The rapid accumulation of municipal solid waste is a significant environmental concern in our rapidly growing world. Due to its low cost, high energy recovery and limited environmental impact anaerobic digestion (AD) is a promising solution for stabilizing the organic fraction of municipal solid waste (OFMSW). Hydrolysis is often the rate-limiting step during AD of wastes with high solid content; this step can be accelerated by pretreatment of waste prior to AD. This thesis presents the results of alkaline pretreatment of OFMSW using NaOH and KOH. Four different pH levels 10, 11, 12 and 13 at two temperatures 23±1°C and 80±1°C were examined to study the effects of the pretreatment on (i) enhancing the solubility of the organic fraction of the waste, and (ii) enhancing the AD process and the biogas production. The effects on solubility were investigated by measuring changes in the soluble COD (SCOD) concentrations of pretreated wastes and the enhanced AD was investigated by measuring volatile solids (VS) destruction, total COD (TCOD) and SCOD removal in addition to biogas and methane production using biochemical methane potential (BMP) assay and semi-continuous laboratory reactor experiments. Pretreatment at pH 13 at 80±1°C demonstrated the maximum solubility for both NaOH and KOH pretreated samples; however the BMP analysis demonstrated that pretreatment at pH 12 at 23±1°C showed the greatest biogas yield relative to the removed VS for both chemicals. Thus pretreatment at pH 12 at 23±1°C using NaOH and KOH were examined using semi-continuous reactors at three different HRTs: 10, 15 and 20 days. Pretreatment demonstrated a significant improvement in the AD performance at SRTs of 10 and 15 days.

Understanding how natural Cs, Rb, and K have been redistributed in Savannah River Site (SRS) soils during pedogenesis is important to understanding how radiocesium released to the soils will behave over the long term. In this effort, it is important to distinguish K that has participated in mineral-water reactions from that still residing in primary silicate structures, particularly in the clay fraction. The impact of different degrees of acid extraction on K and radiogenic Ar in bulk soil and in clay from five SRS soil samples has been determined. Strong treatment (50% HNO3, three hours, 100°C) releases K from primary minerals, as shown also by a concomitant release of radiogenic Ar, but a more moderate treatment (6% HNO3, three hours, 80°C) does not release K. K in the clay fraction is mostly nonexchangeable K in remnants of primary mica, and clay K-Ar age values near 300 Ma indicate the mica originated in the Appalachian mountain belt.

Nous avons étudié par calcul ab initio la structure et la stabilité de différentes phases cristallographiques du trioxyde de tungstène en volume et ensurface, ainsi que l'effet du dopage par le potassium. L'étude a été motivéepar des travaux expérimentaux sur la croissance de nano-bâtonnets WO3 surun substrat de mica ; ces nanostructures adoptent la phase hexagonale, mé-tastable dans le WO3 massif. La première partie du manuscrit est consacrée àl'étude du volume. Les structures atomiques des phases hexagonales et monocliniquessont déterminées et comparées aux différents modèles proposés dansla littérature expérimentale. La stabilité relative de ces deux phases est calculée en fonction du taux de potassium permettant d'obtenir un diagrammede phase approximatif de KxWO3 montrant que la phase hexagonale est stablepour x compris entre 3 et 35%. Par ailleurs, les distorsions disparaissentpour des concentrations de K suffisamment élevées. Ces résultats expliquentla stabilisation de la phase hexagonale dans les nano-bâtonnets par l'insertiond'atomes de K de la surface du mica. Dans la seconde partie, une étudesystématique des surfaces, en phase monoclinique et hexagonale, est présentée. Pour chaque phase, les trois orientations de surface de plus faibles indicesde Miller sont considérées. Toutes les terminaisons non-reconstruitesainsi que plusieurs types de reconstructions ont été analysées en terme depolarité, stabilité et structure atomique. Pour la phase monoclinique, l'orientation(010) avec reconstruction c(2x2) est la surface la plus stable, enaccord avec des données expérimentales. Quant à la phase hexagonale, c'estla surface c(1x1)O2(1120) qui a la plus petite énergie de surface (0.02 eV/Å2).Nous trouvons que la stabilité des différentes orientations est très sensible audopage par le potassium. En effet, pour KxWO3 avec x = 13 , c'est l'orientation (0001) qui est la plus stable, avec une terminaison KO3 et une énergiede surface de 0.05 eV/Å2.

