LD2668 .T4 1966 C434 / Master of Science

No description available.

Dajun DaiRadon is a colorless, odorless, naturally occurring gas. It is currently the second leading cause of lung cancer and the number one cause of lung cancer to non-smokers in the United States. DeKalb County offers free screening for radon for residents. However, screening rates vary across the county. This pilot study focused on 14 selected tracts within DeKalb County with relatively low levels of radon screening. Over 200 households were recruited and homes were tested for indoor radon concentrations on the lowest livable floor over an 8-week period from March – May 2016. Tract-level characteristics were examined to understand the varitations of race, income, education, and poverty status between the 14 selected tracts and all of DeKalb County. The 14 selected tracts were comparable to all of DeKalb County in most factors besides race. Radon was detected in 73% of the homes sample and 4% had levels above the EPA guideline of 4 pCi/L. Multi-variate linear regression was used to compare all housing construction characteristics with radon concentrations and suggested that having a basement was the strongest predictive factor for detectable and/or hazardous levels of radon. Radon screening can identify problems and spur home owners to remediate but low screening rates may impact the potential health impact of free screening programs. More research should be done to identify why screening rates vary in order to identify ways to enhance screening and reduce radon exposure in DeKalb County.

The migration of contaminants from the subsurface into the indoor air environment, in a process described as soil vapor intrusion, is gaining attention as a potential pathway for exposure to contaminated soil and water. Indoor, outdoor and soil air samples were collected from forty homes in North Texas to investigate the attenuation of trichloroethylene (TCE) from contaminated groundwater into residential buildings. The mean and standard deviation of the soil and indoor air attenuation factors (ratio of indoor air concentration to soil vapor concentration) were 0.14 and 0.17, respectively. Five of the 40 values were greater than 0.1 which is the suggested upper-bound by the U.S. EPA (2002). Statistical tools were used to draw correlative relationships between contaminant groundwater, soil air and indoor air concentrations. The VolaSoil model described by Waitz et al. (1996), was modified for use as a screening tool for future investigations of indoor TCE concentration. Using measured soil vapor data, the model under predicted indoor air TCE concentrations likely due to heterogeneities in the unsaturated subsurface. Inputting groundwater TCE concentrations, the model was able to capture the contaminant migration processes and produce results consistent with measured indoor TCE concentrations. Therefore, the model described in this paper maybe appropriate to be use as a screening tool in future investigations in the contamination area. / text

This study addressed the problem of water vapor production and distribution in comet P/Halley, based upon interpretation of observational data obtained during the recent 1985-86 apparition. The data was acquired using the Lunar and Planetary Laboratory charge-coupled device (CCD) on the 154-cm Catalina telescope of the University of Arizona Observatories. Our data acquisition system was employed in two modes. The long-slit (∼200") spectroscopy mode covered the wavelength range 5200-10400 Å at a spectral resolution ∼14 Å. The narrow band filter imaging mode allowed two-dimensional mapping of selected cometary emission features, as well as the continuum, with a field of view of roughly 10 arc-min. Both neutral and ionized (H₂O⁺) water species were studied, with emphasis on the ion distribution. This involved comparing long-slit spatial profiles obtained ∼UT 1986 March 05.5, as well as cuts across filter images (∼ March 06.5) centered on the H₂O⁺ 0,8,0-band emission, with the Vega-1 spacecraft in situ ion density measurements (∼ March 06.3). Our March 05 spectroscopic data revealed a central dip, of order 30% relative to the profile peak, in H₂O⁺ column density in the inner coma (inside ∼ 2 x 10⁴ km from the nucleus), which filled in farther tailward. Similarly the BD - 3 plasma detector aboard Vega-1 measured a decrease in local ion density, of roughly 60% at the closest approach distance (∼ 9000 km sunward of the nucleus), relative to the inbound maximum density at R ≃ 12000 km from the nucleus. These results suggest a bimodal flow of ions out of the coma and/or an extended region over which the H₂0 molecules were being ionized. Our imaging data showed that, while the falloff in ion density was relatively rapid sunward of the nucleus, it was much more gradual in the anti-solar direction. This is due to the solar wind sweeping ions from the head of the comet into the plasma tail, whose width was of order 10⁵ km in the inner coma, diverging slowly and breaking up into a ray pattern farther tailward. The distribution of neutral water was mapped out using the [O I] λ6300 emission as diagnostic probe. In contrast to the ions, the H₂0 molecules were mainly confined to the inner few x 10⁴ km of the coma, and exhibited a much more symmetrical distribution. Integration of the [O I] slit profiles, assuming azimuthal symmetry, allowed calculation of the H₂0 production rate, which ranged from ∼ 10²⁸ molecules s⁻¹, when Halley was at a distance r≳ 2 AU from the sun, to a value of ∼ 1.5 x 10³⁰ molecules s⁻¹ for 1986 March 05 (r ≃ 0.78 AU). Using the latter production rate, and assuming a 100/1 production ratio of H₂0/ H₂O⁺, a spatially-averaged, tailward flow speed of ions out of the inner coma, < v⁺ > ≃ 16 km s⁻¹, was derived by integrating our March 05 H₂O⁺ profile, for which the slit was oriented across the coma, just tailward of the nucleus.

