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[en] Ranigunj coalfield (India) has been facing significant problems due to subsidence as a result of underground mining of coal seams. The occurrence of the thick seams in close proximity, shallow depth, great variation in the nature of superincumbent strata from site to site, followed by the slow rate of extraction, has aggravated subsidence problems. In the recent past, many such workings have collapsed, damaging a large number of surface structures. In view of the aforesaid need, a comprehensive project financed by the Ministry of Energy (Coal), was undertaken by the Department of Mining Engineering, Indian Institute of Technology, Kharagpur, at a Colliery in Ranigunj Coalfield. This investigation revealed that the caving horizon occurred at 4 times the extracted seam height, which differs from the findings in the UK, USA, and Australia. Also, it appears possible to estimate strata displacements from geological and physicomechanical information from the overlying rocks using the bending moment principle. Further, it was observed that the shallow workings could give rise to a sink hole type of subsidence, which is dangerous and could adversely affect the environment, safety of the public and properties. 11 refs., 13 figs., 1 tab
[en] Prior to the late 1960's environment and public health received very little attention. Recently mining and environment has been the subject of increasing concern on the international agenda. Although each country has in the world seems to have developed its own standards, there are however, presently no universally accepted standards to protect human health. The paper discusses the global concern on the impacts of environment caused by mining activities. It also summarises a variety of guidelines that has been produced by various international agencies, which are relevant to environmental management within the mining sector. (authors)
[en] Mesoporous MnO_2–ZnO, Fe_2O_3–ZnO, NiO–ZnO, and CeO_2–ZnO binary metal oxide nanocomposites were studied as sorbent decontaminants against sulfur mustard. They were synthesized by precipitation pyrolysis method and characterized by means of transmission electron microscopy, scanning electron microscopy coupled with energy dispersive analysis of X rays, X ray diffraction, and nitrogen adsorption techniques. The transmission electron microscopy and nitrogen adsorption data indicated the presence of pores with diameter ranging from 10 to 70 nm in the binary metal oxide nanocomposites and these materials exhibited surface area values in the range of 76–134 m"2/g. These binary metal oxide nanocomposites demonstrated large decontamination efficiencies against sulfur mustard when compared to their single component metal oxide nanoparticles. The binary metal oxide nanocomposites effectively decontaminated sulfur mustard into relatively non toxic products such as chloro ethyl vinyl sulfide, divinyl sulfide, 1,4-oxathiane, etc. The promising decontamination properties of binary metal oxide nanocomposites against sulfur mustard were attributed to the basic sites, Lewis acid sites, and the presence of these sites was confirmed by CO_2 and NH_3 temperature programmed desorption. - Graphical abstract: Mesoporous MnO_2–ZnO, Fe_2O_3–ZnO, NiO–ZnO, and CeO_2–ZnO binary metal oxide nanocomposites were studied as sorbent decontaminants against sulfur mustard. - Highlights: • Binary metal oxide nanocomposites were synthesized by co-precipitation method. • They were studied as sorbent decontaminants against sulfur mustard. • They decontaminated sulfur mustard into non toxic products. • MnO_2–ZnO and CeO_2–ZnO nanocomposites showed greater decontamination efficiency.
