Effect of chemical modification of oil fly ash and compatibilization on the rheological and morphological properties of low‐density polyethylene composites

In this study, the effect of oil fly ash (OFA), a by‐product of oil fuel power plants, on the rheological and morphological behavior of low‐density polyethylene (LDPE) is investigated. As received and acid‐functionalized OFA (COOH‐OFA) are used to examine the effect of surface modification of OFA on polymer–filler composites. LDPE/OFA composites were prepared by melt mixing with filler loading in the range 1–10 wt %. The results are compared with pure LDPE. The effect of polyethylene‐grafted‐maleic anhydride (PE‐g‐MA) as a compatibilizer was also studied. Both viscous and elastic properties of composites increased with OFA loading especially at low frequency. The surface modification of OFA has influenced the properties of OFA. As‐received OFA showed some agglomeration at high loading that resulted in two‐phase system as described by scanning electron microscopy (SEM) and Cole–Cole plot. Field emission‐SEM (FE‐SEM) images showed improvement in the dispersion of COOH‐LDPE/OFA composites. In addition, the surface modification reduced the size of agglomeration. In general, the COOH modification of OFA improved both the dispersion and rheological properties of OFA. With chemical modification, the concentration of the filler can be increased to 10% without compromising the properties of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Ameliorating Effects of Exogenously Applied Proline on Seed Composition,Seed Oil Quality and Oil Antioxidant Activity of Maize (Zea mays L.) under Drought Stress

This study was carried out to appraise whether or not the exogenous application of a potential osmoprotectant, proline, could ameliorate the adverse effects of drought stress on maize seed and seed oil composition, as well as oil antioxidant activity. Water stress reduced the kernel sugar, oil, protein and moisture contents and most of the seed macro- and micro-elements analyzed in both maize cultivars but it increased the contents of seed fiber and ash. Water stress increased the oil oleic acid content with a subsequent decrease in the amount of linoleic acid, resulting in an increased oil oleic/linoleic ratio for both maize cultivars. However, no variation was observed in oil stearic and palmitic acids content due to water stress. A considerable drought induced an increase in seed oil α-, γ-, δ- and total tocopherols and flavonoids were observed in both maize cultivars. However, oil phenolic and carotenoid content as well as 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging activity decreased. Foliar-applied proline significantly increased the content of seed sugar, oil, protein, moisture, fiber and ash in both maize cultivars under well irrigated and water deficit conditions. Furthermore, exogenous application of proline increased the oil oleic and linoleic acid contents. The concentrations of antioxidant compounds namely phenolics, carotenoids, flavonoids and tocopherols estimated in the seed oil increased due to foliar-applied proline under water deficit conditions that was positively correlated with the enhanced oil DPPH free radical scavenging activity. Moreover, the increase in the contents of these antioxidant compounds and oil antioxidant activity due to the foliar application of proline was noted to be more pronounced under water deficit conditions.     

Zone-based routing protocol with mobility consideration for wireless sensor networks

Hierarchical routing and clustering mechanisms in Wireless Sensor Networks (WSN) help to reduce the energy consumptions and the overhead created when all the sensor nodes in the network are sending information to the central data collection point. Most of the routing and clustering protocols proposed for WSN assume that the nodes are stationary. However, in applications like habitat monitoring or search and rescue, that assumption makes those clustering mechanisms invalid, since the static nature of sensors is not real. In this paper, we propose Zone-based Routing Protocol for Mobile Sensor Networks (ZoroMSN) that considers the design aspects such as mobility of sensors, zones and routes maintenance, information update and communication between sensor nodes. Simulation results show the effectiveness and strengths of the ZoroMSN protocol such as a low routing and mobility overhead, while achieving a good performance in WSN using small zone sizes and sensors with low speed. Simulation results also show that ZoroMSN outperforms existing LEACH-ME and LEACH-M protocols in terms of network lifetime and energy consumptions.     

