The photodissociation and chemistry of CO isotopologues: applications to interstellar clouds and circumstellar disks

Aims. Photodissociation by UV light is an important destruction mechanism for CO in many astrophysical environments, ranging from interstellar clouds to protoplanetary disks. The aim of this work is to gain a better understanding of the depth dependence and isotope-selective nature of this process. Methods. We present a photodissociation model based on recent spectroscopic data from the literature, which allows us to compute depth-dependent and isotope-selective photodissociation rates at higher accuracy than in previous work. The model includes self-shielding, mutual shielding and shielding by atomic and molecular hydrogen, and it is the first such model to include the rare isotopologues C17O and 13C17O. We couple it to a simple chemical network to analyse CO abundances in diffuse and translucent clouds, photon-dominated regions, and circumstellar disks. Results. The photodissociation rate in the unattenuated interstellar radiation field is 2.6e-10 s^-1, 30% higher than currently adopted values. Increasing the excitation temperature or the Doppler width can reduce the photodissociation rates and the isotopic selectivity by as much as a factor of three for temperatures above 100 K. The model reproduces column densities observed towards diffuse clouds and PDRs, and it offers an explanation for both the enhanced and the reduced N(12CO)/N(13CO) ratios seen in diffuse clouds. The photodissociation of C17O and 13C17O shows almost exactly the same depth dependence as that of C18O and 13C18O, respectively, so 17O and 18O are equally fractionated with respect to 16O. This supports the recent hypothesis that CO photodissociation in the solar nebula is responsible for the anomalous 17O and 18O abundances in meteorites.Comment: Accepted by A&

Molecular excitation in the Interstellar Medium: recent advances in collisional, radiative and chemical processes

We review the different excitation processes in the interstellar mediumComment: Accepted in Chem. Re

Analysis of Resistant Starches in Rat Cecal Contents Using Fourier Transform Infrared Photoacoustic Spectroscopy

Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) qualitatively and quantitatively measured resistant starch (RS) in rat cecal contents. Fisher 344 rats were fed diets of 55% (w/w, dry basis) starch for 8 weeks. Cecal contents were collected from sacrificed rats. A corn starch control was compared against three RS diets. The RS diets were high-amylose corn starch (HA7), HA7 chemically modified with octenyl succinic anhydride, and stearic-acid-complexed HA7 starch. To calibrate the FTIR-PAS analysis, samples from each diet were analyzed using an enzymatic assay. A partial least-squares cross-validation plot generated from the enzymatic assay and FTIR-PAS spectral results for starch fit the ideal curve with a R2 of 0.997. A principal component analysis plot of components 1 and 2 showed that spectra from diets clustered significantly from each other. This study clearly showed that FTIR-PAS can accurately quantify starch content and identify the form of starch in complex matrices.Reprinted with permission from Journal of Agricultural and Food Chemistry 61 (2013): 1818–1822, doi:10.1021/jf3042616. Copyright 2013 American Chemical Society.</p

Partage de charge quasi-statique pour les engrenages cylindriques en polymère

National audienc

Quasi-static load sharing model in the case of Nylon 6/6 cylindrical gears

International audienc

Randomized controlled trial: Comparing the effectiveness of brief group cognitive behavioural therapy and group eye movement desensitisation and reprocessing interventions for PTSD in internally displaced persons, administered by paraprofessionals in Northern Iraq

Structured abstract Background and aims In 2023, 339 million people need humanitarian assistance due to emergencies. In those contexts, prevention and treatment of Post-Traumatic Stress Disorder (PTSD) are extremely important. Trauma Focussed Cognitive Behavioural Therapy (TF-CBT) and Eye Movement Desensitisation and Reprocessing (EMDR) are recommended treatments but their deployment comes up against various obstacles, especially in Low- and Middle-Income Countries (LMIC) where mental health professionals are rare. Developing evidence-based, brief, group interventions by paraprofessionals might be an option for scaling up. Methods The research has been conducted in northern Iraq, in a complex on-going emergency setting. After one psycho-education session on trauma, adults over 18 years of age, willing to participate to the program and with IES-R (Impact Event Scale-Revised, Weiss & Marmar, 1997) score superior or equal to 33 were randomly assigned to TF-CBT or EMDR Group-Traumatic Episode Protocol (G-TEP) interventions. Eighty-six men and women, internally displaced, living in camps, received six sessions of either TF-CBT (n = 46) or EMDR G-TEP (n = 40) in groups settings. Measures included IES-R, Hospital Depression Scales (HADS, (Zigmond & Snaith, 1983)) at admission and after six sessions. Statistical analysis has been done on participants that have attended at least sessions one and six of the protocols. For each group (TF-CBT and G-TEP), results between pre-treatment and post-treatment were compared using Student's t-test paired for quantitative variables and chi-square paired for qualitative variables to measure the effectiveness of each treatment. All tests were bilateral and were considered significant at p < 0.05. Results Results in the TF-CBT group showed a significant reduction in IES-R (t = 7.38; p = 0.001; Effect Size= 1.088), HAD-Depression (t = 6.03; p = 0.001; Effect Size= 0.889) and HAD-Anxiety (t = 6.34; p = 0.001; Effect Size=0.934). Results in the EMDR- G-TEP group showed a significant reduction in IES-R (t = 4.63; p< 0.001; Effect Size= 0.732), HAD-Depression (t = 3.12; p = 0.003; Effect Size=0.494) and HAD-Anxiety (t = 3.01; p = 0.005; Effect Size=0.475). Both populations remained clinical, despite a significant treatment effect. There was no statistical difference between the two treatments. Conclusions Findings open the possibility to scale up EMDR G-TEP or TF-CBT interventions in groups conducted by paraprofessionals for reducing PTSD symptomatology within humanitarian programs

A versatile toolkit to produce sensitive FRET biosensors to visualize signaling in time and space

Genetically encoded, ratiometric biosensors based on fluorescence resonance energy transfer (FRET) are powerful tools to study the spatiotemporal dynamics of cell signaling. However, many biosensors lack sensitivity. We present a biosensor library that contains circularly permutated mutants for both the donor and acceptor fluorophores, which alter the orientation of the dipoles and thus better accommodate structural constraints imposed by different signaling molecules while maintaining FRET efficiency. Our strategy improved the brightness and dynamic range of preexisting RhoA and extracellular signal-regulated protein kinase (ERK) biosensors. Using the improved RhoA biosensor, we found micrometer-sized zones of RhoA activity at the tip of F-actin bundles in growth cone filopodia during neurite extension, whereas RhoA was globally activated throughout collapsing growth cones. RhoA was also activated in filopodia and protruding membranes at the leading edge of motile fibroblasts. Using the improved ERK biosensor, we simultaneously measured ERK activation dynamics in multiple cells using low-magnification microscopy and performed in vivo FRET imaging in zebrafish. Thus, we provide a construction toolkit consisting of a vector set, which enables facile generation of sensitive biosensors