Search

Gold, scheelite, and cinnabar in amounts that might be profitably extracted are found in a placer deposit in the Dutch Flat mining district in north-central Nevada. These materials are the products of at least two and possibly three stages of metallogenic activity recorded in the district. The gold and perhaps most of the scheelite were derived from quartz veins that cut a small granodiorite stock and lower Paleozoic sedimentary rocks. Part of the scheelite may have been derived from contact-metamorphic deposits associated with the granodiorite stock. The cinnabar came from a shear zone that is later than the quartz veins. The proximity of the placer to the source of the minerals is the factor that made a significant concentration of these minerals possible. Incomplete sampling of the placer indicates an average value of $1.50 per cubic yard in combined gold, tungsten, and mercury based on the price of these metals in August 1954.

A method of bioassay distinguishing residual contact from fumigant toxicity is described. Basically the apparatus consists of a series of Buchner funnels set up in series. Woven fiberglass cloth was selected as the substratum. By substitution of a dye in place of Insecticide, it was possible, using colorlmetric analysis, to calculate the total milligrams of dye adhering to the cloth. It was assumed that proportionate amounts of dye and insecticide would be picked up. Musea domestica L.was used as the test insect. Two strains of flies, designated as the SES and Ottawa cultures, were used. Fumigant effect was eliminated by application of negative pressure. Since fumigant effect is proportionate to vapour pressure, the rate of evacuation varied for each insecticide. Elimination of fumigant effect brought about a corresponding decrease in mortality. Dosage-mortality data are given for six insecticides in comparison to a "standard" insecticide (dieldrin) utilizing the concept of toxicity index ( Sun, 1950). Statistical analysis of the data indicate significant heterogeneity in eleven out of twenty-four experiments. An analysis of the Chi-square function is presented. Dosage-mortality data for DDT are given. The SES culture was determined to be 141x as resistant for females and 67x as resistant for males as the Ottawa culture, by topical application. Residual contact application indicated that females of the SES culture were 252x as resistant compared to the Ottawa culture. Variation within the SES culture is discussed as a factor in demonstrating the sensitivity of the technique.

Not available

A study of changes in bananas during ripening at 16 ± 1°C and 25 ± 1°C is described. Peel color was evaluated subjectively and by reflectance spectrophotometry; rheological properties by parallel plate compression and viscometry; selected chemical properties by appropriate tests and histochemical and histological properties by light microscopy. The rate of peel color change at the higher temperature was roughly twice that at the lower. Higher temperature-ripened fruits did not develop a full yellow color due to chlorophyll retention in the peel. Also pulp-to-peel ratio for such fruits tended to be lower than that of fruits ripened at the lower temperature. The pulp of high temperature-ripened fruits became progressively softer and was reflected by a linear increase of deformation under 1 kg force. For a given peel color index, maximum force and linear limit of the tissue as well as a power-law consistency coefficient of the puree were generally lower during ripening at the higher temperature. Reducing sugars increased linearly throughout ripening at the higher temperature while at the lower temperature the reducing sugar content was essentially constant beyond color index 6. On the basis of peel color index, total sugar and moisture content were higher while starch and AIS levels were lower in fruits ripened at the higher temperature. Ripening temperature therefore influences the relations of color index to mechanical and chemical properties. Ripening was characterized by a gradual loss of rigidity as well as an apparent thickening of the cell wall in over-ripe pulp tissue. Tannins decreased during ripening but did not disappear completely. Esterified pectins were not detected in hard green fruit; however, substantial amounts appeared at peel color index 3, then decreased steadily during ripening. Peel color was the best overall index of stage of ripeness for both ripening temperatures. Although rheological and chemical properties at a given color index differed for the two ripening temperatures, these intercorrelations remained higher (P ≤ 0.01). It is recommended, that ripening temperatures be taken into account when the color index chart is used to estimate the stage of ripeness of bananas.