Precipitation of an ordered intermetallic phase in WC-10% Ni

The cause of the variability of the intensity of magnetization of the nickel binder phase in cemented carbides was sought by electron diffraction and dark-field microscopy studies of fractured specimens, one of which was partially magnetic and the other almost non-magnetic. A coherent phase in the nickel binder having either a b c c or a CsCI-type structure was found on the boundaries of crack paths. A coherent non-randomly arranged CsCI-type phase was found in an epitaxial relationship with (12.0) planes of WC. The lattice parametera=0.295 nm for both coherent phases. This phase or phases occurs more frequently in non-magnetic than in magnetic nickel binders of hardmetals. When seen near WC grains the ordered phase is often accompanied by randomly arranged tungsten trioxide particles. The implication is that the ordered phase occurs more readily in carbon-deficient surroundings. The phase is postulated to be NiW because large quantities of tungsten are known to form solid solutions with nickel.     

Floc-based sequential partial nitritation and anammox at full scale with contrasting N2O emissions

New Activated Sludge (NAS^®) is a hybrid, floc-based nitrogen removal process without carbon addition, based on the control of sludge retention times (SRT) and dissolved oxygen (DO) levels. The aim of this study was to examine the performance of a retrofitted four-stage NAS^® plant, including on-line measurements of greenhouse gas emissions (N₂O and CH₄). The plant treated anaerobically digested industrial wastewater, containing 264 mg N L⁻¹, 1154 mg chemical oxygen demand (COD) L⁻¹ and an inorganic carbon alkalinity of 34 meq L⁻¹. The batch-fed partial nitritation step received an overall nitrogen loading rate of 0.18-0.22 kg N m⁻³ d⁻¹, thereby oxidized nitrogen to nitrite (45-47%) and some nitrate (13-15%), but also to N₂O (5.1-6.6%). This was achieved at a SRT of 1.7 d and DO around 1.0 mg O₂ L⁻¹. Subsequently, anammox, denitrification and nitrification compartments were followed by a final settler, at an overall SRT of 46 d. None of the latter three reactors emitted N₂O. In the anammox step, 0.26 kg N m⁻³ d⁻¹ was removed, with an estimated contribution of 71% by the genus Kuenenia, which constituted 3.1% of the biomass. Overall, a nitrogen removal efficiency of 95% was obtained, yielding a dischargeable effluent. Retrofitting floc-based nitrification/denitrification with carbon addition to NAS^® allowed to save 40% of the operational wastewater treatment costs. Yet, a decrease of the N₂O emissions by about 50% is necessary in order to obtain a CO₂ neutral footprint. The impact of emitted CH₄ was 20 times lower.     

Non-digestible fraction of cooked bean (Phaseolus vulgaris L.) cultivar Bayo Madero suppresses colonic aberrant crypt foci in azoxymethane-induced rats

The non-digestible fraction (NDF) of common bean (Phaseolus vulgaris L.) cultivar Bayo Madero was evaluated for its chemopreventive effect on azoxymethane (AOM) induced aberrant crypt foci (ACF) in rats. Diets containing cooked beans (CB) or its non-digestible fraction (NDF) were fed to 72 male rats after 2 azoxymethane injections (15 mg kg(-1) of body weight once a week for 2 weeks). ACF number, short chain fatty acids (SCFA) and β-glucuronidase activity were measured in colon sections from rats sacrificed 7 weeks after the last AOM injection. Food intake and weight gain of rats were unaffected by CB and NDF. CB and NDF suppressed the AOM-induced formation of ACF (0.8 and 1.5 ACF/distal zone, respectively vs. 6.6 ACF/distal zone based on methylene blue stain) and lowered β-glucuronidase activity in cecal, colonic and fecal content compared to AOM group. SCFA production was not significantly different among fecal, cecal and colonic content. These results indicate that CB and NDF from Bayo Madero provide direct chemoprotection against early stage of azoxymethane (AOM)-induced colon cancer in rats.     

