2,832 research outputs found
The multi-frequency angular power spectrum of the epoch of reionization 21 cm signal
Observations of redshifted 21cm radiation from HI at high redshifts is an
important future probe of reionization. We consider the Multi-frequency Angular
Power Spectrum (MAPS) to quantify the statistics of the HI signal as a joint
function of the angular multipole l and frequency separation \Delta\nu. The
signal at two different frequencies is expected to get decorrelated as
\Delta\nu is increased, and quantifying this decorrelation is particularly
important in deciding the frequency resolution for future HI observations. This
is also expected to play a very crucial role in extracting the signal from
foregrounds as the signal is expected to decorrelate much faster than the
foregrounds (which are largely continuum sources) with increasing \Delta\nu. In
this paper we develop formulae relating the MAPS to different components of the
three dimensional HI power spectrum taking into account HI peculiar velocities.
We show that the flat-sky approximation provides a very good representation
over the angular scales of interest, and a final expression which is very
simple to calculate and interpret. We present results considering two models
for the HI distribution, namely, (i) DM: where the HI traces the dark matter
and (ii) PR: where the effects of patchy reionization are incorporated through
two parameters. We find that while the DM signal is largely featureless, the PR
signal peaks at the angular scales of the individual bubbles, and the signal is
considerably enhanced for large bubble size. For most cases of interest at l
\sim 100 the signal is uncorrelated beyond \Delta\nu \sim 1 MHz or even less,
whereas it occurs around \sim 0.1 MHz at l \sim 10^3. The \Delta\nu dependence
also carries an imprint of the bubble size and the bias, and is expected to be
an important probe of the reionization scenario (abridged).Comment: Accepted for publication in MNRAS. Revised to match the accepted
versio
Synthesis of surveillance strategies via belief abstraction
We provide a novel framework for the synthesis of a controller for a robot with a surveillance objective, that is, the robot is required to maintain knowledge of the location of a moving, possibly adversarial target. We formulate this problem as a one-sided partial-information game in which the winning condition for the agent is specified as a temporal logic formula. The specification formalizes the surveillance requirement given by the user by quantifying and reasoning over the agent's beliefs about a target's location. We also incorporate additional non-surveillance tasks. In order to synthesize a surveillance strategy that meets the specification, we transform the partial-information game into a perfect-information one, using abstraction to mitigate the exponential blow-up typically incurred by such transformations. This transformation enables the use of off-the-shelf tools for reactive synthesis. We evaluate the proposed method on two case-studies, demonstrating its applicability to diverse surveillance requirements
Awareness of nursing students towards cancer and their comparison with medical students
Background: Cancer is the 2nd leading cause of mortality worldwide. The three leading cancers in India are cervical cancer, breast cancer and upper aerodigestive tract carcinoma. Cervical carcinoma is the 2nd most common cancer in women next to breast carcinoma. This study has been done to assess the knowledge, causation and preventive methods about the common cancers in India amongst Medical and Nursing students in a tertiary care center in rural Kerala. Preventive measures and early diagnosis of cancer can lead to decrease in mortality and morbidity. This can be achieved by creating awareness. A special emphasis has been made regarding cervical cancer and HPV vaccination in this study.Methods: A total of 337 medical and 148 nursing students from 1st year to final year were included in this study and the results were analysed by descriptive statistics.Results: Out of 337 medical and 148 nursing students, there was significant difference in knowledge between pretest/posttest and amongst the medical/nursing students. Medical students were found be more aware about the cancer, their causation and preventive methods as compared to the nursing students. 76.4% of nursing students were aware about the role of HPV (Human Papilloma Virus) in the causation of cervical cancer pretest. 98.6% of nursing students were aware about the role of HPV in causation of cervical cancer posttest following a short lecture. Following a short lecture both medical and nursing students were found to have more awareness.Conclusions: Creating awareness to the medical and nursing students who are intouch with the community and the patients is essential. Targeted health education in very important in creating a great impact about the knowledge of cancer in the community, thereby leading to decrease in mortality and morbidity
The CMBR ISW and HI 21-cm Cross-correlation Angular Power Spectrum
The late-time growth of large scale structures (LSS) is imprinted in the CMBR
anisotropy through the Integrated Sachs Wolfe (ISW) effect. This is perceived
to be a very important observational probe of dark energy. Future observations
of redshifted 21-cm radiation from the cosmological neutral hydrogen (HI)
distribution hold the potential of probing the LSS over a large redshift range.
