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171.
J. M. Mora-Hernández A. Ezeta-Mejía C. Reza-San Germán S. Citalán-Cigarroa E. M. Arce-Estrada 《Journal of Applied Electrochemistry》2014,44(12):1307-1315
A PdCo catalyst with an atomic ratio of 2:1 was synthesized from elemental powders by mechanical alloying. The structural characterization and composition of the catalyst were determined by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Both the electrocatalytic activity of the catalyst for oxygen reduction in acidic media, as well as attempts to support it on Vulcan XC-72 carbon powder and carbon nanospheres were evaluated by cyclic voltammetry, rotating disc electrode and rotating ring-disk electrode techniques. The X-ray diffraction studies indicated that an intermetallic PdCo compound with an average crystallite size of 25 nm was obtained. According to kinetic and thermodynamic parameters, the electrocatalytic activity of the catalyst toward oxygen reduction was determined as PdCo/CNS > PdCo/C with first-order kinetics, a four-electron multielectronic transference pathway, and a negligible amount of hydrogen peroxide produced. Activation energy values of 40 ± 1 kJ mol?1 and 68 ± 1 kJ mol?1 were determined for reactions with PdCo/CNS and PdCo/C, respectively. 相似文献
172.
José M. Soria Mariana T. Zambon Germán D. Mazza 《American Institute of Chemical Engineers》2012,58(2):412-426
The transient process of heat transfer between a high‐temperature emulsion packet and the wall of an immersed surface is simulated using computational fluid dynamics (CFD). From these simulations, the total heat transfer coefficient and its radiant contribution due to the emulsion (dense) phase are evaluated. The results are compared with experimental data (Ozkaynak et al., “An experimental investigation of radiant heat transfer in high temperature fluidized beds,” in Fluidization IV, 1983:371–378) and with predicted values from the generalized heterogeneous model (GHM), (Mazza et al., “Evaluation of overall heat transfer rates between bubbling fluidized beds and immersed surfaces,” Chem Eng Commun., 1997;162:125–149). The CFD simulations are in good agreement with both, experimental data and theoretical GHM predictions and provide a reliable way to quantify the studied heat transfer process. Also, the GHM is validated as a practical tool to this end. © 2011 American Institute of Chemical Engineers AIChE J, 58: 412–426, 2012 相似文献
173.
Meichtri L Miliwebsky E Gioffré A Chinen I Baschkier A Chillemi G Guth BE Masana MO Cataldi A Rodríguez HR Rivas M 《International journal of food microbiology》2004,96(2):189-198
Between July 1999 and December 2000, the prevalence of Shiga toxin-producing Escherichia coli (STEC) was established in 200 Argentine healthy young beef steers (14-16 months old) grown under local production systems with a feed grain period of 3-4 months, and the STEC strains isolated were examined in regard to their phenotypic and genotypic characteristics. Stool samples (n = 70) and rectal swabs (n = 130) were taken at the slaughterhouse level. By polymerase chain reaction (PCR), Shiga toxin (stx) gene sequences were detected in 69% of the samples. Eighty-six STEC strains were isolated from 39% of the animals. Serogroups identified, in order of frequency, were: O8 (16 strains), O113 (14), O103 (5), O91 (4), O171 (3), O174 (3), O25 (2), O112 (2), O145 (2), O2, O11, O104, O121, O128, O143, O146, O157. The most frequent serotype isolated was O8:H19 (12.9%). A total of 17 serotypes, including E. coli O157:H7 found in one animal (0.5%), have been previously associated with hemolytic uremic syndrome (HUS), bloody and non-bloody diarrhea in different countries, including Argentina. The prevalent genotype isolated was stx2 (51 of 86, 59.3%). Subtyping of stx2 variants showed the prevalence of stx2vh-b (25.6%) and stx2vh-a types (24.4%), and revealed the presence of an atypical stx2-v. Only 7.0% of STEC strains carried eae, and 33.7% harbored EHEC-hlyA gene. The full virulent genotype (stx/eae/EHEC-hlyA) was found to be present in 4 of the 86 (4.7%) STEC strains isolated. This research indicates that young steers from the main beef-producing area of Argentina are an important reservoir of STEC strains; however, its importance as agents of human diseases in our country has still to be established. 相似文献
174.
Mora-Seró I Bisquert J Fabregat-Santiago F Garcia-Belmonte G Zoppi G Durose K Proskuryakov Y Oja I Belaidi A Dittrich T Tena-Zaera R Katty A Lévy-Clément C Barrioz V Irvine SJ 《Nano letters》2006,6(4):640-650
Four different types of solar cells prepared in different laboratories have been characterized by impedance spectroscopy (IS): thin-film CdS/CdTe devices, an extremely thin absorber (eta) solar cell made with microporous TiO2/In(OH)xSy/PbS/PEDOT, an eta-solar cell of nanowire ZnO/CdSe/CuSCN, and a solid-state dye-sensitized solar cell (DSSC) with Spiro-OMeTAD as the transparent hole conductor. A negative capacitance behavior has been observed in all of them at high forward bias, independent of material type (organic and inorganic), configuration, and geometry of the cells studied. The experiments suggest a universality of the underlying phenomenon giving rise to this effect in a broad range of solar cell devices. An equivalent circuit model is suggested to explain the impedance and capacitance spectra, with an inductive recombination pathway that is activated at forward bias. The deleterious effect of negative capacitance on the device performance is discussed, by comparison of the results obtained for a conventional monocrystalline Si solar cell showing the positive chemical capacitance expected in the ideal IS model of a solar cell. 相似文献