CiteULike: Author Baccichet

Cholesterol synthesis and lipoprotein reuptake during synaptic remodelling in hippocampus in adult rats.

J Poirier — 2008-05-18T13:22:55-00:00

Neuroscience, Vol. 55, No. 1. (July 1993), pp. 81-90.

Apolipoprotein E is synthesized and secreted by astrocytes in the hippocampus following lesions of the entorhinal cortex. It was proposed that apolipoprotein E, by analogy to its role in cholesterol transport in circulation, could be involved in the salvage and reutilization of non-esterified cholesterol released during terminal breakdown. The salvaged cholesterol could then be transported to neurons by apolipoprotein E-complexes and taken up via the apolipoprotein E/apolipoprotein B (low-density lipoprotein) receptor. To test this hypothesis, we have examined low-density lipoprotein receptor binding in brain sections of rats undergoing hippocampal reinnervation. The number of neuronal cells labelled by fluorescent Dil-low-density lipoprotein as well as the density of [125I]low-density lipoprotein binding sites in the dentate gyrus were found to increase in parallel with the extent of cholinergic reinnervation occurring in the deafferented hippocampus. In contrast, hippocampal cholesterol synthesis fell by more than 60% at eight days post-lesion, but eventually returned to control levels at 30 days post-lesion. The transient loss of cholesterol synthesis coincided with a peak in hippocampal apolipoprotein E expression. A concomitant accumulation of sudanophilic lipids (cholesterol esters and phospholipids) was detected in the outer molecular layer of the dentate gyrus and in the hilar region. The present findings suggest that non-esterified cholesterol released during terminal breakdown is esterified, transported via the apolipoprotein E transport system to neurons undergoing reinnervation, and take-up through the low-density lipoprotein receptor pathway where it is presumably used as a precursor molecule for the synthesis of new synapses and terminals.

Frame concealment for H.264/AVC decoders

P Baccichet — 2008-05-16T08:32:35-00:00

Consumer Electronics, IEEE Transactions on, Vol. 51, No. 1. (2005), pp. 227-233.

The H.264/AVC offers a high video coding efficiency and is the first standard that provides an explicit support for the transmission of multimedia content over a packed switched network, specifying a network abstraction layer (NAL). If we consider the transmission of a low resolution video sequence over a wireless LAN network or a UMTS link, we can usually observe that a coded picture typically fits the packet size, therefore a transmission error produces the loss of a whole frame. In this paper, we propose a novel technique to perform the concealment of a whole frame for H.264/A VC video decoders.

Low-delay peer-to-peer streaming using scalable video coding

Pierpaolo Baccichet — 2008-05-09T20:50:52-00:00

Packet Video 2007 (2007), pp. 173-181.

Peer-to-peer (P2P) networks represent a valuable architecture for streaming video over the Internet. In these systems, users contribute their resources to relay the media to others and no dedicated infrastructure is required. In order to ensure a low end-to-end delay, P2P overlay networks are often organized as a set of complementary multicast trees. The source of the stream multiplexes the data on top of these trees and the routing of packets is statically defined. In this scenario, the reliability of the overlay links is critical for the performance of the system since temporary link failure or network congestion can cause a significant disruption of the end-user quality. The novel Scalable Video Coding (SVC) standard enables efficient usage of the network capacity by allowing intermediate high capacity nodes in the overlay network to dynamically extract layers from the scalable bit stream to serve less capable peers. On the other hand, SVC incurs a certain loss in terms of coding efficiency with respect to H.264/AVC single-layer coding. We propose a simple model that allows to evaluate the trade-off of using a scalable codec with respect to single-layer coding, given the distribution of the receivers’ capacities in an error-free network. We also report experimental results obtained by using SVC on top of a real-time implementation of the Stanford Peer-to-Peer Multicast (SPPM) protocol that clearly show the benefits of a prioritization mechanism to react to network congestion.

Enhancing Whole-Frame Error Concealment with an Intra Motion Vector Estimator in H.264/AVC

E Quacchio — 2008-04-02T11:20:03-00:00

Acoustics, Speech, and Signal Processing, 2005. Proceedings. (ICASSP '05). IEEE International Conference on, Vol. 2 (2005), pp. 329-332.

Content-Aware P2P Video Streaming with Low Latency

Pierpaolo Baccichet — 2007-09-06T07:34:15-00:00

Multimedia and Expo, 2007 IEEE International Conference on (2007), pp. 400-403.

This paper describes the Stanford P2P Multicast (SPPM) streaming system that employs an overlay architecture specifically designed for low delay video applications. In order to provide interactivity to the user, this system has to keep the end-to-end delay as small as possible while guaranteeing a high video quality. A set of complimentary multicast trees is maintained to efficiently relay video traffic and a Congestion-Distortion Optimized (CoDiO) scheduler prioritizes more important video packets. Local retransmission is employed to mitigate packet loss. Real-time experiments performed on the Planet-Lab show the effectiveness of the system and the benefits of a content-aware scheduler in case of congestion or node failures.