Cambio climático y su efecto en la asimilación de nitrógeno en plántulas de encinos (Quercus spp.)

"Los escenarios de cambio climático predicen que en los bosques estacionalmente secos de México aumentará la temperatura y se reducirá la precipitación. Esto amenaza a las etapas tempranas del ciclo de vida de los árboles que residen en estos ecosistemas, ya que el efecto combinado del calentamiento y la sequía pueden intensificar la mortandad de plántulas durante su primer año de vida. Estos cambios climáticos también pueden afectar los procesos bióticos responsables de incorporar nitrógeno al suelo, lo que alteraría la forma en que las plántulas adquieren y procesan este nutriente. En este contexto, realizamos dos experimentos de campo donde simulamos las condiciones de cambio climático predichas para mediados de siglo en bosques de encinos de la Sierra de Álvarez, San Luis Potosí, México. El primer experimento estuvo destinado a determinar los efectos del incremento de temperatura y la reducción de precipitación sobre la emergencia, la supervivencia, las respuestas funcionales y la asimilación de nitrógeno en plántulas de encinos durante la temporada de lluvias. En el segundo experimento evaluamos la manera en que el cambio climático puede afectar los procesos biológicos de fijación de nitrógeno y sus consecuencias para las plántulas de encino a lo largo de su primer año de vida. Los resultados de ambos experimentos sugieren que el cambio climático afectará de manera negativa la emergencia y el establecimiento de la mayoría de las especies de encino de estos ecosistemas, reduciendo también su crecimiento y desempeño general. Además, nuestros resultados indican que el cambio climático disminuirá las tasas de fijación biológica de nitrógeno, reduciendo su disponibilidad para las plántulas de encinos y, en consecuencia, la eficiencia de los procesos vegetales ligados a este nutriente.""Climate change scenarios predict that temperature will increase, while rainfall will decrease in seasonally dry forests of Mexico. This threatens the early stages of the life cycle of trees that inhabit these ecosystems because the combined effect of warming and drought can intensify seedling mortality during the period of the year in which their establishment occurs (rainy season). These climatic changes can also affect biotic processes responsible of incorporating nitrogen into the soil, which could alter how seedlings acquire and process this nutrient. In this context, we conducted two field experiments where we simulated climate change conditions predicted for the middle of this century in oak forests of Sierra de Álvarez, San Luis Potosí, Mexico. The first experiment was aimed to determine the effects of raising temperature and decreasing rainfall on the emergence, survival, functional responses and assimilation of nitrogen in oak seedlings during the rainy season. In the second experiment we evaluated the manner in which climate change can affect biological processes linked with nitrogen fixation and its consequences for oak seedlings throughout their first year of life. The results of both experiments suggest that climate change will negatively affect the emergence and establishment of most oak species from these ecosystems, also reducing their growth and overall performance. In addition, our results indicate that climate change will decrease the rates of biological nitrogen fixation, reducing its availability for oak seedlings and, consequently, the efficiency of plant processes linked to this nutrient.

Temporal and spatial variation of waterbirds at Sayula Lagoon, Jalisco, Mexico: a five-year winter season study

