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Fluorinated Lanthanide-Based Contrast Agents For Magnetic Resonance Imaging
No full textThe research projects described in this dissertation are focused on fluorous interactions with divalent and trivalent lanthanides. These interactions lay the foundation to overcome concentration dependence of contrast agents for MRI and strategies to synthesize small-molecule thermometers that enable mapping temperatures over a biologically relevant range. Furthermore, dual-mode tumor imaging using probes that are responsive to hypoxia and hypoxia-induced pathological conditions have been described to contextualize the new research described in this dissertation with respect to reported examples. A brief overview of responsive contrast agents for MRI in chapter 1 is followed by chapter 2 that described dual-mode imaging of hypoxia and related pathophysiological conditions using dual-mode imaging modalities. Compared to single-mode imaging techniques, dual-modal imaging enables accurate diagnosis of diseases while overcoming the limitations of single imaging modalities. Chapter 2 also provides detailed descriptions of pre-clinical and clinical examples of different imaging techniques to image hypoxia. These two chapters offer context for the remaining chapters. EuII- and EuIII-containing complexes having 4, 12, and 24 fluorine atoms are described in chapter 3. These complexes were used to quantify hypoxia using a ratiometric method. The ratio between T1 relaxation due to the presence of EuII-containing complex and 19F signal due to the presence of EuIII-containing complex were correlated with the amount of oxygen present in the environment. Out of all three complexes, the complex with 4 fluorine atoms was found to possess the steepest slope of the hypoxia index curve, therefore, it enables more sensitive differentiation between regions with different concentrations of oxygen. However, the complex with 12 fluorine atoms displayed the best combination of signal and solubility of the three complexes. Prior to the research presented in chapter 4, lanthanide-containing contrast agents for MRI have been used to report temperature but there was a lack of small-molecule MRI thermometers that can use without encapsulating in macromolecular hydrogel systems or liposomes to increase contrast enhancement with increasing temperature. A fluorinated GdIII-containing complex is reported in chapter 4 of this dissertation that increases its inner-sphere relaxivity with increasing temperature over a biologically relevant range. The basis of the temperature-dependent relaxivity response of the fluorinated contrast agent is the modulation of water exchange caused by trifluoromethyl groups that forms a cage-like structure around the inner-sphere water molecule. The ability to use fluorinated contrast agents for MRI is important to enhance the sensitivity of the experiment. Furthermore, weak fluorous interactions between fluorine atoms involve in chemical control of parameters relevant to MRI. Therefore, fluorinated lanthanide-based contrast agents not only enhance the quality of MRI experiments but also, they are useful in innovative future biomedical applications. Chapter 5 summarizes the future outlook of the applications of dual-mode hypoxia imaging with responsive probes, potential in vivo applications of fluorinated Eu-based concentration independent probes, and potential modifications to the metal complexes to use fluorinated lanthanide-based contrast agents for MRI thermometry
Digital Entrepreneurs As Instructional Designers: How Black Women Digital Entrepreneurs Make Design Decisions When Designing And Developing Digital Learning Products
No full textMillions of people are part of the global creator economy. As more digital content creators shift from producing entertaining to educational content, the number of digital entrepreneurs who design, develop, and deliver instruction without awareness of the practice and profession of instructional design is likely to increase.
