Elastic properties of chiral,anti-chiral,and hierarchical honeycombs:A simple energy-based approach

The effects of two geometric refinement strategies widespread in natural structures, chirality and self-similar hierarchy, on the in-plane elastic response of two-dimensional honeycombs were studied systematically. Simple closed-form expressions were derived for the elastic moduli of several chiral, anti- chiral, and hierarchical honeycombs with hexagon and square based networks. Finite element analysis was employed to validate the analytical estimates of the elastic moduli. The results were also compared with the numerical and experimental data available in the literature. We found that introducing a hier- archical refinement increases the Young＇s modulus of hexagon based honeycombs while decreases their shear modulus. For square based honeycombs, hierarchy increases the shear modulus while decreasing their Young＇s modulus. Introducing chirality was shown to always decrease the Young＇s modulus and Poisson＇s ratio of the structure. However, chirality remains the only route to auxeticity. In particular, we found that anti-tetra-chiral structures were capable of simultaneously exhibiting anisotropy, auxeticity, and remarkably low shear modulus as the magnitude of the chirality of the unit cell increases.

Correlation of rib fracture patterns with abdominal solid organ injury: A retrospective observational cohort study

Purpose::Rib fractures are one of the most common causes of morbidity and mortality and are associated with abdominal solid organ injury(ASOI).The purpose of this study was to investigate the correlation of ASOI with the number,location,and involved segments of rib fracture(s)in blunt chest trauma.Methods::This retrospective cohort study was conducted on patients with blunt chest trauma over the age of 15 years,who were hospitalized with the diagnosis of rib fractures from July 2015 to September 2020.After ethic committee approval,a retrospective chart review was designed and patients with a diagnosis of rib fractures were selected.Patients who had chest and abdominopelvic CT scan were included in the study and additional data including age,gender,injury severity score,trauma mechanism,number and sides of the fractured ribs(left/right/bilateral),rib fracture segments(upper,middle,lower zone)and results of chest and abdominal spiral CT scan were recorded.The correlation between ASOI and the sides,segments and number of rib fracture(s)was assessed by Pearson's correlation coefficient.Results::Altogether 1056 patients with rib fracture(s)were included.The mean age was(42.76±13.35)years and 85.4%were male.The most common mechanism of trauma was car accident(34.6%).Most fractures occurred in the middle rib zone(60.44%)and the most commonly involved ribs were the 6th and 7th ones(15.7%and 16.4%,respectively).Concurrent abdominal injuries were observed in 103 patients(34.91%)and were significantly associated with middle zone rib fractures.Conclusion::There is a significant relationship between middle zone rib fractures and ASOI.Intra-abdominal injuries are not restricted to fractures of the lower ribs and thus should always be kept in mind during management of blunt trauma patients with rib fractures.