Insights on the dynamical history of the Fomalhaut system - Investigating the Fom c hypothesis

The eccentric shape of the debris disk observed around Fomalhaut was first attributed to Fom b, a companion detected near the belt inner-edge, but new constraints on its orbit revealed that it is belt-crossing, highly eccentric $(e \sim 0.6-0.9)$, and can hardly account for the shape of the belt. The best scenario to explain this paradox is that there is another massive body in this system, Fom c, which drives the debris disk shape. The resulting planetary system is highly unstable, which hints at a dynamical scenario involving a recent scattering of Fom b on its current orbit, potentially with the putative Fom c. Our goal is to give insights on the probability for Fom b to have been set on its highly eccentric orbit by a close-encounter with the putative Fom c. We aim to study in particular the part played by mean-motion resonances with Fom c, which could have brought Fom b sufficiently close to Fom c for it to be scattered on its current orbit, but also delay this scattering event. Using N-body simulations, we found that the generation of orbits similar to that of Fom b, either in term of dimensions or orientation, is a robust process involving a scattering event and a further secular evolution of inner material with an eccentric massive body such as the putative Fom c. We found in particular that mean-motion resonances can delay scattering events, and thus the production of Fom b-like orbits, on timescales comparable to the age of the system, thus explaining the witnessing of an unstable configuration. We conclude that Fom b probably originated from an inner resonance with Fom c, which is at least Neptune-Saturn size, and was set on its current orbit by a scattering event with Fom c. Since Fom b could not have formed from material in resonance, our scenario also hints at former migration processes in this planetary system

Effects of condensed tannins on established populations and on incoming larvae of Trichostrongylus colubriformis and Teladorsagia circumcincta in goats

The use of tanniferous plants or tannins represents one alternative approach to the control of gastrointestinal parasites in ruminants but most data have been obtained in sheep. The current study was therefore performed in goats with two objectives: firstly, to investigate the effects of condensed tannins (CT) on adult populations of Trichostrongylus colubriformis and Teladorsagia circumcincta; secondly, to examine their effects on the establishment of infective larvae of these two species. In experiment 1, two groups of kids were infected with 6 000 L3 of T. colubriformis and 6 000 L3 of T. circumcincta. After 7 weeks, quebracho extracts were administered per os for 8 days to one group. A comparable group which did not receive tannins was included as the control. The kids were slaughtered on week 11. Parasitological and pathophysiological parameters were measured weekly. Worm counts were assessed and mast cells, globule leukocytes and eosinophils were counted in the abomasal and intestinal mucosae. Tannin administration was associated with a decrease in egg excretion, and a decrease in female fecundity, but with no changes in worm numbers. These changes were associated with an increased number of intestinal mast cells. In experiment 2, 24 goats were used according to a 2 2 factorial design, depending on infection and tannin administration. Two groups were either infected with 6 000 L3 of T. colubriformis or T. circumcincta. Within each group, the goats were either drenched or undrenched with tannin extracts. Pathophysiological parameters were measured weekly. Twelve days after the cessation of tannin administration, the goats were slaughtered. Worm counts and female worm fecundity were determined. Tannin consumption was associated with a significant reduction (P < 0.001) of Trichostrongylus populations and a close to significant reduction for Teladorsagia. No effect on fecundity was observed. Our results (1) confirm the consequences of condensed tannins on nematodes in goats as in sheep and (2) indicate divergent effects depending on the parasitic stage exposed to the condensed tannins

Enseigner un savoir stabilisé et une controverse socioscientifique, quelles différences et similitudes ? Exemple d'une pratique ordinaire d'enseignement en physique.

