134 research outputs found
The Solar Neighborhood. XXXIV. A Search for Planets Orbiting Nearby M Dwarfs using Astrometry
Astrometric measurements are presented for seven nearby stars with previously
detected planets: six M dwarfs (GJ 317, GJ 667C, GJ 581, GJ 849, GJ 876, and GJ
1214) and one K dwarf (BD 10 3166). Measurements are also presented for six
additional nearby M dwarfs without known planets, but which are more favorable
to astrometric detections of low mass companions, as well as three binary
systems for which we provide astrometric orbit solutions. Observations have
baselines of three to thirteen years, and were made as part of the RECONS
long-term astrometry and photometry program at the CTIO/SMARTS 0.9m telescope.
We provide trigonometric parallaxes and proper motions for all 16 systems, and
perform an extensive analysis of the astrometric residuals to determine the
minimum detectable companion mass for the 12 M dwarfs not having close stellar
secondaries. For the six M dwarfs with known planets, we are not sensitive to
planets, but can rule out the presence of all but the least massive brown
dwarfs at periods of 2 - 12 years. For the six more astrometrically favorable M
dwarfs, we conclude that none have brown dwarf companions, and are sensitive to
companions with masses as low as 1 for periods longer than two years.
In particular, we conclude that Proxima Centauri has no Jovian companions at
orbital periods of 2 - 12 years. These results complement previously published
M dwarf planet occurrence rates by providing astrometrically determined upper
mass limits on potential super-Jupiter companions at orbits of two years and
longer. As part of a continuing survey, these results are consistent with the
paucity of super-Jupiter and brown dwarf companions we find among the over 250
red dwarfs within 25 pc observed longer than five years in our astrometric
program.Comment: 18 pages, 5 figures, 4 tables, accepted for publication in A
Delays in diagnosis and treatment of pulmonary tuberculosis in patients seeking care at a regional referral hospital, Uganda : a cross sectional study
This study was funded using Authors’ personal resources.Objective: A cross-sectional survey involving 134 pulmonary TB patients started on TB treatment at the TB Treatment Unit of the regional referral hospital was conducted to ascertain the prevalence of individual and health facility delays and associated factors. Prolonged health facility delay was taken as delay of more than 1 week and prolonged patient delay as delay of more than 3 weeks. A logistic regression model was done using STATA version 12 to determine the delays. Results: There was a median total delay of 13 weeks and 110 (82.1%) of the respondents had delay of more than 4 weeks. Patient delay was the most frequent and greatest contributor of total delay and exceeded 3 weeks in 95 (71.6%) respondents. At multivariate analysis, factors that influenced delay included poor patient knowledge on TB (adjOR 6.904, 95% CI 1.648-28.921; p = 0.04) and being unemployed (adjOR 3.947, 95% CI 1.382-11.274; p = 0.010) while being female was found protective of delay; adjOR 0.231, 95% CI 0.08-0.67; p = 0.007). Patient delay was the most significant, frequent and greatest contributor to total delay, and factors associated with delay included being unemployed, low knowledge on TB while being female was found protective of delay.Publisher PDFPeer reviewe
Genotype, development and tissue-derived variation of cell-wall properties in the lignocellulosic energy crop Miscanthus
BACKGROUND AND AIMS: Species and hybrids of the genus Miscanthus contain attributes that make them front-runners among current selections of dedicated bioenergy crops. A key trait for plant biomass conversion to biofuels and biomaterials is cell-wall quality; however, knowledge of cell-wall composition and biology in Miscanthus species is limited. This study presents data on cell-wall compositional changes as a function of development and tissue type across selected genotypes, and considers implications for the development of miscanthus as a sustainable and renewable bioenergy feedstock. METHODS: Cell-wall biomass was analysed for 25 genotypes, considering different developmental stages and stem vs. leaf compositional variability, by Fourier transform mid-infrared spectroscopy and lignin determination. In addition, a Clostridium phytofermentans bioassay was used to assess cell-wall digestibility and conversion to ethanol. KEY RESULTS: Important cell-wall compositional differences between miscanthus stem and leaf samples were found to be predominantly associated with structural carbohydrates. Lignin content increased as plants matured and was higher in stem tissues. Although stem lignin concentration correlated inversely with ethanol production, no such correlation was observed for leaves. Leaf tissue contributed significantly to total above-ground biomass at all stages, although the extent of this contribution was genotype-dependent. CONCLUSIONS: It is hypothesized that divergent carbohydrate compositions and modifications in stem and leaf tissues are major determinants for observed differences in cell-wall quality. The findings indicate that improvement of lignocellulosic feedstocks should encompass tissue-dependent variation as it affects amenability to biological conversion. For gene–trait associations relating to cell-wall quality, the data support the separate examination of leaf and stem composition, as tissue-specific traits may be masked by considering only total above-ground biomass samples, and sample variability could be mostly due to varying tissue contributions to total biomass
