Quantifying global soil respiration (RSG) and its response to temperature change are critical for predicting the turnover of terrestrial carbon stocks and their feedbacks to climate change. ...Currently, estimates of RSG range from 68 to 98 Pg C year−1, causing considerable uncertainty in the global carbon budget. We argue the source of this variability lies in the upscaling assumptions regarding the model format, data timescales, and precipitation component. To quantify the variability and constrain RSG, we developed RSG models using Random Forest and exponential models, and used different timescales (daily, monthly, and annual) of soil respiration (RS) and climate data to predict RSG. From the resulting RSG estimates (range = 66.62–100.72 Pg), we calculated variability associated with each assumption. Among model formats, using monthly RS data rather than annual data decreased RSG by 7.43–9.46 Pg; however, RSG calculated from daily RS data was only 1.83 Pg lower than the RSG from monthly data. Using mean annual precipitation and temperature data instead of monthly data caused +4.84 and −4.36 Pg C differences, respectively. If the timescale of RS data is constant, RSG estimated by the first‐order exponential (93.2 Pg) was greater than the Random Forest (78.76 Pg) or second‐order exponential (76.18 Pg) estimates. These results highlight the importance of variation at subannual timescales for upscaling to RSG. The results indicated RSG is lower than in recent papers and the current benchmark for land models (98 Pg C year−1), and thus may change the predicted rates of terrestrial carbon turnover and the carbon to climate feedback as global temperatures rise.
Quantifying different sources of variability in global soil respiration estimates helped to constrain soil respiration projections. We developed global soil respiration models using Random Forest and exponential models and used different timescales (daily, monthly, and annual) of soil respiration and climate data to predict global soil respiration. We found global soil respiration is closer to 70‐81 Pg C yr‐1. These results highlight the need for understanding and capturing the relevant timescale for upscaling fine‐scale temporal measures to broad‐scale global flux estimates. Assuming a lower global soil respiration could substantially change the carbon‐climate feedback under global warming.
We present results from the "Mint" resolution DC Justice League suite of Milky Way-like zoom-in cosmological simulations, which extend our study of nearby galaxies down into the ultrafaint dwarf ...(UFD) regime for the first time. The mass resolution of these simulations is the highest ever published for cosmological Milky Way zoom-in simulations run to z = 0, with initial star (dark matter) particle masses of 994 (17900) M , and a force resolution of 87 pc. We study the surrounding dwarfs and UFDs, and find that the simulations match the observed dynamical properties of galaxies with −3 > MV > −19, and reproduce the scatter seen in the size-luminosity plane for rh 200 pc. We predict the vast majority of nearby galaxies will be observable by the Vera Rubin Observatory's coadded Legacy Survey of Space and Time. We additionally show that faint dwarfs with velocity dispersions 5 km s−1 result from severe tidal stripping of the host halo. We investigate the quenching of UFDs in a hydrodynamical Milky Way context and find that the majority of UFDs are quenched prior to interactions with the Milky Way, though some of the quenched UFDs retain their gas until infall. Additionally, these simulations yield some unique dwarfs that are the first of their kind to be simulated, e.g., an H i-rich field UFD, a late-forming UFD that has structural properties similar to Crater 2, as well as a compact dwarf satellite that has no dark matter at z = 0.
We present a self-consistent prediction from a large-scale cosmological simulation for the population of "wandering" supermassive black holes (SMBHs) of mass greater than 106 M on long-lived, ...kpc-scale orbits within Milky Way (MW)-mass galaxies. We extract a sample of MW-mass halos from the Romulus25 cosmological simulation, which is uniquely able to capture the orbital evolution of SMBHs during and following galaxy mergers. We predict that such halos, regardless of recent merger history or morphology, host an average of 5.1 3.3 SMBHs, including their central black hole, within 10 kpc from the galactic center and an average of 12.2 8.4 SMBHs total within their virial radius, not counting those in satellite halos. Wandering SMBHs exist within their host galaxies for several Gyr, often accreted by their host halo in the early Universe. We find, with >4 significance, that wandering SMBHs are preferentially found outside of galactic disks.
