Evaluation of commercial alloys as cathode current collector for metal-supported tubular solid oxide fuel cells

Ferritic stainless steels have become promising candidate materials for interconnects in tubular metal-supported solid oxide fuel cell stacks. A number of ferritic alloys containing between 18 and 26 mass% Cr and discrete changes in minor alloying elements and reactive elements were isothermally oxidized at 800 °C in air and their electrical resistance was measured with the objective of obtaining an overview of the properties relevant for applications for cathode side interconnect. The alloys containing Mn showed a (Mn,Cr)₃O₄ spinel layer on top of a Cr₂O₃ oxide. The electrical conductivity of the steels forming this kind of oxide layer was higher than the measured for only Cr₂O₃ former or oxide dispersion strengthened alloys and increased when the alloy contained Ti or Nb. Oxide scale spallation was observed for F18TNb and E-Brite, both containing Si. The influence of different cyclic oxidations was studied for the Crofer22APU steel, showing an irregular oxide growth as well as an increase in conductivity of the oxide scale formed when 12-h cycles were applied.     

But‐2‐ene‐1,4‐diamine and But‐2‐ene‐1,4‐diol as Donors for Thermodynamically Favored Transaminase‐ and Alcohol Dehydrogenase‐Catalyzed Processes

Both cis‐ and trans‐but‐2‐ene‐1,4‐diamines have been prepared and efficiently applied as sacrificial cosubstrates in enzymatic transamination reactions. The best results were obtained with the cis‐diamine. The thermodynamic equilibrium of the stereoselective transamination process is shifted to the amine formation due to tautomerization of 5H‐pyrrole into 1H‐pyrrole, achieving high conversions (78–99%) and enantiomeric excess (up to >99%) by using a small excess of the amine donor. Furthermore, when the reaction proceeded, a strong coloration was observed due to polymerization of 1H‐pyrrole. A structurally related compound, cis‐but‐2‐ene‐1,4‐diol, has been utilized as cosubstrate in different alcohol dehydrogenase (ADH)‐mediated bioreductions. In this case, high conversions (91–99%) were observed due to a lactonization process. Both strategies are convenient from both synthetic and atom economy points of view in the production of valuable optically active products.

     

Comparison between 2.5-D and 3-D realistic models for wind field adjustment

In previous works, many authors have widely used mass consistent models for wind field simulation by the finite element method. On one hand, we have developed a 3-D mass consistent model by using tetrahedral meshes which are simultaneously adapted to complex orography and to terrain roughness length. In addition, we have included a local refinement strategy around several measurement or control points, significant contours, as for example shorelines, or numerical solution singularities. On the other hand, we have developed a 2.5-D model for simulating the wind velocity in a 3-D domain in terms of the terrain elevation, the surface temperature and the meteorological wind, which is consider as an averaged wind on vertical boundaries. Using the meteorological wind as datum, the 2.5-D model provides a 3-D local wind modified by topography and thermal gradients on the surface by solving only a 2-D optimal control problem where the boundary condition is the control. In this case, the finite element discretization consists on a triangular mesh adapted to the terrain topography and roughness length. In both models, the wind field adjusts to several wind speed measurements at several points in the 3-D domain and eventually to an average wind flux on the boundary.In this paper we introduce several advances in the 2.5-D and 3-D wind models and we compare their results on a region located in the Province of Lugo (Spain) with realistic data that have been provided by the company Desarrollos Eólicos S.A. (DESA). In order to obtain the best adjustment of models results to the measurements, the main parameters governing the models are estimated by using genetic algorithms with a parallel implementation.     

Rotating nanoparticle array electrode for the kinetic study of reactions under mixed control

A method for the determination of the intrinsic electrocatalytic activity of metal nanoparticles for reactions under mixed diffusion-activation control is proposed. The working electrode consists of a nanoparticle array supported on a rotating disc of an inert conducting substrate. This electrode configuration reduces significantly the contribution of the reactant diffusion to the experimental current-potential curves and consequently, the kinetic parameters of the reaction can be evaluated more accurately. A model was developed for the diffusion process in the proposed configuration, which includes a parameter related to the degree of dispersion of the nanoparticles on the electrode surface (active area factor). It allows one to evaluate changes in the current-potential plot under conditions of constant particle diameter, which is essential for the appropriate analysis of the electrocatalytic activity of nanoparticles. On this basis the dependences of the current and current density for the hydrogen oxidation reaction on overpotential, rotation rate, particle size and active area factor were derived. The validity of these expressions was verified through the analysis of experimental results.     

Squid gelatin hydrolysates with antihypertensive, anticancer and antioxidant activity

Gelatin obtained from giant squid (Dosidicus gigas) inner and outer tunics was hydrolyzed by seven commercial proteases (Protamex, Trypsin, Neutrase, Savinase, NS37005, Esperase and Alcalase) to produce bioactive hydrolysates. The Alcalase hydrolysate was the most potent angiotensin-converting enzyme (ACE) inhibitor (IC₅₀ = 0.34 mg/mL) while the Esperase hydrolysate showed the highest cytotoxic effect on cancer cells, with IC₅₀ values of 0.13 and 0.10 mg/mL for MCF-7 (human breast carcinoma) and U87 (glioma) cell lines, respectively. The radical scavenging capacity of gelatin increased approximately 3-fold for Protamex, Neutrase and NS37005 hydrolysates and between 7 and 10-fold for Trypsin, Savinase, Esperase and Alcalase hydrolysates. Trypsin, Savinase, Esperase and Alcalase hydrolysates had a metal chelating capacity above 80% whereas Protamex, Neutrase and NS37005 hydrolysates registered less than 25%. The antioxidant activity measured by FRAP (ferric ion reducing power) was largely unaffected by the enzyme used, increasing approximately 2-fold for all hydrolysates. The most active hydrolysates (Alcalase and Esperase) were comprised mostly of peptides with molecular weights ranging from 500 to 1400 Da, however, a clear relationship between bioactive properties and molecular weight distribution of all the hydrolysates was not fully established.     

