Nonlinear finite element analysis and design optimization of thin-walled structures

In this study, an efficient, accurate and robust methodology for nonlinear finite element analysis and design optimization of thin-walled structures is presented. Main parts of this research are: formulation and development of an accurate and efficient shell element, a robust nonlinear finite element analysis technique, and an efficient optimization methodology. In the first part, a new three-node triangular shell element is developed by combining the optimal membrane element and discrete Kirchhoff triangle (DKT) plate bending element, and is then modified for laminated composite plates and shells so as to include the membrane-bending coupling effect. Also, a moderately thick shell element is developed in a similar manner by combining the discrete Kirchhoff-Mindlin triangular (DKMT) plate bending element and the optimal membrane element. Using appropriate shape functions for the bending and membrane modes of the element, the "inconsistent" stress stiffness matrix is formulated and the tangent stiffness matrix is determined. In the second part, a robust nonlinear finite element analysis program based on the corotational technique is developed to analyze thin-walled structures with geometric nonlinearity. The new element is thoroughly tested by solving few popular benchmark problems. The results of the analyses are compared with those obtained based on other membrane elements. In the third part, optimization algorithms based on the optimality criteria are developed and then combined with the nonlinear finite element analysis to optimize different types of thin-walled structures with geometric nonlinearity. The optimization problem considers the thickness or geometry design variables, and aims to maximize the critical load of the structure subject to constant total mass, or minimize the total mass subject to constant applied loads. The optimization results based on the developed design optimization algorithm are compared with those based on the gradient-based sequential quadratic programming method to demonstrate the efficiency and accuracy of the developed procedure. An application of the thickness optimization for locating the potential places to add the stiffeners in stiffened panels is also presented. Also a method is presented to efficiently incorporate the effects of local buckling and mode switching during optimization process for stiffened panels

Spinal Fluid Lactate Dehydrogenase Level Differentiates between Structural and Metabolic Etiologies of Altered Mental Status in Children

