A study was conducted at the Experimental Station of Pastures and Forages «Indio Hatuey» in order to determine the composition, by genera, of the seed bank of a Ferralitic Red soil under livestock production; which was inserted in a multi-associated silvopastoral system with more than 10 years of exploitation. A randomized block design with three repetitions was used, and the treatments were the sampling depths 0-5 and 5-10 cm. The work was done in a 4-ha lot on which three strips were drawn, divided into 8 x 10 m plots. The soil samples were extracted from a 1-m² area. Eight grass and legume genera were identified; the most frequent ones were: Panicum (78,7 %), Leucaena (9,27 %), Neonotonia (6,03 %) and Teramnus (2,35 %). There were significant differences (p < 0,05) in favor of the depth 0-5 cm, in which the highest seed proportion was found. Neonotonia and Leucaena showed the highest percentage of hard seeds, although all the legumes showed high viability. It is concluded that there was a high reserve of Guinea grass seed in the soil of the multi-associated system, as well as diversity of legume genera. In addition, a high percentage of seed was found in the higher stratum of the soil (0-5 cm), which can constitute an advantage in the processes of pastureland renewal with these plants.

En la Estación Experimental de Pastos y Forrajes «Indio Hatuey» se desarrolló una investigación, con el objetivo de determinar la composición, por géneros, del banco de semilla de un suelo Ferralítico Rojo en explotación ganadera; el cual estaba insertado en un sistema silvopastoril multiasociado con más de diez años de explotación. Se empleó un diseño de bloques al azar con tres repeticiones, y los tratamientos fueron las profundidades de muestreo de 0-5 y 5-10 cm. Se trabajó en un lote de 4 ha sobre el que se trazaron tres franjas, divididas en parcelas de 8 x 10 m. Las muestras de suelo se extrajeron de un área de 1 m². Se identificaron ocho géneros de gramíneas y leguminosas; los más frecuentes fueron: Panicum (78,7 %), Leucaena (9,27 %), Neonotonia (6,03 %) y Teramnus (2,35 %). Hubo diferencias significativas a favor de la profundidad de 0-5 cm, en la cual se encontró la mayor proporción de semillas. Neonotonia y Leucaena presentaron el mayor porcentaje de semillas duras, aunque todas las leguminosas mostraron una alta viabilidad. Se concluye que existió una alta reserva de semilla de guinea en el suelo del sistema multiasociado, así como diversidad de géneros de leguminosas. Además, se encontró un alto porcentaje de semilla en el estrato superior del suelo (0-5 cm), lo que puede constituir una ventaja en los procesos de renovación de los pastizales con estas plantas.

This paper presents an analysis and design of discrete-time controllers based on the internal model principle, applied to shunt active power filters. The presented control strategies are aimed to compensate the current harmonics produced by nonlinear loads connected to the point of common coupling in low voltage power grids. The proposed current controllers are based on the internal model principle operating with different sampling frequencies and for even and odd or only odd harmonics. It is demonstrated that the use of a downsampled rate, and fewer poles in the internal model, results in a straightforward digital implementation; improvement of the transient response; increasing of the stability margin of the closed-loop system and it is possible to obtain source currents with reduced total harmonic distortion. To validate the above claims and demonstrate the steady-state and transient performance, simulation results are presented

Introduction. Obesity is associated with a wide range of cardiovascular and metabolic diseases. Objective. To establish an association between the nutritional status of 6-10 year old boys and girls and blood pressure. Population and Methods. A cross-sectional, analytical study was conducted in 6-10 year old schoolboys and schoolgirls. Outcome measures and indicators studied included nutritional status as per body mass index; presence of central fat mass distribution estimated by waist circumference; and blood pressure (height, age and gender tables). Differences in mean values were analyzed using a Student's t test. The relationship between outcome measures was estimated using Pearson's correlation coefficient. Linear regression models were adjusted for systolic blood pressure and diastolic blood pressure using the following explanatory outcome measures: z scores for body mass index, age, gender and waist circumference. Results: Five hundred and fifty five male and female children were evaluated; they were all younger than 11 years old. A total of 26.3% was overweight and 15.1% was obese. The prevalence of hypertension was 1.08%. Results show a positive linear relationship between systolic and diastolic blood pressure, and age and waist circumference, and a trend is observed between systolic blood pressure and the body mass index z score (p= 0.068). Conclusion. Overweight and obesity were the most common nutritional disorders in schoolaged children in the studied district; there is an association between age, waist circumference, and systolic and diastolic blood pressure, and between systolic blood pressure and the body mass index z score.

We determined the genetic components, and the correlation between the F1 and the F2 generations, for traits like seed and seedling vigor using a diallel crossing design. The study involved six tropical maize inbred lines from the CIMMYT. Crosses were formed in CIMMYT's Maize Research Station in Tlaltizapan, Morelos during the summer of 2004. In order to produce F2 seeds, F1 crosses were grown at Tepalcingo, Mor. and Iguala, Guerrero. This was accomplished by controlling pollinations (half sibs). Seeds from the F1 and the F2 crosses were evaluated at the Colegio de Postgraduados, Montecillo, Mexico. F1 and F2 seeds were used to perform a standard germination test. Seed vigor was evaluated after conducting a seed aging treatment, and conductivity and seed weight were also determined. A test for emergence on sand bed was also conducted. Variables recorded included percentage, speed and index of emergence; canopy dry weight; seedling height and vigor indexes I and II. Significant (p≤0.01) effects of the General Combining Ability (GCA) were observed for all traits in both the F1 and F2 generations. GCA effects were greater than those of Specific Combining Ability (SCA). The only exception was vigor after the accelerating age treatment for the F1 seed. Maternal effects in the F1 generation were significant (p≤0.01) for all characters. However, seedling height, canopy dry weight and vigor indexes I and II were not influenced by the female parent in the F2 generation. Parents CML 396 and CML 407 had the highest GCA for seed vigor, while 245 CML expressed the same condition for seedling vigor traits in both generations for most traits evaluated. These materials might be considered for integrating a program of breeding for seed and seedling vigor. On the other hand, there was no direct and significant association of the GCA in the F1 versus the F2 generations for all evaluated traits.

