992 research outputs found
The Molluscan Fauna of the Florida Middle Grounds with Comments on its Zoogeographical Affinities
Recent studies have indicated that the Gulf of Mexico is bounded by a discontinual series of hard substrates which support faunal and floral assemblages of both temperate and tropical origins. This substrate distribution has had a significant impact on molluscan fauna in the Gulf of Mexico. An investigation of the molluscan fauna of the Florida Middle Grounds has produced 75 species associated with this high relief substrate which is also characterized by hermatypic corals. Although the molluscan fauna is comprised of forms which are predominantly Caribbean eurythermic and Caribbean Restricted (76%) which is similar in composition to the West Flower Garden Bank of Texas, their species composition is quite dissimilar (only 23% similarity). For these and other reasons, it is proposed that the zoogeographic status of the Gulf of Mexico should be seriously reconsidered by specialists in other faunal groups
The Ctf18 RFC-like complex positions yeast telomeres but does not specify their replication time
Peer reviewedPreprin
Stability Constraints on Classical de Sitter Vacua
We present further no-go theorems for classical de Sitter vacua in Type II
string theory, i.e., de Sitter constructions that do not invoke
non-perturbative effects or explicit supersymmetry breaking localized sources.
By analyzing the stability of the 4D potential arising from compactification on
manfiolds with curvature, fluxes, and orientifold planes, we found that
additional ingredients, beyond the minimal ones presented so far, are necessary
to avoid the presence of unstable modes. We enumerate the minimal setups for
(meta)stable de Sitter vacua to arise in this context.Comment: 18 pages; v2: argument improved, references adde
GJ 3236: a new bright, very low-mass eclipsing binary system discovered by the MEarth observatory
We report the detection of eclipses in GJ 3236, a bright (I = 11.6) very low
mass binary system with an orbital period of 0.77 days. Analysis of light- and
radial velocity curves of the system yielded component masses of 0.38 +/- 0.02
and 0.28 +/- 0.02 Msol. The central values for the stellar radii are larger
than the theoretical models predict for these masses, in agreement with the
results for existing eclipsing binaries, although the present 5% observational
uncertainties limit the significance of the larger radii to approximately 1
sigma. Degeneracies in the light curve models resulting from the unknown
configuration of surface spots on the components of GJ 3236 currently dominate
the uncertainties in the radii, and could be reduced by obtaining precise,
multi-band photometry covering the full orbital period. The system appears to
be tidally synchronized and shows signs of high activity levels as expected for
such a short orbital period, evidenced by strong Halpha emission lines in the
spectra of both components. These observations probe an important region of
mass-radius parameter space around the predicted transition to fully-convective
stellar interiors, where there are a limited number of precise measurements
available in the literature.Comment: 14 pages, 5 figures, 10 tables, emulateapj format. Accepted for
publication in Ap
Projection methods in conic optimization
There exist efficient algorithms to project a point onto the intersection of
a convex cone and an affine subspace. Those conic projections are in turn the
work-horse of a range of algorithms in conic optimization, having a variety of
applications in science, finance and engineering. This chapter reviews some of
these algorithms, emphasizing the so-called regularization algorithms for
linear conic optimization, and applications in polynomial optimization. This is
a presentation of the material of several recent research articles; we aim here
at clarifying the ideas, presenting them in a general framework, and pointing
out important techniques
Explicating ways of consensus-making in science and society: distinguishing the academic, the interface and the meta-consensus
In this chapter, we shed new light on the epistemic struggle between establishing consensus and acknowledging plurality, by explicating different ways of consensus-making in science and society and examining the impact hereof on their field of intersection, i.e. consensus conferences (in particular those organized by the National Institute of Health). We draw a distinction between, what we call, academic and interface consensus, to capture the wide appeal to consensus in existing literature. We investigate such accounts - i.e. from Miriam Solomon, John Beatty and Alfred Moore, and Boaz Miller - as to put forth a new understanding of consensus-making, focusing on the meta-consensus. We further defend how (NIH) consensus conferences enable epistemic work, through demands of epistemic adequacy and contestability, contrary to the claim that consensus conferences miss a window for epistemic opportunity (Solomon M, The social epistemology of NIH consensus conferences. In: Kincaid H, McKitrick J (ed) Establishing medical reality: methodological and metaphysical issues in philosophy of medicine. Springer, Dordrecht, 2007). Paying attention to the dynamics surrounding consensus, moreover, allows us to illustrate how the public understanding of science and the public use of the ideal of consensus could be well modified
