Recovery Policies for Safe Exploration of Lunar Permanently Shadowed Regions by a Solar-Powered Rover

The success of a multi-kilometre drive by a solar-powered rover at the lunar south pole depends upon careful planning in space and time due to highly dynamic solar illumination conditions. An additional challenge is that the rover may be subject to random faults that can temporarily delay long-range traverses. The majority of existing global spatiotemporal planners assume a deterministic rover-environment model and do not account for random faults. In this paper, we consider a random fault profile with a known, average spatial fault rate. We introduce a methodology to compute recovery policies that maximize the probability of survival of a solar-powered rover from different start states. A recovery policy defines a set of recourse actions to reach a safe location with sufficient battery energy remaining, given the local solar illumination conditions. We solve a stochastic reach-avoid problem using dynamic programming to find an optimal recovery policy. Our focus, in part, is on the implications of state space discretization, which is required in practical implementations. We propose a modified dynamic programming algorithm that conservatively accounts for approximation errors. To demonstrate the benefits of our approach, we compare against existing methods in scenarios where a solar-powered rover seeks to safely exit from permanently shadowed regions in the Cabeus area at the lunar south pole. We also highlight the relevance of our methodology for mission formulation and trade safety analysis by comparing different rover mobility models in simulated recovery drives from the LCROSS impact region.Comment: In Acta Astronautica, vol. 213, pp. 708-724, Dec. 202

Tendre vers une gestion durable du bois traité dans les matériaux de CRD québécois

L’objectif de cet essai est de proposer des alternatives de gestion durable du bois récupéré postconsommation issu des matériaux de la construction, de la rénovation et de la démolition qui transitent par les centres de tri québécois. Ces derniers gèrent lesdits matériaux, parmi lesquels on retrouve entre 30 et 40 % de bois, dans une perspective de recyclage et de valorisation. Une proportion du bois récupéré a subi un traitement de préservation de types fongicide, algicide et insecticide. La plupart des traitements sont faits par l’application de produits toxiques qui génèrent ensuite une variété importante de contaminants dans l’environnement tels que des métaux lourds, des composés organochlorés, des hydrocarbures aromatiques polycycliques ainsi que des dioxines et des furanes. Se faisant, différentes solutions ont été analysées dans le but d’améliorer la situation actuelle. Une étude des meilleures pratiques en gestion du bois traité a révélé que sa réduction et son tri à la source semblent de bonnes solutions afin de minimiser la quantité totale de bois traité acheminée vers les centres de tri. Une bonne planification et une revue des modes opératoires permettraient ainsi de réduire les excédents, le gaspillage et la surconsommation. Puisque le bois traité est difficile à identifier et à ségréger dans les centres de tri, il serait pertinent de le détourner à la source afin qu’il suive un chemin approprié à sa nature contaminée. Une autre solution serait d’améliorer la performance du tri et de rendre le bois traité plus visible, plus facile à retirer. Aussi, des études comparatives au sujet de différentes solutions de remplacement pour le bois traité pourraient proposer l’utilisation de produits de traitement alternatif ainsi que de matériaux de remplacement comme le béton, l’acier galvanisé ou le bois composite. Au terme de cette analyse, plusieurs recommandations ont été fournies afin de tendre vers une gestion plus durable du bois traité au Québec. Les différents paliers de gouvernement devraient notamment : bannir l’enfouissement du bois au Québec, règlementer le secteur du bois traité, informer la population et suivre le bois traité, améliorer à la source les pratiques de gestion du bois traité sur les chantiers, soutenir les initiatives d’utilisation du bois traité résiduel, soutenir également la modernisation des centres de tri ainsi que la recherche et la modernisation dans le domaine des traitements de préservation du bois. En somme, l’utilisation du bois traité dans les principales applications étudiées est encore aujourd’hui la meilleure solution d’un point de vue environnemental et économique

Targeted expression profiling reveals distinct stages of early canine fibroblast reprogramming are regulated by 2-oxoglutarate hydroxylases

Background: Ectopic expression of a defined set of transcription factors allows the reprogramming of mammalian somatic cells to pluripotency. Despite continuous progress in primate and rodent reprogramming, limited attention has been paid to cell reprogramming in domestic and companion species. Previous studies attempting to reprogram canine cells have mostly assessed a small number of presumptive canine induced pluripotent stem cell (iPSC) lines for generic pluripotency attributes. However, why canine cell reprogramming remains extremely inefficient is poorly understood. Methods: To better characterize the initial steps of pluripotency induction in canine somatic cells, we optimized an experimental system where canine fetal fibroblasts (cFFs) are transduced with the Yamanaka reprogramming factors by Sendai virus vectors. We use quantitative PCR arrays to measure the expression of 80 target genes at various stages of canine cell reprogramming. We ask how cFF reprogramming is influenced by small molecules affecting the epigenomic modification 5-hydroxymethylcytosine, specifically L-ascorbic acid and retinoic acid (AA/RA). Results: We found that the expression and catalytic output of a class of 2-oxoglutarate-dependent (2-OG) hydroxylases, known as ten-eleven translocation (TET) enzymes, can be modulated in canine cells treated with AA/RA. We further show that AA/RA treatment induces TET1 expression and facilitates early canine reprogramming, evidenced by upregulation of epithelial and pluripotency markers. Using a chemical inhibitor of 2-OG hydroxylases, we demonstrate that 2-OG hydroxylase activity regulates the expression of a subset of genes involved in mesenchymal-to-epithelial transition (MET) and pluripotency in early canine reprogramming. We identify a set of transcription factors depleted in maturing reprogramming intermediates compared to pluripotent canine embryonic stem cells. Conclusions: Our findings highlight 2-OG hydroxylases have evolutionarily conserved and divergent functions regulating the early reprogramming of canine somatic cells and show reprogramming conditions can be rationally optimized for the generation of maturing canine iPSC

