Explore the vast range of titles available.

Molybdenum concentrate, as Molybdenite (MoS2), is nowadays obtained as a byproduct of the processing of porphyry copper ores, being molybdenite considered a minor component. The procedure for the commercial extraction of molybdenum from such a sulfide ore, involves the operations of roasting the concentrate, purifying the resulting calcination, either by distillation of molybdenum trioxide (MoO3) or by a hydrometallurgical pathway, and finally reducing the trioxide of molybdenum with hydrogen to obtain the metal. The objective of the present work is to study the production of molybdenum from molybdenite concentrates using aqueous solution of hydrochloric acid (HCl) as a lixiviant, sodium chloride (NaCl) as a catalyst, sodium hydroxide (NaOH) as a pH regulator, and lastly ferric chloride (FeCl3) as an oxidant. The results show that working pH greater than 8, temperature of 50 °C, hydrochloric acid concentration of 5%, solid/liquid ratio of 10:1, stirring rate of 200-300 rpm and the addition of 2% ferric chloride. Mo leaching was 70% under experimental conditions at a time of 180 minutes, with a complete removal of iron. El concentrado de molibdenita (MoS2) es obtenido actualmente como un subproducto en el procesamiento de minerales provenientes de un pórfido de cobre, siendo la molibdenita considerada un componente menor. El procedimiento para la extracción comercial de molibdeno desde un sulfuro, la molibdenita, implica tostar el concentrado, purificar el calcinado resultante, ya sea por destilación de tiroxido de molibdeno (MoO3 )o por una ruta hidrometalúrgica, y finalmente reducir el trióxido con hidrógeno para obtener el metal El objetivo del presente trabajo es estudiar la producción de molibdeno desde concentrados de molibdenita usando una solución acuosa de ácido clorhídrico (HCl) como lixiviante, cloruro de sodio (NaCl) como catalizador, hidróxido de sodio (OHNa) como regulador de pH, y por último cloruro férrico (FeCl3) como un oxidante. Los resultados muestran que trabajando en un pH más grande que 8 temperatura de 50ºC, con una concentración de ácido clorhídrico de 5% y una relación solida / liquido de 10:1, velocidad de agitación de 200- 300 rpm y la adición de un 2% de cloruro férrico, La lixiviación de Mo fue del 70% en condiciones experimentales en un tiempo de 180 minutos, con una remoción completa del hierro.

A large genetic screen for sos (for salt overly sensitive) mutants was performed in an attempt to isolate mutations in any gene with an sos phenotype. Our search yielded 28 new alleles of sos1, nine mutant alleles of a newly identified locus, SOS2, and one allele of a third salt tolerance locus, SOS3. The sos2 mutations, which are recessive, were mapped to the lower arm of chromosome V, approximately 2.3 centimorgans away from the marker PHYC. Growth measurements demonstrated that sos2 mutants are specifically hypersensitive to inhibition by Na+ or Li+ and not hypersensitive to general osmotic stresses. Interestingly, the SOS2 locus is also necessary for K+ nutrition because sos2 mutants were unable to grow on a culture medium with a low level of K+. The expression of several salt-inducible genes was superinduced in sos2 plants. The salt tolerance of sos1, sos2, and sos3 mutants correlated with their K+ tissue content but not their Na+ tissue content. Double mutant analysis indicated that the SOS genes function in the same pathway. Based on these results, a genetic model for salt tolerance mechanisms in Arabidopsis is presented in which SOS1, SOS2, and SOS3 are postulated to encode regulatory components controlling plant K+ nutrition that in turn is essential for salt tolerance

In digestion, the red palm weevil, Rhynchophorus ferrugineus, has been adapted to overcome the plant cell wall barrier, specially lignocellulosic and pectic compounds, by producing cellulase and pectinase enzymes. Partial biochemical characterisations of cellulase and pectinase were determined in the larval digestive system of the pest. Larval midgut extract showed an optimum activity for cellulase and pectinase against carboxyl methyl cellulose and pectin at pH 6.0 and 7.0, respectively. Larval midgut cellulase and pectinase were more stable at pH 4.0-8.0 and pH 6.0-8.0 than in highly acidic and alkaline condition, respectively. However, cellulase and pectinase showed to be more stable at pH 6.0 and 7.0, respectively, when the incubation time increased. Maximum activity for cellulase and pectinase incubated at different temperatures was observed at 50 deg C. Cellulase and pectinase activity significantly decreased in the presence of EDTA and SDS. On the contrary, Ca2+, Mg2+, and Na+ significantly affect pectinase activity and K+ did not affect the enzyme activities. Ca2+ and Mg2+ increased cellulase activity as well. KM and Vmax for pectinase activity were 0.92 mg/ml and 290 units/mg. Zymogram analyses revealed the presence of one form of pectin methyl esterase and one form of cellulase in the larval digestive system.

