Phosphorus-defect interactions during thermal annealing of ion implanted silicon

Keys, Patrick Henry University of Florida 2001 해외박사(DDOD)

Ion implantation of dopant atoms into silicon generates nonequilibrium levels of crystal defects that can lead to the detrimental effects of transient enhanced diffusion (TED), incomplete dopant activation, and p-n junction leakage. In order to control these effects, it is vital to have a clear understanding of dopant-defect interactions and develop models that account for these interactions. This research focuses on experimentally investigating and modeling the clustering of phosphorus dopant atoms with silicon interstitials. Damage recovery of 40keV Si<super>+</super> implants in phosphorus doped wells is experimentally analyzed. The effects of background phosphorus concentration, self implant dose, and anneal temperature are investigated. Phosphorus concentrations ranging from 2.0 × 10<super>17</super> to 4.0 × 10<super>19</super> cm<super>−3</super> and Si<super>+</super> doses ranging from 5.0 × 10<super>13</super> cm<super>−2</super> to 2.0 × 10<super>14</super> cm<super>−2</super> are studied during 650–800°C anneals. A dramatic reduction in the number of interstitials bound in {311} defects with increasing phosphorus background concentration is observed. It is suggested that the reduction of interstitials in {311} defects at high phosphorus concentrations is due to the formation of phosphorus-interstitial clusters (PICs). The critical concentration for clustering (approximately 1.0 × 10<super>19</super> cm<super>−3</super> at 750°C) is strongly temperature dependent and in close agreement with the kink concentration of phosphorus diffusion. Information gained from these “well experiments” is applied to the study of direct phosphorus implantation. An experimental study is conducted on 40keV phosphorus implanted to a dose of 1.0 × 10<super>14</super> cm<super>−2</super> during 650–800°C anneals. Electrically inactive PICs are shown to form at concentrations below the solid solubility limit due to high interstitial supersaturations. Data useful for developing a model to accurately predict phosphorus diffusion under nonequilibrium conditions are extracted from the experimental results. A cluster-mediated diffusion model is developed using the Florida Object Oriented Process Simulator (FLOOPS). The nucleation of defects is controlled by the diffusion-limited competition for excess interstitials between PICs and {311} clusters. The release of interstitials is driven by cluster dissolution. Modeling results show a strong correlation to those experimentally observed over a wide temporal and thermal domain using a single set of parameters. Improvements in process simulator accuracy are demonstrated with respect to dopant activation, TED, and dose loss.

For the Survival of Ogoni People: Women's Contribution to Movement-Building in Nigeria and the United States

Keys, Domale Dube ProQuest Dissertations & Theses University of Cali 2019 해외박사(DDOD)

The Ogoni movement has become a key example of civil resistance in postcolonial Africa, yet women's role in the movement has been largely suppressed. Since the early 1990s, the Movement for the Survival of the Ogoni People (MOSOP) has organized against the Nigerian government and multinational corporations' oil drilling activities in Ogoni. This study explains how and why the Ogoni women of Nigeria (1990-2017) joined their community in calling attention to the exploitation of their people at the hands of the Nigerian government and multinational oil companies, while documenting how and why they became key players in nonviolent campaigns in the Niger Delta in seeking correctives and justice. I not only examine women's contribution to the movement by looking at the issues that has drawn women into the movement but also seek to understand how those issues are reflected in the campaigns that they waged. Furthermore, I investigate how Ogoni women continue to participate in both Nigeria and the diaspora since many of them migrated to the United States following the federal government's violent repression of their organizing. For this ethnographic study, I collected data by conducting interviews, focus groups, participant observations, and archival data search in both Nigeria and the United States. Gender-sensitive theoretical frameworks and methodologies including Critical Race Grounded Theory, decolonial feminism, Black feminism, and localization theory guide my study. My findings reveal that women participated in the Ogoni movement using nonviolent methods including singing, dancing, and prayer that enabled them to evade scrutiny from military forces. Their methods reclaimed the types of spiritual leadership for which women had traditionally received formal training before colonialism. Furthermore, women transformed the movement's organizing platform by including women's issues such as women and girls' education. As immigrants in the US, Ogoni women continue to draw upon spiritual practices to maintain connections among each other that facilitate their survival in a new land and their transnational organizing. My research suggests that women's contributions in this mixed-gender social movement has been drastically understated as their participation and methods supported longevity for the movement which, in turn, paved the way for making meaningful gains for women and for the movement as a whole. By examining African women transnationally, this research methodologically corrects the continued separation of immigrant and African studies in contemporary scholarship.

