Abstract
Ultra-hot Jupiters with equilibrium temperatures greater than 2000 K are uniquely interesting targets as they provide us crucial insights into how atmospheres behave under extreme ...conditions. This class of giant planets receives intense radiation from their host star and usually has strongly irradiated and highly inflated atmospheres. At such a high temperature, cloud formation is expected to be suppressed and thermal dissociation of water vapor could occur. We observed the ultra-hot Jupiter WASP-76b with seven transits and five eclipses using the Hubble Space Telescope and the Spitzer Space Telescope (Spitzer) for a comprehensive study of its atmospheric chemical and physical processes. We detected TiO and H
2
O absorption in the optical and near-infrared transit spectrum. Additional absorption by a number of neutral and ionized heavy metals like Fe, Ni, Ti, and SiO help explain the short-wavelength transit spectrum. The secondary eclipse spectrum shows muted water feature but a strong CO emission feature in Spitzer’s 4.5
μ
m band indicating an inverted temperature pressure profile. We analyzed both the transit and eclipse spectra with a combination of self-consistent PHOENIX models and atmospheric retrieval. Both spectra were well fitted by the self-consistent PHOENIX forward atmosphere model in chemical and radiative equilibrium at solar metallicity, adding to the growing evidence that both TiO/VO and NUV heavy metals opacity are prominent NUV-optical opacity sources in the stratospheres of ultra-hot Jupiters.
ISWI proteins form the catalytic core of a subset of ATP-dependent chromatin remodeling activities in eukaryotes from yeast to man. Many of these complexes have been found to reposition nucleosomes ...but with different directionalities. We find that the yeast Isw1a, Isw2, and Chd1 enzymes preferentially move nucleosomes toward more central locations on short DNA fragments whereas Isw1b does not. Importantly, the inherent positioning properties of the DNA play an important role in determining where nucleosomes are relocated to by all of these enzymes. However, a key difference is that the Isw1a, Isw2, and Chd1 enzymes are unable to move nucleosomes to positions closer than 15 bp from a DNA end, whereas Isw1b can. We also find that there is a correlation between the inability of enzymes to move nucleosomes close to DNA ends and the preferential binding to nucleosomes bearing linker DNA. These observations suggest that the accessibility of linker DNA together with the positioning properties of the underlying DNA play important roles in determining the outcome of remodeling by these enzymes.
As our view of disturbances such as wildfire has shifted from prevention to recognizing their ecological necessity, so too forest management has evolved from timber-focused even-aged management to ...more holistic paradigms like ecosystem-based management. Emulation of natural disturbance (END) is a variant of ecosystem management that recognizes the importance of disturbance for maintaining ecological integrity. For END to be a successful model for forest management we need to describe disturbance regimes and implement management actions that emulate them, in turn achieving our objectives for forest structure and function. We review the different components of fire regimes (cause, frequency, extent, timing, and magnitude), we describe low-, mixed-, and high-severity fire regimes, and we discuss key issues related to describing these regimes. When characterizing fire regimes, different methods and spatial and temporal extents result in wide variation of estimates for different fire regime components. Comparing studies is difficult as few measure the same components; some methods are based on the assumption of a high-severity fire regime and are not suited to detecting mixed- or low-severity regimes, which are critical to END management, as this would affect retention in harvested areas. We outline some difficulties with using fire regimes as coarse filters for forest management, including (i) not fully understanding the interactions between fire and other disturbance agents, (ii) assuming that fire is strictly an exogenous disturbance agent that exerts top-down control of forest structure while ignoring numerous endogenous and bottom-up feedbacks on fire effects, and (iii) assuming by only replicating natural disturbance patterns we preserve ecological processes and vital ecosystem components. Even with a good understanding of a fire regime, we would still be challenged with choosing the temporal and spatial scope for the disturbance regime we are trying to emulate. We cannot yet define forest conditions that will arise from variations in disturbance regime; this then limits our ability to implement management actions that will achieve those conditions. We end by highlighting some important knowledge gaps about fire regimes and how the END model could be strengthened to achieve a more sustainable form of forest management.
Abstract
The effect of stellar multiplicity on planetary architecture and orbital dynamics provides an important context for exoplanet demographics. We present a volume-limited catalog of up to 300 ...pc of 66 stars hosting planets and planet candidates from Kepler, K2, and TESS with significant Hipparcos-Gaia proper motion anomalies, which indicates the presence of companions. We assess the reliability of each transiting planet candidate using ground-based follow-up observations, and find that the TESS Objects of Interest (TOIs) with significant proper anomalies show nearly four times more false positives due to eclipsing binaries compared to TOIs with marginal proper anomalies. In addition, we find tentative evidence that orbital periods of planets orbiting TOIs with significant proper anomalies are shorter than those orbiting TOIs without significant proper anomalies, consistent with the scenario that stellar companions can truncate planet-forming disks. Furthermore, TOIs with significant proper anomalies exhibit lower Gaia differential velocities in comparison to field stars with significant proper anomalies, suggesting that planets are more likely to form in binary systems with low-mass substellar companions or stellar companions at wider separation. Finally, we characterize the three-dimensional architecture of LTT 1445 ABC using radial velocities, absolute astrometry from Gaia and Hipparcos, and relative astrometry from imaging. Our analysis reveals that LTT 1445 is a nearly flat system, with a mutual inclination of ∼2.°88 between the orbit of BC around A and that of C around B. This coplanarity may explain why multiple planets around LTT 1445 A survive in the dynamically hostile environments of this system.
