Landscape controls on fuel moisture variability in fire-prone heathland and peatland landscapes

Background: Cross-landscape fuel moisture content is highly variable but not considered in existing fire danger assessments. Capturing fuel moisture complexity and its associated controls is critical for understanding wildfire behavior and danger in emerging fire-prone environments that are influenced by local heterogeneity. This is particularly true for temperate heathland and peatland landscapes that exhibit spatial differences in the vulnerability of their globally important carbon stores to wildfire. Here we quantified the range of variability in the live and dead fuel moisture of Calluna vulgaris across a temperate fire-prone landscape through an intensive fuel moisture sampling campaign conducted in the North Yorkshire Moors, UK. We also evaluated the landscape (soil texture, canopy age, aspect, and slope) and micrometeorological (temperature, relative humidity, vapor pressure deficit, and windspeed) drivers of landscape fuel moisture variability for temperate heathlands and peatlands for the first time. Results: We observed high cross-landscape fuel moisture variation, which created a spatial discontinuity in the availability of live fuels for wildfire spread (fuel moisture < 65%) and vulnerability of the organic layer to smoldering combustion (fuel moisture < 250%). This heterogeneity was most important in spring, which is also the peak wildfire season in these temperate ecosystems. Landscape and micrometeorological factors explained up to 72% of spatial fuel moisture variation and were season- and fuel-layer-dependent. Landscape factors predominantly controlled spatial fuel moisture content beyond modifying local micrometeorology. Accounting for direct landscape–fuel moisture relationships could improve fuel moisture estimates, as existing estimates derived solely from micrometeorological observations will exclude the underlying influence of landscape characteristics. We hypothesize that differences in soil texture, canopy age, and aspect play important roles across the fuel layers examined, with the main differences in processes arising between live, dead, and surface/ground fuels. We also highlight the critical role of fuel phenology in assessing landscape fuel moisture variations in temperate environments. Conclusions: Understanding the mechanisms driving fuel moisture variability opens opportunities to develop locally robust fuel models for input into wildfire danger rating systems, adding versatility to wildfire danger assessments as a management tool

Practical application of AAPM Report 270 in display quality assurance: A report of Task Group 270

Published in January 2019, AAPM Report 270 provides an update to the recommendations of the AAPM\u27s TG18 report. Report 270 provides new definitions of display types, updated testing patterns, and revised performance standards for the modern, flat-panel displays used as part of medical image acquisition and review. The focus of the AAPM report is on consistent image quality and appearance, and how to establish a quality assurance program to achieve those two goals. This work highlights some of the key takeaways of AAPM Report 270 and makes comparisons with existing recommendations from other references. It also provides guidance for establishing a display quality assurance program for different-sized institutions. Finally, it describes future challenges for display quality assurance and what work remains

Decoupling microporosity and nitrogen content to optimise CO2 adsorption in modified xerogels

Selected melamine-resorcinol-formaldehyde (MRF) xerogels have been synthesised and analysed to determine the influence of nitrogen (N) incorporated into the gel structure, as well as, resorcinol to catalyst (sodium carbonate) and resorcinol to formaldehyde molar ratios. The aforementioned factors were varied, and their effect on gel properties characterised, allowing a better understanding of how gel characteristics can be tailored, and their impact on gel performance. MRF gels, produced in this study, were characterised using volumetric and gravimetric analyses to determine porous structure and quantify CO2 capture capacities and kinetics, as well as allowing determination of heats of adsorption and activation energies for CO2. MRF10_200_0.25 has exhibited the largest CO2 capacity (1.8mmol/g at 0 °C) of the sample tested. Thermal stability was tested by proximate analysis, and MRF xerogels exhibited high thermal stability, however it was found that volatile matter increases as [M] increases, particularly for [M] 20%w/w and higher. Working capacity was determined from a series of cycling studies and capacities of 0.55, 0.58 and 0.56 mmol/g at 60 °C were observed for [M] of 10, 20 and 30%w/w, respectively. The measured heat of adsorption showed that incorporation of nitrogen functionalities results in a low energy penalty demonstrating that the adsorption mechanism is still driven by physical forces. The results obtained indicate that the family of materials studied here offer potential routes for carbon capture materials, through a combination of micropore structure development and incorporation of favourable Lewis acid-base interactions

Nucleation and growth kinetics of sodium chloride crystallization from water and deuterium oxide

