1,726 research outputs found
Integrating evidence for managing asthma in patients who smoke
Peer reviewedPublisher PD
Detection and Modeling of Radiation Induced Effects in Tissues by Dielectric Spectroscopy
The work presented here is applied physics research in the field of radiation treatment. We address the development of a new and innovative method, in vivo and possibly non-invasive, for tumor and healthy tissues control during and after the radiation treatment. The radiation treatment is delivered in an almost standardized manner for particular classes of tumors. The large variance in the individual radio sensitivity of healthy tissues and tumors often leads to local recurrence of neoplastic growth and/or distant metastatic disease which often remains untreated. The method is based on the measurement and analysis of electrical impedance data in the frequency domain from 50 mHz to 1MHz. The dielectric signature of the tissue carries information about the integrity of the plasma membrane, as well as about the tissue micro-architecture. We present dielectric models for biological materials and correlate their parameters with the subtle changes characterizing oncosis or apoptosis occurring as result of radiation or excision. Five tissue types (blood, kidney, liver, lung and heart) were studied and specific impedance models were created for each of them. Based on these models, analysis of freshly excised tissue and radiation-induced effects in excised tissue was carried out and model parameters extracted. The data we present shows correlation between known mechanisms of cellular death and the delivery of radiation, thus making possible a quantification of the individual response. Further work will be needed in order to correlate early impedance changes with late tissue changes characterizing the side effects of the radiotherapy
Monte-Carlo simulations of photohadronic processes in astrophysics
A new Monte Carlo program for photohadronic interactions of relativistic
nucleons with an ambient photon radiation field is presented. The event
generator is designed to fulfil typical astrophysical requirements, but can
also be used for radiation and background studies at high energy colliders such
as LEP2 and HERA, as well as for simulations of photon induced air showers.
We consider the full photopion production cross section from the pion
production threshold up to high energies.
It includes resonance excitation and decay, direct single pion production and
diffractive and non-diffractive multiparticle production.
The cross section of each individual process is calculated by fitting
experimental data, while the kinematics is determined by the underlying
particle production process. We demonstrate that our model is capable of
reproducing known accelerator data over a wide energy range.Comment: 39 pages, 17 figures, submitted to Comp.Phys.Co
Influence of the van Hove singularity on the specific heat jump in BCS superconductors
Within the weak-coupling BCS scheme we derive a general form of the
coefficients in the Ginzburg-Landau expansion of the free energy of a
superconductor for the case of a Fermi level close to a van Hove singularity
(VHS). A simple expression for the influence of the VHS on the specific heat
jump is then obtained for the case where gaps for different bands are distinct
but nearly constant at the corresponding sheets of the Fermi surface.Comment: 8 pages, 2 figures, LaTeX2
Conical refraction healing after partially blocking the input beam
In conical refraction, when a focused Gaussian beam passes along one of the
optic axes of a biaxial crystal it is transformed into a pair of concentric
bright rings at the focal plane. We demonstrate both theoretically and
experimentally that this transformation is hardly affected by partially
blocking the Gaussian input beam with an obstacle. We analyze the influence of
the size of the obstruction both on the transverse intensity pattern of the
beam and on its state of polarization, which is shown to be very robust
Neutrinos: the Key to UHE Cosmic Rays
Observations of ultrahigh energy cosmic rays (UHECR) do not uniquely
determine both the injection spectrum and the evolution model for UHECR sources
- primarily because interactions during propagation obscure the early Universe
from direct observation. Detection of neutrinos produced in those same
interactions, coupled with UHECR results, would provide a full description of
UHECR source properties.Comment: three pages, three figures. corrected typo
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