Stopping rules for approximation procedures

Stroup, Donna Fox U. M. I. 1980 국내박사

Stopping rules for stoachastic approximation procedures

Stroup, Donna Fox U. M. I. 1984 국내박사

Stopping rules for stochastic approximation procedures

Stroup, Donna Fox UMI 1979 해외박사

Stoopping Rules for Stochastic Approximation Procedures

Stroup, D. P University Microfilms International 1979 국내박사

Holocene fluctuations of Quelccaya Ice Cap, Peru

Stroup, Justin Sirico Dartmouth College 2015 해외박사(DDOD)

The tropics are critical for paleoclimate study because of their ability to influence global climate through ocean and atmospheric circulation. In this dissertation, I reconstruct the fluctuations of Quelccaya Ice Cap (QIC), located in the Peruvian Andes to provide information about Holocene (11,600 years ago-present) climate. QIC is an ideal location for Holocene paleoclimate research since extensive geological archives such as moraines, lake sediments, stratigraphic sections, in situ plant remains and ice cores register past ice cap extents and climate conditions. I utilize these archives, and extensive prior work from the area, to develop detailed records of Holocene QIC extents and climate. First, I reconstruct the late Holocene extents of Qori Kalis glacier, an outlet of QIC, using 10Be surface exposure dating of moraines. Qori Kalis advanced prior to 0.58 ka and retreated from its late Holocene maximum extent by ~0.58 ka. Qori Kalis retreat continued until ~0.28 ka, interrupted by a small readvance at ~0.41-0.36 ka. Based on a comparison of Qori Kalis extents and Quelccaya ice core net accumulation, I infer that temperature was a dominant influence on late Holocene QIC fluctuations. Second, I develop a late Holocene sediment core record from a glacially fed lake (Challpacocha) near QIC and compare this with the Qori Kalis moraine record to interpret the type of sediment deposited during ice cap advance and retreat. I find that organic sedimentation occurred primarily during ice cap advance and clastic sedimentation occurred during ice cap retreat. This result is valuable for other studies using lake sediments to interpret past glacial fluctuations. Third, I develop a near-continuous, Holocene-long record of QIC fluctuations using sediment cores from Challpacocha in combination with prior work. From ~10.8 to 6.5 ka, QIC was small or absent. From 6.5 to 5 ka, QIC was present on the landscape and ice cap growth may have been influenced by cooler temperatures. At 3-2.4 and 0.62-.31 ka QIC experienced phases of ice advance and retreat. Collectively, my research provides new information about the Holocene fluctuations of QIC and helps constrain past tropical South American climate conditions.

Making and using siroheme: The X-ray crystallographic structures of siroheme synthase and sulfite reductase

Stroupe, Margaret Elizabeth The Scripps Research Institute 2002 해외박사(DDOD)

Siroheme is an unusual but useful cofactor found in sulfite and nitrite reductases. In these systems, siroheme serves alongside a [4Fe-4S] cluster to catalyze the six-electron reduction of sulfide to sulfite or nitrite to ammonia. Like other tetrapyrrolic cofactors, siroheme is derived from uroporphyrinogen III. To make siroheme, uroporphyrinogen III undergoes two <italic>S</italic>-adenosyl-<smcap> L</smcap>-methionine-dependent methylations, nicotinamide adenine diphosphate-dependent ring oxidation, and ferrous iron chelation. In <italic>Salmonella typhimurium </italic>, a single enzyme called siroheme synthase (CysG) performs all four chemical transformations. CysG is the product of a gene fusion event, in which transcription of two distinct modules became linked, creating a multifunctional enzyme [1, 2]. Our three-dimensional x-ray crystallographic structure of this “two-in-one” protein reveals the tight, homodimeric assembly of each module. The N-terminus (CysG<super>Fe</super>, residues 1–214) folds into a three-domain, homodimeric structure that is homologous to another known precorrin-2 dehydrogenase/sirohydrochlorin ferrochelatase called Met8p [3]. The C-terminus (CysG<super>Me</super>, residues 215–457) folds into a two-domain homodimeric structure that is homologous to another precorrin methylase, CbiF [4]. CysGFe bears an unexpected phosphoserine at position 128 and, based on our analysis of several point mutations at Ser128, we propose a model for phosphorylation-based regulation of CysG<super>Fe</super>'s dehydrogenase activity. Based on our mutational analysis of CysG<super>Me </super>, we propose a mechanism for substrate recognition and methyl transfer. To complement our structural analysis of the enzyme that makes siroheme, we also present ultra-high resolution analysis of the active site of the assimilatory sulfite reductase hemoprotein.

