Customer premise service study for 30/20 GHz satellite system

Satellite systems in which the space segment operates in the 30/20 GHz frequency band are defined and compared as to their potential for providing various types of communications services to customer premises and the economic and technical feasibility of doing so. Technical tasks performed include: market postulation, definition of the ground segment, definition of the space segment, definition of the integrated satellite system, service costs for satellite systems, sensitivity analysis, and critical technology. Based on an analysis of market data, a sufficiently large market for services is projected so as to make the system economically viable. A large market, and hence a high capacity satellite system, is found to be necessary to minimize service costs, i.e., economy of scale is found to hold. The wide bandwidth expected to be available in the 30/20 GHz band, along with frequency reuse which further increases the effective system bandwidth, makes possible the high capacity system. Extensive ground networking is required in most systems to both connect users into the system and to interconnect Earth stations to provide spatial diversity. Earth station spatial diversity is found to be a cost effective means of compensating the large fading encountered in the 30/20 GHz operating band

Intra/extracardiac fenestrated modification leads to lower incidence of arrhythmias after the Fontan operation

ObjectiveThe study objective was to compare the incidence of short- and intermediate-term arrhythmias among 3 different surgical modifications of the Fontan procedure.MethodsWe performed a retrospective review of all patients who underwent the Fontan operation at a single institution between January 2004 and May 2010 for preoperative, perioperative, and follow-up variables. Three surgical modifications were studied: intra/extracardiac conduit with limited atriotomy, standard extracardiac conduit, and lateral tunnel. Rhythm was classified as normal or abnormal. A rhythm dysfunction grading was devised and used to identify worsening of rhythm for patients with abnormal rhythm preoperatively. Multivariable logistic regression was used to determine predictors of abnormal rhythm. To eliminate confounding effects of transient immediate postoperative arrhythmias, data were analyzed for abnormal rhythm within the first 2 weeks and for more than 2 weeks after surgery.ResultsOf the 134 patients (n = 50 with intra/extracardiac conduit with limited atriotomy, n = 19 with standard extracardiac conduit, n = 65 with lateral tunnel) (median follow-up, 36 months; interquartile range, 22–50 months; 2 operative deaths and 6 late deaths), rhythm data for more than 2 weeks postoperatively were available in 88 (40 with lateral tunnel, 14 with standard extracardiac conduit, 34 with intra/extracardiac conduit with limited atriotomy). These patients constituted the study groups. Patients in the lateral tunnel group were relatively younger at the time of the Fontan operation (P < .001) and had a longer follow-up (P < .001). Multivariable logistic regression confirmed that greater than moderate atrioventricular valve regurgitation was the only independent predictor of abnormal rhythm during the first 2 postoperative weeks. Older age at Fontan (odds ratio, 1.20; 95% confidence interval, 1.05–1.38; P = .012) and higher preoperative mean pulmonary artery pressure (odds ratio, 1.2; 95% confidence interval, 1.03–1.44; P = .026) were predictors of abnormal rhythm more than 2 weeks postoperatively. Intra/extracardiac conduit with limited atriotomy Fontan modification was associated with a significantly lower incidence of abnormal rhythm after 2 weeks postoperatively compared with lateral tunnel modification (odds ratio, 0.28; 95% confidence interval, 0.10–0.84; P = .015).ConclusionsIntra/extracardiac conduit with limited atriotomy Fontan modification has a significantly lower risk of abnormal rhythm postoperatively in the short and intermediate term when compared with the lateral tunnel