Investigation on the Autonomic Structural Self-Healing of FRPC using Microencapsulated 5E2N/Grubbs Catalyst System for Low Temperature Applications

ABSTRACT Investigation on the autonomic structural self-healing of FRPC using microencapsulated 5E2N/Grubbs catalyst system for low temperature applications Mohammad Asgar Khan, Ph.D. Concordia University, 2016 Structural self-healing of Fiber Reinforced Polymer Composites (FRPC) using microencapsulated 5E2N/Grubbs catalyst system is investigated in this work for low temperature applications. Microcapsule containing liquid 5E2N monomer in poly melamine urea formaldehyde (PMUF) shells have been synthesized following the in-situ polymerization technique. The effects of stirring speed and concentration of surfactant on the quality of microcapsules in terms of their average sizes, size distribution, surface morphology and shell thickness are investigated. An optimum combination of stirring speed-SLS concentration is established through numerous synthesis trials of microcapsules. The feasibility of self-healing with the current materials system is first demonstrated by visually observing the healing of crack network that is created on unreinforced epoxy samples impacted with high velocity projectiles. Different strength-based approaches like impact-heal-flexure, flexure-heal-flexure are examined to evaluate the self-healing performance of FRPC in the preliminary investigations. A fracture based approach based on the mode II delamination of FRPC which deals with determining material properties independent of geometry of samples is found to be a better choice for the evaluation of healing performance of FRPC. In the new proposed protocol, healing performance is evaluated by measuring and comparing the mode II fracture toughness of regular neat (not incorporated with healing agents) and modified (incorporated with healing agents) FRPC samples during the Non pre-cracked (NPC) and Pre-cracked (PC) test post healing without any manual intervention for achieving healing. Healing performance index, instead of healing efficiency, is defined by comparing the fracture toughness of regular and modified samples taking into account the possible toughening or weakening effect of incorporating healing agents into the composites. Healing performance index is shown to be a better and realistic indicator of actual healing performance than conventional healing efficiency definition. Effects of average size and concentration of microcapsules on the self-healing performance of FRP composites are investigated at room temperature using the proposed protocol. Finally, the effect of low temperature on self-healing performance of FRP composites is evaluated

Thermodynamic modeling of the Mg-Mn-(Al, Zn) systems

A self-consistent thermodynamic model of the Mg-Mn, Al-Mn, Mn-Zn binary systems as well as the Mg-Al-Mn and Mg-Mn-Zn ternary systems has been developed. The major difference between this work and the already existing assessments of these systems is the application of the modified quasichemical model for the liquid phase in each system while most of the existing descriptions use the random mixing model. Further, this model is also used to describe one intermediate solid solution phase in the Mn-Zn system. In the absence of key experimental data for the Mg-Mn system, the calculated thermodynamic quantities from the model have been found comparable with other similar systems. The critical temperature of the Mg-Mn liquid miscibility gap has been estimated with the available empirical equation and found to be in acceptable agreement with the calculated value. A comparison between the current work and the most recent work on the Al-Mn system that uses the same model for the liquid phase reveals that better agreement with the experimental data with less number of model parameters has been achieved in the current work. The Mn-Zn system has been modeled for the entire compositon range and wide temperature range starting from room temperature. The accepted experimental data are well reproduced with the current description of the Mn-Zn system. Kohler symmetric extrapolation model has been used to calculate both Mg-Al-Mn and Mg-Mn-Zn systems. The thermodynamic description of the Mg-Al-Mn system has been verified by extensive comparison with the available experimental data from numerous independent experiments. However, the calculated Mg-Mn-Zn system could not be thoroughly verified due to the lack of experimental data. The model can satisfactorily reproduce all the invariant points and the key phase diagram and thermodynamic features of the Mg-Al-Mn, Mg-Mn-Zn ternary systems and the binary sub-systems

Citric Acid-catalyzed Solvent Free, an Efficient One-pot Synthesis of 2, 3-Dihydro-1H-1, 5-Benzodiazepine Derivatives

2,3-Dihydro-1H-1,5-benzodiazepines are synthesized by reaction of o-Phenylenediamine with ketones (acyclic / cyclic) under solvent free conditions in the presence of citric acid in short reaction time with excellent yield

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P < 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

An Efficient One-Pot Synthesis of 1, 5-Benzodiazepine Derivatives Catalyzed by TBAB under Mild Conditions

2,3-Dihydro-1H-1,5-benzodiazepines were synthesized by reaction of o-phenylenediamine with ketones (acyclic / cyclic) under solvent free conditions in the presence of tetra butyl ammonium bromide (TBAB) in short reaction time with excellent yield

Nanostructured lipid carrier system for topical delivery of terbinafine hydrochloride

The main aim of the present study was to develop and evaluate Terbinafine HCl (TH)-loaded nanostructured lipid carrier (NLC) for the treatment of fungal infection via topical administration. Fungal infections are tremendously widespread and the treatments are effective but associated toxicities restrict their use. TH-NLC was prepared using high pressure homogenization technique using Glyceryl Monostearate (GMS) as solid lipid, Labrasol as liquid lipid and Pluronic F-127 as surfactant, binary lipid phase was selected in the ratio 6:4 w/w (solid:liquid lipid ratio). The mean diameter of optimized TH-NLCs was found to be 128 ± 4.5 nm. Spherical shape and size were confirmed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. The in vitro release studies showed 92.60 ± 0.87% drug release over 24 h as compared to the marketed formulation which showed only 82.826 ± 0.29%. Ex vivo skin permeation study showed about 86.35% permeation however from the marketed formulation it showed 69.41%. The pharmacodynamic studies indicated that TH-NLC (771 ± 41.797 CFUs) gel efficiently reduced the fungal burden in shorter duration of time as compared to marketed formulation (1558 ± 140.524 CFUs) and dispersion (95,582 ± 2316.619 CFUs) (p value > 0.001). Therefore, it can be concluded that the developed NLCs showed a sustained release pattern and reduction of fungal burden in the infected area. Hence, TH-NLC could be a potential alternative for treatment of topical fungal infection after clinical evaluation in near future