2,020 research outputs found

    Constant-angle surfaces in liquid crystals

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    We discuss some properties of surfaces in R3 whose unit normal has constant angle with an assigned direction field. The constant angle condition can be rewritten as an Hamilton-Jacobi equation correlating the surface and the direction field. We focus on examples motivated by the physics of interfaces in liquid crystals and of layered fluids, and discuss the properties of the constant-angle surfaces when the direction field is singular along a line (disclination) or at a point (hedgehog defect

    The lemur diversity of the Fiherenana-Manombo Complex, southwest Madagascar

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    We conducted the first comprehensive lemur survey of the Fiherenana - Manombo Complex (Atsimo-Andrefana Region), site of PK32-Ranobe, a new protected area within the Madagascar Protected Area System. Our cross-seasonal surveys of three sites revealed the presence of eight lemur species representing seven genera and four families, of which three are diurnal and five are nocturnal species. Six species were only recorded in the riparian and transitional forests of the Fiherenana and Manombo river valleys, while the spiny thicket at Ranobe contains only Microcebus (two species), all larger species having been extirpated by hunting in recent years. Two of our records (Mirza coquereli and Cheirogaleus sp.) represent new locality records or range extensions, but we failed to record one species (Phaner pallescens) expected to occur in the area, and question the literature supporting its presence south of the Manombo river. Our findings highlight the importance of the Fiherenana-Manombo Complex for the conservation of lemurs in southwest Madagascar, but also show that PK32 - Ranobe fails to protect the full lemur diversity of the Complex. The protected area does not include the riparian forests of the Manombo and Fiherenana rivers, and at least three lemur species are therefore unprotected. We strongly support the proposed extension of the protected area to include these riparian forests as well as other important habitats for locally endemic bird and reptile taxa.RÉSUMÉ La zone du Complexe Fiherenana - Manombo (RĂ©gion d’Atsimo- Andrefana), site de PK32-Ranobe, une nouvelle aire protĂ©gĂ©e dans le SystĂšme des Aires ProtĂ©gĂ©es de Madagascar (SAPM), a fait l’objet d’un premier inventaire de lĂ©muriens. Nos prospections dans trois sites Ă  diffĂ©rentes saisons ont rĂ©vĂ©lĂ© la prĂ©sence de huit espĂšces de lĂ©muriens reprĂ©sentĂ©s dans sept genres et trois familles, dont trois sont des espĂšces diurnes et cinq sont des espĂšces nocturnes. Nous n’avons pas pu identifier l’espĂšce du genre Lepilemur ni celle du genre Cheirogaleus Ă  dĂ©faut de disposer de spĂ©cimens. Six espĂšces ne se trouvaient que dans les forĂȘts riveraines et les forĂȘts de transition des vallĂ©es des fleuves Fiherenana et Manombo. Le fourrĂ© Ă©pineux de Ranobe n’abrite que des Microcebus (deux espĂšces), toutes les espĂšces plus grandes ayant dĂ©jĂ  Ă©tĂ© exterminĂ©es par la chasse au cours des derniĂšres annĂ©es. Nos estimations de densitĂ© indiquent que la population des Microcebus est deux fois plus importante dans le fourrĂ© Ă©pineux que dans la forĂȘt riveraine (1,078 individus / kmÂČ vs. 546 individus / kmÂČ). Nous avons estimĂ© la densitĂ© d’Eulemur rufus Ă  40 groupes / kmÂČ dans la vallĂ©e du Fiherenana, mais nos transects ne nous ont pas permis d’obtenir des estimations fiables pour les densitĂ©s de Lemur catta et de Propithecus verreauxi. Deux des espĂšces rĂ©pertoriĂ©es (Mirza coquereli et Cheirogaleus sp.) reprĂ©sentent de nouvelles observations pour la zone ou des extensions de leurs aires de rĂ©partition connues, mais nous n’avons pas pu trouver l’espĂšce Phaner pallescens qui devait ĂȘtre prĂ©sente dans la zone et nous Ă©mettons des doutes portant sur les rĂ©fĂ©rences publiĂ©es rapportant la prĂ©sence de l’espĂšce au sud du fleuve Manombo. Nos rĂ©sultats mettent en exergue l’importance du Complexe Fiherenana - Manombo pour la conservation des lĂ©muriens dans le sud-ouest de Madagascar, mais ils indiquent que l’aire protĂ©gĂ©e de PK32 - Ranobe ne protĂšge pas la diversitĂ© complĂšte des lĂ©muriens du Complexe. Les forĂȘts riveraines des fleuves Fiherenana et Manombo ne sont pas incluses dans l’aire protĂ©gĂ©e de sorte qu’au moins trois espĂšces de lĂ©muriens ne bĂ©nĂ©ficient alors d’aucune protection. Compte tenu des objectifs du SAPM et plus particuliĂšrement de l’Objectif 1, Ă  savoir ‘Conserver l’ensemble de la biodiversitĂ© unique de Madagascar’, nous estimons que la nouvelle aire protĂ©gĂ©e du PK32-Ranobe n’atteint pas ces objectifs et nous appuyons les efforts des promoteurs afin de re-dĂ©limiter l’aire protĂ©gĂ©e pour inclure les forĂȘts riveraines ainsi que d’autres habitats importants pour la conservation des oiseaux et des reptiles localement endĂ©miques

    Common and Rare Variant Prediction and Penetrance of IBD in a Large, Multi-ethnic, Health System-based Biobank Cohort

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    BACKGROUND AND AIMS: Polygenic risk scores (PRS) may soon be used to predict inflammatory bowel disease (IBD) risk in prevention efforts. We leveraged exome-sequence and single nucleotide polymorphism (SNP) array data from 29,358 individuals in the multiethnic, randomly ascertained health system-based BioMe biobank to define effects of common and rare IBD variants on disease prediction and pathophysiology. METHODS: PRS were calculated from European, African American, and Ashkenazi Jewish (AJ) reference case-control studies, and a meta-GWAS run using all three association datasets. PRS were then combined using regression to assess which combination of scores best predicted IBD status in European, AJ, Hispanic, and African American cohorts in BioMe. Additionally, rare variants were assessed in genes associated with very early-onset IBD (VEO-IBD), by estimating genetic penetrance in each BioMe population. RESULTS: Combining risk scores based on association data from distinct ancestral populations improved IBD prediction for every population in BioMe and significantly improved prediction among European ancestry UK Biobank individuals. Lower predictive power for non-Europeans was observed, reflecting in part substantially lower African IBD case-control reference sizes. We replicated associations for two VEO-IBD genes, ADAM17 and LRBA, with high dominant model penetrance in BioMe. Autosomal recessive LRBA risk alleles are associated with severe, early-onset autoimmunity; we show that heterozygous carriage of an African-predominant LRBA protein-altering allele is associated with significantly decreased LRBA and CTLA-4 expression with T-cell activation. CONCLUSIONS: Greater genetic diversity in African populations improves prediction across populations, and generalizes some VEO-IBD genes. Increasing African American IBD case-collections should be prioritized to reduce health disparities and enhance pathophysiological insight.Peer reviewe
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