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Title: “IMFUNDO” THE STUDENT; THE EVOLUTION ADAPTATION, AND PRACTICE OF African CENTERED EDUCATION AT THE KARA HERITAGE INSTITUTE IN PRETORIA SOUTH AFRICA
Creator: George III, Clarence
Date: 2021
Collection: Electronic Theses & Dissertations
Description: ABSTRACT“IMFUNDO” THE STUDENT; THE EVOLUTION ADAPTATION, AND PRACTICE OF AFRICAN CENTERED EDUCATION AT THE KARA HERITAGE INSTITUTE IN PRETORIA SOUTH AFRICAByClarence George III This dissertation study (Imfundo) seeks to explore, the practice and evolution of African centered education at the Kara Heritage Institute from 2016 to 2019. This project seeks to study African centered education at Kara focusing on how the Heritage Institute instills notions of African consciousness, notions of Pan...
Show moreABSTRACT“IMFUNDO” THE STUDENT; THE EVOLUTION ADAPTATION, AND PRACTICE OF AFRICAN CENTERED EDUCATION AT THE KARA HERITAGE INSTITUTE IN PRETORIA SOUTH AFRICAByClarence George III This dissertation study (Imfundo) seeks to explore, the practice and evolution of African centered education at the Kara Heritage Institute from 2016 to 2019. This project seeks to study African centered education at Kara focusing on how the Heritage Institute instills notions of African consciousness, notions of Pan-Africanism, structural pedagogy, and culturally relevant pedagogy. This research project evaluated and observed African-centered education in South Africa at the Kara Heritage institute in Pretoria South Africa. Over 4 years of data collected has yielded a great deal of information about South Africa's unique approach to education, culture, and heritage restoration.
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Title: Towards Proprioceptive Grasping With Soft Robotic Hands
Creator: da Silva Pinto, Thassyo
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Various robotic hands, gloves, and grippers have been developed for manufacturing, prosthetics, and rehabilitation. However, the use of rigid links and joints presents challenges in control and safe interactions with humans. The emerging field of soft robotics seeks to create machines that are soft, compliant, and capable of withstanding damage, wear and high stress. This dissertation is focused on advancing soft actuators, soft sensors, and perception for ultimately realizing proprioceptive...
Show moreVarious robotic hands, gloves, and grippers have been developed for manufacturing, prosthetics, and rehabilitation. However, the use of rigid links and joints presents challenges in control and safe interactions with humans. The emerging field of soft robotics seeks to create machines that are soft, compliant, and capable of withstanding damage, wear and high stress. This dissertation is focused on advancing soft actuators, soft sensors, and perception for ultimately realizing proprioceptive grasping with soft robotic hands.In this work, several types of soft pneumatic actuators (SPAs) have been tested, fabricated, and tested, including one embedded with 3D-printed conductive polylactic acid (CPLA) layer capable of stiffness tuning and shape modulation. A gripper made of two soft actuators has been prototyped to demonstrate grasping of objects of different sizes and shapes, with desired posture-holding capabilities. Carbon nanotube (CNT)-based flexible sensor arrays have been designed, fabricated, and integrated to SPAs to provide distributed strain measurements. The presented approach allows customized design of stretchable sensor arrays with varied size and shape. Simulation and experimentation have been performed in order to analyze the soft actuator deformation during bending, and to confirm the capability of the integrated sensor array for capturing the actuator deformation. 3D printing of touch and pressure sensors has been further investigated for potential use in robotic hands. In particular, a novel process has been introduced for producing soft conductors and pressure sensors, involving first 3D-printing microchannels in soft substrates and then filling the channel with liquid metal. With a PolyJet printer, functional straight microchannels have been fabricated with sizes down to 150 x 150 micrometers in the cross-section area. In addition, spiral-shaped pressure sensors have been developed with a cross-section size of 350 x 350 micrometers and overall thickness of 1.5 mm (50A and 70A Shore Hardness). Although the sensors require a relatively large pressure threshold to operate, they have shown the ability to withstand high pressures up to 1 MPa and thus have potential to be used in industrial applications among others. Finally, preliminary computational exploration of intelligent grasping has been performed. In particular, the classification of soft grasped objects has been examined through a neuroevolution process for artificial brains. Simulation with SOFA (Simulation Open Framework Architecture) has been conducted to produce the emulated contact force measurements, which have been used to train artificial neural networks, including Markov Brains from the Modular Agent-Based Evolver (MABE) platform, to properly classify the shape and stiffness of the grasped objects.
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Title: POLYMERS AND POLYMER-CONJUGATES FOR CANCER IMMUNOTHERAPY : FOREIGN CYTOTOXIC T LYMPHOCYTE EPITOPE DELIVERY, CYTOTOXIC T LYMPHOCYTE ACTIVATION, AND NK92 CELL SURFACE ENGINEERING
Creator: Lang, Shuyao
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Cancer immunotherapy is considered as the fourth pillar of anti-cancer treatment, along with the traditional three pillars: surgery, radiotherapy, and chemotherapy. Polymers and polymer conjugates have been widely investigated as cancer immunotherapy carriers. The polymeric materials can not only prolong the circulation time of their small molecular cargoes, but also enhance immune activation via multiple mechanisms such as passively or actively targeting immune cells and specific tissue...
Show moreCancer immunotherapy is considered as the fourth pillar of anti-cancer treatment, along with the traditional three pillars: surgery, radiotherapy, and chemotherapy. Polymers and polymer conjugates have been widely investigated as cancer immunotherapy carriers. The polymeric materials can not only prolong the circulation time of their small molecular cargoes, but also enhance immune activation via multiple mechanisms such as passively or actively targeting immune cells and specific tissue environment. With their great flexibility of monomer selection and post-polymerization modification, polymers and polymer conjugates can satisfy the various needs for immunotherapy. In this dissertation, three different polymer/polymer conjugates have been investigated for facilitating different immunotherapy strategies.pH responsive acetalated dextran microparticles were (Ac-Dex MPs) investigated for the delivery of a high affinity foreign cytotoxic T lymphocyte (CTL) epitope, ovalbumin peptide (OVA), to tumor tissues. Successful OVA delivery to tumor tissue was observed. Both intratumorally and systematically administration of OVA encapsulated Ac-Dex MPs protected mice from pre-established “antigen-loss variant” tumor models. Ultra-pH sensitive nanoparticles (NPs) based on methoxy poly(ethylene glycol)-b-[poly(diisopropylamino)ethyl methacrylate] have been synthesized as a platform for anti-cancer vaccine delivery. Representative CTL antigen OVA and adjuvant imiquimod (IMQ), were covalently conjugated to the polymer backbone through an acid responsive carboxy-dimethylmaleic amide linker (CDM) resulting in polymer P-CDM-OVA and P-CDM-IMQ, respectively. The P-CDM-OVA NPs greatly enhanced CTL responses in vivo compared to the free peptide or the previously reported Ac-Dex MPs encapsulating OVA. Co-administration of P-CDM-OVA NPs with P-CDM-IMQ NPs further improved CTL responses in vivo and effectively reduced tumor growth in mice. Besides serving as delivery carriers, polymers can also be used for surface engineering of immune cells. NK92 cells are a natural killer cell line which is highly cytotoxic, but lack of inherent selectivity toward cancer. We investigated the surface engineering of NK92 with two different strategies: metabolic glycoengineering, and hydrophobic insertion of a polymer grafted with multiple copies of trisaccharide CD22 ligands and a cholesterol terminal. Both methods can successfully modify the surface of NK92 with CD22 ligand and enhance the specific lysis of CD22+ cell lines in vitro. Further investigation of metabolic glycoengineering method showed significant protection against CD22+ tumor in vivo.
