3,241 research outputs found
Combined risk factors for melanoma in a Mediterranean population
A case–control study of non-familial melanoma including 183 incident cases and 179 controls was conducted in North-Eastern Italy to identify important risk factors and determine how combination of these affects risk in a Mediterranean population. Presence of dysplastic nevi (OR = 4.2, 95% CI = 2.4–7.4), low propensity to tan (OR = 2.4, 95% CI = 1.1–5.0), light eye (OR = 2.4, 95% CI = 1.1–5.2), and light skin colour (OR = 4.1, 95% CI = 1.4–12.1) were significantly associated with melanoma risk after adjustment for age, gender and pigmentation characteristics. A chart which identifies melanoma risk associated with combinations of these factors is presented; it can be used to identify subjects who would most benefit from preventive measures in Mediterranean populations. According to the combination of these factors, a relative risk range from 1 to 98.5 was found. Light skin colour, high number of sunburns with blistering, and low propensity to tan were significantly associated with melanoma thickness, possibly indicating that individuals with these characteristics underestimate their risk and seek attention when their lesion is already advanced. © 2001 Cancer Research Campaig
Broad band time-resolved E_{p,i}--L_{iso} correlation in GRBs
We report results of a systematic study of the broad band (2--2000 keV) time
resolved prompt emission spectra of a sample of gamma-ray bursts (GRBs)
detected with both Wide Field Cameras on board the \sax\ satellite and the
\batse\ experiment on board CGRO. In this first paper, we study the
time-resolved dependence of the intrinsic peak energy of the
spectrum on the corresponding isotropic bolometric luminosity .
The -- relation or the equivalent relation between
and the bolometric released energy , derived using the time
averaged spectra of long GRBs with known redshift, is well established, but its
physical origin is still a subject of discussion. In addition, some authors
maintain that these relations are the result of instrumental selection effects.
We find that not only a relation between the measured peak energy and the
corresponding energy flux, but also a strong versus
correlation are found within each burst and merging together the time resolved
data points from different GRBs. We do not expect significant instrumental
selection effects that can affect the obtained results, apart from the fact
that the GRBs in our sample are sufficiently bright to perform a time-resolved
spectroscopy and that they have known redshift. If the fundamental physical
process that gives rise to the GRB phenomenon does not depend on its
brightness, we conclude that the found versus
correlation within each GRB is intrinsic to the emission process, and that the
correlations discovered by Amati et al. and Yonetoku et al. are likely not the
result of selection effects. We also discuss the properties of the correlations
found.Comment: 27 pages,4 tables, 7 figure, accepted for publication in The
Astrophysical Journa
Joint fluctuation theorems for sequential heat exchange
We study the statistics of heat exchange of a quantum system that collides
sequentially with an arbitrary number of ancillas. This can describe, for
instance, an accelerated particle going through a bubble chamber. Unlike other
approaches in the literature, our focus is on the \emph{joint} probability
distribution that heat is exchanged with ancilla 1, heat is
exchanged with ancilla 2, and so on. This allows one to address questions
concerning the correlations between the collisional events. The joint
distribution is found to satisfy a Fluctuation theorem of the
Jarzynski-W\'ojcik type. Rather surprisingly, this fluctuation theorem links
the statistics of multiple collisions with that of independent single
collisions, even though the heat exchanges are statistically correlated
Noncommutative geometry, topology and the standard model vacuum
As a ramification of a motivational discussion for previous joint work, in
which equations of motion for the finite spectral action of the Standard Model
were derived, we provide a new analysis of the results of the calculations
herein, switching from the perspective of Spectral triple to that of Fredholm
module and thus from the analogy with Riemannian geometry to the pre-metrical
structure of the Noncommutative geometry. Using a suggested Noncommutative
version of Morse theory together with algebraic -theory to analyse the
vacuum solutions, the first two summands of the algebra for the finite triple
of the Standard Model arise up to Morita equivalence. We also demonstrate a new
vacuum solution whose features are compatible with the physical mass matrix.Comment: 24 page
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