165 research outputs found
Investigating the physical properties of transiting hot Jupiters with the 1.5-m Kuiper Telescope
We present new photometric data of 11 hot Jupiter transiting exoplanets
(CoRoT-12b, HAT-P-5b, HAT-P-12b, HAT-P-33b, HAT-P-37b, WASP-2b, WASP-24b,
WASP-60b, WASP-80b, WASP-103b, XO-3b) in order to update their planetary
parameters and to constrain information about their atmospheres. These
observations of CoRoT-12b, HAT-P-37b and WASP-60b are the first follow-up data
since their discovery. Additionally, the first near-UV transits of WASP-80b and
WASP-103b are presented. We compare the results of our analysis with previous
work to search for transit timing variations (TTVs) and a wavelength dependence
in the transit depth. TTVs may be evidence of a third body in the system and
variations in planetary radius with wavelength can help constrain the
properties of the exoplanet's atmosphere. For WASP-103b and XO-3b, we find a
possible variation in the transit depths that may be evidence of scattering in
their atmospheres. The B-band transit depth of HAT-P-37b is found to be smaller
than its near-IR transit depth and such a variation may indicate TiO/VO
absorption. These variations are detected from 2-4.6, so follow-up
observations are needed to confirm these results. Additionally, a flat spectrum
across optical wavelengths is found for 5 of the planets (HAT-P-5b, HAT-P-12b,
WASP-2b, WASP-24b, WASP-80b), suggestive that clouds may be present in their
atmospheres. We calculate a refined orbital period and ephemeris for all the
targets, which will help with future observations. No TTVs are seen in our
analysis with the exception of WASP-80b and follow-up observations are needed
to confirm this possible detection.Comment: 18 pages, 7 figures, 9 Tables. Light Curves available online.
Accepted to MNRAS (2017 August 25
In situ epitaxial MgB2 thin films for superconducting electronics
A thin film technology compatible with multilayer device fabrication is
critical for exploring the potential of the 39-K superconductor magnesium
diboride for superconducting electronics. Using a Hybrid Physical-Chemical
Vapor Deposition (HPCVD) process, it is shown that the high Mg vapor pressure
necessary to keep the MgB phase thermodynamically stable can be achieved
for the {\it in situ} growth of MgB thin films. The films grow epitaxially
on (0001) sapphire and (0001) 4H-SiC substrates and show a bulk-like of
39 K, a (4.2K) of A/cm in zero field, and a
of 29.2 T in parallel magnetic field. The surface is smooth with a
root-mean-square roughness of 2.5 nm for MgB films on SiC. This deposition
method opens tremendous opportunities for superconducting electronics using
MgB
Collectivity and configuration mixing in 186,188Pb and 194Po
Lifetimes of prolate intruder states in 186Pb and oblate intruder states in 194Po have been determined by employing, for the first time, the recoil-decay tagging technique in recoil distance Doppler-shift lifetime measurements. In addition, lifetime measurements of prolate states in 188Pb up to the 8+ state were carried out using the recoil-gating method. The B(E2) values have been deduced from which deformation parameters |β2|=0.29(5) and |β2|=0.17(3) for the prolate and the oblate bands, respectively, have been extracted. The results also shed new light on the mixing between different shapes
Collectivity and Configuration Mixing in \u3csup\u3e186,188\u3c/sup\u3ePb and \u3csup\u3e194\u3c/sup\u3ePo
Lifetimes of prolate intruder states in 186Pb and oblate intruder states in 194Po have been determined by employing, for the first time, the recoil-decay tagging technique in recoil distance Doppler-shift lifetime measurements. In addition, lifetime measurements of prolate states in 188Pb up to the 8+state were carried out using the recoil-gating method. The B(E2) values have been deduced from which deformation parameters lβ2l = 0.29(5) and lβ2l = 0.17(3) for the prolate and the oblate bands, respectively, have been extracted. The results also shed new light on the mixing between different shapes
Lifetimes of intruder states in 186 Pb, 188 Pb and 194 Po
Lifetimes of prolate intruder states in 186Pb and 188Pb and oblate intruder states in 194Po have been determined through recoil distance Doppler-shift lifetime measurements. Deformation parameters of | β2 | = 0.29 (5) and | β2 | = 0.17(3) have been ext
The Homeobox Transcription Factor Barx2 Regulates Plasticity of Young Primary Myofibers
