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Synthesis of N-Heterocyclic Carbene Complexes of Coinage Metals and Their Application in the Activation of Hydrogen
Full text linkThe main cause of the ongoing global climate crisis is the emission of greenhouse gases, and current climate reports emphasize the need to transition to low-emission renewable energy sources. Urgently needed are methods for storing renewable energy, such as synthetic fuels like hydrogen (H2) gas; however, a challenge to the widespread implementation of hydrogen fuel is its low volumetric energy density. This thesis describes an effort to synthesize a catalyst that takes advantage of hard-soft acid-base (HSAB) mismatches to activate H2 and facilitate its reaction with CO2 to form hydrocarbon fuels, thereby providing a sustainable means of storing renewable energy in high-density carbon-neutral fuels. The catalyst design features an exceptionally bulky N-heterocyclic carbene (NHC) ligand known as IPr** (3-Bis[2,6-bis[bis(4-tert-butylphenyl)methyl]-4-methylphenyl]-1H-imidazol-3-ium chloride), a coinage metal acting as a soft acid, and a hard base such as an alkoxide ion. Herein is reported a modified synthetic route of IPr**, along with its metalation with silver, and preliminary results of the addition of an alkoxide base. The ligand and its complex with silver are structurally characterized by nuclear magnetic resonance (NMR) spectroscopy. Further work is needed to complete the characterization of IPr**-supported HSAB mismatch complexes and investigate their potential to activate H2
Examining the Effect of Aromatic Substituents in Peptoid Catalysts of Stereoselective Trifluoromethylation
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The identification and visualization of candidate early embryonic patterning genes in \u3ci\u3eBradysia coprophila\u3c/i\u3e
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Activation of Hydrogen by Sterically Modulated Coinage Metal Catalysts via Mutual Quenching of Hard/Soft Acid/Base Mismatches
Full text linkTo mitigate the devastating environmental impacts of climate change in the coming decades, it is imperative that we replace the use of fossil fuels with renewable energy sources such as wind, solar, and hydroelectric. As these renewable energy sources are inherently intermittent, there exists a need for sustainable mechanisms to store renewable energy for later use. While the direct use of dihydrogen (H2) as a combustible fuel would allow for energy storage without the harmful release of carbon dioxide (CO2) upon combustion, the practicality of H2 as a synthetic fuel is limited by its low volumetric energy density. Combining sustainable H2 production (e.g. electrolysis using energy from renewable sources) with subsequent carbon fixation (e.g. the hydrogenation of CO2) represents a promising pathway to the sustainable production of high-density synthetic fuels. We hypothesize that such a process could be catalyzed by an IPr**-supported catalyst containing a hard/soft acid/base (HSAB) mismatch, with a polarizable coinage metal acting as a soft acid. As such, the aim of our project is the construction of a catalogue of IPr**-supported copper, silver, and gold catalysts that we anticipate will facilitate the heterolysis of dihydrogen and subsequent hydrogenation of CO2. In the present paper, we report the synthesis and characterization of an IPr**-silver complex which will serve as a precursor to many of our proposed HSAB mismatch catalysts and discuss next steps as we construct our catalogue of catalysts
An AGN as a Counterpart for Neutrino Event IceCube-220303A
Full text linkCosmic rays have been detected for over a century. While some sources have been confirmed, they cannot explain the high energy of the particles (\u3e 10^15 eV), so it remains unclear where and how they are accelerated to extreme energies. The study of astrophysical high-energy neutrinos may help solve the puzzle. These neutrinos are produced by cosmic rays interacting with other charged particles or photons. Moreover, while cosmic rays do not reveal their sources of origin because they can be deflected by magnetic fields, cosmic neutrinos detected by the IceCube Observatory can be traced back to their sources of origin. We will consider an active galactic nucleus (AGN) as a candidate source for a high-energy neutrino.This thesis examines the AGN WISEA J175051.31+105645.3 as a potential source for IceCube-220303A, a high-energy neutrino with a 78% probability of being astrophysical in origin. Using follow-up NuSTAR and Swift/XRT observations, WISEA J175051.31+105645.3 was the only viable source we found in IceCube-220303A’s uncertainty region. We used follow-up X-ray data to construct a multi-wavelength spectral energy distribution (SED) through which we calculated the AGN’s neutrino energy flux. This calculation yields the number of neutrinos we would expect to detect from the AGN in a given time period. We used this number to calculate the probability that IceCube-220303A was emitted by WISEA J175051.31+105645.3. Finding a statistically significant link between IceCube-220303A and WISEA J175051.31+105645.3 may help us better understand what processes can accelerate particles like cosmic rays to extreme energies and learn more about AGN
The Forest Before Us: Storying the North Maine Woods
