Search for H I emission from superdisk candidates associated with radio galaxies

Giant gaseous layers(termed “superdisks”) have been hypothesized in the past to account for the strip-like radio emission gap(or straight-edged central brightness depression) observed between twin radio lobes, in over a dozen relatively nearby powerful Fanaroff-Riley Class II radio galaxies. They could also provide a plausible alternative explanation for a range of observations. Although a number of explanations have been proposed for the origin of the superdisks, little is known about their material content. Some X-ray observations of superdisk candidates indicate the presence of hot gas, but a cool dusty medium also seems to be common. If they are entirely or partly composed of neutral gas, then it may be directly detectable and we report here a first attempt to detect/image any neutral hydrogen gas present in the superdisks that are inferred to be present in four nearby radio galaxies. We have not found a positive H I signal in any of the four sources, resulting in tight upper limits on the H I number density in the postulated superdisks,estimated directly from the central rms noise values of the final radio continuum subtracted image. The estimated ranges of the upper limit on neutral hydrogen number density and column density are 10^-4-10^-3 atoms per cm3 and 10^19-10^20 atoms per cm^2, respectively. No positive H I signal is detected even after combining all the four available H I images(with inverse variance weighting). This clearly rules out an H I dominated superdisk as a viable model to explain these structures, however, the possibility of a superdisk being composed of warm/hot gas still remains open.

Production,activation,and applications of biochar in recent times

Biomass is a green energy source and is available in abundance.Biochar is a carbon-rich material derived from a wide range of biomass or organic waste through the thermochemical route.Biochar has received increasing attention because of its distinctive properties such as high carbon content,greater specific surface area,cation exchange capacity,nutrient retention capacity,and stable structure.This review paper extensively studies and reports the different pyrolysis processes,reactor types,the effect of process parameters on biochar yield,and its physicochemical properties,biochar activation methods,and applications.It also details the status of the research and development(R&D)progress in biochar production through conventional and advanced technologies.The study found that unlike many products(at R&D stage)biochar has high potential to scale up and has a direct impact on crop yield,water purification(for domestic and industrial application),alternative fuels(clean solid fuel for cookstove),air purification,catalyst,biogas production,purification,and storage.In addition,the paper lists the merits and challenges in the novel biochar applications like hydrogen storage,electrochemical capacitor,and fuel cell technology.