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

Heterostructure Interface Construction of Cobalt/Nickle Diselenides Hybridized with sp²–sp³ Bonded Carbon to Boost Internal/External Sodium and Potassium Storage Dynamics

Metal selenides exhibit great potential in energy storage systems owing to their diversified species, large interlayer spaces, and high theoretical specific capacity according to multiple ion-storage behaviors. In this work, heterostructured CoSe2/NiSe2 coupled with sp3 bonded N-doped carbon coating layers and interconnected with sp2 bonded carbon nanotubes is synthesized through a room-temperature wet-chemistry approach and a selenization route with Co–Ni Prussian blue analogues as the precursor. The hybrid exhibits enhanced energy storage properties when utilized as an anode material for sodium- and potassium-ion batteries. The excellent performance of the hybrid can be indexed to the delicately design of the CoSe2/NiSe2 heterostructure and the hybridization of it with sp2 and sp3 bonded carbonaceous materials synchronously. Experimental and theoretical calculation results demonstrate the heterostructure is constructed to acquire charge transfer driving forces to boost internal reaction dynamics. And there is a combination of the dual advantages of sp3 and sp2 bonded carbon, possessing not only the exceptional mechanics buffer capability of N-doped carbon coating layers but also the excellent electrical characteristics of carbon nanotubes to promote external reaction dynamics. In addition, to elucidate the differential sodium/potassium storage capability of the hybrid, theoretical calculations are further performed to indagate the adsorption energy of sodium and potassium on the CoSe2/NiSe2 heterointerface by establishing five Na/K adsorption sites. The research provides an effective strategy for the melioration of internal/external reaction dynamics to deliver ions durably and efficiently in energy storage regions

Exploration of Major Cognitive Deficits in Medication-Free Patients With Major Depressive Disorder

Background: Major depressive disorder (MDD) is associated with a wide range of cognitive deficits. However, it remains unclear whether there will be a major cognitive deficit independently caused by depression at acute episodes of MDD. Method: A comprehensive neurocognitive test battery was used to assess the executive function, processing speed, attention, and memory in 162 MDD patients and 142 healthy controls (HCs). A multivariate analysis of variance, hierarchical regression analyses and general linear regression analyses were used to explore the possible major cognitive deficits and their predictor variables. Results: MDD patients showed extensive impairment in all four cognitive domains. Impairment of executive function and processing speed were found to persist even with other cognitive domains and clinical variables being accounted for. Executive function and processing speed were further predicted by total disease duration and depression severity, respectively. Conclusions: Executive function and processing speed may be two distinct major deficits at acute episodes of MDD. Furthermore, the executive function is likely originated from the cumulative effect of disease duration and processing speed is possibly derived from the temporary effect of current depressive episode.</p