Carbonate chemistry of CO₂ manipulation experiments on sea ice brine algae from McMurdo Sound, 2012.

<p>Units for DIC, TA and CO₃ is µmol l⁻¹. Unit for pCO₂ is µatm. Standard deviation (sd) is based on five replicates.</p

Growth rate changes in sea ice brine algae based on chl-<i>a</i> and biovolume.

<p>a: Growth rate of the brine algal incubations with varying pH, based on changes in chl-<i>a</i> and biovolume, in November 2012, experiment 1. b: Growth rate of the brine algal incubations (chlorophyll a and biovolume) with constant pH and varying CO₂ in November 2012, experiment 2. Vertical grey line signifies initial pH and pCO₂.</p

Maximum quantum yield (F_v/F_m) of brine algae with varying pH and pCO₂.

<p>a: Maximum quantum yield (F_v/F_m) of the brine algal incubations with varying pH in November 2012, experiment 1. b: Maximum quantum yield (F_v/F_m) of the brine algal incubations with constant pH and varying CO₂ in November 2012, experiment 2. Vertical grey line signifies initial pH and pCO₂.</p

Autonomous Thermal-Oxidative Composition Inversion and Texture Tuning of Liquid Metal Surfaces

Droplets capture an environment-dictated equilibrium state of a liquid material. Equilibrium, however, often necessitates nanoscale interface organization, especially with formation of a passivating layer. Herein, we demonstrate that this kinetics-driven organization may predispose a material to autonomous thermal-oxidative composition inversion (TOCI) and texture reconfiguration under felicitous choice of trigger. We exploit inherent structural complexity, differential reactivity, and metastability of the ultrathin (∼0.7–3 nm) passivating oxide layer on eutectic gallium–indium (EGaIn, 75.5% Ga, 24.5% In w/w) core–shell particles to illustrate this approach to surface engineering. Two tiers of texture can be produced after ca. 15 min of heating, with the first evolution showing crumpling, while the second is a particulate growth above the first uniform texture. The formation of tier 1 texture occurs primarily because of diffusion-driven oxide buildup, which, as expected, increases stiffness of the oxide layer. The surface of this tier is rich in Ga, akin to the ambient formed passivating oxide. Tier 2 occurs at higher temperature because of thermally triggered fracture of the now thick and stiff oxide shell. This process leads to inversion in composition of the surface oxide due to higher In content on the tier 2 features. At higher temperatures (≥800 °C), significant changes in composition lead to solidification of the remaining material. Volume change upon oxidation and solidification leads to a hollow structure with a textured surface and faceted core. Controlled thermal treatment of liquid EGaIn therefore leads to tunable surface roughness, composition inversion, increased stiffness in the oxide shell, or a porous solid structure. We infer that this tunability is due to the structure of the passivating oxide layer that is driven by differences in reactivity of Ga and In and requisite enrichment of the less reactive component at the metal–oxide interface

Le Courrier

13 août 18341834/08/13 (N225)

Megahertz pulse trains enable multi-hit serial femtosecond crystallography experiments at X-ray free electron lasers

The European X-ray Free Electron Laser (XFEL) and Linac Coherent Light Source (LCLS) II are extremely intense sources of X-rays capable of generating Serial Femtosecond Crystallography (SFX) data at megahertz (MHz) repetition rates. Previous work has shown that it is possible to use consecutive X-ray pulses to collect diffraction patterns from individual crystals. Here, we exploit the MHz pulse structure of the European XFEL to obtain two complete datasets from the same lysozyme crystal, first hit and the second hit, before it exits the beam. The two datasets, separated by <1 µs, yield up to 2.1 Å resolution structures. Comparisons between the two structures reveal no indications of radiation damage or significant changes within the active site, consistent with the calculated dose estimates. This demonstrates MHz SFX can be used as a tool for tracking sub-microsecond structural changes in individual single crystals, a technique we refer to as multi-hit SFX