Molecular characterization of occult hepatitis B virus infection in patients with end-stage liver disease in Colombia.

ABSTARCT: Hepatitis B virus (HBV) occult infection (OBI) is a risk factor to be taken into account in transfusion, hemodialysis and organ transplantation. The aim of this study was to identify and characterize at the molecular level OBI cases in patients with end-stage liver disease. METHODS: Sixty-six liver samples were obtained from patients with diagnosis of end-stage liver disease submitted to liver transplantation in Medellin (North West, Colombia). Samples obtained from patients who were negative for the surface antigen of HBV (n = 50) were tested for viral DNA detection by nested PCR for ORFs S, C, and X and confirmed by Southern-Blot. OBI cases were analyzed by sequencing the viral genome to determine the genotype and mutations; additionally, viral genome integration events were examined by the Alu-PCR technique. RESULTS: In five cases out of 50 patients (10%) the criteria for OBI was confirmed. HBV genotype F (subgenotypes F1 and F3), genotype A and genotype D were characterized in liver samples. Three integration events in chromosomes 5q14.1, 16p13 and 20q12 affecting Receptor-type tyrosine-protein phosphatase T, Ras Protein Specific Guanine Nucleotide Releasing Factor 2, and the zinc finger 263 genes were identified in two OBI cases. Sequence analysis of the viral genome of the 5 OBI cases showed several punctual missense and nonsense mutations affecting ORFs S, P, Core and X. CONCLUSIONS: This is the first characterization of OBI in patients with end-stage liver disease in Colombia. The OBI cases were identified in patients with HCV infection or cryptogenic cirrhosis. The integration events (5q14.1, 16p13 and 20q12) described in this study have not been previously reported. Further studies are required to validate the role of mutations and integration events in OBI pathogenesis

Fuzzy logic congestion control for broadband wireless IPTV

It is demonstrated that interval type-2 fuzzy logic control (IT2 FLC) is more robust than traditional fuzzy logic congestion control of video streaming. An IT2 FLC is compared to the well-known TFRC and TEAR congestion controllers for internet multimedia streaming. On an all-IP network with broadband wireless access, delivered video quality is improved with the IT2 FLC by about 1 dB for each client, once the offered traffic (up to 50 video streams) exceeds the capacity available to video over the wireless link

Rate-adaptive video streaming through packet dispersion feedback

The anticipated growth of IPTV makes selection of suitable congestion controllers for video-stream traffic of vital concern. Measurements of packet dispersion at the receiver provide a graded way of estimating congestion, which is particularly suited to video as it does not rely on packet loss. A closed-loop congestion controller, which dynamically adapts the bitstream output of a transcoder or video encoder to a rate less likely to lead to packet loss, is presented. The video congestion controller is based on fuzzy logic with packet dispersion and its rate of change forming the inputs. Compared with TCP emulators such as TCP-friendly rate control (TFRC) and rate adaptation protocol (RAP), which rely on packet loss for real-time congestion control, the fuzzy-logic trained system's sending rate is significantly smoother when multiple video-bearing sources share a tight link. Using a packet dispersion method similarly results in a fairer allocation of bandwidth than TFRC and RAP. These gains for video traffic are primarily because of better estimation of network congestion through packet dispersion but also result from accurate interpretation by the fuzzy-logic controller

Engineering congestion control of internet video streaming with fuzzy logic

Congestion control of video streaming over the Internet is necessary, as access to these telecommunications networks is unregulated. A commercial IPTV service in this environment faces unacceptable quality degradation, if the video stream does not respond to the presence of other competing traffic flows. As a solution, fuzzy logic control offers real-time performance, comparatively simple models, fairness to other traffic, and a smooth response. This Chapter introduces the control problem faced in designing a fuzzy logic congestion controller in terms of the restrictions of a compressed video bitstream and the uncertainties that affect congestion control. The Chapter outlines the design of a congestion controller that relies on network packet delay and delay trend as inputs. The controller has been extensively tested and favorably compared to the standard congestion controller. Multimedia applications over telecommunications networks are a promising area to apply computational intelligence. © 2012 Bentham Science Publishers. All rights reserved

All-IP Network Video Streaming through Interval Type-2 Fuzzy Logic Congestion Control

All-IP network delivery of video is a promising application of congestion control. This paper compares the advantage of a fuzzy logic controller over existing controllers for this type of network. The acceptance of fuzzy logic for video control has gained ground but its advantages will become even more apparent through interval type-2 (IT2) logic rather than traditional type-1 logic. This paper demonstrates that the new logic provides robustness to uncertainty both in modeling the network and in measuring congestion. The paper establishes that under conditions of heavy congestion, with multiple video sources, an IT2 fuzzy controller consistently outperforms traditional controllers, resulting in an improvement of several dB in video quality when streaming across a bottleneck link

All-IP network video streaming through interval type-2 fuzzy logic congestion control

All-IP network delivery of video is a promising application of congestion control. This paper compares the advantage of a fuzzy logic controller over existing controllers for this type of network. The acceptance of fuzzy logic for video control has gained ground but its advantages will become even more apparent through interval type-2 (IT2) logic rather than traditional type-1 logic. This paper demonstrates that the new logic provides robustness to uncertainty both in modeling the network and in measuring congestion. The paper establishes that under conditions of heavy congestion, with multiple video sources, an IT2 fuzzy controller consistently outperforms traditional controllers, resulting in an improvement of several dB in video quality when streaming across a bottleneck link

Interval Type-2 Fuzzy Logic Congestion Control for Video Streaming Across IP Networks

Intelligent congestion control is vital for encoded video streaming of a clip or film, as network traffic volatility and the associated uncertainties require constant adjustment of the bit rate. Existing solutions, including the standard Transmission Control Protocol (TCP) friendly rate control equation-based congestion controller, are prone to fluctuations in their sending rate and may respond only when packet loss has already occurred. This is a major problem, because both fluctuations and packet loss affect the end-user's perception of the delivered video. A type-1 (T1) fuzzy logic congestion controller (FLC) can operate at video display rates and can reduce packet loss and rate fluctuations, despite uncertainties in measurements of delay arising from congestion and network traffic volatility. However, a T1 FLC employing precise T1 fuzzy sets cannot fully cope with the uncertainties associated with such dynamic network environments. A type-2 FLC using type-2 fuzzy sets can handle such uncertainties to produce improved performance. This paper proposes an interval type-2 FLC that achieves a superior delivered video quality compared with existing traditional controllers and a T1 FLC. To show the response in different network scenarios, tests demonstrate the response both in the presence of typical Internet cross-traffic as well as when other video streams occupy a bottleneck on an All-internet protocol (IP) network. As All-IP networks are intended for multimedia traffic, it is important to develop a form of congestion control that can transfer to them from the mixed traffic environment of the Internet. It was found that the proposed type-2 FLC, although it is specifically designed for Internet conditions, can also successfully react to the network conditions of an All-IP network. When the control inputs were subject to noise, the type-2 FLC resulted in an order of magnitude performance improvement in comparison with the T1 FLC. The type-2 FLC also showed reduced packet loss when compared with the other controllers, again resulting in superior delivered video quality. When judged by established criteria, such as TCP-friendliness and delayed feedback, fuzzy logic congestion control offers a flexible solution to network bottlenecks. These findings offer the type-2 FLC as a way forward for congestion control of video streaming across packet-switched IP networks. © 2009 IEEE