Metropolized Randomized Maximum Likelihood for sampling from multimodal distributions

This article describes a method for using optimization to derive efficient independent transition functions for Markov chain Monte Carlo simulations. Our interest is in sampling from a posterior density $\pi(x)$ for problems in which the dimension of the model space is large, $\pi(x)$ is multimodal with regions of low probability separating the modes, and evaluation of the likelihood is expensive. We restrict our attention to the special case for which the target density is the product of a multivariate Gaussian prior and a likelihood function for which the errors in observations are additive and Gaussian

New species, records, and a synonymy of African Sisyridae (Neuroptera)

Two species of the genus Sisyra Burmeister (Neuroptera: Sisyridae), S. cameroonensis, n. sp., and S. gruwelli, n. sp., are described from the African Republic of Cameroon. Sisyra pallida Meinander is synonymized with Sisyra delicata Smithers, new synonymy, after comparison of the types of the former with topotypic paratypes of the latter. Type material of Sisyra nilotica Tjeder appears to be lost. Examples of Sisyra are recorded from Nigeria, Ethiopia and Uganda. A second species of the endemic African genus, Sisyborina, Monserrat, S. scitula, n. sp., is described from Cameroon, Guinea, and Zambia

Statistical constraints on the IR galaxy number counts and cosmic IR background from the Spitzer GOODS survey

We perform fluctuation analyses on the data from the Spitzer GOODS survey (epoch one) in the Hubble Deep Field North (HDF-N). We fit a parameterised power-law number count model of the form dN/dS = N_o S^{-\delta} to data from each of the four Spitzer IRAC bands, using Markov Chain Monte Carlo (MCMC) sampling to explore the posterior probability distribution in each case. We obtain best-fit reduced chi-squared values of (3.43 0.86 1.14 1.13) in the four IRAC bands. From this analysis we determine the likely differential faint source counts down to $10^{-8} Jy$, over two orders of magnitude in flux fainter than has been previously determined. From these constrained number count models, we estimate a lower bound on the contribution to the Infra-Red (IR) background light arising from faint galaxies. We estimate the total integrated background IR light in the Spitzer GOODS HDF-N field due to faint sources. By adding the estimates of integrated light given by Fazio et al (2004), we calculate the total integrated background light in the four IRAC bands. We compare our 3.6 micron results with previous background estimates in similar bands and conclude that, subject to our assumptions about the noise characteristics, our analyses are able to account for the vast majority of the 3.6 micron background. Our analyses are sensitive to a number of potential systematic effects; we discuss our assumptions with regards to noise characteristics, flux calibration and flat-fielding artifacts.Comment: 10 pages; 29 figures (Figure added); correction made to flux scale of Fazio points in Figure

Fuels for Future Electric Power

OVER THE NEXT FORTY YEARS, THE U.S. WILL EXPERIENCE PROBLEMS BECAUSE OF DWINDLING SUPPLIES OF FOSSIL FUELS AND AN INCREASING DEPENDENCE ON FOREIGN OIL. SEVERAL ALTERNATIVES ARE AVAILABLE, SUCH AS MORE STRINGENT CONSERVATION MEASURES OR ALTERNATIVE SOURCES OF ENERGY. HOWEVER, NO SINGLE ALTERNATIVE WILL BE SUFFICIENT. A STUDY WAS CONDUCTED TO DETERMINE THE MOST EFFICIENT ALLOCATION POSSIBLE OF RESOURCES. THE ANALYSIS WAS CONDUCTED ON THE BASIS OF ASSUMED HAPPENINGS IN THE FUTURE RATHER THAN BY PROJECTING HISTORIC TRENDS INTO THE FUTURE. FOR EXAMPLE, AS ONE SOURCE OF ENERGY SUCH AS OIL BECOMES MORE SCARCE, THE COST WILL GO UP, INDUCING A CHANGE TO ANOTHER SOURCE. SYNTHETIC FUELS FROM COAL AND HYDROGEN FROM ELECTROLYSIS WILL BECOME MORE PRACTICAL BY THE END OF THE CENTURY. COAL AND OIL WILL BE USED. HEAVILY THIS CENTURY WITH NUCLEAR FUEL BECOMING MORE EFFICIENT EARLY IN THE NEXT CENTURY. CHART