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Search Results: 1 - 10 of 464964 matches for " María Custodio "
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Influence of Water Quality on the Variation Patterns of the Communities of Benthic Macroinvertebrates in the Lakes of the Central Highlands of Peru  [PDF]
María Custodio, Richard Pe?aloza
Open Journal of Marine Science (OJMS) , 2019, DOI: 10.4236/ojms.2019.91001
Abstract:
The influence of water quality on the variation patters of benthic macroin-vertebrate communities in the lakes in the central highlands of Peru was eva-luated. Samples of water and sediments were collected in 23 different sam-pling sites last 2017. The physiochemical variables of water quality deter-mined on site were: DO, TDS, EC, temperature and pH. The results obtained revealed that the physiochemical indicators are within the environmental quality standards for water, except COD and BOD5. Regarding the benthic macroinvertebrates, four phyla were identified wherein the most common is the phylum Arthropoda having the abundance and richness of taxa. The PCA reduced the variables to a few significant components that caused variation in water quality between lakes. The cluster analysis in relation to the relative abundance of benthic macroinvertibrates grouped the 22 sampling sites into three groups with the similar characteristics. The PCoA analysis of the ben-thic macroinvertebrate communities showed a clear separation of sites. The SIMPER analysis at the family-level showed the distribution of the most common species. Therefore, at a significance level of 0.01 it demonstrates that there are significant differences between the number of species and abun-dance of the areas that were evaluated.
Distribution and Accumulation of Heavy Metals in Surface Sediment of Lake Junín National Reserve, Peru  [PDF]
María Custodio, Fisher Huaraca, Ciro Espinoza, Walter Cuadrado
Open Journal of Marine Science (OJMS) , 2019, DOI: 10.4236/ojms.2019.91003
Abstract: The distribution and accumulation of heavy metals in the surface sediment of Lake Junin National Reserve was evaluated using the pollution factor (CF), pollution load index (PLI) and geoaccumulation index (Igeo), during 2018. Surface sediment samples were collected from 10 sampling sites, with three repetitions, during the rainy and dry seasons. The heavy metals determined were Fe, Cu, Cr, Cd, Pb and Zn; As, was also determined. The results revealed the descending order of Fe > Cu > Zn > As > Pb > Cd > Cr concentrations recorded in the three sampling sectors. The values of the CF obtained for the metals qualified as low CF, in times of rain and low water. The CF values of Cd were qualified as moderate contamination factors at all sampling sites, except at LJ1 where it qualified as CF considerable. The
Capacity of Absorption and Removal of Heavy Metals from Scirpus californicus and Its Potential Use in the Remediation of Polluted Aquatic Environment  [PDF]
Walter Cuadrado, María Custodio, Ciro Espinoza, Carmela Vicu?a, Marilú Uribe
Open Journal of Marine Science (OJMS) , 2019, DOI: 10.4236/ojms.2019.92006
Abstract: The research aimed to evaluate the absorption and removal capacity of Cu, Pb, Fe and Zn from Scirpus californicus for potential use in the remediation of polluted aquatic environments. Initially, Scirpus californicus plants were conditioned in 1.5 liters of 10 ppm Cu solution at a pH of 2.3 as well as Pb, Fe and Zn. Subsequently, the concentration of heavy metals in the root-rhizome, submerged stem and aerial stem was determined; the solution and pH were also analyzed. The greatest capacity of absorption and accumulation occurred in the root-rhizome reaching values for Cu of 491.84, Pb of 739.43, Zn of 830.71 and Fe of 2624.72 mg/kg dry followed by the submerged stem and low values for the aerial stem. The removal efficiency of Cu from the solution was 52.10%, Pb 53.50%, Fe 48.00% and Zn 50.20%. It is concluded that the contact time has a significant effect on the absorption and removal capacity of the metals under study.
