Fluorescent polymer coated capillaries as optofluidic refractometric sensors

A capillary microresonator platform for refractometric sensing is demonstrated by coating the interior of thick-walled silica capillaries with a sub-wavelength layer of high refractive index, dye-doped polymer. No intermediate processing, such as etching or tapering, of the capillary is required. Side illumination and detection of the polymer layer reveals a fluorescence spectrum that is periodically modulated by whispering gallery mode resonances within the layer. Using a Fourier technique to calculate the spectral resonance shifts, the fabricated capillary resonators exhibited refractometric sensitivities up to approximately 30 nm/RIU upon flowing aqueous glucose through them. These sensors could be readily integrated with existing biological and chemical separation platforms such as capillary electrophoresis and gas chromatography where such thick walled capillaries are routinely used with polymer coatings. A review of the modelling required to calculate whispering gallery eigenmodes of such inverted cylindrical resonators is also presented.Kristopher J. Rowland, Alexandre François, Peter Hoffmann, and Tanya M. Monr

Highly stable, 100 W average power from fiber-based ultrafast laser system at 1030 nm based on single-pass photonic-crystal rod amplifier

We report on a fiber-based, Yb-doped, ultrafast laser system capable of outputting 100 W average power at a repetition rate of 500 kHz. The system uses chirped pulse amplification, employing a custom-made pulse-stretching fiber and a grating based compressor, to generate highly energetic, 330 fs pulses at 1030 nm. A diode-pumped photonic-crystal rod delivers amplification of pulses up to 400 μJ while maintaining near diffraction-limited mode quality. The system is highly robust and offers excellent short and long term power stability

Evaluation of Bacillus subtilis strain IS53 for the production of Bacillus anthracis protective antigen

An asporogenous strain of Bacillus subtilis, IS53, transformed with plasmid pPA102, produces the protective antigen (PA) component of the tripartite toxin of B. anthracis. Addition of yeast extract was required to support growth and PA production in all the media examined. Protective antigen expression was down-regulated during exponential growth and extracellular proteases caused marked degradation of the mature protein

Sedimentary and drainage evolution of the Condamine Valley Transition Zone (eastern Australia)

The basal succession of the Condamine Valley, which overlays the boundary between the Surat and Clarence-Moreton basins (eastern Australia), contains a clay-rich horizon ‘the Transition Zone’ that marks a pronounced unconformity between the Jurassic Walloon Coal Measures and the Quaternary Condamine Alluvium. This paper provides insights into the tectonic and drainage evolution of the Condamine Valley through integrated analysis of U–Pb ages of detrital zircon from three samples (494 concordant analyses), stable oxygen isotope analysis on eight authigenic clay samples, X-ray fluorescence of primary and trace elements, and hyperspectral mineral analysis from two drill cores (Lone Pine 17 and Daandine 164). The Transition Zone is interpreted to consist of both weathered Jurassic sediments and Cenozoic clay deposits. Two sequential cycles of erosion, deposition and pedogenesis, related to geomorphological and climatic conditions are recognised. Distinctive oxygen isotope signatures of the two weathering fronts demonstrated an initial Early Cretaceous phase (δO = 11.9–15.7‰ VSMOW) associated with laterisation and possible uplift, followed by Paleogene (δO = 16.4–17.3‰ VSMOW) silcretisation of reworked Jurassic sediments. Detrital zircon geochronology yielded Jurassic maximum constraints for the age of deposition of three samples that are indistinguishable within error, the oldest of which (163 ± 8 Ma from the lateritic profile) corresponds to the age of the underlying Walloon Coal Measures. The two overlaying samples from a silcrete profile and granular alluvium yielded overlapping yet younger ages of 150 ± 6 Ma and 156 ± 9 Ma, respectively. Vitrinite reflectance used as a proxy for the thermal condition of the coal strata enabled an estimated 2–3 km of burial and subsequent (likely Early Cretaceous) uplift. Geochemical insights from the Condamine Valley correspond to broad-scale climatic and tectonic conditions, suggesting that ‘transition zone equivalents’ and corresponding groundwater dynamics may occur in similar sedimentary settings throughout eastern Australia