Mutagenicity testing of 9-N-substituted adenines and their N-oxidation products.

Adenine together with certain 9-N-substituted derivatives such as 9-methyl, 9-benzyl, 9-benzhydryl, and 9-trityl were tested against Salmonella typhimurium strains TA97, TA98, and TA100 in the absence and presence of rat hepatic S9 prepared from Aroclor 1254 pretreated rats. All compounds were positive toward TA98 in the presence of the metabolic activating system, whereas they all lacked mutagenic activity in the absence of S9, and toward TA97 and TA100 with or without S9 when tested at 100 ng/plate. A similar pattern was observed for the corresponding 1-N-oxides. 6-Hydroxylaminopurine was not mutagenic toward TA100 at 100 ng/plate, whereas it was toxic toward TA97 and TA98 at this level. When tested at 1 ng/plate, hydroxylaminopurine was still toxic to TA98 but produced twice the spontaneous reversion rate to TA97 without metabolic activation. Surprisingly, 9-methyl-6-hydroxylaminopurine was only active toward TA98 in the presence of S9, whereas 9-benzyl-6-hydroxylaminopurine was highly active toward TA97 and TA100 in the absence of S9 and even more active in the presence of S9. This compound was inactive toward TA98 in the absence of S9. The results generally support the concept that nuclear N-oxidation of aminoazaheterocycles is a detoxication process, whereas N-hydroxylation of the exo amino group is a toxication reaction

A Bayesian test for the appropriateness of a model in the biomagnetic inverse problem

This paper extends the work of Clarke [1] on the Bayesian foundations of the biomagnetic inverse problem. It derives expressions for the expectation and variance of the a posteriori source current probability distribution given a prior source current probability distribution, a source space weight function and a data set. The calculation of the variance enables the construction of a Bayesian test for the appropriateness of any source model that is chosen as the a priori infomation. The test is illustrated using both simulated (multi-dipole) data and the results of a study of early latency processing of images of human faces. [1] C.J.S. Clarke. Error estimates in the biomagnetic inverse problem. Inverse Problems, 10:77--86, 1994.Comment: 13 pages, 16 figures. Submitted to Inverse Problem

Cyprus' image—a sun and sea destination—as a detrimental factor to seasonal fluctuations. Exploration into motivational factors for holidaying in Cyprus

Cyprus is established as a summer destination. To aid the destination in developing its winter season as well, this research uses a qualitative inductive approach to explore the tourists’ current image of the island and their motivations of visiting it. The research indicates that the current image, which essentially portrays Cyprus as a sun-and-sea destination is thought to dissuade tourists from perceiving the island as a year-round destination. Nonetheless, increasing the pull factors of the destination through the development of unique special interest products can help in extending the tourism season as well as broaden its narrow image

WTC2005-63800 THERMO-MECHANICAL MODEL FOR MOVING LAYERED ROUGH SURFACE CONTACTS

ABSTRACT A numerical model designed to simulate a moving line contact of two rough layered bodies is presented. The model predicts contact pressures and deformations, contact temperature rise and resulting thermal stresses. The heat division between the contacting components is fully accounted for as is the interaction between the mechanical and thermal displacements. Some results are presented to illustrate the potential importance of a full thermo-mechanical analysis as compared to a purely mechanical one. INTRODUCTION Tribological coatings are often used in situations where liquid lubrication is inadequate or completely absent. In such situations of dry contact the performance of coatings is often ultimately limited by thermal effects. Thermal effects in layered contacts have been studied by a number of authors. Ling [1973] and Ju et al [1984, 1988] used the method of Fourier transforms to provide a steady state solution for a prescribed heat source moving over a layered half-space. Leroy et al [1989, 1990] utilized FFT techniques for the same purpose. Kennedy et al [1987] formulated a steady state finite element solution to a uniform band source. Vick et al [1994] presented a transient 3D boundary element model which could account for variable heat division fraction across the interface although they only provide results obtained with a single boundary element for the whole contact. However, these simulations, almost exclusively, considered smooth surfaces and prescribed the heat flux distribution rather than deducing it from the contact conditions. By ignoring the effect of thermal deformation on contact pressure distribution and area, they do not account for the crucial interaction between the mechanical and thermal effects. For rough homogenous bodies such interactions were taken into account by The thermo-mechanical model presented here addresses some of these shortcomings while also being capable of dealing with layered bodies

The Unique Determination of Neuronal Currents in the Brain via Magnetoencephalography

The problem of determining the neuronal current inside the brain from measurements of the induced magnetic field outside the head is discussed under the assumption that the space occupied by the brain is approximately spherical. By inverting the Geselowitz equation, the part of the current which can be reconstructed from the measurements is precisely determined. This actually consists of only certain moments of one of the two functions specifying the tangential part of the current. The other function specifying the tangential part of the current as well as the radial part of the current are completely arbitrary. However, it is also shown that with the assumption of energy minimization, the current can be reconstructed uniquely. A numerical implementation of this unique reconstruction is also presented