Influence of meridional constraints and eddy feedbacks on low-frequency variability and its response to climate change

Keys, Elizabeth Adrianne Barnes University of Washington 2012 해외박사(DDOD)

Two aspects of the internal variability of the atmosphere are examined. The first concerns the interactions and feedbacks between synoptic-scale Rossby waves (eddies) and the large-scale mean flow. We study the variability of the midlatitude jets in observations, comprehensive global circulation models and a barotropic model on the sphere and quantify the persistence of this variability and the corresponding strength of the feedback between the eddies and the mean flow. We demonstrate that factors such as zonal asymmetries, the strength of the subtropical jet, and spherical geometry all play an important role in modulating the eddy-mean flow feedback and thus the resulting jet variability. The results predict a reduction in eddy-mean flow feedback strength with human-induced climate change, which implies a reduction in the time scale of the leading mode of variability in the troposphere. The second addresses the behavior of the eddies themselves. Rossby waves play a crucial role in modulating the low-frequency variability of the atmosphere, and changes in their characteristics such as size, speed and momentum fluxes have been put forth as possible explanations for general circulation trends under human-induced global warming. We contribute to the understanding of synoptic, midlatitude eddies by quantifying the global distribution of eddy-length scales in observations. Using a barotropic model on the sphere, we also demonstrate how these scales change as the position of the jet varies. The dependence of eddy momentum fluxes on the background meridional vorticity gradient is addressed, and the results are compared to the response of a comprehensive global circulation model to updating the sea-surface roughness parameterization. A novel Rossby wave breaking identification method is also presented. The algorithm looks for overturning of absolute vorticity contours on pressure surfaces and is used to quantify wave breaking in the observations and general circulation models. The results suggest that the meridional constraints of wave breaking identified in the barotropic model are also present in more realistic atmospheres and the implications for future climate predictions is explored.

Minority drug resistant variants of HIV-1 and response to early combination therapy

Keys, Jessica R The University of North Carolina at Chapel Hill 2014 해외박사(DDOD)

Initial HIV-1 therapy selection is informed by sequencing of a bulk PCR product to screen for antiretroviral resistance mutations. However, this method does not reliably sample drug resistant variants that occur in <20% of the viral population, and these may re-emerge and impair treatment response once therapy is administered. Alternatively, ultra deep sequencing can detect minority drug resistant variants, but it is difficult to distinguish very low abundance mutations from error. To address deep sequencing error, two regions of the HIV-1 genome spanning reverse transcriptase (RT) codons 34-245 were tagged with a random 8-nucleotide sequence (Primer ID) prior to PCR and sequencing. Primer ID allowed us to use resampled raw sequences sharing the same Primer ID to construct consensus sequences, each representing an original viral template within that sample. We first established a residual error rate for Primer ID using known sequences for both the Roche 454 and Illumina MiSeq deep sequencing platforms. Primer ID reduced 454 and MiSeq errors from 71 to 2.6 and from 24 to 1.2 errors/10,000 nucleotides, respectively. Applying Primer ID corrected 454 deep sequencing to 184 therapy-naive patients from North Carolina that went on to receive RT inhibitor based combination therapy, we found that 14% of had at least one RT inhibitor mutation, compared to 2.7% using standard bulk sequence analysis. Nearly 10% of 184 patients received regimens that contained fewer than 3 active antiretrovirals, according to the Stanford resistance algorithm. While patients on suboptimal therapy failed faster than patients on fully-active regimens, the effect was driven by resistance detected by standard methods rather than previously undetected minority variants. Overall, the use of Primer ID revealed limited template utilization, limiting the depth of deep sequencing sampling. Primer ID addresses important limitations of deep sequencing and produces less biased estimates of low level resistance mutations in the viral population, which may allow us to more accurately define a threshold at which minority drug resistant variants of HIV-1 begin to compromise treatment response.

