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Here, we report a comprehensive paleogenomic study of archaeological and ethnographic sunflower remains that provides significant new insights into the process of domestication of this important crop. DNA from both ancient and historic contexts yielded high proportions of endogenous DNA, and although archaeological DNA was found to be highly degraded, it still provided sufficient coverage to analyze genetic changes over time. Shotgun sequencing data from specimens from the Eden's Bluff archaeological site in Arkansas yielded organellar DNA sequence from specimens up to 3,100 years old. Their sequences match those of modern cultivated sunflowers and are consistent with an early domestication bottleneck in this species. Our findings also suggest that recent breeding of sunflowers has led to a loss of genetic diversity that was present only a century ago in Native American landraces. These breeding episodes also left a profound signature on the mitochondrial and plastid haplotypes in cultivars, as two types were intentionally introduced from other Helianthus species for crop improvement. These findings gained from ancient and historic sunflower specimens underscore how future in‐depth gene‐based analyses can advance our understanding of the pace and targets of selection during the domestication of sunflower and other crop species.

Here, we report a comprehensive paleogenomic study of archaeological and ethnographic sunflower remains that provides significant new insights into the process of domestication of this important crop. DNA from both ancient and historic contexts yielded high proportions of endogenous DNA, and although archaeological DNA was found to be highly degraded, it still provided sufficient coverage to analyze genetic changes over time. Shotgun sequencing data from specimens from the Eden's Bluff archaeological site in Arkansas yielded organellar DNA sequence from specimens up to 3,100 years old. Their sequences match those of modern cultivated sunflowers and are consistent with an early domestication bottleneck in this species. Our findings also suggest that recent breeding of sunflowers has led to a loss of genetic diversity that was present only a century ago in Native American landraces. These breeding episodes also left a profound signature on the mitochondrial and plastid haplotypes in cultivars, as two types were intentionally introduced from other Helianthus species for crop improvement. These findings gained from ancient and historic sunflower specimens underscore how future in‐depth gene‐based analyses can advance our understanding of the pace and targets of selection during the domestication of sunflower and other crop species.

The complex evolutionary history of maize (Zea mays L. ssp. mays) has been clarified with genomic-level data from modern landraces and wild teosinte grasses [1, 2], augmenting archaeological findings that suggest domestication occurred between 10,000 and 6,250 years ago in southern Mexico [3, 4]. Maize rapidly evolved under human selection, leading to conspicuous phenotypic transformations, as well as adaptations to varied environments [5]. Still, many questions about the domestication process remain unanswered because modern specimens do not represent the full range of past diversity due to abandonment of unproductive lineages, genetic drift, on-going natural selection, and recent breeding activity. To more fully understand the history and spread of maize, we characterized the draft genome of a 5,310-year-old archaeological cob excavated in the Tehuacan Valley of Mexico. We compare this ancient sample against a reference panel of modern landraces and teosinte grasses using D statistics, model-based clustering algorithms, and multidimensional scaling analyses, demonstrating the specimen derives from the same source population that gave rise to modern maize. We find that 5,310 years ago, maize in the Tehuacan Valley was on the whole genetically closer to modern maize than to its wild counterpart. However, many genes associated with key domestication traits existed in the ancestral state, sharply contrasting with the ubiquity of derived alleles in living landraces. These findings suggest much of the evolution during domestication may have been gradual and encourage further paleogenomic research to address provocative questions about the world's most produced cereal.

The origin of maize (Zea mays mays) in the US Southwest remains contentious, with conflicting archaeological data supporting either coastal(1-4) or highland(5,6) routes of diffusion of maize into the United States. Furthermore, the genetics of adaptation to the new environmental and cultural context of the Southwest is largely uncharacterized(7). To address these issues, we compared nuclear DNA from 32 archaeological maize samples spanning 6,000 years of evolution to modern landraces. We found that the initial diffusion of maize into the Southwest about 4,000 years ago is likely to have occurred along a highland route, followed by gene flow from a lowland coastal maize beginning at least 2,000 years ago. Our population genetic analysis also enabled us to differentiate selection during domestication for adaptation to the climatic and cultural environment of the Southwest, identifying adaptation loci relevant to drought tolerance and sugar content.

