2,547 research outputs found
Multi-filter transit observations of WASP-39b and WASP-43b with three San Pedro M\'artir telescopes
Three optical telescopes located at the San Pedro M\'artir National
Observatory were used for the first time to obtain multi-filter defocused
photometry of the transiting extrasolar planets WASP-39b and WASP-43b. We
observed WASP-39b with the 2.12m telescope in the U filter for the first time,
and additional observations were carried out in the R and I filters using the
0.84m telescope. WASP-43b was observed in VRI with the same instrument, and in
the i filter with the robotic 1.50m telescope. We reduced the data using
different pipelines and performed aperture photometry with the help of custom
routines, in order to obtain the light curves. The fit of the light curves
(1.5--2.5mmag rms), and of the period analysis, allowed a revision of the
orbital and physical parameters, revealing for WASP-39b a period ( days) which is seconds larger than
previously reported. Moreover, we find for WASP-43b a planet/star radius
() which is larger in the i filter
with respect to previous works, and that should be confirmed with additional
observations. Finally, we confirm no evidence of constant period variations in
WASP-43b.Comment: 13 pages, 7 figures, accepted in PASP, scheduled for the February 1,
2015 issu
Investigations of elastic vibration periods of reinforced concrete moment-resisting frame systems with various infill walls
Phylogenetic analysis of HpnP reveals the origin of 2-methylhopanoid production in Alphaproteobacteria
Hopanoids are bacterial steroid-like lipids that can be preserved in the rock record on billion-year timescales. 2-Methylhopanoids are of particular interest to geobiologists because methylation is one of the few chemical modifications that remain after diagenesis and catagenesis. 2-Methylhopanes, the molecular fossils of 2-methylhopanoids, are episodically enriched in the rock record, but we do not have a robust interpretation for their abundance patterns. Here, we exploit the evolutionary record found in molecular sequences from extant organisms to reconstruct the biosynthetic history of 2-methylhopanoids using the C-2 hopanoid methylase, HpnP. Based on HpnP phylogenetic analysis, we find that 2-methylhopanoids originated in a subset of the Alphaproteobacteria. This conclusion is statistically robust and reproducible in multiple trials varying the outgroup, trimming stringency, and ingroup dataset used to infer the evolution of this protein family. The capacity for 2-methylhopanoid production was likely horizontally transferred from the Alphaproteobacteria into the Cyanobacteria after the Cyanobacteria's major divergences. Together, these results suggest that the ancestral function of 2-methylhopanoids was not related to oxygenic photosynthesis but instead to a trait already present in the Alphaproteobacteria. Moreover, given that early 2-methylhopane deposits could have been made solely by Alphaproteobacteria before the acquisition of hpnP by Cyanobacteria, and that the Alphaproteobacteria are thought to be ancestrally aerobic, we infer that 2-methylhopanoids likely arose after the oxygenation of the atmosphere. This finding is consistent with the geologic recordâthe oldest syngenetic 2-methylhopanes occur after the rise of oxygen, in middle Proterozoic strata of the Barney Creek Formation
The Optical and Near-Infrared Transmission Spectrum of the Super-Earth GJ1214b: Further Evidence for a Metal-Rich Atmosphere
We present an investigation of the transmission spectrum of the 6.5 M_earth
planet GJ1214b based on new ground-based observations of transits of the planet
in the optical and near-infrared, and on previously published data.
Observations with the VLT+FORS and Magellan+MMIRS using the technique of
multi-object spectroscopy with wide slits yielded new measurements of the
planet's transmission spectrum from 0.61 to 0.85 micron, and in the J, H, and K
atmospheric windows. We also present a new measurement based on narrow-band
photometry centered at 2.09 micron with the VLT+HAWKI. We combined these data
with results from a re-analysis of previously published FORS data from 0.78 to
1.00 micron using an improved data reduction algorithm, and previously reported
values based on Spitzer data at 3.6 and 4.5 micron. All of the data are
consistent with a featureless transmission spectrum for the planet. Our K-band
data are inconsistent with the detection of spectral features at these
wavelengths reported by Croll and collaborators at the level of 4.1 sigma. The
planet's atmosphere must either have at least 70% water by mass or optically
thick high-altitude clouds or haze to be consistent with the data.Comment: (v2) ApJ in press, no major changes from v
The subelliptic heat kernel on SU(2): Representations, Asymptotics and Gradient bounds
The Lie group SU(2) endowed with its canonical subriemannian structure
appears as a three-dimensional model of a positively curved subelliptic space.
The goal of this work is to study the subelliptic heat kernel on it and some
related functional inequalities.Comment: Update: Added section + Correction of typo
Dependence of the Ce(III)/Ce(IV) ratio on intracellular localization in ceria nanoparticles internalized by human cells
CeO2 nanoparticles (CNPs) have been investigated as promising antioxidant agents with significant activity in the therapy of diseases involving free radicals or oxidative stress. However, the exact mechanism responsible for CNP activity has not been completely elucidated. In particular, in situ evidence of modification of the oxidative state of CNPs in human cells and their evolution during cell internalization and subsequent intracellular distribution has never been presented. In this study we investigated modification of the Ce(iii)/Ce(iv) ratio following internalization in human cells by X-ray absorption near edge spectroscopy (XANES). From this analysis on cell pellets, we observed that CNPs incubated for 24 h showed a significant increase in Ce(iii). By coupling on individual cells synchrotron micro-X-ray fluorescence (ÎŒXRF) with micro-XANES (ÎŒXANES) we demonstrated that the Ce(iii)/Ce(iv) ratio is also dependent on CNP intracellular localization. The regions with the highest CNP concentrations, suggested to be endolysosomes by transmission electron microscopy, were characterized by Ce atoms in the Ce(iv) oxidation state, while a higher Ce(iii) content was observed in regions surrounding these areas. These observations suggest that the interaction of CNPs with cells involves a complex mechanism in which different cellular areas play different roles
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