Three new and remarkable species of mosses from China and the Philippines

Distichophyllum meizhii Tan & Lin and D. wanianum Tan & Lin (Hookeriaceae) collected from southwestern region of China are described as new to science. Also, Horikawaea redfearnii Tan & Lin is described as a new species based on collections from Hainan Island of China and Palawan Island of the Philippines. The sporophytic specimen of Horikawaea Nog. was collected for the first time and support a family placement in Pterobryaceae

On the Formation of Runaway Stars BN and x in the Orion Nebula Cluster

We explore scenarios for the dynamical ejection of stars BN and x from source I in the Kleinmann-Low nebula of the Orion Nebula Cluster (ONC), which is important for being the closest region of massive star formation. This ejection would cause source I to become a close binary or a merger product of two stars. We thus consider binary-binary encounters as the mechanism to produce this event. By running a large suite of $N$-body simulations, we find that it is nearly impossible to match the observations when using the commonly adopted masses for the participants, especially a source I mass of $7\:{\rm{M}}_\odot$. The only way to recreate the event is if source I is more massive, i.e., $\sim20\:{\rm{M}}_\odot$. However, even in this case, the likelihood of reproducing the observed system is low. We discuss the implications of these results for understanding this important star-forming region.Comment: 7 pages, 4 figures, 1 table. Accepted by A&A Letter

Star Cluster Formation from Turbulent Clumps. I. The Fast Formation Limit

We investigate the formation and early evolution of star clusters assuming that they form from a turbulent starless clump of given mass bounded inside a parent self-gravitating molecular cloud characterized by a particular mass surface density. As a first step we assume instantaneous star cluster formation and gas expulsion. We draw our initial conditions from observed properties of starless clumps. We follow the early evolution of the clusters up to 20 Myr, investigating effects of different star formation efficiencies, primordial binary fractions and eccentricities and primordial mass segregation levels. We investigate clumps with initial masses of $M_{\rm cl}=3000\:{\rm M}_\odot$ embedded in ambient cloud environments with mass surface densities, $\Sigma_{\rm cloud}=0.1$ and $1\:{\rm g\:cm^{-2}}$. We show that these models of fast star cluster formation result, in the fiducial case, in clusters that expand rapidly, even considering only the bound members. Clusters formed from higher $\Sigma_{\rm cloud}$ environments tend to expand more quickly, so are soon larger than clusters born from lower $\Sigma_{\rm cloud}$ conditions. To form a young cluster of a given age, stellar mass and mass surface density, these models need to assume a parent molecular clump that is many times denser, which is unrealistic compared to observed systems. We also show that in these models the initial binary properties are only slightly modified by interactions, meaning that binary properties, e.g., at 20 Myr, are very similar to those at birth. With this study we set up the basis of future work where we will investigate more realistic models of star formation compared to this instantaneous, baseline case.Comment: 25 pages, 19 figures. Accepted by Ap

Hunting for Runaways from the Orion Nebula Cluster

We use Gaia DR2 to hunt for runaway stars from the Orion Nebula Cluster (ONC). We search a region extending 45{\deg} around the ONC and out to 1 kpc to find sources that overlapped in angular position with the cluster in the last ~10 Myr. We find ~17,000 runaway/walkaway candidates satisfy this 2D traceback condition. Most of these are expected to be contaminants, e.g., caused by Galactic streaming motions of stars at different distances. We thus examine six further tests to help identify real runaways, namely: (1) possessing young stellar object (YSO) colors and magnitudes based on Gaia optical photometry; (2) having IR excess consistent with YSOs based on 2MASS and WISE photometry; (3) having a high degree of optical variability; (4) having closest approach distances well constrained to within the cluster half-mass radius; (5) having ejection directions that avoid the main Galactic streaming contamination zone; and (6) having a required radial velocity (RV) for 3D overlap of reasonable magnitude (or, for the 7% of candidates with measured RVs, satisfying 3D traceback). Thirteen sources, not previously noted as Orion members, pass all these tests, while another twelve are similarly promising, except they are in the main Galactic streaming contamination zone. Among these 25 ejection candidates, ten with measured RVs pass the most restrictive 3D traceback condition. We present full lists of runaway/walkaway candidates, estimate the high-velocity population ejected from the ONC and discuss its implications for cluster formation theories via comparison with numerical simulations.Comment: 22 pages, 10 figures, and 5 tables. Accepted for publication in Ap

