Acute transverse myelitis of childhood due to novel coronavirus disease 2019: The first pediatric case report and review of literature

The global coronavirus disease 2019 (COVID-19) pandemic appears to have some streaks of severity in pediatrics. These streaks include variable signs of respiratory distress, a new entity called multisysteminflammatory syndrome, and some evidences of neurological symptoms involving both central and peripheral nervous systems.Here, we described the first pediatric patient with COVID-19 who presented with acute transverse myelitis. An 11-year-old otherwise healthy girl presented to our clinic with acute onset of lower limbs paresis, urinary and fecal retention, alongside epigastric pain, and fever for 3 days. A neurological examination revealed a severe flaccid paraplegia in her lower limbs associated with a sensory level at T5. She was evaluated systematically for all probable causes of her symptoms, and finally, due to having a positive nasopharyngeal PCR test, she was considered to suffer from post-COVID-19 transverse myelitis. She underwent intravenous-immunoglobulin, methylprednisolone pulse, and other supportive cares without obvious results. Therefore, she underwent seven sessions of plasma exchange with little effects on muscle strength. The focal inflammation and injury of the spinal cord, otherwise known as transverse myelitis, have a wide array of potential etiologies. Transverse myelitis has been well documented to be the result of viral and bacterial infections. We believe our patient was not involved in a cytokine storm status due to good CRP, IL-6 and Ferritin levels. Albeit, we cannot certainly consider the patient to have a direct viral impact or involved in a late immunity process. To our knowledge, this is the first report of TM in the field of pediatrics occurred after COVID-19. Thus, this is critical to note that children can present with some severe types of COVID-19

Lyapunov-Based Controller for a Class of Stochastic Chaotic Systems

This study presents a general control law based on Lyapunov’s direct method for a group of well-known stochastic chaotic systems. Since real chaotic systems have undesired random-like behaviors which have also been deteriorated by environmental noise, chaotic systems are modeled by exciting a deterministic chaotic system with a white noise obtained from derivative of Wiener process which eventually generates an Ito differential equation. Proposed controller not only can asymptotically stabilize these systems in mean-square sense against their undesired intrinsic properties, but also exhibits good transient response. Simulation results highlight effectiveness and feasibility of proposed controller in outperforming stochastic chaotic systems

Determination of combined hardening material parameters under strain controlled cyclic loading by using the genetic algorithm method

In this paper, experimental and numerical investigations on mechanical behaviors of SS304 stainless steel under fully reversed strain-controlled, relaxation, ratcheting and multiple step strain-controlled cyclic loading have been performed. The kinematic and isotropic hardening theories based on the Chaboche model are used to predict the plastic behavior. An iterative method is utilized to analyze the mechanical behavior under cyclic loading conditions based on the Chaboche hardening model. A set of kinematic and isotropic parameters was obtained by using the genetic algorithm optimization approach. In order to analyze the effectiveness of this optimization procedure, numerical and experimental results for an SS304 stainless steel are compared. Finally, the results of this research show that by using the material parameters optimized based on the strain-controlled and relaxation data, good agreement with the experimental data for ratcheting is achieved

Ratcheting behavior of cylindrical pipes based on the Chaboche kinematic hardening rule

In this study, cyclic loading behavior of thick cylindrical pipes are described. Effects of internal pressure level and axial strain amplitude on the ratcheting rate under different types of loading histories are investigated. The kinematic hardening theory based on the Chaboche model is used to predict the plastic behavior of the structures. An iterative method is developed to analyze the structural behavior under cyclic loading conditions based on the Chaboche kinematic hardening model