Momentum-resolved tunneling between Luttinger liquids

We study tunneling between two nearby cleaved edge quantum wires in a perpendicular magnetic field. Due to Coulomb forces between electrons, the wires form a strongly-interacting pair of Luttinger liquids. We calculate the low-temperature differential tunneling conductance, in which singular features map out the dispersion relations of the fractionalized quasiparticles of the system. The velocities of several such spin-charge separated excitations can be explicitly observed. Moreover, the proposed measurement directly demonstrates the splintering of the tunneling electrons into a multi-particle continuum of these quasiparticles, carrying separately charge from spin. A variety of corrections to the simple Luttinger model are also discussed.Comment: 4 pages, 5 figures (1 in color

Code Mixing in Narratives of Spanish-English Dual Language Learners

As the U.S. diversifies, the number of Spanish-English dual language learners (DLLs) has grown significantly and is projected to continue to do so through 2060 (Colby & Ortman, 2015). Although research has shown that DLLs implement strategies, like code mixing, to compensate for varying language proficiencies (Vu, Bailey, & Howes, 2010), what elements of code mixing are typical has not been widely researched. This study aims to add to the body of work on typical development of DLL children by examining code mixing in narratives of 212 Spanish-English dual language learners at the beginning of preschool, to determine if differences in language exposure correspond to differences in the types and frequency of code mixing. Close inspection of English and Spanish narratives revealed that the participants preserved the mean length of utterance (MLU) in their code mixes, the majority of which were nouns, and that they code mixed more frequently in their Spanish narratives than their English narratives

Qualitative Narrative Research Investigating the Value of Visual Art Education Captured through the Stories of High School Students Labeled At-Risk

My personal and professional experiences in education led me to develop a unique perspective on the value of the visual arts. Existing literature about the impact of visual art education on students is written primarily from the point of view of educators and researchers. I wondered what the stories of high school students who have been labeled at-risk might reveal about their visual art experiences. As a participant-observer, I studied my own students using a postmodern approach to qualitative narrative research. I chose six students, three of whom were labeled at-risk, to share their stories and opinions about their visual art experiences. Semi-structured interviews were the primary source of data collection, while daily observations and analysis of artworks triangulated the findings. Common themes expressed by the participants included an appreciation for the freedom and sense of control offered within art activities, as well as positive responses to the upbeat and casual art environment. Art processes were described to be engaging, fun, and relaxing. The student stories revealed a belief that personal growth is also associated with visual arts involvement, including improved self-esteem, motivation, and personal relationships. The research revealed that for my students, the value of visual arts experiences is personal and experience-based. I learned that by allowing students to regain an element of control over their education, they perceive their learning experiences with greater value. I also learned that the presence or absence of a label such as “at-risk” does not necessarily define a student’s potential, nor is it always an accurate way to identify those who are facing challenges in their personal or academic life

Distribution of the number of pivots needed using Gaussian elimination with partial pivoting on random matrices

Gaussian elimination with partial pivoting (GEPP) is a widely used method to solve dense linear systems. Each GEPP step uses a row transposition pivot movement if needed to ensure the leading pivot entry is maximal in magnitude for the leading column of the remaining untriangularized subsystem. We will use theoretical and numerical approaches to study how often this pivot movement is needed. We provide full distributional descriptions for the number of pivot movements needed using GEPP using particular Haar random ensembles, as well as compare these models to other common transformations from randomized numerical linear algebra. Additionally, we introduce new random ensembles with fixed pivot movement counts and fixed sparsity, $\alpha$. Experiments estimating the empirical spectral density (ESD) of these random ensembles leads to a new conjecture on a universality class of random matrices with fixed sparsity whose scaled ESD converges to a measure on the complex unit disk that depends on $\alpha$ and is an interpolation of the uniform measure on the unit disk and the Dirac measure at the origin

Modeling the relationship between women’s perceptions and future intention to use institutional maternity care in the Western Highlands of Guatemala

