We analyze the time reversal of waves in a turbulent medium using the parabolic Markovian model. We prove that the time reversal resolution can be a nonlinear function of the wavelength and independent of the aperture. We establish a duality relation between the turbulence-induced wave spread and the time-reversal resolution which can be viewed as an uncertainty inequality for random media. The...

We study the relation between the performance of the randomized rumor spreading (push model) in a d-regular graph G and the performance of the same algorithm in the percolated graph Gp. We show that if the push model successfully broadcast the rumor within T rounds in the graph G then only (1 + ǫ)T rounds are needed to spread the rumor in the graph Gp when T = o (pd).

This paper describes preliminary work with radiophosphorus (P-32) undertaken by the author at the S.A.S.A. Experiment Station, Mount Edgecombe. In order to study the root spread of N :Co.376, radiophosphorus in solution was injected into the soil at various distances, positions and depths in relation to the cane row. (Cane planted 3rd October, 1962.) Uptake of this radiophosphorus by the plant ...

I am greatly honored to write about Dr. Herman Lent, a well-known researcher, professor of entomology, helminthology and above all a “Professor of Life”. A man who spread his knowledge and thoughts throughout his work, attitudes and way of life. His life, both personal and scientific, had two bases: honesty and strength. His expectations were always very high with regard to others but especiall...

Human Chagas disease originated in Latin America, being spread around the world in relation with multiple bioecological, sociocultural, and political factors. The process of the disease production and dispersion is discussed, emphasizing the human migration and correlated aspects, in the context of globalization. Positive and negative consequences concern the future of this trypanosomiasis, mai...

The theoretical relation between the number of post main sequence stars from stellar populations and their total mass is investigated. This is used to derive some basic relations between the stellar number counts of stellar populations with an age spread and the star formation history which produced them. The main purpose of this investigation is to offer a guideline for the construction of sim...

Time-hopping patterns can be constructed from simple difference sets. By studying such constructions, we prove that whenever n 2, n, n 1, or n + 1 is a prime power, then we can construct timehopping patterns that have n terms, and are of length less than n2. We show by computation that such patterns can have length less then n2 n’ for all n 5 150. We also show that time-hopping patterns of n te...

In this paper we consider the Anderson type model and show that the density of states is analytic in an interval for large disorder. The examples we have allow for the single site distributions to have some singular components. We also allow non-nearest neighbour hopping terms.

From a hopping rate equation for disordered materials we derive a macroscopic drift{di usion equation. For this purposes two space{time scales are simultaneously considered. The microscopic dynamics is characterized by the distribution of localized states and the hopping rate. On the macroscopic space scale both the hopping rate and the disordered material are allowed to be inhomogeneous.

Electro Discharge Machining (EDM) is a very efficient machining process widely used in manufacturing components of complicated geometry. Based on its nature, i.e. material removal by electric discharge, the process induces thermal stresses that in turn result in generation of wide spread micro-cracks on the surface of the machined part. In this paper the influence of EDM characteristic paramete...