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Ex Situ And In Situ Transmission Electron Microscopy Analysis Of Bimetallic Nanocatalysts
No full textMajor industrial processes rely on heterogeneous catalysis to transform and process chemicals. In fact, many chemical reactions are accelerated with metallic nanocatalysts. The reduction of the environmental impact of the chemical industry is necessary to address today\u27s challenges. This can be only done by creating innovative nanocatalysts, requiring lower temperatures and pressures to accelerate a chemical reaction with a high yield. However, new nanostructures for heterogeneous catalysis are not always well understood, especially at the atomic scale. Additionally, catalysts are usually precious transition metals (Pt, Pd, Ru, Rh) which may benefit from being diluted into an alloyed phase with a less expensive metal to adjust the activity and selectivity of the catalyst. This leads to complex bimetallic structures, which can substantially change under reaction conditions. Understanding the structure of nanocrystals and dynamical changes in reaction conditions is crucial to guide the rational design of active, selective, and stable catalysts. To this end, transmission electron microscopy (TEM) with ex situ and in situ techniques is a valuable tool to perform diagnostics at the nanoscale. To understand changes in activity and selectivity in Au-Pd nanoparticles used for the hydrogenation of alkynes, ex situ and in situ TEM was performed to track segregation phenomena and changes of facets. The analysis of Au-Pd particles revealed segregation of Pd to the surface for systems with high Pd concentrations. Changes in facets were also observed in reductive and oxidative environments. The analysis was expanded to other bimetallic systems, namely Co-Pt and Ni-Cu systems. Ex situ and in situ TEM and X-ray absorption spectroscopy (XAS) showed dynamical changes in O2-rich and H2-rich environments at elevated temperatures, which could be linked to catalytic properties. To further investigate bimetallic particles, Cu-Ru, Cu-Rh, and Cu-Ir nanoparticles with a core-shell configuration were synthesized and studied with TEM and catalytic testing. The remarkable catalytic properties of these systems are promising for catalytic reactions involving precious metals. Finally, electron pair distribution (ePDF) function analysis was performed on the Cu-precious metals particles to gain further insight into the crystallographic properties of these alloys. The combination ex situ and in situ characterization techniques with the synthesis of novel bimetallic nanocatalysts expands the knowledge on dynamical changes in bimetallic nanocrystals and widens the tools to achieve sustainable catalysis
Essays On The Intersection Of Healthcare Operations And Economics
Get PDFThe essays in this dissertation wrestle with unique challenges presented by multiple, interacting entities within the healthcare industry. The essay, Searching for the Best Yardstick: Cost of Quality Improvements in the U.S. Hospital Industry, takes the perspective of the regulator in improving incentive programs designed to induce hospitals to invest in quality. The key challenge in evaluating potential changes to such programs is to understand the underlying incentives that hospitals have in responding to the new incentives. Using structural estimation methods, the parameters of each hospital’s decision-making process are estimated. The counterfactual analyses quantify the effects of recalibrating the Hospital Value-based Purchasing Program. The essay, The Spillover Effects of Capacity Pooling in Hospitals, focuses on the unintended effects of off-service placement, a common capacity pooling strategy. Building on previous studies that document negative first-order effects on patients who are placed off service themselves, the spillover effects onto patients who are placed on service are analyzed. The instrumental variables approach reveals that there is a significant causal impact of off-service placement on patients who are placed on service. The essay, Should We Worry About Moral Hazard? Estimation of the Slutsky Equation Using Indemnity Health Insurance Contracts, uncovers the differential response of consumers to different designs of health insurance. While previous studies have convincingly shown that ex-post moral hazard in health care does exist, there has been a lack of empirical evidence on the degree in which such moral hazard is welfare-reducing. Using a novel setting, the analysis provides evidence that moral hazard can lead to a significant welfare loss
Thinking, Seeing, Practicing Architecture: From The Smithsons To Scott Brown And Venturi
No full textThis dissertation situates the thought, vision, and design approach of Alison and Peter Smithson in relation to that of Denise Scott Brown and Robert Venturi to reveal a shared attitude toward “the real.” I argue that each couple utilized a mode of visual research that was inspired by the social sciences; each relied on straightforward photographic documentation to represent their findings; and each made similar claims to “defer judgment” and embrace reality on its own terms: “as found.” Their novel attitudes were first prompted by postwar conditions and progressed during a period when the discourse of architecture was shifting away from Modernism and toward Postmodernism. During this period there was a dissolution of Utopia and an energetic embrace of the status quo. Thus, the Smithsons and Scott Brown and Venturi adopted a method of architectural observation that tended to favor realism over utopianism and tended to look outside of the traditional academic bounds for sources of design inspiration. The question at the center of this research – what are the external forces that influence an architect’s mindset and design process? – is vital to the historiography of architecture and urban planning for all periods and styles. The specific contribution of this narrative, however, is the acknowledgement that an architect’s method of engaging and visually analyzing a site at the onset of a project affects production and determines the value of their work. Furthermore, the attitude of reserved judgement and method of sociological observation and photographic documentation outlined in this dissertation, I believe, is noteworthy and offers important lessons for present and future practitioners and students of architecture