No full textGrounded in the soil of the territory now known as the North Maine Woods (NMW), where for millennia Wabanaki peoples lived on and engaged with the land, this thesis explores how the longstanding history of human habitation in and around the Maine woods clashes with colonial narratives that depict the concepts of forest and civilization at complete odds with one another. Instead of offering a comparative look at Western and non-Western cosmologies through the lens of the forest, however, I strive to destabilize the concept of forest itself, foregrounding how multiplicities of meanings, irreducible particularities, and, ultimately, confusion make the forest into fecund insurgent space—ideologically and ecologically. While tidy forest narratives attempt to organize the chaotic matrices of our lives and others’, exploring narrative threads in the North Maine Woods, seeking out knots and loose ends, threatens to undo what we think we know about the stories, the worlds, and the woods enveloping us. Ultimately, my argument is simple: storytelling makes and unmakes how we understand and engage with the Maine woods. Storying the forest produces and reproduces historical yet constantly shifting networks of meaning that decenter any singular (human) perspective while maintaining the entanglements between human and non-human worlds. There is no telling the forest, but this thesis enacts forest kind of storytelling to focus on the relational aspects of getting lost in the Maine woods and reframe conversations about land use, history, and human imaginations of others
The French Official Mistress: Fashioning Female Political Power in the \u3ci\u3eAncien Régime\u3c/i\u3e
Full text linkThis thesis focuses on the French official mistress as a position of unofficial female political power under the French monarchy from the 16th to the 18th century. Centering on three case studies – Diane de Poitiers, Madame de Maintenon, and Madame de Pompadour – this thesis argues that the role of the official mistress extended beyond sexual companion to advisor, negotiator, diplomat, artistic patron, and cultural trendsetter. By taking a deep look at the epistolary and artistic record of these three official mistresses from across France’s modern history, the extent of their autonomy and political maneuvering becomes clear in the tactics they used to project and solidify their power. Diane de Poitiers, Madame de Maintenon, and Madame de Pompadour all existed in unique contexts of the French court and constructed their own methods of fulfilling the role of the official mistress, revealing both changes in the monarchy and their impacts upon it. Notably, the ways in which they projected identity through self-fashioning resulted in a reflection of this image back onto the monarch, expanding the extent of their impact on the monarchy. In striving to understand the political reality of women in France under Salic law and today, the position of maîtresse-en-titre is a crucial framework to recognize the significance of female power structures at court and in the monarchy, and the degree to which women were able to shape these structures themselves
The Power of In-Person Digital Repatriation: Returning Historic Photographs to West Greenland Communities
No full textThis thesis is about the research potential of historic photograph digital repatriation in combination with in-person anthropological fieldwork. I draw on four weeks of fieldwork in West Greenland. Returning historic photographs to Indigenous communities works toward recentering Indigenous stories and memories of people, places, and events. I discuss how my methodology of photo sharing was effective in establishing a rapport with informants and evoking memories. This is seen through examples of interactions with informants and the memories they shared with me. Given the success of my project, which took place during only four weeks in the field, I consider my methodology’s potential in future research
Evaluation of design parameters for monosaccharide probes used in the metabolic labeling of bacterial glycans
No full textThe dangerous rise of antibiotic resistant bacteria in clinical infections demands the development of new antibiotics. Bacterial glycans are attractive antibiotic targets due to the highly divergent structures observed across bacterial species and their involvement in pathogenesis. Here, we turned to metabolic oligosaccharide engineering as a tool to probe the presence of bacterial monosaccharaides on the pathogenic bacteria Staphylococcus aureus, Helicobacter pylori, Plesiomonas shigelloides, and Vibrio vulnificus and commensal bacterium Bacteroides fragilis. In particular, we assessed the metabolic incorporation of peracetylated versus free N-azidoacetyl analogs of glucosamine, L-pneumosamine and L-rhamnosamine. Incorporation of the azido sugar probes into cellular glycans was assayed on live cells and in cell lysates. All pathogenic species preferentially incorporated the peracetylated probes, with strong incorporation onto cell surface glycans. Both S. aureus and B. fragilis were able to incorporate free sugars in addition to or in place of the peracetylated equivalent. Esterase activity assays in live cells and cell lysates revealed the presence of active esterase enzymes within these bacteria, supporting the use of peracetylated probes. These studies reveal insight into optimal design parameters of metabolic probes to study glycans in these bacteria
How do Robinhood Investors React to Macroeconomic News?
No full textThis research looks at the trading app Robinhood and how retail investors trading on this app behave in reaction to macroeconomic news releases. Robinhood is a new trading platform that has become popular recently with its focus on increasing access to investing with zero commission trading. This research focuses its study on retail investors trading on Robinhood and uses the news from monthly unemployment releases to understand how these users react to news. I look at how users buying a stock after an event relates to that stock\u27s excess returns in order to assess over or underreactions by these retail investors. While there is evidence supporting different trading behaviors on good and bad news events, there is no evidence supporting over or underreactions