Controlled synthesis and methanol sensing capabilities of Pt-incorporated ZnO nanospheres

Platinum nanoparticles incorporated ZnO hybrid nanospheres (PtZONS) have been synthesized via electrodeposition which is easy to control over the size distribution range. The Pt nanoparticles in ZnO nanospheres have been identified with high-resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy (EDS). Methanol sensing capabilities of the nanospheres have been investigated through electrochemical measurements. The electrochemical measurements prove that these nanospheres demonstrate the abilities to electrocatalyze the oxidation of methanol and substantially raise the response current. The sensitivity of the Nafion/PtZONS/glassy carbon modified electrode to methanol is 235.47 μA M⁻¹ cm⁻², which is much higher than that of a pure ZnO and Pt nanospheres modified electrodes. Furthermore, it has been revealed that the electrode exhibits a good anti-interference and long-term stability. Our investigation demonstrates that the Pt-ZnO nanospheres can be employed for various applications.     

Characterization of Al2O3-TiO2 nano porous solar absorbers derived via MAO/sol-gel hybrid process

Micro arc oxidation combined with sol-gel process was used to develop solar selective absorber systems for the first time. Phase structure and chemical composition of the layers were studied by XRD and XPS techniques. The layers consisted of anatase, rutile, α-alumina, γ-alumina, and Al₂TiO₅ phases with varying fractions with the growth conditions. SEM and AFM investigations revealed a porous structure (pore size: 60-550 nm) with a rough surface where pore size and surface roughness increased with the applied voltage. Solar absorption and emission coefficients were measured using UV-Vis-NIR and IR spectrophotometry. In spite of being so thin, the fabricated samples revealed a high solar absorptivity of α = 0.99 and low thermal emissivity of ε = 0.06. A formation mechanism was proposed based on the electrochemical foundations as well.     

Investigation of the effect of temperature and layup on the press forming of polyvinyl chloride-based composite laminates and fiber metal laminates

Semi-crystalline thermoplastic-based composite laminates and fiber metal laminates have a narrow forming temperature window, which limits formability of these products. The intention of this study was investigation of non-melting amorphous polyvinyl chloride as a proper matrix to increase the formability and forming temperature window of these products. For this, [45/?45] and [0/90] layups of polyvinyl chloride-based composite laminates and fiber metal laminates were produced using the film-stacking procedure and later press formed into channel sections at six temperatures in the range of 80 to 200 °C. The effects of the layups and forming temperatures on the forming loads and spring back of the formed profiles were measured, and their effects on the fiber buckling, wrinkling, and delamination of the profiles were evaluated using optical microscope images. The effects of layups and forming temperatures on the deformation mechanisms were also analyzed using the grid strain analysis method. Of the fiber metal laminates, 160 °C was found as the minimum forming temperature, and for the composite laminates, 120 and 160 °C were found as the minimum proper forming temperatures of [45/?45] and [0/90] layups, respectively. Finally, the forming temperature windows and formability of polyvinyl chloride matrix composite laminates and fiber metal laminates were found higher than semi-crystalline matrices.     

A mathematical model for prediction of microporosity in aluminum alloy A356

In the present work, a mathematical model was developed based on finite difference method to predict the microporosity distribution in A356 aluminum alloy casting. Heat, mass, and gas conservation equations were solved in this model. Moreover, Darcy’s equation was considered in the mushy zone. Results show that the distribution and concentration of microporosities in cast parts vary with both cooling rate and initial gas content. Simulation results were compared with experimental data where proportionally good agreement with experimental results was found. Finally, a complex cast part was simulated presenting the ability of the model to predict the porosities in industrial cast parts.     

Downward movement of nitrate and ammonium nitrogen in a flatland ultisol

Three field trials were conducted in the early and late rainy season on a Piarco Series soil (Aquoxic Tropudults) in Central Trinidad to monitor downward movement of NH ₄ ⁺ -N and NO ₃ ^- -N under flat-tilled and ridge-tilled conditions as affected by mulch application. The first experiment was carried out in the early rainy season under bare-fallowed conditions, while okra (Abelmoschus esculentus) was the test crop used in the two remaining trials, which were conducted during the early and late rainy season periods. The plots were fertilized with urea seven days after crop emergence and 14 days after land preparation for the cropped and bare-fallowed experiments respectively. Soil samples were collected weekly after fertilizer application and analyzed for NH ₄ ⁺ -N, NO ₃ ^- -N and soil water.Urea application increased NH ₄ ⁺ -N levels in the soil and NH ₄ ⁺ -N was the dominant inorganic N form observed for the first four weeks after fertilization. Mulch application decreased NH ₄ ⁺ -N and NO ₃ ^- -N soil levels. Ridging the soil increased downward movement of NH ₄ ⁺ -N and NO ₃ ^- -N. Under bare-fallowed conditions, downward movement of NH ₄ ⁺ -N was noted in the 30 to 45 cm soil layer at seven days after fertilization, while under cropped conditions its movement was restricted to the 15 to 30 cm layer within the same period. In bare-fallowed soil, increased NO ₃ ^- -N and its downward movement was noted after four weeks of fertilization. In the cropped soil, downward movement of NO ₃ ^- -N was observed one week after fertilization in the early rainy season and three weeks after fertilization in the late rainy season.     

