212 research outputs found
Rest-frame properties of 32 gamma-ray bursts observed by the Fermi Gamma-Ray Burst Monitor
Aims: In this paper we study the main spectral and temporal properties of
gamma-ray bursts (GRBs) observed by Fermi/GBM. We investigate these key
properties of GRBs in the rest-frame of the progenitor and test for possible
intra-parameter correlations to better understand the intrinsic nature of these
events. Methods: Our sample comprises 32 GRBs with measured redshift that were
observed by GBM until August 2010. 28 of them belong to the long-duration
population and 4 events were classified as short/hard bursts. For all of these
events we derive, where possible, the intrinsic peak energy in the spectrum (\eprest), the duration in the rest-frame, defined as the
time in which 90% of the burst fluence was observed (\tninetyrest) and the
isotropic equivalent bolometric energy (\eiso). Results: The distribution of
\eprest has mean and median values of 1.1 MeV and 750 keV, respectively. A
log-normal fit to the sample of long bursts peaks at ~800 keV. No high-\ep
population is found but the distribution is biased against low \ep values. We
find the lowest possible \ep that GBM can recover to be ~ 15 keV. The
\tninetyrest distribution of long GRBs peaks at ~10 s. The distribution of
\eiso has mean and median values of erg and erg, respectively. We confirm the tight correlation between \eprest
and \eiso (Amati relation) and the one between \eprest and the 1-s peak
luminosity () (Yonetoku relation). Additionally, we observe a parameter
reconstruction effect, i.e. the low-energy power law index gets softer
when \ep is located at the lower end of the detector energy range. Moreover, we
do not find any significant cosmic evolution of neither \eprest nor
\tninetyrest.Comment: accepted by A&
SGR J1550-5418 bursts detected with the Fermi Gamma-ray Burst Monitor during its most prolific activity
We have performed detailed temporal and time-integrated spectral analysis of
286 bursts from SGR J1550-5418 detected with the Fermi Gamma-ray Burst Monitor
(GBM) in January 2009, resulting in the largest uniform sample of temporal and
spectral properties of SGR J1550-5418 bursts. We have used the combination of
broadband and high time-resolution data provided with GBM to perform
statistical studies for the source properties. We determine the durations,
emission times, duty cycles and rise times for all bursts, and find that they
are typical of SGR bursts. We explore various models in our spectral analysis,
and conclude that the spectra of SGR J1550-5418 bursts in the 8-200 keV band
are equally well described by optically thin thermal bremsstrahlung (OTTB), a
power law with an exponential cutoff (Comptonized model), and two black-body
functions (BB+BB). In the spectral fits with the Comptonized model we find a
mean power-law index of -0.92, close to the OTTB index of -1. We show that
there is an anti-correlation between the Comptonized Epeak and the burst
fluence and average flux. For the BB+BB fits we find that the fluences and
emission areas of the two blackbody functions are correlated. The
low-temperature BB has an emission area comparable to the neutron star surface
area, independent of the temperature, while the high-temperature blackbody has
a much smaller area and shows an anti-correlation between emission area and
temperature. We compare the properties of these bursts with bursts observed
from other SGR sources during extreme activations, and discuss the implications
of our results in the context of magnetar burst models.Comment: 13 pages, 10 figures, 2 tables; minor changes, ApJ in pres
Fermi observations of high-energy gamma-ray emission from GRB 080825C
The Fermi Gamma-ray Space Telescope (FGST) has opened a new high-energy
window in the study of Gamma-Ray Bursts (GRBs). Here we present a thorough
analysis of GRB 080825C, which triggered the Fermi Gamma-ray Burst Monitor
(GBM), and was the first firm detection of a GRB by the Fermi Large Area
Telescope (LAT). We discuss the LAT event selections, background estimation,
significance calculations, and localization for Fermi GRBs in general and GRB
080825C in particular. We show the results of temporal and time-resolved
spectral analysis of the GBM and LAT data. We also present some theoretical
interpretation of GRB 080825C observations as well as some common features
observed in other LAT GRBs.Comment: 18 pages, 7 figures. Accepted for publication in ApJ. Corresponding
authors: A. Bouvier, J. Granot, A.J. van der Hors
Inventory and review of the Mio–Pleistocene São Jorge flora (Madeira Island, Portugal): palaeoecological and biogeographical implications
The occurrence of plant fossils on Madeira Island has been known since the mid-nineteenth century. Charles Lyell and
George Hartung discovered a leaf bed rich in Lauraceae and fern fossils at S~ao Jorge in 1854. The determinations were
controversial but a full review was never performed. Here we propose possible geological settings for the fossiliferous
outcrop, and present an inventory and a systematic review of the surviving specimens of the S~ao Jorge macroflora. The S~ao
Jorge leaf bed no longer outcrops due to a landslide in 1865. It was possible to establish the two alternative volcano stratigraphical settings in the sedimentary intercalations from the Middle Volcanic Complex, ranging in age from 7 to
1.8 Ma. The descriptions of Heer (1857), Bunbury (1859) and Hartung & Mayer (1864) are reviewed based on 82
surviving specimens. From the initial 37 taxa, we recognize only 20: Osmunda sp., Pteridium aquilinum, Asplenium cf.
