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NMR analysis and crystal structure of hydroxyclerodanes from Mexican Salvia species
Get PDF"NMR and single crystal X-ray diffraction analysis of seven clerodanes from Mexican Salvia species was performed. We focused on clerodanes with tertiary hydroxyl group at C-4, C-8, and C-10, in which the establishment of absolute configuration around these chiral centers is nontrivial and the 13C NMR signals can be misassigned. In addition, the analysis by 1H NMR in aprotic solvent allowed us to establish a common pattern that correlates the chemical shift with the position of the hydroxyl groups, which constitute a good methodology for future structural elucidation of these kinds of compounds. The obtained data allowed us to establish the absolute configuration of five of these diterpenes and the structural revision of salvimicrophyllin D (7).
Desulfuración y desnitrogenación de un diésel modelo mediante carbón activado modificado con (oxi)hidróxidos de Fe y Mn
Get PDFTesis (Maestría en Ciencias Ambientales)"Las actividades petroquímicas han aumentado en los últimos años y con ellas las emisiones de óxidos de nitrógeno y de azufre como consecuencia de la quema de combustibles fósiles; las cuales impactan directamente en el medio ambiente y en la salud de los seres humanos. Actualmente, la principal estrategia para controlar o reducir estas emisiones es el hidrotratamiento aplicado al diésel para remover compuestos azufrados y nitrogenados antes de ser utilizado en el sector industrial o transporte. Este tratamiento permite disminuir la concentración de compuestos azufrados y nitrogenados en un intervalo de 300 a 500 ppm, sin embargo, llegar a las concentraciones permitidas (15 ppm) resulta complicado, por lo tanto, se requieren procesos alternos como la adsorción con la finalidad de cumplir con las regulaciones ambientales. En este estudio, un carbón activado comercial (F-400) fue modificado con óxidos de Fe y Mn mediante hidrólisis térmica asistida por microondas (MH), y fue evaluado en la adsorción de compuestos azufrados y nitrogenados refractarios como dibenzotiofeno (DBT), 4,6-dimetildibenzotiofeno (DMDBT), indol (I) y quinolina (Q) en un diésel modelo preparado con una mezcla de decano-hexadecano con 200 ppm-S y 200 ppm-N. El carbón activado granular comercial F400 (CAG) y los materiales modificados (CAG-Mn, CAG-Fe y CAG- FeMn) fueron caracterizados fisicoquímicamente mediante las técnicas analíticas de DRX, ATG, MEB y FN. Los resultados mostraron que se obtuvo un aumento en el área específica de los 3 materiales modificados hasta en un 14%. Se encontró que el Mn controla los hábitos cristalinos de los (oxi)hidróxidos de hierro anclados en el CAG, lo cual incrementa la capacidad de adsorción de las moléculas nitrogenadas y azufradas en más del 20%. Las cinéticas de adsorción mostraron que el tiempo requerido para alcanzar el equilibrio de adsorción, para las 4 moléculas y los 4 materiales, es de 12-17 horas aproximadamente. Los principales mecanismos de adsorción propuestos son interacciones tipo π-π entre los anillos aromáticos de los adsorbatos y las láminas grafíticas del carbón activado, así como interacciones ácido-base entre las moléculas orgánicas y los grupos funcionales del carbón activado. ""Petrochemical activities have been increased in recent years and with it the
emissions of nitrogen and sulfur oxides as consequence of burning fossil fuels
having a direct impact on the environment and human health. Currently, the main
strategy to control or reduce these emissions is the hydrotreatment process, which
is applied to remove sulfur and nitrogen compounds from diesel before being used
in the industry or transport. This treatment allows the reduction of sulfur and nitrogen
compounds in an interval of 300-500 ppm, however is not enough and hence
alternative processes like adsorption are required with the aim of achieving
concentrations below 15 ppm, to accomplish environmental regulations. In this
study, a commercial activated carbon (F400) was modified with Fe and Mn oxides
by microwave thermal hydrolysis (MH), and was evaluated for the adsorption of
sulfur and nitrogen refractory compounds such as dibenzothiophene (DBT), 4,6-
dimethyldibenzothiophene (DMDBT), indole (I) and quinoline (Q) in a model diesel
prepared in a mixture of decane-hexadecane with 200 ppm-S and 200 ppm-N. The
commercial granular activated carbon F400 (CAG) and the modified materials (CAGMn,
CAG-Fe and CAG-FeMn) were physicochemically characterized by the
analytical techniques XRD, TGA, SEM and FN. The results have shown an increase
in the specific area of 14 % by means of microwave thermal hydrolysis for the 3
modified materials. It was found that Mn controls the crystalline habits of the iron
(oxy)hydroxides anchored on CAG, allowing an increase in the adsorption capacity
of the nitrogen and sulfur molecules by more than 20 %. The adsorption kinetics
show that the time to reach the adsorption equilibrium, for the 4 molecules and the
4 materials, is of approximately 12-17 hours. The main adsorption mechanisms
proposed are π-π interactions between aromatic rings of the adsorbates and
graphitic sheets of activated carbon, as well as acid-base interactions between
organic molecules and functional groups of activated carbons.
