Although the preponderance of current data points to semivolatile diesel nuclei particles composed of sulfuric acid and heavy hydrocarbons, the question remains as to what extent, if any, they contain solid cores. We present evidence here of a "solid" particle nucleation mode that accompanies normal soot emissions in the case of two modern light-duty diesel vehicles run with ultralow sulfur fuel. This mode is most prominent at idle, but also appears at speeds below approximately 30 mph, and is highly sensitive to the level of exhaust gas recirculation (EGR). The nuclei particles are examined for their volatility and electrical charge. In stark contrast to "conventional" nuclei particles, they remain nonvolatile to >400 degrees C and exhibit a bipolar charge with a Boltzmann temperature of 580 degrees C. Their nonvolatile nature rules out sulfate and heavy hydrocarbons as primary constituents, and their electrical charge requires formation in a high-temperature environment capable of generating bipolar ions. This suggests that "solid" nuclei particles form during combustion but remain distinct from soot particles, analogous to what has been found recently in flames. As concerns about potential emissions of nonvolatile nanoparticles have already surfaced, an important conclusion of this study is that diesel particulate filters remove the "solid" nucleation mode with an efficiency comparable to soot
Limb long bones are essential to an animal's locomotion, and are thus expected to be heavily influenced by factors such as mass or habitat. Because they are often the only organs preserved in the fossil record, understanding their adaptive trends is key to reconstructing the paleobiology of fossil taxa. In this regard, the Bovidae has always been a prized group of study. This family is extremely diverse in terms of both mass and habitat, and it is expected that their bones will possess adaptations to both factors. Here, we present the first 3D geometric morphometric study focusing on bovid limb long bones. We used anatomical landmarks as well as curve and surface sliding semi‐landmarks to accurately describe the stylopod and zeugopod bones. We included 50 species from ten of the twelve currently recognized tribes of bovids, ranging from 4.6 to 725 kg, and living in open plains, forests, mountains, or anywhere in‐between. Shape data were correlated with the mean mass of the species and its habitat, even when taking into account the phylogenetic history of our sample. Bones pertaining to heavy species are more robust, adapted for a better repartition of stronger forces. Articulations are especially affected, being proportionally much larger in heavier species. Muscle insertion areas are unevenly affected. Insertion areas of muscles implied in body support and propulsion show a strong increase in their robustness when compared to insertion areas of muscles acting on the limb mostly when it is off the ground. Habitat influences the shape of the humerus, the radius‐ulna, and the femur, but not of the tibia, whether the phylogeny is taken into account or not. Specific habitats tend to be associated with particular features on the bones. Articulations are proportionally wider in open‐habitat species, and the insertion areas of muscles involved in limb extension and propulsion are wider, reflecting the fact that open habitat species are more cursorial and rely on fast running to avoid predators. Forest and mountain species generally present similar adaptations for increased manoeuvrability, such as a round femoral head, and generally have more gracile bones.
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