We present a study into the formation of planetary systems around low mass stars similar to Trappist-1, through the accretion of either planetesimals or pebbles. The aim is to determine if the ...currently observed systems around low mass stars could favour one scenario over the other. To determine these differences, we ran numerous N-body simulations, coupled to a thermally evolving viscous 1D disc model, and including prescriptions for planet migration, photoevaporation, and pebble and planetesimal dynamics. We mainly examine the differences between the pebble and planetesimal accretion scenarios, but we also look at the influences of disc mass, size of planetesimals, and the percentage of solids locked up within pebbles. When comparing the resulting planetary systems to Trappist-1, we find that a wide range of initial conditions for both the pebble and planetesimal accretion scenarios can form planetary systems similar to Trappist-1, in terms of planet mass, periods, and resonant configurations. Typically these planets formed exterior to the water iceline and migrated in resonant convoys into the inner region close to the central star. When comparing the planetary systems formed through pebble accretion to those formed through planetesimal accretion, we find a large number of similarities, including average planet masses, eccentricities, inclinations, and period ratios. One major difference between the two scenarios was that of the water content of the planets. When including the effects of ablation and full recycling of the planets’ envelope with the disc, the planets formed through pebble accretion were extremely dry, whilst those formed through planetesimal accretion were extremely wet. If the water content is not fully recycled and instead falls to the planets’ core, or if ablation of the water is neglected, then the planets formed through pebble accretion are extremely wet, similar to those formed through planetesimal accretion. Should the water content of the Trappist-1 planets be determined accurately, this could point to a preferred formation pathway for planetary systems, or to specific physics that may be at play.
At a distance of 1.295 parsecs, the red dwarf Proxima Centauri (α Centauri C, GL 551, HIP 70890 or simply Proxima) is the Sun's closest stellar neighbour and one of the best-studied low-mass stars. ...It has an effective temperature of only around 3,050 kelvin, a luminosity of 0.15 per cent of that of the Sun, a measured radius of 14 per cent of the radius of the Sun and a mass of about 12 per cent of the mass of the Sun. Although Proxima is considered a moderately active star, its rotation period is about 83 days (ref. 3) and its quiescent activity levels and X-ray luminosity are comparable to those of the Sun. Here we report observations that reveal the presence of a small planet with a minimum mass of about 1.3 Earth masses orbiting Proxima with a period of approximately 11.2 days at a semi-major-axis distance of around 0.05 astronomical units. Its equilibrium temperature is within the range where water could be liquid on its surface.
Our recent N-body simulations of planetary system formation, incorporating models for the main physical processes thought to be important during the building of planets (i.e. gas disc evolution, ...migration, planetesimal/boulder accretion, gas accretion on to cores, etc.), have been successful in reproducing some of the broad features of the observed exoplanet population (e.g. compact systems of low-mass planets, hot Jupiters), but fail completely to form any surviving cold Jupiters. The primary reason for this failure is rapid inward migration of growing protoplanets during the gas accretion phase, resulting in the delivery of these bodies on to orbits close to the star. Here, we present the results of simulations that examine the formation of gas giant planets in protoplanetary discs that are radially structured due to spatial and temporal variations in the effective viscous stresses, and show that such a model results in the formation of a population of cold gas giants. Furthermore, when combined with models for disc photoevaporation and a central magnetospheric cavity, the simulations reproduce the well-known hot-Jupiter/cold-Jupiter dichotomy in the observed period distribution of giant exoplanets, with a period valley between 10 and 100 d.