"Comparación de metodologías para la separación de barita del circón detrítico"
Get PDF"Los granos de circón detrítico son ampliamente usados para obtener
información acerca de la roca donde se hospedan ya que estos sirven como
indicadores de la procedencia sedimentaria, para correlacionar secuencias, para
determinar el límite máximo de edad de deposición y para estudiar la evolución de
la corteza. Geológicamente esta información es muy importante, pero adquirirla
depende en gran medida del número de granos analizados y de cómo se realiza la
selección de granos para su análisis.
Cuando se tienen minerales accesorios, como la barita con el circón, aún
después de las separaciones habituales: separación por agua, magnética y
líquidos densos; se requiere el método de trituración, donde los minerales
accesorios (barita) se rompen. Analizando este método de trituración para la
separación de barita y circón surgen dos preguntas: ¿Hay algún rompimiento de
los granos de circón además de los de barita con este método? ¿Hay otro método
para separar estos minerales sin riesgo de rompimiento de granos de circón? Los
objetivos de este estudio fueron: (1) demostrar que el método de trituración rompe
no solo los granos de barita sino también los de circón y (2) separar la barita del
circón con una disolución química. Para el método de trituración física, se agitaron
1) la misma cantidad de granos de circón y barita y 2) granos de circón y diez
veces más granos de barita entre 10 y 40 minutos respectivamente. Para el
método de disolución química se realizaron 18 experimentos a diferentes
condiciones para lograr obtener las condiciones óptimas para la disolución de la
barita.
En el método de trituración, para 10 minutos se observó que el 25%
aproximadamente de granos se había roto (en su totalidad o parcialmente)
mientras que para 40 minutos más del 50% aproximadamente de granos se había
roto total o parcialmente. En el método de disolución química la disolución de
barita se logró con: (1) 0.208 g de muestra real en 20mL de una solución 0.98M de
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Na2CO3, 150°C y 4h, y (2) 30mL de una solución 15.81M de HNO3, 190°C y 1h;
sin afectar la composición química del circón.
Por lo tanto, los resultados muestran que con el método de trituración hay
un rompimiento de los granos, lo cual causa sesgo en los análisis de procedencia
para las rocas sedimentarias o en los análisis cuantitativos, ya que se pueden
perder grupos de circón; generando así interpretaciones incorrectas. Los
resultados de este estudio demuestran que el método de trituración provoca la
ruptura de granos de circón detrítico. Mientras que los resultados del método de
disolución química no presentan dicho problema, obteniendo información menos
sesgada y por tanto más significativa para su interpretación geológica. ""The common accessory mineral barite cannot be separated from zircon
using standard isolation steps based on density and magnetic properties. When
barite is present, trituration often is used to preferentially break the barite, followed
by removal of the small barite pieces from the zircon. Several questions arise upon
consideration of the trituration method. Is there any breaking of the zircon grains
with this method? Is there another method to separate these minerals without risk
of zircon grains?
The aim of this study was: (1) to demonstrate that the trituration method
breaks not only the barite grains but also the zircon grains and (2) to separate the
barite from the zircon by dissolving the barite. For the trituration method 1) the
same volume of zircon grains and barite and 2) zircon grains with an approximately
ten times greater volume of barite were shaken for 10 and 40 minutes respectively.
For the chemical dissolution method, 18 experiments were performed under
different conditions to obtain the optimal conditions for the dissolution of barite.
In the trituration method, 10 minutes of shaking resulted that about 25% of
grains had been broken (in whole or partly) while 40 minutes of shaking over 50%
of grains had been broken in whole or partly. In the chemical dissolution method,
the barite dissolution was obtained with: (1) 0.208 g of real sample in 20 mL of a
0.98M solution of Na2CO3 at 150°C for 4h, followed by (2) 30 mL of a 15.81M
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solution of HNO3 at 190°C for 1h. Similar conditions attained in a separate
experiment did not affect the chemical composition of zircon.