The objective of the present research was the evaluation of some fresh and hardenedstate properties of concretes, in which coarse aggregates were partially replaced by lightweight ones previously saturated, in percentages of 15% and 25 %. The lightweight aggregates were calcined clays and crushed clay bricks. In parallel, the effect of an internal curing agent composed of superabsorbent polymers (SAP) was evaluated. The properties evaluated in the fresh and hardenedstate of concretes with a/c of 0,30 were: slum, air content, density, compression resistance, modulus of elasticity, initial superficial absorption and chlorine resistance. Results showed the efficiency of crushed clay bricks as internal curing, as well as the need for deeper research on the use of the evaluated lightweight aggregate as internal curing aggregate in concrete. Results indicate that the crushed clay bricks and the internal curing agent fulfill the behavior expected, in terms of strength and durability. However, the evaluated lightweight aggregate produces a reduction in the resistance and durability of the concrete. The observed behavior in strength and durability is especially variable for the age of 180 days, compared with conventional concretes.

This paper evaluates the use of cedar tree exudate in chloride penetration and the probability of steel corrosion in reinforced concrete (rc), considering 0.3, 0.5, 0.7, and 0.9 % exudate by  cement weight in the mixture at water/cement (w/c) ratios of 0.55 and 0.60. Under these conditions, cylindrical specimens of 4 inches in diameter and 8 inches in height were constructed. The water-sol- uble chloride content of the extracted concrete powder was measured at 0.5, 1.0, and 2.0 cm depth according to astm C1218/C1218M, while the probability of corrosion was determined by measuring electric potentials with astm C876. A favorable incidence of 0.46 % by weight of concrete was found when using 0.7 % exudate at the w/c ratio of 0.55 at the closest depth to the steel, compared to the 0.55 % target. The probability of steel corrosion is reduced to 10 % with potentials higher than -0.2 V with more prolonged exposure to chlorides.

The objectives of this study were to evaluate the effects of partial substitution of 25% and 50% NaCl with KCl coupled with high pressure processing (100 MPa for 5 min at 25°C), on sensory and chemical qualities of beef sausage for 28 days' storage at 4°C. Three sausage formulations were produced with different concentrations of NaCl (100%, 75% and 50%) and KCl (0%, 25% and 50% respectively). High pressure application reduced the total NaCl content and improved the sensory acceptance for taste and flavor compared to control beef sausages. The addition of KCl showed the lowest values for Na + content; the highest scores for all sensory parameters, improved hardness and chewiness, with results not statistically different from the results obtained by combining HPP and KCl. Therefore, the use of HPP in combination with KCl was considered a technological and sensorial viable alternative to produce low sodium beef sausages.

This study aimed to investigate the impact of the combination of Benzalkonium chloride (BAC) and sodium hypochloride (NaOCl) and its application after ethylenediaminetetraacetic acid (EDTA) in root canal irrigation procedures on the microhardness and mineral content of dentin. Distal roots of mandibular third molars were embedded in auto-polymerizing acrylic resin, sectioned coronally to apically resulting in fifty-four root sections. Thirty sections underwent microhardness evaluation, and twenty-four sections were randomly chosen for mineral analysis. The microhardness assessment comprised three groups: Group 1 (2.5% NaOCl), Group 2 (2.5% NaOCl with 0.084% BAC), and Group 3 (2.5% NaOCl with 0.084 BAC post-17% EDTA). Initial and post-irrigation microhardness values were measured for each group. For mineral analysis, samples were categorized into four groups: distilled water, 2.5% NaOCl, 2.5% NaOCl with 0.084% BAC, and 17% EDTA+2.5% NaOCl with 0.084% BAC. X-ray photoelectron spectroscopy immediately measured magnesium, phosphorus, and calcium mineral contents on dentin surfaces post-irrigation. Results indicated a significant reduction in root dentin microhardness for all solutions (p<0.05). However, no statistically significant difference in the percentage of reduction was observed among the groups (p>0.05). XPS analysis revealed no significant disparity in dentin surface mineral content among the groups (p>0.05). In conclusion, the addition of Benzalkonium chloride to sodium hypochloride, either alone or after EDTA, did not induce a significant alteration in dentin microhardness or mineral content. These findings contribute to a nuanced understanding of dental irrigation protocols and their effects on dentin properties during endodontic procedures. Este estudio tuvo como objetivo investigar el impacto de la combinación de cloruro de benzalconio (BAC) e hipocloruro de sodio (NaOCl) y su aplicación después del ácido etilendiaminotetraacético (EDTA) en procedimientos de irrigación del conducto radicular sobre la microdureza y el contenido mineral de la dentina. Las raíces distales de los terceros molares mandibulares se incluyeron en resina acrílica autopolimerizable y se seccionaron de coronal a apical, lo que dió como resultado cincuenta y cuatro secciones de raíz. Treinta secciones se sometieron a una evaluación de microdureza y veinticuatro secciones fueron elegidas al azar para el análisis mineral. La evaluación de la microdureza comprendió tres grupos: Grupo 1 (2,5% NaOCl), Grupo 2 (2,5% NaOCl con 0,084% BAC) y Grupo 3 (2,5% NaOCl con 0,084 BAC post-17% EDTA). Para cada grupo se midieron los valores de microdureza inicial y post-irrigación. Para el análisis mineral, las muestras se clasificaron en cuatro grupos: agua destilada, 2,5% NaOCl, 2,5% NaOCl con 0,084% BAC y 17% EDTA+2,5% NaOCl con 0,084% BAC. La espectroscopía fotoelectrónica de rayos X midió inmediatamente el contenido de minerales de magnesio, fósforo y calcio en las superficies de la dentina después de la irrigación. Los resultados indicaron una reducción significativa en la microdureza de la dentina radicular para todas las soluciones (p<0,05). Sin embargo, no se observó diferencia estadísticamente significativa en el porcentaje de reducción entre los grupos (p>0,05). El análisis XPS no reveló ninguna disparidad significativa en el contenido mineral de la superficie de la dentina entre los grupos (p>0,05). En conclusión, la adición de cloruro de benzalconio al hipocloruro de sodio, solo o después de EDTA, no indujo una alteración significativa en la microdureza o el contenido mineral de la dentina. Estos hallazgos contribuyen a una comprensión matizada de los protocolos de irrigación dental y sus efectos sobre las propiedades de la dentina durante los procedimientos de endodoncia.

