4,784 research outputs found

    Geologic mapping of northern Lunae Planun, Mars

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    Lunae Planum is an elevated region east of the Tharsis rise, and ridged plains containing numerous Sacra Dorsa wrinkle ridges, cross-cutting Sacra Fossae grabens, and lobate scarps compose this Martian Plateau. Geologic mapping of the northern Lunae Planum region was undertaken to better understand to emplacement history of the ridge plains, the structural history of deformation, and the periods of fluvial processes that have modified the region. These investigations are important for several reasons: (1) the history of plains emplacement yields information valuable for understanding the evolution of Tharsis volcanism; (2) interpretation of structural deformation has implications on the lithology of the Martian crust; and (3) determining the history and fate of Martian volatiles is dependent upon knowing the periods of outflow activity. A discussion of the findings is presented

    Ancient fluvial processes in the equatorial highlands of Mars

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    Martian highland craters typically lack ejecta deposits, have no noticeable rim, and are flat floored. In addition, crater size frequency distribution curves show that highland craters have depleted populations less than 20 km in diameter. A variety of processes have been suggested to explain these observations including deposition of aeolian or volcanic materials up to the crater rim crests, thermal creep, terrain softening, and mass wasting. However, none of these processes adequately explains both the crater morphology and population distribution. In order to explain both the Martian highland crater morphology and population distribution, a fluvial process is proposed which is capable of removing the loose crater rim material. The resulting effect is to decrease the crater diameter, thereby causing the population curves to bendover. The eroded material is redistributed, burying or partially burying smaller diameter craters before complete erosion. This material may also be deposited into local topographic lows, creating the depositional basins observed. A fluvial process explains both sets of observations: crater morphology and crater population distribution curves

    A Bayesian approach to bandwidth selection for multivariate kernel regression with an application to state-price density estimation.

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    Multivariate kernel regression is an important tool for investigating the relationship between a response and a set of explanatory variables. It is generally accepted that the performance of a kernel regression estimator largely depends on the choice of bandwidth rather than the kernel function. This nonparametric technique has been employed in a number of empirical studies including the state-price density estimation pioneered by Aït-Sahalia and Lo (1998). However, the widespread usefulness of multivariate kernel regression has been limited by the difficulty in computing a data-driven bandwidth. In this paper, we present a Bayesian approach to bandwidth selection for multivariate kernel regression. A Markov chain Monte Carlo algorithm is presented to sample the bandwidth vector and other parameters in a multivariate kernel regression model. A Monte Carlo study shows that the proposed bandwidth selector is more accurate than the rule-of-thumb bandwidth selector known as the normal reference rule according to Scott (1992) and Bowman and Azzalini (1997). The proposed bandwidth selection algorithm is applied to a multivariate kernel regression model that is often used to estimate the state-price density of Arrow-Debreu securities. When applying the proposed method to the S&P 500 index options and the DAX index options, we find that for short-maturity options, the proposed Bayesian bandwidth selector produces an obviously different state-price density from the one produced by using a subjective bandwidth selector discussed in Aït-Sahalia and Lo (1998).Black-Scholes formula, Likelihood, Markov chain Monte Carlo, Posterior density.

    The Pines of Texas, a Study in Lumbering and Public Policy, 1880-1930

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    Ellis W. Shuler and the University Libraries

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    One day, forty years ago, curious folk in Cambridge could have seen a tall, thin young man pushing a wheelbarrow load of books across the Harvard Yard. The books, about 35 volumes of the U.S. Geological Survey reports, were the beginnings of the Southern Methodist University geological collection

    Maximum size-density relationships in mixed-species and monospecific stands of the southeastern United States

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    Maximum size-density relationships (MSDR) are used to quantify differences across sites in the number of trees of a given size and species that can be supported per hectare. These relationships are important to managers who are trying to maximize basal area and wood volume. In my study, I examined MSDR across Alabama, Georgia, Louisiana, and Mississippi using US Forest Service, Forest Inventory and Analysis (FIA) data. I determined the impact of species-specific, specific gravity, functional traits, and environmental factors on MSDR using a quantile regression approach. Overall, I found that climatic factors had the greatest influence on MSDR, and that species shade and drought tolerance were more influential than specific gravity across the southeastern US

    A review of corporate insurance (risk) management

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    Thesis (M.B.A.)--Boston Universit

    Interstate Land Sales Regulation: The Case for an Expanded Federal Role

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    Public awareness of the need for protection from fraudulent vendors of undeveloped land recurs periodically and has led to brief flurries of legislative and journalistic attention since the Florida land boom of the 1920s. Despite the rush of state and federal legislation enacted in recent years to combat sharp practices in the land development field, the need for stronger regulation has been revealed by testimony at public hearings held by the Office of Interstate Land Sales Registration as well as by numerous news accounts of questionable tactics employed by some land development promoters. The recent actions of the Federal Trade Commission against deceptive advertising and the warnings of the Better Business Bureau and consumer publications confirm that the present land sales regulation laws have not provided the answer to abuses in the field. The role of the federal government in regulating private sales of subdivided land is currently confined to enforcement of the disclosure requirements of the Interstate Land Sales Full Disclosure Act (Act) through the Office of Interstate Land Sales Registration (OILSR), an agency of the Department of Housing and Urban Development (HUD). The current reports of the persistence of sales practices which the Federal Act was enacted to prevent necessitate an examination of this narrow role

    Civil Rights and West Virginia: A Centennial View

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