3,192 research outputs found
Exploring the formation by core accretion and the luminosity evolution of directly imaged planets: The case of HIP 65426 b
A low-mass companion to the two-solar mass star HIP65426 has recently been
detected by SPHERE at around 100 au from its host. Explaining the presence of
super-Jovian planets at large separations, as revealed by direct imaging, is
currently an open question.
We want to derive statistical constraints on the mass and initial entropy of
HIP65426b and to explore possible formation pathways of directly imaged objects
within the core-accretion paradigm, focusing on HIP65426b.
Constraints on the planet's mass and post-formation entropy are derived from
its age and luminosity combined with cooling models. For the first time, the
results of population synthesis are also used to inform the results. Then, a
formation model that includes N-body dynamics with several embryos per disc is
used to study possible formation histories and the properties of possible
additional companions. Finally, the outcomes of two- and three-planet
scattering in the post-disc phase are analysed, taking tides into account.
The mass of HIP65426b is found to be Mp = 9.9 +1.1 -1.8 MJ using the hot
population and Mp = 10.9 +1.4 -2.0 MJ with the cold-nominal population. Core
formation at small separations from the star followed by outward scattering and
runaway accretion at a few hundred AU succeeds in reproducing the mass and
separation of HIP65426b. Alternatively, systems having two or more giant
planets close enough to be on an unstable orbit at disc dispersal are likely to
end up with one planet on a wide HIP65426b-like orbit with a relatively high
eccentricity (>~ 0.5).
If this scattering scenario explains its formation, HIP65426b is predicted to
have a high eccentricity and to be accompanied by one or several roughly
Jovian-mass planets at smaller semi-major axes, which also could have a high
eccentricity. This could be tested by further direct-imaging as well as
radial-velocity observations.Comment: 17 pages, 11 figures. A&A in press. Bern EXoplanet cooling curves
(BEX) available upon request. v2: Language and other minor changes; Fig. 4
now has labels summarising a possible formation pathway discussed in the tex
Witnessing causal nonseparability
Our common understanding of the physical world deeply relies on the notion
that events are ordered with respect to some time parameter, with past events
serving as causes for future ones. Nonetheless, it was recently found that it
is possible to formulate quantum mechanics without any reference to a global
time or causal structure. The resulting framework includes new kinds of quantum
resources that allow performing tasks - in particular, the violation of causal
inequalities - which are impossible for events ordered according to a global
causal order. However, no physical implementation of such resources is known.
Here we show that a recently demonstrated resource for quantum computation -
the quantum switch - is a genuine example of "indefinite causal order". We do
this by introducing a new tool - the causal witness - which can detect the
causal nonseparability of any quantum resource that is incompatible with a
definite causal order. We show however that the quantum switch does not violate
any causal nequality.Comment: 15 + 12 pages, 5 figures. Published versio
User-assisted intrinsic images
For many computational photography applications, the lighting and
materials in the scene are critical pieces of information. We seek
to obtain intrinsic images, which decompose a photo into the product
of an illumination component that represents lighting effects
and a reflectance component that is the color of the observed material.
This is an under-constrained problem and automatic methods
are challenged by complex natural images. We describe a new
approach that enables users to guide an optimization with simple
indications such as regions of constant reflectance or illumination.
Based on a simple assumption on local reflectance distributions, we
derive a new propagation energy that enables a closed form solution
using linear least-squares. We achieve fast performance by introducing
a novel downsampling that preserves local color distributions.
We demonstrate intrinsic image decomposition on a variety
of images and show applications.National Science Foundation (U.S.) (NSF CAREER award 0447561)Institut national de recherche en informatique et en automatique (France) (Associate Research Team “Flexible Rendering”)Microsoft Research (New Faculty Fellowship)Alfred P. Sloan Foundation (Research Fellowship)Quanta Computer, Inc. (MIT-Quanta T Party
A multicountry randomized controlled trial of comprehensive maternal nutrition supplementation initiated before conception: the Women First trial.
Background: Reported benefits of maternal nutrition supplements commenced during pregnancy in low-resource populations have typically been quite limited.
Objectives: This study tested the effects on newborn size, especially length, of commencing nutrition supplements for women in low-resource populations ≥3 mo before conception (Arm 1), compared with the same supplement commenced late in the first trimester of pregnancy (Arm 2) or not at all (control Arm 3).
