The design and implementation of a new framework for adaptive mesh refinement calculations are described. It is intended primarily for applications in astrophysical fluid dynamics, but its flexible ...and modular design enables its use for a wide variety of physics. The framework works with both uniform and nonuniform grids in Cartesian and curvilinear coordinate systems. It adopts a dynamic execution model based on a simple design called a "task list" that improves parallel performance by overlapping communication and computation, simplifies the inclusion of a diverse range of physics, and even enables multiphysics models involving different physics in different regions of the calculation. We describe physics modules implemented in this framework for both nonrelativistic and relativistic magnetohydrodynamics (MHD). These modules adopt mature and robust algorithms originally developed for the Athena MHD code and incorporate new extensions: support for curvilinear coordinates, higher-order time integrators, more realistic physics such as a general equation of state, and diffusion terms that can be integrated with super-time-stepping algorithms. The modules show excellent performance and scaling, with well over 80% parallel efficiency on over half a million threads. The source code has been made publicly available.
Abstract
We describe the
Blacklight
code, intended for postprocessing general-relativistic magnetohydrodynamic simulation data. Beyond polarized ray tracing of synchrotron radiation, it can produce a ...number of outputs that aid in analyzing data sets, such as maps of auxiliary quantities and false-color renderings. Additional features include support for adaptive mesh refinement input, slow-light calculations, and adaptive ray tracing. The code is written with ease of use, readability, and transparency as primary objectives, while it still achieves high performance.
Blacklight
is publicly available and released into the public domain.
ABSTRACT We present a new general relativistic magnetohydrodynamics (GRMHD) code integrated into the Athena++ framework. Improving upon the techniques used in most GRMHD codes, ours allows the use of ...advanced, less diffusive Riemann solvers, in particular HLLC and HLLD. We also employ a staggered-mesh constrained transport algorithm suited for curvilinear coordinate systems in order to maintain the divergence-free constraint of the magnetic field. Our code is designed to work with arbitrary stationary spacetimes in one, two, or three dimensions, and we demonstrate its reliability through a number of tests. We also report on its promising performance and scalability.
In this trial, patients with femoropopliteal artery disease were assigned to standard angioplasty or treatment with a paclitaxel-coated balloon. At 12 months, primary patency was seen more frequently ...with the drug-coated balloon than with standard angioplasty.
Atherosclerotic disease in the femoral and popliteal (femoropopliteal) arteries compromises perfusion to the legs and feet. Although treatment with percutaneous transluminal angioplasty is effective in initially restoring blood flow, restenosis from vessel recoil and neointimal hyperplasia occur in more than 60% of patients within 1 year after the procedure.
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Stents act as scaffolds to prevent recoil and reduce the incidence of restenosis,
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but the permanent presence of an intravascular prosthesis may limit subsequent therapeutic options. Stent fracture, although infrequent, can have negative consequences.
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Results with drug-eluting stents in peripheral vessels have varied,
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although a recent study showed . . .
Protection of biological assemblies is critical to applications in biotechnology, increasing the durability of enzymes in biocatalysis or potentially stabilizing biotherapeutics during transport and ...use. Here we show that a porous hydrogen-bonded organic framework (HOF) constructed from water-soluble tetra-amidinium (1·Cl4) and tetracarboxylate (2) building blocks can encapsulate and stabilize biomolecules to elevated temperature, proteolytic and denaturing agents, and extend the operable pH range for catalase activity. The HOF, which readily retains water within its framework structure, can also protect and retain the activity of enzymes such as alcohol oxidase, that are inactive when encapsulated within zeolitic imidazolate framework (ZIF) materials. Such HOF coatings could provide valid alternative materials to ZIFs: they are metal free, possess larger pore apertures, and are stable over a wider, more biologically relevant pH range.
