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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 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.

  3. Discovery of Extended Blue Horizontal Branches in Two Metal-Rich Globular Clusters

    CERN Document Server

    Rich, R M; Djorgovski, S G; Piotto, G; King, I R; Renzini, A; Phinney, E S; Dorman, B; Liebert, J; Meylan, G; Sosin, Craig; Piotto, Giampaolo; King, Ivan R.; Renzini, Alvio; Dorman, Ben; Liebert, James; Meylan, Georges

    1997-01-01

    We have used WFPC2 to construct B, V color-magnitude diagrams of four metal-rich globular clusters, NGC 104 (47 Tuc), NGC 5927, NGC 6388, and NGC 6441. All four clusters have well populated red horizontal branches (RHB), as expected for their metallicity. However, NGC 6388 and 6441 also exhibit a prominent blue HB (BHB) extension, including stars reaching as faint in V as the turnoff luminosity. This discovery demonstrates directly for the first time that a major population of hot HB stars can exist in old, metal-rich systems. This may have important implications for the interpretation of the integrated spectra of elliptical galaxies. The cause of the phenomenon remains uncertain. We examine the possibility that NGC 6388 and 6441 are older than the other clusters, but a simple difference in age may not be sufficient to produce the observed distributions along the HB. The high central densities in NGC 6388 and 6441 suggest that the existence of the blue HB (BHB) tails might be caused by stellar interactions in...

  4. 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...

  5. 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

  6. 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...

  7. 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 ...

  8. 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...

  9. 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.

  10. 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.

  11. 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.

  12. 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

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

    Science.gov (United States)

    Beers, Timothy C.; Placco, Vinicius M.; Carollo, Daniela; Santucci, Rafael; Rossi, Siliva; Lee, Young Sun; Denissenkov, Pavel; Tumlinson, Jason; Tissera, Patricia; Lentner, Geoffrey

    2016-01-01

    In a pioneering effort, Preston et al. (1991, AJ 375, 121) 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 concentrated in the central ~15 kpc of the Galaxy. Within this centralregion, which we refer to as the Ancient Chronographic Sphere (ACS), the age difference spans a mean color range of about 0.05 mag (~0.8 Gyrs). Interestingly, the ACS extends far enough to include the Solar Neighborhood, suggesting that ancient metal-poor stars should be readily detectable in the vicinity of the Sun. Furthermore, we show that chronographic maps can be used to identify individual substructures, such as the Sagittarius Stream, and overdensities in the direction of Virgo and Monoceros, based on the observed contrast in their mean BHB colors with respect to the foreground/background field population.We acknowledge partial support from the grant PHY 14-30152; Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE), awarded by the US National Science Foundation.

  14. 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.

  15. 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.

  16. MAPPING THE GALACTIC HALO WITH BLUE HORIZONTAL BRANCH STARS FROM THE TWO-DEGREE FIELD QUASAR REDSHIFT SURVEY

    International Nuclear Information System (INIS)

    We use 666 blue horizontal branch 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 about 1500 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 toward 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.

  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. Blue supergiant model for ultra-long gamma-ray burst with superluminous-supernova-like bump

    International Nuclear Information System (INIS)

    Long gamma-ray bursts (LGRBs) have a typical duration of ∼30 s, and some of them are associated with hypernovae, such as 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 ∼104 s, two of them are accompanied by superluminous-supernova-like (SLSN-like) bumps, which are ≲ 10 times brighter than typical hypernovae. Wolf-Rayet progenitors cannot explain ULGRBs because of durations that are too long and SN-like bumps that are too bright. A blue supergiant (BSG) progenitor model, however, can explain the duration of ULGRBs. Moreover, SLSN-like bumps 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 smoking gun evidence of the BSG model for ULGRBs. In this paper, we examine u-, g-, r-, i-, and J-band light curves of three ULGRBs and demonstrate that they can be fitted quite well by our BSG model with the appropriate choices of the jet opening angle and the number density of the ambient gas. In addition, we predict that for 121027A, SLSN-like bump could have been observed for ∼20-80 days after the burst. We also propose that some SLSNe might be CFPEs of off-axis ULGRBs without visible prompt emissions.

  19. 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).

  20. 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...

  1. 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...

  2. 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...

  3. How long does a burst burst?

    International Nuclear Information System (INIS)

    Several gamma-ray bursts (GRBs) last much longer (∼hours) in γ-rays than typical long GRBs (∼minutes), and it has recently been 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 suggest 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 X-Ray Telescope observations to investigate GRB central engine activity duration and to determine whether ultra-long GRBs are unusual events. We define burst duration t burst based on both γ-ray and X-ray light curves rather than using γ-ray observations alone. We find that t burst can be reliably measured in 343 GRBs. Within this 'good' sample, 21.9% GRBs have t burst ≳ 103 s and 11.5% GRBs have t burst ≳ 104 s. There is an apparent bimodal distribution of t burst in this sample. However, when we consider an 'undetermined' sample (304 GRBs) with t burst possibly falling in the gap between GRB duration T 90 and the first X-ray observational time, as well as a selection effect against t burst falling into the first Swift orbital 'dead zone' due to observation constraints, the intrinsic underlying t burst distribution is consistent with being a single component distribution. We found that the existing evidence for a separate ultra-long GRB population is inconclusive, and further multi-wavelength observations are needed to draw a firmer conclusion. We also discuss the theoretical implications of our results. In particular, the central engine activity duration of GRBs is generally much longer than the γ-ray T 90 duration and it does not even correlate with T 90. It would be premature to make a direct connection between T 90 and the size of the progenitor star.

  4. Postpartum Blues

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  5. Gamma bursts

    International Nuclear Information System (INIS)

    The Vela satellite series has recently detected gamma bursts in the 0.2-1.5MeV energy range. These bursts last an average of from 0.1 to 10s and have a fine time structure, with pulses lasting less than several tens of milliseconds. With simultaneous observations from different satellites it has been possible to determine the spatial origin of some of the bursts. No correlation, however, has been made with known objects. In spite of the fragmentary character of the information received to date, several theories have already been proposed to account for these phenomena

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  9. Postpartum Blues

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  19. 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 ...

  20. 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 ...

  1. 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 ...

  2. Postpartum Blues

    Medline Plus

    Full Text Available ... articles March of Dimes Premature Birth Report Card Grades Cities, Counties; Focuses on Racial and Ethnic Disparities ... baby blues: Talk to your partner or a good friend about how you feel Get plenty of ...

  3. Postpartum Blues

    Medline Plus

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

  4. 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 ...

  5. 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

  6. Blue Nile

    OpenAIRE

    Ramos, Manuel João

    2000-01-01

    The Blue Nile, whose source lies in highland Ethiopia, is known as “Al-Bahr al- Azraq” in Arabic, and as “Abbay” in Amharic. Along with the Atbara, it contributes more than 80 per cent of the Nile’s total water supply, the remainder coming mainly from the White Nile that stretches down to the Great Lakes plateau in Central Africa.

  7. 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...

  8. Thermonuclear burst oscillations

    CERN Document Server

    Watts, Anna L

    2012-01-01

    Burst oscillations, a phenomenon observed in a significant fraction of Type I (thermonuclear) X-ray bursts, involve the development of highly asymmetric brightness patches in the burning surface layers of accreting neutron stars. Intrinsically interesting as nuclear phenomena, they are also important as probes of dense matter physics and the strong gravity, high magnetic field environment of the neutron star surface. Burst oscillation frequency is also used to measure stellar spin, and doubles the sample of rapidly rotating (above 10 Hz) accreting neutron stars with known spins. Although the mechanism remains mysterious, burst oscillation models must take into account thermonuclear flame spread, nuclear processes, rapid rotation, and the dynamical role of the magnetic field. This review provides a comprehensive summary of the observational properties of burst oscillations, an assessment of the status of the theoretical models that are being developed to explain them, and an overview of how they can be used to...

  9. 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.

  10. 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

  11. GLAST's GBM Burst Trigger

    Science.gov (United States)

    Band, D.; Briggs, M.; Connaughton, V.; Kippen, M.; Preece, R.

    2003-01-01

    The GLAST Burst Monitor (GBM) will detect and localize bursts for the GLAST mission, and provide the spectral and temporal context in the traditional 10 keV to 25 MeV band for the high energy observations by the Large Area Telescope (LAT). The GBM will use traditional rate triggers in up to three energy bands, and on a variety of timescales between 16 ms and 16 s.

  12. Horizontal Equity, Once More

    OpenAIRE

    Richard A. Musgrave

    1990-01-01

    Reconsiders the proposition that vertical equity is the primary norm for tax design, with horizontal equity a mere derivative therefrom. In the case of limited policy options, vertical and horizontal equity goals may conflict so that a trade-off will be needed. Independent values must then be assigned to each, confirming the standing of a horizontal as well as vertical equity as a primary norm.

  13. 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...

  14. 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

  15. 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...

  16. 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.

  17. Mixed Burst Error Correcting Codes

    OpenAIRE

    Sethi, Amita

    2015-01-01

    In this paper, we construct codes which are an improvement on the previously known block wise burst error correcting codes in terms of their error correcting capabilities. Along with different bursts in different sub-blocks, the given codes also correct overlapping bursts of a given length in two consecutive sub-blocks of a code word. Such codes are called mixed burst correcting (mbc) codes.

  18. 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).

  19. Horizontal Integration of Knowledge

    Czech Academy of Sciences Publication Activity Database

    Klimešová, Dana; Vostrovský, V.

    Palma de Mallorca: IASTED, 2008, s. 191-196. ISBN 978-0-88986-755-0. [ Artificial Intelligence and Soft Computing (ASC 2008). Palma de Mallorca (ES), 01.09.2008-03.09.2008] Institutional research plan: CEZ:AV0Z10750506 Keywords : Intelligent systems * horizontal knowledge integration * multi-criteria evaluation * decision support Subject RIV: IN - Informatics, Computer Science http://library.utia.cas.cz/separaty/2008/ZOI/klimesova-horizontal integration of knowledge.pdf

  20. 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.

  1. 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.

  2. 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

    2016-03-10

    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. PMID:26934226

  3. 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

  4. 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.

  5. 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.

  6. Star bursts and giant HII regions

    International Nuclear Information System (INIS)

    Massive star formation bursts occur in a variety of galactic environments and can temporarily dominate the light output of a galaxy even when a relatively small proportion of its mass is involved. Inferences about their ages, the IMF and its dependence on chemical composition are still somewhat wobbly owing to an excess of unknowns, but certain things can be deduced from emission spectra of associated H II regions when due regard is paid to the effects of chemical composition and ionization parameter: In particular, largest ionization parameters and effective temperatures of exciting stars, at any given oxygen abundance, are anti-correlated with the abundance, and the second effect suggests an increasing proportion of more massive stars at lower abundances, although this is not yet satisfactorily quantified. A new blue compact galaxies could be very young, but it is equally possible that there is an older population of low surface brightness. Some giant H II regions may be self-polluted with nitrogen and helium due to winds from massive stars in the associated burst. (orig.)

  7. Sky Coverage and Burst Repetition

    OpenAIRE

    Band, David L.

    1996-01-01

    To investigate the repeater content of gamma ray burst samples I develop two models where sources burst at a constant average rate. I find that the sky coverage affects the number of repeaters in a sample predominantly through the detector livetime, and that the number of bursts in the sample is the primary parameter. Thus the repeater content of burst samples should be compared within the context of a repetition model; a direct comparison between two samples is possible only if the samples h...

  8. UWB dual burst transmit driver

    Science.gov (United States)

    Dallum, Gregory E.; Pratt, Garth C.; Haugen, Peter C.; Zumstein, James M.; Vigars, Mark L.; Romero, Carlos E.

    2012-04-17

    A dual burst transmitter for ultra-wideband (UWB) communication systems generates a pair of precisely spaced RF bursts from a single trigger event. An input trigger pulse produces two oscillator trigger pulses, an initial pulse and a delayed pulse, in a dual trigger generator. The two oscillator trigger pulses drive a gated RF burst (power output) oscillator. A bias driver circuit gates the RF output oscillator on and off and sets the RF burst packet width. The bias driver also level shifts the drive signal to the level that is required for the RF output device.

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

    OpenAIRE

    V.KAVITHA; Palanisamy, V.

    2013-01-01

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

  10. 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.

  11. 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.

  12. 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.

  13. 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...

  14. 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...

  15. 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...

  16. Burst propagation in Texas Helimak

    Science.gov (United States)

    Pereira, F. A. C.; Toufen, D. L.; Guimarães-Filho, Z. O.; Caldas, I. L.; Gentle, K. W.

    2016-05-01

    We present investigations of extreme events (bursts) propagating in the Texas Helimak, a toroidal plasma device in which the radial electric field can be changed by application of bias. In the experiments analyzed, a large grid of Langmuir probes measuring ion saturation current fluctuations is used to study the burst propagation and its dependence on the applied bias voltage. We confirm previous results reported on the turbulence intermittency in the Texas Helimak, extending them to a larger radial interval with a density ranging from a uniform decay to an almost uniform value. For our analysis, we introduce an improved procedure, based on a multiprobe bidimensional conditional averaging method, to assure precise determination of burst statistical properties and their spatial profiles. We verify that intermittent bursts have properties that vary in the radial direction. The number of bursts depends on the radial position and on the applied bias voltage. On the other hand, the burst characteristic time and size do not depend on the applied bias voltage. The bias voltage modifies the vertical and radial burst velocity profiles differently. The burst velocity is smaller than the turbulence phase velocity in almost all the analyzed region.

  17. 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.

  18. 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.

  19. 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.

  20. Scheduling start time in CDMA burst admission

    OpenAIRE

    Zhuge, L; Li, VOK

    2002-01-01

    Burst transmission protocols have been proposed in the next generation CDMA cellular systems to support short-time high-speed data communications. The existing burst admission algorithm considers only the current interference condition in the system. The burst transmission request will be rejected if the interference in the system will exceed the acceptable level with the burst admitted. In this paper we propose a new burst admission algorithm where a currently-unacceptable burst request can ...

  1. Burst Detector Sensitivity: Past, Present & Future

    OpenAIRE

    Band, David L.

    2006-01-01

    I compare the burst detection sensitivity of CGRO's BATSE, Swift's BAT, the GLAST Burst Monitor (GBM) and EXIST as a function of a burst's spectrum and duration. A detector's overall burst sensitivity depends on its energy sensitivity and set of accumulations times Delta t; these two factors shape the detected burst population. For example, relative to BATSE, the BAT's softer energy band decreases the detection rate of short, hard bursts, while the BAT's longer accumulation times increase the...

  2. Blue-green algae

    Science.gov (United States)

    ... Lac Klamath, Anabaena, Aphanizomenon flos-aquae, Arthrospira maxima, Arthrospira platensis, BGA, Blue Green Algae, Blue-Green Micro-Algae, Cyanobacteria, Cyanobactérie, Cyanophycée, Dihe, Espirulina, Hawaiian Spirulina, Klamath, Klamath Lake Algae, Lyngbya wollei, Microcystis aeruginosa, ...

  3. Blue-green algae

    Science.gov (United States)

    ... unresponsive to other treatments, taking 500 mg of spirulina blue-green algae by mouth 3 times daily for 6 months ... was seen in undernourished children who were given spirulina blue-green algae with a combination of millet, soy and peanut ...

  4. Templated blue phases.

    Science.gov (United States)

    Ravnik, Miha; Fukuda, Jun-ichi

    2015-11-21

    Cholesteric blue phases of a chiral liquid crystal are interesting examples of self-organised three-dimensional nanostructures formed by soft matter. Recently it was demonstrated that a polymer matrix introduced by photopolymerization inside a bulk blue phase not only stabilises the host blue phase significantly, but also serves as a template for blue phase ordering. We show with numerical modelling that the transfer of the orientational order of the blue phase to the surfaces of the polymer matrix, together with the resulting surface anchoring, can account for the templating behaviour of the polymer matrix inducing the blue phase ordering of an achiral nematic liquid crystal. Furthermore, tailoring the anchoring conditions of the polymer matrix surfaces can bring about orientational ordering different from those of bulk blue phases, including an intertwined complex of the polymer matrix and topological line defects of orientational order. Optical Kerr response of templated blue phases is explored, finding large Kerr constants in the range of K = 2-10 × 10(-9) m V(-2) and notable dependence on the surface anchoring strength. More generally, the presented numerical approach is aimed to clarify the role and actions of templating polymer matrices in complex chiral nematic fluids, and further to help design novel template-based materials from chiral liquid crystals. PMID:26412643

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

    Science.gov (United States)

    Balamurugan, A M; Sivasubramanian, A

    2014-01-01

    The optical burst switching (OBS) is an emergent result to the technology concern that could achieve a feasible network in future. They are endowed with the ability to meet the bandwidth requirement of those applications that require intensive bandwidth. There are more domains opening up in the OBS that evidently shows their advantages and their capability to face the future network traffic. However, the concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution, and quality of service (QoS). This paper deals with employing RC4 (stream cipher) to encrypt and decrypt bursts thereby ensuring the confidentiality of the burst. Although the use of AES algorithm has already been proposed for the same issue, by contrasting the two algorithms under the parameters of burst encryption and decryption time, end-to-end delay, it was found that RC4 provided better results. This paper looks to provide a better solution for the confidentiality of the burst in OBS networks. PMID:24578663

  6. 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.

  7. Concept for LEU Burst Reactor

    International Nuclear Information System (INIS)

    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.

  8. 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

  9. 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.

  10. Interference Resilience of Burst-by-burst Adaptive Modems

    OpenAIRE

    Torrance, J.M.; Hanzo, L.; Keller, T

    1997-01-01

    Adaptive modulation can achieve channel capacity gains by adapting t h e number of bits per transmission symbol on a burst-by-burst basis, in harmony with channel quality fluctuations. In this treatise their interference resilience is quantified and the modem mode switching levels are determined under interfered conditions. The associated performance curves are portrayed in Figures 6, 7 and 8 for target bit error rates of 1 and 0.01 %, respectively. The corresponding modem mode switching leve...

  11. Analysis of Burst Assembly Modeling for Optical Burst Switched Network

    Directory of Open Access Journals (Sweden)

    Bhumika Patel

    2013-11-01

    Full Text Available In this paper, we have study the current state of the technology, the Optical burst Switched (OBS network is the most practical in all-optical architecture. Here we define how Burst Assembly will carried out and also here in the network architecture each node is consist of Core router and Edge router. Moreover we define challenges faced at practical implementation of OBS and proposed its unique solution at the node as Delay model.

  12. 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.

  13. Horizontally shaken impact pendulums

    Science.gov (United States)

    Alexander, T. J.; Xu, Y.; Sidhu, H.

