Abstract
Stellar distances constitute a foundational pillar of astrophysics. The publication of 1.47 billion stellar parallaxes from Gaia is a major contribution to this. Despite Gaia’s precision, ...the majority of these stars are so distant or faint that their fractional parallax uncertainties are large, thereby precluding a simple inversion of parallax to provide a distance. Here we take a probabilistic approach to estimating stellar distances that uses a prior constructed from a three-dimensional model of our Galaxy. This model includes interstellar extinction and Gaia’s variable magnitude limit. We infer two types of distance. The first, geometric, uses the parallax with a direction-dependent prior on distance. The second, photogeometric, additionally uses the color and apparent magnitude of a star, by exploiting the fact that stars of a given color have a restricted range of probable absolute magnitudes (plus extinction). Tests on simulated data and external validations show that the photogeometric estimates generally have higher accuracy and precision for stars with poor parallaxes. We provide a catalog of 1.47 billion geometric and 1.35 billion photogeometric distances together with asymmetric uncertainty measures. Our estimates are quantiles of a posterior probability distribution, so they transform invariably and can therefore also be used directly in the distance modulus (
). The catalog may be downloaded or queried using ADQL at various sites (see
http://www.mpia.de/~calj/gedr3_distances.html
), where it can also be cross-matched with the Gaia catalog.
For the vast majority of stars in the second Gaia data release, reliable distances cannot be obtained by inverting the parallax. A correct inference procedure must instead be used to account for the ...nonlinearity of the transformation and the asymmetry of the resulting probability distribution. Here, we infer distances to essentially all 1.33 billion stars with parallaxes published in the second Gaia data release. This is done using a weak distance prior that varies smoothly as a function of Galactic longitude and latitude according to a Galaxy model. The irreducible uncertainty in the distance estimate is characterized by the lower and upper bounds of an asymmetric confidence interval. Although more precise distances can be estimated for a subset of the stars using additional data (such as photometry), our goal is to provide purely geometric distance estimates, independent of assumptions about the physical properties of, or interstellar extinction toward, individual stars. We analyze the characteristics of the catalog and validate it using clusters. The catalog can be queried using ADQL at http://gaia.ari.uni-heidelberg.de/tap.html (which also hosts the Gaia catalog) and downloaded from http://www.mpia.de/~calj/gdr2_distances.html.
Purpose: To develop and validate criterion-referenced fitness standards for older adults that predict the level of capacity needed for maintaining physical independence into later life. The proposed ...standards were developed for use with a previously validated test battery for older adults--the Senior Fitness Test (Rikli, R. E., & Jones, C. J. (2001). Development and validation of a functional fitness test for community-residing older adults. Journal of Aging and Physical Activity, 6, 127-159; Rikli, R. E., & Jones, C. J. (1999a). Senior fitness test manual. Champaign, IL: Human Kinetics.). Methods: A criterion measure to assess physical independence was identified. Next, scores from a subset of 2,140 "moderate-functioning" older adults from a larger cross-sectional database, together with findings from longitudinal research on physical capacity and aging, were used as the basis for proposing fitness standards (performance cut points) associated with having the ability to function independently. Validity and reliability analyses were conducted to test the standards for their accuracy and consistency as predictors of physical independence. Results: Performance standards are presented for men and women ages 60-94 indicating the level of fitness associated with remaining physically independent until late in life. Reliability and validity indicators for the standards ranged between 0.79 and 0.97. Implications: The proposed standards provide easy-to-use, previously unavailable methods for evaluating physical capacity in older adults relative to that associated with physical independence. Most importantly, the standards can be used in planning interventions that target specific areas of weakness, thus reducing risk for premature loss of mobility and independence.
The frequency of COPD exacerbations during treatment with a triple inhaler — delivering a long-acting beta-agonist (LABA), a long-acting muscarinic antagonist (LAMA), and an inhaled glucocorticoid — ...was compared with that with a LABA–LAMA or LABA–inhaled glucocorticoid.