Emotion work in women's abortion experiences

Keys, Jennifer Lynn State University of New York at Albany 2002 해외박사(DDOD)

Women who have abortions are caught in the crossfire of a heated ideological battle. The prochoice contention is that most women feel relieved after terminating an unwelcome pregnancy. The antiabortion camp asserts that killing an unborn child psychologically scars the mother. The findings presented in this dissertation shed light on how this dialogue and more generally the broader social context shapes a woman's emotional response to abortion. The research design is a qualitative analysis based on in-depth interviews with forty women who have terminated a pregnancy. The emotion work perspective developed by Arlie Hochschild (1975; 1979; 1983) is utilized as the central theoretical framework. This exploratory study has uncovered a preliminary set of feeling rules that script the abortion experience. Failing to feel joyful about the pregnancy violates the “Motherhood Mandate.” The corollary proposition is that a woman should “Be At Least a Little Sad” about the abortion. To avoid possible sanctions for “misfeeling,” women should not joke or be nonchalant, particularly in an abortion clinic where emotional display is likely to be under surveillance. There also appear to be guidelines about how long particular feelings should last. The cognitive, bodily, and expressive emotion management techniques previously identified by Hochschild were clearly visible in the abortion experience. I also observed a strategy of approach/avoidance. Women may attempt to bring about the desired feeling state by regulating contact with environmental stimuli (i.e. social movement discourse, antiabortion protestors, the ultrasound image, babies). If a woman's interactions, religious upbringing, or abortion ideology dictate post-abortion grief and remorse, she might actually subject herself to one of these hazards. The abortion experience can be conceptualized as running a gauntlet. Some paths appear to be virtually trouble-free, while others are laden with potential dangers. Understanding how women navigate this course helps to explain why we see divergent emotional outcomes.

College Student Persistence in the Two-year Setting: Identifying Risk Early to Guide Early Integration

Keys, Margo A University of Minnesota 2013 해외박사(DDOD)

College student persistence is examined. The unique nature of the students and environment of the two-year college setting warrant concentrated research effort. The purpose of the study is to examine student variables associated with persistence and program completion to develop a pre-entrance risk assessment in the two-year college setting. Identifying student risk early to triage students toward interventions such as counseling, tutoring and developmental education courses may lead to answers to student integration, eventually leading to improved student retention. Definitions and limitations of the study are outlined. A literature review includes the theoretical underpinnings surrounding the study of student persistence. Relevant research related to risk factors of attrition pre-matriculation and post-matriculation are included. Ex post facto research will be completed to examine entering students in the 2008-09 academic year at a two-year technical college in the Midwest who participated in the voluntary intake assessment program (n=1127). Student entrance variables readily available at the time of enrollment were used. Variables studied included: Placement exam scores, age, enrollment status, gender, financial aid as independent variables. Student persistence and program completion serves as the dependent variables. Binary logistic regression was used. The independent variables did not have a notable relationship with student persistence or program completion for this two-year college population.