"Wetlands in central Mexico are important habitats for assemblages of migratory and resident birds. To study variation in richness and abundance of waterbirds, we conducted monthly observations in 30 permanent plots throughout the Sayula Lagoon, Jalisco, Mexico, during the winter season (from October to March) from 2004-2007 and from 2009-2011. Seventy-three species were recorded; 39 species were winter visitors, and eight species are included in some risk category. The best represented families were: Anatidae, Scolopacidae and Ardeidae. Spatula clypeata and Anser caerulescens were the most abundant species. We found variation in richness between zones (only two were similar), but not between the seasons (only WS4 was different) or months (only NOV was different). Sayula lagoon is a highly dynamic ecosystem influenced by migration and the water inputs occurring during the rainy season.""Los humedales del centro de México son hábitats importantes para ensambles de aves tanto migratorias como residentes. A fin de estudiar la variación en cuanto a riqueza y abundancia de las aves acuáticas, se realizaron observaciones mensuales en 30 parcelas permanentes de toda la laguna de Sayula, Jalisco, México, durante las temporadas invernales (de octubre a marzo) de los años 2004 a 2007 y 2009 a 2011. Se registraron 73 especies. Un total de 39 especies son visitantes invernales y ocho están incluidas en alguna categoría de riesgo. Las familias mejor representadas fueron: Anatidae, Scolopacidae y Ardeidae. Spatula clypeata y Anser caerulescens fueron las especies más abundantes. Se observó variación de la riqueza entre zonas (sólo dos fueron similares), pero no entre estaciones (solo WS4 fue diferente) ni entre meses (solo el mes de noviembre fue diferente). La laguna de Sayula es un ecosistema muy dinámico influido por la migración y el aporte de agua durante la temporada de lluvias.""Els aiguamolls del centre de Mèxic són hàbitats importants tant per a ensambles d’ocells migratoris com residents. Per tal d’estudiar la variació quant a riquesa i abundància dels ocells aquàtics es van portar a terme observacions mensuals en 30 parcel·les permanents de tota la llacuna de Sayula, Jalisco, Mèxic, durant les temporades hivernals (d’octubre a març) dels anys 2004 a 2007 i 2009 a 2011. S’hi van registrar 73 espècies. Un total de 39 espècies són visitants invernals i vuit estan incloses en alguna categoria de risc. Les famílies més ben representades van ser: Anatidae, Scolopacidae i Ardeidae. Spatula clypeata i Anser caerulescens van ser les espècies més abundants. Es va observar una variació de la riquesa entre zones (només dues van ser similars), però no entre estacions (només WS4 va ser diferent) ni entre mesos (només el mes de novembre va ser diferent). La llacuna de Sayula és un ecosistema molt dinàmic influït per la migració i l’aportació d’aigua durant la temporada de pluges.

Histone acetyltransferase TGF-1 regulates Trichoderma atroviride secondary metabolism and mycoparasitism

"Some filamentous fungi of the Trichoderma genus are used as biocontrol agents against airborne and soilborne phytopathogens. The proposed mechanism by which Trichoderma spp. antagonizes phytopathogens is through the release of lytic enzymes, antimicrobial compounds, mycoparasitism, and the induction of systemic disease-resistance in plants. Here we analyzed the role of TGF-1 (Trichoderma Gcn Five-1), a histone acetyltransferase of Trichoderma atroviride, in mycoparasitism and antibiosis against the phytopathogen Rhizoctonia solani. Trichostatin A (TSA), a histone deacetylase inhibitor that promotes histone acetylation, slightly affected T. atroviride and R. solani growth, but not the growth of the mycoparasite over R. solani. Application of TSA to the liquid medium induced synthesis of antimicrobial compounds. Expression analysis of the mycoparasitism-related genes ech-42 and prb-1, which encode an endochitinase and a proteinase, as well as the secondary metabolism-related genes pbs-1 and tps-1, which encode a peptaibol synthetase and a terpene synthase, respectively, showed that they were regulated by TSA. A T. atroviride strain harboring a deletion of tgf-1 gene showed slow growth, thinner and less branched hyphae than the wild-type strain, whereas its ability to coil around the R. solani hyphae was not affected. Δtgf-1 presented a diminished capacity to grow over R. solani, but the ability of its mycelium -free culture filtrates (MFCF) to inhibit the phytopathogen growth was enhanced. Intriguingly, addition of TSA to the culture medium reverted the enhanced inhibition growth of Δtgf-1 MFCF on R. solani at levels compared to the wild-type MFCF grown in medium amended with TSA. The presence of R. solani mycelium in the culture medium induced similar proteinase activity in a Δtgf-1 compared to the wild-type, whereas the chitinolytic activity was higher in a Δtgf-1 mutant in the absence of R. solani, compared to the parental strain. Expression of mycoparasitism- and secondary metabolism-related genes in Δtgf-1 was differentially regulated in the presence or absence of R. solani. These results indicate that histone acetylation may play important roles in the biocontrol mechanisms of T. atroviride.

