Modeling Plain Vacuum Drying by Considering a Dynamic Capillary Pressure

A coupled drying model for wood is proposed by introducing a dynamic capillary pressure. The pressures of non-wetting phase, the wetting phase, and the capillary pressure at equilibrium has been considered as non-static; this approach includes a two-scale model. According to numerical results, liquid, water vapor and air dynamics in the chamber have strong interactions with re-homogenization in the surface, controlled by capillary forces. The results at 60–100 bar and 70 °C are discussed. The phenomenological one-dimensional drying model is solved by using the COMSOL’s coefficient form and a global equation format. A good description of drying kinetics, moisture redistribution, and mass fluxes is obtained. A comprehensible transition at the fiber saturation point is well simulated

Prevalencia de obesidad y hábitos alimentarios desde el enfoque de género: el caso de Dzutóh, Yucatán, México

El objetivo del estudio fue identificar el esta - do nutricional y los hábitos de alimentación desde un enfoque de género en la selección, preparación y consumo de los alimentos de una comunidad maya en el estado de Yuca - tán, México. Se emplearon mediciones an - tropométricas, encuestas de frecuencia de consumo de alimentos y lista de menús en cada comida, aplicadas a veintiún grupos domésticos, así como entrevistas a profun - didad realizadas a cuatro parejas. Los resul - tados muestran que la obesidad se presenta en la población adulta, mayoritariamente en mujeres, contrario a lo que sucede en la po - blación infantil, claro efecto de una trans - formación en la dieta de la población, no así en la división sexual del trabajo en el proce - so alimentario, la cual continúa apegada a los roles hegemónicos de género

Evaluación externa de la calidad en la determinación de ácido úrico en un grupo de laboratorios clínicos de Mérida-Venezuela

Los programas de evaluación externa de la calidad se inician en Venezuela en 1.977 para glucosa, urea y creatinina, reflejando escaso interés en la calidad de los análisis. Siendo importanteconocer el desempeño analítico en esta área, el objetivo de este trabajo es evaluar la determinación de ácido úrico en un grupo de laboratorios clínicos de Mérida- Venezuela. Para ello, se distribuyeron sueros controles comerciales: CN (“Control Normal”: 5,1 mg/dL) y CA (“ControlAnormal”: 9,70 mg/dL) quincenal y aleatoriamente a 14 laboratorios clínicos (públicos y privados, seleccionados al azar). Estos realizaron 3 determinaciones en cada suero control, utilizando el método uricasa-peroxidasa. Se determinó la precisión intralaboratorio e interlaboratorio mediante el coeficiente de variación (CV) y la exactitud intra e interensayo a través del Desvío Relativo Porcentual (DRP) de cada valor (intraensayo) y para la media de las tres determinaciones(interensayo), con respecto al valor de consenso. La menor imprecisión interlaboratorio se obtuvo en la segunda determinación en el CA (CV=9,75%), 42,9% de los laboratorios obtuvo precisiónintralaboratorio (CV menor o igual a 5%) y exactitud (DRP menor o igual a 15%) interensayo para ambos controles. Además, un 50% obtuvo exactitud en las tres determinaciones en el CA y el 57,14% en el CN. El mejor desempeño estuvo en el segundo envío con un 78,57% de laboratorios con DRP aceptable para el CN y 85,71% para el CA. Se concluyó que es necesario mejorar la confiabilidad en la determinación de ácido úrico en los laboratorios participantes

Evolución costera de la desembocadura del Guadalquivir en los últimos 6000 años (SW de España)

3 páginas, 2 figuras, 5 referencias.Since the last Holocene sea level rise, about 6,900 yr BP, a series of depositional littoral landforms has been generated at the outlet of the Guadalquivir river, with progradation along the predominant longshore drift (towards the east). The littoral spit systems mapped constitute fur progradation phases. The first is dated between the Flandrian maximum (6,900 yr BP) and 4,500 yr BP; the second between 4,200-3,900 yr BP and 2,700-2,600 yr BP; the third between 2,300 yr BP and 1,100 yr BP; and the fourth between 1,000 yr BP and the present. There were separations of successive erosional phases between 4,500-4,200 yr BP, 2,600-2,300 yr BP and, 1,100-1,000 yr BP. Thus, cycles of higher sedimentation are established, with a slight fall and then stability of sea level. Littoral barrier constructions dominate, with the genesis of extensive tidal flats that decrease the size of the estuaries. These sedimentary phases are interrupted by rapid rises in sea level lasting from 100 to 300 years, when the previously constructed littoral barriers are eroded. The cliffs retreat, causing migration inland of dunar constructions, with frequent overlapping layers. Marine influence within the estuaries in creases.Este trabajo ha sido subvencionado por los proyectos coordinados de la DGICYT PB91-0622-C03-0 1 y PB94-1090-C03-0l. Es una contribución al IGCP-367.Peer reviewe

Concentración de nutrientes en la escorrentía de diferentes predios del trópico enmendados con residuos animales bajo condiciones de lluvia natural.

