with early gamma oscillations, spindle bursts synchronize the activity of a local neuronal network organized in a cortical column. Disturbances in spindle burst activity during corticogenesis may contribute to disorders in cortical architecture and in the activity-dependent control of programmed cell death. In this review we discuss (i the functional properties of spindle bursts, (ii the mechanisms underlying their generation, (iii the synchronous patterns and cortical networks associated with spindle bursts, and (iv the physiological and pathophysiological role of spindle bursts during early cortical development.

  6. Spindle Bursts in Neonatal Rat Cerebral Cortex.

    Science.gov (United States)

    Yang, Jenq-Wei; Reyes-Puerta, Vicente; Kilb, Werner; Luhmann, Heiko J

    2016-01-01

    Spontaneous and sensory evoked spindle bursts represent a functional hallmark of the developing cerebral cortex in vitro and in vivo. They have been observed in various neocortical areas of numerous species, including newborn rodents and preterm human infants. Spindle bursts are generated in complex neocortical-subcortical circuits involving in many cases the participation of motor brain regions. Together with early gamma oscillations, spindle bursts synchronize the activity of a local neuronal network organized in a cortical column. Disturbances in spindle burst activity during corticogenesis may contribute to disorders in cortical architecture and in the activity-dependent control of programmed cell death. In this review we discuss (i) the functional properties of spindle bursts, (ii) the mechanisms underlying their generation, (iii) the synchronous patterns and cortical networks associated with spindle bursts, and (iv) the physiological and pathophysiological role of spindle bursts during early cortical development.

  7. Blue-green algae

    Science.gov (United States)

    ... for 6 months relieves allergy symptoms in adults. Arsenic poisoning. Early research shows that taking a combination of blue-green algae and zinc by mouth twice daily for 12 weeks reduces arsenic levels and its effects on the skin in ...

  8. The Blue Denmark

    DEFF Research Database (Denmark)

    Hansen, Carsten Ørts; Sornn-Friese, Henrik

    This paper makes an important contribution to the discussion about knowledge based localised externalities in the context of shipping and the maritime sector in Denmark. In the paper we ask if there is a national, knowledge‐based maritime cluster configured around the shipowners in Denmark. This ...... talk about The Blue Denmark....

  9. The "Blue Banana" Revisited

    NARCIS (Netherlands)

    Faludi, A.K.F.

    2015-01-01

    This essay is about the “Blue Banana”. Banana is the name given subsequently by others to a Dorsale européenne (European backbone) identified empirically by Roger Brunet. In a background study to the Communication of the European Commission ‘Europe 2000’, Klaus Kunzmann and Michael Wegener put forwa

  10. Analysis of horizontal flows in the solar granulation

    CERN Document Server

    Noda, C Quintero; Suematsu, Y

    2016-01-01

    Solar limb observations sometimes reveal the presence of a satellite lobe in the blue wing of the Stokes I profile from pixels belonging to granules. The presence of this satellite lobe has been associated in the past to strong line of sight gradients and, as the line of sight component is almost parallel to the solar surface, to horizontal granular flows. We aim to increase the knowledge about these horizontal flows studying a spectropolarimetric observation of the north solar pole. We will make use of two state of the art techniques, the spatial deconvolution procedure that increases the quality of the data removing the stray light contamination, and spectropolarimetric inversions that will provide the vertical stratification of the atmospheric physical parameters where the observed spectral lines form. We inverted the Stokes profiles using a two component configuration, obtaining that one component is strongly blueshifted and displays a temperature enhancement at upper photospheric layers while the second ...

  11. A HORIZONTAL 2-D HYDRAULIC NUMERICAL MODEL AND IT'S APPLICATIONS TO FLOOD FORECAST

    Institute of Scientific and Technical Information of China (English)

    Minghui YU; Guolu YANG; Jinjun XU

    2002-01-01

    In this paper,a horizontal 2-D numerical model has been developed to simulate flow processes in dike burst. The finite difference method is used in computation. The model employs 2-D flow equations and can simulate complex flows when supercritical flow and sub-critical flow exist simultaneously such as hydraulic jumps. Several simulated results are worked out to demonstrate the applicability of the numerical model,such as flood propagation on a dry bed of a complex terrain.

  12. Leaf Positioning of Arabidopsis in Response to Blue Light

    Institute of Scientific and Technical Information of China (English)

    Shin-ichiro Inoue; Toshinori Kinoshita; Atsushi Takemiya; Michio Doi; Ken-ichiro Shimazaki

    2008-01-01

    Appropriate leaf positioning is essential for optimizing photosynthesis and plant growth. However, it has not been elucidated how green leaves reach and maintain their position for capturing light. We show here the regulation of leaf positioning under blue light stimuli. When 1-week-old Arabidopsis seedlings grown under white light were transferred to red light (25 μmol m-2s-t) for 5 d, new petioles that appeared were almost horizontal and their leaves were curled and slanted downward. However, when a weak blue light from above (0.1 μmol m-2s-1) was superimposed on red light, the new petioles grew obliquely upward and the leaves were flat and horizontal. The leaf positioning required both phototropin1 (phot1) and nonphototropic hypocotyl 3 (NPH3), and resulted in enhanced plant growth. In an nph3 mutant, neither optimal leaf positioning nor leaf flattening by blue light was found, and blue light-induced growth enhancement was drastically reduced. When blue light was increased from 0.1 to 5 μmol m-2s-1, normal leaf positioning and leaf flattening were induced in both phot1 and nph3 mutants, suggesting that phot2 signaling became functional and that the signaling was independent of phot1 and NPH3 in these responses. When plants were irradiated with blue light (0.1 μmol m-2s-1) from the side and red light from above, the new leaves became oriented toward the source of blue light. When we transferred these plants to both blue light and red light from above, the leaf surface changed its orientation to the new blue light source within a few hours, whereas the petioles initially were unchanged but then gradually rotated, suggesting the plasticity of leaf positioning in response to blue light. We showed the tissue expression of NPH3 and its plasma membrane localization via the coiled-coil domain and the C-terminal region. We conclude that NPH3-mediated phototropin signaling optimizes the efficiency of light perception by inducing both optimal leaf positioning and leaf

  13. Alanine/ Bromophenol Blue Polymeric Films For Radiation Dosimetry Applications

    International Nuclear Information System (INIS)

    The Polymeric dyed flexible films are considered to be the most commonly used dosimeters for routine dose monitoring in ionizing-radiation processing. Dyed polymer films prepared by simple technique of casting aqueous solution of poly (vinyl alcohol) containing bromophenol blue on horizontal glass plate are useful for high dose dosimetry. Different concentrations of L-alanine were added in presence of bromophenol blue mixed inside PVA films producing a blue film. The color has a variable absorbance with applied dose in the range from 1-35 kGy. Spectrophotometric evaluation at 602 nm for the absorbance intensity of this color was investigated as a function of dose. The used work method is uncomplicated and very easy for routine application. The radiation chemical yield G (value) was calculated in the presence and absence of alanine. Humidity during irradiation was also studied. These films show a good stability before and after irradiation under different storage conditions

  14. Pre-Existing Superbubbles as the Sites of Gamma-Ray Bursts

    CERN Document Server

    Scalo, J M; Scalo, John

    2001-01-01

    According to recent models, gamma-ray bursts apparently explode in a wide variety of ambient densities ranging from ~ 10^{-3} to 30 cm^{-3}. The lowest density environments seem, at first sight, to be incompatible with bursts in or near molecular clouds or with dense stellar winds and hence with the association of gamma-ray bursts with massive stars. We argue that low ambient density regions naturally exist in areas of active star formation as the interiors of superbubbles. The evolution of the interior bubble density as a function of time for different assumptions about the evaporative or hydrodynamical mass loading of the bubble interior is discussed. We present a number of reasons why there should exist a large range of inferred afterglow ambient densities whether gamma-ray bursts arise in massive stars or some version of compact star coalescence. We predict that many gamma-ray bursts will be identified with X-ray bright regions of galaxies, corresponding to superbubbles, rather than with blue localized re...

  15. The diversity of progenitors and emission mechanisms for ultra-long bursts

    CERN Document Server

    Gendre, B; Atteia, J L; Basa, S; Boer, M; Coward, D M; Cutini, S; D'Elia, V; Howell, E J; Klotz, A; Oates, S; De Pasquale, M; Piro, L

    2013-01-01

    GRB 111209A is the longest ever recorded burst. This burst was detected by Swift and Konus-Wind, and we obtained TOO time from XMM-Newton as well as prompt data from TAROT. We made a common reduction using data from these instruments together with other ones. This allows for the first time a precise study at high signal-to-noise ratio of the prompt to afterglow transition. We show that several mechanisms are responsible of this phase. In its prompt phase, we show that its duration is longer than 20 000 seconds. This, combined with the fact that the burst fluence is among the top 5% of what is observed for other events, makes this event extremely energetic. We discuss the possible progenitors that could explain the extreme duration properties of this burst as well as its spectral properties. We present evidences that this burst belong to a new, previously unidentified, class of GRBs. The most probable progenitor of this new class is a low metalicity blue super-giant star. We show that selection effects could p...

  16. Die erhöhte horizontal Ebene / Plano horizontal plano

    OpenAIRE

    Campo Baeza, Alberto

    2011-01-01

    Artículo sobre el plano horizontal en arquitectura. Esta investigación se inscribe en la línea "Luz y gravedad". Se relacionan conceptos y obras de la historia de la arquitectura con los conceptos desarrollados en los proyectos de Alberto Campo Baeza. La revista Bauwelt está indexada en AVERY y RIBA.

  17. The Blue Emu

    Science.gov (United States)

    Descalzi, Doug; Gillett, John; Gordon, Carlton; Keener, ED; Novak, Ken; Puente, Laura

    1993-01-01

    The primary goal in designing the Blue Emu was to provide an airline with a cost efficient and profitable means of transporting passengers between the major cities in Aeroworld. The design attacks the market where a demand for inexpensive transportation exists and for this reason the Blue Emu is an attractive investment for any airline. In order to provide a profitable aircraft, special attention was paid to cost and economics. For example, in manufacturing, simplicity was stressed in structural design to reduce construction time and cost. Aerodynamic design employed a tapered wing which reduced the induced drag coefficient while also reducing the weight of the wing. Even the propulsion system was selected with cost effectiveness in mind, yet also to maintain the marketability of the aircraft. Thus, in every aspect of the design, consideration was given to economics and marketability of the final product.

  18. Physics of gamma-ray bursts

    Science.gov (United States)

    Lamb, D. Q.

    1984-01-01

    Attention is given to the accumulating evidence for the view that gamma-ray bursts come from strongly magnetic neutron stars, discussing the physical properties of the emission region and the radiation processes expected in strong magnetic fields, and emphasizing that the observed burst spectra require that the emission region be optically thin. This entails that the energy of the emitting plasma and/or the plasma itself be continuously replenished during a burst, and that the cooling time scale of the emitting plasma be much shorter than the observed duration of the bursts. This characteristic of the cooling time scale implies that the burst intensity and spectrum can vary on extremely short time scales, and that the burst duration must have a separate explanation. It is emphasized that synchrotron emission is favored as the gamma-ray production mechanism; it is the only mechanism capable of satisfying the optical thinness constraint while producing the observed luminosity.

  19. Pulse Phase Dependence of the Magnetar Bursts

    Indian Academy of Sciences (India)

    Chetana Jain; Anjan Dutta; Biswajit Paul

    2007-12-01

    We report here results from a study of X-ray bursts from 3 magnetar candidates (SGR 1806–20, SGR 1900+14 and AXP 1E 2259+586). We have searched for a pulse phase dependence of the X-ray burst rate from these sources. X-ray light curves were obtained with the Proportional Counter Array on-board the Rossi X-ray Timing Explorer during the periods of intense burst activity in these sources. On detailed analysis of the three sources, we found a very significant burst rate for all pulsar phases. However, some locations appear to produce bursts slightly more often, rendering the non-isotropic distribution. Only in the case of SGR 1900+14, there is a clear pulse phase dependence of burst rate.

  20. Bursting for enhanced ablation of materials

    Science.gov (United States)

    Hendow, Sami; Rea, Edward; Kosa, Nadhir; Bengtsson, Magnus; Shakir, Sami

    2014-03-01

    A significant enhancement in the rate of material removal is demonstrated using a nanosecond-pulsed UV fiber laser in multi-pulsing burst mode, as compared to the case without bursting. Percussion drilling and scribing of thin-film and bulk material tests show that, in general, laser bursts with increased pulse count and reduced pulse spacing show higher rates of material removal. A considerable improvement in removal rate is demonstrated, when bursting is applied to scribing of mono-crystalline silicon (m-Si) and up to 30% in percussion drilling speed. Likewise, improved material removal is demonstrated for scribing of thin film of indium tin oxide (ITO) on glass or metal film on sapphire. Examples of material processing are given with and without bursting at similar experimental conditions of average power, scan speed, and burst/pulse energies. Experimental results included are for m-Si, ITO thin films on glass, and metal films on sapphire.

  1. Synthesizing a Blue Ocean

    OpenAIRE

    Vester, Daniel

    2012-01-01

    The purpose of this Master thesis was to determine how electronic musical instrument companies could utilize innovation strategies to add value to their products and create new business markets beyond their core. The theoretical framework was established by outlining competitive strategies suitable for adoption by electronic musical instrument companies. The Blue Ocean Strategy was compared to traditional competitive strategies such as Porter’s Five Forces, and subsequently chosen because of ...

  2. United assembly algorithm for optical burst switching

    Institute of Scientific and Technical Information of China (English)

    Jinhui Yu(于金辉); Yijun Yang(杨教军); Yuehua Chen(陈月华); Ge Fan(范戈)

    2003-01-01

    Optical burst switching (OBS) is a promising optical switching technology. The burst assembly algorithm controls burst assembly, which significantly impacts performance of OBS network. This paper provides a new assembly algorithm, united assembly algorithm, which has more practicability than conventional algorithms. In addition, some factors impacting selections of parameters of this algorithm are discussed and the performance of this algorithm is studied by computer simulation.

  3. Bubble burst as jamming phase transition

    CERN Document Server

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

    2010-01-01

    Recently research on bubble and its burst attract much interest of researchers in various field such as economics and physics. Economists have been regarding bubble as a disorder in prices. However, this research strategy has overlooked an importance of the volume of transactions. In this paper, we have proposed a bubble burst model by focusing the transactions incorporating a traffic model that represents spontaneous traffic jam. We find that the phenomenon of bubble burst shares many similar properties with traffic jam formation by comparing data taken from US housing market. Our result suggests that the transaction could be a driving force of bursting phenomenon.

  4. Two classes of gamma-ray bursts

    CERN Document Server

    Katz, J I

    1995-01-01

    Data from the 3B Catalogue suggest that short and long GRB are the results of different classes of events, rather than different parameter values within a single class: Short bursts have harder spectra in the BATSE bands, but chiefly long bursts are detected at photon energies over 1 MeV, implying that their hard photons are radiated by a process not found in short bursts. The values of \\langle V/V_{max} \\rangle for short and long bursts differ by 4.3 \\sigma, implying different spatial distributions. Only the soft gamma-ray radiation mechanisms are the same in both classes.

  5. Bursting behaviour in coupled Josephson junctions.

    Science.gov (United States)

    Hongray, Thotreithem; Balakrishnan, J; Dana, Syamal K

    2015-12-01

    We report an interesting bow-tie shaped bursting behaviour in a certain parameter regime of two resistive-capacitative shunted Josephson junctions, one in the oscillatory and the other in the excitable mode and coupled together resistively. The burst emerges in both the junctions and they show near-complete synchronization for strong enough couplings. We discuss a possible bifurcation scenario to explain the origin of the burst. An exhaustive study on the parameter space of the system is performed, demarcating the regions of bursting from other solutions. PMID:26723143

  6. Helium bubble bursting in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Sefta, Faiza [University of California, Berkeley, California 94720 (United States); Juslin, Niklas [University of Tennessee, Knoxville, Tennessee 37996 (United States); Wirth, Brian D., E-mail: bdwirth@utk.edu [University of Tennessee, Oak Ridge National Laboratory, Knoxville, Tennessee 37996 (United States)

    2013-12-28

    Molecular dynamics simulations have been used to systematically study the pressure evolution and bursting behavior of sub-surface helium bubbles and the resulting tungsten surface morphology. This study specifically investigates how bubble shape and size, temperature, tungsten surface orientation, and ligament thickness above the bubble influence bubble stability and surface evolution. The tungsten surface is roughened by a combination of adatom “islands,” craters, and pinholes. The present study provides insight into the mechanisms and conditions leading to various tungsten topology changes, which we believe are the initial stages of surface evolution leading to the formation of nanoscale fuzz.

  7. Transcriptional burst frequency and burst size are equally modulated across the human genome

    Energy Technology Data Exchange (ETDEWEB)

    Dar, Roy D. [University of Tennessee, Knoxville (UTK); Simpson, Michael L [ORNL; Weinberger, Leor S. [University of California, San Diego; Razooky, B [University of California, San Diego; Cox, Chris D. [University of Tennessee, Knoxville (UTK); McCollum, James M. [Miami University; Trimeloni, Tom [Virginia Commonwealth University, Richland; Singh, A [University of California, San Diego

    2012-01-01

    Gene expression occurs either as an episodic process, characterized by pulsatile bursts or as a constitutive, Poisson-like accumulation of gene products. It is not clear which mode of gene expression (constitutive versus bursty) predominates across a genome or how transcriptional dynamics are influenced by genomic position and promoter sequence. Here, we use time-lapse fluorescence microscopy, building off of theoretical studies that exploit the time-resolved structure of stochastic fluctuations in gene expression, to develop a three-dimensional method for mapping underlying gene-regulatory mechanisms. Over 8,000 individual human genomic loci were analyzed, and at virtually all loci, episodic bursting as opposed to constitutive expression was found to be the predominant mode of expression. Quantitative analysis of the expression dynamics at these 8,000 loci indicates that both frequency and size of transcriptional bursts vary equally across the human genome independent of promoter sequence. Strikingly, weaker expression loci modulate burst frequency to increase activity, while stronger expression loci modulate burst size to increase activity. Transcriptional activators, such as TNF, generate similar patterns of change in burst frequency and burst size. In summary, transcriptional bursting dominates across the human genome, both burst frequency and burst size vary by chromosomal location, and transcriptional activators alter burst frequency and burst size, depending on the expression level of the locus.

  8. Analysis of historic bursts and burst detection in water supply areas of different size

    NARCIS (Netherlands)

    Bakker, M.; Trietsch, E.A.; Vreeburg, J.H.G.; Rietveld, L.C.

    2014-01-01

    Pipe bursts in water distribution networks lead to water losses and a risk of damaging the urban environment. We studied hydraulic data and customer contact records of 44 real bursts for a better understanding of the phenomena. We found that most bursts were reported to the water company shortly aft

  9. Performance assessment of GPS receivers during the September 24, 2011 solar radio burst event

    Directory of Open Access Journals (Sweden)

    Muhammad Bilal

    2015-01-01

    Full Text Available The sudden outburst of in-band solar radio noise from the Sun is recognized as one of the potential Radio Frequency Interference (RFI sources that directly impact the performance of Global Navigation Satellite System (GNSS receivers. On September 24, 2011, the solar active region 1302 unleashed a moderate M7.1 soft X-ray flare associated with a very powerful radio burst at 1415 MHz. The Solar Radio Burst (SRB event spanned over three distinct episodes of solar radio noise emission that reached the maximum radio flux density of 114,144 Solar Flux Units (SFU at 13:04:46 UTC. This paper analyzes the impact of September 24, 2011 SRB event on the performance of a significant subset of NAVSTAR Global Positioning System (GPS receivers located in the sunlit hemisphere. The performance assessment is carried out in terms of Carrier-to-Noise power spectral density ratio (C/N0 degradation, dual-frequency pseudorange measurements availability, pseudorange residual errors, and dual-frequency positioning errors in the horizontal and vertical dimensions. We observed that during the SRB event the GPS C/N0 is reduced at most by 13 dB on L1 and 24 dB on L2. The C/N0 degradation caused the loss of lock on GPS L1 and L2 signals and significant code-tracking errors. We noticed that many stations experienced less than four satellite measurements, which are the minimum required number of measurements for position estimation. The deteriorated satellite-receiver geometry due to loss of signal lock and significant code-tracking errors during the solar radio burst event introduced large positioning errors in both the horizontal and vertical dimensions. Rise in vertical positioning error of 303 m and rise in horizontal positioning of 55 m could be noticed during the solar radio burst event.

  10. Performance assessment of GPS receivers during the September 24, 2011 solar radio burst event

    Science.gov (United States)

    Muhammad, Bilal; Alberti, Valentina; Marassi, Alessandro; Cianca, Ernestina; Messerotti, Mauro

    2015-10-01

    The sudden outburst of in-band solar radio noise from the Sun is recognized as one of the potential Radio Frequency Interference (RFI) sources that directly impact the performance of Global Navigation Satellite System (GNSS) receivers. On September 24, 2011, the solar active region 1302 unleashed a moderate M7.1 soft X-ray flare associated with a very powerful radio burst at 1415 MHz. The Solar Radio Burst (SRB) event spanned over three distinct episodes of solar radio noise emission that reached the maximum radio flux density of 114,144 Solar Flux Units (SFU) at 13:04:46 UTC. This paper analyzes the impact of September 24, 2011 SRB event on the performance of a significant subset of NAVSTAR Global Positioning System (GPS) receivers located in the sunlit hemisphere. The performance assessment is carried out in terms of Carrier-to-Noise power spectral density ratio (C/N0) degradation, dual-frequency pseudorange measurements availability, pseudorange residual errors, and dual-frequency positioning errors in the horizontal and vertical dimensions. We observed that during the SRB event the GPS C/N0 is reduced at most by 13 dB on L1 and 24 dB on L2. The C/N0 degradation caused the loss of lock on GPS L1 and L2 signals and significant code-tracking errors. We noticed that many stations experienced less than four satellite measurements, which are the minimum required number of measurements for position estimation. The deteriorated satellite-receiver geometry due to loss of signal lock and significant code-tracking errors during the solar radio burst event introduced large positioning errors in both the horizontal and vertical dimensions. Rise in vertical positioning error of 303 m and rise in horizontal positioning of 55 m could be noticed during the solar radio burst event.

  11. CENSUS OF BLUE STARS IN SDSS DR8

    Energy Technology Data Exchange (ETDEWEB)

    Scibelli, Samantha [Burnt Hills-Ballston Lake High School, 88 Lake Hill Road, Ballston, NY 12027 (United States); Newberg, Heidi Jo; Carlin, Jeffrey L. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180 (United States); Yanny, Brian, E-mail: heidi@rpi.edu [Experimental Astrophysics Group, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States)

    2015-01-01

    We present a census of the 12,060 spectra of blue objects ((g – r){sub 0} < –0.25) in the Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8). As part of the data release, all of the spectra were cross-correlated with 48 template spectra of stars, galaxies, and QSOs to determine the best match. We compared the blue spectra by eye to the templates assigned in SDSS DR8. 10,856 of the objects matched their assigned template, 170 could not be classified due to low signal-to-noise ratio, and 1034 were given new classifications. We identify 7458 DA white dwarfs, 1145 DB white dwarfs, 273 rarer white dwarfs (including carbon, DZ, DQ, and magnetic), 294 subdwarf O stars, 648 subdwarf B stars, 679 blue horizontal branch stars, 1026 blue stragglers, 13 cataclysmic variables, 129 white dwarf-M dwarf binaries, 36 objects with spectra similar to DO white dwarfs, 179, quasi-stellar objects (QSOs), and 10 galaxies. We provide two tables of these objects, sample spectra that match the templates, figures showing all of the spectra that were grouped by eye, and diagnostic plots that show the positions, colors, apparent magnitudes, proper motions, etc., for each classification. Future surveys will be able to use templates similar to stars in each of the classes we identify to automatically classify blue stars, including rare types.

  12. Estruturas fundamentais no blues

    OpenAIRE

    Silva, Rafael Palmeira da

    2012-01-01

    Resumo: Esta pesquisa tem como objeto de estudo a aplicação e adaptação da teoria de Schenker como ferramenta analítica aplicada ao jazz, tendo em vista a possibilidade de encontrar estruturas fundamentais distintas na música popular. Tendo como base as análises feitas por Larson (1998; 2009), Forte (2011) e Stock (1993) a pesquisa abordará, em um primeiro momento, as origens do jazz (blues e ragtime) como parte essencial para sua abordagem analítica, através da ótica etno-schenkeriana propos...

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

    Science.gov (United States)

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

    2013-03-01

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

  14. The Case of the Disappearing Spindle Burst.

    Science.gov (United States)

    Tiriac, Alexandre; Blumberg, Mark S

    2016-01-01

    Sleep spindles are brief cortical oscillations at 10-15 Hz that occur predominantly during non-REM (quiet) sleep in adult mammals and are thought to contribute to learning and memory. Spindle bursts are phenomenologically similar to sleep spindles, but they occur predominantly in early infancy and are triggered by peripheral sensory activity (e.g., by retinal waves); accordingly, spindle bursts are thought to organize neural networks in the developing brain and establish functional links with the sensory periphery. Whereas the spontaneous retinal waves that trigger spindle bursts in visual cortex are a transient feature of early development, the myoclonic twitches that drive spindle bursts in sensorimotor cortex persist into adulthood. Moreover, twitches-and their associated spindle bursts-occur exclusively during REM (active) sleep. Curiously, despite the persistence of twitching into adulthood, twitch-related spindle bursts have not been reported in adult sensorimotor cortex. This raises the question of whether such spindle burst activity does not occur in adulthood or, alternatively, occurs but has yet to be discovered. If twitch-related spindle bursts do occur in adults, they could contribute to the calibration, maintenance, and repair of sensorimotor systems. PMID:27119028

  15. Photospheric radius expansion during magnetar bursts

    NARCIS (Netherlands)

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

    2010-01-01

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

  16. IMAGING DIAGNOSIS OF THORACOLUMBAR BURST FRACTURES

    Institute of Scientific and Technical Information of China (English)

    Li-yang Dai

    2004-01-01

    Objective To review imaging use in the diagnosis ofthoracolumbar burst fractures and to determine the diagnostic value of different imaging methods.Methods One hundred and fourteen patients with 120 thoracolumbar burst fractures were retrospectively reviewed. Plain radiographs were available in all cases; CT scans and MRI were obtained in 96 and 74 cases, respectively.Results A total of 27 burst fractures were misdiagnosed as other types of fractures on radiographs alone, and accounted for 22.5% of all fractures. The results indicated that plain radiographs often fail to delineate the pathological features of thoracolumbar burst fractures, leading to delay in diagnosis.Conclusion In regard to thoracolumbar injury diagnosis, burst fractures should be differentiated from compression fractures. CT should be routinely indicated and MRI examination, when necessary, may be simultaneously considered.

  17. Bright 30 THz Impulsive Solar Bursts

    CERN Document Server

    Kaufmann, P; Marcon, R; Kudaka, A S; Cabezas, D P; Cassiano, M M; Francile, C; Fernandes, L O T; Ramirez, R F Hidalgo; Luoni, M; Marun, A; Pereyra, P; de Souza, R V

    2015-01-01

    Impulsive 30 THz continuum bursts have been recently observed in solar flares, utilizing small telescopes with a unique and relatively simple optical setup concept. The most intense burst was observed together with a GOES X2 class event on October 27, 2014, also detected at two sub-THz frequencies, RHESSI X-rays and SDO/HMI and EUV. It exhibits strikingly good correlation in time and in space with white light flare emission. It is likely that this association may prove to be very common. All three 30 THz events recently observed exhibited intense fluxes in the range of 104 solar flux units, considerably larger than those measured for the same events at microwave and sub-mm wavelengths. The 30 THz burst emission might be part of the same spectral burst component found at sub-THz frequencies. The 30 THz solar bursts open a promising new window for the study of flares at their origin

  18. Microsecond flares in gamma-ray bursts

    Science.gov (United States)

    Schaefer, Bradley E.; Cohen, Justin; Teegarden, Bonnard J.; Cline, Thomas L.; Fishman, Gerald J.; Meegan, Charles A.; Wilson, Robert B.; Paciesas, William S.; Pendleton, Geoffrey N.; Matteson, James L.

    1993-01-01

    It has been suggested that gamma-ray burst light curves may consist of many superposed flares with a duration shorter than 30/microsec. If true, the implications for the interpretation of burst data are enormous. With the launch of the Compton Gamma-Ray Observatory, four predictions of Mitrofanov's (1989) suggestion can be tested. Our results which contradict this suggestion are (1) the photon arrival times are not correlated between independent detectors, (2) the spectral hardness and intensity does not depend on the detector area, (3) the bursts seen by detectors which measure photon positions do not see microsecond flares, and (4) burst positions deduced from detectors with different projected areas are close to the positions deduced from time-of-flight differences between separated spacecraft. We conclude, therefore, that gamma-ray bursts are not composed of microsecond flares.

  19. FRBCAT: The Fast Radio Burst Catalogue

    Science.gov (United States)

    Petroff, E.; Barr, E. D.; Jameson, A.; Keane, E. F.; Bailes, M.; Kramer, M.; Morello, V.; Tabbara, D.; van Straten, W.

    2016-09-01

    Here, we present a catalogue of known Fast Radio Burst sources in the form of an online catalogue, FRBCAT. The catalogue includes information about the instrumentation used for the observations for each detected burst, the measured quantities from each observation, and model-dependent quantities derived from observed quantities. To aid in consistent comparisons of burst properties such as width and signal-to-noise ratios, we have re-processed all the bursts for which we have access to the raw data, with software which we make available. The originally derived properties are also listed for comparison. The catalogue is hosted online as a Mysql database which can also be downloaded in tabular or plain text format for off-line use. This database will be maintained for use by the community for studies of the Fast Radio Burst population as it grows.

  20. Orphan penumbrae: Submerging horizontal fields

    CERN Document Server

    Jurcak, J; Sobotka, M

    2014-01-01

    We investigate the properties of orphan penumbrae, which are photospheric filamentary structures observed in active regions near polarity inversion lines that resemble the penumbra of regular sunspots but are not connected to any umbra. We use Hinode data from the Solar Optical Telescope to determine the properties of orphan penumbrae. Spectropolarimetric data are employed to obtain the vector magnetic field and line-of-sight velocities in the photosphere. Magnetograms are used to study the overall evolution of these structures, and G-band and Ca II H filtergrams are to investigate their brightness and apparent horizontal motions. Orphan penumbrae form between regions of opposite polarity in places with horizontal magnetic fields. Their magnetic configuration is that of $\\Omega$-shaped flux ropes. In the two cases studied here, the opposite-polarity regions approach each other with time and the whole structure submerges as the penumbral filaments disappear. Orphan penumbrae are very similar to regular penumbr...

  1. Blue ocean leadership.

    Science.gov (United States)

    Kim, W Chan; Mauborgne, Renée

    2014-05-01

    Ten years ago, two INSEAD professors broke ground by introducing "blue ocean strategy," a new model for discovering uncontested markets that are ripe for growth. In this article, they apply their concepts and tools to what is perhaps the greatest challenge of leadership: closing the gulf between the potential and the realized talent and energy of employees. Research indicates that this gulf is vast: According to Gallup, 70% of workers are disengaged from their jobs. If companies could find a way to convert them into engaged employees, the results could be transformative. The trouble is, managers lack a clear understanding of what changes they could make to bring out the best in everyone. Here, Kim and Mauborgne offer a solution to that problem: a systematic approach to uncovering, at each level of the organization, which leadership acts and activities will inspire employees to give their all, and a process for getting managers throughout the company to start doing them. Blue ocean leadership works because the managers' "customers"-that is, the people managers oversee and report to-are involved in identifying what's effective and what isn't. Moreover, the approach doesn't require leaders to alter who they are, just to undertake a different set of tasks. And that kind of change is much easier to implement and track than changes to values and mind-sets. PMID:24956870

  2. Blue ocean leadership.

    Science.gov (United States)

    Kim, W Chan; Mauborgne, Renée

    2014-05-01

    Ten years ago, two INSEAD professors broke ground by introducing "blue ocean strategy," a new model for discovering uncontested markets that are ripe for growth. In this article, they apply their concepts and tools to what is perhaps the greatest challenge of leadership: closing the gulf between the potential and the realized talent and energy of employees. Research indicates that this gulf is vast: According to Gallup, 70% of workers are disengaged from their jobs. If companies could find a way to convert them into engaged employees, the results could be transformative. The trouble is, managers lack a clear understanding of what changes they could make to bring out the best in everyone. Here, Kim and Mauborgne offer a solution to that problem: a systematic approach to uncovering, at each level of the organization, which leadership acts and activities will inspire employees to give their all, and a process for getting managers throughout the company to start doing them. Blue ocean leadership works because the managers' "customers"-that is, the people managers oversee and report to-are involved in identifying what's effective and what isn't. Moreover, the approach doesn't require leaders to alter who they are, just to undertake a different set of tasks. And that kind of change is much easier to implement and track than changes to values and mind-sets.

  3. Blue emitting undecaplatinum clusters

    Science.gov (United States)

    Chakraborty, Indranath; Bhuin, Radha Gobinda; Bhat, Shridevi; Pradeep, T.

    2014-07-01

    A blue luminescent 11-atom platinum cluster showing step-like optical features and the absence of plasmon absorption was synthesized. The cluster was purified using high performance liquid chromatography (HPLC). Electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) suggest a composition, Pt11(BBS)8, which was confirmed by a range of other experimental tools. The cluster is highly stable and compatible with many organic solvents.A blue luminescent 11-atom platinum cluster showing step-like optical features and the absence of plasmon absorption was synthesized. The cluster was purified using high performance liquid chromatography (HPLC). Electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) suggest a composition, Pt11(BBS)8, which was confirmed by a range of other experimental tools. The cluster is highly stable and compatible with many organic solvents. Electronic supplementary information (ESI) available: Details of experimental procedures, instrumentation, chromatogram of the crude cluster; SEM/EDAX, DLS, PXRD, TEM, FT-IR, and XPS of the isolated Pt11 cluster; UV/Vis, MALDI MS and SEM/EDAX of isolated 2 and 3; and 195Pt NMR of the K2PtCl6 standard. See DOI: 10.1039/c4nr02778g

  4. Horizontal mergers and product quality

    OpenAIRE

    Brekke, Kurt Richard; Siciliani, Luigi; Straume, Odd Rune

    2014-01-01

    Using a spatial competition framework with three ex ante identical firms, we study the effects of a horizontal merger on quality, price and welfare. The merging firms always reduce quality. They also increase prices if demand responsiveness to quality is sufficiently low. The non-merging firm, on the other hand, always responds by increasing both quality and prices. Overall, a merger leads to higher average prices and quality in the market. The welfare implications of a merger are not clea...

  5. Bursting neurons and ultrasound avoidance in crickets.

    Science.gov (United States)

    Marsat, Gary; Pollack, Gerald S

    2012-01-01

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

  6. Horizontally oriented plates in clouds

    CERN Document Server

    Bréon, François-Marie

    2011-01-01

    Horizontally oriented plates in clouds generate a sharp specular reflectance signal in the glint direction, often referred to as "subsun". This signal (amplitude and width) may be used to analyze the relative area fraction of oriented plates in the cloud top layer and their characteristic tilt angle to the horizontal. We make use of spaceborne measurements from the POLDER instrument to provide a statistical analysis of these parameters. More than half of the clouds show a detectable maximum reflectance in the glint direction, although this maximum may be rather faint. The typical effective fraction (area weighted) of oriented plates in clouds lies between 10-3 and 10-2. For those oriented plates, the characteristic tilt angle is less than 1 degree in most cases. These low fractions imply that the impact of oriented plates on the cloud albedo is insignificant. The largest proportion of clouds with horizontally oriented plates is found in the range 500-700 hPa, in agreement with typical in situ observation of p...

  7. Postpartum Blues and Postpartum Depression

    Directory of Open Access Journals (Sweden)

    Erdem Ö et al.

    2009-09-01

    Full Text Available Postpartum blues which is seen during the postpartum period is a transient psychological state. Most of the mothers experience maternity blues in postpartum period. It remains usually unrecognized by the others. Some sensitive families can misattribute these feelings as depression. In this article, we tried to review the characteristics of maternity blues and its differences from depression. We defined depression and presented the incidence and diagnostic criteria, of major depression as well as the risk factors and clinic findings of postpartum depression. Thus, especially at primary care we aimed to prevent misdiagnosis of both maternity blues and depression

  8. Spatiotemporal chaos from bursting dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Berenstein, Igal; De Decker, Yannick [Nonlinear Physical Chemistry Unit and Interdisciplinary Center for Nonlinear Phenomena and Complex Systems (CENOLI), Faculté des Sciences, Université libre de Bruxelles (ULB), Campus Plaine, C.P. 231, B-1050 Brussels (Belgium)

    2015-08-14

    In this paper, we study the emergence of spatiotemporal chaos from mixed-mode oscillations, by using an extended Oregonator model. We show that bursting dynamics consisting of fast/slow mixed mode oscillations along a single attractor can lead to spatiotemporal chaotic dynamics, although the spatially homogeneous solution is itself non-chaotic. This behavior is observed far from the Hopf bifurcation and takes the form of a spatiotemporal intermittency where the system locally alternates between the fast and the slow phases of the mixed mode oscillations. We expect this form of spatiotemporal chaos to be generic for models in which one or several slow variables are coupled to activator-inhibitor type of oscillators.

  9. Explicit horizontal open books on some plumbings

    OpenAIRE

    Etgü, Tolga; Ozbagci, Burak

    2005-01-01

    We describe explicit open books on arbitrary plumbings of oriented circle bundles over closed oriented surfaces. We show that, for a non-positive plumbing, the open book we construct is horizontal and the corresponding compatible contact structure is also horizontal and Stein fillable. In particular, we describe horizontal open books on some Seifert fibered 3--manifolds. As another application we describe horizontal open books isomorphic to Milnor open books for some complex surface singulari...

  10. Observing a Burst with Sunglasses

    Science.gov (United States)

    2003-11-01

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

  11. Instant BlueStacks

    CERN Document Server

    Judge, Gary

    2013-01-01

    Get to grips with a new technology, understand what it is and what it can do for you, and then get to work with the most important features and tasks. A fast-paced, example-based approach guide for learning BlueStacks.This book is for anyone with a Mac or PC who wants to run Android apps on their computer. Whether you want to play games that are freely available for Android but not your computer, or you want to try apps before you install them on a physical device or use it as a development tool, this book will show you how. No previous experience is needed as this is written in plain English

  12. The Case of the Disappearing Spindle Burst

    Directory of Open Access Journals (Sweden)

    Alexandre Tiriac

    2016-01-01

    Full Text Available Sleep spindles are brief cortical oscillations at 10–15 Hz that occur predominantly during non-REM (quiet sleep in adult mammals and are thought to contribute to learning and memory. Spindle bursts are phenomenologically similar to sleep spindles, but they occur predominantly in early infancy and are triggered by peripheral sensory activity (e.g., by retinal waves; accordingly, spindle bursts are thought to organize neural networks in the developing brain and establish functional links with the sensory periphery. Whereas the spontaneous retinal waves that trigger spindle bursts in visual cortex are a transient feature of early development, the myoclonic twitches that drive spindle bursts in sensorimotor cortex persist into adulthood. Moreover, twitches—and their associated spindle bursts—occur exclusively during REM (active sleep. Curiously, despite the persistence of twitching into adulthood, twitch-related spindle bursts have not been reported in adult sensorimotor cortex. This raises the question of whether such spindle burst activity does not occur in adulthood or, alternatively, occurs but has yet to be discovered. If twitch-related spindle bursts do occur in adults, they could contribute to the calibration, maintenance, and repair of sensorimotor systems.

  13. Chemical Evolution of Blue Compact Galaxies

    Institute of Scientific and Technical Information of China (English)

    Fei Shi; Xu Kong; Fu-Zhen Cheng

    2006-01-01

    Based on a sample of 72 Blue Compact Galaxies (BCGs) observed with the 2.16 m telescope of the National Astronomical Observatories, Chinese Academy of Sciences (NAOC) and about 4000 strong emission line galaxies from the Sloan Digital Sky Survey,we analyzed their chemical evolution history using the revised chemical evolution model of Larsen et al. Our sample covers a much larger metallicity range (7.2<12+log(O/H) <9.0). We found that, in order to reproduce the observed abundance pattern and gas fraction over the whole metallicity range, a relatively continuous star formation history is needed for high metallicity galaxies, while assuming a series of instantaneous bursts with long quiescent periods (some Gyrs) for low metallicity galaxies. Model calculations also show that only the closed-box model is capable of reproducing the observational data over the whole metallicity range. Models that consider the ordinary winds and/or inflow can only fit the observations in the low metallicity range, and a model with enriched wind cannot fit the data in the whole metallicity range. This implies that the current adopted simple wind and inflow models are not applicable to massive galaxies, where the underlying physics of galactic winds or inflow could be more complicated.

