Spatial variations of rainwash and runoff within apparently homogeneous areas

The magnitude and causes of rainwash and runoff variability within small and supposedly “homogeneous” areas were investigated. Artificial rainfall (at 50 mm hr⁻¹ for 30 minutes) was applied to twenty identical 0.0929 m² (1 ft²) mini-plots arranged within a wetted annular 16.5 m² in area. Despite the uniformity of techniques used for data collection, there was considerable variability in the rainwash and runoff data (coefficient of variation= 21 to 35% and 20 to 75% respectively) at the three locations in southern Ontario. In comparison with laboratory data, field rainwash variability was similar but field runoff variability was substantially higher. Soil strength parameters, surface roughness and microtopography, as well as aggregation indices, are considered to be the potential causes of the observed variabilities. Operator variance was found to be extremely significant in our study. It is suggested, therefore, that comparison of erosion data collected by different researchers must be conducted with great caution.     

Enzyme-linked immunosorbent assay of ochratoxin A in barley

A noncompetitive, double antibody enzyme-linked immunosorbent assay for ochratoxin A using microtitration plates has been developed and applied to samples of barley. The anti-ochratoxin A antiserum, which is used at high dilution, does not cross-react significantly with ochratoxin B or ochratoxin a. Assay sensitivity for determination of the toxin in barley samples is 60 ng/kg. Minimal sample preparation is required before assay.     

A new mechanism for the formation of meteoritic kerogen-like material

The carbon in ancient carbonaceous chondritic meteorites is mainly in a hydrocarbon composite similar to terrestrial kerogen, a cross-linked structure of aliphatic and aromatic hydrocarbons. Until recently, the composite has been commonly thought to have been produced in the early solar nebula by a Fischer-Tropsch-type process, involving the catalytic synthesis of hydrocarbons from carbon monoxide and hydrogen on grain surfaces. Instead, the aromatic hydrocarbons may form in gas-phase pyrolysis of simple aliphatics like acetylene and methane by a mechanism developed recently to explain formation of soot in combustion and of aromatic molecules in circumstellar envelopes. Nonequilibrium chemical kinetic calculations indicate that this mechanism can produce meteoritic aromatics if the initial concentration of simple hydrocarbons in the solar nebula was sufficiently but not unreasonably high.     

Diagnostic ultrasound and sister chromatid exchanges: failure to reproduce positive findings

Human lymphocytes were exposed in vitro to ultrasound from two clinical devices, one of which was previously reported to have increased the frequency of sister chromatid exchanges. The ultrasonic exposures had no significant effect on the frequency of sister chromatid exchanges from three blood donors. Exposure to ultrasound also had no effect on cell cycle progression. A concomitant positive control (mitomycin C) resulted in a significant increase in sister chromatid exchanges.     

Human muscle phosphoglycerate mutase deficiency: newly discovered metabolic myopathy

Muscle phosphoglycerate mutase activity was decreased (5.7 percent of the lowest control value) in a 52-year-old man with intolerance for strenuous exercise and recurrent pigmenturia since adolescence. All of the other enzymes of glycolysis had normal activities, and glycogen concentration was normal. Electrophoretic, heat lability, and mercury inhibition studies showed that the small residual activity in the patient's muscle was represented by the brain (BB) isoenzyme of phosphoglycerate mutase, suggesting a genetic defect of the M subunit which predominates in normal muscle. The prevalence of the BB isoenzyme in other tissues, including muscle culture, may explain why symptoms were confined to muscle.