The role of hierarchical design and morphology in the mechanical response of diatom-inspired structures via simulation.

Diatoms are microscopic algae with intricate shell morphologies and features ranging from the nanometer to the micrometer scale, which have been proposed as templates for drug delivery carriers, optical devices, and metamaterials design. Several studies have found that diatom shells show unique mechanical properties such as high specific strength and resilience. One hypothesis is that these properties stem from the structural arrangement of the material at the nanometer and micrometer length scales, challenging the concept between what constitutes a "material" versus a "structure". In this work, we have conducted a systematic simulation-prototyping study to shed light on the mechanics of diatom-inspired hierarchical microstructures. The Finite Element Method (FEM) was used to replicate three-dimensional diatom shells under compressive forces. The intricate hierarchical shell structure of the Coscinodiscus sp. diatom frustule observed in nature was reproduced in detail. Simulation parameters were selected to reproduce compression experiments, with a force distributed on the surface of the diatom shell. A frustule diameter of 50 µm was used with pore diameters ranging from 0.25 to 1.2 µm across different layers. A "unit cell" FEM model was also created to focus on the basic structural element of a diatom frustule. Both of these models were used to elucidate the relation between morphology and mechanical response. Additionally, select designs were prototyped using 3D Direct Laser Writing (DLW) lithography to evaluate the feasibility of manufacturing diatom-inspired devices at the micro-scale. Distinct correlations between pore size in each frustule layer, or pore shape in the basal layers, and the mechanical response of the diatom shell were established in this study. The 3D-DLW prototypes exhibit a similar level of intricate morphological traits observed in real diatoms, opening the possibility of a simulation-based process for the design and fabrication of diatom-inspired microdevices. This research helps explain how morphology features are central to the mechanical performance of hierarchically arranged structures and biomaterials in general, and it represents a step toward the manufacture of emerging metamaterials and microarchitectures.

A randomized trial of intravenous iloprost (a stable prostacyclin analogue) versus lumbar sympathectomy in the management of Buerger's disease.

AIM: The aim of this study was to compare the effects of iloprost and lumbar sympathectomy (LS) in the treatment of Buerger's disease. METHODS: Two hundred patients with rest pain and/or ischemic ulcers were randomized to undergo LS or 28-day intravenous treatment of iloprost. The primary endpoint was complete healing without pain or major amputation at 4 and 24 weeks. The secondary endpoints were analgesic requirement, reduction in the ulcer size, 50% reduction of the ulcer, and shift in the modified SVS/ISCVS clinical status grading scale. RESULTS: The comparison was carried out in 162 patients (iloprost: n=84; LS: n=78). Complete healing rate was 61.9% in the iloprost group, but 41% in the LS group at the 4th week (P=0.012); respective values for the 24th week were 85.3%, 52.3%, P<0.001. Analgesic requirement was lower in the iloprost group at the 4th and 24th weeks (P=0.01, and P=0.098, respectively). The size of the ulcers decreased more in the iloprost group than the LS group (P=0.044 and P=0.035 at 4th and 24th weeks); 50% reduction in the ulcer size in the iloprost group was greater than in the LS group (P=0.001 and P=0.009 at 4th and 24th weeks). SVS/ISCVS grading scale demonstrated a better clinical benefit in patients treated with iloprost (P<0.001 at 4th week, and P<0.001 and at 24th week). CONCLUSIONS: The results of this independent study indicate that using iloprost relieves ischemic symptoms better than LS. In the era of stable prostacyclin analogues, there is no reliable evidence to support the use of LS in Buerger's disease.

GNB3 gene c.825C>T polymorphism and performance parameters in professional basketball players.

UNLABELLED: This study has been conducted to determine whether mean values of peak oxygen consumption (VO(2peak)), anaerobic test parameters and knee isokinetic test measurements are different among guanine nucleotide-binding protein, beta-3 (GNB3) genotype groups in a group of basketball players. METHODS: Seventy-two healthy male (mean age, 22.9 ± 5.3 years) basketball players from the first division of national league participated. We studied GNB3 gene c.825C>T (rs5443) polymorphism, then divided the subjects into three groups as CC (n = 21), CT (n = 35), and TT (n =1 6). Mean VO(2peak), Wingate anaerobic test results, and isokinetic knee muscle strength measurements were compared among the genotype groups. RESULTS: Mean VO(2peak) (60.1 ± 3.9; 56.7 ± 3.6; and 57.8 ± 3.3, respectively, p < 0.01), mean anaerobic minimum power (5.1 ± 0.4; 5.3 ± 0.5; and 4.4 v 0.5 W/kg, respectively, p < 0.001), mean anaerobic power drop (57.0 ± 6.2; 54.2 ± 6.9; and 62.9 ± 5.3%, respectively, p < 0.001) were significantly different among the study groups, CC, CT, and TT. Individuals with TT genotype exerted lower performance in terms of isokinetic knee muscle strength. CONCLUSION: The presence of 825T-allele may impair athletic performance and may serve as a genetic marker of low capacity for athletic performance in male basketball players.