39 research outputs found
SARAS 2 Constraints on Global 21 cm Signals from the Epoch of Reionization
Spectral distortions in the cosmic microwave background over the 40--200~MHz
band are imprinted by neutral hydrogen in the intergalactic medium prior to the
end of reionization. This signal, produced in the redshift range at
the rest frame wavelength of 21 cm, has not been detected yet; and poor
understanding of high redshift astrophysics results in a large uncertainty in
the expected spectrum. The SARAS~2 radiometer was purposely designed to detect
the sky-averaged 21-cm signal. The instrument, deployed at the Timbaktu
Collective (Southern India) in April--June 2017, collected 63~hr of science
data, which were examined for the presence of the cosmological 21-cm signal. In
our previous work the first-light data from SARAS~2 radiometer were analyzed
with Bayesian likelihood-ratio tests using plausible astrophysical
scenarios. In this paper we re-examine the data using an improved analysis
based on the frequentist approach and forward modeling. We show that SARAS~2
data rejects 27 models, out of which 25 are rejected at a significance
. All the rejected models share the scenario of inefficient heating
of the primordial gas by the first population of X-ray sources along with rapid
reionization
First Results on the Epoch of Reionization from First Light with SARAS 2
Long wavelength spectral distortions in the Cosmic Microwave Background
arising from the 21-cm transition in neutral Hydrogen are a key probe of Cosmic
Dawn and the Epoch of Reionization. These features may reveal the nature of the
first stars and ultra-faint galaxies that transformed the spin temperature and
ionization state of the primordial gas. SARAS~2 is a spectral radiometer
purposely designed for precision measurement of these monopole or all-sky
global 21-cm spectral distortions. We use 63~hr night time observing of the
radio background in the frequency band 110-200~MHz with the radiometer deployed
at the Timbaktu Collective in Southern India to derive likelihoods for
plausible redshifted 21-cm signals predicted by theoretical models. First light
with SARAS 2 disfavors the class of models that feature weak X-ray heating
(with ) and rapid reionization (with peak )
Genotoxicity assessment of a pharmaceutical effluent using four bioassays
Pharmaceutical industries are among the major contributors to industrial waste. Their effluents when wrongly handled and disposed of endanger both human and environmental health. In this study, we investigated the potential genotoxicity of a pharmaceutical effluent, by using the Allium cepa, mouse- sperm morphology, bone marrow chromosome aberration (CA) and micronucleus (MN) assays. Some of the physico-chemical properties of the effluent were also determined. The A. cepa and the animal assays were respectively carried out at concentrations of 0.5, 1, 2.5, 5 and 10%; and 1, 5, 10, 25 and 50% of the effluent. There was a statistically different (p < 0.05), concentration-dependent inhibition of onion root growth and mitotic index, and induction of chromosomal aberrations in the onion and mouse CA test. Assessment of sperm shape showed that the fraction of the sperm that was abnormal in shape was significantly (p < 0.05) greater than the negative control value. MN analysis showed a dose-dependent induction of micronucleated polychromatic erythrocytes across the treatment groups. These observations were provoked by the toxic and genotoxic constituents present in test samples. The tested pharmaceutical effluent is a potentially genotoxic agent and germ cell mutagen, and may induce adverse health effects in exposed individuals
Use of postprocessor femview to interactively view structural displacements
A method to link strutural displacements obtained by any finite element package to the interactive graphic package FEMVIEW availabe in the: ASKA-IKOSS facility at NAL is documente
Recommended from our members