Novel Processing of 1-3 Piezoelectric Ceramic/Polymer Composites for Transducer Applications

Piezoelectric ceramic/polymer composites with 1-3 connectivity were made by weaving sized lead zirconate titanate (PZT) fiber bundles through a honeycomb support. Bundles comprised of fine-scale, 20-50 μm green fibers, made using the viscous suspension spinning process, were sized to increase their manageability. The sizing step comprised of soaking the green PZT fiber bundles in an aqueous solution of poly(vinyl alcohol), then pulling the wet fibers through a steel sizing die. Sizing resulted in dense and flexible fiber bundles, which facilitated composite construction and led to composites with increased volume fractons. Sintering, polymer embedding, and machining produced a composite exhibiting 1-3 connectivity. Composites with 10 vol% PZT yilded d ₃₃ values of 230 pC/N and a dielectric constant of 130.     

Processing of 1-3 Piezoelectric Ceramic/Polymer Composites

Several methods of forming fine-scale 1–3 piezoelectric ceramic/polymer composites for possible transducer applications were demonstrated. These methods include tape casting, honeycomb dicing, and ceramic fiber weaving. In the tape casting technique, laminated structures were formed using thin PZT tapes. The tapes were stacked, with spacers separating the layers, and the stack embedded in polymer. Dicing the stack resulted in a composite with 1–3 connectivity. The thin tape technique can be used to develop composites with ceramic or polymer volume fraction gradients and multifunctional ceramics. Dicing of PZT honeycombs yields 1–3 composites with uniquely shaped rods. Shapes included +, T, and L. In the ceramic fiber weaving technique, green PZT fibers were woven through a PZT honeycomb support structure. The structure was fired to sinter the PZT fibers, and embedded with polymer to yield 1–3 composites. All 1–3 composites showed high and uniform piezoelectric coefficients across the electroded area.     

Role of solute segregation on microstructure and mechanical properties of zircaloy-4

The Microstructure of two different lots of Zircaloy-4 was investigated by using a scanning electron microscope (SEM) attached to an energy dispersive system (EDS). The alloy containing Ni higher than the ASTM specification shows parallel plate structure with segregation of Ni, Fe, and Cr at the triple points of β-grains, and it failed during forging due to crack initiation. The second alloy having Ni content within the ASTM specification has basketweave morphology with minute segregation of Fe and Cr and was forged successfully. The absorbed energy is higher for the successfully forged alloy than for the alloy that failed during forging. It was also observed that the fracture started from the segregated area rich in Ni, Fe, and Cr, and propagated along the plate. The alloy with parallel plate structure is harder than the alloy with basketweave structure.     

Antibiotic sensitivity of isolates of Pseudomonas aeruginosa in Buraidah, Saudi Arabia

To help account for the variable quality and quantity of RNA in human brain, we have studied the effect of premortem (agonal state) and postmortem factors on the detection of poly(A)+mRNA and eight mRNAs. For comparison, the influence of the same factors upon gene products encoded by the mRNAs was studied immunocytochemically or by receptor autoradiography. Brain pH declined with increasing age at death and was related to agonal state severity, but was independent of postmortem interval and the histological presence of hypoxic changes. By linear regression, pH was significantly associated with the abundance of several of the RNAs, but not with poly(A)+mRNA, immunoreactivities, or binding site densities. Postmortem interval had a limited influence upon mRNA and protein products. Freezer storage time showed no effect. Parallel rat brain studies showed no relationship between postmortem interval (0-48 h) and amounts of total RNA, poly(A)+RNA, or two individual mRNAs; however, RNA content was reduced by 40% at 96 h after death. pH is superior to clinical assessments of agonal state or mode of death in predicting mRNA preservation. It provides a simple means to improve human brain gene expression studies. pH is stable after death and during freezer storage and can be measured either in cerebrospinal fluid or in homogenised tissue.     

Managing, Processing, and Communicating Information: What A/E/C/ Organizations Should Know

Global competition and advances in information technology (IT) are placing new demands on the management techniques used on architectural, engineering, and construction (A/E/C) projects. There are opportunities as well as challenges. The revolution under way in the fields of data sharing and transmission, information processing, and telecommunication technology is opening up new possibilities in the A/E/C industry for effectively meeting these market demands. The dynamic nature of construction processes, the interdependence of various participating entities, and the need for teamwork, flexibility, and a high degree of coordination suggest IT can be profitably employed for effective project management in the A/E/C industry. The distinctive features of A/E/C projects make the task of project management particularly appropriate for applications of IT tools.