Global forest restoration targets have been set, yet policy makers and land managers lack guiding principles on how to invest limited resources to achieve them. We conducted a meta-analysis of 166 ...studies in naturally regenerating and actively restored forests worldwide to answer: (1) To what extent do floral and faunal abundance and diversity and biogeochemical functions recover? (2) Does recovery vary as a function of past land use, time since restoration, forest region, or precipitation? (3) Does active restoration result in more complete or faster recovery than passive restoration? Overall, forests showed a high level of recovery, but the time to recovery depended on the metric type measured, past land use, and region. Abundance recovered quickly and completely, whereas diversity recovered slower in tropical than in temperate forests. Biogeochemical functions recovered more slowly after agriculture than after logging or mining. Formerly logged sites were mostly passively restored and generally recovered quickly. Mined sites were nearly always actively restored using a combination of planting and either soil amendments or recontouring topography, which resulted in rapid recovery of the metrics evaluated. Actively restoring former agricultural land, primarily by planting trees, did not result in consistently faster or more complete recovery than passively restored sites. Our results suggest that simply ending the land use is sufficient for forests to recover in many cases, but more studies are needed that directly compare the value added of active versus passive restoration strategies in the same system. Investments in active restoration should be evaluated relative to the past land use, the natural resilience of the system, and the specific objectives of each project.
Hundreds of stellar-mass black holes probably form in a typical globular star cluster, with all but one predicted to be ejected through dynamical interactions. Some observational support for this ...idea is provided by the lack of X-ray-emitting binary stars comprising one black hole and one other star ('black-hole/X-ray binaries') in Milky Way globular clusters, even though many neutron-star/X-ray binaries are known. Although a few black holes have been seen in globular clusters around other galaxies, the masses of these cannot be determined, and some may be intermediate-mass black holes that form through exotic mechanisms. Here we report the presence of two flat-spectrum radio sources in the Milky Way globular cluster M22, and we argue that these objects are black holes of stellar mass (each ∼10-20 times more massive than the Sun) that are accreting matter. We find a high ratio of radio-to-X-ray flux for these black holes, consistent with the larger predicted masses of black holes in globular clusters compared to those outside. The identification of two black holes in one cluster shows that ejection of black holes is not as efficient as predicted by most models, and we argue that M22 may contain a total population of ∼5-100 black holes. The large core radius of M22 could arise from heating produced by the black holes.
Gaia Data Release 2 Luri, X.; Brown, A. G. A.; Sarro, L. M. ...
Astronomy and astrophysics (Berlin),
08/2018, Letnik:
616
Journal Article
Recenzirano
Odprti dostop
Context.
The second
Gaia
data release (
Gaia
DR2) provides precise five-parameter astrometric data (positions, proper motions, and parallaxes) for an unprecedented number of sources (more than 1.3 ...billion, mostly stars). This new wealth of data will enable the undertaking of statistical analysis of many astrophysical problems that were previously infeasible for lack of reliable astrometry, and in particular because of the lack of parallaxes. However, the use of this wealth of astrometric data comes with a specific challenge: how can the astrophysical parameters of interest be properly inferred from these data?
Aims.
The main focus of this paper, but not the only focus, is the issue of the estimation of distances from parallaxes, possibly combined with other information. We start with a critical review of the methods traditionally used to obtain distances from parallaxes and their shortcomings. Then we provide guidelines on how to use parallaxes more efficiently to estimate distances by using Bayesian methods. In particular we also show that negative parallaxes, or parallaxes with relatively large uncertainties still contain valuable information. Finally, we provide examples that show more generally how to use astrometric data for parameter estimation, including the combination of proper motions and parallaxes and the handling of covariances in the uncertainties.
Methods.
The paper contains examples based on simulated
Gaia
data to illustrate the problems and the solutions proposed. Furthermore, the developments and methods proposed in the paper are linked to a set of tutorials included in the
Gaia
archive documentation that provide practical examples and a good starting point for the application of the recommendations to actual problems. In all cases the source code for the analysis methods is provided.
Results.
Our main recommendation is to always treat the derivation of (astro-)physical parameters from astrometric data, in particular when parallaxes are involved, as an inference problem which should preferably be handled with a full Bayesian approach.
Conclusions.
Gaia
will provide fundamental data for many fields of astronomy. Further data releases will provide more data, and more precise data. Nevertheless, to fully use the potential it will always be necessary to pay careful attention to the statistical treatment of parallaxes and proper motions. The purpose of this paper is to help astronomers find the correct approach.
