Associated HI absorption in the z=3.4 radio galaxy B2 0902+343 observed with the GMRT

We have made observations of the associated HI absorption of a high redshift radio galaxy 0902+34 at z=3.395 with the Giant Meterwave Radio Telescope in the $323\pm1$ MHz band. We find a narrow absorption line with a flux density of 11.5 mJy at a redshift of 3.397 consistent with that observed by Uson et al. (1991), Briggs et al. (1993) and de Bruyn (1996).A weak broad absorption feature reported by de Bruyn (1996) has not been detected in our observations. We also place an upper limit of 4 mJy (2 $\sigma$) on emission line strength at the position where Uson et al. (1991) claimed to have found a narrow emission line.Comment: To appear in Journal of Astronomy and Astrophysic

A simple image forming technique suitable for multifrequency observations of solar radio bursts

A simple image forming system using a multielement interferometer for obtaining rapid pictures of solar radio bursts is described. A dispersive transmission line is used to feed the elements in series through directional couplers. Truly instantaneous pictures of solar activity can be obtained by placing a number of narrow frequency filters at the end of the I. F. amplifier in the main receiver, located at one end of the array. The two dimensional extension of this principle is examined in some detail. Multibeaming in the two arrays of a crossed grating interferometer can be combined with fast phase-scanning in one of the arrays to produce rapid pencil beam pictures. If log-periodic antennas are used, observations can even be made at widely different frequencies simultaneously. For illustration, some important parameters for simultaneous observations at 60, 90 and 120 MHz are estimated for an interferometer assumed to be located at a latitude of 30° N. The main advantage of the proposed system is that high-resolution rapid pictures of radio bursts can be obtained simultaneously at a number of frequencies with modest effort

Case History of Tunnelling Through Claystone

A broad gauge railway line is being constructed by Indian Railways in Himalaya. The total route length is 342kms, out of which about 100km is in tunnels. The tunnelling problem while excavating the Tunnel no.1 of Udhampur-Katra section and being faced currently is discussed in the paper. The D-shaped tunnel passes through thickly bedded, moderately soft, sparsely jointed sandstone, sheared claystones, siltstones and overburden comprising boulders/pebbles in sandy/silty matrix. The support pressure and the deformation were monitored to study the performance of the support system. Due to the presence of swelling minerals in claystone and weak & highly jointed rock formations with high rock cover (313m), the tunnel experienced both swelling and squeezing ground conditions resulting in the buckling of wall supports of steel ribs, cracking of tunnel wall concrete lining at places and floor heaving up to 1.2m. With the deformation of wall supports, the tunnel roof support also deformed. Numerical analysis using FLAC3D has been carried out to study the effectiveness of the support system. The study shows that the tunnel with out any support may have the wall deformations up to 2.76m. On the other hand, with rock bolt and 40cm thick steel fibre reinforced shotcrete (SFRS) support, the wall deformation would reduce to 23cm

110th Anniversary: Near-Total Epoxidation Selectivity and Hydrogen Peroxide Utilization with Nb-EISA Catalysts for Propylene Epoxidation

The Nb-EISA catalyst with relatively low Nb loadings (∼2 wt %) shows exceptional propylene epoxidation performance with H2O2 as oxidant at 30–40 °C, 5–9 bar propylene pressure with nearly total propylene oxide (PO) selectivity (>99%), H2O2 utilization (>99%) toward PO formation, high productivity (∼3200 mg/h/g), and mild Nb leaching (3–6%). The predominantly Lewis acidic nature of the Nb-EISA catalysts favors epoxidation while their relatively low Brønsted acidity inhibits H2O2 decomposition and Nb leaching. At higher Nb loadings (8–17 wt %), the catalytic performance deteriorates. However, significant performance improvements were achieved when the Nb-EISA materials are calcined in N2 (instead of air) during synthesis, depositing a carbon layer in the pores. The resulting pore hydrophobicity not only inhibits epoxide ring opening but also increases propylene concentration inside the pores resulting in higher EO productivity and lower H2O2 decomposition. The carbonized Nb-EISA materials also show improved stability to leaching

The Creation of Defects with Core Condensation

Defects in superfluid 3He, high-Tc superconductors, QCD colour superfluids and cosmic vortons can possess (anti)ferromagnetic cores, and their generalisations. In each case there is a second order parameter whose value is zero in the bulk which does not vanish in the core. We examine the production of defects in the simplest 1+1 dimensional scalar theory in which a second order parameter can take non-zero values in a defect core. We study in detail the effects of core condensation on the defect production mechanism.Comment: 9 pages, 7 figures, small corrections, 2 references added, final version to be published in PR

Oxidative Stress in Lead and Cadmium Toxicity and Its Amelioration

Oxidative stress has been implicated to play a role, at least in part, in pathogenesis of many disease conditions and toxicities in animals. Overproduction of reactive oxygen species and free radicals beyond the cells intrinsic capacity to neutralize following xenobiotics exposure leads to a state of oxidative stress and resultant damages of lipids, protein, and DNA. Lead and cadmium are the common environmental heavy metal pollutants and have widespread distribution. Both natural and anthropogenic sources including mining, smelting, and other industrial processes are responsible for human and animal exposure. These pollutants, many a times, are copollutants leading to concurrent exposure to living beings and resultant synergistic deleterious health effects. Several mechanisms have been explained for the damaging effects on the body system. Of late, oxidative stress has been implicated in the pathogenesis of the lead- and cadmium-induced pathotoxicity. Several ameliorative measures to counteract the oxidative damage to the body system aftermath or during exposure to these toxicants have been assessed with the use of antioxidants. The present review focuses on mechanism of lead- and cadmium-induced oxidate damages and the ameliorative measures to counteract the oxidative damage and pathotoxicity with the use of supplemented antioxidants for their beneficial effects