Background Despite global gains, women in hard-to-reach areas are at a relatively higher risk of death and disability related to childbirth. Traditional methods of measuring satisfaction may mask negative experiences (such as disrespect and abuse) that can drive down demand for institutional care. Better measurement of women’s perceptions of care quality, especially among marginalized populations with historically low utilization of institutional care, are needed to inform how to improve services and foster greater utilization of (potentially life-saving) clinical care. Methods A population-based household survey was conducted in 15 purposively selected villages in the rural Western Highlands of Guatemala among women who gave birth to a child within the last 5 years. Demographic and health information including experiences and perceptions of maternity care were collected. Two sets of nested multivariate logistic regression models were estimated to identify factors associated with future intention to give birth in a health facility, separately among women who gave birth to their last child at home and women who gave birth to their last child in a facility. The independent variables of interest were access to care, perceived need for maternity care, and two measures of perceived quality: satisfaction with last birth and disrespect and abuse (perceived or experienced). Thematic analysis was performed on open-ended responses. Results Perceived need for facility-based childbirth services and satisfaction with last childbirth experience, either at home or in a facility, emerged as the key factors influencing intention to give birth in a health institution in the future. Among the facility birth group, reporting disrespect and abuse is a deterrent to seeking facility-based care in the future. However, select perceptions of disrespect and abuse did not have an association with future intention (among the home birth group). Conclusions Women’s perceptions of care quality influence care-seeking. Women who feel they were mistreated in health facilities are more likely to avoid or delay seeking care in the future. Health systems need to reinforce trust and positive perceptions of respectful care. Developing better measures of women’s perceptions of maternity care experiences among indigenous populations in Guatemala can inform improvements in care provision

Invisible City. A Multi-Sensory Approach to the Analysis of Urban Space

This thesis explores the relationship between sensory stimuli and human behaviour in urban space. It seeks to understand how spatial conditions, mediated, and supported by sensory experiences, impact individual and social activities and how this learning might be applied to other cities. This research aims to challenge the “visualism” of planning and urban design approaches and to examine the urban environment through a multi-sensory analysis, focusing on the non-visual senses, such as hearing, smell and touch. It is based on a qualitative case study approach focused on Bishopsgate, in the City of London, an area with a unique variety of urban spaces, compact morphology and land use. This thesis contributes to knowledge in three principal ways: First, the use of “sensewalks” and “sensetalks” as innovative user-centred methods of data collection, enabling in-situ semi-structured interviews with the presence of the researcher. Second, the use of thematic analysis of verbal and semantic descriptions received from participants, establishes a baseline for the exploration. Finally, the creation of a framework of analysis based on the concept of “sensescapes” will facilitate the future exploration of the urban setting through its different dimensions. This framework not only creates a baseline for discussion but also establishes a tool for use in future urban development within the fields of environmental psychology, sensory analysis, urban design and spatial planning. These contributions add to the academic literature and offer methods and techniques of analysis that may support future academic research, practice and policy. As planners and urban designers try to create better and healthier spaces, the analysis and production of urban “sensescapes” can be used as a tool in (re)designing the city in new ways that stimulate the senses – ultimately making the role of the non-visual senses more ‘visible’ in the urban setting

Random matrices and safety rest areas on interstates in the United States

We analyze physical spacings between locations of safety rest areas on interstates in the United States. We show normalized safety rest area spacings on major interstates exhibit Wigner surmise statistics, which align with the eigenvalue spacings for the Gaussian Unitary Ensemble from random matrix theory as well as the one-dimensional gas interactions via the Coulomb potential. We identify economic and geographic regional traits at the state level that exhibit Poissonian statistics, which become more pronounced with increased geographical obstacles in interstate travel. Other regional filters (e.g., historical or political) produced results that did not diverge substantially from the overall Wigner surmise model

Die Expression und die epigenetische Regulation der PD-1- und PD-L1-Gene beim Humanen Lungenkrebs

