Estimation of Distribution Overlap of Urn Models

A classical problem in statistics is estimating the expected coverage of a sample, which has had applications in gene expression, microbial ecology, optimization, and even numismatics. Here we consider a related extension of this problem to random samples of two discrete distributions. Specifically, we estimate what we call the dissimilarity probability of a sample, i.e., the probability of a draw from one distribution not being observed in k draws from another distribution. We show our estimator of dissimilarity to be a U-statistic and a uniformly minimum variance unbiased estimator of dissimilarity over the largest appropriate range of k. Furthermore, despite the non-Markovian nature of our estimator when applied sequentially over k, we show it converges uniformly in probability to the dissimilarity parameter, and we present criteria when it is approximately normally distributed and admits a consistent jackknife estimator of its variance. As proof of concept, we analyze V35 16S rRNA data to discern between various microbial environments. Other potential applications concern any situation where dissimilarity of two discrete distributions may be of interest. For instance, in SELEX experiments, each urn could represent a random RNA pool and each draw a possible solution to a particular binding site problem over that pool. The dissimilarity of these pools is then related to the probability of finding binding site solutions in one pool that are absent in the other.Comment: 27 pages, 4 figure

Stratiform clouds and their interaction with atmospheric motions

During the 1987 to 1988 academic year, three projects were finished and plans were made to redirect and focus work in a proposal now being reviewed. The completed work involves study of waves on an equatorial beta-plane in shear flow, investigation of the influence of orography on the index cycle, and analysis of a model of cloud street development in a thermally-forced, sheared environment. The proposed work involves study of boundary layer circulations supporting stratocumulus decks and investigation of how the radiative effects of these clouds modulate larger-scale flows such as those associated with the index oscillation

Material Morphology and energy barriers to electrical ageing

A distribution of the parameters representing activation energy of the ageing process within the Dissado-Montanari-Mazzanti (DMM) lifetime model has been shown to model experimental lifetime distributions of PET films well. The results imply small differences in the local environments of the moieties involved in the ageing process. Very small changes in the minimum activation energy values have a pronounced effect on the resultant lifetimes of polymer specimens. Changes in the distributions of activation energies with field and temperature can be explained by assuming the ageing process to be one whereby polymer segments on lamella surfaces crystallise to create free volume within the polymer

Risk Behavior, Decision Making, and Music Genre in Adolescent Males

The effects of music on risk behavior and decision-making are still unknown. Previous studies have linked music with risky behaviors such as drinking. Evidence shows that performance and decision-making on certain tasks can be altered by the presence of music. This study seeks to evaluate decision-making while in this altered state of mind. It is hypothesized that decisions made listening to rock music will be more risky than those made in other conditions. Participants were assessed using several questionnaires and the Iowa Gambling Task. Participants were randomly assigned to no music, classical music, or rock music. Results indicate several interesting trends in behavior as well as several significant correlations between risky decision-making and reaction time on the Iowa Gambling Task

Improved diamond coring bits developed for dry and chip-flush drilling

Two rotary diamond bit designs, one operating with a chip-flushing fluid, the second including auger section to remove drilled chips, enhance usefulness of tool for exploratory and industrial core-drilling of hard, abrasive mineral deposits and structural masonry

Effects of classification context on categorization in natural categories

The patterns of classification of borderline instances of eight common taxonomic categories were examined under three different instructional conditions to test two predictions: first, that lack of a specified context contributes to vagueness in categorization, and second, that altering the purpose of classification can lead to greater or lesser dependence on similarity in classification. The instructional conditions contrasted purely pragmatic with more technical/quasi-legal contexts as purposes for classification, and these were compared with a no-context control. The measures of category vagueness were between-subjects disagreement and within-subjects consistency, and the measures of similarity based categorization were category breadth and the correlation of instance categorization probability with mean rated typicality, independently measured in a neutral context. Contrary to predictions, none of the measures of vagueness, reliability, category breadth, or correlation with typicality were generally affected by the instructional setting as a function of pragmatic versus technical purposes. Only one subcondition, in which a situational context was implied in addition to a purposive context, produced a significant change in categorization. Further experiments demonstrated that the effect of context was not increased when participants talked their way through the task, and that a technical context did not elicit more all-or-none categorization than did a pragmatic context. These findings place an important boundary condition on the effects of instructional context on conceptual categorization