Reconstructing the channel shifting pattern of the Torsa River on the Himalayan Foreland Basin over the last 250 years

The varied physiography, incidences of high seasonal discharge, influences of neo-tectonic activity and the young geological foundation with less consolidated cohesive and non-cohesive sediment have left the Himalayan foreland basin a formidable ground, where silt-laden rivers tend to migrate frequently. A set of maps prepared after 1764, space photographs captured in 1970 and current satellite images from 2015 and 2017 were studied to reconstruct the fluvial dynamics of the Torsa River on the foreland basin of Sikkim-Bhutan Himalaya considering a time span of nearly 250 years. Evidence collected from colonial literature, the above-mentioned satellite images and a field survey, were combined to verify results taken from the old maps used as the base of the study. The application of satellite remote sensing and analysis of the topographic signatures of the palaeo-courses in the form of the palaeo-levee, abandoned courses and ox-bow lakes were the major operational attributes in this study. As a consequence of the channel migration of Torsa River since 1764, the historical floodplain of Torsa has been topographically marked by beheaded old distributaries, a misfit channel system and the presence of abandoned segments. Morphometric changes in the old courses, major flood events and neo-tectonic activity guided an overall trend of channel migration eastwards and has led to a couple of channel oscillation events in the Torsa River over the last 250 years. The mechanism of the avulsion events was thoroughly driven by sedimentation-induced channel morphometric changes and occasional high discharge

EFFECT OF SUB-CHRONIC EXPOSURE TO CHROMIUM ON HAEMATOLOGICAL AND BIOCHEMICAL PARAMETERS OF MALE ALBINO RAT

Objectives :  Exposure to chromium, the transition element found in many compounds of earth's crust, leads to various health hazards including cancer, dermatitis, damage of liver  and kidneys and reproductive toxicity in both male and female. Toxic  effect of chronic exposure to chromium at low environmentally relevant dose is recently recognized and less studied. In the present study, we evaluated the effect of sub-chronic exposure to low doses of chromium VI (K2Cr2O7) on various haematological and biochemical parameters in male albino rats.Methods : Male albino rats (160±10 gm) received 1/25, 1/50 and 1/100 of reported oral LD50 dose of chromium VI (K2Cr2O7) for 90 consecutive days. After treatment, the blood was collected for analysis of various haematological and biochemical parameters.Results :  Exposure to chromium VI at 1/25 LD50 dose caused decrease in body weight gain and reduction in the weight of the reproductive organs along with increase in the weight of liver and kidney. Numbers of red blood cells, white blood cells, platelets and haemoglobin concentration reduced with increase in clotting time. The total sperm count and motility was also reduced in exposed rats. There was decrease in plasma protein and albumin concentration, with increase in plasma glucose and cholesterol level. The activity of enzyme alanine aminotransferase and enzyme aspertate aminotransferase was stimulated in treated rats.Conclusion : The results of the present study revealed that chronic low dose  exposure to chromium VI resulted in a toxic effect in experimental male albino rats.    Â

Decay of baryon inhomogeneities in an expanding universe

Baryon inhomogeneities can be generated very early in the universe. These inhomogeneities then decay by particle diffusion in an expanding universe. We study the decay of these baryon inhomogeneities in the early universe using the diffusion equation in the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric. We have studied the decay starting from the electroweak phase transition. We calculate the interaction cross section of the quarks with the neutrinos, the electrons and the muons and obtain the diffusion coefficients. The diffusion coefficients are temperature dependent. We find that the expansion of the universe causes the inhomogeneities to decay at a faster rate. We find that the baryon inhomogeneities generated at the electroweak epoch have very low amplitudes at the time of the quark hadron phase transition. So unless inhomogeneities are generated with a very high amplitude (greater than $10^5$ times the background density), they will have no effect on the quark hadron phase transition. After the quark hadron phase transition, we include the interaction of the muons with the neutrons and the protons till 100 MeV. We also find that large density inhomogeneities generated during the quark hadron transition with sizes of the order of 1 km must have amplitudes greater than $10^5$ times the background density to survive upto the nucleosynthesis epoch in an expanding universe.Comment: 20 pages and 7 figure