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A general orbital-angular-momentum (OAM) mode selection principle is put forward involving the rotationally symmetric superposition of chiral states. This principle is not only capable of explaining the operation of vortex generating elements such as spiral zone plate holograms, but more importantly, it enables the systematic and flexible generation of structured OAM waves in general. This is demonstrated both experimentally and theoretically in the context of electron vortex beams using rotationally symmetric binary amplitude chiral sieve masks. [ABSTRACT FROM AUTHOR]

A clear understanding of catalytic activity enhancement mechanisms in fuel cell operation is necessary for a full degree translation of the latest generation of non-Pt/C fuel cell electrocatalysts into high-performance electrodes in proton-exchange membrane fuel cells (PEMFCs). In this work, PtNi nanowire (NW) array gas diffusion electrodes (GDEs) are fabricated from Pt NW arrays with Ni impregnation. A 2.84-fold improvement in the oxygen reduction reaction catalytic activity is observed for the PtNi NW array GDE (cf. the Pt NW array GDE) using half-cell GDE measurement in a 0.1 M HClO 4 aqueous electrolyte at 25 °C, in comparison to only a 1.07-fold power density recorded in the PEMFC single-cell test. An ionomer is shown to significantly increase the electrochemically active surface area of the GDEs, but the PtNi NW array GDE suffers from Ni ion contamination at a high temperature, contributing to decreased catalytic activities and limited improvement in operating PEMFCs.

Brugada syndrome is a rare cardiac arrhythmia which is associated with right bundle branch block pattern (RBBB) and ST-segment elevation in right precordial leads. SCNA5 mutation is the most common genetic abnormality associated with Brugada syndrome. Brugada pattern not related to genetic mutations has been previously reported in the setting of fever, metabolic conditions, lithium use, marijuana and cocaine abuse, ischemia and pulmonary embolism, myocardial and pericardial diseases. Multiple isolated cases of Brugada pattern associated with diabetic ketoacidosis (DKA) have been previously reported. We here present a case of type 1 Brugada pattern in a 23 year-old-male who presented with DKA. Brugada pattern in DKA is attributed to acidosis and multiple electrolyte abnormalities including hyperkalemia which alter ion channel expression in the heart thus leading to Brugada pattern which subsequently resolved with treatment of DKA. In such patients, Brugada pattern is not reproducible on procainamide induction cardiac electrophysiology study (EPS). Our scoping study demonstrates male predominance 20/22 cases of (DELETE this highlighted area) Brugada pattern in DKA, a finding that is consistent with prevalence of this disease among males.

Electron vortex beams constitute the first class of matter vortex beams which are currently routinely produced in the laboratory. Here, we briefly review the progress of this nascent field and put forward a natural quantum basis set which we show is suitable for the description of electron vortex beams. The normal modes are truncated Bessel beams (TBBs) defined in the aperture plane or the Fourier transform of the transverse structure of the TBBs (FT-TBBs) in the focal plane of a lens with the said aperture. As these modes are eigenfunctions of the axial orbital angular momentum operator, they can provide a complete description of the two-dimensional transverse distribution of the wave function of any electron vortex beam in such a system, in analogy with the prominent role Laguerre-Gaussian (LG) beams played in the description of optical vortex beams. The characteristics of the normal modes of TBBs and FT-TBBs are described, including the quantized orbital angular momentum (in terms of the winding number l) and the radial index p>0. We present the experimental realization of such beams using computer-generated holograms. The mode analysis can be carried out using astigmatic transformation optics, demonstrating close analogy with the astigmatic mode transformation between LG and Hermite-Gaussian beams.This article is part of the themed issue 'Optical orbital angular momentum'., (© 2017 The Author(s).)