No abstract

During a two year period analyses were made every other week on seston collected at three depths in a small hard-water lake in southwestern Michigan. The seston was analyzed for total dry weight, organic material, calcium carbonate, and ash content. During the second year seasonal changes in sestonic particulate organic carbon, Kjeldahl nitrogen, and total phosphorus were assayed.Organic material and ash content of the seston was similar both years, but the calcium carbonate content was five times greater in the second year than in the first. The dissimilarity in calcium carbonate precipitation between the two years was related to degree of vernal circulation and calcium ion concentration in the water column when the ice broke up. During the study an improved sediment trap was designed and constructed. The trap had replicated, discrete upper and lower sections, which permitted correction for attached and non-sedimenting matter.Investigation of calcium ion concentration by flame atomic absorption and a calcium ion electrode revealed an average of 36.7 mg l" 1 of colloidal calcium was suspended in the lake during 1973.Immumz a. w: VMS DOCUMENT !S OPOraiTEB Dr. Ellis willingly gave constructive advice and help in the x-ray diffraction analyses, thermal analysis, surface area determinations, and calcium electrode determinations.

The proper combination of sequential ion implantation and thermal annealing can successfully fabricate binary semiconductor quantum dots (QDs), such as InP, GaP and GaAs QDs. Far-infrared reflectance techniques can be effectively employed to identify the species formed before and after various thermal treatments via probing molecular vibrations and surface phonons of the QDs. This technique is very useful for the characterization of an ultra-thin layer of foreign species on or in the near surface of the bulk substrate materials. In addition, this technique is non-destructive, simple and versatile. The examples given in the present report are InP and GaP QDs formed in fused silica and GaAs QDs formed in fused silica and in [0001] substrates.

A sedimentation trap with replicated, discrete upper and lower sections, which permit correction for nonsedimenting and attached organisms among sedimented matter, is described. A simple arrangement of the collecting framework on the supporting line allows one person to retrieve the collected material.

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