DEVELOPMENT OF ZEOLITIC IMIDAZOLATE FRAMEWORKS FOR ENHANCING POST-COMBUSTION CO2 CAPTURE

Post-combustion CO2 capture is a promising approach for complementing other strategies to mitigate climate change. Liquid absorption is currently used to capture CO2 from post-combustion flue gases. However, the high energy cost required to regenerate the liquid absorbents is a major drawback for this process. As a result, solid sorbents have been investigated extensively in recent years as alternative media to capture CO2 from flue gases. For example, metal organic frameworks (MOFs) are nanoporous materials that have high surface areas, large pore volumes, and flexible designs. A large number of MOFs, however, suffer from 1) low CO2 adsorption capacity at low pressure, which is the typical condition for flue gases, 2) degradation upon exposure to water present in flue gases, and 3) low selectivity of CO2 when present in a mixture of gases. Zeolitic Imidazolate Frameworks (ZIFs) are heavily investigated MOFs for CO2 sorption applications because they have better selectivity for CO2 compared to other MOFs and are resistant to degradation in water due to their hydrophobic nature. However, ZIFs (e.g., ZIF-8) investigated for CO2 sorption applications are typically produced using toxic solvents and their CO2 sorption capacity is drastically lower than other types of MOFs. Post-synthesis modifications with amine functional groups have been known to increase CO2 sorption capacity and selectivity within nanoporous materials. For ZIFs, previous research showed that sufficient loading with linear polyethyleneimine increased their CO2 sorption capacity. Therefore, the objectives of this research were to a) investigate the CO2 sorption capacity of ZIF-8 synthesized by solvothermal methods that use more eco-friendly solvents (e.g., methanol and water) and b) introduce post-synthetic modifications to ZIF-8 using branched polyethyleneimine (bPEI) to enhance its sorption capacity. A custom quartz crystal microbalance (QCM) system was assembled and used to measure the CO2 sorption capacity of unmodified and bPEI-modified ZIF-8 sorbent. The tests were conducted at 0.3 - 1 bar. The results showed that the unmodified ZIF-8 synthesized in methanol (ZIF-8-MeOH) had comparable crystal structure, thermal stability, surface area, and chemical properties to that of literature (Ta et.al 2018). ZIF-8-MeOH had a surface area of 1300 m2/g and a CO2 sorption capacity of 0.85 mmol CO2/g ZIF-8 @ 1 bar. This surface area and sorption capacity are comparable to those of ZIF-8 made in dimethylformamide (DMF). Therefore, ZIF-8-MeOH proved to be a worthy candidate MOF for replacing the ZIF-8 made in DMF for CO2 capture research. Water-based ZIF-8 was also synthesized in this study; however, its CO2 sorption capacity was not tested because it exhibited a significantly lower surface area (732 m2/g) compared to that of ZIF-8-MeOH. Modification of the ZIF-8-MeOH with bPEI resulted in a decrease in its CO2 sorption capacity. This undesired outcome is likely a result of insufficient bPEI load (mass attached), on ZIF-8-MeOH (~ 10% w/w) combined with the surface area lost (~ 770 m2/g) due to bPEI blocking some of the ZIF-8-MeOH pores. Therefore, the bPEI load attained in this study was not enough to compensate for the loss of surface area of the modified ZIF-8 and thus, the CO2 sorption capacity decreased. Future investigations should enhance the post-synthetic modification by increasing the loading of amine functional groups onto the eco-friendlier ZIF-8-MeOH used in this study

Mechanisms of pattern formation during T cell adhesion

T cells form intriguing patterns during adhesion to antigen-presenting cells. The patterns at the cell-cell contact zone are composed of two types of domains, which either contain short TCR/MHCp receptor-ligand complexes or the longer LFA-1/ICAM-1 complexes. The final pattern consists of a central TCR/MHCp domain surrounded by a ring-shaped LFA-1/ICAM-1 domain, while the characteristic pattern formed at intermediate times is inverted with TCR/MHCp complexes at the periphery of the contact zone and LFA-1/ICAM-1 complexes in the center. In this article, we present a statistical-mechanical model of cell adhesion and propose a novel mechanism for the T cell pattern formation. Our mechanism for the formation of the intermediate inverted pattern is based (i) on the initial nucleation of numerous TCR/MHCp microdomains, and (ii) on the diffusion of free receptors and ligands into the contact zone. Due to this inward diffusion, TCR/MHCp microdomains at the rim of the contact zone grow faster and form an intermediate peripheral ring for sufficiently large TCR/MHCp concentrations. In agreement with experiments, we find that the formation of the final pattern with a central TCR/MHCp domain requires active cytoskeletal transport processes. Without active transport, the intermediate inverted pattern seems to be metastable in our model, which might explain patterns observed during natural killer (NK) cell adhesion. At smaller TCR/MHCp complex concentrations, we observe a different regime of pattern formation with intermediate multifocal TCR/MHCp patterns which resemble experimental patterns found during thymozyte adhesion.Comment: 12 pages, 8 figure

