2,791 research outputs found
Determination of the Night Sky Background around the Crab pulsar using its optical pulsation
The poor angular resolution of imaging gamma-ray telescopes is offset by the
large reflector areas of next generation telescopes such as MAGIC (17~m
diameter), which makes the study of optical emission associated with some
gamma-ray sources feasible. Furthermore, the extremely fast time response of
photomultipliers (PMs) makes them ideal detectors for fast (subsecond) optical
transients and periodic sources like pulsars. The optical pulse of the Crab
pulsar was detected with the HEGRA CT1 central pixel using a modified PM,
similar to the future MAGIC camera PMs. The purpose of these periodic
observations was to determine the light of the night sky (LONS) for the
galactic anticenter Crab region.Our results are between 2.5 and 3 times larger
than the previously measured LONS (outside the galactic plane), as expected
since the Crab pulsar is in the galactic plane, which implies a slightly higher
energy threshold for Crab observations, if the higher value of CT1 measured
LONS rate for galactic sources is used.Comment: 19 pages, 6 figures, accepted by Astroparticle Physic
Observations of microquasars with the MAGIC telescope
We report on the results from the observations in very high energy band (VHE,
E_gamma > 100GeV) of the black hole X-ray binary (BHXB) Cygnus X-1. The
observations were performed with the MAGIC telescope, for a total of 40 hours
during 26 nights, spanning the period between June and November 2006. We report
on the results of the searches for steady and variable gamma-ray signals,
including the first experimental evidence for an intense flare, of duration
between 1.5 and 24 hours.Comment: Contribution to the 30th ICRC, Merida Mexico, July 2007 on behalf of
the MAGIC Collaboratio
Brief Report: Surveillance of Congenital Anomalies After Exposure to Raltegravir or Elvitegravir During Pregnancy in the United Kingdom and Ireland, 2008–2018
BACKGROUND: The indisputable benefits of antiretroviral therapy (ART) in the reduction of mother-to-child-transmission of HIV (MTCT) have to be carefully balanced with the risks of embryo-foetal toxicities due to foetal exposure to maternal ART.The recent report of a potential safety signal with Dolutegravir use in pregnancy and potential increased rate of neural tube defects (NTDs), has raised the question of a potential class effect for Integrase Strand Inhibitors. To contribute real-world evidence we evaluated data on pregnant women receiving Raltegravir (RAL) or Elvitegravir (EVG) in the UK and Ireland. METHODS: The National Study of HIV in Pregnancy and Childhood (NSHPC) is a comprehensive population-based surveillance study collecting data on all HIV-positive pregnant women and their children. We collected data on all pregnancies exposed to an ART regimen containing RAL or EVG resulting in livebirth, stillbirth and induced abortion with an expected date of delivery between September 2008 and April 2018. Pregnancies were stratified into three groups of earliest exposure. RESULTS: A total of 908 pregnancies were exposed to a RAL or EVG-based regimen (875 to RAL and 33 to EVG). There were 886 live-born infants exposed to RAL, eight pregnancies ended in stillbirth and nine in induced abortions. Among the 886 live-born infants there were 23 (2.59% 95% CI 1.65, 3.86) reported congenital anomalies, two nervous system defects but no reported NTDs. Of the 33 pregnancies exposed to EVG, 31 resulted in live-born infants with no congenital anomaly and the remaining two pregnancies ended in induced abortion. CONCLUSIONS: The prevalence of congenital anomalies is consistent with national population estimates for 2008-2016 in the UK. More data are needed on safety of RAL and EVG in pregnancy
Un model de formació continuada, reflexiu i participatiu
Els reptes que planteja avui la comprensió del món, posen en evidència que cal una alfabetització cientÃfica i didà ctica dels i de les mestres d’educació infantil i primà ria. La nostra experiència en formació ens porta a afirmar que aquests grans reptes cal abordar-los des d’una perspectiva socioconstructivista de la formació. El model de formació que presentem pretén donar resposta a les necessitats del professorat, en relació als coneixements i a la didà ctica de les ciències. Proposa aprofundir en la reflexió sobre la pròpia prà ctica i sobre noves propostes metodològiques, a fi d’actualitzar i millorar les competències tecnocientÃfiques
Present and Future Gamma-Ray Probes of the Cygnus OB2 Environment
The MAGIC Collaboration has provided new observational data pertaining to the
TeV J2032+4130 gamma-ray source (within the Cygnus OB2 region), for energies
E_gamma >400 GeV. It is then appropriate to update the impact of these data on
gamma-ray production mechanisms in stellar associations. We consider two
mechanisms of gamma-ray emission, pion production and decay (PION) and
photo-excitation of high-energy nuclei followed by prompt photo-emission from
the daughter nuclei (A*). We find that while the data can be accommodated with
either scenario, the A* features a spectral bump, corresponding to the
threshold for exciting the Giant Dipole Resonance, which can serve to
discriminate between them. We comment on neutrino emission and detection from
the region if the PION and/or A* processes are operative. We also touch on the
implications for this analysis of future Fermi and Cerenkov Telescope Array
data.Comment: 6 pp, 2 figs. Matching version publihed in Phys. Rev.