Atomic surface segregation and structural characterization of PdPt bimetallic nanoparticles

"Bimetallic nanoparticles are of interest since they lead to many interesting electrical, chemical, catalytic, and optical properties. They are particularly important in the field of catalysis since they show superior catalytic properties than their monometallic counterparts. The structures of bimetallic nanoparticles depend mainly on the synthesis conditions and the miscibility of the two components. In this work, PdPt alloyed-bimetallic nanoparticles (NPs) were synthesized through the polyol method, and characterized using spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM). High-angle annular dark-field (HAADF)-STEM images of bimetallic nanoparticles were obtained. The contrast of images shows that nanoparticles have an alloy structure with an average size of 8.2 nm. Together with the characterization of nanoparticles, a systematic molecular dynamics simulations study focused on the structural stability and atomic surface segregation trends in 923-atom PdPt alloyed-bimetallic NPs was carried out.

Microbial recovery of metallic nanoparticles from industrial wastes and their environmental applications

"In recent years, metallic nanoparticles (NPs) have been produced by biological methods using bacteria and have been used with remarkable environmental applications. This paper emphasizes the basic aspects of microbial synthesis of metallic nanoparticles, from the selection of the strain to the settings of reaction parameters. Mechanisms involved in the microbial production of NPs are also discussed, summarizing general findings and implications in the process. There is also a section dedicated to the identification of wastes as a source of precious metals and the production of metallic NPs from waste streams containing ionic metals to give a vision of the opportunities to implement microbial synthesis as a treatment–recovery technology. Environmental applications of biogenic NPs are reviewed in detail indicating that the implementation of these nanomaterials enable the achievement of higher removal efficiencies and greater extent of transformation of recalcitrant compounds in wastewater treatment systems. Under this scenario and based on the information reviewed concluding remarks and futures perspectives are enunciated. © 2018 Society of Chemical Industry.

Caracterización geoquímica y geofísica de suelos agrícolas en el área de Cerrito Blanco, Matehuala, San Luis Potosí