  14. Bursting neurons and ultrasound avoidance in crickets

    Directory of Open Access Journals (Sweden)

    Gary eMarsat

    2012-07-01

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

  15. Bubble shape in horizontal and near horizontal intermittent flow

    International Nuclear Information System (INIS)

    Highlights: • The bubble shapes in intermittent flows are presented experimentally. • The nose-tail inversion phenomenon appears at a low Froude number in downward pipe. • Transition from plug to slug flow occurs when the bubble tail changes from staircase pattern to hydraulic jump. - Abstract: This paper presents an experimental study of the shape of isolated bubbles in horizontal and near horizontal intermittent flows. It is found that the shapes of the nose and body of bubble depend on the Froude number defined by gas/liquid mixture velocity in a pipe, whereas the shape of the back of bubble region depends on both the Froude number and bubble length. The photographic studies show that the transition from plug to slug flow occurs when the back of the bubble changes from staircase pattern to hydraulic jump with the increase of the Froude number and bubble length. The effect of pipe inclination on characteristics of bubble is significant: The bubble is inversely located in a downwardly inclined pipe when the Froude number is low, and the transition from plug flow to slug flow in an upward inclined pipe is more ready to occur compared with that in a downwardly inclined pipe

  16. Physical Parameters of Hot Horizontal-Branch Stars in NGC 6752: Deep Mixing and Radiative Levitation

    Science.gov (United States)

    Moehler, S.; Sweigart, A. V.; Landsman, W. B.; Heber, U.; Catelan, M.

    1999-01-01

    Atmospheric parameters (T(sub eff), log g and log n(sub He)/n(sub H-dot)) are derived for 42 hot horizontal branch (HB) stars in the globular cluster NGC 6752. For 19 stars Mg II and Fe II lines are detected indicating an iron enrichment by a factor 50 on average with respect to the cluster abundance whereas the magnesium abundances are consistent with the cluster metallicity. This finding adds to the growing evidence that radiative levitation plays a significant role in determining the physical parameters of blue HB stars. Indeed, we find that iron enrichment can explain part, but not all, of the problem of anomalously low gravities along the blue HB. Thus the physical parameters of horizontal branch stars hotter than about 11,500 K in NGC 6752, as derived in this paper, are best explained by a combination of helium mixing and radiative levitation effects.

  17. Gamma-Ray Bursts: Jets and Energetics

    CERN Document Server

    Frail, D A

    2003-01-01

    The relativistic outflows from gamma-ray bursts are now thought to be narrowly collimated into jets. After correcting for this jet geometry there is a remarkable constancy of both the energy radiated by the burst and the kinetic energy carried by the outflow. Gamma-ray bursts are still the most luminous explosions in the Universe, but they release energies that are comparable to supernovae. The diversity of cosmic explosions appears to be governed by the fraction of energy that is coupled to ultra-relativistic ejecta.

  18. EXIST's Gamma-Ray Burst Sensitivity

    OpenAIRE

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

    2007-01-01

    We use semi-analytic techniques to evaluate the burst sensitivity of designs for the EXIST hard X-ray survey mission. Applying these techniques to the mission design proposed for the Beyond Einstein program, we find that with its very large field-of-view and faint gamma-ray burst detection threshold, EXIST will detect and localize approximately two bursts per day, a large fraction of which may be at high redshift. We estimate that EXIST's maximum sensitivity will be ~4 times greater than that...

  19. Environmental restoration using horizontal wells

    International Nuclear Information System (INIS)

    This paper reports that under sponsorship from the U.S. Department of Energy, technical personnel from the Savannah River Laboratory and other DOE laboratories, universities and private industry have completed a full scale demonstration of environmental remediation using horizontal wells. The test successfully removed approximately 7250 kg of contaminants. A large amount of characterization and monitoring data was collected to aid in interpretation of the test and to provide the information needed for future environmental restorations that employ directionally drilled wells as extraction or delivery systems

  20. Panspermia and horizontal gene transfer

    Science.gov (United States)

    Klyce, Brig

    2009-08-01

    Evidence that extremophiles are hardy and ubiquitous is helping to make panspermia a respectable theory. But even if life on Earth originally came from space, biologists assume that the subsequent evolution of life is still governed by the darwinian paradigm. In this review we show how panspermia could amend darwinism and point to a cosmic source for, not only extremophiles but, all of life. This version of panspermia can be called "strong panspermia." To support this theory we will discuss recent evidence pertaining to horizontal gene transfer, viruses, genes apparently older than the Earthly evolution of the features they encode, and primate-specific genes without identifiable precursors.

  1. The Arecibo Fast Radio Burst: Dense Circum-burst Medium

    CERN Document Server

    Kulkarni, S R; Neill, J D

    2015-01-01

    The nature of fast radio bursts (FRB) has been extensively debated. Here we investigate FRB121102, detected at Arecibo telescope and remarkable for its unusually large spectral index. After extensive study we conclude that the spectral index is caused by a nebula with free-free absorption. We find that putative nebula must lie beyond the Milky Way. We conclude that FRBs are of extra-galactic origin and that they arise in dense star-forming regions. The challenge with extra-galactic models is the the high volumetric rate of FRBs. This high rate allows us to eliminate all models of catastrophic stellar deaths. Hyper-giant flares from young magnetars emerge as the most likely progenitors. Some of the consequences are: (i) Intergalactic FRB models can be safely ignored. (ii) The rich ISM environment of young magnetars can result in significant contribution to DM, Rotation Measure (RM) and in some cases to significant free-free optical depth. (iii) The star-forming regions in the host galaxies can contribute signi...

  2. ESTIMATE OF BURSTING PRESSURE OF MILD STEEL PRESSURE VESSEL AND PRESENTATION OF BURSTING FORMULA

    Institute of Scientific and Technical Information of China (English)

    ZHENG Chuanxiang

    2006-01-01

    In order to get more precise bursting pressure formula of mild steel, hundreds of bursting experiments of mild steel pressure vessels such as Q235(Gr.D) and 20R(1020) are done. Based on statistical data of bursting pressure and modification of Faupel formula, a more precise modified formula is given out according to the experimental data. It is proved to be more accurate after examining other bursting pressure value presented in many references. This bursting formula is very accurate in these experiments using pressure vessels with different diameter and shell thickness.Obviously, this modified bursting formula can be used in mild steel pressure vessels with different diameter and thickness of shell.

  3. The Five Year Fermi/GBM Magnetar Burst Catalog

    NARCIS (Netherlands)

    A.C. Collazzi; C. Kouveliotou; A.J. van der Horst; G.A. Younes; Y. Kaneko; E. Göğüş; L. Lin; J. Granot; M.H. Finger; V.L. Chaplin; D. Huppenkothen; A.L. Watts; A. von Kienlin; M.G. Baring; D. Gruber; P.N. Bhat; M.H. Gibby; N. Gehrels; J. Mcenery; M. van der Klis; R.A.M.J. Wijers

    2015-01-01

    Since launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has detected many hundreds of bursts from magnetar sources. While the vast majority of these bursts have been attributed to several known magnetars, there is also a small sample of magnetar-like bursts of unknown origin. Here, we present

  4. Horizontal versus vertical plate motions

    Directory of Open Access Journals (Sweden)

    M. Cuffaro

    2006-07-01

    Full Text Available We review both present and past motions at major plate boundaries, which have the horizontal component in average 10 to 100 times faster (10–100 mm/yr than the vertical component (0.01–1 mm/yr in all geodynamic settings. The steady faster horizontal velocity of the lithosphere with respect to the upward or downward velocities at plate boundaries supports dominating tangential forces acting on plates. This suggests a passive role of plate boundaries with respect to far field forces determining the velocity of plates. The forces acting on the lithosphere can be subdivided in coupled and uncoupled, as a function of the shear at the lithosphere base. Higher the asthenosphere viscosity, more significant should be the coupled forces, i.e., the mantle drag and the trench suction. Lower the asthenosphere viscosity, more the effects of uncoupled forces might result determinant, i.e., the ridge push, the slab pull and the tidal drag. Although a combination of all forces acting on the lithosphere is likely, the decoupling between lithosphere and mantle suggests that a torque acts on the lithosphere independently of the mantle drag. Slab pull and ridge push are candidates for generating this torque, but, unlike these boundary forces, the advantage of the tidal drag is to be a volume force, acting simultaneously on the whole plates, and being the decoupling at the lithosphere base controlled by lateral variations in viscosity of the low-velocity layer.

  5. Horizontal gene transfer in chromalveolates

    Directory of Open Access Journals (Sweden)

    Bhattacharya Debashish

    2007-09-01

    Full Text Available Abstract Background Horizontal gene transfer (HGT, the non-genealogical transfer of genetic material between different organisms, is considered a potentially important mechanism of genome evolution in eukaryotes. Using phylogenomic analyses of expressed sequence tag (EST data generated from a clonal cell line of a free living dinoflagellate alga Karenia brevis, we investigated the impact of HGT on genome evolution in unicellular chromalveolate protists. Results We identified 16 proteins that have originated in chromalveolates through ancient HGTs before the divergence of the genera Karenia and Karlodinium and one protein that was derived through a more recent HGT. Detailed analysis of the phylogeny and distribution of identified proteins demonstrates that eight have resulted from independent HGTs in several eukaryotic lineages. Conclusion Recurring intra- and interdomain gene exchange provides an important source of genetic novelty not only in parasitic taxa as previously demonstrated but as we show here, also in free-living protists. Investigating the tempo and mode of evolution of horizontally transferred genes in protists will therefore advance our understanding of mechanisms of adaptation in eukaryotes.

  6. Orphan penumbrae: Submerging horizontal fields

    Science.gov (United States)

    Jurčák, J.; Bellot Rubio, L. R.; Sobotka, M.

    2014-04-01

    Aims: We investigate the properties of orphan penumbrae, which are photospheric filamentary structures observed in active regions near polarity inversion lines that resemble the penumbra of regular sunspots but are not connected to any umbra. Methods: We use Hinode data from the Solar Optical Telescope to determine the properties of orphan penumbrae. Spectropolarimetric data are employed to obtain the vector magnetic field and line-of-sight velocities in the photosphere. Magnetograms are used to study the overall evolution of these structures, and G-band and Ca ii H filtergrams are to investigate their brightness and apparent horizontal motions. Results: Orphan penumbrae form between regions of opposite polarity in places with horizontal magnetic fields. Their magnetic configuration is that of Ω-shaped flux ropes. In the two cases studied here, the opposite-polarity regions approach each other with time and the whole structure submerges as the penumbral filaments disappear. Orphan penumbrae are very similar to regular penumbrae, including the existence of strong gas flows. Therefore, they could have a similar origin. The main difference between them is the absence of a "background" magnetic field in orphan penumbrae. This could explain most of the observed differences. Conclusions: The fast flows we detect in orphan penumbrae may be caused by the siphon flow mechanism. Based on the similarities between orphan and regular penumbrae, we propose that the Evershed flow is also a manifestation of siphon flows. A movie attached to Fig. 11 is available in electronic form at http://www.aanda.org

  7. Long Burst Error Correcting Codes Project

    Data.gov (United States)

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

  8. Bursts of intermediate ions in atmospheric air

    Science.gov (United States)

    Hõrrak, U.; Salm, J.; Tammet, H.

    1998-06-01

    The mobility spectrum of air ions has been measured at Tahkuse Observatory in Estonia for several years. The average concentration of intermediate ions with mobilities of 0.05-0.5 cm2 V-1 s-1 in atmospheric air is about 50 cm-3. On the level of this low background, high concentration bursts of intermediate air ions occur occasionally. A burst can be followed by subsequent evolution of intermediate ions into larger ones. To explain the bursts of intermediate air ions, two hypotheses can be advanced: (1)A burst of neutral particles occurs due to homogeneous nucleation, and the particles are charged by the attachment of cluster ions. (2) The cluster ions grow by ion-induced nucleation in proper environmental conditions.

  9. CMEs and frequency cutoff of solar bursts

    Science.gov (United States)

    Stanislavsky, Al.; Konovalenko, Al.; Koval, Ar.; Volvach, Y.; Zarka, P.

    2016-05-01

    Radio observations of solar bursts with high-frequency cutoff by the radio telescope UTR-2 (near Kharkiv, Ukraine) at 8-33 MHz on 17-19 August 2012 are presented. Such cutoff may be attributed to the emergence of the burst sources behind limb of the Sun with respect to an observer on the Earth. The events are strongly associated with solar eruptions occurred in a new active region. Ray tracing simulations show that the CMEs play a constructive role for the behind-limb bursts to be detected in ground-based observations. Likely, due to tunnel-like cavities with low density in CMEs, the radio emission of behind-limb solar bursts can be directed towards the Earth.

  10. FRBCAT: The Fast Radio Burst Catalogue

    CERN Document Server

    Petroff, E; Jameson, A; Keane, E F; Bailes, M; Kramer, M; Morello, V; Tabbara, D; van Straten, W

    2016-01-01

    Here we present a catalogue of known Fast Radio Burst (FRB) sources in the form of an online catalogue, FRBCAT. The catalogue includes information about the instrumentation used for the observations for each detected burst, the measured quantities from each observation, and model-dependent quantities derived from observed quantities. To aid in consistent comparisons of burst properties such as width and signal-to-noise ratios we have reprocessed all the bursts for which we have access to the raw data, with software which we make available. The originally derived properties are also listed for comparison. The catalogue is hosted online as a MySQL database which can also be downloaded in tabular or plain text format for off-line use. This database will be maintained for use by the community for studies of the FRB population as it grows.

  11. Axion Stars and Fast Radio Bursts

    CERN Document Server

    Iwazaki, A

    2014-01-01

    We show that fast radio bursts arise from collisions between axion stars and neutron stars. The bursts are emitted in the atmosphere of the neutron stars. The observed frequencies of the bursts are given by the axion mass $m_a$ such as $m_a/2\\pi\\simeq 1.4\\,\\mbox{GHz}\\,\\big(m_a/(6\\times 10^{-6}\\mbox{eV})\\big)$. From the event rate $\\sim 10^{-3}$ per year in a galaxy, we can determine the mass $\\sim 10^{-11}M_{\\odot}$ of the axion stars. Using these values we can explain short durations ( $\\sim $ms ) and amount of radiation energies ( $\\sim 10^{43}$GeV ) of the bursts.

  12. Design of assembly control algorithm based on burst-size feedback for optical burst switching network

    Institute of Scientific and Technical Information of China (English)

    Minglei Fu; Zichun Le

    2009-01-01

    A novel assembly control algorithm named burst-size feedback adaptive assembly period(BFAAP)is proposed.The major difference between BFAAP and other similar adaptive assembly algorithms is that the control curve of BFAAP is dynamically adjusted according to the feedback of outgoing burst size.BFAAP is compared with two typical algorithms fixed assembly period(FAP)aild min-burst length max assembly period(MBMAP)in simulation in terms of burst size distribution and assembly period.Moreover,the transmission control protocol(TCP)performance over BFAAP is also considered and simulated.

  13. Syudy of Token Generation for Burst Traffic Shaping in Optical Burst Switching Networks

    Institute of Scientific and Technical Information of China (English)

    Tang Wan; So Won-ho; Lu Ji-guang; Kim Young-chon

    2004-01-01

    Traffic shaping is one of important control operation to guarantee the Quality of Service (QoS) in optical burst switching (OBS) networks. The efficiency of traffic shaping is mainly determined by token generation method. In this paper, token generation methods of traffic shaping are evaluated by using three kinds of probability distribution, and are analyzed in terms of burst blocking probability, throughput and correlation by simulation. The simulation results show that the token generation methods decrease the burst correlation of Label Switched Paths (LSPs), and solve traffic congestion as well. The different burst arrival processes have small impact on the blocking probability for OBS networks.

  14. Optimal Codes for the Burst Erasure Channel

    Science.gov (United States)

    Hamkins, Jon

    2010-01-01

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

  15. Census of blue stars in SDSS DR8

    CERN Document Server

    Scibelli, Samantha; Carlin, Jeffrey L; Yanny, Brian

    2014-01-01

    We present a census of the 12,060 spectra of blue objects ($(g-r)_0<-0.25$) in the Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8). As part of the data release, all of the spectra were cross-correlated with 48 template spectra of stars, galaxies and QSOs to determine the best match. We compared the blue spectra by eye to the templates assigned in SDSS DR8. 10,856 of the objects matched their assigned template, 170 could not be classified due to low signal-to-noise (S/N), and 1034 were given new classifications. We identify 7458 DA white dwarfs, 1145 DB white dwarfs, 273 rarer white dwarfs (including carbon, DZ, DQ, and magnetic), 294 subdwarf O stars, 648 subdwarf B stars, 679 blue horizontal branch stars, 1026 blue stragglers, 13 cataclysmic variables, 129 white dwarf - M dwarf binaries, 36 objects with spectra similar to DO white dwarfs, 179 QSOs, and 10 galaxies. We provide two tables of these objects, sample spectra that match the templates, figures showing all of the spectra that were grouped by ...

  16. Neutrinos from Gamma Ray Bursts

    CERN Document Server

    Mannheim, K

    2000-01-01

    The observed fluxes of cosmic rays and gamma rays are used to infer the maximum allowed high-energy neutrino flux allowed for Gamma Ray Bursts (GRBs), following Mannheim, Protheroe, and Rachen (2000). It is shown that if GRBs produce the ultrahigh-energy cosmic rays, they should contribute (a) at least 10% of the extragalactic gamma ray background between 3 MeV and 30 GeV, contrary to their observed energy flux which is only a minute fraction of this flux, and (b) a cumulative neutrino flux a factor of 20 below the AMANDA (Neutrino 2000) limit on isotropic neutrinos. This could have two implications, either GRBs do not produce the ultrahigh energy cosmic rays or that the GRBs are strongly beamed and emit most of their power at energies well above 100 GeV implausibly increasing the energy requirements, but consistent with the marginal detections of a few low-redshift GRBs by MILAGRITO, HEGRA-AIROBICC, and the Tibet-Array. All crucial measurements to test the models will be available in the next few years. Thes...

  17. Bursting the Taylor cone bubble

    Science.gov (United States)

    Pan, Zhao; Truscott, Tadd

    2014-11-01

    A soap bubble fixed on a surface and placed in an electric field will take on the shape of a cone rather than constant curvature (dome) when the electrical field is not present. The phenomenon was introduced by J. Zeleny (1917) and studied extensively by C.T. Wilson & G.I. Taylor (1925). We revisit the Taylor cone problem by studying the deformation and bursting of soap bubbles in a point charge electric field. A single bubble takes on the shape of a cone in the electric field and a high-speed camera equipped with a micro-lens is used to observe the unsteady dynamics at the tip. Rupture occurs as a very small piece of the tip is torn away from the bubble toward the point charge. Based on experiments, a theoretical model is developed that predicts when rupture should occur. This study may help in the design of foam-removal techniques in engineering and provide a better understanding of an electrified air-liquid interface.

  18. Gamma-ray Burst Cosmology

    CERN Document Server

    Wang, F Y; Liang, E W

    2015-01-01

    Gamma-ray bursts (GRBs) are the most luminous electromagnetic explosions in the Universe, which emit up to $8.8\\times10^{54}$ erg isotropic equivalent energy in the hard X-ray band. The high luminosity makes them detectable out to the largest distances yet explored in the Universe. GRBs, as bright beacons in the deep Universe, would be the ideal tool to probe the properties of high-redshift universe: including the cosmic expansion and dark energy, star formation rate, the reionization epoch and the metal enrichment history of the Universe. In this article, we review the luminosity correlations of GRBs, and implications for constraining the cosmological parameters and dark energy. Observations show that the progenitors of long GRBs are massive stars. So it is expected that long GRBs are tracers of star formation rate. We also review the high-redshift star formation rate derived from GRBs, and implications for the cosmic reionization history. The afterglows of GRBs generally have broken power-law spectra, so it...

  19. Gamma Ray Bursts as Neutrino Sources

    CERN Document Server

    Mészáros, P

    2015-01-01

    Gamma-ray burst sources appear to fulfill all the conditions for being efficient cosmic ray accelerators, and being extremely compact, are also expected to produce multi-GeV to PeV neutrinos. I review the basic model predictions for the expected neutrino fluxes in classical GRBs as well as in low luminosity and choked bursts, discussing the recent IceCube observational constraints and implications from the observed diffuse neutrino flux.

  20. Supernovae and gamma-ray bursts connection

    Science.gov (United States)

    Valle, Massimo Della

    2015-12-01

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

  1. Black Hole Lensing and Wave Bursts

    CERN Document Server

    Gogberashvili, Merab

    2016-01-01

    It is shown that close to a black hole horizon wave equations have real-valued exponentially time-dependent solutions and to investigate strong gravitational lensing we need to introduce an effective negative cosmological constant between the Schwarzschild and photon spheres. Then exponentially amplified reflected waves from this effective AdS space could explain properties of some gamma ray bursts, fast radio bursts and gravitational waves.

  2. Supernovae and gamma-ray bursts connection

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-12-17

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

  3. Autaptic Connections Shift Network Excitability and Bursting

    OpenAIRE

    Wiles, Laura; Gu, Shi; Pasqualetti, Fabio; Bassett, Danielle S.; Meaney, David F.

    2016-01-01

    Network architecture forms a critical constraint on neuronal function. Here we examine the role of structural autapses, when a neuron synapses onto itself, in driving network-wide bursting behavior. Using a simple spiking model of neuronal activity, we study how autaptic connections affect activity patterns, and evaluate if neuronal degree or controllability are significant factors that affect changes in bursting from these autaptic connections. We observed that adding increasing numbers of a...

  4. Cosmological parametrization of $\\gamma$ ray burst models

    CERN Document Server

    Linder, E V

    1996-01-01

    Using three parametrizations of the gamma ray burst count data comparison is made to cosmological source models. While simple models can fit and faint end slope constraints, the addition of a logarithmic count range variable describing the curvature of the counts shows that models with no evolution or evolution power law in redshift with index less than 10 fail to satisfy simultaneously all three descriptors of the burst data. The cosmological source density that would be required for a fit is illustrated.

  5. Constraints on Helium Enhancement in the Globular Cluster M3 (NGC 5272): The Horizontal Branch Test

    Science.gov (United States)

    Catelan, M.; Grundahl, F.; Sweigart, A. V.; Valcarce, A. A. R.; Cortes, C.

    2007-01-01

    It has recently been suggested that the presence of multiple populations showing various amounts of helium enhancement is a common feature among globular star clusters. In this scenario, such a helium enhancement would be particularly apparent in the enhanced luminosity of thc blue horizontal branch (HB) stars compared to the red HB stars. In this Letter, wc test this scenario in the case of the Galactic globular cluster M3 (NGC 5272), using high-precision Stromgren photometry and spectroscopic gravities for blue HB stars. We find that any helium enhancement among the cluster's blue HB stars must be significantly less than I%, thus ruling out the much higher helium enhancements that have been proposed in the literature.

  6. Blue-sky thinking

    International Nuclear Information System (INIS)

    Global environmental problems - such as the greenhouse effect, the depletion of natural resources and the accumulation of wastes - have been recognized as common international issues affecting humanity since the 1990s. Sustainable development on a global scale is now sought, for instance, with the establishment of the targets for greenhouse gas reduction in the 1997 Kyoto Protocol, and with the adoption of the Declaration on Sustainable Development at the 2002 Johannesburg Summit. Honda launched the slogan 'Blue Sky for Children' in the 1960s when environmental pollution became a highly visible issue. During that decade we started an aggressive approach aimed at substantial environmental improvement, and unveiled the Compound Vortex Controlled Combustion (CVCC) engine - which used unique low-emission technology - in the United States and Japan. Since then, we have developed the Variable Valve Timing and Lift Electric Control System (VTEC) and the i-VTEC series with innovative engine technology, permitting global production of vehicles that combine high performance with state-of-the-art low-emission technologies. And we continued to work to preserve the global environment by releasing a hybrid vehicle, the Insight, which achieved the most efficient fuel consumption in the world at the time of its introduction in 1998

  7. Blue Man袭东京

    Institute of Scientific and Technical Information of China (English)

    Naomi Saeki; 李宝怡

    2008-01-01

    <正>20年前在美国曼克顿风靡一时的Blue Man Group,最近在东京出现,马上成为城中话题。在东京,每年有不少舞台剧演出,但是像Blue Man Group这样备受注目的,近年罕见。Blue Man Group in Tokyo于上年12月开始公演·1个月的门票早在9月中旬

  8. Blue Angel for green electronics

    Energy Technology Data Exchange (ETDEWEB)

    Boettcher-Tiedemann, C.; Jacobs, B. [Federal Environmental Agency, Berlin (Germany)

    2004-07-01

    The Blue Angel was the first eco-label worldwide. It has been in existence for 26 years. For the last 12 years, modern electronic office and communications equipment has been among the products that are eligible for award of the Blue Angel. The Blue Angel eco-label is an important element of integrated product policy and is aimed towards environmentally sound product design. In addition, health aspects are increasingly being taken into account in criteria development. The use of the label gives innovative companies better market opportunities for products so labelled. For consumers and for purchasers in businesses and public administrations, it gives valuable guidance for product purchase. (orig.)

  9. Horizontal molecular orientation in solution-processed organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, L.; Inoue, M. [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Komino, T. [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Japan Science and Technology Agency (JST), ERATO, Adachi Molecular Exciton Engineering Project, c/o Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Education Center for Global Leaders in Molecular System for Devices, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Kim, J.-H. [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Ribierre, J. C., E-mail: ribierre@opera.kyushu-u.ac.jp, E-mail: adachi@cstf.kyushu-u.ac.jp [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Japan Science and Technology Agency (JST), ERATO, Adachi Molecular Exciton Engineering Project, c/o Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); and others

    2015-02-09

    Horizontal orientation of the emission transition dipole moments achieved in glassy vapor-deposited organic thin films leads to an enhancement of the light out-coupling efficiency in organic light-emitting diodes (OLEDs). Here, our combined study of variable angle spectroscopic ellipsometry and angle dependent photoluminescence demonstrates that such a horizontal orientation can be achieved in glassy spin-coated organic films based on a composite blend of a heptafluorene derivative as a dopant and a 4,4′-bis(N-carbazolyl)-1,1′-biphenyl as a host. Solution-processed fluorescent OLEDs with horizontally oriented heptafluorene emitters were then fabricated and emitted deep blue electroluminescence with an external quantum efficiency as high as 5.3%.

  10. Ecology of blue straggler stars

    CERN Document Server

    Carraro, Giovanni; Beccari, Giacomo

    2015-01-01

    The existence of blue straggler stars, which appear younger, hotter, and more massive than their siblings, is at odds with a simple picture of stellar evolution. Such stars should have exhausted their nuclear fuel and evolved long ago to become cooling white dwarfs. They are found to exist in globular clusters, open clusters, dwarf spheroidal galaxies of the Local Group, OB associations and as field stars. This book summarises the many advances in observational and theoretical work dedicated to blue straggler stars. Carefully edited extended contributions by well-known experts in the field cover all the relevant aspects of blue straggler stars research: Observations of blue straggler stars in their various environments; Binary stars and formation channels; Dynamics of globular clusters; Interpretation of observational data and comparison with models. The book also offers an introductory chapter on stellar evolution written by the editors of the book.

  11. Karner Blue Butterfly Recovery Plan

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This recovery plan has been prepared by the Karner Blue Butterfly Recovery Team under the leadership of Dr. David Andow, University of Minnesota-St. Paul. Dr. John...

  12. China Mobile: Expanding "Blue Ocean"

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Driving force is crucial for realizing high-speed growth. The strong driving force from "Blue Ocean Strategy" is an important advantage for China Mobile to realize harmonious and leap-forward development.

  13. Modeling gamma-ray bursts

    Science.gov (United States)

    Maxham, Amanda

    Discovered serendipitously in the late 1960s, gamma-ray bursts (GRBs) are huge explosions of energy that happen at cosmological distances. They provide a grand physical playground to those who study them, from relativistic effects such as beaming, jets, shocks and blastwaves to radiation mechanisms such as synchrotron radiation to galatic and stellar populations and history. Through the Swift and Fermi space telescopes dedicated to observing GRBs over a wide range of energies (from keV to GeV), combined with accurate pinpointing that allows ground based follow-up observations in the optical, infrared and radio, a rich tapestry of GRB observations has emerged. The general picture is of a mysterious central engine (CE) probably composed of a black hole or neutron star that ejects relativistic shells of matter into intense magnetic fields. These shells collide and combine, releasing energy in "internal shocks" accounting for the prompt emission and flaring we see and the "external shock" or plowing of the first blastwave into the ambient surrounding medium has well-explained the afterglow radiation. We have developed a shell model code to address the question of how X-ray flares are produced within the framework of the internal shock model. The shell model creates randomized GRB explosions from a central engine with multiple shells and follows those shells as they collide, merge and spread, producing prompt emission and X-ray flares. We have also included a blastwave model, which can constrain X-ray flares and explain the origin of high energy (GeV) emission seen by the Fermi telescope. Evidence suggests that gamma-ray prompt emission and X-ray flares share a common origin and that at least some flares can only be explained by long-lasting central engine activity. We pay special attention to the time history of central engine activity, internal shocks, and observed flares. We calculate the gamma-ray (Swift/BAT band) and X-ray (Swift/XRT band) lightcurves for arbitrary

  14. Blue Ocean vs. Five Forces

    OpenAIRE

    Burke, Andrew; Stel, André; Thurik, Roy

    2010-01-01

    textabstractThe article reports on the authors' research in the Netherlands which focused on a profit model in Dutch retail stores and a so-called blue-ocean approach which requires a new market that attracts consumers and increases profits. Topics include the competitive strategy approach to increasing profits. The authors conclude that the blue-ocean strategy or innovation approach is sustainable.

  15. Efficient inhibition of bursts by bursts in the auditory system of crickets.

    Science.gov (United States)

    Marsat, G; Pollack, G S

    2007-06-01

    In crickets, auditory information about ultrasound is carried bilaterally to the brain by the AN2 neurons. The ON1 neuron provides contralateral inhibitory input to AN2, thereby enhancing bilateral contrast between the left and right AN2s, an important cue for sound localization. We examine how the structures of the spike trains of these neurons affect this inhibitory interaction. As previously shown for AN2, ON1 responds to salient peaks in stimulus amplitude with bursts of spikes. Spike bursts, but not isolated spikes, reliably signal the occurrence of specific features of the stimulus. ON1 and AN2 burst at similar times relative to the amplitude envelope of the stimulus, and bursts are more tightly time-locked to stimulus feature than the isolated spikes. As a consequence, spikes that, in the absence of contralateral inhibition, would occur within AN2 bursts are more likely to be preceded by spikes in ON1 (mainly also in bursts) than are isolated AN2 spikes. This leads to a large decrease in the burst rate of the inhibited AN2. We conclude that the match in coding properties of ON1 and AN2 allows contralateral inhibition to be most efficient for those portions of the response that carry the behaviourally relevant information, i.e. for bursts.

  16. Spray controller for horizontal boom movements compensation

    OpenAIRE

    El Bahir, Loussain; Lebeau, Frédéric; Destain, Marie-France; Kinnaert; Hanus, Raymond

    2002-01-01

    Longitudinal spray distribution is mainly affected by the horizontal speed variations of the nozzles. Manufacturers classically try to reduce unwanted nozzles movements using horizontal boom suspension but these methods show performance and price limitations. The purpose of this paper is to propose a spray controller aiming to compensate the effect of the horizontal boom movements on the spray distribution besides the effect of tractor speed variations. The controller is based on ...

  17. Analysis of horizontal flows in the solar granulation

    Science.gov (United States)

    Quintero Noda, C.; Shimizu, T.; Suematsu, Y.

    2016-04-01

    Solar limb observations sometimes reveal the presence of a satellite lobe in the blue wing of the Stokes I profile from pixels belonging to granules. The presence of this satellite lobe has been associated in the past to strong line-of-sight gradients and, as the line-of-sight component is almost parallel to the solar surface, to horizontal granular flows. We aim to increase the knowledge about these horizontal flows studying a spectropolarimetric observation of the north solar pole. We will make use of two state of the art techniques, the spatial deconvolution procedure that increases the quality of the data removing the stray light contamination, and spectropolarimetric inversions that will provide the vertical stratification of the atmospheric physical parameters where the observed spectral lines form. We inverted the Stokes profiles using a two component configuration, obtaining that one component is strongly blueshifted and displays a temperature enhancement at upper photospheric layers while the second component has low redshifted velocities and it is cool at upper layers. In addition, we examined a large number of cases located at different heliocentric angles, finding smaller velocities as we move from the centre to the edge of the granule. Moreover, the height location of the enhancement on the temperature stratification of the blueshifted component also evolves with the spatial location on the granule being positioned on lower heights as we move to the periphery of the granular structure.

  18. Symmetry of oculomotor burst neuron coordinates about Listing's plane.

    Science.gov (United States)

    Crawford, J D; Vilis, T

    1992-08-01

    1. The purpose of this investigation was to determine the axes of eye rotation generated by oculomotor burst neuron populations and the coordinate system that they collectively define. In particular, we asked if such coordinates might be related to constraints in the emergent behavior, i.e., Listing's law for saccades. 2. The mesencephalic rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) was identified in four monkeys with the use of single-unit recording, and then explored with the use of electrical microstimulation and pharmacological inactivation with the inhibitory gamma-aminobutyric acid (GABA) agonist muscimol. Three-dimensional (3-D) eye positions and velocities were recorded in one or both eyes while alert animals made eye movements in response to visual stimuli and head rotation. 3. Unilateral stimulation of the riMLF (20 microA, 200 Hz, 300-600 ms) produced conjugate, constant velocity eye rotations, which then stopped abruptly and held their final positions. This is expected if the riMLF produces phasic signals upstream from the oculomotor integrator. 4. Units that burst before upward or downward saccades were recorded intermingled in each side of the riMLF. Unilateral stimulation of the same riMLF sites produced eye rotations about primarily torsional axes, clockwise (CW) during right riMLF stimulation and counterclockwise (CCW) during left stimulation. Only small and inconsistent vertical components were observed, supporting the view that the riMLF carries intermingled up and down signals. 5. The torsional axes of eye rotation produced by riMLF stimulation did not correlate to external anatomic landmarks. Instead, stimulation axes from both riMLF sides aligned with the primary gaze direction orthogonal to Listing's plane of eye positions recorded during saccades. 6. Injection of muscimol into one side of the riMLF produced a conjugate deficit in saccades and quick phases, including a 50% reduction in all vertical velocities

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

    Science.gov (United States)

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

    2016-03-01

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

  20. An Intelligent Segmented Burst Assembly Mechanism in Optical Burst Switching Networks

    Institute of Scientific and Technical Information of China (English)

    XIE Yi-Yuan; ZHANG Jian-Guo

    2008-01-01

    We focus on the burst assembly mechanism and propose a new intelligent method in which the burst is assembled from several internet protocol (IP) packets in which the number of IP packets is changed according to the traffic load and the burst is segmented into several parts, called the ISOBS mechanism. The average burst assembly time of the ISOBS mechanism decreases as compared with the fixed-assembly-time and fixed-assembly-time-and-length mechanisms. The loss ratio decreases 50% as compared with the general optical burst switching (OBS) mechanism. The last segment can carry high quality of service (QOS) information. We can achieve that the loss ratio of the last segment is almost zero when the traffic load is less than 0.05. When the traffic load is 0.9, the loss ratio of the last segment is 0.0041. The ISOBS can support to transmit different QOS data.

  1. An Intelligent Segmented Burst Assembly Mechanism in Optical Burst Switching Networks

    International Nuclear Information System (INIS)

    We focus on the burst assembly mechanism and propose a new intelligent method in which the burst is assembled from several internet protocol (IP) packets in which the number of IP packets is changed according to the traffic load and the burst is segmented into several parts, called the ISOBS mechanism. The average burst assembly time of the ISOBS mechanism decreases as compared with the fixed-assembly-time and fixed-assembly-time-and-length mechanisms. The loss ratio decreases 50% as compared with the general optical burst switching (OBS) mechanism. The last segment can carry high quality of service (QOS) information. We can achieve that the loss ratio of the last segment is almost zero when the traffic load is less than 0.05. When the traffic load is 0.9, the loss ratio of the last segment is 0.0041. The ISOBS can support to transmit different QOS data. (fundamental areas of phenomenology (including applications))

  2. System for Estimating Horizontal Velocity During Descent

    Science.gov (United States)

    Johnson, Andrew; Cheng, Yang; Wilson, Reg; Goguen, Jay; Martin, Alejandro San; Leger, Chris; Matthies, Larry

    2007-01-01

    The descent image motion estimation system (DIMES) is a system of hardware and software, designed for original use in estimating the horizontal velocity of a spacecraft descending toward a landing on Mars. The estimated horizontal velocity is used in generating rocket-firing commands to reduce the horizontal velocity as part of an overall control scheme to minimize the landing impact. DIMES can also be used for estimating the horizontal velocity of a remotely controlled or autonomous aircraft for purposes of navigation and control.

  3. 21 CFR 73.50 - Ultramarine blue.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Ultramarine blue. 73.50 Section 73.50 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Foods § 73.50 Ultramarine blue. (a) Identity. The color additive ultramarine blue is a blue pigment obtained...

  4. Diagnostics From Three Rising Submillimeter Bursts

    CERN Document Server

    Zhou, Ai-Hua; Wang, Xin-Dong

    2015-01-01

    In the paper we investigate three novel rising submillimeter (THz) bursts occurred sequentially in a super-Active Region NOAA 10486. The average rising rate of the flux density above 200 GHz is only 20 sfu/GHz (corresponding spectral index $\\alpha$ of 1.6) for the THz spectral components of 2003 October 28 and November 4 bursts, while it can attain values of 235 sfu/GHz ($\\alpha$=4.8) for 2003 November 2 burst. The steeply rising THz spectrum can be produced by a population of high relativistic electrons with a low-energy cutoff of 1 MeV , while it only requires a low-energy cutoff of 30 keV for the two slowly rising THz bursts, via gyrosynchrotron (GS) radiation based on our numerical simulations of burst spectra in the magnetic dipole field case. The electron density variation is much larger in the THz source than that in microwave (MW) one. It is interesting that the THz source radius decreased by 20--50$\\%$ during the decay phase for the three events, but the MW one increased by 28$\\%$ for the 2003 Novemb...

  5. Sources of type III solar microwave bursts

    Science.gov (United States)

    Zhdanov, Dmitriy; Lesovoi, Sergey; Tokhchukova, Susanna

    2016-06-01

    Microwave fine structures allow us to study plasma evolution in an energy release region. The Siberian Solar Radio Telescope (SSRT) is a unique instrument designed to examine fine structures at 5.7 GHz. A complex analysis of data from RATAN-600, 4-8 GHz spectropolarimeter, and SSRT, simultaneously with extreme UV data, made it possible to localize sources of III type microwave drift bursts in August 10, 2011 event within the entire frequency band of burst occurrences, as well as to determine the most probable region of primary energy release. To localize sources of III type bursts from RATAN-600 data, an original method for data processing has been worked out. At 5.7 GHz, the source of bursts was determined along two coordinates whereas at 4.5, 4.7, 4.9, 5.1, 5.3, 5.5 and 6.0 GHz, their locations were identified along one coordinate. The size of the burst source at 5.1 GHz was found to be maximum as compared to source sizes at other frequencies.

  6. Bursting synchronization in clustered neuronal networks

    Institute of Scientific and Technical Information of China (English)

    Yu Hai-Tao; Wang Jiang; Deng Bin; Wei Xi-Le

    2013-01-01

    Neuronal networks in the brain exhibit the modular (clustered) property,i.e.,they are composed of certain subnetworks with differential internal and external connectivity.We investigate bursting synchronization in a clustered neuronal network.A transition to mutual-phase synchronization takes place on the bursting time scale of coupled neurons,while on the spiking time scale,they behave asynchronously.This synchronization transition can be induced by the variations of inter-and intracoupling strengths,as well as the probability of random links between different subnetworks.Considering that some pathological conditions are related with the synchronization of bursting neurons in the brain,we analyze the control of bursting synchronization by using a time-periodic external signal in the clustered neuronal network.Simulation results show a frequency locking tongue in the driving parameter plane,where bursting synchronization is maintained,even in the presence of external driving.Hence,effective synchronization suppression can be realized with the driving parameters outside the frequency locking region.

  7. The environment of nearby Blue Compact Dwarf Galaxies

    CERN Document Server

    Lopez-Sanchez, Angel R; van Eymeren, Janine; Esteban, Cesar; Popping, Attila; Hibbard, John

    2009-01-01

    We are obtaining deep multiwavelength data of a sample of nearby blue compact dwarf galaxies (BCDGs) combining broad-band optical/NIR and H$\\alpha$ photometry, optical spectroscopy and 21-cm radio observations. Here we present HI results obtained with the Australia Telescope Compact Array for some BCDGs, all showing evident interaction features in their neutral gas component despite the environment in which they reside. Our analysis strongly suggests that interactions with or between low-luminosity dwarf galaxies or HI clouds are the main trigger mechanism of the star-forming bursts in BCDGs; however these dwarf objects are only detected when deep optical images and complementary HI observations are performed. Are therefore BCDGs real isolated systems?