    2016-03-01

    We consider two pendulum masses attached to the same pivot point and which interact with each other through Hertzian impacts. We show that this splitting of the mass leads to an instability in the conservative case, in which initially synchronized large amplitude motion may evolve into out-of-phase (impacting) motion. We then study in detail the response of the impacting masses in the presence of damping and driving through horizontal shaking of the pivot point. We find that synchronized modes are usually accompanied by small amplitude quasi-periodic, or even chaotic, impacts and a number of multi-period solutions may appear in the bifurcation diagram. We reveal the existence and stability of a number of impact modes and scan the frequency response of the system to a series of initial conditions to identify which modes may be more easily generated in experiment.

  14. 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

  15. 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...

  16. 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.

  17. 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...

  18. Code blue: seizures.

    Science.gov (United States)

    Hoerth, Matthew T; Drazkowski, Joseph F; Noe, Katherine H; Sirven, Joseph I

    2011-06-01

    Eyewitnesses frequently perceive seizures as life threatening. If an event occurs on the hospital premises, a "code blue" can be called which consumes considerable resources. The purpose of this study was to determine the frequency and characteristics of code blue calls for seizures and seizure mimickers. A retrospective review of a code blue log from 2001 through 2008 identified 50 seizure-like events, representing 5.3% of all codes. Twenty-eight (54%) occurred in inpatients; the other 22 (44%) events involved visitors or employees on the hospital premises. Eighty-six percent of the events were epileptic seizures. Seizure mimickers, particularly psychogenic nonepileptic seizures, were more common in the nonhospitalized group. Only five (17.9%) inpatients had a known diagnosis of epilepsy, compared with 17 (77.3%) of the nonhospitalized patients. This retrospective survey provides insights into how code blues are called on hospitalized versus nonhospitalized patients for seizure-like events. PMID:21546315

  19. 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.

  20. 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...

  1. 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.

  2. Burst Suppression: A Review and New Insights

    OpenAIRE

    Jonathan Dillon Kenny; M. Brandon Westover; ShiNung Ching; Brown, Emery N.; Ken Solt

    2014-01-01

    Burst suppression is a pattern of brain electrical activity characterized by alternating periods of high-amplitude bursts and electrical silence. Burst suppression can arise from several different pathological conditions, as well as from general anesthesia. Here we review current algorithms that are used to quantify burst suppression, its various etiologies, and possible underlying mechanisms. We then review clinical applications of anesthetic-induced burst suppression. Finally, we report the...

  3. Mining Gamma-Ray Burst Data

    OpenAIRE

    Hakkila, Jon; Roiger, Richard J.; Haglin, David J.; Mallozzi, Robert S.; Pendleton, Geoffrey N.; Meegan, Charles A.

    2000-01-01

    Gamma-ray bursts provide what is probably one of the messiest of all astrophysical data sets. Burst class properties are indistinct, as overlapping characteristics of individual bursts are convolved with effects of instrumental and sampling biases. Despite these complexities, data mining techniques have allowed new insights to be made about gamma-ray burst data. We demonstrate how data mining techniques have simultaneously allowed us to learn about gamma-ray burst detectors and data collectio...

  4. DRILL BITS FOR HORIZONTAL WELLS

    OpenAIRE

    Paolo Macini

    1996-01-01

    This paper underlines the importance of the correct drill bit application in horizontal wells. Afler the analysis of the peculiarities of horizontal wells and drainholes drilling techniques, advantages and disadvantages of the application of both roller cone and fixed cutters drill bits have been discussed. Also, a review of the potential specific featuries useful for a correct drill bit selection in horizontal small diameter holes has been highlighted. Drill bits for these special applicatio...

  5. PRODUCTIVITY OF FRACTURED HORIZONTAL WELLS

    OpenAIRE

    2009-01-01

    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...

  6. Horizontal drilling in shallow reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Murray, W.F. Jr.; Schrider, L.A.; McCallister, J.V.; Mazza, R.L.

    1993-12-31

    Belden & Blake and the US DOE will cofund a horizontal well to be drilled in the Clinton Sandstone as part of the DOE`s multi well program titled ``Horizontal Drilling in Shallow Geologic Complex Reservoirs.`` This well will be located in Mahoning County, Ohio in an area which has demonstrated above average Clinton gas production. To the best of our knowledge, this will be the first horizontal well drilled to the Clinton Sand formation in Ohio. Since many of the remaining Clinton Sand drilling sites are of poorer reservoir quality, they may not be developed unless technology such as horizontal drilling can be successfully demonstrated.

  7. Inferring horizontal gene transfer.

    Directory of Open Access Journals (Sweden)

    Matt Ravenhall

    2015-05-01

    Full Text Available Horizontal or Lateral Gene Transfer (HGT or LGT is the transmission of portions of genomic DNA between organisms through a process decoupled from vertical inheritance. In the presence of HGT events, different fragments of the genome are the result of different evolutionary histories. This can therefore complicate the investigations of evolutionary relatedness of lineages and species. Also, as HGT can bring into genomes radically different genotypes from distant lineages, or even new genes bearing new functions, it is a major source of phenotypic innovation and a mechanism of niche adaptation. For example, of particular relevance to human health is the lateral transfer of antibiotic resistance and pathogenicity determinants, leading to the emergence of pathogenic lineages. Computational identification of HGT events relies upon the investigation of sequence composition or evolutionary history of genes. Sequence composition-based ("parametric" methods search for deviations from the genomic average, whereas evolutionary history-based ("phylogenetic" approaches identify genes whose evolutionary history significantly differs from that of the host species. The evaluation and benchmarking of HGT inference methods typically rely upon simulated genomes, for which the true history is known. On real data, different methods tend to infer different HGT events, and as a result it can be difficult to ascertain all but simple and clear-cut HGT events.

  8. 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

  9. Evaluation of Burst Loss Rate of an Optical Burst Switching (OBS) Network with Wavelength Conversion Capability

    OpenAIRE

    Reza, Md. Shamim; Hossain, Md. Maruf; Majumder, Satya Prasad

    2010-01-01

    This paper presents a new analytical model for calculating burst loss rate (BLR) in a slotted optical burst switched network. The analytical result leads to a framework which provides guidelines for optical burst switched networks. Wavelength converter is used for burst contention resolution. The effect of several design parameters such as burst arrival probability, wavelength conversion capability, number of slots per burst and number of wavelengths is incorporated on the above performance m...

  10. 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

  11. 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...

  12. 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...

  13. Radiochromic blue tetrazolium film dosimeter

    International Nuclear Information System (INIS)

    The colourless radiochromic chloride salt of blue tetrazolium (BT2+) is reduced radiolytically to the deep violet-coloured formazan. Dosimeter films of this radiation sensor can be produced by dissolving polyvinyl alcohol (PVA) in a heated aqueous solution of the salt, and, upon cooling, by casting the solution on a horizontal glass plate. In the present development, the resulting flexible transparent film is readily stripped from the plate, with a thickness of 0.045 mm. Upon irradiation with gamma rays or electron beams, a permanent image is produced with a broad absorption band in the visible spectrum. The radiation response is approximately a linear function in terms of the increase in optical absorbance (ΔA) measured at λmax 552 nm wavelength versus absorbed dose (D) over the range 5 to 50 kGy. The radiochromic image has a relatively high spatial resolution and can be used to register dose distributions and beam profiles. The value of ΔA shows a gradual increase for the first 24 hours after irradiation but is stable thereafter. The variation of response with irradiation temperature is negligible over the temperature range -20 deg. C to +30 deg. C, but displays a pronounced positive temperature dependence at higher temperatures. The response to gamma radiation shows negligible dose-rate dependence as long as the radiochromic sensor concentration in the PVA matrix is sufficiently high (> 6 % by weight). (author)

  14. 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...

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. Blue spectral inflation

    CERN Document Server

    Schunck, Franz E

    2008-01-01

    We reconsider the nonlinear second order Abel equation of Stewart and Lyth, which follows from a nonlinear second order slow-roll approximation. We find a new eigenvalue spectrum in the blue regime. Some of the discrete values of the spectral index n_s have consistent fits to the cumulative COBE data as well as to recent ground-base CMB experiments.

  2. 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

  3. Preemption window for burst differentiation in OBS

    OpenAIRE

    Klinkowski, Miroslaw; Careglio, Davide; Morató, Daniel; Solé Pareta, Josep

    2008-01-01

    This paper presents a novel control architecture for optical burst switching networks to efficiently apply burst preemption without the resources overbooking, which is specific to conventional OBS. Simulation results prove the effectiveness of this proposal.

  4. 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

  5. Periodicities in gamma ray bursts

    International Nuclear Information System (INIS)

    Gamma ray burst models based on magnetic neutron stars face a problem of account for the scarcity of observed periods. Both this scarcity and the typical period found when any is detected are explained if the neutron stars are accreting in binary systems

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

    OpenAIRE

    Abubakar Muhammad Umaru; Muhammad Shafie Abd Latiff; Yahaya Coulibaly

    2014-01-01

    The optical burst switching (OBS) paradigm is perceived as an intermediate switching technology for future all-optical networks. Burst assembly that is the first process in OBS is the focus of this paper. In this paper, an intelligent hybrid burst assembly algorithm that is based on fuzzy logic is proposed. The new algorithm is evaluated against the traditional hybrid burst assembly algorithm and the fuzzy adaptive threshold (FAT) burst assembly algorithm via simulation. Simulation results sh...

  7. Two-dimensional burst identification codes and their use in burst correction

    OpenAIRE

    1988-01-01

    A new class of codes, called burst identification codes, is defined and studied. These codes can be used to determine the patterns of burst errors. Two-dimensional burst correcting codes can be easily constructed from burst identification codes. The resulting class of codes is simple to implement and has lower redundancy than other comparable codes. The results are pertinent to the study of radiation effects on VLSI RAM chips, which can cause two-dimensional bursts of errors.

  8. 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

  9. 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 ...

  10. 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.

  11. 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 ...

  12. 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.

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

    OpenAIRE

    Balamurugan, A. M.; A. Sivasubramanian

    2014-01-01

    The optical burst switching (OBS) is an emergent result to the technology concern that could achieve a feasible network in future. They are endowed with the ability to meet the bandwidth requirement of those applications that require intensive bandwidth. There are more domains opening up in the OBS that evidently shows their advantages and their capability to face the future network traffic. However, the concept of OBS is still far from perfection facing issues in case of security threat. The...

  14. Bubbles and Monetary Policy: To Burst or not to Burst?

    OpenAIRE

    König, Philipp; POTHIER, David

    2015-01-01

    The question of whether monetary policy should target asset prices remains a contentious issue. Prior to the 2007/08 financial crisis, central banks opted for a wait-and-see approach, remaining passive during the build-up of asset price bubbles but actively seeking to stabilize prices and output after they burst. The macroeconomic and financial turbulence that followed the subprime housing bubble has led to a renewed debate concerning monetary policy’s role in maintaining financial stability....

  15. 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. PMID:27034844

  16. DRILL BITS FOR HORIZONTAL WELLS

    Directory of Open Access Journals (Sweden)

    Paolo Macini

    1996-12-01

    Full Text Available This paper underlines the importance of the correct drill bit application in horizontal wells. Afler the analysis of the peculiarities of horizontal wells and drainholes drilling techniques, advantages and disadvantages of the application of both roller cone and fixed cutters drill bits have been discussed. Also, a review of the potential specific featuries useful for a correct drill bit selection in horizontal small diameter holes has been highlighted. Drill bits for these special applications, whose importance is quickly increasing nowadays, should be characterised by a design capable to deliver a good penetration rate low WOB, and, at the same time, be able to withstand high RPM without premature cutting structure failure and undergauge. Formation properties will also determine the cutting structure type and the eventual specific features for additional gauge and shoulder protection.

  17. Pressure analysis for horizontal wells

    Energy Technology Data Exchange (ETDEWEB)

    Spivak, D.

    1988-01-01

    This study deals with the solution for pressure response of horizontal wells in three different anisotropic media: the infinite reservoir, the limited reservoir and the reservoir with constant pressure at the outer boundaries. Pressure analyses for vertical wells in various reservoirs are abundant, but there has been no comprehensive study of pressure analysis for horizontal wells in these three media. The objectives of this work are to examine and to determine the likely effects of horizontal wells on productivity and on the integration of pressure tests. The method of images, the concept of instantaneous sources and the Newman product method have been used. Integration of the summed source functions is achieved numerically using Simpson's rule. All three solutions are semi-analytical and have been verified and validated. For the infinite reservoir the solution has been compared to a directional well of high angle, and long horizontal well responses have been compared to the solution for the uniform-flux vertical fracture. The solutions to the other two cases (for long horizontal wells) have been compared to published solutions for uniform-flux vertical fractures. New equations, new pseudo-skin factors, new type curves, and new shape factors have been generated in the course of this work. The log-log type curves can be used to determine reservoir characteristics. The influences of different well and reservoir parameters on the well productivity have been investigated and are presented to show the merits of horizontal wells. A major features of this study is that some portions are presented here for the first time.

  18. 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.

  19. 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...

  20. Our Blue Gene Experience

    Czech Academy of Sciences Publication Activity Database

    Jakl, Ondřej; Starý, Jiří

    Ostrava : Ústav geoniky AV ČR, 2009 - (Blaheta, R.; Starý, J.), s. 50-54 ISBN 978-80-86407-60-9. [SNA '09 - Seminar on numerical analysis: modelling and simulation of challenging engineering problems. Ostrava (CZ), 02.02.2009-06.02.2009] R&D Projects: GA ČR(CZ) GA105/09/1830 Institutional research plan: CEZ:AV0Z30860518 Keywords : IBM Blue Gene/P * finite element solver * parallel scalability Subject RIV: BA - General Mathematics

  1. 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...

  2. 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

  3. 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

  4. 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.

  5. 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.

  6. Blue tits are ultraviolet tits

    OpenAIRE

    Hunt, S; Bennett, A.T.D.; Cuthill, I. C.; Griffiths, R.

    1998-01-01

    The blue tit (Parus caeruleus) has been classified as sexually monochromatic. This classification is based on human colour perception yet, unlike humans, most birds have four spectrally distinct classes of cone and are visually sensitive to wavelengths in the near-ultraviolet (300 to 400 nm). Reflectance spectrophotometry reveals that blue tit plumage shows considerable reflection of UV light. For example, the blue crest shows peak reflectance at wavelengths around 352 nm. Furthermore, the bl...

  7. Postpartum Blues and Postpartum Depression

    OpenAIRE

    Erdem Ö et al.

    2009-01-01

    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...

  8. 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.

  9. Ballerina - pirouettes in search of gamma bursts

    DEFF Research Database (Denmark)

    Brandt, Søren Kristian; Lund, Niels; Pedersen, Henrik; Hjorth, J.

    1999-01-01

    The cosmological origin of gamma ray bursts has now been established with reasonable certainty, Many more bursts will need to be studied to establish the typical distance scale, and to map out the large diversity in properties which have been indicated by the first handful of events. We are...... proposing Ballerina, a small satellite to provide accurate positions and new data on the gamma-ray bursts. We anticipate a detection rate an order of magnitude larger than obtained from Beppo-SAX....

  10. 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.

  11. 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

  12. Burst Fragmentation Model Based on Sequential Burst Allocation Algorithm for Mobile WiMAX

    OpenAIRE

    Zaid G. Ali; Prof. R. B. Ahmad; Dr. Abid Yahya

    2013-01-01

    the downlink Bandwidth resources of WiMAX are allocated by the burst allocation algorithm. The algorithm is responsible for calculating the appropriate location of a number of the smallest unit of bandwidth which is called the slot for all users within the downlink subframe in the form of bursts. Resource wastage in the form of unused and unallocated slots is a real common problem accompanies resource management in the burst allocation algorithms. This paper investigates the Sequential Burst ...

  13. Fast radio burst/gamma-ray burst cosmography

    International Nuclear Information System (INIS)

    Recently, both theoretical arguments and observational evidence suggested that a small fraction of fast radio bursts (FRBs) could be associated with gamma-ray bursts (GRBs). If such FRB/GRB association systems are commonly detected in the future, the combination of dispersion measures (DM) derived from FRBs and redshifts derived from GRBs makes these systems a plausible tool to conduct cosmography. We quantify uncertainties in deriving the redshift-dependent DMIGM as a function of z and test how well dark energy models can be constrained with Monte Carlo simulations. We show that with several tens of FRB/GRB systems potentially detected in a decade or so, one may reach reasonable constraints on wCDM models. When combined with Type Ia supernova (SN Ia) data, unprecedented constraints on the dark energy equation of state may be achieved, thanks to the prospects of detecting FRB/GRB systems at relatively high redshifts. The ratio between the mean value and luminosity distance (D L(z)) is insensitive to dark energy models. This gives the prospect of applying SN Ia data to calibrate using a relatively small sample of FRB/GRB systems, allowing a reliable constraint on the baryon inhomogeneity distribution as a function of redshift. The methodology developed in this paper can also be applied if the FRB redshifts can be measured by other means. Some caveats of putting this method into practice are also discussed.

  14. 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.

  15. 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

  16. 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...

  17. Horizontal gene transfer in plants.

    Science.gov (United States)

    Gao, Caihua; Ren, Xiaodong; Mason, Annaliese S; Liu, Honglei; Xiao, Meili; Li, Jiana; Fu, Donghui

    2014-03-01

    Horizontal gene transfer (HGT) describes the transmission of genetic material across species boundaries. HGT often occurs in microbic and eukaryotic genomes. However, the pathways by which HGTs occur in multicellular eukaryotes, especially in plants, are not well understood. We systematically summarized more than ten possible pathways for HGT. The intimate contact which frequently occurs in parasitism, symbiosis, pathogen, epiphyte, entophyte, and grafting interactions could promote HGTs between two species. Besides these direct transfer methods, genes can be exchanged with a vector as a bridge: possible vectors include pollen, fungi, bacteria, viruses, viroids, plasmids, transposons, and insects. HGT, especially when involving horizontal transfer of transposable elements, is recognized as a significant force propelling genomic variation and biological innovation, playing an important functional and evolutionary role in both eukaryotic and prokaryotic genomes. We proposed possible mechanisms by which HGTs can occur, which is useful in understanding the genetic information exchange among distant species or distant cellular components. PMID:24132513

  18. Horizontal gene transfer in fungi

    OpenAIRE

    Fitzpatrick, David A.

    2011-01-01

    Horizontal gene transfer (HGT) is frequently observed in prokaryotes and until recently was assumed to be of limited importance to eukaryotes. However, there is an increasing body of evidence to suggest that HGT is an important mechanism in eukaryotic genome evolution, particularly in unicellular organisms. The transfer of individual genes, gene clusters or entire chromosomes can have significant impacts on niche specification, disease emergence or shift in metabolic capabil...

