An open source software package for modelling thermal neutron transport is presented. The code facilitates Monte Carlo-based transport simulations and focuses in the initial release on interactions ...in both mosaic single crystals as well as polycrystalline materials and powders. Both coherent elastic (Bragg diffraction) and incoherent or inelastic (phonon) scattering are modelled, using basic parameters of the crystal unit cell as input.
Included is a data library of validated crystal definitions, standalone tools and interfaces for C++, C and Python programming languages. Interfaces for two popular simulation packages, Geant4 and McStas, are provided, enabling highly realistic simulations of typical components at neutron scattering instruments, including beam filters, monochromators, analysers, samples, and detectors. All interfaces are presented in detail, along with the end-user configuration procedure which is deliberately kept user-friendly and consistent across all interfaces.
An overview of the relevant neutron scattering theory is provided, and the physics modelling capabilities of the software are discussed. Particular attention is given here to the ability to load crystal structures and form factors from various sources of input, and the results are benchmarked and validated against experimental data and existing crystallographic software. Good agreements are observed.
Program Title: NCrystal
Program Files doi:http://dx.doi.org/10.17632/s3rpb5d9j3.1
Licensing provisions: Apache License, Version 2.0 (for core NCrystal).
Programming language:C++, C and Python
External routines/libraries:Geant4, McStas
Nature of problem: Thermal neutron transport in structured materials is inadequately supported in popular Monte Carlo transport applications, preventing simulations of a range of otherwise interesting setups.
Solution method: Provide models for thermal neutron transport in flexible open source library, to be used standalone or as backend in existing Monte Carlo packages. Facilitate validation and work sharing by making it possible to share material configurations between supported applications.
Gas flaring is a prominent source of VOCs, CO, CO2, SO2, PAH, NOX and soot (black carbon), all of which are important pollutants which interact, directly and indirectly, in the Earth’s climatic ...processes. Globally, over 130 billion cubic metres of gas are flared annually. We review the contribution of gas flaring to air pollution on local, regional and global scales, with special emphasis on black carbon (BC, “soot”). The temporal and spatial characteristics of gas flaring distinguishes it from mobile combustion sources (transport), while the open-flame nature of gas flaring distinguishes it from industrial point-sources; the high temperature, flame control, and spatial compactness distinguishes gas flaring from both biomass burning and domestic fuel-use. All of these distinguishing factors influence the quantity and characteristics of BC production from gas flaring, so that it is important to consider this source separately in emissions inventories and environmental field studies. Estimate of the yield of pollutants from gas flaring have, to date, paid little or no attention to the emission of BC with the assumption often being made that flaring produces a smokeless flame. In gas flares, soot yield is known to depend on a number of factors, and there is a need to develop emission estimates and modelling frameworks that take these factors into consideration. Hence, emission inventories, especially of the soot yield from gas flaring should give adequate consideration to the variation of fuel gas composition, and to combustion characteristics, which are strong determinants of the nature and quantity of pollutants emitted. The buoyant nature of gas flaring plume, often at temperatures in the range of 2000 K, coupled with the height of the stack enables some of the pollutants to escape further into the free troposphere aiding their long-range transport, which is often not well-captured by model studies.
•In-depth analysis of gas flaring and its attendant atmospheric emissions.•Critical review of literature on black carbon emissions from gas flaring.•Important gaps exist in the estimation of emissions from gas flaring.•Review justifies including gas flaring explicitly in inventories and global models.•A framework is proposed for the development of more robust emission factors.
The review identified gaps in the estimation of emissions from the gas flaring process and argues for explicit recognition of gas flaring emissions in emission inventories and global models.
Heatwaves can lead to a range of adverse impacts including increased risk of illness and mortality; the heatwave in August 2003 has been associated with ~70,000 deaths across Europe. Due to climate ...change, heatwaves are likely to become more intense, more frequent and last longer in the future. A number of factors may influence risks associated with heat exposure, such as population age, housing type, and location within the Urban Heat Island, and such factors may not be evenly distributed spatially across a region. We simulated and analysed two major heatwaves in the UK, in August 2003 and July 2006, to assess spatial vulnerability to heat exposure across the West Midlands, an area containing ~5 million people, and how ambient temperature varies in relation to factors that influence heat-related health effects, through weighting of ambient temperatures according to distributions of these factors across an urban area. Additionally we present quantification of how particular centres such as hospitals are exposed to the UHI, by comparing temperatures at these locations with average temperatures across the region, and presenting these results for both day and night times. We find that UHI intensity was substantial during both heatwaves, reaching a maximum of +9.6°C in Birmingham in July 2006. Previous work has shown some housing types, such as flats and terraced houses, are associated with increased risk of overheating, and our results show that these housing types are generally located within the warmest parts of the city. Older age groups are more susceptible to the effects of heat. Our analysis of distribution of population based on age group showed there is only small spatial variation in ambient temperature that different age groups are exposed to. Analysis of relative deprivation across the region indicates more deprived populations are located in the warmest parts of the city.
