A novel nanoreservoir made of carbon nanotubes (CNTs) is proposed for realizing tougher and automated self-healing materials. The advantages of the approach are that CNTs have the potential to play the role of reinforcing elements prior to and after sealing a crack and that the number of voids is reduced after the material and the CNTs themselves are healed. The focus of this paper is on investigating the feasibility of using CNTs as a nanoreservoir by analyzing the dynamics of a fluid flowing out of a ruptured single-walled CNT (SWNT), where the fluid resembles an organic healing agent. With this in mind the escaping mechanism of organic molecules stored inside a cracked SWNT was investigated through a molecular dynamics study. The study shows that, when a SWNT wall suffers the formation of a crack, a certain amount of organic molecules, stored inside the SWNT, escape into space in a few picoseconds. This phenomenon is found to depend on the temperature and on the size of the cracks. The results of this study indicate that CNTs have the potential to be successfully used to realize the next generation of stronger, lighter and self-healing materials.
Cortisol increases have been associated with psychological and physiological stress; however, cortisol dynamics after weight loss (bariatric) surgery have not been defined. Obese participants not using exogenous glucocorticoids were eligible to participate. Female participants (n=24) provided salivary cortisol samples at bedtime, upon awakening the following morning, and 30 min after awakening before, and at 6 or 12 months after bariatric surgery. The Medical Outcomes Study Short Form-12 version 2 questionnaire regarding health-related quality of life was also completed. Preoperatively, mean body mass index was 45.1±8.1 kg/m2. Mean late night (1.8±1.1 nmol/l), awakening (10.7±7.4 nmol/l), and after-awakening (11.5±7.9 nmol/l) salivary cortisol values were within normal ranges. The cortisol awakening response (mean 21.1±79.7%, median 13.7%) was at the low end of normal. Preoperatively, participants had lower mental and physical health-related quality of life scores than US adult norms (p<0.001). Salivary cortisol was not correlated with measures of health-related quality of life. Mean BMI decreased over time (p<0.001) and participants experienced improved physical and mental health-related quality of life (p≤0.011). Postoperative late night salivary cortisol was not different from preoperative values. Awakening and after-awakening cortisol levels were higher than preoperative values (15.3±7.7 nmol/l, p=0.013; 17.5±10.2 nmol/l, p=0.005; respectively), but the cortisol awakening response was not changed (mean 26.7±66.2%; median 7.8%). Morning salivary cortisol increased at long-term follow-up after bariatric surgery. Although self-evaluated mental and physical health improved after surgery, the cortisol awakening response is at the low end of normal, which may indicate continued physiological stress.
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