Stable ℋ∞controller design for systems with time delays

One of the difficult problems of robust control theory is to find strongly stabilizing controllers (i.e. stable controllers leading to stable feedback system) which satisfy a certain ℋ∞ performance objective. In this work we discuss stable ℋ∞controller design methods for various classes of systems with time delays. We consider sensitivity minimization problem in this setting for SISO plants. We also discuss a suboptimal design method for stable ℋ∞controllers for MIMO plants. © 2010 Springer-Verlag Berlin Heidelberg

Extended-spectrum beta-lactamases in ceftazidime-resistant Escherichia coli and Klebsiella pneumoniae isolates in Turkish hospitals

Purpose: To study the prevalence of TEM-, SHV- and GES-type β -lactamases among Escherichia coli and Klebsiella pneumoniae strains having ceftazidime MICs higher than 2 mg/L. Methods: A total of 63 E. coli and 41 K. pneumoniae isolated from five different university hospitals were studied for the existence of TEM-, SHV- and GES-type β -lactamases. Susceptibility tests were carried out according to the criteria of National Committee for Clinical Laboratory Standards. MICs were obtained by agar dilution method. Existence of extended-spectrum β -lactamases (ESBLs) were assessed by double-disc synergy test (DDST). Existence of the above-mentioned β -lactamase genes were studied both by PCR with specific oligonucleotide primers and isoelectric focusing methods. Results: None of the isolates were carbapenem-resistant. DDSTs were positive in 50 (79.3%) and 33 (80.5%) of E. coli and K. pneumoniae , respectively. TEM gene was detected in 41 (65.1%) and 19 (46.3%), whereas SHV gene in 18 (28.6%) and 20 (48.8%) of E. coli and K. pneumoniae strains, respectively. GES genes were not detected. Conclusions: TEM and SHV genes are highly prevalent among ESBL-producing E. coli and K. pneumoniae , whereas GES-type ESBLs are absent and found not to be responsible of ceftazidime resistance in Turkish hospitals

Examination of anastomotic leak with aqueous contrast swallow after total gastrectomy: Should it be carried out routinely?

Aim of the study : Examination of esophagojejunal (EJ) anastomosis with aqueous contrast swallow after total gastrectomy is still routinely conducted by many centres. The present study aimed to answer the question: Is it necessary to evaluate EJ anastomosis in terms of leakage by having every patient drink oral contrast agent before initiation of oral food intake after total gastrectomy (TG) performed due to gastric cancer? Material and methods : Clinical and radiological results of patients on whom total gastrectomy was performed due to gastric cancer between January 2013 and December 2016 were retrospectively reviewed. Diagnostic method used for patients in whom leak developed and therapeutic interventions were assessed. Evaluation results from aqueous contrast agent and clinical, laboratory, and tomographic findings were studied. Results: Sixty of the 69 patients who underwent total gastrectomy with a diagnosis of gastric adenocarcinoma swallowed aqueous contrast agent on postoperative day 7 ±2 days and were evaluated in terms of anastomotic leak. Leak developed in 14 patients (20.2 %), 10 of whom ingested contrast agent. Leak was identified in 6 of those patients; however, diagnosis was made with multislice computed tomography (CT) in four patients (40%). The sensitivity of the examination with aqueous contrast agent was 60%. Conclusions : Evaluating anastomotic leak with aqueous contrast agent after TG has low sensitivity, and it would be wise to resort to this procedure in cases with clinical suspicion, rather than routinely performing it in every patient