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Title: Measurement of 34Ar(α,p)37K using the JENSA Gas Jet Target
Creator: Browne, Justin Edward
Date: 2021
Collection: Electronic Theses & Dissertations
Description: X-ray bursts are very luminous thermonuclear explosions that occur in binary star systems. In these systems, a neutron star accreting matter from a companion star undergoes a runaway thermonuclear explosion, caused by a breakout from the CNO-cycle into the αp-process. The αp-process consists of a series of (α,p) and (p,γ) reactions. In this process, there are “waiting point” nuclei at which the nuclear burning pauses until the stellar conditions change so that the (α,p) reaction rate...
Show moreX-ray bursts are very luminous thermonuclear explosions that occur in binary star systems. In these systems, a neutron star accreting matter from a companion star undergoes a runaway thermonuclear explosion, caused by a breakout from the CNO-cycle into the αp-process. The αp-process consists of a series of (α,p) and (p,γ) reactions. In this process, there are “waiting point” nuclei at which the nuclear burning pauses until the stellar conditions change so that the (α,p) reaction rate increases and burning continues. 34Ar is one of these waiting point nuclei, and sensitivity studies have found that varying the 34Ar(α,p)37K reaction rate significantly impacts the light curve of x-ray bursts.Because the 34Ar(α,p)37K cross section had never been directly measured before, the reaction rates used in simulations are based on Hauser-Feshbach predictions. These predictions are hypothesized to be inaccurate because the Hauser-Feshbach statistical model requires a high level density in the compound nucleus and assumes there are no dominant resonances.This thesis describes an experiment at the National Superconducting Cyclotron Laboratory (NSCL) designed to test Hauser-Feshbach predictions by directly measuring the 34Ar(α,p)37K cross section. A radioactive ion beam of 34Ar15+ with energies of 57.04 MeV and 54.19 MeV was delivered to a (5–8) × 10^18 atoms/cm^2 thick He target, created by the Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas jet target. The recoils and beam were detected by the ANASEN position-sensitive ionization chamber, and the ejectiles were detected by an array of silicon detectors combining SuperORRUBA and SIDAR. The beam included contamination from the decay products of 34Ar, namely 34Cl and 34S. While the contribution from 34S(α,p)37Cl could be subtracted because the cross section had be previously measured, the contributions from 34Cl(α,p)37Ar and 34Ar(α,p)37K could not be separated, so a combined cross section for the two was derived from the data.The combined 34Cl(α,p)37Ar and 34Ar(α,p)37K cross sections were determined to be (70 ± 21) mb at (5.91 ± 0.08) MeV and (52 ± 13) mb at (5.51 ± 0.08) MeV in the center of mass frame. Comparison with Hauser-Feshbach theory indicates that the experimental cross sections are lower by 37 % and 20 %, for the two energies, respectively. This suggests that the hypothesis that the Hauser-Feshbach model overestimates the 34Ar(α,p)37K cross section by 2 orders of magnitude is unlikely to be true at these energies.
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Title: Validation of the beta-Oslo Method; An Indirect Method for Constraining Neutron-Capture Cross Sections
Creator: Childers, Katherine Louise
Date: 2021
Collection: Electronic Theses & Dissertations
Description: One of the prevalent questions in nuclear science is the origin of the elements. There are two stellar nucleosynthesis processes considered to be responsible for the production of the majority of the abundances of the elements heavier than iron; the slow neutron-capture process (s-process) and the rapid neutron-capture process (r-process). Both of these processes are characterized by the successive capture of neutrons on nuclei, with the major differences between the processes being the...
Show moreOne of the prevalent questions in nuclear science is the origin of the elements. There are two stellar nucleosynthesis processes considered to be responsible for the production of the majority of the abundances of the elements heavier than iron; the slow neutron-capture process (s-process) and the rapid neutron-capture process (r-process). Both of these processes are characterized by the successive capture of neutrons on nuclei, with the major differences between the processes being the timescale over which the processes occur and the host environment. The s-process occurs in low neutron-density environments, such as low- to intermediate-mass stars, and proceeds slowly along the valley of stability. Since the nuclei involved are close to stability, the reactions involved are amenable to direct measurements. The r-process progresses through an explosive event with high neutron densities which drives material far from stability. The recent observation of a neutron star merger event by LIGO and Virgo and the subsequent electromagnetic follow up has demonstrated that an r-process event can occur in these rare events, but it has not ruled out other potential astrophysical sites. To better understand and model the r-process, several nuclear properties are needed for a large number of nuclei, including neutron-capture cross sections. R-process nuclei are not viable for direct measurement of neutron-capture cross sections since the nuclei involved are far from stability, and thus have short half-lives. Therefore, several indirect measurement techniques have been developed to provide experimental constraints on neutron-capture cross sections. One such method is the beta-Oslo method, which uses beta decay to populate highly excited states of a nucleus. The resulting de-excitation via the emission of gamma rays is used to extract statistical nuclear properties of the daughter nucleus. These properties are then used as input in a reaction model to constrain the neutron-capture cross section. The beta-Oslo method can provide a large number of constrained neutron-capture cross sections far from stability, but it is necessary to validate the method using a direct neutron capture measurement. This work will present a validation of the beta-Oslo method in the A = 80 mass region with the 82Se(n, gamma)83Se reaction. The nuclide 83Se can be accessed through the beta-decay of 83As, which was studied at the National Superconducting Cyclotron Laboratory with the total absorption spectrometer, SuN. Using the beta-Oslo method, the cross section of the 82Se(n, gamma)83Se reaction was constrained. A direct measurement of the 82Se(n, gamma)83Se reaction was performed with the Detector for Advanced Neutron Capture Experiments and the cross section obtained from the direct measurement is compared to the cross section determined using the beta-Oslo method. The results are in good agreement, validating the beta-Oslo method as a viable method for constraining neutron-capture cross sections.
