Performance study of mobile WiMAX network with changing scenarios under different modulation and coding

WiMAX—the Worldwide Interoperability for Microwave Access is a promising technology for offering high‐speed data, video and multimedia services over mobile platform evolving toward all IP networks. The increasing demand of WiMAX for VoIP and high‐speed multimedia is due to the simplicity of installation and cost reduction compared with the traditional wired DSL cable. The challenges to service providers lie with the Quality of Service (QoS) under varying fading environment while at the same time maximizing for resource utilization. In this paper, a rigorous and comprehensive performance study of mobile WiMAX has been made with respect to adaptive modulation and coding techniques considering the variation in the speed of the mobile, path‐loss, scheduling services and application type for comparing with the fixed type of modulations. The OPNET 14.5.A modeler for WiMAX platform has been used as simulator for adaptation at the physical layer of the transmission in WiMAX OFDMA structure. Observation reveals that dynamic adaptation of modulation and coding schemes based on channel condition enables better QoS while consuming low overall bandwidth of the system. Copyright © 2011 John Wiley & Sons, Ltd.     

Peptide-functionalized colloidal graphene via interdigited bilayer coating and fluorescence turn-on detection of enzyme

Synthesis of colloidal functional graphene is challenging because graphene is water-insoluble and its relatively inert surface made the functionalization a difficult task. Here we report interdigited bilayer type coating that provide both colloidal stability and functionalization option for graphene. Colloidal graphene oxide is first converted into interdigited bilayer coated graphene oxide and next they are transformed into colloidal graphene by hydrazine reduction. These coated graphenes can be further transformed into colloidal functional graphene using covalent conjugation chemistry. Functional graphene has been synthesized for optical detection of enzyme where a fluorescent dye is covalently linked through a peptide so that the dye fluorescence is quenched by graphene but switches on once enzymes cleave the peptide bond. The interdigited bilayer coating reported here is unique as it provides coating thickness <3 nm, offering optically responsive graphene-fluorophore substrate with high colloidal stability.     

Effects of Oxygen and Water Vapor Transmission Rates of Polymeric Pouches on Oxidative Changes of Microwave-Sterilized Mashed Potato

Polymer-based packaging with low oxygen (OTR) and water vapor transmission rates (WVTR) can be used to limit oxidative chemical changes in packaged foods, especially for the 3- to 5-year shelf life required for military rations and long-duration space foods. Microwave-assisted thermal sterilization (MATS) produces higher quality food with a potentially longer shelf life as a result of volumetric heating and the associated shorter process time. This study investigated the effects of the package-MATS process interactions and the resultant package barrier properties on food quality, using a mashed potato model food following MATS process of F₀?=?9 min for 12 weeks at 50 °C. Two poly ethylene terephthalate (PET)-based (MFA, MFC) and one ethylene vinyl alcohol (EVOH)-based (MFB) retort pouches were tested, with OTRs of 0.20, 2.11, and 0.07 cc/m²·day and WVTRs of 2.64, 1.78, and 0.29 g/m²·day for MFA, MFB, and MFC, respectively; a foil double-sealed MFA pouch served as a control (MF0).Barrier properties did not influence oxygen content in polymer pouches during storage (p?>?0.05). From the third week to the fifth week of storage, significant differences (p?<?0.05) were observed in total color difference (ΔE) and oxidation indicators (TBARS, hexanal, and nonanal). The mashed potato treated in higher barrier property pouches exhibited less color change and oxidation than those in lower barrier property pouches. The performance of the MFC pouch was similar overall to that of the metal pouch. These findings suggested that high-barrier packages are suitable for MATS or other commercially sterile foods, particularly for long shelf-life purpose.     

Thermal transition and thermo-physical properties of potato (<Emphasis Type="Italic">Solanum tuberosum L</Emphasis>.) var. Russet brown

Potatoes are an important food in many regions of the world and are commonly used in a variety of food products. Thermal transition and thermo-physical properties of potatoes are important in order to design efficient food processes and select appropriate storage conditions. In this study, we determined the thermal transitions and thermophysical properties of raw and blanched/par-fried potato for a temperature range of ??32 to 21.1 °C. Using differential scanning calorimetry, we found an initial freezing point (T_f) at ??1.8?±?0.1 °C, an onset of melting (T_m^′) at ??9.9?±?0.2 °C and an unfreezable water content (X^′_w) for maximally freeze-concentrated raw potato at 0.21 kg water/kg potato. Corresponding values for blanched/par-fried potatoes were ??0.9?±?0.1 °C, ??11.0?±?0.2 °C and 0.18 kg water/kg potato. Results show that an increase in solids content decreased T_f of both raw and blanched potatoes. We modelled the relationship between them using the Chen model. The apparent specific heat (C_app) increased around T_f to 31.7?±?1.13 kJ/kg K for raw potato and 26.7?±?0.62 kJ/kg K for blanched/par-fried potato. For frozen raw potato at ??32 °C, thermal diffusivity (α) was 0.89?±?0.01?×?10?^?6 m²/s and thermal conductivity (k), 1.82?±?0.14 W/m K, respectively. These values were higher for frozen raw potato than for the unfrozen raw potato (0.15?±?0.01?×?10?^?6 m²/s and 0.56?±?0.08 W/m K, respectively at 21.1 °C). The apparent density (ρ) of frozen raw potato (992?±?4.00 kg/m³ at ??32 °C) was less than that for unfrozen raw potato (1053?±?4.00 kg/m³ at 21.1 °C), and a similar trend was obtained for blanched/par-fried potato (993?±?2.00 kg/m³ at ??32 °C and 1188?±?7.00 kg/m³ at 21.1 °C, respectively). This study established a correlation between thermo-physical properties and temperature. Findings may be used to inform the design and optimization of freezing processes and frozen storage for potato products.     

