ABSTRACT This study investigated the influence of temperature and humidity on the decomposition efficiency of benzene vapor in a packed-bed UV/TiO2 photocatalytical reactor. The packed-bed annular photocatalytical reactor illuminated by a 15-watt ultraviolet lamp was originally designed for this particular study. Pyrex glass beads coated with Degussa P-25 TiO2 (80 % anatase) were packed in the photocatalytical reactor. The operating parameters investigated in this study included reaction temperature (100-260¢J), water vapor concentration (0-1.58¡Ñ104 mg/m3), retention time (3.1-10.3 sec), and inlet benzene concentration (239-478 mg/m3). Experimental results indicated that the decomposition efficiency of benzene increased with reaction temperature whish was lower than 180¢J, for oxygen content of 21 %, water vapor concentration of 4.69¡Ñ103- 1.58¡Ñ104 mg/m3, and reaction temperature lower then 180¢J. However, the decomposition efficiency of benzene could not be further increased for reaction temperature higher than 180¢J. In addition, the decomposition efficiency of benzene increased with water vapor concentration which was lower than 1.16¡Ñ104 mg/m3. For water vapor concentration higher than 1.16¡Ñ104 mg/m3, the decomposition of benzene could not be further enhanced significantly. In this study, up to 100% of benzene decomposition could be achieved at water vapor concentration of 1.58¡Ñ104 mg/m3 and reaction temperature of 180¢J. Moreover, the decomposition efficiency of benzene increased from 57 to 100% as retention time increased from 3.1 to 10.3 seconds, while decreased from 100 to 65% as benzene concentration increased from 239 to 478 mg/m3. Modified Langmiur-Hinshewood kinetic model was applied to simulate the photocatalytic decomposition of benzene in the annular packed-bed photocatalytic reactor. The simulation of experimental results was successfully developed to describe the reaction rate of benzene for various reaction temperatures (160-260¢J) during the UV/TiO2 photocatalytical reaction process. Furthermore, reaction rate constant (KLH) and adsorption equilibrium constant (Kc and Kw) were functions of reaction temperature, where can the described by the Arrihenius Law. The rate controlling steps were either photocatalytic reaction on the surface adsorption of reaction products from the surface photocatalysts.

No description available.

Two strategies to reduce impact of heat stress on high producing dairy cows were examined. The first was to recalculate the temperature-humidity index (THI) using high producing dairy cows under diurnal summer conditions. This re-evaluation confirmed that current THI values underestimate the severity of heat stress levels. Therefore, cooling of dairy cattle during warm summer months should begin at a THI of 68. Previously, a THI equal to or greater than 72 has been used to define onset of heat stress. This study demonstrated that a THI greater than or equal to 68 is sufficient to increase body heat storage, respiration rate, skin evaporative heat loss, declines in feed intake and milk yield. A second objective involved three studies carried out to evaluate use of niacin in dairy cow rations to improve evaporative heat loss and resistance to heat stress. Niacin is known to cause intense vasodilation in human and lab species. We hypothesized that increasing vasodilation would improve evaporative heat loss in dairy cows. In the first niacin study, supplementation of lactating dairy cows with an encapsulated rumen by-pass form of niacin (NIASHURE™; Balchem Corporation, New Hampton, NY) at a dose of 12 g/d proved effective in alleviating some affects of heat stress during mild thermal stress. We hypothesized that encapsulated niacin would induce vasodilation effects documented in humans and lab animals increasing evaporative heat loss. Past research demonstrated that the possible mechanism for vasodilation affects seen by niacin were most likely due to prostaglandin D secretions. Niacin may act through increased prostaglandin D and E production and secretion by Langerhans cells which then act upon vascular endothelial prostaglandin D receptors to increase vasodilation. No studies have evaluated impact of encapsulated niacin on milk yield and composition during periods of thermal stress under commercial dairy conditions. The objective of the last study was to examine the effects of encapsulated niacin during heat stress on milk production and composition as well as core body temperatures under commercial conditions.

No description available.

Records of stable oxygen isotope variations from a variety of proxies have been used in palaeoclimatic research since the 1950’s. Several studies have applied stable isotope analysis of lake sediments to reconstruct past climate changes in central and northern Sweden, including a study of Lake Blektjärnen in Jämtland, central Sweden, by Andersson (2010). In this study, sediments from that same lake were sampled for stable isotope analysis of bulk carbonates with the aim to improve the resolution of the isotopic record for the last two millennia. The results indicate a shift from relatively drier to wetter conditions between ~2,300–1,300 cal. years BP, generally wet conditions close to the Medieval Warm Period (~1,000–750 cal. years BP) and generally dry conditions during the Little Ice Age (~550–150 cal. years BP). These results are in agreement with previous palaeoclimatic reconstructions in the region. The isotopic record of Lake Blektjärnen was completed for the last ~2,350 years at a resolution of ~15 years per sample, three times higher than that of the previous study, displaying the advantages of bulk carbonate sampling for stable isotope analysis and providing a high-resolution dataset on humidity changes in central Sweden during the late Holocene.

No description available.

Thesis--University of Oklahoma. / Bibliography: leaves 62-63.

Thesis (Ph.D.)--Texas Tech University, 2004. / Adviser: Mario G. Beruvides. Includes bibliographical references.

Thesis (M.A.Sc.)--Dalhousie University (Canada), 2007. / Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin, 1963. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 22).