In this study, potassium permanganate was used as the oxidant to remediate TCE¡Vcontaminated groundwater. The objectives of this bench-scale oxidation study include the following: (1) evaluate the overall TCE oxidation rate with the presence of KMnO4, (2) assess the consumption rate of KMnO4, (3) evaluate the effect of the oxidation by-product, manganese dioxide (MnO2), on the TCE oxidation rate. The control factors in this study include (1) four different molar ratios of KMnO4 to TCE [designated as P, (KMnO4/TCE) = 2, 5, 10, and 20]; (2) four different TCE concentration (0.5, 5, 20, and 100 ppm); (3) three different initial pH values (2.1, 6.3, and 12.5); (4) three different oscillator mix rate (0, 50, and 200 rpm); (5) four different molar ratios of dibasic sodium phosphate (Na2HPO4) to Mn2+ [designated as D, (Na2HPO4/Mn2+) = 0, 50, 100, and 300D], and (6) two different medium solutions [deionized (DI) water and groundwater]. Moreover, the effects of D values on TCE oxidation rate and KMnO4 consumption rate were also evaluated. Experimental results indicate that a second-order reaction model could be applied to express the oxidation reaction of TCE by KMnO4, and the calculated rate constant equals 0.8 M-1s-1. Results also show that the higher the P value, the higher the TCE oxidation rate. Moreover, TCE oxidation rate was not affected under low pH conditions (pH = 2.10 and 6.3). However, TCE oxidation rate dropped under high pH condition (pH 12.5) due to the transformation of KMnO4 to manganese dioxide. The following three pathways would cause the production of manganese dioxide: (1) direct oxidation of TCE by KMnO4, (2) production of Mn2+ after the oxidation of TCE by KMnO4, and Mn2+ was further oxidized by KMnO4 to form manganese dioxide, and (3) transformation of KMnO4 to manganese dioxide under high pH condition. Results also show that more manganese dioxide was produced while groundwater was used as the medium solution. Results show that the produced manganese dioxide was 47.2% - 81.5% less with the addition of dibasic sodium phosphate. Moreover, the variations in D values would not affect the TCE oxidation rate. However, the increase in D value would decrease the consumption of KMnO4. Results also reveal that significant inhibition of manganese dioxide production was observed under low pH condition. Furthermore, no TCE oxidation byproducts were detected after the oxidation reaction. Key words: KMnO4, TCE, manganese dioxide and dibasic sodium phosphate

No description available.

Thèse doctorat : Chimie Informatique et Théorique : Nancy 1 : 2004. / Titre provenant de l'écran-titre.

Reproduction de : Thèse de doctorat : Sciences de la vie et de la santé. Médecine : Nantes : 2007. / Bibliogr.

Thesis (Ph. D.)--University of Nevada, Reno, 2002. / Includes bibliographical references. Online version available on the World Wide Web.

Thesis (Ph. D.)--Case Western Reserve University, 2004. / [School of Medicine] Department of Pathology. Includes bibliographical references. Available online via OhioLINK's ETD Center.

This dissertation describes the work done on two distinct projects. In the first part I sought to unravel the mechanisms that underlie the activity-dependent modulation of response in the excitation-secretion coupling of the neurohypophysis. In the second part, I optically monitored and analyzed the secondary structure changes accompanying amyloid fibril formation along multiple pathways, under both denaturing and near-physiological conditions. Neuronal plasticity plays an important role in regulating various biological systems by modulating release of hormones or neurotransmitters. The changing response to the same stimulus, depending on the context and previous stimulation events, is also the basis of learning and all higher order brain functions. The mechanisms behind this modulation are widely varied, and are often poorly understood in specific tissues. In this work, we examined excitation-secretion coupling in the neurohypophysis, a tissue composed of densely packed axons that secretes the hormones arginine vasopressin and oxytocin. The release of hormones depends not only on the overall level of activity in the gland, but also upon the specifics of the temporal pattern of stimulation. By optically monitoring the electrical activity using voltage sensitive dyes, we were able to investigate this plasticity in the intact gland. Varying extracellular potassium concentration in the bath, increasing interstitial space via hypertonic saline, and retarding potassium reuptake with ouabain all showed that extracellular potassium accumulation drives the depression of excitability. This effect is hidden from glass micro-electrode recordings because of the inevitable damage sustained by the surrounding tissue. Furthermore, no calcium mediated release mechanism played any significant role in the depression. Numerical simulations confirmed the findings and give more insight to the details of the mechanism. Deposits of amyloid fibrils, long, unbranched polymeric protein aggregates, are the molecular hallmark for a variety of human diseases, including Alzheimer's disease, Parkinson's disease, and type II diabetes. While the amyloid fibrils all share a characteristic cross-beta sheet structure, the proteins that make up the aggregates have no unifying theme in either native structure or function. In this research, I characterized the structural reordering that accompanies this aggregation using Fourier transform infrared spectroscopy (FTIR). Hen egg white lysozyme forms fibrillar aggregates with two distinct morphologies, depending on the growth conditions. At acidic pH with low ionic concentrations, lysozyme forms the fibrils with standard amyloid morphology. These aggregates are long and stiff but with the cross sectional area of a single monomer. At higher salt concentrations, the aggregation follows another pathway, under which oligomers initially form and later assemble into protofibrils. The oligomeric protofibrils are thicker than the monomeric filaments, but are much more curvilinear. These fibrils are not universally recognized as amyloidogenic aggregates. Using FTIR, I showed that both this aggregates are indeed amyloid structures, but that they are structurally distinct. While it is generally accepted that partial unfolding of the protein is a prerequisite for amyloid fibril formation, we found that native protein can be the substrate for amyloid growth when seeded with preformed oligomeric or protofibrillar aggregates. These seeded fibrils grown under near-physiological conditions are structurally indistinguishable from those grown from partially unfolded protein under denaturing conditions. This incorporation and restructuring of native monomers is characteristic of prion-like assembly.