Background Advantages of the arteriovenous fistula (AVF), including long patency and few complications, were ascertained more than 2 decades ago and may not apply to the contemporary dialysis ...population. Study Design Systematic review and meta-analysis. Estimates were pooled using a random-effects model and sources of heterogeneity were explored using metaregression. Setting & Population Patients treated with long-term hemodialysis using an AVF. Selection Criteria for Studies English-language studies indexed in MEDLINE between 2000 and 2012 using prospectively collected data on 100 or more AVFs. Predictor Age, AVF location, and study location. Outcomes Outcomes of interest were primary AVF failure and primary and secondary patency at 1 and 2 years. Results 7,011 citations were screened and 46 articles met eligibility criteria (62 unique cohorts; n = 12,383). The rate of primary failure was 23% (95% CI, 18%-28%; 37 cohorts; 7,393 AVFs). When primary failures were included, the primary patency rate was 60% (95% CI, 56%-64%; 13 studies; 21 cohorts; 4,111 AVFs) at 1 year and 51% (95% CI, 44%-58%; 7 studies; 12 cohorts; 2,694 AVFs) at 2 years. The secondary patency rate was 71% (95% CI, 64%-78%; 10 studies; 11 cohorts; 3,558 AVFs) at 1 year and 64% (95% CI, 56%-73%; 6 studies; 11 cohorts; 1,939 AVFs) at 2 years. In metaregression, there was a significant decrease in primary patency rate in studies that started recruitment in more recent years. Limitations Low quality of studies, variable clinical settings, and variable definitions of primary AVF failure. Conclusions In recent years, AVFs had a high rate of primary failure and low to moderate primary and secondary patency rates. Consideration of these outcomes is required when choosing a patient's preferred access type.
Abstract Background Participation in cardiac rehabilitation has been shown to decrease mortality after acute myocardial infarction, but its impact on readmissions requires examination. Methods We ...conducted a population-based surveillance study of residents discharged from the hospital after their first-ever myocardial infarction in Olmsted County, Minnesota, from January 1, 1987, to September 30, 2010. Patients were followed up through December 31, 2010. Participation in cardiac rehabilitation after myocardial infarction was determined using billing data. We used a landmark analysis approach (cardiac rehabilitation participant vs not determined by attendance in at least 1 session of cardiac rehabilitation at 90 days post-myocardial infarction discharge) to compare readmission and mortality risk between cardiac rehabilitation participants and nonparticipants accounting for propensity to participate using inverse probability treatment weighting. Results Of 2991 patients with incident myocardial infarction, 1569 (52.5%) participated in cardiac rehabilitation after hospital discharge. The cardiac rehabilitation participation rate did not change during the study period, but increased in the elderly and decreased in men and younger patients. After adjustment, cardiac rehabilitation participants had lower all-cause readmission (hazard ratio HR, 0.75; 95% confidence interval CI, 0.65-0.87; P < .001), cardiovascular readmission (HR, 0.80; 95% CI, 0.65-0.99; P = .037), noncardiovascular readmission (HR, 0.72; 95% CI, 0.61-0.85; P < .001), and mortality (HR, 0.58; 95% CI, 0.49-0.68; P < .001) risk. Conclusions Cardiac rehabilitation participation is associated with a markedly reduced risk of readmission and death after incident myocardial infarction. Improving cardiac rehabilitation participation rates may have a large impact on post-myocardial infarction healthcare resource use and outcomes.
Nitrogen (N) deposition is impacting the services that ecosystems provide to humanity. However, the mechanisms determining impacts on the N cycle are not fully understood. To explore the mechanistic ...underpinnings of N impacts on N cycle processes, we reviewed and synthesised recent progress in ecosystem N research through empirical studies, conceptual analysis and model simulations. Experimental and observational studies have revealed that the stimulation of plant N uptake and soil retention generally diminishes as N loading increases, while dissolved and gaseous losses of N occur at low N availability but increase exponentially and become the dominant fate of N at high loading rates. The original N saturation hypothesis emphasises sequential N saturation from plant uptake to soil retention before N losses occur. However, biogeochemical models that simulate simultaneous competition for soil N substrates by multiple processes match the observed patterns of N losses better than models based on sequential competition. To enable better prediction of terrestrial N cycle responses to N loading, we recommend that future research identifies the response functions of different N processes to substrate availability using manipulative experiments, and incorporates the measured N saturation response functions into conceptual, theoretical and quantitative analyses.