Did pharmaceuticals have a cure for the plague of asymmetric information, or were the 1962 drug amendments efficient?

Stroup, Craig L Clemson University 1996 국내박사

Collaborative execution of exploration and tracking using move value estimation for robot teams (MVERT)

Stroupe, Ashley W Carnegie Mellon University 2003 해외박사(DDOD)

This work presents Move Value Estimation for Robot Teams (MVERT), an architecture specifically designed for selecting low-level actions for multi-agent teams. The design goal for MVERT is to produce reasonable performance that takes advantage of a heterogeneous team while maintaining computational efficiency. MVERT is fully distributed—each agent selects actions based on its knowledge and knowledge provided it by teammates. Each robot approximates the expected next-step teammate contributions and, given these predictions, each robot can select its action to maximize the team's progress. MVERT represents progress with mathematical <italic>value functions</italic> that map state and robot task performance models to a numerical value representing mission utility. Many action selection approaches (optimal trajectory planning, for example) in large state-spaces may be computationally prohibitive, particularly for online mission replanning. However, taking advantage of a team's multi-agent nature to provide efficiency requires consideration of teammate contributions. Thus, in selecting an action with MVERT, each robot approximates the next-step contributions of teammates by applying their sensing models, task capabilities, and current poses in the value functions. The robot then evaluates its candidate actions by applying the value functions and its own sensor models. The action resulting in the overall highest-valued pose is selected and executed. Performance in each task is described by an individual value function. <italic> State</italic> includes current locations of teammates and objects in the environment. <italic>Performance models</italic> include task capabilities and sensor models. <italic>Value functions</italic> may be any mathematical representation of task performance. To determine an actions' overall value, independent task values are combined by weighted average. Weighting each task's value allows prioritizing tasks in accordance with desired performance. As progress reduces potential for improving value on some tasks, the weights automatically shift focus to the other tasks. Weights can be dynamically adapted as mission needs change. MVERT has been applied in simulation and on physical robots for mapping, dynamic target tracking, and complex multi-task missions (planetary exploration). MVERT improves team mission performance time and completeness compared to individual action selection and greatly improves computation time compared to a one-step optimal. MVERT produces contextually appropriate actions for successfully performing complex multi-task, multi-robot missions.

Crystal structures of Sec4 bound to GDP and to a nonhydrolyzable GTP analog

Stroupe, Stephen Christopher Yale University 2000 해외박사(DDOD)

Rab proteins constitute a family of small G proteins essential for membrane trafficking and vesicular transport in eukaryotic cells. I have determined the crystal structures of Sec4, a member of the Rab family, in two states: bound to GDP, and to a nonhydrolyzable GTP analog, guanosine-5<super>′ </super>-(β,γ-imido)-triphosphate (GppNHp). This represents the first structure of a Rab protein bound to GDP. Sec4 in both states grossly resembles other G proteins bound to GDP and GppNHp. However, the conformation of the switch II region of Sec4-GppNHp differs slightly from that of Ras-GppNHp. The switch II region of Sec4-GppNHp closely resembles the switch II regions of other Rab proteins bound to GppNHp, suggesting that this conformation is common to Rab proteins. Additionally, a hydrogen bond between a serine residue in the P-loop and the γ phosphate of the nucleotide is seen in Sec4 and other GppNHp-bound Rab proteins, but not in Ras-GppNHp, in which the equivalent residue is a glycine. The switch I region in Sec4-GDP is highly disordered and displaced relative to the switch I region of Ras-GDP. Also, in two of the four molecules in the asymmetric unit, the switch II region adopts a conformation resembling that of the small G protein Ran in complex with GDP. This allows the conserved residues threonine 76, glutamate 80, and arginine 81 of Sec4 to make contacts with other conserved residues and water molecules important for nucleotide binding. In the other two molecules in the asymmetric unit, residues 76, 80, and 81 are flipped away from the nucleotide and make no contacts with groups involved in binding the nucleotide. This structural variability in the switch I and II regions of GDP-bound Sec4 may explain the high off-rate of GDP bound to Sec4. Additionally, the disorder in the switch regions of Sec4-GDP suggests that the mechanism of GDP dissociation inhibitors (GDIs) may involve stabilization of these regions of Sec4.