This publication describes uniform definitions for cardiovascular and stroke outcomes developed by the Standardized Data Collection for Cardiovascular Trials Initiative and the US Food and Drug ...Administration (FDA). The FDA established the Standardized Data Collection for Cardiovascular Trials Initiative in 2009 to simplify the design and conduct of clinical trials intended to support marketing applications. The writing committee recognizes that these definitions may be used in other types of clinical trials and clinical care processes where appropriate. Use of these definitions at the FDA has enhanced the ability to aggregate data within and across medical product development programs, conduct meta-analyses to evaluate cardiovascular safety, integrate data from multiple trials, and compare effectiveness of drugs and devices. Further study is needed to determine whether prospective data collection using these common definitions improves the design, conduct, and interpretability of the results of clinical trials.
Observed increases in the frequency and intensity of heatwave events, together with the projected acceleration of these events worldwide, has led to a rapid expansion in research on the health ...impacts of extreme heat.
To examine how research on heatwaves and their health-related impact is distributed globally.
A systematic review was undertaken. Four online databases were searched for articles examining links between specific historical heatwave events and their impact on mortality or morbidity. The locations of these events were mapped at a global scale, and compared to other known characteristics that influence heat-related illness and death.
When examining the location of heatwave and health impact research worldwide, studies were concentrated on mid-latitude, high-income countries of low- to medium-population density. Regions projected to experience the most extreme heatwaves in the future were not represented. Furthermore, the majority of studies examined mortality as a key indicator of population-wide impact, rather than the more sensitive indicator of morbidity.
While global heatwave and health impact research is prolific in some regions, the global population most at risk of death and illness from extreme heat is under-represented. Heatwave and health impact research is needed in regions where this impact is expected to be most severe.
•Heatwave and health impact research is not distributed evenly across the globe.•Regions most at risk from heatwaves and health impact are under-represented in the research.•Research focussing on morbidity is under-represented compared with mortality-focussed research.
Peptide macrocycles have found applications that range from drug discovery to nanomaterials. These ring-shaped molecules have shown remarkable capacity for functional fine-tuning. Such capacity is ...enabled by the possibility of adjusting the peptide conformation using the techniques of chemical synthesis. Cyclic peptides have been difficult, and often impossible, to prepare using traditional synthetic methods. For macrocyclization to occur, the activated peptide must adopt an entropically disfavoured pre-cyclization conformation before forming the desired product. Here, we review recent solutions to some of the major challenges in this important area of contemporary synthesis.
We conduct a systematic study of the properties of tilted accretion flows around spinning black holes, covering a range of tilt angles and black hole spins, using the general-relativistic ...magnetohydrodynamics code Athena++. The same initial magnetized torus is evolved around black holes with spins ranging from 0 to 0.9, with inclinations ranging from 0° to 24°. The tilted disks quickly reach a warped and twisted shape that rigidly precesses about the black hole spin axis with deformations in shape large enough to hinder the application of linear bending wave theory. Magnetized polar outflows form, oriented along the disk rotation axes. At sufficiently high inclinations a pair of standing shocks develops in the disks. These shocks dramatically affect the flow at small radii, driving angular momentum transport. At high spins they redirect material more effectively than they heat it, reducing the dissipation rate relative to the mass accretion rate and lowering the heating efficiency of the flow.
We present 3D general relativistic magnetohydrodynamic (GRMHD) simulations of the accretion flow surrounding Sagittarius A* that are initialized using larger-scale MHD simulations of the ∼30 ...Wolf-Rayet (WR) stellar winds in the Galactic center. The properties of the resulting accretion flow on horizon scales are set not by ad hoc initial conditions but by the observationally constrained properties of the WR winds with limited free parameters. For this initial study we assume a non-spinning black hole. Our simulations naturally produce a ∼10−8 M yr−1 accretion rate, consistent with previous phenomenological estimates. We find that a magnetically arrested flow is formed by the continuous accretion of coherent magnetic field being fed from large radii. Near the event horizon, the magnetic field is so strong that it tilts the gas with respect to the initial angular momentum and concentrates the originally quasi-spherical flow to a narrow disk-like structure. We also present 230 GHz images calculated from our simulations where the inclination angle and physical accretion rate are not free parameters but are determined by the properties of the WR stellar winds. The image morphology is highly time variable. Linear polarization on horizon scales is coherent with weak internal Faraday rotation.
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