  19. 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...

  20. 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...

  1. 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.

  2. Real burst traffic amplification in optically gain clamped amplifier

    OpenAIRE

    Ennser, Karin; Taccheo, Stefano; Careglio, Davide; Solé Pareta, Josep; Aracil Rico, Javier

    2008-01-01

    Optical burst amplification in a gain-stabilized amplifier is theoretically investigated using real burst traffic data. The results show that excellent performance are obtained for WDM transmission with negligible interplay due to burst arrival statistics.

  3. Cost-based burst dropping strategy in optical burst switching networks

    OpenAIRE

    Klusek, Bartlomiej; Murphy, John; Barry, Liam P.

    2005-01-01

    Optical burst switching (OBS) is a new paradigm for future all-optical networks. Intentional burst dropping is one of techniques used to achieve desired quality of service. In this paper we note that some bursts are more likely to cause contention. We propose a cost function that can be used to predict the likelihood that a given burst will interfere with other traffic, then we explain how, by using this information a new burst dropping strategy can be designed. We compare our method with a r...

  4. Coding Bounds for Multiple Phased-Burst Correction and Single Burst Correction Codes

    OpenAIRE

    Fong, Wai Han

    2011-01-01

    In this paper, two upper bounds on the achievable code rate of linear block codes for multiple phased-burst correction (MPBC) are presented. One bound is constrained to a maximum correctable cyclic burst length within every subblock, or equivalently a constraint on the minimum error free length or gap within every phased-burst. This bound, when reduced to the special case of a bound for single burst correction (SBC), is shown to be the Abramson bound when the cyclic burst length is less than ...

  5. 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

  6. CT Burst Error Weight Enumerator of Array Codes

    OpenAIRE

    Irfan Siap

    2008-01-01

    Recently, CT burst errors originally dened for block codes havebeen generalized to CT burst errors for array codes [6]. In order to establish aRieger's type bound for array codes with respect to CT burst errors. Here, weintroduce a CT burst error weight enumerator whose coecients represent thenumber of CT burst errors of a particular weight. The method of obtainingthe CT burst error weight enumerator is obtained by generating function likeapproach and it does not involve solving equations as ...

  7. 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.

  8. 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

  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. Horizontal well length optimization considering wellbore hydraulics

    OpenAIRE

    Syed, Adnan

    2014-01-01

    Horizontal wells covering entire length of the reservoirs are not economically suitable. Frictional pressure drops increases with the increase in well length and flow rates. Optimal Horizontal length is estimated through economic analysis i.e. Net present Value of the project (NPV). Well construction costs including incremental costs of drilling horizontal section, friction losses in horizontal section, Hydrocarbon prices and Drainage area affect NPV. This thesis work estimates NPV and Produc...

  11. Horizontal branch morphology in galactic globular clusters dense environment is "a" second parameter

    CERN Document Server

    Buonanno, R; Bellazzini, M; Ferraro, F R; Pecci, F F

    1996-01-01

    The Horizontal Branch (HB) morphology in the color -- magnitude diagram of the Galactic globular clusters depends on many factors, and it is now firmly established that the so-called Second Parameter is not just the cluster age as claimed for several years. As a part of a wider program devoted to the search for the physical processes driving the Horizontal Branch Morphology, we re-address here the problem of the extension of blue HB tails by introducing a new quantitative observable, B2/B+R+V where B2={Number of HB stars with (B-V)_0<-0.02}. We demonstrate that the environmental conditions within a cluster clearly affect its HB morphology, in the sense that, in general, the higher the cluster central density the higher is the relative number of stars populating the most blue region of its HB.

  12. 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.

  13. 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

  14. Fast Luminous Blue Transients from Newborn Black Holes

    CERN Document Server

    Kashiyama, Kazumi

    2015-01-01

    Newborn black holes in collapsing massive stars can be accompanied by a fallback disk. The accretion rate is typically super-Eddington and strong disk outflows are expected. Such outflows could be directly observed in some failed explosions of compact (blue supergiants or Wolf-Rayet stars) progenitors, and may be more common than long-duration gamma-ray bursts. Using an analytical model, we show that the fallback disk outflows produce blue UV-optical transients with a peak bolometric luminosity of ~10^(42-43) erg s^-1 (peak R-band absolute AB magnitudes of -16 to -18) and an emission duration of ~ a few to ~ 10 days. The spectra are likely dominated intermediate mass elements, but will lack much radioactive nuclei and iron-group elements. The above properties are broadly consistent with some of the rapid blue transients detected by Pan-STARRS and PTF. This scenario can be distinguished from alternative models using radio observations within a few years after the optical peak.

  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. 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

  17. 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.

  18. 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

  19. 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.)

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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...

  7. 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.

  8. 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.

  9. 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...

  10. 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.

  11. 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...

  12. 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.

  13. Burst suppression probability algorithms: state-space methods for tracking EEG burst suppression

    OpenAIRE

    Chemali, Jessica; Ching, ShiNung; Purdon, Patrick L; Solt, Ken; Brown, Emery N.

    2013-01-01

    Objective. Burst suppression is an electroencephalogram pattern in which bursts of electrical activity alternate with an isoelectric state. This pattern is commonly seen in states of severely reduced brain activity such as profound general anesthesia, anoxic brain injuries, hypothermia and certain developmental disorders. Devising accurate, reliable ways to quantify burst suppression is an important clinical and research problem. Although thresholding and segmentation algorithms readily ident...

  14. 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%.

  15. Directivity of low-frequency solar type 3 radio bursts

    International Nuclear Information System (INIS)

    The occurrence rate of type 3 solar bursts in the frequency range 4.9 MHz to 30 kHz was analyzed as a function of burst intensity and burst arrival direction. Results show that the occurrence rate of bursts falls off with increasing flux and the distribution of burst arrival directions at each frequency shows a significantly larger number of bursts observed west of the earth--sun line than east of it. This western excess in occurrence rate appears to be correlated with the direction of the average interplanetary magnetic field, and is interpreted as beaming of the observed burst radiation along the magnetic field direction

  16. 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...

  17. Relativistic effects in gamma-ray bursts

    International Nuclear Information System (INIS)

    According to recent models of the sources of gamma-ray bursts the extremely energetic emission is caused by shells expanding with ultrarelativistic velocity. With the recent identification of optical sources at the positions of some gamma-ray bursts these ''fireball'' models have acquired an actuality that invites to use them as a motivating application when teaching special relativity. We demonstrate several relativistic effects associated with these models which are very pronounced due to the great velocity of the shell. For example a burst lasting for a month in the rest frame of an element of the shell lasts for a few seconds only, in the rest frame of our detector. It is shown how the observed properties of a burst are modified by aberration and the Doppler effect. The apparent luminosity as a function of time is calculated. Modifications due to the motion of the star away from the observer are calculated. (Author)

  18. 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.

  19. 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.

  20. Burst Fragmentation Model Based on Sequential Burst Allocation Algorithm for Mobile WiMAX

    Directory of Open Access Journals (Sweden)

    Zaid G. Ali

    2013-07-01

    Full Text Available the downlink Bandwidth resources of WiMAX are allocated by the burst allocation algorithm. The algorithm is responsible for calculating the appropriate location of a number of the smallest unit of bandwidth which is called the slot for all users within the downlink subframe in the form of bursts. Resource wastage in the form of unused and unallocated slots is a real common problem accompanies resource management in the burst allocation algorithms. This paper investigates the Sequential Burst Allocation (SBA that based on sequential slot allocation and burst fragmentation. An analytical model of frame utilization has been derived. Moreover, this paper presents criteria of burst fragmentation and investigates the effect of burst fragmentation to the allocation efficiency. It has been observed from the results that the SBA algorithm outperforms the Standard (ST algorithm in term of number of users and resource wastage reduction per frame. The research results illustrates that burst fragmentation can enhance the proportion of frame utilization with minor effect to the overhead size. As well as, the results are useful to be a heuristic guide line for MAC layer scheduler to decide the best burst size that can be used.

  1. 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.

  2. A Burst-by-Burst Adaptive Joint-Detection Based CDMA Speech Transceiver

    OpenAIRE

    How, HT; Liew, TH; Kuan, EL; Hanzo, L.

    2001-01-01

    A burst-by-burst adaptive speech transceiver is proposed, which can drop its source coding rate and speech quality under transceiver control in order to invoke a more error resilient modem mode amongst less favourable channel conditions. The novel, high-quality, Adaptive Multi-Rate (AMR) speech codec [5], operated at bit rates of 4.75 and 10.2 kbps and combined with sourcesensitivity-matched Redundant Residue Number Systems (RRNS) based channel codes. Burst-by-burst adaptive Joint-Detection b...

  3. 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

  4. 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.

  5. 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%.

  6. 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.

  7. 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...

  8. 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%.

  9. 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...

  10. 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...

  11. Meteor burst communications improvement study

    Science.gov (United States)

    Peterson, David

    1993-07-01

    Two identical Meteor Burst Radio Terminals were developed, fabricated, and delivered to the Air Force. Each is controlled by a PC computer in a menu driven manner. The mode of operation is full duplex. The RF frequency range is 40 to 60 MHz with tuning increments of 25 KHz. Data rates are 4, 8, 16, 32, 64, 128, 256, and 512 kbps. Modulation is coherent Binary Phase Shift Keying (BPSK) and incoherent Differential Phase Shift Keying (DPSK). Protocol includes Automatic Repeat Request (ARQ) with source and destination addressing, message number, start of message, and end of message. Messages are packetized, and Reed Solomon (R-S) coding is an option. The ARQ is under the control of a Cyclic Redundancy Check Code (CRCC) which detects binary errors within each packet. The terminal is intended to increase meteor trail availability and data throughput by several orders of magnitude--by operating with new antennas that provide much higher gains without sacrificing meteor trail acquisition performance.

  12. Propofol and sevoflurane induce distinct burst suppression patterns in rats

    OpenAIRE

    Kenny, Jonathan D.; Westover, M. Brandon; Ching, ShiNung; Brown, Emery N.; Solt, Ken

    2014-01-01

    Burst suppression is an EEG pattern characterized by alternating periods of high-amplitude activity (bursts) and relatively low amplitude activity (suppressions). Burst suppression can arise from several different pathological conditions, as well as from general anesthesia. Here we review current algorithms that are used to quantify burst suppression, its various etiologies, and possible underlying mechanisms. We then review clinical applications of anesthetic-induced burst suppression. Final...

  13. 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?

  14. Blue Stragglers: Spectra of Globular Clusters

    Science.gov (United States)

    Cenarro, A. J.; Cervantes, J. L.; Beasley, M. A.; Marin-Franch, A.; Vazdekis, A.

    2010-04-01

    The integrated Balmer lines of unresolved stellar systems have been widely used as age indicators, since they are sensitive to the temperature of the main sequence turn-off. However, the existence of “non-canonical” stellar stages such as hot horizontal branch stars and blue straggler stars (BSSs) can lead to underestimations of the true stellar population ages. Using an optimized Hβ index in conjunction with HST/WFPC2 color-magnitude diagrams (CMDs), we find that Galactic globular clusters of similar metallicity exhibit a large scatter in their Hβ strengths, which does not correlate with their CMD-derived ages. Instead, we demonstrate that the specific frequency of BSSs is responsible for the observed Hβ scatter at intermediate-to-high metallicity, in the sense that, at fixed metallicity, higher BSS ratios lead to larger integrated Hβ strengths. Therefore, the specific frequency of BSSs sets a fundamental limit on the accuracy for which integrated spectroscopic ages can be determined for globular clusters and, probably, other stellar systems like galaxies. The observational implications of this result are discussed.

  15. 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.

  16. Convergence substitution for paralysed horizontal gaze.

    OpenAIRE

    Beigi, B.; O'Keeffe, M; Logan, P; Eustace, P.

    1995-01-01

    Three patients with paralysed horizontal gaze are presented. Involuntary use of convergence to assist horizontal gaze was noted as a late feature. All patients showed (1) unilateral or bilateral horizontal gaze palsy (two patients had one and a half syndrome, the other had bilateral nuclear sixth nerve palsies), (2) adduction of both eyes on attempted gaze into the paralysed field, (3) miosis which coincided with adduction. Convergence substitution should be considered in the differential dia...

  17. 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 ...

  18. 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.

  19. Methylene blue related sterile endophthalmitis.

    Science.gov (United States)

    Lim, A K E; Ulagantheran V, V; Siow, Y C; Lim, K S

    2008-08-01

    To report a case of methylene blue related endophthalmitis. Observational case report. Review of clinical record, photographs. A 60 year old man developed endophthalmitis after methylene blue was accidentally used to stain the anterior capsule during phacoemulsification of cataract. His left visual acuity deteriorated from 6/12 to 6/36 two weeks after the operation. Despite intensive treatment with topical and intravitreal antibiotics, his condition deteriorated. A vitrectomy and silicone oil injection eventually managed to control the progression of the disease and salvage the eye. However the visual outcome remained poor due to corneal decompensation and retinal ischemia. Both vitreous tap and vitreous biopsy were negative for any organism. Methylene blue is extremely toxic to ocular structures and should not be used intraocularly. PMID:19248701

  20. 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.

  1. 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

  2. A biomechanical study on burst mechanisms of plant fruit: stress analysis of pericarps before bursting.

    Science.gov (United States)

    Endo, Yasuhiro; Sakamoto, Jiro; Kashiwano, Yuki; Yokota, Hideo; Nakamura, Sakiko; Kinoshita, Eichiro

    2010-10-01

    Bursting of fruit is a very interesting biomechanical phenomenon because its mechanism is directly related to the plant's reproduction. A plant that produces fruit that bursts powerfully and spreads the seeds widely has the advantage of reproduction without relying on other mechanisms such as transportation of fruit by insects. The structures of many types of fruit have likely been optimized by evolution, although the structure itself appears rather simplistic. Strain energy is stored in each pericarp because of growth deformation, swelling or desiccation just before bursting. Throughout these changes, the mechanical stress of the pericarps is at equilibrium. At the instant of bursting, the stored strain energy is released very rapidly. Quick and wide motion of the pericarps in a certain direction is advantageous for throwing the seed a long distance. The motion and deformation of bursting pericarps depend on their tissue structure and mechanical stress condition just before the burst. We tracked the bursting motion by using a high-speed camera. Then we calculated the pre-burst stress generated in a pericarp of Impatiens by using the finite-element method. The boundary condition obtained by experiments using a high-speed video camera is given, and the stress was calculated using reverse deformation analysis. The stress distribution of the pericarp is effective in causing the pericarp motion to throw the seeds far away. PMID:20696416

  3. The Cosmic Gamma-Ray Bursts

    Science.gov (United States)

    Djorgovski, S. G.; Frail, D. A.; Kulkarni, S. R.; Sari, R.; Bloom, J. S.; Galama, T. J.; Harrison, F. A.; Price, P. A.; Fox, D.; Reichart, D. E.; Yost, S.; Berger, E.; Diercks, A.; Goodrich, R.; Chaffee, F.

    2002-12-01

    Cosmic γ-ray bursts are one of the great frontiers of astrophysics today. They are a playground of relativists and observers alike. They may teach us about the death of stars and the birth of black holes, the physics in extreme conditions, and help us probe star formation in the distant and obscured universe. In this review we summarise some of the remarkable progress in this field over the past few years. While the nature of the GRB progenitors is still unsettled, it now appears likely that at least some bursts originate in explosions of very massive stars, or at least occur in or near the regions of massive star formation. The physics of the burst afterglows is reasonably well understood, and has been tested and confirmed very well by the observations. Bursts are found to be beamed, but with a broad range of jet opening angles; the mean γ-ray energies after the beaming corrections are ~ 1051 erg. Bursts are associated with faint ( ~ 25 mag) galaxies at cosmological redshifts, with ~ 1. The host galaxies span a range of luminosities and morphologies, but appear to be broadly typical for the normal, actively star-forming galaxy populations at comparable redshifts and magnitudes. Some of the challenges for the future include: the nature of the short bursts and possibly other types of bursts and transients; use of GRBs to probe the obscured star formation in the universe, and possibly as probes of the very early universe; and their detection as sources of high-energy particles and gravitational waves.

  4. 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

  5. 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.

  6. 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))

  7. 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.

  8. Horizontal drilling assessment in Western Canada

    International Nuclear Information System (INIS)

    The first horizontal well was drilled in Saskatchewan in 1987. Since then, the number of horizontal wells drilled has escalated rapidly, averaging approximately 500 per year since 1993. When combined with horizontal wells drilled in Alberta, the major Canadian oil-producing province, the total number drilled in 1995 was 978. This total exceeds the National Energy Board (NEB) projected maximum of 816 wells per year. The NEB projections were based on a break-even point for the drilling of horizontal wells of a return of CDN $285,000 using a discount rate of 15%. This corresponded to a cumulative production from each individual well of some 11,000 m3. The introduction of a royalty-free production volume of 12,000 m3 per horizontal well in Saskatchewan was instrumental in stimulating the rapid expansion in the use of horizontal wells and helping Canada to exceed the forecasted drilling level. Within Saskatchewan, daily production from 1964 active horizontal wells is in excess of 20,000 m3. Comparative analysis indicates that the average daily production per well has increased from approximately by 40% with the advent of horizontal wells. In total production terms, provincial production has increased from 11.7 million cubic metres in 1989 to 20.9 million m3 in 1996. This represents an increase of almost 79% based primarily on the extensive use of horizontal wells. In 1996, horizontal wells produced 36% of the province's oil from 12% of the active wells. In the southeastern producing areas of Saskatchewan, the Williston Basin, declining oil-production has jumped 100%, with horizontal wells accounting for approximately 50% of total regional production. Pay zones in this areas, as in most of the province, tend to be relatively thin, with net pay frequently less that 5 m. The modest investment of some CDN $5 million in government research funding 10 years ago to stimulate the development of horizontal wells, combined with a favourable royalty structure, has been at least

  9. 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.

  10. 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...