Therefore, the results show that with the trituration method there is grains
breaking. Breaking zircon during separation can cause bias in provenance
analyses of sedimentary rocks, thus generating incorrect interpretations. The
results of this study demonstrate that the trituration method causes rupture of
detrital zircon grains while the results of the chemical dissolution method do not
present this problem, allowing the collection of information with less bias and
therefore more significant for its geological interpretation. "Durante la realización del trabajo la autora recibió una beca académica del
Consejo Nacional de Ciencia y Tecnología 590367 y del Instituto Potosino de
Investigación Científica y Tecnológica, A. C
Anchorage of lanthanum oxyhydroxides on activated carbon to increase its fluoride removal from water
Get PDF"El flúor es beneficioso para la salud humana a una concentración de 0.7 mg L-1, pero se considera peligroso cuando es ingerido a concentraciones superiores a 1.5 mg L-1, el cual es el límite recomendado por la Organización Mundial de la Salud (OMS). La contaminación del agua por fluoruros es un problema que se encuentra presente a nivel mundial. Por lo tanto, se requiere invertir en el desarrollo de nuevos materiales y tecnología más eficientes para la remoción de contaminantes prioritarios. El objetivo de esta investigación fue anclar óxidos de lantano sobre un carbón activado granular (CAG) comercial para remover fluoruros presentes en el agua. El CAG modificado con lantano se caracterizó mediante FT-IR, XRD, SEM, distribución de pKa´s y punto de carga cero (PCC) con la finalidad de elucidar el posible mecanismo de anclaje del lantano sobre la superficie del carbón activado y el mecanismo de adsorción de fluoruros en el carbón modificado. realizaron experimentos de adsorción en batch para estudiar el efecto del pH, de la presencia de aniones co-existentes, y la capacidad máxima de adsorción en solución acuosa. Los resultados mostraron que la capacidad de adsorción del carbón modificado con lantano (CAG-La) aumentó 5 veces con respecto al CAG comercial a una concentración inicial de F- de 20 mg L-1, a pH 7 y 25 °C. La presencia de aniones co-existentes no tiene ningún efecto en la capacidad de adsorción del fluoruro a concentraciones menores de 30 mg L-1.""Fluoride is beneficial to humans health at a concentration of 0.7 mg L-1, but it is considered dangerous when ingested at concentrations above 1.5 mg L-1, which is the limit concentration recommended by the World Health Organization (WHO). Water pollution by fluorides occurs in many places around the world. Therefore, more efficient materials and technology are required to overcome this environmental problem. The objective of this research was to anchor lanthanum oxides on a commercial granular activated carbon (GAC) to remove fluorides from water. The modified GAC was characterized by FT-IR, XRD, SEM, pKa’s distribution, and point of zero charge (PZC) in order to suggest how lanthanum anchors on the activated carbon surface and also to propose the fluoride adsorption mechanism on the modified carbon. Adsorption experiments were carried out in batch to study the effect of pH, presence of co-existing anions, and the maximum adsorption capacity in aqueous solution. These results showed that the adsorption capacity of the modified carbon (GAC-La) increased 5 times compared to the commercial GAC at an initial concentration of 20 mg L-1 of F- at pH 7 and 25° C. Finally, the presence of co-existing anions has no effect on the fluoride adsorption capacity at concentrations below 30 mg L-1.
Generation of chaotic attractors without equilibria via piecewise linear systems
Get PDF"In this paper, we present a mechanism of generation of a class of switched dynamical system without equilibrium points that generates a chaotic attractor. The switched dynamical systems are based on piecewise linear (PWL) systems. The theoretical results are formally given through a theorem and corollary which give necessary and sufficient conditions to guarantee that a linear affine dynamical system has no equilibria. Numerical results are in accordance with the theory.
