Progress with optical gas sensors using correlation spectroscopy

The paper reviews recent progress on gas detection using real-time correlation spectroscopy. The general method relies on using a gas sample in a reference cell as a matched optical filter, to preferentially detect similar absorption spectra in a measurement cell. All variations of the method have the advantage of excellent selectivity for gases with narrow line spectra, even when using broadband sources for illumination. They are also suitable for remote detection over optical fibre leads. The recent progress is in two main areas. Firstly, the earlier reported Stark modulation method has been extended to investigate a novel hygrometer. Secondly, we have developed a novel multi-line light source, by combining a broadband optical source with a Michelson interferometer, where the latter contains a gas in one arm

Phase diagram for morphological transitions of wetting films on chemically structured substrates

Using an interface displacement model we calculate the shapes of thin liquidlike films adsorbed on flat substrates containing a chemical stripe. We determine the entire phase diagram of morphological phase transitions in these films as function of temperature, undersaturation, and stripe widthComment: 15 pages, RevTeX, 7 Figure

Fluorescent carbon dioxide indicators

Over the last decade, fluorescence has become the dominant tool in biotechnology and medical imaging. These exciting advances have been underpinned by the advances in time-resolved techniques and instrumentation, probe design, chemical / biochemical sensing, coupled with our furthered knowledge in biology. Complementary volumes 9 and 10, Advanced Concepts of Fluorescence Sensing: Small Molecule Sensing and Advanced Concepts of Fluorescence Sensing: Macromolecular Sensing, aim to summarize the current state of the art in fluorescent sensing. For this reason, Drs. Geddes and Lakowicz have invited chapters, encompassing a broad range of fluorescence sensing techniques. Some chapters deal with small molecule sensors, such as for anions, cations, and CO2, while others summarize recent advances in protein-based and macromolecular sensors. The Editors have, however, not included DNA or RNA based sensing in this volume, as this were reviewed in Volume 7 and is to be the subject of a more detailed volume in the near future

Application of a numerical simulation to improve the separation efficiency of a sperm sorter

This paper describes a study in which numerical simulations were applied to improve the separation efficiency of a microfluidic-based sperm sorter. Initially, the motion of 31 sperm were modeled as a sinusoidal wave. The modeled sperm were expected to move while vibrating in the fluid within the microchannel. In this analysis, the number of sperm extracted at the outlet channel and the rate of movement of the highly motile sperm were obtained for a wide range of flow velocities within the microchannel. By varying the channel height, and the width and the position of the sperm-inlet channel, we confirmed that the separation efficiency was highly dependent on the fluid velocity within the channel. These results will be valuable for improving the device configuration, and might help to realize further improvements in efficiency in the future

Optical gas sensors using correlation spectroscopy. Report for Shell Research

This report reviews the feasibility of detection of impurities, in particular water vapour, in natural gas, using real-time correlation spectroscopy. The general concept relies on using a gas sample, contained in a reference cell, as a matched optical filter, to preferentially detect similar absorption spectra of the same gas in the measurement cell. All variations of the method have the advantage of excellent selectivity, provided the gases to be detected have narrow line spectra, even when using broadband sources for illumination. They are also suitable for direct-path measurements or for remote detection over optical fibre leads.The report focuses on two main areas. Firstly, the Stark modulation method has been used to detect water and ammonia vapour. Secondly, we present an alternative correlation spectroscopic arrangement, in which the route of the light path is modulated. This new arrangement has been tested with both water vapour and ammonia. We give a comparison of the characteristics of both methods and discuss their suitability for determining water vapour contamination in natural gas.Our conclusions are that the switched-path method has some potential of being developed to meet the Shell application for trace measurement of water vapour in high-pressure natural gas

Steady Flow Micro-Reactor Module for Pipelined DNA Computations

Microfiov reactors provide a means of implementing DNA Computing as a vhole, not just individual steps. Contrary to surface based DNA Chips [1], lnicrofiov reactors vith active components in closed fiov systems can be used to integrate complete DNA computa- tions [2]. Microreactors allow complicated flow topologies to be realized which can implement a dataflow-like architecture for the processing of DNA. A technologically feasible scalable approach with many reaction chambers however requires constant hydrodynamic flows. In this work, the experimental construction of a basic constant flow module for DNA processing in such a context is addressed. Limited diffusional exchange in parallel flows is used to establish spario-temporal segregation of reaction conditions which can be crossed by magnetic beads without barriers. As previously outlined [2], linked up with an optical programming tech- nology, this vill enable DNA selection to be programmed and complex population selection to be performed. The basic first experimental step in the realization of this program is described here: the establishment of a stable hydrodynamic fiov pattern vhich is scalable to many reactors in parallel and the demonstration of a scalable and synchronous clocking of magnetic bead-based processing. First results with fiuorescently-labeled DNA transfer vill also be presented at the conference. The way in which this module may be integrated to solve the maximal clique problem has been proposed elsewhere [2]