  8. X-ray bursts observed with JEM-X

    DEFF Research Database (Denmark)

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

    2006-01-01

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

  9. Widespread horizontal transfer of retrotransposons.

    Science.gov (United States)

    Walsh, Ali Morton; Kortschak, R Daniel; Gardner, Michael G; Bertozzi, Terry; Adelson, David L

    2013-01-15

    In higher organisms such as vertebrates, it is generally believed that lateral transfer of genetic information does not readily occur, with the exception of retroviral infection. However, horizontal transfer (HT) of protein coding repetitive elements is the simplest way to explain the patchy distribution of BovB, a long interspersed element (LINE) about 3.2 kb long, that has been found in ruminants, marsupials, squamates, monotremes, and African mammals. BovB sequences are a major component of some of these genomes. Here we show that HT of BovB is significantly more widespread than believed, and we demonstrate the existence of two plausible arthropod vectors, specifically reptile ticks. A phylogenetic tree built from BovB sequences from species in all of these groups does not conform to expected evolutionary relationships of the species, and our analysis indicates that at least nine HT events are required to explain the observed topology. Our results provide compelling evidence for HT of genetic material that has transformed vertebrate genomes.

  10. "Clothed in triple blues": sorting out the Italian blues.

    Science.gov (United States)

    Bimler, David; Uusküla, Mari

    2014-04-01

    Cross-cultural comparisons of color perception and cognition often feature versions of the "similarity sorting" procedure. By interpreting the assignment of two color samples to different groups as an indication that the dissimilarity between them exceeds some threshold, sorting data can be regarded as low-resolution similarity judgments. Here we analyze sorting data from speakers of Italian, Russian, and English, applying multidimensional scaling to delineate the boundaries between perceptual categories while highlighting differences between the three populations. Stimuli were 55 color swatches, predominantly from the blue region. Results suggest that at least two Italian words for "blue" are basic, a similar situation to Russian, in contrast to English where a single "blue" term is basic.

  11. Bursting activity spreading through asymmetric interactions

    CERN Document Server

    Onaga, Tomokatsu

    2014-01-01

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

  12. Variable protostellar accretion with episodic bursts

    CERN Document Server

    Vorobyov, Eduard I

    2015-01-01

    We present the latest development of the disk gravitational instability and fragmentation model, originally introduced by us to explain episodic accretion bursts in the early stages of star formation. Using our numerical hydrodynamics model with improved disk thermal balance and star-disk interaction, we computed the evolution of protostellar disks formed from the gravitational collapse of prestellar cores. In agreement with our previous studies, we find that cores of higher initial mass and angular momentum produce disks that are more favorable to gravitational instability and fragmentation, while a higher background irradiation and magnetic fields moderate the disk tendency to fragment. The protostellar accretion in our models is time-variable, thanks to the nonlinear interaction between different spiral modes in the gravitationally unstable disk, and can undergo episodic bursts when fragments migrate onto the star owing to the gravitational interaction with other fragments or spiral arms. Most bursts occur...

  13. Gamma-ray bursts and cosmology.

    Science.gov (United States)

    Lamb, D Q

    2007-05-15

    I review the current status of the use of gamma-ray bursts (GRBs) as probes of the early Universe and cosmology. I describe the promise of long GRBs as probes of the high redshift (z>4) and very high redshift (z>5) Universe, and several key scientific results that have come from observations made possible by accurate, rapid localizations of these bursts by Swift. I then estimate the fraction of long GRBs that lie at very high redshifts and discuss ways in which it may be possible to rapidly identify-and therefore study-a larger number of these bursts. Finally, I discuss the ways in which both long and short GRBs can be made 'standard candles' and used to constrain the properties of dark energy. PMID:17301023

  14. Study on fault induced rock bursts

    Institute of Scientific and Technical Information of China (English)

    LI Zhi-hua; DOU Lin-ming; LU Cai-ping; MU Zong-long; CAO An-ye

    2008-01-01

    In order to study the rules of rock bursts caused by faults by means of mechanical analysis of a roof rock-mass balanced structure and numerical simulation about fault slip destabilization, the effect of coal mining operation on fault plane stresses and slip displacement were studied. The results indicate that the slip displacement sharply increases due to the decrease of normal stress and the increase of shear stress at the fault plane when the working face advances from the footwall to the fault itself, which may induce a fault rock burst. However, this slip displacement will be very small due to the increase of normal stress and the decrease of shear stress when the working face advances from the hanging wall to the fault itself, which results in a very small risk of a fault rock burst.

  15. On the bursting of gene products

    CERN Document Server

    Yvinec, Romain

    2011-01-01

    In this article we demonstrate that the so-called bursting production of molecular species during gene expression may be an artifact caused by low time resolution in experimental data collection and not an actual burst in production. We reach this conclusion through an analysis of a two-stage and binary model for gene expression, and demonstrate that in the limit when mRNA degradation is much faster than protein degradation they are equivalent. The negative binomial distribution is shown to be a limiting case of the binary model for fast "on to off" state transitions and high values of the ratio between protein synthesis and degradation rates. The gene products population increases by unity but multiple times in a time interval orders of magnitude smaller than protein half-life or the precision of the experimental apparatus employed in its detection. This rare-and-fast one-by-one protein synthesis has been interpreted as bursting.

  16. Gamma Ray Bursts Observations and Theoretical Conjectures

    CERN Document Server

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

    2008-01-01

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

  17. A mechanism for fast radio bursts

    CERN Document Server

    Romero, Gustavo E; Vieyro, Florencia L

    2015-01-01

    Fast radio bursts are mysterious transient sources likely located at cosmological distances. The derived brightness temperatures exceed by many orders of magnitude the self-absorption limit of incoherent synchrotron radiation, implying the operation of a coherent emission process. We propose a radiation mechanism for fast radio bursts where the emission arises from collisionless Bremsstrahlung in strong plasma turbulence excited by relativistic electron beams. We discuss possible astrophysical scenarios in which this process might operate. The emitting region is a turbulent plasma hit by a relativistic jet, where Langmuir plasma waves produce a concentration of intense electrostatic soliton-like regions (cavitons). The resulting radiation is coherent and, under some physical conditions, can be polarised and have a power-law distribution in energy. We obtain radio luminosities in agreement with the inferred values for fast radio bursts. The timescale of the radio flare in some cases can be extremely fast, of t...

  18. Investigation of Primordial Black Hole Bursts Using Interplanetary Network Gamma-ray Bursts

    Science.gov (United States)

    Ukwatta, T. N.; Hurley, K.; MacGibbon, J. H.; Svinkin, D. S.; Aptekar, R. L.; Golenetskii, S. V.; Frederiks, D. D.; Pal'shin, V. D.; Goldsten, J.; Boynton, W.; Kozyrev, A. S.; Rau, A.; von Kienlin, A.; Zhang, X.; Connaughton, V.; Yamaoka, K.; Ohno, M.; Ohmori, N.; Feroci, M.; Frontera, F.; Guidorzi, C.; Cline, T.; Gehrels, N.; Krimm, H. A.; McTiernan, J.

    2016-07-01

    The detection of a gamma-ray burst (GRB) in the solar neighborhood would have very important implications for GRB phenomenology. The leading theories for cosmological GRBs would not be able to explain such events. The final bursts of evaporating primordial black holes (PBHs), however, would be a natural explanation for local GRBs. We present a novel technique that can constrain the distance to GRBs using detections from widely separated, non-imaging spacecraft. This method can determine the actual distance to the burst if it is local. We applied this method to constrain distances to a sample of 36 short-duration GRBs detected by the Interplanetary Network (IPN) that show observational properties that are expected from PBH evaporations. These bursts have minimum possible distances in the 1013–1018 cm (7–105 au) range, which are consistent with the expected PBH energetics and with a possible origin in the solar neighborhood, although none of the bursts can be unambiguously demonstrated to be local. Assuming that these bursts are real PBH events, we estimate lower limits on the PBH burst evaporation rate in the solar neighborhood.

  19. The Progenitor Stars of Gamma-Ray Bursts

    CERN Document Server

    Woosley, S; Woosley, Stan; Heger, Alexander

    2006-01-01

    Those massive stars that, during their deaths, give rise to gamma-ray bursts (GRBs) must be endowed with an unusually large amount of angular momentum in their inner regions, one to two orders of magnitude greater than the ones that make common pulsars. Yet the inclusion of mass loss and angular momentum transport by magnetic torques during the precollapse evolution is known to sap the core of the necessary rotation. Here we explore the evolution of very rapidly rotating, massive stars, including stripped down helium cores that might result from mergers or mass transfer in a binary, and single stars that rotate unusually rapidly on the main sequence. For the highest possible rotation rates (about 400 km/s), a novel sort of evolution is encountered in which single stars mix completely on the main sequence, never becoming red giants. Such stars, essentially massive "blue stragglers", produce helium-oxygen cores that rotate unusually rapidly. Such stars might comprise roughly 1% of all stars above 10 solar masse...

  20. The Optical Afterglow of a Short Gamma-ray Burst

    Science.gov (United States)

    Hjorth, Jens; Watson, Darach; Flynbo, Johan P.U.; Price, Paul A.; Jensen, Brian L.; Jorgensen, Uffe G.; Kubas, Daniel; Gorosabel, Javier; Jakobssonk, Pall; Sollerman, Jesper

    2005-01-01

    It has long been known that there are two classes of gamma-ray bursts (GRBs), principally distinguished by their durations. The breakthrough in our understanding of long-duration GRBs (greater than 2 seconds in duration), that ultimately linked them with energetic Type Ic supernovae, came about from the discovery of their long-lived X-ray and optical "afterglow", when precise and rapid localizations of the sources could finally be obtained. Recently, X-ray localizations have become available for short (less than 2 seconds in duration) GRBs, a hitherto elusive GRB population, that has evaded optical detection for more than thirty years. Here we report the discovery of transient optical emission (R approximately 23 mag) associated with a short GRB. This first short GRB afterglow is localized with sub-arcsecond accuracy onto the outskirts of a blue dwarf galaxy. Unless the optical and X-ray afterglow arise from different mechanisms our observations 33 h after the GRB suggest that, analogously to long GRBs, we observe synchrotron emission from ultrarelativistic ejecta (ZZZ CAN WE LIMIT GAMMA?). In contrast, we did not detect a bright supernova, as found in most nearby long GRB afterglows, which suggests a different origidstrongly constrain the nature of the short GRB progenitors.

  1. Astrophysical and Biological Implications of $\\gamma$-Ray Burst Properties

    CERN Document Server

    Scalo, J M; Scalo, John

    1999-01-01

    Combining results from Schmidt (1999) for the local cosmic rate and mean peakluminosity of gamma-ray bursts (GRBs) with recent work on the history of thecosmic star formation rate, we provide estimates for the local GRB rate perunit blue luminosity in galaxies. These values are used to examine a number ofphenomena with the following conclusions: 1) The ratio of supernova rate to GRBrate is so large that it is difficult to maintain that more than a smallfraction of neutron star or black hole-forming events produced GRBs, evenallowing for generous collimation; 2) The GRB rate is so small that it isimpossible to use these events to account for the majority of large HI holesobserved in our own and other galaxies; the expected number of holes is muchsmaller than observed; 3) Modeling the GRB events in the Milky Way as a spatialPoisson process and allowing for modest enhancement in the star formation ratedue to birth in a spiral arm, we find that the probability that the solarsystem was exposed to a fluence large e...

  2. On the bimodal distribution of gamma-ray bursts

    Science.gov (United States)

    Mao, Shude; Narayan, Ramesh; Piran, Tsvi

    1994-01-01

    Kouveliotou et al. recently confirmed that gamma-ray bursts are bimodal in duration. In this paper we compute the statistical properties of the short (less than or = 2 s) and long (greater than 2 s) bursts using a method of analysis that makes no assumption regarding the location of the bursts, whether in the Galaxy or at a cosmological distance. We find the 64 ms channel on Burst and Transient Source Experiment (BATSE) to be more sensitive to short bursts and the 1024 ms channel to be more sensitive to long bursts. We show that all the currently available data are consistent with the simple hypothesis that both short and long bursts have the same spatial distribution and that within each population the sources are standard candles. The rate of short bursts per unit volume is about 40% of the rate of long bursts. Although the durations of short and long gamma-ray bursts span several orders of magnitude and the total energy of a typical short burst is smaller than that of a typical long burst by a factor of about 20, surprisingly the peak luminosities of the two kinds of bursts are equal to within a factor of about 2.

  3. A new population of ultra-long duration gamma-ray bursts

    CERN Document Server

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

    2014-01-01

    We present comprehensive multiwavelength observations of three gamma-ray bursts (GRBs) with durations of several thousand seconds. We demonstrate that these events are extragalactic transients; in particular we resolve the long-standing conundrum of the distance of GRB 101225A (the "Christmas-day burst"), finding it to have a redshift z=0.847, and showing that two apparently similar events (GRB 111209A and GRB 121027A) lie at z=0.677 and z=1.773 respectively. The systems show extremely unusual X-ray and optical lightcurves, very different from classical GRBs, with long lasting highly variable X-ray emission and optical light curves that exhibit little correlation with the behaviour seen in the X-ray. Their host galaxies are faint, compact, and highly star forming dwarf galaxies, typical of "blue compact galaxies". We propose that these bursts are the prototypes of a hitherto largely unrecognized population of ultra-long GRBs, that while observationally difficult to detect may be astrophysically relatively com...

  4. The Troublesome Broadband Evolution of GRB 061126: Does a Grey Burst Imply Grey Dust?

    CERN Document Server

    Perley, D A; Butler, N R; Pollack, L K; Holtzmann, J; Blake, C H; Kocevski, D; Vestrand, W T; Li, W; Foley, R J; Bellm, E; Chen, H W; Prochaska, J X; Starr, D; Filippenko, A V; Falco, E E; Szentgyorgyi, A H; Wren, J; Wozniak, P R; White, R; Pergande, J

    2007-01-01

    We report on observations of gamma-ray burst (GRB 061126) with an extremely bright (R ~ 12 mag at peak) early-time optical afterglow. The optical afterglow is already fading as a power-law 22 seconds after the trigger, with no detectable prompt contribution in our first exposure, which was coincident with a large prompt-emission pulse. The optical-IR photometric SED is an excellent fit to a power-law but exhibits a moderate red-to-blue evolution in the spectral index at about 500 sec. This color change is contemporaneous with a switch from a relatively fast decay to slower decay. The rapidly decaying early afterglow is broadly consistent with synchrotron emission from a reverse shock, but a bright forward shock component predicted by the intermediate- to late-time X-ray observations under the assumptions of standard afterglow models is not observed. Indeed, despite its remarkable early-time brightness this burst would qualify as a dark burst at later times on the basis of its nearly flat optical-to-X-ray spec...

  5. The short gamma-ray burst revolution

    International Nuclear Information System (INIS)

    Swift, a dedicated gamma-ray burst (GRB) satellite with ultrarapid slewing capability, and a suite of ground-based (ESO) telescopes have recently achieved a major breakthrough: detecting the first afterglows of short-duration GRBs. The faintness of these afterglows and the diversity of old and young host galaxies lend support to the emerging 'standard model', in which they are created during the merging of two compact objects. However, the afterglow light-curve properties and possible high-redshift origin of some short bursts suggests that more than one progenitor type may be involved. (orig.)

  6. Processor Reformats Data For Transmission In Bursts

    Science.gov (United States)

    Steele, Glen F.

    1991-01-01

    Data-processor-and-buffer electronic system receives audio signals digitized in first standard format at relatively low data rate, rearranges data for transmission in bursts in second standard format at relatively high rate, stores second-format bursts, and releases them at higher rate upon request. Conceived for asynchronous, one-way transmission of digitized speech in outer-space communications, concept of system applied in other digital communication systems in which data transmitted from low-rate sources to high-rate sinks not synchronized with sources.

  7. Distribution of whistler mode bursts at Venus

    Science.gov (United States)

    Scarf, F. L.; Jordan, K. F.; Russell, C. T.

    1987-01-01

    Several thousand impulsive whistler mode noise bursts were detected by the Pioneer Venus wave instrument during the first 10 seasons with nightside traversals at low altitudes. The altitude distribution for these events shows that essentially all of the bursts were detected when the orbiter was less than 2000 km above the planet, suggesting that the varying plasma conditions could not maintain coherent whistler mode field-aligned guidance over greater distances. Within the 2000-km range, the distribution of the number of events versus altitude shows that there are two distinct subregions. These results are interpreted in terms of two types of whistler mode propagation from sources below the ionosphere.

  8. A Shotgun Model for $\\gamma$ Ray Bursts

    CERN Document Server

    Heinz, S

    1999-01-01

    We propose that gamma ray bursts (GRBs) are produced by a shower of heavy blobs running into circumstellar material at highly relativistic speeds. The gamma ray emission is produced in the shocks these bullets drive into the surrounding medium. The short term variability seen in GRBs is set by the slowing-down time of the bullets while the overall duration of the burst is set by the lifetime of the central engine. A requirement of this model is that the ambient medium be dense, consistent with a strong stellar wind. In contrast to other external shock scenarios, the efficiency of the shock can be close to unity.

  9. Exploratory depth-of-burst experiments

    Energy Technology Data Exchange (ETDEWEB)

    Reichenbach, H.; Behrens, K. [Fraunhofer-Institut fuer Kurzzeitdynamik - Ernst-Mach-Institut (EMI), Freiburg im Breisgau (Germany); Kuhl, A. [R and D Associates, Los Angeles, CA (United States)

    1991-12-12

    This report describes the first small-scale explosion experiments with aerated grout (i.e., YTONG). Apart from data referring to crater depth and volume versus depth of burst (DOB), isobaric DOB curves in the range of 1.5 psi {le} p {le} 15 psi were established. The comparison with previous HOB values shows that the ground range to a given overpressure is considerably reduced with increasing depth of burst. The authors plan to continue the airblast investigations with different types of soil materials.

  10. Threats in Optical Burst Switched Network

    Directory of Open Access Journals (Sweden)

    P. Siva Subramanian

    2011-05-01

    Full Text Available Optical network is a viable network for future communication, which transmits data at an average rate of 50Tb/s. Optical Burst Switching is a trusted mechanism used for Optical network. There is a good amount of research done in the area of security in Optical networks. In addition, the issues related to physical network security has been dealt with respect to Optical networks. Our proposed work is intend to find the possible security threats that may happen in Optical Burst Switched Networks and the counter measures are examined separately. The NS-2 simulator with modified OBS patch is used to verify and validate the proposed mechanism

  11. Intra-firm Horizontal Knowledge Transfer Management

    Institute of Scientific and Technical Information of China (English)

    WANG Yaowu; WANG Yanhang

    2009-01-01

    Knowledge transfer is widely emphasized as a strategic issue for firm competition. A model for intra-firm horizontal knowledge transfer is proposed to model horizontal knowledge transfer to solve some demerits in current knowledge transfer researches. The concept model of intra-firm horizontal knowledge transfer was described and a framework was provided to define the main components of thetransfer process. Horizontal knowledge transfer is that knowledge is transferred from the source to the same hierarchical level recipients as the target. Horizontal knowledge transfer constitutes a strategic area of knowledge management research. However, little is known about the circumstances under which one particular mechanism is the most appropriate. To address these issues, some significant conclusions are drawn concerning knowledge transfer mechanisms in a real-world setting.

  12. Horizontal Canal Benign Positional Vertigo

    Directory of Open Access Journals (Sweden)

    Mohtaram Najafi

    1998-03-01

    Full Text Available Benign paroxysmal positional vertigo (BPPV is a syndrome characterized by transient episodes of vertigo in association with rapid changes in head position in Dix-Halpike Maneuver. This kind of vertigo is thought to be caused by migration of otoconial debris into canals other than the posterior canal, such as the anterior or lateral canals. It is also theoretically possible for many aberrant patterns of BPPV to occur from an interaction of debris in several canals, location of debris within the canal, and central adaptation patterns to lesions. The symptoms of BPPV are much more consistent with free-moving densities (canaliths in the posterior SCC rather than fixed densities attached to the cupula. While the head is upright, the particles sit in the PSC at the most gravity-dependent position. The best method to induce and see vertigo and nystagmus in BPPV of the lateral semicircular canal is to rotate head 90°while patient is in the supine position, nystagmus would appear in the unaffected side weaker but longer than the affected side. canal paresis has been described in one third of the patients with BPPV. Adaptation which is one of the remarkable features of BPPV in PSC is rarely seen in LSC. Rotations of 270° or 360° around the yaw axis (the so-called barbecue maneuver toward the unaffected ear are popular methods for the treatment of geotropic HC-BPPV. These maneuvers consist of sequential head turning of 90° toward the healthy side while supine. With these maneuvers, the free-floating otoconial debris migrates in the ampullofugal direction, finally entering the utricle through the nonampullated end of the horizontal canal. This kind of vertigo recovers spontaneously more rapidly and suddenly.

  13. SDSS Pre-Burst Observations of Recent Gamma-Ray Burst Fields

    CERN Document Server

    Cool, R J; Brinkmann, J; Eisenstein, D J; Hogg, D W; Schlegel, D J; Schneider, D P; Vanden Berk, Daniel E; Berk, Daniel E. Vanden; Blanton, Michael R.; Cool, Richard J.; Eisenstein, Daniel J.; Hogg, David W.; Schlegel, David J.; Schneider, Donald P.

    2006-01-01

    In this paper, we present Sloan Digital Sky Survey (SDSS) photometry and spectroscopy in the fields of 24 gamma-ray bursts (GRBs) observed by Swift, including bursts localized by Swift, HETE-2, and INTEGRAL, after December 2004. After this bulk release, we plan to provide individual releases of similar data shortly after the localization of future bursts falling in the SDSS survey area. These data provide a solid basis for the astrometric and photometric calibration of follow-up afterglow searches and monitoring. Furthermore, the images provided with this release will allow observers to find transient objects up to a magnitude fainter than possible with Digitized Sky Survey image comparisons.

  14. Why Do Proteins Glow Blue?

    CERN Document Server

    Sarkar, Sohini; Hazra, Partha; Mandal, Pankaj

    2014-01-01

    Recent literatures reported blue-green emission from amyloid fibril as exclusive signature of fibril formation. This unusual visible luminescence is regularly used to monitor fibril growth. Blue-green emission has also been observed in crystalline protein and in solution. However, the origin of this emission is not known exactly. Our spectroscopic study of serum proteins reveals that the blue-green emission is a property of protein monomer. Evidences suggest that semiconductor-like band structure of proteins with the optical band-gap in the visible region is possibly the origin of this phenomenon. We show here that the band structure of proteins is primarily the result of electron delocalization through the peptide chain, rather than through the hydrogen bond network in secondary structure.

  15. New Results on the Spectral Evolution of Magnetar Bright Bursts

    Science.gov (United States)

    Younes, George A.; Kouveliotou, C.; van der Horst, A.; GBM Magnetar Team

    2013-04-01

    Magnetars are isolated neutron stars characterized by long spin periods (2-12 s) and large spin down rates, implying a very strong magnetic field, B>10E14 G. Magnetars exhibit short bursts of hard X-/soft gamma-rays with luminosities ranging from 10E37 to 10E41 erg/s. The magnetar SGR J1550-5418 entered an extremely active bursting episode, starting on 2008 October 03 until 2009 April 17, during which Fermi Gamma-ray Burst Monitor (GBM) observed several hundred bursts from this source. Such wealth of bursts resulted in the largest catalog of detailed temporal and spectral results for SGR J1550-5418. Here, we discuss new results from time-resolved spectral analysis of the brightest bursts from this source. Our analysis, together with the comparison of our results with other magnetar bursts, enabled us to put strong constraints on the theories underlying the magnetar bursts emission mechanism.

  16. The Five Year Fermi/GBM Magnetar Burst Catalog

    Science.gov (United States)

    Collazzi, A. C.; Kouveliotou, C.; van der Horst, A. J.; Younes, G. A.; Kaneko, Y.; Göğüş, E.; Lin, L.; Granot, J.; Finger, M. H.; Chaplin, V. L.; Huppenkothen, D.; Watts, A. L.; von Kienlin, A.; Baring, M. G.; Gruber, D.; Bhat, P. N.; Gibby, M. H.; Gehrels, N.; McEnery, J.; van der Klis, M.; Wijers, R. A. M. J.

    2015-05-01

    Since launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has detected many hundreds of bursts from magnetar sources. While the vast majority of these bursts have been attributed to several known magnetars, there is also a small sample of magnetar-like bursts of unknown origin. Here, we present the Fermi/GBM magnetar catalog, providing the results of the temporal and spectral analyses of 440 magnetar bursts with high temporal and spectral resolution. This catalog covers the first five years of GBM magnetar observations, from 2008 July to 2013 June. We provide durations, spectral parameters for various models, fluences, and peak fluxes for all the bursts, as well as a detailed temporal analysis for SGR J1550-5418 bursts. Finally, we suggest that some of the bursts of unknown origin are associated with the newly discovered magnetar 3XMM J185246.6+0033.7.

  17. ESTIMATION OF THE BURST LENGTH IN OBS NETWORKS

    Directory of Open Access Journals (Sweden)

    Pallavi S.

    2014-05-01

    Full Text Available This paper presents an overview of the optical burst switching (OBS and discusses the major components. In OBS, the length of the burst arriving at a particular node is unknown, and hence, node design is very complex. In OBS first control, packet is transmitted and reserve the path as in circuit switching, thereafter, the data bursts is transmitted. In this paper, a poisson arrival of packets is considered and estimation is made on the size of the burst length. The results presented in the paper clearly reveal that, the very large burst length is un-common. Therefore, most of the times, very short or average length burst is expected. Therefore it is concluded in this paper, buffering of burst at the contending nodes is a good option which increases the throughput and reduces the average delay. Finally, the buffering in conjunction with deflection of bursts will provide very effective solution.

  18. Power Enhancement Cavity for Burst-Mode Laser Pulses

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yun [ORNL

    2015-01-01

    We demonstrate a novel optical cavity scheme and locking method that can realize the power enhancement of picosecond UV laser pulses operating at a burst mode with arbitrary burst (macropulse) lengths and repetition rates.

  19. The Five Year Fermi/GBM Magnetar Burst Catalog

    CERN Document Server

    Collazzi, A C; van der Horst, A J; Younes, G A; Kaneko, Y; Gogus, E; Lin, L; Granot, J; Finger, M H; Chaplin, V L; Huppenkothen, D; Watts, A L; von Kienlin, A; Baring, M G; Gruber, D; Bhat, P N; Gibby, M H; Gehrels, N; McEnery, J; van der Klis, M; Wijers, R A M J

    2015-01-01

    Since launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has detected many hundreds of bursts from magnetar sources. While the vast majority of these bursts have been attributed to several known magnetars, there is also a small sample of magnetar-like bursts of unknown origin. Here we present the Fermi/GBM magnetar catalog, giving the results of the temporal and spectral analyses of 440 magnetar bursts with high temporal and spectral resolution. This catalog covers the first five years of GBM magnetar observations, from July 2008 to June 2013. We provide durations, spectral parameters for various models, fluences and peak fluxes for all the bursts, as well as a detailed temporal analysis for SGR J1550-5418 bursts. Finally, we suggest that some of the bursts of unknown origin are associated with the newly discovered magnetar 3XMM J185246.6+0033.7.

  20. THE FIVE YEAR FERMI/GBM MAGNETAR BURST CATALOG

    Energy Technology Data Exchange (ETDEWEB)

    Collazzi, A. C. [SciTec, Inc., 100 Wall Street, Princeton, NJ 08540 (United States); Kouveliotou, C.; Horst, A. J. van der; Younes, G. A. [Department of Physics, The George Washington University, 725 21st Street NW, Washington, DC 20052 (United States); Kaneko, Y.; Göğüş, E. [Sabancı University, Orhanlı-Tuzla, İstanbul 34956 (Turkey); Lin, L. [François Arago Centre, APC, 10 rue Alice Domon et Léonie Duquet, F-75205 Paris (France); Granot, J. [Department of Natural Sciences, The Open University of Israel, 1 University Road, P.O. Box 808, Raanana 43537 (Israel); Finger, M. H. [Universities Space Research Association, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Chaplin, V. L. [School of Medicine, Vanderbilt University, 1161 21st Avenue S, Nashville, TN 37232 (United States); Huppenkothen, D. [Center for Data Science, New York University, 726 Broadway, 7th Floor, New York, NY 10003 (United States); Watts, A. L. [Anton Pannekoek Institute, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Kienlin, A. von [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Baring, M. G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Gruber, D. [Planetarium Südtirol, Gummer 5, I-39053 Karneid (Italy); Bhat, P. N. [CSPAR, University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35899 (United States); Gibby, M. H., E-mail: acollazzi@scitec.com [Jacobs Technology, Inc., Huntsville, AL (United States); and others

    2015-05-15

    Since launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has detected many hundreds of bursts from magnetar sources. While the vast majority of these bursts have been attributed to several known magnetars, there is also a small sample of magnetar-like bursts of unknown origin. Here, we present the Fermi/GBM magnetar catalog, providing the results of the temporal and spectral analyses of 440 magnetar bursts with high temporal and spectral resolution. This catalog covers the first five years of GBM magnetar observations, from 2008 July to 2013 June. We provide durations, spectral parameters for various models, fluences, and peak fluxes for all the bursts, as well as a detailed temporal analysis for SGR J1550–5418 bursts. Finally, we suggest that some of the bursts of unknown origin are associated with the newly discovered magnetar 3XMM J185246.6+0033.7.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-12-01

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

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

    Science.gov (United States)

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

    2012-12-01

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

  3. The blue-collar brain.

    Science.gov (United States)

    Van Orden, Guy; Hollis, Geoff; Wallot, Sebastian

    2012-01-01

    Much effort has gone into elucidating control of the body by the brain, less so the role of the body in controlling the brain. This essay develops the idea that the brain does a great deal of work in the service of behavior that is controlled by the body, a blue-collar role compared to the white-collar control exercised by the body. The argument that supports a blue-collar role for the brain is also consistent with recent discoveries clarifying the white-collar role of synergies across the body's tensegrity structure, and the evidence of critical phenomena in brain and behavior. PMID:22719730

  4. Horizontal visibility graphs generated by type-I intermittency

    Science.gov (United States)

    Núñez, Ángel M.; Luque, Bartolo; Lacasa, Lucas; Gómez, Jose Patricio; Robledo, Alberto

    2013-05-01

    The type-I intermittency route to (or out of) chaos is investigated within the horizontal visibility (HV) graph theory. For that purpose, we address the trajectories generated by unimodal maps close to an inverse tangent bifurcation and construct their associated HV graphs. We show how the alternation of laminar episodes and chaotic bursts imprints a fingerprint in the resulting graph structure. Accordingly, we derive a phenomenological theory that predicts quantitative values for several network parameters. In particular, we predict that the characteristic power-law scaling of the mean length of laminar trend sizes is fully inherited by the variance of the graph degree distribution, in good agreement with the numerics. We also report numerical evidence on how the characteristic power-law scaling of the Lyapunov exponent as a function of the distance to the tangent bifurcation is inherited in the graph by an analogous scaling of block entropy functionals defined on the graph. Furthermore, we are able to recast the full set of HV graphs generated by intermittent dynamics into a renormalization-group framework, where the fixed points of its graph-theoretical renormalization-group flow account for the different types of dynamics. We also establish that the nontrivial fixed point of this flow coincides with the tangency condition and that the corresponding invariant graph exhibits extremal entropic properties.

  5. Powerful Radio Burst Indicates New Astronomical Phenomenon

    Science.gov (United States)

    2007-09-01

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

  6. Fast Radio Bursts: Searches, Sensitivities & Implications

    CERN Document Server

    Keane, E F

    2016-01-01

    Fast radio bursts (FRBs) are millisecond-duration transient signals discovered over the past decade. Here we describe the scientific usefulness of FRBs, consider ongoing work at the Parkes telescope, and examine some relevant search sensitivity and completeness considerations. We also look ahead to the results from ongoing and future planned studies in the field.

  7. Gamma-ray bursts at high redshift

    NARCIS (Netherlands)

    R.A.M.J. Wijers

    1999-01-01

    Gamma-ray bursts are much brighter than supernovae, and could therefore possibly probe the Universe to high redshift. The presently established GRB redshifts range from 0.83 to 5, and quite possibly even beyond that. Since most proposed mechanisms for GRB link them closely to deaths of massive stars

  8. Neutrino Balls and Gamma-Ray Bursts

    CERN Document Server

    Holdom, B

    1994-01-01

    We propose a mechanism by which the neutrino emission from a supernova-type explosion can be converted into a gamma-ray burst of total energy $\\sim 10^{50}$ ergs. This occurs naturally if the explosion is situated inside a ball of trapped neutrinos, which in turn may lie at a galactic core. There are possible unique signatures of this scenario.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-01-01

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

  10. $\\gamma$-ray Burst Positions from the ASM on RXTE

    CERN Document Server

    Bradt, H V; Bradt, Hale V.; Smith, Donald A.

    1999-01-01

    The RXTE/ASM has detected and positioned 14 confirmed GRB bursts (at this writing, Jan. 1999) including six whose positions were comunicated to the community 2 to 32 hours after the burst. Two of these latter bursts led to measurements of optical red shifts but one, despite an easily detected x-ray afterglow, produced no detectable optical or radio afterglow.

  11. AGILE Mini-Calorimeter gamma-gay burst catalog

    CERN Document Server

    Galli, M; Fuschino, F; Labanti, C; Argan, A; Barbiellini, G; Bulgarelli, A; Cattaneo, P W; Colafrancesco, S; Del Monte, E; Feroci, M; Giannotti, F; Giuliani, A; Longo, F; Mereghetti, S; Morselli, A; Pacciani, L; Pellizzoni, A; Pittori, C; Rapisarda, M; Rappoldi, A; Tavani, M; Trifoglio, M; Trois, A; Vercellone, S; Verrecchia, F

    2013-01-01

    The Mini-Calorimeter of the AGILE satellite can observe the high-energy part of gamma-ray bursts with good timing capability. We present the data of the 85 hard gamma-gay bursts observed by the Mini-Calorimeter since the launch (April 2007) until October 2009. We report the timing data for 84 and spectral data for 21 burst.

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

    DEFF Research Database (Denmark)

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

    2007-01-01

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

  13. Burst Assembly Schemes and Performance Evaluation in Optical Burst Switching Networks

    Institute of Scientific and Technical Information of China (English)

    TANG Jian-jun; JI Yue-feng

    2004-01-01

    Several proposed assemble algorithms for Optical Burst Switching (OBS) network is described, and the feature relative merits is discussed and analyzed in this paper. The authors propose an assembly mechanism FAT where time threshold is fluctuating randomly to reduce continuous blocking rate. With network simulation, the basic performance of these assembly schemes is compared and analyzed. The results show that burst loss ratio and assembly delay of the proposed FAT mechanism is better than that of exist assemble mechanism.

  14. Improved adaptive-threshold burst assembly in optical burst switching networks

    Institute of Scientific and Technical Information of China (English)

    Jiuru Yang; Gang Wang; Shilou Jia

    2007-01-01

    An improved adaptive-threshold burst assembly algorithm is proposed to alleviate the limitation of conventional assembly schemes on data loss and delay. The algorithm will adjust the values of assembly factors according to variant traffic regions. And the simulation results show that, by using the adaptive-factor adaptive assembly scheme, the performance of networks is extensively enhanced in terms of burst loss probability and average queuing delay.

  15. Optimizing of Culture Conditionin Horizontal Rotating Bioreactor

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    1 IntroductionBioreactor is the most important equipment in tissue engineering. It can mimic the micro-environment of cell growth in vitro. At present, horizontal rotating bioreactor is the most advanced equipment for cell culture in the world. 2 Rotating bioreactors2.1 Working principleThere are two kinds of horizontal rotating bioreactor: HARV(high aspect ratio vessel) and RCCS (rotary cell culture system). It is drived by step motor with horizontal rotation, the culture medium and cell is filled between ...

  16. Horizontal gene transfer and bacterial diversity

    Indian Academy of Sciences (India)

    Chitra Dutta; Archana Pan

    2002-02-01

    Bacterial genomes are extremely dynamic and mosaic in nature. A substantial amount of genetic information is inserted into or deleted from such genomes through the process of horizontal transfer. Through the introduction of novel physiological traits from distantly related organisms, horizontal gene transfer often causes drastic changes in the ecological and pathogenic character of bacterial species and thereby promotes microbial diversification and speciation. This review discusses how the recent influx of complete chromosomal sequences of various microorganisms has allowed for a quantitative assessment of the scope, rate and impact of horizontally transmitted information on microbial evolution.

  17. The Blue Revolution in Asia

    DEFF Research Database (Denmark)

    Ponte, Stefano; Kelling, Ingrid; Jespersen, Karen Sau;

    2014-01-01

    In this article, we examine the upgrading trajectories of selected aquaculture value chains in four Asian countries and the links between upgrading and three factors of value chain governance: coordination mechanisms; types of drivers; and domestic regulation. We find instances of improving produ...... of upgrading the "blue revolution" in Asia...

  18. Liquid biofuels from blue biomass

    DEFF Research Database (Denmark)

    Kádár, Zsófia; Jensen, Annette Eva; Bangsø Nielsen, Henrik;

    2011-01-01

    Marine (blue) biomasses, such as macroalgaes, represent a huge unexploited amount of biomass. With their various chemical compositions, macroalgaes can be a potential substrate for food, feed, biomaterials, pharmaceuticals, health care products and also for bioenergy. Algae use seawater as a growth...

  19. Nobel Prize for blue LEDs

    Science.gov (United States)

    Kraftmakher, Yaakov

    2015-05-01

    A brief review of lighting technologies is presented. Unavoidable restrictions for incandescent light bulbs caused by the Planck distribution and properties of the human eye are illustrated. The efficiency and luminous efficacy of thermal radiation are calculated for various temperatures; the results clearly show the limitations for thermal radiators. The only way to overcome these limitations is using non-thermal radiators, such as fluorescent lamps and light-emitting diodes (LEDs). Unique advantages of LEDs undoubtedly made a revolution in this field. A crucial element of this progress is the blue LEDs (Nobel Prize 2014). Some experiments with a blue and a green LED are described: (i) the luminescence triggered in a green-yellow phosphor inside a white LED by the blue LED; (ii) radiant spectra and ‘efficiency droop’ in the LEDs; (iii) modulation of the blue LED up to 4 MHz; and (iv) the h/e ratio from the turn-on voltage of the green LED. The experiments are suitable for undergraduate laboratories and usable as classroom demonstrations.

  20. Blue Ocean vs. Five Forces

    NARCIS (Netherlands)

    A.E. Burke (Andrew); A.J. van Stel (André); A.R. Thurik (Roy)

    2010-01-01

    textabstractThe article reports on the authors' research in the Netherlands which focused on a profit model in Dutch retail stores and a so-called blue-ocean approach which requires a new market that attracts consumers and increases profits. Topics include the competitive strategy approach to increa

  1. Investigation of Primordial Black Hole Bursts using Interplanetary Network Gamma-ray Bursts

    CERN Document Server

    Ukwatta, T N; MacGibbon, J H; Svinkin, D S; Aptekar, R L; Golenetskii, S V; Frederiks, D D; Pal'shin, V D; Goldsten, J; Boynton, W; Fellows, C; Harshman, K; Mitrofanov, I G; Golovin, D V; Kozyrev, A S; Litvak, M L; Sanin, A B; Rau, A; Kienlin, A; Zhang, X; Briggs, M S; Connaughton, V; Meegan, C; Yamaoka, K; Fukazawa, Y; Ohno, M; Ohmori, N; Takahashi, T; Tashiro, M; Terada, Y; Murakami, T; Makishima, K; Feroci, M; Frontera, F; Guidorzi, C; Barthelmy, S; Cline, T; Gehrels, N; Cummings, J; Krimm, H A; Smith, D M; McTiernan, J

    2015-01-01

    The detection of a gamma-ray burst (GRB) in the solar neighborhood would have very important implications for GRB phenomenology. The leading theories for cosmological GRBs would not be able to explain such events. The final bursts of evaporating Primordial Black Holes (PBHs), however, would be a natural explanation for local GRBs. We present a novel technique that can constrain the minimum distance to gamma-ray bursts using detections from widely separated spacecraft. We applied this method to constrain distances to a sample of 36 short duration GRBs detected by the Interplanetary Network (IPN) that show observational properties that are expected from PBH evaporations. These bursts have minimum possible distances in the 10^13-10^18 cm (7-10^5 AU) range, consistent with the expected PBH energetics and with a possible origin in the solar neighborhood, although none of the bursts can be unambiguously demonstrated to be local. Assuming these bursts are real PBH events, we estimate for the first time lower limits ...