"El ejido de Cerrito Blanco, perteneciente al municipio de Matehuala, S.L.P., cuenta con una zona agrícola de 70 hectáreas, las cuales, de acuerdo a estudios previos, reportan que han sido irrigadas por largo tiempo con agua contaminada con arsénico, con valores de hasta 17.78 mg Kg-1. El cual excede 148 veces lo máximo permisible de acuerdo a la norma mexicana. Como consecuencia de una constante irrigación, en la zona agrícola se han reportado concentraciones en suelo de hasta 172.00 mg Kg-1. La falta de información y la carencia de otras fuentes de agua libre de arsénico han permitido que la población local se encuentre expuesta a este tipo de contaminación. Tomando en cuenta estos antecedentes, se planteó como objetivo general de este estudio determinar la distribución espacial de arsénico total en la zona agrícola del ejido Cerrito Blanco y analizar la calidad de los suelos en el sitio de estudio a partir de análisis en muestras de suelo colectadas; así como estimar la conductividad hidráulica de los suelos agrícolas y su relación con la migración de los contaminantes a lo largo de la columna de suelo. Para llevar a cabo este estudio se analizaron 14 muestras de suelo superficial y 11 columnas, a las cuales se les determinó de acuerdo a la NOM-021-SEMARNAT-2000; fosforo aprovechable, carbonatos totales, materia orgánica, cationes intercambiables, micro y macronutrientes, nitrógeno disponible, pH, salinidad, conductividad hidráulica, textura. Además, se determinó arsénico total mediante digestión ácida de elementos totales y arsénico soluble mediante agua de equilibrio el cual fue cuantificado mediante ICP-OES y Fluorescencia de rayos X. La mineralogía fue determinada mediante difracción de rayos X. La resistividad eléctrica del suelo y su humedad fueron medidas in situ de manera simultánea utilizando el método de perfilaje eléctrico y un medidor de humedad relativa del suelo, respectivamente. A los datos obtenidos se les realizó un análisis estadístico multivariante, el cual constó de una matriz de correlación de Pearson, análisis de componentes principales (PCA), análisis clúster e índice de calidad de suelo (ICS). Los resultados obtenidos evidencian que los suelos presentan condiciones favorables para el desarrollo de las plantas de acuerdo al ICS, en el cual se clasifica el suelo con una calidad media. De acuerdo a la correlación estadísticas de las muestras se logró identificar dos grupos, el primero con predominancia en calcita y con tamaños de partículas arcillosa (< 2.0 µm) y el segundo grupo con presencia de yeso y con tamaño de partículas de limos (< 60.0 µm). Lo que respecta al arsénico, los resultados permiten determinar que toda la zona agrícola se encuentra enriquecida de arsénico, con valores de hasta 185 mg Kg-1 el cual excede 8 veces lo permitido. A pesar de la baja conductividad hidráulica del suelo agrícola (predominantemente muy baja), el arsénico es transportado a lo largo del perfil del suelo, presentando concentraciones de hasta 94.29 mg Kg-1 a 60 cm de profundidad. Esta migración vertical del arsénico es debido a la alta solubilidad que presenta llegando a ser en la zona del orden del 10 % del arsénico total, siendo que la textura fina presente permite que el agua contaminada llegue a tener mayor interacción con el suelo, permitiendo la lixiviación del arsénico.""The common Cerrito Blanco, belonging to the municipality of Matehuala, SLP, has an agricultural area of 70 hectares, which, according to previous studies, report that they have been irrigated for a long time with water contaminated with arsenic, with values up to 17.78 mg Kg-1 . Which exceeds 148 times the maximum allowable according to the Mexican norm. As a result of constant irrigation, soil concentrations of up to 172.00 mg Kg-1 have been reported in the agricultural zone. The lack of information and the lack of other sources of arsenic-free water have allowed the local population to be exposed to this type of contamination. Taking this background into account, the general objective of this study was to determine the spatial distribution of total arsenic in the agricultural area of the common Cerrito Blanco and to analyze the quality of the soils at the study site based on analyzes of soil samples collected; as well as estimating the hydraulic conductivity of agricultural soils and their relation to the migration of pollutants along the soil column. To carry out this study, 14 surface soil samples and 11 columns were analyzed, which were determined according to NOM-021-SEMARNAT-2000; usable phosphorus, total carbonates, organic matter, interchangeable cations, micro and macronutrients, available nitrogen, pH, salinity, hydraulic conductivity, texture. In addition, total arsenic was determined by acid digestion of total elements and soluble arsenic by equilibrium water, which was quantified by ICP-OES and X-ray fluorescence. The mineralogy was determined by X-ray diffraction. The electrical resistivity of the soil and its moisture were measured in situ simultaneously using the electrical logging method and a relative humidity meter of the soil, respectively. The data obtained were subjected to a multivariate statistical analysis, which consisted of a Pearson correlation matrix, principal component analysis (PCA), cluster analysis and soil quality index (SCI). The results obtained show that the soils have favorable conditions for the development of the plants according to the ICS, in which the soil with an average quality is classified. According to the statistical correlation of the samples, it was possible to identify two groups, the first with predominance in calcite and with clay particle sizes (<2.0 μm) and the second group with presence of gypsum and with particle size of limes (<60.0 μm). Regarding arsenic, the results allow to determine that the entire agricultural area is enriched with arsenic, with values of up to 185 mg Kg-1 which exceeds 8 times what is allowed. Despite the low hydraulic conductivity of agricultural soil (predominantly very low), arsenic is transported along the soil profile, presenting concentrations of up to 94.29 mg Kg-1 at 60 cm depth. This vertical migration of arsenic is due to the high solubility that it has been reaching in the area of the order of 10% of the total arsenic, being that the fine texture present allows the contaminated water to have greater interaction with the soil, allowing the leaching of arsenic.

