Pleiotropy of positive selection in ancient ACE2 suggests an alternative hypothesis for bat-specific adaptations to host coronaviruses.

Angiotensin-convertingenzyme 2 (ACE2) has dual functions, regulating cardiovascular physiology and serving as the receptor for coronaviruses. Bats, the only true flying mammals and natural viral reservoirs, have evolved positive alterations in traits related to both functions of ACE2. This suggests significant evolutionary changes in ACE2 during bat evolution. To test this hypothesis, we examine the selection pressure in ACE2 along the ancestral branch of all bats (AncBat-ACE2), where powered flight and bat-coronavirus coevolution occurred, and detect a positive selection signature. To assess the functional effects of positive selection, we resurrect AncBat-ACE2 and its mutant (AncBat-ACE2-mut) created by replacing the positively selected sites. Compared to AncBat-ACE2-mut, AncBat-ACE2 exhibits stronger enzymatic activity, enhances mice's performance in exercise fatigue, and shows lower affinity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Our findings indicate the functional pleiotropy of positive selection in the ancient ACE2 of bats, providing an alternative hypothesis for the evolutionary origin of bats' defense against coronaviruses.

Study on the Effect of Rare Earth Oxide Addition on the Microstructure and Properties of Ni60/WC-Ni Coatings Prepared by Laser Cladding.

Rare earth oxides have been proven for their ability to refine grains and have high melting points. In this paper, different contents of rare earth oxide La2O3 were added into the Ni60/WC-Ni composite coating, in order to study its effect on the coating properties. SEM observation confirmed that the grain was refined significantly after the addition of La2O3. Energy Dispersive Spectroscopy (EDS) was applied to investigate the composition and X-Ray Diffraction (XRD) was used to measure the residual stress in the coating samples. In addition, the microhardness and wear resistance of the samples were tested. The results showed that the dilution ratio of coatings with different additions of La2O3 was in the range of 2.4 to 9.8%, and the sample with 1.0% addition of La2O3 exhibited the highest hardness of 66.1 HRC and best wear resistance with a wear volume of 9.87 × 106 µm3, and the residual stress increased from 159.4 MPa to 291.0 MPa. This implies that the performance of the coating has been obviously improved after the addition of La2O3.

The Influences of Ultrasonic Vibrations on Laser Cladding Ni60/WC-TiO2+La2O3 Composite Coating.

The optimal process parameters of ultrasonic-assisted processing were studied to further improve the molding quality and mechanical properties of Ni60/WC-TiO2+La2O3 composite coating. A single-factor experiment was used to explore the influences of ultrasonic vibration frequencies on Ni60/WC-TiO2+La2O3 composite coating. The microstructure, elemental composition, phase composition, hardness, and wear resistance of the coating were studied using scanning electron microscopy (SEM), an X-ray diffractometer (XRD), an energy spectrometer, a microhardness meter, a friction and wear tester, and other equipment. Ultrasonic vibrations significantly improved the problems of pores in the coating, and the porosity was reduced from 0.13 to 0.014%. When the vibration frequency was 32 kHz in the experiment, the aspect ratio of the coating was optimized from 2.06 to 2.48, the dilution rate increased from 5.60 to 5.79%, the hardness increased from 960.25 to 988.45 HZ1.0, and the friction coefficient was reduced from 0.34 to 0.27. The coating performance was significantly improved, and the research results provide a reference for preparing excellent Ni60/WC-TiC+La2O3 composite coating.