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

Penyusunan Hazard Identification Risk Assessment and Risk Control pada Perusahaan Pipa Baja

PT. X, is a local company that manufacturer of wide range of steel pipes/tubes and other related products to meet specifications. PT. X wanted to compose Hazard Identification Risk Assessment and Risk Control (HIRARC) to fulfill one clause of the application of OHSAS 18001:2007. In Preparation of HIRARC, consist of 3 stages: hazard identification, risk assessment, and risk control. Hazard identification performed based on interviews with the workers, the observations at the site, and the historical data of accidents of PT. X. The result of the risk assessment shows that there are some activities with potential hazards. There are 61% moderate risk and 5% high risk. Risk control will be performed on activities with moderate risk, high risk, and extreme risk category