Now showing items 1-20 of 95479

    • Spacer Engineering of Diammonium‐Based 2D Perovskites toward Efficient and Stable 2D/3D Heterostructure Perovskite Solar Cells

      Niu, Tianqi; Xie, Yue‐Min; Xue, Qifan; Xun, Sangni; Yao, Qin; Zhen, Fuchao; Yan, Wenbo; Li, Hong; Brédas, Jean‐Luc; Yip, Hin‐Lap; et al. (Wiley, 2021-10-31)
      Perovskite solar cells (PSCs) based on 2D/3D heterostructures show great potential to combine the advantages of the high efficiency of 3D perovskites and the high stability of 2D perovskites. However, an in-depth understanding of the organic-spacer effects on the 2D quantum well (QW) structures and electronic properties at the 2D/3D interfaces is yet to be fully achieved, especially in the case of 2D perovskites based on diammonium spacers/ligands. Here, a series of diammonium spacers is considered for the construct ion 2D/3D perovskite heterostructures. It is found that the chemical structure and concentration of the spacers can dramatically affect the characteristics of the 2D capping layers, including their phase purity and orientation. Density functional theory calculations indicate that the spacer modifications can induce shifts in the energy-level alignments at the 2D/3D interfaces and therefore influence the charge-transfer characteristics. The strong intermolecular interactions between the 2,2-(ethylenedioxy)bis(ethylammonium) (EDBE) cations and inorganic [PbI6]4− slabs facilitate a controlled deposition of a phase-pure QW structure (n = 1) with a horizontal orientation, which leads to better surface passivation and carrier extraction. These benefits endow the EDBE-based 2D/3D devices with a high power conversion efficiency of 22.6% and remarkable environmental stability, highlighting the promise of spacer-chemistry design for high-performance 2D/3D PSCs.
    • Mining Districts in Arizona

      Garcia, Victor H.; Richardson, Carson A.; Arizona Geological Survey (Arizona Geological Survey (Tucson, AZ), 2021-11-19)
    • Origins and spread of formal ceremonial complexes in the Olmec and Maya regions revealed by airborne lidar

      Inomata, Takeshi; Fernandez-Diaz, Juan Carlos; Triadan, Daniela; García Mollinedo, Miguel; Pinzón, Flory; García Hernández, Melina; Flores, Atasta; Sharpe, Ashley; Beach, Timothy; Hodgins, Gregory W. L.; et al. (Springer Science and Business Media LLC, 2021-10-25)
      City plans symbolizing cosmologies have long been recognized as a defining element of Mesoamerican civilizations. The origins of formal spatial configurations are thus the key to understanding early civilizations in the region. Assessment of this issue, however, has been hindered by the lack of systematic studies of site plans over broad areas. Here, we report the identification of 478 formal rectangular and square complexes, probably dating from 1,050 to 400 bc, through a lidar (laser imaging, detection and ranging) survey across the Olmec region and the western Maya lowlands. Our analysis of lidar data also revealed that the earlier Olmec centre of San Lorenzo had a central rectangular space, which possibly provided the spatial template for later sites. This format was probably formalized and spread after the decline of San Lorenzo through intensive interaction across various regions. These observations highlight the legacy of San Lorenzo and the critical role of inter-regional interaction.
    • Book Review: Sulwe, Lupita Nyong’o

      Settle, Savina; Texas Woman’s University (Worlds of Words: Center for Global Literacies and Literatures (University of Arizona), 2021)
    • Book Review: Sachiko: A Nagasaki Bomb Survivor’s Story, Caren Stelson

      Andersen, Julia; University of Illinois, Urbana-Champaign (Worlds of Words: Center for Global Literacies and Literatures (University of Arizona), 2021)
    • Book Review: The Patron Saints of Nothing, Randy Ribay

      Carmichael, Sherri; University of Arizona (Worlds of Words: Center for Global Literacies and Literatures (University of Arizona), 2021)
    • Book Review: La noche más noche, Sergio Andricaín

      Aguayo, Nallely; University of Arizona (Worlds of Words: Center for Global Literacies and Literatures (University of Arizona), 2021)
    • Book Review: Merci Suárez Changes Gears, Meg Medina

      Gómez, Talle; Texas A&M Commerce (Worlds of Words: Center for Global Literacies and Literatures (University of Arizona), 2021)
    • Book Review: Everything Naomi Loved, Katie Yamasaki, Ian Lendler

      Burke, Amy; Texas Woman’s University (Worlds of Words: Center for Global Literacies and Literatures (University of Arizona), 2021)
    • Book Review: Everlasting Nora, Marie Miranda Cruz

