Relative errors for bootstrap approximations of the serial correlation coefficient

We consider the first serial correlation coefficient under an AR(1) model where errors are not assumed to be Gaussian. In this case it is necessary to consider bootstrap approximations for tests based on the statistic since the distribution of errors is unknown. We obtain saddle-point approximations for tail probabilities of the statistic and its bootstrap version and use these to show that the bootstrap tail probabilities approximate the true values with given relative errors, thus extending the classical results of Daniels [Biometrika 43 (1956) 169-185] for the Gaussian case. The methods require conditioning on the set of odd numbered observations and suggest a conditional bootstrap which we show has similar relative error properties.Comment: Published in at http://dx.doi.org/10.1214/13-AOS1111 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Why Individual Investors Want Dividends

The question of why individual investors want dividends is investigated by submitting a questionnaire to a Dutch investor panel. The respondents indicate that they want dividends partly because the cost of cashing in dividends is lower than the cost of selling shares. Their answers provide strong confirmation for the signaling theories of Bhattacharya (1979) and Miller and Rock (1985). They are inconsistent with the uncertainty resolution theory of Gordon (1961, 1962) and the agency theories of Jensen (1986) and Easterbrook (1984). The behavioral finance theory of Shefrin and Statman (1984) is not confirmed for cash dividends but is confirmed for stock dividends. Finally, our results indicate that individual investors do not tend to consume a large part of their dividends. This raises some doubt as to whether a reduction or elimination of dividend taxes will stimulate the economy.Dividends, individual investors, survey

Human Capital Prices, Productivity and Growth

Separate identification of the price and quantity of human capital has important implications for understanding key issues in economics. Price and quantity series are derived for four education levels. The price series are highly correlated and they exhibit a strong secular trend. Three resulting implications are explored: the rising college premium is found to be driven more by relative quantity than relative price changes, life-cycle wage profiles are readily interpretable as reflecting optimal human capital investment paths using the estimated price series, and adjusting the labor input for quality increases dramatically reduces the contribution of MFP to growth.Human Capital, Productivity and Growth

The milliped genus Euryurus Koch, 1847 (Polydesmida: Euryuridae) west of the Mississippi River; occurrence of E. leachii (Gray, 1832) on Crowley’s Ridge, Arkansas

The milliped genus Euryurus Koch, 1847, and the species, E. leachii (Gray, 1832) (Polydesmida: Euryuridae), are recorded from three sites on the northern part of Crowley’s Ridge (Cross, Lee, and Poinsett counties), Arkansas, where the only prior familial records are of Auturus evides (Bollman, 1887). Coupled with the published locality of E. leachii in Phillips Co., at the southern extremity of the Ridge, the only known occurrences of both the genus and species in Arkansas and west of the Mississippi River are in this physiographic feature. The Arkansas population is geographically peripheral but anatomically intermediate between the two recognized subspecies, E. l. leachii and E. l. fraternus Hoffman, 1978, and we do not assign it to a race. Molecular investigations seem necessary to resolve relationships in the “E. leachii complex.

Human capital prices, productivity and growth

Separate identification of the price and quantity of human capital has important implications for understanding key issues in economics. Price and quantity series are derived for four education levels. The price series are highly correlated and they exhibit a strong secular trend. Three resulting implications are explored: the rising college premium is found to be driven more by relative quantity than relative price changes, life-cycle wage profiles are readily interpretable as reflecting optimal human capital investment paths using the estimated price series, and adjusting the labor input for quality increases dramatically reduces the contribution of MFP to growth

Lab Retriever: a software tool for calculating likelihood ratios incorporating a probability of drop-out for forensic DNA profiles.

BackgroundTechnological advances have enabled the analysis of very small amounts of DNA in forensic cases. However, the DNA profiles from such evidence are frequently incomplete and can contain contributions from multiple individuals. The complexity of such samples confounds the assessment of the statistical weight of such evidence. One approach to account for this uncertainty is to use a likelihood ratio framework to compare the probability of the evidence profile under different scenarios. While researchers favor the likelihood ratio framework, few open-source software solutions with a graphical user interface implementing these calculations are available for practicing forensic scientists.ResultsTo address this need, we developed Lab Retriever, an open-source, freely available program that forensic scientists can use to calculate likelihood ratios for complex DNA profiles. Lab Retriever adds a graphical user interface, written primarily in JavaScript, on top of a C++ implementation of the previously published R code of Balding. We redesigned parts of the original Balding algorithm to improve computational speed. In addition to incorporating a probability of allelic drop-out and other critical parameters, Lab Retriever computes likelihood ratios for hypotheses that can include up to four unknown contributors to a mixed sample. These computations are completed nearly instantaneously on a modern PC or Mac computer.ConclusionsLab Retriever provides a practical software solution to forensic scientists who wish to assess the statistical weight of evidence for complex DNA profiles. Executable versions of the program are freely available for Mac OSX and Windows operating systems

Point mutation of an RGD sequence in the human P2Y2 receptor to a QGD sequence conserves Go-mediated signal transduction

Abstract only availableThe P2Y2 nucleotide receptor is a Go/q coupled receptor that is activated equipotently by extracellular nucleotides such as ATP or UTP and is upregulated in a variety of tissues in response to injury or stress. The biological effects of extracellular nucleotides are mediated through activation of P1 and P2 purinergic receptors. P1 receptors are responsive to adenine and P2 receptors are activated by a variety of nucleotides including ATP and UTP. The P2 receptors are subdivided into two distinct categories, the ionotropic ligand-gated channel (P2X) receptors and G-protein coupled P2Y-receptors, with seven transmembrane domains. Previous studies have shown that the human P2Y2 nucleotide receptor contains an arginine-glycine-aspartic acid (RGD), integrin-binding domain. This domain is located in the first extracellular loop of the receptor and binds specifically to the v3/5 group of integrins. The P2Y2 receptor interacts with the v integrins by the RGD domain to activate Go and induce cell migration. The human and murine P2Y2R's have the RGD integrin-binding domain, whereas the rat homologue has a QGD domain. However, this change in the arginine position in the RGD integrin-binding domain is considered to be a conservative substitution that maintains integrin binding. In order to confirm this assumption we changed the RGD domain of the human P2Y2 receptor into the QGD domain by in vitro mutagenesis. The wild-type and the QGD mutant P2Y2 receptors were transiently transfected into P2 receptor null, 1321 N1 astrocytoma cell line. Preliminary data suggest that the QGD mutant can stimulate PLC dependent intracellular Ca2+ mobilization and also activate cofillin and extracellular signal-regulated kinases (Erk) with equal efficacy and agonist potency as the wild type receptor. Further tests need to be done to verify that integrin bindin and signaling by the Rac and Rho pathways remain unaffected in the QGD mutant to induce integrin dependent cell migration in response to UTP and ATP.NSF-REU Program in Biological Sciences & Biochemistr