Development of graded Ni-YSZ composite coating on Alloy 690 by Pulsed Laser Deposition technique to reduce hazardous metallic nuclear waste inventory.

Alloy 690 based 'nuclear waste vitrification furnace' components degrade prematurely due to molten glass-alloy interactions at high temperatures and thereby increase the volume of metallic nuclear waste. In order to reduce the waste inventory, compositionally graded Ni-YSZ (Y(2)O(3) stabilized ZrO(2)) composite coating has been developed on Alloy 690 using Pulsed Laser Deposition technique. Five different thin-films starting with Ni80YSZ20 (Ni 80 wt%+YSZ 20 wt%), through Ni60YSZ40 (Ni 60 wt%+YSZ 40 wt%), Ni40YSZ60 (Ni 40 wt%+YSZ 60 wt%), Ni20YSZ80 (Ni 20 wt%+YSZ 80 wt%) and Ni0YSZ100 (Ni 0 wt%+YSZ 100 wt%), were deposited successively on Alloy 690 coupons. Detailed analyses of the thin-films identify them as homogeneous, uniform, pore free and crystalline in nature. A comparative study of coated and uncoated Alloy 690 coupons, exposed to sodium borosilicate melt at 1000°C for 1-6h suggests that the graded composite coating could substantially reduced the chemical interactions between Alloy 690 and borosilicate melt.

Involvement of thylakoid membranes in supramolecular organisation of Calvin cycle enzymes in Anacystis nidulans.

The cells of unicellular photosynthetic cyanobacterium Anacystis nidulans were permeated with lysozyme, toluene, toluene-triton, toluene-triton-lysozyme. Transmission electron microscopy of semi-thin sections (500 nm) using TEM at 160 kV showed that cells permeated with only lysozyme or toluene showed the typical concentric arrangement of thylakoid membranes. However, when toluene-treated cells were further treated with triton and lysozyme the thylakoid membranes were disrupted. Sequential reactions of Calvin cycle were studied in the differentially permeated cells in vivo, using various intermediates such as 3-PGA, GA-3-P, FDP, SDP, R-5-P, RuBP and cofactors like ATP, NADPH depending on the requirement. RuBP and R-5-P + ATP dependent activities could be observed in all types of permeated cells. Sequential reactions of the entire Calvin cycle using 3-PGA could be detected in the cells that had retained the internal organisation of the thylakoid membranes after permeation and were lost on disruption of this organisation. Light dependent CO2 fixation could be detected only in the cells permeated with lysozyme. This activity was abolished in the cells after treatment with toluene. The results suggested that the integrity of thylakoid membranes may be essential for the organisation of sequential enzymes of the Calvin cycle in vivo and facilitate their functioning.