The world's staple food crops, and other food crops that optimize human nutrition, suffer from global virus disease pandemics and epidemics that greatly diminish their yields and/or produce quality. ...This situation is becoming increasingly serious because of the human population's growing food requirements and increasing difficulties in managing virus diseases effectively arising from global warming. This review provides historical and recent information about virus disease pandemics and major epidemics that originated within different world regions, spread to other continents, and now have very wide distributions. Because they threaten food security, all are cause for considerable concern for humanity. The pandemic disease examples described are six (maize lethal necrosis, rice tungro, sweet potato virus, banana bunchy top, citrus tristeza, plum pox). The major epidemic disease examples described are seven (wheat yellow dwarf, wheat streak mosaic, potato tuber necrotic ringspot, faba bean necrotic yellows, pepino mosaic, tomato brown rugose fruit, and cucumber green mottle mosaic). Most examples involve long-distance virus dispersal, albeit inadvertent, by international trade in seed or planting material. With every example, the factors responsible for its development, geographical distribution and global importance are explained. Finally, an overall explanation is given of how to manage global virus disease pandemics and epidemics effectively.
Animal models of schizophrenia Jones, CA; Watson, DJG; Fone, KCF
British journal of pharmacology,
October 2011, 2011-Oct, 2011-10-00, 20111001, Letnik:
164, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Developing reliable, predictive animal models for complex psychiatric disorders, such as schizophrenia, is essential to increase our understanding of the neurobiological basis of the disorder and for ...the development of novel drugs with improved therapeutic efficacy. All available animal models of schizophrenia fit into four different induction categories: developmental, drug‐induced, lesion or genetic manipulation, and the best characterized examples of each type are reviewed herein. Most rodent models have behavioural phenotype changes that resemble ‘positive‐like’ symptoms of schizophrenia, probably reflecting altered mesolimbic dopamine function, but fewer models also show altered social interaction, and learning and memory impairment, analogous to negative and cognitive symptoms of schizophrenia respectively. The negative and cognitive impairments in schizophrenia are resistant to treatment with current antipsychotics, even after remission of the psychosis, which limits their therapeutic efficacy. The MATRICS initiative developed a consensus on the core cognitive deficits of schizophrenic patients, and recommended a standardized test battery to evaluate them. More recently, work has begun to identify specific rodent behavioural tasks with translational relevance to specific cognitive domains affected in schizophrenia, and where available this review focuses on reporting the effect of current and potential antipsychotics on these tasks. The review also highlights the need to develop more comprehensive animal models that more adequately replicate deficits in negative and cognitive symptoms. Increasing information on the neurochemical and structural CNS changes accompanying each model will also help assess treatments that prevent the development of schizophrenia rather than treating the symptoms, another pivotal change required to enable new more effective therapeutic strategies to be developed.
LINKED ARTICLES This article is part of a themed issue on Translational Neuropharmacology. To view the other articles in this issue visit http://dx.doi.org/10.1111/bph.2011.164.issue‐4
The analgesic efficacy and adverse effects of a single perioperative dose of dexamethasone are unclear. We performed a systematic review to evaluate the impact of a single i.v. dose of dexamethasone ...on postoperative pain and explore adverse events associated with this treatment.
MEDLINE, EMBASE, CINAHL, and the Cochrane Register were searched for randomized, controlled studies that compared dexamethasone vs placebo or an antiemetic in adult patients undergoing general anaesthesia and reported pain outcomes.
Forty-five studies involving 5796 patients receiving dexamethasone 1.25–20 mg were included. Patients receiving dexamethasone had lower pain scores at 2 h {mean difference (MD) −0.49 95% confidence interval (CI): −0.83, −0.15} and 24 h MD −0.48 (95% CI: −0.62, −0.35) after surgery. Dexamethasone-treated patients used less opioids at 2 h MD −0.87 mg morphine equivalents (95% CI: −1.40 to −0.33) and 24 h MD −2.33 mg morphine equivalents (95% CI: −4.39, −0.26), required less rescue analgesia for intolerable pain relative risk 0.80 (95% CI: 0.69, 0.93), had longer time to first dose of analgesic MD 12.06 min (95% CI: 0.80, 23.32), and shorter stays in the post-anaesthesia care unit MD −5.32 min (95% CI: −10.49 to −0.15). There was no dose–response with regard to the opioid-sparing effect. There was no increase in infection or delayed wound healing with dexamethasone, but blood glucose levels were higher at 24 h MD 0.39 mmol litre−1 (95% CI: 0.04, 0.74).
A single i.v. perioperative dose of dexamethasone had small but statistically significant analgesic benefits.
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