      Horton, Jessica; University of Arizona (Worlds of Words: Center for Global Literacies and Literatures (University of Arizona), 2021)
    • Book Review: Each Kindness Written, Jacqueline Woodson

      Escamilla, Lindsey; Texas Woman’s University (Worlds of Words: Center for Global Literacies and Literatures (University of Arizona), 2021)
    • Book Review: Dancing Hands: How Teresa Carreño Played the Piano for President Lincoln, Margarita Engle

      Maffi-Mahmood, Francis; Texas Woman’s University (Worlds of Words: Center for Global Literacies and Literatures (University of Arizona), 2021)
    • Introduction and Editor’s Note

      Corapi, Susan; Martens, Prisca (Worlds of Words: Center for Global Literacies and Literatures (University of Arizona), 2021)
    • Characterizing Large-Scale Resting State Effective Connectivity Patterns with Functionally Constrained Priors in Individuals with a History of Major Depressive Disorder

      Allen, John J.A.; Ding, Yaohui; Chen, Nan-kuei N.C.; Andrews-Hanna, Jessica J.A.; Wilson, Robert R.W. (The University of Arizona., 2021)
      Major depressive disorder (MDD) is a common mental health condition (Kessler & Bromet, 2013) and the 3rd leading cause of disability worldwide (James et al., 2018). MDD history is a significant risk factor for relapse and recurrence of depression (Buckman et al., 2018; Burcusa & Iacono, 2007). The current study investigated resting state effective connectivity among 13 brain regions from three resting state networks (i.e., default, salience, and central executive), which had been implicated in the pathophysiology of MDD from previous studies (Kaiser et al., 2015; Mulders et al., 2015). In the current study, both within- and between-networks effective connectivity were found to be different in those with a MDD history (N=29) compared to the healthy controls (N=28), through spectral dynamic causal modeling (Friston, Kahan, Biswal, et al., 2014), Bayesian model reduction (Friston et al., 2016), and parametric empirical Bayes (Zeidman, Jafarian, Seghier, et al., 2019) analyses. Of particular interest is the finding that there is more negative effective connectivity from right anterior insula to left dorsolateral prefrontal cortex and left inferior parietal lobe in MDD history. Previous studies have found less causal influence from anterior insula to prefrontal cortex in currently depressed individuals (Hyett et al., 2015; Iwabuchi et al., 2014; Kandilarova et al., 2018). Given the importance of anterior insular in interoception and subjective feelings (Craig & Craig, 2009), the current study provides some preliminary evidence that altered effective connectivity between anterior insula and prefrontal cortex may be related to MDD history as well.
    • Trapping Sets of Iterative Decoders for Quantum and Classical Low-Density Parity-Check Codes

      Vasic, Bane; Guha, Saikat; Raveendran, Nithin; Lazos, Loukas; Tandon, Ravi; Lux, Klaus (The University of Arizona., 2021)
      Protecting logical information in the form of a classical bit or a quantum bit (qubit) is an essential step in ensuring fault-tolerant classical or quantum computation. Error correction codes and their decoders perform this step by adding redundant information that aids the decoder to recover or protect the logical information even in the presence of noise. Low-density parity-check (LDPC) codes have been one of the most popular error correction candidates in modern communication and data storage systems. Similarly, their quantum analogues, quantum LDPC codes are being actively pursued as excellent prospects for error correction in future fault-tolerant quantum systems due to their asymptotically non-zero rates, sparse parity check matrices, and efficient iterative decoding algorithms. This dissertation deals with failure configurations, known as \emph{trapping sets} of classical and quantum LDPC codes when decoded with iterative message passing decoding algorithms, and the \emph{error floor phenomenon} - the degradation of logical error rate performance at low physical noise regime. The study of quantum trapping sets will enable the construction of better quantum LDPC codes and also help in modifying iterative quantum decoders to achieve higher fault-tolerant thresholds and lower error floors. Towards this goal, the dissertation also presents iterative decoders for classical and quantum LDPC codes using the \emph{deep neural network framework}, novel iterative decoding algorithms, and a decoder-aware \emph{expansion-contraction method} for error floor estimation. In this dissertation, we first establish a systematic methodology by which one can identify and classify \emph{quantum trapping sets} (QTSs) according to their topological structure and decoder used. For this purpose, we leverage the known harmful configurations in the Tanner graph, called \emph{trapping sets} (TSs), from the classical error correction world. The conventional definition of a trapping set of classical LDPC codes is generalized to address the syndrome decoding scenario for quantum LDPC codes. Furthermore, we show that the knowledge of QTSs can be used to design better quantum LDPC codes and decoders. In the context of the development of novel decoders, we extend the stochastic resonance based decoders to quantum LDPC codes, propose iteration-varying message passing decoders with their message update rules learned by neural networks tuned for low logical error rate, and present a syndrome based generalized belief propagation algorithm for tackling convergence failure of iterative decoders due to the presence of short cycles. Our analysis of TSs of a layered decoding architecture clearly reveals the dependence of the harmfulness of TSs (classical or quantum) on the iterative decoder, and thus on the error floor estimates. We present a computationally efficient method for estimating error floors of LDPC codes over the binary symmetric channel without any prior knowledge of its trapping sets. The sub-graph expansion-contraction method is a general procedure for TS characterization, which lists all harmful error patterns up to a given weight for the LDPC code and decoder. Based on this decoder-aware trapping set characterization for LDPC codes, we propose a model-driven deep neural network (DNN) framework that unfolds the decoding iterations, to design the \emph{decoder diversity of finite alphabet iterative decoders (FAIDs)}. Our decoder diversity DNN-FAID delivers excellent waterfall performance along with a low error floor.
    • Low-Cost Chromatic Confocal Endomicroscope for the Diagnosis of Cervical Precancer

