Chemical sensor based on a long-period fibre grating modified by a functionalized polydimethylsiloxane coating

A chemical sensor based on a coated long-period grating has been prepared and characterized. Designer coatings based on polydimethylsiloxane were prepared by the incorporation of diphenylsiloxane and titanium cross-linker in order to provide enhanced sensitivity for a variety of key environmental pollutants and optimal refractive index of the coating. Upon microextraction of the analyte into the polymer matrix, an increase in the refractive index of the coating resulted in a change in the attenuation spectrum of the long-period grating. The grating was interrogated using ring-down detection as a means to amplify the optical loss and to gain stability against misalignment and power fluctuations. Chemical differentiation of cyclohexane and xylene was achieved and a detection limit of 300 ppm of xylene vapour was realized

Long-period gratings in chemical sensing

A chemical sensor system consisting of a coated long period grating, which was spliced into a fiber loop cavity, has been prepared and characterized. Designer coatings based on polydimethylsiloxane and nanostructured organically modified silica (ORMOSIL) materials were prepared to provide enhanced sensitivity for a variety of key environmental pollutants. Upon microextraction of the analyte into the polymer matrix, an increase in the refractive index of the coating resulted in a change of the attenuation spectrum of the long period grating. The grating was interrogated using ring-down detection as a means to amplify the optical loss and to gain stability against misalignment and laser power fluctuations. Chemical differentiation of cyclohexane and xylenes was achieved and a detection limit of 300 ppm of xylenes vapour in air was readily realized for PDMS coatings. Ormosil-type coatings were capable of detecting lead cations at concentrations below 1 ppm in water

The genome of the extremophile crucifer Thellungiella parvula

Thellungiella parvula(1) is related to Arabidopsis thaliana and is endemic to saline, resource-poor habitats(2), making it a model for the evolution of plant adaptation to extreme environments. Here we present the draft genome for this extremophile species. Exclusively by next generation sequencing, we obtained the de novo assembled genome in 1,496 gap-free contigs, closely approximating the estimated genome size of 140 Mb. We anchored these contigs to seven pseudo chromosomes without the use of maps. We show that short reads can be assembled to a near-complete chromosome level for a eukaryotic species lacking prior genetic information. The sequence identifies a number of tandem duplications that, by the nature of the duplicated genes, suggest a possible basis for T. parvula’s extremophile lifestyle. Our results provide essential background for developing genomically influenced testable hypotheses for the evolution of environmental stress tolerance