Value-added in higher education: ordinary least squares and quantile regression for a Colombian case

Colombia applies two mandatory National State tests every year. The first, known as Saber 11, is applied to students who finish the high school cycle, whereas the second, called Saber Pro, is applied to students who finish the higher education cycle. The result obtained by a student on the Saber 11 exam along with his/her gender, and socioeconomic stratum are our independent variables while the Saber Pro outcome is our dependent variable.We compare the results of two statistical models for the Saber Pro exam. The first model, multi-lineal regression or ordinary least squares (OLS), produces an overall well fitted result but is highly inaccurate for some students. The second model, quantile regression (QR), weight the population according to their quantile groups. OLS minimizes the errors for the students whose Saber Pro result is close to the mean (a process known as estimation in the mean) while QR can estimate in the -quantile for every . We show that QR is more accurate than OLS and reveal the unknown behavior of the socioeconomic stratum, the gender, and the initial academic endowments (estimated by the Saber 11 exam) for each quantile group.En el sistema educativo de Colombia se realizan dos exámenes nacionales obligatorios al año. El primero, conocido como Saber 11, está dirigido a los estudiantes que finalizan el bachillerato, mientras que el segundo, conocido como Saber Pro, evalúa a los estudiantes que terminan un estudio superior. En este estudio, el resultado obtenido por un estudiante en el examen Saber 11, junto con su género y estrato socioeconómico, son nuestras variables independientes, mientras que el resultado del examen Saber Pro es nuestra variable dependiente.Comparamos los resultados de dos modelos estadísticos para Saber Pro. El primer modelo, regresión multi-lineal o mínimos cuadrados (OLS, por sus siglas en inglés), produce un buen ajuste general pero es impreciso para ciertos estudiantes. El segundo modelo, regresión cuantílica (QR, por sus siglas en inglés), mide la población de acuerdo con su cuantil. El OLS minimiza los errores para los estudiantes cuyo resultado en Saber Pro está cercano a la media (proceso conocido como estimación en la media) mientras que el QR puede estimar un valor en el cuantil θ para cada 0 θ 1. Mostraremos que el QR es más preciso que el OLS y revelaremos el comportamiento desconocido del estrato socio económico, el género y la preparación académica inicial (estimada con el examen Saber 11) para cada cuantil

Value-added in higher education: ordinary least squares and quantile regression for a Colombian case

Colombia applies two mandatory National State tests every year. The first, known as Saber 11, is applied to students who finish the high school cycle, whereas the second, called Saber Pro, is applied to students who finish the higher education cycle. The result obtained by a student on the Saber 11 exam along with his/her gender, and socioeconomic stratum are our independent variables while the Saber Pro outcome is our dependent variable. We compare the results of two statistical models for the Saber Pro exam. The first model, multi-lineal regression or ordinary least squares (OLS), produces an overall well fitted result but is highly inaccurate for some students. The second model, quantile regression (QR), weight the population according to their quantile groups. OLS minimizes the errors for the students whose Saber Pro result is close to the mean (a process known as estimation in the mean) while QR can estimate in the -quantile for every . We show that QR is more accurate than OLS and reveal the unknown behavior of the socioeconomic stratum, the gender, and the initial academic endowments (estimated by the Saber 11 exam) for each quantile group

Análisis de puntos de rocío y contenidos de humedad de mezclas gaseosas n2-h2o y ch4-h2o

