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Haemosporidian parasite prevalence, parasitemia, and diversity in three resident bird species at a shrubland dominated landscape of the Mexican highland plateau
Get PDF"Background:
Studies of avian haemosporidians allow understanding how these parasites affect wild bird populations, and if their presence is related to factors such as habitat loss, degradation and fragmentation, and climate change. Considering the importance of the highland Plateau of Mexico as part of the North American bird migratory route and as a region containing important habitat for numerous bird species, the purpose of this study was to document haemosporidian species richness and how habitat degradation, bird body condition, and distance from water sources correlate with bird parasitemia.
Methods:
We assessed the presence of avian haemosporidians in three resident bird species through microscopy and PCR amplification of a fragment of the haemosporidian cytochrome b gene. Average parasitemia was estimated in each species, and its relationship with habitat degradation through grazing, bird body condition and distance from water bodies was assessed.
Results:
High levels of parasitemia were recorded in two of the three bird species included in this study. Four lineages of haemosporidians were identified in the study area with nearly 50 % prevalence. Areas with highly degraded shrublands and villages showed higher parasitemia relative to areas with moderately degraded shrublands. No strong relationship between parasitemia and distance from water bodies was observed. There were no significant differences in prevalence and parasitemia between the two bird species infected with the parasites. Two of the sequences obtained from the fragments of the parasite's cytochrome b gene represent a lineage that had not been previously reported.
Conclusions:
Haemosporidian diversity in arid zones of the Mexican highland plateau is high. Shrubland habitat degradation associated to the establishment of small villages, as well as tree extraction and overgrazing in the surroundings of these villages, significantly enhances parasitemia of birds by haemosporidians.
Generación de sistemas dinámicos lineales por partes caóticos sin puntos de equilibrio
Get PDF"Los sistemas dinámicos con comportamiento caótico han sido de gran utilidad para el modelado de fenómenos así como para el desarrollo de nueva tecnología en diversas áreas del conocimiento. En 1994 Sprott reportó 19 casos de sistemas caóticos con una o dos no linealidades en las ecuaciones diferenciales de su campo vectorial asociado. Un descubrimiento no esperado fue la ausencia de puntos de equilibrio en uno de estos, el caso conocido como Sistema Sprott A. A partir de esto, surge el interés por generar sistemas dinámicos caóticos sin puntos de equilibrio que ha llevado a la publicación de diferentes sistemas dinámicos con no linealidades de tipo cuadrático, cúbico, función signo y valor absoluto, así como métodos de búsqueda numéricos. En esta tesis se presentan tres sistemas sin puntos de equilibrio de los cuales uno exhibe un atractor multienroscado.""Dynamical systems with chaotic behavior have been useful for modeling phenomena and to develop new technology in various areas of knowledge. In 1994 Sprott reported 19 cases of chaotic systems with one or two non-linearities in the differential equations of its associeted vector field. An unexpected finding was the absence of equilibrium points in one of these, the case known as Sprott System A. From this arise the interest in generating chaotic dynamical systems without equilibria that has led to the publication of different dynamcial systems with quadratic, cubic, sing function and absolute value nonlinearities and numerical search methods. In this thesis three systems without equilibrium points are presented, one of which exhibits a multienroscado attractor.
