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

Thermal radiation, viscous dissipation, ohmic dissipation and mass transfer effects on unsteady hydromagnetic flow over a stretching surface

The aim of present investigation was to study the effects of thermal radiation, viscous dissipation, ohmic dissipation and mass transfer effects on unsteady hydromagnetic boundary layer flow over a stretching surface. The governing equations of momentum, thermal and concentration boundary layers are reduced to a set of ordinary differential equations by means of suitable similarity transformations. Those equations are solved numerically for some arbitrary values of the governing physical parameters such as the Unsteadiness parameter (A), Magnetic interaction parameter (M2), Prandtl number (Pr), Radiation parameter (Rd), Eckert number (Ec) and Schmidt number (Sc) using Runge Kutta method of fourth order along with an efficient shooting method called Nachtsheim Swigert integration technique for the satisfaction of asymptotic boundary conditions. The results obtained are discussed with the help of graphical illustrations. Important physical concepts such as skin friction coefficient, Nusselt number and Sherwood number are also obtained and are discussed in detail. Keywords: Unsteady stretching surface, Radiation heat transfer, Mass transfer, MHD, Viscous dissipation, Ohmic dissipatio

Research Article

Numerical investigation of slip flow effects on unsteady hydromagnetic flow over a stretching surface with thermal radiatio

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Not AvailableThree promising varieties of Bottle, gourd, Sponge gourd and Round melon of cucurbitaceous vegetables were artificially aged at 450C and 100 per cent relative humidity for 9 days. The experimental results revealed that accelerated ageing showed significant effect on loss of germination per cent, seedling growth, dry weight and other vigour parameters in all the varieties. However, ageing was more pronounced in sponge gourd seeds, twice as that of non-aged seeds. The decline in germination during accelerated ageing was related to the initial degree of deterioration of the seed lot. Percentage of electrolyte leakage, increased steadily during the course of ageing and irrespective of the varieties. The EC values of the sponge gourd were high as compared with those of bottle, gourd and round melon seeds after 24 hours of soaking which confirms the changes in the membrane permeability.Not Availabl