Assessment of environmental impacts by mining activities: A case study from Jhansi open cast mining site - Uttar Pradesh, India

Mining and its allied activities have taken big strikes during the last century contributing significant infrastructure development and raising the living standards of mankind. However, they have also brought in their wake, degeneration and degradation of natural resources, pollution, health risk and socio-ecological instabilities. Bundelkhand region, occupying almost 71818km2 in the central planes of India, is known for its rich deposits of pyrophyllite, moram, salt peter, granite, diasporas, sand, etc. Currently, there are around 325 active mining sites in Jhansi district alone. Deforestation, dust generation, water, air and noise pollution and resource depletion are common hazards associated with opencast mining widely prevalent in this region. The present paper attempts to reveal the base line environmental quality and socio-economic setting in and around such mining sites with special reference to the effects on the air, water, changes of land use pattern and occupational health effects of mine workers etc. It also attempts to provide a framework for management strategies to improve the environmental conditions in the mining sites and its adjoining environments

Why Do Elastin-Like Polypeptides Possibly Have Different Solvation Behaviors in Water-Ethanol and Water-Urea Mixtures?

The solvent quality determines the collapsed or the expanded state of a polymer. For example, a polymer dissolved in a poor solvent collapses, whereas in a good solvent it opens up. While this standard understanding is generally valid, there are examples when a polymer collapses even in a mixture of two good solvents. This phenomenon, commonly known as co-non-solvency, is usually associated with smart polymers. Moreover, recent experiments have shown that the elastin-like polypeptides (ELPs) show co-non-solvency behavior in aqueous-ethanol mixtures. In this study, we investigate the phase behavior of ELPs in aqueous binary mixtures using molecular dynamics simulations of all-atom and complementary explicit solvent generic models. The model is parameterized by mapping the solvation free energy obtained from the all-atom simulations onto the generic interaction parameters. For this purpose, we derive segment based generic parameters for four different peptides, namely proline (P), valine (V), glycine (G) and alanine (A). Here we compare the conformational behavior of two ELP sequences, namely VPGGG and VPGVG, in aqueous-ethanol and -urea mixtures. Consistent with recent experiments, we find that ELPs show co-non-solvency in aqueous-ethanol mixtures. Ethanol molecules have preferential binding with all ELP residues and thus driving the coil-to-globule transition. On the contrary, ELP conformations show weak variation in aqueous-urea mixtures. Our simulations suggest that the glycine residues dictate the overall behavior of ELPs in aqueous-urea, where urea molecules have a rather weak preferential binding with glycine, i.e., less than kT. While the validation of the latter findings will require more detailed experimental investigation, the results presented here may provide a new twist to the present understanding of cosolvent interactions with peptides and proteins.Comment: Accepted for publication in Macromolecule

Combined experimental and simulation studies of crosslinked polymer brushes under shear

We have studied the effect of crosslinking on the tribological behavior of polymer brushes using a combined experimental and theoretical approach. Tribological and indentation measurements on poly(glycidyl methacrylate) brushes and gels in the presence of dimethylformamide solvent were obtained by means of atomic force microscopy. To complement experiments, we have performed corresponding molecular-dynamics (MD) simulations of a generic bead-spring model in the presence of explicit solvent and crosslinkers. Our study shows that crosslinking leads to an increase in friction between polymer brushes and a counter-surface. The coefficient of friction increases with increasing degree of crosslinking and decreases with increasing length of the crosslinker chains. We find that the brush-forming polymer chains in the outer layer play a significant role in reducing friction at the interface

Effect of crosslinking on the microtribological behavior of model polymer brushes

Polymer brushes in good solvents are known to exhibit excellent tribological properties. We have modeled polymer brushes and their gels using a multibead-spring model and studied their tribological behavior via nonequilibrium molecular-dynamics (MD) simulations. Simulations of brush- against-wall systems were performed using an implicit solvent-based approach. Polymer chains were modeled as linear chains, randomly grafted on a planar surface. Quantities extracted from the simulations are the normal stress, shear stress and concentration profiles. We find that while an increase in the degree of crosslinking leads to an increase in the coefficient of friction, an increase of the length of crosslinker chains does the opposite. Effect of crosslinking can be understood in two ways: (i) there are fewer polymer chains in the outer layer as the degree of crosslinking increases to take part in brush-assisted lubrication, and (ii) crosslinked polymer chains are more resistant to shear than non-crosslinked ones