Performance of (La,Sr)(Co,Fe)O3−x double-layer cathode films for intermediate temperature solid oxide fuel cell

In this study the performance evaluation of (La,Sr)(Co,Fe)O_3−x (LSCF) double-layer films characterized by impedance spectroscopy between 403 and 603 °C to be used for intermediate temperature solid oxide fuel cells (IT-SOFCs) is presented. Two LSCF layers with different microstructures were sequentially deposited onto Ce_0.9Gd_0.1O_1.95 (CGO) substrates in a symmetrical fashion. A first layer of La_0.6Sr_0.4Co_0.2Fe_0.8O_3−x with a thickness of 7 μm and a nano-scaled particle size was deposited by electrostatic spray deposition (ESD) technique. Different deposition conditions were used in preparing the ESD films to evaluate the influence of film morphology on the electrochemical performance. After annealing, a current collector layer of La_0.58Sr_0.4Co_0.2Fe_0.8O_3−x with ∼45 μm in thickness and a larger particle size was deposited by screen printing. Area specific resistances (ASRs) were determined from impedance spectroscopy measurements performed in air between 403 and 603 °C, at 25 °C steps. A dependence of electrochemical performance on the morphology of the LSCF layer deposited by ESD was observed. The lowest ASR, measured during 130 h of isothermal dwelling at 603 °C, averaged 0.13 Ω cm² with negligible variation and is the lowest reported value for this composition, to the best of our knowledge. Reported results assure an excellent suitability of this type of assembly for IT-SOFCs.     

Plasma amino acids profile of healthy pregnant adolescents in Maracaibo, Venezuela

One hundred female adolescents (13-18 y) were clinical and anthropometrically studied to select only those with adequate nutrition. Most adolescents belonged to IV socio-economic stratum families (worker class). Height, weight, age, body mass index and medial arm circumference were used as anthropometric parameters. After screening, only 41 non pregnant girls (control) and 42 pregnant girls with adequate nutrition were selected to analyze plasma amino acids. Fasting peripheral venous blood was drawn, and plasma amino acids were analyzed by HPLC. Amino acid concentrations were expressed as umol/L +/- SE. SAS/STAT program was used for statistical analysis. Amino acid values of control adolescent group were found in ranges reported by other investigators, with slight variations, mostly in diminution, presumably due to nutritional, metabolic or genetic conditions of people living in tropical regions. In pregnant healthy adolescents, distributed according to gestational age: < 32 weeks (n = 30) and > 32 weeks (n = 12), a diminution of total molar plasma amino acids was found, by comparing with control values. Ten amino acids (Pro, Gly, Gln, Arg, Ser, Orn, Tau, Leu, Thr and Val) appeared significantively diminished throughout gestation, being Gly. Gln and Arg most affected since earlier weeks. During the 2nd period. Thr and Val increased their grade of affectation; whereas some amino acids values (Orn, Pro and Tau) tended to recuperate. Several of affected amino acids are gluconegoenic, thus, they could be utilized to supply the energy required by the pregnant adolescent against her double stress: the fetus development and her own development. The plasma amino acid values reported in both, healthy non pregnant and pregnant adolescents, could be taken as regional referential profile of plasma amino acids in this poblational group for further research on adolescent and fetal--maternal malnutrition.     

Instability of styrene/polystyrene/polybutadiene/polystyrene‐b‐polybutadiene emulsions that emulate styrene polymerization in the presence of polybutadiene

This article investigates the room temperature demixing of oil‐in‐oil emulsions containing styrene (St), polybutadiene (PB), a St‐butadiene star block copolymer (BC), and two polystyrene (PS) samples of different molecular weights and is a contribution toward a better understanding of the stability/instability of the reaction mixture in a bulk high‐impact polystyrene (HIPS) process close to the phase inversion. Twelve bulk prepolymerizations of St in the presence of PB were emulated, at 10%, 15%, and 20% conversion; and with constant grafting efficiencies. All the blends contained 6% in weight of butadiene units. After stirring the blends for 24 h, the decantation demixing process was monitored along 30 days, with daily measurement of the interface levels after appearance of a clear interface. For some of the isolated phases, their unswollen morphologies were observed by transmission electron microscopy. All the isolated phases exhibited macrophase separation into homopolymer‐ and copolymer‐rich macrodomains with lamellar microdomains. The BC showed a greater affinity toward the PS‐rich phase. The separation of an independent BC‐rich phase in the blends containing the high molar mass PS and at high grafting efficiencies, modifies the idea of the graft‐ or BC molecules located at the interface of large PS‐rich and PB‐rich phases. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Nanoscaled La0.6Sr0.4CoO3−δ as intermediate temperature solid oxide fuel cell cathode: Microstructure and electrochemical performance

