ADAPTIVE DYNAMICAL FEEDBACK REGULATION STRATEGIES FOR LINEARIZABLE UNCERTAIN SYSTEMS

In this paper we address the design of adaptive dynamical feedback strategies of the continuous and discontinuous, types for the output stabilization of nonlinear systems. The class of systems considered corresponds to nonlinear controlled systems exhibiting linear parametric uncertainty. Dynamical feedback controllers, ideally achieving output stabilization via exact linearization, are obtained by means of repeated output differentiation and, either, pole placement, or, sliding mode control techniques. The adaptive versions of the dynamical stabilizing controllers are then obtainable through standard, direct, overparamemzed adaptive control strategies available for linearizable systems. Illustrative examples are provided which deal with the regulation of electromechanical systems

Biliary Atresia Etiopathogenesis: On the Way to Solve the Mystery

Biliary Atresia (BA) is the most common cause of chronic cholestasis in infants and the most frequent cause for surgery in cholestatic jaundice in this age group. It is a destructive inflammatory obliterative cholangiopathy that affects varying lengths of both intrahepatic and extrahepatic biliary tree. The extensive research in BA aims at three main aspects; a) understanding the etiopathogenesis, b) achieving early diagnosis, and c) improving the outcome of surgical interventions. The improvements in the latter two are largely based on the advances in further understanding and revealing the etiopathogenesis. Till the moment, the exact etiology remains a mystery. Biliatresone, a recently identified toxin that causes BA phenotype in zibrafish may open a new horizon for future studies in humans in an attempt to solve the mystery

Stem cell therapy in children with acute liver failure: The dream could come true

Acute liver failure (ALF) in children is a severe disease with a high mortality rate. The current treatment strategies are still defective, with many cases die when liver transplantation is unavailable. The current protocol of steroids therapy improved the survival rate of hepatitis A virus (HAV)-related ALF. However, there is still a high mortality for non-HAV cases. Stem cell therapy (SCT) has been tried in experimental animals with ALF and in few adult studies with acute-on-chronic liver failure. No previous trials of SCT have been tested in children with ALF. The absence of SCT application in ALF in children could be due to some issues. These could be related to safety, sources, administration route, optimum dosage, efficacy, and survival. It is proposed that could be the future therapy if these obstacles have been well studied and solved

DYNAMICAL VARIABLE STRUCTURE CONTROL OF A HELICOPTER IN VERTICAL FLIGHT

In this article, a dynamical multivariable discontinuous feedback control strategy of the sliding nlode type is proposed for the altitude stabilization of a nonlinear helicopter model in vertical flight. Vlrhile retaining the basic robustness features associated to sliding mode control policies, the proposed approach also results in smoothed out (i.e., non-chattering) input trajectories and controlled state variable responses

Biliary Atresia: A Challenging Diagnosis

Abstract: Biliary atresia (BA) constitutes about one third of all neonatal cholestasis (NC) and the most common indication (up to 50%) of liver transplantation (LTx) in children. Despite extensive studies, its etiopathogenesis has not been clearly revealed. Treatment is primarily surgical based on reinstitution of bile flow by Kasai portoenterostomy, the success of which is largely dependent on the early diagnosis before 60 days of age. If portoenterostomy is not successful or not performed, LTx is the only life-saving alternative. Accurate diagnosis of BA, particularly distinguishing it from other causes of liver injury in the neonatal period, is challenging as there is a high degree of overlap in clinical, biochemical, imaging, and histological characteristics. There is no single preoperative investigation that enables the diagnosis of BA to be made with certainty. Liver biochemistry assessment, biliary radionuclide excretion scanning, magnetic resonance cholangiopancreatography (MRCP), endoscopic retrograde cholangiopancreatography (ERCP), percutaneous needle liver biopsy, and laparoscopy can all be helpful, but their results are not individually diagnostic. The current review presents an overview of BA with emphasis on the recent diagnostic modalities

Prevalence of Serological Markers of TORCH Infections in Biliary Atresia and Other Neonatal Cholestatic Disorders

Background: Viral infections, congenitally or perinatally acquired, have been associated with neonatal cholestasis. Investigators have suggested a similar link to biliary atresia (BA).&nbsp;&nbsp;Aim: The aim of the current study is to investigate the prevalence of serological markers of congential infections in BA and other neonatal cholestatic disorders.Methods: This retrospective study included 94 patients with confi rmed diagnosis of BA. A nearly comparable number of patients with cholestasis due to causes other than BA (n = 91) were also recruited and termed non-BA group. The data was retrieved from patients’ records. TORCH (toxoplasma, rubella, cytomegalovirus [CMV] and herpes simplex virus [HSV] type 1 and type 2) antibodies (immunoglobulin [Ig] M and IgG) were performed in all the patients using enzyme-linked immunosorbent assay. CMV DNA was detected by polymerase chain reaction (PCR).Results: Both groups were age and sex matched (P&gt;0.05). TORCH IgM antibodies were detedcted in 15.7% of all the study population (8.5% in BA group and 23% in non-BA group), of which CMV was the commonest agent. CMV IgM and CMV DNA by PCR were signifi cantly higher in non-BA group (20.9% and 23% respectively) than in BA group (4.3% and 5.3% respectively). Toxoplasma IgM was positive in only one patient in BA group and rublella IgM was positive only in one patient in the non-BA group. HSV- 1 IgM was found in a total of 4 patients; 3 in BA group and one in non-BA group while HSV-2 IgM was negative in all the patients. CMV infection was the sole incriminated agent in 13 patients (CMV hepatitis), while it was associated with other etiologies such as pregressive familial intrahepatic cholestasis (5 of 29 patients), and intrahepatic biliary paucity (3 of 14 patients). Liver transaminases, prothrombin time and the frequency of&nbsp; growth failure were signifi cantly higher in non-BA group.Conclusions: TORCH IgM antibodies were detedcted in 8.5% of BA and in 23% of non-BA group, of which CMV was the commonest agent. In addition to CMV hepatitis, CMV infection was associated with other causes of neonatal cholestasis. For that, all cases with neonatal cholestasis should be thoroughly evaluated for other causes, even in cases with demonstrable CMV infection.</p

Serum Adiponectin, Vitamin D, and Alpha-Fetoprotein in Children with Chronic Hepatitis C: Can They Predict Treatment Response?

Background & Aims. The currently available treatment for chronic hepatitis C (CHC) in children is costly and with much toxicity. So, predicting the likelihood of response before starting therapy is important. Methods. Serum adiponectin, vitamin D, and alpha-fetoprotein (AFP) were measured before starting pegylated-interferon/ribavirin therapy for 50 children with CHC. Another 21 healthy children were recruited as controls. Results. Serum adiponectin, vitamin D, and AFP were higher in the CHC group than healthy controls (p<0.0001, p=0.071, and p=0.87, resp.). In univariate analysis, serum adiponectin was significantly higher in responders than nonresponders (p<0.0001) and at a cutoff value ≥8.04 ng/mL it can predict treatment response by 77.8% sensitivity and 92.9% specificity, while both AFP and viremia were significantly lower in responders than nonresponders, p<0.0001 and p=0.0003, respectively, and at cutoff values ≤3.265 ng/mL and ≤235,384 IU/mL, respectively, they can predict treatment response with a sensitivity of 83.3% for both and specificity of 85.7% and 78.6%, respectively. In multivariate analysis, adiponectin was found to be the only independent predictor of treatment response (p=0.044). Conclusions. The pretreatment serum level of adiponectin can predict the likelihood of treatment response, thus avoiding toxicities for those unlikely to respond to therapy