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Fabrication and Microstructural Analysis of Metallic Nanoporous Foams for Particulate Filtration
No full textPh.D.Advances in nanofabrication and characterization have demonstrated a wide range of incredibly useful techniques and applications that are transformative to many scientific fields and industries. Additionally, as the COVID-19 pandemic has shown, there is an urgent need for innovation in the field of air filtration to create a smart filter that can be optimized to protect against specific hazards on a case-by-case basis, effectively filter contagious pathogens, and be effectively reused and recycled at the end of its useful lifetime. In this dissertation I will discuss several common nanofabrication techniques, characterization methods, and filtration approaches, and how they can all come together to allow fabrication and study of metallic foams for the purpose of air filtration. Metallic nanowires are grown inside anodized aluminum oxide (AAO) templates through electrodeposition, and then separated into a suspension through a selective etching process. The metallic foams are then fabricated through a freeze-drying process and strengthened using a combination of sintering and electroplating. Relevant nanofabrication techniques, such as sputtering, electrodeposition with nanowire template molds and plating additives are discussed.
Common nanofabrication characterization techniques are used to study the properties of the foam. Characterization techniques covered include scanning electron microscopy (SEM) to measure nanowire and foam dimensions, as well as to study foam morphology and nanogranule growth. Rheometry was used to study the strength evolution of the foam under various growth parameters, including how those parameters influence the evolution of the Young’s modulus and yield strength. Also discussed are the Brunauer–Emmett–Teller theory (BET), the use of isotherms, and how they are used to measure the surface area of nanoporous materials.
Additionally, air filtration mechanisms and common air filtration characterization techniques and how they are used with metallic foams are discussed. This includes pressure drop measurements, qualitative efficiency measurements using smoke tests, and quantitative efficiency measurements using air particle counters. It was found that copper metallic foams can reach an air filtration efficiency of over 99% for the hardest-to-capture 0.3 μm particle size range while having a breathability comparable to an N-95 respirator. Finally, microstructure analysis is performed on the foam to determine what role various characteristics play in the foam in terms of its breathability and particle capture efficiency. Air filtration theory is employed to study what role the nanowire diameter, nanowire density, nanogranule growths, and surface area have for improving capture efficiency and breathability. It was found that nanowire diameter plays a crucial role in determining capture efficiency and breathability in metallic foams, and that deposited nanogranules on the nanowire surface can improve filtration quality substantially
Briggs on Hill, Your Face Belongs to Us
No full textReview: Hill, Kashmir. (2023). Your face belongs to us: The secretive start-up on a mission to end privacy. Simon & Schuster UK Ltd. $28.99. ISBN: 978-0-593-44856-
Contributions to Parametric and Semiparametric Structural Equation Modeling Methods with Applications in the Biomedical Sciences
No full textPh.D.This research work commences by discussing two commonly used fit indices: root mean squared error of approximation (RMSEA) and goodness-of-fit index (GFI), which are employed to assess the goodness of fit of model to the data. Chi-square distribution in the traditional RMSEA may vary with different estimation methods or types of data, leading to inaccurate RMSEA values, therefore, we propose an alternative RMSEA that is not sensitive to changes in degrees of freedom. Furthermore, the traditional GFI tends to underperform on dichotomous data, particularly with small sample sizes. The method to mitigate the effect of a mis-specified fit function in the real world is integrated with a modified version of the GFI, namely, the corrected GFI (CGFI). A simulation study is employed to compare the performance of improved RMSEA and GFI with the previously modified RMSEA and GFI, respectively. Furthermore, as there is no previous research considering the non-linear relationship between confounding variables, manifest variables, and latent variables, the proposed SSEM introduces nonparametric link functions, assumed to be monotone/non-monotone, to classical SEM instead of constructing a mixture multivariate model based on latent variables. Four types of regressions are used to predict the functional forms in the simulation study. Two metabolic syndrome datasets are used to demonstrate the application of the methods
Does Police Violence Pay: The Effect of Police Salary on Use of Force Complaints
No full textM.P.P.DOES POLICE VIOLENCE PAY: THE EFFECT OF POLICE SALARY ON USE OF FORCE COMPLAINTSMarta Alicja Hubbard, B.S.Thesis Advisor: Zeynal Karaca, Ph.D.ABSTRACTThe year 2020 became infamous for many reasons. One of them being the murder of George Floyd by police in Minneapolis, Minnesota. This event caused a wave of outrage worldwide, leading to protests and calls for change. While the murder of George Floyd is far from the first time that police have killed an unarmed civilian nor the first time that such an event led to widespread protesting, a new narrative reached the public at large because of his murder: a call to defund the police. The current literature focuses broadly on how police funding may affect use of force and the crime rate. This thesis tries to answer a subset of these questions: does police salary affect the number of Use of Force complaints that police departments receive? Using the 2020 data from Law Enforcement Management and Administration Statistics, National Incident Based Reporting System, and Social Determinant of Health data from the Agency for Healthcare Research and Quality, we did not find a statistically significant association between the police salary and the number of use of force complaints for any of the 3 salary levels tested
Language Ideological Debates 2.0: Granular Features and the Trouble with ‘Qatar’ and ‘Latinx’
No full textPh.D.Much of what people know about language is bound up in ideological representations. Language ideologies entail beliefs about “languages, speakers, and discursive practices” (Irvine 2012) that structure language and society (van Dijk 2006). Blommaert (1999) proposed that language ideologies can be retraced through time as the product of language ideological debates, moments of struggle for “authoritative entextualization” in which people debate aspects of meaning, correctness, and legitimacy, especially within national contexts. In this dissertation, I expand Blommaert’s (1999) framework by applying it to debates that unfold in social and digital media about (1) the “correct” pronunciation of ‘Qatar,’ and (2) the meaning and legitimacy of ‘Latinx.’ In the case of ‘Qatar,’ I analyze a comment section of an article published by The New York Times about the pronunciation of ‘Qatar’ by conducting a frame analysis (Goffman 1974) of three types of comments that emerge: metalinguistic commentary about pronunciation, language play related to ‘Qatar’ and , and redirection of the question to broader sociopolitical factors. In the case of ‘Latinx,’ I analyze a variety of comments and commentary from social/digital media, focusing on three frames of comments: questions of use and metalinguistic commentary, folk linguistic understandings and language play, and debates about meaning.
