Understanding lubrication mechanisms in Engineered Al2O3-B2O3 Composites

Technology advancements in aerospace, nuclear, marine, and other endeavors heighten the need for more capable self-lubricating and wear-resistant materials. Ceramics have the potential to satisfy such extreme environment application challenges but require improvements in friction and wear properties. Alumina (Al2O3) is a widely used ceramic material that is available in abundance and demonstrates a combination of properties, such as high melting point, hardness, and corrosion resistance. However, the friction and wear properties of alumina limit its tribological applications. A common practice to improve the tribological properties of alumina is by reinforcing materials to form composites. Based on thermodynamic considerations, in the present work, boron oxide (B2O3) was added to Al2O3 matrix to form a double oxide system, i.e., aluminum borate (9Al2O3.2B2O3). Four methods for enhancing the lubrication mechanisms have been developed and investigated for the Al2O3-B2O3 composite. First, the lubrication behavior of Al2O3-B2O3 composite was evaluated in terms of friction and wear. The formation of double oxide (aluminum borate) led to improved wear resistance with a deteriorated coefficient of friction compared to porous alumina. Also, the formation of aluminum borate during sintering generated porosity in the Al2O3-B2O3 composite. One of the methods to reduce the porosity in the Al2O3-B2O3 composite is the incorporation of sintering additives. In this work, CuO and CaO were selected as sintering additive due to their preferential reactivity of Al2O3 and B2O3, respectively in the matrix. Although adding CuO/CaO improved the density and further improved wear resistance of the composites, the manufactured composite adversely affected the COF again, particularly with CaO addition. The observed friction and wear behavior of CuO/CaO incorporated Al2O3-B2O3 composites are discussed by combining the crystal-chemical approach and polarization theory for the multi-oxide systems. Due to the adverse effect of CaO addition on COF, a new method has been adapted by embedding the solid lubricants in the Al2O3-B2O3-CaO matrix to reduce friction. This work chose hBN as secondary reinforcement additive to the composite due to its chemical suitability. The dispersion of hBN in the Al2O3-B2O3-CaO matrix led to less diffused microstructure, resulting in smaller sintered particles. During sliding, smaller sintered particles were smeared with embedded hBN solid lubricant that enhanced the lubricating properties by reducing COF with an increase in wear rate. The amount hBN in the composite can be engineered to achieve optimum friction and wear. To further enhance the lubricating properties of the Al2O3-B2O3 composite, B2O3 coating on the Al2O3-B2O3 composites were made through laser processing to avoid the reaction between B2O3 coating with Al2O3-B2O3 substrate. The B2O3 was chosen as a coating because it reacts with moisture to form boric acid phase, which is a solid lubricant. The rapid heating and cooling during laser processing led to the formation of amorphous B2O3 and boric acid phases (H3BO3/HBO2). The amount of B2O3 phases was controlled by using different laser powers. The amount of amorphous B2O3 was quantified using the crystallinity index. The formation of amorphous B2O3 coating was advantageous to reduce COF while retaining a lower wear rate because it can instantaneously react with moisture to form a boric acid phase.The last method to enhance the lubrication performance involves the utilization of in-situ formed pores in the Al2O3-B2O3 composite that formed during sintering to capture liquid lubricants. A new class of liquid lubricants, ionic liquids (IL), were selected due to their superior tribological performance. The lubrication performance of the ILs impregnated Al2O3-B2O3 composites were tested at four different temperatures and sliding velocities. The lubrication mechanism for this study was observed to be a function of thermal expansion of stored liquid lubricants and their viscosity. The results revealed that the thermal expansion of liquid lubricant, either by frictional heat or external heat, controls the flow of liquid from pores to the sliding interface. Whereas viscosity determines the lubrication performance at the sliding interface. Different sliding velocities were used to evaluate the effect of frictional heat that causes temperature generation at the sliding interface to cause overflow of liquid lubricants. The outcome from this work suggests that the phosphonium saccharinate ILs are suitable for high-temperature applications due to their higher viscosity, which helps achieve lower friction and wear. Whereas phosphonium salicylate and phosphonium benzoate ILs are provided lower friction and wear at low temperatures. The studied approaches of multi-oxide system theory, the addition of solid lubricant, achieving an amorphous phase by laser processing of coating, and effective utilization of in-situ generated pores provide a roadmap for the development of lubrication mechanisms in the oxide ceramic materials