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Title: WILDFIRE IMPACTS ON SOIL CARBON POOLS AND MICROBIAL COMMUNITIES IN MIXED-CONIFER FORESTS OF CALIFORNIA
Creator: Adkins, Jaron
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Forest ecosystems are important reservoirs for long term carbon (C) storage. Forests of the western United States account for 20-40% of total U.S. carbon C sequestration, and nearly half of the total C in these forests is stored in soil. However, many forests in the western U.S are experiencing wildfire conditions that diverge from historical fire regimes. Prior to Euro-American settlement, California’s mixed-conifer forests typically experienced frequent surface fires of low to moderate burn...
Show moreForest ecosystems are important reservoirs for long term carbon (C) storage. Forests of the western United States account for 20-40% of total U.S. carbon C sequestration, and nearly half of the total C in these forests is stored in soil. However, many forests in the western U.S are experiencing wildfire conditions that diverge from historical fire regimes. Prior to Euro-American settlement, California’s mixed-conifer forests typically experienced frequent surface fires of low to moderate burn severity, but, due to the combined effects of altered forest structure and climate change, now experience fires that are larger and more severe than historical conditions. Fires have numerous direct and indirect effects on the soil biological, chemical, and physical characteristics that influence the soil C cycle. Understanding how altered soil characteristics influence the cycling and persistence of soil C, and how they vary with severity, is important for managing forests for C storage and for predicting fire-climate feedbacks. My dissertation work incorporates observational and manipulative experiments to understand the direct and indirect effects of burn severity on soil C cycling and microbial communities over the short to intermediate term, with a particular focus on the distribution of soil C between active and slow cycling pools. Soil C can be conceptualized as discrete pools of variable persistence in soil. The active C pool is quickly decomposed, contributing to the return of CO2 to the atmosphere, whereas the non-active C pool is more stable and contributes to long term C storage. I leveraged a burn severity gradient resulting from a wildfire in a California mixed-conifer forest to determine the structure and kinetics of these C pools at an intermediate time point in post-fire recovery (i.e. three years). I found that the size of the non-active C pool was smaller in burned areas than unburned areas, and the kinetic rate of the non-active C pool was negatively related to burn severity. I also characterized the soil microbial communities across this severity gradient and identified the environmental characteristics responsible for differences. I found that fungal-to-bacterial ratio and oligotroph-to-copiotroph bacteria ratio decreased with burn severity, and these effects were driven by differences in live and dead tree basal area, soil nutrients, and pH. Leveraging another burn severity gradient, I then determined whether differences in microbial communities and soil C pools were related one-year post-fire in a mixed-conifer forest. I again found lower non-active C pool kinetic rates, and higher abundances of copiotrophic bacteria in burned compared to unburned areas. Differences in soil C pool kinetics were related to tree basal area, soil nutrients, and bacterial communities. I determined the short-term impacts of fire on soil C pools and cycling using lab experiments in which I manipulated soil heating intensity and pyrogenic organic matter (PyOM) additions. I found that high intensity soil heating can decrease microbial biomass C (MBC) accumulation, whereas PyOM had minimal effects on MBC in the short-term. Finally, I found that the size of the active C pool increased with soil heating intensity, while the kinetic rate of the non-active C pool decreased; PyOM primarily increased the size of the non-active C pool. Taken as a whole, my research suggests that fire induces short-term soil C losses by increasing the size of the active C pool, but, over the intermediate-term, residual soil C is more persistent. Fire severity is predicted to increase globally throughout the 21st century, and my research contributes to understanding how forest C storage will be affected by disrupted wildfire regimes.
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Title: RESPONSE OF ULTRA HIGH PERFORMANCE FIBER REINFORCED CONCRETE BEAMS UNDER FLEXURE AND SHEAR
Creator: Solhmirzaei, Roya
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Ultra high performance concrete (UHPC) is an advanced cementitious material made with low water to binder ratio and high fineness admixtures, and possesses a unique combination of superior strength, durability, corrosion resistance, and impact resistance. However, increased strength of UHPC results in a brittle behavior. To overcome this brittle behavior of UHPC and improve post cracking response of UHPC, steel fibers are often added to UHPC and this concrete type is designated as Ultra High...
Show moreUltra high performance concrete (UHPC) is an advanced cementitious material made with low water to binder ratio and high fineness admixtures, and possesses a unique combination of superior strength, durability, corrosion resistance, and impact resistance. However, increased strength of UHPC results in a brittle behavior. To overcome this brittle behavior of UHPC and improve post cracking response of UHPC, steel fibers are often added to UHPC and this concrete type is designated as Ultra High Performance Fiber Reinforced Concrete (UHPFRC). Being a relatively new construction material, there are limited guidelines and specifications in standards and codes for the design of structural members fabricated using UHPFRC. To develop a deeper understanding on the behavior of UHPFRC flexural members, seven beams made of UHPFRC are tested under different loading conditions. The test variables include level of longitudinal reinforcement, type of loading (shear and flexure), and presence of shear reinforcement. Further, a finite element based numerical model for tracing structural behavior of UHPFRC beams is developed in ABAQUS. The developed model can account for the nonlinear material response of UHPFRC and steel reinforcement in both tension and compression, as well as bond between concrete and reinforcing steel, and can trace the detailed response of the beams in the entire range of loading. This model is validated by comparing predicted response parameters including load-deflection, load-strain, and crack propagation against experimental data obtained from tests on UHPFRC beams with different material characteristics and under different loading configurations. The validated model is applied to conduct a set of parametric studies to quantify the effect of different parameters on structural response of UHPFRC beams, including the contribution of stirrups and concrete to shear capacity of beams, to explore feasibility of removing the need for shear reinforcement in UHPFRC beams. Results from experiments and numerical model reveal that UHPFRC beams exhibit distinct cracking pattern characterized by the propagation of multiple micro cracks followed by widening of a single crack leading to failure. Also, UHPFRC beams exhibit high flexural and shear capacity, as well as ductility due to high compressive and tensile strength of UHPFRC and fiber bridging developing at the crack surfaces that leads to strain hardening in UHPFRC after cracking. Thus, absence of shear reinforcement in UHPFRC beams does not result in brittle failure, even under dominant shear loading. Data from the conducted experiments as well as those reported in literature is utilized to develop a machine learning (ML) framework for predicting structural response of UHPFRC beams. On this basis, a comprehensive database on reported tests on UHPFRC beams with different geometric, fiber properties, loading and material characteristics is collected. This database is then analyzed utilizing different ML algorithms, including support vector machine, artificial neural networks, k-nearest neighbor, support vector machine regression, and genetic programing, to develop a data-driven computational framework for predicting failure mode and flexural and shear capacity of UHPFRC beams. Predictions obtained from the proposed framework are compared against the values obtained from design equations in codes, and also results from full-scale tests to demonstrate the reliability of the proposed approach. The results clearly indicate that the proposed ML framework can effectively predict failure mode and flexural and shear capacity of UHPFRC beams with varying reinforcement detailing and configurations. The research presented in this dissertation contributes to the development of preliminary guidance on evaluating capacity of UHPFRC beams under different configurations.