Methods: Women First was a 3-arm individualized randomized controlled trial (RCT). The intervention was a lipid-based micronutrient supplement; a protein-energy supplement was also provided if maternal body mass index (kg/m2) was(DRC), Guatemala, India, and Pakistan. The primary outcome was length-for-age z score (LAZ), with all anthropometry obtainedDRC, outcomes were determined for all 4 sites from WHO newborn standards (non-gestational-age-adjusted, NGAA) as well as INTERGROWTH-21st fetal standards (3 sites, gestational age-adjusted, GAA).
Results: A total of 7387 nonpregnant women were randomly assigned, yielding 2451 births with NGAA primary outcomes and 1465 with GAA outcomes. Mean LAZ and other outcomes did not differ between Arm 1 and Arm 2 using either NGAA or GAA. Mean LAZ (NGAA) for Arm 1 was greater than for Arm 3 (effect size: +0.19; 95% CI: 0.08, 0.30, P = 0.0008). For GAA outcomes, rates of stunting and small-for-gestational-age were lower in Arm 1 than in Arm 3 (RR: 0.69; 95% CI: 0.49, 0.98, P = 0.0361 and RR: 0.78; 95% CI: 0.70, 0.88, P \u3c 0.001, respectively). Rates of preterm birth did not differ among arms.
Conclusions: In low-resource populations, benefits on fetal growth-related birth outcomes were derived from nutrition supplements commenced before conception or late in the first trimester. This trial was registered at clinicaltrials.gov as NCT01883193
Covalent organic frameworks
The first members of covalent organic frameworks (COF) have been designed and successfully synthesized by
condensation reactions of phenyl diboronic acid C6H4[B(OH)2]2 and hexahydroxytriphenylene C18H6(OH)6. The
high crystallinity of the products (C3H2BO)6 (C9H12)1 (COF-1) and C9H4BO2 (COF-5) has allowed definitive
resolution of their structure by powder X-ray diffraction methods which reveal expanded porous graphitic layers that
are either staggered (COF-1, P63/mmc) or eclipsed (COF-5, P6/mmm). They exhibit high thermal stability (to
temperatures up to 500- to 600-C), permanent porosity, and high surface areas (711 and 1590 m2/g, respectively)
surpassing those of related inorganic frameworks. A similar approach has been used for the design of other extended
structures
Improving coastal livelihoods through sustainable aquaculture practices - a report to the collaborative APEC Grouper Research and Development Network
Wild-harvest fisheries for live reef fish are largely over-exploited or unsustainable because of over-fishing and the widespread use of destructive fishing practices such as blast and cyanide fishing. Sustainable aquaculture – such as that of groupers – is one option for meeting the
strong demand for reef fish, as well as potentially maintaining or improving the livelihoods of coastal communities. This report from a short study by the STREAM Initiative draws on secondary literature, media sources and four diverse case studies from at-risk reef fisheries, to frame a strategy for encouraging sustainable aquaculture as an alternative to destructive fishing practices. It was undertaken as a component of the APEC-funded project Collaborative Grouper Research and Development Network (FWG/01/2001) to better understand how recent technical advances in grouper culture and other complementary work – including that of the Asia-Pacific Marine Finfish Aquaculture Network (APMFAN) hosted by NACA – could better support the livelihoods of poor coastal communities. (PDF contains 49 pages
Bioportal: Ontologies and integrated data resources at the click of the mouse
BioPortal is a Web portal that provides access to a library of biomedical ontologies and terminologies developed in OWL, RDF(S), OBO format, Protégé frames, and Rich Release Format. BioPortal functionality, driven by a service-oriented architecture, includes the ability to browse, search and visualize ontologies (Figure 1). The Web interface also facilitates community-based participation in the evaluation and evolution of ontology content
Metal-organic and covalent organic frameworks (MOFs and COFs) as adsorbents for environmentally significant gases (H2, CO2, and CH4)
A series of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) possessing
various functionalities, pore structures, and surface areas were evaluated for sorption and storage
properties of environmentally significant gases (H_2, CO_2, and CH_4). It was concluded that the gas
sorption behavior follows a general trend that materials with high surface area show enhanced gas
uptake performance. For example, MOF-177 (SA = 5200 m^2/g) captures 7.2 wt% of H_2 at 77 K and 19
wt% of CH_4 at 298 K. In addition, MOF-177 exhibits exceptionally high gravimetric CO_2 uptake up to
120 wt% at 298 K. Similarly, the gas storage capacity for COFs seems to follow the same trend and it is
determined by the apparent surface area. The architectural stability of both COFs and MOFs upon high
pressure H_2 and CH_4 gas sorption measurements were manifested by isotherms which reach saturation
without significant hysteresis
Analytic Metaphysics versus Naturalized Metaphysics: The Relevance of Applied Ontology
The relevance of analytic metaphysics has come under criticism: Ladyman & Ross, for instance, have suggested do discontinue the field. French & McKenzie have argued in defense of analytic metaphysics that it develops tools that could turn out to be useful for philosophy of physics. In this article, we show first that this heuristic defense of metaphysics can be extended to the scientific field of applied ontology, which uses constructs from analytic metaphysics. Second, we elaborate on a parallel by French & McKenzie between mathematics and metaphysics to show that the whole field of analytic metaphysics, being useful not only for philosophy but also for science, should continue to exist as a largely autonomous field
Low-dose aspirin for the prevention of preterm delivery in nulliparous women with a singleton pregnancy (ASPIRIN): a randomised, double-blind, placebo-controlled trial.
