Comprehensive OPNET based Scalability Analysis and Performance Evaluation of MANET Routing Protocols

A Mobile Ad-hoc Network (MANET) is a collection of communication and computing devices equipped with communication capabilities in which the nodes communicate with each other without any pre-existing infrastructure. Unlike the infrastructure based networks, there are no BTSs and BSCs in MANETs. The nodes involved in the MANETs, therefore, act as both routers and hosts. The nodes involved in the MANETs, therefore, act as both routers and hosts. The network topology varies dynamically and unpredictably due to mobility of the nodes. The conventional IP based routing protocols are not able to handle the unique characteristics of MANETs. Different protocols that can handle the unique characteristics such as dynamic and unpredictably varying topology have therefore been developed. These protocols have different performance and scalability behaviors in different network operation conditions. It is therefore imperative to analyze their scalability and evaluate their performances with respect to the control variables on which MANET networks are mainly optimized and characterized such as the network size, mobility and traffic type and load. In this paper, the scalability and performance behaviors of AODV, DSR and OLSR are analyzed under scalable network size, mobility speed and FTP traffic loads with respect to average end-to-end delay and throughput. OPNET Modeler 14.5 was used as a simulation tool. The results indicated that there is an overall throughput performance increment with increasing network size and FTP traffic load while the delay performance was decreasing. It was also observed that the mobility scaling has not a significant effect on the performance behavior of the protocols. OLSR performs better than the AODV and DSR in terms of delay while AODV performs better than the other two in terms of throughput in all the scenarios considered. Keywords: AODV, Delay, DSR, Throughput, FTP, MANET, OLS

World health organisation guidelines on highly active anti retroviral therapy: implication on palliative care provision in sub-Saharan African

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The role of growth centres in rural development: I. theory, methodology, data

This paper summarizes the basic theory, methodology and data Of an extensive research project carried on in Muranga District from June 1972 to August 1973. This project was a joint venture between the Department of Geography, University of Nairobi and the Department of Geography, Carleton University, Ottawa. The project was funded by the International Development Research Centre, Ottawa, Canada. The concept of growth centres plays an important part in the 1970-74 Development Plan and the basic hypothesis of this project is that the growth centre strategy, if refined and further developed could play a vital role in rural development in Kenya. In essence, it could form the keystone of a spatial strategy of rural development. It is argued that rural problems and urban problems should not be viewed in isolation but as an inter-related spatial system. The small place in the rural areas becomes vital in such a strategy as it is the interface between urban and rural systems, and an effective rural development strategy should concentrate on this interface. The research project set out to answer two basic questions; 1) What is the role of the growth centre in rural development? 2) How can this role be made more effective? To answer these questions it was necessary to build up a comprehensive data bank on the existing small centres and the people in their hinterlands. There were a number of elements involved. These included an understanding of the history of the centres; discernment and measurement of growth indicators especially the performance of the informal sector; the participation and involvement of the people; the linkages and interactions among centres and their hinterlands; the identification of the most likely centres for potential growth and diffusion of innovations and the spatial patterns of the centres together with the distribution of population. This paper will deal primarily with the methodology used and the data collected; a second paper will further develop the basic theory and give the major conclusions

Experiences in effective communication on transgenic technology in Africa – the case of the insect resistant maize for Africa (IRMA) project

The Insect Resistant Maize for Africa (IRMA) Project, aimed to improve food security through developing and deploying locally adapted stem borer resistant maize varieties using both conventional and biotechnology mediated methods, especially Bt technology. This technology uses a gene from the soil bacterium Bacillus thuringiensis (Bt) to create transgenic maize varieties. Transgenic technologies have been a controversial and emotive topic in recent years, and the IRMA project was launched against this backdrop. To ensure widespread acceptance of the IRMA project and its Bt technology, the project carefully planned and implemented its communication and public awareness strategy. Following its public launch in March 2000, the project promoted an open communication environment and continuously engaged with stakeholders to update them on progress. The project achieved this through targeted and diverse communications products such as media articles and broadcast news pieces, newsletters, websites, videos and reports. To complement these, the project conducted annual stakeholders’ meetings, and specialized training for frontline project staff and collaborators, especially extension agents. This paper reviews the IRMA Project’s public awareness and communication strategy and analyzes its effectiveness.Key words: Transgenic technology, Bacillus thuringiensis (Bt) maize technology, communication, public awareness, insect resistant maize for Africa (IRMA) project

Sediment Quality Triad assessment in Kachemak Bay: characterization of soft bottom benthic habitats and contaminant bioeffects assessment

