Thin-film transducers for the detection and imaging of Brillouin oscillations in transmission on cultured cells

Mechanical imaging and characterisation of biological cells has been a subject of interest for the last twenty years. Ultrasonic imaging based on the scanning acoustic microscope (SAM) and mechanical probing have been extensively reported. Large acoustic attenuation at high frequencies and the use of conventional piezo-electric transducers limit the operational frequency of a SAM. This limitation results in lower resolution compared to an optical microscope. Direct mechanical probing in the form of applied stress by contacting probes causes stress to cells and exhibits poor depth resolution. More recently, laser ultrasound has been reported to detect ultrasound in the GHz range via Brillouin oscillations on biological cells. This technique offers a promising new high resolution acoustic cell imaging technique. In this work, we propose, design and apply a thin-film based opto-acoustic transducer for the detection in transmission of Brillouin oscillations on cells. The transducer is used to generate acoustic waves, protect the cells from laser radiation and enhance signal-to-noise ratio (SNR). Experimental traces are presented in water films as well as images of the Brillouin frequency of phantom and fixed 3T3 fibroblast cells

Narrow genetic base in forest restoration with holm oak (Quercus ilex L.) in Sicily

In order to empirically assess the effect of actual seed sampling strategy on genetic diversity of holm oak (Quercus ilex) forestations in Sicily, we have analysed the genetic composition of two seedling lots (nursery stock and plantation) and their known natural seed origin stand by means of six nuclear microsatellite loci. Significant reduction in genetic diversity and significant difference in genetic composition of the seedling lots compared to the seed origin stand were detected. The female and the total effective number of parents were quantified by means of maternity assignment of seedlings and temporal changes in allele frequencies. Extremely low effective maternity numbers were estimated (Nfe $\approx$ 2-4) and estimates accounting for both seed and pollen donors gave also low values (Ne $\approx$ 35-50). These values can be explained by an inappropriate forestry seed harvest strategy limited to a small number of spatially close trees

Logiciel pour une évaluation rapide des conséquences d'une retombée radioactive sur la chaîne alimentaire : applications au milieu tropical

Un logiciel ayant pour but l'évaluation rapide des conséquences d'une retombée radioactive sur la chaîne alimentaire est présenté. A partir de l'activité surfacique mesurée après 24 heures de dépôt, il calcule la dose ingérée par la population à l'issue des soixante premiers jours d'exposition ; cette durée correspond à 2 ou 4 périodes d'élimination mécanique des radionucléides de la surface des végétaux. Lors de son élaboration, il a été tenu compte de la facilité d'accès aux paramètres spécifiques locaux, de son caractère convivial et de la possibilité d'être utilisable sur tout ordinateur PC employant le système d'exploitation MS.DOS