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Recent work on various quantum materials has led to fruitful result including unconventional magnetic states, topological properties, and exotic emergent phenomenon. High Tc superconductivity is one of the prominent properties discovered in quantum materials like strong correlated systems. Though the efforts on understanding this exotic behavior have lasted for years, the mechanism remains elusive owing to the many-body nature of the system and the research scope limitation within cuprates. Recent unravel of Jeff=1/2 state in the iridate square lattice offers alternative to study the complicated many body physics and potentially achieve high Tc superconductivity. In addition, the combination of electron correlation and strong spin-orbital coupling makes iridate a promising material to explore diverse exotic behaviors beyond cuprates. This dissertation work utilizes the epitaxial heterostructure engineering to construct various Jeff=1/2 iridate thin films under different effective dimensionality to study both fundamental physics and explore new emergent phenomenon. Following a detailed survey of thermodynamic stability of Srn+1IrnO3n+1 thin films, the argon gas is found to be helpful in stabilizing Srn+1IrnO3n+1 under intermediate dimensionality. Epitaxial strain can be applied to stabilize chemical substituted SrIrO3 thin film where no bulk single crystal sample has been synthesized so far. Moreover, epitaxial strain is used to tune the correlation in a pseudospin-1/2 iridate superlattice within a Slater-Mott crossover regime. The physical properties of iridate superlattice is shown to be highly susceptible to structural modulation with observation that is rarely found in 3d transition metal oxides. The structural modulation on iridate thin film under 3D limit also successfully induces exotic transport properties which may originate from Berry curvature.

This dissertation is focused on understanding the relationship between rheology and morphology of capillary suspension under various shearing conditions. A model ternary liquid/liquid/particle system is constructed for experimental propose. Particularly in this system, one of the liquid has some preferentiality in wetting towards particles so that liquid meniscus can be formed between particles. Formation of such meniscus can create a network which endows the suspension with a yield stress. Four specific topics are presented: 1) to investigate rheology of pendular network (i.e. only pair-wise connection form between fully wet particles), by examining the dependence of the yielding behavior on flow history, quantify their viscoelasticity, and relate these to the microstructural picture of meniscus rupture; 2) to verify the effect of various wetting conditions on rheology of the capillary suspension. Results show a diminishing solid-like property of such suspension as the particles become less wetting by the minority fluid, which induced particle aggregation; 3) to map the rich variety of morphologies for a model ternary system containing particles which were equally wetted by both polymers, analogous to: Picking emulsions, particle-stabilized foams and bijels 1, 2; 4) to correlate the dynamic morphology of ternary model blend with rheological measurement during creep-recovery via in-situ visualization.

Cereal fibers that can be metabolized by gut microbiota have been shown to promote the growth of beneficial bacteria in the gut. Increased consumption of cereal fibers may improve host / gut microbiota interactions in obesity and other metabolic diseases by normalizing gut dysbiosis. The present dissertation describes four research projects to assess the impact of cereal dietary fibers on gut microbiota and host metabolism. In the first study, we determined the treatment temperatures for production of soluble, non-digestible, feruloylated oligo- and polysaccharides (FOPS) from maize bran and wheat bran, and determined the fermentation properties of partially purified FOPS from maize bran and wheat bran. In vitro fermentation revealed that wheat FOPS were more bifidogenic than maize FOPS. However, maize FOPS led to continual production of short-chain fatty acids (SCFA), resulting in the highest SCFA and butyrate production at the end of the fermentation. In addition, maize FOPS showed significantly higher antioxidant activity than wheat FOPS. The study showed FOPS from maize bran may exhibit enhanced benefits on gut health compared to those of wheat bran. In the second study, we further determined whether the colonic fermentation of FOPS could counteract the deleterious metabolic effects of a high-fat (HF) diet through modulating the gut microbiota using a mouse model. Our results suggest that colonic fermentation of FOPS plays an important role in preventing metabolic disorders in HF-fed mice, and that these metabolic improvements depend on specific alterations of the gut microbiota through FOPS fermentation. Blautia and Akkermansia might be considered potential therapeutic targets for improving body and adipose tissue weights, while SCFA production seems linked to improvements in glucose metabolism. In the third study, by obtaining long-term dietary records from fecal donors, we aimed to determine the correlations between dietary intake variables and dietary fiber degradation and short-/branched-chain fatty acid (BCFA) and ammonia production during in vitro fecal fermentation. We found that butyrate production was correlated with fecal donor intake of many nutrients, of which principal component analysis revealed were mostly contributed by grain-, nut-, and vegetable-based foods. Negative correlations were found for propionate with intake of total carbohydrate, added sugar, and sucrose and for ammonia and BCFA production with intake of unsaturated fats. These results suggest that diets high in plant-based foods and high in unsaturated fats are associated with microbial metabolism that is consistent with host health. In the fourth study, we determined the impacts of long-term dietary pattern on gut microbiota composition and the change in composition of the gut microbiota during fermentation of predigested whole wheat flour. Butyrate production was significantly correlated with the abundance of Butyricicoccus, Coprococcus, Dorea, Faecalibacterium, and Lachnospiracea incertae sedis. BCFA and ammonia production displayed negative correlations with the abundance of Roseburia and Parasutterella. Bifidobacterium and Butyricicoccus were enhanced by pre-digested whole wheat flour. Taken together, these results provide new evidence for modulating the gut microbiota through dietary treatment and indicate its contribution to host metabolism. Advisor: Devin J Rose

