WD 1145+017 was observed from 2015 November to 2016 July, for the purpose of characterizing transit behaviour of the white dwarf by dust clouds thought to be produced by fragments of an asteroid in ...close orbit with the star. Fortuitously, most of these observations were carried out during a time when the overall 'dip' activity was dramatically enhanced over that during its discovery with Kepler K2. By the end of our reported observations, the dip activity had declined to a level close to its K2 discovery state. Three notable events were observed. In 2016 January, a large number of dust clouds appeared that had an orbital period of 4.4912 h, and this event also marked the end of a three-month interval dominated by the K2 'A' period. The second event was a 2016 April 21 appearance of four dip features with drift lines in a waterfall (date versus phase) diagram that diverged from their origin date, at a location away from the 'A' asteroid, and which lasted for two weeks. The third event was the sudden appearance of a dip feature with a period of 4.6064 h, which is essentially the same as the K2 'B' period. The evolution of dip shape, depth, and total fade amount provide constraints on dust production and loss mechanisms. Collisions can account for the sudden appearance of dust clouds, and the sudden increase in dust amount, but another mechanism for continual dust production is also required.
ABSTRACT
Adolescence is a unique period of physical and psychosocial changes as youth transition, over many years, to adulthood. The psychosocial changes that accompany adolescence include emotional ...separation from parents, greater influence of peer groups, an interest in self‐identification and autonomy, and increased risk‐taking behaviors. Substance use is a common form of risk‐taking behavior in the adolescent developmental stage. Alcohol, nicotine, and cannabis are the most common types of substances used in the United States. In the adolescent transplant population, rates of substance use appear to be at, or slightly below, their peer counterparts. Substance use can lead to deleterious health outcomes for adolescent transplant patients as a result of impaired decision‐making, reduction in medication and clinic visit compliance, increases in mental health disorders, and risk for developing dependence and a substance use disorder. Given the close relationship that many pediatric transplant providers have with their patients and families, transplant care teams are in an excellent position to help their patients by addressing adolescent substance use. This narrative review describes how providers can use proactive standardized approaches to identify and intervene with substance use behavior.
Large igneous provinces (LIPs) lie approximately above the margins of the African and Pacific large low shear velocity provinces (LLSVPs) in the deep mantle. This spatial correlation has been used to ...argue that plumes are preferentially generated at the margins of LLSVPs. We perform a series of Monte Carlo-based statistical tests to assess the uniqueness of this conclusion. These tests indicate that (1) the reconstructed locations of LIPs are significantly correlated with both slower-than-average shear wave velocity regions, which contain LLSVPs, and the margins of these structures; and (2) these correlations cannot be statistically distinguished. That is, given current constraints, if plumes were generated randomly throughout regions of slower-than-average shear wave velocity in the deep mantle, then statistical tests are expected to show a significant correlation between the locations of LIPs and the margins of LLSVPs. We therefore conclude that it is premature to argue that the margins of LLSVPs represent preferred zones of plume generation. This conclusion is reinforced in our analysis by a demonstration that the expected mean distance of a set of points randomly placed in slower-than-average shear wave velocity regions is consistent with the observed mean distance between LIPs and the margins of LLSVPs. Finally, we also test the correlation between the reconstructed locations of LIPs and the horizontal gradient in deep mantle shear velocity perturbations. We find, given the uncertainty implied by different tomography models, that there is no statistically significant correlation and that being in a slow region (i.e. in the region of LLSVPs) is a stronger geographic requirement for plume generation than being at a specific (high) gradient.
