Al2O3-ZrO2 Finely Structured Multilayer Architectures from Suspension Plasma Spraying

Suspension plasma spraying (SPS) is an alternative to conventional atmospheric plasma spraying (APS) aiming at manufacturing thinner layers (i.e., 10-100 μm) due to the specific size of the feedstock particles, from a few tens of nanometers to a few micrometers. The staking of lamellae and particles, which present a diameter ranging from 0.1 to 2.0 μm and an average thickness from 20 to 300 nm, permits to manufacture finely structured layers. Moreover, it appears as a versatile process able to manufacture different coating architectures according to the operating parameters (suspension properties, injection configuration, plasma properties, spray distance, torch scan velocity, scanning step, etc.). However, the different parameters controlling the properties of the coating, and their interdependences, are not yet fully identified. Thus, the aim of this paper is, on the one hand, to better understand the influence of operating parameters on the coating manufacturing mechanisms (in particular, the plasma gas mixture effect) and, on the other hand, to produce Al₂O₃-ZrO₂ finely structured layers with large varieties of architectures. For this purpose, a simple theoretical model was used to describe the plasma torch operating conditions at the nozzle exit, based on experimental data (mass enthalpy, arc current intensity, thermophysical properties of plasma forming gases, etc.) and the influences of the spray parameters were determined by mean of the study of sizes and shapes of spray beads. The results enabled then to reach a better understanding of involved phenomena and their interactions on the final coating architectures permitting to manufacture several types of microstructures.     

Emulsifying and Foaming Properties of Protein Concentrates Prepared from Cowpea and Bambara Bean Using Different Drying Methods

Effect of cabinet-drying, vacuum-drying, and freeze-drying methods on the surface hydrophobicity, secondary structure, emulsifying, and foaming properties of protein concentrates prepared from different cultivars of cowpea and Bambara bean was investigated. The vacuum-drying method reduced hydrophobicity, while freeze-dried concentrates presented high hydrophobicity. The concentrates prepared by freeze drying presented more β-sheet (40–43%) and less β-turn (19–24%) structures. Bambara bean protein concentrates prepared by freeze-drying presented higher emulsifying activity (56–59%) compared to those by vacuum-drying and cabinet-drying, while emulsifying activity varied significantly among cultivars of cowpea (46–61%). Protein concentrates prepared by cabinet-drying showed the highest foaming ability.     

Inactivation of Escherichia coli and Listeria innocua in kiwifruit and pineapple juices by high hydrostatic pressure

Escherichia coli and Listeria innocua in kiwifruit and pineapple juices were exposed to high hydrostatic pressure (HHP) at 300 MPa for 5 min. Both bacteria showed equal resistance to HHP. Using low (0 degrees C) or sub-zero (-10 degrees C) temperatures instead of room temperature (20 degrees C) during pressurization did not change the effectiveness of HHP treatment on both bacteria in studied juices. Pulse pressure treatment (multiple pulses for a total holding time of 5 min at 300 MPa) instead of continuous (single pulse) treatment had no significant (p>0.05) effect on the microbial inactivation in kiwifruit juice; however, in pineapple juice pulse treatment, especially after 5 pulses, increased the inactivation significantly (p<0.05) for both bacteria. Following storage of pressure-treated (350 MPa, 20 degrees C for 60 s x 5 pulses) juices at 4, 20 and 37 degrees C up to 3 weeks, the level of microbial inactivation further increased and no injury recovery of the bacteria were detected. This work has shown that HHP treatment can be used to inactivate E. coli and L. innocua in kiwifruit and pineapple juices at lower pressure values at room temperature than the conditions used in commercial applications (>400 MPa). However, storage period and temperature should carefully be optimized to increase the safety of HHP treated fruit juices.     

Applying chemical engineering concepts to non-thermal plasma reactors

Process scale-up remains a considerable challenge for environmental applications of non-thermal plasmas.Undersanding the impact of reactor hydrodynamics in the performance of the process is a key step to overcome this challenge.In this work,we apply chemical engineering concepts to analyse the impact that different non-thermal plasma reactor configurations and regimes,such as laminar or plug flow,may have on the reactor performance.We do this in the particular context of the removal of pollutants by non-thermal plasmas,for which a simplified model is available.We generalise this model to different reactor configurations and,under certain hypotheses,we show that a reactor in the laminar regime may have a behaviour significantly different from one in the plug flow regime,often assumed in the non-thermal plasma literature.On the other hand,we show that a packed-bed reactor behaves very similarly to one in the plug flow regime.Beyond those results,the reader will find in this work a quick introduction to chemical reaction engineering concepts.     

