1,386 research outputs found
A new approach of analyzing GRB light curves
We estimated the Txx quantiles of the cumulative GRB light curves using our
recalculated background. The basic information of the light curves was
extracted by multivariate statistical methods. The possible classes of the
light curves are also briefly discussed.Comment: 4 pages, 8 figure
Diffusion Processes on Power-Law Small-World Networks
We consider diffusion processes on power-law small-world networks in
different dimensions. In one dimension, we find a rich phase diagram, with
different transient and recurrent phases, including a critical line with
continuously varying exponents. The results were obtained using self-consistent
perturbation theory and can also be understood in terms of a scaling theory,
which provides a general framework for understanding processes on small-world
networks with different distributions of long-range links.Comment: 4 pages, 3 figures, added references, modified Fig. 2 with added data
(PRL, in press
The pseudogap phase in (TaSe_4)_2I
We have developed the mean-field theory of coexisting charge-density waves
(CDW) and unconventional charge-density waves (UCDW). The double phase
transition manifests itself in the thermodynamic quantities and in the magnetic
response, such as spin susceptibility and spin-lattice relaxation rate. Our
theory applies to quasi-one dimensional (TaSe_4)_2I, where above the CDW
transition, thermal fluctuations die out rapidly, but robust pseudogap
behaviour is still detected. We argue, that the fluctuations are suppressed due
to UCDW, which partially gaps the Fermi surface, and causes non-Fermi-liquid
(pseudogap) behaviour.Comment: 7 pages, 6 figure
Radon induced hyperplasia: effective adaptation reducing the local doses in the bronchial epithelium
There is experimental and histological evidence that chronic irritation and
cell death may cause hyperplasia in the exposed tissue. As the heterogeneous
deposition of inhaled radon progeny results in high local doses at the peak of
the bronchial bifurcations, it was proposed earlier that hyperplasia occurs in
these deposition hot spots upon chronic radon exposure. The objective of the
present study is to quantify how the induction of basal cell hyperplasia
modulates the microdosimetric consequences of a given radon exposure. For this
purpose, numerical epithelium models were generated with spherical cell nuclei
of six different cell types based on histological data. Basal cell hyperplasia
was modelled by epithelium models with additional basal cells and increased
epithelium thickness. Microdosimetry for alpha-particles was performed by an
own-developed Monte-Carlo code. Results show that the average tissue dose, and
the average hit number and dose of basal cells decrease by the increase of the
measure of hyperplasia. Hit and dose distribution reveal that the induction of
hyperplasia may result in a basal cell pool which is shielded from alpha
radiation. It highlights that the exposure history affects the microdosimetric
consequences of a present exposure, while the biological and health effects may
also depend on previous exposures. The induction of hyperplasia can be
considered as a radioadaptive response at the tissue level. Such an adaptation
of the tissue challenges the validity of the application of the dose dose rate
effectiveness factor from a mechanistic point of view. As the location of
radiosensitive target cells may change due to previous exposures, dosimetry
models considering the tissue geometry characteristic of normal conditions may
be inappropriate for dose estimation in case of protracted exposures. As
internal exposures are frequently chronic, such changes in tissue...Comment: 13 pages, 5 figures, 1 tabl
Direction Dependent Background Fitting for the Fermi GBM Data
We present a method for determining the background of Fermi GBM GRBs using
the satellite positional information and a physical model. Since the polynomial
fitting method typically used for GRBs is generally only indicative of the
background over relatively short timescales, this method is particularly useful
in the cases of long GRBs or those which have Autonomous Repoint Request (ARR)
and a background with much variability on short timescales. We give a Direction
Dependent Background Fitting (DDBF) method for separating the motion effects
from the real data and calculate the duration (T90 and T50, as well as
confidence intervals) of the nine example bursts, from which two resulted an
ARR. We also summarize the features of our method and compare it qualitatively
with the official GBM Catalogue. Our background filtering method uses a model
based on the physical information of the satellite position. Therefore, it has
many advantages compared to previous methods. It can fit long background
intervals, remove all the features caused by the rocking behaviour of the
satellite, and search for long emissions or not-triggered events. Furthermore,
many part of the fitting have now been automatised, and the method have been
shown to work for both Sky Survey mode and ARR mode data. Future work will
provide a burst catalogue with DDBF.Comment: 16 pages, 28 figure
- …