Retrospective study of factors associated with the clinical severity of covid-19 in older adults in Minas Gerais: structural equation modeling.

Background: Studies have shown an association between the clinical severity of coronavirus disease (COVID-19) and sociodemographic and clinical variables in older adults. However, few studies have described the explanatory factors of the relationship between these variables and the clinical severity of COVID-19 using structural equation modeling.

Objective: To analyze the factors directly and indirectly associated with the clinical severity of coronavirus disease (COVID-19) among older adults in Minas Gerais, Brazil.

Echinoid skeleton: an insight on the species-specific pattern of the plate and its microstructural variability.

The skeletal plates of echinoids consist of a peculiar lightweight structure, called stereom, which is organized in a porous three-dimensional lattice-like meshwork. The stereom is characterized by an extremely complex and diverse microarchitecture, largely varying not only from species to species but also among different test plates. It consists of different basic types combined in extremely different ways according to specific functional needs, creating species-specific structural patterns.

Continuous modeling of creased annuli with tunable bistable and looping behaviors.

Creases are purposely introduced to thin structures for designing deployable origami, artistic geometries, and functional structures with tunable nonlinear mechanics. Modeling the mechanics of creased structures is challenging because creases introduce geometric discontinuity and often have complex mechanical responses due to local material damage. In this work, we propose a continuous description of the sharp geometry of creases and apply it to the study of creased annuli, made by introducing radial creases to annular strips with the creases annealed to behave elastically.

Hexagonal Voronoi pattern detected in the microstructural design of the echinoid skeleton.

Repeated polygonal patterns are pervasive in natural forms and structures. These patterns provide inherent structural stability while optimizing strength-per-weight and minimizing construction costs. In echinoids (sea urchins), a visible regularity can be found in the endoskeleton, consisting of a lightweight and resistant micro-trabecular meshwork (stereom).

Flexible sutures reduce bending moments in shells: from the echinoid test to tessellated shell structures.

In the field of structural engineering, lightweight and resistant shell structures can be designed by efficiently integrating and optimizing form, structure and function to achieve the capability to sustain a variety of loading conditions with a reduced use of resources. Interestingly, a limitless variety of high-performance shell structures can be found in nature. Their study can lead to the acquisition of new functional solutions that can be employed to design innovative bioinspired constructions.