Southeastern South America (SESA), a region encompassing Paraguay, Southern Brazil, Uruguay, and northern Argentina, experienced a 23% increase in austral summer precipitation from 1902-2022, one of the largest precipitation trends observed globally. There is little consensus on the drivers of the precipitation trend, but Atlantic multidecadal variability, stratospheric ozone depletion, and greenhouse gas emissions stand out as key contributing factors. The work presented in this dissertation addresses two main questions. First, what are the historical drivers of the SESA precipitation increase? To address this, I investigate simulations from the Coupled Model Intercomparison Project (CMIP) Phases 3, 5, and 6 and find that not only do fully-coupled climate models simulate positive SESA precipitation trends that are much weaker over the historical interval, but some models persistently simulate negative precipitation trends. The same is true of two atmospheric models forced with observed historical sea surface temperatures. While future 21st-century projections yield positive ensemble mean precipitation trends that grow with increasing greenhouse-gas emissions, the mean forced response never exceeds the observed historical trend. Finally, some pre-industrial control runs occasionally simulate centennial-scale trends that fall within the observational range, but most do not. The second question I address is why climate models struggle to simulate the observed SESA precipitation trend. In an attempt to understand the model bias, I investigate one driver of SESA precipitation variability: the South American low-level jet. By developing a jet index from low-level moisture fluxes into SESA, I find that increased moisture flux through the jet accounts for 20-45% of the observed SESA precipitation trend from 1951-2020 in two reanalysis datasets. While results vary among reanalyses, both point to increased humidity as a fundamental driver of increased moisture flux and precipitation. Increased humidity within the jet is consistent with warming sea surface temperatures driven by anthropogenic forcing, although additional natural climate variations also may have played a role. The jet’s velocity also increased, further enhancing precipitation, but without a clear connection to anthropogenic forcing. These findings indicate that the SESA precipitation trend is partly attributable to jet intensification arising from both natural variability and anthropogenic forcing. In my final research chapter, I explore whether CMIP6 models simulate a realistic relationship between SESA precipitation and the jet, as well as whether inaccuracies in the characterization of the jet could explain muted trends in simulated SESA precipitation. I find that the interannual variability in the simulated jet-precipitation relationship aligns well with results from observations from 1951-2014. Interannual precipitation variability across the models is primarily dominated by the jet’s velocity. The models simulate a forced increase in humidity within the jet, consistent with observations and theory, that contributes a positive trend to SESA precipitation. Given that the models generally simulate realistic jet-precipitation relationships, I conclude that model misrepresentation of the jet is not a likely explanation for the discrepancy between simulated and observed SESA precipitation trends. Despite remaining uncertainties, my work sheds new light on our understanding of SESA precipitation variability and trends. Future work is needed to better understand the large-scale drivers of SESA precipitation outside of the jet and why climate models largely underestimate or fail to reproduce the observed precipitation trend. While Atlantic multidecadal variability is often cited as an important contributor to the SESA precipitation trend, I find austral summer forcing from the Atlantic to be ambiguous with regard to SESA precipitation and requires further analysis. Additionally, I highlight the Pacific South American mode as another contributing factor that warrants further exploration.

No description available.

Research for sustainable development is distinguished by its intended focus on socio-ecological systems, and its mandate to bring together the insights and strengths of multiple disciplines. The animal farming system is understudied in the causal inference literature, despite the increasingly apparent environmental and social costs of its industrial form. The flourishing climate-economy literature, largely motivated by impending changes in climate, rests on assumptions that limit the external validity of its findings, and thereby their relevance for the future. This dissertation sheds light on (i) factors that limit the sustainability of animal farming, and (ii) statistical assumptions that limit the relevance of findings for sustainable development, through three empirical analyses. Chapter 1 quantifies the marginal surface water pollution caused by swine feeding operations in the U.S., which suggests the sustainability of animal production requires reducing its concentration in space. Chapter 2 estimates the impacts of humid heat stress on cow milk yield, their potential alleviation through cooling technologies, and provides evidence against the common assumption of time separability of temperature effects in agricultural production. Chapter 3 shows how the standard linear regression model can generate highly misleading conclusions in the climate-conflict literature, and proposes an alternative framework for inference.

Electrical bushings are a type of hollow or solid conductor withinsulation designed to allow a conductor to pass through a conductingbarrier without making electrical contact and are very important forsafe transportation of electricity. The bushings vary in size, but allbushings have a solid or hollow conductor.This project aims to investigate which resistivities of the siliconerubber, in combination with different air conditions for the airsurrounding the bushing (dry, average and humid air) and theirrespective resistivities, to see which combinations allow for anelectrical field that allows the bushing to safely work without beingdamaged. The different air conditions are an important factor since theyall correspond to different absolute humidities present in the air,which have a direct impact on the strength of the electrical fieldsurrounding the bushing. Since this cannot be done by hand, a computersoftware called COMSOL Multiphysics will be used. COMSOL is aMultiphysics software, meaning one can simulate many types of physics atonce. With the help of this software, and a model provided by HitachiEnergy, results could be found stating that dry air overall is the bestcondition of air for the bushing, followed by average (not either dry orhumid) air and lastly humid air.