Análisis funcional del gen PBC1 involucrado en la defensa contra el cáncer bacteriano en tomates silvestres mediante VIGS y CRISPR/Cas 9
Get PDF" El tomate (Solanum lycopersicum) es uno de los productos hortícolas más importantes a nivel mundial, con una producción anual valorada en 88 billion USD annually. Mexico is the 10 th largest producer globally, however its production has been diminished due to pathogens among which stands out Clavibacter michiganensis subsp. michiganensis (Cmm) that is responsible of great losses. The control strategies against this bacterium are not effectives once the disease is detected; however it is known that some wild species such as Solanum peruvianum acc. 2172 and Solanum arcanum acc. 2157 are resistant to Cmm. Some works on tomato wild species resistant to Cmm showed differential expressed genes when uninfected and Cmm infected plants were compared. Some genes were overexpressed after the challenge, among these, the proteasome beta subunit type 3 (PBC1), based on this, we decided to perform a functional analysis of PBC1, through Virus Induced Gene Silencing (VIGS) and CRISPR/Cas9 system. The aim of this work was assessing the role of that gene in plant defense against Cmm. Functional analysis of PBC1 with VIGS was performed in the wild tomato species Solanum peruvianum acc. 2172 and Solanum arcanum acc. 2157 using the Tomato Mottle Virus (ToMoV) vector and delivery was done by biolistic methods. After inoculation with Cmm the phenotype of the healthy and infected plants was compared and correlated to bacterial load and qRT-PCR of PBC1. Knockout of the PBC1 gene was accomplished with the CRISPR/Cas 9 system. Guides specific to the PBC1 gene were designed with two strategies, 1) using single RNA guides and 2) using a multiplex system containing three individual guides. In plants S. peruvianum 2172 silenced by VIGS, PBC1 expression decreased ~80% in some plants and, the Cmm bacterial titer increased, demonstrating an increase in Cmm susceptibility on plants compared with the wild species without silencing. This observation suggests that PBC1 could be involved in resistance against Cmm in wild species and overexpression approaches could help with engineering or breeding for resistance in commercial tomatoes. Nevertheless, in S. arcanum 2157 the bacterial titer was not significantly different in comparison to the control and in some plants the gene expression of PBC1 was unchanged despite VIGS, perhaps due to biolistic technical complications or because of particular characteristics of this plant species.
High tolerance to high-light conditions for the protected species Ariocarpus kotschoubeyanus (Cactaceae)
Get PDF"We determined the seasonal ecophysiological performance under perennial plants and under high solar radiation for adult individuals from the "living rock" cactus Ariocarpus kotschoubeyanus, which occurs equally under nurse plants and in open spaces. We evaluated the effective quantum yield of photosystem II (?PSII) and the dissipation of thermal energy [non-photochemical quenching (NPQ)] thorough the year. The maximum apparent electron transport rate (ETRmax) and the saturating photosynthetically active photon flux density for PSII (PFDsat) were also determined from rapid light curves. We found that although the ?PSII was higher in shaded sites under potential nurse plants than in exposed sites, all values were close to the optimal value of 0.83. The high ?PSII found for A. kotschoubeyanus plants suggests that they use a great proportion of the absorbed light for photosynthesis, under nurse plants as well as in open spaces. We also found higher NPQ values in exposed sites than in shaded ones but only in Autumn, thus reducing the risk of photoinhibition. In addition, the PFDsat was higher in exposed sites than in shaded ones in Spring, Summer and Autumn, but in Winter there were no differences between treatments. We also found high saturating light levels for ETR (PFDsat higher than 1378 ?mol m?2 s?1) in all seasons but in winter for shaded and non-shaded plants. Our findings indicate that A. kotschoubeyanus plants use a great proportion of the light that they absorb for photosynthesis. This high tolerance to high-light conditions could explain why A. kotschoubeyanus do not show preferences for protected sites under nurse plants.
Diversidade de coleópteros em um fragmento do bioma thornscrub e árvores isoladas
Get PDF"Due to land use change mainly for induced agriculture, Tamaulipan thornscrubin northeast Mexico has been cleared and transformed into small patches of vegetation as small as isolated trees surrounded by agricultural fields. In this study, we explored how tree isolation or growing inside a fragment of remnant vegetation influence diversity of coleopterans in two plant species (Prosopis laevigata (Humb. &Bonpl.exWilld.) M.C. Johnst. (mesquite) and Ebenopsis ebano (Berl.) Barneby (Texas ebony). We found 72 coleopteran morphospecies; fifteen occurred mainly in remnant fragments and ten mainly in isolated trees. There were more insects under isolated mesquites than under those immersed in remnant fragments, while in Texas ebony the highest beetle density for isolated trees coincided with periods of bean and maize in surrounding agriculture.""Devido a mudança de uso da terra para induzir principalmente a agricultura, o bioma thornscrub no nordeste México tem sido transformado em fragmentos pequenos como árvores isoladas rodeadas por campos agrícolas. Neste estudo exploramos como o isolamento das árvores influi na diversidade de coleópteros em duas espécies de plantas (Prosopis laevigata (Humb. & Bonpl.ex Willd) M.C. Johnst. (mesquite) e Ebenopsis ebano (Berl.) Barneby (Texas ebony). Encontramos 72 morfospecies do coleópteros; quinze ocorreram principalmente em fragmentos remanescentes e dez em árvores isoladas. No estudo houve mais insetos nas “mesquite” isoladas do que nos fragmentos remanescentes do bioma thornscrub, enquanto que em “Texas ebony” a densidade alta de coleópteros para árvores isoladas coincidiu com períodos de produção de feijão e milho na agricultura ao redor.