The origin of maize (Zea mays mays) in the US Southwest remains contentious, with conflicting archaeological data supporting either coastal(1-4) or highland(5,6) routes of diffusion of maize into the United States. Furthermore, the genetics of adaptation to the new environmental and cultural context of the Southwest is largely uncharacterized(7). To address these issues, we compared nuclear DNA from 32 archaeological maize samples spanning 6,000 years of evolution to modern landraces. We found that the initial diffusion of maize into the Southwest about 4,000 years ago is likely to have occurred along a highland route, followed by gene flow from a lowland coastal maize beginning at least 2,000 years ago. Our population genetic analysis also enabled us to differentiate selection during domestication for adaptation to the climatic and cultural environment of the Southwest, identifying adaptation loci relevant to drought tolerance and sugar content.

The origin of maize (Zea mays mays) in the US Southwest remains contentious, with conflicting archaeological data supporting either coastal(1-4) or highland(5,6) routes of diffusion of maize into the United States. Furthermore, the genetics of adaptation to the new environmental and cultural context of the Southwest is largely uncharacterized(7). To address these issues, we compared nuclear DNA from 32 archaeological maize samples spanning 6,000 years of evolution to modern landraces. We found that the initial diffusion of maize into the Southwest about 4,000 years ago is likely to have occurred along a highland route, followed by gene flow from a lowland coastal maize beginning at least 2,000 years ago. Our population genetic analysis also enabled us to differentiate selection during domestication for adaptation to the climatic and cultural environment of the Southwest, identifying adaptation loci relevant to drought tolerance and sugar content.

Bottle gourd (Lagenaria siceraria) was one of the first domesticated plants, and the only one with a global distribution during pre-Columbian times. Although native to Africa, bottle gourd was in use by humans in east Asia, possibly as early as 11,000 y ago (BP) and in the Americas by 10,000 BP. Despite its utilitarian importance to diverse human populations, it remains unresolved how the bottle gourd came to be so widely distributed, and in particular how and when it arrived in the New World. A previous study using ancient DNA concluded that Paleoindians transported already domesticated gourds to the Americas from Asia when colonizing the New World [Erickson et al. (2005) Proc Natl Acad Sci USA 102(51):18315-18320]. However, this scenario requires the propagation of tropical-adapted bottle gourds across the Arctic. Here, we isolate 86,000 base pairs of plastid DNA from a geographically broad sample of archaeological and living bottle gourds. In contrast to the earlier results, we find that all pre-Columbian bottle gourds are most closely related to African gourds, not Asian gourds. Ocean-current drift modeling shows that wild African gourds could have simply floated across the Atlantic during the Late Pleistocene. Once they arrived in the New World, naturalized gourd populations likely became established in the Neotropics via dispersal by megafaunal mammals. These wild populations were domesticated in several distinct New World locales, most likely near established centers of food crop domestication.

The objective of this report is to quantitatively examine the problem determining parameters of a resistive layer in the earth's crust by electrical sounding methods. The advantages and disadvantages of a quantitive assessment of the resolution of model parameters is briefly examined. Particular electrical sounding methods considered here are; (1) magnetotelluric and audio magnetotelluric methods (MT-AMT); (2) direct current (DC) Schlumberger (VES) method; and (3) DC dipole-dipole sounding methods with a finite source and receiver. These methods constitute, in principle, the majority of electrical methods which have been used to determine electrical parameters of the earth's crust. An important class of electrical sounding methods, the artificial or controlled source electromagnetic induction methods, is not considered. First described are general aspects of qualitative and quantitative methods to estimate the resolving power of a given set of crustal sounding measurements. Resolving power is the capability of the measurements to determine the bounds of a set of earth model parameters. For the crustal sounding problem, the model parameters are the resistivities and the layer thicknesses of a horizontally stratified earth. Finally the resolving power of a particular set of sounding measurements is described.

The principle issue addressed in this dissertation is generalized tomographic reconstruction from fan-beam and cone-beam data. One consequence of the generalized tomographic reconstruction method developed in this dissertation is that it allows one to collect fan-beam data along a more general path than previously developed methods that require collecting the data along a circular path about the object. The lack of knowledge concerning reconstruction from cone-beam data has hindered the development of exact closed-form convolution-backprojection reconstruction methods for cone-beam data. In this dissertation necessary and sufficient conditions for reconstructing from cone-beam data are derived and exact convolution-backprojection reconstruction methods are developed. The most efficient of these methods require a stringent condition on the path of source points. A search is made for paths which satisfy the requirements of the most efficient method. Additionally, the most efficient method is compared with that of Feldkamp et al. and found equivalent when the path of source points is a circle.

