The structure of rotating polytropes (second order)

In order to carry out a numerical study of the structure of rotationally distorted polytropes, the Monaghan and Roxburgh (1965) method is extended to include the second-order term in the perturbation parameter, .     

The structure of tidally distorted polytropes

A numerical study of the structure of tidally-distorted polytropes has been carried out by using the Monaghan and Roxburgh (1965) method.     

Adiabatic radial pulsations of a composite stellar model

Small adiabatic radial oscillations of composite models have been investigated. The effect of central condensation ρ_c√ρ on the period of pulsation have also been examined. In has been shown that the second moment of mass concentration characterize the periods of pulsation more effectively than central condensation.     

Anthropogenic sulphate aerosols and large Cl-deficit in marine atmospheric boundary layer of tropical Bay of Bengal

Our long-term study provides an unequivocal evidence for near-quantitative (80–100%) depletion of chloride from sea-salts in the marine atmospheric boundary layer (MABL) of tropical Bay of Bengal. During the late NE-monsoon (Jan-Mar), continental outflow from south and south-east Asia dominate the wide-spread dispersal of pollutants over the Bay of Bengal. Among anthropogenic constituents, SO ₄ ^2? (range: 0.6–35 μg m^?3) is the most dominant. The non-sea-salt SO ₄ ^2? (nss-SO ₄ ^2? ) constitutes a major fraction (55–65%) of the aerosol water-soluble ionic composition (WSIC), whereas contribution of NO ₃ ^? is relatively minor. The magnitude of Cl-deficit (with respect to its sea-salt proportion) exhibits linear increase with the excess-nss-SO ₄ ^2? (excess over NH ₄ ⁺ ). We propose that displacement of HCl from sea-salt aerosols by H₂SO₄ is a dominant reaction mechanism for the chloride-depletion. These results also suggest that sea-salts could serve as a potential sink for anthropogenic SO₂ in the downwind polluted marine environment. Furthermore, loss of hydrogen chloride, representing a large source of reactive chlorine, has implications to the oxidant chemistry in the MABL (oxidation of hydrocarbons and dimethyl sulphide).     

Tectonic control on exhumation and seismicity in the Garhwal‐Kumaun Himalaya,NW‐India

Despite similar geological and tectonic setting along the Himalayan orogen, distinct thermochronological/exhumational and seismicity variability exists between the Kumaun and the Garhwal regions of the NW‐ Himalaya. The processes responsible for such variability are still debated. To understand this, published thermochronological ages from several traverses across the Higher Himalayan Crystalline (HHC) and Lesser Himalayan Crystalline (LHC) have been correlated with the seismicity pattern in both Garhwal and Kumaun segments. The seismicity pattern coincides with the zone of rapid uplift and exhumation. The profiles of seismicity across the Kumaun and the Garhwal regions agree with the existence of the Main Himalayan Thrust (MHT) underlying the regions and reflect its geometry and architecture. Slip along the MHT is responsible for occurrence of seismicity on decade time‐scale and exhumation pattern on Myr time‐scale of the Himalaya.     

The structure of the tidally and rotationally distorted polytropes

A study of the structure of tidally and rotationally distorted polytropes has been carried out using Monaghan and Roxburgh (1965) method for rapidly rotating polytropes, at the new interfacial points (Singh and Singh, 1982), ξ_f = 3.025, 3.470, and 4.950 for the polytropic models with the indicesn=1.5, 2.0, and 3.0, respectively. The structure has been studied for various mass ratios too.     

Trace Determination of Strontium and Barium in River Waters by Inductively Coupled Plasma-Atomic Emission Spectrometry Using an Ultrasonic Nebulizer

Inductively coupled plasma-atomic emission spectrometry in conjunction with an ultrasonic nebulizer was employed for the determination of Sr and Ba in river waters at parts per billion (μg l⁻¹) levels without pre-concentration. The ultrasonic nebulizer, equipped with a desolvation system, enhanced the analytical sensitivity by ten to twenty fold compared to conventional pneumatic nebulizers. The detection limits for Sr and Ba, ascertained from blanks and reference samples made in 0.05% NaCl solution, were 0.045 μg l⁻¹ and 0.16 μg l⁻¹ respectively. The accuracy of measurements, based on analyses of solutions of reference materials (G-2 and W-1) and multielement commercial standards (Merck®), was ± 10%. Replicate analyses of samples and reference samples showed measurement precision to be to be better than ± 5%, which is adequate considering that the concentration of Sr and Ba in river waters varies by one to two orders of magnitude.     

A review of present techniques and methodological advances in analyzing Th in aquatic systems

The short-lived thorium isotope ²³⁴Th (half-life 24.1 days) has been used as a tracer for a variety of transport processes in aquatic systems. Its use as a tracer of oceanic export via sinking particles has stimulated a rapidly increasing number of studies that require analyses of ²³⁴Th in both marine and freshwater systems. The original ²³⁴Th method is labor intensive. Thus, there has been a quest for simpler techniques that require smaller sample volumes. Here, we review current methodologies in the collection and analysis of ²³⁴Th from the water column, discuss their individual strengths and weaknesses, and provide an outlook on possible further improvements and future challenges. Also included in this review are recommendations on calibration procedures and the production of standard reference materials as well as a flow chart designed to help researchers find the most appropriate ²³⁴Th analytical technique for a specific aquatic regime and known sampling constraints.     

Spectral Interference in the Determination of Molybdenum in Geological Samples by ICP-AES: A Reassessment

Molybdenum concentrations in USGS reference materials and marine sediments have been measured using ICP-AES following dissolution of samples in HF-HNO₃-HCl with final aliquots made in 1 mol l⁻¹ HCl. The concentrations determined at one of the recommended wavelengths, 281.615 nm, are found to be severely affected by a spectral interference from Al, leading to inaccurate analytical results. At an alternative wavelength, 202.030 nm, the Mo emission signal is attenuated in the window size 0.094 nm due to the presence of an Fe line (202.074 nm), thus affecting the analytical sensitivity of measurements. The attenuation of the emission signal at 202.030 nm could severely limit the determination of Mo in geological samples.