Effects of artificial light at night on avian behavior and physiology

As urbanization increases worldwide, the proliferation of artificial light at night (ALAN) is dramatically altering nighttime environments. ALAN disrupts natural light-dark patterns used by both humans and wildlife to synchronize behavior and biochemical processes with their environment. Exposure to ALAN has been linked to sleep disruption, physiological stress, metabolic disorders, cardiovascular disease, and cancer. However, the mechanisms underlying these responses and potential long-term consequences, remain elusive. Consequences of ALAN may also be exacerbated by the spectral composition of light sources. Short wavelengths are more stimulatory to vertebrate visual systems and are becoming prominent in the environment since the recent transition to LEDs as a low-cost and energy-efficient alternative to previous outdoor light technologies. It is not fully understood how spectral composition of light plays a role in organismal responses. In this dissertation I address several of the most pressing knowledge gaps regarding the effects of ALAN on vertebrate behavior and physiology, using the zebra finch (Taeniopygia guttata) as a model system. In Chapter 1, I asked whether ALAN affects sleep behavior and physiological stress, using two commonly available spectras of LED (Alaasam et al., 2018). In chapter 2, I investigated molecular mechanism by asking whether ALAN affects behavioral and physiological processes via alteration of circadian clock gene expression. In chapter 3 I test whether individuals can habituate to ALAN in long-term exposure, or incur long-term physiological consequences

Improvements in the Frequency and Accuracy of I Cannot Know Type Answers to Three Term Series Word Problems by Multiple Exemplar Training of Relational Skills and Instructional Content.

The ability to accurately use “Not Enough Information” or “I Cannot Know” (ICK) types of responses in everyday life may contribute to the degree to which an individual responds sustainably in situations likely to evoke biased outcomes. This skill may have an analog function previously described but rarely investigated within the Relational Frame Theory (RFT) literature.This dissertation describes a series of surveys and increasingly elaborate multiple exemplar training (MET) protocol experiments aimed at replicating common ICK inaccuracy in three term series problems and improving that performance via training Known-Unknown (KU) relational responding and introducing an instructional intervention. Accuracy and frequency of ICK responses were analyzed for indications of training effects and evidence of relational responding. Forms of inaccurate use of ICK responses were tested for indications of KU functioning. Results suggest that (1) US and Irish participants infrequently and inaccurately respond with ICK responses to free response three term series word problems where it is appropriate; (2) KU relational responding can be trained to mastery criterion via MET protocols; (3) KU training is enhanced by building a relational response repertoire of more common functions such as equivalence and comparative relations; (4) trained KU responding can improve the accuracy of ICK responding on three term series word problems; (5) instructions can evoke more frequent, though inaccurate, ICK responding; (6) observed improvements on three term series problems from training KU relations are undetectable against instructional effects; and (7) ICK responses likely serve multiple behavioral functions

Retrospective Cue Benefits in Visual Working Memory are Limited to a Single Item at a Time

Working memory (WM) performance can be improved by an informative cue presented during storage. This effect, termed a retrocue benefit, can be used to study limits on how human observers select and prioritize information stored in WM for behavioral output. There is disagreement about whether retrocue benefits extend to multiple WM items. One possibility is that relative to no- or neutral-cue trials multiple retrocues improve some aspects of memory performance (e.g., a reduction in random guessing) while worsening others (e.g., an increase in the probability of reporting a non-probed item). We tested this possibility in three experiments. Participants remembered arrays of four orientations or colors over a brief delay. One, two, or all four of these items were retrospectively cued, and at the end of the trial a single item was probed for recall. Participants’ recall errors were lower during cue-one relative to cue-two and cue-four trials, and this benefit was driven primarily by a reduction in random guessing during cue-one trials. Moreover, recall precision, swap errors (i.e., reporting a non-probed item), and guessing rates were statistically indistinguishable across cue-two and cue-four trials. Thus, multiple simultaneously presented retrospective cues led to no performance improvement relative to an uninformative cue, providing further evidence that retrocue benefits in WM performance are limited to a single item at a time

