In this paper a novel filtered back-projection algorithm for inversion of a discretized Radon transform is presented. It makes use of invariance properties possessed by both the Radon transform and its dual. By switching to log-polar coordinates, both operators can be expressed in a displacement invariant manner. Explicit expressions for the corresponding transfer functions are calculated. Further

It has been known for nearly 30 years that the theoretical and experimental values for the energy of the 2s3s S-1 level in singly ionized boron, B it, differ strongly. Since there is much better agreement for other B II levels, it has been concluded that the experimental value for 2s3s S-1 must be revised. Despite a number of recordings over the years of sliding-spark, hollow cathode and beam-foil

The type material of Physcia magara Kremp., which is the type species of Seirophora Poelt (Teloschistaceae), is shown to be heterogeneous. It is a mixture of Teloschistes villosus (Ach.) Norman and Ramalina maciformis (Delile) Bory. Physcia magara Kremp. is typified on the T. villosus-part. Teloschistes species with multiseriate hairs, spores with short septa, thick and strongly conglutinated cort

Internal erosion is a major reason for embankment dam failures. Resistivity measurements is an essentially non-destructive technique, which may have the possibility of detecting internal erosion processes and anomalous seepage at an early stage before the safety of the dam is at stake. This paper presents results from part of a dam safety investigation conducted at the Enemossen tailings dam in so

The problem of constructing generalized point interactions of the second derivative operator in L-2( R) leading to the same scattering data as for reflectionless potentials is considered. It is proved that this problem has a solution only if extensions in Pontryagin spaces are involved. The solution of the inverse scattering problem is not unique, this is illustrated by considering the scattering

We introduce a new notion of independence based on the Borel-Cantelli lemma. We study this characteristic in the context of i.i.d. stochastic processes and processes driven by equilibrium dynamics.

We investigate the symmetry of magnetoconductance fluctuations of phase-coherent, two-terminal quantum dots in the nonlinear regime of transport. Specifically, we consider open, ballistic quantum dots (electron billiards) with and without symmetry axes parallel and perpendicular to the current direction and formulate a set of novel symmetry relations not observed in devices with lower symmetry. We

Abstract is not available

The orchid genus Nigritella constitutes a polyploid complex which is widespread in mountain regions in Europe. Diploid members of the genus have sexual reproduction, whereas polyploid members are characterised by agamospermy. We used allozyme data to estimate levels of variation at different hierarchical levels and to describe the evolution of polyploids. - The variation patterns at allozyme loci

Purpose: alpha-Melanocyte stimulating hormone (alpha-MSH; Fluka Chemie AG, Geneva, Switzerland) and oxytocin induce erection in rats after intracerebroventricular administration. We studied possible interactions of alpha-melanocyte stimulating hormone with mechanisms pertaining to oxytocin or nitric oxide. Materials and Methods: We used 78 anesthetized male Sprague-Dawley rats. Catheters were impl

Along with an increasingly globalized business environment and a strongly held corporate belief that the world can be rationally managed, the last two decades have witnessed a growing demand for normative models dealing with cross-cultural management issues. This trend has allowed cross-cultural management to establish itself as a significant research field, with much of the initial inspiration co

beta-Microseminoprotein (MSP) is a small cysteine-rich protein (molecular mass about 10 kDa) first isolated from human seminal plasma and later identified in several other organisms. The function of MSP is not known, but a recent study has shown MSP to bind CRISP-3, a protein present in neutrophilic granulocytes. The amino acid sequence is highly variable between species raising the question of th