Excessive nutrient losses from agricultural soils represent a major source of surface water contamination. In this study we quantified concentrations of total Kjeldahl nitrogen (TKN), dissolved and total phosphorus (DP,TP), and dissolved organic carbon (DOC) in runoff from two animal farm operations of Puerto Rico. The farms, one dairy and one poultry, represented typical conditions (i.e., topography, ecological zone, management system) of these production systems.Two fields were selected for the runoff studies on each farm, and two runoff collectors were installed in each field. Runoff samples were collected under natural rainfall conditions. The average phosphorus concentration in runoff from the poultry fields (5.87 mg TP/L, 4.82 mg DP/L) was significantly greater than that observed from the dairy fields (2.29 mg TP/L, 1.79 mg DP/L). Dissolved phosphorus concentrations represented more than 90% of the total P concentrations on both farms, a situation that may exacerbate the impact on receiving water bodies. Average DP concentrations exceeded 1 mg/L, a limit proposed for the regulation of runoff P concentrations from agricultural lands, in 70% of the runoff events at the dairy farm, and 100% of the events at the poultry farm. The magnitude of the nutrient concentrations on both farms was significantly affected by the time lapse between the manure applications and the first precipitation event. Nutrient concentrations in runoff samples were also significantly affected by rainfall depth.La pérdida excesiva de nutrientes de suelos agrícolas representa una fuente primaria de contaminación de los cuerpos de agua. En este estudio se cuantificaron las concentraciones de nitrógeno total Kjeldahl (NTK), fósforo total y disuelto (PD, PT), y carbón orgánico disuelto (COD) en la escorrentía de dos fincas productoras de animales de Puerto Rico. Las fincas, una vaquería y una avícola, son representativas de las condiciones típicas (i.e., topografía, zona ecológica, sistema de manejo) de estos sistemas de producción. En cada finca se seleccionaron dos predios para estudios de escorrentía y en cada predio se instalaron dos fraccionadores de escorrentía. Se recolectaron muestras de escorrentía generadas por eventos de lluvia natural. La concentración promedio de fósforo en la escorrentía de los predios avícolas (5.87 mg TP/L, 4.82 mg PD/L) fue significativamente mayor que la observada en los predios de la vaquería (2.29 mg PT/L, 1.79 mg PD/L). La concentración de PD representó cerca del 90% de la concentración de PT observada en ambas fincas, situación que puede agravar el impacto en las aguas circundantes. La concentración de PD promedio excedió 1 mg/L, límite propuesto para controlar la escorrentía de fósforo de predios agrícolas, en 70% de los eventos de escorrentía en el caso de la vaquería y en un 100% de los casos en la finca avícola. La magnitud de las concentraciones en ambas fincas se afectó significativamente por el lapso de tiempo transcurrido entre la aplicación de los residuos orgánicos y el primer evento de lluvia. La concentración de nutrientes en la escorrentía también se afectó significativamente con la profundidad de la lámina de lluvia

Mathematical Knowledge to Teach Physics and Teacher Training: The case of Kinematics graphs

It is mentioned in the literature that the theoretical construct called Pedagogical Knowledge of Content(CPC) provides methodological elements for the design of teacher training and updating programs. This work presents a proposal for the design of an update course for physics teachers in high school service, in the specific topic of kinematic graphs. The design of this was based on a previous work by the authors, in which they propose to characterize the CPC of the teachers inservice, by means of a closed scale Likert test. Based on this instrument, a course consisting of 10 tasks was designed, and where it is promoted in use of two digital tools: GeoGebra and Tracker

Solar photocatalytic degradation of polyethylene terephthalate nanoplastics: Evaluation of the applicability of the TiO2/MIL-100(Fe) composite material

