Tape casting of strontium and cobalt doped lanthanum chromite suspensions

Lanthanum chromite (LaCrO₃) is currently the most widely studied material as interconnector layers for solid oxide fuel cells (SOFC). The complexity of microstructures and geometries of SOFC devices, which are usually built-up by lamination of the different constitutive layers, make it necessary a precise control of processing parameters to achieve the desired combination of properties. Much effort has been devoted to the processing of electrodes and electrolytes but the other layers, such as that of interconnecting material, have received scarce attention. This work deals with the preparation and optimisation of the rheological behaviour of concentrated suspensions of Sr- and Co-doped LaCrO₃ and the subsequent tape casting to produce homogeneous thin sheets to be used in the SOFC stack.The starting powder was produced by combustion synthesis from the corresponding nitrates and urea as a fuel, and had a final composition of La_0.80Sr_0.20Cr_0.92Co_0.08O₃. These powders were dispersed in ethanol with commercial copolymers (Hypermer, KD6) to solids loading of up to 58 wt%. The binding system (BS) consisted of a mixture of a binder, polyvinyl butyral-co-vinyl alcohol-co-vinyl acetate (PVA-PVAc), and two plasticizers, polyethyleneglycol (PEG400) and benzylbutylphthalate (BBP). The effect of the binding system content and the binder-to-plasticizer ratio on the tape casting performance and the characteristics of the green and the sintered tapes, were studied, as well as the influence of the casting parameters (casting speed and blades height).     

Experimental design of the kinetic resolution of a key precursor of high‐value bioactive myo‐inositols by an immobilized lipase

BACKGROUND: The response surface methodology was successfully applied to the optimization of the reaction variables for the kinetic resolution of a precursor of high‐value myo‐inositols, ( ± )‐1,2‐O‐isopropylidene‐3,6‐di‐O‐benzyl‐myo‐inositol (( ± )‐1), by Novozym 435. The resolutions were run separately, with two acylating agents, ethyl acetate and vinyl acetate, in a solvent‐free system. The variables analyzed were reaction temperature, substrate concentration, water concentration and enzyme activity. A statistical model was employed for the evaluation of the influence of the variables on conversion and enantiomeric excess (ee). RESULTS: The optimal conditions for this resolution using vinyl acetate as acylating agent were 45 °C, 5 mg mL^?1 of substrate, 71 U of enzyme activity and 0%w/w of water concentration. The high conversion (49.2 %) and ee (>99%) reached in the chemoenzymatic synthesis of acylated product, L‐(?)‐5‐O‐Acetyl‐3,6‐di‐O‐benzyl‐1,2‐O‐isopropylidene‐myo‐inositol, secure the efficient synthesis of the D enantiomorph present in the original racemic mixture (( ± )‐1) as well. CONCLUSIONS: The use of the experimental design strategy was productive, leading to a 14‐fold increase in the productivity of the reaction compared with the non‐optimized conditions. Both derivative L‐(?)‐2 and remaining substrate D‐(+)‐1 were obtained at high ee. © 2012 Society of Chemical Industry     

On the Mediation of Everything: ICA Presidential Address 2008

As our field moves beyond the traditional dualism of mass and interpersonal forms of communication to encompass new, interactive, networked forms of communication whose influence may be traced across multiple spheres of modern life, it is commonly claimed that "everything is mediated" and that this represents a historically significant change. This article inquires into these rhetorically grand claims: first, noting the parallels with other processes of mediation (e.g., language, money, and myths); second, raising questions of value since, unlike for other forms of mediation, the media's role is typically construed as negative rather than positive; and third, observing that the difficulties of translating "mediation" into a range of languages reveals some conceptual confusions. As a step toward clarification, I contrast the terms "mediation" and "mediatization," these roughly mapping onto situational and historical influences, conceived primarily at micro- and macrolevels of analysis, respectively. I then argue for a broad conception of mediation that encompasses those processes variously referred to as "mediatization,""mediazation," or "medialization." The analysis is illustrated by unpacking the claim that "childhood is mediated," before concluding that distinct aspects of the concept of mediation invite communication scholars to attend to the specific empirical, historical, and political implications of the claim that "everything is mediated."     

Imaging the proteins pseudoazurin and apo-pseudoazurin on gold by STM in air: effect of the bias voltage

We have applied scanning tunnelling microscopy (STM) to the study of two proteins: pseudoazurin and apo-pseudoazurin. Both proteins adsorbed onto a Au (1 1 1) surface are visible to STM individually, forming into layers and multilayers, with currents from about 55 to 600 pA. The images reproduce well the expected dimensions laterally but not in the z direction. The apparent height of the proteins varies with the voltage polarity, being higher at negative sample voltages. The bias also affects their shape. Negative sample voltages of more than 1.5 V orient the proteins present on a gold terrace in parallel rows. The layer of water adsorbed on surfaces in ambient conditions can be related to our results to explain the reduced z dimensions, the asymmetry with the voltage polarity and the alignment of proteins at voltages more negative than -1.5 V.     

Optimal Layout of Sewer Systems: A Deterministic versus a Stochastic Model

The optimization of a new or partially existing urban drainage system may be modeled as a subproblems sequence of layout and optimal design within the discrete search space. The design optimization, incorporating the optimal selection of the pumping stations, intermediate manholes, pipe sections, and installation depths, for a general system fixed layout in plan, is a high level sequential decision problem which may be efficiently solved deterministically through a multilevel dynamic programming model. The optimal general layout may be selected in a deterministic way by means of a simple economical comparison of all plan solutions having optimized designs, for small to medium sized systems (if the specific restrictions of the applications are appropriately exploited) in practicable computer time. For larger dimension networks, where it is clearly impossible to achieve plan optimization with full enumeration (which is a NP complete), stochastic search models can be used. For the subproblem layout, an effective enumeration model is presented; the results of a stochastic model proposed previously, using simulated annealing for an application example, are compared and discussed in detail.     

