Thymocyte development requires a complex orchestration of multiple transcription factors. Ablating either TCF-1 or HEB in CD4
CD8
thymocytes elicits similar developmental outcomes including increased ...proliferation, decreased survival, and fewer late Tcra rearrangements. Here, we provide a mechanistic explanation for these similarities by showing that TCF-1 and HEB share ~7,000 DNA-binding sites genome wide and promote chromatin accessibility. The binding of both TCF-1 and HEB was required at these shared sites for epigenetic and transcriptional gene regulation. Binding of TCF-1 and HEB to their conserved motifs in the enhancer regions of genes associated with T cell differentiation promoted their expression. Binding to sites lacking conserved motifs in the promoter regions of cell-cycle-associated genes limited proliferation. TCF-1 displaced nucleosomes, allowing for chromatin accessibility. Importantly, TCF-1 inhibited Notch signaling and consequently protected HEB from Notch-mediated proteasomal degradation. Thus, TCF-1 shifts nucleosomes and safeguards HEB, thereby enabling their cooperation in establishing the epigenetic and transcription profiles of CD4
CD8
thymocytes.
Muscle analysis using pQCT, DXA and MRI Erlandson, M.C; Lorbergs, A.L; Mathur, S ...
European journal of radiology,
08/2016, Letnik:
85, Številka:
8
Journal Article
Recenzirano
Highlights • Review of skeletal muscle parameters using pQCT, DXA and MRI. • Advantages and limitations of each of the imaging modalities. • No one tool is suitable for all research questions. • ...Current lack of standardized analysis protocols is limiting utility.
Manual vegetable transplanting is a time-consuming, labor-intensive, operation. The objective of the study was to design, develop, and evaluate an automatic vegetable transplanter (AVT) for plug ...seedlings of chili (Capsicum annuum L.). Metering mechanisms in an AVT are affected by the transmission system and changes in desired plant spacing. To overcome problems, a novel rotating finger device with a push-type mechanism was developed for automatic transplanting of vegetable plug seedlings. The AVT consists of a pair of L-shaped rotating fingers, feed roller unit, metering mechanism, and delivery unit. Clearance between the feed roller and fingers is adjustable. The average values of performance parameters: plant spacing (Ps), planting depth (Pd), mis-planting (Mp), multiple planting (Mt), seedling mortality (Sm), transplanting efficiency (Et), and field transplanting efficiency (Ef) were 599.8 mm, 46.4 mm, 4.9%, 1.1%, 0.9%, 92.6%, and 76.12%, respectively. Effective field capacity (Fc) with the transplanter was 0.093 ha∙h
−1
and 0.027 ha∙h
−1
with the manual method. The two-row AVT can be used with a small tractor and may make up for labor shortage during peak season.
Dihydrogen sulphide (H2S) is a dangerous pollutant released in fossil combustion processes. Here, p-CuO (particle)/n-SnO2 (nanowire) heterostructures were evaluated as selective H2S sensors, and the ...working principle behind their good performance was qualitatively modelled. It was concluded that the main sensing mechanism was dissimilar to standard redox reactions typical of simple metal oxide devices, but ascribable to the sulphurization of CuO and the consequent variation of the pn-junction band structure at the CuO–SnO2 interfaces. Experimental data showed that these H2S sensors suit well for alarm applications with extremely high selectivity and sensitivity to this gas for concentrations between 1ppm and 10ppm.
Kepler ultra-high precision photometry of long and continuous observations provides a unique dataset in which surface rotation and variability can be studied for thousands of stars. Because many of ...these old field stars also have independently measured asteroseismic ages, measurements of rotation and activity are particularly interesting in the context of age-rotation-activity relations. We study the surface rotation and photometric magnetic activity of a subset of 540 solar-like stars on the main-sequence and the subgiant branch for which stellar pulsations have been measured. The photometric magnetic activity levels of these stars were computed, and for 61.5% of the dwarfs, this level is similar to the range, from minimum to maximum, of the solar magnetic activity. We demonstrate that hot dwarfs, cool dwarfs, and subgiants have very different rotation-age relationships, highlighting the importance of separating out distinct populations when interpreting stellar rotation periods. Our sample of cool dwarf stars with age and metallicity data of the highest quality is consistent with gyrochronology relations reported in the literature.
In this article, we first review the past decade of efforts in detecting the missing baryons in the warm hot intergalactic medium and summarize the current state of the art by updating the baryon ...census and physical state of the detected baryons in the local Universe. We then describe observational strategies that should enable a significant step forward in the next decade, while waiting for the step‐up in quality offered by future missions. In particular, we design a multi‐megasecond and multiple cycle XMM‐Newton legacy' program (which we name the Ultimate Roaming Baryon Exploration, or URBE), aimed at securing detections of the peaks in the density distribution of the Universe of missing baryons over their entire predicted range of temperatures.
ABSTRACT
We analysed 68 candidate planetary systems first identified during Campaigns 5 and 6 (C5 and C6) of the NASA K2 mission. We set out to validate these systems by using a suite of follow-up ...observations, including adaptive optics, speckle imaging, and reconnaissance spectroscopy. The overlap between C5 with C16 and C18, and C6 with C17, yields light curves with long baselines that allow us to measure the transit ephemeris very precisely, revisit single transit candidates identified in earlier campaigns, and search for additional transiting planets with longer periods not detectable in previous works. Using vespa, we compute false positive probabilities of less than 1 per cent for 37 candidates orbiting 29 unique host stars and hence statistically validate them as planets. These planets have a typical size of 2.2 R⊕ and orbital periods between 1.99 and 52.71 d. We highlight interesting systems including a sub-Neptune with the longest period detected by K2, sub-Saturns around F stars, several multiplanetary systems in a variety of architectures. These results show that a wealth of planetary systems still remains in the K2 data, some of which can be validated using minimal follow-up observations and taking advantage of analyses presented in previous catalogues.
