DEVELOPMENT AND CHARACTERIZATION OF POLYCAPROLACTONE (PCL)/POLY ((R)-3-HYDROXYBUTYRIC ACID) (PHB) BLEND MICROSPHERES FOR TAMOXIFEN DRUG RELESE STUDIES

Objective: The objective of this study was to formulate and evaluate the drug release studies using Poly (ε-caprolactone) (PCL)/and Poly (R)-3-hydroxy butyric acid (PHB) blend microspheres for controlled release of Tamoxifen, an anticancer drug.Methods: Poly (ε-caprolactone), Poly ((R)-3-Hydroxybutyric acid) blend microspheres were prepared through a modified Water/Oil/Water (W/O/W) double emulsion-solvent diffusion method using Dichloromethane as solvent. Tamoxifen (TAM), an anti Cancer drug, was used for encapsulation within PCL/PHB blend microspheres. Morphology, size, encapsulation efficiency and drug release from these microspheres were evaluated by different characterization techniques such as Fourier transform infrared spectroscopy (FT-IR), Differential scanning calorimetry(DSC), Scanning electron microscopy(SEM), X-ray diffraction studies(X-RD) and dissolution test studies respectively.Results: Drug loaded microspheres were analyzed by FT-IR, which indicates the interaction between drug and polymers. DSC thermograms on drug-loaded microspheres confirmed the polymorphism of Tamoxifen and indicated a molecular level dispersion of drug in the microspheres. SEM confirmed the spherical nature and smooth surface of the microspheres produced. X-RD study was performed to understand the crystalline nature of the drug after encapsulation into the microspheres and confirmed the complete dispersion of the drug in the polymer matrix. In-vitro release studies conducted in different pH which indicated a dependence of release rate on the amount of drug loading and the amount of PCL/PHB, but slow release rates were extended up to 12 h. Kinetic analysis of dissolution data showed a good fit in Peppas equation confirming diffusion controlled drug release.Conclusions: The research findings obtained from the studies were found to be satisfactory. It can be concluded that biodegradable polymer blend (PCL/PHB) microspheres can be effectively used for preparation of controlled release matrices. Â

Fronts, water masses and heat content variability in the Western Indian sector of the Southern Ocean during austral summer 2004

High density CTD and XBT sections were covered from 35° to 56°S along 45°E and 57°30'E to investigate the morphology of the main fronts in the southwest Indian Ocean, as a part of the Indian pilot expedition to the Southern Ocean on board ORV Sagar Kanya. Northern branch of the Subtropical Front (NSTF) was observed at ~35°30'S along 45°E. Along 57°30'E, the signature of the Agulhas Return Front (ARF) + Subtropical Front (STF) was identified with a rapid decrease in surface temperature between 43°30' and 45°S and it is located with a southward shift compared to that at 45°E. The Subantarctic Front (SAF) was distinguished as two fronts as northern SAF (SAF1) and southern SAF (SAF2) along both the meridional sections. Polar Front1 (PF1) was identified between 49° and 50°S whereas Polar Front2 (PF2) was identified between 52° and 54°S along 45°E. This study reveals a southward shift of the oceanic fronts (ARF + STF) from west to east, with a maximum southward displacement of > 2° latitude at 57°30'E. A novel finding of this study is that along 45°E, SAF1 merged with ARF and SSTF and SAF2 ~4° latitude southwards from the merged fronts whereas along 57°30'E, SAF1 was not identified as a merged front with ARF and STF as opposed to earlier studies [Belkin, I.M., Gordon, A.L., 1996. Southern Ocean fronts from the Greenwich Meridian to Tasmania. Journal of Geophysical Research 101, 3675-3696]. The thermocline region was absent south of PF. An enhancement in the mixed layer thickness from 42° to 52°S occurred in association with the strengthening of the wind forcing. Major water masses like Subtropical Surface Water, Subantarctic Surface Water, Mode Water, Antarctic Intermediate Water, Circumpolar Deep Water and Antarctic Bottom Water were identified along 45°E. Upper-ocean heat-content computation revealed a remarkable drop of 989×107 J m−2 at ~42°S and 1405×107 J m−2 at ~44°S along 45° and 57°30'E, respectively. We believe that this sudden drop in heat content affects the meridional heat transfer which is crucial to the regional climatic variability