Barrier coverage with line-based deployed mobile sensors

Barrier coverage of a wireless sensor network is a critical issue in military and homeland security applications, aiming to detect intruders that attempt to cross the deployed region. While a range of problems related to barrier coverage have been investigated, little effort has been made to explore the effects of different sensor deployment strategies and mechanisms to improve barrier coverage of a wireless sensor network after it is deployed. In this paper we study the barrier coverage of a line-based sensor deployment strategy and explore how to exploit sensor mobility to improve barrier coverage. We first establish a tight lower bound for the existence of barrier coverage under the line-based deployment. Our results show that the barrier coverage of the line-based deployment significantly outperforms that of the Poisson model when the random offsets are relatively small compared to the sensor’s sensing range. To take advantage of the performance of line-based deployment, we further devise an efficient algorithm to relocate mobile sensors based on the deployed line so as to improve barrier coverage. The algorithm finds barrier gaps and then relocates mobile sensors to fill the gaps while at the same time balancing the energy consumption among mobile sensors. Simulation results show that the algorithms can effectively improve the barrier coverage of a wireless sensor network for a wide range of deployment parameters. Therefore, in wireless sensor network applications, the coverage goal, possible sensor deployment strategies, and sensor mobility must be carefully and jointly considered. The results obtained in this paper will provide important guidelines and insights into the deployment and performance of wireless sensor networks for barrier coverage.     

A Comparison of ZnO Nanowires and Nanorods Grown Using MOCVD and Hydrothermal Processes

A comparison of ZnO nanowires (NWs) and nanorods (NRs) grown using metalorganic chemical vapor deposition (MOCVD) and hydrothermal synthesis, respectively, on p-Si (100), GaN/sapphire, and SiO₂ substrates is reported. Scanning electron microscopy (SEM) images reveal that ZnO NWs grown using MOCVD had diameters varying from 20 nm to 150 nm and approximate lengths ranging from 0.7 μm to 2 μm. The NWs exhibited clean termination/tips in the absence of any secondary nucleation. The NRs grown using the hydrothermal method had diameters varying between 200 nm and 350 nm with approximate lengths between 0.7 μm and 1 μm. However, the NRs grown on p-Si overlapped with each other and showed secondary nucleation. x-Ray diffraction (XRD) of (0002)-oriented ZnO NWs grown on GaN using MOCVD demonstrated a full-width at half-maximum (FWHM) of 0.0498 (θ) compared with 0.052 (θ) for ZnO NRs grown on similar substrates using hydrothermal synthesis, showing better crystal quality. Similar crystal quality was observed for NWs grown on p-Si and SiO₂ substrates. Photoluminescence (PL) of the NWs grown on p-Si and SiO₂ showed a single absorption peak attributed to exciton–exciton recombination. ZnO NWs grown on GaN/sapphire had defects associated with oxygen interstitials and oxygen vacancies.     

Room-Temperature Quantum Cascade Laser: ZnO/Zn1−x Mg x O Versus GaN/Al x Ga1−x N

A ZnO/Zn_1?x Mg _x O-based quantum cascade laser (QCL) is proposed as a candidate for generation of THz radiation at room temperature. The structural and material properties, field dependence of the THz lasing frequency, and generated power are reported for a resonant phonon ZnO/Zn_0.95Mg_0.05O QCL emitting at 5.27 THz. The theoretical results are compared with those from GaN/Al _x Ga_1?x N QCLs of similar geometry. Higher calculated optical output powers [ $ {P}_{\rm{ZnMgO}} $  = 2.89 mW (nonpolar) at 5.27 THz and 2.75 mW (polar) at 4.93 THz] are obtained with the ZnO/Zn_0.95Mg_0.05O structure as compared with GaN/Al_0.05Ga_0.95N QCLs [ $ {P}_{\rm{AlGaN}} $  = 2.37 mW (nonpolar) at 4.67 THz and 2.29 mW (polar) at 4.52 THz]. Furthermore, a higher wall-plug efficiency (WPE) is obtained for ZnO/ZnMgO QCLs [24.61% (nonpolar) and 23.12% (polar)] when compared with GaN/AlGaN structures [14.11% (nonpolar) and 13.87% (polar)]. These results show that ZnO/ZnMgO material is optimally suited for THz QCLs.     