Aims. We report 20 new lithium-rich giants discovered within the Gaia-ESO Survey, including the first Li-rich giant with an evolutionary stage confirmed by CoRoT (Convection, Rotation and planetary ...Transits) data. We present a detailed overview of the properties of these 20 stars. Methods. Atmospheric parameters and abundances were derived in model atmosphere analyses using medium-resolution GIRAFFE or high-resolution UVES (Ultraviolet and Visual Echelle Spectrograph) spectra. These results are part of the fifth internal data release of the Gaia-ESO Survey. The Li abundances were corrected for non-local thermodynamical equilibrium effects. Other stellar properties were investigated for additional peculiarities (the core of strong lines for signs of magnetic activity, infrared magnitudes, rotational velocities, chemical abundances, and Galactic velocities). We used Gaia DR2 parallaxes to estimate distances and luminosities. Results. The giants have A(Li) > 2.2 dex. The majority of them (14 of 20 stars) are in the CoRoT fields. Four giants are located in the field of three open clusters, but are not members. Two giants were observed in fields towards the Galactic bulge, but likely lie in the inner disc. One of the bulge field giants is super Li-rich with A(Li) = 4.0 dex. Conclusions. We identified one giant with infrared excess at 22 μm. Two other giants, with large v sin i, might be Li-rich because of planet engulfment. Another giant is found to be barium enhanced and thus could have accreted material from a former asymptotic giant branch companion. Otherwise, in addition to the Li enrichment, the evolutionary stages are the only other connection between these new Li-rich giants. The CoRoT data confirm that one Li-rich giant is at the core-He burning stage. The other giants are concentrated in close proximity to the red giant branch luminosity bump, the core-He burning stages, or the early-asymptotic giant branch. This is very clear from the Gaia-based luminosities of the Li-rich giants. This is also seen when the CoRoT Li-rich giants are compared to a larger sample of 2252 giants observed in the CoRoT fields by the Gaia-ESO Survey, which are distributed throughout the red giant branch in the Teff-log g diagram. These observations show that the evolutionary stage is a major factor for the Li enrichment in giants. Other processes, such as planet accretion, contribute at a smaller scale.
ABSTRACT
We report on precise Doppler measurements of L231-32 (TOI-270), a nearby M dwarf (d = 22 pc, M⋆ = 0.39 M⊙, R⋆ = 0.38 R⊙), which hosts three transiting planets that were recently discovered ...using data from the Transiting Exoplanet Survey Satellite (TESS). The three planets are 1.2, 2.4, and 2.1 times the size of Earth and have orbital periods of 3.4, 5.7, and 11.4 d. We obtained 29 high-resolution optical spectra with the newly commissioned Echelle Spectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO) and 58 spectra using the High Accuracy Radial velocity Planet Searcher (HARPS). From these observations, we find the masses of the planets to be 1.58 ± 0.26, 6.15 ± 0.37, and 4.78 ± 0.43 M⊕, respectively. The combination of radius and mass measurements suggests that the innermost planet has a rocky composition similar to that of Earth, while the outer two planets have lower densities. Thus, the inner planet and the outer planets are on opposite sides of the ‘radius valley’ – a region in the radius-period diagram with relatively few members – which has been interpreted as a consequence of atmospheric photoevaporation. We place these findings into the context of other small close-in planets orbiting M dwarf stars, and use support vector machines to determine the location and slope of the M dwarf (Teff < 4000 K) radius valley as a function of orbital period. We compare the location of the M dwarf radius valley to the radius valley observed for FGK stars, and find that its location is a good match to photoevaporation and core-powered mass-loss models. Finally, we show that planets below the M dwarf radius valley have compositions consistent with stripped rocky cores, whereas most planets above have a lower density consistent with the presence of a H-He atmosphere.
Context. The study of stellar activity is important because it can provide new constraints for dynamo models when combined with surface rotation rates and the depth of the convection zone. We know ...that the dynamo mechanism, which is believed to be the main process that rules the magnetic cycle of solar-like stars, results from the interaction between (differential) rotation, convection, and magnetic field. The Kepler mission has already been collecting data for a large number of stars during four years allowing us to investigate magnetic stellar cycles. Aims. We investigated the Kepler light curves to look for magnetic activity or even hints of magnetic activity cycles. Based on the photometric data we also looked for new magnetic indexes to characterise the magnetic activity of the stars. Methods. We selected a sample of 22 solar-like F stars that have a rotation period shorter than 12 days. We performed a time-frequency analysis using the Morlet wavelet yielding a magnetic proxy for our sample of stars. We computed the magnetic index Sph as the standard deviation of the whole time series and the index ⟨ Sph ⟩, which is the mean of standard deviations measured in subseries of length five times the rotation period of the star. We defined new indicators, such as the contrast between high and low activity, to take into account the fact that complete magnetic cycles are not observed for all the stars. We also inferred the Rossby number of the stars and studied their stellar background. Results. This analysis shows different types of behaviour in the 22 F stars. Two stars show behaviour very similar to magnetic activity cycles. Five stars show long-lived spots or active regions suggesting the existence of active longitudes. Two stars in our sample seem to have a decreasing or increasing trend in the temporal variation of the magnetic proxies. Finally, the last group of stars shows magnetic activity (with the presence of spots) but no sign of cycle.
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