448 research outputs found
Planetary Candidates Observed by Kepler V: Planet Sample from Q1-Q12 (36 Months)
The Kepler mission discovered 2842 exoplanet candidates with 2 years of data.
We provide updates to the Kepler planet candidate sample based upon 3 years
(Q1-Q12) of data. Through a series of tests to exclude false-positives,
primarily caused by eclipsing binary stars and instrumental systematics, 855
additional planetary candidates have been discovered, bringing the total number
known to 3697. We provide revised transit parameters and accompanying posterior
distributions based on a Markov Chain Monte Carlo algorithm for the cumulative
catalogue of Kepler Objects of Interest. There are now 130 candidates in the
cumulative catalogue that receive less than twice the flux the Earth receives
and more than 1100 have a radius less than 1.5 Rearth. There are now a dozen
candidates meeting both criteria, roughly doubling the number of candidate
Earth analogs. A majority of planetary candidates have a high probability of
being bonafide planets, however, there are populations of likely
false-positives. We discuss and suggest additional cuts that can be easily
applied to the catalogue to produce a set of planetary candidates with good
fidelity. The full catalogue is publicly available at the NASA Exoplanet
Archive.Comment: Accepted for publication, ApJ
Planetary Candidates Observed by Kepler. VII. The First Fully Uniform Catalog Based on The Entire 48 Month Dataset (Q1-Q17 DR24)
We present the seventh Kepler planet candidate catalog, which is the first to
be based on the entire, uniformly processed, 48 month Kepler dataset. This is
the first fully automated catalog, employing robotic vetting procedures to
uniformly evaluate every periodic signal detected by the Q1-Q17 Data Release 24
(DR24) Kepler pipeline. While we prioritize uniform vetting over the absolute
correctness of individual objects, we find that our robotic vetting is overall
comparable to, and in most cases is superior to, the human vetting procedures
employed by past catalogs. This catalog is the first to utilize artificial
transit injection to evaluate the performance of our vetting procedures and
quantify potential biases, which are essential for accurate computation of
planetary occurrence rates. With respect to the cumulative Kepler Object of
Interest (KOI) catalog, we designate 1,478 new KOIs, of which 402 are
dispositioned as planet candidates (PCs). Also, 237 KOIs dispositioned as false
positives (FPs) in previous Kepler catalogs have their disposition changed to
PC and 118 PCs have their disposition changed to FP. This brings the total
number of known KOIs to 8,826 and PCs to 4,696. We compare the Q1-Q17 DR24 KOI
catalog to previous KOI catalogs, as well as ancillary Kepler catalogs, finding
good agreement between them. We highlight new PCs that are both potentially
rocky and potentially in the habitable zone of their host stars, many of which
orbit solar-type stars. This work represents significant progress in accurately
determining the fraction of Earth-size planets in the habitable zone of
Sun-like stars. The full catalog is publicly available at the NASA Exoplanet
Archive.Comment: Accepted to the Astrophysical Journal Supplement Series. 30 pages, 9
figures, 7 tables. We make the DR24 robovetter decision code publicly
available at http://github.com/JeffLCoughlin/robovetter, with input and
output examples provided using the same data as contained in the full paper's
table
Substrate Micropatterning as a New in Vitro Cell Culture System to Study Myelination
Artículo de publicación ISIMyelination is a highly regulated developmental
process whereby oligodendrocytes in the central nervous system
and Schwann cells in the peripheral nervous system ensheathe axons
with a multilayered concentric membrane. Axonal myelination
increases the velocity of nerve impulse propagation. In this work,
we present a novel in vitro system for coculturing primary dorsal root
ganglia neurons along with myelinating cells on a highly restrictive
and micropatterned substrate. In this new coculture system, neurons
survive for several weeks, extending long axons on defined Matrigel
tracks. On these axons, myelinating cells can achieve robust myelination, as demonstrated by the distribution of compact myelin
and nodal markers. Under these conditions, neurites and associated myelinating cells are easily accessible for studies on the
mechanisms of myelin formation and on the effects of axonal damage on the myelin sheath.Regenerative Medicine and Nanomedicine Initiative of the Canadian Institutes of Health Research (CIHR)
RMF-7028
FONDECYT
1080252
CIHR
Ministry of Industry of Canada
Rio Tinto Alcan
Molson Foundatio
Discovery of a Third Transiting Planet in the Kepler-47 Circumbinary System