Síntesis de pozos cuánticos de GaN/InGaN/GaN en estructura cúbica para emisión sintonizada de luz
No full text"En años recientes la utilización de dispositivos de iluminación de luz blanca de estado sólido ha ido aumentando de forma significativa. El ahorro en energía y por tanto económico a largo plazo que dispositivos como LED's pueden traer a nivel mundial son considerables. Por ello, la búsqueda de una mayor eficiencia en dichos dispositivos ha sido un tema constante de investigación en las empresas fabricantes de diodos emisores de luz que existen en el mercado. Los diodos emisores de luz blanca que existen actualmente contienen la fase hexagonal de la aleación ternaria InGaN. Teóricamente se sabe que la fase cúbica podría ser más eficiente que la hexagonal. Con la ayuda de técnicas de caracterización como difracción de rayos X, difracción de electrones de altas energías, microscopía de barrido, microscopía de fuerza atómica y fotoluminiscencia, en esta tesis se analizaron las condiciones óptimas de crecimiento de GaN, InN y InGaN en fase cúbica crecidas mediante epitaxia por haces moleculares. Una vez que se encontraron las condiciones óptimas, se sintetizaron pozos cuánticos individuales de InGaN con barreras de GaN. Luego, una heterestructura de pozos de InGaN en fase cúbica se construyó. Mediante fotoluminiscencia se encontraron distintas emisiones de la muestra dentro del espectro visible""In recent years, the use of solid-state white light emitting devices has increased signi cantly. There are considerable long-term energy and economic savings that devices such as LED's can provide worldwide. Therefore, the search for greater efficiencies in these devices has been a constant theme of research for manufacturers of light emitting diodes. The white light emitting diodes currently on the market contain the hexagonal phase of the ternary InGaN alloy. Theoretically, it is know that the InGaN cubic phase might be more efficient than the hexagonal phase. With the help of characterization techniques such as X-ray diffraction, reflection high energy electron diffraction, electronic scanning microscopy, atomic force microscopy and photoluminescence, in this thesis the optimal conditions for growing cubic GaN, InN and InGaN by molecular beam epitaxy were found. Once the optimum conditions were found, InGaN single quantum wells with GaN barriers were synthesized.Then, a heterestructure with cubic phase InGaN quantum wells was constructed, achieving different emission within the visible spectrum.
Modelo Geofísico-Estructural de la Porción Norte del Graben de Colima
Get PDF"La presente investigación se realizó en la porción norte del Graben de Colima, donde se aplicaron métodos geofísicos potenciales (Magnetometría Aérea y Gravimetría) con el objetivo de definir la estructura interna del graben y las fallas geológicas asociadas. La información generada a partir del procesamiento de los datos Aeromaganéticos mostró lineamientos magnéticos correlacionados a posibles fallas geológicas. Se identificaron seis Dominios Aeromagnéticos (DAM), de los cuales, los asociados a la porción norte del Graben de Colima son: DAM II, localizado en la parte central, correspondiente a rocas vulcano-sedimentarias; y DAM IV, localizado en el flanco occidental, asociado a flujos basaltico-andesiticos El análisis del mapa de Anomalía Residual de Bouguer permitió delimitar la fosa del graben, identificándola como una zona de anomalías negativas (-7 a -3.8 mGal), mientras que los flancos se caracterizaron por presentar anomalías positivas (> 2.4 mGal). Se realizaron tres perfiles gravimétricos que muestran variaciones del espesor del relleno sedimentario (2100 m al N y 2200 m hacia la parte central) y fallas internas inferidas. Se utilizó información de gravedad satelital para observar el comportamiento de las estructuras geológicas regionales. Se generaron dos mapas de la topografía del basamento (basamento magnético y basamento gravimétrico), mostrando profundidades de: -2090 a -3400 m y 1931 a -4274 m respectivamente.
El análisis conjunto de los métodos geofísicos aplicados demostró ser útil para lograr los objetivos propuestos. Con la investigación presentada se actualizan y amplían las interpretaciones de la Porción Norte del Graben de Colima y se sientan las bases para futuras investigaciones.""This research was conducted in the northern portion of Colima Graben, where potential geophysical methods (magnetic airborne and gravity were applied in order to define the internal structure of the graben and the geological faults associated. The information generated from the processing of magnetic airborne data showed magnetic lineaments that were associated with possible geological faults. Six magnetic domains (DAM) were identified, the ones associated with the northern portion of Colima Graben are: DAM II, corresponding to volcano-sedimentary rocks; and DAM IV correspond to basaltic-andesite flows. The analysis of the Residual Bouguer anomaly map, allowed to delimit the graben’s pit, identifying it as an area of negative anomalies (-7 to -3.8 mGal), while the flanks were characterized by positive anomalies (> 2.4 mGal). Three gravity profiles were performed, showing variations in the thickness of the sedimentary infill (2100 m in the northern and 2200 m towards the central part) and inferred internal faults. Satellite gravity information was used to observe the behavior of the regional geological structures. Two maps of the topography of the basement were generated (magnetic and gravity), showing depths from -2090 to -3400m and -1931 to -4274m respectively. The set of geophysical methods applied to the analysis proved to be useful in achieving the objectives. The presented research updates and expands the interpretations of the northern portion of Colima Graben and set a basis for future research.
