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Wildfires are an increasing source of emissions into the air, with health effects modulated by the abundance and toxicity of individual species. In this work, we estimate reactive organic compounds (ROC) in western U.S. wildland forest fire smoke using a combination of observations from the 2019 Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) field campaign and predictions from the Community Multiscale Air Quality (CMAQ) model. Standard emission inventory methods capture 40–45% of the estimated ROC mass emitted, with estimates of primary organic aerosol particularly low (5–8×). Downwind, gas-phase species abundances in molar units reflect the production of fragmentation products such as formaldehyde and methanol. Mass-based units emphasize larger compounds, which tend to be unidentified at an individual species level, are less volatile, and are typically not measured in the gas phase. Fire emissions are estimated to total 1250 ± 60 g·C of ROC per kg·C of CO, implying as much carbon is emitted as ROC as is emitted as CO. Particulate ROC has the potential to dominate the cancer and noncancer risk of long-term exposure to inhaled smoke, and better constraining these estimates will require information on the toxicity of particulate ROC from forest fires.

Byline: VNR. Das, K. Pandey, D. Singh, C. Forwood, C. Lal, P. Das We report two cases, one male (33 years) and a female (14 years), that developed Post-Kala-azar Dermal [...]

The simultaneous two-beam method for identifying defects in grain boundaries developed in Part I is demonstrated by using image matching to determine the Burgers vectors of GBDs introduced into coherent twin boundaries in copper by deformation at room temperature. The choice of this special twin system involves no loss of generality in the identification procedure, but provides an idealized test case where the diffraction parameters, the twin crystallography and the expected Burgers vectors of the GBDs are well defined. Furthermore, this system also allows the 'same-g' diffraction condition to be set up and tested.It is found that for the general simultaneous two-beam case the Burgers vectors of GBDs can be easily and positively identified and the high degree of agreement between matching sets of theoretical and experimental micrographs indicates that the assumptions used in computing the theoretical images are a good approximation to the experimental conditions. However, the matches between theoretical and experimental images in the same-g case, whilst adequate for identification purposes, were not quite so good as those obtained for the general case. This is thought to be due to the fact that, in the particular experimental cases encountered here, the diffracting vectors in each grain were not exactly the same so that the perfect coupling between the diffracted beams at the boundary, assumed in the theoretical images, was not being achieved in practice.The Burgers vectors which are identified in the coherent twin boundaries are of the type 1/6〈112〉 lying in the boundary, 1/3 〈111〉 normal to the boundary and 1/2〈110〉 oriented relative to the dislocation line direction so that they are sessile (Lomer) dislocations. It is shown how the positive identification of these dislocations leads to a description of the detailed structure of the boundary and the way in which the GBDs have been formed. The question as to whether the dislocations lie in the boundary or merely close to it is discussed.

An examination is made of the method for identifying grain boundary dislocations (GBDs) by applying g · b rules to images taken under conditions where one crystal is oriented for good two-beam diffraction and the other is not diffracting any beam strongly. It is suggested that the use of g · b rules is unreliable and that there is a need for image computation. However, these diffraction conditions are unsuitable for this purpose since they involve many-beam diffraction in the 'non-diffracting' crystal for which no simple approximation was found which would make routine image computation practical. A method of identifying GBDs is proposed using images taken when both crystals are simultaneously in good two-beam diffracting conditions. It is shown that, in general, it should be possible to approximate these conditions by a simple two-beam theory of diffraction in each crystal which may therefore be used to obtain theoretical micrographs of GBDs for image matching. The expression for the displacement field of a dislocation lying in a plane welded boundary between two elastically anisotropic half-spaces is given and the way in which this is used in integrating the Howie-Whelan equations to produce theoretical images of GBDs is described. The conditions which need to be satisfied to provide a reliable identification of GBDs are discussed.