Of the nine confirmed transiting circumbinary planet systems, only Kepler-47 is known to contain more than one planet. Kepler-47 b (the "inner planet") has an orbital period of 49.5 days and a radius of about 3 R⊕. Kepler-47 c (the "outer planet") has an orbital period of 303.2 days and a radius of about 4.7 R⊕. Here we report the discovery of a third planet, Kepler-47 d (the "middle planet"), which has an orbital period of 187.4 days and a radius of about 7 R⊕. The presence of the middle planet allows us to place much better constraints on the masses of all three planets, where the 1σranges are less than 26 M⊕, between 7–43 M⊕, and between 2–5 M⊕ for the inner, middle, and outer planets, respectively. The middle and outer planets have low bulk densities, with ρ_(middle) < 0.68 g cm^(−3) and ρ_(outer) < 0.26 g cm^(−3) at the 1σ level. The two outer planets are "tightly packed," assuming the nominal masses, meaning no other planet could stably orbit between them. All of the orbits have low eccentricities and are nearly coplanar, disfavoring violent scattering scenarios and suggesting gentle migration in the protoplanetary disk
No association between the aluminium content of trabecular bone and bone density, mass or size of the proximal femur in elderly men and women
BACKGROUND: Aluminium is considered a bone toxic metal since poisoning can lead to aluminium-induced bone disease in patients with chronic renal failure. Healthy subjects with normal renal function retain 4% of the aluminium consumed. They might thus also accumulate aluminium and eventually be at risk of long-term low-grade aluminium intoxication that can affect bone health. METHODS: We therefore examined 62 patients with femoral neck fractures or osteoarthritis of the hip (age range 38–93), with the aim of examining whether aluminium in bone is associated with bone-mineral density (BMD), content (BMC) or width of the femoral neck measured by dual-energy X-ray absorptiometry (DXA). During operations bone biopsies were taken from the trabecular bone of the proximal femur. The samples were measured for their content of aluminium using a mass spectrometer. RESULTS: No significant association between the aluminium content in bone and femoral neck BMD, BMC or width could be found after multivariate adjustment. CONCLUSION: Our results indicate that the accumulated aluminium content in bone during life does not substantially influence the extent of osteoporosis
Planetary Candidates Observed by Kepler VI: Planet Sample from Q1-Q16 (47 Months)
\We present the sixth catalog of Kepler candidate planets based on nearly 4
years of high precision photometry. This catalog builds on the legacy of
previous catalogs released by the Kepler project and includes 1493 new Kepler
Objects of Interest (KOIs) of which 554 are planet candidates, and 131 of these
candidates have best fit radii <1.5 R_earth. This brings the total number of
KOIs and planet candidates to 7305 and 4173 respectively. We suspect that many
of these new candidates at the low signal-to-noise limit may be false alarms
created by instrumental noise, and discuss our efforts to identify such
objects. We re-evaluate all previously published KOIs with orbital periods of
>50 days to provide a consistently vetted sample that can be used to improve
planet occurrence rate calculations. We discuss the performance of our planet
detection algorithms, and the consistency of our vetting products. The full
catalog is publicly available at the NASA Exoplanet Archive.Comment: 18 pages, to be published in the Astrophysical Journal Supplement
Serie
Kepler eclipsing binary stars. VII. the catalogue of eclipsing binaries found in the entire Kepler data set
The primary Kepler Mission provided nearly continuous monitoring of ~200,000 objects with unprecedented photometric precision. We present the final catalog of eclipsing binary systems within the 105 deg2 Kepler field of view. This release incorporates the full extent of the data from the primary mission (Q0-Q17 Data Release). As a result, new systems have been added, additional false positives have been removed, ephemerides and principal parameters have been recomputed, classifications have been revised to rely on analytical models, and eclipse timing variations have been computed for each system. We identify several classes of systems including those that exhibit tertiary eclipse events, systems that show clear evidence of additional bodies, heartbeat systems, systems with changing eclipse depths, and systems exhibiting only one eclipse event over the duration of the mission. We have updated the period and galactic latitude distribution diagrams and included a catalog completeness evaluation. The total number of identified eclipsing and ellipsoidal binary systems in the Kepler field of view has increased to 2878, 1.3% of all observed Kepler targets