Development Of A Ph-Sensitive Probe For In Vivo Cerenkov Imaging Of The Tumor Microenvironment
Get PDFAcidity in the tumor microenvironment (TME) is related to invasion, metastasis, and chemotherapeutic resistance, all of which are contributors to poor prognoses in cancer patients. In this thesis, we propose the application of Cerenkov radiation as a tool for imaging pH in vivo through the measurement of Selective Bandwidth Quenching (SBQ) and Cerenkov Radiation Energy Transfer (CRET) in triple negative human breast cancer models MDA-MB-231 and 4175-Luc+. To test the hypothesis that SBQ and CRET signals could provide measurements of TME pH in vivo, a Cerenkov-active molecule, NFbD, was conjugated and chelated with 68Ga. Cerenkov imaging was performed with NFbD-Ga in vitro to construct pH titration curves, later used to interpolate in vivo Cerenkov pH values. In vivo Cerenkov imaging was performed on athymic nude mice bearing 4175-Luc+ triple negative breast cancer xenografts after intratumoral injections of NFbD-Ga (40 μCi). CRET values obtained from in vivo Cerenkov imaging were used to estimate TME pH values, which were validated by 31P Magnetic Resonance Spectroscopy (31P MRS) following i.p. injection of 3-APP. Tissue scattering, and absorption effects were evaluated in vitro with tissue phantoms. NFbD maintained its pH-sensitivity after conjugation (pKa= 7.8, λex= 599 nm, λem= 669 nm at pH 9). SBQ and CRET were observed in vitro inter-and intramolecularly, at 600 nm and 700 nm, respectively. SBQ and CRET were also observed in vivo. CRET measurements following intratumoral injections of NFbD-Ga yielded a tumor pHCerenkov= 6.90 ± 0.16, 31P-MRS on the same tumors yielded a pHMRS= 6.92 ± 0.04. Chicken tissue phantoms provided insight on tissue attenuation effects, showing that 1 mm of tissue can attenuate 64% of the Cerenkov signal, in the absence of naphthofluorescein and further attenuation to 17% is achieved with the addition of naphthofluorescein. The synthesis and development of this Cerenkov-active, pH sensitive probe for the determination of TME pH provided detectable CRET signals in vivo, allowing Cerenkov to be used as a potential technique for non-invasive pH imaging
Penn Library\u27s LJS 417 - [Books III-V of al-Qānūn fī al-ṭibb]. (Video Orientation)
No full texthttps://repository.upenn.edu/sims_video/1167/thumbnail.jp
Penn Library\u27s LJS 420 - [Perpetual calendar with Metonic cycle]. (Video Orientation)
No full texthttps://repository.upenn.edu/sims_video/1168/thumbnail.jp
Penn Library\u27s LJS 422 - [Haft paykar]. = [هفت پيکر]. (Video Orientation)
No full texthttps://repository.upenn.edu/sims_video/1170/thumbnail.jp
Penn Library\u27s LJS 429 - Natural Philosophy (Video Orientation)
No full texthttps://repository.upenn.edu/sims_video/1176/thumbnail.jp
A House’s Speech Divided: Novel Applications of Text-As-Data for the Study of Elite Polarization in the U.S. House of Representatives (1983-2016)
No full textCurrent models of elite polarization imply that the behaviors and ideologies of Democrats and Republicans have become increasingly distinct. The congressional roll-call voting record is the most relied-on indicator of congressional polarization, however, voting behavior is limited in its scope, ability to provide deeper insights into the nature of elite polarization, and can be affected by external non-ideological factors. This dissertation leverages the richness of the congressional record and introduces a flexible computational method, the dynamic topic model, to study three unique but related indicators of political polarization across three decades of debate from the floor of the House of Representatives (1983-2016). Using the output of the dynamic topic mode – and through the lens of political communication – this dissertation reveals patterns of increasing polarization in not only what Democrats and Republicans talk about, but also how political issues are discussed. Furthermore, this dissertation interrogates elite ideologies through belief network analysis and finds that the networks of political beliefs held by Democrats and Republicans have not significantly diverged since 1983. This dissertation introduces a novel approach to the study of political polarization in Congress and provides three applied use-cases for studying political polarization through text-as-data and relevant quantities to political communication
Investigation of Metabolism and Autism-Relevant Behaviors in Drosophila Lacking Neurexin-1
No full textAutism is a neurodevelopmental condition that is highly heterogeneous in its clinical presentation. In addition to differences in social interaction and communication, and the presence of restrictive, repetitive behaviors, metabolic dysfunction is becoming more widely known and studied as a co-occurring condition seen in autistic individuals. However, the etiology of these metabolic alterations in autism remains unclear. Here, we utilized a combination of metabolomic, physiological, and behavioral assays to investigate how disruption of the autism-risk gene, neurexin-1, influences energy metabolism and associated behaviors in Drosophila melanogaster. These analyses revealed that Drosophila lacking neurexin-1 expression exhibit decreased resistance to environmental stressors, specifically starvation stress and heat stress. These findings lead us to consider whether the neurexin-1 mutant flies have an altered metabolic status, thus we performed metabolomics and complementary colorimetric assays and found that these flies have a distinct metabolic profile, with decreased lipid and carbohydrate stores. Moreover, neurexin-1-null Drosophila exhibit decreased levels of NAD+, an important cofactor in many energy production pathways. Interestingly, loss of neurexin-1 also results in disruptions in mitochondrial morphology in Drosophila flight muscle, in addition to decreased flight ability. Finally, we observed mechanically-induced seizure like activity in the neurexin-1 mutant flies, which closely mimics clinical data wherein patients with deletions in Neurexin-1 experience seizures. Together, these findings point to a novel role for neurexin-1 in the regulation of energy metabolism and autism-related behavioral phenotypes in Drosophila, in addition to providing a foundation for further investigation into the etiology of metabolic dysfunction and seizures in autism