6,239 research outputs found
Modelado de las curvas de supervivencia de E.Coli en bebidas refrescantes y en preparados lácteos (modelo Baranyi)
E. coli O157:H7 es un microorganismo perteneciente a la familia Enterobacteriaceae. Forma parte de la flora normal del intestino del hombre y de los animales de sangre caliente; está implicada en una serie de enfermedades transmitidas por los alimentos, causando brotes de colitis hemorrágica y síndrome urémico hemolítico.
Entre los alimentos implicados se incluyen carnes elaboradas y cocidas de manera insuficiente, frutas y hortalizas crudas, productos lácteos y zumos de frutas no pasteurizados.
Se ha aplicado el modelo matemático de Baranyi y Roberts (1994) para la estimación de los parámetros de supervivencia de Escherichia coli no patógeno CECT 516 (EC) y Escherichia coli O157:H7 CECT 4076 y CECT 4267 (ECO) en Bebidas refrescantes comerciales y Preparados lácteos comerciales pasteurizados a 4 y 20ºC. El modelo permite estimar el tiempo de latencia, la velocidad máxima de decrecimiento y la población final.
A 20ºC el tiempo necesario en no detectarse células viables fue de 3-5 días en el caso de las Bebidas refrescantes tipo A y B, y de 6-17 días en el caso de los Preparados lácteos tipo A y B. A 4ºC el tiempo necesario fue de 7 días en el caso de las Bebidas refrescantes tipo A y B y de 11- 24 días en el caso de los Preparados lácteos Tipo A y B.
El tiempo necesario para no detectarse células viables es menor a 20ºC que a 4ºC; a su vez es menor en las Bebidas refrescantes que en los Preparados lácteos. Dentro de los distintos tipos de Bebidas refrescantes y Preparados lácteos la inactivación del microorganismo es más rápida en los Tipo A que en los Tipo B. En los Preparados lácteos el tiempo en inactivar EC fue menor que en inactivar ECO mientras que en las Bebidas refrescantes no hubo diferencias significativas en el tiempo empleadoGrado en Nutrición Humana y Dietétic
Dieta de Phrynosoma orbiculare (Squamata: Phrynosomatidae) en una población del Estado de México
Se logró determinar los factores bióticos y abióticos que afectan la dieta de una especie de lagartija amenzada y endémica en MéxicoLa dieta es un elemento primordial en la vida diaria de los organismos, ya
que gracias a ésta obtienen la energía necesaria que les permita sobrevivir y
reproducirse. En reptiles, la dieta se ha determinado mediante diversos métodos,
entre ellos: la extracción estomacal; sin embargo, también se han utilizado heces
fecales, lavado estomacal, isotopos estables o mediante observación directa. De
acuerdo a diversos estudios, se ha registrado que la dieta de las lagartijas del
género Phrynosoma está compuesta principalmente de hormigas (i. e.,
mirmecofagia), aunque coleópteros y ortópteros también han sido encontrados
frecuentemente. La evidencia disponible indica que el grado de mirmecofagia varía
intra e interespecíficamente. En este estudio se observó la composición alimentaria
(incluyendo el grado de mirmecofagia) y su variación individual, sexual y estacional
de Phrynosoma orbiculare en una población del Parque Estatal Sierra Morelos
(PESM), en Toluca, Estado de México. Se capturaron individuos adultos a los que
se les aplicó la técnica de lavado estomacal. Las presas se determinaron al nivel
taxonómico más bajo, se contó cada presa, se tomó su largo y ancho y se calculó
su volumen con la fórmula de un elipsoide. Para cada categoría de presa se
calcularon los siguientes parámetros: (1) volumen relativo, (2) abundancia relativa,
(3) incidencia de presa, y (4) valor de importancia. Adicionalmente, se calculó la
amplitud del nicho trófico mediante el índice estandarizado de Levin’s para la
población, para cada sexo y en cada estación; el índice de similitud de Pianka se
calculó entre sexos; se determinó la variación individual en el volumen consumido
de himenópteros por estación y se realizó una regresión lineal para determinar si
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existía una correlación entre la LHC y las medidas morfométricas de las presas
consumidas. Se capturaron 68 individuos, sin embargo solo se utilizaron 62 (29
machos y 33 hembras). Los individuos se obtuvieron en tres estaciones climáticas:
primavera (n = 16), verano (n = 39) y otoño (n = 7); debido a una actividad
prácticamente nula, durante invierno no se capturaron individuos. Se registraron 13
categorías de presa; adicionalmente se registró en dos individuos el consumo de
muda. Los resultados indicaron que P. orbiculare en el PESM es especialista, con
un elevado grado (91.2%) de mirmecofagia (se registraron 1365 himenópteros de
un total de 1494 presas). Aunque existen variaciones ligeras en la abundancia de
himenópteros, coleópteros e isópodos, existe un alto solapamiento de nicho entre
sexos. Existe variación en el grado de mirmecofagia entre estaciones, donde el
mayor consumo se presentó en primavera y el menor en otoño. Individualmente el
volumen consumido de himenópteros disminuye entre las estaciones o tiende a
mantenerse. No se encontró relación de la LHC de los individuos con la morfometría
de sus presas. P. orbiculare en el PESM presenta el mayor grado de mirmecofagia
dentro del clado Tapaja y el segundo más elevado dentro del género Phrynosoma.
