CO Preferential Oxidation Activity of CuO/CeO2 Supported on Zirconium Doped Mesoporous MSU Type Silica

In this paper the comparison of activity of hopcalite (Mn–Cu mixed oxides) modified with noble metals (Pd, Pt and Au) calcined at 300, 400 and 500 °C in oxidation of thiophene was presented. Hopcalite modified with Pd demonstrated the highest activity among the studied samples, thus the results of a more detailed study of the most promising palladium catalyst were also shown. Surface and bulk properties of catalyst were studied with BET, XRD, TPR_H2 and TG-DTA-MS. The redox properties and distribution of active components on the catalyst surface seem to be important factors influencing the modified hopcalite performance in the oxidation reactions. It was found that irreversible changes occurred during thermal treatment in the Pd-modified hopcalite structure, however they have no marked influence on activity of modified catalysts.     

Supercritical antisolvent micronisation of synthetic all‐trans‐β‐carotene with tetrahydrofuran as solvent and carbon dioxide as antisolvent

BACKGROUND: Supercritical antisolvent (SAS) micronisation of synthetic trans ‐β‐carotene was studied using tetrahydrofuran (THF) as solvent and supercritical carbon dioxide (CO₂) as antisolvent, with the objective of increasing its bioavailability and facilitating its dispersion in oil and emulsion formulations as a result of its smaller particle size. The micronised powder was analysed by scanning electron microscopy and high‐performance liquid chromatography. Micronisation experiments were performed in order to evaluate the effects of temperature (308.15–333.15 K), pressure (6.5–13 MPa) and concentration of the liquid solution (6–9 g L^?1). The effect of the supercritical CO₂/THF flow ratio in the range between 4 and 44 (on a mass basis) was also analysed. Determinations of equilibrium concentrations of β‐carotene in the CO₂/THF mixture were also performed. RESULTS: The particle size obtained ranged from 1 to 500 µm, with mean particle diameters around 100 µm. Three types of morphology were found in the precipitated powder: crystalline with superficial pores and leaf‐like appearance; crystalline with regular shapes and blade‐like edges; and crystalline without superficial pores and leaf‐like apearance. The Peng–Robinson equation of state was used to calculate the density of the CO₂/THF binary mixture, and the solubility of β‐carotene in this mixture was correlated with its density. CONCLUSION: The use of the SAS technique to micronise β‐carotene proved to be efficient, and the absence of degradation in the micronised powder allows the industrial application of this technique. Copyright © 2008 Society of Chemical Industry     

Three-dimensional electrical impedance tomography: a topology optimization approach.

Electrical impedance tomography is a technique to estimate the impedance distribution within a domain, based on measurements on its boundary. In other words, given the mathematical model of the domain, its geometry and boundary conditions, a nonlinear inverse problem of estimating the electric impedance distribution can be solved. Several impedance estimation algorithms have been proposed to solve this problem. In this paper, we present a three-dimensional algorithm, based on the topology optimization method, as an alternative. A sequence of linear programming problems, allowing for constraints, is solved utilizing this method. In each iteration, the finite element method provides the electric potential field within the model of the domain. An electrode model is also proposed (thus, increasing the accuracy of the finite element results). The algorithm is tested using numerically simulated data and also experimental data, and absolute resistivity values are obtained. These results, corresponding to phantoms with two different conductive materials, exhibit relatively well-defined boundaries between them, and show that this is a practical and potentially useful technique to be applied to monitor lung aeration, including the possibility of imaging a pneumothorax.     

Synergetic tuning of electrical/thermal transport via dual-doping in Bi0.96−xMgxPb0.06CuSeO

The layered oxyselenides BiCuSeO was recently discovered as potential thermoelectric. Our result reveals that the substitute for atom Bi³⁺ by Pb²⁺ & Mg²⁺ in (Bi₂O₂)²⁻ play an important role in electrical transport properties. The maximum electrical conductivity obtained is 460 Scm⁻¹ for Bi_0.84Mg_0.10Pb_0.06CuSeO at RT, highly above the 15 Sm⁻¹ for BiCuSeO. In synergy with low thermal conductivity (0.6-0.4 Wm⁻¹ K⁻¹) and large thermopower (300-500 μVK⁻¹), the highest ZT is achieved about 0.80 at 873 K for Bi_0.88Mg_0.06Pb_0.06CuSeO.     

Study of the effects of flow channel with non-uniform cross-sectional area on PEMFC species and heat transfer

In this study it is investigated the performance of a proton exchange membrane fuel cell. The results show that an inclination of 0.75° in the flow channel can effectively increase the current density generated by almost 9.5% and the maximum power density by 8%. With the use of more tapered channels the distribution of the reactants in the porous media leads to a better effective oxygen distribution, affecting directly the heat transfer inside the cell. In contrast, the pressure drop in the flow channel increase by factors of approximately 2 and 3.5 for angles of 0.5° and 0.75°, respectively.     

