On volatile/mobile trace element trends in E3 chondrites

Contents of 3 non-mobile trace elements (U, Co, Au) and 12 slightly-to-highly volatile ones (Rb, Sb, Ag, Ga, Se, Cs, Te, Zn, Cd, Bi, Tl and In) determined by RNAA in the Yamato (Y)-691 and Qingzhen E3 chondrites generally fall within ranges reported for E4 chondrite falls. Contents of most elements are similar in the two E3 chondrites : highly volatile Cd, Bi and Tl differ markedly, with the Y-691 data falling at C1 levels and those of Qingzhen near the bottom of the E4 ranges. Trace element abundances and interelement comparisons indicate that both E3 chondrites compositionally reflect only nebular condensation, with Y-691 parent material having condensed at lower temperatures than Qingzhen. Both escaped the post-accretionary metamorphic episode that compositionally altered other enstatite chondrites. For volatiles, E3,4 chondrites differ markedly from E5,6 : for siderophiles, E3-5 differ markedly from E6. These trends could reflect enstatite chondrites\u27 origin in 1 or 2 parent bodies : we interpret the data as indicating a single body

The effects on bronchial epithelial mucociliary cultures of coarse, fine, and ultrafine particulate matter from an underground railway station

We have previously shown that underground railway particulate matter (PM) is rich in iron and other transition metals across coarse (PM10–2.5), fine (PM2.5), and quasi-ultrafine (PM0.18) fractions and is able to generate reactive oxygen species (ROS). However, there is little knowledge of whether the metal-rich nature of such particles exerts toxic effects in mucus-covered airway epithelial cell cultures or whether there is an increased risk posed by the ultrafine fraction. Monolayer and mucociliary air-liquid interface (ALI) cultures of primary bronchial epithelial cells (PBECs) were exposed to size-fractionated underground railway PM (1.1–11.1 µg/cm2) and release of lactate dehydrogenase and IL-8 was assayed. ROS generation was measured, and the mechanism of generation studied using desferrioxamine (DFX) and N-acetylcysteine (NAC). Expression of heme oxygenase-1 (HO-1) was determined by RT-qPCR. Particle uptake was studied by transmission electron microscopy. Underground PM increased IL-8 release from PBECs, but this was diminished in mucus-secreting ALI cultures. Fine and ultrafine PM generated a greater level of ROS than coarse PM. ROS generation by ultrafine PM was ameliorated by DFX and NAC, suggesting an iron-dependent mechanism. Despite the presence of mucus, ALI cultures displayed increased HO-1 expression. Intracellular PM was observed within vesicles, mitochondria, and free in the cytosol. The results indicate that, although the mucous layer appears to confer some protection against underground PM, ALI PBECs nonetheless detect PM and mount an antioxidant response. The combination of increased ROS-generating ability of the metal-rich ultrafine fraction and ability of PM to penetrate the mucous layer merits further research

“Astonishing successes” and “bitter disappointment”: The specific heat of hydrogen in quantum theory

The specific heat of hydrogen gas at low temperatures was first measured in 1912 by Arnold Eucken in Walther Nernst’s laboratory in Berlin, and provided one of the earliest experimental supports for the new quantum theory. Even earlier, Nernst had developed a quantum theory of rotating diatomic gas molecules that figured in the discussions at the first Solvay conference in late 1911. Between 1913 and 1925, Albert Einstein, Paul Ehrenfest, Max Planck, Fritz Reiche, and Erwin Schrödinger, among many others, attempted theoretical descriptions of the rotational specific heat of hydrogen, with only limited success. Quantum theory also was central to the study of molecular spectra, where initially it was more successful. Moreover, the two problems interacted in sometimes surprising ways. Not until 1927, following Werner Heisenberg’s discovery of the behavior of indistinguishable particles in modern quantum mechanics, did American theorist David Dennison find a successful theory of the specific heat of hydrogen

Strengthening mechanisms in polycrystalline multimodal nickel-base superalloys

Polycrystalline γ-γ′ superalloys with varying grain sizes and unimodal, bimodal, or trimodal distributions of precipitates have been studied. To assess the contributions of specific features of the microstructure to the overall strength of the material, a model that considers solid-solution strengthening, Hall-Petch effects, precipitate shearing in the strong and weak pair-coupled modes, and dislocation bowing between precipitates has been developed and assessed. Cross-slip-induced hardening of the Ni3Al phase and precipitate size distributions in multimodal microstructures are also considered. New experimental observations on the contribution of precipitate shearing to the peak in flow stress at elevated temperatures are presented. Various alloys having comparable yield strengths were investigated and were found to derive their strength from different combinations of microconstituents (mechanisms). In all variants of the microstructure, there is a strong effect of antiphase boundary (APB) energy on strength. Materials subjected to heat treatments below the γ′ solvus temperature benefit from a strong Hall-Petch contribution, while supersolvus heat-treated materials gain the majority of their strength from their resistance to precipitate shearing. © The Minerals, Metals & Materials Society and ASM International 2009