Steady state equivalence among autocatalytic peroxidase-oxidase reactions
Get PDF"Peroxidase-oxidase is an enzymatic reaction that can exhibit dynamical scenarios such as bistability, sustained oscillations, and Shilnikov chaos. In this work, we apply the chemical reaction network theory approach to find kinetic constants such that the associated mass action kinetics ordinary differential equations induced by three four dimensional structurally different enzymatic reaction systems can support the same steady states for several chemical species despite differences in their chemical nature.
Studies of adsorption of heavy metals onto spent coffee ground: equilibrium, regeneration, and dynamic performance in a fixed-bed column
Get PDF"Equilibrium and dynamic adsorption of heavy metals onto spent coffee ground (SCG) were studied. The equilibrium adsorption of Cd2+, Cu2+, and Pb2+ in a batch system was modeled by an ion-exchange model (IEM) based on an ion-exchange of heavy metals with calcium and protons bonded to active sites on SCG surface. The maximum amount of adsorbed metal ions obtained using the IEM was 0.12, 0.21, and 0.32 mol/g of Cd2+, Cu2+, and Pb2+, respectively. Regeneration of SCG was evaluated using citric acid, calcium chloride, and nitric acid. The observed trend of desorption efficiency through four adsorption-desorption cycles was HNO3 > CaCl2 > C6H8O7. The effect of process variables such as flow rate and bed height during the dynamic adsorption was evaluated. Moreover, the applicability of a mass transfer model based on external mass transfer resistance, axial dispersion, and ion-exchange isotherm was evaluated, and the results were in good agreement with the experimental data for the adsorption in SCG packed column. The sensitivity analysis of the model parameters showed that axial dispersion coefficient is the most significant parameter in the dynamic simulation. The results obtained showed the potential of SCG as a low-cost material for wastewater metal removal in continuous systems.
Structural insights into the IgE mediated responses induced by the allergens Hev b 8 and Zea m 12 in their dimeric forms
Get PDF"Oligomerization of allergens plays an important role in IgE-mediated reactions, as effective crosslinking of IgE-Fc epsilon RI complexes on the cell membrane is dependent on the number of exposed B-cell epitopes in a single allergen molecule or on the occurrence of identical epitopes in a symmetrical arrangement. Few studies have attempted to experimentally demonstrate the connection between allergen dimerization and the ability to trigger allergic reactions. Here we studied plant allergenic profilins rHev b 8 (rubber tree) and rZea m 12 (maize) because they represent an important example of cross-reactivity in the latex-pollen-food syndrome. Both allergens in their monomeric and dimeric states were isolated and characterized by exclusion chromatography and mass spectrometry and were used in immunological in vitro experiments. Their crystal structures were solved, and for Hev b 8 a disulfide-linked homodimer was found. Comparing the structures we established that the longest loop is relevant for recognition by IgE antibodies, whereas the conserved regions are important for cross-reactivity. We produced a novel monoclonal murine IgE (mAb 2F5), specific for rHev b 8, which was useful to provide evidence that profilin dimerization considerably increases the IgE-mediated degranulation in rat basophilic leukemia cells.
Molecular and electrophysiological characterization of P2X receptors in human monocytes
Get PDFTesis (Doctorado en Ciencias en Biología Molecular)"Usando técnicas de electrofisiología y biología molecular se analizó la expresión de los receptores P2X en monocitos humanos. Se encontró el mRNA de la subunidad P2X1 y su variante de splicing llamada P2X1del, así como del receptor P2X4 en un alto porcentaje de monocitos, en cambio el receptor P2X7 se encontró en un porcentaje mínimo. El análisis en células únicas y electrofisiológico sugiere la expresión heterogénea de subunidades P2X en los monocitos. Las corrientes mediadas por los canales P2X1 (EC50=1.9±0.8 µM) Y P2X1del (EC50 >1000 µM) expresados en ovocitos de Xenopus laevis presentaron diferente cinética y sensibilidad al ATP. Ambas corrientes mediadas por estos receptores mostraron incremento en la amplitud de la corriente bajo un estimulo prolongado con altas concentraciones de ATP. La activación de receptores P2X1 nativos en monocitos humanos mostró una EC50=6.3±0.2 µM. Estas corrientes presentaron características similares a las observadas cuando se expreso a los receptores P2X1 y P2X1del en ovocitos. La co-expresión del P2X1 y P2X1del mostro una EC50=4.5±1.34 µM y propiedades diferentes a las observadas en ovocitos que expresaron solo a uno de