Wildfire is an important natural disturbance agent in Canadian forests, but it has also caused significant economic damage nationwide. Spatial fire growth models have emerged as important tools for ...representing wildfire dynamics across diverse landscapes, enabling the mapping of key wildfire hazard metrics such as location-specific burn probabilities or likelihoods of fire ignition. While these summary metrics have gained popularity, they often fall short in capturing the directional spread of wildfires and their potential spread distances. The metrics depicting the directional spread of wildfire can be derived from raw outputs generated with fire growth models, such as the perimeters and ignition locations of individual fires, but extracting this information requires complex data processing. To address this data gap, we present PostBP, an open-source Python package designed for post-processing the raw outputs of fire growth models — the ignition locations and perimeters of individual fires simulated over multiple stochastic iterations — into a matrix of fire spread likelihoods between all pairs of forest patches in a landscape. The PostBP also generates several other summary outputs, such as the source-sink ratio and the fire spread rose diagram. We provide an overview of PostBP's capabilities and demonstrate its practical application to a forested landscape.•Wildfire growth models generate large amounts of outputs, which are hard to summarize for practical decision-making.•The PostBP package calculates the summary metrics characterizing the directional spread of wildfires.•The fire risk summaries generated with PostBP can support the assessments of wildfire risk and mitigation measures.
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In the cell, DNA is wrapped on histone octamers, which reduces its accessibility for DNA interacting enzymes. We investigated de novo methylation of nucleosomal DNA in vitro and show that the Dnmt3a ...and Dnmt1 DNA methyltransferases efficiently methylate nucleosomal DNA without dissociation of the histone octamer from the DNA. In contrast, the prokaryotic SssI DNA methyltransferase and the catalytic domain of Dnmt3a are strongly inhibited by nucleosomes. We also found that full-length Dnmt1 and Dnmt3a bind to nucleosomes much stronger than their isolated catalytic domains, demonstrating that the N-terminal parts of the MTases are required for the interaction with nucleosomes. Variations of the DNA sequence or the histone tails did not significantly influence the methylation activity of Dnmt3a. The observation that mammalian methyltransferases directly modify nucleosomal DNA provides an insight into the mechanisms by which histone tail and DNA methylation patterns can influence each other because the DNA methylation pattern can be established while histones remain associated to the DNA.
Here, singular expression relies on the presence of a site for antigen gene expression, and switching to new variants is achieved by recombination into the expression site.\n It is also perplexing ...that the rate of switching appears unaltered in DOT1B mutants. ...only a single ESB is visible in the DOT1B ES double expresser, whereas two extranucleolar sites of ES transcription are found in such putative switch intermediates in wild-type cells 37. ...epigenetic strategies are now being recognised as important mediators of antigenic variation, though most likely T. brucei and P. falciparum have arrived at this commonality through convergent evolution.
Astrometric satellite positions are derived from timings of their eclipses in the shadow of Jupiter. The 548 data points span 20
years and are accurate to about 0.006
arcsec for Io and Europa and ...about 0.015
arcsec or better for Ganymede and Callisto. The precision of the data set and its nearly continuous distribution in time allows measurement of regular oscillations with an accuracy of 0.001
arcsec. This level of sensitivity permits detailed evaluation of modern ephemerides and reveals anomalies at the 1.3
year period of the resonant perturbations between Io, Europa and Ganymede. The E5 ephemeris shows large errors at that period for all three satellites as well as other significant anomalies. The L1 ephemeris fits the observations much more closely than E5 but discrepancies for the resonant satellites are still apparent and the measured positions of Io are drifting away from the predictions. The JUP230 ephemeris fits the observations more accurately than L1 although there is still a measurable discordance between the predictions and observations for Europa at the resonance period.
The boreal forests of Alberta have extensive networks of legacy seismic exploration lines that have been linked to the decline of boreal woodland caribou (Rangifer tarandus caribou) populations ...throughout the region. In order to improve habitat quality for caribou, energy companies are investing significant resources in the restoration of many of these seismic lines in key areas, however, frequent large and intense wildfires may compromise the effectiveness of these conservation measures. To minimize the wildfire risk, managers need to know the likelihood of wildfire and the effectiveness of mitigation measures. We undertook a wildfire risk assessment across the Cold Lake caribou range where we used the Burn-P3 model to determine: a) burn probability; b) wildfire risk to restored seismic line areas; and c) the effectiveness of mitigation measures. The burn probability of the landscape was highly heterogeneous, and recent large burns and some waterbodies provided “shields” that reduced burn probability on their leeward sides. We designed mitigation scenarios to mimic the shielding effect of waterbodies and large recent burns by modeling the effects of increase suppression activity and fuel conversion within intensive management zones upwind of the resources to be protected. We found that these intensive management zones reduced the burn probability and wildfire hazard in the restored habitat areas but the effect declined rapidly as distance from the treatment zones increased. If land managers want to minimize the risk of losing their investments in caribou conservation to wildfire, it would be preferable to have mitigation measures spatially targeted closer to the conservation areas. Furthermore, it would be advisable to have redundancy in any conservation measures and wildfire-risk mitigations to ensure that losses due to wildfire on one area do not jeopardize all conservation projects within the landscape.
•Locations for conservation often based on current landscape conditions.•Assessments often ignore wildfire risk, which can destroy habitat restoration.•Use Burn Probability Modeling to examine fire risk to caribou conservation projects.•Intensive management reduces burn probability and fire hazard.•These effects decline as the distance from the treated area increases.
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