Adult mammalian muscle retains incredible plasticity. Muscle growth and repair involves the activation of undifferentiated myogenic precursors called satellite cells. In some circumstances, it has been proposed that existing myofibers may also cleave and produce a pool of proliferative cells that can re-differentiate into new fibers. Such myofiber dedifferentiation has been observed in the salamander blastema where it may occur in parallel with satellite cell activation. Moreover, ectopic expression of the homeodomain transcription factor Msx1 in differentiated C2C12 myotubes has been shown to induce their dedifferentiation. While it remains unclear whether dedifferentiation and redifferentiaton occurs endogenously in mammalian muscle, there is considerable interest in induced dedifferentiation as a possible regenerative tool.We previously showed that the homeobox protein Barx2 promotes myoblast differentiation. Here we report that ectopic expression of Barx2 in young immature myotubes derived from cell lines and primary mouse myoblasts, caused cleavage of the syncytium and downregulation of differentiation markers. Microinjection of Barx2 cDNA into immature myotubes derived from primary cells led to cleavage and formation of mononucleated cells that were able to proliferate. However, injection of Barx2 cDNA into mature myotubes did not cause cleavage. Barx2 expression in C2C12 myotubes increased the expression of cyclin D1, which may promote cell cycle re-entry. We also observed differential muscle gene regulation by Barx2 at early and late stages of muscle differentiation which may be due to differential recruitment of transcriptional activator or repressor complexes to muscle specific genes by Barx2.We show that Barx2 regulates plasticity of immature myofibers and might act as a molecular switch controlling cell differentiation and proliferation
A Novel Molecular Solution for Ultraviolet Light Detection in Caenorhabditis elegans
For many organisms the ability to transduce light into cellular signals is crucial for survival. Light stimulates DNA repair and metabolism changes in bacteria, avoidance responses in single-cell organisms, attraction responses in plants, and both visual and nonvisual perception in animals. Despite these widely differing responses, in all of nature there are only six known families of proteins that can transduce light. Although the roundworm Caenorhabditis elegans has none of the known light transduction systems, we show here that C. elegans strongly accelerates its locomotion in response to blue or shorter wavelengths of light, with maximal responsiveness to ultraviolet light. Our data suggest that C. elegans uses this light response to escape the lethal doses of sunlight that permeate its habitat. Short-wavelength light drives locomotion by bypassing two critical signals, cyclic adenosine monophosphate (cAMP) and diacylglycerol (DAG), that neurons use to shape and control behaviors. C. elegans mutants lacking these signals are paralyzed and unresponsive to harsh physical stimuli in ambient light, but short-wavelength light rapidly rescues their paralysis and restores normal levels of coordinated locomotion. This light response is mediated by LITE-1, a novel ultraviolet light receptor that acts in neurons and is a member of the invertebrate Gustatory receptor (Gr) family. Heterologous expression of the receptor in muscle cells is sufficient to confer light responsiveness on cells that are normally unresponsive to light. Our results reveal a novel molecular solution for ultraviolet light detection and an unusual sensory modality in C. elegans that is unlike any previously described light response in any organism
A Novel Tetrameric PilZ Domain Structure from Xanthomonads
PilZ domain is one of the key receptors for the newly discovered secondary messenger molecule cyclic di-GMP (c-di-GMP). To date, several monomeric PilZ domain proteins have been identified. Some exhibit strong c-di-GMP binding activity, while others have barely detectable c-di-GMP binding activity and require an accessory protein such as FimX to indirectly respond to the c-di-GMP signal. We now report a novel tetrameric PilZ domain structure of XCC6012 from the plant pathogen Xanthomonas campestris pv. campestris (Xcc). It is one of the four PilZ domain proteins essential for Xcc pathogenicity. Although the monomer adopts a structure similar to those of the PilZ domains with very weak c-di-GMP binding activity, it is nevertheless interrupted in the middle by two extra long helices. Four XCC6012 proteins are thus self-assembled into a tetramer via the extra heptad repeat α3 helices to form a parallel four-stranded coiled-coil, which is further enclosed by two sets of inclined α2 and α4 helices. We further generated a series of XCC6012 variants and measured the unfolding temperatures and oligomeric states in order to investigate the nature of this novel tetramer. Discovery of this new PilZ domain architecture increases the complexity of c-di-GMP-mediated regulation
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