Intergranular and pitting corrosion mechanisms of sensitized aluminum alloy AA5083

The motivation and objectives of this project is to examine the mechanisms of intergranular corrosion (IGC) and pitting corrosion of sensitized AA5083. In this regard, different characterization techniques were used, including optical analysis of microstructure, cyclic potentiodynamic polarization with Tafel fitting, electrochemical impedance spectroscopy with electrical equivalent circuit (EEC) fitting, and potentiostatic current transient monitoring. The transition from IGC to pitting corrosion occurs when the grain boundaries become saturated with the β-phase (Mg2Al3). It was found that AA5083 becomes more vulnerable to pitting corrosion as the degree of sensitization increases

Engine balance apparatus and accessory drive device

A balancing mechanism for an engine that has a rotating crankshaft and reciprocating pistons. The balancing mechanism comprises a primary balance mass assembly non-rotatably and removably affixed to the crankshaft. The primary mass assembly comprises a primary mass affixed to a primary hub portion and a primary cap portion removably affixed to the primary hub portion to clamp a portion of the crankshaft therebetween. A secondary balance mass assembly may be rotatably and removably supported on the crankshaft. A driver assembly is affixed to the crankshaft to cause the secondary balance mass to rotate in a direction that is opposite to the direction in which the crank shaft is rotating. The driver assembly may include auxiliary gears configured to transport rotary power to auxiliary components. The gears are readily detachable from the apparatus to facilitate inspection and repair operations

Understanding the Mechanisms by which E. coli can Adapt to Disruption of the Pathway for the Synthesis of Pyridoxal-5’-phosphate

Escherichia coli possesses a remarkable ability to adapt to new environments and overcome disruption of synthetic pathways. In this thesis, I show that E. coli with a deleted pdxB gene is able to bypass a disruption in the pyridoxal-5’-phosphate (PLP) synthesis pathway. The ΔpdxB strain cannot synthesize its own PLP via the traditional pathway, so it must create a new pathway to synthesize this essential vitamin. One way the ΔpdxB strain adapts is via serendipitous pathways that emerge as a direct result of mutations in PLP-depleted environments. These pathways appear when the strain is grown on both solid and liquid media. Mutations restoring PLP synthesis occurred in the ΔpdxB strain when plated on solid M9 minimal medium supplemented with 0.2% (w/v) glucose or glycerol, or when supplemented with over 2% (w/v) pyruvate, succinate, and acetate. The ΔpdxB strain adapted in liquid M9/glycerol, but only in favorable conditions. These conditions, such as when the strain was supplemented with D-alanine or after the strain synthesized a proteome tailored to glycerol, allow survival of the bacterium by helping minimize the detriment of its weak cell wall. The longer the bacteria can survive, the more opportunity there is for mutations to appear. Whole-genome sequences of adapted strains were analyzed using breseq, revealing that the adapted ΔpdxB strains acquired mutations, which are assumed to result in the synthesis of PLP. It is currently unclear the exact effect these mutations have and whether or not they are all involved in a serendipitous pathway

INVESTIGATING MEDIATION WHEN COUNTERFACTUALS ARE NOT METAPHYSICAL: DOES SUNLIGHT UVB EXPOSURE MEDIATE THE EFFECT OF EYEGLASSES ON CATARACTS?

We investigate the degree to which a reduction in ocular sunlight ultra-violet B (UVB) exposure mediates a relationship between wearing eyeglasses and a decreased risk of cataracts. An estimand is proposed in which causal effects are estimated locally within strata based on potential UVB exposure without glasses and the degree to which glasses use reduces UVB exposure. We take advantage of the structure of the data in which the counterfactual UVB exposures if the participants in the study who wore glasses had not worn glasses are considered observable

Understanding and Modifying the Properties of Permanently Microporous Liquids: Towards Selective and Scalable Systems