Throughout, I demonstrate that online comment sections reflect structured and coherent language ideologies: debates about ‘Qatar’ and ‘Latinx’ are ways of working through problems at the nexus of language and society and the “trouble” the words reveal is as social as it is linguistic. I highlight the role that and as “problematic” segments play in indexing linguistic and social problems, showing that even small letters carry heavy ideological weight. I also argue that “correctness” and “standardness” often implicate matters of decorum and aesthetics rather than grammaticality per se. My central findings are that (a) language ideological debates, beyond structuring ideologies, profoundly affect the meanings of the words and languages they target; part of the meaning of ‘Qatar’ and ‘Latinx’ is that they are “up for debate” and (b) “small” segments play an outsized yet often overlooked role in language ideological debates
Land Value Taxation’s Impact on Housing Supply Within the State of Pennsylvania
No full textM.P.P.The last two decades have seen a widening housing supply shortage across the United States. The poorest Americans can barely afford rent and basic necessities, and hundreds of thousands of Americans experience homelessness. The crisis in part stems from a housing market that incentivizes developers to keep housing unit supply lower for higher profits. To combat development issues, 14 municipalities in Pennsylvania employ a land value tax, or a tax based upon the value of land rather than the building that sits upon the land (also known as a building or property tax). In theory, this tax scheme incentivizes property development while disincentivizing landowners from maintaining empty plots. Therefore, the impacts of a land value tax should increase housing supply and mitigate the current housing shortage. I use Pennsylvania municipality-level data from 2010 to 2021 to measure the relationship between land value tax policy implementation and housing supply. This study expands on previous work because of the recent data improvements on housing statistics from the US Census Bureau and by specifically examining housing supply itself rather than land or property values. My analysis finds a strong, positive relationship between the presence of a land value tax policy and the total housing units of a municipality
Oil in Bahia: From Early Cretaceous to the Anthropocene
No full textPh.D.This is an environmental history of the first oil fields in Brazil, located around the Bay of All Saints, in the Recôncavo Baiano. The search for oil entails many layers of history, coming
together through human action. In this dissertation each of these layers is a chapter. The first
layer is geological. It involves the massive timescales of geology, going back 145 million years
to uncover oil’s own history. In a different timescale, the second layer is the ecology of the
Recôncavo Baiano. It went from lush Atlantic Forest, to sprawling sugar cane plantations over
the course of three hundred years, with the help of several human and non-human actors. The
third layer of the story is humans transforming the landscape after finding oil. Humans pierced
through hundreds of meters of accumulated matter looking for oil around the Bay of All Saints,
turning it into petroscapes. Humans finding oil were essential in this story - but we were not
alone. Accompanying humans was the ‘portmanteau biota’ of pathogens that infected people in
and around the fields. They form the fourth layer. Finally, the fifth is the materiality layer. It is
the very world we created using oil. Having struck oil in 1939, Brazil was on the cusp of the
Great Acceleration. This is by no means merely background to this story. The search for fossil
fuels was driven by global movements of capitalism and industrialization. What happened to
specific people and environments involved in such global movements brings the focus to a local
scale. Framing it in the context of the Anthropocene, takes it back to a planetary scale. The Bay
of All Saints took shape during the opening of the South Atlantic Ocean, its rift movement
allowing for the perfect geological conditions to form and accumulate oil over 145 million years.
Today, its inner beaches are lined with massive petrochemical infrastructure of fields, refineries,
ports, pipelines, storage tanks and spheres. This is a short narrative of that long and layered
story
Veterans Interest Newsletter Issue 65
No full textTopics include a report from the Institute for Defense Analysis on extremism in the military that debunks the perception that more extremists exist in the military than in the general population, an update on the Department of Veterans Affairs (VA) programs to address homelessness among the veteran population, the propensity for women veterans in the VA's homeless programs to struggle with military sexual trauma, the pioneering work being done by the VA to delivery virtual medical services to the veterans enrolled in their program, veterans disability benefits being targeted by scammers, challenges facing U.S. allies left in Afghanistan including slow visa processing and reprisal killings by the Taliban, the reopening of the Voluntary Retired Return to Service Program by the Air Force to fill as many as 1000 mid-career commissioned and enlisted jobs currently available, and an excerpt from the 1842 poem “Horatio,” by Thomas Babington McCauley which tells the story of Horatius Cocles and his fellow soldiers focusing on themes of bravery, sacrifice and loyalty. Also includes statistics from the Department of Defense on military recruiting numbers from fiscal year 2022-2023