T. G. Prasad

Formation and spreading of Arabian Sea high‐salinity water mass

The formation and seasonal spreading of the Arabian Sea High-Salinity Water (ASHSW) mass were studied based on the monthly mean climatology of temperature and salinity in the Arabian Sea, north of the equator and west of 80°E, on a 2° × 2° grid. The ASHSW forms in the northern Arabian Sea during winter and spreads southward along a 24 sigma-t surface against the prevailing weak zonal currents. The eastern extent of the core is limited by the strong northward coastal current flowing along the west coast of India. During the southwest monsoon the northern part of the core shoals under the influence of the Findlater Jet, while the southern part deepens. Throughout the year the southward extent of the ASHSW is inhibited by the equatorial currents. The atmospheric forcing that leads to the formation of ASHSW was delineated using the monthly mean climatology of heat and freshwater fluxes. Monsoon winds dominate all the flux fields during summer (June-September), while latent heat release during the relative calm of the winter (November-February) monsoon, driven by cool, dry continental air from the north, results in an increased density of the surface layer. Thus excess evaporation over precipitation and turbulent heat loss exceeding the radiative heat gain cool the surface waters of the northern Arabian Sea during winter and drive convective formation of ASHSW.

Seasonal spreading of the Persian Gulf water mass in the Arabian Sea

The characteristics of the subsurface salinity maximum associated with the Persian Gulf Water mass (PGW) are used to quantify the spreading and mixing of PGW in the thermocline of the Arabian Sea based on a bimonthly climatology of temperature and salinity. Examination of the seasonal cycles of heat and freshwater fluxes in the Persian Gulf region indicates that PGW forms as a result of elevated evaporative cooling in conjunction with reduced insolation during winter. Maps are presented of the distributions of depth, salinity, and geostrophic flow on σθ = 26.5, which nearly coincides with the core of the PGW. After intense mixing in the Strait of Hormuz, the property fields suggest that warm (>17°C) and high-salinity (>36.2 psu) PGW enters the Arabian Sea to form a subsurface salinity extremum between 200 and 300 m. We have found variability in the distribution of PGW in the Arabian Sea associated with monsoonal changes in the Arabian Sea circulation. During the winter monsoon, there is southward spreading of PGW along the western boundary; during summer it is not present. Lateral mixing with low-salinity water from the Bay of Bengal in the region south of 10°N and along the west coast of India during winter accounts for changes in the characteristics of PGW along these paths. Associated with the Findlater Jet during summer, the entire thermohaline structure is vertically displaced along the coasts of Somalia and Arabia. Ekman convergence in the central Arabian Sea accounts for deepening of the PGW. Either lateral or vertical mixing would cause changes in PGW properties in these regions. During this time, PGW spreads predominantly southward along the central Arabian Sea, as indicated by a tongue of high salinity.

Spring evolution of Arabian Sea High in the Indian Ocean

The seasonal formation of a large anticyclonic circulation pattern, Southern Arabian Sea High (SAH), appears in the southern Arabian Sea during the northeast monsoon. SAH is studied on the basis of the recent observations that include the World Ocean Circulation Experiment (WOCE)/Tropical Ocean-Global Atmosphere (TOGA) experiment drifting buoys along with TOPEX/ERS-2 satellite altimeter data in conjunction with the climatological hydrography observations. The SAH forms west of the Laccadive High (LH), first appears in January, and grows rapidly in situ to form a well-developed anticyclonic eddy, extending across the southern Arabian Sea by March. The center of the eddy is ∼65°E, 5°N. The SAH is bounded by a strong eastward current to the north and a weak southward flow between 65° and 70°E, which separates SAH from the LH. The westward flowing North Equatorial Current (NEC) is on the southern flank. A strong northward flow along 55°E during January and February marks the western boundary. SAH propagates westward as a Rossby wave between March and April. The arrival of SAH in the western boundary in April is accompanied by intensification of current along the coast of Somalia. In May, part of the SAH has subsequently moved northward to form an anticyclonic eddy with an apparent center 13°N, 53°E in the vicinity of the Gulf of Aden (Gulf of Aden Eddy (GAE)). The GAE extends horizontally nearly 600 km (along 13°) and is vertically extended down through the upper main thermocline to ∼250 m. Comparisons of hydrography, buoy, and altimetry reveal a good agreement in eddy size, location, and time of appearance of the GAE.

Granuloma with langhans giant cells: An overview

Granuloma formation with multinucleated giant cells is seen in numerous diseases. A granuloma is a focus of chronic inflammation consisting of a microscopic aggregation of macrophages surrounded by a collar of lymphocytes and plasma cells. In this article, we present a case of granuloma formation with multiple Langhans giant cells along with an overview of the differential diagnoses, which include mycobacterium diseases, other bacterial infections, fungal infections, protozoal infections, and other granulomatous diseases.

Idiopathic multiple impacted unerupted teeth: Case report and discussion

Multiple impacted permanent teeth are usually related to syndromes, metabolic and hormonal disorders. However, in some cases, impaction of multiple teeth is not associated with any syndrome. In this report, we present a case of 17-year-old male patient with missing teeth. Radiographs revealed multiple impacted permanent teeth, though medical and family history along with physical examination was not suggestive of any syndromes. If other investigations are negative, an idiopathic case of multiple impacted teeth is suggested to be the possible diagnosis. The objective of this report is to increase awareness of such cases especially in the absence of hereditary/genetic/metabolic factors usually inherent in such scenarios. The patient management in such cases needs to be planned specifically from a multidisciplinary standpoint.

Determination of carbonic anhydrase activity using infra-red gas analysis

Abstract A technique for the estimation of carbonic anhydrase (CA) using the infra-red-gas analyser (IRGA) has been developed. Instead of determining pressure changes in the dehydration reaction catalysed by the enzyme, the IRGA was used to determine the increase in carbon dioxide content in the enzymatic and non-enzymatically catalysed dehydration reaction. The reliability of this method was assessed using pure carbonic anhydrase. Although the method has not been compared with other methods, the known sensitivity of the IRGA (resolution of 0.1–1.0 μmol/mol) was exploited. The differences in CA activity of two finger millet (Eleusine coracana) genotypes differing markedly in photosynthetic rate but showing similar leaf conductances was assessed.