3,166 research outputs found
Delayed soft X-ray emission lines in the afterglow of GRB 030227
Strong, delayed X-ray line emission is detected in the afterglow of GRB
030227, appearing near the end of the XMM-Newton observation, nearly twenty
hours after the burst. The observed flux in the lines, not simply the
equivalent width, sharply increases from an undetectable level (<1.7e-14
erg/cm^2/s, 3 sigma) to 4.1e-14 erg/cm^2/s in the final 9.7 ks. The line
emission alone has nearly twice as many detected photons as any previous
detection of X-ray lines. The lines correspond well to hydrogen and/or
helium-like emission from Mg, Si, S, Ar and Ca at a redshift z=1.39. There is
no evidence for Fe, Co or Ni--the ultimate iron abundance must be less than a
tenth that of the lighter metals. If the supernova and GRB events are nearly
simultaneous there must be continuing, sporadic power output after the GRB of a
luminosity >~5e46 erg/s, exceeding all but the most powerful quasars.Comment: Submitted to ApJL. 14 pages, 3 figures with AASLaTe
Influence of Fatigue on Planned Agility Performance in Soccer Players.
International Journal of Exercise Science 13(1): 656-666, 2020. We investigated the acute fatiguing effects of sprint interval training (SIT) on change of direction performance in male and female soccer players. A T-test was performed once before (PRE) and twice following (POST 1 and POST 2) the completion of four sets of 4 s cycle ergometer sprints protocol. The sprint intervals were separated by 25 s active recovery. POST 1 was performed approximately 25 s following the final cycle sprint and POST 2 began two minutes after completing POST 1. Repeated measures ANOVA and Bonferroni post hoc tests were used to determine any significant differences in the time to complete the T-tests. The average power output drop measured during cycle SIT was 30.7 ± 9%. Time to complete the T-test significantly differed among the three tests (PRE: 10.46 ± .17 s; POST 1: 11.67 ± .33 s; POST 2: 10.96 ± .19 s; F (2, 54) = 6.174, p = .003). Post hoc test revealed an increase in time from PRE to POST 1 (p = .002) but no difference between PRE and POST 2 (p = .473). Nine participants (48%) were unable to complete POST 1 without errors; however, ten (52%) participants recovered enough to perform POST 1 without error. These results show that acute fatigue from SIT impairs change of direction performance, but performance can be recovered within a few minutes of rest. Coaches can combine fatigue inducing drills and change of direction training into same sessions with the right rest interval between the training modes
Swift Identification of Dark Gamma-Ray Bursts
We present an optical flux vs. X-ray flux diagram for all known gamma-ray
bursts (GRBs) for which an X-ray afterglow has been detected. We propose an
operational definition of dark bursts as those bursts that are optically
subluminous with respect to the fireball model, i.e., which have an
optical-to-X-ray spectral index beta_OX < 0.5. Out of a sample of 52 GRBs we
identify 5 dark bursts. The definition and diagram serve as a simple and quick
diagnostic tool for identifying dark GRBs based on limited information,
particularly useful for early and objective identification of dark GRBs
observed with the Swift satellite.Comment: 4 pages, 1 figure. ApJ Letters, in pres
Cast-as-Intended Mechanism with Return Codes Based on PETs
We propose a method providing cast-as-intended verifiability for remote
electronic voting. The method is based on plaintext equivalence tests (PETs),
used to match the cast ballots against the pre-generated encrypted code tables.
