212 research outputs found
The rise and fall of the high-energy afterglow emission of GRB 180720B
The Gamma Ray Burst (GRB) 180720B is one of the brightest events detected by
the Fermi satellite and the first GRB detected by the H.E.S.S. telescope above
100 GeV. We analyse the Fermi (GBM and LAT) and Swift (XRT and BAT) data and
describe the evolution of the burst spectral energy distribution in the 0.5 keV
- 10 GeV energy range over the first 500 seconds of emission. We reveal a
smooth transition from the prompt phase, dominated by synchrotron emission in a
moderately fast cooling regime, to the afterglow phase whose emission has been
observed from the radio to the GeV energy range. The LAT (0.1 - 100 GeV) light
curve initially rises (), peaks at 78 s, and
falls steeply () afterwards. The peak, which we
interpret as the onset of the fireball deceleration, allows us to estimate the
bulk Lorentz factor under the assumption of a
wind-like (homogeneous) circum-burst medium density. We derive a flux upper
limit in the LAT energy range at the time of H.E.S.S. detection, but this does
not allow us to unveil the nature of the high energy component observed by
H.E.S.S. We fit the prompt spectrum with a physical model of synchrotron
emission from a non-thermal population of electrons. The 0 - 35 s spectrum
after its peak (at 1 - 2 MeV) is a steep power law extending to
hundreds of MeV. We derive a steep slope of the injected electron energy
distribution . Our fit parameters point towards a
very low magnetic field ( G) in the emission region.Comment: 10 pages, 6 figures, submitted to A&
Self-validating technique for the measurement of the linewidth enhancement factor in semiconductor lasers
A new method for measuring the linewidth enhancement factor (α-parameter) of semiconductor lasers is proposed and discussed. The method itself provides an estimation of the measurement error, thus self-validating the entire procedure. The α-parameter is obtained from the temporal profile and the instantaneous frequency (chirp) of the pulses generated by gain switching. The time resolved chirp is measured with a polarization based optical differentiator. The accuracy of the obtained values of the α-parameter is estimated from the comparison between the directly measured pulse spectrum and the spectrum reconstructed from the chirp and the temporal profile of the pulse. The method is applied to a VCSEL and to a DFB laser emitting around 1550 nm at different temperatures, obtaining a measurement error lower than ± 8%
Fine Scale Analysis of Crossover and Non-Crossover and Detection of Recombination Sequence Motifs in the Honeybee (Apis mellifera)
BACKGROUND: Meiotic exchanges are non-uniformly distributed across the genome of most studied organisms. This uneven distribution suggests that recombination is initiated by specific signals and/or regulations. Some of these signals were recently identified in humans and mice. However, it is unclear whether or not sequence signals are also involved in chromosomal recombination of insects. METHODOLOGY: We analyzed recombination frequencies in the honeybee, in which genome sequencing provided a large amount of SNPs spread over the entire set of chromosomes. As the genome sequences were obtained from a pool of haploid males, which were the progeny of a single queen, an oocyte method (study of recombination on haploid males that develop from unfertilized eggs and hence are the direct reflect of female gametes haplotypes) was developed to detect recombined pairs of SNP sites. Sequences were further compared between recombinant and non-recombinant fragments to detect recombination-specific motifs. CONCLUSIONS: Recombination events between adjacent SNP sites were detected at an average distance of 92 bp and revealed the existence of high rates of recombination events. This study also shows the presence of conversion without crossover (i. e. non-crossover) events, the number of which largely outnumbers that of crossover events. Furthermore the comparison of sequences that have undergone recombination with sequences that have not, led to the discovery of sequence motifs (CGCA, GCCGC, CCGCA), which may correspond to recombination signals
Factors influencing adherence to standard precautions among nursing professionals in psychiatric hospitals
OBJECTIVE Evaluate and correlate individual, work-related and organizational factors that influence adherence to standard precautions among nursing professionals of psychiatric hospitals in São Paulo. METHOD An exploratory cross-sectional study conducted with 35 nursing professionals, using the assessment tool for adherence to standard precautions through the Likert scale, ranging from 1 to 5. RESULTS Knowledge of the precautions received a high score (4.69); adherence received (3.86) and obstacles (3.78), while intermediaries and the scales of organizational factors received low scores (2.61). There was a strong correlation between the magnitude adherence scale and the personal protective equipment availability (r = 0.643; p = 0.000). The training scale for prevention of HIV exposure (p = 0.007) was statistically different between the nurses and nursing assistants. CONCLUSION The organizational factors negatively contributed to adherence to standard precautions, indicating that psychiatric institutions lack safe working conditions, ongoing training and management actions to control infections
A model of the role of education in 2015 UN international migration data
Migration on a global scale is clearly linked to a multiplicity of causes that, in addition to economic factors, include conflicts, natural disasters and local political conditions. However, it is possible to pinpoint what are the main variables that underlie migratory movements between macro areas of the planet. This study analyzes the 2015 UN report data and interprets them through a gravitational model, whose independent variables are indicators of the socio-economic situation of a population. Progressively eliminating the less significant contributions, the level of education of migrants emerges as one of the most important factors
Molecular Approaches to Neuronal Regeneration: Opportunities in Neurodegenerative Diseases, Bologna, 27 Ottobre 2006, Oratorio San Filippo Neri, Via Manzoni 5
Neurodegenerative diseases represent some of today\u2019s most devastating diseases afflicting man. With an aging population, thanks to improved medicine and healthcare, the incidence of diseases such as Alzheimer\u2019s disease, Multiple Sclerosis (MS), Parkinson\u2019s disease and other neurodegenerative disorders is increasing, and is taking a significant toll on patients, their families and caregivers, health care providers and worldwide economies.
For example, MS alone affects about 2.5 million people worldwide and it is not considered a fatal disease, since the vast majority of patients live to a normal life span. Few therapies exist which modify the progression of the disease.
This meeting brings together key thought leaders from the field of neurodegeneration research to share their latest findings and to highlight therapeutic opportunities that may reduce or even reverse the devastating effects of neurodegenerative diseases
Il colesterolo e i fosfolipidi renali dopo legatura dell'arteria epatica nel ratto
Il colesterolo e i fosfolipidi renali dopo legatura dell'arteria epatica nel ratt
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