Searches for physics beyond the standard model inf-f production at LEP II

Preliminary combinations of measurements of the 4 LEP Collaborations of the processe ⁺ e ⁻→f-f at LEP II are presented. The combined results are interpreted in terms of contact interactions and the exchange ofZ′ bosons and within models of low-scale gravity in large extra dimensions.     

Delivering quality for the measurement of immunosuppressive drugs: current performance and future needs

Whilst it is generally agreed that measurement of immunosuppressive drugs is of value as a guide to therapy, there are a number of problems associated with the analytical techniques available. Proficiency testing schemes enable laboratories to judge their performance for the measurement of these drugs with their peers. However, current schemes only compare accuracy within-methods to document performance. This paper summarizes current findings and points out the limitations of our own schemes, and the measures we intend to use to address these deficiencies.     

Periodic reflecting paths in right triangles

A reflecting path in a Jordan curve has the ready physical analogies of a billiards ball bouncing off the cushions of a custom billiards table and of a laser beam reflecting off the mirrored boundary of a thin cavity. What does the curve tell us about the possible reflecting paths? Two types of reflecting paths are of perennial interest — periodic paths and dense paths. In 1927, G. D. Birkhoff applied a theorem of Poincaré to the billiards ball analogy to show that for anyk>1 and anyw<k/2, with (w, k)=1, a smooth convex curve admits at least two periodic reflecting paths ofk reflections per cycle and winding numberw. Unfortunately Birkhoff's proof does not extent to polygons, nor has any other method been found to yield such sweeping results. Various techniques have produced results for polygons-with-angles-commensurable-with-π and for acute triangles. It was not clear whether an arbitrary right triangle admitted periodic paths. Two simple constructions demonstrate the existence of periodic reflecting paths in right triangles. This paper explores these two constructions, focusing on the simplest result: Let β represent the smallest interior angle of some right triangle, and letN=[π/2β]?1. Then each point interior to the shorter leg of the right triangle lies on a unique reflecting path of (4k+2) reflections per cycle for allk=1,2,...,N?1; and each point interior to some subsegment of the shorter leg lies on a unique reflecting path of 4N+2 reflections per cycle.