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Title: The necessary and sufficient conditions in weighted inequalities for singular integrals and a local Tb theorem with an energy side condition.
Creator: Grigoriadis, Christos
Date: 2021
Collection: Electronic Theses & Dissertations
Description: We provide an essentially complete dictionary of all implications among the basic and fundamental conditions in weighted theory such as the doubling, one weight $A_p(w)$, $A_\infty$ and $C_p$ conditions as well as the two weight $\A_p(\o,\s)$ and the ``buffer" Energy and Pivotal conditions. The most notable implication is that in the case of $A_\infty$ weights the two weight $\A_p$ condition implies the $p-$Pivotal condition hence giving an elegant and short proof of the known NTV-conjecture...
Show moreWe provide an essentially complete dictionary of all implications among the basic and fundamental conditions in weighted theory such as the doubling, one weight $A_p(w)$, $A_\infty$ and $C_p$ conditions as well as the two weight $\A_p(\o,\s)$ and the ``buffer" Energy and Pivotal conditions. The most notable implication is that in the case of $A_\infty$ weights the two weight $\A_p$ condition implies the $p-$Pivotal condition hence giving an elegant and short proof of the known NTV-conjecture with $p=2$ for $A_\infty$ weights in terms of existing T1 theory. We also provide a quite technical construction inspired by \cite{GaKS} proving that we can have doubling weights satisfying the $C_p$ condition which are not in $A_\infty$. We obtain a local two weight $Tb$ theorem with an energy side condition for higher dimensional fractional Calder\'{o}n-Zygmund operators. The proof follows the general outline of the proof for the corresponding one-dimensional $Tb$ theorem in \cite{SaShUr12}, but encountering a number of new challenges, including several arising from the failure in higher dimensions of T. Hyt\"{o}nen's one-dimensional two weight $A_{2}$ inequality. Hyt\"{o}nen used this inequality to deal with estimates for measures living in adjacent intervals. Hyt\"{o}nen's theorem states that the off-testing condition for the Hilbert transform is controlled by the Muckenhoupt's $A_2$ and $A^*_2$ conditions. So in attempting to extend the two weight $T_b$ theorem to higher dimensions, it is natural to ask if a higher dimensional analogue of Hyt\"{o}nen's theorem holds that permits analogous control of terms involving measures that live on adjacent cubes.We show that it is not the case even in the presence of the energy conditions used in one dimension \cite{SaShUr12}. Thus, in order to obtain a local $T_b$ theorem in higher dimensions, it was necessary to find some substantially new arguments to control the notoriously difficult nearby form. More precisely, we show that Hyt\"{o}nen's off-testing condition for the two weight fractional integral and the Riesz transform inequalities is not controlled by Muckenhoupt's $A_2^\alpha$ and $A_2^{\alpha,*}$ conditions and energy conditions.
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Title: TWO WEIGHTED CARLESON EMBEDDINGS ON MULTI-TREES AND MULTI-DISK
Creator: Psaromiligkos, Georgios
Date: 2021
Collection: Electronic Theses & Dissertations
Description: Given two measures μ,w on a multi-tree T^n we prove a two weighted multi-parameterdyadic embedding theorem for the Hardy operator, assuming w is a product weight and a certain “Box” condition holds. The main result has been long proven for dimension n = 1, however, for higher dimensions the result was not known. There was a general feeling such an embedding was not possible under the Box condition, due to a famous counterexample by Lennart Carleson. In this counterexample, the measure μ was...
Show moreGiven two measures μ,w on a multi-tree T^n we prove a two weighted multi-parameterdyadic embedding theorem for the Hardy operator, assuming w is a product weight and a certain “Box” condition holds. The main result has been long proven for dimension n = 1, however, for higher dimensions the result was not known. There was a general feeling such an embedding was not possible under the Box condition, due to a famous counterexample by Lennart Carleson. In this counterexample, the measure μ was the two-dimensional Lebesgue measure, which is a product measure along with a non-product weight w. Shortly after, A. Chang imposed a (strictly) more general condition than the Box one and showed it is sufficient to get the same embedding in dimension n = 2. This was later used by A. Chang and R. Fefferman to characterize the dyadic n-dimensional product BMO, denoted by BMO_{prod}^d(R^n). Recently, the question of embedding the Dirichlet space on the bi-disk D^2 into L^2(D^2) appeared. This is equivalent to proving a general measure μ is “Carleson” for the Dirichlet space on D^2. It was shown that proving the (discrete) analogue of the embedding on a bi-tree is enough to get the same for the bi-disc. To do this, however, we need to change the restrictions on the measures; we will assume μ to be general and w to be a product weight. Given these restrictions, we managed to prove the surprising result that the Box condition is enough to imply the embedding for dimensions n = 2, 3. This is not contradictory to Carleson’s counterexample as the weight w was non-product.
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Title: High Functional Density Through Rigid-Flex
Creator: Gjokaj, Vincens
Date: 2021
Collection: Electronic Theses & Dissertations
Description: In the last decade Additive Manufacturing (AM), often referred to as 3D printing, has garnered signficant interest in systems packaging. It has proven as an effective way of producing Radio Frequency (RF) to millimeter wave (mmWave) components and modules. AM enables flexible and rapid realization of structures with arbitrary shapes and complexity. AM is considered as one of the most important emerging material processing technologies that will drive the future designs of high functional...
