SOIL POTASSIUM BIOAVAILABILITY AND ROOT GROWTH FACTORS IN RIDGE AND CONVENTIONALLY TILLED SOILS

OLDHAM, JAMES LARRY UNIVERSITY OF MINNESOTA 1997 해외박사

FORMATION AND STABILITY OF MERCURIC SULFIDE IN SUBSURFACE ENVIRONMENTS (METACINNABAR)

BARNETT, MARK OLDHAM THE UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL 1998 해외박사

Multicommodity and generalized flow algorithms: Theory and practice

Oldham, Jeffrey David Stanford University 1999 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

We present several simple, practical, and fast algorithms for linear programs, concentrating on network flow problems. Since the late 1980s, researchers developed different combinatorial approximation algorithms for fractional packing problems, obtaining the fastest theoretical running times to solve multicommodity minimum-cost and concurrent flow problems. A direct implementation of these multicommodity flow algorithms was several orders of magnitude slower than solving these problems using a commercial linear programming solver. Through experimentation, we determined which theoretically equivalent constructs are experimentally efficient. Guided by theory, we designed and implemented practical improvements while maintaining the same worst-case complexity bounds. The resulting algorithms solve problems orders of magnitude faster than commercial linear programming solvers and problems an order of magnitude larger. We also present simple, combinatorial algorithms for generalized flow problems. These problems generalize ordinary network flow problems by specifying a flow multiplier μ(<italic>a</italic>) for each arc <italic>a</italic>. Using multipliers permit a flow problem to model transforming one type into another, e.g., currency exchange, and modification of the amount of flow, e.g., water evaporation from canals or accrual of interest in bank accounts. First, we show the generalized shortest paths problem can be solved using existing network flow ideas, i.e., by combining the Bellman-Ford-Moore shortest path framework and Megiddo's parametric search. Second, we combine this algorithm with fractional packing frameworks to yield the first polynomial-time combinatorial approximation algorithms for the generalized versions of the nonnegative-cost minimum-cost flow, concurrent flow, multicommodity maximum flow, and multicommodity nonnegative-cost minimum-cost flow problems. These algorithms show that generalized concurrent flow and multicommodity maximum flow have strongly polynomial approximation algorithms.

The doctrine of description: Gustav Kirchhoff, classical physics, and the "purpose of all science" in 19th-century Germany

Oldham, Kalil T. Swain University of California, Berkeley 2008 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

In 1875 Berlin University hired Gustav Robert Kirchhoff (1824--1887) to fill its first chair in theoretical physics. When he introduced his inaugural series of lectures that summer, on mechanics, Kirchhoff argued that physics should avoid seeking causal explanations and limit itself only to simple and accurate descriptions of natural phenomena. He held to this position, a brand of epistemological phenomenalism, until his retirement nearly ten years later. Kirchhoff's 1875 lectures represent a manifestation of the complicated relationship between philosophy and physics, which characterizes the history of nineteenth-century German science. Using Kirchhoff's story as a wedge, this dissertation examines that relationship. Kirchhoff's philosophical and methdological stance foreshadowed a rising tide of ambivalence about claims to absolute truth in the natural sciences. Looking at episodes from the history of classical physics (electrodynamics, physical chemistry, and thermodynamics) and the history of philosophy of science, this dissertation highlights the complex ways in which physics and philosophy intertwined in the nineteenth century. A close-knit group of professors---including Kirchhoff, Hermann von Helmholtz, Emil du Bois-Reymond, Robert Bunsen, and Eduard Zeller---negotiated the boundaries of their particular disciplines as they debated the purpose and limits of scientific inquiry in general. While philosophical reflections by natural scientists were not uncommon, the methodological and epistemological positions developed by Kirchhoff and his colleagues---at Heidelberg and Berlin---are important because they provided a framework for discussions of the foundations of modern theoretical physics. Occurring in the generation after Kirchhoff's, these foundational discussions paved the way for the modern revolutions in physics and their profound philosophical implications. Kirchhoff's decision to divorce the natural sciences from metaphysical notions, therefore, had significant consequences for science and philosophy in the years around the fin de siecle. The audience for this dissertation will include historians of German physics, historians of nineteenth-century science in general, scholars interested in the intersection between the history of science and philosophy, and those interested in the broader interaction between science and culture.