For the first time, TiO2/MIL-100(Fe) photocatalysts supported on perlite mineral particles prepared by the solvothermal/microwave methods and post-annealing technique were tested in the degradation of polyethylene terephthalate nanoplastics (PET NPs). Powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, N2 physisorption, photoluminescence emission spectroscopy, photocurrent response, and electrochemical impedance spectroscopy were used to characterize the as-prepared materials. The response surface methodology approach was used to study the effects: pH of the NPs suspension and incorporated amount of MIL-100(Fe) on the TiO2/MIL-100(Fe) catalyst to optimize the photocatalytic degradation of the PET NPs under simulated solar light. The degradation of the PET NPs was evaluated by measuring turbidity and carbonyl index (FTIR) changes. The total organic carbon (TOC) in the solution during the degradation of the PET NPs was assessed to measure NPs oxidation into water-soluble degradation by-products. The active species involved in the photocatalytic degradation of PET NPs by the TiO2/MIL-100(Fe) composite was further examined based on trapping experiments. The use of 12.5 wt% TiO2/MIL-100(Fe) catalyst showed improved photocatalytic efficacy in the oxidation of PET NPs at pH 3 under simulated sunlight compared to bare TiO2. The increase in the carbonyl index (CI = 0.99), the reduction in the turbidity ratio (0.454), and the increase in the content of TOC released (3.00 mg/L) were possible with 12.5 wt% TiO2/MIL-100(Fe) material. In contrast, the PET NPs were slowly degraded by TiO2-based photocatalysis (CI = 0.96, turbidity ratio = 0.539, released TOC = 2.12 mg/L). The mesoporous TiO2/MIL-100(Fe) composites with high specific surface area, capacity to absorb visible light, and effective separation of photogenerated electron-hole charges clearly demonstrated the enhancement of the photocatalytic performance in the PET NPs degradation under simulated solar light

An asymptotic LMPI test for cyclostationarity detection with application to cognitive radio

We propose a new detector of primary users in cognitive radio networks. The main novelty of the proposed detector in comparison to most known detectors is that it is based on sound statistical principles for detecting cyclostationary signals. In particular, the proposed detector is (asymptotically) the locally most powerful invariant test, i.e. the best invariant detector for low signal-to-noise ratios. The derivation is based on two main ideas: the relationship between a scalar-valued cyclostationary signal and a vector-valued wide-sense stationary signal, and Wijsman's theorem. Moreover, using the spectral representation for the cyclostationary time series, the detector has an insightful interpretation, and implementation, as the broadband coherence between frequencies that are separated by multiples of the cycle frequency. Finally, simulations confirm that the proposed detector performs better than previous approaches.The work of P. Schreier was supported by the Alfried Krupp von Bohlen und Halbach Foundation, under its program “Return of German scientists from abroad”. The work of I. Santamaría and J. Vía was supported by the Spanish Government, Ministerio de Ciencia e Innovación (MICINN), under project RACHEL (TEC2013-47141-C4-3-R). The work of L. Scharf was supported by the Airforce Office of Scientific Research under contract FA9550-10-1-0241

A regularized maximum likelihood estimator for the period of a cyclostationary process

We derive an estimator of the cycle period of a univariate cyclostationary process based on an information-theoretic criterion. Transforming the univariate cyclostationary process into a vector-valued wide-sense stationary process allows us to obtain the structure of the covariance matrix, which is block-Toeplitz, and its block size depends on the unknown cycle period. Therefore, we sweep the block size and obtain the ML estimate of the covariance matrix, required for the information-theoretic criterion. Since there are no closed-form ML estimates of block-Toeplitz matrices, we asymptotically approximate them as block-circulant. Finally, some numerical examples show the good performance of the proposed estimator.The work of P. Schreier was supported by the Alfried Krupp von Bohlen und Halbach Foundation, under its program “Return of German scientists from abroad”. The work of I. Santamaría and J. Vía was supported by the Spanish Government, Ministerio de Ciencia e Innovación (MICINN), under project RACHEL (TEC2013-47141-C4-3-R). The work of L. Scharf was supported by the Airforce Office of Scientific Research under contract FA9550-10-1-0241

An asymptotic GLRT for the detection of cyclostationary signals

We derive the generalized likelihood ratio test (GLRT) for detecting cyclostationarity in scalar- valued time series. The main idea behind our approach is Gladyshev’s relationship, which states that when the scalar-valued cyclostationary signal is blocked at the known cycle period it produces a vectorvalued wide-sense stationary (WSS) process. This result amounts to saying that the covariance matrix of the vector obtained by stacking all observations of the time series is block-Toeplitz if the signal is cyclostationary, and Toeplitz if the signal is wide-sense stationary. The derivation of the GLRT requires the maximum likelihood estimates of Toeplitz and block-Toeplitz matrices. This can be managed asymptotically (for large number of samples) exploiting Szegö’s theorem and its generalization for vector-valued processes. Simulation results show the good performance of the proposed GLRT.The work of L. Scharf was supported by the Airforce Office of Scientific Research under contract FA9550-10-1-0241. The work of I. Santamaría and J. Vía was supported by the Spanish Government, Ministerio de Ciencia e Innovación (MICINN), under project COSIMA (TEC2010-19545-C04-03) and project COMONSENS (CSD2008-00010, CONSOLIDER-INGENIO 2010 Program). The work of P. Schreier was supported by the Alfried Krupp von Bohlen und Halbach Foundation, under its program “Return of German scientists from abroad