Invasive species and habitat degradation in Iberian streams: An analysis of their role in freshwater fish diversity loss
Mediterranean endemic freshwater fish are among the most threatened biota in the world. Distinguishing the role of different extinction drivers and their potential interactions is crucial for achieving conservation goals. While some authors argue that invasive species are a main driver of native species declines, others see their proliferation as a co-occurring process to biodiversity loss driven by habitat degradation. It is difficult to discern between the two potential causes given that few invaded ecosystems are free from habitat degradation, and that both factors may interact in different ways. Here we analyze the relative importance of habitat degradation and invasive species in the decline of native fish assemblages in the Guadiana River basin (southwestern Iberian Peninsula) using an information theoretic approach to evaluate interaction pathways between invasive species and habitat degradation (structural equation modeling, SEM). We also tested the possible changes in the functional relationships between invasive and native species, measured as the per capita effect of invasive species, using ANCOVA. We found that the abundance of invasive species was the best single predictor of natives' decline and had the highest Akaike weight among the set of predictor variables examined. Habitat degradation neither played an active role nor influenced the per capita effect of invasive species on natives. Our analyses indicated that downstream reaches and areas close to reservoirs had the most invaded fish assemblages, independently of their habitat degradation status. The proliferation of invasive species poses a strong threat to the persistence of native assemblages in highly fluctuating environments. Therefore, conservation efforts to reduce native freshwater fish diversity loss in Mediterranean rivers should focus on mitigating the effect of invasive species and preventing future invasions
Calculations of He+p elastic scattering cross sections using folding approach and high-energy approximation for the optical potential
Calculations of microscopic optical potentials (OP's) (their real and
imaginary parts) are performed to analyze the He+p elastic scattering data
at a few tens of MeV/nucleon (MeV/N). The OP's and the cross sections are
calculated using three model densities of He. Effects of the regularization
of the NN forces and their dependence on nuclear density are investigated.
Also, the role of the spin-orbit terms and of the non-linearity in the
calculations of the OP's, as well as effects of their renormalization are
studied. The sensitivity of the cross sections to the nuclear densities was
tested and one of them that gives a better agreement with the data was chosen.Comment: 13 pages, 11 figures, to be published in Eur. Phys. J.
Differences in Self-Rated Versus Parent Proxy–Rated Vision-Related Quality of Life and Functional Vision of Visually Impaired Children
PURPOSE: To investigate disagreement between children's self-reported vision-related quality of life (VQoL) and functional vision (FV), and their parents' proxy-reports. DESIGN: Cross-sectional study. METHODS: 152 children aged 7-18 years with visual impairment (VI) (defined by the World Health Organization), and their parents, were recruited from 22 National Health Service (NHS) Ophthalmology Departments in the United Kingdom. Age-appropriate versions of 2 vision-specific instruments capturing VQoL and FV, were administered to children alongside modified versions for completion by parents on behalf of their child (i.e. parent proxy-report). Disagreement between self- and parent proxy-report was examined using the Bland-Altman (BA) method, and a threshold of disagreement based on 0.5 standard deviation. Disagreement was analysed according to participants' age, gender and clinical characteristics, using logistic regression analyses. RESULTS: Children rated themselves as having better outcomes than their parents did, although parents both under- and over-estimated their child's VQoL (mean score difference = 7.7). With each year of increasing age, there was a 1.18 (1.04 - 1.35) higher odds of children self-rating their VQoL better than their parents (p = 0.013). Although parents consistently under-estimated their child's FV (mean score difference = -4.7), no characteristics were significantly associated with differences in disagreement. CONCLUSIONS: Disagreement between child self-report on the impact of VI, and their parents' proxy-reports varies by age. This implies that self-report from children must remain the gold standard. Where self-reporting is not possible, parent proxy-reports may provide useful insights, but must be interpreted with caution
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