1,783 research outputs found
Increased risk of malignant mesothelioma of the pleura after residential or domestic exposure to asbestos: a case-control study in Casale Monferrato, Italy.
The association of malignant mesothelioma (MM) and nonoccupational asbestos exposure is currently debated. Our study investigates environmental and domestic asbestos exposure in the city where the largest Italian asbestos cement (AC) factory was located. This population-based case-control study included pleural MM (histologically diagnosed) incidents in the area in 1987-1993, matched by age and sex to two controls (four if younger than 60). Diagnoses were confirmed by a panel of five pathologists. We interviewed 102 cases and 273 controls in 1993-1995, out of 116 and 330 eligible subjects. Information was checked and completed on the basis of factory and Town Office files. We adjusted analyses for occupational exposure in the AC industry. In the town there were no other relevant industrial sources of asbestos exposure. Twenty-three cases and 20 controls lived with an AC worker [odds ratio (OR) = 4.5; 95% confidence interval (CI), 1.8-11.1)]. The risk was higher for the offspring of AC workers (OR = 7.4; 95% CI, 1.9-28.1). Subjects attending grammar school in Casale also showed an increased risk (OR = 3.3; 95% CI, 1.4-7.7). Living in Casale was associated with a very high risk (after selecting out AC workers: OR = 20.6; 95% CI, 6.2-68.6), with spatial trend with increasing distance from the AC factory. The present work confirms the association of environmental asbestos exposure and pleural MM, controlling for other sources of asbestos exposure, and suggests that environmental exposure caused a greater risk than domestic exposure
Renormalization Group Flows for Brane Couplings
Field theories in the presence of branes encounter localized divergences that
renormalize brane couplings. The sources of these brane-localized divergences
are understood as arising either from broken translation invariance, or from
short distance singularities as the brane thickness vanishes. While the former
are generated only by quantum corrections, the latter can appear even at the
classical level. Using as an example six-dimensional scalar field theory in the
background of a 3-brane, we show how to interpret such classical divergences by
the usual regularization and renormalization procedure of quantum field theory.
In our example, the zero thickness divergences are logarithmic, and lead
classically to non-trivial renormalization group flows for the brane couplings.
We construct the tree level renormalization group equations for these couplings
as well as the one-loop corrections to these flows from bulk-to-brane
renormalization effects.Comment: 16 pages, LaTeX. References and an appendix adde
Supergravity loop contributions to brane world supersymmetry breaking
We compute the supergravity loop contributions to the visible sector scalar
masses in the simplest 5D `brane-world' model. Supersymmetry is assumed to be
broken away from the visible brane and the contributions are UV finite due to
5D locality. We perform the calculation with N = 1 supergraphs, using a
formulation of 5D supergravity in terms of N = 1 superfields. We compute
contributions to the 4D effective action that determine the visible scalar
masses, and we find that the mass-squared terms are negative.Comment: 12 pages, LaTeX 2
Fermion Mass Hierarchies and Small Mixing Angles from Extra Dimensions
In this paper we study renormalization-group evolutions of Yukawa matrices
enhanced by Kaluza-Klein excited modes and analyze their infrared fixed-point
structure. We derive necessary conditions to obtain hierarchies between
generations on the fixed point. These conditions restrict how the fields in the
models can extend to higher dimension. Several specific mechanisms to realize
the conditions are presented. We also take account of generation mixing effects
and find a scenario where the mixing angles become small at low energy even
with large initial values at high-energy scale. A toy model is shown to lead
realistic quark mass matrices.Comment: 23 pages, 7 figures, LaTeX, a supplementary explanation and
references adde
Brane fluctuations and suppression of Kaluza-Klein mode couplings
In higher dimensional models where the gauge and gravity fields live in the
bulk and the matter fields only in a brane, we point out the importance of the
brane (transverse) coordinate modes, which are the Nambu-Goldstone bosons
appearing as a result of spontaneous breaking of the translation symmetry. The
brane recoil effect suppresses the couplings of higher Kaluza-Klein modes to
the matter, and gives a natural resolution to the divergence problem caused by
the exchange of infinitely many Kaluza-Klein modes.Comment: 11 pages, 1 eps figure, references adde
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