International audienceCet article vise à décrire et comprendre la pratique ordinaire d'un enseignant de physique en 1e Scientifique à l'occasion de l'enseignement d'une controverse socioscientifique (le changement climatique). Une perspective comparatiste est adoptée dans cette étude de cas : c'est par comparaison avec l'enseignement d'un savoir stabilisé (l'énergie) que des éléments génériques et spécifiques de la pratique de cet enseignant ont été dégagés. L'étude mobilise à la fois la théorie de l'action conjointe en didactique (Sensevy, 2007, 2011), l'analyse communicationnelle (Mortimer et Scott, 2003) et l'analyse des jeux de langage (Wittgenstein, 1953). Les résultats que nous présentons dans cet article oncernent principalement la manière dont l'avancée des savoirs est répartie entre professeur et élèves, et l'épistémologie pratique de l'enseignant telle qu'elle apparaît lors des séances observées

The Nuclear dsRNA Binding Protein HYL1 Is Required for MicroRNA Accumulation and Plant Development, but Not Posttranscriptional Transgene Silencing

AbstractMicroRNAs (miRNAs) are 21–24 nucleotides long molecules processed from imperfect double-stranded RNAs (dsRNAs). They regulate gene expression by targeting complementary mRNA for cleavage or interfering with their translation [1–6]. In Arabidopsis, point mutations in or short truncations of the nuclear DICER-LIKE1 (DCL1) or HEN1 protein reduce miRNA accumulation and increase uncleaved target mRNAs accumulation, resulting in developmental abnormalities [7–12]. Here, we show that miRNA accumulation also depends on the activity of HYL1, a nuclear dsRNA binding protein [13]. hyl1 mutants exhibit developmental defects overlapping with that of dcl1 and hen1 mutants, suggesting that DCL1, HEN1, and HYL1 act together in the nucleus. We validate additional target mRNAs and show that reduced miRNA accumulation in hyl1 correlates with an increased accumulation of uncleaved target mRNAs, including meristem- and auxin-related genes, providing clues for the developmental abnormalities of hyl1 and for the previous identification of hyl1 as a mutant with altered responses to phytohormones [13]. Lastly, we show that posttranscriptional transgene silencing occurs in hyl1, suggesting that HYL1 has specialized function in the plant miRNA pathway, whereas the HYL1-related RDE-4 and R2D2 proteins associate with DICER in the cytoplasm and act in the RNAi pathway in C. elegans and Drosophila, respectively [14–15]

Scientometric analysis of the forensic science literature for fibre as an evidence type:Access and data availability

The large volume of information available within citation databases has become a challenge to manage and distil in all areas of research. In this study, a scientometric approach has been applied to fibres as an evidence type using information contained in Scopus and Web of Science. A comparison was also made with the references listed in the INTERPOL International Forensic Science Managers Symposium Science (IFSMS) reports (2004–2019) where only a limited number of documents were common with the citation databases, illustrating the value of the IFSMS reports. Finally, this study also highlights that data availability and location are generally omitted in publications. The forensic science community has an opportunity to change this culture and lead the way in making their data available, aligning with the ideals of fairness, openness and transparency of the underpinning data upon which scientific developments are based

Formation aux écrits professionnels : vers une sociolinguistique impliquée

Cet article présente une recherche en cours qui s’effectue sur le terrain de la formation linguistique à visée professionnelle pour des salariés des métiers de la Propreté. Elle s’intéresse à l’articulation entre la part langagière du travail, la littératie professionnelle, et la formation. Les premiers résultats montrent la difficulté de transformer cette part langagière du travail en contenus didactiques. Au-delà de cette étude, nous montrons qu’il est impossible de comprendre ce qui se passe dans la salle de cours sans remonter tout le fil de l’enquête et des contacts sur le terrain. Cette étude nous amène alors à réfléchir à un nouveau cadre théorique en ce qui concerne l’approche méthodologique que nous proposons d’appeler sociolinguistique impliquée.This article presents ongoing research that is concerned with the provision of language training for employees in the industrial cleaning sector. It deals with the links between the linguistic component of work, literacy in the workplace and the provision of training. Initial results have shown the difficulty arising from trying to deal adequately with the linguistic component of work in terms of language tuition. Beyond this study, we demonstrate here that it is impossible to fully understand what takes place in the classroom without considering the whole of the survey and the contacts in the field. This study invites us to rethink our theoretical framework with regard to the methodological approach; we propose to call this “implied sociolinguistics”