How to Cite This Article: Khosroshahi N, Alizadeh P, Khosravi M, Salamati P, Kamrani K. Spinal Fluid Lactate Dehydrogenase Level Differentiates between Structural and Metabolic Etiologies of Altered Mental Status in Children. Iran J Child Neurol. 2015 Winter;9(1):31-36.AbstractObjectiveAltered mental status is a common cause of intensive care unit admission inchildren. Differentiating structural causes of altered mental status from metabolic etiologies is of utmost importance in diagnostic approach and management of the patients. Among many biomarkers proposed to help stratifying patients with altered mental status, spinal fluid lactate dehydrogenase appears to be the most promising biomarker to predict cellular necrosis.Materials & MethodsIn this cross sectional study we measured spinal fluid level of lactatedehydrogenase in children 2 months to 12 years of age admitted to a single center intensive care unit over one year. Spinal fluid level of lactate dehydrogenase in 40 pediatric cases of febrile seizure was also determined as the control group.ResultsThe study group included 35 boys (58.3%) and 25 girls (41.7%). Their meanage was 2.7+/-3 years and their mean spinal fluid lactate dehydrogenase levelwas 613.8+/-190.4 units/liter. The control group included 24 boys (55.8%) and19 girls (44.2%). Their mean age was 1.3+/-1.2 years and their mean spinalfluid lactate dehydrogenase level was 18.9+/-7.5 units/liter. The mean spinalfluid lactate dehydrogenase level in children with abnormal head CT scan was246.3+/-351.5 units/liter compared to 164.5+/-705.7 in those with normal CTscan of the head (p=0.001).ConclusionSpinal fluid lactate dehydrogenase level is useful in differentiating structural andmetabolic causes of altered mental status in children. ReferencesFesk SK. Coma and confusional states: emergency diagnosis and management. Neurol Clin 1998; 16: 237- 56.Cucchiara BL, Kanser SE, Wolk DA, et al. Early impairment in consciousness Predicts mortality after hemispheric ischemic stroke. Crit care med 2004; 32: 241-5.Teasdale G, Jennett B. Assessment of coma and impaired consciousness: a practical scale. Lancet 1974; 2: 81-4.Wityk RJ, Stern BJ. Ischemic stroke: today and tomorrow. Crit care med 1994; 22: 1278-93.Vázquez Jorge Alejandro, Adducci Maria del Carmen, Monzón Daniel Godoy, Iserson Kenneth V. Lactic dehyrogenase in cerebrospinal fluid may differentiate between structural and non-strucfiular central nervous system lesion in patient with diminished levels of consciousness. The Journal of Emergency Medicine2009; 37(1): 93–97.Kärkelä J, Pasanen M, Kaukinen S, Mörsky P, Harmoinen A. Evaluation of hypoxic brain injury with spinal fluid enzymes, lactate, and pyruvate. Crit Care Med. 1992 Mar; 20(3):378-86. 2007: pp. 835. ISBN 0-7817-7087-4.DV Kamat, BP Chakravorty. Comparative values of CSF-LDH isoenzymes in neurological disorders. Indian Journal of Medical Sciences 1999; 53 (1): 1-6.Pollak AN, Gupton CL. Emergency Care and Transportation of the Sick and Injured. Boston: Jones and Bartlett 2002: pp. 140. ISBN 0-7637-1666-9.Nayak BS, Bhat R. Cerebrospinal fluid lactate dehydrogenase and glutamine in meningitis. Indian J Physiol Pharmacol. 2005 Jan; 49(1):108-10.A Twijnstra, A P van Zanten, A A Hart, et al. al. Serial lumbar and ventricle cerebrospinal fluid lactate dehydrogenase activities in patients with leptomeningeal metastases from solid and haematological tumours. J Neurol Neurosurg Psychiatry 1987 50: 313-320.Nussinovitch M, Finkelstein Y, Politi K, Harel D, Klinger G, Razon Y, Nussinovitch U, Nussinovitch N. Cerebrospinal fluid lactate dehydrogenase isoenzymes in children with bacterial and aseptic meningitis. Translational Research 2009. 154 (4): 214-218.Feldman William E. Cerebrospinal Fluid Lactic Acid Dehydrogenase Activity. Levels in Untreated and Partially Antibiotic-Treated Meningitis. Am J Dis Child. 1975; 129(1): 77-80.Lutsar I, Haldre S, Topman M, Talvik T. Enzymatic changes in the cerebrospinal fluid in patients with infections ofthe central nervous system. Acta Paediatr 1994; 83(11):1146-1150.Kepa L, Oczko-Grzesik B, Błedowski D. Evaluation of cerebrospinal fluid and plasma lactate dehydrogenase activity in patients with purulent, bacterial meningoencephalitis. Przegl Epidemiol. 2006; 60(2):291-8.Ruzak-Skocir B, Trbojevic-Cepe M. Study of serum and cerebrospinal fluid enzymes in diagnosis and differential diagnosis of cerebrovascular diseases. Neurologija. 1990; 39(4):239-50.Nand N, Sharma M, Saini DS. Evaluation of lactic dehydrogenase in cases of meningitis. Indian J Med Sci. 1993; 47(4): 96-100.Neches William, Platt Martin. Cerebrospinal Fluid LDH in 287 Children, Including 53 Cases of Meningitis of Bacterial and non-Bacterial Etiology. Pediatrics 1968; 41:1097-1103.Engelke S; Bridgers S, Saldanha R, Trought W. Cerebrospinal Fluid Lactate Dehydrogenase in Neonatal Intracranial Hemorrhage. American Journal of the Medical Sciences 1986; 291 (6): 391-395.Parakh N, Gupta HL, Jain A. Evaluation of enzymes in serum and cerebrospinal fluid in cases of stroke. Neurology India 2002; 50 (4): 518-9.Lampl Y, Paniri Y, Eshel Y, Sarova-Pinhas I. Cerebrospinal fluid lactate dehydrogenase levels in early stroke and transient ischemic attacks. Stroke 1990; 21: 854-857.Hall Robert T., Kulkarni Prakash B., Sheehan Michael B., Rhodes Philip G. Cerebrospinal Fluid Lactate Dehydrogenase in Infants with Perinatal Asphyxia. Developmental Medicine & Child Neurology 1980. 22 (3): 300-307.Nussinovitch M, Volovitz B, Finkelstein Y, Amir J, Harel D. Lactic dehydrogenase isoenzymes in cerebrospinal fluid associated with hydrocephalus. Acta Paediatr 2001; 90: 972-974

Intravenous Acetaminophen vs. Ketorolac in Terms of Pain Management in Prehospital Emergency Services: A Randomized Clinical Trial

Introduction: Although pain management in EDs has been fully addressed in clinical trials, prehospital settings have rarely been investigated. Objective: The present study was conducted to compare the effectiveness of intravenous acetaminophen with that of ketorolac in pre-hospital pain control. Method: This randomized clinical trial (RCT) was performed at a prehospital setting during EMS missions in Tehran, Iran. The eligible candidates comprised all patients over the age of 7 years with a complaint of moderate to severe pain. The patients were randomly assigned to two groups, one receiving 30 mg of intravenous (IV) ketorolac and the other 1 g of IV acetaminophen. The pain intensity was measured using a visual analog scale (VAS) before administering the analgesic and upon admission to the ED. Results: The present study was conducted on 150 patients aged 8-81 years with a mean age of 40.4 ± 17.7, including 84 (56%) males. The mean reduction in the pain score was 14.9±8.6 in the acetaminophen group and 16.0±8.8 in the ketorolac group. Univariate analyses suggested no statistically significant differences between the two groups in terms of delta pain score (pain reduction) (P=0.429). Conclusion: Based on the obtained findings, both ketorolac and acetaminophen could be administered for pain management in prehospital settings in both traumatic and non-traumatic patients in case their contraindications are considered

