Hormonal contraceptive use and the risk of sexually transmitted infections: a systematic review and meta-analysis

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Constraints on the Stellar/Sub-stellar Mass Function in the Inner Orion Nebula Cluster

We present the results of a 0.5-0.9" FWHM imaging survey at K (2.2 micron) and H (1.6 micron) covering 5.1' x 5.1' centered on Theta 1C Ori, the most massive star in the Orion Nebula Cluster (ONC). At the age and distance of this cluster, and in the absence of extinction, the hydrogen burning limit (0.08 Mo) occurs at K~13.5 mag while an object of mass 0.02 Mo has K~16.2 mag. Our photometry is complete for source detection at the 7 sigma level to K~17.5 mag and thus is sensitive to objects as low-mass as 0.02 Mo seen through visual extinction values as high as 10 magnitudes. We use the observed magnitudes, colors, and star counts to constrain the shape of the inner ONC stellar mass function across the hydrogen burning limit. After determining the stellar age and near-infrared excess properties of the optically visible stars in this same inner ONC region, we present a new technique that incorporates these distributions when extracting the mass function from the observed density of stars in the K-(H-K) diagram. We find that our data are inconsistent with a mass function that rises across the stellar/sub-stellar boundary. Instead, we find that the most likely form of the inner ONC mass function is one that rises to a peak around 0.15 Mo, and then declines across the hydrogen-burning limit with slope N(log M) ~ M^(0.57+/-0.05). We emphasize that our conclusions apply to the inner 0.71 pc x 0.71 pc of the ONC only; they may not apply to the ONC as a whole where some evidence for general mass segregation has been found.Comment: Accepted for publication in the Astrophysical Journal. Preprints/tables also available at http://phobos.caltech.edu/~jmc/papers/onc

Improving access to emergency contraception pills through strengthening service delivery and demand generation: A systematic review of current evidence in low and middle-income countries

© 2014 Dawson et al. Objectives: Emergency contraception pills (ECP) are among the 13 essential commodities in the framework for action established by the UN Commission on Life-Saving Commodities for Women and Children. Despite having been on the market for nearly 20 years, a number of barriers still limit women's access to ECP in low- and middle-income countries (LMIC) including limited consumer knowledge and poor availability. This paper reports the results of a review to synthesise the current evidence on service delivery strategies to improve access to ECP.Methods: A narrative synthesis methodology was used to examine peer reviewed research literature (2003 to 2013) from diverse methodological traditions to provide critical insights into strategies to improve access from a service delivery perspective. The studies were appraised using established scoring systems and the findings of included papers thematically analysed and patterns mapped across all findings using concept mapping.Findings: Ten papers were included in the review. Despite limited research of adequate quality, promising strategies to improve access were identified including: advance provision of ECP; task shifting and sharing; intersectoral collaboration for sexual assault; m-health for information provision; and scale up through national family planning programs.Conclusion: There are a number of gaps in the research concerning service delivery and ECP in LMIC. These include a lack of knowledge concerning private/commercial sector contributions to improving access, the needs of vulnerable groups of women, approaches to enhancing intersectoral collaboration, evidence for social marketing models and investment cases for ECP

Workforce interventions to improve access to emergency contraception pills: A systematic review of current evidence in low- and middle-income countries and recommendations for improving performance Health systems and services in low and middle income settings

