General Model for Infrastructure Multi-channel Wireless LANs

In this paper we develop an integrated model for request mechanism and data transmission in multi-channel wireless local area networks. We calculated the performance parameters for single and multi-channel wireless networks when the channel is noisy. The proposed model is general it can be applied to different wireless networks such as IEEE802.11x, IEEE802.16, CDMA operated networks and Hiperlan\2.Comment: 11 Pages, IJCN

Leptin, insulin like growth factor-1 and thyroid profile in a studied sample of Egyptian children with Down syndrome

Background: Several mechanisms have been suggested for obesity in Down syndrome. Aim of the study: Assessment of serum levels of leptin, insulin like growth factor-I (IGF-I), thyroid stimulating hormone (TSH) and free thyroxin (FT4) in a prepubertal Egyptian sample of children with DS compared to their age and sex matched healthy controls and sibs of some of them.Subjects and methods: A prospective case control study was conducted on 80 children, classified as follows: Groups I & II: enrolled 20 cases with DS for each, sibs were studied only for group I, Group III: 20 healthy siblings of group I, and Group IV: 20 healthy controls. Anthropometric measurements, serum leptin, IGF-1, TSH, and FT4 assessment using enzyme linked immuno-sorbent assay (ELISA) were carried out for all studied children.Results: DS children whether with studied sibs or without studied sibs had significantly higher mean values of leptin levels compared to sibs of group I & IV (P = 0.0001 for all). Meanwhile, mean values of IGF-I showed statistically insignificant differences between all studied groups (p> 0.05 for all). Studied DS children whether with studied sibs or without studied sibs had significantly higher mean values of TSH levels compared to sibs of group I and controls (P = 0.0001 for all). Mean values of FT4 were significantly higher in enrolled DS without their studied sibs compared to sibs of group I (p= 0.01), while mean values of FT4 were significantly lower in sibs of group I compared to controls (p= 0.001).Conclusion: Serum leptin levels were significantly higher in studied DS children compared to both studied sibs and healthy controls and they were also positively correlated with BMI in studied DS children and their sibs highlighting a possible role of body fat% and leptin values in the pathogenesis of obesity in DS children.Keywords: Leptin; IGF-I; TSH; FT4; Obesity; Down syndrom

Rejecting spam during SMTP sessions

This paper analyzes a spam rejection scheme at Simple Mail Transfer Protocol (SMTP) sessions. This scheme utilizes a layer-3 e-mail pre-classification technique to estimate e-mail classes before an SMTP session ends. We study the spam rejection scheme using discrete-time Markov chain analysis and analyze the performance of the proposed scheme under different e-mail traffic loads and service capacities. The proposed scheme reduces the e-mail volume to be queued and processed by e-mail servers. This reduces non-spam e-mail queuing delay and loss, and protects e-mail servers from being overloaded by spam traffic

A Parameterized Centrality Metric for Network Analysis

A variety of metrics have been proposed to measure the relative importance of nodes in a network. One of these, alpha-centrality [Bonacich, 2001], measures the number of attenuated paths that exist between nodes. We introduce a normalized version of this metric and use it to study network structure, specifically, to rank nodes and find community structure of the network. Specifically, we extend the modularity-maximization method [Newman and Girvan, 2004] for community detection to use this metric as the measure of node connectivity. Normalized alpha-centrality is a powerful tool for network analysis, since it contains a tunable parameter that sets the length scale of interactions. By studying how rankings and discovered communities change when this parameter is varied allows us to identify locally and globally important nodes and structures. We apply the proposed method to several benchmark networks and show that it leads to better insight into network structure than alternative methods.Comment: 11 pages, submitted to Physical Review

Oxidative Stress -a Phenotypic Hallmark of Fanconi Anemia and Down Syndrome: The Effect of Antioxidants

Background: Oxidative stress plays a major role in the pathogenesis of leukemia.prone diseases such as Fanconi anemia (FA) and Down syndrome (DS). Aim: To explore the oxidative stress state in children with DS and FA by estimating the levels of antioxidants (e.g., malondialdehyde [MDA], total antioxidant capacity, and superoxide dismutase [SOD] activity) and DNA damage, and to evaluate of the effect of antioxidant treatment on these patients.Subjects and Methods: The study included 32 children clinically diagnosed with (15 patients) and FA (17 patients) in addition to 17 controls matched for age and sex. MDA, total antioxidant capacity, SOD activity, and DNA damage were measured. Antioxidants including Vitamin A, E, and C were given to the patients according to the recommended daily allowance for 6 months. Clinical follow.up and re.evaluation were conducted for all patients. Laboratory tests including complete blood count, karyotyping, DNA  damage, and oxidative stress were re.evaluated. Statistical analysis was performed using statistical computer program Statistical Package for the Social Sciences version 14.0. Results: Children with FA and DS had elevated levels of oxidative stress and more DNA damage than controls. Oxidative stress parameters and DNA damage improved in FA and DS patients after antioxidant administration. Conclusion: Early administration of antioxidants to FA and DS patients is recommended for slowing of the disease course with symptoms   amelioration and improvement of general health.Keywords: Down syndrome, Oxidative DNA damage, Oxidative stres

Analytical modelling of congestion for 6LoWPAN networks

The IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) protocol stack is a key part of the Internet of Things (IoT) where the 6LoWPAN motes will account for the majority of the IoT ‘things’. In 6LoWPAN networks, heavy network traffic causes congestion which significantly affects the overall performance and the quality of service metrics. In this paper, a new analytical model of congestion for 6LoWPAN networks is proposed using Markov chain and queuing theory. The derived model calculates the buffer loss probability and the channel loss probability as well as the number of received packets at the final destination in the presence of congestion. Also, we calculate the actual wireless channel capacity of IEEE 802.15.4 with and without collisions based on Contiki OS implementation. The validation of the proposed model is performed with different scenarios through simulation by using Contiki OS and Cooja simulator. Simulation results show that the analytical modelling of congestion has an accurate agreement with simulation

Architecture of the chromatin remodeler RSC and insights into its nucleosome engagement.

Eukaryotic DNA is packaged into nucleosome arrays, which are repositioned by chromatin remodeling complexes to control DNA accessibility. The Saccharomyces cerevisiae RSC (Remodeling the Structure of Chromatin) complex, a member of the SWI/SNF chromatin remodeler family, plays critical roles in genome maintenance, transcription, and DNA repair. Here, we report cryo-electron microscopy (cryo-EM) and crosslinking mass spectrometry (CLMS) studies of yeast RSC complex and show that RSC is composed of a rigid tripartite core and two flexible lobes. The core structure is scaffolded by an asymmetric Rsc8 dimer and built with the evolutionarily conserved subunits Sfh1, Rsc6, Rsc9 and Sth1. The flexible ATPase lobe, composed of helicase subunit Sth1, Arp7, Arp9 and Rtt102, is anchored to this core by the N-terminus of Sth1. Our cryo-EM analysis of RSC bound to a nucleosome core particle shows that in addition to the expected nucleosome-Sth1 interactions, RSC engages histones and nucleosomal DNA through one arm of the core structure, composed of the Rsc8 SWIRM domains, Sfh1 and Npl6. Our findings provide structural insights into the conserved assembly process for all members of the SWI/SNF family of remodelers, and illustrate how RSC selects, engages, and remodels nucleosomes