Recubrimientos de quitosano/fosfato de calcio obtenidos por electrodeposición sobre una aleación de titanio
Pe?a Ballesteros,Darío Yesid; Estupi?án Durán,Hugo Armando; Córdoba Tutta,Elcy María; Martínez,Ricardo; Vásquez Quintero,Custodio;
Revista Facultad de Ingeniería Universidad de Antioquia , 2010,
Abstract: calcium phosphate coatings in orthopedic implants ti6al4v are known to accelerate bone growth and improve the fixation of bone. electrolytic deposition of bioactive compounds has provided greater advantages than the coatings obtained by conventional methods. the electrolytic method has facilitated the ability to add chitosan to the solution of calcium and phosphate ions and fix this compound, functionally and structurally. in this way, composites of calcium phosphate-chitosan on a substrate ti6al4v eli has been obtained by cathodic electrodeposition, which are morphologically and chemically characterized by sem-edx, xrd and ftir, showing the chemical structure and associations between calcium phosphate and chitosan. furthermore, the impact of the current density, electrodeposition time and the concentration of chitosan solution on the polarization resistance of coated substrates obtained were evaluated by eis. equivalent circuits were used to model the physicochemical behavior of the coatings from an electrochemical view point.
MEDIDA DE LA BASICIDAD Y POTENCIAL DE OXíGENO DEL SISTEMA ACERO 1020- SAL 80%V2O5-20%Na2SO4- GAS 1%SO2-99%O2 A 700oC
VáSQUEZ,CUSTODIO; PE?A,DARíO;
DYNA , 2007,
Abstract: two reference electrodes to calculate oxygen and sodium activity were built to be used in an electrochemical system which was conformed by a molten salt of 80% v2o5-20% na2so4 in weight, 1%so2-99%o2 oxidizing atmosphere and aisi 304h, 9cr-1mo modified steel and 2 1/4cr-1mo at 700°c. results were superimposed in a stability diagrams of na-v-s-o at the same temperature, indicating that the navo3 was the compound predominating in a molten system. the fluxing mechanism was corroborated for the hot corrosion of these materials.
Medida de la basicidad y potencial de oxígeno del sistema acero 1020- sal 80%v2o5-20%na2so4- gas 1%so2-99%o2 a 700oc
CUSTODIO VáSQUEZ,DARíO PE?A
DYNA , 2007,
Abstract: Se construyeron dos electrodos de referencia para calcular la actividad de oxígeno y de sodio en un sistema compuesto por una sal de 80% V2O5-20% Na2SO4 en peso, una atmósfera de 1%SO2-99%O2 y los aceros AISI304H, 9Cr 1Mo modificado (T91) y 2 Cr 1Mo (T22) a una temperatura de 700oC, Los resultados se superpusieron en el diagrama de estabilidad Na-V-S-O a 700°C, indicando que la especie predominante en el fundido fue el NaVO3. Se comprobó que el mecanismo que rige la corrosión en caliente para estos materiales fue el Fluxing.
ESTUDIO DE LA CORROSIóN EN CALIENTE DE LA ALEACIóN AISI-SAE 304H, MEDIANTE LA TéCNICA DE ESPECTROSCOPíA DE IMPEDANCIA ELECTROQUíMICA (EIS)
TRISTANCHO,JOSé; VáSQUEZ,CUSTODIO; PE?A,DARIO;
DYNA , 2007,
Abstract: hot corrosion is one of the most important corrosion problems in power generation industry, especially in vapor generations components. corrosion phenomena in molten salts is partially electrochemical nature and therefore, it can be studied by using the impedance electrochemical technique, which can be adapted to the conditions of corrosive environments and temperature. in this research, the corrosion behavior of aisi304h steel exposed to 80%v2o5 - 20%na2so4 molten salt at a range temperature between 550oc and 700oc was evaluated.
Relaciones sociales e interacción en el aula en secundaria
Mejía Custodio, Amalia;ávila Meléndez, Luis Arturo;
Revista mexicana de investigación educativa , 2009,
Abstract: in this article, we emphasize a conceptual distinction between "interaction" and "social relationship"-a distinction that is rejected by one of the predominant currents that analyzes the effects of teacher/students relationships on teaching and learning. we carried out ethnographic research with a group of eighth-graders in spanish class during the 2004-2005 school year. the results show that establishing social relationships over the year implied agreements on respect and authority that influenced learning. focusing on social relationships as probabilities of the occurrence of a certain type of interaction, implies emphasizing the temporality and precariousness of their establishment, as well as understanding their formation in the school according to the region's specific cultural principles. we emphasize individuals' social constitution and not only the morphology and techniques of face-to-face interpretation and interaction.