Spatial distribution of factors that may relate to risks associated with heat-health effects across the West Midlands. Display omitted
•Multiple factors are associated with health effects of heat exposure.•Cities in the West Midlands have a pronounced UHI.•Care homes and hospitals are exposed to higher ambient temperatures than average.•Housing types more likely to overheat are located in the warmest parts of the city.
Birmingham is the second most populous city in the United Kingdom and observations indicate that it has a pronounced urban heat island (UHI), i.e. higher ambient temperatures in the city centre ...compared with surrounding suburban and rural areas, particularly at night. The effects of UHIs are often amplified during anticyclonic summer weather conditions, which can cause or exacerbate heatwaves. Enhanced temperatures in highly populated regions can mean that significant numbers of people are at risk from heat‐related illness during hot weather. Climate change projections often do not include the effects of the UHI, which can mean that assessments of heat‐related health effects using these projections underestimate the actual magnitude of future health impacts. We present numerical simulations of the UHI in Birmingham and the West Midlands Metropolitan region during the heatwave of August 2003 using the high‐resolution, regional meteorological Weather Research and Forecasting (WRF) model, with an urban canopy scheme. We evaluated the model using local air‐temperature observations, and found good model performance in capturing the temporal and spatial signature of the UHI. We performed a sensitivity test, replacing urban land categories with rural ones, and found that the difference in temperature between the two model runs throughout the heatwave period (2–11 August 2003) was around 3°C on average, and reached a maximum of 7°C. Finally, we present a novel generic methodology to enable the examination of the extent of horizontal advection of warm air downwind of the conurbation area. We found that during the heatwave, temperatures downwind of Birmingham were up to 2.5°C warmer than those upwind. This methodology has the potential for improvements to, or parametrizations for, diagnostic models that do not explicitly include dynamics and where local conditions are driven largely by land‐surface type.
Alloy design based on single-principal-element systems has approached its limit for performance enhancements. A substantial increase in strength up to gigapascal levels typically causes the premature ...failure of materials with reduced ductility. Here, we report a strategy to break this trade-off by controllably introducing high-density ductile multicomponent intermetallic nanoparticles (MCINPs) in complex alloy systems. Distinct from the intermetallic-induced embrittlement under conventional wisdom, such MCINP-strengthened alloys exhibit superior strengths of 1.5 gigapascals and ductility as high as 50% in tension at ambient temperature. The plastic instability, a major concern for high-strength materials, can be completely eliminated by generating a distinctive multistage work-hardening behavior, resulting from pronounced dislocation activities and deformation-induced microbands. This MCINP strategy offers a paradigm to develop next-generation materials for structural applications.
The NCrystal library provides a range of models for simulation of both elastic and inelastic scattering of thermal neutrons in a range of material structures. This article presents the available ...models for elastic scattering, and includes detailed discussion of their theoretical background, their implementation, and in particular their validation. The lineup includes a model for Bragg diffraction in crystal powders as well as one for incoherent elastic scattering, but the main focus is given to models of Bragg diffraction in ideally imperfect single crystals: both for the most widely applicable model of isotropic Gaussian mosaicity, and for a more specific model of layered single crystals which is relevant for materials such as pyrolytic graphite. Although these single crystal models are utilising computationally efficient approximations where appropriate, attention is given to the provision of precise and trustworthy results also for the extreme cases of back-scattering, forward-scattering, and crystals with very large mosaic spreads. Together with NCrystal's other features for crystal structure initialisation and inelastic physics, the presented models enable realistic modelling of components at neutron scattering instruments in frameworks like Geant4 and McStas, including monochromators, analysers, filters, support materials, shielding, and many kinds of samples. As a byproduct of the work, an improved formula for approximating cross sections in isotropic single crystals with Gaussian mosaicity is provided.
Program Title: NCrystal
CPC Library link to program files:https://doi.org/10.17632/rzmmzgpg7g.1
Licensing provisions: Apache License, Version 2.0.
Programming language:C++, C and Python
Nature of problem: Thermal neutron transport in structured materials is inadequately supported in popular Monte Carlo transport applications, preventing simulations of a range of otherwise interesting setups.
Solution method: Provide models for thermal neutron transport in open source library NCrystal, to be used standalone or as backend in existing Monte Carlo packages. Specifically, the present publication details the implemented elastic scattering models in crystalline materials.