A reconnaissance study of ²²²Rn concentrations in the ground water of the North-Central Tucson basin revealed a range of concentrations from 80 to 1400 pCi/L in wells, and 60 to 1260 pCi/L in domestic waters. Estimated degradation of Rn in water from wells to homes ranges from 8 to 50%. The interior well field of mid-Tucson, may represent background concentrations of Rn with a mean value of 250 pCi/L. The limited data define an anomalous trend (500 to 1400 pCVL) of ²²²Rn paralleling the Santa Cruz River area. 222Rn concentrations above 500 pCVL correlate positively with temperature, and no low temperature water contains high ²²²Rn levels. Weak inverse correlations of ²²²Rn with pumping bowl depth, pumping water level and average upper perforation intervals are evident. It is concluded that the source of ²²²Rn is close to the well bore. Considered are several possible hypothesis and mechanisms responsible for the anomalous Santa Cruz ²²²Rn trend, including mechanisms related to water circulation along the Santa Cruz fault, lithology, and aquifer compaction.

A reconnaissance study of ²²²Rn concentrations in the ground water of the North-Central Tucson basin revealed a range of concentrations from 80 to 1400 pCi/L in wells, and 60 to 1260 pCi/L in domestic waters. Estimated degradation of Rn in water from wells to homes ranges from 8 to 50%. The interior well field of mid-Tucson, may represent background concentrations of Rn with a mean value of 250 pCi/L. The limited data define an anomalous trend (500 to 1400 pCVL) of ²²²Rn paralleling the Santa Cruz River area. 222Rn concentrations above 500 pCVL correlate positively with temperature, and no low temperature water contains high ²²²Rn levels. Weak inverse correlations of ²²²Rn with pumping bowl depth, pumping water level and average upper perforation intervals are evident. It is concluded that the source of ²²²Rn is close to the well bore. Considered are several possible hypothesis and mechanisms responsible for the anomalous Santa Cruz ²²²Rn trend, including mechanisms related to water circulation along the Santa Cruz fault, lithology, and aquifer compaction.

This paper considers three questions: (1) what is the role of financial markets in development, (2) why do some economies have such poorly developed financial markets, and (3) can government policy be used to promote financial market development? With respect to the first question, we formalize the widely-held notion that financial markets promote entrepreneurship, specialization. and learning-by-doing. However, if economic incentives for specialization are absent, financial markets may fail to form. This occurs when real interest rates are too low. We also discuss policies that can be used to promote financial market development. When these policies are successful, they will be growth promoting. Finally, we examine policies intended to manipulate returns on savings, which are often important components of "financial liberalizations." We describe conditions under which such policies will be conducive to growth.

What is the relationship between markets and development? It is argued that markets promote growth, and that growth in turn encourages the formation of markets. Two models with endogenous market formation are presented to analyze this issue. The first examines the role that financial markets - banks and stockmarkets - play in allocating funds to the highest valued use in the economic system. It is shown that intermediation will arise under weak conditions. The second focuses on the role that markets play in supporting specialization in economic activity. The consequences of perfect competition in market formation are highlighted.

This paper considers three questions: (1) what is the role of financial markets in development, (2) why do some economies have such poorly developed financial markets, and (3) can government policy be used to promote financial market development? With respect to the first question, we formalize the widely-held notion that financial markets promote entrepreneurship, specialization. and learning-by-doing. However, if economic incentives for specialization are absent, financial markets may fail to form. This occurs when real interest rates are too low. We also discuss policies that can be used to promote financial market development. When these policies are successful, they will be growth promoting. Finally, we examine policies intended to manipulate returns on savings, which are often important components of "financial liberalizations." We describe conditions under which such policies will be conducive to growth.

What is the relationship between markets and development? It is argued that markets promote growth, and that growth in turn encourages the formation of markets. Two models with endogenous market formation are presented to analyze this issue. The first examines the role that financial markets - banks and stockmarkets - play in allocating funds to the highest valued use in the economic system. It is shown that intermediation will arise under weak conditions. The second focuses on the role that markets play in supporting specialization in economic activity. The consequences of perfect competition in market formation are highlighted.