Optimization and performance of an optical cardio-magnetometer

Cardiomagnetometry is a growing field of noninvasive medical diagnostics that has triggered a need for affordable high-sensitivity magnetometers. Optical pumping magnetometers are promising candidates satisfying that need since it was demonstrated that they can map the heart magnetic field. For the optimization of such devices theoretical limits on the performance as well as an experimental approach is presented. The promising result is a intrinsic magnetometric sensitivity of 63 fT / Hz^1/2 a measurement bandwidth of 140 Hz and a spatial resolution of 28 mm

Theory of double resonance magnetometers based on atomic alignment

We present a theoretical study of the spectra produced by optical-radio-frequency double resonance devices, in which resonant linearly polarized light is used in the optical pumping and detection processes. We extend previous work by presenting algebraic results which are valid for atomic states with arbitrary angular momenta, arbitrary rf intensities, and arbitrary geometries. The only restriction made is the assumption of low light intensity. The results are discussed in view of their use in optical magnetometers

A sound card based multi-channel frequency measurement system

For physical processes which express themselves as a frequency, for example magnetic field measurements using optically-pumped alkali-vapor magnetometers, the precise extraction of the frequency from the noisy signal is a classical problem. We describe herein a frequency measurement system based on an inexpensive commercially available computer sound card coupled with a software single-tone estimator which reaches Cram\'er--Rao limited performance, a feature which commercial frequency counters often lack. Characterization of the system and examples of its successful application to magnetometry are presented.Comment: 4 pages, 3 figures, 1 tabl

om matters the interaction effects between indel and substitution costs

There is increasing interest in, and use of, Optimal Matching techniques in sequence analysis. In recent years especially, both the uses and the software tools that enable this type of analysis have multiplied. Taking up Abbott's inheritance, many scholars have continued with epistemological and methodological analysis of the application of OM to the social sciences. Nevertheless, many criticisms and doubts have been raised concerning the capacity of the technique to capture common patterns of sequences. Diverse epistemological, methodological and technical questions are awaiting answers. Among the numerous problems one, which has not yet been noticed, concerns the interaction effects between OM elementary operations. This article discusses the interaction effect between indel and substitution costs in Optimal Matching Analysis (henceforth OMA). By means of a simulation based on the eight sequences obtained as element permutation of a binary string of length 3, it will show that varying the substitution a..