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Who Has the Creator Named
No full textWho Has the Creator Named is a meditation, a thoughtful dialogue between a middle-aged woman and her younger self. An exploration of Black faith and all faith and a God who has His favorites. Zenique Gardner Perry writes deftly about family, race and faith in this series of personal essays that explores her own journey with spirituality and the gods of her ancestors
Top-down Control and Bottom-up Salience Guide Attention During Visual Search
No full textWe search the visual world using different strategies, some of them relying on bottom-up salience, others on top-down expectations. However, little is known about how we arbitrate between them. Here, we report a study investigating whether people are sensitive to environmental regularities that incentivize different strategies with differential effort requirements. To test this, we used a visual search task in which people need to search a target in a field of items, each of which is printed in one of two colors. This task allows us to parametrically manipulate bottom-up salience by varying the number of items with the less numerous (“minority”) color, and top-down expectations by adjusting the probability that the target is contained in the set with the minority color. We found that even though people’s attention tended to be captured by the group of items with the minority color, they used environmental regularities to adapt their strategy to improve search efficiency. Interestingly, we found that people could only be biased away from their natural inclination to be captured by salient information if the task promotes serial visual search, suggesting an asymmetry in how top-down expectations can modulate bottom-up tendencies
Design of Hydrogen Powered High Altitude Canard-Wing Aircraft for Aerosol Injection into the Stratosphere
No full textThis paper presents the conceptual design and preliminary performance assessment of a hydrogen-powered, high-altitude canard-wing aircraft intended for stratospheric aerosol injection missions. The aircraft is designed to deliver a 50,000 lb aerosol payload at 65,000 ft while sustaining cruise for approximately 3.5 hours. Liquid hydrogen propulsion is employed to eliminate carbon dioxide emissions, minimizing the aircraft\u27s environmental footprint and enhancing the climate impact of the stratospheric aerosol injection mission. An iterative design process using established aircraft sizing methods and RDSwin was conducted to refine the geometry, propulsion, weights, aerodynamics, stability, and mission capabilities of this aircraft. The final configuration features a swept canard-wing layout with high-aspect-ratio lifting surfaces, winglets, and ten hydrogen-fueled turbofan engines derived from the GE F118 baseline. Mission analysis indicates sustained cruise at Mach 0.84 and 65,000 ft for 210 minutes, with a takeoff gross weight of approximately 220,800 lb and a cruise lift-to-drag ratio near 20. While operating close to its performance ceiling, this aircraft satisfies the primary mission requirements, demonstrating the feasibility of hydrogen-powered canard-wing aircraft for high-altitude aerosol delivery
Design of an FSAE Muffler
No full textTo compete in the dynamic events at the the Formula SAE IC competition, each vehicle must undergo a rigorous technical inspection. One element of the inspection is the Noise Test, which states that each car must be quieter than 103 dBc when idling and less than 110 dBc at the engine redline. Over the past few years, WashU Racing has used off-the-shelf mufflers with a guess and check system to find muffler combinations that satisfy the noise requirement. The results of that method have yielded either heavy and performance damaging muffler configurations or mufflers that have failed to meet the sound requirement. Historically, they have struggled to be below the redline noise threshold.
The study detailed in this paper aims to design a custom muffler for WashU Racing to meet the Noise Test requirement while minimizing both weight and performance loss. Specifically, the muffler aimed to target the redline RPM, 11000. First, physical testing was performed to figure out which sound wave frequencies created the largest dBc peaks. Then, using Gamma Technologies\u27 GT Suite software including GT Power, GEM3d, and GT Post, mufflers were iterated on to target the sound wave frequencies producing the greatest noise.%\u3c --this sentence could be improved
The C-Weighted Total Pulsation SPL was used to measure the sound output. Muffler perforation holes were also studied to determine the optimal number of holes and the optimal hole size. The final design yielded a 16 inch long muffler with a 12 inch shell, two J-Pipe resonators, and perforations along the inner tube. The expected sound output of the vehicle at redline is 96.55 dBc, which will allow WashU Racing to pass the Noise Test
Is Public Website Design an Administrative Burden? The Case of SNAP
No full textHow do websites for public-benefit programs affect access to benefits?