A cell wall reference profile for Miscanthus bioenergy crops highlights compositional and structural variations associated with development and organ origin
Miscanthus spp. are promising lignocellulosic energy crops, but cell wall recalcitrance to deconstruction still hinders their widespread use as bioenergy and biomaterial feedstocks. Identification of cell wall characteristics desirable for biorefining applications is crucial for lignocellulosic biomass improvement. However, the task of scoring biomass quality is often complicated by the lack of a reference for a given feedstock. A multidimensional cell wall analysis was performed to generate a reference profile for leaf and stem biomass from several miscanthus genotypes harvested at three developmentally distinct time points. A comprehensive suite of 155 monoclonal antibodies was used to monitor changes in distribution, structure and extractability of noncellulosic cell wall matrix glycans. Glycan microarrays complemented with immunohistochemistry elucidated the nature of compositional variation, and in situ distribution of carbohydrate epitopes. Key observations demonstrated that there are crucial differences in miscanthus cell wall glycomes, which may impact biomass amenability to deconstruction. For the first time, variations in miscanthus cell wall glycan components were comprehensively characterized across different harvests, organs and genotypes, to generate a representative reference profile for miscanthus cell wall biomass. Ultimately, this portrait of the miscanthus cell wall will help to steer breeding and genetic engineering strategies for the development of superior energy crops
TESS Discovery of an ultra-short-period planet around the nearby M dwarf LHS 3844
Data from the newly-commissioned \textit{Transiting Exoplanet Survey
Satellite} (TESS) has revealed a "hot Earth" around LHS 3844, an M dwarf
located 15 pc away. The planet has a radius of and
orbits the star every 11 hours. Although the existence of an atmosphere around
such a strongly irradiated planet is questionable, the star is bright enough
(, ) for this possibility to be investigated with transit and
occultation spectroscopy. The star's brightness and the planet's short period
will also facilitate the measurement of the planet's mass through Doppler
spectroscopy.Comment: 10 pages, 4 figures. Submitted to ApJ Letters. This letter makes use
of the TESS Alert data, which is currently in a beta test phase, using data
from the pipelines at the TESS Science Office and at the TESS Science
Processing Operations Cente
Observations of Binary Stars with the Differential Speckle Survey Instrument. IX. Observations of Known and Suspected Binaries, and a Partial Survey of Be Stars
We report 370 measures of 170 components of binary and multiple star systems,
obtained from speckle imaging observations made with the Differential Speckle
Survey Instrument at Lowell Observatory's Discovery Channel Telescope in 2015
through 2017. Of the systems studied, 147 are binary stars, 10 are seen as
triple systems, and 1 quadruple system is measured. Seventy-six high-quality
non-detections and fifteen newly resolved components are presented in our
observations. The uncertainty in relative astrometry appears to be similar to
our previous work at Lowell, namely linear measurement uncertainties of
approximately 2 mas, and the relative photometry appears to be uncertain at the
0.1 to 0.15 magnitude level. Using these measures and those in the literature,
we calculate six new visual orbits, including one for the Be star 66 Oph, and
two combined spectroscopic-visual orbits. The latter two orbits, which are for
HD 22451 (YSC 127) and HD 185501 (YSC 135), yield individual masses of the
components at the level of 2 percent or better, and independent distance
measures that in one case agrees with the value found in the Gaia DR2, and in
the other disagrees at the 2- level. We find that HD 22451 consists of
an F6V+F7V pair with orbital period of days and masses of
and . For HD 185501, both stars
are G5 dwarfs that orbit one another with a period of days,
and the masses are and . We
discuss the details of both the new discoveries and the orbit objects
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Characteristics and outcomes of admitted patients infected with SARS-CoV-2 in Uganda
© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.Rationale: Detailed data on the characteristics and outcomes of patients with COVID-19 in sub-Saharan Africa are limited. Objective: We determined the clinical characteristics and treatment outcomes of patients diagnosed with COVID-19 in Uganda . Measurements: As of the 16 May 2020, a total of 203 cases had been confirmed. We report on the first 56 patients; 29 received hydroxychloroquine (HCQ) and 27 did not. Endpoints included admission to intensive care, mechanical ventilation or death during hospitalisation. Main results: The median age was 34.2 years; 67.9% were male; and 14.6% were 130/90 mm Hg, and 27.8% had BP of >140/90 mm Hg. Laboratory derangements were leucopenia (10.6%), lymphopenia (11.1%) and thrombocytopenia (26.3%). Abnormal chest X-ray was observed in 14.3%. No patients reached the primary endpoint. Time to clinical recovery was shorter among patients who received HCQ, but this difference did not reach statistical significance. Conclusion: Most of the patients with COVID-19 presented with mild disease and exhibited a clinical trajectory not similar to other countries. Outcomes did not differ by HCQ treatment status in line with other concluded studies on the benefit of using HCQ in the treatment of COVID-19.Publisher PDFPeer reviewe
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