As prominent components of the Internet-of-Things (IoT) front-end, sensors capable of intelligently collecting sensing information from the surrounding environment with increasingly lower prices are required. Planar microwave chipless sensors could be a valid solution and will be the focus of this PhD research proposal. With a completely passive solution, that in its basic configuration is composed by only microstrip resonant structures and sensitive materials, this frequency-domain sensing technology results particularly adapt for the integration in smart devices. The objectives of the PhD activity will be to contribute with a further investigation of sensitive materials in the context of environmental monitoring and to test their reliability as sensitive components in controlled wired condition. The purpose is, then, to move from a wired controlled measurement to a wireless reading acquisition of the microwave sensing node response. Finally, the sensor potentialities will be further enriched by adopting fabrication techniques typical of the flexible electronics field. An inkjet printing strategy is investigated for the purpose trying to ensure good detection properties as in the case of standard fabricated tags.

No description available.

No description available.

No description available.

The goal of this work was to quantify the mechanical properties of cellulose nanocrystal (CNC)-based thin films using a polystyrene (PS) structuring approach. This structuring approach was used to biaxially wrinkle CNC-polymer and all-CNC films, in order to assess how changes in the film fabrication process affected the elastic modulus of these films. All films were prepared on pre-stressed PS substrates and structured by heating them above the glass transition temperature of PS, which caused the substrates to shrink and the films to wrinkle biaxially. CNC-polymer films were prepared using the layer-by-layer approach, where three parameters were modified to obtain films of varying compositions: 1) type of polymer (xyloglucan, XG, or polyethyleneimine, PEI), 2) polymer concentration (0.1 wt% or 1 wt%), and 3) film thickness (i.e., number of deposited bilayers). After these films were structured, their elastic moduli were calculated to be 70 ± 2 GPa for CNC-XG0.1, 72 ± 2 GPa for CNC-PEI0.1, and 32.2 ± 0.8 GPa for CNC-PEI1.0 films, indicating that the mechanical properties of CNC-polymer films changed with film composition. This structuring method was also found to provide a humidity-independent measurement of the modulus due to the irreversible nature of the wrinkling. Next, to prepare all-CNC films, CNC suspensions were evaporated under conditions designed to control the film thickness (using 0.005 wt% – 8 wt% CNC suspensions) and CNC nanoparticle orientation (chiral nematic, isotropic, or uniaxial). Suspensions were dried slowly under vacuum, quickly by heating, or by spin-coating to form films with chiral nematic, isotropic, or uniaxial (radial) CNC orientations, respectively. Following structuring, these wrinkled films showed unique morphologies that changed with nanoparticle orientation, suggesting that their mechanical properties are dependent on the CNC orientation within the films. The work presented in this thesis implies that the mechanical properties of films fabricated from hygroscopic bio-based nanomaterials can be assessed in a humidity-independent way by using the structuring method presented. Quantifying the mechanical properties of these films is critical to assess the potential applications of CNCs, where CNC-based materials may be used in developing paper-based electronics, extracellular matrix mimics, and plant cell wall mimics. / Thesis / Master of Science (MSc)

The objectives of this research were to study the gas transport properties of proton exchange membranes (PEM), namely disulfonated poly(arylene ether sulfone) (BPSH-35), post sulfonated diels-alder poly(phenylene) (SDAPP), and poly(perfluoro sulfonic acid) (Nafion). The O2 gas permeabilities were found to be lower in BPSH and SDAPP as compared to poly(perfluoro sulfonic acid) because of difference in Tg (TgBSPH= 250 oC, TgSDAPP= 330 oC versus TgNafion=150 oC). Higher Tg polymers have a more rigid, inflexible polymer segments causing a reduction in gas permeability. In comparison to SDAPP, BPSH has a lower O2 gas permeability because of the bulky side groups in the SDAPP backbone. O2 sorption measurements were carried out both under non-humidified and humidified conditions as a function of relative humidity and temperature at a normal PEM operating pressure of 1 atm. Under non-humidified conditions, BPSH, SDAPP, and Nafion 112 exhibited Henry's Law sorption, consistent with dilute dissolution of O2 into the polymer matrix. The enthalpies of sorption were calculated to determine the interaction of O2 with each membrane. The sorption enthalpies in BPSH and SDAPP increased with increasing pressure indicating the formation of more O2-O2 interactions. The enthalpies in Nafion 112 were relatively constant with increasing pressure. In the presence of moisture, the sorption behavior changed from Henry's Law to Type IV sorption behavior, which is common in hydrophilic polymers. The SDAPP membrane was found to have the highest percent wet O2 mass uptake because of a higher number of sulfonic acid groups interacting with the water/O2 system. Finally the O2 sorption for various porous catalyst powders, consisting of platinum supported on carbon was measured in the non-humidified and humidified state. The catalysts were found to have Knudsen diffusion in the non-humidified state with 20 wt% Pt-C having the largest O2 sorption. In the humidified state, the highest O2 mass uptake was achieved with 40 wt% Pt-C. These results are explained in terms of the trade-off between catalyst dispersion and catalyst size. Furthermore, O2 sorption measurements were utilized for membrane electrode assemblies containing 40 wt% Pt-C and hot pressed at 210 oC for BPSH-35 (25 and 80K) and Nafion 112 membranes. The same sorption behavior occurred in the MEAs as in the neat membrane, but at a lower capacity. This is because the electrode introduces a more tortuous path to the gas molecules permeating across the membrane. / Ph. D.