An investigation on the role of ytterbium in ytterbium promoted γ-alumina-supported nickel catalysts for dry reforming of methane

Addition of low quantities of ytterbium to sol–gel prepared Ni/γ-Al₂O₃ catalysts has been shown to lead to significant increases in catalytic activity and long term stability in the catalytic conversion of CO₂ and CH₄ into syngas (H₂ and CO). The role of ytterbium in these catalysts was investigated in this study through detailed investigations on the structure and composition of ytterbium promoted Ni/γ-Al₂O₃ catalysts using the following techniques: synchrotron X-ray diffraction, X-ray Photoemission Spectroscopy, Transmission Electron Microscopy, Scanning Electron Microscopy/Energy Dispersive X-ray analysis, Temperature Programmed Reduction techniques and N₂ adsorption–desorption isotherms. The results obtained indicated that ytterbium, at small quantities (up to 2 wt%), interacted strongly with the support which in turn altered the interaction between nickel and the support (most notably it was found to completely inhibit the formation of NiAl₂O₄). This decreased interaction between Ni and the support also led to a higher quantity of Ni being present in the catalyst in the form of Ni.     

Anthelmintic treatment improves the hemoglobin and serum ferritin concentrations of Tanzanian schoolchildren

To investigate the relationships between helminth infections and iron status among school-aged children, 1,115 Tanzanian children in grades 2 through 5 were randomly assigned to treatment or control groups. The children in the treatment group were screened for infection with Schistosoma haematobium and hookworm at baseline, 3 months, and 15 months; infected children were given albendazole against hookworm and praziquantel against schistosomiasis. The control group received a placebo and did not undergo parasitological screening until 15 months after the baseline. Hematological variables were compared between the treatment and control groups. The main results were, first, that the hemoglobin concentration significantly improved after treatment for hookworm (p < .001) by 9.3 g/L in children treated for hookworm only and by 8.8 g/L in children treated for hookworm and schistosomiasis. The ferritin concentration also improved in children treated for schistosomiasis (p = .001) or hookworm (p = .019). Second, a longitudinal analysis of the data from the children in the control group showed that hookworm and schistosomiasis loads were negatively associated with hemoglobin and ferritin concentrations. Moreover, ferritin concentrations increased as C-reactive protein levels increased. Overall, the results showed that anthelmintic treatment is a useful tool for reducing anemia in areas with high hookworm and schistosomiasis endemicity. The empirical relationship between ferritin and C-reactive protein indicated that simple procedures for adjusting cutoff points for the use of ferritin as an indicator of low iron stores were unlikely to be useful in this population.     

Nanoscale adhesion,friction and wear studies of biomolecules on silane polymer-coated silica and alumina-based surfaces

Proteins on biomicroelectromechanical systems (BioMEMS) confer specific molecular functionalities. In planar FET sensors (field-effect transistors, a class of devices whose protein-sensing capabilities we demonstrated in physiological buffers), interfacial proteins are analyte receptors, determining sensor molecular recognition specificity. Receptors are bound to the FET through a polymeric interface, and gross disruption of interfaces that removes a large percentage of receptors or inactivates large fractions of them diminishes sensor sensitivity. Sensitivity is also determined by the distance between the bound analyte and the semiconductor. Consequently, differential properties of surface polymers are design parameters for FET sensors. We compare thickness, surface roughness, adhesion, friction and wear properties of silane polymer layers bound to oxides (SiO₂ and Al₂O₃, as on AlGaN HFETs). We compare those properties of the film–substrate pairs after an additional deposition of biotin and streptavidin. Adhesion between protein and device and interfacial friction properties affect FET reliability because these parameters affect wear resistance of interfaces to abrasive insult in vivo. Adhesion/friction determines the extent of stickage between the interface and tissue and interfacial resistance to mechanical damage. We document systematic, consistent differences in thickness and wear resistance of silane films that can be correlated with film chemistry and deposition procedures, providing guidance for rational interfacial design for planar AlGaN HFET sensors.     

Synthesis of submicron size hollow carbon spheres by a chemical reduction — solvothermal method using carbon tetrachloride as carbon source

A simple, rapid and energy efficient approach based on copper mediated chemical reduction — solvothermal method was employed to prepare submicron size hollow carbon spheres (SHCS) using carbon tetrachloride as carbon source. The obtained SHCS were characterized by means of various physico-chemical techniques like nitrogen adsorption-desorption measurements at 77 K, XRD, SEM, TEM, EDX and FT-Raman techniques. Thus characterized samples displayed macroporous nature of carbon with carbon and chloride contents of about 73% and 12% on atomic basis respectively. The presence of chloride content may open new avenues for surface modifications of SHCS in the area of catalysis and separation science.     

Performance of an inexpensive rural solar collector

In this paper we discuss an inexpensive solar collector in which the heat storage material is sand or sand mixed with iron filings. The heat is absorbed by the blackened portion of the heat storage material. The heat is withdrawn from the system by water flowing through a network of plastic pipes buried in the heat storage material at an appropriate depth. The large efficiency is obtained when the material is sand mixed with iron filings. It is shown that the efficiency of the system can be judged from the glass cover temperature. As the glass cover temperature decreases, the efficiency of the system increases.     