los receptores. Nuestro estudio muestra por primera vez la expresión heterogénea de los receptores P2X y su distribución entre las sub- poblaciones de monocitos humanos, la formación de canales funcionales al expresar al receptor P2X1del, y el incremento en la amplitud de corriente en los receptores P2X1y P2X1del homoméricos cuando se estimulan con concentraciones altas de ATP por tiempos prolongados, de manera similar a los canales P2X7, P2X2 y P2X4.""In order to characterize the general properties and the presence of P2X receptors in single human monocytes we used RT-PCR, flow cytometry, patch-clamp and the two-electrode voltage-clamp techniques. A high percentage of monocytes expressed the canonical P2X1, its splicing variant P2X1del and P2X4 mRNAs. P2X7 transcript was found in a minimal fraction of cells. P2X1 receptor immunoreactivity was observed in most monocytes but lower immunoreactivity was found for P2X4 and P2X7. Our data suggest heterogeneous expression of P2X receptors in monocytes and is supported by the electrophysiological data obtained. Currents mediated by P2X1 (EC50=1.9±0.8 μM) and P2X1del (EC50 >1000 μM) channels, expressed in Xenopus leavis oocytes, have different ATP sensitivity and kinetics. Both currents mediated by P2X1 and P2X1del channels kept increasing during the continuous presence of high ATP concentrations. Currents mediated by the native P2X1 receptors in human monocytes showed an EC50=6.3±0.2 μM. Currents have kinetics that resemble those observed for P2X1 and P2X1del receptors in oocytes. Co-expression of both receptors showed an EC50= 4.65±1.34 μM and different properties to the observed for each receptor expressed alone. This study is the first to demonstrate heterogeneous expression of P2X receptors in human monocytes and their distribution among monocyte subpopulations classified by their expression of CD14 and CD16. Our study is the first in demonstrate the expression of P2X1 receptor and its splicing variant P2X1del in most human monocytes. We also, for the first time, described functional homomeric P2X1del channels and showed that currents mediated by P2X1 or P2X1del increased in amplitude when activated with high ATP concentrations in a similar fashion to those channels that increase their conductance under similar conditions, such as P2X7, P2X2, and P2X4 channels.
On-line estimation of VFA concentration in anaerobic digestion via methane outflow rate measurements
Get PDF"This paper deals with the design of a robust nonlinear observer as a software sensor to achieve the on-line estimation of the concentration of Volatile Fatty Acids (VFA) in a class of continuous anaerobic digesters (AD). Taking into account the limited availability of on-line sensors for AD process, in this contribution is assumed that only the methane outflow rate is available for on-line measurement. The estimation method is based on a modified version for a two-dimensional mathematical model of AD process. From the differential algebraic observability approach it is shown that the VFA concentration is detectable from the methane outflow rate measurements. The observer convergence is analyzed by using Lyapunov stability techniques. Numerical simulations illustrate the effectiveness of the proposed estimation method for a four-dimensional AD model with uncertainties associated with unmodeled dynamics and disturbances in the inflow composition.
Influence of Fe doping and magnetic field on martensitic transition in Ni–Mn–Sn melt-spun ribbons
Get PDF"Mn-rich Ni-Mn-Sn metamagnetic shape memory alloys exhibiting magnetostructural transformation are of a great potential as the base materials for solid-state refrigeration. With the aim of fine tuning of the transformation characteristics and improving functional properties, in the present work we have fabricated polycrystalline Ni50-xFexMn40Sn10 (x = 0, 2, 4, 6, 8 at.%) melt-spun ribbons, starting from the base alloy with x = 0, which is weakly magnetic in both austenitic and martensitic phases. By exploring martensitic transformation (MT) and magnetic behaviors as a function of Fe doping and magnetic field, we have found that Fe and/or magnetic field reduce the MT temperature and Curie temperature of austenite phase, becoming closer to each other as the Fe-content increases, accompanied by an increase of the magnetic moment of austenite, magnetization jump at MT, transformation volume, and magnetic contribution, Delta S-M, to the total entropy change at MT. The ribbons present moderate values of Delta S-M equal to 11 J kg(-11)K(-1) at 5 T for x = 8, moderate thermal hysteresis (10-14 K) nearly independent of Fe doping or magnetic field, and adjustable structural and magnetic transition temperatures close to room temperature. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.