Porous liquids are a new class of material defined by their permanent microporosity and fluidity. In this thesis, an investigation of control over the properties of these materials is described, transferring knowledge of microporous solids into the liquid state. The progress made to date in this relatively young field is outlined, as well as an overview of the properties of microporous solids. New type 2 and 3 porous liquids with modified gas uptake and selectivity were generated using synthetic pore control in porous organic cages, based on previous understanding of these organic cage molecules. In a type 2 porous liquid cage solution, introduction of methyl groups to occlude the pore window effect was used to invert selectivity for Xe. New type 3 porous liquid dispersions were prepared from organic cage microcrystals, pore modification among the materials was also shown to enhance or reduce gas uptake. Hydrophobicity is also explored as a driving force for introducing porosity in a liquid, microporous polymer dispersions were investigated for gas and liquid absorption

Longitudinal Data with Follow-up Truncated by Death: Match the Analysis Method to Research Aims

Diverse analysis approaches have been proposed to distinguish data missing due to death from nonresponse, and to summarize trajectories of longitudinal data truncated by death. We demonstrate how these analysis approaches arise from factorizations of the distribution of longitudinal data and survival information. Models are illustrated using cognitive functioning data for older adults. For unconditional models, deaths do not occur, deaths are independent of the longitudinal response, or the unconditional longitudinal response is averaged over the survival distribution. Unconditional mod- els, such as random effects models fit to unbalanced data, may implicitly impute data beyond the time of death. Fully conditional models stratify the longitudinal response trajectory by time of death. Fully conditional models are effective for describing in- dividual trajectories, in terms of either aging (age, or years from baseline) or dying (years from death). Causal models (principal stratification) as currently applied are fully conditional models, since group differences at one timepoint are described for a cohort that will survive past a later timepoint. Partly conditional models summarize the longitudinal response in the dynamic cohort of survivors. Partly conditional models are serial cross-sectional snapshots of the response, reflecting the average response in survivors at a given timepoint rather than individual trajectories. Joint models of sur- vival and longitudinal response describe the evolving health status of the entire cohort. Researchers using longitudinal data should consider which method of accommodating deaths is consistent with research aims, and use analysis methods accordingly

Hand-book of tree-planting; or, Why to plant, where to plant, what to plant, how to plant

Gerald W. Williams Collectio

Melt-quenched porous organic cage glasses

The discrete molecular nature of porous organic cages (POCs) has allowed us to direct the formation of crystalline materials by crystal engineering. It has also been possible to create porous amorphous solids by deliberately disrupting the crystalline packing, either with chemical modification or by processing. More recently, organic cages were used to form isotropic porous liquids. However, the connection between solid and liquid states of POCs, and the glass state, are almost completely unexplored. Here, we investigate the melting and glass-forming behaviour of a range of organic cages, including both shapepersistent POCs formed by imine condensation, and reduced and synthetically post-modified amine POCs that are more flexible and lack shape-persistence. The organic cages exhibited melting and quenching of the resultant liquids provides molecular glasses. One of these molecular glasses exhibited improved gas uptake for both CO2 and CH4 compared to the starting amorphous cage. In addition, foaming of the liquid in one case resulted in a more stable and less soluble glass, which demonstrates the potential for an alternative approach to forming materials such as membranes without solution processing

Modular Type III Porous Liquids Based on Porous Organic Cage Microparticles

The dispersion of particulate porous solids in size-excluded liquids has emerged as a method to create Type III porous liquids, mostly using insoluble microporous materials such as metal–organic frameworks and zeolites. Here, the first examples of Type III porous liquids based on porous organic cages (POCs) are presented. By exploiting the solution processability of the POCs, racemic and quasiracemic cage microparticles are formed by chiral recognition. Dispersion of these porous microparticles in a range of size-excluded liquids, including oils and ionic liquids, forms stable POC-based Type III porous liquids. The flexible pairing between the solid POC particles and a carrier liquid allows the formation of a range of compositions, pore sizes, and other physicochemical properties to suit different applications and operating conditions. For example, it is shown that porous liquids with relatively low viscosities or high thermal stability can be produced. A 12.5 wt% Type III porous liquid comprising racemic POC microparticles and an ionic liquid, [BPy][NTf2], shows a CO2 working capacity (104.30 µmol gL−1) that is significantly higher than the neat ionic liquid (37.27 µmol gL−1) between 25 and 100 °C. This liquid is colloidally stable and can be recycled at least ten times without loss of CO2 capacity