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Kourousias, G.

Publications and source records attributed to Kourousias, G..

2 recordsLinked to original sources

Advances on sparse Dynamic Scanning in Spectromicroscopy through Compressive Sensing

Scanning microscopies and spectroscopies like X-ray Fluorescence (XRF), Scanning Transmission X-ray Microscopy (STXM), and Ptychography are of very high scientific importance as they can be employed in several research fields. Methodology and technology advances aim at analysing larger samples at better resolution, improved sensitivities and higher acquisition speeds. The frontiers of those advances are on detectors, radiation sources, motors, but also on acquisition and analysis software together with general methodology improvements. Weve e recently introduced and fully implemented on a soft X-ray microscopy beamline an intelligent scanning methodology based on compressive sensing. This demonstrated sparse low energy XRF scanning of dynamically chosen regions of interest in combination with STXM. It resulted in a sparse megapixel-rage low energy XRF spectroimaging through dynamic scanning that was previously not feasible. This research has been further developed and has been applied in scientific applications in biology. The developments are mostly on the dynamic triggering decisional mechanism in order to incorporate modern Machine Learning and real-time XRF fitting but also on the suitable integration of the method in the control system making it available for other beamlines and imaging techniques. On the applications front, the method was successfully used on different samples, from lung and ovarian human tissues to plant root sections. This manuscript introduces the latest advances of the method and demonstrates applications in life and environmental sciences. Finally it highlights an auxiliary development of a mobile application that assists the selection of specific regions of interest in an easy way.

biophysics↗

Alleviation of Al toxicity by Si is associated with the formation of Al-Si complexes in root tissues of sorghum

Silicon is reported to reduce the toxic effects of Al on root elongation but the in planta mechanism by which this occurs remains unclear. Using seedlings of soybean (Glycine max) and sorghum (Sorghum bicolor), we examined the effect of up to 2 mM Si on root elongation rate (RER) in Al-toxic nutrient solutions. Synchrotron-based low energy X-ray fluorescence (LEXRF) was then used for the in situ examination of the distribution of Al and Si within cross-sections cut from the apical tissues of sorghum roots. The addition of Si potentially increased RER in Al-toxic solutions, with RER being up to ca. 0.3 mm h-1 (14 %) higher for soybean and ca. 0.2 mm h-1 (17 %) higher for sorghum relative to solutions without added Si. This improvement in RER could not be attributed to a change in Al-chemistry of the bulk nutrient solution, nor was it due to a change in the concentration of Al within the apical (0-10 mm) root tissues. Using LEXRF to examine sorghum, it was demonstrated that in roots exposed to both Al and Si, much of the Al was co-located with Si in the mucigel and outer apoplast. These observations suggest that Si reduces the toxicity of Al in planta through formation of Al-Si complexes in mucigel and outer cellular tissues, thereby decreasing the binding of Al to the cell wall where it is known to inhibit wall loosening as required for cell elongation.

plant biology↗