Microeconometric Essays on Entrepreneurship

This dissertation empirically analyzes decisions taken to support the growth of small, young, entrepreneurial firms. It is a collection of three Microeconometric essays. These papers broadly fit within the field of Behavioral Empirical Microeconomics as they analyze the beliefs and biases of entrepreneurs. The first paper: Local Supply Shocks of Bank Credit Deter Young Firms from Loan Applications, co-authored with Frank M. Fossen, estimates changes in rates of young firms who are deterred from applying for commercial bank loans following a change in the credit supply due to their belief that they will be denied credit. By estimating short-run firm responses to an identified supply shock, we reveal unmet demand and inefficiencies in small business credit markets that have previously been masked in loan application and approval data due to the adverse selection problem in banking and a lack of information about individual entrepreneurs beliefs relative to their creditworthiness. The methodology for this paper is instrumental variable (IV) regression. We utilize start-up firm panel data from The Kauffman Firm Survey and lending data from U.S. Community Reinvestment Act mandated reporting. The second paper: Public Entrepreneurship Training for Startup Firms: Evidence from the Kauffman Firm Survey studies the selection decision of small young entrepreneurial firms into start-up firm specific entrepreneurship training. The Kauffman Firm Survey offers a unique opportunity to observe entrepreneurs who selected no training, private, and public training. I estimate outcomes relevant to the development of start-ups: survival, growth rates of profit, growth rates of employment, commercial bank loan applications, loan approvals, loan deterrence, and forecasting ability. I use probit propensity score matching methodology to analyze selection and differences in performance outcomes between training program types including U.S. Small Business Administration (SBA) training. The third paper: The Art Market as Keynes’ Beauty Contest with a $10,000 Prize, co-authored with Federico L. Guerrero estimates income differences between myopic and strategic artists. We discuss visual fine arts as assets and find an income premium at a threshold level of secondary market strategic awareness without full information. This study demonstrates incentives for content convergence in arts and cultural production

From Micro to Macro: Investigating mechanisms involved in the convergent evolution of feather lice ecomorphs

Over the last hundreds of millions of years, the diversity of species that have evolved prompts questions about how and why species diversify and adapt to novel environments. In some instances, distantly related species will evolve similar traits, in a process called convergent evolution. These occurrences provide opportunities to investigate the mechanisms that drive species diversification and adaptation and whether different mechanisms can lead to similar evolutionary outcomes. Under what conditions is evolution repeatable? Are we able to predict how species may evolve under similar environments and selective pressures in the future? In some systems, distinct morphological traits emerge repeatedly among species that inhabit similar environments. Known as ecomorphs, these traits enable species to specialize within specific microhabitats. Such systems are ideal for studies investigating the mechanisms that drive the evolution of convergent traits. Here, we explore the evolution of ecomorphs in a host-parasite system from a micro and macroevolutionary perspective. Parasitic feather lice in the family Philopteridae (Order: Psocodea) are found on almost all species of birds and have repeatedly diversified into ecomorphs specific to areas of their host’s body. These morphological characteristics allow them to avoid being groomed off by the host. They have repeatedly evolved across their hosts since the Cretaceous-Paleogene boundary (~65 million years ago). Consequently, they have a long coevolutionary history with their hosts. Exploring the influence of different macroevolutionary events (e.g., cospeciation, duplication, and host-switching) across their evolutionary histories and the level of molecular convergence involved in ecomorph evolution can reveal some of the mechanisms involved in the convergence of feather lice ecomorphs. We began by assembling the protein coding genes of 57 species of feather lice to quantify the variation in GC content among and within species. Feather lice were GC poor (mean GC = 42.96%) with a significant amount of variation within and between species (GC range: 19.57-73.33%). Next, using the protein dataset we prepared in the previous study, we investigated molecular convergence of feather lice ecomorphs. For each ecomorph, candidate genes were selected if a minimum of two species of the same ecomorph were under positive selection. We found over 1,000 candidate genes for each ecomorph. Of these genes, a gene ontology (GO) analysis indicated that a smaller number of genes than expected were involved in gene expression (GO:0010467), which may suggest evolutionary constraints or strong stabilizing selection on regulatory processes. Additionally, wing ecomorphs had a disproportionate number of genes involved in biological and developmental processes. We found a significantly higher number of amino acid changes occurring at the same site than expected by chance for both body and head ecomorphs and fewer than expected for wing and generalists. Overall, we found evidence for molecular convergence at the gene level, particularly in wing ecomorphs. In this last project, we investigated these ecomorph transitions at a macroevolutionary scale. Specifically, we investigated how cospeciation, duplication, and host-switching events influenced ecomorph transitions. We found that macroevolutionary events play an important role in the convergent evolution of ecomorphs, with body and generalist ecomorphs significantly associated with duplication and host-switching events, respectively. We also found most transitions occur from a generalist state. These three studies have provided a better understanding of feather lice ecomorph evolution through a micro and macro lens. We show that feather lice, while GC poor, have a high level of variation in their base composition, which could reduce genetic constraints during convergent evolution. We identified molecular convergence at the gene level within feather lice ecomorphs. Further investigations into these genes and amino acid changes can provide more detailed results on the similarities and differences in molecular convergence. Specifically, future studies should measure the relative genotype and allele frequencies across feather lice to quantify standing genetic variation for which evolution can act upon. This would provide more information on the genetic constraints that influence molecular convergence. Cospeciation, duplication, and host-switching events also have a significant influence on ecomorph evolution. Identifying the different barriers feather lice ecomorphs experiencing during dispersal and establishment will improve our understanding of the macroevolutionary patterns across this group. Incorporating these new genetic findings into future macroevolutionary studies will enrich our understanding of the evolution and diversification of feather lice ecomorphs

