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

MMC-MTDC transmission system with partially hybrid branches

This paper proposes a hybrid submodule modular multilevel converter (MMC) topology which is suitable for multi terminal direct current (MTDC) transmission systems. Each arm of the proposed MMC topology consists of a half-bridge submodule (HBSM) branch and two parallel full-bridge submodule (FBSM) branches. Comparing with the conventional MTDC transmission system, the proposed topology can selectively block the DC fault current and isolate the corresponding fault line without expensive DC circuit breakers (DCCBs). Thus, the influence range of the DC fault can be reduced and the reliability of the power supply can be improved as well. The corresponding modulation and voltage balancing strategies are developed for the proposed hybrid MMC topology. The feasibility of the proposed topology and control strategy is verified in the MATLAB/ Simulink simulation

Detection method based on improved faster R-CNN for pin defect in transmission lines

Defects such as insulator, pins, and counterweight in highvoltage transmission lines affect the stability of the power system. The small targets such as pins in the unmanned aerial vehicle (UAV) inspection images of transmission lines occupy a small proportion in the images and the characteristic representations are poor which results a low defect detection rate and a high false positive rate. This paper proposed a transmission line pin defect detection algorithm based on improved Faster R-CNN. First, the pre-training weights with higher matching degree are obtained based on transfer learning. And it is applied to construct defect detection model. Then, the regional proposal network is used to extract features in the model. The results of defect detection are obtained by regression calculation and classification of regional characteristics. The experimental results show that the accuracy of the pin defect detection of the transmission line reaches 81.25

Compact quartz-enhanced photoacoustic sensor for ppb-level ambient NO2 detection by use of a high-power laser diode and a grooved tuning fork

A compact quartz-enhanced photoacoustic sensor for ppb-level ambient NO2 detection is demonstrated, in which a high-power blue laser diode module with a small divergence angle was employed to take advantages of the directly proportional relationship between sensitivity and power, hence improving the detection sensitivity. In order to extend the stability time, a custom grooved quartz tuning fork with 800-um prong spacing is employed to avoid complex signal balance and/or optical spatial filter components. The sensor performance is optimized and assessed in terms of optical coupling, power, gas flow rate, pressure, signal linearity and stability. A minimum detectable concentration (1 sigma) of 7.3 ppb with an averaging time of 1 s is achieved, which can be further improved to be 0.31 ppb with an averaging time of 590 s. Continuous measurements covering a five-day period are performed to demonstrate the stability and robustness of the reported NO2 sensor system

Description of a CO2 Enhanced Coal Bed Methane Field Trial Using a Multi-Lateral Horizontal Well

AbstractEnhanced recovery of coal bed methane by CO2 injection (CO2-ECBM) offers the potential of increasing recovery of the gas in place over primary recovery methods and at the same time storing CO2. This paper describes a CO2-ECBM field trial using a multi-lateral horizontal well for injection. The trial, preforemed in China's Ordos basin, involved transport of liquid CO2 to the injection site and pumping of this directly into the injection well. A u-tube sampling system was installed in a monitoring well approximately 20m from the main horizontal branch close to the vertical section of the injection well. This u-tube system comprised three intervals separated by inflatable packers from which gas and water samples were automatically collected and recovered to an on-site field laboratory for gas analysis. The middle interval of this packer assembly sampled the target coal seam. At the start of injection a pulse of a non- adsorbing tracer gas was added to the CO2. There was clear breakthrough of the tracer in the middle packer interval of the monitoring well demonstrating the good connection between injection and monitoring wells. The CO2 composition of the gas sample from the coal seam gradually increased over time as injected CO2 migrated to the monitoring well. Some significant aspects of this trial are the use of a multi-lateral horizontal well for ECBM, tracer gas in coal bed methane, the monitoring of gas displacement during ECBM and the u-tube sampling system