Patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019, suffer from respiratory and non-respiratory symptoms. Among these symptoms, the loss of smell has attracted considerable attention. The objectives of this study were to determine which cells are infected, what happens in the olfactory system after viral infection, and how these pathologic changes contribute to olfactory loss. For this purpose, Syrian golden hamsters were used. First, we verified the olfactory structures in the nasal cavity of Syrian golden hamsters, namely the main olfactory epithelium, the vomeronasal organ, and their cellular components. Second, we found angiotensin-converting enzyme 2 expression, a receptor protein of SARS-CoV-2, in both structures and infections of supporting, microvillar, and solitary chemosensory cells. Third, we observed pathological changes in the infected epithelium, including reduced thickness of the mucus layer, detached epithelia, indistinct layers of epithelia, infiltration of inflammatory cells, and apoptotic cells in the overall layers. We concluded that a structurally and functionally altered microenvironment influences olfactory function. We observed the regeneration of the damaged epithelium, and found multilayers of basal cells, indicating that they were activated and proliferating to reconstitute the injured epithelium.

This study examined the effect of the unit weight and compressive strength of concrete on the punching shear capacity of flat slabs without shear reinforcements. The slabs were prepared using all-lightweight aggregate concrete (ALWAC), sand-lightweight aggregate concrete (SLWAC), and normal-weight concrete (NWC) at the different compressive strengths of concrete of 24 and 45 MPa. Based on the upper-bound theorem of concrete plasticity, the failure surface generatrix is generalized to account for the increased horizontal extension with a decrease in the unit weight of concrete. Thus, the punching shear capacity of concrete flat slabs is mathematically driven considering the reduced effective strengths of LWAC under tension and compression. Test results showed that the radius of the punching shear tended to increase with a decrease in the unit weight of concrete. This yielded a lower normalized punching shear capacity observed for ALWAC or SLWAC flat slabs than NWC flat slabs. The proposed model accurately estimated the punching shear capacity, indicating that the mean and standard deviation of the ratios between the experiments and predictions were 1.10 and 0.05, respectively. This indicated that the proposed model reasonably reflects the reduced aggregate interlock action of lightweight aggregates.

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