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X-ray imaging scintillators and detectors play a critical role in numerous everyday life applications, including medical radiography, high-energy physics research, and security inspections. Despite its importance, current X-ray imaging technologies are not fully equipped to meet the growing demands for flexible, cost-efficient, and environment-friendly solutions. To overcome the limitations associated with traditional imaging scintillators, recent research efforts have focused on developing lead-free luminescent materials. Of particular interest are Cu(I) complexes, which exhibit excellent photoluminescence behavior, a facile synthesis process, and a high atomic number, making them an ideal candidate for X-ray imaging applications. Our work focuses on developing a low-dimensional Cu(I) organometallic halide and utilizing it as an imaging scintillator for real-life X-ray imaging. By utilizing the 0D Cu(I)-based imaging scintillators, we successfully obtained detailed images of both biological and non-biological objects, with a low detection limit of 458.3 nGy/s and high resolution of 16.8 lp/mm. This study not only provides a design roadmap for Cu(I) luminescent materials, but also highlights their potential for high-impact real-life X-ray imaging applications. Overall, our findings represent a significant step forward for X-ray imaging technology and its widespread applications in fields such as medicine and security.

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The cytosolic iron sulfur cluster assembly (CIA) pathway is responsible for the maturation of >40 cytosolic and nuclear iron sulfur (FeS) proteins critical for fundamental processes such as DNA replication, transcription, and translation. The final stages of the pathway require the CIA targeting complex, which is composed of Cia1, Cia2, and Met18. This large multiprotein complex is proposed to recognize apo-enzyme substrates and insert their FeS clusters. However, it is unclear how these substrates are identified and how the CIA targeting complex mediates cofactor insertion. In this thesis, I mapped the protein-protein interaction sites critical for formation of the CIA targeting complex and discovered the first peptide motif that is both necessary and sufficient for recognition of a subset of FeS proteins by the CIA system. Cia1’s seventh beta-propeller blade was found to bind to Cia2, while Cia2’s fifth conserved region mainly interacts with Cia1, via an in vitro affinity co-purification assay. A quantitative MicroScale Thermophoresis assay supported these findings, in addition this approach affirmed that Cia2’s N-terminal intrinsically disordered domain and hyperreactive cysteine are dispensable for CIA targeting complex assembly. In collaboration with the Drennan Lab at MIT, Met18 was discovered to form a hexamer via cryo-EM. Met18 is proposed to arrange into a hexamer before its CIA-related function. Hexamer formation and Cia2 binding depend on Met18’s C-terminus, whereas Leu1 recognition relies on Met18’s N-terminus. A C-terminal W motif was demonstrated as both necessary and sufficient for identification of a subset of FeS proteins by the CIA targeting complex. A bioinformatics analysis revealed roughly 20% of CIA client proteins, including substrates, factors, and adaptors, terminate in a conserved [LTQ]-[DE]-[W]-COO- motif. CIA recognition depends on the C-terminal aromatic side chain and the carboxy terminus. This tripeptide motif is also sufficient for identification by the CIA system when attached to SUMO. Moreover, a series of competition experiments showed that the CIA targeting complex contains distinct, non-overlapping binding sites for client proteins where Cia1 serves as the docking site for the C-terminal W motif. Altogether, the first recognition motif is defined for one in five of CIA client proteins. / 2024-11-03T00:00:00Z

A globular cluster is a collection of stars that orbits the center of its galaxy as a single satellite. Understanding what influences the formations of these clusters provides understanding of galaxy structure and insight into their early development. We continue the work of Harris et al. (2013), who identified a set of predictors that accurately determined the number of clusters Ngc, through analysis of an incomplete dataset. We aimed to improve upon these results through imputation of the missing data. A small amount of precision was gained for the slope of Ngc~ R_e*sigma_ e, while the intercept suffered a small loss of precision. Estimates of intrinsic variance also increased with the addition of imputed data. We also found galaxy morphological type to be a significant predictor of Ngc in a model with R_e*sigma_ e. Although it increased precision of the slope and reduced the residual variance, its overall contribution was negligible. / Thesis / Master of Science (MSc)