Show moreIn the last decade Additive Manufacturing (AM), often referred to as 3D printing, has garnered signficant interest in systems packaging. It has proven as an effective way of producing Radio Frequency (RF) to millimeter wave (mmWave) components and modules. AM enables flexible and rapid realization of structures with arbitrary shapes and complexity. AM is considered as one of the most important emerging material processing technologies that will drive the future designs of high functional density modules and systems. This thesis investigates the us of AM for the design and fabrication of microwave and mmWave circuits and systems.Different AM technologies are used to design and demonstrate a range of high frequency passive and active components. Stereolithography printing is utilized to create passive components in the X-band (10-18 GHz) and K-band (18-27 GHz) frequency bands. These passive component designs are then combined with active RF circuits to design transmit and receive modules. Aerosol jet printing (AJP) is used to create an entirely printed mmWave components that avoids the use of traditional photolithography fabrication methods. All the designs are compared to their counterparts fabricated using conventional techniques. It is demonstrated that self-packaged RF components 3D form can readily be produced using AM leading to high functional density systems working well into the W-band frequency band.
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Title: FROM SITTING TO LIVING : EXAMINING THE ROLE OF MEDITATION IN UNDERSTANDING THE EMOTION REGULATORY MECHANISMS OF MINDFULNESS
Creator: Lin, Yanli
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Mindfulness has received widespread interest for its purported benefits to emotional well-being. Despite a rapidly growing literature base supporting the salutary relationship between mindfulness and emotion regulation, little is known about how mindfulness confers its emotion regulatory benefits. A pertinent, yet underexplored, approach to addressing this question is to examine neural mechanisms involved in the effects of mindfulness training via meditative practice to “off-the-cushion”...
Show moreMindfulness has received widespread interest for its purported benefits to emotional well-being. Despite a rapidly growing literature base supporting the salutary relationship between mindfulness and emotion regulation, little is known about how mindfulness confers its emotion regulatory benefits. A pertinent, yet underexplored, approach to addressing this question is to examine neural mechanisms involved in the effects of mindfulness training via meditative practice to “off-the-cushion” changes in emotion regulation. The primary aim of the present study was therefore to determine the extent to which change in neural oscillatory activity (i.e., alpha and theta power) during mindfulness meditation related to subjective (i.e., self-reported negative affect) and neural (i.e., late positive potential [LPP]) measures of emotional reactivity elicited during a subsequent affective picture viewing task. Toward this end, a multimodal experimental paradigm was employed to test three predictions: 1) participants randomized to engage in brief guided mindfulness meditation, relative to those randomized to a control condition, would exhibit increased alpha and theta power during meditation relative to rest; 2) participants in the meditation group, but not those in the control group, would exhibit attenuated LPP responses and report lower negative affect during the picture viewing task; 3) the predicted increases in alpha and theta power during meditation would correlate with the predicted reductions in the LPP and self-reported negative affect during picture viewing. Contrary to expectations, the guided meditation did not produce demonstrable effects on alpha and theta power, the LPP, or self-reported negative affect relative to the control condition. Change in theta, but not alpha, power during meditation was, however, positively correlated with the early time window of the LPP, suggesting that change in neural activity during meditation may relate to subsequent emotion processing. Overall, the study demonstrated the utility of investigating the relationship between what occurs during mindfulness meditation and its purported effects on emotion regulation. Moreover, reflections on the unexpected nature of the null findings dovetail with the prevailing consensus that theoretical and methodological factors unique to the construct of mindfulness are integral in shaping the direction, design, and interpretability of mindfulness research.
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Title: SYSTEMATIC ANALYSIS OF THE SIGNAL RESPONSIVE GENE REGULATORY NETWORK GOVERNING MYXOCOCCUS XANTHUS DEVELOPMENT
Creator: Saha, Shreya
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Studies of signal-induced gene expression in bacteria have contributed to understanding of how bacteria cope with environmental stress. As an extensively studied model, Myxococcus xanthus provides fascinating insights into how changes at the level of gene expression enable which bacteria to survive environmental insults such as nutrient limitation. Upon starvation M. xanthus cells glide into aggregates and form mounds that mature into fruiting bodies as some cells form spores. Previously, our...
Show moreStudies of signal-induced gene expression in bacteria have contributed to understanding of how bacteria cope with environmental stress. As an extensively studied model, Myxococcus xanthus provides fascinating insights into how changes at the level of gene expression enable which bacteria to survive environmental insults such as nutrient limitation. Upon starvation M. xanthus cells glide into aggregates and form mounds that mature into fruiting bodies as some cells form spores. Previously, our group defined 24-30 h poststarvation as the critical period for commitment to spore formation, when cells commit to form spores despite perturbation of the starvation signal by nutrient addition. The process of multicellular development that culminates in sporulation is governed by a network of signal-responsive transcription factors that integrate signals for starvation and cellular alignment. In this dissertation I present the first systematic approach to elucidate the network dynamics during the commitment period.In the network, MrpC is a starvation-responsive transcription factor, whereas FruA is a transcription factor that responds to cellular alignment conveyed by C-signaling. Transcription of fruA is dependent on MrpC binding, and FruA activity is proposed to be posttranslationally regulated by C-signaling, although the mechanism is unknown. FruA and MrpC cooperatively regulate transcription of the dev operon. My systematic analysis of the network dynamics supported a model in which posttranslational activation of FruA by C-signaling is critical for dev transcription and for commitment to spore formation. Similar to dev, MrpC and C-signal-activated FruA combinatorially controlled transcription of the late-acting fadIJ operon involved in spore metabolism. Regulation of late-acting operons implicated in spore coat biogenesis (exoA-I, nfsA-H, MXAN_3259-MXAN_3263) was discovered to be under complex control by MrpC and FruA. My evidence suggests that transcription of these operons depends at least in part on a C-signal-dependent switch from negative regulation by unactivated FruA to positive regulation by activated FruA during the period leading up to and including commitment to sporulation. MrpC negatively regulated exo and MXAN_3259 during mound formation, but positively regulated nfs. During commitment to sporulation, MrpC continued to positively regulate nfs, switched to positive regulation of MXAN_3259, and continued to negatively regulate exo. A third transcription factor, Nla6, appeared to be a positive regulator of all the late genes. We propose that in combination with regulation by Nla6, differential regulation by FruA in response to C-signaling and by MrpC controls late gene expression to ensure that spore resistance and surface characteristics meet environmental demands.
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Title: NEW APPROACHES TO ASSESS AND IMPROVE PROTEIN EFFICIENCY IN LACTATING DAIRY COWS
Creator: Liu, Enhong
Date: 2020
Collection: Electronic Theses & Dissertations
Description: The long-term goal of the work is to improve protein efficiency in lactating dairy cows. To achieve this goal, four specific objectives were proposed: 1) determine the relationship of residual feed intake (RFI) to protein efficiency in lactating Holstein cows fed high or low protein diets, 2) determine whether low protein resilience (LPR) is an indicator of protein efficiency in individual dairy cows, 3) examine the association of digestibility with RFI and LPR in lactating dairy cows, and 4)...
