Carlos Severiche-Sierra

Determination of thermal properties of the ionic system xAgI-(1-x)NH4I by differential scanning calorimetry

The research focuses on the search for more experimental evidence of the thermal, electrical behavior of the family MI AgI (where M = NH4), which results when NH4 + is exchanged for Ag in the binary system xAgI-(1-x)NH4I as a study model with concentrations of x = 0.4, 0.5.0.6, 0.7.0.8 and 0.9. The thermal properties were identified by the Differential Scanning Calorimetry (DSC) technique. For this system in each of the concentrations, there is evidence of a decrease in temperature to the quality that occurs in the transition from poor phase conductor called β / γ to highly conductive called α compared with that of pure Agi that is given in 420 K (147 oC).

Model dynamics of Rosenzweig - MacArthur considering the proportional refuge function to the number of dams

The qualitative analysis of the two-dimensional systems of autonomous differential equations of Rosenzweig-MacArthur, representing a predator-prey interaction, is carried out. Considering the use of shelters by dams with the functions proposed by Maynard-Smith. For the analytical study, the qualitative theory of the systems of differential equations is used. It is shown that the refuge influences the stability of the single equilibrium point inside the first quadrant and produces important effects in the dynamics of the Rosenzweig-MacArthur model.

Rosenzweig-MacArthur model considering the function that protects a fixed amount of prey for population dynamics

Populations can grow, disappear or remain in time and this depends on their birth rates, mortality, immigration and emigration. For a long time, species have disappeared and others are at the same risk if protective policies are not implemented to guarantee their survival. It is necessary to consider mathematical models that help conserve the environment. The analysis of the Rosenzweig MacArthur model was performed considering the function that protects a fixed amount of prey. For the analytical study, the qualitative theory of the systems of differential equations is used. Considering the use of shelters by dams with the functions proposed by Maynard-Smith. It is shown that the refuge influences the stability of the only equilibrium point inside the first quadrant and produces important effects in the dynamics of the prey-prey model.

Complex impedance analysis by Nyquist diagram for the system xAgI-(1-x)NH4I

Conductivity was characterized for the MI AgI family (where M = NH4), which results when NH4 is exchanged for Ag+ in the binary system xAgI-(1-x)NH4I as a study model with concentrations of x = 0.4, 0.5, 0.6, 0.7.0.8 and 0.9. The study samples were grown using the slow evaporation method, and their properties were identified by Impedance Spectroscopy techniques. For this system in each of the concentrations, there was a decrease in the temperature at which the transition from poorly conductive phases called β/γ to very conductive occurs, called α compared with that of the pure AgI that is given at 420 K (147 oC).

Efectos tóxicos del paracetamol en la salud humana y el ambiente

En este articulo se detallan los efectos toxicos del paracetamol en la salud humana y el ambiente, detallando las generalidades del paracetamol APAP. El metabolismo del APAP y factores potenciales que influyen en su toxicidad, pasando por estudios de toxicidad y por ultimo el destino ambiental. El paracetamol es un analgesico de uso comun, presenta alta hidrosolubilidad, eliminandose hasta un 90% por gluconacion o sulfacion; pero su metabolito N-acetil-para-benzoilquinoneimina en ocasiones se expulsa por medio de las heces y orina, volviendose un compuesto toxico persistente. Se observan efectos cronicos principalmente en organismos acuaticos, a traves de la exposicion a diferentes concentraciones de APAP durante un prolongado periodo de tiempo.

Physicochemical characterization and calorific value measurement in residual oils used in the petrochemical industry of Cartagena de indias (Colombia)

Residual oils from combustion engines, from the industrial sector of Mamonal in Cartagena de Indias, were characterized by densimetry, karl fischer, viscosimetry, atomic absorption and pump density, percentage of humidity, viscosity, metals in suspension and calorific value Designed, constructed and tuned according to ASTM D 240-02. The calorimetric pump was designed in stainless steel 304 schedule 40, with circular section and internal volume of 355,71 mL. It works in an atmosphere of oxygen with pressures between 25 and 30 atm. The temperature sensor used was the SEE TMP-BTA with stainless steel probe and the data-software acquisition system used was VERNIER Internationals GOLink SEE with a sensitivity to the hundredth degree. It was determined that the higher calorific value (PCS) of the samples of used oils from the industrial sector of Mamonal have an average value of 19934.3 Btu / Lb. Keyword Calorimetric pump, Heat power, Oil reused, Physicochemical variables, Recycling.

Association between self-regulation of learning, student attitude, provenance and age in engineering students

The relationship between the self-regulated learning inventory (SRLI) and the factors student attitude, collegiate origin and age in 960 students of engineering programs in universities of the city of Cartagena between the years 2014 and 2016 were analyzed; Through the χ2 independence test. Initially the instrument was validated; The self-regulation for learning and the independent variables were analyzed: age, attitude and collegial origin, and finally a mosaic chart was drawn between SRLI and variables with which a significant relationship was obtained. The results indicate that the instrument is valid according to the Alpha values of Cronbach and that there is an important association between SRLI and the variables attitude and student origin; Showing that students with a high student attitude and coming from public schools, are those who generally have very good self-regulation of learning. 666 Waldyr Fong-Silva et al.

Development of a scalded meat product added with modified bean starch Zaragoza (Phaseolus lunatus) red variety

A sausage type food was elaborated including different levels of modified starch of Zaragoza bean (Phaseolus lunatus) red variety. We applied analysis of variance, Tukey test and descriptive statistics. The results indicate that the levels of modified starch did not affect the nutritional quality of the sausages, presenting on average 57.003 ± 0.639% of moisture, 17,073 ± 0.385% of protein, 12,791 ± 0.217% of fat and 3,678 ± 0.297% of starch. In the texture profile analysis, no significant differences were found, but it was found that when the modified starch concentration increased, the product presented an increase in its elasticity and adhesiveness, for the firmness an equal relation was not obtained, since the treatment 4 (2.5% modified starch) obtained the lowest values, while treatment 3 was the one that obtained the highest values. Sensory analysis revealed a slightly greater acceptance as to the taste by the panelists towards treatment 3 (2% modified starch).