© 2015 Dawson et al.; licensee BioMed Central. Background: Emergency contraceptive pills (ECP) are one of the 13 essential commodities addressed by the UN Commission on Life-Saving Commodities for Women and Children. Although ECP have been available for 20 years, a number of barriers still limit women's access ECP in low and middle-income countries (LMIC). The workforce who prescribe or dispense ECP are diverse reflecting the varied contexts where ECP are available across the health, commercial and justice sectors and in the community. No reviews currently exist that examine the roles and experiences of the workforce that provide ECP in LMIC. Method: We present a narrative synthesis of research to: identify provider factors that facilitate and constraint access to ECP; assess the effectiveness of associated interventions and; explore associated health system issues in LMIC. A search of bibliographic databases, meta-indexes and websites was undertaken to retrieve peer reviewed and grey literature. Literature was screened and identified documents examined to appraise quality. Results: Thirty-seven documents were included in the review. Studies focused on formal health workers revealing knowledge gaps concerning the role of private sector and non-health providers who increasingly provide ECP. Data from the findings section in the documents were coded under 4 themes: provider knowledge; provider attitudes and beliefs; provider practice and provider training. The analysis revealed provider knowledge gaps, less than favourable attitudes and practice issues. The findings provide limited insight into products prescribed and/or dispensed, the frequency of provision, and information and advice offered to consumers. Pre and in-service training needs were noted. Conclusion: As the provision of ECPs shifts from the clinic-based health sector to increasing provision by the private sector, the limited understanding of provider performance and the practice gaps revealed in this review highlight the need to further examine provider performance to inform the development of appropriate workforce interventions. A standardized approach to assessing performance using agreed outcomes measures may serve to ensure a systematic way forward that is inclusive of the diverse workforce that deliver ECP. Recommendations are outlined to enhance the performance of providers to improve access to ECP. A framework is offered to help guide this process with indicators

First Detection of Millimeter Dust Emission from Brown Dwarf Disks

We report results from the first deep millimeter continuum survey targeting Brown Dwarfs (BDs). The survey led to the first detection of cold dust in the disks around two young BDs (CFHT-BD-Tau 4 and IC348 613), with deep JCMT and IRAM observations reaching flux levels of a few mJy. The dust masses are estimated to be a few Earth masses assuming the same dust opacities as usually applied to TTauri stars.Comment: 5 pages, accepted for ApJ

An HST/WFPC2 Survey for Brown Dwarf Binaries in the alpha Per and the Pleiades Open Clusters

We present the results of a high-resolution imaging survey for brown dwarf (BD) binaries in two open clusters. The observations were carried out with WFPC2 onboard HST. Our sample consists of 8 BD candidates in the alpha Per cluster and 25 BD candidates in the Pleiades. We have resolved 4 binaries in the Pleiades with separations in the range 0".094--0".058, corresponding to projected separations between 11.7~AU and 7.2~AU. No binaries were found among the alpha Per targets. Three of the binaries have proper motions consistent with cluster membership in the Pleiades cluster, and for one of them we report the detection of Halpha in emission and LiI absorption obtained from Keck~II/ESI spectroscopy. One of the binaries does not have a proper motion consistent with Pleiades membership. We estimate that BD binaries wider than 12~AU are less frequent than 9% in the alphaPer and Pleiades clusters. This is consistent with an extension to substellar masses of a trend observed among stellar binaries: the maximum semimajor axis of binary systems decreases with decreasing primary mass. We find a binary frequency of 2 binaries over 13 BDs with confirmed proper motion membership in the Pleiades, corresponding to a binary fraction of 15%(1 sigma error bar +15%/-5%). These binaries are limited to the separation range 7-12~AU and their mass ratios are larger than 0.7. The relatively high binary frequency (>10%), the bias to separations smaller than about 15 AU and the trend to high mass ratios (q>0.7) are fundamental properties of BDs. Current theories of BD formation do not appear to provide a good description of all these properties.Comment: Accepted by ApJ (scheduled publication in volume 594, September 1, 2003

The Discovery of a Companion to the Very Cool Dwarf Gl~569~B with the Keck Adaptive Optics Facility

We report observations obtained with the Keck adaptive optics facility of the nearby (d=9.8 pc) binary Gl~569. The system was known to be composed of a cool primary (dM2) and a very cool secondary (dM8.5) with a separation of 5" (49 Astronomical Units). We have found that Gl~569~B is itself double with a separation of only 0".101$\pm$0".002 (1 Astronomical Unit). This detection demonstrates the superb spatial resolution that can be achieved with adaptive optics at Keck. The difference in brightness between Gl~569~B and the companion is $\sim$0.5 magnitudes in the J, H and K' bands. Thus, both objects have similarly red colors and very likely constitute a very low-mass binary system. For reasonable assumptions about the age (0.12~Gyr--1.0~Gyr) and total mass of the system (0.09~M$_\odot$--0.15~M$_\odot$), we estimate that the orbital period is $\sim$3 years. Follow-up observations will allow us to obtain an astrometric orbit solution and will yield direct dynamical masses that can constrain evolutionary models of very low-mass stars and brown dwarfs