  2. Powerful Radio Burst Indicates New Astronomical Phenomenon

    Science.gov (United States)

    2007-09-01

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

  3. Assessing the continuity of the blue ice climate record at Patriot Hills, Horseshoe Valley, West Antarctica

    OpenAIRE

    Winter, Kate; Woodward, John; Dunning, Stuart; Turney, Chris; Fogwill, Christopher; Hein, Andrew; Golledge, Nicholas; Bingham, Robert; Marrero, Shasta; Sugden, David; Ross, Neil

    2016-01-01

    We use high resolution Ground Penetrating Radar (GPR) to assess the continuity of the Blue Ice Area (BIA) horizontal climate record at Patriot Hills, Horseshoe Valley, West Antarctica. The sequence contains three pronounced changes in deuterium isotopic values at ~18 cal ka, ~12 cal ka and ~8 cal ka. GPR surveys along the climate sequence reveal continuous, conformable dipping isochrones, separated by two unconformities in the isochrone layers, which correlate with the two older deuterium shi...

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

    DEFF Research Database (Denmark)

    Pedersen, Morten Gram

    2007-01-01

    Pancreatic beta-cells show bursting electrical activity with a wide range of burst periods ranging from a few seconds, often seen in isolated cells, over tens of seconds (medium bursting), usually observed in intact islets, to several minutes. The phantom burster model [Bertram, R., Previte, J., ...

  5. Productivity and injectivity of horizontal wells

    Energy Technology Data Exchange (ETDEWEB)

    Aziz, Khalid

    2000-03-06

    One of the key issues addressed was pressure drop in long horizontal wells and its influence on well performance. Very little information is available in the literature on flow in pipes with influx through pipe walls. Virtually all of this work has been in small diameter pipes and with single-phase flow. In order to address this problem new experimental data on flow in horizontal and near horizontal wells have been obtained. Experiments were conducted at an industrial facility on typical 6 1/8 ID, 100 feet long horizontal well model. The new data along with available information in the literature have been used to develop new correlations and mechanistic models. Thus it is now possible to predict, within reasonable accuracy, the effect of influx through the well on pressure drop in the well.

  6. High hydraulic performance in horizontal waterwheels

    Energy Technology Data Exchange (ETDEWEB)

    Pujol, T.; Montoro, L. [Area de Mecnica de Fluids, Escola Politcnica Superior, Universitat de Girona, 17071 Girona, Catalonia (Spain)

    2010-11-15

    Slow rotating waterwheels have been recently proposed as affordable sources of renewable energy in rural areas. In terms of hydraulic efficiency, classical horizontal waterwheels reach values on the order of 50%, being well below those obtained from overshot (71%), waterfall (66%) and, even, undershot (65%) vertical ones. Based on the study of an horizontal waterwheel built prior to 1940s that includes features from both elementary turbines and antique waterwheels, we conclude that horizontal waterwheels may actually reach hydraulic efficiencies as high as 81%. These quantitative results are obtained by analytical approximations and, more important, by numerical integrations through accurate computational fluid dynamics (CFD) simulations. In addition, we show that such a high hydraulic efficiency does not substantially vary when changing the net available head. We suggest that this relevant progress made on improving the efficiency of classical horizontal waterwheels may have implications in future designs of nano/micro hydropower devices. (author)

  7. Gravitational-wave bursts with memory and experimental prospects

    International Nuclear Information System (INIS)

    The authors show that for any kind of detector the best way to search for a ''bursts with memory'' (BWM) gravitation wave is to integrate up the signal for an integration time tau-circumflex approx.= 1/fsub(opt), where fsub(opt) is the frequency at which the detector has optimal amplitude sensitivity to ordinary bursts (bursts with memory). In such a search the sensitivity to BWM with duration Δt < or approx. 1/fsub(opt) is independent of the burst duration Δt and is approximately equal to the sensitivity to ordinary bursts one cycle long with frequency fsub(opt). (author)

  8. X-Ray Observations of Gamma-Ray Burst Afterglows

    OpenAIRE

    Frontera, Filippo

    2004-01-01

    The discovery by the BeppoSAX satellite of X-ray afterglow emission from the gamma-ray burst which occurred on 28 February 1997 produced a revolution in our knowledge of the gamma-ray burst phenomenon. Along with the discovery of X-ray afterglows, the optical afterglows of gamma-ray bursts were discovered and the distance issue was settled, at least for long $\\gamma$-ray bursts. The 30 year mystery of the gamma-ray burst phenomenon is now on the way to solution. Here I rewiew the observationa...

  9. Rock Burst Mechanics: Insight from Physical and Mathematical Modelling

    OpenAIRE

    Vacek, J.; J. Chocholoušová

    2008-01-01

    Rock burst processes in mines are studied by many groups active in the field of geomechanics. Physical and mathematical modelling can be used to better understand the phenomena and mechanisms involved in the bursts. In the present paper we describe both physical and mathematical models of a rock burst occurring in a gallery of a coal mine.For rock bursts (also called bumps) to occur, the rock has to possess certain particular rock burst properties leading to accumulation of energy and the pot...

  10. Horizontal flow fields in and around a small active region-- The transition period between flux emergence and decay

    CERN Document Server

    Verma, M; Balthasar, H; Kuckein, C; Manrique, S J González; Sobotka, M; González, N Bello; Hoch, S; Diercke, A; Kummerow, P; Berkefeld, T; Collados, M; Feller, A; Hofmann, A; Kneer, F; Lagg, A; Löhner-Böttcher, J; Nicklas, H; Yabar, A Pastor; Schlichenmaier, R; Schmidt, D; Schmidt, W; Schubert, M; Sigwarth, M; Solanki, S K; Soltau, D; Staude, J; Strassmeier, K G; Volkmer, R; von der Lühe, O; Waldmann, T

    2016-01-01

    Aims. Combining high-resolution and synoptic observations aims to provide a comprehensive description of flux emergence at photospheric level and of the growth process that eventually leads to a mature active region. Methods. Small active region NOAA 12118 was observed on 2014 July 18 with the 1.5-meter GREGOR solar telescope on 2014 July 18. High-resolution time-series of blue continuum and G-band images acquired in the blue imaging channel (BIC) of the GREGOR Fabry-P\\'erot Interferometer (GFPI) were complemented by LOS magnetograms and continuum images obtained with the HMI onboard the SDO. Horizontal proper motions and horizontal plasma velocities were computed with local correlation tracking (LCT) and the differential affine velocity estimator, respectively. Morphological image processing was employed to measure the photometric/magnetic area, magnetic flux, and the separation profile of the EFR during its evolution. Results. The computed growth rates for photometric area, magnetic area, and magnetic flux ...

  11. Horizontal Evaluation: Stimulating social learning among peers

    OpenAIRE

    Thiele, Graham; Devaux, Andre; Velasco, Claudio; Manrique, Kurt

    2006-01-01

    Horizontal evaluation is a flexible evaluation method that combines self-assessment and external review by peers. We have developed and applied this method for use within an Andean regional network that develops new methodologies for research and development (R&D). The involvement of peers neutralizes the lopsided power relations that prevail in traditional external evaluations, creating a more favourable atmosphere for learning and improvement. The central element of a horizontal evaluation ...

  12. Horizontal Brand Extension and Customer perception

    OpenAIRE

    Khan, Khalid; Janthimapornkij, Rattanawilai

    2011-01-01

    Company use different method for extended their business to different market and to different segment. They use different method; brand extension is one of popular strategy for extension of business. Brand extension does not become successful for every brand, it is very risky. The purpose of this thesis is to study horizontal brand extension and customer perception. We will discuss horizontal brand extension and its two main types franchise brand extension and line extension. Brand extension ...

  13. Probing the Structure of Jet Driven Core-Collapse Supernova and Long Gamma Ray Burst Progenitors with High Energy Neutrinos

    CERN Document Server

    Bartos, Imre; Marka, Szabolcs

    2012-01-01

    Times of arrival of high energy neutrinos encode information about their sources. We demonstrate that the energy-dependence of the onset time of neutrino emission in advancing relativistic jets can be used to extract important information about the supernova/gamma-ray burst progenitor structure. We examine this energy and time dependence for different supernova and gamma-ray burst progenitors, including red and blue supergiants, helium cores, Wolf-Rayet stars, and chemically homogeneous stars, with a variety of masses and metallicities. For choked jets, we calculate the cutoff of observable neutrino energies depending on the radius at which the jet is stalled. Further, we exhibit how such energy and time dependence may be used to identify and differentiate between progenitors, with as few as one or two observed events, under favorable conditions.

  14. Flavour production of Stilton blue cheese microflora

    OpenAIRE

    Gkatzionis, Konstantinos

    2010-01-01

    In the blue cheese Stilton the starter mould Penicillium roqueforti grows and sporulates during the ripening period and is considered to be responsible for the unique blue cheese aroma. However, the sporulation of the mould, which results in the formation of blue veins, takes place in a fraction of the Stilton matrix which overall is very heterogeneous. Most blue cheeses develop a secondary microflora of yeasts which may affect their aroma. The aim of this study was to investigate the yeast f...

  15. An Analysis of Burst Disc Pressure Instability

    Energy Technology Data Exchange (ETDEWEB)

    S. L. Robinson; B. C. Odegard, Jr.; N. r. Moody; S. H. Goods

    2000-06-01

    During the development stage of the 1X Acorn burst disc, burst pressure test results exhibited an unexpected increase of 8 to 14% over times of 90--100 days from initial fabrication. This increase is a concern where design constraints require stability. The disc material, 316L stainless steel sheet, is formed to a dome-like geometry and scored to produce a thin-walled, high-strength ligament. The fracture events controlling burst occur in that ligament. Thus it has been characterized both for tensile properties and microstructure through nanoindentation, magnetic measurements, optical and transmission electron microscopy. These results compare favorably with finite element simulation of the properties of the ligament. The ligament exhibits a highly heterogeneous microstructure; its small volume and microstructural heterogeneity make it difficult to identify which microstructural feature controls fracture and hence burst pressure. Bulk mechanical test specimens were fabricated to emulate mid-ligament properties, and aged at both room and elevated temperatures to characterize and accelerate the temporal behavior of the burst disc. Property changes included yield and ultimate tensile strength increases, and fracture strain decreases with aging. Specimens were subjected to a reversion anneal identical to that given the burst disc to eliminate the martensite phase formed during rolling. Reversion-annealed samples exhibited no change in properties in room temperature or accelerated aging, showing that the reversion-anneal eliminated the aging phenomenon. Aging was analyzed in terms of diffusion controlled precipitate growth kinetics, showing that carbon migration to dislocations is consistent with the strength increases. A vacancy-assisted diffusion mechanism for carbon transport is proposed, giving rise to rapid aging, which replaces interstitial carbon diffusion until excess vacancies from deformation are consumed. Mechanical activation parameters in stress relaxation

  16. Fermi/GAMMA-RAY BURST MONITOR OBSERVATIONS OF SGR J0501+4516 BURSTS

    International Nuclear Information System (INIS)

    We present our temporal and spectral analyses of 29 bursts from SGR J0501+4516, detected with the gamma-ray burst monitor on board the Fermi Gamma-ray Space Telescope during 13 days of the source's activation in 2008 (August 22- September 3). We find that the T90 durations of the bursts can be fit with a log-normal distribution with a mean value of ∼123 ms. We also estimate for the first time event durations of soft gamma repeater (SGR) bursts in photon space (i.e., using their deconvolved spectra) and find that these are very similar to the T90 values estimated in count space (following a log-normal distribution with a mean value of ∼124 ms). We fit the time-integrated spectra for each burst and the time-resolved spectra of the five brightest bursts with several models. We find that a single power law with an exponential cutoff model fits all 29 bursts well, while 18 of the events can also be fit with two blackbody functions. We expand on the physical interpretation of these two models and we compare their parameters and discuss their evolution. We show that the time-integrated and time-resolved spectra reveal that Epeak decreases with energy flux (and fluence) to a minimum of ∼30 keV at F = 8.7 x 10-6 erg cm-2 s-1, increasing steadily afterward. Two more sources exhibit a similar trend: SGRs J1550-5418 and 1806-20. The isotropic luminosity, Liso, corresponding to these flux values is roughly similar for all sources (0.4-1.5 x 1040 erg s-1).

  17. On associating Fast Radio Bursts with afterglows

    CERN Document Server

    Vedantham, H K; Mooley, K; Frail, D; Hallinan, G; Kulkarni, S R

    2016-01-01

    A radio source that faded over 6 days, with a redshift $z\\approx0.5$ host, has been identified by Keane et al. (2016) as the transient afterglow to a Fast Radio Burst (FRB 150418). We report follow-up radio and optical observations of the afterglow candidate, and find a source that is consistent with an active galactic nucleus (AGN). If the afterglow-candidate is nonetheless a prototypical FRB afterglow, existing surveys limit the fraction of FRBs that produce afterglows to 0.25 for modulation-index $m=\\Delta S/\\bar{S}\\geq0.7$, and 0.07 for $m\\geq1$, at 95\\% confidence. Afterglow associations with the barrage of bursts expected from future FRB surveys must satisfy constraints on the afterglow rate set by state of the art slow-transient surveys.

  18. The Supernova -- Gamma-Ray Burst Connection

    CERN Document Server

    Woosley, S E

    2006-01-01

    Observations show that at least some gamma-ray bursts (GRBs) happen simultaneously with core-collapse supernovae (SNe), thus linking by a common thread nature's two grandest explosions. We review here the growing evidence for and theoretical implications of this association, and conclude that most long-duration soft-spectrum GRBs are accompanied by massive stellar explosions (GRB-SNe). The kinetic energy and luminosity of well-studied GRB-SNe appear to be greater than those of ordinary SNe, but evidence exists, even in a limited sample, for considerable diversity. The existing sample also suggests that most of the energy in the explosion is contained in nonrelativistic ejecta (producing the supernova) rather than in the relativistic jets responsible for making the burst and its afterglow. Neither all SNe, nor even all SNe of Type Ibc produce GRBs. The degree of differential rotation in the collapsing iron core of massive stars when they die may be what makes the difference.

  19. Bursting behaviours in cascaded stimulated Brillouin scattering

    Institute of Scientific and Technical Information of China (English)

    Liu Zhan-Jun; He Xian-Tu; Zheng Chun-Yang; Wang Yu-Gang

    2012-01-01

    Stimulated Brillouin scattering is studied by numerically solving the Vlasov-Maxwell system.A cascade of stimulated Brillouin scattering can occur when a linearly polarized laser pulse propagates in a plasma.It is found that a stimulated Brillouin scattering cascade can reduce the scattering and increase the transmission of light,as well as introduce a bursting behaviour in the evolution of the laser-plasma interaction.The bursting time in the reflectivity is found to be less than half the ion acoustic period.The ion temperature can affect the stimulated Brillouin scattering cascade,which can repeat several times at low ion temperatures and can be completely eliminated at high ion temperatures.For stimulated Brillouin scattering saturation,higher-harmonic generation and wave-wave interaction of the excited ion acoustic waves can restrict the amplitude of the latter.In addition,stimulated Brillouin scattering cascade can restrict the amplitude of the scattered light.

  20. Are gamma-ray bursts cosmological?

    CERN Document Server

    Horvath, I

    2015-01-01

    Gamma-ray burst sources are distributed with a high level of isotropy, which is compatible with either a cosmological origin or an extended Galactic halo origin. The brightness distribution is another indicator used to characterize the spatial distribution in distance. In this paper the author discusses detailed fits of the BATSE gamma-ray burst peak-flux distributions with Friedmann models taking into account possible density evolution and standard candle luminosity functions. A chi-square analysis is used to estimate the goodness of the fits and the author derives the significance level of limits on the density evolution and luminosity function parameters. Cosmological models provide a good fit over a range of parameter space which is physically reasonable

  1. Coherence resonance in bursting neural networks

    Science.gov (United States)

    Kim, June Hoan; Lee, Ho Jun; Min, Cheol Hong; Lee, Kyoung J.

    2015-10-01

    Synchronized neural bursts are one of the most noticeable dynamic features of neural networks, being essential for various phenomena in neuroscience, yet their complex dynamics are not well understood. With extrinsic electrical and optical manipulations on cultured neural networks, we demonstrate that the regularity (or randomness) of burst sequences is in many cases determined by a (few) low-dimensional attractor(s) working under strong neural noise. Moreover, there is an optimal level of noise strength at which the regularity of the interburst interval sequence becomes maximal—a phenomenon of coherence resonance. The experimental observations are successfully reproduced through computer simulations on a well-established neural network model, suggesting that the same phenomena may occur in many in vivo as well as in vitro neural networks.

  2. Bursts of activity in collective cell migration

    CERN Document Server

    Chepizhko, Oleksandr; Mastrapasqua, Eleonora; Nourazar, Mehdi; Ascagni, Miriam; Sugni, Michela; Fascio, Umberto; Leggio, Livio; Malinverno, Chiara; Scita, Giorgio; Santucci, Stephane; Alava, Mikko J; Zapperi, Stefano; La Porta, Caterina A M

    2016-01-01

    Dense monolayers of living cells display intriguing relaxation dynamics, reminiscent of soft and glassy materials close to the jamming transition, and migrate collectively when space is available, as in wound healing or in cancer invasion. Here we show that collective cell migration occurs in bursts that are similar to those recorded in the propagation of cracks, fluid fronts in porous media and ferromagnetic domain walls. In analogy with these systems, the distribution of activity bursts displays scaling laws that are universal in different cell types and for cells moving on different substrates. The main features of the invasion dynamics are quantitatively captured by a model of interacting active particles moving in a disordered landscape. Our results illustrate that collective motion of living cells is analogous to the corresponding dynamics in driven, but inanimate, systems.

  3. Burst Detector X-Ray IIR

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-02-01

    The Burst Detector X-Ray (BDX) instrument for the Block IIR series of Global Positioning System satellites is described. The BDX instrument can locate and characterize exoatmospheric nuclear detonations by using four sensors consisting of sets of filters over silicon diodes to detect x rays of various energies from the burst. On the BDX-IIR, a fifth sensor with a response spanning those of the other sensors confirms coincidences among the four main channels. The mechanical and electronic features of the BDX-IIR and its sensors are described. The calibrations and the system tests used in flight are presented. The commands for the BDX-IIR are given. The messages sent from the BDX-IIR are described in detail.

  4. Environmental Effects of Gamma Ray Bursts

    International Nuclear Information System (INIS)

    Gamma rays bursts, coming from very massive stars, are the most powerful explosions in our Universe. Some authors have linked them to some of the climatic changes and consequent biological mass extinctions of the Phanerozoic eon. However, the consequences of their direct impact on primitive Earth, is today a hot topic of debate. On the other hand, it is usually assumed that they were more common in earlier stages of our galaxy. So it is important to evaluate its potential effects on terrestrial paleoenvironments. We outline some simple models to estimate their influence mainly on the primordial atmospheric chemistry of Earth and on the climate in general. To do that, we consider different scenarios where the atmospheric composition diverges substantially from the atmosphere today, and compute the evolution of principal chemical species under the intense radiational stress of a gamma ray burst. Furthermore, the possible impact on the isotopic composition, geochemistry and the biosphere are mentioned in general way

  5. Coherence resonance in bursting neural networks.

    Science.gov (United States)

    Kim, June Hoan; Lee, Ho Jun; Min, Cheol Hong; Lee, Kyoung J

    2015-10-01

    Synchronized neural bursts are one of the most noticeable dynamic features of neural networks, being essential for various phenomena in neuroscience, yet their complex dynamics are not well understood. With extrinsic electrical and optical manipulations on cultured neural networks, we demonstrate that the regularity (or randomness) of burst sequences is in many cases determined by a (few) low-dimensional attractor(s) working under strong neural noise. Moreover, there is an optimal level of noise strength at which the regularity of the interburst interval sequence becomes maximal-a phenomenon of coherence resonance. The experimental observations are successfully reproduced through computer simulations on a well-established neural network model, suggesting that the same phenomena may occur in many in vivo as well as in vitro neural networks.

  6. Food habits of blue grouse

    Science.gov (United States)

    Stewart, R.E.

    1944-01-01

    The food habits of Blue Grouse vary from a simple winter diet that is made up predominantly of coniferous needles to a complex diet during the summer months, characterized by great variety of foods including green leaves, fruits and seeds, flowers, animal matter and coniferous needles. The spring and fall, which represent the transition periods between these two, are characterized by feeding habits that are generally intermediate. The diets of the two species of Blue Grouse, Dendrugapus obscurus and Dendragapus juliginosus, are quite similar as far as major types of food are concerned, but they differ considerably in the species that are taken. Such differences reflect differences in the vegetation within the ecologic and geographic ranges occupied by the two species.

  7. Thermoluminescence (TL) of Egyptian Blue

    Energy Technology Data Exchange (ETDEWEB)

    Schvoerer, M.; Delavergne, M.-C.; Chapoulie, R.

    1988-01-01

    Egyptian Blue is a synthesized crystalline pictorial pigment with formula CaCuSi/sub 4/O/sub 10/. It has been used in Egypt and Mesopotamia from the 3rd millenium B.C. A preliminary experiment on a recently synthesized sample showed that this pigment is thermoluminescent after ..beta.. irradiation (/sup 90/Sr). As the signal intensity grows linearly with the administered dose within the temperature range commonly used in TL dating, we have been looking for this phenomenon from archaeological pigments. It was encountered with two samples found in excavation. From its intensity and stability we concluded that Egyptian Blue can be dated using TL. This first and positive result encouraged us to extend the method to other types of mineral pigments synthesized by early man, and to suggest that it may be used for direct dating of ancient murals.

  8. The Physics of the Blues

    Science.gov (United States)

    Gibson, J. Murray

    2009-03-01

    In looking at the commonalities between music and science, one sees that the musician's palette is based on the principles of physics. The pitch of a musical note is determined by the frequency of the sound wave. The scales that musicians use to create and play music can be viewed as a set of rules. What makes music interesting is how musicians develop those rules and create ambiguity with them. I will discuss the evolution of western musical scales in this context. As a particular example, ``Blue'' notes are very harmonic notes that are missing from the equal temperament scale. The techniques of piano blues and jazz represent the melding of African and Western music into something totally new and exciting. Live keyboard demonstrations will be used. Beyond any redeeming entertainment value the talk will emphasize the serious connections between science and art in music. Nevertheless tips will be accepted.

  9. GAMMA-RAY BURSTS, NEW COSMOLOGICAL BEACONS

    Directory of Open Access Journals (Sweden)

    V. Avila-Reese

    2009-01-01

    Full Text Available Long Gamma-Ray Bursts (GRBs are the brightest electromagnetic explosions in the Universe, associated to the death of massive stars. As such, GRBs are potential tracers of the evolution of the cosmic massive star formation, metallicity, and Initial Mass Function. GRBs also proved to be appealing cosmological distance indicators. This opens a unique opportunity to constrain the cosmic expansion history up to redshifts 5-6. A brief review on both subjects is presented here.

  10. Identifying crucial parameter correlations maintaining bursting activity.

    Directory of Open Access Journals (Sweden)

    Anca Doloc-Mihu

    2014-06-01

    Full Text Available Recent experimental and computational studies suggest that linearly correlated sets of parameters (intrinsic and synaptic properties of neurons allow central pattern-generating networks to produce and maintain their rhythmic activity regardless of changing internal and external conditions. To determine the role of correlated conductances in the robust maintenance of functional bursting activity, we used our existing database of half-center oscillator (HCO model instances of the leech heartbeat CPG. From the database, we identified functional activity groups of burster (isolated neuron and half-center oscillator model instances and realistic subgroups of each that showed burst characteristics (principally period and spike frequency similar to the animal. To find linear correlations among the conductance parameters maintaining functional leech bursting activity, we applied Principal Component Analysis (PCA to each of these four groups. PCA identified a set of three maximal conductances (leak current, [Formula: see text]Leak; a persistent K current, [Formula: see text]K2; and of a persistent Na+ current, [Formula: see text]P that correlate linearly for the two groups of burster instances but not for the HCO groups. Visualizations of HCO instances in a reduced space suggested that there might be non-linear relationships between these parameters for these instances. Experimental studies have shown that period is a key attribute influenced by modulatory inputs and temperature variations in heart interneurons. Thus, we explored the sensitivity of period to changes in maximal conductances of [Formula: see text]Leak, [Formula: see text]K2, and [Formula: see text]P, and we found that for our realistic bursters the effect of these parameters on period could not be assessed because when varied individually bursting activity was not maintained.

  11. Are Gamma-Ray Bursts Standard Candles?

    OpenAIRE

    Li, Li-Xin

    2007-01-01

    By dividing a sample of 48 long-duration gamma-ray bursts (GRBs) into four groups with redshift from low to high and fitting each group with the Amati relation log Eiso = a + b log Epeak, I find that parameters a and b vary with the mean redshift of the GRBs in each group systematically and significantly. The results suggest that GRBs evolve strongly with the cosmic redshift and hence are not standard candles.

  12. The Euclidean distribution of Fast Radio Bursts

    OpenAIRE

    Oppermann, Niels; Connor, Liam; Pen, Ue-Li

    2016-01-01

    We investigate whether current data on the distribution of observed flux densities of Fast Radio Bursts (FRBs) are consistent with a constant source density in Euclidean space. We use the number of FRBs detected in two surveys with different characteristics along with the observed signal-to-noise ratios of the detected FRBs in a formalism similar to a V/V_max-test to constrain the distribution of flux densities. We find consistency between the data and a Euclidean distribution. Any extension ...

  13. Bursting of sensitive polymersomes induced by curling

    OpenAIRE

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

    2009-01-01

    Polymersomes, which are stable and robust vesicles made of block copolymer amphiphiles, are good candidates for drug carriers or micro/nanoreactors. Polymer chemistry enables almost unlimited molecular design of responsive polymersomes whose degradation upon environmental changes has been used for the slow release of active species. Here, we propose a strategy to remotely trigger instantaneous polymersome bursting. We have designed asymmetric polymer vesicles, in which only one leaflet is com...

  14. Gamma Ray Bursts and their Optical Counterparts

    International Nuclear Information System (INIS)

    Gamma Ray Bursts (GRB) have been discovered 38 years ago and still remain one of the most intriguing puzzles of astrophysics. In this paper we remind briefly the history of GRB studies and review the current experimental evidence with the emphasis on GRB optical counterparts. At the end we introduce '' π of the Sky '' project designed to catch prompt optical emission from GRB sources. (author)

  15. Gamma-ray bursts - a critical review

    International Nuclear Information System (INIS)

    We present a short general introduction into the field of gamma-ray bursts (GRBs) research, summarizing the past and the present status. We give an general view of the GRBs observations to date, both in the prompt emission phase as well as in the afterglow phase, and a brief primer into the theory, mainly in the frame-work of the fireball model. (authors)

  16. Horizontal roof gap of backfill hydraulic support

    Institute of Scientific and Technical Information of China (English)

    张强; 张吉雄; 邰阳; 方坤; 殷伟

    2015-01-01

    For the backfill hydraulic support as the key equipment for achieving integration of backfilling and coal mining simultaneously in the practical process, its characteristics will directly influence the backfill body’s compression ratio. Horizontal roof gap, as a key parameter of backfilling characteristics, may impact the backfilling effect from the aspects of control of roof subsidence in advance, support stress, backfilling process and the support design. Firstly, the reason why horizontal roof gap exists was analyzed and its definition, causes and connotation were introduced, then adopting the Pro/E 3D simulation software, three typical 3D entity models of backfill hydraulic supports were built, based on the influence of horizontal roof gap on backfilling effect, and influence rules of four factors, i.e. support height, suspension height, suspension angle and tamping angle, were emphatically analyzed on horizontal roof gap. The results indicate that, the four factors all have significant impacts on horizontal roof gap, but show differences in influence trend and degree, showing negative linear correlation, positive linear correlation, positive semi-parabolic correlation and negative semi-parabolic correlation, respectively. Four legs type is the most adaptive to the four factors, while six legs (II) type has the poorest adaptability, and the horizontal roof gap is small under large support height, small suspension height, small suspension angle and large tamping angle situation. By means of optimizing structure components and their positional relation and suspension height of backfill scrape conveyor in the process of support design and through controlling working face deployment, roof subsidence in advance, mining height and backfilling during engineering application, the horizontal roof gap is optimized. The research results can be served as theoretical basis for support design and guidance for backfill support to have better performance in backfilling.

  17. The WHIQII Survey: Metallicities and Spectroscopic Properties of Luminous Compact Blue Galaxies

    CERN Document Server

    Tollerud, Erik J; van Zee, Liese; Cooke, Jeff

    2009-01-01

    As part of the WIYN High Image Quality Indiana Irvine (WHIQII) survey, we present 123 spectra of emission-line galaxies, selected on intermediate redshift (.4blue colors that appear physically compact. The sample includes 15 true Luminous Compact Blue Galaxies (LCBGs) and an additional 27 slightly less extreme emission-line systems. These galaxies represent a highly evolving class that may play an important role in the decline of star formation since z~1, but their exact nature and evolutionary pathways remain a mystery. Here, we use emission lines to determine metallicities and ionization parameters, constraining their intrinsic properties and state of star formation. Some LCBG metallicities are consistent with a "bursting dwarf" scenario, while a substantial fraction of others are not, further confirming that LCBGs are a highly heterogeneous population but are broadly consistent with the intermediate redshift field. In agreement with previous studies, we observe overall evolution ...

  18. The Hottest Horizontal-Branch Stars in Omega Centauri: Late Hot Flasher vs. Helium Enrichment

    Science.gov (United States)

    Moehler, S.; Dreizler, S.; Lanz, T.; Bono, G.; Sweigart, A V.; Calamida, A.; Monelli, M.; Nonino, M.

    2007-01-01

    UV observations of some massive globular clusters uncovered a significant population of very hot stars below the hot end of the horizontal branch (HB), the so-called blue hook stars. This feature might be explained either by the late hot flasher scenario here stars experience the helium flash while on the white dwarf cooling curve or by the helium-rich sub-population recently postulated to exist in some clusters. Spectroscopic analyses of blue hook stars in omega Cen and NGC 2808 support the late hot flasher scenario, but the stars contain much less helium than expected and the predicted C, N enrichment could not be verified from existing data. We want to determine effective temperatures, surface gravities and abundances of He, C, N in blue hook and canonical extreme horizontal branch (EHB) star candidates. Moderately high resolution spectra of stars at the hot end of the blue horizontal branch in the globular cluster omega Cen were analysed for atmospheric parameters (T(sub eff), log g) and abundances using LTE and Non-LTE model atmospheres. In the temperature range 30,000 K to 50,000 K we find that 37% of our stars are helium-poor (log nHe/nH less than -2), 49% have solar helium abundance within a factor of 3 (-1.5 less than or equal to log nHe/nH less than or equal to -0.5) and 14% are helium rich (log nHe/nH greater than -0.4). We also find carbon enrichment in step with helium enrichment, with a maximum carbon enrichment of 3% by mass. At least 30% of the hottest HB stars in omega Centauri show helium abundances well above the predictions from the helium enrichment scenario (Y = 0.42 corresponding to log nHe/nH approximately equal to -0.74). In addition the most helium-rich stars show strong carbon enrichment as predicted by the late hot flasher scenario. We conclude that the helium-rich HB stars in omega Cen cannot be explained solely by the helium-enrichment scenario invoked to explain the blue main sequence.

  19. Methylene blue microbubbles as a model dual-modality contrast agent for ultrasound and activatable photoacoustic imaging.

    Science.gov (United States)

    Jeon, Mansik; Song, Wentao; Huynh, Elizabeth; Kim, Jungho; Kim, Jeesu; Helfield, Brandon L; Leung, Ben Y C; Goertz, David E; Zheng, Gang; Oh, Jungtaek; Lovell, Jonathan F; Kim, Chulhong

    2014-01-01

    Ultrasound and photoacoustic imaging are highly complementary modalities since both use ultrasonic detection for operation. Increasingly, photoacoustic and ultrasound have been integrated in terms of hardware instrumentation. To generate a broadly accessible dual-modality contrast agent, we generated microbubbles (a standard ultrasound contrast agent) in a solution of methylene blue (a standard photoacoustic dye). This MB2 solution was formed effectively and was optimized as a dual-modality contrast solution. As microbubble concentration increased (with methylene blue concentration constant), photoacoustic signal was attenuated in the MB2 solution. When methylene blue concentration increased (with microbubble concentration held constant), no ultrasonic interference was observed. Using an MB2 solution that strongly attenuated all photoacoustic signal, high powered ultrasound could be used to burst the microbubbles and dramatically enhance photoacoustic contrast (>800-fold increase), providing a new method for spatiotemporal control of photoacoustic signal generation.

  20. A Fast Radio Burst Host Galaxy

    CERN Document Server

    Keane, E F; Bhandari, S; Barr, E; Bhat, N D R; Burgay, M; Caleb, M; Flynn, C; Jameson, A; Kramer, M; Petroff, E; Possenti, A; van Straten, W; Bailes, M; Burke-Spolaor, S; Eatough, R P; Stappers, B W; Totani, T; Honma, M; Furusawa, H; Hattori, T; Morokuma, T; Niino, Y; Sugai, H; Terai, T; Tominaga, N; Yamasaki, S; Yasuda, N; Allen, R; Cooke, J; Jencson, J; Kasliwal, M M; Kaplan, D L; Tingay, S J; Williams, A; Wayth, R; Chandra, P; Perrodin, D; Berezina, M; Mickaliger, M; Bassa, C

    2016-01-01

    In recent years, millisecond duration radio signals originating from distant galaxies appear to have been discovered in the so-called Fast Radio Bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity which, in tandem with a redshift measurement, can be used for fundamental physical investigations. While every fast radio burst has a dispersion measurement, none before now have had a redshift measurement, due to the difficulty in pinpointing their celestial coordinates. Here we present the discovery of a fast radio burst and the identification of a fading radio transient lasting $\\sim 6$ days after the event, which we use to identify the host galaxy; we measure the galaxy's redshift to be $z=0.492\\pm0.008$. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionised baryons in the intergalactic medium of $\\Omega_{\\mathrm{IGM}}=4.9 \\pm 1.3\\%$, in agreement with the expectation from WMAP, and i...

  1. The Swift Gamma-Ray Burst Mission

    CERN Document Server

    Gehrels, N; Burrows, D N; Chincarini, G L; Cominsky, L R; Giommi, P; Hurley, K C; Marshall, F E; Mason, K O; Mészáros, P; Nousek, J A; Roming, P W A; Wells, A A; White, N E; Team, Swift Science

    2004-01-01

    The Swift mission, scheduled for launch in early 2004, is a multiwavelength observatory for gamma-ray burst (GRB) astronomy. It is the first-of-its-kind autonomous rapid-slewing satellite for transient astronomy and pioneers the way for future rapid-reaction and multiwavelength missions. It will be far more powerful than any previous GRB mission, observing more than 100 bursts per year and performing detailed X-ray and UV/optical afterglow observations spanning timescales from 1 minute to several days after the burst. The objectives are to determine the origin of GRBs; classify GRBs and search for new types; study the interaction of the ultra-relativistic outflows of GRBs with their surrounding medium; and use GRBs to study the early universe out to z>10. The mission is being developed by a NASA-led international collaboration. It will carry three instruments: a new-generation wide-field gamma-ray (15-150 keV) detector; a narrow-field X-ray telescope; and a narrow-field UV/optical telescope. Redshift determin...

  2. Supercollapsars and their X-ray Bursts

    CERN Document Server

    Komissarov, S S

    2009-01-01

    The very first stars in the Universe can be very massive, frequently reaching $10^3M_\\odot$. If born in large numbers such massive stars can have strong impact on the subsequent star formation producing strong ionising radiation and contaminating the primordial gas with heavy elements. They would leave behind massive black holes that could act as seeds for growing supermassive black holes of active galactic nuclei. Given the anticipated fast rotation such stars would end their live as supermassive collapsars and drive powerful magnetically-dominated jets. In this letter we investigate the possibility of observing the bursts of high-energy emission similar to the Long Gamma Ray Bursts associated with normal collapsars. We show that during the collapse of supercollapsars, the Blandford-Znajek mechanism can extract up to $10^{56}$erg at a rate of few$\\times10^{52}$erg/s. Due to the higher intrinsic time scale and higher redshift the observed burst duration increases by a factor of $\\simeq 1000$ and can reach one...

  3. Composite-flywheel burst-containment study

    Energy Technology Data Exchange (ETDEWEB)

    Sapowith, A D; Handy, W E

    1982-04-08

    A key component impacting total flywheel energy storage system weight is the containment structure. This report addresses the factors that shape this structure and define its design criteria. In addition, containment weight estimates are made for the several composite flywheel designs of interest so that judgements can be made as to the relative weights of their containment structure. The requirements set down for this program were that all containment weight estimates be based on a 1 kWh burst. It should be noted that typical flywheel requirements for regenerative braking of small automobiles call for deliverable energies of 0.25 kWh. This leads to expected maximum burst energies of 0.5 kWh. The flywheels studied are those considered most likely to be carried further for operational design. These area: The pseudo isotropic disk flywheel, sometimes called the alpha ply; the SMC molded disk; either disk with a carbon ring; the subcircular rim with cruciform hub; and Avco's bi-directional circular weave disk. The flywheel materials for the disk are S-glass; the subcircular rim is Kevlar over S-glass. Test data on flywheel bursts and containment failures were analyzed. Recommendations are made for further testing.

  4. Dihydroxyoctadecamonoenoate esters inhibit the neutrophil respiratory burst

    Indian Academy of Sciences (India)

    David Alan Thompson; Bruce D Hammock

    2007-03-01

    The leukotoxins [9(10)- and 12(13)-EpOME] are produced by activated inflammatory leukocytes such as neutrophils. High EpOME levels are observed in disorders such as acute respiratory distress syndrome and in patients with extensive burns. Although the physiological significance of the EpOMEs remains poorly understood, in some systems, the EpOMEs act as a protoxin, with their corresponding epoxide hydrolase metabolites, 9,10- and 12,13-DiHOME, specifically exerting toxicity. Both the EpOMEs and the DiHOMEs were also recently shown to have neutrophil chemotactic activity. We evaluated whether the neutrophil respiratory burst, a surge of oxidant production thought to play an important role in limiting certain bacterial and fungal infections, is modulated by members of the EpOME metabolic pathway. We present evidence that the DiHOMEs suppress the neutrophil respiratory burst by a mechanism distinct from that of respiratory burst inhibitors such as cyclosporin H or lipoxin A4, which inhibit multiple aspects of neutrophil activation.

  5. Radio flares from gamma-ray bursts

    CERN Document Server

    Kopac, D; Kobayashi, S; Virgili, F J; Harrison, R; Japelj, J; Guidorzi, C; Melandri, A; Gomboc, A

    2015-01-01

    We present predictions of centimeter and millimeter radio emission from reverse shocks in the early afterglows of gamma-ray bursts with the goal of determining their detectability with current and future radio facilities. Using a range of GRB properties, such as peak optical brightness and time, isotropic equivalent gamma-ray energy and redshift, we simulate radio light curves in a framework generalized for any circumburst medium structure and including a parametrization of the shell thickness regime that is more realistic than the simple assumption of thick- or thin-shell approximations. Building on earlier work by Mundell et al. (2007) and Melandri et al. (2010) in which the typical frequency of the reverse shock was suggested to lie at radio, rather than optical wavelengths at early times, we show that the brightest and most distinct reverse-shock radio signatures are detectable up to 0.1 -- 1 day after the burst, emphasizing the need for rapid radio follow-up. Detection is easier for bursts with later opt...

  6. Automatic Cloud Bursting under FermiCloud

    Energy Technology Data Exchange (ETDEWEB)

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

    1900-01-01

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

  7. Horizontal alveolar bone loss: A periodontal orphan

    Directory of Open Access Journals (Sweden)

    Jayakumar A

    2010-01-01

    Full Text Available Background: Attempts to successfully regenerate lost alveolar bone have always been a clinician′s dream. Angular defects, at least, have a fairer chance, but the same cannot be said about horizontal bone loss. The purpose of the present study was to evaluate the prevalence of horizontal alveolar bone loss and vertical bone defects in periodontal patients; and later, to correlate it with the treatment modalities available in the literature for horizontal and vertical bone defects. Materials and Methods: The study was conducted in two parts. Part I was the radiographic evaluation of 150 orthopantomographs (OPGs (of patients diagnosed with chronic periodontitis and seeking periodontal care, which were digitized and read using the AutoCAD 2006 software. All the periodontitis-affected teeth were categorized as teeth with vertical defects (if the defect angle was ≤45° and defect depth was ≥3 mm or as having horizontal bone loss. Part II of the study comprised search of the literature on treatment modalities for horizontal and vertical bone loss in four selected periodontal journals. Results: Out of the 150 OPGs studied, 54 (36% OPGs showed one or more vertical defects. Totally, 3,371 teeth were studied, out of which horizontal bone loss was found in 3,107 (92.2% teeth, and vertical defects were found only in 264 (7.8% of the teeth, which was statistically significant (P<.001. Search of the selected journals revealed 477 papers have addressed the treatment modalities for vertical and horizontal types of bone loss specifically. Out of the 477 papers, 461 (96.3% have addressed vertical bone loss, and 18 (3.7% have addressed treatment options for horizontal bone loss. Two papers have addressed both types of bone loss and are included in both categories. Conclusion: Horizontal bone loss is more prevalent than vertical bone loss but has been sidelined by researchers as very few papers have been published on the subject of regenerative treatment

  8. Localized Eruptive Blue Nevi after Herpes Zoster

    Science.gov (United States)

    Colson, Fany; Arrese, Jorge E.; Nikkels, Arjen F.

