ABSTRACT
A computational study is presented of a complex of thallium with a neutral ß-triketimine ligand which was found to form dimers with close Tl-Tl interactions. Single point energies, using the crystallographic structures, suggest that the system is bound only when BArF counter ions are included in the calculations. Energy decomposition analysis of the system was carried out in order to investigate the nature of the bonding. Across the methods, calculations show the electrostatic interaction to be repulsive for the dimer with no counter ions, but attractive when BArF counter ions are included. This suggests the metallophilic interaction is counter ion-mediated, requiring the anions to provide favourable electrostatics, even in the case of spatially diffuse and distant counter ions such as the 3,5-bistrifluoromethylphenyl borate ions used here.
ABSTRACT
A multidisciplinary approach has been applied to examine the population structure of sardine Sardinops sagax off South Africa, where this species supports significant fisheries and is also of ecological and eco-tourism importance. Observations of discontinuous sardine distribution patterns, discrete spawning grounds and significant spatial differences in a variety of phenotypic characteristics have suggested the existence of discrete western, southern and eastern sardine sub-populations or stocks. The use of parasites as biological tags to elucidate sardine population structure has recently been investigated, and strong spatial gradients around South Africa in the prevalence, mean infection intensity and mean abundance of a digenean 'tetracotyle' type metacercarial endoparasite considered to be of the genus Cardiocephaloides and found in the humours of fish eyes support and have proved particularly convincing evidence for the sardine multiple stock hypothesis. A discontinuous distribution in the occurrence of another parasite, the coccidean Eimeria sardinae found in fish testes, has provided additional but weaker evidence of discrete stocks. These results have contributed to a changed understanding of the population structure of South African sardine and have significant implications for management of the fisheries for this species.
Subject(s)
Fish Diseases/parasitology , Fishes/parasitology , Parasites/isolation & purification , Parasitic Diseases, Animal/parasitology , Animals , Ecology , Population Dynamics , South Africa , Trematoda/isolation & purificationABSTRACT
PURPOSE: To determine the feasibility of Ultra wide-field intravenous fundus fluorescein angiography (UWF-IV-FFA) in infants. METHODS: A retrospective review of infants who underwent UWF-IV-FFA with the Optos P200MA was performed. The ability to capture different phases of the angiogram, the total image acquisition time and the presence of image artefacts were analysed. RESULTS: Twelve infants with a variety of proliferative retinopathies underwent UWF-IV-FFA over a 7-month period. The mean age was 3.4 months (range 2-6 months) and the mean image acquisition time was 4 min (range 3-5). Pseudocolour fundus images and the venous, recirculation and late phases of UWF-IV-FFA were captured successfully in all infants (100%). Choroidal and arterial phases were captured in one (8.3%) and 10 (83.3%) infants, respectively. Image artefacts due to eyelashes and corneal desiccation occurred in nine (75%) and six (50%) infants, respectively. No adverse medical problems were noted. CONCLUSIONS: We have shown that UWF-IV-FFA can be successfully and safely performed in infants using the Optos P200MA system. It is a feasible new alternative to RetCam for obtaining an IV-FFA in the outpatients setting.