Se analizó el efecto de la densidad de plantación de la especie Limonium perezzi sobre la efectividad de humedales artificiales a escala de laboratorio para el tratamiento de aguas residuales de la etapa de remojo en curtiembres. La densidad de plantación fue de 10.27 plantas/m2 (HAP4) y 15.4 plantas/m2 (HAP6), el tiempo de retención hidráulica en cada humedal fue de 4.5 días y los experimentos fueron realizados por 32 días, tiempo en el que las plantas comenzaron a marchitarse, dentro de los cuales fueron tomadas muestras de agua para el respectivo análisis. Los humedales fueron operados por 8 semanas a fin de observar el deterioro de estas con respecto al tiempo. El periodo de estabilización de los humedales varió entre 7 y 10 días hasta que la concentración del efluente fue poco variable. El análisis estadístico de los resultados indica que la densidad de plantación influye sobre la efectividad del humedal en términos de porcentaje de disminución de concentración, los humedales plantados con 15.4 plantas/m2 fueron más eficientes, lo cual se determinó a partir de la prueba T de Student (p < 0.05). Los porcentajes de disminución de la demanda química de oxígeno, cloruros y sólidos disueltos totales para la mayor densidad de plantación fueron de 81 %, 54 % y 55 % respectivamente. Al igual que en estudios previos, se observó que la especie plantada tiene la habilidad de tomar sal y liberarla a través de hojas y tallos, hecho que se pudo apreciar a partir del séptimo día de operación.

In this study, the effects were investigated of salinity, foliar and soil applications of humic substances on the growth and mineral nutrients uptake of Corn (Hagein, Fardy10), and the comparison was carried out of the soil and foliar applications of humic acid treatments at different NaCl levels. Soil organic contents are one of the most important parts that they directly affect the soil fertility and textures with their complex and heterogenous structures although they occupy a minor percentage of the soil weight. Humic acids are an important soil component that can improve nutrient availability and impact on other important chemical, biological, and physical properties of soils. The effects of foliar and soil applications of humic substances on the plant growth and some nutrient elements uptake of Corn (Hagein, Fardy10) grown at various salt concentrations were examined. Sodium chloride was added to the soil to obtain 20 and 60mM saline conditions. Solid humus was applied to the soil one month before planting and liquid humic acids were sprayed on the leaves twice on 20th and 40th day after seedling emergence. The application doses of solid humus were 0, 2 and 4 g/kg and those of liquid humic acids were 0, 0.1 and 0.2%. Salinity negatively affected the growth of corn; it also decreased the dry weight and the uptake of nutrient elements except for Na and Mn. Soil application of humus increased the N uptake of corn while foliar application of humic acids increased the uptake of P, K, Mg,Na,Cu and Zn. Although the effect of interaction between salt and soil humus application was found statistically significant, the interaction effect between salt and foliar humic acids treatment was not found significant. Under salt stress, the first doses of both soil and foliar application of humic substances increased the uptake of nutrients.