ABSTRACT
We use the romulus25 cosmological simulation volume to identify the largest-ever simulated sample of field ultradiffuse galaxies (UDGs). At z = 0, we find that isolated UDGs have average ...star formation rates (SFRs), colours, and virial masses for their stellar masses and environment. UDGs have moderately elevated H i masses, being 70 per cent (300 per cent) more H i rich than typical isolated dwarf galaxies at luminosities brighter (fainter) than MB = −14. However, UDGs are consistent with the general isolated dwarf galaxy population and make up ∼20 per cent of all field galaxies with 107 < M⋆/M⊙ < 109. The H i masses, effective radii, and overall appearances of our UDGs are consistent with existing observations of field UDGs, but we predict that many isolated UDGs have been missed by current surveys. Despite their isolation at z = 0, the UDGs in our sample are the products of major mergers. Mergers are no more common in UDG than non-UDG progenitors, but mergers that create UDGs tend to happen earlier – almost never occurring after z = 1, produce a temporary boost in spin, and cause star formation to be redistributed to the outskirts of galaxies, resulting in lower central SFRs. The centres of the galaxies fade as their central stellar populations age, but their global SFRs are maintained through bursts of star formation at larger radii, producing steeper negative g −r colour gradients. This formation channel is unique relative to other proposals for UDG formation in isolated galaxies, demonstrating that UDGs can potentially be formed through multiple mechanisms.
Abstract
Formation models in which terrestrial bodies grow via the pairwise accretion of planetesimals have been reasonably successful at reproducing the general properties of the Solar System, ...including small-body populations. However, planetesimal accretion has not yet been fully explored in the context of the wide variety of recently discovered extrasolar planetary systems, in particular those that host short-period terrestrial planets. In this work, we use direct
N
-body simulations to explore and understand the growth of planetary embryos from planetesimals in disks extending down to ≃1 day orbital periods. We show that planetesimal accretion becomes nearly 100% efficient at short orbital periods, leading to embryo masses that are much larger than the classical isolation mass. For rocky bodies, the physical size of the object begins to occupy a significant fraction of its Hill sphere toward the inner edge of the disk. In this regime, most close encounters result in collisions, rather than scattering, and the system does not develop a bimodal population of dynamically hot planetesimals and dynamically cold oligarchs, as is seen in previous studies. The highly efficient accretion seen at short orbital periods implies that systems of tightly packed inner planets should be almost completely devoid of any residual small bodies. We demonstrate the robustness of our results to assumptions about the initial disk model, and we also investigate the effects that our simplified collision model has on the emergence of this non-oligarchic growth mode in a planet-forming disk.
Near‐term freshwater forecasts, defined as sub‐daily to decadal future predictions of a freshwater variable with quantified uncertainty, are urgently needed to improve water quality management as ...freshwater ecosystems exhibit greater variability due to global change. Shifting baselines in freshwater ecosystems due to land use and climate change prevent managers from relying on historical averages for predicting future conditions, necessitating near‐term forecasts to mitigate freshwater risks to human health and safety (e.g., flash floods, harmful algal blooms) and ecosystem services (e.g., water‐related recreation and tourism). To assess the current state of freshwater forecasting and identify opportunities for future progress, we synthesized freshwater forecasting papers published in the past 5 years. We found that freshwater forecasting is currently dominated by near‐term forecasts of water quantity and that near‐term water quality forecasts are fewer in number and in the early stages of development (i.e., non‐operational) despite their potential as important preemptive decision support tools. We contend that more freshwater quality forecasts are critically needed and that near‐term water quality forecasting is poised to make substantial advances based on examples of recent progress in forecasting methodology, workflows, and end‐user engagement. For example, current water quality forecasting systems can predict water temperature, dissolved oxygen, and algal bloom/toxin events 5 days ahead with reasonable accuracy. Continued progress in freshwater quality forecasting will be greatly accelerated by adapting tools and approaches from freshwater quantity forecasting (e.g., machine learning modeling methods). In addition, future development of effective operational freshwater quality forecasts will require substantive engagement of end users throughout the forecast process, funding, and training opportunities. Looking ahead, near‐term forecasting provides a hopeful future for freshwater management in the face of increased variability and risk due to global change, and we encourage the freshwater scientific community to incorporate forecasting approaches in water quality research and management.
Near‐term freshwater forecasts, defined as sub‐daily to decadal future predictions of a freshwater variable with quantified uncertainty, are urgently needed to improve water quality management. We synthesized recent freshwater forecasting papers to provide a conceptual framework of recommendations (in bold) for advancing the field of freshwater quality forecasting and operational near‐term freshwater quality forecasts. Effective forecasts lie at the intersection of freshwater science, end‐user needs, and relevant tools and skills, all of which require funding support. Looking ahead, near‐term forecasting provides a hopeful future for freshwater management in the face of increased ecosystem variability due to global change.
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