Show moreThe long-term goal of the work is to improve protein efficiency in lactating dairy cows. To achieve this goal, four specific objectives were proposed: 1) determine the relationship of residual feed intake (RFI) to protein efficiency in lactating Holstein cows fed high or low protein diets, 2) determine whether low protein resilience (LPR) is an indicator of protein efficiency in individual dairy cows, 3) examine the association of digestibility with RFI and LPR in lactating dairy cows, and 4) quantify the importance of including body weight (BW) change in the cow response to decreased dietary protein content and develop models for predicting BW change when dietary protein is altered. Lactating Holstein cows (n= 166; 92 primiparous, 77 multiparous) with initial milk yield (MY) of 41 ± 9.8 kg/d were fed high (HP) and low (LP) protein diets in crossover experiments of two 28-35 d periods. Experiments were repeated in 69 of the 166 cows (42 primiparous, 27 multiparous) in late lactation. Low protein diets were 14% CP in peak lactation and 13% CP in late lactation and were formulated to contain adequate rumen-degraded protein to maintain rumen function. Expeller soybean meal was added to formulate the HP diet, which contained 18% CP in peak lactation and 16% CP in late lactation. Cows were milked twice daily; DMI and MY were recorded once daily. Milk composition was measured over 4 consecutive milkings weekly, and BW was measured 3 times weekly. Samples of feed ingredients, orts and feces were collected in the last 5 days of each period and analyzed to determine digestibilities of DM, NDF, and CP for each cow on each diet. Fixed effects of diet, parity, treatment sequence nested in experiment, treatment period nested in experiment, interaction of parity and diet, and random effects of experiment and cow nested within experiment were included in models to compare production of cows fed different levels of CP. Protein efficiency was calculated for each cow on each diet in both peak lactation and late lactation. Residual feed intake was estimated for each cow on each treatment based on the actual intake, milk energy output, metabolic BW, and body energy change (estimated from BW change and BCS). Low protein resilience was estimated for each cow in peak lactation and also late lactation, based on protein captured in milk and body tissue when fed the LP vs HP diet. A negative correlation was observed between RFI and protein efficiency in cows fed the HP and LP diets in peak lactation and cows fed the HP diet in late lactation. Cows with higher LPR values had similar protein efficiency on the HP diet but significantly higher protein efficiency on the LP diet. Neither RFI nor LPR was correlated with digestibility regardless of diets or lactation stages. When dietary protein content was reduced, 40-50 % of the total energy loss, 10-20 % of total protein loss, and 15-25% of total income loss were due to BW loss, indicating that considering only changes in milk production underestimates the impact of dietary protein changes. In conclusion, 1) cows with lower RFI values utilized protein more efficiently, and protein efficiency will be improved in the process of selecting dairy cattle for low RFI, 2) cows with higher LPR values are better able to maintain production and have higher protein efficiency to adapt to low-protein feeding conditions, 3) variation in digestibility cannot explain the variations of RFI or LPR among lactating dairy cows, and we suggest that post-absorptive metabolism explains most of the variation in RFI and LPR when lactating cows are fed diets with minimal NDF in peak lactation and 40% NDF in late lactation, and 4) body reserve mobilization should not be neglected when assessing the cow response to changes in dietary protein.
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Title: Using manipulatives to support secondary students with high-incidence disabilities in algebra
Creator: Bone, Erin
Date: 2020
Collection: Electronic Theses & Dissertations
Description: All students, including students with disabilities, are expected to learn mathematics at high levels. As algebra is considered to be the gatekeeper to higher level mathematics and beyond, it is essential for teachers to use effective practices, including the use of manipulatives, to support student learning. This alternative dissertation is comprised of three studies that explored teaching algebra to secondary students with high-incidence disabilities. The first was an evidence-based...
Show moreAll students, including students with disabilities, are expected to learn mathematics at high levels. As algebra is considered to be the gatekeeper to higher level mathematics and beyond, it is essential for teachers to use effective practices, including the use of manipulatives, to support student learning. This alternative dissertation is comprised of three studies that explored teaching algebra to secondary students with high-incidence disabilities. The first was an evidence-based systematic review of literature investigating instructional practices to teach algebra to secondary students with high-incidence disabilities. Twenty studies published from 1999-2019 were reviewed and analyzed, of which 14 met the standards of high quality set by the Council for Exceptional Children (CEC), and five practices earned the label of potentially evidence-based (i.e., concrete-representational-abstract framework, manipulatives, enhanced anchor instruction, schema based instruction, and peer-assisted learning strategies). The second study used an alternating treatment design to compare the effectiveness of concrete algebra tiles to virtual algebra tiles to support middle school students with disabilities as they solved linear equations. Students were successful solving linear equations regardless of the type of manipulative they used, but preferred using the virtual tool. The final study used a multiple probe across behaviors, replicated across participant design to examine the effectiveness of the VA framework to support secondary students with high-incidence disabilities in their acquisition of algebra skills. A functional relationship existed between the VA framework and student performance on algebra probes, and students scored better on maintenance probes compared to baseline data. While there remains a need for more high-quality research examining effective practices in supporting secondary students with high-incidence disabilities in the area of algebra, the studies in this alternative dissertation suggest manipulatives, both as a stand-alone tool and as part of a process is an effective, and efficient intervention.
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Title: Antiracist teacher education and whiteness : towards a collective humanization
Creator: Moore, Ashley E.
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Using Critical Whiteness Studies (CWS) as theoretical grounding, this three-article dissertation offers perspectives on antiracist teacher education praxis, and the ways that White teacher educators can be more thoughtful and critical of our participation in perpetuating Whiteness. Across the articles, I explore how my attempts to embody antiracist praxis as a White teacher educator are still fraught with performances of Whiteness.In the first article, I use interviews from student-nominated...
