Folic acid and D-gluconic acid-capped gadolinium oxide nanorods and nanocuboids were synthesized via co-precipitation method.Comparative study of relaxivity factor on the role of capping and morphology for enhancing c...Folic acid and D-gluconic acid-capped gadolinium oxide nanorods and nanocuboids were synthesized via co-precipitation method.Comparative study of relaxivity factor on the role of capping and morphology for enhancing contrast ability for T_(1) and T_(2) magnetic resonance imaging(MRI) was investigated.The obtained r_(2)/r_(1) ratio for folic acid and D-gluconic acid-capped gadolinium oxide nanorods and nanocuboids was 1.5 and 1.3,respectively.The nanocrystals were characterized and presented with properties such as good dispersity and stability required for standard contrast agent used in MRI.The characterization and the analysis of capping agent for nanocrystals suggest the preferable use of carbohydrate moieties with higher number of hydroxyl functional group reacted with urea and hydrogen peroxide for desired morphology and anisotropic growth.Thermogravimetric-differential thermal analysis(TG-DTA) illustrated the amount of capping,transition temperature from Gd(OH)3 to GdOOH and crystallization temperature from GdOOH to Gd2O3.These nanocrystals would be significant for other biomedical applications such as drug delivery when equipped with well-functionalized drug molecules.展开更多
We investigate nucleosynthesis inside the gamma-ray burst （GRB） accre- tion disks formed by the Type II collapsars. In these collapsars, the core collapse of massive stars first leads to the formation of a proto-neu...We investigate nucleosynthesis inside the gamma-ray burst （GRB） accre- tion disks formed by the Type II collapsars. In these collapsars, the core collapse of massive stars first leads to the formation of a proto-neutron star. After that, an out- ward moving shock triggers a successful supernova. However, the supernova ejecta lacks momentum and within a few seconds the newly formed neutron star gets trans- formed to a stellar mass black hole via massive fallback. The hydrodynamics of such an accretion disk formed from the fallback material of the supernova ejecta has been studied extensively in the past. We use these well-established hydrodynamic models for our accretion disk in order to understand nucleosynthesis, which is mainly ad- vection dominated in the outer regions. Neutrino cooling becomes important in the inner disk where the temperature and density are higher. The higher the accretion rate （M） is, the higher the density and temperature are in the disks. We deal with accre- tion disks with relatively low accretion rates： 0.001 Mo s-1 ~ 3）/~ 0.01 Mo S--1 and hence these disks are predominantly advection dominated. We use He-rich and Si- rich abundances as the initial condition of nucleosynthesis at the outer disk, and being equipped with the disk hydrodynamics and the nuclear network code, we study the abundance evolution as matter inflows and falls into the central object. We investigate the variation in the nucleosynthesis products in the disk with the change in the initial abundance at the outer disk and also with the change in the mass accretion rate. We report the synthesis of several unusual nuclei like 31p, 39K, 43Sc＇ 35C1 and various isotopes of titanium, vanadium, chromium, manganese and copper. We also confirm that isotopes of iron, cobalt, nickel, argon, calcium, sulphur and silicon get synthe- sized in the disk, as shown by previous authors. Much of these heavy elements thus synthesized are ejected from the disk via outflows and hence they should leave their signature in observed data.展开更多
文摘Folic acid and D-gluconic acid-capped gadolinium oxide nanorods and nanocuboids were synthesized via co-precipitation method.Comparative study of relaxivity factor on the role of capping and morphology for enhancing contrast ability for T_(1) and T_(2) magnetic resonance imaging(MRI) was investigated.The obtained r_(2)/r_(1) ratio for folic acid and D-gluconic acid-capped gadolinium oxide nanorods and nanocuboids was 1.5 and 1.3,respectively.The nanocrystals were characterized and presented with properties such as good dispersity and stability required for standard contrast agent used in MRI.The characterization and the analysis of capping agent for nanocrystals suggest the preferable use of carbohydrate moieties with higher number of hydroxyl functional group reacted with urea and hydrogen peroxide for desired morphology and anisotropic growth.Thermogravimetric-differential thermal analysis(TG-DTA) illustrated the amount of capping,transition temperature from Gd(OH)3 to GdOOH and crystallization temperature from GdOOH to Gd2O3.These nanocrystals would be significant for other biomedical applications such as drug delivery when equipped with well-functionalized drug molecules.
基金partly supported by the ISRO grant ISRO/RES/2/367/10-11
文摘We investigate nucleosynthesis inside the gamma-ray burst （GRB） accre- tion disks formed by the Type II collapsars. In these collapsars, the core collapse of massive stars first leads to the formation of a proto-neutron star. After that, an out- ward moving shock triggers a successful supernova. However, the supernova ejecta lacks momentum and within a few seconds the newly formed neutron star gets trans- formed to a stellar mass black hole via massive fallback. The hydrodynamics of such an accretion disk formed from the fallback material of the supernova ejecta has been studied extensively in the past. We use these well-established hydrodynamic models for our accretion disk in order to understand nucleosynthesis, which is mainly ad- vection dominated in the outer regions. Neutrino cooling becomes important in the inner disk where the temperature and density are higher. The higher the accretion rate （M） is, the higher the density and temperature are in the disks. We deal with accre- tion disks with relatively low accretion rates： 0.001 Mo s-1 ~ 3）/~ 0.01 Mo S--1 and hence these disks are predominantly advection dominated. We use He-rich and Si- rich abundances as the initial condition of nucleosynthesis at the outer disk, and being equipped with the disk hydrodynamics and the nuclear network code, we study the abundance evolution as matter inflows and falls into the central object. We investigate the variation in the nucleosynthesis products in the disk with the change in the initial abundance at the outer disk and also with the change in the mass accretion rate. We report the synthesis of several unusual nuclei like 31p, 39K, 43Sc＇ 35C1 and various isotopes of titanium, vanadium, chromium, manganese and copper. We also confirm that isotopes of iron, cobalt, nickel, argon, calcium, sulphur and silicon get synthe- sized in the disk, as shown by previous authors. Much of these heavy elements thus synthesized are ejected from the disk via outflows and hence they should leave their signature in observed data.