    2016-01-01

    A 52-year-old White man presented with a dozen small, well-restricted, punctiform, asymptomatic, blue-gray macules on the left shoulder. A few months earlier, he had been treated with oral acyclovir for herpes zoster (HZ) affecting the left C7–C8 dermatomes. All the blue macules appeared over a short period of time and then remained stable. The patient had not experienced any previous trauma or had tattooing in this anatomical region. The clinical diagnosis suggested blue nevi. Dermatoscopy revealed small, well-limited, dark-blue, compact, homogeneous areas evoking dermal blue nevi. An excisional biopsy was performed and the histological examination confirmed a blue nevus. As far as we are aware of, this is the first report of eruptive blue nevi following HZ, and it should be included in the differential diagnosis of zosteriform dermatoses responding to an isotopic pathway. In addition, a brief review concerning eruptive nevi is presented. PMID:27462219

  9. Inflation and alternatives with blue tensor spectra

    International Nuclear Information System (INIS)

    We study the tilt of the primordial gravitational waves spectrum. A hint of blue tilt is shown from analyzing the BICEP2 and POLARBEAR data. Motivated by this, we explore the possibilities of blue tensor spectra from the very early universe cosmology models, including null energy condition violating inflation, inflation with general initial conditions, and string gas cosmology, etc. For the simplest G-inflation, blue tensor spectrum also implies blue scalar spectrum. In general, the inflation models with blue tensor spectra indicate large non-Gaussianities. On the other hand, string gas cosmology predicts blue tensor spectrum with highly Gaussian fluctuations. If further experiments do confirm the blue tensor spectrum, non-Gaussianity becomes a distinguishing test between inflation and alternatives

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

    Directory of Open Access Journals (Sweden)

    Nicholas A Lesica

    2006-07-01

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

  11. Polish Terms for "Blue" in the Perspective of Vantage Theory

    Science.gov (United States)

    Stanulewicz, Danuta

    2010-01-01

    The Polish set of terms for blue includes, inter alia, the following adjectives: "niebieski" "blue", "blekitny" "(sky) blue", "granatowy" "navy blue", "lazurowy" "azure", "modry" "(intense) blue" and "siny" "(grey) violet-blue". The adjective "niebieski" is the basic term; however, it shares some of its functions with "blekitny", which is…

  12. HORIZONTAL WELL DRILL-IN FLUIDS

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    1998-12-01

    Full Text Available Main objective of horizontal driling is to place a drain-hole for a long distance within the pay zone to enhance productivity or injectivity. In drilling horizontal wells, more serious problems appear than in drilling vertical wells. These problems are: poor hole cleaning, excessive torque and drag, hole filling, pipe stucking, wellbore instability, loss of circulation, formation damage, poor cement job, and difficulties at logging jobs. From that reason, successful drilling and production of horizontal well depends largely on the fluid used during drilling and completion phases. Several new fluids, that fulfill some or all of required properties (hole cleaning, cutting suspension, good lubrication, and relative low formation damage, are presented in this paper.

  13. Horizontal stirring in the global ocean

    CERN Document Server

    Hernández-Carrasco, I; Hernández-García, E; Turiel, A

    2011-01-01

    Horizontal mixing and the distribution of coherent structures in the global ocean are analyzed using Finite-Size Lyapunov Exponents (FSLE), computed for the surface velocity field derived from the Ocean general circulation model For the Earth Simulator (OFES). FSLEs measure horizontal stirring and dispersion; additionally, the transport barriers which organize the oceanic flow can roughly be identified with the ridges of the FSLE field. We have performed a detailed statistical study, particularizing for the behaviour of the two hemispheres and different ocean basins. The computed Probability Distributions Functions (PDFs) of FSLE are broad and asymmetric. Horizontal mixing is generally more active in the northern hemisphere than in the southern one. Nevertheless the Southern Ocean is the most active ocean, and the Pacific the less active one. A striking result is that the main currents can be classified in two 'activity classes': Western Boundary Currents, which have broad PDFs with large FSLE values, and Eas...

  14. Diffuser Augmented Horizontal Axis Tidal Current Turbines

    Directory of Open Access Journals (Sweden)

    Nasir Mehmood

    2012-09-01

    Full Text Available The renewal energy technologies are increasingly popular to ensure future energy sustenance and address environmental issues. The tides are enormous and consistent untapped resource of renewable energy. The growing interest in exploring tidal energy has compelling reasons such as security and diversity of supply, intermittent but predictable and limited social and environmental impacts. The tidal energy industry is undergoing an increasing shift towards diffuser augmented turbines. The reason is the higher power output of diffuser augmented turbines compared to conventional open turbines. The purpose of this study is to present a comprehensive review of diffuser augmented horizontal axis tidal current turbines. The components, relative advantages, limitations and design parameters of diffuser augmented horizontal axis tidal current turbines are presented in detail. CFD simulation of NACA 0016 airfoil is carried out to explore its potential for designing a diffuser. The core issues associated with diffuser augmented horizontal axis tidal current turbines are also discussed.

  15. The Fermi-GBM X-ray burst monitor: thermonuclear bursts from 4U 0614+09

    CERN Document Server

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

    2012-01-01

    Thermonuclear bursts from slowly accreting neutron stars (NSs) have proven difficult to detect, yet they are potential probes of the thermal properties of the neutron star interior. During the first year of a systematic all-sky search for X-ray bursts using the Gamma-ray Burst Monitor (GBM) aboard the Fermi Gamma-ray Space Telescope we have detected 15 thermonuclear bursts from the NS low-mass X-ray binary 4U 0614+09, when it was accreting at nearly 1% of the Eddington limit. We measured an average burst recurrence time of 12+/-3 d (68% confidence interval) between March 2010 and March 2011, classified all bursts as normal duration bursts and placed a lower limit on the recurrence time of long/intermediate bursts of 62 d (95% confidence level). We discuss how observations of thermonuclear bursts in the hard X-ray band compare to pointed soft X-ray observations, and quantify such bandpass effects on measurements of burst radiated energy and duration. We put our results for 4U 0614+09 in the context of other bu...

  16. Fourth international seminar on horizontal steam generators

    Energy Technology Data Exchange (ETDEWEB)

    Tuomisto, H. [ed.] [IVO Group, Vantaa (Finland); Purhonen, H. [ed.] [VTT, Espoo (Finland); Kouhia, V. [ed.] [Lappeenranta Univ. of Technology (Finland)

    1997-12-31

    The general objective of the International Seminars of Horizontal Steam Generator Modelling has been the improvement in understanding of realistic thermal hydraulic behaviour of the generators when performing safety analyses for VVER reactors. The main topics presented in the fourth seminar were: thermal hydraulic experiments and analyses, primary collector integrity, feedwater distributor replacement, management of primary-to-secondary leakage accidents and new developments in the VVER safety technology. The number of participants, representing designers and manufacturers of the horizontal steam generators, plant operators, engineering companies, research organizations, universities and regulatory authorities, was 70 from 10 countries.

  17. Fourth international seminar on horizontal steam generators

    International Nuclear Information System (INIS)

    The general objective of the International Seminars of Horizontal Steam Generator Modelling has been the improvement in understanding of realistic thermal hydraulic behaviour of the generators when performing safety analyses for VVER reactors. The main topics presented in the fourth seminar were: thermal hydraulic experiments and analyses, primary collector integrity, feedwater distributor replacement, management of primary-to-secondary leakage accidents and new developments in the VVER safety technology. The number of participants, representing designers and manufacturers of the horizontal steam generators, plant operators, engineering companies, research organizations, universities and regulatory authorities, was 70 from 10 countries

  18. Long X-ray burst monitoring with INTEGRAL

    DEFF Research Database (Denmark)

    X-ray bursts are thermonuclear explosions on the surface of accreting neutron stars in low mass X-ray binary systems. In the frame of the INTEGRAL observational Key Programme over the Galactic Center a good number of the known X-ray bursters are frequently being monitored. An international....... Of special interest are low luminosity bursting sources that exhibit X-ray bursts of very different durations allowing to study the transition from a hydrogen-rich bursting regime to a pure helium regime and from helium burning to carbon burning. I will present results obtained from INTEGRAL archive data...... and from our previous proposal for the observation period 2006-2007. Comparing these observations with the current burst theories confirms the relation between bursting regimes and the accretion states of the system....

  19. Strain bursts in plastically deforming Molybdenum micro- and nanopillars

    OpenAIRE

    Zaiser, Michael; Schwerdtfeger, Jan; Schneider, Andreas; Frick, Carl; Clark, Blythe Gore; Gruber, Patric; Arzt, Eduard

    2009-01-01

    Abstract Plastic deformation of micron and sub-micron scale specimens is characterized by intermittent sequences of large strain bursts (dislocation avalanches) which are separated by regions of near-elastic loading. In the present investigation we perform a statistical characterization of strain bursts observed in stress-controlled compressive deformation of monocrystalline molybdenum micropillars. We characterize the bursts in terms of the associated elongation increments and pea...

  20. Full System Bifurcation Analysis of Endocrine Bursting Models

    OpenAIRE

    Rieß, Thorsten; Sherman, Arthur; Tsaneva-Atanasova, KT; Osinga, HM

    2010-01-01

    Plateau bursting is typical of many electrically excitable cells, such as endocrine cells that secrete hormones and some types of neurons that secrete neurotransmitters. Although in many of these cell types the bursting patterns are regulated by the interplay between voltage-gated calcium channels and calcium-sensitive potassium channels, they can be very different. For example, in insulin-secreting pancreatic β-cells, plateau bursting is characterized by well-defined spikes during the depola...

  1. A Limited Deflection Routing Algorithm Based on Burst Loss Threshold in OBS Networks

    Institute of Scientific and Technical Information of China (English)

    WANG Ru-yan; LONG Ke-ping; WU Wei; YANG Xiao-long; ZHU Wei-le

    2005-01-01

    The deflection routing protocol is an effective contention resolution in Optical Burst Switching network. However, it can worsen loss performance of non-deflected burst on the deflection route. To improve the burst loss performance, a limited deflection routing scheme based on burst loss threshold is proposed to prevent injudicious deflection routing. By using threshold check function, it restrainedly allows the deflected burst to preemptive network resource, consequently, improve the QoS performance of non-deflected burst. Simulation results show that the scheme can efficiently prevent deflected burst contending with non-deflected burst on deflection route, and effectively improve the burst loss performance of entire networks.

  2. Various Shades of Blue's Functions

    CERN Document Server

    Janik, R A; Papp, G; Zahed, I; Janik, Romuald A.; Nowak, Maciej A.; Papp, Gabor; Zahed, Ismail

    1997-01-01

    We discuss random matrix models in terms of elementary operations on Blue's functions (functional inverse of Green's functions). We show that such operations embody the essence of a number of physical phenomena whether at/or away from the critical points. We illustrate these assertions by borrowing on a number of recent results in effective QCD in vacuum and matter. We provide simple physical arguments in favor of the universality of the continuum QCD spectral oscillations, whether at zero virtuality, in the bulk of the spectrum or at the chiral critical points. We also discuss effective quantum systems of disorder with strong or weak dissipation (Hatano-Nelson localization).

  3. Blue lobes in the Hydra A cluster central galaxy

    Science.gov (United States)

    Mcnamara, Brian R.

    1995-01-01

    We present new U- and I-band images of the centrally dominant galaxy in the Hydra A cluster, obtained with the 2.5 m Isaac Newton Telescope at La Palma. The galaxy is centered in a poor, X-ray-luminous cluster whose gaseous intracluster medium is apparently cooling at a rate of m-dot(sub CF) approximately 3000 solar masses/yr. The galaxy's structure is that of a normal giant elliptical galaxy, apart from the central approximately 8 x 6 arcsec (approximately 12 x 9 kpc) region which contains an unusually blue, lobelike structure that is spatially coincident with a luminous emission-line nebula in rotation about the nucleus. Based on near spatial coincidence of the central continuum structure and the emission-line nebula, we suggest that the blue continuum is due to a warm stellar population in a central disk. In order to isolate and study the structure of the disk, we have subtracted a smooth galactic background model from the U-band image. The disk's surface brightness profiles along its major and minor axes decline roughly exponentially with radius. The disk's axial ratio is consistent with a nearly edge-on thick disk or a thin disk that is inclined with respect to the line of sight. The bluest regions, located a few arcsec on either side of the nucleus (giving the lobelike appearance), may be due to locally enhanced star formation or a seeing-blurred ring of young stars embedded in the disk observed nearly edge-on. If star-formation is occurring with the local initial mass function, the central color, surface brightness, and dynamical mass would be consistent with models for star formation at a rate of less than and approximately 1 solar masses/yr which has persisted for the past approximately 10(exp 9) yr, a short burst (10(exp 7) yr) of star formation at a rate of approximately 30 solar masses/yr which occurred less than and approximately 10(exp 8) yr ago, or an instantaneous burst of star formation which occurred approximately 5 x 10(exp 7) yr ago. While the

  4. ESTIMATION OF THE BURST LENGTH IN OBS NETWORKS

    OpenAIRE

    Pallavi S.; M. Lakshmi

    2014-01-01

    This paper presents an overview of the optical burst switching (OBS) and discusses the major components. In OBS, the length of the burst arriving at a particular node is unknown, and hence, node design is very complex. In OBS first control, packet is transmitted and reserve the path as in circuit switching, thereafter, the data bursts is transmitted. In this paper, a poisson arrival of packets is considered and estimation is made on the size of the burst length. The results presented in the p...

  5. The Fermi-GBM X-ray burst monitor

    Science.gov (United States)

    Linares, M.; Fermi GBM X-ray Burst Collaboration

    2010-12-01

    We discuss the first results of the Fermi-GBM all-sky search for X-ray bursts. The very large field of view and X-ray response of the Fermi-GBM make it a unique instrument to study rare, bright and short-lived X-ray bursts. We are performing a systematic search that exploits such capabilities. We present results on long/intermediate type I X-ray bursts, an unusual kind of thermonuclear bursts from accreting neutron stars, and show how Fermi-GBM is giving for the first time robust measurements of their recurrence time.

  6. The long and the short of gamma-ray bursts

    CERN Document Server

    Katz, J I

    1995-01-01

    We report evidence from the 3B Catalogue that long (T_{90} > 10 s) and short (T_{90} 1 MeV. This implies different spatial origin and physical processes for long and short bursts. Long bursts may be explained by accretion-induced collapse. Short bursts require another mechanism, for which we suggest neutron star collisions. These are capable of producing neutrino bursts as short as a few ms, consistent with the shortest observed time scales in GRB. We briefly investigate the parameters of clusters in which neutron star collisons may occur, and discuss the nuclear evolution of expelled and accelerated matter.

  7. The First Swift BAT Gamma-Ray Burst Catalog

    OpenAIRE

    Sakamoto, T.; Barthelmy, S. D.; Barbier, L.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Hullinger, D.; Krimm, H. A.; Markwardt, C. B.; Palmer, D. M.; Parsons, A. M.; Sato, G.; Stamatikos, M.; Tueller, J.; Ukwatta, T. N.

    2007-01-01

    We present the first Swift Burst Alert Telescope (BAT) catalog of gamma-ray bursts (GRBs), which contains bursts detected by the BAT between 2004 December 19 and 2007 June 16. This catalog (hereafter BAT1 catalog) contains burst trigger time, location, 90% error radius, duration, fluence, peak flux, and time averaged spectral parameters for each of 237 GRBs, as measured by the BAT. The BAT-determined position reported here is within 1.75' of the Swift X-ray Telescope (XRT)-determined position...

  8. Study on cosmic gamma bursts in the ''KONUS'' experiment

    International Nuclear Information System (INIS)

    Made are the investigations of cosmic gamma bursts with the help of the ''Konus'' apparatus, positioned on the ''Venera 11'' and ''Venera 12'' automatic interplanetary stations. 37 gamma bursts have been recorded in the energy range from 50 to 150 keV during the observation period from September to December 1978. Time profiles of bursts on 4, 9 and 24.11.1978 are presented. For the most events the time of burst increase and decrease constitute parts and units of seconds. Differential energy spectra are measured for all recorded bursts. In many cases the spectrum shape is similar to the grade one with the 1.5-2.3 index. In a graphical form built up are the integral distributions of gamma bursts appearence frequency in dependence on their intensity and maximum capacity in the burst peak. Galaxy coordinates of the 17-teen bursts, for which a simple localization is possible, are put on the celestial sphere map. The type of the integral distributions and the source distribution about the celestial sphere show that the gamma burst sources are whithin the Galaxy

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

    DEFF Research Database (Denmark)

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

    1995-01-01

    19 Cosmic Gamma-Ray Bursts were detected by the WATCH wide field X-ray monitor during the 11 months flight of EURECA. The identification of the bursts were complicated by a high frequency of background of events caused by high energy cosmic ray interactions in the detector and by low energy......, trapped particle streams. These background events may simulate the count rate increases characteristic of cosmic gamma bursts. For 12 of the detected events, their true cosmic nature have been confirmed through consistent localizations of the burst sources based on several independent WATCH data sets...

  10. Observations of the structure of Type IIIb radio bursts

    International Nuclear Information System (INIS)

    The authors have observed short duration, narrow band Type IIIb radio bursts that occur just before the onset of a normal Type III burst. These observations were made with a multichannel radiometer with a center frequency of 25 MHz, time constant of 10 milliseconds and frequency resolution of 100 KHz. The average half power duration of a typical element of a Type III burst was determined. It was found to be very similar to the time profile of a normal Type III burst, i.e., sharp rise and exponential type decay. (Auth.)

  11. Percussion drilling of metals using bursts of nanosecond pulses.

    Science.gov (United States)

    Hendow, Sami T; Romero, Rosa; Shakir, Sami A; Guerreiro, Paulo T

    2011-05-23

    The effect of ns bursting on percussion drilling of metal is investigated experimentally and analytically, and compared with the efficiency and quality of drilling using single ns pulses. Key advantages are demonstrated, correlating well with the results from a thermal theoretical model. The 1064 nm bursts contain up to 14 pulses of various pulse widths and spacing, and at frequencies of tens of MHz within the burst. The individual pulses have pulse widths of 10 to 200 ns, and up to 12 kW peak power. Burst repetition frequency is single shot to 500 kHz. PMID:21643280

  12. A behavioral role for feature detection by sensory bursts.

    Science.gov (United States)

    Marsat, Gary; Pollack, Gerald S

    2006-10-11

    Brief episodes of high-frequency firing of sensory neurons, or bursts, occur in many systems, including mammalian auditory and visual systems, and are believed to signal the occurrence of particularly important stimulus features, i.e., to function as feature detectors. However, the behavioral relevance of sensory bursts has not been established in any system. Here, we show that bursts in an identified auditory interneuron of crickets reliably signal salient stimulus features and reliably predict behavioral responses. Our results thus demonstrate the close link between sensory bursts and behavior.

  13. Coupled hydro-neutronic calculations for fast burst reactor accidents

    International Nuclear Information System (INIS)

    Methods are described for determining the fully coupled neutronic/hydrodynamic response of fast burst reactors (FBR) under disruptive accident conditions. Two code systems, PAD (1 -D Lagrangian) and NIKE-PAGOSA (3-D Eulerian) were used to accomplish this. This is in contrast to the typical methodology that computes these responses by either single point kinetics or in a decoupled manner. This methodology is enabled by the use of modem supercomputers (CM-200). Two examples of this capability are presented: an unreflected metal fast burst assembly, and a reflected fast burst assembly typical of the Skua or SPR-III class of fast burst reactor

  14. Emergent synchronous bursting of oxytocin neuronal network.

    Directory of Open Access Journals (Sweden)

    Enrico Rossoni

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

  15. Cues for localization in the horizontal plane

    DEFF Research Database (Denmark)

    Jeppesen, Jakob; Møller, Henrik

    2005-01-01

    manipulated in HRTFs used for binaural synthesis of sound in the horizontal plane. The manipulation of cues resulted in HRTFs with cues ranging from correct combinations of spectral information and ITDs to combinations with severely conflicting cues. Both the ITD and the spectral information seem to be...

  16. Stabilities of Parallel Flow and Horizontal Convection

    OpenAIRE

    Sun, Liang

    2009-01-01

    In the first part, the stability of two-dimensional parallel flow is discussed. A more restrictively general stability criterion for inviscid parallel flow is obtained analytically. In the second part, we report the numerical simulations of the partial-penetrating flow in horizontal convection within a squire cavity tank at high Rayleigh numbers $10^7

  17. Teaching Activities on Horizontal Nuclear Proliferation.

    Science.gov (United States)

    Zola, John

    1990-01-01

    Provides learning activities concerning the horizontal proliferation of nuclear weapons. Includes step-by-step directions for four activities: (1) the life cycle of nuclear weapons; (2) nuclear nonproliferation: pros and cons; (3) the nuclear power/nuclear weapons connection; and (4) managing nuclear proliferation. (NL)

  18. Third international seminar on horizontal steam generators

    International Nuclear Information System (INIS)

    The Third International Seminar on Horizontal Steam Generators held on October 18-20, 1994 in Lappeenranta, consisted of six sessions dealing with the topics: thermal hydraulic experiments and analyses, primary collector integrity, management of primary-to-secondary leakage accidents, feedwater collector replacement and discussion of VVER-440 steam generator safety issues

  19. Horizontal Axis Levitron--A Physics Demonstration

    Science.gov (United States)

    Michaelis, Max M.

    2014-01-01

    After a brief history of the Levitron, the first horizontal axis Levitron is reported. Because it is easy to operate, it lends itself to educational physics experiments and analogies. Precession and nutation are visualized by reflecting the beam from a laser pointer off the "spignet". Precession is fundamental to nuclear magnetic…

  20. Evaluation of horizontal magnification on panoramic images

    Directory of Open Access Journals (Sweden)

    Maryam Raoof

    2013-01-01

    Full Text Available Aims: This study evaluated the horizontal magnification of images taken from adults and pediatrics with PM 2002 CC Planmeca analogue machine. Materials and Methods: A series of 120 panoramic radiographs were obtained of 60 adults and 60 pediatrics. For all patients, negative impressions were used to make positive casts of the teeth. A caliper was used to measure the maximum mesiodistal length of the buccal surface of all teeth except canines on both casts and radiographs. The horizontal magnification factor was calculated for incisor, premolar, and molar regions by dividing the values obtained from the casts by the values obtained from the radiographs. Statistical Analysis: Independent t-test and one-way analysis of variance (ANOVA were used. Results: The results indicated that with regard to adults, maxillary and mandibular incisor regions, unlike the other two sessions, didn′t show significant difference of the mean magnification of horizontal dimension (P = 0.5. In pediatrics, the comparison between mean magnification factors of all subgroups showed significant difference (P < 0.0001. Despite the adults′ radiographs, the results of pediatrics′ radiographs showed significantly higher magnification than the index listed by the manufacturer of the radiographic machine used. Conclusion: The present study results point to the fact that PM 2002 CC Proline panoramic machine makes possible precise measurements on radiographs of adults′ jaws in the horizontal dimension.

  1. Horizontal gene transfer in the phytosphere

    NARCIS (Netherlands)

    Elsas, van J.D.; Turner, S.; Bailey, M.J.

    2003-01-01

    Here, the ecological aspects of gene transfer processes between bacteria in the phytosphere are examined in the context of emerging evidence for the dominant role that horizontal gene transfer (HGT) has played in the evolutionary shaping of bacterial communities. Moreover, the impact of the putative

  2. Flow mapping for ESS horizontal target

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Y.; Kikura, H.; Taishi, T. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    Flow behaviour for ESS horizontal target is studied experimentally using two dimensional water model. A velocity field of stationary flow in reaction zone has been obtained. Three dimensional effect was also studied as a spanwise flow structure. (author) 3 figs., 3 refs.

  3. Parametric study for horizontal steam generator modelling

    Energy Technology Data Exchange (ETDEWEB)

    Ovtcharova, I. [Energoproekt, Sofia (Bulgaria)

    1995-12-31

    In the presentation some of the calculated results of horizontal steam generator PGV - 440 modelling with RELAP5/Mod3 are described. Two nodalization schemes have been used with different components in the steam dome. A study of parameters variation on the steam generator work and calculated results is made in cases with separator and branch.

  4. Third international seminar on horizontal steam generators

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-12-31

    The Third International Seminar on Horizontal Steam Generators held on October 18-20, 1994 in Lappeenranta, consisted of six sessions dealing with the topics: thermal hydraulic experiments and analyses, primary collector integrity, management of primary-to-secondary leakage accidents, feedwater collector replacement and discussion of VVER-440 steam generator safety issues.

  5. Fast Radio Bursts - I: Initial Cogitation

    CERN Document Server

    Keane, E F

    2014-01-01

    Fast radio bursts (FRBs) are millisecond-duration radio signals thought to originate from cosmological distances. Many authors are endeavouring to explain their progenitors, with others outlining their potential uses as cosmological probes. Here we describe some sub-optimal performance in existing FRB search software, which can reduce the volume probed by over 20%, and result in missed discoveries and incorrect flux densities and sky rates. Recalculating some FRB flux densities, we find that FRB 010125 was approximately 50% brighter than previously reported. Furthermore we consider incompleteness factors important to the population statistics. Finally we make data for the archival FRBs easily available, along with software to analyse these.

  6. Prompt Emission Observations of Swift BAT Bursts

    Science.gov (United States)

    Barthelmy, Scott

    2009-01-01

    We review the prompt emission properties of Swift BAT gamma-ray bursts (GRBs). We present the global properties of BAT GRBs based on their spectral and temporal characteristics. The BAT T90 and T50 durations peak at 80 and 20 s, respectively. The peak energy (Epeak) of about 60% of BAT GRBs is very likely to be less than 1.00 keV. We also present the BAT characteristics of GRBs with soft spectra, so called Xray flashes (XRFs). We will compare the BAT GRBs and XRFs parameter distribution to the other missions.

  7. Spectral Lag Evolution among -Ray Burst Pulses

    Indian Academy of Sciences (India)

    Lan-Wei Jia; Yun-Feng Liang; En-Wei Liang

    2014-09-01

    We analyse the spectral lag evolution of -ray burst (GRB) pulses with observations by CGRO/BATSE. No universal spectral lag evolution feature and pulse luminosity-lag relation within a GRB is observed.Our results suggest that the spectral lag would be due to radiation physics and dynamics of a given emission episode, possibly due to the longer lasting emission in a lower energy band, and the spectral lag may not be an intrinsic parameter to discriminate the long and short GRBs.

  8. Burst-Mode Asynchronous Controllers on FPGA

    Directory of Open Access Journals (Sweden)

    Duarte L. Oliveira

    2008-01-01

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

  9. Gamma Ray Bursts in the HAWC Era

    CERN Document Server

    Mészáros, Peter; Murase, Kohta; Fox, Derek; Gao, He; Senno, Nicholas

    2015-01-01

    Gamma-Ray Bursts are the most energetic explosions in the Universe, and are among the most promising for detecting multiple non-electromagnetic signals, including cosmic rays, high energy neutrinos and gravitational waves. The multi-GeV to TeV gamma-ray range of GRB could have significant contributions from hadronic interactions, mixed with more conventional leptonic contributions. This energy range is important for probing the source physics, including overall energetics, the shock parameters and the Lorentz factor. We discuss some of the latest observational and theoretical developments in the field.

  10. Gamma-Ray Bursts: A Mystery Story

    Science.gov (United States)

    Parsons, Ann

    2007-01-01

    With the success of the Swift Gamma-Ray Burst Explorer currently in orbit, this is quite an exciting time in the history of Gamma Ray Bursts (GRBs). The study of GRBs is a modern astronomical mystery story that began over 30 years ago with the serendipitous discovery of these astronomical events by military satellites in the late 1960's. Until the launch of BATSE on the Compton Gamma-ray Observatory, astronomers had no clue whether GRBs originated at the edge of our solar system, in our own Milky Way Galaxy or incredibly far away near the edge of the observable Universe. Data from BATSE proved that GRBs are distributed isotropically on the sky and thus could not be the related to objects in the disk of our Galaxy. Given the intensity of the gamma-ray emission, an extragalactic origin would require an astounding amount of energy. Without sufficient data to decide the issue, a great debate continued about whether GRBs were located in the halo of our own galaxy or were at extragalactic - even cosmological distances. This debate continued until 1997 when the BeppoSAX mission discovered a fading X-ray afterglow signal in the same location as a GRB. This discovery enabled other telescopes, to observe afterglow emission at optical and radio wavelengths and prove that GRBs were at cosmological distances by measuring large redshifts in the optical spectra. Like BeppoSAX Swift, slews to new GRB locations to measure afterglow emission. In addition to improved GRB sensitivity, a significant advantage of Swift over BeppoSAX and other missions is its ability to slew very quickly, allowing x-ray and optical follow-up measurements to be made as early as a minute after the gamma-ray burst trigger rather than the previous 6-8 hour delay. Swift afterglow measurements along with follow-up ground-based observations, and theoretical work have allowed astronomers to identify two plausible scenarios for the creation of a GRB: either through core collapse of super massive stars or

  11. Thermal radiation from a nuclear weapon burst

    International Nuclear Information System (INIS)

    The different methods and correlations used to calculate the propagation of thermal radiation are reviewed and compared. A simple method to account for radiation enhancement by reflection from a superior cloud deck or snow cover, as well as attenuation of radiation by cloud cover below the burst is presented. The results show that the thermal reach may vary considerably. Additional calculation show that a significant fraction of the thermal energy may be incident after the arrival of the shock wave. Results for a range of weapon yields are presented, and the implications for blast-induced (secondary) fire starts are discussed

  12. The repeating Fast Radio Burst FRB 121102: Multi-wavelength observations and additional bursts

    CERN Document Server

    Scholz, P; Hessels, J W T; Chatterjee, S; Cordes, J M; Kaspi, V M; Wharton, R S; Bassa, C G; Bogdanov, S; Camilo, F; Crawford, F; Deneva, J; van Leeuwen, J; Lynch, R; Madsen, E C; McLaughlin, M A; Mickaliger, M; Parent, E; Patel, C; Ransom, S M; Seymour, A; Stairs, I H; Stappers, B W; Tendulkar, S P

    2016-01-01

    We report on radio and X-ray observations of the only known repeating Fast Radio Burst (FRB) source, FRB 121102. We have detected six additional radio bursts from this source: five with the Green Bank Telescope at 2 GHz, and one at 1.4 GHz at the Arecibo Observatory for a total of 17 bursts from this source. All have dispersion measures consistent with a single value ($\\sim559$ pc cm$^{-3}$) that is three times the predicted maximum Galactic value. The 2-GHz bursts have highly variable spectra like those at 1.4 GHz, indicating that the frequency structure seen across the individual 1.4 and 2-GHz bandpasses is part of a wideband process. X-ray observations of the FRB 121102 field with the Swift and Chandra observatories show at least one possible counterpart; however, the probability of chance superposition is high. A radio imaging observation of the field with the Jansky Very Large Array at 1.6 GHz yields a 5$\\sigma$ upper limit of 0.3 mJy on any point-source continuum emission. This upper limit, combined wit...

  13. The Second SWIFT Burst Alert Telescope (BAT) Gamma-Ray Burst Catalog

    Science.gov (United States)

    Sakamoto, T.; Barthelmy, S. D.; Baumgartner, W. H.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Krimm, H. A.; Markwardt, C. B.; Palmer, D. M.; Parsons, A. M.; Sato, G.; Stamatikos, M.; Tueller, J.; Ukwatta, T. N.; Zhang, B.

    2012-01-01

    We present the second Swift Burst Alert Telescope (BAT) catalog of gamma-ray bursts. (GRBs), which contains 476 bursts detected by the BAT between 2004 December 19 and 2009 December 21. This catalog (hereafter the BAT2 catalog) presents burst trigger time, location, 90% error radius, duration, fluence, peak flux, time-averaged spectral parameters and time-resolved spectral parameters measured by the BAT. In the correlation study of various observed parameters extracted from the BAT prompt emission data, we distinguish among long-duration GRBs (L-GRBs), short-duration GRBs (S-GRBs), and short-duration GRBs with extended emission (S-GRBs with E.E.) to investigate differences in the prompt emission properties. The fraction of L-GRBs, S-GRBs and S-GRBs with E.E. in the catalog are 89%, 8% and 2% respectively. We compare the BAT prompt emission properties with the BATSE, BeppoSAX and HETE-2 GRB samples.. We also correlate the observed prompt emission properties with the redshifts for the GRBs with known redshift. The BAT T(sub 90) and T(sub 50) durations peak at 70 s and 30 s, respectively. We confirm that the spectra of the BAT S-GRBs are generally harder than those of the L-GRBs.

  14. The LOFT Burst Alert System and its Burst On-board Trigger

    DEFF Research Database (Denmark)

    Schanne, Stephane; Götz, Diego; Provost, Herve Le;

    2014-01-01

    year) and other transient sources, and to deliver their localization in less than 30 seconds to the observers, via a VHF antenna network. Real-time full resolution data download to ground being impossible, the real-time data processing is performed onboard by the LBOT (LOFT Burst On-board Trigger...

  15. An HST/WFC3 view of stellar populations on the Horizontal Branch of NGC 2419

    CERN Document Server

    Di Criscienzo, M; Milone, A P; D'Antona, F; Ventura, P; Dotter, A; Brocato, E

    2015-01-01

    We use images acquired with the Hubble Space Telescope Wide Field Camera 3 and new models to probe the Horizontal Branch (HB) population of the We use images acquired with the Hubble Space Telescope Wide Field Camera 3 and new models to probe the horizontal branch (HB) population of the Galactic globular cluster (GC) NGC 2419. A detailed analysis of the composite HB highlights three populations:(1) the blue luminous HB, hosting standard helium stars (Y=0.25) with a very small spread of mass, (2) a small population of stars with intermediate helium content (0.26blue hook' stars) are identified as possible 'late flash mixed stars'. The initial helium abundance of this extreme population is in nice agreement with the predicted helium abundance in the ejecta of massive asymptotic giant branch (AGB) stars of the same metallicity as NGC 2419. Thi...

  16. A new population of ultra-long duration gamma-ray bursts

    International Nuclear Information System (INIS)

    We present comprehensive multiwavelength observations of three gamma-ray bursts (GRBs) with durations of several thousand seconds. We demonstrate that these events are extragalactic transients; in particular, we resolve the long-standing conundrum of the distance of GRB 101225A (the 'Christmas-day burst'), finding it to have a redshift z = 0.847 and showing that two apparently similar events (GRB 111209A and GRB 121027A) lie at z = 0.677 and z = 1.773, respectively. The systems show extremely unusual X-ray and optical light curves, very different from classical GRBs, with long-lasting, highly variable X-ray emission and optical light curves that exhibit little correlation with the behavior seen in the X-ray. Their host galaxies are faint, compact, and highly star-forming dwarf galaxies, typical of 'blue compact galaxies'. We propose that these bursts are the prototypes of a hitherto largely unrecognized population of ultra-long GRBs, which while observationally difficult to detect may be astrophysically relatively common. The long durations may naturally be explained by the engine-driven explosions of stars of much larger radii than normally considered for GRB progenitors, which are thought to have compact Wolf-Rayet progenitor stars. However, we cannot unambiguously identify supernova signatures within their light curves or spectra. We also consider the alternative possibility that they arise from the tidal disruption of stars by massive black holes and conclude that the associated timescales are only consistent with the disruption of compact stars (e.g., white dwarfs) by black holes of relatively low mass (<105 M ☉).

  17. A new population of ultra-long duration gamma-ray bursts

    Energy Technology Data Exchange (ETDEWEB)

    Levan, A. J.; Brown, G. C.; Tunnicliffe, R. L. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Tanvir, N. R.; Starling, R. L. C.; Wiersema, K.; Page, K. L.; Wynn, G. A.; O' Brien, P. T. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Perley, D. A. [Department of Astronomy, California Institute of Technology, MC 249-17, 1200 East California Blvd., Pasadena, CA 91125 (United States); Schulze, S. [Pontificia Universidad Católica de Chile, Departamento de Astronomía y Astrofísica, Casilla 306, Santiago 22 (Chile); Chornock, R.; Malesani, D.; Watson, D.; Berger, E. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hjorth, J. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Københaven Ø (Denmark); Cenko, S. B. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Fruchter, A. S. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD21218 (United States); Jakobsson, P. [Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, IS-107 Reykjavk (Iceland); Bersier, D., E-mail: a.j.levan@warwick.ac.uk [Astrophysics Research Institute, Liverpool John Moores University, Egerton Wharf, Birkenhead CH41 1LD (United Kingdom); and others

    2014-01-20

    We present comprehensive multiwavelength observations of three gamma-ray bursts (GRBs) with durations of several thousand seconds. We demonstrate that these events are extragalactic transients; in particular, we resolve the long-standing conundrum of the distance of GRB 101225A (the 'Christmas-day burst'), finding it to have a redshift z = 0.847 and showing that two apparently similar events (GRB 111209A and GRB 121027A) lie at z = 0.677 and z = 1.773, respectively. The systems show extremely unusual X-ray and optical light curves, very different from classical GRBs, with long-lasting, highly variable X-ray emission and optical light curves that exhibit little correlation with the behavior seen in the X-ray. Their host galaxies are faint, compact, and highly star-forming dwarf galaxies, typical of 'blue compact galaxies'. We propose that these bursts are the prototypes of a hitherto largely unrecognized population of ultra-long GRBs, which while observationally difficult to detect may be astrophysically relatively common. The long durations may naturally be explained by the engine-driven explosions of stars of much larger radii than normally considered for GRB progenitors, which are thought to have compact Wolf-Rayet progenitor stars. However, we cannot unambiguously identify supernova signatures within their light curves or spectra. We also consider the alternative possibility that they arise from the tidal disruption of stars by massive black holes and conclude that the associated timescales are only consistent with the disruption of compact stars (e.g., white dwarfs) by black holes of relatively low mass (<10{sup 5} M {sub ☉}).

  18. Blue-sheet instability of Schwarzschild wormholes

    International Nuclear Information System (INIS)

    The Schwarzschild wormhole geometry is found to be unstable against the gravitational effects of accumulated, blue-shifted matter and radiation, or ''blue sheets'', accreting along the past horizons. This is shown by constructing a simple model of a wormhole geometry featuring such blue sheets and manifesting their effects. In this model the blue sheets are treated as null delta-function surface layers, and we derive here general conditions for matching spacetime geometries across such null hypersurfaces of discontinuity. These junction conditions are then applied to the construction of the wormhole model. The wormhole evolution depicted in this model shows that the gravitational focussing produced by the blue-sheet mass-energy eventually encloses the blue sheets and past horizons within future horizons, leaving a black-hole geometry. These effects limit emission processes from the region of a wormhole's past singularity into the external universe, and severely restrict the possible role of wormholes in cosmological contexts. (author)

  19. Geothermal Technologies Program Blue Ribbon Panel Recommendations

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2011-06-17

    The Geothermal Technologies Program assembled a geothermal Blue Ribbon Panel on March 22-23, 2011 in Albuquerque, New Mexico for a guided discussion on the future of geothermal energy in the United States and the role of the DOE Program. The Geothermal Blue Ribbon Panel Report captures the discussions and recommendations of the experts. An addendum is available here: http://www.eere.energy.gov/geothermal/pdfs/gtp_blue_ribbon_panel_report_addendum10-2011.pdf

  20. African Music: Source of the Blues

    OpenAIRE

    Bayer, Konrad Sidney

    2010-01-01

    [Abstract] African music is the primary source for the blues. Scholars have supplied ample evidence to support this assertion. However, the African retentions still present in the blues are not immediately apparent. African music and the blues share many similarities, including the predominance of rhythm, the uses of music as social commentary and critique, types of instruments, and musical structure. Slaves brought their culture with them to the New World when they were forcibly taken from t...

  1. Variable blue straggler stars in NGC 5466

    International Nuclear Information System (INIS)

    Nine variable blue stragglers have been found in the globular cluster NGC 5466. The six dwarf Cepheids in this cluster coexist in the instability strip with other nonvariable stars. The three eclipsing binaries are among the hottest of the blue stragglers. The hypothesis is discussed that all blue stragglers in this cluster have undergone mass transfer in close binaries. Under this hypothesis, rotation and spin-down play important roles in controlling the evolution of blue stragglers in old clusters and in affecting some of their observational properties. 14 refs

  2. Biomechanics of Thoracolumbar Burst and Chance-Type Fractures during Fall from Height

    Science.gov (United States)

    Ivancic, Paul C.