Show moreUsing Critical Whiteness Studies (CWS) as theoretical grounding, this three-article dissertation offers perspectives on antiracist teacher education praxis, and the ways that White teacher educators can be more thoughtful and critical of our participation in perpetuating Whiteness. Across the articles, I explore how my attempts to embody antiracist praxis as a White teacher educator are still fraught with performances of Whiteness.In the first article, I use interviews from student-nominated exemplary social justice faculty to describe concrete practices of antiracist teacher education praxis. The four practices that emerge include: model vulnerability, shift agency to students, build community, and pose questions. Consistent across these findings is the belief that teacher education should be a project in collective humanization; and further, that it must be grounded in critical race theories.The second article follows my attempts to employ each of the four practices listed above throughout one semester of teaching a diversity-related course. The purpose of this article is to highlight the tensions I feel trying to embody this pedagogical stance as a White female teacher educator. My findings, presented in the form of fictionalized vignettes, reveal very concrete ways that I continue to perform Whiteness as I attempt to subvert it. I therefore argue that White teacher educators must engage with more critical tools--such as autoethnography--to identify and combat the impact of our best intentions.The final article is a poetic inquiry that explores one of the aforementioned practices--model vulnerability--through a more critical lens. Vulnerability is something commonly described in normative ways, particularly in the work of Dr. Brene Brown. I explore how, as a White woman, I have more freedom to express emotions such as vulnerability without fear of repercussion or of being perceived as weak. Moreover, through using poetry as both a method of inquiry and subsequent data to analyze, I find that even the process I use to write and think about Whiteness is, in fact, reflective of my Whiteness. We as teacher educators therefore must be mindful not to describe vulnerability in normative ways that do not take into account the ever-present sociopolitical context in which we live--a context that privileges the humanity and feelings of White people while disparaging the humanity and feelings of people of Color.By using CWS across all three articles of this dissertation, I am able to highlight myriad ways that my Whiteness continues to operate insidiously even as I attempt to counter it. I offer considerations for other White teacher educators who want to move their praxis closer to being actively antiracist, ultimately hoping that more will endeavor to do this kind of work.
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Title: Influence of landscape composition, landscape diversity, and conservation management on bee health via a pollen nutrition mechanism
Creator: Quinlan, Gabriela Marie
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Bees are the most important pollinators in agricultural systems, with honey bees (Apis mellifera L.) in particular providing the majority of pollination services on commercial farms. However, due to interacting stressors including lack of nutrition and disease, honey bees and other bee species are experiencing elevated loss rates compared to historical records. Access to abundant, high quality, continuous nutrition in the landscape has been suggested as a means of promoting bee health. To...
Show moreBees are the most important pollinators in agricultural systems, with honey bees (Apis mellifera L.) in particular providing the majority of pollination services on commercial farms. However, due to interacting stressors including lack of nutrition and disease, honey bees and other bee species are experiencing elevated loss rates compared to historical records. Access to abundant, high quality, continuous nutrition in the landscape has been suggested as a means of promoting bee health. To test this, I studied honey bee and bumble bee colonies in 12 apiaries that ranged in land cover composition of the surrounding forage landscape. Honey bee colony cluster size and brood area at the end of the summer were most closely related to post-spring pollination colony size and other colony-level variation, whereas bumble bee colony weight, gyne and drone production were related to surrounding land covers. This demonstrates the importance of accounting for potentially confounding honey bee colony variation in landscape-scale studies. To determine if diversity of land covers affected honey bee pollen foraging and colony size, I also measured honey bee colony size and incoming pollen at 12 apiaries located within landscapes of differing land cover diversity, and found that the relationship between land cover diversity, incoming pollen quantity and colony cluster size changed over time. This suggests that land cover diversity alone is insufficient for predicting patterns in honey bee landscape nutrition studies in this region. Conservation Reserve Program (CRP) land may include flowering, herbaceous species in seed mixes, but in states such as Michigan with abundant forage in unmanaged habitats, it is unclear if CRP investments have unique floral composition, and foraging by honey bees and wild bees. I assessed floral composition and bee visitation on CRP land as compared to analogous unmanaged fields and roadside ditches in 31 triplicate sites. Floral abundance, species richness, native flower abundance, and inflorescence coverage were all higher on CRP land, as were honey bee and wild bee visitation, indicating that herbaceous CRP promotes bee foraging through unique floral composition, namely floral density. By assessing the quantity and quality of incoming pollen at apiaries while concurrently surveying floral communities in nearby grassy-herbaceous forage habitat, I found that crude protein in collected pollen decreased throughout the summer, concurrent with decreasing floral richness and abundance. This suggests pollinator plantings should include protein-rich, late-blooming species in their seed mixes. Because nutrition is closely tied to disease in honey bees, supplementing protein may promote recovery from diseases such as European foulbrood. To compare different approaches to managing this disease, European foulbrood-infected colonies were treated with traditional antibiotics, antibiotics with a soy-based protein supplements, soy-based supplement alone, pollen-based supplement, probiotics, or left untreated. There was no significant difference among non-antibiotic treatments in post-treatment recovery speed or nurse bee physiology, suggesting these supplemental feeding treatments and probiotics provide no treatment benefits for European foulbrood. Based on this research, accounting for colony-level variation is essential in honey bee landscape studies. Adding pollinator conservation habitat with an increased emphasis on late-season, protein-rich pollen species in seed mixes can benefit honey bees and wild bee species. This work provides new insights into the effects of landscapes on honey bee and wild bee foraging, nutrition and health by examining different aspects of these indirect relationships.
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Title: Finding, creating, and following footprints : the integration of indigenous knowledge in Palau Community College
Creator: Hannibal, Joy Renee
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Little research exists on the specific ways that Indigenous ways of being, knowing and doing are integrated in institutions of higher education across Micronesia. This research study illuminates through case study the position of Palauan Knowledge within Palau Community College. An Indigenous methodology set within a broader Indigenous research paradigm (Wilson, 2008) is utilized to align with Palauan values of respect (omenguul) and responsibility (ngerachel). Through interviews (chelededuch...
Show moreLittle research exists on the specific ways that Indigenous ways of being, knowing and doing are integrated in institutions of higher education across Micronesia. This research study illuminates through case study the position of Palauan Knowledge within Palau Community College. An Indigenous methodology set within a broader Indigenous research paradigm (Wilson, 2008) is utilized to align with Palauan values of respect (omenguul) and responsibility (ngerachel). Through interviews (chelededuch) with nine collaborators, in addition to fieldnotes, observations, and archival documents, this study aimed to answer the following research questions: How is Indigenous Knowledge incorporated within Palau Community College (PCC)? Secondly, how do stories from Indigenous teachers and Indigenous learning environments inform PCC? Findings from this study reveal experiences of separation from Palauan Knowledge and the actions some collaborators took to preserve Palauan Knowledge. Collaborators' narratives highlight several instances where Palauan knowledge is honored within the college through visual and oral representations as well as with academic and community programming. Continuity of Palauan Knowledge through ongoing opportunities to sustain practices in and outside of the college is explored in the final reflections of collaborators who continue to challenge perspectives that Indigenous Knowledge is in the past. Ultimately, this study lays a foundation for the argument that Palauan Knowledge is demonstrated as resilient, dynamic and adaptive to the needs of community. Recommendations concerning the elevation of Indigenous Knowledge at Palau Community College and other institutions of higher education that reside on Indigenous land are offered.
