Simulating Titan's upper atmosphere and its photochemistry in the vacuum ultra-violet (VUV)

International audienceTitan, the largest moon of Saturn, has a dense atmosphere whose upper layers are mainly composed of methane (CH4) and molecular nitrogen (N2). The Cassini mission revealed that the interaction between those molecules and the solar VUV radiation, as well as the electrons from Saturn’s magnetosphere, leads to a complex chemistry above an altitude of 800km.Cassini instruments such as INMS or CAPS revealed that this naturally ionized environment contains heavy organic molecules like benzene (C6H6) even at altitudes higher than 900 k

VUV photo-processing of PAH cations: quantitative study on the ionization versus fragmentation processes

Interstellar polycyclic aromatic hydrocarbons (PAHs) are strongly affected by the absorption of vacuum ultraviolet (VUV) photons in the interstellar medium (ISM), yet the branching ratio between ionization and fragmentation is poorly studied. This is crucial for the stability and charge state of PAHs in the ISM in different environments, affecting in turn the chemistry, the energy balance, and the contribution of PAHs to the extinction and emission curves. We studied the interaction of PAH cations with VUV photons in the 7-20 eV range from the synchrotron SOLEIL beamline, DESIRS. We recorded by action spectroscopy the relative intensities of photo-fragmentation and photo-ionization for a set of eight PAH cations ranging in size from 14 to 24 carbon atoms, with different structures. At photon energies below ~13.6 eV fragmentation dominates for the smaller species, while for larger species ionization is immediately competitive after the second ionization potential (IP). At higher photon energies, all species behave similarly, the ionization yield gradually increases, leveling off between 0.8 and 0.9 at ~18 eV. Among isomers, PAH structure appears to mainly affect the fragmentation cross section, but not the ionization cross section. We also measured the second IP for all species and the third IP for two of them, all are in good agreement with theoretical ones confirming that PAH cations can be further ionized in the diffuse ISM. Determining actual PAH dication abundances in the ISM will require detailed modeling. Our measured photo-ionization yields for several PAH cations provide a necessary ingredient for such models

Effects of a lagoon on performances of a freshwater fishpond in a multi-trophic aquaculture system

Integrated multi-trophic aquaculture (IMTA) is a way to help preserve the environment while maintaining a good level of total production. An ecologically semi-intensive pond system was designed in which a polyculture fishpond was associated with a lagoon planted with macrophytes to bioremediate the water. The properties of this “semi-intensive coupled” system (SIC) were compared to those of semi-intensive (SI) and extensive (E) systems, each of which was contained in a single fishpond with the same fish polyculture (common carp (Cyprinus carpio), roach (Rutilus rutilus), and perch (Perca fluviatilis)) as SIC. E differed in that it had half the initial density of fish, and the fish were not fed. Fish growth performances, water quality (chemical and biological indicators), chlorophyll concentrations, and invertebrate production were measured. The systems were compared based on fish production performances and physicochemical and biological characteristics, and were then described using principal component analysis (PCA). Carp and roach in the two fed systems had higher growth performances than those in E. Compared to SI, the planted lagoon in SIC, induced a decrease of 15% in fish growth performances and of 83% in total chlorophyll concentration (a proxy for phytoplankton) but improved water quality (−34%, −60% and −80%, for the concentrations of total nitrogen, total phosphorus, and blue green algae (for micro-algae in class Cyanophyceae), respectively). According to the PCA, SIC clearly differed from SI in benthic macro-invertebrate production and concentrations of total nitrogen, total phosphorus, and brown algae (for micro-algae in class Dinophyceae or a branch of Bacillariophyta) in the water. SIC differed from E in oxygen parameters (dissolved and saturation), estimated annual zooplankton production, and pH. In conclusion, the properties of a lagoon reveal perspectives for environmentally friendly practices, while using biodiversity and secondary production in order to enhance fish production

While allied health students prefer face-to-face clinical placement, telehealth can support competency development: results from a mixed-methods study

Introduction: Student clinical placements are a mandatory requirement within most accredited health programs. During the COVID-19 pandemic, many health settings that had traditionally provided placements cancelled their offerings. Telehealth services however, increased and emerged as an alternative placement setting. Aim: To compare the learning experiences for allied health students provided by telehealth and face-to-face accredited health placements. Methods: Health students, from a university clinic between March to December 2020, delivering both face-to-face and telehealth consultations, were invited to complete a telephone survey with 3 demographic questions; and 10-items comparing their telehealth and face-to-face learning experiences. Pearson’s chi-squared/Fisher’s exact test was used to examine the association between each item and consultation setting. Qualitative survey data was thematically analysed using a descriptive approach. Results: 49 students from 2 universities and 5 disciplines completed the survey. Students rated their face-to-face experiences significantly higher than their telehealth experiences across all items (all p-values <0.01). Across 9 items students reported positive learning experiences in both settings. Students had greater opportunities to work in a multidisciplinary team in a face-to-face setting. Four themes were generated: (1) placements can vary in quality regardless of setting; (2) telehealth can provide valuable learning experiences and support competency development; (3) enablers for telehealth placements and (4) barriers for telehealth placements. Conclusion: While telehealth can support student learning and competency development, in this study students preferred face-to-face experiences. To optimise telehealth placements consideration needs to be given to barriers and enablers such as technological issues and university curricula preparation