    2014-01-01

    Study Design In vitro biomechanical study. Objective To investigate the biomechanics of thoracolumbar burst and Chance-type fractures during fall from height. Methods Our model consisted of a three-vertebra human thoracolumbar specimen (n = 4) stabilized with muscle force replication and mounted within an impact dummy. Each specimen was subjected to a single fall from an average height of 2.1 m with average velocity at impact of 6.4 m/s. Biomechanical responses were determined using impact load data combined with high-speed movie analyses. Injuries to the middle vertebra of each spinal segment were evaluated using imaging and dissection. Results Average peak compressive forces occurred within 10 milliseconds of impact and reached 40.3 kN at the ground, 7.1 kN at the lower vertebra, and 3.6 kN at the upper vertebra. Subsequently, average peak flexion (55.0 degrees) and tensile forces (0.7 kN upper vertebra, 0.3 kN lower vertebra) occurred between 43.0 and 60.0 milliseconds. The middle vertebra of all specimens sustained pedicle and endplate fractures with comminution, bursting, and reduced height of its vertebral body. Chance-type fractures were observed consisting of a horizontal split fracture through the laminae and pedicles extending anteriorly through the vertebral body. Conclusions We hypothesize that the compression fractures of the pedicles and vertebral body together with burst fracture occurred at the time of peak spinal compression, 10 milliseconds. Subsequently, the onset of Chance-type fracture occurred at 20 milliseconds through the already fractured and weakened pedicles and vertebral body due to flexion-distraction and a forward shifting spinal axis of rotation. PMID:25083357

  3. CRITICAL HYDROLOGIC CONDITIONS FOR OVERFLOW BURST OF MORAINE LAKE

    Institute of Scientific and Technical Information of China (English)

    JIANG Zhong-xin; CUI Peng; JIANG Liang-wei

    2004-01-01

    Floodwater and debris flow caused by glacial lake burst is an important land process and a serious mountain disaster in glacial area of Xizang (Tibet) Autonomous Region, and the overflow burst is mainly caused by glacial landslide falling into moraine lake. On the premise that moraine lake is full, instantaneous burst in part of the lake bank happens, as flow velocity at burst mouth caused by overflow head is higher than threshold flow velocity of glacial till. Under some supposes, d90 and d10 of the glacial till in the bank were used as the threshold sizes of coarse and fine grains respectively. Thus, the formula of calculating threshold flow velocity of uniform sand was simplified,and threshold flow velocity of glacial till was calculated with the formula. Then, with synthesis formula calculating flow velocity of instantaneous part burst, flow velocity at overflow burst mouth was calculated, and calculation formula of critical height (H0) of overflow head was derived. Overflow head was caused by volume and surge of glacial landslide falling into moraine lake, calculation formulas of ascendant height (H1) of lake water surface and surge height (H2) on burst mouth caused by glacial landslide falling into moraine lake were derived. To sum up, critical hydrologic conditions of moraine lake burst with overflow form are: the burst is inevitable as H1 >H0; the burst is possible as H1 <H0 and (H1+H2) >H0; the burst is impossible as (H1+H2) <H0. In the factors influencing the burst critical conditions, it is advantageous for the burst that scale of the lake is 105n2 range; terminal glacial till is more fine and is even more uniform; the width of overflow mouth is even smaller than the length of the bank; the landslide haslarge scale and steep slip surface; and glacial end is close to the lake. With burst of Guangxiecuo Lake in Midui Valley of the Polongzanghu River in Xizang as an example, the burst critical conditions were tested.

  4. The interplanetary gamma ray burst network

    Science.gov (United States)

    Cline, T.

    The Interplanetary Gamma-Ray Burst Network (IPN) is providing gamma-ray burst (GRB) alerts and localizations at the maximum rate anticipated before the launch of the Swift mission. The arc-minute source precision of the IPN is again permitting searches for GRB afterglows in the radio and optical regimes with delays of only hours up to 2 days. The successful addition of the Mars Odyssey mission has compensated for the loss of the asteroid mission NEAR, to reconstitute a fully long- baseline interplanetary network, with Ulysses at > 5 AU and Konus-Wind and HETE-2 near the Earth. In addition to making unassisted GRB localizations that enable a renewed supply of counterpart observations, the Mars/Ulysses/Wind IPN is confirming and reinforcing GRB source localizations with HETE-2. It has also confirmed and reinforced localizations with the BeppoSAX mission before the BeppoSAX termination in May and has detected and localized both SGRs and an unusual hard x-ray transient that is neither an SGR nor a GRB. This IPN is expected to operate until at least 2004.

  5. $\\gamma$-Ray Bursts the Four Crises

    CERN Document Server

    Tavani, M

    1998-01-01

    We discuss some open problems concerning the origin and the emission mechanism of gamma-ray bursts (GRBs) in light of recent developments. If GRBs originate at extragalactic distances, we are facing four crises: (1) an energy crisis, models have to account for more than 10^{53} ergs of energy emitted in the gamma-ray energy band; (2) a spectral crisis, emission models have to account for the surprising `smoothness' of GRB broad-band spectra, with no indication of the predicted spectral `distorsions' caused by inverse Compton scattering in large radiation energy density media, and no evidence for beaming; (3) an afterglow crisis, relativistic shock models have to explain the complexity of the afterglow behavior, the longevity of optical transients detectable up to six months after the burst, the erratic behavior of the radio emission, and the lack of evidence for substantial beaming as indicated by recent searches for GRB afterglows in the X-ray band; (4) a population crisis, from data clearly indicating that ...

  6. Gamma Ray Bursts Cook Book I: Formulation

    CERN Document Server

    Ziaeepour, Houri

    2008-01-01

    Since the suggestion of relativistic shocks as the origin of gamma-ray bursts (GRBs) in early 90's, the mathematical formulation of this process has stayed at phenomenological level. One of the reasons for the slow development of theoretical works in this domain has been the simple power-law behaviour of the afterglows hours or days after the prompt gamma-ray emission. Nowadays with the launch of the Swift satellite, gamma-ray bursts can be observed in multi-wavelength from a few tens of seconds after trigger onward. These observations have leaded to the discovery of features unexplainable by the simple formulation of the shocks and emission processes used up to now. But "devil is in details" and some of these features may be explained with a more detailed formulation of phenomena and without adhoc addition of new processes. Such a formulation is the goal of this work. We present a consistent formulation of the collision between two spherical relativistic shells. The model can be applied to both internal and ...

  7. Gamma Ray Bursts Cook Book II: Simulation

    CERN Document Server

    Ziaeepour, Houri

    2008-01-01

    In Paper I we presented a detailed formulation of the relativistic shocks and synchrotron emission in the context of Gamma-Ray Burst (GRB) physics. To see how well this model reproduces the observed characteristics of the GRBs and their afterglows, here we present the results of some simulations based on this model. They are meant to reproduce the prompt and afterglow emission in some intervals of time during a burst. We show that this goal is achieved for both short and long GRBs and their afterglows, at least for part of the parameter space. Moreover, these results are the evidence of the physical relevance of the two phenomenological models we have suggested in Paper I for the evolution of the "active region", the synchrotron emitting region in a shock. The dynamical active region model seems to reproduce the observed characteristics of prompt emissions better than the quasi-steady model which is more suitable for afterglows. Therefore these simulations confirm the arguments presented in Paper I about the ...

  8. Distribution of Gamma-Ray Bursts

    Science.gov (United States)

    Diaz Rodriguez, Mariangelly; Smith, M.; Tešic, G.

    2014-01-01

    Gamma-Ray Bursts (GRBs) are known to be bright, irregular flashes of gamma rays that typically last just a few seconds, believed to be caused by stellar collapse or the merger of a pair of compact objects. Through previous work, it has been found that GRBs are distributed roughly uniformly over the entire sky, rather than being confined to the relatively narrow band of the Milky Way. Using the Python programming language, we generated a model of GRBs over cosmological distances, based on current empirical GRB distributions. The grbsim python module uses the acceptance-rejection Monte Carlo method to simulate the luminosity and redshift of a large population of GRBs, including cosmological effects such as dark energy and dark matter terms that modify the large-scale structure of space-time. The results of running grbsim are demonstrated to match the distribution of GRBs observed by the Burst Alert Telescope on NASA’s Swift satellite. The grbsim module will subsequently be used to simulate gamma ray and neutrino events for the Astrophysical Multimessenger Observatory Network.

  9. $\\gamma$-Ray Bursts and Related Phenomena

    CERN Document Server

    Piran, T

    1999-01-01

    Gamma-ray bursts (GRBs) have puzzled astronomers since their accidental discovery in the sixties. The BATSE detector on the COMPTON-GRO satellite has been detecting one burst per day for the last six years. Its findings have revolutionized our ideas about the nature of these objects. They have shown that GRBs are at cosmological distances. This idea was accepted with difficulties at first. However, the recent discovery of an x-ray afterglow by the Italian/Dutch satellite BeppoSAX led to a detection of high red-shift absorption lines in the optical afterglow of GRB970508 and to a confirmation of its cosmological origin. The simplest and practically inevitable interpretation of these observations is that GRBs result from the conversion of the kinetic energy of ultra-relativistic particles flux to radiation in an optically thin region. The "inner engine" that accelerates the particles or generates the Poynting flux is hidden from direct observations. Recent studies suggest the ``internal-external'' model: intern...

  10. Photospheric Emission in Gamma-Ray Bursts

    CERN Document Server

    Pe'er, Asaf

    2016-01-01

    A major breakthrough in our understanding of gamma-ray bursts (GRB) prompt emission physics occurred in the last few years, with the realization that a thermal component accompanies the over-all non-thermal prompt spectra. This thermal part is important by itself, as it provides direct probe of the physics in the innermost outflow regions. It further has an indirect importance, as a source of seed photons for inverse-Compton scattering, thereby it contributes to the non-thermal part as well. In this short review, we highlight some key recent developments. Observationally, although so far it was clearly identified only in a minority of bursts, there are indirect evidence that thermal component exists in a very large fraction of GRBs, possibly close to 100%. Theoretically, the existence of thermal component have a large number of implications as a probe of underlying GRB physics. Some surprising implications include its use as a probe of the jet dynamics, geometry and magnetization.

  11. Fast Radio Bursts from Axion Stars

    CERN Document Server

    Iwazaki, Aiichi

    2014-01-01

    Axions are one of the most promising candidates of dark matter. The axions have been shown to form miniclusters with masses $\\sim 10^{-12}M_{\\odot}$ and to become dominant component of dark matter. These axion miniclusters condense to form axion stars. We show a possible origin of fast radio bursts ( FRBs ) by assuming the axion stars being dark matter: FRBs arise from the collisions between the axion stars and neutron stars. The FRBs are caused by the rapid conversion of the axions into electromagnetic fields under strong magnetic fields. Electric fields are induced on the axion stars under strong magnetic fields of neutron stars. The electric fields parallel to the magnetic fields oscillate with a frequency and make electrons in atmospheres of neutron stars coherently oscillate. Thus, the coherent radiations are emitted. The observed frequencies ( $\\sim 1.4$GHz ) of the bursts are given by the axion mass $m_a$ such as $m_a/2\\pi\\simeq 2.3\\,\\mbox{GHz}\\,\\big(m_a/10^{-5}\\mbox{eV}\\big)$. The frequency is affecte...

  12. Articulating Support for Horizontal Resistive Exercise

    Science.gov (United States)

    Gundo, Daniel; Schaffner, Grant; Bentley, Jason; Loehr, James A.

    2005-01-01

    A versatile mechanical device provides support for a user engaged in any of a variety of resistive exercises in a substantially horizontal orientation. The unique features and versatility of the device promise to be useful in bedrest studies, rehabilitation, and specialized strength training. The device affords a capability for selectively loading and unloading of portions of the user s body through its support mechanisms, so that specific parts of the body can be trained with little or no effect on other parts that may be disabled or in the process of recovery from injury. Thus, the device is ideal for rehabilitation exercise programs prescribed by physicians and physical therapists. The capability for selective loading and support also offers potential benefits to strength and conditioning trainers and athletes who wish to selectively strengthen selected parts. The principal innovative aspect of the device is that it supports the subject s weight while enabling the subject, lying substantially horizontally, to perform an exercise that closely approximates a full standing squat. The device includes mechanisms that support the subject in such a way that the hips are free to translate both horizontally and vertically and are free to rotate about the line connecting the hips. At the same time, the shoulders are free to translate horizontally while the upper back is free to rotate about the line connecting the shoulders. Among the mechanisms for hip motion and support is a counterbalance that offsets the weight of the subject as the subject s pelvis translates horizontally and vertically and rotates the pelvis about the line connecting the hips. The counterbalance is connected to a pelvic support system that allows these pelvic movements. The subject is also supported at the shoulder by a mechanism that can tilt to provide continuous support of the upper back while allowing the rotation required for arching the back as the pelvis is displaced. The shoulder support

  13. Helium enhanced stars and multiple populations along the horizontal branch of NGC2808: direct spectroscopic measurements

    CERN Document Server

    Marino, A F; Przybilla, N; Bergemann, M; Lind, K; Asplund, M; Cassisi, S; Catelan, M; Casagrande, L; Valcarce, A A R; Bedin, L R; Cortes, C; D'Antona, F; Jerjen, H; Piotto, G; Schlesinger, K; Zoccali, M; Angeloni, R

    2013-01-01

    We present an abundance analysis of 96 horizontal branch (HB) stars in NGC2808, a globular cluster exhibiting a complex multiple stellar population pattern. These stars are distributed in different portions of the HB and cover a wide range of temperature. By studying the chemical abundances of this sample, we explore the connection between HB morphology and the chemical enrichment history of multiple stellar populations. For stars lying on the red HB, we use GIRAFFE and UVES spectra to determine Na, Mg, Si, Ca, Sc, Ti, Cr, Mn, Fe, Ni, Zn, Y, Ba, and Nd abundances. For colder, blue HB stars, we derive abundances for Na, primarily from GIRAFFE spectra. We were also able to measure direct NLTE He abundances for a subset of these blue HB stars with temperature higher than ~9000 K. Our results show that: (i) HB stars in NGC2808 show different content in Na depending on their position in the color-magnitude diagram, with blue HB stars having higher Na than red HB stars; (ii) the red HB is not consistent with an uni...

  14. Review of GRANAT observations of gamma-ray bursts

    DEFF Research Database (Denmark)

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

    1995-01-01

    The GRANAT observatory was launched into a high apogee orbit on 1 December, 1989. Three instruments onboard GRANAT - PHEBUS, WATCH and SIGMA are able to detect gamma-ray bursts in a very broad energy range from 6 keV up to 100 MeV. Over 250 gamma-ray bursts were detected. We discuss the results o...

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

    NARCIS (Netherlands)

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

    1995-01-01

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

  16. The mesoscopic modelling of burst suppression during anaesthesia

    Directory of Open Access Journals (Sweden)

    David eLiley

    2013-04-01

    Full Text Available The burst suppression pattern is well recognised as a distinct featureof the mammalian electroencephalogram (EEG waveform. Consisting ofalternating periods of high amplitude oscillatory and isoelectricactivity It can be induced in health by deep anaesthesia as well asbeing evoked by a range of pathophysiological processes that includecoma and anoxia. While the electroencephalographic phenomenon andclinical implications of burst suppression have been studiedextensively, the physiological mechanisms underlying its emergenceremain unresolved and obscure.Because electroencephalographic bursting phenomenologically resemblesthe bursting observed in single neurons, it would be reasonable toassume that the theoretical insights developed to understand burstingat the cellular (``microscopic'' level would enable insights into thedynamical genesis of bursting at the level of the whole brain(``macroscopic''. In general action potential bursting is the resultof the interplay of two time scales: a fast time scale responsible forspiking, and a slow time scale that modulates such activity. Wetherefore hypothesise that such fast-slow systems dynamically underpinelectroencephalographic bursting. Here we show that a well known mean field dynamical model of theelectroencephalogram, the Liley model, while unable to produce burstsuppression unmodified, is able to give rise to a wide variety ofburst-like activity by the addition of one or more slow systemsmodulating model parameters speculated to be major ``targets'' foranaesthetic action. The development of a physiologically plausibletheoretical framework to account for burst suppression will lead to amore complete physiological understanding of the EEG and themechanisms that serve to modify ongoing brain activity necessary forpurposeful behaviour and consciousness.

  17. Nanoemulsions obtained via bubble bursting at a compound interface

    NARCIS (Netherlands)

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

    2014-01-01

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

  18. Statistical properties of SGR 1806-20 bursts

    NARCIS (Netherlands)

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

    2000-01-01

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

  19. Periodic bursts of Jovian non-Io decametric radio emission.

    Science.gov (United States)

    Panchenko, M; Rucker, H O; Farrell, W M

    2013-03-01

    During the years 2000-2011 the radio instruments onboard Cassini, Wind and STEREO spacecraft have recorded a large amount of the Jovian decametric radio emission (DAM). In this paper we report on the analysis of the new type of Jovian periodic radio bursts recently revealed in the decametric frequency range. These bursts, which are non-Io component of DAM, are characterized by a strong periodic reoccurrence over several Jovian days with a period [Formula: see text] longer than the rotation rate of the planet's magnetosphere (System III). The bursts are typically observed between 4 and 12 MHz and their occurrence probability has been found to be significantly higher in the sector of Jovian Central Meridian Longitude between 300° and 60° (via 360°). The stereoscopic multispacecraft observations have shown that the radio sources of the periodic bursts radiate in a non-axisymmetric hollow cone-like pattern and sub-corotate with Jupiter remaining active during several planet's rotations. The occurrence of the periodic non-Io DAM bursts is strongly correlated with pulses of the solar wind ram pressure at Jupiter. Moreover the periodic bursts exhibit a tendency to occur in groups every [Formula: see text] days. The polarization measurements have shown that the periodic bursts are right hand polarized radio emission associated with the Northern magnetic hemisphere of Jupiter. We suggest that periodic non-Io DAM bursts may be connected with the interchange instability in Io plasma torus triggered by the solar wind. PMID:23585696

  20. Gamma Ray Burst Follow-Ups with Bootes-4

    Science.gov (United States)

    Guziy, Sergey; Castro-Tirado, Guziy, Alberto J.; Jelinek, Martin; Gorosabel, Javier; Kubanek, Petr; Cunniffe, Ronan; Lara-Gil, Oscar; Tello, Juan C.; Jeong, Soomin; Oates, Samantha R.; Xu, Youdong; Perez-Ramirez, Dolores; Cui, Chenzou; Fan, Yufeng; Wan, Chuanjun; Bai, Jinming; Kheyfets, I.

    The Burst Observer and Optical Transient Exploring System (BOOTES), is a global robotic observatory network, which started in 1998 with Spanish leadership devoted to study optical emissions from gamma ray bursts (GRBs) that occur in the Universe. We present shot history and current status of BOOTES-4 telescope. Some details of 38 GRBs followed-up with BOOTES-4 are discussed.

  1. Solar U- and J- radio bursts at the decameter waves

    Science.gov (United States)

    Dorovskyy, V. V.; Melnik, V. N.; Konovalenko, A. A.; Rucker, H. O.; Abranin, E. P.; Lecacheux, A.

    2010-01-01

    The results of the first observations of solar U- and J- bursts with the radiotelescope UTR-2 at the decameter wavelengths are reported. During 2003-2004 more than 50 J- bursts and only 7 U- bursts were registered. It is the first case of ground based observations of J- and U- bursts with turning frequencies below 25 MHz. For the first time the harmonic structure of J- bursts in the form of Jb-J pairs was found. The mean harmonic ratio appeared to be 1.8. Also a group of J-bursts with unusual Turning Frequency Drift (TFD) of -2 kHz/s was detected. Such TFD corresponds to the velocity of coronal loop elevation of about 60 km/s. Coronal loops with similar elevation velocities were also detected by SOHO-LASCO coronagraph in white light. The dynamic spectra of unusual U- and J- bursts are shown. Simplified model of the coronal loop in the form of semicircle was created on the base of the U- burst dynamic spectrum and the Newkirk coronal density model. With this loop model the linear velocity of the source along the loop, the height of the Turning Frequency point and the geometrical size of the loop were calculated.

  2. 34 First Callisto solar burst spectrometer station in Greenland

    Science.gov (United States)

    Monstein, Christian

    2016-04-01

    In mid of March 2016 a new long wavelength station in Greenland was set into operation. It is a dual circular polarization, frequency agile solar radio burst spectrometer based on two Callisto spectrometers and the Long Wavelength Array antenna. During the commissioning phase several nice radio burst observations proved that the system works as expected.

  3. Supernova sheds light on gamma-ray bursts

    CERN Multimedia

    2003-01-01

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

  4. Ionospheric response to gamma ray bursts of cosmic origin

    International Nuclear Information System (INIS)

    The paper examines the limiting conditions under which is detectable, through the VLF phase-meter, a gamma-ray burst of cosmic origin like those recently observed by Vela spacecrafts. The discussion focuses on the flux density and burst duration and leads to a definition of the threshold needed for a measurable effect

  5. Dependence of X-ray Burst Models on Nuclear Masses

    CERN Document Server

    Schatz, H

    2016-01-01

    X-ray burst model predictions of light curves and final composition of the nuclear ashes are affected by uncertain nuclear physics. Nuclear masses play an important role. Significant progress has been made in measuring the masses of very neutron deficient rare isotopes along the path of the rapid proton capture process (rp-process) in X-ray bursts. This paper identifies the remaining nuclear mass uncertainties in X-ray burst models using a one zone model that takes into account the changes in temperature and density evolution caused by changes in the nuclear physics. Two types of bursts are investigated - a typical mixed H/He burst with a limited rp-process and an extreme mixed H/He burst with an extended rp-process. Only three remaining nuclear mass uncertainties affect the light curve predictions of a typical H/He burst, and only three additional masses affect the composition strongly. A larger number of mass uncertainties remains to be addressed for the extreme H/He burst. Mass uncertainties of better than...

  6. Long-persistence blue phosphors

    Science.gov (United States)

    Yen, William M. (Inventor); Jia, Weiyi (Inventor); Lu, Lizhu (Inventor); Yuan, Huabiao (Inventor)

    2000-01-01

    This invention relates to phosphors including long-persistence blue phosphors. Phosphors of the invention are represented by the general formula: MO . mAl.sub.2 O.sub.3 :Eu.sup.2+,R.sup.3+ wherein m is a number ranging from about 1.6 to about 2.2, M is Sr or a combination of Sr with Ca and Ba or both, R.sup.3+ is a trivalent metal ion or trivalent Bi or a mixture of these trivalent ions, Eu.sup.2+ is present at a level up to about 5 mol % of M, and R.sup.3+ is present at a level up to about 5 mol % of M. Phosphors of this invention include powders, ceramics, single crystals and single crystal fibers. A method of manufacturing improved phosphors and a method of manufacturing single crystal phosphors are also provided.

  7. Horizontal Bilayer for Electrical and Optical Recordings

    Directory of Open Access Journals (Sweden)

    Alf Honigmann

    2012-12-01

    Full Text Available Artificial bilayer containing reconstituted ion channels, transporters and pumps serve as a well-defined model system for electrophysiological investigations of membrane protein structure–function relationship. Appropriately constructed microchips containing horizontally oriented bilayers with easy solution access to both sides provide, in addition, the possibility to investigate these model bilayer membranes and the membrane proteins therein with high resolution fluorescence techniques up to the single-molecule level. Here, we describe a bilayer microchip system in which long-term stable horizontal free-standing and hydrogel-supported bilayers can be formed and demonstrate its prospects particularly for single-molecule fluorescence spectroscopy and high resolution fluorescence microscopy in probing the physicochemical properties like phase behavior of the bilayer-forming lipids, as well as in functional studies of membrane proteins.

  8. Buoyancy Driven Natural Ventilation through Horizontal Openings

    DEFF Research Database (Denmark)

    Heiselberg, Per; Li, Zhigang

    2009-01-01

    An experimental study of the phenomenon of buoyancy driven natural ventilation through single-sided horizontal openings was performed in a full-scale laboratory test rig. The measurements were made for opening ratios L/D ranging from 0.027 to 4.455, where L and D are the length of the opening...... and the diameter of the opening, respectively. The basic nature of airflow through single-sided openings, including airflow rate, air velocity, temperature difference between the rooms and the dimensions of the horizontal openings, were measured. A bi-directional airflow rate was measured using the constant...... injection tracer gas technique. Smoke visualizations showed that the airflow patterns are highly transient and unstable, and that the airflow rate oscillates with time. Correlations between the Froude (Archimedes) number Fr (Ar) and the L/D ratio are presented. In some cases the measured airflow rates fit...

  9. Buoyancy Driven Natural Ventilation through Horizontal Openings

    DEFF Research Database (Denmark)

    Heiselberg, Per

    2009-01-01

    An experimental study of the phenomenon of buoyancy driven natural ventilation through single-sided horizontal openings was performed in a full-scale laboratory test rig. The measurements were made for opening ratios L/D ranging from 0.027 to 4.455, where L and D are the length of the opening...... and the diameter of the opening, respectively. The basic nature of airflow through single-sided openings, including airflow rate, air velocity, temperature difference between the rooms and the dimensions of the horizontal openings, were measured. A bi-directional airflow rate was measured using the constant...... quite well with the Epstein's formula ratio are presented. In some cases the measured airflow rates fit quite well with the Epstein's formula but in other cases the measured data show clear deviations from the Epstein's formula. Thus, revised formulas for natural ventilation are proposed....

  10. Detecting series periodicity with horizontal visibility graphs

    CERN Document Server

    Núñez, Angel M; Valero, Eusebio; Gómez, Jose Patricio; Luque, Bartolo

    2011-01-01

    The horizontal visibility algorithm has been recently introduced as a mapping between time series and networks. The challenge lies in characterizing the structure of time series (and the processes that generated those series) using the powerful tools of graph theory. Recent works have shown that the visibility graphs inherit several degrees of correlations from their associated series, and therefore such graph theoretical characterization is in principle possible. However, both the mathematical grounding of this promising theory and its applications are on its infancy. Following this line, here we address the question of detecting hidden periodicity in series polluted with a certain amount of noise. We first put forward some generic properties of horizontal visibility graphs which allow us to define a (graph theoretical) noise reduction filter. Accordingly, we evaluate its performance for the task of calculating the period of noisy periodic signals, and compare our results with standard time domain (autocorre...

  11. Cosmic Gamma-Ray Bursts The Remaining Mysteries

    CERN Document Server

    Hurley, K

    1998-01-01

    To anyone who has read a scientific journal or even a newspaper in the last six months, it might appear that cosmic gamma-ray bursts hold no more mysteries: they are cosmological, and possibly the most powerful explosions in the Universe. In fact, however, bursts remain mysterious in many ways. There is no general agreement upon the nature of the event which releases the initial energy. One burst at least appears to strain the energy budget of the merging neutron star model. There is evidence that another recent event may have come from a nearby supernova. Finally, while the number count statistics clearly show a strong deviation from the -3/2 power law expected for a Euclidean, homogeneous distribution, the distributions of some classes of bursts appear to follow a -3/2 power law rather closely. The recent data on bursts is reviewed, some of the mysteries discussed, and future experiments are outlined.

  12. Cosmology and the Subgroups of Gamma-ray Bursts

    Directory of Open Access Journals (Sweden)

    A. Mészáros

    2011-01-01

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

  13. Do Gamma-Ray Bursts Come from the Oort Cloud?

    CERN Document Server

    Clarke, T E; Tremaine, S; Tremaine, adn S.

    1993-01-01

    We examine the possibility that gamma-ray bursts arise from sources in the Oort comet cloud, basing most of our arguments on accepted models for the formation and spatial distribution of the cloud. We identify three severe problems with such models: (1) There is no known mechanism for producing bursts that can explain the observed burst rate and energetics without violating other observational constraints. (2) The bright source counts cannot be reconciled with standard models for the phase-space distribution of objects in the Oort cloud. (3) The observed isotropy of the available burst data is inconsistent with the expected angular distribution of sources in the Oort cloud. We therefore assert that Oort cloud models of gamma-ray bursts are extremely implausible.

  14. Evaluating the risk of coal bursts in underground coal mines

    Institute of Scientific and Technical Information of China (English)

    Mark Christopher⇑; Gauna Michael

    2016-01-01

    Coal bursts involve the sudden, violent ejection of coal or rock into the mine workings. They are almost always accompanied by a loud noise, like an explosion, and ground vibration. Bursts are a particular haz-ard for miners because they typically occur without warning. Despite decades of research, the sources and mechanics of these events are not well understood, and therefore they are difficult to predict and control. Experience has shown, however, that certain geologic and mining factors are associated with an increased likelihood of a coal burst. A coal burst risk assessment consists of evaluating the degree to which these risk factors are present, and then identifying appropriate control measures to mitigate the hazard. This paper summarizes the U.S. and international experience with coal bursts, and describes the known risk factors in detail. It includes a framework that can be used to guide the risk assessment process.

  15. The supernova-gamma-ray burst-jet connection.

    Science.gov (United States)

    Hjorth, Jens

    2013-06-13

    The observed association between supernovae and gamma-ray bursts represents a cornerstone in our understanding of the nature of gamma-ray bursts. The collapsar model provides a theoretical framework for this connection. A key element is the launch of a bipolar jet (seen as a gamma-ray burst). The resulting hot cocoon disrupts the star, whereas the (56)Ni produced gives rise to radioactive heating of the ejecta, seen as a supernova. In this discussion paper, I summarize the observational status of the supernova-gamma-ray burst connection in the context of the 'engine' picture of jet-driven supernovae and highlight SN 2012bz/GRB 120422A--with its luminous supernova but intermediate high-energy luminosity--as a possible transition object between low-luminosity and jet gamma-ray bursts. The jet channel for supernova explosions may provide new insights into supernova explosions in general. PMID:23630379

  16. Ablation of silicon with bursts of femtosecond laser pulses

    Science.gov (United States)

    Gaudiuso, Caterina; Kämmer, Helena; Dreisow, Felix; Ancona, Antonio; Tünnermann, Andreas; Nolte, Stefan

    2016-03-01

    We report on an experimental investigation of ultrafast laser ablation of silicon with bursts of pulses. The pristine 1030nm-wavelength 200-fs pulses were split into bursts of up to 16 sub-pulses with time separation ranging from 0.5ps to 4080ps. The total ablation threshold fluence was measured depending on the burst features, finding that it strongly increases with the number of sub-pulses for longer sub-pulse delays, while a slowly increasing trend is observed for shorter separation time. The ablation depth per burst follows two different trends according to the time separation between the sub-pulses, as well as the total threshold fluence. For delays shorter than 4ps it decreases with the number of pulses, while for time separations longer than 510ps, deeper craters were achieved by increasing the number of subpulses in the burst, probably due to a change of the effective penetration depth.

  17. X-ray bursts and superbursts - recent developments

    CERN Document Server

    Zand, Jean in 't

    2011-01-01

    The past decade and a half has seen many interesting new developments in X-ray burst research, both observationally and theoretically. New phenomena were discovered, such as burst oscillations and superbursts, and new regimes of thermonuclear burning identified. An important driver of the research with present and future instrumentation in the coming years is the pursuit of fundamental neutron star parameters. However, several other more direct questions are also in dire need of an answer. For instance, how are superbursts ignited and why do burst oscillations exist in burst tails? We briefly review recent developments and discuss the role that MAXI can play. Thanks to MAXI's large visibility window and large duty cycle, it is particularly well suited to investigate the recurrence of rare long duration bursts such as superbursts. An exploratory study of MAXI data is briefly presented.

  18. Taming desynchronized bursting with delays in the Macaque cortical network

    Institute of Scientific and Technical Information of China (English)

    Wang Qing-Yun; Murks Aleksandra; Perc Matja(z); Lu Qi-Shao

    2011-01-01

    Inhibitory coupled bursting Hindmarsh-Rose neurons are considered as constitutive units of the Macaque cortical network. In the absence of information transmission delay the bursting activity is desynchronized, giving rise to spatiotemporally disordered dynamics. This paper shows that the introduction of finite delays can lead to the synchroization of bursting and thus to the emergence of coherent propagating fronts of excitation in the space-time domain.Moreover, it shows that the type of synchronous bursting is uniquely determined by the delay length, with the transitions from one type to the other occurring in a step-like manner depending on the delay. Interestingly, as the delay is tuned close to the transition points, the synchronization deteriorates, which implies the coexistence of different bursting attractors. These phenomena can be observed be different but fixed coupling strengths, thus indicating a new role for information transmission delays in realistic neuronal networks.

  19. The Na-O anticorrelation in horizontal branch stars. V. NGC 6723

    CERN Document Server

    Gratton, R G; Sollima, A; Carretta, E; Bragaglia, A; Momany, Y; D'Orazi, V; Salaris, M; Cassisi, S; Stetson, P B

    2014-01-01

    We used FLAMES+GIRAFFE (Medusa mode) at the VLT to obtain moderately high resolution spectra for 30 red horizontal branch (RHB) stars, 4 RR Lyrae variables, and 17 blue horizontal branch (BHB) stars in the low-concentration, moderately metal-rich globular cluster NGC6723 ([Fe/H]=-1.22+/-0.08 from our present sample). The spectra were optimized to derive O and Na abundances. In addition, we obtained abundances for other elements, including N, Fe, Mg, Ca, Ni, and Ba. We used these data to discuss the evidence of a connection between the distribution of stars along the horizontal branch (HB) and the multiple populations that are typically present in globular clusters. We found that all RHB and most (13 out of 17) BHB stars are O-rich, Na-poor, and N-poor; these stars probably belong to the first stellar generation in this cluster. Only the four warmest observed stars are (moderately) O-poor, Na-rich, and N-rich, and they probably belong to the second generation. While our sample is not fully representative of th...

  20. Horizontal mergers, entry, and efficiency defences

    OpenAIRE

    Spector, David

    2002-01-01

    This paper addresses the effect of horizontal mergers on prices. It is shown that if firms compete in quantities and marginal costs are nondecreasing, any profitable merger failing to generate technological synergies must harm consumers through higher prices, irrespective of entry conditions in the industry. However this result does not hold if products are differentiated and firms compete in prices. The implications for merger policy are discussed.

  1. Gas reservoir evaluation for underbalanced horizontal drilling

    Directory of Open Access Journals (Sweden)

    Li Gao

    2014-01-01

    Full Text Available A set of surface equipment for monitoring the parameters of fluid and pressure while drilling was developed, and mathematical models for gas reservoir seepage and wellbore two-phase flow were established. Based on drilling operation parameters, well structure and monitored parameters, the wellbore pressure and the gas reservoir permeability could be predicted theoretically for underbalanced horizontal drilling. Based on the monitored gas production along the well depth, the gas reservoir type could be identified.

  2. Cues for localization in the horizontal plane

    DEFF Research Database (Denmark)

    Jeppesen, Jakob; Møller, Henrik

    2005-01-01

    Spatial localization of sound is often described as unconscious evaluation of cues given by the interaural time difference (ITD) and the spectral information of the sound that reaches the two ears. Our present knowledge suggests the hypothesis that the ITD roughly determines the cone of the perce...... independently in HRTFs used for binaural synthesis. The ITD seems to be dominant for localization in the horizontal plane even when the spectral information is severely degraded....

  3. Examining Horizontal Fiscal Equalisation in Australia

    OpenAIRE

    Jonathan Pincus

    2011-01-01

    In 2010-11 over $45 billion GST monies, and about $24b of other grants, will be distributed between the States and Territories on the recommendation of the Commonwealth Grants Commission. The Commission is instructed to implement Horizontal Fiscal Equalisation (HFE); and not to be concerned with efficiency. The paper examines how the CGC pursues fiscal equality, and finds some systematic flaws. The adjustments made by the CGC for demography and mining, but not for wages, undoubtedly reduce in...

  4. Maximal liquid bridges between horizontal cylinders

    OpenAIRE

    Cooray, Himantha; Huppert, Herbert E.; Neufeld, Jerome A

    2016-01-01

    We investigate two-dimensional liquid bridges trapped between pairs of identical horizontal cylinders. The cylinders support forces due to surface tension and hydrostatic pressure which balance the weight of the liquid. The shape of the liquid bridge is determined by analytically solving the nonlinear Laplace-Young equation. Parameters that maximize the trapping capacity (defined as the cross-sectional area of the liquid bridge) are then determined. The results show that these parameters can ...

  5. Neutrino masses, magnetic moments, and horizontal symmetries

    International Nuclear Information System (INIS)

    We investigate the general structure of the neutrino mass and magnetic matrices in the presence of an unbroken horizontal symmetry. In particular, we study the compatibility of masslessness induced by such a symmetry and a non-zero magnetic moment. We show that in this case at least two of the charged leptons must have equal masses. Furthermore, we give a general definition of Dirac neutrinos and demonstrate that they are not necessarily associated with a lepton number. (Author) 15 refs

  6. Blue Skies, Coffee Creamer, and Rayleigh Scattering

    Science.gov (United States)

    Liebl, Michael

    2010-01-01

    The first physical explanation of Earths blue sky was fashioned in 1871 by Lord Rayleigh. Many discussions of Rayleigh scattering and approaches to studying it both in and out of the classroom are available. Rayleigh scattering accounts for the blue color of the sky and the orange/red color of the Sun near sunset and sunrise, and a number of…

  7. Short Gamma-Ray Bursts with Extended Emission

    Science.gov (United States)

    Norris, J. P.; Bonnell, J. T.

    2005-01-01

    The recent association of several short gamma-ray bursts (GRBs) with early type galaxies with low star formation rate demonstrates that short bursts arise from a different progenitor mechanism than long bursts. However, since the duration distributions of the two classes overlap, membership is not always easily established. The picture is complicated by the occasional presence of softer, extended emission lasting tens of seconds after the initial spike- like emission comprising an otherwise short burst. Using the large BATSE sample with time-tagged event (TTE) data, we show that the fundamental defining characteristic of the short burst class is that the initial spike exhibits negligible spectral evolution at energies above approx. 25 keV. This is behavior is nearly ubiquitous for the 260 bursts with T(sub 90) less than 2s where the BATSE TTE data type completely included the initial spike: Their spectral lags measured between the 25-50 keV and 100-300 energy ranges are consistent with zero in 90-95% of the cases, with most outliers probably representing the tail of the long burst class. We also analyze a small sample of "short" BATSE bursts - those with the most fluent, intense extended emission. The same lack of evolution on the pulse timescale obtains for the extended emission in the brighter bursts where significant measurements can be made. One possible inference is that both emission components may arise in the same region. We also show that the dynamic range in the ratio of peak intensities, spike : extended, is at least approx. l0(exp 3), and that for some bursts, the extended emission is only a factor of 2-5 lower. However, for our whole sample the total counts fluence of the extended component equals or exceeds that in the spike by a factor of several.

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

    KAUST Repository

    Ali, Mohammed L.

    2011-10-10

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

  9. Spectroscopic analyses of the blue hook stars in NGC 2808:A more stringent test of the late hot flasher scenario

    OpenAIRE

    Moehler, S.; Sweigart, A. V.; Landsman, W. B.; Hammer, N. J.; Dreizler, S.

    2004-01-01

    Recent UV observations of the globular cluster NGC 2808 (Brown et al. 2001) show a significant population of hot stars fainter than the zero-age horizontal branch ("blue hook" stars), which cannot be explained by canonical stellar evolution. Their results suggest that stars which experience unusually large mass loss on the red giant branch and which subsequently undergo the helium core flash while descending the white dwarf cooling curve could populate this region. Theory predicts that these ...

  10. Triboelectric Nanogenerators for Blue Energy Harvesting.

    Science.gov (United States)

    Khan, Usman; Kim, Sang-Woo

    2016-07-26

    Blue energy in the form of ocean waves offers an enormous energy resource. However, it has yet to be fully exploited in order to make it available for the use of mankind. Blue energy harvesting is a challenging task as the kinetic energy from ocean waves is irregular in amplitude and is at low frequencies. Though electromagnetic generators (EMGs) are well-known for harvesting mechanical kinetic energies, they have a crucial limitation for blue energy conversion. Indeed, the output voltage of EMGs can be impractically low at the low frequencies of ocean waves. In contrast, triboelectric nanogenerators (TENGs) are highly suitable for blue energy harvesting as they can effectively harvest mechanical energies from low frequencies (blue energy harvesting. In this Perspective, we describe some of the recent progress and also address concerns related to durable packaging of TENGs in consideration of harsh marine environments and power management for an efficient power transfer and distribution for commercial applications.

  11. Synchrotron masers and fast radio bursts

    CERN Document Server

    Ghisellini, Gabriele

    2016-01-01

    Fast Radio Bursts (FRBs), with a typical duration of 1 ms and 1 Jy flux density at GHz frequencies, have brightness temperatures exceeding 1e33 K, requiring a coherent emission process. This can be achieved by bunching particles in volumes smaller than the typical wavelength, but this may be challenging. Alternatively, we can have maser emission. Under certain conditions, the synchrotron stimulated emission process can be more important than true absorption, and a synchrotron maser can be created. This occurs when the emitting electrons have a very narrow distribution of pitch angles and energies. This process overcomes the difficulties of having extremely dense bunches of particles and relaxes the light crossing time limits, since there is no simple relation between the actual size of the source and the observed variability timescale.