A baseline environmental characterization of the inner Kachemak Bay, Alaska was conducted using the sediment quality triad approach based on sediment chemistry, sediment toxicity, and benthic invertebrate community structure. The study area was subdivided into 5 strata based on geophysical and hydrodynamic patterns in the bay (eastern and western intertidal mud flats, eastern and western subtidal, and Homer Harbor). Three to seven locations were synoptically sampled within each stratum using a stratified random statistical design approach. Three sites near the village of Port Graham and two sites in the footprint of a proposed Homer Harbor expansion were also collected for comparison. Concentrations of over 120 organic and metallic contaminants were analyzed. Ambient toxicity was assessed using two amphipod bioassays. A detailed benthic community condition assessment was performed. Habitat parameters (depth, salinity, temperature, dissolved oxygen, sediment grain size, and organic carbon content) that influence species and contaminant distribution were also measured at each sampling site. Sediments were mostly mixed silt and sand; characteristic of high energy habitats, with pockets of muddy zones. Organic compounds (PAHs, DDTs, PCBs, cyclodienes, cyclohexanes) were detected throughout the bay but at relatively low concentrations. Tributyltin was elevated in Homer Harbor relative to the other strata. With a few exceptions, metals concentrations were relatively low and probably reflect the input of glacial runoff. Relative to other sites, Homer Harbor sites were shown to have elevated concentrations of metallic and organic contaminants. The Homer Harbor stratum however, is a deep, low energy depositional environment with fine grained sediment. Concentrations of organic contaminants measured were five to ten times higher in the harbor sites than in the open bay sites. Concentration of PAHs is of a particular interest because of the legacy of oil spills in the region. There was no evidence of residual PAHs attributable to oil spills, outside of local input, beyond the confines of the harbor. Concentrations were one to ten times below NOAA sediment quality guidelines. Selected metal concentrations were found to be relatively elevated compared to other data collected in the region. However, levels are still very low in the scale of NOAA’s sediment quality guidelines, and therefore appear to pose little or no ecotoxicity threat to biota. Infaunal assessment showed a diverse assemblage with more than 240 taxa recorded and abundances greater than 3,000 animals m-22 in all but a few locations. Annelid worms, crustaceans, snails, and clams were the dominant taxa accounting for 63 %, 19%, 5%, and 7 % respectively of total individuals. Specific benthic community assemblages were identified that were distributed based on depth and water clarity. Species richness and diversity was lower in the eastern end of the bay in the vicinity of the Fox River input. Abundance was also generally lower in the eastern portion of the study area, and in the intertidal areas near Homer. The eastern portions of the bay are stressed by the sediment load from glacial meltwater. Significant toxicity was virtually absent. Conditions at the sites immediately outside the existing Homer Harbor facility did not differ significantly from other subtidal locations in the open Kachemak Bay. The benthic fauna at Port Graham contained a significant number of species not found in Kachemak Bay. Contaminant conditions were variable depending on specific location. Selected metal concentrations were elevated at Port Graham and some were lower relative to Kachemak Bay, probably due to local geology. Some organic contaminants were accumulating at a depositional site

Sediment quality triad assessment in Kachemak Bay: characterization of soft bottom benthic habitats and contaminant bioeffects assessment condensed. A NOAA/NOS/NCCOS/CCMA Special Report

A baseline environmental characterization of the inner Kachemak Bay, Alaska was conducted using standardized National Status and Trends Bioeffects Program methods. Three sites near the village of Port Graham were also sampled for comparison. Concentrations of over 120 organic and metallic contaminants were analyzed. Ambient toxicity was assessed using two bioassays. A detailed benthic community condition assessment was performed. Habitat parameters (e.g. depth, salinity, temperature, dissolved oxygen, sediment grain size, and organic carbon content) that influence species and contaminant distribution were also measured at each sampling site. The following is the synopsis of findings • Sediments were mostly mixed silt and sand with pockets of muddy zones. Organic compounds (PAHs, DDTs, PCBs, chlorinated pesticides) were detected throughout the bay but at relatively low concentrations. With some exceptions, metals concentrations were relatively low and probably reflect the input of glacial runoff. • Homer Harbor had elevated concentrations of metallic and organic contaminants. Concentrations of organic contaminants measured were five to ten times higher in the harbor sites than in the open bay sites. Tributyltin was elevated in Homer Harbor relative to the other areas. • There was no evidence of residual PAHs attributable to oil spills, outside of local input in the confines of the harbor. • The benthic community is very diverse. Specific community assemblages were distributed based on depth and water clarity. Species richness and diversity was lower in the eastern end of the bay in the vicinity of the Fox River input. Abundance was also generally lower in the eastern portion of the study area, and in the intertidal areas near Homer. The eastern portions of the bay are stressed by the sediment load from glacial meltwater. • Significant toxicity was virtually absent. • The benthic fauna at Port Graham contained a significant number of species not found in Kachemak Bay. • Selected metal concentrations were elevated at Port Graham relative to Kachemak Bay, probably due to local geology. Organic contaminants were elevated at a site south of the village

Multimodal analysis of the effects of dexamethasone on high-altitude cerebral oedema : protocol for a pilot study

Background Acute mountain sickness (AMS) is a cluster of symptoms that commonly occur in those ascending to high altitudes. Symptoms can include headaches, nausea, insomnia and fatigue. Exposure to high altitude can also lead to high-altitude cerebral oedema (HACE), which is a potential cause of death whilst mountaineering. Generally, AMS precedes the development of HACE. Historical studies have demonstrated the effectiveness of regular dexamethasone administration in reducing the symptoms of AMS. However, the mechanism by which dexamethasone works to reduce symptoms AMS remains poorly understood. Further studies, simulating altitude using hypoxic tents, have characterised the effect of prolonged exposure to normobaric hypoxia on cerebral oedema and blood flow using MRI. This randomised trial assesses the effect of dexamethasone on hypoxia-induced cerebral oedema in healthy adult volunteers. Methods/design D4H is a double-blind placebo-controlled randomised trial assessing the effect of dexamethasone on hypoxia-induced cerebral oedema. In total, 20 volunteers were randomised in pairs to receive either 8.25 mg dexamethasone or normal saline placebo intravenously after 8 h of hypoxia with an FiO2 of 12%. Serial MRI images of the brain and spinal cord were obtained at hours 0, 7, 11, 22 and 26 of the study along with serum and urinary markers to correlate with the severity of cerebral oedema and the effect of the intervention. Discussion MRI has been used to identify changes in cerebral vasculature in the development of AMS and HACE. Dexamethasone is effective at reducing the symptoms of AMS; however, the mechanism of this effect is unknown. If this study demonstrates a clear objective benefit of dexamethasone in this setting, future studies may be able to demonstrate that dexamethasone is an effective therapy for oedema associated with brain and spinal cord ischaemia beyond AMS