Effect of copper chromite and copper chromitecopper oxide mixture catalysts on the thermal decomposition of ammonium perchlorate and composite solid propellant

Thermal decomposition of powdered ammonium perchlorate (AP), polystyrene (PS) and $\text{AP}\text{PS}$ propellant, catalysed by freshly-prepared CuCr₂O₄ and mixtures of CuCr₂O₄ and CuO, has been studied with a low concentration (1% by mass) of the catalysts. It appears that decomposition is increased due to heterogeneous catalysis. The kinetics of thermal decomposition of AP in the presence of CuCr₂O₄ in the orthorhombic region of AP have also been studied.     

Generalised plane strain problem for a circular inclusion in anisotropic elasticity

This paper is concerned with a generalised plane deformation problem in the linear theory of anisotropic elasticity. As is well known, the generalised plane deformation is the deformation of a body of infinite length bounded by a cylindrical surface, when all the stress and strain components exist but they are functions of two co-ordinates x₁, and x₂ only. It may be shown that if u₃ = 0, it is impossible to satisfy all the three equations of equilibrium of anisotropic elastic body. One has to choose u₃ as a non-zero function of x₁, x₂ for satisfying equations of equilibrium. In isotropic elasticity, u₃ = 0, makes the third equation of equilibrium identically equal to zero.The problem in this paper concerns an elastic circular cylindrical inclusion embedded in a matrix of different anisotropic material. The matrix and the inclusion are perfectly bonded at the interface. Each of the two materials possesses anisotropy of a general form with all the 21 elastic constants. The matrix is subjected to a uniform stress at infinity. The equations of elasticity theory demand that the rotation component ω₃ must also be prescribed at infinity. The complex variable technique is used and exact analytical expressions are derived for the elastic field in both the regions.     

Time-resolved Fourier transform infrared spectroscopic imaging

Fourier transform infrared (FT-IR) imaging allows simultaneous spectral characterization of large spatial areas due to its multichannel detection advantage. The acquisition of large amounts of data in the multichannel configuration results, however, in a poor temporal resolution of sequentially acquired data sets, which limits the examination of dynamic processes to processes that have characteristic time scales of the order of minutes. Here, we introduce the concept and instrumental details of a time-resolved infrared spectroscopic imaging modality that permits the examination of repetitive dynamic processes whose half-lives are of the order of milli-seconds. As an illustration of this implementation of step-scan FT-IR imaging, we examine the molecular responses to external electric-field perturbations of a microscopically heterogeneous polymer-liquid crystal composite. Analysis of the spectroscopic data using conventional univariate and generalized two-dimensional (2D) correlation methods emphasizes an additional capability for accessing of simultaneous spatial and temporal chemical measurements of molecular dynamic processes.     

Dielectric constants by multifrequency non-contact atomic force microscopy

We present a method to obtain capacitive forces and dielectric constants of ultra-thin films on metallic substrates using multifrequency non-contact atomic force microscopy with amplitude feedback in air. Capacitive forces are measured via cantilever oscillations induced at the second bending mode and dielectric constants are calculated by fitting an analytic expression for the capacitance (Casuso et al 2007 Appl. Phys. Lett. 91 063111) to the experimental data. Dielectric constants for self-assembled monolayers of thiol molecules on gold (2.0±0.1) and sputtered SiO2 (3.6±0.07) were obtained under dry conditions, in good agreement with previous measurements. The high Q-factor of the second bending mode of the cantilever increases the accuracy of the capacitive measurements while the low applied potentials minimize the likelihood of variation of the dielectric constants at high field strength and of damage from dielectric breakdown of air.     

Application of an energy source power system stabilizer on the 10MW battery energy storage system at Chino substation

Southern California Edison (SCE) installed a 10 MW battery energy storage system (BESS) at its Chino substation facility in 1988. The BESS facility has been in operation for six years and has been used for load leveling and peaking functions. The BESS power conversion system was built with the then state of the art technology and has a very fast response rate when changing power output of the batteries. SCE installed an energy source power system stabilizer (ESPSS) to test the concept of providing damping of power system swings using the ESPSS. The ESPSS basically modulates the power output/input of the energy storage batteries to respond to system frequency deviations caused by power system oscillations. The ESPSS differs from a conventional power system stabilizer. It is designed to change the power output of the power source rather than the voltage or the reactive power output. While installing the ESPSS several upgrades to the BESS were made to improve reliability. Installation of the ESPSS on the battery enables SCE to test the concept of system stabilization using power source output modulation instead of reactive power modulation. The energy storage batteries provide an easy test bed for conducting field tests and response of the ESPSS to system disturbances. This paper discusses the BESS, the ESPSS and presents recorded results from system disturbance monitoring and field tests conducted on the ESPSS and the batteries