Atomic-Scale Surface Demixing in a Eutectic Liquid BiSn Alloy

Resonant x-ray reflectivity of the surface of the liquid phase of the Bi43Sn57 eutectic alloy reveals atomic-scale demixing extending over three near-surface atomic layers. Because of the absence of an underlying atomic lattice which typically defines adsorption in crystalline alloys, studies of adsorption in liquid alloys provide unique insight on interatomic interactions at the surface. The observed composition modulation could be accounted for quantitatively by the Defay-Prigogine and Strohl-King multilayer extensions of the single-layer Gibbs model, revealing a near-surface domination of the attractive Bi-Sn interaction over the entropy.Engineering and Applied Science

Anomalous layering at the liquid Sn surface

X-ray reflectivity measurements on the free surface of liquid Sn are presented. They exhibit the high-angle peak, indicative of surface-induced layering, also found for other pure liquid metals (Hg, Ga and In). However, a low-angle peak, not hitherto observed for any pure liquid metal, is also found, indicating the presence of a high-density surface layer. Fluorescence and resonant reflectivity measurements rule out the assignment of this layer to surface-segregation of impurities. The reflectivity is modelled well by a 10% contraction of the spacing between the first and second atomic surface layers, relative to that of subsequent layers. Possible reasons for this are discussed.Comment: 8 pages, 9 figures; to be submitted to Phys. Rev. B; updated references, expanded discussio

Atomic-scale surface demixing in a eutectic liquid BiSn alloy

Resonant x-ray reflectivity of the surface of the liquid phase of the Bi$_{43}$Sn$_{57}$ eutectic alloy reveals atomic-scale demixing extending over three near-surface atomic layers. Due to the absence of underlying atomic lattice which typically defines adsorption in crystalline alloys, studies of adsorption in liquid alloys provide unique insight on interatomic interactions at the surface. The observed composition modulation could be accounted for quantitatively by the Defay-Prigogine and Strohl-King multilayer extensions of the single-layer Gibbs model, revealing a near-surface domination of the attractive Bi-Sn interaction over the entropy.Comment: 4 pages (two-column), 3 figures, 1 table; Added a figure, updated references, discussion; accepted at Phys. Rev. Let

Crystalline Surface Phases of the Liquid Au-Si Eutectic Alloy

A two-dimensional crystalline layer is found at the surface of the liquid eutectic Au82Si18 alloy above its melting point TM=359 °C. Underlying this crystalline layer, we find a layered structure, 6–7 atomic layers thick. This surface layer undergoes a first-order solid-solid phase transition occurring at 371 °C. The crystalline phase observed for T>371 °C is stable up to at least 430 °C. Grazing-incidence x-ray diffraction data at T>371 °C imply lateral order comprising two coexisting phases of different oblique unit cells, in stark contrast with the single phase with a rectangular unit cell found for low-temperature crystalline phase, 359 °C<T<371 °C.Engineering and Applied Science

A woolly mammoth (Mammuthus primigenius) carcass from Maly Lyakhovsky Island (New Siberian Islands, Russian Federation)

A partial carcass of an adult woolly mammoth (Mammuthus primigenius) found in 2012 on Maly Lyakhovsky Island presents a new opportunity to retrieve associated anatomical, morphological, and life history data on this important component of Pleistocene biotas. In addition, we address hematological, histological, and microbiological issues that relate directly to quality of preservation. Recovered by staff from North-Eastern Federal University in Yakutsk, this individual is a relatively old female preserving soft tissue of the anteroventral portion of the head, most of both fore-quarters, and the ventral aspect of much of the rest of the body. Both tusks were recovered and subjected to computed tomographic analysis in which annual dentin increments were revealed as cycles of variation in X-ray attenuation. Measurements of annual increment areas (in longitudinal section) display a pulsed pattern of tusk growth showing cycles of growth rate variation over periods of 3-5 years. These intervals are interpreted as calving cycles reflecting regular shifts in calcium and phosphate demand for tusk growth vs. fetal ossification and lactation. Brown liquid associated with the frozen carcass turned out to include remains of hemolyzed blood, and blood samples examined microscopically included white blood cells with preserved nuclei. Muscle tissue from the trunk was unusually well preserved, even at the histological level. Intestinal contents and tissue samples were investigated microbiologically, and several strains of lacticacid bacteria (e.g., Enterococcus faecium, Enterococcus hirae) that are widely distributed as commensal organisms in the intestines of herbivores were isolated. (C) 2017 Elsevier Ltd and INQUA. All rights reserved