Decision making is a skill instructional designers use at every phase of the design process. A growing body of research explores how formally educated or trained designers develop their decision-making capabilities and the factors that influence their design decisions. But what guides the design decisions of designers who do not have any formal education or training in instructional design? Based on semi-structured interviews with nine Black women digital entrepreneurs from various industries, this qualitative research study explores how Black women digital entrepreneurs make decisions when designing and developing digital learning products. Implications for practicing, teaching, and researching issues in instructional design; integrating principles of design justice and inclusive design into the practice and profession; and designing instruction for informal learning in virtual spaces are discussed. Recommendations for future research about justice, diversity, equity, and inclusion in instructional design; decision making in instructional design; the intersection of digital entrepreneurship and instructional design; and designer identity are also shared
The Testimonios Of Latina Higher Education Leaders At Four-Year Predominantly White Institutions In Michigan
No full textThe purpose of this qualitative research study was to explore the lived experiences of Latina higher education leaders at four-year predominantly White institutions (PWIs). The number of Latinas in leadership positions within higher education does not reflect the growing Latina college student representation. A qualitative research approach using the testimonio method was ideal in exploring the experiences of higher education Latina leaders. The testimonios were analyzed from a LatCrit lens which allowed to name some of the oppressions Latinas have encountered in search of administrative positions within the academy. The participants consisted of ten women identified as Latinas, holding roles of director or associate/assistant dean at a four-year PWI in Michigan. From the data, the following themes emerged: Experiences as a Latina Student and Professional, Family, Community, Mentorship, Support, Resources, Opportunities, Barriers and Challenges, Identity, Structural Issues in Higher Education, and Participant Recommendations. Moreover, these testimonios are intended to serve as an urgency to change higher education structural inequities, while motivating aspiring Latinas leaders to strive for senior-level positions within higher education
A Disposition-Belief-Motivation Approach To Predicting Self-Rated Health And Subjective Wellbeing Over The Course Of The Menopause Transition
No full textThe present work replicates cross-sectional menopause literature identifying correlations among personality traits, attitudes, coping, and postmenopausal health and wellbeing. Using a subsample of the Midlife in the United States cohort assessed across 20 years, this work highlights the prospective effects of premenopausal traits and expectancies on peri- and post-menopausal health and wellbeing in a theoretically-informed multivariate framework. The modeling resulted in inadequate estimated fit, owing to the weak and primarily insignificant effects of premenopausal variables in predicting perimenopausal perceptions of health and wellbeing. Despite this, attitudes toward menopause emerged as the sole significant direct prospective predictor of postmenopausal self-rated health. Exploratory Bayesian estimation of the model found the direct effect of premenopausal attitudes on postmenopausal self-rated health to be reliable. Premenopausal conscientiousness and functional wellbeing (via the IADL) emerged as significant indirect prospective predictors of postmenopausal self-rated health via perimenopausal health. When controlling for its association with other baseline constructs, age was a significant indirect prospective predictor of postmenopausal subjective wellbeing via perimenopausal wellbeing. The discussion highlights similarities and unique characteristics of the present findings in comparison to extant literature, measurement and analytic limitations, and the contribution of this work in the identification of worry about developmental changes as a key predictor of quality of life across this transitional stage
Déambulations Globales : Espace (s) Et Mobilité (s) Dans Les Romans De Jean-Philippe Toussaint Et De Jean Echenoz
No full textIn this dissertation, I explore the complex relation between man and space, place, and mobility in the context of increasingly globalized societies where transit spaces (airports, train stations, hotels) proliferate, and people, goods, technologies, and capital circulate at an accelerated pace and frequency. Drawing on the views of anthropologist Marc Augé, of geographers Michel Lussault, Mathis Stock, Tim Cresswell and of prominent mobilities studies scholars John Urry and Mimi Sheller, I argue that the paradoxical dynamic of stasis and mobility that permeates Jean Echenoz and Jean-Philippe Toussaint’s novels prompts us to reconsider the concepts of space, place, non-place through the notion of hyperplace. I specifically stress the relativity and porosity of the concept of non-place which cannot be exclusively used to interpret the greater homogenization of spaces and the increasing urbanization of the world since the 1980s. Additionally, I show that, in these novels, some of the transit spaces encountered are not entirely non-relational. They have the potential to become hyper-places, at least in part, even if they are weakened on one or more of their criteria. I also posit that the integrated web of intensified circulation and inertia defines our contemporary way of life which reflects issues of instability, anxiety, and sense of place while concomitantly