Despite the ubiquity of crystallization of sodium chloride (NaCl) throughout history, few detailed, well-controlled quantitative studies of the kinetics of NaCl crystallization have been published. Taking advantage of recent advances in technology such as image analysis for crystallite counting and ’high-throughput’ techniques for characterizing the highly stochastic nucleation process, we report on a detailed examination of primary and secondary nucleation kinetics of NaCl, crystallizing from solution, in water (H2O) and in the isotopologue D2O. We show that crystallization conditions, especially sample agitation, have a very  significant effect on crystallization kinetics. We also critically evaluate the workflow employed and the associated nucleation/growth models used to interpret its results, comparing outcomes from NaCl with those fromorganic crystal systems with which the workflow was originally developed and demonstrated. For primary nucleation, some key assumptions of the workflow and data interpretation are called into question for the NaCl system. Even so it can still provide direct measurements of secondary nucleation and crystal growth from crystal counting and sizing, providing valuable characterisation under consistent controlled conditions to enhance and ’bring up to date’ the literature on the crystallization of this ubiquitous system

Nucleation and growth kinetics of sodium chloride crystallization from water and deuterium oxide

Despite the ubiquity of the crystallization of sodium chloride (NaCl) throughout history, few detailed, well-controlled quantitative studies of the kinetics of NaCl crystallization have been published. Taking advantage of recent advances in technology such as image analysis for crystallite counting and ‘high-throughput’ techniques for characterizing the highly stochastic nucleation process, we report on a detailed examination of the primary and secondary nucleation kinetics of NaCl, crystallized from solution, in water (H 2O) and in the isotopologue D 2O. We show that crystallization conditions, especially sample agitation, have a very significant effect on crystallization kinetics. We also critically evaluate the workflow employed and the associated nucleation/growth models used to interpret its results, comparing outcomes from NaCl with those from organic crystal systems with which the workflow was originally developed and demonstrated. For primary nucleation, some key assumptions of the workflow and data interpretation are called into question for the NaCl system. Even so, it can still provide direct measurements of secondary nucleation and crystal growth from crystal counting and sizing, providing valuable characterization under consistent controlled conditions to enhance and ‘bring up to date’ the literature on the crystallization of this ubiquitous system

Enhanced localization and protection of topological edge states due to geometric frustration

Topologically nontrivial phases are linked to the appearance of localized modes in the boundaries of an open insulator. On the other hand, the existence of geometric frustration gives rise to degenerate localized bulk states. The interplay of these two phenomena may, in principle, result in an enhanced protection/localization of edge states. In this paper, we study a two-dimensional Lieb-based topological insulator with staggered hopping parameters and diagonal open boundary conditions. This system belongs to the C2v class and sustains one-dimensional (1D) boundary modes except at the topological transition point, where the C4v symmetry allows for the existence of localized (0D) corner states. Our analysis reveals that, while a large set of boundary states have a common well-defined topological phase transition, other edge states reflect a topological nontrivial phase for any finite value of the hopping parameters, are completely localized (compact) due to destructive interference, and evolve into corner states when reaching the higher symmetry point. We consider the robustness of these compact edge states with respect to time-dependent perturbations and indicate ways that these states could be prepared and measured in experiments with ultracold atoms

On the projection of future fire danger conditions with various instantaneous/mean-daily data sources

Fire danger indices are descriptors of fire potential in a large area, and combine a few variables that affect the initiation, spread and control of forest fires. The Canadian Fire Weather Index (FWI) is one of the most widely used fire danger indices in the world, and it is built upon instantaneous values of temperature, relative humidity and wind velocity at noon, together with 24 hourly accumulated precipitation. However, the scarcity of appropriate data has motivated the use of daily mean values as surrogates of the instantaneous ones in several studies that aimed to assess the impact of global warming on fire. In this paper we test the sensitivity of FWI values to both instantaneous and daily mean values, analyzing their effect on mean seasonal fire danger (seasonal severity rating, SSR) and extreme fire danger conditions (90th percentile, FWI90, and FWI>30, FOT30), with a special focus on its influence in climate change impact studies. To this aim, we analyzed reanalysis and regional climate model (RCM) simulations, and compared the resulting instantaneous and daily mean versions both in the present climate and in a future scenario. In particular, we were interested in determining the effect of these datasets on the projected changes obtained for the mean and extreme seasonal fire danger conditions in future climate scenarios, as given by a RCM. Overall, our results warn against the use of daily mean data for the computation of present and future fire danger conditions. Daily mean data lead to systematic negative biases of fire danger calculations. Although the mean seasonal fire danger indices might be corrected to compensate for this bias, fire danger extremes (FWI90 and specially FOT30) cannot be reliably transformed to accommodate the spatial pattern and magnitude of their respective instantaneous versions, leading to inconsistent results when projected into the future. As a result, we advocate caution when using daily mean data and strongly recommend the application of the standard definition for its calculation as closely as possible. Threshold-dependent indices derived from FWI are not reliably represented by the daily mean version and thus can neither be applied for the estimation of future fire danger season length and severity, nor for the estimation of future extreme events.The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement 243888 (FUME Project). J.F. acknowledges nancial support from the Spanish R&D&I programme through grant CGL2010-22158-C02 (CORWES project). The ESCENA project (200800050084265) of the Spanish \Strategic action on energy and climate change" provided the WRF RCM simulation used in this study. We acknowledge three anonymous referees for their useful comments that helped to improve the original manuscript

