In Atrial Fibrillation, Omnipolar Voltage Maps More Accurately Delineate Scar Than Bipolar Voltage Maps.

BACKGROUND: Optimal method for voltage assessment in AF remains unclear. OBJECTIVES: This study evaluated different methods for assessing atrial voltage and their accuracy in identifying pulmonary vein reconnection sites (PVRSs) in atrial fibrillation (AF). METHODS: Patients with persistent AF undergoing ablation were included. De novo procedures: voltage assessment in AF with omnipolar voltage (OV) and bipolar voltage (BV) methodology and BV assessment in sinus rhythm (SR). Activation vector and fractionation maps were reviewed at voltage discrepancy sites on OV and BV maps in AF. AF voltage maps were compared with SR BV maps. Repeat ablation procedures: OV and BV maps in AF were compared to detect gaps in wide area circumferential ablation (WACA) lines that correlated with PVRS. RESULTS: Forty patients were included: 20 de novo and 20 repeat procedures. De novo procedure: OV vs BV maps in AF; average voltage 0.55 ± 0.18 mV vs 0.38 ± 0.12 mV; P = 0.002, voltage difference of 0.20 ± 0.07 mV; P = 0.003 at coregistered points and proportion of left atrium (LA) area occupied by low-voltage zones (LVZs) was smaller on OV maps (42.4% ± 12.8% OV vs 66.7% ± 12.7% BV; P < 0.001). LVZs identified on BV maps and not on OV maps correlated frequently to wavefront collision and fractionation sites (94.7%). OV AF maps agreed better with BV SR maps (voltage difference at coregistered points 0.09 ± 0.03 mV; P = 0.24) unlike BV AF maps (0.17 ± 0.07 mV, P = 0.002). Repeat ablation procedure: OV was superior in identifying WACA line gaps that correlated with PVRS than BV maps (area under the curve = 0.89, P < 0.001). CONCLUSIONS: OV AF maps improve voltage assessment by overcoming the impact of wavefront collision and fractionation. OV AF maps correlate better with BV maps in SR and more accurately delineate gaps on WACA lines at PVRS

Pt accelerated coarsening of A15 precipitates in Cr-Si alloys

The effect of alloying Cr-rich Cr-Si alloys with Pt was investigated by a combination of complementary experimental methods and atomic scale modelling. The investigated Cr-Si and Cr-Si-Pt (Cr ⩾86 at.%) alloys developed a two-phase microstructure consisting of Cr solid solution (Crss) matrix and strengthened by A15 precipitates during annealing at 1200\ub0C. It was found that additions of 2 at.% Pt increase the coarsening rate by almost five times considering annealing times up to 522 h. Pt was found to change the precipitate matrix orientation relationship, despite its low influence on the Crss matrix/A15 precipitate misfit. Through this experimental and modelling approach new insight has been gained into mechanisms of enhanced coarsening by Pt addition. The increased coarsening is principally attributed to a change in interface composition and structure resulting in different thermodynamic stabilities: Pt-containing A15 phase was found to have a broader compositional range if both elements, Pt and Si, are present compared to only Si. Additionally, the Crss phase was found to have a higher solubility of Pt and Si over just Si. Both factors additionally facilitated Ostwald ripening

Opening the Gate:Framework Flexibility in ZIF-8 Explored by Experiments and Simulations

ZIF-8 is a zeolitic imidazole-based metal-organic framework with large cavities interconnected by narrow windows. Because the small size of the windows, it allows in principle for molecular sieving of gases such as H-2 and CH4. However, the unexpected adsorption of large molecules on ZIF-8 suggests the existence of structural flexibility. ZIF-8 flexibility is explored in this work combining different experimental techniques with molecular simulation. We show that the ZIF-8 structure is modified by gas adsorption uptake in the same way as it is at a very high pressure (i.e., 14 700 bar) due to a swing effect in the imidazolate linkers, giving access to the porosity. Tuning the flexibility, and so the opening of the small windows, has a further impact on the design of advanced molecular sieving membrane materials for gas separation, adjusting the access of fluids to the porous network.</p

Divalent Metal Vinylphosphonate Layered Materials: Compositional Variability, Structural Peculiarities, Dehydration Behavior, and Photoluminescent Properties

A family of M-VP (M = Ni, Co, Cd, Mn, Zn, Fe, Cu, Pb; VP = vinylphosphonate) and M-PVP (M = Co, Cd; PVP = phenylvinylphosphonate) materials have been synthesized by hydrothermal methods and characterized by FTIR, elemental analysis, and thermogravimetric analysis (TGA). Their structures were determined either by single crystal X-ray crystallography or from laboratory X-ray powder diffraction data. The crystal structure of some M-VP and M-PVP materials is two-dimensional (2D) layered, with the organic groups (vinyl or phenylvinyl) protruding into the interlamellar space. However, the Pb-VP and Cu-VP materials show dramatically different structural features. The porous, three-dimensional (3D) structure of Pb-VP contains the Pb center in a pentagonal pyramid. A Cu-VP variant of the common 2D layered structure shows a very peculiar structure. The structure of the material is 2D with the layers based upon three crystallographically distinct Cu atoms; an octahedrally coordinated Cu2+ atom, a square planar Cu2+ atom and a Cu+ atom. The latter has an unusual co-ordination environment as it is 3-coordinated to two oxygen atoms with the third bond across the double bond of the vinyl group. Metal-coordinated water loss was studied by TGA and thermodiffractometry. The rehydration of the anhydrous phases to give the initial phase takes place rapidly for Cd-PVP but it takes several days for Co-PVP. The M-VP materials exhibit variable dehydration-rehydration behavior, with most of them losing crystallinity during the process.Proyecto nacional MAT2010-15175 (MICINN, España

Generating large starting configurations for molecular Reverse Monte Carlo modelling of an unique non-linear optical amorphous solid

We report on the recent advances regarding the source code optimization of Reverse Monte Carlo modelling used in scattering data analysis of an amorphous molecular solid which has recently attracted attention as a new brilliant white light emitter if irradiated by a simple infrared laser diode. The algorithm used for generating random molecular starting configurations without overlapping molecules in a box with periodic boundary conditions has been accelerated by a factor of roughly 400 in a 54k atom case. The resulting bigger independent starting configurations are used to gain further insight into previously presented x-ray scattering data. New improved scattering data have been obtained, revealing new structural features in the lower Q range