      Kang, Dongkyun; Kulkarni, Nachiket; Gmitro, Arthur; Barton, Jennifer (The University of Arizona., 2021)
      Cervical cancer is one of the major cancers in women living in low- and middle-income countries (LMICs). The resources needed to conduct the gold standard histopathological diagnosis, such as a trained personnel and lab equipment, are scarce in LMICs. Hence, low-cost approaches such as visual inspection with acetic acid (VIA) are used to diagnose cervical cancer. VIA and other low-cost approaches, however, often lead to overdiagnosis and overtreatment of the patient due to their low specificity. There is an unmet need for a low-cost tool that can provide both high sensitivity and specificity.This dissertation discusses the design and development of a chromatic confocal endomicroscope (CCE) that can examine the cervical tissue in vivo with a goal of aiding the diagnosis of cervical malignancy. The novelty of this device is to use longitudinal chromatic aberration to acquire cross-sectional images of the tissue without any scanning mechanisms. A custom hyperchromatic objective lens was optimally designed to focus different wavelengths of the illumination light into different depths: 500-700 nm was focused over a depth range of 110 µm. Slit apertures were used for illumination and detection, which eliminated the need for beam scanning along the slit length direction and enabled cross-sectional, two-dimensional imaging without any mechanical scanners. A custom miniature spectrometer was used to analyze the spectrum of light scattered back from the tissue and generate confocal images. The manufactured CCE device had a small form factor with an overall device diameter and length of 9 mm and 70 mm, respectively. The material cost was less than $1,500. The measured lateral and axial resolution was 2 µm and 4 µm over an axial depth of 100 µm. The CCE device was able to visualize cellular structures of human tissue, in vivo at different axial depths. Cellular nuclei of the lower lip epithelium were clearly visualized from the CCE images, which might indicate that other epithelial tissues such as the cervical epithelium can also be visualized with CCE. This might merit clinical evaluation of CCE for the diagnosis of cervical malignancy.
    • Prospective Teachers’ Narrative Sense-Making of Equity

      Wood, Marcy B.; Neihaus, Aubrey; McGraw, Rebecca; Clift, Renee; Gunckel, Kristin (The University of Arizona., 2021)
      Equity has been a persistent focus of research in education and in particular teacher education. While numerous studies have investigated instructional interventions aimed at supporting teachers’ learning about equity, few studies have investigated teachers’ learning of equity. In this study, I used narrative inquiry as a lens through which to investigate how prospective elementary teachers make sense of equity. From eight participants’ stories, I developed ten categories of types of experiences that are drawn on in these equity narratives. I also documented eleven narrative techniques used in the stories that make equity sense-making visible. I delve into how two of these techniques (explicit re-narration and visual metaphors) make sense-making visible to researchers and teacher educators. These findings have implications for future research on teacher education research in equity as well as teacher education practice.
    • Examining Protective and At-Risk Factors on Children’s Social and Emotional Development and School Readiness