Impacts of climate change on plant diseases – opinions and trends
There has been a remarkable scientific output on the topic of how climate change is likely to affect plant diseases in the coming decades. This review addresses the need for review of this burgeoning literature by summarizing opinions of previous reviews and trends in recent studies on the impacts of climate change on plant health. Sudden Oak Death is used as an introductory case study: Californian forests could become even more susceptible to this emerging plant disease, if spring precipitations will be accompanied by warmer temperatures, although climate shifts may also affect the current synchronicity between host cambium activity and pathogen colonization rate. A summary of observed and predicted climate changes, as well as of direct effects of climate change on pathosystems, is provided. Prediction and management of climate change effects on plant health are complicated by indirect effects and the interactions with global change drivers. Uncertainty in models of plant disease development under climate change calls for a diversity of management strategies, from more participatory approaches to interdisciplinary science. Involvement of stakeholders and scientists from outside plant pathology shows the importance of trade-offs, for example in the land-sharing vs. sparing debate. Further research is needed on climate change and plant health in mountain, boreal, Mediterranean and tropical regions, with multiple climate change factors and scenarios (including our responses to it, e.g. the assisted migration of plants), in relation to endophytes, viruses and mycorrhiza, using long-term and large-scale datasets and considering various plant disease control methods
Kepler Eclipsing Binary Stars. Vii. The Catalog Of Eclipsing Binaries Found In The Entire Kepler Data Set
The Kepler mission has provided unprecedented, nearly continuous photometric data of ~200,000 objects in the ~105 deg2 field of view (FOV) from the beginning of science operations in May of 2009 until the loss of the second reaction wheel in May of 2013. The Kepler Eclipsing Binary Catalog contains information including but not limited to ephemerides, stellar parameters, and analytical approximation fits for every known eclipsing binary system in the Kepler FOV. Using target pixel level data collected from Kepler in conjunction with the Kepler Eclipsing Binary Catalog, we identify false positives among eclipsing binaries, i.e., targets that are not eclipsing binaries themselves, but are instead contaminated by eclipsing binary sources nearby on the sky and show eclipsing binary signatures in their light curves. We present methods for identifying these false positives and for extracting new light curves for the true source of the observed binary signal. For each source, we extract three separate light curves for each quarter of available data by optimizing the signal-to-noise ratio, the relative percent eclipse depth, and the flux eclipse depth. We present 289 new eclipsing binaries in the Kepler FOV that were not targets for observation, and these have been added to the catalog
Practicing Politics: technical project templates and political practice in a DFID country office
Development agencies including the UK Department for International Development (DFID) increasingly agree that if aid is to be effective, it should be politically smart and locally led. However, both the critical and the reformist literature have argued that development agencies persist with technical, template-driven programming: political analysis and practice have not been widely institutionalized. This study aims to identify why development representations are persistently technical in their form, and what blockages have existed for developing locally grounded and politically aware programmes. The article presents an ethnography of the process of developing the core elements of the governance portfolio in an (anonymized) DFID country office. Focusing on a key design workshop, the study is situated within a wider organizational ethnography. The persistently technical justifications for programmes are a result of the bureaucratic form itself, its accountability and approval processes. Political analyses represent countries in such a way that officials can prioritize selection from a repertoire of technical models. However, scepticism about the tractability of governance problems to such analyses and programming has led to an emerging understanding of politics that creates space within the bureaucratic form for politically aware practice. Politically aware programming should emphasize good operational practice over explicit analysis and should continue to emphasize technical models like the adaptive management models which create room for such practice
- …