The performance of multilayer thin film optical filters depends largely on the microstructure of the component layers. This microstructure varies with the deposition parameters inside the coating chamber. By controlling these parameters, optical filters can be produced to exacting specifications. In 1947, R. M. Rice established the technique of bombarding the substrate with electrons of several kilovolts as the fils were being deposited. This process improved the durability of zinc sulfide films dramatically. This study was performed to quantitatively analyze the effects of bombardment on film microstructure and subsequent effects on optical and mechanical properties. I installed an electron source filament inside the coating chamber and electrically isolated the substrate holder, which was connected to a positive high voltage supply. An accelerating loop placed just above the filament enhanced its efficiency. The source was calibrated by measuring the current through the substrate holder. Single layer films of five different materials were deposited, each at its own set of electron bombardment parameters. The microstructure was analyzed with an X-ray diffractometer and a transmission electron microscope. Optical properties were measured with guided waves, induced absorption, and spectrophotometric analysis. Film durability was analyzed with scotch tape, eraser, and controlled humidity tests. Antimony trioxide films showed a shift in lattice orientation, but this did not affect columnar structure or macroscopic quantities. Potassium hexafluorozirconate films showed elimination of both crystal structure and columnar growth, resulting in slightly reduced durability and some absorption. Silicon monoxide films suffered no change in structure or properties. Zinc sulfide films demonstrated the change in crystal structure, which was quantified and shown to improve moisture resistance. Optical properties were unaffected. Magnesium fluoride films showed a slight increase in crystallinity with only subtle changes in durability and optical properties. Generally, electron bombardment reduced or rearranged crystal structure. The effects on macroscopic properties varied with each material, with no clear trend evident.

A computationally efficient and accurate model is derived for the calculation of the atmospheric transmittance along inhomogeneous paths and within spectral bands dominated by molecular line absorption. It is a Stieltjes integration of transmission weighted by the frequency of occurrence of absorption coefficient within the band. Path inhomogeneitites are accounted for by assuming that the rank of absorption coefficient at any wavenumber is independent of temperature and pressure. The technique is then applied to the ground based radiometric determination of precipitable water. It is found that the technique predicts the behavior of the ρστ water vapor absorption band very well. An RMS disagreement of 11% is found when the model predictions are compared to radiosonde determinations of precipitable water. The model is also applied to the determination of vertical water vapor distributions in the stratosphere given measured effective optical depths as a function of tangent height from a limb scanning satellite. A new iterative reduction technique is introduced which incorporates the transmission model and it is shown to be both numerically stable and rapidly convergent. A comparison of the results with an independent reduction technique shows good overall agreement with a small systematic difference above 20 km. The uncertainty in the measurements, which yields solution uncertainties on the order of 30%, renders this systematic difference unimportant.

No description available.

Diseñador Industrial / Este proyecto busca generar un set de utensilios de uso doméstico para cocinar al vapor, integrándolo a la forma de vida occidental de nuestro país al simplificar el proceso de cocción de los alimentos, el lavado, servido y guardado del utensilio, incentivando la cocción al vapor a través de una nueva experiencia de cocina que no requiere tener un entrenamiento profesional previo. El set consiste en un conjunto de artefactos de cerámica autocalzables que permite su conjugación de manera vertical por niveles en el proceso de la cocción, generando un sistema estable en el cocido debido a la forma de cada una de las piezas, las cuales a su vez funcionan a modo de vajilla en la mesa. Posibilitando además la mantención de la temperatura de los alimentos por un tiempo más prolongado, reduciendo la labor del traspaso de los alimentos a otros recipientes y posterior lavado de loza.

Call number: LD2668 .T4 1959 T34