[en] Purpose: To see if changes in tumor/blood glutathione (GSH) levels after one fraction of radiotherapy can be correlated with the treatment response in patients with carcinoma of the uterine cervix. Methods and Materials: The study was done on 45 patients with squamous cell carcinoma of the uterine cervix, FIGO Stages IIB (17 patients) and IIIB (28 patients). Stage IIB patients received 35 Gy of cobalt-60 external radiotherapy (RT) in 16 fractions over 4 weeks with a concurrent high-dose-rate intracavitary dose of 8.5 Gy to point A once a week. Stage IIIB patients were given 45 Gy of RT in 20 fractions over 5 weeks, followed by two doses of intracavitary therapy once a week. Blood and tumor samples were collected before and after one dose of RT and GSH was estimated. Tumor response was assessed clinically at 1 month after treatment. Results: Glutathione levels in both blood and tumor showed a significant decrease after one fraction of RT, but the degree of decrease varied among patients. There was a good correlation between the extent of GSH decrease and the tumor response. All patients who had complete response (CR) (seven Stage IIB and eight Stage IIIB) showed ≥70% decrease in both tumor and blood GSH, while those who had <50% regression (NR) (five Stage IIB and 13 Stage IIIB) showed <50% decrease in GSH. The partial responders recorded an intermediate level (50-70%) of depletion in blood and tumor GSH. Conclusions: The results indicate that the changes in tumor/blood GSH levels after one fraction of RT could serve as an index of tumor response to therapy and may help in identifying radioresistant tumors, at least in the case of cervix carcinoma
[en] This paper reports on effect of forging and Heat Treatment on Tribological characteristics of aluminium alloy-silicon nitride. Cast aluminium alloy and composite were subjected to open die hot forging process. Alloy and its composites were examined to characteristics hardness and wear test under both primary and secondary processing conditions. Effect of heat treatment on hardness and tribological behaviour were also studied. Microstructure shows even spreading of particles in cast and forged conditions. hot forged alloy and composite shows a noticeable improvement in wear resistance and COF compare to their primary counter parts. Heat treatment has a considerable effect on hardness, friction and wear characteristics of composites. (paper)
[en] Equipment cooling is highly essential for safe operation of devices in applications such as nuclear reactors etc. To remove large amount of heat from an operational device, Nucleate Boiling regime is highly preferred due to its high bailing heat transfer coefficient (BI-ITC). However heat transfer is highly brought down due to regime transition from Nucleate Boiling to Film Boiling at a transition point called Critical Heat Flux (CHF). The high heat transfer drop in film boiling is due to the vapour blanket formed due to the coalescence of bubbles in Nucleate Boiling regime which blocks the heat transfer heated surface to fluid. There is a need to enhance the Critical Heat flux which can facilitate in the improvement of heat transfer characteristics. Increase in Critical Heat flux or enhancement in Nucleate boiling is observed by using Active or passive techniques. Passive technique can be performed either by surface manipulation (creating artificial nucleation sites) or addition of additives to coolant (used to decrease the surface tension). On the other hand, Active technique involves the implementation of Electrohydrodynamics (external electric fields), Magneto hydrodynamics (external magnetic fields), surface vibrations etc. It has been demonstrated that application of electric fields has augmented the heat transfer. Further physical insights and mechanisms of electrohydrodynamic enhanced Boiling heat transfer can be obtained through numerical modelling. The numerical model involves complex coupling of Maxwell coupling electric stresses with mass, momentum, energy and Level set equations. The first term in (1) is Colournbic component of Maxwell electric force which arises due to the charge created in fluid upon the action of electric fields. The second term arises due to spatial change in permittivity of system and third term arises due to the inhomogeneous fields created in a system. For a single phase system second and third term disappears whereas for a two-phase system each term contributes to significant amount of electric force
[en] A variational calculation based on the Lee-Low-Pines-Huybrechts method is performed to obtain the polaronic binding energies corresponding to the ground state and the first excited state of an electron in a polar quantum wire with parabolic confinement in the transverse direction. It is shown that the polaronic effects are considerably large and size-dependent if the effective radius of the wire is reduced below a certain length scale. It is also shown that even the longitudinal effective mass of the polaron is strongly enhanced by the transverse confinement in a quantum wire
[en] We have measured by means of neutron inelastic scattering the spin-wave dispersion in the pseudo 1-d ferromagnet RbFeCl3 at T=1.5 K. The observed dispersion in the hexagonal plane is found to disagree both with the planar triangular magnetic structure and with the small interchain exchange previously assumed. A new model with conical structure (theta=540) and Spin Hamiltonian parameters J=4.2 K J'=-1.2 K D*=8 K is proposed
[en] Tailoring the synthesis of a suitable Ziegler-Natta (ZN) catalyst coupled with optimized polymerization conditions using a suitable activator holds the key for an array of differentiated polymers with diverse and unique properties. Ultra high molecular weight polyethylene (UHMWPE) is one such polymer which we have synthesized using TiCl4 anchored on MgCl2 as the support and activated using AlRR'2 (where R, R' = iso-prenyl or isobutyl) under specific conditions. Here in we have accomplished a process for synthesizing UHMWPE in hydrocarbon as the medium with molecular weights ranging from 5 to 10 million g/mole. The differentiated polymers exhibited the desired properties such as particle size distribution (PSD), average particle size (APS), bulk density (BD) and molecular weight (MW) with controlled amount of fine and coarse particles. Scanning electron micrographs (SEM) reflected the material to have uniform particle size distribution with a spherical morphology. The extent of entanglement was determined from thermal studies and it was found to be highly entangled.