Hysteresis curves reveal the microscopic origin of cooperative CO2_2 adsorption in diamine-appended metal{organic frameworks

Diamine-appended metal{organic frameworks (MOFs) of the form Mg2(dobpdc)(diamine)2 adsorb CO2 in a cooperative fashion, exhibiting an abrupt change in CO2 occupancy with pressure or temperature. This change is accompanied by hysteresis. While hysteresis is suggestive of a firstorder phase transition, we show that hysteretic temperature-occupancy curves associated with this material are qualitatively unlike the curves seen in the presence of a phase transition; they are instead consistent with CO2 chain polymerization, within one-dimensional channels in the MOF, in the absence of a phase transition. Our simulations of a microscopic model reproduce this dynamics, and point the way toward rational control, in and out of equilibrium, of cooperative adsorption in this industrially important class of materials

An original phylogenetic approach identified mitochondrial haplogroup T1a1 as inversely associated with breast cancer risk in BRCA2 mutation carriers

Introduction: Individuals carrying pathogenic mutations in the BRCA1 and BRCA2 genes have a high lifetime risk of breast cancer. BRCA1 and BRCA2 are involved in DNA double-strand break repair, DNA alterations that can be caused by exposure to reactive oxygen species, a main source of which are mitochondria. Mitochondrial genome variations affect electron transport chain efficiency and reactive oxygen species production. Individuals with different mitochondrial haplogroups differ in their metabolism and sensitivity to oxidative stress. Variability in mitochondrial genetic background can alter reactive oxygen species production, leading to cancer risk. In the present study, we tested the hypothesis that mitochondrial haplogroups modify breast cancer risk in BRCA1/2 mutation carriers. Methods: We genotyped 22,214 (11,421 affected, 10,793 unaffected) mutation carriers belonging to the Consortium of Investigators of Modifiers of BRCA1/2 for 129 mitochondrial polymorphisms using the iCOGS array. Haplogroup inference and association detection were performed using a phylogenetic approach. ALTree was applied to explore the reference mitochondrial evolutionary tree and detect subclades enriched in affected or unaffected individuals. Results: We discovered that subclade T1a1 was depleted in affected BRCA2 mutation carriers compared with the rest of clade T (hazard ratio (HR) = 0.55; 95% confidence interval (CI), 0.34 to 0.88; P = 0.01). Compared with the most frequent haplogroup in the general population (that is, H and T clades), the T1a1 haplogroup has a HR of 0.62 (95% CI, 0.40 to 0.95; P = 0.03). We also identified three potential susceptibility loci, including G13708A/rs28359178, which has demonstrated an inverse association with familial breast cancer risk. Conclusions: This study illustrates how original approaches such as the phylogeny-based method we used can empower classical molecular epidemiological studies aimed at identifying association or risk modification effects.Peer reviewe

Cluster Formation in One-Patch Colloids: Low Coverage Results

We perform Monte Carlo simulations of a simple one-patch colloidal model to investigate the cluster formation and the phase behavior of the system on changing the width of the patch. We investigate the parameter region where the coverage (defined as the ratio between attractive and total surface) varies from 50% (the Janus case) to zero (hard-sphere). Simulation results indicate that on decreasing the coverage, particles self-assemble into clusters of different shapes, from micelles close to the Janus case, to one and two dimensional aggregates (wires and lamellae) for smaller coverage. Close to the hard-sphere limit, small micelles and dimers dominate the scene. We never find evidence of a gas-liquid (colloidal-rich/colloidal-poor) phase separation: it confirms that self-assembly into clusters which expose to their neighbors mostly repulsive surfaces suppresses phase separation and stabilizes cluster phases

Phase Diagram of One-Patch Colloids Forming Tubes and Lamellae

We numerically calculate the equilibrium phase diagram of one-patch particles with 30% patch coverage. It has been previously shown that in the fluid phase these particles organize into extremely long tubelike aggregates (G. Munao et al. Soft Matter 2013, 9, 2652). Here, we demonstrate by means of free-energy calculations that such a disordered tube phase, despite forming spontaneously from the fluid phase below a density-dependent temperature, is always metastable against a lamellar crystal. We also show that a crystal of infinitely long packed tubes is thermodynamically stable, but only at high pressure. The full phase diagram of the model, beside the fluid phase, displays four different stable crystals. A gas-liquid critical point, and hence a liquid phase, is not detected

Layout of Ancient Greek Papyri Through Lead-Drawn Ruling Lines Revealed by Macro X-Ray Fluorescence Imaging

The use of lead-drawn ruling lines by ancient scribes for the layout of Greek papyrus rolls was known to us only from classical authors and was postulated by a few scholars in modern times. In situ application of noninvasive Macro X-Ray Fluorescence Imaging Spectroscopy (MA-XRF) to unrolled papyri from Herculaneum, dating from about 200 BC to the 1st century AD, has provided the first direct evidence of such practice in ancient book production. The key experimental proof of periodic lines drawn in lead was gathered by a highly sensitive MA-XRF mobile instrument, which allowed detection of ultra-low trace residues of metals with detection limits that rival synchrotron light instruments. Elemental distribution maps of Pb have revealed three different systems of textual layout in ancient papyrus rolls and have resolved the dispute around so-called Maas' Law, by delivering experimental proof that slanted text columns were a deliberate aesthetic choice of scribes