Accelerated ageing of styrene–butadiene rubber nanocomposites stabilized by phenolic antioxidant

Organoclay‐reinforced styrene butadiene rubber (SBR) was subjected to accelerated thermo‐oxidative ageing and its physical properties were compared to the virgin material. The oxidative degradation was studied in absence and in presence of a phenolic antioxidant. Ageing test was conducted at 70°C for 7, 14, and 28 days. Then, mechanical and dynamomechanical properties were measured and related to chemical and morphological changes. The elongation at break of samples without antioxidant was found to decrease whereas the modulus and hardness of SBR and its nanocomposite increased with ageing time. Also, the storage modulus and the glass transition temperature increased monotonously with time. These results were attributed to main chain scission and crosslinks formation. The ageing mechanism, determined by infrared spectroscopy, was independent on the nanoclay presence. When the antioxidant was added, thermo‐oxidative stability markedly increased. The retention in the physical properties upon ageing 28 days suggests that the addition of 0.5–1 phr antioxidant was sufficient to provide stability of SBR nanocomposite with minimum loss in physical properties. Also, SEM images showed no signs of degradation; this demonstrates that the antioxidant protects the surface from oxidative degradation. Moreover, infrared spectroscopy suggests that nanoclay could protect the elastomer surface from deterioration. POLYM. COMPOS., 35:334–343, 2014. © 2013 Society of Plastics Engineers     

Chilled storage of high pressure and heat-induced gels of blue whithing (Micromesistius poutassou) muscle

 Microbiological, rheological and chemical characteristics were examined in gels made from the muscle of blue whiting (Micromesistius poutassou) and subjected to three different combinations of pressure, temperature and time: 200 MPa at 3  °C for 10 min (lot L), 375 MPa at 38  °C for 20 min (lot H) and atmospheric pressure at 37  °C for 30 min followed by 90  °C for 50 min (lot T), and kept in chilled storage for 20 days. The microorganism content dropped at the outset as pressurizing took effect, the highest microbial content being found in lot L; however as the effect was not lethal, the total load increased over the following days. Microbial load was significantly lower in lot T. During chilled storage, the values of breaking deformation, breaking force and cohesiveness of lot L were higher than those of the other lots, although they did decrease with storage. The heat-induced gel was much harder, had greater water-holding capacity and was considerably more stable than the high-pressure-induced gels. The lightness value was higher in lot H than in the other two lots. In general, changes in protein solubility tended towards the cleavage of strong bonds as a result of microbial action. The electrophoretic profiles evolved differently in each of the lots over the chilled storage period. However, all of them exhibited large numbers of bands of lower molecular mass which could have been the result of degradation. This was particularly evident in lot H. The heat-induced gels exhibited a highly porous ultrastructure, quite different from the high-pressure-induced gels; these had a more compact matrix which expanded as storage progressed. Received: 26 May 1997     

An 8-Bit Digitally Controlled Programmable Phase Shifter Circuit for Sinusoidal Signals with 252∘ Phase Control Range

In this paper, the synthesis, design, and implementation of a programmable phase shifter circuit for sinusoidal signals is presented. The proposed circuit, built-up herein with operational amplifiers (OPAMPs), high precision resistors and low voltage switches, consists of a digitally controlled amplitude attenuator in combination with a single-tone orthogonalizer. Experimental results agree with theoretical background: the attained phase range was 252^° in 256 steps with a median step of 0.9^°. The inaccuracy of the circuit was determined to be of 0.03 %. Contrary to other OPAMP approaches for sinusoidal signals reported in the literature and based on a first-order all-pass filter structure, the approximation suggested in this work is based on a different concept. The achieved results demonstrate the functionality of the system for the case of a sinusoidal signal with frequency of 1 kHz. Notwithstanding, the proposed architecture can be extended to operate at higher frequencies by using different building blocks with larger bandwidth. Furthermore, it can be extended as well to work out with other periodic input waveforms, like triangular shapes or square waves, with the use of an appropriate orthogonalizer.     

Cs Promoted Triglyceride Transesterification Over MgO Nanocatalysts

The influence of Cs on the structure and basicity of nanocrystalline MgO was assessed via electron microscopy, CO₂ chemisorption, XRD and XPS. Caesium incorporation via co-precipitation under supercritical conditions generates Cs₂Mg(CO₃)₂ nanocrystallites with an enhanced density and strength of surface base sites. Wet impregnation proved less effective for modifying MgO nanocrystals. A strong synergy between Cs and Mg components in the co-precipitated material dramatically enhanced the rate of tributyrin transesterification with methanol relative to undoped MgO and homogeneous Cs₂CO₃ catalysts. On-stream deactivation of Cs-doped MgO reflects heavy surface carbon deposition and loss of the high activity Cs₂Mg(CO₃)₂ phase due to limited Cs dissolution.