Prevalence of Clostridium botulinum in food raw materials used in REPFEDs manufactured in France

Food raw materials used in refrigerated processed foods of extended durability (REPFEDs) manufactured in France were surveyed for Clostridium botulinum types A, B and E using PCR-Enzyme-linked Immunosorbent assay (PCR-ELISA) and mouse bioassay for detection respectively of cells and toxins in enrichment broth. Portions of 25 to 50 g of food were analysed. A total of 8 out of the 102 samples of fish and shellfish, 12 out of the 143 samples of meat and poultry, 1 out of the 62 samples of aroma, sauce and gravy, 4 out of the 25 samples of thickening agents, 3 out of the 26 samples of dehydrated dairy ingredients, and none of the 65 samples of spices, herbs and dehydrated mushroom were positive for C. botulinum in PCR-ELISA, i.e., 6.6% of all the samples tested. The 28 positive samples comprised 10 type A, 10 type B, 4 with both types A and B, and 4 undetermined by PCR typing. No sample positive for type E was detected. Of the 28 samples positive in PCR-ELISA, 15 were also positive in the mouse bioassay. The MPN count was between 1 and 3 C. botulinum/kg of food, which is similar to or in the lower range of values reported in the literature.     

A new procedure for treatment of oily slurry using geotextile filters

A new procedure to mitigate the environmental impacts and reduce the cost of disposal of oil slurry is present in this paper. Waste from the petroleum industry has a high environmental impact. Systems for oil–water separation have been used to mitigate the contamination potential of these types of effluents. At the outlet of these systems, the oil is skimmed-off the surface, while the slurry is removed from the base. Due to the high concentration of contaminants, the disposal of this slurry is an environmentally hazardous practice. Usually this type of waste is disposed of in tanks or landfills after removal from the industrial plant. Basically, the proposed procedure utilizes drying beds with geotextile filters to both reduce the water content in the slurry and obtain a less contaminated effluent. Laboratory tests were carried out to simulate the drying system. Four types of filters were analyzed: two non-woven geotextiles, one woven geotextile, and a sand filter.     

Functionalized silicon membranes for selective bio-organism capture

Membranes with various pore size, length, morphology and density have been synthesized from diverse materials for size-exclusion-based separation. An example is the sterilization of intravenous lines by exclusion of bacteria and viruses using polyvinylidene fluoride membranes with 0.1-microm-diameter pores. Chemically specific filtration has recently been addressed for small molecules. Nevertheless, specific bio-organism immobilization and detection remains a great technical challenge in many biomedical applications, such as decontamination or analysis of air and liquids such as drinking water and body fluids. To achieve this goal, materials with controlled pore diameter, length and surface chemistry are required. In this letter, we present the first functionalized silicon membranes and demonstrate their ability to selectively capture simulated bio-organisms. These extremely versatile and rigid devices open the door to a new class of materials that are able to recognize the external fingerprints of bio-organisms-such as size and outer membrane proteins-for specific capture and detection applications.     

Chemical Ecological Characteristics of Herbivory of Siparuna guianensis Seeds by Buffy-Headed Marmosets (Callithrix flaviceps) in the Atlantic Forest of Southeastern Brazil

The buffy-headed marmoset (Callithrix flaviceps) is apparently the only predispersal herbivore of the seeds of Siparuna guianensis at the Caratinga Biological Station in southeastern Brazil. Both the fruit receptacles and the frutioles (seeds) of S. guianensis are relatively rich in nutrients such as carbohydrates, proteins, and lipids, but the receptacles contain high concentrations of benzylisoquinoline alkaloids. The latter presumably act as a qualitative chemical defense, impeding the access of potential predators to the alkaloid-poor frutioles. However, on ripening, the receptacle splits open, exposing the frutioles, which enables C. flaviceps to avoid the plant's chemical defenses effectively. Taking care to avoid contact with the receptacle, the marmosets pluck out the frutioles and ingest the seeds. Qualitative and quantitative changes (in particular a significant reduction in daily ranging) in the marmosets' behavior during the period when S. guianensis frutioles were accessible indicate that this was a preferred plant resource. This is the first record of the consumption of S. guianensis seeds by callitrichine monkeys (which are not known to be systematic seed eaters), despite the fact that both are widely distributed in the Neotropics. It is thus possible that the behavioral strategy observed here is a unique phenomenon resulting from a specific combination of factors, including the abundance of S. guianensis within the study area. The lack of other records may nevertheless be a result of insufficient sampling effort, in which case, the feeding strategies of callitrichines may have an important influence on the reproductive biology of S. guianensis in many areas.     

DC-Amplifier-Input-Offset-Voltage Control in a Constant-Temperature Thermoresistive-Sensor-Measurement Instrument

In this paper, the effect of dc amplifier input offset voltage on the static and dynamic performances of a generic constant-temperature thermoresistive-sensor-feedback circuit (CTC) is reviewed. A negative-feedback automatic control circuit for the input offset voltage is proposed in order to assure a stable operation of the CTC and to obtain optimal response time. Experimental evaluation results of the proposed circuit performance are presented