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Applications requiring real-time communication (RTC) between Internet peers are ever increasing. RTC requires not only congestion control but also minimization of queuing delays to provide interactivity. It is known that the well-established transmission control protocol congestion control is not suitable for RTC due to its retransmissions and in-order delivery mechanisms, which induce significant latency. In this paper, we propose a novel congestion control algorithm for RTC, which is based on the main idea of estimating—using a Kalman Filter—the end-to-end one-way delay variation which is experienced by packets traveling from a sender to a destination. This estimate is compared with a dynamic threshold and drives the dynamics of a controller located at the receiver, which aims at maintaining queuing delays low, while a loss-based controller located at the sender acts when losses are detected. The proposed congestion control algorithm has been adopted by Google Chrome. Extensive experimental evaluations have shown that the algorithm contains queuing delays while providing intra and inter protocol fairness along with full link utilization.

Shortage of homografts prompted us to replace the transplanted pulmonary trunk with stentless xenografts during the Ross procedure. The 5-year follow-up in comparison with pulmonary homografts is presented.From April 1997 to March 2002, of 51 patients undergoing a modified Ross procedure 15 patients (age range 55 to 65 years, mean 59 +/- 5) received a stentless xenograft, and 36 patients (15 to 56 years, mean 36 +/- 11) a pulmonary homograft for right ventricular outflow tract (RVOT) reconstruction. Follow-up was complete for a mean of 3.1 years (range 6 to 60). Regularly performed echocardiography included determination of valve annulus, peak instantaneous gradient, leaflet performance, location of obstruction, and degree of regurgitation.There was 1 late death and 1 reoperation for homograft stenosis. The homograft annulus diameter decreased by a mean of 10% (range 3 to 10 mm; p0.01), and peak Doppler gradient increased significantly (p0.001). All patients except 1 had gradients less than 25 mm Hg. Gradients in xenograft patients were stable at a low level (6.5 +/- 4.3 mm Hg to 8.8 +/- 7.4 mm Hg at the latest follow-up). Mild pulmonary regurgitation was noted in 46.6% (xenografts) and 19.5% (homografts). Leaflet quality and mobility were maintained in all patients.Pulmonary homografts underlie a process of annular reduction after the Ross procedure, which is usually not associated with graft stenosis. Mild pulmonary regurgitation is more common in xenografts than in homografts. RVOT reconstruction using stentless xenografts represents a satisfactory treatment modality for aged patients.

The superior hemodynamic performance of the pulmonary autograft in aortic position is expected to reflect complete regression of hypertrophy and improved ventricular function. We evaluated and compared early and midterm transthoracic color-Doppler echocardiography (TTE) and magnetic resonance imaging (MRI) assessment concerning left ventricular (LV) function, LV mass regression, and performance of the semilunar valves. A total of 42 consecutive patients, mean age 36 +/- 6 years (range 15 to 56 years), were studied. TTE and MRI were performed preoperatively, at discharge, and at 6 and 12 months postoperatively. Left ventricular diameters and function and LV wall thickness and mass were assessed. There was no early and one late postoperative death. Maximum and mean LV outflow gradients were significantly reduced (p = 0.0001 and p = 0.0001, respectively). There was a significant reduction in left ventricular mass to near normal for all patients (p = 0.001) seen after 6 months. This was paralleled by significant reductions in the interventricular septum and posterior wall thickness, but difference was slight during further follow-up. There was a strong correlation between the results obtained by TTE and MRI for LV mass and ejection fraction (r = 0.86 and 0. 87, respectively). The pulmonary autograft operation gives excellent results that are translated into greater, rapid, and near complete regression of LV hypertrophy. Magnetic resonance imaging is a sensitive and noninvasive methodology that provides reliable visualization and quantification of ventricular performance.