Ultrasound and endocrine evaluation of the ovarian cycle and early pregnancy in the Sumatran rhinoceros, Dicerorhinus sumatrensis

Longitudinal ultrasound and endocrine evaluations were conducted in two adult female Sumatran rhinoceroses (Dicerorhinus sumatrensis) over a period of 12-22 months to learn more about their reproductive physiology. Rectal ultrasonography was conducted to monitor ovarian activity. Blood samples were collected and analysed for progesterone and LH, and faecal samples were analysed for progestin metabolites. One female showed cyclic ovarian activity during the study period, whereas the other female showed no evidence of ovarian activity. The cyclic Sumatran rhinoceros appeared to be an induced ovulator, the first of its kind reported within the Perrisodactyla. Ultrasound examinations of the ovaries revealed the formation of anovulatory haemorrhagic follicles when the animal was not mated. These follicles appeared to undergo varied degrees of luteinization that resulted in irregular faecal progestin profiles. When allowed to mate, the female showed a 21 day reproductive cycle that was reflected in both faecal progestin and serum progesterone profiles. The concentration of serum LH was baseline before mating, increased approximately 30-fold within 1-2 h of intromission and returned to baseline within 22 h. Ovulation occurred within 46 h of copulation. The female conceived three times during the study. Pregnancy was detected using ultrasonography 14-16 days after mating, and the concentration of both serum progesterone and faecal progestins remained high. Early embryogenesis appeared to be similar to that in horses. However, each pregnancy terminated unexpectedly within the first 3 months of gestation. This study demonstrates the important role that basic research and reproductive technology can play in developing a natural breeding programme for an endangered animal in captivity.     

Radiation Effects on GaAs Charge Coupled Devices with High Resistivity Gate Structures

The results of a study on the effects of 1 MeV electrons and 1 MeV neutrons on the operation of high speed GaAs Charge Coupled Devices (CCDs) are presented. Radiation-induced trapping levels are characterized using a linear array CCD structure and the periodic pulse technique. 1 MeV electron irradiation introduced traps at 0.1 eV and 0.39 eV with bulk trap introduction rates of 1 cm-1 and 0.33 cm-1, respectively. The devices were irradiated to a maximum fluence of 9×1014 electrons/cm2. 1 MeV neutron irradiation introduced an electron trap level at 0.64 eV with a bulk trap introduction rate of 0.5 cm-1. Catastrophic device failure occurred at neutron fluences of 6×1013 neutrons/cm2. Device charge transfer efficiency was characterized pre- and post-irradiation over the temperature range of 80°K to 300°K.