  12. The Gamma-Ray Burst - Supernova Connection

    CERN Document Server

    Hjorth, Jens

    2011-01-01

    A preponderance of evidence links long-duration, soft-spectrum gamma-ray bursts (GRBs) with the death of massive stars. The observations of the GRB-supernova (SN) connection present the most direct evidence of this physical link. We summarize 30 GRB-SN associations and focus on five ironclad cases, highlighting the subsequent insight into the progenitors enabled by detailed observations. We also address the SN association (or lack thereof) with several sub-classes of GRBs, finding that the X-ray Flash (XRF) population is likely associated with massive stellar death whereas short-duration events likely arise from an older population not readily capable of producing a SN concurrent with a GRB. Interestingly, a minority population of seemingly long-duration, soft-spectrum GRBs show no evidence for SN-like activity; this may be a natural consequence of the range of Ni-56 production expected in stellar deaths.

  13. The Euclidean distribution of fast radio bursts

    Science.gov (United States)

    Oppermann, Niels; Connor, Liam D.; Pen, Ue-Li

    2016-09-01

    We investigate whether current data on the distribution of observed flux densities of fast radio bursts (FRBs) are consistent with a constant source density in Euclidean space. We use the number of FRBs detected in two surveys with different characteristics along with the observed signal-to-noise ratios of the detected FRBs in a formalism similar to a V/Vmax-test to constrain the distribution of flux densities. We find consistency between the data and a Euclidean distribution. Any extension of this model is therefore not data-driven and needs to be motivated separately. As a byproduct we also obtain new improved limits for the FRB rate at 1.4 GHz, which had not been constrained in this way before.

  14. The Euclidean distribution of Fast Radio Bursts

    CERN Document Server

    Oppermann, Niels; Pen, Ue-Li

    2016-01-01

    We investigate whether current data on the distribution of observed flux densities of Fast Radio Bursts (FRBs) are consistent with a constant source density in Euclidean space. We use the number of FRBs detected in two surveys with different characteristics along with the observed signal-to-noise ratios of the detected FRBs in a formalism similar to a V/V_max-test to constrain the distribution of flux densities. We find consistency between the data and a Euclidean distribution. Any extension of this model is therefore not data-driven and needs to be motivated separately. As a byproduct we also obtain new improved limits for the FRB rate at 1.4 GHz, which had not been constrained in this way before.

  15. Solution To The Gamma Ray Burst Mystery?

    CERN Document Server

    Dar, Arnon

    1996-01-01

    Photoexcitation and ionization of partially ionized heavy atoms in highly relativistic flows by interstellar photons, followed by their reemission in radiative recombination and decay, boost star-light into beamed $\\gamma$ rays along the flow direction. Repeated excitation/decay of highly relativistic baryonic ejecta from merger or accretion induced collapse of neutron stars in dense stellar regions (DSRs), like galactic cores, globular clusters and super star-clusters, can convert enough kinetic energy in such events in distant galaxies into cosmological gamma ray bursts (GRBs). The model predicts remarkably well all the main observed temporal and spectral properties of GRBs. Its success strongly suggests that GRBs are $\\gamma$ ray tomography pictures of DSRs in galaxies at cosmological distances with unprecedented resolution: A time resolution of $dt\\sim 1~ms$ in a GRB can resolve stars at a Hubble distance which are separated by only $D\\sim 10^{10}cm$. This is equivalent to the resolving power of an optica...

  16. The Swift Burst and Transient Telescope (BAT)

    Science.gov (United States)

    Mushotzky, Richard

    2008-01-01

    The Swift Burst and Transient telescope (BAT) has surveyed the entire sky for the last 3.5 years obtaining the first sensitive all sky survey of the 14-195 kev sky. At high galactic latitudes the vast majority of the detected sources are AGN. Since hard x-rays penetrate all but Compton thick obscuring material (Column densities of 1.6324 atms/sq cm) this survey is unbiased with respect to obscuration, host galaxy type, optical , radio or IR properties. We will present results on the broad band x-ray properties, the nature of the host galaxies, the luminosity function and will discuss a few of the optical, IR and x-ray results in detail.

  17. Critical Test Of Gamma Ray Burst Theories

    CERN Document Server

    Dado, Shlomo

    2016-01-01

    Long and precise follow-up measurements of the X-ray afterglow (AG) of very intense gamma ray bursts (GRBs) provide a critical test of GRB afterglow theories. Here we show that the power-law decline with time of X-ray AG of GRB 130427A, the longest measured X-ray AG of an intense GRB with the Swift, Chandra and XMM Newton satellites, and of all other well measured late-time X-ray afterglow of intense GRBs, is that predicted by the cannonball (CB) model of GRBs from their measured spectral index, while it disagrees with that predicted by the widely accepted fireball (FB) models of GRBs.

  18. Microstructural path analysis of martensite burst

    Directory of Open Access Journals (Sweden)

    Paulo Rangel Rios

    2010-03-01

    Full Text Available Modeling the martensite reaction requires reckoning with spatial aspects of the reaction. For that, we used formal kinetics, more specifically, the microstructural path method (MPM to analyze the microstructure observed in a burst. The microstructural path analysis revealed that the size of the spread cluster in extended space, characterized by the Vandermeer and Juul-Jensen's impingement compensated mean intercept length, λG, remained constant, independently of the parent austenite grain size. Moreover, current analysis introduced a purely formal description of the reaction progress by taking the parent austenite grain size as the progress variable. This description worked very well and resulted in a relationship between the volume fraction of partially transformed austenite, V VG, and austenite grain size, λG. The significance of these findings in the light of the advantages and disadvantages of formal kinetics is discussed.

  19. The Gamma Ray Bursts Hubble diagram

    CERN Document Server

    Capozziello, S; Dainotti, M G; De Laurentis, M; Izzo, L; Perillo, M

    2011-01-01

    Thanks to their enormous energy release, Gamma Rays Bursts (GRBs) have recently attracted a lot of interest to probe the Hubble diagram (HD) deep into the matter dominated era and hence complement Type Ia Supernovae (SNeIa). We consider here three different calibration methods based on the use of a fiducial LCDM model, on cosmographic parameters and on the local regression on SNeIa to calibrate the scaling relations proposed as an equivalent to the Phillips law to standardize GRBs finding any significant dependence. We then investigate the evolution of these parameters with the redshift to obtain any statistical improvement. Under this assumption, we then consider possible systematics effects on the HDs introduced by the calibration method, the averaging procedure and the homogeneity of the sample arguing against any significant bias.

  20. High Energy Radiation from $\\gamma$ Ray Bursts

    CERN Document Server

    Dermer, C D; Dermer, Charles D.; Chiang, James

    1999-01-01

    Gamma-ray burst (GRB) engines are probed most intimately during the prompt gamma-ray luminous phase when the expanding blast wave is closest to the explosion center. Using GRBs 990123 and 940217 as guides, we briefly review observations of high-energy emission from GRBs and summarize some problems in GRB physics. \\gamma\\gamma transparency arguments imply relativistic beaming. The parameters that go into the external shock model are stated, and we show numerical simulation results of gamma-ray light curves from relativistic blast waves with different amounts of baryon loading. A distinct component due to the synchrotron self-Compton process produces significant emission at GeV and TeV energies. Predictions for spectral and temporal evolution at these energies are presented for a blast wave expanding into uniform surroundings. Observations of the slow decay of GeV-TeV radiation provide evidence for ultra-high energy cosmic ray acceleration in GRBs.

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

    OpenAIRE

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

    2013-01-01

    The long gamma-ray burst (GRB) rate is essential for revealing the connection between GRBs, supernovae and stellar evolution. Additionally, the GRB rate at high redshift provides a strong probe of star formation history in the early universe. While hundreds of GRBs are observed by Swift, it remains difficult to determine the intrinsic GRB rate due to the complex trigger algorithm of Swift. Current studies usually approximate the Swift trigger algorithm by a single detection threshold. However...

  2. Does Twitter trigger bursts in signature collections?

    Directory of Open Access Journals (Sweden)

    Rui Yamaguchi

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

  3. SGR J1550-5418 BURSTS DETECTED WITH THE FERMI GAMMA-RAY BURST MONITOR DURING ITS MOST PROLIFIC ACTIVITY

    Energy Technology Data Exchange (ETDEWEB)

    Van der Horst, A. J.; Finger, M. H. [Universities Space Research Association, NSSTC, Huntsville, AL 35805 (United States); Kouveliotou, C. [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Gorgone, N. M. [Connecticut College, New London, CT 06320 (United States); Kaneko, Y.; Goegues, E.; Lin, L. [Sabanc Latin-Small-Letter-Dotless-I University, Orhanl Latin-Small-Letter-Dotless-I -Tuzla, Istanbul 34956 (Turkey); Baring, M. G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Guiriec, S.; Bhat, P. N.; Chaplin, V. L.; Goldstein, A. [University of Alabama, Huntsville, CSPAR, Huntsville, AL 35805 (United States); Granot, J. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Watts, A. L. [Astronomical Institute ' Anton Pannekoek' , University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Bissaldi, E.; Gruber, D. [Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, Postfach 1312, 85748 Garching (Germany); Gehrels, N.; Harding, A. K. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Gibby, M. H.; Giles, M. M., E-mail: A.J.VanDerHorst@uva.nl [Jacobs Technology, Inc., Huntsville, AL (United States); and others

    2012-04-20

    We have performed detailed temporal and time-integrated spectral analysis of 286 bursts from SGR J1550-5418 detected with the Fermi Gamma-ray Burst Monitor (GBM) in 2009 January, resulting in the largest uniform sample of temporal and spectral properties of SGR J1550-5418 bursts. We have used the combination of broadband and high time-resolution data provided with GBM to perform statistical studies for the source properties. We determine the durations, emission times, duty cycles, and rise times for all bursts, and find that they are typical of SGR bursts. We explore various models in our spectral analysis, and conclude that the spectra of SGR J1550-5418 bursts in the 8-200 keV band are equally well described by optically thin thermal bremsstrahlung (OTTB), a power law (PL) with an exponential cutoff (Comptonized model), and two blackbody (BB) functions (BB+BB). In the spectral fits with the Comptonized model, we find a mean PL index of -0.92, close to the OTTB index of -1. We show that there is an anti-correlation between the Comptonized E{sub peak} and the burst fluence and average flux. For the BB+BB fits, we find that the fluences and emission areas of the two BB functions are correlated. The low-temperature BB has an emission area comparable to the neutron star surface area, independent of the temperature, while the high-temperature BB has a much smaller area and shows an anti-correlation between emission area and temperature. We compare the properties of these bursts with bursts observed from other SGR sources during extreme activations, and discuss the implications of our results in the context of magnetar burst models.

  4. In situ fabrication of blue ceramic coatings on wrought Al Alloy 2024 by plasma electrolytic oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Wang Zhijiang; Nie Xueyuan; Hu, Henry; Hussein, Riyad O. [Department of Mechanical, Automotive and Materials Engineering, University of Windsor, Windsor, Ontario N9B 3P4 (Canada)

    2012-03-15

    In situ formation of ceramic coatings on 2024 Al alloy with a blue color was successfully achieved using a plasma electrolytic oxidation process working at atmospheric pressure. This novel blue ceramic coating overcomes the shortcomings of surface treatments resulting from conventional dyeing processes by depositing organic dyes into the porous structure of anodic film, which has poor resistance to abrasion and rapid fading when exposed to sunlight. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy were employed to characterize the microstructure of the blue ceramic coating. The fabricated ceramic coating was composed of CoAl{sub 2}O{sub 4}, {alpha}-Al{sub 2}O{sub 3}, and {gamma}-Al{sub 2}O{sub 3.} By controlling the working parameters, the distribution of the CoAl{sub 2}O{sub 4} phase on the surface can be adjusted, and plays a key role in the appearance of the coating. Electrochemical testing, thermal cycling method, and pin-on-disk sliding wear testing were employed to evaluate corrosion, thermal cycling, and wear resistance of the ceramic coatings. The results indicate that the blue ceramic coating has a similar polarization resistance to that of conventional anodic film and can significantly enhance the corrosion resistance of aluminum alloy. There are no destructive horizontal cracks observed within the blue ceramic coating when subjected to 120 times of thermal cycling, which heats the samples up to 573 K and followed by submersion in water at room temperature for 10 min. Compared with the aluminum substrate as well as a conventional anodic film coated aluminum sample, the wear resistance of the blue ceramic coating coated sample was significantly increased while the coefficient of friction was decreased from 0.34 to 0.14.

  5. Strange Nonchaotic Bursting in A Quasiperiodially-Forced Hindmarsh-Rose Neuron

    CERN Document Server

    Lim, Woochang; 10.3938/jkps57.1356

    2011-01-01

    We study the transition from a silent state to a bursting state by varying the dc stimulus in the Hindmarsh-Rose neuron under quasiperiodic stimulation. For this quasiperiodically forced case, a new type of strange nonchaotic (SN) bursting state is found to occur between the silent state and the chaotic bursting state. This is in contrast to the periodically forced case where the silent state transforms directly to a chaotic bursting state. Using a rational approximation to the quasiperiodic forcing, the mechanism for the appearance of such an SN bursting state is investigated. Thus, a smooth torus (corresponding to a silent state) is found to transform to an SN bursting attractor through a phase-dependent subcritical period-doubling bifurcation. These SN bursting states, together with chaotic bursting states, are characterized in terms of the interburst interval, the bursting length, and the number of spikes in each burst. Both bursting states are found to be aperiodic complex ones. Consequently, aperiodic c...

  6. Application of Luxol Fast Blue staining in locating the corticospinal tract in adult rats

    Institute of Scientific and Technical Information of China (English)

    Su Liu; Guangyu Shen; Guangming Lü; Xiaosong Gu

    2006-01-01

    BACKGROUND: There are many methods for myelin staining,mordant,or the special reaction of osmic acid with lipoid is used according to different principles.The commonly used methods are classic Well staining ,classic lithium carbonate-haematine staining,fast green staining,silver staining ,etc.Luxol Fast Blue can brightly stain myelin sheath,and has certain specificity .The background can be very clean if there is proper differentiation,whereas Luxol Fast Blue is cheap and convenient to operate,thus it is an ideal staining reagent for routine myelin sheath.OBJECTIVE: To show the coricospinal tract of normal adult rats with Luxol Fast Blue shaining method.DESIGN:A repetitive measurement design.SETTINGS: Institute of Nuerobiology,Nantong University;Department of Rehabilitation Medicine,Affiliated Hospital of Nantong University.MATERIALS: Six healthy adult male SD rats of clean dergree,weighing averagely 300 g.were provided by the experimental animal center of Nantong University.1 g/L Luxol Fast Blue solution was provided by Sigma Company;Leica CM1900 cryostat microtome by Leica Company;Leica DMR microscope by Leica Company.METHODS:The experiment was carried out in the Staff Room of Human Anatomy,Nantong University in May 2005.The rats were given intraperitoneal injection of combined anesthetic(2 mL/kg),then the chest was open for perfusing saline and phosphate buffer containing formamint via heart. Brain and spinal cord were removed after 1 hour then fixed,then changed to phosphate buffer(pH 7.4)containing 300 g/L saccharu at 4 ℃.and stayed overnight,tissue blocks at pyramid,decussation of pyramid and cervical,thoracic,lumbar and sacral segments of spinal cord were removed to prepare continuous horizontal frozen sections(30 μm) after sedimentation,the sections were dried at room temperature.The corticospinal tract of normal adult rats were shown with Luxol Fast Blue staining method,and observed under Leica DMR microscope.MAIN OUTCOME MEASURES:Positive fibers in

  7. Study of the Local Horizon. (Spanish Title: Estudio del Horizonte Local.) Estudo do Horizonte Local

    Science.gov (United States)

    Ros, Rosa M.

    2009-12-01

    The study of the horizon is fundamental to easy the first observations of the students at any education center. A simple model, to be developed in each center, allows to easy the study and comprehension of the rudiments of astronomy. The constructed model is presented in turn as a simple equatorial clock, other models (horizontal and vertical) may be constructed starting from it. El estudio del horizonte es fundamental para poder facilitar las primeras observaciones de los alumnos en un centro educativo. Un simple modelo, que debe realizarse para cada centro, nos permite facilitar el estudio y la comprensión de los primeros rudimentos astronómicos. El modelo construido se presenta a su vez como un sencillo modelo de reloj ecuatorial y a partir de él se pueden construir otros modelos (horizontal y vertical). O estudo do horizonte é fundamental para facilitar as primeiras observações dos alunos num centro educativo. Um modelo simples, que deve ser feito para cada centro, permite facilitar o estudo e a compreensão dos primeiros rudimentos astronômicos. O modelo construído apresenta-se, por sua vez, como um modelo simples de relógio equatorial e a partir dele pode-se construir outros modelos (horizontal e vertical)

  8. Application of Horizontal Well Technology to Liaohe Oilfield

    Institute of Scientific and Technical Information of China (English)

    HanYun

    2008-01-01

    @@ Horizontal well technology has become one of the main technologies enabling Liaohe Oilfield to realize stable development. By the end of 2006, 296 horizontal wells of various kinds had been completed in Liaohe Oil Field,273 wells had been put into production, Among uhich 237 were horizontal wells (see Table 1).

  9. Explicit horizontal open books on some Seifert fibered 3--manifolds

    OpenAIRE

    Ozbagci, Burak

    2006-01-01

    We describe explicit horizontal open books on some Seifert fibered 3--manifolds. We show that the contact structures compatible with these horizontal open books are Stein fillable and horizontal as well. Moreover we draw surgery diagrams for some of these contact structures.

  10. High power doubly resonant all-intracavity deep blue laser at 447 nm based on sum-frequency-mixing technology

    Institute of Scientific and Technical Information of China (English)

    YongjiYu; Guangyong Jin; Chao Wang; Xinyu Chen; Jiaxi Guo; Yibo Wang

    2009-01-01

    @@ A high power continuous-wave deep blue laser at 447 nm is obtained by using a doubly cavity and a type Π critical phase matching KTP crystal for intracavity sum-frequency-mixing.With the incident pump power of 240 W for the Nd:YAP crystal and 120 W for the other Nd:YAP crystal, the deep blue laser output of 5.7 W at 447 nm with near fundamental mode is obtained, and the beam quality M2 value equals 2.53 in both horizontal and vertical directions at the maximum output power.The power stability is better than 2% at the maximum output power during half an hour.The experimental results show that the intracavity sum-frequency mixing by doubly resonant is an effective method for high power blue laser.

  11. Radio fiber bursts and fast magnetoacoustic wave trains

    CERN Document Server

    Karlický, M; Jelínek, P

    2012-01-01

    We present a model for dm-fiber bursts that is based on assuming fast sausage magnetoacoustic wave trains that propagate along a dense vertical filament or current sheet. Eight groups of dm-fiber bursts that were observed during solar flares were selected and analyzed by the wavelet analysis method. To model these fiber bursts we built a semi-empirical model. We also did magnetohydrodynamic simulations of a propagation of the magnetoacoustic wave train in a vertical and gravitationally stratified current sheet. In the wavelet spectra of the fiber bursts computed at different radio frequencies we found the wavelet tadpoles, whose head maxima have the same frequency drift as the drift of fiber bursts. It indicates that the drift of these fiber bursts can be explained by the propagating fast sausage magnetoacoustic wave train. Using new semi-empirical and magnetohydrodynamic models with a simple radio emission model we generated the artificial radio spectra of the fiber bursts, which are similar to the observed ...

  12. Full system bifurcation analysis of endocrine bursting models.

    Science.gov (United States)

    Tsaneva-Atanasova, Krasimira; Osinga, Hinke M; Riess, Thorsten; Sherman, Arthur

    2010-06-21

    Plateau bursting is typical of many electrically excitable cells, such as endocrine cells that secrete hormones and some types of neurons that secrete neurotransmitters. Although in many of these cell types the bursting patterns are regulated by the interplay between voltage-gated calcium channels and calcium-sensitive potassium channels, they can be very different. We investigate so-called square-wave and pseudo-plateau bursting patterns found in endocrine cell models that are characterized by a super- or subcritical Hopf bifurcation in the fast subsystem, respectively. By using the polynomial model of Hindmarsh and Rose (Proceedings of the Royal Society of London B 221 (1222) 87-102), which preserves the main properties of the biophysical class of models that we consider, we perform a detailed bifurcation analysis of the full fast-slow system for both bursting patterns. We find that both cases lead to the same possibility of two routes to bursting, that is, the criticality of the Hopf bifurcation is not relevant for characterizing the route to bursting. The actual route depends on the relative location of the full-system's fixed point with respect to a homoclinic bifurcation of the fast subsystem. Our full-system bifurcation analysis reveals properties of endocrine bursting that are not captured by the standard fast-slow analysis. PMID:20307553

  13. Short Gamma-Ray Bursts with Extended Emission

    CERN Document Server

    Norris, J P; Bonnell, Jerry T.; Norris, Jay P.

    2006-01-01

    The recent association of several short gamma-ray bursts (GRBs) with early type galaxies with low star formation rate demonstrates that short bursts arise from a different progenitor mechanism than long bursts. However, since the duration distributions of the two classes overlap, membership is not always easily established. The picture is complicated by the occasional presence of softer, extended emission lasting tens of seconds after the initial spike-like emission. We show that the fundamental defining characteristic of the short burst class is that the initial spike exhibits negligible spectral evolution at energies above ~ 25 keV. This behavior is nearly ubiquitous for the 260 bursts with T90 < 2 s, where the BATSE TTE data completely included the initial spike. The same signature obtains for one HETE-2 and six Swift/BAT short bursts. Analysis of a small sample of "short" BATSE bursts with the most intense extended emission shows that the same lack of evolution on the pulse timescale obtains for the ex...

  14. Large Aerial Bursts: An Important Class of Terrestrial Accretionary Events

    Science.gov (United States)

    Wasson, John T.

    2003-01-01

    Large aerial bursts similar to the 1908 Tunguska bolide but much larger in magnitude have surely been responsible for many catastrophic events in the history of the Earth. Because aerial bursts produce shallow (or even negligible) craters, their existence is difficult to document in the geological record. Even aerial bursts as small as Tunguska deposit enough energy to melt ~1mm of dry soil. Silica-rich glass formed in such melts has the potential to survive in the soil for many Ma, thus a potential indicator of large aerial bursts is glass that was formed as thick regions within silicate melt sheets. The layered tektites from Southeast Asia and the Libyan desert glass may have formed by a combination of sedimentation and downslope flow of silicate melt heated by radiation from large aerial bursts. The alternative, formation of layered tektites as crater ejecta, cannot account for observations such as uniformly high 10Be contents, the orientation of the magnetic remanence field, and the absence of splash-form (e.g., teardrop or dumbbell) tektites in regions where layered tektites are common. The largest asteroids or comets make craters no matter what their strength. Recent reviews suggest that, for events in the energy range up to 1019-1020 J (about two orders of magnitude larger than the Meteor Crater impact), aerial bursts are more likely than cratering events, and the layered tektites of Southeast Asia imply the existence of aerial bursts one to two orders of magnitude larger still.

  15. Behaviorally relevant burst coding in primary sensory neurons.

    Science.gov (United States)

    Sabourin, Patrick; Pollack, Gerald S

    2009-08-01

    Bursts of action potentials in sensory interneurons are believed to signal the occurrence of particularly salient stimulus features. Previous work showed that bursts in an identified, ultrasound-tuned interneuron (AN2) of the cricket Teleogryllus oceanicus code for conspicuous increases in amplitude of an ultrasound stimulus, resulting in behavioral responses that are interpreted as avoidance of echolocating bats. We show that the primary sensory neurons that inform AN2 about high-frequency acoustic stimuli also produce bursts. As is the case for AN2, bursts in sensory neurons perform better as feature detectors than isolated, nonburst, spikes. Bursting is temporally correlated between sensory neurons, suggesting that on occurrence of a salient stimulus feature, AN2 will receive strong synaptic input in the form of coincident bursts, from several sensory neurons, and that this might result in bursting in AN2. Our results show that an important feature of the temporal structure of interneuron spike trains can be established at the earliest possible level of sensory processing, i.e., that of the primary sensory neuron.

  16. Tapered photonic crystal fibers for blue-enhanced supercontinuum generation

    DEFF Research Database (Denmark)

    Møller, Uffe; Sørensen, Simon Toft; Larsen, Casper;

    2012-01-01

    Tapering of photonic crystal fibers is an effective way of shifting the blue edge of a supercontinuum spectrum down in the deep-blue. We discuss the optimum taper profile for enhancing the power in the blue edge.......Tapering of photonic crystal fibers is an effective way of shifting the blue edge of a supercontinuum spectrum down in the deep-blue. We discuss the optimum taper profile for enhancing the power in the blue edge....

  17. BROADBAND SPECTRAL INVESTIGATIONS OF SGR J1550-5418 BURSTS

    Energy Technology Data Exchange (ETDEWEB)

    Lin Lin; Goegues, Ersin; Kaneko, Yuki [Faculty of Engineering and Natural Sciences, Sabanc Latin-Small-Letter-Dotless-I University, Orhanl Latin-Small-Letter-Dotless-I Tuzla, Istanbul 34956 (Turkey); Baring, Matthew G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Granot, Jonathan [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Kouveliotou, Chryssa [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Van der Horst, Alexander; Watts, Anna L. [Astronomical Institute ' Anton Pannekoek' , University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Gruber, David; Von Kienlin, Andreas [Max-Planck-Institut fuer extraterrestrische Physik, Postfach 1312, D-85748 Garching bei Mnchen (Germany); Younes, George [USRA, National Space Science and Technology Center, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Gehrels, Neil, E-mail: linlin@sabanciuniv.edu [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2012-09-01

    We present the results of our broadband spectral analysis of 42 SGR J1550-5418 bursts simultaneously detected with the Swift/X-ray Telescope (XRT) and the Fermi/Gamma-ray Burst Monitor (GBM), during the 2009 January active episode of the source. The unique spectral and temporal capabilities of the XRT windowed timing mode have allowed us to extend the GBM spectral coverage for these events down to the X-ray domain (0.5-10 keV). Our earlier analysis of the GBM data found that the SGR J1550-5418 burst spectra were described equally well with either a Comptonized model or with two blackbody functions; the two models were statistically indistinguishable. Our new broadband (0.5-200 keV) spectral fits show that, on average, the burst spectra are better described with two blackbody functions than with the Comptonized model. Thus, our joint XRT-GBM analysis clearly shows for the first time that the SGR J1550-5418 burst spectra might naturally be expected to exhibit a more truly thermalized character, such as a two-blackbody or even a multi-blackbody signal. Using the Swift and RXTE timing ephemeris for SGR J1550-5418 we construct the distribution of the XRT burst counts with spin phase and find that it is not correlated with the persistent X-ray emission pulse phase from SGR J1550-5418. These results indicate that the burst emitting sites on the neutron star need not to be co-located with hot spots emitting the bulk of the persistent X-ray emission. Finally, we show that there is a significant pulse phase dependence of the XRT burst counts, likely demonstrating that the surface magnetic field of SGR J1550-5418 is not uniform over the emission zones, since it is anticipated that regions with stronger surface magnetic field could trigger bursts more efficiently.

  18. Broadband Spectral Investigations of SGR J1550-5418 Bursts

    Science.gov (United States)

    Lin, Lin; Goegues, Ersin; Baring, Matthew G.; Granot, Jonathan; Kouveliotou, Chryssa; Kaneko, Yuki; van der Horst, Alexander; Gruber, David; von Kienlin, Andreas; Younes, George; Watts, Anna L.; Gehrels, Neil

    2012-01-01

    We present the results of our broadband spectral analysis of 42 SGR J1550-5418 bursts simultaneously detected with the Swift/X-ray Telescope (XRT) and the Fermi/Gamma-ray Burst Monitor (GBM), during the 2009 January active episode of the source. The unique spectral and temporal capabilities of the XRT windowed timing mode have allowed us to extend the GBM spectral coverage for these events down to the X-ray domain (0.5-10 keV). Our earlier analysis of the GBM data found that the SGR J1550-5418 burst spectra were described equally well with either a Comptonized model or with two blackbody functions; the two models were statistically indistinguishable. Our new broadband (0.5-200 keV) spectral fits show that, on average, the burst spectra are better described with two blackbody functions than with the Comptonized model. Thus, our joint XRT-GBM analysis clearly shows for the first time that the SGR J1550-5418 burst spectra might naturally be expected to exhibit a more truly thermalized character, such as a two-blackbody or even a multi-blackbody signal. Using the Swift and RXTE timing ephemeris for SGR J1550-5418 we construct the distribution of the XRT burst counts with spin phase and find that it is not correlated with the persistent X-ray emission pulse phase from SGR J1550-5418. These results indicate that the burst emitting sites on the neutron star need not to be co-located with hot spots emitting the bulk of the persistent X-ray emission. Finally, we show that there is a significant pulse phase dependence of the XRT burst counts, likely demonstrating that the surface magnetic field of SGR J1550-5418 is not uniform over the emission zones, since it is anticipated that regions with stronger surface magnetic field could trigger bursts more efficiently.

  19. Flow pathways of bromide and Brilliant Blue FCF tracers in caliche soils

    Science.gov (United States)

    Nobles, M. M.; Wilding, L. P.; Lin, H. S.

    2010-10-01

    Land use of caliche soils in limestone regions of Texas is increasingly shifting from traditional ranchland to residential and industrial development. However, little information is available on water flow and solute transport through soils of these landscapes, or their potential suitability for wastewater disposal and bioremediation. This study determined the impacts of landscape position on soil hydrologic functions by using Brilliant Blue FCF and Br - tracers to characterize flow pathways through soils of stepped terrains. Aqueous tracer solution was applied to surface (and in some cases subsurface) horizons of selected riser, tread, floodplain, and upland summit sites. Brilliant Blue FCF and Br - pathways were analyzed based on vertical sections excavated through each application site. While Brilliant Blue FCF demonstrated preferential flow along macropores, Br - moved through soil matrix primarily in piston flow pattern. In most cases, Br - was less retarded and moved to greater vertical and horizontal distances than Brilliant Blue FCF. Cemented Bk, Bkm, C, Cr, Crk, and R horizons acted as aquitards, resulting in considerable horizontal transport of both tracers beyond the direct infiltration zone. Significant volumes of limestone rock clasts, together with soil, were involved in solute transport and thus contributed to the soil's ability to serve as bioremediation and moisture storage media. High limestone gravel content and rapid solute transport through subsurface horizons to aquitards in deep riser soils indicate that they may serve as hydrological recharge sites with potential for ephemeral water tables, increased water storage and greater bioremediation potential. Shallow tread sites may be capable of producing seasonal saturation above restrictive horizons and increased surface runoff, becoming local hydrological discharge sites. This could conceivably lead to surface water contamination; however, these locales are hydrologically buffered by recharge

  20. The Black Hole Central Engine for Ultra-long Gamma-Ray Burst 111209A and Its Associated Supernova 2011kl

    Science.gov (United States)

    Gao, He; Lei, Wei-Hua; You, Zhi-Qiang; Xie, Wei

    2016-08-01

    Recently, the first association between an ultra-long gamma-ray burst (GRB) and a supernova was reported, i.e., GRB 111209A/SN 2011kl, enabling us to investigate the physics of central engines or even progenitors for ultra-long GRBs. In this paper, we inspect the broadband data of GRB 111209A/SN 2011kl. The late-time X-ray light curve exhibits a GRB 121027A-like fallback bump, suggesting a black hole (BH) central engine. We thus propose a collapsar model with fallback accretion for GRB 111209A/SN 2011kl. The required model parameters, such as the total mass and radius of the progenitor star, suggest that the progenitor of GRB 111209A is more likely a Wolf–Rayet star instead of a blue supergiant, and the central engine of this ultra-long burst is a BH. The implications of our results are discussed.

  1. INTEGRAL monitoring of unusually long X-ray bursts

    DEFF Research Database (Denmark)

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

    2008-01-01

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

  2. Neutron Stars and Thermonuclear X-ray Bursts

    Science.gov (United States)

    Bhattacharyya, Sudip

    2007-01-01

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

  3. Understanding Neutron Stars using Thermonuclear X-ray Bursts

    Science.gov (United States)

    Bhattacharyya, S.

    2007-01-01

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

  4. Dissecting the Phase Response of a Model Bursting Neuron

    CERN Document Server

    Sherwood, William Erik

    2009-01-01

    We investigate the phase response properties of the Hindmarsh-Rose model of neuronal bursting using burst phase response curves (BPRCs) computed with an infinitesimal perturbation approximation and by direct simulation of synaptic input. The resulting BPRCs have a significantly more complicated structure than the usual Type I and Type II PRCs of spiking neuronal models, and they exhibit highly timing-sensitive changes in the number of spikes per burst that lead to large magnitude phase responses. We use fast-slow dissection and isochron calculations to analyze the phase response dynamics in both weak and strong perturbation regimes.

  5. The Etiology and Outcome Analysis of Neonatal Burst Suppression EEG

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lian; ZHOU Yanxia; XU Sanqing

    2007-01-01

    The neonatal burst suppression is a severe EEG pattern and always demonstrates serious damage of nerve system. But the outcome of these patients depends on the different etiology. A total of 256 cases of video EEG recordings were analyzed in order to summarize the etiology and outcome of burst suppression. The results showed that some patients in all 17 cases of burst suppression showed EEG improvement. The etiology was the dominant factor in long term outcome. It was sug-gested that effective video EEG monitoring is helpful for etiologic study and prognosis evaluation.

  6. The supernova/gamma-ray burst/jet connection

    OpenAIRE

    Hjorth, Jens,

    2013-01-01

    The observed association between supernovae and gamma-ray bursts represents a cornerstone in our understanding of the nature of gamma-ray bursts. The collapsar model provides a theoretical framework for this connection. A key element is the launch of a bi-polar jet (seen as a gamma-ray burst). The resulting hot cocoon disrupts the star while the 56Ni produced gives rise to radioactive heating of the ejecta, seen as a supernova. In this discussion paper I summarise the observational status of ...

  7. Does horizontal transmission invalidate cultural phylogenies?

    Science.gov (United States)

    Greenhill, Simon J; Currie, Thomas E; Gray, Russell D

    2009-06-22

    Phylogenetic methods have recently been applied to studies of cultural evolution. However, it has been claimed that the large amount of horizontal transmission that sometimes occurs between cultural groups invalidates the use of these methods. Here, we use a natural model of linguistic evolution to simulate borrowing between languages. The results show that tree topologies constructed with Bayesian phylogenetic methods are robust to realistic levels of borrowing. Inferences about divergence dates are slightly less robust and show a tendency to underestimate dates. Our results demonstrate that realistic levels of reticulation between cultures do not invalidate a phylogenetic approach to cultural and linguistic evolution.

  8. Gilberto Freyre e o horizonte do modernismo

    Directory of Open Access Journals (Sweden)

    Mariza Veloso

    2000-12-01

    Full Text Available O artigo discute a inserção de Gilberto Freyre no horizonte do modernismo brasileiro e constrói seu argumento a partir dos ideais que o intelectual compartilha com sua geração. As principais linhas de interpretação responsáveis pela renovação do pensamento brasileiro podem ser sumarizadas pela substituição do conceito de Raça pelo de Cultura e pela alteração que provoca nos conceitos de História, Memória, Tempo e Tradição.

  9. Impulse absorption by horizontal magnetic granular chain

    Directory of Open Access Journals (Sweden)

    Dingxin Leng

    2016-02-01

    Full Text Available The granular medium is known as a protecting material for shock mitigation. We study the impulse absorption of an alignment of magnetic spheres placed horizontally under a non-uniform magnetic field. The phenomenon of the wave dispersion is presented. This system can absorb 85% ∼ 95% (88% ∼ 98% of the incident peak force (energy under the applied magnetic field strength in 0.1 T ∼ 1.0 T. The shock attenuation capacities are enhanced by the increment of field strength. With an intelligent control system, it is conceivable that the magnetic granular chain may offer possibilities in developing adaptive shock protectors.

  10. Horizontal axis Levitron—a physics demonstration

    Science.gov (United States)

    Michaelis, Max M.

    2014-01-01

    After a brief history of the Levitron, the first horizontal axis Levitron is reported. Because it is easy to operate, it lends itself to educational physics experiments and analogies. Precession and nutation are visualized by reflecting the beam from a laser pointer off the ‘spignet’. Precession is fundamental to nuclear magnetic resonance, magnetic resonance imaging, particle traps and the movement of bodies in space. Longitudinal and lateral bounce behaviour is explained via ‘the principle of gentle superposition’ of two traps: the micro-precessional and the macro-trap. Theory is initiated. Scaling experiments are mentioned. Industrial applications might follow. Patent pending.

  11. Flow film boiling heat transfer for subcooled liquids flowing upward perpendicular to single horizontal cylinders

    International Nuclear Information System (INIS)

    The knowledge of flow film boiling heat transfer on a horizontal cylinder in various liquids flowing upward perpendicular to the cylinder is important as the database for the safety evaluation of the accidents such as rapid power burst and pressure reduction in the nuclear power plants. Flow film boiling heat transfer from single horizontal cylinders in water and Freon-113 flowing upward perpendicular to the cylinder under subcooled conditions was measured under wide experimental conditions. The flow velocities ranged from 0 to 1 m/s, the system pressures ranged from 100 to 500 kPa, and the surface superheats were raised up to 800 K for water and 400 K for Freon-113, respectively. Platinum horizontal cylinders with diameters ranging from 0.7 to 5 mm were used as the test heaters. The test heater was heated by direct electric current. The experimental data of film boiling heat transfer coefficients show that they increase with the increase of flow velocity, liquid subcooling, system pressure and with the decrease of cylinder diameter. Based on the experimental data, a correlation for subcooled flow film boiling heat transfer including the effects of liquid subcooling and radiation was presented, which can describe the experimental data obtained within 20% for the flow velocities below 0.7 m/s, and within -30% to +20% for the higher flow velocities. The correlation also predicted well the data by Shigechi (1983), Motte and Bromley (1957), and Sankaran and Witte (1990) obtained for the larger diameter cylinders and higher flow velocities in various liquids at the pressures of near atmospheric. The Shigechi's data were in the range from about -20% to +15%, the data of Motte and Bromley were about 30%,and the data of Sankaran and Witte were within +20 % of the curves given by the corresponding predicted values. (authors)

  12. Blue jays nest in an unusual structure

    Science.gov (United States)

    Muths, Erin L.; Lyons, Curtis P.; Sedgwick, James A.

    2007-01-01

    We describe a successful Blue Jay (Cyanocitta cristata) nest in an unusual structure on the side of a building.  The nest was located near the edge of the species' range along the Front Range of the Rocky Mountains in Colorado.  The nest was completely obvious, suggesting that the structure itself provided adequate cover and sercurity for the jays.  Blue Jays appear to be declining in some areas of the United States such as the Southeast.  Structures such as the one we describe may be more useful in attracting Blue Jays than the nesting platforms available commercially.

  13. Stratigraphic control and formation evaluation of horizontal wells with MWD

    Energy Technology Data Exchange (ETDEWEB)

    Hammons, L.R.B. (Eastman Teleco (United States)); Sellers, D.H.; Fisher, E.K. (Texaco Inc. (United States))

    1992-10-01

    Sandstone reservoirs in the Gulf of Mexico typically do not form horizontal planes, and a predetermined course for a horizontal well cannot ensure that the well path will remain within the producing interval throughout the horizontal section. Detecting approaching bed boundaries and fluid contacts early enough to make the changes necessary to keep the well path in the producing interval is an important technical issue during the planning and drilling of horizontal wells. This paper reports that the first two horizontal wells drilled in the Gulf of Mexico achieved this objective with measurement-while-drilling (MWD) resistivity measurements and with supporting computer modeling for bed boundary detection.

