Optical measurements of the density of helium in small bubbles in aluminium films

Some preliminary measurements are reported on the density of helium in bubbles in metal films using optical spectroscopy in the far vacuum ultra-violet. The technique consists of measuring (by transmission through the films) the optical absorption resulting from the transition View the MathML source due to the helium in the bubbles. This transition, in a rarefied gas, occurs at 584 Å (21.2eV) but because of the gas density in the bubbles is observed to be broadened and shifted to higher energy (blue shifted). The measurements imply, for specimens with high gas concentrations (0.5–3 at% He), a gas density in the bubbles greater than 1023 atoms cm−3

Distinctive features of the Gac‐Rsm

Productive plant–bacteria interactions, either beneficial or pathogenic, require that bacteria successfully sense, integrate and respond to continuously changing environmental and plant stimuli. They use complex signal transduction systems that control a vast array of genes and functions. The Gac-Rsm global regulatory pathway plays a key role in controlling fundamental aspects of the apparently different lifestyles of plant beneficial and phytopathogenic Pseudomonas as it coordinates adaptation and survival while either promoting plant health (biocontrol strains) or causing disease (pathogenic strains). Plant-interacting Pseudomonas stand out for possessing multiple Rsm proteins and Rsm RNAs, but the physiological significance of this redundancy is not yet clear. Strikingly, the components of the Gac-Rsm pathway and the controlled genes/pathways are similar, but the outcome of its regulation may be opposite. Therefore, identifying the target mRNAs bound by the Rsm proteins and their mode of action (repression or activation) is essential to explain the resulting phenotype. Some technical considerations to approach the study of this system are also given. Overall, several important features of the Gac-Rsm cascade are now understood in molecular detail, particularly in Pseudomonas protegens CHA0, but further questions remain to be solved in other plant-interacting Pseudomonas.This research was supported by grants BIO2014-55075-P and BIO2017-83533-P from the ERDF/Spanish Ministry of Science, Innovation and Universities - State Research Agency. M.D.F. was supported by a FPU contract from the Spanish MECD/MEFP (ECD/1619/2013)