Passivation of a Co–Ru/γ-Al2O3 Fischer–Tropsch catalyst

Passivation of highly dispersed metal catalysts after reduction is necessary prior to exposure to air due to the exothermicity of metal oxidation. This exothermicity can result in a significant increase in temperature of the catalyst resulting in catalyst degradation and a potential fire hazard. This paper reports the results of a study of passivation of Ru-promoted Co/alumina. Passivations using CO and CO+H₂ mixtures were compared to the standard method of passivation using small concentrations of O₂. Passivation by CO+H₂ resulted in a lower temperature rise upon exposure to air than oxygen passivation. Passivation using CO/H₂=10 resulted in a catalyst whose catalytic activity for CO hydrogenation was able to be recovered after exposure to air by re-reduction similar to after oxygen passivation. CO passivation yielded a catalyst that was not able to be as well recovered upon re-reduction, probably due to the formation of graphitic carbon. Exposure of the CO/H₂ passivated catalyst to air for at least 90 min actually made it easier to recover the original activity upon re-reduction. This is probably related to the oxidation of the carbidic passivation layer during air exposure.     

The gap in circumventing the impossibility of consensus

The impossibility of reaching deterministic consensus in an asynchronous and crash prone system was established for a weak variant of the problem, usually called weak consensus, where a set of processes need to decide on a common value in {0,1}, so that both 0 and 1 are possible decision values. On the other hand, approaches to circumventing the impossibility focused on a stronger variant of the problem, called consensus, where the processes need to decide on one of the values they initially propose (0 or 1). This paper studies the computational gap between the two problems. We show that any set of deterministic object types that, combined with registers, implements weak consensus, also implements consensus. Then we exhibit a non-deterministic type that implements weak consensus, among any number of processes, but, combined with registers, cannot implement consensus even among two processes. In modern terminology, this type has consensus power 1 and weak consensus power ∞.     

La théorie des jeux non-coopératifs appliquée aux réseaux de télécommunication

In this paper, we present various tools originating from non-cooperative Game Theory, which allow us to study competition situations in telecommunication networks. We describe the mathematical tools while providing examples from a variety of areas in telecommunication networks.     

Removal of Refractory Organic Compounds in Liquid Swine Manure Obtained from a Biofiltration Process Using an Electrochemical Treatment

Swine wastewaters contain varied and high amounts of organic matter (proteins, antibiotic compounds, organic acids) which are difficult to oxidize biologically or chemically. The discharge of such effluents is undesirable and can cause excessive oxygen demand in the receiving water. In order to produce an effluent suitable for stream discharge, electrochemical techniques have been explored at the laboratory pilot scale, for refractory residual organic compound removal in liquid swine manure (LSM) following a biofiltration process. Two types of electrolytic cells (monopolar and bipolar electrode cells) using aluminum and mild steel electrodes were studied. Effectiveness was measured in terms of chemical oxygen demand (COD) and biological oxygen demand (BOD) reduction. The amount of residue sludge produced and energy consumed have been also considered. Results showed that the best performances of COD and BOD removal from LSM were obtained using either aluminum bipolar (Al-BP) electrodes or mild steel monopolar (Fe-MP) electrodes operated at current intensities of 0.5 and 2.0?A, respectively, through 30?min of treatment. The COD removal yields varied from 65 to 68%, whereas BOD removal reached 87%. The optimal conditions determined for organic compound removal, including energy consumption and metallic sludge disposal, involved a total cost of only $0.24?and?$0.29?United?States/m3 of treated LSM. The treatment using the Fe-MP system was found to be more economical and practical than the chemical treatment using FeCl3 as a coagulating agent.     

Synthesis and characterization of polystyrene coated iron oxide nanoparticles and asymmetric assemblies by phase inversion

Films with a gradient concentration of magnetic iron oxide nanoparticles are reported, based on a phase inversion membrane process. Nanoparticles with ～13 nm diameter were prepared by coprecipitation in aqueous solution and stabilized by oleic acid. They were further functionalized by ATRP leading to grafted polystyrene brush. The final nanoparticles of 33 nm diameter were characterized by TGA, FTIR spectroscopy, GPC, transmission electron microscopy, and dynanmic light scattering. Asymmetric porous nanoparticle assemblies were then prepared by solution casting and immersion in water. The nanocomposite film production with functionalized nanoparticles is fast and technically scalable. The morphologies of films were characterized by scanning electron microscopy and atomic force microscopy, demonstrating the presence of sponge‐like structures and finger‐like cavities when 50 and 13 wt % casting solutions were, respectively, used. The magnetic properties were evaluated using vibrating sample magnetometer. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41368.     

EWOD-based chip characterization under AC voltage

This paper addresses one basic issue of EWOD chip as a consumable: how to detect the alteration of hydrophobic layers? We investigate the possibility of using droplet oscillations to finely characterize chip ability to EWOD protocols. Experiments are performed in coplanar electrodes configuration. Dedicated setup and software have been developed for a simple in situ characterization. When a low-frequency AC voltage is used, drop surface oscillations are created from the time-varying component of the normal electrostatic stress at drop surface near the contact line. As an analysis tool, our software is based on droplet contour detection and delivers dynamical contact angle and contact line motion. Careful attention is brought to surface wetting or dewetting of the droplet during long-term AC actuation and surface ageing.     