Finalmente, se registra por vez primera el consumo de muda para el clado Tapaj
Las mujeres cuentan
Brave women, women who made themselves, women who did not allow themselves to be dominated and who gave everything. Working, funny, fighting, sensual and crafty women. All of them are the main characters of this storytelling. Stories from the oral tradition and literary tales.Mujeres valientes, mujeres que se hicieron a ellas mismas, mujeres que no se dejaron dominar y que lo dieron todo. Mujeres trabajadoras, divertidas, luchadoras, sensuales y pícaras. Todas ellas son las protagonistas de esta sesión de cuentos. Cuentos de la tradición oral y cuentos literarios
Geographic web information system for the control of construction licenses for the planning office of La Vega Cundinamarca
La secretaria de planeación municipal de La Vega Cundinamarca, dentro de sus funciones, otorga las licencias de construcción necesarias para el desarrollo de obras civiles de construcción o ampliación en los predios que se van a ejecutar dentro del territorio municipal. Estas licencias tienen una vigencia de tres años en promedio y se debe ejercer vigilancia sobre la ejecución de las licencias otorgadas, no solo en el tiempo, sino en sus parámetros que las limitan.
El sistema de información geográfica web para el control de licencias de construcción para el municipio de La Vega, Cundinamarca pretende ser una herramienta para la gestión de seguimiento, verificación y control de las licencias de construcción otorgadas en el municipio, permitiendo georreferenciar cada una de las licencias dentro del área municipal, facilitando así dicho control, permitiendo verificar el estado de cada una en el tiempo de vigencia, ayudando al visitador o verificador en su tarea.Alcaldía de La VegaThe Secretary of planning office of la Vega Cundinamarca municipality has within their functions to grant cnstruction licenses as needed for the development of civil construction work or to execute the improvement of property within the bounds of the municipality. These licenses have an average effective life of three years and must practice vigilance in the execution of the granted licenses, not only during the time period but also within the parameters limits.
The geographic web information system for the control of construction licenses for the La Vega Cundinamarca municipality pretend to be a tool for the gestion of pursuit the verification and control of the construction licenses granted in the municipality permiting and georefering each one of the licenses in the municipal area to ease this control and permiting to verifiy the stage of each one during the time to be efective, helping the inspector or the verificator in his job
Biogeographical patterns of species richness, range size and phylogenetic diversity of ferns along elevational-latitudinal gradients in the tropics and its transition zone
Although elevational-latitudinal patterns of plant and animal diversity have been studied for centuries, factors driving the observed patterns are still controversially discussed. Tropical mountains offer an excellent natural experiment to unravel these drivers of biogeographical patterns and the integration of multiple elevational gradients along an extended latitudinal gradient is an outstanding opportunity to decipher underlying mechanism of large-scale patterns of species richness. In this research the data obtained from Mexico were unified with elevational transects in America spanning 0° to 23°N degrees of latitude, mostly between sea level and mountain tops (200-4000 m a.s.l.). Hereby, the latitudinal gradient covered by this investigation runs from most studied tropics through the transition zone of sub-tropical regions in order to integrate increasingly seasonal and dry climates, which are known to limit the diversity of ferns as humidity-dependent organisms.
How the fern and lycophytes (hereafter ferns) richness and species range size patterns change along elevational-latitudinal gradients is poorly explored, as well as the phylogenetic relationships within species assemblages. The objective of this research was to describe such patterns and understand the broad scale distribution of other important components of biodiversity as the phylogenetic diversity and associated metrics, using a standardized methodology that allows the comparison of elevational transects. In order to assess these patterns, I first intensively sampled an elevational gradient in the Sierra de Juárez, Oaxaca, Mexico, known as the “ferns hunter paradise”, a hotspot of biodiversity in a hyperhumid tropical region. Following the uniform sampling protocol of the working group around Michael Kessler (Zurich) and Jürgen Kluge (Marburg), I sampled at each elevation four to eight plots of 20 x 20 m (400m2) and analyzed changes in fern assemblages along this elevational gradient. The plots were established in natural zonal forest, avoiding special structural features and disturbed areas whenever possible. In each plot, DNA samples were taken and all fern species and their abundances were recorded for terrestrials and epiphytes. The results are presented in a series of chapters starting from the analyses of the gradient in Mexico, followed by the central work of this research, where richness and range size patterns of eight elevational transects in Mexico were analyzed together with climatic correlates, and the assessment of the historical component (phylogenetics) of 11 elevational gradients understanding the processes that governs the species richness. In the following the central questions and results of the three studies will be briefly described.