Predicting the status of COVID-19 active cases using a neural network time series

The design of intelligent systems for analyzing information and predicting the epidemiological trends of the disease is rapidly expanding because of the coronavirus disease (COVID-19) pandemic. The COVID-19 datasets provided by Johns Hopkins University were included in the analysis. This dataset contains some missing data that is imputed using the multi-objective particle swarm optimization method. A time series model based on nonlinear autoregressive exogenou (NARX) neural network is proposed to predict the recovered and death COVID-19 cases. This model is trained and evaluated for two modes: predicting the situation of the affected areas for the next day and the next month. After training the model based on the data from January 22 to February 27, 2020, the performance of the proposed model was evaluated in predicting the situation of the areas in the coming two weeks. The error rate was less than 5%. The prediction of the proposed model for April 9, 2020, was compared with the actual data for that day. The absolute percentage error (AE) worldwide was 12%. The lowest mean absolute error (MAE) of the model was for South America and Australia with 3 and 3.3, respectively. In this paper, we have shown that geographical areas with mortality and recovery of COVID-19 cases can be predicted using a neural network-based model

Comparison of outcome following dacryocystorhinostomy with or without silicon stent appliance; a randomized clinical trial

peer reviewe

Evaluating factors associated with uncontrolled hypertension: Isfahan cohort study, Iran

BACKGROUND: Hypertension (HTN) considers as one of the most common risk factors, which potentially raises the risk of cardiovascular disease. Regarding high prevalence of HTN among Iranian population this study designed to examine a range of socio-demographic and clinical variables to determine the association with failure to achieve blood pressure control in a cohort of hypertensive subjects. METHODS: This retrospective cohort study is a part of Isfahan cohort study which carried out on adults aged 35 years old or more. Subjects with confirmed HTN entered in this sub-study. For all subjects questionnaire included socio-demographic characteristics, clinical data and lifestyle behavior completed by trained nurses. Uncontrolled HTN was defined as systolic and diastolic blood pressure more than 140/90 in the presence or absent of pharmacological treatment. RESULTS: The prevalence of uncontrolled men was significantly higher than controlled in both 2001 and 2007 (P < 0.001). A significant association was found between sex and control of blood pressure: compared with women, being men [odds ratio (OR) = 2.31; 95 % confidence interval (CI) = 1.64-3.24] was significantly associated with uncontrolled HTN in 2001 and (OR = 2.38; 95% CI = 1.78-3.18). Among lifestyle behaviors, tendency for more consumption of salty foods increased the risk of uncontrolled HTN in 2001 by 1.73 times [OR = 1.73, 95% CI = 1.20-2.50, (P = 0.003)]. Patients who were naive to mono-therapy without considering the type of antihypertensive drug were found to be associated with uncontrolled blood pressure (OR = 0.14; 95 % CI =0.1-0.2). CONCLUSION: Uncontrolled HTN was sex, marital status, diabetes, tendency to salty foods and medication adherence. Assessment of them presence of these risk factors is warranted to recommend an aggressive HTN management with the goal of reducing excessive risk of cardiovascular events caused by uncontrolled HTN

Comparison of quality of life, anxiety, and satisfaction with rehabilitation services among mothers of children with autism spectrum disorders and those without autistic children in Ahvaz-Iran

Background. Mothers with autistic children suffer a lot of psychological and physical pressures that can affect their quality of life, emotional states, and judgment about medical services. This study aimed to evaluate the quality of life, anxiety, and satisfaction with rehabilitation services for mothers of children with autism spectrum disorders and of non-autistic children in Ahvaz-Iran. Methods. In this cross-sectional descriptive-analytical study, 128 mothers with autistic children and 30 mothers with non-autistic children needing rehabilitation interventions were selected from Ahvaz rehabilitation centers. All participants were asked to complete Quality of Life (WHOQOL-BREIF) questionnaire, 14-item Perceived Stress Scale as well as Satisfaction Questionnaire. Data analysis was performed using a multivariate three-way ANOVA test. Results. It was found that mothers of autistic children had a significantly lower quality of life score than those without autistic children (P<0.001). However, the two groups had no significant difference in anxiety score (P=0.114) and satisfaction (P=0.079). Factors such as age, education, and occupation of mothers significantly affected the results (P<0.05). Moreover, mothers whose autistic children received rehabilitation services under one month had lower quality of life (P=0.003) and a higher level of anxiety (P=0.025) than those who received rehabilitation over six months. Conclusion. Middle-aged housewives with autistic children had the lowest mean quality of life score among all mothers studied. Mothers with a university education reported a lower level of satisfaction compared to mothers without a university education, indicating a higher level of expectations for their rehabilitation outcome. Practical Implications. Research findings can be applied in managing rehabilitation services for autistic children and their families