Lignin‐polyethylene glycol matrices and ethylcellulose to encapsulate highly soluble herbicides

The blending of lignin with polyethylene glycol (PEG) allowed us to obtain formulations with controlled release properties in which metribuzin have been successfully trapped with encapsulation efficiency higher than 85%. Moreover, the modification of the lignin's viscoelastic properties by the addition of PEG led to obtain herbicide formulations with active ingredient contents lower than 15%, suitable for its application in soil. Fourier transformed infrared spectroscopy and differential scanning calorimetry studies indicated the compatibility between polymers and metribuzin in lignin‐based controlled release formulations (CRFs). Lignin‐based formulations were coated in a Wurster‐type fluidized‐bed equipment using ethylcellulose and dibutylsebacate. Scanning electron microscope pictures showed a homogeneous film in ethylcellulose‐coated CRFs. The kinetic release studies showed that the release rate of metribuzin was mainly controlled either by selecting the granule size of controlled release lignin‐PEG matrixes, or by changing the thickness of coating film for ethylcellulose coated CRFs. These results could help to increase the efficiency of delivery of the highly soluble herbicide metribuzin and prevent the environmental pollution derived from its use. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41422.     

Modeling P(3HB) production by Bacillus megaterium

BACKGROUND: The poly(3‐hydroxybutyrate)—P(3HB)—is a polyester synthesized by many bacteria and stored as an energy reserve material in the cell cytoplasm as water‐insoluble inclusions. The aim of this research was to present a mathematical modeling approach in order to describe the culture kinetics of the bacterium Bacillus megaterium for the production of poly(3‐hydroxybutyrate). RESULTS: Four different models were proposed, differing in the expressions used for specific growth and polymer production rates. The predictions of these models were compared with experimental data and against the results of other models reported in the literature. CONCLUSION: Analysis of the experimental data under controlled and uncontrolled pH conditions showed that the inclusion of a correction factor for products formation, as well as a term related to the influence of H⁺ cations, are important for the correct modeling of this bioprocess. Compared with earlier models reported in the literature the proposed models show better fitting, with less or equal numbers of parameters, and provide parameter estimates with much lower variability. Copyright © 2011 Society of Chemical Industry     

Septic arthritis caused by Streptococcus pneumoniae

BACKGROUND: Streptococcus pneumoniae is an uncommon agent of infective arthritis. In this report three cases of pneumococcal arthritis are described. METHODS: Retrospective review of synovial fluids processed in our laboratory yielding bacteria. The study period was from January 1991 to December 1995. The clinical records of patients with the clinical and microbiological diagnosis of septic arthritis were reviewed. RESULTS: Twenty-eight out of a total of 43 clinical records had the clinical and microbiological diagnosis of septic arthritis and three (11%) were caused by Streptococcus pneumoniae. The infective source in two of these three cases was probably the respiratory tract, and the most common location was the knee. CONCLUSIONS: In our cases immunosuppression seemed to be the major risk factor involved in the development of pneumococcal arthritis.     

High stability of Ce-promoted Ni/Mg-Al catalysts derived from hydrotalcites in dry reforming of methane

Ce-promoted Ni/Mg-Al catalysts were synthesized by means of a methodology that involves the doping of Ni-Mg-Al mixed oxides derived from hydrotalcites with [Ce(EDTA)]⁻ and subsequent thermal decomposition. The effect of the nominal load of Ce in the catalytic performance of the materials was studied. The solids were characterized by means of XRD, BET area, TPR-H₂, TPD-CO₂, chemical analysis by ICPs, TGA, SEM and TEM and were evaluated in CO₂ reforming of methane at 700 °C. The results indicate the partial reconstruction of the periclase phase during the doping with [Ce(EDTA)]⁻ and the formation of a mixture of crystalline periclase and fluorite phases after the calcination. Catalysts with particle sizes of Ni⁰ between 5 and 9 nm were obtained. Ce presents a promote effect in the degree of reduction of Ni and the amount and strength of the basic sites. It was evident a beneficial effect of cerium in the catalytic activity and selectivity of the doped materials. The increase of the nominal Ce load between 1 and 10% causes no considerable effect in the catalytic activity and selectivity or in the size of crystallite in these materials but in the inhibition of the coke formation. The catalysts show excellent catalytic performance under drastic conditions of reaction and long operation times. The Ce-doped Ni/Mg-Al catalyst is stable up to 100 h of reaction using a feed mixture of CH₄/CO₂/He 10/10/80 at 24 L g⁻¹ h⁻¹, up to 20 h of reaction using CO₂/CH₄ 20/20 at 48 L g⁻¹ h⁻¹ and up to 15 h of reaction using CO₂/CH₄ 40/40 at 96 L g⁻¹ h⁻¹. The filamentous coke formation is demonstrated on the surface of the catalyst when gas of dilution in the reactants is not used. The developed method of synthesis becomes an interesting methodology for obtaining catalysts for CO₂ reforming of methane.     