Static room-temperature 27Al nuclear magnetic resonance (NMR) spectra for Ti1-xAlx alloys in the range 0·25 ≤ × ≤ 0.55 are reported for the first time. The main resonances associated with the α2 and γ phases are clearly identified. The spectra follow the phase distribution in that, for samples annealed at 1473 K for 6h in the range 0·43 ≤ × ≤ 0·48, resonances from both α2 and γ are observed. Careful quantitative analysis of the 27Al NMR spectra indicates that from single-phase samples all aluminium nuclei from the central transition are recorded, whereas for two-phase samples there is a loss of signal that is a consequence of the two-phase alloy microstructure. For the γ-phase the NMR centre band shows a distinctive, largely second-order quadrupolar line shape together with associated satellite transitions which yield a quadrupolar coupling constant CQ = 8·15 MHz and an axial Knight shift anisotropy of 130ppm. For the α2 phase the centre-band simulation requires only an axial Knight shift anisotropy of 270ppm and no quadrupolar interaction. An additional resonance associated with the γ-phase is also detected and quantified, and this is attributed to aluminium on antisites.

The fine structure in diffraction patterns from general grain boundaries and the way it changes with boundary normal are used to analyse the intrinsic structure of two boundaries in 99.999% Cu with misorientations of ∼6° and ∼11°. It is shown in both cases that the total misorientation is accommodated by three arrays of dislocations with non-coplanar Burgers vectors. For the 6° boundary the Burgers vectors are simple 1/2〈111〉 lattice vectors from either grain, but for the 11° boundary the Burgers vectors required involve linear combinations of 1/2〈110〉 lattice vectors. It is shown how the geometrical method of analysis developed and tested here can be applied to the case of general high-angle boundaries in polycrystals.

A new statistical method for atom location by channelling-enhanced micro-analysis is applied to γ - α2 duplex Ti-Al based alloys containing ternary element additions of V, Cr, Mn, Ga, Y, Zr, Nb, Mo, La, Hf, Ta and W at the 1 at.% level. Incoherent channelling patterns, formed by the variation in characteristic X-ray emission as a function or orientation, are collected from a number of different zone axes from both phases. Comparisons of experimental patterns with calculated maps for various crystallographic sites indicate that the ternary atoms are incorporated substitutionally in the atomic structure of both the γ and the α2-phases and do not occupy interstitial sites. The crystallographic site distribution of the ternary elements is determined through χ2-minimization techniques, together with quantitative error limits. The structure of the non-stoichiometric α2-phase is investigated by convergent-beam electron diffraction.

Recent advances in the theory of characteristic X-ray emission from crystals under dynamic electron diffraction conditions are used in developing a new fully quantitative statistical method for atom location by channelling-enhanced microanalysis (ALCHEMI). Limitations imposed by delocalization, disorder and occupancy of interstitial sites are clarified. A fully computerized method for automated data collection and analysis from incoherent channelling patterns formed by the variation in characteristic X-ray emission as a function of orientation is used for the fist time. The precision and accuracy of this method are investigated using both experimental and simulated data from the ordered γ phase in ternary Ti-Al alloys. It is shown that 1 at. % Ga, Hf and Mo additions partition onto Al sites, Ti sites and both sites respectively, and contrast in X-ray incoherent channelling patterns conforms that these ternary atoms are not located on interstitial sites. The traditional ratio ALCHEMI technique is shown to have severe limitations in comparison with statistical methods.

Glide on prismatic planes has been observed in the neighbourhood of a high-angle grain boundary in stainless steel, where the misorientation between neighbouring grains is about a common axis close to [110]. Detailed analysis, of the senses as well as the magnitudes of the Burgers vectors involved, indicates that a continuity of slip can occur across a high-angle boundary by the activation of prismatic glide.

Observations on rigid body displacements between grains, which move atoms away from coincidence sites, have shown that such displacements always occur at Σ9, Σ27a, Σ27b and Σ81 grain boundaries in polycrystals of a Cu-6 at.%Si alloy. Sometimes, small rigid body displacements were also observed at coherent {111} Σ3 boundaries when these occurred at triple junctions between grains.

It is shown that partial grain boundary dislocations (GBDs) form two of the three independent arrays of secondary GBDs in incoherent Σ3 boundary facets on {421}/{1085} planes in a f.c.c. Cu+6at%Si alloy. Two states of rigid-body displacement between the grains exist at these interfaces and these rigid-body displacements, together with the Burgers vectors of the partial GBDs, arc determined. The difference in grain boundary energy between the two states of rigid-body displacement is estimated as 2·5 mJ m-2 from the determined Burgers vectors and the measured separations of the partial GBDs.