Excitation of Electrostatic Cyclotron Harmonic Waves in Magnetosphere

135-139Wave-particle interaction in the magnetosphere has been studied for wave frequencies at the cyclotron harmonics of electrons and ions. A generalized dispersion relation for electrostatic wave, propagating nearly perpendicular to the magnetic field in non-Maxwellian plasma has been considered. Expressions of damping and growth rate for electrostatic electron and ion cyclotron harmonic (ICH) waves have been derived and computed results have been demonstrated for the magnetospheric plasma parameters. The growth of electron cyclotron harmonic waves may be interpreted in terms of the observed electron cyclotron harmonic emissions due to energetic electrons and ICH waves by energetic ions in the magnetospheric plasma. The damping of the waves may explain the heating of the magnetospheric plasma

IEC and equivalent slab-thickness at Taiwan

61-64The diurnal and seasonal variations of IECmax and IECmin, noontime biteout, nighttime enhancement in ionospheric electron content (IEC), and equivalent slab-thickness over Taiwan (24.9°N, 121.3°E) have been studied for the quiet days. In general, in the diurnal and seasonal variations of IEC, it is observed that IEC attains minimum value around 0400-0500 hrs LT except in winter months, and the rate of decrease of IEC after reaching maximum is more steep during pre-midnight hours than that during post-midnight hours. The effect of noontime biteout is found more pronounced during summer rather than winter or equinoctial months of 1983-84. Moreover, the nighttime enhancement phenomenon shows the same trend. The seasonal variation of the equivalent slab-thickness of the ionosphere at Taiwan has also been studied and the occurrence of the secondary enhancement has also been observed and discussed

Cyclotron instabilities of low frequency, parallel propagating electromagnetic waves in the magnetosphere

118-126Electromagnetic electron- and ion-cyclotron instabilities incorporating the details of wave-particle interactions have been studies with reference to low frequency waves in the magnetosphere. The general dispersion relation for transverse electromagnetic waves propagating along the ambient magnetic field in an anisotropic bi-Maxwellian plasma with a mirror loss-cone configuration has been considered. The growth/damping rates for electron-cyclotron waves (whistler) and ion-cyclotron waves have been derived. The electron- and ion-cyclotron wave growths have been computed from the magnetospheric VLF data from ISIS-2 satellite for equatorial and midlatitude auroral regions of the magnetosphere. The dependence of the growth rate of these waves on the temperature anisotropy and mirror loss-cone has been discussed. Loss-cone and electron-cyclotron instabilities are interpreted as the generation mechanism for the low frequency waves in the magnetosphere

Generation mechanism and interpretation of attenuation band of VLF-saucers

130-133An analysis of the ISIS-VLF data detected by magnetometer in the auroral region of the magnetosphere has been carried out for VLF-saucers. The generation mechanism of VLF-saucers has been studied in terms of excitation of electrostatic cyclotron harmonic emission due to energetic ions and electrons in the magnetospheric plasma. The attenuation bands of VLF-saucers, as observed by ISIS-2 satellite, have been discussed and it is interpreted that the cyclotron absorption of low energy protons at harmonics of local proton-cyclotron frequencies may be the cause for attenuation bands in VLF-saucers

Polymer brushes under shear: molecular dynamics simulations compared to experiments

Surfaces coated with polymer brushes in a good solvent are known to exhibit excellent tribological properties. We have performed coarse-grained equilibrium and nonequilibrium molecular dynamics (MD) simulations to investigate dextran polymer brushes in an aqueous environment in molecular detail. In a first step, we determined simulation parameters and units by matching experimental results for a single dextran chain. Analyzing this model when applied to a multichain system, density profiles of end-tethered polymer brushes obtained from equilibrium MD simulations compare very well with expectations based on self-consistent field theory. Simulation results were further validated against and correlated with available experimental results. The simulated compression curves (normal force as a function of surface separation) compare successfully with results obtained with a surface forces apparatus. Shear stress (friction) obtained via nonequilibrium MD is contrasted with nanoscale friction studies employing colloidal-probe lateral force microscopy. We find good agreement in the hydrodynamic regime and explain the observed leveling-off of the friction forces in the boundary regime by means of an effective polymer–wall attraction

Free Standing Dry and Stable Nanoporous Polymer Films Made through Mechanical Deformation

Abstract A new straight forward approach to create nanoporous polymer membranes with well defined average pore diameters is presented. The method is based on fast mechanical deformation of highly entangled polymer films at high temperatures and a subsequent quench far below the glass transition temperature Tg. The process is first designed generally by simulation and then verified for the example of polystyrene films. The methodology does not need any chemical processing, supporting substrate, or self assembly process and is solely based on polymer inherent entanglement effects. Pore diameters are of the order of ten polymer reptation tube diameters. The resulting membranes are stable over months at ambient conditions and display remarkable elastic properties