This brief examines the state websites for the Supplemental Nutrition Assistance Program (SNAP), investigating whether there is a relationship between site design and experience of administrative burdens in SNAP. The authors examine page design using Google’s Lighthouse service and draw upon data from the Workforce Economic Inclusion and Mobility Survey of a nationally representative sample of 2,511 low-wage U.S. workers to examine administrative burdens in SNAP. Data from the U.S. Department of Agriculture are used to investigate the relationship between SNAP page design and SNAP quality-control measures. The finding suggest that improvements to main-page accessibility can reduce some administrative burdens
MEMS 4110: Improving Restaurant Efficiency: Automatic Egg Peeler
No full textNeon Greens is a salad restaurant in St. Louis, MO that focuses on serving fresh, locally sourced ingredients. One of their signature menu items includes soft and hard-boiled eggs, which are used in large quantities every day. Currently, these eggs are peeled by hand, which can be slow, inconsistent, and difficult to keep up with during busy hours. Because of this, Neon Greens needs a faster and more reliable way to peel eggs without increasing labor. Our project aims to design a device that can peel eggs automatically, reduce prep time, and stay safe and easy to clean in a commercial kitchen
Selenium Removal by Iron Electrocoagulation: Effects of Water Chemistry, Operating Conditions, and Post-treatment Processes
No full textSelenium (Se) contamination poses significant risks to aquatic ecosystems and human health, particularly in waters affected by mining operations, coal-fired power plants, and agricultural drainage. While Se is an essential trace element, elevated concentrations can cause reproductive failure in fish and birds and neurological abnormalities in humans. Se predominantly exists in four oxidation states (+VI, +IV, 0, and -II) in the environment, with Se(VI) (i.e., SeO42-) and Se(IV) (i.e., HSeO3- and SeO32-) being the dominant species in most contaminated waters. Se(VI) is highly soluble and exhibits limited adsorption affinity to mineral surfaces, making it challenging to remove in water treatment. Se(IV) is of particular environmental concern due to its greater toxicity compared to Se(VI). Despite its high reactivity and stronger affinity for adsorbents such as iron and manganese oxyhydroxides, Se(IV) still poses significant challenges in water treatment, especially in achieving concentrations below regulatory limits. Iron electrocoagulation (EC) is a promising treatment technique as it generates reactive Fe(II)/Fe(III) solids that serve as both adsorbents and reductants for Se removal. This work investigates the mechanisms governing Se(VI) and Se(IV) removal during iron EC under environmentally relevant conditions. Specifically, a series of batch experiments were conducted to determine Se removal rates and extents as a function of water chemistry and operational conditions. In addition, the temporal dynamics of dissolved Se during and after EC treatment were investigated, and the comparative performance of EC and chemical coagulation was examined. In simple aqueous systems, Se(VI) removal exhibited distinct pathways under oxic and anoxic conditions, with the removal extents being significantly affected by pH. Under oxic conditions, Se(VI) removal was dominated by adsorption onto Fe(III) (oxy)hydroxides, with enhanced performance at acidic pH. Under anoxic conditions, Se(VI) removal proceeded by chemical reduction on mixed-valence iron-containing solids, achieving better removal at neutral to alkaline pH. Higher ionic strength decreased Se(VI) removal rates and extents by altering surface potential profiles and decreasing the activity of SeO42- ion. Se(VI) removal rates and extents increased with increasing charge loading rates due to faster Fe(II) dosage rate. A reaction-based model was developed for Se(VI) removal under oxic conditions, enabling performance prediction and system optimization. In complex aqueous matrices, the effects of co-occurring constituents such as sulfate, nitrate, bicarbonate, and natural organic matter (NOM) on Se(VI) removal were investigated under both oxic and anoxic conditions. These constituents affect not only the availability of adsorption sites but also the mineralogy and reactivity of iron-containing solids essential for Se removal from water. Under oxic conditions, sulfate decreased Se(VI) removal rates and extents through competitive adsorption. Under anoxic conditions, sulfate and bicarbonate suppressed Se(VI) removal by favoring the formation of less reactive forms of green rust (GR-SO4 and GR-CO3) over chloride green rust (GR-Cl) and magnetite. Nitrate had minimal effects under oxic conditions but inhibited Se(VI) removal under anoxic conditions by acting as a competing electron acceptor. NOM had negligible effects under oxic conditions but decreased Se(VI) removal rates under anoxic conditions due to competitive adsorption. Iron EC performance for Se removal was further evaluated in two synthetic challenge waters (representing mining and agricultural sectors) and one real flue gas desulfurization (FGD). Se(VI) removal was limited in all three challenge waters (\u3c15%), confirming that the presence of co-occurring solutes substantially limited treatment efficiency. A pretreatment strategy for sulfate removal substantially improved Se(VI) removal from mining water (achieving 80% removal) but offered limited benefit for the agricultural and FGD waters, where