offering opportunities for reconfigurations and renewal of the way we experience and use space. I contend that despite such challenges, the protagonists adapt to the fluid nature of today’s world emphasizing the complexity and ambiguities of the dynamics of our global world driven by speed and mobility. In doing so, the authors also unveil a posture of resistance towards this contemporary way of life. Moreover, I consider that, despite their wanderings, the protagonists inhabit the places and spaces they cross through their varied spatial practices which are anchored in their daily routine, physical gestures, and comings and goings. Yet, the authors maintain a form of ambivalence regarding the ability of the characters to dwell or inhabit the spaces and places they go through. Indeed, because of the filtered relationship they develop with their environment, the emotional attachment to these places or sense of place cannot entirely be determined. In this way, inhabiting is never fully complete, it is a process being constantly elaborated which can be done, undone, and experimented. The notion of dwelling or inhabiting spaces for Echenoz and Toussaint reflects a way of living and being in the world which accounts for the vicissitudes of life and for the passage of time, reminding us of our mortality. Finally, as the protagonists seek the presence of others defying their solitary nature, the authors show that there are still possibilities for users of the same space, and by extension, for humans to cohabitate and live together in this contemporary world
Genetic Determinants Of Peripheral Neuropathies
No full textPeripheral nerves are composed of various cell types that are highly regulated to form anatomical features during the early development. These characteristics enable acquisition of an optimal conduction velocity (CV). Therefore, CV changes mark specific stages of nerve development. This study aimed to examine the developmental changes in peripheral nerves at critical time points determined by CV in rat nerves. Transcriptome analysis of peripheral nerve tissues from 20-day-old animals, exhibiting the fastest increment in CV, and 70-day-old animals, displaying CV at its plateau, revealed genes crucial for nerve development. These genes are predominantly involved in immune pathways, extracellular matrix, and collagen organization. Protein-protein network analysis of differentially expressed genes demonstrated significant interactions with genes associated with various peripheral neuropathies, emphasizing the importance of these genes in peripheral nerve function. Preliminary analysis of spatial transcriptome from these peripheral nerve tissues identified genes enriched in specific cell populations and offered insights into spatio-temporal transcriptome changes during peripheral nervous development. Functional and behavioral assessments of patients with peripheral neuropathies revealed a strong correlation between physical functions and disease severity. Genetic burden score calculated from variants in the genes identified through the transcriptome study exhibited a significant correlation with disease severity, highlighting the contribution of genetic background on these identified genes to peripheral neuropathies. Taken together, this study advances our understanding in genetic regulation of peripheral nerve development, and their relevance to the peripheral nerve diseases
Inclusivity, Access, And Identity In Contraceptive Health Discourses
No full textContraception and reproductive health have historically been—and continue to be—constructed as women’s health issues. But, for all the ways in which contraception circulates in the public mind, little attention is paid to the individual, embodied experiences of learning about, discussing, and using various contraceptive technologies, or to the texts that facilitate this learning, discussing, and using. In this dissertation, I aim to investigate how understandings of sex and gender/gender identity manifest in contraception texts and whether they recognize, in addition to cis-women, cis-men, trans, nonbinary, genderqueer, & other non-cis identities as users of contraception and contraception texts. Through two studies, this dissertation examines how gender and sex are constructed in contraceptive texts on Planned Parenthood’s website and explores the varied experiences of individuals seeking out contraception information
Electrical Percolation And Magnetoresistance In Randomly Packed Metal-Insulator Nanocomposites
No full textPercolation is a random probabilistic process that triggers a continuous phase transition from a finite cluster within a network below the critical value of the percolation threshold p_c to an infinite cluster above p_c. While classical percolation is well understood, percolation effects in randomly packed or jammed disordered systems are much less well-explored. Disordered systems exhibit different packing fractions or filling factors compared to ordered systems, determining the system\u27s critical behavior, which in turn, influences its functionality. By selecting a particular kind of matrix and filler, one can tailor the desired properties of a composite for specific applications.
In this study, we investigated experimentally the electrical percolation in a binary composite system of disordered spherocylinders composed of conducting (CrO2) and insulating (Cr2O3) rod-like nanoparticles, with nominally identical geometries. By preparing composite samples with varying volume fractions of the two constituents and performing four-point electrical transport measurements, we determined the classical percolation threshold of CrO2, p_c=0.305±0.026 and the conductivity critical exponent t=2.52±0.03. Our experimental observations align well with theoretical simulations and modeling.