Gender, Violence, and Piety: Performance of Masculinity in Colonial Potosi

The Imperial Villa of Potosí since its inception was a unique place. The enormous wealth produced by the silver mines created a peculiar environment in which a heterogenous, ethnically diverse group of men congregated in search of a share of that bonanza. Those men that made Potosí their temporary home displayed an also unique form of masculinity defined by the contrasting aspects of violence and piety. This dissertation centers on the performance of such masculinity and how it was performed in Colonial Potosí. I ague that three main characteristics displayed by male Potosinos --violent behavior, piety, and gender relations-- were brought about by the Imperial Villa’s particular circumstances: a) isolation in harsh physical conditions; b) immense wealth; c) large diverse population

The Winter of Desegregation: Civil Rights Activism in Reno and the 1960 Winter Olympics

In February of 1960, the Olympic Winter Games came to Palisades Tahoe. The Games brought the eyes of the world to the region and the city of Reno, Nevada became known as the Gateway to the Winter Olympic Games as it was the closest city of notable size to Palisades. Because of this and the international attention the Games necessarily brought, Reno was thrust into the national and international spotlight in a way it never had been before. This provided an opportunity for Reno’s civil rights activists to lobby for an end to discriminatory policies that existed widely in the city and the state of Nevada. Activists used the attention on the Games as leverage to advocate for more equal treatment in public accommodations and casinos. In this process, Reno’s activists made important allies including organized labor, religious organizations, and others. They also worked with officials at every level of government and found roadblocks and a largely racist or ambivalent society in their search for progress. In spite of this, the activism leading up to the Olympics led to Reno’s casinos and hotels ending their discriminatory policies for the two-week duration of the Olympics. It also led to more vocal and militant activism in Reno later in 1960 and the following years, a crucial point as they pushed Reno and Nevada towards greater civil rights for African Americans prior to the 1964 Civil Rights Act

Toward Terabit-per-second Networks: Developing Data Transfer Solutions for Next-Generation Research Networks

Research networks provide high-speed wide-area network connectivity between research and education institutions to facilitate large-scale data transfers. However, scalability issues of legacy transfer applications (e.g., scp and FTP) and their extensions (e.g., GridFTP and rsync) hinder the effective utilization of these networks. In this dissertation, we propose online optimization algorithms to tune the degree of parallelism for file transfers to maximize transfer throughput while keeping system overhead at a minimum. First, we introduce Falcon that utilizes game theory-inspired novel utility function to evaluate the performance of various parallelism levels such that competing transfers are guaranteed to converge to a fair and stable solution. We assessed the performance of Falcon in isolated and production high-speed networks and found that it can discover optimal transfer parallelism in as little as 20 seconds and outperform the state-of-the-art solutions by more than 2x. On the other hand, Falcon uses the same level of parallelism for network and I/O operations which may result in increased system overhead and unfair resource allocation. To address this issue, we developed modular file transfer architecture, Marlin, that separates I/O and network operations so that parallelism can be independently adjusted for each component. Marlin adopts online gradient descent algorithm to swiftly search the solution space and find the optimal level of parallelism for read, transfer, and write operations. Experimental results collected under various network settings show that Marlin can identify and use a minimum parallelism level for each component, reducing system overhead (e.g., low CPU usage and I/O contention) and improving fairness among competing transfers