BACKGROUND: Preterm birth remains a common cause of neonatal mortality, with a disproportionately high burden in low-income and middle-income countries. Meta-analyses of low-dose aspirin to prevent pre-eclampsia suggest that the incidence of preterm birth might also be decreased, particularly if initiated before 16 weeks of gestation.
METHODS: ASPIRIN was a randomised, multicountry, double-masked, placebo-controlled trial of low-dose aspirin (81 mg daily) initiated between 6 weeks and 0 days of pregnancy, and 13 weeks and 6 days of pregnancy, in nulliparous women with an ultrasound confirming gestational age and a singleton viable pregnancy. Participants were enrolled at seven community sites in six countries (two sites in India and one site each in the Democratic Republic of the Congo, Guatemala, Kenya, Pakistan, and Zambia). Participants were randomly assigned (1:1, stratified by site) to receive aspirin or placebo tablets of identical appearance, via a sequence generated centrally by the data coordinating centre at Research Triangle Institute International (Research Triangle Park, NC, USA). Treatment was masked to research staff, health providers, and patients, and continued until 36 weeks and 7 days of gestation or delivery. The primary outcome of incidence of preterm birth, defined as the number of deliveries before 37 weeks\u27 gestational age, was analysed in randomly assigned women with pregnancy outcomes at or after 20 weeks, according to a modified intention-to-treat (mITT) protocol. Analyses of our binary primary outcome involved a Cochran-Mantel-Haenszel test stratified by site, and generalised linear models to obtain relative risk (RR) estimates and associated confidence intervals. Serious adverse events were assessed in all women who received at least one dose of drug or placebo. This study is registered with ClinicalTrials.gov, NCT02409680, and the Clinical Trial Registry-India, CTRI/2016/05/006970.
FINDINGS: From March 23, 2016 to June 30, 2018, 14 361 women were screened for inclusion and 11 976 women aged 14-40 years were randomly assigned to receive low-dose aspirin (5990 women) or placebo (5986 women). 5780 women in the aspirin group and 5764 in the placebo group were evaluable for the primary outcome. Preterm birth before 37 weeks occurred in 668 (11·6%) of the women who took aspirin and 754 (13·1%) of those who took placebo (RR 0·89 [95% CI 0·81 to 0·98], p=0·012). In women taking aspirin, we also observed significant reductions in perinatal mortality (0·86 [0·73-1·00], p=0·048), fetal loss (infant death after 16 weeks\u27 gestation and before 7 days post partum; 0·86 [0·74-1·00], p=0·039), early preterm delivery (\u3c34 \u3eweeks; 0·75 [0·61-0·93], p=0·039), and the incidence of women who delivered before 34 weeks with hypertensive disorders of pregnancy (0·38 [0·17-0·85], p=0·015). Other adverse maternal and neonatal events were similar between the two groups.
INTERPRETATION: In populations of nulliparous women with singleton pregnancies from low-income and middle-income countries, low-dose aspirin initiated between 6 weeks and 0 days of gestation and 13 weeks and 6 days of gestation resulted in a reduced incidence of preterm delivery before 37 weeks, and reduced perinatal mortality.
FUNDING: Eunice Kennedy Shriver National Institute of Child Health and Human Development
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