Microwave Components with MEMS Switches

RF MEMS switches with metal-metal contacts are being developed for microwave applications where broadband, high linearity performance is required. These switches provide less than 0.2 dB insertion loss through 40 GHz. This paper describes the integration of these switches into selected microwave components such as reconfigurable antenna elements, tunable filters, switched delay lines, and SPDT switches. Microwave and millimeter wave measured results from these circuits are presented

Finite covers of random 3-manifolds

A 3-manifold is Haken if it contains a topologically essential surface. The Virtual Haken Conjecture posits that every irreducible 3-manifold with infinite fundamental group has a finite cover which is Haken. In this paper, we study random 3-manifolds and their finite covers in an attempt to shed light on this difficult question. In particular, we consider random Heegaard splittings by gluing two handlebodies by the result of a random walk in the mapping class group of a surface. For this model of random 3-manifold, we are able to compute the probabilities that the resulting manifolds have finite covers of particular kinds. Our results contrast with the analogous probabilities for groups coming from random balanced presentations, giving quantitative theorems to the effect that 3-manifold groups have many more finite quotients than random groups. The next natural question is whether these covers have positive betti number. For abelian covers of a fixed type over 3-manifolds of Heegaard genus 2, we show that the probability of positive betti number is 0. In fact, many of these questions boil down to questions about the mapping class group. We are lead to consider the action of mapping class group of a surface S on the set of quotients pi_1(S) -> Q. If Q is a simple group, we show that if the genus of S is large, then this action is very mixing. In particular, the action factors through the alternating group of each orbit. This is analogous to Goldman's theorem that the action of the mapping class group on the SU(2) character variety is ergodic.Comment: 60 pages; v2: minor changes. v3: minor changes; final versio

Reading Graphic Novels in School: texts, contexts and the interpretive work of critical reading

This paper uses the example of an extra-curricular Graphic Novel Reading Group in order to explore the institutional critical reading practices that take place in English classrooms in the senior years of secondary school. Drawing on Stanley Fish's theory of interpretive communities, it questions the restrictive interpretive strategies applied to literary texts in curriculum English. By looking closely at the interpretive strategies pupils apply to a different kind of text (graphic novels) in an alternative context (an extra-curricular space) the paper suggests that there may be other ways of engaging with text that pupils find less alienating, more pleasurable and less reminiscent of 'work'

LAMPF: a nuclear research facility

A description is given of the recently completed Los Alamos Meson Physics Facility (LAMPF) which is now taking its place as one of the major installations in this country for the support of research in nuclear science and its applications. Descriptions are given of the organization of the Laboratory, the Users Group, experimental facilities for research and for applications, and procedures for carrying on research studies