The influence of risk and protective processes on the competence of children growing up in poverty

Oldham, Erin Elizabeth University of California, Los Angeles 1999 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This study investigated the risk and protective processes that were important to the social and cognitive outcomes of children growing up in poverty. We examined risk and protection with the lives of 703 African-American mothers and their children (304 boys) who were living in Fulton County, Georgia. These families were part of the National Evaluation of Welfare to Work Strategies Child Outcomes Study that followed children for two years from when the children were three to five years of age. Discriminant function analyses were used to determine “sensitive” risk indices for resilient cognitive (Bracken Basic Concept Scale) and behavioral (Behavior Problems Index, Positive Child Behavior Scale) outcomes. Structural Equation Models were estimated to determine the importance of the timing and duration of risk and protection, to determine what variables interact with risk levels to “protect” high risk children and to determine whether risk and protection operates differently for boys and girls. We found that sensitive risk indices and protective variables (early cognitive skills. early social maturity, early education and care, cognitive stimulation, maternal warmth, social support, and maternal employment) contributed to reasonable models of children's social and cognitive competence. Specifically, early cognitive and social skills as well as the early risk environment were strong predictors of later cognitive and social skills. Cognitive stimulation in the home and outside of the home (e.g., in early education and care arrangements) was protective for cognitive outcomes among higher risk children. There was evidence of direct ameliorative effects of early behavior and maternal warmth in relation to behavioral competence but no evidence of protection among the examined variables. Finally, risk and protection operated differently in relation to male and female children.

Transcriptome organization in human and chimpanzee brains

Oldham, Michael Clark University of California, Los Angeles 2009 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Humans possess a unique and powerful brand of cognition that is seemingly discontinuous from the rest of the animal kingdom. Yet at a molecular level, our genome is remarkably similar to that of our closest living relative, the chimpanzee. At the heart of this apparent paradox is the finite set of molecular instructions that distinguish human and chimpanzee brain development and function. These instructions can be directly studied by comparing the organization of human and chimpanzee brain transcriptomes through systematic analysis of gene coexpression relationships. In this dissertation, two studies are presented that provide a new perspective on the molecular evolution of the brain. In the first, gene coexpression networks in human and chimpanzee brains were compared across matched cortical and sub-cortical brain regions. This study found that large modules of coexpressed genes corresponded to functionally relevant brain anatomy and introduced an approach for comparing module conservation between the species. Module conservation was significantly weaker in cortex than in sub-cortical brain regions. This study also provided evidence that interspecies differences in a gene's network position could be related to differences in expression levels and protein sequence, suggesting that differential connectivity in gene coexpression networks might serve as a unifying principle for disparate types of evolutionary change. In the second study, region-specific gene coexpression networks were generated from human cerebral cortex, caudate nucleus, and cerebellum. This study identified modules of coexpressed genes that corresponded to neurons, oligodendrocytes, astrocytes, and microglia, invalidating the commonly held assumption that cellular heterogeneity precludes the recovery of cell type-specific information in microarray data generated from whole brain tissue and providing an initial description of the transcriptional programs that distinguish the major cell classes of the human brain. Other modules distinguished additional cell types, organelles, synaptic function, response to hypoxia, gender differences, and the subventricular neurogenic niche. The characterization of gene coexpression network architecture in specific human brain regions provides a new foundation for exploring molecular changes that have occurred in specific cell types or functional processes during recent human and chimpanzee brain evolution.

An investigation of item fit and functioning of an algebra assessment for English language learners

Sampson, Shannon Oldham University of Kentucky 2005 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Important decisions are often made based on assessment results, but there are questions about whether they really assess what is intended for all students, including English Language Learning (ELL) students. This study asks the following questions: (1) Do the data from a multiple choice assessment designed to measure the algebra ability of a group of high school students fit the requirements of the Rasch model for both ELL and English-proficient students? (2) How do the item difficulties compare for ELL and English-proficient students? (3) If certain data fit the model poorly and/or have divergent difficulty measures for the ELL students and their English-proficient classmates, can these idiosyncrasies be attributed to the linguistic complexity of the items?. The Rasch model was selected because deviations from the expectations of the model may indicate problematic features that can be controlled for or explained, especially when they are related to a demographic subgroup such as ELL students. Furthermore, it supports the relatively small sample of ELL students included in the study. Through the application of the Rasch model, along with a systematic method of selecting an item set varying in linguistic complexity and mathematical content difficulty, this study provides a look at the role linguistic complexity plays in determining item difficulty for ELL students on a mathematics assessment. Empirical evidence revealed that proportionately more ELL students misfit than English-proficient students. Surprisingly, poor fit resulted from many ELL students answering certain difficult items correctly, and all but one of these items required students to translate a verbal expression into a mathematical one. The five differentially difficult items for the ELL students contained a key word or phrase important to understanding the item, and contained material that students new to the United States may not have had the opportunity to learn. The findings challenge current notions about linguistic complexity confounding content assessment, although further studies should be conducted before definitively countering others' work. This study offers new ideas to consider, and a methodology for conducting the future studies to further explore these ideas.