In utero exposure to cigarette smoke dysregulates human fetal ovarian developmental signalling

STUDY QUESTION How does maternal cigarette smoking disturb development of the human fetal ovary?<p></p> SUMMARY ANSWER Maternal smoking increases fetal estrogen titres and dysregulates several developmental processes in the fetal ovary.<p></p> WHAT IS KNOWN ALREADY Exposure to maternal cigarette smoking during gestation reduces human fetal ovarian cell numbers, germ cell proliferation and subsequent adult fecundity.<p></p> STUDY DESIGN, SIZE, DURATION The effects of maternal cigarette smoking on the second trimester human fetal ovary, fetal endocrine signalling and fetal chemical burden were studied. A total of 105 fetuses were studied, 56 from mothers who smoked during pregnancy and 49 from those who did not.<p></p> PARTICIPANTS/MATERIALS, SETTING METHODS Ovary, liver and plasma samples were collected from electively terminated, normally progressing, second trimester human fetuses. Circulating fetal hormones, levels of 73 fetal ovarian transcripts, protein localization, density of oocytes/primordial follicles and levels of 16 polycyclic aromatic hydrocarbons (PAHs) in the fetal liver were determined.<p></p> MAIN RESULTS AND THE ROLE OF CHANCE Circulating fetal estrogen levels were very high and were increased by maternal smoking (ANOVA, P = 0.055–0.004 versus control). Smoke exposure also dysregulated (two-way ANOVA, smoking versus gestation weeks interaction, P = 0.046–0.023) four fetal ovarian genes (cytochrome P450 scc [CYP11A1], NOBOX oogenesis homeobox [NOBOX], activator of apoptosis harakiri [HRK], nuclear receptor subfamily 2, group E, member 1 [NR2E1]), shifted the ovarian Inhibin βA/inhibin α ratio (NHBA/INHA) transcript ratio in favour of activin (ANOVA, P = 0.049 versus control) and reduced the proportion of dominant-negative estrogen receptor 2 (ERβ: ESR2) isoforms in half the exposed fetuses. PAHs, ligands for the aryl hydrocarbon receptor (AHR), were increased nearly 6-fold by maternal smoking (ANOVA, P = 0.011 versus control). A fifth transcript, COUP transcription factor 1 (nuclear receptor subfamily 2, group F, member 1: NR2F1, which contains multiple AHR-binding sites), was both significantly increased (ANOVA, P = 0.026 versus control) and dysregulated by (two-way ANOVA, smoking versus gestation weeks interaction, P = 0.021) maternal smoking. NR2F1 is associated with repression of FSHR expression and smoke-exposed ovaries failed to show the normal increase in FSHR expression during the second trimester. There was a significantly higher number of DEAD (Asp-Glu-Ala-Asp) box polypeptide 4 (DDX4) VASA-positive (ANOVA, P = 0.016 versus control), but not POU domain, class 1, transcription factor 1 (POU5F1) OCT3/4-positive, oocytes in smoke-exposed fetuses and this matched with a significantly higher number of primordial follicles (ANOVA, P = 0.024 versus control).<p></p> LIMITATIONS, REASONS FOR CAUTION The effects of maternal smoking on establishment of the maximum fetal primordial follicle pool cannot be reliably studied in our population since the process is not completed until 28 weeks of gestation and normal fetuses older than 21 weeks of gestation are not available for study. Our data suggest that some fetal ovaries are affected by smoke exposure while others are not, indicating that additional studies, with larger numbers, may show more significant effects.<p></p> WIDER IMPLICATIONS OF THE FINDINGS Fetal exposure to chemicals in cigarette smoke is known to lead to reduced fecundity in women. Our study suggests, for the first time, that this occurs via mechanisms involving activation of AHR, disruption of inhibin/activin and estrogen signalling, increased exposure to estrogen and dysregulation of multiple molecular pathways in the exposed human fetal ovary. Our data also suggest that alterations in the ESR2 positive and dominant negative isoforms may be associated with reduced sensitivity of some fetuses to increased estrogens and maternal smoking