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We estimated the concentration of Chlorophyll-a (Chl-a) along with physical and biological factors including sea surface temperature (SST), wind speed and concentration of nitrate and phosphate in the Western, Central and Eastern Equatorial Indian Oceans (WEIO, CEIO and EEIO) using data from the Copernicus Marine Service and ERA-5 for the years 1994 to 2019. Our results show that along with the concentration of Chl-a, nitrate and phosphate have decreased, and sea surface temperature has increased in the EEIO. Due to coastal upwelling off the coast of Somalia and offshore Ekman transport throughout the summer, the southwest monsoon caused a significant increase in concentrations of Chl-a, nitrate, phosphate and wind speed in WEIO during June-July-August-September (JJAS) and October-November-December (OND). SST decreased at this time and deeper water interacted with surface water, increasing biological production. In EEIO, the upwelling zone is primarily maintained by wind-induced divergence throughout the year, whereas stratification in winter prevented surface Chl-a increase. High wind speed and low SST led to increased productivity in WEIO. Comparison of EEIO with WEIO and CEIO demonstrates low levels of Chl-a, phosphate and nitrate. The trends signify that these oceanic zones are highly vulnerable to developing into ecological deserts in the near future. [ABSTRACT FROM AUTHOR]

An equiatomic quinary TiVZrMoW refractory high entropy alloy (RHEA) is selected for studying phase evolution and stability. The prediction of phases that may form on synthesis is made by (i) Semi-empirical /empirical methods (based on extended Hume-Rothery rules), (ii) CALPHAD and (iii) ab-initio methods. Mixing enthalpy (calculated by Miedema method) and valence electron concentration predicted the formation of the BCC phase ( ; and VEC = 5). However, the atomic mismatch factor, δ (7.17%) value being higher than the desired value, can de-stabilize the lattice to form a multi-phase structure. CALPHAD technique predicted that at room temperature three BCC and two Laves phases would form. The enthalpy of mixing (4.25 kJ/mol) calculated using Density Functional Theory (DFT) also suggests phase separation at room temperature. The phases and microstructure that evolved in the as-cast and annealed samples are studied by X-ray diffraction (XRD), scanning electron and transmission electron microscopy (TEM) techniques. Two BCC phases and a minor amount of ordered B2 and C15 type Laves phase are found to co-exist in the as-cast sample. The primary BCC phase (BCC#1) is rich in Mo and W (a = 3.17 ± 0.02 Å), while the minor BCC phase (BCC#2) is rich in Zr and Ti (a = 3.65 ± 0.02 Å). The annealed sample shows the transformation of both the disordered BCC phase to the ordered B2 phases and the increase in the amount of C15 Laves phase. The phase evolution and their relative stability in this RHEA has been discussed after analysing the experimental and theoretical results. [ABSTRACT FROM AUTHOR]