An output-feedback global continuous control scheme with desired gravity compensation for the finite-time and exponential regulation of bounded-input robotic systems

"A Saturating-Proportional Saturating-Derivative type global continuous control scheme with desired gravity compensation for the finite-time or (local) exponential stabilization of robotic systems with constrained inputs, avoiding velocity variables in the feedback, is presented. The proposed output-feedback controller proves to need a closed-loop analysis with considerably higher degree of complexity, and entail more involved consequent requirements, than in the on-line compensation case. Other analytical limitations are further overcome through the developed algorithm. Simulation tests corroborate the efficiency of the proposed approach.

Self-association of enolase from Trichomonas vaginalis. monomers, dimers, and octamers coexist in solution

"We used small-angle X-ray scattering to study the self-association of enolase from Trichomonas vaginalis as a function of the protein concentration and cosolute type. We observed coexisting monomers, dimers, and octamers in variable relative populations, depending on whether Tris–acetate, Tris–HCl, or potassium phosphate buffers were used. Phosphate ions hindered the formation of dimers and octamers. In contrast, the populations of dimers and octamers increased in Tris–acetate or Tris–HCl buffers and additionally increased by augmenting protein concentration or adding magnesium. Single oligomeric species could not be isolated in any of the experimental conditions tested. Furthermore, the secondary and tertiary structures, as well as the temperature-induced denaturation of the mixtures of species, were investigated. The acquired species lost enzymatic activity, but they were prone to interact with plasminogen, as judged from changes in the secondary and tertiary structures upon complex formation.

Optimization of biohydrogen production by the novel psychrophilic strain N92 collected from the Antarctica

"In this study, the response surface methodology (RSM) with central composite design (CCD) was employed to improve the hydrogen production by the psychrophilic N92 strain (EU636058) isolated from Antarctica, which is closely related to Pseudorhodobacter sp. (KT163920). The influence of operational conditions such as temperature (4.7–55.2 °C), initial pH (3.44–10.16), and initial glucose concentration (4.7–55.23 g/dm3), as well as the initial concentrations of (NH4)2SO4 (0.05–3.98 g/dm3), FeSO4 (0.02–1.33 g/dm3) and NaHCO3 (0.02–3.95 g/dm3) was evaluated. The linear effect of glucose concentration, along with the quadratic effect of all the six factors were the most significant terms affecting the biohydrogen yield by N92 strain. The optimum conditions for the maximum hydrogen yield of 1.7 mol H2/mol glucose were initial pH of 6.86, glucose concentration of 28.4 g/dm3, temperature 29 °C and initial concentration of (NH4)2SO4, FeSO4 and NaHCO3 of 0.53, 1.55 and 1.64 g/dm3 respectively. Analysis of the metabolites produced under the optimum conditions showed that the most abundant were acetic acid (0.8 g/dm3), butyric acid (0.7 g/dm3) and ethanol (2.1 g/dm3). We suggest that the bioprocess established in this study using the strain N92 could be an alternative for hydrogen production with the advantages of constituting low energy costs in fermentation.

Implementación analógica del mapeo casa de campaña

"En este trabajo se presenta la implementación electrónica del sistema dinámico discreto conocido como casa de campaña (tent map). En el diseño del circuito electrónico han sido considerados componentes pasivos y activos, logrando obtener resultados experimentales del mapeo casa de campaña en correspondencia con los resultados de la simulaciones numéricas del mismo. Al igual que el caso teórico, el circuito electrónico del mapeo casa de campaña presenta puntos fijos, periódicos, doblamiento de periodo, caos e intermitencia. El diseño del circuito electrónico es simple, utiliza componentes comerciales y puede ser construido por estudiantes a nivel licenciatura.