The present paper explores the enhancement in hydrogen sorption behavior of MgH2 with TiO2 nanoparticles. The catalytic effect of TiO2 nanoparticles with different sizes (7, 25, 50, 100 and 250 nm) were used for improving the sorption characteristics of MgH2. The MgH2 catalyzed with 50 nm of TiO2 exhibited the optimum catalytic effect for hydrogen sorption behavior. The desorption temperature of MgH2 catalyzed through 50 nm TiO2 was found to be 310 degrees C. This is 80 degrees C lower as compared to MgH2 having a desorption temperature of 390 degrees C. It was noticed that the dehydrogenated MgH2 catalyzed with 50 nm TiO2 reabsorbed 5.1 wt% of H2 within 6 minutes at temperature and pressure of 250 degrees C and 50 atm, respectively. The 50 nm TiO2 catalyst lowered the absorption activation energy of MgH2 from - 92 to - 52.7 kJ mol(-1).

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Pre-monsoon dust aerosols over Indian regions are closely linked to the monsoon dynamics and Indian summer monsoon rainfall. Past observational studies have shown a decline in dust loading over the Indian landmass potentially caused by changing rainfall patterns over the desert regions. Such changes are expected to have far reaching impact on regional energy balance and monsoon rainfall. Using a regional climate-chemistry model, RegCM4.5 with an updated land module, we have simulated the long-term (2001-2015) changes in dust over the arid and semi-arid dust source regions of the North-Western part of the sub-continent. It is found that the area-averaged dust aerosol optical depth (AOD) over the arid and semi-arid desert regions has declined by 17% since the start of this millennium. The rainfall over these regions exhibits a positive trend of 0.1 mm day-1year-1 and a net increase of > 50%. The wet deposition is found to be dominant and ~5 fold larger in magnitude over dry deposition and exhibits total changes of ~ 79 % and 48% in the trends in atmospheric dust. As a response, significant change in the surface (11%), top of the atmosphere radiative forcing (7%), and widespread atmospheric cooling are observed in short wave domain of radiation spectrum, over the Northern part of the Indian landmass. Such quantification and long term change studies are necessary for understanding the regional climate change and the water cycle.

Plasticity in physiological traits is necessary for the survival and development of woody species in the severe conditions of tropical dry forest. We selected five study sites in a gradient of soil moisture availability, located in dry forest of India. We identified 12 physiological traits (viz., relative water content, RWC; leaf dry matter content, LDMC; specific leaf area, SLA; leaf carbon concentration, LCC; leaf nitrogen concentration, LNC; leaf phosphorus concentration, LPC; chlorophyll concentration, Chl; stomatal conductance, Gs max ; photosynthetic rate, A max ; intrinsic water use efficiency, WUEi; biomass increment, Bio Incr; relative growth rate, RGR), which are considered important for the survival and growth of plant species in tropical dry forest, and measured their range and plasticity in woody species, including trees and shrubs, across the selected study sites. Further, we analysed the response of physiological traits to variations in soil moisture content (SMC) across species as well as across study sites. Across the five study sites, the selected traits exhibited remarkable plasticity, both within as well as among species. The associations of physiological traits with soil properties were also significant. The study shows that all physiological traits under study affect RGR directly or indirectly. However, the strength of effect is determined by environmental parameters, particularly the SMC. Step wise multiple regression indicates that more than 80% variability in RGR can be explained by SLA and WUEi alone. We suggest that for predicting the vulnerability of tropical dry forest communities to changes in climatic conditions, further investigations examining trade-offs among physiological traits and habitat conditions are needed.