When the Stars Align: A 5 {\sigma} Concordance of Planetary Nebulae Major Axes in the Centre of our Galaxy

We report observations of a remarkable major axes alignment nearly parallel to the Galactic plane of 5{\sigma} significance for a subset of bulge "planetary nebulae" (PNe) that host, or are inferred to host, short period binaries. Nearly all are bipolar. It is solely this specific PNe population that accounts for the much weaker statistical alignments previously reported for the more general bulge PNe. It is clear evidence of a persistent, organised process acting on a measurable parameter at the heart of our Galaxy over perhaps cosmologically significant periods of time for this very particular PNe sample. Stable magnetic fields are currently the only plausible mechanism that could affect multiple binary star orbits as revealed by the observed major axes orientations of their eventual PNe. Examples are fed into the current bulge planetary nebulae population at a rate determined by their formation history and mass range of their binary stellar progenitors.Comment: 12 pages, 6 figures, 2 tables, matches version published in ApJ

Low-threshold optically pumped lasing in highly strained Ge nanowires

The integration of efficient, miniaturized group IV lasers into CMOS architecture holds the key to the realization of fully functional photonic-integrated circuits. Despite several years of progress, however, all group IV lasers reported to date exhibit impractically high thresholds owing to their unfavorable bandstructures. Highly strained germanium with its fundamentally altered bandstructure has emerged as a potential low-threshold gain medium, but there has yet to be any successful demonstration of lasing from this seemingly promising material system. Here, we demonstrate a low-threshold, compact group IV laser that employs germanium nanowire under a 1.6% uniaxial tensile strain as the gain medium. The amplified material gain in strained germanium can sufficiently surmount optical losses at 83 K, thus allowing the first observation of multimode lasing with an optical pumping threshold density of ~3.0 kW cm^-^2. Our demonstration opens up a new horizon of group IV lasers for photonic-integrated circuits.Comment: 31 pages, 9 figure

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Simulation of Amorphous Silicon Carbide Photonic Crystal Absorption Layer for Solar Cells

In this work, the amorphous silicon carbide (a-SiC) with low cost and high extinction coefficient was used as the light absorption layer of solar cells, and the photonic crystal (PC) structure and defect structure were introduced. By optimizing the scatterer shape, structural parameters and defect types of photonic crystal, the absorption efficiency of the light absorption layer was further improved. The results show that the photonic crystal absorption layer with vacancy line defect is better than the perfect photonic crystal absorption layer. Meanwhile, the absorption efficiency of the photonic crystal absorption layer significantly improves in the case that the scatterer is an elliptical cylindrical air hole scatterer. When the incident light is in the wavelength range of 0.30~0.80 μm and the absorption layer height is 0.60 μm, the absorption efficiency of the absorption layer can reach 95.60%. Compared with the absorption layer without photonic crystal structure, the absorption layer is increased by 43.24%. At the same time, the absorption layer has little dependence on the incidence angle of sunlight. When the incidence angle is 65°, the absorption efficiency is still higher than 80%

Growth of noble metal nanoparticles on single-layer TiS2 and TaS2 nanosheets for hydrogen evolution reaction

The preparation of single-layer TiS2 and TaS2 nanosheets is realized by optimizing the electrochemical lithium interaction and exfoliation method. As a proof of concept, Pt and Au nanoparticles are grown on the aforementioned ultra-thin nanosheets to form functional composites. Notably, the Pt–TiS2 hybrid presents good electrocatalytic activity in the hydrogen evolution reaction