Antifouling activity of novel polyisoprene-based coatings made from photocurable natural rubber derived oligomers

Natural rubber is a renewable resource with a potential as precursor of a very wide range of novel polymers, including polyisoprene-based surfaces with antifouling (AF) activity. In this work, new ionic and non-ionic coatings were prepared by the photocrosslinking reaction of photosensitive cis-1,4-oligoisoprenes, bearing a variable number of ammonium groups. The photochemical crosslinking was achieved using radical (via acrylate groups) or cationic (via epoxy groups) processes. Surface properties of these coatings were studied by static contact angle measurements and AFM imaging. Assessment of bioactivity demonstrated that most of the resulting coatings showed AF potential against fouling organisms: growth inhibition of marine bacteria (Pseudoalteromonas elyakovii, Shewanella putrefaciens, Cobetia marina, Polaribacter irgensii, Vibrio aestuarianus) and fungi (Halosphaeriopsis mediosetigera, Asteromyces cruciatus, Lulworthia uniseptata, Zalerion sp., Monodictys pelagica); decreased adhesion of microalgae (Navicula jeffreyi, Cylindrotheca closterium, Chlorarachnion globosum, Pleurochrysis roscoffensis, Exanthemachrysis gayraliae, Amphora coffeaeformis); inhibition of attachment and/or germination of spores of Ulva intestinalis. The best AF activity was obtained with the ionic surfaces. These new coatings prepared from precursors obtained from natural rubber are in essence active by contact. As the biocidal functions are fixed covalently to the polymer chain, detectable release of biocidal products in the marine ecosystem is prevented so that a valuable environment-friendly alternative for new AF coatings is hereby proposed.     

Evaluation of different supplementary nutrients for enhanced biohydrogen production by Enterobacter aerogenes NRRL B 407 using waste derived crude glycerol

Crude glycerol (CG) has several advantages over a range of conventional substrates used for biohydrogen production by Enterobacter aerogenes NRRL B 407. Meanwhile, high process cost due to requirement of expensive supplementary media component is a concern. Therefore, different less expensive (or wastes) materials have been evaluated as supplementary nutrient for H₂ production by CG (meat processing and restaurant waste based biodiesel derived) bioconversion. Among the materials selected, slaughterhouse liquid waste (SL), brewery waste biomass (BWB) and urea was found to improve the production by 18.81 ± 3.56, 27.30 ± 3.54 and 38.57 ± 3.66%, respectively. Further, in the case of urea (10 mg/L), cumulative production as high as 116.41 ± 3.72 mmol H₂/L media has been achieved; which is comparable to other reports available on CG bioconversion. Thus, present study demonstrates successful replacement of large amount (∼5–6 g/L) of expensive nutrients/buffering agents by negligible amount (∼10 mg/L) of different waste materials, without compromising the cumulative H₂ yield. Further, the strain used in the present study was found to grow at an acidic pH as low as 3.3, indicating its prospective application for dark fermentative H₂ production.     

Comparison between two approximation methods of state space fractional systems

A large number of real dynamic systems are better characterized using a non-integer order dynamic model based on fractional order differential equations. Nevertheless, their analytical solutions are rather complicated. In this paper we present two alternative methods of simulation of the fractional order dynamical system in state space. We particularly present a comparison between two approximation methods. The first one is based on the differentiation operator approximation and thus uses the usual form of the state space representation D^(α)(x)=Ax+Bu. The second method is based on the approximation of the integration operator and uses, in this case, the new representation w=AI^(α)(w)+Bu. The comparison between these two methods is made on the basis of initial and steady state approximation state and output errors which are characterized in this present paper. Numerical examples are also given to support this comparison.     

Iron role in the electrochemical cyclopropanation reaction of activated olefins and halogenated compounds

The electrochemical procedure for cyclopropanation reaction between benzal chloride (BC) and dimethyl itaconate (DMI), using Cu(I) salt, iron rod as sacrificial anode, and low temperature (−10 °C < T < −5 °C), was investigated by cyclic voltammetry and electrolysis. The variation of the experimental parameters of electrolyses, such as the absence or the presence of CuBr during the pre-electrolysis step, or its substitution by an initial amount of iron salt (FeCl₂, FeBr₂ or FeI₂), and pyridine addition to the reaction medium showed that the presence of dissociated Fe(II) is essential to the cyclopropanation process. The Cu(I) salt is deposited on the cathode surface during the pre-electrolysis, providing the accumulation of Fe(II) in solution, which does not act as catalyst in the electrochemical process. The best cyclopropanation yield (81%) was reached in DMF/pyridine (9:1) in the presence of FeI₂ salt. A cyclopropanation mechanism involving two possible pathways was suggested, implying both an anionic and a radical BC intermediates.