ABSTRACT
Nanocrystalline Gd2O2S:Pr powders were successfully synthesized by the co-participation method. The changes of size, shape and luminescence properties of these nanocrystalline powders were studied under different gamma doses (0-50 kGy) during the synthesizing process. Also, the structural, morphology and luminescence properties of these nanocrystalline powders were characterized using the X-ray diffraction, field emission scanning electron microscopy, energy dispersion of X-ray spectroscopy, photoluminescence, and thermoluminescence. The XRD results confirmed that the nanocrystalline Gd2O2S:Pr powders have a pure hexagonal structure with the high crystallinity at a temperature of 900 °C, and the gamma radiation doses have no effect on the structure. The SEM images showed that the nanocrystalline Gd2O2S:Pr powders have a spherical shape and are agglomerated when the irradiation dose increases. These nanopowders, which were prepared at an irradiation dose of 40 kGy, show the lowest crystallite size and hence the highest intensity of emission peaks at the wavelengths of 506, 515 and 671 nm, which are corresponded to the transitions of the 3P1-3H4, 3P0-3H4 and 3P0-3F2 of Pr ions, respectively. The X-ray radiography image was obtained by the screen of Gd2O2S:Pr nanopowders (prepared at 40 kGy gamma dose), coupled with a radiographic film. The TL glow curves of the sample, prepared at 40 kGy gamma dose, were recorded under the X-ray irradiation in the times of 5 and 10 min. The heating rate and preheat temperature were obtained 2 and 50 °C, respectively. The obtained results were investigated in details.
ABSTRACT
The purpose of the present study was to hasten the resumption of ovarian activity early postpartum in lactating dairy cows, using equine chorionic gonadotropin (eCG), to enhance follicular growth, followed by hCG, to induce ovulation. Primiparous Holstein dairy cows (n=21) were assigned equally into eCG, eCG-hCG and Control groups. Cows in the eCG and eCG-hCG groups received an i.m. injection of eCG (500 IU Folligon®) on Day 6 postpartum. Cows in the eCG-hCG group were also given an i.m. injection of hCG (500 IU Chorulon®), once dominant follicle reached the diameter of 13-16 mm following eCG injection. Cows in Control group did not receive any treatment. Daily blood sampling and ultrasound examination were conducted, starting at Day 6 postpartum until confirming the third ovulation. Follicles ≥10 mm in diameter were detected on Day 11.5±1.48, 10.1±0.52 and 11.1±1.36 after calving in Control, eCG and eCG-hCG groups, respectively (P>0.05). The first wave dominant follicle ovulated in 71.4% of cows treated with eCG and eCG-hCG. In contrast, none of the first wave dominant follicles ovulated in Control cows. By Day 20 postpartum, all cows in eCG group, 6/7 cows in eCG-hCG group and none of the cows in Control group ovulated (P<0.05). Short estrous cycles (≤16 days) were detected in 2/7, 1/7 and 6/7 cows in eCG, eCG-hCG and control groups, respectively (P<0.05). In conclusion, injection of eCG on Day 6 postpartum could assist the early resumption of ovarian activity by enhancing ovarian follicle growth and early ovulation in postpartum cows. In this context, subsequent hCG injection may not provide any more beneficial effect.