Optimization of biomass fast pyrolysis for the production of monomers

Fast pyrolysis is a promising method for producing advanced biofuels and chemicals from lignocellulosic biomass. The process will however require further optimization to produce fuels and chemicals at a price competitive to conventional fossil fuel-derived products. Research in this dissertation focuses on both pre- and post-processes for optimizing fast pyrolysis to produce increased yields of valuable anhydrosugars and phenolic monomers. The concept of alkali and alkaline earth metal (AAEM) passivation using sulfuric acid had only previously been demonstrated in batch micropyrolyzer trials. A bench-scale, continuous-flow auger pyrolyzer was used in this work to demonstrate AAEM passivation on both woody and herbaceous feedstocks. Alkali and alkaline earth metal passivation of red oak and switchgrass increased total sugars by more than 105% and 260%, respectively. Light oxygenates simultaneously decreased by nearly 50% from each feedstock. The synchronous increase in sugars and decrease in light oxygenates provides evidence of the hypothesis that AAEM passivation prevents pyranose ring fragmentation and promotes glycosidic bond cleavage in holocellulose. An undesirable consequence of AAEM passivation was an increase in biochar from both lignin and carbohydrates. Demonstration of the enhanced production of sugars from AAEM passivated feedstocks in a continuous auger pyrolyzer at the kilogram scale is an important step in determining the feasibility of using fast pyrolysis to produce sugars from lignocellulosic biomass. Lignin-derived biochar increased from AAEM passivated feedstocks which led to suspicions that thermally active AAEMs catalyze lignin pyrolysis. Effect of thermally active AAEMs on lignin pyrolysis was therefore investigated in more detail. Experimental results indicated that sodium was the most active AAEM on lignin pyrolysis in which it increased overall volatile aromatic monomers by over 16% compared to the control. Alkali metals as a group both increased char and decreased alkenyl side chains amongst volatile aromatics. Alkenyl side chains are known to result from the cleavage of certain bonds within the lignin structure. Therefore AAEMs are predicted to catalyze the cleavage of linkages within the lignin structure during pyrolysis. The rate at which pyrolysis vapors are cooled in bio-oil collection equipment has been noted to have an influence on bio-oil composition, however prior to this research has never been quantified. A novel cold-gas quench system was developed that utilizes liquid nitrogen to quickly quench pyrolysis products, which produced a more than seven fold increase in cooling rate compared to a conventional shell and tube condenser. The increased cooling rate and elimination of radial temperature gradients in the quench system increased levoglucosan yield from cellulose by 23% compared to the conventional system

For Sale or Rent: Preventing Demolition by Neglect in Iowa\u27s Downtowns

The National Trust for Historic Preservation describes demolition by neglect as “an epidemic within historic areas and a challenging issue for state and local authorities.” For small towns in social and economic distress, downtown buildings present opportunities for community renewal given their historic and cultural importance, yet it is in these towns where building neglect often results in nuisance-laden commercial districts and the demolition of built assets. The State of Iowa recognized the pervasiveness of this problem by offering financial assistance to cities with competitive applications, but this alone is not a remedy. Through participant observation and the Community Capitals Framework, this report looks at a local case in Ackley, Iowa to demonstrate how outdated building codes, economic hardship, and deferred maintenance can permanently and negatively transform an array of local capitals. Drawing from this case, it identifies strategies for Iowa’s small towns that could both prevent demolition by neglect and serve as catalysts for positive community transformation