Validación de la prueba de dibujo del reloj - versión de Manos - como prueba de cribado para detectar demencia en una población adulta mayor de Lima, Perú Validation of the clock drawing test - Manos′ version - as a screening test for detection of dementia in older persons of Lima, Peru
Nilton Custodio,Alberto García,Rosa Montesinos,David Lira
Revista Peruana de Medicina Experimental y Salud Pública , 2011,
Abstract: Introducción. La prueba de dibujo del reloj versión de Manos (PDR-M) es un instrumento de evaluación cognitiva breve para la detección de demencia. Objetivos. Evaluar la validez y confiabilidad de la PDR-M para discriminar entre pacientes con demencia y sujetos controles sanos. Materiales y métodos. Se evaluaron sujetos mayores de 65 a os de edad, excluyendo los que presentaban enfermedades concomitantes graves y con dificultades auditivas o visuales. Se recogieron datos demográficos y se les realizó PDR-M y Mini Mental State Examination (MMSE). A los individuos del grupo de demencia se les realizó además evaluaciones clínicas, de laboratorio, neuropsicológicas y tomografía cerebral. Se calculó la sensibilidad y especificidad de la PDR-M así como el área bajo la curva ROC. Resultados. Se evaluó 210 individuos, 103 con diagnóstico confirmado de demencia y 107 controles sanos, con edad y sexo similares en ambos grupos; y mayor nivel educativo en el grupo control. Estableciendo un punto de corte de 7 se obtuvo una sensibilidad de 99,0% y una especificidad de 83,5%. Cuando se compararon las áreas bajo la curva ROC de la PDR-M y del MMSE no se encontraron diferencias significativas. Conclusiones. La PDR-M es un instrumento breve y confiable para la detección de demencia en la población urbana de Lima en el Perú. Introduction. The clock drawing test (PDR-M) - Manos′ version - is a brief cognitive assessment tool for dementia detection. Objectives. To assess the validity and reliability of the PDR-M to discriminate between patients with dementia and healthy control subjects. Materials and methods. We evaluated subjects over 65 years of age, excluding those with severe concomitant diseases and those with hearing or visual impairment. We obtained demographic data and performed the PDR-M and Mini Mental State Examination (MMSE). Subjects of the dementia group were also submitted to clinical, laboratory and neuropsychological evaluations as well as computed tomography scanning. Sensitivity and specificity of the PDR-M were calculated as well as the area under the ROC curve. Results. We evaluated 210 individuals, 103 with confirmed diagnosis of dementia and 107 healthy controls with similar age and sex in both groups, but a higher educational level in the control group. Setting a cutoff point of 7, a sensitivity of 99.0% and a specificity of 83.5% were found. When comparing the areas under the ROC curves of the PDR-M and MMSE we found no statistically significant difference. Conclusions. The PDR-M is a brief and reliable instrument for the detection of dementia in
Estudio de la corrosión en caliente de la aleación aisi-sae 304h, mediante la técnica de espectroscopía de impedancia electroquímica (eis)
JOSé TRISTANCHO,CUSTODIO VáSQUEZ,DARIO PE?A
DYNA , 2007,
Abstract: La corrosión en caliente es uno de los mayores problemas que se presentan en la industria generadora de energía eléctrica, especialmente en los componentes que conforman los equipos generadores de vapor (calderas). El fenómeno corrosivo que presentan las sales fundidas, es por lo menos parcialmente, de naturaleza electroquímica y por lo tanto, puede ser estudiado empleando la técnica de impedancia electroquímica (EIS), adaptada a las condiciones especiales de temperatura y composición del medio corrosivo. En esta investigación se evalúo el comportamiento del acero AISI304H expuesto a un electrolito compuesto de 80%V2O5 20%Na2SO4 fundido, en un intervalo de temperatura comprendido entre 550oC y 700oC
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