Hot-Corrosion Studies of Separator Plates of AISI-310 Stainless Steels in Molten-Carbonate Fuel Cells

The corrosion behavior of a stainless steel 310S was investigated in amolten carbonate electrolyte at 650°C. The LiFeO₂ andLiCrO₂ oxides were formed in contact with the eutectic 62 mol%Li₂CO₃–38 mol% K₂CO₃mixture. Despite the low solubility of these oxides, the presence offissures in the LiFeO₂ layer does not provide good protection ofthe metallic material. The electrochemical-impedance spectroscopy (EIS)technique has shown low values of polarization resistance up to 80 hr and anincrease of the electrolyte resistance because of the dissolution of part ofthe scale after immersion. A mechanism for the corrosion of stainless steel310S in molten carbonates is proposed between 0 and 80 hr, taking intoaccount thermodynamic simulations, X-ray diffraction (XRD), scanningelectron microscopy (SEM) characterizations, and ac-impedance (EIS)results. This mechanism confirms a high corrosion rate and nonprotectivescale formation during the first hours of immersion. An external anddiscontinuous iron-rich oxide layer covered by a thin chromium-rich oxidelayer and an intermediate chromium-rich oxide and an internal spinel layerwere observed. Internal oxidation of the substrate also occurred to form(Fe, Cr)₂O₃ oxide. The dissolution in the melt of apart of the scale has been detected by EIS.     

The role of surface reactions on the active and selective catalyst design for bioethanol steam reforming

In order to study the role of surface reactions involved in bioethanol steam reforming mechanism, a very active and selective catalyst for hydrogen production was analysed. The highest activity was obtained at 700 °C, temperature at which the catalyst achieved an ethanol conversion of 100% and a selectivity to hydrogen close to 70%. It also exhibited a very high hydrogen production efficiency, higher than 4.5 mol H₂ per mol of EtOH fed. The catalyst was operated at a steam to carbon ratio (S/C) of 4.8, at 700 °C and atmospheric pressure. No by-products, such as ethylene or acetaldehyde were observed. In order to consider a further application in an ethanol processor, a long-term stability test was performed under the conditions previously reported. After 750 h, the catalyst still exhibited a high stability and selectivity to hydrogen production. Based on the intermediate products detected by temperature programmed desorption and reaction (TPD and TPR) experiments, a reaction pathway was proposed. Firstly, the adsorbed ethanol is dehydrogenated to acetaldehyde producing hydrogen. Secondly, the adsorbed acetaldehyde is transformed into acetone via acetic acid formation. Finally, acetone is reformed to produce hydrogen and carbon dioxide, which were the final reaction products. The promotion of such reaction sequence is the key to develop an active, selective and stable catalyst, which is the technical barrier for hydrogen production by ethanol reforming.     

Immobilization of zirconocene within silica–tungsten by entrapment: Tuning electronic effects of the support on the supported complex

The immobilization of Cp₂ZrCl₂ was performed by entrapment within the binary oxide SiO₂–WO₃ using a non-hydrolytic sol–gel route. The catalyst and oxide matrix were characterized by complementary techniques (Rutherford backscattering spectrometry, ultraviolet–visible diffuse reflectance and infrared transmission spectroscopy, differential pulse voltammetry, adsorption–desorption of N₂, and X-ray diffraction). The catalyst performance in terms of catalytic activity and polymer properties was evaluated by ethylene polymerization. Catalyst characterization suggested that the entrapped complex exhibited lower Zr electronic density than the corresponding unsupported metallocene. The polymerization results also revealed that this low Zr electronic density is optimized in terms of complex activation with low MAO concentration (low [Al/Zr] ratio) and reactivity. This fine tuning results in a catalyst system that is active with a low [Al/Zr] ratio and that achieves high catalytic activity. The results demonstrate that the entrapping method allows the generation of a catalyst system in which part of the activation process is attributed to the support. In this sense, the support may partially play MAO functions by stabilizing the active catalytic species.     

Trustworthy Privacy-Preserving Car-Generated Announcements in Vehicular Ad Hoc Networks

Vehicular ad hoc networks (VANETs) allow vehicle-to-vehicle communication and, in particular, vehicle-generated announcements. Provided that the trustworthiness of such announcements can be guaranteed, they can greatly increase the safety of driving. A new system for vehicle-generated announcements is presented that is secure against external and internal attackers attempting to send fake messages. Internal attacks are thwarted by using an endorsement mechanism based on threshold signatures. Our system outperforms previous proposals in message length and computational cost. Three different privacy-preserving variants of the system are also described to ensure that vehicles volunteering to generate and/or endorse trustworthy announcements do not have to sacrifice their privacy.     

Single cell study of electrodeposited cathodic electrodes based on Pt-WO3 for polymer electrolyte fuel cells

Cathodic electrodes based on electrodeposited Pt-WO₃ material for proton exchange membrane fuel cells (PEMFC) were studied in single cell configuration. Preparation of the electrodes was carried out by electrodeposition of Pt and WO₃ on commercial gas diffusion layer substrates (microporous carbon black layer on carbon cloth, ELAT E-TEK). The process of simultaneous electrodeposition of Pt and WO₃ is first analyzed from voltammetric curves. It is observed that the deposition of Pt is enhanced when WO₃ is present. Compositional analysis of the electrodes shows metallic platinum and WO₃ in variable proportions. The electrodeposited electrodes were characterized in single PEMFC. Membrane-electrode assemblies were prepared with Nafion^® 117 electrolyte membrane and a standard Pt/C anode. Pt-WO₃ electrodes showed enhanced stability and good response in single cell up to 1500 h. Performance degradation is attributed to a decrease in Pt electroactive area and increase of the internal resistance of the cell. These effects are possibly a consequence of the production of mobile tungsten species, like soluble WO₂ at high current demands and low cathode potentials.