Summary
Porcine reproductive and respiratory syndrome virus (PRRSV) is a major economically significant pathogen that has adversely affected China's swine industry. Currently, a novel type 2 PRRSV, ...called the NADC30‐like strain, is epidemic in numerous provinces of China, and commercial vaccines provide limited protection for infected animals. The extensive recombination phenomenon among NADC30‐like PRRSVs is identified as a unique molecular characteristic of the virus. However, our understanding of how recombination influences NADC30‐like PRRSVs is largely inadequate. In this study, we analysed the genetic characteristics of a recombinant NADC30‐like PRRSV (SC‐d) and examined its pathogenicity compared with a non‐recombinant NADC30‐like PRRSV (SD‐A19) and a highly pathogenic PRRSV (HuN4). SC‐d has three discontinuous deletions in nsp2, consistent with NADC30 isolated from the United States in 2008. Furthermore, we identified four recombination breakpoints in the SC‐d genome, which separated the SC‐d genome into four regions (regions A, B, C and D). Regions A and C are closely related to the JXA1‐like strain, one of the earliest Chinese HP‐PRRSV strains, and regions B and D are closely related to the NADC30 strain. Moreover, SC‐d inoculated piglets exhibited a persistent fever, moderate weight loss, mild thymus atrophy and obvious microscopic lung lesions. In summary, the recombinant NADC30‐like PRRSV SC‐d strain displayed a higher pathogenicity than the non‐recombinant NADC30‐like PRRSV SD‐A19 strain; however, the pathogenicity of the NADC30‐like PRRSV SC‐d was lower compared with the HP‐PRRSV HuN4 strain in piglets. Our findings demonstrate that recombination is responsible for the enormous genetic diversity and pathogenicity variance of the NADC30‐like PRRSV in China. This study provides a theoretical basis for developing a more reasonable PRRSV control and prevention strategy.
Forests cover nearly a third of the Earth's land area and exchange mass, momentum, and energy with the atmosphere. Most studies of these exchanges, particularly using numerical models, consider ...forests whose structure has been heavily simplified. In many landscapes, these simplifications are unrealistic. Inhomogeneous landscapes and unsteady weather conditions generate fluid dynamical features that cause observations to be inaccurately interpreted, biased, or over‐generalized. In Part I, we discuss experimental, theoretical, and numerical progress in the understanding of turbulent exchange over realistic forests. Scalar transport does not necessarily follow the flow in realistic settings, meaning scalar quantities are rarely at equilibrium around patchy forests, and significant scalar fluxes may form in the lee of forested hills. Gaps and patchiness generate significant spatial fluxes that current models and observations neglect. Atmospheric instability increases the distance over which fluxes adjust at forest edges. In deciduous forests, the effects of patchiness differ between seasons; counter intuitively, eddies reach further into leafy canopies (because they are rougher aerodynamically). Air parcel residence times are likely much lower in patchy forests than homogeneous ones, especially around edges. In Part II, we set out practical ways to make numerical models of forest‐atmosphere more realistic, including by accounting for reconfiguration and realistic canopy structure and beginning to include more chemical and physical processes in turbulence resolving models. Future challenges include: (a) customizing numerical models to real study sites, (b) connecting space and time scales, and (c) incorporating a greater range of weather conditions in numerical models.
Plain Language Summary
Plants live by an intricate set of exchanges with the atmosphere. They draw carbon dioxide from the air—while being buffeted by the wind—and release water vapor, oxygen, pollen, and a variety of organic compounds. These exchanges are especially intricate in forests, where microbes and animals add to the quantity and variety of exchanges. Forests' patchwork structures mean that trees may experience profoundly different climates to others only meters away. These exchanges are made yet more complicated by the fragmentation of forests by human activity. Here we review recent developments in the understanding of exchanges between the air and realistic, patchy forests. We focus on applying this understanding to improve the realism of computer models. No model can recreate all the exchanges in detail. However, capturing more of the edges, gaps, and patches in real forests, as well as non‐ideal weather conditions, will improve our understanding of forest‐atmosphere exchanges. This will aid scientific understanding and policy making for forest ecology, meteorology and climatology, and air and water quality.
Key Points
Most forests are naturally patchy. Many are being fragmented by humans. Studies of forest‐air exchange rarely consider this heterogeneity
Gaps, edges, and patchy sources/sinks generate fluxes of momentum and scalars. Scalar quantities are rarely at equilibrium around forests
Better representations of forest structure, for example, from laser scans, should be included in models, along with more physics and chemistry
Quercetin (QC) is a typical plant flavonoid, possesses diverse pharmacologic effects including antiinflammatory, antioxidant, anti-cancer, anti-anaphylaxis effects and against aging. However, the ...application of QC in pharmaceutical field is limited due to its poor solubility, low bioavailability, poor permeability and instability. To improve the bioavailability of QC, numerous approaches have been undertaken, involving the use of promising drug delivery systems such as inclusion complexes, liposomes, nanoparticles or micelles, which appear to provide higher solubility and bioavailability. Enhanced bioavailability of QC in the near future is likely to bring this product to the forefront of therapeutic agents for treatment of human disease.
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