Time Decay of the Activity of the Reduction Reaction of NO by CO on a Pd/Al2O3 Catalyst

An experimental study is made of the time decay of activity of the CO–NO reaction on a Pd/Al₂O₃ looking at the effect on reaction order and apparent activation energy. The optimum kinetics parameters fitting the steady state data at moderate pressures are determined. The time decay curves are analyzed through various catalyst deactivation models.     

Interconnected power systems with superconducting magnetic energy storage

The objective of this work is to discuss the concept of back‐to‐back interconnection systems with energy storage, especially with a Superconducting Magnetic Energy Storage (SMES) incorporated into a back‐to‐back DC link. In this case, each converter of the back‐to‐back system is used as a power conditioning system for the SMES coils. Since the AC–DC converter can be designed independently of the frequency of the power system, a two‐way switch is connected to the AC side of each converter. This two‐way switch can select the interconnected power systems. By using the two‐way switches, this system can provide the stored energy in the SMES system to each interconnected power system through two AC–DC converters. For instance, lower‐cost power of each power network can be stored through two converters during the off‐peak hours and made available for dispatch to each power network during periods of demand peak. Then this system increases the reliability of electric power networks and enables the economical operations depending on the power demand. This paper describes the unique operations of the back‐to‐back interconnection with SMES and discuses the optimal SMES configuration for a 300‐MW‐class back‐to‐back interconnection. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 37–43, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20482     

Dietetic study of pregnant women of Santa Maria Cauqué, Guatemala. I. Variability of protein indicators and analysis by the time of meals

The distribution of the protein energy ratio indicators (Pe%), amino acid score and protein value (NDpCal%) in the three daily meals (breakfast, lunch and dinner) of the diet of pregnant women from Santa María Cauqué, Guatemala, was studied. The results were compared with those obtained for the total daily food intake. The differences observed were not significant, confirming the validity of the determination of amino acid score, Pe% and NDpCal% in the foods consumed during the whole day in this type of populations. It also reflects the nutritional benefit of the food pattern, since protein utilization would not be decreased by a different distribution of protein quality and concentration throughout the three daily meals. The variability among individuals of Pe% intake, amino acid score and NDpCal% gave the following values: 16.0, 9.3 and 15.6, respectively. It is noteworthy to add that the variability of Pe% observed is similar to that reported for populations of developed countries.     

Physicochemical and Theoretical Characterization of a New Small Non-Metal Schiff Base with a Differential Antimicrobial Effect against Gram-Positive Bacteria

Searching for adequate and effective compounds displaying antimicrobial activities, especially against Gram-positive bacteria, is an important research area due to the high hospitalization and mortality rates of these bacterial infections in both the human and veterinary fields. In this work, we explored (E)-4-amino-3-((3,5-di-tert-butyl-2-hydroxybenzylidene)amino) benzoic acid (SB-1, harboring an intramolecular hydrogen bond) and (E)-2-((4-nitrobenzilidene)amino)aniline (SB-2), two Schiff bases derivatives. Results demonstrated that SB-1 showed an antibacterial activity determined by the minimal inhibitory concentration (MIC) against Staphylococcus aureus, Enterococcus faecalis, and Bacillus cereus (Gram-positive bacteria involved in human and animal diseases such as skin infections, pneumonia, diarrheal syndrome, and urinary tract infections, among others), which was similar to that shown by the classical antibiotic chloramphenicol. By contrast, this compound showed no effect against Gram-negative bacteria (Klebsiella pneumoniae, Escherichia coli, and Salmonella enterica). Furthermore, we provide a comprehensive physicochemical and theoretical characterization of SB-1 (as well as several analyses for SB-2), including elemental analysis, ESMS, ¹H and ¹³C NMR (assigned by 1D and 2D techniques), DEPT, UV-Vis, FTIR, and cyclic voltammetry. We also performed a computational study through the DFT theory level, including geometry optimization, TD-DFT, NBO, and global and local reactivity analyses.     

Flexible oligomeric silicon-containing poly(ether-azomethine)s obtained from epoxide derivatives. Synthesis and characterization

Three new diamines derived from epoxide compounds were synthesized. The preparation of diamine monomers implied the reaction between a phenoxyalkyloxirane (alkyl: H, methyl, isopropyl) and bisphenol A, obtaining the respective aliphatic diols, which produced the corresponding dinitro derivatives. Finally, these derivatives were reduced by using palladium/carbon activated as catalyst and hydrazine as a hydrogen source. Then, six oligomeric poly(ether-azomethine)s (PEAzMs) were obtained from a polycondensation reaction between the new diamines and bis(4-formylbiphenyl-4-yl)dialkylsilane (alkyl: methyl, phenyl) with 84–93% yields. The structural characterization of the diamines and PEAzMs was performed by elemental analysis, infrared spectroscopy, and nuclear magnetic resonance spectroscopy (¹H, ¹³C, and ²⁹Si). Furthermore, polymers were analyzed by solubility tests, gel permeation chromatography, ultraviolet–visible (UV–vis) spectroscopy, thermogravimetry, and differential scanning calorimetry analysis. The results showed PEAzMs with 2–11 repetitive units, where the design of the monomers allowed to obtain improved solution processability in comparison with previously reported silylated poly(azomethine)s and good thermal stability. Additionally, all samples showed high transparency in the UV–vis region. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48055.     