  11. The Fermi Gamma-Ray Burst Monitor

    CERN Document Server

    Meegan, Charles; Bhat, P N; Bissaldi, Elisabetta; Briggs, Michael S; Connaughton, Valerie; Diehl, Roland; Fishman, Gerald; Greiner, Jochen; Hoover, Andrew S; van der Horst, Alexander J; von Kienlin, Andreas; Kippen, R Marc; Kouveliotou, Chryssa; McBreen, Sheila; Paciesas, W S; Preece, Robert; Steinle, Helmut; Wallace, Mark S; Wilson, Robert B; Wilson-Hodge, Colleen

    2009-01-01

    The Gamma-Ray Burst Monitor (GBM) will significantly augment the science return from the Fermi Observatory in the study of Gamma-Ray Bursts (GRBs). The primary objective of GBM is to extend the energy range over which bursts are observed downward from the energy range of the Large Area Telescope (LAT) on Fermi into the hard X-ray range where extensive previous data exist. A secondary objective is to compute burst locations on-board to allow re-orientiong the spacecraft so that the LAT can observe delayed emission from bright bursts. GBM uses an array of twelve sodium iodide scintillators and two bismuth germanate scintillators to detect gamma rays from ~8 keV to ~40 MeV over the full unocculted sky. The on-board trigger threshold is ~0.7 photons/cm2/s (50-300 keV, 1 s peak). GBM generates on-board triggers for ~250 GRBs per year.

  12. Swift: A Gamma Ray Bursts Explorer

    Science.gov (United States)

    Gehrels, Neil

    2003-01-01

    Swift is a NASA gamma-ray burst MIDEX mission that is in development for launch in December 2003. It is a multiwavelength transient observatory for GRB astronomy. The goals of the mission are to determine the origin of GRBs and their afterglows and use bursts to probe the early Universe. It will also.perform a survey of the hard X-ray sky to a sensitivity level of -1 mCrab. A wide-field camera will detect more than a hundred GRBs per year to 5 times fainter than BATSE. Sensitive narrow-field X-ray and UV/optical telescopes will be pointed at the burst location in 20 to 70 sec by an autonomously controlled 'swift' spacecraft. For each burst, arcsec positions will be determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Measurements of redshift will be made for many of the bursts. The instrumentation is a combination of superb existing flight-spare hardware and design from XMM and Spectrum-X/JET-X contributed by collaborators in the UK and Italy and development of a coded-aperture camera with a large-area (approximately 0.5 square meter) CdZnTe detector array. The hardware is currently in final stages of fabrication and initial stages of integration and test. Key components of the mission are vigorous follow-up and outreach programs to engage the astronomical community and public in Swift.

  13. The Cosmic Gamma-Ray Bursts

    CERN Document Server

    Djorgovski, S G; Kulkarni, S R; Sari, R; Bloom, J S; Galama, T J; Harrison, F A; Price, P A; Fox, D; Reichart, D; Yost, S; Berger, E; Diercks, A H; Goodrich, R; Chaffee, F H

    2001-01-01

    Cosmic gamma-ray bursts are one of the great frontiers of astrophysics today. They are a playground of relativists and observers alike. They may teach us about the death of stars and the birth of black holes, the physics in extreme conditions, and help us probe star formation in the distant and obscured universe. In this review we summarise some of the remarkable progress in this field over the past few years. While the nature of the GRB progenitors is still unsettled, it now appears likely that at least some bursts originate in explosions of very massive stars, or at least occur in or near the regions of massive star formation. The physics of the burst afterglows is reasonably well understood, and has been tested and confirmed very well by the observations. Bursts are found to be beamed, but with a broad range of jet opening angles; the mean gamma-ray energies after the beaming corrections are ~ 10^51 erg. Bursts are associated with faint ~ 25 mag) galaxies at cosmological redshifts, with ~ 1. The host gal...

  14. 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.

  15. X-ray bursts observed with JEM-X

    DEFF Research Database (Denmark)

    Brandt, Søren Kristian; Chenevez, Jérôme; Lund, Niels; Budtz-Jørgensen, Carl; Westergaard, Niels Jørgen Stenfeldt

    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....

  16. 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....

  17. 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.

  18. 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...

  19. 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.

  20. 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...

  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. High sensitivity neutron bursts detecting system

    International Nuclear Information System (INIS)

    Technique and instrumentation to detect multiplicity of fast neutrons, emitted in sharp bursts, has been developed. A bank of 16 BF3 detectors, in an appropriate thermalising assembly, efficiency ∼ 16%, is used to detect neutron bursts. The output from this setup, through appropriate electronics, is divided into two paths. The first is directly connected to a computer controlled scalar. The second is connected to another similar scalar through a delay time unit (DTU). The DTU design is such that once it is triggered by a count pulse than it does not allow any counts to be recorded for a fixed dead time set at ∼ 100 μs. The difference in counts recorded directly and through DTU gives the total number of neutrons produced in bursts. This setup is being used to study lattice cracking, anomalous effects in solid deuterium systems and various reactor physics experiments. (author). 3 refs., 1 fig

  3. 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.

  4. Unveiling the Secrets of Gamma Ray Bursts

    CERN Document Server

    Gomboc, A

    2012-01-01

    Gamma Ray Bursts (GRBs) are unpredictable and brief flashes of gamma rays that occur about once a day in random locations in the sky. Since gamma rays do not penetrate the Earth's atmosphere, they are detected by satellites, which automatically trigger ground-based telescopes for follow-up observations at longer wavelengths. In this introduction to Gamma Ray Bursts we review how building a multi-wavelength picture of these events has revealed that they are the most energetic explosions since the Big Bang and are connected with stellar deaths in other galaxies. However, in spite of exceptional observational and theoretical progress in the last 15 years, recent observations raise many questions which challenge our understanding of these elusive phenomena. Gamma Ray Bursts therefore remain one of the hottest topics in modern astrophysics.

  5. 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...

  6. Bursting activity spreading through asymmetric interactions

    CERN Document Server

    Onaga, Tomokatsu

    2014-01-01

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

  7. Localised Microwave Bursts During ELMs on MAST

    Directory of Open Access Journals (Sweden)

    Freethy Simon

    2015-01-01

    Full Text Available Bursts of microwave emission are observed during ELM events on the Mega Ampère Spherical Tokamak. In agreement with observations on other machines, these bursts are up to 3 orders of magnitude more intense than the thermal background, but are electron cyclotron in nature. The peak in microwave emission is ~20μ before the peak in midplane Dα emission. Using the Synthetic Aperture Microwave Imaging radiometer, we are able to demonstrate that these bursts are often highly spatially localised and preferentially occur at the tokamak midplane. It is hypothesised that the localisation is a result of Doppler resonance broadening for electron Bernstein waves and the high perpendicular electron energies could be the result of pitch angle scattering in high collisionality regions of the plasma.

  8. 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...

  9. Gamma-ray burst polarimeter (GAP)

    International Nuclear Information System (INIS)

    The gamma-ray burst polarimeter (GAP: GAmma-ray burst Polarimeter), which had been almost handcrafted by scientists, has succeeded in working normally in interplanetary space, and in detecting the polarization of the gamma-ray from a mysterious astronomical object 'gamma-ray burst'. It is the first result of the detectors in the world exclusively aiming at detecting gamma-ray polarization. We mainly describe the hardware of our GAP equipment and show the method of preparing equipment to work in the cosmic space with a tight budget. The mechanical structure, the electronic circuits, the software on the equipment, the data analysis on the earth, and the scientific results gained by the observation just over one year, are presented after explaining the principle of gamma-ray polarization detection. Our design to protect equipment against mechanical shock and cosmic radiation may provide useful information for future preparation of compact satellite. (J.P.N.)

  10. 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...

  11. 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.

  12. 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.

  13. Burst investigation on zircaloy-4 claddings in inert environment

    International Nuclear Information System (INIS)

    Highlights: • Burst investigations on zircaloy-4 cladding in argon environment. • Clad wall displacement measurement. • Effect of internal overpressure and heating rate on burst parameters. • Semi-empirical correlation for burst stress has been proposed. - Abstract: An extensive burst investigation has been carried out on the zircaloy-4 claddings in an inert environment to simulate clad burst during a postulated loss-of-coolant-accident (LOCA) conditions. The parameters varied during the burst experiments were heating rate and internal overpressure. The temperature, internal overpressure and ballooning data were monitored online and recorded during the heating process of burst specimen. In addition, post-experiment measurements were also conducted on the burst specimen to determine various burst parameters–burst strains and burst stress. A semi-empirical correlation was developed to predict the burst stress for a given burst temperature. A reasonable agreement between the predicted and experimental data has been observed. The proposed correlation was also compared with available established correlation for steam environment

  14. Bursting Smoke as an Infrared Countermeasure

    Directory of Open Access Journals (Sweden)

    Amarjit Singh

    1998-07-01

    Full Text Available This paper describes the experimental setup for the evaluation of bursting smoke for anti-infrared role using SR-5000 spectroradiometer and a source of IR radiation (8-13 micrometer using cadmium-mercury-telluride (CMI detector cooled by liquid nitrogen. The particle size and shape of the powders used in the bursting smokes were determined microscopically using Carl Zeiss Jena Neophot- 21. Highest attenuation of 97 -lOO percent was produced for about 12 s using a mixture of bronze flakes and chaff, and for about 8 s using a mixture of bronze copper lined flakes, bronze flakes and chaff.

  15. 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.)

  16. 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

  17. 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.

  18. Spike Bursts from an Excitable Optical System

    Science.gov (United States)

    Rios Leite, Jose R.; Rosero, Edison J.; Barbosa, Wendson A. S.; Tredicce, Jorge R.

    Diode Lasers with double optical feedback are shown to present power drop spikes with statistical distribution controllable by the ratio of the two feedback times. The average time between spikes and the variance within long time series are studied. The system is shown to be excitable and present bursting of spikes created with specific feedback time ratios and strength. A rate equation model, extending the Lang-Kobayashi single feedback for semiconductor lasers proves to match the experimental observations. Potential applications to construct network to mimic neural systems having controlled bursting properties in each unit will be discussed. Brazilian Agency CNPQ.

  19. 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.

  20. 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.

  1. 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...

  2. 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.

  3. 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 ...

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Statistical properties of SGR 1806-20 bursts

    CERN Document Server

    Gogus, E; Kouveliotou, C; Van Paradijs, J; Briggs, M S; Duncan, R C; Thompson, C; Gogus, Ersin; Woods, Peter M.; Kouveliotou, Chryssa; Paradijs, Jan van; Briggs, Michael S.; Duncan, Robert C.; Thompson, Christopher

    2000-01-01

    We present statistics of SGR 1806-20 bursts, combining 290 events detectedwith RXTE/PCA, 111 events detected with BATSE and 134 events detected with ICE.We find that the fluence distribution of bursts observed with each instrumentare well described by power laws with indices 1.43, 1.76 and 1.67,respectively. The distribution of time intervals between successive bursts fromSGR 1806-20 is described by a lognormal function with a peak at 103 s. There isno correlation between the burst intensity and either the waiting times tillthe next burst or the time elapsed since the previous burst. In all thesestatistical properties, SGR 1806-20 bursts resemble a self-organized criticalsystem, similar to earthquakes and solar flares. Our results thus support thehypothesis that the energy source for SGR bursts is crustquakes due to theevolving, strong magnetic field of the neutron star, rather than any accretionor nuclear power.

  9. 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.

  10. 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.

  11. 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.

  12. IPN localizations of Konus short gamma-ray bursts

    CERN Document Server

    Pal'shin, V D; Svinkin, D S; Aptekar, R L; Golenetskii, S V; Frederiks, D D; Mazets, E P; Oleynik, P P; Ulanov, M V; Cline, T; Mitrofanov, I G; Golovin, D V; Kozyrev, A S; Litvak, M L; Sanin, A B; Boynton, W; Fellows, C; Harshman, K; Trombka, J; McClanahan, T; Starr, R; Goldsten, J; Gold, R; Rau, A; von Kienlin, A; Savchenko, V; Smith, D M; Hajdas, W; Barthelmy, S D; Cummings, J; Gehrels, N; Krimm, H; Palmer, D; Yamaoka, K; Ohno, M; Fukazawa, Y; Hanabata, Y; Takahashi, T; Tashiro, M; Terada, Y; Murakami, T; Makishima, K; Briggs, M S; Kippen, R M; Kouveliotou, C; Meegan, C; Fishman, G; Connaughton, V; Boer, M; Guidorzi, C; Frontera, F; Montanari, E; Rossi, F; Feroci, M; Amati, L; Nicastro, L; Orlandini, M; Monte, Del; Costa, E; Donnarumma, I; Evangelista, Y; Lapshov, I; Lazzarotto, F; Pacciani, L; Rapisarda, M; Soffitta, P; Di Cocco, G; Fuschino, F; Galli, M; Labanti, C; Marisaldi, M; Atteia, J -L; Vanderspek, R; Ricker, G

    2013-01-01

    Between the launch of the GGS Wind spacecraft in 1994 November and the end of 2010, the Konus-Wind experiment detected 314 short-duration gamma-ray bursts (including 24 bursts which can be classified as short bursts with extended emission). During this period, the IPN consisted of up to eleven spacecraft, and using triangulation, the localizations of 276 bursts were obtained. We present the IPN localization data on these events.

  13. 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 ...

  14. 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.

  15. Status of Blue Ridge Reservoir

    Energy Technology Data Exchange (ETDEWEB)

    1990-09-01

    This is one in a series of reports prepared by the Tennessee Valley Authority (TVA) for those interested in the conditions of TVA reservoirs. This overview of Blue Ridge Reservoir summarizes reservoir and watershed characteristics, reservoir uses and use impairments, water quality and aquatic biological conditions, and activities of reservoir management agencies. This information was extracted from the most current reports and data available, as well as interview with water resource professionals in various federal, state, and local agencies. Blue Ridge Reservoir is a single-purpose hydropower generating project. When consistent with this primary objective, the reservoir is also operated to benefit secondary objectives including water quality, recreation, fish and aquatic habitat, development of shoreline, aesthetic quality, and other public and private uses that support overall regional economic growth and development. 8 refs., 1 fig.

  16. 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.

  17. 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)

  18. 47 CFR 90.250 - Meteor burst communications.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Meteor burst communications. 90.250 Section 90... PRIVATE LAND MOBILE RADIO SERVICES Non-Voice and Other Specialized Operations § 90.250 Meteor burst communications. Meteor burst communications may be authorized for the use of private radio stations subject...

  19. $\\gamma$-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.

  20. The position and polarization of Type III solar bursts

    Science.gov (United States)

    Dulk, G. A.; Suzuki, S.

    1980-01-01

    The position and polarization of Type III solar bursts in the range of 24-220 MHz are studied, with emphasis on the bursts continuing to frequencies lower than 24 MHz. Consideration is given to the statistics of burst polarization, the relation between polarization and source position, and brightness temperature, flux densities, and source sizes.

  1. Search for bursts in air shower data

    Science.gov (United States)

    Bruce, T. E. G.; Clay, R. W.; Dawson, B. R.; Protheroe, R. J.; Blair, D. G.; Cinquini, P.

    1985-01-01

    There have been reports in recent years of the possible observation of bursts in air shower data. If such events are truly of an astrophysical nature then, they represent an important new class of phemonenon since no other bursts have been observed above the MeV level. The spectra of conventional gamma ray bursts are unknown at higher energies but their observed spectra at MeV energies appear generally to exhibit a steepening in the higher MeV range and are thus unlikely to extrapolate to measurable fluxes at air shower energies. An attempt has been made to look for deviations from randomness in the arrival times of air showers above approx. 10 to the 14th power eV with a number of systems and results so far are presented here. This work will be continued for a substantial period of ime with a system capable of recording bursts with multiple events down to a spacing of 4 microns. Earlier data have also been searched for the possible association of air shower events with a glitch of the Vela pulsar.

  2. 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.

  3. PHYSICAL CONSTRAINTS ON FAST RADIO BURSTS

    International Nuclear Information System (INIS)

    Fast radio bursts (FRBs) are isolated, ms radio pulses with dispersion measure (DM) of order 103 pc cm–3. Galactic candidates for the DM of high latitude bursts detected at GHz frequencies are easily dismissed. DM from bursts emitted in stellar coronas are limited by free-free absorption and those from H II regions are bounded by the nondetection of associated free-free emission at radio wavelengths. Thus, if astronomical, FRBs are probably extragalactic. FRB 110220 has a scattering tail of ∼5.6 ± 0.1 ms. If the electron density fluctuations arise from a turbulent cascade, the scattering is unlikely to be due to propagation through the diffuse intergalactic plasma. A more plausible explanation is that this burst sits in the central region of its host galaxy. Pulse durations of order ms constrain the sizes of FRB sources implying high brightness temperatures that indicates coherent emission. Electric fields near FRBs at cosmological distances would be so strong that they could accelerate free electrons from rest to relativistic energies in a single wave period

  4. Gamma-Ray Bursts and Cosmology

    Science.gov (United States)

    Norris, Jay P.

    2003-01-01

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

  5. The Swift Gamma Ray Burst Mission

    Science.gov (United States)

    Gehrels, Neil

    2004-01-01

    Swift is an international mission managed by NASA as part of its MIDEX program. It is a multiwavelength transient observatory for GRB astronomy that will launch in 2004. The goals of the mission are to determine the origin of GRBs and their afterglows and use bursts to probe the early Universe. A wide field gamma-ray camera will detect more than a hundred GRBs per year to 2-5 times fainter than BATSE. Sensitive narrow-field X-ray, and UV/optical telescopes will be pointed at the burst location in 20 to 75 sec by an autonomously controlled 'swift' spacecraft. For each burst, arcsec positions will be determined and optical/UV/x-ray/gamma-ray spectrophotometry performed. Measurements of redshift will be made for many of the bursts. The instrumentation is a combination of superb existing flight-spare hardware and design from XMM and Spectrum-X/JET-X contributed by collaborators in the UK and Italy and development of a coded-aperture camera with a large-area (approx. 0.5 square meter) CdZnTe detector array. The instruments have now completed their fabrication phase and are integrated on the observatory for final testing. Key components of the mission are vigorous follow-up and outreach programs to engage the astronomical community and public in Swift. The talk will describe the mission and its status and give a summary of our plans for GRB operations.

  6. The Swift Gamna-Ray Burst Mission

    Science.gov (United States)

    Gehrels, Neil

    2005-01-01

    Swift is a NASA Explorer mission that will be launched in late 2004. It is a multiwavelength observatory for transient astronomy. The goals of the mission are to determine the origin of gamma-ray bursts and their afterglows and use bursts to probe the early Universe. The mission will also perform a hard x-ray survey at the 1 milliCrab level and will continuously monitor the sky for transients. A wide-field gamma-ray camera will detect more than a hundred GRBs per year to 3 times fainter than BATSE. Sensitive narrow-field X-ray and UV/optical telescopes will be pointed at the burst location in 20 to 70 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions will be determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. The instrumentation is a combination of existing flight-spare hardware and design from XMM and Spectrum-X/JET-X contributed by collaborators in the UK and Italy and development of a coded-aperture camera with a large-area (-0.5 square meter) CdZnTe detector array. The ground station in Malindi is contributed by the Italian Space Agency. Key components of the mission are vigorous follow-up and outreach programs to engage the astronomical community and public in Swift.