Optical Spectroscopy of the Surface Population of the rho Ophiuchi Molecular Cloud: The First Wave of Star Formation

We present the results of optical spectroscopy of 139 stars obtained with the Hydra multi-object spectrograph. The objects extend over a 1.3 square degree area surrounding the main cloud of the rho Oph complex. The objects were selected from narrowband images to have H alpha in emission. Using the presence of strong H alpha emission, lithium absorption, location in the Hertzsprung-Russell diagram, or previously reported x-ray emission, we were able to identify 88 objects as young stars associated with the cloud. Strong H alpha emission was confirmed in 39 objects with line widths consistent with their origin in magnetospheric accretion columns. Two of the strongest emission-line objects are young, x-ray emitting brown dwarf candidates with M8 spectral types. Comparisons of the bolometric luminosities and effective temperatures with theoretical models suggest a medianage for this population of 2.1 Myr which is signifcantly older than the ages derived for objects in the cloud core. It appears that these stars formed contemporaneously with low mass stars in the Upper Scorpius subgroup, likely triggered by massive stars in the Upper-Centaurus subgroup.Comment: 35 pages of postscript which includes seven figures (some of which are multi-panel) and four postscript tables. Astronomical Journal (in press

The orbit of the brown dwarf binary Gl 569B

We present photometric, astrometric and spectroscopic observations of the nearby (9.8 pc) low-mass binary Gl 569Bab (in turn being a companion to the early-M star Gl 569A), made with the Keck adaptive optics facility. Having observed Gl 569Bab since August 1999, we are able to see orbital motion and to determine the orbital parameters of the pair. We find the orbital period to be 892 +/- 25 days, the semi-major axis to be 0.90 +/- 0.02 AU, the eccentricity to be 0.32 +/- 0.02 and the inclination of the system to be 34+/- 3 degrees (1-sigma). The total mass is found to be 0.123 (-0.022/+0.027) Msun (3-sigma). In addition, we have obtained low resolution (R=1500-1700) near-infrared spectra of each of the components in the J- and K-bands. We determine the spectral types of the objects to be M8.5V (Gl 569Ba) and M9V (Gl 569Bb) with an uncertainty of half a subclass. We also present new J- and K-band photometry which allows us to accurately place the objects in the HR diagram. Most likely the binary system is comprised of two brown dwarfs with a mass ratio of 0.89 and with an age of approximately 300 Myr.Comment: Accepted for publication in ApJ, 28 pages, figures include

Membership and Multiplicity among Very Low-Mass Stars and Brown Dwarfs in the Pleiades Cluster

We present near-infrared photometry and optical spectroscopy of very low-mass stars and brown dwarf candidates in the Pleiades open cluster. The membership status of these objects is assessed. Eight objects out of 45 appear to be non-members. A search for companions among 34 very low-mass Pleiades members (M$\le$0.09 M$_\odot$) in high-spatial resolution images obtained with the Hubble Space Telescope and the adaptive optics system of the Canada-France-Hawaii telescope produced no resolved binaries with separations larger than 0.2 arcsec (a ~ 27 AU; P ~ 444 years). Nevertheless, we find evidence for a binary sequence in the color-magnitude diagrams, in agreement with the results of Steele & Jameson (1995) for higher mass stars. We compare the multiplicity statistics of the Pleiades very low-mass stars and brown dwarfs with that of G and K-type main sequence stars in the solar neighborhood (Duquennoy & Mayor 1991). We find that there is some evidence for a deficiency of wide binary systems (separation >27 AU) among the Pleiades very low-mass members. We briefly discuss how this result can fit with current scenarios of brown dwarf formation. We correct the Pleiades substellar mass function for the contamination of cluster non-members found in this work. We find a contamination level of 33% among the brown dwarf candidates identified by Bouvier et al. (1998). Assuming a power law IMF across the substellar boundary, we find a slope dN/dM ~ M^{-0.53}, implying that the number of objects per mass bin is still rising but the contribution to the total mass of the cluster is declining in the brown dwarf regime.Comment: to be published in The Astrophysical Journa