Flexible supercapacitor-like actuator with carbide-derived carbon electrodes

Soft and flexible electric driven transducers based on carbide-derived carbon (CDC), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF₄), polyvinylidenefluoride-co-hexafluoropropylene (PVdF(HFP)) are proposed, and electroactive performances of these materials are reported. By its nature, the synthesized device has two features when voltage is applied. Firstly, it is a bending-type electrochemical actuator. Besides the external change of shape, this device is also an electrochemical capacitor, providing opportunity to store a considerable amount of charge. Laminated actuators can work in open air at low voltages (1–3 V). Their operating frequency is between 5 × 10⁻³ – 1 × 10¹ Hz (it is from 5 millihertz to 200 hertz) and 10 Hz and the maximum strain calculated from transducer displacement is 0.6%. The gravimetric capacitance of CDC in actuator electrodes was found to be 119 F g⁻¹ at 1 mV s⁻¹ sweep rate of the applied triangle voltage. The effects of synthesis temperature of CDC and associated changes in the porosity and surface area on the actuator displacement are discussed. The results of this study demonstrated a great potential of CDC as an active material for actuator electrodes, especially in these applications where the performance of the actuator has to be standardized and highly predictable.     

Bacteriological evaluation of goat milk and cheese distributed in the Metropolitan Area of San José, Costa Rica

In the last years, there has been an increase in the production, industrialization and consumption of goat's milk and derivate products, including cheese, worldwide. Nevertheless, in Costa Rica there is no study of these products, reason why the objective of this work was to determine the microbiological characteristics of goat's milk and fresh cheese distributed in the Metropolitan Area of San José, Costa Rica, in order to evaluate its impact in the economical field and as a potential risk for Public Health. A total of 25 raw goat's milk samples, obtained by manual milking from 5 different producers tested in five different dates and 15 cheese samples, elaborated with pasteurized milk, commercially available and coming from three different producers were analyzed. The study included the analysis of spoilage bacteria (total aeobic count and lactic bacteria count), indicators of hygiene (total coliforms), fecal contamination (fecal coliforms), manipulation (Staphylococcus aureus) and pathogens (Listeria monocytogenes and Salmonella spp). High results were obtained for the total aerobic count and lactic bacteria count of the milk and cheese samples, showing a reduced shelf life. Total coliforms, in limits beyond the established ones by the Costa Rican legislation for human consumption raw milk, were found in 100% of milk samples, as well as for fecal coliforms in 76% of them. All cheese samples, except one, were negative for these indicators, suggesting good manufacturing practices. S. aureus counts were low and both Salmonella spp. and L. monocytogenes were not isolated from samples analyzed.     

Fabrication of bilayered YSZ/SDC electrolyte film by electrophoretic deposition for reduced-temperature operating anode-supported SOFC

Bilayered Y₂O₃-stabilized ZrO₂ (YSZ)/Sm₂O₃-doped CeO₂ (SDC) electrolyte films were successfully fabricated on porous NiO–YSZ composite substrates by electrophoretic deposition (EPD) based on electrophoretic filtration followed by co-firing with the substrates. In EPD, positively charged YSZ and SDC powders were deposited directly on the substrates, layer by layer from ethanol-based suspensions. Delamination between YSZ and SDC films was avoided by reducing the SDC films’ thickness to ca. 1 μm. A single cell was constructed on the bilayered electrolyte films composed of ca. 4 μm-thick YSZ and ca. 1 μm-thick SDC films. As a cathode in the cell, La_0.6Sr_0.4Co_0.2Fe_0.8O_3−x (LSCF) was used. Maximum output power densities greater than 0.6 W cm⁻² were obtained at 700 °C for the bilayered YSZ/SDC electrolyte cells thus constructed.     

天生桥一级水电站混凝土面板堆石坝位移监测

天生桥一级电站混凝土面板堆石坝的填筑坝体位移监测通过水管式沉降仪和水平位移计进行。坝本内安装了５０支水管式沉降仪（瑞曲盒式）、３１支水平位移计（钢丝型伸缩仪）和２８支总压力计。监测结果表明，施工期末（１９９９年３月）最大坝体沉降是２．９４ｍ，相当于坝体高度的１．７％，施工期末堆石坝变形模量Ｅｒｃ平均４５ＭＰａ，为最大坝体变形，促使上游边坡出现裂缝以及面板浇筑前上游边坡明显沉降。