We have obtained extensive photometric observations of the polluted white dwarf WD 1145+017 which has been reported to be transited by at least one, and perhaps several, large asteroids with dust ...emission. Observation sessions on 37 nights spanning 2015 November to 2016 January with small to modest size telescopes have detected 237 significant dips in flux. Periodograms reveal a significant periodicity of 4.5004 h consistent with the dominant ('A') period detected with K2. The folded light curve shows an hour-long depression in flux with a mean depth of nearly 10 per cent. This depression is, in turn, comprised of a series of shorter and sometimes deeper dips which would be unresolvable with K2. We also find numerous dips in flux at other orbital phases. Nearly all of the dips associated with this activity appear to drift systematically in phase with respect to the 'A' period by about 2.5 min d super( -1) with a dispersion of ~0.5 min d super( -1), corresponding to a mean drift period of 4.4928 h. We are able to track ~15 discrete drifting features. The 'B'-'F' periods found with K2 are not detected, but we would not necessarily have expected to see them. We explain the drifting motion as due to smaller fragmented bodies that break off from the asteroid and go into a slightly smaller orbit. In this interpretation, we can use the drift rate to determine the mass of the asteroid, which we find to be ...10 super( 23) g, or about 1/10th the mass of Ceres. (ProQuest: ... denotes formulae/symbols omitted.)
The dual-action HIV-1 protease and reverse transcriptase inhibition potential of coumarin–AZT conjugates has been explored using saturation transfer difference (STD) NMR, computer modelling and ...enzyme inhibition techniques.
Baylis–Hillman-derived 3-(benzylaminomethyl)coumarins have been treated, sequentially, with chloroacetyl chloride and propargylamine to afford alkynylated coumarins as substrates for Click Chemistry reactions with azidothymidine (AZT) in the presence of a Cu(I) catalyst. The dual-action HIV-1 protease (PR) and reverse transcriptase (RT) inhibition potential of the resulting N-benzylated cycloaddition products, and a series of non-benzylated analogues, has been explored using saturation transfer difference (STD) NMR, computer modelling and enzyme inhibition techniques.
ABSTRACT
We report the discovery in TESS Sectors 3 and 4 of a compact triply eclipsing triple star system. TIC 209409435 is a previously unknown eclipsing binary with a period of 5.717 d, and the ...presence of a third star in an outer eccentric orbit of 121.872-d period was found from two sets of third-body eclipses and from eclipse timing variations. The latter exhibits signatures of strong third-body perturbations. After the discovery, we obtained follow-up ground-based photometric observations of several binary eclipses as well as another of the third-body eclipses. We carried out comprehensive analyses, including the simultaneous photodynamical modelling of TESS and ground-based light curves (including both archival WASP data, and our own follow-up measurements), as well as eclipse timing variation curves. Also, we have included in the simultaneous fits multiple star spectral energy distribution data and theoretical PARSEC stellar isochrones. We find that the inner binary consists of near twin stars of mass 0.90 M⊙ and radius 0.88 R⊙. The third star is just 9 per cent more massive and 18 per cent larger in radius. The inner binary has a rather small eccentricity, while the outer orbit has e = 0.40. The inner binary and outer orbit have inclination angles within 0.1° and 0.2° of 90°, respectively. The mutual inclination angle is ≲1/4°. All of these results were obtained without radial velocity observations.
Abstract
For many species, a well documented response to anthropogenic climate change is a shift in various aspects of its life history, including its timing or phenology. Often, these phenological ...shifts are associated with changes in abiotic factors used as proxies for resource availability or other suitable conditions. Resource availability, however, can also be impacted by competition, but the impact of competition on phenology is less studied than abiotic drivers. We fit generalized additive models (GAMs) to a long‐term experimental dataset on small mammals monitored in the southwestern United States and show that altered competitive landscapes can drive shifts in breeding timing and prevalence, and that, relative to a dominant competitor, other species exhibit less specific responses to environmental factors. These results suggest that plasticity of phenological responses, which is often described in the context of annual variation in abiotic factors, can occur in response to biotic context as well. Variation in phenological responses under different biotic conditions shown here further demonstrates that a more nuanced understanding of shifting biotic interactions is useful to better understand and predict biodiversity patterns in a changing world.
