Catalytic performance of a copper–promoted CeO2 catalyst in the CO oxidation: Influence of the operating variables and kinetic study

A study of the CO oxidation reaction was conducted on a CuO–CeO₂ catalyst, with a copper content of 20 at%. The stability, activity and selectivity of this sample were evaluated in the absence of H₂ and also under PROX conditions (i.e. in great H₂ excess). The influence of the reaction temperature and the feed composition was also analyzed. It was found that water and CO₂ have a negative effect on the catalytic activity. Except for the undesired oxidation of hydrogen, the occurrence of other lateral reactions that could be present in the PROX reactor can be discarded. A kinetic study was carried out in order to fit a classical power-law expression for CO oxidation rate. Although this mathematical expression gave a good fit in limited concentration ranges, it was found that the partial reaction orders depend on the reactant molar fractions.     

自动归零放大器噪声降低一半的并行技术

自动归零放大器几乎可实现零漂移,其输出偏移值从1μV～20μV.可以补偿传感电路中自动归零放大器的初始电压偏移,如直流放大器和积分器,需要处理10μV～1mV的电压.由于剩余低频输出噪声还存在于自动归零放大器中,总补偿降到0V偏移是一种假象.     

Cylindrical FDTD Analysis of LWD Tools Through Anisotropic Dipping-Layered Earth Media

Electrical logging-while-drilling (LWD) tools are commonly used in oil and gas exploration to estimate the conductivity (resistivity) of adjacent Earth media. In general, Earth media exhibit anisotropic conductivities. This implies that when LWD tools are used for deviated and horizontal drilling, the resulting borehole problem may include dipping-layered media with dipping beds having full 3 times 3 conductivity tensors. To model this problem, we describe a 3-D cylindrical finite-difference time-domain (FDTD) algorithm extended to fully anisotropic conductive media and implemented with cylindrical perfectly matched layers to mimic open-domain problems. The 3-D FDTD algorithm is validated against analytical results in simple formations, showing good agreement, and used to simulate the response of LWD tools through anisotropic dipping beds for various values of anisotropic conductivities and dipping angles     

Random field of initial deflections and strength of thin rectangular plates

The use of an integral measure of initial deflections of thin plates, based on the strain energy, has proved to be of importance in studying the influence of the imperfections on the strength of plates subjected to in-plane compression. The energy measure allows for a straightforward definition of compound modes and for a computational determination of the lower bound strength. The last quantity may be essential for assessment of plate design strength considering the imperfections as a random field.     

Physical properties of edible coatings and films made with a polysaccharide from Anacardium occidentale L.

The effect of the concentrations of the polysaccharide from Anacardium occidentale L. (Policaju) and a surfactant (Tween 80) on relevant properties of edible coatings/films, in view of their application on apples (cv. Golden) was evaluated. The influence of the interactions between those two constituents on apples’ surface properties and on the coating/film’s wettability, water vapor permeability, opacity and mechanical properties was evaluated. The effects of the studied variables (polysaccharide and surfactant concentrations) were analyzed according to a 2² factorial design. Pareto bar charts were used to understand the most significant factors on the studied properties. The addition of surfactant reduced the cohesion forces, therefore reducing the surface tension and increasing the wettability; this resulted in an improved compatibility between the solution and the fruit skin surface. The opacity was also reduced. The results of each of the analyzed properties were adjusted to a polynomial, multifactor model, which provided a good fitting accuracy. This model is important once it will reduce the characterization work needed in subsequent applications of these coatings/films on foods.     

Bitwise Implementation of a Two-Dimensional Cellular Automata Biofilm Model

Mathematical modeling using the cellular automata (CA) approach is an attractive alternative to models based on partial differential equations when the domains to be simulated have complex boundary conditions. The computational efficiency of CA models is readily observed when using parallel processors, but implementations in personal computers are, although feasible, not quite efficient. In an effort to improve the computational efficiency of CA implementations in personal computers, we introduce in this paper a bitwise implementation based on the use of each bit as a different CA cell. Thus, in a 32-bit processor, each computer word stores information about 32 different CA cells. We illustrate the bitwise implementation with a biofilm model that simulates substrate diffusion and microbial growth of a single-species, single-substrate, structurally heterogeneous biofilm. The efficiency of the bitwise implementation was evaluated by comparing the computational time of equivalent CA biofilm models that used more common low-level implementations, namely, if-then operators and look-up tables. The processing speed of the bitwise implementation was over an order of magnitude higher than the processing speed of the other two implementations. Regarding the biofilm simulations, the CA model exhibited self-organization of the biofilm morphology as a function of kinetic and physical parameters.     

