Seasonality of Deaths in the U.S. by Age and Cause

In this paper, we analyze seasonality of deaths by age and cause in the U.S. using public use files for the years 1994 to 1998 by the methods of regression and a variation of Census Method II. We answer the following questions: For each age cohort, how much does each cause of death contribute to seasonality of deaths? What is the reason for the variation in seasonality of deaths with respect to age? We also analyze death records of Social Security Administration over a longer time period to examine how seasonality of deaths has changed since the mid-1970’s. We found that in general, the degree of seasonality in deaths has decreased over time for younger cohorts and has increased over time for older cohorts.mortality, seasonality

Cosmologies with Two-Dimensional Inhomogeneity

We present a new generating algorithm to construct exact non static solutions of the Einstein field equations with two-dimensional inhomogeneity. Infinite dimensional families of $G_1$ inhomogeneous solutions with a self interacting scalar field, or alternatively with perfect fluid, can be constructed using this algorithm. Some families of solutions and the applications of the algorithm are discussed.Comment: 9 pages, one postscript figur

Generating Black Strings in Higher Dimensions

Starting with a Zipoy-Voorhees line element we construct and study the three parameter family of solutions describing a deformed black string with arbitrary tension.Comment: 11 pages, 2 figures, accepted for publication in J. Mod. Phys. Lett.

Penrose Limits, the Colliding Plane Wave Problem and the Classical String Backgrounds

We show how the Szekeres form of the line element is naturally adapted to study Penrose limits in classical string backgrounds. Relating the "old" colliding wave problem to the Penrose limiting procedure as employed in string theory we discuss how two orthogonal Penrose limits uniquely determine the underlying target space when certain symmetry is imposed. We construct a conformally deformed background with two distinct, yet exactly solvable in terms of the string theory on R-R backgrounds, Penrose limits. Exploiting further the similarities between the two problems we find that the Penrose limit of the gauged WZW Nappi-Witten universe is itself a gauged WZW plane wave solution of Sfetsos and Tseytlin. Finally, we discuss some issues related to singularity, show the existence of a large class of non-Hausdorff solutions with Killing Cauchy Horizons and indicate a possible resolution of the problem of the definition of quantum vacuum in string theory on these time-dependent backgrounds.Comment: Some misprints corrected. Matches the version in print. To appear in Classical & Quantum Gravit