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Non-exhaust emissions (e.g., automotive brake and tire wear) are quickly replacing exhaust emissions as the dominant traffic particulate pollutant. A significant fraction of the emissions are complex mixtures of organic compounds whose composition is not well known. Due to their unique health implications, knowledge of the composition of ultrafine particles (<100 nm in diameter) is of particular interest. Here we report on the size-selected organic composition of ultrafine particles nucleated during high brake temperature conditions generated using a custom brake dynamometer system and two common brake pad types. Using high resolution mass spectrometry, we find that the organic composition of these particles is dominated by species containing oxygen (CHO) and nitrogen (CHN/CHON). Many of these compounds are unsaturated and are attributed to the thermal degradation of resin material used in the pad formulation. Other abundant compounds include various glycols and amines, several of which are unequivocally identified and discussed as potential marker compounds for brake wear emissions. A significant fraction of highly oxidized, low volatility species observed in ultrafine particles could not be conclusively attributed to the thermal degradation of the brake material, indicating the presence of chemical pathways unique to the frictional heating process. This emphasizes the importance of using a brake dynamometer to generate brake wear particles as opposed to other strategies. 

Scaled physical experiments allow us to directly observe deformational processes that take place on time and length scales that are impossible to observe in the Earth’s crust. Successful evaluation of advection and uplift of material within a restraining bend along a strike-slip fault zone depends on capturing the evolution of strain in three dimensions. Consequently, we require deformation within the horizontal plane as well as vertical motions. While 3D digital image correlation systems can provide this information, their high costs have prompted us to develop techniques that require only two DSLR cameras and a few Matlab® toolboxes, which are available to researchers at many institutions. Matlab® plug-ins can perform particle image velocimetry (PIV), a technique used in many analog modeling studies to map the incremental displacements fields. For tracking material advection throughout experiments more suitable Matlab® plug-ins perform particle tracking velocimetry (PTV), which tracks the complete two-dimensional displacement path of individual particles. To capture uplift the Matlab® Computer Vision ToolboxTM, uses pairs of photos to capture the evolving topography of the experiment. The stereovision approach eliminates the need to stop the experiment to perform 3D laser scans, which can be problematic when working with materials that have time dependent rheology. We demonstrate how the combination of PIV, PTV, and stereovision analysis of experiments that simulate the Mount McKinley restraining bend reveal the evolution of the fault system and three-dimensional advection of material through the bend. 

We report an improved measurement of the valence $u$and $d$quark distributions from the forward-backward asymmetry in the Drell-Yan process using $8.6{\mathrm{fb}}^{-1}$of data collected with the D0 detector in $p\overline{p}$collisions at $\sqrt{s}=1.96$. This analysis provides the values of new structure parameters that are directly related to the valence up and down quark distributions in the proton. In other experimental results measuring the quark content of the proton, $d$quark contributions are mixed with those from other quark flavors. In this measurement, the $u$and $d$quark contributions are separately extracted by applying a factorization of the QCD and electroweak portions of the forward-backward asymmetry. Published by the American Physical Society2024 

Two additions impacting tables 3 and 4 in ref. [1] are presented in the following. No significant impact is found for other results or figures in ref. [1].