Furthermore, we investigated the tunneling percolation in CrO2-Cr2O3 binary composites below the classical percolation threshold. We observed the characteristic tunneling staircase associated with the presence of the tunneling percolation transitions in this system through interparticle contacts, with the two tunneling thresholds determined at p_T^1 = 0.259 and p_T^2 = 0.165, the latter corresponding to the conductivity onset in this system. We discussed possible mechanisms of higher order tunneling and proposed a simple model which is in good agreement with the experimental data. We also performed detailed magnetotransport measurements in CrO2-Cr2O3 nanoparticle composites at different temperatures. We found significant variations of magnetoresistance (MR) which was highly sensitive to the constituents composition near the tunneling percolation threshold p_T^1, with the maximum value of MR = 44.37% at T = 5 K near the tunneling threshold p=0.26. This research contributes to our understanding of percolation phenomena and its effects on electrical and magnetotransport properties in metal-insulator nanocomposites. These findings have significant implications for tailoring and optimizing composite materials for diverse technological applications
Characterizing Metal Loading And Utilization In Iron-Sulfur Cluster Assembly Systems
No full textIron is an essential metal in biology, requiring strong cellular regulatory mechanisms. In prokaryotes, the Ferric Uptake Regulation (Fur) pathway helps control Iron-Sulfur (Fe-S) cluster biosynthesis. Fe-S clusters are ubiquitous in nature and they are conserved biological cofactors that are found in almost all life forms. There are however multiple pathways that control iron-sulfur cluster biosynthesis, including the Iron-Sulfur Cluster Assembly Pathway, a pathway found in both prokaryotic and eukaryotic organisms. The ISC multiprotein complex that accomplishes Fe-S cluster assembly consists of six proteins, complexed as a dimer of hexomers that includes the scaffold and frataxin proteins, which are the topic of my work, as well as 4 additional proteins. The scaffold is the protein upon which Fe-S clusters are assembled, and the interaction between the scaffold and frataxin is important for Fe-S cluster assembly and cell (and organism) viability, as illustrated in the human diseases Friedreich’s ataxia and ISCU Myopathy. Here we study the role of the bacterial protein YlaN as it relates to the Fur pathway in S. aureus, and we determined that YlaN acts as an iron-binding protein that relieves Fur-repression of gene expression. We study the C-terminus of the scaffold protein as part of the ISC pathway, and we found that the protein’s C-terminus is required for cluster assembly but not for iron-binding. Finally, we studied the effect of Fe and multiprotein complex formation on the biophysical characteristics of Isu1, followed by studying the same biophysical characteristics at a variety of pH levels. Understanding the dynamic characteristics of YlaN and Isu1 helps advance our understanding of the different iron-sulfur cluster biosynthesis pathways
Time-Modulated And Topological Microwave Components For Wireless Communication Systems
No full textCommunication systems play pivotal role in the state-of-the-art technologies. There are two prevalent communication systems, which are half duplex and full duplex. In full duplex communication systems both receiving and transmitting modules work simultaneously, while in half duplex systems they work one by one. Here we focus on full duplex communication systems. One of the key components in full duplex systems is circulator, which is a nonreciprocal microwave component. There are some attempts in the literature to realize circulator, but most of them were based on magnetic biasing of circulators by using ferrite as the magnetic material. These types of circulators are bulky, expensive, non-integrable with other microwave components in transceiver chain. Hence, STM gyrator, which is a fundamental nonreciprocal component, based on Wheatstone bridges of varactors is presented in this dissertation to deal with these hurdles. We present an implementation of the proposed approach based on a double-balanced circuit with Wheatstone bridges of varactors, which provides large isolation between the input signal and the sidebands. Weprovide a theoretical and an experimental analysis of the circuit with excellent agreement to each other. In addition to introducing a topology of STM gyrators with improved bandwidth compared with existing designs, our results highlight a potential connection between the bandwidth of STM devices and their harmonic order, which might also find applications in other STM systems, like isolators, circulators, and photonic topological insulators.
Moreover, the other part of the dissertation is dedicated to microwave topological insulator, which plays important role in recent academic research for its unique features, including bandgaps in the dispersion diagram, and robust edge mode propagation, which are immune to discontinuities. In this dissertation, a microwave topological insulator based on a dual lattice of differential transmission lines is presented. The operation principle of the proposed unit cell along with the related theoretical and simulation results for infinite and truncated lattice are presented to verify that the structure has topological property. It is worth mentioning that the proposed microwave topological insulator has potential applications in various microwave components as well as phased array antennas and leaky wave antennas