Economic feasibility for acquisition of efficient refrigerators in Brazil

Since 1993, the Brazilian National Program of Electricity Conservation has been developing the PROCEL Label Program, oriented towards helping consumers to buy more efficient home appliances. In this context, an energy savings of 1379 GWh and a reduction of 197 MW in the Brazilian demand in 2007 are estimated as resulting from efficiency labeling in refrigerators and freezers. This paper aims to evaluate the economic feasibility of purchasing labeled refrigerators instead of inefficient ones, from the consumer’s point of view, considering actual market conditions and buying in cash or financing. The evaluation of energy saving was done for 22 different models of refrigerators and the economy was calculated considering the retail price in the Brazilian market and two actual electricity tariffs, taking into account, respectively, high and low household electricity consumption. The effect of ambient temperature on refrigerator performance was evaluated in two conditions: according to the Brazilian standard for performance tests (32 °C) and using the average temperature of Southern Brazil (18 °C), the mildest region. The benefit in buying labeled refrigerators was evaluated using the Internal Rate of Return and the Payback Time for a cash flow during the appliance life, estimated as 16 years. The results indicate that for cash purchase, for any electricity tariff and for both ambient temperatures studied, the consumers are economically benefited buying labeled refrigerators instead of less efficient models. For credit purchases, in the evaluated conditions, high-tariff consumer typically gains selecting labeled refrigerator, on the other hand, for low-tariff consumer and in colder areas, it is economically advisable to buy less efficient appliances. Sensitivity analysis of energy tariff and financing conditions are presented.     

Effects of co-exposure to extremely low frequency (50 Hz) magnetic fields and xenobiotics determined in vitro by the alkaline comet assay

In the present study, we used human peripheral blood leukocytes from 4 different donors, to investigate in vitro the possible genotoxic and/or co-genotoxic activity of extremely low frequency magnetic fields (ELF-MF) at 3 mT intensity. Two model mutagens were used to study the possible interaction between ELF-MF and xenobiotics: N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and 4-nitroquinoline N-oxide (4NQO). Primary DNA damage was evaluated by the alkaline single-cell microgel-electrophoresis ("comet") assay. Control cells (leukocytes not exposed to ELF-MF, nor treated with genotoxins) from the different blood donors showed a comparable level of basal DNA damage, whereas the contribution of individual susceptibility toward ELF-MF and the tested genotoxic compounds led to differences in the extent of DNA damage observed following exposure to the genotoxins, both in the presence and in the absence of an applied ELF-MF. A 3 mT ELF-MF alone was unable to cause direct primary DNA damage. In leukocytes exposed to ELF-MF and genotoxins, the extent of MNNG-induced DNA damage increased with exposure duration compared to sham-exposed cells. The opposite was observed in cells treated with 4NQO. In this case the extent of 4NQO-induced DNA damage was somewhat reduced in leukocytes exposed to ELF-MF compared to sham-exposed cells. Moreover, in cells exposed to ELF-MF an increased concentration of GSH was always observed, compared to sham-exposed cells. Since following GSH conjugation the genotoxic pattern of MNNG and 4NQO is quite different, an influence of ELF-MF on the activity of the enzyme involved in the synthesis of GSH leading to different activation/deactivation of the model mutagens used was hypothesized to explain the different trends observed in MNNG and 4NQO genotoxic activity in the presence of an applied ELF-MF. The possibility that ELF-MF might interfere with the genotoxic activity of xenobiotics has important implications, since human populations are likely to be exposed to a variety of genotoxic agents concomitantly with exposure to this type of physical agent.     

Role of the Endocannabinoid/Endovanilloid System in the Modulation of Osteoclast Activity in Paget’s Disease of Bone

The role of the endocannabinoid/endovanilloid (EC/EV) system in bone metabolism has recently received attention. Current literature evidences the modulation of osteoclasts and osteoblasts through the activation or inhibition of cannabinoid receptors in various pathological conditions with secondary involvement of bone tissue. However, this role is still unclear in primary bone diseases. Paget’s disease of the bone (PDB) could be considered a disease model for analyzing the role of the EC/EV system on osteoclasts (OCs), speculating the potential use of specific agents targeting this system for managing metabolic bone disorders. The aim of the study is to analyze OCs expression of EC/EV system in patients with PDB and to compare OCs activity between this population and healthy people. Finally, we investigate whether specific agents targeting EC/EV systems are able to modulate OCs activity in this metabolic bone disorder. We found a significant increase in cannabinoid receptor type 2 (CB2) protein expression in patients with PDB, compared to healthy controls. Moreover, we found a significant reduction in multi-nucleated tartrate-resistant acid phosphatase (TRAP)–positive OCs and resorption areas after treatment with JWH-133. CB2 could be a molecular target for reducing the activity of OCs in PDB, opening new therapeutic scenarios for the management of this condition.     

A strategic and tactical model for closed-loop supply chains

In this paper, a strategic location-allocation model is developed for the simultaneous design of forward and reverse supply chains. Strategic decisions such as network design are accounted for together with tactical decisions, namely, production, storage and distribution planning. The integration between strategic and tactical decisions is achieved by considering two interconnected time scales: a macro and a micro time. At macro level, the supply chain is designed in order to account for the existing demands and returns, whose satisfaction is planned simultaneously at the micro level where tactical decisions are taken. A Mixed Integer Linear Programming formulation is obtained which is solved to optimality using standard Branch & Bound techniques. Finally, the model accuracy and applicability is illustrated through the resolution of a case study.     

Coherent optical reflectance from a monolayer of large particles adsorbed on a glass surface

We develop a coherent-scattering model for the reflection of light from a monolayer of large particles and low surface coverage. The model takes into account multiple scattering between particles of the monolayer and with the substrate, and it can be used around the critical angle in an internal reflection configuration. We compare the results of the model with our own reflectivity data taken with latex particles adsorbed on a glass-water interface and with a simpler effective-medium model.