Improving Potable Reuse Water Quality by Understanding N-nitrosodimethylamine Precursors and Bulk Organic Matter Present during Advanced Oxidation Processes

Planned potable reuse is becoming a common strategy to relieve water scarcity throughout the world. Full-advanced treatment (FAT) systems consist of ultrafiltration/microfiltration, reverse osmosis (RO), and ultraviolet/advanced oxidation processes (UV-AOP) and are utilized at potable reuse facilities to degrade or remove contaminants present in wastewater effluents. Oxidants including hydrogen peroxide (H2O2), free chlorine (HOCl), and monochloramine (NH2Cl) are added during UV-AOP to produce radicals which degrade contaminants. Oxidant performance regarding specific contaminant removal has been compared in prior research, but there is no consensus on the overall comparative performance of these oxidants because the contaminants selected for each study are usually different. To address this, I investigated oxidant performance by considering a broader fraction of contaminants including known compounds and unknown/unidentified compounds via nontarget analysis and bioassays. Based on greater destruction of organic compounds, reduced transformation products, and a lack of oxidative stress induction, H2O2 was the most suitable oxidant tested for ultraviolet advanced oxidation in water reuse.Disinfection byproducts form when precursor chemicals are oxidized by disinfectants to new hazardous products. N-nitrosodimethylamine (NDMA), a carcinogenic disinfection byproduct, has been regulated with 10 ng/L drinking water notification level. Controlling specific regulated contaminants such as N-nitrosodimethylamine (NDMA) is also crucial for regulatory compliance, improving potable reuse water quality, and public acceptance. Its precursors can persist through advanced treatment trains including RO and UV-AOP contributing to NDMA formation during conveyance, and these precursors are not yet identified, making them difficult to treat. Dimethylamine (DMA) is a model NDMA precursor, which is usually present in wastewater that serves as potable reuse influent. DMA has been used extensively by others in bench-scale experiments to understand NDMA formation pathways but it has also been thought that it is not an important NDMA precursor in treated wastewater and surface water due to its low yield combined with relatively low concentrations in drinking water and wastewater samples. However, its occurrence in water reuse facilities has not been investigated. Samples from one pilot plant and four full-scale water reclamation facilities were collected to study DMA occurrence in FAT facilities. The median DMA concentrations in product and finished waters were 0.4 μg/L across six sampling events. DMA accounted for 5%-43% of the total NDMA precursor pool of the UV-AOP product water at one facility, and up to 40 of ng/L of NDMA at another. Although DMA substantially contributed to NDMA formation in potable reuse facilities, the complete NDMA precursor pool that enters typical surface water treatment plants has not been identified. Further, it is commonly thought that most NDMA precursors present in drinking water intakes originate from wastewater-derived anthropogenic chemicals but no study has conclusively determined the contribution from anthropogenic vs. naturally occurring precursors due to the difficulty in finding an appropriate environmental system to conduct such an experiment. The only study which attempted to answer whether the dominant surface water NDMA precursors are anthropogenic or environmental in origin compared NDMA precursor concentrations in wastewater effluents, a eutrophic water, stormwater/agricultural runoff, and a pristine river source. Wastewater effluents tended to contain relatively high concentrations of NDMA precursors but it was not clear how much they contributed to NDMA formation after dilution into the river systems. Although region-specific relationships between NDMA precursors and sucralose (one anthropogenic pharmaceutical) have also been reported, suggesting NDMA precursor sources are anthropogenic, the relationship is highly watershed specific, and does not lend itself to applications outside of the watershed where the relationship was original derived. To determine if the dominant NDMA precursor sources are wastewater effluents (anthropogenic source), I investigated NDMA precursors in Truckee River, which has only one anthropogenic point source. The background of NDMA precursors in the Truckee River is relatively low, and an apparent increase was observed downstream of wastewater effluents, suggesting that anthropogenic sources dominate NDMA precursor loading in surface waters within a limited length from wastewater effluent in the Truckee River