Optical studies of individual InAs quantum dots in GaAs: few-particle effects

Optical emission from individual strained indium arsenide (InAs) islands buried in gallium arsenide (GaAs) was studied. At low excitation power density, the spectra from these quantum dots consist of a single line. At higher excitation power density, additional emission lines appeared at both higher and lower energies, separated from the main line by about 1 millielectron volt. At even higher excitation power density, this set of lines was replaced by a broad emission peaking below the original line. The splittings were an order of magnitude smaller than the lowest single-electron or single-hole excited state energies, indicating that the fine structure results from few-particle interactions in the dot. Calculations of few-particle effects give splittings of the observed magnitude.     

In Vitro Production of Equine Embryos

The development of methods to produce embryos in vitro in the horse has been delayed compared with other domestic species. Oocytes can be collected from excised ovaries or from the small or preovulatory follicles of live mares. Intracytoplasmic sperm injection is the only reliable method to fertilize equine oocytes in vitro. Intracytoplasmic sperm injection-produced embryos can be transferred into the oviducts of recipient mares or cultured to the morula or blastocyst stage of development for nonsurgical embryo transfers into recipients' uteri. Embryos cultured in vitro have some morphological differences compared with embryos collected from the mares' uteri. Most notably, the embryonic capsule does not form in culture, and the zona pellucida fails to expand completely. However, embryo produced in vitro can result in viable pregnancies and healthy offspring.     

Signs of Sympathetic Denervation Associated With a Thoracic Melanoma in a Horse

Sympathetic denervation in a 20-year-old, gray, Thorough-bred-Percheron gelding was manifested by cutaneous hyperthermia and sweating over the right side of the body, demarcated by a line from the withers to the elbow and extending cranially. There was cutaneous hyperthermia over the right side of the head, but other signs of Horner's syndrome (sweating, ptosis, miosis, enophthalmos) were not present. The pattern of cutaneous hyperthermia and sweating was consistent with sympathetic denervation localized to the cervicothoracic ganglion, and thoracic radiographs revealed increased density in the craniodorsal thorax. Cytologic evaluation of a sample of pleural effusion revealed mesothelial cells containing melanin and cells suggestive of melanocytes or melanoblasts. Treatment with oral cimetidine and intrapleural cisplatin was not successful. A necropsy was not performed, but the clinical findings supported a diagnosis of thoracic melanoma involving the cervicothoracic ganglion.