  14. Closest Gamma Ray Burst Providing Scientists With Crucial Test for Burst Physics

    Science.gov (United States)

    2003-05-01

    The closest Gamma Ray Burst (GRB) yet known is providing astronomers with a rare opportunity to gain information vital to understanding these powerful cosmic explosions. Extremely precise radio-telescope observations already have ruled out one proposed mechanism for the bursts. "This is the closest and brightest GRB we've ever seen, and we can use it to decipher the physics of how these bursts work," said Greg Taylor of the National Radio Astronomy Observatory (NRAO) in Socorro, NM. Taylor worked with Dale Frail, also of the NRAO, along with Prof. Shri Kulkarni and graduate student Edo Berger of Caltech in studying a GRB detected on March 29, 2003. The scientists presented their findings to the American Astronomical Society's meeting in Nashville, TN. VLBA image of GRB 030329 VLBA IMAGE of GRB 030329 CREDIT: NRAO/AUI/NSF (Click on Image for Larger Version) Taylor and Frail used the National Science Foundation's (NSF) Very Long Baseline Array (VLBA) and other radio telescopes to study the burst, known as GRB 030329. In a series of observations from April 1 to May 19, they determined the size of the expanding "fireball" from the burst and measured its position in the sky with great precision. At a distance of about 2.6 billion light-years, GRB 030329 is hardly next door. However, compared to other GRBs at typical distances of 8-10 billion light-years, it presents an easier target for study. "We only expect to see one burst per decade this close," said Frail. The precise measurement of the object's position allowed the scientists to show that one theoretical model for GRBs can be ruled out. This model, proposed in 2000, says that the radio-wave energy emitted by the GRB comes from "cannonballs" of material shot from the explosion at extremely high speeds. "The 'cannonball model' predicted that we should see the radio-emitting object move across the sky by a specific amount. We have not seen that motion," Taylor said. The currently standard "fireball model" of GRBs

  15. Gamma-Ray Bursts 2012 Conference

    Science.gov (United States)

    It is a pleasure to announce the next combined Fermi/Swift GRB conference covering recent advances in all aspects of gamma-ray burst observations and theory. This conference will be held in Munich, Germany, on 7-11 May 2012, and follows similar previous combined Fermi/Swift meetings in Huntsville (Oct. 2008) and Annapolis (Nov. 2010). Gamma-ray bursts are the most energetic explosions in the Universe and are thought to be the birth signatures of black holes. This is an exciting time in the GRB field as various missions provide a wealth of new data on this still puzzling phenomenon. The Fermi misson provides unprecedented spectral coverage over 7 decades in energy, and among others discovered new spectral components which challenge our standard picture of the prompt emission. The Swift mission continuous to swiftly monitor and locate GRBs in multiple wavebands, providing the basis for all ground-based follow-up observations towards redshift measurements and afterglow and host property investigations. AGILE, INTEGRAL, Suzaku and Konus continue to provide crucial information on GRB properties, and the MAXI mission provides an all sky X-ray monitoring of transients. There is also growing capability for follow-up observations by ground-based telescopes at basically all wavelengths. Besides the classical optical/infrared/radio observations, searches are underway for TeV emission, neutrinos and gravitational waves. Moreover, new experiments are expected to have returned first data, among others POGO on the prompt polarization properties, UFFO on very early optical emission, or ALMA on sub-millimeter properties. And last but not least, the unexpected is bringing us child-like astonishments at least once per year with a "GRB-trigger" which turns out to be not related to GRBs. Complementing all these new observational results, a huge theoretical effort is underway to understand the GRB phenomenon and keep up with the constant new puzzles coming from the data. This conference

  16. In-situ bioremediation via horizontal wells

    International Nuclear Information System (INIS)

    This project is designed to demonstrate in situ bioremediation of groundwater and sediment contaminated with chlorinated solvents. Indigenous microorganisms were stimulated to degrade TCE, PCE and their daughter products in situ by addition of nutrients to the contaminated zone. In situ biodegradation is a highly attractive technology for remediation because contaminants are destroyed, not simply moved to another location or immobilized, thus decreasing costs, risks, and time, while increasing efficiency and public and regulatory acceptability. Bioremediation has been found to be among the least costly technologies in applications where it will work (Radian 1989). Subsurface soils and water adjacent to an abandoned process sewer line at the SRS have been found to have elevated levels of TCE (Marine and Bledsoe 1984). This area of subsurface and groundwater contamination is the focus of a current integrated demonstration of new remediation technologies utilizing horizontal wells. Bioremediation has the potential to enhance the performance of in situ air stripping as well as offering stand-alone remediation of this and other contaminated sites (Looney et al. 1991). Horizontal wells could also be used to enhance the recovery of groundwater contaminants for bioreactor conversions from deep or inaccessible areas (e.g., under buildings) and to enhance the distribution of nutrient or microbe additions in an in situ bioremediation

  17. Horizontal stresses below two agricultural vehicles

    DEFF Research Database (Denmark)

    Lamande, Mathieu André Maurice; Munkholm, Lars Juhl; Nielsen, Janne Aalborg;

    and the number of wheels. We measured horizontal stress at two depths (0.3 and 0.5 m) below tires of two slurry spreaders: one self-propelled machine equipped with wide tires (1.050 m) and low inflation pressure (150 kPa) but carrying a high wheel load (120 kN), and one tractor towing a three-axle slurry......) and at three depths (0.3, 0.5 and 0.7 m). The maximum rooting depths of spring barley was recorded below the center of the tire, below the edge of the tire, and outside the tracks. Horizontal stresses had about the same magnitude for 0.3 and 0.5 m depths for the self-propelled machine, while it was much higher...... at 0.3 than at 0.5 m for the tractor-trailer combination. At 0.3 m depth it was significantly higher for the tractor-trailer system than for the self-propelled machine. Generally, air permeability was reduced in the track of the tractor-trailer system, while no significant reduction was observed...

  18. Pattern selection in a horizontally vibrated container

    International Nuclear Information System (INIS)

    We present results of an experimental and numerical investigation of the patterns realized by surface waves within an open rectangular container subjected to horizontal vibrations at frequencies of 40–100 Hz. The first instability exhibited by the primary harmonic wave field is subharmonic, and may be identified with the cross-wave instability often seen in wave tank experiments. We show that, contrary to common theoretical and experimental assumptions, and despite their name, these subharmonic waves are not oriented crosswise, but at an intermediate angle with respect to the axis of vibration. Hence, the pattern selection problem for horizontally forced Faraday waves is more complex than has previously been assumed. We establish the robustness of this obliquely oriented surface wave pattern by varying the forcing frequency and amplitude, the fluid viscosity, the fluid depth, and the boundary conditions. Previous work on cross-waves is reviewed and discussed in relation to the current results. Finally, numerical simulations using a reduced model with an appropriate forcing term are used to support the generality of the experimental observations. (paper)

  19. Properties of blue-stained wood

    Directory of Open Access Journals (Sweden)

    Miha Humar

    2008-07-01

    Full Text Available Discoloration of wood is frequently caused by blue-stain fungi. Among them Aureobasidium pullulans and Sclerophoma pithyophila are reported as the most important staining organism. In previous researches, it was generally considered that blue-stain fungi do not influence mechanical properties. However, there were some opposite results published as well. In order to elucidate this issue, specimens made of Scots pine (Pinus sylvestris sapwood were exposed to two blue stain fungi A. pullulans and S. pithyophila for periods between two and eight weeks. FTIR, weight, colour and non-destructive modulus of elasticity measurements were performed before and after exposure. The results showed that blue stain fungi, besides considerable discoloration, do not cause any significant damage to wood. Surprisingly the non-destructive MoE analysis showed that modulus of elasticity even slightly increase after fungal exposure.

  20. Blue Ribbon Panel Report - BRP - Cancer Moonshot

    Science.gov (United States)

    The Blue Ribbon Panel Report outlines 10 recommendations to accelerate progress against cancer. The panel was established to ensure that the Cancer Moonshot's approaches are grounded in the best science.

  1. Blue Ribbon Panel 2016 Video Playlist

    Science.gov (United States)

    Blue Ribbon Panel members discuss recommendations from the panel report that was presented to the National Cancer Advisory Board on September 7, 2016. The playlist includes an overview video and 10 videos on the specific recommendations.

  2. The Hot Horizontal-Branch Stars in NGC288 - Effects of Diffusion and Stratification on Their Atmospheric Parameters*

    Science.gov (United States)

    Moehler, S.; Dreizler, S.; LeBlanc, F.; Khalack, V.; Michaud, G.; Richer, J.; Sweigart, Allen V.; Grundahl, F.

    2014-01-01

    Context. NGC288 is a globular cluster with a well developed blue horizontal branch covering the so-called u-jump which indicates the onset of diffusion. It is therefore well suited to study the effects of diffusion in blue horizontal branch (HB) stars. Aims. We compare observed abundances to predictions from stellar evolution models calculated with diffusion and from stratified atmospheric models. We verify the effect of using stratified model spectra to derive atmospheric parameters. In addition we investigate the nature of the overluminous blue HB stars around the u-jump. Methods. We define a new photometric index sz from uvby measurements that is gravity sensitive between 8 000K and 12 000 K. Using medium-resolution spectra and Stroemgren photometry we determine atmospheric parameters (Teff, logg) and abundances for the blue HB stars. We use both homogeneous and stratified model spectra for our spectroscopic analyses. Results. The atmospheric parameters and masses of the hot HB stars in NGC288 show a behaviour seen also in other clusters for temperatures between 9 000K and 14 000 K. Outside this temperature range, however, they follow rather the results found for such stars in (omega)Cen. The abundances derived from our observations are for most elements (except He and P) within the abundance range expected from evolutionary models that include the effects of atomic diffusion and assume a surface mixed mass of 10(exp -7) M. The abundances predicted by stratified model atmospheres are generally significantly more extreme than observed, except for Mg. The use of stratified model spectra to determine effective temperatures, surface gravities and masses moves the hotter stars to a closer agreement with canonical evolutionary predictions. Conclusions. Our results show definite promise towards solving the long-standing issue of surface gravity and mass discrepancies for hot HB stars, but there is still much work needed to arrive at a self-consistent solution.

  3. Second sound in bursting freely suspended smectic-A films.

    Science.gov (United States)

    Müller, Frank; Bohley, Christian; Stannarius, Ralf

    2009-04-01

    We describe the bursting of macroscopic spherical bubbles formed by smectic liquid crystals. During rupture, strong light scattering is observed. It is suggested here that peristaltic undulations of the films are responsible for this scattering. This phenomenon distinguishes bursting smectic films from bursting soap films. The dynamics of these mechanical waves are strongly influenced by the internal layered structure of the smectic films, viz. by the elasticity of the molecular layers, expressed by the smectic layer compression modulus B. We study experimentally the optical properties of bursting smectic films by means of optical transmission measurements and laser scattering. The typical wavelength range of the propagating peristaltic waves is in the micrometer range. The wavelength spectrum rather is independent of the initial film thickness delta, but the scattering intensity strongly depends on delta. PMID:19518341

  4. A burst-correcting algorithm for Reed Solomon codes

    Science.gov (United States)

    Chen, J.; Owsley, P.

    1990-01-01

    The Bose, Chaudhuri, and Hocquenghem (BCH) codes form a large class of powerful error-correcting cyclic codes. Among the non-binary BCH codes, the most important subclass is the Reed Solomon (RS) codes. Reed Solomon codes have the ability to correct random and burst errors. It is well known that an (n,k) RS code can correct up to (n-k)/2 random errors. When burst errors are involved, the error correcting ability of the RS code can be increased beyond (n-k)/2. It has previously been show that RS codes can reliably correct burst errors of length greater than (n-k)/2. In this paper, a new decoding algorithm is given which can also correct a burst error of length greater than (n-k)/2.

  5. Design and analysis of optical burst-switched networks

    Science.gov (United States)

    Xiong, Yijun; Vandenhoute, Marc; Cankaya, Hakki C.

    1999-08-01

    Optical burst switching (OBS) is a promising solution for building terabit optical routers and realizing IP over D- WDM. In this paper, we describe the basic concept of OBS and a general architecture of optical routers. The key design issues related to the OBS are discussed, notably, burstification, offset-time management and channel scheduling. A simple channel scheduling algorithm called LAUC (Latest Available Unscheduled Channel) algorithm is presented, which is also called Horizon algorithm in the literature. The performance of optical routers under random and self-similar traffic is thoroughly studied via computer simulations. Our study indicates that the distribution of burst length is not exponential any more. For the FDL (fiber delay line) optical buffer, the burst loss ratio is quite sensitive to the traffic characteristic of bursts when using the LAUC algorithm.

  6. Self-similar traffic analysis in optical burst assembly

    Institute of Scientific and Technical Information of China (English)

    Sui Zhicheng; Zeng Qingji; Xiao Shilin

    2005-01-01

    This paper investigates the traffic properties before and after assembly at edge node of Ethernet over optical burst switching (OBS) network for the first time. Burst and inter-arrival time distributions are simulated under time-based and length-based assembly schemes. Self-similar traffic Hurst parameter is compared through R/S and V/T plot. Finally three self-similar traffic generating methods are given. Simulation results demonstrate that, multi-source traffic increases self-similar degree, however after assembly, time-based scheme can decrease self-similar degree, and aggregated burst size is close to Gaussian distribution. Length-based method has no effects on the self-similarity of input traffic. RMD is fit for study of burst network with large self-similarity.

  7. Nonrelativistic phase in γ-ray burst afterglows

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The discovery of multiband afterglows definitely shows that most γ-ray bursts are of cosmological origin. γ-ray bursts are found to be one of the most violent explosive phenomena in the Universe, in which astonishing ultra-relativistic motions are involved.In this article, the multiband observational characteristics of γ-ray bursts and their afterglows are briefly reviewed. The standard model of γ-ray bursts, i.e. the fireball model, is described. Emphasis is then put on the importance of the nonrelativistic phase of afterglows. The concept of deep Newtonian phase is elaborated. A generic dynamical model applicable in both the relativistic and nonrelativistic phases is introduced. Based on these elaborations, the overall afterglow behaviors, from the very early stages to the very late stages, can be conveniently calculated.

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

    DEFF Research Database (Denmark)

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

    1994-01-01

    . However we conclude that there is no strong evidence of concentration of the bursts towards the Galactic Center or Plane. Around ∼10% of the 70 bursts showed x‐ray precursor or/and X‐ray tail. We discuss the possibility that two events, GRB 900126 and GRB 920311, would have been produced by the same......The first WATCH/GRANAT Gamma‐Ray Burst Catalogue comprises 70 events which have been detected by WATCH during the period December 1989–September 1992. 32 GRBs could be localized within a 3σ error radii of 1°. We have found a weak (2.2σ) clustering of these 32 bursts towards the Galactic Center...

  9. Stationarity of extreme bursts in the solar wind.

    Science.gov (United States)

    Moloney, N R; Davidsen, J

    2014-05-01

    Recent results have suggested that the statistics of bursts in the solar wind vary with solar cycle. Here, we show that this variation is basically absent if one considers extreme bursts. These are defined as threshold-exceeding events over the range of high thresholds for which their number decays as a power law. In particular, we find that the distribution of duration times and energies of extreme bursts in the solar wind ε parameter and similar observables are independent of the solar cycle and in this sense stationary, and show robust asymptotic power laws with exponents that are independent of the specific threshold. This is consistent with what has been observed for solar flares and, thus, provides evidence in favor of a link between solar flares and extreme bursts in the solar wind.

  10. The ultraviolet lines of carbon, nitrogen, and oxygen in the IUE spectrum of the field horizontal-branch A star HD 109995

    Science.gov (United States)

    Leckrone, David S.; Adelman, Saul J.

    1986-01-01

    Photospheric abundances of C, N and O of an evolved halo Population 2 star, the field horizontal-branch star HD 109995, based on observations of ultraviolet resonance or low excitation lines are presented. The logarithmic abundance ratio with respect to the Sun O/Fe = +1.5 is substantially higher than previously determined values for Pop. 2 red giants or RR Lyrae stars, but agrees well with a derived value from the OI infrared triplet. This may be direct evidence of Tinsley's (1979) scenario of localized sharply rising interstellar oxygen abundances immediately following bursts of massive star formation. Star HD 109995 may have formed from such highly oxygen-enriched material prior to its dilution by gas with the pre-burst composition. The ratio C/N = -1.3 may reflect the composition of material from which the star formed or CN processing within the star during its evolution.

  11. X-ray Spectroscopy of Bursts from SGR 1806-20 with RXTE

    CERN Document Server

    Strohmayer, T E; Strohmayer, Tod E.; Ibrahim, Alaa

    1998-01-01

    We report on new RXTE X-ray spectral analysis of bursts from SGR 1806-20, the most prolific SGR source known. Previous studies of bursts from this source revealed a remarkable lack of spectral variability both in single bursts as well as from burst to burst. We present here some of the first evidence for significant spectral evolution within SGR bursts. We find that optically thin thermal bremsstrahlung (OTTB) spectra including photoelectric absorption provide the best fits to most bursts, however, other models (power law, Band GRB) can also produce statistically acceptable fits. We confirm the existence of a rolloff in the photon number spectrum below 5 keV.

  12. Blue Ocean Strategy and marketing Icelandic fish

    OpenAIRE

    Sigrún Guðbjartsdóttir 1976

    2012-01-01

    The aim of the thesis is to explore if practice of Blue Ocean Strategy, through value innovation, or certain tools and framework of the strategy can be useful for Icelandic fish marketing companies. Blue Ocean Strategy is an innovative strategy that pushes companies to look beyond conventional boundaries of an industry and discover new market space through value innovation and consequently make competition irrelevant. Data was gathered through qualitative research methods, interviews as we...

  13. Blue Flag: a Symbol of Environmental Protection

    Directory of Open Access Journals (Sweden)

    Ioan Petroman

    2010-10-01

    Full Text Available Blue Flag is a high standard symbol of environmental protection and it is awarded to the beaches and agreement ports by the Foundation of Education for the Environment. The beaches having been awarded this distinction warrant particular protection for their visitors, which is a particular point of tourism attractiveness: the result, they are preferred by tourists and, therefore, by tour operators selling tourism packages for the littoral. In 2009, Romanian beaches were not awarded any Blue Flags.

  14. Blue emitting organic semiconductors under high pressure

    DEFF Research Database (Denmark)

    Knaapila, Matti; Guha, Suchismita

    2016-01-01

    This review describes essential optical and emerging structural experiments that use high GPa range hydrostatic pressure to probe physical phenomena in blue-emitting organic semiconductors including π-conjugated polyfluorene and related compounds. The work emphasizes molecular structure and inter......This review describes essential optical and emerging structural experiments that use high GPa range hydrostatic pressure to probe physical phenomena in blue-emitting organic semiconductors including π-conjugated polyfluorene and related compounds. The work emphasizes molecular structure...

  15. Blue Whales Respond to Anthropogenic Noise

    OpenAIRE

    Mariana L Melcón; Amanda J Cummins; Kerosky, Sara M; Lauren K Roche; Wiggins, Sean M.; John A. Hildebrand

    2012-01-01

    Anthropogenic noise may significantly impact exposed marine mammals. This work studied the vocalization response of endangered blue whales to anthropogenic noise sources in the mid-frequency range using passive acoustic monitoring in the Southern California Bight. Blue whales were less likely to produce calls when mid-frequency active sonar was present. This reduction was more pronounced when the sonar source was closer to the animal, at higher sound levels. The animals were equally likely to...

  16. The Nature of Gamma Ray Burst Supernovae

    CERN Document Server

    Cano, Zach

    2012-01-01

    Gamma Ray Bursts (GRBs) and Supernovae (SNe) are among the brightest and most energetic physical processes in the universe. It is known that core-collapse SNe arise from the gravitational collapse and subsequent explosion of massive stars (the progen- itors of nearby core-collapse SNe have been imaged and unambiguously identified). It is also believed that the progenitors of long-duration GRBs (L-GRBs) are massive stars, mainly due to the occurrence and detection of very energetic core-collapse su- pernovae that happen both temporally and spatially coincident with most L-GRBs. However many outstanding questions regarding the nature of these events exist: How massive are the progenitors? What evolutionary stage are they at when they explode? Do they exist as single stars or in binary systems (or both, and to what fractions)? The work presented in this thesis attempts to further our understanding at the types of progenitors that give rise to long-duration GRB supernovae (GRB-SNe). This work is based on optical ...

  17. Blueshifting may explain the gamma ray bursts

    CERN Document Server

    Krasiński, Andrzej

    2015-01-01

    It is shown that the basic observed properties of the gamma-ray bursts (GRBs) are accounted for if one assumes that the GRBs arise by blueshifting the emission radiation of hydrogen and helium generated during the last scattering epoch. The blueshift generator for a single GRB is a Lema\\^{\\i}tre -- Tolman (L--T) region with a nonconstant bang-time function $t_B(r)$ matched into a Friedmann background. Blueshift visible to the observer arises \\textit{only on radial rays} that are emitted in the L--T region. The paper presents three L--T models with different Big Bang profiles, adapted for the highest and the lowest end of the GRB frequency range. The models account for: (1) The observed frequency range of the GRBs; (2) Their limited duration; (3) The afterglows; (4) Their hypothetical collimation into narrow jets; (5) The large distances to their sources; (6) The multitude of the observed GRBs. Properties (2), (3) and (6) are accounted for only qualitatively. With a small correction of the parameters of the mo...

  18. Detecting fast radio bursts at decametric wavelengths

    CERN Document Server

    Rajwade, Kaustubh

    2016-01-01

    Fast radio bursts (FRBs) are highly dispersed, sporadic radio pulses that are likely extragalactic in nature. Here we investigate the constraints on the source population from surveys carried out at frequencies $<1$~GHz. All but one FRB has so far been discovered in the 1--2~GHz band, but new and emerging instruments look set to become valuable probes of the FRB population at sub-GHz frequencies in the near future. In this paper, we consider the impacts of free-free absorption and multi-path scattering in our analysis via a number of different assumptions about the intervening medium. We consider previous low frequency surveys alongwith an ongoing survey with the University of Technology digital backend for the Molonglo Observatory Synthesis Telescope (UTMOST) as well as future observations with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and the Hydrogen Intensity and Real-Time Analysis Experiment (HIRAX). We predict that CHIME and HIRAX will be able to observe $\\sim$ 30 or more FRBs per da...

  19. Studying the WHIM with Gamma Ray Bursts

    CERN Document Server

    Branchini, E; Corsi, A; Martizzi, D; Amati, L; Herder, J W den; Galeazzi, M; Gendre, B; Kaastra, J; Moscardini, L; Nicastro, F; Ohashi, T; Paerels, F; Piro, L; Roncarelli, M; Takei, Y; Viel, M

    2009-01-01

    We assess the possibility to detect and characterize the physical state of the missing baryons at low redshift by analyzing the X-ray absorption spectra of the Gamma Ray Burst [GRB] afterglows, measured by a micro calorimeters-based detector with 3 eV resolution and 1000 cm2 effective area and capable of fast re-pointing, similar to that on board of the recently proposed X-ray satellites EDGE and XENIA. For this purpose we have analyzed mock absorption spectra extracted from different hydrodynamical simulations used to model the properties of the Warm Hot Intergalactic Medium [WHIM]. These models predict the correct abundance of OVI absorption lines observed in UV and satisfy current X-ray constraints. According to these models space missions like EDGE and XENIA should be able to detect about 60 WHIM absorbers per year through the OVII line. About 45 % of these have at least two more detectable lines in addition to OVII that can be used to determine the density and the temperature of the gas. Systematic error...

  20. An updated Gamma Ray Bursts Hubble diagram

    CERN Document Server

    Cardone, V F; Dainotti, M G

    2009-01-01

    Gamma ray bursts (GRBs) have recently attracted much attention as a possible way to extend the Hubble diagram to very high redshift. To this aim, the luminosity (or isotropic emitted energy) of a GRB at redshift z must be evaluated from a correlation with a distance independent quantity so that one can then solve for the luminosity distance D_L(z) and hence the distance modulus mu(z). Averaging over five different two parameters correlations and using a fiducial cosmological model to calibrate them, Schaefer (2007) has compiled a sample of 69 GRBs with measured mu(z) which has since then been widely used to constrain cosmological parameters. We update here that sample by many aspects. First, we add a recently found correlation for the X - ray afterglow and use a Bayesian inspired fitting method to calibrate the different GRBs correlations known insofar assuming a fiducial LCDM model in agreement with the recent WMAP5 data. Averaging over six correlations, we end with a new GRBs Hubble diagram comprising 83 ob...

  1. Quark nova model for fast radio bursts

    Science.gov (United States)

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

    2016-05-01

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

  2. Energy Injections in Gamma Ray Bursts

    Science.gov (United States)

    Yu, Y. B.; Wu, X. F.; Huang, Y. F.; Xu, M.

    2016-06-01

    In this study, we will introduce some special events, such as GRBs 081029, 100814A and 111209A. Unexpected features, such as multiple X-ray flares and significant optical rebrightenings, are observed in their afterglow light curves, unveiling the late-time activities of the central engines. Here, we will summarize our previous numerical results of these three bursts by using the energy injection model. Especially, we will focus on GRB 100814A, with an early-time shallow decay phase and a late-time significant rebrightening in its optical afterglow light curve. To explain the complex multi-band afterglow emission of GRB 100814A, we invoke a magnetar with spin evolution as its central engine. We argue that the optical shallow decay phase and the X-ray plateau are due to energy injection from t he magnetar in its early spin-down stage, while the significant optical rebrightening observed at late time naturally comes from the spin-up process of the magnetar, which is caused by subsequent fall back accretion.

  3. Nucleosynthesis in Gamma Ray Burst Accretion Disks

    CERN Document Server

    Pruet, J; Hoffman, R D; Pruet, Jason

    2003-01-01

    We follow the nuclear reactions that occur in the accretion disks of stellar mass black holes that are accreting at a very high rate, 0.01 to 1 solar masses per second, as is realized in many current models for gamma-ray bursts (GRBs). The degree of neutronization in the disk is a sensitive function of the accretion rate, black hole mass, Kerr parameter, and disk viscosity. For high accretion rates and low viscosity, material arriving at the black hole will consist predominantly of neutrons. This degree of neutronization will have important implications for the dynamics of the GRB producing jet and perhaps for the synthesis of the r-process. For lower accretion rates and high viscosity, as might be appropriate for the outer disk in the collapsar model, neutron-proton equality persists allowing the possible synthesis of 56Ni in the disk wind. 56Ni must be present to make any optically bright Type Ib supernova, and in particular those associated with GRBs.

  4. The SVOM gamma-ray burst mission

    CERN Document Server

    Cordier, B; Atteia, J -L; Basa, S; Claret, A; Daigne, F; Deng, J; Dong, Y; Godet, O; Goldwurm, A; Götz, D; Han, X; Klotz, A; Lachaud, C; Osborne, J; Qiu, Y; Schanne, S; Wu, B; Wang, J; Wu, C; Xin, L; Zhang, B; Zhang, S -N

    2015-01-01

    We briefly present the science capabilities, the instruments, the operations, and the expected performance of the SVOM mission. SVOM (Space-based multiband astronomical Variable Objects Monitor) is a Chinese-French space mission dedicated to the study of Gamma-Ray Bursts (GRBs) in the next decade. The SVOM mission encompasses a satellite carrying four instruments to detect and localize the prompt GRB emission and measure the evolution of the afterglow in the visible band and in X-rays, a VHF communication system enabling the fast transmission of SVOM alerts to the ground, and a ground segment including a wide angle camera and two follow-up telescopes. The pointing strategy of the satellite has been optimized to favor the detection of GRBs located in the night hemisphere. This strategy enables the study of the optical emission in the first minutes after the GRB with robotic observatories and the early spectroscopy of the optical afterglow with large telescopes to measure the redshifts. The study of GRBs in the...

  5. Galactic bursts signature in Antarctica 10Be

    CERN Document Server

    Omerbashich, M

    2006-01-01

    I detected a very strong (25 %var) period of 3592+-57 years at 99% confidence level in the 10Be deposition rates from Vostok, Antarctica ice core raw (gapped, unaltered) data. The period was verified at 99% confidence level against the 10Be concentration raw data at both Vostok, as 3700+-57 years at very strong 38 %var, and Taylor Dome, Antarctica, as 3800+-61 years at very strong 23 %var. The noisy Mg concentration data from Taylor Dome also show an extremely strong (44 %var) period of 3965+-16 years. The Vostok data also show the Hallstadzeit Solar cycle, as 2296+-57 years at 12 %var, perhaps its best estimate yet. I use for all analyses the 99% confidence strict Gauss-Vanicek spectral analysis (GVSA) that estimates periods in incomplete records. Based on recent 500-parsec Galactic Center (GC) GeV/TeV Gamma ray surveys by the H.E.S.S. and INTEGRAL telescopes, the GC extremely active central region makes the best candidate host for bursts leaving the discovered signature. A previously reported 3600 years per...

  6. Neuronal networks and energy bursts in epilepsy.

    Science.gov (United States)

    Wu, Y; Liu, D; Song, Z

    2015-02-26

    Epilepsy can be defined as the abnormal activities of neurons. The occurrence, propagation and termination of epileptic seizures rely on the networks of neuronal cells that are connected through both synaptic- and non-synaptic interactions. These complicated interactions contain the modified functions of normal neurons and glias as well as the mediation of excitatory and inhibitory mechanisms with feedback homeostasis. Numerous spread patterns are detected in disparate networks of ictal activities. The cortical-thalamic-cortical loop is present during a general spike wave seizure. The thalamic reticular nucleus (nRT) is the major inhibitory input traversing the region, and the dentate gyrus (DG) controls CA3 excitability. The imbalance between γ-aminobutyric acid (GABA)-ergic inhibition and glutamatergic excitation is the main disorder in epilepsy. Adjustable negative feedback that mediates both inhibitory and excitatory components affects neuronal networks through neurotransmission fluctuation, receptor and transmitter signaling, and through concomitant influences on ion concentrations and field effects. Within a limited dynamic range, neurons slowly adapt to input levels and have a high sensitivity to synaptic changes. The stability of the adapting network depends on the ratio of the adaptation rates of both the excitatory and inhibitory populations. Thus, therapeutic strategies with multiple effects on seizures are required for the treatment of epilepsy, and the therapeutic functions on networks are reviewed here. Based on the high-energy burst theory of epileptic activity, we propose a potential antiepileptic therapeutic strategy to transfer the high energy and extra electricity out of the foci.

  7. Reactive and proactive routing in labelled optical burst switching networks

    OpenAIRE

    Klinkowski, Miroslaw; Careglio, Davide; Solé Pareta, Josep

    2009-01-01

    Optical burst switching architectures without buffering capabilities are sensitive to burst congestion. The existence of a few highly congested links may seriously aggravate the network throughput. Proper network routing may help in congestion reduction. The authors focus on adaptive routing strategies to be applied in labelled OBS networks, that is, with explicit routing paths. In particular, two isolated alternative routing algorithms that aim at network performance improvement because o...

  8. Dark gamma-ray bursts: possible role of multiphoton processes

    CERN Document Server

    Perel'man, Mark E

    2009-01-01

    The absence of optical afterglow at some gamma-ray bursts (so called dark bursts) requires analyses of physical features of this phenomenon. It is shown that such singularity can be connected with multiphoton processes of frequencies summation in the Rayleigh- Jeans part of spectra, their pumping into higher frequencies. It can be registered most probably on young objects with still thin plasma coating, without further thermalization, i.e. soon after a prompt beginning of the explosive activity.

  9. Estimating Redshifts for Long Gamma-Ray Bursts

    OpenAIRE

    Xiao, Limin; Schaefer, Bradley E.

    2009-01-01

    We are constructing a program to estimate the redshifts for GRBs from the original Swift light curves and spectra, aiming to get redshifts for the Swift bursts \\textit{without} spectroscopic or photometric redshifts. We derive the luminosity indicators from the light curves and spectra of each burst, including the lag time between low and high photon energy light curves, the variability of the light curve, the peak energy of the spectrum, the number of peaks in the light curve, and the minimu...

  10. Real Life Science with Dandelions and Project BudBurst

    OpenAIRE

    Johnson, Katherine A.

    2016-01-01

    Project BudBurst is a national citizen-science project that tracks bloom times and other phenological data for plants across the country. Data from Project BudBurst are being used to measure the effects of climate change. Students can participate in this project by watching any of the plants on the list, including the common dandelion, which makes the program easy and accessible to everyone. Journal of Microbiology & Biology Education

  11. Burst suppression in sleep in a routine outpatient EEG

    Directory of Open Access Journals (Sweden)

    Ammar Kheder

    2014-01-01

    Full Text Available Burst suppression (BS is an electroencephalogram (EEG pattern that is characterized by brief bursts of spikes, sharp waves, or slow waves of relatively high amplitude alternating with periods of relatively flat EEG or isoelectric periods. The pattern is usually associated with coma, severe encephalopathy of various etiologies, or general anesthesia. We describe an unusual case of anoxic brain injury in which a BS pattern was seen during behaviorally defined sleep during a routine outpatient EEG study.

  12. Survivability of meteor burst communication under adverse operating conditions.

    OpenAIRE

    Gates, Mark A.

    1992-01-01

    Approved for public release; distribution is unlimited This thesis is a study of the survivability and reliability issues associated with operating meteor burst communication systems under adverse conditions. Meteor burst communication relies on the phenomenon of reflecting radio waves off the ionized trails left by meteors as they enter the atmosphere and disintegrate. The system's rapid deployment capability, mobility, and operating characteristics make it ideal for disast...

  13. The host galaxy of a fast radio burst.

    Science.gov (United States)

    Keane, E F; Johnston, S; Bhandari, S; Barr, E; Bhat, N D R; Burgay, M; Caleb, M; Flynn, C; Jameson, A; Kramer, M; Petroff, E; Possenti, A; van Straten, W; Bailes, M; Burke-Spolaor, S; Eatough, R P; Stappers, B W; Totani, T; Honma, M; Furusawa, H; Hattori, T; Morokuma, T; Niino, Y; Sugai, H; Terai, T; Tominaga, N; Yamasaki, S; Yasuda, N; Allen, R; Cooke, J; Jencson, J; Kasliwal, M M; Kaplan, D L; Tingay, S J; Williams, A; Wayth, R; Chandra, P; Perrodin, D; Berezina, M; Mickaliger, M; Bassa, C

    2016-02-25

    In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty in pinpointing their celestial coordinates. Here we report the discovery of a fast radio burst and the identification of a fading radio transient lasting ~6 days after the event, which we use to identify the host galaxy; we measure the galaxy's redshift to be z = 0.492 ± 0.008. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionized baryons in the intergalactic medium of ΩIGM = 4.9 ± 1.3 per cent, in agreement with the expectation from the Wilkinson Microwave Anisotropy Probe, and including all of the so-called 'missing baryons'. The ~6-day radio transient is largely consistent with the radio afterglow of a short γ-ray burst, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting that there are at least two classes of bursts. PMID:26911781

  14. Identification of Bursting Water Maser Features in Orion KL

    CERN Document Server

    Hirota, Tomoya; Fujisawa, Kenta; Honma, Mareki; Kawaguchi, Noriyuki; Kim, Mi Kyoung; Kobayashi, Hideyuki; Imai, Hiroshi; Omodaka, Toshihiro; Katsunori,; Shibata, M; Shimoikura, Tomomi; Yonekura, Yoshinori

    2011-01-01

    In February 2011, a burst event of the H$_{2}$O maser in Orion KL (Kleinmann-Low object) has started after 13-year silence. This is the third time to detect such phenomena in Orion KL, followed by those in 1979-1985 and 1998. We have carried out astrometric observations of the bursting H$_{2}$O maser features in Orion KL with VERA (VLBI Exploration of Radio Astrometry), a Japanese VLBI network dedicated for astrometry. The total flux of the bursting feature at the LSR velocity of 7.58 km s$^{-1}$ reaches 4.4$\\times10^{4}$ Jy in March 2011. The intensity of the bursting feature is three orders of magnitudes larger than that of the same velocity feature in the quiescent phase in 2006. Two months later, another new feature appears at the LSR velocity of 6.95 km s$^{-1}$ in May 2011, separated by 12 mas north of the 7.58 km s$^{-1}$ feature. Thus, the current burst occurs at two spatially different features. The bursting masers are elongated along the northwest-southeast direction as reported in the previous burs...

  15. Rock burst prevention based on dissipative structure theory

    Institute of Scientific and Technical Information of China (English)

    Song Dazhao; Wang Enyuan; Li Nan; Jin Mingyue; Xue Shipeng

    2012-01-01

    Dynamic collapses of deeply mined coal rocks are severe.In order to explore new ideas for rock burst prevention,the relationship between entropy equations and dissipative structure was studied,and a concept-rock burst activity system (RAS) was proposed and its entropy was analyzed.The energy features of RAS were analyzed,and the relationship between electromagnetic radiation (EMR) intensity E and dissipated energy Ud was initially established.We suggest that rock burst normally happens only when d,S<< -des in RAS:RAS is the dissipative structure before collapse,and after which it become a new orderly structure,i.e.,a "dead",a statically orderly structure.We advanced that the effective way to prevent rock burst is to introduce entropy to the system for it keeps the system away from the dissipative structure.E and Ud of RAS are positively related,which is used as a bridge between dissipative structure theory and rock burst prevention engineering applications.Based on this.and using the data of rock burst prevention for working face No.250205up of Yanbei coal mine,an engineering verification for the dissipative structure of RAS was carried out,which showed good results.

  16. Thermonuclear bursts from slowly and rapidly accreting neutron stars

    Science.gov (United States)

    Linares, Manuel

    2012-07-01

    Models of thermonuclear burning on accreting neutron stars predict different ignition regimes, depending mainly on the mass accretion rate per unit area. For more than three decades, testing these regimes observationally has met with only partial success. I will present recent results from the Fermi-GBM all-sky X-ray burst monitor, which is yielding robust measurements of recurrence time of rare and highly energetic thermonuclear bursts at the lowest mass accretion rates. I will also present RXTE observations of thermonuclear bursts at high mass accretion rates, including the discovery of millihertz quasi-periodic oscillations and several bursting regimes in a neutron star transient and 11 Hz X-ray pulsar. This unusual neutron star, with higher magnetic field and slower rotation than any other known burster, showed copious bursting activity when the mass accretion rate varied between 10% and 50% of the Eddington rate. I will discuss the role of fuel composition and neutron star spin in setting the burst properties of this system, and the possible implications for the rest of thermonuclear bursters.

  17. Understanding the Continuum Spectra of Short Soft Gamma Repeater Bursts

    Science.gov (United States)

    Gogus, Ersin; Woods, Peter M.; Kouveliotou, Chryssa; Finger, Mark H.; Lenter, Geoffrey; Patel, Sandeep K.; Swank, Jean

    2006-01-01

    The spectra of short soft gamma repeater (SGR) bursts at photon energies above -15 keV are often well described by an optically thin thermal bremsstrahlung model (i.e., F(E) - E^-1 * exp(-E/kT) ) with kT=20-40 keV. However, the spectral shape burst continuum at lower photon energies (down to -2 keV) is not well established. It is important to better understand the SGR burst spectral properties at lower energies since inadequate description of the burst spectral continuum could lead to incorrect conclusions, such as existence of spectral lines. Here, we present detailed spectral investigations (in 2-200 keV) of 163 bursts from SGR 1806-20, all detected with Rossi X-ray Timing Explorer during the 2004 active episode that included the giant flare on 27 December 2004. We find that the great majority of burst spectra are well represented by the combination of a blackbody plus a OTTB models.

  18. Observation of a Metric Type N Solar Radio Burst

    CERN Document Server

    Kong, Xiangliang; Feng, Shiwei; Du, Guohui; Li, Chuanyang; Koval, Artem; Vasanth, V; Wang, Bing; Guo, Fan; Li, Gang

    2016-01-01

    Type III and type-III-like radio bursts are produced by energetic electron beams guided along coronal magnetic fields. As a variant of type III bursts, Type N bursts appear as the letter "N" in the radio dynamic spectrum and reveal a magnetic mirror effect in coronal loops. Here, we report a well-observed N-shaped burst consisting of three successive branches at metric wavelength with both fundamental and harmonic components and a high brightness temperature ($>$10$^9$ K). We verify the burst as a true type N burst generated by the same electron beam from three aspects of the data. First, durations of the three branches at a given frequency increase gradually, may due to the dispersion of the beam along its path. Second, the flare site, as the only possible source of non-thermal electrons, is near the western feet of large-scale closed loops. Third, the first branch and the following two branches are localized at different legs of the loops with opposite sense of polarization. We also find that the sense of p...

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

    Directory of Open Access Journals (Sweden)

    Alireza Shameli-Sendi

    2013-01-01

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

  20. THRESHOLD FOR EXTENDED EMISSION IN SHORT GAMMA-RAY BURSTS

    International Nuclear Information System (INIS)

    The initial pulse complex (IPC) in short gamma-ray bursts is sometimes accompanied by a softer, low-intensity extended emission (EE) component. In cases where such a component is not observed, it is not clear if it is present but below the detection threshold. Using Bayesian Block (BB) methods, we measure the EE component and show that it is present in one-quarter of a Swift/BAT sample of 51 short bursts, as was found for the Compton/BATSE sample. We simulate bursts with EE to calibrate the BAT threshold for EE detection and show that this component would have been detected in nearly half of BAT short bursts if it were present, to intensities ∼10-2 counts cm-2 s-1, a factor of 5 lower than actually observed in short bursts. In the BAT sample, the ratio of average EE intensity to IPC peak intensity, Rint, ranges over a factor of 25, Rint ∼ 3 x 10-3 to 8 x 10-2. In comparison, for the average of the 39 bursts without an EE component, the 2σ upper limit is Rint -4. These results suggest that a physical threshold effect operates near Rint ∼ few x 10-3 below which the EE component is not manifest.