Genetic diversity confers adaptive capacity to populations under changing conditions but its role in mediating impacts of climate change remains unresolved for most ecosystems. This lack of knowledge ...is particularly acute for foundation species, where impacts may cascade throughout entire ecosystems. We combined population genetics with eco-physiological and ecological field experiments to explore relationships among latitudinal patterns in genetic diversity, physiology and resilience of a kelp ecosystem to climate stress. A subsequent 'natural experiment' illustrated the possible influence of latitudinal patterns of genetic diversity on ecosystem vulnerability to an extreme climatic perturbation (marine heatwave). There were strong relationships between physiological versatility, ecological resilience and genetic diversity of kelp forests across latitudes, and genetic diversity consistently outperformed other explanatory variables in contributing to the response of kelp forests to the marine heatwave. Population performance and vulnerability to a severe climatic event were thus strongly related to latitudinal patterns in genetic diversity, with the heatwave extirpating forests with low genetic diversity. Where foundation species control ecological structure and function, impacts of climatic stress can cascade through the ecosystem and, consequently, genetic diversity could contribute to ecosystem vulnerability to climate change.
Lipid droplets (LDs) store metabolic energy and membrane lipid precursors. With excess metabolic energy, cells synthesize triacylglycerol (TG) and form LDs that grow dramatically. It is unclear how ...TG synthesis relates to LD formation and growth. Here, we identify two LD subpopulations: smaller LDs of relatively constant size, and LDs that grow larger. The latter population contains isoenzymes for each step of TG synthesis. Glycerol-3-phosphate acyltransferase 4 (GPAT4), which catalyzes the first and rate-limiting step, relocalizes from the endoplasmic reticulum (ER) to a subset of forming LDs, where it becomes stably associated. ER-to-LD targeting of GPAT4 and other LD-localized TG synthesis isozymes is required for LD growth. Key features of GPAT4 ER-to-LD targeting and function in LD growth are conserved between Drosophila and mammalian cells. Our results explain how TG synthesis is coupled with LD growth and identify two distinct LD subpopulations based on their capacity for localized TG synthesis.
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► Triacylglyceride (TG) synthesis is coupled with lipid droplet (LD) growth ► Two LD populations exist: growing LDs, containing TG enzymes, and small LDs ► Specific TG synthesis enzymes move from the ER to LDs through membrane bridges ► LD localization of TG enzymes mediates expansion of a subset of LDs
Lipid droplets (LDs) store metabolic energy and membrane lipid precursors. Wilfling et al. identify two LD populations distinct in their capacity for localized triacylglycerol (TG) synthesis, which is coupled to LD growth. TG synthesis enzymes relocate via membrane bridges from the ER to the LD surface to mediate LD expansion.
Persons with continuous complex care needs frequently require care in multiple settings. During transitions between settings, this population is particularly vulnerable to experiencing poor care ...quality and problems of care fragmentation. Despite how common these transitions have become, the challenges of improving care transitions have received little attention from policy makers, clinicians, and quality improvement entities. This article begins with a definition of transitional care and then discusses the nature of the problem, its prevalence, manifestations of poorly executed transitions, and potentially remediable barriers. Necessary elements for effective transitions are then presented, followed by promising new directions for quality improvement at the level of the delivery system, information technology, and national health policy. The article concludes with a proposed research agenda designed to advance the science of high‐quality transitional care.
Open radical cystectomy (ORC) has proven to be an important component in the treatment of high-risk bladder cancer (BCa). ORC surgical morbidity remains high; therefore, minimally invasive surgical ...techniques have been introduced in an attempt to improve patient outcomes.
To compare cancer outcomes in BCa patients managed with ORC or robotic-assisted radical cystectomy (RARC).
A prospective, randomized trial was completed between 2010 and 2013. Patients were randomized to ORC/pelvic lymphadenectomy (PLND) or RARC/PLND, with all undergoing open/extracorporeal urinary diversion. Median follow-up was 4.9 (IQR: 3.9–5.9) yr after surgery among surviving patients.
Secondary outcomes to the trial included recurrence-free, cancer-specific, and overall survival.
The trial randomized 118 patients who underwent RC/PLND and urinary diversion. Sixty were randomized to RARC and 58 to ORC. Four RARC-assigned patients refused randomization and received ORC; however, an intention to treat analysis was performed. No differences were observed in recurrence (hazard ratio HR: 1.27; 95% confidence interval CI: 0.69–2.36; p=0.4) or cancer-specific survival (p=0.4). No difference in overall survival was observed (p=0.8). However, the pattern of first recurrence demonstrated a nonstatistically significant increase in metastatic sites for those undergoing ORC (sub-HR sHR: 2.21; 95% CI: 0.96–5.12; p=0.064) and a greater number of local/abdominal sites in the RARC-treated patients (sHR: 0.34; 95% CI: 0.12–0.93; p=0.035). The major limitation to this study is that the trial was not powered to determine differences in cancer recurrences, survival outcomes, or patterns of recurrence.