onopteris, aff. Asplenium, cf. Polystichum, cf. Davallia, Woodwardia radicans, Filicopsida gen. et sp. indet. 1 and 2,
Ocotea foetens, Salix sp., Erica arborea, cf. Vaccinium, Rubus sp, cf. Myrtus, Magnoliopsida gen. et sp. indet. 1 to 3,
Liliopsida gen. et sp. indet. 1. Magnoliopsida gen. et sp. indet. 4 is based on one previously undescribed flower or fruit.
The floristic composition of the S~ao Jorge fossils resembles the current floristic association of temperate stink laurel
(Ocotea foetens) forest, suggesting a warm and humid palaeoclimate and indicating that laurel forests were present in
Macaronesia at least since the Gelasian, a time when the palaeotropical geofloral elements were almost extinct in Europe.info:eu-repo/semantics/publishedVersio
SEARCHING the GAMMA-RAY SKY for COUNTERPARTS to GRAVITATIONAL WAVE SOURCES: FERMI GAMMA-RAY BURST MONITO R and LARGE AREA TELESCOPE OBSERVATIONS of LVT151012 and GW151226
We present the Fermi Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) observations of the LIGO binary black hole merger event GW151226 and candidate LVT151012. At the time of the LIGO triggers on LVT151012 and GW151226, GBM was observing 68% and 83% of the localization regions, and LAT was observing 47% and 32%, respectively. No candidate electromagnetic counterparts were detected by either the GBM or LAT. We present a detailed analysis of the GBM and LAT data over a range of timescales from seconds to years, using automated pipelines and new techniques for characterizing the flux upper bounds across large areas of the sky. Due to the partial GBM and LAT coverage of the large LIGO localization regions at the trigger times for both events, differences in source distances and masses, as well as the uncertain degree to which emission from these sources could be beamed, these non-detections cannot be used to constrain the variety of theoretical models recently applied to explain the candidate GBM counterpart to GW150914
Image overlay surgery based on augmented reality : a systematic review
Acknowledgements We thank the staff of the Medical Library of the University of Aberdeen for their advice and Prof. Jennifer Cleland and Dr Jenny Gregory for discussion and support. This work was funded by the Roland Sutton Academic Trust (0053/R/17) and an Elphinstone PhD Scholarship from the University of Aberdeen.Postprin
Understanding the nature and mechanism of foot pain
Approximately one-quarter of the population are affected by foot pain at any given time. It is often disabling and can impair mood, behaviour, self-care ability and overall quality of life. Currently, the nature and mechanism underlying many types of foot pain is not clearly understood. Here we comprehensively review the literature on foot pain, with specific reference to its definition, prevalence, aetiology and predictors, classification, measurement and impact. We also discuss the complexities of foot pain as a sensory, emotional and psychosocial experience in the context of clinical practice, therapeutic trials and the placebo effect. A deeper understanding of foot pain is needed to identify causal pathways, classify diagnoses, quantify severity, evaluate long term implications and better target clinical intervention
Fermi/GBM observations of the ultra-long GRB 091024: A burst with an optical flash
In this paper we examine gamma-ray and optical data of GRB 091024, a
gamma-ray burst (GRB) with an extremely long duration of T90~1020 s, as
observed with the Fermi Gamma-Ray Burst Monitor (GBM). We present spectral
analysis of all three distinct emission episodes using data from Fermi/GBM.