additional factors such as high ionic strength and bicarbonate concentration likely limited performance. The temporal dynamics of Se following EC treatment demonstrated distinct behaviors under oxic and anoxic conditions, driven by differences in removal mechanisms and solid-phase transformations. Under oxic conditions, Se removal occurred through instantaneous adsorption onto Fe(III) (oxy)hydroxides, with removal extent determined entirely by iron dose. Under anoxic conditions, Se removal proceeded through rapid adsorption followed by slow reduction on mixed-valence solids such as chloride green rust and magnetite. A transient release was observed at lower iron dose (≤ 31 mg/L) due to the transformation of chloride green rust to magnetite and the limited capacity of the resulting solids to retain Se. In contrast, higher iron doses (≥ 78 mg/L) enabled sustained Se immobilization after treatment due to the enhanced magnetite formation, which facilitated both adsorption and reduction of Se species. While Se(IV) and Se(VI) exhibited similar removal mechanisms via iron EC, Se(IV) achieved faster kinetics and greater removal extents than Se(VI) at the same pH values under both oxic and anoxic conditions. Under anoxic conditions, both Se(VI) and Se(IV) removal proceeded through chemical reduction on mixed-valence iron-containing solids. The faster removal of Se(IV) suggested that the reduction of Se(VI) to Se(IV) was the rate-limiting step in the EC treatment process for Se(VI) removal. Under oxic conditions, both Se(VI) and Se(IV) removal were governed by adsorption onto Fe(III)(oxy)hydroxides, with Se(IV) achieving greater removal for a given amount of iron solids. This was due to the stronger adsorption affinity of Se(IV) compared to Se(VI). Sulfate had only minor effects on Se(IV) removal even at concentrations up to 500 mg/L, while Se(VI) removal was substantially inhibited under the same conditions, indicating the stronger binding affinity of Se(IV) compared to Se(VI) to iron-containing solids. Toxicity characteristic leaching procedure tests confirmed that Se remained largely immobilized in the solid phase, with aqueous concentrations well below regulatory limits. Compared to chemical coagulation, EC provides several mechanistic and operational advantages for Se (both Se(VI) and Se(IV)) removal. These include higher localized pH near the cathode, in situ coagulant generation, and precise control of iron dosage through current application. EC outperformed Fe(II) chemical coagulation for Se removal at pH 4 under oxic conditions, while chemical Fe(III) addition resulted in faster Se(IV) removal than EC due to more immediate Fe(III) solids formation. Under anoxic conditions at pH 8, Se removal performance was similar between EC and Fe(II) chemical coagulation due to similar iron dosage rates. Collectively, these findings advance mechanistic understanding of Se behavior during and after EC and demonstrate its potential as a flexible and effective treatment technology for Se-laden waters across diverse environmental contexts
Mechanisms of Antibody-Mediated Protection in Severe Acute Respiratory Syndrome Coronavirus 2 Infection
No full textABSTRACT OF THE DISSERTATION Mechanisms of Antibody-Mediated Protection in Severe Acute Respiratory Syndrome Coronavirus 2 Infection by Samantha Rae Mackin Doctor of Philosophy in Biology and Biomedical Sciences Immunology Washington University in St. Louis, 2025 Professor Michael S. Diamond, Chair Coronaviruses (CoVs) are enveloped, non-segmented, positive-sense RNA viruses belonging to the Coronaviridae family. The subfamily Coronavirinae includes four genera: alpha-, beta-, gamma-, and deltacoronaviruses. While gamma- and deltacoronaviruses primarily circulate in wild or domestic birds and have shown the potential for cross-species transmission, alpha- and betacoronaviruses mainly infect mammals, resulting in respiratory illnesses that can be mild or severe. Over the past 25 years, two epidemic CoVs have emerged in humans: severe acute respiratory syndrome (SARS)-CoV in 2002 and Middle East respiratory syndrome (MERS)-CoV in 2012, respectively. SARS-CoV, first detected in Guangdong Province, China, triggered an outbreak of viral pneumonia that quickly spread to 29 countries, infecting over 8,000 individuals and resulting in a 10% fatality rate. The virus was believed to have originated in bats and was transmitted to humans via wild game. MERS-CoV was first identified in Saudi Arabia, responsible for another outbreak of viral pneumonia that spread to 27 countries. Approximately 2,500 people were infected with a fatality rate of 35%. Transmission to humans primarily occurred through contact with dromedary camels. The zoonotic origins of SARS-CoV and MERS-CoV demonstrate the potential threat of coronaviruses for subsequent spillover infections to humans with epidemic or pandemic potential. At the end of 2019, a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged in Wuhan, China, likely originating from a spillover event involving animals and humans in a market setting. Infection with SARS-CoV-2 causes coronavirus disease 2019 (COVID-19), which has led to approximately 778 million recorded infections and 6.8 million deaths globally. In response, vaccines were rapidly developed and deployed, significantly reducing symptomatic infections, hospitalizations, and mortality. SARS-CoV-2 vaccines all have targeted the viral spike protein derived from strains that circulated in early 2020. However, the continuing evolution of SARS-CoV-2 has jeopardized the immunity