Photodesorption of H2O, HDO, and D2O ice and its impact on fractionation

The HDO/H2O ratio measured in interstellar gas is often used to draw conclusions on the formation and evolution of water in star-forming regions and, by comparison with cometary data, on the origin of water on Earth. In cold cores and in the outer regions of protoplanetary disks, an important source of gas-phase water comes from photodesorption of water ice. This research note presents fitting formulae for implementation in astrochemical models using previously computed photodesorption efficiencies for all water ice isotopologues obtained with classical molecular dynamics simulations. The results are used to investigate to what extent the gas-phase HDO/H2O ratio reflects that present in the ice or whether fractionation can occur during the photodesorption process. Probabilities for the top four monolayers are presented for photodesorption of X (X = H, D) atoms, OX radicals, and X2O and HDO molecules following photodissociation of H2O, D2O, and HDO in H2O amorphous ice at ice temperatures from 10-100 K. Significant isotope effects are found for all possible products: (1) H atom photodesorption probabilities from H2O ice are larger than those for D atom photodesorption from D2O ice by a factor of 1.1; the ratio of H and D photodesorbed upon HDO photodissociation is a factor of 2. This process will enrich the ice in deuterium atoms over time; (2) the OD/OH photodesorption ratio upon D2O and H2O photodissociation is on average a factor of 2, but the OD/OH photodesorption ratio upon HDO photodissociation is almost constant at unity for all ice temperatures; (3) D atoms are more effective in kicking out neighbouring water molecules than H atoms. However, the ratio of the photodesorbed HDO and H2O molecules is equal to the HDO/H2O ratio in the ice, therefore, there is no isotope fractionation when HDO and H2O photodesorb from the ice. Nevertheless, the enrichment of the ice in D atoms due to photodesorption can over time lead to an enhanced HDO/H2O ratio in the ice, and, when photodesorbed, also in the gas. The extent to which the ortho/para ratio of H2O can be modified by the photodesorption process is discussed briefly as well

Methanol along the path from envelope to protoplanetary disc

Interstellar methanol is considered to be a parent species of larger, more complex organic molecules. A physicochemical simulation of infalling parcels of matter is performed for a low-mass star-forming system to trace the chemical evolution from cloud to disc. An axisymmetric 2D semi-analytic model generates the time-dependent density and velocity distributions, and full continuum radiative transfer is performed to calculate the dust temperature and the UV radiation field at each position as a function of time. A comprehensive gas–grain chemical network is employed to compute the chemical abundances along infall trajectories. Two physical scenarios are studied, one in which the dominant disc growth mechanism is viscous spreading, and another in which continuous infall of matter prevails. The results show that the infall path influences the abundance of methanol entering each type of disc, ranging from complete loss of methanol to an enhancement by a factor of >1 relative to the prestellar phase. Critical chemical processes and parameters for the methanol chemistry under different physical conditions are identified. The exact abundance and distribution of methanol is important for the budget of complex organic molecules in discs, which will be incorporated into forming planetary system objects such as protoplanets and comets. These simulations show that the comet-forming zone contains less methanol than in the precollapse phase, which is dominantly of prestellar origin, but also with additional layers built up in the envelope during infall. Such intriguing links will soon be tested by upcoming data from the Rosetta mission

Pre-diagnostic concordance with the WCRF/AICR guidelines and survival in European colorectal cancer patients : a cohort study

Background: Cancer survivors are advised to follow lifestyle recommendations on diet, physical activity, and body fatness proposed by the World Cancer Research Fund/American Institute of Cancer Research (WCRF/AICR) for cancer prevention. Previous studies have demonstrated that higher concordance with these recommendations measured using an index score (the WCRF/AICR score) was associated with lower cancer incidence and mortality. The aim of this study was to evaluate the association between pre-diagnostic concordance with WCRF/AICR recommendations and mortality in colorectal cancer (CRC) patients. Methods: The association between the WCRF/AICR score (score range 0-6 in men and 0-7 in women; higher scores indicate greater concordance) assessed on average 6.4 years before diagnosis and CRC-specific (n = 872) and overall mortality (n = 1,113) was prospectively examined among 3,292 participants diagnosed with CRC in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort (mean follow-up time after diagnosis 4.2 years). Multivariable Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for mortality. Results: The HRs (95% CIs) for CRC-specific mortality among participants in the second (score range in men/women: 2.25-2.75/3.25-3.75), third (3-3.75/4-4.75), and fourth (4-6/5-7) categories of the score were 0.87 (0.72-1.06), 0.74 (0.61-0.90), and 0.70 (0.56-0.89), respectively (P for trend Conclusions: Greater concordance with the WCRF/AICR recommendations on diet, physical activity, and body fatness prior to CRC diagnosis is associated with improved survival among CRC patients.Peer reviewe

