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

Purification of sepiolite and preparation of silica

Purification of sepiolite using beneficiation, and preparation of silica using active acid leaching were studied. The sepiolite content in the purified product is about 90%. The silica obtained may be used as a reinforcement agent in rubber industry, substituting for precipitated silica.Xianzhen Yu, Chuyi Zhou. Purification of sepiolite and preparation of silica. In: Proceedings of the 9th international Clay Conference, Strasbourg, 1989. Vol V : Industrial applications of clays. Analytical techniques and teaching of clay mineralogy. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1990. pp. 25-32. (Sciences Géologiques. Mémoire, 89

Synthesis, Properties, and Derivatization of Poly(dihydrogermane): A Germanium-based Polyethylene Analogue

Polygermanes are germanium-based analogues of polyolefins and possess polymer backbones made up catenated Ge atoms. In the present contribution we report the preparation of a stable germanium polyethylene analogue – polydihydrogermane (i.e., (GeH2)n) – via two straightforward approaches that involve topotactic deintercalation of the CaGe Zintl phase. The resulting (GeH2)n possess morphologically dependent chemical and electronic properties and thermally decompose to yield amorphous hydrogenated Ge. We also show that the resulting (GeH2)n provide a platform from which functionalized polygermanes can be prepared via thermally-induced hydrogermylation-mediated pendant group substitution. This facile one-step derivatization reaction exploits Ge–H reactivity and opens the door to a wide array of tailored functional polygermanes. </div