This dissertation research focuses on evaluating the nonlinear dynamics of driveline systems employed in motor vehicles with emphasis on characterizing the excitations and response of right-angle, precision hypoid-type geared rotor structure. The main work and contribution of this dissertation is divided into three sections. Firstly, the development of an asymmetric and nonlinear gear mesh coupling model will be discussed. Secondly, the enhancement of the multi-term harmonic balance method (HBM) is presented. Thirdly and as the final topic, the development of new dynamic models capable of evaluating the dynamic coupling characteristics between the gear mesh and other driveline structures will be addressed. A new asymmetric and nonlinear mesh model will be proposed that considers backlash, and the fact that the tooth surfaces of the convex and concave sides are different. The proposed mesh model will then be fed into a dynamic model of the right-angle gear pair to formulate the dimensionless equation of motion of the dynamic model. The multi-term HBM will be enhanced to simulate the right-angle gear dynamics by solving the resultant dimensionless equation of motion. The accuracy of the enhanced HBM solution will be verified by comparison of its results to the more computationally intensive direct numerical integration calculations. The stability of both the primary and sub-harmonic solutions predicted by applying multi-term HBM will be analyzed using the Floquent Theory. In addition, the stability analysis of the multi-term HBM solutions will be proposed as an approximate approach for locating the existence of sub-harmonic and chaotic motions. In this dissertation research, a new methodology to evaluate the dynamic interaction between the nonlinear hypoid gear mesh mechanism and the time-varying characteristics of the rolling element bearings will also be developed. The time-varying mesh parameters will be obtained by synthesizing a 3-dimensional loaded tooth contact analysis (TCA) results. The time-varying stiffness matrix approach will be used to represent the dynamic characteristics of the rolling element bearings. An overall nonlinear dynamic model of the hypoid gear box considering elastic housing structure will be developed as well. A lumped parameter model of the flexible housing will be extracted form an appropriate set of frequency response functions through modal parameter identification method. In order to obtain the rotational coordinates, a rigid body interpolation of the translational responses at the bearing locations on the housing structure will be applied. The reduced model will be then coupled with the hypoid gear-shaft-bearing assembly model by applying a proposed dynamic coupling procedure. Finally, a hypoid geared rotor system model considering the propeller shaft flexibility will be established. The propeller shaft bending flexibility will be modeled as lumped parameter model through using the component mode synthesis (CMS). The torsional flexibility of propeller shaft will be simplified as a torsional spring connecting the inertia of moment of engine and pinion. Physically, the pinion input shaft is driven by the propeller shaft through a universal joint, which will be modeled as a flexible simple supported boundary condition as well as fluctuating rotation speed and torque excitation.

There has been a dramatic increase in obesity, which presents a risk of many chronic health problems. Recent studies have shown that obese individuals harbor an abnormal gut microbiota (dysbiosis), which has sparked interest in the gut microbiota as a target for weight management. Dietary fiber and whole grains that can be metabolized by gut microbiota have been shown to promote the growth of beneficial bacteria in the gut. Increased consumption of dietary fiber and whole grains may improve host / gut microbiota interactions in obesity and other metabolic diseases by normalizing gut dysbiosis. The present thesis describes two research projects to assess the impact of dietary fibers and whole grain on gut microbiota. In the first study, six dietary fibers [pectin, guar gum, inulin, arabinoxylan, β-glucan, and resistant starch type 2 (RS-2)] were subjected to in vitro digestion and fermentation using fecal samples from obese and normal weight individuals. Pyrosequencing was used to assess the impact of each dietary fiber on the gut microbiota community. Short/branched chain fatty acids (SCFA/BCFA) and carbohydrate utilization were correlated with proportions of bacterial taxa. The data showed that RS-2 caused the most dynamic change of the whole microbiota community and Bifidobacterium increased almost 10-fold on pectin substrate compared with the control. Certain taxa may be targeted to increase SCFA production or increase dietary fiber utilization. For instance, Ruminococcaceae and Faecalibacterium displayed positive correlations with butyrate production and while a strong positive relationship was shown between β-glucan utilization and Firmicutes. In the second study, since SCFA can influence hormones involved in energy absorption, utilization, and storage, the SCFA profile from five whole grains (wheat, rye, corn, rice, and oats) using an in vitro method was evaluated. There were large differences in fermentation profiles among individuals, even when supplied with the same dietary fiber. The obese type microbiota was less efficient at butyrate production and less metabolically active than the normal weight type microbiota initially, but given sufficient whole grain substrates the bacteria quickly became metabolically active.