Quotient Types in Typer

Ce travail décrit l’ajout des types quotients dans Typer, un langage avec des types dépendants. Les types quotients permettent aux programmeurs de construire de nouveaux types à base des types existants en redéfinissant la notion d’égalité du type de départ. Typiquement, cela repose sur des relations d’équivalence définies sur le type de base. Les termes qui sont équivalents selon la relation sont donc vus comme égaux dans le type quotient résultant. Par exemple, les nombres rationnels peuvent être définis comme le quotient des paires d’entiers par une relation d’équivalence basée sur le produit en croix. Pour accueillir l’ajout des types quotients dans Typer, on a redéfini et amélioré l’égalité intégré de Typer en s’inspirant de la théorie des types cubique qui a introduit le type d’intervalle et aussi les assistants de preuve qui l’implémentent. De ce fait, la nouvelle égalité de Typer est basé sur les fonctions qui ont comme argument notre nouvelle primitive d’intervalle. Une telle égalité est plus puissante et expressive, elle se prête bien à la construction des preuves liées aux types quotients. Dans ce travail, on s’intéresse également au côté pratique de l’utilisation des types quotients dans un langage tel que Typer, à la fois en termes d’efficacité d’exécution et de facilité d’utilisation pour les développeurs. Les types quotients ne sont pas offerts dans la plupart des langages avec des types dépendants principalement parce que leur utilisation nous entraîne à des obligations de preuves pénibles. Pour faciliter l’utilisation des types quotients, on a fourni une bibliothèque qui simplifie la manipulation des types quotients. On a profité de cette nouvelle addition au langage pour introduire de nouvelles primitives, telle que les nombres rationnels, la troncation propositionnelle, etc. Finalement, ce travail étudie également le développement des preuves en Typer. À notre connaissance, ceci est la première tentative d’écrire une quantité importante de preuves en Typer puisque le langage se veut un langage de programmation à usage général. On décrit notre expérience et les défis auxquels on a dû faire face en cours de route. En outre, on a introduit de nouvelles primitives pour faciliter le développement de preuves en Typer.This work describes the introduction of quotient types to Typer, a dependently-typed programming language. Quotient types allow programmers to construct new types based on existing types by redefining the notion of equality of the base type. This is typically based on equivalence relations defined on the base type. Terms that are equivalent according to the relation are thus treated as equal in the resulting quotient type. For instance, rational numbers may be defined as the quotient of pairs of integers under an equivalence relation based on cross-multiplication. To better accommodate the introduction of quotient types to Typer, we revamped the built-in equality type by drawing inspiration from cubical type theory that features the interval type and proof assistants that implement it. As such, Typer’s new equality type is based on functions that have our new interval primitive as an argument. Such an equality type is more powerful and expressive, it notably lends itself well to the writing of proofs related to quotient types. In this work, we also investigate the practicality of the usage of quotient types in a language such as Typer, both in terms of run-time efficiency and developer-friendliness. Quotient types do not exist in most modern dependently typed languages, principally because their usage entails burdensome proof obligations. To facilitate the usage of quotient types, we provide a library that helps simplify the manipulation of quotient types. We also leverage this new addition to the language to introduce new built-in types, such as rational numbers, propositional truncation, etc. Finally, this work also explores the development of proofs in Typer, to our knowledge this is the first attempt to write a substantial amount of proofs using the language since the language is primarily intended to be a general-purpose programming language. We describe our experience and the challenges faced in the process. Additionally, we introduce several constructs to streamline proof development in Typer

Star Cluster Formation from Turbulent Clumps. III. Across the mass spectrum

We study the formation and early evolution of star clusters that have a wide range of masses and background cloud mass surface densities, $\Sigma_{\rm cloud}$, which help set the initial sizes, densities, and velocity dispersions of the natal gas clumps. Initial clump masses of 300, $3,000$ and $30,000$ $M_\odot$ are considered, from which star clusters are born with an assumed 50% overall star formation efficiency and with 50% primordial binarity. This formation is gradual, i.e., with a range of star formation efficiencies per free-fall time from 1% to 100%, so that the formation time can range from 0.7 Myr for low-mass, high-$\Sigma_{\rm cloud}$ clumps to $\sim30$ Myr for high-mass, low-$\Sigma_{\rm cloud}$ clumps. Within this framework of the Turbulent Clump model, for a given $\Sigma_{\rm cloud}$, clumps of higher mass are of lower initial volume density, but their dynamical evolution leads to higher bound fractions and causes them to form much higher density cluster cores and maintain these densities for longer periods. This results in systematic differences in the evolution of binary properties, degrees of mass segregation and rates of creation of dynamically ejected runaways. We discuss the implications of these results for observed star clusters and stellar populations.Comment: 28 pages, 20 Figures. Submitted to MNRA

Antiresorptive-associated spontaneous fractures of both tibiae, followed by an atypical femur fracture during the sequential treatment with alendronate, denosumab then teriparatide.

A 35-year-old man with juvenile idiopathic arthritis since childhood presented with bilateral atypical tibial fractures, followed by a later, single atypical fracture of the femur. The fractures were associated with 6 years of oral alendronate treatment immediately followed by subcutaneous denosumab therapy and later teriparatide therapy for osteoporosis. Atypical fractures are known to occur in the femur following bisphosphonate therapy; however, there are only a few documented cases of atypical fractures in the tibia. Our case highlights a rare but serious complication of a commonly prescribed antiresorptive agent. It also shows that teriparatide, while helpful in increasing bone mass, does not fully prevent the development of atypical fractures. Careful investigation should be considered in patients on long-term antiresorptive therapy presenting with bony tenderness to exclude an atypical fracture.Cambridge NIHR Biomedical Research Centr

Achieving the WHO/UNAIDS antiretroviral treatment 3 by 5 goal: what will it cost?

The "3 by 5" goal to have 3 million people in low and middle income countries on antiretroviral therapy (ART) by the end of 2005 is ambitious. Estimates of the necessary resources are needed to facilitate resource mobilisation and rapid channelling of funds to where they are required. We estimated the financial costs needed to implement treatment protocols, by use of country-specific estimates for 34 countries that account for 90% of the need for ART in resource-poor settings. We first estimated the number of people needing ART and supporting programmes for each country. We then estimated the cost per patient for each programme by country to derive total costs. We estimate that between US5.1 billion dollars and US5.9 billion dollars will be needed by the end of 2005 to provide ART, support programmes, and cover country-level administrative and logistic costs for 3 by 5