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

Automotive Waste Heat Recovery: A Semi-Truck Exhaust Application

The goal of this project was to determine the feasibility of using thermoelectric generation as a method of collecting waste heat from a standard semi-truck exhaust system. Prior research regarding the efficacy of thermoelectric generators to reclaim wasted energy in mechanical processes inspired this project. A device for housing thermoelectric generators on the exhaust stack of a semi-truck was designed and optimized based on its structural integrity, potential power generation, and subsequent cost savings. Results from simulation models predict that the device would improve fuel efficiency by at least 4.96%

Co-designing Community Infrastructure in Dwenase, Ghana

The goal of this project was to create a drainage system for the parking lot of the Dwenase Health Center. During the rainy season the area in front of the Center became flooded by rains flowing in from the road and poor parking lot grading. As engineers, we have had experience with designing, but we lack the regional understanding and expertise of the local residents. For this project, then, we utilized our experience as designers while incorporating their knowledge of the problem. Co-design involves a free exchange of ideas between partners. We thought we were co-designing with the community. However, they were co-designing us. This applied to our work and our personal lives. Thus, knowledge flows both ways—even when do not think we are coproducing, we are

Reversible addition–fragmentation chain transfer polymerization of 2-chloro-1,3-butadiene

Controlled polymerization of 2-chloro-1,3-butadiene using reversible addition–fragmentation chain transfer (RAFT) polymerization has been demonstrated for the first time. 2-Chloro-1,3-butadiene, more commonly known as chloroprene, has significant industrial relevance as a crosslinked rubber, with uses ranging from adhesives to integral automotive components. However, problems surrounding the inherent toxicity of the lifecycle of the thiourea-vulcanized rubber have led to the need for control over the synthesis of poly(2-chloro-1,3-butadiene). To this end, four chain transfer agents in two different solvents have been trialed and the kinetics are discussed. 2-Cyano-2-propylbenzodithioate (CPD) is shown to polymerize 2-chloro-1,3-butadiene in THF, using AIBN as an initiator, with complete control over the target molecular weight, producing polymers with low polydispersities (Mw/Mn < 1.25 in all cases)

Massive stars and their supernovae

Stars more massive than about 8-10 solar masses evolve differently from their lower-mass counterparts: nuclear energy liberation is possible at higher temperatures and densities, due to gravitational contraction caused by such high masses, until forming an iron core that ends this stellar evolution. The star collapses thereafter, as insufficient pressure support exists when energy release stops due to Fe/Ni possessing the highest nuclear binding per nucleon, and this implosion turns into either a supernova explosion or a compact black hole remnant object. Neutron stars are the likely compact-star remnants after supernova explosions for a certain stellar mass range. In this chapter, we discuss this late-phase evolution of massive stars and their core collapse, including the nuclear reactions and nucleosynthesis products. We also include in this discussion more exotic outcomes, such as magnetic jet supernovae, hypernovae, gamma-ray bursts and neutron star mergers. In all cases we emphasize the viewpoint with respect to the role of radioactivities