Se usó un diseño de cruzas dialélicas involucrando seis líneas endogámicas de maíz tropical para determinar los componentes genéticos y la correlación entre las generaciones F1 y F 2 para caracteres de vigor (1) de semilla y (2) de plántula. Dichas líneas endogámicas fueron producidas en Tlaltizapan, Mor. en Verano de 2004. Para producir la generación F2, las cruzas F1 fueron sembradas en Tepalcingo, Mor. e Iguala, Gro., usando polinización controlada (medios hermanos). Las semillas de las cruzas F1 y F2 fueron evaluadas en el Colegio de Postgraduados, Montecillo, Méx . En semilla se determinó el porcentaje de germinación estándar. El vigor se midió a través de la prueba de envejecimiento acelerado, la conductividad eléctrica y el peso de semilla. Mediante la prueba de emergencia en cama de arena, se determinaron el porcentaje, la velocidad y el índice de la tasa de emergencia, el peso seco de la parte aérea, la altura de plántula, y los índices de vigor I y II. Los efectos de la Aptitud Combinatoria General (ACG) en todos los caracteres evaluados en las dos generaciones (F1 y F2) fueron significativos (p≤0,01). Estos efectos fueron mayores a los de la Aptitud Combinatoria Específica (ACE), excepto para el vigor a través de la prueba de envejecimiento acelerado de semilla en la F1. Los efectos maternos en la F1 fueron significativos (p≤0,01) para todos los caracteres. Sin embargo en la F2, la altura de plántula, el peso seco de la parte aérea y los índices de vigor I y II no fueron afectados por el progenitor femenino. Los progenitores CML 396 y CML 407 presentaron la más alta ACG para vigor de semillas, mientras que la línea CML 245 manifestó la misma condición para caracteres de vigor de plántula en ambas generaciones para la mayoría de los caracteres evaluados. Estos materiales pueden ser considerados para integrarlos a un programa de mejoramiento genético para vigor de semilla y de plántula. Por otro lado, no existió asociación directa y significativa entre la ACG de las generaciones F1 y F2 para los caracteres evaluados.

The aim of the present work was to describe the distribution of lymphocyte P-glycoprotein activity on a population of healthy individuals, taking also into account sex and age. P-glycoprotein activity in lymphocytes was measured by the Rhodamine 123 efflux assay using flow cytometry, in the presence and absence of verapamil, a P-glycoprotein inhibitor. We obtained a range of P-glycoprotein activity from 1.04 to 3.79. The distribution of the activity in the population studied was better described by a bimodal model, according with the Kolmogorov-Smirnov test. The frequency adjusted to the following equation: F = 0.70 N (2.11; 0.43) + 0.30 N(3.29; 0.26), in which 0.70 and 0.30 represented the proportion of each group, and 0.43 and 0.26 were the standard deviations of the activity of each group, respectively. The study of the relationship between subjects´ age and P-glycoprotein activity showed no statistical significance. When healthy volunteers were separated according to sex, similar distributions were observed, although for men an increase in proportion of higher P-glycoprotein function group was observed. The variability observed in the population studied was important, with some volunteers with very scarce activity and some with a fourfold higher activity. Characterization of P-glycoprotein functionality in the population represents a useful contribution to the beginning of pharmacological treatments that consider its effect on pharmacokinetics and pharmacodynamics of individualized patients.

El objetivo del presente trabajo fue describir la distribución de la actividad de la glicoproteína P linfocitaria en una población de individuos sanos, considerando a su vez el sexo y la edad. La funcionalidad de la glicoproteína P fue determinada mediante el ensayo de eflujo de Rodamina 123, en presencia y ausencia de verapamilo, un inhibidor competitivo de este transportador, determinando la fluorescencia intracelular remanente mediante citometría de flujo. Obtuvimos un rango de actividades de entre 1.04 y 3.79. La distribución de la actividad en la población evaluada se ajusta a un modelo bimodal, según el test de Kolmogorov-Smirnov. La frecuencia ajusta a la siguiente ecuación: F = 0.70 N (2.11; 0.43) + 0.30 N (3.29; 0.26) donde 0.70 y 0.30 representan las proporciones de cada grupo, mientras que 0.43 y 0.26 corresponden al desvío estándar de la actividad de cada grupo respectivamente. Al estudiar la correlación entre la edad de los sujetos y la función de la proteína, no se observaron diferencias significativas. Cuando los individuos fueron clasificados en función del sexo, las distribuciones obtenidas fueron semejantes, aunque para los varones se observó un aumento en la proporción de individuos con alta actividad. La variabilidad observada fue importante, comprendiendo individuos con escasa actividad y otros que presentaron una actividad hasta cuatro veces mayor. La caracterización de la función de la glicoproteína P en la población representa una contribución indispensable para el desarrollo de tratamientos farmacológicos personalizados que consideren el efecto de dicho transportador en la farmacocinética y farmacodinámica de cada paciente.