  7. 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.

  8. K+ channels and the microglial respiratory burst.

    Science.gov (United States)

    Khanna, R; Roy, L; Zhu, X; Schlichter, L C

    2001-04-01

    Microglial activation following central nervous system damage or disease often culminates in a respiratory burst that is necessary for antimicrobial function, but, paradoxically, can damage bystander cells. We show that several K+ channels are expressed and play a role in the respiratory burst of cultured rat microglia. Three pharmacologically separable K+ currents had properties of Kv1.3 and the Ca2+/calmodulin-gated channels, SK2, SK3, and SK4. mRNA was detected for Kv1.3, Kv1.5, SK2, and/or SK3, and SK4. Protein was detected for Kv1.3, Kv1.5, and SK3 (selective SK2 and SK4 antibodies not available). No Kv1.5-like current was detected, and confocal immunofluorescence showed the protein to be subcellular, in contrast to the robust membrane localization of Kv1.3. To determine whether any of these channels play a role in microglial activation, a respiratory burst was stimulated with phorbol 12-myristate 13-acetate and measured using a single cell, fluorescence-based dihydrorhodamine 123 assay. The respiratory burst was markedly inhibited by blockers of SK2 (apamin) and SK4 channels (clotrimazole and charybdotoxin), and to a lesser extent, by the potent Kv1.3 blocker agitoxin-2. PMID:11245596

  9. Models of Individual Blue Stragglers

    CERN Document Server

    Sills, Alison

    2014-01-01

    This chapter describes the current state of models of individual blue stragglers. Stellar collisions, binary mergers (or coalescence), and partial or ongoing mass transfer have all been studied in some detail. The products of stellar collisions retain memory of their parent stars and are not fully mixed. Very high initial rotation rates must be reduced by an unknown process to allow the stars to collapse to the main sequence. The more massive collision products have shorter lifetimes than normal stars of the same mass, while products between low mass stars are long-lived and look very much like normal stars of their mass. Mass transfer can result in a merger, or can produce another binary system with a blue straggler and the remnant of the original primary. The products of binary mass transfer cover a larger portion of the colour-magnitude diagram than collision products for two reasons: there are more possible configurations which produce blue stragglers, and there are differing contributions to the blended ...

  10. Models of Individual Blue Stragglers

    Science.gov (United States)

    Sills, Alison

    This chapter describes the current state of models of individual blue stragglers. Stellar collisions, binary mergers (or coalescence), and partial or ongoing mass transfer have all been studied in some detail. The products of stellar collisions retain memory of their parent stars and are not fully mixed. Very high initial rotation rates must be reduced by an unknown process to allow the stars to collapse to the main sequence. The more massive collision products have shorter lifetimes than normal stars of the same mass, while products between low mass stars are long-lived and look very much like normal stars of their mass. Mass transfer can result in a merger, or can produce another binary system with a blue straggler and the remnant of the original primary. The products of binary mass transfer cover a larger portion of the colour-magnitude diagram than collision products for two reasons: there are more possible configurations which produce blue stragglers, and there are differing contributions to the blended light of the system. The effects of rotation may be substantial in both collision and merger products, and could result in significant mixing unless angular momentum is lost shortly after the formation event. Surface abundances may provide ways to distinguish between the formation mechanisms, but care must be taken to model the various mixing mechanisms properly before drawing strong conclusions. Avenues for future work are outlined.

  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 WELL DRILL-IN FLUIDS

    OpenAIRE

    Nediljka Gaurina-Međimurec

    1998-01-01

    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...

  13. In Situ Remediation using Horizontal Wells

    OpenAIRE

    ECT Team, Purdue

    2007-01-01

    Horizontal well technology has been widely used in petroleum and underground utility installation. Since late 1980's, the technology has been adapted for environmental remediation applications. Two general methods in drilling horizontal wells have been used in remediation, trenched and directionally-drilled. The first method involves the excavation of a relatively large diameter borehole, with simultaneous installation of well materials and backfill. The second method, directional drilling, p...

  14. CORRECTED CALCULATION OF HORIZONTAL GATING SYSTEMS

    Directory of Open Access Journals (Sweden)

    I. A. Zayatz

    2015-05-01

    Full Text Available In the course of fulfillment of work the specified calculations of horizontal gating systems for various parts produced in dispensable molds were carried out. The results of work showed that the weight removal value in gating systems fluctuates in big intervals and the specified calculation of horizontal gating systems enables to calculate precisely their weight that allows to calculate quantity of metal in metal charge.

  15. 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 ...

  16. Emotion recognition (sometimes) depends on horizontal orientations

    OpenAIRE

    Huynh, Carol M; Balas, Benjamin

    2014-01-01

    Face recognition depends critically on horizontal orientations (Goffaux & Dakin, 2010). Face images that lack horizontal features are harder to recognize than those that have that information preserved. Presently, we asked if facial emotional recognition also exhibits this dependency by asking observers to categorize orientation-filtered happy and sad expressions. Furthermore, we aimed to dissociate image-based orientation energy from object-based orientation by rotating images 90-degrees in ...

  17. 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.

  18. 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.

  19. Emotion recognition (sometimes) depends on horizontal orientations.

    Science.gov (United States)

    Huynh, Carol M; Balas, Benjamin

    2014-07-01

    Face recognition depends critically on horizontal orientations (Goffaux & Dakin, Frontiers in Psychology, 1(143), 1-14, 2010): Face images that lack horizontal features are harder to recognize than those that have this information preserved. We asked whether facial emotional recognition also exhibits this dependency by asking observers to categorize orientation-filtered happy and sad expressions. Furthermore, we aimed to dissociate image-based orientation energy from object-based orientation by rotating images 90 deg in the picture plane. In our first experiment, we showed that the perception of emotional expression does depend on horizontal orientations, and that object-based orientation constrained performance more than image-based orientation did. In Experiment 2, we showed that mouth openness (i.e., open vs. closed mouths) also influenced the emotion-dependent reliance on horizontal information. Finally, we describe a simple computational analysis that demonstrates that the impact of mouth openness was not predicted by variation in the distribution of orientation energy across horizontal and vertical orientation bands. Overall, our results suggest that emotion recognition largely does depend on horizontal information defined relative to the face, but that this bias is modulated by multiple factors that introduce variation in appearance across and within distinct emotions. PMID:24664854

  20. 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

    cells are subjected to stochastic fluctuations in plasma membrane currents, which are likely to disturb the bursting mechanism and transform medium bursters into spikers or very fast bursters. We present a polynomial, minimal, phantom burster model and show that noise modifies the plateau fraction and......-called compound bursting can be converted to apparent slow bursting by noise, which could explain why compound bursting and mixed Ca oscillations are seen mainly in intact islets....

  1. Imaging assessment of vertebral burst fracture

    International Nuclear Information System (INIS)

    Objective: To investigate the diagnostic value of radiography, CT and MRI in diagnosis of vertebral burst fracture. Methods: 51 patients with vertebral burst fracture were evaluated with X-ray, CT and MRI, including 3 cases in cervical vertebra, 18 cases in thoracic vertebra, and 30 cases in lumbar vertebra. The imaging features were comparatively studied. Results: Radiography showed decreased height of the vertebral body, increased antero-posterior diameter and the transverse diameter, and/or the widened interpedicle distance, the inter-spinous distance, as well as the bony fragment inserted into the vertebral canal in 28 cases(54.90%). X-ray findings similar to the compression fracture were revealed in 20 cases(39.21%). And missed diagnosis was made in 3 cases (5.88%). CT clearly demon-strated the vertebral body vertically or transversely burst crack in 49 cases (96.07%); bony fragment inserted into the vertebral canal and narrowed vertebral canal in 35 cases(68. 62% ); fracture of spinal appendix in 22 cases(43.14%). Meanwhile MRI showed abnormal signals within the spinal cord in 35 cases (68.62%),injured intervertebral disk in 29 cases(56.86% ), extradural hematoma in 12 cases(23.52% ) and torn posterior longitudinal ligament in 6 cases (11.76%). Conclusions: Radiography is the routine examination, while with limited diagnostic value in vertebral burst fracture. These patients who have nervous symptoms with simple compression fracture or unremarkable on X-ray should receive the CT or MRI examination. CT is better than MRI in demonstrating the fracture and the displaced bony fragment, while MRI is superior to CT in showing nervous injuries. CT and MRI will provide comprehensive information guiding clinical treatment of vertebral burst fracture. (authors)

  2. 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 ...

  3. 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

  4. 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

  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. 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...

  7. 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 a...... intermediate between pure He and mixed H/He burning. The long burst is the result of the accumulation of a thick He layer, while the short one is a prematurate H-triggered He burning burst at a slightly lower accretion rate....

  8. 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)

  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. 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.

  11. Directivity of low frequency solar type III radio bursts

    International Nuclear Information System (INIS)

    The occurrence rate of type III solar bursts in the frequency range 4.9 MHz to 30 kHz is analyzed as a function of burst intensity and burst arrival direction. It is found that (a) the occurrence rate of bursts falls off with increasing flux, S, according to the power law Ssup(-1.5), and (b) the distribution of burst arrival directions at each frequency shows a significantly larger number of bursts observed west of the Earth-Sun line than east of it. This western excess in occurrence rate appears to be correlated with the direction of the average interplanetary magnetic field, and is interpreted as beaming of the observed burst radiation along the magnetic field direction. (Auth.)

  12. 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

  13. 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).

  14. 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

  15. Blue and UV Semiconductor Lasers

    International Nuclear Information System (INIS)

    Despite many technological difficulties the group III nitrides: GaN, AlN and InN and their alloys are primary candidates for electro-optical coherent light sources. In the recent years the research and technology of the nitride based continuous wave (CW) laser diodes (LDs) led to creation of blue-violet coherent light sources of power up to 200 mW. The progress has been attained by using various ways to attack the main obstacles in the technology of these devices such as insufficient size of high quality lattice matched substrates, low p-doping efficiency of Mg acceptor, poor contact to p-type semiconductor and low efficiency of radiative recombination. The two different approaches were used to overcome the substrate problem: hetero-epitaxy and homoepitaxy. Homoepitaxy used high pressure GaN high quality crystals. Heteroepitaxy used sapphire, SiC or GaAs substrates and very sophisticated techniques of reduction of the dislocation density. The low p-doping efficiency by using Mg acceptor is related to creation of Mg - H complexes due to hydrogen presence during the growth of laser diode quantum structures. In addition, Mg acceptor has low efficiency due to its high energy. High Mg concentrations can be obtained by using either MOCVD or ammonia source MBE growth. An alternative route is to use hydrogen-free plasma activated MBE (PA-MBE) method. The recent advances and the prospects of both approaches will be discussed. Solid AlGaInN solution offers a possibility to cover wide spectral range, starting from near UV to blue, green and red. Arsenide based laser diodes (LDs) are efficient coherent red light sources. Therefore, nitride based LDs are considered to be devices of choice for green, blue and UV spectral range. So far only blue and violet laser has been realized. The progress toward green and UV lasers is far less spectacular. The results in all these areas and future prospects will be discussed. (author)

  16. 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...... medium, light as energy source and they capture CO2 for the synthesis of new organic material, thus can grow on non-agricultural land, without increasing food prices, or using fresh water. Due to all these advantages in addition to very high biomass yield with high carbohydrate content, macroalgaes can...

  17. Spectroscopy of blue stellar objects

    Science.gov (United States)

    Mitchell, K. J.; Warnock, A., III; Nations, H. L.; Barden, S. C.

    1983-01-01

    Spectra have been obtained for the brightest objects from a list of blue stellar objects found in a Palomar Schmidt field centered on Kapteyn Selected Area 28. Four of the objects presented here comprise a complete sample of objects with UV excess and magnitudes brighter than or equal to B = 16.3 mag. The object with the largest UV excess is a previously undiscovered quasar of redshift 0.25 and cataloged B magnitude of 15.6 mag. The object shows some evidence of variability. Spectroscopy for one bright object in a companion field centered on Selected Area 29 is also presented.

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

    CERN Document Server

    Zhang, Guobao; Zamfir, Michael; Cumming, Andrew

    2015-01-01

    Coherent oscillations and the evolution of the X-ray spectrum during thermonuclear X-ray bursts in accreting neutron-star X-ray binaries have been studied intensively but separately. We analysed all the X-ray bursts of the source 4U 1728-34 with the Rossi X-ray Timing Explorer. We found that the presence of burst oscillations can be used to predict the behaviour of the blackbody radius during the cooling phase of the bursts. If a burst shows oscillations, during the cooling phase the blackbody radius remains more or less constant for ~2 - ~8s, whereas in bursts that do not show oscillations the blackbody radius either remains constant for more than ~2 - ~8s or it shows a rapid (faster than ~2s) decrease and increase. Both the presence of burst oscillations and the time-dependent spectral behaviour of the bursts are affected by accretion rate. We also found that the rise time and convexity of the bursts' light curve are different in bursts with and without oscillations in 4U 1728--34. Bursts with oscillations ...

  19. 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...... cells are subjected to stochastic fluctuations in plasma membrane currents, which are likely to disturb the bursting mechanism and transform medium bursters into spikers or very fast bursters. We present a polynomial, minimal, phantom burster model and show that noise modifies the plateau fraction and...... lowers the burst period dramatically in phantom bursters. It is therefore unlikely that slow bursting in single cells is driven by the slow phantom bursting mechanism, but could instead be driven by oscillations in glycolysis, which we show are stable to random ion channel fluctuations. Moreover, so...

  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. 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

  3. 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.

  4. Gamma-Ray Burst Prompt Emission

    CERN Document Server

    Zhang, Bing

    2014-01-01

    The origin of gamma-ray burst (GRB) prompt emission, bursts of gamma-rays lasting from shorter than one second to thousands of seconds, remains not fully understood after more than 40 years of observations. The uncertainties lie in several open questions in the GRB physics, including jet composition, energy dissipation mechanism, particle acceleration mechanism, and radiation mechanism. Recent broad-band observations of prompt emission with Fermi sharpen the debates in these areas, which stimulated intense theoretical investigations invoking very different ideas. I will review these debates, and argue that the current data suggest the following picture: A quasi-thermal spectral component originating from the photosphere of the relativistic ejecta has been detected in some GRBs. Even though in some cases (e.g. GRB 090902B) this component dominates the spectrum, in most GRBs, this component either forms a sub-dominant "shoulder" spectral component in the low energy spectral regime of the more dominant "Band" co...

  5. 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.

  6. Downhole drilling network using burst modulation techniques

    Science.gov (United States)

    Hall; David R. , Fox; Joe

    2007-04-03

    A downhole drilling system is disclosed in one aspect of the present invention as including a drill string and a transmission line integrated into the drill string. Multiple network nodes are installed at selected intervals along the drill string and are adapted to communicate with one another through the transmission line. In order to efficiently allocate the available bandwidth, the network nodes are configured to use any of numerous burst modulation techniques to transmit data.

  7. 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.

  8. 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 ...

  9. 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)

  10. 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)

  11. 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.

  12. 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...

  13. 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.

  14. Holographic Charge Excitations on Horizontal Boundary

    CERN Document Server

    Hotta, M

    2002-01-01

    We argue that states with nontrivial horizontal charges of BTZ black hole can be excited by ordinary falling matter including Hawking radiation. The matter effect does not break the integrability condition of the charges on the horizon. Thus we are able to trace the proccesses in which the matter imprints the information on the horizon by use of the charged states. It is naturally expected that in the thermal equilibrium with the Hawking radiation the black hole wanders ergodically through different horizontal states due to thermal fluctuation of incoming matter. This fact strengthens plausibility of the basic part of Carlip's idea. We also discuss some aspects of the quantum horizontal symmetry and conjecture how the precise black hole entropy will be given from our point of view.

  15. 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)

  16. 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...

  17. 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...

  18. 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...

  19. 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.

  20. Gamma-Ray Burst Physics with GLAST

    Energy Technology Data Exchange (ETDEWEB)

    Omodei, N.; /INFN, Pisa

    2006-10-06

    The Gamma-ray Large Area Space Telescope (GLAST) is an international space mission that will study the cosmos in the energy range 10 keV-300 GeV, the upper end of which is one of the last poorly observed region of the celestial electromagnetic spectrum. The ancestor of the GLAST/LAT was the Energetic Gamma Ray Experiment Telescope (EGRET) detector, which flew onboard the Compton Gamma Ray Observatory (CGRO). The amount of information and the step forward that the high energy astrophysics made thanks to its 9 years of observations are impressive. Nevertheless, EGRET uncovered the tip of the iceberg, raising many questions, and it is in the light of EGRET's results that the great potential of the next generation gamma-ray telescope can be appreciated. GLAST will have an imaging gamma-ray telescope, the Large Area Telescope (LAT) vastly more capable than instruments own previously, as well as a secondary instrument, the GLAST Bursts Monitor, or GBM, to augment the study of gamma-ray bursts. Gamma-Ray Bursts (GRBs) science is one of the most exciting challenges for the GLAST mission, exploring the high energy emission of one of the most intense phenomena in the sky, shading light on various problems: from the acceleration of particles to the emission processes, to more exotic physics like Quantum Gravity effect. In this paper we report the work done so far in the simulation development as well as the study of the LAT sensitivity to GRB.

  1. Bursting emission from B0611+22

    CERN Document Server

    Seymour, Andrew; Ridley, Josh

    2014-01-01

    Over the past decade it has become apparent that a class of `bursting pulsars' exist with the discovery of PSR J1752+2359 and PSR J1938+2213. In these pulsars, a sharp increase in the emission is observed that then tends to systematically drop-off from pulse-to-pulse. In this paper we describe the discovery of such a relationship in high-sensitivity observations of the young (characteristic age of 90,000 yrs) 0.33 s pulsar B0611+22 at both 327 MHz and 1400 MHz with the Arecibo radio telescope. While Nowakowski previously showed that B0611+22 has mode-switching properties, the data presented here show, for the first time, that this pulsar emits bursts with characteristic time-scales of several hundred seconds. At 327 MHz, the pulsar shows steady behaviour in one emission mode which is enhanced by bursting emission slightly offset in pulse phase from this steady emission. Contrastingly at 1400 MHz, the two modes appear to behave in a competing operation while still offset in phase. Using a fluctuation spectrum ...

  2. 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...

