Multiwavelength investigation of a near-solar metallicity sub-DLA at z =1.3647 towards PKS 0237-233

We searched for 21-cm absorption associated with the z_abs = 1.3647 absorption system toward PKS 0237-233 using the GMRT. A high quality UVES spectrum shows that C I and C I* are detected at this redshift together with C II*, Mg I, Mg II, Si II, Al II, Fe II and Mn II. The complex profiles, spread over ~300 km/s, are fitted with 21 Voigt profile components. None of these components are detected in 21-cm absorption down to a detection limit of \tau(3\sigma)\le 3x10^{-3} (or N(HI)/T_S <10^{17} cm ^-2 K^-1). We derive log N(HI)<19.30$\pm$0.30 using the Lyman alpha absorption line detected in the IUE spectrum of the quasar. Mg II, Si II and Al II column densities are consistent with near solar metallicity and we measure [O/H]>-0.33. Using photoionization models constrained by the fine-structure excitations of C I and C II, and the 21-cm optical depth, we show that the C I absorption arises predominantly either in WIM or WNM in ionization and thermal equilibrium with the meta-galactic UV background dominated by QSOs and star forming galaxies. The estimated thermal pressure of the gas is of the same order of magnitude over different velocity ranges through the absorption profile (2.6\le log [P/k cm^{-3} K]\le 4.0). The gas-phase metallicity corrected for ionization is Z>0.5 Z_\odot with a signature of Fe co-production elements being under abundant compared to \alpha-process elements by ~0.5 dex. At z>1.9, C I absorption is usually associated with H_2 absorption arising from cold gas in DLAs. This system and the z=2.139 toward Tol 1037-270 are the only two systems known which show that C I absorption can also be detected in warm gas provided the metallicity is high enough. Interestingly, both the systems are part of unusual concentrations of absorption lines.Comment: 12 pages, 9 figures, accepted for publication in MNRA

Ultrastructure of the scales of Channa punctatus: A fresh water fish

In order to study scales of Channa punctatus live specimens were collected, after acclimatization the scales were collected from the fishes. The clean and air-dried scales were mounted on the metal stubs. After coating they were subjected to the scanning electron microscope study. Scales showed the presence of circuli, radii, chromatophores and denticles like structures called as lepidonts

Smart Grid is the Key to Enhance the Penetration of Renewable Energy into Electric Power Systems

Dear researchers, Due to the rapid development of renewable energy technologies because of environmental concerns, the electric power grid is experiencing a significant change. The electrical power structure is no longer a vertically integrated structure due to the large grid parity of renewables and as a result, smart grid is the key to enhance the penetration of renewable energy into electric power systems. However, due to the intermittent probabilistic nature of renewable energy sources, design and management of power are a great challenge to both power and computing industry. Furthermore, it has been anticipated that future energy structure will be “two-way streetsâ€, allowing every energy user to be not only a customer, but an energy provider as well. So, a smart grid structure is the need in the present scenario. This transition from classical power structure inevitably demands significant research for many rapidly rising issues.This Special Issue focuses on smart grid that can accommodate renewable energy into electric utility systems. The Special Issue is interested but not limited to the following issues relevant to increased renewable energy penetration:1) Prediction of sustainable energy resources.2) Stability and control of sustainable energy in supporting grid frequency and voltage.3) Steady-state and transient assessment of system, etc.4) Extent to which dispatchable generation reserves required and under what circumstances.5) Effect on reliability be compromised with increased sustainable energy penetration.6) Cost considerations with renewable’s variability7) Effect on system operating strategies with sustainable energy generation8) Effect on various measuring devices for effective monitoring and evaluation of electric power system operation, etc. Dr. Neeraj Gupt

HI gas in rejuvenated radio galaxies: GMRT observations of the DDRG J1247+6723

We report the detection of HI absorption towards the inner double of the double-double radio galaxy (DDRG) J1247+6723 with the Giant Metrewave Radio Telescope (GMRT). The inner double is a Giga-hertz peaked spectrum (GPS) source with a linear size of 14 pc while the overall size defined by the outer double is 1195 kpc, making it a giant radio source. The absorption profile is well resolved and consists of a number of components on either side of the optical systemic velocity. The neutral hydrogen column density is estimated to be N(HI)=6.73*10^{20}(T_s/100)(f_c/1.0) cm^{-2}, where T_s and f_c are the spin temperature and covering factor of the background source respectively. We explore any correlation between the occurrence of HI absorption and rejuvenation of radio activity and suggest that there could be a strong relationship between them.Comment: 5 pages, 2 figures, accepted for publication in MNRAS Letter