In this study, 'Hass' avocado samples were stored at different temperatures to determine changes in firmness, color and other physicochemical support properties throughout the storage time and to represent shelf life depending on temperature from the evolution of these quality properties. From the experimental data, a set of models were adjusted to represent the change of each property as a function of time and temperature by using a first-order kinetics to represent the evolution of lightness (L*) and the chromatic coordinate b*, and a logistic equation to represent firmness and a*. The effect of temperature was represented by using Arrhenius equations. From the models of firmness and color, suitable equations were obtained to predict shelf life considering the relationship with the senescence stage (between 20 and 33 days). All the models were adjusted satisfactorily, obtaining regression coefficients higher than 0.95. In order to determine the predictive capacity of the proposed models, a validation experiment was carried out by storing fruits at 12 C until reaching the senescence stage. With the models, it was possible to satisfactorily predict the changes in color and firmness and it was possible to estimate the shelf life time at 12 C (28 AE 3.1 days).
This research paper presents the results of the behavior of productivity and profitability indicators in the oil and gas sector in Colombia in the years 2008 and 2010 by means of discriminant analysis. Initially there is an analysis of the sector and a theoretical review of the financial management assessment, strategic leverage, stakeholders, agency theory, productivity and profitability indicators and basic concepts of discriminant analysis. In the methodology used, productivity and profitability indicators were calculated for 116 companies in the oil and gas sector from the financial statements in the periods of study. Then, the discriminant analysis technique was used to explain the belonging and discrimination of the indicators studied. From the discriminant function and the means obtained it can be concluded that the analyzed indicators do not present significant differences, which shows a period of stagnation in the periods studied. With the research work it was concluded, by discriminant analysis, that there is a significant difference just for the indicator gross margin. The discriminant function model allows an effective classification of 57.3%.
In this study cut, pineapple slices of 1 cm thick were packaged and stored at different temperatures and equilibrium modified atmosphere packages (EMAPs) to determine changes of color and firmness over time to represent physicochemical shelf life. From the experimental data, a variance analysis was performed to determine the effect of temperature and O2 level on the evolution of color (CIELAB coordinates) and firmness. It was observed that the evolution in L*, a*, and b* coordinates is independent on O2 concentration in the EMAP system. After that, suitable models were adjusted to represent the change of the quality properties as a function of temperature by using first‐order models to represent color and a power model for firmness. Likewise, a modified normal distribution function was adjusted to represent the coefficient of firmness loss depending on the O2 level besides the temperature effect. The firmness model was used to obtain a suitable equation to predict shelf life of the pineapple slices for different EMAP systems. Finally, a validation experiment was performed at 8 °C obtaining a high capacity of prediction (R2adj > 0.90) compared with the experimental data. The adjusted model can be used to configure a satisfactory EMAP system for the best preservation of minimally processed pineapple from the predicted evolution of color, firmness, and shelf life depending on temperature and O2 concentration.
Practical Application
In this work, we built a mathematical model to simulate the shelf life of pineapple cut into slices based on changes in color and firmness and as a function of temperature and oxygen level. These properties are truly relevant because they are very clear evidence of the fruit deterioration, and for that reason, we chose them for the model. The model we developed can be applied in retail and supermarket systems to determine precisely how long the product on the shelf can last before being disposed of, reducing material losses.
EL PRESENTE ESTUDIO analiza dos aspectos cuantitativos de la población activa de México: 1) niveles y tendencias de su participación en la actividad económica, durante 1950-1970, y 2) la estimación de sus componentes de cambio-crecimiento natural y crecimiento social-en el mismo período. El análisis se presenta a nivel regional y la regionalización es idéntica a la utilizada en estudios previos. 1 I. FUENTES DE INFORMACIÓN Las fuentes de información utilizadas son el censo de 1950, la muestra del censo de 1960 e información preliminar del censo de 1970. Las dos primeras fuentes de información no presentan problemas de comparabilidad; sin embargo, cabe mencionar que la información sobre población activa en 1950 fue publicada por sexo y por grandes grupos de edad. Los datos por grupos quinquenales y por sexos que aquí se utilizan son estimaciones. 2 En el censo de 1970, por el contrario, se introdujeron algunos cambios que en gran medida afectan la comparabilidad con los dos censos anteriores. Algunos de estos cambios son: a) En el censo de 1970 se incluyeron dos períodos de referencia: el de la semana anterior a la fecha del levantamiento y el del año anterior. El introducir ambos períodos de referencia durante la misma entrevista da origen a sesgos en la respuesta dada por el entrevistado. Uno de los efectos consiste en que las cifras de fuerza de trabajo referentes al año * El presente trabajo es una versión modificada del trabajo que presentó el autor como alumno del Population Studies Center de la Universidad de Pennsylvania cuyo título es: "The Components of Change in Mexican Labor Forcé". El autor agradece los comentarios que al trabajo original hiciera la doctora Ann R. Miller. 1 La citada regionalización ha sido utilizada en:
Se presenta un método para definir y evaluar los perfiles de eficiencia financieros. Como fundamentación teórica se utilizó el cálculo multivariado y sus herramientas de Análisis de Conglomerado y Análisis Discriminante Multivariado ADM, también se utilizó Análisis Envolvente de Datos DEA con optimización en las salidas. Para esto se realizó una investigación con un enfoque racional y empírico, considerando 58 empresas medianas del sector exportador de la ciudad de Barranquilla-Colombia. Como resultado se aportó un método para establecer y evaluar perfiles de eficiencia financiera en las empresas exportadoras medianas de la zona. Se determinan también los perfiles de eficiencia financiera del sector exportador. Los niveles de eficiencia de los perfiles financieros de los clúster fueron 41,17%, 53,82% y 54,01 % respectivamente. Se concluye que el análisis de conglomerados mostró condiciones favorables para clasificar grupos empresariales con perfiles de eficiencia financiera diferenciada.
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