The secondary outcomes from our randomized trial did not definitively demonstrate differences in cancer outcomes in patients treated with ORC or RARC. However, differences in observed patterns of first recurrence highlight the need for future studies.
Of 118 patients randomly assigned to undergo radical cystectomy/pelvic lymphadenectomy and urinary diversion, half were assigned to open surgery and half to robot-assisted techniques. We found no difference in risk of recurring or dying of bladder cancer between the two groups.
In this secondary analysis of cancer outcomes from our randomized controlled trial, we did not find a difference in overall recurrence rates and cancer-specific survival between open radical cystectomy and robot-assisted radical cystectomy for high-risk bladder cancer. Variations in patterns of recurrence require further study.
Bladder cancer is the fifth most prevalent cancer in the U.S., yet is understudied, and few laboratory models exist that reflect the biology of the human disease. Here, we describe a biobank of ...patient-derived organoid lines that recapitulates the histopathological and molecular diversity of human bladder cancer. Organoid lines can be established efficiently from patient biopsies acquired before and after disease recurrence and are interconvertible with orthotopic xenografts. Notably, organoid lines often retain parental tumor heterogeneity and exhibit a spectrum of genomic changes that are consistent with tumor evolution in culture. Analyses of drug response using bladder tumor organoids show partial correlations with mutational profiles, as well as changes associated with treatment resistance, and specific responses can be validated using xenografts in vivo. Our studies indicate that patient-derived bladder tumor organoids represent a faithful model system for studying tumor evolution and treatment response in the context of precision cancer medicine.
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•Efficient generation of a biobank of patient-derived bladder cancer organoids•Organoids recapitulate the histological and molecular spectrum of human bladder cancer•Bladder tumor organoids display clonal evolution in culture and as xenografts•Drug response of organoids can be validated in xenografts
A biobank of patient-derived bladder tumor organoids faithfully recapitulates features of human cancer and enables analysis of clonal evolution and drug responses.
Kelp forests dominated by species of Laminariales are globally recognized as key habitats on subtidal temperate rocky reefs. Forests characterized by fucalean seaweed, in contrast, receive relatively ...less attention despite being abundant, ubiquitous, and ecologically important. Here, we review information on subtidal fucalean taxa of Australia's Great Southern Reef, with a focus on the three most abundant and widely distributed genera (Phyllospora, Scytothalia, and Sargassum) to reveal the functionally unique role of fucoids in temperate reef ecology. Fucalean species span the entire temperate coastline of Australia (~71,000 km2) and play an important role in supporting subtidal temperate biodiversity and economic values on rocky reefs as well as in adjacent habitats. Climatic and anthropogenic stressors have precipitated significant range retractions and declines in many fucoids, with critical implications for associated assemblages. Such losses are persistent and unlikely to be reversed naturally due to the life history of these species and colonization of competitors and grazers following loss. Active restoration is proving successful in bringing back some fucoid species (Phyllospora comosa) lost from urban shores and will complement other passive and active forms of conservation. Fucalean forests play a unique role on subtidal temperate reefs globally, especially in Australia, but are comparatively understudied. Addressing this knowledge gap will be critical for understanding, predicting, and mitigating extant and future loss of these underwater forests and the valuable ecosystem services they support.
Underwater forests dominated by fucoids are largely understudied relative to their laminarian counterparts, but are equally as abundant and ecologically important. We show that Australia's dominant subtidal fucoids support important biodiversity and economic values, but are declining with critical implications for associated assemblages. Although active restoration is proving successful in bringing these forests back, the dearth of knowledge on underwater fucoid forests requires prompt action to properly manage and protect these key habitats.
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