Objective. Aloe vera is an herbal medicinal plant with biological activities, such as antimicrobial, anticancer, anti-inflammatory, and antidiabetic ones, and immunomodulatory properties. The purpose of this study was investigation of in vitro antimicrobial activity of A. vera gel against multidrug-resistant (MDR) Pseudomonas aeruginosa isolated from patients with burn wound infections. Methods. During a 6-month study, 140 clinical isolates of P. aeruginosa were collected from patients admitted to the burn wards of a hospital in Tehran, Iran. Antimicrobial susceptibility test was carried out against the pathogens using the A. vera gel and antibiotics (imipenem, gentamicin, and ciprofloxacin). Results. The antibiogram revealed that 47 (33.6%) of all isolates were MDR P. aeruginosa. The extract isolated from A. vera has antibacterial activity against all of isolates. Also, 42 (89.4%) isolates were inhibited by A. vera gel extract at minimum inhibitory concentration (MIC) ≤ 200 µg/mL. MIC value of A. vera gel for other isolates (10.6%) was 800 µg/mL. All of MDR P. aeruginosa strains were inhibited by A. vera at similar MIC50 and MIC90 200 µg/mL. Conclusion. Based on our results, A. vera gel at various concentrations can be used as an effective antibacterial agent in order to prevent wound infection caused by P. aeruginosa.
Ceramic materials, despite their high strength and modulus, are limited in many structural applications due to inherent brittleness and low toughness. Nevertheless, ceramic-based structures, in nature, overcome this limitation using bottom-up complex hierarchical assembly of hard ceramic and soft polymer, where ceramics are packaged with tiny fraction of polymers in an internalized fashion. Here, we propose a far simpler approach of entirely externalizing the soft phase via conformal polymer coating over architected ceramic structures, leading to damage tolerance. Architected structures are printed using silica-filled preceramic polymer, pyrolyzed to stabilize the ceramic scaffolds, and then dip-coated conformally with a thin, flexible epoxy polymer. The polymer-coated architected structures show multifold improvement in compressive strength and toughness while resisting catastrophic failure through a considerable delay of the damage propagation. This surface modification approach allows a simple strategy to build complex ceramic parts that are far more damage-tolerant than their traditional counterparts.
Abstract. The pre-and post-peak performance features of two widely used damage-plasticity constitutive formulations are assessed for modeling the multiaxial response behavior of pressure sensitive quasi-brittle materials such as concrete. Two benchmark problems have been solved using commercial software packages; ABAQUS which implements the two invariant LeeFenves damaged plasticity formulation as its main feature for concrete has been used along with LS-DYNA which is using Duvaut-Lion damage and plasticity model, a three invariant formulation. In order to have consistent results, the parameter identification and calibration for both models has been performed and response of both models has been compared to each other under uniaxial tension and compression. The two benchmark problem are triaxial compression CTC and triaxial tension CTE. The aim of this study is to observe the difference between two well-known material models in capturing the compaction to extension regime in the yielded material. The difference between the response of each material model and also the efficiency of input parameters in controlling of this transition has been studied in this paper. Based on these failure diagnostics, the main shortcomings of each formulation are discussed and possible enhancements and remedies are proposed for the pre-and post-peak feature.
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