Approach to stress tests in SIP environment based on marginal analysis

In the field of performance metrics and measurements of SIP (Session Initiation Protocol) Proxy and B2BUA (Back-to-Back User Agent) no standardized methodology has been presented yet. This gap results in a problematic determination of a hardware, the performance of which would be cost-effective and sufficient for the running the SIP Server in a given environment. Today practice relies on the administrator’s skills and experience with the needs of the telephony infrastructure. From this and the increasing usage of SIP based VoIP technologies come the main reasons for creating a methodology that would allow administrators to precisely measure the SIP Server performance and compare it to other software and hardware platform. This work also utilizes SIP Server performance measurements to comparison the results taken when transcoding was in use and when it was not and provides the means for comparison of B2BUAs platform independently.     

Prediction of Speech Quality Based on Resilient Backpropagation Artificial Neural Network

The paper presents a system for monitoring and assessment the speech quality in the IP telephony infrastructures using modular probes. The probes are placed at key nodes in the network where aggregating packet loss data. The system dynamically measures speech quality and results are collected on a central server. For data analysis we applied four-state Markov model for modeling the impact of network impairments on speech quality, afterwards, the resilient back propagation (Rprop) algorithm was used to train a neural network. Information about the speech quality are displayed in the form of automatically generated graphs and tables. The proposed solution has been tested with selected codecs and further generalizes the already presented concepts of the speech quality estimation in the IP environment.

     

Structure of poliovirus type 2 Lansing complexed with antiviral agent SCH48973: comparison of the structural and biological properties of three poliovirus serotypes

BACKGROUND: Polioviruses are human pathogens and the causative agents of poliomyelitis. Polioviruses are icosahedral single-stranded RNA viruses, which belong to the picornavirus family, and occur as three distinct serotypes. All three serotypes of poliovirus can infect primates, but only type 2 can infect mice. The crystal structures of a type 1 and a type 3 poliovirus are already known. Structural studies of poliovirus type 2 Lansing (PV2L) were initiated to try to enhance our understanding of the differences in host range specificity, antigenicity and receptor binding among the three serotypes of poliovirus. RESULTS: The crystal structure of the mouse neurovirulent PV2L complexed with a potent antiviral agent, SCH48973, was determined at 2.9 A resolution. Structural differences among the three poliovirus serotypes occur primarily in the loop regions of the viral coat proteins (VPs), most notably in the loops of VP1 that cluster near the fivefold axes of the capsid, where the BC loop of PV2L is disordered. Unlike other known structures of enteroviruses, the entire polypeptide chain of PV2L VP4 is visible in the electron density and RNA bases are observed stacking with conserved aromatic residues (Tyr4020 and Phe4046) of VP4. The broad-spectrum antiviral agent SCH48973 is observed binding in a pocket within the beta-barrel of VP1, in approximately the same location that natural 'pocket factors' bind to polioviruses. SCH48973 forms predominantly hydrophobic interactions with the pocket residues. CONCLUSIONS: Some of the conformational changes required for infectivity and involved in the control of capsid stability and neurovirulence in mice may occur in the vicinity of the fivefold axis of the poliovirus, where there are significant structural differences among the three poliovirus serotypes in the surface exposed loops of VP1 (BC, DE, and HI). A surface depression is located at the fivefold axis of PV2L that is not present in the other two poliovirus serotypes. The observed interaction of RNA with VP4 supports the observation that loss of VP4 ultimately leads to the loss of viral RNA. A model is proposed that suggests dual involvement of the virion fivefold and pseudo-threefold axes in receptor-mediated initiation of infection by picornaviruses.     

Two new naphthoquinones with antiviral activity from Rhinacanthus nasutus

Two new naphthoquinones, rhinacanthin-C (1) and rhinacanthin-D (2), exhibit inhibitory activity against cytomegalovirus (CMV), with EC50 values of 0.02 and 0.22 microgram/mL, respectively, against human CMV. They were isolated from the medicinal plant Rhinacanthus nasutus (Acanthaceae). The structures of the compounds were determined by analysis of their spectroscopic data, in particular, 2D NMR.     

SCH 43478 and analogs: in vitro activity and in vivo efficacy of novel agents for herpesvirus type 2

Previous surveys have suggested that preschool children in the North and Northeast of Thailand are at risk of inadequate vitamin A nutriture. Therefore, vitamin A status was assessed in 996 children aged 2-6 years in the North and Northeast Thailand during the dry (Feb.-April) and rainy (Sept.-Nov.) seasons. Approximately 1 per cent of samples during both periods exhibited serum retinol concentrations below 10 mcg/dl with means (+/-SD) concentration of 29 +/- 9.8 mcg/dl in the dry season and 37 +/- 15.4 mcg/dl in the rainy season. About one fifth of the studied children showed abnormal CIC and depleted liver stores (RDR > 20%). High risk areas were ranked and corresponded well by these 2 indicators. Therefore, it is concluded that the magnitude of the problem estimated by RDR and CIC are a more precise measurement of marginal vitamin A status than serum vitamin A level alone and about one-fifth of preschool children in the North and Northeast regions of Thailand experience subclinical vitamin A deficiency.