We have investigated the possibility of detecting the ISW through
cross-correlations between the CMBR anisotropies and redshifted 21-cm
observations. Assuming that the HI traces the dark matter, we find that the
ISW-HI cross-correlation angular power spectrum at an angular multipole l is
proportional to the dark matter power spectrum evaluated at the comoving wave
number l/r, where r is the comoving distance to the redshift from which the HI
signal originated. The amplitude of the cross-correlation signal depends on
parameters related to the HI distribution and the growth of cosmological
perturbations. However the cross-correlation is extremely weak as compared to
the CMBR anisotropies and the predicted HI signal. As a consequence the
cross-correlation signal is smaller than the cosmic variance, and a
statistically significant detection is not very likely.Comment: 13 pages, 4 eps figures, submitte
Synthesis of minimum-cost shields for multi-agent systems
In this paper, we propose a general approach to derive runtime enforcement implementations for multiagent systems, called shields, from temporal logical specifications. Each agent of the multi-agent system is monitored, and if needed corrected, by the shield, such that a global specification is always satisfied. The different ways of how a shield can interfere with each agent in the system in case of an error introduces the need for quantitative objectives. This work is the first to discuss the shield synthesis problem with quantitative objectives. We provide several cost functions that are utilized in the multi-agent setting and provide methods for the synthesis of cost-optimal shields and fair shields, under the given assumptions on the multi-agent system. We demonstrate the applicability of our approach via a detailed case study on UAV mission planning for warehouse logistics and simulating the shielded multi-agent system on ROS/Gazebo
Free-energy functional for freezing transitions: Hard sphere systems freezing into crystalline and amorphous structures
A free-energy functional that contains both the symmetry conserved and
symmetry broken parts of the direct pair correlation function has been used to
investigate the freezing of a system of hard spheres into crystalline and
amorphous structures. The freezing parameters for fluid-crystal transition have
been found to be in very good agreement with the results found from
simulations. We considered amorphous structures found from the molecular
dynamics simulations at packing fractions lower than the glass close
packing fraction and investigated their stability compared to that
of a homogeneous fluid. The existence of free-energy minimum corresponding to a
density distribution of overlapping Gaussians centered around an amorphous
lattice depicts the deeply supercooled state with a heterogeneous density
profile
Involvement of B cells in non-infectious uveitis
This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/Non-infectious uveitis—or intraocular inflammatory disease—causes substantial visual morbidity and reduced quality of life
amongst affected individuals. To date, research of pathogenic mechanisms has largely been focused on processes involving
T lymphocyte and/or myeloid leukocyte populations. Involvement of B lymphocytes has received relatively little attention. In
contrast, B-cell pathobiology is a major field within general immunological research, and large clinical trials have showed that
treatments targeting B cells are highly effective for multiple systemic inflammatory diseases. B cells, including the terminally
differentiated plasma cell that produces antibody, are found in the human eye in different forms of non-infectious uveitis; in
some cases, these cells outnumber other leukocyte subsets. Recent case reports and small case series suggest that B-cell
blockade may be therapeutic for patients with non-infectious uveitis. As well as secretion of antibody, B cells may promote
intraocular inflammation by presentation of antigen to T cells, production of multiple inflammatory cytokines and support of
T-cell survival. B cells may also perform various immunomodulatory activities within the eye. This translational review
summarizes the evidence for B-cell involvement in non-infectious uveitis, and considers the potential contributions of B cells to
the development and control of the disease. Manipulations of B cells and/or their products are promising new approaches to the
treatment of non-infectious uveitis
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