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

Research on explosion characteristics and consequences of compressor room in compressor station of long-distance natural gas pipeline

As the core place in the compressor station, the compressor room has the possibility of gas leakage and explosion during its operation. In this paper, an equal proportional physical model is established based on FLCAS software, the effects of different stoichiometric ratios on the explosion temperature, flame propagation velocity and overpressure in the compressor room are investigated. The results show that when the stoichiometric ratio is in the range of 0.8–1.4, the indoor temperature peak, flame propagation velocity and peak overpressure generated by the explosion in the compressor room all increase first and then decrease with the increase of the stoichiometric ratio. The outdoor temperature peak and the flame propagation velocity increase with the increase of the stoichiometric ratio in the range of 0.8–1.4, and the flame acceleration during the flame propagation process can effectively promote the increase of the explosion overpressure inside the flame surface. In addition, in order to avoid more serious consequences in the event of an explosion in the compressor room, a fire sprinkler system should be laid between the adjacent compressor room doors, and the doors of the adjacent compressor rooms should be installed in staggered positions to prevent the occurrence of secondary danger

Experimental study of gas composition in the equilibrium state of a light alkane combustion reaction

Oil field-associated gas is typically a mixture of light alkanes. To ensure production safety, it is essential to investigate the combustion characteristics and the reaction mechanism of light alkane gas mixtures to uncover the underlying mechanisms of the combustion reaction. This paper investigates the equilibrium gas component concentrations resulting from the reaction of a gas mixture of methane, ethane, and propane at specific ratios through experimental tests. The study's results demonstrate that the equilibrium concentrations of methane, ethane, and propane initially decrease and then increase with the rise of the equivalence ratio under the same initial pressure conditions. In oxygen-poor conditions, the equilibrium concentration ratio of methane gradually increases in proportion to the equilibrium ratio, confirming that ethane and propane are the preferred participants in the reaction. Furthermore, a study of the equilibrium concentration of the critical intermediate product, ethylene, revealed that it does not completely oxidize in the combustion reaction. It can persist under both oxygen-rich and oxygen-poor conditions, with an equilibrium concentration of approximately 0.02%. The findings of this paper can serve as a theoretical supplement to the research on explosive gas combustion and explosions

Experimental and numerical study on natural gas explosion evolution in open space under different initial conditions

The vapor cloud explosion in open space are greatly affected by the initial conditions of gas cloud and the surrounding environment, while in the gas compressor station, these factors are ubiquitous. While the researches of external influencing factors like the obstacle and initial turbulence effect on natural gas explosion in open space are rare. In this paper, a series of natural gas explosion experiments were conducted and a long-distance natural gas pipeline compressor station was taking as an example to simulate the natural gas leakage and explosion in the typical location. Results showed that the greater the initial turbulence, the greater the peak overpressure of gas explosion. When the initial wind speed is 5 m/s, the peak overpressure can promote 73.4 % higher than that without initial turbulence. However, the overpressure doesn't linearly increase with the increasing of initial wind speed. What's more, the flame speed showed the same law with the overpressure, and the effect of concentration on overpressure is lower than that of initial turbulence and obstacle density. The explosion damaging range in the condenser area is larger than that in the separator area, and the maximum overpressure can reach about 21 kPa and the temperature can reach above 2280K, which provides an important basis for the safety prevention and personnel protection in natural gas compressor station

Transaldolase inhibits CD36 expression by modulating glutathione-p38 signaling, exerting protective effects against macrophage foam cell formation