A differential inclusion approach for modeling and analysis of dynamical systems under uncertainty

In this paper we deal with the application of differential inclusions to modeling nonlinear dynamical systems under uncertainty in parameters. In this case, differential inclusions seem to be better suited to modeling practical situations under uncertainty and imprecision than formulations by means of fuzzy differential equations. We develop a practical algorithm to approximate the reachable sets of a class of nonlinear differential inclusion, which eludes the computational problems of a previous set-valued version of the Heun’s method. Our algorithm is based on a complete discretization (time and state space) of the differential inclusion and it suits hardware features, handling the memory used by the method in a controlled fashion during all iterations. As a case of study, we formulate a differential inclusion to model an epidemic outbreak of dengue fever under Cuban conditions. The model takes into account interaction of human and mosquito populations as well as vertical transmission in the mosquito population. It is studied from the theoretical point of view to apply the Practical Algorithm. Also, we estimate the temporal evolution of the different human and mosquito populations given by the model in the Dengue 3 epidemic in Havana 2001, through the computation of the reachable sets using the Practical Algorithm.     

Electroseparation of an antibacterial peptide fraction from snow crab by-products hydrolysate by electrodialysis with ultrafiltration membranes

Recently, a snow crab by-products hydrolysate has demonstrated antibacterial properties due to a peptide with a molecular weight of about 800 Da, but only at high concentration. Consequently, peptide hydrolysate has been fractionated to obtain peptides in a more purified form. The aim of this work was to separate a snow crab by-products hydrolysate by electrodialysis with ultrafiltration membranes (EDUF). EDUF, which allows separation of molecules according to their charges and molecular weights, was used to recover and concentrate the active antibacterial fraction. Two different ultrafiltration membranes (20 and 50 kDa) and two electrical field strengths (2 and 14 V/cm) were used as separation parameters. After EDUF separation, the 300-600 Da peptide molecular weight range was the most recovered with an abundance of 94%. Moreover, fractionation at 14 V/cm with ultrafiltration membranes of 50 kDa allowed the recovery of an anionic fraction which showed antibacterial properties on Escherichia coli ATCC 25922 and Listeria innocua HPB 13.     

A cross‐cultural comparison of colour emotion for two‐colour combinations

Psychophysical experiments were conducted in the UK, Taiwan, France, Germany, Spain, Sweden, Argentina, and Iran to assess colour emotion for two‐colour combinations using semantic scales warm/cool, heavy/light, active/passive, and like/dislike. A total of 223 observers participated, each presented with 190 colour pairs as the stimuli, shown individually on a cathode ray tube display. The results show consistent responses across cultures only for warm/cool, heavy/light, and active/passive. The like/dislike scale, however, showed some differences between the observer groups, in particular between the Argentinian responses and those obtained from the other observers. Factor analysis reveals that the Argentinian observers preferred passive colour pairs to active ones more than the other observers. In addition to the cultural difference in like/dislike, the experimental results show some effects of gender, professional background (design vs. nondesign), and age. Female observers were found to prefer colour pairs with high‐lightness or low‐chroma values more than their male counterparts. Observers with a design background liked low‐chroma colour pairs or those containing colours of similar hue more than nondesign observers. Older observers liked colour pairs with high‐lightness or high‐chroma values more than young observers did. Based on the findings, a two‐level theory of colour emotion is proposed, in which warm/cool, heavy/light, and active/passive are identified as the reactive‐level responses and like/dislike the reflective‐level response. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2012     

Bulk and Surface Properties of Liquid Al-Li and Li-Zn Alloys

Physicochemical properties like density, surface tension, and viscosity of liquid binary Al-Li and Li-Zn alloys have been measured using draining crucible method. The experimentally measured surface-tension values have been compared to theoretical results based either on the Butler model or the compound formation model assuming the existence of the most favored A ₁ B ₂ and A ₂ B ₃ clusters. Several models for viscosity calculation have been also applied and discussed in confrontation with measured data. Finally, the clustering effects in the liquid Al-Li and Li-Zn alloys have been examined using two microscopic functions, i.e., the concentration fluctuation function in the long-wavelength limit and the Warren-Cowley short-range order parameter.     

Towards a Practical and Efficient Copper-Catalyzed Trifluoromethylation of Aryl Halides

The first copper-catalyzed trifluoromethylation of aryl halides was developed that utilizes inexpensive trifluoroacetates. Providing low concentrations of the most economically attractive and atom-efficient trifluoromethylation reagent this new protocol is advantageous compared to known procedures both economically and ecologically.