Maîtriser la reproduction des petits ruminants

En élevage biologique, les traitements hormonaux pour gérer la reproduction des animaux (induction et synchronisation des chaleurs) sont interdits, alors qu'ils sont fréquemment utilisés en élevages ovins et caprins conventionnels. Leur utilisation dans ces derniers pourrait toutefois être remise en cause par une nouvelle réglementation. Afin de proposer des alternatives en termes de gestion de la reproduction en élevages ovins et caprins, le programme Casdar Reprobio s'est penché sur deux innovations : - l'utilisation de phéromones de synthèse pour induire les chaleurs ; - des appareils de détection automatisés des chaleurs. Grâce à une enquête, ces deux outils ont été soumis, pour avis, à des éleveurs et des professionnels de l'élevage, en agricultures biologique et conventionnelle. Leurs retours sont présentés dans cet article. L'utilisation des phéromones, qui doit toutefois faire face à un vide juridique en bio, suscite l'intérêt, alors que les détecteurs automatisés de chaleurs posent davantage de questions

Patterns of Ultraviolet Radiation Exposure and Skin Cancer Risk: the E3N-SunExp Study

International audienceBackground: While ultraviolet (UV) radiation exposure is a recognized risk factor for skin cancer, associations are complex and few studies have allowed a direct comparison of exposure profiles associated with cutaneous melanoma, basal-cell carcinoma (BCC), and squamous-cell carcinoma (SCC) within a single population.Methods: We examined associations between UV exposures and skin cancer risk in a nested case-control study within E3N, a prospective cohort of 98,995 French women born in 1925–1950. In 2008, a lifetime UV exposure questionnaire was sent to all reported skin cancer cases and three controls per case, which were matched on age, county of birth, and education. Analyses were performed using conditional logistic regression and included 366 melanoma cases, 1,027 BCC cases, 165 SCC cases, and 3,647 controls.Results: A history of severe sunburns <25 years was associated with increased risks of all skin cancers (melanoma: OR 2.7; BCC: OR 1.7; SCC: OR 2.0 for ≥6 sunburns vs. none), while sunburns ≥25 years were associated with BCC and SCC only. While high-sun protection factor sunscreen use before age 25 was associated with lower BCC risk (P trend = 0.02), use since age 25 and reapplication of sunscreen were associated with higher risks of all three types of skin cancer. There were positive linear associations between total UV score and risks of BCC (P trend = 0.01) and SCC (P trend = 0.09), but not melanoma. While recreational UV score was strongly associated with BCC, total and residential UV scores were more strongly associated with SCC.Conclusions: Melanoma, BCC, and SCC are associated with different sun exposure profiles in women

Maîtriser la reproduction des petits ruminants

National audienceEn agriculture conventionnelle (AC), pour gérer la reproduction des ovins et caprins, des traitements hormonaux sont utilisés. Ils permettent de préparer l'insémination animale (IA) ou de grouper les mises-bas par l'induction et la synchronisation des chaleurs. En AB, ces traitement hormonaux sont interdits, et leur utilisation pourrait se voir limitée en conventionnel par des évolutions réglementaires. Ainsi, le programme Casdar Reprobio amis à l'étude deux nouveaux outils : les phéromones de synthèse (alternative à la synchronisation hormonale de chaleurs) et la détection automatisée des chaleurs (pour faciliter la mise en place de l'IA sur chaleurs synchronisées ou pas). Voici les retours d'éleveurs et d’intervenants en élevages sur ces innovations