The present study was undertaken to investigate some of the factors influencing job stability among the women employees of the Dallas Independent School District's lunchrooms.

Soils with inherently low soil fertility, and nutrient depletion of fertile soils, are the root causes of declining per capita food production in Africa. On the other hand, demand for better water quality and strict environmental laws have led to an increase in biosolid production. Accumulation of this waste poses an increasing environmental pollution risk. Disposal methods like incineration, ocean dumping and land filling are causing enormous environmental and economic problems. Therefore, municipal authorities have been challenged with the environmental management of biosolids, whilst many farmers are facing a problem of soil fertility decline. Biosolids of “Exceptional quality class A” contain high organic matter, plant nutrients and have few restrictions on use for land application. Therefore, it is a valuable resource. Beneficiation of sewage sludge through land application is an optional solution to address both soil fertility and environmental problems. Scientific management of sewage sludge utilization must be observed to minimize environmental problems. The study of N release and the rate of nitrification from biosolids is essential to improve nutrient use efficiency, as well as to prevent environmental pollution. Mineralization and nitrification processes are influenced by several factors, for instance, the origin and quality of organic material, and soil environmental conditions, of which moisture and temperature are the most important factors. The study aims to: (i) evaluate biosolid stability, temperature and soil water effects on net N release from municipal and industrial sludge amended soil, and (ii) generate important parameters for modeling N dynamics (rate constants and half life). This dissertation consists of two major experiments: The first experiment was a fifty six day laboratory incubation study to assess N release and nitrification rate constants in a biosolid amended soil, as well as the biosolid’s half life time. The experiment was conducted using three types of biosolids originated from three different wastewater treatment processes, subjected to three levels of temperature and three of soil water potentials. The second experiment was an investigation on sample handling strategy for accurate nitrate (NO3-) and ammonium (NH4+) determinations. Different handling procedures: Direct field extraction, Field drying extraction and Laboratory drying extraction were tested on biosolid amended soils. In conclusion, biosolid stability, temperature and soil water interaction significantly influence mineralization and nitrification processes. Unstable sludges had higher N mineralization rate constant and shorter half life times compared to stable sludge, and the Direct field extraction procedure proved to be the most representative sample handling strategy for determination of N speciation in soils and biosolid amended soils to get representative time specific data. / Dissertation (MSc(Agric))--University of Pretoria, 2011. / Plant Production and Soil Science / unrestricted

The aim of this diploma thesis is the preparation of liposome nanoparticles enriched with PHA and PHA nanofibers. The nanostructures served to encapsulate extracts of lipophilic and hydrophilic nature. The characterization of the properties of nanostructures such as polydispersity, size, colloidal stability, long-term stability after exposure to various environments such as seawater, water from the Brno dam and tap water, and finally the cytotoxicity of fibers with extracts was addressed. The theoretical part is focused on different types of water, human skin, coffee and subsequently carotenoids. It continues by describing of possibilities of extraction and preparation of lipophilic and hydrophilic extracts and possibilities of their determination is discussed. Finally, it describes the possibilities of preparation and characterization of PHA based nanomaterials. The practical part deals with the preparation of liposome particles and fibers enriched with PHA with encapsulated extracts, their characterization, and their subsequent exposure to various environments. Monitoring of their long-term stability was carried out, but the release of the encapsulated extracts into the environment to which the nanoparticles and nanofibers were exposed was also measured. Finally, the interaction of nanofibers with live HaCaT cells was monitored, and cytotoxicity assays determined the viability of the cells after interaction with the nanofibers.

This thesis contains some results on the behavior of a delay differential equation (DDE) with two delays, at a Hopf bifurcation, for the nonzero equilibrium, using the growth rate, r, as bifurcation parameter. This DDE is a model for population growth, incorporating a maturation delay, and a second delay in the harvesting term. Considering a Taylor expansion of the non-dimensionalized model, we find a region of stability for the nonzero equilibrium, after which we find a pair of ODEs which help define the flow on the center manifold. We then find an expression for the first Lypapunov coefficient, which changes sign, so we also find the second Lyapunov coefficient, allowing us to predict multi-stability in the model. Numerical simulations provide examples of the behavior expected. For a similar model with one delay (PMC model), we prove the Hopf bifurcation at the nonzero equilibrium is always supercritical.

In this thesis, we study the stability and its trade-off with optimization error for stochastic gradient descent (SGD) algorithms in the pairwise learning setting. Pairwise learning refers to a learning task which involves a loss function depending on pairs of instances among which notable examples are bipartite ranking, metric learning, area under ROC curve (AUC) maximization and minimum error entropy (MEE) principle. Our contribution is twofold. Firstly, we establish the stability results for SGD for pairwise learning in the convex, strongly convex and non-convex settings, from which generalization errors can be naturally derived. Moreover, we also give the stability results of buffer-based SGD and projected SGD. Secondly, we establish the trade-off between stability and optimization error of SGD algorithms for pairwise learning. This is achieved by lower-bounding the sum of stability and optimization error by the minimax statistical error over a prescribed class of pairwise loss functions. From this fundamental trade-off, we obtain lower bounds for the optimization error of SGD algorithms and the excess expected risk over a class of pairwise losses. In addition, we illustrate our stability results by giving some specific examples and experiments of AUC maximization and MEE.