      Cimetta, Adriana D.; Medina, Margaret Ariana; Cheng, Katherine; Smith, Eric D. (The University of Arizona., 2021)
      Early childhood is critical for a child’s healthy development. Such development can affect children throughout the lifespan. In particular, social emotional development has been used as a predictor for school readiness, delinquency, career outcomes and earnings, and overall quality of life (Denham et al., 2009). This study examined the relationships of protective factors and at-risk factors on 3,988 children between the ages of two to six years on children’s social emotional development and if these variables are also predictive of a child’s social emotional development. Additionally, this study assessed if children’s social emotional development is predictive of children's literacy and math school readiness. This study intended to investigate a strength-based model by examining moderating effects of poverty on a child’s social emotional development in determining methods for assisting children living in poverty. Pearson’s R correlations and stepwise linear regression models were run. Results indicated that protective factors have statistically significant relationships and predict higher social emotional development scores and at-risk factors have statistically significant relationships and predict lower social emotional development scores. Lastly, implications, limitations, and future directions for research are also discussed.Keywords: social emotional development, school readiness, protective factors, at-risk factors
    • Elevated Fibroblast Growth Factor 23 Mediates Cardiac Fibrosis in the Setting of Chronic Kidney Disease

      Wilson, Jean M.; Crawford, Monique; Streicher, John; Runyan, Raymond (The University of Arizona., 2021)
      Background: CKD (chronic kidney disease) is a progressive disease with a global prevalence of 11-13% (Hill et al., 2016). CKD disrupts homeostasis resulting in large majority of patients with CKD also suffering from CVD (cardiovascular disease), with over 90% of CKD patients having cardiac fibrosis (Graham-Brown et al., 2017). FGF23, a phosphaturic hormone derived from bone, has been found to be elevated in patients with CKD and is associated with increased mortality in this patient population. Elevated serum FGF23 levels lead to LVH (left ventricular hypertrophy) and cardiac fibrosis, however, the mechanism by which fibrosis develops is unknown. We hypothesize that FGF23 mediates cardiac fibrosis by activation of the RAAS (renin-angiotensin-aldosterone-system), TGF-β (transforming growth factor-β), and wnt/β-catenin pathways in cardiac myocytes and fibroblasts. Methods:A literature review was conducted to identify the current literature on FGF23, CKD, cardiac fibrosis, RAAS, TGF-β, wnt/β-catenin and the molecular mechanisms leading to pathology. Search engines used were PubMed, Elsevier, NCBI (National Center for Biotechnology Information), University of Arizona Library, Google, and Wikipedia. Keywords included: CKD prevalence and mortality, bone and mineral metabolism, FGF23 mortality, angiotensin II (ANGII) and cardiac fibrosis, and phosphate homeostasis. Conclusion: In a series of steps, systemic FGF23 mediates cardiac fibrosis via non-conical signaling pathways by first activating the RAAS in cardiac myocytes. RAAS activation in cardiac myocytes increases ANGII expression. ANGII crosstalk with cardiac fibroblasts leads to activation of fibroblasts and TGF-β pathways. TGF-β and 5wnt3a/β-catenin in cardiac fibroblasts activate pro-fibrotic gene expression. TGFβ and wnt3a/β-catenin from cardiac fibroblasts crosstalk with cardiac myocytes to induce pro-fibrotic gene expression and augment RAAS signaling pathway, respectively.
    • Development of New Anionic Cascades and Analysis of US FDA Drug Architectures

      Njardarson, Jon T.; Delost, Michael D.; Wondrak, Georg; Hulme, Christopher; Sun, Daekyu; Jewett, John (The University of Arizona., 2021)
      This dissertation is divided into five chapters, encompassing innovative synthetic contributions in the area of Darzens annulations, anionic-amino-Cope cascades, structural analysis of FDA-approved pharmaceuticals as well as book chapter contributions in highlighting synthetic contributions in oxirane and aziridine chemistry. Chapter 1 presents two-book chapter contributions made which highlight synthetic contributions made with oxiranes and aziridines. Part 1: focuses on synthetic contributions made with oxiranes (epoxides) from 2008-2018. Part II focuses on homologation approaches to access oxiranes and aziridines from carbonyl and imines. Chapter II presents two-published perspectives, published in the Journal of Medical Chemistry. Part I analyzes oxygen-heterocycles seen in FDA-approved pharmaceuticals. Part II analyzes the structural diversity in FDA-approved combination drugs. Chapter III: presents novel contributions made in the arena of anionic-amino-Cope rearrangements (Part I) and applications (Part II). Chapter IV presents novel contributions made with vinylogous (Aza)-Darzens annulations. Part I discusses an asymmetric-vinylogous Aza-Darzens protocol with a bromo-butenolide nucleophile. Part II describes phenyl sulfone-containing vinylogous (Aza)-Darzens routes. Chapter V describe mild protocols to obtain trisubstituted trifluoromethylthiolated (SCF3) aziridines and cyclopropanes.