Warm pool thermodynamics from the Arabian Sea Monsoon Experiment (ARMEX)

Before the onset of the south Asian summer monsoon, sea surface temperature (SST) of the north Indian Ocean warms to 30–32°C. Climatological mean mixed layer depth in spring (March–May) is 10–20 m, and net surface heat flux (Q net ) is 80–100 W m−2 into the ocean. Previous work suggests that observed spring SST warming is small mainly because of (1) penetrative flux of solar radiation through the base of the mixed layer (Q pen ) and (2) advective cooling by upper ocean currents. We estimate the role of these two processes in SST evolution from a two-week Arabian Sea Monsoon Experiment process experiment in April–May 2005 in the southeastern Arabian Sea. The upper ocean is stratified by salinity and temperature, and mixed layer depth is shallow (6 to 12 m). Current speed at 2 m depth is high even under light winds. Currents within the mixed layer are quite distinct from those at 25 m. On subseasonal scales, SST warming is followed by rapid cooling, although the ocean gains heat at the surface: Q net is about 105 W m−2 in the warming phase and 25 W m−2 in the cooling phase; penetrative loss Q pen is 80 W m−2 and 70 W m−2. In the warming phase, SST rises mainly because of heat absorbed within the mixed layer, i.e., Q net minus Q pen ; Q pen reduces the rate of SST warming by a factor of 3. In the second phase, SST cools rapidly because (1) Q pen is larger than Q net and (2) advective cooling is ∼85 W m−2. A calculation using time-averaged heat fluxes and mixed layer depth suggests that diurnal variability of fluxes and upper ocean stratification tends to warm SST on subseasonal timescale. Buoy and satellite data suggest that a typical premonsoon intraseasonal cooling event occurs under clear skies when the ocean is gaining heat through the surface. In this respect, premonsoon SST cooling in the north Indian Ocean is different from that due to the Madden-Julian oscillation or monsoon intraseasonal oscillation

Warm pool thermodynamics from the Arabian Sea Monsoon Experiment (ARMEX)

Before the onset of the south Asian summer monsoon, sea surface temperature (SST) of the north Indian Ocean warms to 30-32&#176; C. Climatological mean mixed layer depth in spring (March-May) is 10-20 m, and net surface heat flux (Q <SUB>net</SUB> ) is 80-100 W m<SUP>-2</SUP> into the ocean. Previous work suggests that observed spring SST warming is small mainly because of (1) penetrative flux of solar radiation through the base of the mixed layer (Q <SUB>pen</SUB> ) and (2) advective cooling by upper ocean currents. We estimate the role of these two processes in SST evolution from a two-week Arabian Sea Monsoon Experiment process experiment in April-May 2005 in the southeastern Arabian Sea. The upper ocean is stratified by salinity and temperature, and mixed layer depth is shallow (6 to 12 m). Current speed at 2 m depth is high even under light winds. Currents within the mixed layer are quite distinct from those at 25 m. On subseasonal scales, SST warming is followed by rapid cooling, although the ocean gains heat at the surface: Q<SUB> net</SUB> is about 105 W m<SUP>-2</SUP> in the warming phase and 25 W m<SUP>-2</SUP> in the cooling phase; penetrative loss Q <SUB>pen</SUB> is 80 W m<SUP>-2</SUP> and 70 W m<SUP>-2</SUP>. In the warming phase, SST rises mainly because of heat absorbed within the mixed layer, i.e., Q <SUB>net</SUB> minus Q <SUB>pen</SUB> ; Q<SUB> pen</SUB> reduces the rate of SST warming by a factor of 3. In the second phase, SST cools rapidly because (1) Q <SUB>pen</SUB> is larger than Q<SUB> net</SUB> and (2) advective cooling is ~85 W m<SUP>-2</SUP>. A calculation using time-averaged heat fluxes and mixed layer depth suggests that diurnal variability of fluxes and upper ocean stratification tends to warm SST on subseasonal timescale. Buoy and satellite data suggest that a typical premonsoon intraseasonal cooling event occurs under clear skies when the ocean is gaining heat through the surface. In this respect, premonsoon SST cooling in the north Indian Ocean is different from that due to the Madden-Julian oscillation or monsoon intraseasonal oscillation