Nursing as a career choice by Hispanic/Latino college students

Stroup, Linda M Colorado State University 2013 해외박사(DDOD)

A culturally competent healthcare workforce is essential to meet the needs of an increasingly diverse society. Greater diversity in the healthcare workforce is expected have many benefits, including improved access to care for the medically underserved and the promotion of research in areas of societal need (Cohen, Gabriel, & Terrell, 2002). The need for a culturally diverse healthcare workforce includes the profession of registered nursing. There is a significant disparity between the percentage of Hispanic/Latino individuals in the United States population and the percentage of Hispanic/Latino nurses. Although the number of Hispanic/Latino college students has increased over the past several years, Hispanic/Latino students remain significantly underrepresented in pre-licensure nursing programs. It is necessary for the number of Hispanic/Latino nursing students to increase in order to expand the number of Hispanic/Latino nurses in the healthcare workforce. A quantitative research design was used for this study. The Career Search Questionnaire (CSQ) developed by Roberts (2008) was administered with the addition of four questions and modifications in the demographic section of the instrument. The survey was administered to students enrolled in freshman or sophomore level college courses at three comprehensive state public universities and one community college in a Western state. The total number of participants in the sample was 961. Study findings indicated that Hispanic/Latino students were just as interested in and had as high feelings of confidence about activities associated with nursing as a career choice when compared with non-Hispanic/Latino students. Very few statistically significant differences were found between the two groups of students (Hispanic/Latino and non-Hispanic/Latino), and there were few differences in the correlations of Hispanic/Latino and non-Hispanic/Latino students with demographic and CSQ variables. One exception was that gender was not statistically significant for Hispanic/Latino students, suggesting that gender was not a predictive variable for interest in activities associated with nursing among Hispanic/Latino students. Additional findings indicated that both Hispanic/Latino and non-Hispanic/Latino students identified having lower feelings of confidence in successfully completing math and science courses that are often required pre-requisite courses for nursing programs. Shadowing a nurse, mentoring by a nurse, healthcare work experience, and volunteer healthcare experience were the top factors identified by both Hispanic/Latino and non-Hispanic/Latino students as necessary for success in a nursing program. Analysis of the Career Search Questionnaire indicated that the instrument differentiated between interest in activities associated with nursing and non-nursing careers and, likewise, the CSQ differentiated between nursing and non-nursing career self-efficacy. The CSQ appears to be a better predictor of interest in a healthcare career in general rather than specifically nursing. Implications for practice include use of the CSQ questionnaire as an advising tool for students in the career decision-making process, and identification of strategies that could be implemented by nursing programs to promote success for Hispanic/Latino students considering nursing as a career choice. Future research studies could include broadening the sample to include Hispanic/Latino students enrolled in community colleges, private, and proprietary higher education institutions. Consideration of nursing as a career choice by healthcare providers in related fields such as medical assistants and nursing assistants could also be investigated. Finally, research could be conducted to determine if Hispanic/Latino students who indicate an interest in nursing as a career choice are actually applying to nursing programs and if so, what factors facilitate their acceptance into a nursing program as well as barriers to admission.