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

A Development and Validation of the Perceived Language Discrimination Scale

This study was conducted to develop the Perceived Language Discrimination (PLD) scale across three samples of international students. In Sample 1 (N ϭ 224), the seven items of the PLD were selected (␣ ϭ .94) through an exploratory factor analysis. In Sample 2, a confirmatory factor analysis (N ϭ 222) provided a cross-validation of the one-factor model. Validity was supported by moderate positive associations of perceived language discrimination with depression (r ϭ .35) and anxiety (r ϭ .36), as well as small negative associations of perceived language discrimination with self-esteem (r ϭ Ϫ.24) and life satisfaction (r ϭ Ϫ.26). Moreover, perceived language discrimination had a large positive association with perceived racial discrimination (r ϭ .62), a moderate negative association with perceived English proficiency (r ϭ Ϫ.49), and a relatively weak association with social desirability (r ϭ .14). Finally, perceived language discrimination added significant incremental variance in predicting depression and anxiety over and above perceived racial discrimination and perceived English proficiency, respectively. The results indicated measurement invariance and validity equivalency for the PLD between males and females as well as between the English and Non-English groups. In Sample 3, the estimated 2-week test-retest reliability (N ϭ 31) was .83

Optical toroidal response in three-dimensional plasmonic metamaterial

Toroidal dipole moments, the third kind of fundamental dipole moment, have unusual electromagnetic properties different from the electric and magnetic multipoles. We fabricate a new type of 3D plasmonic toroidal metamaterial by using mutual coupling between dumbbell-shaped gold apertures with vertical split-ring resonators (VSRRs) at optical frequency. The radiated power of multipole moments are calculated and analyzed to improve the meta-system is dominated by the toroidal dipole moment. This result paves a way for practical application on metamaterial based devices, such as biosensor and lasing spaser