Projection algorithms for large scale optimization and genomic data analysis

Keys, Kevin Lawrence ProQuest Dissertations & Theses University of Cali 2016 해외박사(DDOD)

The advent of the Big Data era has spawned intense interest in scalable mathematical optimization methods. Traditional approaches such as Newton's method fall apart whenever the features outnumber the examples in a data set. Consequently, researchers have intensely developed first-order methods that rely only on gradients and subgradients of a cost function. In this dissertation we focus on projected gradient methods for large-scale constrained optimization. We develop a particular case of a proximal gradient method called the proximal distance algorithm. Proximal distance algorithms combine the classical penalty method of constrained minimization with distance majorization. To optimize the loss function f( x) over a constraint set C, the proximal distance principle mandates minimizing the penalized loss f(x) + rho / 2 dist (x,C)2 and following the solution xrho to its limit as rho → infinity. At each iteration the squared Euclidean distance dist (x, C)2 is majorized by ||x -- pi C(xk)||2, where pi C(xk) denotes the projection of the current iterate xk onto C. The minimum of the surrogate function f(x) + rho / 2||x -- piC(x k)||2 is given by the proximal map prox rho--1f[pi C(xk)]. The next iterate xk+1 automatically decreases the original penalized loss for fixed rho. Since many explicit projections and proximal maps are known in analytic or computable form, the proximal distance algorithm provides a scalable computational framework for a variety of constraints. For the particular case of sparse linear regression, we implement a projected gradient algorithm known as iterative hard thresholding for a particular large-scale genomics analysis known as a genome-wide association study. A genome-wide association study (GWAS) correlates marker variation with trait variation in a sample of individuals. Each study subject is genotyped at a multitude of SNPs (single nucleotide polymorphisms) spanning the genome. Here we assume that subjects are unrelated and collected at random and that trait values are normally distributed or transformed to normality. Over the past decade, researchers have been remarkably successful in applying GWAS analysis to hundreds of traits. The massive amount of data produced in these studies present unique computational challenges. Penalized regression with LASSO or MCP penalties is capable of selecting a handful of associated SNPs from millions of potential SNPs. Unfortunately, model selection can be corrupted by false positives and false negatives, obscuring the genetic underpinning of a trait. Our parallel implementation of IHT accommodates SNP genotype compression and exploits multiple CPU cores and graphics processing units (GPUs). This allows statistical geneticists to leverage desktop workstations in GWAS analysis and to eschew expensive supercomputing resources. We evaluate IHT performance on both simulated and real GWAS data and conclude that it reduces false positive and false negative rates while remaining competitive in computational time with penalized regression.

The dictatorship of sport: Nationalism, internationalism, and mass culture in the 1930s

Keys, Barbara Jean Harvard University 2001 해외박사(DDOD)

This study examines the roots of modern Western sport's global hegemony, focusing on the interaction between nationalism and internationalism in the creation of a global cultural form. It argues that the 1930s were a critical era in the internationalization of modern sport, as rising nationalism pushed sport into preeminence and marginalized competing visions of physical culture. Part One describes the increasing popularity of sport and international competitions in the interwar years and traces the growing powers of international nongovernmental organizations like the International Olympic Committee and the Fédération Internationale de Football Association, as they asserted monopoly control over rules and membership policies and embarked on globally expansionist policies. The United States also played a central role in this expanding global culture of sport. As the dominant power in many amateur sports, its practices and methods were widely emulated. Many Americans were eager internationalists in the realm of sport, convinced that popularizing sport was an effective means of spreading democracy and freedom. Part Two examines the defeat of ideological challenges posed by Nazi Germany and the Soviet Union. The Nazi Party's racist ideology was fundamentally hostile to the universalizing and democratic vision embodied in modern sport. The Nazis, moreover, could draw on the indigenous German gymnastics movement known as <italic>Turnen</italic>, which had a long tradition of opposition to sport. Yet the Nazis quickly became among the most eager adherents of the international sport structure. The Soviet Union's attempt to develop an anti-capitalist, “proletarian” sport system was similarly unsuccessful. By the 1930s the regime was avidly emulating Western sport, with significant domestic consequences. A major reason why the Nazi and Soviet regimes chose rapprochement with the international sport community constructed and controlled by organizations in liberal democratic countries was the apparent ease of comparison offered by sport's universalism, which made the international sport system an attractive means of asserting national power on an international stage. The result was that nationalist impulses pushed culture in internationalist directions.