Steganoscription : exploring techniques for privacy-preserving crowdsourced transcription of handwritten documents

textThe focus my research is the historical document format represented by the Central State Hospital (CSH) dataset, handwritten medical records. The specific problem innate to the CSH dataset in question is how to transcribe sensitive, cursive-handwritten documents via a manual vehicle- such as crowdsourcing. Manual methods are necessarily no matter the sophistication of the optical character recognition system used because of the inconsistencies within cursive script. To address this problem I've developed an application that enables users to transcribe sensitive, handwritten, document images while preserving the privacy of the context around the transcribed text via random word selection and visual manipulation of the displayed text. This is made possible through several algorithms that process documents from a top-down approach. These system operations detect and segment lines of text in images, reverse the slant common to cursive script, detect and segment words, and finally, manipulate word-images before they are displayed to users; combinations of color, noise, and geometric manipulations are currently supported and used randomly. This system, called Steganoscription, combines the concepts of steganography and transcription.Informatio

Predicting Student Success Using Digital Textbook Analytics in Online Courses

In the digital era, students are generating and institutions are collecting more data than ever before. With the constant change in technology, new data points are being created. Digital textbooks are becoming more popular, and textbook publishers are shifting more of their efforts to creating digital content. This shift creates new data points that have the potential to show how students are engaging with course material. The purpose of this correlational study is to determine if digital textbook usage data, pages read, number of days, reading sessions, highlights, bookmarks, notes, searches, downloads and prints can predict student success. This study used a multiple regression to determine if digital textbook usage data is a predictor of course or quiz success in five online undergraduate courses at a private liberal arts university. The analysis used digital textbook data from VitalSource and consisted of 1,602 students that were enrolled in an eight-week online course at a private liberal arts university. The analysis showed that there is a significant relationship between digital textbook usage data and total points earned and average quiz grade. This study contributes to the limited knowledge on digital textbook analytics and provides valuable insight into how students engage with digital textbooks in online courses

The Realm of Appearances

My work references images from social media to construct a world that exists somewhere between our physical world and the digital. I do this to help me understand how our reliance on technology, and our use of social media affects how we process information. I examine the cultural implications this media saturation has had, or will have on our society. Specifically, I am looking at the “digital divide.” My work explores the divide between the way we often think and behave online, and how it differs from our offline self. This is accomplished by elevating the value of the original image through paint. Using a high key palette, I construct an image that is more synthetic than the original to emphasize the absurd nature of the original image. The synthetic image I create is done to make my world more interesting than our actual world. However, the world I am creating is also ambiguous and confusing. My paintings depict spaces that suggest an exaggerated version of reality. I use images that are heavily constructed. I then distort the image to emphasize the constructed qualities of our image world. This is done to provoke the viewer’s imagination and have them evaluate the image differently than they typically would. I am inviting them to contemplate the absurd nature of our world, and contemplate how they contribute to it’s creation

INDIVIDUAL DIFFERENCES IN ESCALATION OF TOBACCO USE: IMPULSIVITY AND ALCOHOL USE

Like adolescents, young adults are at risk of initiating tobacco use and escalating to daily use and tobacco dependence. However, not every young adult who uses cigarettes intermittently becomes tobacco dependent, and the time-course of those who transition to daily use varies widely. Individual differences likely contribute to the variability observed in patterns of tobacco use. This dissertation uses a multi-modal research approach to examine dimensions of impulsivity and alcohol use that are associated with vulnerability for escalation of cigarette smoking, and whether alcohol’s effects on behavioral disinhibition impact cigarette consumption. Study 1 investigated the associations between dimensions of trait impulsivity, alcohol use, and smoking behavior in a cross-sectional sample of young adults who varied in frequency of cigarette smoking. Study 2 expanded on the results of Study 1 by examining the separate and combined effects of impulsivity and alcohol use on escalation of tobacco use in a longitudinal study of young adults in their first three years of college to determine whether alcohol use and dimensions of impulsivity influenced trajectories of smoking behavior, and whether alcohol use and behavioral impulsivity changed across time as a function of tobacco use trajectories. Study 3 utilized a randomized, within-subject, placebo controlled design to examine whether alcohol-induced impairments in behavioral inhibition mediated the relationship between acute alcohol administration and ad-libitum cigarette consumption. Results from studies 1 and 2 indicated that alcohol use was associated with smoking frequency, and that dimensions of impulsivity (i.e. sensation seeking, lack of premeditation, and urgency) differentiated smoking groups. Study 3 found that acute alcohol increased smoking behavior, but alcohol impairment of inhibitory control did not mediate the relationship between alcohol and smoking consumption. Taken together, the results of these studies demonstrate that alcohol use and impulsivity play a significant role in tobacco use escalation, though more research is needed to determine the mechanism(s) that drive alcohol-induced increases in cigarette consumption