  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. Burst fracture of the fifth lumber vertebra

    International Nuclear Information System (INIS)

    Objective: To investigate the stability of the fifth lumber vertebra after burst fracture. Methods: 7 patients with burst fracture of the fifth lumber vertebra were examined by X-ray and CT, and followed for 6-36 months. The changes of wedge index, lordosis, degree of spinal canal stenosis and neurological features were observed during the episode and followed up. Results: The three spinal column structure was disrupted in 6 of 7 patients. The anterior and mid columns were involved in 1 case. Spinal stenosis of first and second degrees was seen in 3 cases, and in one case, there was no spinal canal stenosis. Lower lumber motor-root deficits were found in 2 of 7 patients and resolved in follow up. There was no tendency of progressive collapse of the vertebral body and spinal stenosis. Conclusions: Burst fracture of the fifth lumber vertebra was specific, most of them were stable fractures, although two or three columns of the spine were disrupted and accompanied by spinal canal stenosis

  5. Uncovering Blue Diffuse Dwarf Galaxies

    CERN Document Server

    James, Bethan L; Stark, Daniel P; Belokurov, Vasily; Pettini, Max; Olszewski, Edward W

    2014-01-01

    Extremely metal poor (XMP) galaxies are known to be very rare, despite the large numbers of low-mass galaxies predicted by the local galaxy luminosity function. This paper presents a sub-sample of galaxies that were selected via a morphology-based search on SDSS images with the aim of finding these elusive XMP galaxies. By using the recently discovered extremely metal-poor galaxy, Leo P, as a guide, we obtained a collection of faint, blue systems, each with isolated HII regions embedded in a diffuse continuum, that have remained undetected until now. Here we show the first results from optical spectroscopic follow-up observations of 12 of ~100 of these blue, diffuse dwarf (BDD) galaxies yielded by our search algorithm. Oxygen abundances were obtained via the direct method for eight galaxies, and found to be in the range 7.45<12+log(O/H)<8.0, with two galaxies being classified as XMPs. All BDDs were found to currently have a young star-forming population (<10 Myr) and relatively high ionisation parame...

  6. 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...

  7. 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

  8. The Red-Blue Transportation Problem

    OpenAIRE

    Vancroonenburg, Wim; Della Croce, Federico; Goossens, Dries; Spieksma, Frits

    2014-01-01

    This paper considers the Red-Blue Transportation Problem (Red-Blue TP), a generalization of the transportation problem where supply nodes are partitioned into two sets and so-called exclusionary constraints are imposed. We encountered a special case of this problem in a hospital context, where patients need to be assigned to rooms. We establish the problem's complexity, and we compare two integer programming formulations. Furthermore, a maximization variant of Red-Blue TP is presented, for...

  9. 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.

  10. Causes and characteristics of horizontal positional nystagmus.

    Science.gov (United States)

    Lechner, Corinna; Taylor, Rachael L; Todd, Chris; Macdougall, Hamish; Yavor, Robbie; Halmagyi, G Michael; Welgampola, Miriam S

    2014-05-01

    Direction changing horizontal positional nystagmus can be observed in a variety of central and peripheral vestibular disorders. We tested sixty subjects with horizontal positional nystagmus and vertigo on the Epley Omniax(®) rotator. Monocular video recordings were performed with the right or left ear down, in the supine and prone positions. Nystagmus slow-phase velocity (SPV) was plotted as a function of time. Thirty-one subjects diagnosed with horizontal canalolithiasis had paroxysmal horizontal geotropic nystagmus with the affected ear down (onset 0.8 ± 1 s, range 0-4.9 s, duration 11.7-47.9 s, peak SPV 79 ± 67°/s). The SPV peaked at 5-20 s and declined to 0 by 60 s; at 40 s from onset, the average SPV was 1.8 % of the peak. Nine subjects diagnosed with cupulolithiasis had persistent apogeotropic horizontal nystagmus (onset 0.7 ± 1.4 s, range 0-4.3 s). Peak SPV was 54.2 ± 31.8°/s and 26.6 ± 12.2°/s with unaffected and affected ears down, respectively. At 40 s, the average SPV had decayed to only 81 % (unaffected ear down) and 65 % (affected ear down) of the peak. Twenty subjects were diagnosed with disorders other than benign positional vertigo (BPV) [vestibular migraine (VM), Ménière's Disease, vestibular schwannoma, unilateral or bilateral peripheral vestibular loss]. Subjects with VM (n = 13) had persistent geotropic or apogeotropic horizontal nystagmus. On average, at 40 s from nystagmus onset, the SPV was 61 % of the peak. Two patients with Ménière's Disease had persistent apogeotropic horizontal nystagmus; the peak SPV at 40 s ranged between 28.6 and 49.5 % of the peak. Symptomatic horizontal positional nystagmus can be observed in canalolithiasis, cupulolithiasis and diverse central and peripheral vestibulopathies; its temporal and intensity profile could be helpful in the separation of these entities. PMID:24676938

  11. 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

  12. UWB multi-burst transmit driver for averaging receivers

    Science.gov (United States)

    Dallum, Gregory E

    2012-11-20

    A multi-burst transmitter for ultra-wideband (UWB) communication systems generates a sequence of precisely spaced RF bursts from a single trigger event. There are two oscillators in the transmitter circuit, a gated burst rate oscillator and a gated RF burst or RF power output oscillator. The burst rate oscillator produces a relatively low frequency, i.e., MHz, square wave output for a selected transmit cycle, and drives the RF burst oscillator, which produces RF bursts of much higher frequency, i.e., GHz, during the transmit cycle. The frequency of the burst rate oscillator sets the spacing of the RF burst packets. The first oscillator output passes through a bias driver to the second oscillator. The bias driver conditions, e.g., level shifts, the signal from the first oscillator for input into the second oscillator, and also controls the length of each RF burst. A trigger pulse actuates a timing circuit, formed of a flip-flop and associated reset time delay circuit, that controls the operation of the first oscillator, i.e., how long it oscillates (which defines the transmit cycle).

  13. 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

  14. 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...

  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. Upper-Bound Performance of a Wideband Burst-by-Burst Adaptive Modem

    OpenAIRE

    Wong, C. H.; Hanzo, L.

    1999-01-01

    In this contribution, adaptive modulation is applied in conjunction with a Decision Feedback Equalizer (DFE) in order to mitigate the effects of the slowly varying wideband multi-path Rayleigh fading channel. The upper-bound mean BER and Bits Per Symbol (BPS) performance of this scheme is determined by utilizing the pseudo-SNR at the output of the DFE, in order to switch the modulation schemes on a burst-by-burst basis. The performances of each individual modulation schemes and their amalgama...

  17. 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...

  18. 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

  19. Comparing cost and performance of horizontal wells

    Energy Technology Data Exchange (ETDEWEB)

    Pocovi, A.S.; Gustavino, L.L. (Gerencia de Mineria y Geologica de Exploracion, YPF (AR)); Pozzo, A.; Musmarra, J.A. (Gerencia General de Exploracion, YPF, Buenos Aires (AR))

    1991-02-01

    Argentina's state oil company, YPF, was forced through technical and economic constraints to undertake a four-well pilot horizontal drilling program in its Neuquen fields. This article discusses techniques used, the results and costs, and compares them to costs incurred by the area's original vertical wells.

  20. Terrain slugging in near horizontal oilwells

    OpenAIRE

    Fozard, J.

    2001-01-01

    In this thesis we consider the problem of terrain slugging in near horizontal producing wells. We formulate a simple model for stratified two-phase flow, and consider the linear stability of steady states. We then study the possibility of the formation of roll waves, and make a tentative attempt at a resolution of the problem.

  1. 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…

  2. 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...

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Horizontally separated 1-in-1 crossing insertions

    Energy Technology Data Exchange (ETDEWEB)

    Syphers, M.J. [Fermi National Accelerator Lab., Batavia, IL (United States)

    1985-10-01

    Previous to this workshop, realistic lattices have been developed for vertically separated l-in-l (e.g., D.E. Johnson, A.A. Garren) and 2-in-1 (e.g., S. Heifets) magnets as well as for horizontally separated 2-in-l magnets (e.g., SSC RDS). Bringing together the widely separated ({approximately}60-70 cm) beams in a reasonable length of tunnel and keeping the dispersion zero at the interaction point has been difficult in the vertical l-in-l case. Most designs have required spacial 2-in-1 quadrupoles near the interaction point where the beams are separated by 15 cm or less. It is not clear that such magnets, as dictated by some of these lattice designs, can easily be built. The purpose of this exercise is to provide a crossing insertion for a realistic lattice which involves horizontally separated l-in-l magnets. The following horizontal crossing insertions, which incorporate the dispersion suppressors and phase trombones into the major arcs, need no special 2-in-1 magnets near the interaction point. The dispersion at the IP created by the horizontal crossing can be cancelled by the dispersion suppressor and one set of triplets.

  9. Implications of fast radio bursts for superconducting cosmic strings

    International Nuclear Information System (INIS)

    Highly beamed, short-duration electromagnetic bursts could be produced by superconducting cosmic string (SCS) loops oscillating in cosmic magnetic fields. We demonstrated that the basic characteristics of SCS bursts such as the electromagnetic frequency and the energy release could be consistently exhibited in the recently discovered fast radio bursts (FRBs). Moreover, it is first showed that the redshift distribution of the FRBs can also be well accounted for by the SCS burst model. Such agreements between the FRBs and SCS bursts suggest that the FRBs could originate from SCS bursts and thus they could provide an effective probe to study SCSs. The obtained values of model parameters indicate that the loops generating the FRBs have a small length scale and they are mostly formed in the radiation-dominated cosmological epoch

  10. 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. The...... derived positions of the bursts are reported. Additionally, most of the events have been confirmed by coincident detections with instruments on other spacecrafts. The features of two of the bursts and the results of searches for related events in the optical are described....

  11. INTEGRAL monitoring of unusually long X-ray bursts

    DEFF Research Database (Denmark)

    Thermonuclear bursts on the surface of accreting neutron stars in low mass X-ray binaries have been studied for many years and have in a few cases confirmed theoretical models of nuclear ignition and burning mechanisms. The large majority of X-ray bursts last less than 100s. A good number of the...... known X-ray bursters are frequently observed by INTEGRAL, in particular in the frame of the Key Programmes. Taking advantage of the INTEGRAL instrumentation, an international collaboration led by the JEM-X team at the Danish National Space Institute has been monitoring the occurrence of uncommon burst...... events lasting more than a few minutes. Of special interest are exceptional X-ray bursts which duration about a few tens of minutes is intermediate between usual short bursts and hour long superbursts. The processes driving such long bursts are not yet fully understood: depending on the composition of...

  12. Power Density Spectra of $\\gamma$-Ray Bursts

    CERN Document Server

    Beloborodov, A M

    1999-01-01

    Power density spectra (PDSs) of long gamma-ray bursts provide useful information on GRBs, indicating their self-similar temporal structure. The best power-law PDSs are displayed by the longest bursts (T_90 > 100 s) in which the range of self-similar time scales covers more than 2 decades. Shorter bursts have apparent PDS slopes more strongly affected by statistical fluctuations. The underlying power law can then be reproduced with high accuracy by averaging the PDSs for a large sample of bursts. This power-law has a slope alpha\\approx -5/3 and a sharp break at 1 Hz. The power-law PDS provides a new sensitive tool for studies of gamma-ray bursts. In particular, we calculate the PDSs of bright bursts in separate energy channels. The PDS flattens in the hard channel (h\

  13. III-nitride blue microdisplays

    International Nuclear Information System (INIS)

    Prototype blue microdisplays have been fabricated from InGaN/GaN quantum wells. The device has a dimension of 0.5x0.5mm2 and consists of 10x10 pixels 12 μm in diameter. Emission properties such as electroluminescence spectra, output power versus forward current (L--I) characteristic, viewing angle, and uniformity have been measured. Due to the unique properties of III-nitride wide-band-gap semiconductors, microdisplays fabricated from III nitrides can potentially provide unsurpassed performance, including high-brightness/resolution/contrast, high-temperature/high-power operation, high shock resistance, wide viewing angles, full-color spectrum capability, long life, high speed, and low-power consumption, thus providing an enhancement and benefit to the present capabilities of miniature display systems

  14. 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.

  15. Ecology of Blue Straggler Stars

    CERN Document Server

    Boffin, H M J; Beccari, G

    2014-01-01

    The existence of blue straggler stars (BSS), which appear younger, hotter, and more massive than their siblings, is at odds with a simple picture of stellar evolution, as such stars should have exhausted their nuclear fuel and evolved long ago to become cooling white dwarfs. As such, BSS could just be some quirks but in fact their understanding requires a deep knowledge of many different areas in astronomy, from stellar evolution through cluster dynamics, from chemical abundances to stellar populations. In November 2012, a workshop on this important topic took place at the ESO Chilean headquarters in Santiago. The many topics covered at this workshop were introduced by very comprehensive invited reviews, providing a unique and insightful view on the field. These reviews have now become chapters of the first ever book on BSS.

  16. Burst suppression electroencephalogram with mushroom poisoning, Amanita pantherina

    OpenAIRE

    Yuka Ogawa; Hiromasa Sato; Motoyoshi Yamamoto; Hiroyuki Tada; Takao Hashimoto

    2015-01-01

    We report on a patient with Amanita pantherina poisoning who showed a burst suppression pattern on electroencephalography during a comatose state. The patient recovered without sequelae a week after ingestion. Burst suppression pattern is defined as alternating bursts and periods of electrical silence, and it is associated with comatose states of various causes. The major toxins contained in A. pantherina are ibotenic acid, an excitatory amino acid at the glutamate receptors, and muscimol, an...

  17. Burst Fractures as a Result of Attempted Suicide by Jumping

    OpenAIRE

    Kim, Do Young; Choi, Hong June; Park, Jeong Yoon; Kim, Kyung Hyun; Kuh, Sung Uk; Chin, Dong Kyu; Kim, Keun Su; Cho, Yong Eun; Jin, Byoung Ho

    2014-01-01

    Objective Jumping from high place for the purpose of suicide results in various damages to body area. A burst fracture of vertebrae is representative of them and we reviewed eight patients who were diagnosed with spinal burst fracture following suicide falling-down. The demographics, characteristics, performed operation, combined injuries, psychological past histories of the patients were analyzed. Methods A retrospective study was made of patients who are diagnosed with vertebral burst fract...

  18. 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...

  19. Detecting Pipe Bursts Using Heuristic and CUSUM Methods

    OpenAIRE

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

    2014-01-01

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

  20. 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. Are designers making the most of new bursting disc devices

    International Nuclear Information System (INIS)

    Recent years have seen significant advances in the technology of bursting discs for protecting plants against excess pressure. The recently developed scored reverse buckling discs burst within an accuracy of +- 3 percent. Also the pressure can rise to 90 percent of the disc's minimum burst pressure without affecting its performance. It is argued that it would now be a desirable feature in modern PWRs to update rupture disc design. (author)

  2. Blue enhanced light sources: opportunities and risks

    Science.gov (United States)

    Lang, Dieter

    2012-03-01

    Natural daylight is characterized by high proportions of blue light. By proof of a third type of photoreceptor in the human eye which is only sensitive in this spectral region and by subsequent studies it has become obvious that these blue proportions are essential for human health and well being. In various studies beneficial effects of indoor lighting with higher blue spectral proportions have been proven. On the other hand with increasing use of light sources having enhanced blue light for indoor illumination questions are arising about potential health risks attributed to blue light. Especially LED are showing distinct emission characteristics in the blue. Recently the French agency for food, environmental and occupational health & safety ANSES have raised the question on health issues related to LED light sources and have claimed to avoid use of LED for lighting in schools. In this paper parameters which are relevant for potential health risks will be shown and their contribution to risk factors will quantitatively be discussed. It will be shown how to differentiate between photometric parameters for assessment of beneficial as well as hazardous effects. Guidelines will be discussed how blue enhanced light sources can be used in applications to optimally support human health and well being and simultaneously avoid any risks attributed to blue light by a proper design of lighting parameters. In the conclusion it will be shown that no inherent health risks are related to LED lighting with a proper lighting design.

  3. 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…

  4. Blue collection bag after ileal diversion.

    Science.gov (United States)

    Hildreth, T A; Cass, A S

    1978-02-01

    Five children with ileal diversions have shown asymptomatic blue staining of the urine collection bags. A tryptophan derivative (indican) in the urine that oxidizes to indigo blue on exposure to air is thought to be the cause of this benign transient phenomenon. PMID:628994

  5. 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 ☉).

  6. 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 ☉}).

  7. Energy sources in gamma-ray burst models

    Science.gov (United States)

    Taam, Ronald E.

    1987-01-01

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

  8. Gamma-ray burst interaction with dense interstellar medium

    OpenAIRE

    Barkov, Maxim; Bisnovatyi-Kogan, Gennady

    2004-01-01

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

  9. Broad-band solar bursts of the spike type

    International Nuclear Information System (INIS)

    Observations of high-resolution dynamic spectra of solar broad-band spike bursts (BSB), consisting of the instantaneous brightening of the continuum in the entire spectrograph range of 175-235 MHz, are reported. In noise storms events of the BSB type are rarely encountered and have the form of individual bursts with an average duration of 0.1-0.2 sec or groups of such bursts connected with type III bursts at lower frequencies. Series of aperiodic BSB structures unconnected with type III bursts and observed together with one-second pulsations and fiber bursts, predominate in type IV bursts. In noise storms BSB bursts can be emitted by electrons accelerated instantaneously as a result of the reconnection of magnetic fields, both in a small source (about 10 to the 8th cm) with a broad velocity dispersion and in an extended source (about 5 x 10 to the 9th cm). Structures of the BSB type in type IV bursts may be the result of the scattering of Langmuir waves on whistlers in a large height range. 30 references

  10. Broad-band solar bursts of the spike type

    Energy Technology Data Exchange (ETDEWEB)

    Bakunin, L.M.; Chernov, G.P.

    1985-10-01

    Observations of high-resolution dynamic spectra of solar broad-band spike bursts (BSB), consisting of the instantaneous brightening of the continuum in the entire spectrograph range of 175-235 MHz, are reported. In noise storms events of the BSB type are rarely encountered and have the form of individual bursts with an average duration of 0.1-0.2 sec or groups of such bursts connected with type III bursts at lower frequencies. Series of aperiodic BSB structures unconnected with type III bursts and observed together with one-second pulsations and fiber bursts, predominate in type IV bursts. In noise storms BSB bursts can be emitted by electrons accelerated instantaneously as a result of the reconnection of magnetic fields, both in a small source (about 10 to the 8th cm) with a broad velocity dispersion and in an extended source (about 5 x 10 to the 9th cm). Structures of the BSB type in type IV bursts may be the result of the scattering of Langmuir waves on whistlers in a large height range. 30 references.

  11. 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.

  12. 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...

  13. 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.)

