A Survey on Scheduling in IEEE 802.16 Mesh Mode

Cataloged from PDF version of article.IEEE 802.16 standard (also known as WiMAX) defines the wireless broadband network technology which aims to solve the so called last mile problem via providing high bandwidth Internet even to the rural areas for which the cable deployment is very costly. The standard mainly focuses on the MAC and PHY layer issues, supporting two transmission modes: PMP (Point-to-Multipoint) and mesh modes. Mesh mode is an optional mode developed as an extension to PMP mode and it has the advantage of having an improving performance as more subscribers are added to the system using multi-hop routes. In 802.16 MAC protocol, mesh mode slot allocation and reservation mechanisms are left open which makes this topic a hot research area. Hence, the focus of this survey will mostly be on the mesh mode, and the proposed scheduling algorithms and performance evaluation methods

Effects of rosmarinic acid on cognitive and biochemical alterations in ovariectomized rats treated with D-galactose

Introduction. Animal models designed to mimic certain features of Alzheimer’s disease (AD) can help us to in­crease our understanding of the underlying mechanisms of disease. Previous studies have revealed that long-term D-galactose injection combined with ovariectomy results in pathophysiologic alterations associated with AD. Thus, the aim of the present study was to investigate the effects of rosmarinic acid (RA) administration on pathological changes associated with ovariectomy and D-galactose injection, which serve as a two-insult model for AD. Material and methods. One hundred female Wistar rats were divided into five equal groups: control (C), Sham (Sh), rosmarinic acid treated (R), ovariectomized rats treated with D-galactose (OD), ovariectomized rats treated with D-galactose and rosmarinic acid (ODR) groups. D-galactose (80 mg/kg/day) was administered by i.p. injection and RA (50 mg/kg/day) was given via gavage for 60 days. Open field and Y-maze tests were used to assess locomotor activity and short-term spatial memory, respectively. Biochemical and histopathological analyses of the brain tissue were performed. Results. Open field testing showed that the locomotor activity and exploratory behavior of rats were prominent­ly impaired in the OD group as compared to the other studied groups. Similarly, Y-maze test results revealed a decrease of short-term spatial memory in the OD rats. A concomitant treatment with RA significantly restored altered locomotor activity and cognitive functions in the ODR group. Lipid peroxidation levels, cyclooxygen­ase-2 expression and prostaglandin E2 levels in the brain tissue were higher in the OD group and RA treatment inhibited these changes. AD-like histopathological alterations and amyloid b peptide (Ab) depositions were observed in the OD group. Normal cell structure and lower Ab depositions were observed in the ODR group compared with the OD group. Conclusions. RA could have the potential to prevent some psychological and biochemical alterations of brain tissue found in a rat model of AD probably by attenuating lipid peroxidation and inflammatory response

Enhanced microbial methane oxidation in biochar-amended landfill cover soils

Erin Yargicoglu - Graduate Research Assistant, Department of Earth and Environmental Sciences at the University of Illinois at Chicago. Landfill gas is the third largest worldwide source of anthropogenic methane, an important greenhouse gas. Biochar amendments to landfill cover soils are proposed as an economic solution to reduce methane emissions from landfills without gas recovery systems, or in conjunction with gas recovery for near-complete methane removal in new landfills. Biochar’s high porosity, surface area, and organic content allow it to readily adsorb methane, while providing pore spaces and nutrients for microorganisms, promoting methanotrophic growth. Column and batch incubation experiments were used to simulate the effects of biochar amendments to landfill cover soils and determine kinetic parameters of methane oxidation, respectively. The qPCR of DNA extracted from the column soil targeting the pmoA (particulate methane monooxygenase) gene indicates higher abundance of methanotrophs in the biochar-amended column, supporting the observed higher rates of methane oxidation compared to soil alone. Initial results indicate that biochar is effective in increasing methanotroph populations and promoting methane oxidation.Ope

Biotic And Abiotic Characterization Of Biochar-Amended Landfill Covers Based On Column And Field Studies

Landfills contribute nearly one fifth of the human-derived methane emissions in the U.S., which together pose a significant negative impact on global climate. In order to mitigate the negative impacts of landfill CH4 emissions, alternate landfill covers are being investigated as a means to enhance microbial oxidation of CH4 into CO2 within cover soils. The objective of this research was to determine the feasibility and effectiveness of biochar amendment in enhancing the oxidation of methane in soil-based landfill covers under field-relevant settings. A pinewood-derived biochar was selected following characterization of six locally available biochars for column and field studies due to its high fixed carbon content, favorable adsorption properties, and low content of total and leachable heavy metals and polycyclic aromatic hydrocarbons (PAHs). Large column tests were conducted to simulate different biochar-amended soil covers constructed to evaluate their performance under simulated landfill cover conditions. Concurrent with column testing, a field study was carried out to evaluate the performance of three biochar-amended cover designs examined in column tests. Highest surface emissions across the field trial were positively correlated with average air and ground temperature. A strong positive correlation was observed among CH4 oxidation rates and CH4 concentrations in soil gas at 90 cm depth within the plots (R2 = 0.986). Oxidation rates were also positively correlated (R2 = 0.90) with the relative abundance of methanotrophic taxa as determined via 16SrRNA gene sequencing. In field samples, Type I methanotrophs (primarily Methylomonas and Crenothrix species) prevailed over Type II methanotrophs. This study showed that the activity of methanotrophic bacteria in landfill covers is strongly influenced by environmental factors, such as average air and ground temperature, soil moisture, methane exposure history, and characteristics of the landfill itself