Hintergrund: Die aberrante Expression von PD-1 und PD-L1 kann zur Tumorevasion beitragen, indem eine immunsuppressive Tumormikroumgebung (TME) geschaffen wird. Ziele: Die Analyse der Expressionsprofile der PD-1- und PD-L1-Gene auf mRNA-Ebene in Lungentumorzelllinien und auf Proteinebene in primären Lungentumoren. Die Untersuchung der Rolle der epigenetischen Modifikationen, einschließlich DNA-Methylierung und Histonacetylierung, in der Regulation der Genexpression von PD-1 und PD-L1. Methoden: Die mRNA-Expressionen von PD-1 und PD-L1 wurden in Lungenkarzinomzelllinien mittels qPCR analysiert. Die Untersuchung der epigenetischen Regulation erfolgte mittels Demethylierung, Deacetylierung und Bisulphit-Sequenzierung. Die Proteinexpression von PD-1 und PD-L1 wurde immunhistochemisch in primären Lungentumoren unter Verwendung von Tissue Microarrays untersucht. Ergebnisse: PD-1 und PD-L1 zeigten unterschiedliche Expressionsmuster in Lungenkrebszelllinien mit PD-1-Überexpression in vier Zelllinien (H1299, COLO677, H1975 und H82) und PD-L1-Überexpression in zwei Zelllinien (H82 und H2228). Eine signifikante Reexpression der beiden Gene wurde nach der Behandlung mit dem DNMTi 5-aza und dem HDACi TSA festgestellt. Allerdings wurde keine DNA- Methylierung im Promotorbereich der PD-1- und PD-L1-Gene mittels Bisulphit-Sequenzierung detektiert. Die Proteinexpression von PD-1 und PD-L1 ist mittels Immunhistochemie in primären Lungentumoren untersucht worden. Als PD-1-positiv erwiesen sich 60,25 % der Proben, PD-L1-positiv waren 25,21 % der Proben. PD-1 war signifikant mit der Tumorgröße (pT3–4) in primären Lungentumoren assoziiert. Die PD-L1-positiven Proben zeigten eine signifikante Assoziation mit dem histologischen Tumortyp (Plattenepithelkarzinom). Unsere Daten ergaben, dass weder PD-1 noch PD-L1 signifikant mit dem Überleben der erkrankten Personen korrelierte

AGN oscurati nel campo J1030: prospettiva in banda X e ottico/infrarossa

In questo lavoro di tesi si presenta uno studio multibanda di un campione di 30 candidati AGN oscurati, selezionati in banda X nel campo profondo centrato su J1030+0524 (J1030), un quasar a z=6.31. La selezione viene fatta tramite un Hardness Ratio (HR) >0, che può essere considerato come una sorta di indice di colore in banda X. La statistica del campione ha un valore mediano di 120 conteggi netti in banda 0.5-7 keV. Con un totale di 500 ks osservati con il telescopio Chandra, il campo di J1030 è attualmente la quarta survey X più profonda mai osservata, il che la rende il laboratorio ideale per studiare oggetti deboli come gli AGN oscurati. Grazie alla profondità del campo, è stato possibile analizzare gli spettri X in cerca di features come la riga in emissione del ferro neutro a 6.4 keV e la edge del ferro a 7.1 keV. Non avendo a disposizione la spettroscopia ottica, è stato ideato un metodo di indagine innovativo sulla base dei dati X: sono state elaborate simulazioni in modo da riprodurre gli spettri delle sorgenti osservate, per poter verificare la significatività delle features sopracitate. Inoltre, sempre tramite simulazioni, è stato verificato fino a che punto la statistica X possa essere utilizzata per ottenere indicazioni sul redshift delle sorgenti. Per verificare i risultati ottenuti è stata utilizzata la tecnica dei redshift fotometrici, attraverso una procedura di SED fitting. Si è sfruttata l'ampia copertura fotometrica disponibile in J1030 nelle bande ottiche e infrarosse, utilizzato osservazioni (LBC/LBT, WIRCam/CFHT, la survey MUSYC e IRAC). I risultati ottenuti con questa tecnica, seppur con incertezze non trascurabili, confermano le soluzioni trovate dall'analisi in banda X, verificando la bontà del metodo ideato