Metamaterial Blueprints for Reflectionless Waveguide Bends

A derivation of metamaterial blueprints for the reflectionless (perfectly matched) guiding of electromagnetic waves through waveguide bends is performed. The sensitivity of the response with respect to small perturbations in the associated constitutive tensors is examined.     

Degradation of the compressive strength of rectangular plates due to initial deflection

The paper addresses the problem of the influence of initial deflections on the collapse strength of thin rectangular plates in longitudinal compression. Measured data on distortions of stiffened plating in ships are considered in studying the strength of plates. For comparison of the strength values, the initial deflections are normalised by an energy measure and by the commonly employed amplitude to thickness ratio. It is suggested that this energy measure is able to provide an integral measure of the degree of initial deflections.     

Inflorescences of Brassicacea species as source of bioactive compounds: A comparative study

Two Brassica oleracea varieties (B. oleracea L. var. costata DC and B. oleracea L. var. acephala) and Brassica rapa L. var. rapa inflorescences were studied for their chemical composition and antioxidant capacity. Phenolic compounds and organic acids profiles were determined by HPLC–DAD and HPLC–UV, respectively. B. oleracea var. costata and B. oleracea L. var. acephala inflorescences presented a similar qualitative phenolic composition, exhibiting several complex kaempferol derivatives and 3-p-coumaroylquinic acid, while B. rapa var. rapa was characterized by kaempferol and isorhamnetin glycosides and several phenolic acids derivatives. B. oleracea L. var. costata and B. rapa var. rapa showed the highest phenolics content. The three Brassica exhibited the same six organic acids (aconitic, citric, pyruvic, malic, shikimic and fumaric acids), but B. oleracea L. var. acephala presented a considerably higher amount. Each inflorescence was investigated for its capacity to act as a scavenger of DPPH radical and reactive oxygen species (superoxide radical, hydroxyl radical and hypochlorous acid), exhibiting antioxidant capacity in a concentration dependent manner against all radicals. These samples were also studied for its antimicrobial potential against Gram-positive and Gram-negative bacteria and fungi, displaying antimicrobial capacity only against Gram-positive bacteria.     

Injection of marinade with actinidin increases tenderness of porcine M. biceps femoris and affects myofibrils and connective tissue

BACKGROUND: Marination of beef muscles with brine solutions containing proteolytic enzymes from fruit extracts has been shown to tenderize meat. However, the effect of marination with actinidin on tenderness of pork muscles has not been investigated. Tenderness and eating quality of porcine M. biceps femoris was investigated by Warner–Bratzler (WB) shear test and sensory evaluation after injection of brine containing up to 11 g L^?1 actinidin‐containing kiwi fruit powder and 2, 5 or 9 days of storage. RESULTS: Actinidin decreased WB shear force, increased tenderness and did not affect flavour and juiciness. Injection of 2.8 g L^?1 actinidin powder and storage for 2 days resulted in WB shear force values similar to control samples stored for 5 or 9 days. In samples injected with 10 g L^?1 actinidin powder, degradation of desmin and percentage of heat‐soluble collagen (P < 0.05) increased compared to control samples. Myofibrillar particle size tended to decrease (P < 0.1) with increasing actinidin concentration. No major changes were observed by proteome analysis. Atomic force microscopy showed actinidin‐induced damage of endomysium surrounding isolated single muscle fibres. CONCLUSION: Our results indicate that actinidin tenderizes pork M. biceps femoris by affecting both the myofibrils and connective tissue. Copyright © 2009 Society of Chemical Industry