Bacteria-mediated delivery of nanoparticles and cargo into cells

Nanoparticles and bacteria can be used, independently, to deliver genes and proteins into mammalian cells for monitoring or altering gene expression and protein production. Here, we show the simultaneous use of nanoparticles and bacteria to deliver DNA-based model drug molecules in vivo and in vitro. In our approach, cargo (in this case, a fluorescent or a bioluminescent gene) is loaded onto the nanoparticles, which are carried on the bacteria surface. When incubated with cells, the cargo-carrying bacteria ('microbots') were internalized by the cells, and the genes released from the nanoparticles were expressed in the cells. Mice injected with microbots also successfully expressed the genes as seen by the luminescence in different organs. This new approach may be used to deliver different types of cargo into live animals and a variety of cells in culture without the need for complicated genetic manipulations.     

Modeling the oxygen diffusion of nanocomposite-based food packaging films

Polymer-layered silicate nanocomposites have been shown to improve the gas barrier properties of food packaging polymers. This study developed a computer simulation model using the commercial software, COMSOL Multiphysics to analyze changes in oxygen barrier properties in terms of relative diffusivity, as influenced by configuration and structural parameters that include volume fraction (φ), aspect ratio (α), intercalation width (W), and orientation angle (θ) of nanoparticles. The simulation was performed at different φ (1%, 3%, 5%, and 7%), α (50, 100, 500, and 1000), and W (1, 3, 5, and 7 nm). The θ value was varied from 0° to 85°. Results show that diffusivity decreases with increasing volume fraction, but beyond φ = 5% and α = 500, diffusivity remained almost constant at W values of 1 and 3 nm. Higher relative diffusivity coincided with increasing W and decreasing α value for the same volume fraction of nanoparticles. Diffusivity increased as the rotational angle increased, gradually diminishing the influence of nanoparticles. Diffusivity increased drastically as θ changed from 15° to 30° (relative increment in relative diffusivity was almost 3.5 times). Nanoparticles with exfoliation configuration exhibited better oxygen barrier properties compared to intercalation. The finite element model developed in this study provides insight into oxygen barrier properties for nanocomposite with a wide range of structural parameters. This model can be used to design and manufacture an ideal nanocomposite-based food packaging film with improved gas barrier properties for industrial applications. PRACTICAL APPLICATIONS: The model will assist in designing nanocomposite polymeric structures of desired gas barrier properties for food packaging applications. In addition, this study will be helpful in formulating a combination of nanoparticle structural parameters for designing nanocomposite membranes with selective permeability for the industrial applications including membrane separation techniques.     

Multiplex fiber optic biosensor for detection of Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella enterica from ready-to-eat meat samples

Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella enterica are the most common foodborne bacterial pathogens and are responsible for many outbreaks. Therefore, multiplex detection of these three using a single assay platform is highly desirable. The objective was to develop and optimize a fiber optic sensor for simultaneous detection of these three from food. The streptavidin coated optical waveguides were immobilized with biotinylated polyclonal antibodies and exposed to the bacterial suspensions or enriched food samples for 2 h. Pathogens were detected after reacting with Alexa-Fluor 647-labeled monoclonal antibodies. Ready-to-eat beef, chicken and turkey meats were inoculated with each pathogen (∼100 cfu/25 g), enriched in SEL (Salmonella, E. coli, Listeria), a multipathogen selective enrichment broth for 18 h and tested with the biosensor. The biosensor was able to detect each pathogen, individually or in a mixture with very little cross-reactivity. The limit of detection for the sensor was ∼10³ cfu/ml for all three pathogens. Furthermore, the biosensor successfully detected each pathogen, grown in a mixture from enriched meat samples under 24 h. The pathogen presence was further verified by PCR and immunofluorescence assay. The multiplex fiber optic sensor shows promise for detection of the three pathogens if present in the same sample eliminating the use of multiple single pathogen detection platforms.     

A fast progressive image transmission scheme using block truncation coding by pattern fitting

In this paper, we have proposed a novel progressive image transmission scheme. In the present method, the concept of the BTC-PF is used for faster decoding. Here, images are decomposed into a number of blocks based on smoothness criterion. The smooth blocks are encoded by block means and the others are by BTC-PF method. To encode a block by BTC-PF method, the codebook is organized like a full search progressive transmission tree which helps greatly in efficient progressive transmission. The present method provides good image quality at low bit-rate and faster decoding compared to other spatial domain progressive transmission methods. We extend this method for color images also. In color image coding, each color plane is encoded separately and then the encoded information of the planes are transmitted in interleaving manner to obtain color images right from the early stages.     

Predicting the effective thermal conductivity of carbon nanotube based nanofluids

Adding a small volume fraction of carbon nanotubes (CNTs) to a liquid enhances the thermal conductivity significantly. Recent experimental findings report an anomalously wide range of enhancement values that continue to perplex the research community and remain unexplained. In this paper we present a theoretical model based on three-dimensional CNT chain formation (percolation) in the base liquid and the corresponding thermal resistance network. The model considers random CNT orientation and CNT-CNT interaction forming the percolating chain. Predictions are in good agreement with almost all available experimental data. Results show that the enhancement critically depends on the CNT geometry (length), volume fraction, thermal conductivity of the base liquid and the nanofluid (CNT-liquid suspension) preparation technique. Based on the physical mechanism of heat conduction in the nanofluid, we introduce a new dimensionless parameter that alone characterizes the nanofluid thermal conductivity with reasonable accuracy (～ ± 5%).