Our solution provides an attractive balance of security and functional
properties. It is based on well-known cryptographic building blocks and relies
on standard cryptographic assumptions, which allows for relatively simple
security analysis. Our scheme is designed with a built-in fine-grained
distributed trust mechanism based on threshold decryption. It, finally, imposes
only very little additional computational burden on the voting platform, which
is especially important when voters use devices of restricted computational
power such as mobile phones. At the same time, the computational cost on the
server side is very reasonable and scales well with the increasing ballot size
Ukupni i specifiÄŤni mortalitet u radnika izloĹľenih azbestu od 1907. do 1985. godine
Total and cause-specific mortality data for the 1907 -1985 period were compared between cohorts of male asbestos-cement workers (N = 1908) and referents (N = 726), using Poisson regression modelling. The rate ratio (RR) for total mortality was significantly increased (1.3) among the exposed workers, as was mortality from non-malignant respiratory disease (RR= 2.2). Numerically, but not statistically significantly, raised ratios were found for respiratory (RR= 1.6) and gastrointestinal (RR= 1.3) cancers. The trend in the rate ratio for total mortality with time was better fitted with a curved line, than with a monotonic one, because of a period of increased risk up to the 1950s, and another one starting after 1970.Ukupni i specifični mortalitet za razdoblje od 1907. do 1985. godine uspoređen je u kohortama muških radnika koji su bili izloženi azbestu (N = 1908) s kontrolama (N = 726) pomoću Poissonove regresijske analize. Koeficijent regresije (RR) za ukupni mortalitet, kao i mortalitet od nemalignih respiratornih bolesti bio je statistički značajno viši i iznosio je 1,3, odnosno 2,2. Povećanje ovog koeficijenta nađeno je i za plućni (1,6) i gastrointestinalni karcinom (1,3), ali vrijednosti nisu statistički značajne
Biopsy findings in giant cell arteritis: relationship to baseline factors and corticosteroid treatment.
On the nature of the short duration GRB 050906
The definitive version is available at www.blackwell-synergy.com. Copyright Blackwell Publishing DOI : 10.1111/j.1365-2966.2007.11953.xPeer reviewe
The distribution of equivalent widths in long GRB afterglow spectra
The extreme brightness of gamma-ray burst (GRB) afterglows and their simple
spectral shape make them ideal beacons to study the interstellar medium of
their host galaxies through absorption line spectroscopy. Using 69
low-resolution GRB afterglow spectra, we conduct a study of the rest-frame
equivalent width (EW) distribution of features with an average rest-frame EW
larger than 0.5 A. To compare an individual GRB with the sample, we develop EW
diagrams as a graphical tool, and we give a catalogue with diagrams for the 69
spectra. We introduce a line strength parameter (LSP) that allows us to
quantify the strength of the absorption features as compared to the sample by a
single number. Using the distributions of EWs of single-species features, we
derive the distribution of column densities by a curve of growth (CoG) fit. We
find correlations between the LSP and the extinction of the GRB, the UV
brightness of the host galaxies and the neutral hydrogen column density.
However, we see no significant evolution of the LSP with the redshift. There is
a weak correlation between the ionisation of the absorbers and the energy of
the GRB, indicating that, either the GRB event is responsible for part of the
ionisation, or that galaxies with high-ionisation media produce more energetic
GRBs. Spectral features in GRB spectra are, on average, 2.5 times stronger than
those seen in QSO intervening damped Lyman-alpha (DLA) systems and slightly
more ionised. In particular we find larger excess in the EW of CIV1549 relative
to QSO DLAs, which could be related to an excess of Wolf-Rayet stars in the
environments of GRBs. From the CoG fitting we obtain an average number of
components in the absorption features of GRBs of 6.00(-1.25,+1.00). The most
extreme ionisation ratios in our sample are found for GRBs with low neutral
hydrogen column density, which could be related to ionisation by the GRB
emission.Comment: 37 pages, 31 figures, 15 tables. Accepted for publication in Astonomy
and Astrophysic
On the sensitivity of the energy of vanishing flow towards mass asymmetry of colliding nuclei
We demonstrate the role of the mass asymmetry in the energy of vanishing flow
by studying asymmetric reactions throughout the periodic table and over entire
colliding geometry. Our results, which are almost independent of the system
size and as well as of the colliding geometries indicate a sizable effect of
the asymmetry of the reaction on the energy of vanishing flow
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