  14. 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

  15. Statistical properties of SGR 1900+14 bursts

    CERN Document Server

    Gogus, E; Kouveliotou, C; Van Paradijs, J; Briggs, M S; Duncan, R C; Thompson, C; Gogus, Ersin; Woods, Peter M.; Kouveliotou, Chryssa; Paradijs, Jan van; Briggs, Michael S.; Duncan, Robert C.; Thompson, Christopher

    1999-01-01

    We study the statistics of soft gamma repeater (SGR) bursts, using a data base of 187 events detected with BATSE and 837 events detected with RXTE PCA, all from SGR 1900+14 during its 1998-1999 active phase. We find that the fluence or energy distribution of bursts is consistent with a power law of index 1.66, over 4 orders of magnitude. This scale-free distribution resembles the Gutenberg-Richter Law for earthquakes, and gives evidence for self-organized criticality in SGRs. The distribution of time intervals between successive bursts from SGR 1900+14 is consistent with a log-normal distribution. There is no correlation between burst intensity and the waiting times till the next burst, but there is some evidence for a correlation between burst intensity and the time elapsed since the previous burst. We also find a correlation between the duration and the energy of the bursts, but with significant scatter. In all these statistical properties, SGR bursts resemble earthquakes and solar flares more closely than ...

  16. 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...

  17. 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

  18. 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...

  19. 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

  20. 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.

  1. Gamma ray bursts of black hole universe

    Science.gov (United States)

    Zhang, T. X.

    2015-07-01

    Slightly modifying the standard big bang theory, Zhang recently developed a new cosmological model called black hole universe, which has only a single postulate but is consistent with Mach's principle, governed by Einstein's general theory of relativity, and able to explain existing observations of the universe. In the previous studies, we have explained the origin, structure, evolution, expansion, cosmic microwave background radiation, quasar, and acceleration of black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This study investigates gamma ray bursts of black hole universe and provides an alternative explanation for the energy and spectrum measurements of gamma ray bursts according to the black hole universe model. The results indicate that gamma ray bursts can be understood as emissions of dynamic star-like black holes. A black hole, when it accretes its star or merges with another black hole, becomes dynamic. A dynamic black hole has a broken event horizon and thus cannot hold the inside hot (or high-frequency) blackbody radiation, which flows or leaks out and produces a GRB. A star when it collapses into its core black hole produces a long GRB and releases the gravitational potential energy of the star as gamma rays. A black hole that merges with another black hole produces a short GRB and releases a part of their blackbody radiation as gamma rays. The amount of energy obtained from the emissions of dynamic star-like black holes are consistent with the measurements of energy from GRBs. The GRB energy spectra derived from this new emission mechanism are also consistent with the measurements.

  2. 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.

  3. 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.

  4. Classification of Fermi Gamma-RAY Bursts

    CERN Document Server

    Horvath, I; Hakkila, J; Bagoly, Z; Preece, R D

    2015-01-01

    The Fermi GBM Catalog has been recently published. Previous classification analyses of the BATSE, RHESSI, BeppoSAX, and Swift databases found three types of gamma-ray bursts. Now we analyzed the GBM catalog to classify the GRBs. PCA and Multiclustering analysis revealed three groups. Validation of these groups, in terms of the observed variables, shows that one of the groups coincides with the short GRBs. The other two groups split the long class into a bright and dim part, as defined by the peak flux. Additional analysis is needed to determine whether this splitting is only a mathematical byproduct of the analysis or has some real physical meaning.

  5. The Birthplaces of Gamma-Ray Bursts

    CERN Document Server

    Young, P A; Young, Patrick A.

    2007-01-01

    We use population synthesis to construct distributions of gamma-ray bursts (GRBs) for different proposed progenitor models. We use a description of star formation that takes into account the evolution of metallicity with redshift and galaxy mass, the evolution of galaxy mass with redshift, and the star formation rate with galaxy mass and redshift. We compare predicted distributions with redshift and metallicity to observations of GRB host galaxies and find that the the simple models cannot produce the observed distributions, but that current theoretical models can reproduce the observations within some constraints on the fraction of fallback black holes that produce GRBs.

  6. Are Gamma-ray Bursts Universal?

    OpenAIRE

    Eichler, David; Levinson, Amir

    2006-01-01

    It is noted that the Liang-Zhang correlation can be accounted for with the viewing angle interpretation proposed earlier. The Ghirlanda correlation, recently generalized by Nava et al (2006) to a wind profile, can be accounted for by the viewing angle interpretation accordingly generalized to a wind profile. Most of the scatter in the spectra and time-integrated brightness in $\\gamma$-ray bursts (GRB) can thus be accounted for by variation in two parameters, 1) the viewing angle and 2) the je...

  7. Thermomechanical analysis of fast-burst reactors

    International Nuclear Information System (INIS)

    Fast-burst reactors are designed to provide intense, short-duration pulses of neutrons. The fission reaction also produces extreme time-dependent heating of the nuclear fuel. An existing transient-dynamic finite element code was modified specifically to compute the time-dependent stresses and displacements due to thermal shock loads of reactors. Thermomechanical analysis was then applied to determine structural feasibility of various concepts for an EDNA-type reactor and to optimize the mechanical design of the new SPR III-M reactor

  8. Decay time of type III solar bursts

    International Nuclear Information System (INIS)

    Sixty-four Type III bursts that drifted to frequencies below 600 kHz between March 1968 and February 1970 were analyzed. Decay times were measured and combined with published data ranging up to about 200 MHz. By fitting power functions to the computed and observed decay times, and using the local plasma hypothesis, it was found that the ratio rho of computed to observed values varies with radiocentric radial distance according to a power function rho = 3r0.7. (U.S.)

  9. 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.

  10. 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.

  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. Plasma bursts in deep penetration laser welding

    Czech Academy of Sciences Publication Activity Database

    Mrňa, Libor; Šarbort, Martin

    Amsterdam: Elsevier, 2014, s. 1-1436. ISSN 1875-3892. [LANE 2014. International Conference on Photonic Technolgies /8./. Fürth (DE), 08.09.2014-11.09.2014] R&D Projects: GA MŠk ED0017/01/01; GA MŠk(CZ) LO1212; GA MŠk EE2.4.31.0016; GA MPO 2A-3TP1/113 Institutional support: RVO:68081731 Keywords : laser welding * plasma bursts * intensity oscillations * frequency analysis Subject RIV: BH - Optics, Masers, Lasers

  13. 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...

  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. 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.

  16. 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

  17. 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 ...

  18. HORIZONTAL DRILLING ACTIVITY IN HUNGARY AND SPECIAL QUESTIONS OF BLOWOUT PREVENTION IN HORIZONTAL WELLS

    Directory of Open Access Journals (Sweden)

    Jozsef Szepesi

    1996-12-01

    Full Text Available Described is horizontal drilling in the world and data on such activity in Hungary. Results show that there is an increase of such activity in spite of complex problems in drilling and completion of horizontal wells. Since these wells are often drilled in partialy exhausted hydrocarbon fluid reservoirs with slightly over-balanced or even with under-balanced conditions, there is an increased danger of blowouts. Prevention methods and suggested procedures are elaborated.

  19. HORIZONTAL DRILLING ACTIVITY IN HUNGARY AND SPECIAL QUESTIONS OF BLOWOUT PREVENTION IN HORIZONTAL WELLS

    OpenAIRE

    Jozsef Szepesi

    1996-01-01

    Described is horizontal drilling in the world and data on such activity in Hungary. Results show that there is an increase of such activity in spite of complex problems in drilling and completion of horizontal wells. Since these wells are often drilled in partialy exhausted hydrocarbon fluid reservoirs with slightly over-balanced or even with under-balanced conditions, there is an increased danger of blowouts. Prevention methods and suggested procedures are elaborated.

  20. 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

  1. THE HORIZONTAL BRANCH OF NGC 1851: CONSTRAINTS FROM ITS RR LYRAE VARIABLES

    International Nuclear Information System (INIS)

    We use the pulsational properties of the RR Lyrae variables in the globular cluster NGC 1851 to obtain detailed constraints of the various sub-stellar populations present along its horizontal branch. On the basis of detailed synthetic horizontal branch modeling, we find that minor helium variations (Y ∼ 0.248-0.280) are able to reproduce the observed periods and amplitudes of the RR Lyrae variables, as well as the frequency of fundamental and first-overtone RR Lyrae stars. Comparison of number ratios among the blue and red horizontal branch components and the two observed subgiant branches also suggest that the RR Lyrae variables originated from the progeny of the bright subgiant branch. The RR Lyrae variables with slightly enhanced helium (Y ∼ 0.270-0.280) have longer periods at a given amplitude, as is seen with Oosterhoff II (OoII) RR Lyrae variables, whereas the RR Lyrae variables with Y ∼ 0.248-0.270 have shorter periods, exhibiting properties of Oosterhoff I (OoI) variables. This correlation does suggest that the pulsational properties of RR Lyrae stars can be very useful for tracing the various subpopulations and can provide suitable constraints on the multiple population phenomenon. It appears to be of great interest to explore whether this conclusion can be generalized to other globular clusters hosting multiple populations.

  2. Hydrogen peroxide generated by NADPH oxidase is involved in high blue-light-induced chloroplast avoidance movements in Arabidopsis

    Science.gov (United States)

    Wen, Feng; Xing, Da; Zhang, Lingrui

    2009-08-01

    One of the most important functions of blue light is to induce chloroplast movements by reducing the damage to photosynthetic machinery under excess light. Hydrogen peroxide (H2O2), generated by various environmental stimuli, can act as a signaling molecule that regulates a number of developmental processes and environmental responses. To investigate whether H2O2 is involved in high blue light-induced chloroplast avoidance movements, we use luminescence spectrometer to observe H2O2 generation with the assistance of the fluorescence probe dichlorofluorescin diacetate (H2DCF-DA). After treatment with high blue light, a large quantity of H2O2 indicated by the fluorescence intensity of DCF is produced in a dose-dependent manner in leaf strip of Arabidopsis. Enzymatic assay shows that the activity of NADPH oxidase, which is a major site for H2O2 generation, also rapidly increases in treated strips. Exogenously applied H2O2 can promote the high blue light-induced chloroplast movements. Moreover, high blue light-induced H2O2 generation can be abolished completely by addition of exogenous catalase (CAT), and partly by diphenylene iodonium (DPI) and dichlorophenyl dimethylurea (DCMU), which are an NADPH oxidase inhibitor and a blocker of electron transport chain. And subsequent chloroplast movements can be abolished by CAT and DPI, but not by DCMU. These results presented here suggested that high blue light can induce oxidative burst, and NADPH oxidase as a major producer for H2O2 is involved in blue light-induced chloroplast avoidance movements.

  3. Horizontal gene transfer between bacteria and animals.

    Science.gov (United States)

    Dunning Hotopp, Julie C

    2011-04-01

    Horizontal gene transfer is increasingly described between bacteria and animals. Such transfers that are vertically inherited have the potential to influence the evolution of animals. One classic example is the transfer of DNA from mitochondria and chloroplasts to the nucleus after the acquisition of these organelles by eukaryotes. Even today, many of the described instances of bacteria-to-animal transfer occur as part of intimate relationships such as those of endosymbionts and their invertebrate hosts, particularly insects and nematodes, while numerous transfers are also found in asexual animals. Both of these observations are consistent with modern evolutionary theory, in particular the serial endosymbiotic theory and Muller's ratchet. Although it is tempting to suggest that these particular lifestyles promote horizontal gene transfer, it is difficult to ascertain given the nonrandom sampling of animal genome sequencing projects and the lack of a systematic analysis of animal genomes for such transfers. PMID:21334091

  4. Formation evaluation of a horizontal well

    International Nuclear Information System (INIS)

    In Upper Zakum Field, the interest in horizontal drilling has continued. A second horizontal well was drilled during the second half of 1989. This necessitated running logging tools for well control and to evaluate the reservoir characteristics. The logging tool selected for this well is that of Sperry-Sun. Tools configuration and tolerance were found to fulfil SADCO's requirements and specifications. This paper reports on the services produced which included Measurement While Drilling (MWD) directional services and RLL (Recorded Lithology Logging). The RLL services cover Dual Gamma Ray (DGR), Electromagnetic Wave Resistivity (EWR) and Compensated Neutron Porosity (CN porosity). All the RLL tools were an integrated part of the Bottom Hole Drilling Assembly. Data acquired while surveying was recorded in a recording sub down-hole and retrieved when the tools were up at the surface. A PC assisted quick look interpretation was carried out using Archie's equation in shale free limestone to calculate: Effective porosity, Water Saturation and, Bulk water volume

  5. Ballistocardiography in sitting and horizontal positions

    International Nuclear Information System (INIS)

    The purpose of this study is to examine the effect of posture in the sitting and supine positions on ballistocardiography (BCG) measurements by using EMFi (electromechanical film) sensors. The experiment, measuring the subject's electrocardiography (ECG), BCG and carotid pulse (CP) signal, was repeated in the sitting and different horizontal positions. Additionally, the duration and the amplitudes of the BCG and CP signal components were studied. Certain properties of BCG differed significantly in the sitting and horizontal positions. Amplitudes of measured signals were larger, and time intervals were greater in the sitting position compared to the supine position. Thus, posture significantly influences cardiac performance evaluated by BCG. Sitting and supine positions are clearly distinguishable in the BCG signal. This provides new methods for evaluation of the hemodynamic changes induced by the body position

  6. 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...

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

    International Nuclear Information System (INIS)

    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 CoAl2O4, α-Al2O3, and γ-Al2O3. By controlling the working parameters, the distribution of the CoAl2O4 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.

  8. 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.

  9. Throwing and jumping for maximum horizontal range

    CERN Document Server

    Linthorne, N P

    2006-01-01

    Optimum projection angles for achieving maximum horizontal range in throwing and jumping events are considerably less than 45 degrees. This unexpected result arise because an athlete can generate a greater projection velocity at low projection angles than at high angles. The range of a projectile is strongly dependent on projection speed and so the optimum projection angle is biased towards low projection angles. Here we examine the velocity-angle relation and the optimum projection angle in selected throwing and jumping events.

  10. 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....

  11. 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 ...

  12. 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

  13. 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.

  14. Horizontal vibrations of piles in a centrifuge

    International Nuclear Information System (INIS)

    The aim of the thesis is the study of soil dynamics for important structures like nuclear power plants, offshore platforms, dams etc. Experimental results of horizontal vibrations on a pile partially anchored in a soil scale model put into a centrifuge are presented. Mechanical similitude conditions from equilibrium equations or rheologic laws are described. After a description of testing equipment (centrifuge, electrodynamic excitator) experimental results are interpreted with a model. Non-linearities on frequency response curves are characterized

  15. Horizontal gene transfer between bacteria and animals

    OpenAIRE

    Dunning Hotopp, Julie C.

    2011-01-01

    Horizontal gene transfer is increasingly described between bacteria and animals. Such transfers that are vertically inherited have the potential to influence the evolution of animals. One classic example is the transfer of DNA from mitochondria and chloroplasts to the nucleus after the acquisition of these organelles by eukaryotes. Even today, many of the described instances of bacteria to animal transfer occur as part of intimate relationships like those of endosymbionts and their invertebra...

  16. 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

  17. Some Comments On Fast Radio Burst

    CERN Document Server

    Luan, Jing

    2014-01-01

    Fast Radio Bursts (FRBs) are single $\\mathrm{ms}$ radio pulses with dispersion measures (DM) ranging up to $\\sim 10^3\\mathrm{pc cm^{-3}}$. It has been proposed that they originate from galactic flare stars, and that their DMs come from propagation through the stellar corona. We disapprove this hypothesis by showing that free-free absorption would conceal any radio signal emitted from below the corona. It appears that FRBs come from extragalactic sources. FRB 110220 has a scattering tail of several $\\mathrm{ms}$ Propagation through the intergalactic plasma is unlikely to account for scattering of this magnitude unless the intergalactic magnetic field is as large as $2.4\\times 10^{-9}\\mathrm{G}$. This suggests that this burst originated in the central region of an external galaxy. Extrapolated to cosmological distances and sources sizes of order $c\\Delta t$, the electric fields of FRBs are strong in the sense that they would accelerate thermal electrons to relativistic energies in less than a nanosecond.

  18. $\\gamma$-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...

  19. 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 ...

  20. 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 ...

  1. 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.

  2. 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...

  3. 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.

  4. 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.

  5. 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....

  6. Productivity and Injectivity of Horizontal Wells

    International Nuclear Information System (INIS)

    The work on modeling hydraulically fractured horizontal wells has moved forward. A literature review on the subject was done and some of the existing models have been coded and applied to example problems for evaluation purposes. Previous work on the elects of heterogeneities on the performance of horizontal wells was continued by conducting a sensitivity study on various parameters that were kept constant in the earlier study. For example, we have studied the elect of gas cap and aquifer size, well location, fluid viscosity, etc. The experimental work on using horizontal wells as injectors and producers in a gas injection gravity drainage process continued. New and repeat experiments were conducted. Work on streamline grids was advanced by considering example problems with highly distorted grids which cannot be directly used for flow simulation. Grid smoothing and domain mapping techniques were investigated to handle such situations. A technique was developed for the computation o f well index with consideration to wellbore pressure drop. A recently developed reservoir/wellbore coupling model was used for this purpose

  7. c horizontal convexity on Carnot groups

    CERN Document Server

    Calogero, Andrea

    2010-01-01

    Given a real-valued function $c$ defined on the cartesian product of a generic Carnot group $\\G$ and the first layer $V_1$ of its Lie algebra, we introduce a notion of $c$ horizontal convex ($c$ H-convex) function on $\\G$ as the supremum of a suitable family of affine functions; this family is defined pointwisely, and depends strictly on the horizontal structure of the group. This abstract approach provides $c$ H-convex functions that, under appropriate assumptions on $c,$ are characterized by the nonemptiness of the $c$ H-subdifferential and, above all, are locally H-semiconvex, thereby admitting horizontal derivatives almost everywhere. It is noteworthy that such functions can be recovered via a Rockafellar technique, starting from a suitable notion of $c$ H-cyclic monotonicity for maps. In the particular case where $c(g,v)=,$ we obtain the well-known weakly H-convex functions introduced by Danielli, Garofalo and Nhieu. Finally, we suggest a possible application to optimal mass transportation.

  8. OPERATION UPSHOT-KNOTHOLE Project 6.12 DETERMINATION OF HEIGHT OF BURST AND GROUND ZERO

    Energy Technology Data Exchange (ETDEWEB)

    Tiede, Roland V.; Kelly, Daniel F.; Burger, Kenneth C.