Kepler-16: A Transiting Circumbinary Planet
We report the detection of a planet whose orbit surrounds a pair of low-mass
stars. Data from the Kepler spacecraft reveal transits of the planet across
both stars, in addition to the mutual eclipses of the stars, giving precise
constraints on the absolute dimensions of all three bodies. The planet is
comparable to Saturn in mass and size, and is on a nearly circular 229-day
orbit around its two parent stars. The eclipsing stars are 20% and 69% as
massive as the sun, and have an eccentric 41-day orbit. The motions of all
three bodies are confined to within 0.5 degree of a single plane, suggesting
that the planet formed within a circumbinary disk.Comment: Science, in press; for supplemental material see
http://www.sciencemag.org/content/suppl/2011/09/14/333.6049.1602.DC1/1210923.Doyle.SOM.pd
The landscape of extreme genomic variation in the highly adaptable Atlantic killifish
© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Genome Biology and Evolution 9 (2017): 659-676, doi:10.1093/gbe/evx023.Understanding and predicting the fate of populations in changing environments require knowledge about the mechanisms that support phenotypic plasticity and the adaptive value and evolutionary fate of genetic variation within populations. Atlantic killifish (Fundulus heteroclitus) exhibit extensive phenotypic plasticity that supports large population sizes in highly fluctuating estuarine environments. Populations have also evolved diverse local adaptations. To yield insights into the genomic variation that supports their adaptability, we sequenced a reference genome and 48 additional whole genomes from a wild population. Evolution of genes associated with cell cycle regulation and apoptosis is accelerated along the killifish lineage, which is likely tied to adaptations for life in highly variable estuarine environments. Genome-wide standing genetic variation, including nucleotide diversity and copy number variation, is extremely high. The highest diversity genes are those associated with immune function and olfaction, whereas genes under greatest evolutionary constraint are those associated with neurological, developmental, and cytoskeletal functions. Reduced genetic variation is detected for tight junction proteins, which in killifish regulate paracellular permeability that supports their extreme physiological flexibility. Low-diversity genes engage in more regulatory interactions than high-diversity genes, consistent with the influence of pleiotropic constraint on molecular evolution. High genetic variation is crucial for continued persistence of species given the pace of contemporary environmental change. Killifish populations harbor among the highest levels of nucleotide diversity yet reported for a vertebrate species, and thus may serve as a useful model system for studying evolutionary potential in variable and changing environments.This work was primarily supported by a grant from the National Science Foundation (collaborative research grants DEB-1265282, DEB-1120512, DEB-1120013, DEB-1120263, DEB-1120333, DEB-1120398 to J.K.C., D.L.C., M.E.H., S.I.K., M.F.O., J.R.S., W.W., and A.W.). Further support was provided by the National Institute of Environmental Health Sciences (1R01ES021934-01 to A.W., P42ES7373 to T.H.H., P42ES007381 to M.E.H., and R01ES019324 to J.R.S.), the National Institute of General Medical Sciences (P20GM103423 and P20GM104318 to B.L.K.), and the National Science Foundation (DBI-0640462 and XSEDE-MCB100147 to D.G.)
The K2 & TESS Synergy II: Revisiting 26 systems in the TESS Primary Mission
The legacy of NASA's K2 mission has provided hundreds of transiting
exoplanets that can be revisited by new and future facilities for further
characterization, with a particular focus on studying the atmospheres of these
systems. However, the majority of K2-discovered exoplanets have typical
uncertainties on future times of transit within the next decade of greater than
four hours, making observations less practical for many upcoming facilities.
Fortunately, NASA's Transiting exoplanet Survey Satellite (TESS) mission is
reobserving most of the sky, providing the opportunity to update the
ephemerides for 300 K2 systems. In the second paper of this series, we
reanalyze 26 single-planet, K2-discovered systems that were observed in the
TESS primary mission by globally fitting their K2 and TESS lightcurves
(including extended mission data where available), along with any archival
radial velocity measurements. As a result of the faintness of the K2 sample, 13
systems studied here do not have transits detectable by TESS. In those cases,
we re-fit the K2 lightcurve and provide updated system parameters. For the 23
systems with , we determine the host star parameters
using a combination of Gaia parallaxes, Spectral Energy Distribution (SED)
fits, and MESA Isochrones and Stellar Tracks (MIST) stellar evolution models.
Given the expectation of future TESS extended missions, efforts like the K2 &
TESS Synergy project will ensure the accessibility of transiting planets for
future characterization while leading to a self-consistent catalog of stellar
and planetary parameters for future population efforts.Comment: Accepted for publication in ApJ. 29 pages, 9 figures, 12 table
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