EI conocimiento actual del contenido de humedad de mezclas gaseosas saturadas es aún incompleto, especialmente en la región de altas presiones y bajas temperaturas. Por tanto se realizaron medidas experimentales de punta de rocío con los sistemas nitrógeno-agua y metano-agua, a presiones de 3 y 6 MPa y a temperaturas de 258 K a 288 K. Los puntos de rocío se determinaron con el método del espejo de punta de rocío y los contenidos de humedad por medio de la titulación de Karl-Fischer. Los valores experimentales se compararon con correlaciones de la literatura. El método de Sharma-Campbell resultó ser la mejor descripción del sistema nitrógeno-agua. Para temperaturas inferiores a 273 K la suposición de comportamiento de gas ideal mostro ser suficiente para el sistema metano-agua, mientras que para temperaturas superiores a 273 K los cálculos mediante el principio de estados correspondientes con dos parámetros, en combinación con una corrección de fugacidad, manifestó ser la mejor.The actual knowledge of the exact water content in saturated gas mixtures still is incomplete, especially in the high pressure and low temperature region. Hence, dew point measurements with nitrogen water and methan-water mixtures were performed, at pressures of 3 and 6MPa and temperatures from 258 K to 288 K. The dew points were determined with the dew point mirror method and the water content by means of the Karl-Fischer-titration. The experimental values were compared to correlations from the literature. The approach by Sharma-Campbell resulted in the best description of the system nitrogen water. For temperatures below 273 K the assumption of ideal behavior proved to be sufficient for the system methan-water, whereas for temperatures above 273 K calculations with the two-parameter corresponding states principle in combination with a fugacity correction turned out to be the best

Biodeterioration of plasma pretreated LDPE sheets by Pleurotus ostreatus.

Low-density polyethylene (LDPE) waste generates an environmental impact. To achieve the most suitable option for their degradation, it is necessary to implement chemical, physical and biological treatments, as well as combining procedures. Best treatment was prognosticated by Plackett-Burman Experimental Design (PB), evaluating five factors with two levels (0.25 mM or 1.0 gL-1 glucose, 1.0 or 2.0 mM CuSO4, 0.1 or 0.2 mM ABTS [2, 20-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)], pH 4.5 ± 0.2 or 7.0 ± 0.2 and 30 or 90 day incubation), which was reproduced for 150 days. Therefore, PB identified a sequential treatment (plasma followed by fungus) for partial LDPE biodeterioration. Sheets were pretreated with glow discharge plasma (O2, 3.0 x 10(-2) mbar, 600 V, 6 min.), followed by Pleurotus ostreatus biodeterioration. Fungus growth, colonization percentage, and pigment generation followed. Laccase (Lac), manganese peroxidase (MnP) and lignin peroxidase (LiP) activities were appraised. Additionally, contact angle (CA), functional group presence and changes and carbonyl and vinyl indices (Fourier transformed infrared spectroscopy) were evaluated. LDPE surface changes were assessed by Young's modulus, yield strength, scanning electronic microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Plasma discharge increased hydrophilicity, decreasing CA by 76.57% and increasing surface roughness by 99.81%. P. ostreatus colonization was 88.72% in 150 days in comparison with untreated LDPE (45.55%). After this treatment carbonyl groups (C = O), C = C insaturations, high hydrophilicity CA (16 ± 4) °, and low surface roughness (7 ± 2) nm were observed. However, the highest Lac and LiP activities were detected after 30 days (Lac: 2.817 U Lac g-1 and LiP: 70.755 U LiP g-1). In addition, highest MnP activity was observed at day 120 (1.097 U MnP g-1) only for P. ostreatus treated LDPE. Plasma favored P. ostreatus adsorption, adherence, growth and colonization (88.72%), as well as partial LDPE biodeterioration, supported by increased hydrophilicity and presence of specific functional chemical groups. The approximate 27% changes in LDPE physical properties support its biodeterioration

Biodeterioration of plasma pretreated LDPE sheets by Pleurotus ostreatus

supplementary material supporting the Low-density polyethylene (LDPE) partial deterioration after a combined treatment composed by glow discharge plasma (100% oxygen, 3.0 x10^-2mbar pressure, and 600 V voltage at a cathode distance of 5.6 cm), followed by <i>P. ostreatus </i>adherence, growth, and colonization

Diffusion problems on fractional nonlocal media

AbstractIn this paper, the nonlocal diffusion in one-dimensional continua is investigated by means of a fractional calculus approach. The problem is set on finite spatial domains and it is faced numerically by means of fractional finite differences, both for what concerns the transient and the steady-state regimes. Nonlinear deviations from classical solutions are observed. Furthermore, it is shown that fractional operators possess a clear physical-mechanical meaning, representing conductors, whose conductance decays as a power-law of the distance, connecting non-adjacent points of the body