Lessons from the Laureates

This paper uses as source material twenty-three autobiographical essays by Nobel economists presented since 1984 at Trinity University (San Antonio, Texas) and published in Lives of the Laureates (MIT Press). A goal of the lecture series is to enhance understanding of the link between biography and the development of modern economic thought. We explore this link and identify common themes in the essays, relying heavily on the words of the laureates. Common themes include the importance of real-world events coupled with a desire for rigor and relevance, the critical influence of teachers, the necessity of scholarly interaction, and the role of luck or happenstance. Most of the laureates view their research program not as one planned in advance but one that evolved via the marketplace for ideas.autobiography, Nobel economists, economic thought

A statistical framework for testing functional categories in microarray data

Ready access to emerging databases of gene annotation and functional pathways has shifted assessments of differential expression in DNA microarray studies from single genes to groups of genes with shared biological function. This paper takes a critical look at existing methods for assessing the differential expression of a group of genes (functional category), and provides some suggestions for improved performance. We begin by presenting a general framework, in which the set of genes in a functional category is compared to the complementary set of genes on the array. The framework includes tests for overrepresentation of a category within a list of significant genes, and methods that consider continuous measures of differential expression. Existing tests are divided into two classes. Class 1 tests assume gene-specific measures of differential expression are independent, despite overwhelming evidence of positive correlation. Analytic and simulated results are presented that demonstrate Class 1 tests are strongly anti-conservative in practice. Class 2 tests account for gene correlation, typically through array permutation that by construction has proper Type I error control for the induced null. However, both Class 1 and Class 2 tests use a null hypothesis that all genes have the same degree of differential expression. We introduce a more sensible and general (Class 3) null under which the profile of differential expression is the same within the category and complement. Under this broader null, Class 2 tests are shown to be conservative. We propose standard bootstrap methods for testing against the Class 3 null and demonstrate they provide valid Type I error control and more power than array permutation in simulated datasets and real microarray experiments.Comment: Published in at http://dx.doi.org/10.1214/07-AOAS146 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

William Taylor Barry letter to Moses Dawson

Letter from Barry (Washington) to Dawson (Cincinnati, Ohio) expresses concern over alleged administration interference in Kentucky elections. Barry writes that Van Buren had nothing to do with it and no interference was meant.https://www.exhibit.xavier.edu/dawson_correspondence/1016/thumbnail.jp

Free-piston Stirling engine conceptual design and technologies for space power, phase 1

As part of the SP-100 program, a phase 1 effort to design a free-piston Stirling engine (FPSE) for a space dynamic power conversion system was completed. SP-100 is a combined DOD/DOE/NASA program to develop nuclear power for space. This work was completed in the initial phases of the SP-100 program prior to the power conversion concept selection for the Ground Engineering System (GES). Stirling engine technology development as a growth option for SP-100 is continuing after this phase 1 effort. Following a review of various engine concepts, a single-cylinder engine with a linear alternator was selected for the remainder of the study. The relationships of specific mass and efficiency versus temperature ratio were determined for a power output of 25 kWe. This parametric study was done for a temperature ratio range of 1.5 to 2.0 and for hot-end temperatures of 875 K and 1075 K. A conceptual design of a 1080 K FPSE with a linear alternator producing 25 kWe output was completed. This was a single-cylinder engine designed for a 62,000 hour life and a temperature ratio of 2.0. The heat transport systems were pumped liquid-metal loops on both the hot and cold ends. These specifications were selected to match the SP-100 power system designs that were being evaluated at that time. The hot end of the engine used both refractory and superalloy materials; the hot-end pressure vessel featured an insulated design that allowed use of the superalloy material. The design was supported by the hardware demonstration of two of the component concepts - the hydrodynamic gas bearing for the displacer and the dynamic balance system. The hydrodynamic gas bearing was demonstrated on a test rig. The dynamic balance system was tested on the 1 kW RE-1000 engine at NASA Lewis

Rapid detection and quantification of features such as damage or flaws in composite and metallic structures

An apparatus, system, and method for non-destructible evaluation (NDE) of a material use thermography to rapidly detect and/or generally locate a feature such as, for example, damage or a defect in the material. The apparatus, system, and method also use ultrasound to specifically locate the feature in the material for quantification and/or evaluation either by an operator or by an external device suited for such purpose. Accordingly, the apparatus, system and method are particularly useful for NDE in applications such as the analysis of the structure of an aircraft, for example, in which the scale of the material to be analyzed is large, thus requiring the rapid NDE afforded by thermography, and in which quantification and/or evaluation of a feature must be performed with precision, thus requiring the relatively high-resolution NDE afforded by ultrasound

Resampling-based tests of functional categories in gene expression studies

DNA microarrays allow researchers to measure the coexpression of thousands of genes, and are commonly used to identify changes in expression either across experimental conditions or in association with some clinical outcome. With increasing availability of gene annotation, researchers have begun to ask global questions of functional genomics that explore the interactions of genes in cellular processes and signaling pathways. A common hypothesis test for gene categories is constructed as a post hoc analysis performed once a list of significant genes is identified, using classically derived tests for 2x2 contingency tables. We note several drawbacks to this approach including the violation of an independence assumption by the correlation in expression that exists among genes. To test gene categories in a more appropriate manner, we propose a flexible, permutation-based framework, termed SAFE (for Significance Analysis of Function and Expression). SAFE is a two-stage approach, whereby gene-specific statistics are calculated for the association between expression and the response of interest and then a global statistic is used to detect a shift within a gene category to more extreme associations. Significance is assessed by repeatedly permuting whole arrays whereby the correlation between all genes is held constant and accounted for. This permutation scheme also preserves the relatedness of categories containing overlapping genes, such that error rate estimates can be readily obtained for multiple dependent tests. Through a detailed survey of gene category tests and simulations based on real microarray, we demonstrate how SAFE generates appropriate Type I error rates as compared to other methods. Under a more rigorously defined null hypothesis, permutation-based tests of gene categories are shown to be conservative by inducing a special case with a maximum variance for the test statistic. A bootstrap-based approach to hypothesis testing is incorporated into the SAFE framework providing better coverage and improved power under a defined class of alternatives. Lastly, we extend the SAFE framework to consider gene categories in a probabilistic manner. This allows for a hypothesis test of co-regulation, using models of transcription factor binding sites to score for the presence of motifs in the upstream regions of genes