Lowering the operation temperature of solid oxide fuel cells to the range of 400-600 °C has generated new concepts for materials choice, interfacial design and electrode microstructures. In this study nanometer scaled and nanoporous La_0.6Sr_0.4CoO_3−δ (LSC) was derived from metal-organic precursors as thin film cathodes of about 200 nm thickness with mean grain sizes ranging from 17 to 90 nm and porosities of up to 45%. These microstructures resulted from different processing parameters such as heating rate, calcination temperature and post calcination annealing, and made it possible to study the influence of the electrode microstructure on the electrochemical performance. Microstructural characteristics were analyzed by scanning and transmission electron microscopy and the performance was evaluated in terms of area specific polarization resistance by means of electrochemical impedance spectroscopy in a temperature range of 400-600 °C. Polarization resistances as low as 0.023 Ω cm² were measured at 600 °C, facilitated by a substantial increase of the inner surface area of the nanoscaled microstructure, resulting from low temperature processing at ≤800 °C, and by enhanced catalytic properties determined for nanoscaled La_0.6Sr_0.4CoO_3−δ prepared by metal organic deposition.     

Maturation study of low fat Chanco cheese made with homogenized milk

The purpose of this study was to evaluate the influence the use of homogenization of different proportions of milk--which allow to increase the yield in the process and probably to improve sensorial characteristics of the cheese--has on the ripening of low fat Chanco cheese. Five treatments (three replicates each) were studied, two corresponded to control (normal fat and low fat) and the other three treatments were low fat using partially homogenized milk in the following percentages of the total volume of milk; 12.5, 25 and 50%. Standard methodology was used to monitor the evolution of ripening in terms of moisture, fat and total protein content, ripening index (NS/NT%), lipolysis (ADV), pH, sensorial quality and micro structure of the product. The low fat treatments with homogenized milk showed less fat losses in the whey and consequently increased yields. This study allowed us to know the low fat Chanco cheese maturation profile, low fat treatments with homogenisation showed a higher degree of lipolysis than the non--homogenized low-fat control although it was lower than normal fat control. No differences in terms of the development of proteolysis were observed. The low--fat homogenized treatments did not show improvement in the flavor neither in the cheese firmness probably due to the short ripening period (21 days) of this cheese variety, nevertheless T3 presented some advantages which could be improved applying simultaneously another technological helps.     

Incentives to Cooperate in Network Formation

We propose a simple mechanism based on taxes and subsidies to enhance high cooperation in evolutionary networks. The interactions among agents are based on the Spatial Prisoners' Dilemma game in which each agent interacts with the same strategy with its local neighbors, collects an aggregate payoff and imitates the strategy of its best neighbor. First we study the mechanism in a regular lattice where it is well-known that the asymptotic fraction of cooperators fluctuates around a constant value for almost all starting proportions and configurations of cooperators. We also explore the mechanism in random and adaptive networks, where adaptability refers to the ability of agents to change their local neighborhood. For theses networks it has been reported that the starting proportion of cooperation has to be sufficiently high in order to obtain highly cooperative levels in the long-run time. The implementation of our mechanism produces successful results in such evolutionary networks, higher levels of cooperation are reached for all initial fractions of cooperation, including the most adverse case of just one cooperator in the network. Additionally, we observe that the network reaches a spatial configuration such that the fraction of cooperators remains in high level even when the mechanism is switched off. As a result the mechanism can work as an ignition engine to achieve highly cooperative level since it can be implemented for a finite period of time.