Characterization of dissolved organic matter in an agricultural wastewater-irrigated soil, in semi arid Mexico
Get PDF"Most agricultural soils in semi-arid regions present a deficiency of organic matter (SOM). In order to improve this soil, wastewater is used due to its high organic carbon content. The objective of the present work was to characterize the dissolved organic matter in five residual water samples and ten soil samples from the agricultural area of the municipality of San Luis Potosí by 3D fluorescence spectroscopy. The changes in some physical and chemical properties of the soil were also analyzed. The soil samples were collected at different depths to observe the anthropogenic organic matter presence, their retention in the soil profile, their fluorescence intensity changes and their migration into the aquifer. Temperature, electrical conductivity, dissolved oxygen, oxidation- reduction potential and total dissolved solids were determined in situ. The major anions and cations: Na+, K+, Mg2+, Ca2+, PO43–, SO42–, NO3–, NO2–, were analysed in laboratory. The results show the great contribution of organic matter (>2020 mg/L) in the residual water used for irrigation, as well as, the low content of SOM. The physical and chemical results indicate that the high electrical conductivity of the water, represents a risk of salinization for soils, but not of short term sodicity. The 3D fluorescence spectra of the soil profile, shows the presence of humic and fulvic acids, aromatic proteins and products of microbial degradation. The latter observed in that depth where there is a greater percentage of clay.""La mayoría de los suelos agrícolas en regiones semiáridas presentan una deficiencia de materia orgánica (MOS) y para compensarla se recurre al uso de agua residual por su alto contenido de carbono orgánico. El objetivo del presente trabajo fue caracterizar la materia orgánica disuelta con espectroscopía de fluorescencia 3D, en cinco muestras de agua residual y 10 de suelo de la zona agrícola del municipio de San Luis Potosí. Se analizaron los cambios de algunas propiedades físicas y químicas del suelo y del agua. Las muestras se colectaron a diferentes profundidades para observar la presencia de materia orgánica, su retención a lo largo del perfil de suelo y su migración hacia el acuífero. La temperatura, la conductividad eléctrica, el oxígeno disuelto, el potencial de oxido-reducción y los sólidos totales disueltos se determinaron in situ. En laboratorio fueron analizados los aniones y cationes mayoritarios: Na+, K+, Mg2+, Ca2+, PO4 3–,SO42–, NO3–, NO2–. Los resultados muestran el gran aporte de materia orgánica del agua residual empleada para el riego, así como, el bajo contenido de MOS. Los resultados físicos y químicos indican que la alta conductividad eléctrica del agua representa un riesgo de salinización para los suelos, pero no de sodicidad a corto plazo. Los espectros de fluorescencia 3D del perfil del suelo evidencian la presencia de ácidos húmicos, acidos fúlvicos, proteínas aromáticas y productos de degradación microbiana. Estos últimos, observados en la profundidad donde se presenta mayor contenido de arcilla.
Effects of catalase on chloroplast arrangement in Opuntia streptacantha chlorenchyma cells under salt stress
Get PDF"In arid and semiarid regions, low precipitation rates lead to soil salinity problems, which may limit plant establishment, growth, and survival. Herein, we investigated the NaCl stress effect on chlorophyll fluorescence, photosynthetic-pigments, movement and chloroplasts ultrastructure in chlorenchyma cells of Opuntia streptacantha cladodes. Cladodes segments were exposed to salt stress at 0, 100, 200, and 300 mM NaCl for 8, 16, and 24 h. The results showed that salt stress reduced chlorophyll content, F-v/F-m, Phi PSII, and qP values. Under the highest salt stress treatments, the chloroplasts were densely clumped toward the cell center and thylakoid membranes were notably affected. We analyzed the effect of exogenous catalase in salt-stressed cladode segments during 8, 16, and 24 h. The catalase application to salt-stressed cladodes counteracted the NaCl adverse effects, increasing the chlorophyll fluorescence parameters, photosynthetic-pigments, and avoided chloroplast clustering. Our results indicate that salt stress triggered the chloroplast clumping and affected the photosynthesis in O. streptacantha chlorenchyma cells. The exogenous catalase reverted the H2O2 accumulation and clustering of chloroplast, which led to an improvement of the photosynthetic efficiency. These data suggest that H2O2 detoxification by catalase is important to protect the chloroplast, thus conserving the photosynthetic activity in O. streptacantha under stress.