We have recently described a novel method of estimating neutral rates and patterns of spontaneous mutation (Petrov et al., 1996). This method takes advantage of the propensity of non-LTR retrotransposable elements to create non-functional, 'dead-on-arrival' copies as a product of transposition. Maximum parsimony analysis is used to separate the evolution of actively transposing lineages of a no...

Petrov (1996) proved the connection between general moment conditions and the applicability of the strong law of large numbers to a sequence of pairwise independent and identically distributed random variables. This note examines this connection to a sequence of pairwise negative quadrant dependent (NQD) and identically distributed random variables. As a consequence of the main theorem ...

Let M be a Lorentzian space-time manifold. If p G 31, let TV(M) denote the tangent space to M at p and let I e Tp (M ) be a null vector. Because of the identification of radiation in General Relativity with null geodesic congruences of curves in M, one is led to study the geometrical properties of the wave surfaces of I. These are the two dimensional subspaces of TP(M), each member of which is ...

Two-sided conformally recurrent 4-dimensional self-dual spaces are considered. It is shown that such equipped with nonexpanding congruences of null strings. The general structure weak hyperheavenly given. Finally, the metrics Petrov-Penrose type $[D] x [-]$ presented.

The class of Petrov type I curvature tensors is further divided into those for which the span set distinct principal null directions has dimension four (maximally spanning I) or three (nonmaximally I). Explicit examples are provided both vacuum and nonvacuum spacetimes.