In atherosclerosis, macrophage-derived foam cell formation is considered to be a hallmark of the pathological process; this occurs via the uptake of modified lipoproteins. In the present study, we aim to determine the role of transaldolase in foam cell formation and atherogenesis and reveal the mechanisms underlying its role. Bone marrow-derived macrophages (BMDMs) isolated from mice successfully form foam cells after treatment with oxidized low-density lipoprotein (80 μg/mL). Elevated transaldolase levels in the foam cell model are assessed by quantitative polymerase chain reaction and western blot analysis. Transaldolase overexpression and knockdown in BMDMs are achieved via plasmid transfection and small interfering RNA technology, respectively. We find that transaldolase overexpression effectively attenuates, whereas transaldolase knockdown accelerates, macrophage-derived foam cell formation through the inhibition or activation of cholesterol uptake mediated by the scavenger receptor cluster of differentiation 36 (CD36) in a p38 mitogen-activated protein kinase (MAPK) signaling-dependent manner. Transaldolase-mediated glutathione (GSH) homeostasis is identified as the upstream regulator of p38 MAPK-mediated CD36-dependent cholesterol uptake in BMDMs. Transaldolase upregulates GSH production, thereby suppressing p38 activity and reducing the CD36 level, ultimately preventing foam cell formation and atherosclerosis. Thus, our findings indicate that the transaldolase-GSH-p38-CD36 axis may represent a promising therapeutic target for atherosclerosis

Giant enhancement of Raman scattering by a hollow-core microstructured optical fiber allows single exosome probing

Microstructured optical fibers (MOFs) provide solutions for breaking through the bottlenecks in areas of high-power transmission and high-efficiency optical waveguides. Other than transporting light waves, MOFs can synergistically combine microfluidics and optics in a single fiber with an unprecedented light path length not readily achievable by planar optofluidic configurations. Here, we demonstrate that hollow-core anti-resonant optical fibers (HcARFs) can significantly enhance Raman scattering by over three orders of magnitude (EF ≈ 5000) compared with a planar setup, due to the joint mechanisms of strong light–matter interaction in the fiber core and the cumulative effect of the fiber. The giant enhancement enables us to develop the first optical fiber sensor to achieve single cancer exosome detection via a sandwich-structured strategy. This enables a multiplexed analysis of surface proteins of exosome samples, potentially allowing an accurate identification of the cellular origin of exosomes for cancer diagnosis. Our findings could expand the applications of HcARF in many exciting areas beyond the waveguide

Hepatocyte-specific TMEM16A deficiency alleviates hepatic ischemia/reperfusion injury via suppressing GPX4-mediated ferroptosis

Abstract Ischemia/reperfusion (I/R)-induced liver injury with severe cell death is a major complication of liver transplantation. Transmembrane member 16A (TMEM16A), a component of hepatocyte Ca2+-activated chloride channel, has been implicated in a variety of liver diseases. However, its role in hepatic I/R injury remains unknown. Here, mice with hepatocyte-specific TMEM16A knockout or overexpression were generated to examine the effect of TMEM16A on hepatic I/R injury. TMEM16A expression increased in liver samples from patients and mice with I/R injury, which was correlated with liver damage progression. Hepatocyte-specific TMEM16A knockout alleviated I/R-induced liver damage in mice, ameliorating inflammation and ferroptotic cell death. However, mice with hepatic TMEM16A overexpression showed the opposite phenotype. In addition, TMEM16A ablation decreased inflammatory responses and ferroptosis in hepatocytes upon hypoxia/reoxygenation insult in vitro, whereas TMEM16A overexpression promoted the opposite effects. The ameliorating effects of TMEM16A knockout on hepatocyte inflammation and cell death were abolished by chemically induced ferroptosis, whereas chemical inhibition of ferroptosis reversed the potentiated role of TMEM16A in hepatocyte injury. Mechanistically, TMEM16A interacted with glutathione peroxidase 4 (GPX4) to induce its ubiquitination and degradation, thereby enhancing ferroptosis. Disruption of TMEM16A–GPX4 interaction abrogated the effects of TMEM16A on GPX4 ubiquitination, ferroptosis, and hepatic I/R injury. Our results demonstrate that TMEM16A exacerbates hepatic I/R injury by promoting GPX4-dependent ferroptosis. TMEM16A–GPX4 interaction and GPX4 ubiquitination are therefore indispensable for TMEM16A-regulated hepatic I/R injury, suggesting that blockades of TMEM16A–GPX4 interaction or TMEM16A inhibition in hepatocytes may represent promising therapeutic strategies for acute liver injury