Crust formation and plate motion in the early archean

Mounting evidence for voluminous continental crust formation in the early Archean involving intracrustal melting and selective preservation of granitoid rocks suggests that initial crust formation crust formation and growth were predominantly by magmatic underplating in plumegenerated Iceland-type settings. Collision of these early islands to give rise to larger blocks is suggested by extensive horizontal shortening in both supracrustal and granitoid assemblages. Preservation of early Archean high-grade gneisses that were once at depths of 20 to 30 kilometers implies that these blocks developed thick, subcrustal roots despite high mantle heat flow. Rigid continental plates must have existed since at least 3.5 billion years ago, and greenstone belts (composed of mixed metavolcanic and metasedimentary sequences intruded by granitoid plutons) probably developed on or near these microcontinents. Paleomagnetic data with good age control from at least one ancient craton suggest that plate motion was at normal minimum average velocities of about 17 millimeters per year with respect to the poles during the period 3.5 billion to 2.4 billion years ago. If this is true on a global scale, Archean plate motion was not faster than in later geologic times.     

Radar detection of the nucleus and coma of comet hyakutake

Radar observations of comet Hyakutake (C/1996 B2) made at the Goldstone Deep Space Communications Complex in California have detected echoes from the nucleus and from large grains in the inner coma. The nucleus of this bright comet was estimated to be only 2 to 3 kilometers in diameter. Models of the coma echo indicate backscatter from porous, centimeter-size grains ejected anisotropically at velocities of tens of meters per second. The radar observations suggest that a comet's activity may be a poor indicator of its size and provide evidence that large grains constitute an important component of the mass loss from a typical active comet.     

Pharmacokinetics of carprofen and firocoxib for medication control in racing greyhounds

Animals used in sport should be treated as required to ensure animal welfare but any such use of medication should also be controlled to ensure integrity. Pharmacokinetic studies on groups of six greyhounds were performed to measure plasma and urine levels of carprofen and firocoxib to inform medication control advice. Using the standard methodology for medication control the Irrelevant Plasma Concentration was determined as 20 and 2 ng/mL for carprofen and firocoxib, respectively. The Irrelevant Urine Concentration was also determined as 0.3 and 2 ng/mL for carprofen and firocoxib, respectively. These Irrelevant Plasma and Urine Concentrations will allow laboratory Screening Limits, Detection Times and Withdrawal Time advice to be determined and publicised by regulators of greyhound racing. The Screening Limits will also inform Recommended Limits of Detection if meat-containing residues of these medications are fed to greyhounds.     

Residues of endosulfan in the tissues of lactating goats

SUMMARY: The sites of tissue accumulation in lactating goats of the organochlorine insecticide endosulfan were studied. Twelve lactating goats were dosed orally with endosulfan (1 mg/kg body weight per day) for 28 days. Groups of 3 animals were killed on days 1, 8, 15, and 21 after endosulfan treatment ended and their tissues examined for the presence of endosulfan. Total residues of α and β endosulfan and endosulfan sulphate (mg/kg) were detected in kidney (0.29), gastro-intestinal tract (0.20), liver (0.12), brain (0.06), muscle and spleen (0.04), lung and heart (0.01) and milk (0.02) on the flrst sampllng day but within 15 days, concentrations had fallen to < 0.01 mg/kg in all tissues except kidney (0.20). Endosulfan could not be detected in animals 21 days after dosing had ceased. The residue in milk could only be detected on day 1 of sampling. This study indicates that kidney rather than fatty tissue should be used to monitor the presence of endosulfan in animals intended for human consumption.     

Disease-husbandry associations in farmed crocodiles in Queensland and the Northern Territory

SUMMARY To investigate husbandry-disease associations in farmed crocodiles 7 farms in Queensland and the Northern Territory were visited and details of past and present farm design and husbandry practices were recorded. In addition pathological examination of 300 (mostly young) crocodiles was carried out (85 necropsied, one biopsied and 214 examined retrospectively). Mortality rate and occurrence of disease, especially opportunistic infections with bacteria and fungi, were highest during winter months and in farms located at greater latitudes. A difference in the presence and prevalence of disease between the initial establishment phase of Northern Territory crocodile farms (1984–87) and currently (1988–91) was apparent; parasitic infections are now relatively infrequent and bacterial septicaemias and mycoses less common as a result of some provision of artificial heating for juveniles. Gross and microscopic changes observed in visceral and periarticular gout, bacterial hepatitis/septicaemia, deep and superficial mycosis, pentastomiasis and other parasitic infections are described.     

Efficacy of praziquantel in the treatment of green sea turtles with spontaneous infection of cardiovascular flukes

Objective To assess the efficacy of praziquantel as a treatment for cardiovascular flukes in turtles.
Procedure Six green sea turtles ( Chelonia mydas ) spontaneously infected with cardiovascular flukes (Digenea: Spirorchiidae) were treated orally with praziquantel, and necropsied 3 or 7 days later to look for flukes in the heart and major blood vessels. Six similar animals were maintained as untreated controls.
Results Absence of flukes in treated, but not control turtles, indicated that a one day course of treatment at a dose rate of 3 times 50 mg/kg body weight is effective.
Conclusion This result should be of value for preventing disease in wild caught green turtles introduced into farms or aquaria.