L'aquaculture multi-trophique intégrée en étang: identification de la structure du réseau trophique à l'aide des isotopes stables du carbone et de l'azote

RésuméRésuméL'aquaculture multi-trophique intégrée en étang: identification de la structure du réseau trophique à l'aide des isotopes stables du carbone et de l'azote. Journées d'Animation Scientifique du département Phase (JAS Phase 2018

Effects of a lagoon on performances of a freshwater fishpond in a multi-trophic aquaculture system

Integrated multi-trophic aquaculture (IMTA) is a way to help preserve the environment while maintaining a good level of total production. An ecologically semi-intensive pond system was designed in which a polyculture fishpond was associated with a lagoon planted with macrophytes to bioremediate the water. The properties of this “semi-intensive coupled” system (SIC) were compared to those of semi-intensive (SI) and extensive (E) systems, each of which was contained in a single fishpond with the same fish polyculture (common carp (Cyprinus carpio), roach (Rutilus rutilus), and perch (Perca fluviatilis)) as SIC. E differed in that it had half the initial density of fish, and the fish were not fed. Fish growth performances, water quality (chemical and biological indicators), chlorophyll concentrations, and invertebrate production were measured. The systems were compared based on fish production performances and physicochemical and biological characteristics, and were then described using principal component analysis (PCA). Carp and roach in the two fed systems had higher growth performances than those in E. Compared to SI, the planted lagoon in SIC, induced a decrease of 15% in fish growth performances and of 83% in total chlorophyll concentration (a proxy for phytoplankton) but improved water quality (−34%, −60% and −80%, for the concentrations of total nitrogen, total phosphorus, and blue green algae (for micro-algae in class Cyanophyceae), respectively). According to the PCA, SIC clearly differed from SI in benthic macro-invertebrate production and concentrations of total nitrogen, total phosphorus, and brown algae (for micro-algae in class Dinophyceae or a branch of Bacillariophyta) in the water. SIC differed from E in oxygen parameters (dissolved and saturation), estimated annual zooplankton production, and pH. In conclusion, the properties of a lagoon reveal perspectives for environmentally friendly practices, while using biodiversity and secondary production in order to enhance fish production

Effects of euthanasia methods on stable carbon (δ 13 C value) and nitrogen (δ 15 N value) isotopic compositions of fry and juvenile rainbow trout Oncorhynchus mykiss

International audienceRationaleCarbon and nitrogen stable isotope analyses of fish tissues are now commonly used in ecological studies but mostly require the sacrifice of the animal. Ethical considerations recommend the use of anesthetics for tissue sampling. This study examines how anesthetics affect stable isotope ratios of fish compared with other euthanasia methods.MethodsRainbow trout fry and juveniles were sacrificed using ice-freezing (as this common method used to kill fish does not affect natural isotopic ratios), electronarcosis or an overdose of chemical anesthetics (2-phenoxyethanol, benzocaine and clove oil). For fry, we sampled the whole animal whereas, for juveniles, white dorsal muscle, liver, red blood cells, plasma, external tegument and pectoral fin were sampled. Isotopic ratios and the elemental compositions of carbon and nitrogen were then measured.ResultsThe δ15N values, and the C and N contents of all considered tissues as well as δ13C values of muscle, liver, red blood cells and plasma, were not affected by the use of chemical anesthetics. Clove oil and to a lesser extent 2-phenoxyethanol and benzocaine decreased δ13C values of whole fry and juvenile external tegument and pectoral fin. The use of electronarcosis drastically affects the δ13C and δ15N values of all fish tissues.ConclusionsAnesthetics should be avoided for δ13C analysis when tissues are in contact with the water containing the anesthetic. Ice-immersion has to be preferred when approved by guidelines. If not, benzocaine and 2-phenoxyethanol should be preferred over clove oil. Electronarcosis should not be used to kill fish until further investigations are performed

Improved Comet assay for the assessment of UV genotoxicity in Mediterranean sea urchin eggs.

International audienceGametes and embryos of broadcast spawners are exposed to a wide range of chemical and physical stressors which may alone, or in conjunction, have serious consequences on reproductive outcomes. In this study, two Mediterranean echinoid species, Paracentrotus lividus and Sphaerechinus granularis, were chosen as models to study the genotoxicity of UV radiation (UVR) on the eggs of broadcast-spawning marine invertebrates. The single cell gel electrophoresis, or Comet assay, was successfully adapted to assess DNA strand breakage in sea urchin eggs. The results demonstrated that the genetic material of sea urchin eggs is susceptible to environmentally realistic UV exposure. The induction of DNA damage in the irradiated unfertilized eggs suggests that the previously described defense mechanisms in sea urchin eggs do not completely protect the egg's DNA against UV toxicity. Taken together, our results suggest that UV-impairment of the genetic integrity of the eggs might have a role in postfertilization failures and abnormal embryonic development. Although both species were vulnerable to UVR, embryonic development was less dramatically impaired in P.Lividus. This observation supports the postulation that species inhabiting shallower environments possess more efficient mechanisms to overcome UV-induced DNA alterations. The present demonstration of the utility and sensitivity of the Comet assay to evaluate DNA integrity in eggs from marine invertebrates opens new perspectives for monitoring the long-term effects of environmental exposure on populations and for the routine screening of substances for genotoxicity in marine systems