Using Campaign 15 data from theK2mission, we have discovered a triply eclipsing triple star system: EPIC 249432662. The inner eclipsing binary system has a period of 8.23 d, withshallow∼3 per cent ...eclipses. During the entire 80-d campaign, there is also a single eclipse event of a third body in the system that reaches a depth of nearly 50 per cent and has a total duration of 1.7 d, longer than for any previously known third-body eclipse involving unevolved stars. The binary eclipses exhibit clear eclipse timing variations. A combination of photodynamical modeling of the light curve, as well as seven follow-up radial velocity measurements, has led to a prediction of the subsequent eclipses of the third star with a period of 188 d. A campaign of follow-up ground-based photometry was able to capture the subsequent pair of third-body events as well as two further 8-d eclipses. A combined photo-spectro-dynamical analysis then leads to the determination of many of the system parameters. The 8-d binary consists of a pair of M stars, while most of the system light is from a K star around which the pair of M stars orbits.
Context
Dynamic feedbacks between physical structure and ecological function drive ecosystem productivity, resilience, and biodiversity maintenance. Detailed maps of canopy structure enable ...comprehensive evaluations of structure–function relationships. However, these relationships are scale-dependent, and identifying relevant spatial scales to link structure to function remains challenging.
Objectives
We identified optimal scales to relate structure heterogeneity to ecological resistance, measured as the impacts of wildfire on canopy structure, and ecological resilience, measured as native shrub recruitment. We further investigated whether structural heterogeneity can aid spatial predictions of shrub recruitment.
Methods
Using high-resolution imagery from unoccupied aerial systems (UAS), we mapped structural heterogeneity across ten semi-arid landscapes, undergoing a disturbance-mediated regime shift from native shrubland to dominance by invasive annual grasses. We then applied wavelet analysis to decompose structural heterogeneity into discrete scales and related these scales to ecological metrics of resilience and resistance.
Results
We found strong indicators of scale dependence in the tested relationships. Wildfire effects were most prominent at a single scale of structural heterogeneity (2.34 m), while the abundance of shrub recruits was sensitive to structural heterogeneity at a range of scales, from 0.07 – 2.34 m. Structural heterogeneity enabled out-of-site predictions of shrub recruitment (R
2
= 0.55). The best-performing predictive model included structural heterogeneity metrics across multiple scales.
Conclusions
Our results demonstrate that identifying structure–function relationships requires analyses that explicitly account for spatial scale. As high-resolution imagery enables spatially extensive maps of canopy heterogeneity, models for scale dependence will aid our understanding of resilience mechanisms in imperiled arid ecosystems.
ABSTRACT
In this work we report the discovery and analysis of three new triply eclipsing triple star systems found with the TESS mission during its observations of the northern skies: TICs 193993801, ...388459317, and 52041148. We utilized the TESS precision photometry of the binary eclipses and third-body eclipsing events, ground-based archival and follow-up photometric data, eclipse timing variations, archival spectral energy distributions, as well as theoretical evolution tracks in a joint photodynamical analysis to deduce the system masses and orbital parameters of both the inner and outer orbits. In one case (TIC 193993801) we also obtained radial velocity measurements of all three stars. This enabled us to ‘calibrate’ our analysis approach with and without ‘truth’ (i.e. RV) data. We find that the masses are good to 1–3 per cent accuracy with RV data and 3–10 per cent without the use of RV data. In all three systems we were able to find the outer orbital period before doing any detailed analysis by searching for a longer-term periodicity in the ASAS-SN archival photometry data – just a few thousand ASAS-SN points enabled us to find the outer periods of 49.28 d, 89.86 d, and 177.0 d, respectively. From our full photodynamical analysis we find that all three systems are coplanar to within 1°−3°. The outer eccentricities of the three systems are 0.003, 0.10, and 0.62, respectively (i.e. spanning a factor of 200). The masses of the three stars {Aa, Ab, and B} in the three systems are: {1.31, 1.19, 1.34}, {1.82, 1.73, 2.19}, and {1.62, 1.48, 2.74} M⊙, respectively.
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