<p> Dicobalt octacarbonyl reacts with a wide variety of molecules containing trichloromethyl functionalities to yield carbynyl tricobalt nonacarbonyl clusters of the general formula R-CCo 3 (CO) 9 . While these clusters have been shown to undergo many reactions, mechanistic studies on these systems are sparse. In particular, their rather facile decarbonylation processes are not well understood. </p> <p> Complexes of the type Ar-CO-CCo 3 (CO)9 readily lose CO to produce the corresponding Ar-CCo 3 (C0) 9 clusters but the origin of the carbon monoxide extruded was not known . Speculation had focussed on two possibilities: firstly, direct elimination of the ketonic carbonyl - perhaps via radical intermediates - and, secondly, via initial loss of a cobalt carbonyl ligand (to produce a 16-electron cobalt vertex) with subsequent migration of the original ketonic group onto the coordinatively unsaturated cobalt center. These two mechanistic possibilities are differentiable by labelling either the cobalt carbonyl sites or the ketonic position with carbon-13 and then examining the decarbonylated product to locate the isotopically enriched positions by 13c NMR spectroscopy. It is shown that the carbon monoxide initially eliminated is a cobalt carbonyl and the ketonic CO migrates from its apical position onto a cobalt atom. </p> <p> A second project involves the synthesis and characterization of a cobalt cluster derived from the reaction of dicobalt octacarbonyl with the insecticide DDT . This cluster contains the bis(4-chlorophenyl)methylcarbynyl capping group which is so bulky that it has the potential to stop the rotation of the carbynyl ligand and also prevent carbonyl exchange on the metal triangle. The DDT-tricobalt cluster was characterized by X-ray crystallography. The compound crystallizes in the space group P21/n: the monoclinic cell has dimensions a = 13.083 A, b = 14.222 A, c = 14.165 A, B = 95.871 degrees and Z = 4. The molecule adopts almost Cs symmetry except that the phenyl rings are twisted slightly so as to destroy the potential mirror plane. At low temperature, the cobalt carbonyl ligands are non-equivalent on the NMR time-scale and the possible causes for this behaviour are discussed. </p> / Thesis / Master of Science (MSc)

Galaxy properties are known to correlate with their environment, suggesting that environment plays a significant role in galaxy evolution. In particular, blue star forming spiral galaxies are preferentially found in low density regions while red, passive elliptical galaxies are found in the densest clusters. This suggests galaxies falling into groups and clusters experience a decrease in their star formation rate (SFR) and a morphological transformation from spiral to elliptical, but the timescales associated with these changes are not well constrained. This thesis explores the impact of environment on galaxy SFRs and morphologies for a large sample of galaxies from the Sloan Digital Sky Survey. We separate galaxies into two environments (groups and clusters) and use location in projected phase space as an estimate for how long a galaxy has been a part of its current environment. We calculate the timescales associated with the changes in galaxy SFRs and morphologies, and determine SFRs change more quickly than morphology. By comparing to a sample of field galaxies, we find evidence that prior group environments impact current galaxy properties via pre-processing. / Thesis / Master of Science (MSc)

I present Hubble Space Telescope photometry in optical (F475X, 475 nm) and near-infrared (F110W, 1.1 μm) bands of the globular cluster (GC) system of the inner haloes of a sample of 15 brightest cluster galaxies (BCGs). I also present a quantitative model of the relation between (F475X - F110W) colour and cluster metallicity, using simulated GCs. The sample comprises massive elliptical galaxies in a range of environments, from sparsely populated groups to dense clusters. Because the material available for large galaxies to accrete varies with environment and GC systems of such galaxies are built up through accretion, I expect the metallicity distribution of the GC systems in my sample to vary with galaxy environment. GC systems in massive elliptical galaxies tend to follow a bimodal colour distribution, with two subpopulations of blue (metal-poor) and red (metal-rich) clusters. The photometry is used to create a completeness-corrected metallicity histogram for each galaxy in my sample, and to fit a double Gaussian curve to each histogram in order to model the two subpopulations. Finally, the properties of the GC metallicity distribution are correlated against each BCG environment. I found that almost no GCS properties and host galaxy environmental properties are correlated, with the exception of weak but consistent correlations between number of GCs and nth-nearest neighbour surface density and between blue fraction and nth-nearest neighbour surface density. / Thesis / Master of Science (MSc)

A spatial analysis was used to examine location of Mississippi’s forest products manufacturers and identify potential forest business clusters. A Poisson regression was used to examine the impact of transportation infrastructure, labor and availability of raw materials on location of these manufacturers. Spatial analysis indicated that manufacturers tended to cluster and identified four potential forest business clusters. Regression analysis indicated that volume of harvested sawlogs had a positive impact on location of primary and secondary forest products manufacturers, whereas volume of harvested pulpwood had a positive impact on location of only secondary forest products manufacturers. Presence of four-lane interstate highways was associated with decreased location likelihood for secondary manufacturers, whereas railway presence increased location likelihood. Presence of primary manufacturers had a positive impact on location of secondary manufacturers, whereas labor force also had a positive impact on location of secondary forest product manufacturers.