When many objects make contact, they will adopt some collective behavior. For example, sand particles jam together to form a "solid" aggregate (a beach) that you can walk on, hair collects into locks, and sticks can be arranged to form nests and dams. In all of these cases, the collective behavior depends on both the "granular" nature of the objects, i.e. their tendency to jam or rearrange, and their "elasticity," that is, their tendency to deform in response to load. For example, both sand, which is relatively stiff, and cells, which are relatively soft, can rearrange and "flow," however, jammed aggregates of these objects (beaches and biological tissues) vary drastically in their mechanical properties. Here we will unravel the interplay between elasticity and granularity by first separately considering how individual soft objects deform, and many hard particles jam. We will then combine these behaviors step-by-step. First we will consider a single object (an elastic plate) in contact with a hard ring. Then, we will study rearrangement and deformation in two systems where an aggregate made up of stiff particles comes in contact with slender deformable objects, the former reminiscent of plant roots digging into the dirt, and the latter akin to coffee beans jammed in an air-tight bag. Finally, we will consider a system of slender contacting elastic objects, and find that the collective behavior results in the emergence of order. This thesis will illuminate novel physics and functionalities -- building materials which are reformable in real-time and soft robots which can arbitrarily deform, and along the way we will develop tools that could be used to study such diverse systems as the jamming of fibers such as in felt or a collagen network, the properties of a knitted scarf, and the growth and shape of villi in the gut.

Raw bio-oil is produced by fast pyrolysis of biomass. The high level of oxygen content in bio-oil causes negative properties of polymerization over time, high acidity, pungent odor and low heating value relative to petroleum fuels. The objective of this study was to develop and identify upgrading processes to produce a boiler fuel with reduced acid value, reduced polymerization over time and increased higher heating value. By one upgrading method, raw bio-oil was upgraded by esterification over acid catalyst by batch reaction; a second approach was an in-reactor reaction, produced by injecting methanol or 1-butanol with acid catalyst into the pyrolysis vapor stream. An olefination reaction method combined with an alcoholation reaction was also studied. The resulting fuel produced from in-reactor esterification fuel was compared in terms of physical and chemical properties with esterifed bio-oil produced by the batch method. The olefination reaction was examined in terms of higher heating value, acid value, viscosity, and water content. The influence of reaction conditions such as reaction time, reaction temperature, and catalyst content relative to upgraded bio-oil properties were examined, and optimal conditions were identified. Analysis of variance (ANOVA) and empirical analysis was utilized to analyze the difference in physical and chemical properties between treatment groups.

A high-performance liquid chromatography (HPLC) method with ultraviolet (UV) detection was developed and validated for the quantification of lorazepam in oral solution. The chromatographic conditions include an isocratic separation (25% water / 75% methanol at a flow rate of 0.500 ml/min) on a Waters X=Bridge C18 column (150 x 4.6 mm; 3.5-micron particle size). The method was validated using guidance from the United States Pharmacopeia (USP) chapter, including investigation of system suitability, precision, accuracy, linearity, and specificity. The calibration curves on three non-consecutive days met the linearity criteria R2 >0.99. Each chromatogram for 200 mcg/mL calibration samples, designated as 100% assay level, met system suitability criteria of resolution ≥2.0, tailing factor ≤2.0, column efficiency (theoretical plates) ≥2000, and precision of prior metrics % RSD ≤1.0. Three replicates of each concentration, 150 mcg/mL at 75% assay, 200 mcg/mL at 100% assay, and 250 mcg/mL at 125% assay were assessed for precision and accuracy over 3 days. Precision and accuracy were evaluated and met the inter-day (repeatability) criteria % RSD and % Error ≤ 2% and intra-day (intermediate) criteria % RSD and % Error ≤ 5% at the 75%, 100%, and 125% assay levels. To assess for specificity, 200 mcg/mL samples were assessed for degradation after being subjected to heat (>60°C), oxidation (3% H2O2), acidic (0.1M HCl), and basic (0.1M NaOH) environments. Samples from each condition were evaluated for lorazepam recovery at 0, 24, and 48 hours. Most drug loss was observed with the samples subjected to acidic and oxidative environments, with 14.71% and 13.16% drug loss, respectively after 48 hours. This method was developed to support the 30-day stability investigation of lorazepam oral solution when stored in oral syringes at room and refrigerated temperatures.

Yes / Tailing dams are commonly used to safely store tailings without damaging the environment. Sand tailings (also called Sediment tailings) usually have a high water content and hence undergo consolidation during their placement. As the sediment tailings are usually placed above the ground water level, the degree of saturation and permeability of the sediment tailing is associated with the unsaturated condition due to the presence of negative pore-water pressure or suction. Current practices normally focus on the analyses saturated conditions. However, this consolidation process requires the flow of water between saturated and unsaturated zones to be considered. The objective of this study is to investigate the stability and consolidation of sediment tailings for the construction of road pillars considering the water flow between saturated and unsaturated zones. The scope of this study includes the unsaturated laboratory testing of sediments and numerical analyses of the road pillar. The results show that the analyses based on saturated conditions overestimate the time required to achieve a 90% degree of consolidation. The incorporation of the unsaturated soil properties is able to optimize the design of slopes for road pillars into steeper slope angles.

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