In Chapter 2 we analyzed in detail one of the most diverse elevational transect in Mexico with 15 elevational steps in Sierra de Juárez Oaxaca, a hotspot of biodiversity, comparing the richness patterns with central and South America. In 121 plots we found 195 fern species, with the highest species numbers recorded at mid-elevations (1,100–2,200 m) and lower richness at both gradient extremes. This hump-shaped pattern was mainly driven by epiphytes, which contributed about 40% to the total species richness. This species group had wider elevational ranges than terrestrial species, which contributed 38% to the total richness (20 % were recorded within both life forms), and were more or less constant at low to mid elevations about 2,500 m, followed by a gradual decline. Overall, richness per plot was low compared to other elevational gradients within the tropics closer to the Equator. This decline of species richness towards the subtropics and temperate regions appears to be rather abrupt within Central America, but additional data are needed to close the remaining gap of knowledge between Costa Rica and Mexico. This work has been published 2018 in the American Fern Journal (Hernández-Rojas et al. 2018).
In the central work of this research (Chapter 3), we assessed the richness and range size patterns of ferns and lycophytes along seven elevational gradients (with in total 658 plots) at different latitudes and searched for predictors of range size from a set of environmental factors. We calculated the latitudinal range using the northern and southern limits of each species and averaged the latitudinal range of all species within assemblages weighted by their abundances. We related climatic factors and the changes with latitude and elevation with range size using linear mixed-effects models. Species richness per plot increased with elevation up to about 1,500-2,000 m, with strong differences in overall species richness between transects and a reduction with increasing latitude. The mean weighted range size of species within assemblages declined with elevation, and increased with latitude. However, we also found marked differences between the Atlantic and Pacific slopes of Mexico, as well as low range size in humid regions. The best models described about 76%–80% of the variability in range size and included the seasonality of both temperature and precipitation, and annual cloud cover. As a conclusion, latitudinal and elevational patterns of range size in fern assemblages are driven by an interplay of factors favoring wide-ranging species (higher latitudes with increasing temperature seasonality and dryer habitat conditions) and those favoring species with restricted ranges (higher elevations with more humid habitat conditions), with additional variation introduced by the specific conditions of individual mountain ranges. Climatically stable, humid habitats apparently provide favorable conditions for small-ranged fern species, and should accordingly be given high priority in regional conservation planning. This work was published 2020 in the Journal of Biogeography (Hernández-Rojas et al. 2020).
Finally, phylogenetic approaches should be seen as an integral component of studies of the causal basis of community structure, which permits the understanding of how communities have evolved through time, and a deeper understanding of biogeographical processes. This historical aspect is included as the final part of this research (Chapter 4) that was aimed to unfold the complex changes in the phylogenetic structure along elevation (200-4000 m.a.s.l.) and latitude (0°-23° N). We compiled a comprehensive data set including eleven elevational transects (more than 900 spp. and 868 plots), closing the gap of information observed in Chapter 2. At this point I should highlight the relevance of this research as a product of the work of many researchers that I have the honor to synthesize to get a complete view of biogeographic and phylogenetic patterns. One of the major tasks before analyzing the data was to compile the phylogenetic information of the more than 900 species, of which only 70 % were already present in the most recent dissolved phylogenetic tree, and the remaining 30 % species had to be added on the basis of putative closest relatives due to exhaustive examination of morphological characteristics and expert knowledge. Our results showed that latitude and elevation per se are weak explanatory variables for phylogenetic diversity, but incorporating climatic variables clearly enhance the explanatory power of the models. We used different phylogenetic measures in order to capture different aspects of evolutionary history of this plant group and were thus able to understand, how species groups have evolved to currently form the observed gradients in Central America. Overall, the phylogenetic diversity decreased with increased latitude and elevation, as could be observed by increasingly clustering of closely related species. Additionally, it is worthwhile to look at taxonomic group of ferns separately for the main lifeforms, as they are not only ecologically different, but also not congruent in their evolutionary history. Epiphytic phylogenetic diversity had a positive relationship with humidity, while the phylogenetic diversity of terrestrial was determined by temperature. The general pattern of phylogenetic diversity is mainly driven for the suppression of the old, basal tropical, terrestrial lineages rather than by recent evolutionary history and better explained by climatic variables. This work was submitted to frontiers of biogeography. In continuation of this work and as an outlook to further studies, I am heading for to continue the research in tropical areas, where the deforestation and disturbance, respectively, and general human activities play a central role, which are impacting tremendously the legacy of millions of years of evolution. In the context of the species richness patterns, it is necessary to fill the gaps of knowledge present in America. In this regard, I will intend t
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