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The ongoing COVID-19 pandemic, caused by SARS-CoV-2 infection, has resulted in hundreds of thousands of deaths. Cellular entry of SARS-CoV-2, which is mediated by the viral spike protein and host ACE2 receptor, is an essential target for the development of vaccines, therapeutic antibodies, and drugs. Using a mammalian cell expression system, we generated a recombinant fluorescent protein (Gamillus)-fused SARS-CoV-2 spike trimer (STG) to probe the viral entry process. In ACE2-expressing cells, we found that the STG probe has excellent performance in the live-cell visualization of receptor binding, cellular uptake, and intracellular trafficking of SARS-CoV-2 under virus-free conditions. The new system allows quantitative analyses of the inhibition potentials and detailed influence of COVID-19-convalescent human plasmas, neutralizing antibodies and compounds, providing a versatile tool for high-throughput screening and phenotypic characterization of SARS-CoV-2 entry inhibitors. This approach may also be adapted to develop a viral entry visualization system for other viruses.

Direct evaporative cooling (DEC) uses evaporating water, combined with a wetted medium to cool the temperature of air as it passes through. Evaporative cooling devices can reduce the energy consumption of HVAC&R (Heating, Ventilating, Air Conditioning, and Refrigeration Equipment). Heat is absorbed whenever water is evaporated and converted to water vapor. By passing through or around a wetted surface, heat is removed from the surrounding air in the vaporization of the water. The process approximates the adiabatic-saturation process and the path lies on a constant wet-bulb temperature which is a constant enthalpy line. This paper suspects the relationship between system parameters and cooling efficiency. Effects of three system parameters on cooling performance were evaluated. The three parameters selected for focus were the speed of frontal air, the dry-bulb temperature of frontal air, and the temperature of the incoming water. Each parameter was varied while holding all other variables like air, water mass flow rates and so on constant respectively, and data was collected using several different levels of each parameter. The general relationship between each parameter and efficiency was determined by graphing the data collected and observing trends. The empirical correlation between supply frontal air velocity and cooling efficiency for DEC system in a typical applied environment was established and verified by experiment data. Within certain ranges, DEC cooling efficiency increases with frontal air dry-bulb temperature; decreases with frontal air velocity and incoming water temperature correspondingly.