Denial of the Subjective Body: An Intersubjective-Embodied Feminist Psychotherapy

Keys, Christina M Fuller Theological Seminary, School of Psychology 2020 해외박사(DDOD)

In this paper, the author demonstrates that while there are theorists who address the problem of dualism in psychoanalytic theory, there remains a lack of well-accepted, coherent working metatheory for the role of the body, especially the female body, in psychological theory and practice. Specifically, the female body is often treated as an object, rather than a subject. The author traces the problem of dualism in psychoanalytic theory, including a call to philosophical awareness on the part of the clinician. Intersubjective systems theory (IST) and embodied cognition (EC) are proposed as antidotes to the mind-body problem in psychological theory and practice. The author then reviews literature on the female body in psychoanalysis, explores feminist critiques, and proposes an Intersubjective-Embodied Feminist Psychotherapy (IEFP) in response to the problem of dualism and lack of subjectivity for the female body in psychoanalytic therapy. IEFP brings an awareness that is rooted in a woman’s embodied, embedded self and therefore moves her understanding of self from an object to a subject.

Intracellular Forces and Nuclear Mechanobiology during Confined Cell Migration in 3-Dimensions

Keys, Jeremy Thomas ProQuest Dissertations & Theses Cornell University 2022 해외박사(DDOD)

Cell migration is a required step in many biological and pathological processes. During wound healing, embryogenesis, and immune surveillance, cells migrate to sites where they can repair, develop, and protect tissues, which are all essential for maintaining healthy physiology. In contrast, during cancer metastasis, individual cancer cells escape from the primary tumor and migrate into blood and lymphatic vessels, where they spread through the body to form secondary tumors. This process of cancer metastasis is responsible for 90% of cancer related deaths. Despite its centrality to these essential phenomena, there is still much that is unknown about how cells migrate in vivo.The nucleus limits the rate at which cells can migrate through tissues, as it is the largest and stiffest organelle in the cell. As cells move through narrow spaces in the dense matrix of endothelial cell layers and extracellular fibers that make up biological tissues, they must apply considerable intracellular force to squeeze the nucleus through these spaces. It is still unclear how exactly cells apply sufficient force to complete this deformation of the nucleus through constrictions.Here, we established a microfluidic platform for studying nuclear deformation through precisely defined constrictions. Using this platform, we demonstrate evidence of a novel mechanism by which cells push their nucleus through constrictions through contraction of the rear cortex. We subsequently demonstrate that contraction of the rear cortex induces nuclear blebbing in cancer cells through pressure-driven nuclear influx. This rear cortex-contraction mechanism is significant as it represents a previously unrecognized mechanism which enables confined migration, opening future avenues of study which can inform the treatment of metastatic cancer.We also used this microfluidic platform to evaluate the viability of engineered enucleated mesenchymal stromal cells (MSCs) as a targeted therapeutic delivery system. This work revealed that enucleated cells showed improved invasive ability in comparison to their nucleus-containing counterparts. These findings are significant in that they both support the use of these enucleated MSCs as a targeted therapeutic delivery platform, and that they revealed that cells do not require a nucleus to migrate through 3D constrictions.Later, we assessed the impact of nuclear size restoring compounds on the invasion of prostate cancer cells. This work identified compounds which reversed nuclear size defects commonly observed in cancer cells, and reduced migration in 2D wound healing assays and Boyden chambers, but not through microfluidic constrictions. While ample evidence has shown that the deformability of the nucleus limits its ability to squeeze through constrictions, changes in nuclear size have not shown a consistent relationship with cell’s invasive ability. These findings are significant as they provide evidence that a variety of compounds may present viable treatments for reducing the metastatic capacity of some cancer cell lines. However, it is unclear whether the principal mechanism which reduces migration is directly related to the observed changes in nuclear size.This thesis expands the existing knowledge on the role of the nucleus in confined migration, and the impact of intracellular force generation on nuclear movement.