Because of the long nature of this event, many ground-based optical telescopes
slewed to its location within a few minutes and thus were able to observe the
GRB during its active period. We compare the optical and gamma-ray light
curves. Furthermore, we estimate a lower limit on the bulk Lorentz factor from
the variability and spectrum of the GBM light curve and compare it with that
obtained from the peak time of the forward shock of the optical afterglow. From
the spectral analysis we note that, despite its unusually long duration, this
burst is similar to other long GRBs, i.e. there is spectral evolution (both the
peak energy and the spectral index vary with time) and spectral lags are
measured. We find that the optical light curve is highly anti-correlated to the
prompt gamma-ray emission, with the optical emission reaching the maximum
during an epoch of quiescence in the prompt emission. We interpret this
behavior as the reverse shock (optical flash), expected in the
internal-external shock model of GRB emission but observed only in a handful of
GRBs so far. The lower limit on the initial Lorentz factor deduced from the
variability time scale ()is consistent within
the error to the one obtained using the peak time of the forward shock
() and is also consistent with Lorentz factors of other long
GRBs.Comment: accepted for publication in A&
Application of Multi-SNP Approaches Bayesian LASSO and AUC-RF to Detect Main Effects of Inflammatory-Gene Variants Associated with Bladder Cancer Risk
The relationship between inflammation and cancer is well established in several tumor types, including bladder cancer. We
performed an association study between 886 inflammatory-gene variants and bladder cancer risk in 1,047 cases and 988
controls from the Spanish Bladder Cancer (SBC)/EPICURO Study. A preliminary exploration with the widely used univariate
logistic regression approach did not identify any significant SNP after correcting for multiple testing. We further applied two
more comprehensive methods to capture the complexity of bladder cancer genetic susceptibility: Bayesian Threshold
LASSO (BTL), a regularized regression method, and AUC-Random Forest, a machine-learning algorithm. Both approaches
explore the joint effect of markers. BTL analysis identified a signature of 37 SNPs in 34 genes showing an association with
bladder cancer. AUC-RF detected an optimal predictive subset of 56 SNPs. 13 SNPs were identified by both methods in the
total population. Using resources from the Texas Bladder Cancer study we were able to replicate 30% of the SNPs assessed.
The associations between inflammatory SNPs and bladder cancer were reexamined among non-smokers to eliminate the
effect of tobacco, one of the strongest and most prevalent environmental risk factor for this tumor. A 9 SNP-signature was
detected by BTL. Here we report, for the first time, a set of SNP in inflammatory genes jointly associated with bladder cancer
risk. These results highlight the importance of the complex structure of genetic susceptibility associated with cancer risk.The work was partially supported by the Fondo de Investigacion Sanitaria, Instituto de Salud Carlos III (G03/174, 00/0745, PI051436, PI061614, PI09-02102, G03/174 and Sara Borrell fellowship to ELM) and Ministry of Science and Innovation (MTM2008-06747-C02-02 and FPU fellowship award to VU), Spain; AGAUR-Generalitat de Catalunya (Grant 2009SGR-581); Fundaciola Maratode TV3; Red Tematica de Investigacion Cooperativa en Cancer (RTICC); Asociacion Espanola Contra el Cancer (AECC); EU-FP7-201663; and RO1-CA089715 and CA34627; the Spanish National Institute for Bioinformatics (www.inab.org); and by the Intramural Research Program of the Division of Cancer Epidemiology and Genetics, National Cancer Institute, USA. MD Anderson support for this project included U01 CA 127615 (XW); R01 CA 74880 (XW); P50 CA 91846 (XW, CPD); Betty B. Marcus Chair fund in Cancer Prevention (XW); UT Research Trust fund (XW) and R01 CA 131335 (JG)
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