In vitro maturation in the presence of Leukemia Inhibitory Factor modulates gene and miRNA expression in bovine oocytes and embryos

Altres ajuts: OECD Co-operative Research Programme: Biological Resource Management for Sustainable Agricultural Systems ; Natural Sciences and Engineering Research Council of CanadaMembers of the interleukin-6 (IL-6) family of cytokines are important for reproductive function that are mediated through changes in gene and miRNA expression. Herein, we characterized the expression of miR-21, miR-155, miR-34c and miR-146a in bovine oocytes and cumulus cells during in vitro maturation (IVM) with leukemia inhibitory factor (LIF), IL-6 and IL-11 or unsupplemented controls. LIF-exposed COCs showed higher expression of miR-21 and miR-155 in oocytes, whereas miR-146a expression was increased in oocytes matured with IL-6 and IL-11. In cumulus cells, miR-155 expression was elevated by all treatments while only LIF increased miR-21 expression. Based on these results, we next examined how LIF exposure during IVM affected oocyte competence, through IVF and the expression of specific genes in GV- and MII-oocytes, in 2- and 8-cell embryos, and in Day 8-blastocysts. LIF supplementation did not affect cleavage rate, blastocyst yield or several other developmental parameters, but did increase hatching rate. LIF suppressed DPPA3, ZAR1 and NPM2 expression in 2 cell- and/or 8-cell embryos. LIF increased the expression of KAT2A and HSPA1A in MII-oocytes, and that of HDAC1, KAT2A and HSP90AA1 and the BAX:BCL2L1 ratio in 2-cell embryos. In contrast, HDAC1, KAT2A and HSP90AA1 expression and BAX:BCL2L1 ratio was lower in 8-cell embryos derived from LIF oocytes. IVM with LIF also increased the expression of DNMT3A, HSPA1A and HSP90AA1 in blastocysts. In conclusion, supplementation with LIF during IVM was consistently associated with changes in the relative abundance of transcripts in mature bovine oocytes and in specific embryo developmental stages

Structurally plastic peptide capsules for synthetic antimicrobial viruses

A conceptual design for artificial antimicrobial viruses is described.</p

Evaluating the use of testate amoeba for palaeohydrological reconstruction in permafrost peatlands

The melting of high-latitude permafrost peatlands is a major concern due to a potential positive feedback on global climate change. We examine the ecology of testate amoebae in permafrost peatlands, based on sites in Sweden (~ 200 km north of the Arctic Circle). Multivariate statistical analysis confirms that water-table depth and moisture content are the dominant controls on the distribution of testate amoebae, corroborating the results from studies in mid-latitude peatlands. We present a new testate amoeba-based water table transfer function and thoroughly test it for the effects of spatial autocorrelation, clustered sampling design and uneven sampling gradients. We find that the transfer function has good predictive power; the best-performing model is based on tolerance-downweighted weighted averaging with inverse deshrinking (performance statistics with leave-one-out cross validation: R2 = 0.87, RMSEP = 5.25 cm). The new transfer function was applied to a short core from Stordalen mire, and reveals a major shift in peatland ecohydrology coincident with the onset of the Little Ice Age (c. AD 1400). We also applied the model to an independent contemporary dataset from Stordalen and find that it outperforms predictions based on other published transfer functions. The new transfer function will enable palaeohydrological reconstruction from permafrost peatlands in Northern Europe, thereby permitting greatly improved understanding of the long-term ecohydrological dynamics of these important carbon stores as well as their responses to recent climate change

Unexpected diversity in socially synchronized rhythms of shorebirds

The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring). The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood. Here we investigate these rhythms in the context of biparental care, a particularly sensitive phase of social synchronization where pair members potentially compromise their individual rhythms. Using data from 729 nests of 91 populations of 32 biparentally incubating shorebird species, where parents synchronize to achieve continuous coverage of developing eggs, we report remarkable within-and between-species diversity in incubation rhythms. Between species, the median length of one parent's incubation bout varied from 1-19 h, whereas period length-the time in which a parent's probability to incubate cycles once between its highest and lowest value-varied from 6-43 h. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis (the ability to avoid detection by other animals) had longer incubation bouts than those that are readily visible or who actively protect their nest against predators. Rhythms entrainable to the 24-h light-dark cycle were less prevalent at high latitudes and absent in 18 species. Our results indicate that even under similar environmental conditions and despite 24-h environmental cues, social synchronization can generate far more diverse behavioural rhythms than expected from studies of individuals in captivity. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms.</p