generated by these vaccines and the control of virus infection and transmission. Emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants with antigenic changes in the spike protein are neutralized less efficiently by serum antibodies elicited by legacy vaccines against the ancestral Wuhan-1 virus. Nonetheless, these vaccines, including mRNA-1273 and BNT162b2, retained their ability to protect against severe disease and death, suggesting that other aspects of immunity control infection in the lung. Vaccine-elicited antibodies can bind Fc gamma receptors (FcγRs) and mediate effector functions against SARS-CoV-2 variants, and this property correlates with improved clinical coronavirus disease 2019 outcome. However, a causal relationship between Fc effector functions and vaccine-mediated protection against infection has not been established. In our studies, using passive and active immunization approaches in wild-type and FcγR-knockout mice, we determined the requirement for Fc effector functions to control SARS-CoV-2 infection. The antiviral activity of passively transferred immune serum was lost against multiple SARS-CoV-2 strains in mice lacking expression of activating FcγRs, especially murine FcγR III (CD16), or depleted of alveolar macrophages. After immunization with the pre-clinical mRNA-1273 vaccine, control of Omicron BA.5 infection in the respiratory tract also was lost in mice lacking FcγR III. Our passive and active immunization studies in mice suggest that Fc–FcγR engagement and alveolar macrophages are required for vaccine-induced antibody-mediated protection against infection by antigenically changed SARS-CoV-2 variants, including Omicron strains. Over the course of the SARS-CoV-2 pandemic, many monoclonal antibodies (mAbs) that neutralized infection against early strains also experienced reduced neutralization potency against Omicron variants due to the large number of mutations in the receptor binding domain of the spike protein. Nonetheless, some antibodies, including S309, the parent antibody of Sotrovimab, retained protective capacity in animals due to Fc effector function activity. In our experiments, using humanized Fc receptor transgenic mice and genetically modified antibodies, we identify an Fc variant of human S309 that confers optimal protection against SARS-CoV-2. We demonstrate that introducing the G236A (GA) mutation and afucosylation (AFUC) to S309 increases binding to Fc receptors IIA and IIIA, respectively, resulting in enhanced virologic protection in the airways of transgenic mice challenged with SARS-CoV-2 B.1.351. We also identify CCR2+-expressing cells as important mediators of this protection. Furthermore, using MA30, a mouse-adapted strain of SARS-CoV-2, we demonstrate that S309-GA-AFUC improved clinical outcomes, reducing lung pathology and restoring pulmonary function more effectively than the parental S309 antibody. Overall, this work contributes to the characterization and optimization of vaccines and antibody-mediated therapies in murine models of virus pathogenesis. These findings support the critical role of Fc effector functions in antibody-mediated protection against SARS-CoV-2, providing mechanistic insight for the design of future vaccines and therapeutic antibodies
Effects of Mechanical Anisotropy on Physiology and Pathology of iPSC-Derived Engineered Heart Tissue Models of Healthy and Diseased Myocardium
No full textABSTRACT OF THE DISSERTATION Effects of Mechanical Anisotropy on Physiology and Pathology of iPSC-Derived Engineered Heart Tissue Models of Healthy and Diseased Myocardium by Ghiska Ramahdita Doctor of Philosophy in Mechanical Engineering Washington University in St. Louis, 2025 Professor Nathaniel Huebsch, Chair Professor Guy Genin, Co-Chair Heart disease progression is characterized by changes in cardiomyocytes as well as significant cardiac fibrosis. This dissertation is motivated by the premise that mechanical forces on cardiomyocytes and fibroblasts may play a key role in the fibrotic response of the heart. Given that heart fibers are uniaxially aligned, the force is distributed anisotropically during the cycle of systolic contraction. However, there is a significant gap in our understanding of the impact that tensional anisotropy has on the physiology of cardiac cells and the processes of fibrosis. This dissertation addresses the gap by developing a medium throughput micro-engineered tissue platforms to study how tensional anisotropy affects fibroblasts and iPSC-derived cardiomyocytes. Using this platform, I found that tensional anisotropy has a significant effect on fibroblast morphology, alignment and transition toward a myofibroblast state. In addition, these processes were further accelerated by increased cell density. In cardiac micro-tissues, high tensional anisotropy promoted cellular alignment, uniaxial contractility, and electrophysiological maturation. Notably, improved action potential dynamics were linked to increased expression of the voltage-gated sodium channel Nav1.5 in tissues with tensional anisotropy. These results highlighted the critical role of mechanical anisotropy in affecting both physiological and pathological responses in engineered cardiac tissues. Incorporating anisotropic cues into in vitro heart models not only improves their physiological relevance but also opens a new way for designing regenerative therapies, such as cardiac patches for myocardial infarction. This work advances our understanding of cardiac mechanobiology and offers new directions for modeling and treating heart disease