Aeration as a tool to improve water quality and reduce the growth of hydrilla

Aeration of artificial, model lake systems was studied as a tool to improve water quality and to control the growth of a nuisance aquatic weed, Hydrilla verticillata (L.F.) Royle, which has been recognized as a plant pest since the mid-1960s. Aeration decreased the growth of Hydrilla by 20% fresh weight and 18% dry weight on average after 21 days. The effect was due to the oxygenation of the water and not the mechanical effect of the bubbles, as verified by studies using pure nitrogen. Aeration also affected water quality. Inorganic carbon decreased; nitrate-nitrite-nitrogen decreased, more slowly in test systems than in control systems; dissolved oxygen increased to saturation within 24 h and pH increased 0.5–1.5 unit over the period of study. Phosphate-phosphorus concentration was unaffected. The concentrations of zinc, calcium and iron decreased as well. The effect of aeration upon Hydrilla growth appears to be correlated with a decrease of iron. After 7 days, iron concentrations decreased to less than 20 ppb. Iron toxicity is proposed as the mechanism responsible for creating a limiting condition for Hydrilla growth.     

Immunologic and electrophoretic characteristics of two species of Crithidia

Crithidia harmosa and Crithidia fasciculata were compared immunologically by the indirect fluorescent antibody (FA) method and by agglutination. The FA technic yielded more specific results with cellular-debris than with whole-cell antigens. The immune sera collected from chickens 9 days after the last inoculations with whole-cell antigens had higher homologous titers than those collected after 4 days. Major antigenic differences between the 2 species were revealed by both methods. The electrophoretic patterns of C. harmosa and C. fasciculata obtained by polyacrylamide gel slab electrophoresis differed in the numbers and relative mobilities of their component bands.     

Effects of artificially introduced ground water on the chemical and biochemical characteristics of six Hillsborough County (Florida) lakes

Six lakes in Northwest Hillsborough County, Florida, were sampled synoptically and the water samples were analyzed for selected chemical and biochemical characteristics. The lakes are closely grouped geographically and had four different histories of being pumped. i.e., having water from a deep aquifer pumped into the lake to maintain levels. The histories included two lakes that had never been pumped, two that had been recently pumped, one that had been pumped sporadically and one that had been continuously pumped for several years. Chemical analyses of the water samples included: pH, dissolved oxygen, carbon (inorganic and organic), calcium, hardness, major macronutrients (orthophosphate, nitrate and nitrite nitrogen), tannic acid, color and total iron. Two of the lakes are infested with hydrilla (Hydrilla verticillata Royle), and a biochemical characteristic was measured: the rate of growth of hydrilla in the various water samples. The growth characteristic was defined as the per cent dissolved oxygen increase in the presence of hydrilla under defined conditions. Analysis of the data suggest that the lakes can be divided into two groups based upon the growth characteristic and water hardness: those that have never been pumped and those that have been pumped. The first had comparatively low values for hardness (30 ppm) and growth characteristic (19 ± 1% increase in dissolved oxygen); the second group had significantly higher values of 68 ± 5 ppm and 74 ± 6% for the hardness and growth characteristic, respectively, the significance and limitations of these observations are discussed, particularly in reference to the potential for hydrilla proliferation.     

High Damping Indium-Tin Alloys

This research is directed toward the development of materials of high stiffness and high mechanical damping for the purpose of damping vibrations in structures and machinery. To this end, indium-tin alloys are considered. Cast In-Sn exhibits substantial damping for a metal. Quenching substantially improved the damping of indium-tin alloy but the effect gradually disappeared due to aging. Cold work of 1.3% permanent shear strain had the effect of moderately increasing the damping of indium-tin, and 10–100% permanent strain substantially increased the damping of tin, with 30% giving the largest damping below 5 Hz. This revised version was published online in August 2006 with corrections to the Cover Date.