Fabrication and Characterization of Jute Fiber-Reinforced PET Composite: Effect of LLDPE Incorporation

The aim of the research was to study the effect of LLDPE incorporation in the jute fiber-reinforced PET composites (50% fiber by wt). The effect of LLDPE incorporation into PET was investigated by measuring the mechanical properties of the LLDPE blended jute fiber-reinforced PET composites. LLDPE was blended (20-80% by wt) with PET and the thin films were made by compression molding. Water uptake of the composites was also investigated. Degradation of all the composites was carried out in soil medium.     

Study of magnetic entropy change in La0.65Sr0.35Cu0.1Mn0.9O3 complex perovskite

The magnetocaloric properties of new complex magnetic material La_0.65Sr_0.35Cu_0.1Mn_0.9O₃, suitable for the Ericsson cycle, have been investigated. For this material, the effect of Cu doping can be attributed to a combination of doping disorder, Cu-Mn super exchange interactions and a site-percolation mechanism, which suppress the metallic conduction and Curie temperature. The Curie temperature decreases to 355 K. The magnetocaloric study exposes a comparable value of the magnetic entropy change for La_0.65Sr_0.35Cu_0.1Mn_0.9O₃ sample, the value of the maximum entropy change, increases from 1.132 J/kgK to 3.11 J/kgK as magnetic field increases from 1 T to 4 T. A large relative cooling power (RCP) has been observed for La_0.65Sr_0.35Cu_0.1Mn_0.9O_3. As a result, the studied sample can be considered as potential material for magnetic refrigeration.     

Laminar free convection from a continuously-moving vertical surface in thermally-stratified non-Darcian high-porosity medium: Network numerical study

A mathematical model is presented for the two-dimensional, steady, incompressible, laminar free convection flow boundary layer flow over a continuously moving plate immersed in a thermally-stratified high-porosity non-Darcian porous medium, in an (x,y) coordinate system where x is directed along the plate. Stratification is assumed to be stable and is analyzed using an algebraic formulation relating the stratification rate of the gradient of ambient temperature with the vertical distance along the plate (x). A Darcy–Forchheimer drag force model is used to simulate the bulk porous resistance at low Reynolds numbers, and the inertial quadratic drag at higher Reynolds numbers. The governing conservation equations are non-dimensionalized with appropriate transformations into a (ξ,η) coordinate system and they are solved using the Network Simulation Method (NSM) using the Pspice algorithm database.     

Current Concepts on Genetic Aspects of Mitochondrial Dysfunction in Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS), neurodegenerative motor neuron disorder is characterized as multisystem disease with important contribution of genetic factors. The etiopahogenesis of ALS is not fully elucidate, but the dominant theory at present relates to RNA processing, as well as protein aggregation and miss-folding, oxidative stress, glutamate excitotoxicity, inflammation and epigenetic dysregulation. Additionally, as mitochondria plays a leading role in cellular homeostasis maintenance, a rising amount of evidence indicates mitochondrial dysfunction as a substantial contributor to disease onset and progression. The aim of this review is to summarize most relevant findings that link genetic factors in ALS pathogenesis with different mechanisms with mitochondrial involvement (respiratory chain, OXPHOS control, calcium buffering, axonal transport, inflammation, mitophagy, etc.). We highlight the importance of a widening perspective for better understanding overlapping pathophysiological pathways in ALS and neurodegeneration in general. Finally, current and potentially novel therapies, especially gene specific therapies, targeting mitochondrial dysfunction are discussed briefly.