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Title: There is no such thing as the voiceless : listening to the voices of elementary youth to affect school change
Creator: Mauldin, Courtney Camille
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Using an arts-based methodology, this dissertation project moves beyond the traditional bounds of student and leader in schools by examining how elementary-aged youth of color are positioned to affect change within their school by way of centering student voice. Further, this study examines how school leaders engage the voices of elementary-aged youth of color. While there has been emerging research on the inclusion of student voice in the field of educational leadership, there is limited...
Show moreUsing an arts-based methodology, this dissertation project moves beyond the traditional bounds of student and leader in schools by examining how elementary-aged youth of color are positioned to affect change within their school by way of centering student voice. Further, this study examines how school leaders engage the voices of elementary-aged youth of color. While there has been emerging research on the inclusion of student voice in the field of educational leadership, there is limited literature that provides an in-depth description of how school leaders implement student voice in the elementary school setting. Drawing from a critical leadership framework and Black feminist practices and epistemologies, the aims of this study are to contribute to the literature on student voice in the educational leadership field and to examine the ways in which youth voice can influence more critically reflexive approaches to school leadership practice. Using an art-based approach in our weekly dialogue group allowed for students to create poetry, collage, and other constructed artifacts that conveyed their ideas about what leadership should encompass and the changes they desired to see in their school, society, and local community. Through a thematic analysis of field notes, artifacts composed by the youth, recorded dialogue sessions with youth and repetitive interview sessions with the school leader, this study documents both youth and school leader perceptions of student voice and leadership in the elementary school context.
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Title: Determination of the role of ventral tegmental area SGK1 catalytic activity and phosphorylation in drug behavior
Creator: Doyle, Marie Althea
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Substance use disorder is a chronic, relapsing disease that affects 20.3 million people in the United States. Despite its prevalence, treatments remain inadequate in part due to our limited understanding of the neuroadaptations induced by drug use. Drugs of abuse are known to regulate the activity of the mesolimbic dopamine (DA) system, a key circuit for drug action and reward. Specifically, drug-induced changes in ventral tegmental area (VTA) cellular activity and gene regulation have been...
Show moreSubstance use disorder is a chronic, relapsing disease that affects 20.3 million people in the United States. Despite its prevalence, treatments remain inadequate in part due to our limited understanding of the neuroadaptations induced by drug use. Drugs of abuse are known to regulate the activity of the mesolimbic dopamine (DA) system, a key circuit for drug action and reward. Specifically, drug-induced changes in ventral tegmental area (VTA) cellular activity and gene regulation have been linked to behavioral outputs associated with addiction. Previous work determined that serum- and glucocorticoid-inducible kinase 1 (SGK1) mRNA expression, catalytic activity, and phosphorylation were increased by chronic administration of cocaine or morphine; however, it was unknown if these changes contributed to drug reward behaviors. In this thesis, I utilized transgenic and viral-mediated SGK1 manipulations to determine the impact of altered SGK1 expression and function on cocaine and morphine related-behaviors, primarily assessed by cocaine conditioned place preference (CPP) and voluntary morphine intake using a two-bottle choice task. I first established that that while SGK1 is transcriptionally upregulated and biochemically modified by chronic-drug administration, SGK1 deletion in either the VTA or in DA neurons was not capable of altering drug reward behaviors. Though SGK1 gene deletion did not alter reward, I next showed that viral-mediated overexpression of SGK1 mutants in the VTA of adult mice produced behaviorally relevant effects on cocaine and morphine reward. Specifically, intra-VTA infusion of a catalytically inactive SGK1 mutant (K127Q) significantly decreased cocaine CPP and morphine preference, suggesting that decreased VTA SGK1 activity is sufficient to impair drug reward. To more fully understand the role of VTA SGK1 in behaviors relevant to addiction, I manipulated SGK1 expression in a cell type-specific manner to determine whether SGK1 activity in VTA DA or GABA neurons drove the observed behavioral effects. Utilizing novel Cre-dependent viral constructs, I found that reduced SGK1 activity in VTA DA neurons significantly decreases cocaine CPP, while this same manipulation in VTA GABA neurons had no effect. Interestingly, this manipulation did not alter morphine preference. Future studies seek to determine a potential mechanism for these behavioral effects using ex vivo slice electrophysiology, and parallel studies currently explore the potential effects of a similarly regulated SGK1 phosphorylation site (Ser78) in drug-related behaviors. Altogether, these studies will allow for the identification of the specific cells and circuits that are critical for SGK1-mediated effects on drug reward and intake, a necessary step in assessing the feasibility of SGK1 inhibition as a novel therapeutic avenue for addiction.
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Title: The effects of genetic background on the evolution of antibiotic resistance and its fitness costs
Creator: Card, Kyle Joseph
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Antibiotic resistance is a growing public-health concern. Efforts to control the emergence and spread of resistance would benefit from an improved ability to forecast when and how it will evolve. To predict the evolution of resistance with accuracy, we must understand and integrate information about many factors, including a bacterium's evolutionary history. This dissertation centers on the effects of genetic background on the evolution of phenotypic resistance, its genetic basis, and its...
Show moreAntibiotic resistance is a growing public-health concern. Efforts to control the emergence and spread of resistance would benefit from an improved ability to forecast when and how it will evolve. To predict the evolution of resistance with accuracy, we must understand and integrate information about many factors, including a bacterium's evolutionary history. This dissertation centers on the effects of genetic background on the evolution of phenotypic resistance, its genetic basis, and its fitness costs. To address these issues, I used Escherichia coli strains from the long-term evolution experiment (LTEE) that independently evolved for multiple decades in an environment without antibiotics.First, I examined how readily these LTEE strains could overcome prior losses of intrinsic resistance through subsequent evolution when challenged with antibiotics. Second, I investigated whether lineages founded from different genotypes take parallel or divergent mutational paths to achieve increased resistance. Third, I tested whether fitness costs of resistance mutations are constant across different genetic backgrounds. In these studies, I focused attention on the interplay between repeatability and contingency in the evolutionary process. My findings demonstrate that genetic background can influence both the phenotypic and genotypic evolution of resistance and its associated fitness costs. I conclude this dissertation with a broader discussion about these and other factors that can influence the evolution of antibiotic resistance, and their clinical and public-health implications.
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