Neoproterozoic age based on microbiotas from the Raipur Group of Baradwar sub-basin,Chhattisgarh

An assemblage of structurally preserved organic-walled microfossils (OWMs) from the macerated residue of black carbonaceous shale belonging to Saradih Formation, the youngest carbonate horizon of the Raipur Group, Chhattisgarh Supergroup exposed at on the right bank of Mahanadi River, NE of Sarangarh township in Raigarh district, Chhattisgarh is being reported for the first time. The assemblage is comprised of 19 taxa of 13 genera belong to eukaryotes and prokaryotes viz. Leiosphaeridia, Stictosphaeridium, Dictyotidium, Synsphaeridium, Symplassosphaeridium, Satka, Trachysphaeridium, Goniosphaeridium, Trachyhystrichosphaera, Vandalosphaeridium, Siphonophycus, Oscillatoriopsis and Polythrichoides. The comprehensive account of recovered microbiotic assemblage can be correlated with globally known Neoproterozoic (early Cryogenian) assemblages, deposited in tidal complexes of shallow sea.     

Size Distributions of Aerosol Sulfates and Nitrates in Beijing during the 2008 Olympic Games: Impacts of Pollution Control Measures and Regional Transport

For the 2008 Olympic Games, drastic control measures were implemented on industrial and urban emissions of sulfur dioxide (SO₂), nitrogen oxides (NO_x) and other pollutants to address the issues of poor air quality in Beijing. To investigate the effects of SO₂ and NO_x reductions on the particulate sulfate and nitrate concentrations as well as their size distributions, size-segregated aerosol samples were collected using micro-orifice uniform deposit impactors (MOUDIs) at urban and downwind rural sites in Beijing before and after full-scale controls. During the sampling period, the mass concentrations of fine particles (PM_1.8) at the urban and rural sites were 94.0 and 85.9 μg m^-3, respectively. More than 90% of the sulfates and ～60% of nitrates formed as fine particles. Benefiting from the advantageous meteorological conditions and the source controls, sulfates were observed in rather low concentrations and primarily in condensation mode during the Olympics. The effects of the control measures were separately analyzed for the northerly and the southerly air-mass-dominated days to account for any bias. After the control measures were implemented, PM, sulfates, and nitrates were significantly reduced when the northerly air masses prevailed, with a higher percentage of reduction in larger particles. The droplet mode particles, which dominated the sulfates and nitrates before the controls were implemented, were remarkably reduced in mass concentration after the control measures were implemented. Nevertheless, when the polluted southerly air masses prevailed, the local source control measures in Beijing did not effectively reduce the ambient sulfate concentration due to the enormous regional contribution from the North China Plain.     

Ararki (L5) chondrite: The first meteorite find in Thar Desert of India

Abstract— We report here a chance find of a meteorite in the sand dunes of Ararki village of Hanumangarh district in the Rajasthan desert of northwest India. Chemical and petrological evidence in conjunction with isotopic composition of oxygen indicate that it is an L5 chondrite. The fayalite content of olivines is 26.3 mol%. The meteorite has some serpentinized olivines and 0.3% carbon having a terrestrial isotopic composition, indicating that it is moderately weathered. The absence of ²²Na indicate that the meteorite fell to Earth more than a decade ago. The cosmic‐ray exposure age based on cosmogenic ²¹Ne is 7.2 Ma. Low density of cosmic‐ray heavy nuclei tracks, low ²⁶A1 activity, the shielding parameter [(²²Ne/²¹Ne)_C = 1.094] and absence of neutron capture effects indicate cosmic‐ray shielding in a meteoroid having radius of about 16 cm, implying a meteoroid mass of about 60 kg and ablation of about 93%. The gas retention ages, based on U/Th‐⁴He and K‐⁴⁰Ar are 1.1 and 0.58 Ga, respectively, suggesting a heating and degassing event late in the history of this meteorite.     

Hypersurface-homogeneous bulk viscous fluid space–times with time-dependent cosmological term

Some hypersurface-homogeneous cosmological models with bulk viscous fluid and time-dependent cosmological term are investigated. These expanding, shearing and non-rotating cosmological models of the universe evolve from initial big-bang singularities and give an essentially empty space for large times. Some physical and geometric behaviors of these models are also discussed.     

Bulk viscous fluid hypersurface–homogeneous cosmological models with time varying G and Λ

Hypersurface–homogeneous cosmological models containing a bulk viscous fluid with time varying G and Λ have been presented. We have shown that the field equations are solvable for any arbitrary cosmic scale function. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of the energy density. Exact solutions of Einstein’s field equations are obtained which represent an expanding, shearing and accelerating/decelerating models of the universe. The physical and kinematical behaviours of the models are also discussed.     

A note on the stability of helical velocity and magnetic fields

The stability of nonparallel helical velocity and magnetic fields in a plasma cylinder with free boundaries is examined. It is shown that, in case of weak helicity, the stability of the system remains unaffected.     

Nonlinear waves in superposed fluids

A weakly nonlinear theory of wave propagation in superposed fluids in the presence of magnetic fields is presented in this paper. We derive the equations governing the evolution of the amplitude of the progressive as well as the standing waves. It is demonstrated that the waves can be unstable against modulation in the presence of the magnetic fields. We also obtain the nonlinear cut off wave number which separates the region of stability from instability.     

Chhotanagpur granite gneiss in relation to the schistose rocks around Murhu,Ranchi district,Bihar: a structural approach

Structural analysis of the Chhotanagpur gneiss and the adjoining schistose rocks of the Singhbhum Group indicates perfect conformity in their structures on macroscopic, mesoscopic and microscopic scales. This precludes the possibility of the gneissic rocks having intruded into the deformed and metamorphozed schistose rocks. The observed features can be best explained by considering the gneissic rocks as the basement and the schistose rocks as the cover, both deformed and metamorphozed together. However, this does not exclude the possibility of the gneissic rocks being reactivated and intruding elsewhere.     

Sensitivity analysis of electromagnetic measurements over exponentially varying conductivity earth models

Sensitivity analysis of electromagnetic (EM) measurements is important to quantify the effect of the subsurface conductivity on the measured response. Knowledge of the sensitivity functions helps in solving inverse problems related to field data. In the present paper, we have derived the sensitivity functions for exponentially varying conductivity earth models. The effect of the exponential variation of conductivity has been illustrated graphically on the sensitivity functions. The effect of varying the periods of the electromagnetic waves on the sensitivity functions has also been studied, which gives the characteristic behaviour of the sensitivity functions. This characteristic behaviour provides information about the exponentially decreasing or increasing conductivity earth models.