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

Fluidity of Cement Pastes with Admixtures and Super Plasticizer

The Marsh cone is a simple device for measuring viscosity by observing the time it takes for a known volume of liquid to flow from a cone through a short tube. It is standardized for use by mud engineers to check the quality of drilling mud. Other cones with different geometries and orifice arrangements are called flow cones, but have the same operating principle. The Marsh Cone (SS with Stand) is a simple device used for routine quick measurements of fluid viscosity. It’s a type of viscometer. It is an excellent indicator of changes in drilling fluid properties. The Marsh Funnel conical in shape - 152 mm in diameter at the top and 305 mm long with a capacity of 1,500 cm3. A 12- mesh screen covers half of the top and is designed to remove any foreign matter and drilled cuttings from the fluid. The fluid runs through a fixed orifice at the end of the funnel, which is 50mm long by 4.7 mm diameter in size</jats:p

Flexural Strengthening of Light Weight Reinforced Concrete Beams by Using Glass Fiber Reinforced Polymer

The use of Lightweight concretes has gained acceptance and popularity worldwide in the recent years in the construction and development of both the infrastructure and residential buildings. Light weight aggregate concrete has become more popular in recent advancements owing to the tremendous advantages it offers over the conventional concrete but at the same time light in weight and strong enough to be used for structural purposes. Replacement of natural aggregate with concrete such as light weight concrete by using sintered fly ash aggregate (natural aggregate), The main disadvantage of conventional concrete it is high self -weight. This heavy self-weight will make it to some extent an uneconomical structural material. Light weight concrete having low density facilitates reduction of dead load and to increase thermal insulation.</jats:p

Intelligent Companion for Blind: Smart Stick

Blindness is a state of lacking the visual perception due to physiological or neurological factors. According to World Health Organization, approximately 1.3 billion people live with some form of visual impairment with 36 million people being completely blind. These people face great difficulty in independent and safe mobility. Almost 89% of such people live in low and middle income countries, and are unable to afford existing mobility aid devices. Addressing these difficulties, the proposed research aims to design a low-cost and user- friendly guidance system “Smart Stick” which serves as an Electronic travel Aid and as a Position Locator Device. It helps to improve the mobility of both blind and visually impaired people, enabling them to navigate safely by avoiding any obstacles that may encounter and providing facility to communicate its current location to any of his/her relative. This device is tested under natural environmental conditions, and has performed excellent under low and high light environments too. The proposed design achieves reduction in cost by 44% in comparison to existing devices</jats:p

ChassiDex: A microbial database useful for synthetic biology applications

ChassiDex is an open-source, non-profit online host organism database that houses a repository of molecular, biological and genetic data for model organisms with applications in synthetic biology. The structured user-friendly environment makes it easy to browse information. The database consists of a page for each model organism subdivided into sections such as Growth Characteristics, Strain diversity, Culture sources, Maintenance protocol, Transformation protocol, BioBrick parts and commonly used vectors. With tools such as CUTE built for codon usage table generator, it is also easy to generate and download accurate novel codon tables for unconventional hosts in suitable formats. This database was built as a project for the International Genetically Engineered Machine Competition in 2017 with the mission of making it easy to shift from working with one host organism to another unconventional host organism for any researcher in the field of synthetic biology. The code along with other instructions for the usage of the database and tools are publicly available at the GitHub page. We encourage the synthetic biology community to contribute to the database by adding data for any additional or existing host organism.https://chassidex.org;https://github.com/ChassiDex</jats:p

Author Correction: Robust estimation of bacterial cell count from optical density

An amendment to this paper has been published and can be accessed via a link at the top of the paper.</jats:p

Robust estimation of bacterial cell count from optical density

AbstractOptical 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  &lt;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.</jats:p