    1955-05-01

    requirement for speed in processing required the use of this film. The camera used was a modification of an experimental flash ranging camera /part of Flash Ranging Set AN/TVS-1 (XE-2)_7with the conventional refractive optics replaced by a pinhole. A high speed shutter tripped hy a blue box was employed. It was determined experimentally that a given pinhole aperture with a fixed delay time provided photographs of the fireball with adequate resolution for accurate angular measurements over a wide range of yields and distances. Average angular accuracies of 0.73 mils were obtained. It was estimated that ground zero locations and burst heights could be provided by this method under tactical conditions in 5 to 10 minutes. Conventional Bhangpeters furnished yield determinations under non-line-of-sight conditions at ranges out to UO miles with an accuracy of the order of 20 per cent or better. Attempts to utilize a Bhangmeter type instrument with a lead sulfide cell detector indicated that extensive investigation would be required to establish the correlation between yield and time to minimum in the light intensity-time curve for the spectral response of the lead sulfide cell. Attempts to modify a Mark III Type Bhangmeter by substituting a lead sulfide cell for the photo cell made possible successful time of flight measurements on the 260 mm gun when firing conventional ammunition. Design parameters were established for such a time of flight measuring equipment.

  9. The First Detection of Blue Straggler Stars in the Milky Way Bulge

    CERN Document Server

    Clarkson, William I; Anderson, Jay; Rich, R Michael; Smith, T Ed; Brown, Thomas M; Bond, Howard E; Livio, Mario; Minniti, Dante; Renzini, Alvio; Zoccali, Manuela

    2011-01-01

    We report the first detections of Blue Straggler Stars (BSS) in the bulge of the Milky Way galaxy. Proper motions from extensive space-based observations along a single sight-line allow us to separate a sufficiently clean and well-characterized bulge sample that we are able to detect a small population of bulge objects in the region of the color-magnitude diagram commonly occupied young objects and blue strgglers. However, variability measurements of these objects clearly establish that a fraction of them are blue stragglers. Out of the 42 objects found in this region of the color-magnitude diagram, we estimate that at least 18 are genuine BSS. We normalize the BSS population by our estimate of the number of horizontal branch stars in the bulge in order to compare the bulge to other stellar systems. The BSS fraction is clearly discrepant from that found in stellar clusters. The blue straggler population of dwarf spheroidals remains a subject of debate; some authors claim an anticorrelation between the normali...

  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. Observations of cosmic gamma ray bursts with WATCH on EURECA

    DEFF Research Database (Denmark)

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

    1995-01-01

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

  12. 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.

  13. The WATCH solar X-ray burst catalogue

    DEFF Research Database (Denmark)

    Crosby, N.; Lund, Niels; Vilmer, N.; Sunyaev, R.

    1998-01-01

    The WATCH experiment aboard the GRANAT satellite provides observations of the Sun in the deka-keV range covering the years 1990 through mid-1992. An introduction to the experiment is given followed by an explanation of how the WATCH solar burst catalogue was created. The different parameters listed...... for each burst is given and are furthermore explained....

  14. Large tundra methane burst during onset of freezing

    DEFF Research Database (Denmark)

    Mastepanov, Mikhail; Sigsgaard, Charlotte; Dlugokencky, Edward J.; Houweling, Sander; Ström, Lena; Tamstorf, Mikkel Peter; Christensen, Torben R.

    2008-01-01

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

  15. On the existence of optimum cyclic burst-correcting codes

    OpenAIRE

    1986-01-01

    It is shown that for each integer b >= 1 infinitely many optimum cyclic b-burst-correcting codes exist, i.e., codes whose length n, redundancy r, and burst-correcting capability b, satisfy n = 2^{r-b+1} - 1. Some optimum codes for b = 3, 4, and 5 are also studied in detail.

  16. Gamma ray bursts observed with WATCH‐EURECA

    DEFF Research Database (Denmark)

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

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

  17. The INTEGRAL view of intermediate long X-ray bursts

    DEFF Research Database (Denmark)

    CONCLUSIONS Most intermediate bursts are observed from low luminosity sources and are interpreted as long pure He bursts. If no H is accreted, they are consistent with the burning of a slowly accreted, thick He layer, in Ultra Compact X-ray Binaries (UCXB) where the donor star is probably a...

  18. Spike-type broad-band solar bursts

    International Nuclear Information System (INIS)

    High-resolution dynamical spectra of solar broad-band spike bursts (BSB) have been observed. They represent an instantaneous brightening of the continuum emission in the range 175-235 MHz. In the noise stoms the BSB-type events occur seldom and have the form of either individual bursts with the average lifetime of 0.1-0.2 s or the groups of such bursts, related with type 3 bursts at lower frequencies. In type 4 bursts, the series of nonperiodic structures of BSB predominate. They are not related with type 3 bursts, but are observed together with the second pulsations and fiber bursts. In the noise storms, the BSB can be excited by electrons instantaneously accelerated owing to the magnetic field reconnection. The group delay leads to a negative frequency drift approximately -600 MHz/s in small sources and positive drift approximately 300 MHz/s in the extended ones. Such a high drift velocity cannot compensate the moderate frequency drift associated with the exciter motion in the corona. The BSB-structure in type 4 bursts can be the result of scattering of the Langmuir waves on the whistlers in a large height interval

  19. 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)

  20. Testing and Performance of UFFO Burst Alert & Trigger Telescope

    DEFF Research Database (Denmark)

    Rípa, Jakub; Bin Kim, Min; Lee, Jik;

    2014-01-01

    The Ultra-Fast Flash Observatory pathfinder (UFFO-p) is a new space mission dedicated to detect Gamma-Ray Bursts (GRBs) and rapidly follow their afterglows in order to provide early optical/ultraviolet measurements. A GRB location is determined in a few seconds by the UFFO Burst Alert & Trigger...

  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. 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

  3. 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

  4. 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.

  5. Inclusion of horizontal branch stars in the derivation of star formation histories of dwarf galaxies: The Carina dSph

    Science.gov (United States)

    Savino, Alessandro; Salaris, Maurizio; Tolstoy, Eline

    2015-11-01

    We present a detailed analysis of the horizontal branch of the Carina dwarf spheroidal galaxy by means of synthetic modelling techniques, taking consistently into account the star formation history and metallicity evolution as determined from main sequence and red giant branch spectroscopic observations. We found that a range of integrated red giant branch mass loss values of 0.1-0.14 M⊙ increasing with metallicity is able to reproduce the colour extension of the old horizontal branch. Nonetheless, leaving the mass loss as the only free parameter is not enough to match the detailed morphology of Carina horizontal branch. We then investigated the role played by the star formation history on the discrepancies between synthetic and observed horizontal branches. We derived a "toy" bursty star formation history that reproduces well the observed horizontal branch star counts, and also matches qualitatively the red giant and the turn-off regions. This bursty star formation history is made of a subset of age and [M/H] components of the star formation history based on turn off and red giants only, and entails four separate bursts of star formation of different strengths, centred at 2, 5, 8.6, and 11.5 Gyr, respectively, with mean [M/H] decreasing from ~-1.7 to ~-2.2 when the age of the burst increases, and with a Gaussian spread of σ 0.1 dex around these mean values. The comparison between the metallicity distribution function of our bursty star formation history and the one measured from the infrared CaT feature using a CaT-[Fe/H] calibration shows a qualitative agreement, once the range of [Ca/Fe] abundances measured in a sample of Carina stars have been taken into account, that causes a bias of the derived [Fe/H] distribution toward values that are too low. In conclusion, we show how the information contained within the horizontal branch of Carina (and dwarf galaxies in general) can be extracted and interpreted to refine the star formation history derived exclusively

  6. 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.

  7. Models for Gamma-Ray Burst Progenitors and Central Engines

    CERN Document Server

    Woosley, S E

    2011-01-01

    Most gamma-ray bursts are made during the deaths of massive stars. Here the environmental circumstances, stellar evolutionary paths, and explosion physics that might produce the bursts are reviewed. Neither of the two leading models - collapsar and millisecond magnetar - can be excluded, and both may operate in progenitor stars of different masses, metallicities, and rotation rates. Potential diagnostics are discussed and uncertainties highlighted. Both models are capable of producing a wide variety of transients whose properties vary with both stellar properties and viewing angle. Some of these are reviewed including the possibility of very long (days) low luminosity bursts, so far undiscovered, short hard bursts from massive stellar progenitors, and bursts from very massive Population III stars.

  8. 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

  9. 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.

  10. First Results from the Swift Gamma Ray Burst Mission

    Science.gov (United States)

    Gehreis, Neil

    2005-01-01

    Swift is now in orbit after a beautiful launch on November 20, 2004. It is a multiwavelength observatory designed specifically to study the fascinating gamma-ray bursts. The goals are to determine the origin of bursts and use them to probe the early Universe. A new-technology wide-field gamma-ray camera detects more than a hundred bursts per year. Sensitive narrow-field X-ray and UV/optical telescopes are pointed at the burst location in 20 to 70 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. First results from the mission will be presented, including observations of bright GRBs, faint GRBs, short GRBs and a super-giant flare from the soft gamma repeater SGRl806-20.

  11. 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.

  12. Amplitude sorting of oscillatory burst signals by sampling

    Science.gov (United States)

    Davis, Thomas J.

    1977-01-01

    A method and apparatus for amplitude sorting of oscillatory burst signals is described in which the burst signal is detected to produce a burst envelope signal and an intermediate or midportion of such envelope signal is sampled to provide a sample pulse output. The height of the sample pulse is proportional to the amplitude of the envelope signal and to the maximum burst signal amplitude. The sample pulses are fed to a pulse height analyzer for sorting. The present invention is used in an acoustic emission testing system to convert the amplitude of the acoustic emission burst signals into sample pulse heights which are measured by a pulse height analyzer for sorting the pulses in groups according to their height in order to identify the material anomalies in the test material which emit the acoustic signals.

  13. 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.

  14. IDENTIFICATION OF BURSTING WATER MASER FEATURES IN ORION KL

    International Nuclear Information System (INIS)

    In 2011 February, a burst event of the H2O maser in Orion KL (Kleinmann-Low object) has started after a 13 year silence. This is the third time such phenomena has been detected in Orion KL, followed by the events in 1979-1985 and 1998. We have carried out astrometric observations of the bursting H2O maser features in Orion KL with the VLBI Exploration of Radio Astrometry (VERA), a Japanese very long baseline interferometry network dedicated for astrometry. The total flux of the bursting feature at the local standard of rest (LSR) velocity of 7.58 km s-1 reaches 4.4 x 104 Jy in 2011 March. The intensity of the bursting feature is three orders of magnitude 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 2011 May, 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 burst in 1998. We determine the absolute positions of the bursting features for the first time ever with a submilliarcsecond (mas) accuracy. Their positions are coincident with the shocked molecular gas called the Orion Compact Ridge. We tentatively detect the absolute proper motions of the bursting features toward the southwest direction. It is most likely that the outflow from the radio source I or another young stellar object interacting with the Compact Ridge is a possible origin of the H2O maser burst.

  15. 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)

  16. Automatic recognition of type III solar radio bursts. Automated radio burst identification system method and first observations

    International Nuclear Information System (INIS)

    Complete text of publication follows. Because of the rapidly increasing role of technology, including complicated electronic systems, spacecraft, etc., modern society has become more vulnerable to a set of extraterrestrial influences (space weather) and requires continuous observation and forecasts of space weather. The major space weather events like solar flares and coronal mass ejections are usually accompanied by solar radio bursts, which can be used for a real-time space weather forecast. Coronal type III radio bursts are produced near the local electron plasma frequency and near its harmonic by fast electrons ejected from the solar active regions and moving through the corona and solar wind. These bursts have dynamic spectra with frequency rapidly falling with time, the typical duration of the coronal burst being about 1-3 s. This paper presents a new method developed to detect coronal type III bursts automatically and its implementation in a new Automated Radio Burst Identification System (ARBIS), which is working in real-time. The central idea of the implementation is to use the Radon transform for more objective detection of the bursts as approximately straight lines in dynamic spectra. Preliminary tests of the method with the use of the spectra obtained during 13 days show that the performance of the current implementation is quite high, ∼84%, while no false positives are observed and 23 events not listed previously are found. The first automatically detected coronal type III radio bursts are presented.

  17. 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.

  18. 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...

  19. 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 (distribution for commercial applications. PMID:27408982

  20. 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.

  1. 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.

  2. A POSSIBLE CONNECTION BETWEEN FAST RADIO BURSTS AND GAMMA-RAY BURSTS

    International Nuclear Information System (INIS)

    The physical nature of fast radio bursts (FRBs), a new type of cosmological transient discovered recently, is not known. It has been suggested that FRBs can be produced when a spinning supra-massive neutron star loses centrifugal support and collapses to a black hole. Here, we suggest that such implosions can happen in supra-massive neutron stars shortly (hundreds to thousands of seconds) after their births, and an observational signature of such implosions may have been observed in the X-ray afterglows of some long and short gamma-ray bursts (GRBs). Within this picture, a small fraction of FRBs would be physically connected to GRBs. We discuss possible multi-wavelength electromagnetic signals and gravitational wave signals that might be associated with FRBs, and propose an observational campaign to unveil the physical nature of FRBs. In particular, we strongly encourage a rapid radio follow-up observation of GRBs starting from 100 s after a GRB trigger

  3. 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.

  4. 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...

  5. 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...

  6. Cosmic-Rays and Gamma Ray Bursts

    Science.gov (United States)

    Meli, A.

    2013-07-01

    Cosmic-rays are subatomic particles of energies ranging between a few eV to hundreds of TeV. These particles register a power-law spectrum, and it seems that most of them originate from astrophysical galactic and extragalactic sources. The shock acceleration in superalfvenic astrophysical plasmas, is believed to be the main mechanism responsible for the production of the non-thermal cosmic-rays. Especially, the importance of the very high energy cosmic-ray acceleration, with its consequent gamma-ray radiation and neutrino production in the shocks of the relativistic jets of Gamma Ray Bursts, is a favourable theme of study. I will discuss the cosmic-ray shock acceleration mechanism particularly focusing on simulation studies of cosmic-ray acceleration occurring in the relativistic shocks of GRB jets.

  7. Heliospheric Origin of $\\gamma$-Ray Bursts

    CERN Document Server

    Li Ti Pei

    1997-01-01

    Systematic variations of average observational characteristics and correlation properties between different parameters of gamma-ray bursts (GRBs) with time from 1991 April to 1994 September are revealed. It is hard to explain the observed long-term variability by variations of experimental conditions. The variability of GRB properties with the time scale of months to years, together with the similarity between GRBs, solar hard X-ray flares and terrestrial gamma-ray flashes, may indicate an origin of GRBs, at least partly, within the heliosphere. Large-voltage and high-temperature pinch plasma columns produced by disruptive electrical discharges in the outer heliosphere can generate hard X-ray and gamma-ray flashes with energy spectra and spectral evolution characters consistent with that observed in GRBs.

  8. 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.

  9. Super Luminous Supernova and Gamma Ray Bursts

    CERN Document Server

    Dado, Shlomo

    2012-01-01

    We use a simple analytical model to derive a closed form expression for the bolometric light-curve of super-luminus supernovae (SLSNe) powered by a plastic collision between the fast ejecta from ordinary core collapse supernovae (SNe) of type Ib/c and slower massive circum-stellar shells, ejected in major eruptions of their progenitor stars during the late stage of their life preceding their SN explosion. We demonstrate that this expression reproduces well the bolometric luminosity of SLSNe with and without an observed gamma ray burst (GRB), and requires only a modest amount ($M\\lsim 0.1\\,M_\\odot$) of radioactive $^{56}$Ni synthesized in the SN explosion in order to explain their late-time luminosity. Ordinary stripped-envelope SNe of type Ib/c, rather than 'hypernovae', can produce most of the SLSNe and long duration GRBs.

  10. 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.

  11. Gamma-Ray Bursts as Cosmological Tools

    CERN Document Server

    Petrosian, Vahe; Ryde, Felix

    2009-01-01

    In recent years there has been considerable activity in using gamma-ray bursts as cosmological probes for determining global cosmological parameters complementing results from type Ia supernovae and other methods. This requires a characteristics of the source to be a standard candle. We show that contrary to earlier indications the accumulated data speak against this possibility. Another method would be to use correlation between a distance dependent and a distance independent variable to measure distance and determine cosmological parameters as is done using Cepheid variables and to some extent Type Ia supernovae. Many papers have dealt with the use of so called Amati relation, first predicted by Lloyd, Petrosian and Mallozzi, or the Ghirlanda relation for this purpose. We have argued that these procedure involve many unjustified assumptions which if not true could invalidate the results. In particular, we point out that many evolutionary effects can affect the final outcome. In particular, we demonstrate th...

  12. 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.

  13. 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.

  14. Directivity of X radiation of solar bursts

    International Nuclear Information System (INIS)

    To study the directivity of X radiation of solar bursts, the investigation into distributions of X-ray splashes over the range lambda=0.5-3 and 1-8 A in heliolongitudinal and intensity was carried on. The integral distribution of splashes in intensity has the exponential form with the exponent α approximately 1.1 and the bend on low intensities. In heliolongitudinal distribution the east-west asymmetry is observed. The absence of directivity of splash radiation is concluded on the basis of investigation of peculiarities of splash distribution functions in heliolongitude and intensity. The observed east-west asymmetry can't be connected with directivity, but is conditioned by probably by statistic fluctuations of the number of splashes

  15. 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.

  16. Search for Gamma Ray Bursts at Chacaltaya

    CERN Document Server

    Vernetto, S

    2001-01-01

    A search for Gamma Ray Bursts in the GeV-TeV energy range has been performed by INCA, an air shower array working at 5200 m of altitude at the Chacaltaya Laboratory (Bolivia). The altitude of the detector and the use of the "single particle technique" allows to lower the energy threshold up to few GeVs. No significant signals are observed during the occurrence of 125 GRBs detected by BATSE, and the obtained upper limits on the energy fluence in the interval 1-1000(100) GeV range from 3.2(8.6) 10^-5 to 2.6(7.0) 10^-2 erg/cm^2 depending on the zenith angle of the events. These limits, thanks to the extreme altitude of INCA, are the lowest ever obtained in the sub-TeV energy region by a ground based esperiment.

  17. 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.

  18. 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...

  19. 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...

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

    OpenAIRE

    Dar, Roy D.; Razooky, Brandon S; Singh, Abhyudai; Trimeloni, Thomas V.; McCollum, James M.; Cox, Chris D.; Simpson, Michael L.; Weinberger, Leor S.

    2012-01-01

    Gene expression occurs either as an episodic process, characterized by pulsatile bursts, or as a constitutive process, characterized by a 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 to analyze 8,000 individual human genomic loci and find that at virtually...